skytron® energy GmbH 08 / 2011 Page 1
Power Plant Controlfor Utility‐Scale Photovoltaic Installations
skytron® energy GmbHErnst‐Augustin‐Str. 12D – 12489 BerlinGermany, Berlin
www.skytron‐energy.com
skycontrol
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1. Monitoring, Control and Supervision
2. Control... of what? And Why?
3. Different Control Approaches
4. skytron’s Power Plant Controller
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Monitoring, Control and Supervision
• Plant operation always “in view”• Reduced downtimes• Availability tracing• Enhanced efficiency and yield• Secured investment (ROI)
• Monitoring• Control• Supervision• Operation & Maintenance (O & M)• Asset Management
Your Benefit
Our Job
POWER CONVERSION CHAIN
… covering the entire power plant!
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SupervisoryLevel
Plant ControlLevel
Data AcquisitionLevel
Field Level
PVGuard®Remote SCADA platform for multi‐vendor multi‐site
power plant supervision
skycontrolPower plant controller for grid stability
Data Acquisition Level
skylog®High resolution real‐time data logging and
preprocessing
Data Acquisition Level
ArrayGuard®Intelligent combiner boxes
skyCONNiField sensorics
StringGuard®String current monitoring
EnergyGuardEnergy meter monitoring
Power Plant Architecture
Monitoring, Control and Supervision
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Electricalfield quantities
Ambient field quantities
Plant fault / status information
Measurement & Data Acquisition
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Remote Plant Supervision
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1. Monitoring, Control and Supervision
2. Control... of what? And Why?
3. Different Control Approaches
4. skytron’s Power Plant Controller
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Utility‐Scale PV Installations
• Plant operation always “in view”• Reduced downtimes• Availability tracing• Enhanced efficiency and yield• Secured investment (ROI)
• Monitoring• Control• Supervision• Operation & Maintenance (O & M)• Asset Management
Your Benefit
Our Job
POWER CONVERSION CHAIN
… covering the entire power plant!
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Why is Control Required?
Source: Siemens AG
TODAY:
• Distributed bulk power systems feed into an electricity grid which originally was designed forcentralized, top‐down electricity distribution and supply.
• At low‐voltage andmedium‐voltage levels
• ‐Wind power plants‐ Photovoltaic power plants‐ CSP power plants‐ Biogas power plants‐ Tidal wave plant‐ Geothermal plants
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The Effect Upon the Electricity GridDa
ily m
eanload
/ gen
eration [GW]
Load Solar Wind Water Biomass Geothermal Residual load
Time
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• Fluctuating load profiles (day, night)
• Fluctuating energy injection by “Renewables” due to variable weather conditions
• Irregular energy injection and energy extraction in sub‐grids
• Limited energy transport capacities of “historic” transmission and distribution grids
• Limited capabilities of conventional power plants to balance out those fluctuations
• Grid faults ‐ sudden load shedding and short circuits
Grid Security Grid Stability
Today’s Electricity Grid Characteristics
Grid security management measures
‐ On‐demand reduction of energy injectionin the event of grid overload
Decentralized grid stability measures
‐ Voltage support
‐ Injection of reactive power (cos ø)
‐ Frequency stability monitoring
‐ Fault ride through
‐ Provision of short circuit current (LVFRT)
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• Improved grid stability thanks todecentralized grid support:
‐ Voltage support‐ Injection of reactive power‐ Frequency monitoring
• The controllable power plant improvesthe grid quality
‐ either instantly, according to actualdemand of power supply company
‐ or according to an agreed specification
Grid Stability
overexcited
unde
rexcite
d
0.95
0.95
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1. Monitoring, Control and Supervision
2. Control... of what? And Why?
3. Different Control Approaches
4. skytron’s Power Plant Controller
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Power Plant Control: Two Approaches
Controller PlantPsetpointQsetpoint
+ -
Pactual
Qactual
Inverter Level Plant Level
• Typically open‐loop control
• Feedback of actual value P, Q ?
