A new hybrid energy storage controller is designed for a centralized control system that operates multiple energy storage devices (ESDs) and distributed generators to provide energy and ancillary services that can be shared among electric utilities, independent system operators, and balancing authorities. This new controller design supports the increased integration of renewable energy onto the grid.

Simulation results of using a hybrid energy storage system composed of flywheel and hydro to provide regulation service.

The objective of the controller design is to coordinate the operation of expensive, but highly flexible energy storage devices at the system level so that the hybrid combination of energy storage and conventional generation can provide low-cost energy and high-value ancillary services. Among the ESDs being considered for use with this technology are pumped-hydro power plants, grid-scale batteries — such as sodium-sulfur, lithium-ion, or redox flow batteries — and flywheels.

The scope of automated generator control is extended from solely controlling generators to controlling a mix of energy resources, including ESDs, demand response programs, dynamic interchange schedules, and conventional regulating units. The wide-area energy storage management system can save up to 30% on regulation capacity due to fast response characteristics. It also allows balancing authorities to share energy storage resources and reduce reserve requirements by taking advantage of the statistical averaging effects of simultaneously supplying the ramping requirements of several independent balancing areas.

The new controller reduces the wear and tear on traditional generation units by decreasing regulation signal fluctuations, maintains a desired state of charge on ESDs, prevents energy balancing violations, and maintains traditional generation unit output close to the most efficient operating point.

Without technological breakthroughs in batteries or other storage devices, the device significantly reduces the cost of electricity storage for not only energy services such as peak-shaving and load-shifting, but also ancillary services such as regulation and load-following applications. The same concept can be applied to a variety of ESDs, and is not dependent on any single storage technology. It is compatible with current grid operation mechanisms, making the integration of energy storage an easy task for both independent system operators and utilities.

For more information, contact Gordon Graff at This email address is being protected from spambots. You need JavaScript enabled to view it.; 509-375-6786.

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This article first appeared in the July, 2018 issue of Tech Briefs Magazine.

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