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This paper presents development of a hardware simulator for the DC–AC inverters of electric compressors (e-compressors). In general, early-release EVs often feature a nominal battery voltage of around 400 V. However, EVs with a 400 V battery have drawbacks such as slow battery charging speeds and limited driving distances. To overcome these drawbacks, the nominal battery voltage has recently been increased from 400 V to around 800 V. Accordingly, research on electrical components applicable to EVs with an 800 V battery has been conducted. However, research on the DC–AC inverter used in the e-compressor, as a core component of an electric air conditioning system for EVs with 800 V battery, is insufficient. Therefore, the development of a hardware simulator of DC–AC inverters for the e-compressors used in EVs with an 800 V battery is proposed in this paper. The validity of the proposed hardware simulator is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a diagnostic and fault-tolerant method for an open-fault condition in dual inverters with open-end winding interior permanent magnet synchronous motors (OEW-IPMSMs). Certain switch pairs show similar behavior in the output current in an open-fault condition due to the structural characteristics of the two-level dual inverter. This work presents a method for detecting open-fault conditions and ensuring a fault-tolerant operation. The proposed method is applied in dual inverters with isolated voltage sources for driving OEW-IPMSM. In the event of an open-fault condition, a pair of switches containing the faulty switch is identified based on the stator current. Subsequently, the switch with the open-fault condition is determined, and fault-tolerant control for a faulty switch is immediately performed through a single-mode operation using zero-voltage vectors. The effectiveness of the proposed detection and tolerant control method is confirmed through simulation and experimental results. [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 multi-level inverter (MLI) is more efficient due to its ability to eliminate low-order harmonics. Thus, it is widely used in renewable energy generation, electric vehicles (EVs), etc. The choice of the neutral-point clamped (NPC) converter topology as a research object is of great significance in practical engineering. However, complex modulation algorithms and neutral-point voltage unbalance are two inherent problems for such NPC inverters. In this paper, an improved multi-voltage vector model predictive control (MVV-MPC) strategy based on neighboring four voltage vector synthesis is presented for three-phase NPC inverters. The duty cycle calculation and derivation methods for the proposed method are very simple, and they were obtained through the action time of each voltage vector being inversely proportional to the value of the corresponding cost function. Moreover, the fixed switching frequency of this strategy is maintained and the current peak ripple is reduced, guaranteeing the preferred total harmonic distortion of the output waveform. Furthermore, a voltage balancing method based on zero-sequence voltage injection is utilized to achieve dynamic balancing of the midpoint voltage difference and to limit the oscillation magnitude of the midpoint voltage difference to within ± 1 V. Finally, MATLAB simulations and an HIL experimental platform are built to demonstrate the effectiveness of the proposed method. [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]

The conventional topological approach to eliminate the multiple-input DC voltage requirement in multilevel inverter configurations for synthesizing high-output voltage levels is to deploy split capacitor banks at the input terminal. This method stipulates a less expensive, light weight, and reduced size inverter system. However, the excessive demand for several capacitor banks and the complex voltage balancing strategy associated with this conceptual approach poses numerous limitations in their deployment. In view of these drawbacks, this study proposes a self-balanced, single-phase, nine-level switched-capacitor-based inverter topology consisting of a single-input DC voltage, an auxiliary circuit, and an H-bridge circuit unit. A commensurate single carrier-based sinusoidal pulse-width modulation scheme is developed for the proposed power circuit control, enabling the synthesis of a nine-level output voltage waveform whose amplitude is four times the input voltage value. Detailed power circuit operations and switching functions are adequately provided in the proposed topology. A comparison between the proposed inverter and its recent counterparts in terms of component count, cost involvement, and output voltage-boosting ability is duly carried out using Python data visualization. Results reveal that the proposed inverter competes well in these three criteria. For varying R–L load values, the inverter has the capability of high active and reactive power delivery. Its dynamic response for step changes in the modulation index under these power-mode operations is presented in this paper. For high active power-mode operation, efficiencies of 98.27% and 98.92% under light- and heavy-load conditions, respectively, are obtained on a 3-kW-rated inverter prototype. [ABSTRACT FROM AUTHOR]

