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

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.

Distribution-Level Flexibility Markets—A Review of Trends, Research Projects, Key Stakeholders and Open Questions

“…When network reconfiguration and flexibility services are not an option, alternatives are islanding, black-start, emergency load control and mobile generation capacity. Similar solutions are also valid during extreme events [85].…”

Fast detection technique for voltage unbalance in three-phase power system

“…Besides, the space vector value and the sum of these voltages should be calculated to detect the voltage unbalance quickly and precisely. The number of samples per cycle (ns) is given by (4).…”

“…The three-phase power systems suffer from different challenging problems, e.g., unbalanced voltages at the load side [1]- [3]. The voltage unbalance usually degrades the power quality of the electrical system [4], [5]. As a result, the U.S. economy loses between 15 to 24 billion dollars a year in power quality problems [6].…”

“…As a result, the U.S. economy loses between 15 to 24 billion dollars a year in power quality problems [6]. In modern buildings, the frequent use of photovoltaics (PVs), battery storages, and charging stations for electric vehicles (EV) intensify the voltage unbalance problem [4], [7]. Additionally, the malfunctions of the electrical equipment in the power distribution systems normally lead to unbalanced voltages [8].…”

Aprovechamiento de Sistemas de Almacenamiento Energético Mediante Baterías para la Mitigación de Desequilibrios en Microrredes Eléctricas

“…El efecto del desequilibrio es mucho más notorio en redes débiles y aisladas, debido a su elevado valor de impedancia en el punto de conexión de la carga trifásica (Etxegarai et al, 2015). El desequilibrio de tensión afecta de manera directa a la calidad de la energía suministrada a los consumidores (industrial, comercial, residencial y otros), y puede impactar de forma negativa al funcionamiento de cargas trifásicas, como motores, hornos eléctricos, variadores de frecuencia y sistemas de carga de vehículos eléctricos, entre otros; esto provoca la reducción de la eficiencia y de vida útil de estos artefactos (Adouni & J. Marques Cardoso, 2021;Antić et al, 2021). Consecuencias similares podría experimentar el equipamiento eléctrico instalado aguas arriba de la carga (generadores y transformadores) si son sometidos a elevados niveles de desequilibrio (de tensión y/o corriente) de forma sostenida en el tiempo.…”