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BASIC PRINCIPLES FOR DESIGN AND CONSTRUCTION OF PHOTOVOLTAIC PLANTS PowerPoint PPT Presentation


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TRAINING COURSE. BASIC PRINCIPLES FOR DESIGN AND CONSTRUCTION OF PHOTOVOLTAIC PLANTS. Ing. Salvatore Castello ENEA - Renewable Energy Technical Unit - Photovoltaic Lab. Summary. Criteria for selecting PV modules Strings and PV generator Supporting structures Fire prevention

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BASIC PRINCIPLES FOR DESIGN AND CONSTRUCTION OF PHOTOVOLTAIC PLANTS

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Basic principles for design and construction of photovoltaic plants

TRAINING COURSE

BASIC PRINCIPLES FOR DESIGN ANDCONSTRUCTION OF PHOTOVOLTAIC PLANTS

Ing. Salvatore Castello

ENEA - Renewable Energy Technical Unit - Photovoltaic Lab


Summary

Summary

  • 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

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

INDICATIVE SOLUTIONS FOR THE CONNECTION


General diagram of connection

GENERAL DIAGRAM OF CONNECTION

deliveryand accounting equipment

Utility grid

Point of connection

User grid

Generaldevice

loads

Interface device

loads able to operate

In islanding mode

Generatordevice

PV generator(controller for ordinary conditions management)


Connection to the lv grid

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

User lines

Counter

Utility grid

PoC


Connection to the lv grid1

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

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


Basic principles for design and construction of photovoltaic plants

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


Basic principles for design and construction of photovoltaic plants

LV GRID CONNECTION

Single generator

LV Utility grid

kWh < >

PoC

GD

LV loads

ID =

Generator Device

The interface device managed by the interface protection system can be integrated in the inverter

IPS

Inverter


Basic principles for design and construction of photovoltaic plants

LV GRID CONNECTION

Multiple generators

LV Utility grid

kWh < >

PoC

a single interface device managed by a interface protection system

GDL FV

Genarl Device of line

LV load

ID

IPS

for large systems must be foreseen a reinforcement device

Generator Device N

Inverter 1

Inverter 2

Inverter N


Basic principles for design and construction of photovoltaic plants

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.

ID=

Gen. Dev.

IPS

IPS

IPS

OR logic

Typically for N>3

Inverter 1

Inverter 2

Inverter N


The connection to the mv grid

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

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

CONNECTION TO THE MV GRIDmultiple inverter system

MV Utility grid

kWh < >

PoC

MV User grid

GD

GPS

MV loads

  • the ID is normally unique

  • The ID can be installed in LV or MV side

D

Y

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 system1

CONNECTION TO THE MV GRIDmultiple 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

IPS

IPS

IPS

LV loads

kWh

ID=genD

OR logic

Inverter 1

Inverter 2

Inverter N


The conformity of grid interface devices

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 producedFactory Inspection Certificate issued by a Certification body

  • To identify the origin of the product (Inverter made ​​in EU countries) is produced Factory Inspection Attestation


Basic principles for design and construction of photovoltaic plants

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 grid1

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

BEHAVIOUR OF PLANTS AT GRID VOLTAGE TRANSIENT

  • Typical limit allowed

  • 60% drop for 400 ms

  • 100% drop for 200 ms

  • The PV plants are maintained connected to the grid during rapid voltage drop


Behavior at grid frequency transient

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

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 absenceof fault

  • Whileisrestrictedto 49,7(0,1s) ≤ f ≤ 50,3 (0,1s) in presenceof 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

    Delayed tripping 0.1s

    Grid frequency

    grid fault signal

    remote trip

    instantaneous tripping


    Basic principles for design and construction of photovoltaic plants

    DESIGN DOCUMENTATION


    The design of the plant

    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

    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

    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 report1

    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 report2

    TECHNICAL REPORT

    • PLANT DESCRIPTION

      • Electrical characteristics of the PV generator, strings and sub-array

      • 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

    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

    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

    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

    UNIFILAR ELECTRICAL DIAGRAM conversion system

    Generator Device

    INVERTER


    Unifilar electrical diagram mv section

    UNIFILAR ELECTRICAL DIAGRAM MV section

    Energy Counter

    GD & ID

    General Protection Syste

    IPS


    Graphic documents

    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


    Basic principles for design and construction of photovoltaic plants

    PLANIMETRY EXCERPT OF THE SITE

    North

    1:5000 scale

    PV Site

    GPS


    Basic principles for design and construction of photovoltaic plants

    GENERAL PLAN OF PV ARRAY

    XX street

    Subarray 1

    Subarray 2

    • rows of modules

    equipment room

    North

    Subarray 3

    YY street


    Basic principles for design and construction of photovoltaic plants

    CONDUITS LAYOUT

    AND STRING BOX POSITIONING

    50 m

    North

    String box

    50 m

    conduit

    Subarray box


    Basic principles for design and construction of photovoltaic plants

    GROUNDING SYSTEM LAYOUT

    cabin


    Basic principles for design and construction of photovoltaic plants

    ELECTRICAL EQUIPMENT ROOM

    14 m

    2.80 m

    Protection devices and counters

    MV transfor.

    INVERTER 1

    INVERTER 3

    INVERTER 2

    3,5 m


    Basic principles for design and construction of photovoltaic plants

    MODULE SUPPORTING STRUCTURES

    Lateral view

    Construction details

    300 cm

    PV module

    String box

    180 cm

    50 cm

    cordoli

    275 cm

    Front view

    8,40 m

    180 cm


    Constructive details

    CONSTRUCTIVE DETAILS

    • Conduits and cables disposal

    • grounding network detail

    • Copper stake


    Executive calculations

    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

    FINAL DOCUMENTATION OF PLANT

    • After PV plant completion, will be released to the customer

      • user manual

      • maintenance manualcertificate 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


    Basic principles for design and construction of photovoltaic plants

    THANK YOU FOR YOUR KIND ATTENTION

    for information:

    [email protected]


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