303 results
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2. Variable-Voltage Bus Concept for Aircraft Electrical Power System.
- Author
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Yeoh, Seang Shen, Rashed, Mohamed, Sanders, Mike, and Bozhko, Serhiy
- Subjects
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HYBRID electric airplanes , *VOLTAGE control , *DIRECT currents , *CONVERTERS (Electronics) , *ELECTRIC power systems - Abstract
This paper deals with the innovative “variable-voltage” bus concept for future more-electric aircraft platforms. Using new functionalities and opportunities offered by innovative sources actively controlled by power electronics, there is an opportunity for a significant increase of their output power (within powertrain capabilities, machine thermal limits, and power converter maximum current) to supply increased load demands under certain conditions. This paper investigates applications of this concept to satisfy power demands for the wing ice-protection system for business jet. The study includes a detailed study into the control challenges of the proposed approach and suggests corresponding theoretical solutions. Furthermore, the controller design aspects are explored with considerations to achieve stable operation. The concept is tested in simulation environment and validated through experimental studies. This paper might be of interest for the researchers and engineers focused on innovative solutions for future aircraft platforms. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
3. A Novel Bidirectional Solid-State Circuit Breaker for DC Microgrid.
- Author
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Wang, Yufeng, Li, Weilin, Wu, Xuanlyu, and Wu, Xiaohua
- Subjects
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MICROGRIDS , *DIRECT currents , *SHORT circuits , *ELECTRIC circuit breakers , *ELECTRIC potential - Abstract
DC microgrid has attracted more and more attention due to its unique characteristics, but the development of a dc microgrid is also facing some challenges, such as interruption and isolation of short-circuit fault currents. Therefore, the dc circuit breaker plays an important role in ensuring the normal work of a dc microgrid. In this paper, a novel bidirectional dc solid-state circuit breaker is proposed to realize the bidirectional flow of energy, which ensures the higher operating efficiency of the dc microgrid. Compared with other solid-state circuit breakers, the proposed novel topology has simpler structure, common ground, and fewer components. First, this paper makes a detailed analysis of the different working stages of the circuit when the fault occurs in combination with simulation results of the circuit topology. Then, the standard of selecting the components through the calculation and analysis of the circuit is given in this paper. Finally, the performance of the novel bidirectional solid-state circuit breaker is verified by experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
4. An Active Modulation Scheme to Boost Voltage Utilization of the Dual Converter With a Floating Bridge.
- Author
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Huang, Zhen, Yang, Tao, Giangrande, Paolo, Chowdhury, Shajjad, Galea, Michael, and Wheeler, Pat
- Subjects
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CASCADE converters , *HYBRID electric airplanes , *ELECTRIC potential , *VOLTAGE control , *DIRECT currents - Abstract
This paper proposes a capacitor voltage regulation method for the dual converter with a floating bridge for aerospace applications. This topology has previously been reported, but with a constrained voltage utilization factor due to the need for capacitor voltage regulations. In this paper, the effect of switching states on the voltage variation of capacitor is quantitatively modeled and an enhanced space vector modulation scheme with current feedback is proposed to achieve an active control of the floating capacitor voltages. This proposed method also allows further exploitation and utilization of converter voltage. The relationship between the allowed modulation index of dual converter and load power factor is obtained and expressed using a fitted polynomial equation. The advantages of the proposed method include boosted voltage utilization and superior performance in term of capacitor voltage balance. These advantages have been proven through simulation and experimental results on RL loads as well as with an open-end winding induction motor. The proposed modulation scheme can boost the converter voltage utilization by at least 10% while achieving full four-level operation. More importantly, the higher available voltage allows extending the constant torque region of the motor, the further beginning of field weakening operation could be postponed. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
5. Improved Fault-Tolerant Method for Modular Multilevel Converters by Combined DC and Neutral-Shift Strategy.
- Author
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Farzamkia, Saleh, Iman-Eini, Hossein, Noushak, Masoud, and Hadizadeh, Alireza
- Subjects
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CAPACITORS , *FAULT tolerance (Engineering) , *DIRECT currents , *FAULT currents , *ELECTRIC potential - Abstract
In this paper, an improved postfault strategy is introduced for modular multilevel converters, which utilizes the remaining healthy capacity of the converter more efficiently and increases the line voltage amplitude under these circumstances. Previous works proposed to use the neutral point shift in ac side and dc side of the converter simultaneously. This paper adds a comprehensive and coherent formulation, deep analyzation, and experimental validation. The main improvement of the proposed method is maximizing the line voltage amplitude using the optimum dc component and the best neutral point position. Indeed, fewer restrictions in fault numbers, fewer restrictions in load power factor, and fewer nonsolution conditions are among other improvements of a combined dc and neutral-shift method. Comparative simulation and experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
6. Three-Switch Three-Phase Inverter With Improved DC Voltage Utilization.
- Author
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Farhadi, Masoud and Abapour, Mehdi
- Subjects
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DIRECT currents , *ELECTRIC inverters , *SEMICONDUCTOR switches , *PULSE width modulation transformers , *CAPACITORS - Abstract
This paper proposes a new dc–ac converter with a reduced number of semiconductor switches and gate drive and control circuit components. A salient feature of this inverter is its pure sinusoidal line-to-line voltages with no need for output filter. Also, the proposed inverter improves the voltage utilization factor of the input dc supply compared to the four-switch three-phase inverter (first best topology in the literature from the number of switches point of view) and standard six-switch inverter with sine pulsewidth modulation. The proposed inverter is capable of operating with a wide range of output voltages from zero to the full value of the dc input voltage by appropriately altering the instantaneous duty cycle. A three-phase universal inverter with only three power switch has been proposed in this paper for the first time ever, to our knowledge. For the purpose of providing a good compromise between fast transient response and stability, a model predictive controller is proposed. All the design expressions have been derived. A comparison with other dc–ac converters is given to show the merits of the proposed converter. Finally, satisfactory circuit operation is confirmed by experimental results from a laboratory prototype. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
7. Current Prediction Based Zero Sequence Current Suppression Strategy for the Semicontrolled Open-Winding PMSM Generation System With a Common DC Bus.
- Author
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Zhang, Xiaoguang and Wang, Keqin
- Subjects
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DIRECT currents , *ELECTRIC potential , *SYNCHRONOUS electric motors , *COMPUTER simulation , *DIODES - Abstract
In this paper, the model predictive current control is introduced in the semicontrolled open-winding permanent magnet synchronous motor (OW-PMSM) generation system with a common dc bus to suppress the zero-sequence current for the first time. Particularly, the basic voltage vectors of the semicontrolled OW-PMSM, which are synthesized by the three-phase full-controlled converter and the three-phase uncontrollable diode bridge, is analyzed and their influences on the zero-sequence current are investigated for the first time in this paper. Then the current-error-based cost function that includes dq-axis current error and zero-sequence current error is designed to evaluate all the voltage vectors. Moreover, to further improve the steady-state control performance of the whole generation system, a zero-sequence current suppression method based on the uncontrollable side voltage vector adjustment, which has the advantage of low computation burden, is developed. In this method, two voltage vectors of the controllable converter are applied during one control period. Based on the distribution character of the basic voltage vector in the semicontrollable OW-PMSM generation system, the first voltage vector is selected according to the three-phase current direction to adjust equivalent vector of the uncontrollable diode bridge, whereas for the second voltage vector, the selection method based deadbeat voltage vector sector is designed to reduce the range of the candidate voltage vector. In addition, the vector durations are also computed. Finally, simulation and experiment are carried out to validate the proposed control approaches. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
8. Improved Saliency-Based Position Sensorless Control of Interior Permanent-Magnet Synchronous Machines With Single DC-Link Current Sensor Using Current Prediction Method.
