A passive protection-based active power distribution network fault location system and method thereof

Abstract

The application relates to an active power distribution network fault positioning system based on passive protection and a method thereof, the system comprising passive protection terminals installed in switch cabinets and looped network cabinets of an active power distribution network, uPMUs installed in distributed power source access points and voltage busbars of a power distribution network system, the passive protection terminals and the uPMUs being connected with a fault positioning host computer, and the fault positioning host computer being connected with a power distribution network dispatching automation system. The method comprises the following steps: according to a distributed power source grid-connected inverter control strategy, a controlled current source model is established, and a distributed power source grid-connected point impedance branch model is obtained; an active power distribution network sequence component calculation network is established to calculate branch currents of power distribution network feeder lines; passive protection terminals collect current of the power distribution network feeder lines, uPMU synchronous measurement terminals collect voltage measurement data, and the data are transmitted to the fault positioning host computer for matching to search for a fault point position and isolate a fault section. Compared with the prior art, the application can accurately perform fault positioning and improve power distribution network power supply reliability.

Description

Technical Field

[0001] This invention relates to the field of distribution network protection technology, and in particular to an active distribution network fault location system and method based on passive protection. Background Technology

[0002] Traditional distribution networks are unidirectional power flow networks. However, with the integration of distributed generation (DG), electric vehicles, and controllable loads (DER), traditional distribution networks face many new challenges. The integration of DG will inevitably affect the network structure and power flow direction, turning traditional distribution networks into complex networks with multiple power sources. As the penetration rate of DG continues to increase, the fault characteristics of distribution networks change under the influence of distributed power sources and their control strategies, and the reliability of distribution network protection is affected.

[0003] After a high proportion of new energy sources are connected to the distribution network, the fault current is affected by the control strategy of distributed power sources. The sensitivity and coordination of the passive protection installed on the ring main unit are problematic. Furthermore, the fault current may be bidirectional. Since the passive protection terminal of the ring main unit does not measure the line voltage, it cannot determine the direction of the fault point and cannot reliably identify the location of the fault point.

[0004] Rapid fault location, isolation, and recovery after a distribution network failure is crucial for improving network reliability and ensuring the normal operation of economic and social activities and residents' lives. Modern active distribution networks have complex structures with numerous branch lines and widespread distributed power generation, making fault location difficult. Currently, fault location mainly relies on distribution network automation equipment such as feeder terminal units and intelligent terminal units, but this is only suitable for distribution networks with a distributed generation penetration rate of less than 25%.

[0005] The traveling wave method, which is widely used in relatively simple transmission lines, determines the location of the fault point by measuring the propagation time of voltage and current traveling waves between the fault point and the bus. However, its high requirements for time synchronization rate and sampling rate limit its application range, and it is difficult to adapt to distribution networks. Furthermore, it lacks universality for complex fault situations such as double or multiple faults. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an active distribution network fault location system and method based on passive protection. By integrating passive protection data from ring main units and measurement data from micro phasor measurement units (uPMUs), fault location can be accurately performed and the reliability of power supply in the distribution network can be improved.

[0007] The objective of this invention can be achieved through the following technical solution: an active distribution network fault location system based on passive protection, comprising a passive protection terminal installed in the active distribution network switchgear and ring network cabinet, and a uPMU installed at the distributed power access point and the voltage bus of the distribution network system. The passive protection terminal and the uPMU are respectively connected to the fault location host. The fault location host is connected to the distribution network dispatch automation system. The passive protection terminal is used to collect the current of the distribution network feeder line and transmit it to the fault location host.

[0008] The uMPU is used to collect voltage measurement data and transmit it to the fault location host;

[0009] The fault location host searches for and determines the location of the fault point based on the current and voltage measurement data of the distribution network feeder lines and the remote signaling and telemetry information of the distribution network dispatch automation system, based on the adaptive protection setting calculation model, and outputs corresponding control commands to the passive protection terminal to control the conduction and cutoff of each switch in the passive protection terminal.

[0010] An active distribution network fault location method based on passive protection includes the following steps:

[0011] S1. Based on the grid-connected inverter control strategy of distributed power sources, establish a controlled current source model to obtain the impedance branch model of the grid connection point of the distributed power source.

[0012] S2. Establish an active distribution network sequence component calculation network to calculate the branch current of the distribution network feeder lines;

[0013] S3. The passive protection terminal collects the current of the distribution network feeder line, and the uPMU synchronous measurement terminal collects the voltage measurement data. The data is then transmitted to the fault location host for matching in order to search for the location of the fault point and isolate the fault section.

