Active Current Sharing of a Parallel DC-DC Converters System Using Bat Algorithm Optimized Two-DOF PID Control

This paper presents a current sharing method to actively balance the output currents of a parallel dc-dc converters' (PDCC) system regarding the demanded power. First, the operating principle of the PDCC system with parallel-connected bidirectional converters is studied. To regulate the output voltage in dc bus and share the output currents of the individual converters, a dual-loop control architecture comprising an outer voltage control loop and multiple inner current control loops is designed based on the automatic master-slave control scheme. Moreover, a feedback-type two-degree-of-freedom proportional-integral-derivative (FB2PID) controller is introduced to obtain the pulse-width modulation control signals for the converters. In order to improve the dynamic response and robustness of the active current-sharing control performances of the FB2PID controlled PDCC system, a bat algorithm (BA)-optimized FB2PID control system is further proposed to concurrently and dynamically optimize the control parameters of the FB2PID controller in the current control loop. Thus, the output current of each converter can be controlled to share the demand power equally in the presence of uncertainties. Finally, the simulation and experimental results reveal that the proposed BA-optimized FB2PID control system outperforms the conventional PID and FB2PID control systems with regard to the voltage regulation and current sharing performances under the time-varying electric load condition.