Multi-stage protection method and device for power distribution network, storage medium and electronic equipment

Abstract

The invention provides a multi-stage protection method and device for a power distribution network, a storage medium and electronic equipment. The method comprises the following steps: determining a current setting value of each stage of fault short circuit of each circuit breaker in the power distribution network and an operation parameter of a distributed power supply; a detection current flowing through a target circuit breaker is obtained, the current direction of the detection current is determined, and the target circuit breaker is one of multiple circuit breakers in the power distribution network; when the current direction of the detection current is the positive direction and the measured value of the detection current is greater than the corresponding setting value, disconnecting the target circuit breaker; and under the condition that the current direction of the detected current is the reverse direction, the target circuit breaker is controlled to be switched on or switched off according to the distance between the target circuit breaker and the fault point. According to the method, a current adaptive protection mechanism is utilized, a direction criterion is introduced, the phenomena of protection operation refusal and maloperation caused by high-proportion DER access to the power distribution network are reduced, and the fault processing level of the power distribution network and the reliability of power supply are improved.

Description

Technical Field

[0001] The present application relates to the field of multi-level protection of distribution networks, and in particular, to a multi-level protection method for distribution networks, a multi-level protection device for distribution networks, a computer-readable storage medium, and an electronic device. Background Art

[0002] At present, multi-level protection has been widely used in the local fault isolation method of distribution network due to its rapid action. It is mainly used to improve the fault handling level of distribution network and improve the coordination and cooperation of each outgoing line switch, section switch, branch switch and boundary switch protection.

[0003] In terms of protection configuration, all protection levels except the outgoing line protection have withdrawn from the quick-break (stage I) protection to avoid over-tripping, and the stage II and stage III protections are coordinated step by step through action delay. The traditional outgoing line stage I protection is set according to the maximum short-circuit current at the end of the line, the setting value is low, and over-tripping is frequent. In terms of automatic devices, the reclosing switch operates according to the preset logic and delay to reduce the scope of power outages. Among them, the number of reclosing switches at the outgoing line protection generally does not exceed 2 times, and the number of reclosing switches at the other levels of protection does not exceed 1 time.

[0004] The new distribution network has the characteristic of extremely high proportion of distributed energy resources (DER) access. The high proportion of DER access to the distribution network will cause problems such as protection failure and false operation. That is, the existing multi-level protection scheme will cause protection failure or false operation. Summary of the invention

[0005] The main purpose of the present application is to provide a multi-level protection method for a distribution network, a multi-level protection device for a distribution network, a computer-readable storage medium and an electronic device, so as to at least solve the problem in the prior art that distributed power sources may cause misoperation or refusal of protection in the multi-level protection scheme of the distribution network.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a multi-level protection method for a distribution network is provided, comprising: determining the current setting value of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting value and the operating parameters of the distributed power source, the operating parameters of the distributed power source at least including the output current of the distributed power source; obtaining the detection current flowing through the target circuit breaker, and determining the current direction of the detection current, the target circuit breaker is one of the multiple circuit breakers in the distribution network; when the current direction of the detection current is in a positive direction and the measured value of the detection current is greater than the corresponding setting value, disconnecting the target circuit breaker; when the current direction of the detection current is in a reverse direction, controlling the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point.

[0007] Optionally, determining the current setting value of each level of fault short circuit of each circuit breaker in the distribution network includes: obtaining a first formula The first formula is a formula for calculating the three-phase short-circuit setting value of the first-level fault short circuit. is the three-phase short-circuit setting value of the first-level fault short circuit, is the positive sequence voltage at the outlet of the distribution network, Z x is the equivalent impedance corresponding to the protection range of the circuit breaker when the fault point is a two-phase short circuit; according to the first formula, determine the three-phase short circuit setting value of the first-level fault short circuit; obtain the second formula The second formula is a formula for calculating the two-phase short-circuit setting value of the first-level fault short circuit. is the two-phase short-circuit setting value of the first-level fault short circuit, Z s is the equivalent impedance of the system power supply of the distribution network; according to the second formula, the two-phase short-circuit setting value of the first-level fault short circuit is determined.

[0008] Optionally, determining the current setting value of each level of fault short circuit of each circuit breaker in the distribution network includes: obtaining a third formula The third formula is a formula for calculating the setting value of the outgoing line circuit breaker for the second-level fault short circuit. is the setting value of the outgoing circuit breaker for the second level fault short circuit, is the positive sequence voltage at the line outlet of the distribution network,

[0009] is the output current of the distributed power supply, Z TC is the equivalent impedance of the line between the access point T of the distributed power source and the first node C downstream of the distributed power source, Z AT is the equivalent impedance of the line between the second node A upstream of the distributed power source and the access point T of the distributed power source; the fourth formula is obtained The fourth formula is a formula for calculating the setting value of the branch circuit breaker for the second-level fault short circuit. is the setting value of the branch circuit breaker for the second-level fault short circuit; obtain the fifth formula The fifth formula is a formula for calculating the setting value of the boundary circuit breaker for the second-level fault short circuit. The formula for the setting value of the boundary circuit breaker for the second-level fault short circuit.

[0010] Optionally, determining the current direction of the detection current includes: obtaining a discriminant factor formula in, is the discriminant factor, is the final line current flowing through the line outlet, is the reference current flowing through the line outlet protection, is the voltage to ground of the fault point in the fault additional network, is the system power supply of the power distribution network, is the voltage of the second node A upstream of the distributed power source; according to the discrimination factor formula, the discrimination factor is determined; according to the value of the discrimination factor, the current direction of the detection current is determined.

[0011] Optionally, determining the current direction of the detection current according to the value of the discrimination factor includes: when the value of the discrimination factor satisfies In the case of, determining that the current direction of the detection current is the positive direction, is the discrimination factor, θ is the locking angle of the directional element; when the value of the discrimination factor satisfies In this case, it is determined that the current direction of the detection current is in the reverse direction.

[0012] Optionally, when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value, the target circuit breaker is disconnected, including: when the current direction of the detection current is positive, judging whether the negative sequence current of the detection current is 0; when the negative sequence current of the detection current is 0, determining that the detection current is a three-phase short-circuit current, and when the measured value of the detection current is greater than the three-phase fault setting value, disconnecting the target circuit breaker; when the negative sequence current of the detection current is not 0, determining that the detection current is a two-phase short-circuit current, and when the measured value of the detection current is greater than the two-phase fault setting value, disconnecting the target circuit breaker.

