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This paper presents the study and evaluation of a medium-voltage grid-tied cascaded H-bridge (CHB) three-phase inverter for battery energy storage systems using SiC devices as an enabling technology. The high breakdown voltage capability of SiC devices provide the advantage to significantly minimize the complexity of the CHB multilevel converter, with less power loss compared to when Silicon (Si) devices are used. The topology in this study has been selected based on high voltage SiC devices. In order to reach 13.8 kV, a nine-level CHB is needed when using 6.5 kV SiC MOSFETs. However, if 10 kV SiC MOSFETs are used, only five-levels of the CHB are required. The controls were developed, simulated and verified through an experimental prototype. The results from the scaled-down prototype proved the controls and the verification of the performance of five-level CHB three-phase inverter. For the system reliability, both open-loop and short-circuit faults are analyzed. 

This paper investigates the use of power semiconductor devices in a nine - level cascaded H-bridge (CHB) multilevel inverter topology with an integrated battery energy storage system (BESS) for a 13.8kV medium voltage distribution system. In this topology, the bulky conventional step-up 60 Hz transformer is not used. The purpose of this study is to analyze the use of SiC MOSFET and Si IGBT devices in the inverter system to evaluate their respective performances. SiC MOSFET and Si IGBT switching devices are modeled and characterized using Saber® modeling software. The switching losses, thermal performance, and efficiency of the inverter system are investigated, and measurements are obtained from the simulation. Saber® provides a good capability for characterizing semiconductor models in the real world, with great features of computation. A three-phase SiC power MOSFET-based multilevel CHB inverter prototype is presented for experimental verification. In the investigation, better performances of SiC MOSFET devices are recorded. SiC devices demonstrate promising performance at different switching frequency and temperature ranges. 

This paper describes the study of a topology of modular multilevel converters for integrating battery energy storage into a medium (13.8 kV) distribution system. The main benefit of this topology is to remove the need for a bulk 60 Hz transformer that is normally used to step up the output of a voltage source inverter to the medium voltage level. A SiC-based power electronics interface presented in this paper provides an efficient solution without the large and costly transformer. Using medium voltage SiC devices (≥ 10 kV SiC MOSFETs), with their high breakdown voltage, enables the system to meet and withstand medium voltage application, using a minimized number of cascaded modules. This SiC-based power electronics interface significantly reduces the complexity usually faced when Si devices are used directly in medium voltage applications. The voltage and state of charge balancing control for battery modules is also simplified and performs well. The simulation and experimental results, performed on a low-voltage prototype, verify the proposed topology that is presented in this paper. 

The increasing importance of power electronic converters in supplying electrical energy to utility grids places a higher priority to detect and protect against fault conditions. Fault detection and isolation are particularly important for inverters that provide black-start recovery for microgrids since these converters provide the energy source for restoration after a power outage. This paper presents a new fault detection and location method for Cascaded H-Bridge (CHB) multilevel inverters. The new fault detection method is based on monitoring the output voltage of each cell and output current directions along with each switch’s state. By monitoring each cell’s output voltage and current direction, the faulty cell can be detected and isolated. After the faulty cell is detected, the faulty switch can be located by comparing the current direction with the switching states. This technique is implemented with Level-Shifted Pulse Width Modulation (LS-PWM) in order to maintain acceptable total harmonic distortion (THD) levels at the converter. The proposed method can be implemented for a CHB with any number of cells, can operate with nonlinear loads, and offers very fast detection times. Simulation and experimental results verify the performance of this method. 

To address power quality issues in the residential split-phase distribution systems, a novel residential power router (RPR) is proposed in this paper. It consists of a dual-half bridge (DHB) converter and a split-phase inverter. The DHB provides the galvanic isolation and bidirectional power flow channel for the distributed generation terminal. The split-phase inverter can work as the active power filter, the reactive power compensator, and balance the power of two phases. The power balancing mode is critical to a residential microgrid, especially when the utility grid is not accessible. A proportional quasi-resonance and resonance (PQRR) controller is adopted to eliminate the steadystate error for harmonics compensation. Simulation and experimental results are presented in this paper to validate the feasibility and effectiveness of the proposed RPR for residential applications.