In this paper, a level-shift-based voltage modulation method for dual inverters used to drive open-end winding interior permanent magnet synchronous motors is presented. Notably, the conventional level-shift-based voltage modulation method used for dual inverters presents a disadvantage, since the differential mode voltage (DMV) significantly increases compared with that in the basic control method of dual inverters. This defect can be attributed to the fact that the conventional level-shift-based voltage modulation method uses a voltage vector combination that generates the maximum DMV peak value. To address this problem, the proposed method reduces the DMV by explicitly switching the voltage vectors that generate a large DMV. In this paper, the DMV generation process in a dual-inverter system is analyzed. Moreover, the DMV tendencies of the conventional and proposed methods are divided into operating regions according to the modulation index, which are further analyzed. The effectiveness and performance of the proposed voltage modulation method for a dual inverter are verified based on simulation and experimental results. [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]

T-type three-level inverters (T23LIs) are widely used in the electric drive system of new energy vehicles. However, the open-circuit (OC) faults of their switching devices will cause serious damage to the entire system operation. To mitigate the impact of switching faults, this paper proposes an OC fault diagnosis method based on the variations of common-mode voltage in small sectors of T23LI. Firstly, the normal characteristics of T23LI under SVPWM control algorithm are analyzed, and the correspondence between the space voltage vectors and the values of common-mode voltage is established. Then, the common-mode voltage variations under fault conditions are analyzed, and a fault diagnosis method based on these variations is proposed. The faults of the four switching devices in one phase is divided into two groups through the qualitative analysis of common-mode voltage variations, and the specific location of the faulty switch is located by further quantitative analysis. Finally, by analyzing the changes in the three-phase bridge output voltages after faults, the accurate location of the faults in the 12 switches of the three phases is located. Simulation and experimental results verify that the proposed method can accurately and quickly diagnose the single-switch OC faults of all switches, and it effectively accelerates the diagnosis speed and reduces costs by only requiring the collection of a single voltage signal. [ABSTRACT FROM AUTHOR]

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]

Multistage inverters containing DC-DC converters are more common in grid-tied photovoltaic (PV) systems, because of the low DC voltage value provided by the PV generator, which requires a two-stage topology. The challenge in the latter case is to control the DC-link voltage with an accurate estimation of the current injected into the grid by PV system. In this paper, a two-stage grid-tied PV design based on a high-gain DC-DC converter and a 7 level packed U cells (7L-PUC) inverter, controlled by Finite-Control-Set Model Predictive Control (FCS-MPC) is presented, with the proposal of a novel model for controlling the DC-link voltage by considering system losses. The simulation and experimental results demonstrate the high effectiveness of the proposed control strategy in terms of power quality as well as response time and accuracy under changes in weather conditions and demonstrate the feasibility of the proposed system. [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]

This paper presents an inverter average input power estimation algorithm in the low-frequency modulation index such as a low sampling to operating frequency ratio. When the current sampling frequency to operating frequency is low, the error between the sampled phase current and the average phase current is large. This results in an error of the inverter average input power estimation, because it is calculated with the sampled phase current. Thus, in this paper, the average phase currents are calculated for every voltage vector duration within a current sampling period. The average phase currents are multiplied by the phase voltages to estimate the inverter average input power. Then, the inverter average input power is estimated as the sum of the three phases in the active voltage durations. Simulation and experimental results are presented to verify the proposed inverter average input power estimation. [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]

A novel single-phase seven-level inverter using a cross-switch cell (CSC) is presented in this paper. Compared with conventional inverters, the proposed topology can generate seven-level output, triple boost gain with one dc source and a reduced number of switches. The CSC provides different charging paths for the capacitors to realize self-balance. Hence, the proposed inverter can realize self-balancing without additional control methods or sensors. Moreover, the proposed structure inherently generates negative output voltage levels without a back-end H-bridge circuit, which reduces the voltage stress on switches. This paper has fully illustrated the operation principles, and presents capacitance calculation and loss analysis. Afterward, a comparative study against recently proposed seven-level inverters is introduced, illustrating the merits of the proposed topology in terms of reduced switches, high voltage-boosting capacity, and self-balancing. Ultimately, a laboratory prototype is built for the validation of the proposed inverter. [ABSTRACT FROM AUTHOR]