[0013] Optionally, when the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point, including: when the current direction of the detection current is in the negative direction, determining whether the target circuit breaker is the circuit breaker closest to the fault point; when the target circuit breaker is the circuit breaker closest to the fault point, controlling the target circuit breaker to be turned off; when the target circuit breaker is not the circuit breaker closest to the fault point, controlling the target circuit breaker to be protected and locked until the reverse current disappears, and when the reverse current disappears, controlling the target circuit breaker to be protected and unlocked, the protection lock being an operation to control the target circuit breaker to be turned on.

[0014] According to another aspect of the present application, a multi-stage protection device for a distribution network is provided, the distribution network comprising a plurality of circuit breakers and a plurality of distributed power sources, the device comprising: a determination unit, for determining current setting values ​​of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting values ​​and operating parameters of the distributed power sources, the operating parameters of the distributed power sources at least including the output current of the distributed power sources; an acquisition unit, for acquiring a detection current flowing through a target circuit breaker and determining a current direction of the detection current, the target circuit breaker being one of the plurality of circuit breakers in the distribution network; a first control unit, for disconnecting the target circuit breaker when the current direction of the detection current is a positive direction and the measured value of the detection current is greater than the corresponding setting value; and a second control unit, for controlling the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point when the current direction of the detection current is a reverse direction.

[0015] According to another aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute any one of the multi-level protection methods for the distribution network.

[0016] According to another aspect of the present application, an electronic device is provided, comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include a method for executing any one of the multi-level protection methods for the distribution network.

[0017] Applying the technical solution of the present application, the multi-level protection method of the distribution network mentioned above first determines the current setting values ​​of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting values ​​and the operating parameters of the distributed power source, and the operating parameters of the distributed power source at least include the output current of the distributed power source; then obtains the detection current flowing through the target circuit breaker, and determines the current direction of the detection current, the target circuit breaker is one of the multiple circuit breakers in the distribution network; then, when the current direction of the detection current is in the positive direction and the measured value of the detection current is greater than the corresponding setting value, the target circuit breaker is disconnected; finally, when the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point. The method uses the positive sequence components of voltage and current to perform adaptive setting calculations on the protection, uses the electrical quantities of the protection before the fault to determine the output characteristics of the DER, calculates the output current during the fault and sets the protection, introduces a directional criterion, calculates the phase between the system power supply voltage and the positive sequence current at the protection, calculates the adaptive branching coefficient based on the positive and negative sequence currents at the protection installation, establishes the local protection that relies only on local information, such as the impedance setting value of the distance protection section II, solves the problem in the prior art that the distributed power source may cause the protection to malfunction or refuse to operate in the multi-level protection scheme of the distribution network, and improves the fault handling level and the reliability of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 A hardware structure block diagram of a mobile terminal for executing a multi-level protection method for a distribution network provided in an embodiment of the present application is shown;

[0020] Figure 2 A schematic diagram of a flow chart of a multi-stage protection method for a distribution network provided according to an embodiment of the present application is shown;

[0021] Figure 3 A schematic diagram of a 10kV low-resistance grounding system phase-to-phase fault simulation model provided according to an embodiment of the present application is shown;

[0022] Figure 4 A schematic flow chart of a multi-stage protection method for an active distribution network based on positive sequence voltage provided according to an embodiment of the present application is shown;

[0023] Figure 5 A structural block diagram of a multi-stage protection device for a distribution network provided according to an embodiment of the present application is shown.

[0024] The above drawings include the following reference numerals:

[0025] 102, processor; 104, memory; 106, transmission device; 108, input and output devices. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] For the convenience of description, some nouns or terms involved in the embodiments of the present application are explained below:

[0030] Distributed energy resource: DER.

[0031] As introduced in the background technology, in the prior art, when a fault occurs downstream of the DER access point, the short-circuit current flowing through the upstream protection becomes smaller due to the current draining effect, resulting in the failure of the protection of the second stage of each level; when a fault occurs upstream of the DER, a reverse current will be provided, and when the fault current is greater than its setting value, the protection will be malfunctioned; when a fault occurs in the adjacent line of the DER access point, the short-circuit current flowing through the outlet circuit breaker will be increased due to the boosting effect, expanding its original protection range and increasing the probability of over-tripping. In addition, when a branch line fails, the branch circuit breaker can isolate the fault within hundreds of milliseconds, but under the boosting effect, the fault can only be correctly isolated through multiple reclosings of the reclosing switch at the outlet circuit breaker, which may cause a power outage of the entire line for tens of seconds and the entire distributed photovoltaic disconnection from the grid. In order to solve the problem in the prior art that distributed power sources may cause the protection malfunction or failure to operate of the multi-level protection scheme of the distribution network, the embodiments of the present application provide a multi-level protection method for the distribution network, a multi-level protection device for the distribution network, a computer-readable storage medium and an electronic device.

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0033] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking running on a mobile terminal as an example, Figure 1 FIG. 1 is a hardware structure block diagram of a mobile terminal of a multi-level protection method for a distribution network according to an embodiment of the present invention. Figure 1 As shown, the mobile terminal may include one or more ( Figure 1 Only one is shown in the figure) a processor 102 (the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input / output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the mobile terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations shown.

[0034] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the Z method in the embodiment of the present invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, the above method is implemented. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the mobile terminal via a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The above-mentioned specific examples of the network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0035] In this embodiment, a Z method running on a mobile terminal, a computer terminal or a similar computing device is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0036] Figure 2 1 is a flow chart of a multi-level protection method for a distribution network according to an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0037] Step S201, determining the current setting values ​​of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network, part of the above-mentioned current setting values ​​and the operating parameters of the above-mentioned distributed power sources, and the operating parameters of the above-mentioned distributed power sources at least include the output current of the above-mentioned distributed power sources;

[0038] Specifically, when a short circuit occurs in the active distribution network, the method re-sets the section I protection at the line outlet and the section II protection at all levels of protection. The current value after setting is (The healthy output is I 1i , the fault line is I 1up ), (Healthy output line is Fault line out ). Determine the required electrical quantity information including: the positive sequence voltage U at each outgoing line protection installation 1 , the equivalent impedance Z corresponding to the protection range when the two phases of the original outgoing line section I are short-circuited x , the positive sequence current I of each outgoing line-branch-boundary protection installation 1 , I 11 , I 111 And the three-phase short-circuit current I k.s.N This provides specific values ​​for the subsequent re-calculation of the protection values ​​of the outgoing line section I and each section II using the positive sequence voltage. In addition, in terms of the automatic device, the reclosing time of the reclosing switch in the proposed method avoids the island protection, improves the operating efficiency of the reclosing switch, reduces the power outage range, and reduces the power outage time of the system.

