PAOLO MASTROGIACOMO. Low voltage products Solar applications

Transcription

1 PAOLO MASTROGIACOMO Low voltage products Solar applications

2 Photovoltaic systems Technical Standards January 30, CDC N0201 Slide 2

3 Photovoltaic technology IEC and Local Standard PV Modules Reference Title IEC61215 IEC IEC IEC UL 1703 Siliconterrestrialphotovoltaic(PV)modules Design qualificationandtypeapproval Thin-filmterrestrialphotovoltaic(PV)modules - Design qualification and type approval Photovoltaic (PV) module safety qualification - Part 1: Requirements for construction Photovoltaic (PV) module safety qualification - Part 2: Requirements for testing Standard for Flat-Plate Photovoltaic Modules and Panels IEC Saltmistcorrosiontestingof photovoltaic(pv) modules IEC UVtestforphotovoltaic(PV) modules IEC IEC EN50380 EN IEC Photovoltaic(PV)modules-Ammonia corrosion testing Photovoltaic (PV) module performance testing and energy rating - Part 1:Irradiance and temperature performance measurements and power rating Datasheetandnameplateinformationfor photovoltaic modules Junctionboxesforphotovoltaicmodules Environmental testing - Part 2-68: Tests - Test L: Dustand sand

4 Photovoltaic technology IEC and Local Standard Inverters Reference IEC IEC UL 1741 EN EN IEC Title Safety of power converters for use in photovoltaicpower systems - Part 1:General requirements Safetyofpowerconvertersforusein photovoltaicpower systems-part2:particular requirementsforinverters Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources Overallefficiencyofgridconnected photovoltaic inverters Data sheet and name plate for photovoltaic inverters This European Standard describes data sheet and name plate information for photovoltaicinverters in grid parallel operation Utility-interconnectedphotovoltaicinverters - Test procedure of islanding prevention measures

5 Photovoltaic technology IEC and Local Standard EMC Reference IEC IEC IEC IEC Title Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current 16 A per phase) Electromagnetic compatibility (EMC) - Part 3-12: Limits - Limits for harmonic currents produced by equipment connected to public low-voltage systems with input current >16 A and 75 A per phase Electromagnetic compatibility (EMC) - Part 2-2: Environment - Compatibility levels for low-frequency conducted disturbances and signallinginpubliclow-voltagepowersupply systems Electromagnetic compatibility (EMC) - Part 3-3: Limits - Limitation of voltage changes, voltagefluctuationsand flickerinpubliclow- voltagesupply systems, forequipmentwith ratedcurrent 16Aperphase andnotsubject toconditionalconnection

6 Photovoltaic technology IEC and Local Standard EMC Reference IEC IEC IEC IEC IEC IEC/TR IEC/TR IEC/TR IEC/TR Title Electromagnetic compatibility (EMC) - Part 3-11:Limits - Limitation of voltagechanges, voltage fluctuations and flicker in public low-voltage supply systems - Equipment with rated current 75 A and subject to conditional connection Electromagnetic compatibility (EMC) - Part6-1:Generic standards- Immunity for residential,commercial andlight-industrial environments Electromagnetic compatibility (EMC) - Part6-2:Generic standards- Immunity for industrial environments Electromagneticcompatibility(EMC)-Part 6-3:Genericstandards -Emissionstandard forresidential,commercialandlightindustrial environments Electromagnetic compatibility (EMC) - Part 6-4:Generic standards- Emissionstandard for -industrial environments Electromagnetic compatibility (EMC) - Part3-14:Assessment ofemissionlimits forharmonics,interharmonics,voltage fluctuationsandunbalanceforthe connectionofdisturbinginstallations tolv power systems Electromagneticcompatibility(EMC)-Part 3-6:Limits-Assessmentof emissionlimits fortheconnectionofdistortinginstallations tomv, HVandEHVpowersystems Electromagnetic compatibility (EMC) - Part 3-7:Limits-Assessmentofemissionlimitsfor theconnectionof fluctuating installations to MV,HVandEHVpowersystems Electromagnetic compatibility (EMC) - Part3-13:Limits - Assessmentof emission limits for the connection of unbalanced installations to MV, HV and EHV power systems

