Reduction of Energy Storage Requirements in Future Smart Grid Using Electri

ABSTRACT:

The electric spring is an emerging technology proven to be effective in i) stabilizing smart grid with substantial penetration of intermittent renewable energy sources and ii) enabling load demand to follow power generation. The subtle change from output voltage control to input voltage control of a reactive power controller offers the electric spring new features suitable for future smart grid applications. In this project, the effects of such subtle control change are highlighted, and the use of the electric springs in reducing energy storage requirements in power grid is theoretically proven and practically demonstrated in an experimental setup of a 90 kVApower grid.Unlike traditional Statcom and StaticVar Compensation technologies, the electric spring offers not only reactive power compensation but also automatic power variation in non-critical loads. Such an advantageous feature enables noncritical loads with embedded electric springs to be adaptive to future power grid. Consequently, the load demand can follow power generation, and the energy buffer and therefore energy storage requirements can be reduced.

KEYWORDS:

1.      Distributed power systems

2.      Energy storage

3.      Smart grid

4.      Stability

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Experimental setup based on the 90 kVA Smart Grid Hardware Simulation

System at the Maurice Hancock Smart Energy Laboratory.

EXPECTED SIMULATION RESULTS:

Fig. 2. Measured rms power line voltage (v_s) and non-critical load voltage (v_o)

Fig. 3. Measured average powers of the wind power simulator (P_G+P_R), battery storage (P_S) and non-critical load(P₁)

Fig. 4. Measured power (P_s) and energy change (E_s) of the battery storage.

Fig. 5. Measured electric spring reactive power (Q_ES), critical load voltage (V_R2) and power (P2).

CONCLUSION:

In this paper, the differences between the output voltage control and the input voltage control of a reactive power controller are highlighted. While energy storage is an effective but expensive means to balance power supply and demand, an analysis and practical confirmation are presented to show that electric springs can reduce energy storage requirements in a power grid. Electric springs allow the non-critical load power to vary with the renewable energy profile. By reducing the instantaneous power imbalance of power supply and demand, electric springs allow the non-critical load demand profile to follow the power generation profile and reduce the energy storage requirements in power grid. This important point has been theoretically proved and practically verified in an experimental setup. Due to the advantageous features such as enabling the load demand to follow the power generation, the reduction of energy storage requirements, the reactive power compensation for voltage regulation, and the possibility of both active and reactive power control [28], electric springs open a door to distributed stability control for future smart grid with substantial penetration of intermittent renewable energy sources.

REFERENCES:

[1] D. Westermann and A. John, “Demand matching wind power generation with wide-area measurement and demand-side management,” IEEE Trans. Energy Convers., vol. 22, no. 1 , pp. 145–149, 2007.

[2] P. Palensky and D. Dietrich, “Demand side management: Demand response, intelligent energy systems, and smart loads,” IEEE Trans. Ind. Inform., vol. 7 , no. 3 , pp. 381–388, 2011.

[3] P. Varaiya, F. Wu, and J. Bialek, “Smart operation of smart grid: Risklimiting dispatch,” Proc. IEEE, vol. 99, no. 1 , pp. 40–57, 2011.

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

Droop Control of Distributed Electric Springs for Stabilizing Future Power Grid

ABSTRACT:

This paper describes the droop control method for parallel operation of distributed electric springs for stabilizing ac power grid. It provides a methodology that has the potential of allowing reactive power controllers to work in different locations of the distribution lines of an ac power supply and for these reactive power controllers to support and stabilize the ac mains voltage levels at their respective locations on the distribution lines. The control scheme allows these reactive power controllers to have automatically adjustable voltage references according to the mains voltage levels at the locations of the distribution network. The control method can be applied to reactive power controllers embedded in smart electric loads distributed across the power grid for stabilizing and supporting the ac power supply along the distribution network. The proposed distributed deployment of electric springs is envisaged to become an emerging technology potentially useful for stabilizing power grids with substantial penetration of distributed and intermittent renewable power sources or weakly regulated ac power grid.

