Super capacitor state of charge calculation method and device, storage medium and computing equipment

Abstract

The application discloses a super capacitor state of charge calculation method and device, a storage medium and a computing device. The super capacitor state of charge and ordinary capacitor voltage are used as observation values. On the basis of a traditional exponential approach law, an integral term of an output variable, a variable exponential integral power term of a state variable and a saturation function are introduced to construct a sliding mode observer. The super capacitor state of charge is calculated through the sliding mode observer. Compared with a traditional method, the accuracy is high.

Description

Technical Field

[0001] This invention relates to a method, apparatus, storage medium, and computing device for calculating the state of charge of a supercapacitor, belonging to the field of energy storage components. Background Technology

[0002] With the rapid development of energy storage technology, supercapacitors have received widespread attention due to their advantages such as high power density, wide operating temperature range, and long cycle life. In power grids with high penetration of new energy sources, they play a role in suppressing power fluctuations, compensating for load power, regulating system peaks, and improving power quality. They are suitable for high energy input / output applications.

[0003] As a complex nonlinear energy storage component, the safe and reliable operation of supercapacitors is crucial for the normal operation of the power grid, and corresponding real-time status monitoring and optimization management strategies are indispensable. In practical applications, the State of Charge (SOC) characterizes the remaining stored energy of a supercapacitor. Influenced by various internal parameters, operating conditions, and temperature, this value cannot be directly obtained and requires accurate calculation. Commonly used methods for supercapacitor SOC calculation include offline identification and ampere-hour metering, but both have low accuracy. Summary of the Invention

[0004] This invention provides a method, apparatus, storage medium, and computing device for calculating the state of charge of a supercapacitor, which solves the problem of low accuracy in existing methods.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] Methods for calculating the state of charge of supercapacitors include:

[0007] Collect the terminal current and terminal voltage of the supercapacitor;

[0008] Based on the terminal current and terminal voltage of the supercapacitor, a pre-constructed sliding mode observer with the supercapacitor's state of charge and ordinary capacitor voltage as observation values ​​is used to calculate the supercapacitor's state of charge. The approach law of the sliding mode observer is based on the traditional exponential approach law, with the addition of an integral term for the output variable and a variable exponential integral power term for the state variable, and the use of a saturation function instead of a sign function.

[0009] A sliding mode observer is pre-constructed using the supercapacitor's state of charge and the ordinary capacitor's voltage as observations, including:

[0010] The supercapacitor is equivalent to a second-order RC equivalent circuit.

[0011] Using the terminal current of the supercapacitor as the input variable and the terminal voltage as the output variable, the input-output state space equation of the supercapacitor is obtained based on the second-order RC equivalent circuit.

[0012] Based on the input-output state-space equation of the supercapacitor, a sliding mode observer is constructed with the supercapacitor's state of charge and the ordinary capacitor's voltage as the observation values.

[0013] The input-output state-space equations of a supercapacitor are:

[0014]

[0015]

[0016] Where U1 is the voltage of the main capacitor in the second-order RC equivalent circuit, U2 is the voltage of the secondary capacitor in the second-order RC equivalent circuit, C1 is the capacitance of the main capacitor, C2 is the capacitance of the secondary capacitor, R1 is the resistance of the parallel resistor of the main capacitor, R2 is the resistance of the parallel resistor of the secondary capacitor, SOC is the state of charge of the supercapacitor, and Q... N I is the rated capacitance of the supercapacitor. SC R0 is the terminal current of the supercapacitor, U1′ is the resistance value of the series resistor in the second-order RC equivalent circuit, U2′ is the derivative of U1, U2′ is the derivative of U2, SOC′ is the derivative of SOC, and y is the terminal voltage of the supercapacitor.

[0017] The reaching law of the sliding mode observer is:

[0018]

[0019] Where s′ is the reaching law of the sliding mode observer, k, k1, k2, and W are all constants greater than 0, ε is the gain, sgn is the sign function, and sat is the saturation function. γ is a coefficient. The values ​​observed by the observer include the observed state of charge (SOC) of the supercapacitor and the observed voltage of the ordinary capacitor, where t is time. is the output of the sliding mode observer, is the estimated value of the supercapacitor terminal voltage, and y is the supercapacitor terminal voltage.