Gird impedance variations in a weak grid can easily lead to the instability of grid-connected inverters with an LCL filter. In this paper, a robust back-stepping sliding mode control strategy for the LCL-type grid-connected inverter is proposed to ensure local asymptotic stability. First, due to its nonlinear switching problem, the model is transformed into the Brunovsky canonical form of a linear system, using the exact feedback linearization theory. Then, to ensure global stability and rapid dynamic performance, a back-stepping sliding mode control strategy is recursively derived. Furthermore, under the premise of asymptotic stability, a robust scheme is developed to obtain appropriate parameters against grid impedance variations. Hence, the expected stability performance can be achieved and the dynamic performance can be improved in a weak grid. Finally, a 2 kW prototype is constructed, and experimental results demonstrate the effectiveness of the proposed controller when compared with the conventional back-stepping scheme. [ABSTRACT FROM AUTHOR]

In this paper, a balancing control scheme of DC-link capacitor voltages for five-level hybrid T-type (5L-HT) inverters is proposed, where existing auxiliary balancing circuit is eliminated. The 5L-HT inverter has a significant advantage of the reduced number of devices compared with other five-level inverter topologies. However, this inverter requires an auxiliary balancing circuit, which is used to rectify the voltage imbalance at the DC-link capacitors, and thus negates the competitiveness of this topology in terms of device count and converter volume. To eliminate the auxiliary circuit, a carrier-overlapped PWM (COPWM) is applied in place of the conventional level-shifted PWM (LSPWM) to control the neutral-point currents, where the duty ratios of switches are adjusted by PI controllers. As a result, although the THD of the output voltage is rather increased, the cost and volume are saved by 27% and 52%, respectively, for a 1-MW/6.6-kV system. The effectiveness of the proposed balancing control method for the 5L-HT inverter has been verified through the simulation and experimental results for the prototype hardware. [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]

Integration of multilevel inverters with renewable energy sources have been the subject of many research projects. Numerous topologies of multilevel inverters have been investigated for stand-alone and grid-connected PV systems. The high number of switching devices, complexity, large size, voltage imbalance, and high cost are main drawbacks of the conventional topologies. This paper presents a new three-phase, three-port, five-level inverter based on a switched-capacitor circuit for PV applications. Compared to the conventional topologies, the proposed inverter has voltage boosting capability and multilevel operation without using clamping diodes or flying capacitors, simplifying the control algorithms and improving the reliability, efficiency, and lifetime. The presented multilevel inverter offers 25% reduction in power devices counts and 50% reduction in flying capacitors. The proposed inverter solves the capacitor voltage balancing issue of the conventional topologies and achieves the lowest voltage stress, making it suitable for high voltage applications. Additionally, the new topology harnesses the superior features of silicon-carbide devices; hence, a fast-switching speed can be employed to reduce size of the storage elements and output filter requirements. Furthermore, the soft-switching operation is realized to regulate the charging current of the capacitor. The operating principle of the proposed topology is investigated, and its properties are compared to the traditional multilevel inverters. A laboratory prototype was built to validate the effectiveness of the proposed circuit, simulation and experimental results for the proposed inverter are provided. [ABSTRACT FROM AUTHOR]

With the rapid development of renewable energy, large amounts of power need to be transmitted to load centers, and series-capacitor compensation (SCC) plays an important role in renewable power transmission. However, it has been pointed out that SCC interacts with inverters and threatens system stability. This paper investigates the influence of SCC on inverter control, and proposes strategies for enhancing system stability based on the instability mechanism. First, the impacts of SCC on inverter current control and synchronization control are analyzed. A current control model is established by a system transfer function, and a synchronization control model focusing on transient stability is established based on the traditional synchronous reference frame phase-locked loop (SRF-PLL). Bode and nonlinear analysis methods are utilized in the stability analysis of both current control and synchronization control. It is found that SCC has little effect on inverter current control. However, it seriously affects synchronization control. SCC reduces the stability range of synchronization control, and causes system instability when there is a large frequency disturbance. In order to improve system stability, two approaches have been proposed. These approaches are optimizing a PI controller, and designing a band-pass filter (BPF) inside the PLL. Finally, simulations and experiments are presented to verify the correctness of theories. [ABSTRACT FROM AUTHOR]

