A method and circuit for extracting the AC component of fuel cell voltage

Abstract

The present invention provides a method and a circuit for extracting the AC component of a fuel cell voltage, including: after obtaining the output voltage of the fuel cell, obtaining the voltage value across a voltage-dividing resistor connected in parallel with the fuel cell to be measured, controlling a differential amplifier circuit to perform differential and amplification processing on the voltage value across the voltage-dividing resistor, where the non-inverting input terminal of the differential amplifier circuit is the voltage value across the voltage-dividing resistor, and the inverting input terminal of the differential amplifier circuit is a DC approximation signal matching the output signal of the differential amplifier circuit, determining whether the output signal of the differential amplifier circuit is within a preset voltage range, and if so, performing FFT spectrum analysis on the output signal of the differential amplifier circuit, and the AC component of the fuel cell voltage can be extracted through the FFT spectrum analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to a method, device, and equipment for extracting the AC component of the fuel cell voltage. Background Art

[0002] In fuel cell technology, the magnitude of the impedance parameter affects the power generation efficiency of the fuel cell. Its magnitude depends on the current density, internal humidity, and membrane temperature, etc., and reflects the internal electrochemical reaction state of the fuel cell. Therefore, real-time measurement of the impedance parameter is crucial for the analysis of the health state of the fuel cell.

[0003] When testing the internal resistance of a fuel cell based on electrochemical impedance spectroscopy, it is necessary to first extract the AC components of the current and voltage at the output end of the fuel cell, and then calculate through the amplitude and phase to achieve the solution of the fuel cell impedance. In the existing technologies for extracting the AC components of the voltage signal, the extraction method of the AC components of the fuel cell voltage signal is achieved by blocking the DC component through a capacitor and then conditioning and sampling the obtained AC signal components.

[0004] The applicant has found through research that due to the existence of the blocking capacitor, the RC high-pass filter circuit composed of the blocking capacitor and the output resistance will cause different degrees of delay to the phase of the AC signal; at the same time, after the output voltage of the fuel cell passes through the blocking capacitor, it takes a certain time for the measurement and control unit to stably extract the AC signal, thereby weakening the accuracy and real-time performance of the internal resistance calculation. Therefore, adopting a suitable method for extracting the AC component of the fuel cell voltage has important application value for improving the accuracy and real-time performance of impedance testing. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a method and circuit for extracting the AC component of the fuel cell voltage to achieve the extraction of the AC component of the fuel cell voltage.

[0006] To achieve the above object, the embodiments of the present invention provide the following technical solutions:

[0007] A method for extracting the AC component of the fuel cell voltage includes:

[0008] Obtaining the voltage value across the voltage-dividing resistor, where the voltage-dividing resistor is connected in parallel with the fuel cell to be measured;

[0009] Controlling a differential amplifier circuit to perform differential and amplification processing on the voltage value across the voltage-dividing resistor, where the non-inverting input terminal of the differential amplifier circuit is the voltage value across the voltage-dividing resistor, and the inverting input terminal of the differential amplifier circuit is a DC approximation signal matching the output signal of the differential amplifier circuit;

[0010] Determine whether the output signal of the differential amplifier circuit is within a preset voltage range. If so, perform FFT spectrum analysis on the output signal of the differential amplifier circuit.

[0011] Optionally, in the above fuel cell voltage AC component extraction method, it further includes:

[0012] Determine whether the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range or less than the lowest amplitude in the preset voltage range;

[0013] When it is greater than the highest amplitude or less than the lowest amplitude, obtain an approximation coefficient corresponding to the comparison result;

[0014] Calculate a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

[0015] Optionally, in the above fuel cell voltage AC component extraction method, the calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient includes:

[0016] Based on the formula Calculate the DC approximation signal P matching the output signal of the differential amplifier circuit sum , where the a 1 , a 2 ... a n are the approximation coefficients used when calculating the DC approximation signal for the nth time, n is the number of times of calculating the DC approximation signal, and each time the DC approximation signal is calculated, the value of n is incremented by 1.

