JP2012244723A - Charge/discharge controller of power storage device and electric vehicle loading the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly set an allowable charge/discharge power value when charge/discharge limitation of a power storage device is temporarily alleviated so that output voltage of the power storage device does not deviate from within a voltage range from lower limit voltage to upper limit voltage.SOLUTION: An operation point 520 when discharge current increases by temporary alleviation of discharge limitation from a current operation point 510 of a battery is calculated based on a current internal resistance estimation value R. Furthermore, the operation point of the battery transits to an operation point 530 on an equal power line 525 by continuous discharge at the operation point 520. The maximum dischargeable power when the discharge limitation is temporarily alleviated is set so that voltage at the operation point 530 becomes equal to or more than lower limit voltage Ve. Namely, the maximum dischargeable power when the discharge limitation is temporarily alleviated is set by further considering not only a voltage change amount from the operation point 510 to the operation point 520 depending on internal resistance but a voltage change amount ΔVdyn from the operation point 520 to the operation point 530 due to continuation of temporary discharge alleviation.

Description

  The present invention relates to a charge / discharge control device for a power storage device and an electric vehicle equipped with the same, and more specifically, relates to control for temporarily relaxing a charge / discharge limit of the power storage device.

  Systems that drive and control electric devices that are loads are widely used in association with charging and discharging of power storage devices represented by secondary batteries (hereinafter also simply referred to as batteries). For example, in an electric vehicle capable of generating a vehicle driving force by electric energy, a system in which an electric motor for generating the vehicle driving force is used as a load of an in-vehicle power storage device is applied. The electric vehicle includes, in addition to an electric vehicle using only an electric motor as a power source, a hybrid vehicle or a fuel cell vehicle further mounted with another power source.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-306771) discloses a control that temporarily relaxes the charge / discharge restriction in response to a request from a load in order to sufficiently exhibit the performance of a battery mounted on a hybrid vehicle. Is described. Furthermore, it describes that the allowable value of charge / discharge power when temporarily relaxing charge / discharge is set so that the battery voltage does not deviate from the voltage range from the lower limit voltage to the upper limit voltage.

  Specifically, the change in the output voltage of the power storage device when the charge / discharge current is increased from the current voltage value and current value is estimated by extrapolation based on the current internal resistance. Then, the current value when the output voltage reaches the lower limit voltage or the upper limit voltage is obtained as the maximum current value that can be charged and discharged. Furthermore, by setting the discharge power allowance based on the product of the lower limit voltage and the maximum dischargeable current, the battery voltage will not drop below the lower limit voltage even if the discharge limit is temporarily relaxed. Can do. Similarly, by setting the charge power allowance based on the product of the upper limit voltage and the maximum current that can be charged, the battery voltage can be prevented from rising above the upper limit voltage even if the charge limit is temporarily relaxed. .

Japanese Patent Laid-Open No. 2007-306771

  Some power storage devices have a phenomenon in which dynamic output voltage fluctuations depend on charge / discharge history. For example, in a battery, the output voltage decreases due to continuous discharge, while the output voltage increases due to continuous charging. Such a phenomenon is also called “polarization”. Polarization is considered to occur due to an imbalance in chemical change during charge and discharge between the vicinity of and inside the surface of the electrode active material inside the battery.

  For this reason, when the charge / discharge power limit of the battery is temporarily relaxed according to Patent Document 1, there is a possibility that a further voltage change may occur as the charge / discharge current after relaxation continues for a predetermined time. At this time, in Patent Document 1, the allowable charge / discharge power value is determined so as to maximize the battery performance based on the current internal resistance. Sometimes the battery voltage may be lower than the lower limit voltage, or the battery voltage may be higher than the upper limit voltage during charge relaxation.

  The present invention has been made to solve such problems, and an object of the present invention is to allow charging / discharging power when temporarily relaxing the charging / discharging limit of a power storage device such as a secondary battery. To provide a charge / discharge control device for a power storage device that can accurately set the value so that the output voltage of the power storage device does not fall outside the voltage range from the lower limit voltage to the upper limit voltage, and an electric vehicle equipped with the same It is.

  One aspect of the present invention is a charge / discharge control device for maintaining an output voltage of a power storage device within a voltage range from a lower limit voltage to an upper limit voltage, and a state for acquiring a measured value indicating a state of the power storage device An internal resistance estimating unit for estimating the internal resistance of the power storage device based on the measurement value acquired by the acquisition unit, the state acquisition unit, and charging / discharging power limitation of the power storage device based on the state of the power storage device The first limit setting means for setting the allowable discharge power value and the allowable charge power value, and the output voltage from the voltage range only during the first time in response to a request from the load of the power storage device And a second limit setting means for temporarily relaxing the charge / discharge power limit within a range that does not deviate. The second limit setting means includes a first voltage change amount based on a product of a change amount of the charge / discharge current due to temporary relaxation of the charge / discharge power limit and the internal resistance estimated by the internal resistance estimation means; At least one of the discharge power allowance and the charge power allowance based on both the second voltage change caused by the charge / discharge current after being increased by the relaxation being continued for the first time. The absolute value is set larger than the value set by the first limit setting means.

  Preferably, the second limit setting means determines the first-order function model based on the means for estimating the second voltage change amount by the first-order function model using the current of the power storage device as a variable, and the temperature of the power storage device. Means.

  Preferably, the first time is variably set according to the load condition. The second limit setting means is a linear function based on the means for estimating the second voltage change amount by a linear function model with the current of the power storage device as a variable, the first time and the temperature of the power storage device. Means for determining a model.

  More preferably, the second limit setting means discharges when the voltage obtained by subtracting the first and second voltage change amounts from the current output voltage of the power storage device is equal to the lower limit voltage when the power storage device is discharged. The allowable discharge power value is set based on the product of the current and the lower limit voltage.

  Alternatively, more preferably, when the power storage device is charged, the second limit setting means is configured such that a voltage obtained by adding the first and second voltage variations to the current output voltage of the power storage device is equal to the upper limit voltage. Based on the product of the charging current and the upper limit voltage, the allowable charging power is set.

