EP3818384A1 - Système éolien et procédé pour détecter des oscillations de basse fréquence dans un réseau d'alimentation électrique - Google Patents

Système éolien et procédé pour détecter des oscillations de basse fréquence dans un réseau d'alimentation électrique

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Publication number
EP3818384A1
EP3818384A1 EP19737082.8A EP19737082A EP3818384A1 EP 3818384 A1 EP3818384 A1 EP 3818384A1 EP 19737082 A EP19737082 A EP 19737082A EP 3818384 A1 EP3818384 A1 EP 3818384A1
Authority
EP
European Patent Office
Prior art keywords
signal
gradient
frequency
voltage
test
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19737082.8A
Other languages
German (de)
English (en)
Inventor
Kai BUSKER
Angelo MENDONCA
Aramis SCHWANKA TREVISAN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wobben Properties GmbH
Original Assignee
Wobben Properties GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wobben Properties GmbH filed Critical Wobben Properties GmbH
Publication of EP3818384A1 publication Critical patent/EP3818384A1/fr
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
    • G01R19/2513—Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/177—Analysis of very low frequencies
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B15/00—Systems controlled by a computer
    • G05B15/02—Systems controlled by a computer electric
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Definitions

  • the present invention relates to a method for detecting low-frequency vibrations, in particular subsynchronous resonances, in an electrical supply network.
  • the invention also relates to a wind energy system, namely a wind energy installation or a wind farm with a plurality of wind energy installations, for carrying out a method for detecting low-frequency vibrations, in particular subsynchronous resonances, in an electrical supply network.
  • Wind energy systems namely wind energy plants or wind farms, are known and they generate electrical power from wind and feed it into an electrical supply network.
  • low-frequency vibrations are vibrations between two elements or areas in the electrical supply network, one can also speak of subsynchronous resonances.
  • low-frequency vibrations, including subsynchronous resonances can be caused in particular by the vibration behavior of one or more synchronous generators directly coupled to the electrical supply network.
  • the low frequency of the vibrations can also result in the fact that such low-frequency vibrations can only be detected or recognized comparatively late, or make a long evaluation time necessary.
  • the German Patent and Trademark Office researched the following prior art: DE 10 2014 200 740 A1 and WO 2013/102791 A1.
  • the invention is therefore based on the object of addressing at least one of the above problems.
  • a solution is to be proposed that enables low-frequency vibrations to be quickly recognized in the electrical supply network for wind energy systems.
  • At least an alternative solution to previously known solutions is to be proposed.
  • a method for detecting low-frequency vibrations in an electrical supply network is proposed.
  • subsynchronous resonances are to be recognized as low-frequency vibrations, but other low-frequency vibrations are also possible.
  • An electrical supply network is assumed that has a network voltage with a nominal network frequency.
  • the low-frequency vibrations to be detected have a lower frequency than the nominal network frequency.
  • the low-frequency vibrations therefore preferably have a lower frequency than the fundamental frequency of the electrical supply network.
  • the low-frequency vibrations can have values of 1 Hz and less. However, they can also reach up to five times the nominal network frequency.
  • Low-frequency vibrations are vibrations with a frequency of at most five times the nominal network frequency, preferably with a frequency that corresponds at most to the nominal network frequency.
  • the low-frequency oscillation has no frequency that corresponds to a multiple of the nominal network frequency. It should be noted that the examination and consideration of low-frequency vibrations is used in particular to investigate or to ensure system stability of the electrical supply network. This differs from an assessment of the network quality or signal quality of the voltage signal in the electrical supply network, in which harmonics are particularly important.
  • At least one electrical signal of the electrical supply network be recorded as at least one test signal.
  • An electrical voltage and in particular or alternatively an electrical current are particularly suitable as the electrical signal.
  • a three-phase voltage at a network connection point can be recorded as the electrical voltage, or an electrical voltage that is equivalent, in particular proportional, to the electrical voltage at the network connection point.
  • This wind energy system can feed into the electrical supply network at a grid connection point and record the voltage there.
  • a transformer is also used to transform the voltage from the wind energy system up to the level in the electrical supply network.
  • the electrical voltage on the low-voltage side of the transformer can also be used here.
  • An output voltage on an inverter can also be used regularly for the grid voltage, namely especially the electrical voltage at the network connection point of the electrical supply network, representative voltage.
  • the electrical current fed into the electrical supply network is used as the electrical current.
  • This current is also preferably taken up in three phases.
  • This electrical current fed into the electrical supply network can in particular be an electrical current generated by the wind energy system.
  • the at least one recorded test signal is filtered and / or transformed into at least one test signal.
  • a filtering or transforming comes into consideration here in particular that, in addition to measuring noise, the fundamental frequency of the test signal is also filtered, namely ideally eliminated.
