JP2017127169A - Power storage system for storing surplus power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a conventional power storage system for solar power generation in which a storage battery hardly reaches 100% in SOC after the end of charge or DOD after the end of discharge and thus, an electrode active material not participating in an electrode reaction tends to arise because of its unfixed amount of power generation in solar power generation that the electrode active material not participating in the electrode reaction over a long time loses its activity, which leads to the worsening of the capacity of the storage battery.SOLUTION: A power storage system according to the present invention comprises n groups of assembled batteries, provided that the n groups are connected in parallel. In charge/discharge, a particular group of assembled batteries sequentially selected from the n groups of assembled batteries is charged/discharged preferentially to the other groups of assembled batteries to reach 100% in SOC or DOD. So, all the groups of assembled batteries are allowed to reach 100% in SOC or DOD once every n cycles. Therefore, an electrode active material not participating in an electrode reaction over a long time hardly arises in every storage battery.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage system for storing surplus power, and more particularly to a power storage system for storing surplus power for solar power generation.

  Solar power generation (solar power generation) is regarded as the ultimate clean energy for humanity. Solar power generation also has the great advantage of being able to generate the necessary power off-grid (without using transmission lines) where it is needed. If the power used in each household is covered by a solar power off-grid system, the effect is tremendous in protecting a clean global environment.

  Since power generation by solar power generation is limited to the sunshine hours, it is indispensable to store surplus power in order to completely supply power used in each home by solar power generation. If the surplus power of solar power generation is stored in a power storage system (power storage device) with a large capacity (about 10 to 40 kWh), power other than the sunshine hours required in each home can be covered by this.

  A power storage system of about 20 to 50 kWh that uses a storage battery has already been used as a power source for driving an electric vehicle. For example, an energy storage system installed in an electric vehicle in the United States uses 6831 general-purpose 18650 type lithium-ion batteries, 99 are connected in parallel, and 69 are connected in series as an assembled battery. It is configured. In this specification, an assembled storage battery configured by connecting single cells (single cells) in series or in parallel is referred to as an assembled battery.

  An energy storage system for solar power generation can cope with a wide range of surplus power with an assembled battery in which the number of single cells connected in series (voltage) and the number of parallel connections (current capacity) are adjusted. However, the power storage system for storing surplus power is normally not fully charged or discharged. In this respect, the power storage system for storing surplus power is fundamentally different from conventional battery use.

  Until now, the basic use of storage batteries is to charge to the full capacity and discharge all the charged electricity. For example, to ensure the longest mileage, the longest working time and the longest call time for electric cars, forklifts and mobile phones, the batteries installed in each are fully charged, and all of the charged electricity Basically used.

  However, in the power storage system that stores the surplus power of solar power generation, more than surplus power is not charged, and more than necessary power is not discharged, so it is charged to the fullest on a daily basis. There is nothing. Therefore, in the power storage system for storing surplus power, an electrode active material that does not participate in the charge / discharge reaction is likely to be generated in the storage battery constituting the power storage system. The activity and reversibility of the electrode active material that does not participate in the charge / discharge reaction gradually decrease.

  The life of a storage battery depends on how the activity and reversibility of the electrode active material is sustained. Currently, there are four main types of storage batteries: lead storage battery, nickel cadmium battery, nickel metal hydride battery and lithium ion battery, all of which utilize the reversible electrochemical redox reaction of the electrode active material. In this power storage device, the activity and reversibility of the electrode active material gradually decrease and reach the lifetime.

  In general, the activity and reversibility of an electrode active material that does not participate in the charge reaction or discharge reaction is reduced. However, if the period that is not involved in the charge / discharge reaction is short, the activity or reversibility that has decreased due to the participation in the electrode reaction again. Sex is restored. The recovery may be recovered through a charge reaction or may be recovered through a discharge reaction, and varies depending on the type of active material.

  For example, in a nickel metal hydride battery or a nickel cadmium battery, β-NiOOH, which is a positive electrode active material in a charged state, changes to inactive γ-NiOOH and is greatly deteriorated in performance when left for a long period of time. In other words, nickel-metal hydride batteries and nickel-cadmium batteries are so-called “memory effects”, in that if they are repeatedly charged and discharged without being fully discharged, the unused charge that should have been discharged cannot be discharged. The performance is greatly deteriorated due to the phenomenon. Therefore, in order to maintain the performance of the nickel metal hydride battery or the nickel cadmium battery, it is necessary to be frequently discharged to a 100% discharge state.

  In addition, if lead-acid batteries are repeatedly charged and discharged without being fully charged, unutilized lead sulfate, which should have been able to be recharged, will not be able to be recharged due to crystal expansion, resulting in a so-called “sulfation” phenomenon. Deteriorates. Therefore, in order to maintain the performance of the lead storage battery, charging close to 100% needs to be frequently performed.

  Even if it is not as remarkable as the memory effect of the nickel electrode or the sulfation of the lead electrode, the activity is reduced if any electrode active material does not participate in the electrode reaction (redox reaction). Therefore, in order to maintain the performance of any storage battery, it is important to reach a state of charge (SOC) or a state of discharge (DOD) close to 100% frequently. In addition, the electrode reaction rate (charge / discharge current) is also related to maintaining the activity of the electrode active material. Incidentally, it has been reported that in a lithium secondary battery, the cycle life becomes shorter as the charging current becomes larger, and the cycle life becomes shorter as the discharge current becomes smaller (see IEICE Technical Report Vol. 90, CPM 90-101 (1991)). ). Therefore, the most standard charge / discharge cycle method is that a storage battery is generally charged slowly at a rate of 6 to 10 hours and discharged at a rate of 3 to 5 hours.

  The state of charge of the storage battery is generally indicated by SOC (Stage Of Charge). Normally, the state where the storage system or the storage battery is charged to 100% of the rated capacity is SOC = 100%. Further, the discharge state of the storage battery is generally indicated by DOD (Depth Of Discharge), and normally, the state in which the storage system or storage battery is discharged to 0% SOC is DOD = 100%. Here, the rated capacity means the maximum charging capacity (capacity that can be discharged) that the power storage system or the storage battery can be charged by a standard charging method.

  The power storage cost of the power storage system varies depending on the initial cost and life of the storage battery constituting the power storage system. A storage battery with a high initial cost requires a longer life, but in any case, if the life of the storage battery is short, the power storage cost will be high. Therefore, whether an off-grid system for solar power generation can be realized depends on the life of the storage battery in this application.

  On the other hand, in the off-grid system of solar power generation, the power required outside the sunshine hours is covered by the surplus power stored in the power storage system, so if the amount of surplus power stored is insufficient, it is required outside the sunshine hours I can't cover my power. Therefore, the off-grid system of solar power generation requires a design in which the amount of stored surplus power exceeds the power required outside the sunshine hours.

  In a power storage system having a power storage amount that exceeds the power required outside the daylight hours, it is not completely discharged on a daily basis. That is, charging and discharging are repeated leaving a margin in the DOD. Therefore, since the electrode active material which does not participate in the discharge reaction at all is produced in the storage battery constituting the power storage system and is cheap, the life of the storage battery is shortened.

