Instability Risk Assessment of Large Scale Photovoltaic Access to Railway Traction Power Supply System

To address the resonance risks potentially introduced by the large-scale integration of photovoltaic (PV) systems into railway traction power supply systems (TPSS) through high-capacity grid-connected inverters, an impedance model for both the high-capacity grid-connected inverter and the TPSS is established. The stability risk of the resulting “sourcenetwork” coupled system is evaluated using impedance analysis. First, the inverter impedance model based on a dual-compensation multiple quasi-proportional resonance (DC-MQPR) control strategy is derived, and the model's accuracy is validated using a frequency sweep method. On this basis, the impedance model of the “source-network” coupled system is established, and the effects of inverter control parameters, circuit parameters, and TPSS parameters on the stability of the coupled system are thoroughly analyzed. The research results indicate that the integration of large-scale PV systems into railway TPSS increases the risk of system instability. Specifically, the integration capacity of the PV system, inverter control parameter <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{p}$</tex>, transformer turn ratio <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K_{T}$</tex>, and filtering parameter <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$L$</tex> are closely related to the system's instability risk.