  Preferably, the power storage device, the internal combustion engine for generating vehicle driving force, the first and second electric motors configured to be able to exchange power between the power storage device and the charge / discharge control device described above In the electric vehicle including the first electric motor, the first electric motor is configured to be able to start the internal combustion engine by being rotationally driven by the discharge electric power of the power storage device, and the second electric motor has a vehicle driving force by the electric power discharged from the electric power storage device. Configured to generate. The charge / discharge control device sets the allowable discharge power value by the second limit setting means when the internal combustion engine is started.

  Preferably, in the electric vehicle including the power storage device, the electric motor configured to be able to exchange power bidirectionally with the power storage device, and the charge / discharge control device described above, the electric motor is driven by the discharge power of the power storage device. It is comprised so that generation | occurrence | production of the vehicle driving force of a vehicle is possible. The charge / discharge control device sets the allowable discharge power value by the second limit setting means when the output request to the electric motor becomes equal to or greater than a predetermined value.

  Alternatively, preferably, in the electric vehicle including the electric power storage device, the electric motor configured to be able to exchange electric power between the electric power storage device and the charge / discharge control device described above, the electric motor has a regenerative torque when the electric vehicle is decelerated. The regenerative braking power generation due to the generation of the power storage device is configured to generate the charging power of the power storage device. The charge / discharge control device sets the allowable charge power value by the second limit setting means when the absolute value of the regenerative torque required for the electric motor is larger than a predetermined value.

  According to the present invention, the allowable charge / discharge power value when temporarily relaxing the charge / discharge limit of a power storage device such as a secondary battery is out of the voltage range from the lower limit voltage to the upper limit voltage. It can be set accurately so that there is no.

1 is a control block diagram of a hybrid vehicle shown as a representative example of an electric vehicle equipped with a charge / discharge control device for a power storage device according to an embodiment of the present invention. It is a block diagram which shows schematic structure of the charging / discharging control of the electrical storage apparatus by embodiment of this invention. It is a flowchart explaining the setting of the discharge power allowable value by embodiment of this invention. It is a conceptual diagram explaining the calculation method of the maximum dischargeable electric power. It is a 1st conceptual diagram explaining the characteristic of the polarization voltage with respect to battery current (discharge). It is a 2nd conceptual diagram explaining the characteristic of the polarization voltage with respect to battery current (discharge). It is a flowchart explaining the calculation processing procedure of the maximum dischargeable electric power. It is a flowchart explaining the setting of the charging power allowable value by embodiment of this invention. It is a conceptual diagram explaining the calculation method of the maximum chargeable electric power. It is a conceptual diagram explaining the characteristic of the polarization voltage with respect to battery current (charge). It is a flowchart explaining the calculation process procedure of maximum chargeable electric power.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

(System configuration example)
FIG. 1 is a control block diagram of a hybrid vehicle shown as a representative example of an electric vehicle equipped with a power storage device control device according to an embodiment of the present invention. The electric vehicle is not limited to the hybrid vehicle shown in FIG. 1, and may be a hybrid having another aspect as long as it has a configuration for inputting and outputting electric power between the power storage device and the vehicle driving motor. The present invention can also be applied to a vehicle (for example, a series type hybrid vehicle), an electric vehicle, or a fuel cell vehicle.

  Referring to FIG. 1, the hybrid vehicle includes an internal combustion engine (hereinafter simply referred to as an engine) 120 such as a gasoline engine or a diesel engine, and a motor generator (MG) 140 as drive sources. The motor generator 140 includes a motor generator 140A that mainly functions as a motor (hereinafter also referred to as a motor 140A for convenience of description) and a motor generator 140B that mainly functions as a generator (hereinafter also referred to as a generator 140B for convenience of description). Including. Note that the motor 140A functions as a generator or the generator 140B functions as a motor according to the traveling state of the hybrid vehicle.

  Hybrid vehicle further includes a reduction gear 180, a power split mechanism 200, a main battery 220 shown as a representative example of a power storage device, inverters 240 and 241, and a converter 242. Reducer 180 is configured to transmit the power generated by engine 120 and motor generator 140A to drive wheel 160, or to transmit the driving force of drive wheel 160 to engine 120 and motor generator 140A. Power split device 200 distributes the power generated by engine 120 to two paths of drive wheel 160 and generator 140B. Main battery 220 is formed of a rechargeable secondary battery, and accumulates electric power for driving motor generators 140A and 140B. Inverter 240 performs bidirectional power conversion between the DC power of main battery 220 and the AC power of motor generator 140A. Inverter 241 performs bidirectional power conversion between the DC power of main battery 220 and the AC power of motor generator 140B. Converter 242 performs bidirectional DC voltage conversion between the DC voltage of main battery 220 and the DC link voltage of inverters 240 and 241.

  The hybrid vehicle further includes a battery control unit (hereinafter referred to as a battery ECU (Electronic Control Unit)) 260, an engine ECU 280, an MG_ECU 300, and an HV_ECU 320. Battery ECU 260 manages and controls the charge / discharge state of main battery 220. Engine ECU 280 controls the operating state of engine 120. MG_ECU 300 controls motor generators 140A and 140B, battery ECU 260, inverter 240, and the like according to the state of the hybrid vehicle. The HV_ECU 320 controls and controls the battery ECU 260, the engine ECU 280, the MG_ECU 300, and the like so that the hybrid vehicle can operate most efficiently.

  An accelerator pedal sensor 415 is connected to the accelerator pedal 410 operated by the driver. The accelerator pedal sensor 415 generates an output voltage corresponding to the amount of operation (depression amount) of the accelerator pedal 410 by the driver. Similarly, a brake pedal sensor 425 is connected to the brake pedal 420 operated by the driver. The brake pedal sensor 425 generates an output voltage corresponding to the amount of operation (depression amount) of the brake pedal 420 by the driver. Output voltages of the accelerator pedal sensor 415 and the brake pedal sensor 425 are transmitted to the HV_ECU 320. Therefore, the HV_ECU 320 can detect the accelerator pedal operation amount and the brake operation amount by the driver.

  In the present embodiment, converter 242 is provided between main battery 220 and inverter 240. Thus, even if the rated voltage of main battery 220 is lower than the rated voltage of motor generator 140A or motor generator 140B, the voltage is boosted or lowered by converter 242 so that the voltage between main battery 220 and motor generators 140A and 140B is increased. It is possible to send and receive electric power. This converter 242 has a built-in smoothing capacitor, and when the converter 242 performs a boosting operation, charges can be stored in the smoothing capacitor.