  In addition, in a power storage system that stores surplus power, if the rated capacity is insufficient with respect to surplus power, a part of surplus power cannot be stored and the storage efficiency of surplus power is reduced. A decrease in storage efficiency increases the power storage cost. Therefore, in the off-grid system of solar power generation, the power storage system needs to be designed with a rated capacity that can afford surplus power.

  A power storage system with sufficient rated capacity is not fully charged on a daily basis. That is, charging and discharging are repeated leaving a margin in the SOC. For this reason, an electrode active material that does not participate in the charging reaction at all is produced in the storage battery constituting the storage system, and the life of the storage battery is shortened.

  The present invention has been made in view of the above problems, and the purpose of the power storage system is that the storage battery constituting the power storage system is frequently used even when charging and discharging are repeated leaving a margin in the SOC and DOD. The goal is to make it possible to reach 100% SOC and DOD.

  In order to solve the above-mentioned problem, an electricity storage system according to the present invention is an electricity storage system configured by connecting a plurality of assembled batteries in parallel in units of assembled batteries, and is a specific one selected in order from the assembled batteries. The assembled battery is charged or discharged with priority over other assembled batteries.

  In the power storage system according to the present invention, a specific assembled battery is sequentially selected from a plurality of n assembled batteries and charged or discharged in preference to other assembled batteries. Even if charging is terminated (without reaching 100%), a specific assembled battery charged with priority can reach 100% SOC.

  Further, even if the discharge is terminated with a margin (without reaching 100%) as the DOD of the power storage system, the specific assembled battery that has been preferentially discharged can reach 100% DOD.

  As a result, in the power storage system according to the present invention, all n sets of assembled batteries are sequentially selected as specific battery packs. Therefore, as a power storage system, even if charging and discharging are repeated leaving a margin in SOC and DOD, The assembled battery can reach 100% SOC and DOD at a frequency of once every n cycles. Therefore, the electrode active material that the power storage system according to the present invention does not participate in the charge / discharge reaction for a long time in all assembled batteries is drastically reduced, and the life of the storage battery is not shortened even when used as a power storage system for solar power generation.

  Problems other than those described above and solutions and effects thereof will be described in more detail with reference to the following embodiments.

  It is a single line connection figure which shows the structure of the electrical storage system which concerns on this invention.   It is a single line connection figure which shows the structure of the electrical storage system which concerns on this invention.   It is a schematic diagram which shows the time of completion | finish of discharge of the electrical storage system which concerns on this invention.   It is a single line connection figure which shows the structure of the electrical storage system which concerns on this invention.   It is a schematic diagram which shows the time of completion | finish of charge of the electrical storage system which concerns on this invention.   It is a schematic diagram which shows the time of completion | finish of charge of the electrical storage system which concerns on this invention.   It is a graph which shows the relationship of the margin of SOC of the electrical storage system which concerns on this invention, and the number n of assembled batteries.   It is a single line connection figure which shows the structure of the electrical storage system which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  1, FIG. 2 and FIG. 4 are single line connection diagrams showing the configuration of a power storage system according to the present invention. As shown in FIGS. 1, 2, and 4, the power storage system (20) according to the present invention includes n assembled batteries connected in parallel for each assembled battery. That is, the input / output terminals of each assembled battery are connected in parallel.

  The battery system (20) shown in FIGS. 1, 2 and 4 includes a battery pack connection terminal (8-1) in which battery packs (1-1) to (1-n) are provided in the control device (15). ) To (8-n). The control device (15) is provided with a charging input terminal (7) for inputting surplus power of solar power generation and the like, and an output terminal (9) for outputting stored power to an external circuit. The assembled batteries (1-1) to (1-n) are connected in parallel to the charging input terminal (7) via the switch (4) and to the output terminal (9) via the switch (5). Yes.

  In the power storage system (20) shown in FIG. 2, the assembled battery constituting the battery has a function capable of being frequently discharged to 100% DOD. In the power storage system (20) shown in FIG. 1 has a function of being able to be charged to SOC of FIG. 1, and the power storage system (20) shown in FIG. 1 is configured by combining the power storage system (20) shown in FIG. 2 and the power storage system (20) shown in FIG. The assembled battery frequently has a function capable of being charged to 100% SOC and a function capable of being frequently discharged to 100% DOD.

  First, based on FIG. 2, an embodiment of the present invention will be described for a power storage system (20) in which a specific assembled battery is “preferentially discharged” over other assembled batteries.

  In the power storage system (20) shown in FIG. 2, power to be stored (hereinafter, also referred to as main power) such as surplus power of solar power generation is input to the charging input terminal (7b). 1) to (1-n) are charged when the switch (4b) is in the ON state, and the charging is stopped in the OFF state.

  When the charging is stopped, the assembled batteries (1-1) to (1-n) can basically be output from the output terminal (9) to the external circuit while the switch (5) is in the ON state. At this time, if only the switch (2-m) among the switches (2-1) to (2-n) is selectively turned on, the specific assembled battery (1-m) is replaced with another assembled battery. It is discharged preferentially.

  Therefore, in the power storage system (20) shown in FIG. 2, even if the discharge ends before the DOD of the power storage system reaches 100%, only the specific assembled battery (1-m) is discharged preferentially, so Can reach 100%. Here, m is an arbitrary integer from 1 to n. If m is sequentially changed from 1 to n every charge / discharge cycle, the assembled batteries (1-1) to (1-n) are either Also, a specific assembled battery is selected in order, and the DOD can reach 100% once every n cycles.

  For example, FIG. 3 shows an example in which the discharge ends when the DOD of the power storage system (20) reaches 70%. FIG. 3 is a schematic diagram in which four battery packs (1-1) to (1-4) are connected in parallel to each other, with the storage system (20) configured with n = 4 in the configuration of FIG. For the assembled battery, the bar graph (32) indicates the SOC of each assembled battery, and the dotted line (31) indicates the SOC of the power storage system (20). However, there is a relationship of DOD = (100% −SOC).

  FIG. 3 shows a case where in the configuration of FIG. 2, the switch (2-1) is selectively turned ON and the assembled battery (1-1) is selected as a specific assembled battery. In FIG. 3, a specific assembled battery (1-1) is discharged in preference to other assembled batteries and reaches 100% DOD (SOC = 0%), and then switches (2-2) to ( 2-4) are turned ON together, and the assembled batteries (1-2) to (1-4) are continuously discharged, and the DOD of the power storage system (20) reaches 70% (SOC = 30%). The case where the discharge is terminated at the time is shown.

  As shown in FIG. 3, even if the DOD of the power storage system (20) is 70% and the discharge is completed, the DOD of the specific assembled battery (1-1) reaches 100%. The DOD of 2) to (1-4) remains at 60% (SOC = 40%). On the other hand, since each of the assembled batteries (1-1) to (1-4) is sequentially selected as a specific assembled battery, it is the same as the assembled battery (1-1) shown in FIG. 100% DOD can be reached.

  The surplus power of solar power generation can be charged to the power storage system to cover the power required outside sunshine hours. In this case, surplus power from solar power generation is considered to occur in about 8 hours from about 8 am to about 4 pm, so the power storage system will be charged in about 6 to 8 hours. It is close to the standard charge rate (6 to 10 hour rate) of storage batteries. However, during the discharge, the surplus power charged in the power storage system may be used at the standard discharge rate (3-5 hours rate) of the storage battery, but it continues for 16-18 hours outside the sunshine hours. Sometimes used. The discharge for 16 to 18 hours is considerably lighter than the standard discharge rate (3 to 5 hours) of the storage battery.

