A PWM rectifier control system with DC current control based on the space vector modulation and AC stabilisation

This paper presents a control strategy to apply in the control of current type PWM rectifiers. These converters use LC filters on the AC side, and as a consequence, undesired oscillations take place. These oscillations are not dependent on the PWM technique used but depend on the LC filter size. A simple, cost effective and efficient damping system is presented and discussed in this paper. This damping system uses the voltages across the AC inductors as feedback variables. The DC current is controlled with an outer linear PI controller with anti-reset windup and a nonlinear function that determines the AC current references by the product of the PI output and the actual DC current. This allows a transfer function linearization between the modulation index, that is the output of the PI controller, and the DC current. The system is analysed with a simplified model and analytical expressions are presented to synthesise the feedback loops. The PWM space vector modulation technique adapted to current inverters is used to verify the performance of the proposed feedback loops. The results presented show excellent behaviour in steady state and in transient regime