Transcript IPS

TRAINING COURSE
BASIC PRINCIPLES FOR DESIGN AND
CONSTRUCTION OF PHOTOVOLTAIC PLANTS
Ing. Salvatore Castello
ENEA - Renewable Energy Technical Unit - Photovoltaic Lab
Summary
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Criteria for selecting PV modules
Strings and PV generator
Supporting structures
Fire prevention
Power conditioning unit
The connection to the grid
Design documentation
THE CONNECTION TO THE GRID
• Is generally regulated by
• Administrative rules that define
• relationship between the User and the electric Utility
• administrative cost
• grid balancing fees
• value of energy fed into the grid or exchanged
• Technical standards for the connection to the LV or MV grid
• define the modality and characteristics of the components necessary
for the connection to the grid
INDICATIVE SOLUTIONS FOR THE CONNECTION
Popwer
[kW]
Voltage level of Utility grid
≤6
LV
single phase
≤ 100
LV
100 - 200
LV or MV (*)
200 – 6 000
MV
6 000 – 10 000
MV or HV (*)
> 10 000
HV
(*) depending on the characteristics of the grid and loads connected
GENERAL DIAGRAM OF CONNECTION
delivery
and accounting equipment
Utility grid
Point of connection
User grid
General device
loads
Interface device
loads able to operate
In islanding mode
Generator device
PV generator
(controller for ordinary
conditions management)
CONNECTION TO THE LV GRID
•
GENERAL DEVICE (GD)
• Disconnect the User grid from the Utility grid in case of faults on the
User grid
• can be composed of multiple Line General Devices (DGL) up to a
maximum of 3
• must be placed immediately downstream the point of connection
(PoC) and a connecting cable (C) of negligible length
Connecting
cable
Counter
Utility grid
User lines
PoC
CONNECTION TO THE LV GRID
• INTERFACE DEVICE (ID)
• Disconnect the User from the grid in case of malfunctioning on the grid
• Is managed by an Interface Protection System (IPS)
• for systems with multiple generators
• usually a single ID managed by a single IPS
• more ID managed by more IPS acting in OR logic (the anomaly
detected by an IPS causes the release of all ID)
• In small plants The ID and the IPS can be integrated in the inverter
• in large plants is foreseen a backup device in case of failure of the
interface device
• The resetting of the backup device is performed manually
FURTHER REQUIREMENTS IN LV PLANT
• DC components fed into the grid
• The production facilitry must be equipped with a system able to limit the
DC fed into the grid by means of :
• LF transformer
• Protection device able to disconnect the inverter from the grid when
DC component > %
• Unbalance among phases
• Permanent: generated in three-phase systems made ​with different
single-phase units.
The Utility generally allow unbalance within fixed limit
• Transient: can be generate in particular operating conditions.
The plant should be equipped with an automatism that returns the
umbalance within the limits allowed
REVIEW OF MAJOR CASES IN LV
The general scheme can be applied in different ways according
to plants size and
to the grid voltage level
LV GRID CONNECTION
Single generator
LV Utility grid
kWh < >
PoC
GD
LV loads
ID =
Generator
Device
Inverter
IPS
The interface device
managed by the interface
protection system can be
integrated in the inverter
LV GRID CONNECTION
Multiple generators
LV Utility grid
kWh < >
PoC
Genarl Device
of line
LV load
a single interface device
managed by a interface
protection system
GDL FV
ID
IPS
for large systems must be
foreseen a reinforcement
device
Generator
Device N
Inverter 1
Inverter 2
Inverter N
LV GRID CONNECTION
Multiple generators
LV Utility grid
kWh < >
PoC
GD
multiple interface device
managed by more interface
protection system acting in
OR logic
LV loads
ID=
Gen. Dev.
OR logic
Typically for N>3
Inverter 1
IPS
IPS
Inverter 2
ID=
Gen. Dev.
