New energy power supply station AC line outlet fault direction discrimination method and system

Abstract

The invention discloses a new energy power supply station AC line outlet fault direction discrimination method and system, and relates to the technical field of power system relay protection, and the method comprises the following steps: collecting a voltage measurement value UM and a current measurement value IM at a protection installation position; recording a fault moment of a near-area alternating-current line of the new energy power supply station, and calculating a fault current value Ifcal after the fault is generated by using a memory voltage at a protection installation position at a certain moment before the fault is generated; calculating a waveform similarity coefficient r (Ifcal, IM) between the fault current value Ifcal and the current IM at the protection installation position; and judging the outlet fault direction according to the magnitude between the waveform similarity coefficient r (Ifcal, IM) and the setting value rset. According to the method, the criterion is simple, outlet fault direction discrimination can be reliably and sensitively carried out on the new energy power supply station near-area alternating-current line, and the problem that a power frequency variation direction element is not suitable any more under the condition that the new energy power supply station alternating-current outgoing line is a single loop line is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection of electric power systems, and in particular to a method and system for determining the fault direction of an AC line outlet of a new energy power supply station. Background Art

[0002] When an AC line near a new energy power station fails, the AC voltage drops, causing the output of the new energy power station to be distorted, which will have an adverse effect on the performance of the relay protection. Directional elements are an important part of longitudinal directional protection and distance protection. Accurately identifying the fault direction is a prerequisite for the reliable operation of longitudinal directional protection and distance protection. However, when a short circuit fault occurs near the line outlet, the measured voltage at the protection installation is very low, and it is difficult to identify the fault direction. If the fault direction cannot be determined in time and the fault cannot be removed, the safe and stable operation of the power system will be endangered.

[0003] In the study of the fault direction identification principle of the AC lines near the renewable energy power station, when the AC outgoing line of the renewable energy power station is a single-loop line, the directional element based on the industrial frequency phasor will be affected by the power electronic equipment of the renewable energy power station, making it difficult to accurately determine the fault direction, and even causing false operation or refusal to operate. Summary of the invention

[0004] In view of the problems existing in the fault direction determination of AC line outlets in existing new energy power supply stations and in the system, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is that it is difficult to accurately determine the fault direction based on the directional element of the power frequency phasor.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a method for determining the fault direction of an AC line outlet of a new energy power supply station, which comprises the following steps:

[0008] Collect the voltage measurement value U at the protection installation M and the current measurement value I M ;

[0009] Record the time when the AC line near the new energy power station fails, and use the memory voltage at the protection installation at a certain time before the fault occurs to calculate the fault current value I after the fault occurs f_cal ;

[0010] Calculate the fault current value I f_cal The protection installation current I M The waveform similarity coefficient r(I f_cal ,I M );

[0011] According to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

[0012] As a preferred solution of the method for determining the fault direction of the AC line outlet of the new energy power station described in the present invention, when a fault occurs in the AC line near the new energy power station, the fault phase is determined according to the phase selection criterion, and the voltage and current measured at the protection installation corresponding to the fault are collected.

[0013] As a preferred solution of the method for determining the fault direction of the AC line outlet of the new energy power station of the present invention, wherein: the fault current value I f_cal The calculation is expressed as,

[0014]

[0015] Where U MΦ , U MΦΦ are the single-phase memory voltage and the phase-to-phase memory voltage at the protection installation respectively, and Z1 and Z0 are the positive-sequence impedance and the zero-sequence impedance of the protected line and the equivalent AC system respectively.

[0016] As a preferred solution of the method for distinguishing the fault direction of the AC line outlet of the new energy power station of the present invention, wherein: the waveform similarity coefficient r(I f_cal ,I M ) is expressed as,

[0017]

[0018] In the formula, I f_cal (i) and (I) M (i) are respectively the calculated value of the fault current and the sampled value of the current measured at the protection installation at the i-th moment, and N is the data window length for calculating the waveform similarity coefficient.

[0019] As a preferred solution of the method for determining the fault direction of the AC line outlet of the new energy power station of the present invention, the method for determining the fault direction of the outlet includes:

[0020] If the waveform similarity coefficient r(I f_cal ,I M ) is greater than or equal to the set value r set , it is considered that a forward export failure has occurred;

[0021] If the waveform similarity coefficient r(I f_cal ,I M ) is less than the set value r set , it is considered that a reverse export failure has occurred;

[0022] The criterion for forward export failure is:

[0023] r(I f_cal ,I M )≥r set ;

[0024] The reverse direction exit fault criterion is:

[0025] r(I f_cal ,I M )<r set .