[0014] Furthermore, step S1 specifically includes the following steps:

[0015] S11. Determine the inverter output characteristics based on the distributed power grid-connected inverter control strategy;

[0016] S12. Based on the grid-connected inverter control system structure, derive the relationship between modulation voltage and current, and establish the voltage-current equation for the grid connection point of new energy power sources.

[0017] S13. Based on the relationship between fault output and grid connection point, establish the relationship between DG fault output and control strategy, power output, reactive power support coefficient, and grid connection point voltage.

[0018] Furthermore, the inverter output characteristics in step S11 are specifically as follows:

[0019]

[0020]

[0021]

[0022] Among them, I * , These represent the DG fault output current, the d-axis and q-axis components of the fault current under fault conditions, respectively, where K is the reactive power support coefficient, and U... PCC P is the grid connection point voltage. ref Contribute your efforts for reference.

[0023] Furthermore, the specific process of step S12 is as follows:

[0024] The inverter controls the current through the adjustment of the terminal voltage. The modulation voltage and current satisfy the following relationship:

[0025]

[0026] Among them, V * is the inverter output voltage, k is the PI controller adjustment coefficient, and i and u are the voltage and current values ​​at the measurement points;

[0027] From the AC side, establish the relationship between the inverter terminal voltage and the equivalent resistance R and inductance L between the measurement points:

[0028]

[0029]

[0030] In practice, the PWM carrier frequency can reach several kilohertz, and the inverter terminal voltage is equivalent to the modulation voltage. Therefore, the relationship between the control side and AC side currents is established, as shown in the following formula:

[0031]

[0032]

[0033] Furthermore, the specific process of step S13 is as follows:

[0034] Knowing the relationship between the fault output and the grid connection point after a fault occurs, by substituting the inverter output current into the relationship between the control side and the AC side current, we can obtain the relationship between the DG fault output and the control strategy, output, reactive power support coefficient, and grid connection point voltage, as shown in the following formula:

[0035]

[0036]

[0037]

[0038] Among them, i f To provide assistance during malfunctions.

[0039] Furthermore, the specific process of step S2 is as follows:

[0040] Based on different types of distributed power sources and different control strategies, node voltage equations are established to convert voltage source branches into current source branches, as follows:

[0041] Y B =(y1...y n ) T

[0042]

[0043]

[0044]

[0045] The resulting nodal admittance matrix is:

[0046] Y = AY B A T

[0047] The node voltage equations and branch current equations are as follows:

[0048]

[0049]

[0050] in, This is the branch voltage, formed by the node voltage.

[0051] Furthermore, the search for the fault location in step S3 specifically includes the following steps:

[0052] S31. Modify the admittance matrix during the fault search process;

[0053] S32. Match the fault current to determine the location of the fault point.

[0054] Furthermore, the specific process of step S31 is as follows:

[0055] Assuming the original power system has N independent nodes, its node admittance matrix during normal operation can be expressed as:

[0056]

[0057] When a power system fails, it is equivalent to adding a node to the original network, where Y' is of order (N+1), specifically:

[0058]

[0059] After adding a new node f, compared with Y, only the admittance between faulty nodes changes in Y', that is, only the self-admittance and mutual admittance of nodes i, j, and f change, but the diagonal elements are still equal. The faults are divided into ground faults and phase-to-phase faults.

[0060] If a ground fault occurs, a new node is added between nodes i and j, and a new grounding branch is also added, specifically as follows:

[0061] Y' ii =(Y ii -Y fj )

[0062] Y if =Y fj

[0063] Y ij '=Y ji '=0

[0064] Y jj '=(Y jj -Y if )

[0065] ΔY ff =Y ff -|Y if +Y fj |

[0066] Where, ΔY ff This is the fault point grounding admittance under non-metallic grounding fault conditions;

[0067] If the fault is a phase-to-phase short circuit, it is equivalent to adding a new node and an ungrounded branch between nodes i and j, Y' ii Y ij '、Y jj '、Y if The changes are the same as for ground faults, and the node admittance matrix changes as follows:

[0068] Y ff =|Y if +Y fj |

[0069] Furthermore, step S32 specifically involves matching the fault current acquisition value with the active distribution network fault current search formula. If the fault current search value and the current value acquired by the passive protection terminal satisfy the matching formula, then the fault current is considered to be completely matched, and the corresponding fault point location result is output.

