Junction temperature calculation method and device for IGBT (Insulated Gate Bipolar Translator) module of converter and converter

Abstract

The invention relates to a junction temperature calculation method and device for an IGBT module of a converter and the converter. The method comprises the following steps: acquiring real-time distortion power loss of the IGBT module of the converter during low voltage ride through; establishing a heat supply network parameter data set matched with the distortion power under different voltage drop degrees; acquiring real-time voltage and current data, and judging the voltage drop degree during the low-voltage ride-through period according to the calculated real-time distortion power loss; substituting the heat supply network parameters into a heat supply network model, and updating heat supply network model parameters; and calculating the junction temperature of the IGBT module during the low voltage ride through period by using the updated heat supply network model parameters. Compared with the prior art, the method has the advantages of fast junction temperature calculation, high accuracy and the like, and provides a basis for effectively inhibiting the junction temperature rise of the converter.

Description

Technical Field

[0001] The present invention relates to the technical field of converter IGBT junction temperature calculation, and in particular to a converter IGBT module junction temperature calculation method, device and converter. Background Art

[0002] As renewable energy becomes more prevalent in the global power system, the challenges facing grid stability are increasing. In particular, wind power and photovoltaic power generation systems must be able to handle local voltage drop events caused by short-circuit faults in the grid, the so-called low voltage ride-through (LVRT) capability. This capability is essential to maintain the overall stability of the grid and uninterrupted power supply. In this context, key components in power electronic devices such as converters, such as insulated gate bipolar transistors (IGBTs), must be able to handle and control the resulting thermal stress during transient faults in the grid, especially during low voltage ride-through events. Transient faults such as short circuits can cause a significant instantaneous increase in the current in the device, which in turn generates a large amount of heat in a short period of time, affecting its performance and life.

[0003] At present, the junction temperature estimation technology mainly relies on two methods: equivalent thermal network model and finite element analysis. The equivalent thermal network model is widely used in industrial applications due to its fast calculation speed and easy implementation. However, this type of model is mainly designed for steady-state thermal conditions, and is not suitable for the conduction evolution of millisecond-level transient thermal shocks, resulting in limited accuracy of junction temperature. Especially when describing complex low voltage ride-through events, it cannot accurately reflect the reciprocating thermal shock, heat conduction and heat loss, which affects the control of the key parameter of the IGBT temperature of the core component of the converter during the fault voltage ride-through of the new power system. In contrast, the finite element method, although it can provide accurate temperature distribution prediction, is not suitable for online monitoring or real-time control due to its huge amount of calculation. Therefore, it is urgent to develop a new technology that can accurately calculate the transient junction temperature of the power device IGBT during low voltage ride-through in a short time scale to improve the reliability of the converter and the stability of the power grid. This technology should be able to optimize the thermal management strategy of the device, prevent damage caused by overheating, and provide accurate data support for the long-term operation life assessment of the power device.

[0004] After searching, Chinese invention patent publication number CN113343447B discloses a method, system and medium for estimating the junction temperature of IGBT under low voltage ride-through conditions. The method includes: discretizing the power curve of the converter with the transient distortion power duration tLVRT as the time granularity, matching the discrete power with the thermal time constant of each layer of the IGBT module; obtaining a continuous thermal network expression through continuous processing; matching the discrete power with the continuous thermal network expression to obtain a reconstructed thermal network model; and calculating the junction temperature of the IGBT module based on the reconstructed thermal network model. The existing patent does not clearly indicate how to dynamically update the thermal network parameters according to the real-time changing environmental conditions, which limits the application effect of the method under variable conditions.

