光伏系统电压穿越控制策略研究

Research on Control Strategy of Photovoltaic System for Voltage Ride Through

针对两级光伏系统在电网电压穿越时难以对直流系统电压进行快速稳定调控的问题,提出一种功率-电压混合控制策略。并网电压较为稳定时,并网逆变器进行直流电压调控,升压电路工作在最大功率跟踪(Maximum power point tracking,MPPT)模式;并网电压穿越时,逆变器保持对直流电压的调控能力,升压电路由MPPT控制切换到电压控制,实现对直流电压的快速、稳定调控,降低直流电压波动量,提高直流系统的电压稳定性。为了证实提出的功率-电压混合控制策略在电压穿越时对直流系统的稳定调控能力,基于RT-LAB半实物测试平台,进行了并网光伏系统电压穿越时的动态试验。试验结果表明,相比于传统控制策略,在电压穿越时,改进的功率-电压混合控制策略能够将直流系统的电压波动量从78V减小到7.7V,将电压波动率从19.5%降低到1.9%,提高了直流系统的电压稳定性。

Aiming at the problem that it is hard to fast and rapidly regulate DC system’s voltage during grid voltage ride through in two-stage photovoltaic system,a power-voltage hybrid control strategy is proposed.When grid-connected voltage is relatively stable,inverter participates in DC voltage regulation,and boost converter works in maximum power point tracking(MPPT)mode.When grid voltage ride through happens,inverter maintains ability to control DC voltage,while boost converter switches from MPPT mode to voltage control to realize stable DC voltage regulation rapidly,with reduced fluctuation and improved DC system stability.To verify stable regulation ability of proposed power-voltage hybrid control strategy during grid voltage ride through,a dynamic experiment of grid-connected photovoltaic system under grid voltage ride through is carried out based on RT-LAB hardware-in-the-loop test platform.The results show that compared with traditional control strategy,the improved power-voltage hybrid control strategy can decrease DC voltage fluctuation from 78 V to 7.7 V,and reduce voltage fluctuation rate from 19.5%to 1.9%,which improves voltage stability of DC system.