Information energy equipment operation reliability evaluation method and system and electronic equipment

Abstract

The invention discloses an information energy equipment operation reliability evaluation method and system and electronic equipment, and relates to the field of power system reliability determination. According to the method, the Foster thermal resistance model is adopted to determine the junction temperature of the selected device in the information energy equipment, so that the average junction temperature and the junction temperature fluctuation are obtained. Adopting a Coffin-Manson-Arrhenius model to determine the number of failure cycles of the selected device based on the average junction temperature and junction temperature fluctuation so as to determine the degree of damage caused by the set number of junction temperature stress cycles; determining the fault rate of the selected device based on the damage degree, and obtaining the fault rate of the H bridge + DAB combination unit; the fault rate of the half-bridge arm can be obtained on the basis of the fault rate of the H-bridge + DAB combination unit, and the fault rate of the rectification subsystem can be accurately obtained under the condition of considering the bridge arm inductance fault rate of the half-bridge arm, so that the reliability of the digital battery energy storage system can be simply and effectively analyzed.

Description

Technical Field

[0001] The present application relates to the technical field of power system reliability determination, and in particular, to a method, a system, and an electronic device for evaluating the operation reliability of information energy equipment. Background Art

[0002] The digital battery energy storage system is connected to the power grid through a power conversion system (PCS). The link connected to the AC power grid can adopt a cascaded converter, which has the characteristics of high withstand voltage level and large transmission power. In addition, the PCS also needs to connect different battery modules through a DC isolation stage. The isolation stage usually adopts the form of a dual active bridge, and through phase-shift regulation control, power balance and electrical isolation can be flexibly achieved, which is especially suitable for differential charge and discharge control of battery modules with large differences in state of charge (SOC). Therefore, the modular cascaded converter has gradually become a research hotspot for battery energy storage system grid-connected equipment, and its reliability will directly affect the reliable level of battery energy storage grid connection safety. According to the relevant research report on the reliability of power electronic systems, the power switch device is the component with the highest failure rate in the converter system, accounting for about 34%. Among them, about 55% of the failures of power electronic systems are induced by the factor of increased junction temperature. However, in most of the reliability evaluations of power electronic devices, the component failure rate still mainly uses the statistical average value, which belongs to the category of traditional static reliability evaluation, ignoring the influence of the component health status and operating conditions on the reliability of devices, especially semiconductor devices such as insulated gate bipolar transistors (IGBTs) and diodes. It has little guiding significance for short-time scale operation. At present, the research on incorporating power electronic operating conditions into the reliability evaluation category is relatively few, and it is necessary to fully incorporate environmental factors, operating conditions, and the historical operating status of equipment into the analysis. Some research on the operation reliability of power electronic equipment mainly focuses on grid-connected equipment with simple structures such as wind power converters, mainly considering the influence of IGBT fatigue accumulation under the influence of wind speed, and there is still a lack of research on the reliability of complex energy storage PCSs involving multi-stage conversions such as input and isolation.

[0003] Although some solutions for the reliability research of complex devices such as complex energy storage PCSs involving multi-stage conversions such as input and isolation have been disclosed (for example, the Chinese patent with the publication number CN111585298B), during the process of determining the junction temperature, it needs to rely on the power consumption of each semiconductor component, increasing the complexity of reliability evaluation. Summary of the Invention

[0004] To solve the above problems existing in the prior art, the present application provides a method, a system and an electronic device for evaluating the operation reliability of information energy equipment.

[0005] To achieve the above object, the present application provides the following solutions:

[0006] A method for evaluating the operation reliability of information energy equipment, including:

[0007] Using the Foster thermal resistance model to determine the junction temperature of selected devices in the information energy equipment, and determining the average junction temperature and junction temperature fluctuation based on the junction temperature; the selected devices in the information energy equipment include: H-bridge IGBT module, H-bridge diode, DAB primary side IGBT module, DAB primary side diode, DAB secondary side IGBT module, DAB secondary side diode, capacitor, inductor and high-frequency transformer;

[0008] Using the Coffin-Manson-Arrhenius model to determine the failure cycle number of selected devices in the information energy equipment based on the average junction temperature and the junction temperature fluctuation;

[0009] Based on the failure cycle number, determining the damage degree caused by the set number of junction temperature stress cycles of the selected devices in the information energy equipment under the conditions of the junction temperature and the junction temperature fluctuation;

[0010] Based on the damage degree, determining the failure rate of the selected devices in the information energy equipment;

[0011] Based on the failure rate of the selected devices in the information energy equipment, determining the failure rate of the H-bridge + DAB combined unit;

[0012] Based on the failure rate of the H-bridge + DAB combined unit, determining the failure rate of the half-bridge arm;

[0013] Considering the failure rate of the arm inductor of the half-bridge arm, determining the failure rate of the rectifier subsystem based on the failure rate of the half-bridge arm;

[0014] Based on the failure rate of the rectifier subsystem, completing the analysis of the operation reliability of the information energy equipment.

[0015] Preferably, the formula for determining the junction temperature of the selected devices in the information energy equipment is:

[0016]

[0017] In the formula, T jm is the junction temperature, n is the thermal resistance order of the Foster thermal resistance model, i = 1, 2,..., n, R i is the thermal resistance value of the thermal resistance order i in the Foster thermal resistance model, P loss is the amplitude of the current source input to the Foster thermal resistance model, Tcase is the housing temperature of the selected device in the information energy equipment.

[0018] Preferably, the Coffin-Manson-Arrhenius model is a model improved based on the Coffin-Manson model.

[0019] Preferably, the Coffin-Manson-Arrhenius model is:

[0020]

[0021] In the formula, N f is the number of failure cycles, a is the first parameter, ΔT j is the junction temperature fluctuation, b is the second parameter, K B is the Boltzmann constant, T j is the average junction temperature, E a is the activation energy related to the material.

[0022] Preferably, under the conditions of the junction temperature and junction temperature fluctuation of the selected device in the information energy equipment, the damage degree caused by the set number of junction temperature stress cycles is:

[0023]

[0024] In the formula, D x (T jm , ΔT j ) is the damage degree caused by the set number of junction temperature stress cycles under the conditions of the junction temperature T jm and the junction temperature fluctuation ΔT j ; n x (T jm , ΔT j ) is the set number of cycles under the conditions of the junction temperature T jm and the junction temperature fluctuation ΔT j ; N f (T jm , ΔT j ) is the number of failure cycles under the conditions of the junction temperature T jm and the junction temperature fluctuation ΔT j .

[0025] Preferably, the failure rate of the selected device in the information energy equipment is:

[0026]

[0027] In the formula, λ ＊ is the failure rate of the selected device in the information energy equipment, N is the number of H-bridge + DAB combined units contained in each half-bridge arm in the information energy equipment, D x (T m, ΔT m ) is the total damage degree caused by all junction temperature stress cycles within the set time period, T m is the sum of all junction temperatures within the set time period, and ΔT m is the sum of all junction temperature fluctuations within the set time period.