[0017] Optionally, in the above fuel cell voltage AC component extraction method, when it is greater than the highest amplitude or less than the lowest amplitude, obtaining an approximation coefficient corresponding to the comparison result includes:

[0018] When the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range, the value of the approximation coefficient is 1;

[0019] When the output signal of the differential amplifier circuit is less than the lowest amplitude in the preset voltage range, the value of the approximation coefficient is -1.

[0020] Optionally, in the above fuel cell voltage AC component extraction method, the calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient includes:

[0021] Determine whether the value of n reaches a preset upper limit approximation number. If so, output a prompt message indicating that the AC signal setting is too large. If it does not reach the preset upper limit approximation number, calculate a DC approximation signal that matches the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

[0022] Optionally, in the above fuel cell voltage AC component extraction method, determining whether the output signal of the differential amplifier circuit is within a preset voltage range includes:

[0023] Determine whether the output signal of the differential amplifier circuit is within the range of 0V to 5V.

[0024] A fuel cell voltage AC component extraction circuit includes:

[0025] A voltage dividing circuit, connected in parallel with the fuel cell;

[0026] A differential amplifier circuit, which performs a differential amplification operation on the voltage dividing resistors in the voltage dividing circuit. The inverting input terminal of the differential amplifier circuit is a DC approximation signal that matches the output signal of the differential amplifier circuit;

[0027] A microprocessor, which is used to generate a DC approximation signal based on the output signal of the differential amplifier circuit, determine whether the output signal of the differential amplifier circuit is within a preset voltage range, and if so, perform FFT spectrum analysis on the output signal of the differential amplifier circuit.

[0028] Optionally, in the above fuel cell voltage AC component extraction circuit, it further includes:

[0029] An AD sampling circuit disposed between the microprocessor and the output terminal of the differential amplifier circuit;

[0030] A DA conversion circuit disposed between the microprocessor and the inverting input terminal of the differential amplifier circuit.

[0031] Optionally, in the above fuel cell voltage AC component extraction circuit, the microprocessor is further used for:

[0032] Determine whether the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range or less than the lowest amplitude in the preset voltage range;

[0033] When it is greater than the highest amplitude or less than the lowest amplitude, obtain an approximation coefficient corresponding to the comparison result;

[0034] Calculate a DC approximation signal that matches the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

[0035] Optionally, the fuel cell voltage AC component extraction circuit further includes:

[0036] An electrical isolation circuit disposed between the differential amplification circuit and the voltage division circuit.

[0037] Based on the above technical solution, in the above solution provided by the embodiments of the present invention, after obtaining the output voltage of the fuel cell, the voltage value across the voltage dividing resistor connected in parallel with the fuel cell under test is obtained, and the differential amplification circuit is controlled to perform differential and amplification processing on the voltage value across the voltage dividing resistor. The non-inverting input terminal of the differential amplification circuit is the voltage value across the voltage dividing resistor, and the inverting input terminal of the differential amplification circuit is a DC approximation signal matching the output signal of the differential amplification circuit. It is determined whether the output signal of the differential amplification circuit is within a preset voltage range. If so, FFT spectrum analysis is performed on the output signal of the differential amplification circuit, and the fuel cell voltage AC component can be extracted through the FFT spectrum analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0039] Figure 1 It is a schematic flowchart of the fuel cell voltage AC component extraction method disclosed in the embodiments of the present application;

[0040] Figure 2 It is a schematic structural diagram of the fuel cell voltage AC component extraction circuit disclosed in another embodiment of the present application;

[0041] Figure 3 It is a schematic diagram of the adjustment process of the DC approximation signal disclosed in another embodiment of the present application;

[0042] Figure 4 It is a curve showing the change of the fuel cell voltage Us with time T disclosed in the embodiments of the present application;

[0043] Figure 5 It is a curve showing the change of the fuel cell voltage signal u with time T disclosed in the embodiments of the present application;

[0044] Figure 6 It is the 0-5V AD sampling signal S disclosed in the embodiments of the present application voltage Changing curve with time T. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] In the existing technical solution that uses a blocking capacitor to remove the DC component and extract the AC signal, there are certain time delays and phase delays, which reduce the real-time performance and calculation accuracy of impedance calculation. Moreover, the blocking capacitor generally uses a power electrolytic capacitor with a large withstand voltage value and capacitance value, and has a large volume, which increases the difficulty of hardware layout of the AC signal extraction unit. In order to improve the efficiency of AC signal extraction, eliminate the influence of the existing technical solution on the phase delay of the AC signal, simplify the hardware structure, and increase the reliability of the AC signal extraction circuit, this patent proposes a method for extracting the AC component of the fuel cell voltage based on the successive approximation algorithm.

