Patent Description:
Ultracapacitors can be used to power a load in a pitch drive system of a wind turbine system during adverse conditions, such as a grid fault. The ultracapacitors can be stored in a pitch cabinet of the wind turbine. In some instances, a user (e.g., maintenance personnel) may need to perform maintenance on the ultracapacitors or other components located within the cabinet. However, before the user can perform maintenance on the ultracapacitor or the other components in the cabinet, the ultracapacitors must be grounded.

<CIT> and <CIT> describe wind turbine backup power supplies comprising ultracapacitors.

In one aspect, a grounding circuit for a backup power source used to power a pitch motor of a pitch system in a wind turbine is provided. The grounding circuit includes one or more switching elements configured to selectively couple the backup power source to a charging circuit based on a state of a first interface element. The grounding circuit further includes one or more switching elements configured to selectively couple the backup power source to ground based on a state of a second interface element. The grounding circuit includes at least one circuit protection device coupled between the backup power source and the charging circuit. When the backup power source is coupled to the charging circuit and subsequently coupled to ground, the at least one circuit protection device is configured to decouple the backup power source from the charging circuit.

In another aspect, a method of grounding an ultracapacitor configured to operate a pitch motor of a pitch system in a wind turbine is provided. The method includes receiving, at a first interface element, a first input associated with decoupling the ultracapacitor from a charging circuit. In response to receiving the first input, the method includes decoupling, by one or more switching elements of a grounding circuit, the ultracapacitor from the charging circuit. The method further includes receiving, at a second interface element of the grounding circuit, a second input associated with coupling the ultracapacitor to ground. In response to receiving the second input, the method includes coupling, by one or more switching elements of the grounding circuit, the ultracapacitor to ground.

In yet another aspect, a wind turbine is provided. The wind turbine includes a pitch system comprising one or more pitch motors. The wind turbine includes an ultracapacitor configured to power the one or more pitch motors. The wind turbine includes a grounding circuit for the ultracapacitor. The grounding circuit includes one or more switching elements configured to selectively couple the ultracapacitor to a charging circuit based on a state of a first interface element. The grounding circuit further includes one or more switching elements configured to selectively couple the ultracapacitor to ground based on a state of a second interface element. The grounding circuit includes at least one circuit protection device coupled between the ultracapacitor and the charging circuit. When the ultracapacitor is coupled to the charging circuit and subsequently coupled to ground, the at least one circuit protection device is configured to decouple the ultracapacitor from the charging circuit.

In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the appended claims.

Example aspects of the present disclosure are directed to a grounding circuit for a backup power source (e.g., ultracapacitor) used to power induction motors of a pitch system in a wind turbine. The grounding circuit can include one or more switching elements (e.g., contactors) configured to selectively couple the backup power source to a charging circuit based on a state of a first interface element (e.g., switch, lever, pushbutton, control panel, etc.). For instance, when the first interface element is in a first state, the one or more switching elements can move to a closed position to couple the backup power source to the charging circuit. When the first interface element is in a second state, the one or more switching elements move to an open position to decouple the backup power source from the charging circuit.

The grounding circuit can further include one or more switching elements (e.g., contactors) configured to selectively couple the backup power source to ground based on a state of a second interface element (e.g., switch, lever, pushbutton, control panel, etc.). When the second interface element is in a first state, the one or more switching elements move to an open position to decouple the backup power source from ground. In contrast, when the second interface element is in a second state, the one or more switching elements move to a closed position to couple the ultracapacitor to ground. As will be discussed below in more detail, a user (e.g., maintenance personnel) can operate the first and second interface elements in a predefined sequence to properly ground the backup power source.

In order to operate the first and second interface elements in the predefined sequence, the first interface element must be placed in the second state prior to placing the second interface element in the second state. In this manner, the backup power source can be decoupled from the charging circuit before being coupled to ground. When the first and second interface elements are operated in the predefined sequence, the backup power source can, in some embodiments, discharge through a resistor of the grounding circuit. More specifically, the resistor can be coupled to ground and via the one or more switching elements configured to selectively couple the backup power source to ground.

