JP3812420B2 - Secondary battery control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery control device, and more particularly to charge / discharge amount control of a secondary battery.
[0002]
[Prior art]
Conventionally, a secondary battery is mounted on an electric vehicle, a hybrid vehicle, or the like. In a hybrid vehicle, a motor is driven by electric power from a secondary battery in addition to an engine to run the vehicle. For example, the vehicle is driven only by the motor at a low speed, and the engine is cranked and started when the speed is high, and the vehicle is driven by the engine and the motor. At the time of vehicle braking, the secondary battery is charged by converting the kinetic energy into electric energy by causing the motor to function as a generator. The state of the secondary battery is always monitored by a microcomputer, and charge / discharge is controlled so that the state of charge (SOC) becomes a constant value (for example, 60% of the fully charged state). Accordingly, when the SOC of the secondary battery is low even at a low speed when the vehicle is driven only by the motor, the engine is cranked and the vehicle is driven by the engine.
[0003]
The engine cranking can be performed, for example, by causing a generator connected to the engine to function as a motor (cell starter) with electric power from the secondary battery. In other words, the generator primarily generates power from the engine output and supplies the power to the motor to drive the motor, but it controls the inverter connected to the generator to function as a starter motor and starts the engine. Thus, the secondary battery is charged by running the engine, increasing the engine output, and regenerating.
[0004]
[Problems to be solved by the invention]
However, in the past, since the SOC of the secondary battery has actually started to decrease, the driving by the motor has shifted from the driving by the engine, so it is not always guaranteed whether the engine can be cranked by the current SOC of the secondary battery. There was a problem that was not.
[0005]
Of course, it is possible to set a threshold value with a sufficient margin and crank the engine when the SOC reaches this threshold value. In this case, however, there is still a margin in the output of the secondary battery. In spite of this, since the engine is started, the capacity of the secondary battery cannot be fully utilized, leading to a reduction in fuel consumption and a reduction in usage efficiency of the secondary battery.
[0006]
Furthermore, during high-load driving, such as when the driver fully opens the accelerator, it is necessary to continuously supply power from the secondary battery to the motor to perform torque assist. It is a fact that the process of supplying power until the voltage of the secondary battery reaches a predetermined lower limit is not understood, whether the power necessary for the motor can be supplied from the battery. Efficient control has been desired.
[0007]
The present invention has been made in view of the above-described problems of the prior art, and its purpose is to accurately control the input / output power of the secondary battery and the duration in which input / output is possible, thereby increasing the load on the motor and the like. An object of the present invention is to provide an apparatus that can be accurately controlled.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a means for detecting a state quantity of a secondary battery and capable of inputting or outputting the secondary battery at a certain power using at least a predetermined voltage model based on the state quantity. And calculating means for calculating the duration.
[0009]
Here, the electric power is electric power necessary for driving the load, the calculating means calculates an outputable duration time during which the electric power required for driving the load is obtained, and the device calculates It is preferable to have a control unit that drives the load with the power of the secondary battery when the obtained continuous time reaches a predetermined duration required for load driving.
[0010]
Further, in the present apparatus, the load is an engine, and the control means uses the power of the secondary battery when the duration time obtained by the calculation reaches a predetermined duration time required for starting the engine. Is preferably started.
[0011]
The voltage model is represented by V = g (x, i) where x is the state quantity, i is the current value, and V is the voltage value, and the calculation means has power P = g (x, i). The current value i satisfying xi is calculated, the state quantity of the secondary battery after the time T due to the current i flowing is calculated, and the time is calculated using the voltage model based on the calculated current value and the state quantity. A voltage after T can be calculated, and an integrated value of the time T when the voltage reaches a predetermined voltage lower limit value of the secondary battery can be calculated as the duration.
[0012]
According to another aspect of the present invention, there is provided a means for detecting a state quantity of a secondary battery, and a calculation for calculating power in a certain duration that can be input or output from the secondary battery using at least a predetermined voltage model based on the state quantity Means.