[0020] A supercapacitor state of charge calculation device includes:

[0021] The acquisition module collects the terminal current and terminal voltage of the supercapacitor;

[0022] The calculation module calculates the state of charge (SOC) of the supercapacitor based on its terminal current and voltage using a pre-built sliding mode observer that takes the SOC of the supercapacitor and the voltage of a regular capacitor as observations. The sliding mode observer's approach law is based on the traditional exponential approach law, with the addition of an integral term for the output variable and a variable exponential power term for the state variable, and the use of a saturation function instead of a sign function.

[0023] It also includes a pre-built module; the pre-built module pre-builds a sliding mode observer with supercapacitor state of charge and ordinary capacitor voltage as observations;

[0024] Pre-built modules include:

[0025] The equivalent module equates the supercapacitor to a second-order RC equivalent circuit.

[0026] The state-space equation module takes the terminal current of the supercapacitor as the input variable and the terminal voltage as the output variable, and obtains the input-output state-space equation of the supercapacitor based on the second-order RC equivalent circuit.

[0027] The sliding mode observer construction module constructs a sliding mode observer with the supercapacitor's state of charge and the ordinary capacitor's voltage as the observation values, based on the supercapacitor's input-output state-space equations.

[0028] The supercapacitor input-output state-space equations obtained from the state-space equation module are as follows:

[0029]

[0030]

[0031] Where U1 is the voltage of the main capacitor in the second-order RC equivalent circuit, U2 is the voltage of the secondary capacitor in the second-order RC equivalent circuit, C1 is the capacitance of the main capacitor, C2 is the capacitance of the secondary capacitor, R1 is the resistance of the parallel resistor of the main capacitor, R2 is the resistance of the parallel resistor of the secondary capacitor, SOC is the state of charge of the supercapacitor, and Q... N I is the rated capacitance of the supercapacitor. SC R0 is the terminal current of the supercapacitor, U1′ is the resistance value of the series resistor in the second-order RC equivalent circuit, U2′ is the derivative of U1, U2′ is the derivative of U2, SOC′ is the derivative of SOC, and y is the terminal voltage of the supercapacitor.

[0032] The reaching law of the sliding mode observer is:

[0033]

[0034] Where s′ is the reaching law of the sliding mode observer, k, k1, k2, and W are all constants greater than 0, ε is the gain, sgn is the sign function, and sat is the saturation function. γ is a coefficient. The values ​​observed by the observer include the observed state of charge (SOC) of the supercapacitor and the observed voltage of the ordinary capacitor, where t is time. is the output of the sliding mode observer, is the estimated value of the supercapacitor terminal voltage, and y is the supercapacitor terminal voltage.

[0035] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform the steps of a supercapacitor state of charge calculation method.

[0036] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include steps for performing a method for calculating the state of charge of a supercapacitor.

[0037] The beneficial effects achieved by this invention are as follows: This invention uses the state of charge of a supercapacitor and the voltage of a regular capacitor as observation values. Based on the traditional exponential reaching law, it introduces an integral term for the output variable, a variable exponential integral power term for the state variable, and a saturation function to construct a sliding mode observer. The state of charge of the supercapacitor is calculated through the sliding mode observer, which has higher accuracy than the traditional method. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall principle of the calculation method of the present invention;

[0039] Figure 2 The equivalent circuit diagram is a second-order RC circuit.

[0040] Figure 3 A schematic diagram for improving the exponential reaching law;

[0041] Figure 4 This is a schematic diagram of a sliding mode observer. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0043] The method for calculating the state of charge of a supercapacitor includes the following steps:

[0044] Step 1: Collect the terminal current and terminal voltage of the supercapacitor;

[0045] Step 2: Based on the terminal current and terminal voltage of the supercapacitor, a pre-constructed sliding mode observer with the supercapacitor's state of charge and the ordinary capacitor voltage as observation values ​​is used to calculate the supercapacitor's state of charge. The sliding mode observer's approach law is based on the traditional exponential approach law, with the addition of an integral term for the output variable and a variable exponential integral power term for the state variable, and the use of a saturation function instead of a sign function.

[0046] The above method uses the state of charge of supercapacitors and the voltage of ordinary capacitors as observations. Based on the traditional exponential reaching law, it introduces the integral term of the output variable, the variable exponential integral power term of the state variable, and the saturation function to construct a sliding mode observer. The state of charge of supercapacitors is calculated through the sliding mode observer, which has higher accuracy than the traditional method.

[0047] Before implementing the above method, it is necessary to pre-construct a sliding mode observer based on the supercapacitor's state of charge and the ordinary capacitor voltage as observation values. The specific process can be as follows:

[0048] 1) Equivalent the supercapacitor to a second-order RC equivalent circuit.

