Modeling and Stability Analysis of Three-Phase PWM Rectifier

According to the instantaneous active power balance, the small-signal mathematical model from active current to dc-side bus voltage is proposed. When the rectifier operates in the rectification mode, it has a right-half-plane (RHP) zero and exhibits a non-minimum phase feature which causes a phase lag and affects system stability. The stable regions and how system stability is affected by variation of converter parameters under the modeling methods proposed in this paper is analyzed in detail. The results show the proportional gain of voltage outer-loop, AC-side filter inductor, DC-side capacitor, load resistor have an influence on system instability. At last experimental results illustrate the validity of theoretical analysis.

I. Introduction

Traditional rectifiers mainly used diodes or thyristors to provide dc voltage. Although that solution is very simple to implement, it has problems of poor power quality in terms of injected current harmonics, poor power factor at input ac mains and large dc output voltage ripple on the dc side. In order to increase the power factor and decrease the input current harmonics, obtain stable and adjustable dc output voltage, a pulse-width modulation (PWM) rectifier is widely adopted in ac-dc conversion with sinusoidal input current at a fully regulated power factor, bidirectional power delivery capability, and controllable and stable dc output voltage. They provide the necessary interfaces for many power conversion systems to exchange power directly with power grid. Current applications include Uninterruptible Power Supply (UPS), Active power filter (APF), HVDC, wind energy generation system et al. [1]–[5].