Furthermore, even if the user operates the first and second interface elements out of sequence (e.g., placing second interface element in the second state prior to placing first interface element in the second state), the grounding circuit includes a circuit protection device (e.g., a fuse) coupled between the charging circuit and the one or more switching elements configured to selectively couple the ultracapacitor to the grounding circuit. In this manner, the current associated with coupling the backup power source to ground must flow through the circuit protection device. In example embodiments, the circuit protection device can blow when the first and second interface elements are operated out of sequence and, in the process, create an open circuit. In this manner, the circuit protection device can prevent damage to the charging circuit due to the first and second interface elements being operated out of sequence.

Aspects of the present disclosure are discussed with reference to a grounding circuit for a backup power source (e.g., ultracapacitor) used to power a pitch system in a wind turbine. Those of ordinary skill in the art, using the disclosures provided herein, will understand that aspects of the present embodiments can be used with other applications without deviating from the scope of the present disclosure.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of a wind turbine <NUM> according to example aspects of the present disclosure. As shown, the wind turbine <NUM> includes a tower <NUM> extending from a support surface <NUM>, a nacelle <NUM> mounted on the tower <NUM>, and a rotor <NUM> coupled to the nacelle <NUM>. The rotor <NUM> includes a rotatable hub <NUM> and at least one rotor blade <NUM> coupled to and extending outwardly from the hub <NUM>. For example, in the illustrated embodiment, the rotor <NUM> includes three rotor blades <NUM>. However, in an alternative embodiment, the rotor <NUM> may include more or less than three rotor blades <NUM>. Each rotor blade <NUM> may be spaced about the hub <NUM> to facilitate rotating the rotor <NUM> to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub <NUM> may be rotatably coupled to an electric generator <NUM> (<FIG>) positioned within the nacelle <NUM> to permit electrical energy to be produced.

Referring now to <FIG>, a simplified, internal view of one embodiment of the nacelle <NUM> of the wind turbine <NUM> is illustrated. As shown, a generator <NUM> may be disposed within the nacelle <NUM>. The generator <NUM> may be coupled to the rotor <NUM> of the wind turbine <NUM>. In this manner, rotational energy generated by the rotor <NUM> can be converted into electrical power. In example embodiments, the rotor <NUM> may include a main shaft <NUM> coupled to the hub <NUM> for rotation therewith. The generator <NUM> may then be coupled to the main shaft <NUM> such that rotation of the main shaft <NUM> drives the generator <NUM>. For instance, in the illustrated embodiment, the generator <NUM> includes a generator shaft <NUM> rotatably coupled to the main shaft <NUM> through a gearbox <NUM>. However, in other embodiments, it should be appreciated that the generator shaft <NUM> may be rotatably coupled directly to the main shaft <NUM>. Alternatively, the generator <NUM> may be directly rotatably coupled to the main shaft <NUM>.

It should be appreciated that the main shaft <NUM> may generally be supported within the nacelle <NUM> by a support frame or bedplate <NUM> positioned atop the wind turbine tower <NUM>. For example, the main shaft <NUM> may be supported by the bedplate <NUM> via a pair of pillow blocks <NUM> mounted to the bedplate <NUM>.

As shown in <FIG> and <FIG>, the wind turbine <NUM> may also include a turbine control system or a turbine controller <NUM> within the nacelle <NUM>. For example, as shown in <FIG>, the turbine controller <NUM> is disposed within a control cabinet <NUM> mounted to a portion of the nacelle <NUM>. However, it should be appreciated that the turbine controller <NUM> may be disposed at any location on or in the wind turbine <NUM>, at any location on the support surface <NUM> or generally at any other location. The turbine controller <NUM> may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine <NUM>.

Each rotor blade <NUM> may also include a pitch adjustment mechanism <NUM> configured to rotate each rotor blade <NUM> about its pitch axis <NUM>. Further, each pitch adjustment mechanism <NUM> may include a pitch drive motor <NUM> (e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox <NUM>, and a pitch drive pinion <NUM>. In such embodiments, the pitch drive motor <NUM> may be coupled to the pitch drive gearbox <NUM> so that the pitch drive motor <NUM> imparts mechanical force to the pitch drive gearbox <NUM>. Similarly, the pitch drive gearbox <NUM> may be coupled to the pitch drive pinion <NUM> for rotation therewith. The pitch drive pinion <NUM> may, in turn, be in rotational engagement with a pitch bearing <NUM> coupled between the hub <NUM> and a corresponding rotor blade <NUM> such that rotation of the pitch drive pinion <NUM> causes rotation of the pitch bearing <NUM>. Thus, in such embodiments, rotation of the pitch drive motor <NUM> drives the pitch drive gearbox <NUM> and the pitch drive pinion <NUM>, thereby rotating the pitch bearing <NUM> and the rotor blade <NUM> about the pitch axis <NUM>. Similarly, the wind turbine <NUM> may include one or more yaw drive mechanisms <NUM> communicatively coupled to the turbine controller <NUM>, with each yaw drive mechanism(s) <NUM> being configured to change the angle of the nacelle <NUM> relative to the wind (e.g., by engaging a yaw bearing <NUM> of the wind turbine <NUM>).

