基于相位补偿和虚拟阻抗优化的LCL型并网变流器改进控制

LCL型并网变流器常采用同步旋转坐标系下基于变流器侧电感电流的并网控制,但LCL型滤波器和数字延迟的dq轴模型均存在轴间耦合,制约了并网性能,且随着开关频率降低,性能恶化更为明显。针对该问题,文中在建立LCL型并网变流器复矢量模型的基础上,对并网变流器耦合特性和传统解耦方案进行分析。针对现有方案的不足,提出了一种基于相位补偿和虚拟阻抗优化的LCL型并网变流器改进控制策略,通过零极点图详细分析了虚拟阻抗对系统耦合程度及系统阻尼特性的影响,进而给出了确定3个参数优化值的方法。最后,仿真和实验结果表明,与现有方案相比,所提策略能够实现对系统耦合程度及阻尼特性的独立控制,有效实现解耦并改善系统动态性能。

Improved Control of Grid-connected Converter with LCL Filter Based on Phase Compensation and Virtual Impedance Optimization

The grid-connected control based on inductor current on the side of converter in synchronous rotating coordinate system is widely applied in the grid-connected converter with LCL-filter. However, the axe-cross-coupling exist in the dq models of LCL filter and digital delay, which constrains the grid-connected performance and become worse as the switching frequency decreases. To address this issue, based on the complex vector modeling of grid-connected converter with LCL-filter, this paper analyzes the coupling characteristics of the grid-connected converter and the conventional decoupling scheme. Aiming at the shortcomings of the existing control strategies, this paper proposes an improved control strategy of the grid-connected converter with LCL-filter based on phase compensation and virtual impedance optimization. Then, the effect of virtual impedance on system coupling and system damping characteristics is analyzed in detail through the zero-pole plots. And the method for determining optimization values of three parameters are given. Finally, the simulation and experimental results show that the proposed strategy can achieve independent control of system coupling degree and damping characteristics, while effectively realize decoupling and improve system dynamic performance.