Power electronic system protection method and system

Abstract

The invention relates to the technical field of power system protection, in particular to a power electronic system protection method and system, and the method comprises the steps: injecting a harmonic signal with a preset amplitude into a three-phase voltage modulation wave of a new energy converter for harmonic modulation; obtaining harmonic current signals of protection device installation positions on two sides of a sending-out line connected with the new energy converter after harmonic modulation, carrying out Fourier transform by using the harmonic current signals, and determining harmonic characteristic parameters corresponding to the protection device installation positions on two sides of the sending-out line; and the fault occurrence position is identified through the harmonic characteristic parameters, and the protection action of the protection device is executed in the internal fault. According to the embodiment of the invention, the method is not affected by the operation condition and control strategy of the new energy side in a mode of actively injecting the harmonic signal, avoids the risk that a power electronic system protection mode is liable to cause misoperation or operation rejection, and guarantees the stable operation of a power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection, and in particular to a power electronic system protection method and system. Background Art

[0002] With the development and construction of new power system projects, power electronic power systems will be constructed in typical scenarios of new power systems. The fault response of power electronic power systems has significant nonlinear characteristics. Traditional fault analysis methods and relay protection principles based on synchronous power supply and linear superposition principle are difficult to adapt to. The risk of false operation or refusal of traditional AC protection increases, which seriously affects the stable operation of the power system. Summary of the invention

[0003] In view of this, the present invention provides a power electronic system protection method and system, which solves the technical problem that the traditional power electronic system protection method is prone to the risk of false operation or refusal to operate, affecting the stable operation of the power system.

[0004] A first aspect of the present invention provides a power electronic system protection method, comprising:

[0005] In response to a harmonic signal active injection request, a harmonic signal of a preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation;

[0006] Acquire harmonic current signals at the locations where protection devices are installed on both sides of the transmission line to which the new energy converter is connected after harmonic modulation;

[0007] Performing Fourier transformation on the harmonic current signal, and determining harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transformation; wherein the harmonic characteristic parameters are determined by the harmonic current ratio of the installation locations of the protection devices on both sides of the transmission line;

[0008] According to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, it is judged whether the fault location is an internal fault or an external fault;

[0009] When it is determined that the fault occurrence location is an in-zone fault, the protection action of the protection device is executed.

[0010] Preferably, in response to the active harmonic signal injection request, the harmonic voltage signal of the preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the method also includes:

[0011] Obtaining a positive-sequence voltage and a negative-sequence voltage of a grid-connected point of the new energy converter;

[0012] Determining whether the positive-sequence voltage and the negative-sequence voltage simultaneously satisfy a preset harmonic signal injection start criterion;

[0013] When it is determined that the positive-sequence voltage and the negative-sequence voltage simultaneously satisfy the preset harmonic signal injection start criterion, the harmonic signal active injection request is generated.

[0014] Preferably, the harmonic signal of the preset amplitude is obtained by tracking and controlling the actual output value of the current of the harmonic signal through a proportional-integral controller based on the current reference value of the harmonic signal, and the tracking control is used to modulate the error between the actual output value of the current of the harmonic signal and the current reference value of the harmonic signal within a preset error threshold.

[0015] Preferably, the transfer function of the current control link of the harmonic signal of the proportional-integral controller is:

[0016]

[0017] In the formula, , are the d-axis and q-axis components of the harmonic voltage reference value, , are the d-axis and q-axis components of the measured harmonic voltage at the grid connection point of the new energy converter, , are proportional gain and integral gain respectively, is the Laplace operator, , are the d-axis and q-axis components of the current reference value of the harmonic signal, , are the d-axis and q-axis components of the measured harmonic current at the grid connection point of the new energy converter, is the harmonic order, is the angular frequency, For inductance.

[0018] Preferably, a harmonic signal of a preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the obtained harmonic modulation signal is:

[0019]

[0020] In the formula, are the voltage modulation amplitudes of phase a, phase b and phase c of the new energy converter, is the voltage modulation amplitude of the new energy converter, t is the time, is the modulation phase of the new energy converter, is the amplitude of the harmonic signal, is the angular frequency of the harmonic signal, is the initial phase of the harmonic signal.

