Abstract
This paper investigates effects of voltage unbalance and energy losses due to the connection of rooftop photovoltaic systems in a low voltage distribution system of a housing estate, which has light loads during daytime. The paper presents a case study of a real distribution power system of housing estate in Thailand. Voltage unbalance and energy losses were simulated by using system characteristic and load data from GIS database of PEA with the DIgSILENT Power Factory program. The key findings of our analysis are as follows. Firstly, the number of installable 1-phase rooftop PV systems varies directly with load density. Secondly, the number of installed 1-phase rooftop PV systems can be increased if the installation locations are closer to the transformer. For 3-phase rooftop PV systems, their installations do not have any effects on the voltage unbalance. Furthermore, system energy loss relates to the load density and PV system installation locations in the same way as the voltage unbalance. The key implication of our study is that the installation of 1-phase rooftop PV system should be granted based on a careful consideration of the installation location and the load density.
Highlights
Three-phase voltage unbalance occurs when phase or line voltages are different from the nominal balanced situation
This paper examines the unbalance voltage and energy loss of 1-phase and 3-phase rooftop PV system installation in the residential low voltage (LV) distribution system, for which results and discussions are as follows: 5.1 Voltage unbalance for installation of 1-phase rooftop PV systems
The number of installed rooftop PV systems can be increased if the installation locations are closer to the transformer
Summary
Three-phase voltage unbalance occurs when phase or line voltages are different from the nominal balanced situation. The voltage unbalance at terminals causes high current unbalance in three phase wye systems. It may decrease efficiency and lifetime of 3-phase transformers, motors and other loads. Energy losses of systems can be increased because unbalanced current will flow in neutral lines. Voltage unbalance is caused by large and/or unequal distribution of 1-phase generation and/or load. 1-phase grid-connected rooftop photovoltaic (PV) systems are widely installed by residential customers because of encouraging policies in many countries
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