JP2021190257A - Voltage estimation method and voltage estimation device of zinc battery - Google Patents

Abstract

To provide a voltage estimation method and a voltage estimation device capable of accurately estimating a terminal voltage of a zinc battery.SOLUTION: A voltage estimation method includes a step of calculating a terminal voltage on the basis of a voltage generated in a DC resistance unit, which is calculated on the basis of a current flowing through an equivalent circuit model having the DC resistance unit. The DC resistance unit includes a linear DC resistance component and a non-linear DC resistance component that is connected in series with the linear DC resistance component and whose resistance value changes according to the current. At least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the non-linear DC resistance component is selected from a plurality of values according to the SOC of a zinc battery to be estimated.SELECTED DRAWING: Figure 6

Description

The present invention relates to a voltage estimation method and a voltage estimation device for a zinc battery.

Patent Document 1 discloses a technique relating to a simulation method of a power storage device. The method described in this document is based on a step of calculating the current flowing through the equivalent circuit model, a step of calculating the DC resistance voltage which is the voltage generated in the DC resistance component of the equivalent circuit model, and a terminal based on the DC resistance voltage. Includes steps to calculate the voltage. The DC resistance component includes a linear DC resistance component and a non-linear DC resistance component connected in series with each other. The resistance value of the non-linear DC resistance component changes according to the current.

2018-040685 Publication No.

In recent years, techniques for modeling a secondary battery and estimating the terminal voltage of the secondary battery have been used in various applications. For example, in a vehicle fuel consumption simulation, various power sources such as an engine and a secondary battery and a load are modeled, and a predetermined driving pattern is input to the model to calculate the fuel consumption. Further, by estimating the terminal voltage of the secondary battery in operation, the state of the secondary battery can be detected. When estimating the terminal voltage of the secondary battery, the estimation accuracy is important. One aspect of the present invention is to provide a voltage estimation method and a voltage estimation device capable of accurately estimating the terminal voltage of a zinc battery among secondary batteries.

The voltage estimation method according to one aspect of the present invention is a method of estimating the terminal voltage of a zinc battery, and includes a step of calculating the terminal voltage. In this step, the terminal voltage is calculated based on the voltage generated in the DC resistance section, which is calculated based on the current flowing through the equivalent circuit model having the DC resistance section. The DC resistance unit includes a linear DC resistance component and a non-linear DC resistance component that is connected in series with the linear DC resistance component and whose resistance value changes according to a current. At least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the nonlinear DC resistance component is selected from a plurality of values according to the SOC of the zinc battery to be estimated, and is a nonlinear DC. The resistance value of the resistance component differs between charging and discharging.

The voltage estimation device according to one aspect of the present invention is a device for estimating the terminal voltage of a zinc battery, and includes a parameter setting unit and a terminal voltage calculation unit. The parameter setting unit sets the characteristic parameters of the equivalent circuit model having the DC resistance unit. The terminal voltage calculation unit calculates the terminal voltage based on the voltage generated in the DC resistance unit, which is calculated based on the current flowing through the equivalent circuit model. The DC resistance unit includes a linear DC resistance component and a non-linear DC resistance component that is connected in series with the linear DC resistance component and whose resistance value changes according to a current. The parameter setting unit sets at least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the nonlinear DC resistance component from a plurality of values according to the SOC of the zinc battery to be estimated. Select and make the resistance value of the non-linear DC resistance component different between charging and discharging.

The above-mentioned Patent Document 1 discloses a method of using an equivalent circuit model including a linear DC resistance component and a non-linear DC resistance component in order to estimate a terminal voltage of a lead battery or the like. However, when estimating the terminal voltage of a zinc battery, the following problem arises. That is, unlike lead batteries and the like, zinc batteries are used in a wide SOC (State Of Charge) range. This is because lead-acid batteries deteriorate faster when used at a low SOC, but zinc batteries have a relatively small degree of deterioration even when used at a low SOC. In the secondary battery, if the SOC fluctuates greatly, the parameters such as the resistance value of the DC resistance component also fluctuate. Therefore, if the parameters are constant regardless of the SOC, the estimation error becomes large. To solve this problem, in the above method and device, at least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the nonlinear DC resistance component is the SOC of the zinc battery to be estimated. Select from multiple values that differ in size from each other. In this case, at least a part of the parameters of the equivalent circuit model can be changed to an appropriate size according to the fluctuating SOC. Therefore, it is possible to suppress an increase in estimation error due to a change in SOC. That is, according to the above method and apparatus, the terminal voltage of the zinc battery among the secondary batteries can be estimated with high accuracy.

In the above voltage estimation method and voltage estimation device, the resistance value of the nonlinear DC resistance component is made different between the time of charging and the time of discharging. In a zinc battery, the resistance value of the nonlinear DC resistance component differs between charging and discharging. Therefore, in this case, the estimation accuracy of the terminal voltage of the zinc battery can be further improved.

