Method and device for evaluating reliability of inverter bridge of photovoltaic inverter

Abstract

The invention provides a reliability evaluation method and device for an inverter bridge of a photovoltaic inverter, and belongs to the field of inverters. The method comprises the following steps: firstly, judging each working bridge arm in a working state in a to-be-evaluated inverter bridge at the current moment, determining the actual working duration of each working bridge arm at the current moment, then obtaining the reliability evaluation parameter of each device in each working bridge arm at the current moment, and further determining the reliability evaluation parameter of each device in each working bridge arm at the current moment. And obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameter and the actual working time corresponding to each device, and finally determining the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm. According to the method, the real-time reliability of devices in the real-time working bridge arm of the inverter bridge is adopted, the real operation condition of the inverter bridge at the current moment can be truly reflected, the reliability evaluation deviation of the inverter bridge can be effectively avoided, meanwhile, the reliability and timeliness of evaluation are improved, and a powerful basis is provided for real-time decision support.

Description

Technical Field

[0001] The present invention relates to the field of inverters, and in particular to a reliability assessment method and device for an inverter bridge of a photovoltaic inverter. Background Art

[0002] The photovoltaic inverter is the core equipment of the photovoltaic power generation system. It is responsible for converting the direct current provided by the previous photovoltaic array into stable three-phase alternating current for use by the load or access to the power grid. Whether the photovoltaic inverter can work stably and reliably has a direct impact on the power generation capacity of the photovoltaic power station and the safe and economic operation of the power grid. If the photovoltaic inverter fails, the entire photovoltaic power generation system will be abnormal, and even cause unplanned shutdowns, which will cause huge economic losses or incalculable catastrophic accidents. The inverter bridge is the core component of the inverter. Therefore, studying the online evaluation method to improve the working reliability of the photovoltaic inverter bridge is of great significance for the intelligent operation and maintenance of the photovoltaic power generation system and avoiding the loss of power generation caused by unplanned shutdowns.

[0003] In the prior art, the reliability of the photovoltaic inverter bridge is quantitatively calculated based on the empirical failure rate curve of the device provided in the reliability evaluation manual and according to the system reliability comprehensive method.

[0004] However, the failure rate curve on which this method relies is based on laboratory data and lacks the support of real-time operation data evidence, and cannot achieve real-time and accurate reliability assessment of the inverter bridge. Summary of the invention

[0005] The embodiment of the present invention provides a reliability assessment method and device for an inverter bridge of a photovoltaic inverter, so as to solve the problem that the reliability assessment of the inverter bridge cannot be performed in real time and accurately.

[0006] In a first aspect, an embodiment of the present invention provides a reliability assessment method for an inverter bridge of a photovoltaic inverter, comprising:

[0007] Identify each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determine the actual working time of each working bridge arm at the current moment;

[0008] Obtaining the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time;

[0009] According to the device reliability of each device in each working bridge arm, the reliability index of the inverter bridge to be evaluated is determined.

[0010] In a possible implementation, the step of determining each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment includes:

[0011] Acquire pre-stored redundant design information of the inverter bridge to be evaluated; wherein the pre-stored redundant design information is used to characterize whether the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm or a fixed redundant bridge arm;

[0012] If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, then, according to the pre-stored bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment is determined;

[0013] If the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm, then according to the pre-stored bridge arm fault information, or according to the pre-stored redundant design information and the bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment is determined;

[0014] If the inverter bridge to be evaluated is not provided with a dynamic redundant bridge arm and a fixed redundant bridge arm, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in a working state is a preset bridge arm.

[0015] In a possible implementation, determining, according to the pre-stored bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment includes:

[0016] Query the bridge arm fault information; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the bridge arms pre-set for the inverter bridge to be evaluated;

[0017] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, determining that the working bridge arms in the inverter bridge to be evaluated that are in working state include the fixed redundant bridge arms that replace the faulty bridge arms and the pre-set bridge arms;

[0018] If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, then the working bridge arm in the inverter bridge to be evaluated that is in working state is determined to be the pre-set bridge arm.

[0019] In a possible implementation, the determining, according to the pre-stored bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment, according to the pre-stored redundant design information and the bridge arm fault information, further includes:

[0020] Querying the bridge arm fault information of the inverter bridge to be evaluated; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the inverter bridge to be evaluated;

[0021] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, determining that the working bridge arms in the inverter bridge to be evaluated that are in working state include the dynamic redundant bridge arms that replace the faulty bridge arms and the pre-set bridge arms;

[0022] If a bridge arm failure occurs in the dynamic redundant bridge arm, determining that the working bridge arm in the inverter bridge to be evaluated that is in working state includes a pre-set bridge arm;

[0023] If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated and the dynamic redundant bridge arms, the working bridge arm currently in working state in the inverter bridge to be evaluated is determined according to the redundant round-robin period in the pre-stored redundant design information.

[0024] In a possible implementation, the method further includes:

[0025] If the working bridge arms of the inverter bridge to be evaluated are all pre-set bridge arms, then determining that the devices corresponding to each working bridge arm are two power semiconductor devices;

[0026] If the working bridge arm of the inverter bridge to be evaluated includes a pre-set bridge arm and a redundant bridge arm that replaces the faulty bridge arm or the pre-set bridge arm, it is determined that the devices corresponding to the pre-set bridge arm in the working bridge arm are two power semiconductor devices, and the devices corresponding to the redundant bridge arm that replaces the faulty bridge arm in the working bridge arm include two power semiconductor devices and a phase-changing switch corresponding to the faulty bridge arm.

[0027] In a possible implementation manner, determining the actual working time of each working bridge arm at the current moment includes:

[0028] If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, and there is a faulty bridge arm among the bridge arms pre-set by the inverter bridge to be evaluated, then the actual working time of the device corresponding to the redundant bridge arm replacing the faulty bridge arm is determined to be the difference between the current time and the time when the fault occurs;

[0029] Otherwise, the actual working time of the working bridge arm is determined to be the difference between the start-up time of the inverter bridge to be evaluated and the current time.

[0030] In a possible implementation, the reliability evaluation parameter includes a basic failure rate corresponding to the device and an influencing factor corresponding to the basic failure rate at the current moment; the obtaining the reliability evaluation parameter of each device in each working bridge arm at the current moment, and obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameter corresponding to each device and the actual working time, includes:

[0031] Obtaining the basic failure rate corresponding to each device in each working bridge arm and the influencing factor corresponding to the basic failure rate at the current moment, wherein the influencing factor includes a device quality factor, a device application factor, a device environment factor, and a device temperature factor, and the device temperature factor is associated with the real-time working junction temperature of the device;

[0032] According to λ(t)=λ b ·π Q ·π A ·π E ·π T , determine the device failure rate of each device at the current moment; where λ(t) is the device failure rate of the device at the current moment, t is the current moment, λ b is the basic failure rate of the device, π Q is the device quality factor, π A is the device application factor, π E is the device environment factor, π T is the device temperature factor;

[0033] according to Get the device reliability of each device in each working bridge arm; where R(t) is the device reliability of the device at the current moment; where t s The actual working time.

