A method for optimizing EMC of high-power DC-DC for hydrogen fuel cells

Abstract

The present invention relates to the technical field of DCDC electromagnetic compatibility optimization, and in particular to a method for optimizing the EMC of a high-power DCDC system used in a hydrogen fuel cell. The method comprises a DCDC conversion circuit and a control system for performing software control on the DCDC conversion circuit. The DCDC conversion circuit comprises N parallel DCDC conversion branches, each of which is connected to a power switching device. The control system comprises a carrier frequency generation module capable of separately configuring carrier frequencies for the power switching devices in the N DCDC conversion branches. The control system of the present invention comprises the carrier frequency generation module capable of adjusting the carrier frequency of the power switching device in each DCDC conversion branch. The method performs EMC optimization at the hardware function level based on a software control algorithm, does not require increasing hardware circuit costs, and has significant functional and cost advantages.

Description

Technical Field

[0001] The present invention relates to the technical field of EMC optimization, and in particular to a method for optimizing EMC of a high-power DC / DC device applied to a hydrogen fuel cell. Background Art

[0002] As people's quality of life gradually improves, the requirements for the environment have become the main contradiction at this stage. The main content of my country's energy strategy is the research and development of new energy vehicles, which is of great significance to solving my country's energy and environmental protection problems. During the working process, hydrogen fuel cells mainly rely on the combination of hydrogen, oxygen and proton exchange membranes to directly generate electricity without generating any pollution. In addition, the energy conversion efficiency of hydrogen fuel cells is greater than that of existing internal combustion engines. The application of hydrogen fuel in automobile production is a new revolution.

[0003] A DC-DC converter, also known as a DC-DC converter, is an on-board device that converts electrical energy from one voltage level to another in a DC circuit. Hereinafter referred to as a DC-DC converter, the basic function of a DC-DC converter in electric vehicles is to convert the high-voltage power provided by the power battery into a voltage level suitable for onboard electrical use. Different vehicles have different voltage platforms, and high-power DC-DC converters in electric vehicles are used for this purpose. Currently, a major goal of technological development is to increase power density, and the most mainstream approach is to increase the switching frequency. This presents a problem: power devices operate in a high-frequency switching mode, which easily generates high-frequency interference during turn-on and turn-off. This has become a major source of electromagnetic interference in electric vehicle electrical systems and is expected to increase. This leads to poor electromagnetic compatibility (EMC) in DC-DC power supplies.

[0004] Due to the limitations of hydrogen fuel cells, the electricity generated suffers from low and unstable output voltage and large fluctuations in output power. Therefore, the output voltage of the hydrogen fuel cell must be stabilized and transformed through a DC-DC converter (DC-CDC) to ensure stable and efficient power supply to downstream stages and loads. DC-CDC is used at the output of the hydrogen fuel cell stack to power the vehicle and charge the power battery. The power required is significantly higher than that of DC-CDC in general applications. To ensure long-range driving, the DC-CDC power conversion efficiency must be as high as possible. These two factors are why high-frequency SiC power switching devices are typically used in DC-CDCs. When the DC-CDC power supply uses a fixed switching frequency, these high-order harmonics are concentrated in a fixed frequency range and have large spectral peaks. This results in particularly noticeable high-frequency noise when the DC-CDC power supply is operating at certain boost ratios or power ranges. Therefore, optimizing the EMC characteristics of the DC-CDC in hydrogen fuel cells is a pressing issue. Summary of the Invention

[0005] The present invention aims to provide a method for optimizing EMC in a high-power DC-DC power supply for a hydrogen fuel cell, so as to solve the problem in the prior art that, when a fixed switching frequency is used in the DC-DC power supply driving process, these high-order harmonics are concentrated in a fixed frequency range and have a large spectrum peak, resulting in particularly obvious high-frequency noise in the DC-DC power supply operating at a certain step-up ratio or power range.

