SIZING OF ENERGY STORAGE FOR

MICROGRID

Introduction To Microgrid

What is Microgrid? Small-Scale Power Supply Network to

provide Power for a Small Community. Local Power Generation for local loads. Small Power Generating sources

Highly Flexible Efficient.

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Contd..

What is Microgrid? It is connected to both the local generating

units and the utility grid thus preventing power outages.

Excess power can be sold to the utility grid. Size of the Microgrid may range from housing

estate to municipal regions.

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The Need Of Microgrid

Microgrid could be the answer to our energy crisis.

Transmission losses gets highly reduced. Microgrid results in substantial savings and

cuts emissions without major changes to lifestyles.

Provide high quality and reliable energy supply to critical loads

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Microgrid components

wind turbine Microturbine Photovoltaic system Controller Fuel cell Energy storage system

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Wind turbine

Wind pushes the fan blades of wind turbine and produce energy output.

No control over the energy output.

Microturbine microturbine are single staged combustion

turbine. Usually powered by biogas, natural gas,

propane.

Photovoltaic system

PV cell is a self-contained electricity producing device consist of semiconducting material.

Light striking on the semiconducting material in PV cell, creating dc.

Fuel cell FC uses an electrochemical process to turn

hydrogen and oxygen to electricity.

Energy storage system

ESS include electrochemical battery, super capacitor, compressed air energy storage, super conducting energy storage, flywheel energy storage etc. .

Lithium ion is commonly used because best energy to weight ratio and slow loss of charge when not in use.

ESS store energy at the time of surplus and redispatch it when needed.

Contd.. ESS plays an important role in microgrid. Sizing of ESS to be considered first when

considering ESS in MG. ESS increase the reliability of power system. The cost of ESS includes one time ESS cost and

the annual maintenance cost. The battery storage system made up of small

battery blocks.

Flywheel ess

Microgrid Operating Modes Island Mode:

Utility grid is not supplying power Static switch is open. Feeder A, B, C are being supplied

by Microsources.

Feeder D (not sensitive ) is dead.

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Microgrid Operating Modes

Grid Connected Mode:

Utility grid is active. Static switch is closed All the feeders are being

supplied by utility grid.

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ESS in islanded microgrid

Sizing of a suitable battery bank in terms of power and energy help in shaving the peak demand.

Stores excess renewable energy and supply load when renewable energy is low.

When ESS discharges its energy to power grid its generating positive real power

ESS in grid connected microgrid

The upstream grid can be treated as bidirectional generator which generate positive power when power is transferred from the MG and generate negative power when the power transferred from the MG to upstream grid.

The output of bidirectional generator is limited by the capacity of transmission line between the MG and upstream grid.

Algorithm to solve optimal bess size capacity

Algorithm steps

1.Enter forecasting renewable power and load. Calculate minimum BESS capacity CEmin.

2.Set CEmax , ∆ CE and initialize the variables.

3.Solve the objective function for CE. Minimize the TC for islanded MG and maximize TB for grid connected MG.

4.If CE < CE max, update CE using the above equation . The algorithm will stop when

CE ≥ CEmax.

Conclusion

BESS for MG decrease the schedule cost of MG in islanded MG and increase benefit of MG.

As the size of BESS increases, the benefit increases.

The TCPD increases in a constant rate and when the size of BESS is greater than optimal size TC will increase in islanded MG and TB will reduce in grid connected MG.

REFERENCES

[1] Microgrid Energy Management Framework Jul. 2009 [2] H. T. Le and T. Q. Nguyen, “Sizing energy storage

systems for wind power firming: An analytical approach and a cost-benefit analysis,” in Proc. Power Energy Soc. Gen. Meet., 2008

[3] S. Chen and H. Gooi, “Scheduling of energy storage in a grid-connected pv/battery system via simplorer,” in Proc. TENCON IEEE Region 10 Conf., Nov. 2009