[0034] In a possible implementation, each device has a built-in thermistor; the method further includes:

[0035] Get the temperature value and collector current value of the thermistor corresponding to the device at the current moment;

[0036] Determine the operating junction temperature of each device at the current moment based on the temperature value and the collector current value;

[0037] A device temperature factor of the device at the current moment is determined according to the operating junction temperature.

[0038] In a possible implementation, determining the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm includes:

[0039] Multiply the device reliability of each device in each working bridge arm to obtain the reliability product;

[0040] Based on the product of the reliabilities, a reliability index of the inverter bridge to be evaluated is determined.

[0041] In a second aspect, an embodiment of the present invention provides a reliability assessment device for an inverter bridge of a photovoltaic inverter, the device comprising:

[0042] A determination unit, used to determine each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determine the actual working time of each working bridge arm at the current moment;

[0043] A first processing unit, used to obtain the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtain the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time;

[0044] The second processing unit is used to determine the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm.

[0045] The embodiment of the present invention provides a reliability assessment method and device for an inverter bridge of a photovoltaic inverter. First, the various working bridge arms in the inverter bridge to be assessed at the current moment are identified to be in a working state, and the actual working time of each working bridge arm at the current moment is determined. Then, the reliability assessment parameters of each device in each working bridge arm at the current moment are obtained. Then, according to the reliability assessment parameters corresponding to each device and the actual working time, the device reliability of each device in each working bridge arm is obtained. Finally, according to the device reliability of each device in each working bridge arm, the reliability index of the inverter bridge to be assessed is determined. The real-time reliability of the devices in the real-time working bridge arms of the inverter bridge adopted in this method can truly reflect the actual operating conditions of the inverter bridge at the current moment, can effectively avoid the deviation of the reliability assessment of the inverter bridge, and at the same time improve the reliability and timeliness of the assessment, providing a strong basis for real-time decision support. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 is a flow chart of an implementation method of a reliability assessment method for a photovoltaic inverter bridge provided by an embodiment of the present invention;

[0048] Figure 2 It is a flow chart of another implementation method of a reliability assessment method of an inverter bridge of a photovoltaic inverter provided by an embodiment of the present invention;

[0049] Figure 3 It is a structural schematic diagram of an inverter bridge with fixed redundant bridge arms provided by an embodiment of the present invention;

[0050] Figure 4 It is a structural schematic diagram of an inverter bridge with a dynamic redundant bridge arm provided by an embodiment of the present invention;

[0051] Figure 5 It is a structural schematic diagram of an inverter bridge without redundant bridge arms provided by an embodiment of the present invention;

[0052] Figure 6 It is a schematic structural diagram of a reliability assessment device for a photovoltaic inverter bridge provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention. SUMMARY OF THE INVENTION

[0055] The photovoltaic inverter is the core equipment of the photovoltaic power generation system. It is responsible for converting the direct current provided by the previous photovoltaic array into stable three-phase alternating current for use by the load or access to the power grid. Whether the photovoltaic inverter can work stably and reliably has a direct impact on the power generation capacity of the photovoltaic power station and the safe and economic operation of the power grid. If the photovoltaic inverter fails, the entire photovoltaic power generation system will be abnormal, and even cause unplanned shutdowns, which will cause huge economic losses or inestimable catastrophic accidents. According to statistics, in the entire photovoltaic power generation system, the failure rate of photovoltaic inverters is higher than that of other parts. Therefore, studying the online evaluation method to improve the working reliability of photovoltaic inverters is of great significance for the intelligent operation and maintenance of photovoltaic power generation systems and avoiding the loss of power generation caused by unplanned shutdowns.

[0056] The photovoltaic inverter is a hybrid system, including direct current-direct current (DC-DC), AC / DC filtering, direct current-alternating current (DC-AC), AC / DC protection and other links. These links contain capacitors, insulated gate bipolar transistors (IGBT), inductors, sensors and other devices. These devices work under wide temperature and high frequency conditions for a long time, and the performance of the devices shows a gradual degradation trend. When the degradation reaches a certain degree and the external conditions are applied, some components will first fail suddenly. When a certain device, such as the inverter IGBT, fails suddenly, the photovoltaic inverter with redundancy function will enable the backup bridge arm; if the inverter IGBT fails suddenly, the fault-tolerant operation mode can be enabled, but this fault-tolerant operation mode cannot be sustained for a long time. If the faulty device is not handled in time, it will cause a larger range of failures, seriously affecting the working reliability of the photovoltaic inverter, and even causing production accidents of the power generation system.

[0057] The inventor has found that the traditional reliability assessment method is generally based on the empirical failure rate curves of capacitors, IGBTs and other devices provided in the reliability assessment manual to perform quantitative reliability calculations on photovoltaic inverters. However, the failure rate curves relied on by this method come from laboratory data support under standard test conditions, without considering the service conditions of photovoltaic inverters. The reliability assessment of photovoltaic inverters lacks the support of real-time operation data evidence; in addition, the relevant technology also establishes a fault prediction model by real-time monitoring of key parameters such as temperature, voltage, and current, combined with signal processing and machine learning methods, to achieve fault warning, remaining life prediction and operation and maintenance optimization. However, the fault prediction model established by this method not only needs to challenge complex failure modes, environmental interference and the acquisition of training data, but also cannot clarify the relationship between the real-time operating performance of the device and the probability of inverter failure. It can be seen that the existing technology is difficult to quickly and accurately realize the online evaluation of the inverter bridge.

[0058] In order to achieve the purpose of fast and accurate online evaluation of the inverter bridge, in the implementation mode of the present application, firstly, the various working bridge arms in the inverter bridge to be evaluated at the current moment that are in working state are identified, and the actual working time of each working bridge arm at the current moment is determined, and then the reliability evaluation parameters of each device in each working bridge arm at the current moment are obtained, and then, according to the reliability evaluation parameters and actual working time corresponding to each device, the device reliability of each device in each working bridge arm is obtained, and finally, according to the device reliability of each device in each working bridge arm, the reliability index of the inverter bridge to be evaluated is determined. The real-time reliability of the devices in the real-time working bridge arms of the inverter bridge adopted by this method can truly reflect the actual operating conditions of the inverter bridge at the current moment, can effectively avoid the deviation of the reliability evaluation of the inverter bridge, and at the same time improve the reliability and timeliness of the evaluation, providing a strong basis for real-time decision support.

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0060] Figure 1 The implementation flow chart of the reliability assessment method of the photovoltaic inverter bridge provided by the embodiment of the present invention is described in detail as follows:

[0061] Step 101 , identifying each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determining the actual working time of each working bridge arm at the current moment.

