CN110323773B - Commutation failure prediction method and system considering multi-factor influence - Google Patents
Commutation failure prediction method and system considering multi-factor influence Download PDFInfo
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Abstract
The invention discloses a commutation failure prediction method and a system considering multi-factor influence, which comprises the following steps: calculating the value of each influence factor; calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor; and comparing the commutation failure risk value with a preset commutation failure risk criterion to predict whether commutation failure occurs in the commutation station. The commutation failure prediction method considering the multi-factor influence considers various influence factors causing commutation failure, determines commutation failure risk criteria, and predicts whether commutation failure occurs according to the commutation failure risk value and the commutation failure risk criteria determined by the factors; whether the commutation failure occurs can be well identified according to the transient characteristic of the phase angle of the alternating-current side current of the converter station when the commutation failure occurs; meanwhile, the accuracy and efficiency of prediction and identification are improved by utilizing the method provided by the invention.
Description
Technical Field
The invention relates to the technical field of relay protection, in particular to a commutation failure prediction method and system considering multi-factor influence.
Background
The converter station of the high-voltage direct-current transmission project has the function of converting alternating current and direct current into each other. When the converter valve on the inversion side is interfered by the outside or the inside, the converter valve which should be turned off bears forward voltage again when the blocking capability is not recovered, so that the turned-off valve is turned on again to generate reverse phase. At this time, the valve of the other pole still normally changes phase, and the valve of the reversed phase forms a bypass to cause a short circuit on the direct current side of the valve, which is called phase change failure. When the phase commutation of the dc system fails, the power sent by the dc system fluctuates to a large extent. Because the commutation failure is caused by the inherent element characteristics of a thyristor in the direct current converter valve, single commutation failure cannot be avoided, if the commutation failure is not detected, identified and inhibited in time, multiple commutation failures of the direct current system can be caused to cause direct current locking, or multiple direct currents can be caused to simultaneously cause commutation failures, and serious impact is caused on the safety and stability of the direct current receiving end alternating current system.
At present, the detection method for commutation failure in engineering is mainly divided into two types, namely an actual measurement type and a prediction type. The actual measurement type calculates a time interval of a difference between a time when each valve current is zero and a time when the commutation voltage crosses zero, converts the time interval into an angle to obtain an arc-quenching angle, and compares the angle with a limit arc-quenching angle to judge whether commutation failure occurs, for example, in a skyhook direct current system. The prediction mode is to judge whether a direct current fault occurs by extracting a negative sequence component after the alternating current fault occurs or comparing the difference between the direct current and the maximum value of the valve current to judge that the commutation fails, but a recognition dead zone still exists, for example, the control system can be misjudged due to loss of trigger pulses, harmonic influence and the like, and the consideration factor is insufficient. And the method for judging the commutation failure by using single factors such as commutation voltage, direct current and the like reduces the accuracy under the complex working conditions of multi-feed direct current access and large-scale distributed power supply grid connection.
Therefore, a method for predicting commutation failure considering multi-factor influence is required.
Disclosure of Invention
The invention provides a commutation failure prediction method and a commutation failure prediction system considering multi-factor influence, which aim to solve the problem of predicting whether commutation failure occurs in a converter station.
In order to solve the above problem, according to an aspect of the present invention, there is provided a commutation failure prediction method considering multi-factor influence, the method including:
calculating the value of each influence factor; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor;
calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor;
and comparing the commutation failure risk value with a preset commutation failure risk criterion to predict whether commutation failure occurs in the commutation station.
Preferably, wherein said calculating a value for each impact factor comprises:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
when the influence factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs presetTriggering a pulse factor maximum; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state.
Preferably, the calculating a commutation failure risk value according to the value of each influence factor and the influence degree of commutation failure of the influence factor includes:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piThe value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between.
