GE Patent Rides Through Mitsubishi Attacks


A previous post discussed one of GE’s more recent wind patent infringement suits against Mitsubishi.

Filed in the Northern District of Texas in Dallas, the complaint (gecomplaint.pdf) alleges that Mitsubishi’s 2.4 megawatt wind turbine infringes U.S. Patent Nos. 6,879,055 (’055 Patent) and 7,629,705 (’705 Patent). The ’055 Patent is directed to a two-part base frame for arranging a drive train on the tower of a wind turbine.

The ’705 Patent relates to methods of facilitating zero voltage ride through so the turbine can remain online during voltage dips down to zero volts.

The patented systems and methods include a phase-locked loop (PLL) regulator to receive voltage measurement signals from a plurality of voltage transducers. The PLL regulator includes a PLL that receives the sinusoidal voltage measurement signals.

If a voltage amplitude is outside a pre-determined range, an algorithm within the PLL generates a control signal and the PLL regulator changes to a different mode or state of operation. A plurality of states of operation are possible, with varying parameters such as gain constants.

According to the ’705 Patent:

the plurality of states of operation facilitate zero voltage ride through (ZVRT) as well as other grid faults while also facilitating normal operation.

GE recently survived a motion for summary judgment in which Mitsubishi argued (1) that it does not infringe the ’705 Patent and (2) that the patent is invalid based on a prior sale of the patented technology, lack of enablement of claim 1 of the patent, and that claim 1 is anticipated by a prior art patent application.

The court denied the motion and rejected all of Mitsubishi’s arguments (GE_Order).

Key to the infringement ruling was the court’s prior construction of claim 1 of the ’705 Patent, which requires that the wind turbine be configured to remain connected during and after grid-voltage fluctuations for “an undetermined period of time.” This term was construed to mean “an indeterminable or unknowable period of time.”

Mitsubishi noted that its wind turbine rides through grid disturbances lasting less than a predetermined period of time and disconnects when the disturbance lasts longer than that predetermined time period. Therefore, it argued, the turbine does not literally infringe claim 1 of the ’705 Patent because it does not remain connected during and after fluctuations lasting for “an undetermined period of time.”

However, in construing claim 1, the court also held that the “undetermined period of time” refers to the voltage fluctuation taking place on the grid itself, not the connection between the grid and the wind turbine. Thus, the time period a wind turbine remains connected to the grid is not dispositive of infringement of the ’705 Patent:

As such, the Court has already determined that the claim term “undetermined period of time” does not necessarily foreclose wind turbines that impose limits on the period of time the machine remains connected while the voltage is outside of the predefined range. Therefore, the Court cannot decide as a matter of law that Mitsubishi’s turbines do not infringe the patent literally or under the doctrine of equivalents.

On invalidity, Mitsubishi first argued that GE offered to sell the technology of the ’705 Patent more than a year before filing the patent application. For a patent to be invalid based on a prior sale, the product has to be the subject of a commercial offer for sale, and the invention must have been ready for patenting.

The parties did not dispute that two sales contracts before the critical one-year date were for the later-patented turbines. However, GE showed that pre-critical date descriptions of the invention did not include certain important features of the invention, such as gain and limit values, and later modifications added converter shutdown to the zero voltage ride through methodology.

Accordingly, the court held that Mitsubishi could not show that the technology of claim 1 of the ’705 Patent was ready for patenting and denied the motion for invalidity based on prior sale.

Mitsubishi also came up short on its enablement argument and couldn’t demonstrate that a prior art patent application anticipated the type of connectivity recited by claim 1 of the ’705 Patent.

So this case will move forward, perhaps to trial. This is just one of several suits in a large legal battle between these wind turbine rivals. The disputes also include patent infringement allegations and antitrust claims by Mitsubishi.

Eric Lane is a patent attorney at Luce, Forward, Hamilton & Scripps in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at

About Author

Walter’s contributions to CleanTechies over the past 4 years have been instrumental in growing the publications social media channels via his ongoing editorial and data driven strategies. He is the founder and managing director of Sunflower Tax, a renewable energy tax and finance consultancy based in San Diego, California. Active in the San Diego clean technology community, participating in events sponsored by CleanTech San Diego, EcoTopics, and Cleantech Open San Diego, Walter has also been a presenter at numerous California Center for Sustainability (CCSE) programs. He currently serves as an adjunct professor at the University of San Diego School of Law where he teaches a course on energy taxation and policy.

1 Comment

  1. Good reason why patents need to be extremely limited in the US (and around the world). Consumers lose when 1 company is able to set pricing and eliminate competition.

    Acts 2:44 And all that believed were together, and had all things common; Acts 2:45 And sold their possessions and goods, and parted them to all [men], as every man had need.