[0006] The technical solution of the present invention is: a method for optimizing EMC of a high-power DC-DC converter for a hydrogen fuel cell, comprising a DC-DC converter circuit and a control system for performing software control on the DC-DC converter circuit; the DC-DC converter circuit comprises N parallel DC-DC converter branches, each of which is connected to a power switching device; the control system comprises a carrier frequency generation module for respectively configuring carrier frequencies for the power switching devices in the N DC-DC converter branches; the method for optimizing EMC of a high-power DC-DC converter comprises the following steps:

[0007] S1. During the initialization process of the control system, each power switching device in the DCDC conversion branch is configured with a fixed carrier frequency f;

[0008] S2. When the DCDC conversion circuit is running, select whether to adjust the carrier frequency of the power switching device by the carrier frequency generation module as needed; yes, proceed to S3; no, proceed to S4, the fixed carrier frequency f is configured to a fixed period to each corresponding power switching device of the DCDC conversion branch;

[0009] S3. The carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range, and the carrier frequency points that cause poor EMC in the EMC test records of the DCDC conversion circuit are removed from the new carrier frequencies f1 and regenerated to cover them. The new carrier frequencies f1 are respectively configured to the power switching devices of each corresponding DCDC conversion branch at a fixed period;

[0010] Alternatively, a predetermined range of carrier frequencies is divided into a predetermined number of carrier frequency intervals, and a carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within the corresponding carrier frequency intervals. The new carrier frequencies f1 have carrier frequency points that cause poor EMC as recorded in the EMC test of the DCDC conversion circuit removed and regenerated to cover them. The new carrier frequencies f1 are respectively allocated to the power switching devices of the corresponding DCDC conversion branches at a fixed period.

[0011] S4. Run the DCDC conversion circuit to realize the main function.

[0012] Preferably, in step S3, when the carrier frequency generation module configures the same new carrier frequency f1 for the same power switching device for two consecutive cycles, and the next cycle still generates the same new carrier frequency f1 as the previous two cycles for the power switching device, the new carrier frequency f1 generated in the next cycle is subjected to continuous same-frequency correction processing to obtain a carrier frequency f2 after the continuous same-frequency correction processing is completed, and the carrier frequency f2 is configured to the power switching device;

[0013] The continuous co-frequency correction processing method is: add 5% of the fixed carrier frequency f to the same new carrier frequency f1; if the calculated carrier frequency result value exceeds the upper limit of the corresponding carrier frequency interval, subtract 5% of the fixed carrier frequency f from the same new carrier frequency f1.

[0014] Preferably, when there are N parallel DCDC conversion branches, and N is an even number, every two DCDC conversion branches form a DCDC conversion group, and the N parallel DCDC conversion branches are divided into A DCDC conversion group is formed; the two DCDC conversion branches in each DCDC conversion group share a coupled inductor, the two DCDC conversion branches in each DCDC conversion group are phase-staggered by 180°, the N parallel DCDC conversion branches are commonly connected to a carrier frequency generation module, and the power switching devices in the two DCDC conversion branches in each DCDC conversion group are configured with the same carrier frequency.

[0015] Preferably, the method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range of a lower limit amplitude fmin=(f-20)Khz and an upper limit amplitude fmax=(f+20)Khz. A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC test record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching devices of each corresponding DCDC conversion group at a fixed period;

[0016] Alternatively, the carrier frequency within a given range is divided into a given number of carrier frequency intervals, and the carrier frequency generation module randomly generates a given number of new carrier frequencies f1 within the corresponding carrier frequency interval by dividing the carrier frequency within the range of the lower limit amplitude fmin=(f-20)Khz and the upper limit amplitude fmax=(f+20)Khz into the same number of carrier frequency intervals as the number of groups of the even-numbered DCDC conversion branches, that is, into The carrier frequency intervals are: , , … ;or, , , … ;Carrier frequency generation module in In the carrier frequency interval, each frequency interval generates a new carrier frequency f1, and a total of A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC experiment record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching devices of each corresponding DCDC conversion group with a fixed period.

[0017] Preferably, when there are N parallel DCDC conversion branches, and N is an odd number, the N parallel DCDC conversion branches are commonly connected to the carrier frequency generation module.

[0018] Preferably, the method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates N new carrier frequencies f1 within a range of a lower limit amplitude of fmin=(f-20)Khz and an upper limit amplitude of fmax=(f+20)Khz, and the carrier frequency points that cause poor EMC as recorded in the EMC experiment of the DCDC conversion circuit are removed from the new carrier frequencies f1 and regenerated to cover them; the carrier frequency f1 or f2 is respectively configured to the power switching device of each corresponding DCDC conversion branch at a fixed period;

[0019] Alternatively, the carrier frequency within a given range is divided into a given number of carrier frequency intervals, and the carrier frequency generation module randomly generates a given number of new carrier frequencies f1 within the corresponding carrier frequency interval by dividing the carrier frequency within the range of an upper limit amplitude of fmax=(f+20)Khz and a lower limit amplitude of fmin=(f-20)Khz into carrier frequency intervals equal to the number of odd-numbered DCDC conversion branches. The carrier frequency intervals are:

[0020] , , … ;or, , , … The carrier frequency generation module randomly generates N new carrier frequencies f1 within the corresponding carrier frequency interval; and the carrier frequencies f1 or f2 are respectively configured to the power switching devices of each corresponding DCDC conversion branch with a fixed period.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) In the present invention, when there are N parallel DCDC conversion branches, and N is an even number, the two DCDC conversion branches in each DCDC conversion group share a coupled inductor, and the two DCDC conversion branches in each DCDC conversion group are phase-staggered by 180°; the design scheme based on the coupled inductor can significantly improve the power density of the DCDC power supply under a certain space volume utilization rate, and realize a more compact solution for power supply application in terms of volume and mass; the high-frequency software control method based on phase staggering can suppress the magnitude of the bus ripple current, thereby improving the efficiency of the DCDC controller; the present invention realizes automatic change adjustment of the carrier frequency of the DCDC on the basis of maintaining high frequency by combining software and hardware control and applying the coupled inductor and superimposing the high-frequency phase staggered software control algorithm.

[0023] (2) The control system of the present invention includes a carrier frequency generation module that can adjust the carrier frequency of the power switching device in each DCDC conversion branch. It performs EMC optimization at the hardware function level based on the software control algorithm as the core, and does not require increasing the hardware circuit cost, which has great functional and cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0025] Figure 1 This is a flow chart of a method for optimizing EMC of a high-power DCDC applied to a hydrogen fuel cell according to this embodiment;

[0026] Figure 2 Schematic diagram of the circuit structure of four parallel DCDC conversion branches when N is an even number 4 in Example 1, Example 2, and Example 3;

[0027] Figure 3 Schematic diagram of the circuit structure of three parallel DCDC conversion branches when N is an odd number 3 in Embodiment 4, Embodiment 5, and Embodiment 6. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to specific embodiments:

[0029] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the invention.

[0030] like Figure 1 As shown, a method for optimizing EMC of a high-power DC-DC converter for a hydrogen fuel cell includes a DC-DC converter circuit and a control system for performing software control on the DC-DC converter circuit. The DC-DC converter circuit includes N parallel DC-DC converter branches, each of which is connected to a power switching device. The control system includes a carrier frequency generation module for respectively configuring carrier frequencies for the power switching devices in the N DC-DC converter branches. The method for optimizing EMC of a high-power DC-DC converter includes the following steps:

[0031] S1. During the control system initialization process, the power switching devices in each DCDC conversion branch are configured with a fixed carrier frequency f;

[0032] S2. When the DCDC conversion circuit is running, select whether to adjust the carrier frequency of the power switching device through the carrier frequency generation module as needed; yes, proceed to S3; no, proceed to S4, the fixed carrier frequency f is configured to the corresponding power switching device of each DCDC conversion branch with a fixed period;

[0033] S3. The carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range. The new carrier frequencies f1 remove the carrier frequency points that resulted in poor EMC performance as recorded in the EMC test of the DC-DC converter circuit and regenerate these new carrier frequencies (i.e., if, in the EMC test of the DC-DC converter circuit, the EMC performance was poor when the entire DC-DC converter circuit was configured with a carrier frequency of 75 kHz, then if the randomly generated carrier frequency f1 is 75 kHz, the 75 kHz value is removed and a new carrier frequency f1 is generated). The new carrier frequencies f1 are assigned to the corresponding power switching devices of each DC-DC converter branch at a fixed period.

[0034] Alternatively, a predetermined range of carrier frequencies is divided into a predetermined number of carrier frequency intervals. The carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within the corresponding carrier frequency intervals. The new carrier frequencies f1 have carrier frequency points that cause poor EMC as recorded in the EMC test of the DCDC conversion circuit removed and regenerated to cover them. The new carrier frequencies f1 are respectively allocated to the power switching devices of the corresponding DCDC conversion branches at a fixed period.

[0035] Furthermore, in step S3, when the carrier frequency generation module configures the same new carrier frequency f1 for the same power switching device for two consecutive cycles, and the next cycle still generates the same new carrier frequency f1 for the power switching device as in the previous two cycles, the new carrier frequency f1 generated in the next cycle is subjected to continuous frequency co-ordination correction processing to obtain a carrier frequency f2 after the continuous frequency co-ordination correction processing is completed, and the carrier frequency f2 is configured to the power switching device;

[0036] The continuous co-frequency correction processing method is: add 5% of the fixed carrier frequency f to the same new carrier frequency f1. If the calculated carrier frequency result value exceeds the upper limit of the corresponding carrier frequency range, subtract 5% of the fixed carrier frequency f from the same new carrier frequency f1.

