GE DMC490 Software Configuration Manual page 13

This is a parameter between 0 and 1, multiplied by the upper bound of renewable power generation unit, and
decided by the operator based on meteorological observation data.
Optimal Dispatch
The primary function of the MGC is optimal dispatch, which is the process of allocating the required load
demand among the available resources such that the cost of operation is minimized. The MGC minimizes cost
of electricity and/or heat in a microgrid, for example daily, and the prediction horizon can extend up to 48
hours.
Within a microgrid, resources include conventional generators and storage devices. The cost of operation is
typically defined by fuel cost but can include maintenance and other costs.
An optimal dispatch algorithm is used to minimize the total operational cost of the microgrid. This cost is the
sum of the fuel cost required to run the non-renewable generators, cost of electricity, which needs to be
bought from a grid when one exists, and the operational cost of renewable and storage devices. Other factors
include maintenance, start-up/shut-down costs, cost/revenue components associated with
importing/exporting power to the grid, minimum energy/power requirements for various generation assets and
minimum up/down times for some of the assets. The power bought from the grid plus the power generated
internally must equal the total load and the power exported to the grid at any instant of time. The algorithm
does not treat loads as dispatchable except to avoid situations of grid instability associated with imbalance
between supply and demand. In other words, the microgrid always supplies enough power to satisfy its loads
provided that this is physically possible given the power limits on the generators.
The optimal dispatch algorithm uses a technique known as model predictive control. It makes use of historical
data as follows: daily, weekly, and annual load profiles; hydro, wind, and solar forecasts; and fuel or electricity
market pricing information (when a bulk grid connection exists). Given this information, the algorithm
determines the cost of operation for a fixed period in the future, typically 24 hours. It then solves the
optimization problem with the objective to minimize the total costs and to determine the required control
actions. These control actions include selecting the best machines to be operated at any given time, by issuing
start/stop commands and sending proper isochronous or non-isochronous commands to dispatchable or
renewable power generation units. It determines when energy is stored and when it is supplied to the system.
Finally, it determines the best power reference point for each droop (non-isochronous) machine and for each
storage device. Figure 10 shows data flow between the MGC and the different component devices within the
microgrid.
DMC490 Overview
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