基于无源性的并网逆变器扩展阻尼区域方法研究

三相LCL型并网逆变器通常采用电容电流反馈有源阻尼控制方式，但由于控制延时的存在，使系统的有源阻尼特性在1/6采样频率 fs 处发生改变，在弱电网情况下可能发生系统失稳。针对此问题，提出一种改进电容电流反馈的超前延时补偿方法。该方法基于无源理论的稳定性设计要求，通过对控制内环的稳定性分析，给出了内环控制参数及改进方法下电容电流反馈系数的可行域。通过对控制外环的稳定性分析，给出了外环控制参数的可行域。采用逐步由内环到外环的参数分析及设计流程，将有效正阻尼区域扩展到接近0.45fs，有效保证逆变器输出导纳的无源性。离散稳定性分析与仿真结果表明，在电网阻抗增加、逆变器并联耦合以及滤波器参数波动等工况下，所提方法相较于传统电容电流反馈方法具有更好的系统稳定性、鲁棒性以及动态响应特性。

A method of extending the damping region of a grid-connected inverter based on passivity

The capacitor current feedback active damping control method is often used in a three-phase LCL grid-connected inverter. However, because of the existence of control delay, the active damping characteristics of the system change at 1/6fs, and system instability may occur in a weak grid. A leading delay compensation method based on improved capacitor current feedback is proposed to solve this problem. Based on the stability design requirements of passive theory, and through a stability analysis of the control inner loop, the control parameters of the inner loop and the feasible region of improved capacitor current feedback coefficient are given. Through the stability analysis of the control outer loop, the feasible region of the control parameters of the outer loop is given. A parameter analysis and design process from inner loop to outer loop is adopted to expand the effective positive damping region to nearly 0.45fs, which effectively ensures the passivity of the output admittance of the inverter. Discrete stability analysis and simulation results show that the proposed method has better system stability, robustness, and dynamic response characteristic than the traditional capacitive current feedback method under increased grid impedance, parallel coupling of inverters, and fluctuation of filter parameters. This work is supported by the National Key Research and Development Program of China (No. 2021YFB2400900).