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The main aim of the research work presented in this paper consists of proposing an effective control scheme for a grid-connected single-phase photovoltaic (PV) system to enhance not only the power quality at the point of common coupling (PCC) but also to operate with a maximum power point tracking (MPPT) controller. Moreover, an orthogonal signal generator (OSG) module for effective grid synchronization, a current reference generation controller, and a PWM generating block have also been designed and included in this paper. The proposed control strategy allows the MPPT controller to switch to faulty mode and maintains the voltage according to network requirements using an adaptive neuro-fuzzy inference system (ANFIS)-based control whenever a fault occurs at the PCC. The performance of the analyzed control strategy, which is based on the static compensation of the DC-link voltage fluctuations in a grid-connected inverter powered by PV, is further explored through simulations in MATLAB, and the results are included in this paper. Moreover, the control scheme is implemented experimentally using a dSPACE DS 1104 control board and then assessed on a small laboratory-scale single-phase PV system that is subjected to some fault scenarios. The simulation and experimental results have shown improved power quality and robustness against grid fluctuations, resulting in better dynamic performance. [ABSTRACT FROM AUTHOR]

This paper introduces a mathematical design and analysis of three-phase inverters used in electric drive applications such as aerospace, electric vehicles, and pumping applications. Different wide bandgap (WBG) semiconductor technologies are considered in this analysis. Using SiC MOSFETs and Si IGBTs, two drive systems are developed in order to show the improvement in the efficiency of the inverter. The efficiency, total losses of the drive systems and the power losses of two inverters are computed and compared for both drive systems at the same operating condition. The drive system with SiC MOSFET shows much better performance compared to the drive system with Si IGBT. The SiC MOSFET system provides a 59.39%, 86.13%, and 29.76% lower conduction losses, switching losses and drive's total losses, respectively, compared to the Si IGBT system. The efficiency of the SiC MOSFET system is 2.46%pu higher than the efficiency of the Si IGBT drive system. Moreover, this paper introduces a detailed analysis for the dc-link voltage and current ripples in three-phase inverters. Furthermore, the minimal dc-link capacitor needed to deal with the ripple current and voltage is investigated. Finally, the performance of the drive with Si IGBT is experimentally tested under different operating speeds and loads. [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]

With the emergence of renewable energy sources (RESs), the power grid all over the world is going through a paradigm shift. The inverter based RESs are replacing the conventional rotating synchronous generators and this trend is expected to continue in coming years. Consequently, the grid strength is decreasing, which can pose significant challenges on the grid stability, especially during integration of IRESs. This paper presents a thorough analysis on the integration challenges of IRESs in weak grids. The paper also presents a comprehensive investigation on the impacts of factors, such as available fault level at the point of interconnection (POI), feeder length and grid nature on the POI voltage, and maximum allowable power injection by IRES. This is followed by maximum allowable IRES power injection sensitivity analysis to quantify the impacts of the aforementioned factors. The paper concludes with a thorough case study on the IEEE 39‐bus test system to numerically show the impact of diminishing grid strength on the integration of IRESs. [ABSTRACT FROM AUTHOR]

The paper presents a D-STATCOM Multilevel Cascade Inverter model, which bases on synchronous reference frame control strategy to reduce the current total harmonic distortion. The non-linear loads produce this current harmonic distortion when this load is connected to the analysis bus. The harmonic content of the network is evaluated before and after the strategy compensation. There are different connection and disconnection times of the compensator, to differentiate between distorted waveforms and perfect sine waves. As a result, it is established the strategy performance. The system implementation was carried in MATLAB and Simulink platform, to do the simulation and analysis of the research result. The THD reduction underline the reliability of the proposed strategy. [ABSTRACT FROM AUTHOR]

Changes are being implemented in the electrical power grid to accommodate the increased penetration of renewable energy sources interfaced with grid-connected inverters. The grid-forming (GFM) control paradigm of inverters in active power grids has emerged as a technique through which to tackle the effects of the diminishing dominance of synchronous generators (SGs) and is preferred to the grid-following (GFL) control for providing system control and stability in converter-dominated grids. Therefore, the development of the GFM control is important as the grid advances towards 100% inverter-based grids. In this paper, therefore, we aim to review the changing grid scenario; the behaviour of grid-connected inverter control paradigms and major GFM inverter controls, including their modifications to tackle low inertia, reduced power quality, fault-ride through capability, and reduced stability; and the state-of-the-art GFM models that are pushing the universality of GFM inverter control. [ABSTRACT FROM AUTHOR]

The negative-sequence current component and harmonic components generated when an asymmetrical fault occurs in the power grid seriously affect the normal operation of the photovoltaic (PV) grid-connected inverter. In order to suppress the negative-sequence current component and the harmonic component of the grid-connected current, and to meet the normal grid-connected operation requirements of the PV grid-connected inverter when asymmetrical faults occur in the grid, this paper proposes the proportional integral double-resonant (PI-DR) current controller, which consists of the PI controller and double-resonant controllers. The PI-DR current controller can directly control the negative-sequence current component and the grid-connected current harmonic component in the output current in the forward synchronous rotating coordinate system, without decomposing the positive and negative sequence currents. The PI-DR current controller ensures that the PV grid-connected inverter can realize normal grid-connected operation and improves the quality of the power when an asymmetrical fault occurs in the power grid. MATLAB/Simulink experiments show that the PI-DR current controller can improve the dynamic characteristics of the PV grid-connected inverter and improve the operating capability of the system when an asymmetrical fault occurs in the power grid. [ABSTRACT FROM AUTHOR]

