Fault determination method and device, three-phase power converter and power system

Abstract

The invention discloses a fault determination method and device, a three-phase power converter and a power system.The fault determination method comprises the steps that the terminal temperature of each phase of alternating current wiring terminal of the three-phase power converter is obtained; according to the terminal temperature of each phase of AC wiring terminal, determining a temperature difference value between each two-phase AC wiring terminal; determining whether the three-phase power converter meets a preset virtual connection fault condition or not according to the determined temperature difference value between the two-phase AC wiring terminals; wherein the preset virtual connection fault condition comprises that a temperature difference value between any two phases of AC wiring terminals is greater than a preset temperature difference threshold value. According to the method, whether the virtual connection fault occurs in the three-phase power converter or not can be identified in advance through the temperature difference value between the two-phase alternating current wiring terminals of the three-phase power converter, so that the timeliness of fault identification is improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a fault determination method, apparatus, three-phase power converter and power system. Background Technology

[0002] As a core component of power generation, the electrical safety, fire safety, and equipment quality safety of photovoltaic inverters are of paramount importance. To ensure the electrical safety of photovoltaic inverters, related technologies employ measures such as overload protection, short-circuit protection, and over-temperature protection. While these protective measures can guarantee electrical safety, they are somewhat delayed for certain faults that do not exhibit obvious electrical characteristics in their early stages. For example, if there are problems such as loose connections, poor contact, or loose connections in the AC terminals on the AC side, overcurrent or overload protection will not be triggered in the initial stage of the loose connection. However, the inverter is already in a faulty state. If grid connection is attempted under fault conditions, it will pose a safety risk, thereby affecting the reliability of the photovoltaic system. Summary of the Invention This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose a fault determination method that identifies in advance whether a three-phase power converter has a loose connection fault by using the temperature difference between the AC terminals of each pair of phases, thereby improving the timeliness of fault identification.

[0003] A second objective of this invention is to provide a computer-readable storage medium.

[0004] The third objective of this invention is to provide a three-phase power converter.

[0005] The fourth objective of this invention is to provide a fault determination device.

[0006] The fifth objective of this invention is to provide an electric power system.

[0007] To achieve the above objectives, a fault determination method is proposed according to a first aspect of the present invention, comprising: acquiring the terminal temperature of each phase AC terminal of a three-phase power converter; determining the temperature difference between any two phase AC terminals based on the terminal temperatures of each phase AC terminal; determining whether the three-phase power converter meets a preset intermittent connection fault condition based on the determined temperature difference between any two phase AC terminals; wherein the preset intermittent connection fault condition includes: the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0008] According to the fault determination method of this invention, the terminal temperature of each phase AC terminal of a three-phase power converter is obtained, and the temperature difference between any two phase AC terminals is determined based on the terminal temperatures of each phase AC terminal. Furthermore, the method determines whether the three-phase power converter meets a preset intermittent connection fault condition based on the determined temperature difference between any two phase AC terminals. The preset intermittent connection fault condition includes: the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold. Therefore, by using the temperature difference between any two phase AC terminals of the three-phase power converter, it is possible to identify in advance whether an intermittent connection fault has occurred in the three-phase power converter, thereby solving the problem of safety risks to the three-phase power converter caused by the lag in detection methods in related technologies, and thus improving the reliability of the photovoltaic system.

[0009] According to one embodiment of the present invention, determining whether a three-phase power converter meets the condition for a loose connection fault based on the determined temperature difference between each two-phase AC terminal block includes: determining the maximum temperature difference value based on the determined temperature difference between each two-phase AC terminal block; determining whether the three-phase power converter meets the condition for a loose connection fault based on the maximum temperature difference value; wherein, the preset condition for a loose connection fault further includes: the maximum temperature difference value is greater than a preset temperature difference threshold.

[0010] According to one embodiment of the present invention, determining whether a three-phase power converter meets the condition for a loose connection fault based on the determined temperature difference between each pair of AC terminals includes: determining whether the three-phase power converter meets the condition for a loose connection fault based on the terminal temperature of each phase AC terminal and the determined temperature difference between each pair of AC terminals; wherein, the preset condition for a loose connection fault further includes: the terminal temperature of any phase AC terminal is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0011] According to one embodiment of the present invention, determining whether a three-phase power converter meets the conditions for a loose connection fault based on the terminal temperature of each phase AC terminal and the determined temperature difference between any two phase AC terminals includes: determining the maximum terminal temperature based on the terminal temperature of each phase AC terminal; determining whether the three-phase power converter meets the conditions for a loose connection fault based on the maximum terminal temperature and the determined temperature difference between any two phase AC terminals; wherein the preset loose connection fault conditions further include: the maximum terminal temperature is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0012] According to one embodiment of the present invention, determining whether a three-phase power converter meets the conditions for a loose connection fault based on the terminal temperatures of each phase AC terminal and the determined temperature difference between each pair of phase AC terminals includes: determining the maximum terminal temperature based on the terminal temperatures of each phase AC terminal; determining the maximum temperature difference based on the determined temperature difference between each pair of phase AC terminals; and determining whether the three-phase power converter meets the conditions for a loose connection fault based on the maximum terminal temperature and the maximum temperature difference. The preset loose connection fault conditions further include: the maximum terminal temperature is greater than a preset temperature threshold, and the maximum temperature difference is greater than a preset temperature difference threshold.

[0013] According to one embodiment of the present invention, the method further includes: determining a preset temperature threshold based on the current operating state of the three-phase power converter.

[0014] According to one embodiment of the present invention, determining a preset temperature threshold based on the current operating state of a three-phase power converter includes: determining a normal terminal temperature based on at least one of the current current and current power of the three-phase power converter; and determining the preset temperature threshold based on the normal terminal temperature and a preset margin.

[0015] According to one embodiment of the present invention, determining the normal terminal temperature based on at least one of the current current and the current power of the three-phase power converter includes: determining the terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determining the terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determining a first terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions and a second terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions, and determining the smaller value of the first terminal temperature and the second terminal temperature as the normal terminal temperature.

