Differential protection method, device and equipment for static frequency converter of pumped storage unit and medium

Abstract

The invention provides a differential protection method, device and equipment for a static frequency converter of a pumped storage unit and a medium. The differential protection method comprises the steps of determining a first current value of a network bridge side and a second current value of a machine bridge side of the static frequency converter of the pumped storage unit; carrying out matrix processing by using the static frequency converter time domain model to obtain a first bridge arm equivalent current matrix at a network bridge side and a second bridge arm equivalent current matrix at a machine bridge side; processing the equivalent current matrixes of the two bridge arms by using a time domain model of the static frequency converter, and determining a differential current value; if the differential current value is smaller than the preset protection setting value, an external fault exists, and the differential protection function is closed; and if the differential current value of preset times is greater than or equal to the preset protection setting value and the internal fault exists in the preset sampling total times, executing the differential protection function. The protection method is suitable for the intermittent commutation stage and the natural commutation stage of static frequency conversion starting of the pumping and storage unit, and rapid and accurate action on the internal fault of the static frequency converter in the whole starting process of the pumping and storage unit is achieved.

Description

Technical Field

[0001] The present disclosure relates to the field of relay protection for power systems, and in particular to a static inverter differential protection method, device, equipment and medium for a pumped storage unit. Background Art

[0002] Large-scale pumped storage power stations mostly use static inverters to start the units smoothly and reliably to reduce the interference and impact on the power grid when the units are started and connected to the grid. The control strategy of the static inverter system in the pumping start process of the pumped storage unit is relatively complex, requiring the implementation of different commutation control methods and switching, and coordinating with the control strategy of the synchronous motor.

[0003] Since the static inverter has a variable frequency current of 0-50Hz on the bridge side, the inconsistency of the current frequency on both sides of the machine and the grid makes it difficult to configure conventional differential protection based on power frequency phasors. Summary of the invention

[0004] In view of this, the purpose of the present disclosure is to propose a static inverter differential protection method, device, equipment and medium for a pumped storage unit to solve or partially solve the above-mentioned problems.

[0005] Based on the above purpose, a first aspect of the present disclosure provides a static inverter differential protection method for a pumped storage unit, the method comprising:

[0006] Determine a first current value on the network bridge side and a second current value on the machine bridge side of the static frequency converter of the pumped storage unit;

[0007] Obtain a preset static frequency converter time domain model, and use the static frequency converter time domain model to perform matrix processing on the first current value and the second current value to obtain a first bridge arm equivalent current matrix on the network bridge side and a second bridge arm equivalent current matrix on the machine bridge side;

[0008] Using the static frequency converter time domain model, performing difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix to determine a differential current value;

[0009] comparing the differential current value with a preset protection setting value;

[0010] In response to the differential current value being less than the preset protection setting value, it is determined that the static frequency converter has an out-of-zone fault, and the differential protection function is turned off; or,

[0011] In response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times, it is determined that an internal fault exists in the static frequency converter, and a differential protection function is executed.

[0012] Optionally, in response to the differential current value being greater than the preset protection setting value, determining that there is an internal fault in the static frequency converter, and executing the differential protection function include:

[0013] Continuously collecting the first current value and the second current value for a preset total number of sampling times, and respectively determining the differential current value corresponding to the first current value and the second current value collected each time;

[0014] In response to the differential current value being greater than the preset protection setting value at least a preset number of times in the preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and the differential protection function is executed.

[0015] Optionally, the static frequency converter includes a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side;

[0016] The step of determining a first current value on a network bridge side and a second current value on a machine bridge side of a static frequency converter of a pumped storage unit comprises:

[0017] Acquire a target current flow direction of an upper bridge arm of a static frequency converter, determine a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determine a second target thyristor from a plurality of second thyristors;

[0018] The current value passing through the first target thyristor is taken as a first current value, and the current value passing through the second target thyristor is taken as a second current value.

[0019] Optionally, determining a first target thyristor from a plurality of first thyristors and determining a second target thyristor from a plurality of second thyristors according to the target current flow direction includes:

[0020] respectively collecting the current value of the first current of each phase corresponding to the three-phase alternating current input to the static frequency converter;

[0021] In response to the first current having a current value greater than zero, determining that the current flow direction of the first current of the phase is the same as the target current flow direction, using the corresponding first thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static frequency converter corresponds to a first thyristor;

[0022] respectively collecting the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter;

[0023] In response to the second current having a current value greater than zero, it is determined that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding second thyristor is used as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

[0024] Optionally, performing difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix by using the static inverter time domain model includes:

[0025] Using the static frequency converter time domain model to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the network bridge side;

[0026] Using the time domain model of the static frequency converter to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix, to obtain an instantaneous value of the second equivalent direct current on the machine bridge side;

[0027] The first equivalent direct current instantaneous value and the second equivalent direct current instantaneous value are subjected to difference processing to obtain a differential current value, and the differential current value is expressed by the formula:

[0028] i d =|i dcn (t)-i dcm (t)|

[0029] Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0030] Optionally, the using the static frequency converter time domain model to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix to obtain the instantaneous value of the first equivalent direct current on the network bridge side includes:

[0031] A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0032] i dcn (t) = B1·i VT1

[0033] B1=(1 1 1)

[0034] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0035] Optionally, the instantaneous calculation conversion of the second bridge arm equivalent current matrix by using the static inverter time domain model to obtain the instantaneous value of the second equivalent direct current on the machine bridge side includes:

[0036] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0037] i dcm (t) = B2·i VT2

[0038] B2=(1 1 1)

[0039] Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0040] Based on the same inventive concept, the second aspect of the present disclosure proposes a static inverter differential protection device for a pumped storage unit, comprising:

[0041] A current determination module, configured to determine a first current value on a network bridge side and a second current value on a machine bridge side of a static frequency converter of a pumped storage unit;

[0042] A matrix processing module is configured to obtain a preset static frequency converter time domain model, and use the static frequency converter time domain model to perform matrix processing on the first current value and the second current value to obtain a first bridge arm equivalent current matrix on the network bridge side and a second bridge arm equivalent current matrix on the machine bridge side;

[0043] A differential current determination module is configured to perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix using the static inverter time domain model to determine a differential current value;

[0044] A comparison module, configured to compare the differential current value with a preset protection setting value;

[0045] The first judgment module is configured to determine that there is an out-of-zone fault in the static frequency converter in response to the differential current value being less than the preset protection setting value, and to turn off the differential protection function; or

[0046] The second judgment module is configured to determine that a fault exists in the static frequency converter and execute a differential protection function in response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times.

[0047] Optionally, the second determination module is specifically configured to:

[0048] Continuously collecting the first current value and the second current value for a preset total number of sampling times, and respectively determining the differential current value corresponding to the first current value and the second current value collected each time;

[0049] In response to the differential current value being greater than the preset protection setting value at least a preset number of times in the preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and the differential protection function is executed.

