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This paper presents a novel reduced switch multilevel inverter based on switched capacitor technique for grid integration. It generates nine-level output voltage waveform with only 10 switches. It is suitable for high gain applications since it has a boosting ability of four times. Another feature is that the capacitors have built-in self-voltage balancing. The level shifted pulse width modulation (LSPWM) technique is used to explore the performance of the proposed topology. To determine its optimal performance, the suggested topology is compared to the state-of-the-art topologies in the literature. Simulation of the proposed topology is done under different parameter variations. Further, the thermal design of the proposed topology is done using PLECS software to find the efficiency. Finally, the hardware prototype is implemented using dSPACE 1104 controller to verify its performance. [ABSTRACT FROM AUTHOR]

This study is dedicated to develop a single-phase modified Y-source inverter (m-YSI) topology having a high boost factor and low switch voltage stress by adding a switch to the low voltage region. Thanks to this structure, continuous input current and wide control range are achieved regardless of winding factor. Since an external switch is used in the recommended modified Y-source inverter, the modulation index and duty ratio are controlled independently. Detailed analyses of the modified Y-source inverter were performed using Matlab/Simulink and its performance was compared with conventional Y-source inverters. Compared to selected conventional Y-source inverters, the proposed m-YSI has almost three times less voltage stress. A lower-cost topology has been obtained in which state-of-the-art control methods can be applied, thanks to a wide control range and circuit components with a low power ratio. This proposed model can be used as a double-stage micro-inverter in photovoltaic systems. [ABSTRACT FROM AUTHOR]

This article proposes a novel 9L-switched capacitor inverter circuit with a voltage-boosting feature. The presented circuit uses fewer energy-stored capacitors, which reduces the size and cost. The conventional Active Neutral Point Clamped (ANPC) inverter output voltage is half of the input voltage, i.e. dc-link voltage requirement is double the output voltage which leads to several challenges such as high dc-link capacitor size and voltage ratings, front-end DC-DC boost converter, etc. These issues are eliminated in the proposed topology due to boosting features, but a soft-charging method is required to suppress the inrush current. A detailed comparison between the proposed and existing SC-based 9L- inverter is presented. To validate the proposed circuit, the simulation is carried out using MATLAB/Simulink tool and the same is verified in a prototype setup for 0.8 kW and its efficiency is 97.02% which is superior than the other topologies relating to this research work.

ABSTRACT In this article, a bidirectional DC‐AC modulation strategy for series resonant dual active bridge converter (SR‐DAB) is proposed. This modulation strategy combines phase shift (PS) and variable frequency (VF), which utilize four control variables, namely, three PS ratios and switching frequency. Three of four control variables are used for every operating scenario. Modulation methods under both buck and boost modes are considered and designed to attain a wide voltage gain range. Situations when modulation variables reach near transition limits are also given attention by introducing the notion of transition mode to realize smooth transition. The modulation strategy is optimized and designed by considering the operating constraints and the power losses in all aspects. Comparison of this optimization strategy with other strategies is carried out to prove the advantages of the proposed strategy. Finally, a 500‐W prototype is designed and built, which can operate under the condition of input DC voltage 10–50 V and output AC voltage 220 Vrms, 50 Hz, and the measured peak efficiency reaches 96.2%. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a single stage buck–boost DC–AC converter based on coupled inductors is presented for renewable energy and electric vehicle applications. The proposed topology works with only three semiconductor switches, two diodes, and three coupled inductors to transfer input DC voltage to a high gain or low gain output AC voltage. A coupled inductor is used instead of normal inductors, which will reduce core and size requirements. The sinusoidal pulse width modulation strategy is used in this paper for controlling the main switch. There are many merits in the presented topology, like high gain up to five times of input voltage, compact size, less number of components, which results in reducing the overall cost, reducing switching loss, and increasing the converter efficiency. The simulation study is carried out using MATLAB/SIMULINK to simulate the operation of the proposed converter. Also, an experimental setup is built up to examine the actual operation of the proposed converter. There is a good agreement between simulation and experimental results which increases the validation and confidence of the model.

A new multiport DC–AC converter is proposed for standalone and off‐grid tied applications. The configuration converts power from DC to AC form in a single stage with suitable voltage gain. To increase the certainty of supporting power, the converter is designed to operate in four modes, including battery‐alone mode. The other advantage of the presented work is supplying the output power during unbalanced voltage conditions of the input ports. The advanced features of the converter for being used in standalone applications are related to the suitable placement and structure of the bidirectional port. In addition, the configuration is designed in a way to contain appropriate structural properties such as the existence of a common ground between the DC section and inverter, continuity of input currents, configured by an acceptable number of components, and low‐voltage stress on the DC–DC section's switches. Furthermore, it has an impedance network to protect the inverter's switches in a shoot‐through state. To confirm the converter advantages from the mentioned points of view, it has been compared with similar configurations. A prototype rated at 110 V is prepared to demonstrate the advantages of the converter performance per different conditions. The results of the steady‐state and transient experiments validate the suitability of the presented converter. [ABSTRACT FROM AUTHOR]

Researchers are focusing on extracting maximum energy from photovoltaic cells due to non-linear characteristics like solar radiation, temperature, carrier, misdirection, and internal current. Advanced DC-Link controllers and current controllers, DC/DC boost converter, MPPT controller, DC-AC inverter phase reactive power compensation operation, synchronization and current grid supply are required. Synergetic control SC is introduced as a new tool in PV control, and we compared it with sliding mode control SMC stands out as a powerful and effective tool. We have implemented techniques such as sliding mode-based MPPT controller and synergetic control SC to allow us to conduct a general study and a comprehensive, taking into account factors such as efficiency, complexity and response time. SC algorithms show efficiency and superiority over MPPT-SMC algorithms in terms of stability, efficiency, speed of response, and maximum power point output without chattering. A PV Grid-Connected System model was created at Simulink to confirm the effectiveness of the proposed global synergistic control mechanism.