The min-projection strategy (MPS) is a switching rule with better convergence speed, which can improve the dynamic characteristics of three-phase grid-connected inverters. However, the grid-connected current harmonics of the system are large when the MPS is used directly in the digital control framework due to the limitations of the sampling frequency. To solve this problem, an improved min-projection strategy is proposed in this paper by introducing a zero voltage vector to the control. First, the non-zero voltage vector is selected through the switching law function of the MPS. Then the time occupied by the non-zero voltage vector and the zero voltage vector can be obtained through an error function, which is established by the principle of minimum current error. Finally, the switching signal can be obtained for control, based on the method of duty cycle modulation. This method can realize fast current tracking and current decoupling control, reduce the grid-connected current harmonics, and improve the steady state performance of the system without increasing costs. The effectiveness of the proposed method is verified by simulations and experimental results. [ABSTRACT FROM AUTHOR]

The LCL-type grid-connected inverter based on finite control set model predictive control (FCS-MPC) is suitable for weak grids because of its good robustness and fast dynamic response. However, in an FCS-MPC-based system, the variable switching frequency causes the spread of the inverter-side current harmonic spectrum. Thus, the grid-side current may be distorted because the harmonics are amplified to the grid side due to the resonance peak of the LCL filter. To solve the above problem, this paper proposes an adaptive active damping (AD) method to eliminate the resonant effects. First, the system based on an MPC controller is regarded as a closed-loop system of the grid-side current, and the resonance peak is suppressed effectively by an AD, which consists of a virtual resistor and a virtual capacitor. Second, to balance the resonance suppression and dynamic performance of the system under weak grid conditions, the grid impedance is measured and the optimal AD values for different grid impedance are calculated online. Compared with the fixed-value AD, the proposed method has better resonance suppression and higher bandwidth. The effectiveness and feasibility of the proposed control strategy are verified by simulations and experiments. [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]

Nowadays all-metal induction heating (IH) cooktops have become popular for heating various pots quickly and safely. A load adaptive modulation (LAM) method was proposed to improve the IH power delivery capability and the cost-effectiveness of an all-metal IH system. However, this method shows poor power conversion efficiency under light-load conditions since a high switching loss is induced using the pulse frequency modulation (PFM) method in the series resonant inverters for IH applications. In this paper, a multi-mode control strategy for an IH system employing the LAM method is proposed to improve light-load efficiency when compared with the conventional LAM method. The proposed multi-mode control algorithm automatically changes its modulation according to the pots' material-dependent resistance. The modulation method is selected to improve the light-load efficiency using the proposed control strategy. Experimental results demonstrate the validity and performance of the proposed multi-mode control algorithm with a 2-kW prototype IH series resonant inverter and various-material pots. [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]

These days FACTS devices are predominantly used to improve the power quality in distribution networks to meet the standards. The dynamic voltage restorer (DVR) plays a vital role in maintaining voltage in a distribution power substation at standard levels. DVRs can compensate a short period of sag or swell in a power network. Currently, many industries employ a servo-controlled voltage stabilizer at their premises to compensate voltage fluctuations and swells that occur for a longer period of time. Servo-controlled voltage stabilizers take about 20–30 power cycles to compensate fluctuation. The operation of sensitive equipment fails due to this inefficient compensation. This paper presents a solution for both voltage fluctuations and prolonged low voltage profiles at distribution networks. The proposed switching algorithm for the H-bridge inverter compensates grid voltage fluctuations by injecting compensating voltage without utilizing a DC bulk capacitor unlike a DVR. A prototype developed in the laboratory is tested experimentally and the obtained test results verify the extended feature of the proposed solution. [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]

