DC / DC converter control method and control device, fuel cell system and vehicle

Abstract

The embodiment of the invention relates to the technical field of DC / DC converters, in particular to a DC / DC converter control method, which comprises the following steps: determining the actual input power (Pactual) and the maximum allowable input power (Plimit) of a DC / DC converter (1); and determining a derating strategy for the DC / DC converter (1) on the basis of a comparison of the actual input power (Pactual) and the maximum allowable input power (Plimit). The embodiment of the invention further relates to a corresponding DC / DC converter control device, a fuel cell system and a vehicle. Through the embodiment of the invention, the use of the maximum power capacity of the DC / DC converter can be maximized especially in a relatively low output voltage demand range, so that the power utilization rate of a fuel cell stack can be improved more favorably when the DC / DC converter is implemented in a fuel cell system; and the charging behavior of the vehicle battery may be optimized when implemented in a fuel cell vehicle.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of DC / DC converters, and specifically to a DC / DC converter control method, a DC / DC converter control device, a fuel cell system including the DC / DC converter control device, a vehicle including the DC / DC converter control device or the fuel cell system, and a corresponding computer storage medium. Background Art

[0002] A DC / DC converter (direct current / direct current converter) is an electronic device that converts a DC input voltage of a certain level into a DC output voltage of another level. By controlling the on / off states of the respective switching components in the DC / DC converter, the current in the circuit can be adjusted, thereby achieving the regulation of the output voltage of the DC / DC converter. Usually, this control is accomplished by a control signal, such as a pulse width modulation (PWM) signal, issued by a corresponding controller communicating with the DC / DC converter. According to the magnitudes of the input voltage and the output voltage, the DC / DC converter can be classified into a boost DC / DC converter, a buck DC / DC converter, and a buck-boost DC / DC converter (also known as a bidirectional DC / DC converter).

[0003] The derating function of a DC / DC converter is an important design consideration for ensuring the reliability and stability of electronic products. The derating function means reducing the output power of the converter under certain conditions to ensure that the relevant electronic components in the circuit can operate safely and have a long service life. Under specific (especially over-temperature or over-load) conditions, the DC / DC converter needs to be derated to reduce the output power to protect the entire circuit system.

[0004] In addition, in a fuel cell vehicle, a DC / DC converter is required to connect between the fuel cell stack and the battery to achieve voltage matching. That is, as Figure 1 shown, the input end of the DC / DC converter 1 is connected to the fuel cell stack 3, and its input voltage U in and input current I in depend on the fuel cell stack 3; while the output end of the DC / DC converter is connected to the (high-voltage) battery 4. In addition, the DC / DC converter 1 receives, for example, a control signal issued by the fuel cell control unit 2 via a CAN bus and responds thereto. Summary of the Invention

[0005] The purpose of the present application is to provide an improved DC / DC converter control method, which can maximize the use of the maximum power capacity of the DC / DC converter.

[0006] According to the first aspect of the present application, there is provided a DC / DC converter control method, including the following steps:

[0007] - S1: Determine the actual input power and the maximum allowable input power of the DC / DC converter; and

[0008] - S2: Determine a derating strategy for the DC / DC converter based on a comparison of the actual input power and the maximum allowable input power.

[0009] According to an optional embodiment of the present application, the actual input power of the DC / DC converter is calculated by collecting the input current and input voltage of the DC / DC converter.

[0010] According to an optional embodiment of the present application, the maximum allowable input power of the DC / DC converter is obtained by utilizing a preset look-up table based on the output voltage of the DC / DC converter.

[0011] According to an optional embodiment of the present application, the derating strategy for the DC / DC converter includes: when the actual input power is greater than the maximum allowable input power, controlling the DC / DC converter such that its input current is equal to the maximum allowable input power divided by the input voltage.

[0012] According to an optional embodiment of the present application, the DC / DC converter control method further includes: when the actual input power is less than or equal to the maximum allowable input power, controlling the DC / DC converter such that its input current is equal to the maximum allowable input current.

