Impedance Control Strategy for Optimizing AC Bidirectional Power Stability Differences in Railroad Power Conditioners

Directional power flow in AC-DC hybrid equipment makes the system show different stability, and Railroad Power Conditioner (RPC) faces the same problem due to the different control strategies of the converters on both sides (α or β side). In this paper, a bidirectional stability analysis of the converter AC impedance on both sides of the RPC is carried out, and it’s found that the negative impedance characteristics of the AC impedance on the power control side (α side) in the reverse power flow as well as the existence of the high-frequency coupling in the dq-axis impedance will degrade the stability of the system. Aiming at the above problems, this paper proposes an impedance optimization control strategy, which improves the degree of AC impedance coupling while optimizing the negative impedance characteristics, and improves the stability of the system. Finally, the feasibility of the impedance optimization control is verified by simulation.