基于滑模控制理论的MMC-MTDC自适应下垂控制策略

传统MMC-MTDC下垂控制策略中常采用PI双闭环控制,系统的暂态特性较差。为提高系统响应速度和稳定性,提出基于滑模理论的自适应下垂控制策略。控制器采用双闭环级联控制结构,其中内环控制器根据滑模变结构在dq坐标系下对MMC非线性数学模型进行建模,设计积分滑模面和降低系统抖振的指数趋近律控制器;外环控制器根据MMC实时容量与功率参考指令的比较设计自适应下垂控制器,使MMC根据实际情况"量力而行"。最后在PSCAD/EMTDC中建立4端MTDC模型,在2种工况下进行验证,结果表明所提控制策略可以有效避免系统暂态时裕度较小的MMC满载,还具有较高的动态性能和响应速度。

Adaptive Droop Control Strategy Based on Sliding Mode Control for MMC-MTDC

PI double closed loop control is often used in traditional MMC-MTDC droop control strategy, and the transient characteristics of the system are poor. In order to improve the response speed and stability of the system, in this paper an adaptive droop control strategy based on sliding mode theory is proposed. The controller adopts double closed loop cascade control structure, the inner loop controller is used to model the MMC nonlinear mathematical model in the dq coordinate system according to the sliding mode variable structure, the integral sliding surface and the exponential reaching law controller are designed to reduce the chattering of the system. The outer loop controller is designed according to the comparison of MMC real time capacity and power reference instruction to make the MMC run according to the actual situation. A simulation model of MMC-MTDC including four stations is established in PSCAD/EMTDC. The simulation is set under two conditions, the results show that the proposed control strategy can effectively avoid the full load margin of the system when the MMC is small, and the system also has high dynamic performance and response speed.