Calculation of the rated power of a photovoltaic solar power plant to be connected to a low-voltage network

Abstract

Connecting a photovoltaic solar power plant (PVSP) to a radial low-voltage network can significantly influence the power quality. According to grid rules in our country, the PVSP with rated power of up to 150 kW can be connected to the low-voltage power distribution network. Common case is that the PVSP with rated power of approximately 100 kW is installed at the rooftop of a residential or commercial building and connected to one connection point. Usually, the owner tends to regulate PVSP to operate at unity power factor to maximize profit. However, when the power plant operates with unity power factor, voltages at the connection point and at the nearby buses are often increased. Also, a significant increase of power losses can occur. This paper describes the procedure for determining the maximum power of the PVSP operating with unity power factor while simultaneously meeting the following criteria: (1) the range of slow voltage variations must be within the limits defined by the EN 50160 standard; (2) after connecting the PVSP, the active power losses should be less or equal to active power losses calculated with the disconnected PVSP.