[0039] Among them, the anti-islanding protection adopts a fast action scheme of voltage / frequency, requiring the photovoltaic power station to have low voltage ride-through capability, that is, when the voltage at the photovoltaic power station grid connection point drops due to a fault or disturbance, in order to avoid the photovoltaic power station disconnecting from the grid and causing further deterioration of the grid operation, the IIDER needs to ensure continuous operation without disconnecting from the grid. When the system fails, the maximum disconnection time of the IIDER is 2s. Therefore, it is necessary to add a reserved time on the basis of 2s to ensure that the IIDER is disconnected from the grid when reclosing. Therefore, the line outlet protection is configured with a secondary reclosing switch, with a first action time limit of 2.2s and a second action time limit of 21s. The branch-boundary protection is configured with a single reclosing switch, and the action time limit is set to 2.5s.

[0040] Wherein, determining the current setting value of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network comprises the following steps:

[0041] Step S2011, obtaining the first formula The first formula is used to calculate the three-phase short-circuit setting value of the first-level fault short circuit. is the three-phase short-circuit setting value of the first-level fault short circuit mentioned above, is the positive sequence voltage at the outlet of the above distribution network, Z x is the equivalent impedance corresponding to the protection range of the circuit breaker when the fault point is a two-phase short circuit;

[0042] Step S2012, determining the three-phase short-circuit setting value of the first-level fault short circuit according to the first formula;

[0043] Specifically, in the case of a three-phase short circuit, when the current amplitude of each outgoing line protection section I reaches I set0 When the setting action is triggered, I set0 =0.53I k.s.N , the three-phase short-circuit setting value of the first-level fault short circuit is obtained It is the fault current value I measured at the subsequent protection installation. 1 The protection threshold value for comparison is the criterion value for preventing over-tripping and refusal to operate protection in this application.

[0044] Step S2013, obtaining the second formula The second formula is used to calculate the two-phase short-circuit setting value of the first-level fault short circuit. is the two-phase short-circuit setting value of the first-level fault short circuit, Z s is the equivalent impedance of the system power supply of the above distribution network;

[0045] Step 2014: Determine the two-phase short-circuit setting value of the first-level fault short circuit according to the second formula.

[0046] Specifically, in the case of a two-phase short circuit, when the current amplitude of each outgoing line protection section I reaches I set0 When the setting action is triggered, I set0 =0.53I k.s.N , the two-phase short-circuit setting value of the first-level fault short circuit is obtained It is the fault current value I measured at the subsequent protection installation. 1 The protection threshold value for comparison is the criterion value for preventing over-tripping and refusal to operate protection in this application.

[0047] Wherein, determining the current setting value of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network comprises the following steps:

[0048] Step 301, obtain the third formula The third formula is used to calculate the setting value of the outgoing line circuit breaker for the second-level fault short circuit. is the setting value of the outgoing circuit breaker for the second-level fault short circuit mentioned above, is the positive sequence voltage at the line outlet of the above distribution network, is the output current of the above distributed power supply, Z TC is the equivalent impedance of the line between the access point T of the distributed power source and the first node C downstream of the distributed power source, Z AT is the equivalent impedance of the line between the second node A upstream of the distributed power source and the access point T of the distributed power source;

[0049] Step 302, obtain the fourth formula The fourth formula is a formula for calculating the setting value of the branch circuit breaker for the second-level fault short circuit. is the setting value of the branch circuit breaker for the second-level fault short circuit mentioned above;

[0050] Step 303, obtain the fifth formula The fifth formula is a formula for calculating the setting value of the boundary circuit breaker for the second-level fault short circuit. This is the formula for the setting value of the boundary circuit breaker for the above second-level fault short circuit.

[0051] Specifically, for each outgoing line-branch-boundary II protection, the branch line II protection is 0.9 times the upper II protection setting value, and the boundary II protection is 0.9 times the upper II protection setting value. set The value is used as the protection threshold value and is the criterion for preventing over-tripping and refusal to operate protection in this application.

[0052] Step S202, obtaining a detection current flowing through a target circuit breaker, and determining a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network;

[0053] Specifically, this method adds a direction discrimination element ( The current phase difference before and after the fault at the protection installation is the current value measured at the protection installation. When the system is operating normally, the load current is directed from the system side to the end of the line. The detection current value is compared with the setting value to prevent over-tripping. Direction discrimination elements are installed at each protection point upstream of the DER access point to increase the reverse fault lockout protection function to avoid false protection.

[0054] Wherein, determining the current direction of the above detection current includes the following steps:

[0055] Step S2021, obtain the discriminant factor formula in, is the discriminant factor, is the final line current flowing through the line outlet, is the reference current flowing through the line outlet protection, is the voltage to ground of the fault point in the fault additional network, is the system power supply of the above distribution network, is the voltage of the second node A upstream of the above-mentioned distributed power source;

[0056] Specifically, in this application, the network after the failure is equivalent to the superposition of the normal operation state and the failure additional state. Figure 3 It is shown that under normal operation, the current flowing through the line outlet protection and branch circuit breaker QF 23 The reference currents are The reference direction is from the busbar to the line, as shown in formula (1):

[0057]

[0058] First, the line outlet protection in the positive direction is analyzed. According to the superposition theorem, represents the voltage to ground of the fault point in the fault additional network, then the additional fault current flowing through the line outlet is as shown in formula (2):

[0059]

[0060] After superposition, the final fault current flowing through the line outlet is shown in formula (3):

[0061]

[0062] Difference of current phase angle before and after fault occurs, and analysis of current phase angle change at line outlet in, is the fault point k 1 The voltage in normal operation, α is the multiple of the short circuit location to the length of line AB, Z AT is the equivalent impedance from the second node A upstream of the distributed power source to the node B of the distributed power source;

[0063] Step S2022, determining the above discriminant factor according to the above discriminant factor formula;

[0064] Step S2023, determining the current direction of the detection current according to the value of the discrimination factor.

[0065] Specifically, since the initial phase angle of the system power supply is 0, the power and current directions are from the system to the end of the line during normal operation, that is, Determine the current direction to be positive; Figure 3 As shown, according to the above method, k 1 When short-circuited, QF 23 direction, there are That is, the current direction is negative, so it can be divided into two situations according to the current direction of the detection current, making the fault type clearer.

