JP6988132B2 - Simulation method and simulation equipment - Google Patents

Description

The present invention relates to a simulation method and a simulation apparatus.

Patent Document 1 describes a battery model identification method. In this method, the current waveform input to the battery is measured using a current sensor, and the voltage waveform of the terminal voltage of the battery is measured using the voltage sensor. Then, the system identification calculation unit performs system identification of the battery model based on these current waveforms and voltage waveforms.

Japanese Unexamined Patent Publication No. 2016-3963

Currently, various power storage devices such as lead storage batteries, lithium ion batteries, and lithium ion capacitors are used as vehicle power storage devices. By combining these batteries, various types of hybrid systems have been put into practical use. For example, the so-called μHEV (Hybrid Electric Vehicle) method, in which a sub-storage device for energy regeneration during deceleration and power supply to auxiliary equipment is provided separately from the main storage device, has been particularly useful in recent years.

On the other hand, for example, in a fuel consumption simulation of a vehicle, various power sources such as an engine and a power storage device and a load are modeled, and a predetermined driving pattern is input to the model to calculate the fuel consumption. In the simulation of the power storage device included in such a fuel consumption simulation or the like, it is extremely important to accurately model the complicated power storage device configuration in the hybrid method in order to perform the simulation accurately. However, in the conventional simulation, the power storage device is modeled without considering the deterioration due to the use of the power storage device. Therefore, in order to accurately estimate the characteristics of the power storage device when it deteriorates, the characteristic parameters of the model are used. At the time of identification, there is a problem that it is necessary to prepare an actually deteriorated power storage device.

An object of the present invention is to provide a simulation method and a simulation device capable of accurately estimating the characteristics of a power storage device when it is deteriorated without actually using a deteriorated power storage device.

In order to solve the above-mentioned problems, the simulation method according to the embodiment of the present invention is a method of performing a simulation using an equivalent circuit model of a power storage device, and the equivalent circuit model is based on the current flowing through the equivalent circuit model. The equivalent circuit model contains a plurality of characteristic parameters, including the step of calculating the terminal voltage, and at least one characteristic parameter is represented by a mathematical formula containing a term representing the effect of deterioration of the power storage device.

Further, the simulation device according to the embodiment of the present invention is a device that performs simulation using an equivalent circuit model of a power storage device, and is a voltage calculation that calculates the terminal voltage of the equivalent circuit model based on the current flowing through the equivalent circuit model. The equivalent circuit model contains a plurality of characteristic parameters, and at least one characteristic parameter is expressed by a mathematical formula including a term representing the influence of deterioration of the power storage device.

In these simulation methods and simulation devices, at least one characteristic parameter is expressed by a mathematical formula including a term representing the effect of deterioration of the power storage device. This makes it possible to reflect the degree of deterioration of the power storage device in the characteristic parameters. Therefore, according to the above method and device, it is possible to accurately estimate the input / output characteristics of the power storage device at the time of deterioration without actually using the deteriorated power storage device, and the fuel consumption using the deteriorated power storage device can be estimated. Simulation etc. can be performed with high accuracy. The power storage device is, for example, a lead storage battery.

In the above simulation method, the term representing the influence of deterioration of the power storage device may include a term including a time integral of a numerical value representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integral. good. By inputting an appropriate time within the usage period (total cycle time) of the power storage device (for example, the operation time related to the numerical value indicating the operating state) in such a time function, the degree of deterioration of the power storage device after the usage period elapses. Can be reflected in the characteristic parameters. Then, according to the finding of the present inventor, the time function has a numerical time integral (that is, usage history of the power storage device) representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integration. By including it, the degree of deterioration of the power storage device can be accurately represented. Therefore, the input / output characteristics of the power storage device at the time of deterioration can be estimated with higher accuracy, and the fuel consumption simulation using the deteriorated power storage device can be performed with higher accuracy.

In the above simulation method, the numerical value representing the operating state of the power storage device may be the above current. As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of deterioration (energization deterioration) based on the total amount of current flowing through the power storage device during the period of use. In this case, the above term may further include the Depth of Discharge (DOD) multiplied by the time integral. The DOD according to the present invention is defined as DOD (%) = 100-SOC (%) (State Of Charge). As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration of the power storage device based on the DOD during the period of use.

In the above simulation method, the numerical value representing the operating state of the power storage device may be one or both of the SOC during dark current discharge and the SOC during hibernation of the power storage device. This makes it possible to more accurately estimate the input / output characteristics of the deteriorated power storage device in consideration of the influence of deterioration during dark current discharge or hibernation during the period of use.

In the above simulation method, the term representing the effect of deterioration of the power storage device includes a term including the number of specific events causing the deterioration of the power storage device and a coefficient representing the deterioration rate multiplied by the number of times. May be good. By inputting an appropriate number of specific events within the usage period (total cycle time) of the power storage device in such a section, the degree of deterioration of the power storage device after the usage period elapses is reflected in the characteristic parameter. Can be done. Then, according to the knowledge of the present inventor, the term includes the number of specific events causing deterioration of the power storage device and the coefficient representing the deterioration rate multiplied by the number of times, so that the power storage device can be used. The degree of deterioration can be expressed accurately. Therefore, the input / output characteristics of the power storage device at the time of deterioration can be estimated with higher accuracy, and the fuel consumption simulation using the deteriorated power storage device can be performed with higher accuracy.

In the above simulation method, the specific event may be a refresh charge of the power storage device. As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the refresh charging of the power storage device during the usage period.

In the above simulation method, the specific event may be a long pause of the power storage device. As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the long pause of the power storage device during the usage period.

In the above simulation method, the specific event may be the discharge of the power storage device at the time of starting the engine. Thereby, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the discharge at the time of starting the engine during the use period.

In the above simulation method, the specific event may be a dark current discharge of the power storage device. Thereby, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the dark current discharge during the use period.

In the above simulation method, the coefficient may change depending on the temperature of the power storage device. This makes it possible to accurately represent the degree of deterioration that changes according to the temperature of the power storage device.

According to the simulation method and the simulation apparatus according to the present invention, it is possible to accurately estimate the characteristics of the power storage device when it is deteriorated without actually using the deteriorated power storage device.

FIG. 1 is a diagram showing a schematic configuration of a device for performing fuel consumption simulation. FIG. 2 is a diagram showing an example of an equivalent circuit model. FIG. 3 is a diagram showing a schematic configuration of a simulation device according to an embodiment. FIG. 4 is a diagram showing an example of the hardware configuration of the simulation device of FIG. FIG. 5 is a diagram illustrating a calculation process of the terminal voltage executed by the simulation device. 6 (a) to 6 (d) are graphs conceptually showing an example of a waveform of a current flowing through a power storage device. FIG. 7 is a graph showing changes in DC resistance when the current waveforms of FIGS. 6A to 6C are input, taking a lithium ion battery as an example. FIG. 8 is a graph in which the calculated values of the time integral of the energization deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. FIG. 9 is a graph in which the calculated values of the time integral of the self-heating deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. FIG. 10 is a graph in which the calculated values of the time integral of the pause deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. 11 (a) to 11 (c) are graphs conceptually showing the state of curve fitting. FIG. 12 is a chart showing numerical examples of coefficients of each characteristic parameter. FIG. 13 compares the maximum value of the fuel consumption error between the case where the characteristic parameter of one embodiment is used for the equivalent circuit model of the power storage device and the case where the characteristic parameter that does not consider the influence of deterioration is used in the fuel consumption simulation of the vehicle. It is a graph which shows the result of this. FIG. 14 is a diagram showing a current waveform used for identification of each characteristic parameter. FIG. 15 is a graph showing an example of a fuel consumption simulation result according to one embodiment.

