JP6737023B2 - Simulation method and simulation device - Google Patents

Description

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

Patent Document 1 describes a battery model identification method. In this method, the current waveform input to the battery is measured using the 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 waveform and voltage waveform.

JP, 2016-3963, A

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

On the other hand, in a fuel consumption simulation of a vehicle, for example, various power sources and loads such as an engine and a power storage device are modeled, and a prescribed traveling pattern is input to the model to calculate fuel consumption. In the simulation of the electricity storage device included in such a fuel consumption simulation, it is extremely important to accurately model the complicated electricity storage device configuration in the hybrid system in order to perform the simulation accurately. However, in the conventional simulation, the electricity storage device is modeled without considering the deterioration due to the use of the electricity storage device. Therefore, in order to accurately estimate the characteristics of the electricity storage device when it deteriorates, the characteristic parameters of the model are set. There is a problem that it is necessary to prepare an actually deteriorated power storage device for identification.

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

A simulation method according to an embodiment of the present invention is a method of performing simulation using an equivalent circuit model of an electricity storage device, including a step of calculating a terminal voltage of the equivalent circuit model based on a current flowing through the equivalent circuit model, The equivalent circuit model includes a plurality of characteristic parameters, at least one characteristic parameter includes a time function representing the influence of deterioration of the electricity storage device, and the time function is the SOC and the pause during dark current discharge of the electricity storage device. It has a term including a time integral of one or both of SOC of time and a coefficient representing a deterioration rate multiplied by the time integral.

A simulation device according to an embodiment of the present invention is a device that performs simulation using an equivalent circuit model of an electricity storage device, and is a voltage calculation device that calculates a terminal voltage of the equivalent circuit model based on a current flowing through the equivalent circuit model. Part, the equivalent circuit model includes a plurality of characteristic parameters, at least one characteristic parameter includes a time function representing the influence of deterioration of the electricity storage device, the time function is the dark current discharge of the electricity storage device Of SOC and/or SOC at rest, and a term including a time integration of the SOC and a coefficient representing the deterioration rate multiplied by the time integration.

In these simulation methods and simulation devices, at least one characteristic parameter includes a time function representing the influence of deterioration of the power storage device. By inputting an appropriate time (for example, an operating time relating to a numerical value indicating an operating state) within the usage period (total cycle time) of the power storage device to such a time function, the degree of deterioration of the power storage device after the usage time elapses. Can be reflected in the characteristic parameter. According to the knowledge of the inventor of the present invention, the degree of deterioration of the power storage device greatly changes depending on the SOC during dark current discharge or at rest. In the above method and apparatus, the time function includes a term that is obtained by multiplying a coefficient indicating a deterioration rate by a time integral of one or both of SOC during dark current discharge of the electricity storage device and SOC during rest. This makes it possible to accurately represent the degree of deterioration based on the SOC of the electricity storage device during dark current discharge or at rest. Therefore, according to the method and apparatus described above, it is possible to accurately estimate the input/output characteristics of the power storage device when the power storage device deteriorates without using the power storage device that actually deteriorates, and the fuel consumption using the deteriorated power storage device can be estimated. A simulation or the like can be performed accurately. The power storage device is, for example, a lead storage battery.

In the above simulation method, the coefficient may change according to 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 of the present invention, it is possible to accurately estimate the characteristics of the storage device when it deteriorates, without using the storage device that actually deteriorates.