Inverter N
IPS
THE CONNECTION TO THE MV GRID
Interface Device (ID) and Interface Protection System (IPS)
• For systems with multiple inverters
• the ID is normally unique
• can be used more ID + IPS (one for each inverter) in OR logic
• The IPS must be equipped with protection able to detect
• Grid voltage or frequency out of fixed limits
• single-phase faults to ground
• Faults between two-phase
• three-phase faults isolated from ground
THE GENERAL PROTECTION IN MV
General Protection System
• Manages The GD
• must be integrated with the
protection able to detect:
• overcurrent of phase
• Maximum vectorial sum
of the 3 currents of
phases
• fault to ground (only for
long distances from GD to
ID
GPS
DG
General
Device
CONNECTION TO THE MV GRID
multiple inverter system
MV Utility grid
kWh < >
PoC
MV User grid
GD
GPS
MV loads
the ID is normally unique
D
Y
The ID can be installed in
LV or MV side
LV loads
ID
IPS
Generator Device
(can be integrated
into the inverter)
Inverter 1
Inverter 2
Inverter N
CONNECTION TO THE MV GRID
multiple inverter system
MV Utility grid
kWh < >
MV User grid
GD
GPS
MV loads
Can be used multiple
ID + IPS (one for each
inverter) operating in
OR logic
LV loads
kWh
ID=genD
IPS
IPS
IPS
OR logic
Inverter 1
Inverter 2
Inverter N
THE CONFORMITY OF GRID INTERFACE DEVICES
• the declaration of conformity to applicable rules
• Is typically issued by the manufacturer, in the form of self-certification
• Is required by the Utility for the connection to the grid
• contain the information necessary to identify the device
• The environmental compatibility (insulation, and EMC) is tested by Accredited
Laboratory
• It also state that the device has been produced in the framework of quality
system (ISO 9001)
• To certify that the quality levels remain constant over time must be produced
Factory Inspection Certificate issued by a Certification body
• To identify the origin of the product (Inverter made ​in EU countries) is
produced Factory Inspection Attestation
GRID STABILITY
In order to contribute to the stability of the grid, the inverter must
be able to:
• maintain the insensitivity to rapid voltage drops;
• increase the selectivity of the protections in order to prevent
the untimely disconnection of the PV system;
• allow disconnection from the grid as a result of a remote
command;
• avoid the possibility that the inverter can supply the loads in
the absence of voltage in the grid cabin;
• enable the delivery or absorption of reactive power;
• limit the power fed into the grid (to reduce voltage variations
of the grid);
THE CONNECTION TO THE GRID
OPERATING RANGE OF THE PRODUCTION SYSTEMS
• In order to guarantte the grid stability, IPS must be able to keep the
production system connected to the grid (by means of the ID) for
• Grid voltage values at the point of delivery, ranging between
85% Vn ≤ V ≤ 110% Vn
• and grid frequency values ranging
47.5 Hz ≤ f ≤ 51.5 Hz
BEHAVIOUR OF PLANTS AT GRID VOLTAGE TRANSIENT
The PV plants are maintained connected to the grid during rapid voltage drop
Typical limit allowed
• 60% drop for 400 ms
• 100% drop for 200 ms
BEHAVIOR AT GRID FREQUENCY TRANSIENT
• To reduce grid voltage variations, the production system should have the
possibility to reduce the power fed into the grid in response to frequency
raise
• The restart should be
• conditioned to a stabilized frequency
• increasing the power gradually
SELECTIVITY OF INTERFACE DEVICES
Adopted to prevent untimely disconnection
If the Utility make a “grid failure “ signal available (ground faults in LV or MV) then
the operating range of IPS
• 47,5 (4s) ≤ f ≤ 51,5 (1s) in absence of fault
• While is restricted to 49,7(0,1s) ≤ f ≤ 50,3 (0,1s) in presence of fault
If the Utility don’t make available a “grid failure “ signal, the operatin range is:
47,5(0,1s) ≤ f ≤ 51,5(0,1s)
Delayed tripping 4s
Delayed tripping 1s
Grid frequency
Delayed tripping 0.1s
grid fault signal
remote trip
instantaneous tripping
DESIGN DOCUMENTATION
THE DESIGN OF THE PLANT
• ensemble of studies that produces the necessary information for the
construction of the plant in accordance with
• applicable rules
• performance requirements
• consists of
• Preliminary draft
• defines the qualitative features and the performance to be
provided
• Final draft prepared on the basis of the preliminary draft,
• contains the elements necessary for the request of authorization
for plant construction
• Working design