[0005] How to quickly and accurately calculate the transient junction temperature of the inverter IGBT power chip has become a technical problem that needs to be solved. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a method and device for calculating the junction temperature of an IGBT module of a converter, and a converter.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] According to one aspect of the present invention, a method for calculating the junction temperature of an IGBT module of a converter is provided, the method comprising the following steps:

[0009] Step S1: obtaining the real-time distorted power loss of the IGBT module of the converter during low voltage ride-through;

[0010] Step S2: Establishing a heating network parameter data set matching the distorted power under different voltage drops;

[0011] Step S3: acquiring real-time voltage and current data, and judging the voltage drop degree during the low voltage ride-through period according to the real-time distortion power loss calculated in step S1;

[0012] Step S4: Substituting the heating network parameters established in step S2 into the heating network model, and updating the heating network model parameters;

[0013] Step S5: using the updated thermal network model parameters, the real-time voltage and current data and loss data obtained in step S3 are used to calculate the junction temperature of the IGBT module during the low voltage ride-through period.

[0014] Preferably, the real-time distortion power loss includes IGBT loss and diode loss, wherein the IGBT loss includes IGBT conduction loss and IGBT switching loss, and the diode loss includes diode conduction loss and diode reverse recovery loss;

[0015] The calculation formula of the IGBT on-state loss is:

[0016]

[0017]

[0018] Among them, V ce(sat) is the saturation voltage drop of IGBT; i t is the on-state current corresponding to time t; r i is the on-state resistance of IGBT; D (t) is the conduction duty cycle, + and - correspond to the rectification and inversion modes respectively; m is the modulation index; ω is the angular frequency; φ is the phase between the fundamental voltage and current;

[0019] The IGBT switching loss calculation formula is:

[0020] P sw_IGBT (i t ) = f sw (E on (i t )+E off (i t ))

[0021] Among them, f sw is the switching frequency of the device, E on (i t ) and E off (i t ) represent the current i t The turn-on loss and turn-off loss of IGBT under the action;

[0022] Diode conduction loss P con_Diode and switching loss P sw_Diode The calculation formulas are:

[0023]

[0024] Among them, V F0 is the pn junction voltage; I F is the effective value of the forward current of the diode; r F is the slope resistance; f sw is the switching frequency of the IGBT; V nom is the rated voltage of the module; I nom is the rated current of the module; E rr is the reverse recovery loss of the diode at rated voltage; V dc is the DC bus voltage; M is the modulation ratio; cosα is the output power factor of the converter.

[0025] More preferably, the total loss P of the N IGBT modules islot for:

[0026] P lot =N·(P loss_lGBT +P loss_Diode )

[0027] P loss_IGBT =P con_IGBT +P sw_IGBT

[0028] P loss_Diode =P con_Diode +P sw_Diode

[0029] Where N is the number of IGBT modules, P con_IGBT is the IGBT conduction loss, P sw_IGBT is the IGBT switching loss, P con_Diode is the diode conduction loss, P sw_Diode is the diode turn-off loss.

[0030] Optionally, the step S2 includes:

[0031] Step S21: importing the three-dimensional geometric model of the IGBT and the diode into the finite element simulation software, and specifying material properties for each part in the three-dimensional geometric model;

[0032] Step S22: according to the heat transfer finite element theory, iterate the heat conduction finite element equation, the electric field equation and the thermal stress finite element equation to solve the multi-field coupling result, wherein the multi-field is heat conduction, electrical conduction and thermal stress;

[0033] Step S23: meshing the entire three-dimensional geometric model, creating a finite element mesh and setting boundary conditions;

[0034] Step S24: injecting real-time distorted power loss under different voltage drop levels, performing finite element solution of transient thermal impedance curve, and obtaining transient thermal impedance data corresponding to different voltage drop levels;

[0035] Step S25: fitting the transient thermal impedance data to obtain a data set of thermal resistance and thermal capacitance parameters corresponding to different voltage drop levels.

[0036] More preferably, the transient thermal impedance data corresponding to different voltage drop degrees are obtained as follows:

[0037] In the thermal network, temperature is used as a voltage signal and device loss is used as a current signal, so the transient thermal impedance Z from chip to case is jc(t) Expressed as the temperature difference T from chip to case j(t) -T c(t)The ratio of the device loss P on the heat transfer path is calculated as:

[0038]

[0039] Where, T j(t) Represents the instantaneous temperature of the IGBT chip, T c(t) is the instantaneous temperature of the IGBT case;

[0040] Thus, a set of transient thermal impedance curves corresponding to different voltage drop degrees is obtained.

