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Solid-state transformer has been a major area of research in recent years because of its multifunctionality as compared to conventional low-frequency transformers. Bidirectional isolated dual-activ...

In the existing electric power distribution network, a large number of AC/DC Micro-Grids are playing their role independently to provide the desired power supply to all the consumers. However, under short time outages, natural disasters, or sudden changes in system parameters, this AC/DC Micro-grid needs to interface with the existing power grid or with each other or to be disconnected from each other to help out for seamless power supply to all the consumers in the distribution network. Conventional, low-frequency transformer used in such network, is having so many drawbacks such as low power density, poor voltage regulation, and no control over power flow with poor power quality. Sold State Transformer (SST) is a viable solution for such applications. This paper presents a structure of SST for AC/DC Micro-Grid converter (MGC). A bidirectional boost converter and a stacked half -bridge inverter are integrated with the AC/DC Micro-Grid converter. The designed 6 KW Micro-Grid Converter has a bidirectional power flow controllability with a soft switching feature to improve the overall efficiency of the converter. The designed AC/DC MGC is simulated in PSIM/Simulink co-environment to verify it's performance indices under different operating conditions.

Amidst growing environmental and energy concerns, electric vehicles (EVs) are potential solution for reducing carbon emission. All-electric green energy objectives heavily rely on standardization of electric vehicle service equipment (EVSE), associated protocols, smart chargers and battery technology. However, no generic approach for EVSE for charging different categories of electric vehicle exists. Therefore, in this paper, an off-board unidirectional conductive type DC fast charger for light and heavy electric vehicles is presented. The converter is adaptable for charging of light as well as heavy electric vehicles. The proposed charger is based on resonant series converter with adaptable restructured multiplier rectifier. The restructuring element for adaptable rectifier is a simple bi-directional switch. The doubler configuration is recommended for light electric vehicles (400V Class) while quadrupler configuration is recommended for heavy electric vehicles (800V Class). In this paper, both the configurations and their associated operation modes are explained with respective waveforms. Further, all semiconductor switches and rectifier diodes are naturally soft switched owing to resonant converter above resonant frequency operation for minimizing losses. The charging rates and power levels can be scaled up or down by adopting modular approach. To validate the presented theoretical analysis, a 1.25 kW hardware prototype is designed and tested in the laboratory and experimental results are presented.

A two-stage grid-tied efficient solar photovoltaic (SPV) system with zero voltage switching (ZVS) and zero current switching (ZCS) at the dc–dc converter stage and adaptive synchronization at the inverter stage is proposed. In the first stage, an improved high step-up boost-integrated flyback converter with quasi resonant voltage multiplier cell is proposed. ZVS turn-on of all mosfet s and ZCS turn-off of all diodes of resonant voltage multiplier cell results in high efficient power conversion compared with the conventional boost-integrated flyback converters. Small-sized coupled inductor enhances magnetic utilization in this converter. Second stage consists of a single-phase H-bridge grid interfaced inverter with variable band hysteresis current control technique. Amplitude adaptive notch filter is used to extract fundamental unit voltage vector of grid voltage required for estimation of synchronized reference current for hysteresis controller. A 250 W laboratory prototype is developed and experimentally evaluated. Experimental results demonstrate efficient renewable energy conversion at dc–dc converter stage and quality power injection at dc–ac inverter stage of the proposed grid-tied SPV system under changing solar insulation levels.

Solid State Transformer (SST)is playing crucial role in implementation of MVDC grid integration with various energy sources. Bidirectional Isolated Dual Active Bridge (DAB) is an integral part of SST. When control scheme such as Single Phase Shift technique is used, it causes high circulating power and high $\frac{{dv}}{{dt}}$. It leads more voltage stress and less efficiency of the system. Moreover, this scheme has only one degree of freedom for controlling power i.e by changing phase shift only. It confines its ability to regulate power flow. In this paper, symmetrical five level Bidirectional Dual Active Bridge is proposed with five degrees of freedom. It increases its ability to regulate power flow. As number of voltage level increases, it leads to less $\frac{{dv}}{{dt}}$ thus reducing the voltage stress on the system with elimination of the circulating power resulting in more efficient system. Performance of the proposed topology has been verified via simulation in MATLAB software.

The research in semiconductor technology and power electronics gives scope to replace a conventional low frequency transformer by power electronic converter based transformer which is known as solid state transformer (SST). Reliability issue is one of the major drawbacks of SST because as it contains power electronic switching devices, the chances of occurring open and short circuit faults are more. Therefore, it requires suitable fault tolerant operation. The basic SST topology consists of AC-DC-DC-AC conversion stages. This paper presents fault tolerant operation of third stage of SST (DC-AC converter) for open circuit faults. In this paper, a novel topology of fault tolerant multilevel inverter (FTMLI) is proposed, which can sustain single switch and some specified multi switch faults. The component count also taken into consideration here and the balancing of capacitors also properly maintained. The proposed topology is giving better results in terms of efficiency, cost and THD under fault tolerant operation. The proposed circuit topology is simulated using MATLAB/SIMULINK tool.

