Multi-Mode Operation of Different PV/BESS Architectures in ... · • Two PV/BESS systems at...
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Multi-Mode Operation of Different
PV/BESS Architectures in a Microgrid:
Grid-connected and Islanded
Thursday, April 17, 2014
Manohar Chamana, Iman Mazhari,
Badrul H. Chowdhury and Babak Parkhideh
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Table of Contents
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1 Photovoltaic/Battery Architectures
Different Modes in a Reconfigurable Solar Converter (RSC)
Comparison between two PV/BESS inverter control
5 Results and Comparison
6 Conclusion
4 Comparison between two BESS converters control
(a) Direct Integration I (b) Indirect Integration (TSC) (c) Direct Integration II (RSC)
(a) Direct Integration I: o Simplest option
o Low efficiency operation of the overall conversion system
o Not considered for utility-scale PV/battery applications
o No option to charge battery from PV
(b) Indirect Integration: (Two Stage Converter) o Most Common configuration (two stage converter)
o PV and battery are connected indirectly using two stage power conversion.
(c) Direct Integration II: (Reconfigurable Solar Converter) o Divided in two different sections which would be
• DC/AC for delivering power to the grid
• DC/DC for delivering the power from the PV to the battery.
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PV/BESS Architectures
a
m
𝐵𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑎𝑟𝑒 𝑢𝑠𝑒𝑑 𝑓𝑜𝑟 𝑝𝑒𝑎𝑘 𝑠ℎ𝑖𝑓𝑡𝑖𝑛𝑔, 𝑠𝑚𝑜𝑜𝑡ℎ𝑖𝑛𝑔, 𝑎𝑛𝑑 𝑝𝑜𝑤𝑒𝑟 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛𝑖𝑛𝑔 𝑖𝑛
𝑃𝑉 𝑠𝑦𝑠𝑡𝑒𝑚𝑠.
3-5% conversion efficiency gain compared to existing solutions.
30-40% cost reduction on PV/battery power electronics
If not exceed, no compromise on battery charging techniques
Retrofit and expandable Platform for existing and future PV power plants
PV to Grid (Mode 1) Battery to Grid (Mode 4)
PV+Battery to Grid (Mode 3) PV to Battery (Mode 2)
RSC Benefits
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Operation Modes of RSC
o PV Array operated
at MPPT.
o Battery is
connected to the
DC link directly.
Synchronous-
reference frame
current-mode control
𝑃𝑟𝑒𝑓 𝑎𝑛𝑑 𝑄𝑟𝑒𝑓 are the reference
power values
o In grid connected mode the reference phase angle is measured using a phase
locked loop that utilizes the system frequency 𝜔0 = 60 𝐻𝑧.
o In Mode 3, 4 and 5 the 𝑃𝑟𝑒𝑓 𝑎𝑛𝑑 𝑄𝑟𝑒𝑓 are activated
o In Mode 1 𝑉𝑚𝑝𝑝𝑡/ and 𝑄𝑟𝑒𝑓 are activated.
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Inverter side control system comparison for
Reconfigurable Solar and Two Stage Converter
is the
reference DC link
Voltage.
𝑉𝑚𝑝𝑝𝑡 is the
MPPT Voltage.
ref
DCV
ref
DCV
o PV Array operated
at MPPT utilizing a
Boost converter.
o Battery connect to
the DC link though
a Synchronous
Buck for
discharging and
charging process.
o Discharging
DC link voltage
is regulated at
its nominal
value.
o Charging
DC link voltage is
regulated at its nominal
value.
Synchronous buck
converter
Also Connects the PV
to the grid
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Battery side control system:
Two-Stage Architecture
o Charging
PV voltage is regulated
at the maximum power
point voltage.
o Charging
DC link voltage is
constant at battery
Voltage.
Boost
converter
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Battery side control system:
RSC Architecture
• Microgrid test-bed implemented
in PSCAD /EMTDC environment
Grid connected
Islanded mode
• Two PV/BESS systems at
different locations with different
architectures.
• Diesel generator
connected near the point
of common coupling for
regulating and meeting
deficiency in islanded
mode.
• During the simulation period loads
and PV output are assumed to be
constant.
Single Line Diagram of the Microgrid
PV + Battery
System (RSC)
G
Bus 0
Bus 1
Bus 2
Bus 3
Bus 4
Bus 5 Bus 11
Bus 10
Bus 9Bus 6
Bus 7
Bus 8
L
L
L
L L
L
L L
L
L
L
2
8
7
6
an
1
3
4
5bn
9
1.2 km
1.0 km
0.6 km
0.6 km 0.5 km
0.3 km
0.8 km0.3 km 1.7 km
0.2 km
1.3 kmL
L
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PCC
12.47/0.48 kV
2 MVA, x = 2 %
PV + Battery
System (TS)
DG
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Microgrid Testbed
o During Simulations PV constant and load changes at time t = 3 sec and t = 6 sec in the
microgrid.
Active Power Outputs Reactive Power Outputs
Time Microgrid State PV/BESS
mode
Diesel Generator
State
1-4 seconds Grid connected Mode 1 Disconnected
4-8 seconds Islanded Mode 3 Connected
8-12 seconds Islanded Mode 4 Connected
12-16 seconds Grid Connected Mode 2 Connected
a) Grid
b) Diesel
Generator
c) RSC
d) TS
PV systems
maintain a
constant
reactive
power of 0.3
p.u.
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Power Outputs at Source Terminals
a) PV power at the DC link b) Battery Power
o Transients are higher in case of the
RSC during discharging mode.
o Transients are higher in case of the
TSC during charging mode.
o Reason – Inductance
RSC
o Battery voltage is applied in parallel
with the PV.
o Forces the PV to move away from
the MPPT point.
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PV/BESS Internal Power Outputs
All Voltages are within band of
0.95<Vrms<1.05 p.u.
• Frequency is maintained constant at 60
Hz.
• Some distortion in the island mode due
to harmonic injection by PV/BESS
systems.
(a) Voltage at PCC, (b) Voltage at DG (b) Voltage at RSC (c) Voltage at
two-stage converter
System frequency
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Voltages and frequency within Microgrid
• Simulations were performed on a microgrid test-bed.
Internally connected loads
Two different PV/BESS architectures.
• Distributed Generators
A single stage converter (RSC)
A two stages converter (TSC)
Diesel Generator Islanded mode – regulate voltage and frequency
Grid connected mode –meet deficiency
• Both architectures show satisfactory results with
many similarities and few dissimilarities
If economics of conversion stage is important,
RSC offers higher benefits.
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Conclusions
Thank You
Questions ?
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