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.

 

 

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