Research And Equipment Development Of Modular Combined High Voltage DC/DC Converter

High-voltage DC power supplies are widely used in industrial,agricultural,scientific,and medical fields today.There are many applications where low-voltage DC input requires high-voltage DC output,and the power level,output accuracy,and power density of the entire converter are also gradually increasing.Traditional linear power supplies have been difficult to meet the growing needs of people.The research and development of switching power supplies using modern power electronics and control technologies has become a solution to this problem.Modular combined High-voltage DC conversion technology is one of the key technologies of switching power supply.DC/DC converters that use multiple modules combined in series-parallel can be applied to high input-voltage high-power occasions.The input-parallel-output-series(IPOS)combination DC/DC converter is the outstanding choice for high input voltage and low output voltage applications.Achieving output voltage sharing(OVS)and input current sharing(ICS)is critical for the normal operation of the IPOS combined converter.The focus of this paper is mainly reflected in the following aspects:(1)The structure of the IPOS-DC/DC converter is studied by taking full bridge(FB)DC/DC converter as the basic module.The working principles of the full-bridge DC/DC converter are researched and the influence of the transformer leakage inductance on the full-bridge DC/DC converter is analyzed,and then the small-signal model of full bridge DC/DC converter is established.On the basis above,the FB-ISOP overall small-signal model is built,and the frequency domain analysis of the system is carried out by using perturbation analysis method,then the transfer function relation between each disturbance variable is deduced.(2)The input current sharing and output voltage sharing control strategy are compared,which reveal the reason why the input power sharing control strategy cannot achieve power sharing effectively.The theoretical research and simulation design of the IPOS output voltage sharing control strategy are performed.For the linear control method,it is difficult to realize the precise control of the nonlinear,multivariable,and strongly coupled system of the IPOS converter.Thus,a nonlinear control strategy is designed for the output voltage controller,and the Lyapunov stability of is guaranteed theoretically.Detailed parameters design and stability analyses are carried out.The simulation results show that the control strategy and the designed parameters can realize the stable output of the system as well as OVS and ICS.(3)The principles and steps of main circuit parameters selection are described in details by taking a 10 kV/200 kW IPOS converter design as an example,and according to the parameter design principles above,a five-module ISOP experiment platform is built,then the control system for the platform is designed.The experimental results show the validity and correctness of the research.