  • the nominal network frequency is to be regarded as the basic frequency here, that is usually a frequency of 50 Hz or 60 Hz.
  • a low-frequency signal can be superimposed here, which can lead to a slight fluctuation.
  • the detected variables are preferably transformed into space pointer sizes and the space pointer sizes thus transformed are then used further, in particular further filtered.
  • such variables can also be constant at a constant operating point. If, however, low-frequency vibrations occur, they can be reflected in changes in these detected variables, especially in changes in the respective space vector size.
  • the at least one test signal is derived in time in order to obtain a gradient signal in each case. If the test signal reproduces the effective value of the test signal, for example, the derivation of such a test signal would ideally be 0, namely if the test signal were ideally sinusoidal and without fluctuations. If, however, at least one low-frequency oscillation is superimposed, this can emerge from the time derivative of the test signal.
  • the gradient signal obtained by the time derivation then not only has the value 0, but essentially shows the derivation of the superimposed signal.
  • test criterion is a test limit that can be specified and that the test criterion is met if this specified test limit is exceeded.
  • the evaluation is ultimately carried out via the evaluation of the gradient signal. The time derivative is therefore checked from the at least one filtered or transformed test signal and if this at least exceeds a test limit for the test signal of one of the signals, the existence of a low-frequency oscillation is assumed. Whether a low-frequency oscillation is present is therefore only recognized via the gradient formation.
  • the gradient formation is not applied to an already recognized oscillation, for example in order to recognize whether the oscillation is increasing or decreasing, but rather the oscillation is recognized at all by the gradient formation.
  • the comparison of the gradients recorded in this way with a test limit forms a test for absolute values. An oscillation is therefore already assumed when this test limit is exceeded. It is not necessary to consider the further development of the vibration. This also enables a quick detection to be realized, because a single exceeding of the test limit can be sufficient to detect the vibration.
  • the criterion is also easy to implement. This method is particularly well suited for online use. Values can be recorded continuously, the at least one electrical test signal can thus be continuously recorded and it can also be continuously filtered or transformed and this in turn can be derived continuously over time.
  • This derivation can be continuously subjected to the test criterion, in particular, this gradient signal can be continuously compared with a predefined test limit. Fulfilling the test criterion, in particular exceeding the test limit, can therefore trigger a measure immediately. In particular, a support measure can be triggered immediately. For example. power supply can be reduced immediately. It is also possible for a controller parameterization to be changed immediately, namely from a controller with a low time constant and / or weakly damped behavior to a controller with a larger time constant and / or more damped behavior.
  • the gradient signal can also be obtained by performing a difference formation of temporally spaced values of the test signal.
  • the difference between each sample value corresponds to the time derivation anyway.
  • a difference is formed for a predetermined difference period, which is preferably greater than a sampling interval.
  • Such a difference can be successively repeated accordingly.
  • Such differences are preferably carried out in predetermined time windows. Noise can also be suppressed in this way.
  • Such a formation of differences in time windows can act like filtering and can be set by the size of the time window.
  • a gradient maximum value be specified as the test criterion and that the presence of the low-frequency oscillation is recognized if the gradient signal exceeds the gradient maximum value at least once.
  • the presence of the low-frequency oscillation is recognized when the gradient signal is above the gradient maximum value for at least a predetermined minimum period.
  • the duration of one or two sampling steps can already be selected as the predetermined minimum period. Then, the presence of the low-frequency oscillation is only recognized when the gradient signal is above the maximum gradient value for at least two measured values, or at least for three measured values.
  • the maximum gradient value can also depend on a test period over which the gradient is formed and which is described below.
  • the gradient maximum value is preferably also selected with regard to the test period so that it corresponds to a maximum oscillation amplitude of the electrical signal to be tested.
  • the gradient maximum value is preferably selected from a range which corresponds to a range from 0.1% to 2% of the corresponding maximum oscillation amplitude. According to one embodiment, it is proposed that a difference between the maximum and minimum value of the test signal be used as the gradient signal in a test period under consideration. Accordingly, a test period is specified in which the gradient signal is viewed.
  • the difference between two values that are separated by a predetermined time interval is not considered, but the minimum and maximum value of the test signal that occurs in this test period is considered and its difference is used as a gradient signal, in particular compared to a predetermined test limit ,
  • the test period is chosen so that there are 10 or more values or in particular up to 50 values of the gradient signal. This enables a clearly defined test criterion to be set up and, with a high sampling rate, the period until which the test criterion is checked is comparatively short.
  • the test period under consideration is preferably used as a sliding window and is thus shifted one scanning step further in each new scanning step, and the test signal then located in the window is evaluated accordingly.
