JP2024167508A - Charge/discharge control device and charge/discharge control method - Google Patents

Abstract

To provide a charge/discharge control device and a charge/discharge control method capable of grasping the influence of battery degradation factors associated with charge/discharge, to suppress the battery degradation.SOLUTION: A charge/discharge control device for controlling charge/discharge of a storage battery connected to a load includes means of: setting a reference operation pattern of charge/discharge of the storage battery and calculating a reference degradation quantity being a degradation quantity of the storage battery in the reference operation pattern; calculating, when charge/discharge of the storage battery is operated in an actual operation pattern different from the reference operation pattern, an actual operation degradation quantity being a degradation quantity of the storage battery in the actual operation pattern; calculating a degradation quantity difference being a difference between the reference degradation quantity and the actual operation quantity; and calculating respective contribution degrees of a plurality of degradation factors being factors of degradation of the storage battery on the basis of the degradation quantity difference.SELECTED DRAWING: Figure 8

Description

The present invention relates to a charge/discharge control device and a charge/discharge control method.

When implementing V2H (Vehicle to Home), which connects electric vehicles (EVs) to homes, V2G (Vehicle to G), which connects to power grids, V2L (Vehicle to Load), which connects to electrical loads, V2V (Vehicle to Vehicle), which connects vehicles to each other, and V2X (Vehicle to Everything), which collectively refers to connecting to any device that receives and transmits power, the batteries installed in electric vehicles EVs have more opportunities to be charged and discharged, which makes them more susceptible to battery deterioration.

Battery deterioration also depends heavily on the operating method. Even when the same total charge/discharge amount is used in the same temperature environment, it is known that the amount of deterioration varies depending on the cycle depth, which indicates the rate of increase/decrease in the battery's State of Charge (SOC), the average SOC, charging time, etc. While fulfilling its role as a battery tested for V2X operation, it is necessary to minimize the deterioration of the battery State of Health (SOH) through appropriate charge/discharge control.

Conventionally, there are techniques for estimating the relationship between a battery operation pattern and the state of health (SOH) when the operation pattern is not uniform but changes gradually, such as in V2X, such as those described in Patent Documents 1 and 2.

Patent document 1 describes a device that includes a memory unit that stores a degradation line that indicates the correspondence between the amount of battery usage and the full charge capacity of the battery for each method of battery use, and that determines the method of battery use. When it is determined that the method of use has changed, the device offsets the current degradation line of the battery so that the full charge capacity of the degradation line before the change in method of use matches the full charge capacity of the degradation line after the change in method of use, estimating the full charge capacity of the battery.

Patent Document 2 describes that a specified current percentage distribution indicating the current percentage distribution when each of a plurality of preset driving patterns is driven is stored, and that a driving pattern percentage indicating the percentage of each specified current percentage distribution when the actual current percentage distribution is expressed as a combination of a plurality of specified current percentage distributions is derived based on the actual current percentage in actual driving and the specified current percentage distribution.

JP 2020-159990 A JP 2022-144152 A

Even in cases where the operating pattern is not uniform but fluctuates, such as V2X, it is necessary to minimize the deterioration of the battery state of health (SOH) through appropriate charge and discharge control while still fulfilling the role of a battery tested as a power storage facility on the power grid.

The technology described in Patent Document 1 requires that deterioration lines for battery usage methods be prepared in advance for the number of expected charging and discharging patterns, making it difficult to accommodate a wide range of charging and discharging patterns, from driving to grid connection, such as those used in EVs tested for V2X.

The technology described in Patent Document 2 makes it possible to accommodate a wide range of driving patterns with a finite number of pre-stored patterns by fitting the actual complex charging and discharging patterns to a specified current ratio distribution that indicates the current ratio distribution when each of multiple pre-set driving patterns is driven. However, the results only indicate the dominant driving pattern, making it difficult to obtain guidelines for suppressing battery deterioration.

As described above, existing patent documents are unable to grasp the impact of battery degradation factors when operational patterns change continuously, and therefore have the problem of being unable to perform appropriate operations to suppress battery degradation over the long term.

In view of the above problems, the object of the present invention is to provide a charge/discharge control device and a charge/discharge control method that can grasp the effects of battery degradation factors associated with charging and discharging and suppress battery degradation.

In view of the above, the present invention provides a "charge/discharge control device that controls the charging and discharging of a storage battery connected to a load, comprising: means for setting a standard operation pattern for charging and discharging the storage battery, and calculating a standard deterioration amount that is the deterioration amount of the storage battery in the standard operation pattern; means for calculating an actual operation deterioration amount that is the deterioration amount of the storage battery in the actual operation pattern when the charging and discharging of the storage battery is operated in an actual operation pattern different from the standard operation pattern; means for calculating a deterioration amount difference that is the difference between the standard deterioration amount and the actual operation deterioration amount; and means for calculating the contribution degree of each of a plurality of deterioration factors that are factors in the deterioration of the storage battery based on the deterioration amount difference."