State-space modeling is often used to design power converters so that the performance of the closed-loop control system can meet design requirements. However, single-phase DC-AC converters based on constant state feedback control have some issues, including long response times and unpredictable robustness. To solve these problems, a novel control strategy based on state feedback control (SFC), called the smooth projection adaptive strategy (SPAS), is developed by adaptively changing the state feedback coefficient according to the projection value of the system. First, a state space model of the DC-AC converter with the adaptive state feedback control law is established. Then based on the SPAS and considering parameters perturbation, two control laws named current-mode control (CMC) and voltage-mode control (VMC) are proposed, and their robustness are further discussed. Furthermore, the design method of the proposed control system in the digital control framework is presented. Finally, experiments on a 400 W prototype, and comparative analyses among the proposed control laws and the conventional PI control method are carried out. The results show that the proposed CMC has apparent superiority in terms of both static and dynamic performance. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a new single‐phase multi‐port DC–AC converter with high voltage gain in low duty cycle. The operation of the proposed converter consists of four modes, especially battery‐alone mode, which makes it appropriate for stand‐alone renewable applications. Using a suitable boosting method, this converter can achieve high voltage gain in all modes. The high gain performance of the converter occurs at both low shoot‐through duty cycle and high modulation index. Therefore, the output voltage and current harmonics as well as the filter size are reduced. In addition, the converter transfers the power with a continuous current through its input ports and has a common ground between the input sources and the inverter bridge. The positive features of this converter are the result of the appropriate design and localization of the bidirectional port that connects the battery to the converter. The proposed configuration includes an impedance network that protects the converter in the shoot‐through states and takes the advantage of the shoot through in its boosting performance. Another advantage of the proposed converter is that the voltage stress on the power switches on the DC side is considerably low. In order to validate the feasibility and effectiveness of the converter, a prototype rated at 110 V is prepared and tested. [ABSTRACT FROM AUTHOR]

This paper presents a novel integration scheme of solar Photovoltaic (PV) with a large-capacity Doubly Excited Induction Generator (DFIG)-based wind energy system. The proposed scheme leverages both the grid and rotor-side power converters of the DFIG to inject PV power into the grid, eliminating the need for a dedicated converter for PV power processing and offering a cost-effective PV-grid integration solution. The system effectively delivers a substantial amount of PV power to the grid when compared to an equivalent rating inverter used in conventional PV-grid systems. Moreover, the proposed scheme prevents circulating power during sub-synchronous operation in the presence of solar radiation, enhancing overall system efficiency. Additionally, the system's stability benefits from turbine inertia, allowing for higher PV penetration into the power grid. The intermittent complementary nature of solar PV and wind energy sources significantly improves the utilization of the converters. Furthermore, the proposed scheme minimally impacts Maximum Power Point Tracking (MPPT) for PV and wind sources, except in rare environmental glitches, which the PV power control algorithm is adept at handling. The study provides a comprehensive system model used to design the control strategy, supported by analysis, simulations, and experiments conducted on a laboratory prototype. [ABSTRACT FROM AUTHOR]

Flywheels are nowadays a solution for the dynamic charging of electric vehicles since they act as transient energy storage. The need for a top efficient reversible power converter for the flywheel system is crucial to assure high dynamic performance. The paper presents the design of a 50 kW highly efficient reversible three-phase DC–AC inverter involving the most recent silicon carbide metal oxide semiconductor field effect transistors, and its experimental validation on a home-made emulator. Highest efficiency in reversible mode, compactness, and thermal enhancement are the targeted objectives that have been achieved. The power converter prototype evaluated on an original pulse width modulation testing-bench is able to emulate the working of the flywheel system. High frequency pulse width modulation switching, speed cycle operating, and thermal losses are evaluated. In addition, an efficiency above 99% for the converter has been attained, enabling robust functioning of the flywheel system emulator to perform specific charging profiles for electric vehicles. [ABSTRACT FROM AUTHOR]

In this proposed paper, multicarrier sinusoidal pulse width modulation (M-SPWM) method is implemented for design of 15 level reduced switches inverter topology. This inverter topology generates 15 level output-voltage with suitablelswitching pulse production using M-SPWM and altered level of voltages are attained with distinction of modulationlindex. The split inductor is used to diminish the harmoniclcontent and flatted output current. This type of system which contains different range of different range of voltage supplies. As a result, this inverter reduces the difficulty in gating time calculation and there is no neutral point fluctuation issue. This paper illuminates the modes of switching and minimization of stress in voltage and harmonic diminution are examined. The grades of the projected multilevel inverter (MLI) system are verified using Matlab/Simulink and dsPIC controller respectively. [ABSTRACT FROM AUTHOR]

