Kunisuke Kono is director of the New Energy Promotion Department within Japan's New Energy and Industrial Technology Development Organisation (NEDO). He is leading the IEA  PVPS Task 5 project on Grid Interconnection of Building Integrated and Other Dispersed PV Power Systems.

Could you briefly describe what the purpose of Task 5 is?
Grid-connected photovoltaic systems are attracting growing interest, particularly in heavily developed countries, as a means of helping meet future power demands in an environmentally benign way. However, whilst our experience of such systems is gradually increasing, at the moment there is little information available internationally regarding guidelines to serve their installation. The objective of Task 5 of the PVPS Programme is to develop and verify suitable technical guidelines to enable PV connections to the grid to be made safely, reliable and at the lowest possible cost.

What is the particular attraction of grid-connected PV systems?
PV systems typically in the power range of 1 to 50 kWp, can be readily mounted onto buildings or other suitable support structures, enabling otherwise redundant surfaces to be used to generate electricity. This is of special interest in countries such as Japan and many Northern European nations where land availability is limited and realty prices are high. Many building mounted systems, particularly those on commercial premises, present the opportunity for generating a proportion of the building's energy needs on-site. This has the advantage of reducing transmission and distribution losses commonly associated with centrally generated electricity grids. The advantage of having the grid-connection means that any surplus power can be exported, so storage batteries, such as are common in applications remote from a grid, are not needed.

How does the Rokko Island Test Facility fit into the project?
The Rokko Test Centre for Advanced Energy Systems has an important function within the Task. It is being used to verify the practicability both of existing technical interconnection guidelines and any new ones that are proposed. In Rokko, we have a very flexible simulation facility - 200 fixed arrays of 2-5 kWp, together with the requisite balance of system components and actual or simulated loads. These feed a simulated distribution system, which is equivalent to 10 km n length, so we can easily assess the impact - by which I mean effects on power quality, operational reliability and safety - that such dispersed systems have on the utility grid and vice-versa.
We have already been able to gain some helpful data relating to the effect of changes in weather condition on power output of individual systems, and how increasing the number of grid interconnections affects distribution line harmonics. These results will be useful for prediction the total impact as more and more systems are connected to the grid.

Surely Rokko Island is configured to simulate Japanese systems. How will this be of benefit to other countries?
Of course, the facility which has been operational since 1997 - well before the commencement of the IEA  PVPS programme - was originally designed to simulate a Japanese distribution network, and to test PV systems using, for instance, Japanese inverter system specifications. However, as part of the Task activities, we are now completing modification of the facilities so that the performance of European and US inverters and distribution systems can be accurately modelled too. It should point out, that it is expected that other test facilities around the world will also contribute valuable experimental information under Task 5 to complement data gathered at Rokko.

Guidelines vary from country to country. What can Task 5 do to overcome national variations?
The early work of Task 5 concentrated on collating the experiences of grid-connection that have been gained in the participating countries to date. As you point out, there are, in general, no common guidelines for PV connections to the utility grid, largely because in most countries it is up to individual utilities to define rules for connecting independent power generators to their grid. As a result, rules vary from country to country, and often between different regions of the same country. Austria, Germany and Switzerland, for instance, do have national specifications, which are only slightly modified by local utilities, but certain other countries at present have to adopt guidelines for other dispersed generation equipment.
We - PVPS - cannot legislate international installation procedures, but what we can do is gather information on grid-connection and make recommendations as to standard procedures for safe, reliable and cost effective installation and connection measures. The international survey that we have undertaken, which we are committed to regularly updating, will also enable developers to have a central reference for regional connection regulations.

So would a wider objective be to develop international standards?
That is really an issue beyond the scope of Task 5. We expect, though, that internationally recognized guidelines will be an important contribution. For these PV systems to penetrate the market to any significant degree we must make the job of installing and connecting them tot the grid as trouble-free as possible. Don't misinterpret this - we are not trying to move PV grid-connection into the domain of the home-enthusiast. But we must have some methodology to enable skilled technicians to accomplish the installation and be confident that the system they install is safe, is compliant with all appropriate regulations and will perform to its best ability.

Presumably the survey has also been useful for highlighting those areas which require further work? Exactly. This is the stage that we are now at. The participating countries all have some field experience of PV grid-connections to contribute tot the development of future guidelines. Each participating country has detailed the areas, which it feels are most in need of attention. More than 50 topics for further work were suggested. Based on these inputs, we have been able to prioritize research activities (see box). The results of the ongoing investigations will eventually be made widely available. Some will be issue as concept guidelines, others will be presented in technical papers, at workshops or in IEA reports. The International Electrotechnical Committee (IEC) is the major body for overseeing electrical connection standards. Is there much collaboration with the IEC? There is no formal agreement as such with the IEC, but there is some overlap of experts on various PVPS Tasks and the IEC's Technical Committee 83 (PV conversion of solar energy). This can only be beneficial for assisting the development of international standards for PV.

Definition of guidelines A number of grid-connection aspects have been identified as urgently needing further work. For each topic, a complete list of the problems to be addressed and the progress which must be made to ensure compliance in each of the participating countries have been identified. This should ensure that the measures eventually devised to overcome these problems are acceptable by all countries. Areas identified to be in need of further research include: • Isolation transformers to prevent DC-injection to the AC mains • Identification and testing of suitable overvoltage protection measures • Review and comparison of grounding methods and protective measures in the event of a ground fault. • Investigation of problems in connecting Module Integrated Converters • Eliminating islanding problems • Reducing harmonics, which could cause AC voltage distortion, and overcoming electromagnetic interference problems • Addressing whether there is a need for a grid-disconnection facility. For more information contact Bas Verhoeven, KEMA, The Netherlands, Fax: +31 26 351 3683.

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