FIG. 1 is a diagram showing a schematic configuration of a device that performs a 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 the simulation apparatus according to the embodiment. FIG. 4 is a diagram showing an example of the hardware configuration of the simulation apparatus of FIG. FIG. 5 is a diagram illustrating a terminal voltage calculation process executed by the simulation apparatus. FIG. 6A to FIG. 6C are graphs conceptually showing examples of the waveform of the current flowing through the electricity storage device. FIG. 7 is a graph showing a change in DC resistance when the current waveforms of FIGS. 6A to 6C are input using a lithium ion battery as an example. FIG. 8 is a graph in which the calculated values of the time integration of the energization deterioration term are plotted, which correspond to the current waveforms of FIGS. 6(a) to 6(c). FIG. 9 is a graph in which the calculated values of the time integration of the self-heating deterioration term corresponding to the current waveforms of FIGS. 6A to 6C are plotted. FIG. 10 is a graph in which the calculated values of the time integration of the pause deterioration term are plotted, which correspond to the current waveforms of FIGS. 6(a) to 6(c). 11A to 11C are graphs conceptually showing the state of curve fitting. FIG. 12 is a chart showing a numerical example of the coefficient of each characteristic parameter. FIG. 13 compares the maximum value of the fuel consumption error between the case where the characteristic parameter of the embodiment is used for the equivalent circuit model of the electricity 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. FIG. 14 is a diagram showing a current waveform used to identify each characteristic parameter. FIG. 15 is a graph showing an example of a fuel consumption simulation result according to one embodiment.

Hereinafter, embodiments of a simulation method and a 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 will be denoted by the same reference symbols, without redundant description. In the following description, the current flowing through the electricity storage device refers to both the charging current input to the electricity storage device and the discharging current output from the electricity storage device, and when the sign of the current is positive, it represents charging, If the sign is negative, it represents a discharge.

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

[Outline of fuel consumption simulation device]
FIG. 1 is a diagram showing a schematic configuration of a device that performs a 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 the input data is a traveling pattern of the vehicle. In addition to the above, parameters that determine the characteristics of various devices such as an engine mounted on a vehicle, types of control methods for charging and discharging the power storage device, configuration of the power storage device, power consumption of auxiliary devices mounted on the vehicle, and vehicle Data such as the weight of the can be entered.

The control unit 92 uses the data input by the input unit 91 to perform a fuel consumption simulation. The specific method of fuel consumption simulation is not particularly limited, but, for example, the following procedure is performed.

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 example, for each section based on the traveling pattern input by the input unit 91. To calculate. The sections include a stop section, an acceleration section, a constant speed traveling section, and a deceleration section. The required power is relatively large in the acceleration section and relatively small in the constant speed traveling section. The required power may be 0 in the stop section and the deceleration section. The current consumption of the auxiliary machine differs depending on the type of the auxiliary machine. For example, the amount of current consumption of an auxiliary device that is continuously used, such as an audio device, is substantially 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, increases only when it is used.

Next, the control unit 92 calculates the output of the engine for each section. The output of the engine is, for example, 0 when the engine is stopped in the stop section and is 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 machinery and the power storage device. When the electric power supplied from the alternator exceeds the power consumption of the auxiliary machine, 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 falls below 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 the power storage device is estimated using, for example, an equivalent circuit model for calculating the terminal voltage of the power storage device. Details of the estimation of the terminal voltage will be described later. The control unit 92 also calculates charge/discharge power of the power storage device for each section from the charge/discharge current of the power storage device and the terminal voltage of the power storage device.

After that, the control unit 92 calculates the integrated value of the output of the engine and the charging/discharging power of the power storage device in all the sections. The integrated value of the output of the engine in all the sections indicates the amount of energy that the engine will consume when the vehicle travels in the travel pattern input by the input unit 91. The integrated value of the charging/discharging power of the power storage device in all the sections indicates the amount of energy that will increase or decrease in the power storage device when the vehicle travels in the travel pattern input by input unit 91. The total energy amount of the energy amount that the engine will consume and the energy amount that will decrease in the power storage device will be the energy amount required for the vehicle to travel in the traveling pattern input by the input unit 91. Since the traveling distance of the vehicle can be known from the traveling pattern, the control unit 92 calculates the travelable distance per predetermined energy amount as the fuel consumption based on the traveling distance and the energy amount required for the traveling distance.

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 or the like input by the input unit 91 is 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 improved by improving the estimation accuracy of the terminal voltage of the power storage device, the simulation device (power storage device simulator) according to the embodiment is used for the purpose of improving the calculation accuracy of fuel consumption. Good. In the following description, a single lead storage battery is used as the electricity storage device. The power storage device is not limited to the lead storage battery, and may be another power storage device or a composite type power storage device in which a plurality of power storage devices are combined.