[0013]
The apparatus may further include a control unit that drives the load with the electric power obtained by the calculation unit and the duration, and the load may be a motor.
[0014]
As described above, the secondary battery control device of the present invention uses the voltage model of the secondary battery to calculate the duration that can be input or output corresponding to the power from the current state quantity (SOC, temperature, etc.). In other words, the duration that can be input or output corresponding to a certain power is predicted. By predicting the duration that can be input and output, it is possible to determine whether or not a necessary duration condition is satisfied, and to accurately control charging and discharging of the secondary battery based on the determination result. When the secondary battery of the present invention is mounted on a vehicle and switched from motor driving to engine driving according to the state of the secondary battery, whether or not the secondary battery satisfies the power and duration required for engine cranking. Therefore, it is not necessary to secure an unnecessary margin for the secondary battery, and engine cranking can be guaranteed.
[0015]
On the other hand, instead of calculating the input / output duration corresponding to the power from the current state quantity, it is also possible to calculate the power corresponding to the input / output duration by the reverse operation. For example, when the discharge duration required for the secondary battery is given, electric power corresponding to this discharge duration is obtained. As a result, even if it is necessary to charge / discharge at least a certain amount of power for a certain period of time, it is possible to accurately determine whether or not the current secondary battery satisfies this condition, and the controllability of charge / discharge is improved. To do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a configuration block diagram of the present embodiment. The vehicle is provided with a motor / generator (MG) 14, an engine 16 and a generator 19. The motor / generator 14 and the engine 16 are coupled by a power distribution mechanism such as a planetary gear mechanism, for example, and a part of the motor / generator 14 and the engine 16 is connected to a drive shaft to which driving wheels are coupled. As a result, the output of the motor / generator 14 or the engine 16 is transmitted to the drive wheels to drive the vehicle.
[0018]
The engine ECU 17 controls the output and the number of revolutions of the engine 16 based on environmental conditions such as an accelerator pedal operation amount and cooling water temperature detected by an accelerator sensor, and an operating state of the motor / generator 14.
[0019]
The generator 19 is connected to the engine 16 and generates electric power from the output of the engine 16 to drive the motor / generator 14 or supplies the secondary battery 10 to charge the secondary battery 10.
[0020]
The motor / generator 14 is controlled by a hybrid (HV) ECU 20. The HVECU 20 supplies power from the secondary battery 10 to the motor / generator 14 by controlling each switch of the inverter 12 via the motor ECU. Electric power from the generator 14 is regenerated to the secondary battery 10 to charge the secondary battery 10. Secondary battery 10 and inverter 12 are connected via system main relay SMR.
[0021]
Control of the inverter 12 by the HVECU 20 includes information on the operating state of the engine 16 from the engine ECU 17, the operation amount of the accelerator pedal, the operation amount of the brake pedal from the brake computer, the shift range from the shift position sensor, and the secondary from the battery ECU 18. This is executed based on the state of charge SOC of the battery 10 or the like. For example, the HVECU 20 controls the switching timing from the motor drive to the engine drive based on the SOC of the secondary battery 10 supplied from the battery ECU 18. The engine is started by controlling the inverter 12 to supply power from the secondary battery 10 to the generator 19 and causing the generator 19 to function as a starter motor. The switching from motor drive to engine drive will be described later.
[0022]
The secondary battery 10 includes a plurality of blocks connected in series, and each block includes a plurality of cells. A voltage sensor is provided for each block, and the detection voltage of each block is supplied to the battery ECU 18. Further, the current value of the secondary battery 10 detected by the current sensor is also supplied to the battery ECU 18. Further, the temperature detected by the temperature sensor is also supplied to the battery ECU 18. As the secondary battery 10, for example, a nickel metal hydride battery can be used.