[0028] Preferably, the failure rate of the H-bridge + DAB combined unit is:

[0029] λ HNDAB = 4(λ HI + λ HD + λ DABI1 + λ DABD1 + λ DABI2 + λ DABD2 ) + 2λ C + λ Ls + λ trans ;

[0030] In the formula, λ HNDAB is the failure rate of the H-bridge + DAB combined unit, λ HI is the failure rate of the H-bridge IGBT module, λ HD is the failure rate of the H-bridge diode, λ DABI1 is the failure rate of the DAB primary-side IGBT module, λ DABD1 is the failure rate of the DAB primary-side diode, λ DABI2 is the failure rate of the DAB secondary-side IGBT module, λ DABD2 is the failure rate of the DAB secondary-side diode, λ C is the failure rate of the capacitor, λ Ls is the failure rate of the inductor, λ trans is the failure rate of the high-frequency transformer.

[0031] Preferably, the failure rate of the rectifier subsystem is:

[0032] λ subsys-recti = 6(λ hb + λ Larm );

[0033] In the formula, λ subsys-recti is the failure rate of the rectifier subsystem, λ hb is the failure rate of the arm inductor of the half bridge arm, λ Larm is the failure rate of the half bridge arm.

[0034] According to the specific embodiments provided by this application, the following technical effects are disclosed in this application:

[0035] The information energy equipment operation reliability evaluation method provided by this application uses the Foster thermal resistance model to determine the junction temperature of selected devices in the information energy equipment, and obtains the average junction temperature and junction temperature fluctuation. The Coffin-Manson-Arrhenius model is used to determine the failure cycle times of the selected devices based on the average junction temperature and junction temperature fluctuation, and the damage degree caused by the set number of junction temperature stress cycles of the selected devices can be further determined; based on the damage degree, the failure rate of the selected devices in the information energy equipment is determined to obtain the failure rate of the H-bridge + DAB combined unit; based on the failure rate of the H-bridge + DAB combined unit, the failure rate of the half-bridge arm can be obtained, and then considering the failure rate of the arm inductor of the half-bridge arm, the failure rate of the rectifier subsystem is determined. Based on the rectifier subsystem, a simple and effective analysis of the reliability of the digital battery energy storage system can be realized, and the accurate evaluation of the reliability of the digital battery energy storage system can be achieved.

[0036] Furthermore, this application also provides the following implementation structure:

[0037] An information energy equipment operation reliability evaluation system applies the information energy equipment operation reliability evaluation method provided above; the system includes:

[0038] A junction temperature determination module is used to determine the junction temperature of selected devices in the information energy equipment using the Foster thermal resistance model, and determine the average junction temperature and junction temperature fluctuation based on the junction temperature; the selected devices in the information energy equipment include: H-bridge IGBT module, H-bridge diode, DAB primary side IGBT module, DAB primary side diode, DAB secondary side IGBT module, DAB secondary side diode, capacitor, inductor, and high-frequency transformer;

[0039] A failure cycle times determination module is used to determine the failure cycle times of selected devices in the information energy equipment based on the average junction temperature and the junction temperature fluctuation using the Coffin-Manson-Arrhenius model;

[0040] A damage degree determination module is used to determine the damage degree caused by the set number of junction temperature stress cycles of selected devices in the information energy equipment under the conditions of the junction temperature and junction temperature fluctuation based on the failure cycle times;

[0041] A first failure rate determination module is used to determine the failure rate of selected devices in the information energy equipment based on the damage degree;

[0042] A second failure rate determination module is used to determine the failure rate of the H-bridge + DAB combined unit based on the failure rate of selected devices in the information energy equipment;

[0043] A third failure rate determination module is used to determine the failure rate of the half-bridge arm based on the failure rate of the H-bridge + DAB combined unit;

[0044] The fourth failure rate determination module is configured to determine the failure rate of the commutation subsystem based on the failure rate of the half-bridge arm while considering the failure rate of the arm inductor of the half-bridge arm;

[0045] The reliability analysis module is configured to complete the analysis of the operation reliability of the information energy equipment based on the failure rate of the commutation subsystem.

[0046] An electronic device includes:

[0047] A memory for storing a computer program;

[0048] A processor, connected to the memory, for retrieving and executing the computer program to implement the method for evaluating the operation reliability of the information energy equipment provided above.

[0049] Since the technical effects achieved by the above two implementation structures provided in this application are the same as those achieved by the method for evaluating the operation reliability of the information energy equipment provided in this application, they will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 It is a flowchart of the method for evaluating the operation reliability of the information energy equipment provided in this application; Figure 2 It is a schematic structural diagram of a PCS in the form of a cascaded H-bridge provided in this application;

[0052] Figure 3 It is a schematic diagram of voltage level division of the cascaded H-bridge control strategy provided in this application;

[0053] Figure 4 It is a schematic diagram of the circuit topology and unit structure of the cascaded H-bridge provided in this application;

[0054] Figure 5 It is a schematic diagram of the basic structure of the cascaded H-bridge and the DAB circuit provided in this application;

[0055] Figure 6 It is a current waveform diagram when K>1 provided in this application;

[0056] Figure 7 It is a current waveform diagram when K<1 provided in this application;

[0057] Figure 8Schematic diagram of the Foster thermal resistance model provided for this application;

[0058] Figure 9 Schematic diagram of the junction temperature fluctuation distribution of the IGBT module in the H-bridge unit provided for this application;

[0059] Figure 10 Schematic diagram of the junction temperature fluctuation distribution of the IGBT module in the DAB circuit provided for this application;

[0060] Figure 11 Curve graph of the failure rate of cascade H-bridge circuit devices varying with the load multiple provided for this application;

[0061] Figure 12 Curve graph of the failure rate of DAB circuit devices varying with the load multiple provided for this application. Detailed implementation manners

[0062] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0063] The purpose of this application is to provide a method, system, and electronic device for evaluating the operation reliability of information energy equipment, which can simply and effectively analyze the reliability of a digital battery energy storage system, and then accurately evaluate the reliability of the digital battery energy storage system.

[0064] To make the above objects, features, and advantages of this application more obvious and understandable, the following further describes this application in detail in conjunction with the accompanying drawings and specific implementation manners.

[0065] As Figure 1 shown, the method for evaluating the operation reliability of information energy equipment provided by this application includes:

[0066] Step 100: Use the Foster thermal resistance model to determine the junction temperature of the selected devices in the information energy equipment, and determine the average junction temperature and junction temperature fluctuation based on the junction temperature. The selected devices in the information energy equipment include: H-bridge IGBT module, H-bridge diode, DAB primary-side IGBT module, DAB primary-side diode, DAB secondary-side IGBT module, DAB secondary-side diode, capacitor, inductor, and high-frequency transformer.

[0067] Step 101: Use the Coffin-Manson-Arrhenius model to determine the failure cycle times of the selected devices in the information energy equipment based on the average junction temperature and junction temperature fluctuation.

[0068] Step 102: Based on the number of failure cycles, determine the damage degree caused by the set number of junction temperature stress cycles under the conditions of junction temperature and junction temperature fluctuation for the selected device in the information energy equipment.

[0069] Step 103: Based on the damage degree, determine the failure rate of the selected device in the information energy equipment.

[0070] Step 104: Based on the failure rate of the selected device in the information energy equipment, determine the failure rate of the H-bridge + DAB combined unit.

[0071] Step 105: Based on the failure rate of the H-bridge + DAB combined unit, determine the failure rate of the half-bridge arm.

[0072] Step 106: Considering the failure rate of the arm inductor of the half-bridge arm, based on the failure rate of the half-bridge arm, determine the failure rate of the rectifier subsystem.

[0073] Step 107: Based on the failure rate of the rectifier subsystem, complete the analysis of the operation reliability of the information energy equipment.