[0041] Preferably, the process of determining the voltage drop degree during the low voltage ride-through period in step S3 includes:

[0042] Step S31: collect voltage and current data in real time, and detect the three characteristic quantities of start and end time, phase jump, and drop depth;

[0043] Step S32: The effective value of the voltage is obtained by using the root mean square of the sampling value of one cycle. The calculation formula of the voltage drop depth D is:

[0044]

[0045] U s is the voltage before the fault, U RMS It is the effective value of voltage in one cycle.

[0046] Preferably, the updating of the heating network model parameters includes:

[0047] Step S41, defining the input and output of the thermal network model, wherein the input parameters include voltage drop, ambient temperature and current flowing through the IGBT, and the output parameters include the thermal resistance and thermal capacity after the thermal network model is updated;

[0048] Step S42, updating heating network model parameters: matching heating network model parameters from existing data according to input parameters, and substituting them into the heating network model to update relevant parameters in the heating network model.

[0049] Preferably, the calculation of the IGBT module junction temperature during the low voltage ride-through period is specifically:

[0050] Calculation model of small time scale IGBT module junction temperature during low voltage ride-through:

[0051]

[0052]

[0053] Where, T j_IGBT (t+t LVRT ) represents the junction temperature of the IGBT over a whole time scale, T j_Diode(t+t LVRT ) represents the junction temperature of the diode over a whole time scale, t LVRT is the fault voltage duration; T c Indicates ambient temperature; P loss_IGBT Indicates the power loss value of IGBT; P loss_Diode Represents the power loss value of the diode; R i represents the thermal resistance of the thermal network at layer i before updating, R j Represents the thermal resistance of the j-th thermal network after update.

[0054] According to another aspect of the present invention, a junction temperature calculation device for an IGBT module of a converter is provided, the device comprising:

[0055] The first processing unit (101) is used to obtain the real-time distorted power loss of the IGBT module of the converter during the low voltage ride-through period; wherein the real-time distorted power loss includes the loss of the IGBT and the loss of the diode, wherein the loss of the IGBT includes the conduction loss and the switching loss, and the loss of the diode includes the conduction loss and the reverse recovery loss;

[0056] A second processing unit (102) is used to establish a heating network parameter data set matching the distorted power under different voltage drops;

[0057] A third processing unit (103) is used to obtain real-time voltage and current data, and determine the voltage drop degree during the low voltage ride-through period according to the real-time distortion power loss calculated by the first unit 101;

[0058] A fourth processing unit (104) is used to substitute the heating network parameters into the heating network model and update the heating network model parameters;

[0059] The fifth processing unit (105) calculates the junction temperature of the IGBT module during the low voltage ride-through period using the updated thermal network model parameters.

[0060] According to a third aspect of the present invention, a converter is provided, wherein the converter uses the fast junction temperature calculation method to estimate the junction temperature.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1) The present invention determines the voltage drop degree during low voltage ride-through according to the collected real-time voltage and current data and the real-time distortion power loss of the converter IGBT module calculated during low voltage ride-through, updates the thermal network model parameters with a thermal network parameter data set that matches the distortion power under different voltage drops, calculates the small-time-scale IGBT module junction temperature under transient conditions based on the updated thermal network model parameters, and realizes fast and accurate IGBT module junction temperature detection, thereby providing a junction temperature basis for formulating a thermal management strategy that effectively suppresses the increase and large fluctuation of the converter junction temperature and the life assessment of the converter power module.

[0063] 2) The method of the present invention establishes a heat network parameter data set that matches the distorted power under different voltage drops, and is therefore not affected by the degree of voltage drop and can adapt to different degrees of voltage drops. This adaptability improves the reliability and calculation effect of the method under the ever-changing actual power grid conditions.