In the above voltage estimation method and voltage estimation device, the equivalent circuit model may further have a polarization model unit connected in series with the DC resistance unit. The polarization model unit may include at least an RC parallel circuit in which a variable resistor and a variable capacitor are connected in parallel. In the above step (the terminal voltage calculation unit), the terminal voltage may be further calculated based on the voltage generated in the polarization model unit calculated based on the current flowing through the equivalent circuit model. The parameter setting unit may select at least one of the resistance value of the variable resistor and the time constant of the RC parallel circuit from a plurality of values according to the SOC of the zinc battery to be estimated. In this case, the characteristics of the equivalent circuit model can be made closer to the characteristics of the zinc battery, and the terminal voltage of the zinc battery can be estimated more accurately.

In the above voltage estimation method and voltage estimation device, the equivalent circuit model may not include a DC resistance component based on gassing in which a capacitor and a switching element are connected in parallel. Equivalent circuit models of lead-acid batteries include such DC resistance components that represent gassing. However, since gassing does not occur in the zinc battery, the estimation accuracy of the terminal voltage of the zinc battery can be further improved by excluding the capacitance component from the equivalent circuit model of the zinc battery.

According to one aspect of the present invention, it is possible to provide a voltage estimation method and a voltage estimation device capable of accurately estimating the terminal voltage of a zinc battery among secondary batteries.

FIG. 1 is a diagram showing a schematic configuration of a fuel consumption calculation device that calculates fuel consumption of a vehicle. FIG. 2 is a circuit diagram showing an example of an equivalent circuit model of a zinc battery. FIG. 3 is a diagram showing a schematic configuration of a voltage estimation device according to an embodiment. FIG. 4 is a diagram showing an example of the hardware configuration of the voltage estimation device of FIG. FIG. 5 is a graph conceptually showing an example of a waveform of a charge / discharge current input from an input unit. FIG. 6 is a diagram illustrating a terminal voltage calculation process (voltage estimation method) executed by the voltage estimation device. FIG. 7 is a chart showing an example of subdivided characteristic parameters. FIG. 8 is a diagram conceptually showing a look-up table showing the correlation between the value of the characteristic parameter and the SOC. FIG. 9 is a graph showing an example of the voltage estimation result by the equivalent circuit model. FIG. 10 is a graph showing an example of the voltage estimation result by the equivalent circuit model. FIG. 11 is a graph showing an example of the voltage estimation result by the equivalent circuit model. FIG. 12 is a graph showing an example of the voltage estimation result by the equivalent circuit model. FIG. 13 is a graph showing an example of the voltage estimation result by the polarization symmetry two-stage polarization model.

Hereinafter, embodiments of the zinc battery voltage estimation method and the voltage estimation device according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In the following description, the zinc battery is a concept including a nickel-zinc battery, a zinc-air battery, and a silver-zinc battery.

The zinc battery voltage estimation method and voltage estimation device according to the embodiment are used, for example, in fuel consumption simulation of a vehicle equipped with a zinc battery. This zinc battery is, for example, a main battery mounted on a vehicle adopting the μHEV method, or a sub-battery provided separately from the main battery. When the zinc battery is a sub-battery, the zinc battery is used to cover the current consumption of the 12V system auxiliary machine mounted on the vehicle.

FIG. 1 is a diagram showing a schematic configuration of a fuel consumption calculation device that calculates fuel consumption of a vehicle. As shown in FIG. 1, the fuel consumption calculation device 90 includes an input unit 91, a control unit 92, and an output unit 93 as its functional blocks. The input unit 91 inputs data necessary for fuel consumption calculation. An example of input data is a vehicle running pattern. Other than that, the parameters that determine the characteristics of various devices such as the engine mounted on the vehicle, the type of charge / discharge control method for the zinc battery, the configuration of the zinc battery, the power consumption of the auxiliary equipment mounted on the vehicle, and the vehicle. Data such as the weight of the can be input.

The control unit 92 performs a fuel consumption simulation using the data input by the input unit 91. The specific method of fuel consumption simulation is not particularly limited, but for example, the procedure is as follows. First, the control unit 92 determines the power required for the vehicle to travel (hereinafter, simply referred to as “required power”) and the current consumption of the auxiliary machine for each section, for example, from the travel pattern input by the input unit 91. Is calculated. The section includes a stop section, an acceleration section, a constant speed running section, a deceleration section, and the like. The required power is relatively large in the acceleration section and relatively small in the constant speed running section. The required power may be 0 in the stop section and the deceleration section. The current consumption of auxiliary equipment varies depending on the type of auxiliary equipment. For example, the magnitude of the current consumption of continuously used auxiliary equipment such as audio equipment is almost constant regardless of the section. On the other hand, the magnitude of the current consumption of the auxiliary equipment temporarily used such as the ignition device of the engine becomes large only at the time of use.

Next, the control unit 92 calculates the output of the engine for each section. The output of the engine is, for example, zero in the stopped section when the engine is stopped, and is set to a predetermined output in the other sections. Of the output of the engine, the output exceeding the required power is converted into electric power by the alternator and supplied from the alternator to the auxiliary machine and the zinc battery. When the power supplied from the alternator exceeds the power consumption of the auxiliary machine, a current flows from the alternator to the zinc battery to charge the zinc battery. When the power supplied from the alternator is lower than the power consumption of the auxiliary machine, a current flows from the zinc battery to the auxiliary machine, and the zinc battery is discharged. Here, the terminal voltage of the zinc battery depends on the SOC of the zinc battery, the magnitude of the charge / discharge current, and the like. The terminal voltage of this zinc battery is estimated using the equivalent circuit model of the zinc battery. The details of the terminal voltage estimation will be described later. From the charge / discharge current of the zinc battery and the terminal voltage of the zinc battery, the control unit 92 also calculates the charge / discharge power of the zinc battery for each section.

