Electric Spring for Voltage and Power Stability and Power Factor Correction

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

 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)

CONCLUSION

In this paper as well as earlier literature s, 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.

Control Scheme

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. 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 in sit u
power factor correction in a renewable energy powered
micro-grids. It would be a unique demand side management
(D S M) 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. Ch a u d h u r i, B. Ch a u d h u r i, 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. Ch a u d h u r i, 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. Che n g, and W. M. N g, “Load characterization of electric
spring,” in 2013 IEEE Energy Conversion Congress and Exposition, Sept
2013, pp. 4665–4670.

Performance of Electric Springs with Multiple Variable Loads

 

ABSTRACT:

Electric Spring is an emerging smart grid technology, which can provide voltage support to weakly regulated system. This paper studies the effect of load variation on the performance of electric springs. Two different single phase circuits with intermittent power supply have been simulated for the study – with one electric spring and with two electric springs. The loads considered are linear and are identical. Results obtained in MATLAB/Simulink environment show that line voltage is regulated by electric spring irrespective of variation in load. A brief comparative study is done between the simulation results obtained from the two circuits to observe the effect of the additional electric spring. This study tests the effectiveness of electric springs in a circuit designed to be more realistic, i.e., when the loads are not ON all the time and multiple electric springs are distributed all over the grid.

 KEYWORDS:

  1. Demand Side Management
  2. Electric Spring
  3. Renewable Energy Sources

 SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

Fig. 1. Schematic Diagram of Electric Spring connected with Intermittent Renewable Energy Source

 BLOCK DIAGRAM:

Fig. 2. Block Diagram for Circuit with Two Electric Springs

EXPECTED SIMULATION RESULTS:

 

 Fig. 3. RMS Voltage for Boosting action in single ES circuit

Fig. 4. Active and Reactive power consumption of ES during Boosting action in single ES circuit

Fig. 5. RMS Voltage for Reduction action in single ES circuit

Fig. 6. Active and Reactive power consumption of ES during Reduction action in single ES circuit

Fig. 7. RMS Voltage for Boosting action in double ES circuit

Fig. 8. Active and Reactive power consumption of ES during Boosting action in double ES circuit

Fig. 9. RMS Voltage for Reduction action in double ES circuit

Fig. 10. Active and Reactive power consumption of ES during Reduction action in double ES circuit

CONCLUSION:

This paper demonstrates the effects of load variation on the performance of ES. From the simulation results, it can be noted that, for boosting mode of operation, the ES can regulate the line voltage at the reference value irrespective of variation in load. However, for reduction mode of operation, the load variation causes fluctuations in the line voltage even when the ES is operating. This might be improved by making the circuit more inductive, which will assist the ES for reduction action. The basic single ES circuit was modified by adding an extra ES to it. It was observed that the reactive power consumption of each ES decreased by almost 50% for both modes of operation. Therefore we can conclude that as the number of ES in the circuit increases by a factor of ‘n’, the reactive power consumed by each ES to carry out the same magnitude of regulation decreases by a factor of ‘n’. This decreases the stress on each ES as well as the inverter rating for ES. For this study, the linear and identical loads have been considered, which can be further extended to non-linear and non-identical loads. Also, the random load profile can be replaced with a real time load profile.

REFERENCES:

[1] IEA, World Energy Outlook 2015: IEA. Available:

http://www.worldenergyoutlook.org/media/weowebsite/2015/WEO2015 _Factsheets.pdf

[2] P. P. Varaiya, F. F. Wu and J. W. Bialek, “Smart Operation of Smart Grid: Risk-Limiting Dispatch,” in Proceedings of the IEEE, vol. 99, no. 1, pp. 40-57, Jan. 2011.

[3] D. Westermann and A. John, “Demand Matching Wind Power Generation With Wide-Area Measurement and Demand-Side Management,” in IEEE Transactions on Energy Conversion, vol. 22, no. 1, pp. 145-149, March 2007.

[4] P. Palensky and D. Dietrich, “Demand Side Management: Demand Response, Intelligent Energy Systems, and Smart Loads,” in IEEE Transactions on Industrial Informatics, vol. 7, no. 3, pp. 381-388, Aug. 2011.

[5] A. Mohsenian-Rad, V. W. S. Wong, J. Jatskevich, R. Schober, and A. Leon-Garcia, “Autonomous demand-side management based on gametheoretic energy consumption scheduling for the future smart grid,” IEEE Trans. Smart Grid, vol. 1, no. 3, pp. 320–331, Dec. 2010.

Electric Spring for Voltage and Power Stability and Power Factor Correction

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

 EXPECTED SIMULATION RESULTS:

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: Power 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.