CN112928989B - Fault diagnosis method and device - Google Patents
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Abstract
The invention provides a fault diagnosis method and a fault diagnosis device, which respond to a fault diagnosis instruction, acquire characteristic data of a plurality of quadrants of an IV curve of a photovoltaic power generation device, perform fault diagnosis on the photovoltaic power generation device by utilizing the mutual cooperation of the characteristic data of the plurality of quadrants of the IV curve, avoid the problem that the photovoltaic power generation device cannot be accurately diagnosed due to the fact that the fault diagnosis is performed only by utilizing characteristic data of a first quadrant, and improve the accuracy of fault diagnosis on the photovoltaic power generation device.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a fault diagnosis method and device.
Background
The photovoltaic power generation equipment is an important component of the photovoltaic power generation system, and if the photovoltaic power generation equipment fails, the power generation efficiency of the photovoltaic power generation system is seriously influenced. In order to find out faulty equipment in time and remove faults as soon as possible, fault diagnosis needs to be performed on the photovoltaic module.
Currently, fault diagnosis is generally performed by performing an IV scan on a photovoltaic power generation device and calculating an open-circuit voltage and a series resistance of the photovoltaic power generation device according to an IV scan result. However, the current IV curve obtained by IV scanning is the first-quadrant IV curve, and since the first-quadrant IV curve represents the characteristics of series and parallel resistors, the current sampling precision is poor at low current near the open-circuit voltage of the first-quadrant IV curve, so that the IV data points near the open-circuit voltage are severely jittered, the calculation errors of the open-circuit voltage and the series resistors are increased, and accurate fault diagnosis of the photovoltaic power generation equipment cannot be realized.
Disclosure of Invention
In view of this, the invention provides a fault diagnosis method and device, which can realize accurate fault diagnosis of photovoltaic power generation equipment.
In order to achieve the above purpose, the invention provides the following specific technical scheme:
a fault diagnosis method comprising:
responding to a fault diagnosis instruction, and acquiring characteristic data of multiple quadrants of an IV curve of the photovoltaic power generation equipment;
according to the characteristic data of multiple quadrants of the IV curve, fault diagnosis is carried out on the photovoltaic power generation equipment;
and outputting the diagnosis information for system display or alarm.
Optionally, the obtaining characteristic data of multiple quadrants of an IV curve of the photovoltaic power generation device includes:
controlling an external source current to be reversely injected into the photovoltaic power generation equipment to obtain characteristic data of a fourth quadrant of the IV curve;
and calculating the open-circuit voltage and the series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve.
Optionally, the obtaining characteristic data of multiple quadrants of an IV curve of the photovoltaic power generation device includes:
acquiring characteristic data of a first quadrant of the IV curve under the condition that the external source current is reversely injected;
and correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
Optionally, the controlling the current of the external source to be reversely injected into the photovoltaic power generation device to obtain the feature data of the fourth quadrant of the IV curve includes:
controlling an inverter to convert alternating current of an external source into direct current with different values, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
Optionally, the controlling the inverter to convert the ac current of the external source into the dc current of different values includes:
according to a preset current interval, controlling an inverter to convert alternating current of an external source into direct current with different numerical values in the current interval.
Optionally, the calculating the open-circuit voltage and the series resistance of the photovoltaic power generation device according to the fourth quadrant IV curve of the photovoltaic power generation device includes:
performing linear fitting on current data and voltage data of a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation;
determining the open-circuit voltage of the photovoltaic power generation equipment according to a fitted linear equation;
and determining the inverse of the absolute value of the slope of the fitted straight line as the series resistance of the photovoltaic power generation equipment.
Optionally, the performing fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of the multiple quadrants of the IV curve includes:
judging whether the series resistance of the photovoltaic power generation equipment is larger than a series resistance threshold value;
if the series resistance is larger than the series resistance threshold value, determining that the series resistance of the photovoltaic power generation equipment is too large;
and judging whether series current mismatch exists in the photovoltaic power generation equipment or not according to the corrected characteristic data of the first quadrant of the IV curve.