Hereinafter, embodiments of the simulation method and the simulation apparatus 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 current flowing through the power storage device refers to both the charge current input to the power storage device and the discharge current output from the power storage device. If the sign is negative, it indicates a discharge.

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

[Overview of fuel consumption simulation device]
FIG. 1 is a diagram showing a schematic configuration of a device for performing fuel consumption simulation. As shown in FIG. 1, the fuel consumption simulation 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 simulation. 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 of the power storage device, the configuration of the power storage device, 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 equipment and the power storage device. When the power supplied from the alternator exceeds the power consumption of the auxiliary device, a current flows from the alternator to the power storage device, and the power storage device is charged. When the power supplied from the alternator is lower than the power consumption of the auxiliary device, a current flows from the power storage device to the auxiliary device, and the power storage device is discharged. Here, the terminal voltage of the power storage device depends on the SOC of the power storage device, the magnitude of the charge / discharge current, and the like. The terminal voltage of this power storage device is estimated using, for example, an equivalent circuit model for calculating the terminal voltage of the power storage device. The details of the terminal voltage estimation will be described later. From the charge / discharge current of the power storage device and the terminal voltage of the power storage device, the control unit 92 also calculates the charge / discharge power of the power storage device for each section.

After that, the control unit 92 calculates the integrated value of the output of the engine and the charge / discharge power of the power storage device 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 in the traveling pattern input by the input unit 91. The integrated value of the charge / discharge power of the power storage device in all sections indicates the magnitude of the amount of energy that will increase or decrease in the power storage device when the vehicle travels in the travel pattern input by the input unit 91. The total energy amount of the energy amount that the engine will consume and the energy amount that will be reduced in the power storage device is the energy amount required for the vehicle of the traveling 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 power storage device is estimated. Since the accuracy of fuel consumption simulation is also improved by improving the estimation accuracy of the terminal voltage of the power storage device, for example, the simulation device (power storage device simulator) according to the embodiment is used for the purpose of improving the calculation accuracy of fuel consumption. May be good. In the following description, a single lead storage battery is used as the power storage device. The power storage device is not limited to the lead storage battery, and may be another power storage device, or may be a composite type power storage device in which a plurality of power storage devices are combined.

In the present embodiment, the simulation device estimates the terminal voltage of the power storage device by using the power storage device model for calculating the terminal voltage of the power storage device. In the present embodiment, the equivalent circuit model of the power storage device is used as the power storage device model. First, an example of an equivalent circuit model will be described with reference to FIG.

[Equivalent circuit model of power storage device]
In the example shown in FIG. 2, the equivalent circuit model 40 includes a circuit 10, a circuit 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 power storage device and provide a 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 power storage device. The node N ₁ is an anode and gives a current I (t) flowing through the power storage device. 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 circuit 10 is a DC resistance unit that simulates the DC impedance (DC resistance component) of the power storage device. The circuit 10 includes a resistor 11. The resistor 11 simulates the linear DC resistance component of the power storage device. Examples of the linear DC resistance component include the resistance of the electrode. The resistance value of the resistor 11 is a constant. The impedance of the circuit 10 is determined by the resistance value of the resistor 11 of the circuit 10. If the impedance of the circuit 10 is determined, when the current I (t) flows through the equivalent circuit model 40, the current I (t) also flows through the circuit 10, so that the current I (t) and the impedance of the circuit 10 Therefore, the voltage generated in the circuit 10 can be calculated. The voltage generated in the circuit 10 is referred to as a DC resistance voltage Vdc (t) and is shown in the figure.

The circuit 20 is a polarization model unit that simulates the polarization impedance component of the power storage device. The circuit 20 includes a resistor and a capacitor (RC parallel circuit) connected in parallel. In the example shown in FIG. 2, two RC parallel circuits are connected in series. Specifically, the resistor 21 and the capacitor 22 (first RC parallel circuit) connected in parallel and the resistor 23 and the capacitor 24 (second RC parallel circuit) connected in parallel are connected in series. There is. The resistance value of the resistor 21 and the capacitance value of the capacitor 22 constituting the first RC parallel circuit are constants. The resistor 21 simulates the first polarization resistance component of the power storage device, and the capacitor 22 simulates the first polarization capacitance component of the power storage device. The resistance value of the resistor 23 and the capacitance value of the capacitor 24 constituting the second RC parallel circuit are constants. The resistor 23 simulates the second polarization resistance component of the power storage device, and the capacitor 24 simulates the second polarization capacitance component of the power storage device.

In the example shown in FIG. 2, the circuit 20 includes the first and second RC parallel circuits, but the circuit 20 includes at least the first RC parallel circuit (resistor 21 and capacitor 22). I just need to be there. Further, the circuit 20 may include three or more RC parallel circuits.

The impedance of the circuit 20 is determined by the resistance value of each resistor in the circuit 20 and the capacitance value of each capacitor. If the impedance of the circuit 20 is determined, when the current I (t) flows through the equivalent circuit model 40, the current I (t) also flows through the circuit 20, so that the current I (t) and the impedance of the circuit 20 Therefore, the voltage generated in the circuit 20 can be calculated. The voltage generated in the circuit 20 is referred to as a polarization voltage Vpol (t) and is illustrated.

The polarization voltage Vpol is the total voltage of the voltage generated in the resistor 21 and the capacitor 22 and the voltage generated in the resistor 23 and the capacitor 24. The voltage generated in the resistor 21 and the capacitor 22 is referred to as a first polarization voltage Vp1 (t) and is shown in the figure. The voltage generated in the resistor 23 and the capacitor 24 is referred to as a second polarization voltage Vp2 (t) and is shown in the figure. That is, in the circuit 20, the following relational expression (1) is established.