Summary: Nowadays, Z‐source inverter (ZSI) has received several attentions compared to other power converters owing to their simplicity and reliability. In this paper, a refine control methodology of capacitor voltage control is presented based on third‐order small signal analysis. The proposed control is applied to the improved switched inductor ZSI (ISL‐ZSI). Proportional, integral, and derivative controller (PID) is adopted due to their capability to operate with large operation levels, reliable operation, and cheaper implementation. In addition, the function of this control can be achieved even with incomplete system data or parameters variations. ISL‐ZSI has been presented because of its advantages such as the high gain of direct current voltage, low voltage stress for both the Z‐network and the inverter bridge switches, and ensuring good soft starting. In addition, the inrush current has been removed based on its configuration. The proposed control is validated by both experimental and simulation results under input voltage change, load change, and steady‐state operations using DSP F28335 and MATLAB SIMULINK Real‐Time Workspace. [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]

Virtual synchronous generators (VSGs) are one of the most relevant solutions to integrate renewable energy in weak grids and microgrids. They indeed provide inverters characteristics of rotating machines (inertia for instance) that are useful for stabilizing the system, notably in the context of the high variability of the production. Thanks to the virtual characteristics of the VSG, the virtual parameters of the emulated synchronous machine can be optimally adapted online as a function of the electric environment of the inverter. We call that inverter's control a polymorphic VSG. The online adaptation of the critical control parameters of the VSG helps reduce the risk of deterioration of the inverter's constituents that might be induced by harsh events (frequent in weak grids) but, more importantly, improves the robustness of the system. In this paper, four implementations of a polymorphic VSG controller are compared on a simple microgrid study case to a complete VSG model. For the test, polymorphic VSGs have to minimize frequency and voltage oscillations while withstanding short circuits, which is typically a requirement for units in this context. One of the controls is based on recurrent optimization over a prediction time horizon, and two sub-optimal ones target practical implementation in industrial inverters with limited computational power. Results show a clear reduction in incidents in the microgrid thanks to the controllers. The error reduction with the complete polymorphic VSG is up to 100% for the voltage, 32% for the currents, and 79% for the duty ratio. Those values are decreased by 30 to 50% with the sub-optimal controllers but for a reduction in the computational burden of more than 97%. Recommendations are proposed for the development of an auto-adaptive polymorphic VSG from a high technology-readiness-level perspective, i.e., targeting a compromise between error reduction and computational burden. [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]

• A CFD fluid-solid coupling simulation model to study the temperature distribution of stator coils and inverter of an electric scroll compressor was developed and validated. • The temperature distribution of stator coils and inverter under different refrigerant conditions was simulated and analyzed. • The working reliability of stator coils and IGBT modules under the studied refrigeration conditions was checked. • The heat dissipation of IGBT modules and the proportion of heat exchange amount between different parts of compressor housing and suction gas were analyzed. In the electric scroll compressor for vehicle air conditioning, the heat generated by motor and inverter is mainly taken away by suction gas. It is necessary to maintain the working temperature of motor and inverter within a safe range to void overheat or burnout. The temperature distribution of motor and inverter under refrigeration conditions are studied using computational fluid dynamics (CFD) simulation in this paper. At first, a CFD fluid-solid coupling simulation model is developed and verified by temperature measurement experiment. The maximum deviation between the simulated temperature at three points on the compressor housing and the measured results does not exceed ±3°C. Then the velocity and pressure distribution of fluid domain, and the temperature distribution of solid domains including the compressor housing, the stator coils and insulated gate bipolar transistor (IGBT) modules are analyzed. Next, the effects of operation conditions on the maximum working temperature and temperature distribution unevenness of stator coils and IGBT modules are discussed in detail. In addition, the working reliability of IGBT modules under refrigeration conditions is checked and the heat dissipation of IGBT modules is analyzed. [ABSTRACT FROM AUTHOR]

The conventional proportional-gain-feedback link can only obtain the smallest effective damping region (EDR) due to the control delay among all the active damping methods regarding the capacitor current feedback. The digitally controlled system tends to be unstable when the system resonant frequency reaches the critical frequency caused by the grid impedance variation. To weaken the adverse effect on the system caused by the control delay, phase-lead feedback links are applied along the feedback path to provide phase compensation. By taking the simplicity and reliability of the feedback links into account, this paper proposes an alternative to an ideal differentiator, which consists of the Tustin discrete form of 's' and a digital low-pass filter. This proposed method has an identical phase frequency characteristic as an ideal differentiator but a better magnitude frequency characteristic, and its EDR can reach [0, fs/3]. The system stability analysis is conducted under different resonant frequencies, and under the condition of a weak grid, the co-design approach of the active damper and digital controller is presented. Finally, the experimental results are shown to verify the proposed method. [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]