[0064] 3) The comparative experiments between the present invention and the finite element method show that the present invention is comparable to the simulation results of the finite element method in terms of accuracy, and far exceeds the finite element method in terms of calculation speed, which is at the same order of magnitude as the calculation speed of the equivalent thermal network, achieving a double improvement in calculation speed and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic flow chart of a method for calculating the junction temperature of an IGBT module of a wind power converter during low voltage ride-through of the present invention;

[0066] Figure 2 A schematic diagram showing the comparison of the results of the method of the present invention and the finite element method;

[0067] Figure 3 It is a schematic diagram of the structure of the junction temperature calculation device of the converter IGBT module in the present invention;

[0068] In the drawings, 101 is the first unit, 102 is the second unit, 103 is the third unit, 104 is the fourth unit, and 105 is the fifth unit. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0070] Example 1

[0071] This embodiment relates to a method for calculating the junction temperature of an IGBT module of a converter, which improves the accuracy and calculation efficiency of the junction temperature calculation under transient conditions.

[0072] like Figure 1 , the method comprises the following steps:

[0073] Step S1: setting parameters of different voltage drop levels to obtain real-time distorted power loss of the converter power module during low voltage ride-through, such as relevant parameters of the permanent magnet wind turbine output, including voltage and current data sets;

[0074] Step S11: The relevant parameters of the permanent magnet wind turbine set include the induced current and induced voltage of the IGBT under different voltage drop levels, the DC bus voltage V dc , switching frequency f sw .

[0075] Step S12: Real-time power loss calculation of the power module of the converter during low voltage ride-through, including IGBT loss and diode loss, wherein the IGBT loss includes conduction loss and switching loss, and the diode loss includes conduction loss and reverse recovery loss, specifically the steps are as follows:

[0076] The calculation formula for IGBT conduction loss is:

[0077]

[0078] Where: V ce(sat) is the saturation voltage drop of the IGBT; i t is the on-state current corresponding to time t; r i is the on-state resistance of the IGBT. From the data sheet, we can get V ce(sat) and r i relationship; D (t) is the on-duty ratio, which satisfies the following conditions under the SPWM strategy:

[0079]

[0080] Where + and - correspond to rectification and inversion modes respectively; m is the modulation index; ω is the angular frequency; and φ is the phase between the fundamental voltage and current.

[0081] The switching loss of IGBT can be expressed as:

[0082] P sw_IGBT (i t ) = f sw (E on (i t )+E off (i t )) (3)

[0083] Where: f sw is the switching frequency of the device, E on (it ) and E off (i t ) represent the current i t The turn-on loss and turn-off loss of the IGBT under the action of the current. The turn-on loss is based on the quadratic function of the current, and the turn-off loss is based on the linear function of the current. These loss parameters can be obtained by fitting the data sheet.

[0084] Diode conduction loss P con_Diode and switching loss P sw_Diode It can be calculated using the following formula:

[0085]

[0086]

[0087] Among them, V F0 I is the pn junction voltage, which refers to the built-in potential difference formed by the PN junction (the interface connecting the P-type and N-type semiconductors) inside the IGBT; F is the effective value of the forward current of the diode; r F is the slope resistance; f sw is the switching frequency of the IGBT; V nom is the rated voltage of the module; I nom is the rated current of the module; E rr is the reverse recovery loss of the diode at rated voltage; V dc is the DC bus voltage; M is the modulation ratio; cosα is the output power factor of the converter.

[0088] Step S13: IGBT loss P loss_IGBT is the conduction loss P con_IGBT and switching loss P sw_IGBT The sum of the diode losses P loss_Diode is the conduction loss P con_Diode and turn-off loss P sw_Diode The sum of the IGBT loss and the IGBT loss is shown in formula (7). loss_IGBT and diode loss P loss_Diode The total loss of N IGBT modules is shown in formula (8).