[0066] Wherein, according to the value of the above-mentioned discrimination factor, determining the current direction of the above-mentioned detection current includes the following steps:

[0067] Step S401, when the value of the above-mentioned discriminant factor satisfies In the case of, it is determined that the current direction of the above detection current is the positive direction, is the above-mentioned discriminant factor, θ is the locking angle of the directional element;

[0068] Step S402: When the value of the above-mentioned discriminant factor satisfies In this case, it is determined that the current direction of the above-mentioned detection current is in the opposite direction.

[0069] Specifically, according to the general situation of the current phase in the power grid, considering The calculation error of , thereby reducing the positive and negative action area. Compare the measured value and the set value to determine whether the protection is activated or not. Protection lockout, this action characteristic is not affected by DER penetration rate and installation location, and the set value is adaptively adjusted according to the actual operating conditions of the system, thereby improving the stability and reliability of the system.

[0070] Step S203, disconnecting the target circuit breaker when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value;

[0071] Specifically, for the fault line, I 1 >I set And the protection action time is reached, the protection action; for the healthy outgoing line, there is I 1 <I set , protection does not work.

[0072] This action characteristic is not affected by the access location and capacity of DER, which can ensure that the outgoing line protection does not trip when the branch line fails and that the outgoing line protection does not refuse to operate when the trunk line fails.

[0073] Wherein, when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value, disconnecting the target circuit breaker comprises the following steps:

[0074] Step S2031, when the current direction of the detection current is in the positive direction, determining whether the negative sequence current of the detection current is 0;

[0075] Step 2032, when the negative sequence current of the detection current is 0, determining that the detection current is a three-phase short-circuit current, and disconnecting the target circuit breaker when the measured value of the detection current is greater than the three-phase fault setting value;

[0076] Step 2033, when the negative sequence current of the detection current is not zero, determine that the detection current is a two-phase short-circuit current, and when the measured value of the detection current is greater than the two-phase fault setting value, disconnect the target circuit breaker.

[0077] Specifically, the method proposed in the present application takes into account the fault characteristic that DER does not output negative sequence current, introduces a negative sequence component to distinguish the fault type, configures corresponding protection schemes based on different fault types, and adaptively adjusts the set value according to the actual operating conditions of the system, thereby improving the stability and reliability of the system.

[0078] In some embodiments, the active distribution network multi-level protection method based on positive sequence voltage includes the following steps:

[0079] Step S1: Collect the positive sequence voltage U at the line outlet 1 And the current phase angle difference at each protection installation

[0080] Step S2: When When the protection starts;

[0081] Step S3: Recalculate the setting values ​​of each level of protection to obtain I set ;

[0082] Step S4: If the current measurement value I 1 >I set , and when the protection action time is reached, the protection action proposed by the present invention will be activated, otherwise the protection will be restored.

[0083] Step S204: When the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point.

[0084] Specifically, for Protection lockout, this action characteristic is not affected by DER penetration rate and installation location, so that when the system is connected to distributed power sources, it can adaptively adjust the set value according to the actual operating conditions, thereby improving the stability and reliability of the system.

[0085] Wherein, when the current direction of the detection current is in the reverse direction, controlling the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point comprises the following steps:

[0086] Step 2041, when the current direction of the detection current is negative, determining whether the target circuit breaker is the circuit breaker closest to the fault point;

[0087] Step 2042, when the target circuit breaker is the circuit breaker closest to the fault point, control the target circuit breaker to be disconnected;

[0088] Step 2043, when the target circuit breaker is not the circuit breaker closest to the fault point, control the target circuit breaker to be protected and locked until the reverse current disappears, and when the reverse current disappears, control the target circuit breaker to be protected and unlocked, and the protection lock is an operation to control the target circuit breaker to be turned on.

[0089] Specifically, through the above steps, it can be determined that when the current direction of the detected current is in the reverse direction, the protection locking and unlocking can be accurately controlled to avoid malfunction of irrelevant circuit breakers, thereby improving the stability and reliability of the system.

[0090] In some instances, Figure 3 DER 2 For separate access, Table 1 shows the protection startup status according to the existing protection scheme and the adaptive I-stage configuration proposed in this application when the DER penetration rate is 70% and 100% respectively and faults occur at different locations.

[0091] like Figure 3 As shown, the original outlet I protection setting value is 5000A, L1 is k 2 The distance to the branch line outlet, I1, I2.1, I2.2 are the line outlet currents before access to DER, at 70% DER penetration and 100% penetration, respectively. I1.set and I2.set are the improved stage I protection settings at 70% and 100% DER penetration, respectively.

[0092] Table 1. Export adaptive protection verification

[0093]

[0094] As can be seen from Table 1, the access of DER increases the fault current of the adjacent line, causing the over-tripping of the protection of section I at the line outlet, and the over-tripping is serious when a three-phase short circuit occurs.

[0095] When the DER penetration rate is 70% and 100%, the adaptive stage I protection proposed in the present invention can effectively avoid the line outlet current and avoid over-tripping, which greatly improves the adaptability of multi-level protection to distributed power access.

[0096] in, Figure 3 This is a typical circuit diagram of a phase-to-phase fault in a 10kV low-resistance grounding system. The two outgoing lines in the figure are cable lines, and the neutral point grounding resistance R n =10Ω, the fault trigger time is set at 0.1s, the fault type is two-phase short circuit and three-phase short circuit, the fault point (k 1 , k 2 ) is located at different positions of the trunk line and branch line, QF 1 , QF 2 , QF 21 , QF 22 , QF 23 , QF 24 Protection devices installed at all levels of protection; DER 1 DER 2 DER 3It is a distributed power source, adopts PQ control strategy and has voltage ride-through control function. PCC is a common connection point used to connect the power loads of multiple users. The transformer capacity is 20MVA, the positive sequence impedance per unit length of the line is (0.13+j0.35)Ω / km, the length of line I is 3km, the length of line II is 15km, and the DER 1 At the outlet circuit breaker QF 1 1km away from the grid, DER 2 At the outlet circuit breaker QF 2 The DER is connected to the grid at 0.5 km, and each node can be connected to the load. The power factor of the load and DER is 0.8.

[0097] In some instances, Figure 3 DER 1 For separate access, Table 2 shows the protection startup status of the current protection scheme and the adaptive II-stage configuration proposed in this paper when the DER penetration rate is 70% and 100% respectively, at faults in different locations.

