Single-phase earth fault zero-sequence current transfer method, system, equipment, medium and product

Abstract

The invention relates to the technical field of power systems, and discloses a single-phase earth fault zero-sequence current transfer method, system, device, medium and product, and the method comprises the steps: determining the line-to-earth voltage of a fault phase according to the difference value between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase earth fault under the condition that a power distribution network has the single-phase earth fault, and obtaining the zero-sequence current of the single-phase earth fault; determining a reference current value of the cascaded H bridge according to the line-to-ground voltage and the zero-sequence parameter, adjusting an output current of the cascaded H bridge by adopting a proportional-integral controller according to the reference current value, enabling the output current to track the reference current value, and enabling a zero-sequence current of a fault phase to be transferred to a power electronic branch, and the energy generated when the zero-sequence current flows through the cascaded H bridge is distributed to other nodes, so that the fault current can be effectively inhibited through an accurate zero-sequence current transfer strategy, and the impact of the fault on the system is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a single-phase grounding fault zero-sequence current transfer method, system, equipment, medium and product. Background Art

[0002] With the increasing penetration of distributed energy resources, active distribution networks are gradually transitioning to hybrid AC / DC systems based on power electronics. During this process, the system's power amplitude and direction exhibit random fluctuations, potentially causing traditional protective devices to fail and exacerbating the negative impact of single-phase ground faults. Statistics show that over 70% of faults in medium-voltage distribution networks are single-phase ground faults, which can cause arcing, leading to serious consequences such as fires, electric shocks, and widespread power outages. Therefore, improving the self-healing capabilities of distribution networks is an urgent issue.

[0003] In existing technologies, superconducting fault current limiters (SFCLs), while capable of lossless current limiting, are difficult to implement in large-scale applications due to their high manufacturing and maintenance costs and the requirement for a low-temperature environment. In DC systems, reactors can suppress fault currents, but their installation can affect system stability. Thyristor-based power electronic current limiters, while more cost-effective, are limited to the transient component of current. For AC systems, Peterson coils can limit fault currents but are prone to resonant overvoltages. Independent converters, while improving the system's dynamic performance, require additional equipment, significantly increasing system costs.

[0004] In addition, DC current limiter technology has explored energy interaction mechanisms. The secondary active current limiters proposed in some studies can recover fault energy, but the recovered energy is mainly dissipated in the form of heat energy, and energy storage and reuse are not achieved. This leads to large energy loss in the distribution network after a single-phase grounding fault occurs, which can easily cause damage to equipment and make it difficult to ensure the dynamic and stable operation of the distribution network during the fault. Summary of the Invention

[0005] In view of this, the present invention provides a single-phase grounding fault zero-sequence current transfer method, system, equipment, medium and product, which solves the technical problems that the distribution network has large energy loss after a single-phase grounding fault occurs, which easily causes damage to equipment and is difficult to ensure the dynamic and stable operation of the distribution network during the fault.

[0006] A first aspect of the present invention provides a method for transferring zero-sequence current of a single-phase grounding fault, comprising:

[0007] In the event of a single-phase grounding fault in the distribution network, determining the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault;

[0008] Determining a reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter;

[0009] According to the reference current value, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge so that the output current tracks the reference current value, and the zero-sequence current of the faulty phase is transferred to the power electronic branch, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes.

[0010] Preferably, the method further comprises:

[0011] Real-time collection of phase-to-ground leakage resistance and phase-to-ground capacitance of overhead lines and cables in the distribution network;

[0012] Determining an equivalent zero-sequence resistance and an equivalent zero-sequence capacitance according to the phase-to-ground leakage resistance and the phase-to-ground capacitance;

[0013] determining a fault branch current according to the equivalent zero-sequence resistance and the equivalent zero-sequence capacitance;

[0014] Whether the single-phase grounding fault occurs in the distribution network is identified based on the fault branch current and a preset fault current threshold.