A self-regulated phase estimator (SRPE)-based DQ algorithm for a DC-AC converter with dynamic voltage restoring (DVR) ability is presented in this paper. When compared to the conventional phase-locked loop (PLL), the provided controller can significantly reduce phase distortions and low-order harmonics from the load voltage while attaining quicker dynamic response. Furthermore, the fundamental attribute of the load voltage allows the integrated DC-AC converter to operate at a consistent frequency eliminating frequency oscillations. The SRPE is utilized primarily in the DQ control theory as the reference voltage generator which can compensate for the grid voltage. SRPE has good band-pass filtering properties and a mathematically simple structure that can thoroughly attenuate voltage imbalance and has quick dynamic response. The SRPE has been made to be frequency-adaptive using a damping factor and robust grid frequency estimation. The SRPE can maintain the fundamental frequency at 50 Hz and keep the total harmonic distortions (THD) within the 5% limit even during grid disruptions. The DC-AC converter and SRPE-DQ's stability are thoroughly examined. The experiment is carried out to show the efficacy of the suggested complete control system. There are also comparative simulation studies to show the benefits of the suggested technique. The results reveal that the suggested approach can immediately identify and correct for any grid voltage imbalance while also assisting in maintaining the constant voltage at the load side despite voltage sag/swell and distortions. [ABSTRACT FROM AUTHOR]

This paper presents an enhanced power DC-AC buck converter. The main aim of this research paper is to ensure that the conventional H-bridge DC-AC buck converter is operated practically without delay time between the complementary power switches on the same leg. The enhanced version is realized by serially connecting sized inductor-capacitor-diode topology between the drains and the sources of the high sides of the H-bridge converters. The significant improvement in this kind of converter is that it offers short-circuit immune systems that are not obtainable in the traditional buck DC-AC converter and it triggers the complementary power switches without delay time. The power circuit is obtained by an amalgamation of two Y-closed-up topologies to form an H-bridge converter. The proposed system has a power rating of 3.25 kW, THD of 0.2717%, and pure sine waveforms of output voltage and current of 311.00V and 10.63A under resistive loads. Under RL loads, it offers 3.25 kW, THD of 0.2807%, and pure sine waveforms of output voltage and current of 297.5V and 10.925A. [ABSTRACT FROM AUTHOR]

Starting from the general topology and the main elements that connect a microgrid represented by a DC power source to the main grid, this article presents the performance of the control system of a DC-AC converter. The main elements of this topology are the voltage source inverter represented by a DC-AC converter and the network filters. The active Insulated Gate Bipolar Transistor (IGBT) or Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET) elements of the DC-AC converter are controlled by robust linear or nonlinear Port Controlled Hamiltonian (PCH) controllers. The outputs of these controllers are modulation indices which are inputs to a Pulse-Width Modulation (PWM) system that provides the switching signals for the active elements of the DC-AC converter. The purpose of the DC-AC converter control system is to maintain ud and uq voltages to the prescribed reference values where there is a variation of the three-phase load, which may be of balanced/unbalanced or nonlinear type. The controllers are classic PI, robust or nonlinear PCH, and their performance is improved by the use of a properly trained Reinforcement Learning-Twin Delayed Deep Deterministic Policy Gradient (RL-TD3) agent. The performance of the DC-AC converter control systems is compared using performance indices such as steady-state error, error ripple and Total Harmonic Distortion (THD) current value. Numerical simulations are performed in Matlab/Simulink and conclude the superior performance of the nonlinear PCH controller and the improvement of the performance of each controller presented by using an RL-TD3 agent, which provides correction signals to improve the performance of the DC-AC converter control systems when it is properly trained. [ABSTRACT FROM AUTHOR]

In this article, the Wiener variable step size with variance smoothening (WVSSV) technique is introduced for the utility supportive solar photovoltaic (PV) system. This system performs the function of power factor correction, compensation of nonactive component, and reduction of total harmonics distortion (THD) from the utility grid. The dc–ac converter is used in between the PV array and the common connection point and it is controlled through the WVSSV technique to produce the switching signals. The WVSSV technique presents impressive robustness and good adaptation in highly adverse nonlinear load conditions by estimating the clean and harmonic less fundamental component. The presented technique has a good convergence rate even at the starting of adapting and the step size is adjusted to eliminate the variety of noise and harmonics of nonlinear loads. The efficacy of the WVSSV control technique is presented through simulated and test results and depicts the improved steady-state as well as dynamic performances of the PV system. The THDs of grid parameters are found under the IEEE-519 standard in different working conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a novel three-phase transformer-based multilevel inverter (MLI) topology to maximize the output voltage levels for high-power high-voltage applications while reducing component counts as compared to its transformer-based counterparts. The proposed hybrid topology is formed by connecting a three-level T-type module with full H-bridge cells through single-phase transformers. The T-type module is fixed while the full H-bridge cell can be repeated for enlarging the output voltage levels without increasing the voltage stress on switches. Key features of the proposed topology include low part count, capacitor-free, diode-free, voltage boosting, simple control, and modularity. Within the framework, a simple low-frequency pulse width modulation (LFPWM) switching scheme is used to control the output voltage, and the working principle is detailed for seven-, nine-, and N-level operation. The operability and performance of the proposed topology are numerically verified and experimentally validated at different loads. Moreover, its conversion efficiency is experimentally examined. Finally, a comparative study with existing transformer-based MLI circuits is conducted to prove its key merits.