[0037] S4. Run the DCDC conversion circuit to realize the main function.

[0038] The following embodiments are provided regarding step S3. It should be noted that, when the present invention is applied in a specific manner, the most suitable embodiment can be selected as needed to generate a new carrier frequency through the carrier frequency generation module to control the on or off of the power switching device: the fixed carrier frequency f in the following embodiments is 80Khz. Of course, the value of the fixed carrier frequency f in actual applications can also be other values, which is specifically determined by the software function and the average heat dissipation requirement of the hardware.

[0039] Example 1

[0040] When there are N parallel DCDC conversion branches, and N is an even number, every two DCDC conversion branches form a DCDC conversion group, and the N parallel DCDC conversion branches are divided into A DCDC conversion group is formed; the two DCDC conversion branches in each DCDC conversion group share a coupled inductor, the two DCDC conversion branches in each DCDC conversion group are phase-staggered by 180°, the N parallel DCDC conversion branches are commonly connected to a carrier frequency generation module, and the power switching devices in the two DCDC conversion branches in each DCDC conversion group are configured with the same carrier frequency to achieve a phase-staggered function.

[0041] Specifically, such as Figure 2 As shown, when N is equal to 4 and the fixed carrier frequency f is 80 kHz; when there are four parallel DCDC conversion branches, each two DCDC conversion branches form a DCDC conversion group, and the four parallel DCDC conversion circuits are divided into two DCDC conversion groups; further, the two DCDC conversion groups are, from left to right, a first DCDC conversion group and a second DCDC conversion group, the two DCDC conversion branches in the first DCDC conversion group share a coupling inductor, and the phases of the two DCDC conversion branches in the first DCDC conversion group are staggered by 180°; similarly, the two DCDC conversion branches in the second DCDC conversion group share a coupling inductor, and the phases of the two DCDC conversion branches in the second DCDC conversion group are staggered by 180°; the first DCDC conversion group and the second DCDC conversion group are connected to a carrier frequency generation module in common, the power switching devices in the two DCDC conversion branches in the first DCDC conversion group are configured with the same carrier frequency, and the power switching devices in the two DCDC conversion branches in the second DCDC conversion group are configured with the same carrier frequency. like Figure 2 As shown, in this embodiment, the power switching device is a MOSFET tube. In each DCDC conversion branch, the power supply is connected in series with the coupled inductor and then in parallel with the MOSFET tube. The power supply is connected in series with the coupled inductor and then in series with the diode to boost the output voltage of the fuel cell stack; the carrier frequency generation module generates the frequency for controlling the on and off of the MOSFET tube.

[0042] The method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range of a lower limit amplitude fmin=(f-20)Khz and an upper limit amplitude fmax=(f+20)Khz. A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC test record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching devices of the first group of DCDC conversion groups and the second group of DCDC conversion groups with a fixed period. For example, when the fixed carrier frequency f is 80 kHz, the lower limit amplitude fmin = (f-20) kHz of the carrier frequency generation module is 60 kHz, and the upper limit amplitude fmax = (f+20) kHz is 100 kHz. The carrier frequency generation module randomly generates two new carrier frequencies f1 within the range of (60, 100) kHz. The new carrier frequencies f1 have removed the carrier frequency points that cause poor EMC as recorded in the EMC test of the DCDC conversion circuit and regenerated to cover them. Assuming that the new carrier frequencies f1 are 67 kHz and 99 kHz, 67 kHz is configured in a fixed period to the power switching devices of the first DCDC conversion group, that is, the power switching devices in the two DCDC conversion branches in the first DCDC conversion group are both configured with 67 kHz; and 99 kHz is configured in a fixed period to the power switching devices of the second DCDC conversion group, that is, the power switching devices in the two DCDC conversion branches in the second DCDC conversion group are both configured with 99 kHz.

[0043] Furthermore, if the carrier frequency generation module configures 99Khz for the power switching devices in the two DCDC conversion branches in the second group of DCDC conversion groups for two consecutive cycles, and the next cycle still generates 99Khz for the power switching devices in the two DCDC conversion branches in the second group of DCDC conversion groups, the carrier frequency 99Khz generated in the next cycle is subjected to continuous same-frequency correction processing to obtain the carrier frequency f2 after the continuous same-frequency correction processing is completed, and the carrier frequency f2 is configured to the power switching device; the continuous same-frequency correction processing method is: the same new The carrier frequency f1 is added with 5% of the fixed carrier frequency f. If the calculated carrier frequency value exceeds the upper limit of the corresponding carrier frequency range, the same new carrier frequency f1 is subtracted by 5% of the fixed carrier frequency f. For example, 99Khz+5%×80Khz=103Khz. 103Khz exceeds the (60, 100)Khz range of the carrier frequency generation module, then 99Khz-5%×80Khz=95Khz. 95Khz is configured as f2 to the power switching devices of the two DCDC conversion branches of the second DCDC conversion group.