[0074] Next, starting from the overall concept, the design principle and implementation effect provided above in this application will be described.

[0075] For a reconfigurable battery module, which contains a large number of controllable switch tubes, to achieve precise control, within the battery module, each minimum control unit needs to be connected to multiple controllable switches, and at the same time, power electronic switches are also used to connect between the battery modules to achieve precise control of the overall module. Such power electronic switches usually use MOSFET semiconductor devices, which have characteristics such as low loss and high reliability, and the discontinuous on-off operation has little impact on their lifespan. Therefore, this application does not delve deeply into the reliability change level during their operation process, and mainly focuses on the research of the operation reliability of the energy storage PCS.

[0076] A. Analyze the working characteristics of the cascaded H-bridge PCS: The PCS structure in the form of a cascaded H-bridge is as Figure 2 shown, mainly including a cascaded H-bridge link and an active bidirectional bridge link (Double Active Bridge, DAB). The cascaded H-bridge is a rectifier circuit used for medium and high voltage levels, and different control strategies directly affect its loss magnitude. Currently, a large number of literatures have conducted research on the control strategies of the cascaded H-bridge. In this application, the control strategy adopts a method combining PWM high-frequency modulation and low-frequency modulation, divides the input-stage AC voltage into N levels, where N is the number of H-bridge units on the half-bridge arm, and sets the voltage difference V C as the capacitor voltage of the H-bridge unit, as Figure 3 shown.

[0077] First, define the four states of the H-bridge unit. The cascaded H-bridge can be divided into unidirectional and bidirectional types according to whether the power flow can flow bidirectionally. The power flow of the unidirectional cascaded H-bridge can only flow unidirectionally and is commonly used in motor speed regulation; the bidirectional cascaded H-bridge is mainly used in PCS, etc. The circuit topology and unit structure of the cascaded H-bridge are as Figure 4 shown. Based on this, define the four states of the H-bridge unit as: positive input, negative input, zero input, and PWM, which are respectively represented as "+1", "-1", "0", and "PWM". When the H-bridge unit is in positive input, the two diagonal anti-parallel diodes D1 and diode D4 are conducting, and all the remaining devices are in the off state and there is no switching action. Corresponding to the positive input, when in negative input, diodes D2 and D3 in the H-bridge unit are conducting. There are multiple implementation combinations for the PWM state. When the input sinusoidal voltage is positive, it can be completed by the combination of the conduction of diodes D1 and D4 and the PWM control of switch tube S2, or by the combination of the conduction of diodes D1 and D4 and the PWM control of switch tube S3; when the input sinusoidal voltage is negative, it can be completed by the combination of the conduction of diodes D2 and D3 and the PWM control of switch tube S1, or by the combination of the conduction of diodes D2 and D3 and the PWM control of switch tube S4. There are also multiple implementation combinations for zero input. When the input sinusoidal voltage is positive, it can be completed by the simultaneous conduction of switch tube S2 and diode D4, or by the simultaneous conduction of switch tube S3 and diode D1; when the input sinusoidal voltage is negative, it can be completed by the simultaneous conduction of switch tube S1 and diode D3, or by the simultaneous conduction of switch tube S4 and diode D2.

[0078] The basic idea of the above control strategy is: when the input sinusoidal voltage is positive, through the combination of the three states of positive input, zero input, and PWM, the voltage waveform of the entire half-bridge arm is made to coincide with the input voltage waveform; when the input sinusoidal voltage is negative, through the combination of the three states of negative input, zero input, and PWM, the voltage waveform of the entire half-bridge arm is made to coincide with the input voltage waveform. For example, when the instantaneous value of the input sinusoidal voltage is in the interval (kV C , (k + 1)V C ), in each half-bridge arm, k units will be in positive input, providing kV C of voltage, and the input voltage is greater than kV C and less than (k + 1)V C . The insufficient part will be supplemented by one H-bridge unit in the PWM state, and the remaining H-bridge units will be in the zero input state. The specific logic is shown in Table 1.

[0079] Table 1 Device conduction state table under different modes of the cascaded H-bridge

[0080]

[0081] Assume that the input pattern and losses of each cascaded H-bridge circuit are uniform. Taking the positive half-cycle as an example, there is always one H-bridge unit in the PWM mode. It should be noted that for the convenience of calculating the conduction loss, when the diodes D1 and D4 are conducting and the PWM mode is realized by the PWM control of the switch S2, it can be assumed that the conduction current only passes through the diode D4 and the switch S2, that is, the PWM mode can be simplified to a zero-input mode. Since the cascaded H-bridge is at the high-voltage end, the conduction current is not large, and due to the relatively large number of modules, the influence of the conduction loss error is very small.

[0082] Taking the positive half-cycle as an example, as shown in Table 1, in the “+1” mode, the diodes D1 and D4 are conducting, and the conduction loss E of any one diode in half a cycle D_m1 is as follows:

[0083]

[0084] In the formula, u c is the conduction voltage drop of the semiconductor device, t i represents the time point when the instantaneous voltage is iV C , t i+1 represents the time point when the instantaneous voltage is (i + 1)VC, f is the power frequency, V m is the peak value of the input voltage, i is the i-th H-bridge unit, and i c (t) is the conduction current of the semiconductor device.

[0085] In the “0” mode, it can be realized by the conduction of the switch S2 and the diode D4 or the conduction of the switch S3 and the diode D1. The rest of the devices are in the cut-off state. Assuming that the number of times of the two combinations is the same, the total energy consumption of the diode D4 (D1) or the switch S2 (S3) in the entire positive half-cycle can be obtained as E D_M0 and E I_M0 :

[0086]

[0087] In addition, when the cascaded H-bridge circuit switches from the “+1” mode to the “0” mode, the diodes D1 or D4 will generate a loss E Drec during reverse recovery, and the expression is as follows:

[0088]

[0089] In the formula, E rec (i c (t i )) is the diode reverse recovery energy consumption function, which can be obtained by curve fitting of the data sheet. i c (t i ) is the conduction current of the semiconductor device at the ti moment.

[0090] Similar to the calculation of the reverse recovery loss of a diode, when the cascaded H-bridge circuit switches between the "0" mode and the "+1" mode, the turn-off of switch S2 or S3 will also generate losses, which is E lsw :

[0091]

[0092] In the formula, E on (i c (t i )) and E off (i c (t i ) are the turn-off losses of the IGBT at different conduction currents respectively.

[0093] Finally, for the PWM mode, under the simplified calculation conditions, the current only flows through diode D4 and switch S2 or diode D1 and switch S3. Thus, the IGBT turn-off loss E Iswpwm and the diode switching loss E Dswpwm are as follows. In the formula, f c is the PWM carrier frequency.

[0094]

[0095] In the formula, E d (i c (t i )) is the energy consumption when the conduction current of the semiconductor device is i c .

[0096] To sum up, if it is assumed that only diodes D1, D4, switches S2 and S3 have conduction or turn-off losses in the positive half-cycle, and the losses of diodes D1 and D4 and the losses of switches S2 and S3 are equal. Similarly, in the negative half-cycle, only diodes D2, D3, switches S1 and S4 have losses. Therefore, finally, the total loss P Dloss，H of the diodes and the total loss P Iloss，H of the IGBTs in the cascaded H-bridge can be obtained, which are specifically as follows:

[0097] P Dloss，H = f(E Dm1 + E Dm0 + E Drec + E Dswpwn ) / N.

