Converter power semiconductor junction temperature online calculation method, system and processor

Abstract

The invention discloses a converter power semiconductor junction temperature online calculation method and system and a processor. The method comprises the following steps: fitting loss parameters of a power semiconductor by combining a chart and actual measurement; measuring and fitting transient thermal impedance parameters of the power semiconductor relative to the NTC temperature; measuring and fitting an inductance value curve of the bridge side filter inductor; calculating the loss energy of the power semiconductor in the sampling period by considering the influence of the modulation mode and the ripple current; determining a conversion mode and loss mapping relation in the sampling period; calculating the loss power of the power semiconductor on line; and calculating the junction temperature of the power semiconductor on line. According to the method, the junction temperature of the power semiconductor of the converter can be directly calculated on line according to the actually measurable physical quantity of the converter, the executability is good, and the accuracy of junction temperature calculation is higher.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to an online calculation method, system and processor for the junction temperature of a power semiconductor of a converter. Background Art

[0002] The basic building block of the converter is a three-port bridge switch unit, which follows similar commutation rules, among which two-level converters and three-level converters are typical representatives. Figure 1 It is a topology of a two-level converter; Figure 2 This is the topology of the NPC (Neutral Point Clamped) converter, which is a typical three-level converter. The design of the converter needs to take into account both reliability and economy, and it is necessary to ensure the safety and reliability of power semiconductors and improve overload capacity under complex working conditions, variable heat dissipation conditions and limited filter conditions. Therefore, a fast and accurate online calculation method of junction temperature has become a key technology for optimizing the converter control and protection strategy, improving the converter output flexibility and operating reliability.

[0003] The patent with the authorization announcement number CN115392140B discloses a method and device for establishing a power device junction temperature prediction model in a power converter, the method comprising: offline measuring the on-state voltage data and gate voltage overshoot data of the power device under different bus voltage conditions at different temperatures, and the on-state voltage data and gate voltage overshoot data of the power device under different load current conditions at different temperatures; establishing a neural network model, and using the measured data to train, test and verify the neural network model to obtain a trained neural network model. However, prediction through offline state cannot cover various complex working conditions and heat dissipation conditions.

[0004] The patent with the publication number CN110502720A proposes an online calculation method for the loss of a power semiconductor module and its application method and device. During the operation of the power semiconductor module, the estimated junction temperature of the power semiconductor module obtained by the junction temperature observer at the previous moment is used as a closed-loop feedback, and the conduction loss and switching loss of the device generating loss in the power semiconductor module are calculated by switching cycle by switching cycle using loss-related parameters; that is, the real-time loss power is calculated online based on the real-time sampled data and the estimated junction temperature observed at the previous moment. However, the influence of the ripple current on the bridge side of the converter and the modulation method used on the loss calculation is not considered, the accuracy of the junction temperature calculation is not high enough, and the loss and junction temperature of each power semiconductor cannot be directly calculated based on the physical quantities that can be actually measured by the converter. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method, system and processor for online calculation of junction temperature of power semiconductors of a converter.

[0006] The present invention adopts the following technical solution.

[0007] A first aspect of the present invention provides an online calculation method for the junction temperature of a power semiconductor of a converter, the method comprising the following contents:

[0008] Fitting the loss functions of the power semiconductors used in the converter;

[0009] The NTC temperature is obtained by measuring the temperature with the thermistor NTC, and the transient thermal impedance parameters of the power semiconductor relative to the NTC temperature are fitted. The transient thermal impedance matrix is ​​composed of the transient thermal impedance vectors of all power semiconductors.

[0010] Fitting the inductance curve of the converter bridge-side filter inductor;

[0011] Combined with the modulation mode and ripple current influence, the loss energy of the power semiconductor during the sampling period is calculated by fitting the loss function of the power semiconductor and the inductance curve of the bridge-side filter inductor;

[0012] Determine the commutation mode and loss mapping relationship within the sampling period;

[0013] Based on the loss energy and loss mapping relationship of the power semiconductor within the sampling period, the loss power of the power semiconductor is calculated online;

[0014] Calculate the junction temperature of power semiconductors online based on the power dissipation and the transient thermal impedance matrix.

[0015] Preferably, the loss function of the power semiconductor used in the fitting converter is specifically:

[0016] The chart curve is adjusted based on the IGBT turn-on loss energy, IGBT turn-off loss energy and diode reverse recovery loss energy obtained from actual tests, and the loss function of the power semiconductor is fitted into an analytical function. The chart curve is provided by the component manufacturer, including the curve of IGBT switch loss energy with respect to IGBT current, voltage and junction temperature, and the curve of IGBT on-state voltage drop with respect to IGBT current and junction temperature.

[0017] Preferably, the loss function of the power semiconductor includes an IGBT conduction voltage drop function, an IGBT turn-on loss energy function, an IGBT turn-off loss energy function, a diode forward conduction voltage drop function, and a diode reverse recovery loss energy function;

[0018] Among them, the IGBT conduction voltage drop function is fitted as a function of the IGBT collector current and the IGBT junction temperature; the IGBT turn-on loss energy and the IGBT turn-off loss energy are fitted as functions of the IGBT collector current, the IGBT junction temperature, the IGBT gate resistance and the parallel bus voltage respectively;

[0019] The diode forward voltage drop function is fitted as a function of the diode forward current and the diode junction temperature; the diode reverse recovery loss energy is fitted as a function of the diode forward current, the diode junction temperature, the gate resistance of the commutated IGBT tube and the parallel bus voltage;

[0020] For a two-level converter, the parallel bus voltage is the voltage across the DC capacitor; for an NPC converter, the parallel bus voltage is the voltage across the upper half of the DC capacitor.