[0015] Preferably, determining the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault includes:

[0016] After a single-phase grounding fault occurs, obtaining the fault phase voltage and the zero-sequence voltage;

[0017] Separating the fundamental component of the fault phase voltage and filtering out harmonic interference by a second-order generalized integrator to obtain a filtered fault phase voltage;

[0018] The line-to-ground voltage of the fault phase is obtained by subtracting the filtered fault phase voltage from the zero-sequence voltage.

[0019] Preferably, the zero-sequence parameters include equivalent zero-sequence resistance and equivalent zero-sequence capacitance;

[0020] The determining of the reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter includes:

[0021] A reference current value of the cascaded H-bridge is determined according to the line-to-ground voltage, the equivalent zero-sequence resistance, and the equivalent zero-sequence capacitance.

[0022] Preferably, the method of adjusting the output current of the cascaded H-bridge using a proportional-integral controller according to the reference current value so that the output current tracks the reference current value, and transferring the zero-sequence current of the faulty phase to the power electronic branch, and distributing the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes includes:

[0023] A proportional-integral controller is used to adjust a PWM modulation signal according to the reference current value; wherein the PWM modulation signal is used to drive the output current of the cascaded H-bridge to track the reference current value, so that the zero-sequence current of the fault phase is transferred to the power electronic branch, and the current of the fault branch is suppressed to be less than the preset fault current threshold;

[0024] The energy generated by the zero-sequence current flowing through the cascade H-bridge is distributed to other nodes through an energy routing network.

[0025] Preferably, distributing the energy generated by allowing the zero-sequence current to flow through the cascaded H-bridge to other nodes through an energy routing network includes:

[0026] Based on an isolated DC converter, the voltage of the cascaded H-bridge is adjusted through a single-phase shift control method to balance the DC bus voltage of the cascaded H-bridge, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes through an energy routing network; wherein the nodes include an energy storage device and a common DC bus.

[0027] In a second aspect, the present invention further provides a single-phase ground fault zero-sequence current transfer system, comprising:

[0028] A ground voltage determination module is used to determine the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase ground fault when a single-phase ground fault occurs in the distribution network;

[0029] A reference current determination module, configured to determine a reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter;

[0030] The zero-sequence current transfer module is used to adjust the output current of the cascaded H-bridge using a proportional-integral controller according to the reference current value, so that the output current tracks the reference current value, transfers the zero-sequence current of the fault phase to the power electronic branch, and distributes the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes.

[0031] In a third aspect, the present invention further provides an electronic device comprising a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the single-phase grounding fault zero-sequence current transfer method as described in the first aspect.

[0032] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the steps of the single-phase grounding fault zero-sequence current transfer method as described in the first aspect.

[0033] In a fifth aspect, the present invention also provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the steps of the single-phase ground fault zero-sequence current transfer method as described in the first aspect.

[0034] As can be seen from the above technical solution, the present invention determines the line-to-ground voltage of the fault phase based on the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase ground fault in the distribution network. Based on the line-to-ground voltage and the zero-sequence parameter, it determines the reference current value of the cascaded H-bridge. Based on the reference current value, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge so that the output current tracks the reference current value, transfers the zero-sequence current of the fault phase to the power electronic branch, and distributes the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes. This precise zero-sequence current transfer strategy effectively suppresses the fault current and significantly reduces the impact of the fault on the system. This current control not only reduces energy loss but also avoids equipment damage and arcing, ensuring the dynamic and stable operation of the distribution network during the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 An application environment diagram of a single-phase ground fault zero-sequence current transfer method provided by an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of an equivalent zero-sequence circuit for a single-phase grounding fault provided by an embodiment of the present invention;

[0038] Figure 3A flow chart of a method for transferring zero-sequence current of a single-phase ground fault provided by an embodiment of the present invention;

[0039] Figure 4 A schematic structural diagram of a single-phase ground fault zero-sequence current transfer system provided by an embodiment of the present invention;

[0040] Figure 5 A schematic structural diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] The single-phase ground fault zero-sequence current transfer method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the terminal 101 communicates with the server 102 through the network. The data storage system can store data that the server 102 needs to process. The data storage system can be integrated on the server 102, or it can be placed on the cloud or other network servers. In the event of a single-phase grounding fault in the distribution network, the terminal 101 or the server 102 determines the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault; determines the reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter; and according to the reference current value, uses a proportional-integral controller to adjust the output current of the cascaded H-bridge so that the output current tracks the reference current value, and transfers the zero-sequence current of the fault phase to the power electronic branch, and distributes the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes.