In order to improve the conversion efficiency and mitigate the EMI problem of conventional hard-switching inverters, a new soft-switching DC-AC inverter with a compact structure and a low modulation complexity is proposed in this paper. In the proposed structure, resonant inductors are connected in series for the arm branches, and resonant capacitors are connected in parallel for the neutral point branches. With the help of resonant components, the proposed structure achieves zero-current switching on the arm branches and zero-voltage switching on the neutral point branches. When compared with state-of-art soft-switching topologies, the proposed topology does not need auxiliary switches. Moreover, the commutation algorithm to realize soft-switching can be easily implemented. In this paper, the principle of the resonant operation of the proposed soft-switching converter is presented and its performance is verified through simulation studies. The feasibility of the proposed inverter is evaluated experimentally with a 2.4-kW prototype. [ABSTRACT FROM AUTHOR]

This paper presents a dual-motor drive system with a three-phase two-level inverter for independent speed control of a three-phase motor and a single-phase motor. The single-phase motor is connected in series between the neutral point of the three-phase motor and the midpoint of two split DC-link capacitors. As the single-phase motor current is a zero-sequence component flowing in the three-phase motor, it does not affect the operation of the three-phase motor. The proposed drive system can reduce the number of power switches compared with the conventional drive system that uses a single-phase and a three-phase inverter. Thus, the proposed system can reduce the cost of the drive system. Simulations and experiments are presented to verify the proposed drive system. [ABSTRACT FROM AUTHOR]

The paper presents a novel approach for low-order harmonic power mitigation in a single-phase, three-level DC/AC inverter. Traditionally, a bulk electrolytic capacitor is used at the DC bus to eliminate the low-frequency ripple. However, owing to the low-frequency components and large capacitor, this technique is not a practical solution. A new active filtering technique using a ripple port without an external circuit or additional switching power devices is proposed. The new technique harnesses the superior features of switched-capacitor circuits to create a topology with a multiport structure. As a result, a small DC-link capacitor can be applied by controlling the modulating reference waveforms between the different ports of the inverter. Additionally, the use of fast wide bandgap devices will allow for smaller passive components, and with high operating temperatures, the heat sink size can be greatly reduced. The theoretical analysis of the ripple reduction technique is explained in detail. The prototype was built in a laboratory, and experimental results are provided. [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]

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]

This paper proposes a novel soft starting algorithm by using PWM inverter technique to control an amplitude of the motor starting current at a single-phase induction motor (SPIM). Traditional SPIM starting methods such as a Split-Phase, Capacitor- Start, Permanent-Split Capacitor (PSC), Capacitor-Start Capacitor-Run (CSCR), basically cannot control the magnitude of starting current due to the fixed system structures. Therefore, in this paper, a soft starting algorithm based on a proportional resonant (PR) control with a variable and constant frequency is proposed to reduce the inrush current and starting up time. In addition, a transition algorithm for operation modes is devised to generate a constant voltage and constant frequency (CVCF). The validity and effectiveness of the proposed soft starting method and transition algorithm are verified through experimental results. [ABSTRACT FROM AUTHOR]

The overmodulation operation of a three-phase inverter can enhance the output torque capacity of the AC motors. In this case, the enhancement varies depending on the overmodulation schemes applied for the overmodulation operation. Steady-state overmodulation schemes are usually employed to give the unit voltage gain up to the six-step mode of an inverter. However, these schemes lead to a slow transient response of the output torque and require a complex algorithm for implementation. On the other hand, dynamic overmodulation schemes can achieve a rapid transient response of the output torque and are simple to implement. However, inverters using these schemes cannot work up to the six-step mode since the voltage gain of the inverter is less than one in the overmodulation region. In this paper, a technique is proposed that can increase the DC voltage utilization of an inverter by improving the voltage gain in dynamic overmodulation operation. An inverter with dynamic overmodulation using the proposed technique can work up to a six-step mode. Hence, AC motors can obtain enhanced torque capacity during flux-weakening operation. Consequently, an improved transient torque response can be achieved in the high-speed region. From simulation and experimental results, it was validated that the proposed technique can be used for dynamic overmodulation operation for not only the continuous PWM but also the DPWMs (discontinuous pulse width modulations). [ABSTRACT FROM AUTHOR]

