Fault detection method of grid-connected equipment and power equipment

Abstract

The invention belongs to the technical field of power electronics, and relates to a fault detection method for grid-connected equipment. The method comprises the following steps: taking the number of sampling times of periodically carrying out voltage sampling on a grid-connected port of grid-connected equipment as a judgment basis, and when the number of sampling times is smaller than a first preset number of times and a zero crossing point occurs, if a grid voltage effective value exceeds an overvoltage threshold value, judging that the grid has an overvoltage fault. And when the sampling times are greater than or equal to the first preset times, emptying the sampling times, and continuing sampling. The method provided by the invention can improve the problem that the overvoltage fault of the power grid may be misreported when the power grid is powered off.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and in particular, relates to a fault detection method for grid-connected equipment, power equipment, and a computer-readable storage medium. Background Art

[0002] Power equipment, such as power consumption equipment and power generation equipment, may have two normal operating conditions: grid-connected operation and off-grid operation. When the power equipment is in grid-connected operation, the grid voltage is too high, that is, a grid overvoltage fault occurs, which will damage system components and cause the system to crash. Therefore, quickly and accurately judging the grid overvoltage fault is of great significance for the safe and stable operation of power equipment.

[0003] The conventional grid overvoltage fault judgment method compares the effective value of the grid voltage with the fault threshold. If the effective value of the grid voltage is greater than the fault threshold, an overvoltage fault is reported. However, if the instantaneous value of the voltage at the moment of grid power outage is relatively large, the conventional grid overvoltage fault judgment method may falsely report a grid overvoltage fault, affecting user experience and interfering with fault troubleshooting. Summary of the invention

[0004] The purpose of the present application is to provide a fault detection method for grid-connected equipment, power equipment and computer-readable storage medium, aiming to solve the problem in the related art that the conventional grid overvoltage fault judgment method may falsely report a grid overvoltage fault when the grid is powered off.

[0005] In a first aspect, an embodiment of the present application provides a fault detection method for a grid-connected device, comprising:

[0006] Periodically sampling the voltage of the grid-connected port of the grid-connected device to obtain an instantaneous value of the grid voltage and accumulating the number of sampling times;

[0007] When the sampling number is greater than or equal to a first preset number, clearing the sampling number;

[0008] When the sampling number is less than the first preset number and the instantaneous value of the grid voltage crosses a zero point, calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number;

[0009] When the effective value of the grid voltage is greater than the overvoltage threshold, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

[0010] In one of the embodiments, after calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number, the method further includes:

[0011] When the effective value of the grid voltage is less than or equal to the overvoltage threshold, the sampling times are cleared.

[0012] In one embodiment, the method further comprises:

[0013] When the voltage polarities of two adjacently sampled instantaneous values ​​of the grid voltage are different, it is determined that the instantaneous value of the grid voltage has a zero crossing point.

[0014] In one embodiment, when the voltage polarities of two adjacent grid voltage instantaneous values ​​sampled are different, determining that the grid voltage instantaneous value has a zero crossing point includes:

[0015] When a negative voltage and a positive voltage appear in sequence in two adjacently sampled instantaneous values ​​of the grid voltage, it is determined that the grid voltage has a zero crossing point.

[0016] In one embodiment, disconnecting the grid-connected device from the grid includes:

[0017] The electronic switch that controls the connection between the grid-connected equipment and the grid is disconnected.

[0018] In one of the embodiments, when the effective value of the grid voltage is greater than the overvoltage threshold, determining that an overvoltage fault occurs and disconnecting the grid-connected device from the grid includes:

[0019] When the effective value of the grid voltage is greater than the overvoltage threshold, increasing the number of overvoltage detection times;

[0020] When the increased overvoltage detection number is greater than or equal to the second preset number, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

[0021] In one of the embodiments, after increasing the number of overvoltage detection times, the method further includes:

[0022] When the increased overvoltage detection times is less than the second preset times, the sampling times are cleared.

[0023] In one embodiment, the method further comprises:

[0024] When the sampling number is greater than or equal to the first preset number, the overvoltage detection number is cleared.

[0025] In the second aspect, an embodiment of the present application also provides an energy storage device, including a power conversion circuit, a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the power conversion circuit is connected to a power grid and a processor, and when the processor executes the computer program, the steps of the fault detection method for a grid-connected device as described above are implemented.

