JP6701699B2 - Battery control system, hybrid vehicle, and battery control method - Google Patents

Description

  The present invention relates to a battery control system, a hybrid vehicle, and a battery control method, and more particularly, to a motor generator that is a power source for driving a vehicle, a battery connected to the motor generator via an inverter, and a control device. And a battery control system, a hybrid vehicle, and a battery control method.

  2. Description of the Related Art In recent years, a hybrid vehicle (hereinafter referred to as “HEV”) having a hybrid system including an engine and a motor generator that are controlled in a complex manner according to a driving state of the vehicle has been attracting attention from the viewpoint of improving fuel efficiency and environmental measures. There is. In this HEV, the driving force is assisted by the motor generator at the time of acceleration or starting of the vehicle, while regenerative power generation is performed by the motor generator at the time of inertial running or at the start (for example, refer to Patent Document 1).

  On the other hand, a motor generator is used as a power source for running a vehicle, such as an HEV or an electric motor vehicle (hereinafter referred to as “EV”) that uses only a motor generator as a power source for running the vehicle without mounting an engine. In the installed vehicle, a battery for driving the vehicle (such as a lithium-ion battery or a nickel-hydrogen battery) is connected to the motor generator via an inverter. Then, charging/discharging is repeated between the motor generator and the battery based on the running state of the vehicle.

  The charging/discharging between the motor generator and the battery is performed so that the charging rate of the battery falls within a certain range (used charging rate range). The used charge rate range is, for example, 30 (%) to 50 (%) when the electric capacity of the battery (maximum amount of electricity that can be stored in the battery) is 100%, and the vehicle is shipped in advance through experiments or the like. Set when (new).

  However, the electric capacity of the battery gradually decreases as the battery is charged and discharged. When such deterioration of the battery (reduction in the battery capacity) progresses, the amount of power that can be used within the range of the charging rate of the battery decreases, so the amount of driving power assisted by the motor generator and the amount of regenerative power decrease. However, the fuel efficiency of the engine may deteriorate.

  In connection with this problem, the charge/discharge is controlled so that the SOC of the main battery always falls within the target value or the target SOC range, and when the main battery deteriorates, the lower limit value of the target SOC range is raised to output the output when new. There has been proposed a hybrid vehicle battery control device that obtains an output close to (see, for example, Patent Document 2).

  In the above hybrid vehicle battery control device, when the output is reduced due to the deterioration of the main battery, the driving force of the motor is reduced and the power performance is deteriorated, so in order to suppress the deterioration of the power performance, Raising the lower limit of the target SOC range. However, increasing the lower limit of the target SOC range narrows the target SOC range. Therefore, as the deterioration of the main battery progresses, it is necessary to further improve the charge/discharge control accuracy, which imposes a burden on the control device. There is a problem of getting bigger.

JP, 2002-238105, A Japanese Patent Laid-Open No. 2000-030753

  An object of the present invention is to suppress deterioration of fuel efficiency performance of an engine without increasing a load on a control device for controlling charge/discharge of a battery when the battery for traveling the vehicle is deteriorated. It is to provide a battery control system, a hybrid vehicle, and a battery control method capable of improving the power consumption.

A battery control system of the present invention which achieves the above object, is a hybrid system having an engine and a motor generator that are power sources for vehicle running, a battery connected to the motor generator via an inverter, and a battery A control system for a battery, comprising: a control device that controls charging/discharging between the motor generator and the battery within a range of use rate of charge; wherein the control device is a first power storage device that is an amount of electricity stored in the battery. Is a value obtained by integrating a charge/discharge current value, which is a current value charged/discharged with respect to the battery via the inverter, for a preset time with the first charge amount calculated in the previous control. The integrated current value is calculated by adding and subtracting the value calculated at the time of this control, and the calculated first storage amount is divided by the rated electric capacity to calculate the first charging rate, and the charging rate of the battery is also calculated. And the open circuit voltage of the battery are used to calculate a second charging rate of the battery based on the open circuit voltage of the battery, and a capacity that is a difference between the first charging rate and the second charging rate. Based on the deterioration determination index, while estimating and calculating the reduction rate of the electric capacity in the fully charged state with respect to the rated electric capacity of the battery , based on the estimated reduction rate of the electric capacity in the fully charged state of the battery, It is configured to perform control to expand both the upper limit value and the lower limit value of the used charging rate range.