  • a test limit especially for a vibration amplitude
  • the test limit is therefore preferably not included compared to an absolute value, but it is compared with a maximum oscillation amplitude.
  • Such an oscillation amplitude basically describes the distance between a positive and a negative envelope of an oscillating signal. If a signal fluctuates, for example, by a value of 10, to name just one example, and in the extreme case the signal fluctuates from the value 9 to the value 1 1 and back, the oscillation amplitude would have the value 2 in this example. If, in order to stay with this illustrative example, the associated test limit, for example the value 3, this test limit would not have been reached. If the value of the test limit were 1, 5, for example, it would have been reached.
  • a mains voltage of the electrical supply network in particular three-phase
  • a feed current in particular three-phase
  • fed into the electrical supply network is recorded as a second test signal, and in particular the first and second test signal in at least one test signal be transformed.
  • Information about low-frequency vibrations can be detected via the grid voltage, in particular at the relevant grid connection point, and the feed-in current, which a wind energy system in particular feeds into the electrical supply network. It is particularly important to take into account that a low-frequency oscillation can regularly affect the oscillation of electrical power in the electrical supply network.
  • the input power and the input reactive power can thus be recorded by detecting the feed current and at the same time detecting the mains voltage, that is to say the voltage with which the feed current is fed in. From this in turn, the oscillation of power in the electrical supply network can be derived or it can be detected thereby.
  • This detected mains voltage and this detected feed-in current are preferably transformed into at least one test signal. It is also possible to transform them into a common test signal or to transform them together into several test signals. A transformation into an active power signal as a test signal and / or a reactive power signal as a test signal is particularly suitable.
  • Such a first and second test signal that is to say the detected mains voltage and the detected fed-in feed current, are preferably transformed into a voltage signal, an active power signal and a reactive power signal, which then form a voltage test signal, active power test signal or reactive power test signal.
  • the voltage signal then represents the mains voltage, the active power signal the active power fed in and the reactive power signal the reactive power fed in.
  • test signals are then derived in time in order to obtain a gradient signal, namely a voltage gradient signal, an active power gradient signal and a reactive power gradient signal.
  • the time derivation can also be realized in each case by forming a difference, or instead of the time derivation, a difference is formed for values separated by time.
  • the voltage gradient signal, the active power gradient signal and the reactive power gradient signal are then checked for the presence of a low-frequency oscillation.
  • the test is carried out in such a way that the presence of a low-frequency oscillation is assumed if a low-frequency oscillation was detected at least in the voltage gradient signal and the active power gradient signal, or if a low-frequency oscillation was detected in the voltage gradient signal and the reactive power gradient signal. It is also contemplated that a low frequency oscillation is assumed if a low frequency oscillation was detected in all three gradients, i.e. if a low frequency oscillation was detected in the voltage gradient signal, in the active power gradient signal and in the reactive power gradient signal.
  • the positive test of the presence of a low-frequency oscillation in at least two of the gradient signals mentioned avoids in particular that a measurement error or excessive noise already leads to incorrect detection of low-frequency oscillations.
  • the simultaneous test in the voltage gradient signal on the one hand and the active power gradient signal or the reactive power gradient signal on the other hand has been recognized as advantageous because the voltage gradient signal can quickly detect fluctuations in the voltage signal, which may not be related to low-frequency vibrations.
  • the current component is also taken into account and not only voltage fluctuations are recognized, which can also have another cause and do not necessarily have to indicate a low-frequency oscillation immediately.
  • a network frequency of the electrical supply network is detected as a further test signal, the further test signal is transformed into a frequency signal as a frequency test signal, and the frequency test signal is derived in time, or a difference is formed in order to obtain a frequency gradient signal.
  • the frequency gradient signal and in particular at least one further gradient signal are then checked for the presence of a low-frequency oscillation, in particular in such a way that the presence of a low-frequency oscillation is assumed if a low-frequency oscillation was detected in the frequency gradient signal and in at least one of the gradient signals, namely in one Voltage gradient signal, an active power gradient signal and / or a reactive power gradient signal.
  • the network frequency is recorded and evaluated as such as a signal.
  • a signal would ideally be constant, especially at 50Hz or 60Hz. In fact, however, it will fluctuate and this fluctuation, to put it graphically, forms the frequency signal.
  • Such a frequency signal can then basically be processed like the other signals described.
  • the frequency signal it is possible not only to evaluate the frequency signal, but also to take into account at least one further signal, in particular the active power gradient signal.
  • the detection of the low-frequency vibration can be additionally secured.
  • these variables can also be taken into account as effective values.
  • a transformation can take place in each case in its effective values, and then only the fluctuation of the effective values is considered by deriving them.