- Author
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Im, Jun-Hyuk and Kim, Rae-Young
- Subjects
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PERMANENT magnet motors , *SYNCHRONOUS electric motors , *SENSORLESS control systems , *DIRECT currents , *DETECTORS - Abstract
This paper presents an improved saliency-based position sensorless drive of an interior permanent-magnet synchronous machine (IPMSM) with a single current sensor, used for low cost applications. The phase current, reconstructed from a dc-link current, shows a reconstruction error resulted from the difference of the sampling point from that of a full current sensor drive. This reconstruction error results in degradation of the overall sensorless control performance. In this paper, we analyze the impact of the reconstruction error depending on the injection frequency for a high frequency voltage signal injection sensorless control. Based on this analysis, we propose an improved position sensorless drive that employs a new current reconstruction method. In order to minimize the reconstruction error, the proposed current reconstruction method predicts the dq-axis currents with the same sampling point as a full current sensor drive. Several experimental results are provided to verify the analysis of the reconstruction error and the proposed method's improved sensorless control performances. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
9. A Z-Source-Derived Coupled-Inductor-Based High Voltage Gain Microinverter.
- Author
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Surapaneni, Ravi K. and Das, Pritam
- Subjects
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ELECTRIC inverters , *DIRECT currents , *ELECTRIC potential , *ELECTRIC inductors , *IMPEDANCE parameters (Computer networks) , *PHOTOVOLTAIC effect - Abstract
Microinverters require high voltage gain capability for interfacing the low dc voltage output of photovoltaic (PV) module to single-phase ac grid. A two-stage nonisolated inverter is proposed in this paper, with a first boost stage and a second traditional pulse width modulated grid-tied inverter stage. The proposed boost stage consists of a coupled inductor added with a voltage multiplier to achieve the required high voltage gain at high efficiency and to operate over a wide input voltage range. Among the coupled inductor topologies, adding a clamp circuit is a common solution to limit the voltage spike caused by leakage inductance. In the proposed converter, the resonance between the coupled inductor and voltage multiplier is used to address the issue of voltage spike, thereby reducing both component count and device voltage stress. Detailed analysis and design procedure of the proposed converter is presented in this paper. Experimental results of a 250-W microinverter are presented to validate the proposed converter. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
10. A Carrier-Based Modulation Scheme to Reduce the Third Harmonic Component of Common-Mode Voltage in a Three-Phase Inverter Under High DC Voltage Utilization.
- Author
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Huang, Jin, Liu, Quanhui, Wang, Xulong, and Li, Kaicheng
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DIRECT currents , *VOLTAGE regulators , *AMPLITUDE estimation , *ELECTRIC inverters , *PULSE width modulation transformers , *EXPERIMENTS - Abstract
High dc voltage utilization is one of the important requirements in a three-phase inverter. Under some carrier-based pulse width modulations (PWMs), the dc voltage utilization can reach the same maximum as that under the space vector modulation. But the third harmonic component of common-mode voltage (CMV) will be increased markedly while using these carrier-based PWMs in inverters. To improve the situation, this paper proposes that a midpoint-fluctuation carrier (MFC) scheme should be used in the three-phase inverter. The MFC is formed by adding a midpoint-fluctuation signal on the standard symmetrical triangular carrier. By analyzing the linear modulation region of the midpoint-fluctuation signals, a minimum fluctuant signal in the linear modulation region is designed in the paper. Compared with the use of other conventional schemes in the three-phase inverter, the use of minimum MFC scheme has higher fundamental amplitude in the output line voltage and smaller magnitude of the third harmonic in the CMV. The feasibility and validity of the MFC are proved by experiment results in a three-phase inverter. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
11. Analysis of Chaos and Bifurcation Due to Slotting Effect and Commutation in a Current Discontinuous Permanent Magnet Brushed DC Motor Drive.
- Author
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Ghosh, Mousam, Panda, Goutam Kumar, and Saha, Pradip Kumar
- Subjects
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PERMANENT magnets , *DIRECT currents , *PROPULSION systems , *ELECTRIC potential , *ENERGY density , *BIFURCATION theory - Abstract
The aim of this paper is to study the dynamics of a permanent magnet direct current (PMDC) brushed motor while two crucial space-domain effects, namely, slotting effect and commutation phenomenon are taken into account. Semi-analytical dynamic time-domain PMDC brushed motor model inclusive of these space-domain effects is used to analyze and investigate the dynamics. Pulse width modulation operated discontinuous current PMDC brushed motor drive with steady duty cycle is employed to acquire the bifurcation patterns. The chaotic nature due to slotting effect and commutation is identified from the bifurcation patterns and reported. It also has to be admired that such nonlinear dynamical behavior with the same set of parameters at similar operating condition has not been observed when a conventional PMDC brushed motor dynamic model is considered. These space-domain effects, namely, slotting effect and commutation also have a prominent impact to make some time-domain states of a PMDC brushed motor drive chaotic. The role of slotting effect and commutation phenomenon to analyze the chaos over time-domain state variables of the PMDC brushed motor drive is investigated and validated experimentally in this paper. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
12. Effects of Front-End Converter and DC-Link of a Utility-Scale PV Energy System on Dynamic Stability of a Power System.
- Author
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Moradi-Shahrbabak, Zahra and Tabesh, Ahmadreza
- Subjects
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DYNAMIC stability , *PHOTOVOLTAIC power systems , *EIGENVALUES , *DIRECT currents , *CAPACITORS - Abstract
This paper presents a method for small-signal dynamic studies of power systems including utility-scale PV energy systems considering the effects of dc-side components. Existing methods commonly model a PV energy system as a dc source connected to a grid-tied inverter. This paper shows that the dc components of a PV energy system can also contribute in the dynamics of the power system in the range of small-signal studies. The paper first develops the model of a PV energy system by merging the submodels of dc- and ac-side components. Then, a method to obtain the augmented model of the power system including a PV energy system will be explained using a study system. The study system consists of a PV energy system in parallel with a synchronous generator connected to a grid. Then, based on eigenvalue analysis, verified by time-domain simulations, it is shown that the dc-link capacitor, front-end converter, and its controller can introduce oscillatory modes in subsynchronous range of frequencies. Furthermore, it is shown that the damping of the sensitive modes can significantly vary with respect to the parameters of the dc-side components. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
13. Arm-Balancing Control and Experimental Validation of a Grid-Connected MMC With Pulsed DC Load.
- Author
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Jankovic, Marija, Costabeber, Alessandro, Watson, Alan, and Clare, Jon C.
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DIRECT currents , *ELECTRIC power distribution grids , *PULSE circuits , *FLUCTUATIONS (Physics) , *HEURISTIC algorithms - Abstract
This paper focuses on the operation of a grid-connected modular multilevel converter (MMC) supplying a pulsed dc load. The goal is to achieve minimum ac power fluctuation despite the high power fluctuation present on the dc side. The MMC has been selected for its inherent ability to decouple ac and dc current controllers. However, if no additional provisions are taken, the pulsed load causes imbalance of cell capacitor voltages between upper and lower arms in each phase. This paper presents the theoretical analysis of the imbalance problem and proposes a simple arm-balancing controller to enable the operation of the converter under pulsed dc load. The effectiveness of the controller has been successfully verified on a 7 kW MMC experimental prototype with a 3 kA pulsed dc load. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
14. Computationally Efficient Coordinate Transformation for Field-Oriented Control Using Phase Shift of Linear Hall-Effect Sensor Signals.