[0026] In a third aspect, an embodiment of the present application further provides a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a controller, the steps of the fault detection method for the grid-connected device as described above can be implemented.

[0027] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0028] When the sampling times are less than the first preset times and a zero crossing occurs, if the effective value of the grid voltage exceeds the overvoltage threshold, it is determined to be a grid overvoltage fault. If the sampling times are greater than or equal to the first preset times, the sampling times are cleared and sampling continues.

[0029] When the number of sampling times is less than the first preset number of times, if a zero crossing occurs, it means that the voltage of the grid-connected port is still periodic alternating current, and the grid is not powered off. At this time, if the effective value of the grid voltage exceeds the overvoltage threshold, it means that an overvoltage fault has occurred in the grid. Therefore, after adopting the method provided by the present application, overvoltage detection can be performed when it is determined that the grid is not powered off, thereby improving the problem of false reporting of grid overvoltage faults when the grid is powered off. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the structure of a photovoltaic energy storage system provided in an embodiment of the present application;

[0031] Figure 2 A flowchart of a fault detection method for a grid-connected device provided in one embodiment of the present application;

[0032] Figure 3 A flowchart of a fault detection method for a grid-connected device provided in one embodiment of the present application;

[0033] Figure 4 A schematic diagram of a module of a fault detection device for a grid-connected device provided in one embodiment of the present application;

[0034] Figure 5 A schematic diagram of the structure of an electric power device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0038] Electrical equipment such as general household electrical equipment, industrial electrical equipment, energy storage equipment or power conversion devices with power conversion circuits, power generation equipment such as photovoltaic power generation (grid-connected) equipment, wind power generation equipment, fuel power generation equipment, etc. Figure 1 The general photovoltaic grid-connected system shown includes a photovoltaic panel (PV) 11, an inverter 12 and a battery module 13. The battery module 13 may include one or more battery packs. The PV input port of the inverter 12 is connected to the photovoltaic panel 11, the DC bus of the inverter 12 is connected to the battery module 13, and the AC end of the inverter 12 is externally connected to the power grid and / or the load. Generally, the AC end of the inverter 12 is provided with a first electronic switch S1, which is used to control the photovoltaic grid-connected system to switch between off-grid and on-grid. The AC end of the inverter 12 is also provided with a second electronic switch S2, which is used to control the connection and disconnection of the photovoltaic grid-connected system and the load. Generally, data interaction can be carried out between different devices through wired communication and / or wireless communication, for example, data is transmitted through communication methods such as CAN (Controller Area Network) bus.

[0039] When the photovoltaic grid-connected system is in grid-connected operation, if a grid overvoltage fault occurs, it will cause damage to system components and cause the system to crash. Therefore, it is of great significance to quickly and accurately determine the grid overvoltage fault for the safe and stable operation of the photovoltaic grid-connected system. The conventional grid overvoltage fault judgment method compares the effective value of the grid phase voltage with the overvoltage threshold. If the effective value of the grid phase voltage is greater than the overvoltage threshold (for example, 1.2*U, U is the rated grid voltage effective value), an overvoltage fault is reported.

[0040] However, under certain working conditions, when the grid is powered off, the voltage at the grid-connected port of the photovoltaic grid-connected system (for example, the end of the first electronic switch S1 connected to the grid) will not decay to 0 immediately, but will slowly decay from the instantaneous value at the time of power failure. Figure 2 , if the instantaneous voltage value at the time of power failure is relatively large, for example, at the time of the voltage peak at 90° of the A-phase grid voltage phase ( Figure 2 At the moment corresponding to the dotted line in the middle), the grid is powered off. Due to the effect of the hardware discharge circuit, the grid voltage after the power failure presents a DC decay form. Assuming that the decay effect is ignored, the voltage change of phase A in a short period of time will be as follows: Figure 2 The voltage of phase B and phase C will change as shown by the red line, and the voltage of phase B and phase C will change as shown by the blue line. Assuming that the attenuation effect is ignored, Figure 2 It can be seen that the moment of power outage in the power grid is random. If the phase A voltage starts to decay from the peak value 1.414*U (assuming that U is the effective value of the grid voltage when the power grid is working normally) after the power outage, the effective value of the grid voltage calculated by sampling the phase A of the grid-connected port after the power outage is 1.414*U, which exceeds the grid overvoltage fault threshold and will cause a false alarm of the grid overvoltage fault, affecting the user experience and interfering with fault troubleshooting.

