基于有源阻尼的多逆变器并网谐振抑制

何国锋， 徐德鸿

(1.河南城建学院 电气与控制工程学院，河南 平顶山 467036；2. 浙江大学 电气工程学院，浙江 杭州 310027)

基于有源阻尼的多逆变器并网谐振抑制

何国锋1， 徐德鸿2

(1.河南城建学院 电气与控制工程学院，河南 平顶山 467036；2. 浙江大学 电气工程学院，浙江 杭州 310027)

由于电网阻抗的耦合作用，基于LCL滤波器并网的光伏逆变器之间会产生并联谐振。针对多逆变器并网的谐振问题，提出了一种基于多逆变器并网闭环控制模型的有源阻尼控制策略。基于多逆变器并网拓扑，依据戴维南等效定理建立了多逆变器并网的闭环数学模型，分析了多逆变器之间的谐振机理；采用电容电流反馈构成有源阻尼以抑制并网谐振，给出了基于滤波电容电流反馈的多逆变器并网闭环控制框图；依据谐振阻尼表达式研究了有源阻尼系数对并网系统的稳态及动态特性的影响。在三台10 kW并网逆变器上进行了无阻尼环并网控制算法与加入有源阻尼环控制算法的对比实验，实验结果表明了所提出的有源阻尼控制方法的有效性和可行性。

有源阻尼；并网谐振；戴维南定理；电容电流反馈；谐振机理

Abstract:Under the influence of grid impedance, the resonance will occur among the grid PV inverters which are connected to grid with LCL filters. In order to restrict the resonant of Multi-inverter parallel under grid-connected mode, an active damping control strategy, based on closed-loop control model for multiple grid-connected inverters, is proposed. The equivalent mathematical model of the closed-loop control circuit was established by the Thevenin Equivalent Principle firstly. Then the resonant mechanism based on the established control mathematical model was analyzed. To effectively suppress the resonant of Multi-inverter parallel, the active damping control method by the feedback of capacitor current of LCL filter was adopted, and the mathematical model of multiple inverters with the active damping control was given. The influence of active damping coefficient on the steady and dynamic response of the grid inverters was studied according to the resonance equation. Finally, the presented control method was verified by experiments on three grid inverters by comparing with and without damping control algorithms. The experimental results show that the presented control strategy can effectively suppress the resonance among paralleled inverters.

Keywords:active damping; grid resonance; Thévenin’s theorem; feedback by capacitance current; resonance mechanism

0 引 言

在并网运行模式下，所有并网逆变器在公共耦合点(point of common coupling，PCC)和电网相连，能够通过他们的注入电流改变PCC点电压。理想情况下并网阻抗Zg为零，则逆变器相互之间的耦合作用将不会存在。然而，实际考虑到低压配电网络经常有更高的PCC点电网阻抗，并联逆变器之间产生的复杂谐振问题将不能被忽略[1]。……