  However, when the surplus power of the solar power generation is charged into the power storage system (20) shown in FIG. 2, the specific battery pack (1-m) is selectively turned on when discharging the switch (2-m). Is discharged preferentially, the specific assembled battery (1-m) is discharged first in 16 / n-18 / n hours even when the surplus power charged is used for 16-18 hours. DOD will reach 100%. Here, if the number n of assembled batteries is set to 3 ≦ n ≦ 6, the discharge of the specific assembled battery (1-m) substantially matches the standard discharge rate (3 to 5 hour rate) of the storage battery. .

  That is, when the power storage system (20) shown in FIG. 2 is used as a power storage system for solar power generation, if the number n of assembled batteries is configured as 3 ≦ n ≦ 6, the storage battery is once every 3 to 6 cycles. It will always be discharged at a standard discharge rate, and most of the electrode active material will be involved in the charge / discharge reaction at a standard rate, and its activity will be maintained leading to a long life of the storage battery. .

  The embodiment in which the specific assembled battery (1-m) is “preferentially discharged” over the other assembled batteries has been described based on FIG. 2, but the specific assembled battery will be hereinafter described based on FIG. 4. An embodiment in which (1-m) is preferentially charged to other assembled batteries will be described.

  In the power storage system (20) shown in FIG. 4, the battery packs (1-1) to (1-n) are each charged with two charges by providing the charge input terminal (7a) in addition to the charge input terminal (7b). An input path is secured.

  In other words, the batteries (1-1) to (1-n) are connected to the charging input terminal (7a) via the switches (3-1) to (3-n) and the switch (4a), respectively. An input path (hereinafter also referred to as “priority charge input path”) and a charge input path connected to the charge input terminal (7b) via the switch (4b) are secured.

  In the power storage system (20) shown in FIG. 4, the stored power (main power) is input to the charging input terminals (7a) and (7b). The input current I from the main power has a relationship of I = Ia + Ib, where Ia is input from the charge input terminal (7a), Ib is input from the charge input terminal (7b).

  Therefore, if the switch (4a) and the switch (3-m) are turned on, the charging input Ia from the input terminal (7a) is input only to the specific assembled battery (1-m), and the specific assembled battery ( 1-m) charging is started. However, m is an arbitrary integer from 1 to n, and if m is changed in order from 1 to n, each of the assembled batteries (1-1) to (1-n) becomes a specific assembled battery in order. Selected. At the same time, if the switch (4b) is turned on, the charging input Ib from the input terminal (7b) is input and charging of the other assembled batteries is started.

  The charging current Ia at the start of charging satisfies the relationship of Ia >> I / n, and the SOC of the specific assembled battery (1-m) reaches 100% in the scheduled charging time (for example, the time during which surplus power continues to be generated). The current value to be obtained is set. Under this condition, the specific assembled battery assembled battery (1-m) is charged with a charging current larger than that of the other assembled batteries, so that the charging voltage is higher than that of the other assembled batteries. 1-m) is not input.

  In the power storage system for solar power generation, the estimated charging time is expected to be about 6 to 8 hours. Specifically, the current value Ia at which the SOC of the specific assembled battery (1-m) can reach 100% is specifically described. It is set to about 0.2 CA. However, the rated capacity of the assembled battery (1-m) is 1 CAh. The discharge current value at which the assembled battery (1-m) discharges in 5 hours from 100% to 0% in the constant current discharge is 0.2 CA. Incidentally, in a commercially available lead storage battery, nickel metal hydride battery, or lithium ion battery, a current setting of about 0.2 CA is standard for constant current and constant voltage charging of about 6 to 8 hours.

  In the case where the charging current I input to the power storage system (20) shown in FIG. 4 is equally input to n sets of assembled batteries, I / n is input to each assembled battery. If the relationship of I / n is satisfied, the specific assembled battery (1-m) charged with the charging input Ia is charged with a charging current larger than that of the other assembled batteries, so that it is charged with priority over other assembled batteries. The Therefore, when the scheduled charging time elapses and charging ends, the specific assembled battery (1-m) charged with priority is 100 even if the SOC of the other assembled batteries has not reached 100%. % SOC is reached. If the SOC of the other assembled battery does not reach 100%, the SOC of the power storage system (20) does not reach 100%.

  FIG. 5 shows examples of cases where the SOC of the power storage system (20) reaches 85% and 35% and the discharge is terminated. FIG. 5 shows a schematic diagram in which four battery packs (1-1) to (1-4) are connected in parallel to each other, with the storage system (20) configured with n = 4 in the configuration of FIG. For the assembled battery, the bar graph (32) indicates the SOC of each assembled battery, and the dotted line (31) indicates the SOC of the power storage system (20).

  FIG. 5A shows a case where charging ends when the power storage system (20) reaches 85% SOC (31). FIG. 5A shows a case where the assembled battery (1-3) happens to be selected as a specific assembled battery, but the power storage system (20) is configured based on FIG. When it is finished, the specific assembled battery (1-3) has reached 100% SOC.

  In FIG. 5A, the rated capacity of the power storage system (20) is four times the rated capacity of the assembled battery, and when the power storage system (20) reaches 85% SOC (31), 25% of the SOC of the power storage system. The equivalent battery is charged to the specific assembled battery (1-3), the remaining 60% is charged to the other assembled battery, and the SOC of the other assembled battery remains at about 80%. That is, in the power storage system based on FIG. 4, even when charging / discharging is repeated when the SOC at the end of charging is about 85%, all the assembled batteries are selected as a specific assembled battery in order. As with the 5A battery pack (1-3), 100% SOC can be reached once every n cycles.

  Further, FIG. 5B shows a case where the charging ends when the power storage system (20) reaches only 35% SOC (31). Naturally, a storage system for solar power generation is conceivable depending on the weather. FIG. 5B shows a case where the assembled battery (1-2) happens to be selected as the specific assembled battery, but the power storage system (20) is similarly configured based on FIG. 4 and the specific assembled battery (1-2). Has reached 100% SOC after the scheduled charging time.

  In FIG. 5B as well, 25% of the 35% SOC of the power storage system (20) is charged to the specific assembled battery (1-2), and the remaining 10% is charged to the other assembled battery. Therefore, the SOC of other assembled batteries is limited to about 13.3% (4 × 10% ÷ 3). That is, in the power storage system based on FIG. 4, even when charging / discharging is repeated to the extent that the SOC reaches only about 35%, all the assembled batteries are shown in FIG. ) Can reach 100% SOC.

  As can be seen from the comparison between FIG. 5A and FIG. 5B, the power storage system (20) based on FIG. 4 has a large number n of assembled batteries because the SOC of the power storage system is determined by the average value of the SOCs of all the assembled batteries. The SOC of the specific assembled battery can reach 100% even when the SOC of the power storage system (20) is low. From this point of view, it is preferable that the number n of assembled batteries is larger in the power storage system based on FIG.

  On the other hand, the greater the number n of assembled batteries, the less frequently the specific assembled battery is selected. The activity (reversibility) of the electrode active material of the storage battery can be recovered through the electrode reaction, but it is difficult to recover unless it is involved in the electrode reaction for a long time. Therefore, it is preferable that the storage battery reaches 100% SOC more frequently. From this point of view, it is preferable that the power storage system based on FIG.

