Charge / discharge control device and control method of charge / discharge control device

Abstract

Provided is a charge / discharge control device that can increase opportunities for an on-vehicle battery to be used as an auxiliary power supply for V2H (Vehicle to Home) and the like while suppressing storage deterioration and cycle deterioration of the on-vehicle battery. The charge / discharge control device controls a charge / discharge device capable of external charging, in which a battery of an electric vehicle is charged using an external power source, and external discharging, in which the power of the battery is discharged to an external device, the charge / discharge control device being characterized in that: a reference value of the state of charge of the battery at a predetermined time between a control start time and a target completion time is set on the basis of the state of charge of the battery, the target completion time, a target value of the state of charge at the target completion time, and the output of the charge / discharge device; a target charge / discharge range defined by a state-of-charge upper limit value at a predetermined time between the control start time and the target completion time is set; and if, after control has started, the state of charge of the battery is in a region between the state-of-charge upper limit value and the reference value, then when the battery is being charged, charging is performed with an output that is smaller than the charging output in other regions.

Description

Charge / discharge control device and control method for charge / discharge control device

[0001] The present invention relates to a configuration of a charge / discharge control device that controls the charging and discharging of a battery and a control method thereof, and more particularly to a technique that is effective when applied to a charge / discharge control device for an in-vehicle battery that can be used as an auxiliary power source.

[0002] Electric vehicles use an electric motor as a driving force source, are equipped with a battery that serves as the power source for the electric motor, and run on the electricity stored in the battery.In addition to this, electric vehicles can also charge their batteries using external power supplied from outside the vehicle, or by using a generator built into the electric vehicle.

[0003] By supplying the power from the batteries installed in electric vehicles to homes or power grids, it is possible to perform external discharge and use it as an auxiliary power source, and there are high expectations for the use of electric vehicles.

[0004] Examples of how electric vehicle batteries can be used as auxiliary power sources include V2H (Vehicle to Home), which connects electric vehicles (EVs) to homes, V2G (Vehicle to G), which connects to a power grid, V2L (Vehicle to Load), which connects to an electrical load, V2V (Vehicle to Vehicle), which connects vehicles to each other, and V2X (Vehicle to Everything), which collectively refers to connecting any device that receives or transmits power.As electric vehicles are used not only as a means of transportation but also as a power source, battery degradation becomes a problem.

[0005] It is known that battery degradation can be classified into storage degradation due to storage and cycle degradation due to charging and discharging. Storage degradation of a battery is influenced by the state of charge and temperature during storage, while cycle degradation is influenced by the magnitude of the current (output) during charging and discharging and the range of the state of charge during charging and discharging (also called Depth of Discharge (DoD)), as well as temperature, just like storage degradation.

[0006] The state of charge (SOC) is defined as the ratio of the amount of power charged to the battery relative to its full charge capacity, ranging from 0 to 1 or 0% to 100%. The closer the SOC is to 1, and the higher the temperature, especially at temperatures above room temperature (25°C), the more rapidly the battery deteriorates.

[0007] Battery degradation reduces the discharge capacity that a battery can discharge. This reduction in discharge capacity reduces the driving distance of an electric vehicle or reduces the auxiliary power capacity, reducing convenience. Battery degradation also increases the battery's internal resistance, leading to reduced output and increased heat generation in the electric vehicle. This reduction in driving distance and auxiliary power capacity requires more frequent charging, which in turn increases the amount of heat generated by the increased resistance, raising the battery temperature and further accelerating battery degradation, creating a vicious cycle.

[0008] An example of a charge / discharge control method for suppressing such deterioration is disclosed in Japanese Patent Application Laid-Open No. 2003-222299.

[0009] According to Patent Document 1, a charge / discharge control device controls charging and discharging of a drive battery. The planned start time of use of the electric vehicle is set as a target charge end time, and a full charge start time is set based on that. A plurality of storage charge amounts smaller than the full charge amount of the drive battery are set for each temperature of the drive battery as the charge amount to be maintained in the drive battery during a storage period in which the electric vehicle is not in use prior to the full charge start time.

[0010] During the storage period, a storage charge amount is selected based on temperature information and charge state information of the driving battery, and a charge / discharge control device is shown that instructs the charging / discharging equipment to charge or discharge the driving battery so that the charge amount of the driving battery is maintained at the selected storage charge amount.

[0011] JP 2014-87236 A

[0012] When an electric vehicle is used as a power source in addition to being a means of transportation, it is necessary to suppress storage deterioration due to storage and cycle deterioration due to charging and discharging, while still being able to charge and discharge even when the electric vehicle is parked and connected to a house or the like via a charging and discharging device, and to minimize the decrease in discharge capacity and the increase in resistance.

[0013] The above-mentioned Patent Document 1 discloses a method for suppressing the progression of storage degradation by selecting an SOC suitable for storage based on temperature, but focuses only on storage degradation. However, as described above, cycle degradation exists in addition to storage degradation, and since no consideration is given to this type of degradation, there is a risk that the progression of cycle degradation cannot be suitably suppressed when the battery is used as an auxiliary power source.

[0014] Furthermore, the storage period continues until the time designated as the start time for full charging is reached, and the charge level of the driving battery is maintained at the level that should be maintained. Therefore, during the storage period, the battery of the electric vehicle cannot be used as an auxiliary power source.

[0015] In other words, the method disclosed in Patent Document 1 has the problem that it is not possible to effectively suppress the progression of cycle deterioration that occurs when the battery of an electric vehicle is used as an auxiliary power source, and this limits the opportunities to use the battery of an electric vehicle as an auxiliary power source.

[0016] Therefore, an object of the present invention is to provide a charge / discharge control device and a control method thereof that can suppress storage deterioration and cycle deterioration of an in-vehicle battery while increasing the opportunities to use it as an auxiliary power source for V2H (Vehicle to Home) and the like.

[0017] In order to solve the above problems, the present invention provides a charge / discharge control device that controls a charge / discharge device capable of external charging, in which the battery of an electric vehicle is charged using an external power source, and external discharging, in which the power of the battery is discharged to an external device, and is characterized in that it sets a reference value for the charge state of the battery at a predetermined time from the start of control to the target completion time based on the charge state of the battery, a target completion time, a target value for the charge state at the target completion time, and an output of the charge / discharge device, sets a target charge / discharge range defined by an upper limit value of the charge state at a predetermined time from the start of control to the target completion time, and when the charge state of the battery is in a range between the upper limit value of the charge state and the reference value after the start of control, charges the battery with an output that is smaller than the charging output in other ranges.

[0018] The present invention also provides a control method for a charge / discharge control device that controls a charge / discharge device capable of external charging, which charges a battery of an electric vehicle using an external power source, and external discharging, which discharges the power of the battery to an external device, the control method comprising the steps of: (a) setting a reference value for the state of charge of the battery at a predetermined time from the start of control to the target completion time, based on the state of charge of the battery, the target completion time, a target value for the state of charge at the target completion time, and an output of the charge / discharge device; (b) setting a target charge / discharge range defined by an upper limit value of the state of charge at a predetermined time from the start of control to the target completion time, based on the state of charge of the battery, the target completion time, the target value for the state of charge at the target completion time, and an output of the charge / discharge device; and (c) when the state of charge of the battery is in a range between the upper limit value of the state of charge and the reference value after the start of control, charging the battery at an output that is smaller than the charging output in other ranges.

[0019] According to the present invention, it is possible to realize a charge / discharge control device and a control method thereof that can suppress storage deterioration and cycle deterioration of an in-vehicle battery while increasing the opportunities to use it as an auxiliary power source for V2H (Vehicle to Home) and the like.

[0020] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0021] 17 is a block diagram showing a schematic configuration of a power supply system according to a first embodiment of the present invention. FIG. 17 is a block diagram showing a modified example of FIG. 1. FIG. 17 is a block diagram showing an example configuration of the charge / discharge control device 1 of FIGS. 1 and 2. FIG. 4A is a diagram showing an example of an upper limit state of charge, a lower limit state of charge, a reference state of charge (reference value), and a target charge / discharge range. FIG. 4B is a diagram showing an example of a temperature state of a driving battery calculated in the process of setting each set value in FIG. 4A. FIG. 4C is a flowchart showing a control method for the charge / discharge control device according to the first embodiment of the present invention. FIG. 17 is a flowchart showing a control flow for subroutine R1. FIG. 17 is a flowchart showing a calculation flow for an allowable output. FIG. 17 is a flowchart showing a control flow for subroutine R2. FIG. 17 is a flowchart showing a control flow for subroutine R3. FIG. 17 is a flowchart showing a control flow for subroutine R4. FIG. 17 is a diagram showing an example of a storage deterioration test result of a battery cell. FIG. 17 is a diagram showing a constant deterioration rate line calculated from the storage deterioration test result of a battery cell. FIG. 17 is a diagram showing an example of a map function used to set an upper limit state of charge according to a second embodiment of the present invention. FIG. 17 is a diagram showing a difference between a target charge completion time and a time when an electric vehicle is actually used according to a third embodiment of the present invention. FIG. 17 is a diagram showing an example of a table function for determining a correction amount for the target charge completion time according to the third embodiment of the present invention. FIG. 17 is a diagram showing an example of setting a band-shaped reference state of charge according to a fourth embodiment of the present invention. FIG. 17 is a flowchart showing a control method for the charge / discharge control device according to the fourth embodiment of the present invention. 10 is a flowchart showing the control flow of a subroutine R5.

