The assessment of voltage disturbing emission sources still lacks adequate models for customer side incorporating mixed loads and distributed power generation. The paper proposes a solution for this challenging task. It includes the determination of topology and parameters of equivalent circuits representing customers’ installations with local power sources in three- and four-wire networks. The equivalent circuits are developed on the basis of two-staged transformation, meet requirements of IEC 61000-4-30 and can be used for the on-line assessment of the emission sources of linear voltage disturbances.
Słowa kluczowe: customer installation, distributed generation, equivalent circuit, point of evaluation, voltage disturbance, voltage unbalance.
W artykule zaproponowano rozwiązanie problemu konkurujących zadań w sieci zawierającej różne obciążenia I rozproszone generatiry. Określono topologię I parametry obwodów zastępczych reprezentujących instalacje klientów w sieci trzy- I czteroprzewodowej. Schematy zastępcze okręslono na bazie dwustopniowej transformacji z uwzględnieniem normy IEC 61000-4-30. Pozwoliło to na okręślanie on-line źródeł emisji zakłóceń.
Keywords: customer installation, distributed generation, equivalent circuit, point of evaluation, voltage disturbance, voltage unbalance.
Among other challenging topical problems in modern electrical power systems, there are the identification of disturbing sources (DSs) in network and assessment of their contributions into power quality (PQ) deterioration at a point of evaluation (POE). The proliferation of renewable energy sources like PV panels and wind generators in electrical systems is transforming centralized power supply systems (PSSs) into those with distributed generation (DG) and increasing importance of PQ problems. There are still no enough good methods for modelling customers’ installations especially those incorporating generating units. This paper considers how to identify DSs in such installations and assess their impact on PQ at a random POE that is usually some point of common coupling (PCC). The presented study offers DS topologies and the procedure for defining the parameters of a DS equivalent circuit on the basis of standard measurements . There are presently a lot of methods proposed to find a solution for the problem. The contemporary methods used to identify and assess impact of voltage disturbing sources on PQ at a POE are shortly described below. A more comprehensive review can be found in [2-5]. The list of used abbreviations is provided at the end of the paper. Review of existing methods The models based on single-line Thevenin or Norton equivalent circuits (Fig. 1) are the prevailing ones [3-12]. Both a customer’s installation (CI) and an upstream power system (PS) are represented as a voltage source in series with impedance for each sequence q and harmonic. Such an assessment of disturbing sources is simple, but it is applicable only for the case with a single POE, a single CI and a single dominating DS on either utility or consumer’s side. Another disadvantage explained below is a need to have an equivalent circuit for each symmetrical component. There are also some methodological problems related to th [...]
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