[0043] The terminal 101 may be, but is not limited to, various personal computers, laptops, smart phones, tablet computers, and the like.

[0044] The server 102 may be an independent physical server, a server cluster or a distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0045] like Figure 2 As shown, Figure 2 The equivalent zero-sequence circuit of a single-phase ground fault is shown. and Represent the output voltage and output current of the cascaded H-bridge branch respectively, is the filter inductor in this branch. According to Kirchhoff’s voltage law and current law in the circuit, when the output current provided by the cascaded H-bridge branch is Exactly equal to the zero-sequence current of the system When the current in the ground fault branch is Will drop to 0, zero sequence voltage Equal to the line-to-ground voltage corresponding to the fault point The opposite number of .

[0046] Under this control strategy, the zero-sequence current originally flowing through the single-phase ground fault branch is completely transferred to the cascade H-bridge branch, which is equivalent to temporarily losing the current path of the ground fault branch, making the current in the fault branch is dynamically adjusted to zero, the equivalent ground resistance Therefore, it is equivalent to infinity, which greatly reduces the energy loss at the fault point. At this time, there is no effective power transmission in the fault branch, that is, the effective power , the system successfully avoids energy dissipation and equipment damage caused by zero-sequence current.

[0047] For this reason, Figure 3 As shown, the embodiment of the present application provides a method for transferring zero-sequence current of a single-phase ground fault. Figure 1 The terminal 101 or the server 102 in the embodiment is used as an example to illustrate the method, which includes the following steps S1 to S3.

[0048] Step S1: When a single-phase grounding fault occurs in the distribution network, the line-to-ground voltage of the fault phase is determined according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault.

[0049] The system monitors the distribution network for single-phase grounding faults. Once a single-phase grounding fault is detected, the fault identification phase begins immediately to identify the fault type and location. The fault phase voltage and zero-sequence voltage are collected in real time, and the difference between the fault phase voltage and the zero-sequence voltage is calculated to extract the line-to-ground voltage of the fault phase.

[0050] Step S2: Determine the reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter.

[0051] Among them, the cascaded H-bridge is a power electronic device composed of multiple H-bridge units cascaded together, which can regulate the power flow of the power system by controlling its output voltage and current. When determining the reference current value of the cascaded H-bridge, it is necessary to first obtain the line-to-ground voltage of the fault phase, which reflects the potential situation at the fault point. Subsequently, combined with the zero-sequence parameters of the power system, including equivalent zero-sequence resistance and equivalent zero-sequence capacitance, these parameters describe the electrical characteristics of the power system in the zero-sequence state. By combining the line-to-ground voltage and zero-sequence parameters of the fault phase and utilizing relevant algorithms for power system analysis, the reference current value that the cascaded H-bridge needs to output can be accurately calculated to ensure that the zero-sequence current of the fault phase can be effectively transferred.

[0052] Step S3: Based on the reference current value, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge so that the output current tracks the reference current value, and the zero-sequence current of the fault phase is transferred to the power electronic branch, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes.

[0053] Among them, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge so that it accurately tracks the reference current value, so that the zero-sequence fault current is directed from the fault branch (such as the branch where the faulty line or equipment is located) to the power electronics branch (the branch where the cascaded H-bridge is located), thereby limiting the current in the fault branch.

[0054] The energy generated by the zero-sequence current flowing through the cascaded H-bridge is obtained by measuring the output current and voltage of the cascaded H-bridge in real time. Through the output current and voltage, combined with the circuit topology of the cascaded H-bridge, the power generated when the zero-sequence current flows through the cascaded H-bridge can be derived as the energy generated by the zero-sequence current flowing through the cascaded H-bridge.

[0055] Furthermore, through an energy management system or energy routing network, this energy can be efficiently distributed to other nodes in the distribution network, such as energy storage devices or a public DC bus, to achieve optimal energy utilization and rapid fault recovery.