Noise, Vibration & Harshness (NVH) is one of the key parameters associated with comfort of an automobile. An Electric Vehicle (EV) consists of transmission driven by electric motor which ultimately gets its power or current supply from inverter. As per Electric vehicle architecture, motor ranks first followed by transmission and inverter in terms of NVH performance. The function of an inverter is to convert DC current from battery source to 3-phase AC current which goes to electric motor. Torque and speed characteristics of motor is dependent on current and voltage supply from inverter. Hence it is important to assess NVH characteristics of inverter as well. In this paper, vibration and acoustic performance of a standalone EV inverter have been studied by testing it at different vehicle operating conditions. Ideally the output 3 phase AC current from inverter should contain only electrical frequency, but it is observed that AC current contains harmonics in the form of linear combination of electrical frequency and switching frequency. From this study, observations from NVH tests on an EV inverter is highlighted in frequency range where relatively high vibration and noise levels were present. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate and analyze the operation mechanism and power control principle of a bolted Langevin type (BLT)-loaded phase-shifted control inverter and to find a safe power control method for a phase-shifted control inverter used to drive a high-power BLT by preventing the differential current (shock current) from occurring in the right branches of a phase-shifted full-bridge circuit. In this paper, by allowing the inverter operating frequency to operate under inductive loads that coincide with the zero points of voltage and current rather than the resonant frequency of the BLT, which results in the generation of a shock current in the right branch of the full-bridge circuit, the switches of the right-branch also enabled zero-voltage, zero-current switching on (ZVZCS turn-on). The proposed method can fundamentally eliminate the generation of shock current by realizing ZVZCS turn-on on the right-branch switch elements of the inverter. The phase-shift angle control limit for power control by this scheme is 90° and the power control range is 20%–100%. [ABSTRACT FROM AUTHOR]

In traditional grid-tied photovoltaic (PV) installations, when partial shadowing occurs between different PV modules in a string, bypass diodes short-circuit the output terminals of shadowed modules, and the whole system forgoes their potential energy production. This loss can be recovered if a dc-dc converter (micro-converter) is coupled to every PV module, and operated at the maximum power point (MPP). In this scenario, without communication links between the distributed micro-converter and the grid-tied inverter, a start-up procedure must be carefully designed to seamlessly allow the system to transfer PV power to the grid. During this phase, potentially damaging over-voltages and abrupt transients occurring at the micro-converters/inverter interface must be avoided. In this paper, the control algorithm of each micro-converter is enhanced to provide a smooth start-up operation so that PV units can safely start transferring power to the inverter and the grid. Improving from previous works, the proposed control technique is simple and removes the need for current sensors at the output of each micro-converter and at the inverter dc-link, with an economical advantage. Simulation results demonstrate the successful system start-up behavior, whilst confirming the benefits of the proposed control technique. First, the dc-link is energized from the rectified grid voltage. Then, the micro-converters raise the dc-link voltage so that the available PV power is transferred to the grid, with this sequence of operations not causing any abrupt electrical transient. The results also demonstrate the robust behavior of the PV system under non-uniform solar irradiation conditions. [ABSTRACT FROM AUTHOR]

Green energy from Solar PV is getting increased attention in the industries due to the falling price of solar panels in the world market. A grid-tied inverter is one of the major components in such a system, where the DC energy from PV is converted to AC and synchronized with the grid to obtain power sharing between the PV and the grid for the industrial drives. In this paper, a DC link has been proposed instead of an AC link for interconnection between the solar PV system and the grid to run those industrial drives. In most modern industrial applications, induction motors are driven by VVVF (Variable Voltage and Variable Frequency) inverters to achieve efficient speed control. The inverters commonly have a rectifier section at the front end that rectifies the input AC to DC and the DC is then used in PWM mode to generate the required voltage and frequency for the induction motor operating under variable speed and load conditions. Such an inverter can use both AC or DC as the input so long the supply voltage has the right value for the inverter to operate. In our proposition, we eliminate the grid-tied inverter and use a DC link, created from the rectified AC and the regular Solar PV, to obtain the power-sharing between the PV output and the grid. Using the DC link output directly to energize the VVVF inverter has an impact on the performance of the inverter. In the proposed system, the solar PV array is designed in such a way that the grid remains as the supplementary power source only to supplement any shortfall in the PV output due to variable sunshine conditions. The control circuit used in this novel technique is inexpensive, efficient, and simple in design when compared to the grid-tied inverters. The proposed system has been implemented at Niagara Textiles in Gazipur, Bangladesh. The experimental/practical results are presented to validate the basic concept. Around a 20% reduction in the cost of energy has been reported in this paper, with a more than 90% efficient system. This will definitely make solar PV energy more competitive with regular energy and attractive to industries for its simplicity. [ABSTRACT FROM AUTHOR]

This paper addresses the synchronization and operation of a 140 kVA inverter system connected to the main grid as part of a decentralized microgeneration system. The considerations for the supply of electrical energy stored in battery banks, mostly of photovoltaic origin, involve a study of the details of a rigid nonlinear system, which parallels the generation and distribution standards typical of hydroelectric and thermoelectric plants. Considering aspects related to power electronics operation, this paper presents both the modeling and the controlling aspects necessary to synchronize and ensure a stable operation of the microgeneration systems when connected to the main grid. Statistical processing was developed to guarantee synchronization between the systems without presenting electric shocks by simulating the magnetic link in asynchronous generators to meet this aim. The proposed model simulates the increase in power by a phase shift by maintaining a constant frequency based on a Chirp wave generator. The proposed process considers a generation power baseband operation. A Mamdani-type fuzzy proportional-integral controller is used to determine the power setpoint, which sets the Chirp generator phase shift setpoint, which includes a Mamdani fuzzy proportional-type controller. Both controllers are connected in a cascade. The applied correlational technique to achieve the synthesis of the sinusoid and the synchronization presented optimal performance when using 17 samples per signal period. The design of the transformer primarily, guaranteed a phase shift of −4.3018°, allowed for a THD below 2.75%. [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]