[0070] Furthermore, the active distribution network fault current search formula is as follows:

[0071]

[0072] Where k is the branch number being searched, and d k The distance from the fault point to the beginning of the line is used to perform the search by changing the distance length according to the set step size. Let n be the positive sequence voltages collected by n uPMUs in the power grid. This is the negative sequence voltage of the system;

[0073] The matching formula is as follows:

[0074]

[0075] in, The fault current is the value collected in the active distribution network, i.e., the current value collected by the passive protection terminal. When the above matching formula holds true, it indicates that the fault current is perfectly matched, and the fault branch and fault location d are output. k value.

[0076] Compared with the prior art, the present invention has the following advantages:

[0077] I. High Fault Location Accuracy: This invention focuses on active distribution networks and employs a current matching fault location method that integrates multi-source data and establishes an admittance equation to calculate a mathematical model. This method can reliably identify the fault location and quickly isolate the faulty line. Based on the control strategy of distributed generation, this invention establishes a controlled current source model and a sequence component network model of the distribution network to calculate the branch current of the distribution network feeder lines. By collecting the synchronization voltage from the distributed generation access point and the distribution network system access point as the excitation voltage, the feeder branch current is calculated and matched with the terminal current collected by the passive protection of the ring main unit to search for the fault location and isolate the faulty section. It can reliably and accurately locate the fault section under both short-circuit and open-circuit faults, and is unaffected by the fault type or location. It has good resistance to transition resistance, thus exhibiting high fault location accuracy.

[0078] II. High Protection Reliability: This invention installs a passive protection terminal on the ring main unit (RMU) of the active distribution network switchgear and RMU to collect the current of the distribution network feeder lines and calculate the real and imaginary parts of the current, which are then transmitted to the fault location host via communication. The invention also installs a uPMU synchronous measurement terminal at the access point of the distributed power source to transmit the real and imaginary parts of the voltage measurement data marked with time stamps to the fault location host. The passive protection terminal does not require synchronous measurement, while the voltage at the distributed power source access point is measured synchronously via the uPMU. To ensure rapid fault detection after a fault occurs, current and voltage data are uploaded at set time intervals. Upon fault detection, a trip command is issued, directly disconnecting the feeder line through the passive protection terminal to isolate the faulty line. This invention integrates the passive protection data of the RMU and the measurement data of the uPMU into an active distribution network adaptive protection setting calculation model, providing a better measurement data foundation for fault location. This is of great significance for achieving rapid and accurate fault location in the distribution network and improving the power supply reliability of the distribution network; therefore, the protection reliability is high. Attached Figure Description

[0079] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0080] Figure 2 This is a schematic diagram of the method flow of the present invention;

[0081] Figure 3 This is the structure of the grid-connected inverter control system in the embodiment;

[0082] Figure 4 This is the active distribution network model provided in the embodiments;

[0083] Figure 5 This is the wiring diagram of the active distribution network model provided in the embodiment;

[0084] Figure 6 This is the positive-sequence calculation network of the active distribution network model provided in the embodiment;

[0085] Figure 7 The negative order calculation network for the active distribution network model provided in this embodiment is an example. Detailed Implementation

[0086] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0087] Example

[0088] like Figure 1As shown, an active distribution network fault location system based on passive protection includes a passive protection terminal installed in the active distribution network switchgear and ring network cabinet, and a uPMU installed at the distributed power source access point and the voltage bus of the distribution network system. The passive protection terminal and uPMU are respectively connected to the fault location host, and the fault location host is connected to the distribution network dispatch automation system. The passive protection terminal is used to collect the current of the distribution network feeder line and transmit it to the fault location host.

[0089] The uMPU is used to collect voltage measurement data and transmit it to the fault location host.

[0090] The fault location host searches for and determines the location of the fault point based on the current and voltage measurement data of the distribution network feeder lines and the remote signaling and telemetry information of the distribution network dispatch automation system, based on the adaptive protection setting calculation model, and outputs corresponding control commands to the passive protection terminal to control the conduction and cutoff of each switch in the passive protection terminal.

[0091] Using the above system, a method for active distribution network fault location based on passive protection is implemented, such as... Figure 2 As shown, it includes the following steps:

[0092] S1. Based on the grid-connected inverter control strategy of distributed power sources, establish a controlled current source model to obtain the impedance branch model of the grid connection point of the distributed power source.

[0093] S2. Establish an active distribution network sequence component calculation network to calculate the branch current of the distribution network feeder lines;

[0094] S3. The passive protection terminal collects the current of the distribution network feeder line, and the uPMU synchronous measurement terminal collects the voltage measurement data. The data is then transmitted to the fault location host for matching in order to search for the location of the fault point and isolate the fault section.

