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Inverter is required to operate at both grid-connected and grid-forming mode for microgrid. When an unplanned microgrid disconnecting to grid circumstance happens, the transition will cause severe current shock to system with multi-parallel microgrid inverters. This paper adopts a dynamic virtual resistance-based droop control strategy and small signal analysis method to reduce the current shock, improve the system stability and safety. The large dynamic virtual resistance is added to the control loop when the mode transition event occurs so the shock current is limited. Comparison between the capacitor current feedback for seamless mode transition method and the proposed method is made to prove the validation, and parameters' impact on the system is also analyzed. Results, which are conducted on MATLAB/Simulation and Hardware-in-the-Loop (HIL) experimental platform verify the feasibility of the proposed method in this paper, effectively reduce the current shock by more than 60%. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MIs) are widely used in voltage source inverter applications due to their advantages of high-quality output voltage waveform, low power loss and low voltage stress. Compared with multiple DC source MI (MDCS-MI), single DC source MI (SDCS-MI) needs one DC source. This makes SDCS-MI more simplified and avoid voltage unevenness among multiple sources, which are advantageous in renewable energy (RE) applications. In order to understand SDCS-MI, this paper classifies and compares existing SDCS-MIs according to classical topologies based on isolated and non-isolated construction, summarizes the advantages and limitations of each type of topologies, and briefly introduces various control strategies of SDCS-MI. Finally, this paper discusses the SDCS-MI in RE systems. In addition, the development trend of SDCS-MI is also analyzed in this paper. [ABSTRACT FROM AUTHOR]

This paper demonstrates the controlling abilities of a large PV-farm as a Solar-PV inverter for mitigating the chaotic electrical, electromechanical, and torsional oscillations including Subsynchronous resonance in a turbogenerator-based power system. The oscillations include deviations in the machine speed, rotor angle, voltage fluctuations (leading to voltage collapse), and torsional modes. During the night with no solar power generation, the PV-plant switches to PV-STATCOM mode and works as a Solar-PV inverter at its full capacity to attenuate the oscillations. During full sun in the daytime, on any fault detection, the PV-plant responds instantly and stops generating power to work as a Solar-PV inverter. The PV-farm operates in the same mode until the oscillations are fully alleviated. This paper manifests the control of the DC-link capacitor voltage of the Solar-PV inverter with a bacterial foraging optimization-based intelligent maximum power point tracking controller for the optimal control of active and reactive power. Kundur's multi-machine model aggregated with PV-plant is modeled in the Matlab/Simulink environment to examine the rotor swing deviations with associated shaft segments. The results for different test cases of interest demonstrate the positive outcomes of deploying large PV-farms as a smart PV-STATCOM for controlling power system oscillations. [ABSTRACT FROM AUTHOR]

Industries using electrical power have a critical and pressing need for improved power quality (PQ). Several important problems have already been identified, such as voltage swell, sag, and harmonics. However, PQ fluctuation issues remain unresolved. A series of active power filters are used to shield delicate loads from PQ related problems. This paper present a low-complexity control technique for voltage compensation using a type of custom power device used with different inverter topologies called Dynamic Voltage Restorer (DVR). In this study, a three-phase Z-Source Inverter-based DVR is employed to reduce voltage disruption, including voltage fluctuation, sag, swell, and harmonics. Error-driven Proportional-Integral-Derivative (PID) controller provides higher PQ performance in terms of voltage augmentation, stabilization, and reduction in harmonic distortion in the distribution system. This strategy keeps the load voltage near or close to the nominal value and addresses many other voltage issues. The gain parameter of a PID controller is tuned using Harris Hawks Optimization (HHO) method. The proposed work is compared with traditional controllers as well as Genetic Algorithm-based PID controllers, and the distortion of total harmonics comparisons are also conducted to show the accuracy of the proposed Z-DVR. To demonstrate the effectiveness of the suggested methodology, it is implemented in MATLAB/Simulink R2020a tool and the results of the mitigated sag, swell fluctuation, and total harmonic distortion (THD) are studied. [ABSTRACT FROM AUTHOR]

Dead-time is the most important disturbance in a voltage-source inverter's operation. It introduces low-order harmonics at the inverter's output voltage. To compensate for the dead-time effects in three-phase grid-tied inverters, this paper proposes a Linear Quadratic Gaussian (LQG) multivariable control approach. The LQG multivariable control is known as a robust control approach while provides a high band-width for the closed-loop system. Therefore, it promises significant attenuations in the dead-time introduced harmonics. To achieve a high performance, we run the three-phase grid-tied inverter in the current-controlled mode. Based on the nominal multivariable model derived for the three-phase grid-tied inverter in a synchronous reference frame, the LQG controller is composed such that the closed-loop system exhibits robust stability while attenuates disturbances significantly. The dead-time introduced harmonics produce disturbances in the synchronous reference frame with the highest frequencies. This is the reason for considering the dead-time as the most important disturbance in an inverter's operation. For an experimental set-up manufactured for the three-phase grid-tied inverter, we developed a detailed model in MATLAB/Simulink. It is employed for the performance verifications of designed LQG controller. Extensive results are presented for different important scenarios, based on which, the excellent performance of proposed approach is proven. In fact, by employing the proposed approach, the dead-time introduced harmonics are significantly attenuated such that a Total Harmonics Distortions (THD) of about 5% is achieved for the injected currents to grid which meets the IEEE 1547 standard. [ABSTRACT FROM AUTHOR]

