直流微网低电压穿越控制策略研究

LVRT control strategy for DC micro-grid

针对直流微网低电压穿越问题,基于光伏直流微网在综合考虑低电压穿越控制要求以及故障期间光伏出力、负荷随机波动性大对系统运行造成影响的基础上,分析了系统在不同运行工况下的能量流动特性,提出一种光储荷协调控制以及有功无功协调控制的系统整体控制方法。在低电压期间,通过光储荷协调配合控制稳定直流母线电压,同时平衡系统能量;网侧变流器根据电网电压幅值,实现有功无功协调限流控制,提供无功功率支撑网侧电压恢复,同时避免网侧变流器输出过流。最后,在Matlab/Simulink平台搭建仿真实例,仿真结果表明所提控制策略能够实现系统能量最优利用,满足系统低电压穿越要求,保障系统可靠运营,从而验证了该LVRT控制方案的有效性。

In view of the low voltage ride through （LVRT） issue of DC micro-grid system, the power flow characteristics under different operating conditions are analyzed, and an overall control method of the coordinated control for pho- tovohaic/battery storage/loads as well as the coordinated control for the active and reactive power is put forward, which is based on the comprehensive considerations of the LVRT control requirements and the effect for system opera tion comes from the random fluctuations of PV outputs and load during the fault. During low voltage of the system, the coordinated control for photovoltaic/battery storage/load can maintain the constant DC bus voltage and balance the power of system. Meanwhile, the grid-side converter is employed to realize the coordinated control for the active and reactive power according to the grid voltage change level, thus providing reactive power to support grid-side voltage recovery and avoid over-current of the grid-side converter output. Finally, the resuhs implemented in Matlab/Simulink platform show that the proposed control strategy can achieve the optimal utilization of energy, meet the LVRT control requirements and ensure the reliable operation of the system, so that the effectiveness of the LVRT control strategy is verified.