[0021] Preferably, the transient thermal impedance parameters of the fitted power semiconductor relative to the NTC temperature are composed of transient thermal impedance vectors of all power semiconductors to form a transient thermal impedance matrix, specifically:

[0022] Combined with the thermal coupling between power semiconductors, the unit step response of the transient thermal impedance of the power semiconductor relative to the NTC temperature is measured and a transient thermal impedance model is constructed. It is fitted according to the analytical model and then converted into a discrete fourth-order low-pass filter model. The transient thermal impedance vector containing all power semiconductors is obtained to form a transient thermal impedance matrix.

[0023] Preferably, the specific process of measuring the unit step response of the transient thermal impedance of the power semiconductor relative to the NTC temperature and obtaining the transient thermal impedance matrix composed of the transient thermal impedance vectors of all power semiconductors is:

[0024] Apply a step power excitation to one power semiconductor in the power semiconductor module of the converter in turn. Each time the power excitation is applied to one of the power semiconductors, measure and record the highest junction temperature curve and the NTC temperature curve of all power semiconductor chips, make a difference, and then divide by the excitation to obtain the unit step response of the transient thermal impedance of the power semiconductor.

[0025] After converting the transient thermal impedance of each power semiconductor in the power module to all power semiconductors into a discrete fourth-order low-pass filter model, a transient thermal impedance vector is formed. The transient thermal impedance vector Z of the kth IGBT tube Tk and the jth diode Dj in the power semiconductor is Tk and Z Dj The expression is:

[0026] Z Tk =(Z TkT1 ,Z TkT2 ,…,Z TkTm ,Z TkD1 ,ZTkD2 ,…,Z TkDn ) T

[0027] Z Dj =(Z DjT1 ,Z DjT2 ,…,Z DjTm ,Z DjD1 ,Z DjD2 ,…,Z DjDn ) T

[0028] Where k = 1, 2, ..., m; j = 1, 2, ..., n; Z TkT1 ,Z TkT2 ,…,Z TkTm and Z DjT1 ,Z DjT2 ,…,Z DjTm are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first IGBT tube T1, the second IGBT tube T2 and the mth IGBT tube Tm in sequence, Z TkD1 ,Z TkD2 ,…,Z TkDn and Z DjD1 ,Z DjD2 ,…,Z DjDn are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first diode D1, the second diode D2 and the nth diode Dn in sequence, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module;

[0029] The transient thermal impedance vectors of all power semiconductors are combined into a transient thermal impedance matrix. The expression of the transient thermal impedance matrix Z is:

[0030] Z=(Z T1 ,Z T2 ,…,Z Tm ,Z D1 ,Z D2 ,…,Z Dn )

[0031] Among them, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

[0032] Preferably, the inductance value curve of the fitted converter bridge-side filter inductor is specifically:

[0033] The curve of the inductance value of the bridge-side filter inductor changing with the current is measured and fitted into an analytical function, and the expression is:

[0034] L1=f L (i L )

[0035] Among them, l1 is the inductance value of the bridge side filter inductor, i L is the current of the bridge side filter inductor.

[0036] Preferably, the calculation of the power semiconductor loss energy within the sampling period based on the modulation mode and the ripple current influence is specifically as follows:

[0037] At the carrier peak and carrier bottom in each switching cycle, a sampling interrupt is entered to collect the bridge-side filter inductor current, AC filter capacitor phase voltage, and DC bus voltage or DC half bus voltage, and read the current modulation wave and switching frequency;

[0038] Sampling is performed at the carrier peak and carrier bottom points. The time between the two sampling moments is a sampling period, and a switching period is divided into two sampling periods. The conduction time of the power semiconductor is calculated based on the modulation wave and the switching period at the sampling moment.

[0039] Whether switching occurs during the sampling period is determined based on the debugging wave or the conduction time. If switching occurs, the current sampling period is continuous pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to continuous pulse width modulation; if no switching occurs, the current sampling period is intermittent pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to intermittent pulse width modulation.

[0040] Preferably, the energy loss of the power device during the sampling period is calculated according to the continuous pulse width modulation as follows:

[0041] Calculate the conduction loss energy, turn-on loss energy, turn-off loss energy or reverse recovery loss energy of power semiconductors.

[0042] Preferably, the energy loss of the power device within the sampling period is calculated according to the intermittent pulse width modulation, specifically:

[0043] Only the conduction loss energy of the power semiconductor is calculated, while the turn-on loss energy, turn-off loss energy or reverse recovery loss energy of the power semiconductor are not calculated and are directly assigned to zero.

[0044] Preferably, based on the influence of ripple current on loss calculation, the slope of the bridge-side filter inductor current is calculated, and then the current value at the turn-on moment, turn-off moment or reverse recovery moment of the power semiconductor is calculated, and then the IGBT tube conduction voltage drop and diode conduction voltage drop, turn-on loss energy, turn-off loss energy and reverse recovery loss energy of the power semiconductor within the sampling period are calculated by the fitting function, wherein the junction temperature is calculated using the junction temperature calculated in the previous sampling period, and the conduction loss energy is calculated by the IGBT tube conduction voltage drop and the diode conduction voltage drop.

[0045] Preferably, the determining of the commutation mode and loss mapping relationship within the sampling period is specifically as follows: judging the commutation mode of the converter according to the modulation wave, carrier and bridge-side filter inductor current values ​​of the sampling period, and mapping the loss energy calculated within the sampling period to a specific power semiconductor;

[0046] For a two-level converter, the loss mapping relationship is a two-dimensional lookup table of the bridge-side filter inductor current and the sampling time; for an NPC converter, the loss mapping relationship is a three-dimensional lookup table of the bridge-side filter inductor current, the modulation wave and the sampling time.

