Method for improving reliability of energy storage converter based on life consumption distribution rule

Abstract

The invention discloses an energy storage converter reliability improvement method based on a life consumption distribution rule. The method comprises the following steps: S1, calculating life consumption of an energy storage converter under a long-time mission profile; s2, comparing the sizes of the two service life consumption types, and further determining a junction temperature fluctuation suppression type; s3, determining a junction temperature fluctuation control target and the maximum allowable operation junction temperature of the IGBT module in combination with the service life consumption distribution rule and the junction temperature fluctuation suppression type; s4, based on the maximum allowable operation junction temperature of the IGBT module, determining a working interval, needing thermal management, of the energy storage converter; s5, determining a switching frequency adjustment value of the IGBT module according to iterative calculation of the junction temperature numerical value; and S6, comparing life improvement effects before and after thermal management. The method for improving the reliability of the energy storage converter based on the life consumption distribution rule has the advantages of being simple in heat management control and easy to implement.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a method for improving the reliability of an energy storage converter based on a life consumption distribution law. Background Art

[0002] In recent years, new power generation methods, with wind and solar power generation as the mainstream, have gradually replaced traditional power generation. However, due to the fact that the output time and load of wind power and photovoltaic power cannot match the power consumption time and load, coupled with their intermittent and volatile characteristics, these renewable energy sources have an increasing impact on the power grid. Energy storage power stations can decouple the generation and use of electricity, and can improve the reliability and stability of renewable energy access to the power grid, which is of great significance for dealing with the intermittent and volatile characteristics of renewable energy. As a vital component of energy storage power stations, the life of energy storage converters directly affects the long-term stable operation and economic benefits of energy storage power stations. However, according to the statistical results of system failure rate, converters are the main failure components. The failure of energy storage converters is largely attributed to the failure of the power device IGBT used in them. The failure of IGBT in the converter is largely affected by the impact of thermal cycles during the working process. Further research shows that the number of thermal cycles before the failure of the IGBT module gradually decreases with the increase of the junction temperature fluctuation amplitude. Therefore, reducing the junction temperature fluctuation can extend the service life of the IGBT module and avoid economic losses caused by the shutdown of the energy storage converter.

[0003] Existing literature has mainly carried out a lot of research work on how to smooth the junction temperature fluctuation of IGBT through thermal management. However, most of the thermal management research of IGBT modules is aimed at the converter on the new energy side, and few literatures study how to reduce the junction temperature fluctuation of the power module of the energy storage converter by changing the switching frequency. Because for the energy storage converter, its thermal management is more complicated. It not only needs to consider the fluctuation of the power on the power generation side of the new energy side, but also needs to consider the dynamic changes of the power demand on the load side. This dual volatility makes the energy storage converter frequently switch between the two working states of rectification and inversion, which puts higher requirements on thermal management. In this case, the present invention proposes a method for improving the reliability of energy storage converters based on the life consumption distribution law. First, the life consumption distribution law of the IGBT module is quantitatively analyzed to determine the type of junction temperature fluctuation that needs to be managed and the control target of junction temperature fluctuation. Then, the maximum junction temperature of the energy storage converter and the maximum junction temperature of the device at different switching frequencies are quickly estimated by using the junction temperature numerical calculation method combined with the operating conditions of a whole year. By comparing the junction temperature fluctuation control target and the maximum junction temperature, the working range and switching frequency adjustment value of thermal management are clarified. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for improving the reliability of an energy storage converter based on the law of life consumption distribution.

[0005] Technical solution: The method for improving the reliability of an energy storage converter based on the life consumption distribution law of the present invention comprises the following steps:

[0006] S1. Calculate the life consumption of the energy storage converter under a long-term mission profile, wherein the life consumption includes base frequency life consumption and low frequency life consumption;

[0007] S2. Compare the sizes of the two life consumption types, and then determine the junction temperature fluctuation suppression type, where the junction temperature fluctuation type includes fundamental frequency junction temperature fluctuation and low frequency junction temperature fluctuation;

[0008] S3. Determine the junction temperature fluctuation control target and the maximum allowable operating junction temperature of the IGBT module based on the life consumption distribution law and the junction temperature fluctuation suppression type;

[0009] S4. Determine the working range of the energy storage converter that needs thermal management based on the maximum allowable operating junction temperature of the IGBT module. The thermal management range refers to the output power range of the energy storage converter that needs thermal management. The power range includes a rectification state power range and an inverter state power range.

