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Conventionally, single phase shift control technique is used, for dual active bridge (DAB) which works efficiently at unity voltage conversion ratio and full load. However, when there is mismatch between primary voltage and reflected secondary voltage on primary side at light load, its efficiency reduces because of increased current stress and circulating power. Moreover, due to single control variable, its power flow controllability is confined. In this paper, isolated bi-directional T-type multilevel dual active bridge dc-dc converter topology is presented. It has five level voltages on both the primary and secondary side of high frequency transformer, which reduces the current stress and circulating power over wide operating range. It also has five control variables which gives extra edge for enhancing power flow controllability. Comparative analysis reveals that the proposed converter has high efficiency over wide operating range, due to reduced circulating power and current stress. Performance of the proposed T- type multilevel dual active bridge DC-DC converter topology has been verified via simulation in MATLAB.

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...

This article proposes an enhanced single-phase self-tuning pre-filter for estimating the fundamental grid voltage frequency. The known extended self-tuning filter (STF) adheres to an increased structural complexity, which may consume memory in the digital hardware to estimate the fundamental grid voltage signal. The proposed STF, which relies on a simple non-adaptive comb filter, may address this issue. Consequently, the introduction of imaginary zeros ensures better rejection of the DC-offset and the harmonic components while keeping the proposed filter structure simpler to implement. Furthermore, a simple open-loop frequency estimator is proposed, which does not involve any inverse trigonometric function to estimate the fundamental frequency. This entire proposal is cost-effective and has good frequency tracking abilities with a reduced computational load. The experimental results imply the suitability of the proposed scheme for weak inertia power grid networks where synthetic inertia controllers require a rapid frequency information to control the injected power under adverse grid voltage conditions.

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 review of the bidirectional DC-DC converter (BDC) based on control methodology and switching techniques is presented. Each converters control scheme benefit is highlighted, and a summary of it is presented. Some of the control techniques are applied to BDC like as proportional-integral-derivative (PID), model predictive (MPC), fuzzy logic control (FLC), digital control system (DCS), sliding mode control (SMC), etc. Performance of the converter was improved by using switching techniques like single-phase-shift (SPS), dual-phase-shift (DPS), triple-phase-shift (TPS) etc.

There is a huge pervasive consideration of integrating renewable energy sources (RES) to DC power system. Most of the modern loads are DC. Photovoltaic (PV) integrated DC microgrids feature remarkable advantages such as providing DC which can be directly utilized in DC grids that eliminates major step of AC-DC conversion. However, intermittency of RES and presence of some non- idealistic like voltage fluctuation, droop effect, faults and harmonics causes instability problems in DC microgrid. This leads to voltage weakening, potential blackout and damage to equipment. To deal with inconsistency and improbability of RES new emerging demand side management (DSM) technology has been developed called Electric Spring (ES). ES can be employed in AC or DC grid for supply-demand management. DC Electric Spring (DC-ES) is a unique method of distributed voltage control over traditional single point control by effectively handling supply. This paper comprises one of the types of DC-ES called the shunt DC-ES for voltage regulation and Fault Ride Through (FRT) support with various mode of operation on DC bus. To demonstrate the performance analysis and to alleviate DC microgrid issues, DC-ES is implemented on 48V DC system. Moreover, the detail comprehensive characteristics behavior of shunt DC-ES is presented and validated using MATLAB software.

Solid state transformers have a major role to play in grid integration of renewables in smart grid networks. Unidirectional, step up solid state transformers are state of the art in wind energy systems and solar PV parks. Modular SST topologies have gained significant impetus in recent research. Many research works have focussed on resonant tank converter topologies for modular SST applications. However, passive rectifier part remained uninvestigated and hence only secondary side rectifier and associated HF transformer is investigated in this work. In this work, three rectifier configurations are considered. Steigerwald's constant is derived for each independently and it is proved that irrespective of rectifier configuration, ac equivalent resistance remains unchanged for similar voltage and power ratings. Thus design methodology remains unchanged. Simulation results are analysed and various losses are estimated for full load operation. High frequency transformer design for minimum footprint and loss minimization are discussed. Further, it is concluded that bridge rectifier configuration yields minimum power losses.