Controllable regenerative braking process for hybrid battery–ultracapacitor electric drive systems

This study proposes a controllable regenerative braking process for hybrid battery–ultracapacitor electric drive systems. The motor in the system is controlled to brake with a constant torque. To this end, a control framework is proposed which includes a circuit topology, decentralised active disturbance rejection controllers (ADRCs) and an operational modes switch controller (OMSC). The motor brakes with ultracapacitor when its speed is fast, and brakes with a dissipative resistor when its speed is slow. Decentralised ADRCs guarantee that ultracapacitor-based braking mode and dissipative resistor-based braking mode can be controlled individually. OMSC coordinates the decentralised ADRCs working cooperatively. Modified ADRC is proposed to implement bumpless transfer when the operational mode or braking mode is switched. The advantages of the proposed control system are as follows: (i) the control of the regenerative braking process based on ultracapacitor and dissipative resistor is linked with the control of the motor; (ii) speed of the motor in the electric drive system is controllable during the regenerative braking process; and (iii) bumpless transfer is guaranteed when braking mode changes from ultracapacitor-based braking mode to dissipative resistor-based braking mode. The following experimental results validate the proposed control framework for the controllable regenerative braking process.