JP2022143641A - Redox flow battery system and operation method for redox flow battery system - Google Patents

Abstract

To provide a redox flow battery system and an operation method for the redox flow battery system, capable of implementing stable operation.SOLUTION: A redox flow battery system 10 comprises a battery cell 100, a circulation unit 300, an open voltage measurement unit 500, and a control unit 600. The battery cell 100 includes: a positive electrode chamber 110a in which a positive electrode 105a is disposed; a negative electrode chamber 110c in which a negative electrode 105c is disposed; and a diaphragm 120 that separates the positive electrode chamber 110a and the negative electrode chamber 110c. The circulation unit 300 makes a positive electrode electrolyte PL circulate in the positive electrode chamber 110a and makes a negative electrode electrolyte NL circulate in the negative electrode chamber 110c. The open voltage measurement unit 500 measures open voltage of the battery cell 100. The control unit 600 calculates a moving average value of the open voltage measured by the open voltage measurement unit 500 depending on charge depth of the positive electrode electrolyte PL and the negative electrode electrolyte NL and, on the basis of the calculated moving average value of the open voltage, controls charging/discharging of the positive electrode electrolyte PL and the negative electrode electrolyte NL.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to redox flow battery systems and methods of operating redox flow battery systems.

A redox flow battery is known as a large-capacity storage battery. In a redox flow battery, charge and discharge are performed by circulating a positive electrode electrolyte and a negative electrode electrolyte in a battery cell provided with an ion exchange membrane between a positive electrode and a negative electrode. A solution containing a metal whose valence number changes due to an oxidation-reduction reaction is used as a positive electrode electrolyte and a negative electrode electrolyte, and an electrolyte containing vanadium as an active material is widely used.

In the operation of the redox flow battery, charging and discharging are controlled by grasping the charge depth of the electrolyte (also referred to as SOC (State of Charge)) in order to realize stable operation. For example, in Patent Document 1, at least one of stopping battery charging and discharging is performed based on an open circuit voltage obtained from an auxiliary cell used to measure the charging rate of the electrolyte.

JP-A-2003-317788

In Patent Document 1, the depth of charge of the electrolytic solution is grasped from the measured value of the open circuit voltage of the auxiliary cell (that is, the instantaneous open circuit voltage). When measuring the open-circuit voltage of the auxiliary cell, the route of the electrolyte passing through the auxiliary cell, variations in the valence of the active material in the electrolyte, air bubbles generated in the electrolyte, etc. may cause variations in the measured value. values are sometimes measured. Therefore, in the operation method of Patent Document 1, there is a possibility that the redox flow battery cannot be operated in a sufficiently stable state.

The present disclosure has been made in view of the circumstances described above, and aims to provide a redox flow battery system and a method of operating the redox flow battery system that can achieve stable operation.

In order to achieve the above object, the redox flow battery system according to the first aspect of the present disclosure includes
a battery cell having a positive electrode chamber in which a positive electrode is arranged, a negative electrode chamber in which a negative electrode is arranged, and a diaphragm separating the positive electrode chamber and the negative electrode chamber;
a circulation unit that circulates a positive electrode electrolyte in the positive electrode chamber and circulates a negative electrode electrolyte in the negative electrode chamber;
an open-circuit voltage measuring unit that measures the open-circuit voltage of the battery cell;
A moving average value of the open-circuit voltage measured by the open-circuit voltage measuring unit is obtained according to the charge depth of the positive electrode electrolyte and the negative electrode electrolyte, and based on the obtained moving average value of the open-circuit voltage, the and a controller for controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte.

A method for operating a redox flow battery system according to a second aspect of the present disclosure includes:
a measuring step of measuring the open-circuit voltage of the battery cell;
From the measured open-circuit voltage, a moving average value of the open-circuit voltage is calculated according to the charge depth of the positive electrode electrolyte supplied to the positive electrode chamber of the battery cell and the negative electrode electrolyte supplied to the negative electrode chamber of the battery cell. a desired calculation process;
and a control step of controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte based on the obtained moving average value of the open-circuit voltage.

According to the present disclosure, the charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte are controlled based on the moving average value of the open circuit voltage obtained according to the charge depth of the positive electrode electrolyte and the negative electrode electrolyte. can realize driving.