After that, the control unit 92 calculates the integrated value of the engine output and the charge / discharge power of the zinc battery in the entire section. The integrated value of the output of the engine in all sections indicates the amount of energy that the engine will consume when the vehicle travels according to the travel pattern input by the input unit 91. The integrated value of the charge / discharge power of the zinc battery in all sections indicates the magnitude of the amount of energy that will increase or decrease in the zinc battery when the vehicle travels according to the travel pattern input by the input unit 91. The total amount of energy of the amount of energy that the engine will consume and the amount of energy that will be reduced in the zinc battery is the amount of energy required for running the vehicle of the running pattern input by the input unit 91. Since the mileage of the vehicle can also be known from the mileage pattern, the control unit 92 calculates the mileage per predetermined energy amount as the fuel consumption based on the mileage and the amount of energy required for the mileage.

The output unit 93 outputs the fuel consumption calculated by the control unit 92. As a result, the result of the fuel consumption simulation based on the traveling pattern and the like input by the input unit 91 can be obtained.

As described above, in the fuel consumption simulation, the terminal voltage of the zinc battery is estimated. Since the accuracy of the fuel consumption simulation is also improved by improving the estimation accuracy of the terminal voltage of the zinc battery, for example, the voltage estimation device according to the embodiment may be used for the purpose of improving the calculation accuracy of the fuel consumption. In the present embodiment, the voltage estimation device estimates the terminal voltage of the zinc battery by using an equivalent circuit model for calculating the terminal voltage of the zinc battery.

FIG. 2 is a circuit diagram showing an example of an equivalent circuit model of a zinc battery. The equivalent circuit model 40 includes a DC resistance unit 10, a polarization model unit 20, and a constant voltage source 30 connected in series between _{nodes N 1} and N _{2 having opposite polarities.} Node N ₁ and node N ₂ are portions that are electrically connected to external elements of the zinc battery and provide the voltage generated in the equivalent circuit model 40. The voltage generated in the equivalent circuit model 40 is the terminal voltage V (t) of the zinc battery. The node N ₁ is an anode and gives a current I (t) flowing into the zinc battery. In addition, (t) or the like may be added to a code indicating a physical quantity that changes with time such as voltage and current, and the physical quantity indicated in this way means the value of the physical quantity at time t. Further, the time t is an integer of 0 or more, and indicates the elapsed time from the start time of the estimation of the terminal voltage V (t). Time t = 0 is the start time of estimation of the terminal voltage V (t).

The DC resistance unit 10 is a portion that simulates the DC impedance (DC resistance component) of the zinc battery. The DC resistance unit 10 includes a resistor. In the example shown in FIG. 2, the resistor 11 and the resistor 12 are connected in series with each other. The resistor 11 simulates the linear DC resistance component of a zinc battery. Examples of the linear DC resistance component include the resistance of the electrode. The resistance value _R0 of the resistor 11 is a constant. The resistor 12 simulates the nonlinear DC resistance component of a zinc battery. The non-linear DC resistance component includes liquid resistance. The resistance value R (I) of the resistor 12 is variable. The resistance value R (I) changes according to the current I (t), and is different between, for example, charging and discharging. That is, the DC resistance component simulated by the DC resistance unit 10 includes a linear DC resistance component simulated by the resistor 11 and a nonlinear DC resistance component simulated by the resistor 12. The impedance of the DC resistance unit 10 is determined by the resistance value of each resistor in the DC resistance unit 10. If the impedance of the DC resistance section 10 is determined, when the current I (t) flows through the equivalent circuit model 40, the current I (t) also flows through the DC resistance section 10, so that the current I (t) and the direct current are DC. The voltage (DC resistance voltage Vdc (t)) generated in the DC resistance unit 10 is calculated from the impedance of the resistance unit 10. The DC resistance voltage Vdc (t) is the total voltage of the voltage Vdc1 (t) generated in the resistor 11 and the voltage Vdc2 (t) generated in the resistor 12. That is, the following relational expression (1) is established in the DC resistance unit 10.

The polarization model unit 20 is a part that simulates the polarization impedance component of the zinc battery. The polarization model unit 20 includes a resistor and a capacitor (RC parallel circuit) connected in parallel. In the example shown in FIG. 2, three RC parallel circuits are connected in series. Specifically, the variable resistor 21 and the variable capacitor 22 (first RC parallel circuit) connected in parallel, and the fixed resistor 23 and the fixed capacitor 24 (second RC parallel circuit) connected in parallel are connected in parallel. The fixed resistor 25 and the fixed capacitor 26 (third RC parallel circuit) are connected in series. The variable resistor 21, the fixed resistor 23, and the fixed resistor 25 simulate the polarization resistance component of the zinc battery. The variable capacitor 22, the fixed capacitor 24, and the fixed capacitor 26 simulate the polarization capacitance component of the zinc battery. The resistance value and the capacitance value of the variable resistor 21 and the variable capacitor 22 are variable, and the resistance value and the capacitance value of the fixed resistors 23 and 25 and the fixed capacitors 24 and 26 are constant. In the example shown in FIG. 2, the polarization model unit 20 includes three RC parallel circuits, but the polarization model unit 20 includes at least the first RC parallel circuit (variable resistor 21 and variable capacitor 22). I just need to be there. Further, the polarization model unit 20 may include four or more RC parallel circuits.