[0044] Example 2

[0045] like Figure 2 As shown, when N is equal to 4 and the fixed carrier frequency f is 80Khz, there are 4 parallel DCDC conversion branches, and every two DCDC conversion branches form a DCDC conversion group, and the 4 parallel DCDC conversion circuits are divided into 2 groups of DCDC conversion groups; the second embodiment is basically the same as the first embodiment, except that the carrier frequency in a given range is divided into a given number of carrier frequency intervals, and the carrier frequency generation module randomly generates a given number of new carrier frequencies f1 in the corresponding carrier frequency interval as follows: the carrier frequency within the range of the lower limit amplitude fmin=(f-20)Khz and the upper limit amplitude fmax=(f+20)Khz is divided into the same number of carrier frequency intervals as the number of groups of the even-numbered DCDC conversion branches, that is, divided into The carrier frequency intervals are: , , … ;Carrier frequency generation module in In the carrier frequency interval, each frequency interval generates a new carrier frequency f1, and a total of A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC test record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching device of each DCDC conversion group with a fixed period.

[0046] For example, the fixed carrier frequency f is 80Khz, the lower limit amplitude fmin=(f-20)Khz of the carrier frequency generation module is 60Khz, and the upper limit amplitude fmax=(f+20)Khz is 100Khz. The carrier frequency within the range of the lower limit amplitude of 60Khz and the upper limit amplitude of 100Khz is divided into the same number of carrier frequency intervals as the number of groups of the even-numbered DCDC conversion branches, that is, the carrier frequency within the range of (60-100)Khz is divided into two carrier frequency intervals, namely: (60, 60+ ), (100- , 100), namely (60, 80) Khz and (80, 100) Khz; the carrier frequency generation module randomly generates two new carrier frequencies f1 in the intervals of (60-80) Khz and (80-100) Khz, and the carrier frequency points that cause poor EMC as recorded in the EMC experiment of the DCDC conversion circuit have been removed from the new carrier frequencies f1 and regenerated to cover them. The two newly generated carrier frequencies f1 are, for example, 74 Khz and 86 Khz. 74 Khz is configured to the power switching devices of the first DCDC conversion group at a fixed period, that is, the power switching devices in the two DCDC conversion branches in the first DCDC conversion group are both configured with 74 Khz; 86 Khz is configured to the power switching devices of the second DCDC conversion group at a fixed period, that is, the power switching devices in the two DCDC conversion branches in the second DCDC conversion group are both configured with 86 Khz.

[0047] Example 3

[0048] like Figure 2 As shown, when N is equal to 4 and the fixed carrier frequency is 80Khz; when there are 4 parallel DCDC conversion branches, every two DCDC conversion branches form a DCDC conversion group, and the 4 parallel DCDC conversion circuits are divided into 2 groups of DCDC conversion groups; Example 3 is basically the same as Example 2, except that the carrier frequency within the range of the lower limit amplitude of 60Khz and the upper limit amplitude of 100Khz is divided into the same number of carrier frequency intervals as the number of groups of the even-numbered DCDC conversion branches, 2. , , … ; That is (60,60+ )、(100- , 100), the carrier frequency in the range of (60-100) Khz is divided into two carrier frequency intervals, namely: (60-86.666) Khz and (73.333-100) Khz, and the carrier frequency points that cause poor EMC in the EMC experiment record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered. The two newly generated carrier frequencies f1 are, for example, 80 Khz and 88 Khz. 80 Khz is configured to the power switching devices of the first DCDC conversion group with a fixed period, that is, the power switching devices in the two DCDC conversion branches in the first DCDC conversion group are both configured with 80 Khz; 88 Khz is configured to the power switching devices of the second DCDC conversion group with a fixed period, that is, the power switching devices in the two DCDC conversion branches in the second DCDC conversion group are both configured with 88 Khz.