[0098] P Iloss，H = f(E Im0 + E Isw + E Ispwm ) / N.

[0099] Wherein, E Dm1 is the energy consumption of the semiconductor device in the m1 segment, E Dm0 is the energy consumption of the semiconductor device in the m0 segment, E Drec is the energy consumption of the semiconductor device in the rec segment, E Dswpwm is the energy consumption of the semiconductor device in the PWM mode, E Im0 is the energy loss of the semiconductor device in the mo segment, E Isw is the diode switching loss, E Iswpwm is the IGBT turn-off loss in the PWM mode.

[0100] The second important link is the DAB for electrical isolation. The DAB is a commonly used isolation stage in the energy storage PCS and is the key structure for the PCS to achieve bidirectional energy flow. The DAB circuit is also applied in fuel cell electric vehicles, energy storage systems, and DC microgrids. With the research on power electronic transformers becoming a hot research direction and the rapid rise of new energy vehicles, the DAB circuit has gradually become an important hot research direction in the field of power electronics in recent years. The structure of the DAB circuit is as Figure 5 shown.

[0101] The control logic of the DAB circuit is relatively simple. After analyzing its current waveform, its switching logic can be clarified simultaneously. The following ratios are defined in an ideal AC transformer:

[0102]

[0103] Wherein, n is the turns ratio of the transformer; N 1 , N 2 are the number of turns of the primary and secondary windings respectively. In an ideal AC transformer, the turns ratio is also the voltage ratio. However, in the DAB circuit, due to the effect of the inductor LS, the ratio of the primary-side DC voltage U 1 to the secondary-side DC voltage U 2 is not necessarily equal to the turns ratio n of the intermediate high-frequency transformer. Therefore, the following ratios are defined:

[0104]

[0105] Wherein, K is called the voltage transfer ratio. In the single-phase phase-shift control mode, the current waveform flowing through the inductor LS in the DAB circuit is related to the value of K. When K = 1, the current is a standard trapezoidal wave; when K ≠ 1, the current waveform is as Figure 6 and Figure 7 shown.

[0106] Figure 6 and Figure 7The current waveform diagram contains the switching times of power electronic devices. Therefore, loss analysis can be directly carried out based on this. First, solve the phase shift ratio of the DAB circuit, which can be solved by the following formula:

[0107]

[0108] In the formula, P is the power of the flowing current, and D is the phase shift ratio. After reaching a steady state, the waveform of the current is symmetric about the time axis. Thus, the following set of equations can be listed:

[0109]

[0110] In the formula, i 1 is the current value of phase A, i 2 is the current value of phase B, i 0 is the current value of phase C, and L s is the inductance value.

[0111] From the set of equations, i 1 and i 2 can be solved:

[0112]

[0113] To perform subsequent loss calculations, the time-domain expression of the current needs to be solved. To obtain the time-domain expression of the current, t 1 and t 2 need to be obtained. According to the definitions of the switching frequency f and the phase shift ratio D, t 1 and t 2 can be obtained from the following formula:

[0114]

[0115] Based on the above formula and the current waveform diagram (i.e., Figure 6 and Figure 7 ), the time-domain expression of the current flowing through the inductor LS on the primary side can be obtained as:

[0116]

[0117] Next, analyze the situation of the power electronic devices through which the current flows. Figure 6 and Figure 7 not only give the current waveform but also the time points at which the IGBT switching actions occur. Combining with the voltage situation, the on-off situation of the diodes can be obtained. Based on this, the positive half-switching period of the DAB circuit is divided into three time periods:

[0118] a) The time period corresponding to t = 0 to the first current zero-crossing point: The switching transistors S1, S4, Q2, and Q3 are conducting. The primary-side current flows through the diodes SD1 and SD4, and the secondary-side current flows through the diodes QD2 and QD3;

[0119] b) The time period from the first current zero-crossing point to t 1 : The switching transistors S1, S4, Q2, and Q3 are turned on. The primary-side current flows through the switching transistors S1 and S4, and the secondary-side current flows through the switching transistors Q2 and Q3;

[0120] c) The time period from t 1 to t 2 : The switching transistors S1, S4, Q1, and Q4 are turned on. The primary-side current flows through the switching transistors S1 and S4, and the secondary-side current flows through the diodes QD1 and QD4;

[0121] The time periods and switching actions of the negative half-switching cycle are completely symmetric with those of the positive half-cycle at the time points, except that the relevant power electronic devices are replaced with the corresponding symmetric devices.

[0122] Therefore, the three time periods of the negative half-switching cycle of the DAB circuit can be defined as:

[0123] d) The time period from t 2 to the second current zero-crossing point: The switching transistors S2, S3, Q1, and Q4 are turned on. The primary-side current flows through the diodes SD2 and SD3, and the secondary-side current flows through the diodes QD1 and QD4;

[0124] e) The time period from the first zero-crossing point to t1: The switching transistors S2, S3, Q1, and Q4 are turned on. The primary-side current flows through the switching transistors S2 and S3, and the secondary-side current flows through the switching transistors Q1 and Q4;

[0125] f) The time period from t 1 to t 2 : The switching transistors S2, S3, Q2, and Q3 are turned on. The primary-side current flows through the switching transistors S2 and S3, and the secondary-side current flows through the diodes QD2 and QD3;

[0126] From the above time period division, it can be seen that the current is 0 during the reverse recovery of the power diode, so there is no reverse recovery loss. When transitioning from the time period in b) to the time period in c), the turning-off of the switching transistors Q2 and Q3 and the turning-on of the switching transistors Q1 and Q4 of the IGBT module occur; when transitioning from the time period in c) to the time period in d), the turning-off of the switching transistors S1 and S4 and the turning-on of the switching transistors S2 and S3 of the IGBT module occur. The switching actions of the negative half-switching cycle correspond one-to-one with those of the positive half-switching cycle, except that the relevant power electronic devices are replaced with the corresponding symmetric devices.

[0127] The diodes SD1 and SD4 on the primary side are connected in series and conduct during the positive half-switching cycle, with the same conduction energy consumption, denoted as E PD . The corresponding diodes SD2 and SD3 have the same energy consumption during the negative half-switching cycle, and it is also E PD(When in a steady state, the current waveforms in the positive and negative half-cycles are symmetric about the time axis). This energy consumption is only generated during period a), from which it can be obtained that:

[0128]

[0129] In the formula, t P0 is the time point of the first zero-crossing of the current; V dd (i s (t)) is the conduction voltage drop function of the diode with the conduction current as the independent variable; i(t) is the current-time expression. Any primary-side diode only has conduction loss, and its average loss in the entire switching period is:

[0130] P PD = fE PD .

[0131] The switching transistors S1 and S4 of the IGBT module on the primary side participate in the conduction of the primary-side current during periods b) and c). Since they are in series conduction, the conduction energy consumption is the same, denoted as E PI-cond ; it turns off at t 2 in the positive half-switching period and turns on in the negative half-switching period; the corresponding turn-on and turn-off energy consumptions are denoted as D PI-on and E PI-off , respectively. From this, it can be obtained that:

[0132]

[0133] In the formula, V id (x) is the conduction voltage drop function of the IGBT with the conduction current as the independent variable; E ion (x) and E ioff (x) are the turn-on energy consumption and turn-off energy consumption of the IGBT with the conduction current as the independent variable, respectively; P PI is the average loss of the IGBT module on the primary side in the entire period.

