适用于低压微电网的逆变器控制策略设计

低压微电网中线路阻抗呈阻性,为保证逆变器输出阻抗与线路阻抗相匹配,在逆变器控制策略中引入了阻性虚拟阻抗。分析了逆变器电压环积分参数对逆变器输出阻抗的影响,在保证逆变器稳定运行的前提下,提高电压环积分系数可使逆变器输出阻抗呈阻性。对微电网等效电路分析得出,调节逆变器输出电压幅值可以调节逆变器输出的有功功率,调节逆变器的频率可以调节逆变器输出的无功功率。微电网并网运行时,分析了参数检测误差对逆变器输出功率的影响,在下垂特性控制中,引入幅值和频率微调的比例—积分(PI)调节器,可实现逆变器输出功率的无静差跟踪。仿真结果表明,所提逆变器控制策略运行稳定,在并网和孤岛运行时都具有优良的性能。

Control Strategy Design for Inverters in Low Voltage Microgrids

The line impedance is resistive in low voltage microgrids.In order to ensure that the output impedance matches the line impedance,virtual impedance is introduced to the control strategy for inverters.The impact of integral coefficient voltage loop on output impedance is analyzed.The improvement of voltage loop integral coefficient can make the output impedance become resistive provided that the inverter is in a stable operation state.From the analysis on equivalent circuit of a low voltage microgrid,it is concluded that the active power and reactive power can be changed by adjusting the output voltage amplitude and frequency of the inverter respectively.The impact of parameter examination error on output power of the power inverter is analyzed.The amplitude and frequency proportional-integral(PI) regulators are introduced to droop control strategy,which can realize zero-error tracking of the output power.The simulation results verify that the performance of the proposed control strategy is excellent both in grid-connected mode and islanded mode.