[0049] Example 4

[0050] like Figure 3As shown, when there are N parallel DCDC conversion branches, N is an odd number, specifically when N is equal to 3, and the fixed carrier frequency f is 80Khz, the three DCDC conversion branches are connected in parallel, and from left to right are the first DCDC conversion branch, the second DCDC conversion branch, and the third DCDC conversion branch; in the three parallel DCDC conversion branches, the power supply and the inductor are connected in series and then in parallel with the MOSFET tube, and the positive electrode of the power supply is connected to the inductor and then in series with the diode to boost the output voltage of the fuel cell stack; the carrier frequency generation module generates the frequency for controlling the turning on and off of the MOSFET tube.

[0051] The method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates N new carrier frequencies f1 within a range of a lower limit amplitude fmin=(f-20)Khz and an upper limit amplitude fmax=(f+20)Khz, and the new carrier frequencies f1 have carrier frequency points that cause poor EMC as recorded in an EMC experiment of a DCDC conversion circuit removed and regenerated to cover them; the carrier frequency f1 or f2 is respectively configured to the power switching device of each corresponding DCDC conversion branch at a fixed period.

[0052] For example, when the fixed carrier frequency f is 80 kHz, the lower limit amplitude fmin=(f-20) kHz of the carrier frequency generation module is 60 kHz, and the upper limit amplitude fmax=(f+20) kHz is 100 kHz. The carrier frequency generation module randomly generates three new carrier frequencies f1 within the range of (60-100) kHz. The new carrier frequencies f1 have removed the carrier frequency points that cause poor EMC as recorded in the EMC experiment of the DCDC conversion circuit and regenerated and covered them. For example, the new carrier frequencies f1 are 65 kHz, 80 kHz, and 96 kHz. 65 kHz is configured to the power switch device of the first DCDC conversion branch with a fixed period, 80 kHz is configured to the power switch device of the second DCDC conversion branch with a fixed period, and 96 kHz is configured to the power switch device of the third DCDC conversion branch with a fixed period.

[0053] Furthermore, when the carrier frequency generation module configures 96Khz for the power switching device of the third DCDC conversion branch for two consecutive cycles, and the next cycle still generates 96Khz for the power switching device of the third DCDC conversion branch, the carrier frequency 96Khz generated in the next cycle is subjected to continuous frequency correction processing to obtain the carrier frequency f2 after the continuous frequency correction processing is completed, and the carrier frequency f2 is configured to the power switching device; the continuous frequency correction processing method is: add 5% of the fixed carrier frequency f to the same new carrier frequency f1. If the calculated carrier frequency If the result value exceeds the upper limit of the corresponding carrier frequency interval, the same new carrier frequency f1 is subtracted from 5% of the fixed carrier frequency f, for example, 96Khz+5%×80Khz=100Khz. Since the (60-100)Khz range of the carrier frequency generation module does not include 60Khz and 100Khz, the calculated carrier frequency result value exceeds the upper limit of the corresponding carrier frequency interval, then 96Khz-5%×80Khz=92Khz, and 92Khz is configured as f2 in the power switching devices of the two DCDC conversion branches of the second DCDC conversion group.

[0054] Example 5

[0055] like Figure 3 As shown, when there are N parallel DCDC conversion branches, N is an odd number, specifically when N is equal to 3, and the fixed carrier frequency is 80Khz, three DCDC conversion branches are connected in parallel, from left to right, namely the first DCDC conversion branch, the second DCDC conversion branch, and the third DCDC conversion branch.

[0056] Example 5 is basically the same as Example 4, except that the carrier frequency in a predetermined range is divided into a predetermined number of carrier frequency intervals, and the carrier frequency generation module randomly generates N new carrier frequencies f1 in the corresponding carrier frequency interval by dividing the carrier frequency within the range of the upper limit amplitude fmax=(f+20)Khz and the lower limit amplitude fmin=(f-20)Khz into the same number of carrier frequency intervals as the number of odd-numbered DCDC conversion branches, and the carrier frequency intervals are: , , … The carrier frequency generation module randomly generates N new carrier frequencies f1 within the corresponding carrier frequency interval; and configures the carrier frequency f1 or f2 to the power switch device of each corresponding DCDC conversion branch at a fixed period.