[0049] Supercapacitors can be equivalently represented as follows: Figure 2 The second-order RC equivalent circuit shown is essentially an RC parallel branch added to the classic RC model to further simulate the charging and discharging characteristics of a supercapacitor.

[0050] U in the figure SC and I SC These are the terminal voltage and terminal current of the supercapacitor, respectively, which can be directly detected by sensors. C1 is the main capacitor (also represented by the corresponding capacitance value in the following formula), describing the main capacitive reactance characteristic of the supercapacitor. C2 is the secondary capacitor (also represented by the corresponding capacitance value in the following formula), describing the secondary capacitive reactance characteristic of the supercapacitor. R0 is the equivalent series resistance (also represented by the corresponding resistance value in the following formula), characterizing the contact resistance between the electrodes and the electrodes themselves, the resistance of the electrolyte, and the resistance of the electrodes themselves. R1 and R2 are the equivalent parallel resistances (also represented by the corresponding resistance values ​​in the following formula), used to simulate the self-discharge phenomenon of the energy storage element.

[0051] The parallel RC branch characterizes the dynamic and frequency characteristics of the supercapacitor during charging and discharging. The parameters of this second-order RC equivalent circuit are easy to identify, and the model has high accuracy.

[0052] 2) Using the terminal current of the supercapacitor as the input variable and the terminal voltage as the output variable, the input-output state space equation of the supercapacitor is obtained based on the second-order RC equivalent circuit.

[0053] Assuming the supercapacitor is in a charging state, according to circuit principles, we can obtain:

[0054] ISC =I1+I2=I3+I4

[0055] U SC =I SC ×R0+U1+U2

[0056]

[0057] Where I1 is the current flowing through R1, I2 is the current flowing through C1, I3 is the current flowing through R2, and I4 is the current flowing through C2. U1 is the voltage across the main capacitor in the second-order RC equivalent circuit, U2 is the voltage across the secondary capacitor in the second-order RC equivalent circuit, R1 is the resistance of the parallel resistor connecting the main capacitor, R2 is the resistance of the parallel resistor connecting the secondary capacitor, C1 is the capacitance of the main capacitor, C2 is the capacitance of the secondary capacitor, R0 is the resistance of the series resistor in the second-order RC equivalent circuit, and Q... N The rated capacity of the supercapacitor is related to its internal resistance and capacitance parameters. SOC0 is the initial value of SOC, and SOC is the state of charge of the supercapacitor.

[0058] Simplifying the above equation, we get:

[0059]

[0060]

[0061]

[0062] Where U1′ is the derivative of U1, U2′ is the derivative of U2, and SOC′ is the derivative of SOC.

[0063] Choose the state variables as [x1 x2 x3] T =[U1 U2 SOC] T The input and output are u = I SC y=U SC The state-space equations for the second-order RC equivalent circuit, x′=Ax+Bu and y=Cx+Du, can be obtained. Their specific expressions are:

[0064]

[0065]

[0066] Among them, coefficient coefficient Coefficient C = [1 1 0], coefficient D = R0.

[0067] 3) Construct a sliding mode observer with the supercapacitor's state of charge and the ordinary capacitor's voltage (i.e., U1 and U2) as the observation values.

[0068] Based on the above state-space equations, higher-order sliding mode observers can be designed:

[0069] First, define the state variable error as... The values ​​observed by the observer include the observed values ​​of the state of charge (SOC) of the supercapacitor and the observed values ​​of the voltage of the ordinary capacitor.

[0070] The traditional exponential law of convergence is Where ε is the gain and sgn is the sign function. The output of the sliding mode observer is the estimated value of the supercapacitor terminal voltage in this invention, and y is the actual value, where y = U in this invention. SC This is the collected supercapacitor terminal voltage.

[0071] Improvements are made to the traditional exponential reaching law, specifically as follows: Figure 3 As shown, the improved reaching law is

[0072] Where k, k1, k2, and W are all constants greater than 0, and sat is a saturation function. γ is a coefficient, and t is time.

[0073] The improved reaching law, based on the traditional exponential reaching law, introduces an integral term for the output variable, a variable exponential integral power term for the state variable, and a saturation function, which makes the switching of the sliding surface smoother. Specifically, replacing the sign function with a saturation function reduces sliding mode chattering; the presence of a variable exponential integral power term in the improved exponential reaching law allows the system to adaptively change the power of the state variable as the control system operates, reducing chattering when the sliding surface approaches zero; the integral term smooths the power change, further reducing system chattering.

