A Comprehensive Analysis of the Voltage Unbalance Factor in PV and EV Rich Non-Synthetic Low Voltage Distribution Networks

Tomislav Antić,Tomislav Capuder,Martin Bolfek

doi:10.3390/en14010117

Abstract

With the development of technology and the decrease in prices, power systems are facing a strong growth in the number of end-users with photovoltaics (PVs), battery storages and electric vehicles (EVs). A penetration of low carbon (LC) technologies has an impact not only on the financial aspect, but also on parameters of the power quality (PQ) in the power system. Since most of end-users with renewable energy sources (RES) are connected to a low-voltage (LV) distribution network, there is a high number of single-phase loads and distributed generators (DG) that can cause unwanted effects in LV networks. According to standards, electric energy must be of a certain quality in order to avoid harmful effects on the power system, being both the network or the end-users equipment. One of the PQ parameters is the voltage unbalance. Voltage unbalance occurs in networks with the high share of single-phase loads and generators. Since most loads in households are connected to the only one phase, the voltage unbalance is constantly present in the network, even without LC technologies. Single-phase connected PVs, residential battery storages and EV charging stations can increase voltage unbalance in the system. This paper systematically analyzes a real-world LV network and different stages and shares of connected PVs, residential battery storages and EVs to different phases. The value of the voltage unbalance factor (VUF) is observed for one week in January and August in 10-min intervals. It is shown that connected systems can significantly increase the VUF and potentially cause negative impact on the equipment and the power system as a whole. In turn we analyze a three-phase connection of these new LC technologies and demonstrate how in all analyzed cases PQ values remain within boundaries defined by the EN 50160 and the IEC 61000-3-13.

Highlights

In the past years, a number of governments have become aware of the power system’s impact on the environment
The authors in this paper model a specific real-world distribution network of an entire distribution area in Croatia, composed of the MV and LV elements, and provide a comprehensive analysis of the impact that the behind-the-meter low carbon (LC) technologies will have on voltage unbalance factor (VUF) in LV networks under different shares and operating regimes
The aim of the paper is to provide a large set of scenarios and through a comprehensive analysis draw general conclusions on the impact of different LC technologies on power quality (PQ) aspects in LV distributions networks

Summary

Introduction

A number of governments have become aware of the power system’s impact on the environment. In order to accomplish that goal, governments are creating different instruments to stimulate end-users to invest in low carbon (LC) technologies and in that way, to contribute to accomplishing set goals. Prices of LC technologies have been decreasing through years. The solar modules price reduction was driven by a technological development and by market conditions and increasing electricity prices. Similar as the solar modules price, the price of a residential battery storage has decreased through years and it is expected to continue decreasing in coming years. With the decrease of prices and financial reliefs from governments, more end-users are able to invest in LC technologies. In that way end-users can reduce their electricity bill and help in accomplishing goals set by EU and other governments

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