Optionally, the acquiring the characteristic data of the multiple quadrants of the IV curve of the photovoltaic power generation apparatus includes:
and controlling the forward injection of external source current into the photovoltaic power generation equipment to acquire the characteristic data of the second quadrant of the IV curve.
Optionally, the performing fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of the multiple quadrants of the IV curve includes:
determining the current when the photovoltaic power generation equipment reaches a specific voltage according to the characteristic data of the second quadrant of the IV curve, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted;
and determining whether the photovoltaic power generation equipment has a bypass diode fault or not by judging whether the current of the photovoltaic power generation equipment reaching the specific voltage is smaller than a preset value or not.
A fault diagnosis device comprising:
the IV curve acquisition unit is used for responding to the fault diagnosis instruction and acquiring characteristic data of multiple quadrants of an IV curve of the photovoltaic power generation equipment;
the fault diagnosis unit is used for carrying out fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of the multiple quadrants of the IV curve;
and the diagnostic information output unit is used for outputting diagnostic information for system display or warning.
Optionally, the IV curve obtaining unit includes:
the fourth quadrant data acquisition subunit is used for controlling the reverse injection of an external source current into the photovoltaic power generation equipment and acquiring the characteristic data of the fourth quadrant of the IV curve;
and the voltage resistance calculating subunit is used for calculating the open-circuit voltage and the series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve.
Optionally, the IV curve obtaining unit further includes:
the first quadrant data acquisition subunit is used for acquiring the characteristic data of the first quadrant of the IV curve under the condition that the external source current reverse injection is finished;
and the first quadrant data correction subunit is used for correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
Optionally, the fourth quadrant data obtaining subunit is specifically configured to:
controlling an inverter to convert alternating current of an external source into direct current with different values, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
Optionally, the fourth quadrant data obtaining subunit is specifically configured to:
according to a preset current interval, controlling an inverter to convert alternating current of an external source into direct current with different values in the current interval, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
Optionally, the voltage resistance calculating subunit is specifically configured to:
performing linear fitting on current data and voltage data of a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation;
determining the open-circuit voltage of the photovoltaic power generation equipment according to a fitted linear equation;
and determining the inverse of the absolute value of the slope of the fitted straight line as the series resistance of the photovoltaic power generation equipment.
Optionally, the fault diagnosis unit is specifically configured to:
judging whether the series resistance of the photovoltaic power generation equipment is greater than a series resistance threshold value;
if the series resistance is larger than the series resistance threshold value, determining that the series resistance of the photovoltaic power generation equipment is too large;
and judging whether series current mismatch exists in the photovoltaic power generation equipment or not according to the corrected characteristic data of the first quadrant of the IV curve.
Optionally, the IV curve obtaining unit includes:
and the second quadrant data acquisition subunit is used for controlling the forward injection of external source current into the photovoltaic power generation equipment to acquire the characteristic data of the second quadrant of the IV curve.
Optionally, the fault diagnosis unit is specifically configured to:
determining the current when the photovoltaic power generation equipment reaches a specific voltage according to the characteristic data of the second quadrant of the IV curve, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted;
and determining whether the photovoltaic power generation equipment has a bypass diode fault or not by judging whether the current when the photovoltaic power generation equipment reaches the specific voltage is smaller than a preset value or not.
