Impact of Distributed Virtual Inertia from Photovoltaic Sources on Frequency Regulation in Hybrid Power System

Abstract

As a consequence of the recent progress in solar photovoltaic technology and advancement in converter technology, solar photovoltaic (PV) sources have emerged as one of the most promising renewable sources for utility-scale power generation. However, the control mechanism of the PV system is completely decoupled from the grid. Hence PVs do not inherently participate in inertial frequency regulation leading to a total reduction in system inertia. Besides this, the irradiance variation and stochastic nature of loads create severe stress on the conventional sources and possibly results in large frequency deviation. To address the issue of reduced inertial responses at higher PV penetration level this paper proposes a concept of emulated inertia from PV generators by the de-loaded operation. This mechanism will allow PV to participate in system frequency regulation and provides better inertial responses compared to the PV system operating in maximum powerpoint. The study also analyses the small-signal stability of the system and its response to irradiance change when multiple PV generators are connected in a hybrid power system. It is found that PV generators in a single area have a large influence on frequency stability. Due to the derived inertial response from PV, the power fluctuations due to irradiance variations are counterbalanced and bring better frequency regulations even at a high level of penetration. The result of the analysis shows that the proposed method improves the frequency regulation and significantly reduces the stress on other conventional sources.