Quasi proportional-resonant control for the grid current of hybrid distribution transformer

Abstract

Hybrid distribution transformer (HDT) has powerful control ability, which is significant for the intelligentisation of the distribution network. A kind of HDT is presented here, the grid current control system of which is emphatic researched. Based on the mathematical model of ideal HDTs, a grid current control system is designed with quasi proportional-resonant controller (QPR). Using the characteristics that infinite gain and large bandwidth at the resonant frequency of QPR controller, the grid current system achieve the effects of unit power factor and sinusoidal symmetrical waveform. Tracking control with no static error of grid current was achieved in MATLAB. Compared with the traditional PI control, QPR controller can modulate AC signals in the static coordinate system, rather than rotary coordinate system. So the QPR controller has advantages of lower steady-state error, stronger anti-interference ability, and simpler calculation. Simulation results show that it has good dynamic and steady performance.

Keywords

• PI control
• power grids
• power factor
• electric current control
• distribution networks
• power transformers
• control system synthesis
• Matlab
• tracking control
• QPR controller
• rotary coordinate system
• quasiproportional-resonant control
• hybrid distribution transformer
• HDT
• quasiproportional-resonant controller
• PI control
• grid current control system design
• power factor
• sinusoidal symmetrical waveform