[0050] Optionally, the static frequency converter includes a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side;

[0051] The current determination module specifically includes:

[0052] a target flow direction determining unit configured to obtain a target current flow direction of an upper bridge arm of the static frequency converter, determine a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determine a second target thyristor from a plurality of second thyristors;

[0053] The current determining unit is configured to use a current value passing through the first target thyristor as a first current value and a current value passing through the second target thyristor as a second current value.

[0054] Optionally, the current determination unit is specifically configured as follows:

[0055] respectively collecting the current value of the first current of each phase corresponding to the three-phase alternating current input to the static frequency converter;

[0056] In response to the existence of a current value of the first current being greater than zero, determining that the current flow direction of the first current of the phase is the same as the target current flow direction, using the corresponding first thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static frequency converter corresponds to a first thyristor;

[0057] respectively collecting the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter;

[0058] In response to the second current having a current value greater than zero, it is determined that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding second thyristor is used as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

[0059] Optionally, the differential current determination module specifically includes:

[0060] A first instantaneous value determination unit is configured to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a first equivalent direct current instantaneous value on the network bridge side;

[0061] A second instantaneous value determination unit is configured to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a second equivalent direct current instantaneous value on the machine bridge side;

[0062] The differential current determination unit is configured to perform a difference process on the instantaneous value of the first equivalent DC current and the instantaneous value of the second equivalent DC current to obtain a differential current value, wherein the differential current value is expressed by the formula:

[0063] i d =|i dcn (t)-i dcm (t)|

[0064] Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0065] Optionally, the first instantaneous value determining unit is specifically configured to:

[0066] A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0067] i dcn (t) = B1·i VT1

[0068] B1=(1 1 1)

[0069] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0070] Optionally, the second instantaneous value determining unit is specifically configured to:

[0071] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0072] i dcm (t) = B2·i VT2

[0073] B2=(1 1 1)

[0074] Among them, i dcm(t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0075] Based on the same inventive concept, the third aspect of the present disclosure proposes an electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable by the processor, wherein the processor implements the static inverter differential protection method of the pumped storage unit as described above when executing the computer program.

[0076] Based on the same inventive concept, the fourth aspect of the present disclosure proposes a non-transitory computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable a computer to execute the static inverter differential protection method of the pumped storage unit as described above.

[0077] Based on the same inventive concept, the fifth aspect of the present disclosure provides a vehicle, comprising the static inverter differential protection device of the pumped storage unit described in the second aspect or the electronic device described in the third aspect or the storage medium described in the fourth aspect.

[0078] From the above, it can be seen that the present disclosure proposes a static inverter differential protection method, device, equipment and medium for a pumped storage unit, determines the first current value on the network bridge side and the second current value on the machine bridge side of the static inverter of the pumped storage unit, obtains a pre-set static inverter time domain model, and uses the static inverter time domain model to matrix the first current value and the second current value to obtain the first bridge arm equivalent current matrix on the network bridge side and the second bridge arm equivalent current matrix on the machine bridge side, so as to subsequently determine the differential current value according to the two matrices. At the same time, a static inverter time domain model is constructed in the time domain, without the need for frequency domain conversion and idealized equivalence, to solve the problem of inconsistent current frequencies on both sides of the machine network. The static inverter time domain model is used to perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix to determine the differential current value, that is, there is no need to perform current conversion in the frequency domain to improve the protection speed. Compare the differential current value with the preset protection setting value. When the differential current value is less than the preset protection setting value, the static inverter has an out-of-zone fault and no differential protection is required. Turn off the differential protection function. When the differential current value is greater than or equal to the preset protection setting value for a preset number of times within the preset total number of sampling times, it indicates that the static inverter has an in-zone fault and the differential protection function is executed. By comparing the differential current value with the preset protection setting value, as long as the differential current value is greater than or equal to the preset protection setting value, it indicates that there is an in-zone fault, which is applicable to both the intermittent commutation stage and the natural commutation stage of the static inverter, so that the static inverter can be quickly and accurately acted upon during the entire process of starting the pumped storage unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the technical solutions in the present disclosure or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0080] Figure 1 A flowchart of a static inverter differential protection method for a pumped storage unit according to an embodiment of the present disclosure;

[0081] Figure 2 This is a schematic diagram of the topological structure of the 12-6 pulsating SFC converter bridge body according to an embodiment of the present disclosure;

[0082] Figure 3 This is a flow chart of a differential protection method for a static inverter of a pumped storage unit according to another embodiment of the present disclosure;

[0083] Figure 4 A schematic diagram of the topology of a 12-6 pulse, high-low-high static frequency converter according to an embodiment of the present disclosure;

[0084] Figure 5 This is a schematic diagram of the stator and rotor magnetic fields of an embodiment of the present disclosure;

[0085] Figure 6 1 is a subroutine flow chart of discontinuous commutation control according to an embodiment of the present disclosure;

[0086] Figure 7 It is a structural block diagram of a static inverter differential protection device of a pumped storage unit according to an embodiment of the present disclosure;

[0087] Figure 8 It is a schematic diagram of the structure of an electronic device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0088] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0089] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0090] The terms used in this disclosure are explained as follows:

[0091] SFC: Static Frequency Converter (SFC) is a power electronic power supply device that can provide simultaneous changes in frequency and voltage. It can be divided into two categories: indirect frequency converter and direct frequency converter.

[0092] PSCAD: Electromagnetic transient simulation software, pscad (PSCAD / EMTDC) (full name Power Systems Computer Aided Design) is the most widely used electromagnetic transient simulation software in the world. EMTDC is its simulation calculation core. PSCAD provides a graphical operation interface for EMTDC (Electromagnetic Transients including DC).

[0093] In order to build a new power system and a new energy system, the construction and development of clean energy such as wind energy, solar energy and nuclear energy are rapid. Due to the volatility, intermittency and randomness of new energy power generation, it brings many problems such as peak load regulation, frequency regulation and energy consumption to the power grid, which puts forward higher requirements for the construction of new power systems. Therefore, it is urgent to improve the balance control of power systems based on energy storage technology. Among the many energy storage methods that solve the regulation needs of power systems and ensure the stable operation of systems, pumped storage technology is still the most economical and effective means at present and in the future.

[0094] Most large-scale pumped storage power stations use static frequency converters (SFCs) to start the units smoothly and reliably, so as to reduce the interference and impact on the power grid when the units are started and connected to the grid. The control strategy of the SFC system in the pumping start process of the pumped storage unit is relatively complex, requiring the implementation of different commutation control methods and switching, and coordinating with the control strategy of the synchronous motor.

[0095] Since the SFC machine bridge side uses variable frequency current of 0-50Hz, the inconsistency of the current frequency on both sides of the machine and the grid makes it difficult to configure the conventional differential protection based on the power frequency phase. In addition, the existing protection scheme has great deficiencies in speed and reliability.