Bidirectional Isolated Dual Active Bridge (DAB) plays a vital role in implementation of Solid State Transformer(SST) and DC Bus isolation. Conventionally, it is controlled by Single Phase Shift (SPS) technique, which leads to high $\frac{dv}{dt}$ & high circulating power. It causes high voltage stress and less efficiency of the system. In SPS technique power can be varied by changing phase shift only thus, having only one controllable parameter, resulting into limited controllability. In this paper, five level Bidirectional Dual Active Bridge with symmetrical configuration is proposed with five degrees of freedom. It increases its ability to regulate power flow. As number of voltage level increases, it leads to less $\frac{dv}{dt}$ thus reducing the voltage stress on the system with elimination of the circulating power, resulting into more efficient system. Performance of the proposed topology has been verified via simulation in MATLAB environment.

Multilevel inverters (MLI) gained much importance in recent times for their better harmonic profile and low switching stress. But, the major concern with MLI is the requirement of more number of power semiconductor devices. The reduced switch topologies diminished the redundancies and so the chances of occurring fault increased, drastically the system reliability gets affected. Therefore, in this work, a fault tolerant optimum switch count MLI is proposed. It operates in normal mode to realize a five-level output and when an open circuit fault in bidirectional switch of the inverter, the output voltage levels reduce to three levels but maintains the peak output voltage and power. In any single quadrant switch if an open circuit fault occurs, then the output voltage level and magnitude get reduced. The proposed five-level inverter is simulated in the MATLAB/SIMULINK platform and the results are shown for distinct fault conditions to confirm the efficacy of the proposed inverter. The cascading of modules makes a generalized structure of the proposed topology.

Solid State Transformer (SST) is the main focus of research in recent years. Bidirectional Isolated Dual Active Bridge is an important component in SST. When conventional control scheme such as Single Phase Shift (SPS) is used it reduces the system efficiency due to circulating power and has high dv/dt across switches. It has only one degree of freedom which confine its ability to regulate power flow. In this paper, 5-level Dual Active Bridge is proposed with three degree of freedom which improves its ability to regulate power flow. Moreover due to increase in voltage levels, dv/dt across switches reduces significantly and it also reduces the circulating power which improved the efficiency of system. Performance of the proposed topology has been varified in MATLAB.

Common mode voltage (CMV) generation is a major problem in switching power converter fed induction motor drive systems. CMV is the zero sequence voltage generated due to the switching action of power converters. Even a small magnitude of CMV with a high rate of change may circulate large bearing currents which may damage a machine’s bearings and shorten its life. There are several methods of controlling CMV. This paper presents 3-level sinusoidal pulse width modulation based techniques to control the magnitude and rate of change of CMV in multilevel AC-DC-AC drive systems. Simulation and experimental investigations have been presented to validate the performance of proposed technique to control CMV in 3-level neutral point clamped inverter based AC-DC-AC system.

A total harmonic distortion (THD) optimization based 5-level selective harmonic elimination pulse width modulated (SHE-PWM) single-phase reduced device count (RDC) voltage source inverter (VSI) is presented in this paper. A MATLAB program is developed for offline calculation of switching angles based on quarter wave (QW) symmetry of the output and overall THD optimization method of SHE-PWM. The inverter circuit operation and SHE-PWM scheme to generate 5-level voltage output along with performance parameters are provided. The theoretical discussion in the paper is also supported by simulation and experimental results.

This paper proposes a simple control technique of Unified Power Quality Conditioner with Distributed Generation (UPQC DG ) for grid integration of solar photovoltaic (PV) system. In proposed technique shunt Active Power Filter (APF) of UPQC DG is controlled using Synchronous Reference Frame (SRF) theory and series APF is controlled using Unit Vector Template Generation (UVTG) method. Proposed control technique utilizes only one PI controller and incorporates directly measured PV array current without estimating power generated by PV array. Performance of proposed system is validated in the presence of non-linear load. System performance is also studied during grid disturbances such as voltage sag, change in load and solar irradiation variation. Simulation carried out in MATLAB/Simulink validates system performance.

This paper proposes the fundamental-frequency modulated novel six-level inverter topology for single-phase stand-alone photovoltaic (PV) system. It consists of a full-bridge inverter circuit with two pairs of anti-parallel connected switching devices, four diodes and three independent DC sources (PV modules) to obtain six level output. The theoretical discussion of proposed system is also supported by simulation and laboratory prototype results.

The use of power electronics converters influencing the generation of harmonics and reactive power flow in a power system. Therefore, three-phase improved power quality AC-DC converters are gaining lot of popularity in power conversion applications. This paper deals with the control of three-phase neutral point clamped (NPC) 3-level AC-DC converter under balanced and unbalanced load condition. A unity power factor controller (UPC) is designed and developed for unity power factor operation of the converter under steady state and transient conditions. Further, the UPC is validated through experimentation performed on prototype developed in the laboratory.