End-Use Systems Integration
The Distributed Energy Program of the DOE seeks to encourage further widespread adoption and implementation of distributed power generation. A large portion of the existing distributed generation and the potential for future distributed generation installations is found in the industrial and commercial sectors.
The foci of the ORNL efforts are to identify and assess promising applications for integrated distributed energy (DE) systems and to conduct projects that validate and demonstrate the benefits of DE technologies.
Reactive power is already purchased by many independent system operators (ISOs), such as New England ISO and the California ISO. In addition, reactive power supplied locally, as in CHP projects, will provide much greater value than when supplied from distant generating stations. Many distributed energy systems, such as reciprocating engine generators, already contain the needed equipment to supply reactive power - a synchronous generator. Systems using a microturbine will also be candidates with changes to the inverter design.
When end users supply reactive power, there will be three significant benefits that would encourage the adoption and implementation of distributed energy systems:
- Another source of income would be provided to amortize the distributed energy system investment.
- Local power quality would be improved. Reactive power could be used to provide
local voltage regulation.
- A significant benefit would be provided to the bulk power system. In many parts of the country, transmission grid congestion is caused by the "lumpiness" of the supply of dynamic reactive reserve. If dynamic reactive reserves could be supplied locally, as in CHP projects, this would provide a huge benefit to the nation's electrical transmission systems, and would "free up" a significant amount of transmission capacity.
In the next 20 years, it is probable that Distributed Energy (DE) will comprise 20% or more of our nation's electrical generation supply. The advantages of modern DER are that they are clean, quick to install, can be located near loads because they do not require extensive real estate, and are highly efficient. The disadvantages are that they will have to be controlled in large numbers and they do not behave like conventional large turbine generators. The transmission grid and their control system infrastructures have evolved over the years to handle conventional turbine generators. However, we believe that advances in power electronics and in control theory will enable the connection of large numbers of DER to the grid, and will actually result in greater reliability, improved efficiency and lower grid costs.
Power electronics conversion and conditioning systems will enable DER to appear to the grid like large, high inertia, turbine generators, and to perform all the functions of the large generators. When equipped with energy storage devices such as ultra-capacitors, power electronics conversion systems will be able to provide voltage sag support and other reliability services to the grid and user. In addition, power electronic designs are becoming more reliable because of topologies that incorporate redundant switching sections and lower stress on the switches. Power electronic advances also mean that less fault current will be supplied to the grid in the event of a short circuit, thus allowing the use of much less expensive circuit breakers and other protection equipment.
In addition, power electronics and distributed control will enable DER to provide a range of reliability services. These services will include, in addition to providing uninterruptible power and support of voltage sags, such traditional services as voltage and frequency regulation, control of capacitive resonance, control of subsynchronous oscillation, and other stability problems.