并网逆变器高频纹波抗混叠滤波器设计研究

Study of the Design of Grid-connected Inverter High-frequency Ripple Anti-aliasing Filter

逆变器的数字控制系统基于模数转换器对信号进行采样以实现灵活的控制。然而逆变器开关拓扑的高频动作向被控电压、电流量中引入了明显的高频纹波,这些纹波在采样过程中易被混叠至低频段,造成逆变器输出电流波形畸变。该问题通常通过在被控量反馈通道串接模拟低通抗混叠滤波器来解决。但根据分析,常规低通滤波器在滤除高频分量的同时,会明显地滞后与衰减控制频段信号,降低逆变器的稳定裕度。因此,此处提出了一种基于低通+陷波的新型抗混叠滤波器,能够在有效滤除高频纹波的同时,保证逆变器充足的稳定裕度。该方案在一台5 kVA的逆变器中进行实验,通过观察稳态电流波形畸变和暂态电流波形振荡情况,验证了所提方案的有效性和优越性。

The digital control system of inverter executes flexible controlling by sampling of signals based on analog to digital converter.However,high-frequency switching of the inverter’s topology causes obvious high-frequency ripples in voltage and current under control.These ripples can be easily aliased to low frequency range in sampling process,making distortion in output current waveform of inverter.This trouble is often solved by adding series analog low-pass anti-aliasing filters into signal feedback channels.But according to analysis,regular low-pass filter will delay and attenuate signal in control frequency range obviously when it filters high-frequency signal components,which reduces stable margin of the inverter.Therefore,a new kind of anti-aliasing filter based on low-pass and notch filters is proposed,which filters high-frequency ripples effectively and guarantees sufficient stable margin at the same time.The scheme is tested in a 5 kVA inverter.Effectiveness and advantage of the proposed scheme are verified by observing distortion in stable state current waveform and oscillation in transient current waveform.