[0074] Therefore, based on the improved convergence law, we can construct... Figure 4 The sliding mode observer, where the governing equations can be expressed as:

[0075]

[0076] Among them, u=I SC For the input of the sliding mode observer, I SC This refers to the terminal current of the supercapacitor. for The derivative of .

[0077] Collect the terminal current and terminal voltage of the supercapacitor, such as Figure 1 Terminal current I SC and terminal voltage U SCInputting into a sliding mode observer allows for the calculation of the supercapacitor's state of charge. The sliding mode observer outputs a condition when the estimated value differs from the actual value. The difference between y and y is not equal, thus generating an error signal. This error is fed back to the input of each integrator in the observer via a reaching law, participating in the adjustment of the observer's state. This allows it to approach the true state of the system with a certain level of accuracy and speed.

[0078] Based on the same technical solution, this invention also discloses a software device for the above method, a supercapacitor state of charge calculation device, comprising:

[0079] The acquisition module collects the terminal current and terminal voltage of the supercapacitor.

[0080] The calculation module calculates the state of charge (SOC) of the supercapacitor based on its terminal current and voltage using a pre-built sliding mode observer that takes the SOC of the supercapacitor and the voltage of a regular capacitor as observations. The sliding mode observer's approach law is based on the traditional exponential approach law, with the addition of an integral term for the output variable and a variable exponential power term for the state variable, and the use of a saturation function instead of a sign function.

[0081] Pre-build modules to pre-build sliding mode observers with supercapacitor state of charge and ordinary capacitor voltage as observation values.

[0082] Pre-built modules include:

[0083] The equivalent module equates the supercapacitor to a second-order RC equivalent circuit.

[0084] The state-space equation module uses the terminal current of the supercapacitor as the input variable and the terminal voltage as the output variable. Based on the second-order RC equivalent circuit, it obtains the input-output state-space equations of the supercapacitor.

[0085] The supercapacitor input-output state-space equations obtained from the state-space equation module are as follows:

[0086]

[0087]

[0088] Where U1 is the voltage of the main capacitor in the second-order RC equivalent circuit, U2 is the voltage of the secondary capacitor in the second-order RC equivalent circuit, C1 is the capacitance of the main capacitor, C2 is the capacitance of the secondary capacitor, R1 is the resistance of the parallel resistor of the main capacitor, R2 is the resistance of the parallel resistor of the secondary capacitor, SOC is the state of charge of the supercapacitor, and Q... N I is the rated capacitance of the supercapacitor. SCR0 is the terminal current of the supercapacitor, U1′ is the resistance value of the series resistor in the second-order RC equivalent circuit, U2′ is the derivative of U1, U2′ is the derivative of U2, SOC′ is the derivative of SOC, and y is the terminal voltage of the supercapacitor.

[0089] The sliding mode observer construction module constructs a sliding mode observer with the supercapacitor's state of charge and the ordinary capacitor's voltage as the observation values.

[0090] The reaching law of the sliding mode observer is:

[0091]

[0092] Where s′ is the reaching law of the sliding mode observer, k, k1, k2, and W are all constants greater than 0, ε is the gain, sgn is the sign function, and sat is the saturation function. γ is a coefficient. The values ​​observed by the observer include the observed state of charge (SOC) of the supercapacitor and the observed voltage of the ordinary capacitor, where t is time. is the output of the sliding mode observer, is the estimated value of the supercapacitor terminal voltage, and y is the supercapacitor terminal voltage.

[0093] Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform the steps of a supercapacitor state of charge calculation method.

[0094] Based on the same technical solution, the present invention also discloses a computing device, including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include steps for performing a supercapacitor state of charge calculation method.

[0095] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0096] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0097] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0098] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0099] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for calculating the state of charge of a supercapacitor, characterized in that, include: Collect the terminal current and terminal voltage of the supercapacitor; Based on the terminal current and terminal voltage of the supercapacitor, a pre-constructed sliding mode observer, using the supercapacitor's state of charge (SOC) and the voltage of a regular capacitor as observations, is used to calculate the SOC. The sliding mode observer's approach law is based on the traditional exponential approach law, but adds an integral term for the output variable and a variable exponential power term for the state variable, and uses a saturation function instead of a sign function. The approach law of the sliding mode observer is: in, For the reaching law of the sliding mode observer, All are constants greater than 0. Let sgn be the gain, sgn be the sign function, and sat be the saturation function. , , For coefficients, The values ​​observed by the observer include the observed state of charge (SOC) of the supercapacitor and the observed voltage of the ordinary capacitor, where t is time. The output of the sliding mode observer is denoted as , and the estimated value of the supercapacitor terminal voltage is denoted as . This is the terminal voltage of the supercapacitor.