[0062] Exemplarily, in this embodiment, various methods may be used to identify each working bridge arm in the inverter bridge to be evaluated that is in a working state.

[0063] In a feasible implementation, the present embodiment can install a current sensor at the output end of each bridge arm or at a key position of the main circuit. When the switch device in the bridge arm is turned on, current will flow through the bridge arm. Whether the bridge arm is in working state is determined by detecting the presence or absence of current. For example, for a simple inverter circuit, when the current sensor detects that a current greater than a certain threshold value (considering factors such as sensor accuracy and circuit noise) flows through a certain bridge arm, it can be determined that the bridge arm is in working state.

[0064] In another feasible implementation, the present embodiment can also detect the voltage across the bridge arm to determine the working state. When the switch device in the bridge arm is turned on, the voltage across the bridge arm will change. For example, for a bridge arm with a freewheeling diode, when the switch device is turned on, the voltage across the bridge arm is approximately zero (ignoring the conduction voltage drop of the switch device); and when the switch device is turned off, the voltage across the bridge arm will change according to other components of the circuit and the load condition. This voltage change can be monitored to determine whether the bridge arm is in working condition.

[0065] Among them, when determining the actual working time of the working bridge arm in the working state, this embodiment can be implemented based on a timer. For example, once it is detected that the bridge arm starts to work, a timer is started. When the bridge arm stops working, for example, when the current drops to zero or the voltage returns to the value corresponding to the non-working state, the timer is stopped. The time recorded by the timer is the actual working time of the bridge arm at the current moment.

[0066] In addition, in this embodiment, a high-precision clock source can be set in the inverter bridge system to record the current timestamp when the bridge arm starts working and another timestamp when the bridge arm stops working. The difference between the two timestamps is the actual working time.

[0067] Step 102, obtaining the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time.

[0068] Illustratively, after determining the working bridge arm at the current moment, this embodiment obtains the reliability evaluation parameters of the working devices corresponding to each working bridge arm, and then obtains the device reliability of each device in each working bridge arm based on the reliability evaluation parameters and the corresponding actual working time.

[0069] In this embodiment, the device reliability refers to the device reliability value, which represents the probability that the device can complete a specified function under specified conditions and within a specified time.

[0070] In this embodiment, the actual working time of the working bridge arm may be equal to the actual working time of the devices in the working bridge arm.

[0071] The reliability evaluation parameters may include the basic failure rate corresponding to the device and the influencing factor corresponding to the basic failure rate at the current moment. The influencing factor may include the device quality factor, the device application factor, the device environment factor and the device temperature factor, wherein the device temperature factor is associated with the real-time operating junction temperature of the device.

[0072] Step 103: Determine the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm.

[0073] Exemplarily, this embodiment determines the reliability index of the inverter bridge to be evaluated based on the device reliability of each device in each working bridge arm.

[0074] In one example, after determining the reliability index of the inverter bridge to be evaluated, this embodiment can guide the optimization of the circuit topology, monitor and maintain the inverter bridge based on the size of the reliability index, and further evaluate the reliability of the inverter based on the reliability index.

[0075] In a feasible implementation, the present embodiment pre-constructs a structural schematic diagram of an inverter bridge, and based on the connection relationship between the bridge arms and the devices in the structural schematic diagram, determines the calculation method of the reliability index corresponding to the inverter bridge. Therefore, after determining the device reliability of each device in each working bridge arm, the reliability index of the inverter bridge to be evaluated can be further obtained based on these data. For example, in a series inverter bridge, the working bridge arms between the phases are connected in series, so the reliability index of the inverter bridge can be obtained by multiplying the device reliability of each device in each working bridge arm.

[0076] In summary, the reliability assessment method of the inverter bridge of the photovoltaic inverter provided by the embodiment of the present invention first identifies each working bridge arm in the working state in the inverter bridge to be assessed at the current moment, and determines the actual working time of each working bridge arm at the current moment, and then obtains the reliability assessment parameters of each device in each working bridge arm at the current moment, and then, according to the reliability assessment parameters and actual working time corresponding to each device, obtains the device reliability of each device in each working bridge arm, and finally determines the reliability index of the inverter bridge to be assessed according to the device reliability of each device in each working bridge arm. The real-time reliability of the devices in the real-time working bridge arm of the inverter bridge adopted by this method can truly reflect the actual operating conditions of the inverter bridge at the current moment, can effectively avoid the deviation of the reliability assessment of the inverter bridge, and at the same time improve the reliability and timeliness of the assessment, providing a strong foundation for real-time decision support.

[0077] In order to accurately identify the various working bridge arms in the inverter bridge to be evaluated at the current moment and their corresponding actual working time, this embodiment first pre-stores redundant design information to identify the redundant design of the inverter bridge, and then performs differential identification processes for inverter bridges with different redundant designs, such as non-redundant inverter bridges, fixed redundant inverter bridges and dynamic redundant inverter bridges, thereby improving the accuracy of determining the working bridge arms and their corresponding actual working time; in terms of the reliability of the devices in the working bridge arms, this embodiment combines the real-time temperature value and collector current of the built-in thermistor of the device to determine the real-time working junction temperature of the device, and then determines the real-time reliability value of the device based on the real-time working junction temperature, relying on the reliability calculation of real-time data, thereby improving the accuracy and authenticity of the device reliability value; in addition, this embodiment also determines the corresponding number of devices for different types of working bridge arms, comprehensively considering the actual operating conditions of the inverter bridge, and further improving the accuracy of the inverter bridge reliability evaluation.

[0078] Figure 2 Another implementation flow chart of a reliability assessment method for a photovoltaic inverter bridge provided by an embodiment of the present invention is described in detail as follows:

[0079] Step 201 : obtaining pre-stored redundant design information of the inverter bridge to be evaluated; wherein the pre-stored redundant design information is used to indicate whether the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm or a fixed redundant bridge arm.

[0080] Exemplarily, when performing reliability evaluation on the inverter bridge to be evaluated, this embodiment first reads pre-stored redundant design information of the inverter bridge to be evaluated to determine whether the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm or a fixed redundant bridge arm.

[0081] Among them, the fixed redundant bridge arm in this embodiment refers to an additional spare bridge arm in the inverter bridge design, and a fixed redundancy strategy is designed in the inverter bridge, that is, the spare bridge arm does not participate in the work under normal circumstances, but when other bridge arms fail, it can cooperate with the phase-changing switch set in each phase to take over the work of the faulty bridge arm to maintain the basic function of the inverter bridge.

[0082] In this embodiment, the dynamic redundant bridge arm refers to an additional spare bridge arm in the inverter bridge design, and a dynamic redundant strategy is designed in the inverter bridge, and the spare bridge arm is flexibly deployed and enabled according to the real-time operating status and fault conditions of the inverter bridge. For example, in a three-phase inverter bridge, under normal circumstances, the spare bridge arm works together with the three-phase bridge arm, and in each cycle, three of the four bridge arms work; if any of the four bridge arms fails, the remaining three bridge arms work.