[0013] According to an optional embodiment of the present application, the determination and comparison of the actual input power and the maximum allowable input power are performed at a preset time interval.

[0014] According to a second aspect of the present application, there is provided a DC / DC converter control device, including:

[0015] - A collection module, which includes a collection unit for collecting the input current, input voltage, and output voltage of the DC / DC converter; and

[0016] - A control module, which is communicatively connected to the DC / DC converter and is configured to be able to execute any of the DC / DC converter control methods according to the first aspect of the present application based on the input current, input voltage, and output voltage collected by the collection module.

[0017] According to a third aspect of the present application, there is provided a fuel cell system, including:

[0018] - A DC / DC converter;

[0019] - A fuel cell stack and a battery respectively connected to the input end and the output end of the DC / DC converter; and

[0020] - A DC / DC converter control device according to the second aspect of the present application.

[0021] According to an optional embodiment of the present application, the DC / DC converter is a boost or buck-boost DC / DC converter.

[0022] According to the fourth aspect of the present application, a vehicle is provided, including a DC / DC converter control device according to the second aspect of the present application or a fuel cell system according to the third aspect of the present application.

[0023] According to the fifth aspect of the present application, a computer storage medium is provided, storing program instructions that can execute any of the DC / DC converter control methods according to the first aspect of the present application when running.

[0024] The present application creatively proposes to determine the derating strategy for the DC / DC converter based on the comparison between the actual input power and the maximum allowable input power of the DC / DC converter. Compared with the existing derating strategy based on the comparison between the actual input current and the maximum allowable input current of the DC / DC converter, the DC / DC converter control method according to the present application can maximize the use of the maximum power capacity of the DC / DC converter especially in the range where the output voltage requirement is relatively low. Furthermore, it can be more beneficial to improve the power utilization rate of the fuel cell stack when implemented in a fuel cell system, and can optimize the charging behavior of the vehicle battery when implemented in a fuel cell vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Hereinafter, the present application will be described in more detail by referring to the drawings, and the principles, features and advantages of the present application can be better understood. In the drawings:

[0026] Figure 1 The structure of the fuel cell system is schematically shown;

[0027] Figure 2 A schematic flowchart of a DC / DC converter control method according to an embodiment of the present application is shown;

[0028] Figure 3 A schematic flowchart of a DC / DC converter control method according to another embodiment of the present application is shown;

[0029] Figure 4 An exemplary correspondence between the output voltage and the maximum allowable input current of the DC / DC converter is shown; and

[0030] Figure 5 The difference in the output power of the DC / DC converter between the DC / DC converter control method according to an embodiment of the present application and the existing DC / DC converter control method is shown.

[0031] List of reference numerals

[0032] 1 DC / DC converter

[0033] 2 Control module of DC / DC converter control device

[0034] 3 Fuel cell stack

[0035] 4 Battery

[0036] 100 Fuel cell system Detailed implementation manners

[0037] In order to make the technical problems to be solved, technical solutions and beneficial technical effects of this application clearer, the following will further elaborate on this application in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the principle of this application, rather than to limit the protection scope of this application.

[0038] Existing derating strategies for DC / DC converters usually rely on monitoring the input current and output voltage of the DC / DC converter. Specifically, after the circuit is closed, the output voltage of the DC / DC converter is collected by a sensor. Then, using, for example Figure 4 the corresponding relationship between the output voltage and the maximum allowable input current of the DC / DC converter shown exemplarily, the corresponding maximum allowable input current is determined based on the collected output voltage. As Figure 4 shown, when the output voltage U out is in the range of [650, 850] V, the corresponding maximum allowable input current I in is 600 A, which means that there is no need to execute a derating strategy for the DC / DC converter at this time. When the collected output voltage U out is less than 650 V or greater than 850 V, if the current is too large, it may cause overload or overheating of the load at the output end of the DC / DC converter. Therefore, a derating strategy needs to be executed for the DC / DC converter at this time. And, in the conventional derating strategy, the maximum allowable input current I in and the output voltage U out vary linearly. For example, when the output voltage U out is 500 V, the corresponding maximum allowable input current I in is 150 A; when the output voltage U out increases to 600 V, the corresponding maximum allowable input current I inIncrease to 450 A. After determining the maximum allowable input current, compare the actually measured input current with it to determine whether derating needs to be implemented. In other words, the existing derating strategy for the DC / DC converter is determined based on the output voltage and input current of the DC / DC converter (in this document, this derating strategy is also referred to as the existing DC / DC converter control method).

