Analysis of Asymmetric Operating Modes in Three-Phase Network with the Use of Exchange Power

Abstract

The work analyzes the operation modes of renewable energy sources as part of autonomous power supply systems. The possible variants of distortion in the system and the influence of these distortions on three-phase power generators are presented. The problems of electromagnetic compatibility of renewable sources, in particular, wind generators, and autonomous systems (Smart Grid) are considered. A simplified model of a three-phase low-power generator and its exposure with a single-phase model is presented.

The analysis of asymmetric modes in three-phase autonomous power supply systems is carried out. A mathematical simulation of the operation of a simplified single-phase power supply system with nonsynchronous sinusoidal generators has shown that the quadratic residual of the current values of currents makes it possible to detect the mutual exchange between the generators, but does not provide an opportunity to estimate energy flows even in such a simple model of two generators feeding a single load. The expediency of using the integral indicator of exchange capacity for both single-phase systems and three-phase systems is proved. The effect on the three-phase autonomous power supply system of the source of interference of a variable frequency has been assessed.

Exchange processes are analyzed through the common section "Generator - Load", after complete equivalence of the circuit. It is indicated that such an approach does not allow to fully appreciate the energy flows in the three-phase system as a whole and in the generator in particular, but takes into account only the energy generating a three-phase generator and consumes three-phase loads. The analysis of the model is presented and the necessity to detail the exchange processes for each generator and load and between phases is argued.

The balance of energy flows along the intervals of energy invariant states is given, which makes it possible to use this approach not only for a specific model but for any three-phase system. Also presented is a technique that will allow evaluating the energy processes of a group of three-phase generators that can operate in various incompatible modes.