The energy transition is a crucial effort from many sectors and levels to create a more integrated, carbon-neutral society. More than 20% of all greenhouse gas emissions are attributed to the transportation sector, predominantly concentrated in metropolitan areas. As a result, various technological hurdles are encountered and overcome. It facilitates the adoption of electric vehicles (EVs) run on renewable energy, making them a practical option in the fight against climate change and the completion of the energy revolution. Recent developments suggest that EVs will replace internal combustion engine (ICE) during the next few months. The EV either gets all of its power from batteries and ultra capacitors or some of it from both. In a plug-in electric vehicle, the battery or ultra-capacitor is charged by an AC supply connected to a grid line. In a hybrid electric vehicle, the ICE charges the battery or ultra-capacitor. Regenerative braking is another way to charge the battery from the traction motor. In a plug-in electric vehicle, the energy from of the battery or ultra-capacitor is put back into the AC grid line. Electronic converters are essential to converting power from the grid line to the traction motor and back again. This paper examines the current state of the electric vehicle market throughout the world and its potential future developments. Power electronics converters (PEC) and energy storage devices significantly impact electric vehicles’ efficiency. Furthermore, general opinions about EVs are soon in this sector, as well as research topics that are still open to industry and University researchers.

Universal power converters (UPCs) have aroused significant attention in performing multiple operations in a single power converter. Furthermore, they contribute to economic operation and improved system performance. In this work, a new configuration of the universal power converter (UPC) was proposed by using a simple switching arrangement. It can perform different modes of operations, such as AC–DC, DC–DC, DC–AC, AC–AC, and cyclo-converter operations. In DC–DC conversion, the proposed configuration can perform buck mode, boost mode, and buck–boost mode of operations. Moreover, in DC–AC conversion, it gives better total harmonic distortion (THD). The effectiveness of the proposed configuration was verified by an extensive simulation, using MATLAB/Simulink environment. A low-power prototype circuit was designed to test the viability of the proposed circuit configuration and validated with simulation results. [ABSTRACT FROM AUTHOR]

This article presents a novel concept of a universal solar converter suitable for application in both in the dc or single-phase ac grids using the same terminals. The idea lies in the utilization of the same semiconductors in the dc–dc and in the dc–ac configuration, resulting in minimal redundancy. Possible semiconductor stages are considered. The particular attention is focused on the output filter design along with proper protection circuit selection for dc and ac grids. The design example and comparative analysis between dc–dc, dc–ac, and universal solutions are given. The experimental prototype of the universal solar converter that is rated for 3.6 kVA power in the ac mode and 5 kW in the dc mode is presented. The experimental results demonstrate the ability of operation in ac or dc grids with main correspondent modes. Possible fields of application along with main benefits are addressed in conclusions. [ABSTRACT FROM AUTHOR]

In the present paper, an efficient and performant nonlinear regulator is designed for the control of the pulse width modulation (PWM) voltage inverter that can be used in a standalone photovoltaic microgrid. The main objective of our control is to produce a sinusoidal voltage output signal with amplitude and frequency that are fixed by the reference signal for different loads including linear or nonlinear types. A comparative performance study of controllers based on linear and non-linear techniques such as backstepping, sliding mode, and proportional integral derivative (PID) is developed to ensure the best choice among these three types of controllers. The performance of the system is investigated and compared under various operating conditions by simulations in the MATLAB/Simulink environment to demonstrate the effectiveness of the control methods. Our investigation shows that the backstepping controller can give better performance than the sliding mode and PID controllers. The accuracy and efficiency of the proposed backstepping controller are verified experimentally in terms of tracking objectives. [ABSTRACT FROM AUTHOR]

This novel converter proposes a Multiple Input and Multiple Output (MIMO) power conversion approach for step-up and step-down processes in AC-DC, DC-DC, AC-AC and DC-AC conversions. This versatile converter is designed by using power electronic switches, for AC-DC and AC-AC conversions thyristors are preferred, whereas DC-DC and DC-AC operations require both turn-on and turn-off control so that transistor (IGBT) is the most suitable switch. The proposed converter is highly recommended for multiple source and multiple output operations, but it can perform one conversion at a time. Power rating of the converter can be up to kilowatts during DC-DC and DC-AC conversions process and AC-AC and AC-DC conversions rating may extend up to megawatts. Simulation model of the MIMO converter is examined in the MATLAB simulink model and the same verified in the real-time test bench model. Conversion in all the stages can be controlled by a digital controller according to the requirement. All four conversions can perform step-up as well as step-down process, so design of inductor and capacitor values are very much important. All four modes of operations for thyristor-based transistors and two diode-based transistors are used to ensure switching operations. Novelty of the research work is conversion of power in all the modes can be bidirectional and also in single-stage process, but in the existing systems of power conversions is a unidirectional process. Proposed single-stage power conversion has more efficiency because of low switching losses. This proposed converter was designed by using mathematical analysis, tested at simulation level and verified in the real-time experiment. [ABSTRACT FROM AUTHOR]

