The Effectiveness of Energy Exchange Processes in Traction Electric Drives with Onboard Capacitive Energy Storages
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Regenerative braking with return of energy to an aerial contact wire in principle makes it possible to reduce the energy consumption for traction needs, but in real conditions the effectiveness of this braking type as a means of reducing the consumption of energy resources is often limited. The electric braking of rolling stock is more effective and independent of the external conditions in which the generated energy is stored in onboard energy storages. The largest reduction of consumption of energy resources for traction needs when using onboard energy storages composed of traction the electric drives can be achieved for rolling stock operating with frequent starts and stops. These types of rolling stock include suburban electric trains, subway trains, and urban electric transport, to the specific operation of which capacitive energy storages based on supercapacitors correspond best. This work considers the processes of energy exchange in traction drive systems with onboard capacitive energy storages during acceleration and electric braking of rolling stock. The energy exchange processes are considered in relation to resistive charging–discharging circuits and circuits with reactors, and the main attention is devoted to the effectiveness of energy exchange processes. The energy consumer in an energy-storage discharging circuit and the source of energy in the charging circuit are represented by an EMF source, which in general can change with time. The dependences of energy effectiveness of charging and discharging processes of capacitive energy storage on its initial voltage and on the rate of change in the EMF of energy consumer are obtained.