Pilot protection method and system for sending-out line of photovoltaic hydrogen production field station

Abstract

The invention provides a photovoltaic hydrogen production station sending-out line pilot protection method and system. The photovoltaic hydrogen production station sending-out line pilot protection method comprises the steps that current data of the two sides of a photovoltaic hydrogen production station sending-out line are acquired; based on the field station side and system side fault current amplitude and phase characteristics, an improved shape distance algorithm is adopted to quantify the current amplitude and the change trend; and constructing a pilot protection criterion by using the improved shape distance, and identifying internal and external faults. According to the method, the amplitude and the phase difference of the current waveforms at the station side and the system side when the photovoltaic hydrogen production station sends out the line area internal and external faults are analyzed by using the improved shape distance algorithm, the line area internal and external faults can be accurately and flexibly identified, and the method is not influenced by the output characteristics of the new energy station; the problem that traditional protection performance is reduced or even fails can be effectively solved, and the method has high sensitivity and reliability and can be better suitable for photovoltaic hydrogen production field station sending-out line protection.

Description

Technical Field

[0001] The present invention relates to the field of relay protection for transmission lines of new energy stations, and in particular to a longitudinal protection method and system for transmission lines of photovoltaic hydrogen production stations. Background Art

[0002] At present, a high proportion of new energy and power electronic equipment has become the basic characteristics of the development of the power system. The output of large-scale new energy stations is affected by the converter control strategy, and its fault current presents characteristics such as limited amplitude, controlled phase angle, and frequency offset, which reduces the performance of the protection principle based on the traditional power frequency component and even causes protection misoperation and refusal to operate, thus affecting the safe and stable operation of the power system.

[0003] Considering the obvious difference in fault current characteristics between the photovoltaic hydrogen production site and the grid side, the protection principle based on the current on both sides of the transmission line has a strong engineering practical value. Most existing studies use correlation coefficients to describe the similarity of current waveforms on both sides of the line, such as the Pearson correlation coefficient, cosine correlation coefficient, Tanimoto correlation coefficient, etc., which usually perform amplitude normalization processing, weakening the difference in current amplitude, and it is difficult to fully reflect the difference in time domain waveforms. At the same time, if the new energy site is zero output, there will be calculation problems that make the protection principle invalid. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for longitudinal protection of a photovoltaic hydrogen production station transmission line. Starting from the amplitude and phase differences of the fault currents on both sides of the line, an improved shape distance algorithm is used to construct line longitudinal protection.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for longitudinal protection of a photovoltaic hydrogen production station transmission line, comprising:

[0007] Obtain current data on both sides of the transmission line of the photovoltaic hydrogen production station;

[0008] Based on the fault current amplitude and phase characteristics on the station side and the system side, an improved shape distance algorithm is used to quantify the current amplitude and change trend;

[0009] The improved shape distance is used to construct the longitudinal protection criterion to identify the faults inside and outside the zone.

[0010] Furthermore, the current data on both sides of the transmission line of the photovoltaic hydrogen production station are expressed as:

[0011] (1)

[0012] Among them, I r ,I sare the current on the station side and the current on the system side respectively; F r 、F s are the current amplitude on the station side and the current amplitude on the system side respectively; ω is the signal frequency; t is the time; φ r ,φ s They are the initial current phase on the station side and the initial current phase on the system side respectively.

[0013] Furthermore, the amplitude and phase characteristics of the fault current include: the fault current on the station side is affected by the dynamic response of the converter control link and presents the characteristics of limited amplitude and controlled phase angle, and the fault current waveform on the system side is an industrial frequency sine wave that decays according to the exponential law. It is stipulated that the busbar flows to the line as the positive direction of the current. When the photovoltaic hydrogen production station transmission line has an in-area fault, the fault current flows from the station side and the system side to the line, that is, the fault current on both sides of the line has the same direction and the waveform is different; when an out-of-area fault occurs, a through current flows in the line, that is, the fault current on both sides of the line has opposite directions and the waveform is consistent; when the normal working condition is, the current flowing through the line is the same as the out-of-area fault current, that is, the current direction is opposite and the waveform is consistent.