[0083] Step 202: If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, then the working bridge arms in the inverter bridge to be evaluated that are in working state at the current moment are determined according to the pre-stored bridge arm fault information, and the actual working time of each working bridge arm at the current moment is determined.

[0084] In a feasible implementation manner, step 202 includes the following steps:

[0085] Query the bridge arm fault information; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the pre-set bridge arm of the inverter bridge to be evaluated.

[0086] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arms in the inverter bridge to be evaluated that are in working state include the fixed redundant bridge arms replacing the faulty bridge arms and the pre-set bridge arms.

[0087] If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, then the working bridge arm in the inverter bridge to be evaluated that is in working state is determined to be the pre-set bridge arm.

[0088] In this embodiment, the actual working time of each working bridge arm at the current moment is determined, including: if the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, and there is a faulty bridge arm among the bridge arms pre-set in the inverter bridge to be evaluated, then the actual working time of the device corresponding to the redundant bridge arm that replaces the faulty bridge arm is determined to be the difference between the current moment and the moment when the fault occurs; otherwise, the actual working time of the working bridge arm is determined to be the difference between the start-up moment of the inverter bridge to be evaluated and the current time.

[0089] Exemplarily, after step 201, if it is determined that the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, this embodiment determines each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment according to the bridge arm fault information pre-stored in the inverter bridge system, and determines the actual working time of each working bridge arm at the current moment.

[0090] In one example, Figure 3 It is a structural schematic diagram of an inverter bridge with a fixed redundant bridge arm provided by an embodiment of the present invention. Taking a three-phase inverter bridge as an example, as shown in the figure, when none of the pre-set three-phase bridge arms fails, the pre-set bridge arms in phases A, B, and C work normally as working bridge arms, and the D-phase bridge arm is used as a fixed redundant bridge arm as a standby. If a k-phase bridge arm fails, the phase-changing switch corresponding to k and its fixed redundant bridge arm D take over the K-phase to work.

[0091] In this embodiment, the inverter bridge system records and stores bridge arm fault information in real time, including the location of the faulty bridge arm and the time when the fault occurs.

[0092] This embodiment queries the bridge arm fault information to determine whether there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated; if there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in a working state includes a fixed redundant bridge arm that replaces the faulty bridge arm and a pre-set bridge arm; if there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in a working state is a pre-set bridge arm.

[0093] After determining the working bridge arm, determine the actual working time of each working bridge arm, which is divided into two cases. The first case: if the working bridge arm at the current moment includes both fixed redundant bridge arms and pre-set bridge arms, the actual working time of the fixed redundant bridge arm and the devices therein is the difference between the current moment and the moment when the fault occurs. The second case: if the working bridge arm at the current moment only includes the pre-set bridge arm, the actual working time of the working bridge arm is determined to be the difference between the start-up time of the inverter bridge to be evaluated and the current time.

[0094] Step 203, if the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm, then according to the pre-stored bridge arm fault information, or according to the pre-stored redundant design information and bridge arm fault information, determine each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment, and determine the actual working time of each working bridge arm at the current moment.

[0095] In a feasible implementation manner, step 203 includes the following steps:

[0096] The bridge arm fault information of the inverter bridge to be evaluated is queried; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the inverter bridge to be evaluated.

[0097] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arms in the inverter bridge to be evaluated that are in working state include the dynamic redundant bridge arms replacing the faulty bridge arms and the pre-set bridge arms.

[0098] If a bridge arm failure occurs in the dynamic redundant bridge arm, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in working state includes a pre-set bridge arm.

[0099] If there is no faulty bridge arm in the pre-set bridge arms and the dynamic redundant bridge arms of the inverter bridge to be evaluated, the working bridge arm currently in working state in the inverter bridge to be evaluated is determined according to the redundant round-robin period in the pre-stored redundant design information.

[0100] In a feasible implementation manner, in this embodiment, if the working bridge arms of the inverter bridge to be evaluated are all pre-set bridge arms, it is determined that the devices corresponding to each working bridge arm are two power semiconductor devices;

[0101] If the working bridge arm of the inverter bridge to be evaluated includes a pre-set bridge arm and a redundant bridge arm that replaces the faulty bridge arm or the pre-set bridge arm, it is determined that the devices corresponding to the pre-set bridge arm in the working bridge arm are two power semiconductor devices, and the devices corresponding to the redundant bridge arm that replaces the faulty bridge arm in the working bridge arm include two power semiconductor devices and a phase-changing switch corresponding to the faulty bridge arm.

[0102] Illustratively, after step 201, if the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm, this embodiment queries the bridge arm fault information to determine whether the inverter bridge to be evaluated has a faulty bridge arm.

[0103] The first case: If there is a faulty bridge arm in the inverter bridge to be evaluated, the type of the faulty bridge arm is first determined: this can be divided into two cases (1): If the faulty bridge arm is one of the pre-set bridge arms, then the working bridge arm in the inverter bridge to be evaluated that is in working condition includes the dynamic redundant bridge arm that replaces the faulty bridge arm and the pre-set bridge arm; (2) If the faulty bridge arm is a dynamic redundant bridge arm, then the working bridge arm in the inverter bridge to be evaluated that is in working condition includes the pre-set bridge arm.

[0104] The second case: if there is no faulty bridge arm in the inverter bridge to be evaluated, the working bridge arm currently in working state in the inverter bridge to be evaluated is determined according to the redundant round-robin period in the pre-stored redundant design information.

[0105] In this embodiment, the devices may include IGBT, capacitor, inductor, sensor and other devices, and the following description will be made taking IGBT as an example.

[0106] In one example, Figure 4 It is a structural schematic diagram of an inverter bridge with a dynamic redundant bridge arm provided by an embodiment of the present invention. Taking a three-phase inverter bridge as an example, when there is no fault in the bridge arm, the dynamic redundant bridge arm participates in the cycle together with the other three pre-set bridge arms to ensure the long-term equalization of thermal stress, reduce the thermal stress level, and improve the reliability of the inverter system. The cycle period can be set in advance, and at each moment three of the four bridge arms work normally as working bridge arms.

[0107] After determining the working bridge arm, determine the actual working time of each working bridge arm, which is also divided into two cases. The first case: if the working bridge arm at the current moment includes both the dynamic redundant bridge arm and the pre-set bridge arm, the actual working time of the dynamic redundant bridge arm and the components therein is the difference between the current moment and the moment when the fault occurs. The second case: if the working bridge arm at the current moment only includes the pre-set bridge arm, the actual working time of the working bridge arm is determined to be the difference between the start-up time of the inverter bridge to be evaluated and the current time.

[0108] Step 204: if the inverter bridge to be evaluated is not provided with a dynamic redundant bridge arm and a fixed redundant bridge arm, determine that the working bridge arm in the inverter bridge to be evaluated is a pre-set bridge arm, and determine the actual working time of each working bridge arm at the current moment.