Temperature fluctuation is the primary reason for gradual failure of IGBT (Insulated Gate Bipolar Transistor) module in inverter system, and overall thermal management is an effective way to smooth temperature fluctuation and prolong the service life of IGBT module. Currently there are a series of problems with the module temperature management method of inverter system, including complicated control method, limited adjustment range, slow response, and poor control accuracy, etc. To cope with these matters, this paper aims to study a thermal management strategy for inverter system. At first, this paper built a model for temperature prediction and control of inverter system based on linear time-varying state space, the model measures system state based on estimation and can calculate the control variables with the mutual effect between different variables taken into consideration but without the necessity of system decoupling. Then, this paper proposed a thermal management strategy for inverter system based on predictive control and optimized it further. At last, the validity of the constructed model and the proposed strategy were verified by experimental results. [ABSTRACT FROM AUTHOR]

Distributed power generation plays a critical role in the stability and reliability of modern power systems. Due to the rapid growth of renewable energy generation, the requirements of the transmission and distribution system operators are becoming more stringent. Among these requirements, one of the most important is the Low-Voltage Ride-Through (LVRT) capability, which demands that the inverters remain connected to the grid and provide support during voltage sags. For this purpose, flexible current control algorithms stand out because they can manage unbalanced voltages and simultaneously achieve other control objectives. With the aim of presenting a concrete document focused on describing fundamental principles and discussing common design guidelines, this paper presents an overview of flexible current control strategies applied to LVRT capability. The operation features and design aspects of experiences reported in the literature are reviewed. Moreover, the paper proposes a general methodology to design LVRT flexible current control algorithms. Finally, current and future trends are discussed. [ABSTRACT FROM AUTHOR]

Purpose: The conventional two-level inverter suffers from harmonics, higher direct current (DC) link voltage requirement, higher dv/dt and heating of the rotor. This study aims to overcome by using a multilevel inverter for brushless DC (BLDC) drive. Design/methodology/approach: This paper presents a comparative analysis of the conventional two-level and three-level multilevel inverter for electric vehicle (EV) application using BLDC drive. Findings: A three-level Active Neutral Point Clamped Multilevel inverter (ANPCMLI) is proposed in this paper which provides DC link voltage control. Simulation studies of the multilevel inverter and BLDC motor is carried out in MATLAB. Originality/value: The ANPCMLI fed BLDC simulation results shows that there is the significant reduction in the BLDC motor torque ripple, switching stress and harmonic distortion in the BLDC motor fed ANPCMLI compared to the conventional two-level inverter. A prototype of ANPCMLI fed BLDC drive along with field programmable gate array (FPGA) control is built and MATLAB simulation results are verified experimentally. [ABSTRACT FROM AUTHOR]

This paper prompt fifteen level packed U cell (PUC) based multilevel-inverter (MLI) topology for standalone and grid-connected applications. The 15PUC required only eight IGBTs compared with other conventional MLIs (FC, NPC, HCHB and CHB). This paper describes and proposes a sensorless proportional resonant (SLPR) controller with radical multicarrier (RMC) based LS PD-PWM and a novel switching algorithm. These proposed controllers compensate for DC-link capacitor voltages, control third, higher and zeroorder harmonics. The stability analysis and robustness of the proposed SLPR controller with the PUC system have been verified through Bode and Nyquist plots. In addition, the 15PUC system is proving highly efficient-based system through power loss analysis. The effectiveness and performance of 15PUC with proposed controllers are evaluated by using experimentally and MATLAB simulations also. The results are verified through FFT analysis and obtained THD% comes under the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) energy systems have found diverse applications in fulfilling the increasing energy demand worldwide. Transformer-less PV inverters convert the DC energy from PV systems to AC energy and deliver it to the grid through a non-isolated connection. This paper proposes a new transformer-less grid-connected PV inverter. A closed-loop control scheme is presented for the proposed transformer-less inverter to connect it with the power grid. The proposed transformer-less inverter reduces extra leakage current and holds the common-mode voltage at a constant point. To eliminate extra leakage current, as well as achieve constant common-mode voltage, a midpoint clamping method is utilized to operate the inverter. The proposed transformer-less inverter is formed of seven insulated gate bipolar transistors (IGBTs) employing a unipolar sinusoidal pulse width modulation (SPWM) technique for switching purposes. An LCL filter is employed to reshape the two-level inverter output voltage and current to obtain closer sinusoidal waveforms. The output voltage and current total harmonic distortion (THD) of the proposed transformer-less inverter were found to be 1.25% and 0.94%, respectively, in the grid-connected mode. The leakage current elimination mechanism with the proposed transformer-less inverter is deeply analyzed in this paper. The performances of the proposed transformer-less inverter were evaluated with MATLAB/Simulink simulation and validated in a laboratory scale experiment. [ABSTRACT FROM AUTHOR]

In this paper, the method and a control algorithm for detecting resonant destruction of a resonant auxiliary power supply for railway vehicle are proposed. It is essential to reduce the weight of the electric equipment attached to the lower part of the railway vehicle because it greatly affects the life of the railway vehicle, such as wheel and bearing. In order to reduce the weight and volume of the auxiliary power supply, in the case of windings, high-speed switching should be performed by lowering the input voltage. Therefore, in this paper, the auxiliary power supply control algorithm using an LLC resonant converter to reduce the weight of auxiliary power supply for railway vehicle is proposed, and the method of detecting resonant destruction due to device failure of a resonant converter is proposed. The proposed algorithm steps down the wire voltage using an input buck converter for high-speed switching, and the inverter input voltage is controlled through the LLC resonant converter. In addition, ZVS (Zero Voltage Switching) is operated to minimize the loss of the resonant converter, and the optimal design of the resonant tank is also proposed. In order to detect resonant destruction, a detection method formulated by analyzing the resonant current peak value for the load capacity is proposed. The algorithm proposed in this paper is verified by simulation and experiment. [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]