[0089] P loss_IGBT =P con_IGBT +P sw_IGBT (6)

[0090] P loss_Diode =P con_Diode +P sw_Di ode (7)

[0091] P lot=N·(P loss_lGBT +P loss_Diode ) (8)

[0092] Step S2: Establish a heat network parameter data set that matches the real-time distortion power under different voltage drops. The material characteristic parameters of the IGBT module include the thermal conductivity, heat flux density, transient thermal resistance and thermal capacity of each layer, and use finite element analysis to establish the relationship between different voltage drops and heat network parameters, including:

[0093] Step S21: Import the three-dimensional geometric model of the IGBT and the diode into the finite element simulation software, and specify the material properties for each part in the model according to the data manual, including elastic modulus, Poisson's ratio, thermal conductivity, density, etc.

[0094] Step S22: According to the heat transfer finite element theory, the heat conduction finite element equation is:

[0095]

[0096] Among them C t is the heat capacity matrix, K t is the heat transfer matrix, T is the node temperature, is the temperature vector, which indicates the rate of change of temperature over time, Q nd is the nodal heat flow rate vector, Q c is the heat flux vector, Q g is the heat flow load vector, Q j is the heat source heat vector, and the temperature vector Q is the sum of the heat transfer vectors.

[0097] When the IGBT module is working, the heat generated by the chip causes the temperature to rise. The temperature change causes the resistance, thermal conductivity, specific heat capacity and other parameters to change, thus generating thermoelectric coupling. j It can be calculated according to the electric field equation:

[0098] Q j =∫ v NV g 2 [σ(T)]dv (10)

[0099] Where N is the shape function matrix, V g is the potential gradient vector matrix, and σ(T) is the conductivity.

[0100] The thermal stress finite element equation is:

[0101] K·a=P (11)

[0102] Where K is the unit node force matrix, a is the node displacement, and P is the node temperature load. There is coupling between heat conduction, electrical conduction, and thermal stress, so iterative equations (9) to (11) can solve the multi-field coupling results.

[0103] Step S23: Mesh the entire model, create a finite element mesh and set boundary conditions. The 3D finite element simulation is limited to a cube, and the length, width and height are set according to the actual situation. Set fixed constraints at the four corners of the copper substrate, and set Z-direction constraints around the substrate, that is, the displacement u z = 0. To simulate the real environment, set the ambient temperature, the forced convection coefficient of the copper substrate, and the forced convection coefficients of the four surfaces of the copper substrate.

[0104] Step S24: Apply the corresponding thermal load according to the working conditions of the IGBT, that is, inject the distorted power loss under different voltage drop levels, and perform finite element solution of the transient thermal impedance curve. In the thermal network, the temperature is used as a voltage signal and the device loss is used as a current signal. Therefore, the transient thermal impedance Z from the chip to the shell is jc(t) It can be expressed as the temperature difference T from chip to case j(t) -T c(t) The ratio of the device loss P on the heat transfer path is shown in formula (12).

[0105]

[0106] Where, T j(t) Represents the instantaneous temperature of the IGBT chip, T c(t) is the instantaneous temperature of the IGBT shell. Thus, a set of transient thermal impedance curves corresponding to different voltage drop degrees are obtained.

[0107] Step S25: In the data fitting toolbox of MATLAB, the transient thermal impedance data is fitted in the form of a fourth-order exponential function to obtain four groups of thermal resistances R in the Foster network. i and heat capacity C i Parameters, the exponential function expression of transient thermal impedance is shown in formula (10).

[0108]

[0109] Thus, the thermal resistance R corresponding to different voltage drop degrees is obtained. i and heat capacity C i A data set of parameters.

[0110] Step S3: Acquire real-time voltage and current data and loss data, wherein the loss data includes power loss values ​​of IGBT and diode; use effective value method to determine the voltage drop depth during voltage ride-through;

[0111] Step S31: collect voltage and current data in real time, and detect the three characteristic quantities of start and end time, phase jump, and drop depth;

[0112] Step S32: derive the effective value of the voltage by using the root mean square of the sampling value of one cycle, and the expression is:

[0113]

[0114] Where N is the number of samples in one cycle, and u(n) is the voltage sample value at a certain moment. In the actual detection process, the effective value method often uses the sliding average method to calculate the data collected in one cycle, and replaces the old data with the new data. The calculation formula of this method is:

[0115]

[0116] The calculation formula for voltage drop depth D is:

[0117]

[0118] U s is the voltage before the fault.