[0095] This technical solution addresses the low accuracy of fault location in current active distribution networks. Considering the application of micro phasor measurement units (uPMUs) in distribution networks, which can acquire high-precision phase information, thus providing conditions for fault location based on online parameter identification; furthermore, traditional protection systems lack an adaptive protection framework and are not designed for distribution networks with numerous ring main units. Therefore, this solution utilizes passive overcurrent protection with its protection and data communication functions as the distribution network protection terminal, combines it with existing adaptive protection research results, and integrates uPMU phasor information to construct an active distribution network adaptive protection setting calculation model that fuses passive protection data from ring main units and uPMU measurement data. This is of great significance for improving the performance of active distribution network protection systems.

[0096] This embodiment applies the above technical solution and mainly includes the following:

[0097] I. By establishing a controlled current source model through the grid-connected inverter control strategy of distributed power sources, the impedance branch model of the grid connection point of the distributed power source is obtained.

[0098] When the grid connection point voltage is greater than 0.95 pu, the inverter control strategy remains unchanged; when it is less than the minimum grid connection operating voltage, the DG output only inverts the reactive current iq, which is normally taken as 1.2I. N Within this range, the inverter output current Ipcc is:

[0099]

[0100]

[0101]

[0102] In the formula, I * , These represent the DG fault output current, the d-axis fault current, and the q-axis components of the fault current under fault conditions; K is the reactive power support coefficient, usually taken as 2, and U... PCC P is the grid connection point voltage. ref Contribute your efforts for reference.

[0103] The structure of the grid-connected inverter control system is as follows: Figure 3 As shown, the inverter controls the current through the adjustment of the terminal voltage. The modulation voltage and current satisfy the following relationship:

[0104]

[0105] In the formula, V * is the inverter output voltage, k is the PI controller adjustment coefficient, and i and u are the voltage and current values ​​at the measurement points.

[0106] From the AC side, the relationship between the inverter terminal voltage and the equivalent resistance R and inductance L between the measurement points is established, specifically expressed as follows:

[0107]

[0108]

[0109] In practice, the PWM carrier frequency is as high as several kilohertz, so the inverter terminal voltage can be considered equivalent to the modulation voltage, thus establishing the relationship between the control side and the AC side current:

[0110]

[0111]

[0112] Knowing the relationship between the fault output and the grid connection point after a fault occurs, by substituting the inverter output current into the relationship between the control side and the AC side current, we can obtain the relationship between the DG fault output and the control strategy, output, reactive power support coefficient, and grid connection point voltage, as shown in the following formula:

[0113]

[0114]

[0115]

[0116] 2. Establish an active distribution network sequence component calculation network for calculating branch currents of distribution network feeder lines.

[0117] From the relationship between DG fault output and control strategy, output, reactive power support coefficient, and grid connection point voltage, it can be seen that the node voltage equation of the distributed generation can be equivalent to a voltage-controlled current source. The magnitude of its current value can be obtained by solving the differential equation using the voltage at the connection point as the excitation quantity. Since the load current is very small compared to the short-circuit current and can be ignored, the distribution network can be considered unloaded, and the voltage of the grid system connected to the distribution network is known. Therefore, the solution for the fault current of the distribution network becomes: under the unload condition, using the equivalent current source of the distributed generation and the grid voltage source as the excitation quantity, and the line current of the distribution network including the fault point as the response calculation model.

[0118] To obtain the voltage at the point of access for distributed generation (DG) and the voltage of the distribution network system, synchronous measurement units (uPMUs) are installed at both the DG access point and the voltage bus of the distribution network system. These uPMUs acquire the synchronous measurement voltage of the entire distribution network and the excitation quantity for the fault current calculation model. A specific active distribution network model is shown below. Figure 4 As shown.

[0119] If the online calculation model of an active distribution network is analyzed as a three-phase system with n branches, the admittance matrix becomes 3n*3n, resulting in a large computational load. However, by performing order network decomposition on the calculation network, the order admittance matrix becomes n*n, reducing the computational load.

[0120] Due to the varying fault durations during fault ride-through, the control strategies of distributed generation (DG) play different roles. Based on different types of DG and their control strategies, node voltage equations are established to transform voltage source branches into current source branches. Specifically:

[0121] Y B =(y1...y n ) T

[0122]

[0123]

[0124] In the formula,

[0125] The resulting nodal admittance matrix is ​​as follows:

[0126] Y = AY B A T

[0127] The node voltage equations and branch current equations are as follows:

[0128]

[0129]

[0130] In the formula, This is the branch voltage, formed by the node voltage.