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components or components having similar functions are designated by the same reference numerals, and detailed descriptions of overlapping parts will be omitted.

[0023] A charge / discharge control device and a control method thereof according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 10. FIG.

[0024] 1 is a block diagram showing a schematic configuration of a power supply system including an electric vehicle 100 equipped with an integrated controller 101 having a charge / discharge control device 1 according to a first embodiment of the present invention. The power supply system including the electric vehicle 100 is connected to a house 200 using an AC charging port 105.

[0025] 1 shows an example in which an electric vehicle 100, which is an electric car or a plug-in hybrid car, is connected to a house 200, but the house 200 is not necessarily limited to a detached house in which the owner or user of the electric vehicle 100 resides. For example, the present invention can be applied to an apartment building, or even if the facility corresponding to the house 200 is a business office or a parking lot. Furthermore, a configuration in which a plurality of electric vehicles 100 are connected may also be used.

[0026] 1 , the charge / discharge control device 1 of this embodiment is a system that charges / discharges a driving battery 102 mounted on an electric vehicle 100 using power supplied through a house 200. In addition to the driving battery 102, the electric vehicle 100 has an integrated controller 101 that includes the charge / discharge control device 1, an on-board charger / discharger 103, and a battery control unit (hereinafter referred to as BCU as appropriate; BCU: Battery control unit) 104 that detects the state of the driving battery 102.

[0027] The driving battery 102 may be, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and the present invention is particularly effective in suppressing the deterioration of lithium-ion secondary batteries. The driving battery 102 is configured as a battery module that can achieve desired output characteristics by connecting multiple secondary battery cells (not shown) in series or parallel.

[0028] Furthermore, a low-voltage battery (not shown) is mounted on the electric vehicle 100 as a power source for instruments and lights (not shown). In addition to the above-mentioned secondary batteries, a lead-acid battery or the like can also be suitably used as the low-voltage battery.

[0029] To detect the state of the driving battery 102, the BCU 104 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 capable of detecting the temperature of the driving battery 102. The voltage measurement unit is configured by attaching voltage lines between the battery cells so that the terminal voltage of each of the multiple battery cells can be measured individually. The current measurement unit can detect current by measuring the voltage across a shunt resistor, or it can use a sensor such as a Hall element. The temperature measurement unit can use a thermistor, thermocouple, or the like.

[0030] In this way, the BCU 104 detects the state of the driving battery 102 by converting it into voltage information. Therefore, it can be configured with semiconductor devices such as a general-purpose analog front-end IC or an ASIC (Application Specific Integrated Circuit). Furthermore, by including an A / D converter, the state quantity of the driving battery 102, detected as a voltage, can be converted into a digital value that can be used in arithmetic processing such as a program.

[0031] The state of the driving battery 102 detected by the BCU 104 is transmitted to the integrated controller 101 via the communication bus 107. The integrated controller 101 includes a CPU that performs calculation processing, a RAM that stores calculation results and programs being executed, and a storage unit that is composed of a memory such as a ROM that stores programs, control setting values, etc., and a recording medium, and realizes each functional block of the integrated controller 101 by executing the programs stored in the storage unit.

[0032] The integrated controller 101 is capable of acquiring the operating states of the power converter 111 and the traction motor 112 and the state of the drive battery 102 as necessary, and is also configured to be able to communicate with components described below via a communication bus 107, and with components external to the electric vehicle 100 via the communication bus 107 and a communication unit 109. Communication methods such as a controller area network (CAN) or a local interconnect network (LIN) are used within the electric vehicle 100, and communication between the electric vehicle 100 and the house 200 may use different methods, such as an Ethernet connection, or may use power line communication (PLC). Furthermore, wireless communication may be used in addition to wired communication.

[0033] Although not shown, on-board charger / discharger 103 is equipped with a power converter that converts AC power obtained through AC charging port 105 into DC power required to charge driving battery 102, and also has the function of changing DC voltage and current to adjust the charging power of driving battery 102. Furthermore, on-board charger / discharger 103 has the function of converting DC power from driving battery 102 into AC power that can be used in house 200.

[0034] That is, in-vehicle charger / discharger 103 is configured to be capable of bidirectional power transfer so that it can charge driving battery 102 with power supplied from house 200 and also discharge (supply) power from driving battery 102 to house 200. Power is input and output via AC charging port 105 and charging cable 106 through outlet 201 of house 200.

[0035] In the house 200, the outlet 201 is further connected to a power adjustment means 203. The power adjustment means 203 is further connected to a power grid 204 via an ampere breaker and a watt-hour meter (not shown). In addition to the solar power generation system 205, the power adjustment means 203 is also connected to a storage battery system 206 that can charge and discharge power generated by the solar power generation system 205, power purchased from the power grid 204, and power obtained from the driving battery 102, and a communication means 207.

[0036] Furthermore, in the house 200, an independent load 208 is connected from the power adjustment means 203 via the distribution board 202. The independent load 208 is the housing equipment of the house 200 or so-called electrical appliances, and for example, white goods such as the air conditioner, hot water supply system, lighting, cooking appliances, refrigerator, and washing machine of the house 200, black goods such as a television and audio equipment, and information appliances such as a personal computer and a telephone are connected to the independent load 208.

[0037] The power adjustment means 203 may be a system called a Home Energy Management System (HEMS), which can adjust the amount of power generated by the solar power generation system 205, adjust the operating state of the hot water supply system, adjust the timing of boiling water in the hot water supply system according to the power demand of the house 200 obtained from a power meter, adjust the operating state of the air conditioner, and sell surplus power from the solar power generation system 205 to the power grid 204.

[0038] The power adjustment means 203 may be configured to enable the power demand of the house 200 to be queried from outside via the communication means 207, and the integrated controller 101 of the electric vehicle 100 is configured to be able to acquire information such as the power demand of the house 200 held by the power adjustment means 203 via the communication unit 109 of the electric vehicle 100.

[0039] In addition, the power adjustment means 203 can also issue a command to prohibit discharge from the driving battery 102 or the storage battery system 206 so as not to discharge more power than can be obtained by the solar power generation system 205 to the power grid 204, depending on the amount of power generated by the solar power generation system 205.

[0040] An independent load 208 such as an air conditioner or hot water supply system operates by consuming power purchased from the power grid 204, power generated by a solar power generation system 205, or power stored in a storage battery system 206, as well as power from the driving battery 102. The house 200 may also be equipped with a solar power generation system 205 or a fuel cell system (not shown) as a power source in place of the power grid 204.

[0041] On-board charger / discharger 103 is equipped with power conversion unit 113 which has a DC / DC converter unit capable of transforming DC voltage, a rectifier unit which rectifies AC power to DC power when driving battery 102 is charged with AC power from distribution board 202, and an inverter unit which can convert DC power output from the DC / DC converter unit into AC power when power from driving battery 102 is supplied to house 200. In order to control these components, on-board charger / discharger 103 is also configured with power sensing unit 114 which can detect the current, voltage, and frequency of the power line connected to on-board charger / discharger 103, and power conversion control unit 115 which controls power conversion unit 113 based on information obtained through power sensing unit 114.

[0042] When charging the driving battery 102, so-called CC-CV (Constant Current, Constant Voltage) charging is performed, which combines constant current charging and constant voltage charging corresponding to the battery cells in the driving battery 102.

[0043] Specifically, when the driving battery 102 has a low state of charge, constant current charging is performed, and the charging rate is adjusted so that the current flowing through the battery cells in the driving battery 102 does not exceed a predetermined value. If excessive current flows through the battery cells, lithium ions are not absorbed between the negative electrode active material layers in the battery cells, but are precipitated as lithium metal on the negative electrode, causing an internal short circuit and potentially leading to thermal runaway that can result in the battery cell catching fire or exploding. To prevent this, it is necessary to control the charging rate, i.e., the current, so that excessive current does not flow.