  Therefore, an appropriate number n of assembled batteries when the power storage system based on FIG. 4 is used as a power storage system for solar power generation will be described below.

  Since the storage battery must move to constant voltage charging at the end of charging, a constant charging current cannot be continuously input until the charging is completed. Therefore, if charging is performed for about 8 hours in a state where surplus power is excessive, the power storage system and the storage battery can reach 100% SOC. However, when all surplus power is input and charging is performed in about 8 hours, the power storage system and the storage battery cannot reach 100% SOC.

  Since the surplus power of solar power generation varies greatly depending on the weather, there is a great possibility that charging will end when the SOC is low in a solar power storage system. As shown in FIG. 5B, the storage battery (20) based on FIG. 4 is capable of frequently reaching 100% SOC even when charging is terminated with a low SOC. This is an extremely great advantage as a power storage system. Taking advantage of this advantage, when storing the surplus power of solar power generation in the power storage system (20) shown in FIG. 4, all surplus power can be input even when the surplus power is large, and the surplus power is small. Even when a specific assembled battery can reach 100% SOC.

力量の変化に対しては対応し易いことになる。Therefore, under the condition that the maximum SOC that can be reached under the condition that the power storage system (20) shown in FIG. 4 can input all of the surplus power is defined as SOCmax, and a specific assembled battery can reach 100% SOC. When the minimum SOC that the power storage system (20) can reach is SOCmin,

It will be easy to respond to changes in competence.

  When the power storage system reaches SOCmax, the SOC of the specific battery pack reaches 100%, and the charging voltage of another battery pack reaches the upper limit voltage. That is, after the other assembled battery reaches the upper limit charging voltage, the other assembled battery also shifts to constant voltage charging, so that the surplus power that can be input decreases, and the SOC of the power storage system has already exceeded SOCmax.

  In the storage system of solar power generation, the estimated charging time is expected to be about 6 to 8 hours. Therefore, the current value Ia at which the SOC of a specific assembled battery (1-m) can reach 100% regardless of the type of the storage battery What is necessary is just to set to about 0.2CA.

Therefore, if the SOC when the battery pack constituting the power storage system (20) shown in FIG. 4 reaches the upper limit voltage with constant current charging of 0.2 CA is S%, the SOCmax of the power storage system (20) is It can be approximated by the following equation (1). However, the rated capacity of the assembled battery constituting the power storage system (20) is 1 CAh.
SOCmax = (SOC of specific assembled battery + S × number of other assembled batteries) ÷ total number of assembled batteries n (1)
Note that the SOC (S%) at the time when the charging voltage reaches the upper limit voltage with constant current charging of 0.2 CA varies depending on the type of battery, the battery structure, the temperature environment, etc., but generally, S = 75 to 90%. It is in.

  On the other hand, the minimum SOC that can be reached by the power storage system (20) shown in FIG. 4 is charged under the condition that the SOC of the specific assembled battery (1-m) reaches 100% after the scheduled charging time has elapsed. This is a case where Ia at the start is Ia = I, that is, Ib = 0. That is, it is a case where all the stored and stored power (surplus power) is input to the specific assembled battery (1-m) at the start of charging.

  Even in this case, if the assembled battery (1-m) shifts to constant voltage charging, charging proceeds while the charging current Ia decreases, and the amount of decrease in the charging current Ia is input to another assembled battery. Therefore, even if charging is started with Ia = I and Ib = 0, the SOC of the specific assembled battery (1-m) cannot reach 100% without charging other assembled batteries.

  If Ia in the constant voltage charging period of the specific assembled battery (1-m) is averaged, it roughly decreases to about Ia = I / 3. Therefore, while the specific assembled battery (1-m) is charged with constant voltage charging, the other assembled batteries are roughly charged with Ib = (I−I / 3) = 2Ia. Therefore, under the condition that the SOC of the specific assembled battery (1-m) reaches 100% after the scheduled charging time has elapsed, the minimum SOC that can be reached by the power storage system (20) shown in FIG. (SOCmin) is obtained by the following calculation formula (2).

SOCmin = (SOC of specific battery pack + (100−S) × 2) ÷ number of battery packs n (2)
In the formula (2), S (%) is the SOC at the time when the battery pack constituting the power storage system reaches the upper limit voltage with constant current charging of 0.2 CA. However, the rated capacity of the assembled battery constituting the power storage system is 1 CAh.

えられる。

available.

Ｓは蓄電池の種類や電池構造や温度環境などによって異なるが、既存の蓄電池ではＳ＝７５〜９０％程度にある。従って、既存の蓄電池を使用して図４に示す蓄電システム（２０）

S varies depending on the type of storage battery, battery structure, temperature environment, and the like, but in existing storage batteries, S is about 75 to 90%. Therefore, the power storage system (20) shown in FIG.

が小さければ、幅広い余剰電力の変化には対応できない。FIG. 6 is a graph of the expression (3). It is preferable that the storage battery reaches 100% SOC more frequently, and in that sense, it is preferable that the number n of assembled batteries is smaller.

Is small, it cannot cope with a wide range of surplus power changes.

合、図４に示す蓄電システム（２０）はソーラー発電の余剰電力量の＋／−１０％の変化にしか対応できない。これに対してｎ＝３では＋／−２０％の、ｎ＝４では＋／−２５％のそれぞれ余剰電力量の変化に対して対応できることが分かる。As shown in FIG. 6, for example, a storage battery having S of 80%, that is, a storage battery in which the SOC when the charging voltage reaches the upper limit voltage by constant current charging of 0.2 CA reaches S% is used in FIG. 4. Show

In this case, the power storage system (20) shown in FIG. 4 can only cope with a change of +/− 10% in the surplus power amount of solar power generation. On the other hand, it can be seen that it is possible to cope with changes in surplus power amount of +/− 20% when n = 3 and +/− 25% when n = 4.

ないこともわかる。蓄電池がより頻繁に１００％のＳＯＣに達する方が好ましく、基本的には組電池数ｎが少ない方が好ましいわけであり、図４に示す蓄電システム（２０）がソーラー発電の蓄電システムとして適用される場合には組電池数ｎは３≦ｎ≦６が好ましいことになる。

I understand that there is no. It is preferable that the storage battery reaches 100% SOC more frequently. Basically, it is preferable that the number n of assembled batteries is small, and the storage system (20) shown in FIG. 4 is applied as a storage system for solar power generation. In this case, the number n of assembled batteries is preferably 3 ≦ n ≦ 6.

  As described above, the specific assembled battery (1-m) is “prioritizedly discharged” based on FIG. 2, and the specific assembled battery (1-m) is “prioritized” based on FIG. 1 is described, the power storage system (20) shown in FIG. 1 is configured by combining the power storage system (20) shown in FIG. 2 and the power storage system (20) shown in FIG. The embodiment in is the same as the power storage system (20) shown in FIG. 4, and the embodiment in the discharge is the same as the power storage system (20) shown in FIG. Therefore, when the power storage system (20) shown in FIG. 1 is applied as a solar power storage system, the number n of assembled batteries is preferably 3 ≦ n ≦ 6.