[0016] According to one embodiment of the present invention, the method further includes: issuing a fault alarm message when it is determined that the three-phase power converter meets the conditions for a virtual connection fault.

[0017] According to one embodiment of the present invention, a three-phase power converter includes a plurality of temperature sensing elements, each of which is used to detect the temperature of the conductive layer of a phase AC terminal. The method of obtaining the terminal temperature of each phase AC terminal of the three-phase power converter includes: determining the terminal temperature of each phase AC terminal based on the temperature sensing information of each temperature sensing element.

[0018] According to one embodiment of the present invention, each temperature sensing element is disposed on the conductive layer of a phase AC terminal.

[0019] According to one embodiment of the present invention, each temperature sensing element is disposed on the AC junction box of a three-phase power converter to detect the temperature around the conductive layer of one phase AC terminal.

[0020] According to one embodiment of the present invention, each temperature sensing element is disposed on the surface of a circuit board and is disposed corresponding to a conductive layer of an AC terminal; wherein, at least one layer of the circuit board is provided with a conductive layer of at least one AC terminal.

[0021] According to one embodiment of the present invention, the conductive layer is a copper-clad layer.

[0022] To achieve the above objectives, a computer-readable storage medium is provided according to a second aspect of the present invention, having stored thereon a computer program that, when processed by a processor, executes the fault determination method of any of the foregoing embodiments.

[0023] According to the computer-readable storage medium of the present invention, by executing the computer program of the above-described fault determination method, the temperature difference between the AC terminals of each two phases of the three-phase power converter can be used to identify in advance whether a loose connection fault has occurred in the three-phase power converter. This solves the problem that the detection method in the related art has a lag, which leads to a safety risk in the three-phase power converter, and thus improves the reliability of the photovoltaic system.

[0024] To achieve the above objectives, a three-phase power converter is proposed according to a third aspect of the present invention, including a memory, a processor, and a fault determination program stored in the memory and executable on the processor. When the processor executes the fault detection program, it implements the fault determination method of any of the foregoing embodiments.

[0025] According to an embodiment of the present invention, the three-phase power converter, by executing the above-described fault determination method program through a processor, can identify in advance whether a loose connection fault has occurred in the three-phase power converter by using the temperature difference between the AC terminals of each two phases of the three-phase power converter. This solves the problem of safety risks to the three-phase power converter caused by the lag in the detection method in related technologies, thereby improving the reliability of the photovoltaic system.

[0026] To achieve the above objectives, a fault determination device is provided according to a fourth aspect of the present invention, comprising: an acquisition module for acquiring the terminal temperature of each phase AC terminal of a three-phase power converter; a first determination module for determining the temperature difference between any two phase AC terminals based on the terminal temperatures of each phase AC terminal; and a second determination module for determining whether the three-phase power converter meets a preset intermittent connection fault condition based on the determined temperature difference between any two phase AC terminals; wherein the preset intermittent connection fault condition includes: the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0027] According to an embodiment of the present invention, the fault determination device acquires the terminal temperature of each phase AC terminal of a three-phase power converter through an acquisition module, determines the temperature difference between any two phase AC terminals based on the terminal temperatures of each phase AC terminal through a first determination module, and determines whether the three-phase power converter meets a preset intermittent connection fault condition based on the determined temperature difference between any two phase AC terminals through a second determination module. The preset intermittent connection fault condition includes: the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold. Therefore, by using the temperature difference between any two phase AC terminals of the three-phase power converter, it is possible to identify in advance whether an intermittent connection fault has occurred in the three-phase power converter, thereby solving the problem of safety risks to the three-phase power converter caused by the lag in detection methods in related technologies, and thus improving the reliability of the photovoltaic system.

[0028] To achieve the above objectives, a power system is provided according to a fifth aspect embodiment of the present invention, comprising: the aforementioned three-phase power converter, or the aforementioned fault determination device.

[0029] According to the power system of the present invention, by employing the power converter or fault determination device described above, the temperature difference between the AC terminals of each two phases of the three-phase power converter can be used to identify in advance whether a loose connection fault has occurred in the three-phase power converter. This solves the problem of safety risks to the three-phase power converter caused by the lag in the detection method in the related technology, thereby improving the reliability of the photovoltaic system.

[0030] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a fault determination method according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating a fault determination method according to another embodiment of the present invention; Figure 3 These are curves showing the terminal temperatures corresponding to different power levels according to an embodiment of the present invention; Figure 4 These are curves showing the terminal temperatures corresponding to different current levels according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a first mounting position of a temperature sensing element according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a second mounting position of a temperature sensing element according to an embodiment of the present invention; Figure 7 This is a schematic diagram of a third mounting position of a temperature sensing element according to an embodiment of the present invention; Figure 8 This is a system schematic diagram of a three-phase power converter according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the structure of a fault determination device according to an embodiment of the present invention; Figure 10 This is a schematic diagram of a power system according to an embodiment of the present invention; Figure 11 This is a schematic diagram of a power system according to another embodiment of the present invention. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] The following description, with reference to the accompanying drawings, outlines an embodiment of the fault determination method, apparatus, storage medium, three-phase power converter, and power system of the present invention.

[0034] Figure 1 This is a flowchart illustrating a fault determination method according to an embodiment of the present invention. Figure 1 As shown, the fault determination methods include: S101, obtain the terminal temperature of each phase AC terminal of the three-phase power converter.

[0035] Specifically, each phase output of the three-phase power converter is provided with at least one AC terminal, which is used to connect the AC power source (e.g., the power grid) and / or the load. In related technologies, the presence of a loose connection fault between the AC power source or load and the AC output of the three-phase power converter is typically determined by detecting voltage or power anomalies. However, this method often only detects the fault when the loose connection fault is severe, causing significant voltage or power anomalies. Therefore, the method in related technologies suffers from a lag, resulting in poor detection timeliness.

