JP6699390B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system, and more particularly to a battery system including a nickel hydrogen battery.

  It is known that a memory effect occurs in a nickel hydrogen battery. The memory effect is when the nickel-metal hydride battery discharge voltage is normal (when the memory effect occurs when the charging is repeated when the power stored in the nickel-metal hydride battery is not completely consumed (so-called additional charging)). It is a phenomenon that becomes lower than that of (when not). The memory effect may also occur on the charging side of the nickel-hydrogen battery, and the charging voltage on the charging side will be higher than in the normal state.

  A technique for estimating a voltage change amount (hereinafter, also referred to as “memory amount”) due to a memory effect of a nickel-hydrogen battery has been proposed. This is because the estimation accuracy of the state of charge (SOC) of the nickel-hydrogen battery can be improved by estimating the memory amount. For example, Japanese Unexamined Patent Application Publication No. 2007-333447 (Patent Document 1) calculates an electromotive force of a nickel-hydrogen battery based on the open-circuit voltage of the nickel-hydrogen battery, and calculates the electromotive force using the relationship between the calculated electromotive force and SOC. A state-of-charge estimation device that estimates SOC is disclosed. In the state-of-charge estimation device disclosed in Patent Document 1, the SOC estimation accuracy is improved by correcting the open circuit voltage according to the memory amount prior to SOC estimation.

JP, 2007-333447, A

  In order to properly control the charge/discharge of the battery, it is necessary to estimate the memory amount with high accuracy. In the technique disclosed in Patent Document 1, there is room for improvement in the estimation accuracy of the memory amount.

  In addition, generally, in a battery system, charging and discharging of the battery are limited for the purpose of protecting the battery. More specifically, the charging power to the battery does not exceed the charging power upper limit value Win indicating the control upper limit value, and the discharging power from the battery does not exceed the discharging power upper limit value Wout indicating the control upper limit value. The charge/discharge of the battery is controlled. In addition, the upper limit value UL and the lower limit value LL of the usage range are defined for the voltage of the battery, and the battery is charged so that the voltage does not exceed the upper limit value UL and the voltage does not fall below the lower limit value LL. The discharge is controlled.

  Since the voltage when the battery is discharged is lower than the voltage (OCV: Open Circuit Voltage) when the battery is not discharged, by the amount of voltage drop due to the discharge, the voltage becomes lower as the discharge power increases. When the memory effect on the discharge side occurs in the battery, the voltage becomes lower than in the normal time when the memory effect does not occur, and the voltage easily reaches the lower limit value LL as the battery discharges. Therefore, in order to prevent the voltage from falling below the lower limit value LL, it is desirable to set the discharge power upper limit value Wout (absolute value) lower than in the normal state. However, if the discharge power upper limit value Wout is set too low, the battery can be protected, but the discharge of the battery may be excessively limited and the battery may not be fully utilized.

  On the contrary, the voltage when charging the battery is higher than the voltage (OCV) when the battery is not charged, and the higher the charging power, the higher the voltage. When the memory effect on the charging side occurs in the battery, the voltage becomes higher than that in the normal state, so that the voltage easily reaches the upper limit value UL as the battery is charged. Therefore, in order to prevent the voltage from exceeding the upper limit value UL, it is desirable to set the charging power upper limit value Win (absolute value) lower than in the normal state. However, if the charging power upper limit Win is set too low, the battery can be protected, but charging of the battery may be excessively limited and the battery may not be fully utilized.

  The present invention has been made to solve the above problems, and an object thereof is to accurately estimate the memory amount of a battery including a nickel-hydrogen battery and to fully utilize the battery while appropriately protecting the battery. To provide the technology for

  A battery system according to an aspect of the present invention supplies electric power to an external device. The battery system includes a battery including a nickel-hydrogen battery, a power conversion device configured to convert power between the battery and an external device, and a control device. The control device controls the power conversion device so that the charging power to the battery does not exceed the control upper limit value of the charging power and the discharging power from the battery does not exceed the control upper limit value of the discharging power. The control device stores data indicating a correspondence relationship between a memory amount indicating a voltage change amount due to a memory effect of the battery and an elapsed time from the start of use of the battery. The data is defined separately for each use condition defined including the open circuit voltage and temperature of the battery. The control device sequentially refers to the stored data to sequentially calculate the memory amount within a period in which the category of the usage condition does not change, and the current memory of the battery is calculated by integrating the calculated memory amount from the start of use. The amount of charge is estimated, and the control upper limit value of charging power and the control upper limit value of discharging power are set using the estimated memory amount.

