A control strategy for safe bypass of limit switches in wind turbine pitch control systems

Abstract

The present invention relates to a control strategy for safely bypassing a limit switch in a wind turbine pitch control system, comprising the following steps: S1: a master controller sends a limit switch bypass signal to the pitch control system to determine whether the 96° limit switch is triggered. If so, the controller proceeds to step S2; if not, no operation is performed; S2: the pitch drive controls the bypass relay to be turned on to determine whether the motor continues to rotate uncontrollably. If not, the controller proceeds to step S3; if so, the controller proceeds to step S5; S3: the pitch drive controls the motor to slowly reverse to disengage the 96° limit switch and determine whether the encoder feedback angle continues to decrease. If so, the controller proceeds to step S4; if not, the controller proceeds to step S5; S4: determines whether the 96° limit switch is disengaged. If not, the controller returns to step S3; if so, the controller proceeds to step S5; S5: disconnects the bypass relay. The present invention remotely resolves the problem of the pitch system triggering the 96° limit switch, avoiding the time wasted by maintenance personnel going to the offshore tower to troubleshoot the problem, thereby improving operational efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a control strategy for a safe bypass of a limit switch in a wind power pitch control system. Background Art

[0002] Wind energy is a new, renewable and environmentally friendly energy source. As one of the core systems of wind turbines, the variable pitch system has high requirements for its reliability, safety and rationality of fault handling.

[0003] Currently, most variable pitch systems on the market are equipped with limit switches at both 91° and 96° on each blade as a safety measure. When the blade reaches 91°, triggering the first limit switch, the software controls the motor to shut down. If the shutdown fails, continued rotation to 96° triggers the second limit switch. The normally closed contacts of the 96° limit switch and the hardware enable signal of the variable pitch system driver are directly connected in series within a circuit. When the 96° limit switch is triggered, its normally closed contacts open, opening the driver's enable circuit and forcing the driver to shut down. This measure is intended to ensure the safety of the variable pitch system, but it also has a significant disadvantage: once this fault is triggered, regardless of whether the cause has been corrected, maintenance personnel must enter the tower nacelle, switch the pitch system to manual mode, and then disengage the blade from the 96° limit switch. For offshore units, due to the uncertainty of sea time, triggering this type of fault could cause a prolonged downtime, seriously impacting the unit's power generation efficiency. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by this patent application is how to provide a control strategy for the safe bypass of the limit switch of a wind turbine pitch control system. While ensuring the safety of the pitch system, the main control can send instructions to remotely resolve the fault of the pitch system triggering the 96° limit switch, thereby avoiding the time waste caused by maintenance personnel going out to the offshore tower to troubleshoot the fault and improving the operating efficiency of the wind turbine generator set.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A control strategy for a safe bypass of a limit switch in a wind turbine pitch control system includes the following steps:

[0007] S1: The master controller sends a limit switch bypass signal to the pitch control system to determine whether the 96° limit switch is triggered. If so, it proceeds to step S2; if not, it does not perform any operation.

[0008] S2: The pitch drive control bypass relay is turned on to determine whether the motor continues to rotate out of control. If not, proceed to step S3; if so, proceed to step S5;

[0009] S3: The pitch drive controls the motor to slowly reverse and disengage the 96° limit switch, and determines whether the encoder feedback angle continues to decrease. If so, proceed to step S4; if not, proceed to step S5.

[0010] S4: Determine whether the 96° limit switch is disengaged. If not, return to step S3. If so, proceed to step S5.

[0011] S5: Disconnect the bypass relay.

[0012] The present invention discloses a bypass control strategy for the limit switch of a variable pitch control system. While connecting the normally closed signal of the 96° limit switch of the variable pitch system to the hardware enable of the driver, a circuit controlled by a relay is connected in parallel to form a bypass. The driver realizes the bypass function of the limit switch by controlling the on-off of the relay. When the variable pitch system fails and the propeller is out of control and stops at the 96° limit switch, if the fault has been remotely corrected, the main control can send a bypass signal to the variable pitch system to enable the bypass function. The variable pitch driver then comprehensively judges the actual condition of the blade and turns on the bypass relay while ensuring the safety of the system. The variable pitch system then controls the blade to automatically move to a safe position and disengage the 96° limit switch. The present invention can remotely resolve the fault of the variable pitch system triggering the 96° limit switch by sending a command through the main control while ensuring the safety of the variable pitch system, avoiding the time wasted by maintenance personnel going to the offshore tower to correct the fault, thereby improving the operating efficiency of the wind turbine generator set.

[0013] In summary, the present invention has the following beneficial effects:

[0014] 1. The present invention can remotely resolve the fault of the pitch system triggering the 96° limit switch, thereby avoiding the time wasted by maintenance personnel going out to the offshore tower to resolve the fault and improving the operating efficiency of the wind turbine generator set.

