基于下垂控制的微电网并网预同步控制研究

Research on Pre Synchronization Control of Microgrid Grid Connection Based on Droop Control

微电网主要有孤岛和并网两种运行模式,若将逆变器直接并网运行会引起冲击电流,使微网电压与网侧电压产生偏离导致设备损坏,因此,平滑切换是微电网稳定运行的关键技术。基于三相电压源型逆变器提出一种下垂控制的并网预同步控制策略,通过Clark变换和Park变换得到旋转坐标系下逆变器输出电压相位和电网电压的相位关系,计算两者的相位差值,经过PI控制调节得到并网相角频率的补偿值,按照一定步长调节逆变器侧输出电压的幅值和相位,使得逆变侧与网侧电压相位幅值保持一致,解决了模式切换时电压功率波动问题,实现微电网孤岛与并网运行模式间的平滑切换。最后,在MATLAB/Simulink仿真平台上搭建了电路仿真模型,验证了所提控制策略的合理性和有效性。

The microgrid mainly has two operation modes: islanding and grid connection. If the inverter is directly connected to the grid, it may cause impulse current, make the voltage of the microgrid to deviate from the grid side voltage and cause equipment damage. Therefore, smooth switching is the key technologies for stable operation of the microgrid. This paper proposes a droop-controlled grid-connected pre-synchronization control strategy based on a three-phase voltage source inverter. The phase relationship between the output voltage phase of the inverter and the grid voltage in the rotating coordinate system was obtained by Clark and Park transformation. The phase difference value of the inverter was adjusted through PI control to obtain the compensation value of the grid-connected phase angle frequency, the fluctuation problem of voltage and power during mode switching was solved, and the amplitude and phase of the output voltage of the inverter side were adjusted according to a certain step, so that the phase amplitudes of the voltage side of the inverter and the grid side remains were consistent to achieve smooth switching between microgrid islands and grid-connected operation modes. Finally, a circuit simulation model was built on the MATLAB/Simulink simulation platform to verify the rationality and effectiveness of the proposed control strategy.