Fuel cell DC-DC conversion device and method

Abstract

The invention provides a DC-DC conversion device and method for a fuel cell, and belongs to the technical field of circuit control, and the device comprises a plurality of channels which are electrically connected with a fuel cell stack and comprise a highest-level channel and a low-level channel, and the channels are DC-DC conversion circuits formed by MOS tubes; the controller is used for determining a target channel based on the target input current and a preset current threshold value corresponding to each channel except the lowest-level channel, controlling the channels in the current working state to stop working, controlling the target channel to enter the working state, and adjusting the real-time input current of the target channel to the target input current; the highest-level channel is a channel meeting the maximum output current of the fuel cell stack, the low-level channel is a channel meeting the condition that the rated current is smaller than the maximum output current, and the preset current threshold value of the next-level channel is equal to the rated current of the previous-level channel. The DC-DC conversion circuit can solve the problem that an existing DC-DC conversion circuit cannot be suitable for the use environment of a fuel cell system.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit control, and in particular to a fuel cell DC-DC conversion device and method. Background Art

[0002] Since the fuel cell stack has a soft output characteristic and large current fluctuation, a DC-DC converter (direct current-to-direct current converter) must be equipped. The fuel cell DC-DC converter is the main current conversion and power control device of the fuel cell system, so its power conversion efficiency directly affects the overall energy conversion efficiency of the fuel cell system. At present, under normal circumstances, when the operating power of the BUCK type and BOOST type DC-DC conversion circuit is less than 10% of the rated power, its conversion efficiency will be significantly reduced.

[0003] There is a method for improving the efficiency of the DC-DC conversion circuit in the prior art solution: by detecting the current size of the inductor coil in the DC-DC conversion circuit, the working number of multiple MOSFET field effect transistors in the circuit is controlled, so that the current of each MOSFET field effect transistor is within a reasonable range, thereby ensuring that the efficiency of the DC-DC conversion circuit is always at a high level. However, DC-DC is the main source of interference in the fuel cell system. If the overall operating frequency of a single or multiple MOSFET field effect transistors is a fixed value, the impact of DC-DC on the fuel cell system can be reduced through electromagnetic compatibility design. However, in this solution, the overall operating frequency of multiple MOSFET field effect transistors changes continuously with the current, and their conduction and emission characteristics also change continuously, seriously affecting the operating stability of the entire fuel cell system. Therefore, this method of improving the efficiency of the DC-DC conversion circuit is not suitable for the fuel cell system.

[0004] The existing technical solution also has a DC-DC converter system architecture with high light-load efficiency: by using the DC-DC conversion module and the LDO conversion module in parallel, the load voltage and current information is detected in real time when the system is running, and the DC-DC conversion module and the LDO conversion module are switched according to the changes in the load conditions, ensuring the high conversion efficiency of the converter system at light load and full load, and improving the overall efficiency of the system. However, the LDO conversion module, as a low-power step-down regulator, is completely unsuitable for the high-power and current-controlled use environment in the fuel cell system.

[0005] In summary, the DC-DC conversion circuit provided by the existing technical solution is not suitable for the use environment of the fuel cell system. Summary of the invention

[0006] In view of this, it is necessary to provide a fuel cell DC-DC conversion device and method to solve the technical problem that the existing DC-DC conversion circuit is not suitable for the use environment of the fuel cell system.

[0007] In order to solve the above problems, on the one hand, the present invention provides a fuel cell DC-DC conversion device, comprising: A plurality of channels, the plurality of channels are connected in parallel and are all electrically connected to the fuel cell stack, the plurality of channels include a highest-level channel and at least one low-level channel, and each channel is a DC-DC conversion circuit composed of a MOS tube; A controller, for determining a target channel to be switched based on a target input current and a preset current threshold corresponding to each channel other than the lowest level channel, and controlling the channel in the current working state to stop working, controlling the target channel to enter the working state, and adjusting the real-time input current of the target channel to the target input current; Among them, the highest level channel is the channel that meets the maximum output current of the fuel cell stack, the low level channel is the channel that meets the rated current less than the maximum output current, and the preset current threshold corresponding to the next level channel is equal to the rated current of the previous level channel.