  Here, the used charging rate range of the battery is a target range of the charging rate that is set in advance by experiments or the like, and charging/discharging between the motor generator and the battery is controlled so as to be within this target range. Further, the electric capacity of the battery is the maximum chargeable amount of the battery.

  In addition, the hybrid vehicle of the present invention that achieves the above-mentioned object configures the motor-generator as a motor-generator connected to an output shaft that transmits the power of the engine, and includes a hybrid system having the motor-generator and the battery described above. It is configured with a control system.

A battery control method of the present invention that achieves the above object includes a hybrid system having an engine and a motor generator that are power sources for driving a vehicle, and a battery connected to the motor generator via an inverter. In a battery control method for controlling charging/discharging between the motor generator and the battery within a range of a charging rate of use of the battery , a first storage amount, which is an amount of electricity stored in the battery, is calculated at a previous control. Regarding the current accumulated value, which is a value obtained by accumulating the charging/discharging current value, which is the current value charged/discharged to/from the battery via the inverter, for the preset time from the first stored amount The first charge rate is calculated by adding and subtracting the calculated value and dividing the calculated first charge amount by the rated electric capacity, and the correlation between the charge rate of the battery and the open circuit voltage of the battery is calculated. Using the relationship, the second charging rate of the battery is calculated based on the open-circuit voltage of the battery, and based on the capacity deterioration determination index which is the difference between the first charging rate and the second charging rate, A first step of estimating and calculating a rate of decrease of the fully charged electric capacity with respect to the rated electrical capacity of the battery; and the use of the battery based on the rate of decrease of the fully charged electric capacity estimated and calculated in the first step. And a second step of performing control for expanding both the upper limit value and the lower limit value of the state of charge range.

  According to the battery control system, the hybrid vehicle, and the battery control method of the present invention, when the electric capacity of the battery decreases due to the deterioration of the battery for vehicle traveling, the battery is reduced based on the decrease rate of the electric capacity. It is possible to suppress a decrease in the amount of regenerative electric power due to the motor generator simply by changing the control to control for expanding the usable charging rate range. As a result, deterioration of the fuel efficiency of the engine can be suppressed, and the fuel efficiency of the engine after several years of use of the vehicle can be made substantially the same as that of the engine at the time of shipment of the vehicle. Therefore, the product strength of the vehicle can be improved.

  In addition, since the range of battery charge rate is expanded, it is not necessary to improve the control accuracy of charge/discharge between the motor generator and the battery as the battery deteriorates, and the load on the control device increases. Nor.

  In addition, if the range of battery charge rates expanded based on the rate of decrease in battery capacity is further expanded based on the rate of decrease in charge/discharge efficiency of the battery due to the increase in internal resistance of the battery, It is possible to more reliably suppress the deterioration of the fuel efficiency performance of the engine due to the deterioration of the charge/discharge efficiency.

1 is a configuration diagram of a hybrid vehicle including a battery control system according to an embodiment of the present invention. It is a figure which shows the control flow of the control method of the battery which consists of embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hybrid vehicle equipped with a battery control system according to an embodiment of the present invention.

  This hybrid vehicle (hereinafter referred to as “HEV”) is a vehicle including not only ordinary passenger vehicles but also buses, trucks, etc., and has an engine 10 and a motor generator 31 that are controlled in a complex manner according to the operating state of the vehicle. A hybrid system 30 is provided.

  In the engine 10, the crankshaft 13 is rotationally driven by the thermal energy generated by the combustion of the fuel in the plurality of (four in this example) cylinders 12 formed in the engine body 11. A diesel engine or a gasoline engine is used as the engine 10. The rotational power of the crankshaft 13 is transmitted to the transmission 20 through a clutch 14 (for example, a wet multi-plate clutch) connected to one end of the crankshaft 13.

  The rotational power changed by the transmission 20 is transmitted to the differential 23 through the propeller shaft 22 and distributed to the pair of drive wheels 24 as a driving force.

