JP2003132959A - Method for deciding degradation of secondary battery used for power source system, and power source system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately device degradation of a secondary battery of a power source system provided with a secondary battery which supplies the output from an independent power source to a load and stores a surplus output of the independent power source, while supplying a shortfall if the output of the independent power source is insufficient for the load, and to provide a power source system capable of assuring power supply from the secondary battery even if the secondary battery degrades to some extent. SOLUTION: There are provided a means for detecting SOC (state of charge) of a secondary battery, a means for detecting a discharge current of the secondary battery, and a means for detecting a discharge voltage of the secondary battery. The degradation of the secondary battery is decided based on relationship between the SOC, discharge current, and discharge voltage of the secondary battery. If degradation is admitted, the controlled lower-limit value of the SOC is raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply system for supplying electric power to a load by using an independent power supply such as a fuel cell, and particularly to deterioration of a secondary battery in a power supply system including a secondary battery for output leveling. The present invention relates to a determination method and a power supply system technology using the determination method.

[0002]

2. Description of the Related Art As a power supply system using an independent power supply such as a fuel cell, for example, one disclosed in Japanese Patent Laid-Open No. 50-116925 is known. In these power supply systems, as shown in FIG.
Connected to the load 43 than the output power of the fuel cell 42.
When the load power of the
Closed to supply power from the secondary battery 41 to the load 43,
On the contrary, the fuel cell 4 produced when the electric power of the load 43 decreases
By storing the surplus power of 2 in the secondary battery 41 via the charge control means 45 such as a DC-DC converter, the power generation efficiency of the system is improved. Reference numeral 46 denotes a power converter, and the output of the fuel cell 42 is connected to the load 43 via the power converter 46 depending on the form of power required by the load 43.

In such a secondary battery, the discharge time is shortened and the internal resistance is increased due to the deterioration of the active material as it deteriorates to the end of deterioration, so that the discharge voltage is also decreased as compared with the initial stage.

Therefore, in the power supply system as described above, in order to measure the deterioration state of the secondary battery 41 and judge the deterioration, the secondary battery voltage at the time of discharging is detected by the discharge voltage detecting means 47, and this discharge voltage is detected. In general, the deterioration determination voltage / discharge voltage comparison means 48 compares the values with each other, and when the voltage drops below the deterioration determination voltage, it is determined as deterioration, and the deterioration display means 49 is used to notify the user of the deterioration of the secondary battery. In order to improve the accuracy of the deterioration determination, a method of correcting the deterioration determination value with the battery temperature or the discharge current value has been proposed.

However, in order to efficiently store the surplus power in the storage battery, it is necessary to maintain the storage battery in a partially charged state. In addition, since the storage battery is constantly charged and discharged, its state of charge (hereinafter referred to as SOC) is not constant. In such a situation, it is difficult to accurately determine the deterioration state of the storage battery by simply measuring the discharge voltage.

[0006] Further, the SOC of the storage battery is controlled within a certain range, but when the deterioration of the storage battery has progressed to some extent, the SO
When C is at the control lower limit value, sufficient electric power may not be supplied from the storage battery.

[0007]

SUMMARY OF THE INVENTION The present invention supplies the output from an independent power source as described above to a load, stores the surplus output of this independent power source, and outputs the output of the independent power source to the load. In a power supply system in which a secondary battery that supplies the insufficient power is provided and the SOC of the secondary battery is controlled within a predetermined range, deterioration of the secondary battery can be accurately determined, and An object of the present invention is to provide a power supply system capable of ensuring the supply of electric power to the load from the secondary battery even if the deterioration of the secondary battery progresses to some extent.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention supplies an output from a stand-alone power source to a load, and outputs a surplus output of the stand-alone power source. A power supply that stores a power and has a secondary battery that supplies the insufficient power when the output of the independent power supply is insufficient for the load, and the SOC of the secondary battery is controlled within a predetermined range. In the system, the S of the secondary battery
The secondary battery has a means for detecting an OC, a means for detecting a discharge current of the secondary battery, and a means for detecting a discharge voltage of the secondary battery, and the SOC of the secondary battery and the discharge current of the secondary battery. And a discharge voltage of the secondary battery, the deterioration determination of the secondary battery is performed, and the deterioration determination method of the secondary battery used in the power supply system is shown.

According to a second aspect of the present invention, the output from the independent power source is supplied to the load, the surplus output of the independent power source is stored, and the output of the independent power source is applied to the load. In the case of a shortage, in the power supply system including a secondary battery that supplies the insufficient power, means for detecting the SOC of the secondary battery, and discharging the secondary battery at a predetermined current for a predetermined time at predetermined intervals. And a means for detecting the discharge voltage of the secondary battery, the deterioration determination of the secondary battery based on the relationship between the SOC of the secondary battery and the discharge voltage of the secondary battery. It shows a method of determining deterioration of a secondary battery used in a characteristic power supply system.

