PTAB

IPR2018-01563

Vestas-American Wind Technology, Inc. v. General Electric Co.

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1. Case Identification

2. Patent Overview

  • Title: Wind Turbine Generator with Low Voltage Ride-Through Capability
  • Brief Description: The ’985 patent relates to wind turbines with "low voltage ride through" (LVRT) capability, which allows them to remain connected to an electrical grid during grid faults or voltage drops. The technology combines known protective systems, such as current-shunting circuits and blade pitch control, with an uninterruptible power supply (UPS) to ensure these systems remain operational during a low voltage event.

3. Grounds for Unpatentability

Ground 1: Obviousness of Shunt-Circuit Claims - Claims 15-18, 20, and 22-28 are obvious over Feddersen, EON, Nielsen, Patentee's own admissions, and one or more of Rosch, McDowall, and Kasper.

  • Prior Art Relied Upon: Feddersen (Patent 7,015,595), EON (Supplemental Network Connection Rules for Wind Energy Systems), Nielsen (PCT/DK2002/000729), McDowall (an 1999 IEEE publication), Kasper (a 1980 publication on switchgear control), and Rosch (a 1986 PC Magazine article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the "Shunt-Circuit Claims" recite a wind turbine with a circuit to shunt excess current from the inverter, controlled by a controller that is backed by a UPS. Feddersen was cited to teach a doubly-fed induction generator (DFIG) wind turbine that includes a "power-dissipating element" (e.g., a brake chopper) to shunt excess current from the inverter and generator rotor during abnormal states, such as a grid fault. This element is controlled by a computerized "converter processor." The remaining references (Rosch, McDowall, Kasper) were presented as teaching the widespread and long-standing practice of using a UPS (such as a battery or capacitor bank) to provide reliable backup power to critical control systems, including computerized controllers for industrial equipment, during power failures or undervoltage conditions.
    • Motivation to Combine: The primary motivation asserted was the need to comply with then-contemporary grid codes, such as the EON rules from 2001. These codes mandated that wind turbines remain connected to the grid during severe low-voltage events, with voltage dropping as low as 15% of nominal for specified durations. Petitioner contended that a person of ordinary skill in the art (POSA) would be motivated to ensure the operability of protective systems, like the shunt circuit in Feddersen, to meet these requirements. Combining Feddersen’s computerized control system with a standard UPS as taught by Rosch, McDowall, or Kasper was argued to be an obvious design choice to ensure the protective shunt circuit could function during the very low-voltage events it was designed to handle.
    • Expectation of Success: Petitioner asserted a POSA would have had a high expectation of success. The combination involved applying a well-known solution (a UPS) to power a known component (a controller for a shunt circuit) to solve a known problem (maintaining operation during a power loss). The result would have been predictable: the shunt circuit would continue to operate during a low-voltage event, as intended.

Ground 2: Obviousness of Hybrid Claims - Claims 9-11, 21, 46-63, and 65-69 are obvious over Feddersen, Cousineau, EON, Nielsen, Patentee's own admissions, and one or more of Rosch, McDowall, and Kasper.

  • Prior Art Relied Upon: Cousineau (Patent 6,265,785), in addition to the references cited in Ground 1.
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the "Hybrid Claims" add a UPS-backed blade pitch control system to the features of the Shunt-Circuit Claims. The petition asserted that Feddersen already disclosed the use of both a current-shunting circuit and a blade pitch controller to manage energy and rotor speed during abnormal conditions. Cousineau was cited for its explicit teaching of an apparatus for overspeed detection that uses a "secondary power source" (a UPS, such as a battery) to power a blade pitch control system for aerodynamic braking during a power outage. This prevents the turbine from accelerating to unsafe speeds when the grid connection is lost.
    • Motivation to Combine: The motivation again stemmed from the need to comply with LVRT grid codes like EON. A grid fault creates two main problems: excess current (addressed by the shunt circuit) and rotor acceleration due to the loss of electrical load (addressed by pitch control). Petitioner argued a POSA would be motivated to address both problems simultaneously using the known solutions taught in the art. Feddersen already combined both control systems. To ensure both systems would work during a low-voltage event, a POSA would obviously power both with a UPS. Cousineau explicitly teaches powering the pitch control system with a UPS to handle overspeed during a power outage, the very condition that occurs during an LVRT event.
    • Expectation of Success: Success was argued to be highly predictable. A POSA would be combining known solutions (shunt circuit, pitch control, UPS) according to their established functions to solve the known, multifaceted problem of riding through a grid fault.

4. Key Claim Construction Positions

  • "turbine controller": Petitioner argued this term should be construed broadly to comprise one or more circuits, microprocessors, or logic implementations that control any of the wind turbine's electromechanical systems (e.g., power converter, pitch system, cooling system). It does not require a single, monolithic structure.
  • "circuit coupled with the input of the inverter ... to shunt current from the inverter": Petitioner noted that the Federal Circuit had previously construed this term in the context of claim 15. The construction requires the circuit to be coupled to the inverter's input and the converter controller to shunt current from the inverter and rotor, but it does not limit the placement of the shunting circuitry to a location entirely external to the inverter. Petitioner adopted this construction for the petition.

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 Patent 6,921,985 as unpatentable.