Smart Grid and Stability of Power Systems
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By Hassan Bevrani, Qobad Shafiee, and Hêmin Golpîra
Frequency stability and control is one of the most important problems in interconnected power grids design and operation. Several control loops are operating to maintain the system frequency at its set-point. Each one has its particular specification and relies on a given amount of power reserve that is kept available to cope with power deviations. The majority of supply-demand balancing is achieved by controlling the output of dispatchable generating units.
By István Táczi, Bálint Hartmann, István Vokony
Non-synchronous generation – principally wind and solar power - expels conventional synchronous generation as the renewable energy technologies gain higher shares worldwide. These units are connected to the grid via a power electronic converter, which practically decouples the generator from the electrical grid as the control sets the parameters. It also means that any rotating mass of the generation is also decoupled; therefore, the conventional – electromechanical principle based – angle and frequency stability theories could not be applied. This process has a great effect on the dynamics of the power system, due to the decreasing synchronous rotational mass, which is often described by the so-called inertia.
By Zhaoyu Wang
Enormous pressure is looming over utility companies as they try to improve responses to severe weather events and power outages. Natural disasters have been causing major disruptions around the world and the trend is increasing. In 2016, the average outage duration for customers in the United States ranged from 27 minutes in Nebraska to 6 hours in West Virginia, to 20 hours in South Carolina due to Hurricane Matthew. More recently in 2017, nearly 280,000 Texas customers were left without power after Hurricane Harvey. In 2018, approximately 1.9 million customers experienced power outages during Hurricane Florence, while 1.7 million customers lost power after Hurricane Michael in the Southeast United States. In 2019, severe storms caused multiple outages in Michigan and Wisconsin, where more than 500,000 customers were left without electricity. Power outage can cause significant social-economic impacts and is potentially life threatening. Utilities use outage management systems (OMS) to manage the grid during outages and restore power to customers. An OMS identifies and predicts potential grid outages and manages restoration activities. Moreover, OMS can assist in prioritizing restoration efforts and managing repair resources after outages. OMS can potentially reduce the outage duration by up to 25%. Recent development in Artificial intelligence (AI) and advanced optimization provides an opportunity to greatly improve existing OMS. This article will introduce how these new techniques help disaster preparation, outage prediction, damage assessment and service restoration.
By Aref Pouryekta, Vigna K. Ramachandaramurthy
A growing number of Voltage Source Converter (VSC) based generators in modern power systems results in a decrease of inertia and, consequently, to frequency instability. The reduced number of synchronous machines and the integration of wind turbines via VSCs into the power systems decouples the rotational components from the grid. Hence, reduction of inertia in the system threatens frequency stability. Virtual inertia is a solution in the described premises. Here, the VSC will be able to produce virtual inertia using appropriate control structure that enables it to behave as a synchronous generator and improve the frequency stability profile of the system.
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