  The power storage system (20) shown in FIG. 1 has the same function as the power storage system (20) shown in FIG. 2 as long as the switches (3-1) to (3-n) are all kept in the OFF state. If the switches (2-1) to (2-n) are always maintained in the ON state, they have the same function as the power storage system (20) shown in FIG.

  Further, in the power storage system (20) shown in FIG. 1, normally, when the scheduled charging time elapses, the switches (4a) and (4b) are turned off and the charging by the stored power (power to be stored) is terminated. The After completion of charging, the switches (2) and (5) are turned on, and each assembled battery can be output from the output terminal (9) to an external circuit. At this time, the switches (2-1) to (2-n) shown in FIG. 1 can be individually turned on to discharge each assembled battery individually.

  When discharging each assembled battery individually, if the discharge order of the specific assembled battery (1-m) charged with priority is made last, the specific assembled battery (1-m) is discharged until the discharge. The waiting time can be. Therefore, the specific assembled battery (1-m) can be additionally charged with auxiliary power using the standby time.

  FIG. 7 shows a mechanism in which a specific assembled battery (1-m) that has been preferentially charged is additionally charged by auxiliary power after charging by main power (storage power) is stopped. FIG. 7 shows only the addition of the auxiliary power charger (13) to the power storage system shown in FIG. FIG. 7 shows a mechanism in which auxiliary power is provided by a charger (13) that uses a discharge output of an assembled battery other than a specific assembled battery (1-m) as an operating power source.

  In the power storage system (20) shown in FIG. 7, a charger (13) using a part of the discharge output of the assembled battery as an operating power supply is connected in parallel to the “priority charge input path”. In the power storage system (20) shown in FIG. 7, when the scheduled charging time elapses, the switch (3-m) remains in the ON state and the switches (4a) and (4b) are in the OFF state to store the main power (storage power). ) Is terminated.

  After charging with the main power (stored power) is completed, the switch (2-m) remains in the OFF state, and the other switch (2) and the auxiliary power supply switch (6) are in the ON state. The discharge output of the assembled battery other than the battery (1-m) serves as an operating power source to operate the charger (13), and the output of the charger (13) is switched to the switch (3- If m) is in the ON state, it is input to the specific assembled battery (1-m). As a result, the specific assembled battery (1-m) is additionally charged.

  When the switch (5) is in the ON state, the discharge output from other than the specific assembled battery can be output to the external circuit from the output terminal (9) as long as the switch (5) is in the ON state. In this case, since the specific assembled battery has already reached a high SOC by charging with the main power, the additional charging input from the charger (13) is considerably attenuated. Therefore, the discharge output of the assembled battery is consumed by the charger (13), and most of the discharge output of the assembled battery can be output to an external circuit.

  On the other hand, even if charging with the main power ends before the specific assembled battery reaches 100% SOC because the charging time with the main power (storage power) is short, the specific assembled battery (1-m) is added. 100% SOC can be reached by charging.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  In a power storage system designed so that the amount of power stored by solar power generation exceeds the amount of power required outside the sunshine hours, charging and discharging are repeated with a margin in the DOD on a daily basis. Therefore, when the power storage system is composed of a nickel metal hydride battery or a nickel cadmium battery, performance deterioration due to the “memory effect” appears in the nickel metal hydride battery or the nickel cadmium battery. If it is a nickel metal hydride battery used for a small electric device, it is possible to eliminate the memory effect by discharging the battery, but it is not easy to discharge the battery with a solar power storage system.

  In this example, an electricity storage system composed of nickel metal hydride batteries was produced with the structure shown in FIG. 2, and an attempt was made to eliminate the “memory effect” by preferential discharge of a specific assembled battery (1-m). In this embodiment, assuming that surplus power of 12A is generated continuously for 8 hours a day, this surplus power is charged into the power storage system, and the discharge of the power storage system is stored on the assumption that the DOD ends at about 90%. A system was created.

  In a power storage system for solar power generation, surplus power can be stored with high storage efficiency by charging with a margin in the rated capacity. If the rated capacity of the power storage system is insufficient with respect to the surplus power, a part of the surplus power cannot be stored and the storage efficiency of surplus power is reduced. Therefore, the power storage system of this example was designed on the condition that at least all of the generated surplus power can be input continuously for 8 hours.

  As a nickel metal hydride battery for constituting the power storage system, a commercially available AA nickel metal hydride battery (nominal voltage 1.2 V, nominal capacity 1.3 Ah) was prepared. The prepared nickel-metal hydride batteries were connected in 24 cells in parallel, and 10 of them were connected in series to produce four sets of assembled batteries.

  Each of the assembled batteries was a constant current of 6A, the upper limit voltage was set to 14V, the constant current charge was performed for 8 hours, and then the 6A constant current discharge was performed up to the final voltage of 10V to measure each discharge capacity. did. As a result, the discharge capacity was about 30 Ah, so the rated capacity of the assembled battery was determined to be 30 Ah.

  The power storage system in the present embodiment uses four prepared battery packs (total of 120 Ah) as shown in FIG. 2 and connects the battery packs (1-1) to (1-4) to the control device (15). It connected to terminal (8-1)-(8-4), and produced it by n = 4. The rated capacity of the power storage system (20) in this embodiment is 120 Ah, and the planned charge input (96 Ah) is about 80% of the rated capacity.

  A commercially available constant voltage constant current DC power source is connected to the charging input terminal (7b) of the control device (15) shown in FIG. 2, the output current Ib of this DC power source is set to 12A, and the upper limit voltage is set to 14.5V. Then, the switch (4b) was turned on to start charging the power storage system (20).

  In this example, the charging of the power storage system (20) was continuously input with a charging current of 12A, and the charging was terminated when 8 hours had elapsed. After that, first, the switch (2-m) is turned on to select the assembled battery (1-m) as a specific assembled battery, and discharging is performed at a constant current of 6A until the discharge voltage reaches the final voltage (10V). It was. Thereafter, the switches (2) other than the switch (2-m) were sequentially turned on, and the 6A constant current discharge was continued for the other assembled batteries. In this embodiment, since it is assumed that the discharge is terminated with leaving about 10% of the rated capacity of the power storage system, the discharge is terminated when the discharge voltage reaches 12.6 V in the last discharge of the assembled battery. In this way, charge / discharge of one cycle per day was repeated.

  The last assembled battery that stops discharging at a discharge voltage of 12.6 V has an SOC of only about 40%. Therefore, when converted to the rated capacity of the power storage system, the discharge ends with about 10% remaining. That is, the discharge is finished when the DOD of the power storage system reaches 90%. However, in this embodiment, m is an integer from 1 to 4, and each time charging is repeated, m is sequentially changed from 1 to 4, and the assembled batteries (1-1) to (1-4) are sequentially specified. Selected as an assembled battery.

  The discharge amount of each assembled battery in each cycle is calculated from each discharge time, and the total discharge amount of each assembled battery is the discharge amount of the power storage system. Since all three sets except the last assembled battery reached the end voltage (10V) in about 4.3 hours, the discharge amount was 26 Ah, and the discharge amount of the power storage system was 92 Ah (26 × 4-30 × 0.4). ). The discharge time of the power storage system is 15.3 hours, which is considerably longer than the standard discharge time of the storage battery, but each assembled battery is discharged at a 5-hour rate (standard discharge rate of the storage battery).

