Analysis of the Influence of System Strength on Transient Overvoltage for Power Systems with Renewable Energy Sources

Renewable energy sources (RESs) with dynamic reactive power support capability are important reactive power sources that cause the transient overvoltage (TOV) in the power system with high penetration of RESs. The TOV problem is more severe in the weaker system. This paper establishes a mathematical relationship model of the short-circuit ratio (SCR) and the node voltage to quantify the impact of system strength on the TOV. First, the mechanism of the TOV caused by RESs is explained. Then, we use a multi-in feed SCR index to indicate the strength of power systems with high penetration RESs. The analytical expression of the TOV as the function of the multi-infeed SCR is derived. It considers the mutual influence of multi-infeed branches on the TOV level in power systems with RESs. The more significant the grid-connected scale of RESs is, the lower the SCR and the higher the TOV are. Furthermore, the effect of synchronous condensers (SCs) on improving the system strength is also analyzed. The TOV problem can be improved by SCs. Simulations verify the analysis of this paper.