Soc online estimation method and system for super capacitor

Abstract

The application provides an SOC online estimation method and system for super capacitors, relates to the technical field of super capacitor SOC calculation, and comprises the following steps: periodically collecting operating state parameters of the super capacitor, wherein the operating state parameters comprise an ambient temperature, a terminal voltage and a working current; correcting the internal resistance of the super capacitor according to the working current and the ambient temperature to obtain a corrected internal resistance; establishing an equivalent circuit model of the super capacitor based on the working current and the corrected internal resistance, wherein the equivalent circuit model is used for describing the functional relationship between the terminal voltage and an open circuit voltage; outputting an open circuit voltage estimation value through a Kalman filter based on the equivalent circuit model; and calculating the SOC of the super capacitor according to the open circuit voltage estimation value. The application has the advantage of improving the accuracy of SOC estimation.

Description

Technical Field

[0001] This invention relates to the field of SOC calculation technology for supercapacitors, and more specifically, to a method and system for online SOC estimation of supercapacitors. Background Technology

[0002] Supercapacitors have outstanding features such as high-rate charging and discharging, long life (up to about 1 million cycles), strong environmental adaptability (able to work stably in environments ranging from -40°C to 70°C), and extremely fast response speed, making them a reliable guarantee for the efficient and stable operation of power systems.

[0003] To monitor and manage the operating status of supercapacitors, it is necessary to acquire their State of Charge (SOC) in real time. Currently, the SOC estimation method for supercapacitors is mainly based on the linear relationship between the supercapacitor's terminal voltage and SOC. However, in actual operation, supercapacitors are usually under high-current charging and discharging or sudden load changes. Under high-current transient conditions, due to the presence of internal resistance, the terminal voltage fluctuates drastically, leading to significant errors in the SOC estimation results based on the instantaneous terminal voltage.

[0004] Therefore, it is necessary to optimize the SOC estimation method for supercapacitors to improve the accuracy of SOC estimation. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for online SOC estimation of supercapacitors, which improves the accuracy of SOC estimation.

[0006] This invention is achieved through the following technical solution: The online SOC estimation method for supercapacitors includes the following steps: The operating status parameters of the supercapacitor are periodically collected, including ambient temperature, terminal voltage and operating current. The internal resistance of the supercapacitor is corrected based on the operating current and ambient temperature to obtain the corrected internal resistance. An equivalent circuit model of the supercapacitor is established based on the operating current and the corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open-circuit voltage. Based on the equivalent circuit model, the open-circuit voltage estimate is output through a Kalman filter. Calculate the SOC of the supercapacitor based on the estimated open-circuit voltage.

[0007] Preferably, the method for correcting the internal resistance of the supercapacitor is as follows: Obtain the supercapacitor at a reference temperature Standard internal resistance below ; A transient internal resistance correction factor is established based on the rate of change of the operating current. A temperature correction factor is established based on the ambient temperature and the reference temperature; The corrected internal resistance is obtained by calculating the product of the standard internal resistance, the transient internal resistance correction factor, and the temperature correction factor.

[0008] Preferably, the method for establishing the transient internal resistance correction factor based on the rate of change of the operating current is as follows: ; in, Representative moment The transient internal resistance correction factor, and They are time points and time The operating current, The sampling period is and These are the adjustment coefficient and the adjustment index, respectively.

[0009] Preferably, the method for establishing the temperature correction factor based on the ambient temperature and the reference temperature is to use an Arrhenius model for fitting: ; in, Representative moment The temperature correction factor, It is a natural exponential function. Representative moment The ambient temperature, This is the temperature sensitivity coefficient obtained through calibration.

[0010] Preferably, the method for establishing the equivalent circuit model of the supercapacitor is as follows: ; in, , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, and Representing time respectively The corrected internal resistance and the operating current.

[0011] Preferably, the method for estimating the open-circuit voltage based on the equivalent circuit model using a Kalman filter is as follows: Construct a state vector, the elements of which include the open-circuit voltage and the polarization voltage; A state prediction equation is constructed based on the charge conservation relationship of the supercapacitor and the dynamic changes in polarization voltage. This state prediction equation is used to describe the time-varying states. State vector and time The relationship between state vectors; Establish a terminal voltage observation model based on the equivalent circuit model; Based on the state prediction equation and the terminal voltage observation model, the time is calculated using a Kalman filter. The estimated value of the state vector is used to extract the estimated value of the open-circuit voltage.