[0057] For example, when the fixed carrier frequency f is 80Khz, the lower limit amplitude fmin=(f-20)Khz of the carrier frequency generation module is 60Khz, and the upper limit amplitude fmax=(f+20)Khz is 100Khz. The carrier frequency within the range of the lower limit amplitude of 60Khz and the upper limit amplitude of 100Khz is divided into the same carrier frequency interval as the number of odd DCDC conversion branches, that is, the carrier frequency within the range of (60-100)Khz is divided into 3 carrier frequency intervals, namely: (60, 60+ ), (60+ , 60+2 ), (100- ,100), that is, (60-73.333)Khz, (73.333-86.666)Khz, (86.666-100)Khz, and the carrier frequency points that cause poor EMC in the EMC experiment record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered. The three newly generated carrier frequencies f1 are, for example, 63Khz, 82Khz, and 91Khz. 63Khz is configured to the power switching device of the first DCDC conversion branch with a fixed period, 82Khz is configured to the power switching device of the second DCDC conversion branch with a fixed period, and 91Khz is configured to the power switching device of the third DCDC conversion branch with a fixed period.

[0058] Example 6

[0059] like Figure 3 As shown, when there are N parallel DCDC conversion branches, N is an odd number, specifically when N is equal to 3, and the fixed carrier frequency is 80Khz, three DCDC conversion branches are connected in parallel, from left to right, namely the first DCDC conversion branch, the second DCDC conversion branch, and the third DCDC conversion branch.

[0060] Example 6 is basically the same as Example 5, except that the carrier frequency in a predetermined range is divided into a predetermined number of carrier frequency intervals, and the carrier frequency generation module randomly generates N new carrier frequencies f1 in the corresponding carrier frequency interval by dividing the carrier frequency within the range of the upper limit amplitude fmax=(f+20)Khz and the lower limit amplitude fmin=(f-20)Khz into the same number of carrier frequency intervals as the number of odd-numbered DCDC conversion branches, and the carrier frequency intervals are: , , … The carrier frequency generation module randomly generates N new carrier frequencies f1 within the corresponding carrier frequency interval; and configures the carrier frequency f1 or f2 to the power switch device of each corresponding DCDC conversion branch at a fixed period.

[0061] For example, when the fixed carrier frequency f is 80Khz, the lower limit amplitude fmin=(f-20)Khz of the carrier frequency generation module is 60Khz, and the upper limit amplitude fmax=(f+20)Khz is 100Khz. The carrier frequency within the range of the lower limit amplitude of 60Khz and the upper limit amplitude of 100Khz is divided into the same carrier frequency interval as the number of odd DCDC conversion branches, that is, the carrier frequency within the range of (60-100)Khz is divided into 3 carrier frequency intervals, namely: (60, 60+2 ), (60+ , 60+3 ), (100-2 ,100), namely (60-80)Khz, (70-90)Khz, (80-100)Khz, and the carrier frequency points that cause poor EMC in the EMC experiment record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered. The three newly generated carrier frequencies f1 are, for example, 63Khz, 82Khz, and 91Khz. 63Khz is configured to the power switching device of the first DCDC conversion branch with a fixed period, 82Khz is configured to the power switching device of the second DCDC conversion branch with a fixed period, and 91Khz is configured to the power switching device of the third DCDC conversion branch with a fixed period.

[0062] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they are not intended to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A method for optimizing EMC of a high-power DC-DC system for a hydrogen fuel cell, characterized by: The invention relates to a method for optimizing EMC of a high-power DCDC system, comprising a DCDC conversion circuit and a control system for performing software control on the DCDC conversion circuit; the DCDC conversion circuit comprises N parallel DCDC conversion branches, each of which is connected to a power switching device; the control system comprises a carrier frequency generation module for respectively configuring carrier frequencies for the power switching devices in the N DCDC conversion branches; the method for optimizing EMC of the high-power DCDC system comprises the following steps: S1. During the initialization process of the control system, each power switching device in the DCDC conversion branch is configured with a fixed carrier frequency f; S2. When the DCDC conversion circuit is running, select whether to adjust the carrier frequency of the power switching device by the carrier frequency generation module as needed; yes, proceed to S3; no, proceed to S4, the fixed carrier frequency f is configured to a fixed period to each corresponding power switching device of the DCDC conversion branch; S3. The carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range, and the carrier frequency points that cause poor EMC in the EMC test records of the DCDC conversion circuit are removed from the new carrier frequencies f1 and regenerated to cover them. The new carrier frequencies f1 are respectively configured to the power switching devices of each corresponding DCDC conversion branch at a fixed period; Alternatively, a predetermined range of carrier frequencies is divided into a predetermined number of carrier frequency intervals, and a carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within the corresponding carrier frequency intervals. The new carrier frequencies f1 have carrier frequency points that cause poor EMC as recorded in the EMC test of the DCDC conversion circuit removed and regenerated to cover them. The new carrier frequencies f1 are respectively allocated to the power switching devices of the corresponding DCDC conversion branches at a fixed period. S4. Run the DCDC conversion circuit to realize the main function; In step S3, when the carrier frequency generation module configures the same new carrier frequency f1 for the same power switching device for two consecutive cycles, and the next cycle still generates the same new carrier frequency f1 for the power switching device as the previous two cycles, the new carrier frequency f1 generated in the next cycle is subjected to continuous frequency co-ordination correction processing to obtain a carrier frequency f2 after the continuous frequency co-ordination processing is completed, and the carrier frequency f2 is configured to the power switching device; The continuous co-frequency correction processing method is: add 5% of the fixed carrier frequency f to the same new carrier frequency f1; if the calculated carrier frequency result value exceeds the upper limit of the corresponding carrier frequency interval, subtract 5% of the fixed carrier frequency f from the same new carrier frequency f1.

