The last full review of load models used for power system studies occurred in the 1980s. Since
then, new types of loads have been introduced and system load mix has changed considerably.
The examples of newly introduced loads include drive-controlled motors, low energy
consumption light sources and other modern power electronic loads. Their numbers have been
steadily increasing in recent years, a trend which is expected to escalate. Accordingly, the
majority of load models used in traditional power system studies are becoming outdated, as
they are unable to accurately represent power demand characteristics of existing and future
loads. Therefore, in order to accurately predict both active and non-active power demand
characteristics of aggregated modern power system loads in different load sectors (e.g.
residential, commercial or industrial), existing load models should be updated and new models
developed.
This thesis aims to fill this gap by developing individual, generic and aggregated steady state
models of the most common loads in use today, as well as of those expected to show significant
growth in the future. The component-based approach is adopted for load modelling, where
individual load models are obtained in detailed simulations of physical devices. Whenever
possible, the developed individual load models are validated by measurements. These detailed
individual load models are then simplified and expressed as equivalent circuit and analytical
models, which allowed the establishment of generic load models that can be easily aggregated.
It should be noted that since all non-active power characteristics are correctly represented, the
developed aggregated load models allow for a full harmonic analysis, which is not the case with
the standard steady state load models. Therefore, the proposed load models form an extensive
library of comprehensive load models that are suitable for use in multiple areas of power system
research.
Based on the results of research related to typical domestic/residential sector load mix, the
newly developed load models are aggregated and then applied to a typical UK/Scotland
distribution network. Considerable differences are seen between network characteristics
of newly proposed and previously developed models. The voltage distortion of a typical
distribution system bus is investigated, and it is shown that distortion of the system voltage
is likely to increase significantly in the future. The results of the presented research also
suggest that neglecting the harmonic characteristics from the set of general load attributes may
introduce errors in standard load flow studies