1 is a schematic diagram of a redox flow battery system according to Embodiment 1. FIG. 4 is a diagram showing the relationship between the depth of charge of the electrolytic solution and the open-circuit voltage according to Embodiment 1. FIG. 3 is a block diagram showing a control unit according to Embodiment 1; FIG. 4 is a diagram showing measured values of open-circuit voltages and moving average values of open-circuit voltages according to Embodiment 1. FIG. 3 is a diagram showing the hardware configuration of a control unit according to the first embodiment; FIG. 4 is a flow chart showing a method of operating the redox flow battery system according to Embodiment 1. FIG. FIG. 10 is a diagram showing an example of the relationship between the amount of solar power generation, the charge/discharge power from the redox flow battery system, and the solar power output after charge/discharge control, according to Embodiment 2;

Hereinafter, a redox flow battery system according to an embodiment will be described with reference to the drawings.

<Embodiment 1>
A redox flow battery system 10 according to the present embodiment will be described with reference to FIGS. 1 to 6. FIG.

The redox flow battery system 10 includes, as shown in FIG. The redox flow battery system 10 includes an open circuit voltage measurement unit 500 that measures the open circuit voltage (OCV) of the battery cell 100, a control unit 600 that controls charging and discharging of the positive electrolyte PL and the negative electrolyte NL, Further prepare. In this embodiment, a redox flow battery using vanadium ions as the active materials of the positive electrode electrolyte PL and the negative electrode electrolyte NL will be described as an example. Also, the positive electrode electrolyte PL and the negative electrode electrolyte NL are collectively referred to as electrolyte solutions.

Redox flow battery system 10 is connected between a power plant and a load via power converter 610 of control unit 600 . A power plant is, for example, a renewable energy power plant such as a solar power plant, a wind power plant, or the like. The load is the power system and power consumers. The redox flow battery system 10 charges power supplied from a power plant. Also, the redox flow battery system 10 supplies the charged power to the load.

First, a specific configuration of the battery cell 100 of the redox flow battery system 10 will be described. Battery cell 100 has positive electrode 105 a , positive electrode chamber 110 a , negative electrode 105 c , negative electrode chamber 110 c and diaphragm 120 .

A carbon fiber electrode, for example, is used for the positive electrode 105a of the battery cell 100 . The positive electrode 105 a is arranged in the positive electrode chamber 110 a of the battery cell 100 . The positive electrode chamber 110a of the battery cell 100 is provided with the positive electrode 105a and separated from the negative electrode chamber 110c by the diaphragm 120 . A positive electrode electrolyte PL circulates in the positive electrode chamber 110a. During charging, tetravalent vanadium ions in the positive electrode electrolyte PL are oxidized to pentavalent vanadium ions. During discharge, the pentavalent vanadium ions in the positive electrode electrolyte PL are reduced to tetravalent vanadium ions.

For the negative electrode 105c of the battery cell 100, for example, a carbon fiber electrode is used. The negative electrode 105 c is arranged in the negative electrode chamber 110 c of the battery cell 100 . A negative electrode chamber 110 c of the battery cell 100 is provided with a negative electrode 105 c and separated from the positive electrode chamber 110 a by a diaphragm 120 . A negative electrode electrolyte NL circulates in the negative electrode chamber 110c. During charging, trivalent vanadium ions in the negative electrode electrolyte NL are reduced to divalent vanadium ions. During discharge, divalent vanadium ions in the negative electrode electrolyte NL are oxidized to trivalent vanadium ions.

The diaphragm 120 of the battery cell 100 is an ion exchange membrane. The diaphragm 120 separates the positive electrode chamber 110a and the negative electrode chamber 110c and allows predetermined ions to pass therethrough.

The battery cell 100 is used in the form of a cell stack in which a plurality of battery cells 100 are stacked. The cell stack is configured by stacking, for example, a cell frame provided with a bipolar plate, a positive electrode 105a, a diaphragm 120, and a negative electrode 105c. The positive electrode 105a is arranged on one side of the bipolar plate and the negative electrode 105c is arranged on the other side of the bipolar plate, thereby forming the battery cell 100 between adjacent cell frames. The positive electrode electrolyte PL and the negative electrode electrolyte NL circulate through manifolds formed in the frame of the cell frame, the frame supporting the positive electrode 105a, the frame supporting the negative electrode 105c, and the like. In addition, the structure of the battery cell 100 can utilize a well-known structure suitably.