[0047] Preferably, the second bridge-side filter inductor current of the cycle calculated in the previous sampling cycle is equal to the first bridge-side filter inductor current of the cycle calculated in the next sampling cycle, and the turn-on loss energy, turn-off loss energy or reverse recovery energy occurring under this current can be calculated in any sampling cycle.

[0048] Preferably, a calculation window with a length of N switching cycles is set, and the average value of the loss energy in each power semiconductor switching cycle in the window is calculated, multiplied by the current switching frequency, and then accumulated according to the power semiconductor to obtain the power semiconductor loss power. The power semiconductor includes an IGBT tube and a diode. The loss energy includes the conduction loss energy, turn-on loss energy and turn-off loss energy of the IGBT tube and the conduction loss energy and reverse recovery loss energy of the diode.

[0049] Preferably, the variables are written in the form of vectors to calculate the junction temperature of the power semiconductor. The expression is as follows:

[0050] T=(T T1 ,T T2 ,…,T Tm ,T D1 ,T D2 ,…,T Dn ) T

[0051] P=(P T1 ,P T2 ,…,P Tm ,P D1 ,P D2 ,…,P Dn ) T

[0052] T=ZP+T NTC

[0053] Among them, T NTC is the online measured NTC temperature, P is the online calculated power loss, T is the online junction temperature of the power semiconductor, Z is the transient thermal impedance matrix, T T1 ,T T2 ,…,TTm and P T1 ,P T2 ,…,P Tm are the junction temperature and power of the first IGBT tube T1, the second IGBT tube T2, and the mth IGBT tube Tm in sequence; T D1 ,T D2 ,…,T Dn and P D1 ,P D2 ,…,P Dn They are the junction temperature and power of the first diode D1, the second diode D2 to the nth diode Dn in sequence, where m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

[0054] The second aspect of the present invention provides an online calculation system for junction temperature of a converter power semiconductor using the online calculation method for junction temperature according to the first aspect of the present invention, comprising:

[0055] Function fitting module: Fitting the loss parameter function of power semiconductors, fitting the transient thermal impedance parameter function of power semiconductors relative to NTC temperature, and fitting the inductance curve of bridge-side filter inductance;

[0056] Loss energy calculation module: Combines the modulation mode and ripple current influence to calculate the loss energy of power semiconductors within the sampling period;

[0057] Loss mapping lookup module: determines the commutation mode and loss mapping relationship within the sampling period by looking up the table;

[0058] Power loss calculation module: calculates the power loss of power semiconductors;

[0059] The junction temperature calculation and storage module calculates and stores the junction temperature through the power loss and transient thermal impedance matrix.

[0060] A third aspect of the present invention provides a processor for executing the online calculation method of the junction temperature of a power semiconductor of a converter according to the first aspect of the present invention.

[0061] The beneficial effect of the present invention is that, compared with the prior art, the actual operation of the converter is performed by sampling and calculating twice in each switching cycle;

[0062] Considering the influence of the ripple current on the converter bridge side on the loss calculation, the current at the time of power semiconductor switching on and off is calculated according to the physical quantities collected in each sampling period, which is used to calculate the switching loss energy, switching loss energy and reverse recovery loss energy;

[0063] According to the modulation wave in each sampling period, it can judge whether the actual opening and closing occurs, which can adapt to both continuous pulse width modulation and intermittent pulse width modulation;

[0064] Determine the commutation mode and loss mapping relationship within the sampling period according to the modulation wave, the bridge-side filter inductor current and the sampling time;

[0065] The junction temperature is calculated using a transient thermal impedance model relative to the NTC temperature, with tight thermal coupling;

[0066] In summary, the present invention can directly calculate the junction temperature of the power semiconductor of the converter online according to the physical quantity that can be actually measured by the converter, has good executability, and the accuracy of the junction temperature calculation is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the topological structure of a two-level converter in the prior art;

[0068] Figure 2 It is a schematic diagram of the topological structure of the NPC converter in the prior art;

[0069] Figure 3 It is a flow chart of an online calculation method of the junction temperature of a power semiconductor of a converter in the present invention;

[0070] Figure 4 It is a schematic diagram of sampling within a switching cycle in the present invention. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0072] like Figure 3 As shown, Embodiment 1 of the present invention provides an online calculation method for the junction temperature of a power semiconductor of a converter, comprising the following contents:

[0073] Fitting the loss functions of the power semiconductors used in the converter;

[0074] Preferably, the loss parameter function of the power semiconductor is fitted, specifically:

[0075] The chart curve is adjusted based on the IGBT turn-on loss energy, IGBT turn-off loss energy and diode reverse recovery loss energy obtained from actual tests, and the loss function of the power semiconductor is fitted into an analytical function. The chart curve is provided by the component manufacturer, including the curve of IGBT switch loss energy with respect to IGBT current, voltage and junction temperature, and the curve of IGBT on-state voltage drop with respect to IGBT current and junction temperature.

[0076] Preferably, the loss function of the power semiconductor includes an IGBT conduction voltage drop function, an IGBT turn-on loss energy function, an IGBT turn-off loss energy function, a diode forward conduction voltage drop function, and a diode reverse recovery loss energy function;

[0077] Among them, the IGBT conduction voltage drop function is fitted as a function of the IGBT collector current and the IGBT junction temperature; the IGBT turn-on loss energy and the IGBT turn-off loss energy are fitted as functions of the IGBT collector current, the IGBT junction temperature, the IGBT gate resistance and the parallel bus voltage respectively;

[0078] The diode forward voltage drop function is fitted as a function of the diode forward current and the diode junction temperature; the diode reverse recovery loss energy is fitted as a function of the diode forward current, the diode junction temperature, the gate resistance of the commutated IGBT tube and the parallel bus voltage;

[0079] For a two-level converter, the parallel bus voltage is the voltage across the DC capacitor; for an NPC converter, the parallel bus voltage is the voltage across the upper half of the DC capacitor.

