Method and system for smoothing junction temperature fluctuation of IGBT module of grid-connected converter

Abstract

The present invention proposes a method and system for smoothing the junction temperature fluctuation of an IGBT module of a grid-connected converter, comprising: performing high and low frequency digital filtering on the loss of the IGBT module to separate the low frequency component with large loss fluctuation from the high frequency component with small loss fluctuation to obtain the low frequency component and the high frequency component; calculating the average switching frequency and loss coefficient of pulse width modulation according to the fluctuation degree of the low frequency component and the high frequency component of the loss; and simultaneously smoothing the high and low frequency loss components based on the average switching frequency and the loss coefficient of pulse width modulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid-connected converter junction temperature control, and in particular relates to a method and a system for smoothing the junction temperature fluctuation of an IGBT module of a grid-connected converter. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The widespread application of power electronic devices benefits from the rapid development of technologies such as renewable energy generation, power transmission, and hybrid vehicles. With the continuous improvement of semiconductor chip manufacturing technology and the maturity of packaging technology, the power level and density of insulated gate bipolar transistors (IGBT) are also increasing.

[0004] The grid-connected converter uses the pulse width modulation (SPWM) method to achieve power conversion. Due to the non-ideal conductive characteristics and switching characteristics of the power switching device, the switching device will generate power consumption during operation, resulting in an increase in junction temperature. The greater the power passing through the power switching device, the more heat is generated and the higher the junction temperature. When the IGBT operates under complex conditions such as high power density and cyclic load, its case temperature will rise rapidly, resulting in an increase in device temperature and rapid temperature fluctuations. Data show that thermal fatigue failure caused by material thermal fatigue damage or bonding wire shedding due to excessively high average junction temperature and junction temperature fluctuations accounts for 55% of the factors that cause damage to power switching devices, and is the main factor in damage to power switching devices.

[0005] However, the application of new energy power generation such as wind power and photovoltaic power is characterized by randomness, volatility and intermittency. Due to the frequent changes in input and output power, the average temperature inside the device rises more significantly and the temperature fluctuations become more severe, thereby increasing the risk of power module failure.

[0006] Therefore, in order to improve the stability of IGBT and reduce the operation and maintenance cost of the converter, it is an effective method to take active thermal management control measures, including power device loss calculation and real-time junction temperature monitoring. In this way, the working status of the device can be monitored and measures can be taken to control the temperature, thereby keeping the IGBT operating within a safe temperature range.

[0007] In the grid-connected converter of the renewable energy power generation system, low-frequency junction temperature fluctuations are usually related to changes in environmental conditions, such as wind force level and light intensity affecting input and output power and thus causing junction temperature changes, and air temperature changes directly causing junction temperature fluctuations, etc., and the fluctuation range of low-frequency junction temperature fluctuations is generally large. High-frequency junction temperature fluctuations are related to many factors such as sampling errors and control strategies, and the fluctuation range of high-frequency junction temperature fluctuations is generally small. The active thermal control methods of power devices can be roughly divided into external thermal control and internal thermal control. External thermal control is to add a heat sink outside the device to adjust the device's heat dissipation method and heat dissipation rate. Internal thermal control is to directly control the source of device heat generation, such as adjusting the device switching frequency, driving voltage, etc. Among them, the traditional method of adjusting the switching frequency to smooth junction temperature fluctuations has been widely used.

[0008] However, since the switching frequency is one of the main factors affecting the junction temperature, directly adjusting the switching frequency may cause unnecessary fluctuations or overshoot of the junction temperature. It is difficult to find a balance between speed and accuracy, and it is difficult to smooth both high-frequency and low-frequency junction temperature fluctuations. Summary of the invention

[0009] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for smoothing the junction temperature fluctuation of the IGBT module of a grid-connected converter. The method of the present invention can reduce the junction temperature fluctuation amplitude while suppressing the increase of the average junction temperature without affecting the total harmonic distortion rate of the grid-connected current, thereby reducing the damage to the IGBT caused by the junction temperature increase and junction temperature fluctuation, and enhancing the reliability of the converter.