Further, the turbine controller <NUM> may also be communicatively coupled to each pitch adjustment mechanism <NUM> of the wind turbine <NUM> (one of which is shown) through a separate or integral pitch controller <NUM> (<FIG>) for controlling and/or altering the pitch angle of the rotor blades <NUM> (i.e., an angle that determines a perspective of the rotor blades <NUM> with respect to the direction <NUM> of the wind).

In addition, as shown in <FIG>, one or more sensors <NUM>, <NUM>, <NUM> may be provided on the wind turbine <NUM>. More specifically, as shown, a blade sensor <NUM> may be configured with one or more of the rotor blades <NUM> to monitor the rotor blades <NUM>. Further, as shown, a wind sensor <NUM> may be provided on the wind turbine <NUM>. For example, the wind sensor <NUM> may be a wind vane, an anemometer, a LIDAR sensor, or another suitable sensor that measures wind speed and/or direction. In addition, a pitch sensor <NUM> may be configured with each of the pitch drive mechanism(s) <NUM>, e.g. with one or more ultracapacitors associated with the pitch drive motors <NUM> thereof, which will be discussed in more detail below. As such, the sensors <NUM>, <NUM>, <NUM> may further be in communication with the pitch controller <NUM>, and may provide related information to the pitch controller <NUM>.

Referring now to <FIG>, a schematic diagram of one embodiment of a pitch system <NUM> for the wind turbine <NUM> (<FIG>) is provided. More specifically, as shown, the pitch system <NUM> includes a plurality of pitch drive mechanisms <NUM>, i.e. one for each pitch axis <NUM> (<FIG>). Further, as shown, each of the pitch drive mechanisms <NUM> may be communicatively coupled to a power grid <NUM> as well as a ultracapacitors <NUM>. More specifically, as shown, ultracapacitors <NUM> associated with each pitch drive mechanism <NUM> can be stored in a cabinet <NUM>. In some embodiments, the cabinet <NUM> can be a thermally isolated container.

During normal operation of the wind turbine <NUM>, a primary power converter <NUM> of the wind turbine <NUM> (<FIG>) receives alternating current (AC) power from the power grid <NUM> and converts the AC power to AC power suitable for driving the pitch drive motors <NUM> (e.g., AC motors) of each pitch drive mechanism <NUM>. Additionally, the primary power converter <NUM> can convert AC power received from the power grid <NUM> into direct current (DC) power suitable for charging the bank ultracapacitors <NUM>. In some instances (e.g., adverse grid event or grid loss), the pitch drive motors <NUM> may be driven (e.g., powered) by the ultracapacitors <NUM>.

<FIG> depicts an example embodiment of the primary power converter <NUM> according to example embodiments of the present disclosure. The primary power converter <NUM> can include an AC rectifier <NUM> configured to receive AC power from the power grid <NUM> at a first AC voltage and convert the first AC voltage to DC power at a first DC voltage. Additionally, the AC rectifier <NUM> can be coupled to a power inverter <NUM> of the primary power converter <NUM>. More specifically, the first AC rectifier <NUM> can be coupled to the power inverter <NUM> via one or more conductors (e.g., wires). In this manner, the output (e.g., DC power at first DC voltage) of the AC rectifier <NUM> can be provided to the power inverter <NUM>. As shown, the primary power converter <NUM> can include one or more capacitors <NUM> (e.g., electrolytic capacitors) coupled between the output of the AC rectifier <NUM> and the input of the power inverter <NUM>. In example embodiments, the one or more capacitors <NUM> can be configured to reduce or eliminate noise associated with the DC power the AC rectifier <NUM> provides to the power inverter <NUM>.