[0080] Preferably, because the on-state voltage drop of the IGBT tube v ce is about the collector current i c and its junction temperature T Tk function, so we can fit v by the following formula ce About i c and T Tk The analytical function of , specifically, this embodiment is fitted as a two-variable linear function.

[0081] v ce =f ic (i c ,T Tk )

[0082] Because the IGBT tube turn-on loss energy E on and turn-off loss energy E off is about the collector current i c , Junction temperature T Tk , Gate resistance R g and the parallel bus voltage v dc function, and directly determine R by actual measurement g , and E on 、E off Average and v dc It can be fitted into a proportional relationship, and E can be fitted according to the following relationship. on and E off The analytical function of f Eon (i c ,TTk ) and f Eoff (i c ,T Tk ) is fitted as a two-variable linear function, Yes dc The per-unit value of the switch-on loss energy and the switch-off loss energy obtained by actual measurement are used as the basis to adjust the chart curve and fit the function.

[0083]

[0084] Because the forward conduction voltage drop of the diode is v f is about the forward conduction current i f and its junction temperature T Dj function, so we fit v as follows f About i f and T Dj The analytical function of , specifically, this embodiment is fitted as a two-variable linear function.

[0085] v f =f if (i f ,T Dj )

[0086] Because the reverse recovery energy loss of the diode is E rec is about the forward conduction current i f , Junction temperature T Dj , commutation IGBT gate resistance R g and the parallel bus voltage v dc function, and use actual measurements to determine R g , E rec and v dc It can be fitted into a proportional relationship, so E is fitted according to the following formula rec The analytical function of f Erec (i f ,T Dj ) is a linear function of two variables, Yes dc The per-unit value of ; the fitting function is adjusted based on the actual reverse recovery loss energy measured.

[0087]

[0088] The NTC temperature is obtained by measuring the temperature with a thermistor NTC, and the transient thermal impedance parameters of the power semiconductor relative to the NTC temperature are fitted. The transient thermal impedance matrix is ​​composed of the transient thermal impedance vectors of all power semiconductors.

[0089] Preferably, the transient thermal impedance parameters are fitted to obtain a transient thermal impedance matrix, specifically:

[0090] A step power excitation P is applied to a power semiconductor Uk′ in the power semiconductor module of the converter. Uk′ , measure and record the maximum junction temperature curve T of all power semiconductors Vj′ (t) and NTC temperature curve T NTC (t) The maximum junction temperature of all power semiconductors is subtracted from the NTC temperature and then divided by the applied power excitation to obtain the unit step response of the power semiconductor Uk′ to the transient thermal impedance of all power semiconductors;

[0091] The formula for calculating the unit step response of power semiconductor Uk′ to power semiconductor Vj′ is as follows:

[0092]

[0093] Among them, U=T,D, V=T,D, T represents IGBT tube, D represents diode; Uk′ represents the power semiconductor corresponding to the k′th U; Vj′ represents the power semiconductor corresponding to the j′th V;

[0094] Repeat the above steps for all power semiconductors;

[0095] A transient thermal impedance model is constructed, and the unit step response is fitted according to the analytical model to fit four groups of thermal resistances and thermal resistance time constants, which are then converted into a discrete fourth-order low-pass filter model to obtain the transient thermal impedance of each power semiconductor in the power module to all power semiconductors, which is written as a transient thermal impedance vector. The transient thermal impedance vector Z of the kth IGBT tube Tk and the jth diode Dj in the power semiconductor Tk and Z Dj The expression is:

[0096] Z Tk =(Z TkT1 ,Z TkT2 ,…,Z TkTm ,Z TkD1 ,Z TkD2 ,…,Z TkDn ) T

[0097] Z Dj =(Z DjT1 ,Z DjT2 ,…,Z DjTm ,Z DjD1 ,Z DjD2 ,…,Z DjDn ) T

[0098] Where k = 1, 2, ..., m; j = 1, 2, ..., n; Z TkT1 ,Z TkT2 ,…,Z TkTmand Z DjT1 ,Z DjT2 ,…,Z DjTm are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first IGBT tube T1, the second IGBT tube T2 and the mth IGBT tube Tm in sequence, Z TkD1 ,Z TkD2 ,…,Z TkDn and Z DjD1 ,Z DjD2 ,…,Z DjDn are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first diode D1, the second diode D2 and the nth diode Dn in sequence, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module;

[0099] The transient thermal impedance vectors of all power semiconductors are combined into a transient thermal impedance matrix Z, which is expressed as:

[0100] Z=(Z T1 ,Z T2 ,…,Z Tm ,Z D1 ,Z D2 ,…,Z Dn )

[0101] Among them, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

[0102] Preferably, the transient thermal impedance model is specifically:

[0103]

[0104] Among them, U=T,D, V=T,D, T represents IGBT tube, D represents diode; Uk′ represents the power semiconductor corresponding to the k′th U; Vj′ represents the power semiconductor corresponding to the j′th V; Z Uk′vj′ (t) is the unit step response of the transient thermal impedance of Uk′ to Vj′; r zk′zj′,i is the thermal resistance of the ith Uk′ to Vj′, τ Zk′Zj′,i is the thermal resistance time constant of the ith Uk′ to Vj′; t is the current moment.