[0036] This embodiment identifies loose connection faults in advance by detecting the terminal temperature of each phase AC terminal. Specifically, when a loose connection fault occurs at the AC output terminal of the three-phase power converter, the contact resistance increases, leading to local overheating and thus raising the temperature of the corresponding AC terminal. Therefore, before the operating parameters of the three-phase power converter (such as power, current, and voltage) exceed the limits, the temperature of each phase AC terminal can be used to effectively monitor loose connection faults, thereby enabling early identification of such faults.

[0037] It should be noted that the time interval for obtaining the terminal temperature of each phase AC terminal can be in seconds, so as to detect the loose connection fault of the three-phase power converter in a timely manner.

[0038] S102, determine the temperature difference between any two phase AC terminals based on the terminal temperatures of each phase AC terminal.

[0039] It should be noted that the temperature difference between any two AC phase terminals is the larger terminal temperature minus the smaller terminal temperature, or the absolute value of the temperature difference between any two AC phase terminals. Assuming the three phases of the three-phase power converter are R-phase, S-phase, and T-phase, calculate the temperature T of the R-phase AC terminal. R Temperature T of the AC terminal block of phase S S Temperature difference |T R -T S | Temperature T of S-phase AC terminal S Temperature T of phase T AC terminal T Temperature difference |T S -T T | Temperature T of R-phase AC terminals R Temperature T of phase T AC terminal T Temperature difference |T R -T T |, to obtain the temperature difference between the two phase AC terminals.

[0040] S103, determine whether the three-phase power converter meets the preset intermittent connection fault conditions based on the determined temperature difference between the two phase AC terminals; wherein, the preset intermittent connection fault conditions include: the temperature difference between any two phase AC terminals is greater than the preset temperature difference threshold.

[0041] Specifically, when a three-phase power converter experiences a loose connection fault, the terminal temperature of the AC terminal of the phase with the loose connection rises, and the temperature difference between the terminal and the normally connected AC terminal is significant. Therefore, the presence of a loose connection fault in the three-phase power converter can be determined based on the temperature difference between any two AC terminals. When the temperature difference between any two AC terminals exceeds a preset temperature difference threshold, i.e., the calculated |T... R -T S |、|T S -T T | and | T R -T T If at least one temperature difference is greater than a preset temperature difference threshold, it can be determined that the three-phase power converter may have a loose connection fault. When the temperature difference between any two AC terminals is less than or equal to the preset temperature difference threshold, it can be determined that the three-phase power converter has not experienced a loose connection fault.

[0042] It should be noted that those skilled in the art can select an appropriate preset temperature difference threshold based on the actual operating scenario of the three-phase power converter.

[0043] In the above embodiments, the temperature difference between the AC terminals of each two phases of the three-phase power converter can be used to identify in advance whether a loose connection fault has occurred in the three-phase power converter, thereby improving the timeliness of fault identification. This solves the problem that the detection method in related technologies has a lag, which leads to safety risks in the three-phase power converter, and thus improves the reliability of the photovoltaic system.

[0044] In some embodiments, determining whether a three-phase power converter meets the condition for a loose connection fault based on the determined temperature difference between each pair of AC terminals may include: determining the maximum temperature difference based on the determined temperature difference between each pair of AC terminals, and then determining whether the three-phase power converter meets the condition for a loose connection fault based on the maximum temperature difference; wherein, the preset condition for a loose connection fault further includes: the maximum temperature difference is greater than a preset temperature difference threshold.

[0045] Understandably, the maximum temperature difference can also be used to determine whether a three-phase power converter has a loose connection fault. First, the maximum temperature difference is determined based on the temperature difference between the terminals of each pair of AC phases. If the maximum temperature difference is greater than a preset temperature difference threshold, it indicates that at least one pair of AC terminals has a temperature difference greater than the preset temperature difference threshold, and thus a loose connection fault in the three-phase power converter can be determined.

[0046] In this embodiment, the maximum temperature difference is used to determine the loose connection fault, which eliminates the need to compare each temperature difference with a preset temperature difference threshold, thereby simplifying the judgment logic and further improving the timeliness of fault identification.

[0047] In some embodiments, to improve the accuracy of diagnosing loose connection faults, the terminal temperature of each phase's AC terminals can be further combined to determine whether a loose connection fault exists in the three-phase power converter. For example... Figure 2 As shown, the determination of whether the three-phase power converter meets the conditions for a loose connection fault is based on the determined temperature difference between the two AC terminals of each phase, including: S201, based on the terminal temperature of each phase AC terminal and the determined temperature difference between any two phase AC terminals, determine whether the three-phase power converter meets the conditions for a virtual connection fault; wherein, the preset virtual connection fault conditions also include: the terminal temperature of any phase AC terminal is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0048] Specifically, when the three-phase load of a three-phase power converter is unbalanced or the ambient heat dissipation conditions are uneven, even if the three-phase power converter does not experience a loose connection fault, the temperature difference between any two phase AC terminals may be relatively large, leading to misjudgment. Therefore, when determining whether a loose connection fault has occurred in the three-phase power converter, the terminal temperature of each phase AC terminal is also introduced. If the terminal temperature of any phase AC terminal is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold, then a loose connection fault is determined to have occurred in the three-phase power converter; if at least one judgment condition is not met, then a loose connection fault has not occurred in the three-phase power converter.

[0049] It should be noted that the preset temperature threshold can be a fixed temperature value or it can be determined based on the current operating status of the three-phase power converter. The specific determination method will be described in detail later.

[0050] In the above embodiments, the terminal temperature of each phase AC terminal and the temperature difference between each pair of phase AC terminals are used to jointly determine whether a three-phase power converter has a loose connection fault. This can avoid misjudgment and improve the accuracy and reliability of the diagnosis of loose connection faults in the three-phase power converter.