2. The method for calculating the state of charge of a supercapacitor according to claim 1, characterized in that, A sliding mode observer is pre-constructed using the supercapacitor's state of charge and the ordinary capacitor's voltage as observations, including: The supercapacitor is equivalent to a second-order RC equivalent circuit. Using the terminal current of the supercapacitor as the input variable and the terminal voltage as the output variable, the input-output state space equation of the supercapacitor is obtained based on the second-order RC equivalent circuit. Based on the input-output state-space equation of the supercapacitor, a sliding mode observer is constructed with the supercapacitor's state of charge and the ordinary capacitor's voltage as the observation values.

3. The method for calculating the state of charge of a supercapacitor according to claim 2, characterized in that, The input-output state-space equations of a supercapacitor are: in, This represents the voltage across the main capacitor in the second-order RC equivalent circuit. The voltage across the secondary capacitor in the second-order RC equivalent circuit is given. The capacitance value of the main capacitor. This is the capacitance value of the secondary capacitor. The resistance value of the resistor connected in parallel with the main capacitor. The resistance value is the parallel resistor of the secondary capacitor, and SOC is the state of charge of the supercapacitor. This refers to the rated capacitance of the supercapacitor. This represents the terminal current of the supercapacitor. This represents the resistance value of the series resistor in the second-order RC equivalent circuit. for The derivative, for The derivative, The derivative of SOC This is the terminal voltage of the supercapacitor.

4. A supercapacitor state of charge calculation device, characterized in that, include: The acquisition module is used to acquire the terminal current and terminal voltage of the supercapacitor. The calculation module is used to calculate the state of charge (SOC) of a supercapacitor based on its terminal current and voltage using a pre-built sliding mode observer that takes the SOC of the supercapacitor and the voltage of a regular capacitor as observations. The sliding mode observer's reaching law is based on the traditional exponential reaching law, but adds an integral term for the output variable and a variable exponential power term for the state variable, and uses a saturation function instead of a sign function. The reaching law of the sliding mode observer is as follows: in, For the reaching law of the sliding mode observer, All are constants greater than 0. Let sgn be the gain, sgn be the sign function, and sat be the saturation function. , , For coefficients, The values ​​observed by the observer include the observed state of charge (SOC) of the supercapacitor and the observed voltage of the ordinary capacitor, where t is time. The output of the sliding mode observer is denoted as , and the estimated value of the supercapacitor terminal voltage is denoted as . This is the terminal voltage of the supercapacitor.

5. The supercapacitor state of charge calculation device according to claim 4, characterized in that, It also includes pre-built modules; A pre-built module is used to pre-build a sliding mode observer with supercapacitor state of charge and ordinary capacitor voltage as observations; Pre-built modules include: Equivalent module, used to convert a supercapacitor into a second-order RC equivalent circuit; The state-space equation module is used to obtain the input-output state-space equations of the supercapacitor by taking the terminal current as the input variable and the terminal voltage as the output variable, based on the second-order RC equivalent circuit. The sliding mode observer construction module is used to construct a sliding mode observer with the supercapacitor's state of charge and the ordinary capacitor's voltage as observations, based on the supercapacitor's input-output state-space equations.

6. The supercapacitor state of charge calculation device according to claim 5, characterized in that, The supercapacitor input-output state-space equations obtained from the state-space equation module are as follows: in, This represents the voltage across the main capacitor in the second-order RC equivalent circuit. The voltage across the secondary capacitor in the second-order RC equivalent circuit is given. The capacitance value of the main capacitor. This is the capacitance value of the secondary capacitor. The resistance value of the resistor connected in parallel with the main capacitor. The resistance value is the parallel resistor of the secondary capacitor, and SOC is the state of charge of the supercapacitor. This refers to the rated capacitance of the supercapacitor. This represents the terminal current of the supercapacitor. This represents the resistance value of the series resistor in the second-order RC equivalent circuit. for The derivative, for The derivative, The derivative of SOC This is the terminal voltage of the supercapacitor.

7. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the steps of the method according to any one of claims 1 to 3.

8. A computing device, characterized in that, include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including steps for performing the method according to any one of claims 1 to 3.

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