基于改进电容电流反馈的含非线性负载光伏并网系统振荡抑制策略

在含非线性负载的光伏并网系统中，光伏发电单元、非线性负载、电网三者之间的相互作用可能导致系统出现振荡，因此提出一种改进的电容电流反馈有源阻尼(capacitor current feedback active damping, CCFAD)控制方法。首先，采用谐波线性化方法建立含非线性负载的光伏并网系统序阻抗模型，并基于阻抗模型和对数频率稳定判据揭示含非线性负载的光伏并网系统振荡特性。随后，基于负电阻理论定义阻抗相对灵敏度指标，评价不同参数变化对系统阻抗特性的影响程度，获取影响系统稳定性的关键参数。基于不同参数的阻抗相对灵敏度分析，提出一种改进的CCFAD方法。该方法拓展了传统CCFAD的正阻尼区域，有效地改善了系统输出阻抗的相位裕度，提高了系统稳定性。最后，在Matlab/Simulink中搭建仿真模型，验证了分析方法的正确性和所提控制策略的有效性。

Oscillation suppression strategy of a PV grid-connected system with nonlinear loads based on improved capacitor current feedback

The interaction of photovoltaics (PV), nonlinear load, and the AC grid may lead to oscillation in a PV grid-connected system with nonlinear loads. To address this issue, an improved capacitor current feedback active damping (CCFAD) control method is proposed. The harmonic linearization method is used to establish the sequence impedance model of the PV grid-connected system with nonlinear loads first. Then the resonant characteristics of the system are revealed based on the impedance model and a stability criterion. Subsequently, based on negative-resistance theory, impedance relative sensitivity is developed to evaluate the impacts of parameter change on system impedance characteristics and to identify the key factors influencing the resonant properties of the system. An improved CCFAD method is proposed based on impedance relative sensitivity analysis. This not only extends the positive damping region of the traditional CCFAD, but also improves the phase margin of the system output impedance. The stability of the system is effectively improved. Finally, the correctness of the analysis and the effectiveness of the proposed control strategy are verified by Matlab/Simulink simulation analysis.