[0021] Preferably, performing Fourier transform on the harmonic current signal and determining harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after Fourier transform respectively include:

[0022] Performing Fourier transformation on the harmonic current signal, and extracting the harmonic frequency current amplitudes corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transformation;

[0023] Based on the communication channel of the longitudinal protection, the currents at the installation locations of the protection devices on both sides of the transmission line are mutually transmitted;

[0024] Determine the harmonic current ratio of the protection device installation locations on both sides of the transmission line according to the harmonic frequency current amplitudes corresponding to the protection device installation locations on both sides of the transmission line obtained after mutual transmission;

[0025] The harmonic current ratio is compared with a preset harmonic ratio threshold, and the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are assigned values ​​according to the comparison result.

[0026] Preferably, comparing the harmonic current ratio with a preset harmonic ratio threshold, and assigning values ​​to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line according to the comparison result, includes:

[0027] For the protection device installation location on either side of the transmission line, when the harmonic current ratio is greater than or equal to the preset harmonic ratio threshold, the harmonic characteristic parameter at the protection device installation location on one side of the transmission line is assigned a value of 1;

[0028] When the harmonic current ratio is less than the preset harmonic ratio threshold, the harmonic characteristic parameter at the installation location of the protection device on one side of the transmission line is assigned a value of 0;

[0029] The determining, based on harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, whether the fault location is an internal fault or an external fault, includes:

[0030] When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are both 1, it is determined that the fault location is an internal fault;

[0031] When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are not all 1, it is determined that the fault location is an out-of-zone fault.

[0032] In a second aspect, the present invention further provides a power electronic system protection system, comprising:

[0033] A harmonic injection module, for responding to a harmonic signal active injection request, injecting a harmonic signal of a preset amplitude into the three-phase voltage modulation wave of the new energy converter for harmonic modulation;

[0034] A harmonic acquisition module, used to acquire harmonic current signals at the installation locations of protection devices on both sides of the transmission line to which the new energy converter is connected after harmonic modulation;

[0035] A harmonic characteristic determination module, used for performing Fourier transform on the harmonic current signal, and determining the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transform; wherein the harmonic characteristic parameters are determined by the harmonic current ratios of the installation locations of the protection devices on both sides of the transmission line;

[0036] A fault location module, used to determine whether the fault location is an internal fault or an external fault according to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line;

[0037] The protection execution module is used to execute the protection action of the protection device when it is determined that the fault occurrence location is an in-zone fault.

[0038] In a third aspect, the present invention further provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the power electronics system protection method as described in the first aspect.

[0039] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed, implements the steps of the power electronics system protection method as described in the first aspect.

[0040] It can be seen from the above technical solutions that the present invention performs harmonic modulation by injecting a harmonic signal of a preset amplitude into the three-phase voltage modulation wave of the new energy converter, obtains the harmonic current signal of the protection device installation on both sides of the transmission line connected to the new energy converter after harmonic modulation, and uses the harmonic current signal to perform Fourier transform, and determines the harmonic characteristic parameters corresponding to the protection device installation on both sides of the transmission line, and identifies the fault location through the harmonic characteristic parameters, and executes the protection action of the protection device in the zone fault. The embodiment of the present application is not affected by the operating conditions and control strategies of the new energy side by actively injecting harmonic signals, does not need to install additional signal injection devices, and has a low application cost. It also identifies the fault location through harmonic characteristic parameters, and executes the protection action of the protection device in the zone fault, avoiding the risk of false operation or refusal to operate in the power electronic system protection mode, and ensuring the stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative labor.

[0042] Figure 1 An application environment of a power electronic system protection method provided by an embodiment of the present invention;

[0043] Figure 2 A structural topology diagram of a power electronics system provided by an embodiment of the present invention;

[0044] Figure 3 A flow chart of a power electronic system protection method provided by an embodiment of the present invention;

[0045] Figure 4 A control strategy for injecting harmonic signals by PWM modulation of a photovoltaic side converter provided in an embodiment of the present invention;

[0046] Figure 5 A schematic diagram of the structure of a power electronic system protection system provided by an embodiment of the present invention;

[0047] Figure 6 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The power electronic system protection method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the power electronics system of the new energy connected to the grid by flexible direct current communicates with the server 102 through the network. The data storage system can store the data that the server 102 needs to process. The data storage system can be integrated on the server 102, or it can be placed on the cloud or other network servers. In response to the active injection request of the harmonic signal, the server 102 injects the harmonic signal of the preset amplitude into the three-phase voltage modulation wave of the new energy converter for harmonic modulation; obtains the harmonic current signal of the protection device installation on both sides of the transmission line connected to the new energy converter after harmonic modulation; Fourier transforms the harmonic current signal, and determines the harmonic characteristic parameters corresponding to the protection device installation on both sides of the transmission line obtained after Fourier transform; wherein the harmonic characteristic parameters are determined by the harmonic current ratio of the protection device installation on both sides of the transmission line; according to the harmonic characteristic parameters corresponding to the protection device installation on both sides of the transmission line, the fault location is judged to be an internal fault or an external fault; when the fault location is judged to be an internal fault, the protection action of the protection device is executed.

