Research Of Digital Buck Converter With Constant Power Load

In the cascade system of power electronics,the closed-loop load converter can be seen as a constant power load(CPL)and the negative impedance characteristic of CPL will affect the stability of the cascade system.In this paper,a Buck converter with CPL is taken as research object.A state feedback control method is proposed to solve the instability problem of cascade system.The studied system is mainly composed of two stages Buck converter.The load converter is used as a constant power load and it is controlled by voltage closed-loop method.The source converter is controlled by state feedback control method which contains integral element to keep the system stable.In this paper,the Buck converter is modeled and analyzed by means of the state space averaging method,the characteristics of Buck converter with constant power load and the reasons for the instability of the system are analyzed in detail.Then the paper analyzes the rationality that a CPL system uses the state feedback control method which contains integral element.According to the MATLAB simulation,the results show that the control method has good control effect on the cascaded system.Based on the theoretical analysis,an 800W prototype system of digital Buck converter with constant power load is developed.the source converter is controlled by state feedback control method based on DSP2812 chip,and the load converter is controlled by voltage closed-loop method based on SG3525AN chip.According to the test results of the prototype,it is verified that the state feedback control method can make the digital Buck converter with constant power load have good steady and dynamic performance.