DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cell
By integrating EIS detection into a hydrogen-oxygen fuel cell system using a DC-DC converter control method and employing a dual closed-loop control and disturbance injection strategy, the problems of slow speed, high cost, and large size of traditional EIS detection are solved, enabling online, in-situ, and rapid condition monitoring and fault diagnosis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2026-03-13
AI Technical Summary
Traditional EIS measurement methods are slow, costly, bulky, and cannot perform real-time online detection, thus failing to meet the real-time status monitoring and fault diagnosis requirements of space hydrogen-oxygen fuel cell systems.
A DC-DC converter control method is adopted, which utilizes voltage and current dual closed-loop control to generate a sinusoidal disturbance signal at the voltage loop reference value through a parallel resonant stage. The disturbance signal is injected into different frequency ranges through open-loop and closed-loop disturbance injection control, and EIS detection is performed by combining fast Fourier analysis to achieve online and in-situ detection.
It enables online and in-situ detection, improves detection efficiency and real-time performance, increases the detection frequency range, maintains stable operation of the converter, and simplifies the system structure.
Smart Images
Figure CN121663946A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronics technology, and specifically to a DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells. Background Technology
[0002] Space hydrogen-oxygen fuel cells offer advantages such as high energy density, zero pollution, no overcharge or over-discharge, and high reliability, leading to their wider application in future space missions. However, the performance degradation and limited lifespan of fuel cells severely impact the long-term operating efficiency and reliability of the system. Therefore, electrochemical impedance spectroscopy (EIS) has been applied to fuel cell systems. By measuring the impedance of the fuel cell at different frequencies, its electrochemical characteristics are reflected, providing ample data support for fuel cell condition monitoring and fault diagnosis.
[0003] However, traditional EIS measurement methods are implemented through electrochemical workstations, which have a series of drawbacks such as slow speed, high cost, large size, and inability to perform online real-time detection, severely limiting their application scenarios. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of existing EIS measurement methods, such as slow speed, high cost, large size, and inability to perform online real-time detection. This invention provides a DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells, solving the problem that traditional EIS measurement methods cannot achieve online real-time monitoring, and realizing state monitoring and fault diagnosis of space hydrogen-oxygen fuel cell systems.
[0005] To achieve the above objectives, the present invention provides a DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells, the control method comprising the following steps: Step S1: Provide a DC-DC converter, wherein the DC-DC converter adopts voltage and current dual closed-loop control to maintain stability during normal operation; Step S2: During online EIS detection, a resonant circuit is connected in parallel at the voltage loop reference value to generate a sinusoidal disturbance signal; Step S3: If the frequency of the disturbance signal is less than or equal to 200Hz, use open-loop disturbance injection control; if the frequency of the disturbance signal is greater than 200Hz, add a disturbance signal amplitude control loop and use closed-loop disturbance injection control. Step S4: When stopping online EIS detection, switch the DC-DC converter to voltage and current dual closed-loop control.
[0006] Optionally, in step S1, both the voltage and current dual closed-loop control adopt proportional-integral control to maintain the stability of its output voltage.
[0007] Optionally, in step S2, the expression for the resonant element is as shown in (1): (1) in, f p The frequency of the disturbance signal, k It is a proportionality constant. s For Laplace variables, ω p ω is the angular frequency, π is pi, and the reference signal is... V ref The result obtained after this step is transformed into a convolutional form in the time domain, as shown in expression (2): (2).
[0008] Optionally, in step S3, the amplitude of the disturbance signal is set to 10% of the input current.
[0009] Optionally, in step S3, the closed-loop disturbance injection control includes: analyzing the amplitude of the input current disturbance signal using Fast Fourier Transform, comparing the measured amplitude with a reference amplitude, and correcting the resonant element coefficient using proportional-integral control. k .
[0010] Optionally, the output impedance of the fuel cell is calculated by the disturbance signal of the voltage and current on the output side of the fuel cell through online EIS detection, as shown in expression (3): (3).
[0011] Optionally, steps S1 to S4 can be repeated several times.
[0012] Optionally, the DC-DC converter is a super-boost converter with a ripple cancellation branch.
[0013] Compared to the prior art, the beneficial effects of the present invention include at least the following: This invention utilizes the control loop of the DC-DC converter itself to inject and detect disturbance signals, eliminating the need for an external electrochemical workstation. It directly embeds the EIS detection function into the running power conversion unit, ensuring that the detection process does not affect the normal power supply of the fuel cell, thus achieving online and in-situ detection.
