The General Electric Company (GE) is the U.S. leader in installed wind capacity, and patent enforcement plays a part in that success. Earlier this month GE sued Mitsubishi in the Southern District of Texas, alleging that its Japanese competitor’s 2.4MW turbine models infringe U.S. Patent Nos. 5,083,039 (’039 Patent), 6,921,985 (’985 Patent) and 7,321,221 (’221 Patent).
The complaint (ge_complaint.pdf) cites the sale and installation of Mitsubishi’s turbines at the Penascal and Gulf Wind wind farms in Kenedy County, Texas as infringing activities.
The asserted patents relate to energy conversion and control technology for wind turbines. The ’039 Patent, which issued back in 1992, is directed to a variable speed wind turbine that provides responsive control of generator torque. The patented turbine controls the torque reacted by the generators (16, 18) by controlling the stator currents or voltages and basing commands on turbine performance parameters.
Shaft speed sensors (42, 44) monitor the rotor speed of the generators and supply rotor speed information to the generator controllers (38, 40) and to a torque command device (46). Specifically, the torque command device (46) monitors wind turbine performance parameters and sends torque control signals to the generator cotrollers (38, 40) and pitch angle control signals to a pitch control unit (48).
The ’985 Patent is directed to a wind turbine that includes a blade pitch control system and a turbine controller coupled with the blade pitch control system. To increase the reliability of the turbine’s power supply, the turbine controller causes the blade pitch control system to vary pitch in response to transitions between different power sources.
The ’221 Patent is directed to improved methods for stabilizing the supply voltage to a wind turbine after voltage drops without jeopardizing the electrical components of the turbine. According to the ’221 Patent, a key step in the patented method is to resume feeding of the rotor current after variations in voltage amplitude cause decoupling of the feed-in unit.
This lawsuit appears to be the second part of a two-pronged strategy to enforce these patents against Mitsubishi. As mentioned in the complaint, GE obtained an initial favorable decision from the U.S. International Trade Commission (ITC) that Mitsubishi had not successfully challenged the validity and enforceability of these patents and that the accused wind turbines infringe the patents (ge_itc_initial_determination.pdf) (see the CleanIP blog post here).
The ITC action and this new federal court case squeeze Mitsubishi both with respect to importation of its turbines at the U.S. border and as to domestically produced equipment.