Research On Modulation And Control Strategy Of Modular High-frequency Link Matrix Converter

Development Plan for New Energy Vehicle Industry indicates that the development of electric vehicles are an important way to solve environmental pollution and energy shortage.However,the vehicle to station ratio is still high,so charging stations have become a key constraint on the development of the electric vehicle industry.With the increasing demand of users,high-power DC fast charging is the development trend of charging stations.The traditional charging station adopts a two-level topology,requiring a large capacity DC bus,which has low energy conversion efficiency and low power density.High-frequency link matrix converter(HFLMC)is a single stage power conversion topology that uses bidirectional switches and high-frequency transformers to achieve bidirectional energy flow and isolation of the input and output sides;Without DC bus link,HFLMC has the advantages of small size and high efficiency,so it is very suitable for the design and application of high-power DC charging station.Aiming at the requirements of high-power and modularization of charging station,combined with the characteristics of input-parallel and output-series(IPOS)structure,which can improve output voltage and power level,and reduce switch stress,this paper studies the modulation and control strategy of IPOS-HFLMC,and the main research results include:This article explores four types of modular HFLMC topologies,especially IPOS-HFLMC.The working principle of IPOS-HFLMC is analyzed in detail and its mathematical model in dq coordinate system is established.Bipolar current space vector(B-C-SVM)modulation strategy is introduced to achieve IPOS-HFLMC sinusoidal three-phase input current and stable system operation.The rationality and feasibility of the topology and modulation strategy are verified through MATLAB/Simulink.A 10 kW experimental platform for IPOS-HFLMC is built based on the dSPACE 1007 digital control system,further verifying the correctness of the simulation results.Aiming at the problems of high switching loss and slow commutation speed in IPOS-HFLMC topology,firstly,the commutation process of switches in different sectors is deeply investigated,and the current flow paths of four step and two step commutation strategies are analyzed.This paper proposes a voltage type fast and efficient one step commutation strategy.This strategy effectively reduces the dynamic loss of the switch and accelerates the commutation speed by adjusting the commutation process and the switching order.Finally,the advantages and reliability of the proposed one step commutation strategy are verified on simulation and experimental platforms.In order to solve the puzzle that the driving signal of IPOS-HFLMC is prone to generate narrow pulses during operation,which leads to the system being unable to safely commutation,this paper first discloses the principle of narrow pulse generation in the B-C-SVM modulation strategy and one-step commutation strategy,analyzes the hazards of narrow pulse commutation,and proposes a narrow pulse suppression strategy based on zero vector configuration optimization.This strategy selects the optimal zero vector configuration,which can effectively suppress the generation of narrow pulses,to ensure the safe operation of the system.A hybrid modulation strategy is proposed to solve the problem of large ripple on the output side by adjusting the carrier phase.Finally,simulations and experiments show the effectiveness of the proposed narrow pulse suppression strategy and hybrid modulation strategy.Aiming at the hard requirements of high immunity and output side rapidity during charging,this paper designs a control framework of IPOS-HFLMC centralized current or voltage outer loop and distributed current inner loop,which reduces the difficulty of controller design;The super-twisting sliding mode control strategy is studied.By optimizing the sliding mode control rate design,the system chattering is weakened and the rapidity is improved.According to the requirements of different charging modes,a current outer loop and a voltage outer loop super-twisting sliding mode controller are proposed.Finally,simulation and experiments verify that the proposed super-twisting sliding mode control has faster speed and better robustness than traditional sliding mode control.In summary,this paper conducts research on four aspects of IPOS-HFLMC:fast and efficient commutation strategy,narrow pulse suppression strategy,hybrid modulation strategy,and fast disturbance rejection control strategy,providing theoretical support for the application of IPOS-HFLMC on high-power DC charging station.