Preferably, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor; piThe value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
Preferably, the preset commutation failure risk criterion comprises:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
Preferably, wherein the method further comprises:
when the prediction result indicates that the converter station is likely to have the phase change failure, calculating an integral value of the absolute value of the derivative of the current phase angle on the alternating current side of the converter station, and when the integral value is less than 0, determining that the converter station has the phase change failure.
According to another aspect of the present invention, there is provided a commutation failure prediction system considering multi-factor influence, the system comprising:
the value calculating unit of the influence factor, is used for calculating the value of each influence factor; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor;
the commutation failure risk value calculating unit is used for calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor;
and the commutation failure prediction unit is used for comparing the commutation failure risk value with a preset commutation failure risk criterion so as to predict whether commutation failure occurs in the commutation station.
Preferably, the value calculation unit of the influence factors calculates the value of each influence factor, including:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
when the influence factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs the maximum value of the preset trigger pulse factor; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state.
Preferably, the commutation failure risk value calculating unit calculates the commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor, and includes:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piThe value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between.
Preferably, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor; piThe value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
Preferably, the preset commutation failure risk criterion comprises:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
Preferably, wherein the system further comprises:
and the commutation failure identification unit is used for calculating an integral value of the absolute value of the derivative of the current phase angle at the alternating side of the collected converter station when the prediction result indicates that the converter station is possible to generate commutation failure, and determining that the converter station has generated commutation failure when the integral value is less than 0.
The invention provides a commutation failure prediction method and a system considering multi-factor influence, which comprises the following steps: calculating the value of each influence factor; calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor; and comparing the commutation failure risk value with a preset commutation failure risk criterion to predict whether commutation failure occurs in the commutation station. The method considers various influence factors causing commutation failure, determines commutation failure risk criteria, and predicts whether commutation failure occurs according to the commutation failure risk value and the commutation failure risk criteria determined by the factors; whether the commutation failure occurs can be well identified according to the transient characteristic of the phase angle of the alternating-current side current of the converter station when the commutation failure occurs; meanwhile, the accuracy and efficiency of prediction and identification are improved by utilizing the method provided by the invention.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a flow diagram of a commutation failure prediction method 100 that takes into account multi-factor effects, according to an embodiment of the present invention;
FIG. 2 is a diagram of a valve current waveform according to an embodiment of the present invention;
FIG. 3 is a logic diagram for commutation failure prediction based on commutation failure risk values, according to an embodiment of the present invention;
FIG. 4 is a general logic diagram for performing commutation failure determination in accordance with an embodiment of the present invention; and
FIG. 5 is a block diagram of a commutation failure prediction system 500 that considers multi-factor effects according to an embodiment of the invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
FIG. 1 is a flow chart of a commutation failure prediction method 100 considering multi-factor effects according to an embodiment of the invention. As shown in fig. 1, in the commutation failure prediction method considering multi-factor influence according to the embodiment of the present invention, a plurality of influence factors causing commutation failure are considered, commutation failure risk criteria are determined, and whether commutation failure occurs is predicted according to commutation failure risk values and commutation failure risk criteria determined by the factors; whether the commutation failure occurs can be well identified according to the transient characteristic of the phase angle of the alternating-current side current of the converter station when the commutation failure occurs; meanwhile, the accuracy and efficiency of prediction and identification are improved by utilizing the method provided by the invention. The commutation failure prediction method 100 considering multi-factor influence provided by the embodiment of the invention starts with step 101, and calculates the value of each influence factor in step 101; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor.
Preferably, wherein said calculating a value for each impact factor comprises:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
when the influence factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if miningSample point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs the maximum value of the preset trigger pulse factor; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state.