The impedance of the polarization model unit 20 is determined by the resistance value of each resistor in the polarization model unit 20 and the capacitance value of each capacitor. If the impedance of the polarization model unit 20 is determined, when the current I (t) flows through the equivalent circuit model 40, the current I (t) also flows through the polarization model unit 20, so that the current I (t) and the polarization occur. From the impedance of the model unit 20, the voltage (polarization voltage Vpol (t)) generated in the polarization model unit 20 can be calculated. The polarization voltage Vpol is a first polarization voltage Vp1 (t) generated in the variable resistor 21 and the variable capacitor 22, a second polarization voltage Vp2 (t) generated in the fixed resistor 23 and the fixed capacitor 24, and a fixed resistor. It is the total voltage with the third polarization voltage Vp3 (t) generated in 25 and the fixed capacitor 26. That is, the following relational expression (2) is established in the polarization model unit 20.

Here, the time constant τ1 of the first RC parallel circuit is determined as a value obtained by multiplying the resistance value of the variable resistor 21 and the capacitance value of the variable capacitor 22. The time constant τ1 is reflected in the time change of the first polarization voltage Vp1 (t) generated in the variable resistor 21 and the variable capacitor 22. For example, the larger the time constant τ1, the slower the time change of the first polarization voltage Vp1 (t). Similarly, the time constant τ2 of the second RC parallel circuit is reflected in the time change of the second polarization voltage Vp2 (t) generated in the fixed resistor 23 and the fixed capacitor 24. The time constant τ3 of the third RC parallel circuit is reflected in the time change of the third polarization voltage Vp3 (t) generated in the fixed resistor 25 and the fixed capacitor 26. The time constant τ1, the time constant τ2, and the time constant τ3 may be set to different values. By including the RC parallel circuit having a plurality of different time constants, the polarization model unit 20 can more accurately represent the time change of the polarization voltage Vpol (t). Each time constant may be set, for example, so that τ1 <τ2 <τ3.

The constant voltage source 30 has a constant direct current (DC) voltage. The voltage possessed by the constant voltage source 30 is the open circuit voltage (OCV: Open Circuit Voltage) Vocv (t) of the zinc battery. The impedance of the constant voltage source 30 is 0. The open circuit voltage Vocv (t) is obtained from, for example, the SOC of the zinc battery. In that case, the open circuit voltage Vocv (t) is a function with SOC as an argument. The temperature of the zinc battery and the like may be included in the argument.

The DC resistance voltage Vdc (t) generated in the DC resistance unit 10, the polarization voltage Vpol (t) generated in the polarization model unit 20, the open circuit voltage Vocv (t) of the constant voltage source 30, and the terminal voltage described above. The following relational expression (3) is established with V (t). Using the zinc battery equivalent circuit model 40 described above, the voltage estimation device according to the embodiment estimates the terminal voltage V (t) of the zinc battery.

FIG. 3 is a diagram showing a schematic configuration of the voltage estimation device 1 according to the embodiment. The voltage estimation device 1 has an input unit 2, an SOC calculation unit 3, a parameter setting unit 4, a DC resistance calculation unit 5, a polarization calculation unit 6, an OCV calculation unit 7, and a terminal voltage calculation as its functional blocks. Including part 8.

FIG. 4 is a diagram showing an example of the hardware configuration of the voltage estimation device 1 of FIG. As shown in FIG. 4, the voltage estimation device 1 physically includes one or a plurality of CPUs (Central Processing Units) 51, a RAM (RandomAccess Memory) 52 as a main storage device, and a ROM (Read Only Memory). As a computer including 53, a communication module 54 as a data transmission / reception device, an auxiliary storage device 55 such as a hard disk and a flash memory, an input device 56 for receiving user input such as a keyboard, and an output device 57 such as a display. It is configured. Each function of the voltage estimation device 1 shown in FIG. 3 is a communication module 54 and an input device under the control of the CPU 51 by loading one or a plurality of predetermined computer software on hardware such as the CPU 51 and the RAM 52. This is realized by operating the 56 and the output device 57, and reading and writing data in the RAM 52 and the auxiliary storage device 55. Although the above description has been given as the hardware configuration of the voltage estimation device 1, the fuel consumption calculation device 90 includes a main storage device such as a CPU 51, a RAM 52 and a ROM 53, a communication module 54, an auxiliary storage device 55, an input device 56, and an output. It may be configured as a normal computer system including the device 57 and the like.

The details of each function of the voltage estimation device 1 will be described with reference to FIG. 3 again. The input unit 2 is a part for inputting a designated value (bat_demand) to the zinc battery. The specified value includes, for example, the magnitude of the charge / discharge current and the magnitude of the charge / discharge power required for the zinc battery in the fuel consumption calculation by the fuel consumption calculation device 90 described above. The input unit 2 outputs the input specified value to the DC resistance calculation unit 5. FIG. 5 is a graph conceptually showing an example of a waveform of a charge / discharge current input from the input unit 2. In FIG. 5, the horizontal axis represents time and the vertical axis represents the amount of current. The waveform shown in this example includes an engine start period A1, a constant voltage charge period A2, a constant current discharge period A3, and a rest period A4. Then, the same waveform is repeated over a plurality of cycles, with cycle A0 including these periods A1 to A5 a predetermined number of times as one cycle.

