PID - The Problem and How to Solve It



Similar documents
Communication Interface for SMA Inverters SMA SPEEDWIRE/WEBCONNECT DATA MODULE

Central Inverter Planning of a PV Generator

HIGH FREQUENCY TRANSFORMER WITH TRANSFORMER SWITCHOVER

EFFICIENT EAST-WEST ORIENTATED PV SYSTEMS WITH ONE MPP TRACKER

Listed are common requirements that apply to existing solar installations when altered, added to or reconfigured.

Three phase connection

Consumer Products Services Germany GmbH Türkheim Germany

SUNNY TRIPOWER 5000TL 12000TL

SolarMax P series The power package for residential solar plants

12 SOLAR PHOTOVOLTAIC POWER SUPPLY SYSTEMS by John Ware. PV modules are current-limiting

PV And Storage: Solutions with Potential

Replacing Fuel With Solar Energy

Solar Solutions and Large PV Power Plants. Oscar Araujo Business Development Director - Americas

Designing PV Plants Optimised for Economic Efficiency

PHOTOVOLTAIC SYSTEMS. Alessandro Massi Pavan

Introduction for Photovoltaic Power System Test in China. Zou Xinjing Institute of Electrical Engineering Chinese Academy of Sciences Nov.

Medium-voltage Transformers

Technical Information Short-Circuit Currents Information on short-circuit currents of SMA PV inverters

Fronius IG Plus. The next generation grid-connected PV inverter

Enphase Microinverters and Ungrounded Renewable Energy Systems: Canadian Electrical Code Compliance

Technical Information POWER PLANT CONTROLLER

ABB central inverters PVS to 1000 kw

Photovoltaic System Overcurrent Protection

How To Make A Fronius Cl Power Inverter

White Paper SolarEdge Three Phase Inverter System Design and the National Electrical Code. June 2015 Revision 1.5

PERFORMANCE OF MPPT CHARGE CONTROLLERS A STATE OF THE ART ANALYSIS

Modeling Grid Connection for Solar and Wind Energy

Solar Inverter Product Overview. Solar inverters, monitoring and support for PV installations of all sizes.

Electrical safety of grid-connected solar installations in Western Australia December 2011

THE SUPERFLEX DESIGN OF THE FRONIUS SYMO INVERTER SERIES

SOLAR POWER. Information Book

ENERGY STAR Market and Industry Scoping Report Solar Inverters December Executive Summary. 2. Definitions

The Current status of Korean silicon photovoltaic industry and market Sangwook Park LG Electronics Inc.

SFxxx-S PID Test Report (Potential Induced Degradation) TUV Rheinland Japan. ARC Product Management Ver. 1

Sunny Family 2012 PRODUCT CATALOG

SUNNY BOY 2000HF / 2500HF / 3000HF

PHOTOVOLTAIC (PV) solar panels. Specification. Electricity - CE & ISO 9000 certified. 83W panel. 180W panel Maximum power:

Design of Grid Connect PV systems. Palau Workshop 8 th -12 th April

/ The personal storage solution for 24H Sun. / Dynamic Peak Manager. / Smart Grid Ready THREE-PHASE

Yield Reduction due to Shading:

SOLAR PV INFORMATION. January, 2015

2.06. Version. Kinglong New Energy Technology Co.Ltd. Sunteams 1500 Sunteams Sunteams 4000 Sunteams 5000

ASI OEM Outdoor Solar Modules

SA Power Networks Planning for Solar PV? Customer information guide to network connected solar PV inverter systems

POTENTIAL INDUCED DEGRADATION OF SOLAR CELLS AND PANELS

DAVID WILSON LIBRARY

APPLICATION NOTE TESTING PV MICRO INVERTERS USING A FOUR QUADRANT CAPABLE PROGRAMMABLE AC POWER SOURCE FOR GRID SIMULATION. Abstract.

Data Sheet. PIKO-Inverter

PSIM Tutorial. How to Use Solar Module Physical Model Powersim Inc.

Clean, Sustainable Energy from the Sun Now, and for Our Children s Future

JSI Series Single Phase String Inverter. Features. Typical Efficiency Curve JSI-1500TL JSI-2000TL JSI-2500TL

Solar power Availability of solar energy

INVERTER SYSTEM PRODUCT BROCHURE

We're with you... solar. Call today FOR THE LIFE OF THE SYSTEM YEAR WARRANTY * YEAR OLD BACKED BY CSR BRADFORD CSR A AUSTRALIAN COMPANY

Power transformers. Special transformers Railway

Solar Energy Discovery Lab

PV projects by Bosch.