- Author
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Yu, Zhangguo, Qin, Mingyue, Chen, Xuechao, Meng, Libo, Huang, Qiang, and Fu, Chenglong
- Subjects
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COORDINATE transformations , *PERMANENT magnet motors , *TRIGONOMETRIC functions , *DETECTORS , *DIRECT currents - Abstract
Linear Hall-effect sensors are integrated into permanent magnet motors and provide positional feedback with the advantages of compact size and low cost. Field-oriented control (FOC) is widely used in high-performance situations yet limited by its computational cost. This paper proposes a novel simplified FOC that uses the linear Hall outputs directly to obtain the coefficients required to perform coordinate transformations through linear combination; neither the computation of trigonometric functions nor the flux position estimations are required. The method is computationally efficient because it involves less latency and fewer hardware resources, when implemented on digital controllers. Furthermore, the method has been used for sensor delay compensation, which has been verified as important to eliminate direct current. The experimental results validate the feasibility and effectiveness of the proposed method with a 126 W motor under various speed and load conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. An Enhanced Strategy to Inhibit Commutation Failure in Line-Commutated Converters.
- Author
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Mirsaeidi, Sohrab and Dong, Xinzhou
- Subjects
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DIRECT currents , *AREA measurement , *ELECTRIC inductance , *REACTIVE power , *PULSE width modulation transformers , *ELECTRIC inverters , *TESTING laboratories - Abstract
Failure of the commutation process is a serious malfunction in line-commutated high-voltage direct current (HVdc) converters, which mainly occurs due to inverter ac faults and may lead to outage of the HVdc system. In this paper, an improved strategy is developed that functions based on the SIEMENS HVdc control system under normal conditions and switches to a designed commutation failure inhibition module (CFIM) during an inverter ac fault. From the response speed point of view, since the designed CFIM does not require any proportional-integral controller, the inverter control system has a quick performance in prevention of the commutation failure. This is achieved by direct measurement of the overlap area using the waveforms of the valves anode–cathode and commuting voltages. In addition, from the accuracy aspect, the proposed method has a superior performance in comparison with the existing strategies. It is because of the fact that by direct measurement of the overlap area, variations of both direct current and the commutation inductance are considered, and hence, the unnecessary increase of the inverter reactive power consumption during the fault and the repetitive commutation failures are prevented. The practical performance and feasibility of the proposed strategy is validated through the laboratory testing, using the real-time Opal-RT hardware prototyping platform. The experimental results demonstrate that the proposed strategy can effectively inhibit the commutation failure or repetitive commutation failures under different fault types by considering the lowest possible reactive power consumption. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
16. Advanced Control Methods for Power Converters in Distributed Generation Systems and Microgrids.
- Author
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Dragicevic, T., Vazquez, S., and Wheeler, P.
- Subjects
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AC DC transformers , *MICROGRIDS , *DISTRIBUTED power generation , *VOLTAGE references , *DIRECT currents , *ALTERNATING currents - Abstract
The twenty-two papers in this special section focus on flexible control of power converters which serve as interfaces between the distributed generation (DG) units and the legacy alternating current (ac) grid or the ac or direct current (dc) microgrid (MG), is the key to realization of high penetration of renewable energy in a safe and stable fashion. When connected to the ac legacy grid, these power converters need to provide ancillary services such as frequency and voltage support, harmonic compensation, as well as synthetic inertia emulation. Another emerging solution is to interface the DG units with the ac legacy grid through an intermediate entity called anMG. MG can be based either on ac and dc architecture and can work in both stand-alone and grid-connected modes. Since it is responsible for multiple power converters, an MG has higher operational flexibility than individual units.However, due to a lack of stiff voltage reference source and natural inertia, control of MGs is generally more challenging than control of individual grid-connected power converters. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. A Novel Approach for Speed and Failure Detection in Brushless DC Motors Based on Chaos.
- Author
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Medeiros, Ramon L. V., Filho, Abel C. Lima, Ramos, Jorge Gabriel G. S., Nascimento, Tiago P., and Brito, Alisson Vasconcelos
- Subjects
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BRUSHLESS electric motors , *DIRECT currents , *SPEED - Abstract
This paper presents an approach developed to quantify the chaotic behavior for the characterization of electromechanical systems. A technique named Signal Analysis based on Chaos using Density of Maxima (SAC-DM) is presented. This technique uses a simple peak counting algorithm in the time domain of the current signal to detect faults. To demonstrate the potential of SAC-DM, an experiment is presented where a small brushless direct current (BLdc) motor at different speeds, with a regular and an unbalanced propeller, is used. The results demonstrate that the SAC-DM was able to detect the speed of the BLdc motor in 99.16% of the cases, and to identify the unbalanced system in 99.79% of the cases, when the speed is at 50%. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
18. Current-Fed Hybrid Dual Active Bridge DC?DC Converter for a Fuel Cell Power Conditioning System With Reduced Input Current Ripple.
- Author
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Sha, Deshang, Xu, Yaxiong, Zhang, Jiankun, and Yan, Yu
- Subjects
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FUEL cells , *DIRECT currents , *ZERO voltage switching , *NOTCH filters , *PROTON exchange membrane fuel cells - Abstract
In this paper, a novel current fed hybrid dual active bridge dc–dc converter is proposed, which is suitable for a low-voltage fuel cell power conditioning system. The high-frequency input current ripple can be reduced to minimum because the input side switches are always switched at 50% duty cycles in spite of the fuel cell voltage and the load variation. Notch filter is used in the voltage feedback path to reduce the low-frequency input current ripple when interfaced with a single-phase inverter load. All of the power devices can achieve zero voltage switching by the proposed control strategy. The mode analysis, the operation principle, zero-voltage switching (ZVS) conditions, and parameter design are given in this paper. A 1 kW prototype has been fabricated to verify the effectiveness of the proposed converter and control strategy. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
19. Reduced-State-Observer-Based Feedback Control System Design of a Two-Staged AC?DC Converter.
- Author
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Mallik, Ayan and Khaligh, Alireza
- Subjects
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FEEDBACK control systems , *PID controllers , *ELECTRIC power factor correction , *ALTERNATING currents , *DIRECT currents , *EQUIPMENT & supplies ,DESIGN & construction - Abstract
This paper presents a methodology to control a two-staged ac/dc converter, which is a cascade combination of a three-phase ac–dc boost power factor correction (PFC) rectifier and a phase-shifted full-bridge (PSFB) dc/dc converter. This paper explains the issues of instability and losing unity power factor operation, i.e., high reactive power transfer with conventional PI compensator due to the sensitive variation of output impedance of the PFC stage at different loads. In this paper, this instability issue is resolved by the proposed state-feedback control methodology, which shows that there exists a load-insensitive range of controller parameters, providing unity PFC. As an additional benefit of this control, total number of sensors are reduced by three (an input phase current, a dc/dc primary current, and an output dc voltage), in comparison to the conventional PI-based control. This reduction is achieved by introducing two augmented state variables followed by their reduced state observer design. A 6-kW laboratory prototype of the integrated three-phase PFC and PSFB dc/dc is developed and designed to validate the proposed control algorithm. The experimental results show a conversion efficiency of 95.4% at full load, input total harmonic distortion of 4.1%, power factor of 0.998, and output voltage ripple of ±1%. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
20. Sensorless Frequency and Voltage Control in the Stand-Alone DFIG-DC System.
- Author
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Marques, Gil D. and Iacchetti, Matteo F.