[0039] In contrast, the present inventor creatively proposed an improved DC / DC converter control method. This control method abandons the solution of judging whether the input current of the DC / DC converter reaches the maximum allowable input current in the existing derating strategy, but instead uses whether the input power of the DC / DC converter reaches the maximum allowable input power as the key to determining the derating strategy.

[0040] Next, in conjunction with Figures 1 to 5 detail the technical solution provided by the embodiments of the present application.

[0041] Refer to Figure 2 , the DC / DC converter control method according to an embodiment of the present application includes the following steps:

[0042] - S1: Determine the actual input power P actual of the DC / DC converter and the maximum allowable input power P limit ; and

[0043] - S2: Based on the comparison between the actual input power P actual and the maximum allowable input power P limit , determine the derating strategy for the DC / DC converter.

[0044] S0 in the figure represents the start, and this start can particularly refer to the closing of the circuit. In addition, the derating strategy can include whether derating is required (or derating demand) and the specific derating method.

[0045] Figure 5 shows the difference between the DC / DC converter control method according to an embodiment of the present application and the existing DC / DC converter control method in terms of the output power of the DC / DC converter. Among them, the output power corresponding to the DC / DC converter control method according to the present application is marked with "circles", while the output power corresponding to the existing DC / DC converter control method is marked with "squares".

[0046] As Figure 5As shown, for output voltages greater than or equal to 650V (including the interval where no derating strategy needs to be implemented and the high output voltage demand interval), there is no significant difference in output power between the two methods. However, for output voltages less than 650V (i.e., the low output voltage demand interval), the output power obtained by the DC / DC converter control method according to the embodiments of the present application is significantly higher than that of the existing DC / DC converter control method. Therefore, the DC / DC converter control method according to the embodiments of the present application can maximize the use of the maximum power capacity of the DC / DC converter especially in the range where the output voltage demand is relatively low. That is to say, compared with the existing DC / DC converter control method, the DC / DC converter control method according to the embodiments of the present application can achieve a relatively small derating amplitude and a more reasonable derating range in the low output voltage demand interval, and will not cause excessive loss of output power while ensuring that the derating meets the requirements.

[0047] In an exemplary embodiment, the actual input power P of the DC / DC converter 1 actual can be calculated by collecting the input current I of the DC / DC converter 1 in and the input voltage U in Specifically, the input current I of the DC / DC converter 1 in and the input voltage U in can be collected by sensors connected to the input end of the DC / DC converter 1, and the actual input power P can be calculated by the following formula 1 actual :

[0048] P actual = I in ×U in (Formula 1)

[0049] In an exemplary embodiment, the maximum allowable input power P of the DC / DC converter 1 limit can be obtained by using a preset look-up table based on the output voltage U of the DC / DC converter 1 out The preset look-up table can be set as needed, and optionally, the loss of the DC / DC converter 1 can be additionally considered (the present application does not limit this, and it can be modified according to the actual working conditions without exceeding the scope of the present application).

[0050] Here, a voltage sensor can be set between the DC / DC converter 1 and the battery 4 adjacent to the output end of the DC / DC converter 1, so as to collect the output voltage U of the DC / DC converter 1 after the circuit is closed by using the voltage sensor outThus, the actual output voltage of the DC / DC converter 1 can be determined during the power transfer process, so that the abnormal output voltage of the DC / DC converter 1 caused by various reasons can be monitored in a timely manner, and a corresponding derating strategy can be provided in a timely manner for the abnormality, which helps to ensure the stability of the circuit structure where the DC / DC converter 1 is located and the robustness of the DC / DC converter control method according to the present application.