[0050] The server 102 may be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0051] Among them, Figure 2 The structural topology of the power electronic system shown in the figure takes the photovoltaic station as an example. The power electronic system includes a photovoltaic power generation end, which is connected to the first flexible DC side transformer through a transmission line, and the flexible DC side transformer is connected to the new energy converters MMC1 and MMC2, and the new energy converter MMC2 is connected to the second flexible DC side transformer, and the second flexible DC side transformer is connected to the receiving end power grid. Among them, the photovoltaic power generation end includes multiple groups of photovoltaic stations and photovoltaic side transformers, and the photovoltaic stations are connected to the photovoltaic side transformer, and the photovoltaic side transformer is connected to the first flexible DC side transformer.

[0052] like Figure 3 As shown, the embodiment of the present application provides a power electronic system protection method, which is applied to Figure 1The server 102 in the example is used as an example to illustrate the method, which includes the following steps S1 to S5. Among them:

[0053] Step S1: In response to a harmonic signal active injection request, a harmonic signal of a preset amplitude is injected into a three-phase voltage modulation wave of a new energy converter for harmonic modulation.

[0054] Among them, combined with the low-voltage fault ride-through control strategy, a harmonic signal injection start-up criterion suitable for various short-circuit scenarios is constructed, so that the harmonic signal injection start-up criterion is used to determine the active harmonic signal injection request.

[0055] Specifically, the process of generating a harmonic signal active injection request includes:

[0056] Step S11, obtaining the positive sequence voltage and negative sequence voltage of the grid connection point of the new energy converter.

[0057] Step S12: determine whether the positive sequence voltage and the negative sequence voltage simultaneously meet the preset harmonic signal injection start criterion.

[0058] Among them, the harmonic signal injection startup criterion is:

[0059]

[0060]

[0061] In the formula, is the per unit value of the positive sequence voltage at the grid connection point of the new energy converter, It is the negative sequence voltage per unit value at the grid connection point of the new energy converter; is the positive sequence voltage start threshold value, which is taken as 0.9 according to the low voltage fault ride-through requirement; is the positive sequence voltage starting threshold value, which can be taken as 0.1 and can be adjusted appropriately according to the sensitivity requirements.

[0062] When the harmonic signal injection start criterion is met, a harmonic signal active injection request may be generated.

[0063] Step S13: When it is determined that the positive sequence voltage and the negative sequence voltage simultaneously meet the preset harmonic signal injection start criterion, a harmonic signal active injection request is generated.

[0064] Among them, the harmonic signal of preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, which is to superimpose the harmonic voltage signal of fixed amplitude on the original modulation wave. The harmonic signal of preset amplitude is obtained by tracking and controlling the actual output value of the current of the harmonic signal through the proportional integral controller based on the current reference value of the harmonic signal. The tracking control is used to modulate the error between the actual output value of the current of the harmonic signal and the current reference value of the harmonic signal within the preset error threshold, and finally realize the quantitative output of the harmonic signal current based on PWM modulation.

[0065] Among them, the transfer function of the current control link of the harmonic signal of the proportional integral controller is:

[0066]

[0067] In the formula, , are the d-axis and q-axis components of the harmonic voltage reference value, , are the d-axis and q-axis components of the measured harmonic voltage at the grid connection point of the new energy converter, , are proportional gain and integral gain respectively, is the Laplace operator, , are the d-axis and q-axis components of the current reference value of the harmonic signal, , are the d-axis and q-axis components of the measured harmonic current at the grid connection point of the new energy converter, is the harmonic order, is the angular frequency, For inductance.

