Distributed photovoltaic constant value remote controllable directional protection power distribution method and system

Abstract

The invention provides a distributed photovoltaic constant-value remote controllable directional protection power distribution method and system, relates to the technical field of cable or line system protection, and can significantly improve the protection accuracy and selectivity on the premise of distortion of traditional protection criteria and difficult cooperation caused by distributed photovoltaic access, avoid the unnecessary off-network of distributed photovoltaic, and improve the power distribution efficiency. The method guarantees safe and stable operation of the power distribution network, and comprises the steps: obtaining an electrical quantity signal of a distributed photovoltaic access point; power grid synchronization information is obtained, and a protection constant value set is adjusted based on the current operation condition of a grid-connected system formed by distributed photovoltaic and a power distribution network; judging a fault direction based on the electrical quantity signal and the power grid synchronization information, and determining the direction of a fault point relative to a protection device; determining a protection action triggering state based on the direction of the fault point relative to the protection device, the electrical quantity signal and the adjusted protection constant value set; and triggering protection execution logic based on the protection action triggering state.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of cable or line protection, and particularly relates to a fixed-value remote controllable directional protection power distribution method and system for distributed photovoltaics. BACKGROUND

[0002] With the transformation of global energy structure to clean and low carbon, the penetration rate of new energy represented by distributed photovoltaics in the distribution network is rapidly increasing. However, the large-scale grid connection of distributed photovoltaics has profoundly changed the topology structure and operating characteristics of the traditional distribution network, bringing severe challenges to the original relay protection system.

[0003] In the prior art, the protection scheme of the distribution network is mainly based on a fixed fault current level and a stable voltage reference. However, the access of distributed photovoltaics not only provides a fault current with limited amplitude and complex characteristics, which leads to the decrease in sensitivity of traditional overcurrent protection and even the refusal of operation, but also causes a dramatic shift in the voltage phase at the grid connection point during a fault, which makes the traditional directional element misjudge due to the distortion of the voltage reference, destroys the selectivity and coordination of the protection, and may cause over-reach tripping and expand the accident range. Meanwhile, the protection setting value is fixed once it is set and cannot be dynamically adjusted according to the photovoltaic output change and the power grid operating mode, lacking the necessary adaptability and flexibility. Therefore, how to construct a protection method that can adapt to the access characteristics of distributed photovoltaics, has remote collaboration and adaptive adjustment capability, so as to solve the deficiencies of the existing protection technology in selectivity, speed and reliability, has become a technical problem to be solved in the field. SUMMARY

[0004] The application provides a fixed-value remote controllable directional protection power distribution method and system for distributed photovoltaics, which can significantly improve the accuracy and selectivity of protection, avoid unnecessary off-grid of distributed photovoltaics, and ensure the safe and stable operation of the distribution network, by combining remote synchronization information to correct the fault direction, adaptively adjusting the protection setting value, and using remote collaborative execution logic, under the premise that the access of distributed photovoltaics leads to distortion of the traditional protection criterion and coordination difficulties.

[0005] To achieve the above purpose, the application adopts the following technical solutions:

[0006] In a first aspect, a fixed-value remote controllable directional protection power distribution method for distributed photovoltaics is provided, and the method comprises the following steps:

[0007] An electrical quantity signal of a distributed photovoltaic access point is obtained, and the electrical quantity signal at least includes a voltage signal and a current signal;

[0008] Grid synchronization information is obtained, and the protection setting value set is adjusted based on the current operating condition of a grid-connected system formed by the distributed photovoltaics and the distribution network;

[0009] Based on the electrical quantity signal and the power grid synchronization information, a fault direction is determined, and the direction of the fault point relative to the protection device is determined, wherein the protection device refers to an intelligent protection unit arranged at the distributed photovoltaic grid-connected point.

[0010] Based on the direction of the fault point relative to the protection device, the electrical quantity signal, and the adjusted protection setting value set, a protection action triggering state is determined.

[0011] Based on the protection action triggering state, a protection execution logic is triggered, and the protection execution logic includes a local execution logic and a remote control execution logic.

[0012] According to the above technical means, by introducing the remote synchronization information to correct the fault direction, combining the remote controllable setting value and the cooperative execution logic, the problems of protection misoperation and refusal caused by the distributed photovoltaic access are solved, and the accuracy, adaptability of the protection and the stability of the power grid operation are significantly improved.

[0013] Preferably, the determination of the direction of the fault point relative to the protection device includes:

[0014] The local power direction angle is calculated according to the voltage signal and the current signal.

[0015] The power grid synchronization information is received, and the power grid synchronization information includes a reference phase angle of a stable reference point.

[0016] The local power direction angle is compared with the reference phase angle, and a corrected fault direction angle is calculated.

[0017] Based on the corrected fault direction angle and the positive direction interval, the fault direction is determined, and the direction of the fault point relative to the protection device is determined.