[0044] As charging of the driving battery 102 progresses and the battery cell voltage rises, the charging mode shifts to constant voltage charging. If the battery cell voltage rises excessively, excessive lithium ions are extracted from the positive electrode active material, embrittling the electrode structure. In addition, the increased reactivity of the positive electrode accelerates the decomposition reaction of the electrolyte, generating gas within the battery cell. The electrolyte decomposition reaction also generates heat. Because the gas and electrolyte generated within the battery cell are flammable, ignition of these may lead to destruction, such as the battery cell catching fire or exploding due to increased gas pressure. As with current, voltage must also be controlled to prevent excessive voltage.

[0045] Taking the on-board charger / discharger 103 as an example, the power conversion unit 113 rectifies the AC power obtained through the AC charging port 105 to DC, and controls the duty ratio of the switching elements of the DC / DC converter unit inside the power conversion unit 113 to control the charging current and charging voltage flowing to the battery cells and, ultimately, to the driving battery 102. As described above, the on-board charger / discharger 103 can charge the driving battery 102.

[0046] When power from driving battery 102 is supplied to house 200, the DC / DC converter unit of power conversion unit 113 of on-board charger / discharger 103 adjusts the voltage to match the AC power used in house 200 detected by power sensing unit 114. The inverter unit of power conversion unit 113 generates AC power so that the frequency and phase of the AC power used in house 200 are synchronized.

[0047] The power conversion control unit 115 adjusts the duty ratio of the switching signal that is sent to the switch elements of the DC / DC converter unit to adjust the voltage, and also feeds back the frequency and phase of the AC power within the house 200 and adjusts the switching command of the inverter unit to synchronize with this, while slightly adjusting the voltage and phase to transfer AC power to the house 200.

[0048] By making it possible for the power of the driving battery 102 to be used in the house 200 through the on-board charger / discharger 103, it is possible to use the power of the driving battery 102 in the house 200 when there is no power supply from the power grid 204 during a disaster, or to reduce the amount of power purchased from the power grid 204 and thereby cut the electricity bill for the house 200.

[0049] The driving battery 102 is connected to a power converter 111. The power converter 111 is a bidirectional inverter that drives a traction motor 112 used to drive the electric vehicle 100. The bidirectional inverter is composed of a DC / DC converter unit and an inverter unit. The DC / DC converter unit converts the DC voltage of the driving battery 102 to a voltage required to drive the traction motor 112, and the inverter unit converts the DC power to AC power, thereby performing frequency control according to the rotational speed of the traction motor 112 to power the traction motor 112. This provides rotational force (driving torque) for accelerating the electric vehicle 100.

[0050] Alternatively, when decelerating the electric vehicle 100, the traction motor 112 is driven in a regenerative manner, and the kinetic energy of the electric vehicle 100 is regenerated as electric power. The regenerated electric power is sent to the drive battery 102 via the DC / DC converter unit, and the drive battery 102 is charged with this electric power.

[0051] Acceleration or deceleration of the electric vehicle 100 is realized by generating a drive command for the power converter 111 by the vehicle control unit 110 in the integrated controller 101. A drive command for the power converter 111 is generated in the vehicle control unit 110 by detecting an acceleration / deceleration request from the driver through operation of an accelerator pedal or a brake pedal (not shown) of the electric vehicle 100.

[0052] If the depression amount of the accelerator pedal increases, it is assumed that the driver is requesting acceleration, and an instruction is given to increase the voltage and frequency generated by the power converter 111 so as to increase the torque of the traction motor 112. Conversely, if the depression amount of the accelerator pedal decreases or the brake pedal is operated, an instruction is given to decrease the voltage and frequency generated by the power converter 111, and a command is given to regeneratively drive the traction motor 112. In this way, the running and stopping operations of the electric vehicle 100 are realized. There is no problem if control other than that described here is realized by the power converter 111 or the traction motor 112.

[0053] Electric vehicle 100 has an HMI (human machine interface) 108 and a communication unit 109. HMI 108 is composed of input means 116 for receiving various settings from the user of electric vehicle 100, and display means 117 for providing information for the user to check and understand the various settings.

[0054] The communication unit 109 provides wireless communication means for connecting to a mobile phone network or a wireless local area network so that the electric vehicle 100 can communicate, and further includes a gateway controller for performing communication by wired connection via the charging cable 106, etc. The communication unit 109 is configured to be connectable to the power adjustment means 203 via the communication means 207.

[0055] Fig. 2 is a block diagram showing a modification of Fig. 1. In this example, a power supply system including electric vehicle 100 is connected to house 200 using DC charging port 118.

[0056] So far, we have described a method of charging and discharging driving battery 102 using on-board charger / discharger 103 and AC charging port 105, but the present invention can also be applied to a connection using stationary charger / discharger 209 and DC charging port 118, as shown in Figure 2. The power conversion unit 113, power sensing unit 114, and power conversion control unit 115 provided in on-board charger / discharger 103 are distributed to stationary charger / discharger 209 and power adjustment means 203.

[0057] The stationary charger / discharger 209 realizes a function equivalent to that of the DC / DC converter unit provided in the power conversion unit 113 of the on-board charger / discharger 103, and adjusts the current and voltage for charging the driving battery 102. The power adjustment means 203 realizes a function equivalent to that of the inverter unit and power sensing unit 114 provided in the power conversion unit 113 of the on-board charger / discharger 103, and in order to supply power to the house 200, it feeds back the frequency and phase of the AC power within the house 200 and adjusts the switching command of the inverter unit to synchronize with this, and when charging the driving battery 102, it converts the AC power within the house 200 into DC power used by the stationary charger / discharger 209. Because the photovoltaic power generation system 205 and the storage battery system 206 are facilities that supply DC power, no power conversion is required and the DC power can be used directly by the stationary charger / discharger 209. In this case, if the system voltage of the solar power generation system 205 or the storage battery system 206 is different from the voltage at which the driving battery 102 is operated, a DC / DC converter unit (not shown) or the like may be further provided, and a mechanism for eliminating the voltage difference may be added to the installed charger / discharger 209 or the power adjustment means 203.

[0058] AC charging through AC charging port 105 and DC charging through DC charging port 118 are used exclusively within on-board charger / discharger 103 by means of a relay or semiconductor switch (not shown). On-board charger / discharger 103 is mounted on electric vehicle 100 and performs bidirectional power conversion between power supplied from an external power source such as house 200 and power discharged from driving battery 102. Stationary charger / discharger 209 is installed outside electric vehicle 100 and house 200 and performs bidirectional power conversion between power supplied from a power source such as house 200 and power discharged from driving battery 102.

[0059] The user of electric vehicle 100 can choose between AC charging through AC charging port 105 and DC charging through DC charging port 118 depending on the available power source. If home 200 is equipped with power conditioning means 203 and a stationary charger / discharger 209, stationary charger / discharger 209, which can directly use DC power, can be used to charge with more power, i.e., faster, than AC charging. On the other hand, AC charging only requires that outlet 201 is available, and drive battery 102 of electric vehicle 100 can be charged even if home 200 is not equipped with power conditioning means 203 or a stationary charger / discharger 209.

[0060] The electric vehicle 100 further includes external sensors 119, such as a temperature detection unit 120 and a position detection unit 121. The temperature detection unit 120 measures the outside air temperature around the electric vehicle 100. The position detection unit 121 is, for example, a global positioning system (GPS), and detects the position of the electric vehicle 100.

[0061] [Charge / Discharge Control Method] As described above, the method disclosed in Patent Document 1 has the problem that it is not possible to effectively suppress the progression of cycle degradation that occurs when the battery of an electric vehicle is used as an auxiliary power source, and that this limits the opportunities for using the battery of an electric vehicle as an auxiliary power source. Hereinafter, a charge / discharge control method that can increase the opportunities for using the battery of an electric vehicle as an auxiliary power source while suppressing cycle degradation in addition to storage degradation, which is an object of the present invention, will be described.

[0062] Battery degradation within the cells of the driving battery 102 is typically caused by storage degradation during storage and cycle degradation due to charging and discharging. The growth of a passive layer (hereinafter referred to as a solid electrolyte interphase (SEI)) formed on the negative electrode of the battery cell is considered to be a major factor in battery storage degradation. A stable and uniform SEI is required to protect the negative electrode current collector from corrosion. However, non-uniform SEI growth is known to cause corrosion of the negative electrode current collector, lithium deposition on the surface of the negative electrode, growth of needle-like crystals (dendrites) of deposited lithium, cracks on the negative electrode surface, and reduced ionic conductivity due to excessive SEI formation.

[0063] Cycle degradation occurs in the positive and negative electrodes of a battery cell, resulting in the loss of positive electrode active material due to the desorption and insertion of lithium ions, corrosion of the positive electrode current collector, and irreversible changes in the crystal structure of transition metal oxides. Lithium ions that should be used in the charge and discharge reactions are consumed in side reactions such as those mentioned above, causing battery capacity degradation and a decrease in discharge capacity, and corrosion of the positive or negative electrode current collector of the battery cell and a decrease in ionic conductivity cause an increase in battery cell resistance.