• Actual value pick‐up at injection point: LV
• Integration in SCADA system possible?
• Closed‐loop control
• Feedback of actual value P, Q: Yes
• Actual value pick‐up at injection point: LV, MV, HV
• Integration in SCADA system possible? Yes
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skytron’s Approach: Power Plant Controller
LOSSES !
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Monitoring, Supervision … … and Control
SYSTEM INTEGRATION
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1. Monitoring, Control and Supervision
2. Control... of what? And Why?
3. Different Control Approaches
4. skytron’s Power Plant Controller
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skytron’s Power Plant Controller: skycontrol
skycontrol
Software
Hardware / Control Cubicle
System / Control Principle
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• Genuine closed‐loop control
• Feedback of actual values at grid injectionpoint at medium or high voltage level
• Grid parameters:‐ effective power P‐ reactive power Q‐ grid frequency f‐ grid voltage V
• Effective power control(NSM – Network Security Management)
• Reactive power compensation
• Reactive power injection(grid support function)
Characteristics and Control Parameters
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skycontrol: The Control Principle
Dynamic grid support‐ short‐circuit current‐ Fault Ride Through
Static grid support‐ effective power control‐ reactive power control
Feedback‐ Setpoint/actual P, Q‐ Generation prognosis
Grid control system
Network Security ManagementEffective power control100% / 60% / 30% / 0%
Communicationand
control unit
Inverters
Generator
High and mediumvoltage switchgear
Medium voltage level(e.g.: 20 kV)
High voltage level(e.g.: 110 kV
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skycontrol: The Hardware
• Different‐size cubicles, depending on required‐ control features‐ housing‐ interfaces
• Customized to suit‐ interfaces specified by power supply company‐mounting space available‐ layout and configuration of PV power plant‐ required functional scope
• skycontrol‐ is NOT a standard power plant controller‐ is a plant control system – adjusted to customer
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Network Security management (NSM)
Effective Power Control
• Discrete switching signals (0%, 30%, 60%, 100%)• Analog signals (4 to 20 mA, 0 to 10 V)• Digital interfaces (MODBUS, BACnet)
Reactive Power Control
• Discrete switching signals (0%, 30%, 60%, 100%)• Analoge signals (4 to 20 mA, 0 to 10 V)• Digital interfaces (MODBUS, BACnet)• Characteristic working curve of grid frequency→ P(f)
• Agreed value, fixed• Discrete switching signals (cos φ: ‐0.9, ‐0.95, 1, +0.95, +0.9)• Analog signals (4 to 20 mA, 0 to 10 V)• Digital interfaces (MODBUS, IEC 60870)• Characteristic working curve of effective power → Q(P)• Characteristic working curve of reactive power → Q(V)
Integration of System Protection Signals
• Grid injection enable• Emergency OFF / Fast trip• Inverter control in the event of MV / HV switch‐off
Functions Setpoint inputs:
skycontrol: The Functional Scope
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SupervisoryLevel
Plant ControlLevel
Data AcquisitionLevel
Field Level
PVGuard®Remote SCADA platform for multi‐vendor multi‐site
power plant supervision
skycontrolPower plant controller for grid stability
Data Acquisition Level
skylog®High resolution real‐time data logging and
preprocessing
Data Acquisition Level
ArrayGuard®Intelligent combiner boxes
skyCONNiField sensorics
StringGuard®String current monitoring
EnergyGuardEnergy meter monitoring
Full System Integration
Instrumentation and Control: Fully Integrated
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• TODAY, more than 1.8 GWp of total capacity installed all over the world, rely on skytron’s monitoring and control system for utility‐scale photovoltaic power plants
• More than 30 power plants are supervised and managed from our Berlin control room
Reference Projects (Excerpt)
Our Partners (Excerpt)
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Ernst‐Augustin‐Str. 12D – 12489 Berlin, Germany
www.skytron‐energy.com
skytron® energy GmbH
+49 (0)30 688 31 59 – 0info@skytron‐energy.com
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