Research On Adaptive Optimization Strategy For Inductance Parameters Of Bidirectional DC-DC Converter

Bidirectional DC converter plays an important role in the dynamic and static energy balance control of DC microgrid system and the energy management of energy storage medium.Considering the comprehensive factors such as the power interaction quality between the energy storage system and the microgrid,as well as the cost and volume of the filter.This paper discusses the mechanism of the influence of the nonlinear inductance variation on the stability margin of the magnetic powder core inductor under different current excitation,and targeted research to improve the stability of the system control methods.This paper takes the three-phase interleaved bidirectional DC-DC converter with magnetic powder core inductor as the research object.Firstly,the mathematical model of the system was established,and the control gain of the inner current loop and outer voltage loop of the system was standardized.Based on this,the interaction between the feedback filter parameters and the parameters of the double closed-loop controller is studied.In addition,the influence mechanism of the magnetic powder core inductance with strong soft magnetic characteristics on the system stability margin is analyzed under the continuous working mode of inductive current.Secondly,in view of the influence of soft magnetic characteristics of magnetic core inductance on system stability,the inductance fitting method and the method to improve the stability margin of the system are studied respectively.Firstly,the electrical characteristic mathematical model of magnetic powder core inductance is established to realize the on-line and real-time fitting of inductance value.To further improve the system performance,Firstly,a prediction link is added to the inductor current feedback loop to widen the bandwidth of the inner loop,The new stability problem is studied.Finally,by adding high frequency damping link,the stability problem introduced by the prediction link is improved,the overall stability margin of the system is enhanced,thereby improving the adaptability of the system to changes in the inductance value of the magnetic powder core.In addition,when the current is small,the system works in the discontinuous state,then the methods used to evaluate and improve the operation characteristics of the continuous system will not be applicable.In order to unify the discontinuous and continuous mode of the control system,a current loop controller based on system model and energy conservation is proposed,realize the discontinuous and continuous unified control.Finally,the average current method is used to realize the effective current sharing among the interleaving circuits.Finally,the correctness of the theoretical analysis and the effectiveness of the research method are verified by simulation and experiment,The results of simulation and experiment both indicate that the stability of the system is significantly improved after the addition of prediction and high-frequency damping.Meanwhile,the discontinuous and continuous unified control can be achieved through the law of conservation of energy.