Effect of solar PV on frequency management in New Zealand

The recent accelerated uptake of solar photo voltaic generation (PV generation) internationally prompted Transpower to investigate the potential effects of new technologies on the New Zealand power system and the system operator's ability to operate the power system. The rising penetration of PV generation will gradually displace grid connected synchronous generation, removing two critical components for management of system frequency: governor response and system inertia. Coupled with the variable nature of PV generation, this displacement could pose a significant challenge for the system operator to manage frequency (with current frequency management practices) if penetration of PV generation is high. Inverter testing and modelling to represent the dynamic behaviour of PV generation inverters responding to an under- frequency event is discussed in this paper. The analysis was carried out with a full New Zealand network model, incorporating all generating plant models, PV inverter models, HVDC model and mitigation measures model.