[0010] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0011] In a first aspect, a method for smoothing junction temperature fluctuations of an IGBT module of a grid-connected converter is disclosed, comprising:

[0012] The IGBT module loss is subjected to high and low frequency digital filtering to separate the low frequency component with large loss fluctuation from the high frequency component with small fluctuation, thus obtaining the low frequency component and the high frequency component;

[0013] Calculate the average switching frequency and loss factor of pulse width modulation according to the fluctuation degree of low-frequency component and high-frequency component of loss;

[0014] The average switching frequency and loss factor based on pulse width modulation are used to smooth out the loss components of both high and low frequencies.

[0015] As a further technical solution, the losses of the IGBT module are subjected to digital filtering at high and low frequencies, specifically:

[0016] The average frequency, modulation slope, modulation ratio, converter output current peak and real-time junction temperature of the IGBT module generated by the PWM are received, and the real-time conduction loss and switching loss of the IGBT module are calculated. The total loss is obtained by adding the two together, and then the low-frequency component is obtained by the first digital low-pass filter, and the high-frequency component is obtained by the second digital low-pass filter.

[0017] As a further technical solution, the low-frequency difference is obtained by subtracting the total loss from the low-frequency component; and the high-frequency difference is obtained by subtracting the total loss from the high-frequency component.

[0018] As a further technical solution, based on the sampled real-time junction temperature of the IGBT module, the forward conduction voltage drop and internal resistance of the IGBT module are calculated;

[0019] Calculate the conduction loss of the IGBT module based on the forward conduction voltage drop and internal resistance;

[0020] Calculate the switching losses of the IGBT module.

[0021] As a further technical solution, the average switching frequency and loss coefficient of pulse width modulation are calculated according to the fluctuation degree of the low-frequency component and the high-frequency component of the loss, specifically including:

[0022] The smooth loss control parameter modulation slope is calculated based on the magnitude relationship between the low-frequency component and the low-frequency difference and the proportional limiting formula. The modulation slope is subsequently calculated to generate a loss coefficient to participate in PWM modulation, which is used to smooth high-frequency junction temperature fluctuations with small amplitudes.

[0023] The average frequency of the smoothing loss control parameter PWM is calculated based on the size relationship between the high-frequency component and the high-frequency difference and the proportional limiting formula. The average frequency directly controls the average frequency of the output PWM and is used to smooth low-frequency junction temperature fluctuations with large amplitude.

[0024] As a further technical solution, it also includes a low-frequency difference judgment step to determine whether the low-frequency difference is less than or equal to 0 or greater than or equal to the set total loss. If neither of the two is satisfied, the low-frequency difference is within the adjustable range. If one of the two is satisfied, the low-frequency difference exceeds the adjustable range.

[0025] As a further technical solution, it also includes a high-frequency difference judgment step to judge whether the absolute value of the high-frequency difference is less than or equal to the set total loss. If it is satisfied, then f b No adjustment is required, f b Continue to maintain the last controlled value f pre If not, determine whether the high-frequency difference is less than the set total loss or greater than or equal to the difference between the theoretical maximum loss and the total loss that meet the fundamental frequency and envelope intercept conditions under the current junction temperature and output current conditions. If neither of the two conditions is met, the high-frequency difference is within the adjustable range. If one of the two conditions is met, the high-frequency difference exceeds the adjustable range.

[0026] As a further technical solution, the loss components of both high and low frequencies are smoothed simultaneously based on the average switching frequency and loss coefficient of pulse width modulation, specifically:

[0027] receiving a modulation slope, an average frequency, a real-time phase generated by a grid voltage phase-locked subsystem, and a sinusoidal modulation wave generated by a current and voltage control subsystem;

[0028] The modulation slope and the real-time phase are calculated in each control cycle of the microcontroller of the grid-connected converter to obtain the loss coefficient, the sinusoidal modulation wave and the loss coefficient are calculated to generate the value of the modulation wave and transmitted to the comparison register, the average frequency and the loss coefficient are calculated to generate the cycle count value of the carrier and transmitted to the time base cycle register;

[0029] The value of the comparison register is compared with the value of the time base period register to generate a PWM signal that controls the operation of the inverter IGBT module.

