Supply Voltage Control Using Booster Transformers

In some situations, the electrical consumers are supplied by the reduced power supply voltage. According to the standard, the permissible variation of its effective value is
$+/-10$
% of 230 V. However, in some small rural villages remote from the power supply it may be reduced to 150 V. In this case the increase in the nominal values can be realized by the use of booster transformers, so the supply voltage is kept within the acceptable range of variation defined in the standards. In this paper, a solution to control the supply voltage with a step of 5 % between 5 % to 35 % is suggested. It is realized by three transformers with secondary windings connected in series to the network voltage. When the voltage is within the acceptable range, the transformers are switched off. When the voltage supplied to the consumers falls below the permissible value, switching off one, two, or three of the transformers is carried out. As a result, additional voltage is added to the network supply. This ensures that the supply voltage is always within the acceptable range. A problem of the functioning of transformers is the switching between on and off state. During the commutation, they are in “a current transformer” mode. It means that unacceptable over-voltages, including insulation breakdowns, are possible. In this paper, a solution to this problem is proposed and an analysis is performed to study the progress of transient responses in the circuit related to the primary of the transformer. The efficiency of the suggested solution is confirmed by simulations with software OrCAD PSpice 9.1. The results of the simulations confirm the reliability and effectiveness of the under-voltage compensation solution.