7 Photovoltaic technology IEC and Local Standard Cables and Connectors Reference EN Title Electriccablesforphotovoltaicsystems EN50521 UL 6703 UL 6703A CEI AK Connectorsforphotovoltaicsystems-Safety requirementsandtests OutlineofInvestigationforConnectorsforUsein Photovoltaic Systems OutlineofInvestigationforMulti-Pole Connectorsfor UseinPhotovoltaicSystems Fire retardant and halogen free electric cable with elastomeric insulation and sheath for rated voltages not exceeding V a.c and V d.c for use in photovoltaic system (PV) Requirements for cables for PV systems 2 Pfg 1169 / Requirementsforcablesforuseinphotovoltaic- systems UL Pfg 1940 /11.12 Standard for Service-EntranceCables Requirements for cables for use on AC- applications in renewable energy systems UL 4703 OutlineofInvestigationforPhotovoltaicWire

8 Photovoltaic technology IEC and Local Standard Switchgears and Controlg. Reference IEC/TR IEC IEC IEC IEC IEC IEC IEC Title Low-voltage switchgear and controlgear assemblies - Part 0: Guidance to specifyingassemblies Low-voltage switchgear and controlgear assemblies - Part 1: General rules Low-voltage switchgear and controlgear assemblies - Part 2:Power switchgear and controlgear assemblies Low-voltage switchgear and controlgear assemblies - Part 3: Distribution boards intended to be operated by ordinary persons (DBO) Low-voltage switchgear and controlgear assemblies - Part 5:Assemblies for power distribution in public networks Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems (busways) Low-voltage switchgear and control gear assemblies - Part 7: Assemblies for specific applications such as marinas, camping sites, market squares, electric vehicles charging stations Low-voltage switchgear and control gear - Part 3: Switches, disconnectors, switch-disconnectors and fusecombination units

9 Photovoltaic technology IEC and Local Standard HV Switch. and Controlg. Reference Title IEC High-voltage switchgear and controlgear - Part 1: Common specifications IEC IEC IEC IEC High-voltage switchgear and controlgear - Part 100: Alternating current circuit-breakers High-voltage switchgear and controlgear - Part 103: Switches for rated voltages above 1 kv up to and including 52 kv High-voltage switchgear and controlgear - Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kv and up to and including 52 kv High-voltage switchgear and controlgear - Part 202: High-voltage/low-voltage prefabricated substation

10 Photovoltaic technology IEC and Local Standard Transformers Reference IEC Title Power transformers - Part 8:Application guide IEC IEC EN IEC Power transformers - Part 11: Dry-type transformers Power transformers- Part 13:Self-protected liquidfilled transformers Three phase dry-type distribution transformers 50Hz, from 100 kva to 3150kVA, with highest voltage for equipment notexceeding 36kV - Part 1:Generalrequirements Safety of power transformers, power supplies, reactors and similar products - Part 1: General requirements and tests

11 Photovoltaic technology IEC and Local Standard Electrical Installation Reference IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC Title Low-voltage electrical installations - Part 1: Fundamental principles, assessment of general characteristics, definitions Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock Low-voltage electrical installations - Part 4-42:Protectionforsafety-Protectionagainst thermaleffects Low-voltage electrical installations - Part 4-43:Protection for safety - Protection against overcurrent Low-voltageelectricalinstallations -Part4-44: Protectionforsafety- Protectionagainstvoltage disturbances and electromagnetic disturbances Low-voltage electrical installations - Part 5-52: Selection and erection of electrical equipment - Wiring systems Electricalinstallationsofbuildings-Part5-53: Selection anderection ofelectrical equipment- Isolation,switchingandcontrol Low-voltage electrical installations - Part 5-54: Selection and erection of electrical equipment - Earthing arrangements and protective conductors Low-voltage electrical installations - Part 6: Verification Electricalinstallations ofbuildings-part 7-712:Requirements for special installations or locations - Solar photovoltaic (PV) power supply systems IEC/TS Photovoltaic (PV) arrays - Design requirements

12 Photovoltaic technology IEC and Local Standard Electrical Installation Reference IEC62446 IEC Title Gridconnectedphotovoltaicsystems-Minimum requirementsfor systemdocumentation, commissioningtestsandinspection Crystalline silicon photovoltaic (PV) array - On- site measurement of I-V characteristics IEC Protection against lightning - Part 1:General principles IEC Protection against lightning - Part 2:Risk management IEC IEC Protection against lightning - Part 3:Physical damage to structures and life hazard Protection against lightning - Part 4:Electrical and electronic systems within structures

