Research On Full-time-domain Multi-target Voltage Security Warning And Prevention

Since the last century, several typical voltage collapse accidents have happened worldwide, causing serious consequences for the power system. With the deepening of the research of voltage stability, great progress has been made in the voltage stability mechanisms, criteria and simulation methods. Some research results have been applied to the actual power systems. Since the development process of the voltage collapse is more complex, instability features vary from system to system and involve different time processes, so far, voltage collapse prevention and control system for different time process and instability features has not been folly established. Therefore, there is an urgent need to monitor and analyze the voltage stabilization in the full time domain, in order to prevent and control the voltage collapse accident.This dissertation, on the basis of the characteristics and mechanism of voltage stability, proposes a full-time-domain multi-target voltage warning and prevention system for the power systems with a consideration of the development characteristics of voltage instability accident in different times processes. In-depth analysis and research are performed on the core algorithms and technologies. Comprehensive control measures of voltage collapse are put forward. The main innovations are as follows:(1) On the basis of summing up the characteristics of typical voltage instability accident, a case study is performed on the whole process simulation of voltage stability of the actual system. The general description and classification method of voltage instability characteristics are given. Combining with the characteristics and simulation calculation of voltage instability accidents, the dynamic adjustment factors affecting the development of the voltage instability processes is discussed. The mechanism explanations targeted at different characteristics of the accident are presented.(2) By integrating several classification methods of voltage stability, the procedures and methods for simulation modeling of voltage stability are put forward. For static, transient and mid-long term voltage instability characteristics, the evaluation methods are respectively introduced. The probability evaluation method of large-disturbance voltage stability is put forward.(3) The main objectives and functional framework of full-time-domain multi-target voltage security warning and prevention system are suggested. On the basis of multiple information sources including EMS/WAMS/stable control, multi-time-scale (static, transient and mid-long term) early warning, prevention and control of voltage instability is realized. The voltage security during the operation of the system is assessed. Potentially dangerous operating status is timely corrected. This system enables rapid response to voltage instability accident. Voltage instability prevention and control strategies are also provided for the reference of dispatchers and control devices.(4) In addition to summing up the existing key algorithms for prevention and control of voltage instability, the improved continuous-flow algorithm based on linear simulation, the accurate calculation method considering the excitation current limit of the generator group and the stepwise whole-process sorting of voltage instability accidents is proposed. The tracking method for Thevenin equivalent parameters based on time-domain simulation is used in the discrimination of transient and mid-long term voltage instability.(5) The principles and processes of undervoltage load shedding configuration are proposed. The predictive control strategy for undervoltage load shedding on the basis of PV curve is proposed. The concentrated load shedding measures for the online determination of voltage collapses based on DSA (online dynamic security analysis) is proposed.This dissertation proposes that on the basis of multiple information sources of EMS and WAMS, a full-time-domain multi-target warning, prevention and control system of voltage instability could be built by comprehensively using the analysis results of static, transient and mid-long term voltage instability warning. This system integrates the functions of voltage stability monitoring, security assessment, early warning analysis, security defense, and coordination of the power system. The system has both important theoretical and practical values for engineering applications.