Because the phase change failure is caused by sudden change of phase change voltage, sudden change of direct current, overhigh harmonic component, sudden change of valve current and loss of trigger pulse, the risk quantity is considered by the risk factor of the phase change failure, so that the risk of the phase change failure is well reflected. In the embodiment of the invention, the voltage U of the converter bus of the converter station is acquiredLD.c. current IdAnd valve current IVThen, the value of each influence factor is calculated. Specifically, the method comprises the following steps: definition of commutation voltage factor by calculating the amount of sudden change in commutation bus voltage
Obtaining the effective value V of the fundamental wave of the commutation voltage through full-wave Fourier transform1rmsAnd h-order harmonic effective value VhrmsContent, defining harmonic factors
Defining a DC factor by calculating a sudden change in DC current
Defining a valve current factor by calculating a second derivative of the valve current
The trigger pulse factor P is defined by the characteristic that when the trigger pulse is lost so that the conducting valve is not conducting, the valve current zero potential of the failed valve is much greater than the valve current zero potential time under normal conditionspulse。
In the valve current waveform under the ideal condition, a zero potential region of a constant time exists in one valve current period, which is a condition that the absolute value of the valve current is smaller than a preset valve current threshold value, as shown in sections AB and CD in fig. 2. The time of the AB section and the CD section is absolutely the same under ideal conditions, and the number of sampling points of the AB section and the CD section after the valve current is sampled is also the same, which is determined by the periodic rule of the valve current. That is, if the valve current is 20ms in one period, the AB segment and the CD segment are both 5ms, and the sampling frequency is set to 10 points/ms, the AB segment and the CD segment are both 50 points, i.e., the number of n.
In an embodiment of the present invention, P is setpulseThe initial value of (1) is 0, and the preset threshold value of the valve current is 1.3 times of the maximum value of the absolute value of the valve current in the zero potential interval under the ideal condition of the valve current.
At point A, the absolute value of the current valve current Iv is smaller than the preset valve current threshold value, the program starts to calculate, and the sampling point is m1Point; under normal conditions, sample point m1The absolute value of Iv at + n-1 should also be less than the predetermined threshold value of valve current, and the absolute value of valve current at sampling point m1+ n begins to be greater than the predetermined threshold value of valve current. But due to the actual time of the AB and CD segmentsThere will be slight fluctuations in between, leaving a 2 point margin.
At sampling point m1At + n +1, if the absolute value of Iv is greater than the preset threshold value of valve current, P is still maintainedpulseAnd zero output is realized until the absolute value of the valve current is smaller than a preset valve current threshold value, namely a point C.
If sampling point m1When the absolute value of Iv is detected to be smaller than the preset valve current threshold value at + n +1, the converter valve is considered to be possible to have pulse loss, and at the moment, PpulseThe output is changed from 0 to PminAnd continues the detection. At sampling point m1+ n +0.5n is detected again; the method comprises the following steps: if sampling point m1When the absolute value of Iv is larger than the preset valve current threshold value at + n +0.5n, PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value, namely a point C; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxAnd C, when the absolute value of the valve current is smaller than a preset valve current threshold value, namely, the absolute value is detected to be the point C. After reaching point C, point C is recorded as m1And detecting the current period of the next valve again.
In step 102, a commutation failure risk value is calculated according to the value of each influence factor and the influence degree of commutation failure of the influence factor.
Preferably, the calculating a commutation failure risk value according to the value of each influence factor and the influence degree of commutation failure of the influence factor includes:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piThe value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between.
Preferably, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor; piThe value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
In the embodiment of the invention, the influence degree factor C of commutation failure is defined by each influence factoriCalculating a commutation failure risk factor PcfThe method comprises the following steps:
wherein, PcfIs a commutation failure risk value;
a value of a commutation voltage factor; c1The influence degree of commutation failure of the commutation voltage factor; phIs the value of the harmonic factor; c2The influence degree of commutation failure of the harmonic factor;
is the value of the direct current factor; c3The influence degree of commutation failure of the direct current factor is obtained; pIvIs the value of the valve current factor; c4The degree of influence of commutation failure as a valve current factor; ppulseIs the value of the trigger pulse factor; c5To trigger the extent of the impact of commutation failure of the pulse factor.