[0030] In a second aspect, a system for smoothing junction temperature fluctuations of an IGBT module of a grid-connected converter is disclosed, comprising:

[0031] The dual low-pass filter IGBT real-time loss calculation module is used to perform high and low frequency digital filtering on the loss of the IGBT module, and is used to separate the low-frequency component with large loss fluctuations from the high-frequency component with small fluctuations to obtain low-frequency components and high-frequency components;

[0032] A smoothing loss control parameter generation module is used to calculate the average switching frequency and loss coefficient of pulse width modulation according to the fluctuation degree of the low-frequency component and the high-frequency component of the loss;

[0033] The carrier and modulation wave generation module is used to smooth the loss components of both high and low frequencies based on the average switching frequency and loss coefficient of pulse width modulation.

[0034] One or more of the above technical solutions have the following beneficial effects:

[0035] The technical solution of the present invention performs high and low frequency digital filtering on the losses of the IGBT, separates the low-frequency component with larger loss fluctuation from the high-frequency component with smaller fluctuation, adds the concept of loss coefficient in pulse width modulation, calculates the average switching frequency and loss coefficient of pulse width modulation according to the fluctuation degree of the low-frequency component and the high-frequency component of the loss, and thus can smooth the loss components of the high and low frequencies at the same time, achieving a good balance between rapidity and accuracy, and reducing the junction temperature fluctuation amplitude while suppressing the increase of the average junction temperature without affecting the total harmonic distortion rate of the grid-connected current, thereby reducing the damage to the IGBT caused by the junction temperature increase and junction temperature fluctuation, and enhancing the reliability of the converter.

[0036] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 A schematic diagram of a system for smoothing two-frequency junction temperature fluctuations of an IGBT module of a grid-connected converter according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of a real-time loss calculation module for a dual low-pass filter IGBT according to an embodiment of the present invention;

[0040] Figure 3(a)-Figure 3(b) It is a calculation flow chart of the sub-smoothing loss control parameter generation module of an embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of a sub-smoothing loss carrier and modulation wave generation module according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0043] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0044] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0045] Embodiment 1

[0046] This embodiment discloses a method for smoothing the junction temperature fluctuation of an IGBT module of a grid-connected converter, comprising the following steps:

[0047] Step (1): Receive the average frequency f of the PWM generated by the previous control once per second avg , modulation slope k, modulation ratio m, converter output current peak I out and IGBT real-time junction temperature T j , calculate the IGBT real-time conduction loss P cond and switching loss P sw The sum of the two gives the total loss P of the IGBT. lossThen, a digital low-pass filter with a small time constant is used to obtain the high-frequency loss reference P. ref_k , a digital low-pass filter with a large time constant is used to obtain the low-frequency loss reference value P ref_f This step facilitates the digitization of the physical quantities required in the entire control process, which is convenient for subsequent calculation and control. The smoothing loss control parameter generation module runs once per second to generate an average frequency favg and a modulation slope k. Here, these two parameters generated in the previous second are received.

[0048] Among them, P ref_k Subtract P loss Get the high frequency loss difference ΔP k ;P ref_f Subtract P loss Get the low frequency loss difference ΔP f .

[0049] Step (2): Receive P ref_k , ΔP k , P ref_f , ΔP f Among them, according to P ref_k and ΔP k The smooth loss control parameter modulation slope k is calculated by the relationship between the size of P and the proportional limiting formula; ref_f and ΔP f The average frequency f of the smoothing loss control parameter PWM is calculated by the size relationship and proportional limit formula avg The modulation slope k is then calculated to generate the loss coefficient C s Participate in PWM modulation to smooth high-frequency junction temperature fluctuations with small amplitude; average frequency f avg Directly control the average frequency of the output PWM to smooth out large low-frequency junction temperature fluctuations.

[0050] It should be noted that the average frequency f avg It is not directly used as the switching frequency of pulse width modulation, but only as the average reference value of the switching frequency of pulse width modulation. In actual operation, it needs to be processed as in step (3-2) to obtain the actual switching frequency of pulse width modulation.