Compared with the prior art, the invention has the following beneficial effects:
according to the fault diagnosis method disclosed by the invention, the characteristic data of the multiple quadrants of the IV curve of the photovoltaic power generation equipment are obtained in response to the fault diagnosis instruction, the characteristic data of the multiple quadrants of the IV curve are matched with each other to carry out fault diagnosis on the photovoltaic power generation equipment, the problem that the photovoltaic power generation equipment cannot be accurately diagnosed due to the fact that the fault diagnosis is carried out only by utilizing the characteristic data of the first quadrant is solved, and the fault diagnosis accuracy of the photovoltaic power generation equipment is improved.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic flow chart of a fault diagnosis method according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of a method for acquiring characteristic data of multiple quadrants of an IV curve of a photovoltaic power generation apparatus according to an embodiment of the present invention;
FIG. 3 is a global IV curve diagram of a photovoltaic power generation apparatus in a normal state according to an embodiment of the disclosure;
FIG. 4 is a global IV curve diagram of the photovoltaic power generation apparatus disclosed in the embodiment of the present invention with an excessively large series resistance;
FIG. 5 is a global IV curve diagram of series current mismatch for a photovoltaic power plant as disclosed in an embodiment of the present invention;
FIG. 6 is a global IV curve diagram of bypass diode failure for a photovoltaic power plant as disclosed in an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a fault diagnosis device according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention discloses a fault diagnosis method which is applied to a control unit in a photovoltaic power generation system.
Referring to fig. 1, a fault diagnosis method disclosed in this embodiment includes the following steps:
s101: and responding to the fault diagnosis instruction, and acquiring characteristic data of multiple quadrants of the IV curve of the photovoltaic power generation equipment.
The photovoltaic power generation equipment can be a photovoltaic module and can also be a photovoltaic string.
In the embodiment, the inverter rectifies the power source obtained by the external source to execute the current-controlled IV scan, and the external source may be a power grid or an energy storage device. And if the external source current is controlled to be reversely injected into the photovoltaic power generation equipment, acquiring a fourth quadrant IV curve of the photovoltaic power generation equipment, and acquiring the characteristic data of the first quadrant of the IV curve under the condition that the external source current is reversely injected.
Referring to fig. 2, an alternative method for acquiring characteristic data of multiple quadrants of an IV curve of a photovoltaic power generation device includes the following steps:
s201: and controlling the current of an external source to be reversely injected into the photovoltaic power generation equipment, and acquiring the characteristic data of the fourth quadrant of the IV curve.
Specifically, the inverter is controlled to convert alternating current of an external source into direct current of different values, and the direct current of different values is reversely injected into the photovoltaic power generation equipment in sequence, so that forward current of the photovoltaic power generation equipment is offset. Collecting current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain fourth quadrant characteristic data of an IV curve of the photovoltaic power generation equipment, wherein if the photovoltaic power generation equipment is normal, an obtained global IV curve graph is shown in figure 3.
Further, in order to avoid damage to the photovoltaic power generation apparatus due to excessive reverse current, it is possible to set the reverseMaximum current injected, I in FIG. 3 2 Corresponding to a voltage of V 2 。
In order to improve the accuracy of the calculation of the series resistor and reduce the influence caused by low-current down-sampling jitter, sampling is preferably performed when the current is large, and the number of sampling points is not less than 2, so that the minimum current for reverse injection needs to be correspondingly set, namely a current interval is preset, and the inverter is controlled to convert the alternating current of an external source into the direct current with different values in the current interval.
S202: and calculating the open-circuit voltage and the series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve.
And performing linear fitting on the current data and the voltage data according to a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation:
I＝kV+b
where k is the slope and b is the coefficient.
The abscissa of the intersection point of the fitting straight line corresponding to the fitting linear equation and the X axis is the open-circuit voltage V of the photovoltaic power generation equipment oc 。
Determining the reciprocal of the absolute value of the slope of the fitted straight line as the series resistance R of the photovoltaic power generation equipment s 。
In the first quadrant, the IV characteristic of a normal photovoltaic power generation device can be expressed by a single-diode five-parameter equation:
wherein I is the output current of the photovoltaic cell, V is the output voltage of the photovoltaic cell, I 0 For reverse saturation current, R S.ref Is the equivalent series resistance, R, of the battery sh.ref Is the equivalent parallel resistance of the battery, a = nKT/q, q is a charge constant with a value of 1.6 × 10 -19 A step of,; k is Boltzmann constant, valueIs 1.38X 10 -23 (ii) a T is the battery temperature and n is the diode quality factor.
