Fuzzy Control Strategies For DC/DC Converter

DC-DC converter modeling analysis is the basis of researching switching power supply and it is of great importance in analysis and design of switching power supply. So this paper analysis the modeling of DC-DC converter, and the modeling contributes to the improvement for the performance and efficiency of switching power supply.On the base of analysising the present and future of DC-DC modeling, a state-space modeling method based on the non-ideal converter is referred to. Taking the non-ideal Buck converter and Buck-Boost converter as examples, we elaborated on the modeling process of the continuous current mode (CCM) and discontinuous current mode (DCM), and established the state equation of the converters.In control methods, this paper first refers to T-S fuzzy control. Based on the nonlinear characteristic and state equation of Buck-Boost converter, this paper constructs the T-S fuzzy model respectively both in CCM and in DCM. Combining with the fine part-linear characteristic of T-S fuzzy model, in each of the local linear model, Adopting PDC control scheme, a fuzzy controller is designed via CQLF method. Then it obtains the controller parameters by using LMI method and compares the simulation results with PI control.After that, Based on the nonlinear characteristic, according to the established state equation of the Boost converter, this paper constructs the T-S fuzzy model of the Boost converter respectively both in CCM and in DCM. In DCM, the state equation of the circuit is a piecewise function; this paper introduces a switching function to integrate the sub-state equation into a state equation. Adjust the parameters of the switch function, transforming the state equation in DCM into the form in CCM, so it unifies the state equation and T-S fuzzy model of the Boost converter both in CCM and in DCM. Combining with the fine part-linear characteristic of T-S fuzzy model, in each of the local linear model, Adopting PDC control scheme, it designs the Boost converter's controller via CQLF method and obtains the controller parameters by using LMI method. Simulation results show that, T-S fuzzy model which based on Boost converter is reliable, and the fuzzy controller via T-S fuzzy model has better effects of stability and immunity to disturbance by comparing with PI control.