Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
2001-04-23
2003-01-28
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S286000, C705S412000, C290S044000, C290S055000
Reexamination Certificate
active
06512966
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a system, method and computer program product that relates to a renewable power production facility, such as a wind turbine generated power production facility that produces electrical power that is applied to a power grid. More specifically, the present invention is directed to systems, methods and computer program product for enhancing the commercial value of electric power produced by wind turbine facilities so as to make that electric power as commercially valuable and fungible as electric power produced by other plants such as fossil fuel power plants, hydroelectric plants, nuclear plants and the like.
2. Discussion of the Background
Wind power is a “natural” power production source that instinctively should be regarded as an optimum source of energy for producing electric power. Wind power does not require the burning of fossil fuels, does not result in nuclear waste by-products, does not require the channeling of water sources, and does not otherwise disturb the environment. On the other hand, wind power is a variable (stochastic) power generation source, thus not offering power production facilities the type of control that the power production and grid facility would like to have in producing commercially reliable power. To address this variability issue, even the early pioneers of wind power attempted to identify ways to “store” wind generated electric power in times of excess, so as to later compensate for times when there are lulls in the wind. For example, Poul La Cour (1846-1908) from Denmark, was one of the early pioneers in wind generated electricity. Poul La Cour built the world's first electricity generating wind turbine in 1891. This design included DC generators and stored energy as hydrogen. Poul La Cour was concerned with the storage of energy because he used the electricity from his wind turbines for electrolysis in order to produce hydrogen for the gas lights in his school. This concept of energy storage has not been abandoned and even modem inventors of wind turbine electric generation facilities are still trying to identify ways to use physical media to store the energy produced by windmills (see e.g., U.S. Pat. No. 5,225,712, which uses fuel cells, batteries, and the like as physical media to store electrical power). In the early days, wind energy plants were generally isolated from one another and provided small scale generation facilities. Through a variety of experiments wind energy plants have generally evolved and now a common theme is to group a number of wind turbines together so as to form farms that can generate up to tens of megawatts via the aggregation of smaller plants that produce slightly above only one megawatt each Most modern rotor blades on large wind turbines are made of glass fiber reinforced plastics (GRP). These wind power plants are today planned to grow slightly above three megawatts per unit, limited by a reliable size of the wind turbine, (the “propeller”).
A perplexing task that has somewhat stifled the use of wind power plants is that there has been no commercially viable way, in light of the price of fuel generated by other power plants, to effectively store electricity generated by windmills during periods of peak production, so as to make up for periods when the wind slows. As a consequence, the capital cost, lack of production control, size, and reliability problems limited the proliferation of such wind plants between the periods of 1890 and 1970. As a consequence, the use of wind power declined sharply both with the spread of steam-engines and with the increase in scale of electrical power utilization. Thus, windmills generally were only limited for small scale processes and were unable to compete with large scale steam powered electrical power facilities. Furthermore, the commercial cost of such wind-generated power was much greater compared to those with generating systems based on coal, oil, gas and hydro.
Nevertheless, being strong advocate for windmills, Denmark pioneered the effort between the era of 1970 and 1985 to bring back windmill technology in an attempt to make windmill generated electricity a mainstay of modern electric generation plants. To this end, Denmark established some rules regarding grid connections from the windmills, (e.g., Specifications for Connecting Wind Farms to the Transmission Network”, ELTRA I/S ELT 1999-411a, as well as Swedish documents TAMP-1122400 and DAMP-1101300, Sv. Elverksforeningen, the entire contents of which being incorporated herein by reference).
As recognized by the present inventors, there are several drawbacks associated with using wind power systems. First, it should be recognized that there is a strict frequency control on the AC power that is provided to the grid. For example, in the power grid in Europe, the AC frequency is held generally constant at 50 hertz, with an attempt to maintain a maximum frequency variation between plus or minus 0.1 hertz. This means that there must be a continuous balance between the input of energy and the output of electrical power in such an AC system. If consumption is greater than production, the grid frequency drops. If production is greater than consumption, the grid frequency rises. Thus, power companies that provide power to the electric grid must be coordinated so that those adding power are doing so at a time when the demand for that power exists, and also is done in coordination with other providers. While there is a system that is employed to coordinate the activities of different power producers as will be discussed with respect to
FIGS. 2-4
, the present discussion will now focus on conventional wind turbine electrical power production facilities so as to further explain conventional practice for how to design such facilities.
A number of different options have been attempted to make wind turbine generated power facilities more reliable and predictable, thus “more mainstream as compared to other power production facilities. In a first typical windmill power generation facility, an asynchronous machine is used that acts as a generator but also inherently consumes reactive power from the AC grid. Consequently, the facility employs a fixed capacitor bank so as to compensate the amount of reactive power that is consumed, thus providing for a more reasonable power factor (cosine of the angle between current and voltage). However, as recognized by the present inventors, there is a risk with such systems, namely where the capacitor bank causes the system to become self-magnetized thus causing the frequency to differ by as much as tens of hertz from the standard oscillation frequency after a fault occurs.
Many wind power plants are erected with a speed adaptation mechanism (usually a gearbox) between the wind turbine and the electric generator so that an AC frequency produced by the wind turbine generator matches that of the power grid. These systems use a mechanical gearbox to increase the speed of the generator shaft. However, the use of this mechanical gearbox increases the cost by three to five times the cost of the generator, also having dramatic increases in the mean time between failure, and mean time to repair of the device, thus not making these designs commercially competitive with the more reliable and less costly fossil fuel power production facilities.
Some windmill-based systems attempt to address power quality aspects at the grid connection, which often manifest themselves as a tower shadow that provides a low-frequency periodic disturbance. This low-frequency periodic disturbance is referred to as “flicker” (e.g. about a 1 hertz variation) that provides for an inconsistent wavering light or power production. These facilities provide static-VAR compensators (SVC) or local energy storage units to provide compensation power.
More elaborate schemes have been developed to make wind-power more competitive with other types of power in the market. Once again the systems are based on the use of energy storage.
FIG. 1
is an
Andren Lars Anders Tommy
Gertmar Lars Gustaf Ingolf
Lof Per-Anders Kristian
ABB AB
Jarrett Ryan
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Picard Leo
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