[0018] Preferably, the determination of the direction of the fault point relative to the protection device based on the corrected fault direction angle and the positive direction interval includes:

[0019] If the corrected fault direction angle is within the positive direction interval, it is determined as a positive direction fault, otherwise it is determined as a reverse direction fault.

[0020] Preferably, the determination of the protection action triggering state based on the direction of the fault point relative to the protection device, the electrical quantity signal, and the adjusted protection setting value set includes:

[0021] In the case of determining a positive direction fault, judging based on the electrical quantity signal, determining the first protection action trigger state or the second protection action trigger state based on the judgment result;

[0022] Or,

[0023] In the case of determining a reverse direction fault, determining the third protection action trigger state.

[0024] Preferably, in the case of determining a positive direction fault, judging based on the electrical quantity signal, determining the first protection action trigger state based on the judgment result, comprising:

[0025] In the case of determining a positive direction fault and the current amplitude in the electrical quantity signal being greater than the action current threshold in the adjusted protection setting value set, starting the timing;

[0026] Determining the first protection action trigger state based on the timing result;

[0027] Or,

[0028] In the case of determining a positive direction fault and the current amplitude in the electrical quantity signal being less than or equal to the action current threshold in the adjusted protection setting value set, determining the second protection action trigger state.

[0029] Preferably, the electrical quantity signal of the distributed photovoltaic access point comprises:

[0030] Collecting instantaneous values of three-phase voltage and three-phase current;

[0031] Sampling the instantaneous values of three-phase voltage and three-phase current;

[0032] Pretreating the sampling data, extracting voltage signals and current signals, and the pretreatment comprises filtering and Fourier transform.

[0033] Preferably, further comprising:

[0034] When the communication with the remote control center is interrupted for more than a preset time length, determining that island operation occurs, and actively triggering the protection execution logic to disconnect the distributed photovoltaic from the power distribution network.

[0035] Preferably, the protection setting value set comprises multiple sets of predefined setting value subsets, and the multiple sets of predefined setting value subsets at least comprise: a normal operation setting value set corresponding to a normal operation condition of the power grid; a weak grid operation setting value set corresponding to an increase in equivalent impedance or a decrease in voltage stability of the power grid; adjusting the protection setting value set based on the current operation condition, comprising:

[0036] Receiving a setting value switching instruction issued by the remote control center, and activating the normal operation setting value set or the weak grid operation setting value set as the currently effective protection setting value set.

[0037] Preferably, when the corrected fault direction angle is in the boundary region of the positive direction interval, the ratio of a specific harmonic component to the fundamental component in the fault current is calculated. The boundary region refers to the angle range of -10° to 10° near the threshold of the positive direction interval.

[0038] If the ratio exceeds the preset harmonic threshold, the judgment result is confirmed as a positive direction fault; otherwise, the original judgment result is maintained.

[0039] Secondly, a remotely controllable directional protection power distribution system for distributed photovoltaic systems is provided, the system including:

[0040] Signal acquisition module: used to acquire electrical quantity signals from distributed photovoltaic access points, including at least voltage and current signals;

[0041] Information acquisition module: used to acquire grid synchronization information and adjust the protection setting set based on the current operating conditions of the grid-connected system composed of distributed photovoltaic and distribution network;

[0042] Direction discrimination module: used to determine the direction of the fault based on electrical quantity signals and grid synchronization information, and to determine the direction of the fault point relative to the protection device. The protection device refers to the intelligent protection unit installed at the distributed photovoltaic grid connection point.

[0043] Protection triggering module: used to determine the protection action triggering state based on the direction of the fault point relative to the protection device, electrical quantity signals, and the adjusted protection setting set;

[0044] Protection Execution Module: Used to trigger protection execution logic based on the protection action trigger status. Protection execution logic includes local execution logic and remote control execution logic.

[0045] The solution provided in the second aspect above is used to implement the method provided in the first aspect above, and its specific implementation will not be described in detail here. The technical effects corresponding to any implementation method in the solution provided in the second aspect above can be found in the technical effects corresponding to any implementation method in the first aspect above, and will not be described in detail here.

[0046] It should be noted that any of the possible implementations of any of the above aspects can be combined, provided that the solutions do not contradict each other. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a remotely controllable directional protection power distribution controller for distributed photovoltaic systems provided in an embodiment of this application.

[0049] Figure 2 A schematic flowchart illustrating the remotely controllable directional protection power distribution method for distributed photovoltaic systems provided in this application embodiment;

[0050] Figure 3 This is a schematic diagram of the structure of a remotely controllable directional protection power distribution system for distributed photovoltaic systems provided in an embodiment of this application. Detailed Implementation

[0051] In the embodiments of this application, in order to clearly describe the technical solutions of the embodiments of this application, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different. The technical features described by "first" and "second" have no sequential or size order.