Microgrid (MG) is not only undergoing rapid upsurge and an effective combination of distributed generations (DGs)-based renewable energy sources, but it also fulfills a significant function in upgrading grid infrastructure. It is necessary for DGs, during and after any disturbances in the voltage, to stay connected in order to enhance the voltage, most importantly guaranteeing the stability of the power system. In this present context, the behavior of the distributed generations control systems has a significant impact on the MG performance. This paper investigates the effect of different control schemes of the inverter-based DG unit on the stable operation of MG after the occurrence of faults that lead to islanding events. In this paper, an appropriate control strategy is proposed to enhance the fault ride-through of MG. Within the scope of the study, the MG consists of a conventional diesel generator and an inverter-based DG unit. The MG also contains several load types; RLC load as a static load and induction motor as a dynamic load. The MATLAB Simulink is used to model the MG and its inverter control schemes. In order to assure MG stability, the variations of the voltage and frequency are possessed as key references. Results indicate that the control strategies of the inverter have a strong influence on the stability of MG. Moreover, the MG configuration with the proposed FRT resists fault effects for longer durations and this enhances the stability. [ABSTRACT FROM AUTHOR]

This article presents a novel 3-Φ inverter that operates from a single direct current source and is based on the idea of switched-capacitor (SC) techniques. Each phase leg of the proposed topology (PT) consists of eight switches, two capacitors, and a diode. This configuration enables the generation of seven levels (line-to-line) voltage waveforms. The proposed design has several advantages, such as the capacitors' natural balancing, the ability to boost, minimum voltage stresses on the power switches, and fewer switching components. When compared to the conventional two-stage design, single-stage dc–ac power converters with boost capabilities present an intriguing option. This paper introduces a novel boost-type inverter for use in a wide variety of applications, including rolling mills, fans, pumps, maritime appliances, mining, tractions, and more. The study explains the proposed design, principle, control mechanism, and loss analysis in great depth. The advantages of the PT have been demonstrated through comparison with recently published SC topologies. Finally, a 1550-W downscale prototype is used to experimentally verify its viability and performance, with an estimated efficiency of around 96.6%. [ABSTRACT FROM AUTHOR]

The paper deals with the construction design, thermal simulation analysis and cooler control proposal of double three-phase inverter suitable for electric vehicles. It gives a discussion on basic mechanical design and electric topology, both having strong influence on electrothermal operability. The paper also presents the thermal analyses of the converter operated at specified loading profile and gives control possibilities. Finally, the paper presents the cooler control design and demonstrates its functionality. The paper also discusses its impact on the converter lifetime and implementation. [ABSTRACT FROM AUTHOR]

The multilevel voltage-source inverter (VSI) topology of the series multicell converter developed in recent years has led to improved converter performance in terms of power density and efficiency. This converter reduces the voltage constraints between all cells, which results in a lower transmission losses, high switching frequencies and the improvement of the output voltage waveforms. This paper proposes an improved topology of the series multicell inverter which minimizes harmonics, reduces torque ripples and losses in a variable-speed induction motor drive. The flying capacitor multilevel inverter topology based on the classical and modified phase shift pulse width modulation (PSPWM, MPSPWM) techniques are applied in this paper to minimize harmonic distortion at the inverter output. Simulation results are presented for a 2-kW induction motor drive and the results obtained demonstrate reduced harmonics, improved transient responses and reference tracking performance of the voltage in the induction motor and consequently reduced torque ripples. [ABSTRACT FROM AUTHOR]

Modularity, efficiency, power quality, and high reliability are the attractive advantages of multilevel inverters (MLIs). But it has limitations in terms of an increased number of semiconductor devices as compared to conventional 2-level inverters. In this paper, a fault-tolerant single-phase 5-level MLI configuration is proposed. The proposed fault-tolerant configuration of the MLI can significantly improve its reliability while maintaining the modularity of its software implementation. Examination, design, and implementing thought for both normal and abnormal operating situations of the proposed MLI are presented in this paper. The feasibility of the proposed fault-tolerant MLI is verified by simulation in MATLAB/Simulink environment and experimental results in a laboratory prototype. [ABSTRACT FROM AUTHOR]

Under the aspect of decreasing costs for power electronic elements due to mass production, machines with feeding from multiphase inverters can be considered where each slot is activated as a separate phase. The number of IGBT switches is increased, but the current rating of the IGBTs becomes very small, thus reaching the region of cheap mass production elements. Additionally, this allows a smaller capacitor in the intermediate circuit and a mechanical structure of the inverter that can be easily integrated into the machine housing. By this, the often critical du/dt problems can be reduced significantly. In the machine, new features such as an ideal sinusoidal or even rectangular distribution of electric loading and flux density become possible. Moreover, if induction machines with squirrel cage are considered, a rather free adjustment of the pole pitch is possible. In the paper, this approach and its consequences on the performance and the construction of the machine are discussed for an exemplary induction machine. [ABSTRACT FROM AUTHOR]

Transformerless grid-connected inverters for photovoltaic (PV) applications provide several advantages such as reduced cost and volume as well as an increased efficiency. However, the removal of the transformer gives rise to several problems related to leakage currents and electromagnetic interferences (EMI). This paper presents different chaotic unipolar sine-pulse width modulation (C-USPWM) techniques for a transformerless grid-connected PV inverter based on parameter selection. The main objective behind this proposed chaotic modulation technique is to reduce the conducted EMI without worsening the power quality and the common-mode voltage (CMV). The method is validated through numerical simulations and experimental tests carried out on laboratory prototype of an optimized H5 inverter (oH5). The obtained results showed its superiority to the conventional unipolar sine-pulse width modulation (USPWM). We showed also that the appropriate parameter selection of the C-UPSWM could advantageously combine an improved EMI performance and an efficient control, making it possible to deliver a significant reduction of the peaks' amplitudes in the frequency spectrum of the common-mode (CM) voltage. [ABSTRACT FROM AUTHOR]

