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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

    1

  • Table of Contents

    2

    2

    3

    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.

    4

    PV/BESS Architectures

    a

    m

    , ,

    .

  • 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

    4 5

    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

    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 0 = 60 .

    o In Mode 3, 4 and 5 the are activated

    o In Mode 1 / and are activated.

    8

    Inverter side control system comparison for

    Reconfigurable Solar and Two Stage Converter

    is the

    reference DC link

    Voltage.

    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

    7

    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

    9

    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

    11

    10

    PCC

    12.47/0.48 kV

    2 MVA, x = 2 %

    PV + Battery

    System (TS)

    DG

    10

    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.

    12

    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.

    13

    PV/BESS Internal Power Outputs

  • All Voltages are within band of

    0.95

  • 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.

    15

    Conclusions

  • Thank You

    Questions ?

    16