  • a three-phase mains voltage is recorded as a test signal for the detection of the at least one electrical signal of the electrical supply network, and a constant, in particular a space vector size of the voltage is formed therefrom via a transformation, in particular that a positive sequence system voltage according to the method of symmetrical components is determined, which forms a test signal and / or a three-phase feed-in current is detected as a test signal and a co-system current is determined therefrom according to the method of symmetrical components, which forms a test signal.
  • the transformation thus determines a constant size, that is to say a non-oscillating variable, which can therefore also be referred to as a DC variable, which basically describes a sinusoidal signal by means of a fixed variable.
  • a DC variable which basically describes a sinusoidal signal by means of a fixed variable.
  • a transformation according to the method of symmetrical components is proposed for the mains voltage and / or the feed current as a transformation into a test signal, in which case only the co-system component, ie basically the symmetrical component, is considered. It was particularly recognized that this transformation using the method of symmetrical components basically results in an effective value which is therefore an equivalent value and which can be used as a description of the basic component. Actual fluctuations, in particular power fluctuations, which are not limited to asymmetries, are then superimposed on this symmetrical component and can then be easily recognized by the suggested time derivation of these test signals.
  • the three-phase voltage or the three-phase current is also considered to be only one component in a simple manner known from other applications. Especially for the further processing and later application of a test criterion, the question does not arise how to apply a single criterion to three phases. It was also recognized that such a transformation, in particular a transformation in co-system and counter-system components, has a filtering effect and thereby particularly high-frequency components are filtered out and that there is sufficient bandwidth for the detection of low-frequency signals. However, other transformations are also possible, such as a d / q transformation, which can also lead to an equivalent value if the reference frequency is selected accordingly.
  • the same size or space vector size of the voltage or the system voltage and the size or space vector size of the current or the system current is transformed into a voltage signal, an active power signal and reactive power signal as a voltage test signal, active power test signal or reactive power test signal.
  • the system voltage can form the voltage test signal directly.
  • the positive sequence current can, together with the positive sequence voltage, be further transformed into an active power signal and a reactive power signal.
  • the electrical supply network is preferably fed into the electrical supply network by means of a wind energy plant or a wind farm, and low-frequency vibrations are detected by means of the wind energy plant or by means of the wind farm. It was particularly recognized here that a wind energy installation or a wind farm can act as very fast control units in the electrical supply network and it can therefore be advantageous to use them to detect low-frequency vibrations. Details of such wind turbines or wind farms are described below.
  • a vibration caused in the electrical supply network is recognized if a low-frequency vibration was detected in the voltage gradient signal and the active power gradient signal or in the voltage gradient signal and the reactive power gradient signal, and these detected low-frequency vibrations have the same vibration frequency, in particular additionally it is checked whether the mains frequency oscillates at the same oscillation frequency.
  • a low-frequency vibration can have different causes and that it can also depend on how such vibrations are to be handled. If a feeder, especially a wind power plant or a wind farm, has caused vibrations, the reason for the vibration is particularly to be found in the dynamics of the wind power plant or the wind farm. It can then also be assumed that the vibrations must be able to be remedied by the wind energy installation or the wind farm.
  • the cause of the vibration then does not necessarily have to lie directly in the area of the feed, but can also relate to a mechanical vibration and / or a vibration in the generator. However, if the cause of the vibration lies in the electrical supply network, the wind energy installation or the wind farm can be used, if at all, to carry out vibration damping, that is to say reduction. In addition, such damping will essentially affect the feed. Therefore, the differentiation of the cause of vibration has been recognized as important.
  • the cause of the vibrations in the electrical supply network is to be sought when at least two of the signals mentioned are recorded simultaneously. Vibrations of the grid voltage and the grid frequency in particular indicate a vibration in the electrical supply network, whereas the active power signal, i.e. the fed-in active power, and the reactive power signal, i.e. the fed-in reactive power, tend to indicate vibrations in the feed unit, particularly in the wind power plant or the Indicate wind farm.
  • the oscillations of the mains voltage and / or the mains frequency have the same oscillation frequency as the oscillations of the active and / or reactive power, then there is an oscillation that affects the feed-in unit, especially the wind turbine or the wind farm, but its cause in the electrical supply network Has. For example. it may be that large electrical consumers that are connected to the electrical supply network interfere with network operation, for example due to power fluctuations and thereby trigger the vibrations.
  • the method is characterized in that a difference between the maximum and minimum value of the corresponding test signal is used in each test period as a voltage gradient signal, active power gradient signal and reactive power gradient signal and an identical oscillation frequency is recognized by using the same test period and / or -
  • the respective time intervals between the maximum and minimum value of the corresponding test signal for the voltage gradient signal, the active power gradient signal and the reactive power gradient signal are the same or similar.
