A Study On Power System Emergency Control Measures

The increasing domestic load demand and the worldwide trends in de-regulation of power systems make many interconnected power systems become transient limited under intensive use of electricity. The cascading outages in power systems all over the world from 1990s to present show that emergency control measures are absolutely necessarily to enhance the transient security in power system. Security stability control systems have been strengthened in power systems in many countries. The transient stability-constrained emergency control is a primary work of transient stability analysis of power system under harmful contingencies. Based on the summarization of previous work, this paper conducts systematical research work on the emergency control strategy.The optimal emergency generator tripping and load shedding measures based on Corrected Transient Energy Function (CTEF) method are proposed in this paper which aims to prevent cascading outages. According to the configuration of stability control system and operation requirements of Guangdong Power System, the frame of decision-making about emergency control in system has been developed. The amount of load tripping can be calculated based on CTEF and the Corrected Potential Energy Boundary Surface (CPEBS), by considering the conservation of CTEF during post dispatch action in transient period.In addition, curves of Energy Margin (EM) calculated by different load shedding show the numerical relation between EM and shedding power. Taken engineering-oriented standard into consideration, the optimal generator tripping scheme is presented. Finally, the emergency control measures are evaluated by the severe faults scenarios in typical operating conditions including four generation-tripping and nine load-shedding substations in Guangdong Power System. The results show that the linearization technique based on EM can reduce calculation burden in searching for optimal scheme. This scheme is applicable to any complex fault scenarios and any detail element models of power system.In optimal control principle, a"performance index"is defined by a quantitative measure and by two unstable rules. A method of calculating the sensitivity of the loads shedding and generator tripping to the constraint function is proposed. Base on the sensitivity and configurations of security substations in Guangdong grid, the optimal emergency control order is determined. It can coordinate kinds of controls, and get more efficient scheme with less cost.The open-loop emergency control technique proposed in this paper. The results show that the method proposed in this paper is applicable for fast emergency control scheme and effective for security enhancement of large power system operations.