[0109] Exemplarily, after step 201, if this embodiment determines that the inverter bridge to be evaluated is not provided with a dynamic redundant bridge arm and a fixed redundant bridge arm, that is, the inverter bridge is a non-redundant inverter bridge, then the working bridge arm in the inverter bridge to be evaluated that is in a working state is determined to be a pre-set bridge arm, and the actual working time of each working bridge arm at the current moment is determined.

[0110] In one example, if it is determined that the working bridge arm at the current moment only includes the preset bridge arm, the actual working duration of the working bridge arm is determined to be the difference between the start-up time of the inverter bridge to be evaluated and the current time.

[0111] In one example, Figure 5 is a schematic diagram of the structure of an inverter bridge without redundant bridge arms provided by an embodiment of the present invention, such as Figure 5 As shown, taking the three-phase inverter bridge as an example, as shown in the figure, when none of the pre-set three-phase bridge arms fails, the pre-set A-phase, B-phase, and C-phase middle bridge arms work normally as working bridge arms. If a k-phase bridge arm fails, the inverter bridge cannot operate normally, that is, the reliability index is zero.

[0112] Step 205, obtain the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtain the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time. The reliability evaluation parameters include the basic failure rate corresponding to the device and the influencing factor corresponding to the basic failure rate at the current moment.

[0113] In one example, step 205 includes the following steps:

[0114] Obtain the basic failure rate corresponding to each device in each working bridge arm, and the influencing factor corresponding to the basic failure rate at the current moment, wherein the influencing factors include device quality factor, device application factor, device environment factor and device temperature factor, and the device temperature factor is associated with the real-time working junction temperature of the device.

[0115] According to λ(t)=λ b ·π Q ·π A ·π E ·π T , determine the device failure rate of each device at the current moment; where λ(t) is the device failure rate of the device at the current moment, t is the current moment, λ b is the basic failure rate of the device, π Qis the device quality factor, π A is the device application factor, π E is the device environment factor, π T is the device temperature factor.

[0116] according to Get the device reliability of each device in each working bridge arm; where R(t) is the device reliability of the device at the current moment; where t s The actual working time.

[0117] Each device has a built-in thermistor; the method further includes:

[0118] Get the temperature value and collector current value of the thermistor corresponding to the device at the current moment.

[0119] Based on the temperature value and the collector current value, the operating junction temperature of each device at the current moment is determined.

[0120] According to the operating junction temperature, the device temperature factor of the device at the current moment is determined.

[0121] Exemplarily, after determining the working bridge arms in the inverter bridge to be evaluated and their corresponding actual working time, this embodiment obtains device information in each working bridge arm, such as the number of devices, device type, and device identification information, and then obtains the corresponding reliability evaluation parameters of each device based on the obtained device information, including, for example, the basic failure rate corresponding to the device and the influencing factor corresponding to the basic failure rate at the current moment; then, based on the reliability evaluation parameters and actual working time corresponding to each device, the device reliability of each device in each working bridge arm is obtained.

[0122] Among them, if the working bridge arm at the current moment includes a redundant bridge arm, that is, a dynamic redundant bridge arm or a fixed redundant bridge arm, the device corresponding to the redundant bridge arm, in addition to the IGBT of its own upper and lower arms, also includes a phase-changing switch device corresponding to the replaced bridge arm, and the phase-changing switch device can also be regarded as an IGBT; if the working bridge arm at the current moment is a pre-set bridge arm, the device corresponding to the working bridge arm is the IGBT of its own upper and lower arms.

[0123] In a feasible implementation manner, the influencing factors corresponding to the basic failure rate of the device in this embodiment at the current moment may include: device quality factor, device application factor, device environment factor and device temperature factor.

[0124] The device temperature factor is associated with the real-time working junction temperature of the device. In this embodiment, the working junction temperature of the device can be obtained by the real-time temperature value of the thermistor built into the device and the current value of the device collector, and then the device temperature factor can be obtained by the real-time working junction temperature, as shown in the following formula:

[0125]

[0126] Among them, T j It is the real-time operating junction temperature of the device.

[0127] In a feasible implementation manner, the present embodiment can be a negative temperature coefficient thermistor (Negative Temperature Coefficient, NTC) temperature T NTC (t) and the real-time effective value of the collector current to estimate the operating junction temperature T j (t) Relational model:

[0128] TNTC(t)=[a+bTj(t)]Ic(t)2+[c+dTj(t)]Ic(t)+[e+fTj(t)]

[0129] The junction temperature estimation model for the operating junction temperature Tj(t) is:

[0130]

[0131] In the formula, the coefficient matrix Calibration under laboratory conditions can be performed based on the real-time monitoring of Ic and T NTC (t) Calculate the junction temperature T j (t).

[0132] In this embodiment, the basic principle of using the temperature of the NTC to infer the working junction temperature of the IGBT module is that an NTC is usually provided on a ceramic substrate in the IGBT module for temperature detection. Since the IGBT junction temperature is a concern in the design, and it is almost impossible to directly measure the IGBT junction temperature, the junction temperature of the IGBT can be inferred by the temperature of the NTC and the thermal resistance between the IGBT chip and the NTC; the inference formula is: T j =P×R th(j-r) +T r

[0133] Where: T j : Junction temperature of IGBT, T r : NTC temperature, P: IGBT loss, R th(j-r) : Thermal resistance between IGBT chip and NTC.

[0134] The entire calculation process includes:

[0135] Step 1: Measure the NTC temperature:

[0136] Use appropriate circuits and ADC (Analog-to-Digital Converter) to detect the voltage value or voltage divider value of the NTC and then calculate the resistance value of the NTC.

[0137] Step 2: According to the temperature-resistance characteristic curve of NTC, convert the resistance value into temperature value; the NTC thermistor temperature calculation formula is: R t =R×EXP(B×(1 / T1-1 / T2)), where R t is the resistance of the thermistor at temperature T1, R is the nominal resistance of the thermistor at room temperature T2, T1 and T2 are Kelvin temperatures, EXP is the nth power of e, and B value is an important parameter of the thermistor. By conversion, we can get the relationship between temperature T1 and resistance R t The relationship T1=1 / (ln(R t / R) / B+1 / T2), the corresponding Celsius temperature t=T1-273.15.

[0138] Step 3. The losses of IGBT include conduction loss and switching loss. These losses will be converted into heat, causing the junction temperature of IGBT to rise. The losses of IGBT can be estimated by measuring the operating current, voltage, switching frequency and other parameters of IGBT and using the loss calculation formula.