[0014] The EIS detection of this invention can be triggered at any time according to a preset program or the system status, and quickly complete the spectrum scan, thereby improving the efficiency and real-time performance of the detection.
[0015] A dual-mode control strategy based on "frequency segmentation" is adopted. By leveraging the high gain and stable response characteristics of dual closed-loop control in the low-frequency band, disturbances are directly injected, avoiding the long time delay required for Fast Fourier Transform (FFT) analysis of low-frequency signals and ensuring the efficiency and accuracy of low-frequency measurements. To address the issue of large gain fluctuations in the control loop in the mid-to-high frequency band, the disturbance amplitude is dynamically adjusted through real-time FFT feedback and PI control, ensuring that the disturbance signal is injected without attenuation or distortion, thus overcoming the deficiency of single open-loop control in guaranteeing accuracy over a wide frequency band.
[0016] It greatly simplifies the system structure and significantly reduces the system size, weight, and complexity. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the steps of a DC-DC converter control method for online EIS detection of a space hydrogen-oxygen fuel cell according to the present invention.
[0018] Figure 2 This is a schematic diagram of the DC-DC converter system structure in this invention.
[0019] Figure 3 This is a schematic diagram of a DC-DC converter control method for online EIS detection of a space hydrogen-oxygen fuel cell according to the present invention.
[0020] Figure 4 This is a schematic diagram of the amplitude-frequency characteristics of the disturbance signal from the output voltage to the input current of the present invention.
[0021] Figure 5 This is a schematic diagram of the low-frequency open-loop disturbance injection control strategy of the present invention.
[0022] Figure 6 This is a schematic diagram of the high-frequency closed-loop disturbance injection control strategy of the present invention.
[0023] Figure 7 This is a schematic diagram of the simulation results of the 100Hz disturbance signal injection of the present invention.
[0024] Figure 8 This is a schematic diagram of the simulation results of the 1000Hz disturbance signal injection of the present invention. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the drawings are in a very simplified form and use non-precise proportions, only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention. To make the objectives, features and advantages of the present invention more apparent and understandable, please refer to the drawings. It should be understood that the structures, proportions, sizes, etc., shown in the accompanying drawings are only used to complement the content disclosed in the specification, for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modification to the structure, change in the proportional relationship or adjustment of the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.
[0026] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.
[0027] definition: Proportional-Integral Control (PI control) is a widely used feedback control algorithm in industry and control. It combines proportional and integral actions to calculate how to correct a system's output to achieve the desired target value as accurately as possible. Specifically, the input signal to a PI controller is typically the system's error signal, i.e., the difference between the reference signal (the desired target value) and the actual output signal. In the PI controller, proportional (P) control adjusts the amplitude of the output signal based on the magnitude of the error signal, making the system response more sensitive, but potentially introducing a larger steady-state error. Integral (I) control adjusts the amplitude of the output signal based on the accumulated value of the error signal, eliminating the steady-state error and making the system response smoother. Adding the output signals of the proportional and integral control yields the final output signal of the PI controller. This output signal is then converted into an actual control quantity by an actuator (such as a motor driver) and applied to the controlled object. Simultaneously, the output signal of the controlled object is used as a feedback signal and compared with the reference signal, thus forming a closed-loop control.
[0028] The applicant team discovered that integrating online EIS detection into the DC-DC converter downstream of the fuel cell allows for impedance detection without additional hardware, offering advantages such as low cost and small footprint. However, integrating online EIS detection into the DC-DC converter also introduces new challenges: firstly, the disturbance signal in online EIS detection is affected by the converter's control loop gain, limiting EIS detection to a finite frequency range; secondly, the introduced disturbance signal may impact the stability of the existing control loop, leading to decreased stability during normal converter operation.
[0029] To address the aforementioned shortcomings, this invention provides a DC-DC converter control method that can increase the detection frequency range and maintain stable converter operation.
[0030] like Figures 1-3 As shown, the control method of the present invention includes the following steps: Step S1: Provide a DC-DC converter, which employs dual closed-loop control of voltage and current to maintain stability during normal operation.