[0056] For example, when the output current of the cascaded H-bridge accurately tracks the reference current, a low-impedance path is formed in the power electronic branch, attracting the zero-sequence current to transfer from the fault branch to this branch; at this time, the current in the fault branch is "shunted" and its current drops to below 1A (reaching the threshold for protecting the faulty device).

[0057] In addition, each H-bridge unit needs to be connected to a DC power supply (usually a capacitor or an independent DC source). Its voltage stability directly affects the output performance of the H-bridge (voltage instability can lead to output waveform distortion and excessive stress on switching devices). In the event of a fault, energy will be injected into the DC bus during the zero-sequence current transfer process, which may cause a sudden voltage rise. The energy generated by the zero-sequence current flowing through the cascaded H-bridge during the fault (absorbed from the DC bus by the isolated DC converter) is distributed to other nodes by distributing the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes, maintaining the DC bus voltage within a stable range (ensuring the normal operation of the cascaded H-bridge).

[0058] It should be noted that, in the case of a single-phase ground fault in the distribution network, the embodiments of the present application determine the line-to-ground voltage of the fault phase based on the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase ground fault. Based on the line-to-ground voltage and the zero-sequence parameter, the reference current value of the cascaded H-bridge is determined. Based on the reference current value, a proportional-integral controller is used to regulate the output current of the cascaded H-bridge, so that the output current tracks the reference current value, and the zero-sequence current of the fault phase is transferred to the power electronic branch. The energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes. Thus, through a precise zero-sequence current transfer strategy, the fault current can be effectively suppressed, greatly reducing the impact of the fault on the system. This current control not only reduces energy loss, but also avoids equipment damage and arcing, ensuring the dynamic and stable operation of the distribution network during the fault.

[0059] In some embodiments, the method further comprises:

[0060] Step S11: collecting phase-to-ground leakage resistance and phase-to-ground capacitance of overhead lines and cables in the distribution network in real time.

[0061] Among them, the insulation parameters of the distribution network (phase-to-ground leakage resistance and phase-to-ground capacitance) are measured in real time to evaluate the current electrical insulation status and continuously monitor whether a single-phase grounding fault occurs.

[0062] Since the insulation state of the distribution network directly affects the fault current distribution and the ground potential, the embodiment of the present application uses a synchronous measurement device to collect the phase-to-ground leakage resistance and phase-to-ground capacitance of overhead lines and cables in real time.

[0063] Step S12: Determine the equivalent zero-sequence resistance and the equivalent zero-sequence capacitance according to the phase-to-ground leakage resistance and the phase-to-ground capacitance.

[0064] The equivalent zero-sequence resistance and the equivalent zero-sequence capacitance are determined based on the following formula.

[0065]

[0066] Where, 、 are the equivalent zero-sequence resistance and equivalent zero-sequence capacitance, R OL 、R CL are the phase-to-ground leakage resistance of the overhead line and the phase-to-ground leakage resistance of the cable, respectively. OL 、C CL They are the phase-to-ground capacitance of overhead lines and the phase-to-ground capacitance of cables respectively.

[0067] Step S13: Determine the fault branch current according to the equivalent zero-sequence resistance and the equivalent zero-sequence capacitance.

[0068] Among them, the fault branch current is the current flowing through the fault location when the fault occurs. After determining the equivalent zero-sequence resistance and equivalent zero-sequence capacitance, combined with the line-to-ground voltage of the fault phase, the current value of the fault branch can be derived using the short-circuit current calculation method of the power system. This step helps to further understand the impact of the fault on the system and provides key parameters for subsequent fault handling. By accurately calculating the fault branch current, the embodiments of the present application can more effectively assess the impact of the fault and provide strong support for quickly restoring the stable operation of the system.

[0069] The fault branch current is:

[0070]

[0071] Where i f is the fault branch current, is the zero sequence current, is the line-to-ground voltage, is the fault resistance, j is the imaginary unit, is the angular frequency.

[0072] Step S14: Identify whether a single-phase grounding fault occurs in the distribution network based on the fault branch current and a preset fault current threshold.