The present invention also provides a "charge/discharge control method for controlling the charging and discharging of a storage battery connected to a load using a computer, the charge/discharge control method being characterized in that the computer sets a standard operation pattern for charging and discharging the storage battery, calculates a standard deterioration amount which is the deterioration amount of the storage battery in the standard operation pattern, and when the charging and discharging of the storage battery is operated in an actual operation pattern different from the standard operation pattern, calculates an actual operation deterioration amount which is the deterioration amount of the storage battery in the actual operation pattern, calculates a deterioration amount difference which is the difference between the standard deterioration amount and the actual operation deterioration amount, and calculates the contribution degree of each of a plurality of deterioration factors which are factors in the deterioration of the storage battery based on the deterioration amount difference."

The present invention makes it possible to accurately and quantitatively grasp changes in battery degradation factors caused by different operating methods, and to suppress battery degradation by performing operations that impose a balanced load on the battery.

FIG. 1 is a diagram showing an example of the overall configuration including a charging system when a vehicle is connected to a V2H network. FIG. 1 is a diagram showing an example of the overall configuration including a charging system when a vehicle is V2H-connected via a stationary DC charger. FIG. 1 is a diagram showing an example of the configuration of a charge/discharge control device according to a first embodiment of the present invention. 11A and 11B are diagrams showing a comparative example between a reference operation pattern and an evaluation target operation pattern. FIG. 13 is a diagram showing an example of extraction of deterioration factors. FIG. 11 is a diagram showing an example of input/output response of a battery deterioration model. 11A and 11B are diagrams showing examples of base deterioration amounts, deterioration amount differences, and contribution degree classifications; 10 is a flowchart showing an example of a control method for a charge/discharge control device according to a second embodiment of the present invention. FIG. 13 is a diagram showing an example of waveforms of current, voltage, and SOC when a battery operation pattern is fixed. 13 is a graph showing the visualization results of the accumulation of battery deterioration factors when the battery operation pattern is fixed. Graph showing battery stress relative to cycle depth. FIG. 13 is a diagram showing an example of waveforms of current, voltage, and SOC when a battery operation pattern is periodically changed. 13 is a graph showing the visualization results of the accumulation of battery deterioration factors when the battery operation pattern is periodically changed. A graph showing three degradation factors that affect a battery: cycle depth, charge time, and average SOC.

Below, the embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and duplicate descriptions will be omitted.

The following describes a charge/discharge control device according to an embodiment of the present invention. Note that common components in each figure are given the same reference numerals.

Figure 1 is a hardware diagram of the overall configuration, including the charging system, when vehicles are connected via a V2H connection. In Figure 1, a home 2 is supplied with power from a power grid 1, and a vehicle 9 equipped with an on-board charger/discharger 10 is supplied with power from each home 2.

Each home 2 is equipped with a HEMS 4, a distribution board 4, and external equipment 7, as well as a photovoltaic power generation system 5 and a home storage battery 6 as appropriate. Note that, here, an example is explained in which a vehicle 9, which is an electric vehicle or plug-in hybrid vehicle, is connected to a house 2, which is assumed to be a detached house, but the house 2 is not necessarily limited to a detached house in which the owner of the vehicle 9 lives. For example, it may be an apartment building, or the facility corresponding to the house 2 may be a business office or a parking lot. A configuration in which multiple vehicles 9 are connected may also be used. Note that, when viewed from an on-board charger or discharger, the home 2 can be considered an external power source.

The vehicle 9 is equipped with an on-board charger/discharger 10, an integrated controller 15, batteries (HV battery 20, LV battery 21), a power conversion device 26, and internal equipment 27. The on-board charger/discharger 10 is equipped with an AC charging port 11, a power conversion control unit 12, a battery sensing unit 13, and a power conversion unit 14. The integrated controller 15 is equipped with a network communication unit 16, an ECM 17, a calculation processing unit 18, and a battery management system (BMS) 19.

By installing such equipment, the charging/discharging system in FIG. 1 charges the batteries (HV battery 20, LV battery 21) installed in the vehicle 9 with power supplied from an external power source (each home 2).

The main devices that make up the charging and discharging system will be described in detail below. First, the HV battery 20, which is one of the batteries, is mounted on the vehicle 9 and is configured as a battery module that can achieve desired output characteristics by connecting multiple battery cells in series or parallel. An example of the HV battery 20 is a lithium-ion battery. The LV battery 21 is used to supply power to 12V devices mounted on the vehicle, and an example of this is a lead-acid battery. The HV battery 20 is connected to a power conversion device 26, and the electric energy is used in the desired manner by the internal device 27. The power conversion device 26 converts the power discharged from the HV battery 20 and supplies it to the internal device 27.

The battery management system BMS19 in the integrated controller 15 is equipped with a voltage measurement unit capable of detecting the voltage of the battery cells, a current measurement unit capable of detecting the current flowing through the battery cells, and a temperature measurement unit for detecting the temperature of the HV battery 20 in order to detect the state of the HV battery 20. The voltage measurement unit is configured in such a way that a voltage line is attached between the battery cells so that the terminal voltage of each battery cell can be measured individually. The current measurement unit can detect the current by measuring the voltage of a shunt resistor Rsht, but a sensor such as a Hall element can also be used. The temperature measurement unit can use a thermistor or a thermocouple. In this way, the BMS19 detects the state of the HV battery 20 by converting it into voltage information. Therefore, it can be configured with semiconductor devices such as a general-purpose analog front-end IC or ASIC (Application Specific Integrated Circuit). By providing an A/D converter, the state quantity of the HV battery 20 detected as a voltage can be converted into a digital value that can be used in calculation processing such as a program.