[0012] Preferably, the method for constructing the state prediction equation is as follows: Constructing time intervals based on the charge conservation principle of supercapacitors State vector and time The relationship between the open-circuit voltages is as follows: ; The timing is constructed based on the dynamic changes in the polarization voltage. State vector and time The relationship between the polarization voltages is as follows: ; Construct the state prediction equation: ; ; ; in, The sampling period is Let be the equivalent capacitance of the supercapacitor, and e be the natural constant. Polarization resistor, Polarized capacitor, For state noise, A and B are both coefficient matrices. , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, Representative moment The operating current, and They are time points and time The state vector; The terminal voltage observation model is as follows: ; ; in, The coefficient matrix, This is voltage noise.

[0013] Preferably, the step of calculating the time using a Kalman filter... The method for estimating the state vector is as follows: The state prediction equation is used as the state transition model of the Kalman filter, and the terminal voltage observation model is used as the measurement update model of the Kalman filter. The state vector is recursively estimated by the Kalman filter, and the estimated value of the state vector is output.

[0014] Preferably, the method for calculating the SOC of the supercapacitor based on the open-circuit voltage estimate is as follows: Substituting the estimated open-circuit voltage into the open-circuit voltage-SOC function relationship, we obtain the SOC of the supercapacitor. The open-circuit voltage-SOC function relationship is as follows: ; in, and They are time points The SOC and the estimated open-circuit voltage of the supercapacitor, and These are the rated maximum operating voltage and minimum operating cutoff voltage of the supercapacitor, respectively.

[0015] The present invention also provides an online SOC estimation system for supercapacitors, applied to the above-mentioned online SOC estimation method for supercapacitors, comprising: The acquisition module is used to periodically acquire the operating status parameters of the supercapacitor, including ambient temperature, terminal voltage, and operating current. The internal resistance correction module is used to correct the internal resistance of the supercapacitor based on the operating current and ambient temperature to obtain the corrected internal resistance. The model building module is used to build an equivalent circuit model of the supercapacitor based on the operating current and corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open circuit voltage. The Kalman filter module is used to output an estimated open-circuit voltage value based on the equivalent circuit model using a Kalman filter. The SOC calculation module is used to calculate the SOC of a supercapacitor based on the open-circuit voltage estimate.

[0016] The technical solution of the present invention has at least the following advantages and beneficial effects: This invention corrects the internal resistance of a supercapacitor based on ambient temperature and operating current, obtaining a corrected internal resistance that changes with the operating state, thereby improving the accuracy of the equivalent circuit model established in subsequent steps and reducing errors caused by changes in internal resistance. This invention treats open-circuit voltage as a parameter that cannot be directly measured. By fusing the operating current input and terminal voltage measurement results through a Kalman filter, the open-circuit voltage is recursively estimated. This effectively suppresses the voltage fluctuations caused by factors such as large current surges and sudden load changes, thereby improving the stability of SOC estimation. This invention is reasonably designed, taking into account the influence of ambient temperature and operating current on the internal characteristics of supercapacitors, so that the SOC estimation process can adapt to different temperature environments and different charging and discharging conditions, improving the estimation accuracy and the adaptability of the estimation method. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the online SOC estimation method for supercapacitors provided in Embodiment 1 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Example This embodiment provides a method for online SOC estimation of supercapacitors. (See attached document.) Figure 1 This includes the following steps: Step S1: Periodically collect the operating status parameters of the supercapacitor, including ambient temperature, terminal voltage and operating current.

[0020] During the operation of a supercapacitor, the operating status parameters of the supercapacitor are periodically collected by a sensing and acquisition module installed in the supercapacitor's working circuit.

[0021] Ambient temperature refers to the temperature of the supercapacitor's operating environment, which can be obtained through a temperature sensor. Terminal voltage is the actual voltage across the positive and negative terminals of the supercapacitor, directly measured by a voltage sensor. Operating current is the current flowing through the supercapacitor during operation, measured by a current sensor.