[0014] The improved shape distance algorithm is used to quantify the current amplitude and change trend as follows:

[0015] (2)

[0016] Where D is the shape distance between the station side and the system side; k is the total number of time points; t ih is the time length of the ith mode; t N is the total time length; I rih ,I sih are the current amplitude of the i-th mode on the station side and the current amplitude of the i-th mode on the system side respectively; M rih 、M sih They are the form representation of the i-th mode on the station side (1 means the current increases, -1 means the current decreases, and 0 means the current remains unchanged) and the form representation of the i-th mode on the system side. Each parameter can be specifically expressed as:

[0017] (3)

[0018] (4)

[0019] (5)

[0020] (6)

[0021] (7)

[0022] Among them, ti+1 ,t i are the i+1th time point and the ith time point respectively; I r (t i+1 ), I r (t i ) are the current amplitude at the i+1th time point and the ith time point on the station side respectively; I s (t i+1 ), I s (t i ) are the current amplitude at the i+1th time point and the ith time point on the system side respectively.

[0023] Under normal operating conditions and out-of-zone fault conditions, after the current on one side is reversed, the current on the station side and the system side coincide, and the calculated shape distance value is 0; in the case of an in-zone fault, the current difference on both sides is large, and the calculated shape distance value is much greater than 0.

[0024] Furthermore, the construction of the longitudinal protection criterion and identification of faults inside and outside the zone includes:

[0025] The startup criterion is constructed by using the current mutation on both sides of the line, which is expressed as:

[0026] (8)

[0027] Where I(t) is the phase current value at the tth sampling point; T is the number of sampling points in one cycle; I e is the current rating.

[0028] When three consecutive sampling values ​​of the phase current satisfy the above formula, the protection is activated, otherwise the protection is reset.

[0029] Set appropriate threshold values ​​to construct the fault identification criterion within the area, expressed as:

[0030] (9)

[0031] Among them, D set It is the shape distance threshold that takes into account communication delay, mutual inductor transmission error and noise.

[0032] When the calculated value of the improved shape distance meets the fault identification criteria within the zone, it is determined to be an within-zone fault and the protection is activated; otherwise, it is determined to be an out-of-zone fault and the protection is not activated.

[0033] The present invention also provides a photovoltaic hydrogen production station transmission line longitudinal protection system, comprising the following modules:

[0034] The data acquisition module acquires the current data on both sides of the transmission line of the photovoltaic hydrogen production station;

[0035] The distance calculation module obtains an improved shape distance calculation value that can characterize the current amplitude and change trend according to the amplitude and phase characteristics of the fault current on the station side and the system side;

[0036] The fault protection judgment module determines whether a fault occurs in the zone and whether the protection is activated through the startup judgment and fault identification judgment.

[0037] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the above-mentioned method for longitudinal protection of a transmission line of a photovoltaic hydrogen production station are implemented.

[0038] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned method for longitudinal protection of a photovoltaic hydrogen production station transmission line are implemented.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention comprehensively considers the amplitude and phase differences of the fault current waveforms on both sides of the line, quantifies the current amplitude and change trend through an improved shape distance algorithm, and can accurately determine the fault phase when a fault occurs in the area. Compared with the existing protection, it has higher sensitivity and reliability.

[0041] 2. The present invention is not affected by the output characteristics of new energy stations, that is, when the output on the photovoltaic hydrogen production station side is zero or the circuit breaker is reclosed in a permanent fault, the protection can still operate reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic flow chart of a method for longitudinal protection of a photovoltaic hydrogen production station transmission line of the present invention;

[0043] Figure 2 This is a topological schematic diagram of the transmission line system of the photovoltaic hydrogen production station of the present invention;

[0044] Figure 3 This is the longitudinal protection flow chart of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] like Figure 1 As shown, a method for longitudinal protection of a photovoltaic hydrogen production station transmission line according to an embodiment of the present invention comprises the following steps:

[0047] Step 1: Obtain the current data on both sides of the transmission line of the photovoltaic hydrogen production station;

[0048] Step 2: Based on the fault current amplitude and phase characteristics on the station side and the system side, the improved shape distance algorithm is used to quantify the current amplitude and change trend;

[0049] Step 3: Use the improved shape distance to construct the longitudinal protection criterion and identify the faults inside and outside the zone.

[0050] Specifically, the step 1 includes:

[0051] According to Figure 2 The topology diagram of the photovoltaic hydrogen production station transmission line system is shown. The photovoltaic hydrogen production station is connected to the system through a 220kV line. A total of 5 fault points are set at different positions of the transmission line. Among them, fault points K1 and K5 are out-of-area faults of the transmission line, and fault points K2, K3, and K4 are in-area faults of the transmission line. The busbar flow direction line is specified as the positive direction of the current. The current data on both sides of the photovoltaic hydrogen production station transmission line are expressed as follows:

[0052] (1)

[0053] Among them, I r ,I s are the current on the station side and the current on the system side respectively; F r 、F s are the current amplitude on the station side and the current amplitude on the system side respectively; ω is the signal frequency; t is the time; φ r ,φ s They are the initial current phase on the station side and the initial current phase on the system side respectively.