[0068] like Figure 4 The PV-side converter PWM modulation injection harmonic signal control strategy shown in the figure is based on the transfer function of the current control link of the harmonic signal of the proportional integral controller, which converts the d-axis and q-axis components of the harmonic voltage reference value into , After the Parker inverse transformation, the stationary dq coordinate system is transformed into the synchronously rotating abc coordinate system to obtain the harmonic signal voltage. The inner loop current reference value is superimposed on the harmonic signal voltage based on the three-phase voltage modulation wave of the new energy converter. The harmonic source converter station can realize the harmonic signal current by simply superimposing a harmonic signal voltage of a fixed amplitude on the basis of the modulation wave. Active injection.

[0069] In some embodiments, a harmonic signal of a preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the obtained harmonic modulation signal is:

[0070]

[0071] In the formula, are the voltage modulation amplitudes of phase a, phase b and phase c of the new energy converter, is the voltage modulation amplitude of the new energy converter, t is the time, is the modulation phase of the new energy converter, is the amplitude of the harmonic signal, is the angular frequency of the harmonic signal, is the initial phase of the harmonic signal.

[0072] In some embodiments, for the selection of parameters related to harmonic signal injection, the measurement link of the injected signal and the impact on the power electronic equipment are considered, a basis for selecting the amplitude of the injected signal is given, and the injection amplitude U is selected considering the tolerance of the power electronic equipment. H It is 0.1pu.

[0073] The inverters at the beginning and end of the line select to inject harmonic signals of different frequencies. Considering the frequency output capability of the injected signal, the transmission attenuation effect of the signal, and the signal frequency selection of the data processing process, it is recommended to inject harmonic signal frequency at the beginning of the line (indicated by M) =200Hz, the frequency of the harmonic signal injected at the end (indicated by N) =300Hz. Initial phase It can take any value, here it can take 0.

[0074] In order to detect the accuracy of the signal and the reliability of the identification, while taking into account the stability of the system and ensuring the power quality of the system, the injected characteristic signal needs to have a certain length. Considering the time margin required for communication delay and data processing, the length of the characteristic signal injected by each distributed power source is 100ms each time. Harmonic signal injection is achieved by changing the duty cycle of the modulation wave.

[0075] Step S2, obtaining harmonic current signals at the locations where protection devices are installed on both sides of the transmission line to which the new energy converter is connected after harmonic modulation.

[0076] Step S3, perform Fourier transform on the harmonic current signal, and determine the harmonic characteristic parameters corresponding to the protection device installation locations on both sides of the transmission line obtained after Fourier transform; wherein the harmonic characteristic parameters are determined by the harmonic current ratio of the protection device installation locations on both sides of the transmission line.

[0077] Among them, the harmonic current signals at the protection device installation locations on both sides of the transmission line connected to the new energy converter are respectively extracted based on Fourier transform to extract the harmonic frequency current amplitude in the harmonic current signal, among which, the line M side is extracted Harmonic current , Frequency harmonic current , Line N side extraction Frequency harmonic current , Frequency harmonic current .

[0078] Specifically, the harmonic current signal is Fourier transformed, and the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transform are determined, including:

[0079] Performing Fourier transformation on the harmonic current signal, and extracting the harmonic frequency current amplitudes corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transformation;

[0080] Step S301: Based on the communication channel of the longitudinal protection, the currents at the installation locations of the protection devices on both sides of the transmission line are transmitted to each other.

[0081] Among them, based on the communication channel of the longitudinal protection, the M side The current is transmitted to the N side, The current is transmitted to the M side, so that both the M side and the Harmonic current , Frequency harmonic current , Frequency harmonic current and Frequency harmonic current .

[0082] Step S302: determine the harmonic current ratio of the protection device installation locations on both sides of the transmission line according to the harmonic frequency current amplitudes corresponding to the protection device installation locations on both sides of the transmission line obtained after mutual transmission.

[0083] Step S303: compare the harmonic current ratio with a preset harmonic ratio threshold, and assign values ​​to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line according to the comparison result.

[0084] In some embodiments, the step S303 compares the harmonic current ratio with a preset harmonic ratio threshold, and assigns values ​​to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line according to the comparison result, including:

[0085] Step S3031: for the protection device installation location on either side of the transmission line, when the harmonic current ratio is greater than or equal to a preset harmonic ratio threshold, the harmonic characteristic parameter of the protection device installation location on one side of the transmission line is assigned a value of 1.

[0086] Step S3032: When the harmonic current ratio is less than a preset harmonic ratio threshold, the harmonic characteristic parameter at the installation location of the protection device on one side of the transmission line is assigned a value of 0.

