Methodology for Calculating the Parameters of a Reactive Compensator of a Linear Asymmetric Load of a Three-Phase Three-Wire Network

Abstract

The article describes the method of calculating the parameters of a reactive compensator of a linear asymmetric load of a three-phase three-wire network, which allows to increase the power factor of an asymmetric load to a unit value. It is shown that as a result of the use of a reactive compensator, the power loss in the transmission line can be reduced to two times. In this paper the main equation for the calculation of the parameters of the reactive compensator is derived. The reactive compensator of the circuit with asymmetrical two-arm active load is synthesized. The method is illustrated by an example of a scheme with asymmetric single-cell active load. As known, the unbalanced load of three-phase three-wire power systems leads to a deterioration in the quality of electricity, which manifests itself in the emergence of reciprocal currents and pulsations of instantaneous power, which cause additional losses on the active supports of the transmission line and asymmetry of supply voltages in the nodes of the overall connection of loads. In order to balance the asymmetric stationary linear load, passive filters on reactive elements are effectively used, the calculation of which is based on two approaches: the removal of the pulsating component of instantaneous power and the compensation of the inactive components of the input currents. Among various possible methods, the inductive-capacitive systems are of particular importance. When the limit values of unbalance factor, specified in standards are exceeded, the use of symmetrization systems is required. A symmetrizator should not cause significant active power losses during operation; it implies that the symmetrization process shall be carried out by means of reactive elements (LC) or using active methods (power electronic systems).The purpose of a compensator is to measure adequate electric quantities of the load and generate in the compensator such currents, that the resultant load: compensator-compensated load, as seen from the supply network, was symmetrical, and the fundamental harmonic reactive current drawn from the network did not exceed the value permitted in the supply conditions. In the work vector diagrams of currents and voltages are constructed, power loss is calculated.As a result of the work done, it was established:1) Increasing the power factor of the three-phase system to the maximum unit value leads to a gain in power loss.2) Losses in the wires unbalanced system in 2 times more loss symmetric system, and power factor for unbalanced system in square root of two times less than a coefficient symmetrical.Ref. 3, fig. 8.