Multi-agent coordination of distributed energy storage systems for mitigating renewable energy resources high ramp-rate issues

Author(s):  
Nader A. El-Taweel ◽  
H. E. Farag
Author(s):  
Reza Arghandeh ◽  
Robert Broadwater

Environmental concerns, global warming and fossil fuel prices are creating a shift in the expectations of consumers and industries to move toward renewable energy resources. However, the inability to control the output of renewable resources, like wind and solar, results in operational challenges in power systems. The operational challenges of renewable resources can be met by energy storage systems. The energy storage systems scheduling can be used to control the effect of intermittent renewable energy resources. Furthermore, energy storage systems can be used for ancillary services, peak reduction, and mitigating contingencies in the distribution and transmission networks [1]. Distributed photovoltaic (DPV) rooftop panels are considered as renewable energy resources in this paper. Depending on the DPV size and solar irradiation, DPV adoption can create problems for the distribution network. In addition, utility companies have to pay different prices for electricity during different times of the day due to the dynamic electricity market. Therefore, the DPV adoption can be controlled with the help of real-time electricity price and the load profile. Facing these challenges, this paper presents an operational optimization algorithm for a Distributed Energy Storage (DES) system. The DES system presents a fleet of batteries connected to distribution transformers. The DES can be used for withholding DPV power before it is bid into the market. Withholding DPV generation represents a gaming method to realize higher revenues due to the time varying cost of electricity. Energy storage systems may be used to control DPV power variation and thus help distribution network operations [2]. The objective of this paper is to present a DES optimal economic control system to improve the DPV adoption in power distribution networks. The control system decisions depend on the load profiles, and the real-time Locational Marginal Price (LMP). Economic operation of the DES is a complex problem because of the time dependency of the battery capacity (where sufficient energy reserves must be maintained in case of power loss), the solar irradiation uncertainty, and the real-time electricity price variability. The mathematical approach used is the Discrete Ascent Optimal Programming (DAOP) algorithm. An advantage of DAOP is its assurance of convergence after a finite number of computational iterations.


Author(s):  
Peggy P. Ip ◽  
Sammy Houssainy ◽  
H. Pirouz Kavehpour

Undeveloped small hydropower generation sites are abundant throughout the water conveyance infrastructure and natural rivers in the United States. Due to its small scale, micro-hydro development requires substantial upfront capital costs, maintenance and operation costs for customized engineering and construction. The significant investments required for developing small hydropower are inhibiting for utilities, residential and commercial users to adopt. An inexpensive energy storage system and a well-designed power controls system can be integrated with small hydropower sites to increase its cost-effectiveness and reliability. This paper introduces the concept of storing low-power generated from small hydro turbines during long off-peak periods and dispatching at high-power as grid-quality electricity during peak periods. The use of an ultra-low cost thermal energy storage (ULCTES) system is examined. Boosting the power output for small hydro generation allows commercial users to avoid significant demand charges during operation, making small hydro an attractive cost saving strategy and therefore breaking down the cost barrier. The ULCTES operates much like a bulk power production unit and a peaker plant, in which it is capable of dispatching constant power over a long period during peak periods when conventional sources are unavailable. Improvements in system reliability and economic value are evaluated using microgrid optimization software HOMER Energy. In particular, two cases are studied with variations in types of end users and energy management goals. Energy costs savings, demand charges savings and renewable energy penetration are determined. Distributed energy storage systems are shown to reduce energy costs and increase the renewable energy penetration for commercial users. With ULCTES, microgrids have the flexibility to manage fluctuating renewable energy generation as well as respond to rapidly changing loads on a daily basis. A larger hydroelectricity system is shown to be more feasible with distributed energy storage systems for isolated users without any connection to the grid.


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