Impact of load frequency dependence on frequency response of a power system with high non-synchronous penetration

Due to significant development of renewable energy sources, such as wind and photovoltaic (PV), conventional synchronous generators are being economically replaced from the traditional generation mix. Modern wind turbine and PV generators are non-synchronous machines, which usually do not provide inherent inertia and governor control to arrest frequency excursion after a major disturbance. Thus, presence of such high non-synchronous generation may introduce a challenge to maintain system frequency within the satisfied limits following a large generator or an interconnection trip. In addition to non- synchronous penetration level, frequency response of a power system may have significant reliance on frequency dependent loads. These loads, for example induction motors consume less power when there is a fall in system frequency. It facilitates faster arrest of frequency decline after a contingency. As a result, frequency response of a power system may enhance. This paper investigates the effects of load frequency dependence on frequency response of a power system in presence of high non- synchronous generation. It also quantifies the amount of load relief and under frequency load shedding, which a system may encounter after a severe disturbance. In this context, a low inertia power system that loosely resembles the South Australian network is investigated and reported.