Cascaded Multilevel Inverter Based Electric Spring for Smart Grid Applications

 

ABSTRACT:

This paper proposes “Electric Spring” (ES) based on Single Phase three-level Cascaded H-Bridge Inverter to achieve effective demand side management for stabilizing smart grid fed by substantial intermittent renewable energy sources (RES). Considering the most attractive features of multilevel inverter (MLI), an effective structure of Electric Spring is proposed for suppressing voltage fluctuation in power distribution network arising due to RES and maintaining the critical load voltage. Also, the operation of ES in capacitive as well as inductive mode is discussed. Further, the paper describes droop control method for parallel operation of distributed electric spring for stabilization the power grid. An exclusive dynamic performance of the system using electric spring has been tested and demonstrated through detailed MATLAB simulation.

KEYWORDS:

  1. Critical load
  2. Cascaded H-Bridge Inverter
  3. Droop control
  4. Electric Spring
  5. MLI
  6. RES
  7. Smart load

 SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

Fig. 1. Schematic of Electric Spring.

EXPECTED SIMULATION RESULTS:

Fig. 2. Observed RMS value of (a) Source voltage (Vs), (b) Non–critical voltage (Vnc), (c) Electric spring voltage (Va) & current (Ia), (d) Critical voltage (Vc) in capacitive mode.

Fig. 3. Observed Instantaneous value of (a) Source voltage (Vs), (b) Non–critical voltage (Vnc), (c) Electric spring voltage (Va) & current (Ia), (d) Critical voltage (Vc) in capacitive mode.

Fig. 4. Observed RMS value of (a) Source voltage (Vs), (b) Non–critical voltage (Vnc), (c) Electric spring voltage (Va) & current (Ia), (d) Critical voltage (Vc) in inductive mode.

Fig. 5. Observed Instantaneous value of (a) Source voltage (Vs), (b) Non– critical voltage (Vnc), (c) Electric spring voltage (Va) & current (Ia), (d) Critical voltage (Vc) in inductive mode.

Fig. 6. THD analysis of (a) Two-level and (b) Three-level CHMLI based ES.

CONCLUSION:

The paper proposes new approach for regulating the mains voltage using MLI based ES for smart grid applications. The implemented Three-level CHMLI based ES for smart grid application effectively regulates the ac mains voltage and reduces the THD content as compared with Two-level VSI based ES. The effectiveness of ES is validated through digital simulation in terms of THD. Lastly simulation results of droop control for Four Electric springs have been implemented in a large-scale distributed pattern in order to make multiple ES act in coordinating manner so as to have robust stabilizing effect.

REFERENCES:

[1] Edward J.Coster, Johanna M.A.Myrzik, BAS Kruimer, “Integration Issues of Distributed Generation Distribution Grids,” Proceedings of the IEEE, vol.99, no.1, pp.28-39, January, 2011.

[2] Koutsopoulos and L. Tassiulas, “Challenges in demand load control for the smart grid,” IEEE Netw., vol. 25, no. 5, pp. 16–21, 2011.

[3] M.H.J.Bollen, “Understanding Power Quality Problems: Voltage Sags and Interruptions,” IEEE Press, 2000.

[4] N. Hingorani and L. Gyugyi, Understanding FACTS, Concepts and Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.

[5] M. Parvania and M. Fotuhi-Firuzabad, “Demand response scheduling by stochastic SCUC,” IEEE Trans. Smart Grid, vol. 1, no. 1, pp. 89–98, Jun. 2010

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