- Subjects
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SENSORLESS control systems , *VOLTAGE control , *INDUCTION generators , *FIELD orientation principle , *ELECTRIC current rectifiers , *DIRECT currents - Abstract
A sensorless stand-alone control scheme of a doubly fed induction generator (DFIG)-DC system is investigated in this paper. In this layout, the stator voltage is rectified by a diode bridge that is directly connected to a dc bus. The rotor-side voltage source inverter is the only controlled converter required in this system and is directly powered by the same dc bus created by the stator-side rectifier. DC voltage and stator frequency are regulated by two independent proportional-integral regulators that give the references for inner current controllers implementing field-oriented control. As it is capable of creating a stable and regulated dc bus, this system can be conveniently adopted to supply dc loads or to form a dc grid. Due to the constraint imposed by the stator diode bridge, the DFIG has to operate under a constant stator voltage, and the conventional stator field-oriented control implemented in stand-alone ac DFIG must be modified. This paper presents the control structure and the theoretical framework for the controller synthesis. Simulation and experimental validations on a small-scale rig are included. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
21. Cascade-Free Model Predictive Control for Single-Phase Grid-Connected Power Converters.
- Author
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Acuna, Pablo, Aguilera, Ricardo P., Ghias, Amer M. Y. M., Rivera, Marco, Baier, Carlos R., and Agelidis, Vassilios G.
- Subjects
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CASCADE converters , *PREDICTIVE control systems , *ELECTRIC power distribution , *DIRECT currents , *ALGORITHMS - Abstract
In a conventional finite control set model predictive control (FCS-MPC) formulation, active and reactive power control loops rely on the predictive controller, whereas the dc-bus voltage is usually governed by a PI-based control loop. This originates from fact that the dynamic equations for describing the predictions of these variables are heavily coupled. In this paper, a cascade-free FCS-MPC for single-phase grid-connected power converters is presented. The proposed control algorithm is formulated in terms of established dynamic references design, which was originally proposed to directly govern active and reactive power, and dc-voltage in three-phase power converters. In this paper, the dynamic reference design concept is extended to control single-phase grid-connected power converters. The proposed control algorithm does not use instantaneous ac-power calculations; instead, it directly formulates the optimal control problem on the grid-current in the original stationary reference frame. The experimental results obtained with a single-phase grid-connected neutral point clamped (NPC) converter confirm a successful design, where system constraints, e.g., maximum power and weighted switching frequency, are easily taken into account. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
22. Online Monitoring Technique for Aluminum Electrolytic Capacitor in Solar PV-Based DC System.
- Author
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Ahmad, Md Waseem, Agarwal, Nikunj, and Anand, Sandeep
- Subjects
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PHOTOVOLTAIC power generation , *SOLAR cells , *DIRECT currents , *CASCADE converters , *SWITCHING theory - Abstract
To interconnect low-voltage solar photovoltaics (PV) with dc system, a dc–dc boost converter is required. To minimize the switching frequency oscillations in solar PV voltage, aluminum electrolytic capacitors (AECs) are connected between solar PV and the converter. Operational life of AECs depends on electrical and environmental parameters and is less than that of solar PV panels. Equivalent series resistance (ESR) of AEC increases with life, thereby increasing the voltage ripple across PV terminals. This results in less power extraction from solar PV. This paper proposes a method for health monitoring of AEC using the parameters measured for maximum power point tracking (MPPT) (PV voltage and current). The proposed technique is applicable for both continuous conduction mode and discontinuous conduction mode of operation of the converter. Effect of temperature on ESR is incorporated for accurate determination of the health of capacitor. Key advantage is that no additional current or voltage sensor is required to implement this technique, thereby offering a low-cost solution. Further, the proposed technique does not require significant processing capabilities and is implemented in the same digital controller used for MPPT. Detailed simulation studies are carried out and results are included in this paper. A laboratory prototype of dc–dc boost converter is developed for experimentation. Results are in agreement with that obtained from simulation studies. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
23. Reduction of Power Electronic Components in Multilevel Converters Using New Switched Capacitor-Diode Structure.
- Author
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Samanbakhsh, Rahim and Taheri, Asghar
- Subjects
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CASCADE converters , *POWER electronics , *CAPACITOR switching , *DIRECT currents , *ELECTRIC potential - Abstract
In this paper, a new structure for symmetric and cascade multilevel converter is presented. This structure requires the least power electronic components, gate driver circuits, power diode, and dc voltage source. The number of output levels is high. Reduction of the number of power electronic switches against voltage levels is an important factor in multilevel converters due to safety in switches, circuit size, cost, installation area, and complexity in control. To maximize the number of output level in the proposed optimized structure in order to attain different goals, such as reduction of stress on switches, the result of comparing the proposed structure and other structures present. The proposed method is robust against the switching faults in multilevel converter for dc source and the equipment. The simulation and experimental results presented in this paper show the performance of the proposed method. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
24. Model Predictive Control for a Dual-Active Bridge Inverter With a Floating Bridge.
- Author
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Chowdhury, Shajjad, Wheeler, Patrick W., Gerada, Chris, and Patel, Chintan
- Subjects
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PREDICTIVE control systems , *ELECTRIC inverters , *ELECTRIC transformers , *DIRECT currents , *ELECTRIC potential - Abstract
This paper presents a model predictive control technique applied to a dual-active bridge inverter where one of the bridges is floating. The proposed floating bridge topology eliminates the need for isolation transformer in a dual inverter system and therefore reduces the size, weight, and losses in the system. To achieve multilevel output voltage waveforms, the floating inverter dc-link capacitor is charged to the half of the main dc-link voltage. A finite-set model predictive control technique is used to control the load current of the converter as well as the floating capacitor voltage. Model predictive control does not require any switching sequence design or complex switching time calculations as used for space vector modulation; thus, the technique has some advantages in this application. A detailed analysis of the converter as well as the predictive control strategy is given in this paper. Simulation and experimental results to validate the approach are also presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
25. Modeling and Analysis of Modular Multilevel Converter in DC Voltage Control Timescale.
- Author
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Hu, Jiabing, Zhu, Jianhang, and Wan, Min
- Subjects
- *
CONVERTERS (Electronics) , *ELECTRIC potential , *DIRECT currents , *INERTIA (Mechanics) , *DAMPING (Mechanics) - Abstract
This paper presents a small-signal model of modular multilevel converter (MMC) based on the motion equation concept in the dc voltage control (DVC) timescale (around 10 Hz). The relations between the active/reactive powers and the phase/magnitude dynamics of the internal voltage vector are developed with considering the submodules (SMs) capacitor voltage ripple. With the proposed model, the stability mechanism of the DVC timescale in an MMC-HVdc system can be well interpreted with the equivalent inertia and damping coefficients. It is found that the fundamental frequency ripple in the capacitor voltage of SMs will result in new oscillation modes in DVC timescale when compared with the conventional two-level voltage source converter. Furthermore, the coupled relationship between the reactive power and phase dynamics of internal voltage is revealed, which has great effect on the system stability property. Then, comparative studies via eigenvalues analysis show the proposed model can hold the main behaviors of concern, and the correctness of the proposed model is verified by comparisons with detailed time-domain simulations and experimental tests. Finally a single MMC connected to infinite-bus grid is taken as an example to validate the feasibility of the proposed model for dynamics analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
