Static voltage stability of photovoltaic grid-connected system based on eigenvalue index

Abstract

With the continuous development of renewable energy, photovoltaic power stations show a trend of large-scale grid connection, but the disorderly development of photovoltaic grid connection induces the static voltage instability in photovoltaic grid-connected system. Firstly, an equivalent model of photovoltaic large-scale grid-connected system using the equivalent admittance of photovoltaics is constructed in this paper, and the impact of photovoltaic grid-connected system on static voltage stability is quantified as the impact of photovoltaic equivalent admittance on the eigenvalue of the admittance matrix. It is concluded that the decrease of the minimum eigenvalue of the admittance matrix reduces the static voltage stability of photovoltaic grid-connected system. Further an evaluation index for static voltage stability of photovoltaic grid-connected system based on eigenvalue-active power sensitivity is proposed. Considering the strong correlation between the admittance matrix and the network topology of photovoltaic grid-connected system, the influence of the network topology on static voltage stability is analyzed. Photovoltaic grid-connected schemes which can improve the static voltage stability are proposed from AC and DC perspectives, and it is concluded that changing the topology of the transmission network reasonably can improve the static voltage stability of photovoltaic grid-connected system. Finally, based on a IEEE 14-node system example, the eigenvalue index and the photovoltaic grid-connected scheme proposed in this paper is validated to ensure the static voltage stability of large-scale photovoltaic grid-connected systems and promote orderly grid connection of photovoltaic system.

Keywords

• large-scale photovoltaic
• static voltage stability
• similarity transformation
• model analysis
• eigenvalue-sensitivity
• photovoltaic grid-connected scheme