[0139] Step 4: Measure or estimate thermal resistance R th(j-r) : Thermal resistance R between IGBT chip and NTC th(j-r) It is affected by many factors, including the location and orientation of the module, the cooling method, the heat sink material, the thermal conductivity and thickness of the thermal grease, and the distance between modules. th(j-r) It can only be tested under a given heat dissipation design. The junction temperature can be measured by "chip surface thermocouple" or "infrared thermal imager" method, and then the thermal resistance R can be theoretically calculated by combining the temperature of the NTC and the loss of the IGBT. th(j-r) However, since the response time of thermocouples and the refresh rate of thermal imagers are relatively slow, dynamic thermal impedance cannot be tested. Therefore, IGBT manufacturers generally use the Vce junction temperature measurement method to measure the thermal resistance and thermal impedance curve of IGBT.

[0140] Step 5: Calculate the IGBT junction temperature: Substitute the measured NTC temperature, IGBT loss, and estimated or measured thermal resistance R th(j-r) Substitute into the calculation formula T j =P×R th(j-r) +T r The junction temperature of the IGBT can be calculated.

[0141] In another feasible implementation manner, this embodiment can also use the saturation on-state voltage drop estimation model VCEsat(Tj,IC) and the junction temperature estimation physical model Tj(VCEsat,IC) to fit and obtain the operating junction temperature, as shown in the following formula:

[0142]

[0143] Among them, the coefficient matrix can also be calibrated under laboratory conditions.

[0144] After obtaining the device temperature, the device failure rate of the device at the current moment is obtained according to the following formula:

[0145] λ(t)=λ b ·π Q ·π A ·π E ·π T ,

[0146] Among them, λ(t) is the device failure rate of the device at the current moment, t is the current moment, λ b is the basic failure rate of the device, π Q is the device quality factor, π A is the device application factor, π E is the device environment factor, π T is the device temperature factor.

[0147] In this embodiment, the device quality factor, the device application factor, and the device environment factor can be set based on the product information of the device and the working environment information thereof.

[0148] After obtaining the device failure rate corresponding to the device at the current moment, this embodiment can obtain the value of the device reliability according to the following formula:

[0149]

[0150] Where R(t) is the device reliability of the device at the current moment; where t s is the actual working time of the device.

[0151] In this embodiment, when the temperature of the IGBT thermistor in any working bridge arm is greater than or equal to the preset temperature threshold, or the failure rate of the IGBT in any working bridge arm is greater than or equal to 1.5%, the device reliability is determined to be zero, and then the inverter bridge life is determined to be terminated.

[0152] Step 206: Determine the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm.

[0153] In one example, step 206 includes the following steps:

[0154] The reliability product is obtained by multiplying the device reliability of each device in each working bridge arm.

[0155] Based on the product of the reliabilities, the reliability index of the inverter bridge to be evaluated is determined.

[0156] Illustratively, after determining the device reliability of each working bridge arm device, this embodiment can determine the calculation method of the reliability index of the inverter bridge to be evaluated based on a pre-constructed reliability block diagram, and then calculate the reliability index of the inverter bridge to be evaluated.

[0157] In a feasible implementation, this embodiment first constructs a corresponding structural schematic diagram based on the structure of the inverter bridge system, and the structural schematic diagram can also be used as a reliability block diagram, and then obtains the reliability of the devices in the diagram, and finally determines the reliability evaluation calculation method of the inverter bridge system based on the connection method of the devices.

[0158] An example, by Figure 3 , Figure 4 as well as Figure 5 From the schematic diagram of the inverter bridge structure, it can be seen that when any IGBT module fails, the entire inverter bridge may not work properly. Therefore, the series connection method can be used to evaluate the reliability of the system. That is, the reliability calculation method of the inverter bridge is to multiply the reliability of the devices in each working bridge arm one by one, and based on the obtained product, the reliability index of the inverter bridge to be evaluated is obtained.

[0159] In one example, Figure 5 It can be seen that Figure 5 The dynamic time-varying reliability R0(t) of the inverter bridge without redundant bridge arm structure shown is:

[0160]

[0161] Among them, R jk (t) is the reliability of the IGBT module in phase j and arm k.

[0162] Depend on Figure 3 As shown in the structural diagram of the inverter bridge, the dynamic reliability R of the inverter bridge with fixed redundant bridge arms is S (t) can be expressed as:

[0163]

[0164] In the formula, t represents the current time. Assume that the system startup time is zero. That is, if the working bridge arm is the preset bridge arm, the actual working time of the working bridge arm at the current time is determined to be the current time t. T1 is the fault time recorded in the bridge arm fault information, R jk (t) is the reliability of the device in the j-phase k-arm, where the reliability calculation formula of the fixed redundant inverter bridge is the same as that of the non-redundant inverter bridge when t≤T1; when t>T1, the m-arm fails, i,j,m=A,B,C and i≠j≠m, R D1 (t-T1) and R D2 (t-T1) are the reliability of the two IGBT modules in the fixed redundant bridge arm without life loss, Rm (t-T1) is the reliability of the fault phase commutation switch, R i1 (t) and R i2 (t) are the reliability of the two IGBT modules in the leading phase bridge arm of the fault phase, R j1 (t) and R j2 (t) are the reliability of the two IGBT modules in the lagging phase bridge arm of the fault phase.

[0165] In another feasible implementation, the dynamic reliability R of the inverter bridge with a fixed redundant bridge arm is S (t) can also be expressed as:

[0166]

[0167] Among them, R m1 (t) represents the reliability of the IGBT module of the upper bridge arm of the fault phase m, R m2 (t) represents the reliability of the IGBT module in the lower bridge arm of the fault phase m.

[0168] Depend on Figure 4 As shown in the structural diagram of the inverter bridge, when there is no fault in the bridge arm, the dynamic reliability R of the inverter bridge with a dynamic redundant bridge arm structure is D (t) can be expressed as:

[0169]

[0170] Among them, T is the cycle, and if all four bridge arms are normal and without fault, one bridge arm is cycled every 0.25T; when the dynamic redundant bridge arm D is connected, the corresponding phase-changing switch is required. According to the numerical relationship between the current time and the cycle, it is determined Which time period does it belong to, and then determine the calculation formula corresponding to the inverter bridge reliability index. In the formula, R C (t) is the phase-changing switch corresponding to the C-phase bridge arm, R B (t) is the phase-changing switch corresponding to the B-phase bridge arm, R A (t) is the phase-changing switch corresponding to the A-phase bridge arm.