  The hybrid system 30 includes a motor generator 31, an inverter 35 electrically connected in sequence to the motor generator 31, a high voltage battery 32, a DC/DC converter 33, and a low voltage battery 34.

  As the high voltage battery 32, a lithium ion battery, a nickel hydrogen battery, or the like is preferably exemplified. A lead battery is used as the low voltage battery 34.

  The DC/DC converter 33 has a function of controlling the charging/discharging direction and the output voltage between the high-voltage battery 32 and the low-voltage battery 34. The low-voltage battery 34 also supplies electric power to various vehicle electrical components 36.

  Various parameters in the hybrid system 30, such as a current value, a voltage value, and an SOC value, are detected by a BMS (battery management system) 39.

  The motor generator 31 is an endless type that is wound between a first pulley 15 attached to a rotating shaft 37 and a second pulley 16 attached to the other end of the crankshaft 13 that is the output shaft of the engine body 11. Power is transmitted to and from the engine 10 via the belt-shaped member 17. Instead of the two pulleys 15 and 16 and the belt-shaped member 17, a gear box or the like may be used to transmit power. The output shaft of the engine body 11 connected to the motor generator 31 is not limited to the crankshaft 13, and may be, for example, the transmission shaft between the engine body 11 and the transmission 20 or the propeller shaft 22.

  The motor generator 31 may have a function of performing cranking instead of a starter motor (not shown) that starts the engine body 11.

  The engine 10 and the hybrid system 30 are controlled by the controller 80. Specifically, at the time of starting or accelerating the HEV, the hybrid system 30 assists at least a part of the driving force by the motor generator 31 supplied with power from the high voltage battery 32, while at the same time during inertial running or braking. Performs regenerative power generation by the motor generator 31, converts excess kinetic energy into electric power, and charges the high-voltage battery 32.

  The battery control system of the present invention includes a motor generator 31, which is a power source for running a vehicle, a high-voltage battery (battery) 32 connected to the motor generator 31 via an inverter 35, and a control device 80. It is a system equipped with.

  Then, the control device 80 estimates and calculates the reduction rate ΔS of the electric capacity S of the high-voltage battery 32, and based on the estimated reduction rate ΔS of the electric capacity S, the used charging rate range R of the high-voltage battery 32. Is configured to be expanded to the range R1.

  Here, the used charging rate range R of the high-voltage battery 32 is a target range of the charging rate that is set in advance by experiments or the like, and the range between the motor generator 31 and the high-voltage battery 32 is set so as to fall within this target range. Charge/discharge is controlled. The electric capacity S of the high-voltage battery 32 is the maximum chargeable amount of the high-voltage battery 32. The method for estimating and calculating the decrease rate ΔS of the electric capacity S will be described later.

  The details of the expansion of the used charging rate range R of the high-voltage battery 32 to the range R1 will be described. For example, when the used charging rate range R is set to 40 (%) to 70 (%) when the vehicle is shipped (when it is new), the electric capacity S of the high-voltage battery 32 is equal to the rated electric capacity (when the vehicle is shipped). The maximum chargeable capacity of the high-voltage battery 32) When the battery capacity deteriorates by 10% from S0, the usable charging rate range R is expanded by 10% so that the usable current capacity of the high-voltage battery 32 does not change. Reset to R1 (35 (%) to 75 (%)).

  The relationship between the reduction rate ΔS of the electric capacity S and the expansion width of the used charging rate range R up to the range R1 is set in advance in the form of a control map or a control formula by experiments or the like. The expansion of the used charging rate range R to the range R1 may be performed by changing one of the upper limit value and the lower limit value of the used charging rate range R. Further, by setting the use charging rate range R of the high-voltage battery 32 to be narrow at the time of shipping the vehicle, the life of the high-voltage battery 32 can be extended.

  Further, the control device 80 estimates and calculates the reduction rate ΔC of the charging/discharging efficiency C of the high-voltage battery 32, and based on the estimated reduction rate ΔC of the charging/discharging efficiency C, determines the reduction rate ΔS of the electric capacity S. Based on this, the control is performed such that the used charging rate range R1 of the high-voltage battery 32 that has been expanded based on the above is further expanded to the range R2.

