Improved control of the grid-connected converter under the harmonically distorted grid voltage conditions

A novel control scheme of the grid-connected voltage source converter (VSC) under harmonically distorted grid voltage conditions is proposed in the paper. A dynamic mathematical model of a PWM converter based on the grid voltage-oriented fundamental frequency synchronous coordinate frame under harmonically distorted grid voltage condition is derived. According to the instantaneous active and reactive powers of the PWM converter during grid harmonic distortions, two alternative control targets are proposed to improve the system operation performance. Meanwhile, based on the grid voltage-oriented fundamental frequency synchronous coordinate frames, a current control scheme consists of a single proportional integral (PI) regulator and a resonant controller tuned at the frequency 6ω, is developed. The feasibility of the proposed algorithms and control scheme is validated by simulation studies on a 0.5MW PWM converter system.