In the second quadrant, because the voltage of the photovoltaic power generation equipment is reversed, after the conduction voltage of all bypass diodes in the photovoltaic power generation equipment is reached, the bypass diodes are conducted, and the IV curve shows the characteristic of an e exponential function:
I D for the current flowing across the diode, I S For reverse saturation current, V T Is the voltage equivalent of the temperature, V D Is the voltage across the diode.
S203: and acquiring the characteristic data of the first quadrant of the IV curve under the condition that the external source current reverse injection is finished.
Specifically, the MPPT unit responds to a fault diagnosis instruction, performs a conventional IV scan from an open-circuit voltage scan to a short-circuit current scan by adjusting a load characteristic, and then obtains characteristic data of a first quadrant of an IV curve of the photovoltaic power generation apparatus by collecting current data and voltage data.
S204: and correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
Because sampling jitter is large due to low current at a near open-circuit voltage point, the first quadrant IV curve of the photovoltaic power generation equipment is corrected according to the open-circuit voltage of the photovoltaic power generation equipment, which is obtained by calculating the characteristic data of the fourth quadrant of the IV curve, so that an accurate first quadrant IV curve can be obtained.
S102: and carrying out fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of a plurality of quadrants of the IV curve.
And after the series resistance is calculated according to the fourth quadrant IV curve and the corrected first quadrant curve of the photovoltaic power generation equipment is obtained, fault diagnosis is carried out on the photovoltaic power generation equipment.
Specifically, it is determined whether the series resistance of the photovoltaic power generation equipment is too large by judging whether the series resistance of the photovoltaic power generation equipment is greater than a series resistance threshold value, if the series resistance is greater than the series resistance threshold value, it is determined that the series resistance of the photovoltaic power generation equipment is too large, and if the series resistance is not greater than the series resistance threshold value, it is determined that the series resistance of the photovoltaic power generation equipment is normal.
Fig. 4 is a global IV graph showing that the series resistance of the photovoltaic power generation apparatus is too large, and it can be seen that, in the fourth quadrant of the IV curve, the absolute value of the slope of the IV curve becomes smaller, the corresponding series resistance becomes larger, and the threshold value of the series resistance can be set to diagnose that the series resistance is too large. Preferably, the series resistance calculated by the fourth quadrant IV curve can be used for verifying the series resistance calculated by the first quadrant IV curve, so that the problem of large calculation error of the series resistance caused by sampling jitter is solved.
And performing inflection point detection according to the slope change rate of the corrected first quadrant IV curve of the photovoltaic power generation equipment and the concave-convex property of the curve, and judging whether series current mismatch exists in the photovoltaic power generation equipment. Fig. 5 is a global IV plot of series current mismatch for a photovoltaic power plant. It can be seen that a current mismatch inflection point characteristic exists on the first quadrant IV curve, and it is further determined that series current mismatch exists in the corresponding photovoltaic power generation device.
S103: and outputting the diagnosis information for system display or warning.
For example, the diagnosis information is output through a system interface, or the diagnosis information is output to a specific person through a mail, a short message or a communication tool for alarming, so that the specific person can know the diagnosis information in time.
Research also finds that the existing IV diagnosis cannot effectively diagnose the fault of the bypass diode in the junction box of the photovoltaic power generation equipment. In order to solve the technical problem, according to the embodiment of the invention, the inverter is controlled to convert the alternating current of the external source into the direct currents with different values, the direct currents are sequentially injected into the photovoltaic power generation equipment in a forward direction, the forward current of the photovoltaic power generation equipment is increased, and then current data and voltage data are collected to obtain the second quadrant IV curve of the photovoltaic power generation equipment.
And determining the current when the photovoltaic power generation equipment reaches a specific voltage according to a second quadrant IV curve of the photovoltaic power generation equipment, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted, and taking the example that the photovoltaic power generation equipment comprises 3 bypass diodes and the voltage of each bypass diode is 0.7V, the corresponding specific voltage is 2.1V.
And determining whether the photovoltaic power generation equipment has a bypass diode fault by judging whether the current when the photovoltaic power generation equipment reaches a specific voltage is smaller than a preset value.