  The rate of decrease ΔC of the charging/discharging efficiency C of the high-voltage battery 32 is determined by, for example, how much the internal resistance of the high-voltage battery 32 is higher than the internal resistance of the vehicle at the time of shipment, or the increase rate of the internal resistance. It can be estimated and calculated based on the above. The internal resistance of the high-voltage battery 32 can be calculated based on the voltage fluctuation of cells inside the high-voltage battery 32 during charging/discharging of the high-voltage battery 32. The relationship between the rate of decrease ΔC of the charging/discharging efficiency C of the high voltage battery 32 and the range of expansion of the used charging rate range R1 to the range R2 is how the increase in the internal resistance of the high voltage battery 32 affects the fuel consumption of the engine 10. It is set in advance in the form of a control map or a control formula by an experiment or the like in consideration of the influence.

  In the above description, the controller 80 estimates and calculates the reduction rate ΔS of the electric capacity S, the estimation and calculation of the decrease rate ΔC of the charging/discharging efficiency C, and the range R1 or the range R1 of the use charging rate range R of the high-voltage battery 32. Although the expansion to R2 is performed, these controls may be performed by the BMS 39.

  A method for estimating and calculating the reduction rate ΔS of the electric capacity S of the high voltage battery 32 will be described. The estimated calculation of the reduction rate ΔS can be calculated by various methods using conventional techniques. For example, the following method devised by the present inventor can be used. By using this method, The accuracy of estimation and calculation of the reduction rate ΔS of the electric capacity S of the high-voltage battery 32 can be improved.

  First, the charging rate (SOC value) of the high-voltage battery 32 is measured at a charging time t, which is a current value charged and discharged through the inverter 35 with respect to the high-voltage battery 32, at a time t preset by experiments or the like. It is estimated and calculated based on the integrated current value Ii, which is the value integrated over the period. This estimated and calculated charging rate is referred to as a first charging rate Cr1. As the calculation method, first, the first stored amount S1 which is the amount of electricity stored in the high voltage battery 32 is added to the first stored amount (stored amount at the start of current integration) S1b calculated in the previous control. The current integrated value Ii calculated during control is added and subtracted (added during charging, subtracted during discharging) for estimation and calculation (S1=S1b±Ii. Unit is usually Ah). Then, when the first storage amount S1 is divided by the rated electric capacity (fixed value) S0 of the high-voltage battery 32, the first storage amount S1 can be converted into the first charging rate Cr1 (the unit is usually percentage). Yes (Cr1=S1/S0×100).

  Next, the charging rate of the high voltage battery 32 is estimated and calculated based on the open circuit voltage V of the high voltage battery 32. This estimated and calculated charging rate is referred to as a second charging rate Cr2. In this estimated calculation, the charging rate of the high-voltage battery 32 and the open circuit voltage V have a correlation (for example, the open circuit voltage V is 2.7V to 4.2V, and the second charging rate Cr2 is 0% to 100%). By utilizing the fact that there is a linear relationship), this correlation is set in the form of a control map or the like, and this set control map or the like is used.

  A capacity deterioration determination index ΔCr (=Cr1-Cr2), which is the difference between the first charging rate Cr1 and the second charging rate Cr2, is calculated. The inventor has found that the electric capacity of the high-voltage battery 32 is deteriorated when the capacity deterioration determination index ΔCr is not zero, and that the electric capacity of the high-voltage battery 32 is deteriorated as the capacity deterioration determination index ΔCr is increased. I found that it would proceed. Then, the reduction rate ΔS of the electric capacity S of the high-voltage battery 32 is estimated based on the capacity deterioration determination index ΔCr that is the difference between the first charging rate Cr1 and the second charging rate Cr2, that is, We considered estimating the capacity deterioration situation.

  Here, the principle that the capacity deterioration state of the high-voltage battery 32 can be estimated based on the capacity deterioration determination index ΔCr will be described. The first charging rate Cr1 estimated and calculated based on the integrated current value Ii is the charging rate for the rated electric capacity (corresponding to new capacity) S0. On the other hand, the second charging rate Cr2 estimated and calculated based on the open circuit voltage V is the charging rate for the fully charged state based on the battery performance at the time of the estimation, including the deterioration of the high voltage battery 32.