26. Robust Analytic Design of Power-Synchronization Control.
- Author
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Harnefors, Lennart, Hinkkanen, Marko, Riaz, Usama, Rahman, F. M. Mahafugur, and Zhang, Lidong
- Subjects
- *
SYNCHRONIZATION , *FREQUENCY-domain analysis , *DIRECT currents , *ROBUST control , *ELECTRIC insulators & insulation - Abstract
This paper addresses robust design of the active-power and dc-link control loops of power-synchronization control. Robustness is obtained by analytic gain selections, which give large enough stability margins. The proposed design allows robust stability irrespective of the grid strength and of the operating point, the latter with one exception. The proposed design is compared to design based on the principle virtual synchronous machine. Experiments show that the time-domain results correlate well with the frequency-domain results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
27. A Fully Soft-Switched Bidirectional DC–DC Converter With Only One Auxiliary Switch.
- Author
-
Rahimi, Saba, Rezvanyvardom, Mahdi, and Mirzaei, Amin
- Subjects
- *
DIRECT currents , *SEMICONDUCTORS , *PROTOTYPES , *CONVERTERS (Electronics) , *TOPOLOGY - Abstract
In this paper, a fully soft-switched bidirectional dc–dc converter is proposed. All semiconductor devices are soft switched, while its control circuit remains pulsewidth modulated. This condition is achieved only by one auxiliary switch. So, the proposed topology has less complexity in comparison with other similar structures. The energy conversion through the proposed topology during buck and boost modes is highly efficient due to achieved soft-switching condition. The auxiliary circuit operates once during each switching cycle. The converter is analyzed and a 250-W laboratory prototype of the proposed converter is constructed. The experimental results are presented that confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
28. Generalized Switching Modification Method Using Carrier Shift for DC-link Capacitor RMS Current Reduction in Real-Time Implementation.
- Author
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Choi, Ki-Young, Kim, Sang-Il, Jung, Sang-Min, and Kim, Rae-Young
- Subjects
- *
STANDARD deviations , *DIRECT currents , *APPROXIMATION theory , *FOURIER series , *ELECTRIC inverters - Abstract
In this paper, a generalized switching modification method is proposed to reduce the root-mean-square (rms) current flowing into a dc-link capacitor in a dc–dc–ac structure consisting of a boost converter and a three-phase inverter. To analyze the current flowing into the capacitor, we analyze the currents at the respective converter and inverter sides. Based on this analysis, we derive an analytical method to find the modification time between the converter and inverter pulsewidth modulation (PWM) carriers through a Fourier series and approximation to facilitate real-time implementation. Real-time implementation of the modification time calculated by the derived method is described. To verify the validity of the proposed method, experimental results are presented based on a 1-kVA dc–dc–ac prototype. The proposed method has a better capacitor rms current reduction performance than the conventional method in various inverter power factors and PWM strategies. Especially, it has an excellent performance in mid-power factor level (0.95–0.1). [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
29. An Adaptive PI Controller Design for DC-Link Voltage Control of Single-Phase Grid-Connected Converters.
- Author
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Merai, Meriem, Naouar, Mohamed Wissem, Slama-Belkhodja, Ilhem, and Monmasson, Eric
- Subjects
- *
ELECTRIC controllers , *CONVERTERS (Electronics) , *ELECTRIC potential , *OSCILLATIONS , *DIRECT currents - Abstract
Conventionally, standard proportional and integral (PI) controllers with constant PI gains are commonly used for the dc-link voltage control of single-phase grid-connected converters (GCCs). For such controllers, the selection of the PI gains will lead to a tradeoff between two control objectives: 1) the reduction of the dc-link voltage fluctuations caused by random swings of the active power drawn by the single-phase GCC; and 2) the reduction of the grid current harmonics mainly caused by the 2f oscillation of the active power in single-phase applications. To solve this tradeoff, this paper presents a systematic approach for the design of an adaptive PI controller for the dc-link voltage control of single-phase GCCs. The proposed design approach is simple and it provides a convenient method to properly determine the adaptive PI controller parameters. Representative simulation and experimental results are presented and discussed in order to show the effectiveness of the proposed dc-link voltage controller. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
30. Control of Direct Voltage Regulated Active DC-Link Capacitance Reduction Circuits to Allow Plug-and-Play Operation.
- Author
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Mutovkin, Alexei, Yuhimenko, Vladimir, Mellincovsky, Martin, Schacham, Shmuel, and Kuperman, Alon
- Subjects
- *
ELECTRIC potential , *DIRECT currents , *ELECTRIC capacity , *SIMULATION methods & models , *ELECTRIC controllers - Abstract
A novel method for controlling direct voltage regulated active dc-link capacitance reduction circuits (ACRC) is proposed in this paper. Instead of forcing the dc-link voltage of the power conversion system to follow a constant reference, the ACRC imposes dc-bus voltage in proportion to the integral of its input current. Consequently, it resembles an adjustable value capacitor from the dc-link side. Therefore, as opposed to existing control strategies, the proposed method simultaneously allows the dc-link voltage to reflect the power balance of the system and the pulsating power component to be diverted into significantly reduced auxiliary capacitance via a bidirectional dc–dc converter. As a result, replacing bulk dc-link capacitance by the proposed circuitry does not require any modification of existing grid-connected power conversion system controllers, thus allowing plug-and-play operation. The proposed approach is validated by application to a commercial power factor correction front end by both simulations and experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
31. Droop-Controlled Rectifiers That Continuously Take Part in Grid Regulation.
- Author
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Zhong, Qing-Chang and Lyu, Zijun
- Subjects
- *
ELECTRIC controllers , *ELECTRIC current rectifiers , *ELECTRIC potential , *DIRECT currents , *CONVERTERS (Electronics) - Abstract
In this paper, a generic framework for a rectifier to continuously take part in the regulation of grid voltage and frequency is proposed. It can automatically change the power consumed to support the grid, without affecting the normal operation of the load. Such a rectifier has a built-in storage port, in addition to the normal ac and dc ports. The flexibility required by the ac port to support the grid is provided by the storage port without affecting the dc port. The grid support of the ac port is achieved through the recently proposed universal droop controller (UDC). A dc-bus voltage controller cascaded to the UDC is proposed to regulate the dc-bus voltage of the storage port within a wide range so as to provide the flexibility needed, while the dc-port voltage is maintained constant. An illustrative example is presented with the recently proposed $\theta$ -converter, which consists of three ports with only four switches. Experimental results are provided to verify the capability of the rectifier to regulate the grid voltage and frequency without affecting the load. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
32. Performance Analysis of Forced Commutated Controlled Series Capacitor Rectifier for More Electric Aircraft.
- Author
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Al-Mhana, Tahani H. M., Pickert, Volker, Zahawi, Bashar, and Atkinson, David J.