  Eventually, in the charge / discharge cycle of this example, the SOC reached (92/120 + 0.1) × 100 = 86% by charging the power storage system with a charging current of 12 A for 8 hours. On the other hand, when discharging, a specific assembled battery (1-m) is first discharged to 0% SOC (DOD = 100%), and then the other two assembled batteries are sequentially discharged to 0% SOC (DOD = 100%). ) Until the last assembled battery reached about 40% SOC.

  Here, if attention is paid to the discharge of the specific assembled battery (1-m), the specific assembled battery (1-m) is already generated when the DOD of the power storage system is discharged to 35% (SOC = 65%). ) Is discharged to 0% SOC (DOD = 100%). In addition, since the specific assembled battery is changed in order every time it is charged and discharged, the battery system in this embodiment has all 4 assembled batteries even if the SOC is repeated between 86% and 65%. It is clear that once a cycle, 0% SOC (DOD = 100%) is reached.

  Therefore, in a power storage system in which a specific assembled battery that is sequentially selected from a plurality of assembled batteries is discharged with priority over other assembled batteries as in the power storage system (20) shown in FIG. Even in the case of cadmium batteries, performance degradation due to the “memory effect” can be avoided.

  In the first embodiment, the nickel hydride battery is used to manufacture the power storage system with the configuration shown in FIG. 2 and the embodiment of the present invention is described. However, the first embodiment is an application example of the configuration shown in FIG. Is not intended to limit the use of nickel metal hydride batteries.

  Since the amount of surplus power generated by solar power generation varies depending on the weather, it is impossible to charge the power storage system for solar power generation to the full rated capacity every day. Therefore, when the power storage system for solar power generation is composed of a lead storage battery, uncharged lead sulfate remains in the lead storage battery, and the performance may be deteriorated by a phenomenon called “sulfation”. High nature.

  In the present embodiment, even in a power storage system including a lead storage battery, when the lead storage battery is based on the configuration of FIG. 4 or FIG. It was confirmed that it was not left for a long time. However, since it is not easy to measure the individual capacity of each assembled battery in the configuration of FIG. 4, it was prepared based on the configuration of FIG. However, even if it is created with the configuration of FIG. 1, if the charge / discharge cycle of the power storage system (20) is performed with all the switches (2) in the ON state, the same result as that obtained with the configuration of FIG. 4 can be obtained.

  This example is based on the premise that the surplus power of solar power generation is a maximum of 33A, 82% (27A) of the maximum value on a day when the surplus power is relatively high, and 36% (12A) of the maximum value on a day with a small amount. ) Was assumed to occur continuously for 8 hours per day. If the rated capacity of the power storage system is insufficient with respect to the surplus power of solar power generation, a part of surplus power cannot be stored and the storage efficiency of surplus power is reduced. Therefore, the design of the power storage system in the present example is based on the condition that the maximum surplus power (33 A) can be continuously input to the power storage system for 8 hours.

  A commercially available lead storage battery (nominal voltage 12 V, nominal capacity 60 Ah, dimensions 388 × 116 × 175 mm, mass about 21 kg) was prepared as a lead storage battery for constituting the power storage system. Each of the prepared lead storage batteries is an assembled battery in which six single cells are connected in series.

  Each of the prepared batteries has a constant current of 12A, the upper limit voltage is set to 14.8V and charging is performed for 8 hours, and then the constant current discharge of 11A is performed up to a final voltage of 10.5V to obtain each discharge capacity. Was measured. As a result, since the discharge capacity was about 58 Ah, the rated capacity of the assembled battery was determined to be 58 Ah. In the present specification, the rated capacity is defined as the maximum charge capacity (= capacity that can be discharged) charged by a standard charging method.

  Therefore, the power storage system in this embodiment uses five prepared battery packs (total 290 Ah) and has the configuration shown in FIG. 1 (the purpose is the implementation of the power storage system of FIG. 4), and the assembled batteries (1-1) to (1-5) was connected to the connection terminals (8-1) to (8-5) of the control device (15) to produce n = 5. The rated capacity of the power storage system (20) in the present embodiment is 290 Ah, and the maximum surplus power (33 A × 8 h) is about 91% of the rated capacity, and the surplus power on a relatively large day (27 A × 8). Is about 74% of the rated capacity, and charging input (12A × 8h) on a small day is about 33% of the rated capacity.

  As the charging input, a commercially available constant voltage constant current DC power source A and constant voltage constant current DC power source B were prepared, and each was connected to the charging input terminals (7a) and (7b) of the control device (15). Here, in the power storage system (20) shown in FIG. 1, the switches (2-1) to (2-5) are turned on and the other switches are turned off to functionally function as the power storage system (20) shown in FIG. Made the same.

  In each of the assembled batteries (1-1) to (1-5), when the charging voltage reaches the upper limit voltage (14.8V) in the constant current charging of 11.6A (0.2CA), the SOC becomes about 80%. Then, constant voltage charging (14.8V) was continued, and it was confirmed that the SOC reached 100% by charging for a total of 8 hours. Therefore, the DC power source A connected to the charging input terminal (7a) has the upper limit voltage set to 14.8V and the current value Ia set to 11.6A. The current value Ia in this embodiment is set to 11.6 A regardless of the magnitude of the charging power to the power storage system (20).

  First, it carried out on the assumption that the maximum of surplus electric power (33A) was inputted into the electrical storage system (20). In this case, since the charging input I to the power storage system (20) is 33A, the DC power source B connected to the charging input terminal (7b) sets the current value Ib to 21.4A from the relationship of I = Ia + Ib = 33A. The upper limit voltage of the DC power supply B was set to 15V.

  Charging of the power storage system (20) is started by turning on the switches (4a) and (4b). The charging current Ia at the start of charging is 11.6A, the charging current Ib is 21.4A, and a total of 33A is input to the power storage system (20). The switch (3-m) is turned on together with the switch (4a), the assembled battery (1-m) is selected as a specific assembled battery, and the charging input 11.6A from the input terminal (7a) is used as the assembled battery. Input only to (1-m). Since the charging current Ia (11.6 A) satisfies the relationship of Ia >> I / n = 6.6 A, the assembled battery (1-m) is charged with priority over other assembled batteries.

  The charging current Ib (21.4A) is input to four sets of assembled batteries other than the assembled battery (1-m). After the specific assembled battery (1-m) shifts to the constant voltage charging, the charging of the assembled battery (1-m) is performed while the charging input Ia is decreased. The current setting value Ib was increased to maintain the relationship of Ia + Ib = 33 +/− 1.5A.

  When 8 hours passed from the start of charging, the switch (3-m), the switch (4a), and the switch (4b) were turned off to finish charging the power storage system (20). At the end of charging, the voltage of the DC power supply B did not reach the set voltage (15 V), and eventually, a charging current of 33 A could be input for 8 hours from the start of charging to the end of charging.

  After the end of charging, the battery was discharged at a constant current of 20 A until the discharge voltage of the assembled battery reached a final voltage (10.5 V). Since the switches (2-1) to (2-5) are turned on in advance when the switch (5) is turned on, the assembled batteries (1-1) to (1-5) are discharged after completion of charging. ) Start discharging in parallel and can be output to an external circuit from the output terminal (9) shown in FIG.

