Page 294 - Mathematical Models and Algorithms for Power System Optimization

286 Chapter 8

8.1.2 Investigating the Feasibility of System Stability Control based on Local
Information

Therefore, under these conditions, what kind of control method is adopted so that the
emergency measures taken locally are not contradictory to the overall stability requirements?
This is the problem of local stability control in emergency situations studied in this chapter.

In other words, although the measures for local stability control have long been adopted for
stabilizing the system, the concept of reclosing and electric braking was proposed as early as the
1930s to maintain the synchronous operation of the generator in the event of a fault. However,
their application has begun to be constrained by various conditions. Our purpose is to find out
what these conditions are, and adopt corresponding control methods to determine the ways and
conditions they switch in.

Studying this problem has great practical significance, because the current power system is
increasingly growing, the internal interconnection is increasingly complicated, and there are
more and more constraints between them, which makes local failure cause local power
interruption as before, but it also endangers the overall system. Many domestic and
international accident cases have confirmed this. For example, in a major blackout in New York
in the 1970s, one of the reasons for the accident was that the localized loss of magnetic
protection was not coordinated with the requirements of global stability. In the 1970s, in an
oscillation accident on the Danhan line in China, the accidental power protection action
destroyed the possibility of pull-in synchronization, thus expanding the accident. These
examples highlight the importance of studying local stability control with new ideas and
methods.

This chapter proposes control criteria and models for local stability control in accordance with
the previously mentioned requirements from an overall power system stability point of view,
and discusses the feasibility of control law through examples of simulation calculation.

8.1.3 Overview of This Chapter

This chapter introduces a new observation decoupling state space from the perspective of
ensuring the stability of the power system. The new state vector is called the local equilibrium
state vector, and its elements are decentralized local reference values or local equilibrium
reference state vectors. In this state space, the state of the system can be obtained by
conventional calculation methods based on traditional local measurements. According to the
dynamic characteristics of the power system, the local online stability control of the system is
divided into two stages from the time domain. The corresponding methods and models for local
online stability control are given in each stage. Finally, the practical feasibility of the proposed
method is discussed through an example of simulation calculation.