ES2688758A1 - Method and analog electronic circuit for the detection of faults in the hydraulic system of variation of blade pitch of a wind turbine (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Analog electronic circuit and method for the detection of faults in the hydraulic system of pitch variation of a wind turbine. The method comprises generating a residual signal (10) representative of a failure estimate in a hydraulic blade pitch variation actuator (107) of the hydraulic system of the turbine (100); and performing a processing, by an analog electronic circuit (190), of said residual signal (10) generated to estimate a failure in said hydraulic actuator (107) including: filtering the residual signal (10) at a cut-off frequency equivalent to a natural resonant frequency of the hydraulic actuator (107) implemented as a dynamic second-order servo-system model; amplify the filtered residual signal; grinding an equivalent, envelope signal of the amplified residual signal; tune a programmable reference voltage threshold value; comparing the equivalent, envelope signal with said programmable reference voltage threshold value providing a compared signal; binarizing said compared signal, and activating an indicator to indicate that a failure has occurred in the hydraulic actuator (107). (Machine-translation by Google Translate, not legally binding)

Description

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DESCRIPTION

Method and analog electronic circuit for the detection of failures in the hydraulic system of variation of blade pitch of a wind turbine

Technical field

The present invention concerns wind turbines in general. In particular, the invention concerns a method and an analog electronic circuit for the detection of failures in the hydraulic system of variation of blade pitch of a wind turbine.

Background of the invention

A large-scale wind turbine (capable of generating an electric power of several megawatts) is usually composed, as illustrated in Fig. 1, by a tower anchored to the ground, a gondola mounted on it, and a rotor coupled to the gondola. The rotor generally includes a rotating hub and three rotor blades, coupled to the hub and extending outwardly therefrom.

In addition, most modern wind turbines control the load on the rotor by varying the pitch of the blades so that it opposes a greater or lesser resistance to the incident wind. The pitch of the blades is varied to optimize the power output or to protect the wind turbine against overloads or harmful overstrain.

In order to perform the step variation, each blade is provided with a variation system comprising a bearing between the hub and the blade, and some type of motor or actuator to provide a force to vary the pitch of the blade and keep it in a position given (Fig. 2). Such systems usually comprise hydraulic blade drives formed by hydraulic actuators and a hydraulic pump to provide pressurized liquid to said actuators.

On the other hand, and since the maintenance of wind turbines is among one of the factors that most increase the total cost of wind projects, the most effective way to reduce this cost is to continuously monitor the status of wind turbines.

Preventive maintenance, based on monitoring, allows early detection of degeneration of the integrity of the wind turbine. This facilitates a proactive response, minimizing downtime and maximizing the life of the turbine and, therefore, its productivity. However, wind power technical reports show that some of the monitoring techniques currently available are not reliable or

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suitable for wind turbine applications, due to the stochastic nature of the wind that affects decision making.

Also, currently, inspection procedures for blade pitch variation systems require that a wind turbine be turned off to allow a maintenance worker to climb to the gondola and access the actuator. In this way, conventional inspection procedures can be very expensive, from an economic point of view, as well as time-consuming. As a result, scheduled inspections of the blade pitch actuators are normally rare, thereby increasing the likelihood of damage to the actuators due to: oil leaks, pressure loss and pump wear, among others.

Additionally, the ability to detect failures in wind turbines and to control said turbines in the presence of failures are also important factors that must be considered in order to achieve a decrease in the cost of wind power generation.

There are several methodologies that currently exist in the scientific literature for fault detection. One of the most used is that based on an exhaustive data collection with the aim of tuning the design parameters of a mathematical algorithm and being able, in this way, to emit a diagnosis of possible failures. However, these techniques linked to the exhaustive collection of data have, in general, a high computational cost and do not allow rapid detection, which is vital in this type of failure.

In [1], of the same inventors of the present invention, a new fault diagnosis (FD) and fault tolerance control (FTC) methodology of the step actuators in wind turbines is disclosed. This is achieved by combining a disturbance compensator with a controller, both formulated in the discrete time domain. The disturbance compensator has a dual purpose: to estimate the actuator fault (which is used by the FD algorithm) and to design the discrete time controller to obtain an FTC.

That is, the actuator faults are evaluated and then the step control laws are appropriately modified to achieve an FTC with behavior comparable to the case without failures. The performance of the FD and FTC are tested in simulations with the aero code FAST [2].