[0119] Step S4: Substituting heating network parameters matching different voltage drops into the heating network model to update the original parameters;

[0120] Step S41: Define the input and output of the heating network model: the input parameters include the voltage drop V drop , and other factors that affect the heating network parameters (such as ambient temperature T tamp , the current I flowing through the IGBT); the output parameters include the thermal network parameters after the thermal network model is updated, including the thermal resistance R i and heat capacity C i ;

[0121] Step S42: Update model parameters: According to the voltage drop and other input parameters, find the corresponding heating network parameters from the existing data or calculate the parameter values ​​that are not directly observed through the interpolation method, substitute the matched heating network parameters into the heating network model, and update the relevant parameters in the model to reflect the actual situation under the current operating conditions.

[0122] Step S5: Using the means of updating the heating network parameters under transient conditions, the calculation model of the small time scale IGBT module junction temperature under transient conditions is expressed by the following formula:

[0123]

[0124]

[0125] Where T j_IGBT (t+tLVRT ) represents the junction temperature of the IGBT over a whole time scale, T j_Diode (t+t LVRT ) represents the junction temperature of the diode over a whole time scale, t LVRT is the fault voltage duration; T c Indicates ambient temperature; P loss_IGBT Indicates the power loss value of IGBT; P loss_Diode Represents the power loss value of the diode; R i represents the thermal resistance of the thermal network at layer i before updating, R j Represents the thermal resistance of the j-th thermal network after update.

[0126] In the experiment under the condition of voltage drop of 80%, the accuracy of the method of the present invention is compared with that of the finite element method. Figure 2 As shown in Table 1, the difference between the simulation result of the finite element method and the method of the present invention is only 0.53°C, indicating that the estimation accuracy of the method of the present invention is comparable to that of the finite element method. The comparison of the estimation time with other methods is shown in Table 1, indicating that only this method can achieve a calculation speed improvement of more than 100 times under the condition of achieving the accuracy of the finite element calculation method, and the calculation speed of the equivalent thermal network is at the same order of magnitude, achieving a double improvement in calculation speed and accuracy.

[0127] Table 1

[0128] method Estimated time (seconds) Method of the present invention 61 Finite Element Method 6188 Equivalent thermal network 27

[0129] Example 2

[0130] This embodiment relates to a device for calculating the junction temperature of an IGBT module of a converter, such as Figure 3 , the device comprises:

[0131] The first processing unit 101 is used to obtain the real-time distorted power loss of the converter IGBT module during low voltage ride-through; wherein the real-time distorted power loss includes the loss of the IGBT and the loss of the diode, wherein the loss of the IGBT includes the conduction loss and the switching loss, and the loss of the diode includes the conduction loss and the reverse recovery loss.

[0132] The second processing unit 102 is used to establish a heating network parameter data set matching the distorted power under different voltage drops;

[0133] The third processing unit 103 is used to obtain real-time voltage and current data, and judge the voltage drop degree during the low voltage ride-through according to the real-time distorted power loss calculated by the first unit 101; it includes a collection subunit and a calculation subunit. The collection subunit is used to obtain real-time voltage and current data, and the calculation subunit is used to judge the voltage drop degree during the low voltage ride-through according to the real-time voltage and current data and the real-time distorted power loss.

