Overall objective

Participants have carried out five subtasks, subtask 10, 20, 30, 40 and 50 in order to achieve these objectives. The objectives of each subtask are as follows:

• Subtask 5.10: Review of Previously Installed PV Experiences
  To review existing technical guidelines, local regulations and operational results of grid interconnection with building integrated and other dispersed PV systems to aid subtask 20: in defining existing guidelines and producing concepts for new requirements and devices.

• Subtask 5.20: Definition of guidelines to be demonstrated
  Utilizing the results of subtask 10 and a questionnaire, existing technical guidelines and requirements to be demonstrated will be defined, and concepts for new requirements and devices will be developed, with safety, reliability, and cost reduction taken into consideration.

• Subtask 5.30: Demonstration Test Using Rokko Island and/or Other Test Facilities
  To evaluate by demonstration tests the performance of existing and new technical requirements and devices defined in subtask 20.

• Subtask 5.40: Summarizing Results
  To summarize the results of Task 5 and to produce a general report for all participating countries of Task 5 and for ExCo members

• Subtask 5.50: Study on highly concentrated penetration of grid- interconnected PV-systems
  To assess the net impact of highly concentrated PV systems on electricity distribution systems and to establish recommendations for both distribution and PV inverter systems to enable widespread deployment of solar energy.

Overview of past activities

• Subtask 5.10: Review of Previously Installed PV Experiences
  Survey of existing guidelines and regulations for grid connection of PV systems and the difference of electrical distribution systems in Task 5 participating countries were completed as the Task 5 internal report opened to IEA member countries. The report on inverter and related protection equipment was distributed to expert members as the Internal Task Working Document. The summary of PV operating experience from participating countries was included in the Task 5 summary report.

• Subtask 5.20: Definition of guidelines to be demonstrated
  Research results on subjects important for interconnection of PV systems were completed as an official IEA report. The following are the report contents for each subject.
  • Harmonics; Harmonic effects, present international rules and experimental results were summarised in the report.
  • AC-Module; Recent situations concerning R&D, commercial products and regulation on AC module in participating countries were summarised.
  • Multiple Inventers and AC Grid; Problems and countermeasures for voltage variation, reverse power flow, and grid short circuit fault were summarized in the report.
  • Grounding of Equipment in PV Systems; Standards and codes for each country for grounding requirements were summarised.
  • Ground-fault Detection and Array Disable for PV systems; Fire safety, grounding fault detection on DC side, etc. were summarised.
  • Over Voltage Protection; Over voltage due to indirect lightning strikes were analyzed with consideration of the grounding structure of the PV system.
  • Islanding; Islanding prevention methods developed and adopted in each country were summarised in the report.
  • Electro Magnetic Compatibility; Standards and codes for electromagnetic emission were collected and summarised.
  • External Disconnect; Standards and codes of each country for the external disconnecting devices were collected and summarised.
  • Re-closing; Theory, problem, and experimental results for the effect of re-closing on PV systems were summarised in this report.
  • DC Injection and Isolation Transformer; Influences of DC injections on utility transformers were investigated by experiments.

• Subtask 5.30: Demonstration Test Using Rokko Island and/or Other Test Facilities
  Demonstration tests for harmonics, islanding, PV output variation etc. were conducted using the Rokko Test Facility in Japan. The Subtask 30 report, summarising demonstration test results using the Rokko Test Facility was completed and published as an official IEA-PVPS report. Contents of the report include, harmonics caused by PV inverters, measurement of islanding, distribution line short circuit fault, AC/DC mixing fault, the effect of PV system output fluctuation and others.

• Subtask 5.40: Summarizing Results
  The summary report of Task 5 activities from 1993 to 1998 was produced as an official IEA-PVPS report. The summary report is composed of:
  • Executive summary
  • Summary of subtask activities
  • Summary of subtask 10
  • Summary of subtask 20
  • Summary of subtask 30
  • Future work recommendations (related to the following subtask 50 work)

• Subtask 5.50: Study on highly concentrated penetration of grid- interconnected PV-systems
  Surveys for the latest PV system grid-interconnection technologies were conducted and reported. These surveys included PV system grid-interconnection and design guidelines or national standards, updated information of inverters and interconnection devices and PV system testing certification and utility inspection and maintenance method.
  Research on islanding related problems has been conducted in highly penetrated PV systems conditions. The probability of load and PV system output matching was determined using real measurement and the risk of islanding was defined. Islanding detection method and test circuit for islanding detection performance were summarized and reported.
  Important factors to decide on the limit of PV system penetration in distribution networks were listed and analysis based on distribution line voltage limit was conducted. Measures to stretch the limit of PV penetration and some financial aspects of PV penetration were also discussed. Power value and capacity value of PV system penetration were evaluated using different customer load profile.

