Quasi-Proportional-Resonant Control Strategy for the Hybrid Distribution Transformer with LCL-Type Converters

Hybrid distribution transformer (HDT) has high controllability for the grid current and load voltage, and it is useful for constructing the future active distribution network. To overcome the limitations of the existing HDT control scheme with PI regulators and improve the performance of high-order harmonic suppression of the existing HDT with L-Type converters, a control scheme with quasi-proportional-resonant (PR) regulator is proposed for HDT constructed with LCL-Type converters in this paper. This control scheme is developed based on the single-phase dynamic model of the improved HDT in static coordinate and, hence, has simple block diagram. The dynamic model is constructed according to the equivalent circuit of HDT. In this dynamic model, the grid current and load voltage coupled weakly and, hence, the quasi-PR regulators for the grid current and load voltage control are designed separately. Simulation results validate the effectiveness of the proposed PR control scheme of HDT.