This paper presents a photovoltaic (PV)-interfaced dual-drive hybrid electric vehicle (PV-DDHEV) based on dual boost three-port DC–DC converter to increase the fuel efficiency of the electric vehicle by increasing the conversion efficiency of the converters. HEV designed with the photovoltaic (PV) power system requires a DC–DC converter to enhance the PV array output voltage to the level demanded by the drive inverters. Normally, the high gain of DC conversion is obtained by connecting two or more DC–DC converters in series with each other. The series connection of the converters reduces the conversion efficiency and increases the cost of the unit. In this paper, a three-port DC–DC converter designed with a two-winding high-frequency transformer is proposed to offer high voltage gain with reduced number of active and passive elements. In addition to this, the power management algorithm incorporated with the proposed PV-DDHEV reduces the power consumption of the drive motor by estimating the drive torque requirement. The MATLAB simulink and experimental prototype results are presented to validate the proposed PV-DDHEV. [ABSTRACT FROM AUTHOR]

This paper proposes a new normalized Huber adaptive control algorithm for shunt compensation. A 5-level cascaded multilevel inverter (CHB-MLI) is controlled as a shunt active power filter (SAPF) unit for a medium voltage distribution system. The proposed algorithm is designed, modelled, and tested to control the SAPF unit under normal and distorted grid conditions. It is employed to extract the fundamental active power component of load current. This extracted effective component is used to generate source reference currents by multiplying with the unit vector template. Furthermore, the switching of CHB-MLI is performed using phase-shifted PWM scheme. The algorithm helps to mitigate the reactive power and unwanted harmonics generated by the nonlinear load. A single-phase scale-down prototype model is developed for experimental investigation and testing purpose in the laboratory. The associated voltage and current sensors and control circuits are controlled by the dSpace 1104 digital microprocessor. Simulation and experimental results show good performance of the proposed algorithm in steady-state and dynamic load conditions. A fair performance comparison is also done with other conventional adaptive algorithms. [ABSTRACT FROM AUTHOR]

This paper implements a 125 level asymmetric cascaded multilevel inverter using fuzzy logic which is used in the dynamic voltage restorer. The inverter is designed with a reduced number of switches. The higher switching frequency is defined for the better performance of the multilevel inverter. The 125 level output is obtained in this proposed approach with only twelve switches and six voltage sources. By changing the switching frequency, the proposed output voltage level is obtained in the inverter. The paper is organized into two phases. In the first step the design of 125 level inverter is proposed, and in the second phase, the power quality improvement using the designed inverter is discussed. The proposed design of an inverter is implemented for dynamic voltage restorer solves the power quality problems such as are voltage sag, voltage swell, and harmonics. The power quality issue mitigation performance is increased with the proposed 125 level inverter. The enrichment of the proposed design is investigated using the comparison of existing works. The proposed work is implemented in the Matlab/Simulink environment. [ABSTRACT FROM AUTHOR]

A general growth is being seen in the use of renewable energy resources, and photovoltaic cells are becoming increasingly popular for converting green renewable solar energy into electricity. Since the voltage produced by photovoltaic cells is DC, an inverter is required to connect them to the grid with or without transformers. Transformerless inverters are often used for their low cost and low power loss, and light weight. However, these inverters suffer from leakage current in the system, a challenge that needs to be addressed. In this paper, a topology with two alternative connection models is presented to stabilize the common mode voltage and reduce the leakage current. The output voltage characteristic of the proposed inverter is five-level, which reduces the harmonic distortion in the output current compared to the two- and three-level inverters. The operation modes and output of the proposed topology are described and analyzed. The structures of the proposed inverter are simulated in MATLAB/Simulink and are compared with some well-known structures. Results show that the proposed structure with both connection models effectively reduces leakage current and improves grid current THD. [ABSTRACT FROM AUTHOR]

In this paper, a proton exchange membrane PEM fuel cell power plant is used to improve the filtering performance of the conventional active power filter, as well as simultaneously contribute with the electric grid to supply the power to the load. The five-level inverter is used as a shunt active power filter, taking advantages of the multilevel inverter such as low harmonic distortion and reduced switching losses. It is capable of compensating power factor, current harmonics and can also make the interface between renewable energy sources and the electric grid, injecting the energy generated by PEM fuel cell to the load. The active power filter control strategy is based on the use of self tuning filters for reference current generation and a fuzzy logic current controller. The MATLAB Fuzzy Logic Toolbox is used for implementing the fuzzy logic control algorithm. The obtained results show that the PEM fuel cell contributes successfully to supply simultaneously the load with the electric grid and produced a sinusoidal supply current with low harmonic distortion and in phase with the line voltage. [ABSTRACT FROM AUTHOR]

This paper presents a novel high multilevel inverter topology which is based on the created DC voltage levels at loads of the inverter. The circuit model is demonstrated by explaining the relationship between switches, sources and loads. According to the proposed inverter topology, the number of power switches connected to negative side of DC source is constant on inverter, while the number of power switches connected to positive side of DC sources is increasing. Therefore, linear pulse-width modulation (LPWM) is described for operating switches after pulse-width modulation method is developed to generate the PWM signals. Then, mathematical equations are given when resistive ( R), inductive ( L) and capacitive ( C) loads are connected in series on a 9-level inverter. Finally, the performances of the proposed inverters are observed through MATLAB/SIMULINK simulations after the designed multilevel inverters are simulated. So, 6-level, 9-level and 11-level inverters are compared with voltages, currents and harmonic distortions. Harmonic distortions reduce with increasing level of inverter, while three multilevel inverters are investigated on different modulation indexes. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of a novel high multilevel inverter topology. [ABSTRACT FROM AUTHOR]