[0064] SEI growth is a chemical reaction, and as the state of charge increases during storage, a voltage rise (overvoltage) occurs that accelerates the reaction. Additionally, an increase in temperature increases the reaction rate, accelerating the degradation process. In cycle degradation, the magnitude of the current (output) during charge / discharge and the range of charge states during charge / discharge increase, which increases the number of lithium ions intercalated and deintercalated, leading to an increase in side reactions. In addition, as with storage degradation, temperature also plays a major role. Therefore, degradation can be suppressed by adjusting the state of charge and charge / discharge rate.

[0065] Fig. 3 is a block diagram showing an example of the configuration of the charge / discharge control device 1 of Fig. 1 and Fig. 2. The charge / discharge control device 1 includes an acquisition unit 2, an estimation unit 3, a range setting unit 4, a command value generation unit 5, and a control unit 6.

[0066] The acquisition unit 2 acquires charge state information relating to the charge state of the driving battery 102, temperature information relating to the temperature, and characteristic information relating to various characteristics of the driving battery 102 from the BCU 104 via the communication bus 107. Furthermore, the acquisition unit 2 acquires weather information via the communication unit 109, including forecasts of the outside air temperature at the location where the electric vehicle 100 will be charging or discharging.

[0067] The target charge completion time of the electric vehicle 100 set via the HMI 108 or the communication unit 109 can also be acquired as target charge completion time information, and the target battery charge state at the time of charge completion can also be acquired as target charge state information.

[0068] The estimation unit 3 includes a scheduled departure time estimation unit, a target state-of-charge estimation unit, and a battery state prediction unit, none of which are shown.

[0069] The scheduled departure time estimation unit estimates the time when electric vehicle 100 is expected to end electrical connection with house 200, that is, the scheduled departure time when electric vehicle 100 will begin to be used for transportation by the user, based on the driving history and charge / discharge history of electric vehicle 100. This can also be used as the target charging completion time.

[0070] The target state of charge estimation unit estimates target state of charge information from the actual state of charge value of driving battery 102 at the time when electric vehicle 100 terminates electrical connection with house 200. The estimated target state of charge may be set as the target state of charge set by the user of electric vehicle 100.

[0071] The battery state prediction unit predicts changes in battery temperature and state of charge when the driving battery 102 is charged or discharged, based on characteristic information of the driving battery 102. The prediction method will be described in detail later.

[0072] If the acquisition unit 2 has acquired the target charge completion time set by the user of the electric vehicle 100, the range setting unit 4 sets the target charge completion time information as the time to complete charging of the driving battery 102. If not, the range setting unit 4 sets the planned departure time estimated by the estimation unit 3 as the time to complete charging of the driving battery 102. The range setting unit 4 also sets an upper limit state of charge that allows charging of the driving battery 102, a lower limit state of charge that allows discharging of the driving battery 102, and a reference state of charge that, starting from the state of charge of the driving battery 102 at the start of control, will be the state of charge based on the target state of charge information at the time charging of the driving battery 102 should complete. The method of setting these will be described later.

[0073] The command value generation unit 5 compares the upper limit charge state, lower limit charge state, and reference charge state set by the range setting unit 4 with the charge state of the driving battery 102, calculates target values ​​for the charge / discharge output when the on-board charger / discharger 103 or the installed charger / discharger 209 charges / discharges the driving battery 102, and issues a command via the communication bus 107.

[0074] The control unit 6 issues commands to execute each function constituting the charge / discharge control device 1 .

[0075] [Details of the battery state prediction section of estimation section 3] Regarding the battery temperature, the change in battery temperature due to charging and discharging is estimated by updating the temperature of the driving battery 102 using the following equations (1) to (6) based on the battery characteristic information, which includes the mass, specific heat, internal resistance, entropy change, surface area, and heat transfer coefficient of the driving battery 102, and the environmental temperature in which the driving battery 102 is stored.

[0076] Equation (1) is an equation for calculating the amount of heat input and output that updates the temperature of the driving battery 102, and calculates the heat input and output associated with heat generation due to current flowing as the driving battery 102 charges and discharges (equation (3)), heat generation or absorption due to entropy changes in the driving battery 102 (equation (5)), and heat dissipation from the driving battery 102 (equation (6)). Using equation (2), the temperature of the driving battery 102 is updated based on the amount of heat generated by equation (1). The current I in equation (3) is calculated using equation (4) from the charge / discharge output of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209 when the driving battery 102 is charged or discharged.

[0077] In equation (4), P is the output when charging or discharging the driving battery 102, and V is the driving battery voltage. Since the entropy change in equation (5) differs depending on the state of charge of the driving battery 102, it is preferable to measure the relationship between the state of charge and the entropy change in advance through an experiment or the like, and organize it in the form of a table function or the like for use.

[0078] Although an example of estimating the battery temperature change using equations (1) to (6) has been shown, any method can be used as long as the battery temperature change can be obtained.

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] Regarding the state of charge, the charge / discharge current is calculated in a manner similar to equation (4) from the charge / discharge output when the driving battery 102 is charged / discharged by the on-board charger / discharger 103 or the stationary charger / discharger 209 and the driving battery voltage corresponding to the state of charge of the driving battery 102, and the current is integrated for a predetermined period as in equation (7), the amount of change in the state of charge relative to the rated capacity of the driving battery 102 is calculated to update the state of charge, and the future state of charge of the driving battery 102 is estimated. The voltage of the driving battery 102 is correlated with the state of charge of the driving battery 102, and it is preferable to use the measurement results of the voltage of the driving battery 102 relative to the state of charge of the driving battery 102 in the form of a table function or the like.

[0086]

[0087] In equation (7), ΔS is the change in the state of charge, I is the charge / discharge current, C ｒａｔｅｄ corresponds to the full charge capacity of the driving battery 102.

[0088] [Details of Range Setting Unit 4] A method for setting the upper limit state of charge, the lower limit state of charge, and the reference state of charge performed by range setting unit 4 will be described with reference to FIGS. 4A and 4B.

[0089] Fig. 4A shows an example of the upper limit state of charge, the lower limit state of charge, and the reference state of charge (reference values) set in the procedure described below, and can be organized with time on the horizontal axis and state of charge on the vertical axis. Fig. 4B shows an example of the temperature state of the driving battery 102 calculated during the process of setting each setting value in Fig. 4A.

[0090] Time T in FIG. ０ corresponds to the time when the electric vehicle 100 and the house 200 are connected via the charging cable 106 or the stationary charger / discharger 209, and time T corresponds to the time when the charging of the electric vehicle 100 should be completed, that is, the target charging completion time. ０ The charging state indicated by the circle above is T ０ State of charge at time S ０ The state of charge indicated by a circle on the time T corresponds to the target state of charge S ｄｅｐ Corresponds to.

[0091] The dashed lines in FIG. 4A indicate the upper limit state of charge and the lower limit state of charge, and the time T ０ The solid line connecting the circles at time T corresponds to the reference state of charge (reference value). ｓ corresponds to the time when charging / discharging of the driving battery 102 is started when the present invention is applied. ０ At time T ｓ The upper limit state of charge, the lower limit state of charge, and the reference state of charge (reference value) are set by this time.

[0092] If the target charging completion time or target charging state corresponding to time T is not set, the target charging completion time is set to 24 hours in the future, and a predetermined value such as 0.5 or 0.7 or the time T ０The target state of charge is set to the state of charge of the driving battery 102 at the time of charging completion or the state of charge of the driving battery 102 when charging was completed in the past. Such a predetermined value can be set so as to be adjustable by the user of the electric vehicle 100 via the HMI 108, or alternatively, an average value of the past target state of charge may be obtained from the charging record of the electric vehicle 100 and set as the target state of charge.

[0093] Such past target states of charge may be referenced by going back a number of times, such as the past 10 or 100 times, or by going back in time, such as the past 10 days, 2 weeks, or 1 month. Information related to past target states of charge may be recorded in storage within the integrated controller 101, or may be recorded on an external server (not shown) via the communication unit 109. At this time, the information may be categorized by day of the week, time period, etc., and a value corresponding to the day of the week or time period closest to the target charging completion time may be referenced.

[0094] The target charge / discharge range is set by the range setting unit 4 at time T ０ At time T ｓ The charge / discharge output of the on-board charger / discharger 103 or the stationary charger / discharger 209 is determined by comparing the target charge / discharge range set by the range setting unit 4 with the state of charge of the driving battery 102 until time T arrives, until the electric vehicle 100 starts running before time T, or until the user of the electric vehicle 100 requests cancellation of the control.