[0047] The innovation of the present invention lies in proposing a method for extracting the AC component of the fuel cell voltage based on the successive approximation algorithm. By means of successive approximation and continuously removing the DC component, the purpose of extracting the AC component is achieved. Compared with the existing technical solution that uses a blocking capacitor to remove the DC component and extract the AC component, the efficiency of AC signal extraction is improved, the problem of phase delay of the AC signal is avoided, the hardware structure is simplified, and the reliability and stability of the AC component extraction circuit are increased.

[0048] Specifically, referring to Figure 1 , this application discloses a method for extracting the AC component of the fuel cell voltage, and the method may include: steps S101 - S105.

[0049] Step S101: Obtain the voltage value across the voltage-dividing resistor, and the voltage-dividing resistor is connected in parallel with the fuel cell under test.

[0050] In this solution, the output voltage of the fuel cell refers to the voltage across the fuel cell. In this solution, the output voltage of the fuel cell is obtained by measuring the voltage of the voltage-dividing resistor in the voltage-dividing circuit. Referring to Figure 2 , the fuel cell is connected in parallel with a voltage-dividing circuit and an AC perturbation regulation circuit. Assume that the voltage-dividing circuit consists of voltage-dividing resistor R 1 and voltage-dividing resistor R 2 ; the resistance values of the voltage-dividing resistor R 1 and voltage-dividing resistor R 2 are designed to be much larger than the equivalent load resistance R load of the AC perturbation regulation circuit., at this time, since the voltage dividing circuit and the AC disturbance regulation circuit are in parallel, the current flowing through the voltage dividing circuit is very small. Therefore, it can be considered that the regulation current of the AC disturbance regulation circuit is the DC bus current of the fuel cell, and the regulation current i 0 = i dc + i ac . Among them, i dc and i ac are respectively the DC component and the AC component of the DC bus current of the fuel cell. Based on this, the output voltage U s of the fuel cell can be obtained as:

[0051] U s = E - Zi 0

[0052] = E - Zi dc - Zi ac

[0053] = U dc - u ac (Formula 1)

[0054] In Formula 1, Z represents the fuel cell impedance; E represents the fuel cell open-circuit voltage; U dc represents the DC component of the fuel cell voltage; u ac is the AC component of the fuel cell voltage.

[0055] The voltage across the voltage dividing resistor R 2 is expressed as:

[0056]

[0057] In Formula 2, the R 1 represents the resistance value of the voltage dividing resistor R 1 , and R 2 represents the resistance value of the voltage dividing resistor R 2 .

[0058] In this step, the voltage dividing resistor refers to a voltage dividing resistor in the voltage dividing circuit connected in parallel with the fuel cell to be measured. For example, in the example shown in Figure 2 , the voltage dividing resistor refers to the resistor R Figure 2 in 2 . Of course, it can also refer to the resistor R Figure 2 in 1 . Which one to choose as the voltage dividing resistor in this step can be selected according to the design requirements.

[0059] When using the resistor R 2 as the voltage dividing resistor in this step, the voltage dividing resistors R 1 and R 2 can be adjustedThe resistance value is such that the voltage value u across the voltage-dividing resistor is within the range of 0 to 5V.

[0060] Step S102: Control the differential amplifier circuit to perform differential and amplification processing on the voltage value across the voltage-dividing resistor.

[0061] The non-inverting input terminal of the differential amplifier circuit is the voltage value across the voltage-dividing resistor, and the inverting input terminal of the differential amplifier circuit is a DC approximation signal that matches the output signal of the differential amplifier circuit.

