Wind pitch adjustment system

Systems and methods for controlling a wind pitch adjustment system associated with a wind turbine system are disclosed. In one embodiment, the wind pitch adjustment system can include a power supply configured to convert an alternating current input signal into a direct current voltage, a controller configured to receive a signal from the power supply, and to provide one or more control commands to a pitch adjustment motor, and a surge stopping device comprising a switching element coupled between the power supply and the controller. The surge stopping device is configured to monitor an input voltage from a grid and to drive the switching element based at least in part on the monitored input voltage, such that the switching element is configured to block current flow through the switching element to the controller when the monitored input voltage is above a voltage threshold.

FIELD OF THE INVENTION

The present subject matter relates generally to wind turbine systems, and more particularly to controlling wind pitch control systems associated with a wind turbine system.

BACKGROUND OF THE INVENTION

During operation of a wind turbine, various components of the wind turbine are subjected to various loads due to the aerodynamic wind loads acting on the blade. The blade loading is dependent on the wind speed, tip speed ratio and/or pitch setting of the blade. Tip speed ratio is the ratio of the rotational velocity of the blade tip to wind speed. It can be desirable to adjust operation of the wind turbine based on signals indicative of tip speed ratio (e.g. various speed readings) to adjust loading of the rotor blades of the wind turbine and/or to increase energy production of the wind turbine.

To reduce rotor blade loading, various methods and apparatus have been developed to allow the rotor blades to shed a portion of the loads experienced thereby. Such methods and apparatus include, for example, pitching the rotor blades and/or reducing generator torque during operation. Accordingly, many wind turbines include a wind turbine controller that can operate the wind turbine in various ways based on the tip speed ratio wind turbine loading. For instance, under various operating conditions, the wind turbine can adjust the torque of a generator and/or the pitch angle of the rotor blades to adjust the tip speed ratio to meet a desired tip speed ratio setpoint to increase energy capture by the wind turbine.

The pitch angle of a rotor blade can be controlled, for instance, using a wind pitch adjustment system. The wind pitch adjustment system can include a motor, such as a direct current (DC) motor driven by a DC/DC converter. In some implementations, a wind pitch adjustment system includes a DC source, a control circuit, an inverter bridge, and/or a DC bus capacitor bank having one or more capacitor devices.

The wind turbine and/or the pitch adjustment system can receive power from an electrical grid. In some instances, voltage surges caused by various grid events, such as a high voltage ride-through grid event can damage various components of the wind turbine system and/or the pitch adjustment system if preventative action is not taken. Some pitch adjustment systems can include a dynamic braking device configured to suppress voltage surges associated with a grid event.

BRIEF DESCRIPTION OF THE INVENTION

One example embodiment of the present disclosure is directed to a wind pitch adjustment system associated with a wind turbine system. The system includes a power supply configured to convert an alternating current input signal into a direct current voltage. The system further includes a controller configured to receive a signal from the power supply and to provide one or more control commands to a pitch adjustment motor. The system further includes a surge stopping device comprising a switching element coupled between the power supply and the controller. The surge stopping device is configured to monitor an input voltage from a grid and to drive the switching element based at least in part on the monitored input voltage, such that the switching element is configured to block current flow through the switching element to the controller when the monitored input voltage is above a voltage threshold.

Another example aspect of the present disclosure is directed to a method of controlling a pitch adjustment system associated with a wind turbine system. The method includes receiving one or more signals indicative of a voltage provided by an electrical grid. The method further includes comparing the voltage provided by the electrical grid to one or more threshold voltages. The one or more threshold voltages are associated with a grid event associated with the electrical grid. The method further includes generating one or more control signals based at least in part on the comparison. The method further includes controlling operation of a surge stopping device based at least in part on the one or more control signals. The surge stopping device is coupled between a power supply associated with the voltage provided by the electrical grid, and a controller associated with the pitch adjustment system. The surge stopping device is configured to regulate current flow through the surge stopping device to the controller based at least in part on the one or more control signals.