[0010] S5, determining the switching frequency adjustment value of the IGBT module according to the iterative calculation of the junction temperature value;

[0011] S6. Compare the life improvement effect before and after thermal management.

[0012] Furthermore, in step S1, the base frequency life consumption and the low frequency life consumption include IGBT chips and Diode chips.

[0013] Further, in step S2, the junction temperature fluctuation types include fundamental frequency junction temperature fluctuation and low frequency junction temperature fluctuation.

[0014] Furthermore, in step S3, the baseband lifetime consumption distribution and the low-frequency lifetime consumption distribution adopt the cumulative distribution function of the junction temperature fluctuation:

[0015]

[0016] Where: ΔT goal N is the set junction temperature fluctuation amplitude control target; j is the total number of junction temperature fluctuations; n(ΔT j >ΔT goal ) is the junction temperature fluctuation amplitude greater than ΔT goal The number of times; then Q(ΔT j >ΔT goal ) is greater than ΔT goalThe ratio of junction temperature fluctuation to total temperature fluctuation. Calculate the life consumption caused by junction temperature fluctuation:

[0017]

[0018] Where: CL(ΔT j >ΔT goal ) is greater than ΔT goal The sum of the lifetime consumption caused by the junction temperature fluctuation; then Q CL( ΔT j >ΔT goal ) is greater than ΔT goal The proportion of lifetime consumption caused by junction temperature fluctuations to all lifetime consumption caused by junction temperature fluctuations.

[0019] Furthermore, in step S3, the maximum allowable operating junction temperature of the IGBT module is determined based on the lowest operating ambient temperature of the energy storage converter in one year and the junction temperature fluctuation control target, which can be expressed as:

[0020] T jmax，allow =T a，min +ΔT goal

[0021] Where: T a，min is the lowest operating ambient temperature of the energy storage converter in one year, ΔT goal To select the target junction temperature fluctuation, T jmax，allow It is the maximum allowable operating junction temperature of the IGBT module.

[0022] Furthermore, in step S4, the thermal management interval refers to when the output power of the energy storage converter reaches a certain value, the maximum operating junction temperature of the IGBT module may exceed T jmax，allow .

[0023] Furthermore, in step S4, the thermal management interval is determined based on the highest operating environment temperature of the energy storage converter in one year. The thermal management interval includes the rectifier state working thermal management interval and the inverter state working thermal management interval, which can be expressed as:

[0024]

[0025] Where: T jmax is the maximum operating junction temperature of the IGBT module, P S is the output power of the energy storage converter, T a，max is the maximum operating ambient temperature of the energy storage converter in one year, P RECT is the rated rectified output power of the energy storage converter, P INV is the rated inverter output power of the energy storage converter, T jmax，allow It is the maximum allowable operating junction temperature of the IGBT module.

[0026] Further, in step S5, the switching frequency adjustment value determined includes the adjustment value of the rectifier state working thermal management interval and the adjustment value of the inverter state working thermal management interval, which can be expressed as:

[0027]

[0028] Where: f is the IGBT module switching frequency, f th_rect is the switching frequency adjustment value in rectification mode, f th_inv It is the switching frequency adjustment value in inverter mode.

[0029] Further, in step S6, the life improvement effect includes a comparison of operating junction temperature before and after thermal management, a comparison of life consumption before and after thermal management, and a junction temperature fluctuation suppression effect before and after thermal management.

[0030] Technical solution: The method for improving the reliability of an energy storage converter based on the life consumption distribution law of the present invention comprises:

[0031] The life consumption distribution law module includes a base frequency life consumption distribution and a low frequency life consumption distribution; the base frequency life consumption distribution and the low frequency life consumption distribution are both calculated using a cumulative distribution function of junction temperature fluctuation.