[0041] In view of the above defects, this application proposes a fault detection method for a grid-connected device, wherein the grid-connected device may be a photovoltaic grid-connected system, an energy storage device with a power conversion circuit, or a power conversion device. Figure 3 , a fault detection method for a grid-connected device provided in an embodiment of the present application includes:

[0042] Step S110, periodically sampling the voltage of the grid-connected port of the grid-connected device to obtain the instantaneous value of the grid voltage and accumulating the number of sampling times.

[0043] Combination Figure 1 The grid-connected device is, for example, a photovoltaic energy storage device, and its grid-connected port, namely, one end of the first electronic switch S1 connected to the grid, can sample the grid voltage through a grid voltage acquisition device (such as a voltage sensor).

[0044] Each time the grid voltage is sampled, the sampling times may be increased by 1, thereby accumulating the sampling times.

[0045] For example, when the grid voltage is normal, assuming that the grid voltage cycle is 50 Hz (Hertz), the sampling cycle of the grid voltage sampling device is 20 kHz. Then, the number of samplings per grid voltage cycle is approximately: 20000 / 50=about 400. That is, when the grid voltage is normal, the grid-connected port will be sampled 400 times per grid voltage cycle, and the number of samplings will increase by 400 cumulatively.

[0046] Step S120, when the sampling times are greater than or equal to the first preset times, clear the sampling times.

[0047] In the embodiment of the present application, the detection of the zero crossing point can be used as a signal of the end of the grid voltage cycle. When the current grid voltage cycle ends, that is, when the zero crossing point is detected, the grid voltage effective value corresponding to the current grid voltage cycle is calculated.

[0048] However, in the scenario of abnormal grid voltage, such as when the grid is powered off, the grid voltage decays in a DC manner and no longer has a zero crossing. In such scenarios, the detection of a zero crossing cannot be used as a signal for the end of the grid voltage cycle. Therefore, a first preset number of times can be set, and when the number of samplings is greater than or equal to the first preset number of times, the current grid voltage cycle is deemed to have ended, the number of samplings can be cleared, and the execution returns to step S110 to continue voltage sampling and cumulative sampling times for the next grid voltage cycle.

[0049] Among them, the first preset number of times can be set according to actual needs. For example, the first preset number of times can be greater than or equal to the number of sampling times in a normal grid voltage cycle. Taking the above-mentioned sampling of 400 times in a grid voltage cycle as an example, the first preset number of times can be set to 400, or greater than 400, such as 500. This application does not limit the specific value of the first preset number of times.

[0050] Step S130, when the sampling number is less than the first preset number and the instantaneous value of the grid voltage crosses a zero point, calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number.

[0051] The sampling times are less than the first preset times, and the instantaneous value of the grid voltage crosses zero, indicating that the voltage of the grid-connected port is still periodic alternating current, and the grid has not experienced a disconnection. Therefore, the overvoltage fault judgment process can be entered to calculate the effective value of the grid voltage, and determine whether the grid voltage has an overvoltage fault based on the effective value of the grid voltage.

[0052] Step S140: When the effective value of the grid voltage is greater than the overvoltage threshold, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

[0053] After calculating the effective value of the grid voltage, the effective value of the grid voltage can be compared with a preset overvoltage threshold. When the effective value of the grid voltage is greater than the overvoltage threshold, it can be determined that an overvoltage fault has occurred, and the connection between the grid-connected device and the grid should be disconnected in time.

[0054] The above-mentioned overvoltage threshold can be set according to the needs of the actual scenario. For example, assuming that the power grid is normal and the effective value of the grid voltage is 220V, the overvoltage threshold can be obtained by adding a preset value or multiplying by a preset proportional coefficient on the basis of 220V, or the overvoltage threshold can also be an empirical value greater than 220V. For example, in one scenario, the overvoltage threshold can be set to 30V greater than 220V, that is, 250V; in another scenario, the overvoltage threshold can be set to 1.2 times of 220V, that is, 265V; in another scenario, the overvoltage threshold can be 260V set according to experience; and so on. The embodiment of the present application does not limit the specific setting method of the overvoltage threshold.