INVERTER WITH MULTIPLE MPP TRACKERS: REQUIREMENTS AND STATE OF THE ART SOLUTIONS

Solar power system installation for homes & businesses

Development of Grid-stabilization Power-storage Systems Using Lithium-ion Rechargeable Batteries

Using the sun to generate electricity

Solar Powered Wireless Sensors & Instrumentation: Energy Harvesting Technology Reduces Operating Cost at Remote Sites

Solar Energy. Airports Going Green Aimee Fenlon

CHAPTER 5 PHOTOVOLTAIC SYSTEM DESIGN

RELAYS Solar Energy Systems

Solar Photovoltaic (PV) Systems

K.Vijaya Bhaskar,Asst. Professor Dept. of Electrical & Electronics Engineering

SMA Service Concept Sunny Central

Criteria for Selecting a Residual-Current Device

Coslight Hybrid Power System with Solar

Technology Advantage

SOLAR PV-WIND HYBRID POWER GENERATION SYSTEM

Transformerless PV inverter withstandardsystem monitoring. Fronius IG TL

Equipment: Power Supply, DAI, Universal motor (8254), Electrodynamometer (8960), timing belt.

Electricity from PV systems how does it work?

Technical Information Battery Management of the Sunny Island Gentle charging control for lead-acid batteries based on current state of the battery

Sunny Boy Accessories SMA POWER BALANCER

Solar Matters III Teacher Page


Communication Interface for SMA Inverters SMA BLUETOOTH PIGGY-BACK

INTERFACES FOR RENEWABLE ENERGY SOURCES WITH ELECTRIC POWER SYSTEMS

SOLAR PV SYSTEM INFORMATION PACK

Accessories SUNNY REMOTE CONTROL

LEHI CITY POWER NET METERING STANDARDS For Customer-Owned Electric Generating Systems

Solar Power Made in Sweden. June 17, 2014

SolarEdge. SolarEdge, Enphase Value Comparison. July 8, 2011

Application Information Improving Efficiency in Smart Grid Applications With Fully Integrated Current Sensing ICs

Technical Information Requirement for MV transformers and transformer for internal power supplies for SUNNY CENTRAL


MAKING MODERN LIVING POSSIBLE. UniLynx Indoor User Manual. ULX 1800i ULX 3000i ULX 3600i ULX 5400i SOLAR INVERTERS

Solar Water Heating and Photovoltaic Electrical Systems Installed on One or Two Family Dwellings

Solar Cell Optimization: Cutting Costs and Driving Performance

Romana Brentgens / photon-pictures.com (2)

MORE POWER. A BETTER INVESTMENT.

Solar Photovoltaic (PV) Cells

CONTROLS DATA MANAGEMENT PROCESS AUTOMATION EUROCUBE. General purpose single phase thyristors and solid state relays Product data.

PREMIUM CLASS PHOTOVOLTAICS

ADDENDUM #1(BID PACKAGE # 3)

SOLAR MICRO INVERTER 260 COMMUNICATION GATEWAY. Apparent Power Control (APC) unique micro inverter with

TEST WINNER REPRINT. Solar modules Which manufacturer? Thin-film o r crystalline silicon? What price? Are there any test results?

Transcription:

Technical Information PID - The Problem and How to Solve It Module Regeneration with the PV Offset Box Content Potential Induced Degradation (PID) is a phenomenon which affects some PV modules with crystalline Si cells and leads to gradual deterioration of performance, reaching up to 30 percent and more after a few years. Some module manufacturers are already working to develop countermeasures by using new materials, but the general trend to three-phase systems and system voltages up to 1,000 V is currently exacerbating the problem rather than alleviating it. In addition to negative earthing of the PV array, SMA Solar Technology AG now offers a simple technical solution to prevent this reduction in power of PV modules reliably, also when using transformerless inverters. This Technical Information first gives a brief overview of the PID effect and then explains how the PV Offset Box works and when it can be used. PID-PVOBox-TI-en-10 Version 1.0 EN