[0051] In one alternative implementation, the location of the loose connection fault in the AC terminal can be determined based on the terminal temperature of each phase's AC terminals and the temperature difference between any two phases' AC terminals. For example, the temperature T of the R-phase AC terminal... R Temperature T of the AC terminal block of phase S S Temperature difference |T R -T S |The temperature is greater than the preset temperature threshold, and the temperature T of the R-phase AC terminal is greater than the preset temperature threshold. RIf the temperature exceeds the preset temperature threshold, it can be determined that a loose connection fault has occurred in the R-phase AC terminal.

[0052] Therefore, by utilizing the terminal temperature of each phase AC terminal and the temperature difference between each pair of phase AC terminals, not only can a loose connection fault be accurately identified, but the fault location of the phase with the loose connection can also be determined. Based on the fault location results, maintenance personnel can perform timely maintenance, thereby improving maintenance efficiency.

[0053] In some embodiments, determining whether a three-phase power converter meets the intermittent connection fault condition based on the terminal temperature of each phase AC terminal and the determined temperature difference between any two phase AC terminals includes: determining the maximum terminal temperature based on the terminal temperature of each phase AC terminal; determining whether the three-phase power converter meets the intermittent connection fault condition based on the maximum terminal temperature and the determined temperature difference between any two phase AC terminals; wherein the preset intermittent connection fault condition further includes: the maximum terminal temperature is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0054] Understandably, if the maximum terminal temperature exceeds a preset temperature threshold, then at least one phase AC terminal has a temperature exceeding the preset temperature threshold. Therefore, the maximum terminal temperature and the temperature difference between any two phase AC terminals can be used to determine whether a loose connection fault has occurred in the three-phase power converter. First, the maximum terminal temperature is determined based on the terminal temperatures of each phase AC terminal. Then, it is determined whether the maximum terminal temperature and the temperature difference between any two phase AC terminals meet the preset loose connection fault conditions. If the maximum terminal temperature and the temperature difference between any two phase AC terminals meet the loose connection fault conditions, then a loose connection fault is determined to have occurred in the three-phase power converter.

[0055] In this embodiment, fault diagnosis is performed by using the maximum terminal temperature and the temperature difference between each pair of AC terminals. Compared with the method of using the terminal temperature of each AC terminal and the temperature difference between each pair of AC terminals, this method simplifies the judgment logic while ensuring the accuracy of fault diagnosis, thereby improving the timeliness of fault identification.

[0056] In some embodiments, determining whether a three-phase power converter meets the conditions for a loose connection fault based on the terminal temperatures of each phase AC terminal and the determined temperature difference between each pair of phase AC terminals includes: determining the maximum terminal temperature based on the terminal temperatures of each phase AC terminal; determining the maximum temperature difference based on the determined temperature difference between each pair of phase AC terminals; and determining whether the three-phase power converter meets the conditions for a loose connection fault based on the maximum terminal temperature and the maximum temperature difference. The preset loose connection fault conditions further include: the maximum terminal temperature is greater than a preset temperature threshold, and the maximum temperature difference is greater than a preset temperature difference threshold.

[0057] In other words, the maximum terminal temperature and the maximum temperature difference can be used to determine whether a loose connection fault has occurred in the three-phase power converter. First, the maximum terminal temperature and the maximum temperature difference need to be determined, and then it is determined whether the maximum terminal temperature and the maximum temperature difference meet the preset loose connection fault conditions.

[0058] In the above embodiments, fault diagnosis is performed by using the maximum terminal temperature and the maximum temperature difference. While ensuring the accuracy of fault diagnosis, the judgment logic is further simplified, thereby further improving the timeliness of fault identification.

[0059] It should be noted that the order of determining the maximum terminal temperature and the maximum temperature difference is not limited to determining the maximum terminal temperature first and then the maximum temperature difference. It is also possible to determine the maximum temperature difference first and then the maximum terminal temperature, or to determine the maximum terminal temperature and the maximum temperature difference simultaneously.

[0060] Optionally, the overload fault of the three-phase power converter can be determined based on the terminal temperature of each phase AC terminal. If the terminal temperature of any phase AC terminal is greater than the preset temperature threshold, the overload fault of the three-phase power converter is determined.

[0061] Specifically, when an overload fault occurs in a three-phase power converter, the current will cause the terminal temperature of the AC terminal of the phase with the overload fault to rise. Therefore, the overload fault can be identified in advance based on the terminal temperature of each phase's AC terminal.

[0062] Similarly, the maximum terminal temperature can be used to determine whether the three-phase power converter has an overload fault, thereby simplifying the judgment logic of overload fault diagnosis and improving the timeliness of overload fault identification.

[0063] In some embodiments, the method further includes: determining a preset temperature threshold based on the current operating state of the three-phase power converter.

[0064] Specifically, the preset temperature threshold is dynamically determined based on the real-time operating status of the three-phase power converter (such as current, power, ambient temperature, etc.). For example, under light load or low temperature conditions, a temperature threshold larger than the preset temperature threshold corresponding to normal operating conditions can be selected, while under heavy load or harsh operating conditions, a temperature threshold smaller than the preset temperature threshold corresponding to normal operating conditions can be selected.

[0065] In this embodiment, by dynamically adjusting the preset temperature threshold of the three-phase power converter, the availability of the power converter can be improved while ensuring its safe and reliable operation.

[0066] In some embodiments, determining a preset temperature threshold based on the current operating state of the three-phase power converter includes: determining a normal terminal temperature based on at least one of the current current and current power of the three-phase power converter; and determining the preset temperature threshold based on the normal terminal temperature and a preset margin.

[0067] Specifically, the current operating state of a three-phase power converter includes at least one of the current current and current power of the three-phase power converter. The temperature thresholds corresponding to different current levels and different power levels of the three-phase power converter are different. When the current and power of the three-phase power converter are higher, the temperature of each phase AC terminal is higher, and the temperature threshold is also higher. Therefore, it is necessary to determine the normal terminal temperature based on at least one of the current current and current power of the three-phase power converter. Then, the preset temperature threshold is calculated according to the following formula (1): (1) Among them, T max T0 is the preset temperature threshold, and T0 is the normal terminal temperature. This is a preset margin.