The power conversion device 26 is, for example, a bidirectional inverter, which drives the traction motor used to drive the vehicle 9. The bidirectional inverter is composed of a DC/DC converter section and an inverter section. The DC/DC converter section converts the DC voltage of the HV battery 20 to the voltage required to drive the traction motor, and the inverter section converts DC power to AC power, and performs frequency control according to the rotation speed of the traction motor to power the traction motor, thereby obtaining rotational force (driving torque) for accelerating the vehicle. Alternatively, when the vehicle decelerates, the vehicle is driven in a regenerative manner, and the kinetic energy of the vehicle is regenerated as electric power, which is then sent via the DC/DC converter section to the HV battery 20 for charging.

The internal device 27 is, for example, the driving motor described above, which accelerates the vehicle 9 by using electric power as a rotational force, and while the vehicle 9 is traveling, works in conjunction with a bidirectional inverter to drive the driving motor as a generator, thereby regenerating the inertial force of the vehicle 9 as electric power.

To achieve such operation, the power conversion device 26 is equipped with a controller (not shown), which adjusts the output voltage of the DC/DC converter by controlling the duty ratio of the switching elements of the DC/DC converter, and adjusts the driving force of the traction motor by adjusting the switching frequency and current phase of the inverter. Various sensors are provided in the internal device 27 so that the power conversion device 26 can control the internal device 27 in the desired manner.

The power conversion device 26 is also an inverter different from the bidirectional inverter for driving the traction motor described above, and the internal device 27 is also a motor for driving a compressor. These drive an air conditioner for conditioning the passenger compartment of the vehicle 9.

That is, the power conversion device 26 and the internal equipment 27 are means for consuming the power of the HV battery 20, in other words, one of the means for discharging the power of the HV battery 20, and the vehicle 9 is provided with a plurality of power conversion devices 26 and internal equipment 27. The HV battery 20 is also connected to the on-board charger/discharger 10 and the DC charging port.

Figure 1 shows an example of an on-board charger/discharger 10 with a charging function installed in the vehicle, but it is also possible to have a system where the charging/discharging function is not installed in the vehicle. Figure 2 is a hardware diagram of the overall configuration when the charging function is not installed in the vehicle. As is clear from comparing Figures 1 and 2, in Figure 2, part of the function of the on-board charger/discharger 10 is separated as a stationary DC charger 28, and a DC charging port 29 and a DC-DC converter 25 are newly installed in the vehicle. This difference can be said to be due to the difference in the charging method, with Figure 1 being AC charging and Figure 2 being DC charging.

As described above, the present invention is capable of handling AC charging via the AC charging port 11 of the on-board charger/discharger 10 and DC charging via the stationary charger 28 and DC charging port 29 shown in FIG. 2 as charging methods for the charging/discharging system of the vehicle 9. AC charging and DC charging are used exclusively within the on-board charger/discharger 10 by relays and semiconductor switches not shown. The on-board charger/discharger 10 is mounted on the vehicle 9 and performs bidirectional power conversion between the power supplied from an external power source such as the house 2 and the power discharged from the HV battery 20. The stationary charger 101 is installed outside the vehicle 9 and the house 2 and performs bidirectional power conversion between the power supplied from a power source such as the house 2 and the power discharged from the HV battery 20.

For AC charging, the vehicle charger/discharger 10 is further connected to a charging cable via the AC charging port 11, and the charging cable is connected to the distribution board 4 of the house 2. The connection to the distribution board 4 may be a direct connection via a ground fault circuit interrupter, or a connection via an AC outlet of the house 2. The distribution board 4 is electrically connected to an ampere breaker and a wattmeter (not shown) and to the power system 1.

For DC charging, the stationary charger 28 is connected to the AC-DC power conversion unit via the DC charging port 26, and the stationary charger 101 is connected to the distribution board 4 in the house 2. Thereafter, it is electrically connected to the power grid 1 in the same manner as for AC charging.

The vehicle charger/discharger 10 is equipped with a DC/DC converter section capable of transforming DC voltage and converting DC voltage to AC voltage, and a power conversion section 14 having an inverter section that rectifies AC power from the distribution board 4 to DC and can convert the DC power output from the DC/DC converter section to AC power. It also has a power conversion control section 12 that controls these, an AC charging port 11 that connects AC power, and a battery sensing section that measures battery data from these currents.

Like the vehicle charger/discharger 10, the stationary charger 28 also has a power conversion unit 14 and a power conversion control unit 12.

When charging the HV battery 20, so-called CC-CV (constant current, constant voltage) charging is performed, which combines constant current charging and constant voltage charging that correspond to the battery cells in the HV battery 20.

