Page 29 - Power Electronic Control in Electrical Systems

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Power electronic control in electrical systems 19

the network exhibits a very different behaviour within different time frames because
of the diversity of its components (de Mello, 1975):
. rotating machinery
. transmission lines and cables
. power transformers
. power electronics based controllers
. protective equipment
. special controls.
The various plant components respond differently to the same stimulus. Accordingly,
it is necessary to simplify, as much as is practicable, the representation of the plant
components which are not relevant to the phenomena under study and to represent
in sufficient detail the plant components which are essential to the study being taken.
A general formulation and analysis of the electrical power network is complex
because electrical, mechanical and thermal effects are interrelated.
For dynamic analysis purposes the power network has traditionally been sub-
divided as follows (Anderson and Fouad, 1977):

. synchronous generator and excitation system
. turbine-governor and automatic generation control
. boiler control
. transmission network
. loads.
The importance of the study, the time scales for which the study is intended and the
time constants of the plant components are some of the factors which influence
model selection (de Mello, 1975). Figure 1.16 gives a classification of power systems'
dynamic phenomena.

Fig. 1.16 Classification of power systems' dynamic studies.