[0095] When the state of charge of the driving battery 102 is equal to or greater than the reference state of charge (reference value) and equal to or less than the upper limit of state of charge, a smaller charging output is selected than when the state of charge of the driving battery 102 is less than the reference state of charge (reference value) and equal to or greater than the lower limit of state of charge. On the other hand, when the state of charge of the driving battery 102 is less than the reference state of charge (reference value) and equal to or greater than the lower limit of state of charge, a smaller discharging output is selected than when the state of charge of the driving battery 102 is equal to or greater than the reference state of charge (reference value) and equal to or less than the upper limit of state of charge.

[0096] Depending on the charge state of the driving battery 102, if the driving battery 102 cannot be charged or discharged at the charge / discharge output selected here, the driving battery 102 will be charged or discharged at an output that allows charging and discharging, with the charge / discharge output selected here as the upper limit. For example, if the driving battery 102 is in a state where CV charging is being performed as described above, increasing the charging output may result in charging exceeding the upper limit charging voltage of the driving battery 102, which is not desirable. In such a case, a charging output that does not exceed the upper limit voltage may be selected.

[0097] In addition, if the electric vehicle 100 is left unused after time T, a new target charge / discharge range is set after a predetermined time, such as 30 minutes, 1 hour, or 3 hours, has elapsed from time T, in the same way as when a target charge completion time or target charge state corresponding to time T is not set.

[0098] <Setting the Upper Limit State of Charge> The upper limit state of charge is set to a value that is lower than the full charge of the driving battery 102 and equal to or greater than the target state of charge, based on the target state of charge information. Fig. 4A shows an example in which a value equal to the target state of charge is set. The higher the value set to the target state of charge, the more surplus power generated by the solar power generation system 205 equipped in the house 200 can be charged into the driving battery 102. This increases the utilization rate of renewable energy and the amount of power that can be used for purposes other than driving the electric vehicle 100, thereby increasing convenience by increasing the amount of power that can be used by the house 200 in the future, but there is a trade-off in that the effect of suppressing storage deterioration of the driving battery 102 is reduced.

[0099] Setting the upper limit SOC in this manner acts to suppress storage deterioration of the drive battery 102. The upper limit SOC may be configured so that the value can be set or adjusted by the user of the electric vehicle 100 via the HMI 108. In this case, the display means 117 of the HMI 108 may be configured to provide information regarding the trade-off between convenience and storage deterioration associated with setting the upper limit SOC high, so that the information can be used as a reference for setting the upper limit SOC.

[0100] <Setting of Lower Limit State of Charge> The lower limit state of charge is set based on the target state of charge information, the target charge completion time information, and the charge output of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209. At time T, the value is equal to the target state of charge, and at time T ｂ Then, charging is started using the charging output of the driving battery 102 that can be realized by the in-vehicle charger / discharger 103 or the stationary charger / discharger 209, and the target charge state is set so that it can be realized at time T.

[0101] Also, at time T ｓ Discharge is started by the discharge output of the driving battery 102, which can be realized by the in-vehicle charger / discharger 103 or the installed charger / discharger 209, at time T ｆ The lower limit of the charge state is set at time T ｆ From time T ｂ The lower limit state of charge up to is set to satisfy the following equation (8).

[0102]

[0103] In equation (8), x is the value of the desired lower limit state of charge, and Qlim is the amount of charge / discharge power allowed per day. This can be set based on the actual amount of charge / discharge power of the electric vehicle 100, for example, by setting the same amount of power as the amount of charge / discharge power of the previous day or by setting the average amount of charge / discharge power over a week. Alternatively, some predetermined value may be set, such as 10%, 20%, or 50% of the rated capacity. This may be set automatically based on the actual amount of charge / discharge power, or by the user of the electric vehicle 100 via the HMI 108. In this case, the actual amount of power may be displayed on the display means 117, and information useful for setting the amount of power may be provided to the user.

[0104] T-T ｓ is time T ｓ corresponds to the elapsed time from time T to time T, and S ０ is time T ０ the charging state of the driving battery 102 at S ｄｅｐ corresponds to the target state of charge. ｒａｔｅｄcorresponds to the rated capacity of the driving battery 102. By limiting the amount of charging and discharging power in this way, an increase in unnecessary charging and discharging opportunities is prevented, and cycle deterioration of the driving battery 102 is suppressed.

[0105] The value of x in the formula (8) can be determined by an iterative calculation algorithm such as a binary search algorithm.

[0106] <Setting the Reference State of Charge (Reference Value)> The reference state of charge (reference value) is set based on the target state of charge information, target charge completion time information, and the charge output of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209, as well as the expected temperature of the driving battery 102. From the expected temperature of the driving battery 102 shown in equations (1) to (6) and the expected state of charge of the driving battery 102 calculated from equations (4) and (7), the charge / discharge output of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209 that minimizes the evaluation value of the following equation (9) is set.

[0107]

[0108] In equation (9), S is the output of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209 to be calculated, and the estimated value of the state of charge of the driving battery 102 calculated using equations (4) and (7), and T ｂａｔ is the temperature forecast of the driving battery 102 calculated by equations (1) to (6).

[0109] In equation (9), a, b, and c are weighting coefficients for each term on the right side of equation (9). The first term on the right side of equation (9) is a penalty term for storage deterioration of the driving battery 102, and φ is a penalty function of storage deterioration. The second term on the right side is a penalty term related to the electricity fee associated with charging and discharging, and the third term on the right side is a termination cost, which evaluates whether the power receiving state of the driving battery 102 at the time of control termination has reached the target charging state.

[0110] By determining the output sequence of the in-vehicle charger / discharger 103 or the stationary charger / discharger 209 that minimizes the evaluation value Z shown in equation (9), the charge state of the driving battery 102 when charging / discharging according to this charge / discharge output becomes the reference charge state (reference value).

[0111] [Charge / Discharge Control Flow] FIG. 5 shows a control flow of the charge / discharge control device 1 of this embodiment.

[0112] When control starts, first, in step S1, charging cable 106 or stationary charger / discharger 209 is connected to electric vehicle 100 to charge or discharge using on-board charger / discharger 103, and the system waits until an electrical connection between electric vehicle 100 and house 200 is established.

[0113] After an electrical connection between electric vehicle 100 and house 200 is established in step S1 (Yes), control from step S2 onwards is carried out, and setting of the target charge / discharge range by range setting unit 4 begins.

[0114] Next, in step S2, the charge state of the driving battery 102 is acquired. The acquired charge state of the driving battery 102 is ０ Corresponds to.

[0115] Next, in step S3, a target state of charge is acquired. The target state of charge may be set by the user of electric vehicle 100 via HMI 108, or may be set by connecting to a setting website from an information terminal (not shown, such as a mobile phone, smartphone, or personal computer) and acquiring the setting on the website via communication unit 109. Alternatively, the target state of charge estimated by estimation unit 3 may be set.

[0116] Next, in step S4, the target charging completion time is acquired. As in step S3, the target charging completion time may be acquired through the HMI 108 or via an information terminal (not shown), and the target charging completion time estimated by the estimation unit 3 may be set.

[0117] Next, in step S5, the range setting unit 4 sets the target charge / discharge range. Ｓ is set.

[0118] Next, in step S6, the current time t is set to the control start time T Ｓ Alternatively, the control start time T ＳIt may be the case that this happens.

[0119] Next, in step S7, it is determined whether an interruption request has been made at time t. If an interruption request has been made (Yes), the process proceeds to step S8, where processing to interrupt charging and discharging of the driving battery 102 is performed.

[0120] Specifically, the exchange of power through on-board charger / discharger 103 or stationary charger / discharger 209 is terminated, and AC charging port 105 and DC charging port 118 are put into a power outage state. In addition, the user of electric vehicle 100 is notified via HMI 108 that charging / discharging of drive battery 102 has been suspended. Alternatively, information regarding the suspension of charging / discharging of drive battery 102 may be transmitted via communication unit 109, and the user of electric vehicle 100 may be notified via an information terminal (not shown).

[0121] On the other hand, if there is no interruption request in step S7 (No), the processing from step S9 onwards continues.

[0122] In step S9, the charge state of the driving battery 102 at time t is obtained.

[0123] Next, in step S10, the upper limit state of charge corresponding to time t is obtained.

[0124] Similarly, in steps S11 and S12, the reference state of charge (reference value) and the lower limit state of charge corresponding to time t are acquired.

[0125] In subsequent steps S13, S14, S15, and S16, the state of charge of the driving battery 102 acquired in step S9 is compared with the upper limit state of charge, the reference state of charge (reference value), and the lower limit state of charge.

[0126] In step S13, it is determined whether the state of charge of the driving battery 102 has exceeded the upper limit of charge. If the state of charge of the driving battery 102 has exceeded the upper limit of charge (Yes), the subroutine R1 is executed to discharge the driving battery 102. If the state of charge has not exceeded the upper limit of charge (No), the process proceeds to step S14.