And setting high and low risk fixed values of the influence degrees corresponding to different influence factors through the influence degrees of the influence factors on the commutation failure risk. Wherein, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor; piThe value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
In step 103, the commutation failure risk value is compared with a preset commutation failure risk criterion to predict whether commutation failure occurs in the commutation station.
Preferably, the preset commutation failure risk criterion comprises:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
Preferably, wherein the method further comprises:
when the prediction result indicates that the converter station is likely to have the phase change failure, calculating an integral value of the absolute value of the derivative of the current phase angle on the alternating current side of the converter station, and when the integral value is less than 0, determining that the converter station has the phase change failure.
In the embodiment of the invention, the starting fixed value f of the commutation failure risk is setqdAnd an outlet constant value fckAs a commutation failure risk criterion, judging the risk of commutation failure, wherein the commutation failure risk criterion is as follows:
i.e. if the commutation failure risk value PcfLess than a predetermined starting constant value fqdIf so, the prediction result indicates that the converter station does not have the commutation failure;
if the commutation failure risk value PcfMore than or equal to the preset starting fixed value fqdAnd is less than a predetermined outlet constant fckIf so, the prediction result indicates that the converter station is likely to have phase change failure;
if the commutation failure risk value PcfGreater than or equal to the preset outlet fixed value fckThe prediction result indicates that a commutation failure of the converter station may occur.
When f is satisfiedqd≤Pcf＜fckAnd then, considering that phase change failure possibly occurs, continuously carrying out phase detection, acquiring the current phase angle theta at the alternating current side of the converter station, and calculating the integral derivative of the phase angle
As a phase detection criterion when
When this occurs, it is considered that a commutation failure has occurred.
When P is satisfiedcf≥fqdWhen a commutation failure is detected, it is considered that a commutation failure has occurred
When this occurs, it is considered that a commutation failure has occurred.
And whether the commutation failure occurs can be well judged according to the transient characteristic of the phase angle of the alternating-current side current of the converter station when the commutation failure occurs.
FIG. 3 is a diagram of a shift-based scheme according to an embodiment of the present inventionAnd the phase failure risk value is used for carrying out a logic diagram of phase commutation failure prediction. As shown in fig. 3, the logical relationship includes: calculating the value P of each influence factorjThe influence degree C of commutation failure corresponding to the influence factori(ii) a According to PjAnd CiCalculating commutation failure risk value Pcf(ii) a And judging according to the commutation failure risk criterion to determine whether commutation failure occurs.
FIG. 4 is a general logic diagram for performing commutation failure determination according to an embodiment of the present invention. As shown in fig. 4, in the embodiment of the present invention, determining whether a commutation failure occurs includes: and judging according to a commutation failure risk criterion or according to a conventional commutation failure criterion, wherein a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor and a trigger pulse factor are determined according to the converter station information, and calculation is performed according to the values of all the influence factors to judge whether the commutation failure risk criterion is met.
In an embodiment of the present invention, predicting and confirming whether a commutation failure occurs includes:
(1) when a single-phase metallic fault occurs at an outlet of an alternating current side of a direct current converter station of an alternating current and direct current hybrid power grid, collecting the voltage U of a converter bus of the converter stationLD.c. current IdAnd valve current IV；
(2) Calculating the value of the commutation voltage factor
Value P of the harmonic factorhValue of the direct current factor
Value P of valve current factorIvAnd the value P of the trigger pulse factorpulse；
(3) Determining the influence degree C corresponding to each influence factor according to whether each influence factor exceeds the corresponding risk fixed valuei；
(4) According to the value of each influence factor and the corresponding influence degree CiCalculating a commutation failure risk value Pcf;
(6) 0.1ms after the occurrence of the fault,determine Pcf≥fqdTherefore, the risk of phase commutation failure is predicted, and phase detection is started;
(7) 0.2ms after the fault occurs, P is judged and readcf≥fckTherefore, commutation failure is predicted to occur;
(8) 1ms after the fault occurs, the adjacent direct current systems have phase commutation failure;
(9) 0.2ms after the commutation failure occurs, judging that
Thus identifying a commutation failure.