In this paper, a higher level symmetrical and asymmetrical multilevel inverter (MLI) with reduced device count is proposed for renewable energy systems. Multilevel inverters are recently gaining importance in renewable energy systems and other DC to AC conversion applications due to reducing voltage stress, low total harmonic distortion (THD) and high-quality output as compared to classical inverters. This paper present a basic cell unit of reduced device count (RDC) MLI with six switching devices is proposed. The topology has advantages of reduced device count over existing topologies for the same number of output levels, thus improving operating efficiency and reliability. Upon cascading two such basic cells with 12 devices synthesizes a 49 level output with an estimated THD of 1.63%. The other advantages accrued due to reduced device count are a reduction in switch driver circuits, less number of required dc voltage sources, less installation space and reduction in cost. The major benefit of the proposed topology is that it can deliver power from an asymmetrical source to load even under sudden variation in environmental conditions. The proposed MLI topology is simulated in MATLAB/Simulink environment and a laboratory prototype is developed and tested in the lab. The control paradigm is developed as the Simulink model, which is interfaced with dSPACE DS-1104 for generating control pulses to drive switches of proposed MLI topology. The experimental results validate the concept and paradigm of the proposed MLI topology. [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]

Using a low pulse ratio, the electromagnetic interference and switching loss of an inverter can be effectively reduced, particularly in high-power applications. However, due to variations in grid impedance, it is a challenging task to achieve stable operation of an LCL-type grid-connected inverter (GCI) using the active damping method with low pulse ratio. Thus, a novel three-phase dual-frequency GCI is presented to ensure the symmetry of the output power and the stable operation of the system address stability issues. The proposed inverter topology in this article is composed of two inverters in parallel, which are, respectively, a power inverter unit (PIU) and an auxiliary harmonic elimination unit (AHEU). To reduce the switching loss and improve the inverter efficiency, the switching frequency of the PIU is relatively low, injecting current into the grid. Moreover, the feedforward compensation method is used in AHEU. AHEU operates at high switching frequency to generate a current component that is symmetrical with the ripple com-ponent, improving the power quality, without extracting the current harmonic as the current reference. The operating principle of feedforward compensation is explained, and a proper parameter design procedure is presented in this paper. Since L filters are used for the proposed inverter, the system can operate stably where the ratio of switching frequency to fundamental frequency is low. A 10 kW laboratory prototype was built. The experimental results showed that the grid current ripple could be effectively eliminated and the THD of the grid current was 3.01%. The proposed inverter has good stability in a weak grid, and the efficiency of the proposed inverter is 95.98% at rated current, which is 0.81% higher than the traditional GCI, effectively increasing the efficiency of the system. [ABSTRACT FROM AUTHOR]

In response to the model predictive control (MPC) driving system, this paper proposes a multi-adjustment strategy for phase current reconstruction based on a coupled current sampling method. The proposed coupled current sampling method eliminates the need to modify the inverter's internal wiring. The current signals utilized in the proposed method are all external current signals from the inverter and do not involve any current signals from the internal circuitry of the inverter. By analyzing the current sampling mechanism of duty-cycle model predictive control (DC-MPC) as a modulation method, the underlying principles of the non-reconstructible current regions in the coupled current sampling method are revealed. The non-reconstructible regions are accurately delineated into low and high-modulation regions using coupled current sampling. A multi-adjustment strategy for phase current reconstruction is proposed to address the non-reconstructible regions. In the low-modulation regions, phase current reconstruction is achieved through compensated voltage vector pulse injection. In the high-modulation regions, phase current reconstruction is accomplished using the zero-voltage vector insertion approximation method, which maintains the symmetry of the PWM waveform and avoids current distortion. Experimental results on a permanent magnet synchronous motor validate the effectiveness and feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review of reduced device count multilevel inverter (RDC MLI) topologies for PV systems. Multilevel inverters are widely used in medium-voltage and high-power applications such as wireless power transform applications, flexible AC transmission (FACT), active filters, AC motor drives, high-voltage DC transmission (HVDC), and renewable energy sources due to their high modularity and high-power quality output. Multilevel inverters have the ability to diminish the harmonics content in the output voltage by applying various modulation techniques. The literature in this field showed that the high-power quality and high modularity of the output demand an undeniable need for multilevel inverter topology. Research in this field has identified various multilevel inverter topologies, each possessing their own merits and demerits. The ubiquitous availability of multilevel inverter topologies illustrates the complexity of their accurate selection. To avoid such complexity, this review shows the state of the art of various reduced device count (RDC) multilevel inverter (MLI) topologies. Details of the various RDC MLIs, along with their comparisons, are provided in this paper. This review will be an important reference tool for future work on RDC MLI for photovoltaic (PV) systems. [ABSTRACT FROM AUTHOR]

