JP4613781B2 - Charge / discharge control method and power supply system for alkaline storage battery - Google Patents

Description

  The present invention relates to a charge / discharge control method for an alkaline storage battery and a power supply system using the same, and more particularly to a technique for minimizing the influence of a memory effect.

  Demand for alkaline storage batteries such as nickel metal hydride storage batteries is expanding mainly in hybrid vehicles (hereinafter referred to as HEV) and industrial applications (such as emergency power supplies). Especially in HEV, the alkaline storage battery, which is the main power source, performs both motor drive (discharge) and storage (charge) of regenerative power from the generator, so the charge depth (hereinafter SOC, 100% when fully charged, fully discharged) It is monitored and controlled by quantifying the time as 0%.

  In alkaline storage batteries using nickel hydroxide as the positive electrode active material, repeated cycles without full charge (SOC is almost 0%) or full charge (SOC is almost 100%) will reduce the electromotive force relative to the remaining capacity of the storage battery. As a result, a phenomenon in which the storage battery capacity decreases (hereinafter referred to as the memory effect) occurs. In order to avoid this, it is desirable to perform charge / discharge in a wide SOC region in an alkaline storage battery.

However, in a power supply system that is continuously charged and discharged with a large current instantaneously, such as for HEV, when a plurality of alkaline storage batteries each having a capacity difference are connected, the storage battery with the smallest capacity is overcharged. In order to avoid overdischarge, an upper limit charge depth (hereinafter referred to as SOC _T ) that prohibits charging to reach an SOC higher than this, and a lower limit charge depth (hereinafter referred to as SOC _B ) that prohibits discharge to reach an SOC lower than this. ), And a method of controlling charging / discharging between SOC _T and SOC _B is employed. Specifically, SOC _T is often set near 80%, and SOC _B is often set near 20%. Thus, a proposal has been made to avoid the memory effect that occurs when the SOC is used only in the vicinity of 50% while avoiding overcharge and overdischarge (for example, Patent Document 1).
JP 2001-69608 A

  However, in a HEV power supply system that repeats charging and discharging in a short time, it is rare to go back and forth across a wide SOC range as in Patent Document 1, and charging and discharging are often repeated only when the SOC is around 50%. However, a memory effect occurs. In order to eliminate the memory effect, it may be possible to utilize the refresh cycle (cycle that intentionally performs full charge and complete discharge) used in consumer use. However, since this cycle takes time, as a power supply system This is not preferable because it reduces the operating time. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is capable of avoiding overcharging and overdischarging while avoiding a memory effect without performing a refresh cycle that requires a long time, and a charge / discharge control method and power supply for an alkaline storage battery The purpose is to provide a system.

In order to solve the above-described problem, the method for controlling charge / discharge of an alkaline storage battery according to the present invention uses an alkaline storage battery between the end-of-discharge charge depth SOC _D and the end-of-charge charge depth SOC _C, and this SOC _D and SOC _{In the case where C} is sequentially changed between the lower limit charging depth SOC _B and the upper limit charging depth SOC _T , in the first cycle, the SOC _C is set to the same value as the SOC _T, and discharge is restricted. cycle, without changing the difference between the SOC _C and SOC _D, sets the SOC _C to a value smaller than the SOC _C of first cycle, in the subsequent cycle, by repeating the setting change, the The SOC _C is reduced and the SOC _D becomes the same value as the SOC _B.
In Tsu it was after the timing cycle, until the same value as the SOC _T, by sequentially varied in multiple cycles of increasing the SOC _C, is evenly charged and discharged between the SOC _B and SOC _T It is characterized by being repeated .

Further, based on the charge / discharge control method described above, the controlled power supply system includes a main power source made of an alkaline storage battery, a voltage sensor for detecting the voltage of the main power source, a lower limit charging depth SOC _B and an upper limit charging depth of the main power source. The main power supply is controlled between discharge end charge depth SOC _D and charge end charge depth SOC _C on the basis of information from the voltage sensor and a storage unit that stores SOC _T , and SOC _D and SOC _C are set to SOC _B and that having a control unit for sequentially vary between SOC _T.

The end-of-discharge charge depth SOC _D and the end-of-charge charge depth SOC _C are sequentially changed, and charge and discharge are repeated uniformly between the lower limit charge depth SOC _B and the upper limit charge depth SOC _T through a plurality of cycles. By controlling in this way, it is possible to avoid the memory effect while maintaining the original compliance item of avoiding overcharge and overdischarge.