  • the detection of the low-frequency oscillation by means of gradient formation can be carried out in a simple and efficient manner by binding the difference between two signal values, namely the maximum and the minimum. This is based on a test period that can be set to the distance between the two values, that is, the maximum and minimum values, and thus the oscillation frequency can also be formed directly. For a check on same frequency is but that is not necessary either, then the time intervals are the same, and the assigned frequencies are also the same.
  • the method is characterized in that a gradient quotient is formed as the quotient of two gradient signals and is recognized depending on the gradient quotient for an oscillation caused in the electrical supply network.
  • the wind energy installation or the wind farm is used as the feed unit and it is examined whether a vibration caused in the electrical supply network or a vibration caused in or by the feed unit is to be assumed.
  • a voltage-active power quotient dU / dP is formed as the gradient quotient as a quotient between the voltage gradient signal and the active power gradient signal and / or that a voltage-reactive power quotient dU / dQ is formed as the quotient between the voltage gradient signal and the reactive power gradient signal.
  • a vibration caused in the electrical supply network is recognized when the voltage-active power quotient dU / dP and / or the voltage-reactive power quotient dU / dQ are negative.
  • a further embodiment proposes a method which is characterized in that vibrations are classified and a found vibration classification is output. The following are particularly considered as vibration classifications:
  • a low-frequency oscillation was recognized for one or the mains voltage signal and one or the active power signal.
  • a low-frequency oscillation was recognized for the mains voltage signal and one or the reactive power signal.
  • a low-frequency vibration was detected for the voltage signal, the active power signal and the reactive power signal.
  • a low-frequency oscillation was recognized for the mains frequency and also for the voltage signal, the active power signal and / or the reactive power signal.
  • the vibration classifications simply indicate the signals for which a low-frequency vibration was recognized.
  • the recipient of this vibration classification can then derive further qualified conclusions from this.
  • An oscillation of the mains voltage together with an oscillation of the fed-in active power can indicate a power oscillation in the electrical supply network, or an oscillation triggered by a change in the active power balance in the electrical supply network.
  • an oscillation of the mains voltage together with an oscillation of the fed reactive power may indicate a problem of voltage stabilization in the electrical supply network, to name another example.
  • a wind energy system is also proposed.
  • the wind energy system can be a single wind energy installation or a wind farm with several wind energy installations. It is prepared for the detection of low-frequency vibrations, in particular subsynchronous resonances, in an electrical supply network.
  • the electrical supply network is based on the assumption that it has a network voltage with a nominal network frequency and that the low-frequency vibrations to be detected have a lower frequency than the nominal network frequency.
  • the proposed wind energy system comprises a detection device for detecting at least one electrical signal of the electrical supply network as at least one test signal.
  • a measuring device at the output of an inverter and / or at the grid connection point at which the wind energy system feeds into the electrical supply network is proposed here.
  • the detection device is preferably set up to detect a voltage, in particular the mains voltage of the electrical supply network.
  • the detection device be provided for detecting an electrical current that is fed in.
  • the wind energy system comprises a filter unit for filtering and / or transforming the at least one detected test signal into at least one test signal.
  • a digital filter or a digital transformation unit comes into consideration, in particular to filter or transform the at least one test signal, if this is present as a digital signal.
  • a filter comes into consideration which filters out frequencies which are at and above the nominal network frequency in order to achieve in particular that frequencies of the expected low-frequency vibrations are retained.
  • a transformation which also functions in whole or in part as a filter in order in particular to transform an effective value of the detected variable.
  • Such a transformation into the effective value can be considered, in particular, when a line voltage or a current fed in is recorded as a test signal. Basically, the fundamental is filtered out or transformed out of the respective test signal.
  • a derivation unit is provided for deriving the at least one test signal in time in order to obtain a gradient signal in each case. Every test signal is thus through changed this derivation unit into a gradient signal.
  • the derivation can also be carried out by forming a difference or, instead of deriving, a difference can be formed by temporally spaced values of the test signal.
  • a time interval can be specified, for example, by which two values of the test signal are to be spaced, if the difference is to be carried out between them.
  • the filter unit Ideally, only a derivation of any low-frequency vibrations present is then present in the gradient signal, when the basic signal, that is to say in particular a 50 Hz signal or a 60 Hz signal, has ideally been removed by the filter unit.
  • the respective signals, in particular the superimposed signals, can be better recognized by the derivation.
  • a detection unit for detecting the presence of a low-frequency vibration. This works in such a way that when the gradient signal or at least one of the gradient signals fulfills a predetermined test criterion, the presence of a low-frequency oscillation is recognized.
  • a test limit is specified as the specified test criterion and the test criterion is met if the at least one specified test limit is exceeded. In particular, if a predetermined test limit was exceeded by the gradient signal.