  According to the results of experiments by the present inventors (described later), the main factors that set the memory amount generated during the predetermined period are the open-circuit voltage and the temperature of the nickel-metal hydride battery. Data indicating the correspondence between the elapsed time from the start of use of the nickel-hydrogen battery and the memory amount is stored for each usage condition defined including the open-circuit voltage and the temperature of the nickel-hydrogen battery. Therefore, the estimation device can highly accurately calculate the memory amount within the time when the category of the usage condition does not change by referring to the data corresponding to the usage condition of the nickel hydrogen battery. Then, by accumulating the memory amounts calculated with high accuracy, the current memory amount of the nickel hydrogen battery can also be estimated with high accuracy.

  Further, according to the above configuration, the charge power upper limit value and the discharge power upper limit value are set using the memory amount estimated as described above. Since this memory amount is estimated with high accuracy, the charging power upper limit value is set too low to make full use of the battery, or the charging power upper limit value is set too high to reduce the battery capacity. Failure to protect properly is prevented. The same applies to the discharge power upper limit value. That is, it becomes possible to fully utilize the battery while appropriately protecting the battery.

  According to the present invention, it is possible to accurately estimate the memory amount of a battery including a nickel-hydrogen battery, and to fully utilize the battery while appropriately protecting the battery.

FIG. 1 is a block diagram schematically showing an overall configuration of a vehicle equipped with a battery system according to the present embodiment. It is a figure which shows the structure of the cell contained in a battery. It is a figure for demonstrating the three types of test results which the inventors performed. It is a time chart which shows the correspondence of the elapsed time and memory amount under each use condition. 7 is a time chart for explaining a memory amount estimation process. It is a flowchart which shows an integrated memory amount estimation process. It is a figure which shows an example of the map for setting charge electric power upper limit Win and discharge electric power upper limit Wout. 6 is a time chart showing the control of the discharge power upper limit value of the battery in the embodiment. 5 is a flowchart showing discharge power upper limit control and charge power upper limit control of the battery in the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

  Hereinafter, a configuration in which the battery system according to the present embodiment of the present invention is mounted on a hybrid vehicle will be described as an example. However, the vehicle in which the battery system according to the present embodiment can be mounted is not limited to a hybrid vehicle, and may be an electric vehicle or a fuel vehicle. Further, the use of the battery system is not limited to the vehicle use, and may be the stationary use.

[Embodiment]
<Vehicle configuration>
FIG. 1 is a block diagram schematically showing the overall configuration of a hybrid vehicle equipped with the battery system according to the present embodiment. The vehicle 1 is a hybrid vehicle, an electric vehicle, or a fuel vehicle, and includes a motor generator (MG: Motor Generator) 10, a power transmission gear 20, drive wheels 30, and a power control unit (PCU) 40. , A system main relay (SMR) 50 and a battery system 2. The battery system 2 includes a battery 100, a voltage sensor 210, a current sensor 220, a temperature sensor 230, and an electronic control unit (ECU) 300.

  Motor generator 10 is, for example, a three-phase AC rotating electric machine. The output torque of the motor generator 10 is transmitted to the drive wheels 30 via a power transmission gear 20 including a speed reducer and a power split mechanism. The motor generator 10 can also generate electric power by the rotational force of the drive wheels 30 during the regenerative braking operation of the vehicle 1. In a hybrid vehicle in which an engine (not shown) is mounted in addition to the motor generator 10, a necessary vehicle driving force is generated by operating the engine and the motor generator 10 in a coordinated manner. Although FIG. 1 shows a configuration in which only one motor generator is provided, the number of motor generators is not limited to this, and a configuration in which a plurality of motor generators (for example, two) are provided may be used.

  Although not shown, PCU 40 includes an inverter and a converter. When the battery 100 is discharged, the converter boosts the voltage supplied from the battery 100 and supplies it to the inverter. The inverter converts the DC power supplied from the converter into AC power and drives the motor generator 10. On the other hand, when charging battery 100, the inverter converts the AC power generated by motor generator 10 into DC power and supplies the DC power to the converter. The converter steps down the voltage supplied from the inverter and supplies it to the battery 100.

  The SMR 50 is electrically connected to the current path connecting the battery 100 and the PCU 40. When SMR 50 is closed in response to a control signal from ECU 300, electric power can be exchanged between battery 100 and PCU 40.

  Battery 100 is a rechargeable DC power supply, and in the present embodiment, is configured to include a nickel hydrogen battery. The detailed configuration of each cell 101 included in the battery 100 will be described with reference to FIG.