[0096] The existing variable frequency differential protection adopts the full-cycle Fourier algorithm to convert the variable frequency current into the industrial frequency before performing differential protection calculation. The protection algorithm performs the conversion in the frequency domain, which prolongs the protection action time and the speed needs to be improved.

[0097] At the same time, the differential protection method based on the effective value of current calculates the period of variable frequency current by judging the zero-crossing point, and then extracts the effective value of current on both sides of the machine and the grid for differential protection setting. This algorithm is not tolerant of the fluctuation of current near the zero-crossing point of the period, which can easily lead to the protection algorithm misjudging the current period, and the anti-noise performance has not been verified, so the reliability needs to be improved.

[0098] The above differential protection methods are only applicable in the natural commutation stage of the static inverter, and cannot be applied in the intermittent commutation stage, and the protection is locked.

[0099] Based on the above description, this embodiment proposes a static inverter differential protection method for a pumped storage unit, such as Figure 1 As shown, the method includes:

[0100] Step 101, determining a first current value on the network bridge side and a second current value on the machine bridge side of a static inverter of a pumped storage unit.

[0101] In specific implementation, under normal starting conditions of the static inverter, at any given moment, only one thyristor on the same phase in the same converter bridge is in the conducting state between the upper and lower bridge arms. Although the bridge arm thyristors of the 6-pulse and 12-pulse converter bridges will have three thyristors and five thyristors turned on at the same time during the commutation process, namely the "2-3 condition" and the "4-5" condition, under normal operating conditions, the bridge arm direct conduction phenomenon will not occur, even during the commutation process.

[0102] Therefore, the DC current flowing through the machine and the grid can be derived and calculated based on the conduction mechanism of the SFC thyristor, which involves the measurement of the bridge arm current. By analyzing the flow direction of the three-phase current on the AC side, the equivalent DC current expression on both sides of the machine and the grid based on the AC side current sampling value at any time can be derived.

[0103] like Figure 2 As shown, Figure 2 It is a 12-6 pulsation SFC converter bridge main body topology structure. Figure 2 The left part is the bridge side. Figure 2 The right part is the bridge side. Figure 2 In the figure, A, B, and C on the left are each phase of the three-phase alternating current flowing into the static inverter, and A, B, and C on the right are each phase of the three-phase alternating current flowing out of the static inverter.

[0104] VT n1 VT n2 VT n3 VT n4 VT n5 VT n6 VT n7 VT n8 VT n9 VT n10 VT n11 VT m1 VT m2 VT m3 VT m4 VT m5 VT m6 All are thyristors, among which VT n1 VT n5 VT n9 is the thyristor corresponding to the upper arm of the bridge side, i n1A 、i n1B 、i n1C VT is the current per phase of the three-phase AC power corresponding to the upper bridge arm on the bridge side. m2 VT m4 VT m6 VT is the thyristor corresponding to the upper bridge arm on the machine bridge side. n1 is the thyristor corresponding to the bridge side A, VT n5 is the thyristor corresponding to the bridge side B, VT n9 VT is the thyristor corresponding to C on the bridge side. m4 is the thyristor corresponding to A on the bridge side, VT m6 is the thyristor corresponding to B on the bridge side, VT m2 It is the thyristor corresponding to C on the bridge side.

[0105] A first current value on the network bridge side and a second current value on the machine bridge side of the static frequency converter of the pumped storage unit are determined, wherein the first current value and the second current value are currents flowing through the turned-on thyristors.

[0106] Step 1022, obtain a preset static inverter time domain model, and use the static inverter time domain model to matrix the first current value and the second current value to obtain the first bridge arm equivalent current matrix on the network bridge side and the second bridge arm equivalent current matrix on the machine bridge side.

[0107] In specific implementation, a static inverter time domain model is constructed in advance in the time domain, and the first current value and the second current value are matrixed using the static inverter time domain model to obtain the first bridge arm equivalent current matrix on the network bridge side and the second bridge arm equivalent current matrix on the machine bridge side.

[0108] When performing matrix processing, the current value of the non-conducting thyristor collected is a negative value, and the current value corresponding to the non-conducting thyristor is set to zero. Matrix processing is performed based on the current values ​​corresponding to all thyristors in the upper bridge arm on the bridge side to obtain the first bridge arm equivalent current matrix on the bridge side. The first bridge arm lighting effect current matrix is ​​expressed by the formula:

[0109]

[0110] Among them, i VTnk (t) is the current flowing through the thyristor VT on the SFC bridge side nk (k=1,5,9) equivalent current instantaneous value, i nA (t) is the sampling value of the AC current on the bridge side. nA (t) is the current value corresponding to A, i nB (t) is the current value corresponding to B, i nC (t) is the current value corresponding to C.

[0111] According to the current values ​​corresponding to all thyristors in the bridge arm on the machine bridge side, matrix processing is performed to obtain the equivalent current matrix of the second bridge arm on the machine bridge side. The second bridge arm equivalent current matrix is ​​expressed by the formula:

[0112]

[0113] Among them, i VTmj (t) is the current flowing through the thyristor VT on the SFC bridge side mj (j=2,4,6) equivalent current instantaneous value, i mA (t) is the sampling value of the AC current on the bridge side. mA (t) is the current value corresponding to A, i mB (t) is the current value corresponding to B, i mC (t) is the current value corresponding to C.

[0114] Step 103: perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix using the static inverter time domain model to determine a differential current value.

[0115] Step 104, comparing the differential current value with a preset protection setting value.

[0116] In specific implementation, the time domain model of the static frequency converter is used to perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix to determine the differential current value. The obtained differential current value is compared with the preset protection setting value to determine whether the static frequency converter is an internal fault or an external fault.

[0117] In this embodiment, the preset protection setting value is preferably 10% of the maximum value of the DC current under normal operating conditions of the static frequency converter.

[0118] Step 105: In response to the differential current value being less than the preset protection setting value, it is determined that an out-of-zone fault exists in the static frequency converter, and the differential protection function is turned off.

[0119] or,

[0120] Step 106, in response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and a differential protection function is executed.

[0121] In specific implementation, if the differential current value is less than the preset protection setting value, it means that the static inverter has an out-of-zone fault and no differential protection is required. If the differential current value is greater than or equal to the preset protection setting value, it means that the static inverter has an in-zone fault and differential protection is required.

[0122] Differential protection is the current vector difference between the two ends of the input CT (current transformer). When the set action value is reached, the action element is activated. The protection range is the equipment between the two ends of the input CT (which can be electrical equipment such as lines, generators, motors, transformers, etc.).

