Evaluating system strength for large-scale wind plant integration

The performance of various components in a power system, from voltage stability perspective, is highly dependent on the system strength. Voltage stability issues can be caused by integrating a large amount of wind generation into a weak grid. Short circuit ratio (SCR) is often used as an index of the system strength. SCR provides wind plants a reference to properly tune controller settings and coordinate with neighboring plants. The commonly used SCR calculation method does not consider interactions between wind plants, therefore gives an overly-optimistic estimation of the system strength. This paper proposes the concept of weighted short circuit ratio (WSCR), which takes interactions between wind plants into account. The WSCR can better reflect the actual system strength when integrating a large amount of wind plants in a weak system. The paper also proposes a procedure to determine the optimal synchronous condenser ratings and locations to improve the overall system strength.