Abdelhay A. Sallam

Small signal stability

Analysing the power system with a goal of determining its stability is based on models of system components encompassing adequate assumptions to formulate an appropriate mathematical model in the time scale that properly describes the phenomenon under study.

Power System Stability: Modelling, Analysis and Control

To ensure stable operation of a power system, it is necessary to analyse the power system performance under various operating conditions. Analysis includes studies such as power flow and both steady-state and transient stability. To perform such studies requires knowledge about the models used to represent the various components that constitute an integrated power system. In situations where there is a risk of loss of stability, it is necessary to apply controls that can ensure stable and uninterrupted supply of electricity following a disturbance. The subject of stability thus encompasses modelling, computation of load flow in the transmission grid, stability analysis under both steady-state and disturbed conditions, and appropriate controls to enhance stability. All these topics are covered in this book, providing a comprehensive treatment of the overall subject of stability of power systems. Topics covered include modelling of the synchronous machine; the synchronous machine connected to power systems; modelling of transformers, transmission lines and loads; power flow analysis; optimal power flow; small signal stability; transient stability; transient energy function methods; artificial intelligent techniques; power system stabilizers; series compensation; shunt compensation; compensation devices; and recent technologies. The subject matter is covered at a level that is suitable for students, scientists and engineers involved in the study, design, analysis and control of power systems.

Transient energy function methods

The key idea that the alternative method is based on is to specify a certain function by which the system transient energy at the end of the disturbance period can be calculated. The calculated value is compared with a critical energy value to assess the transient stability, as the difference between the two values gives an indication of stability.

Calculation of synchronous machine parameters in per unit/normalised form

The appendix is about stator base quantities; synchronous machine voltage equations; alternative per unit-normalising systems; and rotor base quantities.

Power flow analysis

Models of the individual components of the electric power system are described in Part I. The purpose of this chapter is to study mathematical relations between individual components to develop a model for the overall power system network, which is made of an interconnection of the various components. This model showing the currents, voltages, real power and reactive power flows at each bus in the network is known as Power Flow or Load Flow model. It is found that all relationships - between voltage and current at each bus, between the real and reactive power demand at a load bus or the generated real power and scheduled voltage magnitude at a generator bus - are non-linear. Therefore, power flow calculation implies the solution of a set of non-linear equations to give the electrical response of the transmission system to a particular set of loads and generator power outputs. In practice, the distribution system is not represented in power flow studies of bulk transmission systems and the loads are represented at substation levels. In addition, some assumptions regarding component modelling are made depending on the operating condition, whether it is in steady state or under a contingency, and should be consistent with the time period and purpose of study. A single-phase equivalent representation of the power network is used in power flow studies as the system is generally assumed to be balanced. Section 5.1 is focused on the general concepts of AC power flow calculation methods using bus admittance matrix because of its relevance to the needs of the stability studies. In particular, Newton-Raphson and fast-decoupled methods have been explained with illustrative examples because of their accuracy and fast convergence.

Harmonics Effect Mitigation

This chapter contains sections titled: Introduction First Class of Solutions Second Class of Solutions Third Class of Solutions Selection Criterion Case Studies