[0073] The preset fault current threshold is set based on the normal operating conditions and fault tolerance of the distribution network. When the fault branch current exceeds this threshold, the system determines that a single-phase ground fault has occurred. By comparing the fault branch current with the preset threshold, embodiments of the present application can quickly identify the fault state and trigger the fault handling process, thereby shortening fault response time and improving system reliability and safety.

[0074] In some embodiments, determining the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault includes:

[0075] Step S101: After a single-phase grounding fault occurs, the fault phase voltage and the zero-sequence voltage are obtained.

[0076] After a single-phase ground fault occurs, the fault phase voltage and zero-sequence voltage are key parameters for determining the fault type and location. Voltage transformers installed in the distribution network collect these data in real time.

[0077] Step S102 : Separate the fundamental component of the fault phase voltage and filter out harmonic interference using a second-order generalized integrator to obtain a filtered fault phase voltage.

[0078] Applying a second-order generalized integrator to the fault phase voltage effectively separates the fundamental component and filters out harmonic interference, ensuring the accuracy of the extracted fault phase voltage data. This step is crucial for the subsequent calculation of the fault phase's line-to-ground voltage, as it directly determines the accuracy and reliability of subsequent analysis. After processing with the second-order generalized integrator, the filtered fault phase voltage data is smoother and closer to the actual fundamental component, thereby improving the accuracy of the analysis.

[0079] Step S103: Subtract the filtered fault phase voltage from the zero-sequence voltage to obtain the line-to-ground voltage of the fault phase.

[0080] Among them, the line-to-ground voltage of the fault phase is obtained by taking the difference between the filtered fault phase voltage and the zero-sequence voltage, providing a high-precision voltage signal for the fault current path transfer, that is, , where u A is the fault phase voltage after filtering, u o is the zero sequence voltage.

[0081] In some embodiments, the zero-sequence parameters include equivalent zero-sequence resistance and equivalent zero-sequence capacitance;

[0082] Determine the reference current value of the cascaded H-bridge based on the line-to-ground voltage and zero-sequence parameters, including:

[0083] The reference current value of the cascaded H-bridge is determined according to the line-to-ground voltage, the equivalent zero-sequence resistance, and the equivalent zero-sequence capacitance.

[0084] Among them, the reference current value of the cascaded H-bridge is calculated by combining the line-to-ground voltage, equivalent zero-sequence resistance and equivalent zero-sequence capacitance as follows:

[0085] Where, is the reference current value of the cascade H-bridge.

[0086] In some embodiments, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge according to a reference current value, so that the output current tracks the reference current value, and the zero-sequence current of the fault phase is transferred to the power electronic branch, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes, including:

[0087] Step S301: Based on the reference current value, a proportional-integral controller is used to adjust the PWM modulation signal; wherein the PWM modulation signal is used to drive the output current of the cascaded H-bridge to track the reference current value, so that the zero-sequence current of the fault phase is transferred to the power electronic branch, and the fault branch current is suppressed to be less than a preset fault current threshold.

[0088] A proportional-integral controller (PI) is used to adjust the PWM modulation signal, driving the cascaded H-bridge output current to precisely track the reference value, enabling rapid transfer of zero-sequence current from the fault branch to the power electronics branch. This process suppresses the fault branch current to below a preset fault current threshold (e.g., 1A), bringing the fault node potential close to zero and effectively eliminating arcing and electric shock risks.

[0089] Specifically, the working process of the proportional-integral controller is:

[0090] Real-time detection of the error between the actual output current of the cascaded H-bridge and the reference current value;

[0091] Proportional link (P): Instantly outputs the adjustment amount based on the current error (the larger the error, the stronger the adjustment), quickly responding to dynamic changes;

[0092] Integral link (I): accumulates historical errors and eliminates steady-state errors (ensuring that the actual output current has no deviation from the reference current during long-term operation);

[0093] The regulation values ​​of P and I are combined to generate a control signal (such as a PWM pulse width modulation signal) to control the on / off state of each switch device in the cascaded H-bridge, thereby regulating the output current.

