Research On PV/QF Droop Control Technology Of Microgrid Inverter

Microgrid technology has become one of research hotspots in recent years along withthe rapid development of renewable energy distributed generation systems. Most of themicrosources in microgrid connect into the ac power grid side through inverter which is animportant part for energy exchange, so inverter control is the key to the stable and reliableoperation of microgrid. In the paper, suitable methods of microgrid inverter are deeplyresearched according to the characteristics of the microgrid.Droop control technologies of microgrid depend on the output impedance of inverter.In the paper, the output impedance of inverter is analyzed in detail and virtual impedancecontrol method is adopted to make the output impedance of inverter to be resistive, so thePV/QF control method is suitable for microgrid. Small signal model of inverter isestablished. The root locus verify the influence of different parameters on the stability andrapidity of the system and also provide the evidence for parameters selection. Twomicrosources operation system in different line impedances is built for simulation whenvirtual impedance is used or not. Simulation results show that virtual control method canimprove system stability and achieve better power sharing.Better power sharing can be achieved using virtual impedance control method, butsystem steady performance is declined and the deviation of power sharing is still exist. Inthe paper, the reason of power distribution deviation is analyzed and an improved controlmethod which adopts an integrator in the voltage reference generation loop is employed.The steady-state voltage value can be boosted when the improved control method is used,and also power precise control can be achieved. The method has high Robustcharacteristic, do not suffer to the line impedance, disturbance and stray parameters. Themicrogrid simulation model is established using MATLAB/Simulink software to prove thevalidity and rationality of the improved control method.The microgrid experimental platform with three inverters is built in the laboratory. Clanguage is used to program and32-bit TMS320F2812DSP is adopted for digital control.The control methods adopted in the paper are established on the experimental platform. The experimental results show that the control method can not only improve the voltagesteady-state value, but also achieve precise power sharing.