[0008] In a possible implementation, a current sensor is provided at the current input end of each channel, and the current sensor is used to collect real-time input current data of the channel where it is located, and send the real-time input current data to the controller. The range of the current sensor is equal to the maximum allowable current of the channel where it is located.

[0009] In a possible implementation manner, the multiple channels are all of BUCK type or BOOST type.

[0010] In a possible implementation, the number and operating frequency of MOS tubes on each channel are the same, but the rated currents are different.

[0011] In a possible implementation, the controller is further configured to synchronously load or unload the channel in the current working state and the target channel when controlling the channel in the current working state to stop working and controlling the target channel to enter the working state.

[0012] In a possible implementation, the current of the channel in the current working state and the target channel when loading or unloading is performed synchronously is the same.

[0013] In one possible implementation, the current regulation speed rate when the channel in the current working state and the target channel are synchronously loaded or unloaded is determined based on the rated current of the lower-level channel in the channel in the current working state and the target channel and a preset current regulation coefficient.

[0014] In one possible implementation, the current regulation speed rate when the channel in the current working state and the target channel are loaded or unloaded synchronously is equal to the ratio of the rated current of the lower-level channel in the channel in the current working state and the target channel to the preset current regulation coefficient; the preset current regulation coefficient ranges from 0.001 to 10.

[0015] In a possible implementation, the controller is further configured to send a fault alarm when the target input current is greater than the rated current of the highest level channel.

[0016] On the other hand, the present invention further provides a fuel cell DC-DC conversion method, which is applied to any of the above-mentioned devices, and comprises: The controller determines the target channel to be switched based on the target input current and the preset current threshold corresponding to each channel other than the lowest level channel; The controller controls the channel in the current working state to stop working, controls the target channel to enter the working state, and adjusts the real-time input current of the target channel to the target input current.

[0017] The beneficial effect of adopting the above-mentioned implementation method is: the fuel cell DC-DC conversion device and method provided by the present invention, the device includes: multiple channels, the multiple channels are connected in parallel and are electrically connected to the fuel cell stack, the multiple channels include a highest-level channel and at least one low-level channel, each channel is a DC-DC conversion circuit composed of a MOS tube; a controller is used to determine the target channel to be switched based on the target input current and the preset current threshold corresponding to each channel other than the lowest-level channel, and control the channel in the current working state to stop working, control the target channel to enter the working state, and adjust the real-time input current of the target channel to the target input current; wherein the highest-level channel is a channel that meets the maximum output current of the fuel cell stack, the low-level channel is a channel that meets the rated current less than the maximum output current, and the preset current threshold corresponding to the next-level channel is equal to the rated current of the previous-level channel.

[0018] Among them, each level channel corresponds to a different power segment of the fuel cell. According to the power segment corresponding to the fuel cell, the corresponding channel is selected to switch to the working state, so as to ensure that the energy conversion efficiency of the DC-DC conversion device is always in a high state. According to the changes in load conditions, the DC-DC conversion module and the LDO conversion module are switched to ensure the high conversion efficiency of the converter system at light load and full load, improve the overall efficiency of the system, and do not require the LDO conversion module, so it is more suitable for high-power and current control usage environments in fuel cell systems.

[0019] In addition, according to the corresponding power segment of the fuel cell, the corresponding channel is selected to switch to the working state, and the overall operating frequency of the MOSFET field effect transistor (ie, MOS tube) of each channel does not need to change continuously with the current, thereby not seriously affecting the operating stability of the entire fuel cell system.

[0020] Moreover, with the multi-channel redundant design, when one channel fails, the other channels can at least maintain low power operation and maintain the basic functions of the entire fuel cell.

[0021] In summary, the present invention can solve the technical problem that the existing DC-DC conversion circuit is not suitable for the use environment of the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic structural diagram of an embodiment of a fuel cell DC-DC conversion device provided by the present invention; Figure 2 A comparison diagram of the efficiencies of different fuel cell DC-DC converters provided by the present invention; Figure 3 A flow chart of an embodiment of a fuel cell DC-DC conversion method provided by the present invention; Figure 4 The present invention provides a flow chart of another embodiment of the fuel cell DC-DC conversion method. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0026] The terms "including" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment comprising a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules not clearly listed or inherent to these processes, methods, products or equipment.