[0052] In the embodiments of this application, the words "exemplarily" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of the words "exemplarily" or "for example" is intended to present the relevant concepts in a specific manner to facilitate understanding.

[0053] In the embodiments of this application, at least one can also be described as one or more, and multiple can be two, three, four or more, and this application does not impose any restrictions.

[0054] Furthermore, the network architecture and scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0055] The solutions provided by the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0056] Figure 1 This is a schematic diagram of the structure of a remotely controllable directional protection power distribution controller for distributed photovoltaic systems provided in an embodiment of this application.

[0057] like Figure 1As shown in the embodiments of this application, the remotely controllable directional protection distribution controller for distributed photovoltaic systems is used to execute any method step in the embodiments of the remotely controllable directional protection distribution method for distributed photovoltaic systems. This controller can be integrated inside the photovoltaic inverter or deployed as an independent intelligent protection terminal device at the distributed photovoltaic grid connection point 100. The controller includes: an electrical quantity acquisition module 101, an adaptive direction discrimination module 102, a collaborative setting and communication management module 103, a comprehensive fault judgment module 104, and a protection execution module 105.

[0058] The distributed photovoltaic grid connection point 100 refers to the physical location and electrical boundary point where the distributed photovoltaic power generation system is electrically connected to the public distribution network. At this point, the electrical energy generated by the distributed photovoltaic system is injected into the distribution network. Simultaneously, this point is also a key node for electricity metering, power quality monitoring, and the implementation of grid protection and control. Specifically, it typically includes one or more circuit breakers for switching circuits on and off, disconnect switches for electrical isolation, and voltage and current transformers for the controller of this application to collect electrical quantity signals. Therefore, this grid connection point is the core location for the protection controller described in this application to perform data acquisition, status judgment, and protection action execution.

[0059] The electrical quantity acquisition module 101 has its input connected to the distributed photovoltaic grid-connected point 100, i.e., the connection point between the photovoltaic inverter output and the distribution bus, for real-time acquisition of the three-phase voltage and three-phase current signals at that point. This module typically includes a voltage transformer, a current transformer, and a high-sampling-rate analog-to-digital converter, responsible for converting the high-voltage, high-current signals from the primary side into digital electrical quantity signals that the protection controller can process. Its output is connected to the adaptive direction discrimination module 102 and the comprehensive fault judgment module 104.

[0060] The collaborative setting and communication management module 103 serves as the interface for information exchange between the controller and the external remote control center 200. This module includes a communication interface unit, such as a communication chip supporting 5G, fiber optic, or power line carrier communication, a setting storage unit, and an instruction processing unit. Its functions include: receiving power grid synchronization information, protection setting set switching instructions, and collaborative control instructions from the remote control center 200; and simultaneously uploading local fault information, alarm signals, and operating status data to the remote control center 200. Its outputs are connected to the adaptive direction discrimination module 102 and the comprehensive fault judgment module 104, respectively, to provide the currently effective protection setting set and collaborative instructions.

[0061] The adaptive direction discrimination module 102 is one of the core computing units of the controller. This module typically consists of a microprocessor and built-in algorithms. It receives digital electrical quantity signals from the electrical quantity acquisition module 101 and grid synchronization information from the coordinated setting and communication management module 103. This module is configured to perform the steps of the method described in claims 2-3, namely, calculating the local power direction angle, correcting it using a remote reference phase angle, and finally outputting an accurate fault direction discrimination result. Its output is connected to the integrated fault judgment module 104.

[0062] The integrated fault judgment module 104 is the decision center of the controller. This module receives the fault direction result from the adaptive direction discrimination module 102, the real-time electrical quantity signal from the electrical quantity acquisition module 101, and the current protection setting set from the collaborative setting and communication management module 103. Based on all the above information, it performs a comprehensive logical judgment to determine the final protection action trigger state. Its output is connected to the protection execution module 105.

[0063] The protection execution module 105 is the final execution unit of the controller. This module receives the protection action trigger status from the integrated fault judgment module 104. When the status is "preparing to trip" and the final execution conditions are met, the module outputs a physical trip signal through its internal drive circuit to control the operation of the grid-connected switching equipment, thereby disconnecting the distributed photovoltaic system from the distribution network. When the status is "alarm," the module sends alarm information to the remote control center 200 through the communication interface.

[0064] Through the coordinated operation of the above modules, the controller in this embodiment of the application realizes remote controllable directional protection for distributed photovoltaic grid-connected points, which solves the problems of poor adaptability, inaccurate judgment and difficulty in coordination of traditional protection methods in distributed power source access scenarios, and significantly improves the safe and stable operation level of the distribution network.

[0065] like Figure 2 As shown in the embodiments of this application, the remotely controllable directional protection power distribution method for distributed photovoltaic systems may include:

[0066] S201: Obtain electrical quantity signals from distributed photovoltaic access points.