KEYWORDS:

1.      Droop control

2.      Electric springs

3.      Smart gird

4.      Voltage regulation

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

 Fig. 1. Single phase diagram of the experimental setup of the power grid and loads (with 3 distributed electric springs working as a group).

EXPECTED SIMULATION RESULTS:

Fig. 2. (a) Measured root-mean-square values of the mains voltage V_S1,V_S2 and V_S3 (b) Measured root-mean-square values of the mains voltage V_S1,V_S2 and V_S3 from 1800 to 1440 sec (ES activated without the proposed droop control) (c) Measured root-mean-square values of the mains voltage V_S1,V_S2 and V_S3 from 1800 to 2160 sec (ES activated with the proposed droop control).

Fig. 3. Measured average value of reactive power generated by the 3 electric springs (Q_a1 ,Q_a2 and Q_a3 ).

Fig. 4. Measured modulation indexes of the electric springs M₁,M₂ and M₃ .

Fig. 5. Measured average value of the critical load power P_R1,P_R2 and P_R3 .

Fig. 6. Measured root-mean-square values of the non-critical load voltage V_o1 ,V_o2 and V_o3 .

Fig. 7. Measured average value of the non-critical load power P_o1,P_o2 and P_o3

.

CONCLUSION:

A control scheme has been successfully developed and implemented for a group of electric springs. It enables individual electric springs to generate their mains voltage reference values according to their installation locations in the distribution lines and to work in co-operative manner, instead of fighting against one another, therefore allowing the electric springs to work in group to maximize their reactive power compensation effects for voltage regulation. The control method also leads to more evenly distribution of load power shedding among the non-critical loads. The attractive features of the control scheme have been successfully verified in an experimental smart grid setup.

With the droop control scheme,many electric springs of small VA ratings could be embedded into non-critical loads such as electric water heaters and refrigerators to form a new generation of smart loads that are adaptive to power grid with substantial penetration of renewable energy sources of distributed and intermittent nature. If many small electric springs are deployed in the power grid in a distributed manner, their collective voltage stabilizing efforts can be added together. Because the electric springs allow these smart loads to consume power following the varying profile of intermittent renewable energy sources, they have the potential to solve the stability problems arising from the intermittent nature of renewable energy sources and ensure that the load demand will follow power generation, which is the new control paradigm for future smart grid. Since the electric appliances embedded with the electric springs can share load shedding automatically, this approach should be more consumer-friendly when compared with the on-off control of electric appliances. For example, shutting down refrigerators is intrusive and inconvenient to the consumers (and may involve consumers’ rights issues) and requires some forms of central control. Allowing many smart refrigerators to shed some load without being noticed and central control is more consumer- friendly.

The individual operations of the electric springs have previously been evaluated. The successful implementation of the droop control for 3 electric springs working as a group in a small distributed network in this study is a just a step forward to confirm that multiple electric springs can work together without ICT technology. The collective effects of electric springs and their capacity are new topics that deserve further investigations. Extensive simulation studies are needed to confirm the effectiveness of many such electric springs working together in a large-scale power system model.

REFERENCES:

[1] P. P. Varaiya, F. F. Wu, and J. W. Bialek, “Smart operation of smart grid: Risk-limiting dispatch,” Proc. IEEE, vol. 99, no. 1, pp. 40–57, 2011.

[2] D. Westermann and A. John, “Demand matching wind power generation with wide-area measurement and demand-side management,” IEEE Trans. Energy Conversion, vol. 22, no. 1, pp. 145–149, 2007.

[3] P. Palensky and D. Dietrich, “Demand side management: Demand response, intelligent energy systems, and smart loads,” IEEE Trans. Ind. Informatics, vol. 7, no. 3, pp. 381–388, 2011.

[4] 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, 2010.

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

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 (V_s), (b) Non–critical voltage (V_nc), (c) Electric spring voltage (V_a) & current (I_a), (d) Critical voltage (V_c) in capacitive mode.

Fig. 3. Observed Instantaneous value of (a) Source voltage (V_s), (b) Non–critical voltage (V_nc), (c) Electric spring voltage (V_a) & current (I_a), (d) Critical voltage (V_c) in capacitive mode.

