JP5372872B2 - Secondary battery charge rate calculation device and charge rate calculation method - Google Patents

Description

  The present invention relates to a charging rate calculation device and a charging rate calculation method for a secondary battery.

  In the charging rate calculation device described in Patent Document 1, the charging rate of the secondary battery is calculated based on the charging / discharging current of the secondary battery and the terminal voltage.

JP-T-2004-514249

However, the conventional technology has a problem that the charge rate cannot be calculated when an abnormality occurs in the current detection means for detecting the charge / discharge current.
An object of the present invention is to provide a charging rate calculation device and a charging rate calculation method capable of calculating a charging rate of a secondary battery even when an abnormality occurs in a current detection unit that detects charging / discharging current. .

  In order to achieve the above object, in the present invention, when it is determined that an abnormality has occurred in the current detection means for detecting the charge / discharge current, the charging rate is calculated based on the total value of the currents of the respective electric loads of the secondary battery. calculate.

  Since the total value of the current flowing through each electric load of the secondary battery is a value that is substantially close to the charge / discharge current of the secondary battery, the current rate is calculated by calculating the charging rate based on the total value of the current of each electric load. Even when an abnormality occurs in the detection means, the charging rate can be calculated.

1 is a configuration diagram of a battery system 1 of Example 1. FIG. 2 is a control block diagram of a controller 2. FIG. 4 is a control block diagram of the SOC calculation unit 23. FIG. 6 is a battery model 25 showing an internal resistance equivalent circuit of the battery 6. It is a control block diagram of sequential parameter estimation. 6 is an OCV-SOC characteristic diagram of a battery 6. FIG. 3 is a flowchart showing a flow of a charging rate calculation process of a controller 2.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing the charging rate calculation apparatus and charging rate calculation method of the secondary battery of this invention is demonstrated based on the Example shown on drawing.
[Example 1]
First, the configuration of the first embodiment will be described.
FIG. 1 is a configuration diagram of a battery system 1 according to a first embodiment. The battery system 1 according to the first embodiment is mounted on an electric vehicle.
The battery system 1 includes a controller 2, a voltage sensor (terminal voltage detection means) 3, a current sensor (current detection means) 4, a battery (secondary battery) 6, and three electric loads (travel motor 7, electric compressor motor 8 And PTC heater 9).
The voltage sensor 3 detects the terminal voltage of the battery 6 and outputs a sensor voltage V.
The current sensor 4 detects the charge / discharge current of the battery 6 and outputs a sensor current I.

The travel motor 7 is a motor generator that drives the drive wheels, and is connected to the inverter 10. The inverter 10 converts the DC power supplied from the battery 6 into AC power and drives the traveling motor 7. The current sensor (load current detection means) 11 detects the charge / discharge current of the traveling motor 7 and outputs the load current i1.
The electric compressor motor 8 is a motor that drives an air conditioning compressor (not shown), and is connected to the inverter 12. The inverter 12 converts the DC power supplied from the battery 6 into AC power to drive the electric compressor motor 8. The current sensor (load current detection means) 13 detects the current of the electric compressor motor 8 and outputs a load current i2.
A PTC (Positive Temperature Coefficient) heater 9 is disposed in the hot air blowing duct as an auxiliary heater during heating operation, and overheats when energized to warm the air-conditioner wind after passing through the heater core. The PTC heater 9 is connected to the DC / DC converter 14. The DC / DC converter 14 steps down the DC power supplied from the battery 6 to 12V, and the PTC heater 9 and a plurality of 12V electric loads (for example, an electric power steering motor that assists the driver's steering force). To supply. The current sensor (load current detection means) 15 detects the current of the PTC heater 9 and outputs a load current i3.
The relay 16 maintains or cuts off the electrical connection between the battery 6 and each electric load (the inverters 10 and 12 and the DC / DC converter 14).

The controller 2 calculates a state of charge (SOC) of the battery 6 based on the output of each sensor, and controls charging / discharging of the battery 6. Further, the controller 2 presents to the driver the battery remaining amount RC of the battery 6 obtained by multiplying the charging rate SOC by the full charge capacity FCC or the travelable distance predicted from the battery remaining amount RC.
FIG. 2 is a control block diagram of the controller 2.
The controller 2 includes an abnormality determination unit (abnormality determination unit) 20, an adder 21, a switch (input current switching unit) 22, an SOC calculation unit (charge rate calculation unit) 23, and an RC calculation unit 24.