[0105] Fit the inductance curve of the converter bridge-side filter inductor.

[0106] Preferably, the inductance curve of the bridge-side filter inductor is measured and fitted, specifically:

[0107] The curve of the inductance value of the bridge-side filter inductor changing with the current is measured and fitted into an analytical function, and the expression is:

[0108] L1=fL (i L )

[0109] Where, L1 is the inductance value of the bridge side filter inductor, i L is the current of the bridge side filter inductor.

[0110] Combining the modulation mode and the influence of ripple current, the loss energy of the power semiconductor during the sampling period is calculated by fitting the loss function of the power semiconductor and the inductance curve of the bridge-side filter inductor.

[0111] Preferably, the loss energy of the power semiconductor within the sampling period is calculated as follows:

[0112] At the carrier peak and carrier bottom in each switching cycle, the bridge-side filter inductor current, AC filter capacitor phase voltage and DC bus voltage or DC half bus voltage are collected, and the current modulation wave and switching frequency are read;.

[0113] The conduction time of the power semiconductor is calculated based on the modulation wave and the switching period at the sampling moment.

[0114] It should be noted that the two-level converter adopts bipolar PWM modulation, and the NPC converter adopts PWM modulation of two in-phase stacked carriers. The same effect can also be achieved in the form of other modulation waves and carriers. No specific limitation is made here, depending on the application environment, and all are within the protection scope of this application. When the modulation wave is greater than a certain IGBT tube carrier, the IGBT tube is turned on. When the modulation wave is greater than 0 and the current of the IGBT tube is positive, the two intersections of the modulation wave and the carrier in the switching cycle correspond to the turn-on and turn-off moments of the IGBT tube, the carrier bottom point is approximately the midpoint of the conduction interval of the IGBT tube, and the bridge-side filter inductor current sampled at the carrier bottom point is approximately equal to the current average value during the conduction period of the IGBT tube. Conversely, the carrier vertex is approximately the midpoint of the turn-off interval of the IGBT tube, the IGBT tube current is zero, and the bridge-side filter inductor current sampled at the carrier vertex is approximately equal to the current average value during the conduction period of the power semiconductor commutated with the IGBT tube.

[0115] like Figure 4 The sampling diagram in the switching cycle is shown, the modulation wave is greater than 0 and the bridge-side filter inductor current is positive. A switching cycle is divided into two sampling cycles, sampling time 0 is the carrier peak, sampling time 1 is the carrier bottom; the time from sampling time 0 to sampling time 1 is sampling cycle 0, and the time from sampling time 1 to sampling time 0 is sampling cycle 1;

[0116] Preferably, the on-time is calculated as follows:

[0117] For a two-level converter, the on-time calculation formula is:

[0118]

[0119] For NPC converter, the conduction time calculation formula is:

[0120]

[0121] Among them, t dw is the conduction time of the IGBT tube, t up is the conduction time of the diode commutating with the IGBT tube, and are the per-unit values ​​of the modulation wave relative to the carrier amplitude at sampling time 0 and sampling time 1, respectively, s is the switching cycle.

[0122] Whether switching occurs during the sampling period is determined based on the debugging wave or the conduction time. If switching occurs, the current sampling period is continuous pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to continuous pulse width modulation; if no switching occurs, the current sampling period is intermittent pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to intermittent pulse width modulation.

[0123] Preferably, determining whether a switch occurs within a sampling period is specifically as follows:

[0124] For a two-level converter, the modulation wave satisfies or When the switch occurs,

[0125] For NPC converter, the modulation wave satisfies or When the switch occurs, dw, w is the narrow pulse filtering width.

[0126] Preferably, calculating the loss energy of the power device within the sampling period according to the continuous pulse width modulation includes: calculating the on-state loss energy, turn-on loss energy, turn-off loss energy or reverse recovery loss energy of the power semiconductor.

[0127] Preferably, the loss energy of the power device within the sampling period is calculated according to the intermittent pulse width modulation, and the turn-on loss energy, turn-off loss energy and reverse recovery loss energy of the power semiconductor are directly assigned to zero to calculate the conduction loss energy of the power semiconductor.

[0128] Preferably, the on-state loss energy, turn-on loss energy, turn-off loss energy and reverse recovery loss energy of the power semiconductor are calculated as follows:

[0129] For the IGBT tube, at sampling time 1, the voltage and inductance value across the bridge-side filter inductor are sampled to calculate the current slope. The formula is:

[0130]

[0131] Among them, k i is the slope of the bridge-side filter inductor current, v dc is the sampling value of the bus voltage of the IGBT tube in parallel, is the sampling value of the phase voltage, L1 is the inductance value of the bridge side filter inductor; where L1 = f L (i L ),i L is the current of the bridge-side filter inductor;

[0132] Calculate the conduction loss energy E in sampling period 1 cd , opening loss energy E on and turn-off loss energy E off The formula is:

[0133] E cd =f ic (i L ,T′ Tk )·i L ·t dw

[0134]

[0135] in, i L1 is the current when the IGBT is turned on, i L2 is the current when the IGBT is turned off; T′ Tk The IGBT junction temperature calculated in the previous sampling cycle;

[0136] For the diode, at sampling time 0, the voltage and inductance across the bridge-side filter inductor are sampled to calculate the current slope:

[0137]

[0138] Calculate the conduction loss energy E of the diode in sampling period 0 respectively f and reverse recovery loss energy E rec , the formula is:

[0139] E f =f if (i L ,T′ Dj )·i L ·t up

[0140]

[0141] Among them, i L2It is also the current value of the commutating diode at the reverse recovery moment. Calculated using the above formula, T′ Dj The diode junction temperature calculated for the last sampling period.

