可适应宽频带的抗混叠有源阻尼控制策略

Anti-aliasing Active Damping Control Strategy Adaptable for Wide Band

针对LCL型并网逆变器的谐振问题，该文从离散控制的角度分析了谐振机理，得出控制器运算时间带来的滞后影响了系统相频特性，使其不满足奈奎斯特稳定判据而失稳。虚拟电阻法是解决LCL谐振问题的一种有效而稳定的方法，但在工业应用中存在电容电流欠采样导致的混叠问题。选择合理的滤波器可以解决混叠问题，但其带来的相位滞后影响了阻尼效果甚至为系统带来负阻尼，针对这一问题该文提出了带超前补偿的虚拟电阻有源阻尼法。另外，实际系统通常是多台逆变器经LCL并联，系统存在从单机谐振频率到多机谐振频率宽频率范围的谐振，该文基于1．5MW逆变器试验平台，通过改变并联滤波电容组数进行了谐振频率670～1230Hz的阻尼实验。实验结果证明了所提方法的有效性，以及对宽频率范围的适应性。

For the resonance problem of the grid-connected inverter with LCL filters, this paper analyzes the resonance mechanism from the perspective of discrete-time control for the first time. It shows that the controller＇s computing delay impacts the system＇s phase-frequency characteristics, which leads to the break of the Nyquist＇s stability criterion. The virtual resistor method is an effective and stable way to solve the LCL＇s resonance problem, but in industrial applications there would be aliasing caused by the under-sampling of the capacitor currents. Choosing an appropriate filter can solve the aliasing problem, but it brings the phase lag which affects the damping effect and even introduces the negative damping to the system. To solve the above-mentioned problem, this paper presents an active damping method with lead compensation. Moreover, as it usually consists of several inverters connected in parallel via LCL, the actual system has a wide resonance frequency range from single-invertor resonance frequency to multi-invertor resonance frequency. In this paper, the damping experiments of the resonance frequency from 670 Hz to 1 230 Hz are carried out, by changing the group number of the parallel filter capacitors based on a 1.5 MW inverter platform. Experimental results demonstrate the effectiveness of the proposed method, as well as the adaptability for a wide range of resonance frequency.