[0087] For example, define is the harmonic characteristic parameter on the M side, is the harmonic characteristic parameter of the N side. As shown in the following formula, when the M side If the ratio of the harmonic current to the N-side harmonic current amplitude is greater than the set value Kset, Set to 1, otherwise set to 0; when the N side If the ratio of the harmonic current to the harmonic current amplitude on the M side is greater than the set value Kset, Set to 1, otherwise set to 0.

[0088]

[0089]

[0090] The selection of the constant Kset needs to consider the attenuation of the signal during line transmission, data processing errors, the influence of transition resistance, etc., and can be taken as 0.4.

[0091] Step S4: determine whether the fault location is an internal fault or an external fault according to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line.

[0092] In some embodiments, by assigning values ​​to harmonic characteristic parameters, the harmonic characteristic parameters corresponding to the installation locations of protection devices on both sides of the transmission line are used to determine whether the fault location is an in-zone fault or an out-of-zone fault.

[0093] Specifically, the fault location is judged as an internal fault or an external fault based on the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, including:

[0094] Step S401: When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are both 1, it is determined that the fault location is an intra-area fault.

[0095] Step S402: When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are not all 1, it is determined that the fault location is an out-of-zone fault.

[0096] Step S5: When it is determined that the fault location is an internal fault, the protection action of the protection device is executed.

[0097] Among them, the action conditions of the longitudinal protection are proposed as follows:

[0098]

[0099] When the action conditions of the longitudinal protection are met, it is identified as an internal fault and the protection is activated; otherwise, it is an external fault and the protection does not activate.

[0100] It should be noted that the embodiment of the present application performs harmonic modulation by injecting a harmonic signal of a preset amplitude into the three-phase voltage modulation wave of the new energy converter, obtains the harmonic current signal of the protection device installation on both sides of the transmission line connected to the new energy converter after harmonic modulation, and uses the harmonic current signal to perform Fourier transform, and determines the harmonic characteristic parameters corresponding to the protection device installation on both sides of the transmission line, identifies the fault location through the harmonic characteristic parameters, and performs the protection action of the protection device in the fault area. The embodiment of the present application is not affected by the operating conditions and control strategies of the new energy side by actively injecting harmonic signals, does not need to install additional signal injection devices, and has a low application cost. It also identifies the fault location through harmonic characteristic parameters, and performs the protection action of the protection device in the fault area, avoiding the risk of false operation or refusal to operate in the protection mode of the power electronic system, ensuring the stable operation of the power system, and is suitable for the power electronic system of the sending end of the new energy network such as Shagohuang and offshore wind power through flexible direct transmission, and has a good application prospect.

[0101] Based on the same inventive concept, an embodiment of the present application further provides a power electronics system protection system for implementing the power electronics system protection method involved above.

[0102] The implementation solution provided by the system to solve the problem is similar to the implementation solution recorded in the above method, so the specific limitations in one or more power electronic system protection system embodiments provided below can refer to the limitations on the power electronic system protection method above, and will not be repeated here.

[0103] like Figure 5 As shown, the embodiment of the present application provides a power electronic system protection system, including:

[0104] The harmonic injection module 100 is used to respond to the active injection request of the harmonic signal and inject the harmonic signal of the preset amplitude into the three-phase voltage modulation wave of the new energy converter for harmonic modulation;

[0105] The harmonic acquisition module 200 is used to obtain the harmonic current signal at the installation location of the protection device on both sides of the transmission line connected to the new energy converter after harmonic modulation;

[0106] The harmonic characteristic determination module 300 is used to perform Fourier transform on the harmonic current signal and determine the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transform; wherein the harmonic characteristic parameters are determined by the harmonic current ratio of the installation locations of the protection devices on both sides of the transmission line;

[0107] The fault location module 400 is used to determine whether the fault location is an internal fault or an external fault according to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line;

[0108] The protection execution module 500 is used to execute the protection action of the protection device when it is determined that the fault location is an internal fault.

[0109] In some embodiments, the system also includes an injection start module, which is used to obtain the positive-sequence voltage and negative-sequence voltage of the grid-connected point of the new energy inverter; determine whether the positive-sequence voltage and the negative-sequence voltage simultaneously meet the preset harmonic signal injection start criterion; when it is determined that the positive-sequence voltage and the negative-sequence voltage simultaneously meet the preset harmonic signal injection start criterion, a harmonic signal active injection request is generated.