[0051] Step (3): Receive modulation slope k and average frequency f avg , the real-time phase θ generated by the grid voltage phase-locked subsystem and the sinusoidal modulation wave S generated by the current and voltage control subsystem. The modulation slope k and the real-time phase θ are calculated in each control cycle of the grid-connected converter microcontroller to obtain the loss coefficient C s Sinusoidal modulation wave S and loss coefficient C sThe value of the modulation wave is generated after calculation and transmitted to the comparison register of the pulse width modulation module of the grid-connected converter microcontroller. The average frequency f avg and loss coefficient C s The cycle count value of the carrier is generated through calculation and transmitted to the time base cycle register of the pulse width modulation module of the microcontroller of the grid-connected converter.

[0052] About the grid voltage phase-locked subsystem: The grid voltage is a sinusoidal waveform, and its phase changes periodically between 0-2*pi. The grid voltage phase-locked subsystem will calculate the phase of the grid voltage at the current moment based on the sampled grid voltage value.

[0053] Current and voltage control subsystem: It generates the corresponding sinusoidal modulation wave according to the sampled grid voltage and supplies it to the pulse width modulation module to generate PWM wave. The sinusoidal modulation wave generated by it is used here.

[0054] Step (4): Compare the value of the comparison register with the value of the time base period register to generate a PWM signal for controlling the operation of the inverter IGBT.

[0055] The control block diagram of step (1) is as follows Figure 2 As shown, the specific steps include:

[0056] Step (1-1): After receiving the real-time junction temperature of the IGBT sampled by the sampling subsystem, calculate the forward conduction voltage drop V of the IGBT at this time ce0 (T j ) and internal resistance r ce (T j ):

[0057] V ce0 (T j )=-1.3275·10 -3 ·T j +0.9309

[0058] r ce (T j )=8.575·10 -5 ·T j +0.01698

[0059] The coefficient of Tj and the added constant in the above two formulas are obtained by fitting the voltage drop-junction temperature curve and the internal resistance-junction temperature curve in the IGBT manual.

[0060] Step (1-2): Calculate the conduction loss P of the IGBT cond :

[0061]

[0062] in is the power factor angle, and m is the modulation ratio, both of which are fixed values ​​set in advance by the converter. out It is the peak value of the converter output current, and its size depends on the output power of the DC side of the renewable energy power generation.

[0063] Calculate the switching loss P of IGBT sw :

[0064]

[0065] Among them, k is the modulation slope calculated by the smooth loss control parameter generation module in the previous second, T is the sine period of the power frequency fundamental wave 0.02 seconds, E on and E off The rated DC voltage V of the IGBT in the IGBT manual ref , Rated output current I ref , Rated temperature T ref The single turn-on and turn-off losses under dc is the DC side voltage value when the converter is working, TC ESW is the temperature correction coefficient of the switching loss, ω is the angular frequency of the fundamental sine wave of the power frequency, K v is the voltage correction factor for switching loss.

[0066] Calculate the total loss P of the IGBT loss :

[0067] P loss =P cond +P sw

[0068] Step (1-3): P loss Through a low-pass filter with a time constant of τ1, we get P ref_k ; Use P ref_k Subtract P loss , we get ΔP k . loss Through a low-pass filter with a time constant of τ2, we get P ref_f ; Use P ref_f Subtract P loss , we get ΔP f . Among them, take τ1 = 20, τ2 = 1000. ref_k , ΔP k , P ref_f , ΔP f Output.

[0069] The control block diagram of step (2) is shown in FIG. 3(a) and FIG. 3(b), and specifically includes the following steps:

[0070] Step (2-1): Receive P ref_k , ΔPk , P ref_f , ΔP f . Determine ΔP k Is it less than or equal to 0 or greater than or equal to 0.05P loss If neither of the two conditions is satisfied, that is, ΔP k If it is within the adjustable range, then go to step (2-2); if one of the two conditions is met, that is, ΔP k If it exceeds the adjustable range, go to step (2-3).