Accomplishments for 2001

• Activity 5.51. Reporting of PV System Grid-Interconnection Technologies
  The survey result for PV system grid-interconnection and system design guidelines or standards of Task 5 participating countries was summarized and reported. The survey result shows the tendency that PV specific or inverter specific interconnection guideline is becoming common. The survey result for updated information of inverters and interconnection devices was summarized. High performance with high conversion efficiency, low harmonic current generation and good power factor operation have been realized, while cost, volume and weight reduction have been achieved.
  The survey result for certification of PV system components and grid-interconnected PV systems was summarized. Certification test subjects and test sequence were recommended in the final draft of the report.

• Activity 5.52. Research on Islanding
  The result of measurement and calculation for load and PV output profile was summarized and reported. These calculation results are used to determine the probability of islanding, because islanding occurs at the matching condition of load and PV output (for both active power and reactive power). The result suggests that if the total capacity of PV systems is under the minimum load (around 20% of peak load) of the distribution line, the probability of islanding is zero. Even if PV systems are penetrated beyond this level, the possibility of load matching is very small; about 1.0E-6 to 1.0E-5. The probability of islanding is calculated by multiplying the possibility of load matching and the possibility of loss of main (for example 6.3E-8). Therefore, the probability of islanding is far more reduced.
  The risk of islanding was also calculated and we found that the risk of islanding does not significantly increase the risk that already exists. The quality of PV system installation and inverter safety integrity level affects the level of risk.
  Surveys for islanding detection method and islanding detection test circuit were conducted and reported. Various kinds of islanding detection methods were listed with principal, strengths and weakness and characteristics of non-detection zones. Several kinds of anti-islanding test methods and test circuits were also summarized for further consideration of standardization of test circuit.

• Activity 5.54. Capacity of PV Systems
  Factors to decide on the limit of PV system penetration in distribution networks were listed and an analysis based on distribution line voltage limit was conducted. Considering the distribution system line voltage control operation, there will be no problem if the PV systems are penetrated below minimum load level (typically 20% to 25% of distribution line capacity). Measures to stretch the limit of PV penetration and some financial aspects of PV penetration were also discussed. Distribution system planning considering PV system penetration and demand side management using PV system will be the future key to enhance PV penetration.
  Power value and capacity value of PV system penetration were evaluated using different customer load profiles. These values strongly depend on load profile and climate condition. Therefore, it will be difficult to make a general conclusion for the added value of PV systems.

• Task 5 Workshop – The Impact of PV Penetration in Distribution Networks
  A two-day Task 5 workshop was held on January 24 and 25, 2002, at Arnhem, The Netherlands. This workshop was the last activity of Task 5. Seventy five participants from fourteen countries (Australia, Austria, Belgium, Canada, Denmark, France, Germany, Italy, Japan, The Netherlands, Portugal, Switzerland, United Kingdom and the United States of America) took part in the workshop. In the workshop, Task 5 findings for the summary of islanding detection methods, probability of islanding and risk analysis for islanding were presented and discussed on the first day. On the second day, PV related guidelines and standards, inverter technology, impact of PV penetration and value of PV were presented and discussed.

Activities planned for 2002

Industry involvement

Key deliverables (2001 and planned)

The following reports will be submitted to the ExCo and will be published in 2002:

• Report IEA PVPS T5-05: 2002; “Grid Connected PV Power Systems: Survey of Inverter and Related Protection Equipment”
• Report IEA PVPS T5-06: 2002; “International Guidelines for the Certification of PV System Components and Grid Connected PV Systems”
• Report IEA PVPS T5-07: 2002; “Probability of Islanding in Utility Networks Due to Grid Connected PV Power Systems”
• Report IEA PVPS T5-08: 2002; “Risk Analysis of Islanding of PV Power Systems within Low Voltage Distribution Networks”
• Report IEA PVPS T5-09: 2002; “Evaluation of Islanding Detection Methods for PV Utility Interactive Power Systems”
• Report IEA PVPS T5-10: 2002; “Impacts of Power Penetration from PV into a Power System”
• Report IEA PVPS T5-11: 2002; “Power Value and Capacity Value of PV Systems”

Participating countries, key participants in 2001 and their organizations

Meeting schedule (2001 and planned 2002)