| At present, the issue of low power factor and harmonic pollution in traditionalcharge-discharge system is serious, with the development of PWM rectifier technology,PWM rectifier was applied to charge-discharge system. It can charge battery and allowenergy which is discharged by battery to feedback to power grid, while at the same time,power factor of charge-discharge system is improved and electric pollution is reduced.A novel main circuit topology of charge-discharge system with a three-phasevoltage source PWM rectifier (VSR) and Bi-directional DC-DC converter are applied inthis paper. Mathematical model of VSR and Bi-directional DC-DC converter arerespectively established. On this basis, parameters and control system is designed toattain high power factor and meet the character requirement of charge-discharge.Secondly, dc bus voltage stability is important to charge-discharge system. Withthe tradition double-loop control of VSR, load disturbance and power fluctuations havea great influence on the dc bus voltage. The strategy which is based on feed-forwardcompensation and output voltage feedback is proposed in this paper. Simulation resultsshow the effectiveness and validity of control strategies.Then, charge-discharge simulation model is established in Mathlab/Simulink. twomethod which is pulse charge and constant current and limited voltage is used to chargebattery in this paper. Simulation results show compared with traditionalcharge-discharge system, the high power factor system can realize high power factorand bi-directional energy flow.At last, the laboratorial platform based on three phase VSR is built. Experimentalresults show reversible PWM rectifier realizes low AC harmonic and bi-directionalenergy flow. So, PWM rectifier has charge and discharge function. It can be used asbattery charging power supply, but also as a discharge load of battery. Regenerativeenergy is feedback to power grid and the purpose of energy-saving and environmentalprotection are attained. |
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