In the present embodiment, the simulation apparatus 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, an equivalent circuit model of a power storage device is used as the power storage device model. First, an example of the 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 which are connected in series between the nodes N ₁ and N _{2 having} opposite polarities.

The nodes N ₁ and N ₂ are parts electrically connected to elements outside the power storage device, and give 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. It should be noted that (t) or the like may be attached to a code indicating a time-varying physical quantity such as a voltage and a current, but the physical quantity shown in this way means a value of the physical quantity at time t. Moreover, the time t is an integer of 0 or more, and indicates the elapsed time from the start time of 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 electricity storage device. An example of the linear DC resistance component is 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. Therefore, the current I(t) and the impedance of the circuit 10 are From this, 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 illustrated.

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 forming the first RC parallel circuit are constants. The resistor 21 simulates the first polarization resistance component of the electricity storage device, and the capacitor 22 simulates the first polarization capacitance component of the electricity storage device. The resistance value of the resistor 23 and the capacitance value of the capacitor 24 that form the second RC parallel circuit are constants. The resistor 23 simulates the second polarization resistance component of the electricity storage device, and the capacitor 24 simulates the second polarization capacitance component of the electricity storage device.

Note that, 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 (the resistor 21 and the capacitor 22). Just go. The circuit 20 may also include three or more RC parallel circuits.

The impedance of the circuit 20 is determined by the resistance value of each resistor of 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 in the equivalent circuit model 40, the current I(t) also flows in the circuit 20, so that the current I(t) and the impedance of the circuit 20 are equal to each other. From this, 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 the first polarization voltage Vp1(t) and is illustrated. The voltage generated in the resistor 23 and the capacitor 24 is referred to as the second polarization voltage Vp2(t) and is illustrated. 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 including the resistor 21 and the capacitor 22 is the time constant τ1, the time constant τ1 is obtained by multiplying the resistance value of the resistor 21 and the capacitance value of the capacitor 22. Specified 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, when the time constant τ2 is the time constant of the second RC parallel circuit including the resistor 23 and the capacitor 24, the time constant τ2 is obtained by multiplying the resistance value of the resistor 23 and the capacitance value of the capacitor 24. Specified 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 the plurality of different time constants in the circuit 20, the time change of the voltage of the polarization voltage Vpol(t) can be represented more accurately. Each time constant may be set such that time constant τ1<time constant τ2, for example.

The constant voltage source 30 has a constant direct current (DC) voltage. The voltage of the constant voltage source 30 is an open circuit voltage (OCV) of the power storage device. The impedance of the constant voltage source 30 is zero. The open circuit voltage of the power storage device is referred to as open circuit voltage Vocv(t) and is illustrated. The open circuit voltage Vocv(t) is obtained, for example, from 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 and the like may also 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 apparatus 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 the simulation apparatus according to the embodiment. The simulation device 1 has, as its functional blocks, 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. Including 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 apparatus 1 physically includes one or more CPUs (Central Processing Units) 101, a RAM (Random Access Memory) 102 and a ROM (Read Only Memory) that are main storage devices. 103, a communication module 104 that is a data transmission/reception device, an auxiliary storage device 105 such as a hard disk and a flash memory, an input device 106 such as a keyboard that receives user input, and an output device 107 such as a display, and the like. It is configured. Each function of the simulation apparatus 1 shown in FIG. 3 has one or a plurality of predetermined computer software loaded on hardware such as the CPU 101 and the RAM 102, so that the communication module 104 and the input device 106 are controlled under the control of the CPU 101. , And the output device 107 are operated, and data is read and written in the RAM 102 and the auxiliary storage device 105. Although the above description has been given as to the hardware configuration of the simulation device 1, the fuel consumption simulation device 90 includes the CPU 101, the main storage device such as the RAM 102 and the ROM 103, the communication module 104, the auxiliary storage device 105, the input device 106, and the output device. It may be configured as an ordinary 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 unit for inputting a designated value (bat_demand) to the power storage device. The designated 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 apparatus 90 described above. The input unit 2 outputs the input designated value to the DC resistance calculation unit 5.