但し、ｓ＝容量（単位Ａｈ）×３６００（Ｃ／Ａｈ）である。 The SOC calculation unit 3 is a part that calculates the SOC of the zinc battery. For example, the SOC (t) of the zinc battery is calculated from the initial SOC (0) of the zinc battery and the charge / discharge current amount of the zinc battery thereafter. The initial SOC (0) value of the zinc battery is not particularly limited and may be set as appropriate. The charge / discharge current amount of the zinc battery is obtained by integrating the charge / discharge current of the zinc battery with the charge / discharge time. The SOC (t) of the zinc battery is determined based on the charge / discharge current amount of the zinc battery at time t and the full charge capacity of the zinc battery. In the calculation of the SOC (t) at time t, the current I flowing through the equivalent circuit model 40 from time 0 to time t can be used as the current flowing through the zinc battery. In this case, the SOC calculation unit 3 calculates SOC (t) by, for example, the following equation (4). The SOC calculation unit 3 outputs the calculated SOC (t) to the parameter setting unit 4, the polarization calculation unit 6, and the OCV calculation unit 7, respectively.

However, s = capacity (unit: Ah) × 3600 (C / Ah).

The parameter setting unit 4 is a part for setting the values of various characteristic parameters necessary for estimating the terminal voltage of the zinc battery. The characteristic parameters include, for example, the resistance value of the resistor 11, the coefficient included in the function of the resistance value of the resistor 12, the resistance value of the variable resistor 21, the time constant τ1, the resistance value of the fixed resistor 23, and the time constant τ2. , The resistance value of the fixed resistor 25, and the time constant τ3. Of these characteristic parameters, at least one of the resistance value of the resistor 11 and the coefficient included in the function of the resistance value of the resistor 12 is set based on the SOC of the zinc battery to be estimated. Further, at least one of the resistance value of the variable resistor 21 and the time constant τ1 may also be set based on the SOC of the zinc battery to be estimated. The correlation between these characteristic parameters and the SOC of the zinc battery is summarized as a look-up table. In the lookup table, the SOC is divided into a plurality of sections for each of the characteristic parameters, and a plurality of values corresponding to each of the plurality of sections are stored. The parameter setting unit 4 selects the value of each characteristic parameter from the above-mentioned plurality of values by referring to the look-up table. The lower limit of SOC included in the above correlation is, for example, 30%. The upper limit of SOC included in the above correlation is, for example, 70%. The number of sections of the SOC is, for example, four sections. In that case, the SOC division section is, for example, a section of 30% to 50%, a section of 50% to 55%, a section of 55% to 60%, and a section of 60% to 70%. The number of sections of the SOC is not limited to this, and may be 3 sections or less, or 5 sections or more. The section width near the center of the SOC range included in the above correlation may be reduced, and the section width may be increased as the distance from the center of the SOC range increases. Alternatively, as another method of selecting one value from a plurality of values, the value of the characteristic parameter may be calculated using a function having the SOC value as a variable. The value of each characteristic parameter may be set based on the temperature of the zinc battery. In that case, a look-up table for each parameter is prepared in consideration of the temperature of the zinc battery. The parameter setting unit 4 outputs the value of each set characteristic parameter to the DC resistance calculation unit 5 and the polarization calculation unit 6.

The DC resistance calculation unit 5 calculates the DC resistance voltage Vdc (t) generated in the DC resistance unit 10. Further, the DC resistance calculation unit 5 calculates the current I (t) flowing through the equivalent circuit model 40 from the designated value (bat_demand) input by the input unit 2. The polarization calculation unit 6 calculates the polarization voltage Vpol (t) generated in the polarization model unit 20. The OCV calculation unit 7 calculates the open circuit voltage Vocv (t). As described above, the open circuit voltage Vocv (t) is obtained from the SOC of the zinc battery. For example, a table in which the value of each SOC and the value of the open circuit voltage Vocv are associated with each other is prepared in advance. The OCV calculation unit 7 calculates the open circuit voltage Vocv (t) from the SOC (t) received from the SOC calculation unit 3 by referring to the table. The above table may be prepared for each temperature, and in that case, the open circuit voltage Vocv (t) is calculated in consideration of the temperature of the zinc battery.

The terminal voltage calculation unit 8 is a part that calculates the terminal voltage V (t) of the zinc battery. As described above, the DC resistance voltage Vdc (t) calculated by the DC resistance calculation unit 5, the polarization voltage Vpol (t) calculated by the polarization calculation unit 6, and the open circuit voltage calculated by the OCV calculation unit 7. Vocv (t) is sent to the terminal voltage calculation unit 8. The terminal voltage calculation unit 8 calculates the terminal voltage V (t) based on the DC resistance voltage Vdc (t), the polarization voltage Vpol (t), and the open circuit voltage Vocv (t). Specifically, the terminal voltage calculation unit 8 adds the DC resistance voltage Vdc (t), the polarization voltage Vpol (t), and the open circuit voltage Vocv (t) as shown in the above equation (2), and the terminal voltage calculation unit 8 adds the DC resistance voltage Vdc (t), the polarization voltage Vpol (t), and the open circuit voltage Vocv (t). Let the total voltage be the terminal voltage V (t). The terminal voltage calculation unit 8 outputs the calculated terminal voltage V (t) to the outside of the voltage estimation device 1 and to the DC resistance calculation unit 5.

