基于谐振阻尼的三相LCL型并网逆变器谐波抑制优化策略

LCL型并网逆变器对高频谐波的衰减效果显著,但是内部滤波器自身容易出现谐振,而且对电网背景谐波电压引起的电网电流谐波抑制能力有限。针对逆变器中LCL型滤波器自身存在的谐振现象,在逆变器侧电流单环控制的基础上,分析其谐振机理,采用基于电感电流一阶微分前馈的谐振阻尼抑制谐振;同时建立谐波电网下的LCL型并网逆变器微分方程模型。在抑制谐振的基础上,主要分析网侧谐波电流环直接抑制方式,实现对电网电流谐振与谐波复合抑制,同时采用滤波电容临界值作为选择网侧谐波电流闭环的条件。分析闭环参数对系统性能的影响,给出控制参数的设计。实验结果验证了所采用控制策略的正确性和有效性。

Optimized Harmonic Suppression Strategy of Grid-connected Inverter with an LCL-type Filter Based on Resonance Damping

The grid-connected inverter with an LCL-type filter has the ability of easily attenuating the high frequency current harmonics. But its internal filter is prone to cause self-resonance, and the inverter has limited ability to grid current harmonics induced by harmonically distorted voltage. In consideration of the self-resonance phenomenon, the resonance mechanism is analyzed on the basis of the traditional bridge-side current closed-loop, and the resonance damping based on the first-order differential feedforward of inductor current is adopted to damp resonance. Simultaneously the differential equation model of grid-connected inverter with an LCL-type filter is developed under harmonically distorted voltage. On the basis of damping resonance, direct current suppression strategy based grid-side harmonic current is mainly analyzed to achieve grid current compound resonance and harmonic suppression,which is chosen by a critical capacitance of the filter capacitor. The influence of the closed-loop parameters on system performance is analyzed and the design of control parameters is presented. The proposed strategy is finally verified by simulation and experimental results.This work is supported by National Natural Science Foundation of China (No. 51277051, No. 51277050).