[0110] In some embodiments, the harmonic signal of a preset amplitude is obtained by tracking and controlling the actual output value of the current of the harmonic signal through a proportional-integral controller based on a current reference value of the harmonic signal. The tracking control is used to modulate the error between the actual output value of the current of the harmonic signal and the current reference value of the harmonic signal within a preset error threshold.

[0111] In some embodiments, the transfer function of the current control link of the harmonic signal of the proportional-integral controller is:

[0112]

[0113] In the formula, , are the d-axis and q-axis components of the harmonic voltage reference value, , are the d-axis and q-axis components of the measured harmonic voltage at the grid connection point of the new energy converter, , are proportional gain and integral gain respectively, is the Laplace operator, , are the d-axis and q-axis components of the current reference value of the harmonic signal, , are the d-axis and q-axis components of the measured harmonic current at the grid connection point of the new energy converter, is the harmonic order, is the angular frequency, For inductance.

[0114] In some embodiments, a harmonic signal of a preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the obtained harmonic modulation signal is:

[0115]

[0116] In the formula, are the voltage modulation amplitudes of phase a, phase b and phase c of the new energy converter, is the voltage modulation amplitude of the new energy converter, t is the time, is the modulation phase of the new energy converter, is the amplitude of the harmonic signal, is the angular frequency of the harmonic signal, is the initial phase of the harmonic signal.

[0117] In some embodiments, the harmonic characteristic determination module 300 is used to perform Fourier transform on the harmonic current signal, and extract the harmonic frequency current amplitudes corresponding to the protection device installation points on both sides of the transmission line obtained after the Fourier transform; based on the communication channel of the longitudinal protection, the currents at the protection device installation points on both sides of the transmission line are mutually transmitted; according to the harmonic frequency current amplitudes corresponding to the protection device installation points on both sides of the transmission line obtained after the mutual transmission, the harmonic current ratio of the protection device installation points on both sides of the transmission line is determined; the harmonic current ratio is compared with a preset harmonic ratio threshold, and the harmonic characteristic parameters corresponding to the protection device installation points on both sides of the transmission line are assigned according to the comparison results.

[0118] In some embodiments, the harmonic current ratio is compared with a preset harmonic ratio threshold, and the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are assigned values ​​according to the comparison result, including:

[0119] For the installation location of the protection device on either side of the transmission line, when the harmonic current ratio is greater than or equal to the preset harmonic ratio threshold, the harmonic characteristic parameter of the installation location of the protection device on one side of the transmission line is assigned a value of 1;

[0120] When the harmonic current ratio is less than the preset harmonic ratio threshold, the harmonic characteristic parameter at the installation location of the protection device on one side of the transmission line is assigned a value of 0;

[0121] According to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, it is judged whether the fault location is an internal fault or an external fault, including:

[0122] When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are both 1, it is determined that the fault location is an internal fault;

[0123] When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are not all 1, it is determined that the fault location is an out-of-zone fault.

[0124] like Figure 6 As shown, an embodiment of the present application provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, and when the computer program is executed by the processor 30, the processor 30 executes the steps of the power electronics system protection method in the above embodiment.

[0125] An embodiment of the present application provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed, the steps of the power electronics system protection method in the above embodiment are implemented.

[0126] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, electronic device and computer storage medium can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0127] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0128] In several embodiments provided by the present invention, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and a part of a module, a program segment or a code includes one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0129] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0130] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0131] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0132] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for executing all or part of the steps of the method described in each embodiment of the present invention through a computer device (which can be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk, etc. Various media that can store program codes.

[0133] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power electronic system protection method, characterized in that: include: In response to a harmonic signal active injection request, a harmonic signal of a preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation; Acquire harmonic current signals at the locations where protection devices are installed on both sides of the transmission line to which the new energy converter is connected after harmonic modulation; Performing Fourier transformation on the harmonic current signal, and determining harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transformation; wherein the harmonic characteristic parameters are determined by the harmonic current ratio of the installation locations of the protection devices on both sides of the transmission line; According to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, it is judged whether the fault location is an internal fault or an external fault; When it is determined that the fault occurrence location is an in-zone fault, the protection action of the protection device is executed.