  In FIG. 1, each ECU is configured separately, but may be configured as an ECU in which two or more ECUs are integrated (for example, MG_ECU 300 and HV_ECU 320, as shown by a dotted line in FIG. 1). An example is an integrated ECU).

  Power split mechanism 200 is typically constituted by a planetary gear mechanism (planetary gear) in order to distribute the power of engine 120 to both drive wheel 160 and motor generator 140B. By controlling the rotation speed of motor generator 140B, power split device 200 also functions as a continuously variable transmission. The rotational force of the engine 120 is input to a planetary carrier (C) (not shown). The input rotational force is transmitted to the motor generator 140B by a sun gear (S) (not shown) and also transmitted to the motor and the output shaft (drive wheel 160 side) by a ring gear (R) (not shown). When the rotating engine 120 is stopped, since the engine 120 is rotating, the kinetic energy of this rotation is converted into electric energy by the motor generator 140B, and the rotational speed of the engine 120 is reduced.

  A hybrid vehicle equipped with a hybrid system as shown in FIG. 1 travels only by the motor 140 </ b> A of the motor generator 140 when the engine 120 is inefficient, such as when starting or running at a low speed. During normal travel, for example, the power split mechanism 200 divides the power of the engine 120 into two paths, and on the one hand, the drive wheels 160 are directly driven, and on the other hand, the generator 140B is driven to generate power. At this time, the motor 140A is driven by the generated electric power to assist driving of the driving wheels 160. Further, during high speed traveling, power from the main battery 220 is further supplied to the motor 140A to increase the output of the motor 140A and driving force is added to the driving wheels 160.

  On the other hand, at the time of deceleration, motor 140 </ b> A driven by drive wheel 160 functions as a generator to generate power by regenerative braking, and the collected power can be stored in main battery 220. In addition, regenerative braking here means regenerative power generation by braking with regenerative power generation when a driver operating a hybrid vehicle has a foot brake operation or by turning off the accelerator pedal while driving without operating the foot brake. Including decelerating the vehicle (or stopping acceleration) while

  The electric power that can be regeneratively generated is set according to the allowable charging power value for the main battery 220. That is, when charging of main battery 220 is prohibited, regenerative power generation is also prohibited, and the torque command value of motor generator 140A is set to zero.

  When the amount of charge of main battery 220 decreases and charging is particularly necessary, the output of engine 120 is increased to increase the amount of power generated by generator 140B to increase the amount of charge for main battery 220. Further, the amount of charge may be increased by increasing the output of the engine 120 as necessary even during low-speed traveling. For example, when the main battery 220 needs to be charged as described above, an auxiliary device such as an air conditioner is driven, or the temperature of the cooling water of the engine 120 is raised to a predetermined temperature.

  A brake mechanism 460 is provided on each of the driving wheel 160 and a wheel (not shown). The brake mechanism 460 has a braking force of the vehicle by a frictional force generated by pressing a disk rotor 465 provided corresponding to each wheel with a brake pad (friction material) operated by a hydraulic pressure generated by the brake actuator 450. It is comprised so that can be obtained. The amount of hydraulic pressure generated by the brake actuator 450 is controlled by the HV_ECU 320.

  The HV_ECU 320 calculates the required braking force for the entire vehicle from the depression amount of the brake pedal 420 and the like. Further, the HV_ECU 320 performs control so that the calculated overall required braking force is generated cooperatively by the regenerative braking force by the motor 140A and the hydraulic braking force by the brake mechanism 460.

FIG. 2 shows a schematic configuration of charge / discharge control of the power storage device according to the embodiment of the present invention.
A main battery 220 shown as an example of a power storage device is an assembled battery in which a plurality of cells are connected in series as shown in the figure, and is composed of a secondary battery such as a lead storage battery, a lithium ion battery, or a nickel metal hydride battery. Main battery 220 is connected to motor generators 140A and 140B (MG (1) and MG (2)) via inverters 240 and 241 and converter 242. That is, in this embodiment, inverters 240 and 241, converter 242, and motor generators 140 </ b> A and 140 </ b> B (MG (1) and MG (2)) integrally constitute a load of main battery 220.

  Further, a voltage sensor 226 that detects a terminal voltage of the main battery 220 (hereinafter referred to as a battery voltage Vb) and a current sensor 222 that detects a current flowing through the main battery 220 are provided. Hereinafter, the input / output current between the main battery 220 and the load detected by the current sensor 222 is referred to as a battery current Ib. In addition, the battery current Ib defines an arrow direction in the figure as a positive current direction. That is, Ib> 0 (positive) during discharging, and Ib <0 (negative) during charging. Therefore, the input / output power with respect to the load of the main battery 220 is indicated by the product of the battery voltage Vb and the battery current Ib, and has a positive value during discharging and a negative value during charging.

  Further, temperature sensors 224 that detect battery temperatures are provided at a plurality of locations of the main battery 220. The reason why the temperature sensors 224 are provided at a plurality of locations is that the temperature of the main battery 220 may be locally different. The outputs of current sensor 222, voltage sensor 226, and temperature sensor 224 are sent to battery ECU 260.

  The battery ECU 260 calculates the remaining capacity (SOC) of the battery based on these sensor output values, and further executes charge / discharge control. In the charge / discharge control, the estimated SOC matches the target SOC, and the battery voltage Vb becomes higher than the maximum allowable voltage (upper limit voltage Vu) due to overcharge, or the battery voltage Vb becomes the minimum allowable voltage (overvoltage due to overdischarge). It is executed so as not to become lower than the lower limit voltage Ve). Here, the upper limit voltage Vu and the lower limit voltage Ve are determined according to the highest rated voltage and the lowest rated voltage of the main battery 220, the operable (guaranteed) voltage of the device (load) connected to the main battery 220, or the like.

  In particular, as described above, the battery ECU 260 allows the charging power allowable value for the main battery 220 so that the battery voltage Vb is maintained within the voltage range of the lower limit voltage Ve to the upper limit voltage Vu (hereinafter also referred to as a management voltage range). Win (Win ≦ 0) and discharge power allowable value Wout (Wout ≧ 0) are determined and sent to MG_ECU 300 and HV_ECU 320.

