Optimization Of Three-phase Double Active Bridge Control Strategy

Clean energy power generation technology can effectively alleviate the current problems of environmental pollution and energy shortage in energy manufacturing.As the key equipment connecting energy storage device and clean energy power generation system,the efficiency of power electronic converter determines the efficiency of energy utilization.In the converters commonly used in clean energy power generation technology,the three-phase dual active bridge converter is widely used due to its many advantages.However,the traditional single phase shift control will have the problem of loss increase and efficiency reduction when the voltage conversion ratio is not 1 and the light load state,which limits the application of the three-phase dual active bridge converter.Therefore,it is necessary to optimize the control strategy of the three-phase dual active bridge converter.In this paper,the generalized state space averaging(GSSA)second-order model of three-phase dual active bridge converter is established,and the control strategy of asymmetric pulse width modulation(APWM)cascade single phase shift(SPS)control is proposed to expand the soft switching range and improve the efficiency of the converter.The proposed optimal control strategy is verified by simulation.Firstly,this paper analyzes the operation principle and operation loss of a three phase biexciton bridge.By analyzing the operating principle and operating characteristics of the three phase twin mode bridge transformer under SPS control,it is confirmed that the three-phase dual active bridge converter under SPS control,when the voltage conversion ratio is not 1,the area of the zero voltage switch(ZVS)becomes narrow,the converter loss increases,and the efficiency is lowered.In order to increase the efficiency of the converter,the power loss of the converter is analyzed,and the relationship between the loss and the voltage and current of the transducer must be clarified.The calculation formula of the loss of converters under the SPS control has established a theoretical basis for the optimization of the following control strategies.Secondly,the current and power waveforms of the three-phase dual active bridge converter are complex.If it is analyzed by theoretical derivation,it will be very difficult,the calculation is very large,and it takes a long time and is easy to make mistakes.Therefore,based on the working principle and working characteristics of the three-phase dual active bridge converter,combined with the GSSA modeling method,the second-order GSSA model of the three-phase dual active bridge is established,and the selection of electronic components is determined according to the design parameters of the main circuit.The simulation model of the main circuit is established in Simulink,and the accuracy of the second-order GSSA model is verified by the simulation model.Thirdly,based on the analysis of the principle and characteristics of dual phase control(DPS)control,APWM control and APWM + SPS control,the control strategy of APWM cascade SPS is proposed.Through the analysis of DPS control,it is concluded that the extended soft switching region is limited,and it will increase the peak current and the current stress of the switch tube.Therefore,the DPS control is not further studied.Then,by analyzing the APWM +SPS control strategy,the zero voltage switching region diagram of the three-phase dual active bridge converter under APWM + SPS control is drawn.The diagram shows that the APWM +SPS control strategy can achieve zero voltage turn-on in the full load range,but the APWM +SPS control involves the simultaneous change of two control variables,making the control complex and difficult to achieve the optimal control state.It is difficult to implement.Therefore,an APWM cascade SPS control strategy is proposed,which reduces the number of control variables.Only one control variable is adjusted at the same time,which makes the implementation of the control strategy easier.Then the loss of APWM cascade SPS control strategy is analyzed and compared with the loss of SPS control strategy in theory.The results show that the optimal control strategy can effectively reduce the loss,current peak and current RMS of the converter under light load,which proves the feasibility of the optimal control strategy.Finally,for SPS control,DPS control and APWM cascade SPS control strategy,the simulation models of control circuit and drive circuit are built in Matlab / Simulink,and connected with the main circuit simulation model of three-phase dual active bridge converter.The voltage waveform and pulse signal waveform of the forward and reverse power flow process of the converter under rated power,as well as the current peak and effective value at both ends of the transformer in the converter under different output power are simulated.The simulation results show that the three-phase dual active bridge converter using APWM cascade SPS control strategy can significantly reduce the current peak and loss under light load conditions.