[0023]
The battery ECU 18 manages the temperature of the secondary battery 10 based on the detected temperature, and drives the cooling fan (not shown) to keep the temperature of the secondary battery 10 constant when the temperature exceeds a predetermined temperature. . Further, based on the detected current value, the state of charge (SOC) of the secondary battery 10 is detected and supplied to the HVECU 20. The SOC is calculated based on the initial state SOC and the integrated current value.
[0024]
In such a configuration, in the present embodiment, when the HVECU 20 switches from motor drive to engine drive, the output possible duration of the secondary battery 10 is calculated and switched to engine drive at an optimal timing. That is, from the viewpoint of the usage efficiency of the secondary battery 10, the engine is not started until the SOC or voltage of the secondary battery 10 reaches a limit value at which an output necessary for engine cranking can be obtained. It is desirable to perform engine cranking using the remaining output when it reaches. This is because the engine can be started reliably without leaving a margin in the secondary battery 10.
[0025]
Therefore, the HVECU 20 of this embodiment adjusts the switching timing by accurately determining whether or not the known necessary power and output duration required for engine cranking can be obtained from the current state of the secondary battery 10. To do.
[0026]
FIG. 2 shows a process flowchart of the HVECU 20. First, the HVECU 20 calculates the output possible duration TC of the secondary battery 10 for the electric power PE required for cranking the engine 16 (S101). This calculation process will be described later. Next, the obtained duration TC is compared with a known duration TE required for cranking the engine 16 (S102). The duration time TE may be stored in advance in the memory of the HVECU 20. If the duration time TC exceeds TE, it means that the secondary battery 10 still has room, and therefore the cranking of the engine 16 is not executed and the motor 14 runs. On the other hand, when YES in S102, that is, when the calculated duration time TC is equal to or shorter than the duration time TE, in other words, when the duration time TC reaches the duration time TE, there is no room for the secondary battery 10 and the engine 16 Therefore, at this point, the inverter 12 is controlled to cause the generator 19 to function as a motor and start the engine 16 (S103).
[0027]
FIG. 3 shows a process flowchart for calculating the output possible duration TC of the secondary battery 10 for the known power PE required for the process of S101 in FIG. 2, that is, engine cranking.
[0028]
First, the HVECU 20 performs initial setting of various parameters (S201). Specifically, the state quantity detected at the local point is set as the state quantity (SOC or temperature) of the secondary battery 10, and the duration time TC is initialized to zero. Next, in a predetermined voltage model V = g (x, i), a current value i satisfying the relationship of PE = g (x, i) × i is calculated (S202). The predetermined voltage model V = g (x, i) can be obtained by adjusting a parameter of a known voltage model that is theoretically defined by a charge / discharge experiment using the secondary battery 10.
[0029]
After calculating the current value i at which the electric power PE required for engine cranking is obtained, the state quantity x of the secondary battery 10 after the time T due to the current i flowing is calculated (S203). In the case of the SOC, the SOC after T can be calculated by adding or subtracting the integrated value of the current flowing between the SOC in the initial state and T. The temperature can be determined from the temperature increase determined experimentally.
[0030]
Next, based on the current value i obtained in S202 and the state quantity x obtained in S203, the voltage of the secondary battery 10 after time T using a predetermined voltage model V = g (x, i). Is calculated (S204). After calculating the voltage of the secondary battery 10 after the time T, it is determined whether or not this voltage has reached a predetermined lower limit voltage of the secondary battery 10 (S205). This lower limit voltage is a voltage at which the deterioration of the secondary battery 10 progresses rapidly when the voltage drops below this, and is determined in advance according to the secondary battery 10 and stored in the memory. If the voltage of the secondary battery 10 has not yet reached the lower limit voltage, it means that the output or discharge of the secondary battery 10 is still possible, so the time T is added to the duration time TC and continued. The time TC is updated (S206), and the processing after S202 is repeated again. Thus, the time T is sequentially integrated until the voltage of the secondary battery 10 reaches the lower limit value, and this integrated value becomes the duration time TC.