[0134] The diodes QD2 and QD3 on the secondary side have the same conduction energy consumption during period a) of the positive half-switching period, and QD1 and QD4 have the same energy consumption during period c) of the positive half-switching period. From this, it can be obtained that:

[0135]

[0136] In the formula, E SD is the conduction energy consumption of the diodes QD2 and QD3 on the secondary side during period a) of the positive half-switching period, P SD is the conduction energy consumption of QD1 and QD4 during period c) of the positive half-switching period, i s (t) is the secondary-side current expression, which can be obtained from the following formula:

[0137]

[0138] The energy consumption and losses of the secondary-side IGBT module are as follows:

[0139]

[0140] In the formula, E SI-cond is the conduction energy consumption of the secondary-side IGBT, E SI-on is the turn-on energy consumption of the secondary-side IGBT, E SI-off is the turn-off energy consumption of the secondary-side IGBT, P SI is the total energy consumption of the secondary-side IGBT, V id (i s (t)) is the voltage of the secondary-side IGBT, E ion (i s1 ) is the turn-on energy consumption of the secondary-side IGBT, i s1 is the primary-side current corresponding to the secondary-side current when the primary-side current is i 1 , and E ioff (i s1 ) is the turn-off energy consumption of the secondary-side IGBT.

[0141] B. Analyze the junction temperature fluctuation and failure probability of power electronic devices:

[0142] (1) Junction temperature fluctuation on multiple time scales.

[0143] In the data sheets of IGBT modules and diodes, data such as their respective average thermal resistances and the R and τ parameters of each order of the fourth-order Foster model are usually included. In the loss calculation of step A above, a loss calculation formula with current as the independent variable is established. For power electronic devices, when the circuit structure and voltage are determined, the relationship formula between current and power is easy to solve.

[0144] Generally, the junction temperature fluctuation in power electronic devices can be divided into low-frequency junction temperature fluctuation and high-frequency junction temperature fluctuation. Among them, the low-frequency junction temperature fluctuation is caused by load changes. Usually, the load sampling period is 15 minutes, which is much lower than the switching period or the power frequency period; the high-frequency junction temperature fluctuation is caused by the periodic change of current caused by the device switching frequency or the power frequency. Both types of junction temperature stresses will cause device fatigue accumulation, thereby affecting the component life.

[0145] The average junction temperature data of the low frequency can be regarded as the stress applied to the power electronic device, which will cause damage to the device. The 15-minute junction temperature data per year are a series of sampling points in the time domain. To find all the junction temperature fluctuations, means, and the number of cycles at the junction temperature fluctuations and means, the rainflow counting method is required.

[0146] High-frequency junction temperature fluctuation refers to the junction temperature fluctuation caused by the switching actions of the circuit itself or the periodic change of current when the load remains unchanged. For this type of junction temperature fluctuation, the average thermal resistance cannot reflect it, and the Foster thermal resistance model needs to be used for solution. The cascaded H-bridge PCS contains two types of circuits, and the topological structures, control logics, and current waveforms of each circuit are all different. Before using the Foster thermal resistance model to solve the junction temperature fluctuation caused by the circuit itself, it is necessary to determine the specific reasons for the junction temperature fluctuation caused by each circuit when the load remains unchanged and the measurement time scale. For the cascaded H-bridge circuit, the power electronic devices include two modulation modes: high-frequency PWM modulation and low-frequency switching modulation. During the state switching of the H-bridge unit and when the unit is in the PWM mode, there will be corresponding switching actions and the switching between conduction and cut-off, which will result in two states: with loss and without loss. However, the number of cascaded H-bridge circuits is relatively large, and the state switching time points of each unit are different, and the lossy and lossless times caused by the state switching are also different. If considered comprehensively, the solution of the entire junction temperature fluctuation will become very complicated. In fact, due to the relatively high switching frequency of the H-bridge unit state switching and the relatively short switching period, the response time of the thermal impedance model is relatively short, and the junction temperature fluctuation is very small. Therefore, the junction temperature fluctuation on the switching period scale can be ignored. And the switching period of PWM is even shorter, and the junction temperature fluctuation on this time scale can also be ignored. When the cascaded H-bridge circuit is working, the power electronic devices will have obvious participation of a group of diagonal devices in the positive half cycle, with loss generated, and the other group is cut off, without loss; while in the negative half cycle, another group of diagonal devices participates, with loss generated, and the group of diagonal devices with loss in the positive half cycle is cut off without loss. Therefore, it is considered that when the load remains unchanged, the junction temperature fluctuation of the cascaded H-bridge circuit due to its own reasons is caused by the switching of the device working state with the power frequency half cycle, and the power frequency cycle is used as the measurement scale.

[0147] The DAB circuit is very similar to the cascaded H-bridge circuit. There is an obvious situation where two groups of diagonal devices are switched into operation within its own switching period. However, this switching input of the DAB is caused by its own switch, and the response time is its switching period. Therefore, the time scale of the junction temperature fluctuation with unchanged load of the DAB circuit is selected as its switching period.

[0148] After determining the time scale for measuring the junction temperature fluctuation of each circuit when the load remains unchanged, the Foster thermal resistance model can be used to solve this junction temperature fluctuation (that is, the Foster thermal resistance model is used to determine the junction temperature of the selected device in the information energy equipment, and the average junction temperature and junction temperature fluctuation are determined based on the junction temperature). The Foster thermal resistance model is as Figure 8 shown. This is a circuit composed of four RC circuits connected in series. Its input is a current source with an amplitude of P loss , T jm is the junction temperature, and T case is the case temperature of the selected device in the information energy equipment.

[0149] For low-frequency junction temperature fluctuations, the change period is much longer than the response time, and the influence of heat capacity can be ignored. The steady-state junction temperature formula is as follows:

[0150]

[0151] In the formula, n is the thermal resistance order of the Foster thermal resistance model, usually a 4-order circuit, that is, i = 1, 2, 3, 4, and R i is the thermal resistance value of the thermal resistance order i in the Foster thermal resistance model. Combining historical operating conditions, the junction temperature fluctuation curve can be obtained, and the mean value, amplitude, and cycle number of the device junction temperature fluctuation can be obtained by using the rain flow counting method.

[0152] For high-frequency junction temperature fluctuations, the switching frequencies of the cascaded H-bridge and DAB links are relatively high, and the high-frequency junction temperature fluctuations are very small, and the influence on the life can be ignored; while the cascaded H-bridge circuit is directly connected to the power grid, and there are obvious 50Hz fundamental frequency junction temperature fluctuations, which need to be taken into account when analyzing the failure rate; the Foster thermal resistance model can be used to solve the maximum time t max and the minimum value t min of the high-frequency junction temperature fluctuations of different circuits, which are:

[0153]

[0154] In the formula, R(i) and τ(i) are the thermal resistance and response time parameters of the i-th order.

[0155] (2) Analysis of the failure probability of power electronic devices.

[0156] There are mainly three models for calculating the reliability of power electronic devices: the Coffin-Manson model, the Coffin-Manson-Arrhenius model, and the Bayerer model. The expression of the Coffin-Manson model is:

[0157] N f = aΔT j b .

