电网故障时功率变换器并网同步策略

Grid synchronous strategy for three-phase grid-connected power converters under grid faulty conditions

针对传统同步参考系锁相环(synchronous reference frame phase-locked loop,SRF-PLL)在电网故障时检测出的电压幅值与相位等存在低频干扰量,无法保证并网同步要求的问题,提出了一种功率变换器并网同步策略。该并网同步策略是对传统SRF-PLL的拓展,由设计的正序分量提取算法和传统的SRF-PLL组合而成,详细阐述了该并网同步策略的理论依据和实现方法。理论分析表明:在电网故障时,该并网同步策略具有动态响应时间快,结构简单,谐波分量抑制能力强的优点。并且对电网基频在允许范围内(50±0.5Hz)偏移时不敏感,能够有效解决传统SRF-PLL在电网故障时无法保证并网同步要求的缺点。仿真与实验结果验证了理论分析的正确性和可行性以及该并网同步策略应用的有效性。

For the shortcoming of the traditional synchronous reference frame phase-locked loop（SRF-PLL） under unbalanced and distorted grid conditions,a new grid synchronous strategy was presented,which is an extension of the traditional SRF-PLL.This is achieved by combining the proposed positive-sequence voltage detector and the traditional SRF-PLL.The resultant grid synchronous strategy is able to quickly and accurately detect the amplitude,phase and other information of the positive-sequence voltage component even under unbalanced and distorted grid conditions.A detailed description and derivation of the new grid synchronous strategy were presented.Moreover,the behavior of the new grid synchronous strategy with highly unbalanced and distorted grid has been validated by means of simulation and experimental results,demonstrating its excellent performance.