Modulation and Control of a DC-AC Converter with High-Frequency Link Transformer for Grid-Connected Applications

Abstract

The need to integrate energy storage devices with renewable energy sources and improve the employed converters' modulation and control techniques continues to grow. This trend is further activated by utilizing new converter topologies, such as high-frequency (HF) link converters. A dc-Ac with HF link isolated converter is presented in this paper to integrate a battery storage device with a three-phase grid. The proposed converter is composed of two stages. The first stage is a direct three-phase to single-phase bidirectional Matrix Converter (3x 1 MC), which converts the standard three-phase voltages to a single-phase HF waveform. Besides, the MC ensures three-phase sinusoidal grid currents with a unity power factor (UPF). The second stage of the proposed topology is an H-Bridge Converter (HBC), which converts the battery dc-voltage to a single-phase HF waveform synchronized with that of the single-phase output of the MC. Therefore, HF terminals of both stages have been linked by a single-phase HF transformer that provides galvanic isolation to the system. Also, a new mathematical model has been presented to obtain the accurate duty cycles of all matrix converter switches. Moreover, a new Pulse Width Modulation (PWM) technique of the analyzed converter with the controllable voltage limits is introduced. A simple control method is presented to regulate the battery dc-current and match reference value using a single PI controller. A laboratory prototype-based 200V, 2kW has been carried out to investigate the proposed technique's validity.