  In particular, HV_ECU 320 determines the operation command values (typically torque command values) of motor generators 140A and 140B so that main battery 220 is charged and discharged within the range of allowable charging power value Win and allowable discharging power value Wout. Set. For example, as described above, in the output distribution of the vehicle driving force between the engine 120 and the motor 140A according to the traveling situation, the output power of the main battery 220 including the power consumption in the motor 140A is equal to the discharge power allowable value Wout. Considered not to exceed.

  At the time of regenerative braking, the torque command value (generally negative torque) of motor generator 140A is taken into consideration so that the input power to main battery 220 including the power generated by motor generator 140A does not exceed charging power allowable value Win. Is set. As described above, the HV_ECU 320 performs cooperative control so that the required braking force for the entire vehicle can be obtained by the sum of the regenerative braking force by the motor generator 140A and the hydraulic braking force by the brake mechanism 460 during the braking operation by the driver. Therefore, even if the regenerative braking force by the motor generator 140A is limited by the allowable charging power value Win, it is possible to obtain the necessary vehicle braking force. Further, a request flag for requesting temporary relaxation of charging / discharging is input from the HV_ECU 320 to the battery ECU 260. This request flag will be described in detail later.

(Temporary relaxation of discharge restrictions)
Next, the discharge power limitation according to the embodiment of the present invention will be described with reference to FIGS.

  FIG. 3 is a flowchart illustrating the setting of the allowable discharge power value according to the embodiment of the present invention. The flowchart shown in FIG. 3 is executed by battery ECU 260 at predetermined intervals.

  Referring to FIG. 3, battery ECU 260 obtains the battery state quantity (battery voltage Vb, battery current Ib, and battery temperature Tb) from the detection values of current sensor 222, temperature sensor 224, and voltage sensor 226 in step S100. .

  In step S110, battery ECU 260 estimates internal resistance R based on the battery state quantity acquired in step S100. The internal resistance estimation method in step S110 is not particularly limited, and a known estimation method can be arbitrarily used. For example, in a type of battery in which the internal resistance R has temperature dependence, a map reflecting the characteristics of the battery temperature Tb and the internal resistance R obtained in advance by experiments or the like is created, and the battery temperature Tb acquired in step S100 is created. The internal resistance R can be estimated by referring to the map using. Alternatively, as described in Patent Document 1, the internal resistance R is estimated by sequentially obtaining (Vb / Ib) by applying the least square method or the like by appropriately referring to the actual measurement values of the battery current Ib and the battery voltage Vb. May be.

Further, in step S120, battery ECU 260 estimates the SOC based on the battery state quantity acquired in step S100. Also for the SOC estimation, a known estimation method can be arbitrarily used. For example, the SOC may be estimated by sequentially estimating the open circuit voltage (OCV) by substituting the battery state quantity acquired in step S100 into the battery model equation, and the SOC change may be calculated based on the integration of the battery current Ib. The SOC may be estimated by tracing. Alternatively, the SOC may be estimated by combining both SOC estimation based on the battery model and SOC estimation based on current integration.

  Further, in step S130, battery ECU 260 determines basic discharge power allowable value Wout based on the estimated SOC obtained in step S120 and / or the battery state quantity (typically battery temperature Tb) obtained in step S110. # (Wout # ≧ 0) is set. For example, the basic allowable discharge power value (Wout #) is set such that the voltage change of battery voltage Vb falls within a predetermined range even when discharge at Wout # is continued for a predetermined time.

  Subsequently, in step S150, battery ECU 260 determines whether or not the load discharge request is at a normal level. The determination in step S150 is executed based on a request flag from HV_ECU 320. This request flag is a step when the demand for discharging from the load to the battery is large, that is, in a situation where it is desired to temporarily increase the output power from the main battery 220 from the normal time, depending on the state of the battery load. S150 is set to be NO.

  For example, in the hybrid vehicle according to the present embodiment, the required output to motor generator 140A (MG (2)) has become larger than a predetermined value when the engine is started by motor generator 140B (MG (1)) or by an accelerator pedal operation. In a case where the output power from the main battery 220 is desired to be temporarily higher than normal, the request flag is turned on. That is, when such an operation state is detected, step S150 is NO.

  When the determination at step S150 is YES, that is, when the load discharge request is at a normal level, battery ECU 260 sets basic discharge power allowable value Wout # set at step S130 as discharge power allowable value Wout at step S160. By performing (Wout = Wout #), normal discharge restriction is performed.

  In contrast, when the determination at step S150 is NO, that is, when the load discharge request is large, battery ECU 260 temporarily relaxes the discharge limit more than usual at steps S170 and S180. In order to prevent the battery voltage Vb from dropping beyond the lower limit voltage Ve due to the relaxation of the discharge limit at this time, the allowable discharge power value at the time of temporary relaxation of the discharge limit is determined as follows.

  In step S170, based on the current battery voltage Vx and battery current Ix, the battery ECU 260 discharges power when the battery voltage Vb decreases to the lower limit voltage Ve as the discharge current increases (Ib increases) due to relaxation of the discharge limit. The maximum dischargeable power We (We> 0) is predicted.

FIG. 4 is a conceptual diagram illustrating a method for predicting the maximum dischargeable power at this time.
Referring to FIG. 4, operating point 510 corresponds to current battery current Ix and battery voltage Vx. At the operating point 520, a voltage drop due to the internal resistance R occurs as the discharge current (Ib> 0) increases due to relaxation of the discharge restriction. The battery current at the operating point 520 is Ic, and the battery voltage is Vc. At this time, the following equation (1) is established using the internal resistance R.

(Vx−Vc) / (Ix−Ic) = − R (1)
Furthermore, the battery voltage Vb decreases due to the occurrence of polarization by continuing the discharge with the battery current Ic. During polarization due to discharging, the battery voltage Vb decreases and the battery current Ib increases while the output power of the battery is constant. As a result, as shown in FIG. 4, the operating point of the battery transitions from the operating point 520 to the operating point 530 on the equal power line 525. The battery current at the operating point 530 is Io, and the battery voltage is Vo.

  As described above, when the discharge restriction is relaxed at the operating point 510, first, a transition from the operating point 510 to the operating point 520 occurs due to the influence of the internal resistance. Furthermore, by continuing the discharge at the operating point 520, a further transition to the operating point 530 due to polarization occurs.

