Adaptive reactive power injection by solar PV inverter to minimize tap changes and line losses

Deployment of direct grid feeding solar Photovoltaic (PV) inverters are increasing. With the increase in PV penetration, fluctuation in Point of Common Coupling (PCC) voltage occurs more frequently. This happens due to weather dependent active power generation characteristics of PV inverters. Voltage variation might also violate ANSI C84.1 standard. On Load Tap Changing (OLTC) transformers are installed at Medium Voltage level to maintain the PCC voltage to its nominal value. OLTC experiences increased number of tap changing operations due to voltage fluctuations causing reduced life span of the transformer and OLTC components. To address this issue, a scheme is proposed to optimally inject reactive power through PV inverter which ensures minimal number of tap changing operations along with minimum losses in line. To validate this scheme, simulation is carried out with grid connected PV inverters at the distribution level with different levels of reactive power compensation. It is shown that optimal level of reactive power compensation can be chosen to achieve good compromise between the number of tap changes and losses in the line.