  • the wind energy system in particular the detection unit, thus operates in such a way that low-frequency vibrations are detected by considering and evaluating the change of at least one filtered test signal.
  • the detection device, the filter unit, the derivation unit and / or the detection unit can preferably be combined in a process computer and in particular in a control device. It is also possible to consider these elements as program code.
  • the wind energy system works in such a way that it implements a method according to at least one embodiment described above.
  • the wind energy system has a control device and the control device is prepared to carry out a method according to an embodiment described above.
  • the method can be implemented in the control device for this purpose.
  • a method for recognizing low-frequency vibrations and / or a wind energy system for recognizing low-frequency vibrations is also prepared to react in the event of one or more detected low-frequency vibrations, in particular to dampen the electrical supply network.
  • the feeding of electrical power, in particular electrical active power, into the electrical supply network is reduced, in particular by 30% -70%, preferably 50%.
  • the electrical supply network can be calmed with regard to low-frequency vibrations. It should be emphasized here in particular that no detailed information about the detected low-frequency vibration is required. It is sufficient to carry out the proposed steaming measure, ie to trigger it as soon as a low-frequency oscillation has been detected.
  • a damping measure is activated in which, for example, a modulated power is fed in.
  • the decay of the one or more detected low-frequency vibrations is assumed when the at least one gradient signal has fallen below a predetermined termination limit, which is in each case less than the test limit.
  • the termination limit is in each case at least less than 80% of the test limit, in particular in each case less than 50% of the test limit.
  • the detection of the presence of a low-frequency oscillation is assumed if a predetermined test limit is exceeded, but the decay of the low-frequency oscillation is not yet assumed if this predefined test limit is undershot again. Rather, the gradient signal must be significantly smaller than the specified test limit and the specified termination limit is proposed for this, which is selected to be significantly smaller than the test limit. In particular, it should have a maximum of 80%, preferably a maximum of 50% of the test limit.
  • test limit When checking a plurality of gradient signals, that is to say when several test signals have been recorded, an individual test limit can be provided for each gradient signal his.
  • termination limits which are correspondingly individual.
  • a test limit and a termination limit are preferably assigned to each gradient signal, the respective termination variable being smaller than the test limit of the same gradient signal.
  • damping measures that were triggered upon detection of a low-frequency oscillation be ended when the low-frequency oscillations have decayed.
  • the damping measures can therefore be initiated when a gradient signal exceeds the predetermined test limit and they can be terminated when the same gradient signal falls below its termination limit.
  • Figure 1 shows a wind turbine in a perspective view.
  • Figure 2 shows a wind farm in a schematic representation.
  • FIG. 3 schematically shows a sequence structure of a method according to one embodiment.
  • Figure 4 shows a schematic diagram of several test signals
  • FIG. 5 shows a wind energy system with a control device.
  • FIG. 1 shows a wind energy installation 100 with a tower 102 and a nacelle 104.
  • a rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104.
  • the rotor 106 is set into a rotary movement by the wind and thereby drives a generator in the nacelle 104.
  • FIG. 2 shows a wind farm 1 12 with three wind turbines 100 as an example, which can be the same or different.
  • the three wind energy plants 100 are therefore representative of basically any number of wind energy plants of a wind farm 1 12.
  • the wind energy plants 100 provide their output, namely in particular the electricity generated, via an electrical parking network 1 14.
  • the respectively generated are Currents or powers of the individual wind energy plants 100 are added up and mostly a transformer 116 is provided, which transforms up the voltage in the park in order to then feed into the supply network 120 at the feed-in point 118, which is also generally referred to as PCC.
  • FIG. 2 is only a simplified illustration of a wind farm 1 12, which shows no control, for example, although of course there is a control.
  • the parking network 114 can also be designed differently, for example, in that, for example, there is also a transformer at the output of each wind energy installation 100, to name just one other exemplary embodiment.
  • FIG. 3 shows in process structure 300 method steps for the method for recognizing low-frequency vibrations. Accordingly, a voltage detection block 302 and a current detection block 304 are initially provided.
  • the voltage detection block 302 receives the three phase voltages Ui, U2 and U3 and forwards a common voltage signal U to a filter block 306.
  • the three phase voltages Ui, U2 and U3 can be recorded especially as a line voltage at a line connection point.
  • the current detection block 304 receives the three phase currents h, I2 and I3 and forwards a common current signal I to the filter block 306.
  • the three phase currents h, I2 and I3 can in particular have been recorded as feed currents which a wind energy system has generated and feeds into the electrical supply network at the same grid connection point, to which the three phase voltages Ui, U2 and U3 were also recorded.
  • a filtering of the common voltage signal U obtained and the common current signal I obtained is then carried out first.