[0171] In an example, when there is a faulty bridge arm m, if m is a dynamic redundant bridge arm, then the other three bridge arms ( Figure 4 i, s, j) in the figure work; if m is not a dynamic redundant bridge arm, the other three bridge arms ( Figure 4 The dynamic reliability R of the inverter bridge with a dynamic redundant bridge arm structure is D (t) can be expressed as:

[0172]

[0173] In another feasible implementation, when there is a faulty bridge arm m, the dynamic reliability R of the inverter bridge with a dynamic redundant bridge arm structure is D (t) can also be expressed as:

[0174]

[0175] There is a bridge arm fault in A, B, C, and D. C1 (t) represents the reliability of the IGBT module in the upper bridge arm of the C phase bridge arm, R C2 (t) represents the reliability of the IGBT module in the lower bridge arm of the C phase bridge arm; R B1 (t) represents the reliability of the IGBT module on the upper bridge arm of phase B, R B2 (t) represents the reliability of the IGBT module in the lower bridge arm of phase B, R A1 (t) represents the reliability of the IGBT module on the upper bridge arm of phase A, R A2 (t) represents the reliability of the IGBT module in the lower bridge arm of phase A. C (t) is the phase-changing switch corresponding to the C-phase bridge arm, R B (t) is the phase-changing switch corresponding to the B-phase bridge arm, R A (t) is the phase-changing switch corresponding to the A-phase bridge arm.

[0176] In summary, in order to accurately identify the various working bridge arms in the working state in the inverter bridge to be evaluated at the current moment and their corresponding actual working time, this embodiment first pre-stores redundant design information to identify the redundant design of the inverter bridge, and then performs a differentiated identification process for the inverter bridges with different redundant designs, such as a non-redundant inverter bridge, a fixed redundant inverter bridge, and a dynamic redundant inverter bridge, thereby improving the accuracy of determining the working bridge arms and their corresponding actual working time; with respect to the reliability of the devices in the working bridge arms, this embodiment combines the real-time temperature value and collector current of the built-in thermistor of the device to determine the real-time working junction temperature of the device, and then determines the real-time reliability value of the device based on the real-time working junction temperature, relying on the reliability calculation of real-time data, thereby improving the accuracy and authenticity of the device reliability value; in addition, this embodiment also determines the corresponding number of devices for different types of working bridge arms, comprehensively considering the actual operating conditions of the inverter bridge, and further improving the accuracy of the inverter bridge reliability evaluation.

[0177] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0178] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0179] Figure 6 The structure diagram of the reliability assessment device of the photovoltaic inverter bridge provided by the embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0180] like Figure 6 As shown, the reliability evaluation device of the photovoltaic inverter bridge includes:

[0181] The determination unit 61 is used to determine each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determine the actual working time of each working bridge arm at the current moment.

[0182] The first processing unit 62 is used to obtain the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtain the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time.

[0183] The second processing unit 63 is used to determine the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm.

[0184] In a possible implementation, the determination unit 61 is specifically configured to:

[0185] The pre-stored redundant design information of the inverter bridge to be evaluated is obtained; wherein the pre-stored redundant design information is used to indicate whether the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm or a fixed redundant bridge arm.

[0186] If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment is determined according to the pre-stored bridge arm fault information.

[0187] If the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm, each working bridge arm in the inverter bridge to be evaluated that is currently in working state is determined according to pre-stored bridge arm fault information, or according to pre-stored redundant design information and bridge arm fault information.

[0188] If the inverter bridge to be evaluated is not provided with a dynamic redundant bridge arm and a fixed redundant bridge arm, the working bridge arm in the inverter bridge to be evaluated that is in a working state is determined to be a pre-set bridge arm.

[0189] In a possible implementation, the determination unit 61 is specifically configured to:

[0190] Query the bridge arm fault information; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the pre-set bridge arm of the inverter bridge to be evaluated.

[0191] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arms in the inverter bridge to be evaluated that are in working state include the fixed redundant bridge arms replacing the faulty bridge arms and the pre-set bridge arms.

[0192] If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, then the working bridge arm in the inverter bridge to be evaluated that is in working state is determined to be the pre-set bridge arm.

[0193] In a possible implementation, the determination unit 61 is specifically configured to:

[0194] The bridge arm fault information of the inverter bridge to be evaluated is queried; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the inverter bridge to be evaluated.

[0195] If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, it is determined that the working bridge arms in the inverter bridge to be evaluated that are in working state include the dynamic redundant bridge arms replacing the faulty bridge arms and the pre-set bridge arms.

[0196] If a bridge arm failure occurs in the dynamic redundant bridge arm, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in working state includes a pre-set bridge arm.

[0197] If there is no faulty bridge arm in the pre-set bridge arms and the dynamic redundant bridge arms of the inverter bridge to be evaluated, the working bridge arm currently in working state in the inverter bridge to be evaluated is determined according to the redundant round-robin period in the pre-stored redundant design information.

[0198] In a possible implementation manner, the apparatus further includes a third processing unit, configured to:

[0199] If the working bridge arms of the inverter bridge to be evaluated are all preset bridge arms, it is determined that the devices corresponding to each working bridge arm are two power semiconductor devices.

[0200] If the working bridge arm of the inverter bridge to be evaluated includes a pre-set bridge arm and a redundant bridge arm that replaces the faulty bridge arm or the pre-set bridge arm, it is determined that the devices corresponding to the pre-set bridge arm in the working bridge arm are two power semiconductor devices, and the devices corresponding to the redundant bridge arm that replaces the faulty bridge arm in the working bridge arm include two power semiconductor devices and a phase-changing switch corresponding to the faulty bridge arm.

[0201] In a possible implementation, the determination unit 61 is further configured to:

[0202] If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, and there is a faulty bridge arm among the pre-set bridge arms of the inverter bridge to be evaluated, the actual working time of the device corresponding to the redundant bridge arm replacing the faulty bridge arm is determined to be the difference between the current time and the time when the fault occurs.

[0203] Otherwise, the actual working time of the working bridge arm is determined to be the difference between the start time of the inverter bridge to be evaluated and the current time.

[0204] In a possible implementation, the reliability evaluation parameter includes a basic failure rate corresponding to the device and an impact factor corresponding to the basic failure rate at the current moment; the first processing unit 62 is specifically configured to:

[0205] Obtain the basic failure rate corresponding to each device in each working bridge arm, and the influencing factor corresponding to the basic failure rate at the current moment, wherein the influencing factors include device quality factor, device application factor, device environment factor and device temperature factor, and the device temperature factor is associated with the real-time working junction temperature of the device.

[0206] According to λ(t)=λ b ·π Q ·π A ·π E ·π T , determine the device failure rate of each device at the current moment; where λ(t) is the device failure rate of the device at the current moment, t is the current moment, λ b is the basic failure rate of the device, π Q is the device quality factor, π A is the device application factor, π E is the device environment factor, π T is the device temperature factor.

[0207] according to Get the device reliability of each device in each working bridge arm; where R(t) is the device reliability of the device at the current moment; where t s The actual working time.

[0208] In a possible implementation, each device has a built-in thermistor; the apparatus further includes a fourth processing unit, specifically configured to:

[0209] Get the temperature value and collector current value of the thermistor corresponding to the device at the current moment.

[0210] Based on the temperature value and the collector current value, the operating junction temperature of each device at the current moment is determined.

[0211] According to the operating junction temperature, the device temperature factor of the device at the current moment is determined.

[0212] In a possible implementation, the second processing unit 63 is specifically configured to:

[0213] The reliability product is obtained by multiplying the device reliability of each device in each working bridge arm.