• defines completely and in full detail the components and the
action to be executed for plant construction
THE DESIGN DOCUMENTATION
Depends on plant size and typology
Includes
• Technical Report
• Wiring diagrams
• Lay out and drawings
• Executive calculations
• Maintenance Plan
• Safety Plan
• Estimated bill of quantities
• Time schedule
TECHNICAL REPORT
• Desig data
• Description of the system
• Criteria adopted for the design choices
• Description
• protection measures
• operating modes of the system
• calculation criteria, methods of implementation and results
• Reference standards
• List of documents
TECHNICAL REPORT
DESIGN DATA
• Site identification
• weather and climate data (solar radiation, temperature, wind, snow)
• description of the building, or the place of installation
• bearing capacity of the roof
• any architectural constraint
• power supply data
• voltage level
• contractual power committed
• average consumption
• performance requirements
• expected production
• PR
TECHNICAL REPORT
PLANT DESCRIPTION
• Electrical characteristics of the PV generator, strings and subarray
• Functional, electrical and mechanical properties of PV
modules
• String box and AC switchboards features
• Supporting structures
• Power conditioning unit
• Grid connection section (LV or MV)
• Wiring and grounding network
TECHNICA REPORT
CRITERIA ADOPTED FOR THE DESIGN CHOICES
• Plant size
• Maximizing the collection of solar radiation
• Limitation of losses and systematic shading
• Module technology
• Working Voltage
• Plant configuration and conversion system
• Management PV generator
• protections against overcurrent, overvoltage, direct and indirect
contacts, lightning
• Interfacing with the grid
• Modalities for the observance of any architectural constraints
• Solutions that allow to place adequately the photovoltaic generator on
buildings or on ground
ELECTRICAL DIAGRAM
Must show the following details:
• number of strings
• number of modules per string
• switchboards components for string and subarray parallels
• number of inverters and connection mode
• Components in electrical cabinets in AC
• Any protection devices external to the inverter on DC side
• connection point to the utility grid
• protection devices on AC side
• counters (energy produced, to/from the grid)
STRING BOX AND SUBARRAY SWITCHBOARD
To the inverterr
194,4 kW
Subarray switchboard
V
A
21,6 kW 1
2
3 4
5
6
7
8
9
String box
1
2
3
4
5
6
string (18 modules series connected; Pnom = 200 W)
UNIFILAR ELECTRICAL DIAGRAM
conversion system
Generator Device
INVERTER
UNIFILAR ELECTRICAL DIAGRAM
MV section
Energy
Counter
GD & ID
General
Protection
Syste
IPS
GRAPHIC DOCUMENTS
• Planimetry excerpt of the area
• Site plan showing the location of
• rows of modules
• equipment room
• String box
• Layout
• Conduit
• grounding grid and LPS
• Plan of equipment room with electrical equipment positioning
• Constructive details
• cables disposal
• grounding network and lightning protection system
• Assembly and construction details of supporting structures
PLANIMETRY EXCERPT OF THE SITE
North
1:5000 scale
PV Site
GPS
GENERAL PLAN OF PV ARRAY
XX street
Subarray 1
rows of modules
Subarray 2
equipment
room
North
Subarray 3
YY street
CONDUITS LAYOUT
AND STRING BOX POSITIONING
50 m
conduit
Subarray box
String box
North
50 m
GROUNDING SYSTEM LAYOUT
cabin
ELECTRICAL EQUIPMENT ROOM
14 m
2.80 m
Protection devices and
counters
3,5 m
MV
transfor.
INVERTER 1
INVERTER 2
INVERTER 3
MODULE SUPPORTING STRUCTURES
Lateral view
Construction details
300 cm
180
cm
PV module
String box
50 cm
cordoli
275 cm
Front view
8,40 m
180 cm
CONSTRUCTIVE DETAILS
Conduits and cables disposal
grounding network detail
Copper stake
EXECUTIVE CALCULATIONS
• should be related to the operating conditions and must enable to
• evaluate the expected energy production
• sizing:
• electric cables
• Switchboards (thermal)
• Supporting structures
• Grounding network
• LPS
• Must be carried out in conjunction the design of the building in order to
forecast space, shafts, passages
FINAL DOCUMENTATION OF PLANT
• After PV plant completion, will be released to the customer
• user manual
• maintenance manual
certificate issued by an accredited laboratory regarding
compliance with standards
• Modules
• inverter (interface device)
• warranty certificates of installed components
• warranty of the whole plant
• warranty on plant performance
THANK YOU FOR YOUR
KIND ATTENTION
for information:
[email protected]