The abnormality determination unit 20 reads the sensor current I from the current sensor 4, and when the sensor current I is within a normal range, determines that the current sensor 4 is operating normally and outputs a determination signal 1 (true). When the sensor current I deviates from the normal range, it is determined that the current sensor 4 is abnormal and a determination signal 0 (false) is output. For example, when the maximum output power and the maximum input power of the battery 6 are both 90 kW and the terminal voltage is 345 V, the maximum current is 260 A. Therefore, in the first embodiment, the normal range of the sensor current I used for the abnormality determination of the current sensor 4 is set to a range of −270A to 270A obtained by adding a margin of about 10A to −260A to 260A, respectively.
The adder 21 outputs a load current total value i obtained by adding the load currents i1, i2, i3 detected by the current sensors 11, 12, and 13.
The switch 22 inputs the determination signal output from the abnormality determination unit 20 as a link operation selection command.When the link operation selection command is 1 (true), the sensor 22 outputs the sensor current I from the current sensor 4, and 0 (false ), The total load current value i is output.

The SOC calculation unit 23 calculates the charge rate SOC based on the sensor current I or the load current total value i output from the switch 22 and the sensor voltage V output from the voltage sensor 3.
FIG. 3 is a control block diagram of the SOC calculation unit 23. The SOC calculation unit 23 includes a parameter estimation unit 23a, an OCV estimation unit 23b, and an OCV-SOC conversion unit 23c.
The parameter estimation unit 23a estimates each parameter R0, R1, R2, C1, C2 of the battery model 25 shown in FIG.
FIG. 4 shows a battery model 25 showing an internal resistance equivalent circuit of the battery 6. The battery model 25 shows a resistance R0 for setting a direct current component such as an electrolyte resistance and an ohmic resistance, and a dynamic behavior in a charge transfer process. The resistor R1 is set as a reaction resistance to be expressed, C1 is set as an electric double layer, and R2 and C2 are set to indicate dynamic behavior in the diffusion process. Here, an equivalent circuit model of a primary parallel circuit in the charge transfer process and a secondary parallel circuit in the diffusion process is shown, but the respective orders change depending on the situation.

FIG. 5 is a control block diagram of sequential parameter estimation.
The battery 6 receives a measured current (sensor current I or load current total value i) as an input to the control system, and outputs a measured battery voltage V. This battery 6 is set to handle an actual battery.
The battery model 25 is an equivalent circuit that is a model of the battery 6, adjusts the parameters of the equivalent circuit with the corrected output from the adaptive mechanism 26, and outputs the voltage model estimated value V ^. Further, each parameter R0, R1, R2, C1, C2 of the equivalent circuit is output. Note that the resistance values R1 and R2 are used for both the symbol indicating resistance and the symbol indicating resistance value for the sake of explanation.
The adaptive mechanism 26 modifies the calculation contents of the battery model 25 according to the deviation calculated by V and V ^ so that the difference between the terminal voltage of the battery 6 and the estimated terminal voltage V ^ of the battery model 25 disappears. (V ^ represents an estimated value of V, and actually has a notation on V), and each parameter R0, R1, R2, C1, C2 is corrected sequentially. As a result, a battery model that matches the current state of the battery 6 can be obtained. In the first embodiment, a Kalman filter is used as the adaptive mechanism 26.

Returning to FIG. 3, the OCV estimation unit 23b calculates the overvoltage VR from the estimated parameters R0, R1, R2, C1, and C2 and the sensor current I (or the load current total value i), and the overvoltage VR from the sensor voltage V. Is calculated to calculate the open circuit voltage OCV.
The OCV-SOC conversion unit 23c converts the open circuit voltage OCV into the charge rate SOC using a preset OCV-SOC conversion table. FIG. 6 is an OCV-SOC characteristic diagram of the battery 6. Since the relationship between the open circuit voltage OCV and the charging rate SOC is always kept constant regardless of temperature and deterioration, the OCV-SOC of the battery 6 is experimentally determined beforehand. Measure the characteristics and create an OCV-SOC conversion table.
The RC calculator 24 multiplies the calculated charge rate SOC by the full charge capacity FCC to calculate the battery remaining amount RC. In addition, the travelable distance is predicted from the battery remaining amount RC.

