Seamless Transition Mode Control For Sic Energy-Recycling Dc Electronic Loads

Energy recycling of the battery burn-in test is of great importance to reduce the battery testing cost in mass production. A 5-kW three-stage energy-recycling DC electronic load with a wide input voltage range of 150 V-750 V is proposed. The system is composed of a SiC-based interleaved boost DC-DC converter with an input current loop and an input voltage loop, a SiC-based LLC resonant converter (DCX) and a single-phase grid-connected T-type inverter with the double loop control including the outer voltage loop and the inner current loop. A decoupling control strategy with separate control for each stage is presented in this paper. There are four basic operation modes: Constant Current (CC), Constant Voltage (CV), Constant Resistance (CR) and Constant Power (CP). According to the property of the power source as voltage source and the battery pac, seamless transition mode control of the load is proposed. A control method with the boost converter voltage loop and current loop following mutually based on digital control is applied to solve the problem of current and voltage spike during mode transition. The mode switching time of all transition is less than 10 ms. The prototype of the proposed load has the peak full-load efficiency of 95% and high power density of 12.5 W/in(3).