FIG. 6 is a global IV plot of bypass diode failure for a photovoltaic power plant, and it can be seen that in the second quadrant, when the voltage exceeds a certain voltage V 1 Then, the current increase of the photovoltaic power generation equipment is small, the IV curve does not show the characteristic of an e exponential function, and the specific voltage V 1 Corresponding current I 3 Much smaller than I in FIG. 3 1 The problem of disconnection caused by the fault of the bypass diode in the photovoltaic power generation equipment is explained.
Preferably, in order to avoid breakdown damage to the PN junction of the photovoltaic power generation device caused by excessive voltage reverse bias in the bypass diode open-circuit scenario, the scan cut-off voltage can be limited to avoid, for example, V in fig. 7 1 。
Therefore, according to the fault diagnosis method disclosed by the embodiment of the invention, the external source current is controlled to be reversely injected into the photovoltaic power generation equipment, so that the fourth quadrant IV curve of the photovoltaic power generation equipment is obtained, the open-circuit voltage and the series resistance of the photovoltaic power generation equipment can be accurately calculated according to the fourth quadrant IV curve because the fourth quadrant IV curve only represents the characteristics of the series resistance, so that the accurate fault diagnosis of the photovoltaic power generation equipment is realized according to the series resistance of the photovoltaic power generation equipment, and the first quadrant IV curve is corrected by using the fourth quadrant IV curve, so that the accurate fault diagnosis of the photovoltaic power generation equipment is realized according to the corrected first quadrant IV curve. The fault diagnosis of the bypass diode in the junction box of the photovoltaic power generation equipment can be realized.
Based on the fault diagnosis method disclosed in the above embodiments, the present embodiment correspondingly discloses a fault diagnosis device, please refer to fig. 7, and the device includes:
the IV curve acquisition unit 100 is configured to acquire feature data of multiple quadrants of an IV curve of the photovoltaic power generation apparatus in response to the fault diagnosis instruction;
the fault diagnosis unit 200 is used for carrying out fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of the multiple quadrants of the IV curve;
and a diagnostic information output unit 300 for outputting diagnostic information for system display or alarm.
Optionally, the IV curve obtaining unit 100 includes:
the fourth quadrant data acquisition subunit is used for controlling external source current to be reversely injected into the photovoltaic power generation equipment and acquiring the characteristic data of the fourth quadrant of the IV curve;
and the voltage resistance calculating subunit is used for calculating the open-circuit voltage and the series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve.
Optionally, the IV curve obtaining unit 100 further includes:
the first quadrant data acquisition subunit is used for acquiring the characteristic data of the first quadrant of the IV curve under the condition that the external source current reverse injection is finished;
and the first quadrant data correction subunit is used for correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
Optionally, the fourth quadrant data obtaining subunit is specifically configured to:
controlling an inverter to convert alternating current of an external source into direct current with different values, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
Optionally, the fourth quadrant data obtaining subunit is specifically configured to:
according to a preset current interval, controlling an inverter to convert alternating current of an external source into direct current with different values in the current interval, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
Optionally, the voltage resistance calculating subunit is specifically configured to:
performing linear fitting on current data and voltage data of a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation;
determining the open-circuit voltage of the photovoltaic power generation equipment according to a fitted linear equation;
and determining the inverse of the absolute value of the slope of the fitted straight line as the series resistance of the photovoltaic power generation equipment.
Optionally, the fault diagnosis unit 200 is specifically configured to:
judging whether the series resistance of the photovoltaic power generation equipment is greater than a series resistance threshold value;
if the series resistance is larger than the series resistance threshold value, determining that the series resistance of the photovoltaic power generation equipment is too large;
and judging whether series current mismatch exists in the photovoltaic power generation equipment or not according to the corrected characteristic data of the first quadrant of the IV curve.
Optionally, the IV curve obtaining unit 100 includes:
and the second quadrant data acquisition subunit is used for controlling the forward injection of an external source current into the photovoltaic power generation equipment and acquiring the characteristic data of the second quadrant of the IV curve.
