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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]

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]

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]

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]

In this paper, a grid impedance estimation procedure based on the injection of active and reactive powers through a grid-tied inverter is proposed. The estimation is based on Newton–Raphson algorithm acting on the phasors of the voltages and currents at the point of common coupling between the inverter and the grid. Unlike, similar procedures, based on power injections, the method is implemented in the α β frame, avoiding Park transformations. This is an advantage because dq quantities are prone to be too noisy, or oscillating in unbalance grid conditions or in the presence of voltage harmonics. Moreover, the proposed method allows variations of active and reactive to be imposed simultaneously, differently of methods relying on dq voltages and currents. This feature speeds up the estimation. The voltages and current phasors used to estimate the impedance are determined with the aid of a positive sequence extractor and Fourier algorithm providing the method robustness against unbalance grid conditions and harmonic distortions. Besides the impedance estimation, this paper proposes a technique in which the impedance information is applied to enhance the inverter's control. Here, the impedance value is used with a Routh criterion to assure the system's stability. The propositions are verified with PSIM simulations and with a Hardware-in-the-Loop real-time platform. [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]

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]

The multi-level inverter (MLI) plays an emergent role in high and medium-power applications. Due to the numerous advantages like lower power loss, switching loss and harmonics, the MLI is used in various applications. The major drawbacks of MLI are a higher number of switches and complex modulation strategies, thus increasing the voltage stress. Therefore, this paper proposed a novel single-phase cascaded 51-level inverter topology with fewer switches and DC sources to improve system performance. In this proposed topology, 8 IGBT switches along with 2 DC voltage sources are considered for producing 51 levels of voltage. This 51-level inverter is tuned with the help of an EPDB controller, which is a combination of Emperor Penguin Optimization (EPO) and Deep Belief Network (DBN). The EPO is used to optimize the DBN procedure to handle the MLI switches easily. Thus, it generates low harmonics voltage and error-free output voltage. The proposed inverter topology is compared with existing inverter topologies regarding the number of voltage sources, switches, and total harmonics distortion (THD). The comparative analysis demonstrates that the suggested inverter topology provides higher voltages, thereby reducing the THD of voltage to 1.17% and current to 0.10%, which are relatively lower than the existing inverter topologies; moreover, the efficiency of the proposed converter is 99.18%. [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]

In recent years, with depletion of fossil fuel and exponential increase of power demand meeting the customer needs become a significant challenge for service providers. In this paper, Internet of Things (IoT) based bidirectional converter (BC) is designed which enhances the power electronics converters into the next platforms. This bidirectional converter is built with wireless connectivity. Also, the cluster is built in the series of diverse downwind distances (i.e., between the turbines) can be tested with minimum rearrangement effort. In IoT equipped bidirectional converter farm is evaluated in offline mode by collecting the data remotely. The proposed BC is able to operate in renewable energy (like photovoltaic, wind, etc.) based standalone systems. This BC converter is proposed to transfer power from grid/ renewable energy systems to a battery storage system (BSS) as well as BSS to grid power transfer. The proposed work of cascade topology allows maintaining input voltage as well as output voltage level. During discharging, the energy from a battery pack is returned to the grid where the dc link bus is interconnected with electric traction inverter. Input and output voltage values of the converter are used to fix the reference voltage subject to the power demand requirement. Artificial neural networks are used to regulate the voltage of dc link capacitor. The performance of the proposed BC regarding voltage gain, efficiency, and flexible application have been analysed using MATLAB simulation and also with experimental studies. [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]