  • This filtering is tailored to the frequency spectrum that is of interest.
  • the filter is designed so that low-frequency vibrations can be maintained as far as possible and are not filtered out.
  • the signals thus filtered are converted into a rms voltage value Um, an effective power rms value P m and a reactive power rms value Q m . All of these three values are output as signals, that is to say as a voltage signal, active power signal and reactive power signal, each signal representing the effective value of the relevant variable as a function of time. These signals output by filter block 306 can form test signals. These three RMS signals are input to deriving block 308. In the derivation block 308, gradients are determined for the RMS values by derivation or difference formation, and these gradients are each compared with a test limit.
  • the deriving block 308 outputs a corresponding signal, which is referred to here as a trigger signal.
  • the signal is called a trigger signal because it can still be used to trigger reactions.
  • Such triggering reactions can be to take damping measures and, additionally or alternatively, can be a safety shutdown of the wind energy system using this method. It is also possible for the trigger signal to always be output, but depending on the situation detected, that is to say depending on whether a low-frequency oscillation has been detected, has a different value or has a different signal amplitude.
  • FIG. 4 schematically shows the course of three test signals, namely the voltage test signal Um, the active power test signal P m and the reactive power test signal Q m , for measurements taken over a period of about 30 seconds.
  • These three test signals correspond to the three RMS signals Um, P m and Q m according to FIG. 3, which the filter block 306 outputs there.
  • FIG. 4 also shows in the diagram a trigger signal that corresponds to the trigger signal T hg according to FIG. 3 that the deriving block 308 outputs there.
  • the three test signals Um, Pm and Q m are shown standardized, namely standardized to nominal values.
  • the numbers are shown as "milli", so that the scale ranges from -1000 to +1000 instead of -1 to +1.
  • derivations are also formed from these three test signals for further evaluation, especially in the derivation block 308, before a further evaluation takes place. These derivatives are not shown here for the sake of simplicity. It can be seen in FIG. 4 that all three test signals initially have few vibrations.
  • the voltage test signal Um and the reactive power test signal Q m initially initially initially have a constant value. So constant reactive power is fed in.
  • the voltage test signal Um drops slightly, the drop being less than 1%.
  • the active power test signal shows a slightly increasing value. This increase can also be attributed to increasing wind speeds. However, the increase of around 3% in 15 seconds is comparatively small, and in any case does not allow conclusions to be drawn about low-frequency vibrations. Shortly before time h it can be seen that all three test signals have increasing oscillations. In the graph of the schematic representation according to FIG. 4, the increase in the oscillations appears to be obvious and easily recognizable. However, this relationship cannot easily be identified for automatic evaluation by means of a process computer. It is therefore proposed to derive these three test signals, namely the voltage test signal Um, the active power test signal P m and the reactive power test signal Q m . With such a derivation, which is however not shown in FIG. 4, the vibrations then emerge more intensely. The derivatives then become so large at time h that they exceed their respective test limits and were therefore recognized for the presence of a low-frequency oscillation.
  • both criteria are met at time t1.
  • the trigger signal T g shows at the time ti that the trigger signal T rig jumps from 0 to the value 1. If only one of the criteria is met, the trigger signal Thg assumes a smaller value, but which is significantly greater than zero, e.g. 0.8.
  • the trigger signal Thg assumes the value 0 only if none of the criteria is met. For this reason, the trigger signal Thg partially drops to this smaller value of approximately 0.8, because there the active power test signal or the reactive power test signal in the time ranges dropped below their test limit. The voltage test signal did not drop below its test limit during the entire time shown from time h, because in that case the trigger signal T rig would have dropped to the value 0.
  • the trigger signal T rig does not assume the value 0, a damping measure is initiated, or even a wind energy system is shut down, or even the wind energy system is disconnected from the electrical supply network.
  • FIG. 5 shows an illustration of a wind energy installation 500 with a control device 502, which, like the inverter 504 just shown, is to be regarded as part of the wind energy installation 500 and could, for example, be arranged in the tower 506 of the wind energy installation, with the inverter 504 and the only for the sake of clarity Control device is shown outside the remaining wind turbine 500.
  • a control device 502 which, like the inverter 504 just shown, is to be regarded as part of the wind energy installation 500 and could, for example, be arranged in the tower 506 of the wind energy installation, with the inverter 504 and the only for the sake of clarity Control device is shown outside the remaining wind turbine 500.
  • the inverter 504 receives power generated from the wind as a DC voltage signal and executes the inverter based thereon and generates a three-phase feed current li, 2,3 at a three-phase voltage U-1,2,3. This can be fed via a transformer 508 into the electrical supply network 510 at a network connection point 512 indicated there.