[0055] Among them, disconnecting the connection between the grid-connected device and the power grid can be controlling the above-mentioned first electronic switch S1 to be disconnected, or it can also simultaneously control the power circuit of the grid-connected device and the power grid to stop the transmission of electrical signals, so that the grid-connected device no longer draws power from the power grid or feeds power to the power grid, thereby avoiding the abnormal power grid affecting the operation of the grid-connected device and causing unnecessary damage.

[0056] According to the technical solution of the embodiment of the present application, when the number of sampling times is less than the first preset number of times, if a zero crossing occurs, it indicates that the voltage of the grid-connected port is still periodic alternating current, and the grid has not been powered off. At this time, if the effective value of the grid voltage exceeds the overvoltage threshold, it indicates that an overvoltage fault has occurred in the grid. Therefore, after adopting the method provided by the present application, overvoltage detection can be performed when it is determined that the grid is not powered off, thereby improving the problem that a grid overvoltage fault may be falsely reported when the grid is powered off.

[0057] In some embodiments, in step S130, the effective value of the grid voltage (specifically: the effective value of the single-phase grid voltage or the effective value of the voltage of any phase of the three-phase grid) is calculated based on the instantaneous value of the grid voltage corresponding to the sampling number, and the instantaneous value of the grid voltage corresponding to the sampling number specifically refers to the instantaneous value of the grid voltage obtained by each sampling in the sampling number. The effective value of the grid voltage can be calculated according to the following formula:

[0058]

[0059] Among them, U is the effective value of the grid voltage, U i is the instantaneous value of the grid voltage sampled for the i-th time, N is the number of sampling times, and i is a positive integer less than or equal to N.

[0060] In some embodiments, after calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number in step S130, the method further includes: when the effective value of the grid voltage is less than or equal to the overvoltage threshold, clearing the sampling number.

[0061] Among them, the effective value of the grid voltage is less than or equal to the overvoltage threshold value, indicating that no overvoltage fault has occurred. Therefore, the sampling times can be cleared and the process returns to step S110 to continue voltage sampling and cumulative sampling times for the next grid voltage cycle.

[0062] When the grid voltage (for example, a single-phase grid voltage or one phase voltage of a three-phase grid voltage) changes in a sinusoidal wave, the magnitude and direction (i.e., polarity) change periodically over time, and each grid voltage cycle has at least two zero crossing points. Therefore, in some embodiments, the fault detection method further includes:

[0063] When the voltage polarities of two adjacently sampled instantaneous values ​​of the grid voltage are different, it is determined that the instantaneous value of the grid voltage has a zero crossing point.

[0064] A periodic sine wave has at least two zero crossings in one cycle, including a positive zero crossing and a negative zero crossing. For each zero crossing, the voltage polarities on both sides of the zero crossing are different. Therefore, if the voltage polarity of the instantaneous value of the grid voltage changes between two adjacent samplings, it indicates that a zero crossing has occurred, thereby determining that the grid is not disconnected and continuing to perform overvoltage fault judgment.

[0065] In some embodiments, when the voltage polarities of two adjacent grid voltage instantaneous values ​​sampled are different, determining that the grid voltage instantaneous value has a zero crossing point includes:

[0066] When a negative voltage and a positive voltage appear in sequence in two adjacent instantaneous values ​​of the grid voltage sampled, it is determined that the grid voltage has a zero crossing point.

[0067] The sampled instantaneous values ​​of the adjacent grid voltages are negative and positive in turn, that is, the voltage polarities are different. It can be determined that a zero crossing occurs, and the zero crossing is a positive zero crossing, indicating that the grid is not disconnected and the overvoltage fault judgment can continue.

[0068] Accordingly, in some embodiments, when the voltage polarities of two adjacent grid voltage instantaneous values ​​sampled are different, determining that the grid voltage instantaneous value has a zero crossing point includes:

[0069] When a positive voltage and a negative voltage appear in sequence in two adjacent instantaneous values ​​of the grid voltage sampled, it is determined that the grid voltage has a zero crossing point.