[0062] In this step, the voltage value across the voltage-dividing resistor is applied to the non-inverting input terminal of the differential amplifier circuit, and a DC approximation signal is applied to the inverting input terminal of the differential amplifier circuit. The DC approximation signal is calculated based on the output signal of the differential amplifier circuit.

[0063] After the differential amplifier circuit obtains the voltage value across the voltage-dividing resistor and the DC approximation signal, it performs differential amplification processing on the voltage value across the voltage-dividing resistor based on the built-in logic, and outputs the processing result through the output terminal of the differential amplifier circuit. Among them, the built-in logic can be: S voltage =(u - P sum )·G, where P sum is the DC approximation signal, G is the gain coefficient of the differential amplifier circuit, and S voltage is the output result of the differential amplifier circuit.

[0064] In the technical solution disclosed in the embodiments of the present application, G=(R 1 +R 2 ) / R 2 , transform the formula S voltage =(u - P sum )·G:

[0065]

[0066] Among them, in Formula Three, u dc ’ is the DC component of S voltage , and u ac is the AC component of S voltage , that is, the AC component of the fuel cell output voltage.

[0067] In this solution, the inverting input terminal of the differential amplifier is connected to the DC approximation signal P sum , and the voltage value u is input to the non-inverting input terminal. In this way, after the two input voltage signals of the differential amplifier circuit are differentially amplified, the output result S voltage is obtained.

[0068] Step S103: Determine whether the output signal of the differential amplifier circuit is within a preset voltage range. If it is, execute Step S104; otherwise, execute Step S105.

[0069] In this step, it is determined whether the output signal of the differential amplifier circuit is within a preset voltage range, which may refer to 0V - 5V. When it is within the preset voltage range, it indicates that the adjustment is completed. Otherwise, continue to execute Step S105 to continue adjusting the output signal of the differential amplifier circuit.

[0070] Generally, after several approximations of the output signal of the differential amplifier circuit, the fuel cell voltage sampling signal can be stabilized within the range of 0V to 5V.

[0071] Step S104: Perform FFT spectrum analysis on the output signal of the differential amplifier circuit.

[0072] In this step, when determining whether the output signal of the differential amplifier circuit is within the preset voltage range, by performing AD sampling on the output signal of the differential amplifier circuit and performing FFT spectrum analysis on the sampling result, the amplitude and phase parameters of the AC component of the fuel cell voltage can be obtained, thereby realizing the extraction of the AC component of the fuel cell output voltage.

[0073] Step S105: Adjust the value of the DC approximation signal and re - execute Step S102;

[0074] When adjusting the DC approximation signal, refer to Figure 3 the method shown for adjustment. Specifically, it includes:

[0075] Step S301: Determine whether the output signal of the differential amplifier circuit is greater than the highest amplitude value in the preset voltage range. If it is, execute Step S302; otherwise, execute Step S303.

[0076] Step S302: Obtain the first approximation coefficient.

[0077] In the technical solution disclosed in this embodiment, the voltage value across the voltage - dividing resistor can be sampled by the AD sampling circuit. When the output signal of the differential amplifier circuit is greater than the highest amplitude value in the preset voltage range (the preset voltage range is the sampling range of the AD sampling circuit), it indicates that the AD sampling value is in the clipping saturation state, and the value of the approximation coefficient is 1.

[0078] Step S303: Determine whether the output signal of the differential amplifier circuit is less than the lowest amplitude value in the preset voltage range. If it is, execute Step S304; if not, execute Step S105.

[0079] Step S304: Obtain the second approximation coefficient.

[0080] For example, in this step, when the output signal of the differential amplifier circuit is less than the highest amplitude in the preset voltage range, it indicates that the AD sampling value is in the bottom-clipping saturation state, and the value of the approximation coefficient is -1.