[0127] Next, in step S14, it is determined whether the state of charge of the driving battery 102 is below the upper limit of charge and above the reference state of charge. If the state of charge of the driving battery 102 is below the upper limit of charge and above the reference state of charge (Yes), the subroutine R2 is executed to charge or discharge the driving battery 102. If the state of charge is not below the upper limit of charge and not above the reference state of charge (No), the process proceeds to step S15.

[0128] Next, in step S15, it is determined whether the state of charge of the driving battery 102 is less than the reference state of charge and equal to or greater than the lower limit state of charge. If the state of charge of the driving battery 102 is less than the reference state of charge and equal to or greater than the lower limit state of charge (Yes), the subroutine R3 is executed to charge or discharge the driving battery 102. If the state of charge is not less than the reference state of charge and equal to or greater than the lower limit state of charge (No), the process proceeds to step S16.

[0129] Next, in step S16, it is determined whether the state of charge of the driving battery 102 is below the lower limit of charge. If the state of charge of the driving battery 102 is below the lower limit of charge (Yes), the subroutine R4 is executed to charge the driving battery 102.

[0130] If it is determined in step S16 that none of steps S13 to S16 apply (No), it is determined that some problem has occurred in obtaining the charge state of the driving battery 102 or in setting the target charge / discharge range by the range setting unit 4, and the process is restarted from step S2. Alternatively, although not shown, the process may proceed to step S8, where an interruption process is performed to terminate charging / discharging of the driving battery 102. Alternatively, the process may be restarted from step S2 until the number of times that none of the cases up to step S16 apply reaches a predetermined number, at which point the process may proceed to step S8. Restarting the process from step S2 reduces or prevents opportunities to try implementing the present invention from being lost due to a transition to step S8.

[0131] Step S17 is a step that is performed after each of the subroutines R1 to R4 described above is executed, and determines whether the current time t has reached time T, i.e., the target charging completion time. If the current time is before time T (No), the process returns to step S7 to continue charging and discharging the driving battery 102. In this manner, steps S7 to S17 are repeatedly executed until the current time t reaches time T (target charging completion time). If it is determined that the current time t has reached time T (target charging completion time) (Yes), the process proceeds to step S18, where the process ends.

[0132] The following describes the operation of the charger / discharger in each of the subroutines R1 to R4. Each subroutine corresponds to the operation of command value generator 5, and in-vehicle charger / discharger 103 or stationary charger / discharger 209 charges or discharges driving battery 102 based on the generated command value.

[0133] FIG. 6 shows the control flow of the subroutine R1.

[0134] First, in step SR101, the power demand of the house 200 is acquired.

[0135] Next, in step SR102, the allowable output is calculated based on the state of charge and temperature of the driving battery 102 obtained from the BCU 104 and the outside air temperature obtained from the temperature detection means 120, which is the external sensor 119. The allowable output is calculated according to the flow shown in FIG.

[0136] In steps SR201 to SR205, the battery charge state, battery voltage, battery temperature, battery resistance, and outside air temperature are acquired.

[0137] By transforming equation (1) into equation (10), Q ｔｏｔａｌ The allowable heat generation amount Q associated with charging and discharging when ｐ is determined.

[0138]

[0139] Q ｐ Based on the above, equation (11) is obtained from equations (3) and (4), and the allowable output P ａ can be obtained.

[0140]

[0141] After the allowable output is calculated in step SR206, the charge / discharge output of the battery that can be achieved by the charger / discharger used is obtained in step SR207, and in step SR208, the smaller of the allowable output calculated in step SR206 and the charger / discharger output obtained in step SR207 is updated as the allowable output and output.

[0142] In this way, by setting the allowable output based on the temperature, the driving battery 102 is prevented from being excessively heated, and deterioration caused by an increase in battery temperature is suppressed.

[0143] Next, in step SR103, a command is generated to discharge power from the driving battery 102 so as to meet the power demand of the house 200 obtained in step SR101, and the driving battery 102 is discharged through the in-vehicle charger / discharger 103 or the installed charger / discharger 209.

[0144] Finally, in step SR104, the state of the charger / discharger is stored as "discharging."

[0145] Thereafter, the subroutine R1 is ended, and the process proceeds to step S17.

[0146] FIG. 8 shows the control flow of the subroutine R2.

[0147] First, in step SR301, the power demand of the house 200 is acquired from the power adjustment means 203.

[0148] Next, in step SR302, if the residence 200 is equipped with the photovoltaic power generation system 205, the power generation output of the photovoltaic power generation system 205 is acquired. Here, the photovoltaic power generation system 205 is used, but the system is not limited to the photovoltaic power generation system 205 as long as it is equipment capable of supplying power to the residence 200 from sources other than the power grid. For example, a fuel cell system or a wind power generation system may also be used. If the residence 200 does not have either of these facilities, the output of the photovoltaic power generation system 205 that supplies power from sources other than the power grid acquired in step SR302 is deemed to be zero, and the process proceeds to the next step.

[0149] Next, in step SR303, surplus power is calculated from the power demand of house 200 and the output of solar power generation system 205. The surplus power can be found by subtracting the power demand of house 200 from the output of solar power generation system 205. If the surplus power is positive, the output of solar power generation system 205 exceeds the power demand of house 200, and in addition to power consumption in house 200, the drive battery 102 can be charged, the storage battery system 206 in house 200 can be charged, and the power can be sold to the power grid 204.

[0150] On the other hand, when the surplus power is negative, the power consumption of the house 200 exceeds the output of the solar power generation system 205, so demand is met by purchasing power from the power grid 204 or discharging power from the storage battery system 206 or the drive battery 102.

[0151] Next, in step SR304, the allowable output is calculated according to the flow shown in FIG.

[0152] Next, in step SR305, the surplus power calculated in step SR303 is used to determine whether to charge or discharge the driving battery 102. If the surplus power is negative, i.e., if there is a power shortage (Yes), the process proceeds to step SR306, where the driving battery 102 is discharged up to the smaller of the power demand and the allowable output.

[0153] Then, the process proceeds to step SR307, and the charge / discharge state is stored as “discharging.” At this time, if the power demand of house 200 includes charging of storage battery system 206, power adjustment means 203 may operate to stop charging of storage battery system 206 and reduce the power demand of house 200.

[0154] On the other hand, if there is surplus power in step SR305 (No), the process proceeds to step SR308, where the previous control state is used to determine whether to charge or discharge the driving battery 102. If the previous charge / discharge control state was "charging" in step SR308, or if there is no record of the previous charge / discharge state (Yes), the process proceeds to step SR309.

[0155] In step SR309, the charging power smaller than the surplus power is set by multiplying the surplus power by a predetermined value smaller than 1, such as 0.5 or 0.8, or by a value smaller than 1 that decreases as the difference between the reference state of charge and the current driving battery state of charge increases toward the charging side.

[0156] Next, in step SR310, the driving battery 102 is charged with the upper limit being the smaller of the charging power calculated in step SR309 and the allowable power calculated in step SR304.

[0157] Next, in step SR311, the charging state is set to "charging", and the process proceeds to step S17.

[0158] On the other hand, if the previous charge / discharge control state is "discharging" (No) in step SR308, the process proceeds to step SR312, where discharge from the driving battery 102 is stopped and the charge / discharge output is set to zero.

[0159] Thereafter, the process proceeds to step SR313, where the charge / discharge state is not changed and remains set to "discharging", and the process proceeds to step S17.

[0160] FIG. 9 shows the control flow of the subroutine R3.

[0161] The operations from step SR401 to step SR404 are almost the same as the operations from step SR301 to step SR304 of subroutine R2, but in step SR403, an alternative power target value is set as surplus power if house 200 is not equipped with equipment corresponding to photovoltaic power generation system 205. The rest of the operations are the same, so explanations will be omitted and only the method for setting the alternative power target value will be explained.

[0162] The alternative power target value is set to a value obtained by subtracting the power demand from the allowable power of the house 200 and multiplying this value by a specified value such as 0.8 or 0.5. The allowable power of the house 200 is the power value at which an ampere breaker (not shown) of the house 200 operates, that is, the power demand at which the breaker trips. In other words, if the house 200 is not equipped with a photovoltaic power generation system 205 or similar power generation equipment, the power available for charging the driving battery 102 is set as the alternative power target value so that the sum of the power demand of the house 200 and the power required to charge the driving battery 102 does not exceed the allowable power of the house 200.

[0163] In step SR405, the surplus power calculated in step SR403 is used to determine whether to charge or discharge the driving battery 102. If the surplus power is positive, i.e., if surplus power is occurring (Yes), the process proceeds to step SR406, where the driving battery 102 is charged up to the smaller of the surplus power and the allowable output.