Yet another example aspect of the present disclosure is directed to a wind turbine system. The wind turbine system includes a wind pitch adjustment system. The wind pitch adjustment system includes one or more rotor blades. The wind turbine system further includes one or more wind pitch adjustment systems. Each wind pitch adjustment system is configured to adjust a pitch angle of at least one of the one or more rotor blades. Each wind pitch adjustment system includes a power supply configured to convert an alternating current input signal into a direct current voltage, a controller configured to receive a signal from the power supply, and to provide one or more control commands to a pitch adjustment motor, and a surge stopping device comprising a switching element coupled between the power supply and the controller. The surge stopping device is configured to monitor an input voltage from a grid and to drive the switching element based at least in part on the monitored input voltage, such that the switching element is configured to block current flow through the switching element to the controller when the monitored input voltage is above a voltage threshold.

Variations and modifications can be made to these example aspects of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Example aspects of the present disclosure are directed to controlling a wind pitch control system associated with a wind turbine system based at least in part on a grid voltage. For instance, a wind pitch control system can include a surge stopping device configured to regulate current flow to a controller associated with the wind pitch control system. The surge stopping device can include a switching element coupled between the controller and the grid. Operation of the switching element can be controlled based at least in part on the grid voltage. In particular, the surge stopping device can further include a comparator circuit configured to turn on a current source when the grid voltage exceeds a voltage threshold. The current source can control operation of the switching element. For instance, when the current source is turned on, the switching element can block current flow, and when the current source is turned off, the switching element can permit current flow. In this manner, the surge stopping device can permit current to flow through the surge stopping device to the controller when the grid voltage is less than the voltage threshold.

More particularly, the surge stopping device can include a direct current (DC) power supply, a comparator circuit, and a current source. The DC power supply can include a rectifier circuit configured to convert an alternating current (AC) input signal to an isolated DC voltage. The isolated voltage can be used to control operation of the switching element. In some implementations, the switching element can be a metal-oxide-semiconductor field-effect transistor (MOSFET). The comparator can be configured to monitor an input voltage from the grid, and to produce an output signal based at least in part on the input voltage. For instance, the comparator circuit can be configured to output a logic high signal when the input voltage is greater than a high threshold, and to output a logic low signal when the input voltage is less than a low threshold. In some implementations, the high threshold and the low threshold can be different values. For instance, the high threshold may be about 157 volts and the low threshold may be about 154. In such implementations, the comparator circuit may be configured using hysteresis techniques. As used herein, the term “about,” when used in conjunction with a numerical value is intended to refer to within 40% of the numerical value.

The high and low thresholds can correspond to one or more grid events associated with the electrical grid. For instance, the grid event may be a high voltage ride-through (HVRT) grid event.

The output signal of the comparator circuit can be configured to drive the current source. For instance, when the output signal is a logic high signal, the current source can turn on, and when the output signal is a logic low signal, the current source can turn off. The current source can be coupled to the switching element. For instance, in implementations wherein the switching element is a MOSFET, the current source can be coupled to the gate of the switching element. In this manner, operation of the switching element can be controlled based at least in part on the current source. For instance, when the current source is turned on, the gate of the MOSFET can be pulled to ground, thereby turning off the MOSFET. When the current source is turned off, the MOSFET can be turned on.

In this manner, current can be provided to the pitch system controller through the surge stopping device (e.g., through the switching element) when the input voltage is less than the low threshold. When the input voltage is greater than the high threshold, the surge stopping device can block or reduce current flow to the controller through the surge stopping device. When the surge stopping device blocks current to the controller, power may be delivered to the controller via a flyback diode coupled between the DC bus and the control circuit. In particular, the wind pitch system may further include a capacitor bank including one or more capacitor devices. The capacitor bank may be configured to store energy, and to provide energy to the controller via the flyback diode when the switching element of the surge stopping device is turned off.

In some implementations, the comparator circuit of the surge stopping device may be configured to implement a reset process throughout which the comparator outputs a logic high output signal. For instance, the reset process may be implemented when the comparator circuit powers on and may last for a duration of about 20 milliseconds. For instance, the reset process may be implemented to eliminate or reduce contactor bouncing associated with the comparator circuit while the comparator circuit is powering on. In such implementations, the current source can be turned on for the duration of the reset process and the MOSFET can be turned off for the duration of the reset process.