  The voltage sensor 210 detects the voltage Vb of the battery 100. The current sensor 220 detects the current Ib input to and output from the battery 100. The temperature sensor 230 detects the temperature Tb of the battery 100. Each sensor outputs the detection result to ECU 300. Note that one voltage sensor may be provided for each cell, or one voltage sensor may be provided for each of a plurality of cells (for example, several). In this case, a memory amount (described later) may be estimated for each cell or a plurality of cells. Similarly, one temperature sensor may be provided for each cell, or one temperature sensor may be provided for each of a plurality of cells.

  The ECU 300 includes a CPU (Central Processing Unit) 301, a memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 302, a timer 303, an input/output buffer (not shown), and the like. It ECU 300 controls each device based on a signal received from each sensor and a map and a program stored in memory 302 so that vehicle 1 and battery system 2 are in desired states. As main processing executed by ECU 300, there are an estimation process of a voltage change amount due to a memory effect generated in battery 100 and a setting process of charging power upper limit value Win and discharge power upper limit value Wout based on the estimated voltage change amount. Examples of these processes will be described later.

  FIG. 2 is a diagram showing a configuration of the cell 101 included in the battery 100. Since the configuration of each cell 101 is common, only one cell 101 is representatively shown in FIG. The cell 101 is, for example, a prismatic closed cell, and includes a case 102, a safety valve 103 provided in the case 102, an electrode body 104 housed in the case 102, and an electrolytic solution (not shown). In addition, in FIG. 2, a part of the case 102 is seen through to show the electrode body 104.

  The case 102 includes a case main body and a lid body, both of which are made of metal, and is hermetically sealed by welding the entire circumference of the lid body on the opening of the case book. When the pressure inside the case 102 exceeds a predetermined value, the safety valve 103 discharges part of the gas (hydrogen gas or the like) inside the case 102 to the outside. The electrode body 104 includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is inserted in the bag-shaped separator, and the positive electrode plate and the negative electrode plate inserted in the separator are alternately laminated. The positive electrode plate and the negative electrode plate are electrically connected to a positive electrode terminal and a negative electrode terminal (not shown), respectively.

As the material of the electrode body 104 and the electrolytic solution, various conventionally known materials can be used. In the present embodiment, as an example, an electrode plate including a positive electrode active material layer containing nickel hydroxide (Ni(OH) ₂ or NiOOH) and an active material support such as foamed nickel is used as the positive electrode plate. Be done. An electrode plate containing a hydrogen storage alloy is used as the negative electrode plate. As the separator, a nonwoven fabric made of hydrophilized synthetic fibers is used. An alkaline aqueous solution containing potassium hydroxide (KOH) or sodium hydroxide (NaOH) is used as the electrolytic solution.

<Memory effect of battery>
In the battery system 2 configured as described above, it is required to highly accurately estimate the “memory amount” indicating the voltage change amount (voltage drop amount or voltage increase amount) due to the memory effect of the battery 100.

  The present inventor has focused on conditions relating to the voltage Vb (more specifically, the open circuit voltage) of the battery 100 and the temperature Tb as the main factors that determine the size of the memory amount from three types of experimental results described later. Hereinafter, the condition defined including a combination of the open circuit voltage (OCV: Open Circuit Voltage) of the battery 100 and the temperature Tb is also referred to as a “use condition” of the battery 100. Furthermore, the present inventor has noticed that when estimating the memory amount that has occurred during a certain period, it is not necessary to consider the "use condition" of the battery 100 before that period (described later).

  Based on these findings, in the present embodiment, the memory amount as a total amount (hereinafter also referred to as “integrated memory amount”) that is the integrated value is calculated by sequentially integrating the memory amounts generated during a predetermined period. presume. By adopting such a method, if the memory amount during a predetermined period can be estimated with high accuracy by using the experimental result or the simulation result, the accumulated memory amount can also be estimated with high accuracy. This is because. Hereinafter, this method will be described in detail.

  FIG. 3 is a diagram for explaining the results of three types of experiments conducted by the present inventor. As shown in FIG. 3A, the three types of experiments are a constant voltage test, a standing test, and a cycle test of the battery 100.

  The constant voltage test is a test in which the voltage Vb of the battery 100 is kept constant by applying a voltage from the outside of the battery 100 to the battery 100 using an external power supply (not shown) for a predetermined period (several days in the example shown in FIG. 3). Is. The leaving test is a test in which the battery 100 is left for a predetermined period without applying a voltage from an external power source. In the standing test, the influence of SOC decrease due to self-discharge of the battery 100 appears, whereas in the constant voltage test, the influence of SOC decrease due to self-discharge does not appear. Therefore, by comparing these test results, the magnitude of the influence of the self-discharge of the battery 100 on the memory amount can be obtained.

