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Impact of PV-inverters,

associated products and service

on the performance of grid-tied PV-Systems

Mike Meinhardt,Marko Werner

SMA Technologie AG Niestetal, Germanywww.SMA.de

PVPS Task 2 / ISFH Workshop:High Quality PV systems

ISFH, Hameln, Germany, September 28, 2005

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SMA Technologie AG

n Founded in 1981

n Technology leader and trend-setter in PV system technology

n More than 800 MVAAC PV inverter power installed

n Headquartered in Niestetal, Germany

n Approx. 1,000 employees worldwide, more than 15 % are engineers

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SMA worldwide

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Over 800 MWAC power installed since 1981 with SMA Sunny Boy® PV-Inverters

Federal Ministry of Economics, Berlin Airport, MunichTraining Center, Herne

Shenzhen, China White House, Washington DCOlympia Boulevard, Sydney

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Outline of Presentation

1. Introduction

2. Holistic and integral approach to responsibility of PV inverter manufacturer for the performance of PV systemso PV-invertero Additional components / Accessorieso Training, Support and Service

3. Possibilities for a inverter manufacturer to impact on the PV system performance in different phases o Designo Commissioningo Operationo Optimisation

4. Conclusion

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PV inverter is heart and brain of PV system

Solar-ModuleDC Cabeling AC Cabeling

MainsPV inverter

=

~

n The inverter is the heart (and the brain) of a PV system and therefore has a huge impact on the PV system performanceo energy yield, performance ratio, profitability …

n But …

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Holistic and integral approach to responsibility of PV-inverter manufacturer

n The responsibility of the PV inverter manufacturer goes far beyond the very manufacturing of the inverter.

n In the sense of a holistic point of view the PV inverter manufacturer’s impact on an optimum system performance comprises:

o High quality inverter with optimum customers benefit– Reliability, lifetime, efficiency, feature set …

o Associated products and additional components for an overall system design

– Communication, monitoring, data-logging …

o Support and Service

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Four phases for PV inverter manufacturer’s con-tribution to an optimum PV system performance

n The inverter manufacturer can contribute to an optimum system performance in the following four phases of PV system life

1. PV system design– A proper PV system design is the foundation for an optimum

performance and yield

2. PV system commissioning– Skilled and well-trained personnel supported by plug-and-play

and failure-tolerant inverters on-site

3. PV system operation– Robust, long life inverter with high efficiency and low failure rate

4. PV system optimization– Data-logging, monitoring, visualisation, evaluation, know-how

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1. PV-System Design Phase

n PV-System design can positively influence the performance in respect ofo Broad product range for selection of the inverter with the most

appropriate nominal AC power (opt. ratio: nom. inverter AC power / PV MPP power = 0.9)

o Wide input voltage for flexible system design using variety for PV-Modules

o (Multi-)String concept for most flexible PV system design (shading, number of modules per string)

o PV-System design tool comprising all PV-modules and knowledge about local weather conditions

o Training of planner and installer of PV-system

!

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Broad product range for selection of optimum inverter

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MPP Voltage

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PV-System design tool with PV-module and weatherdata

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SMA Training of planners and installers

n Tutorials and practical training courses in the field of:

o Sunny Family (PV-system design, commissioning and optimisation usingString inverters …)

o Sunny Central (design, commissioning of PV systems using central inverters)

o Sunny Communication (interfaces, serial and wireless communication,data-logging, visualisation ...)

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2. PV system commissioning phase

n PV-System commissioning can positively influence the performance in respect of

o Complexity of DC-cabling reduced to the minimum with String-Technology

o Inverter interfaces: easy to use Plug-and-play

o Failure-tolerant inverter design– reverse polarity protection, miswiring protection (DC vs. AC connection),

o Installation manual (focusing on practical aspects, easy understandable)

o Training on the job

o Competent and experienced service and support (hot-line) for trouble shooting on-site

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Easy to use inverter interfaces - Plug-and-play

n Simplification of System InstallationoMulti-Contact®-Plugs (or others) for connection of PVo Plug for communication connection or

wireless communicationo AC-Plug

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Hotline support for trouble shooting on-site

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3. PV system operation phase

n PV-System operationo High efficiency of Inverter

o Local, intelligent and adaptive MPP-Tracking per String

o Robust inverter design – Over-voltage protection (DC- and AC-Side)– Over-temperature protection

o Low failure rate of inverter

o Redundant PV-system concept (String-Concept)

o Diagnosis capability of inverter and associated products– Failure indication, warnings, data-logging, remote access

o 24-hour-Service (replacement of inverter)

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High efficiency of inverter

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Robust inverter design

n Over-voltage protection n Over-temperature protection

thermal fused varistors temperature sensor

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Low failure rate of inverter

n Actions taken for highest reliability if PV inverterso R&D-focus “Design-for-reliability”

o Minimum number of components (high level of integration)

o Inverter design optimised for manufacturability

o Cable-free assembly of inverter components

o Comprehensive test program – Climate chamber tests– Temperature tests – Salt spray testing– Drop tests – Vibration tests– EMI tests (radiated, conducted)– Visual inspection for each inverter– Functional test for each inverter– Burn-in for each inverter– Surge tests for each inverter

[Source: www.EUPEC.com]

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4a. PV system optimisation by customer

n PV System optimisation by customero After commissioning a optimisation and monitoring phase for

a limited duration (e.g. 3 months) is typical

o Monitoring, Data-aquisition and storage

o Comparison of energy yield and behaviour with other systems or based on experience / weather data

o Evaluation and optimisation of PV system performance carried out by owner or installer

o SMA-Tools: Sunny Beam®, Sunny Portal®, Sunny WebBox®

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PV system optimisation by customer using web-portal

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4b. PV system optimisation by SMA

n PV system optimisation and supervision by SMAo Continuous monitoring, evaluation and optimisation of PV

system performance by SMA Service Centre

o Fastest possible identification of failures and response of service

o Identification of very slow and hardly noticeable changes in PV system performance and preventive service

o Identification of hidden failures or defects

o Analysis of failures causes e.g. grid, generator, inverter …

o SMA-Tools: Sunny WebBox®, Sunny Portal®, Service

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Conclusion

n The inverter has a big influence on the performance and behaviour of PV systems

n Beside the inverter, additional components and service together make a good energy yield possible in the four different phases of PV system life:o Design, Commissioning, Operation, Optimization

n Quality of products and services is the key to satisfied customers

n Feedback of customers and third parties is vital for future progress in the field of quality