Summary: This paper presents an efficient Doherty power amplifier (DPA) with optimized harmonic impedance inverter. The proposed design consists of carrier and peaking power amplifiers designed for class F‐ and class F−1‐based operations. Also, multiharmonic non‐uniform stepped‐impedance transmission line‐based input–output matching network is designed for the proposed circuit. The new design maximizes the operating bandwidth by optimizing the control harmonic impedance inverter. The DPA circuit is implemented using the advanced design system simulator, and the chip is made of GaAs 0.25‐μm PHEMT on silicon nitride monolithic microwave integrated circuit die. The fabricated chip exhibits drain efficiency (DE) of 41%–51.5%, power added efficiency of 36.4%–41%, gain of 10.9 dB, and adjacent power leakage ratio of −34.6‐dBc at 30‐dBm peak power. The size of the chip is 2.8 × 1.9 mm2, and it occupies less die area as compared to the existing DPAs. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of 255 kW grid-connected solar photovoltaic (SPV) system. To study the performance characteristics of the grid-connected SPV system, a new hybrid adaptive grasshopper optimization algorithm with the recurrent neural network (AGO-RNN) control technique was implemented. Furthermore, the power quality at the point of common coupling (PCC) has been studied using the conventional (PSO) and proposed AGO-RNN controllers. The characteristics of the PV system were analyzed under varying environmental (variable irradiance and temperature) conditions considering 3 different cases such as (i) standard test conditions (STC), (ii) variable radiation with constant temperature, and (iii) variable radiation with variable temperature. For each case, the total harmonic distortion (THD) has been calculated using the proposed AGO-RNN control technique, and the results were compared with particle swarm optimization (PSO) technique. The 255 kW PV model is initially developed and connected to a three-level NPC inverter, an MPPT-based perturbation and observation algorithm. Later, the PV model is controlled by an AGO-RNN pulse width modulation (PWM) controller and is then integrated to the main grid at PCC. The main advantage of this technique is exploiting the separate DC-DC converter between the SPV module and the inverter. Finally, the proposed grid-connected SPV system was simulated on MATLAB for analyzing the performance of the system based on its I-V and P-V characteristics, inverter voltage, grid power, gird voltage, grid current, power factor, and THD under different environmental conditions. The simulation results demonstrate that the current magnitude and THD of the SPVGC system are improved with the cutting-edge AGO-RNN controller compared to PSO in all three different scenarios, and this value is less than 1.6%, which is within the permitted limits of IEC 61727 standards. [ABSTRACT FROM AUTHOR]

In this paper, the explicit state-space model for a multi-inverter system including grid-following inverter-based generators (IBGs) and grid-forming IBGs is developed by the two-level component connection method (CCM), which modularized inverter control blocks at the primary level and IBGs at the secondary level. Based on the comprehensive state-space model representing full order of system dynamics, eigenvalues of the overall system are thoroughly analyzed, identifying potential adverse impacts of not only grid-following inverters, but also grid forming inverters on the system smallsignal stability, with the underlying principle of oscillations also understood. Numerical and simulation results validate effectiveness of the proposed methodology on IEEE benchmarking 39-bus system. [ABSTRACT FROM AUTHOR]

In recent years, the traditional power inverter systems have been replaced by the modern impedance source inverter (ZSI) circuit topology which became highly popular due to many benefits such as voltage boosting ability, reduced cost, flexibility, and, less sensitivity to electromagnetic noises. This paper presents an improved single-phase quasi-Z-source inverter (qZSI) circuit model. The input inductor of the qZSI circuit has been replaced by a switched-inductor (SL) configuration which is integrated into DC power source and impedance network. The proposed circuit can make use of the stored DC power with the help of the SL form within the shoot-through time interval. In comparison with the conventional qZSI topology, the proposed model increases the boost factor of the qZSI circuit significantly for the same shoot-through time. In addition to that, the circuit draws continuous input current and shares common ground with DC power source. The operation principle is analyzed with the help of the mathematical equations and simulations are carried out using Matlab/Simulink environment. A laboratory prototype is realized to validate the proposed circuit. Simulation and experimental results are presented to illustrate the performance of the proposed inverter topology. The presented circuit model is open to new developments and can be used for low power applications such as photovoltaic (PV) and fuel cell systems. [ABSTRACT FROM AUTHOR]

Recently, the establishment of technical standards for grid connection has gained interest in academia and industry. These standards have focused on the reactive power control function of the grid-connected inverter and maintenance of grid operation, and include detailed information about the grid support function. However, remote control communication and control devices for grid support functions, and other distributed sources, such as wind power and energy storage systems, other than inverters have not been addressed. In this paper, the control of the interlinking converter (ILC) in a hybrid microgrid considering low voltage ride-through (LVRT) among grid support functions is investigated. The proposed method consists of an energy management system considering LVRT and a cooperative control scheme. In the energy management system, an algorithm capable of mode selection was constructed by applying the LVRT curve. Then, considering the LVRT situation, the allowable reactive power range of the ILC was mathematically analyzed through the cooperative control of the energy storage device and the ILC. The proposed method enables us to perform active and reactive power control of the ILC in a hybrid distribution network, considering the power factor under various conditions. This functionality, such as supplying reactive power, significantly contributes to the enhanced grid resilience with distributed power sources, including renewable energy. The proposed strategies were verified through experiments after configuring an experimental set of distributed power sources. [ABSTRACT FROM AUTHOR]