[0027] The naming or numbering of the steps in the embodiments of the present invention does not mean that the steps in the method flow must be executed in the time / logical sequence indicated by the naming or numbering. The execution order of the named or numbered process steps can be changed according to the technical purpose to be achieved, as long as the same or similar technical effects can be achieved.

[0028] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] The present invention provides a fuel cell DC-DC conversion device and method, which are described below respectively.

[0030] like Figure 1 As shown, the present invention provides a fuel cell DC-DC conversion device, comprising: A plurality of channels 101, wherein the plurality of channels 101 are connected in parallel and are electrically connected to a fuel cell stack 103, wherein the plurality of channels 101 include a highest-level channel and at least one low-level channel, and each channel 101 is a DC-DC conversion circuit composed of a MOS tube; The controller 102 is used to determine the target channel to be switched based on the target input current and the preset current threshold corresponding to each channel other than the lowest level channel, and control the channel in the current working state to stop working, control the target channel to enter the working state, and adjust the real-time input current of the target channel to the target input current; Among them, the highest level channel is the channel that meets the maximum output current of the fuel cell stack 103, the low level channel is the channel that meets the rated current less than the maximum output current, and the preset current threshold corresponding to the next level channel is equal to the rated current of the previous level channel.

[0031] Understandably, Figure 1A structural diagram of a fuel cell DC-DC conversion device for improving light-load efficiency provided by an embodiment of the present invention. The device consists of a two-stage channel, a controller 102, and a current sensor for detecting input current. The two-stage channel is connected in parallel to the input and output ends of the DC-DC conversion device. A current sensor is provided at the input end of the DC-DC conversion device to detect input current parameters. Both channels are BUCK type or BOOST type at the same time; the type, operating frequency and number of MOSFET field effect transistors inside the two channels are exactly the same but the rated current is different; the rated current of the light-load channel is 30% or less of the rated current of the full-load channel.

[0032] In this embodiment, the hardware structure of the controller 102 includes a main control chip, a CAN network, a sampling circuit, and a power supply circuit, etc. The power supply circuit is mainly used to supply power to the controller 102, the sampling circuit is mainly used to collect current signals of each channel, and the CAN network is mainly used for network communication between the main control chip and other terminals. The main control chip stores a software program for control, and the main control chip can control the MOS on each channel to be turned on or off, thereby realizing the control of the working state of each channel.

[0033] Each level channel corresponds to a different power segment of the fuel cell. According to the power segment corresponding to the fuel cell, the corresponding channel is selected to switch to the working state, thereby ensuring that the energy conversion efficiency of the DC-DC conversion device is always in a high state. According to the changes in load conditions, the DC-DC conversion module and the LDO conversion module are switched to ensure the high conversion efficiency of the converter system at light load and full load, improve the overall efficiency of the system, and do not require an LDO conversion module, so it is more suitable for high-power and current control usage environments in fuel cell systems.

[0034] In addition, according to the corresponding power segment of the fuel cell, the corresponding channel is selected to switch to the working state, and the overall operating frequency of the MOSFET field effect transistor (ie, MOS tube) of each channel does not need to change continuously with the current, thereby not seriously affecting the operating stability of the entire fuel cell system.

[0035] Moreover, with the multi-channel redundant design, when one channel fails, the other channels can at least maintain low power operation and maintain the basic functions of the entire fuel cell.

[0036] Therefore, the present invention can solve the technical problem that the existing DC-DC conversion circuit is not suitable for the use environment of the fuel cell system.

[0037] In some embodiments, a current sensor is provided at the current input end of each channel, and the current sensor is used to collect real-time input current data of the channel where it is located, and send the real-time input current data to the controller 102. The range of the current sensor is equal to the maximum allowable current of the channel where it is located.

[0038] In some embodiments, the multiple channels are all of BUCK type or BOOST type.

[0039] It can be understood that the BUCK circuit is a DC-DC converter based on the principle of inductive energy storage, mainly used for voltage reduction. Its working principle involves the basic principles of electromagnetic induction and power conversion. By controlling the on and off states of the switch tube by switching the input PWM wave with a variable duty cycle, the BUCK circuit converts the DC voltage provided by the input power supply into an adjustable low-voltage output, thereby meeting the power supply requirements of different circuits.