Specifically, when the charging rate of the HV battery 20 is low, constant current charging is performed and the charging rate is adjusted so that the current flowing through the battery cells in the HV battery 20 does not exceed a predetermined value. If excessive current flows through the battery cells, lithium ions will not be absorbed between the negative electrode active material layers in the battery cells, and lithium metal will precipitate on the negative electrode, causing an internal short circuit and possibly leading to thermal runaway accompanied by fire or explosion of the battery cell. To prevent this, it is necessary to control the charging rate, i.e., the current, so that excessive current does not flow.

When charging of the HV battery 20 progresses and the battery cell voltage rises, constant voltage charging is initiated. If the battery cell voltage rises excessively, lithium ions are extracted from the positive electrode active material, embrittling the electrode structure, and the increased reactivity of the positive electrode causes the electrolyte decomposition reaction to proceed, generating gas within the battery cell, which in turn generates heat. The gas and electrolyte generated within the battery cell are flammable, and ignition of these may lead to destruction, such as the battery cell catching fire or bursting due to an increase in gas pressure. As with current, voltage must also be controlled to avoid excessive voltage.

Taking the on-board charger/discharger 10 as an example, the power conversion unit 14 rectifies the AC power obtained through the AC charging port 11 to DC, and controls the duty ratio of the switching elements of the DC/DC converter unit inside the power conversion unit 14 to control the charging current and charging voltage flowing to the battery cells and ultimately to the HV battery 20. Similarly, in the stationary charger 28, the power conversion unit 14 rectifies the AC power obtained through the distribution board 4 to DC, and controls the duty ratio of the switching elements of the DC/DC converter unit inside the power conversion unit 14 to control the charging current and charging voltage flowing to the battery cells and ultimately to the HV battery 20.

As described above, the HV battery 20 can be charged using the on-board charger/discharger 10 or the stationary charger 28.

When supplying power from the HV battery 20 to the house 2, the DC/DC converter section of the power conversion section 14 of the on-board charger/discharger 10 adjusts the voltage to match the AC power used in the house 2. The inverter section of the power conversion section 14 generates AC so that the frequency and phase of the AC power used in the house 2 are synchronized. The power control conversion control section 12 adjusts the duty ratio of the switching signal that is issued to the switch element of the DC/DC converter section to adjust the voltage, and also adjusts the switching command of the inverter section to feed back the frequency and phase of the AC power in the house 2 and synchronize it with this in order to send power to the house 2.

The same applies when supplying power from the HV battery 20 to the house 2 through the stationary charger 28, and the DC/DC converter section, inverter section, and power conversion control section 12 of the power conversion section 14 are operated in the same manner as the DC/DC converter section, inverter section, and power conversion control section 12 of the power conversion section 14 of the vehicle-mounted charger/discharger 10.

By making it possible for the house 2 to use the power of the HV battery 20 via the on-board charger/discharger 10 or the stationary charger 28, it is possible to use the power of the HV battery 20 when there is no power supply from the power grid 1 during a disaster, for example, or to reduce the amount of power purchased from the power grid 1 and thereby cut the electricity bill for the house 2.

The house 2 may further include a solar power generation system 5 or a fuel cell system (not shown) as a power source to replace the power grid 1.

In addition to the aforementioned solar power generation system 5, external devices 7 are connected to the distribution board 4 of the house 2. The external devices 7 are the housing facilities of the house 2 and so-called electrical appliances, such as white goods such as an air conditioner for conditioning the house 2, a hot water supply system, lighting, cooking utensils, a refrigerator, and a washing machine, as well as black goods such as a television and audio equipment, and information appliances such as a personal computer and a telephone.

Supplying the power of the HV battery 20 to the house 2 via the on-board charger/discharger 10 or the stationary charger 28 consumes the power of the HV battery 20, or in other words, is another means of discharging the power of the HV battery 20.

The house 2 is equipped with a home energy management system HEMS (Home Energy Management System) 3, which can adjust the timing of boiling water in the hot water system as external device 111 according to the power demand of the house 2 acquired from the power meter, the operating state of the air conditioner as external device 111, and the photovoltaic power generation system 5. The HEMS 3 is configured to be able to inquire about the power demand of the house 2 from the outside via a communication module (not shown), and the integrated controller 27 of the vehicle 9 may be configured to be able to acquire information such as the power demand of the house 2 held by the HEMS 3 via the network communication unit 16 of the vehicle 9.

The integrated controller 15 is composed of the following functional blocks: a network communication unit 16, an engine control module (ECM) 17, an arithmetic processing unit 18, and a battery management system (BMS). The operation of each functional block of the integrated controller 15 will be described in detail later.

The calculation processing unit 18 of the integrated controller 15 has a calculation unit consisting of a CPU etc., and a storage unit consisting of memories such as RAM and ROM and recording media, and realizes each functional block of the integrated controller 15 by executing a program stored in the storage unit.

The integrated controller 15 is configured to be able to acquire the operating status of the power conversion device 26 and the internal devices 27 and the status of the HV battery 20 as necessary, and to be able to communicate with the stationary charger 28 through the DC charging port 29. The integrated controller 15 is also able to communicate via the AC charging port 11 and the charging cable. For communication between the vehicle 9 and the house 2, communication methods such as CAN (Controller Area Network) and LIN (Local Interconnect Network) or Ethernet connection can be used, and there is no problem if CAN or LIN is used within the vehicle 9 and Ethernet communication is used for communication within the house 2. Communication using PLC (Power Line Communication) or the like may also be used. Not only wired communication but also wireless communication may be performed.