13 Photovoltaic technology IEC and Local Standard Mounting structure Reference UL 2703 UL 790 UL 1897 UL 2703 Title Outline of Investigation for Mounting Systems, Mounting Devices, Clamping/Retention Devices, and GroundLugs for Use with Flat- Plate Photovoltaic Modules and Panels Standard for Standard Test Methods for Fire Tests of Roof Coverings Standard for Uplift Tests for Roof Covering Systems Outline of Investigation for Mounting Systems, Mounting Devices, Clamping/Retention Devices, and GroundLugs for Use with Flat- Plate Photovoltaic Modules and Panels

14 Photovoltaic technology IEC and Local Standard Grid Connection Reference EN EN EN Title Voltagecharacteristicsofelectricitysupplied bypublic electricitynetworks Requirementsfortheconnectionofmicro- generators in parallelwithpublic low-voltage distribution networks Photovoltaic (PV)systems - Characteristics of the utility interface

15 Photovoltaic technology IEC and Local Standard IEC IEC TS 62548: Photovoltaic (PV) arrays Design requirements IEC 60228:2004, Conductors of insulated cables IEC , Low-voltage fuses Part 6: Supplementary requirements for fuse-links for the protection of solar photovoltaic energy systems IEC (all parts), Electric cables Calculation of the current rating IEC :2004, Tests on electric and optical fibre cables under fire conditions Part 1-2: Test for vertical flame propagation for a single insulated wire or cable Procedure for 1 kw pre-mixed flame IEC :2011, Low-voltage electrical installations Part 5-54: Selection and erection of electrical equipment Earthing arrangements and protective conductors IEC (all parts), Low-voltage electrical installations IEC :2005, Low-voltage electrical installations Part 4-41: Protection for safety Protection against electric shock IEC :2002, Electrical installations of buildings Part 7-712: Requirements for special installations or locations Solar photovoltaic (PV) power supply systems IEC 60529, Degrees of protection provided by enclosures (IP Code) IEC , Circuit-breakers for overcurrent protection for household and similar installations Part 2: Circuit-breakers for a.c. and d.c. operation IEC , Low-voltage switchgear and controlgear Part 1: General rules IEC , Low-voltage switchgear and controlgear Part 2: Circuit breakers IEC , Low-voltage switchgear and controlgear Part 3: Switches, disconnectors, switch-disconnectors and fuse-combination units IEC 61215:2005, Crystalline silicon terrestrial photovoltaic (PV) modules Design qualification and type approval IEC 61646, Thin-film terrestrial photovoltaic (PV) modules Design qualification and type approval IEC :2004, Photovoltaic (PV) module safety qualification Part 1: Requirements for construction IEC :2004, Photovoltaic (PV) module safety qualification Part 2: Requirements for testing IEC :2010, Safety of power converters for use in photovoltaic power systems Part 1: General requirements IEC , Safety of power converters for use in photovoltaic power systems Part 2: Particular requirements for inverters IEC , Protection against lightning Part 2: Risk management IEC , Protection against lightning Part 3: Physical damage to structures and life hazard IEC , Protection against lightning Part 4: Electrical and electronic systems within structures IEC 62446, Grid connected photovoltaic systems Minimum requirements for system documentation, commissioning tests and inspection EN 50521, Connectors for photovoltaic systems Safety requirements and tests

16 Photovoltaic systems The solar panel January 30, CDC N0201 Slide 16

17 Photovoltaic technology The solar panel Introduction to thr PV generator The elementary component of a PV generator is the photovoltaic cell where the conversion of the solar radiation into electric current is carried out. The cell consists of a thin layer of semiconductor material, generally silicon properly treated, with a thickness of about 0.3 mm and a surface from 100 to 225 cm2. Silicon, which has four valence electrons (tetravalent), is doped by adding trivalent atoms (e.g. boron P doping) on one layer and small quantities of pentavalent atoms (e.g. phosphorus N doping) on the other one. The P-type region has an excess of holes, whereas the N-type region has an excess of electrons. January 30, CDC N0201 Slide 17