As shown in FIG. 1, the circulation section 300 of the redox flow battery system 10 has a positive electrode circulation section 300a and a negative electrode circulation section 300c. The positive electrode circulation unit 300 a of the circulation unit 300 circulates the positive electrode electrolyte PL to the positive electrode chamber 110 a of the battery cell 100 . Also, the positive electrode circulation unit 300a circulates the positive electrode electrolyte PL to the monitor cell 510 of the open-circuit voltage measurement unit 500, which will be described later. The negative electrode circulation unit 300 c of the circulation unit 300 circulates the negative electrode electrolyte NL to the negative electrode chamber 110 c of the battery cell 100 . Also, the negative electrode circulation unit 300 c circulates the negative electrode electrolyte NL to the monitor cell 510 . The control unit 600 controls the flow rates of the positive electrode electrolyte PL and the negative electrode electrolyte NL.

The positive electrode circulation part 300a of the circulation part 300 includes a positive electrode electrolyte reservoir 310a, a positive electrode pump 320a, a positive electrode supply pipe 322a, a supply branch pipe 324a, a first positive electrode recovery pipe 326a, and a second positive electrode recovery pipe 328a. have The positive electrode electrolyte reservoir 310a of the positive electrode circulation unit 300a stores the positive electrode electrolyte PL. The positive electrode electrolyte storage tank 310a is connected to a positive electrode pump 320a, a first positive electrode recovery pipe 326a, and a second positive electrode recovery pipe 328a.

The positive electrode pump 320a of the positive electrode circulation unit 300a is a pump that circulates the positive electrode electrolyte PL. The cathode pump 320a is connected to the cathode electrolyte reservoir 310a and the cathode supply pipe 322a. The positive electrode pump 320 a is controlled by the control unit 600 to control the flow rate of the positive electrode electrolyte PL circulating through the positive electrode chamber 110 a of the battery cell 100 and the positive electrode chamber of the monitor cell 510 .

The positive electrode supply pipe 322a of the positive electrode circulation unit 300a is connected to the positive electrode pump 320a and the positive electrode chamber 110a of the battery cell 100 to supply the positive electrode electrolyte PL to the positive electrode chamber 110a. The supply branch pipe 324 a of the positive electrode circulation unit 300 a branches from the positive electrode supply pipe 322 a to supply the positive electrode electrolyte PL to the positive electrode chamber of the monitor cell 510 .

The first positive electrode collection pipe 326a of the positive electrode circulation unit 300a is connected to the positive electrode chamber 110a of the battery cell 100 and the positive electrode electrolyte storage tank 310a. The first positive electrode recovery pipe 326a returns the positive electrode electrolyte PL supplied to the positive electrode chamber 110a from the positive electrode chamber 110a to the positive electrode electrolyte storage tank 310a.

The second positive electrode recovery pipe 328a of the positive electrode circulation unit 300a is connected to the positive electrode chamber of the monitor cell 510 and the positive electrode electrolyte storage tank 310a. The second positive electrode recovery pipe 328a returns the positive electrode electrolyte PL supplied to the positive electrode chamber of the monitor cell 510 from the positive electrode chamber of the monitor cell 510 to the positive electrode electrolyte storage tank 310a.

The negative electrode circulation part 300c of the circulation part 300 includes a negative electrode electrolyte reservoir 310c, a negative electrode pump 320c, a negative electrode supply pipe 322c, a supply branch pipe 324c, a first negative electrode recovery pipe 326c, and a second negative electrode recovery pipe 328c. have The negative electrode electrolyte reservoir 310c of the negative electrode circulation unit 300c stores the negative electrode electrolyte NL. The negative electrode electrolyte reservoir 310c is connected to the negative electrode pump 320c, the first negative electrode recovery pipe 326c, and the second negative electrode recovery pipe 328c.

