Multi-fuel cell service life equalization method based on droop control

Abstract

The invention discloses a multi-fuel cell life equalization method based on droop control, and the method comprises the steps: 1, estimating an output characteristic V-I curve of a fuel cell through the output current and voltage signals of the fuel cell, and carrying out the preprocessing of the current and voltage obtained by a sensor; 2, comparing the V-I characteristic curve obtained in the step 1 with an offline calibrated V-I curve of a healthy fuel cell, and determining the attenuation degree of the service life of the fuel cell; and 3, adjusting the output power of each fuel cell through droop control according to the fuel cell service life attenuation degree obtained in the step 2. A single fuel cell can be modularly designed, an additional communication line or a controller of the whole system does not need to be added, and output can be actively adjusted according to the service life attenuation degree of the fuel cell, so that the fuel cell with relatively high service life attenuation degree outputs higher power; and the fuel cell with a lower degree outputs lower power.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen fuel cell control, and in particular to a multi-fuel cell life balancing method based on droop control. Background Art

[0002] Hydrogen fuel cells will inevitably decay in life due to material aging and the effects of different operating conditions, and after a certain point, the fuel cell can no longer be used. At the same time, the output power of a single fuel cell is limited. In some high-power application scenarios, a single fuel cell cannot be used to meet the load power requirements. Therefore, in these scenarios, multiple fuel cells will be used in parallel to increase the overall output power. At the same time, from the perspective of fuel cell manufacturers, modular production of fuel cells allows different numbers of modular fuel cells to be connected in parallel when receiving application requirements of different power levels, thereby meeting application requirements and reducing production and application costs.

[0003] In a system with multiple fuel cells in parallel, due to differences in production processes, different fuel cells will inevitably have different degrees of life decay. If the degree of life decay cannot be controlled, it may cause the fuel cells that have already decayed to a relatively deep degree to decay further. As a result, when some fuel cells are still healthy and usable, some fuel cells have decayed to the point of being unusable, making the entire multi-fuel cell system unusable. Therefore, a reasonable method is needed to ensure that the life of each fuel cell in the multi-fuel cell parallel system is balanced and consistent.

[0004] At present, the control strategy for life balance of multi-fuel cell systems is mainly based on virtual impedance to adjust the output power of each fuel cell, so as to achieve the purpose of life balance. However, this method requires the characteristics of each fuel cell to be input into the same main control for comparison, so as to determine the ratio of the output power of each fuel cell, and determine the design of the virtual impedance accordingly. However, this solution cannot achieve the purpose of modular fuel cell plug-and-play. Therefore, a reasonable way is needed to make the life of each fuel cell in a multi-fuel cell parallel system balanced and consistent. The present invention provides a multi-fuel cell life balance method based on droop control. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides a multi-fuel cell life balancing method based on droop control. This solution mainly adjusts the output of each fuel cell in the multi-fuel cell system based on the droop control technology. The method includes:

[0006] Step 1: Use the output current and voltage signals of the fuel cell to estimate the output characteristic VI curve of the fuel cell, and pre-process the current and voltage obtained by the sensor;

[0007] Step 2: Compare the VI characteristic curve obtained in step 1 with the VI curve of a healthy fuel cell calibrated offline to determine the degree of fuel cell life attenuation;

[0008] Step 3: According to the fuel cell life attenuation degree obtained in step 2, the output power of each fuel cell is adjusted through droop control.

[0009] Furthermore, in the step 1, the pre-processing uses a low-pass filter to remove noise interference in the original signal of the sensor, and the filtered signal uses the least square method or Kalman filter to estimate the VI curve.

[0010] Furthermore, in step 2, the VI curve of a healthy fuel cell is calibrated offline for the fuel cell, and the data or the fitting formula is stored in the controller of the fuel cell.

[0011] Furthermore, the fuel cell life attenuation degree is expressed as:

[0012]

[0013] Where D represents the fuel cell life attenuation degree, V o_deg and V o_new They respectively represent the output voltage of a fuel cell after life attenuation and a healthy fuel cell. The larger the value of the fuel cell life attenuation degree is, the more serious the fuel cell life attenuation is.