The Single Input quasi‐Z‐Source Cascade Multilevel Inverter (SIqZS‐CMI) has the ability to make use of a single DC input source and to share active power among all cascaded qZS modules. This unique feature, do not present in any other quasi‐Z‐Source (qZS) multilevel inverter in the literature, is accomplished by replacing one of its Z‐impedance inductances by a coupled inductor. With this topology, it is possible to make use of a single low voltage PV string, favoring the use of small size residential rooftop systems. In addition, it simplifies the system grounding and the compliance with many Installation, Maintenance, and Safety Codes and Standards. The proposed control strategy enables high quality current injection into the grid, keeping the DC bus voltage regulation, ensuring precise power balancing with symmetric multilevel waveforms. Experimental results from a 5‐level SIqZS‐CMI prototype demonstrate the system's performance and its advantages. [ABSTRACT FROM AUTHOR]

A dual-dc-port dc–ac converter with virtual space vector pulsewidth modulation (SVPWM) based flexible power control is proposed for photovoltaic (PV)-battery hybrid systems. Two dc ports, in which one dc port is interfaced with PV and the other dc port is interfaced with the battery, are provided simultaneously by the dual-dc-port dc–ac converter. Hence, all the active power is transferred within single power conversion stage, and the dc–dc converter between PV and battery is removed. To realize flexible power control between PV, battery, and ac grid, a new control scheme consisting of an outer power loop and an inner virtual SVPWM is proposed, with fully considering the voltage variation of both PV and battery. Operation principle and power control capability of the dual-dc-port dc–ac converter are analyzed in detail. The effectiveness of the proposed solution is validated by experimental results. [ABSTRACT FROM AUTHOR]

A novel space vector-based approach is introduced in this brief to selectively eliminate the lower order harmonics from the DC-AC converter output waveform by making use of double switching clamping sequences. This technique uses a volt-second balance for control of fundamental voltage while using the dwell time rearrangement of the active vector in a sub-cycle to obtain the elimination of fifth or seventh harmonics. Further, the closed-form expression of the dwell time-division coefficient (DTDC) for the active vector dwell time division rearrangement is expressed. The proposed PWM technique is compared with other space vector-based PWM techniques in terms of voltage weighted total harmonic distortion, switching power loss, and lower order harmonic magnitudes. Further, the experimental results are presented to show the effectiveness of the proposed PWM techniques in terms of harmonic elimination. [ABSTRACT FROM AUTHOR]

A novel bidirectional dual active bridge based dc–ac converter is proposed in this article. The converter has multiphase boost interfaces at both the dc and ac ports. The interleaved operation of the multiphase units cancels the ripple currents and eliminates the input filter requirement. The dc to ac conversion is carried out in a single stage using only eight switches. The converter utilizes the low-frequency and high-frequency components in the inverter output to achieve both power conversion and power transfer across the high-frequency transformer simultaneously. A thorough analysis of the converter is carried out for the proper design of the components. Based on the results, a detailed design method is discussed. A multiresonant controller based phase-shift control is suggested to eliminate the low-frequency ripple in the input dc current. Finally, the effectiveness of the proposed converter is validated using results obtained from a 3-kW hardware prototype. [ABSTRACT FROM AUTHOR]

Active power decoupling (APD) circuits enable the use of long lifetime capacitors (film or ceramic capacitors) in single-phase power converters. Owing to the inclusion of the APD circuits, the literature reports 1.5%–1.8% drop in efficiency of single-phase converter at rated power. This reduction in conversion efficiency is one of the significant challenges in the practical use of APD circuits. This article proposes an approach to reduce the power loss in the bidirectional buck converter based APD circuit. This approach is presented with the help of analytical calculations and graphical representation of operation of APD circuit. The proposed approach requires rapid variation in the average voltage of the buffer capacitor with a change in inverter power. To achieve this, an enhanced control technique is suggested with a duty ratio injection controller. The steady state and transient response of the proposed control technique are validated with simulation and experimentation. Further, the reduction in power losses realized by the proposed approach is verified with the help of a developed laboratory prototype. The proposed approach obtains up to 1% improvement in efficiency of single-phase converter at rated power, when compared with existing APD approaches. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems due to their features of high-quality produced waveforms, modularity, transformerless operation, voltage, and current scalability, and fault-tolerant operation. However, these merits usually come with the cost of a high number of components. Over the past few years, proposing new MLIs with a lower component count has been one of the most active topics in power electronics. The first aim of this article is to update and summarize the recently developed multilevel topologies with a reduced component count, based on their advantages, disadvantages, construction, and specific applications. Within the framework, both single-phase and three-phase topologies with symmetrical and asymmetrical operations are taken into consideration via a detailed comparison in terms of the used component count and type. The second objective is to propose a comparative method with novel factors to take component ratings into account. The effectiveness of the proposed method is verified by a comparative study. [ABSTRACT FROM AUTHOR]

To realise the distributed control of the hybrid energy storage system (HESS) in an islanded AC microgrid, a dynamic HESS power allocation strategy based on the virtual impedance (VI) for supercapacitor (SC) and the battery is proposed. Dynamic power-sharing of two kinds of energy storage devices can be achieved without real-time measuring of load power. The state of charge (SOC) recovery of SC is achieved with a SOC loop integrated into the VI loop. The principle of dynamic power-sharing of HESS is derived based on the establishment of HESS equivalent circuit model. By analysing the influence of the voltage and current double loop controller parameters on the output impedance and the VI of the DC/AC converter, the method of setting the controller parameters for power distribution is presented. A simulation model is established with the designed equivalent power fluctuation conditions. The simulation results show that under various working conditions, the SC loop can compensate for the high-frequency part of the equivalent power fluctuation and the battery loop absorbs the low-frequency part of the power fluctuation. The dynamic power-sharing of HESS with the SC SOC recovery is realised effectively.

