Three-Level Current Push-Pull Bidirectional DC/DC Converters And Power Control

With the development of the concept of the energy internet,the electrical energy router as a core device has become an important element of research.The bidirectional isolated DC/DC converter is the key device in the energy storage link of the energy router,acting as a bridge between the busbar and the energy storage device,realising the voltage gain and controlling the power.In this paper,a three-level current-type push-pull bi-directional DC/DC converter and power control method applied to an electrical energy router are studied as follows.Firstly,the topology of the three-level current-type push-pull bidirectional DC/DC converter is introduced,the working principle of the topology under PWM(Pulse Width Modulation)plus phase shift control method is analysed,and the different operating states of the transmitted inductor voltage are divided into different operating modes: four forward modes(battery discharging),four reverse modes(battery charging).On this basis,the expressions for the transmission power and the transmission inductor current are derived for each mode of operation and a simulation of the typical operating modes is carried out.Secondly,based on the above control,the voltage amplitude before and after the transfer inductor is controlled to be equal to minimise the peak stress on the transfer inductor current,and a state averaging model is modelled to establish the corresponding low order decoupled small signal mathematical model and draw a Byrd diagram.The control loop design scheme is analysed through parameter tuning of the converter regulator,and then theoretical analysis and simulation verification of the performance of the converter with feedforward compensation is carried out.Then,to further improve the dynamic performance of the converter,the focus is on the converter power control method,and the PWM plus phase shifting power model hybrid control and PWM plus phase shifting direct power hybrid control methods suitable for pushpull bidirectional DC/DC converters are proposed.To realise the power balancing of multiple converters operating in parallel,the sag control of the converters is studied with two units in parallel,and the theoretical analysis and simulation verification of the above control methods are carried out.Based on the theoretical analysis and simulation,this paper writes a control program for a three-level current type bidirectional DC/DC converter and verifies the correctness of the theoretical analysis and the effectiveness of the control strategy through experiments on the existing platform.