[Charging rate calculation process]
FIG. 7 is a flowchart showing the flow of the charging rate calculation process of the controller 2, and each step will be described below. This process is repeatedly executed at a predetermined calculation cycle.
In step S1, the sensor voltage V is read from the voltage sensor 3, the sensor current I is read from the current sensor 4, and the load currents i1, i2, i3 are read from the current sensors 11, 13, and 15.
In step S2, the abnormality determining unit 20 determines whether or not the sensor current I is within a normal range (-270A to 270A). If YES, the process proceeds to step S3. If NO, step S4 is performed. Proceed to
In step S3, the sensor current I is set as the input current of the SOC calculation unit 23 in the switch 22.
In step S4, in the switch 22, the load current total value i obtained by totaling the load currents i1 to i3 is set as the input current of the SOC calculation unit 23.

In step S5, the parameter estimation unit 23a estimates the parameters R0, R1, R2, C1, and C2 of the battery model 25 from the input current (sensor current I or load current total value i) and the sensor voltage V.
In step S6, the OCV estimation unit 23b calculates the open circuit voltage OCV from each parameter R0, R1, R2, C1, C2, the input current (sensor current I or load current total value i) estimated in step S5 and the sensor voltage V. calculate.
In step S7, the OCV-SOC conversion unit 23c calculates the charge rate SOC from the open circuit voltage OCV estimated in step S6 with reference to the OCV-SOC conversion table (FIG. 6).

Next, the operation of the first embodiment will be described.
[Charging rate calculation based on load current when current sensor is abnormal]
A conventional charging rate calculation device includes a current sensor that detects a charging / discharging current of a battery and a voltage sensor that detects a terminal voltage, and calculates a charging rate based on output signals of both sensors. For this reason, when an abnormality such as a failure occurs in the current sensor, the charge rate cannot be calculated. In particular, in the case of a battery of an electric vehicle, since the charge rate cannot be calculated, the input / output power of the battery cannot be calculated, so that the vehicle cannot travel.

On the other hand, in the charging rate calculation apparatus of the first embodiment, when it is determined that an abnormality has occurred in the current sensor 4, each electric load of the battery 6 (travel motor 7, electric compressor motor 8, PTC heater 9) The charge current SOC is calculated from the load current total value i and the sensor voltage V using the load current total value i obtained by adding the load currents i1 to i3 as a substitute value for the sensor current I.
Since the total value (load current total value) i of the currents flowing through the electric loads of the battery 6 is substantially close to the charge / discharge current of the battery 6, the charge rate SOC is calculated based on the total load current value i. Thus, even when an abnormality occurs in the current sensor 4, the charge rate SOC close to the actual charge rate can be calculated. Therefore, it is possible to avoid the vehicle from being unable to travel, and to move the vehicle to a dealer or a repair shop. Further, when the driver moves the vehicle, the rough travelable distance can be grasped.

  Here, in the first embodiment, the load currents of all electric loads of the battery 6 are not detected, but the load currents i1 to i3 of the traveling motor 7, the electric compressor motor 8 and the PTC heater 9 are detected, and the total load current is detected. Value i. This is because the calculation of the charging rate SOC using the load current total value i is only a measure for avoiding the vehicle being unable to travel, and an extremely high charging rate SOC is not required. This is because, if current sensors are provided for all electric loads, a significant cost increase is caused.

Further, among the electric loads, the traveling motor 7 and the electric compressor motor 8 flow a larger current than the other 12V electric loads, so that most of the charge / discharge current of the battery 6 is the same as that of the traveling motor 7. It can be considered that it was caused by the exchange of electric current with the electric compressor 8. Therefore, by including the load currents i1 and i2 of the travel motor 7 and the electric compressor motor 8 in the load current total value i, it is possible to obtain the total load current value i close to the actual charge / discharge current, and the charging rate SOC Can be calculated with high accuracy.
The travel motor 7 and the electric compressor motor 8 detect current values for torque control and rotational speed control. Therefore, the current sensors 11 and 13 are indispensable components, and the charging rate of the first embodiment is as follows. There is no need to add a new current sensor for calculation, and there is an advantage that an increase in cost can be suppressed.

Example 1 has the following effects.
(1) Current sensor 4 that detects the charge / discharge current of battery 6 and outputs sensor current I, SOC calculation unit 23 that calculates charge rate SOC based on sensor current I, and provided for each electric load of battery 6 , Current sensor 11, 13, 15 stage that detects the current of the corresponding electric load, abnormality determination unit 20 that determines abnormality of current sensor 4 based on sensor current I, and abnormality of current sensor 4 A switch 22 that inputs the load current total value i, which is the total value of the currents i1 to i3 of each electric load detected by the current sensors 11, 13, and 15, to the SOC calculation unit 23 as an alternative value of the sensor current I. Prepared.
Since the load current total value i substantially matches the charge / discharge current of the battery 6, the charge rate SOC is calculated based on the load current total value i, so even if an abnormality occurs in the current sensor 4, charging Rate SOC can be calculated.