The inceptions of multilevel inverters (MLI) have caught the attention of researchers for medium and high power applications. However, there has always been a need for a topology with a lower number of device count for higher efficiency and reliability. A new single-phase MLI topology has been proposed in this paper to reduce the number of switches in the circuit and obtain higher voltage level at the output. The basic unit of the proposed topology produces 13 levels at the output with three dc voltage sources and eight switches. Three extentions of the basic unit have been proposed in this paper. A detailed analysis of the proposed topology has been carried out to show the superiority of the proposed converter with respect to the other existing MLI topologies. Power loss analysis has been done using PLECS software, resulting in a maximum efficiency of 98.5%. Nearest level control (NLC) pulse-width modulation technique has been used to produce gate pulses for the switches to achieve better output voltage waveform. The various simulation results have been performed in the PLECS software and a laboratory setup has been used to show the feasibility of the proposed MLI topology.

Two techniques for the control of a grid side converter in a wind energy conversion system. The system is composed of a fixed pitch angle wind turbine followed by a permanent magnet synchronous generator and power electronic converters AC-DC-AC. The main interest is in how to control the inverter in order to ensure the stability of the DC link voltage. Two control methods based on the fuzzy approach are applied and compared. First, a direct Mamdani fuzzy logic controller is presented. Then, a T-S fuzzy controller is elaborated based on a T-S fuzzy model. The Lyapunov theorem and H-infinity performance are exploited for stability analysis. Besides, the feedback controller gains are determined using linear matrix inequality tools. Simulation results are derived in order to prove the robustness of the proposed control algorithms and to compare their performances.

To realise the distributed control of the hybrid energy storage system (HESS) in an islanded AC microgrid, a dynamic HESS power allocation strategy based on the virtual impedance (VI) for supercapacitor (SC) and the battery is proposed. Dynamic power-sharing of two kinds of energy storage devices can be achieved without real-time measuring of load power. The state of charge (SOC) recovery of SC is achieved with a SOC loop integrated into the VI loop. The principle of dynamic power-sharing of HESS is derived based on the establishment of HESS equivalent circuit model. By analysing the influence of the voltage and current double loop controller parameters on the output impedance and the VI of the DC/AC converter, the method of setting the controller parameters for power distribution is presented. A simulation model is established with the designed equivalent power fluctuation conditions. The simulation results show that under various working conditions, the SC loop can compensate for the high-frequency part of the equivalent power fluctuation and the battery loop absorbs the low-frequency part of the power fluctuation. The dynamic power-sharing of HESS with the SC SOC recovery is realised effectively. [ABSTRACT FROM AUTHOR]

This article deals with a ride-through strategy for a three-phase grid-tied solar photovoltaic array system. Unlike the conventional control algorithms, this control algorithm does not tradeoff with power quality melioration features while permitting ride-through dynamics of the solar energy conversion system (SECS). As per the revised IEEE-1547 standard, the distributed energy resources have to provide a full range of services even under voltage disturbances caused by faults like existing power plants. In this article, the grid-connected solar power generation system follows the grid code even under ride-through operation with the presence of reactive local load, unlike the traditional algorithms. In order to map future challenges, the low-voltage ride-through features of three-phase SECS at symmetrical/asymmetrical faults, are explored here. This control strategy is capable to operate SECS at various modes. To operate the voltage source converter within a safe limit, a constraint is incorporated on the active power of SECS to avoid overcurrent and energy aggregation in the dc-link capacitor, which reduces the life-time of the dc-link capacitor. Simulated results demonstrate the effectiveness of the control strategy for various operating conditions. The comparative performances of the presented control strategy are analyzed to demonstrate the effectiveness under the presence of distorted grid voltages and non-Gaussian noises in sensed measurements. Test results manifest the dynamics of SECS at various operating conditions. [ABSTRACT FROM AUTHOR]

A three-level three-phase single-stage high-frequency link dc–ac converter is reported in this article for grid integration of photovoltaic sources. The proposed topology employs two three-level neutral point clamp (NPC) half-bridge legs on the dc side. The advantages of using three-level legs over conventional two level are: 1) the three-level legs can be implemented with the devices with lower blocking voltage which are economical; and 2) the low voltage blocking devices have lower on-state drop and lower turn on–off energy losses compared to high voltage blocking devices used in a two-level leg. These help to improve the converter efficiency. The sinusoidal pulsewidth modulation is implemented with the three-level NPC legs. The modulation strategy ensures reduced neutral current drawn by the NPC legs. The inner switches of the NPC legs are zero voltage switched. The turn-on transitions of the outer switches are with zero current. The proposed solution employs two high-frequency transformers to provide galvanic isolation which results in compact, low cost isolated converter solution. The intermediate dc link is pulsating and does not require any filtering. A low-frequency unfolder is employed to generate line frequency ac from pulsating dc. The switching loss of the unfolder is negligible. The proposed topology can support stand-alone load up to $\pm 0.866$ PF. The converter operation is verified on a 2-kW hardware prototype. [ABSTRACT FROM AUTHOR]

