Research On Control Technology Of DC-DC Converters

At present,with the increasing types of electric power and electronic products and the development of all-electric technology,the requirements for power supply of electric equipment are also increasing.Although PI control is commonly used in DC-DC control systems in traditional industries today because the traditional PI control strategy can achieve good steady-state performance and its algorithm is simple and easy to implement,but PI controller has inevitable hysteresis,and its dynamic performance is limited by bandwidth,making it can not meet the demand in some occasions.This paper takes Buck converter as the representative research object.First,the traditional double closed-loop controller is designed and the PI parameter optimization algorithm targeting minimum startup loss is proposed.The optimization algorithm can gradually search out the PI parameter combination that corresponds to the minimum startup loss based on a small amount of experiments.Then,this paper designs and studies the optimal control strategy based on capacitor charge balance,which is generally accepted as the best dynamic response,and analyzes the optimal time dynamics under ideal conditions.In order to improve dynamic performance of the converters,a novel direct energy control strategy,taking energy as its control object,is proposed in this paper.A direct energy controller and its operating mode are designed and its operating characteristics are analyzed.The proposed control method is based on energy balance principle,which can ensure that the energy provided by the circuit for load does not exceed its desired value,so as to effectively avoid the oscillation in dynamic process and shorten the settling time.Buck converter control system model is set up in MATLAB / SIMULINK environment,and the simulation of double closed-loop control,time-optimal control and direct energy control are carried out,respectively.The startup performance with the three control methods as well as the dynamic performance during the step change for load,reference voltage and input voltage is analyzed,respectively.The feasibility and the superiority of the direct energy control strategy are verified.The feasibility and correctness of the PI optimization algorithm are also verified.Finally,this paper builds the hardware experimental platform of the Buck converter control system based on TMS320F28335 microprocessor,and implements the experiments for the operations of startup,load step change and reference voltage step change under double closed-loop control and direct energy control,respectively.The feasibility of direct energy control and its superiority in startup and dynamic performance are verified based on the experiments.The problem of steady-state output jitter in practical applications with the direct energy control is analized and some improvement plans are put forward to be studied later.