Frequency-Divided Resistance-Emulating Control of Grid-Connected Voltage Source Rectifiers Under Unbalanced Grids
Wenjing Xiong, Weihao Yuan, Jianheng Lin, Zhengmei Lu, Shiming Xie, Yonglu Liu, Yao Sun, Mei Su
Abstract
DC-link voltage pulsation is a technical challenge for grid-connected three-phase voltage source rectifiers (VSRs) under unbalanced grids. To suppress DC-link voltage ripples arising from unbalanced grids, a frequency-divided resistance-emulating control strategy is proposed in this paper. According to the frequency-divided idea, the DC-link voltage control loop consists of two parts: one dedicated to regulating the average voltage and the other focused on suppressing pulsating voltage. The inner loop is synchronized based on the resistance-emulating approach. The frequency-divided resistance-emulating control offers the following advantages: 1) grid voltage sensors are eliminated; 2) detailed information about circuit parameters is not required; 3) easy to implement because only one proportional-integral (PI) controller, one quasi-proportional-resonant (QPR) controller, and two band-pass filters (BPFs) are used. To sum up, the proposed method is simple, cost-effective, and robust. Experiments confirm the effectiveness and performance of the proposed method.