  In the present embodiment, allowable discharge power value Wout at the time of temporary discharge relaxation is set so that battery voltage Vo after polarization at operating point 530 becomes equal to Ve. That is, a feature compared with Patent Document 1 is that a voltage change amount due to polarization (hereinafter also referred to as a polarization voltage) ΔVdyn (ΔVdyn = Vc−Vo in FIG. 4) is taken into consideration.

  Here, the polarization voltage ΔVdyn at the time of discharge has characteristics as shown in FIGS.

  Referring to FIG. 5, it was confirmed by experiments by the inventors that the polarization voltage ΔVdyn can be approximated by a linear function model (ΔVdyn = α · Ic + β) with respect to the battery current in a relatively large current region. Furthermore, it was also confirmed that the slope α of the linear function changes depending on the battery temperature Tb and the discharge duration Δt1. Qualitatively, α increases as the battery temperature decreases.

  In addition, as shown in FIG. 6, the slope α decreases as the discharge duration time Δt1 decreases. The characteristics shown in FIGS. 5 and 6 can be obtained in advance by experiments in which conditions such as current, temperature, and discharge duration are changed. That is, according to the experimental result, a function equation or a map for calculating the slope α of the linear function indicating the polarization voltage ΔVdyn can be created in advance based on the battery temperature Tb and the discharge duration Δt1. Depending on the characteristics of the battery, a map for calculating the constant term β of the linear function may be further created. The discharge duration time Δt1 corresponds to the time (temporary relaxation time Δt) for executing temporary discharge restriction relaxation in steps S170 and S180.

FIG. 7 shows details of the process in step S170 of FIG.
Referring to FIG. 7, battery ECU 260 reads discharge restriction temporary relaxation time Δt in step S171. The temporary relaxation time Δt may be a fixed value or a variable value corresponding to the driving situation. For example, temporary relaxation time Δt may be set to a different value between when the engine is started and when the vehicle is accelerated (that is, when the required output to motor generator 140A is large). Further, during vehicle acceleration, the temporary relaxation time Δt can be variably set according to the required vehicle driving force or the required output to the motor generator 140A.

  In step S172, battery ECU 260 determines a linear function model (α, β) for obtaining polarization voltage ΔVdyn based on temporary relaxation time Δt and battery temperature Tb. For example, using the battery temperature Tb read in step S100 and the temporary relaxation time Δt read in step S171, α and β can be determined according to the map or the function equation. When the temporary relaxation time Δt is a fixed value, the linear function model (α, β) can be determined based only on the battery temperature Tb.

  Further, in step S173, battery ECU 260 obtains battery current Ic when battery voltage Vb becomes lower limit voltage Ve (Ic = Ice at this time). As described above, the battery current Ic is the battery current at the operating point 520. As described below, based on both the voltage change amount R · (Ic−Ix) due to the internal resistance R and the voltage change amount ΔVdyn due to polarization, the calculation in step S173 is executed.

  The relationship between the battery current Ic at the operating point 520 and the battery voltage Vo at the operating point 530 considering the influence of polarization is expressed by the following (2) using the polarization voltage ΔVdyn (Ic) that is a linear function of the battery current Ic. It is shown by the formula.

Vc = Vo + ΔVdyn (Ic) = Vo + α · Ic + β (2)
On the other hand, when the formula (1) is modified, the following formula (3) is obtained.

Vc−Vx = R · (Ix−Ic) (3)
By substituting equation (2) into equation (3), the following equation (4) is obtained.

Vo + α · Ic + β−Vx = R · Ix−R · Ic (4)
By solving the equation (4) for Ic, the following equation (5) is obtained.

(Α + R) · Ic = R · Ix + Vx−Vo−β
Ic = (R · Ix + Vx−Vo−β) / (α + R) (5)
In the formula (5), the battery current Ice when Vo = Ve (lower limit voltage) is expressed by the following formula (6).

Ice = (R · Ix + Vx−Ve−β) / (α + R) (6)
In step S173, battery current Ice is calculated by substituting Ix and Vx acquired in step S100, R acquired in step S110, and α and β acquired in step S172 into equation (6). Is done.

  In step S174, battery ECU 260 calculates maximum dischargeable power We based on the product of battery current Ice (Vo = Ve) calculated in step S173 and lower limit voltage Ve. That is, the maximum dischargeable power We is expressed by the following equation (7).

We = Ve · (R · Ix + Vx−Ve−β) / (α + R) (7)
As understood from FIG. 4, the discharge current (battery current Ic) at the operating point 520 is smaller than the discharge current (battery current Io) at the operating point 530 after polarization. However, since Ic and Io do not change so much in the discharge in a short time (Δt), the maximum dischargeable power We is set based on the discharge current (Ice) at the operating point 520. Since Io> Ic, a margin can be provided so as to be on the safe side against overdischarge by setting the maximum dischargeable power We based on Ic instead of Io.

  Referring to FIG. 4 again, in step S180, battery ECU 260 sets discharge power allowable value Wout corresponding to maximum dischargeable power We only during temporary relaxation time Δt for temporary discharge power limitation.

  Typically, the allowable discharge power value Wout = We may be set, but a margin may be further provided to set Wout <We. When the temporary discharge power limit relaxation time exceeds temporary relaxation time Δt, the request flag from HV_ECU 320 is changed so that the determination in step S150 is YES.

  By adopting such a configuration, taking into account the increase in voltage drop due to internal resistance and the generation of polarization voltage due to continuous relaxation of discharge limitation based on the current battery voltage Vb (Vx) and battery current Ib (Ix) In addition, the maximum dischargeable power We when the battery voltage Vb reaches the lower limit voltage Ve can be predicted by relaxing the discharge restriction.

  Then, it is possible to determine the allowable discharge power value Wout when temporarily relaxing the charge / discharge restriction more than usual in correspondence with the predicted maximum dischargeable power. Therefore, when the discharge restriction is temporarily relaxed according to the demand of the load, the output voltage of the main battery 220 (power storage device) is prevented from falling below the lower limit voltage Ve, and the relaxation level of the discharge restriction power is reduced. Can be secured sufficiently.

  Particularly, since the polarization voltage due to continuous discharge restriction relaxation is reflected, the possibility that the output voltage of the power storage device is lower than the lower limit voltage Ve can be suppressed. In addition, since the maximum dischargeable power We (that is, the allowable discharge power value Wout) can be set in conjunction with the temporary relaxation time Δt, the temporary relaxation level can be appropriately set to maximize the performance of the power storage device. .