[0040] The BOOST circuit is a DC-DC converter, which is mainly used to increase the input voltage to the required output voltage. Its basic working principle is to achieve the voltage boost effect through inductor energy storage and diode freewheeling. When the switch is turned on, the input voltage charges the inductor; when the switch is turned off, the inductor discharges to the load through the diode, so that the output voltage is higher than the input voltage.

[0041] In some embodiments, the number and operating frequency of MOS tubes in each channel are the same, but the rated currents are different.

[0042] In some embodiments, the controller 102 is further configured to synchronously load or unload the channel in the current working state and the target channel when controlling the channel in the current working state to stop working and controlling the target channel to enter the working state.

[0043] In some embodiments, the current of the channel in the current working state and the target channel when loading or unloading is performed synchronously is the same.

[0044] In some embodiments, the current regulation speed rate when the channel in the current working state and the target channel are simultaneously loaded or unloaded is determined based on the rated current of the lower-level channel in the channel in the current working state and the target channel and a preset current regulation coefficient.

[0045] In some embodiments, the current regulation speed rate when the channel in the current working state and the target channel are loaded or unloaded synchronously is equal to the ratio of the rated current of the lower-level channel in the channel in the current working state and the target channel to the preset current regulation coefficient; the preset current regulation coefficient ranges from 0.001 to 10.

[0046] It is understandable that the value of the preset current regulation coefficient may be 0.001, 10, 1, 5, etc.

[0047] In some embodiments, the controller 102 is further configured to send a fault alarm when the target input current is greater than the rated current of the highest level channel.

[0048] In some embodiments, an embodiment of the present invention provides a fuel cell DC-DC conversion device with high light-load efficiency: comprising a maximum level channel (i.e., the highest level channel) that meets the maximum output current of the fuel cell stack 103, one or more low-level light-load channels (i.e., low-level channels) with smaller rated currents, and a controller; multiple level channels of the DC-DC conversion device are connected in parallel, and each level of the DC-DC conversion device is a BUCK type or a BOOST type at the same time, the MOSFET field effect transistors (i.e., MOS tubes) inside the multiple channels are of exactly the same type, operating frequency, and quantity but different rated currents, and the rated current levels of each level of the channels are arranged in equal proportions; the rated current ratio between two adjacent levels of channels is between 3:1 and 10:1.

[0049] The controller of the DC-DC converter can control the input current of each channel and the working states of "run" and "stop" respectively; a current sensor is set at the input end of each channel of the DC-DC converter to detect the input current parameters; the range of the current sensor is consistent with the maximum current of the channel. Except for the minimum channel (the lowest level channel), each level of the channel is set with a current threshold, and each level of the current threshold is equal to the rated current of the previous level; the corresponding channel is switched by comparing the target input current of the DC-DC converter with the current threshold. The control of the channels in the DC-DC converter and the switching between the channels of each level adopt flexible control and flexible switching. When the DC-DC converter switches the channels, the two-level channels are not directly cut off and cut in, but the controller loads and unloads the two-level channels synchronously. The currents of the two-level channels are the same, until the current of the unloaded channel reaches the minimum value and enters the "stop" working state. The loading or unloading current adjustment rate k=I m / G, where k is the current regulation rate, I m is the rated current of the smaller channel of the two channels, G is the current adjustment coefficient, and the range of G is 10~0.001.

[0050] The present invention has the following beneficial effects: The DC-DC converter provided by the embodiment of the present invention can effectively improve the energy conversion efficiency of the fuel cell system under light load. Figure 2As shown, when the fuel cell system is in a certain power range, the DC-DC converter controller switches the corresponding channel to the working state, and the energy conversion efficiency of the DC-DC converter is always in a high state. In addition, the multiple channels inside the DC-DC converter are redundant to a certain extent. When one of the channels fails, the other channels can at least maintain low power operation to maintain the basic functions of the entire fuel cell system. In addition, the rated current of the light-load channel is small, and a smaller range current sensor will be configured to improve the current sampling accuracy and current control accuracy under light load. And because the operating frequency of each level of channels is consistent, when the channels at each level switch the working state, the overall operating frequency of the internal MOSFET field effect transistor remains within two frequency points, and there will be no additional impact on the entire fuel cell system.