This paper discusses the design and implementation of a Robust Shrine Affine Projection Sign (RSAPS) adaptive control algorithm for power quality improvement. Various limitations of conventional 2-level inverters can be overcome using a 5-level Cascaded H-Bridge multilevel inverter (CHB-MLI). Such a CHB-MLI is realized and controlled as a distribution static compensator (DSTATCOM) unit in this paper. The DC link of capacitors have been maintained to reference value by using proportional-integral (PI) controllers without using complex balancing circuits. Extensive simulation has been performed and a scaled -down experimental prototype model has been developed in the laboratory to test the system under steady state and dynamic load conditions using dSPACE-1104 digital signal processor. The simulation and experimental results show the source current harmonics, DC voltage regulation, power factor correction, weight updation etc. under varying load. The proposed algorithm gives satisfactory performance in terms of weight convergence, computational burden, mean square error (MSE) etc. under dynamic load conditions and in addition the THD obtained in source voltage and current is within acceptable IEEE-519 limits. [ABSTRACT FROM AUTHOR]

The use of Active Power Filters (APFs) in future power grids with high penetration of nonlinear loads is unavoidable. Voltage Source Inverters (VSIs) interfacing Photovoltaic (PV) generator could play the APF role in addition to power supply. In this paper, the control of a PV-fed multifunctional grid-connected three-phase VSI is addressed with nonlinear and unbalanced load. The control objective is threefold. The first one is to deliver the maximum available power from the PV source to the grid satisfying power quality standards. The second one is the Voltage Balancing Control for DC-link capacitors to guarantee correct operation of the VSI. The last one is shunt APF control to compensate for nonlinear and unbalanced load harmonics, reactive power, and unbalanced sequences. A quasi-Proportional-Resonant (PR) controller with harmonic compensators is proposed for the current control loop. The quasi-PR controller parameters are determined through optimization algorithms such as Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and a combination of both PSO and GA. The aim of the objective function is to improve static and dynamic behavior. The different gains at the fundamental resonant frequency and the selected odd harmonics are obtained for the proposed quasi-PR controller. The dynamic characteristics of the optimized quasi-PR controllers show superiority against conventional ones in terms of gain margin, phase margin, overshoot, and robustness. With the proposed control scheme, the harmonics, reactive power, and unbalanced sequences are appropriately compensated. The performance of the PV-fed VSI shunt APF under irradiance change, load change, and distorted grid voltage conditions is validated through numerical simulations performed on PSIM © software. The results show that the grid currents Total Harmonic Distortion for irradiance change case study are 4.57 % , 4.57 % , and 3.22 % in phase a, b, and c with the proposed control method, while they are 9.25 % , 5.65 % , and 10.12 % with conventional instantaneous p - q theory. [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]

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]

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]

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]

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]

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]

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]

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]

The paper presents the fault recognition and reconfiguration technique for three-phase five-level cascaded H-bridge multilevel inverter operation. The multilevel inverter operation is carried out by using space vector modulation technique. Open switch fault is very frequent in multilevel inverter, which is located using fuzzy logic whereas the fault reconfiguration is done by adding one auxiliary inverter module with the main multilevel inverter which operates in a faulty condition and regulates the output voltage. The operation of auxiliary inverter module is according to the switching state provided which is based on a fault that occurs in a particular switch. In this method continuous operation of the main multilevel inverter is possible even in the fault condition with only one or two voltage level missed at the output. The continuous operation of multilevel inverter with reduced THD is achieved without using filter which is affirmed by MATLAB® simulation. [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]

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]

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 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 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]

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]

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]

A novel transmitter for transient electromagnetic method (TEM) instrument is proposed in this paper, which is based on three-phase to single-phase matrix converter (TSMC), instead of a conventional transmitter which is composed of an AC-DC converter and an H-bridge inverter. The equivalent circuit model of TSMC-based transmitter is built, and the principle is discussed. In order to make output current satisfy the requirement of TEM, which is a bipolar square wave with 50% duty cycle, the hysteresis control strategy with voltage vector is proposed. The switching process of TSMC is present. The simulations of different output frequency and current are completed. A small power prototype is built, and the experiment of 25 Hz output current is implemented. The simulation and experimental results validate the performance of the proposed transmitter and control method. [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]