[0098] The original outlet II protection setting value is 1800A, L1 is k 1 The distance to the line outlet, I1, I2.1, and I2.2 are the line outlet currents before access to DER at 70% distributed generation penetration and 100% penetration, respectively. I1.set and I2.set are the improved stage II protection settings at 70% and 100% penetration, respectively.

[0099] Table 2. Export adaptive II protection verification

[0100]

[0101] As can be seen from Table 2, the access of DER has a draining effect on the protection upstream, resulting in the failure of the line outlet section II to operate, and the failure to operate is serious when the two-phase short circuit occurs. The higher the DER penetration rate, the greater the impact on the existing protection, and the higher the failure probability. When the adaptive section II protection proposed in the present invention is used, when the DER penetration rate is as high as 100%, its setting value is lower than the line outlet current, which avoids the failure of protection and improves the sensitivity of distribution network protection.

[0102] In some instances, Figure 3 DER 1 ,DER 2 For example, when access is performed simultaneously, Table 3 shows the downstream k 1 When the fault occurs at different locations and the DER penetration rate is 100%, the protection startup status according to the current protection scheme and the adaptive II scheme proposed in this paper is shown. L1 is k 1 The distance to the line outlet, I1 and I2 are the line outlet currents before and after connecting to DER respectively, and Iset is the improved stage II protection setting.

[0103] Table 3. Export adaptive II protection verification

[0104]

[0105] It can be seen from Table 3 that compared with the single-point access of DER, the multi-point access has a higher probability of correct operation of the original protection scheme due to the simultaneous generation of boosting and draining effects, but it is far less than the correct operation rate of the adaptive current protection proposed in the present invention.

[0106] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the implementation process of the multi-level protection method for the distribution network of the present application will be described in detail below in combination with specific embodiments.

[0107] This embodiment relates to a specific multi-level protection method for a distribution network, such as Figure 4 As shown, the following steps are included:

[0108] Step S1: determine the current direction;

[0109] Step S2: Case 1, that is, the current direction is positive, then there may be a positive fault, and a three-phase short circuit or a two-phase short circuit is determined based on whether the negative sequence current is 0;

[0110] Step S3: Calculate the corresponding fault setting value according to the short circuit situation;

[0111] Step S4: Compare the measured value and the set value to determine whether to take protection action;

[0112] Step S5: Case 2, that is, the current direction is in the reverse direction, then it is a reverse fault, and protection locking measures are taken. Then, whether the protection is unlocked is determined based on whether the reverse current disappears.

[0113] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0114] The embodiment of the present application also provides a multi-stage protection device for a distribution network. It should be noted that the multi-stage protection device for a distribution network in the embodiment of the present application can be used to execute the multi-stage protection method for a distribution network provided in the embodiment of the present application. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and those that have been described will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0115] The following is an introduction to the multi-level protection device for the distribution network provided in an embodiment of the present application.

[0116] Figure 5 Schematic diagram of a multi-stage protection device for a distribution network according to an embodiment of the present application. Figure 5 As shown, the device includes: a determination unit 10, an acquisition unit 20, a first control unit 30 and a second control unit 40, the determination unit 10 is used to determine the current setting value of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network, part of the above-mentioned current setting value and the operating parameters of the above-mentioned distributed power source, and the operating parameters of the above-mentioned distributed power source at least include the output current of the above-mentioned distributed power source; the acquisition unit 20 is used to obtain the detection current flowing through the target circuit breaker and determine the current direction of the above-mentioned detection current. The above-mentioned target circuit breaker is one of the multiple circuit breakers in the above-mentioned distribution network; the first control unit 30 is used to disconnect the above-mentioned target circuit breaker when the current direction of the above-mentioned detection current is in the positive direction and the measured value of the above-mentioned detection current is greater than the corresponding setting value; the second control unit 40 is used to control the above-mentioned target circuit breaker to be turned on or off according to the distance between the above-mentioned target circuit breaker and the fault point when the current direction of the above-mentioned detection current is in the reverse direction.

[0117] The above-mentioned multi-level protection device for the distribution network of the present application includes: a determination unit, an acquisition unit, a first control unit and a second control unit. The determination unit is used to determine the current setting value of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting value and the operating parameters of the distributed power source, and the operating parameters of the distributed power source at least include the output current of the distributed power source; the acquisition unit is used to obtain the detection current flowing through the target circuit breaker and determine the current direction of the detection current. The target circuit breaker is one of multiple circuit breakers in the distribution network; the first control unit is used to disconnect the target circuit breaker when the current direction of the detection current is in the positive direction and the measured value of the detection current is greater than the corresponding setting value; the second control unit is used to control the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point when the current direction of the detection current is in the reverse direction. The device performs adaptive detection on the fault characteristics of short circuit faults in active distribution networks with DER access, and has protection functions for faulty lines at all levels. When the setting time is reached, the protection will be activated; for the protection on the sound line, Protection does not work; The protection lockout solves the problem in the prior art that distributed power sources may cause misoperation or refusal of protection in the multi-level protection scheme of the distribution network.

[0118] In some examples, the determining unit includes a first acquisition module, a first determination module, a second acquisition module, and a second determination module, wherein the first acquisition module is used to acquire the first formula The first formula is used to calculate the three-phase short-circuit setting value of the first-level fault short circuit. is the three-phase short-circuit setting value of the first-level fault short circuit mentioned above, is the positive sequence voltage at the outlet of the above distribution network, Z x is the equivalent impedance corresponding to the protection range of the circuit breaker when the fault point is a two-phase short circuit; the first determination module is used to determine the three-phase short circuit setting value of the first-level fault short circuit according to the first formula; the second acquisition module is used to obtain the second formula The second formula is used to calculate the two-phase short-circuit setting value of the first-level fault short circuit. is the two-phase short-circuit setting value of the first-level fault short circuit, Z s is the equivalent impedance of the system power supply of the above distribution network; the second determination module is used to determine the two-phase short-circuit setting value of the above first-level fault short circuit according to the above second formula. The current setting value of the first-level fault short circuit at the installation of the outgoing line I section protection in the distribution network is calculated according to the formula, which can be used as a criterion for preventing over-tripping and refusal to operate protection. This action characteristic is not affected by the access location and capacity of DER, and improves the stability and reliability of power supply.