Next, the calculation process (voltage estimation method) of the terminal voltage V (t) executed by the voltage estimation device 1 will be described with reference to FIG. FIG. 6 is a flowchart showing an example of the calculation process of the terminal voltage V (t) executed by the voltage estimation device 1. The processing of the flowchart shown in FIG. 6 is executed, for example, in the fuel consumption calculation of the fuel consumption calculation device 90, when estimating the terminal voltage of the zinc battery at a certain time t.

First, the input unit 2 inputs a designated value (bat_demand) (step S01). For example, the input unit 2 inputs the designated value by receiving the designated value from the external device of the voltage estimation device 1. Then, the input unit 2 outputs the input designated value to the DC resistance calculation unit 5. Then, the SOC calculation unit 3 calculates the SOC of the zinc battery (step S02). The SOC calculation unit 3 calculates SOC (t) using, for example, the above-mentioned equation (3). Then, the SOC calculation unit 3 outputs the calculated SOC (t) to the parameter setting unit 4, the polarization calculation unit 6, and the OCV calculation unit 7.

Subsequently, the parameter setting unit 4 sets each characteristic parameter of the equivalent circuit model 40 (step S03). The characteristic parameters set in step S03 are, for example, the resistance value of the resistor 11, the coefficient included in the function of the resistance value of the resistor 12, the resistance value of the variable resistor 21, the time constant τ1, and the resistance of the fixed resistor 23. The value, the time constant τ2, the resistance value of the fixed resistor 25, and the time constant τ3. As described above, the value of each characteristic parameter is set based on the SOC of the zinc battery. The parameter setting unit 4 refers to a look-up table in which the correlation between each characteristic parameter and the SOC of the zinc battery is described, and sets one value from a plurality of values as the value of each characteristic parameter according to the SOC. do. Then, the parameter setting unit 4 outputs the value of each set characteristic parameter to the DC resistance calculation unit 5 and the polarization calculation unit 6.

Subsequently, the DC resistance calculation unit 5 calculates the current I (t) and the DC resistance voltage Vdc (t) using the resistance value of the resistor 11 provided by the parameter setting unit 4 (step S04). When the charge / discharge mode is a constant current discharge mode (a mode in which a constant current flows regardless of the terminal voltage V (t)), the DC resistance calculation unit 5 is included in the specified value input by the input unit 2. The specified current is set to the current I (t). Then, the DC resistance calculation unit 5 calculates the DC resistance voltage Vdc (t) based on the current I (t). Further, the DC resistance calculation unit 5 is in the case where the charge / discharge mode is a constant voltage charging mode (a mode in which the zinc battery is charged while the output voltage of the voltage source (for example, an alternator) for charging the zinc battery is constant). First, the DC resistance voltage Vdc (t) is calculated. Then, based on this DC resistance voltage Vdc (t), the current I (t) flowing through the equivalent circuit model 40 is calculated.

Subsequently, the polarization calculation unit 6 calculates the polarization voltage Vpol (t) (step S05). Specifically, the polarization calculation unit 6 has the resistance value of the variable resistor 21 provided by the parameter setting unit 4, the time constant τ1, the resistance value of the fixed resistor 23, the time constant τ2, and the resistance value of the fixed resistor 25. , And the time constant τ3 is used to calculate the first polarization voltage Vp1 (t), the second polarization voltage Vp2 (t), and the third polarization voltage Vp3 (t). Then, the polarization calculation unit 6 sets the total value of the first polarization voltage Vp1 (t), the second polarization voltage Vp2 (t), and the third polarization voltage Vp3 (t) as the polarization voltage Vpol (t).

Subsequently, the OCV calculation unit 7 calculates the open circuit voltage Vocv (t) (step S06). For example, the OCV calculation unit 7 calculates the open circuit voltage Vocv (t) from the SOC (t) received from the SOC calculation unit 3 by referring to a table in which the value of each SOC and the value of the open circuit voltage Vocv are associated with each other. do. Then, the OCV calculation unit 7 outputs the calculated open circuit voltage Vocv (t) to the terminal voltage calculation unit 8.

Subsequently, the terminal voltage calculation unit 8 calculates the terminal voltage V (t) (step S07). Specifically, the terminal voltage calculation unit 8 has a DC resistance voltage Vdc (t) calculated by the DC resistance calculation unit 5, a polarization voltage Vpol (t) calculated by the polarization calculation unit 6, and an OCV calculation unit 7. The terminal voltage V (t) is calculated based on the calculated open circuit voltage Vocv (t). More specifically, the terminal voltage calculation unit 8 adds the DC resistance voltage Vdc (t), the polarization voltage Vpol (t), and the open circuit voltage Vocv (t) as shown in the above equation (2). The total voltage is defined as the terminal voltage V (t). Then, the terminal voltage calculation unit 8 outputs the calculated terminal voltage V (t) to the outside of the voltage estimation device 1 and to the DC resistance calculation unit 5. As described above, the calculation process of the terminal voltage V (t) at the time t is completed. The process of step S05 and the process of step S06 may be performed in parallel, or the order in which they are performed may be reversed.