[0026] As a preferred solution of the method for determining the fault direction of the AC line outlet of the new energy power station of the present invention, the faults that occur include:

[0027] Single-phase short circuit ground fault, two-phase short circuit fault and three-phase short circuit fault.

[0028] As a preferred solution of the method for determining the fault direction of the AC line outlet of the new energy power station of the present invention, in which: for a single-phase short-circuit grounding fault, the memory voltage uses the fault phase electrical phase;

[0029] For two-phase short circuit fault and two-phase short circuit grounding fault, the memory voltage uses the fault phase-to-phase voltage;

[0030] For a three-phase short circuit fault, the memorized voltage uses the voltage of one phase.

[0031] In a second aspect, an embodiment of the present invention provides a fault direction determination system for an AC line outlet of a new energy power supply station, which includes a line electrical quantity acquisition module, a current time domain variation calculation module, a waveform similarity coefficient calculation module, and a fault direction determination module;

[0032] The line electrical quantity acquisition module is used to collect the voltage measurement value and the current measurement value at the protection installation when a fault occurs;

[0033] The current time domain variation calculation module is used to use the voltage measurement value and the current measurement value to obtain the memory voltage value of the protection installation at a certain moment before the fault occurs; and calculate the fault current value I after the fault occurs of the AC line near the new energy power station within a preset time after the fault occurs f_cal ;

[0034] The waveform similarity coefficient calculation module is used to calculate the waveform similarity coefficient r(I f_cal ,I M );

[0035] The fault direction judgment module is used to determine the fault direction according to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

[0036] In a third aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the processor executes the computer program, it implements any step of the above-mentioned method for determining the fault direction of the AC line outlet of the new energy power station.

[0037] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, any step of the above-mentioned method for determining the fault direction of the AC line outlet of a new energy power supply station is implemented.

[0038] The beneficial effects of the present invention are as follows: the AC line measured voltage is used to infer the AC line fault current when and after the fault occurs, and the calculated value of the fault current under the fault is compared with the waveform similarity coefficient and the setting value of the measured current at the protection installation to determine the line outlet fault direction. This method of the present invention has a simple criterion and can reliably and sensitively determine the outlet fault direction of the AC line near the new energy power station, effectively solving the problem that the power frequency variable direction element is no longer applicable when the AC outlet line of the new energy power station is a single-loop line. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0040] Figure 1 The figure is a flow chart of the method for determining the fault direction of the AC line outlet of a new energy power station.

[0041] Figure 2 This is a schematic diagram of the waveform similarity coefficient between the AC line current under the fault at protection point M and the current measured at the protection installation when phase A is grounded.

[0042] Figure 3 This is a schematic diagram of the waveform similarity coefficient between the AC line current under fault at protection M and the current measured at the protection installation when the BC two-phase short circuit occurs.

[0043] Figure 4This is a schematic diagram of the waveform similarity coefficient between the AC line current under the fault at protection point M and the current measured at the protection installation when a phase A grounding fault occurs at time 0.216s.

[0044] Figure 5 This is a schematic diagram of the waveform similarity coefficient between the AC line current under the fault at protection point M and the current measured at the protection installation when a phase A grounding fault occurs at time 0.217s.

[0045] Figure 6 This is the structural diagram of the fault direction determination system for the AC line outlet of a new energy power station. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0047] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0049] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0050] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0051] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] Example 1

[0053] Reference Figure 1 to Figure 6 , which is the first embodiment of the present invention, and provides a method for determining the fault direction of an AC line outlet of a new energy power supply station, comprising the following steps:

[0054] S1. Collect the voltage measurement value U at the protection installation location M and the current measurement value I M .

[0055] S2. Record the time when the AC line near the new energy power station fails, and use the memory voltage at the protection installation at a certain time before the fault occurs to calculate the fault current value I after the fault occurs. f_cal .

[0056] When a fault occurs in the AC line near the new energy power station, the fault phase is determined according to the phase selection criteria, and the voltage and current measured at the protection installation corresponding to the fault are collected.

[0057] The fault current value I f_cal The calculation is expressed as,

[0058]

[0059] Where U MΦ , U MΦΦ are the single-phase memory voltage and the phase-to-phase memory voltage at the protection installation respectively, and Z1 and Z0 are the positive-sequence impedance and the zero-sequence impedance of the protected line and the equivalent AC system respectively.