The SOC calculation unit 3 is a unit 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 subsequent charge/discharge electricity amount of the power storage device. The initial SOC(0) value of the power storage device is not particularly limited and may be set appropriately. The charge/discharge amount of 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 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), for example, by 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 unit that sets the values of various characteristic parameters necessary for estimating the terminal voltage of the power storage device. The characteristic parameters include, 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 ( 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 lookup table that describes the value of each parameter. The look-up table is provided for each parameter. The lookup table is, for example, a table in which 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 uses the acquired value for each parameter. Set to the value. Note that each lookup table may be prepared for each temperature of the power storage device. In that case, the value of each parameter is set in consideration of the temperature of the electricity storage device. Moreover, the value of each parameter may be predetermined. The parameter setting unit 4 outputs the set value of each parameter to the DC resistance calculation unit 5 and the polarization calculation unit 6.

The DC resistance calculation unit 5 is a unit that calculates the DC resistance voltage Vdc(t) generated in the circuit 10 in the equivalent circuit model 40. The DC resistance calculation unit 5 is also a unit that calculates the current I(t) flowing in the equivalent circuit model 40 from the specified value (bat_demand) input by the input unit 2. The polarization calculator 6 is a part that calculates the polarization voltage Vpol(t) generated in the circuit 20 in the equivalent circuit model 40. The OCV calculator 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 is associated with the value of the open circuit voltage Vocv is prepared in advance. The OCV calculator 7 calculates the open circuit voltage Vocv(t) from the SOC(t) received from the SOC calculator 3 by referring to the table. Note that 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 unit 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 calculator 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 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 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 process 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 apparatus 1. Then, the input unit 2 outputs the input designated value to the DC resistance calculation unit 5. Then, SOC calculation unit 3 calculates the SOC of the power storage device (step S02). The SOC calculation unit 3 calculates the SOC(t) using the above-mentioned formula (3), for example. 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 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, and acquires the value. The set value is set to the value of each parameter. Then, the parameter setting unit 4 outputs the set parameters to the DC resistance calculation unit 5 and the polarization calculation unit 6.

Then, 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 from 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 includes the specified value input by the input unit 2. The designated current to be set 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 determines that the charging/discharging mode is a constant voltage charging mode (a mode in which the output voltage of a voltage source (for example, an alternator) for charging the storage device is constant and the storage device is charged). First, the DC resistance voltage Vdc(t) is calculated. Then, the current I(t) flowing through the equivalent circuit model 40 is calculated based on the DC resistance voltage Vdc(t).

Subsequently, the polarization calculator 6 calculates the polarization voltage Vpol(t) (step S05). Specifically, the polarization calculation unit 6 uses the resistance value of the resistor 21, the time constant τ1, the resistance value of the resistor 23, and the time constant τ2 provided from the parameter setting unit 4 to calculate the first polarization voltage Vp1. (T) and the second polarization voltage Vp2(t) are calculated. Then, the polarization calculator 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 calculator 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 the table in which the value of each SOC is associated with the value of the open circuit voltage Vocv. To do. Then, the OCV calculator 7 outputs the calculated open circuit voltage Vocv(t) to the terminal voltage calculator 8.

Subsequently, the terminal voltage calculator 8 calculates the terminal voltage V(t) (step S07). Specifically, the terminal voltage calculation unit 8 uses 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 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 the DC resistance calculation unit 5. As described above, the calculation process of the terminal voltage V(t) at time t is completed.

The process of step S05 and the process of step S06 may be performed in parallel, or may be performed in reverse order.

Here, the characteristic parameters forming 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 a resistance value of the container 23 (second polarization resistance) and a time constant τ2 (second polarization time constant). Usually, these characteristic parameters are calculated without considering deterioration due to use of the electricity storage device. In that case, there is a problem in that the input/output characteristics of the power storage device when deteriorated cannot be accurately estimated.