[0070] The sampled instantaneous values ​​of the adjacent grid voltages appear positive voltage and negative voltage in turn, that is, the voltage polarities are different. It can be determined that a zero crossing point occurs, and the zero crossing point is a negative zero crossing point, indicating that the grid is not disconnected and the overvoltage fault judgment can continue to be performed.

[0071] Correspondingly, when the sampling number is less than the first preset number and the instantaneous value of the grid voltage crosses a zero point, the effective value of the grid voltage is calculated based on the instantaneous value of the grid voltage corresponding to the sampling number. This can be understood as calculating the effective value of the grid voltage when any zero crossing occurs, or it can be understood as calculating the effective value of the grid voltage only when a positive zero crossing or a negative zero crossing is detected.

[0072] In some embodiments, disconnecting the grid-connected device from the grid in step S140 includes: controlling an electronic switch connecting the grid-connected device to the grid to disconnect.

[0073] See also Figure 1 The electronic switch is the first electronic switch S1, which may be a relay, a contactor, an isolating switch, etc. The grid-connected device is disconnected from the grid through a reliable electronic switch to prevent the abnormal grid from affecting the operation of the grid-connected device and causing unnecessary damage.

[0074] In order to avoid the instantaneous surge voltage that the grid-connected equipment can withstand due to external reasons in the grid causing an overvoltage fault, the embodiment of the present application also provides a more specific overvoltage fault judgment strategy. In some embodiments, step S140 includes:

[0075] When the effective value of the grid voltage is greater than the overvoltage threshold, the number of overvoltage detections is increased.

[0076] In actual applications, the number of overvoltage detections can be increased within the tolerance range of the grid-connected equipment. When the effective value of the grid voltage is detected to be greater than the overvoltage threshold for multiple consecutive times, it is confirmed that the grid voltage has an overvoltage fault.

[0077] The overvoltage detection number is used to indicate the number of times the effective value of the grid voltage is detected to be overvoltage.

[0078] After detecting that the effective value of the grid voltage is greater than the overvoltage threshold, the number of overvoltage detections may be increased. For example, after detecting that the effective value of the grid voltage is greater than the overvoltage threshold, the number of overvoltage detections may be increased by 1, or by other values.

[0079] When the increased number of overvoltage detection times is greater than or equal to the second preset number, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

[0080] In actual applications, when the increased overvoltage detection times reaches a preset second preset number of times, an overvoltage fault is determined to have occurred, and the connection between the grid-connected device and the grid is disconnected to prevent the abnormal grid from affecting the operation of the grid-connected device and causing unnecessary damage.

[0081] The second preset number of times can be set according to actual needs. For example, the second preset number of times can be set to 3 times, 4 times, 5 times, etc., and this application is not limited to this.

[0082] In some embodiments, after increasing the number of overvoltage detection times in step S140, the method further includes: when the increased number of overvoltage detection times is less than a second preset number, clearing the sampling times.

[0083] Among them, the increased overvoltage detection number is less than the second preset number, indicating that it has not yet been fully determined whether an overvoltage fault has occurred. Therefore, the sampling number is cleared and the process returns to step S110 to continue voltage sampling and cumulative sampling times for the next grid voltage cycle.

[0084] In some embodiments, the fault detection method for grid-connected equipment further includes: when the sampling number is greater than or equal to a first preset number, clearing the overvoltage detection number.

[0085] When the sampling times are greater than or equal to the first preset times, since the zero crossing point has not been detected, it means that the voltage of the grid-connected port may no longer be periodic AC power, and grid abnormalities such as power outages may occur. In this case, if overvoltage detection is performed, false alarms may occur. Therefore, in this case, overvoltage detection can be stopped and the number of overvoltage detections can be cleared to avoid the accumulation of overvoltage detection times in different periods, which may lead to false alarms of overvoltage faults.

[0086] Similarly, in some embodiments, after calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling times, if the effective value of the grid voltage is less than or equal to the overvoltage threshold, it indicates that no overvoltage fault has occurred. At this time, in addition to clearing the sampling times, the overvoltage detection times can also be counted and the overvoltage detection times can be re-accumulated to reduce the occurrence of false overvoltage faults.