In this paper, the increment factor of the iron loss by inverter excitation compared with sine wave excitation was clarified using the magnetic hysteresis curve, and change in the parameter which can be understood intuitively was explained. When α (rate of hysteresis curve between the inverter excitation and the sine wave excitation), β (width of the closed loop using inverter excitation around 0 T) and γ (width of the open loop using the inverter excitation around 0.8 T) are increased by the switching operation of the inverter excitation, they increase the area of the hysteresis curve and increase the iron loss compared with the sine wave excitation. On the other hand, the increase factor of the iron loss by the inverter excitation was clarified, and explanation which can be understood intuitively was given. The low modulation factor, the low career frequency, and the high VDC of the inverter are made to increase the factors such as α and β, and increase the area of the magnetic hysteresis curves, and this causes incremental iron loss. Furthermore, α and β are made to fluctuate by the control method of the motor drive using the inverter. That is, the change of the inverter parameters fluctuates the iron loss due to a tradeoff. [ABSTRACT FROM AUTHOR]

Increasing penetration of photovoltaic power plants (PVPPs) to the electrical grid leads to continuous evaluation of grid interconnection requirements. For this purpose, Malaysian grid representative from Tenaga Nasional Berhad (TNB) issued technical rules and requirements concerning the connection of photovoltaic system to low and medium voltage networks. The objective of this paper is to design a large-scale PV plant connected to the MV side of the Malaysian grid, taking the compliance of TNB technical regulations into consideration. In this study, the PV plant has been modeled using MATLAB/Simulink with nominal rated peak power of 1.5 MW. The sizing of suggested PV system is achieved in which the simulation results matched the sizing calculation results. The paper focuses on the model’s ability to reflect the important requirements that a PVPP should have based on TNB rules for MV connection. The results show that the proposed PVPP is compatible with TNB requirements. [ABSTRACT FROM AUTHOR]

This paper discusses a converter structure appropriate for charging the batteries of an electric vehicle. The structure is obtained by a transformation of a conventional three-phase inverter, which is already present in an electric vehicle’s powertrain system. Since the motor inverter’s semiconductor components and the electric motor’s windings form the battery charger’s circuit, a reduction in the powertrain system’s size and weight is achievable. The proposed fully integrated battery charger can operate in buck and boost modes, while providing power-factor correction capability continuously. This paper also proposes an input current control strategy which ensures smooth operating mode transitions, which occur during the operation of the battery charger. The control is entirely implemented within a microcontroller and ensures operation with a high power factor and low total harmonic distortion of the input current. The performance of the discussed converter using the proposed control scheme was verified experimentally. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to show the impact of the feed of multiphase induction machines by a voltage inverter which produces circulating harmonic currents. To eliminate this extra harmonic currents of stator windings that cause losses, a space vector PWM control strategy is employed and developed, based on the vector space decomposition for double-star induction machine modeling, while taking into account the stator mutual leakage between two stars. The simulation results illustrate the validity and efficiency of the proposed model. [ABSTRACT FROM AUTHOR]

The advancement of multilevel inverters has led to an increase in efficiency and reliability. This paper demonstrates the design and implementation of a reduced switch extendable-level inverter-fed open-end winding permanent magnet synchronous motor (PMSM) drive. Unlike traditional multilevel inverter topologies, output voltage levels in the proposed inverter depend on the operating frequency of the switches. As the frequency of operation is very high, the levels in the output voltage reach infinity and hence the term extendable-level inverter. It achieves infinite voltage output levels, with a reduced component count. The configuration of the open-end winding enables the application of the AC voltage directly to the independent motor phases and hence achieves the merits of operation at a reduced input DC voltage. The proposed drive achieves a very high DC-link voltage utilization, reduced inverter switching losses, enhanced power quality, and excellent dynamic response using a single DC source and a minimum number of components. A comparative analysis of the proposed drive with different MLI-fed OEWPMSM drives in terms of the component count and total harmonic distortion is provided. FPGA-based improved sinusoidal PWM control of the proposed drive reduces execution time and enhances the control performance of the inverter. Dynamic characteristics of the proposed drive are provided for analyzing the dynamic response of the drive to a step change in load torque. The proposed drive is simulated using MATLAB/Simulink platform for theoretical analysis and evaluation. The experimental prototype is designed and implemented for validating the proposed drive operation. [ABSTRACT FROM AUTHOR]

Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to achieve high-performance decoupled control of the active and reactive powers injected to the grid from distributed energy resources (DER). The FCS-MPC scheme instantaneously searches for and applies the optimum inverter switching state that can achieve certain goals, such as minimum deviation between reference and actual power; so that both power components (P and Q) are well controlled to their reference values. In addition, an effective method to attenuate undesired cross coupling between the P and Q control loops, which occurs only during transient operation, is investigated. The proposed method is based on the variation of the weight factors of the terms of the FCS-MPC cost function, so a higher weight factor is assigned to the cost function term that is exposed to greater disturbance. Empirical formulae of optimum weight factors as functions of the reference active and reactive power signals are proposed and mathematically derived. The investigated FCS-MPC control scheme is incorporated with the LVRT function to support the grid voltage in fulfilling and accomplishing the up-to-date grid codes. The LVRT algorithm is based on a modification of the references of active and reactive powers as functions of the instantaneous grid voltage such that suitable values of P and Q are injected to the grid during voltage sag. The performance of the elaborated FCS-MPC PQ scheme is studied under various operating scenarios, including steady-state and transient conditions. Results demonstrate the validity and effectiveness of the proposed scheme with regard to the achievement of high-performance operation and quick response of grid-tied inverters during normal and fault modes. [ABSTRACT FROM AUTHOR]

