Abstract
In recent years, only a small number of publications have been presented addressing power system stability with the increased use of large-scale photovoltaic (PV) generation around the world. The focus of these publications was on classical stability problems, such as transient and small signal stability, without considering frequency stability. Nevertheless, with increased PV generation, its effects on system frequency response during contingencies can no longer be ignored, especially in the case of weakly interconnected networks or isolated power systems. This paper addresses the impacts of large scale PV generation on the frequency stability of power systems. The positive effects of deloaded PV power plants (PV-PPs) able to support system frequency recovery during the initial seconds after major contingencies are also examined. Because this type of frequency support is not covered by current definitions, a new terminology is proposed that includes the frequency response of inertia-less generation units immediately after major power imbalances. We refer to this type of frequency support as fast frequency response (FFR). Finally, a discussion is also presented regarding the applicability and pertinence of frequency-related grid requirements for PV-PPs in the case of real power systems. The investigation is based on the isolated power system of northern Chile. The obtained results indicate that in the case of major power imbalances, no significant effects arise on the system frequency response until PV penetration levels exceed approximately 20%. From a system security perspective, the problems arise for PV penetration levels of approximately 50%, in which case, the frequency response capability in PV-PPs would be justified during certain hours of the year.
Highlights
Several countries around the world have set ambitious targets to achieve high penetration levels of electricity production based on renewable energy sources in the coming years [1,2,3]
The control implemented for fast frequency response (FFR) in PV power plants (PV-PPs) is the control presented in Section 4, where PV arrays operate in deloaded mode
In the present work, the obtained results indicated that in an isolated power system with low inertia and limited frequency control capacities, for PV penetration levels of approximately 50%, deloaded PV-PPs with FFR capability may be more valuable to the system than maximizing the solar energy itself
Summary
Several countries around the world have set ambitious targets to achieve high penetration levels of electricity production based on renewable energy sources in the coming years [1,2,3] This situation, in combination with favorable conditions for photovoltaic (PV) generation projects, such as the maturity of the technology and decreasing investment costs, will most likely lead PV generation to play a significant role in the electric power systems of the future. High levels of inertia-less PV units will reduce the capacity of the system to address frequency deviations during major disturbances, thereby greatly affecting power system frequency stability This situation could be especially critical in the case of isolated power systems due to the relatively low system inertia [11,12] and reduced capabilities for frequency regulation [13], both key factors affecting the system’s ability to recover from a loss of generation
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