Patent Application
20140191780
The testing and commissioning of wind turbines present unique challenges due to the manner in which the turbine power is generated and distributed. As turbines are brought online in a power grid, there are significant spikes in voltage and frequency variance. Conventional programmable logic computer (PLC) driven load banks are unable to meet the testing demands due to these variances. In addition, the voltage spikes and frequency variations causes the testing procedure to fail. This results in delays and financial losses due to the inability to fully establish that the turbine is operating to manufacturer specification and performance metrics, which is a requirement for a wind turbine to become operational.
Load devices for turbine generators are known in the prior art as evidenced by the Gregg US patent application publication No. 2010/0329652 which discloses a turbine generator with an electrical circuit which provides reactive and resistive loads to the stator windings. The values of the reactance and resistance are selected so that the generator produces an output whose voltage and frequency varies with wind speed while the power output remains near a peak power output of the generator.
While the prior load devices operate satisfactorily for maintaining a constant power output, they are not suitable for testing the power output of a wind turbine to insure that the turbine is meeting its performance specifications. In addition, there is no capability of altering the resistance or inductance of the load device under computer control in accordance with the voltage across the inductance or reactance. Furthermore, there is no protection of the computer from voltage spikes and frequency variations in the output from the turbine.
The present invention was developed in order to overcome these and other drawbacks of the prior load devices by providing a resistive reactive load device which creates an electrical load on a power source such as a wind turbine by switching resistive or inductive elements across the terminals of the power source.
Accordingly, it is a primary object of the invention to provide a load device for applying an active load to a power source such as a wind turbine. The device includes an inductor connected in parallel with the power source, a resistor connected in parallel with the power source and the inductor, and first and second relays connected in series with the inductor and resistor, respectively. A control device is connected with the relays to control the operation of the relays to deliver power from the power source to a selected inductor or resistor. This creates a desired load across the power source suitable for testing or evaluating the source without being susceptible to voltage spikes and frequency variations from the power source. If desired, multiple inductors and resistors, each with a series connected relay, are provided in the load device to provide a variety of loads for the power source.
A computer is preferably connected with the control device to select the inductive or resistive load to be applied to the power source in accordance with a testing procedure. In addition, a manual bypass device may be connected with each relay to over-ride the control vice and manually select the inductive or resistive load applied to the power source.
In an alternate embodiment, a load bank is provided which includes a plurality of the load devices as described above. The load bank includes a plurality of outputs which are connected at one end with each load device of the load bank and at the other end with a load step terminal of a power grid formed of a plurality of power sources such as wind turbines. The load bank provides a desired load across selected portions of the power grid for testing. A computer is connected with the load bank. It selectively operates the control devices of the load devices of the load bank to select the inductive or resistive load to be applied across the load step terminals of the power grid in accordance with the testing procedure.
Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which:
As shown in
More particularly, the load device includes an inductor 6 connected in parallel with the wind turbine and a resistive element 8 which is connected in parallel with the inductor and with the wind turbine. A first relay 10 is connected in series with the inductor and a second relay 12 is connected in series with the resistive element. The relays are operable to connect either the inductor or resistive element across the terminals of the wind turbine to provide the load. Operation of the first and second relays is controlled by a controller 14.
In an alternate embodiment, the load device includes a plurality of inductors and a plurality of resistive elements represented in
Referring once again to
A manual bypass 18 such as a selector switch can be provided to override the controller. The bypass is connected with each relay and is used to manually select an inductor or resistive element to be applied across the power source during the testing procedure.
Referring now to
While the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.
