Investigation Of Charge And Discharge For Battery Based On Techniques Of Bidirectional Converter

With the more and more wildly use of storage battery in every field of nation,how to charge the battery safely, quickly and efficiently become very important.Direct rectifying or rectifying using thyristor is adopted by most traditional chargedevice. Through it has complete technique and low price using that method ofrectifying, it also has many disadvantage. So, a high efficiency, high-power andenergy-saving PWM storage battery charge and discharge system is presented inthis paper.This paper first studies the charging and discharging characteristics andworking principle of the battery, and then, puts forward the best suitable for storagebattery charging and discharging technology. According to this paper battery device,the three-phase LCL PWM converter is used to realize two-way flow of energy.Through the analysis of PWM four quadrant working principle, it found that thenets side current is reverse in rectifier and inverter states and the direction of thecurrent instruction can controller the rectifier and inverter state. Therefore, in thispaper, the mathematics model of the converter is only research inverter process.Secondly, a LCL–filter design approach with suitable filter-inductor voltagedrop and good bypass effect for switching ripple provided by capacitor andgrid-side inductor is proposed based on LCL-filter operation characteristic analysis.According to LCL-filter resonant problem, this paper use reactive damping methodand active damping method. The passive damping method is to connect a dampingresistor in series or parallel with the capacitance to eliminate the resonance, and theresearch the harmonic impedance, the resonance peak inhibition effect and powerloss of these two methods. Because of the low stability, this paper puts forward thecapacitance current feedback double loop control and the inverter current feedbackdouble loop control of active damping method. Then the parameters of thecapacitance current feedback double loop controller design. According to storage battery charging and discharging characteristics, thispaper give the voltage or current outside loop control method to stable the dc side’scurrent or voltage, then realize constant current or constant voltage mode. In orderto improve steady-state performance of current loop, one-beat delay control asinner loop and repetitive control as outer loop can be combined together toconstruct double-loop control, so that both fast dynamic repose and smallsteady-state error can be obtained. The simulation results showed that compoundcontrol method in steady-state and dynamic repose is good.Finally, a50KW prototype is studied. It studies hardware and software designon the base of56800F8356controller. The experimental results show that thecompound control is correct.