Research On Single Stage Converter Based On Electric Vehicle Charging Device

With the rapid development of the automobile industry,the amount of oil consumed has increased year by year.In order to resolve the contradiction between the rapid growth of fuel vehicles and increasingly serious environmental problems,governments have begun to develop new energy vehicles.However,there are currently problems such as insufficient charging facilities for electric vehicles.The on-board charger has the advantage of being able to charge whenever the battery needs to be recharged,as long as there is a power outlet available.It can alleviate the problem of difficulty in charging electric vehicles to some extent.In this paper,the on-board charger is taken as the research object.Aiming at the shortcomings of the complicated two-stage car charger circuit and high cost,a single-stage power factor correction circuit(PFC)is proposed.This circuit topology also provides fast regulation of the output voltage while meeting power factor and harmonic requirements.Compared with the two-stage converter topology,this paper proposes to use the leakage inductance of the transformer as the energy storage inductance,which greatly reduces the requirements on the inductance.At the same time,by changing the circuit topology,a small CBB capacitor is used instead of the original large electrolytic capacitor,which increases the power density of the circuit and improves the service life of the converter.Firstly,the working principle of the single-stage PFC proposed in this paper is analyzed in detail.The primary side H-bridge adopts a bipolar modulation with a fixed duty ratio,and achieves the purpose of controlling the output voltage and power factor correction by controlling the on-time of the switching tube on the secondary side.The single-stage isolated PFC proposed in this paper can work in both boost and buck modes.The intermittent operation,critical continuous operation and continuous operation mode of the boost operating state,and the low voltage operation and high voltage operation mode in the step-down operation state are analyzed in detail.Whether operating in boost mode or buck mode,the single-stage isolated PFC proposed in this paper can perform power factor correction and control output voltage.According to the working principle of the circuit,the principle of parameter selection of the main circuit in the single-stage PFC is given.Secondly,the control strategy of single-stage PFC is studied,A double loop control strategy is adopted in the control loop,the outer loop controls the output voltage,and the inner loop controls the waveform of the input current.A large-signal model of a single-stage isolated PFC is established.Based on this,a small perturbation is added to obtain a small-signal model of a single-stage isolated PFC.The parameters in the controller are adjusted in combination with the automatic control principle.Finally,the simulation model and experimental platform were built for verification.The simulation model under the state of boost and buck operation was built in PSIM9.0.The single-stage PFC proposed in this paper is verified,and the output voltage and power factor correction function can be realized under different operating conditions.The comparison of the small CBB capacitors in the main circuit shows that the voltage peaks of the switching tubes can be greatly reduced when the small capacitance CBB capacitors are present.The schematic diagram and PCB diagram of the hardware circuit are designed,and a 200W low-power experimental platform is built.The running program of the dual loop control and the digital phase locked loop is written in the DSP.The experimental results show that the proposed circuit topology can realize the functions of controlling output voltage and power factor correction.It provides certain theoretical and technical support for the research and promotion of on-board chargers.