  As described above, according to the present invention, an effective charge / discharge control method is provided for a power supply system that uses an alkaline storage battery as a main power supply and should also consider the memory effect while avoiding overcharge / overdischarge, such as HEV applications. be able to.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

The invention according to claim 1 uses an alkaline storage battery between the end-of-discharge charge depth SOC _D and the end-of-charge charge depth SOC _C, and uses the SOC _D and SOC _C as the lower limit charge depth SOC _B and the upper limit. in the charge and discharge control method of an alkaline storage battery Ru are sequentially varied between the charging depth SOC _T, 1 cycle is regulated discharge by setting the SOC _C to the same value as the SOC _T, 2 cycle is without changing the difference between the SOC _C and SOC _D, it sets the SOC _C to a value smaller than the SOC _C of first cycle, in the subsequent cycle, by repeating the setting change, reduce the SOC _C and, wherein at SOC _D is after when it becomes the same value as the SOC _B cycle, sequentially varies is in the up to the same value as the SOC _T, multiple cycles of increasing the SOC _C The Rukoto relates method of controlling charge and discharge of the alkaline storage battery, characterized in Rukoto evenly charging and discharging are repeated between the SOC _B and SOC _T.

FIG. 1 is a schematic diagram showing an example of the charge / discharge control method of the present invention. Here, the lower limit charging depth SOC _B is 20%, and the upper limit charging depth SOC _T is 80%. As described above, in applications such as HEV in which charging and discharging are repeated vigorously in a short time, it is rare that a wide range of charging / discharging from the lower limit charging depth SOC _B to the upper limit charging depth SOC _T is performed. As schematically shown, charging / discharging with a small amplitude is repeated in the vicinity of SOC 50%. Therefore, for example, in FIG. 1, in the first cycle, the end-of-charge charge depth SOC _{C is set} to 80% (same as SOC _T ) to control the discharge, and the second cycle SOC _C is set to be higher than the first cycle SOC _C. Set to a smaller value. By repeating this, the SOC _C is decreased for each cycle, and at the time when the end-of-discharge charge depth SOC _D that becomes smaller in conjunction with the SOC _C becomes equal to the lower limit charge depth SOC _B , this time, the same value as SOC _T The SOC _C is increased for each cycle until. In this way, the power supply system can be operated efficiently without causing the memory effect that is a problem of alkaline storage batteries by repeatedly charging and discharging between SOC _B and SOC _T through multiple cycles. Can do.

Note that although the SOC _D per cycle may be irregular, as shown in the schematic diagram of FIG. 2 (not stepwise up and down). This is because the regulation of SOC _C remains only at the level of reduction in regeneration efficiency, but if regulation of SOC _D gradual phenomenon is strictly performed, for example, instantaneous large current discharge in a relatively low SOC region cannot be performed, This is because the function as the main power source is lowered.

In the case where the SOC _D could not regulate be less than SOC _B, because it causes a problem due to over-discharge (such as a voltage drop due to a short circuit occurs) is not preferable. Further, if it is not possible to regulate SOC _C to exceed SOC _T , it is not preferable because it causes problems due to overcharging (shortening of life due to electrolyte depletion accompanying gas generation, etc.).

The SOC can be quantified as a percentage by the following method. That is, grasp the voltage-current characteristics (I-V value, calculated from the voltage drop during high current discharge) at any charging depth in advance, create a calibration curve, measure the IV value as appropriate, and monitor the SOC It is a method to do. In addition to this, by performing correction with a value obtained by integrating the charge / discharge current amount (a theoretical SOC can be calculated), the numerical value of the SOC can be further increased in accuracy.

The invention described in claim 2 is characterized in that, based on the content described in claim 1, SOC _B is 15 to 30% and SOC _T is 70 to 85%. To avoid over-discharge described above, not preferable to the SOC _B to less than 15%, in order to avoid over-discharge, it is not preferable to the SOC _T below 85%. However, if SOC _B is excessively increased, a memory effect on the discharge side occurs, and if SOC _T is excessively decreased, a memory effect on the charge side occurs. By making it within the range of claim 2, the effect of the present invention is more clearly exhibited.

The invention described in claim 3 is characterized in that, based on the content described in claim 1, the difference between SOC _C and SOC _D is in the range of 10 to 40%. As described above, in a power supply system that frequently repeats charging / discharging, in order to avoid the memory effect, a large difference between SOC _C and SOC _D is set to restrict charging / discharging redundantly. Contrary. On the other hand, it is difficult to suppress the memory effect unless the difference between SOC _C and SOC _D is restricted to a certain interval or more. By making it within the range of claim 3, the effect of the present invention is more clearly exhibited.