[0060] Different memory voltages are used for different short-circuit faults. For a single-phase short-circuit grounding fault, the memory voltage uses the fault phase voltage. For a two-phase short-circuit fault and a two-phase short-circuit grounding fault, the memory voltage uses the fault phase-to-phase voltage. For a three-phase short-circuit fault, the memory voltage uses the voltage of one of the phases.

[0061] S3, calculate the fault current value I f_cal The protection installation current I M The waveform similarity coefficient r(I f_cal ,I M ).

[0062] The waveform similarity coefficient r(I f_cal ,I M ) is expressed as,

[0063]

[0064] In the formula, I f_cal (i) and (I) M (i) are respectively the calculated value of the fault current and the sampled value of the current measured at the protection installation at the i-th moment, and N is the data window length for calculating the waveform similarity coefficient.

[0065] S4, according to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

[0066] Methods for determining the direction of an exit fault include:

[0067] If the waveform similarity coefficient r(I f_cal ,I M ) is greater than or equal to the set value r set , it is considered that a forward export failure has occurred;

[0068] If the waveform similarity coefficient r(I f_cal ,I M ) is less than the set value r set , it is considered that a reverse export failure has occurred;

[0069] The criterion for forward export failure is:

[0070] r(I f_cal ,I M )≥r set ;

[0071] The reverse direction exit fault criterion is:

[0072] r(I f_cal ,I M )<r set .

[0073] In order to further illustrate the method for distinguishing the fault direction of the AC line outlet near the new energy power station based on the waveform similarity coefficient provided by the example of the present invention, it is now described in detail as follows in conjunction with the accompanying drawings and specific examples:

[0074] In PSCAD / EMTDC Figure 6The new energy access system shown in FIG. 1 is used as an example for explanation. The new energy power source is connected to the 220kV AC system through a step-up transformer. Among them, the total rated power of the new energy power source unit is 120MVA and the rated voltage is 220kV. The above-mentioned method for distinguishing the fault direction of the AC line outlet near the new energy power source station based on the waveform similarity coefficient is used.

[0075] In this embodiment, setting Figure 6 F1 and F2 are respectively the forward and reverse output faults of protection M. Different types of faults are set at F1 and F2, including A-phase grounding and BC-phase short circuit, and the fault types are recorded as AG and BC respectively. In this embodiment, the waveform similarity coefficient setting value is set to 0.4.

[0076] Figure 2 and Figure 3 The waveform similarity coefficients of the calculated fault current and the measured current at the protection installation are given respectively when the fault occurs at 0.220s in F1 and F2 settings of AG and BC faults. Figure 4 and Figure 5 The waveform similarity coefficients of the calculated fault current at the AG fault protection M set at F1 and F2 at 0.216s and 0.217s respectively and the measured current at the protection installation are given.

[0077] Depend on Figure 2 and Figure 3 It can be seen that for the positive direction outlet fault (F1), the waveform similarity coefficient of the fault current calculated value at the protection M and the measured current at the protection installation is close to 1 after the fault. At this time, the calculated waveform similarity coefficient r(If_cal,IM) is greater than the set value of 0.4, which meets the outlet forward fault judgment criterion and is judged as a positive direction fault; for the reverse direction outlet fault (F2), the waveform similarity coefficient has been maintained near -1, and it is judged as a reverse direction fault.

[0078] Depend on Figure 4 and Figure 5 It can be seen that at different fault moments, for the positive direction outlet fault (F1), the waveform similarity coefficient of the fault current calculated at the protection M and the measured current at the protection installation is close to 1 after the fault. At this time, the calculated waveform similarity coefficient r(If_cal,IM) is greater than the set value of 0.4, which meets the outlet positive fault judgment criterion and is judged as a positive direction fault; for the reverse direction outlet fault (F2), the waveform similarity coefficient is less than the set value of 0.4, and it is judged as a reverse direction fault.

[0079] In summary, the AC line measured voltage is used to estimate the AC line fault current when and after the fault occurs, and the calculated value of the fault current under the fault is compared with the waveform similarity coefficient and the set value of the measured current at the protection installation to determine the line outlet fault direction. This method of the present invention has a simple criterion and can reliably and sensitively determine the outlet fault direction of the AC line near the new energy power station, effectively solving the problem that the power frequency variable direction element is no longer applicable when the AC outlet line of the new energy power station is a single-loop line.