The power inverter <NUM> can be configured to convert the DC power at the first DC voltage to AC power at a second AC voltage. In example embodiments, the second AC voltage can be different (e.g., greater than or less than) than the first AC voltage associated with the AC power the AC rectifier <NUM> receives from the power grid <NUM>. As shown, the output (e.g., AC power at the second AC voltage) can be provided to the pitch drive motor <NUM> of the pitch drive mechanisms <NUM> (<FIG>).

The primary power converter <NUM> can include a DC to DC power converter <NUM>. As shown, the power converter <NUM> can be coupled to one or more input terminals (e.g., leads) associated with the second power inverter <NUM>. In this manner, the power converter <NUM> can receive the DC power at the first DC voltage. Additionally, the power converter <NUM> can be coupled to the ultracapacitors <NUM>. In example embodiments, the power converter <NUM> can convert the DC power at the first DC voltage to DC power at a second DC voltage that is suitable for charging the ultracapacitors <NUM>. It should be appreciated that the second DC voltage can be different (e.g., less than or greater than) than the first DC voltage.

Referring now to <FIG>, a grounding circuit <NUM> for a backup power source for a pitch motor <NUM> of the pitch system <NUM> (<FIG>) in the wind turbine <NUM> (<FIG>) is provided according to example embodiments. As shown, the backup power source for the pitch motor <NUM> comprises the ultracapacitor <NUM> discussed above with reference to <FIG> and <FIG>. It should be appreciated, however, that the backup power source can include any suitable power source configured to power the pitch motor <NUM> when the primary power converter <NUM> (<FIG> and <FIG>) offline.

The grounding circuit <NUM> can, as will be discussed below in more detail, operate based on a state of a first interface element102 and a second interface element <NUM>. In example embodiments, the first interface element <NUM> and the second interface element <NUM> can be input devices (e.g., switches, levers, touchscreen, pushbutton, etc.) configured to transition between at least a first state or positon P1 and a second state or position P2 in response to user-input. More specifically, the first and second interface elements <NUM>, <NUM> can be associated with a control panel <NUM> (e.g., electrical panel) of the wind turbine <NUM> (<FIG>). It should be appreciated, however, that the first and second interface elements <NUM>, <NUM> can include any suitable input device. It should also be appreciated that the first and second interface elements <NUM>, <NUM> can be located at any suitable location on the wind turbine <NUM> (<FIG>).

In example embodiments, the grounding circuit <NUM> includes a switching element <NUM> coupled to a first leg L<NUM> of the ultracapacitor <NUM> and configured to selectively couple the ultracapacitor <NUM> to a charging circuit <NUM> based, at least in part, on a state (e.g., first state P1 or second state P2) of the first interface element <NUM>. More specifically, the switching element <NUM> can move between a closed position (<FIG>) and an open position (<FIG>) to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM> which, in some embodiments, is the DC/DC power converter <NUM> (<FIG>) of the primary power converter <NUM>. Alternatively and/or additionally, the switching element <NUM> can move between the closed position and the open position to selectively couple the ultracapacitor <NUM> to a power converter <NUM> of the wind turbine <NUM> (<FIG>). In example embodiments, the power converter <NUM> can be the secondary power converter <NUM> (<FIG>) of the pitch system <NUM> (<FIG>).

When the first interface element <NUM> is in the first state P1, the switching element <NUM> moves to the closed position to couple the ultracapacitor <NUM> (e.g., first leg L<NUM>) to the charging circuit <NUM> and the power converter <NUM>. When the first interface element <NUM> is in the second state P2, the switching element <NUM> moves to the open position (<FIG>) to decouple the ultracapacitor <NUM> from the charging circuit <NUM> and the power converter <NUM>. In this manner, the ultracapacitor <NUM> can be selectively coupled to the charging circuit <NUM> and the power converter <NUM> based, at least in part, on the state (e.g., first state P1 or second state P2) of the first interface element <NUM>.

In example embodiments, the grounding circuit <NUM> can include one or more switching elements configured to selectively couple the ultracapacitor <NUM> to ground GND. As shown, the grounding circuit <NUM> can include a first switching element <NUM>, second switching element <NUM>, and a third switching element <NUM>. It should be appreciated, however, that the grounding circuit <NUM> can include more or fewer switching elements configured to selectively couple the ultracapacitor <NUM> to ground GND.

