Extended Impedance-Emulating Control for Series-Compensated Grid-Connected Inverter

To increase the long-distance power transmission capacity of renewable energy power stations, series compensation is a common solution. However, oscillation problems are introduced by the interaction between grid-connected inverter (GCI) and series-compensated power lines, threatening the safe operation of the power system. To address this challenge, an extended impedance-emulating control strategy without the phase-locked loop (PLL) is proposed. Compared with the conventional control strategy, the proposed method can stabilize the system in weak grids and high series compensation level (SCL) grids. In addition, the effectiveness of the method is verified by stability analysis. Eigenvalues analysis is performed to guide parameter design. Finally, theoretical analysis and proposed control strategy are validated with simulation and experimental results.