不对称电网电压下基于降阶矢量谐振器的MMC-HVDC直接功率控制策略

Direct Power Control Strategy Based on Reduced Order Vector Resonant Controller for MMC-HVDC Under Unbalanced Grid Voltages

该文引入新型瞬时功率,将新型瞬时功率和传统瞬时功率进行深入对比,建立基于新型瞬时功率的通用功率模型。提出基于新型瞬时功率和比例积分–降阶矢量谐振器(proportional integral plus reduced order vector resonant controller,PI-ROVRC)的直接功率控制策略。PI用于控制瞬时功率中的直流分量,ROVRC用于消除瞬时功率中的2倍频正序波动分量。设计整体的控制结构,对ROVRC的控制性能、模型参数鲁棒性进行深入分析,并给出ROVRC的实现方法。该文所提策略省略了电流内环,实现了有功、无功的直接控制。此外,相比于传统的功率控制策略,无需计算功率补偿项,因而不需要分离出负序电压和正序电流,控制结构简单。仿真结果表明,所提策略在电网电压对称、不对称、电网频率变化和桥臂电感参数偏移等情况下均能取得良好的控制效果。

A novel instantaneous power was introduced and then a deep comparison between traditional instantaneous power and novel instantaneous power was done. A generalized power model based on novel instantaneous power was established. The direct power control strategy was proposed, which is based on novel instantaneous power and proportional integral plus reduced order vector resonant controller（PI-ROVRC）. PI was used to control the dc component of instantaneous power while ROVRC was used to eliminate the double line-frequency positive-sequence ripples. The whole control structure was designed and a deep analysis of ROVRC on the control performance and the robustness for model parameters was carried out. In addition, the implement method of ROVRC was described in detail. The proposed control strategy removes current inner loop and can control active power and reactive power simultaneously. Furthermore, compared with traditional power control strategy, the calculation of power compensation term and the extraction of negative-sequence voltage and positive-sequence current are both avoided which result in a simpler control structure. Simulation results validate that the proposed control strategy can achieve a good control performance under various conditions, i.e., balanced grid voltages, unbalanced grid voltages, changed grid frequency and arm inductance parameter deviation.