[0131] Due to the suppression of negative-sequence current by the distributed power source control strategy, there is no negative-sequence component output during asymmetrical faults, thus the impact of the negative-sequence current of the distributed power source on the calculation model is ignored. The system wiring diagram, positive-sequence wiring, and negative-sequence wiring are shown below. Figure 5 , 6 As shown in Figures 7 and 8.

[0132] III. Locating the fault location and calculating the fault current in the isolated fault section.

[0133] When modifying the admittance matrix during fault search, assuming the original power system has N independent nodes, the node admittance matrix during normal operation can be expressed as:

[0134]

[0135] When a power system fails, it is equivalent to adding a node to the original network, and Y' is of order (N+1).

[0136]

[0137] After adding a new node f, compared to Y, only the admittance between faulted nodes changes in Y'. That is, only the self-admittance and mutual admittance of nodes i, j, and f change, but the diagonal elements remain equal. Faults can be divided into ground faults and phase-to-phase faults.

[0138] When a ground fault occurs, a new node is added between nodes i and j, and a new grounding branch is also added, specifically as follows:

[0139] Y' ii =(Y ii -Y fj )

[0140] Y if =Y fj

[0141] Y ij '=Y ji '=0

[0142] Y jj '=(Y jj -Y if )

[0143] ΔY ff =Y ff -|Y if +Y fj |

[0144] ΔY ff This is the fault point grounding admittance under non-metallic grounding fault conditions.

[0145] When the fault is a phase-to-phase short circuit, it is equivalent to adding a new node between nodes i and j, with an ungrounded branch. ii Y ij '、Y jj '、Y if The changes are the same as those for ground faults, and the node admittance matrix changes as follows:

[0146] Y ff =|Y if +Y fj |

[0147] Since the electrical quantities of the faulty node cannot be directly obtained, the actual admittance matrix of the corresponding node needs to have Y' removed. ff The row and column in which it is located.

[0148] Furthermore, by matching the actual collected current with the model-calculated current, the location of the fault point in the active distribution network is determined. The search formula for the fault current in the active distribution network is as follows:

[0149]

[0150] In the formula, k is the branch number being searched, and d k The distance from the fault point to the beginning of the line is used to perform the search by changing the distance length according to the set step size. Let n be the positive sequence voltages collected by n uPMUs in the power grid. This is the negative sequence voltage of the system.

[0151] When the following formula is satisfied, the fault current is considered to be perfectly matched, and the fault branch and fault location d are output. k The value, specifically expressed as:

[0152]

[0153] In the formula, This represents the collected value of fault current in an active distribution network.

[0154] In summary, this technical solution integrates passive protection data from the ring main unit (RNB) and measurement data from the uPMU (uPMU) for active distribution network fault location. First, a controlled current source model is established using the grid-connected inverter control strategy of the distributed generation (DG) to obtain the impedance branch model of the DG grid connection point. Then, an active distribution network sequence component calculation network is established to calculate the branch currents of the distribution network feeder lines. Next, the passive protection terminal of the RNB collects the current data of the distribution network feeder lines, and the uPMU synchronous measurement terminal collects the voltage measurement data. This data is then transmitted via communication to the fault location host for matching, locating the fault point, and isolating the faulty section. This technical solution effectively improves the accuracy of fault location and the reliability of protection in active distribution networks.