[0158] In the formula, N f is the number of failure cycles, a is the first parameter, ΔT j is the junction temperature fluctuation, and b is the second parameter. The first parameter a and the second parameter b need to be obtained by curve fitting through experiments, and usually take 684258.31 and -2.24. Research shows that the life of the IGBT module is not only related to the junction temperature fluctuation, but also affected by the average junction temperature. Therefore, this application proposes an improved model, the Coffin-Manson-Arrhenius model, based on the Coffin-Manson model:

[0159]

[0160] In the formula, K B is the Boltzmann constant, T j is the average junction temperature, E a is the activation energy related to the material, usually taken as 9.89×10 -20 J.

[0161] The expression of the Bayerer model is:

[0162]

[0163] In the formula, I is the effective value of the current passing through each aluminum bonding wire; U is the IGBT module voltage; t on is the heating time; D’ is the diameter of the aluminum bonding wire; T jmax is the maximum value of the junction temperature. T jmin is the minimum value of the junction temperature. The other parameter values are k = 9.3×10 14 , β 1 = -4.416, β 2 = 1285, β 3 = -0.463, β 4 = -0.716, β 5 = -0.761, β 6 = -0.5.

[0164] Among the three models, the Coffin-Manson-Arrhenius model is an improved model of the Coffin-Manson model. Therefore, the former is selected between the two. Among the parameters of the Bayerer model, parameters such as the diameter of the aluminum bonding wire and the effective value of the current passing through the aluminum bonding wire involve the diameter and quantity of the aluminum bonding wire of specific device models. These are the specific internal structure data of the device and are of a certain confidentiality level and are not given in the data sheet, and relevant data cannot be obtained through other channels either. Therefore, this application finally selects the Coffin-Manson-Arrhenius model to calculate the reliability parameters of power electronic devices (that is, the Coffin-Manson-Arrhenius model is used to determine the number of failure cycles of the selected device in the information energy equipment based on the average junction temperature and the junction temperature fluctuation).

[0165] According to the Miner linear cumulative damage model, for the IGBT module, the damage caused by all stress cycles to the module can be linearly accumulated. Denote N f (T jm , ΔT j ) as the number of failure cycles under the conditions of the junction temperature T jm and the junction temperature fluctuation ΔT j , then under the mean value and fluctuation of this junction temperature, cycle nx (T jm ,ΔT j ) times of causing damage degree (that is, based on the number of failure cycles, the damage degree caused by the set number of cycles of junction temperature stress under the conditions of junction temperature and junction temperature fluctuation for the selected device in the information energy equipment) is as follows:

[0166]

[0167] In the formula, D x (T jm ,ΔT j ) is the damage degree caused by the set number of cycles of junction temperature stress under the conditions of junction temperature T jm and junction temperature fluctuation ΔT j .

[0168] When the damage degree reaches 1, the device will fail. By accumulating the damage caused by all junction temperature stress cycles within one year, the failure rate per year (that is, the failure rate of the selected device in the information energy equipment based on the damage degree) can be obtained, which is:

[0169]

[0170] In the formula, λ ＊ is the failure rate of the selected device in the information energy equipment, N is the number of H-bridge + DAB combined units contained in each half-bridge arm in the information energy equipment, D x (T m ,ΔT m ) is the total damage degree caused by all junction temperature stress cycles during the set period, T m is all junction temperatures during the set period, and ΔT m is all junction temperature fluctuations during the set period.

[0171] Substituting the mean value of the fluctuations of all junction temperature stress cycles under low-frequency junction temperature fluctuations can obtain a series of cycle failure times. Substituting all cycle failure times and the corresponding actual cycle times can obtain the failure rate under low-frequency junction temperature fluctuations, which is called the low-frequency failure rate. Substituting each load data corresponding to high-frequency junction temperature fluctuations to obtain the cycle failure times, and dividing 15 minutes by the junction temperature fluctuation period can obtain the actual cycle times. Substituting the failure cycle times and the actual cycle times can obtain the corresponding failure rate, which is called the high-frequency failure rate.

[0172] C. Evaluate the reliability of the power electronic device:

[0173] Now consider the reliability index of the commutator system without redundancy. The commutator system consists of 3 bridge arms, each bridge arm contains 2 half-bridge arms, and each half-bridge arm contains N basic units of H-bridge + DAB. Each H-bridge unit contains 4 diodes and 4 IGBT modules, and the failure of any device will cause the failure of the entire unit. Therefore, the devices are in a logical series relationship, and the failure rate of the series system is the sum of the failure rates of each component. Thus, the failure rate of the unit is the sum of the failure rates of all devices. Each DAB unit has 4 diodes and 4 IGBTs on the primary side, there is an inductor and a high-frequency transformer connected between the primary and secondary sides, and the secondary side also contains 4 diodes and 4 IGBTs. The failure of any device in the DAB unit will cause the failure of the entire unit, and the devices are in a logical series relationship, and the failure rate of the unit is the sum of the failure rates of all devices. In the combined unit of H-bridge + DAB, filter capacitors are also connected at the input and output ends of the DAB. The failure of any filter capacitor will also cause the failure of the system. Therefore, the filter capacitor and other devices are also in a logical series relationship. Based on the above description, the failure rate of the H-bridge + DAB combined unit can be calculated (that is, the failure rate of the H-bridge + DAB combined unit is determined based on the failure rates of the selected devices in the information energy equipment), as follows:

[0174] λ HNDAB =4(λ HI +λ HD +λ DABI1 +λ DABD1 +λ DABI2 +λ DABD2 )+2λ C +λ Ls +λ trans 。

[0175] In the formula, λ HNDAB is the failure rate of the H-bridge + DAB combined unit, λ HI is the failure rate of the H-bridge IGBT module, λ HD is the failure rate of the H-bridge diode, λ DABI1 is the failure rate of the DAB primary-side IGBT module, λ DABD1 is the failure rate of the DAB primary-side diode, λ DABI2 is the failure rate of the DAB secondary-side IGBT module, λ DABD2 is the failure rate of the DAB secondary-side diode, λ C is the failure rate of the capacitor, λ Ls is the failure rate of the inductor, λ trans is the failure rate of the high-frequency transformer.

[0176] When a fault occurs in any half-bridge arm of the commutator system, if both the input and output are open-circuit faults, the remaining half-bridge arms of the system can continue to operate normally; if it is a short-circuit fault, the system fails. Considering that a fault in any half-bridge arm will cause a sudden increase in the load pressure of other bridge arms, it is easy to cause the remaining bridge arms to fail due to excessive pressure, and then trigger a series of faults leading to the failure of the entire system. Therefore, it is still considered that a fault in any half-bridge arm will cause the failure of the entire commutator system, that is, the logical relationship between each half-bridge arm is in series. Based on this, in the commutator system, all H-bridge + DAB combined units are logically in series. Considering the arm inductance of the 6 half-bridge arms again, the failure rate of the commutator system is:

[0177] λ subsys-recti = 6Nλ HNDAB + 6λ Larm . In the formula, λ subsys-recti is the failure rate of the commutator system, and λ Larm is the failure rate of the half-bridge arm.

