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PV Systems
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PhotoVoltaic Power Systems& Micro-Grids, AAU
Tamas Kerekes
Department of Energy TechnologyAalborg University
PV systems and Micro Grids research programme at Aalborg University, Department of Energy Technology
Control and design of photovoltaic converters and Micro grid systems with grid connections for renewable energy systems
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Members:Remus Teodorescu, Dezso Séra, Tamás Kerekes, Erhan Demirok,Xiaonan Lu, Markos Katsanevakis, Sevnur Eygün
External membersPedro Rodriguez, Marco Liserre, Josep Guererro, Juan Carlos Vasquez
Industrial partners: Danfoss Solar Inverters, Danfoss Drives, Sunsil, Refu Electronic, Risø,Eltra, Gamesa Eolica, Enertron, Gaia, Energinet, APC
Partner Universities:Polytechnic of Bari, Technical University of Catalunia, University of Alcala, University of Vigo, University of Timisoara, Czech Technical University of Prague
PV systems and Micro Grids research programme at Aalborg University, Department of Energy Technology
Control and design of photovoltaic converters and Micro grid systems with grid connections for renewable energy systems
Main research areas:•
Control strategies for single-phase and three-phase grid-connected PV converters•
Grid synchronization and voltage monitoring methods •
Islanding detection algorithms•
On-line grid impedance estimation for PV inverters•
Ride-through capabilities for grid-connected PV converters in case of grid disturbances and faults•
Advanced modelling and simulation of grid-connected PV converters (Simulink, PLECS) •
Low cost DSP (TMS320F28xx) control implementation•
Maximum Power Point Tracking for PV inverters•
Modeling and simulation of PV arrays under various athmospheric conditions•
Real-time PV simulator for testing grid-connected PV inverters•
Characterisations and diagnostics of PV panels•
Hardware design of PV inverters•
Transformerless PV inverter topologies•
Leakage current modeling for transformerless PV inverters (PLECS)•
Interaction of Multiple PV inverters with LV network (Matlab, PSCAD) •
Voltage control and flexible reactive power sharing (grid supporting and forming) for multiple PV inverters
3
PV Systems - Main facilities
4
•
Grid Converters –
up to 5A/400V, single-phase or three-phase with flexible digital control: dSpace DS1103 or TMS320F2812 and F28335 eZdsp Development board
•
PV inverter test setup (includes 32kW Dynamic PV simulator, 4.5-kW Dynamic Grid Simulator, 3-kW Electronic AC Load, Anti-
islanding Test Setup)
•
Residential Micro-Grid setup (includes 1.9-kW Polycrystalline silicone solar panel array, 1.5-kW Danfoss Solar inverter and 1.7-kW SMA Sunny Boy PV inverters, SMA Sunny island inverter, VRB-ESS 5-kW –
4h Flow battery, as well as California Instruments 3kW programmable AC load)
•
PV-E PVPM 1000C - 1000V/20A photovoltaic I-V curve tracer –
for panel/string characterisation
•
Flashing Solar Simulator Mencke & Tegtmeyer -
240V/16A –
for indoor characterisation of PV panels
•
California Instruments Grid Simulator –
for fault simulations
•
High bandwidth Regatron PV Simulator (includes TopCon Quadro Power Supply Module, TC.LIN Linear Post-Processing Unit, and SASControl PC Software). Output ratings: 32 kW, 1000VDC, 40A
PV Systems - Main activities
Advanced Control for Grid Converters
• Control structures –
development of the control
structures in different reference frames such as natural abc, stationary αβ
or synchronously rotating dq for better matching the application.
•
Current controllers –
different linear (PI, resonant) and nonlinear (hysteretic, predictive) controllers
•
Grid synchronization –
phase-locked loop (PLL) based strategies
•
Grid monitoring –
accurate detection of grid voltage magnitude, frequency and phase angle for fast grid fault detection. On-line grid impedance estimation.