[0067] Among them, electrical quantity signals include at least voltage signals and current signals.

[0068] A voltage signal is an electrical signal that reflects the instantaneous change in the AC bus voltage at the grid connection point of a distributed photovoltaic system. It contains key information such as voltage amplitude, frequency, and phase, and serves as a fundamental reference quantity for judging the grid's operating status and identifying the direction of faults.

[0069] The current signal refers to the electrical signal that reflects the instantaneous changes in the alternating current injected into the distribution network by distributed photovoltaic power. It contains information on the amplitude, frequency, and phase of the current. Its magnitude and direction are the core basis for determining the location and nature of the fault, such as a metallic fault or a high-resistance fault, and whether protection actions are triggered.

[0070] In some embodiments, the instantaneous values ​​of three-phase voltage and three-phase current are acquired, the instantaneous values ​​of three-phase voltage and three-phase current are sampled, the sampled data are preprocessed, and voltage and current signals are extracted. The preprocessing includes filtering and Fourier transform.

[0071] Specifically, voltage and current transformers installed at the grid connection point convert the high-voltage signal on the primary side into a low-voltage signal on the secondary side, which is then synchronously sampled by a high-precision analog-to-digital converter at a frequency of not less than 4kHz. This high sampling rate aims to ensure accurate capture of high-order harmonic components generated by the power electronic switching characteristics of the photovoltaic inverter and the rapid transient processes in the early stages of a fault, providing a sufficient data foundation for subsequent accurate analysis. The sampled digital signal first passes through a digital anti-aliasing filter to remove high-frequency noise that may cause spectral aliasing. Subsequently, a Fast Fourier Transform (FFT) algorithm is used to process the filtered data of one or more cycles, decomposing the time-domain signal into a frequency-domain signal. Through FFT, the fundamental phasors of voltage and current can be accurately extracted for traditional power direction calculations; simultaneously, the amplitude and phase of each harmonic component can also be extracted, providing data support for the auxiliary criterion described in claim 10.

[0072] S202: Obtain grid synchronization information and adjust the protection setting set based on the current operating conditions of the grid-connected system composed of distributed photovoltaic and distribution networks.

[0073] The grid synchronization information refers to a set of information provided by the remote control center to ensure that the local protection device maintains time and phase synchronization with the entire power grid reference. It mainly includes a reference phase angle of a stable reference point and a high-precision time synchronization signal, used to correct phase offsets caused by local faults or weak grids, ensuring the accuracy of fault direction determination.

[0074] The current operating condition of the grid-connected system consisting of distributed photovoltaic (PV) power and the distribution network refers to a comprehensive state description that reflects the dynamic interaction between the real-time power generation status of the distributed PV and the structure and operation level of the distribution network. This operating condition is determined by multiple parameters, including network topology changes, PV power output level, and preset operating modes, and is the fundamental basis for determining whether protection settings need to be adjusted.

[0075] The protection setting set includes multiple predefined setting subsets, which include at least: the normal operation setting set corresponding to the normal operation condition of the power grid; and the weak power grid operation setting set corresponding to the increase of the equivalent impedance of the power grid or the decrease of voltage stability.

[0076] In some embodiments, a setting switching instruction issued by a remote control center is received to activate the normal operation setting set or the weak grid operation setting set as the currently effective protection setting set.

[0077] Specifically, the remote control center monitors the entire network's operational status in real time through a wide-area measurement system or a distribution automation system. When a significant change in the network topology is detected, such as a disconnection of the main power supply line leading to a significant increase in the system's equivalent impedance, or a decrease in the system's voltage stability index, the center determines that the grid-connected system has transitioned from normal operating conditions to weak grid operating conditions.

[0078] At this point, the remote control center will generate a concise setpoint switching command, which includes an identifier for the target setpoint. For example, ID=2.

[0079] Upon receiving the instruction via the collaborative setting and communication management module, the local intelligent protection unit immediately retrieves the weak grid operation setting set corresponding to ID=2 from its non-volatile memory. This setting set typically includes more sensitive operating current thresholds and shorter operating delays to adapt to the lower fault current levels characteristic of weak grids, and sets it as the currently effective protection setting set. Conversely, when the grid regains its strength, the remote center issues an instruction to switch back to the normal operating setting set. The entire process is rapid and has low communication overhead, ensuring that the protection strategy can quickly and reliably adapt to macroscopic changes in grid operation.

[0080] S203: Based on electrical quantity signals and grid synchronization information, fault direction is determined to identify the direction of the fault point relative to the protection device.

[0081] Among them, the protection device refers to the intelligent protection unit installed at the grid connection point of the distributed photovoltaic system.