  The cycle test is a test in which the battery 100 is repeatedly charged and discharged with a predetermined SOC width for a predetermined period. By comparing the results of a plurality of cycle tests in which the magnitude of the charge/discharge current is different from each other, the magnitude of the influence of the charge/discharge current on the memory amount can be obtained.

  As a result of performing three types of tests over the same period (the above predetermined period) when the temperature Tb of the battery 100 is T1 (room temperature) and when the temperature Tb is T2 (high temperature) higher than T1. Is shown in FIG. The white square marker shows the constant voltage test result at the temperature T1, the white circular marker shows the standing test result at the temperature T1, and the white diamond-shaped marker shows the cycle test result at the temperature T1. The black square marker shows the constant voltage test result at the temperature T2, the black circular marker shows the standing test result at the temperature T2, and the black diamond-shaped marker shows the cycle test result at the temperature T2.

  In FIG. 3B, the horizontal axis represents the OCV of the battery 100 (or each cell 101), and the vertical axis represents the memory amount (here, the voltage drop amount during discharging) M. As shown in FIG. 4B, the memory amount M is particularly large when the OCV is within the predetermined range. Further, the higher the temperature Tb of the battery 100, the larger the memory amount M. From these results, it is understood that the memory amount generated during the predetermined period is determined according to the use condition (OCV, Tb) defined by the combination of the OCV and the temperature Tb of the battery 100.

  On the other hand, at each of the temperatures T1 and T2, the constant voltage test result (see the square marker) and the leaving test result (see the circular marker) are plotted at positions close to each other. From this, it can be seen that the influence of the self-discharge of the battery 100 on the memory amount is relatively small. Further, the cycle test results (see diamond markers) are also plotted at locations close to the other two test results (see square and circular markers). From this, it is understood that the charge/discharge current of the battery 100 also has a relatively small effect on the memory amount.

  Since there is a correlation between OCV and SOC, the same result as in FIG. 3B can be obtained even when SOC is used instead of OCV on the horizontal axis. Further, although the discharge side memory effect is described as a representative in FIG. 3, the charge side memory effect can also be defined by the use condition (OCV, Tb) although the sign of the voltage change amount is different. .

  By performing the experiment shown in FIG. 3 under various usage conditions (OCV, Tb), the amount of memory generated with the passage of time from the start of use of the battery 100 is changed according to the usage conditions (OCV, Tb). It is possible to estimate.

  FIG. 4 is a time chart showing the correspondence relationship between the elapsed time and the memory amount under each use condition. In FIG. 4, the horizontal axis represents the elapsed time from the start of use of the battery 100, and the vertical axis represents the memory amount. It should be noted that the start of use of the battery 100 (initial value of elapsed time) may be at the time of manufacturing the battery 100, or at the time of complete refresh charge/discharge of the battery 100 (complete elimination of the memory effect generated in the battery 100). Charging and discharging).

By carrying out the above-mentioned experiment for each use condition, as shown in FIG. 4, a curve showing an increase in the memory amount with the passage of time can be obtained for each use condition. Note that, in FIG. 4 and FIG. 5 to be described later, an example in which the curves C _{P to} C _R respectively corresponding to the three types of use conditions _P to _R are acquired will be described in order to facilitate understanding. Similar curves are obtained for many conditions of use.

<Integrated memory amount estimation processing>
The memory amounts generated under the use conditions _P to _R are calculated by referring to the curves C _{P to} C _R , respectively, and the “integrated memory amount” is estimated by repeatedly executing the process of integrating the calculated memory amounts. be able to. This process is also referred to as "integrated memory amount estimation process" and will be described in detail below.

FIG. 5 is a time chart for explaining the integrated memory amount estimation processing according to the present embodiment. In FIG. 5A, the horizontal axis represents the elapsed time from the start of using the battery 100, and the vertical axis represents the usage conditions. In FIG. 5A, a case will be described in which the use condition is determined every predetermined period Δt, and the use condition changes in the order of P, Q, and R. The periods under the use conditions P, Q, R are indicated by L _P , L _Q , and L _R , respectively.

In FIG. 5B, the horizontal axis represents the elapsed time from the start of using the battery 100, and the vertical axis represents the memory amount. First, under the use condition P, the memory amount M is sequentially integrated for each predetermined period Δt with reference to the curve C _P. As a result, the amount of memory that occurred during the period L _P under use conditions P passes becomes M _P. When the integrated result of the memory amount M is described as “integrated memory amount ΣM”, the integrated memory amount ΣM when the period L _P has elapsed is M _P.

