1. Distributed Generation & Power Quality
Wei-Jen Lee, Ph.D., PE
Professor of Electrical Engineering
The University of Texas at Arlington
July 10, 2003

2. Introduction Perspectives on DG Benefits End-User Perspective
Back Generation to Provide Improved Reliability
Reduce Energy Bill
Participation in the Competitive Power Market
Distribution Utility Perspective
Transmission & Distribution Relief
Hedge Against of Uncertain Load Growth
Hedge Against Price Spike
Commercial Power Producer Perspective
Selling Power or Ancillary Service in the Deregulated Market
Integrated Resource Planning

3. Introduction Disadvantages of DG Power Quality
Cost of Operation and Maintenance
Long Term Reliability of the Units
Interconnection

4. Introduction

5. DG Technologies Reciprocating Engine Genset
The Least Expensive DG Technology
High Nox and Sox Emission. This Severely Limits the Number of Hours the Units, Particularly Diesels, May Operate per Year.
Natural Gas-Fire Engine Produce Fewer Emission. However, the Natural Gas Price is Unpredictable.

6. DG Technologies
Reciprocating Engine Genset

7. DG Technologies Combustion Turbine Range from 1 to 10 MW
High Speed: 8 – 12 kRPM
Microturbine
30 – 75 kW
10 – 100 kRPM
Efficiency: 25 – 30 %

8. DG Technologies
Superconducting Magnetic Energy Storage

9. DG Technologies
Carbon Nanotube

10. DG Technologies
Fuel Cell

11. DG Technologies Fuel Cell Phosphoric Acid (PAFC)
PAFCs generate electricity at more than 40% efficiency
Operating temperatures are in the range of 300 to 400 degrees F ( degrees C)
Existing PAFCs have outputs up to 200 kW, and 1 MW units have been tested
One of the main advantages to this type of fuel cell is that it can use impure hydrogen as fuel. PAFCs can tolerate a CO concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed.
PAFCs are the most mature fuel cell technology.

12. DG Technologies Fuel Cell Phosphoric Acid (PAFC)
Disadvantages of PAFCs include: it uses expensive platinum as a catalyst, it generates low current and power comparably to other types of fuel cells, and it generally has a large size and weight.

13. DG Technologies Fuel Cell Proton Exchange Membrane (PEM)
These cells operate at relatively low temperatures (about 175 degrees F or 80 degrees C), have high power density, can vary their output quickly to meet shifts in power demand, and are suited for applications, -- such as in automobiles -- where quick startup is required.
According to DOE, "they are the primary candidates for light-duty vehicles, for buildings, and potentially for much smaller applications such as replacements for rechargeable batteries.
This type of fuel cell is sensitive to fuel impurities.
Cell outputs generally range from 50 to 250 kW.

14. DG Technologies Fuel Cell Molten Carbonate (MCFC)
These fuel cells use a liquid solution of lithium, sodium and/or potassium carbonates, soaked in a matrix for an electrolyte.
They promise high fuel-to-electricity efficiencies, about 60% normally or 85% with cogeneration, and operate at about 1,200 degrees F or 650 degrees C.
To date, MCFCs have been operated on hydrogen, carbon monoxide, natural gas, propane, landfill gas, marine diesel, and simulated coal gasification products.
10 kW to 2 MW MCFCs have been tested on a variety of fuels and are primarily targeted to electric utility applications.
A disadvantage to this, however, is that high temperatures enhance corrosion and the breakdown of cell components.

15. DG Technologies Fuel Cell Solid Oxide (SOFC)
This type could be used in big, high-power applications including industrial and large-scale central electricity generating stations.
Some developers also see SOFC use in motor vehicles and are developing fuel cell auxiliary power units (APUs) with SOFCs.
A solid oxide system usually uses a hard ceramic material of solid zirconium oxide and a small amount of ytrria, instead of a liquid electrolyte, allowing operating temperatures to reach 1,800 degrees F or 1000 degrees C.
Power generating efficiencies could reach 60% and 85% with cogeneration and cell output is up to 100 kW.

16. DG Technologies Fuel Cell Alkaline
Long used by NASA on space missions, these cells can achieve power generating efficiencies of up to 70 percent. They were used on the Apollo spacecraft to provide both electricity and drinking water.
Their operating temperature is 150 to 200 degrees C (about 300 to 400 degrees F).
They typically have a cell output from 300 watts to 5 kW.

17. DG Technologies Fuel Cell Direct Methanol Fuel Cells (DMFC)
These cells are similar to the PEM cells in that they both use a polymer membrane as the electrolyte. However, in the DMFC, the anode catalyst itself draws the hydrogen from the liquid methanol, eliminating the need for a fuel reformer.
Efficiencies of about 40% are expected with this type of fuel cell, which would typically operate at a temperature between degrees F or degrees C.
This is a relatively low range, making this fuel cell attractive for tiny to mid-sized applications, to power cellular phones and laptops.

18. DG Technologies Fuel Cell Regenerative Fuel Cells
Still a very young member of the fuel cell family, regenerative fuel cells would be attractive as a closed-loop form of power generation.
Water is separated into hydrogen and oxygen by a solar-powered electrolyser. The hydrogen and oxygen are fed into the fuel cell which generates electricity, heat and water. The water is then recirculated back to the solar-powered electrolyser and the process begins again.
These types of fuel cells are currently being researched by NASA and others worldwide.