Optionally, the fault diagnosis unit 200 is specifically configured to:
determining the current when the photovoltaic power generation equipment reaches a specific voltage according to the characteristic data of the second quadrant of the IV curve, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted;
and determining whether the photovoltaic power generation equipment has a bypass diode fault or not by judging whether the current of the photovoltaic power generation equipment reaching the specific voltage is smaller than a preset value or not.
According to the fault diagnosis device disclosed by the embodiment of the invention, the fourth quadrant IV curve of the photovoltaic power generation equipment is obtained by controlling the reverse injection of the external source current to the photovoltaic power generation equipment, because the fourth quadrant IV curve only represents the characteristics of the series resistor, the open-circuit voltage and the series resistor of the photovoltaic power generation equipment can be accurately calculated according to the fourth quadrant IV curve, so that the accurate fault diagnosis of the photovoltaic power generation equipment according to the series resistor of the photovoltaic power generation equipment is realized, and the first quadrant IV curve is corrected by utilizing the fourth quadrant IV curve, so that the accurate fault diagnosis of the photovoltaic power generation equipment according to the corrected first quadrant IV curve is realized. The fault diagnosis of the bypass diode in the junction box of the photovoltaic power generation equipment can be realized.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The above embodiments can be combined arbitrarily, and the features described in the embodiments in the present specification can be replaced or combined with each other in the above description of the disclosed embodiments, so that those skilled in the art can implement or use the present application.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (16)
1. A fault diagnosis method, comprising:
responding to a fault diagnosis instruction, acquiring characteristic data of multiple quadrants of an IV curve of photovoltaic power generation equipment, controlling external source current to be reversely injected into the photovoltaic power generation equipment, acquiring characteristic data of a fourth quadrant of the IV curve, and calculating open-circuit voltage and series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve;
according to the characteristic data of the multiple quadrants of the IV curve, fault diagnosis is carried out on the photovoltaic power generation equipment;
and outputting the diagnosis information for system display or alarm.
2. The method of claim 1, wherein the obtaining characterization data for multiple quadrants of an IV curve of a photovoltaic power plant comprises:
acquiring characteristic data of a first quadrant of the IV curve under the condition that the external source current is reversely injected;
and correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
3. The method of claim 1, wherein controlling the reverse injection of the external source current into the photovoltaic power generation device to obtain the characteristic data of the fourth quadrant of the IV curve comprises:
controlling an inverter to convert alternating current of an external source into direct current with different values, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
4. The method of claim 3, wherein controlling the inverter to convert an alternating current from an external source to a different value of direct current comprises:
according to a preset current interval, controlling an inverter to convert alternating current of an external source into direct current with different numerical values in the current interval.
5. The method of claim 1, wherein calculating the open circuit voltage and the series resistance of the photovoltaic power plant from a fourth quadrant IV curve of the photovoltaic power plant comprises:
performing linear fitting on the current data and the voltage data according to a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation;
determining the open-circuit voltage of the photovoltaic power generation equipment according to a fitted linear equation;
and determining the reciprocal of the absolute value of the slope of the fitted straight line as the series resistance of the photovoltaic power generation equipment.
6. The method according to claim 2, wherein the fault diagnosing the photovoltaic power generation equipment according to the characteristic data of the plurality of quadrants of the IV curve comprises:
judging whether the series resistance of the photovoltaic power generation equipment is larger than a series resistance threshold value;
if the series resistance is larger than the series resistance threshold value, determining that the series resistance of the photovoltaic power generation equipment is too large;
and judging whether series current mismatch exists in the photovoltaic power generation equipment or not according to the corrected characteristic data of the first quadrant of the IV curve.
7. The method of claim 1, wherein the obtaining characterization data for multiple quadrants of an IV curve of a photovoltaic power plant comprises:
and controlling the forward injection of an external source current into the photovoltaic power generation equipment to obtain the characteristic data of the second quadrant of the IV curve.