[0214] Based on the product of the reliabilities, the reliability index of the inverter bridge to be evaluated is determined.

[0215] 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.

[0216] Those of ordinary skill in the art will appreciate that the templates, 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 the present invention.

[0217] If the module / 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 invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned reliability assessment method embodiments of the inverter bridge of the photovoltaic inverter can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable media may include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0218] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that 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 invention, and should be included in the protection scope of the present invention.

Claims

1. A reliability assessment method for a photovoltaic inverter bridge, characterized in that: The method comprises: Identify each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determine the actual working time of each working bridge arm at the current moment; Obtaining the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time; According to the device reliability of each device in each working bridge arm, the reliability index of the inverter bridge to be evaluated is determined.

2. The reliability assessment method of a photovoltaic inverter bridge according to claim 1, characterized in that: The step of determining each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment includes: Acquire pre-stored redundant design information of the inverter bridge to be evaluated; wherein the pre-stored redundant design information is used to characterize whether the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm or a fixed redundant bridge arm; If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, then, according to the pre-stored bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment is determined; If the inverter bridge to be evaluated is provided with a dynamic redundant bridge arm, then according to the pre-stored bridge arm fault information, or according to the pre-stored redundant design information and the bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment is determined; If the inverter bridge to be evaluated is not provided with a dynamic redundant bridge arm and a fixed redundant bridge arm, it is determined that the working bridge arm in the inverter bridge to be evaluated that is in a working state is a preset bridge arm.

3. The reliability assessment method of a photovoltaic inverter bridge according to claim 2, characterized in that: The determining, based on the pre-stored bridge arm fault information, each working bridge arm in the inverter bridge to be evaluated that is in a working state at the current moment includes: Query the bridge arm fault information; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the bridge arms pre-set for the inverter bridge to be evaluated; If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, determining that the working bridge arms in the inverter bridge to be evaluated that are in working state include the fixed redundant bridge arms that replace the faulty bridge arms and the pre-set bridge arms; If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, then the working bridge arm in the inverter bridge to be evaluated that is in working state is determined to be the pre-set bridge arm.

4. The reliability assessment method of a photovoltaic inverter bridge according to claim 2, characterized in that: The determining, according to the pre-stored bridge arm fault information, or according to the pre-stored redundant design information and the bridge arm fault information, of each working bridge arm in the inverter bridge to be evaluated at the current moment that is in a working state, further includes: Querying the bridge arm fault information of the inverter bridge to be evaluated; wherein the bridge arm fault information indicates whether there is a faulty bridge arm in the inverter bridge to be evaluated; If there is a faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated, determining that the working bridge arms in the inverter bridge to be evaluated that are in working state include the dynamic redundant bridge arms that replace the faulty bridge arms and the pre-set bridge arms; If a bridge arm failure occurs in the dynamic redundant bridge arm, determining that the working bridge arm in the inverter bridge to be evaluated that is in working state includes a pre-set bridge arm; If there is no faulty bridge arm in the pre-set bridge arms of the inverter bridge to be evaluated and the dynamic redundant bridge arms, the working bridge arm currently in working state in the inverter bridge to be evaluated is determined according to the redundant round-robin period in the pre-stored redundant design information.

5. The reliability assessment method of the photovoltaic inverter bridge according to claim 3 or 4, characterized in that: The method further comprises: If the working bridge arms of the inverter bridge to be evaluated are all pre-set bridge arms, then determining that the devices corresponding to each working bridge arm are two power semiconductor devices; If the working bridge arm of the inverter bridge to be evaluated includes a pre-set bridge arm and a redundant bridge arm that replaces the faulty bridge arm or the pre-set bridge arm, it is determined that the devices corresponding to the pre-set bridge arm in the working bridge arm are two power semiconductor devices, and the devices corresponding to the redundant bridge arm that replaces the faulty bridge arm in the working bridge arm include two power semiconductor devices and a phase-changing switch corresponding to the faulty bridge arm.

6. The reliability assessment method of a photovoltaic inverter bridge according to claim 3 or 4, characterized in that: Determining the actual working time of each working bridge arm at the current moment includes: If the inverter bridge to be evaluated is provided with a fixed redundant bridge arm, and there is a faulty bridge arm among the bridge arms pre-set by the inverter bridge to be evaluated, then the actual working time of the device corresponding to the redundant bridge arm replacing the faulty bridge arm is determined to be the difference between the current time and the time when the fault occurs; Otherwise, the actual working time of the working bridge arm is determined to be the difference between the start-up time of the inverter bridge to be evaluated and the current time.

7. The reliability assessment method of a photovoltaic inverter bridge according to any one of claims 1 to 4, characterized in that: The reliability evaluation parameters include a basic failure rate corresponding to the device and an influencing factor corresponding to the basic failure rate at the current moment; the obtaining of the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtaining the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time, includes: Obtaining the basic failure rate corresponding to each device in each working bridge arm and the influencing factor corresponding to the basic failure rate at the current moment, wherein the influencing factor includes a device quality factor, a device application factor, a device environment factor, and a device temperature factor, and the device temperature factor is associated with the real-time working junction temperature of the device; According to λ(t)=λ b ·π Q ·π A ·π E ·π T , determine the device failure rate of each device at the current moment; where λ(t) is the device failure rate of the device at the current moment, t is the current moment, λ b is the basic failure rate of the device, π Q is the device quality factor, π A is the device application factor, π E is the device environment factor, π T is the device temperature factor; according to Get the device reliability of each device in each working bridge arm; where R(t) is the device reliability of the device at the current moment; where t s The actual working time.

8. The reliability assessment method of a photovoltaic inverter bridge according to claim 7, characterized in that: Each device has a built-in thermistor; the method further includes: Get the temperature value and collector current value of the thermistor corresponding to the device at the current moment; Determine the operating junction temperature of each device at the current moment based on the temperature value and the collector current value; A device temperature factor of the device at the current moment is determined according to the operating junction temperature.

9. The reliability assessment method of a photovoltaic inverter bridge according to any one of claims 1 to 4, characterized in that: Determining the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm includes: Multiply the device reliability of each device in each working bridge arm to obtain the reliability product; Based on the product of the reliabilities, a reliability index of the inverter bridge to be evaluated is determined.

10. A reliability assessment device for a photovoltaic inverter bridge, characterized in that: The device comprises: A determination unit, used to determine each working bridge arm in the inverter bridge to be evaluated that is in working state at the current moment, and determine the actual working time of each working bridge arm at the current moment; A first processing unit, used to obtain the reliability evaluation parameters of each device in each working bridge arm at the current moment, and obtain the device reliability of each device in each working bridge arm according to the reliability evaluation parameters corresponding to each device and the actual working time; The second processing unit is used to determine the reliability index of the inverter bridge to be evaluated according to the device reliability of each device in each working bridge arm.

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