交直流配网混合式接口变流器及其控制策略研究

An integrated grid-interface converter and improved coordinated method for DC grid

交直流接口变流器是在当前交流配电网下构建直流供电系统的关键设备之一。传统的交直流接口变流器通常工作在较低的开关频率以降低大功率运行时的损耗,但同时会导致变流器对直流侧电压控制性能下降,直流电网的电能质量难以保障。由于直流电网的阻抗会随其结构的改变而变化,直流电网电能质量的控制变得更加复杂。为解决传统交直流接口变流器效率与控制性能的矛盾,本文采用了一种前后两级级联的拓扑方案,将传统交直流接口变流器作为整流级,增加了由超级电容构建的功率缓冲级,提出了一种两级协调的控制方法,可在保证接口变流器效率的前提下,提高变流器的控制性能。功率缓冲级同时可实现直流电网电能质量的集中治理,提高交直流接口变流器对直流电网电能质量的控制能力。此外,还探讨了功率缓冲级中超级电容的设计与控制。仿真结果验证了所提方案的可行性与优越性。

Grid interface converter(GIC)was one of the key technologies in the construction of DC power grid under AC distribution network. In order to reduce the loss during high-power operation,traditional GIC usually work at low switching frequency,which seriously affect the control ability of DC side voltage. At the same time,the power quality of the DC grid will be difficult to guarantee. In addition,the power quality of the DC grid will become more complex,because the impedance of DC grid will change with its structure.For the sake of the contradiction between efficiency and control performance of the GIC,a two-stage cascade is adopted in this paper,in which the traditional GIC is used as the rectifier stage,and the power buffer stage was constructed by the super capacitor. The two-stage coordinated control method is proposed to improve the control performance while ensuring the efficiency of the GIC,And the power buffer stage can also realize the centralized management of DC grid and improve the ability of GIC on controlling the power quality of DC grid. Furthermore,the design and control of super capacitor in power buffer stage were also discussed. Simulation results verify the feasibility and superiority of the proposed scheme.