考虑LCC-HVDC实时可调节容量的直流紧急功率支援控制方案

LCC-HVDC Emergency Power Support Control Considering the DC Real-time Available Capacity

传统交直流系统协调控制方案一般没有考虑直流的实时功率裕度,特别是在故障后系统强度下降的情况下,直流调节不当可能导致其不能稳定运行。该文基于直流接入点故障后的电压电流数据,采用适用于大扰动的戴维南等值参数估计方法实时跟踪系统等值参数变化,考虑换相失败和低压限流环节等约束,得到了直流实时安全稳定调节区间,上述可调节区间可为Bang-bang控制提供一个边界,以加速机组和减速机组惯性中心的频率偏差作为系统的状态反馈来确定直流功率控制量。在PSCAD上的仿真结果表明,该控制策略能够保证直流功率稳定运行的情况下,充分利用直流容量使交流系统快速恢复到稳定状态。

The traditional coordinated control scheme of AC/DC system generally does not consider the real-time power margin of the Line-commutated-converter High Voltage Direct Current(LCC-HVDC), especially when the system strength declines after a failure and the improper DC regulation may lead to the unstable operation of the system. To overcome the above issue, a real-time Thevenin equivalent parameter estimation based on the local PMUs is developed to track the change of the system condition. That further allows us to determine the real-time LCC-HVDC maximum capacity considering various constraints. The above power can provide an upper bound for the bang-bang control. Finally, the control strategy can be determined by the frequency deviation between inertia centers of the accelerated and decelerated groups. The simulations in the PSCAD/EMTDC reveal that the proposed strategy can not only ensure the stability of the DC system but also assist the recovery the AC system to a stable condition.