[0022] It should be noted that, due to the influence of operating conditions, the terminal voltage is not equal to the actual voltage corresponding to the current stored energy of the supercapacitor (hereinafter referred to as the open circuit voltage), so the measured terminal voltage cannot be directly used to calculate the SOC.

[0023] Step S2: Correct the internal resistance of the supercapacitor based on the operating current and ambient temperature to obtain the corrected internal resistance.

[0024] The internal resistance of a supercapacitor is a crucial parameter affecting voltage changes. It is not only related to the supercapacitor's specifications but also influenced by external ambient temperature and dynamic load conditions. For example, changes in ambient temperature alter the electrolyte ion migration capacity, causing changes in internal resistance due to temperature drift. Furthermore, during rapid charging and discharging at high currents, transient polarization occurs due to charge migration lag, also resulting in dynamic changes in internal resistance. Therefore, internal resistance correction is necessary. The preferred correction method in this embodiment is: Step S201: Obtain the supercapacitor at a reference temperature Standard internal resistance below .

[0025] For example, it can be done in a normal temperature environment. (Reference temperature) Under these conditions, the internal resistance of the supercapacitor is obtained through methods such as constant current discharge testing and recorded as the standard internal resistance. .

[0026] Step S202: Establish a transient internal resistance correction factor based on the rate of change of the operating current. The method for establishing the transient internal resistance correction factor is as follows: ; in, Representative moment The transient internal resistance correction factor, and They are time points and time The operating current, The sampling period is and These are the adjustment coefficient and the adjustment index, respectively. The preferred value range is 0.001-0.05. The preferred value range is 0.8-1.2.

[0027] When the instantaneous change in current is very small (approaching 0), When the coefficient approaches 1, it contributes almost nothing to the correction; the greater the instantaneous change in current, the greater the amount of correction, in order to compensate for the additional voltage loss caused by the transient current change.

[0028] Step S203: Establish a temperature correction factor based on the ambient temperature and the reference temperature. The method for establishing the temperature correction factor is to fit it using an Arrhenius model. ; in, Representative moment The temperature correction factor, It is a natural exponential function. Representative moment The ambient temperature, This is the temperature sensitivity coefficient obtained through calibration.

[0029] At low temperatures, the increased viscosity of the electrolyte and decreased ion diffusion rate lead to increased internal resistance; at high temperatures, the enhanced ion migration capacity of the electrolyte leads to decreased internal resistance. By establishing a temperature correction factor, compensation for internal resistance drift caused by changes in ambient temperature is achieved.

[0030] Step S204: Obtain the corrected internal resistance by calculating the product of the standard internal resistance, the transient internal resistance correction factor, and the temperature correction factor. ; in, Representative moment The corrected internal resistance.

[0031] Step S3: Establish an equivalent circuit model of the supercapacitor based on the operating current and corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open-circuit voltage.

[0032] The actual measured terminal voltage of a supercapacitor is the open-circuit voltage corresponding to its true energy storage state. Excluding internal resistance voltage drop ( ) and polarization voltage drop (polarization voltage) The result obtained after [further details]. Therefore, the method for establishing the equivalent circuit model of a supercapacitor is as follows: ; in, , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, and Representing time respectively The corrected internal resistance and the operating current.

[0033] Step S4: Based on the equivalent circuit model, output the estimated open-circuit voltage value through a Kalman filter. The method is as follows: Step S401: Construct a state vector, the elements of which include the open-circuit voltage and the polarization voltage.