Power-electronics-based emulators have been showing promising prospects in advanced testing of various applications of power electronics systems. For electric machine applications, typical machine emulators calculate the references of stator current in response to terminal voltages via mathematical models of the machine system, and then, the current behaviors of emulators are regulated by using feedback controls. However, the dynamic and high-frequency performances of these machine emulators could be distorted by the introduced control loops, thus compromising the emulating performances. In this article, the limits of typical machine emulators are analyzed, and a new approach is proposed for the real-time emulation of permanent magnet synchronous machines (PMSM). A linear regulator without feedback control loop is proposed and designed to reshape the frequency-domain characteristics of the converter and current filter inside the emulation system. Compared with typical solutions, the proposed approach has frequency-domain characteristics closer to the target PMSM. The dynamic performances can be more accurately recreated, and the applicable frequency range for emulation can be extended. Simulations and experimental validations are also conducted to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper a novel concept of event triggering control (ETC) for effective resource utilization is proposed for dc microgrid. Matched uncertainty elimination is possible through sliding mode control (SMC) itself as addressed in the literatures. This paper proposes a new approach for suppression of both matched and unmatched uncertainties in grid connected and islanded mode through an integral disturbance observer (IDO) which is designed with super twisting SMC to provide dual filtering phenomena pertaining to system perturbations. The IDO facilitates control algorithm to manage effective event counts during disturbance conditions. The proposed controller is designed in order to regulate DC bus voltage and enhance the microgrid capability to perform stable operation in presence of uncertainties. Chattering free finite time convergent SMC is designed with super twisting reaching law to obtain robust behavior of dc microgrid. Results are compared with power rate reaching SMC, Nonlinear disturbance observer (NDO) based controller and PI controller. In the proposed work event triggering condition is designed first time under super twisting reaching law. Comparative assessment is accomplished in lieu of demonstrating the superior performance of event trigger SMC through MATLAB/Simulink and Typhoon based controller hardware in loop (CHIL) platform. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MLI) with reduced components are becoming popular to achieve higher voltage levels with lower cost and complexities of the circuit. Most of the reduced switch MLIs use a large number of isolated voltage sources that have a large total standing voltage (TSV) and higher losses. Moreover, many reduced component MLIs have been developed to reduce the number of switches only and have not utilized the dc-link voltages properly. Thus, an inverter needs to be designed in which the number of dc sources is also small and utilized fully. In this paper, a novel single-phase, multicell MLI configuration is presented that can generate a maximum number of output voltage levels using a minimum number of switches and dc sources. Two optimal configurations of the proposed MLI are proposed based on the minimum requirements of components with the optimum voltage stress of the highest rated switches. Moreover, the TSV of the proposed optimal MLI also becomes low. A generalized multicell optimum MLI is presented and the number of components, voltage stress of all the switches, and the TSV of the proposed as well as the other inverters also determined by the generalized expressions for comparison purpose. The prototype of a specimen 15-level inverter and the optimal 75-level inverter cell is further developed and implemented using DS 1103 in the laboratory to show the effectiveness of the proposed configuration. The experimental results corresponding to the different modulation indices are presented here for the verification of the simulation results. [ABSTRACT FROM AUTHOR]

The cascaded control method with an outer voltage loop and an inner current loop has been traditionally employed for the voltage and power control of photovoltaic (PV) inverters. This method, however, has very limited power regulation capability. With the fast increasing penetration of PV power generation systems in the distribution network, the voltage rise/drop has become a serious problem impacting negatively on the power quality and grid stability. Therefore, flexible power regulation is highly desired for PV inverters to provide ancillary services. This paper proposes a novel model predictive power control (MPPC) scheme to control and coordinate the dc–dc converter and inverter for grid-connected PV systems with energy storage systems (ESS). By regulating the dc-bus voltage and controlling the active and reactive power flows, MPPC can support the power grid to maintain stable voltage and frequency and improve the power factor. Numerical simulation and controller hardware-in-the-loop (CHIL) testing have been conducted on a PV-ESS system to verify the capability and effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This article presents the behavior of an inverter in both DC-DC and DC-AC configurations controlled with a quasi-sliding control technique known as ZAD-FPIC. An analysis of transient behavior, disturbances in the load, changes in the reference signal, and disturbances in the power supply are presented, and control techniques have been designed to manage an inverter in real-time. The software has been designed to execute the controllers by using Simulink- MATLAB libraries and the ones provided when installing the DS1104 board. The digitally implemented ZAD-FPIC controllers use a DS1104 in order to control the converter and thus meet the requirements of fixed switching frequency, robustness, and good performance in DC signal regulation tasks. The controllers work well during the transient state because they dampen overshoots and reduce settling times. The results show that the system regulates well before changes of the reference and rejects disturbances in the load and the source voltage. Additionally, it has been observed that the regulation error varies depending on the reference voltage level. [ABSTRACT FROM AUTHOR]

The use of renewable energies sources is taking great importance due to the high demand for electricity and the decrease in the use of fossil fuels worldwide. In this context, electricity generation through photovoltaic panels is gaining a lot of interest due to the reduction in installation costs and the rapid advance of the development of new technologies. To minimize or reduce the negative impact of partial shading or mismatches of photovoltaic panels, many researchers have proposed four configurations that depend on the power ranges and the application. The microinverter is a promising solution in photovoltaic systems, due to its high efficiency of Maximum Power Point Tracking and high flexibility. However, there are several challenges to improve microinverter’s reliability and conversion efficiency that depend on the proper control design and the power converter design. This paper presents a review of different control strategies in microinverters for different applications. The control strategies are described and compared based on stability, dynamic response, topologies, and control objectives. One of the most important results showed that there is little research regarding the stability and robustness analysis of the reviewed control strategies.