[0082] Specifically, this step aims to address the potential misjudgment of traditional directional protection in scenarios with a high proportion of distributed generation. Traditional methods rely solely on local voltage and current to calculate power direction. However, during faults, especially when photovoltaic inverters provide short-circuit current, the phase of the grid connection voltage can shift significantly, leading to distortion of the locally calculated power direction angle. This invention introduces synchronization information from a grid stability reference point, providing a global, absolute coordinate system unaffected by local fault disturbances for local fault direction determination, thereby greatly improving the accuracy and reliability of the determination.

[0083] In some embodiments, the local power direction angle is calculated based on voltage and current signals. The grid synchronization information sent by the remote control center is received. The grid synchronization information includes the reference phase angle of the stable reference point. The remote control center refers to the grid dispatch control center. The local power direction angle is compared with the reference phase angle to calculate the corrected fault direction angle. The fault direction is determined based on the corrected fault direction angle and the positive direction interval to determine the direction of the fault point relative to the protection device. The positive direction interval refers to the angle range corresponding to the active power flowing from the distributed photovoltaic to the distribution network with the grid connection point voltage phasor as the reference.

[0084] The local power direction angle refers to the angle reflecting the local apparent power direction, calculated solely based on locally acquired voltage and current signals. It is typically determined by calculating the phase difference between the voltage phasor and the current phasor. It can be obtained, but its accuracy will be reduced due to the phase distortion of the grid connection point voltage during a fault.

[0085] The reference phase angle of the stable reference point refers to a reference node in the power grid, provided by the power grid dispatch and control center, that has a stable voltage phase and is unaffected by local faults. This is typically the voltage phasor phase angle of the main substation bus. It provides a unified, high-precision phase reference for the entire regional power grid.

[0086] The corrected fault direction angle refers to the angle that truly reflects the fault direction after correcting the local power direction angle using the reference phase angle. Its calculation logic essentially involves placing the local current phasor in a global coordinate system to determine the direction.

[0087] For example, by calculating the phase difference between the reference phase angle and the local current phasor. This eliminates the error caused by local voltage phase distortion.

[0088] For example, fault direction determination based on the corrected fault direction angle and the positive direction interval means that if the corrected fault direction angle is within the positive direction interval, it is determined to be a positive direction fault; otherwise, it is determined to be a negative direction fault. The fault point of a positive direction fault is in the positive direction relative to the protection device, and the fault point of a negative direction fault is in the negative direction relative to the protection device.

[0089] The "positive direction" refers to the fault point being located "downstream" of the protection device, meaning the fault occurs on the line extending from the distributed photovoltaic grid connection point to the distribution network. In this direction, the fault current flows from the distributed photovoltaic system to the fault point.

[0090] The "opposite direction" refers to a fault location "upstream" of the protection device, meaning the fault occurs elsewhere in the distribution network, and the fault current flows from the distribution network to the distributed photovoltaic grid connection point. In this case, the distributed photovoltaic system should remain connected to the grid to provide support and should not trip.

[0091] In some embodiments, when the corrected fault direction angle is in the boundary region of the positive direction interval, the ratio of a specific harmonic component to the fundamental component in the fault current is calculated. The boundary region refers to the angle range of -10° to 10° near the threshold of the positive direction interval.

[0092] If the ratio exceeds the preset harmonic threshold, the judgment result is confirmed as a positive direction fault; otherwise, the original judgment result is maintained.

[0093] Specifically, this auxiliary criterion aims to address the issue of fluctuating judgment results due to noise interference when the fault direction angle is in the boundary region. Its core principle utilizes the significant difference in harmonic characteristics between the fault current of distributed photovoltaic inverters and traditional synchronous power sources. When a forward fault occurs in the distribution network, the photovoltaic inverter's power electronic switching devices generate characteristic harmonics to provide fault support, especially the second and third harmonic components, which increase significantly. Conversely, during a reverse fault, the current flowing to the photovoltaic system is mainly provided by traditional rotating motors and line impedance, resulting in relatively low harmonic content. Therefore, by detecting harmonic fingerprints, the fault direction can be effectively distinguished.

[0094] The specific calculation process is as follows: First, the amplitude of the fundamental component I1, the amplitude of the second harmonic component I2, and the amplitude of the third harmonic component I3 of the fault current are extracted by Fourier transform; then, the ratios K2 = I2 / I1 and K3 = I3 / I1 are calculated; finally, these two ratios are compared with the preset harmonic threshold. As long as either ratio exceeds the threshold, it can be confirmed that the fault originates from the photovoltaic side, that is, it is determined to be a positive fault.

[0095] The preset harmonic threshold is a numerical boundary used to distinguish between characteristic harmonics of the photovoltaic inverter and background harmonics of the power grid. It is a key parameter to ensure the accuracy of the auxiliary criterion. This threshold is not a fixed value, but is determined through a combination of theoretical analysis, electromagnetic transient simulation, and statistical analysis of on-site fault recording data. Its goal is to maximize the sensitivity of the discrimination while ensuring reliability. For example, through simulations of specific photovoltaic inverter models under various fault conditions, it can be found that their second harmonic content can typically reach more than 15% of the fundamental frequency, while the harmonic content caused by grid-side faults is usually less than 5%. Based on this, the preset harmonic threshold can be set to a specific value between 10% and 20%. This threshold can be embedded in the protection device's program or used as part of the protection settings, remotely configured and optimized by the remote control center according to the actual situation of the photovoltaic power station.