[0031]
On the other hand, when the calculated voltage based on the voltage model of the secondary battery 10 reaches the lower limit voltage, it means that the output of the secondary battery 10 has no margin and no further discharge is possible. The possible output duration TC at which power PE can be obtained is determined. As described above, using the current state quantity x of the secondary battery 10 and the voltage model, it is possible to accurately calculate the duration TC in which the power PE required for engine cranking can be continuously output. As described above, the calculated TC is compared with the predetermined time TE.
[0032]
Thus, in the present embodiment, the output possible duration time of the secondary battery 10 that can obtain the power required for engine cranking is calculated, and this duration time has reached a predetermined duration time required for engine cranking. Since the timing control is sometimes performed to execute engine cranking, the capacity of the secondary battery 10 can be utilized to the maximum, and the usage efficiency of the secondary battery 10 and the usage efficiency of the motor 14 are improved to improve fuel efficiency. Improvements can be made.
[0033]
In the present embodiment, the output continuation time TC of the electric power PE required for engine cranking is calculated by the processing flowchart shown in FIG. 3. However, the state quantity x, electric power P, and continuation of the secondary battery 10 are calculated. Even if the relationship with the time TC is calculated in advance using a voltage model and mapped and stored in the memory, the current state quantity x and the duration TC corresponding to the required power can be immediately calculated based on this map. Good. Such a map can be represented by the relational expression TC = f (x, P).
[0034]
Further, based on the relationship T = f (x, P) between the power P and the duration T, the duration of the secondary battery 10 is not calculated from the power P, but conversely, the current state quantity of the secondary battery 10 The possible power P of the secondary battery 10 can also be calculated from x and the necessary duration T. That is, P = f ⁻¹ (x, T) is obtained from the relationship T = f (x, P), and the electric power P at which the necessary duration T can be obtained can be calculated from this relationship. Thus, for example, when the vehicle driver needs to drive the motor 14 by continuously discharging the secondary battery 10 for at least a predetermined time (for example, 10 seconds) after fully opening the accelerator, etc. Whether power can be obtained can be grasped in advance. For example, when it is necessary to continuously discharge for at least 10 seconds, electric power that can be output continuously for 10 seconds is obtained, and torque assist can be performed using this electric power. Of course, if the electric power obtained in 10 seconds is not sufficient to obtain the motor torque associated with the accelerator operation, the duration for obtaining the necessary electric power is calculated by the same method as in the above-described embodiment, and the duration is calculated. It may be determined whether it is acceptable.
[0035]
Furthermore, HVECU 20 always calculates a possible combination of output power and duration (P, T) from the current state quantity of secondary battery 10 regardless of when the engine is started or when the vehicle is traveling at a high load such as when the accelerator is fully open, It is also possible to control the discharge of the secondary battery 10 by selecting an optimum combination for the current running state from these.
[0036]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.
[0037]
For example, in the present embodiment, the discharging of the secondary battery 10 has been described, but the charging of the secondary battery 10 can be similarly performed. Specifically, it can be processed as follows. That is, the state quantity detected at the local point is set as the state quantity (SOC and temperature) of the secondary battery 10, and the duration time TC is initialized to zero. Next, in a predetermined voltage model V = g (x, i), a current value i that satisfies the relationship of input power P = g (x, i) × i is calculated. After calculating the current value i corresponding to the power P, the state quantity x of the secondary battery 10 after the time T due to the current i flowing in is calculated. Then, based on the obtained current value i and state quantity x, the voltage of the secondary battery 10 after time T is calculated using a predetermined voltage model V = g (x, i). After calculating the voltage of the secondary battery 10 after the time T, it is determined whether or not this voltage has reached a predetermined upper limit voltage of the secondary battery 10. If the voltage of the secondary battery 10 has not yet reached the upper limit voltage, it means that the secondary battery 10 can still be charged. Therefore, the time T is updated by adding the time T to the time TC. I will do it. Thus, the time T is sequentially accumulated until the voltage of the secondary battery 10 reaches the upper limit value, and this accumulated value becomes the duration time TC. The calculated duration time is compared with a predetermined threshold time, and charging of the secondary battery 10 is permitted if it is within the predetermined threshold time, and charging of the secondary battery 10 is prohibited if the threshold time is exceeded. It is possible to control such as.