[0071] In this step, whether to smooth the high-frequency junction temperature fluctuation and whether the high-frequency junction temperature fluctuation can be smoothed are determined according to the value of the high-frequency loss difference.

[0072] Determine ΔP f Is the absolute value of less than or equal to 0.05P loss If it satisfies, then f avg No adjustment is required, f b Continue to maintain the last controlled value f pre， f pre f generated in the last second avg If not satisfied, judge ΔP f Is it less than -0.05P? loss Or greater than or equal to the theoretical maximum loss P that meets the fundamental frequency and envelope intercept conditions under the current junction temperature and output current conditions loss_max With P loss If neither of the two conditions is satisfied, that is, ΔP f If it is within the adjustable range, then go to step (2-2); if one of the two conditions is met, that is, ΔP f If it exceeds the adjustable range, go to step (2-3).

[0073] In the above, whether to smooth the low-frequency junction temperature fluctuation and whether the low-frequency junction temperature fluctuation can be smoothed are determined based on the value of the low-frequency loss difference.

[0074] Step (2-2): Calculate the value of the modulation slope k according to the ratio:

[0075]

[0076] where k max To control the maximum modulation slope allowed.

[0077] Calculate the average frequency f according to the ratio avg Values:

[0078]

[0079] where f min is the minimum IGBT switching frequency for the converter to meet the grid current harmonic standard, fmax is the rated maximum switching frequency of the IGBT.

[0080] Step (2-3): If ΔP k Less than or equal to 0, then

[0081] k=k max

[0082] If ΔP k Greater than or equal to 0.05P loss ,but

[0083] k=0

[0084] If ΔP f Less than -0.05P loss ,but

[0085] f avg =f min

[0086] If ΔP f The theoretical maximum loss P that meets the average frequency and modulation slope conditions under the conditions of greater than or equal to the current junction temperature and output current loss_max With P loss The difference is

[0087] f avg =f max

[0088] The modulation slope k, average frequency f avg Output.

[0089] The flowchart of step (3) is as follows Figure 4 As shown, the specific steps include:

[0090] Step (3-1): Each time the generated modulation slope k and average frequency f are received avg In the next second, the modulation slope k and average frequency f avg Perform subsequent calculations until a new modulation slope k and average frequency f are received avg First, the loss coefficient C of the current carrier cycle is calculated based on the received modulation slope k and the real-time phase θ locked by the grid voltage phase-locked subsystem. s :

[0091]

[0092] Step (3-2): The value S of the sinusoidal modulation wave generated by the current and voltage control subsystem of the current carrier cycle and the loss coefficient C s The value CMP obtained by multiplying is sent to the comparison register of the pulse width modulation module of the microcontroller of the grid-connected converter. CMP is the comparison count value of the pulse width modulation module of the microcontroller.

[0093] CMP=S×C s

[0094] Average frequency f avg The loss coefficient C of the current carrier cycle s The calculated value PRD is sent to the time base period register of the pulse width modulation module of the microcontroller of the grid-connected converter. PRD is the time base period count value of the pulse width modulation module of the microcontroller.

[0095]

[0096] Embodiment 2

[0097] The purpose of this embodiment is to provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the program.

[0098] Embodiment 3

[0099] The purpose of this embodiment is to provide a computer-readable storage medium.

[0100] A computer-readable storage medium stores a computer program, which executes the steps of the above method when executed by a processor.

[0101] Embodiment 4

[0102] The purpose of this embodiment is to provide a system for smoothing the junction temperature fluctuation of the IGBT module of the grid-connected converter, which mainly includes two parts: a power circuit and a control system. Figure 1 As shown. The power circuit part is the prior art. The control system is divided into a dual-frequency smooth junction temperature PWM wave generation subsystem, a current and voltage control subsystem, a grid voltage phase lock subsystem (Phase LockLoop, PLL), and a sampling subsystem. The current and voltage control subsystem is common knowledge. The basic algorithm of the grid voltage phase lock subsystem is common knowledge.

[0103] Dual frequency smooth junction temperature PWM wave generation subsystem such as Figure 1 As shown, it includes: a dual low-pass filter IGBT real-time loss calculation module, a smoothing loss control parameter generation module, a carrier and modulation wave generation module, and a comparator module.