A single stage inverter is introduced as a replacement for the conventional OTA to implement an inverter-based delta-sigma modulator. It achieves a high power and area efficiency. However, the low DC-gain and gain-bandwidth (GBW) have limited the application. This paper proposes a cascaded-inverter to increase the DC-gain and GBW, while maintaining the advantages of power and area efficiency. By cascading three inverters, the DC-gain is increased from 44 dB to 82 dB, and the GBW is increased from 100 MHz to 697 MHz. A third-order delta-sigma modulator using the proposed cascaded-inverter has been fabricated in a 0.11-μm CMOS process. When operating from a 1.2-V supply and clocked at 80 MHz, the prototype modulator achieves 59.4-dB peak SNDR over 500-kHz signal bandwidth while consuming 249 μW. Measurement results demonstrate that the application of the inverter-based amplifier, which is becoming popular due to its high power efficiency, can be extended to significantly higher speed circuits [ABSTRACT FROM AUTHOR]

Multilevel inverters became a key piece in most energy conversion, transportation and management systems. The present paper encompasses a wide total harmonic distortion (THD) investigation of the multilevel inverter output voltages. Such investigation is conducted with cascaded topology for some reasonable number of inverter levels L and various modulation index m. A novel and efficient approach is developed to express analytically the voltage THD bounds. Found upper and lower THD limits for arbitrary L and m apply also for neutral point clamped and flying capacitor topologies. They could really serve as reference for quality analysis of multilevel inverters. [ABSTRACT FROM AUTHOR]

Shunt active power filters (SAPFs) have been widely used to improve power quality of the grid by mitigating harmonics injected from nonlinear loads. This paper presents a new method for improving the performance of SAPFs using neutral-point-clamped (NPC) three-level inverters. NPC three-level inverters often suffer excessive voltage fluctuations at the neutral-point of DC-link capacitors, which may damage switching devices and cause additional high harmonic distortion of the output voltage. In order to solve the problem, two compensating schemes are proposed to restrict voltage fluctuation in the inverters. The first is voltage dependent, adopting a voltage compensation method, while the second is current dependent, using a current compensation method. The paper describes the respective circuit architectures and principles of operation. Corresponding models are mathematically formulated and evaluated under typical balanced and unbalanced working load conditions. The results show that both schemes are able to alleviate considerably voltage oscillations and hence harmonic distortions, and the current-compensated NPC inverter outperforms the voltage-compensated NPC inverter. Consequently, it is shown that the proposed approaches are effective and feasible for improving power quality of the grid when connected to nonlinear loads. [ABSTRACT FROM AUTHOR]

This paper proposes a circuit-level model of an inverter-based switched-capacitor (SC) integrator involved in a previously published incremental sigma-delta analog-to-digital converter (I Σ Δ ADC) to explain the ADC resolution degradation observed in the post-layout simulation. A fine analysis of post-layout signals led to a new model of the integrator with parasitic capacitors. Then the model has been included in the I Σ Δ ADC model, which has been simulated with Matlab. To get detailed results and be able to handle comparisons, various calibration techniques have been applied to the I Σ Δ ADC outputs coming from post-layout simulation and from the new model so that a better resolution is achieved. The results show a good likeness of the error shapes and magnitudes for the new model compared to post-layout simulations. We deduce that the proposed model is a good representation of the degradation phenomena, this with a high level of confidence. [ABSTRACT FROM AUTHOR]

In this paper, an implementation of the control and the synchronization algorithms for a voltage source inverter (VSI) used in a grid-connected structure is carried out. The main purpose is to show the combined operation of the control and synchronization algorithm for achieving the proper behavior of the grid inverter for the single-phase utility grid system. In order to obtain a proper functionality of the system during perturbation, a proportional integral controller structure along with second-order generalized integrator phase-locked loop is designed and used as synchronization algorithm. Another aim is to control power factor at grid, to feed power into the grid and to decrease phase current distortion of VSI. Secondly, the design of the output LCL filter is proposed in this paper. The results of simulations of the inverter system connected to grid (220 V, 50 Hz) using MATLAB/Simulink are also shown. Simulation results confirm that the grid input power factor is nearly one and the distortion of phase current of the proposed system is reduced, causing the total harmonic distortion for various power conditions falls within 5%. The last chapter shows the experimental verifications of the proposed control algorithm. [ABSTRACT FROM AUTHOR]

The quality of power is always a concern for the high penetration of a grid-connected solar photovoltaic (PV) system due to the variation in solar irradiation and the temperature change of solar output, which in turn varies the fundamental component of power delivered to the grid. A solar source requires an inverter interface to supply the AC load as well as for the grid interconnection. Any reduction in the fundamental component generated by solar PV at a lower irradiation level or at high- temperature results in increasing %THD at the output of inverter for a given fixed switching frequency since harmonics due to PWM technique is comparable with the fundamental component. The selection of high-fixed-switching-frequency PWM reduces harmonics but increases the stress on switches and switching losses. It also suffers from issues of harmonics at carrier frequency and its sideband at multiples of switching frequency that causes acoustic noise and EMI. The random frequency PWM (Random PWM) method overcomes these issues presented by the fixed-frequency PWM method. However, a wide band of Random PWM makes the inverter filter design difficult and causes resonance in the distribution system. In addition, asymmetry in the carrier wave introduces even-order harmonics in the line current. Hence, this paper proposes a narrowband random frequency PWM method to reduce sideband harmonics, lower-order harmonics, even-order harmonics and a total harmonic distortion (THD) for a solar-based grid-connected inverter. Simulation results present a satisfactory performance of the proposed control technique for a steady-state and transient results. Experimental validation of the same is carried out on the OPAL-RT OP4500-based laboratory prototype of a 2-kVA inverter which depicts reduction in harmonics and hence improvement in power quality. [ABSTRACT FROM AUTHOR]

