Page 292 - Mathematical Models and Algorithms for Power System Optimization

284 Chapter 8

8.7 Numerical Model in Simulation Calculation 338
8.7.1 Concrete Formulations of Dynamic Equations and Network Equations 338
8.7.2 Calculation of Fault Equivalent Impedance 341
8.7.3 Braking Power Calculation After Braking Resistor Switched on 343
8.7.4 Calculation of the First Stage Control Criterion (Energy Equilibrium) 343
8.7.5 Calculation of Observation Decoupled State Vector and the Second Stage
Control Criterion 345
8.8 Implementation 353

8.8.1 Network Structure and Parameters 353
8.8.2 Operation Mode hIi 354
8.8.3 Operation Mode hIIi 357
8.8.4 Analysis of Calculation Results 364
8.9 Conclusion 364

8.1 Introduction

8.1.1 Description of the Problem

Power system stability is an important issue to ensure the power supply security of the system,
which has always been of concern and of value.

To ensure the stable operation of the system, people constantly strive to make the grid structure
reasonable and improve the generator to enhance the antidisturbance capability of the system.
At the same time, to cope with serious emergencies that damage normal operation, such as
lightning strikes, maloperation, short circuits, and other unpredictable disasters, urgent
measures are also required to minimize the impact of major interruptions on the stability of the
system’s operation in terms of both time and space.
In the case of emergencies, the following measures ensure the system’s stability in general:
excitation forcing, synthetic reclosing, generator tripping, fast regulation of generator output,
electric braking, automatic switching on-off, intensified compensation of the series
compensation capacitor, and fault load shedding. Obviously, stability measures are taken and
carried out locally in the system.

In case of any power system failure emergency, it is necessary to take one or several of the
previously mentioned control measures at the right time to maintain and restore stability.
However, it is fairly complex to ensure the stable operation of the power system, as it is
determined by system structure, operation mode, fault nature, load distribution, power
supply reliability standard, etc. In other words, in case of any emergency, the selection
and implementation of stability measures will not be arbitrary but subject to certain
rules and requirements. Otherwise, it will go against the will of keeping the power system
stable.