FIG. 3 is a schematic diagram showing an example of a power system controlled based on the charge / discharge control method of the present invention. A voltage sensor 2 for detecting voltage is connected to a main power source 1 composed of a plurality of alkaline storage batteries. On the other hand, the storage unit 3 stores a lower limit charging depth SOC _B and an upper limit charging depth SOC _T of the main power supply 1, and is connected to the control unit 4. The voltage of the main power supply 1 measured by the voltage sensor 2 is sequentially sent to the control unit 4, and the control unit 4 is charged and discharged in each cycle between SOC _B and SOC _T , and discharge-end charging The depth SOC _D and the end-of-charge charge depth SOC _C are always controlled so as to sequentially vary between SOC _B and SOC _T as shown in FIG. The main power supply 1 is charged by a generator (not shown), but for HEV applications, it is common to use an inverter that can convert the kinetic energy of the internal combustion engine and the frictional energy at the time of stopping into a charging current as a generator. Is. It is also efficient to use this inverter when converting electrical energy into kinetic energy during discharge.

A nickel hydride storage battery or a nickel cadmium storage battery can be selected as the alkaline storage battery constituting the main power source 1. Both positive electrodes have nickel hydroxide as the active material, and cobalt, cobalt compounds, light rare earth compounds, zinc oxide, etc. are added as additives, and then filled into the three-dimensional metal porous body or the two-dimensional metal porous body. Constructed by sintering. The negative electrode is a hydrogen storage alloy in the case of a nickel metal hydride storage battery, and in the case of a nickel cadmium storage battery, cadmium is used as an active material, and a carbon material and various binders are added as additives and then filled into a three-dimensional metal porous body. Alternatively, it is configured by being applied to a two-dimensional metal porous body. An electrode group is formed by winding or laminating the positive electrode and the negative electrode through a separator typified by a polyolefin nonwoven fabric, and the electrode group is made of an alkaline aqueous solution after being inserted into a cylindrical or rectangular battery case. By injecting the electrolytic solution, an alkaline storage battery is configured.

  Examples of the present invention will be described in detail below. Needless to say, the present invention is not limited to this embodiment.

Example 1
A long positive electrode using nickel hydroxide as an active material and a long negative electrode using a hydrogen storage alloy as an active material are wound through a separator made of sulfonated polypropylene nonwoven fabric to form an electrode group did. This electrode group was inserted into a cylindrical battery case having an inner diameter of 30 mm and a length of 60 mm, and an electrolyte mainly composed of potassium hydroxide was injected and sealed to obtain a nickel hydride storage battery having a nominal capacity of 6 Ah. This nickel metal hydride storage battery was connected in series in 12 cells to serve as the main power source.

For this main power supply, a voltage sensor / storage unit and a control unit are arranged as shown in FIG. 3, and in the pattern shown in FIG. 1, SOC _B is 20%, SOC _T is 80%, and the difference between SOC _C and SOC _D Was set to 30%. The fluctuation of SOC _C (SOC _D ) for each cycle is 5%, and when the SOC _C reaches SOC _T (80%) or the SOC _D reaches SOC _B (20%), the fluctuation is reversed up and down. Was set as follows. In addition, the SOC value is a percentage by a method of measuring and monitoring the IV value at the time of charging / discharging based on a calibration curve (see (Table 1)) created from the IV value at any charging depth in the initial state. And reflected in the control. This power supply system is referred to as Example 1.

(Examples 2 to 6)
Examples 2 to 6 are power supply systems configured in the same manner as in Example 1 except that SOC _B is set to 10, 15, 25, 30 and 35%.

(Examples 7 to 11)
Except that the SOC _T was set to 65, 70, 75, 85, and 90%, a power supply system configured in the same manner as in Example 1 is referred to as Examples 5 to 7.

(Examples 12 to 15)
Except for the difference between SOC _C and SOC _D being 5, 10, 40, and 45%, power supply systems configured in the same manner as in Example 1 are referred to as Examples 12-15.

(Example 16)
In the pattern shown in FIG. 2, SOC _D is relaxed so that it may be appropriately changed within the range of “the difference between SOC _C and SOC _D is within 10 to 40%” and “not less than SOC _B ”. A power system configured in the same manner as in the first embodiment except for the above is referred to as a sixteenth embodiment.

(Comparative example)
In the pattern shown in the schematic diagram of FIG. 4, a power supply system configured in the same manner as in Example 1 except that the difference between SOC _C and SOC _D is 30% centering on SOC 50% is used as a comparative example.

  Using each of the above power supply systems, 1000 cycles of charge / discharge were performed with a charge / discharge current of 12A. Thereafter, the following evaluation was performed. The results are shown in (Table 2).

(Memory effect)
In order to determine the presence or absence of the memory effect, the difference between the charge end voltage when each main power supply is charged to SOC = 80% at the end of 1000 cycles and the voltage to be determined as SOC = 80% shown in (Table 1) is The memory effect on the charging side is “significant” when the voltage drops below 450 mV, 50
A battery effect of ˜450 mV is “present” on the charging side, and a memory effect of less than 50 mV is “none”. Further, regarding the memory effect on the discharge side, after the various power sources were discharged to SOC = 20% at the end of 1000 cycles, the same evaluation judgment as that on the charge side was performed and described in (Table 2).