[0119] In some examples, the determining unit further includes a third acquisition module, a fourth acquisition module and a fifth acquisition module, wherein the third acquisition module is used to acquire the third formula The third formula is used to calculate the setting value of the outgoing line circuit breaker for the second-level fault short circuit. is the setting value of the outgoing circuit breaker for the second-level fault short circuit mentioned above, is the positive sequence voltage at the line outlet of the above distribution network, is the output current of the above distributed power supply, Z TC is the equivalent impedance of the line between the access point T of the distributed power source and the first node C downstream of the distributed power source, Z AT is the equivalent impedance of the line between the second node A upstream of the distributed power source and the access point T of the distributed power source; the fourth acquisition module is used to obtain the fourth formula The fourth formula is a formula for calculating the setting value of the branch circuit breaker for the second-level fault short circuit. is the setting value of the branch circuit breaker for the second-level fault short circuit; the fifth acquisition module is used to obtain the fifth formula The fifth formula is a formula for calculating the setting value of the boundary circuit breaker for the second-level fault short circuit. The formula for the setting value of the boundary circuit breaker for the second-level fault short circuit mentioned above. According to the formula, the current setting value of the second-level fault short circuit at each outgoing line-branch-boundary II protection installation in the distribution network is calculated, which can be used as a criterion for preventing over-tripping and refusal to operate protection. This action characteristic is not affected by the access location and capacity of DER, and improves the stability and reliability of power supply.

[0120] In some examples, the acquisition unit includes a sixth acquisition module, a third determination module and a fourth determination module, and the sixth acquisition module is used to acquire the discriminant factor formula in, is the discriminant factor, is the final line current flowing through the line outlet, is the reference current flowing through the line outlet protection, is the voltage to ground of the fault point in the fault additional network, is the system power supply of the above distribution network, is the voltage of the second node A upstream of the above distributed power source; the third determination module is used to determine the above discrimination factor according to the above discrimination factor formula; the fourth determination module is used to determine the current direction of the above detection current according to the value of the above discrimination factor. A direction discrimination element is installed at each protection installation. When a reverse fault current is detected, the protection is locked, and the function of reverse fault lock protection is added to avoid false protection. The protection can also be increased to level 4 to shorten the power outage range.

[0121] In some examples, the fourth determination module includes a first determination submodule and a second determination submodule, wherein the first determination submodule is used to determine the value of the above-mentioned discriminant factor when the value of the discriminant factor satisfies In the case of, it is determined that the current direction of the above detection current is the positive direction, is the above-mentioned discriminant factor, θ is the locking angle of the directional element; the second determination submodule is used to determine the value of the above-mentioned discriminant factor when it satisfies In this case, the current direction of the above detection current is determined to be the opposite direction. In this way, according to the general situation of the current phase in the power grid, considering The calculation error is reduced, the positive and negative action areas are narrowed, and the accuracy of current direction judgment is increased.

[0122] In some examples, the first control unit includes a first control module, a second control module and a third control module. The first control module is used to determine whether the negative sequence current of the detection current is 0 when the current direction of the detection current is positive; the second control module is used to determine whether the detection current is a three-phase short-circuit current when the negative sequence current of the detection current is 0, and disconnect the target circuit breaker when the measured value of the detection current is greater than the three-phase fault setting value; the third control module is used to determine whether the detection current is a two-phase short-circuit current when the negative sequence current of the detection current is not 0, and disconnect the target circuit breaker when the measured value of the detection current is greater than the two-phase fault setting value. The negative sequence component is introduced to distinguish the fault type, and the corresponding protection scheme is configured based on different fault types. The set value is adaptively adjusted according to the actual operating status of the system, thereby improving the stability and reliability of the system; it is judged whether the system protection action is performed when the current direction of the detection current is positive, and the accuracy of the action judgment is improved.

[0123] In some examples, the second control unit includes a fourth control module, a fifth control module and a sixth control module, wherein the fourth control module is used to determine whether the target circuit breaker is the circuit breaker closest to the fault point when the current direction of the detection current is negative; the fifth control module is used to determine whether the target circuit breaker is the circuit breaker closest to the fault point when the current direction of the detection current is negative; when the target circuit breaker is the circuit breaker closest to the fault point, the target circuit breaker is controlled to be disconnected; when the target circuit breaker is not the circuit breaker closest to the fault point, the target circuit breaker is controlled to be protected and locked until the reverse current disappears, and when the reverse current disappears, the target circuit breaker is controlled to be protected and unlocked, and the protection lock is an operation to control the target circuit breaker to be turned on. In this way, the situation where the current direction of the detection current is negative can be handled, and the adaptive current protection action has a high accuracy rate.

[0124] The multi-stage protection device for the distribution network includes a processor and a memory. The determination unit and the like are stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions. The modules are all located in the same processor; or, the modules are located in different processors in any combination.

[0125] The processor includes a kernel, which retrieves the corresponding program unit from the memory. One or more kernels can be set, and the problem of the distributed power source causing the protection misoperation or refusal to operate of the multi-level protection scheme of the distribution network in the prior art can be solved by adjusting the kernel parameters.

[0126] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0127] An embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the multi-level protection method for the distribution network.

[0128] Specifically, the multi-level protection method of the distribution network includes:

[0129] Step S201, determining the current setting values ​​of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network, part of the above-mentioned current setting values ​​and the operating parameters of the above-mentioned distributed power sources, and the operating parameters of the above-mentioned distributed power sources at least include the output current of the above-mentioned distributed power sources;

[0130] Step S202, obtaining a detection current flowing through a target circuit breaker, and determining a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network;

[0131] Step S203, disconnecting the target circuit breaker when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value;

[0132] Step S204: When the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point.

[0133] Optionally, determining the current setting value of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network includes: obtaining the first formula The first formula is used to calculate the three-phase short-circuit setting value of the first-level fault short circuit. is the three-phase short-circuit setting value of the first-level fault short circuit mentioned above, is the positive sequence voltage at the outlet of the above distribution network, Z x is the equivalent impedance corresponding to the protection range of the circuit breaker when the fault point is a two-phase short circuit; according to the first formula, determine the three-phase short circuit setting value of the first-level fault short circuit; obtain the second formula The second formula is used to calculate the two-phase short-circuit setting value of the first-level fault short circuit. is the two-phase short-circuit setting value of the first-level fault short circuit, Z sis the equivalent impedance of the system power supply of the above-mentioned distribution network; according to the above-mentioned second formula, the two-phase short-circuit setting value of the above-mentioned first-level fault short circuit is determined.