[0051] In an exemplary embodiment, the derating strategy for the DC / DC converter 1 may include: when the actual input power P actual is greater than the maximum allowable input power P limit , controlling the DC / DC converter 1 such that its input current I in is equal to the maximum allowable input power P limit divided by the input voltage U in , that is

[0052] I in = P limit / U in P actual > P limit

[0053] Thus, the input current of the DC / DC converter 1 can be adjusted so that its input end reaches the maximum allowable input power.

[0054] When the actual input power P actual is less than or equal to the maximum allowable input power P limit , at this time, there is no need to perform derating control on the DC / DC converter 1. Therefore, the DC / DC converter 1 can be controlled such that its input current I in is equal to the maximum allowable input current I limit , that is

[0055] I in = I limit P actual ≤ P limit

[0056] Thus, it can operate at the maximum power of the entire system without derating. The maximum allowable input current I in can be determined by the output voltage U out for example (as in the existing DC / DC control method).

[0057] Figure 3 shows a flowchart of a DC / DC converter control method according to another embodiment of the present application. In Figure 3 , S0 represents the start, Figure 2 the step S1 shown in Figure 3Steps S11, S12, and S13 shown in the figure. Among them, step S11 represents collecting the input current I of the DC / DC converter in , the input voltage U in and the output voltage U out . Step S12 represents using the input current I in and the input voltage U in to calculate the actual input power P based on formula 1 actual . Step S13 represents using a preset look-up table to determine the maximum allowable input power P based on the output voltage U out . After that, compare and determine whether the actual input power P limit is greater than the maximum allowable input power P actual . Step S21 represents that when the actual input power P limit is greater than the maximum allowable input power P actual , controlling the DC / DC converter 1 so that its input current I limit is equal to the maximum allowable input power P in divided by the input voltage U limit . Step S23 represents that when the actual input power P in is less than or equal to the maximum allowable input power P actual , controlling the DC / DC converter 1 so that its input current I limit is equal to the maximum allowable input current I in . limit .

[0058] The above control of the input current can be achieved, for example, by generating a corresponding PWM control signal.

[0059] Exemplarily and preferably, in an embodiment according to the present application, the determination and comparison of the actual input power P actual and the maximum allowable input power P limit can be performed at a preset time interval. The preset time interval can be, for example, 1 ms, 5 ms, or 10 ms. The present application does not limit this and can be adjusted according to actual needs. Specifically, after the circuit is closed, the actual input power P actual can be calculated using the above formula 1 at a preset time interval, and the actual input power P actual and the maximum allowable input power P limit can be compared, so as to determine whether derating is required and the implementation method of the specific derating strategy according to the comparison result. Thus, the actual input power P actual of the DC / DC converter can be continuously monitored regularly, so that the required derating strategy can be provided in time, improving the reliability of the power conversion process and the robustness of the implementation of the DC / DC converter control method.

[0060] Additionally and optionally, in one embodiment according to the present application, the output voltage at the same time point when calculating the actual input power P actual can be collected, and the maximum allowable input power P corresponding to the measured value of the output voltage can be determined by using a preset look-up table based on the measured value of the output voltage limit , so as to compare the actual input power P actual at the same time point with the maximum allowable input power P limit . Thus, continuous monitoring of the maximum allowable input power P limit can be achieved.

