Completely Self-Controlled Power Systems Are Proposed

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Though the first generation of smart grids incorporating digital communications and computing is taking longer than expected to materialize, it is not too soon to start thinking about what the second generation of power systems will look like.

In the issue of the IEEE Smart Grid e-Newsletter that went live this week, Qing-Chang Zhong, a professor in the Department of Automatic Control and Systems Engineering at the University of Sheffield in the U.K., proposes a novel scheme for how autonomous power system control could be achieved in electricity networks that could have millions of active players. Today, Zhong points out, the active participants in a large national grid like China's number just 1500 or so (mostly big central generators delivering 200 megawatts or more). With the introduction of many smaller wind and solar installations, electric vehicles, and energy storage facilities, the number of players is already exploding. The number of players will rise even more sharply as home-energy management and demand-response systems come into their own and start playing a growing role in voltage regulation.

How will it be possible to coordinate all those players and maintain system reliability?

Zhong proposes a model in which the synchroverter technology he co-invented a number of years ago would be widely deployed at all levels of the grid to take care of voltage and frequency regulation autonomously—assuring that the smart grid's communications functions aren't tied up by the blizzard of negotiations determining when and how much new distributed generation sources will contribute to the grid. They would operate like the synchronous machines engineered to provide regulation in today's grids. As Zhong goes on to explain, wind turbines and solar arrays, EVs and battery banks typically are connected to the grid by means of inverters (DC to AC converters), which can be engineered to have the properties of synchronous machines. On the demand side, Internet devices are powered by DC supplies and therefore communicate with the grid by means of rectifiers, as do LEDs [see photo], which seem destined to be the dominant lighting technology of the future. Altogether, three quarters or more of generation and load could be communicating with the grid by means of rectifiers.

That implies, Zhong believes, that synchroverters could be deployed everywhere a rectifier is needed and all the devices could flock together and sing, without central coordination or control.

A second article in the current issue of the IEEE newsletter also addresses a fundamental issue in the emergent smarter grid of the future. Amro M. Farid, an assistant professor of engineering systems and management at the Masdar Institute in Abu Dhabi, points out that in future grids, generation will be much less dispatchable on average (less capable of being ramped up quickly), while load-side assets will be more dispatchable. Farid, who leads the Laboratory for Intelligent Integrated Networks of Engineering Systems at Masdar, believes a solution is to be found in a model involving "holistic assessment for enterprise control." The concept, as Farid explains, originated in manufacturing, where it came to refer not only to management of dynamic production processes but also their integration with business considerations. Farid argues that this model is of obvious relevance to smarter grids that are much more dynamic in terms of inputs and outputs and, at the same time, more responsive to market forces.

Image: Yagi Studio/Getty Images

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