[0087] See also Figure 4 , an embodiment of the present application further provides a fault detection device for a grid-connected device, comprising:

[0088] The sampling module 401 is used to periodically sample the voltage of the grid-connected port of the grid-connected device to obtain the instantaneous value of the grid voltage and accumulate the number of sampling times;

[0089] A processing module 402, configured to clear the sampling times when the sampling times are greater than or equal to a first preset times;

[0090] A calculation module 403, configured to calculate the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number when the sampling number is less than the first preset number and the instantaneous value of the grid voltage crosses a zero point;

[0091] The control module 404 is used to determine that an overvoltage fault occurs and disconnect the grid-connected device from the grid when the effective value of the grid voltage is greater than the overvoltage threshold.

[0092] In some embodiments, the processing module 402 is further configured to: clear the sampling times when the effective value of the grid voltage is less than or equal to the overvoltage threshold.

[0093] In some embodiments, the control module 404 is further configured to determine that a zero-crossing point occurs in the instantaneous value of the grid voltage when the voltage polarities of two adjacent instantaneous values ​​of the grid voltage sampled are different.

[0094] In some embodiments, the control module 404 is further configured to determine that the grid voltage has a zero crossing when a negative voltage and a positive voltage appear in sequence in two adjacent instantaneous values ​​of the grid voltage sampled.

[0095] In some embodiments, the control module 404 controls the disconnection between the grid-connected device and the grid, specifically: controls the disconnection of the electronic switch connecting the grid-connected device and the grid.

[0096] In some embodiments, the control module 404 includes:

[0097] A first control submodule, configured to increase the number of overvoltage detection times when the effective value of the grid voltage is greater than the overvoltage threshold;

[0098] The second control submodule is used to determine that an overvoltage fault occurs and disconnect the grid-connected device from the grid when the increased number of overvoltage detection times is greater than or equal to a second preset number.

[0099] In some embodiments, the processing module 402 is further configured to clear the sampling times when the increased overvoltage detection times is less than a second preset times.

[0100] In some embodiments, the processing module 402 is further configured to clear the overvoltage detection times when the sampling times are greater than or equal to a first preset times.

[0101] For the specific implementation of the fault detection device for grid-connected equipment and the description of related beneficial effects, please refer to the description of the specific embodiment of the fault detection method for grid-connected equipment mentioned above, which will not be repeated here.

[0102] See also Figure 5 The embodiment of the present application also provides an electric power device 50, which includes a power conversion circuit 51, a memory 52, a processor 53, and a computer program 521 stored in the memory 52 and executable on the processor 53. The power conversion circuit 51 is connected to the power grid and the processor 53. When the processor 53 executes the computer program 521, the steps of the fault detection method for the grid-connected device as described above are implemented.

[0103] It is understandable that the power device 50 may be a separate power device, or may be an energy storage converter having a battery module 13 , or may include a plurality of energy storage converters having battery modules 13 .

[0104] It can be understood that in some embodiments, the power generation equipment can be a photovoltaic panel. In this case, the power conversion circuit 51 can include a buck-boost circuit, a DC bus, and a bidirectional inverter circuit for realizing maximum power tracking of the photovoltaic panel. The input end of the buck-boost circuit forms the PV input end of the power device 50, and the battery module 13 is connected to the DC bus.

[0105] Those skilled in the art will understand that Figure 5This is merely an example of the power device 50 and does not constitute a limitation on the power device 50 . The power device 50 may include more or fewer components than shown in the figure, or a combination of certain components, or different components, such as input and output devices, network access devices, etc.

[0106] The processor 53 may be a central processing unit (CPU), or may be other general controllers, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general controller may be a microcontroller or any conventional controller.

[0107] In some embodiments, the memory 52 may be an internal storage unit of the power device 50, such as a hard disk or memory of the power device 50. In other embodiments, the memory 52 may also be an external storage device of the power device 50, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the power device 50. Further, the memory 52 may also include both an internal storage unit of the power device 50 and an external storage device. The memory 52 is used to store an operating system, an application program, a boot loader, data, and other programs. The memory 52 may also be used to temporarily store data that has been output or is to be output.

[0108] The embodiment of the present application further provides a computer-readable storage medium, which stores a computer program 521. When the computer program 521 is executed by the processor 53, the steps in the above-mentioned method embodiments can be implemented.