[0081] Step S305: Calculate a DC approximation signal that matches the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

[0082] In a specific embodiment of the present application, the value of the DC approximation signal is related not only to the approximation coefficient but also to the number of approximation times. Specifically, in this solution, calculating the DC approximation signal that matches the output signal of the differential amplifier circuit based on the preset approximation formula and the approximation coefficient includes:

[0083] Based on the formula calculate the DC approximation signal P that matches the output signal of the differential amplifier circuit sum , where the a 1 , a 2 ... a n are the approximation coefficients when calculating the DC approximation signal for the nth time, that is, the approximation coefficient corresponding to the DC approximation signal calculated for the first time is a 1 , the approximation coefficient corresponding to the DC approximation signal calculated for the second time is a 2 , and the approximation coefficient corresponding to the DC approximation signal calculated for the nth time is a n . The value of each DC approximation signal is, on the basis of the previous approximation coefficient, plus The n is the number of times of calculating the DC approximation signal, that is, the number of approximation times. Each time the DC approximation signal is calculated, the value of n is incremented by 1.

[0084] In the technical solution disclosed in another embodiment of the present application, generally speaking, after several approximations, the fuel cell voltage sampling signal can be stabilized within the preset voltage range. When the number of approximation times n reaches the preset upper limit of the number of approximation times, if the fuel cell voltage sampling signal still has a saturation distortion state, it indicates that the AC component of the fuel cell voltage is too large. At this time, the magnitude of the AC excitation current should be reduced, or the amplification factor of the differential amplifier circuit should be increased, so as to stabilize the fuel cell voltage sampling signal within the preset voltage range. Therefore, in this solution, calculating the DC approximation signal that matches the output signal of the differential amplifier circuit based on the preset approximation formula and the approximation coefficient may specifically include:

[0085] Determine whether the value of n reaches the preset upper limit approximation times. If so, output a prompt message indicating that the AC signal setting is too large. If it does not reach the preset upper limit approximation times, calculate a DC approximation signal that matches the output signal of the differential amplifier circuit based on the preset approximation formula and the approximation coefficient.

[0086] As can be seen from the above solution, the present invention proposes a method for extracting the AC component of the fuel cell voltage based on the successive approximation algorithm. By successive approximation and continuously removing the DC signal, the purpose of extracting the AC signal is achieved. The specific effects that can be achieved by this technical solution are as follows:

[0087] In terms of technical effects, compared with the existing technical solution that uses a DC blocking capacitor to remove the DC component and extract the AC signal, the efficiency of AC signal extraction is improved, the problem of AC signal phase delay is avoided, the hardware structure is simplified, and the reliability and stability of the AC signal extraction circuit are increased, showing significant technical effects.

[0088] In terms of social effects, hydrogen fuel cell vehicles have become an important development direction for future new energy vehicles. The technical solution proposed by the present invention applied to fuel cell vehicles can improve the stability and reliability of the fuel cell impedance measurement and control system, improve the impedance test accuracy, contribute to the development of fuel cell health status monitoring technology, promote the large-scale commercial development process of fuel cells, promote energy conservation and emission reduction, and promote the dual-carbon action, showing obvious social effects.

[0089] In terms of economic effects, this technical solution does not require a DC blocking circuit, simplifies the hardware structure circuit, reduces the overall space of the measurement and control circuit, and helps to reduce the hardware cost of the fuel cell impedance measurement and control system, showing obvious economic effects.

[0090] See Figure 2 , corresponding to the above method, the present application also discloses a circuit for extracting the AC component of the fuel cell voltage, including: a voltage dividing circuit A, a differential amplifier circuit B, and a microprocessor DSP;

[0091] Among them, the voltage dividing circuit A is connected in parallel with the fuel cell;

[0092] The differential amplifier circuit performs a differential amplification operation on the voltage dividing resistors in the voltage dividing circuit, and the inverting input terminal of the differential amplifier circuit is a DC approximation signal that matches the output signal of the differential amplifier circuit;

[0093] The microprocessor DSP is used to generate a DC approximation signal based on the output signal of the differential amplifier circuit, and is also used to determine whether the output signal of the differential amplifier circuit is within a preset voltage range. If so, perform FFT spectrum analysis on the output signal of the differential amplifier circuit. If not, adjust the value of the DC approximation signal.