[0123] Through the above scheme, the first current value on the network bridge side and the second current value on the machine bridge side of the static inverter of the pumped storage unit are determined, and a preset static inverter time domain model is obtained. The first current value and the second current value are matrixed using the static inverter time domain model to obtain the first bridge arm equivalent current matrix on the network bridge side and the second bridge arm equivalent current matrix on the machine bridge side, so as to determine the differential current value according to the two matrices in the future. At the same time, the static inverter time domain model is constructed in the time domain, without the need for frequency domain conversion and idealized equivalence, to solve the problem of inconsistent current frequency on both sides of the machine network. The first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix are differentially processed using the static inverter time domain model to determine the differential current value, that is, there is no need to perform current conversion in the frequency domain to improve the protection speed. The differential current value is compared with the preset protection setting value. When the differential current value is less than the preset protection setting value, the static inverter has an out-of-zone fault at this time, and differential protection is not required, and the differential protection function is turned off. When the differential current value is greater than or equal to the preset protection setting value, it indicates that there is an internal fault in the static inverter, and the differential protection function is executed. By comparing the differential current value with the preset protection setting value, as long as the differential current value is greater than or equal to the preset protection setting value, it indicates that there is an internal fault, which is applicable to both the intermittent commutation stage and the natural commutation stage of the static inverter, so that the internal fault of the static inverter can be quickly and accurately acted upon during the entire process of pumped storage unit startup.

[0124] In some embodiments, step 106 specifically includes:

[0125] Step 1061 : continuously collect the first current value and the second current value for a preset total number of sampling times, and respectively determine the differential current value corresponding to the first current value and the second current value collected each time.

[0126] Step 1062, in response to the differential current value being greater than or equal to the preset protection setting value for at least a preset number of times in the preset total number of sampling times, it is determined that the static frequency converter has an in-zone fault, and a differential protection function is executed.

[0127] In specific implementation, in order to ensure the reliability of protection, it is not rigorous to use only one sampling value as the protection tripping signal. Therefore, in this embodiment, the first current value and the second current value of the preset total number of samplings are continuously collected, and the differential current value corresponding to the first current value and the second current value collected each time is determined by the above method. If there are at least a preset number of differential current values ​​greater than or equal to the preset protection setting value in the preset total number of samplings, it means that the static frequency converter does have an in-zone fault, and the differential protection function is executed.

[0128] The above process can be classified as the R-to-S principle, that is, the protection tripping can only be performed if S sampling values ​​of the R sampling signals meet the action threshold. In this embodiment, the values ​​of R and S are expressed by the following formula:

[0129]

[0130] Among them, T / T S It is determined by the sampling frequency and is the number of signals collected in one power frequency cycle. At the same time, in order to prevent the sampling point from encountering a zero-crossing point and being judged as a non-actuating point when an internal fault occurs, the value of R should be at least two points greater than S.

[0131] Combined with a large number of SFC fault simulation experiment results, in this protection scheme, R is taken as 30 and S is taken as 21.

[0132] Through the above scheme, considering the interference of instantaneous pulses and noise during the SFC startup process, and the equivalent differential current calculated based on the current sampling value has a certain volatility, the differential protection based on the current sampling value cannot rely on the judgment result of a single sampling value. The R-takes-S principle is adopted to perform judgments at multiple consecutive sampling moments, which improves the judgment accuracy.

[0133] In some embodiments, the static frequency converter includes a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side, and step 101 specifically includes:

[0134] Step 1011, obtaining a target current flow direction of an upper bridge arm of the static inverter, determining a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determining a second target thyristor from a plurality of second thyristors.

[0135] Step 1012: taking the current value passing through the first target thyristor as the first current value, and taking the current value passing through the second target thyristor as the second current value.

[0136] During specific implementation, the target current flow direction of the upper bridge arm of the static inverter is obtained. In this embodiment, the power transmission direction when the pumped storage unit is started is taken as the positive direction, that is, the collected current flowing from the grid side to the machine side is defined as the positive direction, and the target current flow direction is the flow direction from the grid bridge side to the machine bridge side.

[0137] According to the determined target current flow direction, a first target thyristor is determined from a plurality of first thyristors, and a second target thyristor is determined from a plurality of second thyristors. The current value passing through the first target thyristor is taken as a first current value, and the current value passing through the second target thyristor is taken as a second current value.

[0138] In some embodiments, step 1011 specifically includes:

[0139] Step 10111, respectively collect the current value of the first current of each phase corresponding to the three-phase alternating current input to the static inverter.

[0140] Step 10112, in response to the first current having a current value greater than zero, determining that the current flow direction of the first current of this phase is the same as the target current flow direction, and using the corresponding first thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static inverter corresponds to a first thyristor.

[0141] In a specific implementation, the current value of the first current of each phase corresponding to the three-phase alternating current input into the upper bridge arm of the static frequency converter is collected respectively to determine whether the current value of the first current is greater than zero.

[0142] If the current value of the first current is greater than zero, it means that the current flow direction of the first current of this phase is the same as the target current flow direction, and the corresponding first thyristor is turned on, and the corresponding thyristor serves as the first target thyristor.

[0143] For example, Figure 2 In, confirm i nA (t) is greater than zero, which means that the current flow direction of the first current of phase A on the bridge side is the same as the target current flow direction, then the thyristor VT corresponding to phase A on the bridge side is n1 conduction, and VT n1 is the first target thyristor.

[0144] Step 10113, respectively collect the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter.

[0145] Step 10114, in response to the second current having a current value greater than zero, determining that the current flow direction of the second current of this phase is the same as the target current flow direction, and using the corresponding second thyristor as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

[0146] In a specific implementation, the current value of the second current of each phase corresponding to the three-phase alternating current outputting the upper bridge arm of the static frequency converter is collected respectively to determine whether the current value of the second current is greater than zero.

[0147] If the current value of the second current is greater than zero, it means that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding thyristor is turned on, and the corresponding thyristor serves as the second target thyristor.

[0148] For example, Figure 2 In, confirm i mA (t) is greater than zero, which means that the current flow direction of the second current of phase A on the bridge side is the same as the target current flow direction, then the thyristor VT corresponding to phase A on the bridge side ism4 conduction, and VT m4 is the second target thyristor.

[0149] In some embodiments, step 103 specifically includes:

[0150] Step 1031: Use the static inverter time domain model to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix to obtain the instantaneous value of the first equivalent direct current on the network bridge side.

[0151] Step 1032: Use the static inverter time domain model to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix to obtain the instantaneous value of the second equivalent DC current on the machine bridge side.

[0152] Step 1033: Perform a difference process on the instantaneous value of the first equivalent DC current and the instantaneous value of the second equivalent DC current to obtain a differential current value. The differential current value is expressed by the formula:

[0153] i d =|i dcm (t)-i dcm (t)|

[0154] Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0155] In specific implementation, the first bridge arm equivalent current matrix is ​​instantaneously calculated and converted using the time domain model of the static frequency converter to obtain the instantaneous value of the first equivalent direct current on the bridge side. The second bridge arm equivalent current matrix is ​​instantaneously calculated and converted using the time domain model of the static frequency converter to obtain the instantaneous value of the second equivalent direct current on the bridge side.