  • current and voltage can first be measured with an indicated measurement sensor 514 and transferred to the detection device 526.
  • the detection device 516 and the measurement sensor 514 can also form a common unit.
  • the detection device 516 thus detects at least one test signal from the transferred measurements.
  • voltage and current can each form a test signal.
  • This test signal or here these test signals are then passed to the filter unit 518, which carries out filtering and in particular carries out this filtering in such a way that essentially only signal components with desired frequencies remain, namely in the range of the expected low-frequency vibrations.
  • These signals filtered in this way are used as test signals and transferred to the derivation unit 520.
  • the symbol of the derivation unit 520 indicates a time-continuous derivation, but of course, especially when discrete signals are present, a discrete derivation by difference formation can also be considered.
  • the signal or signals derived in this way is transferred to the recognition unit 522, which then checks a predetermined test criterion, in particular for each received derived test signal, checks whether a predetermined test limit has been exceeded in each case.
  • the recognition unit 522 can transmit a trigger signal to a process computer 524.
  • the process computer 524 basically controls the inverter, possibly takes on further control tasks, and can also make this control dependent on the trigger signal received by the recognition unit 522. Particularly when one low-frequency oscillation or several low-frequency oscillations have been detected, the process computer 524 can control the inverter 504 accordingly in a modified manner, for example by specifying a reduction in the power to be fed in. For this purpose, which is not shown in FIG. 5, the process computer 524 can also carry out further controls in the wind energy installation, such as, for example, adjusting the rotor blades in order to also draw correspondingly less power from the wind. In addition or alternatively, it is possible that in the event of detected low-frequency vibrations to protect the wind energy installation, the feeding is stopped and, if necessary, a safety switch is opened, which, however, is not shown in FIG.
  • Wind turbines can also help stabilize the energy system or, if handled incorrectly, even destabilize it. It should be noted that the lifespan of a wind turbine can be around 25 years and during this time the energy system can also change and develop significantly.
  • the proposed method can also be implemented as an algorithm in a control device, in particular a process computer.
  • a central parking computer or a central parking control unit on which the method can be implemented can also be considered.
  • the detection device, filter unit, derivation unit and detection unit, as illustrated in FIG. 5, can also be combined in a common control unit or implemented as algorithms or software blocks.
  • the proposed algorithm or the proposed method is based in particular on the analysis of voltage and power gradients. Incidentally, evaluations can be carried out on site at the wind energy installation or in the wind farm, or also in a remote monitoring center. It is then possible for the necessary data to be transferred via SCADA.
  • the proposed method can also be used for consumer units, and in principle also for conventional power plants.
  • consumer units may change their behavior if low-frequency vibrations are detected or may disconnect from the electrical supply network.
  • a solution is also created that enables a method for online detection of energy system vibrations.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mathematical Physics (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

L'invention concerne un procédé pour la détection d'oscillations de basse fréquence, en particulier de résonances sous-synchrones, dans un réseau d'alimentation électrique (510), le réseau d'alimentation électrique (510) présentant une tension de réseau pourvue d'une fréquence nominale de réseau, comprenant les étapes consistant à : détecter au moins un signal électrique du réseau d'alimentation électrique (510) comme au moins un signal de test et filtrer et/ou transformer ledit au moins un signal de test détecté en au moins un signal de test, dériver dans le temps ledit au moins un signal de test ou former une différence de valeurs écartées dans le temps du signal de test pour obtenir à chaque fois un signal à gradient, détecter la présence d'une oscillation de basse fréquence lorsque le signal à gradient ou au moins un des signaux à gradient répond à un critère de test défini, en particulier passe au-dessus d'au moins une limite de test définie.
EP19737082.8A 2018-07-06 2019-07-05 Système éolien et procédé pour détecter des oscillations de basse fréquence dans un réseau d'alimentation électrique Pending EP3818384A1 (fr)

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DE102018116446.7A DE102018116446A1 (de) 2018-07-06 2018-07-06 Windenergiesystem und Verfahren zum Erkennen niederfrequenter Schwingungen in einem elektrischen Versorgungsnetz
PCT/EP2019/068107 WO2020008036A1 (fr) 2018-07-06 2019-07-05 Système éolien et procédé pour détecter des oscillations de basse fréquence dans un réseau d'alimentation électrique

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CN116865269B (zh) * 2023-09-01 2023-11-21 山东泰开电力电子有限公司 一种风电机组高谐波补偿方法及系统

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US20210159705A1 (en) 2021-05-27
US11658490B2 (en) 2023-05-23
CN112384813A (zh) 2021-02-19
CA3105412C (fr) 2023-11-28
CA3105412A1 (fr) 2020-01-09
DE102018116446A1 (de) 2020-01-09

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