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PhotoVoltaic Power Systems & Micro-Grids, AAU Tamas Kerekes Department of Energy Technology Aalborg University

Photovoltaic Power Systems and Micro Grids(2)

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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

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PV Systems - Main facilities

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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

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1.8mH

1.8mH

1.8mH

4.7uF

1.8mH

1.8mH

1.8mH

4.7uF

PON109-25a - GPL

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.

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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

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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

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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

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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

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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

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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

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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

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Green Residential Micro Grid – System Configuration

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Green Residential Micro Grid – Laboratory view

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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

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Research collaboration projects

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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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Questions ?

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PON107-45 - DRIVES lab

PON109-25a - GPL

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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