  Therefore, the difference between the first charging rate Cr1 and the second charging rate Cr2 means that there is a difference between the fully charged state electric capacity S and the rated electric capacity S0 of the high voltage battery 32, and the high voltage battery This means that the capacity deterioration of the high voltage battery 32 can be estimated based on the capacity deterioration determination index ΔCr which is the difference between the first charging rate Cr1 and the second charging rate Cr2. It will be.

  It is also possible to estimate the capacity decrease state from the preset relationship between the internal resistance increase degree and the electric capacity decrease based on the above-described internal resistance increase degree indicating the deterioration index of the high-voltage battery 32.

  Next, a battery control method of the present invention based on the above battery control system will be described with reference to the control flow of FIG. The control flow of FIG. 2 is called and executed by the advanced control flow each time the travel distance (or travel time) of the vehicle increases by a preset determination distance (or determination time). This is shown as a return control flow.

  The control flow of FIG. 2 will be described. When the control flow of FIG. 2 starts, the reduction rate ΔS of the electric capacity S of the high-voltage battery 32 and the reduction rate ΔC of the charging/discharging efficiency C are calculated in step S10. These calculation methods have been described above, and will be omitted. After performing the control of step S10, the process proceeds to step S20.

  In step S20, it is determined whether or not the reduction rate ΔS of the electric capacity S calculated in step S10 is equal to or larger than a set capacity threshold value ΔSc preset by experiments or the like. If the reduction rate ΔS is equal to or greater than the set capacity threshold value ΔSc (YES), the process proceeds to step S30, and in step S30, the used charging rate range R of the high voltage battery 32 is expanded to the range R1. The method of setting the range R1 has also been described above, and will be omitted. After performing the control of step S30, the process proceeds to step S40.

  In step S40, it is determined whether or not the rate of decrease ΔC of the charging/discharging efficiency C calculated in step S10 is equal to or higher than a preset efficiency threshold ΔCc set in advance by experiments or the like. If the reduction rate ΔC is equal to or higher than the set efficiency threshold ΔCc (YES), the process proceeds to step S50, and in step S50, the used charging rate range R1 of the battery 32 is further expanded to the range R2. After performing the control of step S50, the process proceeds to return and the present control flow is ended.

  Further, when it is determined in step S20 that the reduction rate ΔS is less than the set capacity threshold ΔSc (NO), or when it is determined in step S40 that the reduction rate ΔC is less than the set efficiency threshold ΔCc ( In the case of "NO", the process proceeds to the return in any case, and this control flow is ended.

  When the control flow of FIG. 2 is finished, the used charging rate range R of the high voltage battery 32 is updated to the used charging rate range of the high voltage battery 32 at the time of proceeding to the return, and the next FIG. When the control flow is executed, this updated used charge rate range is used as the used charge rate range R in step S30. Further, with respect to the set capacity threshold value ΔSc and the set efficiency threshold value ΔCc, these values may be changed as the used charging rate range R of the high voltage battery 32 is updated.

  As described above, the battery control method according to the present invention, which is based on the above-described battery control system, includes a motor generator 31 which is a power source for driving a vehicle, and a motor generator 31 connected to the motor generator 31 via an inverter 35. In the battery control method including the high-voltage battery 32, the reduction rate ΔS of the electric capacity S of the high-voltage battery 32 is estimated and calculated, and the high rate is reduced based on the estimated reduction rate ΔS of the electric capacity S. The method is characterized in that control is performed to expand the used charging rate range R of the voltage battery 32 to the range R1.

  In addition, in the above battery control method, the decrease rate ΔC of the charging/discharging efficiency C of the high-voltage battery 32 is estimated and calculated, and the electric capacity S is reduced based on the estimated decrease rate ΔC of the charging/discharging efficiency C. It is preferable to perform control to further expand the used charging rate range R1 of the high-voltage battery 32, which is expanded based on the rate ΔS, to the range R2.