Above, we have described an example of the configuration of a charging/discharging system to which the present invention can be applied, using Figures 1 and 2. Next, we will consider the case where the vehicle 9 is stopped and charging is performed from an external power source.

As mentioned above, existing charging methods have the problem that they are unable to grasp the impact of battery degradation factors when the operating pattern changes continuously, and are unable to perform appropriate operation to suppress battery degradation over the long term. For this reason, here we will explain a method for grasping the impact of battery degradation factors associated with charging and discharging and a method for suppressing degradation in the charge/discharge control device of the present invention.

Battery deterioration in the cells of the HV battery 20 progresses mainly due to structural changes in the positive and negative electrodes caused by the charge-discharge cycle. For example, a negative electrode made of graphite material deteriorates due to repeated expansion and contraction caused by the usage environment and charge-discharge. In addition, a positive electrode made of ternary metal materials also deteriorates due to metal corrosion and elution of binder components. In this case, it is thought that repeating the same charge-discharge cycle in a V2G operation pattern may lead to the aggravation of a specific deterioration form and local deterioration within the cell. If a specific part in the battery is completely destroyed, the state of health (SOH) of the battery will decrease and the battery will become unusable even if other parts are healthy. Although it is necessary to avoid local deterioration inside the battery, it is difficult to individually control the deteriorated parts inside the battery, so the burden on the battery is equalized by using operational deterioration factors as evaluation indicators.

Figure 3 is a diagram showing an example of the configuration of a charge/discharge control device according to the first embodiment of the present invention. The charge/discharge control device according to the first embodiment of the present invention is realized, for example, by the arithmetic processing unit 18 in the overall controller 15 in Figures 1 and 2, or is configured on the cloud and the processing results are stored in the overall controller 15 via the network communication unit 16 and used. In the following explanation, the charge/discharge control device will be described as being realized by the arithmetic processing unit 18 as an example.

The processing of the charge/discharge control device is generally realized using a computer, but if the processing contents in the calculation unit are expressed as processing functions, it has the processing functions of a battery state of health (SOH) calculation unit F301, a battery deterioration factor calculation unit F305, and a charge/discharge plan control unit F316, as shown in FIG. 3.

The battery state of health (SOH) calculation unit F301 is composed of an external communication unit F302 that acquires the degradation status of the vehicle's battery from an external degradation diagnosis device such as a stationary charger 28, or a degradation diagnosis unit F303 that acquires the battery degradation status from a degradation diagnosis device of the vehicle such as an on-board charger/discharger 10, and a battery state of health (SOH) diagnosis unit F304 that estimates the battery state of health (SOH) based on that information.

The battery deterioration factor calculation unit F305 quantifies the amount of battery deterioration and the contribution of deterioration factors when a battery is charged and discharged in a certain operation pattern to be evaluated. When evaluating the difference in the amount of deterioration due to two charge/discharge patterns, the majority of the amount of deterioration is accounted for by the reference amount of deterioration that occurs in common regardless of the operation difference, so the difference in the amount of deterioration from day to day due to the operation difference is very small, and there was a problem that if the amount of deterioration of the operation pattern to be evaluated was directly evaluated, the contribution calculation described below could not be performed with high accuracy.

In this invention, therefore, a reference operation pattern and a reference deterioration amount are defined, and the difference between the deterioration amount in the operation pattern to be evaluated is calculated, thereby improving the accuracy of extracting changes in battery deterioration factors due to differences in operation.

Of these, processing of F306, F307, and F308 is performed for the reference operation pattern. Specifically, the reference operation pattern charge/discharge data acquisition unit F306 in FIG. 3 acquires the current, voltage, and temperature history for the reference operation pattern. Next, the reference degradation factor calculation unit F307 extracts feature quantities related to battery degradation from the charge/discharge data, and using these as inputs, the reference state of health (SOH) decrease amount calculation unit F308 calculates the amount of decrease in the battery state of health (SOH) during the reference operation using a battery degradation model. Details of the feature quantities related to battery degradation and the calculation of the state of health (SOH) decrease amount will be described later.

Similarly, processes F310, F311, and F312 are performed for the operation pattern to be evaluated. Specifically, the charge/discharge data acquisition unit F310 for the operation pattern to be evaluated in FIG. 3 acquires the current, voltage, and temperature history for the operation pattern to be evaluated. Next, the operation degradation factor calculation unit F311 extracts feature amounts related to battery degradation from the charge/discharge data, and using these as inputs, the operation state of health (SOH) decrease amount calculation unit F312 calculates the amount of decrease in the state of health (SOH) of the battery during the operation to be evaluated.

Then, the additional degradation amount calculation unit F313 calculates the additional degradation amount caused by the difference in operation by taking the difference between the amount of battery state of health (SOH) degradation between the reference operation pattern and the operation pattern to be evaluated.

