page_title: Solar micro-inverter
section_title: Early examples
hierarchical_section_title: Solar micro-inverter / History / Early examples
caption_attribution_description: English: The Mastervolt 130S appears to be the first micro-inverter to be released commercially (the OK4E-100 was another early model). The inverter would normally be mounted to the back of the panel and connected through the compression fittings on the bottom.
context_page_description: A solar micro-inverter, or simply microinverter, is a plug-and-play device used in photovoltaics, that converts direct current generated by a single solar module to alternating current. Microinverters contrast with conventional string and central solar inverters, in which a single inverter is connected to multiple solar panels. The output from several microinverters can be combined and often fed to the electrical grid.
  Microinverters have several advantages over conventional inverters. The main advantage is that they electrically isolate the panels from one another, so small amounts of shading, debris or snow lines on any one solar module, or even a complete module failure, do not disproportionately reduce the output of the entire array. Each microinverter harvests optimum power by performing maximum power point tracking for its connected module. Simplicity in system design, lower amperage wires, simplified stock management, and added safety are other factors introduced with the microinverter solution.
context_section_description: In 1991 the US company Ascension Technology started work on what was essentially a shrunken version of a traditional inverter, intended to be mounted on a panel to form an AC panel. This design was based on the conventional linear regulator, which is not particularly efficient and dissipates considerable heat. In 1994 they sent an example to Sandia Labs for testing. In 1997, Ascension partnered with US panel company ASE Americas to introduce the 300 W SunSine panel.
  Design of, what would today be recognized as a "true" microinverter, traces its history to late 1980s work by Werner Kleinkauf at the ISET (Institut für Solare Energieversorgungstechnik), now Fraunhofer Institute for Wind Energy and Energy System Technology. These designs were based on modern high-frequency switching power supply technology, which is much more efficient. His work on "module integrated converters" was highly influential, especially in Europe.
  In 1993 Mastervolt introduced their first grid-tie inverter, the Sunmaster 130S, based on a collaborative effort between Shell Solar, Ecofys and ECN. The 130 was designed to mount directly to the back of the panel, connecting both AC and DC lines with compression fittings. In 2000, the 130 was replaced by the Soladin 120, a microinverter in the form of an AC adapter that allows panels to be connected simply by plugging them into any wall socket.
  In 1995, OKE-Services designed a new high-frequency version with improved efficiency, which was introduced commercially as the OK4-100 in 1995 by NKF Kabel, and re-branded for US sales as the Trace Microsine. A new version, the OK4All, improved efficiency and had wider operating ranges.
  In spite of this promising start, by 2003 most of these projects had ended. Ascension Technology was purchased by Applied Power Corporation, a large integrator. APC was in turn purchased by Schott in 2002, and SunSine production was canceled in favor of Schott's existing designs. NKF ended production of the OK4 series in 2003 when a subsidy program ended. Mastervolt has moved on to a line of "mini-inverters" combining the ease-of-use of the 120 in a system designed to support up to 600 W of panels.
caption: Released in 1993, Mastervolt's Sunmaster 130S was the first true microinverter.
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