[0014] Furthermore, in step 3, the droop control adjusts the power output by the fuel cell by adjusting the size of a virtual resistor, wherein the size of the virtual resistor is expressed as:

[0015] R=R base D

[0016] Where R represents the virtual resistance, R base Is a basic virtual resistance value.

[0017] Furthermore, in actual situations, the virtual resistance is obtained by multiplying the life attenuation degree by the base number. When the fuel cell life attenuation value is larger, its virtual resistance is larger and the output power is smaller, thereby suppressing further life attenuation.

[0018] Furthermore, in step 3, the virtual resistance obtained in this step is used to calculate a voltage reference value, and the DC / DC converter of the fuel cell is controlled by closed loop so that the output voltage is equal to the voltage reference value generated by the droop control.

[0019] Beneficial effects:

[0020] The present invention proposes a multi-fuel cell life balancing method based on droop control for the life balancing strategy of a multi-fuel cell system. Based on this solution, a single fuel cell can be modularly designed without adding additional communication lines or controllers of the overall system, and the output of the regulator can be actively adjusted according to the degree of life attenuation of the fuel cell, so that the fuel cell with a deeper degree of life attenuation outputs higher power, while the fuel cell with a lower degree of life attenuation outputs lower power. Thus, each fuel cell module in the multi-fuel cell system can achieve life balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a block diagram of a multi-fuel cell system of the present invention;

[0022] Figure 2 is a flow chart of the method of the present invention;

[0023] Figure 3 A schematic diagram of random pulse signal extraction of the present invention;

[0024] Figure 4 It is a comparison chart of the real-time acquisition and healthy VI curve of the present invention;

[0025] Figure 5 It is a droop control virtual resistance curve diagram of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other. The present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0027] The present invention provides a multi-fuel cell life balancing method based on droop control for the life balancing of a multi-fuel cell system. At the same time, this solution does not rely on additional communication methods, and can enable each fuel cell to be modularly designed to achieve a plug-and-play effect.

[0028] The multi-fuel cell system used in the solution of the present invention is as follows Figure 1 As shown, multiple fuel cell modules are connected in parallel to output to meet the load requirements. Each fuel cell module contains a fuel cell and a dc / dc converter of the fuel cell, wherein the dc / dc converter is mainly used to adjust the output of the fuel cell. The control proposed in the present invention is mainly based on the life balance of the droop control technology, deployed in the fuel cell controller, receiving the output voltage and current of the fuel cell, and then outputting the voltage reference value output by the dc / dc converter. The voltage reference value is input into the closed-loop control of the dc / dc converter to achieve the regulation of the output voltage of the dc / dc converter.

[0029] The multi-fuel cell life balancing solution based on droop control without communication of the present invention has an overall control block diagram of each fuel cell as shown in FIG. Figure 2 As shown, the following steps are included:

[0030] Step 1: Use the output current and voltage signals of the fuel cell to estimate the output characteristic VI curve of the fuel cell. Here, it may be necessary to pre-process the current and voltage obtained by the sensor, such as using a low-pass filter, to remove noise interference in the original sensor signal. After that, the filtered signal is used to estimate the VI curve using the least squares method or Kalman filter.

[0031] The fuel cell VI characteristic curve output by this step is as follows: Figure 3 As shown, the output voltage of the fuel cell decreases as the output current increases. The change of this characteristic curve represents the change of the life of the fuel cell. Generally, as the fuel cell is used and the life decays, the curve will gradually move down along the y-axis. The following steps will use this curve to represent the life of the fuel cell.

[0032] Step 2: Compare the VI characteristic curve obtained in step 1 with the VI curve of the healthy fuel cell calibrated offline to determine the degree of fuel cell life attenuation. It should be noted that the VI curve of the healthy fuel cell here needs to be calibrated offline for the fuel cell, and the data or fitting formula is stored in the fuel cell controller for easy use during online operation.