- Subjects
- *
DC-AC converters , *ELECTRIC power conversion , *CAPACITORS , *DIRECT currents , *HYBRID electric airplanes - Abstract
The forced commutated controlled series capacitor (FCSC) rectifier has been recently proposed to power stand-alone variable-voltage variable-frequency generation systems, such as the full authority digital electronic control (FADEC) system, in more electric aircraft. The employment of this rectifier helps to meet increasing power demand requirements while maintaining low current harmonic levels without the need for bulky filters. The FCSC rectifier is controlled to maintain resonance with line frequency variation by inserting variable capacitive reactance in series with the variable-frequency generator's inductive reactance. Unity power factor operation with nearly pure sinusoidal converter input currents is thus achieved, for better utilization of the generator. The FCSC rectifier operation with a variable dc on-board load is analyzed in this paper, including a description of the principle modes of operation of the circuit. The enhancement in circuit's output voltage and output power achieved by replacing the conventional diode bridge rectifier with the FCSC rectifier is also demonstrated. Both rectifiers are analyzed numerically using Saber/Synopsys over a wide range of operating voltages and frequencies. Results are experimentally verified using 1-kW laboratory test rig. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
33. Decoupled Power Control for Direct-Modulation-Based Modular Multilevel Converter With Improved Stability.
- Author
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Wang, Jinyu and Wang, Peng
- Subjects
- *
ELECTRIC potential , *ELECTRIC currents , *CASCADE converters , *ELECTRIC power conversion , *DIRECT currents - Abstract
Direct modulation principle is widely used in modular multilevel converters (MMCs) for its simplicity and natural stability. However, it results in strong active and reactive power coupling. This paper carefully analyzes and identifies four power coupling paths and two power influence factors with the direct modulation principle. Full power decoupling of the MMC can be realized by cutting off the derived coupling paths and compensating the influence factors. However, this will further deteriorate the already poor damping of the MMC and significantly increase dc-bus current fluctuations. To solve this problem, the sources resulting in poor damping are identified and then a new closed-loop dc-bus current controller is incorporated into the control system. Finally, the proposed power decoupling strategy with the newly designed current controller realizes completely decoupled power regulation, avoids overload operation, and obviously improves the dynamic performance of the MMC. Furthermore, it increases the stability of the MMC system under all possible operation conditions. The proposed control strategy is confirmed by experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
34. A Novel Modulation Strategy With Unconditional Neutral Point Voltage Balance and Three Switching Actions in One Switching Cycle for Neutral Point Clamped Three-Level Converter.
- Author
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Weidong, Jiang, Zhang, Xuewei, Wang, Wei, Wang, Jinping, Zhai, Fei, Li, Jinsong, and Li, Laibao
- Subjects
- *
ELECTRIC current converters , *ELECTRIC potential , *ELECTRIC inverters , *VOLTAGE control , *DIRECT currents - Abstract
The carrier-based pulsewidth modulation (CBPWM) and virtual space vector pulsewidth modulation (VSVPWM) for neutral point clamped three-level converter are reviewed briefly in this paper. A novel modulation strategy is proposed to maintain unconditional neutral point voltage balance under the full range of power factor and modulation index. The proposed PWM strategy is featured with three switching actions in one switching cycle, which is named 3SNPBPWM hereafter. In 3SNPBPWM, one phase is clamped to a certain level without switching action, and the other two phases have one and two switching actions in one switching cycle (SC), respectively. Moreover, a neutral point voltage recovery algorithm for 3SNPBPWM is also proposed. The performance of 3SNPBPWM is analyzed and compared with CBPWM and VSVPWM in terms of switching loss, waveform quality, and ability of neutral point voltage recovery. Finally, the feasibility and superiority of 3SNPBPWM are verified by experiment. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
35. A ZVS APWM Half-Bridge Parallel Resonant DC–DC Converter With Capacitive Output.
- Author
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Pont, Neilor C. Dal, Bandeira, Delvanei G., Lazzarin, Telles B., and Barbi, Ivo
- Subjects
- *
ELECTRIC potential , *DIRECT currents , *CAPACITORS , *ELECTRIC inverters , *CASCADE converters , *ELECTRIC currents - Abstract
In this paper, a modified asymmetric half-bridge (AHB) isolated converter is proposed, which does not have dc current offset in the transformer. The topology operates in the same way as the conventional half-bridge (HB), using asymmetric pulsewidth modulation with constant frequency. A voltage doubler rectifier is used in the output stage, which avoids the flow of the dc component current in the primary side of the transformer. In order to investigate the application of the proposed topology, a parallel-resonant (PR) version of the modified AHB was tested, which uses the parasitic elements of the transformer, such as the leakage inductance and the winding capacitance, to achieve zero voltage switching in the primary side switches over a wide load range. Theoretical and commutation analysis results are reported and design guidelines are presented herein. Experimental data were obtained from a parallel resonant 1-kW prototype, operating with a 50 kHz switching frequency, 400 V input voltage, and 400 V output voltage, to verify the theoretical study, and 97% efficiency was achieved. The proposed solution was also tested at high voltage, operating with a rated power of 1.8 kW, switching frequency of 50 kHz, input voltage of 400 V and series-connected output voltages, the maximum voltage being 8620 V. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
36. Nonlinear PI-Control Approach for Improving the DC-Link Voltage Control Performance of a Power-Factor-Corrected System.
- Author
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Honkanen, Jari, Hannonen, Janne, Korhonen, Juhamatti, Nevaranta, Niko, and Silventoinen, Pertti
- Subjects
- *
ELECTRIC potential , *ELECTRIC inverters , *CASCADE converters , *VOLTAGE control , *DIRECT currents , *ELECTRIC current converters - Abstract
When fast voltage control is used in a power factor control, the ripple of the dc link causes current harmonics. This paper proposes a method to reduce the harmonic content of a fast voltage loop in a power factor correction, which can both produce low distortion during steady-state operation and fast recovery from a load transient. The performance is achieved by using a Takagi–Sugeno-type nonlinear controller for dc-link voltage control. The proposed nonlinear control is compared with linear proportional–integral (PI) control, which is tuned to meet the standardized regulations for the harmonic content in a 3-kW single phase power supply. The results show that the presented nonlinear voltage controller can maintain the dynamic performance of the linear control with reduced current harmonics. It is also shown that the used nonlinear control method requires only marginally more complex control algorithm compared to commonly used linear PI control. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
37. Low Switching Frequency Model Predictive Control of Three-Level Inverter-Fed IM Drives With Speed-Sensorless and Field-Weakening Operations.
- Author
-
Zhang, Yongchang, Bai, Yuning, Yang, Haitao, and Zhang, Boyue
- Subjects
- *
PREDICTIVE control systems , *INDUCTION motors , *SWITCHING circuits , *STATORS , *DIRECT currents - Abstract
This paper proposes a single-vector-based model predictive control (MPC) for an induction motor drive supplied by a three-level neutral-point-clamped inverter operating at a low switching frequency. Unlike the torque and flux control in the conventional MPC, the proposed MPC tries to minimize the error between the applied voltage vector and a reference voltage vector obtained based on the principle of deadbeat control, thereby reducing the number of weighting factors in the cost function. To reduce the computational burden and restrict the high jumps in both phase and line voltages, two switching tables are proposed and compared for the preselection of candidate voltage vectors. The neutral point potential fluctuation and switching frequency are also included in the cost function to achieve the balance between the upper and lower dc voltages and a relatively low switching frequency. Furthermore, a speed adaptive stator flux observer with a novel gain matrix is proposed to achieve speed-sensorless operation, which has a higher speed and flux estimation accuracy than conventional fixed gains. Finally, the proposed MPC is extended to the field-weakening operation by adjusting the torque and stator flux references online, which significantly widens the speed range and improves the practical value of the MPC. The effectiveness of the proposed method is confirmed by the experimental results obtained at an average switching frequency of less than 600 Hz. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