2. The method for optimizing EMC of a high-power DC-DC system for a hydrogen fuel cell according to claim 1, wherein: When there are N parallel DCDC conversion branches, and N is an even number, every two DCDC conversion branches form a DCDC conversion group, and the N parallel DCDC conversion branches are divided into A DCDC conversion group is formed; the two DCDC conversion branches in each DCDC conversion group share a coupled inductor, the two DCDC conversion branches in each DCDC conversion group are phase-staggered by 180°, the N parallel DCDC conversion branches are commonly connected to a carrier frequency generation module, and the power switching devices in the two DCDC conversion branches in each DCDC conversion group are configured with the same carrier frequency.

3. The method for optimizing EMC of a high-power DC-DC system for a hydrogen fuel cell according to claim 2, wherein: The method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates a predetermined number of new carrier frequencies f1 within a predetermined range of a lower limit amplitude fmin=(f-20)Khz and an upper limit amplitude fmax=(f+20)Khz. A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC test record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching devices of each corresponding DCDC conversion group at a fixed period; Alternatively, the carrier frequency within a given range is divided into a given number of carrier frequency intervals, and the carrier frequency generation module randomly generates a given number of new carrier frequencies f1 within the corresponding carrier frequency interval by dividing the carrier frequency within the range of the lower limit amplitude fmin=(f-20)Khz and the upper limit amplitude fmax=(f+20)Khz into the same number of carrier frequency intervals as the number of groups of the even-numbered DCDC conversion branches, that is, into The carrier frequency intervals are: , , … ;or, , , … ; The carrier frequency generation module is In the carrier frequency interval, each frequency interval generates a new carrier frequency f1, and a total of A new carrier frequency f1 is generated; and the carrier frequency points that cause poor EMC in the EMC experiment record of the DCDC conversion circuit have been removed from the new carrier frequency f1 and regenerated and covered, and the carrier frequency f1 or f2 is respectively configured to the power switching devices of each corresponding DCDC conversion group with a fixed period.

4. The method for optimizing EMC of a high-power DC / DC system for a hydrogen fuel cell according to claim 1, wherein: When there are N parallel DCDC conversion branches, and N is an odd number, the N parallel DCDC conversion branches are commonly connected to the carrier frequency generation module.

5. The method for optimizing EMC of a high-power DCDC system for a hydrogen fuel cell according to claim 4, characterized in that: The method for the carrier frequency generation module to randomly generate a predetermined number of new carrier frequencies f1 within a predetermined range is as follows: the carrier frequency generation module randomly generates N new carrier frequencies f1 within a range of a lower limit amplitude fmin=(f-20)Khz and an upper limit amplitude fmax=(f+20)Khz, and the carrier frequency points that cause poor EMC in the EMC test record of the DCDC conversion circuit are removed from the new carrier frequencies f1 and regenerated to cover them; the carrier frequency f1 or f2 is respectively configured to the power switching device of each corresponding DCDC conversion branch at a fixed period; Alternatively, the carrier frequency within a given range is divided into a given number of carrier frequency intervals, and the carrier frequency generation module randomly generates a given number of new carrier frequencies f1 within the corresponding carrier frequency interval by dividing the carrier frequency within the range of an upper limit amplitude of fmax=(f+20)Khz and a lower limit amplitude of fmin=(f-20)Khz into carrier frequency intervals equal to the number of odd-numbered DCDC conversion branches. The carrier frequency intervals are: , , … ;or, , , … ; The carrier frequency generation module randomly generates N new carrier frequencies f1 within the corresponding carrier frequency interval; and configures the carrier frequency f1 or f2 to the power switch device of each corresponding DCDC conversion branch at a fixed period.

Images