In some implementations, the pitch adjustment system may further include a bypass contactor coupled to the DC bus. Operation of the bypass contactor can be controlled based at least in part on a system initialization process. In some implementations, the system initialization process may include a pre-charge process for the capacitor bank. In particular, during the system initialization process, the bypass contactor can be open, such that current in not permitted to flow through the bypass contactor. When the system initialization process is complete, the bypass contactor can be closed thereby allowing current to flow through the bypass contactor.

In some implementations, a dynamic braking resistor may be coupled to the bypass contactor. When the bypass contactor is closed, the dynamic braking resistor may suppress voltage surges associated with various grid events (e.g. HVRT events). In such implementations, the MOSFET of the surge stopping device may not be caused to turn off while the bypass contactor is closed.

The wind turbine10may also include a turbine control system including turbine controller26within the nacelle16or in another location associated with the wind turbine10. In general, the turbine controller26may comprise one or more processing devices. Thus, in several embodiments, the turbine controller26may include suitable computer-readable instructions that, when executed by one or more processing devices, configure the controller26to perform various different functions, such as receiving, transmitting and/or executing wind turbine control signals. As such, the turbine controller26may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine10.

For example, the controller26may be configured to control the blade pitch or pitch angle of each of the rotor blades22(e.g. an angle that determines a perspective of the rotor blades22with respect to the direction28of the wind) to control the loading on the rotor blades22by adjusting an angular position of at least one rotor blade22relative to the wind. For instance, the turbine controller26may control the pitch angle of the rotor blades22, either individually or simultaneously, by transmitting suitable control signals/commands to various pitch drivers or pitch adjustment mechanisms, such as pitch adjustment motor32(FIG. 2) of the wind turbine10. In some implementations, each pitch adjustment motor32can be further controlled by an independent pitch adjustment system, such as pitch adjustment system100ofFIG. 2. Specifically, the rotor blades22may be rotatably mounted to the hub20by one or more pitch bearing(s) (not illustrated) such that the pitch angle may be adjusted by rotating the rotor blades22about their pitch axes34using the pitch adjustment motors32.

In particular, the pitch angle of the rotor blades22may be controlled and/or altered based at least in part on the direction28of the wind. For instance, the turbine controller26and/or a pitch adjustment controller, such as controller106ofFIG. 2may be configured to transmit a control signal/command to each pitch adjustment motor32such that one or more actuators (not shown) of the pitch adjustment motor32may be utilized to rotate the blades22relative to the hub20.

Further, as the direction28of the wind changes, the turbine controller26may be configured to control a yaw direction of the nacelle16about a yaw axis36to position the rotor blades22with respect to the direction28of the wind, thereby controlling the loads acting on the wind turbine10. For example, the turbine controller26may be configured to transmit control signals/commands to a yaw drive mechanism of the wind turbine10such that the nacelle16may be rotated about the yaw axis30.

Still further, the turbine controller26may be configured to control the torque of a generator. For example, the turbine controller26may be configured to transmit control signals/commands to the generator in order to modulate the magnetic flux produced within the generator, thus adjusting the torque demand on the generator. Such temporary de-rating of the generator may reduce the rotational speed of the rotor blades, thereby reducing the aerodynamic loads acting on the blades22and the reaction loads on various other wind turbine10components.

FIG. 2depicts an overview of an example pitch adjustment system100according to example embodiments of the present disclosure. As shown, pitch adjustment system100is associated with a DC power supply102. Power supply102can include a rectifier configured to receive a three-phase AC signal from an electrical grid, and to convert the AC signal to a DC signal. Power supply102can further be configured to provide the DC signal to pitch system100via a DC bus112. System100can further include a surge stopping device104and a controller106. Controller106can receive signals from a turbine controller, such as turbine controller26, and provide control commands to pitch adjustment motor36. As will be described in more detail with regard toFIG. 3, surge stopping device104can include a switching element configured to regulate current flow to controller106.