[0142] Determine the commutation mode and loss mapping relationship within the sampling period;

[0143] Preferably, the commutation mode of the converter is determined according to the modulation wave, carrier wave and bridge-side filter inductor current value of the sampling period, and the loss energy calculated in the sampling period is mapped to a specific power semiconductor;

[0144] For the two-level converter, the loss mapping relationship is shown in Table 1, which is a two-dimensional lookup table of the bridge-side filter inductor current and the sampling time; for the NPC converter, the loss mapping relationship is shown in Table 2, which is a three-dimensional lookup table of the bridge-side filter inductor current, the modulation wave and the sampling time.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149] Preferably, the i calculated in the previous sampling period L2 Equal to i calculated in the next sampling period L1 , the turn-on loss energy, turn-off loss energy or reverse recovery energy occurring under this current can be calculated in any sampling period.

[0150] Based on the loss energy and loss mapping relationship of the power semiconductor within the sampling period, the loss power of the power semiconductor is calculated online;

[0151] Preferably, the online power loss of the power semiconductor is calculated as follows:

[0152] A calculation window with a length of N switching cycles is set, and the average value of the energy loss in each power semiconductor switching cycle in the window is calculated, multiplied by the current switching frequency, and then accumulated according to the power semiconductor to obtain the power semiconductor loss power. The power semiconductor includes an IGBT tube and a diode. The energy loss includes the on-state loss energy, turn-on loss energy and turn-off loss energy of the IGBT tube and the on-state loss energy and reverse recovery loss energy of the diode. The formula is as follows:

[0153]

[0154] P T =P cd +P on +P off

[0155] P D =P f +P rec

[0156] Where P is the current power semiconductor power loss, Fs is the switching frequency, n is the number mark, representing the nth switching cycle from the current switching cycle, E n is the energy loss in the switching cycle represented by the nth counting mark of each power semiconductor, P T is the total power consumption of the IGBT tube, P cd is the conduction loss energy consumption of the IGBT tube, P on is the power consumption of the IGBT tube when it is turned on, P off is the turn-off power consumption of the IGBT tube, P D is the total energy consumption of the diode, P f is the conduction loss energy consumption of the diode, P rec is the reverse recovery loss energy of the diode;

[0157] It should be noted that the value of N depends on the thermal time constant. If the thermal time constant is very short and it is desired to reflect rapid temperature changes, the calculation period is set shorter. If the time constant is very large or it is not required to reflect rapid temperature changes, the period is set longer.

[0158] The junction temperature of the power semiconductor is calculated using the power loss and transient thermal impedance matrix.

[0159] Preferably, the variables are written in the form of vectors to calculate the junction temperature of the power semiconductor. The expression is as follows:

[0160] T=(T T1 ,T T2 ,…,T Tm ,T D1 ,T D2 ,…,T Dn ) T

[0161] P=(P T1 ,P T2 ,…,P Tm ,P D1 ,P D2 ,…,P Dn ) T

[0162] T=ZP+T NTC

[0163] Among them, T NTC is the online measured NTC temperature, P is the online calculated power loss, T is the online junction temperature of the power semiconductor, Z is the transient thermal impedance matrix, T T1,T T2 ,…,T Tm and P T1 ,P T2 ,…,P Tm are the junction temperature and power of the first IGBT tube T1, the second IGBT tube T2, and the mth IGBT tube Tm in sequence; T D1 ,T D2 ,…,T Dn and P D1 ,P D2 ,…,P Dn They are the junction temperature and power of the first diode D1, the second diode D2 to the nth diode Dn in sequence, where m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

[0164] This embodiment provides a method for online calculation of the junction temperature of a power semiconductor of a converter. During the actual operation of the converter, sampling and calculation are performed twice in each switching cycle; considering the influence of the ripple current on the bridge side of the converter on the loss calculation, the current at the time of opening and closing of the power semiconductor is calculated according to the physical quantity sampled in each sampling cycle, which is used to calculate the opening loss energy, the closing loss energy and the reverse recovery loss energy; judging whether the actual opening and closing occurs according to the modulation wave in each sampling cycle, it can adapt to both continuous pulse width modulation and intermittent pulse width modulation; judging the commutation mode and loss mapping relationship in the sampling cycle according to the modulation wave, the bridge side filter inductor current and the sampling time; using the transient thermal impedance model relative to the NTC temperature to calculate the junction temperature, the thermal coupling is tight; in summary, the present invention can directly calculate the junction temperature of the power semiconductor of the converter online according to the physical quantity that can actually be measured by the converter, the executability is good, and the accuracy of the junction temperature calculation is higher.

[0165] Embodiment 2 of the present invention provides a system for online calculation of junction temperature of a converter power semiconductor using the online calculation method of junction temperature described in Embodiment 1, comprising:

[0166] Function fitting module: Fitting the loss parameter function of power semiconductors, fitting the transient thermal impedance parameter function of power semiconductors relative to NTC temperature, and fitting the inductance curve of bridge-side filter inductance;

[0167] Loss energy calculation module: Combines the modulation mode and ripple current influence to calculate the loss energy of power semiconductors within the sampling period;

[0168] Loss mapping lookup module: determines the commutation mode and loss mapping relationship within the sampling period by looking up the table;

[0169] Power loss calculation module: calculates the power loss of power semiconductors;

[0170] The junction temperature calculation and storage module calculates and stores the junction temperature through the power loss and transient thermal impedance matrix.

[0171] Embodiment 3 of the present invention provides a processor for executing the online calculation method of the junction temperature of a power semiconductor of a converter described in Embodiment 1 of the present invention.