This paper presents, ant colony optimization based hybrid algorithm for selective harmonic elimination in single phase seven level multilevel inverter with reduced switches. For high power and high voltage applications, multilevel structure with selective harmonic elimination (SHE) modulation scheme is used. The output voltage of multilevel inverter contains fundamental component along with harmonics. SHE technique aims to solve non-linear transcendental equations maintaining the fundamental harmonic component to its desired value and to eliminate lower order odd harmonics. Many optimization algorithms have been implemented to solve this problem. But these algorithms are complicated and time consuming. The Newton-Raphson algorithm is also very convergent for solving these non-linear equations. The main disadvantage of this method is, it requires strong initial guess. To overcome these drawbacks, hybrid optimization algorithm is used in this paper. This algorithm is performed in two stages, during first stage ant colony optimization has been run and in second stage the solutions obtained from ACO is used as a initial guess for Newton-Raphson algorithm which confirms the exact converged solution. Thus the drawback of Newton’s method i.e. requirement of good initial guess is overcomed by proposed hybrid algorithm. The MATLAB/SlMULINK software is used for comprehensive simulation of seven-level inverter. Experimental results validate the simulated results. [ABSTRACT FROM AUTHOR]

In this paper a new generalized space vector pulse width modulation scheme is proposed based on the principle of reverse mapping to drive the switches of multilevel inverters. This projected scheme is developed based on the middle vector of the subhexagon which holds the tip of the reference vector, which plays a major role in mapping the reference vector. A new approach is offered to produce middle vector of the subhexagon which holds tip of the reference vector in the multilevel space vector plane. By using middle vector of the subhexagon, reference vector is linked towards the inner two level sub-hexagon. Then switching vectors, switching sequence and dwell times corresponding to a particular sector of a two-level inverter are determined. After that, by using the two level stage findings, the switching vectors related to exact position of the reference vector are directly generated based on principle of the reverse mapping approach and do not need to be found at n level stage. In the reverse mapping principle, the middle vector of subhexagon is added to the formerly found two level switching vectors. The proposed generalized algorithm is efficient and it can be applied to an inverter of any level. In this paper, the proposed scheme is explained for a five-level inverter and the performance is analyzed for five level and three level inverters through MATLAB. The simulation results are validated by implementing the propose scheme on a V/f controlled three-level inverter fed induction motor using dSPACE control desk. [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 deals with the instability and resonant phenomena in distribution systems with multiple grid-connected inverters with an LCL output filter. The penetration of roof-top and other types of small photovoltaic (PV) grid-connected systems is rapidly increasing in distribution grids due to the attractive incentives set forth by different governments. When the number of such grid-connected inverters increases, their interaction with the distribution grid may cause undesirable effects such as instability and resonance. In this paper, a grid system with several grid-connected inverters is studied. Since proportional-resonant (PR) controllers are becoming more popular, it is assumed that most inverters use this type of controller. An LCL filter is also considered at the inverters output to make the case as realistic as possible. A complete modeling of this system is presented. Consequently, it is shown that such a system is prone to instability due to the interactions of the inverter controllers. A modification of PR controllers is presented where the output capacitor is virtually decreased. As a result, the instability is avoided. Simulation results are presented and show a good agreement with the theoretical studies. Experimental results obtained on a laboratory setup show the validity of the analysis. [ABSTRACT FROM AUTHOR]

