光伏虚拟同步机低电压穿越的预同步控制策略

Pre-synchronous Control Strategy Based on Low Voltage Ride-through of Photovoltaic Virtual Synchronous Machine

虚拟同步机(VSG)光伏并网发电技术是一种新型的新能源发电模式。然而,在电网故障时,其技术不具有低电压穿越(LVRT)的能力,导致电网电压暂降且难以恢复原来的幅值,电流幅值越限,对系统造成一定的危害。因此,将LVRT技术与VSG技术相结合可以解决由系统故障引起的电网恶化问题,但这两种策略在切换时会产生前后相位不一致、电流幅值波形难以恢复到原幅值等问题。为此,提出一种预同步控制策略。通过引入相角预同步和VSG输出电压预同步,有效地避免了两种模式在切换过程中导致的相位和幅值不一致,提高了电能质量和系统的稳定性。在Matlab/Simulink中仿真,其效果显著。

Virtual synchronous machine(VSG) photovoltaic grid-connected power generation technology is a new energy power generation mode.However,in the event of a grid failure,its technology does not have the ability of low voltage ride-through(LVRT),resulting in a sag of the grid voltage and difficulty in restoring the original amplitude,and the current amplitude exceeds the limit,causing certain harm to the system.Therefore,combining LVRT technology with VSG technology can solve the problem of grid deterioration caused by system failure,but these two strategies will cause inconsistent phase before and after,and it is difficult for the current amplitude waveform to return to the original amplitude during switching.To this end,a pre-synchronization control strategy was proposed.By introducing phase angle pre-synchronization and VSG output voltage pre-synchronization,the phase and amplitude inconsistencies caused by the switching process of the two modes were effectively avoided,and the power quality and system stability were improved.Simulated in Matlab/Simulink,the results are remarkable.