[0032] The maximum allowable operating junction temperature determination module is used to determine the maximum allowable operating junction temperature of the IGBT module based on the lowest operating environment temperature of the energy storage converter in one year and the junction temperature fluctuation control target.

[0033] A thermal management module, the thermal management module includes determining a thermal management interval and determining a switching frequency adjustment value for the thermal management interval: the thermal management interval includes a rectification state working thermal management interval and an inverter state working thermal management interval; the switching frequency adjustment value includes an adjustment value for the rectification state working thermal management interval and an inverter state working thermal management interval adjustment value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a general flow chart of a method for improving the reliability of an energy storage converter based on the life consumption distribution law of the present invention;

[0035] Figure 2 is the maximum junction temperature of the IGBT chip at different output powers;

[0036] Figure 3 is the maximum junction temperature of the IGBT chip at different switching frequencies in the rectification state;

[0037] Figure 4 is the maximum junction temperature of the IGBT chip at different switching frequencies in the inverter state;

[0038] Figure 5 The junction temperature of the IGBT chip before and after thermal management; DETAILED DESCRIPTION

[0039] The present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0040] See also Figure 1 As shown, the present invention discloses a method for improving the reliability of an energy storage converter based on the life consumption distribution law. The method for improving the reliability of an energy storage converter of the present invention comprises the following steps:

[0041] S1. Calculate the life consumption of the energy storage converter under a long-term mission profile, wherein the life consumption includes base frequency life consumption and low frequency life consumption;

[0042] S2. Compare the sizes of the two life consumption types, and then determine the junction temperature fluctuation suppression type, where the junction temperature fluctuation type includes fundamental frequency junction temperature fluctuation and low frequency junction temperature fluctuation;

[0043] S3. Determine the junction temperature fluctuation control target and the maximum allowable operating junction temperature of the IGBT module based on the life consumption distribution law and the junction temperature fluctuation suppression type;

[0044] S4. Determine the working range of the energy storage converter that needs to be thermally managed based on the maximum allowable operating junction temperature of the IGBT module. The thermal management working range refers to the output power range of the energy storage converter that needs to be thermally managed. The power range includes a rectification state working range and an inverter state working range.

[0045] S5, determining the switching frequency adjustment value of the IGBT module according to the iterative calculation of the junction temperature value;

[0046] S6. Compare the life improvement effect before and after thermal management.

[0047] The method for improving the reliability of an energy storage converter of the present invention comprises:

[0048] The life consumption distribution law module includes a base frequency life consumption distribution and a low frequency life consumption distribution; the base frequency life consumption distribution and the low frequency life consumption distribution are both calculated using a cumulative distribution function of junction temperature fluctuation.

[0049] The maximum allowable operating junction temperature determination module is used to determine the maximum allowable operating junction temperature of the IGBT module based on the lowest operating environment temperature of the energy storage converter in one year and the junction temperature fluctuation control target.

[0050] A thermal management module, the thermal management module includes determining a thermal management interval and determining a switching frequency adjustment value for the thermal management interval; the thermal management interval includes a rectification state working thermal management interval and an inverter state working thermal management interval; the switching frequency adjustment value includes an adjustment value for the rectification state working thermal management interval and an inverter state working thermal management interval adjustment value.

[0051] The following is a detailed explanation of a method for improving the reliability of an energy storage converter based on the life consumption distribution law of the present invention.

[0052] Step S1, firstly calculate the life consumption distribution of the energy storage converter under the long-time mission profile, wherein the life consumption distribution includes the base frequency life consumption distribution and the low frequency life consumption distribution.

[0053] In this example, a 3.5MW photovoltaic energy storage converter in a photovoltaic energy storage power station is selected to evaluate the life of its IGBT module based on the operating conditions in 2022 and 2023. The results are shown in Table 1. L and CL F They are the life consumption caused by low-frequency and fundamental-frequency junction temperature fluctuations respectively.

[0054] Table 1 IGBT module life consumption

[0055]

[0056] Step S2: compare the sizes of the two life consumption types, and then determine the junction temperature fluctuation suppression type, where the junction temperature fluctuation type includes fundamental frequency junction temperature fluctuation and low frequency junction temperature fluctuation.