The negative electrode pump 320c of the negative electrode circulation unit 300c is a pump that circulates the negative electrode electrolyte NL. The negative electrode pump 320 c is controlled by the control unit 600 to control the flow rate of the positive electrode electrolyte PL circulating through the negative electrode chamber 110 c of the battery cell 100 and the negative electrode chamber of the monitor cell 510 .

The negative electrode supply pipe 322c of the negative electrode circulation unit 300c is connected to the negative electrode pump 320c to supply the negative electrode electrolyte NL to the negative electrode chamber 110c of the battery cell 100 . A supply branch pipe 324 c of the negative electrode circulation unit 300 c branches from the negative electrode supply pipe 322 c to supply the negative electrode electrolyte NL to the negative electrode chamber of the monitor cell 510 .

The first negative electrode recovery pipe 326c of the negative electrode circulation unit 300c returns the negative electrode electrolyte NL supplied to the negative electrode chamber 110c from the negative electrode chamber 110c to the negative electrode electrolyte storage tank 310c. The second negative electrode recovery pipe 328c of the negative electrode circulation unit 300c returns the negative electrode electrolyte NL supplied to the negative electrode chamber of the monitor cell 510 from the negative electrode chamber of the monitor cell 510 to the negative electrode electrolyte storage tank 310c.

The open-circuit voltage measurement unit 500 of the redox flow battery system 10 measures an open-circuit voltage indicating the state of charge of the electrolyte. The open-circuit voltage measuring section 500 has a monitor cell 510 and a measuring section 520, as shown in FIG.

The monitor cell 510 has the same configuration as the battery cell 100 and is a single redox flow battery cell that does not contribute to charging and discharging. Like the positive electrode chamber 110 a of the battery cell 100 , the positive electrode electrolyte PL stored in the positive electrode electrolyte storage tank 310 a is supplied to the positive electrode chamber of the monitor cell 510 . Further, the negative electrode chamber of the monitor cell 510 is supplied with the negative electrode electrolyte NL stored in the negative electrode electrolyte storage tank 310c in the same manner as the negative electrode chamber 110c of the battery cell 100 .

The measurement unit 520 is a voltmeter that measures the potential difference (that is, open-circuit voltage) between the positive electrolyte PL and the negative electrolyte NL in the monitor cell 510 . Since the positive electrode electrolyte PL and the negative electrode electrolyte NL are supplied to the positive electrode chamber and the negative electrode chamber of the monitor cell 510, respectively, in the same way as the positive electrode chamber 110a and the negative electrode chamber 110c, respectively, which flow into the battery cell 100, the monitor cell By measuring the open circuit voltage of 510, the open circuit voltage of battery cell 100 can be measured. In this embodiment, the measuring unit 520 measures the open-circuit voltage on the supply side of the positive electrode electrolyte PL and the negative electrode electrolyte NL. Moreover, the measurement unit 520 measures the open-circuit voltage at intervals of 1 second (measurement interval Δt0=1 sec).

There is a correlation between the depth of charge of the electrolytes (positive electrolyte PL and negative electrolyte NL) and the open-circuit voltage of the monitor cell 510, and the depth of charge of the electrolyte can be obtained from the open-circuit voltage of the monitor cell 510. can. For example, there is a relationship shown in FIG. 2 between the depth of charge of the electrolyte and the open-circuit voltage of the monitor cell 510 . Also, the depth of charge (SOC) of the electrolytic solution is simply represented by the following formula (1) using the open circuit voltage (OCV) of the monitor cell 510 . Here, F is the Faraday constant, R is the gas constant, T is the absolute temperature, and OCVe is the open-circuit voltage when the concentrations of the oxide and the reduced product are equal.

The control unit 600 of the redox flow battery system 10 obtains a moving average value of the open-circuit voltage according to the charging depth of the positive electrode electrolyte PL and the negative electrode electrolyte NL. The control unit 600 controls charging and discharging of the positive electrode electrolyte PL and the negative electrode electrolyte NL based on the obtained moving average value of the open-circuit voltage. As shown in FIG. 3, the control unit 600 includes an acquisition unit 620, a storage unit 630, a setting unit 640, a calculation unit 650, a determination unit 660, a flow control unit 670, and a charge/discharge control unit 680. have.

