Analysis and Simulation of Three-Input DC-DC Converter with Bipolar Symmetric Outputs

Abstract

This paper presents a three-input high-gain DC-DC converter with bipolar symmetric outputs. The advantages of a bipolar DC grid are higher reliability, flexibility, and efficiency as compared with the unipolar DC grid. Therefore, the proposed converter is designed to connect directly with the bipolar DC grid due to its bipolar symmetric outputs. The three input voltage sources to the converter are operated in a sequential manner from the first voltage source to the last one, with each source providing power at a level proportional to its duty cycle. Similarly, when the sources are equal, they operate in a sequential manner with their specific power. In addition, the proposed converter is designed to provide the required power to the grid under both simultaneous or individual from three input voltage sources. A double-loop PI controller is applied to regulate the converter output voltages and the control loop is analyzed and the transfer function relating reference voltage to output voltage is derived. Voltage balance control is provided to ensure that the outputs remain symmetrical despite changes in load conditions or input voltage. A converter with a power rating of 1000W and output voltage levels of 200V, -200V, and 400V is designed. The three supply voltage of 150V,100V, and 75V are used. The converter is tested under a variation of supply voltages and load using MATLAB/SIMULINK. The results show the feasibility and effectiveness of the proposed converter.