A previous post discussed Mitsubishi’s win over GE in the U.S. International Trade Commission (USITC)Â case involving three of GE’s variable speed turbine patents, one front of the competitors’ major wind patent litigation.
The accused products in that case are Mitsubishi’s models MWT 92 and MWT 95 variable speed wind turbines.
In that proceeding, the USITC held in a January 2010 decision that Mitsubishi did not violate U.S. Patents No. 5,083,039, entitled “Variable speed wind turbine” (‘039 Patent), 6,921,985, entitled “Low voltage ride through for wind turbine generators” (‘985 Patent), and 7,321,221, entitled “Method for operating a wind power plant and method for operating it” (‘221 Patent).Â
A more detailed discussion of the asserted patents can be found in a previous post here.
More particularly, the USITC found that Mitsubishi’s turbines did not infringe the ‘039 Patent or the ‘221 Patent, and there was no domestic industry as to the ‘985 Patent.Â
To be enforceable in the USITC, a patent must have a “domestic industry” associated with it. That is, there must be some U.S. activity such as manufacturing, R&D, or licensing of an article that embodies at least one claim of the asserted patent.
GE appealed, and the U.S. Court of Appeals for the Federal Circuit recently affirmed (GE-Mitsubishi_Fed_Cir) the USITC ruling that the ‘221 Patent is not infringed and reversed the determination of no domestic industry as to the ‘985 Patent. Because the ‘039 Patent expired in February 2011, the Federal Circuit vacated the rulings on that patent as moot.
 The Federal Circuit agreed with the USITC that the disputed claim of the ‘221 Patent is limited to resuming current feed to a turbine at the end of a grid disturbance as measured by the current declining to a “predetermined value,” a term that means only current value and does not include a fixed period of time.
Because the Mitsubishi turbines do not measure current or voltage in determining when to resume the feed-in connection, but instead recouple after a pre-set period of time, the Federal Circuit affirmed non-infringement of the ‘221 Patent.
The issue of whether GE has a domestic industry with respect to the ‘985 Patent turned on interpretation of the term a “circuit coupled with the input of the inverter and with the converter controller to shunt current from the inverter and generator rotor” in claim 15 of the patent.
FIG. 4 of the ‘985 Patent shows two inverters (410, 420) which receive power during a low voltage event to keep the wind turbine connected to and synchronized with the power grid.
The critical claim construction question for claim 15 was whether the claim requires the circuit “coupled with the input of the inverter” that shunts current from the inverter be located entirely outside the inverter.
The USITC held that the shunt circuit had to be separate from the inverter; otherwise the circuit could not shunt current from the inverter.
The Federal Circuit disagreed and held that the shunt circuit does not have to be separate from the inverter:
[T]he function of the shunt circuit does not depend on whether the shunt circuit is entirely outside of the inverter, and the ‘985 specification does not require separation of the inverter and the shunt circuit in order for that circuit to be coupled with the input of the inverter and with the converter controller; rather, the term “coupled with” indicates a connection.
With the broader construction of “coupled with” claim 15 of the ‘985 Patent covers the GE turbines, so the Federal Circuit reversed the USITC and found a domestic industry with respect to the ‘985 Patent.Â
The case will now go back to the USITC for further proceedings with respect to the ‘985 Patent.