[0178] When power electronic devices are usually redundantly designed, they will not be at the level of the commutator system because the redundancy cost at the commutator system level is very high and does not meet the actual engineering requirements. Usually, redundant design is carried out at the unit and module levels. The failure rate of power electronic devices caused by the commutator system itself is not high, but due to the large number of basic units it contains, the failure rate of the entire system is relatively high. Therefore, redundant design is considered for the H-bridge + DAB combined unit. Suppose each half-bridge arm has M combined units, and when the number of non-faulty combined units is not less than N, the half-bridge arm can operate normally; when the number of faulty combined units exceeds, the bridge arm will fail. This is a typical k / n(G) system. Assuming that the reliability function of the combined unit follows an exponential distribution, the failure rate of the half-bridge arm (that is, determining the failure rate of the half-bridge arm based on the failure rate of the H-bridge + DAB combined unit) can be obtained as:

[0179]

[0180] Sum the failure rates of the 6 half-bridge arms, and then add the failure rates of the 6 arm inductances of the half-bridge arms, and the failure rate of the entire commutator system can be obtained (that is, considering the failure rate of the arm inductance of the half-bridge arm, determining the failure rate of the commutator system based on the failure rate of the half-bridge arm), which is: λ subsys-recti = 6(λ hb + λ Larm ). In the formula, λ hb is the failure rate of the arm inductance of the half-bridge arm.

[0181] Furthermore, an example for evaluating and analyzing the reliability of information energy equipment is provided to illustrate the advantages of the information energy equipment operation reliability evaluation method provided above in this application.

[0182] In this embodiment, the types of power electronic devices and other device parameters of each circuit are first determined. For the distributed energy storage system, assuming that the maximum transmission power is 1 MW, the cascaded H-bridge, DAB, and current rating do not exceed 400 A. The IGBT and diode integrated module selected is Infineon FZ400R17KE4. Let the voltage of the H-bridge + DAB combined unit be 1000 V. If it is connected to a 10 kV distribution network, 9 units are required for each half-bridge arm, and at least 54 units are required for the entire cascaded H-bridge circuit. At their respective rated powers, the losses of the cascaded H-bridge and DAB circuits are relatively low because the multi-unit cascade makes the input current smaller, so the losses are smaller. The Foster thermal resistance model is now used to solve the high-frequency junction temperature fluctuations and the mean values of each circuit. For the DAB circuit, the selected switching frequency is f = 9600 Hz; for the BUCK circuit, the chopping frequency is f = 3000 Hz, and the conduction duty cycle of the IGBT module is 0.5. The device losses of each circuit are selected as the losses at the rated power, and a power of 1 MW is transmitted. Assuming that the radiator can ensure that the temperature of the device housing is stable at 45 °C, the calculation results of the Foster thermal resistance model are shown in Table 2.

[0183] Table 2 Calculation results of the Foster thermal resistance model

[0184]

[0185] Combined with the device losses of each circuit in Table 2, it can be seen that the high-frequency junction temperature fluctuations are affected by the losses and the circuit type. Higher losses result in higher corresponding mean junction temperatures and relatively higher junction temperature fluctuations. However, the junction temperature fluctuations are also affected by the response time of the junction temperature change. The most typical example is the comparison of the junction temperature fluctuations between the cascaded H-bridge and DAB. The difference in their losses is not significant, and the mean junction temperatures are also relatively close; however, the former's junction temperature fluctuations are two orders of magnitude higher than the latter's because the junction temperature response time of the cascaded H-bridge is the power frequency cycle while that of the DAB is the switching cycle.

[0186] Now calculate the failure rates of the power electronic devices in each circuit. The input data is the load change situation of one port of a certain power electronic transformer, and the average junction temperature cycle as shown in Figure 9 and Figure 10 is obtained by using the rainflow counting method. Figure 9 and Figure 10 In, Numberofcycles refers to the number of cycles, Average refers to the average temperature, and Amplitude refers to the temperature change amplitude.

[0187] The further calculated failure rate results of each link are shown in Table 3 below. It can be seen that the failure rates of the cascaded H-bridge circuit and the DAB circuit are relatively low. Now, the load data is processed to study the influence of the load on the reliability of power electronic devices. Multiply all data points of the load data by a multiple, and the failure rate changes accordingly, asFigure 11 and Figure 12 as shown

[0188] Table 3 Results Table of Failure Rates of Each Circuit Device

[0189]

[0190] From Figure 11 and Figure 12 it can be seen that as the load increases, the failure rates of most devices increase, and the increasing trend is close to an exponential form. However, the failure rates of the primary-side diodes and secondary-side IGBT modules of the DAB circuit are decreasing. This is because when the parameters of the DAB are designed, the phase shift ratio D is greater than 0.5. According to the transmission power expression, the circuit power is the largest when D is 0.5. As the power increases, D will approach 0.5. Since it was originally greater than 0.5, D is decreasing. According to the time period division, the conduction time of the primary-side diodes and secondary-side IGBTs is shortened, and the magnitude of the current decreases accordingly. Therefore, the losses of the primary-side diodes and secondary-side IGBTs will decrease, and the failure rates will also decrease.

[0191] Furthermore, to calculate the reliability level of the overall PCS subsystem, first calculate the failure rate when the subsystem has no redundancy. The failure rates of other devices such as capacitors are 0.01752 times / year, the failure rate of inductors is 0.004 times / year, and the failure rate of high-frequency transformers is 0.013 times / year. In the rectifier subsystem, the unit voltage of the H-bridge + DAB combined unit is selected as, then 9 combined units are required for each half-bridge arm to work properly. When the subsystem has no redundant design, the calculated failure rate is 1.2714 times / year.

[0192] Now, consider the reliability with redundant standby of the rectifier subsystem and the inverter subsystem separately. For the PCS subsystem, 9 combined units are required for each half-bridge arm to work properly. Let the number of combined units of each half-bridge arm be 10, 11, 13, and 16 respectively. The results are shown in Table 4. From the results, increasing the redundant quantity of the combined units of the H-bridge + DAB can improve the reliability of the rectifier subsystem, but as the redundant quantity increases, the improvement of reliability becomes less and less obvious. From the results of Table 4, when the number of combined units of the half-bridge arm is 10 or 11, the cost and reliability factors can be better balanced.

[0193] Table 4 Calculation Results Table of Failure Rates of the Rectifier Subsystem with Redundant Standby

[0194]

[0195] Based on the above description, the present application incorporates the operating conditions and the health status of components into the scope of reliability analysis, proposes an operating reliability evaluation method for an energy storage system considering battery failure and network reconstruction strategies, effectively reflects the time-varying characteristics of the reliability of the energy storage system, and obtains a state-dependent digital energy storage system operating reliability evaluation and weak-link analysis method, providing a basis for improving the reliability of 5G information energy equipment.

[0196] Furthermore, the present application provides an information energy equipment operating reliability evaluation system to implement the above-provided information energy equipment operating reliability evaluation method. The system includes: a junction temperature determination module, a failure cycle number determination module, a damage degree determination module, a first failure rate determination module, a second failure rate determination module, a third failure rate determination module, a fourth failure rate determination module, and a reliability analysis module. The junction temperature determination module uses the Foster thermal resistance model to determine the junction temperature of selected devices in the information energy equipment, and determines the average junction temperature and junction temperature fluctuation based on the junction temperature. The selected devices in the information energy equipment include: H-bridge IGBT module, H-bridge diode, DAB primary side IGBT module, DAB primary side diode, DAB secondary side IGBT module, DAB secondary side diode, capacitor, inductor, and high-frequency transformer. The failure cycle number determination module uses the Coffin-Manson-Arrhenius model to determine the failure cycle number of selected devices in the information energy equipment based on the average junction temperature and junction temperature fluctuation. The damage degree determination module determines the damage degree caused by the set number of junction temperature stress cycles of selected devices in the information energy equipment under the conditions of junction temperature and junction temperature fluctuation based on the failure cycle number. The first failure rate determination module determines the failure rate of selected devices in the information energy equipment based on the damage degree. The second failure rate determination module determines the failure rate of the H-bridge + DAB combined unit based on the failure rate of selected devices in the information energy equipment. The third failure rate determination module determines the failure rate of the half-bridge arm based on the failure rate of the H-bridge + DAB combined unit. The fourth failure rate determination module determines the failure rate of the rectifier subsystem based on the failure rate of the half-bridge arm considering the arm inductance failure rate of the half-bridge arm. The reliability analysis module completes the analysis of the operating reliability of the information energy equipment based on the failure rate of the rectifier subsystem.