Here, assuming that the time constant of the first RC parallel circuit composed of the resistor 21 and the capacitor 22 is the time constant τ1, the time constant τ1 is multiplied by the resistance value of the resistor 21 and the capacitance value of the capacitor 22. Determined as a value. The time constant τ1 is reflected in the time change of the first polarization voltage Vp1 (t) generated in the resistor 21 and the capacitor 22. For example, the larger the time constant τ1, the slower the time change of the first polarization voltage Vp1 (t). Similarly, assuming that the time constant of the second RC parallel circuit composed of the resistor 23 and the capacitor 24 is the time constant τ2, the time constant τ2 is the product of the resistance value of the resistor 23 and the capacitance value of the capacitor 24. Determined as a value. The time constant τ2 is reflected in the time change of the second polarization voltage Vp2 (t) generated in the resistor 23 and the capacitor 24. The time constants τ1 and τ2 may be set to different values. By including the RC parallel circuit having a plurality of different time constants, the circuit 20 can more accurately represent the time change of the voltage of the polarization voltage Vpol (t). Each time constant may be set, for example, so that the time constant τ1 <time constant τ2.

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) of the power storage device. The impedance of the constant voltage source 30 is 0. The open circuit voltage of the power storage device is referred to as an open circuit voltage Vocv (t) and is shown in the figure. The open circuit voltage Vocv (t) is obtained from, for example, the SOC of the power storage device. In that case, the open circuit voltage Vocv (t) is a function with SOC as an argument. The temperature of the power storage device may be included in the argument.

The DC resistance voltage Vdc (t) generated in the circuit 10 described above, the polarization voltage Vpol (t) generated in the circuit 20, the open circuit voltage Vocv (t) of the constant voltage source 30, and the terminal voltage V (t). In the meantime, the following relational expression (2) is established.

Using the equivalent circuit model 40 of the power storage device described above, the simulation device according to the embodiment estimates the terminal voltage V (t) of the power storage device.

FIG. 3 is a diagram showing a schematic configuration of a simulation device according to an embodiment. The simulation 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 unit as functional blocks thereof. Includes 8 and.

FIG. 4 is a diagram showing an example of the hardware configuration of the simulation device 1 of FIG. As shown in FIG. 4, the simulation device 1 is physically composed of one or a plurality of CPUs (Central Processing Units) 101, RAM (Random Access Memory) 102 as a main storage device, and ROM (Read Only Memory). As a computer including 103, a communication module 104 as a data transmission / reception device, an auxiliary storage device 105 such as a hard disk and a flash memory, an input device 106 for receiving user input such as a keyboard, and an output device 107 such as a display. It is configured. Each function of the simulation device 1 shown in FIG. 3 loads the communication module 104 and the input device 106 under the control of the CPU 101 by loading one or a plurality of predetermined computer software on the hardware such as the CPU 101 and the RAM 102. , And the output device 107 is operated, and the data is read and written in the RAM 102 and the auxiliary storage device 105. Although the above description has been described as the hardware configuration of the simulation device 1, the fuel efficiency simulation device 90 is a main storage device such as CPU 101, RAM 102 and ROM 103, a communication module 104, an auxiliary storage device 105, an input device 106, and an output device. It may be configured as a normal computer system including 107 and the like.

The details of each function of the simulation apparatus 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 power storage device. The specified value includes, for example, the magnitude of the charge / discharge current and the magnitude of the charge / discharge power required for the power storage device in the fuel consumption calculation by the fuel consumption simulation device 90 described above. The input unit 2 outputs the input specified value to the DC resistance calculation unit 5.

The SOC calculation unit 3 is a part that calculates the SOC of the power storage device. For example, the SOC (t) of the power storage device is calculated from the initial SOC (0) of the power storage device and the amount of charge / discharge electricity of the power storage device thereafter. The initial SOC (0) value of the power storage device is not particularly limited and may be set as appropriate. The amount of charge / discharge electricity of the power storage device is obtained by integrating the charge / discharge current of the power storage device with the charge / discharge time. The SOC (t) of the power storage device is obtained based on the amount of charge / discharge electricity of the power storage device at time t and the full charge capacity of the power storage device. 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-1 can be used as the current flowing through the power storage device. In this case, the SOC calculation unit 3 calculates SOC (t) by, for example, the following equation (3). 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.

The parameter setting unit 4 is a part for setting the values of various characteristic parameters necessary for estimating the terminal voltage of the power storage device. The characteristic parameters are, for example, the resistance value of the resistor 11 (DC resistance), the resistance value of the resistor 21 (first polarization resistance), the time constant τ1 (first polarization time constant), and the resistance value of the resistor 23 (first polarization time constant). The second polarization resistance) and the time constant τ2 (second polarization time constant). The value of each characteristic parameter may be changed according to the SOC of the power storage device.

The parameter setting unit 4 sets the value of each parameter, for example, by referring to a look-up table that describes the value of each parameter. A lookup table is provided for each parameter. The lookup table is, for example, a table in which the SOC and the value of each parameter are associated with each other. In this case, the parameter setting unit 4 acquires the value of each parameter associated with the SOC (t) received from the SOC calculation unit 3 by referring to each lookup table, and the acquired value is used for each parameter. Set to a value. It should be noted that each look-up table may be prepared for each temperature of the power storage device. In that case, the value of each parameter is further set in consideration of the temperature of the power storage device. Moreover, the value of each parameter may be predetermined. The parameter setting unit 4 outputs the value of each set parameter to the DC resistance calculation unit 5 and the polarization calculation unit 6.

The DC resistance calculation unit 5 is a part that calculates the DC resistance voltage Vdc (t) generated in the circuit 10 in the equivalent circuit model 40. Further, the DC resistance calculation unit 5 is also a part for calculating 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 is a part that calculates the polarization voltage Vpol (t) generated in the circuit 20 in the equivalent circuit model 40. The OCV calculation unit 7 is a part that calculates the open circuit voltage Vocv (t) of the power storage device. As described above, the open circuit voltage Vocv (t) is obtained from the SOC of the power storage device. 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 power storage device.

The terminal voltage calculation unit 8 is a part that calculates the terminal voltage V (t) of the power storage device. 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). The total voltage is calculated as the terminal voltage V (t). The terminal voltage calculation unit 8 outputs the calculated terminal voltage V (t) to the outside of the simulation device 1 and to the DC resistance calculation unit 5.

Next, the calculation process (simulation method) of the terminal voltage V (t) executed by the simulation device 1 will be described with reference to FIG. FIG. 5 is a flowchart showing an example of the calculation process of the terminal voltage V (t) executed by the simulation device 1. The processing of the flowchart shown in FIG. 5 is executed, for example, in the fuel consumption calculation of the fuel consumption simulation device 90, when estimating the terminal voltage of the power storage device 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 simulation 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 power storage device (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 resistance value of the resistor 21, the time constant τ1, the resistance value of the resistor 23, and the time constant τ2. The parameter setting unit 4 acquires, and acquires the value of each parameter associated with the SOC (t) received from the SOC calculation unit 3, for example, by referring to a lookup table that describes the value of each characteristic parameter. Set the value to the value of each parameter. Then, the parameter setting unit 4 outputs the set 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 power storage device is charged while the output voltage of the voltage source (for example, an alternator) for charging the power storage device 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 uses the resistance value of the resistor 21 provided by the parameter setting unit 4, the time constant τ1, the resistance value of the resistor 23, and the time constant τ2, and uses the first polarization voltage Vp1. (T) and the second polarization voltage Vp2 (t) are calculated. Then, the polarization calculation unit 6 calculates the total value of the first polarization voltage Vp1 (t) and the second polarization voltage Vp2 (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 calculated 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 simulation 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 characteristic parameters constituting the equivalent circuit model 40 will be described in detail. As described above, the equivalent circuit model 40 includes, for example, the resistance value of the resistor 11 (DC resistance), the resistance value of the resistor 21 (first polarization resistance), the time constant τ1 (first polarization time constant), and the resistance. It has a plurality of characteristic parameters such as the resistance value of the device 23 (second polarization resistance) and the time constant τ2 (second polarization time constant). Usually, these characteristic parameters are calculated without considering the deterioration due to the use of the power storage device. In that case, there is a problem that the input / output characteristics of the power storage device when deteriorated cannot be estimated accurately.

