具有变频适应性的重复控制策略在SAPF中的应用

Application of repetitive control strategy with variable frequency adaptability in SAPF

关键词:  有源电力滤波器  重复控制  电流跟踪  谐波抑制  频率波动

Key words:  active power filters  repetitive control  current tracking  harmonic suppression  frequency fluctuation

摘要:

为提高电网频率波动条件下并联型有源电力滤波器（shunt active power filters,SAPF）的补偿电流跟踪控制精度,有效抑制电网的谐波污染,提出一种具有变频适应性的重复控制策略。采用可调整采样频率的选择性重复控制器构建多采样率重复控制系统,利用基于拉格朗日线性插值法的有限脉冲响应（FIR）滤波器将多采样率重复控制系统转换成具有统一采样频率的重复控制系统（frequency-adaptive uniform-rate selective repetitive control system,FUSRCS）,通过跟随电网频率调整重复控制器延迟环节近似表达式系数的方法使FUSRCS能适应电网频率波动,设计了FUSRCS的补偿器,分析了FUSRCS的稳定性、收敛性和稳态误差,建立了三相SAPF的数学模型,依据实际数据设计了基于FUSRCS的补偿电流复合重复控制系统。仿真和实验结果表明:基于FUSRCS的SAPF能够在电网频率存在稳态偏差、电网频率动态变化和负载切换等情况下,保持较高的补偿电流跟踪精度和较好的补偿效果。与经典重复控制相比,FUSRCS在具有变频适应性的同时,减少了控制系统的计算负担,提高了系统的动态响应速度,解决了多采样率重复控制系统带来的问题。

Abstract:

To improve the accuracy of compensating current tracking control for shunt active power filters (SAPF) under the condition of grid frequency fluctuation and suppress the harmonic pollution of power grid effectively, a frequency-adaptive repetitive control strategy is proposed in this paper. A multi-rate repetitive control system is built based on a selective repetitive controller with an adjustable sampling rate. The multi-rate repetitive control system is transformed into a frequency-adaptive uniform-rate selective repetitive control system (FUSRCS) by a finite impulse response (FIR) filter based on Lagrange linear interpolation. To enable the FUSRCS to adapt to grid frequency fluctuations, the coefficients of the approximate expression of the delay link in the repetitive controller are adjusted according to the grid frequency. The compensator is designed and the stability, convergence and steady-state error of FUSRCS are analyzed. The mathematical model of three-phase SAPF is established, and a compensation current compound repetitive control system based on FUSRCS is designed according to the actual data. Simulation and experimental results indicate the SAPF based on FUSRCS can maintain high compensation current tracking accuracy and good compensation effect under steady-state grid frequency deviations, dynamic grid frequency variations, and load switching. Compared with conventional repetitive control, FUSRCS not only offers frequency adaptability, but also reduces the computational burden of the control system, enhances the dynamic response speed, and solves the problems caused by multi-rate repetitive control systems.