统一潮流控制器多目标协调控制策略研究

Study on Multi-Objective Coordinated Control Strategy of Unified Power Flow Controller

统一潮流控制器(unified power flow controller,UPFC)应用到电力系统中,具有调节线路潮流、维持母线电压、提高暂态稳定性等多种控制目标,然而这些控制目标的实现并不完全统一,若UPFC采用单一目标的控制策略,则不能满足电力系统多种运行工况的要求。为此,分析了UPFC各控制目标的实现原理和控制方法,阐述了它们之间的关系及存在矛盾的原因,在此基础上提出了UPFC多目标协调控制策略,采用模糊逻辑设计了附加控制器,能够根据系统运行工况自适应调整附加信号的大小,从而实现多目标之间的协调控制。该策略使得电力系统稳态运行时电压和线路潮流严格跟踪参考值,而电力系统发生暂态扰动后,在维持系统电压和线路潮流在允许范围内的同时能够最大限度提高系统的暂态稳定极限,增加系统阻尼,并快速抑制系统振荡。基于PSCAD/EMTDC四机两区域系统的仿真结果验证了理论分析的正确性及协调控制策略的有效性。

As for the unified power flow controller （UPFC） applied in power grid there are multi control objectives as adjusting line power flows, maintaining bus voltages, improving transient stability and so on, however the implementation of these objectives are not entirely uniform. When UPFC adopts the control strategy for a certain objective, the requirements of multi operating conditions cannot be satisfied, for this reason, the implementing principles and control methods of UPFC’s different control objectives are analyzed and the relationship among these objectives and the reason causing the inconsistency among them are expounded, on this basis, a multi-objective coordinated control strategy is proposed and utilizing fuzzy logic an auxiliary controller, by which the magnitude of additional signal can be adaptively adjusted according to operating conditions of power grid and then the coordinated control among multi-objectives can be implemented, is designed. The proposed control strategy makes the voltage and line power flows enable to rigorously track the reference value during steady state operation of power grid, and after the occurrence of transient disturbance the transient stability limit can be farthest maximized while the system voltage and line power flows can be maintained within allowed ranges, meanwhile the system damping can be increased and the system oscillation can be rapidly suppressed. The correctness of theoretical analysis and effectiveness of the proposed coordinated control strategy are validated by results of PSCAD/EMTDC based simulation of a two-area four-machine system.