Research And Design Of Bidirectional Full Bridge DC/DC Converter On Electric Vehicle

Bidirectional DC/DC converter can achieve step-up or step-down according to the using of energy. With the development of electric vehicle, Bidirectional DC/DC converter is widely applied in the field of automobile, and requirements for volume, weight, efficiency and safety of the DC/DC converter are being much higher.Firstly, this paper made an introduction to the principle and application of the bidirectional DC/DC converter, and analyzed the various bidirectional DC/DC topologies in detailed. Soft switch control technology was introduced briefly. And the full bridge DC/DC converter was chosen as the research object ultimately.According to the applications of the DC/DC converter, this paper designed the parameters of the power switches, inductance and transformer, and also completed the bidirectional full bridge DC/DC converter prototype design, finally made a 2.5 Kw prototype.Then, this paper emphasized the control strategy of bidirectional DC/DC converter. By using the small signal analysis method, the nonlinear DC/DC converter was converted into a linear mathematical model. And then this paper respectively established the open-loop transfer functions of step-up and step-down mode. According to the classical control theory and the discrete PID control algorithm, this paper analyzed the stability of the closed-loop feedback control system and adjusted the PID parameters, which completed the design of compensating network.Furthermore, The MATLAB simulation model is established. The bidirectional full bridge DC/DC converter control strategy is verified by this simulation model. The result showed that the bidirectional full bridge DC/DC converter had reached a good dynamic response and stability. The prototype testing proved the feasibility of the control strategy in practice.Finally according to the negative pulse charging theory, the quick charging control strategies of lead-acid battery and lithium battery were studied. Using this prototype, a series experiments were made. The results showed that the negative pulse charging control strategy didn’t play a role for lithium ion battery’s charging rate and capacity, but it achieved good effects for lead-acid battery. The results also proved the feasibility of the converter’s application to electric cars.