Therefore, new methods and / or devices that allow the online monitoring of hydraulic actuators are required in order to detect, in real time, and with a high degree of reliability the most common failures that occur in said hydraulic actuators.

References:

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[1] Vidal, Y .; Tutivén, C .; Rodellar, J .; Acho, L. Fault Diagnosis and Fault-Tolerant Control of Wind Turbines via a Discrete Time Controller with a Disturbance Compensator. Energies 2015, 8, 43004316.

[2] Jonkman, J., NWTC Informalion Portal (FAST). https: llnwtc.nrel.gov/FAST. Last modified 19- March-2015; Accessed 11-0 October-2016

Exhibition of the invention

The present invention provides in a first aspect a method for the detection of failures in the hydraulic system of variation of blade pitch of a wind turbine, which comprises, like the methods known in the state of the art, generate, by a perturbation compensator of the wind turbine hydraulic system, controlled by a closed-loop control system of some torque control, step control and step actuator variables, a residual signal representative of a fault estimate in a variation hydraulic actuator of shovel of the hydraulic system.

The proposed method, unlike the prior art, performs a processing, by an analog electronic circuit, of said residual signal generated to estimate a failure in said hydraulic actuator of blade pitch variation by performing the following steps:

a) filtering the residual signal at a cut-off frequency equivalent to a natural resonant frequency of the hydraulic blade pitch variation actuator implemented as a dynamic second-order servo-system model;

b) amplify the filtered residual signal;

c) extracting by rectification an equivalent signal, envelope, of the amplified residual signal;

d) tune a programmable reference voltage threshold value depending on the type of fault to be detected;

e) comparing the equivalent signal, envelope, with said programmable reference voltage threshold value by providing a compared signal;

f) binarize said compared signal, and

g) activate an indicator, visual and / or auditory, to indicate that there has been a failure in the hydraulic actuator of blade pitch variation.

Preferably, the processing is performed in real time. However, processing can also be done offline.

The failure of the hydraulic actuator of the blade pitch variation may comprise one or more of the following faults: a failure due to high air content in the oil of the hydraulic actuator of the blade pitch variation, a failure due to wear of an actuator pump hydraulic variation of blade pitch or a failure due to hydraulic leakage in the hydraulic actuator of variation

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shovel In step d) a differential tuning is provided (different reference voltage threshold value) depending on the type of fault to be detected.

The range of the programmable reference voltage of stage d) varies from 0 to 12 volts, the latter being the value of the supply voltage to the analog electronic circuit. This range is preferably divided into two partitions in order to discriminate and detect the failure in the hydraulic actuator of the blade pitch variation of the functional case without failures. These intervals are programmed based on the type of blade and are usually done based on inducing faults in the hydraulic actuator and adjusting the system until they are discriminated from the case without failure. This threshold is set, which is permanently programmed. Also, experimental data can be used for such tuning or tuning work. Depending on the hydraulic actuation blade, which there are of various types, the fault is induced and the said threshold is adjusted. On the other hand, the type of fault induces in the analog electronic circuit voltage levels easily comparable to each other (of each fault) and of the functional case without failure. Hence, they can be programmed based on a particular need to isolate a possible failure of interest compared to the functional scheme without failure.

In an exemplary embodiment, prior to the realization of step a), a pre-scaling of the residual signal is performed, providing a pre-scaled signal in the range of 0 to 5 volts. In addition, the pre-scaled signal can also be modulated by pulse width modulation, providing a pulse width modulation signal. In the latter case, the proposed method uses the pulse width modulation signal as the input signal in step a).

The present invention provides in a second aspect an analog electronic circuit for the detection of failures in the hydraulic system of variation of the blade of a wind turbine, where from a residual signal generated by a disturbance compensator of the hydraulic system of the wind turbine, controlled by a closed-loop control system of some torque control, step control and step actuator variables, and representative of an estimate of failures in a hydraulic actuator of blade pitch variation of the hydraulic system, said Analog electronic circuit is adapted and configured to perform a processing of said residual signal generated to estimate a failure in said hydraulic actuator of blade pitch variation for which it comprises:

- a filtering module such as a low pass filter adapted and configured to filter the residual signal at a cut-off frequency equivalent to a resonant natural frequency of the blade pitch hydraulic actuator implemented as a dynamic second servo-system model order;

- an amplification module adapted and configured to amplify the residual signal

filtered;

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- a rectification module adapted and configured to extract an equivalent, surround signal from the amplified residual signal;

- a tuning-comparison module comprising:

• a tuning module adapted and configured to tune a programmable reference voltage threshold value depending on the type of fault to be detected;

• a comparison module adapted and configured to compare the equivalent, surround signal, with said programmable reference voltage threshold value, providing a compared signal;

• a binary coupling module adapted and configured to binarize the compared signal; Y

• a time control module adapted and configured to activate an indication module for a certain time; Y

- said indication module adapted and configured to indicate that there has been a failure in the hydraulic actuator of blade pitch variation.

