Investigation of non-synchronous penetration level and its impact on frequency response in a wind dominated power system

South Australia is a southern state of Australia, where penetration of wind power has continuously increased over the last few years. In recent times, most of the wind power plants have been constructed based on variable speed wind turbine generators, namely type III and IV machines. These machines, however, do not intrinsically offer any support to control frequency excursion following a major disturbance. These ‘asynchronous’ machines together with a high voltage DC interconnection to the adjacent state Victoria often contribute to a higher level of non-synchronous generation in South Australia. During substantial presence of non-synchronous generation and high import from Victoria, South Australian system may rely on a few synchronous machines for frequency control following a disturbance. Under such operating scenarios, a big contingency such as an interconnection trip could result in unacceptable frequency deviation and rate of change of frequency. Consequently, the network may experience under frequency load shedding, which could affect the security of the system. To explore the above-mentioned issues, this paper evaluates non-synchronous penetration level in South Australia and investigates its effect on network frequency response. It also estimates the maximum allowable non-synchronous penetration level after an interconnection trip to minimise load shedding and keep rate of change of frequency within acceptable range.