38. High Step-Up Transformerless Inverter for AC Module Applications With Active Power Decoupling.
- Author
-
Roy, Jinia, Xia, Yinglai, and Ayyanar, Rajapandian
- Subjects
- *
ELECTRIC inverters , *GALLIUM nitride , *DIRECT currents , *ALGORITHMS , *PHOTOVOLTAIC power systems , *ELECTRIC power factor - Abstract
This paper explores a power-conversion system for single-phase transformerless ac module application. A nonisolated high-gain dc–dc stage is coupled with a doubly grounded dynamic dc-link inverter to implement the microinverter topology. The front-end boost stage steps up the single-module voltage to a higher dc voltage, typically to 200 or 400 V as required for the following inverter stage. It is a hybrid of an interleaved boost and switched capacitor concept capable of achieving high gain while simultaneously maintaining reduced voltage and current stress, and thus lowering switching and conduction loss for most of the switches. By directly connecting the grid neutral to the photovoltaic (PV) negative, the doubly grounded voltage swing inverter has the advantage of zero capacitive-coupled common-mode ground currents, critical for transformerless PV inverters. The two dc links of the inverter stage share the double-line frequency power decoupling with a combination of higher value of mean voltage and relatively large 120-Hz ripple component–the dynamic dc-link approach. Through an optimization algorithm, the decoupling capacitance is minimized enabling an all-film capacitor implementation while satisfying the converter's operating constraints over a wide range of power factors. The simulation as well as experimental results from a GaN-based hardware prototype validate the converter's performance. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. Self-Tuning Proportional-Type Performance Recovery Property Output Voltage-Tracking Algorithm for DC–DC Boost Converter.
- Author
-
Kim, Seok-Kyoon and Ahn, Choon Ki
- Subjects
- *
DIRECT currents , *DIRECT current circuits , *ELECTRIC potential , *SELF-tuning controllers , *ADAPTIVE control systems , *BOOSTING algorithms , *DC-to-DC converters - Abstract
This article exhibits an output voltage-tracking control algorithm incorporating a self-tuning algorithm and disturbance observers (DOBs) for dc–dc boost converters without tracking error integrators, considering model nonlinearities, parameter variations, and load uncertainties. The proposed algorithm is designed such that it forces the output voltage to track its target trajectory driven by a time-varying low-pass filter (LPF), despite model-plant mismatches. This paper makes two main contributions. First, it constructs the self-tuning algorithm by updating the closed-loop cut-off frequency in the time-varying LPF to improve the transient tracking performance. Second, it embeds first-order DOBs in the proportional-type nonlinear controller to achieve both performance recovery and the offset-free properties. The experimental verifications are carried out to illustrate the effectiveness of the closed-loop system driven by the proposed technique with a 3-kW prototype dc–dc boost converter; the 46% improvement of the tracking performance is observed, compared with the conventional feedback-linearization controller. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
40. Hybrid Switched-Capacitor/Switched-Quasi-Z-Source Bidirectional DC–DC Converter With a Wide Voltage Gain Range for Hybrid Energy Sources EVs.
- Author
-
Zhang, Yun, Liu, Qiangqiang, Gao, Yongping, Li, Jing, and Sumner, Mark
- Subjects
- *
DC-to-DC converters , *ELECTRIC vehicles , *CAPACITORS , *DIRECT currents , *ELECTRIC current converters , *ELECTRIC potential - Abstract
In this paper, a hybrid switched-capacitor/switched-quasi-Z-source bidirectional dc–dc converter is proposed for electric vehicles (EVs) with hybrid energy sources, which has a wide voltage gain range in the bidirectional energy flows. Compared with the traditional quasi-Z-source bidirectional dc–dc converter, the proposed converter only changes the position of the main power switch and employs a switched-capacitor cell at the output of the high-voltage side. Therefore, the advantages of the wide voltage gain range and the lower voltage stresses across the power switches can be achieved. The operating principle, the voltage and current stresses across the power switches, and the comparisons with other converters are analyzed in detail. Furthermore, the parameter design of the main components, the dynamic modeling analysis, and the voltage control scheme are also presented. Finally, the experimental results obtained from a 400 W prototype validate the characteristics and the theoretical analysis of the proposed converter. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
41. Evaluation and Suppression of a Low-Frequency Output Voltage Ripple of a Single-Stage AC–DC Converter Based on an Output Impedance Model.
- Author
-
Cai, Yaping, Xu, Jianping, Yang, Ping, Wu, Jiahui, and Sha, Jin
- Subjects
- *
ELECTRIC currents , *ELECTRIC current converters , *ALTERNATING currents , *DIRECT currents , *ELECTRIC impedance , *ELECTRIC potential , *ELECTRIC power factor , *AC DC transformers - Abstract
A single-stage ac–dc converter with high power factor (PF) usually suffers from a significant output voltage ripple at double line frequency. In order to suppress such low-frequency output voltage ripple and maintain high PF, a series compensation circuit (SCC), which generates the same magnitude but 180° phase shifted low-frequency voltage ripple, is connected in series with the output of a power factor correction (PFC) converter. In this paper, an output impedance model of the SCC is established and the relationship between the output impedance of the SCC and the low-frequency output voltage ripple of an ac–dc converter is analyzed. Based on the proposed output impedance model, a low-frequency output voltage ripple can be evaluated. To further reduce the low-frequency output voltage ripple, an output impedance shaping method with a virtual impedance is presented. The implementation of the virtual impedance of the SCC with average current mode control is studied. A flyback PFC converter with a buck SCC is implemented for the study of the suppression of the low-frequency output voltage ripple. A prototype is designed to verify the analysis results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
42. A Distributed Architecture for Robust and Optimal Control of DC Microgrids.
- Author
-
Baranwal, Mayank, Askarian, Alireza, Salapaka, Srinivasa, and Salapaka, Murti
- Subjects
- *
MICROGRIDS , *CONVERTERS (Electronics) , *DIRECT currents , *ELECTRIC controllers , *ROBUST control - Abstract
This paper presents a distributed, robust, and optimal control architecture for a network of multiple dc–dc converters. The network of converters considered form a dc microgrid in order to regulate a desired dc bus voltage and meet prescribed time-varying power sharing criteria among different energy sources. Such coordinated microgrids provide an important framework for leveraging the benefits of distributed power generation and consumption. The proposed control design seamlessly accommodates communication architectures that range from the centralized to decentralized scenarios with graceful degradation of the performance with lessened communication ability. Moreover, the methods developed are applicable to the case where the desired proportion in which the sources provide the power varies with time. A distinguishing feature of the control design approach is that it regards the net load current as a disturbance signal, lending itself to tractable analysis with tools from the robust and optimal control theory. A quantifiable analysis of the closed-loop stability and the performance of the network of converters is performed; the analysis simplifies to studying the closed-loop performance of an equivalent single-converter system. The control approach is demonstrated through simulations and experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
43. Reduction of Open-Circuit DC-Winding-Induced Voltage in Wound Field Switched Flux Machines by Skewing.
- Author
-
Wu, Z. Z., Zhu, Z. Q., Wang, C., Mipo, J. C., Personnaz, S., and Farah, P.
