Sensorless Current Sharing Control of Three-phase Interleaved Bidirectional DC Converter

Aiming at the disadvantages of overabundant control loops and complex design of current detection circuit in the current sharing process of three-phase interleaved bidirectional DC-DC converters, a current-free current sharing control strategy is proposed based on traditional voltage-type control. The converter buck mode is taken as an example, and the equivalent resistance circuit model is established according to the Thevenin theorem. The relationships between the phase-to-phase current and the equivalent resistance or the effective duty cycle are analyzed. It is clear that the cause of the phase-to-phase current imbalance is the impedance mismatch. Moreover, based on one of the phases, the other two correspondingly changed duty cycles ∆D are derived and compensated. At the same time, the design method of the control loop of the current-free current sharing control system is given. The digital control technology is used to discretize the controller, and the duty cycle mismatch at the switch node is compensated to avoid the effects of the low accuracy of the current sensor, and insufficient design on the converter. The simulation and experimental results in a 25 kW prototype show that the current sharing performance is superior under various mismatches and different loads, which verifies the correctness and feasibility of the theoretical analysis. © 2021, High Voltage Engineering Editorial Department of CEPRI. All right reserved.