Further, in the invention according to claim 3 of the present invention, the output from the independent power source is supplied to the load, the surplus output of the independent power source is stored, and the output of the independent power source is applied to the load. In the power supply system, which is provided with a secondary battery that supplies the insufficient power when insufficient, and means for detecting the SOC of the secondary battery in a power supply system in which the SOC of the secondary battery is controlled within a predetermined range, A discharge current of the secondary battery, and a discharge voltage of the secondary battery, the SOC of the secondary battery, the discharge current of the secondary battery, and the discharge of the secondary battery. 1 shows a power supply system characterized by increasing a control lower limit value of SOC of a secondary battery when a detected discharge voltage of the secondary battery is lower than a determination voltage set based on a relationship with a voltage. It is a thing.

According to a fourth aspect of the present invention, the output from the independent power source is supplied to the load, the surplus output of the independent power source is stored, and the output of the independent power source is applied to the load. In the case of a shortage, in the power supply system including a secondary battery that supplies the insufficient power, means for detecting the SOC of the secondary battery, and discharging the secondary battery at a predetermined current for a predetermined time at predetermined intervals. And a means for detecting the discharge voltage of the secondary battery, the detection voltage being detected based on the relationship between the SOC of the secondary battery and the discharge voltage of the secondary battery. The power supply system is characterized in that the control lower limit value of the SOC of the secondary battery is increased when the discharge voltage of the secondary battery is low.

Further, in the invention according to claim 5 of the present invention, in the power supply system having the structure of claim 3 or 4, the secondary battery is replaced when the SOC control lower limit value rises to a predetermined value. 1 shows a power supply system including means for notifying the time.

Further, the invention according to claim 6 of the present invention shows that the fuel cell is applied to an independent power source in the method for determining deterioration of a secondary battery according to claim 1 or 2.

The invention according to claim 7 of the present invention uses a fuel cell as an independent power supply in a power supply system having any one of the structures according to claims 3 to 5.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a power supply system according to an embodiment of the present invention, showing an example in which a fuel cell is used as an independent power supply.

The output of the fuel cell 1 is connected to the load 2 through the power conversion device 3 as needed depending on the form of power required by the load 2. When the load 2 requests AC power, an inverter device is used as the power converter 3, and when the load 2 requests DC power, the power converter 3 is DC-.
A DC converter device is used.

The output of the secondary battery 4 is the power converter 3
When the output of the fuel cell 1 is insufficient for the load 2, the output from the secondary battery 4 is supplied to the load 2 via the power conversion device 3.

A part of the output of the fuel cell 1 is connected to the secondary battery 4 via the charging control means 5 composed of a DC-DC converter or the like. Then, the secondary battery 4 is charged to the specified SOC by the output of the fuel cell 1. The SOC here is controlled to be, for example, 60% to 80% (SOC when the secondary battery is in a fully charged state is 100%), and when the output of the fuel cell 1 has a surplus, this surplus is generated. Is stored in the secondary battery 4, and the SOC of the secondary battery 4 temporarily increases.

In the present invention, the charging / discharging current of the secondary battery 4 is detected by the charging / discharging current detecting / electrical amount integrating means 7 through the current sensor 6, and then the integrated electrical amount is calculated, and the secondary battery 4 is calculated from this value. SOC is calculated by the SOC calculating means 8.

Here, the SOC is controlled within a certain control range, for example, within the above-mentioned range. The SOC upper limit control (90% in the above example) is performed by, for example, the charging control means 5 by the secondary battery 4
It is performed by controlling the charging voltage value of. The lower limit control of the SOC is performed by inputting the SOC value signal obtained by the SOC calculating means 8 to the charging control means 5 and charging the secondary battery 4 by the charging control means 5 so as to increase the SOC.

In the present invention, the deterioration judgment of the secondary battery 4 is carried out by the flow shown in FIG. That is, as described above, after the charge / discharge current detection / electricity integration means 7 has performed the charge / discharge current detection (step S1) and the charge / discharge current integration (step S2), the SOC calculation means 8 is calculated from these values.
Thus, the SOC of the secondary battery 4 is calculated (step S
3). Whether or not the calculated SOC value is within the specified value is determined, and when the calculated SOC value is not within the specified value, for example, when it becomes lower than the SOC lower limit value, the charging control means 5 forcibly charges a certain constant amount of electricity. To increase the SOC value. Further, when the SOC reaches the upper limit value, the charging by the charging control means 5 is stopped, or the secondary battery 4 loads the load 2
The SOC value is controlled to be lowered by supplying electric power to (step S5).

