Hybrid Energy System for Urban Rail Power Supply Based on Multi-Level Multi-Port LCC Resonant Converters

To develop a novel hybrid energy system for urban rail power supply within a dc converter, we propose a multi-level three-port LCC resonant converter capable of operating in multiple modes. The converter integrates a five-level hybrid I-bridge (HI-B), a three-level I-bridge (I-B), and a voltage multiplier circuit, all of which are connected to an LCC resonant tank to establish common, auxiliary, and backup mode for energy transmission. Voltage boost and energy storage functions are realized by building the impedance model, which is also employed to derive power flow analysis for establishing a hybrid control strategy concerning switching frequency and phase shift angle. Then, the application of the hybrid control strategy to the converter enables the supercapacitor to operate in both constant current (CC) and constant voltage (CV) modes. The design of parameters and the control strategy among three ports under the condition of realizing zero-voltage switching (ZVS) are analyzed emphatically. Finally, according to the simulation and prototype experimental results, it can be shown that the performance of the converter is close to the theoretical analysis in each mode.