(2) Since the battery 6 is an in-vehicle battery that uses the travel motor 7 as an electrical load, the input / output power of the battery 6 can be calculated even when an abnormality occurs in the current sensor 4, and the vehicle travels. It is possible to avoid becoming impossible.
(3) As an electric load, an electric compressor motor 8 that drives an electric compressor for air conditioning is provided, and the switch 22 includes the currents i1 and i2 of the traveling motor 7 and the electric compressor motor 8 in the load current total value i.
Thereby, the load current total value i close to the actual charge / discharge current can be obtained without detecting the currents of all electric loads, and the charge rate SOC can be calculated with high accuracy.

(4) In the secondary battery charging rate calculation method for calculating the charging rate SOC based on the sensor current I detected by the current sensor 4, each electric load (running motor 7, electric compressor motor 8, The current i1, i2, i3 of the PTC heater 9) is detected, the abnormality of the current sensor 4 is determined based on the sensor current I, and if it is determined that an abnormality has occurred in the current sensor 4, the total load current i The charging rate SOC is calculated based on the above.
Since the load current total value i substantially matches the charge / discharge current of the battery 6, the charge rate SOC is calculated based on the load current total value i, so even if an abnormality occurs in the current sensor 4, charging The rate SOC can be calculated, and the vehicle can be prevented from being unable to run.

(Other examples)
As mentioned above, although the charging rate calculation device of the secondary battery according to the present invention has been described based on the embodiments, the specific configuration is not limited to the embodiments, and each claim described in the claims. Design changes and additions are allowed without departing from the spirit of the invention.
For example, in the embodiment, the Kalman filter is used for successive parameter estimation, but other estimation methods may be used.

In the example, the open voltage was estimated from the charge / discharge current and the terminal voltage using the equivalent model of the secondary battery, and the charging rate was obtained from the estimated open voltage, but the charge / discharge current was integrated over time. You may ask for a charge rate. Moreover, you may use both together.
In the embodiment, the currents of the traveling motor, the electric compressor motor, and the PTC heater are summed to calculate the total load current. However, at least the currents of the traveling motor and the electric compressor motor may be summed, and the PTC heater The current may be omitted. Moreover, you may add the electric current of other 12V type electric loads, such as an electric power steering motor.

3 Voltage sensor (terminal voltage detection means)
4 Current sensor (current detection means)
6 Battery (secondary battery)
7 Motor for travel (electric load)
8 Electric compressor motor (electric load)
9 PTC heater (electric load)
11 Current sensor (load current detection means)
13 Current sensor (load current detection means)
15 Current sensor (load current detection means)
20 Abnormality judgment unit (abnormality judgment means)
22 Switch (Input current switching means)
23 SOC calculation part (charging rate calculation means)

Claims (4)

Current detection means for detecting the charge / discharge current of the secondary battery;
A charge rate calculating means for calculating a charge rate of the secondary battery based on the charge / discharge current;
Load current detection means provided for each electric load of the secondary battery and detecting the current of the corresponding electric load;
An abnormality determining means for determining an abnormality of the current detecting means based on the charge / discharge current;
When it is determined that the current detection unit is abnormal, the input current switching unit inputs the total value of the currents of the electric loads detected by the load current detection unit to the charge rate calculation unit as an alternative value of the charge / discharge current. When,
A charge rate calculation device for a secondary battery, comprising: In the secondary battery charge rate calculation apparatus according to claim 1,
The secondary battery is an in-vehicle battery having a traveling motor as an electric load. In the rechargeable battery charge rate calculation device according to claim 2,
The electric load includes an electric compressor motor that drives an air conditioning electric compressor,
The input current switching means includes the currents of the motor for traveling and the motor for electric compressor in the total value of the currents of the respective electric loads. In the secondary battery charge rate calculation method for calculating the charge rate based on the charge / discharge current of the secondary battery detected by the current detection means,
Detecting the current of each electric load of the secondary battery,
Determining an abnormality of the current detection means based on the charge / discharge current;
When it is determined that an abnormality has occurred in the current detection means, the charging rate is calculated based on the total value of the detected currents of the electric loads.

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