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時間関数であり、使用期間内の適切な時間を入力することによって、当該使用時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 expression (4). That is, an arbitrary characteristic parameter A

To model as. The first term A _{0 on} the right side is the initial value of the characteristic parameter corresponding to when the electricity storage device is not used, and the second term A _{1 on} the right side is the change in the characteristic parameter after the electricity storage device has been used for a certain period of time. This change amount is a time function representing the influence of deterioration of the power storage device, and by inputting an appropriate time within the usage period, a corresponding deteriorated characteristic parameter can be obtained after the usage time has elapsed. This time is, for example, hundreds of hours to several thousands of hours.

By expressing the characteristic parameter A as in the mathematical expression (4), the characteristic parameter A after an arbitrary period has elapsed is calculated by simply identifying the initial characteristic parameter A ₀ by using, for example, an unused power storage device. be able to.

The second term A ₁ may be different 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, for example, by the following mathematical expression (5). The coefficients a ₁ , a ₂ , and a ₃ are constants, SOC ₁ (t) is the SOC at dark current discharge, and SOC ₂ (t) is the SOC at rest. These SOCs are a function of time t.

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。 A ₁ shown in Expression (5) includes three terms. The first term is

Is. This term includes the time integral of the absolute value of the current I(t) and the 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) is, that is, the total amount of current flowing through the power storage device during the use period, and the coefficient a ₁ represents the rate of deterioration of the electricity storage device with respect to the total amount of current. Therefore, the term represented by Expression (6) represents deterioration (hereinafter referred to as energization deterioration) based on the total amount of current flowing through the power storage device. Note that t1 is the charge/discharge time. Further, there are a plurality of characteristic parameters of the electricity storage device, and the values of these characteristic parameters change as the deterioration progresses. However, the change due to energization deterioration may be increasing or decreasing depending on the characteristic parameter. .. 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 the time integral of the absolute value of the current I(t), the coefficient a ₂ multiplied by the time integral, and the depth of discharge (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 integrated over time. The coefficient a ₂ represents the rate of deterioration of the power storage device with respect to DOD. Therefore, the term represented by the mathematical expression (7) represents deterioration (DOD deterioration) of the electricity storage device based on DOD. The change in the characteristic parameter due to the 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 terms 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 the time integration of SOC ₂ (t) and the coefficient a ₃ common to the third term multiplied by the time integration. SOC ₁ (t) and SOC ₂ (t) are numerical values representing the operating state of the electricity storage device. The coefficient a ₃ represents the rate of deterioration of the power storage device with respect to each SOC during dark current discharge and at rest. The third term and the fourth term represented by the mathematical expression (8) represent deterioration (dark current discharge deterioration and rest deterioration) based on each SOC during dark current discharge and rest of the electricity storage device, respectively. The change amount of the characteristic parameter due to dark current discharge deterioration and rest 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 the car navigation system and clock when the vehicle engine is stopped (that is, the alternator is not generating power, except when idling is stopped). The term "during dark current discharge" refers to a period during which such weakness is flowing. In addition, the term “pause” refers to a state in which no dark current flows at all, and the term “pause” refers to a period in the pause state. Note that t2 is the dark current discharge time and t3 is the rest time. In the mathematical expression (8), _{one of the} time integral terms of SOC ₁ (t) and SOC ₂ (t) (that is, one of the third term and the fourth term) may be omitted as necessary.

Note that SOC ₁ (t)=0 and SOC ₂ (t)=0 during normal charge/discharge. 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.

When the electricity storage device is a lithium-ion battery, the second term A ₁ of the formula (4) is defined as the following formula (9), for example.

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（１１）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（１１）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（１０）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。 A ₁ shown in Expression (9) includes three terms. The first term is an energization deterioration term. The second term is

Is. This term includes the time integral of the absolute value of the current I(t), the coefficient a ₂ multiplied by the time integral, and the self-heating generated by the time integral. That is, the function T of the time τ represented by the following formula (11) represents the self-heating of the electricity storage device.

The self-heating T is obtained by time integration of the square of the current I(τ) as shown in the equation (11). 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 Expression (10) represents deterioration due to self-heating of the electricity 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 term includes the time integration of SOC ₂ (t) at rest and the coefficient a ₃ multiplied by the time integration. These meanings are the same as those in the fourth term in the case of the lead storage battery described above. That is, this term is a pause deterioration term.