[0094] See Figure 2 , the fuel cell voltage AC component extraction circuit disclosed in the above embodiments of the present application further includes:

[0095] An AD sampling circuit disposed between the microprocessor and the output end of the differential amplification circuit;

[0096] A DA conversion circuit disposed between the microprocessor and the inverting input end of the differential amplification circuit.

[0097] Corresponding to the above method, the microprocessor of the fuel cell voltage AC component extraction circuit disclosed in the above embodiments of the present application is further configured to:

[0098] Determine whether the output signal of the differential amplification circuit is greater than the highest amplitude in the preset voltage range or less than the lowest amplitude in the preset voltage range;

[0099] When it is greater than the highest amplitude or less than the lowest amplitude, obtain an approximation coefficient corresponding to the comparison result;

[0100] Calculate a DC approximation signal matching the output signal of the differential amplification circuit based on a preset approximation formula and the approximation coefficient.

[0101] The specific calculation process of the DC approximation signal can be seen in the above method embodiment and will not be repeated here.

[0102] See Figure 2 , the fuel cell voltage AC component extraction circuit disclosed in the above embodiments of the present application further includes:

[0103] An electrical isolation circuit disposed between the differential amplification circuit and the voltage division circuit.

[0104] See Figure 2 , the inverting input end of the differential amplification circuit is connected to the DC approximation signal P sum , and this signal is output by the DA conversion circuit. In this way, the two input voltage signals of the differential amplification circuit are differentially amplified and then transmitted to the DSP through the AD sampling circuit for data processing. The DSP controls the size of the DC approximation signal P voltage in the next approximation process according to the state of the sampling value S sum of the AD sampling circuit.

[0105] In each DC signal approximation process, when the sampling value S voltage of the AD sampling circuit ≥ 5V (the upper limit value of the preset voltage range), it indicates that the sampling value of the AD sampling circuit is in the clipping saturation state. At this time, the DSP should control the DC approximation signal P output by the DA conversion circuitsum Increase by 5 / 2 n , so as to further reduce the magnitude of the DC component in the fuel cell voltage divided signal u; when the AD sampling circuit sampling value S voltage ≤0 (the lower limit of the preset voltage range), it indicates that the sampling value of the AD sampling circuit is in the bottom-clipping saturation state. At this time, the DSP should control the DC approximation signal P output by the DA conversion circuit sum Decrease by 5 / 2 n , so as to further increase the magnitude of the DC component in the fuel cell voltage divided signal u. Thus, after n times of successive approximation of the DC signal After approximation of the DC signal for n ≤ 16 times (the upper limit of the approximation times), the value of P sum can approximate any value within the preset voltage range, thereby realizing the approximation of the DC component in the voltage signal u output by the voltage dividing circuit. Finally, the sampling signal of the AD sampling circuit is stabilized within the preset voltage range.

[0106] In order to judge Figure 2 the reliability of the disclosed circuit, the following uses a specific embodiment to verify the scheme.

[0107] During verification, the AC perturbation regulation circuit realizes the injection of AC perturbation to the fuel cell, so as to generate a weak AC voltage signal at both ends of the fuel circuit, and its peak-to-peak value is generally within 5V; the function of the voltage dividing circuit is to stabilize the fuel cell output voltage to 0 - 5V, and then output the fuel cell voltage signal u; the electrical isolation circuit is used to isolate the strong power circuit of the fuel cell from the AC signal extraction module to reduce the interference of the strong power circuit on the AC signal extraction module, and the magnitude of its output signal is still u; the differential amplifier circuit realizes the subtraction of the output signal of the electrical isolation circuit and the DC approximation signal P output by the DA conversion circuit sum , as well as the amplification of the subtracted signal; the AD sampling circuit is used to sample the output signal of the differential amplifier circuit, and the range of its sampling signal is 0 - 5V. When the signal is higher than 5V or lower than 0V, the sampling signal will generate top-clipping saturation or bottom-clipping distortion; the DSP controls the magnitude of the DC approximation signal output by the DA conversion circuit based on the AD sampling state and the successive approximation algorithm.

