ABSTRACT:
Electric
Spring (ES), a new smart grid technology, has earlier been used for providing
voltage and power stability in a weakly regulated/stand-alone renewable energy
source powered grid. It has been proposed as a demand side management technique
to provide voltage and power regulation. In this paper, a new control scheme is
presented for the implementation of the electric spring, in conjunction with
non-critical building loads like electric heaters, refrigerators and central
air conditioning system. This control scheme would be able to provide power
factor correction of the system, voltage support, and power balance for the
critical loads, such as the building's security system, in addition to the
existing characteristics of electric spring of voltage and power stability. The
proposed control scheme is compared with original ES’s control scheme where only
reactive-power is injected. The improvised control scheme opens new avenues for
the utilization of the electric spring to a greater extent by providing voltage
and power stability and enhancing the power quality in the renewable energy
powered microgrids.
KEYWORDS:
1. Demand
Side Management
2. Electric
Spring
3. Power
Quality
4. Single
Phase Inverter
5. Renewable
Energy
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Electric Spring in a circuit
EXPECTED SIMULATION RESULTS:
Fig.
2. Over-voltage, Conventional ES: Power Factor of system (ES turned on at t =
0.5 sec)
Fig.
3. Over-voltage, Conventional ES: Active and Reactive power across critical
load, non-critical load, and electric spring (ES turned on at t=0.5 sec)
Fig.
4 Under-voltage, Conventional ES: RMS Line voltage, ES Voltage, and
Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
5. Under-voltage, Conventional ES: Power Factor of system (ES turned on at t =
0.5 sec)
Fig.
6. Under-voltage, Conventional ES: Active and Reactive power across critical
load, non-critical load, and electric spring (ES turned on at t=0.5 sec)
Fig.
7. Over-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
8. Over-voltage, Improvised ES: Power Factor of system (ES turned on at t = 0.5
sec)
Fig.
9. Over-voltage, Improvised ES: Active and Reactive power across critical load,
non-critical load, and electric spring (ES turned on at t=0.5 sec)
Fig.
10. Under-voltage, Improvised ES: RMS Line voltage, ES Voltage, and
Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
11. Under-voltage, Improvised ES: Power Factor of system (ES turned
on
at t = 0.5 sec)
Fig.
12. Under-voltage, Improvised ES: Active and Reactive power across critical
load, non-critical load, and electric spring (ES turned on at t=0.5 sec)
CONCLUSION:
In
this paper as well as earlier literatures, the Electric Spring was demonstrated
as an ingenious solution to the problem of voltage and power instability
associated with renewable energy powered grids. Further in this paper, by the
implementation of the proposed improvised control scheme it was demonstrated that
the improvised Electric Spring (a) maintained line voltage to reference voltage
of 230 Volt, (b) maintained constant power to the critical load, and (c)
improved overall power factor of the system compared to the conventional ES.
Also, the proposed ‘input-voltage-input-current’ control scheme is compared to
the conventional ‘input-voltage’ control. It was shown, through simulation and
hardware-in-loop emulation, that using a single device voltage and power
regulation and power quality improvement can be achieved. It was also shown
that the improvised control scheme has merit over the conventional ES with only
reactive power injection. Also, it is proposed that electric spring could be
embedded in future home appliances [1]. If many non-critical loads in the buildings
are equipped with ES, they could provide a reliable and effective solution to
voltage and power stability and insitu power factor correction in a renewable
energy powered microgrids. It would be a unique demand side management (DSM)
solution which could be implemented without any reliance on information and communication
technologies.
REFERENCES:
[1]
S. Y. Hui, C. K. Lee, and F. F. Wu, “Electric springs - a new smart grid
technology,” IEEE Transactions on Smart Grid, vol. 3, no. 3, pp. 1552–1561,
Sept 2012.
[2]
S. Hui, C. Lee, and F. WU, “Power control circuit and method for stabilizing a
power supply,” 2012. [Online]. Available: http://www.google.com/patents/US20120080420
[3]
C. K. Lee, N. R. Chaudhuri, B. Chaudhuri, and S. Y. R. Hui, “Droop control of
distributed electric springs for stabilizing future power grid,” IEEE
Transactions on Smart Grid, vol. 4, no. 3, pp. 1558–1566, Sept 2013.
[4]
C. K. Lee, B. Chaudhuri, and S. Y. Hui, “Hardware and control implementation of
electric springs for stabilizing future smart grid with intermittent renewable
energy sources,” IEEE Journal of Emerging and Selected Topics in Power
Electronics, vol. 1, no. 1, pp. 18–27, March 2013.
[5]
C. K. Lee, K. L. Cheng, and W. M. Ng, “Load characterisation of electric spring,”
in 2013 IEEE Energy Conversion Congress and Exposition, Sept 2013, pp.
4665–4670.
