弱电网下逆变侧电流反馈的并网逆变器稳定性分析及优化

逆变侧电流反馈控制是一种常见的间接进网电流控制方法,其相较于直接进网电流控制具有更好的稳定性。但在实际应用中,并网逆变器常工作在弱电网条件下,因此并网逆变器的稳定性会大幅降低。以三相LCL逆变侧电流反馈并网逆变器为例,通过频域分析法研究系统稳定性下降的机理,提出在并网电压比例前馈环节串联二阶广义积分(Second Order Generalized Integrator, SOGI)的控制方案。该方案可以削弱并网电压比例前馈引入的与线路阻抗相关的额外正反馈,从而提升弱电网下系统稳定性。最后,搭建了三相并网逆变器仿真模型、实物模型,验证了该方案的有效性。

Stability analysis and improvement for LCL filter grid-connected inverter using inverter-side current feedback

The inverter-side current as a feedback parameter is a commonly used type of inverter which uses indirect current control, it has better stability than direct current control. However, in practical applications, the inverter usually works in the weak grid condition, the stability of grid-connected inverter will be greatly reduced. Taking the three-phase LCL inverter-side current feedback grid-connected inverter as an example, this paper analyzes the mechanism of the system stability degradation by using the frequency domain analysis method, and proposes to install a Second-Order Generalized Integrator (SOGI) in the grid voltage feedforward path. This strategy can attenuate the additional positive feedback associated with the impedance, which is introduced by the grid voltage proportional feedback, thereby improving system stability under weak grid. Finally, through the grid-connected inverter model and experiments, the effectiveness of the proposed control strategy is verified. This work is supported by National Natural Science Foundation of China (No. U1804143 and No. 61703144), Key Science and Technology Project of Universities and Colleges of Henan Education Department (No. 17A470010), and Fund of Henan Mine Electrical and Electronic Device and Control Innovation Scientific and Technological Team (No. CXTD2017085).