としてモデル化する。右辺の第１項Ａ₀は蓄電デバイス未使用時に対応する特性パラメータの初期値であり、右辺の第２項Ａ₁は、蓄電デバイスを或る時間使用した後における特性パラメータの変化分である。この変化分は、蓄電デバイスの劣化の影響を表す項であり、使用期間内の適切な時間、及び蓄電デバイスの劣化の原因となる特定の事象の回数を入力することによって、当該使用期間経過後に対応する劣化した特性パラメータが得られる。なお、この時間は、例えば数百時間ないし数千時間といった長さである。 Therefore, in the present embodiment, at least one characteristic parameter among the plurality of characteristic parameters is set as in the following mathematical formula (4). That is, any characteristic parameter A can be set.

Model as. The first term A _{0 on} the right side is an initial value of the characteristic parameter corresponding to when the power storage device is not used, and the second term A _{1 on} the right side is a change in the characteristic parameter after the power storage device is used for a certain period of time. This change is a term that represents the effect of deterioration of the power storage device, and by inputting an appropriate time within the usage period and the number of specific events that cause deterioration of the power storage device, after the usage period has elapsed. The corresponding degraded characteristic parameters are obtained. It should be noted that this time is, for example, a length of several hundred hours to several thousand hours.

By expressing the characteristic parameter A as in the mathematical formula (4), for example, _{by simply identifying the initial characteristic parameter A 0} using an unused power storage device, the characteristic parameter A after an arbitrary period has elapsed can be obtained by calculation. be able to.

The above item 2 A ₁ may differ depending on the type of power storage device. When the power storage device is a lead storage battery, the second term A ₁ is defined as, for example, the following formula (5). The coefficients a ₁ , a ₂ , a ₃ and a ₄ are constants, SOC ₁ (t) is the SOC during dark current discharge, and SOC ₂ (t) is the SOC during rest. These SOCs are a function of time t. K is the number of specific events that cause deterioration of the power storage device.

である。この項は、電流Ｉ（ｔ）の絶対値の時間積分と、該時間積分に乗算された係数ａ₁とを含む。この場合、電流Ｉ（ｔ）は蓄電デバイスの動作状態を表す数値であって、電流Ｉ（ｔ）の絶対値の時間積分は即ち、使用期間中に蓄電デバイスを流れる総電流量を表し、係数ａ₁は、総電流量に対する蓄電デバイスの劣化の速度を表す。従って、数式（６）で表される項は、蓄電デバイスを流れる総電流量に基づく劣化（以下、通電劣化という）を表す。なお、ｔ１は充放電時間である。また、蓄電デバイスの特性パラメータは複数あり、劣化の進行に伴ってこれらの特性パラメータの値が変化するが、通電劣化による変化分は、特性パラメータによって増加傾向の場合と減少傾向の場合とがある。従って、特性パラメータごとに係数ａ₁の符号が決定される。 _{The term A 1} shown in the formula (5) has five terms. The first term is

Is. This term includes a time integral of the absolute value of the current I (t) and a coefficient a ₁ multiplied by the time integral. In this case, the current I (t) is a numerical value representing the operating state of the power storage device, and the time integration of the absolute value of the current I (t) represents the total amount of current flowing through the power storage device during the period of use, and is a coefficient. a ₁ represents the rate of deterioration of the power storage device with respect to the total current amount. Therefore, the term represented by the mathematical formula (6) represents deterioration based on the total amount of current flowing through the power storage device (hereinafter referred to as energization deterioration). In addition, t1 is charge / discharge time. In addition, there are a plurality of characteristic parameters of the power storage device, and the values of these characteristic parameters change as the deterioration progresses. However, the change due to the energization deterioration may be increasing or decreasing depending on the characteristic parameters. .. Therefore, the sign of the coefficient a ₁ is determined for each characteristic parameter.

である。この項は、電流Ｉ（ｔ）の絶対値の時間積分と、該時間積分に乗算された係数ａ₂及び放電深度（ＤＯＤ）とを含む。ＤＯＤは、例えば定数である。或いは、ＤＯＤは時間ｔの関数であってもよく、その場合、Ｉ（ｔ）の絶対値とＤＯＤ（ｔ）との積が時間積分される。また、係数ａ₂は、ＤＯＤに対する蓄電デバイスの劣化の速度を表す。従って、数式（７）で表される項は、蓄電デバイスのＤＯＤに基づく劣化（ＤＯＤ劣化）を表す。なお、ＤＯＤ劣化による特性パラメータの変化分は、特性パラメータによって増加傾向の場合と減少傾向の場合とがある。従って、特性パラメータごとに係数ａ_２の符号が決定される。 The second term is

Is. This term includes a time integral of the absolute value of the current I (t), a coefficient a ₂ multiplied by the time integral, and a discharge depth (DOD). DOD is, for example, a constant. Alternatively, DOD may be a function of time t, in which case the product of the absolute value of I (t) and DOD (t) is time integrated. Further, the coefficient a ₂ represents the rate of deterioration of the power storage device with respect to the DOD. Therefore, the term represented by the mathematical formula (7) represents deterioration (DOD deterioration) based on the DOD of the power storage device. The amount of change in the characteristic parameter due to DOD deterioration may be increasing or decreasing depending on the characteristic parameter. Therefore, the sign of the coefficient a ₂ is determined for each characteristic parameter.

