三相并网逆变器闭环输出阻抗建模及其优化

变压器漏感、线路阻抗等导致实际电网存在阻抗,并网逆变器输出阻抗与电网阻抗不匹配容易导致并网逆变器的稳定性变差,甚至不稳定。采用阻抗稳定判据对系统稳定性分析时,研究并网逆变器的闭环输出阻抗特性至关重要。首先在静止坐标系中建立了并网逆变器的闭环输出阻抗模型,并对电网存在阻抗情况下系统稳定性机理进行了研究。针对数字控制系统中计算延时和PWM调制等效延时对闭环输出阻抗的影响,提出了一种阻抗优化方法,以增大闭环输出阻抗幅值,提高系统的稳定性。采用改进阻抗的方法,以网侧存在RLC阻抗为例,对并网逆变器的稳定性进行了分析以及实验验证,结果表明所提出方法的正确性和有效性。

Closed-Loop Output Impedance Modeling and Optimization of Three-Phase Grid-Connected Inverter

Transformer leakage inductance and line impedance cause the actual power grid existing impendence which easi-ly leads to the deterioration of stability , even unstable as the output impedance of grid-connected inverter mismatches the impendence of the power grid .When we analyze the system stability using impedance stability criterion , the researching work on characteristic of closed-loop output impedance of the grid-connected inverter is critical .Firstly, the closed-loop output impedance model is established in stationary coordinate system , and the stability mechanism is studied when the power grid existing impedance .For the delay of PWM modulation and digital control system equivalent delay impacting on the closed-loop output impedance , this paper presents a method for optimizing the output impedance to increase the magni-tude of the closed-loop output impedance and improve the stability of the system .Using the optimized impendence method proposed in this paper, the stability of grid-connected inverter is analyzed and experimental validated in the case of RLC type grid impedance .Experimental results validate the correctness and effectiveness of proposed method .