[0061] Additionally and preferably, for the input current I in , input voltage U in and output voltage U out of the DC / DC converter, the acquisition can be carried out in real time and continuously, and the required values are extracted from the corresponding continuous data collected at a preset time interval for calculation and comparison. In this case, the control module 2 of the DC / DC converter control device can communicate with the acquisition unit in real time to receive the corresponding current and voltage data collected by the acquisition unit, and the control module 2 then extracts the data for calculation and comparison from the received data at a preset time interval. Alternatively and optionally, for the input current I in , input voltage U in and output voltage U out of the DC / DC converter, the acquisition can also be carried out at a certain preset time interval, that is, the current input current I in , input voltage U in and output voltage U out are collected once every preset time interval, so as to perform corresponding calculations and comparisons using these data. In particular, it should be noted that the time interval for collecting the input current I in , input voltage U in and output voltage U out is preferably less than the time interval for power determination and comparison. In this case, the control module 2 of the DC / DC converter control device can send a data request instruction to the acquisition unit at a preset time interval, and the acquisition unit sends the current corresponding current and voltage data to the control module in response to the data request instruction, and the control module 2 then performs calculations and comparisons based on the received data. The above process of collecting current and voltage can be selected according to the length of the preset time interval and / or the actual monitoring requirements of the DC / DC converter.

[0062] According to a second aspect of the present application, there is provided a DC / DC converter control device, comprising:

[0063] - A collection module (not shown in the figure), which includes a collection unit for collecting the input current I of the DC / DC converter 1 in , the input voltage U in and the output voltage U out ; and

[0064] - A control module 2, which is communicatively connected to the DC / DC converter 1 and configured to be able to execute any DC / DC converter control method according to the present application based on the input current I in , the input voltage U in and the output voltage U out collected by the collection module.

[0065] In one embodiment, the collection unit may include a current sensor and a voltage sensor connected to the input end of the DC / DC converter 1 and used for collecting the input current I in and the input voltage U in , and a voltage sensor connected to the output end of the DC / DC converter 1 and used for collecting the output voltage U out of the DC / DC converter 1.

[0066] The preset look-up table may be stored in the memory of the DC / DC converter control device, the fuel cell system 100 or the corresponding vehicle. The control module 2 of the DC / DC converter control device may communicate with the memory in a wired or wireless manner to read the preset look-up table stored therein. Thus, the preset look-up table can be accessed, read and data queried quickly, so that the time-consuming of the control module 2 in determining the maximum allowable input power P limit and performing power comparison and other links can be shortened.

[0067] Alternatively, in an alternative embodiment, the preset look-up table may also be stored in the cloud memory. The control module 2 of the DC / DC converter control device may access the cloud memory in a wireless communication manner to read the preset look-up table. In this way, the storage location of the preset look-up table can be transferred from a single individual to a shared cloud, which is beneficial to the update, maintenance of the preset look-up table and data synchronization between different DC / DC converter control devices, fuel cell systems 100 or corresponding vehicles.

[0068] The control module 2 may include at least one controller, and the control module 2 may be based on the determined actual input power P actual and the maximum allowable input power P limitDetermine the derating strategy. For example, the control module 2 can generate a PWM signal corresponding to the derating strategy and send the PWM signal to the DC / DC converter 1 through the communication connection with the DC / DC converter 1. The pulse width (switching time) of the PWM signal determines the on / off states of the respective switching devices in the DC / DC converter 1. By adjusting the pulse width, the on / off time ratio (i.e., the duty cycle) of the switching element can be controlled, thereby adjusting the power transfer ratio in the circuit and ultimately achieving the purpose of changing and regulating the input current.

[0069] It should be noted that the technical solution proposed in this application mainly focuses on the control method and does not limit the specific topology of the DC / DC converter 1.

[0070] Refer again to Figure 1 , the fuel cell system 100 according to an embodiment of the present application may include a DC / DC converter 1, a DC / DC converter control device according to an embodiment of the present application, a fuel cell stack 3, and a battery 4. The fuel cell stack 3 and the battery 4 are correspondingly connected to the input end and the output end of the DC / DC converter 1, so that the electric energy provided by the fuel cell stack 3 is transmitted to the battery 4 via the DC / DC converter 1. Here, the battery 4 may particularly refer to the high-voltage battery of the fuel cell system 100 or a fuel cell vehicle.

[0071] Optionally, the DC / DC converter 1 may be a boost DC / DC converter or a buck-boost DC / DC converter.

