Research on DC Voltage Stability Control of Railway Power Conditioner Based on Impedance Matching Principle

When the railway power conditioner (RPC) is used to solve the power quality problem of the electrified railroad, the dc impedance will have a negative impedance characteristic during the bidirectional transmission of RPC power, and this negative impedance characteristic will affect the accuracy of RPC power compensation, cause the fluctuation of RPC dc bus voltage, and affect the effect of negative sequence current management on the grid side. In view of the above problems, this article proposes an RPC control strategy based on the impedance matching principle, which optimizes the negative impedance characteristics into positive impedance characteristics by the cooperative control of dc voltage and power, increases the phase angle margin of the system, improves the stability and dynamic performance of dc voltage under the bidirectional flow of RPC power, and improves the effect of grid-side negative sequence current management. First, this article performs small-signal modeling of the dc-side port impedance and analyzes its impedance characteristics. Second, the working principle of the RPC control strategy based on the impedance matching principle is analyzed. Finally, the proposed control strategy is effectively verified by building a simulation model and an experimental platform.