[0068] In the above embodiments, the normal terminal temperature is determined based on the current current and / or the current power, and a preset margin is added to the normal terminal temperature as a preset temperature threshold, thereby avoiding misjudgment when the current and load of the three-phase power conversion fluctuate, and thus improving the accuracy and reliability of fault identification.

[0069] In some embodiments, determining the normal terminal temperature based on at least one of the current current and the current power of the three-phase power converter includes: determining the terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determining the terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determining a first terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions and a second terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions, and determining the smaller value of the first terminal temperature and the second terminal temperature as the normal terminal temperature.

[0070] Taking the determination of a preset temperature threshold based on the current power as an example, the current power can be determined from... Figure 3 From the normal terminal temperature curves of AC terminals corresponding to different power levels shown, the terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions is determined, and this terminal temperature is defined as the normal terminal temperature. Then, the preset temperature threshold corresponding to the current power is calculated using formula (1).

[0071] Taking the determination of a preset temperature threshold based on the current current as an example, the current current can be used to determine the preset temperature threshold. Figure 4 From the normal terminal temperature curves of AC terminals corresponding to different current levels shown, the terminal temperature corresponding to the current in the normal operation state of the three-phase power converter is determined, and this terminal temperature is defined as the normal terminal temperature. Then, the preset temperature threshold corresponding to the current is calculated using formula (1).

[0072] Taking the determination of a preset temperature threshold based on current power and current current as an example, the current power can be determined from... Figure 3 In the normal terminal temperature curve shown, the terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions is determined, and this terminal temperature is defined as the first terminal temperature. Based on the current current... Figure 4 In the normal terminal temperature curve shown, the terminal temperature corresponding to the current in the normal operation state of the three-phase power converter is determined and the terminal temperature is determined as the second terminal temperature. Then, the smaller value of the first terminal temperature and the second terminal temperature is taken as the normal terminal temperature. Then, the preset temperature threshold corresponding to the current is calculated using formula (1).

[0073] It should be noted that, Figure 3 In this context, Pn represents the maximum power of the power converter. Figure 4 I in max This indicates the maximum current of the power converter.

[0074] In the above embodiments, the normal terminal temperature can be flexibly determined based on at least one of the current power and the current current, which enhances the adaptability of fault diagnosis. Furthermore, when the normal terminal temperature is determined based on both the current power and the current current, selecting the smaller value between the normal terminal temperature corresponding to the current power and the normal terminal temperature corresponding to the current current as the final normal terminal temperature can yield a safer preset temperature threshold, thereby improving the safety of the three-phase power converter.

[0075] Furthermore, as shown in formula (2), based on the normal terminal temperature T0 and the preset margin It is also possible to determine the lower limit of the terminal temperature: (2) Among them, T min This is the lower limit of the temperature.

[0076] Since the focus of this application is on abnormal temperature rise of AC terminals, a lower temperature limit can be omitted. In some embodiments, the method further includes issuing a fault alarm message when it is determined that the three-phase power converter meets the conditions for a loose connection fault.

[0077] Specifically, when it is determined that the three-phase power converter meets the conditions for a loose connection fault, a loose connection fault occurs in the three-phase power converter, and a fault alarm message is issued. The fault alarm message is used to remind maintenance personnel that a loose connection fault has occurred in the three-phase power converter.

[0078] Optionally, when an overload fault is determined to have occurred in the three-phase power converter based on the terminal temperature of each phase AC terminal, a fault alarm message can also be issued to indicate that an overload fault has occurred in the three-phase power converter.

[0079] In one optional implementation, the three-phase power converter further includes a controller (not shown) and a communication unit (not shown). The communication unit is used to communicate with a host computer (not shown). The fault determination method of this embodiment is applied to the controller. When the controller determines that the three-phase power converter meets the conditions for a loose connection fault, it will send a fault alarm message to the host computer through the communication unit. The host computer will display "Fault Alarm". If the three-phase power converter is in normal operation, the controller will not send a fault alarm message to the communication unit, and the host computer will display "Normal Operation". In this way, the operating status of the three-phase power converter can be observed on the host computer.

[0080] In the above embodiments, when a three-phase power converter fails, a fault alarm message is issued in a timely manner. Based on the fault alarm message, maintenance personnel can perform early inspection and cleaning of the power converter, reducing power generation losses caused by insufficient heat dissipation due to dust accumulation and faults, as well as the downtime of the power converter, thereby improving the availability of the power converter and thus improving the power generation efficiency of the photovoltaic system.

[0081] In some embodiments, the three-phase power converter may include multiple temperature sensing elements, each used to detect the temperature of the conductive layer of one phase AC terminal. Obtaining the terminal temperature of each phase AC terminal of the three-phase power converter includes determining the terminal temperature of each phase AC terminal based on the temperature sensing information of each temperature sensing element. The conductive layer may be a copper-clad layer.

[0082] Specifically, each phase AC terminal is set on the corresponding phase copper cladding layer to transmit electrical energy through the copper cladding layer. Therefore, the temperature of each phase copper cladding layer can be used to characterize the temperature of each phase AC terminal. Each temperature sensing element is set close to a phase copper cladding layer to generate temperature sensing information based on the temperature of the corresponding phase copper cladding layer. Based on the temperature sensing information of each temperature sensing element, the temperature of each phase copper cladding layer can be determined, thereby obtaining the terminal temperature of each phase AC terminal.

[0083] Assuming each phase of a three-phase power converter has one AC terminal, there are three AC terminals and three temperature sensing elements. Each temperature sensing element detects the temperature of the copper layer of one AC terminal, and then the terminal temperature of the three AC terminals is obtained based on the temperature sensing information of the three temperature sensing elements.

[0084] For example, the temperature sensing element can be a negative temperature coefficient thermistor. The temperature sensing information is the resistance value of the thermistor. The higher the temperature of the conductive layer of a phase AC terminal, the lower the resistance value of the thermistor. Based on the resistance value of each thermistor, the temperature of the copper clad layer of each phase can be calculated, thereby obtaining the terminal temperature of each phase AC terminal. It should be noted that the temperature sensing element is not limited to thermistors; other devices can also be used, such as thermocouples or infrared sensors, etc., without specific limitations here.