[0108] The verification process includes:

[0109] Step 1: Assume that the open-circuit voltage of the fuel cell E = 550V and the impedance Z = 500mΩ; the magnitude of the AC perturbation regulation circuit's regulation of the fuel cell bus current is i 0 = 100 + 4sin(8πt). Then, according to Formula 1, the variation curve of the fuel cell voltage Us with time T under AC perturbation is as Figure 4 shown. At this time, the frequency of the AC component of the fuel cell voltage is 4Hz, the amplitude is 2V, and the phase is 0;

[0110] Step 2: Assume that in the voltage-dividing circuit, R 1 = 500 kΩ and R 2 = 5 kΩ. Then, the curve of the fuel cell voltage signal u output across the voltage-dividing resistor R 2 versus time T is as shown in Figure 5 ;

[0111] Step 3: Based on the successive approximation algorithm, the AC voltage signal extraction module extracts the AC component of the fuel cell voltage signal u according to the magnitude of the fuel cell voltage signal u. The specific extraction process is as shown in Figure 3 ;

[0112] Step 3.1: The fuel cell voltage signal u is electrically isolated by the electrical isolation circuit and then output. The magnitude of the output signal is the same as that of the fuel cell voltage signal u, and it is still referred to as the fuel cell voltage signal u here;

[0113] Step 3.2: The fuel cell voltage signal u and the DC approximation signal P sum output by the DA conversion circuit are respectively input to the positive and negative input terminals of the differential amplifier circuit. The magnitude of the output signal is S voltage = (u - P sum )·G;

[0114] Step 3.3: The AD sampling circuit samples the signal output by the differential amplifier circuit. The relationship between the AD sampling value and the signal output by the differential amplifier circuit is expressed as

[0115]

[0116] Step 3.3: The AD sampling value of the AD sampling circuit is sent to the DSP. The DSP controls the magnitude of the DC approximation value output by the DA conversion circuit according to the magnitude of the AD sampling value by using the successive approximation algorithm. The successive approximation algorithm is described as:

[0117] In each DC approximation process, when the AD sampling signal is greater than or equal to 5 V, the DSP determines that the AD sampling state is clipping saturation and controls the DA conversion circuit to output a DC approximation value P sum to increase by 5 / (2 ^n ); when the AD sampling signal is less than or equal to 0, the DSP determines that the AD sampling state is bottom clipping distortion and controls the DA conversion circuit to output a DC approximation value P sum to decrease by 5 / (2 ^n ). Here, n is the SAR approximation times, with an initial value of n = 1 and an initial approximation value P sum = 0. It can be expressed by the formula as

[0118]

[0119] In the formula, a n is the successive approximation algorithm coefficient. When the AD sampling value is in the clipping saturation state, a n = 1. When the AD sampling value is in the bottom clipping saturation state, a n = -1.

[0120] When the AD sampling signal value satisfies between 0 and 5V, the approximation stops. At this time, it indicates that the successive approximation is successful. Then, the DSP can obtain the amplitude and phase parameters of the AC component of the fuel cell voltage by performing FFT analysis on the stable 0 - 5V voltage signal, thereby realizing the extraction of the AC component of the fuel cell voltage. When the number of approximation times n is greater than 16 and still cannot make the AD sampling signal value stable between 0 and 5V, the successive approximation fails, indicating that the AC signal setting of the fuel cell is too large, resulting in the AC component signal of the fuel cell voltage exceeding the 0 - 5V range.

[0121] As Figure 6 shown, after 2 DC approximation processes, the AD sampling signal sampled by the AD sampling circuit can be stabilized between 0 and 5V. Then, after FFT spectrum analysis, the amplitude of the signal is 2V, the frequency is 4Hz, and the phase is 0, which is the same as the set AC component parameters of the fuel cell voltage, thereby realizing the extraction of the AC component signal of the fuel cell voltage.

[0122] For the convenience of description, the above system is described by dividing it into various modules according to functions. Of course, when implementing the present invention, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0123] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the system or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative work.