Next, the deterioration factor sensitivity calculation unit F309 calculates the sensitivity of the deterioration factor using gradient information of the battery deterioration model used to calculate the state of health (SOH) decrease amount. Details will be described later. The deterioration factor contribution calculation unit F314 quantifies the contribution of the deterioration factor using the aforementioned additional deterioration amount and the deterioration factor sensitivity. The accumulated deterioration factor storage unit F315 accumulates and stores the calculated deterioration factor contribution.

In the charge/discharge plan control unit F316, the accumulated deterioration factor accumulation status evaluation unit F317 checks whether there is any deterioration accumulation biased toward a specific factor in the deterioration factors accumulated and stored. In the charge/discharge plan correction unit F318, the charge/discharge plan is corrected to avoid biased accumulation of deterioration factors.

A comparison between the reference operating pattern and the operating pattern to be evaluated will be explained using Figure 4. In Figure 4, the horizontal axis shows the 24 hours of a day, and the vertical axis shows the current, voltage, temperature, and SOC from top to bottom. The dotted lines show the time series changes in the current, voltage, temperature, and SOC in the reference operating pattern, while the solid lines show the time series changes in the current, voltage, temperature, and SOC in the operating pattern to be evaluated. Note that the positive direction of the current indicates charging to the battery, and the negative direction indicates discharging to the home. For simplicity, the CV charging curve for CCCV charging is not shown in the current profile.

According to the example of FIG. 4, in the evaluation target operation pattern of the solid line, nighttime power is purchased from point A at midnight and charged to the vehicle 9. Then, at point B, the SOC reaches the charging upper limit and charging is stopped. After that, power is not supplied to the house 2 and the current value is zero until 6:00 a.m. From point c at 6:00 a.m., power consumption of the heating and cooking appliances in the house 2 increases, so power is supplied from the vehicle 9 to the house 2. From point D, the driver of the vehicle 9 leaves for work, etc., and electricity is consumed by the HV battery 20 as it travels. The vehicle 9 finishes traveling, arrives at the workplace or the house 2, and is connected to the power line again. From point E, charging of the power generated by the solar power generation system 5 begins. Although the amount of power generated by solar power generation varies depending on the season, weather, and region, the amount of power generated is generally maximum at point F around noon. After that, as it approaches evening, the solar altitude decreases, the amount of sunlight on the panel of the solar power generation system 5 at the workplace or the house 2 decreases, and the charging current becomes zero at point G. After that, at point H, the driver drives the vehicle home from work, and from point I, the battery is discharged to correspond to the peak of power usage in the evening and at night at house 2. The battery is discharged until the battery SOC reaches a predetermined lower limit, and at point J, the charging current becomes zero.

In addition, in the example of Figure 4, the reference operation pattern indicated by the dotted line is determined as a typical operation pattern in V2G, and the current profile is set assuming the above-mentioned events. The reference operation pattern does not necessarily have to be similar to the operation pattern to be evaluated. In addition, the reference operation pattern does not have to be an actual measurement value, and the results of a simulation analysis may be used.

Next, the extraction of features related to battery degradation will be described. Figure 5 is a diagram showing an example of degradation factor extraction. As in Figure 4, in Figure 5, the horizontal axis shows 24 hours of a day, and the vertical axis shows current, voltage, temperature, and SOC from top to bottom. Here, time-series data of current, voltage, and temperature are taken as charge/discharge data for the HV battery 20, and the SOC can be calculated by assuming that the battery capacity at that time is known. From this data, degradation factor parameters are extracted as input parameters for the battery degradation model.

Here, as examples of degradation factor parameters, we have defined the charging time during which the current value is positive, the discharging time during which the current value is negative, the average battery temperature, the cycle depth calculated by the amount of increase or decrease in SOC, the upper SOC limit value, and the average SOC value.

Next, calculation of the state of health (SOH) decrease amount and deterioration factor sensitivity using the battery deterioration model will be described. FIG. 6 is a diagram showing an example of the input/output response of the battery deterioration model. Processing using this battery deterioration model is executed by the reference SOH decrease amount calculation unit F308 and the operation time SOH decrease calculation unit F312 in FIG. 3. In processing step S601, battery deterioration factors extracted from the charge/discharge data of the HV battery 20 are prepared as input parameters. Then, in processing step S602, the amount of decrease in the state of health (SOH) of the battery caused by the operation is calculated using the battery deterioration prediction model. Then, in processing step S603, the amount of change in the state of health (SOH) of the battery (dSOH) is obtained.

The battery degradation model here may be a database using the results of charge/discharge tests using actual batteries, or may be a simulation model. The battery degradation model in this embodiment is a multivariate function with six input parameters, but these parameters are factors that affect the cycle degradation of the battery. The degradation caused by these input factors has relatively little nonlinear behavior, and when the relationship with the state of health (SOH) is shown using two parameters, a smooth response surface 30 of the battery degradation prediction value is drawn as shown in Figure 6. Note that Figure 6 shows an example of a battery degradation model in which the input parameters are the discharge time and the cycle depth, and the relationship between the discharge time, the cycle depth, and the battery state of health (SOH) change amount dSOH is defined three-dimensionally as the battery degradation model. The battery degradation model expresses the difference between the reference operation pattern and the evaluation target operation pattern.

