基于变下垂系数的直流配电网自适应虚拟惯性控制

直流配电网采用电压下垂控制具有较好的稳定性,但对高频随机功率波动的调节能力较差。文中研究了适用于直流配电网电压下垂控制的虚拟惯性控制方法,以兼顾调压器的快速性和稳定性,改善直流配电网电压质量。所述控制策略在功率波动瞬间通过调压器下垂特性曲线的摆动,快速释放或吸收能量,相当于在直流侧虚拟出比实际电容大得多的虚拟电容,提高了系统惯性,有效抑制了直流电压波动。同时,理论分析了在不同运行情况下该控制策略所能提供的具体的虚拟惯性裕度,在此范围内根据电压大小自适应地调节下垂系数,提供大小可变的惯性支持,从而使系统获得最佳动态响应。最后,在MATLAB/Simulink中搭建了四端风储直流配电网系统并进行仿真验证,结果表明所述控制策略能够起到改善系统暂态响应、提高直流母线电压质量,以及平滑与交流主网交换功率的作用。

Adaptive Virtual Inertia Control of DC Distribution Network Based on Variable Droop Coefficient

A DC distribution network using voltage droop control strategy has good stability, but the ability to adjust the high frequency random power fluctuations is poor. Being suitable for the voltage droop control of DC distribution network, a virtual inertia control method is studied to accommodate the rapidity and stability of the regulator, and to improve the quality of the DC voltage. The control strategy can compensate for the system power shortage by the rapid adjustment of battery''s charging and discharging rate, which is caused by the change in the battery''s droop coefficient. Thus this control strategy can provide a virtual capacitance much larger than the actual capacitance at the DC side and improve the system inertia. At the same time, the theoretical analysis of the specific virtual inertia margin under different operating conditions is provided, so that the control strategy can adjust the droop coefficient on the basis of the allowed swing range adaptively, allowing the battery to provide variable inertia support in accordance with its virtual inertia margin. This ensures the full and rational use of the inertia margin. In order to verify the effectiveness of the proposed control strategy, a four-terminal wind-battery-based DC distribution network is established in MATLAB/Simulink. The results show that the proposed control strategy is able to improve the system''s transient response, improve the quality of DC bus voltage, and smooth the power fluctuation between the AC grid and DC grid. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2015AA050101).