[0085] In this embodiment, the temperature of the conductive layer of each phase AC terminal is detected by multiple temperature sensing elements to obtain the terminal temperature of each phase AC terminal, thereby providing an accurate and reliable data basis for subsequent fault diagnosis.

[0086] In some embodiments, such as Figure 5 As shown, each temperature sensing element 10 is disposed on the conductive layer 30 of a phase AC terminal 20.

[0087] In other words, each temperature sensing element 10 can be directly disposed on the conductive layer 30 (i.e., copper cladding) of the corresponding phase AC terminal 20 to directly detect the temperature of the conductive layer of the corresponding phase AC terminal 20. Because the temperature sensing element 10 is in direct contact with the conductive layer 30 of the AC terminal 20, the temperature sensing element 10 can obtain an accurate conductive layer temperature, and thus an accurate terminal temperature.

[0088] In some embodiments, such as Figure 6 As shown, each temperature sensing element 10 is installed on the AC junction box 40 of the three-phase power converter to detect the ambient temperature of the conductive layer 30 of one phase AC terminal 20.

[0089] It is understandable that each phase AC terminal 20 and its conductive layer 30 are installed inside the AC junction box 40. When the temperature of the conductive layer of one phase AC terminal 20 rises, the temperature of the corresponding position on the AC junction box 40 corresponding to the conductive layer 30 will also rise. Therefore, each temperature sensing element 10 can be installed on the AC junction box 40 to detect the temperature around the conductive layer 30 of each phase AC terminal 20, thereby making the installation of the temperature sensing element 10 more convenient.

[0090] In some embodiments, such as Figure 7 As shown, each temperature sensing element 10 is disposed on the surface of the circuit board 50 and is disposed corresponding to the conductive layer 30 of a phase AC terminal 20; wherein, at least one layer of the circuit board 50 is provided with a conductive layer 30 of at least one phase AC terminal 20.

[0091] Specifically, each temperature sensing element 10 is not limited to Figure 5 and Figure 6 In this position, the temperature sensing element 10 can also be placed on the surface of the circuit board 50, and connected to the conductive layer 30 of each phase AC terminal 20 (because...). Figure 6 (The conductive layer 30 in the circuit board 50 is not visible from the surface of the circuit board 50, so it is represented by a dashed line.) In this way, the heat of the conductive layer 30 of the corresponding AC terminal 20 will be transferred to the surface of the circuit board 50. The temperature sensing element 10 indirectly obtains the temperature of the conductive layer of the corresponding AC terminal 20 by detecting the surface temperature of the circuit board 50.

[0092] Taking circuit board 50 as a four-layer board as an example, assuming that the second, third and fourth layers are copper-clad layers, the temperature sensing element 10 can be placed on the outer surface of the first layer or the outer surface of the fourth layer. Assuming that the third and fourth layers are copper-clad layers, the temperature sensing element 10 can also be placed on the outer surface of the first layer or the fourth layer. Assuming that the first and second layers are copper-clad layers, the temperature sensing element 10 can also be placed on the outer surface of the first layer or the fourth layer.

[0093] In the above embodiments, mounting the temperature sensing element on the surface of the circuit board simplifies the installation process; and by utilizing the thermal conduction of the copper layer inside the circuit board, the temperature rise of the conductive layer can be sensed more quickly compared to when the temperature sensing element is installed in an AC junction box to detect the ambient temperature, thereby ensuring the accuracy of temperature detection.

[0094] It should be noted that the position of the temperature sensing element 10 can be selected according to the actual application scenario. For example, in scenarios where high temperature accuracy is required, the position of the temperature sensing element 10 can be selected. Figure 5 The position shown can be selected for scenarios where temperature accuracy requirements are relatively low. Figure 6 or Figure 7 The location shown.

[0095] In summary, the fault determination method according to the embodiments of the present invention can determine in advance whether a three-phase power converter has a loose connection fault based on at least one of the terminal temperatures of each phase AC terminal and the temperature difference between any two phase AC terminals, as well as various preset loose connection fault conditions, thereby preventing safety accidents, reducing safety risks, and improving the reliability of the photovoltaic system. Furthermore, when a loose connection fault occurs in the three-phase power converter, a fault alarm message can be issued in a timely manner. Maintenance personnel can perform early inspection and cleaning of the three-phase power converter based on the fault alarm message, reducing power generation losses caused by insufficient heat dissipation due to dust accumulation and faults, as well as the downtime of the three-phase power converter, thereby improving the availability of the three-phase power converter and thus improving the power generation efficiency of the photovoltaic system.

[0096] Corresponding to the above embodiments, embodiments of the present invention also propose a computer-readable storage medium storing a computer program thereon, which, when processed by a processor, executes the fault determination method of any of the foregoing embodiments.

[0097] According to the computer-readable storage medium of the present invention, by executing the computer program of the above-described fault determination method, the temperature difference between the AC terminals of each two phases of the three-phase power converter can be used to identify in advance whether a loose connection fault has occurred in the three-phase power converter. This solves the problem that the detection method in the related art has a lag, which leads to a safety risk in the three-phase power converter, and thus improves the reliability of the photovoltaic system.

[0098] Corresponding to the above embodiments, embodiments of the present invention also propose a three-phase power converter. For example... Figure 8 As shown, the three-phase power converter 100 includes a memory 110, a processor 120, and a fault determination program stored in the memory 110 and executable on the processor 120. When the processor 120 executes the fault determination program, it implements the fault determination method of any of the aforementioned embodiments.

[0099] According to an embodiment of the present invention, the three-phase power converter, by executing the above-described fault determination method program through a processor, can identify in advance whether a loose connection fault has occurred in the three-phase power converter by using the temperature difference between the AC terminals of each two phases of the three-phase power converter. This solves the problem of safety risks to the three-phase power converter caused by the lag in the detection method in related technologies, thereby improving the reliability of the photovoltaic system.

