电网不平衡下基于自适应观测器的锁相环研究

Phase-locked loop algorithm based on adaptive observer under unbalanced grid voltage condition

电网不平衡条件下,传统软件锁相环已经不能准确跟踪电网电压的频率和相位信息,且无法直接得到电网电压的正负序分量。针对传统软件锁相环的缺陷,提出了一种静止坐标系下基于自适应观测器的软件锁相环算法。算法设计了电网电压角频率的自适应观测器模型,通过定义Lyapunov函数,推导出电网角频率的自适应律,并设计了使得观测器稳定的增益矩阵。该算法不仅可以观测到电网的频率、相位等信息,同时可以得到电网电压正负序分量。仿真和实验结果表明,基于自适应观测器的锁相环具有检测精度高、动态效果好等优点,当电网处于各种不平衡条件时更能显示其优越性,可为风电网侧变流器的算法改进提供有效的控制基准。

Under the condition of unbalance grid voltage, traditional phase-locked loop （PLL） is incapable to track the frequency and phase of the voltage, and fails to get the positive and negative sequence components of the grid voltage directly. To solve this problem a PLL algorithm based on adaptive observer in the fixed reference coordinates is presented. The adaptive observer model and gain matrix for grid angular frequency estimation is designed. By means of Lyapunov function definition, the adaptive law for the grid angular frequency is deduced. The proposed PLL algorithm not only can observe the frequency and phase angle of the grid voltage, but also can get the positive and negative sequences signals. Simulation and experimental results prove that PLL based on the adaptive observer has advantage of high precision, fast dynamic response and so on. Its advantages are more prominent in the unbalance conditions, so it can provide a reliable control foundation for the improvement of wind energy converter.