According to the traditional voltage and current double closed-loop control mode, the inverter management strategy for photovoltaic grid connection has insufficient anti-interference ability and slow response. This paper proposes a control strategy that applies adaptive-linear active disturbance rejection control (A–LADRC) to the outer loop control to achieve the purpose of anti-interference. The control strategy uses the linear extended state observer (LESO) to evaluate external interference caused by the change of external conditions and the internal disturbance caused by parameter uncertainty. PD controller compensates the disturbances and adds adaptive control to simplify parameter adjustment. Finally, this paper takes advantage of Lyapunov theory to conduct stability analysis. Compared with the traditional linear active disturbance rejection control (LADRC), the superiority of this control strategy is verified. The experimental results show that the system has better control performance and anti-interference ability in the face of various disturbances. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present the design and implementation of a new general-purpose single-phase buck-type inverter. Design/methodology/approach: The operation of the proposed inverter is based on the general-purpose buck converter. The proposed buck-type inverter topology is designed with reduced numbers of passive and active elements to minimize design cost and complexity. Also, an efficient hybrid control technique based on the proportional‐integral‐derivative (PID) supported by open-loop control signal is offered for the control of the proposed inverter. The proposed hybrid control method improves the performance of the PID controller during the change of inverter operation parameters. A close to single-phase sine wave output voltage with low total harmonic distortion (THD) can be produced by the proposed inverter in a wide range of voltage and frequency lower than the inverter input voltage value. Findings: Simulation and experimental test studies are applied to the proposed inverter. The experimental laboratory setup is built for 0–50 Hz, 0–100 Vp, 0.5 kW. Both the simulation and the experimental test results show that the single-phase inverter can produce close to sine wave output voltage with THD level under 5% in a wide range of frequency for various operating conditions and for different loads. Originality/value: In this paper, a new topology and a new hybrid control technique that are patented by the corresponding author are implemented for a single-phase buck-type inverter through a scientific project. The operating results of the study reveal the efficient operating capability with a simple topology structure. [ABSTRACT FROM AUTHOR]

The conventional DC-link type quasi-Z-source inverter has been known as a buck–boost inverter with a low component voltage rating. This paper proposes an active DC-link type quasi-Z-source inverter by adding one active switch and one diode to the impedance-source network to enhance the voltage gain of the inverter. As a result, the component voltage rating of the inverter is significantly reduced, which is demonstrated through some comparisons between the proposed topology and others. A discontinuous pulse width modulation (DPWM) scheme is proposed to control the inverter, which reduces the number of commutations compared to the traditional strategy. Under this approach, the insertion of a shoot-through state does not cause any extra commutations compared to the conventional voltage-source inverter. Details about control implementation, steady-state analysis, and design guidelines are also presented in this paper. Simulation and a laboratory prototype have been built to test the proposed inverter. Both buck and boost operations of the proposed inverter are implemented to validate the performance of the inverter. [ABSTRACT FROM AUTHOR]

Different types of distributed generation (DG) units based on renewable and non-renewable energy sources can create a local energy system in microgrids. The widespread penetration of distributed energy resources (DERs) has affected many power system issues, such as the control and operation of these networks. For the optimal operation of microgrids, optimal energy planning and management in the new space governing the distribution system requires extensive research and analysis. Getting acquainted with the latest research about the evaluation of the problems and challenges in the design of control systems plays an important role in providing a guidance map for researchers to find the recent challenges and propose new solutions. This paper tried to list the challenges of distributed generation sources for MG applications, opportunities, and solutions. These challenges are reported in hierarchical control strategies and power-sharing categories. Therefore, Model Predictive Control (MPC)-based approaches are reviewed for different recent control levels and power sharing strategies in a comprehensive and simple point of view. The performance comparison of MPC methods together and different allocated fitness functions and implementation algorithms are dedicated. Another hand, the potential of MPC methods to control inverters for increasing the reliability of the grid, which this feature could not be achieved by using conventional strategies, while has not been investigated by researchers widely, is introduced in a short review. Therefore, this paper shows an intersection guidance map for readers to facilitate future research works in these exciting and undiscovered fields. [ABSTRACT FROM AUTHOR]

Multilevel Inverters (MLIs) are widely sought after in medium-voltage applications like electric ships, electric aircraft, and renewable energy integration due to excellent advantages like lower device stress, better power quality, and modularity. However, non-sinusoidal excitations from MLIs pose a serious problem to motor-insulation and lead to their premature breakdown. This paper investigates stress in medium-voltage motor insulation when the stator winding is excited by 3-, 5-, and 7-level multilevel inverter output waveforms. The effect of firing angle on insulation stress is also studied for each of the multilevel inverters. Results show that in addition to the number of output voltage levels, PWM wave shape is a critical factor which affects the insulation stress. Both these factors work together to impact the insulation health. A strong correlation is shown between the increase in the voltage root mean square (RMS) value and increase in dielectric stress when ignoring the dv/dt impact for a fixed DC input voltage and operating frequency of the inverter. Similarly, the dielectric stress in the stator insulation increased with an increase in firing angle for each of the MLIs. This paper shows a potential that both the RMSs can be optimized to reduce the insulation stress and improve the power quality of MLIs in medium voltage drives. [ABSTRACT FROM AUTHOR]