1 Cause: Voltage and Potential to Earth SMA Solar Technology AG 1 Cause: Voltage and Potential to Earth If we want to understand PID, we must first define the terms voltage and potential: the electric potential of a point describes its voltage compared with a defined reference and zero point. In most cases, this is the earth. By contrast, the term "voltage" describes a difference in potential between random points, i.e. simply the difference between two electric potentials. Example: If point A has a potential of 380 V to earth and point B has a potential of 430 V, the voltage between A and B is exactly 50 V. Under nominal conditions, typical PV modules supply approximately 30 V. Connection in series to module strings results in a far higher array voltage. It drives a corresponding direct current which the inverter converts into grid-compliant alternating current. The earthing of the PV array, its potential, is prescribed by the potential of the connected electricity grid and the design of the inverter. Ideally, the positive and negative poles of the PV array should be symmetrical to the potential of the (earthed) neutral conductor. For example, if the MPP voltage of the module string is 400 V, the PV module at the negative end has a potential of 200 V to earth, while the module at the positive end of the string has a potential of +200 V (see SB with transformer in Figure 1). For some transformerless inverters, it can also be shifted to the negative side. The problem: a positive or negative potential to earth can have unwelcome side-effects depending on the module type - the PID described here is one of them. Figure 1: The potential (amount, sign and chronological sequence) of the lowest (blue) or highest (red) PV module within a string depends on the type of inverter used and on whether an array pole is earthed. Example for an MPP voltage of 400 V. The range and, in particular, the sign of the array potential can only be specified freely if galvanically isolating inverters are used. As they do not feed their power directly to the electricity grid, but via a magnetic coupling, they always allow the PV array to be earthed. As a result, the potential of the entire PV array can be shifted entirely into the positive or negative range. This option is not available for transformerless inverters, as they are connected to the electricity grid with electric conduction, and earthing would cause internal short circuits. 2 PID-PVOBox-TI-en-10 Technical Information

SMA Solar Technology AG 2 What is Potential Induced Degradation (PID)? 2 What is Potential Induced Degradation (PID)? The phenomenon described here only occurs in modules with cells made of crystalline silicon. If the modules have a negative potential to earth in operation, there is an equally high negative voltage between the cells of the PV module and the aluminium frame, which is earthed for safety reasons. The effect is stronger, the closer the module is to the negative pole of the PV array, as the potential there (and thus the voltage between cells and the aluminium frame) can reach more than half the amount of the array voltage. As a result, electrons from the materials used in the PV module can separate, follow this electric field and finally flow out via the aluminium frame. The result is an increasing charge (polarisation) of the module, which adversely changes its characteristic curve and thus its power (Figure 2) unless countermeasures are taken. Figure 2: The characteristic curve of a PV module in the original state and during the degradation process A decreasing slope with a virtually unchanged open-circuit voltage and short-circuit current, while the maximum power (MPP) decreases by 30 percent or more, is typical.* The electric charge of the PV module is so critical because of the way solar cells work. The photovoltaic effect is based on the combination of two different semiconductor materials to establish an internal electric field by exchanging charges. It is this field that causes the electrons freed by light energy to move from their location and flow past the contacts as electric current. Additional load carriers can considerably interfere with this effect, causing a significant loss of power. However, it has been found that this polarisation can generally be reversed. Accordingly it is not an irreversible effect such as corrosion and normal aging-related deterioration. The term "Potential Induced Degradation"* was first used in the 2010 publication by module manufacturer Solon, which examined the phenomenon in detail. * J. Berghold et.al, Potential Induced Degradation of solar cells and panels, proceedings of the 25th EU PVSEC, 2010 Technical Information PID-PVOBox-TI-en-10 3

3 Further Information on PID SMA Solar Technology AG 3 Further Information on PID In the past, power losses based on PID have been the exception rather than the rule. Recently, however, there are increasing indications that many cell types display this failure pattern, without the manufacturer being aware of it. The abovementioned article by Solon identifies the major influencing factors for PID susceptibility: Solar cells: The structure of the PV cells has an influence on the PID via the charge carrier density of the silicon used and the chemical composition of the anti-glare coating. PV module: The materials used in the PV module also play a role, for example, the laminating film that comes directly into contact with solar cells (usually EVA). System configuration: as described above, the maximum negative potential of the PV modules plays a significant role. This depends on the length of the module strings, the inverter type and possible earthing of the PV array. Time: The PID and the resulting power loss are not immediately apparent - they develop over a period of several months to a few years. 4 PID-PVOBox-TI-en-10 Technical Information

SMA Solar Technology AG 4 PV Offset Box as a Solution 4 PV Offset Box as a Solution In PV plants with galvanically isolating inverters, PID can be prevented reliably by earthing the negative pole of the PV array, as this shifts the potential of the entire PV array to the positive. In PV plants with transformerless inverters which, due to their design principle, are significantly less expensive and more efficient, the required effect can be achieved using the PV Offset Box. The PV Offset Box exploits the fact that the PID effect is reversible and progresses relatively slowly. How it works: If the array voltage falls below a defined threshold after sunset, the PV Offset Box raises the entire PV array to a high positive potential (between +400 V and +1,000 V to earth), reversing the polarisation effect which occurred in operation (Figure 3). When used on a PV array which has been affected by PID for an extended period, full regeneration of the PV modules takes roughly half as long as degradation. The energy drawn from the household grid is negligible, as the current that flows during regeneration at night is minimal, due to the current restriction in the PV Offset Box (P AC nom < 3 W). Figure 3: In plants with separately-operated module strings, the PV Offset Box on the array side is connected to a negative pole and the positive poles of the two strings. The regeneration voltage is not applied until the two string voltages reach a defined threshold. Information: Even if the PV modules are not exposed to higher voltages in the regeneration process than in normal operation, approval of the module manufacturer is required before using the PV Offset Box. Technical Information PID-PVOBox-TI-en-10 5

