CLLC型模块化输入串联输出并联直流变压器

摘要

提出了一种CLLC型模块化输入串联输出并联的直流变压器技术方案,实现了高压直流电网和低压直流电网之间的电压变换和功率的双向传输.直流变压器的子模块采用CLLC串联谐振变压器,通过开环定频控制模式和完全谐振工作模式,效率高、电压增益恒定,同时具有输入自然均压和输出自然均流的特点.为了抑制较大的启动冲击电流,提出了一种软启动控制策略:通过脉冲调制的方式控制输入端全桥电路的输出电压占空比D从Dmin缓慢增加到0.5.搭建了一台500 kW ±7.5 kV/800 V直流变压器实验样机,实验结果验证了所提方案的正确性和可行性.%The technical scheme of a CLLC type modular input-series output-parallel DC transformer is presented, which can achieve voltage conversion and power transmission between high and low voltage of DC grid.CLLC series resonance transformer is adopted as submodule of DC transformer, which works at open loop mode, constant frequency mode and full resonance mode with high efficiency and constant voltage gain, and the input voltage and output current of each submodule are naturally equal.In order to prevent the large impact current, a soft start control strategy is proposed, in which the duty ratio D slowly increases from Dmin to 0.5 by means of pulse modulation control.A 500 kW ±7.5 kV/800 V DC transformer prototype is built, the correctness and feasibility of the proposed topology and design method are verified by the experimental results.