Claims

1. A method for active distribution network fault location based on passive protection, applied to an active distribution network fault location system based on passive protection, characterized in that, The system includes passive protection terminals installed in active distribution network switchgear and ring network cabinets, and uPMUs installed at distributed power access points and distribution network voltage busbars. The passive protection terminals and uPMUs are respectively connected to the fault location host. The fault location host is connected to the distribution network dispatch automation system. The passive protection terminals are used to collect the current of the distribution network feeder lines and transmit it to the fault location host. The uPMU is used to collect voltage measurement data and transmit it to the fault location host; The fault location host searches for and determines the location of the fault point based on the current and voltage measurement data of the distribution network feeder lines and the remote signaling and telemetry information of the distribution network dispatch automation system, based on the adaptive protection setting calculation model, and outputs corresponding control commands to the passive protection terminal to control the conduction and cutoff of each switch in the passive protection terminal. The active distribution network fault location method based on passive protection includes the following steps: S1. Based on the grid-connected inverter control strategy of distributed power sources, establish a controlled current source model to obtain the impedance branch model of the grid connection point of the distributed power source. S2. Establish an active distribution network sequence component calculation network to calculate the branch current of the distribution network feeder lines; S3. The passive protection terminal collects the current of the distribution network feeder line, and the uPMU synchronous measurement terminal collects the voltage measurement data. The data is then transmitted to the fault location host for matching in order to search for the location of the fault point and isolate the fault section. Step S1 specifically includes the following steps: S11. Determine the inverter output characteristics based on the distributed power grid-connected inverter control strategy: in, , , These represent the DG fault output current, the d-axis fault current, and the q-axis components, respectively, under fault conditions. K This is the reactive power support coefficient. The voltage at the grid connection point. P ref Contribute your efforts for reference; S12. Based on the grid-connected inverter control system structure, derive the relationship between modulation voltage and current, and establish the voltage-current equation for the grid connection point of new energy power sources. The specific process of step S12 is as follows: The inverter controls the current through the adjustment of the terminal voltage. The modulation voltage and current satisfy the following relationship: in, This refers to the output voltage of the inverter. This is the adjustment coefficient of the PI controller. , To measure the voltage and current values ​​at the measurement point; From the AC side, establish the equivalent resistance between the inverter terminal voltage and the measurement point. , Relationship between inductors: In practice, the PWM carrier frequency can reach several kilohertz, and the inverter terminal voltage is equivalent to the modulation voltage. Therefore, the relationship between the control side and AC side currents is established, as shown in the following formula: S13. Based on the relationship between fault output and grid connection point, establish the relationship between DG fault output and control strategy, power output, reactive power support coefficient, and grid connection point voltage.

2. The active distribution network fault location method based on passive protection according to claim 1, characterized in that, The specific process of step S13 is as follows: Knowing the relationship between the fault output and the grid connection point after a fault occurs, by substituting the inverter output current into the relationship between the control side and the AC side current, we can obtain the relationship between the DG fault output and the control strategy, output, reactive power support coefficient, and grid connection point voltage, as shown in the following formula: in, i f To provide assistance during malfunctions.

3. The active distribution network fault location method based on passive protection according to claim 2, characterized in that, The specific process of step S2 is as follows: Based on different types of distributed power sources and different control strategies, node voltage equations are established to convert voltage source branches into current source branches, as follows: The resulting nodal admittance matrix is: The node voltage equations and branch current equations are as follows: in, This is the branch voltage, formed by the node voltage.

4. The active distribution network fault location method based on passive protection according to claim 3, characterized in that, The search for the fault location in step S3 specifically includes the following steps: S31. Modify the admittance matrix during the fault search process; S32. Match the fault current to determine the location of the fault point.

5. The active distribution network fault location method based on passive protection according to claim 4, characterized in that, The specific process of step S31 is as follows: Assuming the original power system has N independent nodes, its node admittance matrix during normal operation can be expressed as: A power system failure is equivalent to adding a node to the existing network. It is of order (N+1), specifically: Add a new node f back, and In contrast, only the admittance between faulty nodes changes, meaning only the nodes... i , j , f The node self-admittance and mutual admittance change, but the diagonal elements remain equal. Faults are classified as ground faults and phase-to-phase faults. If a ground short circuit occurs, then at the node i , j A new node is added, and a new grounding branch is also added, specifically as follows: in, This is the fault point grounding admittance under non-metallic grounding fault conditions; If the fault is a phase-to-phase short circuit, it is equivalent to a fault at the node. i , j Add a new node and an ungrounded branch. , , , The changes are the same as for ground faults, and the node admittance matrix changes as follows: 。 6. The active distribution network fault location method based on passive protection according to claim 5, characterized in that, Specifically, step S32 involves matching the fault current acquisition value with the active distribution network fault current search formula. If the fault current search value and the current value acquired by the passive protection terminal satisfy the matching formula, the fault current is considered to be completely matched, and the corresponding fault point location result is output. The active distribution network fault current search formula is as follows: in, k For the branch number being searched, The distance from the fault point to the beginning of the line is used to perform the search by changing the distance length according to the set step size. For the power grid n Positive sequence voltages collected by each uPMU This is the negative sequence voltage of the system; The matching formula is as follows: in, The fault current is the value collected in the active distribution network, i.e., the current value collected by the passive protection terminal. When the above matching formula is true, it indicates that the fault current is perfectly matched, and the fault branch and fault location are output. value.

Images