[0164] Thereafter, the process proceeds to step SR407, the charge / discharge state is stored as "discharging", and the process proceeds to step S17.

[0165] It is not a problem if the charger / discharger output contains some error when charging / discharging the driving battery 102 to compensate for surplus or shortage of power. It is difficult to achieve perfect matching due to power measurement errors and measurement delays, so the intention is to achieve a state where the output roughly matches, or where the surplus or shortage of power is almost entirely compensated for by charging / discharging the driving battery 102.

[0166] On the other hand, if there is a power shortage (No) in step SR405, the process proceeds to step SR408, where charging or discharging of the driving battery 102 is determined based on the previous control state.

[0167] In step SR408, if the previous charge / discharge control state is "discharging" or there is no record of the previous charge / discharge state (Yes), the process proceeds to step SR409.

[0168] In step SR409, a discharge output smaller than the power shortage calculated in step SR403 is calculated. As in step SR309 of subroutine R2, the discharge power smaller than the power shortage is set by multiplying the power shortage by a predetermined value smaller than 1, such as 0.5 or 0.8, or by a value smaller than 1 that decreases as the difference between the reference state of charge and the current driving battery state of charge decreases toward the discharge side and the reference state of charge increases.

[0169] Next, in step SR410, the driving battery 102 is discharged up to the power upper limit that is the smaller of the power shortage (discharge output) determined in step SR409 and the allowable output determined in step SR404.

[0170] Thereafter, in step SR411, the charge / discharge state is set to "discharging", and the process proceeds to step S17.

[0171] On the other hand, if the previous charge / discharge control state is "charging" (No) in step SR408, the process proceeds to step SR412, where charging of the driving battery 102 is stopped and the charge / discharge output is set to zero.

[0172] Thereafter, the process proceeds to step SR413, the charge / discharge state is not changed and remains set to "charging", and the process proceeds to step S17.

[0173] FIG. 10 shows the control flow of the subroutine R4.

[0174] In subroutine R4, the driving battery 102 is charged to prevent the driving battery 102 from becoming insufficiently charged and failing to achieve the target charging state.

[0175] First, in step SR501, the allowable output is calculated according to the flow shown in FIG. 7, and in step SR502, the driving battery 102 is charged with the allowable output.

[0176] In the following step SR503, the charge / discharge state is set to "charging", and the process proceeds to step S17.

[0177] In steps SR312 and SR313 in Fig. 8, or steps SR412 and SR413 in Fig. 9, the charge / discharge output is set to zero without changing the charge / discharge state, and only charging and discharging are stopped. This is a measure to prevent frequent switching between charging and discharging of the driving battery 102 in situations where surplus power occurs intermittently, thereby suppressing the progression of cycle deterioration. If the charge state of the driving battery 102 is equal to or higher than the reference state of charge, there is no need to rush charging. On the other hand, if the state of charge is below the reference state of charge, it is preferable to charge as much as possible when surplus power occurs.

[0178] According to this embodiment, it is possible to provide a charge / discharge control device and a control method thereof that can preferably maintain the charge state of the driving battery 102 near a reference charge state between the upper limit charge state and the lower limit charge state, and suppress output (heat generation) so that fluctuations in the charge state are gradual, thereby preferably suppressing both storage deterioration and cycle deterioration of the battery, while suppressing the loss of opportunities for V2X operations, such as supplying power to the house 200 through the on-board charger / discharger 103 or the stationary charger / discharger 209 and charging surplus power from solar power generation.

[0179] Second Embodiment A charge / discharge control device and a control method thereof according to a second embodiment of the present invention will be described with reference to FIGS.

[0180] The second embodiment is a modification of the method for setting the upper limit state of charge in the first embodiment, and only the method for setting the upper limit state of charge will be described. The other technical features are the same as those of the first embodiment.

[0181] <Setting the upper limit state of charge> The upper limit state of charge is set based on the temperature forecast so that the deterioration of the drive battery 102 will occur at an equal rate. For example, the upper limit state of charge can be organized as a map function that takes the temperature and the reference upper limit state of charge as arguments and returns a target state of charge that will cause the storage deterioration of the battery corresponding to the temperature to occur at an equal rate.

[0182] To create the map function, experiments and simulations are conducted to measure storage deterioration when the state of charge and storage temperature during battery storage are changed. Here, storage deterioration is evaluated by comparing the discharge capacity and resistance of a battery after storage under specified conditions with the characteristics obtained from a new battery. In the experiments and simulations, the conditions for storing the battery (temperature, state of charge) are set, and the discharge capacity and resistance of the battery are measured every two weeks or every month.

[0183] As a result, the characteristics shown in Figure 11 can be obtained, and the obtained results are converted into the amount of deterioration per unit time. The amount of deterioration per unit time corresponds to the slope when the plot in Figure 11 is linearly approximated. By summarizing this by storage conditions (temperature, state of charge), contour lines of the deterioration rate can be obtained, as shown in Figure 12.

[0184] 11, each plot represents the capacity retention rate defined by equation (12). As in equation (12), the capacity retention rate is defined as the ratio of the discharge capacity after storage to the discharge capacity of a new battery.

[0185]

[0186] When a reference upper limit state of charge is set using the relationship in Figure 12, a state of charge that results in the same degradation rate can be obtained by investigating the points where the heights of the contour lines match, and a map function such as that shown in Figure 13 can be created. The map shown in Figure 13 refers to a state of charge that, when a reference state of charge and temperature are given, results in the same degradation rate when the driving battery 102 is stored at the given temperature as when it is stored in a room temperature environment with the reference state of charge.

[0187] By using the reference state of charge and temperature as arguments, the function outputs the upper limit value of the state of charge to be set.

[0188] When setting the upper limit state of charge in the range setting unit 4, the temperature used is the temperature forecast for the driving battery 102 predicted by the estimation unit 3, or the air temperature forecast based on local weather information acquired by the position detection means of the electric vehicle 100 via the communication unit 109. When the temperature estimated by the estimation unit 3 is used, the temperature change of the driving battery 102 is estimated on the assumption that the driving battery 102 will be stored after being charged from the state of charge of the driving battery 102 at the start of control to the reference upper limit state of charge.

[0189] Third Embodiment A charge / discharge control device and a control method thereof according to a third embodiment of the present invention will be described with reference to FIGS.

[0190] The third embodiment is a modification of the method for setting the lower limit state of charge in the first embodiment, and only the method for setting the lower limit state of charge will be described. The other technical features are the same as those of the first embodiment.

[0191] In the first embodiment, the lower limit state of charge is set at time T ｂ When setting the target charging completion time, the amount of retrogression is set according to the variation in the time when the electric vehicle 100 was actually used relative to the time T when the electric vehicle 100 is supposed to start using (target charging completion time), so that the virtual time T is set to a time earlier than the initial time T. In short, the charging and discharging of the driving battery 102 is completed before the actual time T arrives.

[0192] For example, as shown in Fig. 14, the difference between the time slot in which the target charging completion time (scheduled departure time) is set and the time when the electric vehicle 100 is actually used is counted up, and the variation for each time slot is calculated, and the greater the variation with respect to the set target charging completion time, the earlier the virtual time T is set to be. As shown in Fig. 15, this can be used as a table function that calculates the amount of retrogression by which to advance the time T using the variation in departure time as an input.

[0193] By setting the relationship shown in Figure 14 for setting such a retroactive amount by day of the week, month, or location, it is possible to prevent power shortages (lack of power) that occur when the electric vehicle 100 is used before charging of the drive battery 102 is complete.

[0194] Fourth Embodiment A charge / discharge control device and a control method thereof according to a fourth embodiment of the present invention will be described with reference to FIGS.

[0195] In the fourth embodiment, the reference state of charge in the first embodiment is set in a band shape, and the method of controlling the charge / discharge output is adjusted. The method of setting the reference state of charge in the first embodiment and the control flow shown in Fig. 5 are changed, and these will be described below.

[0196] For the reference state of charge, multiple weights are set for the evaluation function shown in equation (9), multiple corresponding reference state of charge values ​​are generated, and the maximum and minimum values ​​of the multiple reference state of charge values ​​are spliced ​​together with respect to time to obtain a band-like reference state of charge as shown by the dark shading in Figure 16. Alternatively, a band-like reference state of charge can be obtained by adding or subtracting a predetermined value to or from the reference state of charge shown in Figure 4A.

[0197] First, it is assumed that the target charge / discharge range shown in FIG. 16 is composed of an upper limit state of charge set by the method for setting the upper limit state of charge described in Example 2 and a lower limit state of charge set by the method for setting the lower limit state of charge described in Example 3.

[0198] In the fourth embodiment, control is performed according to the control flow shown in FIG. 17, which is a partial modification of the control flow shown in FIG. 5, using the band-shaped reference state of charge shown in FIG.