Next, when the use conditions are changed to Q from P, the integrated memory amount? M = curve corresponding to M _P C _{Q (curve} was translated by L _P curve C _Q in the time axis direction shown in FIG. 5) above From this point, the memory amount M is sequentially integrated for each predetermined period Δt with reference to the curve C _Q. If the amount of memory that occurred during the period L _Q under use conditions Q has elapsed is M _Q, period L _Q is accumulated memory amount ΣM when the elapsed, M _P and M _Q and the sum (M P ₊ M _Q ).

Furthermore, the use conditions are changed to R from Q, the integrated amount of memory _{ΣM = (M P + M Q} ) corresponding to the curve _{C R} (curve _{C R} shown in the time axis direction in FIG. 4 _(L P ₊ L Q) The curve C _R is referred to from the point on the curve that has been moved in parallel), and the memory amount M is sequentially integrated for each predetermined period Δt. If the amount of memory that occurred during the period _{L R} under use conditions R has elapsed is _{M R,} the integrated amount of memory ΣM caused the entire period _{(L P + L Q + L R} ) is, _{M P} and _{M Q} And M _R (M _P +M _Q +M _R ).

  As described above, in the present embodiment, when the integrated memory amount ΣM is calculated by shifting to a different curve according to the change of the use condition, the integrated memory amount ΣM calculated according to the curve before the transition can be taken over. It is assumed that. That is, when the integrated memory amount ΣM reaches a predetermined value according to a certain curve and when the integrated memory amount ΣM and the above predetermined value are reached according to another curve, the state of the battery 100 affecting the memory effect (mainly It is premised on the electrochemical knowledge that the states of the positive electrode active material layers are equal to each other.

  As described above, in the present embodiment, the memory amount M according to the usage conditions P to R is calculated for each predetermined period Δt, and the process of sequentially integrating the calculated memory amount M is repeatedly executed, The integrated memory amount ΣM generated over the entire period can be calculated.

  The above contents can be explained using a recurrence formula. That is, as shown in the following equation (1), the integrated memory amount ΣM(N) in the Nth integration process is equal to the integrated memory amount ΣM(N−1) up to the (N−1)th integration process, It can be calculated by adding the memory amount M(N) according to the usage condition from the time of the (N−1)th integration process to the time of the Nth integration process (during the predetermined period Δt). Note that N is a natural number.

ΣM(N)=ΣM(N-1)+M(N) (1)
<Integrated memory amount estimation processing flow>
FIG. 6 is a flowchart showing the integrated memory amount estimation processing according to the present embodiment. The flowchart shown in FIG. 6 and FIG. 9 to be described later is called and executed from a main routine (not shown) every predetermined period or every time a predetermined condition is satisfied. Each step (hereinafter abbreviated as “S”) included in these flow charts is basically realized by software processing by the ECU 300, but a part or all of the hardware (electric circuit) produced in the ECU 300. May be realized by.

  The accumulated memory amount ΣM is sequentially updated by repeatedly executing the processing of the flowchart shown in FIG. 6. This flowchart shows the Nth integration process, and the accumulated memory amount ΣM(N−1) up to the (N−1)th (previous) integration process is stored in the memory.

  In step S110, the ECU 300 reads the integrated memory amount ΣM(N-1) up to the (N-1)th integration processing from the memory.

  In S120, ECU 300 acquires voltage Vb(N) and current Ib(N) of battery 100 using voltage sensor 210 and current sensor 220, respectively. Then, ECU 300 subtracts the voltage drop amount (=Ib(N)×R) due to the charge/discharge current from voltage Vb(N) to calculate OCV(N). The internal resistance of the battery 100 is indicated by R.

  In S130, ECU 300 acquires temperature Tb(N) of battery 100 using temperature sensor 230. As a result, the use condition (combination of OCV(N) and temperature Tb(N)) to be referred to in the map MP1 is set.

  In S140, ECU 300 waits until a predetermined period Δt elapses. In order to properly calculate the memory amount M, it is required that the category of use condition does not change while waiting for a predetermined period Δt. Therefore, it is preferable to set the predetermined period Δt to a time during which the division of the usage condition does not change during the standby.

  In S150, the ECU 300 refers to the curve corresponding to the use condition (OCV(N), Tb(N)) from the map MP1 stored in the memory, and calculates the memory amount M(N) generated in the predetermined period Δt. To do. Since this processing has been described in detail in FIG. 6B, the description will not be repeated.