When the SOC value is within the specified range,
If the secondary battery 4 is in the discharging state, the subsequent deterioration determination is started through step S6 for determining whether the secondary battery 4 is discharging.

That is, the discharge current value Id obtained by the charging / discharging current detecting / electricity integrating means 7 and the discharge voltage detecting means 9 obtain the discharge voltage value Vd in step S7. Here, the discharge current value Id-determination discharge voltage table Vs set for each SOC value is referenced from the SOC value obtained in step S3 (step S8), and the actually measured discharge voltage value Vd and this determination discharge voltage Vs are compared. The comparison is made in step S9. The reference and comparison of these data tables are performed by the SOC-specific data table reference / discharge voltage comparison means 10.

Then, when the measured discharge voltage value Vd is lower than the judgment discharge voltage Vs, it is judged that the secondary battery 4 is deteriorated (step S10). When the deterioration determination is made once, the deterioration display means 11 can display the deterioration of the secondary battery 4, but it is preferable to display the deterioration display only when the deterioration determination is continuously made a plurality of times.

According to the deterioration of the secondary battery used in the power supply system of the present invention, it is possible to accurately judge the deterioration of the secondary battery even if the SOC of the secondary battery changes.

The discharge for determining deterioration (step S6) can be performed by detecting the discharge of the secondary battery 4 as described above. However, instead of step S6, the determination discharge at a constant current is fixed. It is also possible to do it on time. In this case, since the discharge current is constant, the SO
There is an advantage that the amount of data of the discharge current value Id-determination discharge voltage table Vs set for each C value can be reduced. For example, when the discharge current value in the determination discharge is constant at 20 A, it is sufficient to have the discharge voltage and SOC graph data for each deterioration state as shown in FIG. 3 as a table. Of course, since these table values change depending on the battery temperature, the determination accuracy can be further improved by providing the temperature measuring means and correcting the table values by the temperature.

Further, the determination is not made when the SOC is within the specified value, but the narrower SOC within the specified SOC value is used.
It is also possible to set a region and make a decision only when the SOC is in this region. Even in this case, step S8
It is also possible to reduce the amount of data of the discharge current value Id-determination discharge voltage table Vs set for each SOC value in.

It is also possible to set a plurality of SOC regions for making this determination. For example, when the SOC is controlled within the range of 50% to 90%, the first SOC region is set to 50%.
% To 60%, the second SOC region is set to 80% to 90%, and the determination is made only in each region. Further, it is possible to select whether to perform the deterioration determination based on the logical product of the deterioration determinations in each area or to perform the deterioration determination based on the logical sum of the deterioration determinations.

Further, it is possible to change the judgment discharge current according to the SOC value at the time of judgment. In this case, as the SOC value at the time of determination becomes lower, the determination discharge current is made smaller, and conversely, as the SOC value at the time of determination becomes higher,
It is preferable to increase the judgment discharge current. If the SOC is at the control lower limit and a large current is discharged, S
This is because the OC may fall below the control lower limit value, and because the SOC is low, the discharge voltage sharply decreases regardless of the deterioration state, and the determination accuracy decreases. Also, SOC
This is because, in the high range, the discharge voltage does not decrease much even if discharged with a small current suitable for the low SOC range, and the determination accuracy decreases. Therefore, if the control is performed so that the determination discharge current value increases as the SOC value increases during determination,
It is possible to perform deterioration determination with higher accuracy.

The power supply system according to the present invention is configured using the control means for increasing the SOC control lower limit value when the deterioration of the secondary battery is detected by the above-described secondary battery deterioration determination method of the power supply system according to the present invention. be able to.

As described above, in order to store the surplus output of the fuel cell 1, the SOC value is controlled to be less than 100%. However, the electric power of the load 2 increases and the fuel cell 1
Is insufficient for the load electric energy, the output from the secondary battery 4 is supplied to the load 2. Since the SOC value is controlled to be less than 100% while the capacity deterioration of the secondary battery 4 is progressing, the discharge capacity of the secondary battery 4 is reduced and the supply time to the load 2 is shortened. When it is determined by the above-described deterioration determination method of the present invention that the secondary battery 4 has deteriorated, the power supply system that can secure the supply time to the load 2 by increasing the control lower limit value of the SOC value as described above. Can be obtained.

Further, in the power supply system of the present invention, when the deterioration of the secondary battery 4 further progresses and the control lower limit value of the SOC value rises to a certain degree, the storage efficiency of the surplus output from the fuel cell 1 significantly decreases. , Reduces the efficiency of the power supply system. Therefore, it is preferable to provide display means such as turning on a display lamp so as to notify the user of the replacement of the secondary battery 4 when the control lower limit value of the SOC value rises to a certain threshold value. The deterioration display means 11 can also be used as this display means.