である。第３項は、ＳＯＣ₁（ｔ）の時間積分と、この時間積分に乗算された係数ａ₃とを含む。また、第４項は、ＳＯＣ₂（ｔ）の時間積分と、この時間積分に乗算された、第３項と共通の係数ａ₃とを含む。ＳＯＣ₁（ｔ）及びＳＯＣ₂（ｔ）は蓄電デバイスの動作状態を表す数値である。係数ａ₃は、暗電流放電時及び休止時の各ＳＯＣに対する蓄電デバイスの劣化の速度を表す。数式（８）で表される第３項及び第４項は、それぞれ蓄電デバイスの暗電流放電時及び休止時の各ＳＯＣに基づく劣化（暗電流放電劣化および休止劣化）を表す。暗電流放電劣化および休止劣化による特性パラメータの変化分は、特性パラメータによって増加傾向の場合と減少傾向の場合とがある。従って、特性パラメータごとに係数ａ_３の符号が決定される。なお、暗電流放電とは、車両のエンジンが停止している状態（すなわちオルタネータが発電していない状態。但し、アイドリングストップ時を除く）において、カーナビゲーションシステム及び時計などに供給される微弱な電流をいい、暗電流放電時とはこのような微弱な電流が流れている期間をいう。また、休止とは、暗電流が全く流れていない状態をいい、休止時とは休止状態である期間をいう。なお、ｔ２は暗電流放電時間であり、ｔ３は休止時間である。数式（８）においては、必要に応じて、ＳＯＣ₁（ｔ）及びＳＯＣ₂（ｔ）の各時間積分項の一方（すなわち第３項及び第４項の一方）を省略してもよい。 The third and fourth paragraphs are

Is. The third term includes _{the time integral of SOC 1} (t) and the coefficient a ₃ multiplied by this time integral. Further, the fourth term includes _{a time integral of SOC 2 (t) and a coefficient a 3} common to the third term, which is multiplied by this time integral. SOC ₁ (t) and SOC ₂ (t) are numerical values indicating the operating state of the power storage device. Coefficient a ₃ represents the rate of deterioration of the electric storage device for each SOC at the time of the dark current discharge and pause. The third and fourth terms represented by the mathematical formula (8) represent deterioration (dark current discharge deterioration and pause deterioration) based on each SOC during dark current discharge and pause, respectively. The change in the characteristic parameter due to the dark current discharge deterioration and the pause deterioration may be increasing or decreasing depending on the characteristic parameter. Therefore, the sign of the coefficient a ₃ is determined for each characteristic parameter. The dark current discharge is a weak current supplied to a car navigation system, a clock, etc. when the vehicle engine is stopped (that is, the alternator is not generating electricity, except when idling is stopped). The term "dark current discharge" refers to the period during which such a weak current is flowing. Further, the hibernation means a state in which no dark current is flowing at all, and the hibernation time means a period in which the dark current is in a hibernation state. In addition, t2 is a dark current discharge time, and t3 is a pause time. In the formula (8), _{one of the} time integration terms of SOC 1 (t) and SOC ₂ (t) (that is, one of the third term and the fourth term) may be omitted, if necessary.

In normal charging / discharging, SOC ₁ (t) = 0 and SOC ₂ (t) = 0. At the time of dark current discharge, I (t) = 0 and SOC ₂ (t) = 0. At rest, I (t) = 0 and SOC ₁ (t) = 0.

である。この項は、使用期間内における特定の事象の回数Ｋと、該回数に乗算された係数ａ₄とを含む。係数ａ₄は、特定の事象に対する蓄電デバイスの劣化の速度を表す。従って、数式（９）で表される項は、特定の事象に基づく劣化を表す。 Item 5 is

Is. This section includes a number K of a particular event within a period of use, and a coefficient a ₄ multiplied in該回number. Coefficient a ₄ represents the rate of deterioration of the electric storage device for a particular event. Therefore, the term represented by the formula (9) represents deterioration based on a specific event.

Here, examples of specific events that cause deterioration of the power storage device include refresh charging of the power storage device, long-term deactivation of the power storage device, discharge of the power storage device when the engine is started (in other words, the number of times the engine is started), and. The dark current discharge of the power storage device can be mentioned. Refresh charging is charging with SOC = 100 (%), and means charging with a voltage higher than the normal charging voltage. If the number K is refresh charge number of the power storage device, the coefficient a ₄ represents the speed of the electric storage device caused by the refresh charge degradation. Therefore, the term represented by the mathematical formula (9) represents the deterioration of the power storage device based on the refresh charge. Further, the pause of the power storage device refers to a state in which the charging current and the discharging current do not flow at all, and the long-term pause refers to the case where the charging current and the discharging current are paused for, for example, 48 hours or more. If the number K is a long number of pauses of the electric storage device, the coefficient a ₄ represents the rate of deterioration of the electric storage device due to the long rest. Therefore, the term represented by the mathematical formula (9) represents the deterioration of the power storage device due to the long pause. Further, the discharge of the power storage device at the time of starting the engine mainly refers to the discharge of the power storage device for rotating the starter motor at the time of starting the engine. If the number K is a number of discharge at the time of starting the engine, the coefficient a ₄ represents the rate of deterioration of the electric storage device caused by discharge at the time of starting the engine. Therefore, the term represented by the mathematical formula (9) represents the deterioration of the power storage device due to the discharge at the time of starting the engine. Also, if the number K is a number of dark current discharge of the electric storage device, the coefficient a ₄ represents the speed of the electric storage device due to dark current discharge deterioration. Therefore, the term represented by the mathematical formula (9) represents the deterioration of the power storage device due to the dark current discharge.

In the right side of the above formula (5), only one specific event that causes deterioration of the power storage device is considered (only one term including the number of times K is included), but the specific event. A plurality of terms including the number of times may be included. For example. The right side may be included.

Further, the electric storage device may be a lithium ion battery, the second term A ₁ Equation (4) is defined as for example, the following equation (10).

である。この項は、電流Ｉ（ｔ）の絶対値の時間積分と、該時間積分に乗算された係数ａ₂と、該時間積分に乗算された自己発熱とを含む。すなわち、次の数式（１４）によって表される時間τの関数Ｔは、蓄電デバイスの自己発熱を表す。

自己発熱Ｔは、数式（１２）に示されるように、電流Ｉ（τ）の二乗の時間積分によって求められる。また、係数ａ₂は、自己発熱Ｔに対する蓄電デバイスの劣化の速度を表す。従って、数式（１１）で表される項は、蓄電デバイスの自己発熱に基づく劣化（以下、自己発熱劣化という）を表す。 _{The term A 1} shown in the formula (10) has three terms. The first term is an energization deterioration term. The second term is

Is. This term includes a time integral of the absolute value of the current I (t), a coefficient a ₂ multiplied by the time integral, and self-heating multiplied by the time integral. That is, the function T of the time τ represented by the following mathematical formula (14) represents the self-heating of the power storage device.

The self-heating T is obtained by the time integration of the square of the current I (τ) as shown in the equation (12). Further, the coefficient a ₂ represents the rate of deterioration of the power storage device with respect to the self-heating T. Therefore, the term represented by the mathematical formula (11) represents deterioration based on self-heating of the power storage device (hereinafter referred to as self-heating deterioration).

である。この項は、休止時のＳＯＣ₂（ｔ）の時間積分と、該時間積分に乗算された係数ａ₃とを含む。これらの意味付けは、前述した鉛蓄電池の場合の第４項と同様である。すなわち、この項は休止劣化項である。 The third term is

Is. This section includes a time integral of the SOC ₂ (t) at rest, the coefficient a ₃ multiplied to said time integration. These meanings are the same as those in the fourth item in the case of the lead storage battery described above. That is, this term is a dormant deterioration term.

