Investigation of frequency stability during high penetration of CCGTs and variable-speed wind generators in electricity networks

Variable-speed wind generators (VSWGs) are being extensively deployed as the main wind power generation technology around the world. However, when the VSWGs are integrated to gas turbine based (e.g. combined-cycle gas turbines (CCGTs) and open-cycle gas turbines (OCGTs)) electricity networks, potentially threatening dynamic interactions could occur during frequency excursions. This is due to the fact that gas turbines depict unique frequency response characteristics, while VSWGs exhibit either no or emulated inertial response during system frequency events. Thus, stability issues will arise when both technologies have significant penetration levels in electricity networks. This study shows that frequency stability concerns could become more severe due to the non-coherent inertial power release and recovery response of VSWGs equipped with emulated inertial response which can coincide with the unique frequency response characteristics of CCGTs. Therefore, special care must be taken by the system operator to avoid any potentially threatening VSWG and CCGT combinations during system operation.