[0134] The fourth processing unit 104 is used to substitute the heating network parameters into the heating network model and update the heating network model parameters; wherein the heating network model output parameters include the heating network parameters after the heating network model is updated, including the thermal resistance R i and heat capacity C i ;

[0135] The fifth processing unit 105 calculates the junction temperature of the IGBT module during the low voltage ride-through period using the updated thermal network model parameters, and expresses the calculation model of the small time scale IGBT module junction temperature under transient conditions by the following formula:

[0136]

[0137]

[0138] Where, T j_IGBT (t+t LVRT ) represents the junction temperature of the IGBT over a whole time scale, T j_Diode (t+t LVRT ) represents the junction temperature of the diode over a whole time scale, t LVRT is the fault voltage duration; T c Indicates ambient temperature; P loss_IGBT Indicates the power loss value of IGBT; P loss_Diode Represents the power loss value of the diode; R i Represents the thermal resistance of the thermal network at layer i before updating, R j Represents the thermal resistance of the j-th thermal network after update.

[0139] Example 3

[0140] This embodiment relates to a converter, which includes a device for calculating the junction temperature of an IGBT module of the converter. The IGBT module calculates the junction temperature using the method described in Embodiment 1.

[0141] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for calculating the junction temperature of an IGBT module of a converter, characterized in that: The method comprises the following steps: Step S1: obtaining the real-time distorted power loss of the IGBT module of the converter during low voltage ride-through; Step S2: Establishing a heating network parameter data set matching the distorted power under different voltage drops; Step S3: Acquire real-time voltage and current data and loss data, and use the effective value method to determine the voltage drop degree; Step S4: Substituting the heating network parameters established in step S2 into the heating network model, and updating the heating network model parameters; Step S5: using the updated thermal network model parameters, the real-time voltage and current data and loss data obtained in step S3 are used to calculate the junction temperature of the IGBT module during the low voltage ride-through period.

2. The method for calculating the junction temperature of an IGBT module of a converter according to claim 1, characterized in that: The real-time distortion power loss includes the loss of IGBT and the loss of diode, wherein the loss of IGBT includes the conduction loss of IGBT and the switching loss of IGBT, and the loss of diode includes the conduction loss of diode and the reverse recovery loss of diode; The calculation formula of the IGBT on-state loss is: Among them, V ce(sat) is the saturation voltage drop of IGBT; i t is the on-state current corresponding to time t; r i is the on-state resistance of IGBT; D (t) is the conduction duty cycle, + and - correspond to the rectification and inversion modes respectively; m is the modulation index; ω is the angular frequency; φ is the phase between the fundamental voltage and current; The IGBT switching loss calculation formula is: P sw_IGBT (i t )=f sw (E on (i t )+E off (i t )) Among them, f sw is the switching frequency of the device, E on (i t ) and E off (i t ) represent the current i t The turn-on loss and turn-off loss of IGBT under the action; Diode conduction loss P con_Diode and switching loss P sw_Diode The calculation formulas are: Among them, V F0 is the pn junction voltage; I F is the effective value of the forward current of the diode; r F is the slope resistance; f sw is the switching frequency of the IGBT; V nom is the rated voltage of the module; I nom is the rated current of the module; E rr is the reverse recovery loss of the diode at rated voltage; V dc is the DC bus voltage; M is the modulation ratio; cosα is the output power factor of the converter.

3. The method for calculating junction temperature of an IGBT module of a converter according to claim 2, characterized in that: The total loss P of the N IGBT modules lot for: P lot =N·(P loss_lGBT +P loss_Diode ) P loss_IGBT =P con_IGBT +P sw_IGBT P loss_Diode =P con_Diode +P sw_Diode Where N is the number of IGBT modules, P con_IGBT is the IGBT conduction loss, P sw_IGBT is the IGBT switching loss, P con_Diode is the diode conduction loss, P sw_Diode is the diode turn-off loss.

4. The method for calculating junction temperature of an IGBT module of a converter according to claim 1, characterized in that: The step S2 comprises: Step S21: importing the three-dimensional geometric model of the IGBT and the diode into the finite element simulation software, and specifying material properties for each part in the three-dimensional geometric model; Step S22: according to the heat transfer finite element theory, iterate the heat conduction finite element equation, the electric field equation and the thermal stress finite element equation to solve the multi-field coupling result, wherein the multi-field is heat conduction, electrical conduction and thermal stress; Step S23: meshing the entire three-dimensional geometric model, creating a finite element mesh and setting boundary conditions; Step S24: injecting real-time distorted power loss under different voltage drop levels, performing finite element solution of transient thermal impedance curve, and obtaining transient thermal impedance data corresponding to different voltage drop levels; Step S25: fitting the transient thermal impedance data to obtain a data set of thermal resistance and thermal capacitance parameters corresponding to different voltage drop levels.

