LCL并网逆变器二自由度PID单电流有源阻尼方法

提出了一种LCL并网逆变器二自由度比例积分微分(two degrees-of-freedom PID control,2DOF-PID)单电流反馈有源阻尼控制策略,其由比例积分(PI)环节和不完全微分环节两部分构成.比例积分环节控制并网电流高质量接入电网;不完全微分环节增强LCL逆变器的阻尼系数,有效抑制系统与电网形成的谐振尖峰,提高系统可靠性与稳定性,并改善系统的动态响应速度.该方法不用增加电压和电流传感器,系统成本低.建立了2DOF-PID控制系统的传递函数,分析了系统的稳定裕度与动态特性,选取了合适的控制参数,构建了系统仿真模型和实验平台.仿真与实验结果表明:2DOF-PID控制的LCL并网逆变器的满载并网电流畸变率仅为2.2%,远低于国家标准(GB/T 30427-2013)的要求;当系统从半载跳变到满载时,系统超调量低于9%,响应速度比其他方法更快.

A Single Current Active Damping Method Based on Two Degrees-of-freedom PID Control for LCL-type Grid-connected Inverter

This paper presented a single current active damping method based on two- degrees-of-freedom proportional integral derivative (2DOF-PID) control for LCL-type grid-connected inverter, which consists of proportional integral (PI) links and incomplete differential link. PI part is used to control the grid-connected current to inject the grid with high-quality. Incomplete differential part enhances the damping coefficient of LCL inverter, effectively suppresses the resonance peak caused between the inverter and the grid to improve the system reliability and stability, and speeds up the dynamic response. This method does not require additional voltage / current sensor, thus reducing the inverter cost. By establishing the transfer function of the 2DOF-PID controller, the system stability margin and dynamic characteristics were analyzed, and the proper control parameters were selected. The simulation and experiment platforms were built. The simulation and experiment results have shown that, in LCL-type grid-connected inverter under 2DOF-PID controller, the total harmonic distortion (THD) of grid-connected current is only 2.2% at full load, which is far below the national standard (GB/T 30427-2013). When the loads change from a half to all, the system overshoot reduces to 9 %, and the system response is faster than other methods.