•
Ancillary services –
voltage support, frequency control, reactive power compensation, UPS, active filtering, etc. can be implemented in software.
•
Control under grid fault –
symmetrical currents can be injected during unsymmetrical grid faults.
6
•
Advanced grid voltage and
frequency monitoring for passive
anti-islanding detection
•
Active anti-islanding methods
based on:
o Harmonic injection
o P,Q variations
o Phase modulation
PV Systems - Main activities
Software Anti-Islanding of PV Inverters
7
•
Improved MPPT optimized for faster tracking and higher tracking efficiency in cloudy, rapidly changing conditions, typical to northern Europe
•
Intelligent MPPT with detection of slow partial
shading caused by fixed obstacles
•
On-line characterization and performance monitoring of PV panels by series and shunt
resistance estimation, detection of partial shadows caused by dirt or reduction of the transparency of the covering layers as well as rated power estimation
•
Model parameter extraction (Rs, Rp, diode quality factor) from data-sheet
•
Cell/connection failures detection
PV Systems - Main activities
Advanced MPPT and Diagnostics
8
DC- potencial to ground
Leakage current
Output voltage
Bipolar PWM Unipolar PWM
•
Efficiency of commercial PV panels is around 15-
20%
•
The power produced by these PV panels should not be wasted by using inefficient power electronics circuits
•
The efficiency and reliability of both single and three-phase inverters can be improved by using transformerless topologies
•
In case of transformerless topologies new problems related to leakage current and safety need to be dealt with.
PV Systems - Main activities
Analysis and Modelling of Transformerless Photovoltaic Inverter Systems
PV
Arr
ay
Filte
r
G-PVCG-PVI
G-PVIG-PVI
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•
Hardware design of:
•
interleaved DC/DC converter topology for
battery management
•
DC/DC converter for photovoltaic array
•
Integrated into a single 3-phase bridge
•
Energy management for DC coupled micro grids
PV Systems - Main activities
Integrated multi-function DC/DC converter for PV generation and energy storage for micro grids
10
•
Development of new functions for grid-connected PV inverters to increase their penetration level
•
Improve LV network power quality by PV inverters (harmonics, fluctuations, unbalance)
•
Contribution to new LV grid standards regarding PV integration
PV Systems - Main activities
Control of Grid Interactive PV Inverters
1 2 3 40
5
10
15
Out
put P
ower
[kW
]
Node number
Injected PowerCurtailed Power
Vol
tage
[V]
Power Generation Profile
245
246
247
248
249
250
251
252
253
Voltage
1 2 3 4-10
-5
0
5
10
15
Act
ive
and
Rea
cive
Pow
er [k
W],
[kV
A]
Node number
Active PowerReactive Power
Vol
tage
[V]
Power Generation Profile
235
240
245
250
255
Voltage
Reactive power support
Power curtailment
11
PV Systems - Main activities
PV Inverter Testing•
Advanced high-bandwidth PV simulator including dynamic irradiation profiles (pulse, ramp, staircase, custom) and partial shading
•
Dynamic MPPT efficiency tests – dynamic
irradiation profile including sunrise, fast-
and slow-clouds and sunset
•
Grid-fault tests –
ride-through tests with faulty grid using grid simulator (sags, short-circuits,
asymmetry, etc.)