In an exemplary embodiment, the analog electronic circuit comprises a plurality of tuning-comparison modules, each being adapted and configured to detect a failure of a plurality of failures in the hydraulic blade pitch variation actuator.

In an exemplary embodiment, the indication module comprises light visual indicators including light emitting diodes (LED).

Also, the analog electronic circuit may further comprise a pre-scaling module for pre-scaling of the residual signal, providing a prescaling signal in the range of 0 to 5 volts, and a pulse width modulation module to modulate The pre-escalated signal.

Brief description of the drawings

The foregoing and other features and advantages will be more fully understood from the following detailed description of some embodiments, which are merely illustrative and not limiting, with reference to the attached drawings, in which:

Fig. 1 shows a front view of a modern industrial wind turbine as is known in the art.

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Fig. 2 shows a schematic elevation view of an embodiment of the gondola of a wind turbine, with indication of the integral parts thereof.

Fig. 3 schematically shows the controller of a wind turbine described in [1].

Fig. 4 illustrates, in a block diagram, the previous steps of the processing of the residual signal d [k] for its subsequent processing for the detection of real-time faults by means of the proposed analog electronic circuit according to an embodiment example of The present invention.

Fig. 5 illustrates the electronic design of the proposed analog electronic circuit according to an exemplary embodiment of the present invention.

Fig. 6 illustrates the electronic design of the proposed analog electronic circuit according to another embodiment of the present invention.

Fig. 7 illustrates, in a block diagram, a method for detecting failures in the hydraulic system of blade pitch variation of a wind turbine, according to an exemplary embodiment of the present invention.

Detailed description of some embodiments

The present invention relates to a method and to a device (analog electronic circuit 190) for performing a diagnosis, preferably in line, that is, in real time, of the hydraulic actuators 107 responsible for the variation of the blade pitch in a wind turbine 100, as described in Figs. 1 and 2.

Preferably according to the present invention, it is proposed to use as proposed the blade pitch angle controller in [1]. In this work, a robust controller is developed that works collaboratively with a disturbance compensator in discrete time. This perturbation compensator proposed in the theory makes it possible to obtain a residual signal that, thanks to the present invention, will be conveniently post processed. Said post-processing is carried out by means of the aforementioned analog electronic circuit 190, taking into account various practical aspects to estimate the failure of the hydraulic actuator of blade pitch variation 107 in real time and with a rapid detection time.

The present invention is based on the fact that the residual signal d [k] 10 generated by the system shown in Fig. 3 (therefore using as a blade pitch angle controller the one proposed in [1]) needs to be post processed for real-time detection of failures in the hydraulic blade pitch variation actuator 107, particularly failures due to high air content in the oil of the blade pitch variation hydraulic actuator 107,

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wear faults of the hydraulic actuator pump of blade pitch variation 107 and / or failures of hydraulic leakage in the hydraulic actuator of blade pitch variation 107, among others.

With reference to Fig. 4, an exemplary embodiment is shown in which the residual signal 10 of the controller of Fig. 3, prior to its processing by analog electronic circuit 190, is pre-scaled, by a pre-scaling module 170, to give a resulting signal between 0 and 5 volts. The resulting signal feeds a pulse width modulation module 180 (pulse-width modulation, PWM), which, in the current design is preferably tuned to 1 kHz, and then transmitted to the analog electronic circuit 190 In an alternative embodiment, in this case not illustrated, the residual signal 10 is processed directly by the analog electronic circuit 190, ie the pre-scaling and modulation steps are not performed.

With reference to Fig. 5, there is shown an example of an embodiment of the electronic development of the analog electronic circuit 190 to estimate a failure in the hydraulic actuator of blade pitch variation 107 of those described above. The different blocks / modules that make up the analog electronic circuit 190 are described below:

- filtering module 191: It has a low pass filter whose cut-off frequency is adjusted to a natural resonant frequency of the hydraulic stepper actuator 107 implemented as a dynamic second-order servo-system model. As indicated in [1], the hydraulic step system consists of three identical step actuators, one for each blade, which are modeled as a linear differential equation with time-dependent variables, pitch angle P (t) and its reference u (t). In principle, it is a servo system, which can be expressed as a second order differential system:

image 1

where, wn and £ are the natural frequency and the damping coefficient, respectively.