(Temporary relaxation of charging restrictions)
Next, charging power limitation according to the embodiment of the present invention will be described with reference to FIGS.

  FIG. 8 is a flowchart illustrating the setting of the allowable charging power value according to the embodiment of the present invention. The flowchart shown in FIG. 8 is executed by battery ECU 260 at predetermined intervals.

  Referring to FIG. 8, battery ECU 260 obtains a battery state quantity (battery voltage Vb, battery current Ib, and battery temperature Tb) by the processing of steps S100 to S120 similar to FIG. 3 (S100), and internal resistance R Is estimated (S110), and the SOC is estimated (S120). Hereinafter, the magnitude of battery current Ib (Ib <0) during charging, that is, | Ib | is also referred to as a charging current.

  Further, in step S135, battery ECU 260 determines basic charge power allowable value Win based on estimated SOC obtained in step S120 and / or battery state quantity (typically battery temperature Tb) obtained in step S110. # (Win # ≦ 0) is set. For example, the basic allowable charge power value (Win #) is set so that the voltage change of the battery voltage Vb falls within a predetermined range even when charging with Win # is continued for a predetermined time.

  Subsequently, in step S155, battery ECU 260 determines whether or not the charge request from the load is at a normal level. The determination in step S155 is also executed based on the request flag from HV_ECU 320. This request flag is a step in accordance with the load condition of the battery when the charge request from the load to the battery is large, that is, in a situation where it is desired to temporarily increase the input power to the main battery 220 from the normal time. S155 is set to be NO.

  For example, in the hybrid vehicle according to the present embodiment, when the magnitude (absolute value) of regenerative torque required for motor generator 140A is greater than or equal to a predetermined value due to a brake operation by the driver or the like, regenerative power generation by motor generator 140A is performed. In an operating situation where it is desired to increase the power and temporarily increase the input power to the main battery 220 from the normal time, the request flag is set so that step S155 is NO.

  Typically, when the brake operation is performed at a high speed of a predetermined speed or higher, or when the deceleration is large due to the brake operation or the like even at a relatively low speed, the motor generator 140A described above is used. In some cases, the magnitude (absolute value) of the regenerative torque required for the above becomes a predetermined value or more.

  The battery ECU 260 determines that the basic charge power allowable value Win # set in step S135 is set as the charge power allowable value Win in step S165 when YES is determined in step S155, that is, when the load charge request is a normal level. By performing (Win = Win #), normal charging restriction is performed.

  On the other hand, when the determination at step S155 is NO, that is, when the load charge request is large, battery ECU 260 temporarily relaxes the charging limit more than usual at steps S175 and S185. In order to prevent the battery voltage Vb from rising above the upper limit voltage Vu by such charge restriction relaxation, the charge power allowable value at the time of temporary charge restriction relaxation is determined as follows.

  In step S175, based on the current battery voltage Vx and battery current Ix, battery ECU 260 is the maximum chargeable power that is charging power when battery voltage Vb rises to upper limit Vu as the charging current increases due to relaxation of charging restrictions. Electric power Wu (Wu <0) is predicted.

FIG. 9 is a conceptual diagram illustrating a method for predicting the maximum chargeable power at this time.
Referring to FIG. 9, operating point 510 # corresponds to current battery current Ib and battery voltage Vb. At operating point 520 #, as the charging current (Ib <0) increases due to relaxation of the charging restriction, a voltage increase due to internal resistance R occurs. The battery current at operating point 520 # is Ic #, and the battery voltage is Vc #. At this time, the following equation (8) is established using the internal resistance R.

Vc # −Vx # = R · (Ix # −Ic #) (8)
Furthermore, the battery voltage Vb increases due to the occurrence of polarization by continuing charging with the battery current Ic. At the time of polarization due to charging, the battery voltage Vb increases and the battery current Ib increases (the charging current decreases) while the charging power of the battery is constant. Thereby, as shown in FIG. 9, the operating point of the battery changes from operating point 520 # to operating point 530 # on equal power line 525 #. The battery current at the operating point 530 is Io #, and the battery voltage is Vo #.

  As described above, when the charging restriction is temporarily relaxed at the operating point 510, first, a transition from the operating point 510 to the operating point 520 occurs due to the influence of the internal resistance. Furthermore, when charging at operating point 520 # is continued, further transition to operating point 530 # due to polarization occurs.

  In the present embodiment, allowable charging power value Win at the time of temporary charge relaxation is set such that battery voltage Vo # = Vu after polarization at operating point 530 #. That is, a feature compared with Patent Document 1 is that a voltage change amount ΔVdyn due to polarization (ΔVdyn = Vo # −Vc # in FIG. 9) is taken into consideration.

  As shown in FIG. 10, the polarization voltage ΔVdyn at the time of charging is a linear function model (ΔVdyn = −α · Ic #) with respect to the battery current in a relatively large current region, similarly to the polarization voltage at the time of discharging described above. It can be approximated by + β) through experiments by the inventors.

  The slope (| −α |) of the linear function model indicating the polarization voltage ΔVdyn varies depending on the battery temperature Tb and the charge duration time Δt1 #. Qualitatively, the slope increases as the battery temperature decreases. In addition, the shorter the charging duration Δt1 #, the smaller the slope.

  Similar to the polarization voltage at the time of discharging, the characteristics shown in FIG. 10 can be obtained in advance by an experiment in which conditions such as current, temperature, and charging duration are changed. That is, a function equation or a map for calculating the slope of the linear function indicating the polarization voltage ΔVdyn during charging can be created in advance based on the battery temperature Tb and the charging duration time Δt1 # according to the experimental results. Depending on the characteristics of the battery, a map for calculating the constant term β of the linear function may be further created. Charging duration time Δt1 # corresponds to the time (temporary relaxation time Δt #) for executing temporary charge restriction relaxation in steps S175 and S185.

FIG. 11 shows details of the process in step S175 of FIG.
Referring to FIG. 11, battery ECU 260 reads charge restriction temporary relaxation time Δt # in step S176. Temporary relaxation time Δt # may be a fixed value or a variable value according to the driving situation. For example, the temporary relaxation time Δt # can be variably set according to the magnitude (absolute value) of the regenerative torque, the brake pedal operation amount, the vehicle speed when the brake pedal is operated, or the vehicle deceleration.