Here, by partially differentiating the response surface 30 of the battery deterioration prediction value with respect to each deterioration factor, the partial differential coefficient for each factor is obtained. The partial differential coefficient corresponds to the gradient of the response surface, and the larger the gradient, the greater the influence of that deterioration factor on the degree of deterioration. Therefore, the contribution of each deterioration factor is quantified by distributing the deterioration amount difference due to the operation based on the ratio of the gradients of each deterioration factor.

7 is a diagram showing the base degradation amount, the degradation amount difference, and an example of the contribution classification. The base degradation amount dSOH _base in the reference operation pattern on the left side of FIG. 7 is used as a reference, and the degradation amount dSOH in the evaluation target operation pattern is shown on the right side. In the present invention, attention is paid to the degradation amount difference obtained by taking the difference between the degradation amount dSOH and the base degradation amount dSOH _base .

Then, the magnitude of the influence is quantified for each of the deterioration factors (charge time, discharge time, average battery temperature, cycle depth, upper SOC limit, and average SOC value) that cause the deterioration amount difference. By quantifying the magnitude of the influence and distributing it based on the gradient ratio of the response surface 30 in Figure 6, the amount of deterioration due to differences in operation can be extracted with high accuracy and quantified for each deterioration factor.

When rapid charging is performed with a charging current exceeding 1C (1C is the current value at which the capacity of the HV battery 20 can be fully charged in 1 hour), nonlinear degradation such as lithium precipitation may occur in the battery, which may result in maximum and minimum values on the response surface 30 of the battery degradation model. In order to take into account the effects of rapid charging, it is desirable to prepare a separate degradation model for rapid charging using the peak current value during charging and its time integral value as input values, and to correct the response surface 30 of the battery degradation model.

In Example 1, a charge/discharge control device was described, but in Example 2, a charge/discharge control method will be described.

Figure 8 is a flowchart showing an example of a method for controlling a charging/discharging device according to the second embodiment of the present invention. In this process, first, in processing step S801, the base reference operating conditions and the reference deterioration amount are calculated. These base conditions are updated as appropriate when the vehicle owner is changed or when the driver's driving style changes.

In processing step S802, it is determined whether it is time to perform a deterioration diagnosis. A deterioration diagnosis is performed at midnight, for example. When a deterioration diagnosis is performed, a deterioration calculation is started using the operation data for that day. Specifically, in processing step S803, the deterioration status of the vehicle's battery is obtained from an external deterioration diagnosis device such as a stationary charger 28, or the battery deterioration status is obtained from a deterioration diagnosis device of the vehicle such as an on-board charger/discharger 10.

Next, in processing step S804, the deterioration factor is calculated from the charge/discharge data during operation (current, voltage, temperature, SOC). In processing step S805, the deterioration amount during operation and the deterioration factor sensitivity are calculated based on the battery deterioration model. In processing step S806, the output information of the deterioration model is used to calculate the deterioration amount difference between during operation and during standard operation. Then, in processing step S807, the deterioration amount difference is allocated according to the sensitivity ratio of the deterioration factor, and the deterioration factor is quantified and accumulated and stored.

Finally, in processing step S808, the charge/discharge plan for the next time onwards is corrected to avoid the accumulation of specific deterioration factors. In processing step S809, it is determined whether to update the reference operating pattern, and in processing step S810, whether to continue the deterioration accumulation calculation.

Figure 9 shows an example of simulation waveforms of current, voltage, and SOC when the battery operation pattern is fixed. A charge/discharge pattern was created assuming a V2G environment in which a vehicle 9 and a house 2 are connected. Starting from a fully charged state, discharging toward the house is performed from time zero. Next, charging is performed using solar power generation. However, the SOC reaches an upper limit during charging, during which time charging is stopped. Then, discharging toward the house 2 is performed in the latter half of the cycle. In this example, the same charge/discharge pattern was repeatedly executed for 30 days.

Figure 10A is a graph showing the visualization results of the accumulation of battery degradation factors when the battery is operated with a fixed operating pattern. When the accumulation of degradation factors is calculated based on the method of the present invention, it can be seen that the influence of cycle depth is dominant at 98.1%, and that this influence is expanding. This is because the battery capacity decreases due to deterioration of the battery cell, and yet the same charge/discharge pattern is performed, so the amount of change in battery SOC for each charge/discharge increases, and as shown in Figure 10B, it can be seen that a load related to the cycle depth is placed on the battery.

Figure 11 shows an example of the waveforms of current, voltage, and SOC when the battery operation pattern is changed periodically. In this case, the charge/discharge plan is set up so that the upper limit SOC during charge/discharge and the lower limit SOC during discharge are changed periodically, and it can be seen that the voltage and SOC change over time in a wide variety of ways.

Figure 12A is a graph showing the visualization results of the accumulation of battery deterioration factors when the battery operation pattern is periodically changed and operated according to the first embodiment of the present invention. The type and influence of the accumulated deterioration factors change because the battery operation pattern was changed midway (changing the actual operation pattern from the next time onwards to avoid the accumulation of specific deterioration factors), and as shown in Figure 12B, the battery is affected by three deterioration factors: cycle depth, charging time, and average SOC. In this way, by performing charge and discharge control so that the deterioration factors are accumulated evenly without being biased towards a specific factor, it is possible to suppress battery deterioration.