As shown, each of the first switching element <NUM>, second switching element <NUM>, and third switching element <NUM> is movable between an open position (<FIG> and <FIG>) and a closed position (<FIG> and <FIG>) to selectively couple the ultracapacitor <NUM> to ground GND. In example embodiments, the first switching element <NUM> can be coupled to ground GND and the first leg L<NUM> of the ultracapacitor <NUM>. The second switching element <NUM> can be coupled to ground GND and the first leg L<NUM> of the ultracapacitor <NUM>. The third switching element <NUM> can be coupled to a second leg L<NUM> of the ultracapacitor <NUM> and ground GND. As will be discussed below in more detail, each of the switching elements <NUM>, <NUM>, <NUM> can move from the open position to the closed position, or vice versa, based on a state (e.g., first state P1 or second state P2) of the second interface element <NUM>.

When the second interface element <NUM> is in the first state P1(<FIG> and <FIG>), each of the switching elements <NUM>, <NUM>, <NUM> move to the open position (<FIG> and <FIG>) to decouple the ultracapacitor <NUM> from ground GND. In contrast, when the second interface element104 is in the second state P2 (<FIG> and <FIG>), each of the switching elements <NUM>, <NUM>, <NUM> move to the closed position (<FIG> and <FIG>) to couple the ultracapacitor <NUM> to ground GND. In this manner, the ultracapacitor <NUM> can be selectively coupled to ground GND based, at least in part, on the state (e.g., first state P1 or second state P2) of the second interface element <NUM>.

When a maintenance action needs to be performed on the wind turbine <NUM> (<FIG>), a user (e.g., maintenance personnel) can operate the first interface element <NUM> and the second interface element104 in a predefined sequence to properly ground the ultracapacitor <NUM>. First, the user can provide an input to cause the first interface element102 to transition from the first state P1 (<FIG>) to the second state P2 (<FIG>). For instance, if the first interface element is a switch, the input can include moving the switch from a first position to a second position. In response to the first interface element <NUM> transitioning from the first state P1 (<FIG>) to the second state P2 (<FIG>), the switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM> can move from the closed position (<FIG>) to the open position (<FIG>) to decouple the ultracapacitor <NUM> from the charging circuit <NUM> and the power converter <NUM>.

Next, the user can provide an input to cause the second interface element <NUM> to transition from the first state P1 (<FIG>) to the second position (<FIG>). In response to the second interface element <NUM> transitioning from the first state P1 (<FIG> and <FIG>) to the second state P2 (<FIG>), each of the first, second, and third switching elements130, <NUM>, <NUM> configured to selectively couple the ultracapacitor <NUM> to ground GND can move from the open position (<FIG>) to the closed position (<FIG>) to couple the ultracapacitor <NUM> to ground GND.

In some embodiments, the grounding circuit <NUM> can include a resistor <NUM> coupled between ground GND and the first switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to ground GND. As such, when the ultracapacitor <NUM> is decoupled from the charging circuit <NUM> and power converter <NUM> and subsequently coupled to ground GND, the ultracapacitor <NUM> discharges a current I through the resistor <NUM> of the grounding circuit <NUM>. In alternative embodiments, the grounding circuit <NUM> may not include the resistor <NUM> coupled between ground GND and the first switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to ground GND.

When the user does not manipulate the first interface element <NUM> and second interface element <NUM> in the predefined sequence, the current I the ultracapacitor <NUM> discharges when initially coupled to ground GND can potentially damage the charging circuit <NUM>. In order to prevent such damage to the charging circuit <NUM>, the grounding circuit <NUM> can include a circuit protection device <NUM> (e.g., fuse) configured to decouple the ultracapacitor <NUM> from the charging circuit <NUM>. In example embodiments, the circuit protection device <NUM> can be a fuse coupled between the ultracapacitor <NUM> and the charging circuit <NUM>. More specifically, the circuit protection device <NUM> can be coupled to the first leg L<NUM> of the ultracapacitor <NUM> between the charging circuit <NUM> and the switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM>. In example embodiments, the circuit protection device <NUM> (e.g., fuse) can blow when the first interface element <NUM> and the second interface element <NUM> are operated out-of-sequence. In this manner, the charging circuit <NUM> can be isolated from the current I the ultracapacitor <NUM> discharged when initially coupled to ground GND.