FIG. 5 is a block diagram of a commutation failure prediction system 500 that considers multi-factor effects according to an embodiment of the invention. As shown in fig. 5, the commutation failure prediction system 500 considering multi-factor influence according to the embodiment of the present invention includes: a value calculation unit 501 of influence factors, a commutation failure risk value calculation unit 502, and a commutation failure prediction unit 503.
Preferably, the value calculating unit 501 of the influence factors is used for calculating the value of each influence factor; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor.
Preferably, the value calculating unit 501 for influence factors calculates the value of each influence factor, including:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
shadow maskWhen the response factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs the maximum value of the preset trigger pulse factor; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state.
Preferably, the commutation failure risk value calculating unit 502 is configured to calculate a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor.
Preferably, the commutation failure risk value calculating unit 502 calculates the commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor, including:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piThe value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between.
Preferably, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor; piThe value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
Preferably, the commutation failure prediction unit 503 is configured to compare the commutation failure risk value with a preset commutation failure risk criterion, so as to predict whether a commutation failure occurs in a commutation station.
Preferably, the preset commutation failure risk criterion comprises:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
Preferably, wherein the system further comprises: and the commutation failure identification unit is used for calculating an integral value of the absolute value of the derivative of the current phase angle at the alternating side of the collected converter station when the prediction result indicates that the converter station is possible to generate commutation failure, and determining that the converter station has generated commutation failure when the integral value is less than 0.
The commutation failure prediction system 500 considering multi-factor influence according to the embodiment of the present invention corresponds to the commutation failure prediction method 100 considering multi-factor influence according to another embodiment of the present invention, and is not described herein again.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Claims (6)
1. A commutation failure prediction method considering multi-factor influence, the method comprising:
calculating the value of each influence factor; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor;
calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor;
comparing the commutation failure risk value with a preset commutation failure risk criterion to predict whether commutation failure occurs in the commutation station;
wherein, the calculating the commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor comprises:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piIs the value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between;
wherein the calculating of the value of each impact factor comprises:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
when the influence factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs the maximum value of the preset trigger pulse factor; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state;
wherein, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor is obtained; piIs the value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
2. The method of claim 1, wherein the preset commutation failure risk criteria comprise:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
3. The method of claim 2, further comprising:
when the prediction result indicates that the converter station is likely to have the phase change failure, calculating an integral value of the absolute value of the derivative of the current phase angle on the alternating current side of the converter station, and when the integral value is less than 0, determining that the converter station has the phase change failure.
