Research on voltage equalization among multiple supercapacitor modules based on multiwinding transformer

Abstract

To solve the problem of a limited number of units in multiwinding transformer topology(MWTT) equalization, a new type of voltage equalization topology between modules is proposed in this paper. On the basis of the voltage equalization topology between cells, an additional winding for voltage equalization between modules is added, and a power switching device is connected in series with the additional winding. The driving signal of the power device is the same as that of the power device for voltage equalization between cells. Using circuit modelling for the MWTT, the variation law of the equalizing current during a high level of pulse width modulation(PWM) is obtained. As a result, the balanced voltage is approximately equal to the average value of the initial voltage of each series unit. The individual voltage converges to the balanced voltage value in an exponential form, and the estimation formula of the balanced time is given. The proposed topology is validated by both simulation and experiment. The results show that this voltage equalization topology can achieve voltage balancing between cells and modules. The balancing effect is ideal, and it has the characteristics of high reliability, fast balancing speed and simple control.