The effects of small distributed generation on the electrical distribution network

Millers, Paul Gordon (2010) The effects of small distributed generation on the electrical distribution network. [USQ Project]


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[Abstract]: The traditional electrical supply network relies on large remote power generating stations feeding energy radially over long transmission lines, through distribution networks to the electrical energy customer. This network has been optimised for the radial flow of power from the large power stations to the customer.

There has been increasing political and social pressures to move towards renewable power sources to generate electrical energy. A substantial portion of the renewable generation is being installed within the distribution networks. The smallest of the distributed generation (DG) systems are installed at residential and commercial customer’s premises. In Queensland these systems can be up to 10 kW per phase and can export energy back onto the electrical grid.

The addition of large numbers of Small DG Systems onto a distribution network can see the power flowing back into the upstream network. This research project examines the effect that high numbers of these Small DG Systems will have on the protection systems and quality of supply (QoS) of distribution networks.

This research project sought to examine the effects of high penetration of Small DG Systems on two representative distribution feeders. The feeders chosen were a high quality residential feeder called Ross Plains number 4 (ROPL-04) and a long rural single wire earth return (SWER) known at Karara. These two feeders represented the extremes of the possible distribution feeder types. They were chosen so that an understanding of the extent of issues surrounding high penetration of Small DG Systems on distribution networks could be developed.

The power system modelling software PSS Sincal was used to develop models of the two distribution feeders and the Small DG Systems. The models were tested with a number of credible Small DG Systems penetration scenarios in order to see if and at what level of penetration the QoS became unacceptable. This was achieved by modelling the networks with realistic customer load and solar insolation values to see if the feeder low voltage (LV) exceeded prescribed limits. The QoS became unacceptable when the prescribed limits had been exceeded. Testing was also conducted using credible changes in insolation due to cloud movement in order to test for unacceptable LV values. Further testing was carried out using reactive compensation to resolve excessive voltage problems.

The protection systems were tested by comparing the protection device settings and ratings with fault current values obtained from the network models when the Small DG
System penetrations were high.

It was found that the ROPL-04 feeder had substantial resilience to high levels of Small DG System penetrations for both QoS and protection performance. The Karara SWER
network was much less resilient and showed excessive voltage problems at low levels of Small DG System penetrations. The protection systems on the Karara SWER were not seriously compromised by high levels of Small DG System penetration.

It is possible that most grid-connect inverters can be enabled to generate reactive power as well as active power generation. The use of reactive compensation can correct QoS
problems created by the high penetration of Small DG Systems. This compensation can be either large stand alone units or come from the inverter themselves.

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Item Type: USQ Project
Refereed: No
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Electrical, Electronic and Computer Engineering (Up to 30 Jun 2013)
Supervisors: Ahfock, Tony
Date Deposited: 04 Mar 2011 02:25
Last Modified: 03 Jul 2013 00:32
Uncontrolled Keywords: electricity; interconnected power system; distribution network; single wire earth return (SWER); current fault detection; load management modeling; peak electrical demand; electrical energy distribution; grid
Fields of Research (2008): 09 Engineering > 0906 Electrical and Electronic Engineering > 090602 Control Systems, Robotics and Automation
09 Engineering > 0906 Electrical and Electronic Engineering > 090607 Power and Energy Systems Engineering (excl. Renewable Power)
Fields of Research (2020): 40 ENGINEERING > 4007 Control engineering, mechatronics and robotics > 400799 Control engineering, mechatronics and robotics not elsewhere classified
40 ENGINEERING > 4008 Electrical engineering > 400805 Electrical energy transmission, networks and systems

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