Patent Description:
Wind farms include wind turbines spread over a large area of land that harness wind energy to generate power for utility purposes. Wind farms are coupled to a grid with each farm expected to provide a predefined or forecasted amount of power at a fixed power rating to the grid. However, due to the uncontrollable variations in the wind energy, such as wind speed, it is difficult to continuously provide the predefined amount of power at the fixed power ratings, and there is always some difference between the power supplied from the wind farm and the predefined amount of power.

One approach for compensation in a situation where a wind farm is unable to supply the required power is to buy power either neighboring control areas or reserve generators. Another approach is to use supplementary energy storage in the wind farm. However, each of the approaches increases cost of power generated by the wind farms and thus results in higher costs to consumers or losses to power generation organizations. For example, the use of supplementary energy storage creates additional installation, operating, and maintenance costs.

Document <CIT> relates to a method, system and computer program product that enhances the commercial value of electrical power produced from a wind turbine production facility. The document includes the use of a premier power conversion device that provides an alternative source of power for supplementing an output power of the wind turbine generation facility when lull periods for wind speed appear.

Hence, there is a need for an improved system to address the aforementioned issues.

Hence the present invention, as defined by the appended claims, is provided.

Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:.

Embodiments of the present invention include a system for wind power dispatch that includes a wind farm controller that controls operations of wind turbines in a wind farm and regulates real time power output of the wind farm. The system also includes a wind power dispatch management system that further includes a transient wind farm reserve management system which estimates a transient wind farm reserve in the wind farm. The wind power dispatch management system also includes a storage reserve management system that estimates a storage reserve in the wind farm. The wind power dispatch management system further includes a controller that computes a difference between a predefined power output and a real time power output of the wind farm and dispatches the transient wind farm reserve to reduce the difference or, if the transient wind farm reserve is insufficient to reduce the difference, the controller additionally or alternatively dispatches the storage reserve to reduce the difference.

<FIG> is a schematic representation of a wind farm <NUM> including a wind power dispatch management system <NUM> situated inside a wind farm controller <NUM> in accordance with an embodiment of the invention. The wind farm <NUM> includes multiple wind turbines <NUM>, and each wind turbine <NUM> individually generates wind power from wind energy available at the respective wind turbine <NUM>. Each of the wind turbines <NUM> are coupled to a respective power converter <NUM> that converts the wind power generated by the wind turbines <NUM> to a usable power that may be transmitted to a power grid <NUM>. Each of the wind turbines <NUM> is coupled to the power grid <NUM> through the power converter <NUM> and transmits the usable power converted by the respective power converters <NUM> to the power grid <NUM> as represented by solid lines with reference numeral <NUM>. The amount of wind power generated by a respective wind turbine <NUM> depends on the wind energy available at the location of the respective wind turbine <NUM>, as the wind speed may vary at different locations in the wind farm <NUM>.

The wind turbines <NUM> are communicatively coupled to the wind farm controller <NUM> that controls the operations of the wind turbines <NUM> (as represented by dashed lines with reference numeral <NUM>) based on various requirements and inputs provided by sensors and/or an operator (not shown). Although a control unit is illustrated as the wind farm controller <NUM> in <FIG> for purposes of example, in some embodiments each wind turbine has a local controller that is coupled to a central or supervisory controller. As used herein "controller" may include either single control unit or multiple control unit embodiments. The wind farm controller <NUM> is coupled to the wind power dispatch management system <NUM> that controls the amount of wind power generated by the wind turbines <NUM> to meet the power grid requirements such as power schedule submitted to the power grid at any given moment. In the embodiment of <FIG>, the wind power dispatch management system <NUM> is situated within the wind farm controller <NUM>; however, the wind power dispatch management system <NUM> may alternatively be situated outside the wind farm controller <NUM> as represented in <FIG>.

<FIG> is a schematic representation of the wind farm <NUM> depicting control signals used by the wind dispatch management system <NUM> for controlling the wind power dispatch in the wind farm <NUM> in accordance with an embodiment of the invention. In the embodiment of <FIG>, the wind power dispatch management system <NUM> is coupled to a forecasting processor <NUM> that forecasts a wind speed for a predefined interval of time and supplies the forecasted wind speed to the wind power dispatch management system <NUM>. The forecasting processor <NUM> may be communicatively coupled to a remote meteorological station <NUM> and receive weather information from the meteorological station <NUM> to forecast the wind speed for the predefined intervals. Alternatively, the forecasting processor <NUM> may receive wind speed forecasting information from an external source. In one embodiment, the predefined intervals include time periods ranging from about <NUM> minutes to about <NUM> minutes. Since the wind speed may be different at different locations in the wind farm <NUM>, the forecasting processor <NUM> in one embodiment may forecast the wind speed individually for at least some wind turbines <NUM> in the wind farm <NUM> based on the locations of the wind turbines <NUM> in the wind farm <NUM>. The forecasting processor <NUM> transmits the forecasted wind speed or speeds to the wind power dispatch management system <NUM> that is communicatively coupled to each of the wind turbines <NUM> and computes a real time power output generated by the wind farm <NUM>. The wind power dispatch management system <NUM> also determines a transient wind farm reserve <NUM> and a storage reserve <NUM> by communicating with each of the wind turbines <NUM> in the wind farm <NUM>.

