Proportional integral-quasi-resonant-repetitive control strategy for VSC of VSC-HVDC

In order to solve the power quality deterioration of voltage source converter based high voltage DC transmission (VSC-HVDC) caused by the unbalance and distortion of AC grid, in this paper, a hybrid current control strategy combing PI, resonant and repetitive control for the d and q-axis current components is proposed. The reference positive and negative sequence currents are calculated by setting instantaneous ripples of active and reactive powers equal to zero, and then, the positive sequence current components are controlled by proportional integral (PI) controller, the negative sequence currents controlled by resonant controller and harmonics are eliminated by repetitive controller. Furthermore, the effect of non-integral ratio of sampling frequency and the frequency of controlled signal on the repetitive controller, and the improved method of estimating the actual sampling data based on linear interpolation algorithm is proposed to enhance the performance of repetitive controller. Detailed simulation results verify the accuracy and feasibility of the proposed strategy. ©, 2015, Power System Technology Press. All right reserved.