[0124] Those skilled in the art may further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0125] The steps of the methods or algorithms described in combination with the embodiments disclosed herein can be directly implemented by hardware, software modules executed by a processor, or a combination of the two. The software modules can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0126] It should also be noted that in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise", or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including a..." does not exclude the presence of another identical element in the process, method, article, or device including the said element.

[0127] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for extracting the AC component of the fuel cell voltage, characterized in that, comprising: Obtaining the voltage value across the voltage-dividing resistor, where the voltage-dividing resistor is connected in parallel with the fuel cell under test; Controlling a differential amplifier circuit to perform differential and amplification processing on the voltage value across the voltage-dividing resistor, where the non-inverting input terminal of the differential amplifier circuit is the voltage value across the voltage-dividing resistor, and the inverting input terminal of the differential amplifier circuit is a DC approximation signal matching the output signal of the differential amplifier circuit; Judging whether the output signal of the differential amplifier circuit is within a preset voltage range. If so, performing FFT spectrum analysis on the output signal of the differential amplifier circuit; Wherein: Judging whether the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range or less than the lowest amplitude in the preset voltage range; When it is greater than the highest amplitude or less than the lowest amplitude, obtaining an approximation coefficient corresponding to the comparison result; Calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

2. The method for extracting the AC component of the fuel cell voltage according to claim 1, characterized in that, The calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient includes: Based on the formula Calculate the DC approximation signal P that matches the output signal of the differential amplifier circuit sum , where the a 1 , a 2 ... a n are the approximation coefficients used when calculating the DC approximation signal obtained in the nth calculation, where n is the number of times the DC approximation signal is calculated. Each time the DC approximation signal is calculated, the value of n is incremented by 1.

3. The method for extracting the AC component of the fuel cell voltage according to claim 1, characterized in that, When it is greater than the highest amplitude or less than the lowest amplitude, obtaining an approximation coefficient corresponding to the comparison result includes: When the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range, the value of the approximation coefficient is 1; When the output signal of the differential amplifier circuit is less than the lowest amplitude in the preset voltage range, the value of the approximation coefficient is -1.

4. The method for extracting the AC component of the fuel cell voltage according to claim 2, characterized in that, The calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient includes: Judging whether the value of n reaches a preset upper limit approximation number. If so, outputting a prompt message indicating that the AC signal setting is too large. If it does not reach the preset upper limit approximation number, calculating a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

5. The method for extracting the AC component of the fuel cell voltage according to claim 2, characterized in that, Judging whether the output signal of the differential amplifier circuit is within a preset voltage range includes: Judging whether the output signal of the differential amplifier circuit is within the range of 0V to 5V.

6. A circuit for extracting the AC component of the fuel cell voltage, characterized in that, comprising: A voltage-dividing circuit connected in parallel with the fuel cell; A differential amplifier circuit for performing differential amplification operation on the voltage-dividing resistor in the voltage-dividing circuit, where the inverting input terminal of the differential amplifier circuit is a DC approximation signal matching the output signal of the differential amplifier circuit; A microprocessor is configured to generate a DC approximation signal based on the output signal of the differential amplifier circuit, determine whether the output signal of the differential amplifier circuit is within a preset voltage range, and if so, perform FFT spectrum analysis on the output signal of the differential amplifier circuit; The microprocessor is further configured to: Determine whether the output signal of the differential amplifier circuit is greater than the highest amplitude in the preset voltage range or less than the lowest amplitude in the preset voltage range; When it is greater than the highest amplitude or less than the lowest amplitude, obtain an approximation coefficient corresponding to the comparison result; Calculate a DC approximation signal matching the output signal of the differential amplifier circuit based on a preset approximation formula and the approximation coefficient.

7. The fuel cell voltage AC component extraction circuit according to claim 6, wherein, further comprising: An AD sampling circuit disposed between the microprocessor and the output terminal of the differential amplifier circuit; A DA conversion circuit disposed between the microprocessor and the inverting input terminal of the differential amplifier circuit.

8. The fuel cell voltage AC component extraction circuit according to claim 6, wherein, further comprising: An electrical isolation circuit disposed between the differential amplifier circuit and the voltage dividing circuit.

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