2. The power electronic system protection method according to claim 1, characterized in that: In response to the active harmonic signal injection request, the harmonic voltage signal of the preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the method also includes: Obtaining a positive-sequence voltage and a negative-sequence voltage of a grid-connected point of the new energy converter; Determining whether the positive-sequence voltage and the negative-sequence voltage simultaneously satisfy a preset harmonic signal injection start criterion; When it is determined that the positive-sequence voltage and the negative-sequence voltage simultaneously satisfy the preset harmonic signal injection start criterion, the harmonic signal active injection request is generated.

3. The power electronic system protection method according to claim 1, characterized in that: The harmonic signal of the preset amplitude is obtained by tracking and controlling the actual output value of the current of the harmonic signal through a proportional-integral controller based on the current reference value of the harmonic signal. The tracking control is used to modulate the error between the actual output value of the current of the harmonic signal and the current reference value of the harmonic signal within a preset error threshold.

4. The power electronic system protection method according to claim 3, characterized in that: The transfer function of the current control link of the harmonic signal of the proportional integral controller is: In the formula, , are the d-axis and q-axis components of the harmonic voltage reference value, , are the d-axis and q-axis components of the measured harmonic voltage at the grid connection point of the new energy converter, , are proportional gain and integral gain respectively, is the Laplace operator, , are the d-axis and q-axis components of the current reference value of the harmonic signal, , are the d-axis and q-axis components of the measured harmonic current at the grid connection point of the new energy converter, is the harmonic order, is the angular frequency, For inductance.

5. The power electronic system protection method according to claim 1, characterized in that: The harmonic signal of the preset amplitude is injected into the three-phase voltage modulation wave of the new energy converter for harmonic modulation, and the obtained harmonic modulation signal is: In the formula, are the voltage modulation amplitudes of phase a, phase b and phase c of the new energy converter, is the voltage modulation amplitude of the new energy converter, t is the time, is the modulation phase of the new energy converter, is the amplitude of the harmonic signal, is the angular frequency of the harmonic signal, is the initial phase of the harmonic signal.

6. The power electronic system protection method according to claim 1, characterized in that: The Fourier transform of the harmonic current signal is performed, and the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transform are determined, respectively, include: Performing Fourier transformation on the harmonic current signal, and extracting the harmonic frequency current amplitudes corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transformation; Based on the communication channel of the longitudinal protection, the currents at the installation locations of the protection devices on both sides of the transmission line are mutually transmitted; Determine the harmonic current ratio of the protection device installation locations on both sides of the transmission line according to the harmonic frequency current amplitudes corresponding to the protection device installation locations on both sides of the transmission line obtained after mutual transmission; The harmonic current ratio is compared with a preset harmonic ratio threshold, and the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are assigned values ​​according to the comparison result.

7. The power electronic system protection method according to claim 6, characterized in that: The comparing the harmonic current ratio with a preset harmonic ratio threshold, and assigning values ​​to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line according to the comparison result, includes: For the protection device installation location on either side of the transmission line, when the harmonic current ratio is greater than or equal to the preset harmonic ratio threshold, the harmonic characteristic parameter at the protection device installation location on one side of the transmission line is assigned a value of 1; When the harmonic current ratio is less than the preset harmonic ratio threshold, the harmonic characteristic parameter at the installation location of the protection device on one side of the transmission line is assigned a value of 0; The determining, based on harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line, whether the fault location is an internal fault or an external fault, includes: When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are both 1, it is determined that the fault location is an internal fault; When the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line are not all 1, it is determined that the fault location is an out-of-zone fault.

8. A power electronic system protection system, characterized in that: include: A harmonic injection module, for responding to a harmonic signal active injection request, injecting a harmonic signal of a preset amplitude into the three-phase voltage modulation wave of the new energy converter for harmonic modulation; A harmonic acquisition module, used to acquire harmonic current signals at the installation locations of protection devices on both sides of the transmission line to which the new energy converter is connected after harmonic modulation; A harmonic characteristic determination module, used for performing Fourier transform on the harmonic current signal, and determining the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line obtained after the Fourier transform; wherein the harmonic characteristic parameters are determined by the harmonic current ratios of the installation locations of the protection devices on both sides of the transmission line; A fault location module, used to determine whether the fault location is an internal fault or an external fault according to the harmonic characteristic parameters corresponding to the installation locations of the protection devices on both sides of the transmission line; The protection execution module is used to execute the protection action of the protection device when it is determined that the fault occurrence location is an in-zone fault.

9. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the power electronics system protection method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the power electronics system protection method according to any one of claims 1 to 7 are implemented.

Images