In the above example, the dark current discharge deterioration term exists in the mathematical expression (8), but the same dark current discharge deterioration term does not exist in the mathematical expression (12). The reason is as follows. For example, when a single power storage device is used, there is always a period during which dark current flows even if the vehicle engine stops. An example of such a single power storage device used is a lead storage battery. On the other hand, when a main power storage device and a sub power storage device are used as in the μHEV method, for example, a dark current is supplied only from the main power storage device and a dark current is not supplied from the sub power storage device. In such a situation, the dark current state does not occur in the sub power storage device. A lithium-ion battery is often used as such a sub power storage device. Therefore, in equation (12), the dark current discharge deterioration term is omitted.

数式（１３）に示されるＡ₁は、３つの項を含んでいる。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（１３）においては暗電流放電劣化項が省略されている。 When the electricity storage device is a nickel-zinc battery, the second term A ₁ of the formula (4) is defined as the following formula (13), for example.

A ₁ shown in Expression (13) includes three terms. The first term is an energization deterioration term. The second term is the DOD deterioration term. The third term is the rest deterioration term. The nickel-zinc battery is also often used as a sub power storage device, like the lithium-ion battery described above. Therefore, in equation (13), the dark current discharge deterioration term is omitted.

Here, a method of calculating the above-mentioned coefficients a ₁ , a ₂ , and a ₃ will be described. Three different model formulas are needed to calculate the _three coefficients a ₁ , a ₂ , and a ₃ . Therefore, three currents I(t) whose time waveforms are different from each other are input to the equations of the characteristic parameters to make three model equations, and the coefficients a ₁ , a ₂ and a ₃ are obtained based on them. FIGS. 6A to 6C are graphs conceptually showing an example of the waveform of such a 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 charging period Ta, a constant current discharging 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 is lengthened by the larger charging current. FIG. 6B shows a case where the current during the constant voltage charging period Ta is relatively small, and the constant current discharging period Tb is shortened by the smaller charging current. FIG. 6C shows a case where the idle period Tc is longer than that in FIGS. 6A and 6B.

FIG. 7 shows the DC resistance (the resistance value of the resistor 11 of FIG. 2) among a plurality of characteristic parameters when the current waveforms of FIGS. 6A to 6C are input using a lithium ion battery as an example. It is a graph which shows change. The vertical axis represents DC resistance (unit: mΩ), and the horizontal axis represents total cycle time (use time, unit: hours). In addition, in the figure, a rhombic plot P1 shows the case where the current waveform shown in FIG. 6A is input, and a square plot P2 shows the case where the current waveform shown in FIG. 6B is inputted. The triangular plot P3 shows the case where the current waveform shown in FIG. 6C 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 amount of the DC resistance (A _{1 in the} mathematical expression (4)) is changed accordingly.

FIG. 8 is a graph in which the calculated values of the time integration of the energization deterioration term are plotted, which correspond to the current waveforms of FIGS. 6(a) to 6(c). FIG. 9 is a graph in which the calculated values of the time integration of the self-heating deterioration term corresponding to the current waveforms of FIGS. 6A to 6C are plotted. FIG. 10 is a graph in which the calculated values of the time integration of the pause deterioration term are plotted, which correspond to the current waveforms of FIGS. 6(a) to 6(c). 8 to 10, the vertical axis represents the time integrated value and the horizontal axis represents the total cycle time (unit: hours). In these figures, the rhombic plot P4 shows the numerical values 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 triangular plot P6 shows the numerical values when the current waveform shown in FIG. 6C is input.

As shown in FIGS. 8 to 10, the value of the time integration in each of the energization deterioration term, the self-heating deterioration term, and the rest deterioration term is calculated based on the current waveforms in FIGS. 6A to 6C. To be done. Therefore, _three independent functions including the coefficients a ₁ , a ₂ , and a ₃ as variables can be created, and the coefficients a ₁ , a ₂ , and a ₃ are obtained by performing optimization by curve fitting with experimental values. be able to. 11A to 11C are graphs conceptually showing the state of curve fitting. Figure 11 (a) ~ FIG. 11 (c), state of fitting a ₁ obtained by the current waveform, respectively, in FIG 6 (a) ~ FIG 6 (c), a _2, a function of a ₃ and the experimental values Is shown. Plots P7 to P9 in the figure are experimental values, and curves R1 to R3 are estimated values from the function.