Referring now to <FIG>, a schematic of another embodiment of the grounding circuit <NUM> is provided. The grounding circuit <NUM> of <FIG> can be configured in substantially the same manner as the grounding circuit <NUM> of <FIG>. However, unlike the grounding circuit <NUM> of <FIG>, the grounding circuit <NUM> of <FIG> includes a second circuit protection device <NUM>. As shown, the second circuit protection device <NUM> can be coupled between the ultracapacitor <NUM> and the power converter <NUM>. More specifically, the second circuit protection device <NUM> can be coupled to the first leg L<NUM> of the ultracapacitor <NUM> between the power converter <NUM> and the switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to ground GND. It should be appreciated that the second circuit protection device <NUM> can operate in substantially the same manner as the circuit protection device <NUM> discussed above. More specifically, the second circuit protection device <NUM> can blow when the first and second interface elements <NUM>, <NUM> are operated out of sequence. In this manner, damage to the power converter <NUM> due to the first and second interface elements <NUM>, <NUM> being operated out of sequence can be prevented.

Referring now to <FIG>, a schematic of yet another embodiment of the grounding circuit <NUM> is provided. The grounding circuit <NUM> of <FIG> can be configured in substantially the same manner as the grounding circuit <NUM> of <FIG>. However, unlike the grounding circuit <NUM> of <FIG>, the grounding circuit <NUM> of <FIG> can include a second switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM>. It should be appreciated that the second switching element <NUM> can operate in substantially the same manner as the switching element <NUM> (e.g., first switching element) discussed above with reference to <FIG>. More specifically, the second switching element <NUM> can move from a close position (<FIG>) to an open position (<FIG> and <FIG>), or vice versa, to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM> and the power converter <NUM>.

As shown, the second switching element <NUM> can be coupled to the second leg L<NUM> of the ultracapacitor <NUM>. When the first interface element <NUM> is in the first state P1 (<FIG>), switching elements <NUM>, <NUM> move to the closed position (<FIG>) to couple both legs L<NUM>, L<NUM> of the ultracapacitor <NUM> to the charging circuit <NUM> and the power converter <NUM>. When the first interface element <NUM> is in the second position (<FIG>), both switching elements <NUM>, <NUM> move to the open position (<FIG>) to decouple both legs L<NUM>, L<NUM> of the ultracapacitor <NUM> from the charging circuit <NUM> and the power converter <NUM>.

As shown, the grounding circuit <NUM> of <FIG> can include a third circuit protection device <NUM> and a fourth circuit protection device <NUM>. The third circuit protection device <NUM> can be coupled to the second leg L<NUM> of the ultracapacitor <NUM> between the chagrining circuit <NUM> and the second switching <NUM> configured to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM> and the power converter <NUM>. The fourth circuit protection device <NUM> can be coupled to the second leg L<NUM> of the ultracapacitor <NUM> between the power converter <NUM> and the second switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to the charging circuit <NUM> and the power converter <NUM>.

In example embodiments, the grounding circuit <NUM> of <FIG> can include a fourth switching element <NUM> configured to selectively couple the ultracapacitor <NUM> to ground GND. It should be appreciated that the first switching element <NUM> can operated in substantially the same manner as the first, second, and third switch elements <NUM>, <NUM>, <NUM> discussed above with reference to <FIG>. More specifically, the fourth switching element <NUM> can move from an open position (<FIG> and <FIG>) and a closed position (<FIG> and <FIG>), or vice versa, to selectively couple the ultracapacitor <NUM> to ground GND.

As shown, the fourth switching element <NUM> can be coupled to the second leg L<NUM> of the ultracapacitor <NUM> and ground GND. More specifically, the fourth switching element <NUM> can be coupled to the second leg L<NUM> of the ultracapacitor <NUM> between the fourth circuit protection device <NUM> and the power converter <NUM>. In example embodiments, the fourth switching element <NUM> can move from the open position and the closed position, or vice versa, to selectively couple the second leg L<NUM> of the ultracapacitor <NUM> to ground GND.

Referring now to <FIG>, a flow diagram of a method <NUM> for grounding an ultracapacitor used to power pitch motors of a pitch system for a wind turbine is provided according to example embodiments of the present disclosure. It should be appreciated that the method <NUM> can be implemented using the grounding circuit discussed above with reference to <FIG>.