In the above example, the dark current discharge deterioration term exists in the formula (8), but the same dark current discharge deterioration term does not exist in the formula (13). It is due to the following reasons. For example, when a single power storage device is used, there is always a period in which dark current flows even if the engine of the vehicle is stopped. Examples of such a single power storage device include a lead storage battery. On the other hand, when the main power storage device and the sub power storage device are used as in the μHEV method, it is conceivable that the dark current is supplied only from the main power storage device and the dark current is not supplied from the sub power storage device. In such a situation, no dark current state occurs in the sub-storage device. Lithium-ion batteries are often used as such sub-storage devices. Therefore, the dark current discharge deterioration term is omitted in the mathematical formula (13).

数式（１４）に示される項Ａ₁は、３つの項を有している。第１項は通電劣化項である。第２項はＤＯＤ劣化項である。第３項は休止劣化項である。ニッケル亜鉛電池もまた、上述したリチウムイオン電池と同様に、サブ蓄電デバイスとして用いられることが多い。従って、数式（１４）においては暗電流放電劣化項が省略されている。 Further, the electric storage device be a nickel-zinc battery, the second term A ₁ Equation (4) is defined as for example, the following equation (14).

_{The term A 1} shown in the formula (14) has three terms. The first term is an energization deterioration term. The second term is a DOD deterioration term. The third term is a dormant deterioration term. Nickel-zinc batteries are also often used as sub-storage devices, similar to the lithium-ion batteries described above. Therefore, the dark current discharge deterioration term is omitted in the mathematical formula (14).

Here, the calculation method of the coefficients a ₁ , a ₂ , and a _{3 described above will be described.} Three different model equations are required to calculate the _three coefficients a ₁ , a ₂ , and a 3. Therefore, three currents I (t) having different time waveforms are input to the characteristic parameter equations to formulate three model equations, and the coefficients a ₁ , a ₂ , and a ₃ are obtained based on them. 6 (a) to 6 (c) are graphs conceptually showing an example of such a waveform of the current I (t). In these figures, the vertical axis represents the current I (t) and the horizontal axis represents time. These current waveforms include a constant voltage charge period Ta, a constant current discharge period Tb, and a rest period Tc. FIG. 6A shows a case where the current in the constant voltage charging period Ta is relatively large, and the constant current discharging period Tb becomes longer by the larger charging current. FIG. 6B shows a case where the current in the constant voltage charging period Ta is relatively small, and the constant current discharging period Tb is shortened by the smaller charging current. FIG. 6 (c) shows a case where the rest period Tc is longer than that in FIGS. 6 (a) and 6 (b).

FIG. 7 shows the DC resistance (resistance value of the resistor 11 in FIG. 2) among a plurality of characteristic parameters when the current waveforms of FIGS. 6 (a) to 6 (c) are input using a lithium ion battery as an example. It is a graph which shows the change. The vertical axis represents DC resistance (unit: mΩ), and the horizontal axis represents total cycle time (use time, unit: time). Further, in the figure, the diamond-shaped plot P1 shows the case where the current waveform shown in FIG. 6A is input, and the square plot P2 shows the case where the current waveform shown in FIG. 6B is input. Shown, the triangular plot P3 shows the case where the current waveform shown in FIG. 6 (c) is input. As shown in FIG. 7, it can be seen that when the waveform of the input current I (t) is different, the deterioration of the DC resistance (A _{1 in the mathematical formula (4)) changes accordingly.}

FIG. 8 is a graph in which the calculated values of the time integral of the energization deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. FIG. 9 is a graph in which the calculated values of the time integral of the self-heating deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. FIG. 10 is a graph in which the calculated values of the time integral of the pause deterioration term corresponding to the current waveforms of FIGS. 6 (a) to 6 (c) are plotted. In FIGS. 8 to 10, the vertical axis represents the time integral value, and the horizontal axis represents the total cycle time (unit: time). Further, in these figures, the diamond-shaped plot P4 shows the numerical value when the current waveform shown in FIG. 6 (a) is input, and the square plot P5 shows the current waveform shown in FIG. 6 (b). The value when the current waveform is input is shown, and the triangular plot P6 shows the value when the current waveform shown in FIG. 6 (c) is input.

As shown in FIGS. 8 to 10, the value of the time integral in each of the energization deterioration term, the self-heating deterioration term, and the pause deterioration term is calculated based on the current waveforms of FIGS. 6 (a) to 6 (c). Will be done. Therefore, to create a three functions independent of each other containing the coefficients a _1, a _2, a ₃ as a variable, by performing optimization by curve fitting the experimental values to determine the coefficients a _1, a _2, a ₃ be able to. 11 (a) to 11 (c) are graphs conceptually showing the state of curve fitting. 11 (a) to 11 (c) show the fitting of the functions of _{a 1} , a ₂ , and a ₃ obtained from the current waveforms of FIGS. 6 (a) to 6 (c) and the experimental values, respectively. Is shown. The plots P7 to P9 in the figure are experimental values, and the curves R1 to R3 are estimated values from the function.

FIG. 12 is a chart showing numerical examples of _{the coefficients a 1} , a ₂ , and a ₃ of each characteristic parameter obtained by the above-mentioned method. As shown in FIG. 12, the coefficients a ₁ , a ₂ , and a ₃ are preferably obtained by the above-mentioned method. In addition, in FIG. 12, the fitting error (%) is also shown. The error between the first polarization resistance and the second polarization resistance is relatively large, which is considered to be due to the fact that the test period is short and the degree of deterioration is small.

In addition to the coefficients a ₁ , a ₂ , and a ₃ , four different model formulas are required to calculate the coefficient a _4. Therefore, it is advisable to input four currents I (t) having different time waveforms into the characteristic parameter equations to formulate four model equations, and to obtain the coefficients a ₁ , a ₂ , a ₃ , and a _{4 based on them.} .. For example, FIG. 6D is a graph conceptually showing an example of a waveform of a current I (t) in which a discharge waveform (period Td) at the time of starting an engine is added to FIG. 6A. The current waveform shown in FIG. 6D is used to calculate the _{coefficient a 4} when the number K is the number of discharges at the time of engine start (the number of engine starts). In order to calculate the coefficients a ₁ , a ₂ , a ₃ , and a ₄ , the current waveform of FIG. 6 (d) is used in addition to the current waveforms of FIGS. 6 (a) to 6 (c) described above. good.

The simulation method according to the present embodiment described above and the effects obtained by the simulation apparatus 1 will be described. In the simulation method and simulation apparatus 1 of the present embodiment, as shown in the mathematical formula (4), at least one characteristic parameter A is represented by a mathematical formula including _{a term A 1 representing the influence of deterioration of the power storage device.} Thereby, the degree of deterioration of the power storage device after the lapse of the usage period can be reflected in the characteristic parameter A. Therefore, according to the present embodiment, it is possible to accurately estimate the input / output characteristics of the power storage device at the time of deterioration without actually using the deteriorated power storage device, and the fuel consumption simulation using the deteriorated power storage device can be performed. Can be performed with high accuracy.