5. The method for calculating junction temperature of an IGBT module of a converter according to claim 4, characterized in that: The transient thermal impedance data corresponding to different voltage drop degrees are obtained as follows: In the thermal network, temperature is used as a voltage signal and device loss is used as a current signal, so the transient thermal impedance Z from chip to case is jc(t) Expressed as the temperature difference T from chip to case j(t) -T c(t) The ratio of the device loss P on the heat transfer path is calculated as: Where, T j(t) Represents the instantaneous temperature of the IGBT chip, T c(t) is the instantaneous temperature of the IGBT case; Thus, a set of transient thermal impedance curves corresponding to different voltage drop degrees is obtained.

6. The method for calculating junction temperature of an IGBT module of a converter according to claim 1, characterized in that: The process of determining the voltage drop degree during the low voltage ride-through period in step S3 includes: Step S31: collect voltage and current data and loss data in real time, and detect the three characteristic quantities of start and end time, phase jump, and drop depth; Step S32: The effective value of the voltage is obtained by using the root mean square of the sampling value of one cycle. The calculation formula of the voltage drop depth D is: U s is the voltage before the fault, U RMS It is the effective value of the voltage in one cycle.

7. The method for calculating junction temperature of an IGBT module of a converter according to claim 1, characterized in that: The updating heating network model parameters include: Step S41, defining the input and output of the thermal network model, wherein the input parameters include voltage drop, ambient temperature and current flowing through the IGBT, and the output parameters include the thermal resistance and thermal capacity after the thermal network model is updated; Step S42, updating heating network model parameters: matching heating network model parameters from existing data according to input parameters, and substituting them into the heating network model to update relevant parameters in the heating network model.

8. The method for calculating junction temperature of an IGBT module of a converter according to claim 1, characterized in that: The calculation of the IGBT module junction temperature during low voltage ride-through is specifically as follows: Calculation model of small time scale IGBT module junction temperature during low voltage ride-through: Where, T j_IGBT (t+t LVRT ) represents the junction temperature of the IGBT over a whole time scale, T j_Diode (t+t LVRT ) represents the junction temperature of the diode over a whole time scale, t LVRT is the fault voltage duration; T c Indicates ambient temperature; P loss_IGBT Indicates the power loss value of IGBT; P loss_Diode Represents the power loss value of the diode; R i Represents the thermal resistance of the thermal network at layer i before updating, R j Represents the thermal resistance of the j-th thermal network after update.

9. A device using the method for calculating the junction temperature of an IGBT module of a converter according to any one of claims 1 to 8, characterized in that: The device comprises: The first processing unit (101) is used to obtain the real-time distorted power loss of the IGBT module of the converter during the low voltage ride-through period; wherein the real-time distorted power loss includes the loss of the IGBT and the loss of the diode, wherein the loss of the IGBT includes the conduction loss and the switching loss, and the loss of the diode includes the conduction loss and the reverse recovery loss; A second processing unit (102) is used to establish a heating network parameter data set matching the distorted power under different voltage drops; A third processing unit (103) is used to obtain real-time voltage and current data, and determine the voltage drop degree during the low voltage ride-through period according to the real-time distortion power loss calculated by the first unit 101; A fourth processing unit (104) is used to substitute the heating network parameters into the heating network model and update the heating network model parameters; The fifth processing unit (105) calculates the junction temperature of the IGBT module during the low voltage ride-through period using the updated thermal network model parameters.

10. A converter, characterized in that: The junction temperature calculation of the converter IGBT module utilizes the method according to any one of claims 1 to 8.

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