System100can further include a converter108. Converter108can be an H-bridge converter. Converter108can further include a pre-charging system for a capacitor bank110coupled to DC bus112. Capacitor bank110can include one or more capacitor devices. Converter108can further include a dynamic braking device, such as a dynamic brake resistor. The dynamic brake resistor can be configured to suppress voltage in system100during a grid event (e.g. HVRT event). In this manner, a surge in voltage from the electrical grid may not damage pitch system100.

Pitch system100further includes a bypass contactor114computed to DC bus112. Bypass contactor114can be configured to regulate current flow to converter108and capacitor bank110. In this manner, when bypass contactor114is turned on, the DC signal from supply102can flow through bypass contactor114to converter108and capacitor bank110. In this manner, during a grid event while bypass contactor114is closed, the dynamic brake resistor can be configured to suppress the voltage surge from the electrical grid.

When bypass contactor114is open, current will not flow through bypass contactor114and the dynamic brake resistor will not suppress a surge voltage caused by a grid event. In such instances, surge stopping device104can be configured to detect the DC signal from power supply102, and to regulate current flow to controller106based at least in part on the detected signal. In particular, as indicated, surge stopping device104can include a switching element coupled between power supply102and controller106. Operation of the switching element can be controlled based at least in part on the DC signal from power supply102. For instance, the switching element can be configured to permit current flow when the detected voltage signal is greater than a threshold voltage. In some implementations, the switching element can be configured to block current flow when the detected voltage signal is less than a threshold voltage. In some implementations, the threshold voltage can be a threshold range. For instance, the switching element can be configured to open when the detected voltage exceeds the highest value in the threshold range, and the switching element can be configured to close when the detected voltage is less than the lowest value in the threshold range.

Pitch system100further includes a flyback diode116coupled between DC bus112and controller108. Flyback diode116can be configured to provide power to controller106when surge stopper104is open, and is thereby blocking current flow to controller106. In such instances, capacitor bank110can supply power to controller106via flyback diode116. In this manner, controller106can still receive power during a grid event while bypass contactor114is open.

In some implementations, operation of bypass contactor114can be controlled based at least in part on a system initialization process. For instance, in some implementations, the system initialization process can correspond to a “powering on” process by pitch system100. During such system initialization process, bypass contactor114can be operated in an open state. Bypass contactor114can then be closed responsive to the completion of the system initialization process.

FIG. 3depicts an overview of an example surge stopping device104according to example embodiments of the present disclosure. Surge stopping device104includes a power supply202, a switching element204, a comparison circuit206, and a current source208. Power supply202can be a step down power supply. Power supply202includes AC capacitors (AC caps), and a rectifier. The rectifier can be a full-wave rectifier. Power supply202further includes resistors R1, R2, diode D4and capacitor C1. In particular, power supply202can be configured to generate an isolated DC signal (IP15). In some implementations, the isolated DC signal can be about 15 volts.

Comparison circuit206includes a comparator U1, resistors R5, R6, and R8, and a capacitor C3. As indicated, comparison circuit206can be configured to receive an input signal (e.g. Vin), and to produce an output signal based at least in part on the input signal. For instance, comparison circuit206can be configured to produce a logic high signal when Vinis greater than a threshold (e.g. about 157 volts) and to produce a logic low signal when Vinis less than a threshold (e.g. about 154 volts). In some implementations, comparator U1can be configured to compare an input voltage with a reference voltage (Vref) to determine the output signal.

The output signal of comparison circuit206can be configured to drive operation of current source208. Current source208can include transistor Q3, resistors R7, R9, R10, and diodes D6. In particular, operation of transistor Q3can be controlled at least in part by the output signal of comparison circuit206. In this manner, transistor Q3can be configured to turn on when comparison circuit206outputs a logic high signal, thereby causing current source208to produce a current. For instance, in some implementations, current source208can produce a current of about 1 milliamp. Transistor Q3can be configured to turn off when the comparison circuit206outputs a logic low signal. In such instances, no current will be produced by current source208.