Further, as in the present embodiment, the term A ₁ representing the influence of deterioration of the power storage device includes a time integral of a numerical value representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integral. May have. By inputting an appropriate time within the usage time (total cycle time) of the power storage device (for example, the operation time related to the numerical value indicating the operating state) in such a term, the degree of deterioration of the power storage device after the usage period has elapsed can be determined. It can be reflected in the characteristic parameters. Then, the present inventor finds that the term A ₁ is a coefficient representing the deterioration rate (for example, a ₁ , a ₂ , a ₃ or the like) and a numerical value representing the operating state of the power storage device (for example, current I (t), SOC _1). By including a term (for example, mathematical formulas (6) to (8), (11) to (13)) multiplied by the time integral of (t), SOC _{2 (t), etc.), that is, the usage history of the power storage device.} It has been found that the degree of deterioration of the power storage device can be accurately expressed.

FIG. 13 shows a case where the characteristic parameters of the present embodiment are used for the equivalent circuit model of the lithium ion battery in the fuel consumption simulation of the vehicle (graph G11), and the characteristic parameters that do not consider the influence of deterioration (that is, the right side of the mathematical formula (4)). It is a graph which shows the result of having compared the maximum value of the fuel consumption error in the case of using (the thing without the item 2 A _{1) (graph G12).} In FIG. 13, the vertical axis represents the maximum value (unit:%) of the fuel consumption error, and the horizontal axis represents the test period (unit: day). The current waveform shown in FIG. 14 was used as the current I (t) used for identifying the initial value of the characteristic parameter (that is, the first term A _{0 on the right side of the equation (4)).} This current waveform repeats the first to third periods TA to TC including the constant voltage charging period T1, the constant current discharging period T2 after the constant voltage charging period T1, and the cranking period T3 after the constant current discharging period T2. Includes. The voltage value of the constant voltage charging period T1 in the first to third periods TA to TC is constant at 14 (V), and the time of the constant current discharge period T2 and the cranking period T3 is 59 seconds and 1 respectively. It is constant in seconds. The current values in the first to third periods TA to TC are as follows.
<First period TA>
Constant voltage charging period T1: 100 (A)
Constant current discharge period T2: -20 (A)
Cranking period T3: -300 (A)
<Second period TB>
Constant voltage charging period T1: 200 (A)
Constant current discharge period T2: -45 (A)
Cranking period T3: -300 (A)
<Third period TC>
Constant voltage charging period T1: 50 (A)
Constant current discharge period T2: -10 (A)
Cranking period T3: -300 (A)

The maximum value of the fuel consumption error is the maximum value of the difference between the result of the fuel consumption simulation using the equivalent circuit model including the characteristic parameters and the actually measured fuel consumption. Here, there are innumerable combinations of characteristic parameter values in which the voltage error (difference between the measured value of the terminal voltage of the power storage device and the estimated value of the terminal voltage by the model) at the time of extracting the characteristic parameter of the power storage device is the same value. Even if the voltage error value is the same, the fuel consumption calculation result differs depending on the combination of the characteristic parameter values. The above-mentioned "maximum value" means a value of the maximum fuel consumption error among the calculated fuel consumption errors by preparing a plurality of combinations of characteristic parameter values having the same voltage error and calculating the fuel consumption error with each combination.

As shown in FIG. 13, the longer the test period is, the larger the fuel consumption error becomes. However, if the influence of deterioration is not taken into consideration, the maximum value of the fuel consumption error exceeds 0.3% after the test period exceeds 60 days. ing. On the other hand, in the present embodiment in consideration of the influence of deterioration, the maximum value of the fuel consumption error is within 0.05% even if the test period exceeds 60 days. As described above, according to the method and apparatus of the present embodiment, the longer the test period, the more accurately the deterioration state of the power storage device can be reflected in the fuel consumption simulation result.

The fuel consumption simulation result according to the present embodiment can be applied to, for example, the selection of the capacity of the power storage device adopted in the vehicle. In general, the fuel efficiency of a vehicle improves as the capacity of the power storage device mounted on the vehicle increases. On the other hand, as the years have passed since the start of use, the performance of the power storage device deteriorates and the fuel consumption of the vehicle decreases. In the past, it was unclear how much the performance deteriorated due to the deterioration of the power storage device in the simulation, so the power storage device capacity having a sufficient margin was selected from the power storage device capacity selected from the fuel consumption simulation result. With such a selection method, the capacity of the power storage device tends to be larger than necessary, which may hinder the reduction of vehicle cost.

In response to such a problem, the simulation method and the simulation device 1 of the present embodiment can perform a simulation according to the degree of deterioration of the power storage device, so that the fuel consumption simulation in consideration of the number of years from the start of use can be accurately performed. Can be done. Therefore, it is possible to accurately select the capacity of the power storage device that can satisfy the predetermined fuel consumption conditions based on the estimated fuel consumption after a predetermined number of years.

FIG. 15 is a graph showing an example of the fuel consumption simulation result according to the present embodiment. In FIG. 15, the vertical axis represents fuel consumption (unit: km / l), and the horizontal axis represents years of use (unit: year). Further, the diamond-shaped plot P10, the square plot P11, and the triangular plot P12 in the figure show the case where the initial capacity of the power storage device is 3Ah, 5Ah, and 7Ah, respectively. As shown in FIG. 15, the fuel efficiency of the vehicle is better as the capacity of the power storage device is larger, but the fuel efficiency of the vehicle decreases as the number of years of use increases. Therefore, for example, when it is desired to set the fuel consumption to 30 (km / l) or more after 5 years of use, it can be seen from this graph that the initial capacity of the power storage device mounted on the vehicle should be 5 Ah. As described above, according to the present embodiment, it is possible to accurately select the capacity of the power storage device that can satisfy the predetermined fuel consumption condition based on the estimated fuel consumption after a predetermined number of years.

The selection of the storage device capacity is not limited to the case where the estimated fuel consumption is used as a reference. According to the present embodiment, it is possible to accurately select a power storage device capacity that can satisfy a predetermined condition based on the estimation characteristics of the power storage device after a predetermined number of years.

Further, as in the present embodiment, the numerical value that represents the operating state of the power storage device and is time-integrated may be the current I (t) flowing through the equivalent circuit model (for example, mathematical formula (6), mathematical formula (7), See formula (12)). As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of deterioration (energization deterioration) based on the total amount of current flowing through the power storage device during the period of use. In this case, the term obtained by multiplying the coefficient by the time integral may further include the DOD multiplied by the time integral (see, for example, equation (7)). As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration of the power storage device based on the DOD during the period of use.

