常规恒流充电电源输入端的功率随着输出电压的升高而逐渐增加, 充电结束时输入端的功率由最大值迅速降为0, 不仅需要电网能够提供近2倍于平均值的峰值功率, 还会造成电网电压的波动, 特别是在重复频率与工频接近的大功率应用场合时, 可能造成电网滤波系统的振荡, 影响供电可靠性和干扰其他用电设备。提出了一种带有储能环节的电路拓扑, 使得在对负载恒流充电期间, 输入端的功率保持在平均功率水平。充分利用了串联谐振电路断续工作模式的特点, 无需辅助变换器, 仅通过双向开关对电流的控制, 可将充电初期多余能量存储到储能环节, 并在充电后期逐渐将此能量向负载释放, 在充电启停时刻储能环节的净增能量为0。将上述拓扑电路添加到基于DC-link的恒流充电电源中, 进行了分析和控制参数推导, 并在输出电流8 A、最高输出电压5 kV的电源上进行了实验, 结果表明: 充电期间直流母线提供的电流基本稳定, 幅值为常规方案中最大母线电流的一半左右。

The input power of the conventional constant current charging power supply increases with the increase of output voltage, and the input power drops to 0 immediately at the end of the charging, indicating that the conventional CCPS not only needs 2 times power of mean value from grid, but also causes the fluctuation of the grid voltage. Especially when the repetition of high power system is close to the grid frequency, it may cause the oscillation of the power grid, reduce its reliability and have influence on other equipment connected to the same grid. A topology with buffer energy storage is proposed, which keeps the input power of CCPS stable during the charging process. The stable value equals to the average power of whole charging process. The characteristics of series resonant circuit in discontinuous mode are fully used, there is no need of auxiliary converter, only with control of bidirectional switches. The buffer capacitor can be charged in the early stage gradually, and release the energy to the resonant circuit gradually in the later stage. At the starting and ending of charging, the energy in buffer capacitor keeps the same. The proposed topology is added to the DC-link based CCPS. The analysis and deduced process of control parameter are given. The experiment is carried out on a CCPS with 8 A output current and 5 kV output voltage. The experiment results show that at the same charging speed, the DC bus current is stable and is about 1/2 of the maximum value in conventional CCPS.