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A Matrix-based Isolated Bidirectional AC-DC Converter with LCL type Input Filter for Energy Storage Applications

Abstract:

An isolated three-phase AC-DC converter is proposed in this paper for integrating energy storage elements such as batteries to the utility grid. The proposed topology uses a matrix based AC-AC converter for three-phase to single-phase conversion, facilitates the use of high-frequency transformers for galvanic isolation, and provides the necessary turns ratio for matching the required voltages on both sides, and uses a full-bridge controlled rectifier section for ACDC conversion. A Space Vector Modulation (SVM) based switching technique is implemented for the matrix-based converter to obtain superior input power quality and improved power conversion efficiency, and Sinusoidal Pulse Width Modulation (SPWM) is used for the full bridge controlled rectifier. A T-shaped LCL input filter is developed to provide low-pass filtering effect. Also, the filter realizes an inductance dominance, which provides current source characteristics hence, only a capacitive output filter is used. The simulation was carried out using Powersim (PSIM) simulation software. The variation of voltage gain for SVM and SPWM modulation indices is also presented. The converter is able to generate a charging voltage as well as three-phase sinusoidal voltage with a THD of 3%. A closed-loop control is developed for the matrix type AC-AC converter part. The control is capable of performing bidirectional operation of the system. The proposed converter topology and switching scheme are experimentally verified.