Research Of High Power DC Parallel System Supply Based On Digital Current Sharing Current Technique

Nowadays,high-power supplies are widely used in industrial application.It is the main method to achieve high-power applications that several power modules combined to form a power system.In high-power occasions,it is valuable to improve the efficiency,and the soft-switching technology is the key to improve the it.Therefore,it is of great significance to study the parallel DC power supply system based on soft-switching.In this paper,the phase-shifted full-bridge converter is chosen as the module power,which is very suitable for high-power occasions.It is also relatively easy to achieve soft-switching: The zero voltage turn-on of the leading-legs can be achieved through the parallel capacitor,and with series saturation inductance in lagging-legs,the zero current turn-off of the lagging-legs is also achieved.This paper adopts the current double rectifier circuit to suppress the voltage spike and oscillation on the output diode,which improves the converter efficiency,further.the working process of the output diodes as well as the relationship between the output current ripple and the output filter inductance is analyzed in detail,and the design process of the relevant parameters is also given.In order to distribute the current on each power module in the parallel system evenly,appropriate current sharing measure is required.Through introd ucing of the commonly used current sharing methods,a three-loop control method with an added current sharing loop is put forward based on the digital control.Then,the small signal model of the phase-shifted full-bridge main circuit is established,and the parallel control system is also modeled and the stability is analyzed.This method can realize the current sharing between the modules and improve the response speed of the system.With the digital control of the power supply going to be the mainstream of the control method.In this paper,the TMS320F28335 is chosen as the digital control chip,using the built-in CAN module to achieve communication with other modules in the system.The relevant hardware and software program are designed to implement the circuit.Finally,according to the theoretical design,the experimental platform is set up and verified.The experimental results show: the module power can achieve the ZVZCS soft-switching of the IGBTs and the zero-current turn-off of the secondary diodes at the same time;the parallel system can achieve the designed full load power of 10 k W with reliable working condition and an ideal current sharing effect.