Nowadays, energy storage systems, such as batteries, are spreading in many applications. Among the kinds of batteries, the lithium-ion technology is one of the most promising solutions. Considering the photovoltaic (PV) plants, it is very important to perform a correct sizing of the battery pack to both maximise the self-consumption and minimise the total costs. In general, PV plants need a dc–dc converter to maximise the electric power that can be extracted from PV panels and a dc–ac converter to connect them to the ac grid. The battery pack can be connected in three different ways: dc coupled and ac coupled using a dedicated converter or through a direct connection on the dc-link between the dc–dc and dc–ac converters. In the present study, the last solution, without any dedicated converters, is used and a simple control strategy to both maximise the power extracted from the PV panel and regulate the charging/discharging of the battery is proposed.

This paper proposes a soft-switched modulation technique with synchronous rectification for an isolated single-stage single-phase matrix-type dc–ac converter. The dc side consists of a full bridge inverter, and the ac side is a 2×2 matrix converter-based cycloconverter. The proposed unipolar modulation strategy provides zero current switching/zero voltage switching (ZVS) for the ac side devices and ZVS-on for the dc side devices. It also allows natural commutation of the current flowing through the secondary side leakage inductor of the isolation transformer and the grid inductor during unity power factor (UPF) condition, thus eliminates the requirement of snubber circuit. An improved soft-switched flyback-based regenerative snubber circuit is also presented for non-UPF operation. Proposed snubber circuit recycles the energy stored in the snubber capacitors in every switching cycle. A guideline to design snubber circuit along with a comparative study is discussed in this paper. Performance of the proposed hybrid modulation technique is evaluated in an SiC mosfet based 1.2-kW dc–ac converter prototype. A detailed analysis of the converter performance has been presented in this paper considering the circuit non-idealities. [ABSTRACT FROM AUTHOR]

A novel single-stage high-frequency link three-phase ($3\phi$) inverter along with a modulation strategy is presented in this paper. The topology is targeted for grid integration of utility scale renewable and alternative energy sources like solar, fuel cell, and wind, where the power flow is unidirectional (from dc to ac). The primary side converter has a $3\phi$ voltage source inverter (VSI) structure along with an additional half-bridge leg. Sinusoidal pulsewidth modulation is implemented in the primary side converter. The three legs of the primary side VSI are zero voltage switched (ZVS) for most part of the line cycle. The additional half bridge leg is ZVS over the complete line cycle. The active switches in secondary side converter are line frequency switched and thus results in negligible switching loss. The converter switching process is described in detail to show the soft-switching of the primary side converter using the device capacitances and leakage inductances of the high-frequency transformers (HFTs). The HFT galvanic isolation results in high power density. A 4-kW laboratory scale hardware prototype is built and tested with the proposed modulation strategy. The experimental results are presented to verify the converter operation. [ABSTRACT FROM AUTHOR]

This paper proposes a new class of topologies of single-stage high-frequency ac-link power converters, which is capable of providing both voltage step up/down within a wide frequency and voltage ranges. The proposed family, which supports bidirectional power flow, can interface various single/multi-port dc and/or single/multi-phase ac systems to provide dc–dc, dc–ac, ac–dc, or ac–ac power conversion. In this family of converter, which offers a very modular structure, a small inductor that forms the link exchanges power entirely or partially between the source and load. The proposed family can function in buck, boost, and/or buck–boost modes of operation, and a combination of these modes of operation is also feasible. In comparison to the parallel inductive four-quadrant link converters, the proposed family features a significantly reduced link peak current, reduced switch ratings, and reduced total number of power switches. These features enhance the efficiency, reduce the total cost, and increase the power density of the system. In order to further improve the overall efficiency of the system, minimize the current/voltage stress over all utilized semiconductor devices, and lower electromagnetic interference (EMI), a small capacitor is placed in parallel with the link inductor to realize soft-switching operation for the proposed configurations. Moreover, the proposed converters have the potential to incorporate a lightweight single-phase high-frequency transformer for electrical isolation. The proposed circuit topologies prevent reverse recovery issues and eliminate losses corresponding to body diodes of power switching devices via utilizing power switches in conjunction with external fast recovery diodes. The proposed family offers a very high level of reliability owing to its immunity from short circuit of input and output terminals and open circuit of the link inductor, which may occur in other power converters due to commutation problem resulting from a short deadtime or an overlap time between switches, unwanted control command, delay in electronic circuits, or EMI noise's misgating on or off, in addition to the absence of electrolytic capacitors in the power circuit. A control approach is also developed to regulate input and output currents in one stage of power conversion. A detailed theoretical analysis, operation, design methodology, and control strategy of the proposed family are provided in this paper, and the effectiveness and performance of the proposed converter family are verified via simulation results and experimentally. [ABSTRACT FROM AUTHOR]

This paper describes a novel family of single-phase single-stage buck–boost inverters using output unfolding circuits. Operation principles and component design guidelines along with modulation techniques are presented and discussed. The simulation results confirm all theoretical statements. Experimental setup of the most promising solution is assembled and tested, where the efficiency for different operation modes is analyzed. Finally, the pros and cons along with applications of the proposed solutions are discussed in the conclusions. [ABSTRACT FROM AUTHOR]