[0156] When the static inverter is in normal working condition, the equivalent DC current values ​​on both sides of the machine and the grid should be equal. Since a new branch is generated after a fault, the mathematical model of the static inverter under normal working conditions is destroyed, which will cause a certain difference in the calculated equivalent DC current.

[0157] Therefore, the difference processing is performed using the first equivalent DC current instantaneous value on the network bridge side and the second equivalent DC current instantaneous value on the machine bridge side, and the absolute value of the obtained difference is taken as the differential current value, and the differential current value is expressed by the formula:

[0158] i d =|i dcn (t)-i dcm (t)|

[0159] Among them, id is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0160] In some embodiments, step 1031 specifically includes:

[0161] A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0162] i dcn (t) = B1·i VT1

[0163] B1=(1 1 1)

[0164] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0165] In a specific implementation, according to Kirchhoff's current law, at any node, the sum of all currents flowing into the node at any time is equal to the sum of all currents flowing out of the node.

[0166] Therefore, a first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0167] i dcn (t) = B1·i VT1

[0168] B1=(1 1 1)

[0169] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0170] In some embodiments, step 1032 specifically includes:

[0171] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0172] idcm (t) = B2·i VT2

[0173] B2=(1 1 1)

[0174] Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0175] In a specific implementation, according to Kirchhoff's current law, at any node, the sum of all currents flowing into the node at any time is equal to the sum of all currents flowing out of the node.

[0176] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0177] i dcm (t) = B2·i VT2

[0178] B2=(1 1 1)

[0179] Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0180] Based on the same inventive concept, another embodiment of the present disclosure proposes a static inverter differential protection method for a pumped storage unit, such as Figure 3 As shown, the method includes:

[0181] Step 201, start the differential protection function.

[0182] Step 202, collecting AC current data on the network bridge side and the machine bridge side.

[0183] During specific implementation, the target current flow direction of the upper bridge arm of the static inverter is obtained. In this embodiment, the power transmission direction when the pumped storage unit is started is taken as the positive direction, that is, the collected current flowing from the grid side to the machine side is defined as the positive direction, and the target current flow direction is the flow direction from the grid bridge side to the machine bridge side.

[0184] According to the determined target current flow direction, a first target thyristor is determined from a plurality of first thyristors, and a second target thyristor is determined from a plurality of second thyristors. The current value passing through the first target thyristor is taken as a first current value, and the current value passing through the second target thyristor is taken as a second current value.

[0185] Step 203, calculating and obtaining the differential current value according to the static inverter time domain model.

[0186] In specific implementation, a static inverter time domain model is constructed in advance in the time domain, and the first current value and the second current value are matrixed using the static inverter time domain model to obtain the first bridge arm equivalent current matrix on the network bridge side and the second bridge arm equivalent current matrix on the machine bridge side.

[0187] When performing matrix processing, the current value of the non-conducting thyristor collected is a negative value, and the current value corresponding to the non-conducting thyristor is set to zero. Matrix processing is performed based on the current values ​​corresponding to all thyristors in the upper bridge arm on the bridge side to obtain the first bridge arm equivalent current matrix on the bridge side. The first bridge arm equivalent current matrix is ​​expressed by the formula:

[0188]

[0189] Among them, i VTnk (t) is the current flowing through the thyristor VT on the SFC bridge side nk (k=1,5,9) equivalent current instantaneous value, i nA (t) is the sampling value of the AC current on the bridge side. nA (t) is the current value corresponding to A, i nB (t) is the current value corresponding to B, i nC (t) is the current value corresponding to C.

[0190] According to the current values ​​corresponding to all thyristors in the upper bridge arm on the bridge side, matrix processing is performed to obtain the equivalent current matrix of the second bridge arm on the bridge side. The equivalent current matrix of the second bridge arm is expressed by the formula:

[0191]

[0192] Among them, i VTmj (t) is the current flowing through the thyristor VT on the SFC bridge side mj (j=2,4,6) equivalent current instantaneous value, i mA (t) is the sampling value of the AC current on the bridge side. mA (t) is the current value corresponding to A, i mB (t) is the current value corresponding to B, i mC (t) is the current value corresponding to C.

[0193] A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0194] i dcn(t) = B1·i VT1

[0195] B1=(1 1 1)

[0196] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0197] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0198] i dcm (t) = B2·i VT2

[0199] B2=(1 1 1)

[0200] Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0201] When the static inverter is in normal working condition, the equivalent DC current values ​​on both sides of the machine and the grid should be equal. Since a new branch is generated after a fault, the mathematical model of the static inverter under normal working conditions is destroyed, which will cause a certain difference in the calculated equivalent DC current.

[0202] Therefore, the difference processing is performed using the first equivalent DC current instantaneous value on the network bridge side and the second equivalent DC current instantaneous value on the machine bridge side, and the absolute value of the obtained difference is taken as the differential current value, and the differential current value is expressed by the formula:

[0203] i d =|i dcn (t)-i dcm (t)|

[0204] Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0205] Step 204 , determine whether the differential current value is greater than the preset protection setting value and whether it satisfies the R-to-S principle. If so, go to step 205 , otherwise go to step 206 .

[0206] Step 205: In case of fault within the zone, the differential protection function is executed.

[0207] Step 206: Out-of-zone fault, turn off the differential protection function.

[0208] In specific implementation, if the differential current value is less than the preset protection setting value, it means that the static inverter has an out-of-zone fault and no differential protection is required. If the differential current value is greater than or equal to the preset protection setting value, it means that the static inverter has an in-zone fault and differential protection is required.

[0209] In some embodiments, the topology of a 12-6 pulse, high-low-high static frequency converter can meet the requirements of static frequency conversion starting of a pumped storage unit, which includes an input transformer, an output transformer, a thyristor converter, a smoothing reactor, etc. The topology of the 12-6 pulse, high-low-high static frequency converter is shown in FIG. Figure 4 shown.

[0210] The basic working principle of the static frequency converter is as follows: the 12-pulse rectifier on the bridge side is connected to the 50Hz power grid frequency current through the input transformer. After rectification, a DC current is formed and the current ripple is suppressed by the DC smoothing reactor to keep it stable. The corresponding thyristor sequence is determined by determining the electrical position of the rotor to trigger conduction. The 6-pulse inverter on the bridge side inverts the DC current into AC power of different frequencies and outputs it to the stator winding of the synchronous motor to generate the corresponding electromagnetic torque. The static frequency converter adopts the synchronous motor load commutation speed regulation principle to drive the synchronous motor steadily from 0 speed to the rated speed, and the output current frequency on the bridge side also gradually increases. When the motor reaches the rated speed, that is, the current on the bridge side reaches the power frequency of 50Hz and is stable, the unit can be connected to the grid synchronously, and at the same time, the SFC exits operation.