The transient wind farm reserve <NUM> may comprise a reserve power available by using the kinetic energy of the wind turbines <NUM>.

In one embodiment, the storage reserve <NUM> includes an energy storage medium <NUM> such as a battery. The energy storage medium <NUM> may be a centralized energy storage medium <NUM> for the entire wind farm <NUM> or may include plurality of energy storage mediums <NUM> coupled locally to respective wind turbines <NUM>.

The wind power dispatch management system <NUM> computes a difference between the predefined power output and the real time power output. As used herein "predefined" power output may be constant or variable and means the power output that is required by the grid or any load drawing power from the wind farm. Based on the difference, the wind power dispatch management system <NUM> dispatches the transient wind farm reserve <NUM> to reduce the difference or, if the transient wind farm reserve <NUM> is insufficient to reduce the difference, the wind power dispatch management system <NUM> additionally or alternatively dispatches the storage reserve <NUM> to reduce the difference. The difference between the predefined power output and the real time power output includes a positive difference and a negative difference. During situations where the difference is negative, the wind dispatch management system <NUM> transmits a control signal to the storage reserve <NUM> to absorb the differential power. In some situations where the negative difference is greater than the storage reserve capability and the excess power generated by the wind turbines <NUM> cannot be stored in the energy storage mediums <NUM>, the wind turbines <NUM> may be curtailed, and the curtailed wind turbines then form a part of the wind farm reserve <NUM> as discussed below.

<FIG> is a schematic representation of the wind farm <NUM> including a detailed view of the wind power dispatch management system <NUM> coupled to the wind farm controller <NUM> in accordance with a more specific embodiment of the invention. The wind power dispatch management system <NUM> includes a transient wind farm reserve management system <NUM>, a storage reserve management system <NUM> and a dispatch controller <NUM> coupled to management systems <NUM> and <NUM>.

In one embodiment, the transient wind farm reserve management system <NUM> estimates a transient wind farm reserve <NUM> in the wind farm <NUM> by estimating the reserve power that may be generated by temporarily enhancing the power output of the wind turbines <NUM>. The transient wind farm reserve management system <NUM> may also schedule and distribute the power in the wind farm. In one exemplary embodiment, the power output of the wind turbines <NUM> may be enhanced by using a wind boost control mechanism to provide the reserve power. The wind boost control mechanism enables the wind turbines <NUM> to temporarily improve their operations depending on the wind speed and other site atmospheric conditions. The reserve power generated by enhancing the power output of the wind turbines <NUM> varies as a function of total wind farm power output and wind direction and may be averaged over all wind directions using a uniform wind rose, wherein the term "wind rose" is defined as a graphic tool used by meteorologists to give a succinct view of how wind speed and direction are typically distributed at a particular location.

The transient wind farm reserve management system <NUM>, according to the current invention, estimates the reserve power that may be generated by using the kinetic energy of the rotors (not shown) of each of the wind turbines <NUM>. According to the invention, the reserve power may be generated by the kinetic energy of the rotor by using an inertia control mechanism. Short term under-frequency deviations in the wind turbine <NUM> require wind turbines <NUM> to increase real power output to reduce the frequency dips. The wind inertia control mechanism utilizes the mechanical inertia of the rotor to provide a temporary increase in electrical power output over a short period of time. The transient wind farm reserve management system <NUM> is designed to recognize under-frequency events and utilize active power controls to command reserve power in the wind farm <NUM>.

In addition to estimating the reserve power that may be generated by enhancing the power output of the wind turbines <NUM> and the reserve power that may be generated by using the kinetic energy of the rotors of each of the wind turbines <NUM>, the transient wind farm reserve <NUM> may also include another power reserve that is generated by wind turbines <NUM> which are not fully operational in the wind farm <NUM> at a given instant. One such approach to provide the reserve power is wind reserve control mechanism. The wind reserve control approach includes one or more reserve wind turbines <NUM> that are not operated or are operated at less than full power if the wind farm <NUM> is operating at a rated power. Such turbines <NUM> are referred to as reserve turbines. During normal operations, when there is little or no difference between the predefined power output and the real time power output at the wind farm level, the reserve turbines <NUM> are either not operated or are operated at a curtailed mode. The transient wind farm reserve management system <NUM> may estimate the reserve power that may be generated by the reserve turbines <NUM> based on the wind speeds provided by the forecasting processor <NUM>.

