| With the continuous development of the national economy and the continuous deepening of the layout of the new energy automobile industry,product modularization and integration are attracting more and more attention from people because of the outstanding advantages.The mid-cascaded two-stage AC/DC converter has been widely applied in industry because of its simple topology and easy control.However,traditional two-stage topology mostly uses PI control.As a mature control method,PI control has its unique advantages,but at the same time,it also has some inherent shortcomings,making it difficult to satisfy system adjustment requirements under rapid load changes.To this end,it is quite meaningful to design a control strategy with strong anti-interference ability and fast adjustment speed for two-stage converters.This paper set the front-stage Buck PFC converter and the back-stage Full Bridge converter as the main research objects.Considering the shortcomings of traditional Buck PFC converters,the Buck PFC circuit working in the discontinuous capacitor voltage mode was selected as the front-stage main circuit topology.A detailed analysis of its circuit operating characteristics,system boundary conditions,and device parameter designs was conducted.At the same time,based on the full understanding of the working mode of the back-stage Full Bridge converter,the paper completed the design and selection of the high-frequency transformer and power switching devices of the back-stage main circuit.As for the control strategy of the two-stage converter,the front-stage still used PI control.Research focused on the control method of the back-stage Full Bridge converter.Based on the analysis of the sliding mode control theory,a parameter-adaptive terminal sliding mode control strategy was proposed.The proposed control strategy not only inherits the excellent adjustment performance of traditional sliding mode control,but also adds an adaptive algorithm of adjustment parameters,which improves the robustness of the control strategy.As a result,it can ensure optimal adjustment effects under different working conditions.The control effect of the proposed control algorithm was verified based on simulations.Finally,an experimental prototype of a low-power two-stage AC/DC converter was built.The experiment verified that the proposed control strategy under the same load switching conditions can shorten the system adjustment time by 90% compared with traditional PI control,and the voltage adjustment can be reduced by 50%,indicating that the system has a faster dynamic adjustment speed.Both the simulation and experimental results verified the correctness of the theoretical analysis. |