  In S160, the ECU 300 adds the memory amount M(N) calculated in S150 to the integrated memory amount ΣM(N-1) up to the (N-1)th integration process read in S110, An integrated memory amount ΣM(N) up to the Nth integration process is calculated (see the above equation (1)). When the vehicle 1 is shipped, the initial value ΣM(0) of the integrated memory amount is set to 0, for example. Further, the initial value ΣM(0) of the integrated memory amount may be set to 0 even after the refresh charge/discharge of the battery 100 is executed.

  In S170, ECU 300 stores in memory the integrated memory amount ΣM(N) calculated in S160, in case the flowchart shown in FIG. 6 is called next time.

As described above, by using the curves (C _{P to} C _R etc.) in the map MP1 prepared in advance based on the results of the experiments by the present inventors, the memory amount M generated at every predetermined period Δt of the battery 100 is It is calculated according to the usage conditions (OCV and temperature Tb). By adopting the above parameters as the usage conditions, the memory amount M for each predetermined period Δt can be estimated with high accuracy. Further, the integrated memory amount ΣM is calculated by sequentially integrating the highly accurate calculated memory amount M on the assumption that it is possible to inherit the integrated memory amount ΣM between the curves. To be done. This makes it possible to estimate the integrated memory amount ΣM with high accuracy.

Although the process of estimating the memory amount M for each “predetermined period” Δt has been described as an example in FIG. 6, it is not essential to estimate the memory amount M at a constant cycle. The length of the predetermined period Δt may be a variable value according to, for example, the usage condition of the battery 100 or the state of the calculation load of the ECU 300. Alternatively, the usage condition of the battery 100 may be monitored, and the memory amount M may be estimated by using a change in the usage condition as a trigger (in other words, by using the transition between the curves C _{P and} C _R as a trigger). . In this case, the time to change from conditions that use conditions to other conditions (period L _P in FIG. _{5 (B), L Q,} L R) corresponds to the "predetermined period". As a result, the number of times the memory amount M is estimated can be reduced and the calculation load on the ECU 300 can be reduced.

<Limit of charge/discharge power>
In the vehicle 1 configured as described above, the charging and discharging of the battery 100 is limited for the purpose of protecting the battery 100. More specifically, charging/discharging of battery 100 is controlled so that charging power to battery 100 does not exceed charging power upper limit value Win and discharging power from battery 100 does not exceed discharging power upper limit value Wout. Furthermore, the upper limit value UL and the lower limit value LL of the usage range are defined for the voltage Vb of the battery 100, the voltage Vb does not exceed the upper limit value UL, and the voltage Vb does not fall below the lower limit value LL. The charge/discharge of the battery 100 is controlled.

  Here, since the voltage Vb when the battery 100 is discharged is lower than the voltage Vb (OCV) when the battery 100 is not discharged, by the amount of voltage drop due to the discharge, the voltage Vb becomes lower as the discharge power increases. When the memory effect on the discharge side occurs in the battery 100, the voltage Vb becomes lower than in the normal state where the memory effect does not occur, and the voltage Vb easily reaches the lower limit value LL as the battery 100 discharges. Therefore, in order to prevent the voltage Vb from falling below the lower limit value LL, it is desirable to set the discharge power upper limit value Wout (absolute value) lower than in the normal state (in other words, the discharge power upper limit value Wout should be reduced. Is desirable). However, if the discharge power upper limit value Wout is set too low, the battery 100 can be protected, but the discharge of the battery 100 may be excessively limited and the battery 100 may not be fully utilized.

  On the contrary, the voltage Vb at the time of charging the battery 100 is higher than the voltage Vb (OCV) when the battery 100 is not being charged, and the higher the charging power, the higher the voltage Vb. When the memory effect on the charging side occurs in the battery 100, the voltage Vb becomes higher than that in the normal state, so that the voltage Vb easily reaches the upper limit value UL as the battery 100 is charged. Therefore, in order to prevent the voltage Vb from exceeding the upper limit value UL, it is desirable to set the charging power upper limit value Win (absolute value) smaller than that in the normal state (in other words, the charging power upper limit value Win should be reduced. Is desirable). However, if the charging power upper limit Win is set too small, the battery 100 can be protected, but the charging of the battery 100 may be excessively limited and the battery 100 may not be fully utilized.

  Therefore, in the present embodiment, a “discharge memory amount” ΣMdch indicating the discharge side integrated memory amount of the battery 100 and a “charge memory amount” ΣMchg indicating the charge side integrated memory amount of the battery 100 are calculated, The discharge power upper limit value Wout is set according to the discharge memory amount ΣMdch, and the charge power upper limit value Win is set according to the charge memory amount ΣMchg. The discharge memory amount ΣMdch and the charge memory amount ΣMchg are separately (independently) calculated by the integrated memory amount estimation process shown in FIG. 6. Then, the charging power upper limit value Win and the discharging power upper limit value Wout can be set from the charging memory amount ΣMchg and the discharging memory amount ΣMdch using a map MP2 as shown below.