The transient wind farm reserve management system <NUM> estimates the total wind farm reserve <NUM> based on the various above mentioned estimated reserve powers and transmits the wind farm reserve power <NUM> to the controller <NUM> in the wind power dispatch management system <NUM>.

The wind power dispatch management system <NUM> also includes the storage reserve management system <NUM> that estimates the storage reserve <NUM> in the wind farm <NUM>. In one embodiment, the storage reserve <NUM> may include energy storage mediums <NUM>. In more specific embodiment, the energy storage mediums <NUM> include batteries. In another embodiment, the storage reserve <NUM> may also include power generators (not shown) that may provide supplementary power to the wind farm <NUM>. The storage reserve management system <NUM> communicates with the energy storage mediums <NUM>, estimates the reserve power available in the energy storage mediums <NUM>, and transmits the estimated storage reserve <NUM> to the controller <NUM>.

The controller <NUM> receives the estimated transient wind farm reserve <NUM> and the estimated storage reserve <NUM> from the transient wind farm reserve management system <NUM> and the storage reserve management system <NUM> respectively. The controller <NUM> based on the computed difference between the predefined power output and the real time power output sends a wind reserve control command <NUM> to the transient wind farm reserve management system <NUM> to dispatch the wind farm reserve <NUM> for reducing the difference. In a specific embodiment, the controller <NUM> may generate a more specific command or commands to enhance the power output of the wind turbines <NUM>, the reserve power available by using the kinetic energy of the wind turbines <NUM>, and/or the reserve power that is available by using one or more curtailed wind turbines <NUM>. In a more specific example, the controller <NUM> first chooses the power reserve that is generated by wind turbines <NUM> which are curtailed in the wind farm <NUM> at the given instant to reduce the difference and, if the difference is more than the power reserve that is generated by wind turbines <NUM> which are curtailed in the wind farm <NUM>, the controller <NUM> then chooses to generate reserve power by enhancing the power output of the wind turbines <NUM>. And/or, if the power from the curtailed wind turbines is insufficient, the controller <NUM> may choose to generate the reserve power available by using the kinetic energy of the wind turbines <NUM>. In situations, where the difference between the predefined power output and the real time power output is more than the transient wind reserve <NUM>, the controller <NUM> additionally or alternatively sends a storage reserve control command <NUM> to the storage reserve management system <NUM> to dispatch the storage reserve <NUM> to further reduce the difference.

<FIG> is a flow chart representing steps involved in a method <NUM> for dispatching wind in a wind farm in accordance with an embodiment of the invention. The method <NUM> includes forecasting a wind speed in step <NUM>. According to the invention, forecasting the wind speed comprises forecasting the wind speed for a predefined interval wherein the predefined interval comprises a time period ranging from about <NUM> minutes to about <NUM> minutes. In another embodiment, forecasting the wind speed comprises forecasting the wind speed based on weather information received from a meteorological station. In a specific embodiment, forecasting the wind speed comprises individually forecasting the wind speed for at least some wind turbines in the wind farm. The method <NUM> also includes determining a transient wind farm reserve based on the forecasted wind speed in step <NUM>. The method <NUM> further includes determining a storage reserve in the wind farm in step <NUM>. In one embodiment, determining the storage reserve comprises computing a reserve power available in the storage reserve wherein the storage reserve comprises either one of a centralized energy storage medium for the wind farm or a plurality of local energy storage mediums each coupled to a respective one of the wind turbines. The method <NUM> also includes computing a difference between a predefined wind farm power output and a real time power output in step <NUM> and dispatching the transient wind farm reserve to reduce the difference or, if the transient wind farm reserve is insufficient to reduce the difference, additionally or alternatively dispatching the storage reserve to reduce the difference in step <NUM>.

Claim 1:
A wind power dispatch system comprising:
a wind farm controller (<NUM>) for controlling operation of wind turbines (<NUM>) in a wind farm (<NUM>) and regulating real time power output of the wind farm (<NUM>); and
a wind power dispatch management system (<NUM>) including a transient wind farm reserve management system (<NUM>), the transient wind farm reserve management system (<NUM>) being configured to estimate a transient wind farm reserve (<NUM>) based on a forecast of the wind speed for a predefined interval and estimated powers generated by using the kinetic energy of a rotor of one of the wind turbines (<NUM>) using an inertia control mechanism in an under-frequency event, the wind power dispatch management system (<NUM>) being configured for computing a difference between a predefined power output and the real time power output and dispatching the transient wind farm reserve (<NUM>) to reduce the difference or, if the transient wind farm reserve (<NUM>) is insufficient to reduce the difference, additionally or alternatively dispatching a storage reserve (<NUM>) to reduce the difference.