Further, as an independent power source, it is preferable to apply a fuel cell or a gas turbine generator, which is efficient for obtaining a constant output, but is not very suitable for rapidly increasing or decreasing the output.

[0035]

As described above, according to the present invention, the output from the stand-alone power source such as a fuel cell is supplied to the load, the surplus output of the stand-alone power source is stored, and the output of the stand-alone power source is stored. Is insufficient for the load, the deterioration of the secondary battery can be accurately determined in the power supply system including the secondary battery that supplies the insufficient power. Further, by increasing the SOC control lower limit value according to the degree of deterioration of the secondary battery, it is possible to secure the power supply from the secondary battery even if the deterioration of the secondary battery progresses to a certain degree, and when the deterioration further progresses. Can obtain a power supply system capable of notifying the user of the replacement of the secondary battery, and the present invention is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a block diagram showing a power supply system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a method of determining deterioration of a secondary battery used in the power supply system according to the embodiment of the present invention.

FIG. 3 Secondary battery discharge 5 seconds voltage and SOC by deterioration state
Diagram showing the relationship with values

FIG. 4 is a block diagram showing a conventional power supply system.

[Explanation of symbols]

1,42 Fuel cell 2,43 load 3,46 Power converter 4,41 Secondary battery 5,45 Charge control means 6 current sensor 7 Charge / Discharge Current Detection / Electricity Accumulation Means 8 SOC calculation means 9,47 Discharge voltage detection means 10 SOC-specific data table reference / discharge voltage comparison means 11,49 Degradation display means 44 discharge switch 48 Deterioration determination voltage-discharge voltage comparison means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Jimbo             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2G016 CB12 CB21 CB22 CB31 CB32                       CC02 CC04 CC06 CC07 CC13                       CC23 CD01 CE01                 5G003 AA05 BA01 DA07 DA18 EA08                 5H030 AA06 AS03 AS18 BB08 BB22                       DD02 DD06 FF42 FF44

Claims (7)

[Claims] 1. An output from an independent power source is supplied to a load,
While accumulating the surplus output of the independent power source, when the output of the independent power source is insufficient for the load, a secondary battery that supplies the insufficient power is provided, and the state of charge of the secondary battery is In a power supply system controlled within a predetermined range, means for detecting a state of charge of the secondary battery, means for detecting a discharge current of the secondary battery, and means for detecting a discharge voltage of the secondary battery. A power supply system characterized by performing deterioration determination of the secondary battery based on the relationship between the state of charge of the secondary battery, the discharge current of the secondary battery, and the discharge voltage of the secondary battery. Deterioration determination method for secondary battery used. 2. An output from an independent power source is supplied to a load,
Charging the secondary battery in a power supply system including a secondary battery that stores the surplus output of the independent power source and supplies the insufficient power when the output of the independent power source is insufficient for a load. A state detecting means, a means for discharging the secondary battery at a predetermined current for a predetermined time every predetermined period, and a means for detecting a discharge voltage of the secondary battery, and a charging state of the secondary battery A method for determining deterioration of a secondary battery used in a power supply system, comprising determining deterioration of the secondary battery based on a relationship with a discharge voltage of the secondary battery. 3. An output from an independent power source is supplied to a load,
A secondary battery is provided which stores the surplus output of the independent power source and supplies the insufficient power when the output of the independent power source is insufficient for the load, and the state of charge of the secondary battery is predetermined. In a power supply system controlled within a range, means for detecting the state of charge of the secondary battery, means for detecting a discharge current of the secondary battery, and means for detecting a discharge voltage of the secondary battery However, the discharge voltage of the secondary battery detected is lower than the determination voltage set based on the relationship between the state of charge of the secondary battery, the discharge current of the secondary battery, and the discharge voltage of the secondary battery. In some cases, the power supply system is characterized by increasing the control lower limit value of the state of charge of the secondary battery. 4. An output from an independent power source is supplied to a load,
Charging the secondary battery in a power supply system including a secondary battery that stores the surplus output of the independent power source and supplies the insufficient power when the output of the independent power source is insufficient for a load. A state detecting means, a means for discharging the secondary battery at a predetermined current for a predetermined time every predetermined period, and a means for detecting a discharge voltage of the secondary battery, and a charging state of the secondary battery To raise the control lower limit value of the state of charge of the secondary battery when the discharge voltage of the secondary battery detected is lower than the determination voltage set based on the relationship with the discharge voltage of the secondary battery. Characteristic power supply system. 5. The power supply system according to claim 3, further comprising means for notifying the replacement time of the secondary battery when the lower limit control value of the state of charge rises to a predetermined value. . 6. The method for determining deterioration of a secondary battery used in a power supply system according to claim 1, wherein a fuel cell is used as the independent power supply. 7. The power supply system according to claim 3, wherein a fuel cell is used as the independent power supply.