[0199] In the control flow shown in FIG. 17, the operations up to step S9 are the same as those in the control flow shown in FIG. 5, so the operations from step S9 onwards will be explained.

[0200] After the charge state of the driving battery 102 is obtained in step S9, in step S19, a subroutine to be executed is selected as shown in FIG. 18 depending on which shaded area shown in FIG. 16 the current charge state is in, or whether it exceeds the upper limit charge state or is below the lower limit charge state.

[0201] In Fig. 18, in step SR601, it is determined whether the state of charge of the driving battery 102 exceeds the upper limit of the state of charge, and if it does (Yes), subroutine R1 is executed as in Fig. 5. If it does not (No), the process proceeds to step SR602.

[0202] Next, in step SR602, if the charge state of the driving battery 102 corresponds to region A1 shown in Fig. 16 (Yes), the subroutine R2 shown in the flow of Fig. 8 is executed. If not (No), the process proceeds to step SR603.

[0203] Next, in step SR603, if the charge state of the driving battery 102 corresponds to region A2 shown in Fig. 16 (Yes), the subroutine R5 shown in Fig. 19 is executed. If not (No), the process proceeds to step SR604.

[0204] Next, in step SR604, if the charge state of the driving battery 102 corresponds to the charge state in region A3 shown in Fig. 16 (Yes), the subroutine R3 shown in Fig. 9 is executed. If not (No), the process proceeds to step SR605.

[0205] Finally, in step SR605, it is determined whether the state of charge of the driving battery 102 is below the lower limit of charge, and if it is below the lower limit of charge (Yes), subroutine R4 shown in Fig. 10 is executed. If it is not below the lower limit of charge (No), as in the first embodiment, the process transitions to step S2 and transitions to E in Fig. 17 to reset the charge range, or transitions to E' in Fig. 17, where it is determined that some kind of malfunction has occurred and the interruption process is executed in step S8.

[0206] The processes in steps S17 and S18 in FIG. 17 are the same as those in steps S17 and S18 in FIG.

[0207] The subroutine R5 shown in FIG. 19 will now be described.

[0208] Steps SR701 to SR704 are the same as steps SR301 to SR304 in FIG. 8 or steps SR401 to SR404 in FIG.

[0209] After determining the allowable output in step SR704, the previous charge / discharge state is referenced in step SR705. If the previous charge / discharge state was charging or if the charge / discharge state is not set (Yes), the process proceeds to step SR706. On the other hand, if the previous charge / discharge state was discharging (No), the process proceeds to step SR711.

[0210] In step SR706, the surplus power of house 200 is checked, and if there is surplus power (Yes), the process proceeds to step SR707, where driving battery 102 is charged up to the smaller of the surplus power and the allowable output. Thereafter, the process proceeds to step SR708, where the charge / discharge state is set to "charging," subroutine R5 is ended, and the process proceeds to step S17 in FIG. 17.

[0211] On the other hand, if there is no surplus power in step SR706 (No), the process proceeds to step SR709, where the charge / discharge output is set to zero and charging is stopped. After that, in step SR710, the charge / discharge state is not updated, in this case it remains "charging", the subroutine R5 is ended, and the process proceeds to step S17 in FIG.

[0212] If the previous charge / discharge state was "discharging" in step SR705 (No), the process proceeds to step SR711, where it is determined whether the power demand of the house 200 exceeds the power output of the photovoltaic power generation system 205, i.e., whether there is a power shortage. If there is a power shortage (Yes), the process proceeds to step SR712, where the driving battery 102 is discharged up to the smaller of the shortage and the allowable output. Thereafter, in step SR713, the charge / discharge state is set to "discharging," the subroutine R5 is terminated, and the process proceeds to step S17 in FIG. 17 .

[0213] On the other hand, if surplus power is generated in step SR711 (No), the process proceeds to step SR709, where the charge / discharge output is set to zero and discharge is stopped. Thereafter, in step SR710, the charge / discharge state is not updated, in this case it remains "discharging", the subroutine R5 is ended, and the process proceeds to step S17 in FIG.

[0214] This allows the driving battery 102 to continue charging or discharging while in a charging state near the reference charging state. The reference charging state is determined based on equation (9), and allows charging and discharging to continue with little effect on the deterioration of the driving battery 102.

[0215] Furthermore, unlike subroutines R2 and R3, the charge / discharge output during charging / discharging is not suppressed, so that greater power can be charged / discharged when the driving battery 102 is operated via V2X.

[0216] In this way, by increasing the operating rate of the driving battery 102 during V2X operation, suitably charging surplus power, and discharging the shortfall from the driving battery 102, it is possible to obtain the effect of suitably reducing the electricity costs of the house 200.

[0217] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0218] Furthermore, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily represent all the control lines and information lines on the product. In reality, it can be assumed that almost all components are interconnected.

[0219] 1...Charge / discharge control device, 2...Acquisition unit, 3...Estimation unit, 4...Range setting unit, 5...Command value generation unit, 6...Control unit, 100...Electric vehicle (electric vehicle or plug-in hybrid vehicle), 101...Integrated controller, 102...Driving battery, 103...On-board charger / discharger, 104...BCU (battery control unit), 105...AC charging port, 106...Charging cable, 107...Communication bus, 108...HMI (human-machine interface), 109...Communication unit, 110...Vehicle control unit, 11 1...power converter, 112...travel motor, 113...power conversion unit, 114...power sensing unit, 115...power conversion control unit, 116...input means, 117...display means, 118...DC charging port, 119...external sensor, 120...temperature detection means, 121...position detection means, 200...house, 201...outlet, 202...distribution board, 203...power adjustment means, 204...power system, 205...photovoltaic power generation system, 206...storage battery system, 207...communication means, 208...standalone load, 209...installed charger / discharger.

Claims

1. A charge-discharge control device that controls a charge-discharge device capable of external charging for charging a battery of an electric vehicle with an external power source and external discharging for discharging the power of the battery to an external device, based on the charge state of the battery, a target completion time, a target value of the charge state at the target completion time, and the output of the charge-discharge device, sets a reference value of the charge state of the battery at a predetermined time from the start of control to the target completion time, sets a target charge-discharge range defined by a charge state upper limit value at a predetermined time from the start of control to the target completion time, and when charging the battery when the charge state of the battery is in a region between the charge state upper limit value and the reference value after the start of control, charges with an output smaller than the charging output in other regions.

2. The charge-discharge control device according to claim 1, further sets a target charge-discharge range defined by a charge state lower limit value at a predetermined time from the start of control to the target completion time, and when discharging the battery when the charge state of the battery is in a region between the reference value and the charge state lower limit value, discharges with an output smaller than the discharging output in other regions.

3. The charge-discharge control device according to claim 1, wherein the charge state upper limit value is set based on the temperature of the battery.

4. The charge-discharge control device according to claim 2, wherein the charge state lower limit value is set based on the target completion time.

5. The charge-discharge control device according to claim 1, further provides a region in the target charge-discharge range where charging and discharging are not performed with the small output.

6. A control method for a charge-discharge control device that controls a charge-discharge device capable of external charging for charging a battery of an electric vehicle with an external power source and external discharging for discharging the power of the battery to an external device, the method comprising: (a) setting a reference value of the charging state of the battery at a predetermined time from the start of control to the target completion time based on the charging state of the battery, the target completion time, the target value of the charging state at the target completion time, and the output of the charge-discharge device; (b) setting a target charge-discharge range defined by an upper limit value of the charging state at a predetermined time from the start of control to the target completion time based on the charging state of the battery, the target completion time, the target value of the charging state at the target completion time, and the output of the charge-discharge device; (c) when the charging state of the battery is in a region between the upper limit value of the charging state and the reference value after the start of control, performing charging with an output smaller than the charging output in other regions when charging the battery. A control method for a charge-discharge control device, characterized by comprising the above steps.

7. The control method for a charge-discharge control device according to claim 6, further comprising: (d) setting a target charge-discharge range defined by a lower limit value of the charging state at a predetermined time from the start of control to the target completion time; (e) when the charging state of the battery is in a region between the reference value and the lower limit value of the charging state, performing discharging with an output smaller than the discharging output in other regions when discharging the battery. A control method for a charge-discharge control device, characterized by comprising the above steps.

8. The control method for a charge-discharge control device according to claim 6, wherein the upper limit value of the charging state is set based on the temperature of the battery. A control method for a charge-discharge control device, characterized by this.

9. The control method for a charge-discharge control device according to claim 7, wherein the lower limit value of the charging state is set based on the target completion time. A control method for a charge-discharge control device, characterized by this.

10. The control method for a charge-discharge control device according to claim 6, further comprising: (f) providing a region in the target charge-discharge range where charging and discharging are not performed with the small output. A control method for a charge-discharge control device, characterized by comprising the above steps.

Images