In this paper, SHE based on Newton–Raphson algorithm is used for open-loop control of flying capacitor multilevel inverter. Without measuring current and capacitor voltages, as well as not using any controller and voltage feedback, proposed control strategy generates accurate switching angles, capable of balancing flying capacitor voltage and eliminates lower order harmonics while considering load power factor variation. Efficiency and robustness of proposed algorithm are verified by simulation and experiments. Results show that proposed method does effectively eliminate specific low-order harmonics, and inverter output voltage is resulted in low total harmonic distortion with desired number of levels and balanced capacitor voltages. [ABSTRACT FROM AUTHOR]

An indirect field oriented control of a double star induction motor drive with a conventional PI and fuzzy logic controller based on four rules is presented in this paper. To realize a control of this motor, a DC supply and a PWM voltage source inverter (VSI) are introduced. Performance of the proposed control schemes under load disturbances and parameter variations is studied through simulations. The simulation results regarding the speed response with both controllers are presented and discussed. [ABSTRACT FROM AUTHOR]

A simple circuit for duty-cycle correction is proposed in this paper. The configuration is flexible consisting of only three CMOS inverters in a feedback loop. It does not require any reference signal and, therefore, it can be used as a standalone circuit, while it can be applied on a single-ended clock path without breaking the clock line. Simulation results in a 65 nm CMOS technology and 1 V supply voltage give a duty-cycle error less than 1% for a duty-cycle input clock variation between 30 and 70% with a frequency range from 2.4 to 2.9 GHz. [ABSTRACT FROM AUTHOR]

This paper describes an application about detection of bearing defects in inverter fed induction motors, using Concordia transform approach based algorithm. After introduction, brief information is given about bearing structure and type of bearing failures. Next section, Concordia transform theory is mentioned then, RBF neural network structure is summarized. After that, test system information is specified. This paper indicates that Concordia transform approach is a reliable tool to detect bearing faults in inverter fed small induction motors. The generality of the proposed methodology has been experimentally tested on a 1 HP squirrel-cage induction motor. At the end of the paper, an ANN algorithm is proposed that could detect the bearing faults automatically. The obtained results have 93.75% accuracy. This study suggests that proposed Concordia transform based fault detection algorithm could be integrated in an induction motor driver so, bearing condition of the induction motor could be observed while motor is working and bearing faults could be detect before they become serious. [ABSTRACT FROM AUTHOR]

To better capture the phase information of single-phase power grids, a novel single-phase phase-locked loop method is proposed in this paper. The method uses a tracking differentiator as an orthogonal signal generator. Because the generator is sensitive to the input signal's frequency, the amplitudes of the tracking and differential signals may not be equivalent, causing a failed phase tracking. Therefore, the amplitude correction of the differential signal needs to be done. Then, the corrected differential signal and the tracking signal are both input to the phase detector. To further verify the practical feasibility of the method, the voltage sampling and phase tracking experiments were performed on a digital signal processor-based inverter experimental platform, which is aimed to simulate the grid. The experimental results show that the proposed algorithm has strong dynamic performance and steady-state performance under different states of the power grid, and the phase-locked method has a practical feasibility in single-phase grid-connected applications. [ABSTRACT FROM AUTHOR]

The increasing participation of wind turbines based on doubly fed induction generator (DFIG) in the power system around the world is motivating the investigation of novel strategies to enhance the reliability of DFIG and power system connection. This paper proposes the use of a new hybrid multilevel back-to-back converter on DFIG wind turbine to improve its fault ride-through capability and power system transient stability. The proposed topology is built adding single-phase full-bridge inverters in series with each phase of traditional three-phase inverter. This converter is able to generate higher voltages in rotor circuit whenever it is required, which can effectively protect power converter and at the same time contribute with grid transient performance. Simulation results, using PSCAD®, are presented for a 2 MW DFIG machine submitted to symmetrical faults in single machine—infinite bus and three-bus system. Results show that the proposal is effective as a protection and works well as an alternative to traditional solutions, limiting currents and maintaining power control during voltage dips. It is also effective in contribution with the improvement of transient stability margin by the possibility of reactive power injection. [ABSTRACT FROM AUTHOR]

Transformerless inverters are prone to irregular voltage profiles, high harmonics and isolation problems while operating with photovoltaic systems and varying load conditions under stand-alone mode. The aim of the paper is to identify the drawbacks of transformerless inverters operating in stand-alone mode and to propose a new topology with improved performance and control. Further, an intelligent controller is designed to operate the proposed topology with various loads and varying load conditions. The developed controller achieves voltage regulation and low total harmonic distortion for the proposed topology when simulated under MATLAB/Simulink environment. Further, a laboratory prototype of the proposed inverter operating under stand-alone photovoltaic application is developed and operated with the developed control method. The proposed topology along with the developed controller achieves output voltage regulation and reduced THD under varying load conditions. The THD of the proposed system while operating with constant load is observed to be 1.8%, and for varying load condition, it is around 2.12%. Further, the efficiency and power loss of the system are calculated, and it is observed the system exhibits 98.5% efficiency. The achieved results are better when compared with existing work. [ABSTRACT FROM AUTHOR]

