Minimum Synchronous Inertia Requirement of Renewable Power Systems

Abstract

Abstract-The installed capacity of wind generation and photovoltaics (PV) in many countries is going to dominate generation fleets in a bid to meet growing renewable energy targets. Synchronous inertia has never been problematic as there was more available than needed, but it is being significantly reduced due to the increasing integration of non-synchronous renewable generation. When the low bidding priced generation of wind and PV becomes considerably large, conventional economic dispatch algorithms can result in less online synchronous inertia and put power system security at risk. However, the compromise of power system security due to synchronous inertia shortage is not well studied in literature. This paper develops a synchronous inertia constrained economic dispatch algorithm to satisfy the minimum required synchronous inertia of frequency control. Synchronous condensers and wind reserve are economically allocated to alleviate any shortage of synchronous inertia and frequency control ancillary services (FCAS). A Gaussian particle swarm optimization algorithm is introduced to simultaneously co-optimize the dispatch of synchronous generators and their FCAS, wind reserve and synchronous condensers.Index Terms-Synchronous inertia, economic dispatch, wind turbine, renewable energy, power system.  NOMENCLATURE   CtOverall power system operational cost in the economic dispatch cycle t in terms of net load   [2] are also crucial, the most basic and challenging problem lies in the electricity supply side.Economic dispatch algorithms proposed in literature have focused on the improvement of algorithm performance [3,4] and consideration of more operational constraints [5], such as spinning reserve and generator ramp rates. They did not dynamically evaluate the synchronous inertia adequacy of a dispatch result in terms of N-1 contingency [3][4][5]. This is due to the fact that synchronous inertia adequacy is not a problem for a conventional power system with limited non-synchronous generation.However, synchronous inertia is being materially reduced due to ongoing displacement of synchronous generators by asynchronous ones, such as wind turbine generators and photovoltaic (PV) panels. Electronic inverters used in wind turbines and PV panels lack the synchronous inertia that can help an RPS survive a major disturbance.If comprised of less online synchronous inertia, an RPS may routinely suffer a rapid rate of change of frequency (RoCoF) and a large frequency deviation following a disturbance. A great RoCoF of 6 Hz/s was recorded in the South Australian blackout on September 28, 2016 which was caused by the "lightness" of the South Australian power system [6]. The instantaneous penetration level of wind and PV generation was over 50% before the blackout in South Australia and only three thermal power plants were dispatched [6].This paper therefore proposes a synchronous inertia constrained economic dispatch to keep the minimum amount of synchronous inertia online. The proposed algorithm introduces a feedback loop...

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