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This research demonstrates the possibility and expediency of forming local electric
energy systems (LEESs) based on renewable sources of energy (RSE) as balancing groups in
the electric power system (EPS), which can maintain efficiency and provide power supply to
consumers in an autonomous mode. The LEES is a part of the EPS of thermal and nuclear
power plants and is considered as a separate balancing group. LEESs are designed in such a
way that they can operate autonomously in both normal and extreme conditions in the EPS.
The sources of electricity in LEESs are small hydroelectric power plants (SHPPs), photovoltaic
power plants (PVPPs), and wind power plants (WPPs), whose electricity generation is unstable
due to dependence on natural conditions. Therefore, the structure of a LEES with RSE includes
an energy storage system with reserves sufficient to compensate for the unstable generation
and balancing of the mode. LEESs can differ significantly in terms of key technical and
economic indicators (power supply reliability, power losses, and power quality), and therefore,
it is necessary to choose the optimal one. It is not advisable to optimize the quality of power
supply in a LEES by individual indicators, as improvement of one indicator may lead to
deterioration of another. The functional readiness of a LEES should be assessed by the quality
of operation, which depends on reliability, power losses, and power quality. To simplify
the task of assessing the quality of operation, which is a vector optimization problem, a
method for determining the integral indicator as a number that characterizes the LEES and
reflects the compromise between the values of reliability, power losses, and power quality
has been developed. The integral indicator of the functioning of complex systems is based
on a combination of the theory of Markov processes and the criterion method of similarity
theory. The value of the integral indicator of the quality of operation of the LEES allows
for comparing different variants of power transmission and distribution systems without
determining individual components of technical and economic indicators—reliability, power
losses, and power quality. The offered integral indicator of the quality of functioning of a
LEES with RSE corresponds to the general requirements for such indicators. It reflects the
actual operating conditions; allows for assessing the efficiency, quality, and optimality of
power supply systems; and can be easily decomposed into partial indicators
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