FIG. 12 is a table 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 method described above. Note that FIG. 12 also shows the fitting error (%). Although the error between the first polarization resistance and the second polarization resistance is relatively large, it is considered that this is because the test period is short and the progress of deterioration is small.

The effects obtained by the simulation method and the simulation apparatus 1 according to the present embodiment described above will be described. In the simulation method and the simulation apparatus 1 of the present embodiment, at least one characteristic parameter A includes a time function A ₁ that represents the influence of deterioration of the power storage device, as shown in Expression (4). By inputting the usage time (total cycle time) of the power storage device to such a time function A ₁ , the degree of deterioration of the power storage device after the usage time has elapsed can be reflected in the characteristic parameter A.

According to the knowledge of the inventor of the present invention, the degree of deterioration of the power storage device greatly changes depending on the SOC during dark current discharge or at rest. In the present embodiment, the time function A ₁ is _one of the coefficient a ₃ representing the deterioration rate, SOC (SOC ₁ (t)) at the time of dark current discharge of the electricity storage device, and SOC (SOC ₂ (t)) at the time of rest. Alternatively, it includes terms (for example, formula (8), formula (12), etc.) obtained by multiplying both time integrals. This makes it possible to accurately represent the degree of deterioration of the electricity storage device during dark current discharge or during rest. Therefore, according to the present embodiment, it is possible to accurately estimate the input/output characteristics of the power storage device when the power storage device is deteriorated without using the power storage device that is actually deteriorated. Can be performed accurately.

FIG. 13 shows a case where the characteristic parameter of the present embodiment is used for the equivalent circuit model of the lithium-ion battery (graph G11) in the fuel consumption simulation of the vehicle, and a characteristic parameter which does not consider the influence of deterioration (that is, the right side of Expression (4)). it is a graph showing a result of comparing the maximum value of the fuel consumption error in the case with (graph G12) using second term a ₁ that there is no). In FIG. 13, the vertical axis represents the maximum value of fuel consumption error (unit: %), 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 Expression (4)). This current waveform repeats first to third periods TA to TC including a constant voltage charging period T1, a constant current discharging period T2 after the constant voltage charging period T1, and a cranking period T3 after the constant current discharging period T2. Contains. The voltage value of the constant voltage charging period T1 in these first to third periods TA to TC is constant at 14 (V), and the constant current discharging period T2 and the cranking period T3 are 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)

Further, 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 parameter and the actually measured fuel consumption. The fuel consumption error depends on 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 of the model) when the characteristic parameter of the battery is extracted. There are a plurality of characteristic parameters, and the voltage error changes depending on the combination of those values. Therefore, since there are an infinite number of combinations of characteristic parameter values having the same voltage error value, the fuel consumption calculation result varies depending on the combination of characteristic parameter values even if the same voltage error value is present. The above-mentioned “maximum value” means the maximum value of the fuel consumption error, which corresponds to the maximum value of the voltage error with respect to the combination of the values of various characteristic parameters.

As shown in FIG. 13, the longer the test period is, the larger the fuel consumption error becomes, but if the influence of deterioration is not taken into consideration, the maximum value of the fuel consumption error exceeds 0.3% when the test period exceeds 60 days. ing. On the other hand, in the present embodiment that takes into consideration the influence of deterioration such as during rest, the maximum value of the fuel consumption error is within 0.05% even after the test period exceeds 60 days. As described above, according to the method and apparatus of the present embodiment, the longer the test period is, 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, selection of the capacity of a power storage device used in a vehicle. In general, the fuel efficiency of a vehicle improves as the capacity of a power storage device installed therein increases. On the other hand, the performance of the power storage device deteriorates and the fuel consumption of the vehicle decreases as the years after the use starts. Conventionally, it was unclear how much the performance deteriorates due to the deterioration of the electricity storage device in the simulation, so that the electricity storage device capacity having a sufficient margin to the electricity storage device capacity selected from the fuel consumption simulation result was selected. With such a selection method, the capacity of the electricity storage device tends to be unnecessarily large, which may hinder the vehicle cost reduction.