[0015] 2. The control strategy involved in the present invention is rigorous and reliable, and can realize the bypass function of the limit switch while ensuring safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of the control strategy for the safety bypass of the limit switch of a wind turbine pitch control system according to the present invention. DETAILED DESCRIPTION

[0017] The present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that in the description of the present invention, the directions or positional relationships indicated by directional terms such as "upper" and "lower" and "top" and "bottom" are generally based on the directions or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. Unless otherwise indicated, these directional terms do not indicate or imply that the devices or components referred to must have a specific direction or be constructed and operated in a specific direction, and therefore should not be construed as limiting the scope of protection of the present invention. The directional terms "inside" and "outside" refer to the inside and outside relative to the outline of each component itself.

[0018] like Figure 1 As shown, a control strategy for safe bypass of a limit switch in a wind turbine pitch control system includes the following steps:

[0019] S1: The master controller sends a limit switch bypass signal to the pitch control system to determine whether the 96° limit switch is triggered. If so, it proceeds to step S2; if not, it does not perform any operation.

[0020] S2: The pitch drive control bypass relay is turned on to determine whether the motor continues to rotate out of control. If not, proceed to step S3; if so, proceed to step S5;

[0021] S3: The pitch drive controls the motor to slowly reverse and disengage the 96° limit switch, and determines whether the encoder feedback angle continues to decrease. If so, proceed to step S4; if not, proceed to step S5.

[0022] S4: Determine whether the 96° limit switch is disengaged. If not, return to step S3. If so, proceed to step S5.

[0023] S5: Disconnect the bypass relay.

[0024] During specific implementation, if the motor loses control during the process of the pitch system triggering a faulty pitch adjustment, the blades will continue to adjust until the 96° limit switch is triggered. At this time, the motor will be forced to stop because the driver hardware enable signal is disconnected. After this fault occurs, the main control first eliminates the corresponding fault and resets it. Then, it can send a limit switch bypass signal to the pitch system through communication. After receiving this signal, the pitch system first determines whether the 96° limit switch is triggered, so as to prevent the main control from sending a signal by mistake and affecting the safety of the system. When the 96° limit switch is in the triggered state, the pitch drive controls the bypass relay to turn on and gives a motor stop command at the same time. At this time, if the motor is still out of control and continues to rotate forward, the drive immediately disconnects the bypass relay, and the motor is forced to stop due to the loss of the hardware enable signal, ensuring the safety of the system. If the motor returns to normal, the driver will give a slow reverse command and then monitor the encoder angle feedback: if the encoder angle does not continue to decrease, it means that there is still a serious fault in the system. To ensure safety, the system will immediately disconnect the bypass relay; if the encoder angle continues to decrease, it means that the motor has executed a reverse command. After the blade is out of the 96° limit switch, the bypass relay will be disconnected. At this time, the normally closed signal of the 96° limit switch is connected, the driver will no longer lose the hardware enable signal, and the motor can continue to operate normally.

[0025] When implemented, the operations are as follows:

[0026] 1. Complete the wiring of related hardware and the replacement of pitch control and main control programs to ensure normal control feedback of the newly added signals.

[0027] 2. With the pitch control system in manual mode, move the propellers to the 96° limit switch and stop them, simulating a situation where the propeller motor runs out of control and stops at the 96° limit switch.

[0028] 3. Switch the pitch system to automatic mode, and then the master controller sends a limit switch bypass signal to the pitch system.

[0029] 4. After the pitch control system receives the signal, the bypass relay is turned on, the driver restores the hardware enable signal, and the motor starts to reverse slowly.

[0030] 5. After the propeller reverses and disengages from the 96° limit switch, the motor stops running, the bypass relay is disconnected, and the main control cancels the bypass signal.

[0031] 6. The main control resets the system fault, issues a start command, and the propeller blades move to the specified start angle.

[0032] Finally, it should be noted that various modifications and variations of the present invention may be made by those skilled in the art without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations as fall within the scope of the claims and their equivalents.

Claims

1. A control strategy for the safe bypass of a limit switch in a wind turbine pitch control system, characterized in that: The following steps are involved: S1: The master controller sends a limit switch bypass signal to the pitch control system to determine whether the 96° limit switch is triggered. If so, the process proceeds to step S2; if not, no operation is performed. S2: The pitch drive controls the bypass relay to be turned on, and determines whether the motor continues to rotate out of control. If so, the process immediately proceeds to step S5 to disconnect the bypass relay. If not, the process proceeds to step S3. S3: The pitch drive controls the motor to slowly reverse and disengage the 96° limit switch, and determines whether the encoder feedback angle continues to decrease. If not, the process immediately proceeds to step S5 to disconnect the bypass relay. If so, the process proceeds to step S4. S4: Determine whether the 96° limit switch is disengaged. If not, return to step S3. If so, proceed to step S5. S5: Disconnect the bypass relay.

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