- Subjects
- *
OPEN-circuit voltage , *DIRECT currents , *ELECTRIC windings , *FINITE element method , *STATORS - Abstract
In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
44. Accurate Power Sharing With Balanced Battery State of Charge in Distributed DC Microgrid.
- Author
-
Hoang, Khanh Duc and Lee, Hong-Hee
- Subjects
- *
BATTERY storage plants , *MICROGRIDS , *DIRECT currents , *VOLTAGE control , *ELECTRIC resistance - Abstract
This paper presents an accurate power sharing method to balance the state of charge (SoC) among the distributed battery energy units (BEUs) in a dc microgrid. The virtual power rating concept of the proposed control method is introduced, and accurate power sharing is achieved according to the SoC levels and the virtual power ratings, regardless of the line resistance difference. With the accurate power sharing based on SoC, BEUs with higher SoC accurately supply more power to the system than the lower SoC BEUs during the discharging period, and BEUs with lower SoC accurately supply less power to the system than the higher SoC BEUs during the charging period. Moreover, with the voltage restoring method, the dc grid voltage is maintained within the desired voltage level, and with the proposed control method, the system stability is verified. The proposed control scheme is implemented in a distributed manner that relies on low bandwidth communication. The effectiveness of the proposed control method is proved by simulation and experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
45. Zero-Current Switching Control of the Alternate Arm HVdc Converter Station With an Extended Overlap Period.
- Author
-
Liu, Shenquan, Saeedifard, Maryam, and Wang, Xifan
- Subjects
- *
HIGH-voltage direct current transmission , *FAULT currents , *ELECTRIC circuits , *ZERO current switching , *DIRECT currents - Abstract
The alternate arm converter (AAC) is a promising candidate for HVdc converter stations due to its reduced number of devices and capability of blocking the dc fault current. This paper is focused on modeling and control of the AAC with an extended overlap period. First, a generic mathematical model considering all the switching state combinations of the AAC is developed, which governs the characteristic of the time-varying, three-phase imbalanced circuit parameters of the AAC. Based on the developed model, an ac-side current control strategy with a feed-forward compensation method to overcome the time-varying nature of the circuit parameters is proposed. Then, by introducing the so-called “double-overlap period,” a synthetic circulating current strategy is proposed, which enables both dc current active filtering and zero-current switching of the director switches. The validity of the model and effectiveness of the proposed strategies are confirmed by simulation studies on an HVdc system. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
46. Optimal Space Vector Modulation of Current-Source Converter for DC-Link Current Ripple Reduction.
- Author
-
Guo, Xiaoqiang, Yang, Yong, and Wang, Xuehui
- Subjects
- *
CONVERTERS (Electronics) , *DIRECT currents , *SWITCHING circuits , *ELECTRIC inductance , *ELECTRIC inductors - Abstract
DC-link current ripple is one of the important factors for operating the current-source converter. In practice, the dc-link current ripple can be reduced by increasing the switching frequency or inductance. However, it may result in the higher switching losses, larger size, or higher cost. In order to deal with this problem, the inherent limitation of the conventional solution is discussed in this paper. The time-domain equation of the dc-link current is established for the first time. And then, a new space vector control strategy is proposed to reduce the ripple with no need of increasing the switching frequency or inductance. The space vector is divided into 12 sectors, where the dc-link current ripple can be effectively reduced by the optimal vector sequence. Finally, the proposed method is implemented on the TMS320F28335DSP + XC3400FPGA digital control hardware platform. The experimental results verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
47. Simplified Thermal Modeling for IGBT Modules With Periodic Power Loss Profiles in Modular Multilevel Converters.
- Author
-
Zhang, Yi, Wang, Huai, Wang, Zhongxu, Yang, Yongheng, and Blaabjerg, Frede
- Subjects
- *
INSULATED gate bipolar transistors , *THERMAL stresses , *RELIABILITY in engineering , *POWER semiconductors , *DIRECT currents - Abstract
One of the future challenges in modular multilevel converters (MMCs) is how to size key components with compromised costs and design margins, while fulfilling specific reliability targets. It demands better thermal modeling compared to the state-of-the-arts in terms of both accuracy and simplicity. Different from two-level power converters, MMCs have inherent dc-bias in arm currents and the power device conduction time is affected by operational parameters. A time-wise thermal modeling for the power devices in MMCs is, therefore, an iteration process and time-consuming. This paper, thus, proposes a simple analytical thermal modeling method, which adopts equivalent periodic power loss profiles. More importantly, time-domain simulations are not required in the proposed method. Benchmarking of the proposed methods with the prior-art solutions is performed in terms of parameter sensitivity and model accuracy with a case study on a 30-MW MMC system. Experiments are carried out on a specifically designed scaled-down system to verify the electrothermal aspects. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Comparison of DSCC and SDBC Modular Multilevel Converters for STATCOM Application During Negative Sequence Compensation.
- Author
-
Cupertino, Allan Fagner, Farias, Joao Victor Matos, Pereira, Heverton Augusto, Seleme, Seleme Isaac, and Teodorescu, Remus
- Subjects
- *
BRIDGE circuits , *CAPACITORS , *VOLTAGE regulators , *ENERGY storage , *DIRECT currents - Abstract
Among the various topologies proposed in this literature, the modular multilevel converter (MMC) is considered the next generation of converters for medium- and high-voltage applications. This paper presents a comparison between two variants of MMCs for STATCOM applications: The double-star chopper cell-MMC and the single-delta bridge cell-MMC. These converter topologies are compared and benchmarked during positive and negative sequence compensation. The comparisons are supported by analytical results regarding minimum effective dc-link voltage, number of cells, current rating, energy storage requirements, and operation during unbalanced conditions. The dynamic behavior, power losses, and cost of both solutions are evaluated through simulation model of a 15 mega volt-ampère (MVA) MMC STATCOM. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
49. Advanced Control of Grid-Connected Current Source Converter Under Unbalanced Grid Voltage Conditions.
- Author
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Guo, Xiaoqiang, Yang, Yong, and Zhang, Xue
- Subjects
- *
GRID energy storage , *DIRECT currents , *AC DC transformers , *ELECTRIC power system control , *ELECTRIC potential , *ELECTRICAL harmonics , *IDEAL sources (Electric circuits) - Abstract
There are technical challenges when the grid-connected current source converter operates under unbalanced grid voltage conditions. The negative sequence component of the unbalanced grid voltage would result in the low-frequency ripple at dc side, as well as current harmonics at ac side. It has an adverse impact on the system operation. In order to solve the problem, the system mathematical model is established in this paper. The limitation of the conventional control strategy is clearly clarified. And then, the improved control strategy is discussed from the viewpoint of constant instantaneous active power. In order to further enhance the system performance, a new control strategy is proposed. Instead of the complicated instantaneous power theory, the proposed solution is a direct control strategy. Both the low-frequency dc-side ripple and ac-side current harmonics can be significantly reduced with a simple control structure, due to the direct control concept. Finally, the comparison evaluation of the conventional and proposed control strategies is carried out. The experimental results verify the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
50. DC-Link Ripple Current Reduction Method for Three-Level Inverters With Optimal Switching Pattern.
- Author
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Kim, Seok-Min, Won, In Jung, Kim, Juyong, and Lee, Kyo-Beum
- Subjects
- *
SWITCHING circuits , *PHOTOVOLTAIC power systems , *DIRECT currents , *STRAY currents , *TOPOLOGY , *ELECTRIC potential , *ELECTROLYTIC capacitors - Abstract
This paper presents an optimized switching strategy to reduce the dc-link ripple current for three-level photovoltaic (PV) inverters. The large electrolytic capacitors are commonly used for the dc link of power electronics applications to stabilize the dc-link voltage. The most important factor of designing the dc-link capacitor is the allowable current ripple. The over-ripple current flowing through the capacitor causes a high heat loss, shortened lifespan, low stability, and reliability. The proposed switching scheme selects voltage vectors and reconfigures dwelling order of the vectors to reduce the capacitor ripple current. This switching method is able to extend the lifetime of the dc-link capacitors by simple software programming. In addition, this switching method reduces the common-mode voltage and leakage current that represent high reliability and safety of the system. The effectiveness of the proposed method is verified with simulations and experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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