[0134] Optionally, determining the current setting value of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network includes: obtaining the third formula The third formula is used to calculate the setting value of the outgoing line circuit breaker for the second-level fault short circuit. is the setting value of the outgoing circuit breaker for the second-level fault short circuit mentioned above, is the positive sequence voltage at the line outlet of the above distribution network, is the output current of the above distributed power supply, Z TC is the equivalent impedance of the line between the access point T of the distributed power source and the first node C downstream of the distributed power source, Z AT is the equivalent impedance of the line between the second node A upstream of the distributed power source and the access point T of the distributed power source; the fourth formula is obtained The fourth formula is a formula for calculating the setting value of the branch circuit breaker for the second-level fault short circuit. is the setting value of the branch circuit breaker for the second-level fault short circuit; the fifth formula is obtained The fifth formula is a formula for calculating the setting value of the boundary circuit breaker for the second-level fault short circuit. This is the formula for the setting value of the boundary circuit breaker for the above second-level fault short circuit.

[0135] Optionally, determining the current direction of the detection current includes: obtaining a discriminant factor formula in, is the discriminant factor, is the final line current flowing through the line outlet, is the reference current flowing through the line outlet protection, is the voltage to ground of the fault point in the fault additional network, is the system power supply of the above distribution network, is the voltage of the second node A upstream of the distributed power source; according to the discrimination factor formula, the discrimination factor is determined; according to the value of the discrimination factor, the current direction of the detection current is determined.

[0136] Optionally, according to the value of the above-mentioned discrimination factor, determining the current direction of the above-mentioned detection current includes: when the value of the above-mentioned discrimination factor satisfies In the case of, it is determined that the current direction of the above detection current is the positive direction, is the above-mentioned discriminant factor, θ is the locking angle of the directional element; when the value of the above-mentioned discriminant factor satisfies In this case, it is determined that the current direction of the above-mentioned detection current is in the opposite direction.

[0137] Optionally, when the current direction of the above-mentioned detection current is in the positive direction and the measured value of the above-mentioned detection current is greater than the corresponding setting value, the above-mentioned target circuit breaker is disconnected, including: when the current direction of the above-mentioned detection current is in the positive direction, judging whether the negative-sequence current of the above-mentioned detection current is 0; when the above-mentioned negative-sequence current of the above-mentioned detection current is 0, determining that the above-mentioned detection current is a three-phase short-circuit current, and when the measured value of the above-mentioned detection current is greater than the three-phase fault setting value, disconnecting the above-mentioned target circuit breaker; when the above-mentioned negative-sequence current of the above-mentioned detection current is not 0, determining that the above-mentioned detection current is a two-phase short-circuit current, and when the measured value of the above-mentioned detection current is greater than the two-phase fault setting value, disconnecting the above-mentioned target circuit breaker.

[0138] Optionally, when the current direction of the above-mentioned detection current is in the reverse direction, the above-mentioned target circuit breaker is controlled to be turned on or off according to the distance between the above-mentioned target circuit breaker and the fault point, including: when the current direction of the above-mentioned detection current is in the negative direction, determining whether the above-mentioned target circuit breaker is the circuit breaker closest to the above-mentioned fault point; when the above-mentioned target circuit breaker is the circuit breaker closest to the above-mentioned fault point, controlling the above-mentioned target circuit breaker to be turned off; when the above-mentioned target circuit breaker is not the circuit breaker closest to the above-mentioned fault point, controlling the above-mentioned target circuit breaker to be protected and locked until the reverse current disappears, and when the above-mentioned reverse current disappears, controlling the above-mentioned target circuit breaker to be protected and unlocked, and the above-mentioned protection lock is an operation to control the above-mentioned target circuit breaker to be turned on.

[0139] An embodiment of the present invention provides a processor, and the processor is used to run a program, wherein the multi-level protection method of the distribution network is executed when the program is run.

[0140] Specifically, the multi-level protection method of the distribution network includes:

[0141] Step S201, determining the current setting values ​​of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network, part of the above-mentioned current setting values ​​and the operating parameters of the above-mentioned distributed power sources, and the operating parameters of the above-mentioned distributed power sources at least include the output current of the above-mentioned distributed power sources;

[0142] Step S202, obtaining a detection current flowing through a target circuit breaker, and determining a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network;

[0143] Step S203, disconnecting the target circuit breaker when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value;

[0144] Step S204: When the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point.

[0145] An embodiment of the present invention provides a device, the device including a processor, a memory, and a program stored in the memory and executable on the processor, and when the processor executes the program, at least the following steps are implemented:

[0146] The devices in this article can be servers, PCs, PADs, mobile phones, etc.

[0147] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program for initializing at least the following method steps:

[0148] Step S201, determining the current setting values ​​of each level of fault short circuit of each of the above-mentioned circuit breakers in the above-mentioned distribution network, part of the above-mentioned current setting values ​​and the operating parameters of the above-mentioned distributed power sources, and the operating parameters of the above-mentioned distributed power sources at least include the output current of the above-mentioned distributed power sources;

[0149] Step S202, obtaining a detection current flowing through a target circuit breaker, and determining a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network;

[0150] Step S203, disconnecting the target circuit breaker when the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value;

[0151] Step S204: When the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point.

[0152] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0153] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0154] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0155] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0156] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0157] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0158] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0159] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules 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, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, 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. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0160] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0161] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0162] 1) The multi-level protection method for the distribution network of the present application first determines the current setting value of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting value and the operating parameters of the distributed power source, and the operating parameters of the distributed power source at least include the output current of the distributed power source; then obtains the detection current flowing through the target circuit breaker, and determines the current direction of the detection current, the target circuit breaker is one of the multiple circuit breakers in the distribution network; then, when the current direction of the detection current is in the positive direction and the measured value of the detection current is greater than the corresponding setting value, the target circuit breaker is disconnected; finally, when the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point. The method uses the positive sequence components of voltage and current to perform adaptive setting calculations on the protection, uses the electrical quantities of the protection before the fault to determine the output characteristics of the DER, calculates the output current during the fault and sets the protection, introduces a directional criterion, calculates the phase between the system power supply voltage and the positive sequence current at the protection, calculates the adaptive branching coefficient based on the positive and negative sequence currents at the protection installation, establishes the local protection that relies only on local information, such as the impedance setting value of the distance protection section II, solves the problem in the prior art that the distributed power source may cause the protection to malfunction or refuse to operate in the multi-level protection scheme of the distribution network, and improves the fault handling level and the reliability of power supply.

