Research On Control Strategy Of Series Parallel System With Multiple Power Modules

In the fields of power system and space power supply system,the application of HVDC technology is increasing day by day.The traditional power topology is difficulty to be used in these application mainly due to the issues of system insulation and topological reliability.Modula r series parallel technology can solve a series of problems caused by high voltage,which has been widely used in the high input voltage environment.Nowadays,the main research of the current series and parallel technology of standard modules is to innova te and improve the control strategy,so that the performance of the combined system can be comparable to the single module system.Therefore,this dissertation studies a control strategy that can realize automatic hot pluggable function,including two control loops,to improve the system's reliability and ensure the system's voltage sharing.Due to the requirement of voltage sharing characteristic of the input series output parallel system,the input voltage is selected as the control object of the voltage sharing control loop to ensure the precision of the system's voltage sharing.At the same time,the distributed control mode can be used to realize the good dynamic response and the module building function,reducing the research and design period.The output control loop of the system selects voltage control mode,to maintain the stability of the output voltage of the system.Meanwhile,it is connected into the automatic master slave duty cycle mode,to improve the reliability of the output control loop.The output of the two control loops is superimposed,to adjust the duty ratio signals.In the condition of the stable system output,the precision of the system's voltage sharing and dynamic characteristics can be ensured.In order to realize the automatic hot pluggable function of the system,the detection circuit is designed in the input of each module,which can be quickly detected and removed after the failure of the module.Meanwhile,the voltage sharing control loop is automatically adjusted according to the number of remaining normal modules to ensure a proper voltage control.In addition,in view of the problems that may be encountered in practical applications,such as the effect of parameter mismatch and the mode of detection and removal after the module fault,the analysis and applicability are given to all control strategies.And also,a calculation method for the system to withstand voltage and current pressures after the fault removal is studied,so as to facilitate the selection of the appropriate devices and module quantity,to improve the reliability and anti-interference capability of the whole power supply system.In view of the above contents,this dissertation derives the corresponding theoretical derivation by establishing the mathematical model,and uses the simulation software SIMPLIS to verify it from the time domain and the frequency domain under various conditions.In the last two chapters,the hardware platform is built,and the feasibility of the control strategy is verified by experiments.In the simulation and experiment,the control strategy is compared with the same duty cycle control strategy under the conditions of steady and dynamic,and the completion of the proposed control strategy is verified.