The visualization results of the battery deterioration factors as shown in Figures 10A and 12A may be notified via an in-vehicle display or the driver's smartphone. Furthermore, by also notifying the user of the recommended charging and discharging patterns, the user can be encouraged to connect the vehicle 9 to the electrical system at an appropriate time, which makes it easier to implement ideal charging and discharging control for the vehicle 9 and increases the utilization rate of the in-vehicle battery resources.

In this example, lithium-ion batteries have been used as an example, but the invention can also be applied to a variety of batteries, such as all-solid-state batteries. Similar degradation factor visualization and charge/discharge control can also be applied to LV batteries, such as lead-acid batteries.

In this embodiment, the factors listed in FIG. 5 were used as degradation factors, but other factors such as the vehicle's mileage, driving time, and integrated vehicle vibration can also be used as degradation factors. The battery degradation model may also obtain the latest battery information through wired or wireless communication outside the vehicle, and the model used for degradation may be modified or changed. Furthermore, vehicle-to-vehicle communication can be used to share model information between batteries of a specific production lot, improving accuracy.

The present invention is not limited to the above-mentioned embodiments, and various other applications and modifications are possible without departing from the spirit of the present invention as described in the claims.

For example, the above-mentioned embodiment describes the configuration of the device in detail and specifically in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to having all of the configurations described. In addition, it is also possible to add, delete, or replace part of the configuration of this embodiment with other configurations.

In addition, the control lines and information lines shown are those considered necessary for the explanation, and not all control lines and information lines on the product are necessarily shown. In reality, it can be assumed that almost all components are interconnected.

1...Power system,
2. Housing,
3...HEMS,
4...Distribution board,
5...Solar power generation,
6...Home storage battery,
7... External device 9... Vehicle (electric vehicle or plug-in hybrid vehicle)
10... Vehicle charger/discharger,
11...AC charging port,
12...power conversion control unit,
13... Battery sensing unit,
14...power conversion unit,
15...integrated controller,
16...Network communication unit,
17...ECM,
18...arithmetic processing unit,
19... Battery management system,
20...HV battery (high voltage),
21...LV battery (low voltage),
22...AC connection part,
25...DC-DC converter,
26...power conversion device,
27... Internal device 28... Stationary DC charger 29... DC charging port 30... Response surface of predicted battery deterioration value

Claims (8)

A charge/discharge control device that controls charging/discharging of a storage battery connected to a load,
A charge/discharge control device comprising: a means for setting a standard operation pattern for charging and discharging the storage battery, and calculating a standard deterioration amount which is the deterioration amount of the storage battery in the standard operation pattern; a means for calculating an actual operation deterioration amount which is the deterioration amount of the storage battery in the actual operation pattern when the charging and discharging of the storage battery is operated in an actual operation pattern different from the standard operation pattern; a means for calculating a deterioration amount difference which is the difference between the standard deterioration amount and the actual operation deterioration amount; and a means for calculating the contribution of each of a plurality of deterioration factors which are factors contributing to the deterioration of the storage battery based on the deterioration amount difference. The charge/discharge control device according to claim 1,
A charge/discharge control device comprising: a means for changing an actual operation pattern from the next time onwards so as to avoid accumulation of a specific deterioration factor among the plurality of deterioration factors. The charge/discharge control device according to claim 1,
The charge/discharge control device according to claim 1, wherein the reference operation pattern and the reference deterioration amount are calculated or recorded based on the results of a battery deterioration test or a simulation analysis. The charge/discharge control device according to claim 1,
The deterioration factors include at least one of a charging time during which a current value is positive, a discharging time during which a current value is negative, an average battery temperature, a cycle depth calculated by calculating an amount of increase or decrease in SOC, an SOC upper limit value, and an SOC average value. The charge/discharge control device according to claim 1,
The charge/discharge control device according to claim 1, wherein the reference operation pattern and the reference deterioration amount are periodically updated based on a user's past operating history and charge/discharge patterns. The charge/discharge control device according to claim 1,
A charge/discharge control device characterized in that the accumulation status of the deterioration factors and charge/discharge plan-related information such as recommended EV connection time are notified via an in-vehicle display or a driver's smartphone, etc. A charge/discharge control method for controlling charge/discharge of a storage battery connected to a load using a computer, comprising:
a deterioration amount difference that is the difference between the reference deterioration amount and the actual operation deterioration amount when the charging and discharging of the storage battery is operated in an actual operation pattern different from the reference operation pattern, calculates a deterioration amount difference that is the difference between the reference deterioration amount and the actual operation deterioration amount, and calculates the contribution degree of each of a plurality of deterioration factors that are factors in the deterioration of the storage battery based on the deterioration amount difference. The charge/discharge control method according to claim 7,
A charge/discharge control method, characterized in that an actual operation pattern from the next time onwards is changed so as to avoid accumulation of a specific deterioration factor among the plurality of deterioration factors.

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