[0031] The DC-DC converter described in this invention is a super-boost converter with a ripple cancellation branch, which can reduce input current ripple and is beneficial for reducing ripple interference during online EIS detection. During normal operation, both voltage and current dual closed-loop control employ PI control, with the primary objective of maintaining stable output voltage of the DC-DC converter.
[0032] Step S2: During online EIS detection, a resonant circuit is connected in parallel at the voltage loop reference value to generate a sinusoidal disturbance signal.
[0033] The expression for the resonant element is shown in expression (1): (1) in f p The frequency of the disturbance signal, k It is a proportionality constant. s For Laplace variables, ω p Let ω be the angular frequency and π be pi. Therefore, the reference signal... V ref The result obtained through this step can be transformed into a convolutional form in the time domain, as shown in expression (2): (2) This allows sinusoidal signals to be introduced through the control loop without the need for additional disturbance generation circuits or disturbance signals generated via lookup tables.
[0034] Step S3: If the frequency of the disturbance signal is less than or equal to 200Hz, open-loop disturbance injection control is used; if the frequency of the disturbance signal is greater than 200Hz, a disturbance signal amplitude control loop is added, and closed-loop disturbance injection control is used.
[0035] The disturbance signal can be generated by a duty cycle superimposed with a sinusoidal disturbance through voltage-current dual closed-loop control, thereby generating a disturbance signal on the input current side, i.e., the fuel cell output current side. Since the transfer function of voltage-current dual closed-loop control has a sufficiently large gain at low frequencies, the amplitude of the disturbance signal response on the input current side will not attenuate, allowing for open-loop disturbance injection control.
[0036] Here, we set the amplitude of the disturbance signal that finally appears on the input current to be 10% of the input current. Therefore, the output voltage can be determined by the relationship between the input current and the output voltage. k The value of .
[0037] like Figure 6 As shown, when a mid-to-high frequency disturbance signal above 200Hz is injected, the dual-closed-loop control loop will generate a response signal with excessive amplitude variation, which is detrimental to online EIS detection. Therefore, an open-loop disturbance injection control is adopted, adding an additional control loop for the disturbance signal amplitude. The amplitude of the disturbance signal on the input current is analyzed using Fast Fourier Transform, and this amplitude is compared with a reference amplitude. The coefficients of the resonant circuit are then corrected through PI control compensation. k This keeps the amplitude of the disturbance signal on the input current near the rated value; In theory, low-frequency disturbance signals below 200Hz can also be controlled using a closed-loop disturbance injection strategy. However, considering issues such as spectral leakage in FFT, a full cycle of sampling is required before the amplitude of the disturbance signal can be analyzed. Therefore, the lower the frequency of the disturbance signal, the longer the FFT process takes, leading to a significant delay in amplitude feedback control. Thus, low-frequency disturbance signals are controlled using an open-loop disturbance injection strategy, while high-frequency disturbances are controlled using a closed-loop disturbance injection strategy.
[0038] Step S4: When stopping online EIS detection, switch the DC-DC converter to voltage and current dual closed-loop control.
[0039] Online EIS detection mainly calculates the output impedance of the fuel cell by means of the disturbance signal of the voltage and current on the output side, as shown in expression (3): (3) After completing the EIS detection, the resonant control is disconnected, and the DC-DC converter returns to the voltage and current dual closed-loop control mode. Thereafter, the converter will switch between a stable operating state and an online EIS detection state, cyclically performing steps S1 to S4.
[0040] The control method provided by this invention employs dual closed-loop control of voltage and current during normal operation of the DC-DC converter. During online EIS detection, a resonant circuit is connected in parallel at the voltage loop reference value to generate a sinusoidal disturbance signal. For low-frequency disturbance signals below 200Hz, open-loop disturbance injection control is used, directly injecting the disturbance signal into the input current side of the DC-DC converter through the existing control loop. For mid-to-high-frequency disturbance signals above 200Hz, a disturbance signal amplitude control loop is added to the existing control loop. The response signal on the input current is analyzed using Fast Fourier Transform (FFT) to obtain its amplitude and phase at the disturbance frequency. This amplitude is compared with the reference amplitude, and the coefficients of the resonant circuit are corrected after PI control compensation, thereby achieving attenuated disturbance signal injection. After EIS detection is completed, the resonant control is disconnected, and the DC-DC converter returns to the dual closed-loop control mode.