[0104] Different from the dual low-pass filter IGBT real-time loss calculation module and the smoothing loss control parameter generation module which operate once per second, the smoothing loss carrier and modulation wave generation module operates once in each carrier cycle of the microcontroller.

[0105] The dual low-pass filter IGBT real-time loss calculation module is configured to receive the average frequency f of the PWM generated by the last control once per second. avg , modulation slope k, modulation ratio m, converter output current peak I out and IGBT real-time junction temperature T j , calculate the IGBT real-time conduction loss P cond and switching loss P sw The sum of the two gives P loss Then, P is obtained by passing it through a digital low-pass filter with a small time constant. ref_k , through a digital low-pass filter with a large time constant to obtain P ref_f .

[0106] Among them, P ref_k Subtract P loss Get ΔP k ;P ref_f Subtract P loss Get ΔP f .

[0107] The smoothing loss control parameter generation module is configured to: receive P ref_k , ΔP k , P ref_f , ΔP f Among them, according to P ref_k and ΔP k The smooth loss control parameter modulation slope k is calculated by the relationship between the size of P and the proportional limiting formula; ref_f and ΔP f The average frequency f of the smoothing loss control parameter PWM is calculated by the size relationship and proportional limit formula avg The modulation slope k is then calculated to generate the loss coefficient C s Participate in PWM modulation to smooth high-frequency junction temperature fluctuations with small amplitude; average frequency f avg Directly control the average frequency of the output PWM to smooth out large low-frequency junction temperature fluctuations.

[0108] The smooth loss carrier and modulation wave generation module is configured to: receive the modulation slope k, the average frequency f avg , the real-time phase θ generated by the grid voltage phase-locked subsystem and the sinusoidal modulation wave S generated by the current and voltage control subsystem. The modulation slope k and the real-time phase θ are calculated in each control cycle of the grid-connected converter microcontroller to obtain the loss coefficient C s Sinusoidal modulation wave S and loss coefficient C s The value of the modulation wave is generated after calculation and transmitted to the comparison register of the pulse width modulation module of the grid-connected converter microcontroller. The average frequency f avg and loss coefficient Cs The cycle count value of the carrier is generated through calculation and transmitted to the time base cycle register of the pulse width modulation module of the microcontroller of the grid-connected converter.

[0109] The comparator module is configured to compare the value of the comparison register with the value of the time base period register to generate a PWM signal for controlling the operation of the IGBT of the converter.

[0110] The steps involved in the apparatuses of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and the specific implementation methods can refer to the relevant description part of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0111] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0112] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for smoothing junction temperature fluctuations of an IGBT module of a grid-connected converter, characterized in that: include: The IGBT module loss is subjected to high and low frequency digital filtering to separate the low frequency component with large loss fluctuation from the high frequency component with small fluctuation, thus obtaining the low frequency component and the high frequency component; The average switching frequency and loss factor of the pulse width modulation are calculated according to the fluctuation degree of the low-frequency component and high-frequency component of the loss; specifically including: The smooth loss control parameter modulation slope is calculated based on the magnitude relationship between the low-frequency component and the low-frequency difference and the proportional limiting formula. The modulation slope is subsequently calculated to generate a loss coefficient to participate in PWM modulation, which is used to smooth high-frequency junction temperature fluctuations with small amplitudes. The average frequency of the smoothing loss control parameter PWM is calculated based on the magnitude relationship between the high-frequency component and the high-frequency difference and the proportional limiting formula. The average frequency directly controls the average frequency of the output PWM and is used to smooth low-frequency junction temperature fluctuations with large amplitudes. Calculate the average frequency f according to the ratio avg Values: Among them, f min is the minimum IGBT switching frequency for the converter to meet the grid current harmonic standard, f max is the rated maximum switching frequency of the IGBT; P ref_f is the low frequency loss reference value, ΔP f is the low frequency loss difference; Each time the generated modulation slope k and average frequency f are received avg In the next second, the modulation slope k and average frequency f avg Perform subsequent calculations until a new modulation slope k and average frequency f are received avg ; Calculate the loss coefficient C of the current carrier cycle based on the received modulation slope k and the real-time phase θ locked by the grid voltage phase-locked subsystem s : The average switching frequency and loss coefficient based on pulse width modulation smooth the loss components of both high and low frequencies; specifically: receiving a modulation slope, an average frequency, a real-time phase generated by a grid voltage phase-locked subsystem, and a sinusoidal modulation wave generated by a current and voltage control subsystem; The modulation slope and the real-time phase are calculated in each control cycle of the microcontroller of the grid-connected converter to obtain the loss coefficient, the sinusoidal modulation wave and the loss coefficient are calculated to generate the value of the modulation wave and transmitted to the comparison register, the average frequency and the loss coefficient are calculated to generate the cycle count value of the carrier and transmitted to the time base cycle register; The value of the comparison register is compared with the value of the time base period register to generate a PWM signal that controls the operation of the inverter IGBT module.