  As described above, the power storage system (20) was charged with 33A for 8 hours, and then subjected to constant current discharge of 20A to repeat the charge / discharge cycle. In the charge / discharge cycle, the specific assembled battery (1-m) is changed by changing m from 1 to 5 in order. In the middle of the charge / discharge cycle, the switches other than the switch (2-m) are turned off, and only the specific assembled battery (1-m) is discharged with a constant current discharge of 10A until the final voltage (10.5V) is reached. Then, the capacity of the specific assembled battery (1-m) in which m was randomly selected was measured.

  In the storage system (20) of the present embodiment, in the charging / discharging cycle of 33A for 8 hours and 20A constant current discharge, the assembled battery is brought to a final voltage (10.5V) after discharging for about 12.1 hours in any cycle. Reached. Therefore, the amount of discharge of the power storage system (20) was about 242 Ah, and it was confirmed that the power storage system (20) was charged to about 84% SOC. On the other hand, in the capacity measurement of the specific assembled battery (1-m), the discharge voltage of the specific assembled battery (1-m) reached about 58.3 Ah because the end voltage was reached after 350 minutes of discharge. It was confirmed that the battery (1-m) was charged to about 101% SOC. In addition, since a charging current of 33 A is input to the power storage system (20) from the start of charging to the end of charging, the power storage efficiency is about 92%.

  Then, the charging / discharging cycle supposing the case where the surplus electric power 27A is input into an electrical storage system (20) was implemented. In this case, the charging input I to the power storage system (20) is 27A, and the DC power source B connected to the charging input terminal (7b) sets the upper limit voltage to 15V, but the current value Ib is I = Ia + Ib = 15.4A from the relationship of 27A, charging of the power storage system (20) was started.

  Also in this case, after the specific assembled battery (1-m) shifts to constant voltage charging, the charging of the assembled battery (1-m) is performed while the charging input Ia decreases, so once every 30 minutes. The current set value Ib of the DC power supply B is increased to maintain the relationship of Ia + Ib = 27 +/− 1.5A. The voltage of the DC power source B did not reach the set voltage (15 V) even when the charging was completed, and eventually, a charging current of 27 A could be input for 8 hours from the start of charging to the end of charging.

  After the power storage system (20) was charged at 27A for 8 hours, 20A constant current discharge was performed and the charge / discharge cycle was repeated. Again, the specific assembled battery (1-m) is changed by changing m from 1 to 5 in order. In addition, in a certain charge / discharge cycle, m is randomly determined, and the switch (2-m) other than the switch (OFF) is turned off, and only a specific assembled battery (1-m) is discharged at a constant current of 10A to a final voltage (10.5V). The battery was discharged until it reached), and the capacity of the specific assembled battery (1-m) was measured.

  In the power storage system (20), the assembled battery reached the end voltage (10.5 V) after discharging for about 9.9 hours in either cycle of charge / discharge cycles of 27A for 8 hours and 20A constant current discharge. Therefore, the discharge amount of the power storage system (20) was about 197 Ah, and it was confirmed that the power storage system (20) was charged to about 68% SOC. On the other hand, in the capacity measurement of the specific assembled battery (1-m), the final voltage is reached after 350 minutes of discharge, and the discharge amount of the specific assembled battery (1-m) is about 58.3 Ah. The battery (1-m) was again confirmed to be charged to about 101% SOC. In addition, since a charging current of 27 A is input to the power storage system (20) from the start of charging to the end of charging, the power storage efficiency is about 91%.

  Furthermore, the charge / discharge cycle which assumed the case where surplus electric power 12A was input into an electrical storage system (20) was implemented. In this case, the charging input I to the power storage system (20) is 12A, the DC power source B connected to the charging input terminal (7b) has the same upper limit voltage, and the current value Ib has a relationship of I = Ia + Ib = 12A. The charging of the power storage system (20) was started at 0.4A.

  Also in this case, after the specific assembled battery (1-m) shifts to constant voltage charging, the charging of the assembled battery (1-m) is performed while the charging input Ia decreases, so once every 30 minutes. The current set value Ib of the DC power source B is increased to maintain the relationship of Ia + Ib = 12 +/− 1.5A. The voltage of the DC power source B did not reach the set voltage (15 V) even when charging was completed, and a charging current of 12 A could be input from the start of charging to the end of charging.

  The power storage system (20) was charged with 12A for 8 hours, and then was subjected to a constant current discharge of 20A to repeat the charge / discharge cycle. Again, the specific assembled battery (1-m) is changed by changing m from 1 to 5 in order. In addition, in a certain charge / discharge cycle, m is randomly determined, and the switch (2-m) other than the switch (OFF) is turned off, and only a specific assembled battery (1-m) is discharged at a constant current of 10A to a final voltage (10.5V). The battery was discharged until it reached), and the capacity of the specific assembled battery (1-m) was measured.

  In the storage system (20), the assembled battery reached the end voltage (10.5 V) after discharging for about 4.2 hours in any cycle of charging / discharging cycle of 12A for 8 hours and 20A constant current discharge. Therefore, the discharge amount of the power storage system (20) was about 84 Ah, and it was confirmed that the power storage system (20) was charged to about 29% SOC. On the other hand, it was confirmed that the specific assembled battery (1-m) was charged up to about 101% SOC. In addition, since a charging current of 12 A is input to the power storage system (20) from the start of charging to the end of charging, the power storage efficiency is about 88%.

  As described above, in the power storage system in this example, when the charging current changed from 33 A to 12 A, the SOC of the power storage system at the end of charging changed from 84% to 29%. However, since the power storage system in the present embodiment is based on the configuration of FIG. 4 or FIG. 1, the specific assembled battery (1-m) is about 100% regardless of whether the SOC of the power storage system at the end of charging is 84% or 29%. It is charged to SOC. Therefore, even when the power storage system is composed of a lead storage battery, the unused lead sulfate is frequently charged up to 100% before the crystal expands, so that performance degradation due to sulfation is suppressed.

  In the second embodiment, a lead storage battery is used to manufacture the power storage system with the configuration shown in FIG. 1, and the embodiment of the present invention is described. The second embodiment is shown in FIG. 1 or FIG. It shows one application example of the configuration and is not intended to limit the use of lead-acid batteries.

  In this embodiment, a power storage system composed of lithium ion batteries is manufactured based on the configuration shown in FIG. 1, and even if charging and discharging are repeated while leaving a margin in the SOC and DOD as the power storage system, It was confirmed that both DOD and DOD frequently reached 100%.

  In this embodiment, it is assumed that 11A of surplus power is generated continuously for 8 hours, and all the surplus power generated can be input to the power storage system, and the discharge of the power storage system is about 90% DOD. The power storage system was designed on the assumption that the discharge will be terminated.

A commercially available 18650 type NCM type lithium ion battery (nominal voltage 3.7 V, nominal capacity 2.2 Ah) was prepared as a lithium ion battery for constituting the power storage system. The 18650 type is a cylindrical type having a diameter of 18 mm and a length of 65 mm, and the NCM type is a lithium ion battery using LiNi _1/3 Co _1/3 Mn _1/3 O ₂ for the positive electrode. Of the 336 prepared lithium ion batteries, 16 cells were connected in parallel, and seven of them were connected in series to produce three sets of assembled batteries.