[0033] The VI curve after life attenuation is compared with the VI curve of a healthy fuel cell. Figure 4 As the fuel cell's life decays, the VI characteristic curve will gradually move downward, that is, at the same fuel cell output current, its output voltage becomes smaller. Based on the VI curve after life decay and the VI curve of a healthy fuel cell, the rated output current I of the fuel cell is determined. o , we can find the corresponding output voltages are V o_deg and V o_new , so the life attenuation of the fuel cell can be defined as

[0034]

[0035] The larger the fuel cell life attenuation value is, the more serious the fuel cell life attenuation is.

[0036] Step 3: According to the fuel cell life attenuation degree obtained in step 2, the output power of each fuel cell can be adjusted by droop control.

[0037] The present invention adopts a droop control method, which mainly adjusts the power output of the fuel cell by adjusting the size of a virtual resistor. Figure 5 As shown. Among them, the size of the virtual resistance can be calculated using the following formula

[0038] R=R base D

[0039] Among them, R base It is a basic virtual resistance value, and the actual virtual resistance is obtained by multiplying the life attenuation degree by the base number. When the fuel cell life attenuation value is larger, its virtual resistance is larger, which makes its output power smaller, inhibiting its further life attenuation.

[0040] The virtual resistance obtained in this step is used to calculate a voltage reference value, and the DC / DC converter of the fuel cell is controlled by closed loop so that the output voltage is equal to the voltage reference value generated by the droop control.

[0041] The present invention proposes a multi-fuel cell life balancing method based on droop control. The scheme can utilize the characteristic estimation of the fuel cell to achieve the effect of active life balancing. At the same time, the scheme does not require additional communication lines, so that modular fuel cells can be plug-and-play.

[0042] The present invention uses droop control technology to regulate the output power of each fuel cell, and actively adjusts the output power according to the characteristics of the fuel cell, so that the life of each fuel cell module in the multi-fuel cell system can be balanced. Using the solution of the present invention, each fuel cell can be modularly designed and plug-and-play, meeting various application requirements.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "connect", and "fix" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0044] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various equivalent changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-fuel cell life balancing method based on droop control, characterized in that , the method includes: Step 1: Use the output current and voltage signals of the fuel cell to estimate the output characteristic VI curve of the fuel cell and pre-process the current and voltage obtained by the sensor; Step 2: Compare the VI characteristic curve obtained in step 1 with the VI curve of a healthy fuel cell calibrated offline to determine the degree of fuel cell life attenuation; Step 3: According to the fuel cell life attenuation degree obtained in step 2, the output power of each fuel cell is adjusted through droop control.

2. The multi-fuel cell life balancing method based on droop control according to claim 1, characterized in that: In the step 1, a low-pass filter is used for preprocessing to remove noise interference in the original sensor signal, and the filtered signal is used to estimate the VI curve using the least square method or Kalman filter.

3. The multi-fuel cell life balancing method based on droop control according to claim 1, characterized in that: In step 2, the VI curve of a healthy fuel cell is calibrated offline for the fuel cell, and the data or the fitting formula is stored in the controller of the fuel cell.

4. The multi-fuel cell life balancing method based on droop control according to claim 1, characterized in that: The fuel cell life attenuation degree is expressed as: Where D represents the degree of fuel cell life attenuation, V o_deg and V o_new They represent the output voltage of a fuel cell after life attenuation and a healthy fuel cell respectively. The larger the value of the fuel cell life attenuation degree is, the more serious the fuel cell life attenuation is.

5. The multi-fuel cell life balancing method based on droop control according to claim 1, characterized in that: In step 3, the droop control adjusts the power output by the fuel cell by adjusting the size of a virtual resistor, wherein the size of the virtual resistor is expressed as: R=R base D Among them, R represents the virtual resistance, R base Is a basic virtual resistance value.

6. The multi-fuel cell life balancing method based on droop control according to claim 5, characterized in that: In actual situations, the virtual resistance is obtained by multiplying the life attenuation degree by the base number. When the fuel cell life attenuation value is larger, its virtual resistance is larger and the output power is smaller, thereby suppressing further life attenuation.

7. The multi-fuel cell life balancing method based on droop control according to claim 1, characterized in that: In step 3, the virtual resistance obtained in this step is used to calculate a voltage reference value, and the DC / DC converter of the fuel cell is controlled through closed loop so that the output voltage is equal to the voltage reference value generated by droop control.

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