18 Photovoltaic technology The solar panel Introduction to thr PV generator In the contact area between the two layers differently doped (P-N junction), the electrons tend to move from the electron rich region (N) to the electron poor region (P), thus generating an accumulation of negative charge in the P region. A dual phenomenon occurs for the electron holes, with an accumulation of positive charge in the region N. Therefore an electric field is created across the junction and it opposes the further diffusion of electric charges. By applying a voltage from the outside, the junction allows the current to flow in one direction only (diode functioning). When the cell is exposed to light, due to the photovoltaic effect2, some electron-hole couples arise both in the N region as well as in the P region. The internal electric field allows the excess electrons (derived from the absorption of the photons from part of the material) to be separated from the holes and pushes them in opposite directions in relation one to another. As a consequence, once the electrons have passed the depletion region they cannot move back since the field prevents them from flowing in the reverse direction. By connecting the junction with an external conductor, a closed circuit is obtained, in which the current flows from the layer P, having higher potential, to the layer N, having lower potential, as long as the cell is illuminated. January 30, CDC N0201 Slide 18

19 Photovoltaic technology The solar panel Introduction to thr PV generator A photovoltaic cell can be considered as a current generator and can be represented by the equivalent circuit The current I at the outgoing terminals is equal to the current generated through the PV effect Ig by the ideal current generator, decreased by the diode current Id and by the leakage current Il. The resistance series Rs represents the internal resistance to the flow of generated current and depends on the thick of the junction P-N, on the present impurities and on the contact resistances. The leakage conductance Gl takes into account the current to earth under normal operation conditions. In an ideal cell, we would have Rs=0 and Gl=0.On the contrary, in a high-quality silicon cell we have Rs= Ω and Gl=3.5mS. The conversion efficiency of the PV cell is greatly affected also by a small variation of Rs, whereas it is much less affected by a variation of Gl. January 30, CDC N0201 Slide 19

20 Photovoltaic technology The solar panel Introduction to thr PV generator The open circuit voltage Voc occurs when the load does not absorb any current (I=0) and is given by the relation: The diode current is given by the classic formula for direct current: Then, the current supplied to the load is given by: January 30, CDC N0201 Slide 20

21 Photovoltaic module technology The solar panel Introduction to thr PV generator January 30, CDC N0201 Slide 21

22 Photovoltaic technology The solar panel Introduction to thr PV generator The voltage-current characteristic curve of a PV module is shown in Figure. Under short circuit conditions the generated current is at the highest (Isc), whereas, with the circuit open, the voltage (Voc = open circuit voltage) is at the highest. Under the two above mentioned conditions, the electric power produced in the cell is null, whereas under all the other conditions, when the voltage increases, the produced power rises too: at first it reaches the maximum power point (Pm) and then it falls suddenly near to the open circuit voltage value. Then, the characteristic data of a PV module can be summarized as follows: Isc short-circuit current; Voc open circuit voltage; Pm maximum produced power under standard conditions (STC); Im current produced at the maximum power point; Vm voltage at the maximum power point; FF filling factor: it is a parameter which determines the form of the characteristic curve V-I and it is the ratio between the maximum power and the product (Voc. Isc ) of the no-load voltage multiplied by the short-circuit current. January 30, CDC N0201 Slide 22

23 Photovoltaic technology The solar panel Introduction to thr PV generator The voltage-current characteristic curve of a PV module is shown in Figure. Under short circuit conditions the generated current is at the highest (Isc), whereas, with the circuit open, the voltage (Voc = open circuit voltage) is at the highest. Under the two above mentioned conditions, the electric power produced in the cell is null, whereas under all the other conditions, when the voltage increases, the produced power rises too: at first it reaches the maximum power point (Pm) and then it falls suddenly near to the open circuit voltage value. Then, the characteristic data of a PV module can be summarized as follows: Isc short-circuit current; Voc open circuit voltage; Pm maximum produced power under standard conditions (STC); Im current produced at the maximum power point; Vm voltage at the maximum power point; FF filling factor: it is a parameter which determines the form of the characteristic curve V-I and it is the ratio between the maximum power and the product (Voc. Isc ) of the no-load voltage multiplied by the short-circuit current. January 30, CDC N0201 Slide 23

24 Photovoltaic module technology The solar panel Different type of Panels The photovoltaic module (cells) is based on the fact that some semiconductive materials - if properly treated - can convert solar radiation directly into DC electricity (with no moving mechanics) January 30, 2017 Slide 24