In order to solve such a problem, the simulation method and the simulation apparatus 1 according to the present embodiment can perform a simulation according to the degree of deterioration of the power storage device, so that the fuel consumption simulation considering the years from the start of use can be performed accurately. You can Therefore, it is possible to accurately select the storage device capacity that can satisfy the predetermined fuel consumption condition 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). In addition, a rhombic plot P10, a square plot P11, and a triangular plot P12 in the drawing show the cases where the electric storage device initial capacities are 3 Ah, 5 Ah, and 7 Ah, respectively. As shown in FIG. 15, the fuel consumption of the vehicle is better as the capacity of the power storage device is larger, but the fuel consumption of the vehicle decreases as the years of use increase. Therefore, for example, when it is desired to set the fuel consumption to be 30 (km/l) or more after 5 years of use, according to this graph, it is understood 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 power storage device capacity 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 the storage device capacity that can satisfy the predetermined condition, based on the estimated characteristics of the power storage device after a predetermined number of years.

(Modification)
The above embodiment does not describe the relationship between the coefficients a ₁ , a ₂ , and a ₃ and the temperature of the power storage device. That is, the coefficients a ₁ , a ₂ , and a ₃ may be constant regardless of the temperature of the electricity storage device. However, in many cases, the preferred values of the coefficients a ₁ , a ₂ , a ₃ depend on the temperature of the electricity storage device. Therefore, the coefficients a ₁ , a ₂ , and a ₃ may change according to 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 , and a ₃ may be functions a ₁ (TH), a ₂ (TH), and a ₃ (TH) of the temperature TH, or different for each of a plurality of temperatures. The coefficients a ₁ , a ₂ and a ₃ may be set. Therefore, when performing optimization by curve fitting with the experimental value, the experimental value may be acquired while changing the temperature of the power storage device.

The simulation method and the simulation device according to the present invention are not limited to the above-described embodiments and modifications, and various modifications are possible. For example, in the above-described embodiment, the current I(t) flowing through the power storage device, the SOC ₁ (t) at the time of dark current discharge, and the SOC ₂ at the time of rest ( Although t) is illustrated, various numerical values other than these can be adopted as the numerical value in the present invention as long as it represents 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).

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, 21, 23... Resistor, 22, 24... Capacitor, 30... Constant voltage source, 40... Equivalent circuit model, 90... Fuel consumption simulation device, 91... Input section, 92... Control section, 93... Output , N ₁ , N ₂ ... Nodes.

Claims (4)

A method of performing simulation using an equivalent circuit model of an electricity storage device,
Calculating a terminal voltage of the equivalent circuit model based on a current flowing through the equivalent circuit model,
The equivalent circuit model includes a plurality of characteristic parameters,
At least one of the characteristic parameters includes a time function representing the effect of deterioration of the electricity storage device,
The time function has a term including a time integration of one or both of a charging rate during dark current discharge and a charging rate during rest of the electricity storage device, and a coefficient representing a deterioration rate multiplied by the time integration, Simulation method. The simulation method according to claim 1, wherein the coefficient changes according to the temperature of the power storage device. The simulation method according to claim 1, wherein the power storage device is a lead storage battery. A device for performing simulation using an equivalent circuit model of an electricity storage device,
A voltage calculation unit that calculates a terminal voltage of the equivalent circuit model based on a current flowing through the equivalent circuit model,
The equivalent circuit model includes a plurality of characteristic parameters,
At least one of the characteristic parameters includes a time function representing the effect of deterioration of the electricity storage device,
The time function has a term including a time integration of one or both of a charging rate during dark current discharge and a charging rate during rest of the electricity storage device, and a coefficient representing a deterioration rate multiplied by the time integration, Simulation device.

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