2. The method for smoothing the junction temperature fluctuation of the IGBT module of the grid-connected converter according to claim 1, characterized in that: The IGBT module loss is subjected to digital filtering at high and low frequencies, specifically: The generated average frequency, modulation slope, modulation ratio, converter output current peak value and real-time junction temperature of the IGBT module are received, and the real-time conduction loss and switching loss of the IGBT module are calculated. The total loss is obtained by adding the two together, and then the low-frequency component is obtained by passing through the first digital low-pass filter, and the high-frequency component is obtained by passing through the second digital low-pass filter; The low-frequency component minus the total loss gives the low-frequency difference; the high-frequency component minus the total loss gives the high-frequency difference.

3. The method for smoothing the junction temperature fluctuation of the IGBT module of the grid-connected converter according to claim 1, characterized in that: Based on the sampled real-time junction temperature of the IGBT module, calculate the forward conduction voltage drop and internal resistance of the IGBT module; Calculate the conduction loss of the IGBT module based on the forward conduction voltage drop and internal resistance; Calculate the switching losses of the IGBT module.

4. The method for smoothing the junction temperature fluctuation of the IGBT module of the grid-connected converter according to claim 1, characterized in that: It also includes a low-frequency difference judgment step to judge whether the low-frequency difference is less than or equal to 0 or greater than or equal to the set total loss. If neither of the two is satisfied, the low-frequency difference is within the adjustable range. If one of the two is satisfied, the low-frequency difference exceeds the adjustable range.

5. The method for smoothing the junction temperature fluctuation of the IGBT module of the grid-connected converter according to claim 1, characterized in that: It also includes a high-frequency difference judgment step to judge whether the absolute value of the high-frequency difference is less than or equal to the set total loss. If it is satisfied, the average frequency f avg No adjustment is required, and the last controlled value f is maintained. pre , f pre f generated in the last second avg ; If not, determine whether the high-frequency difference is less than the set total loss or greater than or equal to the difference between the theoretical maximum loss and the total loss that meet the fundamental frequency and envelope intercept conditions under the current junction temperature and output current conditions. If neither of the two conditions is met, the high-frequency difference is within the adjustable range. If one of the two conditions is met, the high-frequency difference exceeds the adjustable range.

6. A system for smoothing the junction temperature fluctuation of an IGBT module of a grid-connected converter, using the method for smoothing the junction temperature fluctuation of an IGBT module of a grid-connected converter as claimed in claim 1, characterized in that: include: The dual low-pass filter IGBT real-time loss calculation module is used to perform high and low frequency digital filtering on the loss of the IGBT module, and is used to separate the low-frequency component with large loss fluctuations from the high-frequency component with small fluctuations to obtain low-frequency components and high-frequency components; A smoothing loss control parameter generation module is used to calculate the average switching frequency and loss coefficient of pulse width modulation according to the fluctuation degree of the low-frequency component and the high-frequency component of the loss; The carrier and modulation wave generation module is used to smooth the loss components of both high and low frequencies based on the average switching frequency and loss coefficient of pulse width modulation.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method described in any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method described in any one of claims 1 to 5 are performed.

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