[0197] Furthermore, the present application also provides an electronic device. The electronic device includes: a memory and a processor. The memory is used to store a computer program. The processor is connected to the memory to retrieve and execute the computer program to implement the above-provided information energy equipment operating reliability evaluation method.

[0198] In addition, when the computer program in the above-mentioned memory 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 such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories, random access memories, magnetic disks, or optical discs.

[0199] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0200] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for evaluating the operating reliability of information energy equipment, characterized in that: include: Determine the junction temperature of a selected device in the information energy equipment using a Foster thermal resistance model, and determine an average junction temperature and a junction temperature fluctuation based on the junction temperature; The selected devices in the information energy equipment include: H-bridge IGBT module, H-bridge diode, DAB primary IGBT module, DAB primary diode, DAB secondary IGBT module, DAB secondary diode, capacitor, inductor and high frequency transformer; Determine the number of failure cycles of a selected device in the information energy equipment based on the average junction temperature and the junction temperature fluctuation using a Coffin-Manson-Arrhenius model; Determine, based on the number of failure cycles, the degree of damage caused by a set number of junction temperature stress cycles under the conditions of the junction temperature and junction temperature fluctuations for the selected device in the information energy equipment; Determining a failure rate of a selected component in the information energy equipment based on the damage degree; Determine the failure rate of the H-bridge + DAB combination unit based on the failure rate of selected components in the information energy equipment; Determining the failure rate of the half bridge arm based on the failure rate of the H-bridge+DAB combination unit; Under the condition that the bridge arm inductance failure rate of the half bridge arm is taken into consideration, determining the failure rate of the rectifier subsystem based on the failure rate of the half bridge arm; The analysis of the operational reliability of information energy equipment is completed based on the failure rate of the rectifier subsystem.

2. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The formula for determining the junction temperature of the selected device in information energy equipment is: Where, T jm is the junction temperature, n is the thermal resistance order of the Foster thermal resistance model, i=1,2,...,n, R i is the thermal resistance value of the thermal resistance order i in the Foster thermal resistance model, P loss is the magnitude of the current source input to the Foster thermal resistance model, T case The case temperature of selected devices in information energy equipment.

3. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The Coffin-Manson-Arrhenius model is an improved model based on the Coffin-Manson model.

4. The information energy equipment operation reliability assessment method according to claim 3 is characterized in that: The Coffin-Manson-Arrhenius model is: Where N f is the number of failure cycles, a is the first parameter, ΔT j is the junction temperature fluctuation, b is the second parameter, K B is the Boltzmann constant, T j is the average junction temperature, E a is the activation energy associated with the material.

5. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The damage degree of the selected device in the information energy equipment under the conditions of the junction temperature and junction temperature fluctuation caused by the set number of junction temperature stress cycles is: Where D x (T jm , ΔT j ) is the junction temperature T jm and junction temperature fluctuation ΔT j Under the conditions, the degree of damage caused by the set number of junction temperature stress cycles; n x (T ij , ΔT j ) is the junction temperature T jm and junction temperature fluctuation ΔT j The number of cycles under the condition; N f (T jm , ΔT j ) is the junction temperature T jm and junction temperature fluctuation ΔT j The number of cycles to failure under the given conditions.

6. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The failure rate of selected components in information energy equipment is: In the formula, λ ＊ is the failure rate of the selected device in the information energy equipment, N is the number of H-bridge + DAB combination units contained in each half-bridge arm of the information energy equipment, D x (T m , ΔT m ) is the sum of the damage caused by all junction temperature stress cycles within the set period, T m is the temperature of all junctions within the set period, ΔT m is the sum of all junction temperature fluctuations within the set period.

7. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The failure rate of the H-bridge + DAB combination unit is: l HNDAB =4(λ HI +λ HD +λ DABI1 +λ DABD1 +λ DABI2 +λ DABD2 )+2min C +λ Ls +λ trans ; In the formula, λ HNDAB is the failure rate of the H-bridge + DAB combination unit, λ HI is the failure rate of the H-bridge IGBT module, λ HD is the failure rate of the H-bridge diode, λ DABI1 is the failure rate of the DAB primary-side IGBT module, λ DABD1 is the failure rate of DAB primary diode, λ DBAI2 is the failure rate of the DAB secondary-side IGBT module, λ DABD2 is the failure rate of DAB secondary diode, λ C is the capacitor failure rate, λ Ls is the inductor failure rate, λ trans is the failure rate of high frequency transformer.

8. The information energy equipment operation reliability assessment method according to claim 1 is characterized in that: The failure rate of the rectifier system is: l subsys-recti =6(λ hb +λ Larm ); In the formula, λ subsys-recti is the failure rate of the rectifier system, λ hb is the half-bridge arm inductance failure rate, λ Larm is the failure rate of the half-bridge arm.

9. An information energy equipment operation reliability assessment system, characterized in that: The method for evaluating the operation reliability of information energy equipment according to any one of claims 1 to 8 is applied; the system comprises: A junction temperature determination module, used to determine the junction temperature of selected devices in the information energy equipment by using a Foster thermal resistance model, and determine an average junction temperature and a junction temperature fluctuation based on the junction temperature; the selected devices in the information energy equipment include: an H-bridge IGBT module, an H-bridge diode, a DAB primary-side IGBT module, a DAB primary-side diode, a DAB secondary-side IGBT module, a DAB secondary-side diode, a capacitor, an inductor and a high-frequency transformer; A failure cycle determination module, for determining the failure cycle of a selected device in the information energy equipment based on the average junction temperature and the junction temperature fluctuation using a Coffin-Manson-Arrhenius model; A damage degree determination module, for determining the damage degree of a selected device in the information energy equipment caused by a set number of junction temperature stress cycles under the conditions of the junction temperature and junction temperature fluctuation based on the number of failure cycles; A first failure rate determination module, used to determine the failure rate of a selected device in the information energy equipment based on the damage degree; A second failure rate determination module is used to determine the failure rate of the H-bridge + DAB combination unit based on the failure rate of the selected device in the information energy equipment; A third failure rate determination module, configured to determine a failure rate of a half bridge arm based on a failure rate of the H-bridge+DAB combination unit; a fourth fault rate determination module, configured to determine a fault rate of a rectifier subsystem based on the fault rate of the half bridge arm while taking into account a bridge arm inductance fault rate of the half bridge arm; The reliability analysis module is used to analyze the operational reliability of information energy equipment based on the failure rate of the rectifier subsystem.

10. An electronic device, characterized in that: include: Memory for storing computer programs; A processor, connected to the memory, is used to retrieve and execute the computer program to implement the information energy equipment operation reliability assessment method as described in any one of claims 1-8.

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