  According to the battery control system, the hybrid vehicle, and the battery control method of the present invention, when the electric capacity S of the high-voltage battery 32 decreases due to deterioration of the high-voltage battery 32 for vehicle running, the electric capacity S It is possible to suppress the reduction in the amount of regenerative electric power by the motor generator 31 only by changing the control to control to expand the use charging rate range R of the high-voltage battery 32 based on the reduction rate ΔS of. This makes it possible to suppress the deterioration of the fuel efficiency of the engine 10 so that the fuel efficiency of the engine 10 after several years of use of the vehicle is almost the same as that of the engine 10 at the time of shipment of the vehicle. It is possible to improve the commercial power of the vehicle.

  In addition, in order to expand the use charging rate range R of the high voltage battery 32, it is necessary to improve the control accuracy of charging/discharging between the motor generator 31 and the high voltage battery 32 as the deterioration of the high voltage battery 32 progresses. In addition, the load on the control device 80 does not increase.

  In addition, the used charging rate range R1 of the high voltage battery 32, which is expanded based on the reduction rate ΔS of the electric capacity S of the high voltage battery 32, is charged to the high voltage battery 32 due to the increase of the internal resistance of the high voltage battery 32. Further expansion based on the reduction rate ΔC of the discharge efficiency C can more reliably suppress the reduction in the fuel consumption performance of the engine 10 due to the reduction in the charge/discharge efficiency C of the high-voltage battery 32.

10 engine 11 engine body 30 hybrid system 31 motor generator 32 high-voltage battery (battery)
35 Inverter 80 Controller S Battery electric capacity ΔS Battery electric capacity decrease rate C Battery charge/discharge efficiency ΔC Battery charge/discharge efficiency decrease rate R, R1, R2 Battery charge rate range

Claims (3)

A hybrid system having an engine and a motor generator, which are power sources for running a vehicle, a battery connected to the motor generator via an inverter, and a charge between the motor generator and the battery within a usable charging rate range of the battery. In a battery control system including a control device for controlling discharge,
The control device is
A first charge amount, which is the amount of electricity stored in the battery, is added to the first charge amount calculated during the previous control, and a charge/discharge current that is a current value that is charged/discharged in/from the battery via the inverter. Calculated by adding/subtracting the value calculated during this control with respect to the current integrated value that is the value that has been integrated over a preset time,
The calculated first storage amount is divided by the rated electric capacity to calculate the first charging rate, and
Using the correlation between the charging rate of the battery and the open circuit voltage of the battery, the second charging rate of the battery is calculated based on the open circuit voltage of the battery,
Based on the capacity deterioration determination index which is the difference between the first charging rate and the second charging rate, while estimating and calculating the reduction rate of the fully charged state electric capacity with respect to the rated electric capacity of the battery,
A battery configured to perform control to expand both the upper limit value and the lower limit value of the used charging rate range of the battery based on the estimated reduction rate of the electric capacity in the fully charged state. Control system. A hybrid vehicle comprising the motor generator as a motor generator connected to an output shaft for transmitting power of an engine, and the hybrid system having the motor generator and the battery control system according to claim 1 . A hybrid system having an engine and a motor generator that are power sources for running the vehicle, and a battery connected to the motor generator via an inverter, and between the motor generator and the battery within a usable charging rate range of the battery. In the control method of the battery for controlling the charge and discharge of
A first charge amount, which is the amount of electricity stored in the battery, is added to the first charge amount calculated during the previous control, and a charge/discharge current that is a current value that is charged/discharged in/from the battery via the inverter. Calculated by adding/subtracting the value calculated during this control with respect to the current integrated value that is the value that has been integrated over a preset time,
The calculated first storage amount is divided by the rated electric capacity to calculate the first charging rate, and
Using the correlation between the charging rate of the battery and the open circuit voltage of the battery, the second charging rate of the battery is calculated based on the open circuit voltage of the battery,
A first step of estimating and calculating a reduction rate of the fully charged state electric capacity with respect to the rated electric capacity of the battery , based on a capacity deterioration determination index which is a difference between the first charging rate and the second charging rate ;
A second step of performing control for expanding both the upper limit value and the lower limit value of the used charging rate range of the battery based on the reduction rate of the electric capacity in the fully charged state estimated and calculated in the first step. A method of controlling a battery, characterized by:

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