25 Photovoltaic module technology The solar panel Different type of Panels In the world of photovoltaic (PV) solar power, there are several types of semiconductor technologies currently in use for PV solar panels. Two, however, have become the most widely adopted: crystalline silicon and thin film. Crystalline Silicon Monocrystalline Silicon Multicrystalline (or Polycrystalline) Silicon Homogeneous crystal structure silicon (wafer) Heterogeneous crystal structure silicon (wafer) Commercial module efficiency: 18-20% Commercial module efficiency: 14-16% Cadmium Telluride (CdTe) Cadmium Telluride Commercial module efficiency: % Thin Film Amorphous Silicon Amorphous or microcrystalline silicon deposited on a substrate Commercial module efficiency: 6-10% Copper, Indium, Gallium, Selenide (CIGS) Copper Indium Gallium Selenide Commercial module efficiency: % Slide 25

26 Photovoltaic module technology How the panels are connected Cell PV Panel Cell String/Array Several panels connected in series Photovoltaic generator Different string connected in parallel to obtain the required power

27 Photovoltaic module technology How the panels are connected

28 Photovoltaic module technology How the panels are connected Standard modules Mostly consist of 32 to 72 cells Interconnection of cells add up to a module Series and parallel connection Parallel connection Current increase Series connection Voltage increase January 30, CDC N0201 Slide 28

29 Photovoltaic module technology How the panels are connected Parallel connection Current increases Possibility of reverse current is given Series connection Voltage increases Increase system voltage of the PV generators to the usable voltage January 30, CDC N0201 Slide 29

30 Photovoltaic technology STC (Standard Test Conditions) for PV modules All data-sheet values of a PV module are measured at STC STC defined in IEC : Irradiance of 1000 W/m² at module level Temperature of a solar cell constant at 25 C Spectrum of light after passing through the 1.5 x thickness of the atmosphere (AM 1.5) STC provide the conditions for laboratory measurements which become comparable due to the defined STC January 30, CDC N0201 Slide 30

31 Photovoltaic module technology The PV panels

32 Photovoltaic module technology The PV panels All data-sheet values of a PV module are measured at STC (defined in IEC ): Irradiance of 1000 W/m² at module level Temperature of a solar cell constant at 25 C Spectrum of light after passing through the 1.5 x thickness of the atmosphere (AM 1.5) STC provide the conditions for laboratory measurements which become comparable due to the defined STC

33 Photovoltaic systems Different solar system January 30, CDC N0201 Slide 33

34 Photovoltaic module technology Different Type of PV System PV system type What is it? Where? Stand-alone PV system not connection with the network grid Not in vicinity of pubblic grid Produce energy for own consumption. Grid connected PV system Only Touching grid for voltage reference of V/Hz All the case (network grid) Touching grid for voltage reference of V/Hz and feeding back energy to the grid Produce energy for own consumption and/or Produce energy to sell consumption by anyone connected to grid. Hybrid PV system not connection with the network grid All the case (network grid) Disel genset + Battery?+Grid Produce energy for own consumption and/or Produce energy to sell consumption by anyone connected to grid.

35 Photovoltaic plant technology Grid connected vs Off-grid/Stand alone plants Off-grid: Produce energy for own consumption. Grid connected: Produce energy to sell. Consumption by anyone connected to grid. January 30, 2017 Slide 35

36 Photovoltaic plant technology Stand-alone systems Photovoltaic generator Charge regulator DC/AC Inverter AC Loads Stand-alone plants are mainly used to supply electricity to off-grid utilities that are away from the electrical network and difficult to reach as they are situated in areas which are hard to access or where energy consumption is too low to allow for a grid connection. In these plants, the energy produced by photovoltaic panels must be stocked by means of batteries to ensure continuous operation during the night or when the sun is not shining. These small plants can be totally powered by direct current. To obtain alternate current power, an inverter is needed. Battery DC Loads January 30, 2017 Slide 36