[0100] Corresponding to the above embodiments, embodiments of the present invention also propose a fault determination device. For example... Figure 9 As shown, the fault determination device includes: an acquisition module 210, a first determination module 220, and a second determination module 230.

[0101] The acquisition module 210 is used to acquire the terminal temperature of each phase AC terminal of the three-phase power converter; the first determination module 220 is used to determine the temperature difference between any two phase AC terminals based on the terminal temperature of each phase AC terminal; the second determination module 230 is used to determine whether the three-phase power converter meets the preset loose connection fault conditions based on the determined temperature difference between any two phase AC terminals; wherein the preset loose connection fault conditions include: the temperature difference between any two phase AC terminals is greater than the preset temperature difference threshold.

[0102] In some embodiments, the second determining module 230 is further configured to: determine the maximum temperature difference value based on the determined temperature difference value between each two-phase AC terminal; determine whether the three-phase power converter meets the virtual connection fault condition based on the maximum temperature difference value; wherein the preset virtual connection fault condition further includes: the maximum temperature difference value is greater than the preset temperature difference threshold.

[0103] In some embodiments, the second determining module 230 is further configured to: determine whether the three-phase power converter meets the virtual connection fault condition based on the terminal temperature of each phase AC terminal and the determined temperature difference between each two phase AC terminals; wherein the preset virtual connection fault condition further includes: the terminal temperature of any phase AC terminal is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0104] In some embodiments, the second determining module 230 is further configured to: determine the maximum terminal temperature based on the terminal temperature of each phase AC terminal; determine whether the three-phase power converter meets the virtual connection fault condition based on the maximum terminal temperature and the determined temperature difference between each pair of phase AC terminals; wherein the preset virtual connection fault condition further includes: the maximum terminal temperature is greater than a preset temperature threshold, and the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold.

[0105] In some embodiments, the second determining module 230 is further configured to: determine the maximum terminal temperature based on the terminal temperature of each phase AC terminal; determine the maximum temperature difference based on the determined temperature difference between each pair of phase AC terminals; and determine whether the three-phase power converter meets the virtual connection fault condition based on the maximum terminal temperature and the maximum temperature difference; wherein the preset virtual connection fault condition further includes: the maximum terminal temperature is greater than a preset temperature threshold, and the maximum temperature difference is greater than a preset temperature difference threshold.

[0106] In some embodiments, the apparatus further includes a third determining module, which is used to determine a preset temperature threshold based on the current operating state of the three-phase power converter.

[0107] In some embodiments, the third determining module is further configured to: determine the normal terminal temperature based on at least one of the current current and the current power of the three-phase power converter; and determine a preset temperature threshold based on the normal terminal temperature and a preset margin.

[0108] In some embodiments, the third determining module is further configured to: determine the terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determine the terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions as the normal terminal temperature; or determine the first terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions and the second terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions, and determine the smaller value between the first terminal temperature and the second terminal temperature as the normal terminal temperature.

[0109] In some embodiments, the device further includes an alarm module, which is used to issue a fault alarm message when it is determined that the three-phase power converter meets the conditions for a loose connection fault.

[0110] In some embodiments, the three-phase power converter includes a plurality of temperature sensing elements, each of which is used to detect the temperature of the conductive layer of a phase AC terminal. The acquisition module 210 is further used to determine the terminal temperature of each phase AC terminal based on the temperature sensing information of each temperature sensing element.

[0111] In some embodiments, each temperature sensing element is disposed on the conductive layer of a phase AC terminal.

[0112] In some embodiments, each temperature sensing element is disposed on the AC junction box of a three-phase power converter to detect the temperature around the conductive layer of a phase AC terminal.

[0113] In some embodiments, each temperature sensing element is disposed on the surface of a circuit board and is disposed corresponding to a conductive layer of an AC terminal; wherein at least one layer of the circuit board is provided with a conductive layer of at least one AC terminal.

[0114] In some embodiments, the conductive layer is a copper-clad layer.

[0115] It should be noted that the specific implementation of the fault determination device in this embodiment corresponds one-to-one with the specific implementation of the fault determination method in the foregoing embodiments of this invention, and will not be repeated here.

[0116] According to an embodiment of the present invention, the fault determination device acquires the terminal temperature of each phase AC terminal of a three-phase power converter through an acquisition module, determines the temperature difference between any two phase AC terminals based on the terminal temperatures of each phase AC terminal through a first determination module, and determines whether the three-phase power converter meets a preset intermittent connection fault condition based on the determined temperature difference between any two phase AC terminals through a second determination module. The preset intermittent connection fault condition includes: the temperature difference between any two phase AC terminals is greater than a preset temperature difference threshold. Therefore, by using the temperature difference between any two phase AC terminals of the three-phase power converter, it is possible to identify in advance whether an intermittent connection fault has occurred in the three-phase power converter, thereby solving the problem of safety risks to the three-phase power converter caused by the lag in detection methods in related technologies, and thus improving the reliability of the photovoltaic system.

[0117] Corresponding to the above embodiments, embodiments of the present invention also propose a power system. For example... Figure 10 and Figure 11 As shown, the power system 1000 includes: the aforementioned three-phase power converter 100, or the aforementioned fault determination device 200.

[0118] According to the power system of the present invention, by employing the power converter described above, the temperature difference between the AC terminals of each two phases of the three-phase power converter can be used to identify in advance whether a loose connection fault has occurred in the three-phase power converter. This solves the problem of safety risks to the three-phase power converter caused by the lag in the detection method in related technologies, thereby improving the reliability of the photovoltaic system.

[0119] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0120] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0121] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0122] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0123] Furthermore, the terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this invention can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this invention, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly specified in the embodiments.

[0124] In this invention, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific implementation.

