Electric
Springs—A New Smart Grid Technology
The scientific principle of
“mechanical springs” was described by the British physicist Robert Hooke in the
1660’s. Since then, there has not been any further development of the Hooke’s
law in the electric regime. In this paper, this technological gap is filled by
the development of “electric springs.” The scientific principle, the operating
modes, the limitations, and the practical realization of the electric springs
are reported. It is discovered that such novel concept has huge potential in
stabilizing future power systems with substantial penetration of intermittent
renewable energy sources.
This concept has been successfully
demonstrated in a practical power system setup fed by an ac power source with a
fluctuating wind energy source. The electric spring is found to be effective in
regulating the mains voltage despite the fluctuation caused by the intermittent
nature of wind power. Electric appliances with the electric springs embedded
can be turned into a new generation of smart loads, which have their power
demand following the power generation profile. It is envisaged that electric
springs, when distributed over the power grid, will offer a new form of power
system stability solution that is independent of information and communication
technology.
KEYWORDS:
1. Distributed power systems
2. Smart loads
3. Stability
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.1. Schematic of the experimental setup with an electric spring connected
in series with a resistive-inductive load Z1.
CONCLUSION:
The Hooke’s law on mechanical
springs has been developed into an electric spring concept with new scientific
applications for modern society. The scientific principles, operating modes and
limits of the electric spring are explained. An electric spring has been
practically tested for both voltage support and suppression, and for shaping
load demand (of about 2.5 kW) to follow the fluctuating wind power profile in a
10 kVA power system fed by an ac power source and a wind power simulator. The
electric springs can be incorporated into many existing noncritical electric
loads such as water heaters and road lighting systems [26] to form a new
generation of smart loads that are adaptive to the power grid.
If many non critical loads are
equipped with such electric springs and distributed over the power grid, these
electric springs (similar to the spring array in Fig. 1) will provide a highly
reliable and effective solution for distributed energy storage, voltage
regulation and damping functions for future power systems. Such stability
measures are also independent of information and communication technology
(ICT). This discovery based on the three-century-old Hooke’s law offers a
practical solution to the new control paradigm that the load demand should
follow the power generation in future power grid with substantial renewable
energy sources. Unlike traditional reactive power compensation methods,
electric springs offer both reactive power compensation and real power
variation in the non critical loads. With many countries determined to
de-carbonize electric power generation for reducing global warming by
increasing renewable energy up to 20% of the total electrical power output by
2020 [22]–[25], electric spring is a novel concept that enables human society
to use renewable energy as nature provides. The Hooke’s law developed in the
17th century has laid down the foundation for stability control of renewable
power systems in the 21st century.
EXPECTED SIMULATION RESULTS:
Fig. 4. Measured steady-state electric spring waveforms under
“inductive” mode. Va =94.3 Vac,QES=348.4 Var. [Electric
spring voltage is near zero.]
REFERENCES:
[1]Hooke’s law—Britannica Encyclopedia [Online]. Available: http://
www.britannica.com/ EB checked / topic/271336/Hookes-law
[2] A. M. Wahl, Mechanical Springs, 2nd ed. New
York: McGraw-Hill, 1963.
[3] W. S. Slaughter, The Linearized Theory of Elasticity.
Boston, MA: Birkhauser, 2002.
[4] K. Symon, Mechanics. ISBN 0-201-07392-7.
Reading, MA: Addison- Wesley, Reading,1971.
[5] R. Hooke, De Potentia Restitutiva, or of Spring
Explaining the Power of Springing Bodies. London, U.K.: John Martyn, vol.
1678, p. 23.