[0109] An embodiment of the present application provides a computer program product, which, when executed on a computer, enables the computer to execute the steps in the above-mentioned method embodiments.

[0110] If the integrated unit is implemented in the form of 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 present application implements all or part of the processes in the above method embodiments, which can be completed by instructing the relevant hardware through a computer program 521. The computer program 521 can be stored in a computer-readable storage medium. When the computer program 521 is executed by the processor 53, the steps of the above method embodiments can be implemented. Among them, the computer program 521 includes a computer program 521 code, and the computer program 521 code can be in source code form, object code form, executable file or some intermediate form. The computer readable medium may at least include: any entity or device that can carry the computer program 521 code to the camera device / terminal device, a recording medium, a computer memory 52, a ROM (Read-Only Memory, read-only memory 52), a RAM (Random Access Memory, random access memory 52), a CD-ROM (Compact Disc Read-Only Memory, read-only optical disc), a magnetic tape, a floppy disk and an optical data storage device. The computer-readable storage medium mentioned in the present application may be a non-volatile storage medium, in other words, a non-transitory storage medium.

[0111] It should be understood that all or part of the steps to implement the above embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program 521 product. The computer program 521 product includes one or more computer instructions. The computer instructions can be stored in the above-mentioned computer readable storage medium.

[0112] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0113] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0114] In the embodiments provided in the present application, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely schematic. For example, the division of modules or units is only a logical function division. There may be other division methods in actual implementation, 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 through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0115] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0116] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A fault detection method for a grid-connected device, characterized in that: include: Periodically sampling the voltage of the grid-connected port of the grid-connected device to obtain an instantaneous value of the grid voltage and accumulating the number of sampling times; When the sampling number is greater than or equal to a first preset number, clearing the sampling number; When the sampling number is less than the first preset number and the instantaneous value of the grid voltage crosses a zero point, calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number; When the effective value of the grid voltage is greater than the overvoltage threshold, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

2. The fault detection method according to claim 1, characterized in that: After calculating the effective value of the grid voltage based on the instantaneous value of the grid voltage corresponding to the sampling number, the method further includes: When the effective value of the grid voltage is less than or equal to the overvoltage threshold, the sampling times are cleared.

3. The fault detection method according to claim 1, characterized in that: The method further comprises: When the voltage polarities of two adjacently sampled instantaneous values ​​of the grid voltage are different, it is determined that the instantaneous value of the grid voltage has a zero crossing point.

4. The fault detection method according to claim 3, characterized in that: When the voltage polarities of two adjacent grid voltage instantaneous values ​​sampled are different, determining that the grid voltage instantaneous value has a zero crossing point comprises: When a negative voltage and a positive voltage appear in sequence in two adjacently sampled instantaneous values ​​of the grid voltage, it is determined that the grid voltage has a zero crossing point.

5. The fault detection method according to claim 1, characterized in that: The disconnecting of the grid-connected device from the grid comprises: The electronic switch that controls the connection between the grid-connected equipment and the grid is disconnected.

6. The fault detection method according to claim 1, characterized in that: When the effective value of the grid voltage is greater than the overvoltage threshold, determining that an overvoltage fault occurs and disconnecting the grid-connected device from the grid includes: When the effective value of the grid voltage is greater than the overvoltage threshold, increasing the number of overvoltage detection times; When the increased overvoltage detection number is greater than or equal to the second preset number, it is determined that an overvoltage fault occurs, and the connection between the grid-connected device and the grid is disconnected.

7. The fault detection method according to claim 6, characterized in that: After increasing the number of overvoltage detection times, the method further includes: When the increased overvoltage detection times is less than the second preset times, the sampling times are cleared.

8. The fault detection method according to claim 6, characterized in that: The method further comprises: When the sampling number is greater than or equal to the first preset number, the overvoltage detection number is cleared.

9. An electric power device, characterized in that: The invention comprises a power conversion circuit, a memory, a processor and a computer program stored in the memory and executable on the processor. The power conversion circuit is connected to a power grid and the processor. When the processor executes the computer program, the steps of the fault detection method for a grid-connected device as claimed in any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by the controller, the steps of the fault detection method for a grid-connected device as claimed in any one of claims 1 to 8 can be implemented.

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