At (<NUM>), the method <NUM> includes receiving, at a first interface element of the grounding circuit, a first input associated with decoupling an ultracapacitor from a charging circuit. In example embodiments, the first interface element is a switch movable between at least a first position and a second position to selectively couple the ultracapacitor to the charging circuit. When the switch is in the first position, one or more switching elements (e.g., contactors) of the grounding circuit can move to a closed position to couple the ultracapacitor to the charging circuit. When the switch is in the second position, the one or more switching elements of the grounding circuit can move to the open position to decouple the ultracapacitor from the charging circuit. As such, the first input can be associated with moving the switch from the first position to the second position to decouple the ultracapacitor from the charging circuit.

In some embodiments, a lockout tagout procedure may be implemented to decouple the ultracapacitor from the charging circuit. For instance, the switch may be locked in the first position via a locking mechanism (e.g., padlock) configured to prevent movement of the switch between the first position and the second position. As such, a user must remove (e.g., unlock) the locking mechanism in order to move the switch to the second position to decouple the ultracapacitor from the charging circuit.

At (<NUM>), the method <NUM> includes decoupling, via the one or more switching elements of the grounding circuit, the ultracapacitor from the charging circuit in response to receiving the first input. In example embodiments, the one or more switching elements can move from the closed position to the open position to decouple the ultracapacitor from the charging circuit.

At (<NUM>), the method <NUM> includes receiving, at a second interface element, a second input associated with coupling the ultracapacitor to ground. In example embodiments, the second interface element can be a switch movable between at least a first position and a second position to selectively couple the ultracapacitor to ground. When the switch is in the first position, one or more switching elements of the grounding circuit can move to an open position to decouple the ultracapacitor from ground. When the switch is in the second position, the one or more switching elements of the. As such, the second input can be associated with moving the switch from the first position to the second position to couple the ultracapacitor to ground.

At (<NUM>), the method <NUM> includes coupling, via one or more switching elements of the grounding circuit, the ultracapacitor to ground. In example embodiments, the one or more switching elements can move from the open position to the closed position to couple the ultracapacitor to ground. In example embodiments, the ultracapacitor can discharge through a resistor of the grounding circuit. More specifically, the resistor can be coupled between ground and one of the switching elements configured to selectively couple the ultracapacitor to ground.

It should be appreciated that an amount of time the ultracapacitor requires to discharge can be less compared to the amount of time conventional capacitors require to discharge. In this manner, an amount of time the user (e.g., maintenance person) must wait before performing maintenance on the ultracapacitor or other suitable components of the wind turbine can be reduced.

In some implementations, the first interface element and the second interface element may be operated out-of-sequence. For instance, user-manipulation of the second interface element may occur prior to user-manipulation of the second interface element such that the second input at (<NUM>) is received before the first input at (<NUM>). However, as mentioned, the grounding circuit includes at least one circuit protection device (e.g., fuse) configured to decouple the ultracapacitor from the charging circuit when the first interface element and the second interface element are operated out-of-sequence. As such, the method <NUM> includes decoupling, via a circuit protection device of the grounding circuit, the ultracapacitor from the charging circuit when the first interface element and the second interface element are operated out-of-sequence such the second input at (<NUM>) is received before the first input at (<NUM>). In this manner, the circuit protection device of the grounding circuit safeguards against the user operating the interface elements out-of-sequence.

Claim 1:
A grounding circuit (<NUM>) for a backup power source being an ultracapacitor for a pitch motor (<NUM>) of a pitch system (<NUM>) in a wind turbine (<NUM>), the grounding circuit (<NUM>) comprising:
one or more switching elements (<NUM>) operable by a user and configured to selectively couple the backup power source to a charging circuit (<NUM>) based on a state of a first interface element (<NUM>), the first interface element comprising a switch movable between at least a first position and a second position to selectively couple the backup power source to the charging circuit;
one or more switching elements (<NUM>) operable by a user and configured to selectively couple the backup power source to ground based on a state of a second interface element (<NUM>), the second interface element comprising a switch movable between at least a first position and a second position to selectively couple the backup power source to ground; and
at least one circuit protection device (<NUM>) coupled between the backup power source and the charging circuit (<NUM>),
wherein when the backup power source is coupled to the charging circuit (<NUM>) and subsequently coupled to ground, the at least one circuit protection device (<NUM>) is configured to decouple the backup power source from the charging circuit (<NUM>).