  FIG. 7 is a diagram showing an example of a map MP2 for setting the charging power upper limit value Win and the discharging power upper limit value Wout. FIG. 7 shows a graph conceptually showing the map MP2. The horizontal axis represents the temperature Tb of the battery 100. The upper limit of the discharge power of the battery 100 is shown in the upper part of the vertical axis, and the upper limit of the charge power of the battery 100 is shown in the lower part of the vertical axis. The map MP2 is preferably determined according to the internal pressure Pin of the battery 100 (or the cell 101) (described later). FIG. 7 shows a map MP2 when the internal pressure Pin is P0.

  When the temperature Tb is lower than the predetermined value, the electrolyte of the battery 100 may be frozen, and thus charging/discharging of the battery 100 is prohibited. Therefore, the discharge power upper limit value Wout and the charge power upper limit value Win are both set to zero.

  When the temperature Tb becomes equal to or higher than a predetermined value, charging/discharging of the battery 100 is allowed. The discharge power upper limit value Wout (absolute value) is set higher as the temperature Tb increases. Although not shown, the charging power upper limit value Win and the discharging power upper limit value Wout may be set to 0 at a predetermined temperature or higher from the viewpoint of protecting the battery 100. On the other hand, FIG. 7 shows the case where the discharge memory amount ΣMdch is D0 to D3 (D0<D1<D2<D3). The larger the discharge memory amount ΣMdch, the lower the discharge power upper limit value Wout at the same temperature Tb is set. ..

  Similarly, the charging power upper limit value Win (absolute value) is set higher as the temperature Tb increases. On the other hand, the larger the charging memory amount ΣMchg, the lower the charging power upper limit value Win at the same temperature Tb is set. The relationship as shown in FIG. 7 is stored in the memory 302 of the ECU 300 as the map MP2.

  Here, an example will be described in which the discharge memory amount ΣMdch of the battery 100 is calculated, and the discharge power upper limit value Wout of the battery 100 is set according to the calculation result. Hereinafter, this control is also referred to as discharge power upper limit control of the battery 100.

  FIG. 8 is a time chart showing the discharge power upper limit control of battery 100 in the present embodiment. In FIG. 8, the vertical axis represents the SOC of the battery 100, the discharge memory amount ΣMdch of the battery 100, and the discharge power upper limit Wout of the battery 100 in order from the top. The horizontal axis represents the elapsed time. The length of the elapsed time shown in FIG. 8 is, for example, on the order of several weeks to several months for the discharge memory amount ΣMdch (shown in the middle row) and the discharge power upper limit value Wout (shown in the lower row). Therefore, although not shown for the sake of clarity, the ignition-off (IG-OFF) and the ignition-off (IG-ON) of the vehicle 1 are repeated during that time. On the other hand, the upper part of FIG. 8 shows an enlarged part of the elapsed time shown in the middle part and the lower part. That is, the length of the elapsed time for the SOC (shown in the upper part) of battery 100 is, for example, the period from IG-OFF to IG-ON, and is specifically on the order of several tens of minutes to several hours. ..

  As shown in FIG. 8, at the start of use of the battery 100 (for example, when the battery 100 is new) (0), the discharge memory amount ΣMdch is substantially 0. The discharge power upper limit value Wout of the battery 100 is Wout0 which is the initial value at the start of use of the battery 100.

  The discharge memory amount ΣMdch gradually increases as the vehicle 1 travels. Then, as the discharge memory amount ΣMdch increases, the discharge power upper limit value Wout decreases. The manner of decreasing the discharge power upper limit value Wout is set from the discharge memory amount ΣMdch using the map MP2 shown in FIG. 7.

  When the discharge memory amount ΣMdch reaches the threshold value TH at time t1, the refresh discharge of the battery 100 is started. The refresh discharge is executed during the period from time t1 to time t2. The refresh discharge reduces the discharge memory amount ΣMdch. That is, the memory effect of battery 100 is (at least partially) eliminated. The discharge power upper limit value Wout increases as the discharge memory amount ΣMdch decreases.