[0211] The control strategy of SFC is mainly the commutation control of the thyristors of the bridge commutation bridge on the network bridge side and the machine bridge side. Since the bridge side is connected to the power grid, the power grid can provide sufficient commutation voltage for the thyristors on the bridge side, so that the bridge arm thyristors can be reliably shut down, so the commutation control strategy on the rectifier side is relatively simple. The bridge side adopts a speed-current dual closed-loop control strategy. The inner loop controls the output DC current equal to the given current reference value by controlling the trigger angle, and the outer loop controls the DC current to control the motor speed to the rated speed. Since the machine bridge side is connected to the synchronous motor, it is impossible to provide it with a stable commutation voltage at the initial startup, so the control strategy on the machine bridge side is more complicated, divided into two stages: intermittent commutation control and natural commutation control.

[0212] At the beginning of the pumped storage unit startup, due to the low speed of the synchronous motor, it is impossible to provide sufficient back electromotive force for the thyristor on the inverter side of the SFC. Therefore, when the unit speed is lower than 10% of the rated speed, the inverter side converter adopts the method of forced commutation to control the opening and closing of the thyristor. This stage is also called the intermittent commutation stage. When the thyristor on the inverter side needs to be commutated, the rectifier side is operated by controlling the trigger angle. After the current of the DC circuit drops to zero, all the thyristors on the inverter side can be turned off. Then, according to the position of the rotor, the thyristor on the machine bridge side is triggered according to the corresponding conduction sequence. At this time, the thyristor on the network bridge side is restored to the rectifier state, thereby re-establishing the loop current and realizing the complete process of intermittent commutation. When the motor speed reaches 10% of the rated speed, the synchronous motor can induce a large back electromotive force at the machine end. At this time, the back electromotive force of the motor can be used to smoothly turn off the thyristor on the inverter side. This stage is called the natural commutation stage. However, in order to avoid commutation failure, during the natural commutation stage, the corresponding thyristors need to be triggered a certain electrical angle in advance to ensure sufficient residual commutation angle.

[0213] Figure 5 It is the schematic diagram of the stator and rotor magnetic field during phase change control, n is the rotor speed, The rotor magnetomotive force formed by the excitation current. Assuming that VT3 and VT4 are turned on at this time, the stator current through the UW phase can form the stator magnetomotive force At this time, the stator magnetomotive force is 120° ahead of the rotor magnetomotive force, which can drive the motor rotor to rotate faster and gradually increase the motor speed.

[0214] According to the rule that the inverter-side thyristor is turned on every 60°, the rotor space electrical angle of 360° can be divided into six sectors, and the intermittent commutation stage and the natural commutation stage are given according to the corresponding rules, and the thyristor conduction rule of the rotor position in each sector is given. The intermittent commutation stage is defined as stage I, the natural commutation stage is defined as stage II, and the SFC commutation control thyristor conduction rule is shown in Table 1.

[0215] Table 1

[0216]

[0217] In this embodiment, the control process is implemented in PSCAD / EMTDC. Since the six-pulse Grizzle bridge module in PSCAD cannot realize the commutation valve trigger pulse process of intermittent commutation by its own control method, the intermittent commutation control program is written in C language, interacts with PSCAD, and generates a custom control submodule, thereby realizing the entire control process of SFC intermittent commutation. Figure 6 As shown, Figure 6 The subroutine flow chart of intermittent commutation control is shown, and the specific implementation process is as follows:

[0218] Step A: After the synchronous motor is started, the real-time speed is detected first. When the speed is lower than 10% of the rated speed, the intermittent commutation control process is entered.

[0219] Step B: The rectifier side adopts constant current control and obtains the rotor position at this moment, and determines whether it is in the same sector as the rotor position angle at the previous moment.

[0220] Step C: If they are not in the same sector, set the trigger angle of the rectifier bridge to 135° to make it run in reverse mode. When the DC current drops to 0, turn off all the thyristors on the bridge side to achieve forced commutation.

[0221] Step D: If the rotor angle is in the same sector as the previous moment, or after the forced commutation process is completed, the bridge thyristor that should be turned on after commutation at this moment is triggered according to the sector where the current rotor position angle is located.

[0222] Step E, storing the rotor angle at the current moment and performing speed detection again.

[0223] Step F, when the speed reaches 10% of the rated speed, the intermittent commutation process ends, and the SFC enters the transition process to reach the next stage of natural commutation process.

[0224] Step G: When the speed reaches the rated speed, the static frequency conversion starting process ends and SFC exits operation.

[0225] It should be noted that the method of the embodiment of the present disclosure can be performed by a single device, such as a computer or a server. The method of the present embodiment can also be applied in a distributed scenario and completed by multiple devices cooperating with each other. In the case of such a distributed scenario, one of the multiple devices can only perform one or more steps in the method of the embodiment of the present disclosure, and the multiple devices will interact with each other to complete the described method.

[0226] It should be noted that the above describes some embodiments of the present disclosure. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0227] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, the present disclosure also provides a static inverter differential protection device for a pumped storage unit.

[0228] refer to Figure 7 , Figure 7 The static inverter differential protection device of the pumped storage unit according to the embodiment of the present disclosure comprises:

[0229] The current determination module 701 is configured to determine a first current value on the network bridge side and a second current value on the machine bridge side of the static frequency converter of the pumped storage unit;

[0230] The matrix processing module 702 is configured to obtain a preset static inverter time domain model, and use the static inverter time domain model to perform matrix processing on the first current value and the second current value to obtain a first bridge arm equivalent current matrix on the network bridge side and a second bridge arm equivalent current matrix on the machine bridge side;

[0231] A differential current determination module 703 is configured to perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix using the static inverter time domain model to determine a differential current value;

[0232] A comparison module 704 is configured to compare the differential current value with a preset protection setting value;

[0233] The first judgment module 705 is configured to determine that there is an out-of-zone fault in the static frequency converter in response to the differential current value being less than the preset protection setting value, and turn off the differential protection function; or,

[0234] The second judgment module 706 is configured to determine that a fault exists in the static frequency converter and execute a differential protection function in response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times.

[0235] In some embodiments, the second determination module 706 is specifically configured to:

[0236] Continuously collecting the first current value and the second current value for a preset total number of sampling times, and respectively determining the differential current value corresponding to the first current value and the second current value collected each time;

[0237] In response to the differential current value being greater than or equal to the preset protection setting value for at least a preset number of times in the preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and the differential protection function is executed.

[0238] In some embodiments, the static frequency converter includes a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side; the current determination module 701 specifically includes:

[0239] a target flow direction determining unit configured to obtain a target current flow direction of an upper bridge arm of the static frequency converter, determine a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determine a second target thyristor from a plurality of second thyristors;

[0240] The current determining unit is configured to use a current value passing through the first target thyristor as a first current value and a current value passing through the second target thyristor as a second current value.