Further, as in the present embodiment, the numerical values that represent the operating state of the power storage device and are time-integrated are the SOC at the time of dark current discharge (that is, the SOC ₁ (t) of the mathematical formula (8)) and the SOC at the time of rest (that is, the SOC). It may be one or both of the formula (8) and the SOC ₂ (t) of the formula (13) (see, for example, the formula (8) and the formula (13)). As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of deterioration during dark current discharge or hibernation.

Further, as in the present embodiment, the item A ₁ representing the influence of deterioration of the power storage device includes the number of specific events causing the deterioration of the power storage device and the coefficient representing the deterioration rate multiplied by the number of times. May have a term. By inputting an appropriate number of specific events within the usage period (total cycle time) of the power storage device in such item A _{1, the degree of deterioration of the power storage device after the usage period elapses is reflected in the characteristic parameter.} Can be made to. Then, the inventor of the present invention includes the term A _{1 including} the number of times K of a specific event causing deterioration of the power storage device and the coefficient a _{4 representing the deterioration rate multiplied by the number of times K.} It was found that the degree of deterioration of can be accurately expressed.

Further, as in the present embodiment, the specific event that causes deterioration of the power storage device may be refresh charging of the power storage device. As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the refresh charging of the power storage device during the usage period.

Further, as in the present embodiment, the specific event that causes the deterioration of the power storage device may be a long-term pause of the power storage device. As a result, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the long pause of the power storage device during the usage period.

Further, as in the present embodiment, the specific event that causes the deterioration of the power storage device may be the discharge of the power storage device at the time of starting the engine. Thereby, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the discharge at the time of starting the engine during the use period.

Further, as in the present embodiment, the specific event that causes the deterioration of the power storage device may be the dark current discharge of the power storage device. Thereby, the input / output characteristics of the deteriorated power storage device can be estimated more accurately in consideration of the influence of the deterioration caused by the dark current discharge of the power storage device during the usage period.

(Modification example)
In the above embodiment _{, the relationship between the coefficients a 1} , a ₂ , a ₃ , and a ₄ and the temperature of the power storage device is not described. That is, the coefficients a ₁ , a ₂ , a ₃ , and a ₄ may be constant regardless of the temperature of the power storage device. However, in many cases, the values of the suitable coefficients a ₁ , a ₂ , a ₃ , a ₄ depend on the temperature of the power storage device. Therefore, the coefficients a ₁ , a ₂ , a ₃ , and a ₄ may change depending on the temperature of the power storage device. This makes it possible to accurately represent the degree of deterioration that changes according to the temperature of the power storage device.

Specifically, the coefficients a ₁ , a ₂ , a ₃ , and a ₄ may be the functions a ₁ (TH), a ₂ (TH), a ₃ (TH), and a ₄ (TH) of the temperature TH. _{Alternatively, different coefficients a 1} , a ₂ , a ₃ , and a ₄ may be set for each of a plurality of temperatures. Therefore, when optimizing by curve fitting with the experimental value, it is preferable to acquire the experimental value while changing the temperature of the power storage device.

The simulation method and simulation apparatus according to the present invention are not limited to the above-described embodiments and modifications, and various other modifications are possible. For example, in the above-described embodiment, the current I (t) flowing through the power storage device, the SOC ₁ (t) during dark current discharge, and the SOC _{2 during hibernation are the numerical values that represent the operating state of the power storage device and are time-integrated.} Although t) has been exemplified, various numerical values other than these can be adopted as the numerical values in the present invention as long as they represent the operating state of the power storage device. For example, the terminal voltage of the power storage device may be used as a numerical value _{instead of SOC 1} (t) and SOC _{2 (t).} In addition, as examples of specific events that cause deterioration of the power storage device, refresh charging of the power storage device, long-term deactivation, discharge at engine start, and dark current discharge are shown, but the specific events are not limited to these. It can be various events that cause deterioration of the power storage device.

1 ... Simulation 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, 20 ... Circuit, 11,1,23 ... Resistor, 22,24 ... Capacitor, 30 ... Constant voltage source, 40 ... Equivalent circuit model, 90 ... Fuel simulation device, 91 ... Input unit, 92 ... Control unit, 93 ... Output Department, N ₁ , N ₂ ... Node.

Claims (12)

It is a method of performing a simulation using an equivalent circuit model of a power storage device.
Including the step of calculating the terminal voltage of the equivalent circuit model based on the current flowing through the equivalent circuit model.
The equivalent circuit model contains multiple characteristic parameters.
At least one of the characteristic parameters is expressed by a mathematical expression containing a term representing the effect of deterioration of the power storage device.
A simulation method , wherein a term representing the effect of deterioration of the power storage device includes a term including a time integral of a numerical value representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integral. It is a method of performing a simulation using an equivalent circuit model of a power storage device.
Including the step of calculating the terminal voltage of the equivalent circuit model based on the current flowing through the equivalent circuit model.
The equivalent circuit model contains multiple characteristic parameters.
At least one of the characteristic parameters is expressed by a mathematical expression containing a term representing the effect of deterioration of the power storage device.
A simulation method , wherein a term representing the effect of deterioration of the power storage device includes a term including the number of specific events causing the deterioration of the power storage device and a coefficient representing the deterioration rate multiplied by the number of times. The second aspect of claim 2, wherein the term representing the influence of deterioration of the power storage device includes a term including a time integral of a numerical value representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integral. Simulation method. The simulation method according to claim 1 or 3 , wherein the numerical value representing the operating state of the power storage device is the current. The simulation method according to claim 2 , wherein the specific event is refresh charging of the power storage device. The simulation method according to claim 2 , wherein the specific event is a long-term pause of the power storage device. The simulation method according to claim 2 , wherein the specific event is a discharge of the power storage device when the engine is started. The simulation method according to claim 2 , wherein the specific event is a dark current discharge of the power storage device. The simulation method according to any one of claims 1 to 8 , wherein the coefficient changes according to the temperature of the power storage device. The simulation method according to any one of claims 1 to 9 , wherein the power storage device is a lead storage battery. A device that performs simulations using an equivalent circuit model of a power storage device.
Includes a voltage calculator that calculates the terminal voltage of the equivalent circuit model based on the current flowing through the equivalent circuit model.
The equivalent circuit model contains multiple characteristic parameters.
At least one of the characteristic parameters is expressed by a mathematical expression containing a term representing the effect of deterioration of the power storage device.
A simulation apparatus , wherein a term representing the influence of deterioration of the power storage device includes a term including a time integral of a numerical value representing the operating state of the power storage device and a coefficient representing the deterioration rate multiplied by the time integral. A device that performs simulations using an equivalent circuit model of a power storage device.
Includes a voltage calculator that calculates the terminal voltage of the equivalent circuit model based on the current flowing through the equivalent circuit model.
The equivalent circuit model contains multiple characteristic parameters.
At least one of the characteristic parameters is expressed by a mathematical expression containing a term representing the effect of deterioration of the power storage device.
A simulation apparatus , wherein a term representing the effect of deterioration of the power storage device includes a term including a number of specific events causing deterioration of the power storage device and a coefficient representing a deterioration rate multiplied by the number of times.

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