37 Photovoltaic plant technology Grid-connected systems Photovoltaic generator Meter Energy produced Network Grid-connected plants are connected in parallel with the public network and are designed to supply the energy produced. Therefore, they work as small power plants and can fully or partially meet the energy requirements of public, industrial or private buildings. These plants feature a surface including a number of interconnected photovoltaic modules with special devices that supply power to an inverter. The inverter adjusts the energy produced by the photovoltaic power to the network standards - either single-phase or three-phase - and conveys it to the network. Load Meter Network exchange January 30, 2017 Slide 37

38 Photovoltaic systems DC part how to size January 30, CDC N0201 Slide 38

39 Photovoltaic technology DC Part How to size - Voltage and current PV modules generate a current from 4 to 10A at a voltage from 30 to 40V. To get the projected peak power, the modules are electrically connected in series to form the strings, which are connected in parallel. The trend is to develop strings constituted by as many modules as possible, because of the complexity and cost of wiring, in particular of the paralleling switchboards between the strings. The maximum number of modules which can be connected in series (and therefore the highest reachable voltage) to form a string is determined by the operation range of the inverter and by the availability of the disconnection and protection devices suitable for the voltage achieved. In particular, for efficiency reasons, the voltage of the inverter is bound to its power: generally, when using inverter with power lower than 10 kw, the voltage range most commonly used is from 250V to 750V, whereas if the power of the inverter exceeds 10 kw, the voltage range usually is from 500V to 900V. January 30, CDC N0201 Slide 39

40 Photovoltaic technology DC Part How to size - Variation in the produced energy The main factors which influence the electric energy produced by a PV installation are: Irradiance. Temperature of the modules. Shading. January 30, CDC N0201 Slide 40

41 Photovoltaic technology DC Part How to size - Irradiance As a function of the irradiance incident on the PV cells, their characteristic curve V-I changes as shown in Figure. When the irradiance decreases, the generated PV current decreases proportionally, whereas the variation of the no-load voltage is very small. As a matter of fact, conversion efficiency is not influenced by the variation of the irradiance within the standard operation range of the cells, which means that the conversion efficiency is the same both in a clear as well as in a cloudy day. Therefore, the smaller power generated with a cloudy sky can be referred not to a drop of efficiency, but to a reduced production of current because of lower solar irradiance. January 30, CDC N0201 Slide 41

42 Photovoltaic technology DC Part How to size - Temperature of the modules Contrary to the previous case, when the temperature of the PV modules increases, the current produced remains practically unchanged, whereas the voltage decreases and with it there is a reduction in the performances of the panels in terms of produced electric power The variation in the open circuit voltage Voc of a PV module, with respect to the standard conditions Voc,stc, as a function of the operating temperature of the cells Tcell, is expressed by the following formula: where: - β is the variation coefficient of the voltage according to temperature and depends on the typology of PV module; - Ns is the number of cells in series in the module. Therefore, to avoid an excessive reduction in the performances, it is opportune to keep under control the service temperature trying to give the modules good ventilation to limit the temperature variation on them. In this way it is possible to reduce the loss of energy due to the temperature. January 30, CDC N0201 Slide 42

43 Photovoltaic technology DC Part How to size - Shading Taking into consideration the area occupied by the modules of a PV plant, part of them (one or more cells) may be shaded by trees, fallen leaves, chimneys, clouds or by PV modules installed nearby. In case of shading, a PV cell consisting in a junction P-N stops producing energy and becomes a passive load. This cell behaves as a diode which blocks the current produced by the other cells connected in series and thus jeopardizes the whole production of the module. Besides, the diode is subject to the voltage of the other cells; this may cause the perforation of the junction because of localized overheating (hot spot), and damages to the module. In order to avoid that one or more shaded cells thwart the production of a whole string, some diodes which by-pass the shaded or damaged part of module are inserted at the module level. Thus, functioning of the module is guaranteed but with reduced efficiency. In theory, it would be necessary to insert a by-pass diode in parallel to each single cell, but this would be too onerous for the ratio costs/benefits. January 30, CDC N0201 Slide 43

44 Photovoltaic technology DC Part How to size There are two problems with voltage drop in PV systems. First, it represents wasted energy. Transforming electrical energy into heat in circuit conductors is lost energy production. Second, voltage drop can cause PV inverters to stop working properly under certain conditions. For example, if the dc bus voltage drops below the inverter s minimum MPPT voltage, then the inverter will operate in a limited state. If the ac bus voltage rises above the maximum grid voltage set point, then the inverter will stop operating completely. What you can do? You can optimize the schematic design and layout of equipment strategically to minimize voltage drop. You can also consider upsizing certain system conductors to further reduce voltage drop. January 30, CDC N0201 Slide 44

