交直流输电系统灾变过程模拟及防治措施研究

As a kind of typical complex system, cascading failure processes of large-scale ac/dc power grids are affected by network topology, load redistribution, and loss of stability. While current works have three shortcomings: (1) complex grid theory studies the relation between topology and function of networks, based on graph theory and static indices. So it cannot reflect the difference between DC line and AC line in the control aspect. Furthermore, it is not very effective in evaluating blackout risk. (2) Blackout models mainly focus on AC system, and the mechanism of AC/DC systems' cascading failure is seldom studied. (3)Blackout models often deal with stability problem through time-domain simulation and semi-sensor product, which have heavy computation burden. Considering the above problems, this project will focus on: (1) establish graph model to reflect the controllability of HVDC systems; (2) construct the blackout model of AC/DC system; (3) build blackout models based on input-to-state stability theory; (3) from AC/DC system planning, control system design and operation point of view, study prevention and blocking measures of the AC/DC power system blackout. The study will not only produce new point of growth in complex network fields, but also help to reduce the risk of AC/DC power system blackout.

作为一类典型的复杂网络，大规模交直流混合输电系统的连锁故障及灾变过程既有交直流网络结构的影响，也有潮流转移的作用，更有稳定破坏的参与。现有工作存在三项不足：一是复杂网络理论基于图论和静态统计指标研究网络结构-功能关系，难以准确衡量交流及直流系统的可控性，从而无法有效评估交直流系统停电风险；二是连锁故障模型大多只考虑纯交流系统，对交直流混合系统连锁故障机理尚没有深入分析；三是考虑暂态稳定性的连锁故障模型，主要基于半张量积或时域仿真，计算复杂度高。为此项目开展下述研究：（1）基于复杂网络理论的交直流系统结构特征指标；（2）计及交直流特性的连锁故障模拟；（3）考虑输入-状态稳定（ISS）的连锁故障模型；（4）从规划、控制和调度运行的角度，提出预防和阻断交直流系统停电事故的措施。本项目有望为复杂网络理论产生新的学科增长点，同时为交直流混合输电系统灾变防治提供技术支撑。

本项目的研究工作中解决了交直流电力系统连锁故障建模中的2方面的难题，一是通过短路电压以及保护动作时间等信息建立了连锁故障中直流输电系统的概率闭锁模型，二是通过输入-状态稳定理论的系统化分方法解决了连锁故障过程中交直流电网拓扑变化情况下的稳定性分析问题。提出了相关性网络和改进k核、结构洞等指标量化交直流电网的网络特征。最后，在调度、规划和控制3个方面建立交直流连锁故障预防和阻断的方法：1）建立支路负载率与支路连锁故障风险的关系，求解COR-SOPF（Cascading Outage Risk based Security OPF）模型，以控制系统达到当前控制代价与后续连锁故障风险之和最小，从而有效地降低连锁故障风险。2）通过决策树分析交直流电网的高风险连锁故障关键事故集合，指导系统升级改造减小停电风险。3）提出双馈风力发电机在故障期间的镇定控制策略。有效降低双馈型风力发电机组在连锁故障中的脱网概率，有利于降低含风电的电力系统连锁故障风险。