8. The method according to claim 7, wherein the fault diagnosing the photovoltaic power generation device according to the characteristic data of the plurality of quadrants of the IV curve comprises:
determining the current when the photovoltaic power generation equipment reaches a specific voltage according to the characteristic data of the second quadrant of the IV curve, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted;
and determining whether the photovoltaic power generation equipment has a bypass diode fault or not by judging whether the current of the photovoltaic power generation equipment reaching the specific voltage is smaller than a preset value or not.
9. A failure diagnosis device characterized by comprising:
the IV curve acquisition unit is used for responding to the fault diagnosis instruction and acquiring the characteristic data of a plurality of quadrants of the IV curve of the photovoltaic power generation equipment;
the fault diagnosis unit is used for carrying out fault diagnosis on the photovoltaic power generation equipment according to the characteristic data of the multiple quadrants of the IV curve;
the diagnostic information output unit is used for outputting diagnostic information for system display or alarm;
wherein the IV curve acquiring unit includes:
the fourth quadrant data acquisition subunit is used for controlling the reverse injection of an external source current into the photovoltaic power generation equipment and acquiring the characteristic data of the fourth quadrant of the IV curve;
and the voltage resistance calculating subunit is used for calculating the open-circuit voltage and the series resistance of the photovoltaic power generation equipment according to the characteristic data of the fourth quadrant of the IV curve.
10. The apparatus of claim 9, wherein the IV curve acquisition unit further comprises:
the first quadrant data acquisition subunit is used for acquiring the characteristic data of the first quadrant of the IV curve under the condition that the external source current reverse injection is finished;
and the first quadrant data correction subunit is used for correcting the characteristic data of the first quadrant of the IV curve according to the open-circuit voltage of the photovoltaic power generation equipment.
11. The apparatus according to claim 10, wherein the fourth quadrant data acquisition subunit is specifically configured to:
controlling an inverter to convert alternating current of an external source into direct current with different values, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
12. The apparatus according to claim 10, wherein the fourth quadrant data acquisition subunit is specifically configured to:
according to a preset current interval, controlling an inverter to convert alternating current of an external source into direct current with different values in the current interval, and sequentially injecting the direct current with different values into the photovoltaic power generation equipment in a reverse direction;
and acquiring current data and voltage data of direct current with different values which are reversely injected into the photovoltaic power generation equipment to obtain characteristic data of the fourth quadrant of the IV curve.
13. The apparatus according to claim 10, wherein the voltage resistance calculation subunit is specifically configured to:
performing linear fitting on current data and voltage data of a fourth quadrant IV curve of the photovoltaic power generation equipment to obtain a fitted linear equation;
determining the open-circuit voltage of the photovoltaic power generation equipment according to a fitted linear equation;
and determining the inverse of the absolute value of the slope of the fitted straight line as the series resistance of the photovoltaic power generation equipment.
14. The device according to claim 10, characterized in that the fault diagnosis unit is specifically configured to:
judging whether the series resistance of the photovoltaic power generation equipment is larger than a series resistance threshold value;
if the series resistance is larger than the series resistance threshold value, determining that the series resistance of the photovoltaic power generation equipment is too large;
and judging whether series current mismatch exists in the photovoltaic power generation equipment or not according to the corrected characteristic data of the first quadrant of the IV curve.
15. The apparatus of claim 9, wherein the IV curve obtaining unit comprises:
and the second quadrant data acquisition subunit is used for controlling the forward injection of external source current into the photovoltaic power generation equipment to acquire the characteristic data of the second quadrant of the IV curve.
16. The device according to claim 15, wherein the fault diagnosis unit is specifically configured to:
determining the current when the photovoltaic power generation equipment reaches a specific voltage according to the characteristic data of the second quadrant of the IV curve, wherein the specific voltage is the voltage when all bypass diodes in the photovoltaic power generation equipment are conducted;
and determining whether the photovoltaic power generation equipment has a bypass diode fault or not by judging whether the current of the photovoltaic power generation equipment reaching the specific voltage is smaller than a preset value or not.
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