微网逆变器并联无功功率均分与端口电压补偿策略研究

Research on Parallel Reactive Power Sharing and Port Voltage Compensation Strategy of Microgrid Inverters

  • 摘要: 微网逆变器并联系统多采用下垂控制方法,其可以根据微网状态来分配逆变器的输出功率。然而当线路阻抗存在差异时,传统下垂控制无法使系统输出的无功功率按照下垂系数进行均匀分配,系统中存在无功环流。由此提出一种基于逆变器输出无功功率差异的可变下垂系数与端口电压补偿相结合的控制策略。通过电压电流双闭环参数设计,实现有功、无功功率的解耦,输出阻抗与线路阻抗近似呈感性,使并联系统适用于 P-ω/Q-V 下垂控制方程;在无功-电压环节通过引入两逆变器输出无功功率的平均值以实现下垂系数的可变性,将参考电压按比例引入并通过积分补偿抑制端口输出电压偏移过大。仿真和试验结果证明,所提策略可以使不同线路阻抗系统实现无功功率均分,有效地抑制无功环流。

     

    Abstract: The parallel system of microgrid inverters mostly adopts droopy control method, which can distribute the output power of inverters according to the state of microgrid. However, when the line impedance is different, the traditional sag control can not make the output reactive power evenly distributed according to the sag coefficient, and reactive power circulation exists in the system. A control strategy based on variable sag coefficient of inverter output reactive power difference combined with port voltage compensation is proposed. Through the voltage and current double closed-loop parameter design, the active power and reactive power are decoupled, and the output impedance is approximately sensitive to the line impedance, which makes the parallel system suitable for P-ω/Q-V sag control equation. The average value of the output reactive power of two inverters is introduced to realize the variability of sag coefficient in the reactive power-voltage link. The reference voltage is introduced proportionally and the output voltage deviation is suppressed by integral compensation. Simulation and experimental results show that the proposed strategy can equalize reactive power in different line impedance systems and effectively suppress reactive power circulation.

     

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