For providing better reliability and getting minimal harmonics, multilevel inverters are commonly employed in grid connected photovoltaic systems. This paper presents 27 level inverter with reduced switch topology to get better reliability with low harmonics. This inverter performance completely relies on EANFIS controller which is the combination of ANFIS and Emperor Penguin Optimization (EPO) algorithm. Working procedure of ANFIS will be optimized by EPO to make us easy to deal MLI switching angle and produce harmonic-less control voltage. EPO provides efficient result by means of computational complexity, time and space complexity. In our work, this is the main reason to select EPO for optimizing ANFIS controller. The proposed work will be implemented in Simulink working environment. Resultant outcomes like inverter output, controller output and THD analysis will be compared with recently developed existing works. [ABSTRACT FROM AUTHOR]

Multiple-valued logic such as ternary logic has attracted the digital system designers attention in recent years as it offers the benefits of reduced interconnects, higher operating speeds and smaller chip area. A goal of multi-threshold circuit design could be easily achieved by incorporating the scalable threshold voltage values of carbon nanotube field effect transistors (CNTFETs). This paper proposes a novel design of low-power and high-performance ternary adder and subtractor circuit design by combining the futuristic ternary and conventional binary logic design approaches. The simplified design of ternary to a binary decoder based on negative ternary inverter and positive ternary inverter outputs, and further transmission gate-based ternary multiplexer implementation facilitates the low power consumption and energy efficiency in the implementation of the complex arithmetic circuits. Extensive HSPICE simulations are conducted with the standard 32 nm CNTFET technology in order to evaluate the performance metrics of the realized circuits. According to the simulation results, proposed ternary adder and subtractor cells show the significant improvement in energy consumption (PDP) as compared to their counterparts under different test conditions. Moreover, the ripple adder structure is realized using the proposed adder circuit in order to test the practicability of given circuits in cascaded structures. [ABSTRACT FROM AUTHOR]

The continuous scaling down of circuits has resulted in the development of carbon nanotubes (CNT) which provides a better alternative of silicon. High device packing densities is one of the advantageous factors of CNTFET compared to CMOS technology. This paper describes the new bulk current based built-in current sensor (BBICS) for the detection of single event upset (SEU) in CNTFET SRAM with less number of transistors compared to previous designs. The advantage of it is that its ability to detect low ranges of microcurrent. The complete circuit, both SRAM and Sensor are built with CNTFET. This also possesses the advantage of being used in the detection of negative current pulses with the addition of an inverter circuit. This circuit operates best for two different technology nodes. This built-in current sensor is connected to the bulk terminal of the CNTFET SRAM. PVT analysis and power dissipation analysis were done for the proposed circuit. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study the influence of inverter dead-time on steady as well as dynamic operation of an open-loop induction motor drive fed from a voltage source inverter (VSI). Towards this goal, this paper presents a systematic derivation of a dynamic model for an inverter-fed induction motor, incorporating the effect of inverter dead-time, in the synchronously revolving dq reference frame. Simulation results based on this dynamic model bring out the impact of inverter dead-time on both the transient response and steady-state operation of the motor drive. For the purpose of steady-state analysis, the dynamic model of the motor drive is used to derive a steady-state model, which is found to be non-linear. The steady-state model shows that the impact of dead-time can be seen as an additional resistance in the stator circuit, whose value depends on the stator current. Towards precise evaluation of this dead-time equivalent resistance, an analytical expression is proposed for the same in terms of inverter dead-time, switching frequency, modulation index and load impedance. The notion of dead-time equivalent resistance is shown to simplify the solution of the non-linear steady-state model. The analytically evaluated steady-state solutions are validated through numerical simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper presents a control power supply (CPS) design which is used to feed power to the subsystems of a power converter. The CPS design presented here maintains a constant 24Vdc output even over a wide (90Vrms to 270Vrms ) ac voltage variation at its input for a High Power Converter (HPC). The circuit design and closed loop control design of such a CPS are presented. During starting, the power supply to the control circuitry of the CPS in turn is obtained using a separate start-up power supply. The various design issues and details of the on-board power supply and start-up power circuit to ensure the reliable start-up and shut down of the CPS are analyzed. The CPS was tested for wide input voltage range (vin) and the performance validates the design. The CPS has also been tested for an input side voltage sag and its performance allows the HPC to meet the low voltage ride-through requirements. [ABSTRACT FROM AUTHOR]

This paper proposes an inverter scheme to generate an additional third-harmonic component alongside the fundamental component of the current. The generated third-harmonic component is used to achieve the brushless operation in a wound field synchronous machine (WFSM). Contrary to the traditional schemes used, i.e., dual inverter, single inverter with extra switches schemes, and single inverter with four transistor legs, the proposed scheme comprises a single inverter with three transistor legs that utilizes a modified third-harmonic injection pulse-width modulation. The brushless operation in WFSM requires two windings on the rotor periphery, i.e., harmonic winding and field winding that are interconnected through a rotating diode bridge rectifier. To maximize the usage of generated third-harmonic component, the selection of pole–slot combinations of the machine is carried out considering the winding factors. The proposed inverter scheme is verified in MATLAB, and a 2-D finite element analysis is used to validate the brushless operation of the machine along with its electromagnetic performance. [ABSTRACT FROM AUTHOR]