[0094] When the output current of the cascaded H-bridge accurately tracks the reference current, a low-impedance path is formed in the power electronic branch, attracting the zero-sequence current to transfer from the fault branch to this branch; at this time, the current in the fault branch is "shunted" and its current drops below the fault current threshold (such as 1A).

[0095] Step S302: Energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes through an energy routing network.

[0096] In some embodiments, energy generated by flowing zero-sequence current through a cascaded H-bridge is distributed to other nodes via an energy routing network, including:

[0097] Based on an isolated DC converter, the voltage of the cascaded H-bridge is adjusted through a single-phase shift control method to balance the DC bus voltage of the cascaded H-bridge. The energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes through an energy routing network; wherein, the nodes include energy storage devices and a common DC bus.

[0098] Among them, the isolated DC converter is a DC-DC converter with electrical isolation (such as through a high-frequency transformer), which can achieve high-voltage and low-voltage side isolation (safety protection) and simultaneously adjust the voltage (boost / step down), suitable for energy transmission at different voltage levels.

[0099] The isolated DC converter detects the DC bus voltage (feedback) of the cascaded H-bridge in real time, compares it with the target stable voltage (given value), and adjusts its switching state (such as duty cycle) through closed-loop control (such as PI control):

[0100] If the bus voltage is too high (fault energy injection), the converter operates in "energy absorption" mode, transferring excess energy from the DC bus to the secondary side. If the bus voltage is too low (energy deficiency), the converter can absorb energy from the secondary side (such as an energy storage device) to supplement the DC bus. Ultimately, the DC bus voltage is maintained within a stable range (ensuring normal operation of the cascaded H-bridge).

[0101] Among them, the energy routing network distributes the absorbed fault energy to different nodes for recovery or reuse, and includes lithium-ion batteries, photovoltaic systems and three-phase converters.

[0102] Among them, lithium-ion batteries serve as energy storage units, receiving and storing fault energy (charging), and can release energy when the system returns to normal (such as peak load regulation of the power grid);

[0103] The photovoltaic system can work in conjunction with the energy grid. If the photovoltaic system is generating electricity, the fault energy can be supplemented to the DC side of the photovoltaic system (reducing the photovoltaic system's dependence on the grid); if the photovoltaic system is not generating electricity, it can act as a "load" to receive energy.

[0104] The three-phase converter converts fault energy in the form of DC into three-phase AC (matching the grid voltage and frequency), which can be connected to the grid and fed back to the grid, or transmitted to the public DC bus (for use by other DC devices).

[0105] Specifically, through the single-phase phase-shift control strategy of the isolated DC converter, a fixed duty cycle square wave is applied to the H-bridge on the cascade H-bridge side, and the phase shift angle of the H-bridge on the energy storage side is dynamically adjusted. When the output of the photovoltaic system is insufficient, the energy storage device discharges to the common DC bus through the non-isolated DC / DC converter. The energy caused by the zero-sequence current will be transferred from the single-phase ground fault branch to be absorbed by the cascade H-bridge converter. Although after the single-phase ground fault current is limited, The amplitude is not very large. Phase angle difference Close to 180°. Therefore, Therefore, the active power output of the cascaded H-bridge converter branch can be expressed as:

[0106]

[0107] The isolated DC converter, connected between the cascaded H-bridge and the energy storage device, adaptively adjusts the amount and direction of energy transfer based on the real-time operating status of the distribution network system. By employing a single-phase shift control method, the isolated DC converter effectively directs energy and regulates voltage to stabilize the DC bus voltage, enabling precise control and transfer of zero-sequence current in the event of a fault.

[0108] The fault status is continuously monitored during the fault period. When it is detected that the fault has been eliminated, the system control gradually exits the compensation process, and finally the distribution network is restored to normal operation, completing the dynamic stability control and energy transfer during the fault period.

[0109] Based on the same inventive concept, an embodiment of the present application further provides a single-phase grounding fault zero-sequence current transfer system for implementing the above-mentioned single-phase grounding fault zero-sequence current transfer method.