Fig. 4. Observed RMS value of (a) Source voltage (V_s), (b) Non–critical voltage (V_nc), (c) Electric spring voltage (V_a) & current (I_a), (d) Critical voltage (V_c) in inductive mode.

Fig. 5. Observed Instantaneous value of (a) Source voltage (V_s), (b) Non– critical voltage (V_nc), (c) Electric spring voltage (V_a) & current (I_a), (d) Critical voltage (V_c) 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

A Comparative Study of Different Multilevel Converter Topologies for Battery Energy Storage Application

ABSTRACT:

The integration of Battery Energy Storage Systems (BESS) into the power grids has been proposed as an effective solution for mitigating voltage and frequency instability problems arising from the integration of renewable resources with intermittent patterns. One of the most important applications of BESS is to restore an electric power system to operation without counting on the external transmission network. To prevent potential damage to the expensive equipment of power plant, the converters must generate a high quality and reliable three phase voltage. This research provides a simulation-based investigation in order to scrutinize different multi-level inverter topologies to find the more appropriate multi-level inverter structure for BESS application. The investigation has been done entitled of quantitative and qualitative studies. Throughout the quantitative study, the output specifications of each inverter topology is scrutinized, while other features such as reliability, modularity and functionality are scrutinized as qualitative study. All topologies are simulated in MATLAB/Simulink at the same operating conditions.

KEYWORDS:

1.      Multilevel converter

2.      Battery energy storage

3.      High power application

SOFTWARE: MATLAB/SIMULINK

DIFFERENT TOPOLOGIES:

Fig. 1. One leg representation of multi-level topologies. a) NPCMLI, b)

CCLMLI, c) CMLI, d) ZsMLI, e) QZsMLI.

Fig. 2. Multi-level topologies classification.

EXPECTED SIMULATION RESULTS:

 Fig. 3. Voltage and current waveforms of three level battery source NPC inverter.

Fig. 4. Voltage and current waveforms of three level battery source capacitor clamped inverter.

Fig. 5. Voltage and current waveforms of three level cascaded battery source inverter.

Fig. 6. Voltage and current waveforms of three level Z-source battery connected inverter.

Fig. 7. Voltage and current waveforms of three level Quasi-Z source battery connected inverter.

CONCLUSION:

In this paper the most common multilevel inverter topologies were scrutinized to find the more appropriate topology for BESS application. The investigation has been done entitled of quantitative and qualitative studies. The important output parameters of inverter topologies were investigated as quantitative study, while other features such as reliability, modularity and functionality were scrutinized in qualitative study. Also, various inverter topologies have been evaluated in terms of required capacity in the same operating point. The simulation results proved that the ideal BESS power conversion system, among reviewed multi-level topologies, is Cascaded topology. This topology was chosen for three reasons. First, the efficiency and reliability studies were conducted, and the CMLI was found to be the most efficient and reliable topology with minimum amount of power loss compared to other topologies. Second, it subdivides the battery string and increases the high voltage functionality. Finally, capacitor volume, cost and THD studies were again confirmed the effectiveness of this topology in battery energy storage systems.

REFERENCES:

[1]   H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrial applications. John Wiley & Sons, 2014.

[2]   T. Soong and P. W. Lehn, “Evaluation of emerging modular multilevel converters for bess applications,” IEEE Transactions on Power Delivery, vol. 29, no. 5, pp. 2086–2094, 2014.

[3]   P. Medina, A. Bizuayehu, J. P. Catal˜ao, E. M. Rodrigues, and J. Contreras, “Electrical energy storage systems: Technologies’ state-of-the-art, techno-economic benefits and applications analysis,” in Hawaii IEEE International Conference on System Sciences, 2014, pp. 2295–2304.

[4]   E. H. Allen, R. B. Stuart, and T. E. Wiedman, “No light in august: power system restoration following the 2003 north american blackout,” IEEE Power and Energy Magazine, vol. 12, no. 1, pp. 24–33, 2014.

[5]   L. Yutian, F. Rui, and V. Terzija, “Power system restoration: a literature review from 2006 to 2016,” Journal of Modern Power Systems and Clean Energy, vol. 4, no. 3, pp. 332–341, 2016.