[0241] In some embodiments, the current determination unit is specifically configured as follows:

[0242] respectively collecting the current value of the first current of each phase corresponding to the three-phase alternating current input to the static frequency converter;

[0243] In response to the existence of a current value of the first current being greater than zero, determining that the current flow direction of the first current of the phase is the same as the target current flow direction, and using the corresponding thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static frequency converter corresponds to a first thyristor;

[0244] respectively collecting the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter;

[0245] In response to the second current having a current value greater than zero, it is determined that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding thyristor is used as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

[0246] In some embodiments, the differential current determination module 703 specifically includes:

[0247] A first instantaneous value determination unit is configured to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a first equivalent direct current instantaneous value on the network bridge side;

[0248] A second instantaneous value determination unit is configured to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a second equivalent direct current instantaneous value on the machine bridge side;

[0249] The differential current determination unit is configured to perform a difference process on the instantaneous value of the first equivalent DC current and the instantaneous value of the second equivalent DC current to obtain a differential current value, wherein the differential current value is expressed by the formula:

[0250] i d =|i dcn (t)-i dcm (t)|

[0251] Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

[0252] In some embodiments, the first instantaneous value determining unit is specifically configured to:

[0253] A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula:

[0254] i dcn (t) = B1·i VT1

[0255] B1=(1 1 1)

[0256] Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

[0257] In some embodiments, the second instantaneous value determining unit is specifically configured to:

[0258] A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula:

[0259] i dcm (t) = B2·i VT2

[0260] B2=(1 1 1)

[0261] Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

[0262] For the convenience of description, the above device is described by dividing it into various modules according to its functions. Of course, when implementing the present disclosure, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0263] The device of the above embodiment is used to implement the static inverter differential protection method of the corresponding pumped storage unit in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be repeated here.

[0264] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, the present disclosure also provides an electronic device, including 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 static inverter differential protection method for the pumped storage unit described in any of the above embodiments is implemented.

[0265] Figure 8 A more specific schematic diagram of the hardware structure of an electronic device provided in this embodiment is shown, and the device may include: a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040 are connected to each other through the bus 1050 in the device.

[0266] The processor 1010 can be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0267] The memory 1020 may be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 may store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program codes are stored in the memory 1020 and are called and executed by the processor 1010.

[0268] The input / output interface 1030 is used to connect the input / output module to realize information input and output. The input / output module can be configured in the device as a component (not shown in the figure), or it can be externally connected to the device to provide corresponding functions. The input device may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output device may include a display, a speaker, a vibrator, an indicator light, etc.

[0269] The communication interface 1040 is used to connect a communication module (not shown) to realize communication interaction between the device and other devices. The communication module can realize communication through a wired mode (such as USB, network cable, etc.) or a wireless mode (such as mobile network, WIFI, Bluetooth, etc.).

[0270] The bus 1050 includes a path that transmits information between the various components of the device (eg, the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040).

[0271] It should be noted that, although the above device only shows the processor 1010, the memory 1020, the input / output interface 1030, the communication interface 1040 and the bus 1050, in the specific implementation process, the device may also include other components necessary for normal operation. In addition, it can be understood by those skilled in the art that the above device may also only include the components necessary for implementing the embodiments of the present specification, and does not necessarily include all the components shown in the figure.

[0272] The electronic device of the above embodiment is used to implement the static inverter differential protection method of the corresponding pumped storage unit in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be repeated here.

[0273] Based on the same inventive concept, corresponding to any of the above-mentioned embodiment methods, the present disclosure also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the static inverter differential protection method of the pumped storage unit as described in any of the above embodiments.

[0274] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0275] The computer instructions stored in the storage medium of the above embodiment are used to enable the computer to execute the static inverter differential protection method of the pumped storage unit as described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0276] It is understandable that before using the technical solutions of each embodiment of the present disclosure, the type, scope of use, usage scenarios, etc. of the personal information involved will be informed to the user in an appropriate manner, and the user's authorization will be obtained.

[0277] For example, in response to receiving an active request from a user, a prompt message is sent to the user to clearly remind the user that the operation requested to be performed will require obtaining and using the user's personal information. Thus, the user can independently choose whether to provide personal information to software or hardware such as an electronic device, application, server, or storage medium that performs the operation of the technical solution of the present disclosure according to the prompt message.

[0278] As an optional but non-limiting implementation, in response to receiving the user's active request, the prompt information may be sent to the user in the form of a pop-up window, in which the prompt information may be presented in text form. In addition, the pop-up window may also carry a selection control for the user to choose "agree" or "disagree" to provide personal information to the electronic device.

[0279] It is understandable that the above notification and the process of obtaining user authorization are merely illustrative and do not constitute a limitation on the implementation of the present disclosure. Other methods that meet relevant laws and regulations may also be applied to the implementation of the present disclosure.

[0280] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of simplicity.

[0281] In addition, to simplify the description and discussion, and in order not to make the embodiments of the present disclosure difficult to understand, the known power / ground connections to the integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, the device can be shown in the form of a block diagram to avoid making the embodiments of the present disclosure difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the embodiments of the present disclosure will be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present disclosure, it is apparent to those skilled in the art that the embodiments of the present disclosure can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0282] Although the present disclosure has been described in conjunction with specific embodiments of the present disclosure, many replacements, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed.

[0283] The embodiments of the present disclosure are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A static inverter differential protection method for a pumped storage unit, characterized in that: include: Determine a first current value on the network bridge side and a second current value on the machine bridge side of the static frequency converter of the pumped storage unit; Obtain a preset static frequency converter time domain model, and use the static frequency converter time domain model to perform matrix processing on the first current value and the second current value to obtain a first bridge arm equivalent current matrix on the network bridge side and a second bridge arm equivalent current matrix on the machine bridge side; Using the static frequency converter time domain model, performing difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix to determine a differential current value; comparing the differential current value with a preset protection setting value; In response to the differential current value being less than the preset protection setting value, it is determined that the static frequency converter has an out-of-zone fault, and the differential protection function is turned off; or, In response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times, it is determined that an internal fault exists in the static frequency converter, and a differential protection function is executed.

2. The method according to claim 1, characterized in that In response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within the preset total number of sampling times, determining that there is an internal fault in the static frequency converter, and executing the differential protection function, including: Continuously collecting the first current value and the second current value for a preset total number of sampling times, and respectively determining the differential current value corresponding to the first current value and the second current value collected each time; In response to the differential current value being greater than or equal to the preset protection setting value for at least a preset number of times in the preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and the differential protection function is executed.

3. The method according to claim 1, characterized in that The static frequency converter comprises a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side; The step of determining a first current value on a network bridge side and a second current value on a machine bridge side of a static frequency converter of a pumped storage unit comprises: Acquire a target current flow direction of an upper bridge arm of a static frequency converter, determine a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determine a second target thyristor from a plurality of second thyristors; The current value passing through the first target thyristor is taken as a first current value, and the current value passing through the second target thyristor is taken as a second current value.

