Grid stability with renewables? Yes, Wind can!

A primary advantage that synchronous generators deliver is mechanical inertia which instantly resists speed changes in a grid shock, such as the failure of a large power plant or a transmission line. Generator speed determines grid frequency.

CHRISTCHURCH, New Zealand, June 22, 2017 /PRNewswire/ -- Windflow Technology Ltd (WTL), New Zealand's only designer & manufacturer of wind turbines, announces the licensing opportunity for their synchronous generating drive-train technology. As renewable energy is added to modern grid systems, which have traditionally relied on large spinning turbines with synchronous generators from hydro, coal and thermal power stations contributing inertia to the grid, the requirement for an inertial response from renewables has been brought into sharp focus. This has been highlighted by the recent experience in the South Australian blackout during 2016, and is an issue under discussion by grid operators and regulators internationally. Most countries view their fastest and easiest renewable addition to be solar, however over-reliance will reduce grid stability in case of any shocks to the grid.

A primary advantage that synchronous generators deliver is mechanical inertia which instantly resists speed changes in a grid shock, such as the failure of a large power plant or a transmission line. Generator speed determines grid frequency. The larger the shock or the lower the inertia, the faster the rate of change of frequency. Therefore grids need inertia for stability. Most wind turbine systems provide asynchronously generated energy which contribute no inertia because their spinning masses are decoupled electronically from the grid, although it is suggested this may be overcome via untested synthetic inertia (also known as Fast Frequency Response "FFR") to respond to grid shocks via their power electronics. Solar panels can not provide this due to the lack of a spinning mass.

WTL's drive-train enables its synchronous generator to be directly connected to the grid, providing inertia for instantaneous grid stability the same as traditional power generators, without power electronics. This delivers direct resistance to frequency change as opposed to only providing the proposed response of FFR that most existing wind turbine systems expect to offer. WTL's system has been IEC certified by Lloyds Register and has a track-record of more than 600 turbine-years of synchronous wind power operation. The cost-effectiveness and track record of WTL's system differentiate it from a small number of other synchronous wind turbine systems that have been tried. It enables FFR using the wind turbine's spinning mass as well as the direct generator inertia. It also provides the full range of attributes that synchronous generators provide to the grid:

Voltage support through a full range of reactive power capabilities;
System strength by providing huge "fault currents" (5-10 times rated) to rectify voltage faults;
Synchronous condenser mode even with no wind; and
Controllable power level and ramp rates.
WTL welcomes the release last Friday by the Australian Chief Scientist, Alan Finkel, of his final report recommending a range of changes to the Australian electricity market to improve system security. These recommendations include requirements for minimum amounts of inertia and all of the above attributes that synchronous generators have traditionally provided, and WTL's system provides within the wind industry.

WTL's system has recently been extended with a new patented system to enable broad-band variable-speed operation which wind turbines require in lower wind climates. WTL CEO Geoff Henderson stated "Our patent protected technology, which is scalable to both the mid-size and multi-MW turbine market, eliminates use of power electronics and results in significant noise, weight and cost reductions. Further, and as evidenced by demand for renewable energy to assist grid stability, WTL's proven designs and technology are an idea whose time has come." A cursory examination on grid stability makes it abundantly clear that there is market confusion on these issues. Difficulties are now beginning to be apparent in China, EU, Australia and the Pacific Islands which are investing heavily in renewables including solar.

As the world moves to renewable energy, it will become an issue for all nations as the 21st century progresses.

WTL is actively seeking partnerships with wind turbine manufacturers who are at the forefront of wind energy and interested to license WTL's proven drive-train technology.

WTL is also pleased to communicate directly with grid operators, consultants, academics, journalists and other parties interested in issues in grid stability. For further information, please contact or call +64-3-365-8960.

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