19. DG Technologies Fuel Cell Zinc-Air Fuel Cells (ZAFC)
In a typical zinc/air fuel cell, there is a gas diffusion electrode (GDE), a zinc anode separated by electrolyte, and some form of mechanical separators.
The GDE is a permeable membrane that allows atmospheric oxygen to pass through. After the oxygen has converted into hydroxyl ions and water, the hydroxyl ions will travel through an electrolyte, and reaches the zinc anode. Here, it reacts with the zinc, and forms zinc oxide. This process creates an electrical potential.

20. DG Technologies Fuel Cell Protonic Ceramic Fuel Cell (PCFC)
This new type of fuel cell is based on a ceramic electrolyte material that exhibits high protonic conductivity at elevated temperatures.
PCFCs share the thermal and kinetic advantages of high temperature operation at 700 degrees Celsius with molten carbonate and solid oxide fuel cells, while exhibiting all of the intrinsic benefits of proton conduction in polymer electrolyte and phosphoric acid fuel cells (PAFCs).
The high operating temperature is necessary to achieve very high electrical fuel efficiency with hydrocarbon fuels. PCFCs can operate at high temperatures and electrochemically oxidize fossil fuels directly to the anode. This eliminates the intermediate step of producing hydrogen through the costly reforming process. .

21. DG Technologies
Wind Generation

22. DG Technologies
Photovoltaic

23. Interface to the Utility System
Synchronous Machine
Asynchronous Machine
Electronic Power Inverters

24. Power Quality Issues Sustained Interruptions Voltage Regulation
Voltage Ride Through
Harmonics
Voltage Sags
Load Following
Power Variation
Misfiring of Reciprocating Engines

25. Power Quality Issues
Voltage Support and Ride Through

26. Power Quality Issues
Voltage Support and Ride Through

27. Power Quality Issues
Helping on Voltage Sags

28. Operating Conflicts
Utility Fault-Clearing Requirements

29. Operating Conflicts Reclosing
DG Must Disconnect Early in the Reclose Interval to Allow Time for the Arc to Dissipate.
Reclosing on DG, Particularly Those System Using Rotating Machine Technologies, Can Cause Damage to the Generator or Prime Mover.

30. Operating Conflicts
Reclosing

31. Operating Conflicts
Interference With Relay
Reduction of Reach

32. Operating Conflicts Interference With Relay
Sympathetic Tripping of Feeder Breaker

33. Operating Conflicts
Interference With Relay
Defeat of Fuse Saving

34. Operating Conflicts
Voltage Regulation Issues

35. Operating Conflicts
Voltage Drops Along the Feeder if the DG is Interrupted (Determine the Max. Capacity of DG)

36. Operating Conflicts
Excess DG Can Fool Reverse Power Setting on Line Voltage Regulator

37. Operating Conflicts
Varying DG Output can Cause Excess Duty on Utility Voltage Regulation Equipment

38. Operating Conflicts
Harmonics

39. Operating Conflicts
Islanding DG
Main Utility Grid

40. Operating Conflicts
Ferroresonance

41. Operating Conflicts
Shunt Capacitor Interaction (Overvoltage due to capacitor)

42. Operating Conflicts Transformer Connections Grounded Y-Y Connection
No Phase Shift
Less Concern for Ferroresonance
Allow DG to Feed All Types of Faults on the Utility System
Back Feed of the Triplen Harmonic
Should Insert Ground Impedance to Limit the Current

43. Operating Conflicts
Transformer Connections
D-Y Connection

44. Operating Conflicts
Transformer Connection
Delta-Delta Connection

45. Operating Conflicts
Transformer Connection
Grounded Y-D Connection

46. DG on Low-Voltage Distribution Networks
Spot Network Arrangement

47. DG on Low-Voltage Distribution Networks
Spot Network Arrangement

48. DG on Low-Voltage Distribution Networks
Arrangement of Network Protector Relay

49. DG on Low-Voltage Distribution Networks
A Microcomputer Based Network Protector Relay

50. DG on Low-Voltage Distribution Networks
Operation of A Microcomputer Based Network Protector Relay
Network protector relays are used to monitor and control the power flow of low voltage AC to secondary network systems
The purpose of the network protector is to prevent the system from backfeeding and initiate automatic reclosing when the system returns to normal

51. DG on Low-Voltage Distribution Networks
Tripping Characteristics of A Microcomputer Based Network Protector Relay

52. DG on Low-Voltage Distribution Networks
Reclosing Characteristics of A Microcomputer Based Network Protector Relay

53. DG on Low-Voltage Distribution Networks
Network Primary Feeder Fault

54. DG on Low-Voltage Distribution Networks
Fault Current Contribution From Synchronous Local DG

55. DG on Low-Voltage Distribution Networks
Inverter Based DG on a Spot Network (Possible Solution)

56. DG on Low-Voltage Distribution Networks
Adjustable Reverse Power Characteristics

57. Siting DG
DG to Relieve Feeder Overload

58. Siting DG
DG to Increase Feeder Capacity

59. Siting DG
DG to Provide Voltage Support & Reconfiguration

60. Interconnection of DG
Typical Voltage and Frequency Relay Setting for DG Interconnection for a 60 Hz System

61. Interconnection of DG
Simple Interconnection Protection Scheme for Small DG

62. Interconnection of DG
Interconnection Scheme for Large Synchronous DG