[0034] Step S402: Construct a state prediction equation based on the charge conservation relationship of the supercapacitor and the dynamic change of polarization voltage. The state prediction equation is used to describe the time interval. State vector and time The method for constructing the state prediction equation is based on the relationship between the state vectors: First, the time interval is constructed based on the charge conservation relationship of the supercapacitor. State vector and time The relationship between the open-circuit voltages is as follows: According to circuit principles, charge... , This represents the open-circuit voltage (without considering the sampling time), while the current... and charge The relationship between them is By combining the two equations and discretizing them, we can obtain: ; Secondly, the polarization branch is usually an RC network, and the timing is constructed based on the dynamic changes of the polarization voltage. State vector and time The relationship between the polarization voltages is as follows: ; In the above formula, This represents the polarization voltage remaining after the original polarization voltage has naturally decayed over time. The polarization voltage that increases naturally under the operating current; Based on the above scheme, the state prediction equation can be constructed as follows: ; ; ; in, The sampling period is Let be the equivalent capacitance of the supercapacitor, and e be the natural constant. Polarization resistor, Polarized capacitor, For state noise, A and B are both coefficient matrices. , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, Representative moment The operating current, and They are time points and time The state vector.

[0035] Step S403: Establish a terminal voltage observation model based on the equivalent circuit model. The terminal voltage observation model is as follows: ; ; in, The coefficient matrix, This is voltage noise.

[0036] Step S404: Based on the state prediction equation and the terminal voltage observation model, calculate the time using a Kalman filter. The estimated value of the state vector is used to extract the estimated value of the open-circuit voltage. The specific method is as follows: The state prediction equation is used as the state transition model of the Kalman filter, and the terminal voltage observation model is used as the measurement update model of the Kalman filter. The state vector is recursively estimated by the Kalman filter, and the estimated value of the state vector is output.

[0037] This step is based on the equivalent circuit model established in step S3. The open-circuit voltage and polarization voltage are treated as state variables that cannot be directly measured, and the terminal voltage is treated as a measurable observable. A state-space model for the Kalman filter is constructed, and the state variables are recursively estimated through the Kalman filter to obtain the estimated value of the open-circuit voltage at the current moment.

[0038] Step S5: Calculate the SOC of the supercapacitor based on the estimated open-circuit voltage.

[0039] Since supercapacitors employ an electrochemical double-layer energy storage mechanism, their open-circuit voltage directly reflects their current energy storage level. In this embodiment, the method for calculating the SOC of a supercapacitor is as follows: Substituting the estimated open-circuit voltage into the open-circuit voltage-SOC function relationship, we obtain the SOC of the supercapacitor. The open-circuit voltage-SOC function relationship is as follows: ; in, and They are time points The SOC and the estimated open-circuit voltage of the supercapacitor, and These are the rated maximum operating voltage and minimum operating cutoff voltage of the supercapacitor, respectively.

[0040] Example 2 This embodiment provides an online SOC estimation system for supercapacitors, applied to the online SOC estimation method for supercapacitors in Embodiment 1, including: The acquisition module is used to periodically acquire the operating status parameters of the supercapacitor, including ambient temperature, terminal voltage, and operating current. The internal resistance correction module is used to correct the internal resistance of the supercapacitor based on the operating current and ambient temperature to obtain the corrected internal resistance. The model building module is used to build an equivalent circuit model of the supercapacitor based on the operating current and corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open circuit voltage. The Kalman filter module is used to output an estimated open-circuit voltage value based on the equivalent circuit model using a Kalman filter. The SOC calculation module is used to calculate the SOC of a supercapacitor based on the open-circuit voltage estimate.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for online SOC estimation of supercapacitors, characterized in that, Includes the following steps: The operating status parameters of the supercapacitor are periodically collected, including ambient temperature, terminal voltage and operating current. The internal resistance of the supercapacitor is corrected based on the operating current and ambient temperature to obtain the corrected internal resistance. An equivalent circuit model of the supercapacitor is established based on the operating current and the corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open-circuit voltage. Based on the equivalent circuit model, the open-circuit voltage estimate is output through a Kalman filter. Calculate the SOC of the supercapacitor based on the estimated open-circuit voltage.

2. The online SOC estimation method for supercapacitors according to claim 1, characterized in that, The method for correcting the internal resistance of the supercapacitor is as follows: Obtain the supercapacitor at a reference temperature Standard internal resistance below ; A transient internal resistance correction factor is established based on the rate of change of the operating current. A temperature correction factor is established based on the ambient temperature and the reference temperature; The corrected internal resistance is obtained by calculating the product of the standard internal resistance, the transient internal resistance correction factor, and the temperature correction factor.