In this paper, a digital current control of a three-phase four-leg inverter based on predictive cost function is studied. Inverters are important for power electronics applications in three-phase four-wire systems, such as active power filters and uninterruptible power supplies. There are many methods for control of inverters, such as pulse-width modulation and three-dimensional space vector modulation. These methods are complex. In this paper, a simple way for current control of a three-phase four-leg inverter is presented. Here, by using a predictive cost function and fixed-point computations, the optimal switching state to be applied in the next sampling is selected. Finally, to evaluate the accuracy of the fixed-point computations, several cases for balanced and unbalanced loading conditions are verified. In each case, the parameter that measured to confirm computation accuracy is total harmonic distortion. [ABSTRACT FROM AUTHOR]

In this paper, a new and efficient global optimization method known as teaching-learning-based optimization is adopted to optimally design the parameters of a passive RC-damped LCL filter for grid-connected voltage source inverters. The novel proposed objective function of the optimization algorithm is to minimize the values of inductors and capacitors. The proposed design improves inverter efficiency and minimizes filter stored energy at a predefined operating and switching frequencies. Moreover, the proposed design procedure may reduce the complexity of the passive RC-damped LCL filter by removing one inductor or one capacitor. The optimal design procedure is built based on an accurate mathematical model and description of the filter topology. A detailed comparison between the results of the proposed work and related work in the literature is thoroughly discussed. The optimized filter is designed, built, and validated analytically and experimentally for verification based on a hardware prototype. [ABSTRACT FROM AUTHOR]

To reach the increasing demand for power quality and power rating along with lower harmonic distortion and lesser electromagnetic interference, the multilevel inverter is needed. Solar energy is one of the favorable renewable energy resources, and the multilevel inverter has been proven to be one of the important enabling technologies in photovoltaic utilization. This paper is based on the study of behavior of a nine levels NPC three-phase inverter topology interfacing multistring photovoltaic system to the electric grid. This inverter is controlled by the pulse-width modulated strategy. Eight carrier waves of the same frequency and different amplitudes are compared with two references (a sine wave and its opposite) for generating the control signals of the switches. Some DC/DC boost converters are used to amplify the voltage produced by the photovoltaic generators. Each of these converters is controlled by a fuzzy Logic-based maximum power point tracking algorithm (FLBMPPTA) in order to track the maximum power point of the GPV; results of simulation in Matlab environment are given and discussed. [ABSTRACT FROM AUTHOR]

This paper aims to study the performances of the dual open-end stator winding asynchronous machine with 0∘ shifting supplied by two 2-level cascaded inverters. To establish this study, the effects of shifting in both cases 0∘ and 30∘ are analyzed, when the machine is fed by four classical inverters (two 2-level inverters for each winding input). The obtained simulation results prove that with 30∘, the machine offers good torque quality but decreases the quality of phase current. To overcome this limitation, the dual open-end stator winding machine at 0∘ is supplied by four multilevel converters. Each converter is constituted by two 2-level classical inverters in cascading. This structure allows to increase the number of levels of the voltage and to improve the electromagnetic torque while providing better current quality in the stator. The obtained simulation results for the two shifts and for the two used converters confirm the important advantage of the association of this machine at zero shift with two 2-level classical inverters in cascading. [ABSTRACT FROM AUTHOR]

This paper proposes a new topology for a brushless wound rotor synchronous machine (BL-WRSM) using a specially designed stator winding supplied through a single three-phase inverter. In this topology, a special stator winding, which comprises of two sets of series-connected windings with an unequal number of turns, is used to generate an additional spatial sub-harmonic component in the stator magneto-motive force (MMF). This additional sub-harmonic MMF (SH-MMF) component is utilized for exciting the field winding of the BL-WRSM. The advantage of the proposed brushless topology is the use of a single inverter compared to a dual inverter used in the existing dual inverter BL-WRSM. For the rotor, there are two separate windings: (1) harmonic winding and (2) field winding. Both the harmonic and field windings are connected in parallel with each other through a rotating rectifier. The additional SH-MMF component generates a rotating air-gap magnetic field, which induces the voltage in the harmonic winding. This induced voltage is then rectified and used to supply a dc current to the field winding. A 2-D finite element analysis is performed to analyze and verify the operating principle of this new BL-WRSM. [ABSTRACT FROM AUTHOR]

This paper presents a hardware description methodology for the direct torque control (DTC) of a three-level voltage source inverter (VSI) fed a permanent magnet synchronous motor drive with neutral-point balancing control algorithm based on field programmable gate array (FPGA). The main drawback of the conventional DTC during its digital implementation is the high torque ripple, and to overcome this problem, the use of a three-level VSI and a simple hardware description methodology for DTC based on FPGA is proposed. However, the circuit limitations of the three-level inverter, such as neutral-point balance, should be taken into account in the selection of the future space vector applied to the machine; for this reason, a simple and effective procedure to maintain the neutral-point balance is presented. The proposed methodology has been validated using hardware in the loop simulation, and results under different operating points are presented. [ABSTRACT FROM AUTHOR]

A 3 Gb/s wireline transmitter (Tx) with a tapless pre-emphasis current-mode logic output driver is presented in this paper. The proposed output driver can support 2.5, 6 and 10 dB pre-emphasis without any additional current tap. It can reduce the current consumption of the output driver by 30 %. The 1.5 GHz phase-locked loop (PLL), multi-phase generator, and 26-to-1 serializer are utilized to serialize 26-bit parallel data to 1-bit 3 Gb/s serial data stream. The rms and peak-to-peak jitters of PLL are 2.97 and 22.5 ps, respectively. The eye opening of the proposed output driver at 3 Gb/s is 0.8UI with a 10 dB loss channel. The current consumption of the output driver is only 5.14 mA, and the Tx is 9 mA. The area of the Tx is 0.72 mm using the 0.11 μm CMOS process. [ABSTRACT FROM AUTHOR]