[0096] S204: Determine the protection action trigger state based on the direction of the fault point relative to the protection device, the electrical quantity signal, and the adjusted protection setting set.

[0097] Specifically, the fault direction, electrical quantity characteristics, and currently effective protection strategies are comprehensively and logically judged to ultimately output a clear intermediate decision result that guides the next action.

[0098] The protection action trigger state refers to an intermediate state defined by the internal logic of the protection device, used to characterize the severity of the current fault and the degree to which local protection conditions are met. It is not a final physical action, but a logical state used to drive subsequent protection execution logic. The protection action trigger states defined in this invention include at least "preparing to trip," "normal monitoring," and "alarm," constructing a complete state machine that ensures the rigor and flexibility of protection decisions.

[0099] In some embodiments, if a fault is determined to be in the positive direction, a judgment is made based on electrical quantity signals, and a first protection action trigger state or a second protection action trigger state is determined based on the judgment result; or, if a fault is determined to be in the reverse direction, a third protection action trigger state is determined.

[0100] For example, if a positive fault is determined and the current amplitude in the electrical quantity signal is greater than the operating current threshold in the adjusted protection setting set, timing is started; the trigger state of the first protection action is determined based on the timing result.

[0101] or,

[0102] If the fault is determined to be in the positive direction and the current amplitude in the electrical quantity signal is less than or equal to the operating current threshold in the adjusted protection setting set, the second protection action trigger state is determined.

[0103] Among them, the protection execution logic based on the protection action triggering state refers to: when the protection action triggering state is ready to trip, sending a coordination request containing local fault information to the remote control center and entering the coordination waiting state;

[0104] In the collaborative waiting state, listen for collaborative instructions issued by the remote control center, including executing tripping or prohibiting tripping;

[0105] Upon receiving a trip command, the local execution logic is triggered, and a trip signal is output.

[0106] or,

[0107] If a tripping prohibition command is received, the protection action trigger state is reset and normal monitoring is resumed;

[0108] or,

[0109] If no collaborative instruction is received within the preset collaborative waiting time, the local execution logic is triggered, and a trip signal is output.

[0110] The preset collaborative waiting time refers to a critical time margin reserved for remote collaborative control. This time setting requires a trade-off between the effectiveness of collaborative control and the speed of protection actions. It must be long enough to ensure the remote control center has sufficient time to receive collaborative requests, perform global analysis, and issue instructions; simultaneously, it must be short enough to prevent local protection from losing its speed due to excessive waiting in the event of communication interruption or no response from the remote center, thus preventing the fault from escalating. This time value is typically 100-500 milliseconds and can be configured according to the specific requirements of the power grid for protection speed.

[0111] Among them, the first protection action trigger state is preparing to trip; the first protection action trigger state is normal monitoring; and the third protection action trigger state is alarm.

[0112] Preparing to trip: This state indicates that all the activation conditions of the local protection have been met, and the protection device has the local authority to perform a trip, but the final action is determined by the coordination logic.

[0113] Normal monitoring: This state indicates that although a positive disturbance has been detected, the fault characteristics (such as current amplitude) have not yet reached the action threshold. The system should continue to monitor and this is the default stable state of the protection device.

[0114] Alarm: This status indicates that a reverse fault has been detected. The protection device is strictly prohibited from tripping, but this important event information needs to be reported to the remote center for fault location and system recovery.

[0115] S205: The protection execution logic is triggered based on the protection action trigger state. The protection execution logic includes local execution logic and remote control execution logic.

[0116] Specifically, this step is the final execution stage of the protection decision. Based on the different protection action trigger states determined in S204, it initiates the corresponding execution path and transforms the logical decision into actual physical operation or information interaction.

[0117] The local execution logic refers to the execution mechanism by which the protection device can independently complete protection actions based solely on locally satisfied conditions, without relying on external commands. This is the fundamental guarantee for the security and reliability of the protection system. This logic mainly includes:

[0118] Physical tripping: When the preset final tripping conditions are met, the output relay of the protection device closes and sends a high-level tripping command to the trip coil of the grid-connected circuit breaker, forcibly disconnecting the electrical connection between the distributed photovoltaic system and the distribution network.

[0119] Event logging: At the same time as the protection action is triggered, the fault recording function is activated to record the voltage and current waveforms and the status of all switching quantities for several cycles before and after the fault, providing a basis for post-event analysis.