  Each of the assembled batteries produced had a constant current of 7A, the upper limit voltage was set to 29.4V and constant current / constant voltage charging was performed for 8 hours, and then the constant current discharge of 7A was performed up to a final voltage of 22V. The discharge capacity was measured. As a result, since the discharge capacities were all about 36 Ah, the rated capacity of the assembled battery was determined to be 36 Ah.

  The power storage system in the present embodiment uses three prepared battery packs (total of 108 Ah) as shown in FIG. 1 and connects the battery packs (1-1) to (1-3) to the control device (15). It connected to terminal (8-1)-(8-3), and produced it by n = 3. The rated capacity of the power storage system (20) in the present embodiment is 108 Ah, the planned charge input (88 Ah) is about 81% of the rated capacity, and the discharge ends when the discharge of the power storage system is about 90%. All scheduled charging inputs can be entered.

  As the charging input, as in Example 2, a commercially available constant voltage constant current DC power source A and constant voltage constant current DC power source B were connected to the charging input terminals (7a) and (7b) of the control device (15), respectively. The assembled batteries (1-1) to (1-3) reach 100% SOC when charged by the charging method with the rated capacity determined. That is, if the upper limit voltage is set to 29.4 V at a constant current of 7 A and constant current constant voltage charging is performed for 8 hours, the SOC reaches 100%. Therefore, the DC power source A sets the current value Ia to 7 A and the upper limit voltage to 29.4V.

  In the present embodiment, it is assumed that surplus power of 11A is generated continuously for 8 hours, and the charging input I to the power storage system (20) is 11A. Therefore, the DC power source B connected to the charging input terminal (7b) The current value Ib was set to 4A from the relationship of I = Ia + Ib = 11A, and the upper limit voltage was set to 29.6V.

  Charging of the power storage system (20) is started with the switches (4a) and (4b) turned on. At the start of charging, the charging current Ia was 7A, the charging current Ib was 4A, and the charging input I to the power storage system (20) was 11A. The switch (3-m) is turned on together with the switch (4a), and the assembled battery (1-m) is selected as a specific assembled battery, and the charging current Ia (7A) is only the assembled battery (1-m). Is input. On the other hand, the charging current Ib (4A) is input to two sets of assembled batteries other than the assembled battery (1-m).

  Here, I / n = 3.67A, and the charging current Ia (7A) satisfies the relationship of Ia >> I / n. Therefore, the assembled battery (1-m) is charged with priority over other assembled batteries. In the present embodiment, m is changed every time the battery is charged, and the assembled batteries (1-1) to (1-3) are selected as specific assembled batteries in order. However, m is an arbitrary integer from 1 to 3 in this embodiment.

  On the other hand, the NCM type lithium ion battery also reaches the upper limit voltage when the SOC reaches about 85%, so that the subsequent charging also shifts to constant voltage charging. Also in the present embodiment, after the specific assembled battery (1-m) shifts to constant voltage charging, charging of the assembled battery (1-m) decreases with the progress of charging, so the charging current Ia decreases. Once, the current set value Ib of the DC power source B is increased to maintain the relationship of Ia + Ib = 11 +/− 0.5A.

  At the time when 8 hours passed from the start of charging, the switches (4a) and (4b) were turned off to finish charging the power storage system (20). The voltage of the DC power supply B did not reach the set value of 29.6 V until the end of charging, and the relationship of Ia + Ib = 10 +/− 0.5 A was maintained from the start of charging to the end of charging.

  After completion of charging, the power storage system (20) turned on the switch (2) and the switch (5), and sequentially discharged each assembled battery with 7 A constant current discharge. Here, a specific assembled battery (1-m) is first discharged to 100% DOD (SOC = 0%), and then another set of assembled batteries is discharged to 100% DOD. Ended the discharge when the discharge voltage reached 25.9V. The last assembled battery that stops discharging at a discharge voltage of 25.9V has an SOC of only about 30%. Therefore, when converted to the rated capacity of the power storage system, about 10% remains, that is, when the DOD is 90%. The discharge has ended.

  Eventually, in this example, the power storage system (20) was repeatedly charged and discharged for 1 cycle per day by a method in which the discharge was terminated when the DOD reached 90% and the battery was charged again at 11A for 8 hours. The specific discharge amount of each assembled battery in each cycle is 36 Ah for a specific assembled battery, 30 Ah for the other assembled battery, and 19 Ah for the remaining one assembled battery. The amount was 11 Ah.

  In the power storage system (20) in the present embodiment, the rated capacity of each assembled battery is 36 Ah, and the rated capacity of the power storage system is 108 Ah. Therefore, it can be seen that the SOC of the power storage system at the end of charging in each cycle has reached 89% from the calculation of (36Ah + 30Ah + 19Ah + 11Ah) ÷ 108Ah, and the SOC of a specific assembled battery has reached 100% from the calculation of 36Ah ÷ 36Ah. I understand that.

  As described above, the power storage system configured by the lithium ion battery based on the configuration of FIG. 1 is 89% as a power storage system even if the planned charging input is continuously input from the start of charging to the end of charging. At the assembled battery level, the SOC can reach 100% once every three cycles. On the other hand, at the time of discharging, even if the power storage system stops at 90% DOD, the assembled battery level can reach 100% DOD twice in 3 cycles.

  The embodiment of the present invention has been described above. However, the above embodiment shows one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not. The above-described embodiment can be variously modified without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 assembled battery 2 discharge switch 3 priority charge switch 4a priority charge input switch 4b charge input switch 5 discharge output switch 6 auxiliary power supply switch 7a charge input terminal 7b charge input terminal 8 assembled battery connection terminal 9 discharge output terminal 13 charge 15 Control device 16 Diode 20 Power storage system 31 SOC of power storage system
32 SOC of assembled battery

Claims (8)

  A power storage system in which a plurality of assembled batteries are connected in parallel in units of assembled batteries, and a specific assembled battery selected sequentially from the assembled batteries is discharged with priority over other assembled batteries. A power storage system characterized by this.   A power storage system in which a plurality of assembled batteries are connected in parallel in units of assembled batteries, and a specific assembled battery selected sequentially from the assembled batteries is charged with priority over other assembled batteries. A power storage system characterized by this.   3. The power storage system according to claim 2, wherein the specific assembled battery charged with priority is additionally charged with auxiliary power after charging by main power is stopped.   2. The power storage system according to claim 1, wherein each of the plurality of assembled batteries is connected to a discharge output path via a discharge switch, and a specific assembled battery is selected by selecting whether to open or close the discharge switch. It is characterized by being discharged in preference to the above.   The power storage system according to claim 2, wherein a plurality of charging input paths are provided for each of the plurality of assembled batteries, and a specific assembled battery is selected by selection of the charging input path, giving priority to other assembled batteries. And is charged.   6. The power storage system according to claim 5, wherein each of the plurality of assembled batteries is connected to a charge input path for priority charge via a switch for priority charge.   The power storage system is a power storage system for solar power generation, and the number n of assembled batteries constituting the power storage system is 3 ≦ n ≦ 6.   In a power storage system in which a plurality of assembled batteries are provided with the control device, the control device sequentially selects a specific assembled battery from the assembled batteries, and charges this with priority over other assembled batteries. Or the control apparatus of the electrical storage system characterized by discharging.

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