The Design And Research Of Closed Loop Control System For Bidirectional Full Bridge DC-DC Converter

With the depletion of traditional fossil energy,bi-directional DC-DC converters is more and more widely used in new energy power generation system,two-way energy storage system and new energy vehicles.LLC resonant converter based on DC-DC circuit topology,the range of voltage input is wide,and the switch tube works in soft switching state.The conversion efficiency is higher.This paper studied the topology of DC-DC converter based on LLC circuit,analyzes the working principle and working mode of the circuit topology,and the positive state of the work and the working state of the reverse fundamental analysis,gets its DC gain function.At the same time,the main circuit parameters and the output filter parameters are designed according to the technical requirements of the converter.In the fundamental analysis,it is known that the DC gain is 1 and the output voltage is fixed when the circuit works at the resonant frequency.But the reality is often there are many disturbances and uncertain factors,such as:the input voltage circuit will fluctuate slightly,the output load will change,need to real-time adjust the output voltage value(such as battery,the output voltage is adjusted from 48V to 53V).In order to solve the above problems,the system must be modeled mathematically,and the closed-loop controller is designed to improve the dynamic response and stability of the system.Because the switching frequency and resonant frequency of LLC resonant network are very close,the traditional PWM converter mathematical modeling is no longer applicable.This method has been used to describe the function of the circuit topology of small signal disturbance model,and the design of the compensation network control loop by using Matlab software,through the contrast before and after compensation the open-loop transfer function Bode,found that the frequency response of the system is greatly improved.Finally,the compensation network of the DC-DC converter with synchronous rectifier,energy switching process was simulated by using PSIM software,especially in the simulated load jump,boot etc.,designed the hardware control loop has a good dynamic performance and stability.