考虑电网电压基波锁相环控制的单级式光伏逆变器柔性并网方法

Flexible Grid-Connection Method for Single-Stage Photovoltaic Inverter Based on Phase-Locked Loop Control for Grid Fundamental Frequency Voltage

针对目前光伏并网逆变器存在基波电压定向偏差、直流电压崩溃以及逆变器并网对电网产生冲击的问题,提出一种基于电网电压基波锁相环技术的三环控制方法,应用于单级式光伏并网逆变器,提高逆变器输出性能,并实现柔性并网。该方法首先基于电网电压基波的锁相环技术,实现对电网电压基波分量定向,定向效果取决于锁相环的设计性能;其次采用三环控制结构避免直流电压崩溃问题,减小输出电流总谐波因数;最后采用合理的并网控制逻辑,实现光伏逆变器柔性并网。实验验证了该方法的可行性,可提高系统动态响应实时性与稳态跟踪精度,实现系统高可靠运行。

In allusion to orientation deviation of grid fundamental frequency voltage and DC voltage collapse of existing grid-connecting photovoltaic（PV） inverter and the impact to power grid due to grid-connection of photovoltaic inverter,a three-loop control method based on phase-locked loop（PLL） control for grid fundamental frequency voltage was proposed and applied to single-stage grid-connecting PV inverter to improve output performance of the inverter and implement flexible grid-connection.Firstly,based on PLL control for grid fundamental frequency voltage,the orientation of grid fundamental frequency voltage was performed and the effect of the orientation was dependent on the designed performance of the PLL;secondly,the three loop-control structure was adopted to avoid DC voltage collapse and decrease total harmonic factor of output current;finally reasonable grid-connecting control logic was adopted to implement flexible grid-connection of PV inverter.The feasibility of the proposed method was verified by experiments,and experiment results showed that using the proposed method both real-time performance of dynamic response and steady state tracking accuracy could be improved.