[0038]
It is also possible to calculate the input power P corresponding to the charging duration T based on P = f ⁻¹ (x, T) and charge the secondary battery 10 with this power.
[0039]
Further, in this embodiment, the calculation of the input or output possible duration corresponding to the electric power is executed by the HVECU 20, but of course, it can also be executed by the battery ECU 18, and further executed by an ECU or a microcomputer other than these. May be.
[0040]
In addition, the function form of the voltage model V = g (x, i) in the present invention can be arbitrarily set, and a plurality of function forms are used in accordance with the state quantity x or the current value i instead of a single function form. May be. The processor of the HVECU 20 does not calculate the duration from the power according to a certain relational expression of V = g (x, i), or calculates the power from the duration, but in advance according to this relational expression, the state quantity, the power, and the continuation A set of times may be stored in a memory as a map, and the power or duration corresponding to the state quantity detected using this map may be read. Since the state quantity, power, and duration stored in the map are obtained based on the voltage model, they are included in the present invention.
[0041]
Further, the state quantity in the voltage model V = g (x, i) may include a parameter indicating the charge / discharge history of the secondary battery 10 in addition to the state of charge (SOC) and temperature shown in the present embodiment. .
[0042]
Further, the HVECU 20 calculates the duration T from the power P using the relational expression T = f (x, P) between the power and time, or the duration T using P = f ⁻¹ (x, T). The electric power P can also be calculated from the above, but this equation is also included in the present invention as long as it can be obtained using the voltage model V = g (x, i).
[0043]
【The invention's effect】
As described above, according to the present invention, the secondary battery can be used to the limit, and the charging or discharging efficiency can be increased. In addition, when mounted on a hybrid vehicle or the like, the use efficiency of the secondary battery is improved, and the fuel efficiency is also improved.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of an embodiment.
FIG. 2 is a processing flowchart of the embodiment.
FIG. 3 is a flowchart for calculating a continuous time according to the embodiment.
[Explanation of symbols]
10 secondary battery, 12 inverter, 14 motor / generator, 16 engine, 17 engine ECU, 18 battery ECU, 19 generator, 20HVECU.

Claims (5)

Means for detecting a state quantity of the secondary battery; and a computing means for calculating a duration at which the secondary battery can be input or output at a certain power using a predetermined voltage model based on at least the state quantity;
Have a,
The power is power required for driving a load,
The computing means computes an outputable duration during which power necessary for driving the load is obtained, and the device further comprises:
Control means for driving the load by the power of the secondary battery when the duration obtained by the calculation reaches a predetermined duration required for driving the load;
A secondary battery control device comprising: The apparatus of claim 1.
The load is an engine;
The control means starts the engine by the power of the secondary battery when the calculated duration reaches a predetermined duration required for starting the engine. . The apparatus according to claim 1,
The voltage model is represented by V = g (x, i), where x is the state quantity, i is the current value, and V is the voltage value.
The computing means is
Calculate a current value i satisfying power P = g (x, i) × i,
Calculating the state quantity of the secondary battery after time T due to the current i flowing;
A voltage after time T is calculated using the voltage model based on the calculated current value and state quantity,
The secondary battery control device , wherein the integrated value of the time T when the voltage reaches a predetermined voltage lower limit value of the secondary battery is calculated as the duration . Means for detecting the state quantity of the secondary battery;
A computing means for computing power in a certain duration that can be input to or output from the secondary battery using a predetermined voltage model based on at least the state quantity;
A secondary battery control device comprising: The apparatus of claim 4, further comprising:
Control means for driving the motor with the power and duration obtained by the computing means;
A secondary battery control device comprising:

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