3. The online SOC estimation method for supercapacitors according to claim 2, characterized in that, The method for establishing the transient internal resistance correction factor based on the rate of change of the operating current is as follows: ； in, Representative moment The transient internal resistance correction factor, and They are time points and time The operating current, The sampling period is and These are the adjustment coefficient and the adjustment index, respectively.

4. The online SOC estimation method for supercapacitors according to claim 3, characterized in that, The method for establishing the temperature correction factor based on the ambient temperature and the reference temperature is to use an Arrhenius model for fitting: ； in, Representative moment The temperature correction factor, It is a natural exponential function. Representative moment The ambient temperature, This is the temperature sensitivity coefficient obtained through calibration.

5. The online SOC estimation method for supercapacitors according to claim 1, characterized in that, The method for establishing the equivalent circuit model of a supercapacitor is as follows: ； in, , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, and Representing time respectively The corrected internal resistance and the operating current.

6. The online SOC estimation method for supercapacitors according to claim 5, characterized in that, The method for estimating the open-circuit voltage based on the equivalent circuit model and outputting the Kalman filter is as follows: Construct a state vector, the elements of which include the open-circuit voltage and the polarization voltage; A state prediction equation is constructed based on the charge conservation relationship of the supercapacitor and the dynamic changes in polarization voltage. This state prediction equation is used to describe the time-varying states. State vector and time The relationship between state vectors; Establish a terminal voltage observation model based on the equivalent circuit model; Based on the state prediction equation and the terminal voltage observation model, the time is calculated using a Kalman filter. The estimated value of the state vector is used to extract the estimated value of the open-circuit voltage.

7. The online SOC estimation method for supercapacitors according to claim 6, characterized in that, The method for constructing the state prediction equation is as follows: Constructing time intervals based on the charge conservation principle of supercapacitors State vector and time The relationship between the open-circuit voltages is as follows: ； The timing is constructed based on the dynamic changes in the polarization voltage. State vector and time The relationship between the polarization voltages is as follows: ； Construct the state prediction equation: ； ； ； in, The sampling period is Let be the equivalent capacitance of the supercapacitor, and e be the natural constant. Polarization resistor, Polarized capacitor, For state noise, A and B are both coefficient matrices. , and Representing time respectively The terminal voltage, the open-circuit voltage, and the polarization voltage, Representative moment The operating current, and They are time points and time The state vector; The terminal voltage observation model is as follows: ； ； in, The coefficient matrix, This is voltage noise.

8. The online SOC estimation method for supercapacitors according to claim 7, characterized in that, The time is calculated using a Kalman filter. The method for estimating the state vector is as follows: The state prediction equation is used as the state transition model of the Kalman filter, and the terminal voltage observation model is used as the measurement update model of the Kalman filter. The state vector is recursively estimated by the Kalman filter, and the estimated value of the state vector is output.

9. The online SOC estimation method for supercapacitors according to claim 1, characterized in that, The method for calculating the SOC of a supercapacitor based on the open-circuit voltage estimate is as follows: Substituting the estimated open-circuit voltage into the open-circuit voltage-SOC function relationship, we obtain the SOC of the supercapacitor. The open-circuit voltage-SOC function relationship is as follows: ； in, and They are time points The SOC and the estimated open-circuit voltage of the supercapacitor, and These are the rated maximum operating voltage and minimum operating cutoff voltage of the supercapacitor, respectively.

10. An online SOC estimation system for supercapacitors, applied to the online SOC estimation method for supercapacitors as described in any one of claims 1-9, characterized in that, include: The acquisition module is used to periodically acquire the operating status parameters of the supercapacitor, including ambient temperature, terminal voltage, and operating current. The internal resistance correction module is used to correct the internal resistance of the supercapacitor based on the operating current and ambient temperature to obtain the corrected internal resistance. The model building module is used to build an equivalent circuit model of the supercapacitor based on the operating current and corrected internal resistance. The equivalent circuit model is used to describe the functional relationship between the terminal voltage and the open circuit voltage. The Kalman filter module is used to output an estimated open-circuit voltage value based on the equivalent circuit model using a Kalman filter. The SOC calculation module is used to calculate the SOC of a supercapacitor based on the open-circuit voltage estimate.

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