[0080] Example 2

[0081] Reference Figure 6 , based on the first embodiment, this embodiment further provides a new energy power station AC line outlet fault direction determination system, including a line electrical quantity acquisition module, a current time domain variation calculation module, a waveform similarity coefficient calculation module, and a fault direction determination module;

[0082] The line electrical quantity acquisition module is used to collect the voltage measurement value and the current measurement value at the protection installation when a fault occurs;

[0083] The current time domain variation calculation module is used to use the voltage measurement value and the current measurement value to obtain the memory voltage value of the protection installation at a certain moment before the fault occurs; and calculate the fault current value I after the fault occurs of the AC line near the new energy power station within a preset time after the fault occurs f_cal ;

[0084] The waveform similarity coefficient calculation module is used to calculate the waveform similarity coefficient r(I f_cal ,I M );

[0085] The fault direction judgment module is used to determine the fault direction according to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

[0086] This embodiment also provides a computer device, which is suitable for the method of determining the fault direction of the AC line outlet of a new energy power station, and includes a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the method of determining the fault direction of the AC line outlet of a new energy power station as proposed in the above embodiment.

[0087] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0088] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for determining the fault direction of the AC line outlet of a new energy power station proposed in the above embodiment is implemented.

[0089] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be found in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for determining the fault direction of an AC line outlet at a new energy power station, characterized in that: The following steps are included: Collect the voltage measurement value U at the protection installation M and the current measurement value I M ; Record the time when the AC line near the new energy power station fails, and use the memory voltage at the protection installation at a certain time before the fault occurs to calculate the fault current value I after the fault occurs f_cal ; Calculate the fault current value I f_cal The protection installation current I M The waveform similarity coefficient r(I f_cal ,I M ); According to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

2. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 1, characterized in that: When a fault occurs in the AC line near the new energy power station, the fault phase is determined according to the phase selection criteria, and the voltage and current measured at the protection installation corresponding to the fault are collected.

3. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 2, characterized in that: The fault current value I f_cal The calculation is expressed as, Where U MΦ , U MΦΦ are the single-phase memory voltage and the phase-to-phase memory voltage at the protection installation respectively, and Z1 and Z0 are the positive-sequence impedance and the zero-sequence impedance of the protected line and the equivalent AC system respectively.

4. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 3, characterized in that: The waveform similarity coefficient r(I f_cal ,I M ) is expressed as, In the formula, I f_cal (i) and (I) M (i) are respectively the calculated value of the fault current and the sampled value of the current measured at the protection installation at the i-th moment, and N is the data window length for calculating the waveform similarity coefficient.

5. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 4, characterized in that: Methods for determining the direction of an exit fault include: If the waveform similarity coefficient r(I f_cal ,I M ) is greater than or equal to the set value r set , it is considered that a forward export failure has occurred; If the waveform similarity coefficient r(I f_cal ,I M ) is less than the set value r set , it is considered that a reverse export failure has occurred; The criterion for forward export failure is: r(I f_cal ,I M )≥r set ; The reverse direction exit fault criterion is: r(I f_cal ,I M )<r set 。 6. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 5, characterized in that: The failures that occurred included: Single-phase short circuit ground fault, two-phase short circuit fault and three-phase short circuit fault.

7. The method for determining the fault direction of the AC line outlet of a new energy power supply station according to claim 6, characterized in that: In case of single-phase short-circuit grounding fault, the memory voltage uses the fault phase; For two-phase short circuit fault and two-phase short circuit grounding fault, the memory voltage uses the fault phase-to-phase voltage; For a three-phase short circuit fault, the memorized voltage uses the voltage of one phase.

8. A system for distinguishing the fault direction of an AC line outlet of a new energy power station, based on the method for distinguishing the fault direction of an AC line outlet of a new energy power station according to any one of claims 1 to 7, characterized in that: It includes a line electrical quantity acquisition module, a current time domain variation calculation module, a waveform similarity coefficient calculation module, and a fault direction judgment module; The line electrical quantity acquisition module is used to collect the voltage measurement value and the current measurement value at the protection installation when a fault occurs; The current time domain variation calculation module is used to obtain the memory voltage value of the protection installation at a certain moment before the fault occurs by using the voltage measurement value and the current measurement value; And calculate the fault current value I of the AC line near the new energy power station within the preset time after the fault occurs f_cal ; The waveform similarity coefficient calculation module is used to calculate the waveform similarity coefficient r(I f_cal ,I M ); The fault direction judgment module is used to determine the fault direction according to the waveform similarity coefficient r(I f_cal ,I M ) and the set value r set The size of the two determines the direction of the exit fault.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for determining the fault direction of the AC line outlet of a new energy power supply station according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for determining the fault direction of the AC line outlet of a new energy power supply station according to any one of claims 1 to 7 are implemented.

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