面向柔性低频输电的模块化多电平矩阵变换器分频分层控制

基于全桥结构的模块化多电平矩阵变换器(M3C)提出了三相柔性低频输电系统的分频分层控制策略.从双频功率耦合的机理出发,分析了M3C的工作原理,在旋转坐标系下分别实现了工频侧和低频侧的控制.在保证系统总有功功率平衡的前提下,通过在工频侧注入负序电流实现功率模组电容电压的相间均衡,在静止坐标系下通过桥臂内工频环流控制实现功率模组电容电压的相内均衡,所提的层次化控制可实现系统对称及不对称条件下基于M3C的柔性低频输电系统的稳定运行.根据对相单元瞬时功率的分析,提出仅用2种不同频率的滑差滤波器以确保功率模组电容电压偏差控制的暂稳态特性.搭建了双端柔性低频输电系统仿真模型,验证了所提控制策略的有效性和可行性.

Frequency-division and Hierarchical Control of Modular Multilevel Matrix Converter for Flexible Low-frequency Transmission

This paper proposes a frequency-division and hierarchical control strategy for three-phase flexible low-frequency transmission system based on the full-bridge modular multilevel matrix converter (M3C). The operation principle of M3C is analyzed from the mechanism of dual-frequency power coupling. The control of fundamental-frequency and low-frequency side of M3C is realized in the rotating coordinate system. On the premise of maintaining the total active power balance of the system, the balance of capacitor voltage of power modules among three phases is realized by injecting the negative sequence current into the fundamental-frequency side. And the balance of capacitor voltage of power modules inside each phase is realized by the fundamental-frequency circulating current control inside the bridge arm in the static coordinate system. The proposed hierarchical control can realize the stable operation of the flexible low-frequency transmission system based on M3C under symmetrical and asymmetrical conditions. According to the analysis of the instantaneous power of each phase unit, it is proposed to use only two kinds of sliding filters with different frequencies to ensure the transient stability in the capacitor voltage deviation control of power modules. Finally, a simulation model of the dual-terminal flexible low-frequency transmission system is built to verify the effectiveness and the feasibility of the proposed control strategy.