In this article we will discuss about:- 1. Introduction to Distributed Generation 2. Perspectives on Interconnection of Distributed Generation 3. Advantages 4. Disadvantages.
Introduction to Distributed Generation:
The distributed generation uses smaller-sized generators than does the typical central station plant. They are distributed throughout the power system closer to the loads. The normal distribution system delivers electric energy through wires from a single source of power to a multitude of loads. Thus, several power quality issues arise when there are multiple sources.
The electrical power systems, consisting of relatively small generators configured in isolated islands, used Distributed Generation. That model gave way to the present centralized system largely because of economies of scale. Also, there was the desire to sequester electricity generation facilities away from population centers for environmental reasons and to locate them closer to the source of fuel and water.
In the mid-1990s, interest in Distributed Generation once again peaked with the development of improved DG technologies and the deregulation of the power industry allowing more power producers to participate in the market. Also, the appearance of critical high-technology loads requiring much greater reliability than can be achieved by wire delivery alone has created a demand for local generation and storage to fill the gap.
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Some futurists see a return to a high-tech version of the original power system model. New technologies would allow the generation to be as widely dispersed as the load and interconnected power grids could be small (i.e., microgrids). The generation would be powered by renewable resources or clean-burning, high-efficiency technologies. Energy distribution will be shifted from wires to pipes containing some type of fuel, which many think will ultimately be hydrogen.
Perspectives on Interconnection of Distributed Generation:
There are also opposing perspectives on the issue of interconnecting Distributed Generation to the utility system. This is the source of much controversy in efforts to establish industry standards for interconnection. Figures 6.1 and 6.2 illustrate the views of the two key opposing positions.
Figure 6.1 shows end users and Distributed Generation owners who want to interconnect to extract one or more of the benefits. Drawings like this can be found in many different publications promoting the use of Distributed Generation. The implied message related to power quality is that the Distributed Generation is small compared to the grid. This group often has the view that the grid is a massive entity too large to be affected by their relatively small generator. For this reason, many have a difficult time understanding why utilities balk at interconnecting and view the utility requirements simply as obstructionist and designed to avoid competition.
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Another aspect of the end-user viewpoint that is not captured in this drawing is that despite the large mass of the grid, it is viewed as unreliable and providing “dirty” power. Distributed Generation proponent literature often portrays Distributed Generation as improving the reliability of the system (including the grid) and providing better-quality power.
The perspective on interconnected Distributed Generation of typical utility distribution engineers, most of whom are very conservative in their approach to planning and operations, is captured in Fig. 6.2. The size of customer-owned Distributed Generation is magnified to appear much larger than its actual size, and it produces dirty power. It is also a little off-center in its design, suggesting that it is not built and maintained as well as utility equipment. There are elements of truth to each of these positions.
Advantages of Distributed Generation:
The benefits of Distributed Generation from three different perspectives:
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i. End-User Perspective:
End users who place a high value on electric power can generally benefit greatly by having backup generation to provide improved reliability. Others will find substantial benefit in high-efficiency applications, such as combined heat and power, where the total energy bill is reduced. End users may also be able to receive compensation for making their generation capacity available to the power system in areas where there are potential power shortages.
ii. Distribution Utility Perspective:
The distribution utility is interested in selling power to end users through its existing network of lines and substations. Distributed Generation can be used for transmission and distribution (T&D) capacity relief. In most cases, this application has a limited life until the load grows sufficiently to justify building new T&D facilities.
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Thus, DG serves as a hedge against uncertain load growth. It also can serve as a hedge against high price spikes on the power market.
iii. Commercial Power Producer Perspective:
Those looking at Distributed Generation from this perspective are mainly interested in selling power or ancillary services into the area power market. Commercial aggregators will bid the capacities of several units. The Distributed Generation may be directly interconnected into the grid or simply serve the load off-grid. The latter avoids many of the problems associated with interconnection but does not allow the full capacity of the Distributed Generation to be utilized.
Disadvantages of Distributed Generation:
Disadvantages of Distributed Generation different perspectives are: Utilities are concerned with power quality issues, and a great deal of the remainder of devoted to that concern. End users should be mainly concerned about costs and maintenance. Do end users really want to operate generators? Will electricity actually cost less and be more reliable? Will power markets continue to be favorable toward Distributed Generation? There are many unanswered questions. However, it seems likely that the amount of DG interconnected with the utility system will continue to increase for the foreseeable future.