  In step S177, battery ECU 260 determines a linear function model (−α, β) for obtaining polarization voltage ΔVdyn during charging based on temporary relaxation time Δt # and battery temperature Tb. For example, −α, β can be determined according to the map or the function equation using the battery temperature Tb read in step S100 and the temporary relaxation time Δt # read in step S176. When temporary relaxation time Δt # is a fixed value, a linear function model (−α, β) can be determined based only on battery temperature Tb.

  Further, battery ECU 260 obtains battery current Ic # (in this case, Ic # = Ice #) when battery voltage Vb reaches upper limit voltage Vu in step S178. As described above, battery current Ic # is a battery current at operating point 520 #. As described below, based on both the voltage change amount R · (Ix # −Ic #) due to the internal resistance R and the voltage change amount ΔVdyn due to polarization, the calculation in step S178 is executed.

  The relationship between the battery current Ic # at the operating point 520 # and the battery voltage Vo # at the operating point 530 # in consideration of the influence of polarization is obtained by using the polarization voltage ΔVdyn (Ic) that is a linear function of the battery current Ic. It is shown by the following formula (9).

Vc # = Vo # −ΔVdyn (Ic #) = Vo # + α · Ic # −β (9)
By substituting equation (8) into equation (9), the following equation (10) is obtained.

Vo # + α · Ic # −β−Vx # = R · Ix # −R · Ic # (10)
By solving the equation (10) for Ic #, the following equation (11) is obtained.

(Α + R) · Ic # = R · Ix # + Vx # −Vo # + β
Ic # = (R · Ix # + Vx # −Vo # + β) / (α + R) (11)
In equation (5), battery current Ice # when Vo # = Vu (upper limit voltage) is expressed by the following equation (12).

Ice # = (R · Ix # + Vx # −Vu + β) / (α + R) (12)
In step S178, Ix # and Vx # acquired in step S100, R acquired in step S110, and -α and β acquired in step S177 are substituted into equation (6) to obtain battery current. Ice is calculated.

  In step S179, battery ECU 260 calculates maximum chargeable power Wu based on the product of battery current Ice # (Vo # = Vu) calculated in step S178 and upper limit voltage Vu. That is, the maximum chargeable power Wu is expressed by the following equation (13).

Wu = Vu · (R · Ix # + Vx # −Vu + β) / (α + R) (13)
As understood from FIG. 9, the charging current (| Ic # |) at the operating point 520 # is smaller than the charging current (| Io # |) at the operating point 530 after polarization. However, since Ic # and Io # do not change so much in charging in a short time (Δt #), the maximum chargeable power Wu is set based on the charging current (Ice #) at operating point 520 #. And Since | Io # | <| Ic # |, the maximum chargeable power Wu is set based on Ic instead of Io, so that a margin is provided to be on the safe side against overcharging. Can do.

  Referring to FIG. 8 again, in step S185, battery ECU 260 sets charging power allowable value Win in correspondence with maximum chargeable power Wu only for temporary relaxation time Δt # in order to temporarily limit charging power.

  Typically, the allowable charging power value Win = Wu may be set, but a margin may be provided to set | Win | <| Wu |. When the temporary charging power limit relaxation time exceeds temporary relaxation time Δt #, the request flag from HV_ECU 320 is changed so that the determination in step S155 is YES.

  By adopting such a configuration, taking into account the rise in voltage due to internal resistance and the generation of polarization voltage due to continuous relaxation of charging restrictions based on the current battery voltage Vb (Vx #) and battery current Ib (Ix #) The maximum chargeable power Wu when the battery voltage Vb reaches the upper limit voltage Vu can be predicted by relaxing the charging restriction.

  Then, in correspondence with the predicted maximum chargeable power, it is possible to determine the allowable charge power value Win when temporarily relaxing the charge limit more than usual. Therefore, when the charge restriction is temporarily relaxed according to the demand of the load, the output voltage of the main battery 220 (power storage device) is prevented from rising above the upper limit voltage Vu, and the charge restriction power relaxation level Can be secured sufficiently.

  In particular, since the polarization voltage due to continuous charge restriction relaxation is reflected, the possibility that the output voltage of the power storage device is lower than the lower limit voltage Ve can be suppressed. In addition, since the maximum chargeable power Wu (that is, the allowable charge power value Win) can be set in conjunction with the temporary relaxation time Δt #, the temporary relaxation level is appropriately set to maximize the performance of the power storage device. it can.

  By setting the charge / discharge power allowance as described above, in the charge / discharge control of the power storage device according to the embodiment of the present invention, the output voltage is maintained within the management voltage range while sufficiently drawing out the performance of the power storage device. Thus, charge / discharge control can be performed. As a minimum configuration for realizing the present invention, only one of the allowable charging power value and the allowable discharging power value may be set according to the flowcharts of FIGS. 3 and 7 or FIGS. is there.

  Further, in the present embodiment, charging / discharging limitation of the power storage device mounted on the hybrid vehicle, that is, both power supply (discharge) from the power storage device to the load and power supply (charge) from the load to the power storage device can be performed. Although the setting of the charge / discharge power allowable value when configured is exemplified, the application of the present invention is not limited to such a case. In other words, during driving, at least one of power supply (discharge) from the in-vehicle power storage device to the electric motor (motor generator) or power supply (charge) of the power storage device from the electric motor (motor generator) is executed. The present invention can be applied to a hybrid vehicle having a drive system configuration different from the configuration example of FIG. 1 or an electric vehicle in general such as an electric vehicle and a fuel cell vehicle.

  Further, if it is configured so that only power supply (discharge) from the power storage device to the load or power supply (charge) from the load to the power storage device is executed, the discharge power allowable value or The allowable charge power value can be set by applying the present invention. That is, the present invention can be commonly used for setting the allowable charge / discharge power value for maintaining the output voltage of the power storage device within the voltage range from the lower limit voltage to the upper limit voltage without limiting the configuration of the load. Confirm that this is the case.

  Further, for the power storage device, the battery is exemplified in the present embodiment, but as with the battery, if the power storage device has a characteristic that the output voltage changes due to continuous charge and discharge, the present invention is applied, It is possible to set an allowable charge / discharge power value for maintaining the output voltage within the voltage range from the lower limit voltage to the upper limit voltage.

