Dual active bridge (DAB) converter with single-phase-shifting (SPS) control would produce large backflow power when voltage regulation ratio deviates from 1 or under light load, an asymmetric duty cycle and internal phase shift (ADIPS) control was proposed which controls the transmission power by duty cycle and internal phase-shift ratio and the backflow power can be eliminated under light load therefore improves the efficiency of DAB converter. By establishing mathematical models of inductor current and transmission power, the working principle of the proposed control method was given as well as the cause of backflow power was analyzed. The constraints of zero backflow power and an optimization control method of zero backflow power under ADIPS control was presented. At last, an experimental prototype is used to obtain the validation results, simulation and experimental results verify the excellent performance of the proposed control strategy in eliminating the backflow power of DAB converter under light load.

Energy storage technology has become critical for supporting China’s large-scale access to renewable energy. As the interface between the battery energy storage system (BESS) and power grid, the stability of the PCS (power conversion system) plays an essential role. Here, we present a topology of a 10 kV high-voltage energy storage PCS without a power frequency transformer for the establishment of a large-scale energy storage system. We analyzed the energy storage converter’s mechanism and characteristics and also introduced the power-control strategy of the HVAC (high-voltage AC) and LVDC (low-voltage DC) converter module. On this basis, a 10 kV/1 MW high-capacity PCS prototype was designed. Additionally, by simulation and experiment, we proved the correctness of the PCS scheme. The topology and control strategy proposed in this paper can provide cases and technical support for the subsequent promotion and application of new energy and power station energy storage.