针对电网不平衡与谐波干扰的风电机组锁相环改进设计

Improved Design of Wind Turbine Phase-Locked Loop for Unbalanced and Distorted Grid Voltage Conditions Interference

针对风电机组所用传统锁相环在电网电压不平衡、直流偏移、高次谐波干扰及频率闪变等工况下无法快速准确锁定电网电压频率相位的问题,设计了一种改进的锁相环。首先建立实际电网电压数学模型,推导说明谐波分量与直流偏移对传统锁相环产生的不良影响。其次通过增加一阶低通滤波环节改进二阶广义积分器,在获取电压正序分量的同时增强锁相环对直流偏移量的抑制能力。结合滑动平均滤波器滤除高次谐波分量,并引人频率反馈,对滑动平均滤波器采样窗口时间进行实时矫正,以提升电压频率变化时锁相环谐波消除性能。最后,通过仿真验证所提改进锁相环在不同电压故障工况下的有效性。

To solve the problem that the traditional phase-locked loop used in wind turbines can't quickly and accurately lock the voltage and frequency phase of the power grid under the conditions of unbalanced voltage,DC offset,high-order harmonic interference and frequency flicker,this paper designs an improved phase-locked loop structure.First,the mathematical model of grid voltage is established,and the adverse effects of harmonic components and DC offset on traditional phase-locked loop are deduced.Then the traditional second-order generalized integrator is improved by adding a first-order fltering link,and the positive sequence component of the voltage is obtained,while the suppression ability of the phase-locked loop to the DC component of the power grid voltage is enhanced.Moving average filter is used to flter out higher harmonic components,and real-time frequency feedback is introduced to deal with the frequency flicker of power grid.Finally,the effectiveness of the improved PLL under different voltage fault conditions is verified by simulation.