4. A commutation failure prediction system that accounts for multi-factor effects, the system comprising:
the value calculating unit of the influence factor, is used for calculating the value of each influence factor; wherein the influencing factors include: at least two of a commutation voltage factor, a harmonic factor, a direct current factor, a valve current factor, and a trigger pulse factor;
the commutation failure risk value calculating unit is used for calculating a commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor;
the commutation failure prediction unit is used for comparing the commutation failure risk value with a preset commutation failure risk criterion so as to predict whether commutation failure occurs in the commutation station;
wherein, the commutation failure risk value calculating unit calculates the commutation failure risk value according to the value of each influence factor and the commutation failure influence degree of the influence factor, and comprises:
wherein, PcfIs the commutation failure risk value; ciThe influence degree of commutation failure of the ith influence factor; piIs the value of the ith influencing factor; n is the number of the influence factors; the value range of i is [1, N]A positive integer in between;
wherein the value calculation unit of the influence factors calculates the value of each influence factor, including:
when the influencing factor is the commutation voltage factor,
when the impact factor is a harmonic factor,
when the influencing factor is a direct current factor,
when the influence factor is the valve current factor,
when the impact factor is a trigger pulse factor, P is determined as followspulseThe method comprises the following steps:
in a valve current period, the absolute value of the valve current is smaller than the sampling point m of the preset valve current threshold value1Start calculation if sampling point m1The absolute value of the valve current at + n +1 is greater than the preset valve current threshold value, then PpulseIs 0 until the absolute value of the valve current is smaller than a preset valve current threshold value;
if sampling point m1The absolute value of the valve current at + n +1 is less than the preset valve current threshold value, then PpulseFrom 0 to PminIs maintained until sampling point m1Redetermine P at + n +0.5npulse(ii) a If sampling point m1The absolute value of the valve current at + n +0.5n is greater than the preset valve current threshold value, then PpulseFrom PminChanging the absolute value of the valve current to 0 until the absolute value of the valve current is detected to be smaller than a preset valve current threshold value; if sampling point m1The absolute value of the valve current at + n +0.5n is less than the preset valve current threshold value, then PpulseFrom PminIs changed into PmaxUntil the absolute value of the valve current is detected to be smaller than a preset valve current threshold value;
wherein the content of the first and second substances,
a value of a commutation voltage factor; u shapeLThe voltage of a converter bus of the converter station is acquired; phIs the value of the harmonic factor; v1rmsIs the effective value of the fundamental wave of the commutation voltage; vhrmsIs the effective value of h harmonic;
is the value of the direct current factor; i isdIs direct current; pIvIs the value of the valve current factor; i isVIs the valve current; ppulseIs the value of the trigger pulse factor; pminIs the preset minimum value of the trigger pulse factor; pmaxIs the maximum value of the preset trigger pulse factor; m is1Sampling points for detecting that the absolute value of the valve current is smaller than a preset threshold value; n is the number of sampling points at which the absolute value of the valve current is smaller than a preset threshold value in a normal state;
wherein, the commutation failure influence degree of each influence factor is determined by the following method:
wherein, CiThe influence degree of commutation failure of the ith influence factor; ci_lowThe minimum value of the influence degree of commutation failure of the preset ith influence factor; ci_maxThe maximum value of the influence degree of commutation failure of the preset ith influence factor is obtained; piIs the value of the ith influencing factor; piminIs the minimum value of the preset ith influence factor value; pimaxIs the maximum value of the preset ith influence factor value.
5. The system of claim 4, wherein the preset commutation failure risk criteria comprise:
if the commutation failure risk value is smaller than a preset starting fixed value, the prediction result indicates that no commutation failure occurs in the converter station;
if the commutation failure risk value is greater than or equal to the preset starting fixed value and smaller than a preset outlet fixed value, the prediction result indicates that commutation failure of the converter station is possible to occur;
and if the commutation failure risk value is greater than or equal to the preset exit fixed value, indicating that commutation failure can occur in the converter station by the prediction result.
6. The system of claim 5, further comprising:
and the commutation failure identification unit is used for calculating an integral value of the absolute value of the derivative of the current phase angle at the alternating side of the collected converter station when the prediction result indicates that the converter station is possible to generate commutation failure, and determining that the converter station has generated commutation failure when the integral value is less than 0.
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| CN112510744A (en) * | 2020-04-30 | 2021-03-16 | 中国电力科学研究院有限公司 | Method and system for inhibiting commutation failure |
| CN111781453B (en) * | 2020-07-04 | 2022-07-29 | 国家电网公司华中分部 | Fault moment-based direct current system commutation failure risk assessment method |
| CN112769132B (en) * | 2021-01-06 | 2022-08-12 | 华南理工大学 | Converter valve state and valve current solving method based on valve side current time sequence characteristics |
| CN113484578B (en) * | 2021-07-14 | 2024-01-23 | 南方电网科学研究院有限责任公司 | Commutation state detection method, device and equipment for high-voltage direct-current system |
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