  When the memory amount estimation processing is executed, it is desirable to previously obtain the degree of elimination (elimination amount) of the memory effect due to refresh discharge (or refresh charge). For example, the correlation between the temperature Tb at the time of refresh discharge, the SOC change width at the time of refresh discharge, and the degree of elimination of the memory effect by the refresh discharge is obtained in advance by experiments, and stored in the memory 302 as a map (not shown). Remember. By referring to such a map, it is possible to calculate the decrease amount of the discharge memory amount ΣMdch (or the charge memory amount ΣMchg) each time refresh discharge (or refresh charge) is performed. After the refresh discharge (after the refresh charge), the reduced discharge memory amount ΣMdch (or the charge memory amount ΣMchg) may be integrated again.

  Further, the SOC of the battery 100, which has been around the SOC center C (for example, SOC=50%) until then, temporarily decreases with the refresh discharge. The threshold value TH is preset to a value smaller than the allowable maximum value MAX of the discharge memory amount ΣMdch.

  When the refresh discharge is stopped at time t2, the discharge memory amount ΣMdch starts increasing again as described above, and the discharge power upper limit Wout starts decreasing. Further, the SOC of the battery 100 returns to the SOC center C. After that, at time t3, when the discharge memory amount ΣMdch reaches the threshold value TH again, the refresh discharge of the battery 100 is executed. Since the manner of decreasing the discharge memory amount ΣMdch and the manner of increasing the discharge power upper limit value Wout after time t3 are the same as the manner during the period from time t1 to time t2, the description thereof will not be repeated.

  FIG. 9 is a flowchart showing discharge power upper limit control and charge power upper limit control of battery 100 in the present embodiment. 9A shows the discharge power upper limit control of the battery 100, and FIG. 9B shows the charge power upper limit control of the battery 100.

  First, with reference to FIG. 9A, in S100, EU 300 calculates the discharge memory amount ΣMdch of battery 100 by executing the above-described integrated memory amount estimation process.

  In S11, the ECU 300 sets the discharge power upper limit value Wout corresponding to the discharge memory amount ΣMdch calculated in S100 by referring to the map MP2. After that, the process shown in FIG. 9A is repeatedly executed every predetermined cycle or every time a predetermined condition is satisfied, so that the discharge power upper limit value Wout is maintained at an appropriate value according to the situation of the vehicle 1.

  Next, referring to FIG. 9(B), in S100, EU 300 calculates the charge memory amount ΣMchg of battery 100 by executing the integrated memory amount estimation process.

  In S21, ECU 300 calculates internal pressure Pin of battery 100. Since this calculation method is publicly known, detailed description will not be repeated (for example, refer to JP-A-2007-53058).

  In S31, the ECU 300 sets the charging power upper limit Win corresponding to the internal pressure Pin of the battery 100 and the charging memory amount ΣMchg by referring to the map MP2. When the charging power upper limit Win is set high, it is desirable to set the voltage Vb so that the internal pressure Pin falls below the limit threshold value. After that, the series of processing shown in FIG. 9B is repeatedly executed.

  As described above, according to the present embodiment, charging power upper limit value Win is set using charging memory amount ΣMchg, and discharging power upper limit value Wout is set using discharging memory amount ΣMdch. Since the charging memory amount ΣMchg is estimated with high accuracy, the charging power upper limit Win is set too low to make full use of the battery 100, or the charging power upper limit Win is set high. It is prevented that the battery 100 cannot be properly protected by being passed. The same applies to the discharge side of battery 100 (that is, discharge power upper limit value Wout). Therefore, it becomes possible to fully utilize the battery 100 while appropriately protecting the battery 100.

  The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

  1 vehicle, 2 battery system, 10 motor generator, 20 power transmission gear, 30 drive wheels, 40 PCU, 50 SMR, 100 battery, 101 cell, 102 case, 103 safety valve, 104 electrode body, 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 301 CPU, 302 memory, 303 timer.

Claims (1)

A battery system for supplying power to an external device,
Batteries, including nickel-metal hydride batteries,
A power conversion device configured to convert power between the battery and the external device,
A control device that controls the power conversion device such that charging power to the battery does not exceed a control upper limit value of the charging power, and discharging power from the battery does not exceed a control upper limit value of the discharging power. Prepare,
The control device stores data indicating a correspondence relationship between a memory amount indicating a voltage change amount due to a memory effect of the battery and an elapsed time from the start of use of the battery,
The data is defined separately for each usage condition defined including the open circuit voltage and temperature of the battery,
The control device is
Referring to stored data, while leaving calculate the amount of memory within the time division of the operating conditions do not change, the classification of the use conditions are changed, a memory in a time division after the change persists Calculate the amount,
Estimating the current memory amount of the battery by accumulating the memory amount in the time when the category of the use condition does not change and the memory amount in the time when the category after the change continues ,
A battery system in which the control upper limit value of the charging power and the control upper limit value of the discharging power are set using the estimated memory amount.

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