Abstract
A method of the design of an adaptive balancing reactive compensator in four-wire systems with linear loads and nonsinusoidal voltage is described in this article. The method of compensation is founded on the Currents’ Physical Components (CPC) – based power theory of three-phase systems with nonsinusoidal voltages and currents. The compensator is built of two sub-compensators of Y and structure, respectively. The Y compensator reduces the reactive current and the zero sequence symmetrical component of the unbalanced current. The compensator reduces the negative sequence symmetrical component of the unbalanced current. The positive sequence symmetrical component of the unbalanced current and the scattered current remain uncompensated. It is because shunt reactive compensators do not have any capability for that. Thyristor Switched Inductors (TSIs) enable the susceptance control of the compensator branches, referred to in the article as Thyristor Controlled Susceptance (TCS) branches. Periodic switching of thyristors in these branches causes the generation of harmonic currents, in particular the third-order harmonic. Moreover, in the presence of the supply voltage harmonics, a resonance of the equivalent capacitance of the compensator with the distribution system inductance can occur. These two harmful phenomena in the compensator suggested were reduced by the selection of a special structure of the TCS branches and their LC parameters. The presented method of the adaptive compensator synthesis was verified in the article with a numerical example and results of computer modeling of the load with an adaptive compensator.
Highlights
Degradation of the power factor in large manufacturing plants is a combined effect of the reactive power, the load imbalance, and harmonic currents generated by nonlinear or periodically switched loads
Loads Supplied by Nonsinusoidal Voltage from Four-Wire Lines three-phase systems. These studies started with developing a power theory of three-phase, three-wire systems with nonsinusoidal voltages and currents, known as the Currents’ Physical Components (CPC) – based power theory (PT) [7]
When the supply voltage is nonsinusoidal and the current harmonics generated by thyristors have to be reduced, the Thyristor Switched Inductors (TSIs) is connected with a few reactive elements to shape the frequency properties of the compensator branches
Summary
Degradation of the power factor in large manufacturing plants is a combined effect of the reactive power, the load imbalance, and harmonic currents generated by nonlinear or periodically switched loads. A compensator needed for the power factor improvement should have the capability of compensating the reactive and unbalanced currents and the neutral conductor‘s current. These studies started with developing a power theory of three-phase, three-wire systems with nonsinusoidal voltages and currents, known as the Currents’ Physical Components (CPC) – based power theory (PT) [7] This theory provided fundamentals for developing a method of design of reactive balancing compensators operating in the presence of the supply voltage distortion [8]. Since this article is built upon these results, it would be recommended that the reader, if needed, is acquainted with those details and results [7,8,9,10,11]
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