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
CIRCUIT DIAGRAM:
Fig.
1. Electric Spring in a circuit
Fig.
2. Over-voltage, Conventional ES: RMS Line voltage, ES Voltage, and Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
3. Over-voltage, Conventional ES: ower Factor of system (ES turned on at t =
0.5 sec)
Fig.
4. 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.
5. Under-voltage, Conventional ES: RMS Line voltage, ES Voltage, and
Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
6. Under-voltage, Conventional ES: Power Factor of system (ES turned on at t =
0.5 sec)
Fig.
7. 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.8.
Over-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
9. Over-voltage, Improvised ES: Power Factor of system (ES turned on at t = 0.5
sec)
Fig.
10. 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.
11. Under-voltage, Improvised ES: RMS Line voltage, ES Voltage, and Non-Critical
load voltage (ES turned on at t=0.5 sec)
Fig.
12. Under-voltage, Improvised ES: Power Factor of system (ES turned on at t =
0.5 sec)
Fig.
13. 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.