[0057] As can be seen from Table 1, whether in 2022 or 2023, the life consumption caused by the low-frequency junction temperature fluctuation of the IGBT chip and the diode chip in the energy storage converter is greater than the life consumption caused by the base frequency junction temperature fluctuation. In addition, the life consumption of the IGBT is greater than the life consumption of the diode. Therefore, in this case, the energy storage converter should focus on thermal management of the low-frequency junction temperature fluctuation of the IGBT chip. F In higher situations, the fundamental frequency junction temperature fluctuation can be considered as the main target.

[0058] Step S3, combining the life consumption distribution law and the type of junction temperature fluctuation suppression, determine the junction temperature fluctuation control target and the maximum allowable operating junction temperature of the IGBT module. From the above life consumption results, it can be seen that if the low-frequency junction temperature fluctuation of the IGBT chip can be effectively suppressed, the life of the energy storage converter will be significantly improved. Therefore, the main research here is the distribution law of the low-frequency life consumption of the IGBT chip. Define the cumulative distribution function of the junction temperature fluctuation:

[0059]

[0060] Where: ΔT goal N is the set junction temperature fluctuation amplitude control target; j，L is the total number of low-frequency junction temperature fluctuations; n(ΔT j，L >ΔT goal ) is the junction temperature fluctuation amplitude greater than ΔT goal The number of times; then Q(ΔT j，L >ΔT goal ) is greater than ΔT goal The proportion of low-frequency junction temperature fluctuation to the total low-frequency junction temperature fluctuation. Then define the life consumption caused by low-frequency junction temperature fluctuation:

[0061]

[0062] Where: CL L (ΔT j，L >ΔT goal ) is greater than ΔT goal The sum of the life consumption caused by the low-frequency junction temperature fluctuations; then For amplitude greater than ΔT goal的 The life consumption caused by low-frequency junction temperature fluctuation accounts for the proportion of life consumption caused by all low-frequency junction temperature fluctuations. Based on the above definition, the distribution law of low-frequency life consumption of IGBT chips in energy storage converters is shown in Table 2.

[0063] Table 2 Distribution of low-frequency life consumption of IGBT chips

[0064]

[0065] It can be seen from Table 2 that a large part of the low-frequency life consumption is caused by low-frequency junction temperature fluctuations with higher amplitudes. For example, low-frequency junction temperature fluctuations with amplitudes higher than 90°C in 2022 and 2023 only account for 6.30% and 4.72% of the total low-frequency junction temperature fluctuations, respectively, but the life consumption caused by them accounts for 38.14% and 30.40% of the life consumption caused by all low-frequency junction temperature fluctuations, respectively. Therefore, it is necessary to suppress low-frequency junction temperature fluctuations with higher amplitudes to reduce the life consumption of IGBT. Here, based on the mission profile of the energy storage converter in 2022, the target low-frequency junction temperature fluctuation ΔT is selected. goal Taking 90°C as an example, determine the maximum allowable operating junction temperature of the IGBT module. Based on the minimum operating ambient temperature T of the energy storage converter in 2022 a，min =0.83℃, the maximum junction temperature T allowed by the IGBT chip can be calculated by the formula jmax，allow =90.83℃, the calculation formula is:

[0066] T jmax，allow =T a，min +ΔT goal

[0067] Step S4: Determine the rectification state and inverter state working ranges of the energy storage converter that require thermal management based on the maximum allowable operating junction temperature of the IGBT module. The thermal management working range refers to the output power range of the energy storage converter that requires thermal management, which can be expressed as:

[0068]

[0069] Where: T jmax is the maximum operating junction temperature of the IGBT module, P S is the output power of the energy storage converter, T a，max is the maximum operating ambient temperature of the energy storage converter in one year, P RECT is the rated rectified output power of the energy storage converter, P INV is the rated inverter output power of the energy storage converter, T jmax，allow The maximum allowable operating junction temperature of the IGBT module. Figure 2 As shown in the figure, it can be seen that the corresponding inverter and rectifier output powers are 1.4893MW and -1.6085MW respectively.