[0120] Local indication: Illuminate the fault indicator light on the local panel or activate the buzzer to provide intuitive alarm information to on-site maintenance personnel.

[0121] The remote control execution logic refers to the mechanism by which the protection device, after meeting local conditions, determines whether to execute a protection action through collaborative interaction with the remote control center. This is the core of realizing the intelligence and global optimization of the protection system. This logic is mainly activated in the "preparing to trip" state, and its execution flow is as follows:

[0122] Sending a coordination request: After the device enters the "preparing to trip" state, it does not trip immediately, but instead sends a coordination request message containing key information such as fault direction, fault current amplitude, and voltage sag depth to the remote control center through the communication module.

[0123] Waiting for coordination instructions: The device starts a coordination waiting timer and enters listening mode to wait for coordination instructions issued by the remote control center.

[0124] Responding to collaborative commands:

[0125] If a "trip" command is received, the device immediately triggers the local execution logic to perform a physical trip.

[0126] If a "prohibit tripping" command is received, the device will terminate the current tripping process, reset the protection logic state, and return to the "normal monitoring" state.

[0127] Default execution after timeout: If no valid instruction is received within the preset collaborative waiting time, the device will determine that the communication is interrupted or the remote center is not responding. In this case, in order to ensure local security, it will automatically give up waiting and trigger the local execution logic to perform a physical trip.

[0128] like Figure 3 The diagram illustrates a remotely controllable directional protection power distribution system for distributed photovoltaic systems. The system includes:

[0129] Signal acquisition module 301: used to acquire electrical quantity signals of the distributed photovoltaic access point, the electrical quantity signals including at least voltage signals and current signals; Information adjustment module 302: used to acquire grid synchronization information and adjust the protection setting set based on the current operating conditions of the grid-connected system composed of distributed photovoltaic and distribution network.

[0130] Direction discrimination module 303: It is used to perform fault direction discrimination based on electrical quantity signals and grid synchronization information, and determine the direction of the fault point relative to the protection device. The protection device refers to the intelligent protection unit installed at the distributed photovoltaic grid connection point.

[0131] Protection trigger module 304: used to determine the protection action trigger state based on the direction of the fault point relative to the protection device, electrical quantity signals, and the adjusted protection setting set;

[0132] Protection execution module 305: used to trigger protection execution logic based on the protection action trigger state. The protection execution logic includes local execution logic and remote control execution logic.

[0133] This application embodiment can divide the machine vision-based glass edge defect detection system into functional modules according to the above method embodiment. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division; other division methods may be used in actual implementation.

[0134] The method steps in this embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary embodiment couples a storage medium to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. Additionally, the ASIC can reside in a network device. Alternatively, the processor and storage medium can exist as discrete components in the network device. In the above embodiments, implementation can be entirely or partially achieved through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented entirely or partially as a computer program product. A computer program product includes one or more computer programs or instructions. When a computer program or instruction is loaded and executed on a computer, all or part of the processes or functions of the embodiments of this application are performed. The computer may be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user equipment, or other programmable module. The computer program or instructions may be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, a computer program or instructions may be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium may be any available medium that a computer can access, or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; or an optical medium, such as a digital video disc (DVD); or a semiconductor medium, such as a solid-state drive (SSD). The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0135] Since the remotely controllable directional protection power distribution system for distributed photovoltaic power in the embodiments of the present invention can be applied to the above method, the technical effects it can achieve can also be referred to the above method embodiments. The embodiments of the present invention will not be repeated here. The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims. The method steps in this embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. Additionally, the ASIC can reside in a network device. Alternatively, the processor and storage medium can exist as discrete components in the network device. In the above embodiments, implementation can be entirely or partially achieved through software, hardware, firmware, or any combination thereof. When implemented in software, it can be entirely or partially implemented as a computer program product. A computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, all or part of the processes or functions of the embodiments of this application are performed. The computer can be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user equipment, or other programmable module. The computer program or instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another; for example, the computer program or instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. Computer-readable storage media can be any available medium that a computer can access, or a data storage device such as a server or data center that integrates one or more available media.The usable medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; it can also be an optical medium, such as a digital video disc (DVD); or it can be a semiconductor medium, such as a solid-state drive (SSD). The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A remotely controllable directional protection power distribution method for distributed photovoltaic systems, characterized in that, The method includes: Acquire electrical quantity signals from distributed photovoltaic access points, wherein the electrical quantity signals include at least voltage signals and current signals; Obtain grid synchronization information and adjust the protection setting set based on the current operating conditions of the grid-connected system composed of the distributed photovoltaic and distribution network; Based on the electrical quantity signal and the power grid synchronization information, the fault direction is determined to determine the direction of the fault point relative to the protection device. The protection device refers to the intelligent protection unit installed at the distributed photovoltaic grid connection point. Based on the direction of the fault point relative to the protection device, the electrical signal, and the adjusted protection setting set, the protection action trigger state is determined. The protection execution logic is triggered based on the protection action trigger state. The protection execution logic includes local execution logic and remote control execution logic.