5 Summary of the Advantages SMA Solar Technology AG 5 Summary of the Advantages Permanent and reliable solution of the PID problem Greater energy yields thanks to the use of transformerless inverters Old plants can easily be retrofitted Cost advantages thanks to the use of transformerless inverters Cost advantage as no earthing set is required Negligible energy consumption Compatibility in principle with PV inverters from other manufacturers Alternatives to using the PV Offset Box: Replacing affected PV modules with new PV modules which are not susceptible to PID Use of a galvanically isolating inverter and a negative earthing set 6 Requirements for Operating a PV Offset Box In principle, the SMA PV Offset Box can be combined with any inverter. However, in order to connect the SMA PV Offset Box to a PV plant, approval by both the manufacturer of the PV modules and the inverter manufacturer is required. If necessary, observe additional requirements by the manufacturers. Depending on the operating mode, the SMA PV Offset Box supplies a fixed output voltage or automatically controls its output voltage. With automatic voltage control, the SMA PV Offset Box automatically complies with the maximum permitted system voltage. With a fixed output voltage, it may not exceed the maximum DC voltage of the PV modules and the inverter. See the corresponding product documentation for details of the DC voltage of the components in your PV plant. You will find the specific restrictions for operation with the SMA PV Offset Box in the manufacturer approvals for the PV modules and inverters. 6 PID-PVOBox-TI-en-10 Technical Information

SMA Solar Technology AG 7 General Information on the Procedure in the Event of Power and Yield Losses 7 General Information on the Procedure in the Event of Power and Yield Losses The PID phenomenon described above only affects some module types with solar cells made of crystalline silicon. It is not to be confused with TCO corrosion, an irreversible process which can occur in some thin-film PV modules, especially in CdTe and a-si modules (for further information on TCO corrosion, see the Technical Information "Module Technology"). There is also a variety of other causes for yield losses. If this is the case, we urgently recommend that you have an expert examine the PV plant. Plant operators who suspect that their plants are affected by PID are encouraged to contact their module manufacturer through their electrically qualified persons. However, the following signs may provide an indication that the plant is affected by PID: The ratio of the MPP voltage to the open-circuit voltage (U mpp /U 0 ) and the open-circuit voltage U 0 itself have decreased steadily compared with the values specified in the datasheet. Parts of the plant equipped with identical PV modules but with different inverters do not show any power output losses. This is particularly the case if these plant parts are operated at another string voltage. For further clarification, it may be necessary to ask the manufacturer. If they do not expressly emphasise that their modules have been specifically tested and certified PID-resistant, there is usually a certain risk of PID occurring. Contact SMA Solar Technology AG Sonnenallee 1 34266 Niestetal, Germany www.sma.de SMA Service Line Inverters: +49 561 9522 1499 Communication: +49 561 9522 2499 Fax: +49 561 9522 4699 E Mail: ServiceLine@SMA.de Technical Information PID-PVOBox-TI-en-10 7

SMA Solar Technology www.sma-solar.com SMA Solar Technology AG www.sma.de SMA Australia Pty. Ltd. www.sma-australia.com.au SMA Benelux bvba/sprl www.sma-benelux.com SMA Beijing Commercial Company Ltd. www.sma-china.com.cn SMA Central & Eastern Europe s.r.o. www.sma-czech.com SMA France S.A.S. www.sma-france.com SMA Hellas AE www.sma-hellas.com SMA Ibérica Tecnología Solar, S.L.U. www.sma-iberica.com SMA Solar India Pvt. Ltd. www.sma-india.com SMA Italia S.r.l. www.sma-italia.com SMA Japan K.K. www.sma-japan.com SMA Technology Korea Co., Ltd. www.sma-korea.com SMA Middle East LLC www.sma-me.com SMA Portugal - Niestetal Services Unipessoal Lda www.sma-portugal.com SMA Solar (Thailand) Co., Ltd. www.sma-thailand.com SMA Solar UK Ltd. www.sma-uk.com