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

DC Electric Springs A Technology for Stabilizing DC Power Distribution Systems

 

ABSTRACT:

There is a growing interest in using DC power systems and microgrids for our electricity transmission and distribution, particularly with the increasing penetration of photovoltaic power systems. This paper presents an electric active suspension technology known as the DC electric springs for voltage stabilization and power quality improvement. The basic operating modes and characteristic of a DC electric spring with different types of serially-connected non-critical loads will first be introduced. Then, the various power delivery issues of the DC power systems, namely bus voltage variation, voltage droop, system fault, and harmonics, are briefly described. The operating limits of a DC electric spring in a DC power grid is studied. It is demonstrated that the aforementioned issues can be mitigated using the proposed DC electric spring technology. Experiment results are provided to verify the feasibility of the proposed technology.

KEYWORDS:

  1. Smart load
  2. Distributed power systems
  3. Power electronics
  4. Electric springs
  5. DC grids
  6. Smart grid

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1. The basic configuration of DC electric springs.

EXPECTED SIMULATION RESULTS:

Fig. 2. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

Fig. 3. Enlarged experiment waveforms based on the raw data exported from the oscilloscope corresponding

CONCLUSION:

In this paper, the concept of DC electric springs (ES) is firstly introduced to cope with several issues of DC power grids. The DC-ES is proposed as an active suspension system. Similar to their AC counterparts, the DC-ES can provide dynamic voltage regulation for the DC bus. The DC-ES connected in series with different types of non-critical loads to form a smart load have been analyzed and their operating modes have been identified and explained. Furthermore, the operating limits of the DC-ES under a given set of system parameters is studied, which provides quantitative analytical procedures to estimate the theoretical limits of ES. The paper provides a fundamental study on the DC-ES including the characteristics, the modes of operation, and the operating limits. The theoretical analysis and the performance of the DCES have been practically verified.

REFERENCES:

[1] R. Lobenstein and C. Sulzberger, “Eyewitness to DC history,” Power and Energy Magazine, IEEE, vol. 6, no. 3, pp. 84–90, May 2008.

[2] G. Neidhofer, “Early three-phase power,” Power and Energy Magazine, IEEE, vol. 5, no. 5, pp. 88–100, Sep. 2007.

[3] B. C. Beaudreau, World Trade: A Network Approach. iUniverse, 2004.

[4] H. Kakigano, Y. Miura, and T. Ise, “Distribution voltage control for DC microgrids using fuzzy control and gain-scheduling technique,” IEEE Trans. Power Electron., vol. 28, no. 5, pp. 2246–2258, May 2013.

[5] P. Loh, D. Li, Y. K. Chai, and F. Blaabjerg, “Autonomous operation of hybrid microgrid with AC and DC subgrids,” IEEE Trans. Power Electron., vol. 28, no. 5, pp. 2214–2223, May 2013.