  In the flowcharts of FIGS. 3 and 8, step S100 corresponds to “state acquisition means” of the present invention, step S110 corresponds to “internal resistance estimation means” of the present invention, and steps S130 and S135 correspond to the present invention. Corresponds to “first limit setting means”. Steps S170 and S180 and steps S175 and S185 correspond to “second restriction setting means” in the present invention. Temporary relaxation times Δt and Δt # correspond to “first time”.

  Further, in the present embodiment, the example in which the charge / discharge power allowable value of the power storage device is set based on the voltage Vb of the entire main battery 220 has been described, but the application of the present invention is limited to such an example. It is not a thing. For example, in a configuration in which a plurality of power storage devices are connected in series, it is possible to set a charge / discharge power allowable value according to the present embodiment for each voltage detection unit. For example, when a main battery 220 is configured by connecting a plurality of battery blocks in series and voltage and current can be detected for each battery block, each battery block is regarded as a “power storage device” and It is possible to set a charge / discharge power allowable value according to the present embodiment. In such a configuration, the minimum value of the allowable charge power value and the allowable discharge power value of each of the plurality of battery blocks is set as the allowable charge power value (Win) and the allowable discharge power value (Wout) of the main battery 220. Each is preferably employed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to charge / discharge control of a power storage device.

  120 engine, 140A, 140B motor generator, 160 drive wheel, 180 reducer, 200 power split mechanism, 220 main battery (power storage device), 222 current sensor, 224 temperature sensor, 226 voltage sensor, 240, 241 inverter, 242 converter, 260 battery ECU, 280 engine ECU, 320 HV_ECU, 410 accelerator pedal, 415 accelerator pedal sensor, 420 brake pedal, 425 brake pedal sensor, 450 brake actuator, 460 brake mechanism, 465 disc rotor, 510, 510 # operating point (current) 520, 520 # operating point (change in internal resistance), 525, 525 # equal power line, 530, 530 # operating point (after polarization), Ib, Ic, Io, Ix buffer Territory current, R internal resistance, Tb battery temperature, Vb, Vo, Vx battery voltage, Ve lower limit voltage, Vu upper limit voltage, We maximum dischargeable power, Win charge power allowable value, Wout discharge power allowable value, Wu maximum chargeable power .

Claims (8)

A charge / discharge control device for maintaining an output voltage of a power storage device within a voltage range from a lower limit voltage to an upper limit voltage,
State acquisition means for acquiring a measured value indicating the state of the power storage device;
Based on the measurement value acquired by the state acquisition means, internal resistance estimation means for estimating the internal resistance of the power storage device, and charge / discharge power limitation of the power storage device based on the state of the power storage device First limit setting means for setting the allowable discharge power value and the allowable charge power value;
In response to a request from the load of the power storage device, the charge / discharge power limit is temporarily relaxed within a range in which the output voltage does not deviate from the voltage range only during a first time period. 2 restriction setting means,
The second restriction setting means includes
A first voltage change amount based on a product of a change amount of charge / discharge current due to temporary relaxation of the charge / discharge power limit and the internal resistance estimated by the internal resistance estimation means, and increased by the temporary relaxation. And the absolute value of at least one of the discharge power allowance and the charge power allowance based on both the second voltage change amount caused by the charge / discharge current after being continued for the first time. A charge / discharge control device for a power storage device, wherein a value is set to be larger than a value set by the first limit setting means. The second restriction setting means includes
Means for estimating the second voltage change amount by a linear function model having the current of the power storage device as a variable;
The charging / discharging control apparatus of the electrical storage apparatus of Claim 1 including the means for determining the said linear function model based on the temperature of the said electrical storage apparatus. The first time is variably set according to the load situation,
The second restriction setting means includes
Means for estimating the second voltage change amount by a linear function model having the current of the power storage device as a variable;
The charge / discharge control device for a power storage device according to claim 1, further comprising: means for determining the linear function model based on the first time and the temperature of the power storage device.   The second limit setting means is configured to output a voltage obtained by subtracting the first and second voltage change amounts from the current output voltage of the power storage device when the power storage device is discharged. The charging / discharging control apparatus of the electrical storage apparatus of any one of Claims 1-3 which sets the said discharge power allowable value based on the product of a discharge current and the said lower limit voltage.   The second limit setting means is configured to set a voltage obtained by adding the first and second voltage change amounts to the current output voltage of the power storage device equal to the upper limit voltage when the power storage device is charged. The charging / discharging control apparatus of the electrical storage apparatus of any one of Claims 1-3 which sets the said charging power allowable value based on the product of charging current and the said upper limit voltage. The power storage device;
An internal combustion engine for generating vehicle driving force;
First and second electric motors configured to be capable of bidirectionally transferring power to and from the power storage device;
An electric vehicle comprising the charge / discharge control device for a power storage device according to claim 1 or 4,
The first electric motor is configured to be able to start an internal combustion engine by being rotationally driven by discharge power of the power storage device,
The second electric motor is configured to be able to generate the vehicle driving force by the discharge power of the power storage device,
The charge / discharge control device comprises:
An electric vehicle in which the discharge power allowable value is set by the second limit setting means when the internal combustion engine is started. The power storage device;
An electric motor configured to be able to exchange electric power bidirectionally with the power storage device;
An electric vehicle comprising the charge / discharge control device for a power storage device according to claim 1 or 4,
The electric motor is configured to be able to generate a vehicle driving force of the electric vehicle by a discharge power of the power storage device,
The charge / discharge control device comprises:
An electric vehicle that sets the discharge power allowable value by the second limit setting means when an output request to the electric motor becomes equal to or greater than a predetermined value. The power storage device;
An electric motor configured to be able to exchange electric power bidirectionally with the power storage device;
An electric vehicle comprising the charge / discharge control device for a power storage device according to claim 1 or 5,
The electric motor is configured to be able to generate charging power of the power storage device by regenerative braking power generation by generation of regenerative torque when the electric vehicle is decelerated,
The charge / discharge control device comprises:
An electric vehicle in which the charging power allowable value is set by the second limit setting means when an absolute value of the regenerative torque required for the electric motor is larger than a predetermined value.

Images