(Electrolyte depletion)
When the litmus paper was applied to the sealing part of the storage battery and the color changed to blue, it was judged that there was leakage due to gas generation. Those that immediately changed color were marked as “significant”, those that changed within 1 minute as “yes”, and those that did not show any change as “none”.

(Voltage drop)
The voltage of the main power supply after discharge is A, and the voltage of the main power supply after being left for 3 days is B. When AB exceeds 720 mV, it is “significant”, when 300 to 720 mV is “present”, less than 300 mV The thing was described as (none) in (Table 2).

従来の充放電制御方法に準じた比較例において顕著なメモリー効果が発生したのに対し、本発明の各実施例ではメモリー効果が抑制されていた。ただしＳＯＣ_Bがやや大きい実施例６や、ＳＯＣ_Tがやや小さい実施例７では、比較例ほどではないものの深い充放電ができなかったことに起因するメモリー効果が見られた。またＳＯＣ_Bがやや小さい実施例２では比較的顕著な電圧降下が見られる一方、ＳＯＣ_Tがやや大きい実施例１１では比較的顕著な電解液の枯渇（漏液）が見られた。よってＳＯＣ_Bの好適範囲は１５〜３０％、
ＳＯＣ_Tの好適範囲は７０〜８５％であることがわかる。

In the comparative example according to the conventional charge / discharge control method, a remarkable memory effect occurred, whereas in each example of the present invention, the memory effect was suppressed. However, in Example 6 having a slightly higher SOC _B and Example 7 having a slightly lower SOC _T , a memory effect due to the fact that deep charge / discharge could not be achieved although not as much as the comparative example. Also while the SOC _B slightly smaller in Example 2, a relatively significant voltage drop is observed, SOC _T louder Example 11 relatively pronounced depletion of electrolyte in (leakage) was observed. Therefore, the preferred range of SOC _B is 15-30%,
It can be seen that the preferred range of SOC _T is 70-85%.

On the other hand, Example 12 difference between the SOC _C and SOC _D is 5%, in order to spent large number of cycles to reach the SOC _B to SOC _T, resulting in some relatively mild, the memory effect It came to generate. Therefore, the difference between SOC _C and SOC _D is preferably 10% or more. Although not shown as an evaluation result in (Table 2), Example 15 in which the difference between SOC _C and SOC _D was set to 45% is that regenerative current is accepted (charged) for a long time during discharging. On the other hand, during charging, the instantaneous supply (discharge) of electrical energy must be rejected over a long period of time, which is contrary to the gist of the charge / discharge system of the present invention in which charge / discharge is frequently repeated. . Therefore, it can be seen that the preferable range of the difference between SOC _C and SOC _D is 10 to 40%.

Further, from the results of Example 16, even when SOC _D is appropriately changed within the range where “the difference between SOC _C and SOC _D is within a range of 10 to 40%” and “not less than SOC _B ”, It was found that the effect was sufficiently obtained.

  According to the present invention, a power supply system that does not have a memory effect and that can avoid overcharge and overdischarge can be realized. Therefore, it can be used for tough use (HEV, household cogeneration, industrial), which is an advantage of alkaline storage batteries. Is high and the effect is considered high.

The schematic diagram which shows an example of the charging / discharging control method of this invention The schematic diagram which shows another example of the charging / discharging control method of this invention The schematic diagram which shows an example of the power supply system of this invention Schematic diagram showing aspects of a conventional charge / discharge control method

Explanation of symbols

1 Main power source 2 Voltage sensor 3 Storage unit 4 Control unit

Claims (3)

An alkaline storage battery is used between the end-of-discharge charge depth SOC _D and the end-of-charge charge depth SOC _C, and the SOC _D and SOC _C are between the lower limit charge depth SOC _B and the upper limit charge depth SOC _T. in in method of controlling charge and discharge of the alkaline storage battery Ru is sequentially varied,
In the first cycle, the SOC _C is set to the same value as the SOC _T, and the discharge is restricted. In the second cycle , the difference between the SOC _C and the SOC _D is not changed, and the SOC _C is changed to the first cycle. It is set to a value smaller than SOC _C , and in the subsequent cycles, this setting change is repeated to reduce the SOC _C , and in cycles after the time point when the SOC _D becomes the same value as the SOC _B , until the same value as the SOC _T, by sequentially varied in multiple cycles of increasing the SOC _C, characterized by evenly charging and discharging are repeated between the SOC _B and SOC _T, alkali Storage battery charge / discharge control method. The charge / discharge control method for an alkaline storage battery according to claim 1, wherein the SOC _B is 15 to 30% and the SOC _T is 70 to 85%. The charge / discharge control method for an alkaline storage battery according to claim 1, wherein a difference between the SOC _C and the SOC _D is in a range of 10 to 40%.

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