[0110] The implementation solution provided by this system to solve the problem is similar to the implementation solution recorded in the above method. Therefore, the specific limitations in one or more single-phase ground fault zero-sequence current transfer system embodiments provided below can refer to the limitations of the single-phase ground fault zero-sequence current transfer method above, and will not be repeated here.

[0111] like Figure 4 As shown, the embodiment of the present application provides a single-phase ground fault zero-sequence current transfer system, including:

[0112] The ground voltage determination module 100 is used to determine the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase ground fault when a single-phase ground fault occurs in the distribution network;

[0113] The reference current determination module 200 is used to determine the reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter;

[0114] The zero-sequence current transfer module 300 is used to adjust the output current of the cascaded H-bridge using a proportional-integral controller according to the reference current value, so that the output current tracks the reference current value, transfers the zero-sequence current of the fault phase to the power electronic branch, and distributes the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes.

[0115] In some embodiments, the system further includes a fault identification module configured to:

[0116] Real-time collection of phase-to-ground leakage resistance and phase-to-ground capacitance of overhead lines and cables in the distribution network;

[0117] Determine the equivalent zero-sequence resistance and equivalent zero-sequence capacitance based on the phase-to-ground leakage resistance and phase-to-ground capacitance;

[0118] Determine the fault branch current based on the equivalent zero-sequence resistance and equivalent zero-sequence capacitance;

[0119] Based on the fault branch current and the preset fault current threshold, it is determined whether a single-phase grounding fault occurs in the distribution network.

[0120] In some embodiments, the ground voltage determination module 100 is configured to:

[0121] After a single-phase grounding fault occurs, obtain the fault phase voltage and zero-sequence voltage;

[0122] The fault phase voltage is separated into fundamental components by a second-order generalized integrator and harmonic interference is filtered out to obtain the filtered fault phase voltage.

[0123] The line-to-ground voltage of the fault phase is obtained by taking the difference between the filtered fault phase voltage and the zero-sequence voltage.

[0124] In some embodiments, the zero-sequence parameters include equivalent zero-sequence resistance and equivalent zero-sequence capacitance;

[0125] The reference current determination module 200 is configured to:

[0126] The reference current value of the cascaded H-bridge is determined according to the line-to-ground voltage, the equivalent zero-sequence resistance, and the equivalent zero-sequence capacitance.

[0127] In some embodiments, the zero-sequence current transfer module 300 includes:

[0128] A transfer module is used to adjust the PWM modulation signal using a proportional-integral controller according to the reference current value; wherein the PWM modulation signal is used to drive the output current of the cascaded H-bridge to track the reference current value, so that the zero-sequence current of the fault phase is transferred to the power electronic branch and the current of the fault branch is suppressed to be less than a preset fault current threshold;

[0129] The energy distribution module is used to distribute the energy generated by the zero-sequence current flowing through the cascade H-bridge to other nodes through the energy routing network.

[0130] In some embodiments, the energy distribution module is configured to:

[0131] Based on an isolated DC converter, the voltage of the cascaded H-bridge is adjusted through a single-phase shift control method to balance the DC bus voltage of the cascaded H-bridge. The energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes through an energy routing network; wherein, the nodes include energy storage devices and a common DC bus.

[0132] like Figure 5As shown, an embodiment of the present application provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, and when the computer program is executed by the processor 30, the processor 30 performs the steps of the single-phase ground fault zero-sequence current transfer method in the above embodiment.

[0133] An embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the steps of the single-phase ground fault zero-sequence current transfer method in the above embodiment are implemented.

[0134] An embodiment of the present application provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the steps of the single-phase ground fault zero-sequence current transfer method in the above-mentioned embodiment.

[0135] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, electronic devices, computer storage media, and computer program products can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0136] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0137] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0138] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media, computer program products and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0139] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0140] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0141] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for executing all or part of the steps of the method described in each embodiment of the present invention via a computer device (which can be a personal computer, server, or network device, etc.). The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for transferring zero-sequence current of a single-phase ground fault, characterized in that: include: In the event of a single-phase grounding fault in the distribution network, determining the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault; Determining a reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter; According to the reference current value, a proportional-integral controller is used to adjust the output current of the cascaded H-bridge so that the output current tracks the reference current value, and the zero-sequence current of the faulty phase is transferred to the power electronic branch, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes.