[0054] Specifically, the step 2 includes:

[0055] The fault current on the station side is affected by the dynamic response of the converter control link and shows the characteristics of limited amplitude and controlled phase angle. The fault current waveform on the system side is an industrial frequency sine wave that decays according to the exponential law. When the fault points K2, K3, and K4 of the photovoltaic hydrogen production station transmission line fail, that is, when an in-area fault occurs, the fault current flows from the station side and the system side to the line, that is, the fault current on both sides of the line has the same direction and the waveform is different; when the fault points K1 and K5 of the line fail, that is, when an out-of-area fault occurs, a through current flows in the line, that is, the fault current on both sides of the line has opposite directions and the waveform is consistent; when it is under normal working conditions, the current flowing through the line is the same as the out-of-area fault current, that is, the current direction is opposite and the waveform is consistent.

[0056] The improved shape distance algorithm is used to quantify the current amplitude and change trend as follows:

[0057] (2)

[0058] Where D is the shape distance between the station side and the system side; k is the total number of time points; t ih is the time length of the ith mode; t N is the total time length; I rih ,I sih are the current amplitude of the i-th mode on the station side and the current amplitude of the i-th mode on the system side respectively; M rih 、M sih They are the form representation of the i-th mode on the station side (1 means the current increases, -1 means the current decreases, and 0 means the current remains unchanged) and the form representation of the i-th mode on the system side. The parameters can be specifically expressed as:

[0059] (3)

[0060] (4)

[0061] (5)

[0062] (6)

[0063] (7)

[0064] Among them, t i+1 ,t i are the i+1th time point and the ith time point respectively; I r (t i+1 ), I r (t i ) are the current amplitude at the i+1th time point and the ith time point on the station side respectively; I s (t i+1 ), I s (t i ) are the current amplitude at the i+1th time point and the ith time point on the system side respectively.

[0065] Under normal operating conditions and in the case of out-of-zone faults, after the system-side current is reversed, the currents on the station side and the system side coincide, and the shape distance calculation value is 0; in the case of in-zone faults, the current difference on both sides is large, and the shape distance calculation value is much greater than 0.

[0066] Specifically, the step 3 includes:

[0067] according to Figure 3The longitudinal protection flow chart of the photovoltaic hydrogen production station transmission line shown in the figure first obtains the station side and system current data, pre-processes the current data, and uses the current mutation amount on both sides of the line to construct the start-up criterion, which is expressed as:

[0068] (8)

[0069] Where I(t) is the phase current value at the tth sampling point; T is the number of sampling points in one cycle; I e is the current rating.

[0070] When three consecutive current sampling values ​​satisfy the above formula, the protection is activated, otherwise the protection is reset and the sliding window calculation is used to judge the subsequent data.

[0071] Secondly, the shape distance values ​​on the station side and the system side are calculated based on the improved shape distance algorithm.

[0072] Finally, set the appropriate threshold value to construct the fault identification criterion within the area, which is expressed as:

[0073] (9)

[0074] Among them, D set It is the shape distance threshold that takes into account communication delay, mutual inductor transmission error and noise.

[0075] When the calculated value of the improved shape distance of a phase current meets the fault identification criteria within the zone for three consecutive times, it is determined to be an within-zone fault and the protection is activated; otherwise, it is determined to be an out-of-zone fault and the protection is restored.

[0076] In addition, the present invention also provides a photovoltaic hydrogen production station transmission line longitudinal protection system, including the following modules:

[0077] The data acquisition module acquires the current data on both sides of the transmission line of the photovoltaic hydrogen production station;

[0078] The distance calculation module obtains an improved shape distance calculation value that can characterize the current amplitude and change trend according to the amplitude and phase characteristics of the fault current on the station side and the system side;

[0079] The fault protection judgment module determines whether a fault occurs in the zone and whether the protection is activated through the startup judgment and fault identification judgment.

[0080] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the above-mentioned method for longitudinal protection of a transmission line of a photovoltaic hydrogen production station are implemented.

[0081] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned method for longitudinal protection of a photovoltaic hydrogen production station transmission line are implemented.

[0082] It should be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and interpreted scripting language JavaScript, etc.

[0083] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0084] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0085] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0086] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0087] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations. Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. For those skilled in the art, any modification, change, addition and replacement made within the essential scope of the present invention are included in the protection scope of the present invention.