4. The method according to claim 3, characterized in that: The step of determining a first target thyristor from a plurality of first thyristors and determining a second target thyristor from a plurality of second thyristors according to the target current flow direction includes: respectively collecting the current value of the first current of each phase corresponding to the three-phase alternating current input to the static frequency converter; In response to the first current having a current value greater than zero, determining that the current flow direction of the first current of the phase is the same as the target current flow direction, using the corresponding first thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static frequency converter corresponds to a first thyristor; respectively collecting the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter; In response to the second current having a current value greater than zero, it is determined that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding second thyristor is used as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

5. The method according to claim 1, characterized in that The step of performing difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix by using the static inverter time domain model includes: Using the static frequency converter time domain model to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the network bridge side; Using the time domain model of the static frequency converter to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix, to obtain an instantaneous value of the second equivalent direct current on the machine bridge side; The first equivalent DC current instantaneous value and the second equivalent DC current instantaneous value are subjected to difference processing to obtain a differential current value, and the differential current value is expressed by the formula: i d =|i dcn (t)-i dcm (t)| Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

6. The method according to claim 5, characterized in that The instantaneous calculation conversion of the first bridge arm equivalent current matrix by using the static frequency converter time domain model to obtain the instantaneous value of the first equivalent direct current current on the network bridge side includes: A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula: and dcn (t)=B1 i VT1 B1＝(1 1 1) Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

7. The method according to claim 5, characterized in that The instantaneous calculation conversion of the second bridge arm equivalent current matrix by using the static frequency converter time domain model to obtain the instantaneous value of the second equivalent direct current on the machine bridge side includes: A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula: i dcm (t)=B2·i VT2 B2＝(1 1 1) Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

8. A static inverter differential protection device for a pumped storage unit, characterized in that: include: A current determination module, configured to determine a first current value on a network bridge side and a second current value on a machine bridge side of a static frequency converter of a pumped storage unit; A matrix processing module is configured to obtain a preset static frequency converter time domain model, and use the static frequency converter time domain model to perform matrix processing on the first current value and the second current value to obtain a first bridge arm equivalent current matrix on the network bridge side and a second bridge arm equivalent current matrix on the machine bridge side; A differential current determination module is configured to perform difference processing on the first bridge arm equivalent current matrix and the second bridge arm equivalent current matrix using the static inverter time domain model to determine a differential current value; A comparison module, configured to compare the differential current value with a preset protection setting value; The first judgment module is configured to determine that there is an out-of-zone fault in the static frequency converter in response to the differential current value being less than the preset protection setting value, and to turn off the differential protection function; or The second judgment module is configured to determine that a fault exists in the static frequency converter and execute a differential protection function in response to the differential current value being greater than or equal to the preset protection setting value for a preset number of times within a preset total number of sampling times.

9. The device according to claim 8, characterized in that The second determination module is specifically configured as follows: Continuously collecting the first current value and the second current value for a preset total number of sampling times, and respectively determining the differential current value corresponding to the first current value and the second current value collected each time; In response to the differential current value being greater than or equal to the preset protection setting value for at least a preset number of times in the preset total number of sampling times, it is determined that there is an internal fault in the static frequency converter, and the differential protection function is executed.

10. The device according to claim 8, characterized in that The static frequency converter comprises a plurality of first thyristors on the network bridge side and a plurality of second thyristors on the machine bridge side; The current determination module specifically includes: a target flow direction determining unit configured to obtain a target current flow direction of an upper bridge arm of the static frequency converter, determine a first target thyristor from a plurality of first thyristors according to the target current flow direction, and determine a second target thyristor from a plurality of second thyristors; The current determining unit is configured to use a current value passing through the first target thyristor as a first current value and a current value passing through the second target thyristor as a second current value.

11. The device according to claim 10, characterized in that The current determination unit is specifically configured as follows: respectively collecting the current value of the first current of each phase corresponding to the three-phase alternating current input to the static frequency converter; In response to the first current having a current value greater than zero, determining that the current flow direction of the first current of the phase is the same as the target current flow direction, using the corresponding first thyristor as the first target thyristor, wherein each phase of the three-phase alternating current input to the static frequency converter corresponds to a first thyristor; respectively collecting the current value of the second current of each phase corresponding to the three-phase alternating current outputted from the static frequency converter; In response to the second current having a current value greater than zero, it is determined that the current flow direction of the second current of this phase is the same as the target current flow direction, and the corresponding second thyristor is used as the second target thyristor, wherein each phase of the three-phase alternating current outputting the static inverter corresponds to a second thyristor.

12. The device according to claim 8, characterized in that The differential current determination module specifically includes: A first instantaneous value determination unit is configured to perform instantaneous calculation conversion on the first bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a first equivalent direct current instantaneous value on the network bridge side; A second instantaneous value determination unit is configured to perform instantaneous calculation conversion on the second bridge arm equivalent current matrix using the static frequency converter time domain model to obtain a second equivalent direct current instantaneous value on the machine bridge side; The differential current determination unit is configured to perform a difference process on the instantaneous value of the first equivalent DC current and the instantaneous value of the second equivalent DC current to obtain a differential current value, wherein the differential current value is expressed by the formula: i d =|i dcn (t)-i dcm (t)| Among them, i d is the differential current value, i dcn (t) is the instantaneous value of the first equivalent DC current, i dcm (t) is the instantaneous value of the second equivalent DC current.

13. The device according to claim 12, characterized in that The first instantaneous value determining unit is specifically configured as follows: A first preset correlation matrix is ​​obtained, and the first preset correlation matrix is ​​multiplied by the first bridge arm equivalent current matrix to obtain a first equivalent direct current instantaneous value on the bridge side. The first equivalent direct current instantaneous value is expressed by the formula: and dcn (t)=B1 i VT1 B1＝(1 1 1) Among them, i dcn (t) is the instantaneous value of the first equivalent DC current, B1 is the first preset correlation matrix, i VT1 is the equivalent current matrix of the first bridge arm.

14. The device according to claim 12, characterized in that The second instantaneous value determining unit is specifically configured as follows: A second preset correlation matrix is ​​obtained, and the second preset correlation matrix is ​​multiplied by the second bridge arm equivalent current matrix to obtain a second equivalent direct current instantaneous value on the machine bridge side. The second equivalent direct current instantaneous value is expressed by the formula: i dcm (t)=B2·i VT2 B2＝(1 1 1) Among them, i dcm (t) is the instantaneous value of the second equivalent DC current, B2 is the second preset correlation matrix, i VT2 is the equivalent current matrix of the second bridge arm.

15. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 7 when executing the program. 16 . A non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause a computer to execute the method according to claim 1 .

Images