- amplification module 192: this block has the design of a non-inverting gain 2 amplifier, and also functions as an impedance coupler. It is responsible for amplifying the filtered residual signal.

- rectification module 193: represents a half-wave rectifier with the purpose of extracting an envelope equivalent of the residual signal 10 to be processed, and for

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which can then be easily compared to a programmable voltage reference threshold.

- tuning-comparison module 194: it is formed by a tuning module 195, a comparison module 196, a binary coupling module 197 and a time control module.

- Tuning module 195: shows a simple electronic design to tune a programmable reference voltage threshold value. This module is used to control the sensitivity and accuracy of the fault detection system.

- comparison module 196: it is a simple comparison system, or voltage comparator, to compare the equivalent signal, envelope, with said programmable reference voltage threshold value, providing a compared signal.

- binary coupling module 197: it is a 0 or 5 volt binary coupler as an input reference to the time control module 198 in its monostable configuration.

- time control module 198: timer circuit in its monostable mode to activate an indication module 199 for a certain time.

- indication module 199: complementary configuration of actuators for indicators, in this particular case of LED visuals, to show the result of the pre-processed signal for fault diagnosis.

With reference to Fig. 6, there is shown a second embodiment of the electronic development of the analog electronic circuit 190, in this case to estimate different faults in the hydraulic actuator of blade pitch variation 107 of those described above. It should be noted that the filtering modules 191, amplification 192, rectification 193 and indication 199 are the same as those described above for Fig. 5.

On the contrary, unlike Fig. 5, in this case the analog electronic circuit 190 includes three tuning-comparison modules 194, as described above, each of them to detect a failure in the hydraulic actuator of variation of blade pitch 107, that is, one to detect failures due to high air content in the oil of the blade pitch variation hydraulic actuator 107, another to detect the failures due to wear of the pump of the pitch shift hydraulic actuator blade 107 and another for detecting hydraulic leakage failures in the blade pitch variation hydraulic actuator 107. In case it is desired to detect other failures in the blade pitch variation hydraulic actuator 107 it would only be necessary to include tuning modules -194 additional comparison in analog electronic circuit 190.

The tuning module 195 of each of the three tuning-comparison modules 194 is programmed / configured based on the particular need of the type of fault to be detected.

With reference to Fig. 7, an exemplary embodiment of a method is illustrated therein

5 for fault detection in the turbine blade variation hydraulic system

wind 100, according to this exemplary embodiment, the method first comprises, step 701, generating the residual signal 10, representative of an estimate of faults in the hydraulic actuator of blade pitch variation 107. Subsequently, step 702, is performed a filtering of the residual signal at a cut-off frequency equivalent to the natural resonant frequency of the 10-blade hydraulic variation actuator 107 implemented as a dynamic second-order servo-system model. Next, step 703, the filtered residual signal is amplified and an equivalent, enveloping signal of the amplified residual signal is extracted by rectification (step 704). Then, step 705, a programmable reference voltage threshold value is tuned (depending on the type of fault to be detected), comparing, 15 stage 706, the equivalent signal, envelope, with the reference voltage threshold value

programmable. Finally, step 707, the compared signal is binarized and a

indicator to indicate that there has been a failure in the hydraulic actuator of blade pitch variation 107.

Preferably, said indicator is a visual type indicator, such as the previous 20 type LEDs described. However, alternatively, said indicator may also be an auditory type indicator that provides an audible signal to indicate that a fault has occurred.

The scope of the present invention is defined in the appended claims.

