Negative Sequence Component Compensation Strategy of Grid-side Inverters Without PLL

In grid-connected power generation system, fast and accurate phase synchronization detection is the prerequisite of effective control. The influence of unbalanced voltage on the three-phase inverter with conventional PLL is analyzed. When the grid voltage is unbalanced, the detection of the voltage and the calculation of the phase-locked angle will produce errors, which will affect the control accuracy of the inverter. Therefore, a control strategy without PLL is proposed and a mathematical model is established to verify its feasibility. The control strategy separates the positive sequence components of the grid voltage in the dq coordinate system. By comparing the control without PLL with the conventional PLL, the simulation shows that the control strategy without PLL can quickly and accurately separate the positive sequence components from the unbalanced power grid voltage and has a better dynamic response time.