•
Local grid tests –
stability and robustness tests under the conditions of the local grid, including islanding
•
Efficiency tests –
advanced setup with LabView interface and 0.02% power accuracy YOKOGAWA WT3000, PV Simulator with dSPACE control
•
European efficiency tests –
semi-automated tests
12
5kW –
4h, 28V Flow-Battery+Island-Grid Inverter
Can switch to the grid for selling electric energy, or buying if
there is not enough generation
House3kW Electronic AC load
1.5 kW Wind Turbine + WindyBoy
Inverter1.9 kWp Solar Array
+ PV Inverter
Green Residential Micro Grid – Main Components
13
Flow Battery 5kW-4h - no maintenance - 10,000+ deep cycles - high efficiency - full response over temp - nominal charging current - x2 overloading - ca. 300 USD/kWh
Green Residential Micro Grid – Flow battery
14
Green Residential Micro Grid – On-line monitoring
Monitoring of:
•
generated wind power
•
generated solar (PV) power
•
total power fed into utility network
•
wind speed
•
ambient and PV cell temperature
•
solar irradiation
•
sampling up to 1Hz
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Industrial/Ph.D. Course in "Photovoltaics Power Systems - in theory and practice" by Remus Teodorescu, Aalborg University; Vitezslav Benda, Technical University in Prague; Pedro Rodriguez, Technical University of Catalonia; Dezso Sera and Tamas Kerekes Aalborg University.
Industrial/Ph.D. Course in "Power Electronics for Renewable Energy Systems - in theory and practice" that will be held at Aalborg University, November 15-17 by Remus Teodorescu, Aalborg University; Marco Liserre, Polytechnic of Bari and
Pedro Rodriguez, Technical University of Catalonia.
Industrial/Ph.D. Course in "Micro-Grids - in theory and practice" by Remus Teodorescu and Tamas Kerekes, Aalborg University; Josep Guerrero and Juan C. Vasquez, Technical University of Catalonia.
PhD/Industrial courses
• Reliable Grid Condition Detection (STVF, Risø, ELTRA)• Modelling and control of grid inverter (Gamesa Eolica, Enertron)•
Control Development for Residential PV Inverters with Software Anti-Islanding Feature (PSO, Danfoss Solar A/S)•
Gaia Wind Turbine in Wind-Diesel Systems and as Stand-Alone (MITA A/S, GAIA A/S, AAU, RISØ, UVE)• High Efficiency Solar Inverter (AAU, REFU GmbH)
PhD Projects
•
Control of Grid Interactive PV Inverters (AAU, Danfoss Solar Inverters A/S) –
Erhan Demirok (ongoing)•
Analysis and modelling of transformerless PV inverter systems (PSO, Danfoss Solar Inverters A/S) -
Tamas Kerekes (finalised)•
Real-time Modelling, Diagnostics and Optimised MPPT for Residential PV Systems (AAU, PSO/ELTRA) -
Dezso Sera (finalised)•
Reliable Grid Condition Detection and Control of Single-phase DPGS (AAU, STVF) -
Mihai Ciobotaru (finalised)•
Monitoring and Advanced Control of Three-Phase Distributed Power Generation System (AAU, Risø, Eltra) -
Adrian Timbus (finalised)
In addition, Master student projects related to Micro Grids and PV systems are running continuously
19
Research collaboration projects
20
Smart Photovoltaic Systems (SPVSYS)
• to support the integration of PV systems into the electrical power systems byproposing new, more intelligent converters that are able to interact with the electrical environment at their point of connection
-
Smart control of PV systems, by employing new functionalities that prepare PV inverters for the integration into the smart grids of the future, and help comply with the ever more stringent grid requirements in an environment where many other PV systems are connected to the same grid.
-
Condition Monitoring and Diagnostics functionalities that monitor the state of the entire PV power system including the PV array, inverter and grid, and feature effective measures to maximize availability and reduce maintenance.
Partners:Aalborg University; Danfoss Solar Inverters A/S; Sunsil A/S; Technical University of Catalonia; Technical University of Bari; Technical University
of Warsaw
Future work
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PON107-45 - DRIVES lab
dSPACE system
Danfoss FC302 inverter interface card
Danfoss FC302 inverter2.2kW
LEM modules
DC Power Supply
PCSimulink with RTW &
dSPACE Control Desk
PWM1
UDC-IM
PWM2PWM3EN
Danfoss FC302 inverter interface card
Danfoss FC302 inverter15kW
LEM modules
DC Power Supply
PWM4PWM5PWM6
EN
DCIM PM
IRST-IM
UDC-PM
IRST-PM LEM modules
LEM modules
DC