[0072] The present application also provides a corresponding vehicle including a DC / DC converter control device or a fuel cell system 100. The vehicle may be a fuel cell vehicle (FCV), an electric bus, a passenger vehicle, a commercial vehicle, or a non-road vehicle, etc.

[0073] In addition, the present application also provides a computer storage medium storing program instructions that can execute the DC / DC converter control method during runtime.

[0074] Through the embodiments of the present application, a derating strategy for the DC / DC converter is creatively proposed based on the comparison between the actual input power and the maximum allowable input power of the DC / DC converter. Compared with the existing control method based on the comparison between the actual input current and the maximum allowable input current of the DC / DC converter, the DC / DC converter control method according to the present application can particularly maximize the use of the maximum power capacity of the DC / DC converter in a range where the output voltage requirement is relatively low. Furthermore, it is more beneficial to improve the power utilization rate of the fuel cell stack when implemented in a fuel cell system, and can optimize the charging behavior of the vehicle battery when implemented in a fuel cell vehicle.

[0075] It should be understood that in the description of this specification, the descriptions of terms such as "one embodiment", "some embodiments", and "exemplary embodiments" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment.

[0076] Although specific embodiments of the present invention are described in detail herein, they are given for purposes of explanation only and should not be considered as limiting the scope of the present invention. Various substitutions, alterations, and modifications can be conceived without departing from the spirit and scope of the present invention.

Claims

1. A DC / DC converter control method, comprising the following steps: S1: Determine the actual input power (P actual ) and the maximum allowable input power (P limit ) of the DC / DC converter (1); and S2: Based on the comparison of the actual input power (P actual ) and the maximum allowable input power (P limit ), determine the derating strategy for the DC / DC converter (1).

2. The DC / DC converter control method according to claim 1, characterized in that The actual input power (P actual ) of the DC / DC converter (1) is obtained by collecting the input current (I in ) and the input voltage (U in ) of the DC / DC converter (1) and calculating; and / or The maximum allowable input power (P limit ) of the DC / DC converter (1) is obtained by using a preset look-up table based on the output voltage (U out ) of the DC / DC converter (1).

3. The DC / DC converter control method according to claim 1 or 2, characterized in that, The derating strategy for the DC / DC converter (1) includes: When the actual input power (P actual ) is greater than the maximum allowable input power (P limit ), the DC / DC converter (1) is controlled such that its input current (I in ) is equal to the maximum allowable input power (P limit ) divided by the input voltage (U in ).

4. The DC / DC converter control method according to any one of claims 1-3, characterized in that, The DC / DC converter control method further includes: When the actual input power (P in ) is less than or equal to the maximum allowable input power (P limit ), the DC / DC converter (1) is controlled such that its input current (I in ) is equal to the maximum allowable input current (I limit ).

5. The DC / DC converter control method according to any one of claims 1-4, characterized in that Perform the determination and comparison of the actual input power (P actual ) and the maximum allowable input power (P limit ) at a preset time interval.

6. A DC / DC converter control device, comprising: The acquisition module includes an acquisition unit for acquiring the input current (I in ) and the input voltage (U in ) and the output voltage (U out ) of the DC / DC converter (1); and A control module (2), which is communicatively connected to the DC / DC converter (1) and configured to be capable of executing the DC / DC converter control method according to any one of claims 1-5 based on the input current (I in ), input voltage (U in ), and output voltage (U out ) collected by the acquisition module.

7. A fuel cell system (100), comprising: A DC / DC converter (1); A fuel cell stack (3) and a battery (4) respectively connected to the input end and the output end of the DC / DC converter (1); and The DC / DC converter control device according to claim 6.

8. The fuel cell system (100) according to claim 7, characterized in that The DC / DC converter (1) is a boost or buck-boost DC / DC converter.

9. A vehicle, comprising the DC / DC converter control device according to claim 6 or the fuel cell system (100) according to claim 7 or 8.

10. A computer storage medium storing program instructions that can execute the DC / DC converter control method according to any one of claims 1-5 when running.

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