hybrid energy storage for stand-alone pv microgrid: optimization of battery lifespan through dynamic...

IEEE APPEEC 2015, Brisbane 15th – 18th November 2015

Hybrid Energy Storage for Stand-alone PV

Microgrid: Optimization of Battery Lifespan

through Dynamic Power Allocation

Wenlong JING

Faculty of Engineering, Computing & Science

Swinburne University of Technology

(Sarawak Campus)

1


CHALLENGES AND ISSUES IN STAND-ALONE MICROGRID

•Stochastic and intermittent nature of renewable energy sources.

•Highly dynamic load profile due to low capacity.

Microgrid

Energy Storage Systems • Chemical Battery, supercap, flywheel, pumped

hydro, CAES etc..

• Absorb surplus energy / Supply when deficit

• Regulate line voltage and frequency

• Maintain power quality

PV (DC)

Wind Turbine (AC)

Loads (AC + DC)

Energy Storage (DC)

2


3

STAND-ALONE PV SYSTEM TOPOLOGIES

PV System with Battery Alone

• Passive Connection (a)

• Add MPPT (b)

• Active Connection (c)

PV System with Hybrid Storage

• Passive Connection (d)

• Semi-Passive Connection

• Active Connection (e)

(d)

(e)


• High energy density + High power density

• Fast Response + Slow Response

[1] BoM, Bureau of Meteorology, Australian Government. Available [Online]

at: http://reg.bom.gov.au/.

HYBRID ENERGY STORAGE

4

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6-1

0

1

2

3

4

5

6

7

Hours of the Day

Po

we

r (k

W)

Time Series Plot:

(a) PV Output

(b) Load Profile

(a)

(b)

Typcial 24-hours

(a) PV Output Power and (b) Rural Residential Load Profile


5

HESS POWER ALLOCATION

0 2 4 6 8 10 12 14 16200

400

600

800

1000

1200

1400

1600

Time (s)

Po

we

r

Load Profile

Pmax

P2

P1

Pmin

• Load Profile is divided into parts

• Battery Bank can contain varies type battery

• Reduce the battery DoD and Improve Life Span

Nickel-Iron battery life cycle

– source Wikipedia

Source: http://www.charlesapple.com/2012/04/a-terrific-titanic-

anniversary-graphic-from-south-africa/

http://www.charlesapple.com/2012/04/a-terrific-titanic-anniversary-graphic-from-south-africa/


















6

EXAMPLE PV SYSTEM WITH HESS

• Contains 2 battery modules

• The 1st level battery = first critical load

• The 2nd level battery = second critical load

• Reduce the battery DoD and still satisfy the load demands


7

POWER ALLOCATION STRATEGY

Psc = PHES

Pba1 =0Pba2 =0

Psc = PHES - P1

Pba1 =P1

Pba2 =0

Psc = PHES - P2

Pba1 =P1

Pba2 = P2 –P1

Yes

No

Yes

Yes

Psc = PSCmax

Pba1 =P1

Pba2 = P2 –P1

=

=

No

No

NoYes

Psc =PHES-DPba1 =0.5DPba2 =0.5D

Charging Discharging

PHES < 0

PHES <P1

P1<PHES <P2

P2<PHES <Pmax

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6-1

0

1

2

3

4

5

6

7

Hours of the Day

Po

we

r (k

W)

Time Series Plot:

(a) PV Output

(b) Load Profile(a)

(b)

P1

PMAXD

P2


8

NUMERICAL SIMULATION AND RESULTS

• PV = 6 kW, SC = 500F, Battery = 50 Ah (Limiter for Physical Limitation Simulation)

• All Buck/Boost Converters

• Multi-Level Battery Structure


9

NUMERICAL SIMULATION AND RESULTS

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6-2

-1

0

1

2

3

4

5

6

7

Hours of the Day

Po

we

r (k

W)

(a) Overall Output

(b) SC Output

(c) PV Output

(d) 1st Battery

(e) 2nd Battery

(f) Load Profile(c)

(b)

(d)

(f)

(a)

(e)

The matching rate f of the load profile and system overall output is calculated via Matlab:

f = PL / (PPV +PHES) * 100% = 99.98%

• SC feeds the high frequency power component (release and absorb power)

• Battery bank C/D under a certain power and thus dynamic oscillation is reduced


10

HESS POWER DYNAMIC ALLOCATION • Battery Bank contains varies type battery

• Reconfigurable HESS Bank Architecture => Modularity => Manage Power as Water

• Improve the passive characteristic without using Power Electronic Converters

HESS


11

Thank You!

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