Study On Energy-reused Discharging Device Of Storage Battery

During the producting and using of storage battery, it is necessary to discharge storage battery to ensure good performance of the battery and security of system. The device which uses resistors to deplete the energy of battery has a high temperature-rise and low reliability, and is energy-wasting and ponderous. Transferring the energy into the public utility, the device has a low temperature-rise and high reliability, and is energy-saving, light, and small. Therefore detailed study is made in this paper on the battery-discharging device based on high-frequence PWM voltage-source converter (VSC). This paper analyses the principle of the operation of the high-frequence PWM VSC, and a detailed selection method for the key parameters of the VSC is analyzed and given. The improved period-average-mode of the single-phase PWM VSC is set up, and the current control scheme based on the model is presented. The hardware design of the digital control system is essentially discussed, and the control strategies and its software realization is detailed. Then the relevant program flow charts are given out. The realization of the current control is presented. Based on the power balance concept, mathematic model of discharging current is set up, and the linearized small signal model is then obtained using small perturbation analysis method. A PI controller of discharging current is designed, and effectiveness of the PI and the model of discharging current are verified by simulation. A software phase-locked loop (SPLL) implemented by DSP is designed, and the designing method of the SPLL regulator is proposed. A discharging device prototype is constructed, which uses TMS320F240 DSP as the heart of control system. Experimental results demonstrate that the discharging device based on high-frequence PWM VSC can both discharge battery at a constant current, and can transfer the energy of battery into the public utility with unity power factor.