Here, the parameter setting unit 4 and the parameter setting step S03 will be described in more detail. As described above, the characteristic parameters constituting the equivalent circuit model 40 are, for example, the resistance value of the resistor 11, the resistance value of the resistor 21, the time constant τ1, the resistance value of the resistor 23, the time constant τ2, and the resistor 25. The resistance value and the time constant τ3 of, but in the actual simulation, those that are more subdivided from these characteristic parameters are used. FIG. 7 is a chart showing an example of subdivided characteristic parameters. In FIG. 7, items 1 to 3 are parameters related to the resistance value of the resistor 11, item 4 is a parameter related to the resistance value of the resistor 12, and items 5 to 21 are parameters related to the time constant τ1. Items 22 to 24 are parameters related to the resistance value of the resistor 21, items 25 and 26 are parameters related to the time constant τ2, and items 27 to 30 are parameters related to the resistance value of the resistor 23. 31 and 32 are parameters related to the time constant τ3, and items 33 to 36 are parameters related to the resistance value of the resistor 25. As described above, at least one of the values of the characteristic parameters of the present embodiment is set based on the SOC of the zinc battery to be estimated. As an example, FIG. 8 is a diagram conceptually showing a lookup table showing the correlation between the values of the characteristic parameters and the SOC when the values of all the characteristic parameters are set based on the SOC. In FIG. 8, XXX represents various values of the characteristic parameter, and A _{1 to An} (n is an integer of 3 or more) represents the value of SOC.

The voltage estimation method according to the present embodiment and the effects obtained by the voltage estimation device 1 described above will be described. Patent Document 1 described above discloses a method using an equivalent circuit model of a Butler Volmer including a linear DC resistance component and a non-linear DC resistance component in order to estimate a terminal voltage of a lead battery or the like. Conventionally, when estimating the terminal voltage of a secondary battery (lithium ion battery, etc.) other than a lead battery, a polarization symmetric two-stage polarization model applying the equivalent circuit of Tebunan has been used, but the terminal of a zinc battery has been used. The present inventor considered that the estimation accuracy could be further improved by using the equivalent circuit model of Butler Volmer for voltage estimation. However, when estimating the terminal voltage of a zinc battery, the following problem arises. That is, unlike lead batteries and the like, zinc batteries are used in a wide SOC (State Of Charge) range. This is because lead-acid batteries deteriorate faster when used at a low SOC, but zinc batteries have a relatively small degree of deterioration even when used at a low SOC. When the SOC fluctuates greatly, the characteristic parameters such as the resistance value of the DC resistance component also fluctuate. Therefore, if the characteristic parameters are constant regardless of the SOC, the estimation error becomes large.

To solve this problem, in the voltage estimation method and the voltage estimation device 1 of the present embodiment, the resistance value of the resistor 11 (linear DC resistance component) and the resistance value of the resistor 12 (non-linear DC resistance component) are included in the function. At least one of the coefficients is selected from a plurality of values having different sizes depending on the SOC of the zinc battery to be estimated. In this case, at least a part of the characteristic parameters of the equivalent circuit model 40 can be changed to an appropriate size according to the fluctuating SOC. Therefore, it is possible to suppress an increase in estimation error due to a change in SOC. That is, according to the voltage estimation method and the voltage estimation device 1 of the present embodiment, the terminal voltage V (t) of the zinc battery among the secondary batteries can be estimated with high accuracy.

In the present embodiment, the resistance value of the resistor 12 (non-linear DC resistance component) is made different between the time of charging and the time of discharging. In a zinc battery, the resistance value of the nonlinear DC resistance component differs between charging and discharging. Therefore, in this case, the estimation accuracy of the terminal voltage V (t) of the zinc battery can be further improved.

As in the present embodiment, the parameter setting unit 4 has a plurality of the resistance value of the variable resistor 21 and the time constant τ1 of the RC parallel circuit at least one of them according to the SOC of the zinc battery to be estimated. You may choose from the values. In this case, the characteristics of the equivalent circuit model 40 can be made closer to the characteristics of the zinc battery, and the terminal voltage of the zinc battery can be estimated more accurately.

As in the present embodiment, the equivalent circuit model 40 does not have to include a DC resistance component based on gassing in which a capacitor and a switching element are connected in parallel. The equivalent circuit model of a lead battery includes such a DC resistance component representing gassing (see Patent Document 1). However, since gassing does not occur in the zinc battery, the estimation accuracy of the terminal voltage V (t) of the zinc battery can be further improved by excluding the capacitance component from the equivalent circuit model 40 of the zinc battery.