2. The method according to claim 1, characterized in that, The step of determining the direction of the fault point relative to the protection device based on the electrical quantity signal and the power grid synchronization information includes: The local power direction angle is calculated based on the voltage and current signals. Receive grid synchronization information sent by a remote control center, wherein the grid synchronization information includes the reference phase angle of a stable reference point, and the remote control center refers to the grid dispatch and control center; The local power direction angle is compared with the reference phase angle to calculate the corrected fault direction angle. Based on the corrected fault direction angle and positive direction interval, the fault direction is determined to determine the direction of the fault point relative to the protection device. The positive direction interval refers to the angle range corresponding to the flow of active power from distributed photovoltaic to the distribution network with the grid connection point voltage phasor as the reference.

3. The method according to claim 2, characterized in that, The step of determining the fault direction based on the corrected fault direction angle and the positive direction interval, and determining the direction of the fault point relative to the protection device, includes: If the corrected fault direction angle is within the positive direction range, it is determined to be a positive direction fault; otherwise, it is determined to be a negative direction fault. The fault point of a positive direction fault is in the positive direction relative to the protection device, and the fault point of a negative direction fault is in the negative direction relative to the protection device.

4. The method according to claim 1, characterized in that, The process of determining the protection action trigger state based on the direction of the fault point relative to the protection device, electrical quantity signals, and the adjusted protection setting set includes: In the case of a positive fault, the electrical quantity signal is used to make a judgment, and the first protection action trigger state or the second protection action trigger state is determined based on the judgment result. or, If the fault is determined to be in the opposite direction, the trigger state of the third protection action is determined.

5. The method according to claim 4, characterized in that, In the case of a determined positive fault, the process of making a judgment based on the electrical quantity signal and determining the trigger state of the first protection action based on the judgment result includes: If a positive fault is determined and the current amplitude in the electrical quantity signal is greater than the operating current threshold in the adjusted protection setting set, the timing is started. The trigger state of the first protection action is determined based on the timing results; or, If a positive fault is determined and the current amplitude in the electrical quantity signal is less than or equal to the operating current threshold in the adjusted protection setting set, the second protection action trigger state is determined.

6. The method according to claim 1, characterized in that, The acquisition of electrical quantity signals from distributed photovoltaic access points includes: Collect instantaneous values ​​of three-phase voltage and three-phase current; The instantaneous values ​​of the three-phase voltage and three-phase current are sampled; The sampled data is preprocessed to extract voltage and current signals. The preprocessing includes filtering and Fourier transform.

7. The method according to claim 1, characterized in that, Also includes: When communication with the remote control center is interrupted for more than a preset time, it is determined that islanding has occurred, and the protection execution logic is actively triggered to disconnect the distributed photovoltaic system from the power distribution network.

8. The method according to claim 1, characterized in that, The protection setting set includes multiple predefined subsets of settings, which at least include: a normal operation setting set corresponding to the normal operating conditions of the power grid; and a weak power grid operation setting set corresponding to an increase in the equivalent impedance of the power grid or a decrease in voltage stability. The protection execution logic is triggered based on the protection action trigger state, and the protection execution logic includes local execution logic and remote control execution logic, including: Upon receiving a setting value switching instruction from the remote control center, activate the normal operation setting value set or the weak grid operation setting value set as the currently effective protection setting value set.

9. The method according to claim 1, characterized in that, Also includes: When the corrected fault direction angle is in the boundary region of the positive direction interval, the ratio of a specific harmonic component to the fundamental component in the fault current is calculated. The boundary region refers to the angle range of -10° to 10° near the threshold of the positive direction interval. If the ratio exceeds the preset harmonic threshold, the judgment result is confirmed as a positive fault; otherwise, the original judgment result is maintained.

10. A remotely controllable directional protection power distribution system for distributed photovoltaic systems, characterized in that, The system includes: Signal acquisition module: used to acquire electrical quantity signals of distributed photovoltaic access points, wherein the electrical quantity signals include at least voltage signals and current signals; Information acquisition module: used to acquire grid synchronization information and adjust the protection setting set based on the current operating conditions of the grid-connected system composed of the distributed photovoltaic and distribution network; Direction determination module: used to determine the direction of the fault based on the electrical quantity signal and the power grid synchronization information, and to determine the direction of the fault point relative to the protection device, wherein the protection device refers to the intelligent protection unit installed at the distributed photovoltaic grid connection point; Protection triggering module: used to determine the protection action triggering state based on the direction of the fault point relative to the protection device, electrical quantity signals, and the adjusted protection setting set; Protection execution module: used to trigger protection execution logic based on the protection action trigger state, the protection execution logic includes local execution logic and remote control execution logic.

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