电网电压不平衡和谐波畸变下新型并网锁相环设计

针对日益增加的分布式能源并网,旨在设计一种新型的锁相环(PLL),以克服主流PLL在电网电压不平衡和谐波畸变下难以精确地锁定电压频率和相位的不足。由于电压不平衡静止坐标系下电压正负序交流分量存在耦合关系,采用交叉解耦双复系数滤波器(DCCF)结构提取和分离电压正负序分量。利用多变量滤波器(MVF)对输入电压基波正序分量幅值无衰减、零相移特性,将MVF结构引入交叉解耦DCCF结构中,设计一种新型的PLL结构,以增强在高谐波畸变下的滤波能力。最后进行Matlab/Simulink仿真,证明所提出的PLL在电压不平衡、电压频率阶跃和相角跳变下能够快速精确地锁定频率和相位,且比双复系数滤波器锁相环(DCCF-PLL)具有更好的滤波能力。

A new grid-connected phase-locked loop design under grid voltage imbalance and harmonic distortion conditions

Due to the increase of grid-connected distributed new energies, a new Phase-Locked Loop (PLL) is needed in order to overcome the shortcoming that the most popular PLLs are difficult to lock voltage frequency and phase accurately under grid voltage imbalance and harmonic distortion. Since there exists coupling relationship between voltage positive and negative sequence components in stationary reference frame under voltage imbalance, a crossing decoupling Double Complex Coefficient Filter (DCCF) is used to extract and separate voltage positive and negative sequence components. The Multiple Variable Filter (MVF) has the amplitude non-attenuation and zero-phase shift characteristics for input voltage fundamental positive sequence component. So the new PLL structure with strong filtering ability is designed under highly harmonic distortion by adding MVF into the crossing decoupling DCCF structure. Finally, Matlab/Simulink simulations show that the proposed PLL can lock the frequency and phase quickly and accurately under voltage imbalance, voltage frequency step and phase angle jump, and has a better filtering capability than DCCF-PLL. This work is supported by National Natural Science Foundation of China (No. 61763040 and No. 61403219), Ningxia Key Research and Development Program (Special Talents) (No. 2018BEB04003) and The Third Batch of Ningxia Youth Talents Supporting Program (No. TJGC2018095).