应用在高压直流输电系统中的混合型有源滤波器稳定性分析及控制方法

Stability Analysis and Control Method for Hybrid Active Power Filter Applied to HVDC System

分析了混合型有源滤波器HAPF(hybrid active power filter)在高压直流系统应用时的稳定性问题,其中HAPF采用H桥级联变换器与LC滤波器组合的方案,对高压直流系统的特征谐波电流进行滤波。为了分析在电网阻抗变化时HAPF出现的谐波谐振现象,对HAPF进行了阻抗建模,基于阻抗模型的分析结果,采用了具有延时补偿功能的谐振调节器对阻抗特性进行修正,并从提高稳定性角度提出了相应的控制参数设计方法。阻抗模型分析结果表明,控制系统延时产生的负阻尼是引发稳定性问题的主要原因,采用改进后的控制方法可以将延时产生的负阻尼修正为正阻尼,能够有效避免谐波谐振。在PSCAD中进行仿真建模,并通过阻抗扫描验证了有源滤波器的阻抗特性。仿真案例证实了控制方法的有效性。

In this paper,the stability issue of hybrid active power filters(HPAFs)applied to a high-voltage direct-current(HVDC)system is analyzed.The HAPF which combines a cascaded H-bridge converter and an LC filter is adopted for filtering the characteristic harmonic current of the HVDC system.To analyze the phenomenon of harmonic resonance in HAPF under changes in grid impedance,an impedance model of the HAPF is established,based on which the resonance controllers with time delay compensation are applied for correcting the impedance characteristics and the corresponding design method for control parameters is proposed to improve the stability.The analysis result of the impedance model shows that the negative impedance generated by the control system’s time delay is the main factor that induces the issue of stability,and the modified control method can change the negative impedance caused by time delay into positive impedance,which is effective in avoiding harmonic resonance.A simulation model is built in PSCAD,and the impedance characteristics of the HAPF are verified through impedance scanning.In addition,the effectiveness of the proposed control method is verified by simulation cases.