Enercon v. Kenetech Windpower Inc.

Ben ElkinUC Berkeley – Bioengineering 2011

IE0R 190GNovember 17, 2008

A case about variable speed wind turbines

Parties Involved

• Enercon-Third largest manufacturer of wind turbines in the world-As of November 2008, has over 13,000 turbines installed (15.5 GW power)-Tried to export their E-40 design to the U.S in 1993-1994, contracting with

New World Power Corp (NWP)

• US Int’l Trade Commission-The US ITC provides trade expertise to legislative/executive branches of

government on unfair trade practices including patent, trademark, and copyright infringement

-Independent, non-partisan federal agency

Development-1993: NWP writes Enercon to request price quote for E-40 model-August 1993, Enercon responds with specific price per turbine. States that

deal remains open until March 31, 1994, signed by Enercon officers.-February 1994, NWP submits bid for project in Texas, using E-40 turbines

-Kenetech Windpower Inc, a large US company dealing in windpower-Filed complaint with US ITC, claiming that Enercon’s E-40 turbine infringed

on its existing patent, 5,083,039 (‘039), claim 131.-Patent concerns a method of converting wind power into electrical power

that is usable by a utility company.

TechnologyBackground

-A wind turbine converts wind energy into electrical energy using a wind-driven turbine in combination with an alternating current (AC) induction generator

-In variable speed turbine, frequency of generated power waveform depends on wind speed/strength

-In North America, electrical utilities deliver power at 60 Hz

1) Variable turbine’s frequency (cycles/sec) must match grid’s for optimal power output

2) Also, the wave’s phases (max and min) must match, add constructively

-When waves for both voltage and current are in phase, all of the generator’s power is composed of “real” or usable power

-If the waveforms are out of phase, some of the power is lost, NOT ideal.-The degree to which the waves are out of phase is referred to as the “power

factor angle”

Complications-Inductive loads on a power grid can pull the current wave out of phase with

the voltage waveform. This occurs when a voltage wave reaches is peak before that of the AC current

-It is desirable to pre-correct this distortion by providing a wave that either leads or lags the waveform on the utility grid

Patent ‘039, Claim 131“131. A method for converting electricity generated by a variable speed wind turbine into fixed

frequency output electricity, wherein the wind turbine includes a generator and means for supplying generated electricity to power converter that includes a switched inverter supplying the output electricity, the method comprising the steps of:

forming a reference waveform; rotating the reference waveform by a selected power factor angle to yield a template waveform; using the template waveform to define desired output currents; and controlling the switched inverter to produce output currents corresponding to the desired output

currents.”

In English:The goal is to manipulate the current and voltage wave outputs from the

power converter. First, a reference wave is formed by sampling the waveform on the grid. Claim 131 rotates this wave by a power factor angle to generate a template, model waveform. Then, a switched inverter controls the output wave from the power converter to match the template as closely as possible

Process-Variable frequency AC from generator to direct current

(DC) using a power converter

-Power converter also switches DC back to AC, fixing frequency

-An inverter control unit supplies power to utility grid with an adjustable phase

-The power factor angle is adjusted so that the current supplied by the generator is in phase with utility voltage

-The current’s phase can be adjusted to lead or lag the voltage to compensate for inductive loads on grid

Schematic of the entire system:-Measures wind speed-Inverts current AC ---> DC ---> AC-Filters to appropriate frequency and phase-Exports energy to power grid

Case-The parties’ primary dispute was over the construction of the word “rotating”

-All parties agree that the process of “rotating” a waveform results in a phase shift in a plot against time

-Enercon argues that this term in Claim 131 is limited to a special type of phase shift – a so-called “rotational transformation”

-In trying to demonstrate what the word “rotate” means to one skilled in the art, Enercon submitted references that contain prior art to limitations of Claim 131

Decision – Oct 1996

-ITC had jurisdiction under Section 337 of the Tariff Act of 1930 (ammended 1994), based on Kenetech’s complaint. In particular, this section requires a “sale for importation” before the ITC can step in. Enercon’s involvement with NWP rendered it applicable.

-In past cases, the court has repeatedly states that while claims are construed in light of the specification, they are not necessarily limited by it

-The specification is read to use the terms “rotate” and “shift” interchangeably

-There was no evidence to indicate that the term “rotate” refers to the specialized (Kenetech) method of performing a phase shift by “rotational transformation”

Analysis-Enercon might have had a better case if they vetted their material more

closely, making sure no prior art was involved.-For all practical purposes, a phase shift and a rotation are interchangeable

when discussing sinusoidal functions. -Use more green energy!

Questions?

References• http://altlaw.org/v1/cases/1353130

• http://www.google.com/patents?id=CuIiAAAAEBAJ&printsec=abstract&zoom=4

• http://en.wikipedia.org/wiki/Enercon

• http://www.windenergy.com/news/news_Renewable_Energy_World_4-13-08.html