[0051] The present invention also provides a fuel cell DC-DC conversion method, which is applied to any of the above-mentioned devices, such as Figure 3 As shown, the method includes: S301, the controller determines a target channel to be switched based on a target input current and a preset current threshold corresponding to each channel other than the lowest level channel; S302, the controller controls the channel in the current working state to stop working, controls the target channel to enter the working state, and adjusts the real-time input current of the target channel to the target input current.

[0052] In some embodiments, Figure 4 A flow chart of a control method for a fuel cell DC-DC converter device for improving light-load efficiency provided by an embodiment of the present invention. The DC-DC converter device controller can control the "run" and "stop" working states of the two channels respectively; a current threshold is pre-set in the controller, and the current threshold is equal to the rated current of the light-load channel; and the target input current of the DC-DC converter device is compared with the current threshold. When the target input current is greater than the current threshold, the controller sends a "run" command to the full-load channel (i.e., the target channel) and sends a "stop" command to the light-load channel (i.e., the channel in the current running state); when the target input current is less than the current threshold, the controller sends a "stop" command to the full-load channel and sends a "run" command to the light-load channel.

[0053] like Figure 4 As shown, when one of the channels fails, the controller immediately sends a "stop" command to this channel and a "run" command to another channel, so that the DC-DC converter can at least maintain low power operation.

[0054] The fuel cell DC-DC conversion device and method provided by the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A fuel cell DC-DC converter, characterized in that: include: A plurality of channels, the plurality of channels are connected in parallel and are all electrically connected to the fuel cell stack, the plurality of channels include a highest-level channel and at least one low-level channel, and each channel is a DC-DC conversion circuit composed of a MOS tube; A controller, for determining a target channel to be switched based on a target input current and a preset current threshold corresponding to each channel other than the lowest level channel, and controlling the channel in the current working state to stop working, controlling the target channel to enter the working state, and adjusting the real-time input current of the target channel to the target input current; Among them, the highest level channel is the channel that meets the maximum output current of the fuel cell stack, the low level channel is the channel that meets the rated current less than the maximum output current, and the preset current threshold corresponding to the next level channel is equal to the rated current of the previous level channel.

2. The fuel cell DC-DC converter according to claim 1, characterized in that: The current input end of each channel is provided with a current sensor, which is used to collect real-time input current data of the channel where it is located and send the real-time input current data to the controller. The range of the current sensor is equal to the maximum allowable current of the channel where it is located.

3. The fuel cell DC-DC converter according to claim 1, characterized in that: The multiple channels are all of BUCK type or BOOST type.

4. The fuel cell DC-DC converter according to claim 1, characterized in that: The number and operating frequency of MOS tubes on each channel are the same, but the rated currents are different.

5. The fuel cell DC-DC converter according to claim 1, characterized in that: The controller is also used to synchronously load or unload the channel in the current working state and the target channel when controlling the channel in the current working state to stop working and controlling the target channel to enter the working state.

6. The fuel cell DC-DC converter according to claim 5, characterized in that: The current of the channel in the current working state and the target channel when loading or unloading is performed synchronously is the same.

7. The fuel cell DC-DC converter according to claim 5, characterized in that: The current regulation speed rate when the channel in the current working state and the target channel are synchronously loaded or unloaded is determined based on the rated current of the lower-level channel in the channel in the current working state and the target channel and a preset current regulation coefficient.

8. The fuel cell DC-DC converter according to claim 7, characterized in that: The current regulation speed rate when the channel in the current working state and the target channel are synchronously loaded or unloaded is equal to the ratio of the rated current of the lower-level channel in the current working state and the target channel to the preset current regulation coefficient; The preset current regulation coefficient ranges from 0.001 to 10.

9. The fuel cell DC-DC converter according to any one of claims 1 to 8, characterized in that: The controller is also used to send a fault alarm when the target input current is greater than the rated current of the highest level channel.

10. A fuel cell DC-DC conversion method, characterized in that: The method is applied to the device according to any one of claims 1 to 9, and the method comprises: The controller determines the target channel to be switched based on the target input current and the preset current threshold corresponding to each channel other than the lowest level channel; The controller controls the channel in the current working state to stop working, controls the target channel to enter the working state, and adjusts the real-time input current of the target channel to the target input current.

Images