基于混合子模块与全桥臂电感的三端口模块化多电平变流器:简化建模与电网互联控制策略

Three-port MMC With Hybrid Submodules and Full Arm Inductor Scheme:Simplified Modeling and Grid Interconnection Control Strategy

含有交直流端口的多端口变流器是未来电网中交直流环节互联的关键设备。目前,高压多端口变流器通常以模块化多电平变流器(modular multilevel converter,MMC)或DAB为基础级联扩展构成,存在体积庞大、拓扑复杂、控制难度高等问题。鉴于此,通过对含不同类型子模块的MMC桥臂进行有机组合,提出一种基于混合子模块与全桥臂电感的三端口模块化多电平变流器(three port modular multilevel converter,TP-MMC)。该TP-MMC具有2个交流端口和1个直流端口,从而无需多个拓扑的级联,有效实现2个交流系统与1个直流系统之间的能量流动。在此基础上,进一步提出适用于该TP-MMC的分区最近电平逼近调制方法;建立相应的数学模型,分析各端口基本工作模式,并根据不同的平衡端口设定,提出相应的端口解耦控制策略;计算装置环流的必要成分,提出相应的环流抑制策略。仿真结果验证了所述TP-MMC拓扑及其调制和控制策略的有效性。

Multi-Port converters with both DC and AC ports are key devices for future hybrid DC&AC power grid.They often consist of cascaded two-port MMCs or DAB based converters which bring complex structure and difficult control design.A modular multilevel converter with three ports(TP-MMC),2 AC ports and 1 DC port,was proposed by combining MMC arms with different types of submodules and full arm inductor scheme.Power could be transferred among the three ports freely.The nearest level modulation method for the proposed TP-MMC was designed.Mathematical model was established and the decoupling control strategy was proposed according to different balancing port selection.Circular current components were analyzed and the conclusion that the effective components in the circulating currents were DC and fundamental components was drawn.The circular current control strategy for circular current suppression was proposed.Simulation results show that the proposed TP-MMC and its modulation and control strategies can work effectively and provide precise AC outputs.