Switching element204can be configured to regulate current flow through surge stopping device104, for instance, to a controller, such as controller106. As shown, switching element204can be a MOSFET device. In particular, current source208can be used to pull the gate of switching element204to ground, thereby turning switching element204off. For instance, when current source208produces a current, switching element204can be configured to turn off, thereby blocking current flow through switching element204. When current source208does not produce a current, operation of switching element204can be controlled by power supply202and a transistor Q2. In particular, when current source208produces a current, the base-emitter voltage of transistor Q2can be negative biased, thereby turning transistor Q2off. Switching element204can then be negative biased by diode D5, thereby turning switching element204off. When current source208does not produce a current, transistor Q2can be turned on by power supply202, thereby turning switching element204on.

As described above, surge stopping device104can be coupled to controller106. Accordingly, when switching element204is turned on, current can flow through switching element204to controller106. When switching element204is turned off, switching element204can block current flow to controller106. In such instances, power can be provided to controller106by a capacitor bank, such as capacitor bank110through a flyback diode116. In this manner, power can still be provided to controller106even when switching element204is turned off.

It will be appreciated that the configuration of the surge stopping device depicted inFIG. 3is for illustrative purposes only. In particular, it will be appreciated that various other suitable circuit configurations can be used without deviating from the scope of the present disclosure. For instance, surge stopping device104can be configured to include various other components, devices, or parts without deviating from the scope of the present disclosure.

FIG. 4depicts a flow diagram of an example method (300) of controlling operation of a pitch adjustment system according to example embodiments of the present disclosure. For instance, in some implementations, method (300) can be implemented by one or more of the devices ofFIGS. 2 and/or 3. In addition,FIG. 4depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that various steps of any of the methods disclosed herein can be omitted, rearranged, expanded, and/or adapted in various ways without deviating from the scope of the present disclosure.

At (302), method (300) can include receiving one or more signals indicative of a voltage provided by an electrical grid. For instance, the electrical grid can provide a voltage to a pitch adjustment system associated with a wind turbine system. As indicated above, the pitch control system can include a surge stopping device, a controller, a converter device (e.g. DC/DC converter), and a capacitor bank. The pitch adjustment system can be configured to provide control commands to a pitch adjustment motor.

At (304), method (300) can include comparing the voltage provided by the electrical grid to one or more threshold voltages. In particular, the one or more threshold voltages can be indicative of a grid event associated with the electrical grid, such as an HVRT grid event. In some implementations, the one or more threshold voltages can include a high threshold (e.g. about 157 volts) and a low threshold (e.g. about 154 volts). The one or more thresholds can correspond to operation of a switching element (MOSFET device) associated with the surge stopping device. As indicated, the switching device can be coupled between a power supply and the pitch adjustment system controller.

At (306), method (300) can include generating a control signal based at least in part on the comparison. For instance, the control signal can be a logic high signal or a logic low signal. In some implementations, the control signal can be a logic high signal when the voltage provided by the electrical grid is greater than the high threshold. In some implementations, the control signal can be a logic low signal when the voltage provided by the electrical grid is less than the low threshold.

At (308), method (300) can include controlling operation of the switching element based at least in part on the control signal. For instance, when the control signal is a logic low signal, the switching element can be configured to permit current flow through the switching element (e.g. turn on). When the control signal is a logic high signal, the switching element can be configured to block current flow through the switching element. In this manner, current flow through the switching element to the controller can be regulated based at least in part on the voltage provided by the electrical grid.

At (310), method (300) can include determining whether the switching device is turned off. If the switching device is turned off, method (300) can include providing power to the controller via a flyback diode (312). In some implementations, the power can be provided by a pre-charged capacitor bank associated with the pitch adjustment system. For instance, the capacitor bank can be configured to store energy, and to provide at least a portion of the stored energy to the controller when the switching element is turned off. In this manner, power can still be provided to the controller even when current flow to the controller is blocked by the surge stopping device. Returning back to (310), if the switching device is not turned off, method (300) can return to (302).