Claims

1. A method for longitudinal protection of a photovoltaic hydrogen production station transmission line, characterized in that: include: Obtain current data on both sides of the transmission line of the photovoltaic hydrogen production station; Based on the fault current amplitude and phase characteristics on the station side and the system side, an improved shape distance algorithm is used to quantify the current amplitude and change trend. The improved shape distance is used to construct the longitudinal protection criterion to identify the faults inside and outside the zone.

2. A photovoltaic hydrogen production station transmission line longitudinal protection method according to claim 1, characterized in that: The current data on both sides of the transmission line of the photovoltaic hydrogen production station are expressed as follows: （1） Among them, I r ,I s are the current on the station side and the current on the system side respectively; F r 、F s are the current amplitude on the station side and the current amplitude on the system side respectively; ω is the signal frequency; t is the time; φ r ,φ s They are the initial current phase on the station side and the initial current phase on the system side respectively.

3. A photovoltaic hydrogen production station transmission line longitudinal protection method according to claim 1, characterized in that: The fault current amplitude and phase characteristics based on the station side and the system side include: The fault current on the station side is affected by the dynamic response of the converter control link and presents the characteristics of limited amplitude and controlled phase angle. The fault current waveform on the system side is an industrial frequency sine wave that decays according to the exponential law. The busbar flow direction is stipulated to be the positive direction of the current. When the photovoltaic hydrogen production station transmission line has an in-area fault, the fault current flows from the station side and the system side to the line, that is, the fault current on both sides of the line has the same direction and the waveform is different; when an out-of-area fault occurs, a through current flows in the line, that is, the fault current on both sides of the line has opposite directions and the waveform is consistent; when the normal working condition is, the current flowing through the line is the same as the out-of-area fault current, that is, the current direction is opposite and the waveform is consistent; The improved shape distance algorithm is used to quantify the current amplitude and change trend as follows: （2） Where D is the shape distance between the station side and the system side; k is the total number of time points; t ih is the time length of the ith mode; t N is the total time length; I rih ,I sih are the current amplitude of the i-th mode on the station side and the current amplitude of the i-th mode on the system side respectively; M rih 、M sih They are the morphological representation of the i-th mode on the station side and the morphological representation of the i-th mode on the system side, 1 indicates that the current increases, -1 indicates that the current decreases, and 0 indicates that the current remains unchanged; each parameter is expressed as: （3） （4） （5） （6） （7） Among them, t i+1 ,t i are the i+1th time point and the ith time point respectively; I r (t i+1 ), I r (t i ) are the current amplitude at the i+1th time point and the ith time point on the station side respectively; I s (t i+1 ), I s (t i ) are the current amplitude at the i+1th time point and the current amplitude at the ith time point on the system side respectively; Under normal operating conditions and out-of-zone fault conditions, after the system-side current is reversed, the currents on the station side and the system side coincide, and the shape distance calculation value is 0; in the case of an in-zone fault, the current difference on both sides is large, and the shape distance calculation value is much greater than 0.

4. A photovoltaic hydrogen production station transmission line longitudinal protection method according to claim 1, characterized in that: The construction of longitudinal protection criteria to identify faults inside and outside the zone includes: The startup criterion is constructed by using the current mutation on both sides of the line, which is expressed as: （8） Where I(t) is the phase current value at the tth sampling point; T is the number of sampling points in one cycle; I e is the current rating; When three consecutive sampling values ​​of the phase current meet the above formula, the protection is activated, otherwise the protection is reset; Set appropriate threshold values ​​to construct the fault identification criterion within the area, expressed as: （9） Among them, D set The shape distance threshold is considered to take into account communication delay, mutual inductor transmission error and noise; When the calculated value of the improved shape distance meets the fault identification criteria within the zone, it is determined to be an internal fault and the protection is activated; otherwise, it is determined to be an external fault and the protection is not activated or is reset.

5. A photovoltaic hydrogen production station transmission line longitudinal protection system, whose characteristic value is that it includes the following modules: The data acquisition module acquires the current data on both sides of the transmission line of the photovoltaic hydrogen production station; The distance calculation module obtains an improved shape distance calculation value that can characterize the current amplitude and change trend according to the amplitude and phase characteristics of the fault current on the station side and the system side; The fault protection judgment module determines whether a fault occurs in the zone and whether the protection is activated through the startup judgment and fault identification judgment.

6. Provide an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of a method for longitudinal protection of a photovoltaic hydrogen production station transmission line are implemented as described in any one of claims 1 to 4.

7. A non-transitory 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 a method for longitudinal protection of a photovoltaic hydrogen production station transmission line as described in any one of claims 1 to 4 are implemented.

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