9 to 12 are graphs showing an example of the voltage estimation result by the equivalent circuit model 40 of the present embodiment as an example. FIG. 9 is a graph when the SOC is in the range of 30% to 50%. FIG. 10 is a graph when the SOC is in the range of 50% to 55%. FIG. 11 is a graph when the SOC is in the range of 55% to 60%. FIG. 12 is a graph when the SOC is in the range of 60% to 70%. In FIGS. 9 to 12, the graph G11 shows the estimated voltage, and the graph G12 shows the measured voltage. FIG. 13 is a graph showing an example of the voltage estimation result by the polarizable two-stage polarization model as a comparative example. In FIG. 13, the graph G21 shows the estimated voltage, and the graph G22 shows the measured voltage. In the polarizable two-stage polarization model, characteristic parameters common to all SOCs are used.

Comparing FIGS. 9 to 12 with FIG. 13, in the voltage estimation by the equivalent circuit model 40 of the present embodiment, the error of the estimated voltage with respect to the measured voltage is larger than that of the voltage estimation by the conventional polarization symmetric two-stage polarization model. You can see that it is much smaller. Specifically, the root mean square (RMS) of the estimated voltage error in FIG. 13 is 34.9 mV, whereas the RMS of the estimated voltage error in FIGS. 9 to 12 is very small, 5 to 7 mV. .. As described above, according to the present embodiment, the estimation accuracy can be significantly improved as compared with the conventional method.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the equivalent circuit model 40 can be modified according to the purpose. In the voltage estimation device 1, the calculation in the above embodiment can be appropriately changed depending on the configuration of the equivalent circuit model 40. For example, when the purpose is to improve the estimation accuracy of the portion of the terminal voltage V (t) that is affected by the DC resistance voltage Vdc (t), the configuration of the polarization model unit 20 of the equivalent circuit model 40 is carried out as described above. The configuration is not limited to the form, and any configuration may be used. For example, it may have only a parallel connection configuration of a resistor and a capacitor that simulates linear polarization impedance. In this case, in the voltage estimation device 1, the calculation regarding the resistance value of the variable resistor 21 and the capacitance value of the variable capacitor 22 and the calculation regarding the time constant τ1 may be omitted or changed as appropriate.

1 ... Voltage estimation device, 2 ... Input unit, 3 ... SOC calculation unit, 4 ... Parameter setting unit, 5 ... DC resistance calculation unit, 6 ... Polarization calculation unit, 7 ... OCV calculation unit, 8 ... Terminal voltage calculation unit, 10 ... DC resistance section, 11, 12, 21, 23, 25 ... resistor, 20 ... polarization model section, 22, 24, 26 ... capacitor, 30 ... constant voltage source, 40 ... equivalent circuit model, 51 ... CPU, 52 ... RAM, 53 ... ROM, 54 ... communication module, 55 ... auxiliary storage device, 56 ... input device, 57 ... output device, 90 ... fuel consumption calculation device, 91 ... input unit, 92 ... control unit, 93 ... output unit, A1 ... Engine start period, A2 ... constant voltage charging period, A3 ... constant current discharge period, A4 ... pause period, N ₁ ... node, N ₂ ... node, Vdc ... DC resistance voltage, Vdc1, Vdc2 ... voltage, Vocv ... open voltage, Vp1, Vp2, Vp3 ... Polarization voltage, Vpol ... Polarization voltage.

Claims (4)

It is a method of estimating the terminal voltage of a zinc battery.
It includes a step of calculating the terminal voltage based on the voltage generated in the DC resistance section, which is calculated based on the current flowing through the equivalent circuit model having the DC resistance section.
The DC resistance portion includes a linear DC resistance component and a non-linear DC resistance component that is connected in series with the linear DC resistance component and whose resistance value changes according to the current.
At least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the nonlinear DC resistance component is selected from a plurality of values according to the SOC of the zinc battery to be estimated.
A method for estimating a voltage of a zinc battery, which makes the resistance value of the nonlinear DC resistance component different between charging and discharging. The equivalent circuit model further includes a polarization model unit connected in series with the DC resistance unit.
The polarization model unit includes at least an RC parallel circuit in which a variable resistor and a variable capacitor are connected in parallel.
In the step, the terminal voltage is further calculated based on the voltage generated in the polarization model unit calculated based on the current flowing through the equivalent circuit model.
The voltage of the zinc battery according to claim 1, wherein at least one of the resistance value of the variable resistor and the time constant of the RC parallel circuit is selected from a plurality of values according to the SOC of the zinc battery to be estimated. Estimating method. The voltage estimation method for a zinc battery according to claim 1 or 2, wherein the equivalent circuit model includes a capacitor and a switching element connected in parallel and does not include a DC resistance component based on gassing. A device that estimates the terminal voltage of a zinc battery.
A parameter setting unit that sets the characteristic parameters of an equivalent circuit model having a DC resistance unit,
A terminal voltage calculation unit that calculates the terminal voltage based on the voltage generated in the DC resistance unit, which is calculated based on the current flowing through the equivalent circuit model.
Equipped with
The DC resistance portion includes a linear DC resistance component and a non-linear DC resistance component that is connected in series with the linear DC resistance component and whose resistance value changes according to the current.
The parameter setting unit has at least one of the resistance value of the linear DC resistance component and the coefficient included in the function of the resistance value of the nonlinear DC resistance component, depending on the SOC of the zinc battery to be estimated. A voltage estimator for a zinc battery that selects from the values of and makes the resistance value of the non-linear DC resistance component different between charging and discharging.

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