PTAB

IPR2018-01563

Vestas American Wind Technology Inc v. General Electric Co

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Wind Turbine Generator Low Voltage Ride-Through
  • Brief Description: The ’985 patent relates to wind turbine generators with "low voltage ride through" (LVRT) capability, which allows them to remain connected to an electrical grid during grid fault events. The technology uses an uninterruptible power supply (UPS) to provide backup power to critical control systems, such as current-shunting circuits and blade pitch controllers, ensuring their operation when grid voltage drops.

3. Grounds for Unpatentability

Ground 1: Obviousness of Shunt-Circuit Claims

Claims 15-18, 20, and 22-28 are obvious over Feddersen, EON, Nielsen, and one or more of Rosch, McDowall, and Kasper.

  • Prior Art Relied Upon: Feddersen (Patent 7,015,595), EON (2001 network connection rules publication), Nielsen (WO application PCT/DK2002/000729), Rosch (PC Magazine, May 1986), McDowall (1999 IEEE publication), and Kasper (1980 publication).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Feddersen disclosed a wind turbine with a power-dissipating element (a shunt circuit) controlled by a converter processor to handle excess current during "abnormal states." Petitioner asserted that a person of ordinary skill in the art (POSITA) would understand these abnormal states to include low-voltage grid faults, a known problem detailed in references like Nielsen. The dependent claims, which specified using a crowbar circuit or a UPS comprising a battery or capacitor, were described as reciting well-known, conventional components for these functions.
    • Motivation to Combine: The primary motivation was the strong economic and regulatory pressure to comply with then-contemporary grid codes, such as those published by EON. These codes mandated that wind farms remain connected to the grid during severe voltage drops (e.g., down to 15% of nominal voltage). A POSITA would have been motivated to implement Feddersen’s known overcurrent protection system and ensure its functionality during a grid fault by powering its computerized controller with a standard UPS, a common solution for ensuring the reliability of electronic systems taught by Rosch, McDowall, and Kasper.
    • Expectation of Success: A POSITA would have had a high expectation of success because the combination involved applying a conventional, commercially available solution (a UPS) to power a known type of control system during a predictable event (power loss from a grid fault). The outcome—maintaining control over the shunt circuit—was a predictable result of combining these known elements.

Ground 2: Obviousness of Hybrid Claims

Claims 9-11, 21, 46-63, and 65-69 are obvious over the combination for Ground 1, further in view of Cousineau.

  • Prior Art Relied Upon: Feddersen (Patent 7,015,595), Cousineau (Patent 6,265,785), EON (2001 publication), Nielsen (WO application), and one or more of Rosch, McDowall, and Kasper.
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed the "Hybrid Claims," which added the limitation of a UPS-backed blade pitch control system to the shunt-circuit features from Ground 1. Petitioner argued that Feddersen already disclosed a turbine that used both a shunt circuit and a blade pitch controller as two complementary systems for managing excess energy. The incremental feature—powering the pitch control system with a UPS—was explicitly taught by Cousineau, which disclosed using a "non-volatile power source" (like a battery or capacitor) to power an aerodynamic braking system (i.e., pitch control) to prevent rotor overspeed during a power outage.
    • Motivation to Combine: A POSITA seeking to create a comprehensive LVRT solution to meet EON’s requirements would be motivated to address both known consequences of a grid fault: high currents (managed by the shunt circuit) and rotor overspeed (managed by pitch control). Since Feddersen already taught using both systems, and Cousineau taught that powering the pitch control system with a UPS was an effective way to handle overspeed during power loss, a POSITA would combine these teachings. The motivation was to create a robust system that could manage both electrical and mechanical stresses during a grid fault, thereby ensuring the turbine could remain connected to the grid as required.
    • Expectation of Success: The combination was a predictable aggregation of known solutions to solve distinct aspects of a single, well-understood problem. Since using a UPS to power critical control systems was a known technique, applying it to both the shunt circuit controller and the pitch controller in Feddersen’s turbine would have been a straightforward design choice with a predictable outcome.

4. Key Claim Construction Positions

  • "turbine controller": Petitioner argued this term should be construed to mean "at least one or more circuits, microprocessors, or other implementations of digital or analog logic that control the operation of one or more of the wind turbine's electromechanical systems." This construction was asserted to be important because prior art like Feddersen disclosed functionally-related but physically distributed control units (e.g., a main controller, power controller, and pitch controller) that collectively perform the claimed control function, rather than a single, monolithic controller.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 9-11, 15-18, 20-28, 46-63, and 65-69 of the ’985 patent as unpatentable under 35 U.S.C. §103.