2. The method for transferring zero-sequence current of a single-phase grounding fault according to claim 1, characterized in that: Also includes: Real-time collection of phase-to-ground leakage resistance and phase-to-ground capacitance of overhead lines and cables in the distribution network; Determining an equivalent zero-sequence resistance and an equivalent zero-sequence capacitance according to the phase-to-ground leakage resistance and the phase-to-ground capacitance; determining a fault branch current according to the equivalent zero-sequence resistance and the equivalent zero-sequence capacitance; Whether the single-phase grounding fault occurs in the distribution network is identified based on the fault branch current and a preset fault current threshold.

3. The method for transferring zero-sequence current of a single-phase grounding fault according to claim 1, characterized in that: Determining the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase grounding fault includes: After a single-phase grounding fault occurs, obtaining the fault phase voltage and the zero-sequence voltage; Separating the fundamental component of the fault phase voltage and filtering out harmonic interference by a second-order generalized integrator to obtain a filtered fault phase voltage; The line-to-ground voltage of the fault phase is obtained by subtracting the filtered fault phase voltage from the zero-sequence voltage.

4. The method for transferring zero-sequence current of a single-phase grounding fault according to claim 1, characterized in that: The zero-sequence parameters include equivalent zero-sequence resistance and equivalent zero-sequence capacitance; The determining of the reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter includes: A reference current value of the cascaded H-bridge is determined according to the line-to-ground voltage, the equivalent zero-sequence resistance, and the equivalent zero-sequence capacitance.

5. The method for transferring zero-sequence current of a single-phase grounding fault according to claim 2, characterized in that: The method comprises: adjusting the output current of the cascaded H-bridge using a proportional-integral controller according to the reference current value, so that the output current tracks the reference current value, and transferring the zero-sequence current of the fault phase to the power electronic branch, and distributing the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes, including: A proportional-integral controller is used to adjust a PWM modulation signal according to the reference current value; wherein the PWM modulation signal is used to drive the output current of the cascaded H-bridge to track the reference current value, so that the zero-sequence current of the fault phase is transferred to the power electronic branch, and the current of the fault branch is suppressed to be less than the preset fault current threshold; The energy generated by the zero-sequence current flowing through the cascade H-bridge is distributed to other nodes through an energy routing network.

6. The method for transferring zero-sequence current of a single-phase grounding fault according to claim 5, characterized in that: The energy generated by the zero-sequence current flowing through the cascade H-bridge is distributed to other nodes through an energy routing network, comprising: Based on an isolated DC converter, the voltage of the cascaded H-bridge is adjusted through a single-phase shift control method to balance the DC bus voltage of the cascaded H-bridge, and the energy generated by the zero-sequence current flowing through the cascaded H-bridge is distributed to other nodes through an energy routing network; wherein the nodes include an energy storage device and a common DC bus.

7. A single-phase ground fault zero-sequence current transfer system, characterized in that: include: A ground voltage determination module is used to determine the line-to-ground voltage of the fault phase according to the difference between the fault phase voltage and the zero-sequence voltage corresponding to the single-phase ground fault when a single-phase ground fault occurs in the distribution network; A reference current determination module, configured to determine a reference current value of the cascaded H-bridge according to the line-to-ground voltage and the zero-sequence parameter; The zero-sequence current transfer module is used to adjust the output current of the cascaded H-bridge using a proportional-integral controller according to the reference current value, so that the output current tracks the reference current value, transfers the zero-sequence current of the fault phase to the power electronic branch, and distributes the energy generated by the zero-sequence current flowing through the cascaded H-bridge to other nodes.

8. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory. When the computer program is executed by the processor, the processor performs the steps of the single-phase grounding fault zero-sequence current transfer method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the single-phase grounding fault zero-sequence current transfer method according to any one of claims 1 to 6 are implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer is caused to perform the steps of the single-phase grounding fault zero-sequence current transfer method according to any one of claims 1 to 6.

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