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Microgrid
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1
Smart Grids
Problems &
SolutionsWalid Issa
Exeter University
2
Electrical Grid
3
Electrical Grid
- Dependency on a high capacity fossil-fuel generators
- Increasing carbon emissions- Getting a large amount of power in one
place - Using a long transmission lines to deliver
power - Not economic - Has low reliability against sudden faults
4
Microgrid
5
Microgrid
- Integrate renewable resources- Control the flow of power- Reduce Carbone emissions- Reduce losses- Reliable against sudden faults
- Customer is a part of the grid
6
GRID Micro-GRID
7
Microgrid Modes
Grid-Connected mode
Island mode
Microgrid
Point of Common Coupling (PCC)
GRID
SWITCH
8
Interfacing
Sources
Battery
Grid Loads
INVERTER
DC AC
9
10
Inverter
DC-Link Capacitor
L1
C
L2
PWM Generator Vref
Voltage Controller
LCL Filter
Bidirectional DC/AC Converter (inverter)
SensorsACDC
11
Uses DC Boost to step up the DC
voltage
Uses transformer to step up the AC
voltage
Uses transformer to step up the DC
voltage
Uses many PV to step up the DC
voltage
Inverter’s Topologies
12
DSP ControllersTMS320F28XX
LEM Sensors1 mH
50 µF2000 µF
Inverter
13
Electric Vehicle
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Active & ReactivePower Measurement
90º ¼ cycle ¼ T
15
Sine wave PWM Generation
16
Microgrid Literature
1- Voltage and Current Regulation
Goals: Low Distortion No Resonance Regulated Voltage Smooth Step Response
Proposed Solutions: PI, PID Controllers P+Resonant Controllers Adaptive Controllers Repetitive Controllers
17
Microgrid Literature
2- Power Sharing
Goals: Adequate Power sharing Accurate Power control Without Communication if possible Smooth Step Response
Proposed Solutions: Master – Slave Controllers Current Chain Scheme
Droop Control
18
Microgrid Literature
3- Power Sharing (‘Droop Control’)
Goals: Accurate Reactive Power control Small Frequency and voltage
deviations Harmonics Sharing Smooth Step Response
Proposed Solutions: PID Control Angle droop controller External supplementary loops
19
Microgrid Literature
4- Islanding Detection
Goals: Detect the grid absence within 2
sec Proposed Solutions:
Passive Methods Voltage, Frequency, phase
deviations Active Methods
Positive Feedback, harmonic injection, …
20
Microgrid Literature
5- Power Management and Central Control
Goals: A manager should decide the power
for each inverter Mode Controlling
Proposed Solutions: Hierarchical Control
Primary Control Secondary Control Tertiary Control
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Research Goals- Not concerned about energy sources- Not concerned about sources
fluctuations
BUT .. .. .
Circulation currents Power sharing in island mode Smooth Transition Microgrid stability
Paralleling Inverters operation in Island Mode
22
Parallel Inverters
DC
DC
DC
AC
DC Link Capacitor
Bi-Directional DC/AC Converter
DC
DC
DC
AC
DC Link Capacitor
GridSTSPCC
Bi-Directional DC/AC Converter
UPS
Cenrtal Controller Unit Controller
Unit Controller
Slow
Communication
Stable & Fixed
Stable & Fixed
23
Methodology
- Microgrid Modeling
- Proposing a controller
- MATLAB/SIMULINK
- Practical implementation
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So Far …
IGBT Block
Output Filter
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Voltage Sensor
Current Sensors
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IGBTs and Filters
Voltage and current sensors
Power supply
Interfacing and
switching boards
27
dSpace Control
unit
Loads
Interfacing and monitoring platform
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Active resistive
load
Reactive inductive
load
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Interfacing Platform
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36.32 36.33 36.34 36.35 36.36 36.37
-30
-20
-10
0
10
20
30
10 15 20 25 30 35 40-20
-10
0
10
20
30
40
Time
Rea
ctiv
e P
ower
Inverter 1 Reactive power
Inverter 2 Reactive power
Output Voltage of both
invertersTHD = 1.8%
Results
Reactive Power
sharing
First controlle
r
Second controlle
r
31
40 45 50 55 60 65 7030
40
50
60
70
80
90
100
110
Active Power
sharing
DC link voltage
response
Controller is enabled
40 45 50 55 60 65 70-20
-15
-10
-5
0
5
10
15
20
Time
Act
ive
Pow
er
Inverter 1
Inverter 2
Inverter 2
Inverter 1
Droop Control
DCk
-
--
PavgP
*P
DClinkV
*DClinkV
Threshold
32
Keywords
- Droop control- Voltage & Current controllers- Reactive power sharing in island
mode- Islanding Detection - Supervisory Control- MPPT for solar inverters
33
Projects Ideas- Sine wave PWM Generator- Inverter Voltage controller- Power Measurement- MPPT for solar inverters- Buck-Boost converter- Synchronization (Zero crossing
detection - PLL)- Droop Control for parallel
inverters- Smart Charger based on Droop
control- SCADA for microgrid (Labview)
34
Useful Docs and REfs
Papers
Matlab Files
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36
Thank You …
https://www.facebook.com/pages/Walid-Issa/274572119317029