45 Photovoltaic technology DC Part How to size The cables used in a PV plant must be able to stand, for the whole life cycle (20 to 25 years) of the plant, severe environmental conditions in terms of high temperatures, atmospheric precipitations and ultraviolet radiations. First of all, the cables shall have a rated voltage suitable for that of the plant. The conductors8 on the DC side of the plant shall have double or reinforced isolation (class II) so as to minimize the risk of earth faults and short-circuits (IEC ). The cross sectional area of a cable shall be such as that: its current carrying capacity Iz is not lower than the design current Ib; the voltage drop at its end is within the fixed limits. Under normal service conditions, each module supplies a current near to the short-circuit one, so that the service current for the string circuit is assumed to be equal to: where Isc is the short-circuit current under standard test conditions and the 25% rise takes into account radiation values higher than 1kW/m2. January 30, CDC N0201 Slide 45

46 Photovoltaic technology DC Part How to size When the PV plant is large-sized and divided into subarrays, the PV sub-array cables shall carry a design current equal to: where SSA is the number of strings of the sub-array relating to the same PV string combiner box. The current carrying capacity Io of the cables is usually stated by the manufacturers at 30 C in free air. To take into account also the methods of installation and the temperature conditions, the current carrying capacity Io shall be reduced by a correction factor (when not declared by the manufacturer) equal to: k1 = = 0.52 for solar cables k2 = = 0.53 for non-solar cables. The factor 0.58 considers the installation on the rear of the modules where the ambient temperature reaches 70 C10, the factor 0.9 the installation of solar cables in conduit or trunking system, while the factor 0.91 refers to the installation of non-solar cables into conduit exposed to sun. In PV plants the accepted voltage drop is 1% to 2% (instead of the usual 4% of the user plants) so that the loss of energy produced due to the Joule effect on the cables is limited as much as possible. January 30, CDC N0201 Slide 46

47 Photovoltaic technology DC Part How to size - Voltage Drop The resistance of a given object depends primarily on two factors: What material it is made of, and its shape. The value of the resistance of a conductor of uniform cross section, therefore, can be computed as: L = length in meter of the conductor (in DC side 2 time the length of + cable) (mt) r = electrical conductivity (S/mt) A = section of the conductor The electrical resistivity of most materials changes with temperature. In particular with linear aprox.: α = Temperature coefficient of resistivity r0= electrical conductivity at ambient temperature T0 = pormal ambient temperature (20degree) T= working temperature January 30, CDC N0201 Slide 47

48 Photovoltaic technology DC Part How to size - Voltage Drop (Ohm Law) The resistance of a given object depends primarily on two factors: What material it is made of, and its shape. The value of the resistance of a conductor of uniform cross section, therefore, can be computed as: L = length in meter of the conductor (in DC side 2 time the length of + cable) (mt) r = electrical conductivity (S/mt) A = section of the conductor The electrical resistivity of most materials changes with temperature. In particular with linear aprox.: α = Temperature coefficient of resistivity r0= electrical conductivity at ambient temperature T0 = pormal ambient temperature (20degree) T= working temperature January 30, CDC N0201 Slide 48

49 Photovoltaic systems PV Inverter Sizing January 30, CDC N0201 Slide 49

50 Photovoltaic technology Inverter Sizing The size of the inverter can be determined starting from a value from 0.8 to 0.9 ( PPPPPP ) for the ratio between PPPPPP the active power put into the network and the rated power of the PV generator. Keeps into account the loss of power of the PV modules under the real operating conditions (working temperature, voltage drops on the electrical connections.) and the efficiency of the inverter. This ratio depends also on the methods of installation of the modules (latitude, inclination, ambient temperature ) which may cause a variation in the generated power. For this reason, the inverter is provided with an automatic limitation of the supplied power to get round situations in which the generated power is higher than that usually estimated. January 30, CDC N0201 Slide 50

51 Photovoltaic technology Inverter Sizing Real Example with simulation software January 30, CDC N0201 Slide 51

52 SOLAR INITIATIVE OVERVIEW Schematic PV Plant - Factors impacting efficiency Panels DC circuits DC/AC conversion AC power January 30, 2017 Slide 52