A novel passive lossless soft-switching single inductor dual buck full-bridge inverter (PLSSIDBFBI) is presented in this paper. To accomplish this, a passive lossless snubber circuit is added to a dual buck full-bridge inverter. Therefore, the advantages of the dual buck full-bridge inverter are included in the proposed inverter, and the inverter has just one filter inductor, which can decrease the system volume and improve the integration. In addition, the passive lossless snubber circuit achieves soft-switching by its own resonance, and all of the energy stored in the passive lossless snubber circuit can be transferred to load. A comparison between eight topologies is performed in this paper, and the analysis shows that the proposed soft-switching inverter topology has high reliability and efficiency. Finally, experimental results obtained with a 1 kW prototype verify the theoretical analysis and demonstrate the prominent characteristics of a reduced switching loss and improved efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method. [ABSTRACT FROM AUTHOR]

Conventionally, in order to reduce the ac components of the dc-link capacitors of the two-level Half-Bridge Voltage Source Inverter (HB-VSI), high dc-link capacitances are required. This necessitates the employment of short-lifetime and bulky electrolytic capacitors. In this paper, an analysis for the performance of low dc-link capacitances-based HB-VSI is presented to elucidate its ability to generate an enhanced fundamental output voltage magnitude without increasing the voltage rating of the involved switches. This feature is constrained by the load displacement factor. The introduced enhancement is due to the ac components of the capacitors' voltages. The presented approach can be employed for multi-phase systems through using multi single-phase HB-VSI(s). Mathematical analysis of the proposed approach is presented in this paper. To ensure a successful operation of the proposed approach, a closed loop current controller is examined. An expression for the critical dc-link capacitance, which is the lowest dc-link capacitance that can be employed for unipolar capacitors' voltages, is derived. Finally, simulation and experimental results are presented to validate the proposed claims. [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 Proportional-Integral-Derivative (PID) controller is still the most widespread control strategy in the industry. PID controllers have gained popularity due to their simplicity, better control performance and excellent robustness to uncertainties. This paper presents the optimal tuning of a PID controller for domestic induction heating systems with a series resonant inverter for controlling the induction heating power. The objective is to design a stable and superior control system by tuning the PID controller with a derivative filter (PIDF) through Fuzzy logic. The paper also compares the performance of the Fuzzy PIDF controller with that of a Ziegler-Nichols PID controller and a fine-tuned PID controller with a derivative filter. The system modeling and controllers are simulated in MATLAB/SIMULINK. The results obtained show the effectiveness and superiority of the proposed Fuzzy PID controller with a derivative filter. [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]

All-metal induction heating (IH) systems have been introduced to heat both ferromagnetic and non-ferromagnetic pots using dual resonant frequencies. They are designed for heating ferromagnetic pots using a first harmonic operation mode (FHOM) and for heating the non-ferromagnetic pots using a third harmonic operation mode (THOM). All-metal IH systems employing dual resonant frequencies consist of an IH inverter and a power factor correction (PFC) circuit to transfer desired power to pots by increasing the input voltage of the IH inverter. In this paper, the input voltage is designed to obtain an efficiency-optimized operating point. To obtain an appropriate input voltage, power loss analyses are conducted using first harmonic approximation (FHA). Based on analysis results, the input voltage of the IH inverter can be selected to improve its power conversion efficiency. A 2-kW half-bridge series resonant inverter prototype is implemented to verify the effectiveness of the proposed design by heating ferromagnetic pots using the FHOM with a 2-kW transfer power and by heating non-ferromagnetic pots using the THOM with a 1-kW transfer power. [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]

Due to its theoretically fast dynamic response with unlimited bandwidth for direct switch-driven-based induction machines, the finite control set predictive current control (FCS-PCC) method has been verified to be an effective solution in recent years. However, dynamic limitations of the outer speed PI controller exist, especially with high-order time-varying disturbances. In addition, hardware cost can be reduced. Using the universal proportional integral observer (UPIO) method, a robust deadbeat-like encoderless-based FCS-PCC control scheme is investigated for induction machine systems in this paper. The encoder is avoided using the proposed sensorless method. In addition, the system response and disturbance attenuation are enhanced in presence of time-varying unknown load torque and uncertainties. The squared norm is adopted for the cost function design to ensure system stability. Experimental results illustrate that it has good performance such as fast dynamics, good low-speed steady-state accuracy, and robustness. [ABSTRACT FROM AUTHOR]