[0163] 2) The multi-level protection device for the distribution network of the present application includes: a determination unit, an acquisition unit, a first control unit and a second control unit. The determination unit is used to determine the current setting values ​​of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting values ​​and the operating parameters of the distributed power source, and the operating parameters of the distributed power source include at least the output current of the distributed power source; the acquisition unit is used to obtain the detection current flowing through the target circuit breaker and determine the current direction of the detection current. The target circuit breaker is one of the multiple circuit breakers in the distribution network; the first control unit is used to disconnect the target circuit breaker when the current direction of the detection current is in the positive direction and the measured value of the detection current is greater than the corresponding setting value; the second control unit is used to control the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point when the current direction of the detection current is in the reverse direction. The device performs adaptive detection on the fault characteristics of short circuit faults in active distribution networks with DER access, and has protection functions for faulty lines at all levels. When the setting time is reached, the protection will be activated; for the protection on the sound line, Protection does not work; The protection lockout solves the problem in the prior art that distributed power sources may cause misoperation or refusal of protection in the multi-level protection scheme of the distribution network.

[0164] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-level protection method for a distribution network, characterized in that: The power distribution network includes a plurality of circuit breakers and a plurality of distributed power sources, and the method includes: Determine the current setting value of each level of fault short circuit of each circuit breaker in the distribution network, and some of the current setting values ​​and the operating parameters of the distributed power source, wherein the operating parameters of the distributed power source at least include the output current of the distributed power source; Acquire a detection current flowing through a target circuit breaker, and determine a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network; When the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value, disconnecting the target circuit breaker; In the case that the current direction of the detection current is in the reverse direction, the target circuit breaker is controlled to be turned on or off according to the distance between the target circuit breaker and the fault point.

2. The method according to claim 1, characterized in that: Determining the current setting value of each level of fault short circuit of each circuit breaker in the distribution network includes: Get the first formula The first formula is a formula for calculating the three-phase short-circuit setting value of the first-level fault short circuit. is the three-phase short-circuit setting value of the first-level fault short circuit, is the positive sequence voltage at the outlet of the distribution network, Z x is the equivalent impedance corresponding to the protection range of the circuit breaker when the fault point is a two-phase short circuit; According to the first formula, determining the three-phase short-circuit setting value of the first-level fault short circuit; Get the second formula The second formula is a formula for calculating the two-phase short-circuit setting value of the first-level fault short circuit. is the two-phase short-circuit setting value of the first-level fault short circuit, Z s is the equivalent impedance of the system power supply of the distribution network; According to the second formula, the two-phase short-circuit setting value of the first-level fault short circuit is determined.

3. The method according to claim 1, characterized in that Determining the current setting value of each level of fault short circuit of each circuit breaker in the distribution network includes: Get the third formula The third formula is a formula for calculating the setting value of the outgoing line circuit breaker for the second-level fault short circuit. is the setting value of the outgoing circuit breaker for the second level fault short circuit, is the positive sequence voltage at the line outlet of the distribution network, is the output current of the distributed power supply, Z TC is the equivalent impedance of the line between the access point T of the distributed power source and the first node C downstream of the distributed power source, Z AT is the equivalent impedance of the line between the second node A upstream of the distributed power source and the access point T of the distributed power source; Get the fourth formula The fourth formula is a formula for calculating the setting value of the branch circuit breaker for the second-level fault short circuit. The setting value of the branch circuit breaker for the second-level fault short circuit; Get the fifth formula The fifth formula is a formula for calculating the setting value of the boundary circuit breaker for the second-level fault short circuit. The formula for the setting value of the boundary circuit breaker for the second-level fault short circuit.

4. The method according to claim 1, characterized in that: Determining the current direction of the detection current includes: Get the discriminant factor formula in, is the discriminant factor, is the final line current flowing through the line outlet, is the reference current flowing through the line outlet protection, is the voltage to ground of the fault point in the fault additional network, is the system power supply of the power distribution network, is the voltage of the second node A upstream of the distributed power source; Determine the discriminant factor according to the discriminant factor formula; The current direction of the detection current is determined according to the value of the discrimination factor.

5. The method according to claim 4, characterized in that Determining the current direction of the detection current according to the value of the discrimination factor includes: The value of the discriminant factor satisfies In the case of, determining that the current direction of the detection current is the positive direction, is the discrimination factor, θ is the locking angle of the directional element; The value of the discriminant factor satisfies In this case, it is determined that the current direction of the detection current is in the reverse direction.

6. The method according to claim 1, characterized in that When the current direction of the detection current is positive and the measured value of the detection current is greater than the corresponding setting value, disconnecting the target circuit breaker includes: When the current direction of the detection current is positive, determining whether the negative sequence current of the detection current is 0; When the negative sequence current of the detection current is 0, determining that the detection current is a three-phase short-circuit current, and disconnecting the target circuit breaker when the measured value of the detection current is greater than the three-phase fault setting value; When the negative sequence current of the detection current is not 0, the detection current is determined to be a two-phase short-circuit current, and when the measured value of the detection current is greater than the two-phase fault setting value, the target circuit breaker is disconnected.

7. The method according to claim 1, characterized in that When the current direction of the detection current is in the reverse direction, controlling the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point includes: In a case where the current direction of the detection current is a negative direction, determining whether the target circuit breaker is a circuit breaker closest to the fault point; When the target circuit breaker is the circuit breaker closest to the fault point, controlling the target circuit breaker to be disconnected; When the target circuit breaker is not the circuit breaker closest to the fault point, the target circuit breaker is controlled to be protected and locked until the reverse current disappears, and when the reverse current disappears, the target circuit breaker is controlled to be protected and unlocked, and the protection lock is an operation to control the target circuit breaker to be turned on.

8. A multi-stage protection device for a distribution network, characterized in that: The distribution network includes a plurality of circuit breakers and a plurality of distributed power sources, and the device includes: A determination unit, used to determine the current setting value of each level of fault short circuit of each circuit breaker in the distribution network, part of the current setting value and the operating parameters of the distributed power source, the operating parameters of the distributed power source at least including the output current of the distributed power source; an acquisition unit, configured to acquire a detection current flowing through a target circuit breaker and determine a current direction of the detection current, wherein the target circuit breaker is one of the plurality of circuit breakers in the distribution network; a first control unit, configured to disconnect the target circuit breaker when the current direction of the detection current is a positive direction and the measured value of the detection current is greater than the corresponding setting value; The second control unit is used to control the target circuit breaker to be turned on or off according to the distance between the target circuit breaker and the fault point when the current direction of the detection current is in the reverse direction.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the multi-stage protection method for the distribution network according to any one of claims 1 to 7.

10. An electronic device, characterized in that: include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include a method for executing the multi-level protection method for the distribution network described in any one of claims 1 to 7.

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