[0070] Step S5: determining the switching frequency adjustment value of the IGBT module, wherein the adjustment value includes the adjustment value of the rectifier thermal management interval and the adjustment value of the inverter thermal management interval, which can be expressed as:

[0071]

[0072] Where: f is the IGBT module switching frequency, f th_rect is the switching frequency adjustment value in rectification mode, f th_inv It is the switching frequency adjustment value in inverter mode.

[0073] According to the iterative calculation of the junction temperature value, under the conditions of the rated output rectification and inversion power of the converter and the maximum ambient temperature, the maximum operating junction temperature T of the IGBT chip at different switching frequencies jmax_IGBT See also Figure 3 and Figure 4 As shown. Figure 3 It can be seen that when the IGBT module switching frequency of the energy storage converter drops to 958Hz in the rectification state, the operating junction temperature of the IGBT chip will not be higher than 90.83℃ under the highest ambient temperature and maximum rectification output power. Figure 4It can be seen that when the energy storage converter is in the inverter state, when the switching frequency of the IGBT module drops to 550Hz, under the condition of maximum rectified output power, the operating junction temperature of the IGBT chip will not exceed 90.83°C. Therefore, when the rectified output power of the energy storage converter is greater than 1.6085MW, the switching frequency needs to be adjusted to 958Hz, and when the inverter output power of the energy storage converter is greater than 1.4893MW, the switching frequency needs to be adjusted to 550Hz.

[0074] Step S6: Compare the life improvement effect before and after thermal management. For the comparison of operating junction temperature before and after thermal management, please refer to Figure 5 As shown in the figure, the maximum junction temperature of the IGBT chip without thermal management modulation strategy can reach 150.56℃, and the maximum junction temperature is reduced to only 85.47℃ after thermal management, which is lower than the junction temperature threshold of 90.83℃ set by thermal management.

[0075] The comparison of life consumption before and after thermal management is shown in Table 3. As can be seen from Table 3, the proposed method can not only significantly reduce the life consumption caused by low-frequency junction temperature fluctuations, but also reduce the life consumption caused by fundamental frequency junction temperature fluctuations.

[0076] Table 3 IGBT chip life consumption before and after thermal management

[0077]

[0078] The detailed low-frequency life consumption distribution before and after thermal management is shown in Table 4. After adopting the proposed thermal management optimization control method, the life consumption caused by the junction temperature fluctuation greater than the junction temperature fluctuation control target (90°C) is reduced from 1.193% (not adopted) to 0, achieving effective suppression of the life consumption caused by the low-frequency junction temperature fluctuation higher than the control target, and at the same time, the life consumption caused by the low-frequency junction temperature fluctuation amplitude less than the control target is also reduced.

[0079] Table 4 Distribution of low-frequency life consumption before and after thermal management

[0080]

[0081] The junction temperature fluctuation suppression effect before and after thermal management is shown in Table 5. After adopting thermal management, the junction temperature fluctuation with a low-frequency junction temperature fluctuation amplitude greater than 90°C is reduced from 61 times to 0 times, achieving effective suppression of the junction temperature fluctuation control target, verifying that the proposed thermal management control method can achieve effective suppression of the junction temperature fluctuation to be adjusted.

[0082] Table 5 Effect of suppressing low-frequency junction temperature fluctuations before and after thermal management

[0083]

Claims

1. A method for improving the reliability of an energy storage converter based on the life consumption distribution law, characterized in that: The method comprises the following steps: S1. Calculate the life consumption of the energy storage converter under a long-term mission profile, wherein the life consumption includes base frequency life consumption and low frequency life consumption; S2. Compare the sizes of the two life consumption types, and then determine the junction temperature fluctuation suppression type; the junction temperature fluctuation type includes fundamental frequency junction temperature fluctuation and low frequency junction temperature fluctuation; S3. Determine the junction temperature fluctuation control target and the maximum allowable operating junction temperature of the IGBT module based on the life consumption distribution law and the junction temperature fluctuation suppression type; S4. Determine the working range of the energy storage converter that needs thermal management based on the maximum allowable operating junction temperature of the IGBT module; the thermal management working range refers to the output power range of the energy storage converter that needs thermal management; the power range includes the rectification state power range and the inverter state power range; S5, determining the switching frequency adjustment value of the IGBT module according to the iterative calculation of the junction temperature value; S6. Compare the life improvement effect before and after thermal management.

2. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 1 is characterized in that: The base frequency lifetime consumption distribution and the low frequency lifetime consumption distribution adopt the cumulative distribution function of the junction temperature fluctuation: Where: ΔT goal N is the set junction temperature fluctuation amplitude control target; j is the total number of junction temperature fluctuations; n(ΔT j >ΔT goal ) is the junction temperature fluctuation amplitude greater than ΔT goal The number of times; then Q(ΔT j >ΔT goal ) is greater than ΔT goal The ratio of junction temperature fluctuation to total temperature fluctuation. Calculate the life consumption caused by junction temperature fluctuation: Where: CL(ΔT j >ΔT goal ) is greater than ΔT goal The sum of the lifetime consumption caused by the junction temperature fluctuation; then Q CL (ΔT j >ΔT goal ) is greater than ΔT goal The proportion of lifetime consumption caused by junction temperature fluctuations to all lifetime consumption caused by junction temperature fluctuations.

3. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 1 is characterized in that: The maximum allowable operating junction temperature of the IGBT module is determined based on the lowest operating ambient temperature of the energy storage converter in one year and the junction temperature fluctuation control target, which can be expressed as: T jmax，allow =T a，min +ΔT goal Where: T a，min is the lowest operating ambient temperature of the energy storage converter in one year, ΔT goal To select the target junction temperature fluctuation, T jmax，allow It is the maximum allowable operating junction temperature of the IGBT module.

4. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 1 is characterized in that: The thermal management range refers to the time at which the maximum operating junction temperature of the IGBT module may exceed T jmax,allow .

5. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 4 is characterized in that: The thermal management interval is determined based on the highest operating environment temperature of the energy storage converter in one year; the thermal management interval includes a rectification state thermal management interval and an inverter state thermal management interval, which can be expressed as: Where: T jmax is the maximum operating junction temperature of the IGBT module, P S is the output power of the energy storage converter, T a，max is the maximum operating ambient temperature of the energy storage converter in one year, P RECT is the rated rectified output power of the energy storage converter, P INV is the rated inverter output power of the energy storage converter, T jmax,allow It is the maximum allowable operating junction temperature of the IGBT module.

6. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 1 is characterized in that: The switching frequency adjustment value determined includes the adjustment value of the thermal management interval of the rectifier state and the adjustment value of the thermal management interval of the inverter state, which can be expressed as: Where: f is the IGBT module switching frequency, f th_rect is the switching frequency adjustment value in rectification mode, f th_inv It is the switching frequency adjustment value in inverter mode.

7. The method for improving the reliability of an energy storage converter based on the life consumption distribution law according to claim 1 is characterized in that: The life improvement effect includes a comparison of operating junction temperature before and after thermal management, a comparison of life consumption before and after thermal management, and a junction temperature fluctuation suppression effect before and after thermal management.

8. A method for improving the reliability of an energy storage converter based on the life consumption distribution law, characterized in that: include: A life consumption distribution law module, wherein the life consumption distribution includes a base frequency life consumption distribution and a low frequency life consumption distribution; the base frequency life consumption distribution and the low frequency life consumption distribution are both calculated using a cumulative distribution function of junction temperature fluctuation; A maximum allowable operating junction temperature determination module, wherein the maximum allowable operating junction temperature of the IGBT module is determined based on the lowest operating environment temperature of the energy storage converter in one year and the junction temperature fluctuation control target; A thermal management module, the thermal management module includes determining a thermal management interval and determining a switching frequency adjustment value for the thermal management interval; the thermal management interval includes a rectification state thermal management interval and an inverter state thermal management interval; the switching frequency adjustment value includes an adjustment value for the rectification state thermal management interval and an inverter state thermal management interval adjustment value.

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