Evaluation of the use of short-circuit ratio as a system strength indicator in converter-dominated power systems

Abstract

This paper investigates the applicability of shortcircuit ratio (SCR) as a system strength indicator in power systems with a high penetration of voltage source converters (VSCs). In power systems dominated by synchronous generators, the SCR has been widely used to estimate the system strength by using short-circuit level information obtained at the relevant bus. However, the emerging converter technology such as VSCs has different short-circuit characteristics from synchronous generators, in the sense that the short-circuit currents are typically lower in magnitude and more controllable. Moreover, SCR calculations are based on the static analysis of the power system, neglecting the dynamic and control aspects of VSCs. These aspects raise the question whether the SCR can still be used to evaluate system strength of converter-dominated systems. To this end, in this paper, the fundamental definition of the SCR is revisited, and factors influencing its applicability in converter-dominated power systems are listed. A case study is provided to demonstrate the limitation of the SCR in converter-dominated systems, and the impact of the control strategy on the dynamic performance of the system is also discussed.

Short circuit ratio analysis and voltage stability control of power system with DFIG-based wind turbines

“…According to (9), reducing the d x value can increase the SCR N at the point of interconnection. From figure 5 (a), it can be observed that under the same fault conditions, a larger SCR N results in a smaller voltage drop and a smaller transient overvoltage, indicating a positive correlation between voltage support strength and the SCR N .According to (5), changing the d x value does not affect the magnitude of the conventional SCR.…”

“…The short circuit ratio (SCR) is one of the important indicators for assessing the voltage support capability of new energy grid integration systems [6][7][8]. Traditional SCR calculations neglect the contribution of new energy sources to the system's short circuit capacity [9]. The calculation of the SCR becomes incomplete when considering the reactive power voltage regulation capability of new energy power plants.…”

Optimal transmission switching strategy for multi‐infeed DC receiving‐end power network to prevent over‐limit of short‐circuit current

“…Additionally, it guarantees that the power flow P ijc on that line remains fixed at zero when the line is withdrawn. The upper and lower bounds of the unit active output are shown in Formula (17). The bus voltage phase angle difference constraint upper and lower limitations are given in Formula (18) when the line is operational.…”

“…To limit SCC while ensuring sufficient system strength support for the DC system, it is necessary to express system strength constraints analytically. In engineering applications and theoretical research, the short‐circuit ratio (SCR) index is typically used to characterise the relative strength of the AC and DC systems [16, 17]. Considering the interaction of various DC converter stations in a multi‐infeed DC receiving‐end system, the CIGRE DC Working Group has defined the multi‐infeed short‐circuit ratio (MISCR) [18].…”