As the energy storage unit of the urban rail regenerative braking energy utilization energy storage system, the supercapacitor cabinet, in conjunction with a bidirectional DC converter, stores the regenerative braking energy generated during the braking of urban rail vehicles and releases the stored energy when the vehicle is pulled and started. The urban rail vehicle releases 6kW · h of energy within 20 seconds of braking, which is absorbed by the supercapacitor and released within 20 seconds, fully utilizing the functional characteristics of the supercapacitor. The lifespan of supercapacitors is 1 million charge and discharge cycles, which saves customers a lot of materials and costs compared to the hundreds of thousands of charge and discharge cycles of ordinary lithium batteries.