From SSG to VSG and Synchronverter: twenty years of grid-forming control
Summary: Grid-forming is not a recent feature but twenty years of accumulated research and field work: the IEEE task force proposed the Static Synchronous Generator in 1997, VISMA and VSYNC defined the VSG almost simultaneously in 2007, the Synchronverter embedded a full synchronous-machine model in 2008-2009, companies such as SMA brought it into real microgrids after 2010, and State Grid listed virtual synchronous machines among its ten key innovation programmes in 2016.
Grid-forming is not a recent feature but twenty years of accumulated research and field work: the IEEE task force proposed the Static Synchronous Generator in 1997, VISMA and VSYNC defined the VSG almost simultaneously in 2007, the Synchronverter embedded a full synchronous-machine model in 2008-2009, companies such as SMA brought it into real microgrids after 2010, and State Grid listed virtual synchronous machines among its ten key innovation programmes in 2016.
1997-2009: concept and naming
In 1997 an IEEE task force proposed the Static Synchronous Generator for FACTS, using power electronics to emulate synchronous-machine behaviour; it is regarded as the earliest seed of VSG thinking. In 2007 Professor Beck's German team proposed VISMA (Virtual Synchronous Machine), a current-type VSG controlling converter filter-inductor current. In the same year the European VSYNC project led by K. Visscher formally named the Virtual Synchronous Generator, using voltage-source control closer to a real machine. In 2008-2009 Professor Qing-Chang Zhong proposed the Synchronverter, embedding the complete synchronous-machine model including excitation, and it became the definitive voltage-source VSG scheme.
2010-2016: from laboratory to industry
SMA, Siemens and ABB began developing grid-forming products. SMA validated grid-forming microgrids in the German energy-self-sufficient village of Feldheim and the Bordesholm town storage project; Feldheim has covered all its electricity and heat from local renewables since 2010. In China, Qing-Chang Zhong promoted VSG from 2008 and from 2012 led the virtual synchronous machine programme at the distribution research institute of CEPRI, while State Grid listed the technology among its ten key science and innovation programmes in 2016.
2017 to date and VGRID POWER practice
High renewable penetration turned inertia shortage and frequency stability into industrial requirements. The Foehren project in Germany became the first utility-scale grid-forming storage plant, with grid-forming PCS from SMA, while microgrids added LVRT, short-circuit capability and transient voltage support to the competitive agenda. VGRID POWER was founded in 2019 (originally Zhongteng Microgrid Shenzhen) on a grid-forming roadmap, validated communication-free UPS-model paralleling in 2021, delivered an overseas diesel-genset grid-forming project in 2023, and in 2024 delivered a State Grid seamless-supply grid-forming source project plus batch deliveries for domestic oil and gas hybrid grid-forming sites. The Leona-H135K is its core 100-200 kW product.
Frequently asked questions
How do VISMA and VSYNC differ?
VISMA is a current-type VSG that controls converter filter-inductor current directly. VSYNC uses voltage-source control with external characteristics closer to a real synchronous machine, and became the mainstream route for microgrid products.
Why does the technical library insist on grid-forming units that can also connect to the grid?
It is a difference of starting point: not a grid-following inverter with an island feature added, but an inverter that is always a voltage source and supports grid connection as one of its states.
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FAQ
How do VISMA and VSYNC differ?
VISMA is a current-type VSG that controls converter filter-inductor current directly. VSYNC uses voltage-source control with external characteristics closer to a real synchronous machine, and became the mainstream route for microgrid products.
Why does the technical library insist on grid-forming units that can also connect to the grid?
It is a difference of starting point: not a grid-following inverter with an island feature added, but an inverter that is always a voltage source and supports grid connection as one of its states.