53 EP Division, UAE, Paolo Mastrogiacomo, 01/06/2016 ABB Solar Technology and Solutions Renewable Energy: PV Solar

54 ABB Systems and Solutions Our offering Electrification Products Division Market Segments PV is a scalable power source which can be used for different applications. OFFERING >1000 kw CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING <10 kw kw Commercial Utility Residential

55 ABB Systems and Solutions Our offering Electrification Products Division - Residential OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING Mon Source: MENA region report

56 ABB Systems and Solutions Our offering Electrification Products Division - Commercial OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING Mon

57 ABB Systems and Solutions Our offering Electrification Products Division - Utility OFFERING PV Plant DC Part Inverter PV Plant AC Part Grid CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING January 30, 2017 Slide 58

58 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range OFFERING DC PART INVERTER AC PART GRID CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING PV Panels (not ABB) Wire, cabling (not ABB) Conduit, cable tray, Cable Prot.(ABB) Combiner Box (ABB) Recombiner Box (ABB) DC Switches Discon. (ABB) Tmax PV (ABB) DC MCB (ABB) DC Fuse holder (ABB) DC OVR Surge protect. (ABB) ABB Inverter (centralized) ABB Inverter (String) ABB Compact Substations Solution January 30, 2017 Slide 59 Enclosure, MDB, Junction box, switchboard (ABB) MNS and Artu K AC Switch disconnectors (ABB) AC MCB,MCCB, ACB (ABB) Switch disconnector (ABB) Power Metering (ABB) AC Contactor (ABB) Insulation device (ABB) LPS (ABB) Grid Protection Relay (ABB)

59 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING January 30, 2017 Slide 60

60 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range OFFERING S800 PV-S/ S800 PV-M / S800 PV-M-H CATEGORIES SCHEMATIC PRODUCT RANGE OVR PV STANDARD A AND AF CONTACTORS DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING S204 M UC Z OT-M OT-DC E 90 PV GAF & IOR BAR CONTACTORS TMAX PV January 30, 2017 Slide 61 OT-DC

61 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range 1 to 32 Strings OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING January 30, 2017 Slide 62

62 ABB Systems and Solutions Our offering Electrification Products Division CMS System OFFERING CMS-System up to 64 strings PC/ PLC for processing, storage, visualisation of the measurement data CATEGORIES SCHEMATIC PRODUCT RANGE Modbus RTU DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING Inverter System 001 System 002 Combiner box System 247 January 30, 2017 Slide 63

63 ABB Systems and Solutions Our offering Electrification Products Division & DM Prod. Range OFFERING CATEGORIES SCHEMATIC TRIO (OUTD) 10/12kW TRIO (OUTD) 20/ 27.6 kw PRO 33.0 TRIO (OUTD) 50.0kW PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING January 30, 2017 Slide 64 UNO (OUTD) 2 / 2.5kW TRIO (OUTD) 5.8/7.5/8.5kW TRIO (OUTD) 6.0/8.0 kw TRIO (OUTD) 10/ 12 kw

64 ABB Systems and Solutions Our offering Electrification Products Division & DM Prod. Range OFFERING CATEGORIES ` SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING PLUS PVI 110/165/220/275/330kW (TL) PLUS PVI 134/200/267/330/400kW (TL) ULTRA 700/1050/1400kW (TL) PVS to 1000 kw PVS to 2000 kw January 30, 2017 Slide 65

65 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS INSUL. MONIT.G DEV. ISL-A 600, ISL-C 600 OVR T1 & T2 OVR TC ACB Emax2 EQ Meter SOLAR TRACKING MCB+RCDb S 200, S800, F200, F204 B, F202 PV-B January 30, 2017 Slide 66 MCCB TMAX CONTACTORS GRID FEEDING MONITORING RELAYS (FOR GRID COMPLIANCE) CM-UFD.MXX AF..T RANGE

66 ABB Systems and Solutions Our offering Electrification Products Division Prod. Range OFFERING CATEGORIES SCHEMATIC PRODUCT RANGE DC EQUIPMENTS AC EQUIPMENTS SOLAR TRACKING GRID FEEDING MONITORING RELAYS CM-UFD.MXX

67 January 30, 2017 Slide 68