Research on a Multi-Objective Control Strategy for Current-source PWM Rectifiers under Unbalanced and Harmonic Grid Voltage Conditions

摘要

Unbalanced and distorted grid voltages cause the grid side current of a current source PWM rectifier to be heavily distorted. They can also cause the DC-link current to fluctuate with a huge amplitude. In order to enhance the performance of a current-source PWM rectifier under unbalanced and harmonic grid voltage conditions, a mathematical model of a current-source PWM rectifier is established and a flexible multi-objective control strategy is proposed to control the DC-link current and grid-current. The fundamental positiveegative sequence, 5th and 7th order harmonic components of the grid voltage are first separated with the proposed control strategy. The grid current reference are optimized based on three objectives: 1) sinusoidal and symmetrical grid current, 2) sinusoidal grid current and elimination of the DC-current 2 nd order fluctuations, and 3) elimination of the DC-current 2 nd and 6 th order fluctuations. To avoid separation of the grid current components, a multi-frequency proportional-resonant controller is applied to control the fundamental positiveegative sequence, 5th and 7th order harmonic current. Finally, experimental results verify the effectiveness of proposed control strategy.