[0125] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0126] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A fault determination method, characterized in that, include: Obtain the terminal temperature of each phase AC terminal of the three-phase power converter; The temperature difference between the AC terminals of each pair of phases is determined based on the terminal temperature of each phase's AC terminals. The three-phase power converter is determined to meet the preset intermittent connection fault condition based on the temperature difference between the AC terminals of any two phases; wherein the preset intermittent connection fault condition includes: the temperature difference between any two AC terminals is greater than a preset temperature difference threshold.

2. The method according to claim 1, characterized in that, Determining whether the three-phase power converter meets the conditions for a loose connection fault based on the determined temperature difference between the AC terminals of each pair of phases includes: Based on the determined temperature difference between the AC terminals of each pair of phases, determine the maximum temperature difference value; The three-phase power converter is determined to meet the condition for a loose connection fault based on the maximum temperature difference value; wherein, the preset loose connection fault condition further includes: the maximum temperature difference value is greater than the preset temperature difference threshold.

3. The method according to claim 1, characterized in that, Determining whether the three-phase power converter meets the conditions for a loose connection fault based on the determined temperature difference between the AC terminals of each pair of phases includes: Based on the terminal temperature of each phase's AC terminal and the determined temperature difference between any two phases' AC terminals, it is determined whether the three-phase power converter meets the conditions for a virtual connection fault. The preset virtual connection fault conditions further include: the terminal temperature of any phase's AC terminal is greater than a preset temperature threshold, and the temperature difference between any two phases' AC terminals is greater than the preset temperature difference threshold.

4. The method according to claim 3, characterized in that, Based on the terminal temperatures of the AC terminals of each phase and the determined temperature difference between the AC terminals of any two phases, determine whether the three-phase power converter meets the conditions for a loose connection fault, including: Determine the maximum terminal temperature based on the terminal temperature of each phase's AC wiring terminals; Based on the maximum terminal temperature and the determined temperature difference between any two AC terminals, it is determined whether the three-phase power converter meets the conditions for a loose connection fault; wherein, the preset loose connection fault conditions further include: the maximum terminal temperature is greater than the preset temperature threshold, and the temperature difference between any two AC terminals is greater than the preset temperature difference threshold.

5. The method according to claim 3, characterized in that, Based on the terminal temperatures of the AC terminals of each phase and the determined temperature difference between the AC terminals of any two phases, determine whether the three-phase power converter meets the conditions for a loose connection fault, including: Determine the maximum terminal temperature based on the terminal temperature of each phase's AC wiring terminals; Based on the determined temperature difference between the AC terminals of each pair of phases, determine the maximum temperature difference value; Based on the maximum terminal temperature and the maximum temperature difference, it is determined whether the three-phase power converter meets the conditions for a loose connection fault; wherein, the preset loose connection fault conditions further include: the maximum terminal temperature is greater than the preset temperature threshold, and the maximum temperature difference is greater than the preset temperature difference threshold.

6. The method according to any one of claims 3-5, characterized in that, The method further includes: The preset temperature threshold is determined based on the current operating state of the three-phase power converter.

7. The method according to claim 5, characterized in that, Determining the preset temperature threshold based on the current operating state of the three-phase power converter includes: The normal terminal temperature is determined based on at least one of the current current and current power of the three-phase power converter; The preset temperature threshold is determined based on the normal terminal temperature and the preset margin.

8. The method according to claim 6, characterized in that, Determine the normal terminal temperature based on at least one of the current current and current power of the three-phase power converter, including: The terminal temperature corresponding to the current current of the three-phase power converter under normal operating conditions is determined as the normal terminal temperature; or The terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions is determined as the normal terminal temperature; or Determine the first terminal temperature corresponding to the current current and the second terminal temperature corresponding to the current power of the three-phase power converter under normal operating conditions, and determine the smaller value between the first terminal temperature and the second terminal temperature as the normal terminal temperature.

9. The method according to claim 1, characterized in that, The method further includes: If the three-phase power converter is determined to meet the conditions for a loose connection fault, a fault alarm message is issued.

10. The method according to claim 1, characterized in that, The three-phase power converter includes multiple temperature sensing elements, each of which is used to detect the temperature of the conductive layer of one phase AC terminal. Obtaining the terminal temperature of each phase AC terminal of the three-phase power converter includes: The terminal temperature of each phase AC terminal is determined based on the temperature sensing information of each of the temperature sensing elements.

11. The method according to claim 10, characterized in that, Each of the temperature sensing elements is disposed on the conductive layer of one phase of the AC terminal block.

12. The method according to claim 10, characterized in that, Each of the temperature sensing elements is installed on the AC junction box of the three-phase power converter to detect the temperature around the conductive layer of one phase of the AC terminal block.

13. The method according to claim 10, characterized in that, Each of the temperature sensing elements is disposed on the surface of the circuit board and is disposed corresponding to the conductive layer of one phase of the AC terminal; wherein, at least one layer of the circuit board is provided with the conductive layer of at least one phase of the AC terminal.

14. The method according to claim 12, characterized in that, The conductive layer is a copper-clad layer.

15. A computer-readable storage medium, characterized in that, It stores a computer program, which, when processed by a processor, executes the fault determination method as described in any one of claims 1-14.

16. A three-phase power converter, characterized in that, The system includes a memory, a processor, and a fault determination program stored in the memory and executable on the processor. When the processor executes the fault determination program, it implements the fault determination method according to any one of claims 1-14.

17. A fault determination device, characterized in that, include: The acquisition module is used to acquire the terminal temperature of each phase AC terminal of the three-phase power converter; The first determining module is used to determine the temperature difference between the AC terminals of each pair of phases based on the terminal temperature of the AC terminals of each phase. The second determining module is used to determine whether the three-phase power converter meets the preset loose connection fault condition based on the determined temperature difference between the AC terminals of any two phases; wherein the preset loose connection fault condition includes: the temperature difference between any two AC terminals is greater than the preset temperature difference threshold.

18. An electric power system, characterized in that, include: The three-phase power converter according to claim 16, or the fault determination device according to claim 17.

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