Microgrid generation units optimum dispatch for fuel consumption minimization
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ORIGINAL RESEARCH
Microgrid generation units optimum dispatch for fuel consumption minimization Yi Han
•
Peter Young • Daniel Zimmerle
Received: 29 November 2011 / Accepted: 12 July 2012 Springer-Verlag 2012
Abstract This paper utilizes the Karush–Kuhn–Tucker (KKT) conditions to develop a scheme for economic dispatch of load to generation units in a microgrid. By using the (pure) KKT conditions, the true optimum can be found in the sense of minimizing the fuel consumption. This is the most economic way of dispatching the load to generators, but it may not be directly applicable in the real world. In practice extra constraints, in the form of swing generator(s), base load generator upper and lower operating limits, and spinning reserve are also required. These lead to a set of constrained KKT conditions, which are utilized to solve the problem. Note that although this solution obtained from constrained KKT conditions is not the true optimum, the extra constraints are there to enhance the system stability and reliability.This new approach is tested extensively in simulation against standard dispatch approaches, and its performance is seen to be superior in all cases. Keywords Fuel economy Lagrangian functions Optimization Power generation dispatch Power system Power grids
Y. Han (&) P. Young Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO 80523, USA e-mail: [email protected] P. Young e-mail: [email protected] D. Zimmerle Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA e-mail: [email protected]
1 Introduction The United States Marine Corps (USMC) utilizes generators covering a broad range, from: 2 to over 200 kW, and primarily powered by JP-8, which is used by US military as a replacement for diesel fuel in the engines of nearly all electrical generators. Note that logistic support to deliver this fuel is often both expensive and dangerous, so that minimizing fuel consumption is of paramount importance. These generation units can have very different fuel consumption curves. The highest efficiency normally occurs when the generators are loaded at near rated capacity, with larger generators being typically more efficient than smaller units. Considering fuel consumption as the primary cost, each generation unit has a different cost function. Future plans include the introduction of a ‘‘microgrid’’ into expeditionary bases, where several of these generation units with the same or different rated output power are interconnected to provide sufficient power to multiple loads. Properly designed and equipped with economic load dispatch, such a microgrid can minimize the fuel consumption and improve power stability. There are several existing methods to dispatch load to generators currently implemented in commercial systems, including: All Uniformly Dispatch (AUD), Descend Uniformly Dispatch (DUD) and Maximum Load Uniformly Dispatch (MLUD). These existing approaches, which are briefly explained a
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