Methods for coupling an energy storage system to a variable energy supply system

#This invention relates generally to energy storage systems, and more particularly, methods and apparatus for coupling an energy storage system to a variable energy supply system.

#At least some known wind generation systems produce a fluctuating or intermittent power output due to the variability of wind speed. When multiple generators are electrically coupled together, i.e. in arrangements known as wind farms, the fluctuation in total power output may be reduced. Under ideal conditions the variations of power output will decrease at a factor of 1/√{square root over (n)}, where n represents the number of wind generators coupled together. In areas where wind penetration may be high, coupling a large number of generators generally reduces the overall power fluctuations on a system wide basis, but may still cause power swing stability concerns. Generally the volatile nature of wind generation output limits the amount of wind generation that can be connected to the grid without causing voltage stability problems. As such, wind power generation is generally considered a non-firm resource for system planning purposes.

#It is well known that the demand for electric power fluctuates. Normally power fluctuations occur on a relatively regular basis. For example, in a typical residential electric power grid, generally demand for electric power is low at night, peaks during the morning, levels out during the day, and peaks again in the late afternoon. However, there are circumstances where the demand for electric power suddenly and irregularly increases. From the perspective of an electric power utility company, the associated increase in electric power demand occasioned during such occasions may be difficult to accommodate because the electric power demand are generally short lived.

#FIG. 1 is a schematic view of an exemplary wind turbine power system.

#FIG. 2 is a schematic view of an exemplary wind turbine power system including an energy storage system.

#FIG. 3 is a schematic view of an exemplary embodiment of a multiple wind turbine power system.

#The present invention is directed to a vanadium-based reduction/oxidation (redox) regenerative energy storage system that converts chemical energy into electrical energy for use with wind generation systems. While the invention is described and illustrated in the context of a wind turbine power system, the invention is not limited to wind turbine power systems. The embodiments set forth herein are therefore exemplary only and represent various embodiments of the invention, but are not conclusive of all embodiments. As explained below, these embodiments contribute towards allowing power generating systems to store energy, as well as, provide supplemental power to an electric power grid during demand peaks or store during off-peak times.

#FIG. 1 is a schematic of a wind turbine power system 10 including a wind turbine generator 12 coupled in electrical communication with a power utility grid 14. In the exemplary embodiment, wind turbine generator 12 provides power to grid 14 via a bus 16 including a grid interface unit 18 and a grid interface unit 20. Wind turbine generator 12 also provides power for a critical load 22 coupled in series to bus 16 via a grid interface unit 24. In the exemplary embodiment, wind turbine generator 12 is a 2.7 MW wind turbine generator, bus 16 is a 1100 VDC common DC bus, grid interface device 18 is a 2.7 MW AC/DC inverter, grid interface device 20 is a 3 MVA bidirectional AC/DC, DC/AC inverter, and grid interface 24 is a 100 KW DC/AC inverter. While system 10 is efficient during high wind speeds, it is less efficient during fluctuating or intermittent wind speeds and thus power output to grid system 14 varies due to the variability of the wind speed.

#FIG. 2 is a schematic view of an exemplary embodiment wind turbine power system 100 including an energy storage system 102. Wind turbine power system 100 is substantially similar to wind turbine power system 10, (shown in FIG. 1) and components of wind turbine power system 100 that are identical to components of wind turbine power system 10 are identified in FIG. 2 using the same reference numerals used in FIG. 1.