This paper presents an efficiency analysis of the six‐phase induction motor (SPIM) drive using a five‐level dual three‐phase space vector pulse width modulation technique. A dual three‐phase space vector is obtained by decomposing a five‐level six‐phase space vector into two three‐phase space vectors, which greatly simplifies the algorithm. This paper also presents a comparative efficiency analysis of SPIM drive with its three‐phase counterpart. As a proof of concept, Matlab/Simulink environment was used to simulate the proposed scheme. In addition, a prototype was developed and tested in the laboratory. Experimental results validate the simulation results to a good degree of satisfaction and verify the correctness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In general, severe load imbalances in small AC micro-grid systems can degrade their operational performance and their maintenance. This is because the unbalanced load in the micro-grid affects the energy flow and the voltage regulation functions of each phase. In order to solve the voltage imbalance problem, several algorithms for the 3-phase 4-leg CVCF inverter have been proposed, but the control algorithms are not enough to operate the 4-leg CVCF inverter in a stable manner. Therefore, this paper proposes a single-phase voltage and power control algorithm for the 3-phase 4-leg CVCF inverter based on a dq control in order to improve the voltage imbalance problem caused by a severely unbalanced load, where the single phase voltage control algorithm is composed of an αβ-dq and a dq-αβ transformer, a voltage and a current controller, and an off-set controller and a PWM, and the single-phase power control algorithm is also composed of an αβ-dq and a dq-αβ transformer, an active/reactive power and a current controller, and an off-set controller and a PWM. Additionally, this paper performs modeling of the single-phase voltage and the power controller for a 4-leg CVCF inverter using the Matlab/Simulink S/W. From the simulation results, it is confirmed that the transient stability of the proposed single voltage control algorithm can be improved compared to the conventional control algorithm, and voltage control can also be maintained in a stable manner under extremely unbalanced conditions. Further, it is confirmed that 3-phase currents of the proposed single-phase power control algorithm are controlled in a stable manner under extremely unbalanced conditions. [ABSTRACT FROM AUTHOR]

In this paper, a new control mechanism has been proposed for grid-connected three-phase inverter that provides regenerative energy recuperation in direct current (DC) rail transit. In DC rail transit, line voltage can change dynamically depending on the regenerative energy generated by the trains during braking. In order to respond rapidly to dynamic changes in line voltage, a proportional-integral-derivative (PID) controller designed based on the dominant pole assignment method has been used in the control structure of the inverter. With the proposed control mechanism, the PID controller design has been performed considering the current loop. Thus, the design accuracy has been increased. The derivative effect of the PID provides fast response to these changes in line voltage by increasing the speed of the system response and the slow dynamic response of PI-based control structure has been improved. In addition, a new operating strategy that considers two different voltage values, unlike the systems that operate at constant voltage value in the literature, is proposed. This operating strategy provides more regenerative energy recovery by increasing the inverter operation region and contributes to energy efficiency. Finally, a detailed model of a real system has been developed in Matlab/Simulink environment. The simulation results comparing the performance of the PID-based control structure with the PI-based control has been presented to illustrate the feasibility and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

Summary: Solar photovoltaic (SPV)‐based single‐phase inverters are universally accepted and commercially utilized renewable power converter system. Generally, the magnitude of the inverter output is perturbed on load variations, and the intermediate DC‐DC boost converter output is perturbed because of the solar availability. The main intermediary component is the DC‐Link capacitor. The regulation of DC‐Link voltage is the key factor in maintaining the stability of the system with bilateral power converters. In the existing methods, individual Sliding Mode Control (SMC) are used to maintain the stability of the converters independently. However, the individual SMC's do not have any corelated control to address the common problem of DC‐Link voltage regulation. This paper proposes an alternative solution with Coupled SMC (CSMC) to address the problem of regulating the DC‐Link voltage. Both the Boost‐SMC and Inverter‐SMC are individually developed and controlled in a unified approach by having mutual adjustments in the converter and inverter switching pulses. The CSMC strategy is developed in Matlab and experimented using dSPACE‐MicrolabBox. The validation tests are compared with conventional SMC, which shows the betterment of CSMC in robustness and waveshape tracking. [ABSTRACT FROM AUTHOR]

Summary: The phase‐locked loop, as a method to extract grid voltage phase angle, is commonly used for grid‐connected inverter to synchronize the injected grid current with the grid. However, the phase‐locked loop will also bring some problems. The current loop controller, the phase‐locked loop, and the grid impedance are coupled together under the weak grid. Then, the phase angle of the inverter output impedance will be reduced, causing the system to be unstable. Moreover, the output phase angle of the phase‐locked loop participates in the coordinate transformation under the unbalanced grid voltage condition, which degrades the quality of the injected grid current generated by the inverter with high harmonic content. Therefore, a vector current control strategy without phase‐locked loop derived from direct power control is used in this paper. An adaptive linear Kalman filter algorithm is also applied to observe the voltage information and avoid the harmonic problems caused by power calculation. Finally, simulations and experiments are conducted to verify that the proposed method is effective, and the results are consistent with the theoretical analysis. [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]

To realize the efficient transient simulation of a grid-connected power generation system based on multiple inverters, this paper proposes a hybrid simulation method integrating the models of electromagnetic transient and dynamic phasors. Based on a demonstration of the concepts and properties of dynamic phasors, the models of single-phase and three-phase inverters described by dynamic phasors are established first. Considering the numerical compatibility problem between dynamic phasors and instantaneous values, an interface scheme between dynamic phasors and instantaneous values is designed, and the efficiency and precision differences of various transformation methods are compared in detail. Finally, by utilizing MATLAB/Simulink, a hybrid simulation platform of a multi-inverter grid-connected system is built, and the efficiency and accuracy of the hybrid simulation are validated via comparison with the full electromagnetic transient simulation. [ABSTRACT FROM AUTHOR]

Grid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current and harmonic profile improvement are the challenging tasks owing to change in irradiation conditions. Multi-level inverters in grid connected systems will enhance the power quality of the system in terms of voltage and current total harmonic distortion. This paper proposes a highly reliable, robust and modular single phase solar PV fed fault tolerant hybrid cascaded H-bridge inverter with individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, able to with stand without degrading the performance of the topology even under faulted conditions and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated and validated with experimental results on the developed prototype for different irradiation conditions and tested the performance of the topology with creation of faults on different modules at different times. [ABSTRACT FROM AUTHOR]