[0172] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0173] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0174] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0175] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for online calculation of junction temperature of power semiconductor of converter, characterized in that: The method comprises the following: Fitting the loss functions of the power semiconductors used in the converter; The NTC temperature is obtained by measuring the temperature with the thermistor NTC, and the transient thermal impedance parameters of the power semiconductor relative to the NTC temperature are fitted. The transient thermal impedance matrix is ​​composed of the transient thermal impedance vectors of all power semiconductors. Fitting the inductance curve of the converter bridge-side filter inductor; Combined with the modulation mode and ripple current influence, the loss energy of the power semiconductor during the sampling period is calculated by fitting the loss function of the power semiconductor and the inductance curve of the bridge-side filter inductor; Determine the commutation mode and loss mapping relationship within the sampling period; Based on the loss energy and loss mapping relationship of the power semiconductor within the sampling period, the loss power of the power semiconductor is calculated online; Calculate the junction temperature of power semiconductors online based on the power dissipation and the transient thermal impedance matrix.

2. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 1, characterized in that: The loss function of the power semiconductor used in the fitting converter is specifically: The chart curve is adjusted based on the IGBT turn-on loss energy, IGBT turn-off loss energy and diode reverse recovery loss energy obtained from actual tests, and the loss function of the power semiconductor is fitted into an analytical function. The chart curve is provided by the component manufacturer, including the curve of IGBT switch loss energy with respect to IGBT current, voltage and junction temperature, and the curve of IGBT on-state voltage drop with respect to IGBT current and junction temperature.

3. The online calculation method for the junction temperature of a power semiconductor of a converter according to claim 2, characterized in that: The power semiconductor loss function includes an IGBT conduction voltage drop function, an IGBT turn-on loss energy function, an IGBT turn-off loss energy function, a diode forward conduction voltage drop function, and a diode reverse recovery loss energy function; Among them, the IGBT conduction voltage drop function is fitted as a function of the IGBT collector current and the IGBT junction temperature; the IGBT turn-on loss energy and the IGBT turn-off loss energy are fitted as functions of the IGBT collector current, the IGBT junction temperature, the IGBT gate resistance and the parallel bus voltage respectively; The diode forward voltage drop function is fitted as a function of the diode forward current and the diode junction temperature; the diode reverse recovery loss energy is fitted as a function of the diode forward current, the diode junction temperature, the gate resistance of the commutated IGBT tube and the parallel bus voltage; For a two-level converter, the parallel bus voltage is the voltage across the DC capacitor; for an NPC converter, the parallel bus voltage is the voltage across the upper half of the DC capacitor.

4. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 1, characterized in that: The transient thermal impedance parameters of the fitted power semiconductor relative to the NTC temperature are specifically composed of a transient thermal impedance matrix composed of transient thermal impedance vectors of all power semiconductors: Combined with the thermal coupling between power semiconductors, the unit step response of the transient thermal impedance of the power semiconductor relative to the NTC temperature is measured and a transient thermal impedance model is constructed. It is fitted according to the analytical model and then converted into a discrete fourth-order low-pass filter model. The transient thermal impedance vector containing all power semiconductors is obtained to form a transient thermal impedance matrix.

5. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 4, characterized in that: The specific process of measuring the unit step response of the transient thermal impedance of the power semiconductor relative to the NTC temperature and obtaining the transient thermal impedance matrix composed of the transient thermal impedance vectors of all power semiconductors is as follows: Apply a step power excitation to one power semiconductor in the power semiconductor module of the converter in turn. Each time the power excitation is applied to one of the power semiconductors, measure and record the highest junction temperature curve and the NTC temperature curve of all power semiconductor chips, make a difference, and then divide by the excitation to obtain the unit step response of the transient thermal impedance of the power semiconductor. After converting the transient thermal impedance of each power semiconductor in the power module to all power semiconductors into a discrete fourth-order low-pass filter model, a transient thermal impedance vector is formed. The transient thermal impedance vector Z of the kth IGBT tube Tk and the jth diode Dj in the power semiconductor is Tk and Z Dj The expression is: WITH Tk =(From TkT1 ,WITH TkT2 ,…,WITH TkTm ,WITH TkD1 ,WITH TkD2 ,…,WITH TkDn ) T WITH Dj =(From DjT1 ,WITH DjT2 ,…,WITH DjTm ,WITH DjD1 ,WITH DjD2 ,…,WITH DjDn ) T Where k = 1, 2, ..., m; j = 1, 2, ..., n; Z TkT1 ,Z TkT2 ,…,Z TkTm and Z DjT1 ,Z DjT2 ,…,Z DjTm are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first IGBT tube T1, the second IGBT tube T2 and the mth IGBT tube Tm in sequence, Z TkD1 ,Z TkD2 ,…,Z TkDn and Z DjD1 ,Z DjD2 ,…,Z DjDn are the transient thermal impedances of the kth IGBT tube Tk and the jth diode Dj to the first diode D1, the second diode D2 and the nth diode Dn in sequence, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module; The transient thermal impedance vectors of all power semiconductors are combined into a transient thermal impedance matrix. The expression of the transient thermal impedance matrix Z is: From=(From T1 ,WITH T2 ,…,WITH Tm ,WITH D1 ,WITH D2 ,…,WITH Dn ) Among them, m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

6. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 1, characterized in that: The inductance value curve of the fitted converter bridge-side filter inductor is specifically: The curve of the inductance value of the bridge-side filter inductor changing with the current is measured and fitted into an analytical function, and the expression is: L1=f L (i L ) Where, L1 is the inductance value of the bridge side filter inductor, i L is the current of the bridge side filter inductor.

7. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 1, characterized in that: The calculation of the power semiconductor loss energy during the sampling period is specifically as follows: At the carrier peak and carrier bottom in each switching cycle, a sampling interrupt is entered to collect the bridge-side filter inductor current, AC filter capacitor phase voltage, and DC bus voltage or DC half bus voltage, and read the current modulation wave and switching frequency; Sampling is performed at the carrier peak and carrier bottom points. The time between the two sampling moments is a sampling period, and a switching period is divided into two sampling periods. The conduction time of the power semiconductor is calculated based on the modulation wave and the switching period at the sampling moment. Whether switching occurs during the sampling period is determined based on the debugging wave or the conduction time. If switching occurs, the current sampling period is continuous pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to continuous pulse width modulation; if no switching occurs, the current sampling period is intermittent pulse width modulation, and the loss energy of the power device during the sampling period is calculated according to intermittent pulse width modulation.

8. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 7, characterized in that: The specific calculation of the power device loss energy within the sampling period according to the continuous pulse width modulation is: Calculate the conduction loss energy, turn-on loss energy, turn-off loss energy or reverse recovery loss energy of power semiconductors.

9. The method for online calculation of converter power semiconductor junction temperature according to claim 7, characterized in that: The energy loss of the power device during the sampling period is calculated according to the intermittent pulse width modulation, specifically: Only the conduction loss energy of the power semiconductor is calculated, while the turn-on loss energy, turn-off loss energy or reverse recovery loss energy of the power semiconductor are not calculated and are directly assigned to zero.

10. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 7, characterized in that: Based on the influence of ripple current on loss calculation, the slope of the bridge-side filter inductor current is calculated, and then the current value at the turn-on, turn-off or reverse recovery moment of the power semiconductor is calculated. Then, the IGBT tube conduction voltage drop and diode conduction voltage drop, turn-on loss energy, turn-off loss energy and reverse recovery loss energy of the power semiconductor within the sampling period are calculated through the fitting function. The junction temperature is calculated using the junction temperature calculated in the previous sampling period, and the on-state loss energy is calculated using the IGBT tube conduction voltage drop and diode conduction voltage drop.

11. The method for online calculation of converter power semiconductor junction temperature according to claim 1, characterized in that: The determining of the commutation mode and loss mapping relationship within the sampling period is specifically as follows: judging the commutation mode of the converter according to the modulation wave, carrier wave and bridge-side filter inductor current value of the sampling period, and mapping the loss energy calculated within the sampling period to a specific power semiconductor through a lookup table; For a two-level converter, the loss mapping relationship is a two-dimensional lookup table of the bridge-side filter inductor current and the sampling time; for an NPC converter, the loss mapping relationship is a three-dimensional lookup table of the bridge-side filter inductor current, the modulation wave and the sampling time.

12. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 10, characterized in that: The second bridge-side filter inductor current calculated in the previous sampling cycle is equal to the first bridge-side filter inductor current calculated in the next sampling cycle. The turn-on loss energy, turn-off loss energy or reverse recovery energy occurring under this current can be calculated in any sampling cycle.

13. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 1, characterized in that: The online calculation of the power loss of the power semiconductor is specifically as follows: A calculation window with a length of N switching cycles is set, and the average value of the energy loss in each power semiconductor switching cycle in the window is calculated, multiplied by the current switching frequency, and then accumulated according to the power semiconductor to obtain the power semiconductor loss power. The power semiconductor includes an IGBT tube and a diode. The loss energy includes the on-state loss energy, turn-on loss energy and turn-off loss energy of the IGBT tube and the on-state loss energy and reverse recovery loss energy of the diode.

14. The method for online calculation of the junction temperature of a power semiconductor of a converter according to claim 3, characterized in that: The online calculation of the junction temperature of the power semiconductor is specifically as follows: Writing the variables in vector form, the junction temperature of the power semiconductor is calculated as follows: T=(T T1 ,T T2 ,…,T Tm ,T D1 ,T D2 ,…,T Dn ) T P=(P T1 ,P T2 ,…,P Tm ,P D1 ,P D2 ,…,P Dn ) T T=ZP+T NTC Among them, T NTC is the online measured NTC temperature, P is the online calculated power loss, T is the online junction temperature of the power semiconductor, Z is the transient thermal impedance matrix, T T1 ,T T2 ,…,T Tm and P T1 ,P T2 ,…,P Tm are the junction temperature and power of the first IGBT tube T1, the second IGBT tube T2, and the mth IGBT tube Tm in sequence; T D1 ,T D2 ,…,T Dn and P D1 ,P D2 ,…,P Dn They are the junction temperature and power of the first diode D1, the second diode D2 to the nth diode Dn in sequence, where m is the number of IGBT tubes in the power module, and n is the number of diodes in the power module.

15. An online calculation system for junction temperature of a converter power semiconductor using the online calculation method for junction temperature according to any one of claims 1 to 14, characterized in that: include: Function fitting module: Fitting the loss parameter function of power semiconductors, fitting the transient thermal impedance parameter function of power semiconductors relative to NTC temperature, and fitting the inductance curve of bridge-side filter inductance; Loss energy calculation module: Combines the modulation mode and ripple current influence to calculate the loss energy of power semiconductors within the sampling period; Loss mapping lookup module: determines the commutation mode and loss mapping relationship within the sampling period by looking up the table; Power loss calculation module: calculates the power loss of power semiconductors; The junction temperature calculation and storage module calculates and stores the junction temperature through the power loss and transient thermal impedance matrix.

16. A processor, used to execute the online calculation method of the junction temperature of a power semiconductor of a converter according to any one of claims 1 to 14.

Images