A Fast Modularized Multiwinding Transformer Balancing Topology for Series-Connected Super Capacitors

A fast modularized multiwinding transformer balancing topology (MMTBT) for series-connected supercapacitors is proposed in this paper. With the proposed MMTBT, the voltage balancing inside modules and between modules are completely decoupled and the degree of modularization is high. This is different from the existing MMTBT, with the existing MMTBT, different modules share the same PWM drive. While with the proposed MMTBT, different modules can be driven by different PWM, then the variable frequency control strategy can be used to realize a fast balancing speed. With the proposed variable frequency control strategy, the average balancing current will be large and the balancing speed inside modules will be fast. With the proposed MMTBT, the balancing between modules is realized by discharging the higher voltage modules. The MMTBT of the higher voltage modules will act as a fly-back converter and the excitation current is in continuous current mode (CCM) to realize a great discharging power. First, the extra energy from the higher voltage module is transferred to the filter capacitor of the half-bridge converter. Then, the outputs of the half-bridge converters are connected in series to form a multilevel converter to act as the input of a boost converter. At last, the energy is transferred back to the supercapacitor energy storage system by the boost converter. The higher voltage module will be discharged with a great discharging power, then the balancing speed between modules will be fast. The fast balancing speed is realized inside modules and between modules, then the balancing speed of the whole system will be fast. The variable frequency control strategy and the control strategy of boost converter are analyzed in detail and the fast balancing speed of the proposed balancing topology is proved by experimental results.