[0041] like Figure 4 The diagram shows the amplitude-frequency characteristics of the disturbance signal from the output voltage to the input current: at low frequencies, the amplitude changes gradually, and the disturbance amplitudes of the output voltage and the input current have the relationship shown in (4): (4) in R L For load, D This refers to the duty cycle.
[0042] At mid-to-high frequencies, the amplitude fluctuates drastically and attenuates significantly after exceeding the crossover frequency. At this point, the EIS detection signal injected through this loop will either amplify or attenuate excessively, making it unsuitable for online EIS detection. The control method of this invention is based on the analysis of this figure.
[0043] like Figure 5 The diagram shows a low-frequency open-loop disturbance injection control strategy: The disturbance signal can be generated by a voltage-current dual closed-loop control, producing a duty cycle superimposed with a sinusoidal disturbance, thus generating a disturbance signal on the input current side, i.e., the fuel cell output current side. Since the transfer function of the voltage-current dual closed-loop control has a sufficiently large gain at low frequencies, the amplitude of the disturbance signal response on the input current side will not attenuate, allowing for open-loop disturbance injection control.
[0044] like Figure 7 The figure shows a simulation result of 100Hz disturbance signal injection: Through low-frequency open-loop disturbance injection control, the amplitude of the disturbance signal of the input current can be maintained at around 10% of the input current, which corresponds to the disturbance amplitude set by the output voltage.
[0045] like Figure 8The diagram shown is a simulation result of a 1000Hz disturbance signal injection: Through high-frequency closed-loop disturbance injection control, under the action of the control loop, the amplitude of the disturbance signal of the input current can be maintained at around 10% of the input current, and the disturbance set by the output voltage is adjusted accordingly under the feedback of the control loop.
[0046] In summary, this invention provides a DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells. The control method includes the following steps: Step S1: A DC-DC converter is provided, which employs voltage and current dual closed-loop control to maintain stability during normal operation; Step S2: During online EIS detection, a resonant circuit is connected in parallel at the voltage loop reference value to generate a sinusoidal disturbance signal; Step S3: If the frequency of the disturbance signal is less than or equal to 200Hz, open-loop disturbance injection control is used; if the frequency of the disturbance signal is greater than 200Hz, a disturbance signal amplitude control loop is added, and closed-loop disturbance injection control is used; Step S4: When online EIS detection is stopped, the DC-DC converter is switched to voltage and current dual closed-loop control. This invention achieves online in-situ detection, greatly improving detection efficiency, further increasing the detection frequency range, and maintaining stable converter operation.
[0047] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells, characterized in that, The control method includes the following steps: Step S1: Provide a DC-DC converter, wherein the DC-DC converter adopts voltage and current dual closed-loop control to maintain stability during normal operation; Step S2: During online EIS detection, a resonant circuit is connected in parallel at the voltage loop reference value to generate a sinusoidal disturbance signal; Step S3: If the frequency of the disturbance signal is less than or equal to 200Hz, use open-loop disturbance injection control; if the frequency of the disturbance signal is greater than 200Hz, add a disturbance signal amplitude control loop and use closed-loop disturbance injection control. Step S4: When stopping online EIS detection, switch the DC-DC converter to voltage and current dual closed-loop control.
2. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: In step S1, both the voltage and current dual closed-loop control adopt proportional-integral control to maintain the stability of its output voltage.
3. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: In step S2, the expression for the resonant element is as shown in (1): （1） in, f p The frequency of the disturbance signal, k It is a proportionality constant. s For Laplace variables, ω p ω is the angular frequency, π is pi, and the reference signal is... V ref The result obtained after this step is transformed into a convolutional form in the time domain, as shown in expression (2): （2）。 4. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: In step S3, the amplitude of the disturbance signal is set to 10% of the input current.
5. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 3, characterized in that: In step S3, the closed-loop disturbance injection control includes: analyzing the amplitude of the input current disturbance signal using Fast Fourier Transform, comparing the measured amplitude with the reference amplitude, and correcting the resonant element coefficient using proportional-integral control. k .
6. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: The output impedance of the fuel cell is calculated by the disturbance signal of the voltage and current on the output side of the fuel cell through online EIS detection, as shown in expression (3): （3）。 7. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: Repeat steps S1 to S4 several times.
8. The DC-DC converter control method for online EIS detection of space hydrogen-oxygen fuel cells as described in claim 1, characterized in that: The DC-DC converter is a super-boost converter with a ripple cancellation branch.