Claims (14)

5 10 fifteen twenty 25 30 1. Method for the detection of failures in the hydraulic system of variation of blade pitch of a wind turbine, which comprises generating, by a disturbance compensator of the hydraulic system of the wind turbine, controlled by a closed loop control system of Torque control, step control and step actuator variables, a residual signal (10) representative of a fault estimate in a hydraulic actuator of blade pitch variation (107) of the hydraulic system, the method being characterized in that it comprises performing a processing, by an analog electronic circuit (190), of said residual signal (10) generated to estimate a failure in said hydraulic blade pitch variation actuator (107) by performing the following steps: a) filtering the residual signal (10) at a cut-off frequency equivalent to a natural resonant frequency of the hydraulic blade pitch variation actuator (107) implemented as a dynamic second-order servo-system model; b) amplify the filtered residual signal; c) extracting by rectification an equivalent signal, envelope, of the amplified residual signal; d) tune a programmable reference voltage threshold value depending on the type of fault to be detected; e) comparing the equivalent signal, envelope, with said programmable reference voltage threshold value by providing a compared signal; f) binarize said compared signal, and g) activate an indicator to indicate that there has been a failure in the hydraulic actuator of blade pitch variation (107). 2. Method according to claim 1, wherein said processing is performed in real time. 3. Method according to the preceding claims, wherein said indicator comprises a visual indication or an auditory indication. 4. Method according to the preceding claims, which comprises prior to carrying out step a) pre-scaling the residual signal, providing a pre-scaling signal in the range of 0 to 5 volts. A method according to claim 4, further comprising modulating said prescaled signal by means of a pulse width modulation, providing a pulse width modulation signal, wherein the method comprises using said pulse width modulation signal as a signal of entry into said stage a). 5 10 fifteen twenty 25 30 35 Method according to the preceding claims, wherein the failure of the hydraulic actuator of blade pitch variation (107) of the hydraulic system comprises at least one of the following failures: a failure due to high air content in the hydraulic actuator oil of variation of blade pitch (107), a failure due to wear of a pump of the hydraulic actuator of variation of blade pitch (107) or a failure by hydraulic leakage in the hydraulic actuator of variation of blade pitch (107), having been provided in step d) a differential tuning depending on the type of fault to be detected. 7. Analog electronic circuit (190) for the detection of faults in the hydraulic system of variation of the blade of a wind turbine, where from a residual signal (10) generated by a disturbance compensator of the hydraulic system of the wind turbine (100), controlled by a closed-loop control system of some torque control, step control and step actuator variables, and representative of an estimate of faults in a hydraulic variation actuator of blade variation variation of blade pitch (107) of the hydraulic system, said analog electronic circuit (190) is adapted and configured to perform a processing of said residual signal (10) generated to estimate a failure in said hydraulic blade pitch variation actuator of variation of blade pitch (107) for which it comprises: - a filtering module (191) adapted and configured to filter the residual signal at a cut-off frequency equivalent to a resonant natural frequency of the hydraulic blade pitch variation actuator (107) implemented as a dynamic second servo-system model order; - an amplification module (192) adapted and configured to amplify the filtered residual signal; - a rectification module (193) adapted and configured to extract an equivalent, envelope, signal from the amplified residual signal; - a tuning-comparison module (194) comprising: • a tuning module (195) adapted and configured to tune a programmable reference voltage threshold value depending on the type of fault to be detected; • a comparison module (196) adapted and configured to compare the equivalent, surround signal, with said programmable reference voltage threshold value, providing a compared signal; • a binary coupling module (197) adapted and configured to binarize the compared signal; Y • a time control module (198) adapted and configured to activate an indication module (199) for a certain time; Y 5 10 fifteen twenty 25 - said indication module (199) adapted and configured to indicate that a failure has occurred in the hydraulic actuator of blade pitch variation (107). 8. Analog electronic circuit according to claim 7, comprising a plurality of tuning-comparison modules (194), each being adapted and configured to detect a failure of a plurality of failures in said hydraulic blade pitch variation actuator ( 107). 9. Analog electronic circuit according to claim 8, wherein said plurality of faults comprises at least one failure due to high air content in the oil of the hydraulic actuator of the pitch-pass variation (107), a failure due to wear of a pump of the hydraulic actuator of blade pitch variation (107) and / or a failure due to hydraulic leakage in the hydraulic actuator of blade pitch variation (107). 10. Analog electronic circuit according to claim 7, wherein said filtering module (191) comprises a low pass filter. 11. Analog electronic circuit according to claim 7, wherein said indication module comprises visual light indicators including light emitting diodes, LED. 12. Analog electronic circuit according to claims 7 to 11, further comprising a pre-scaling module (170) adapted and configured to perform a pre-scaling of the residual signal, providing a pre-scaling signal in a range of 0 and 5 volts. 13. Analog electronic circuit according to claim 12, further comprising a pulse width modulation module (180) adapted and configured to modulate the pre-scaled signal. 14. Analog electronic circuit according to claim 7, wherein said threshold value ranges from 0 to 12 Volts.