Acquisition unit 620 of control unit 600 acquires the measurement value of the open-circuit voltage measured by measurement unit 520 of open-circuit voltage measurement unit 500 . Acquisition unit 620 transmits a signal representing the acquired open-circuit voltage measurement value to storage unit 630 and calculation unit 650 .
Storage unit 630 of control unit 600 stores programs, data, measured values of open-circuit voltage, and the like.

The setting unit 640 of the control unit 600 sets conditions for the calculation unit 650 to obtain the moving average value of the open-circuit voltage. Specifically, the setting unit 640 sets an interval Δt1 and a period S (S=n×Δt1: n is a natural number of 2 or more) for obtaining the moving average value of the open-circuit voltage.

In this embodiment, the interval Δt1 for obtaining the moving average value of the open-circuit voltage is set to 1 second (Δt1=1 sec). Further, when the depth of charge of the electrolytic solution is within the predetermined range, the setting unit 640 sets the period S for obtaining the moving average value of the open-circuit voltage to a predetermined first period S1=60 seconds (S1=60×Δt1 , n=60). The predetermined range of the charging depth of the electrolyte is preferably a range in which the correlation between the open-circuit voltage and the charging depth of the electrolyte can be regarded as a proportional relationship. In the present embodiment, the predetermined range of the charging depth of the electrolytic solution is 10% or more and 90% or less of the charging depth of the electrolytic solution.

Furthermore, when the charging depth of the electrolyte is less than the predetermined range (when the charging depth of the electrolyte is less than 10%) and when the charging depth of the electrolyte is greater than the predetermined range (when the charging depth of the electrolyte is 90%), the setting unit 640 sets the period S for obtaining the moving average value of the open-circuit voltage to a predetermined second period S2=5 seconds shorter than the predetermined first period S1 (S2=5 x Δt1, n=5). In the present embodiment, in the correlation between the open-circuit voltage and the charging depth of the electrolyte, when the charging depth of the electrolyte changes abruptly, when the charging depth of the electrolyte is smaller than the predetermined range and when it is greater than the predetermined range. Since the setting unit 640 shortens the period S for obtaining the moving average value of the open-circuit voltage, the control unit 600 can quickly respond to changes in the charging depth of the electrolyte, and stable operation of the redox flow battery system 10 can be realized. .
Setting unit 640 transmits a signal representing the set condition to calculation unit 650 .

The calculation unit 650 of the control unit 600 calculates the moving average value OCV(t) of the open-circuit voltage at the time t from the measured value of the open-circuit voltage acquired by the acquisition unit 620 based on the conditions set by the setting unit 640. . Specifically, the moving average value OCV(t) of the open-circuit voltage at time t is obtained by the following equation (2), and the moving average value OCV(t+Δt1) of the open-circuit voltage at time t+Δt1 is obtained by the following equation (3). . where OCV _n+1 to OCV ₁ are measured values of open-circuit voltages.

FIG. 4 shows the measured value of the open-circuit voltage and the moving average value OCV(t) of the open-circuit voltage in the first period S1. As shown in FIG. 4, by obtaining the moving average value OCV(t) of the open-circuit voltage, it is possible to correct variations in the measured values of the open-circuit voltage.

Further, calculation unit 650 obtains the depth of charge SOC(t) of the electrolytic solution at time t based on the moving average value OCV(t) of the open-circuit voltage. The depth of charge SOC(t) of the electrolytic solution at time t can be obtained, for example, from equation (1). Further, the depth of charge SOC(t) of the electrolyte at time t may be obtained from the correlation between the depth of charge of the electrolyte and the open-circuit voltage as shown in FIG. The correlation between the depth of charge of the electrolytic solution and the open-circuit voltage can be obtained in advance through experiments. In the present embodiment, since the state of charge SOC(t) of the electrolyte is obtained from the moving average value OCV(t) of the open-circuit voltage without variations, the state of charge of the electrolyte can be accurately grasped.
Calculation unit 650 transmits to setting unit 640 and determination unit 660 a signal representing the calculated depth of charge SOC(t) of the electrolytic solution.

Determination unit 660 of control unit 600 determines the state of charge of the electrolyte based on the depth of charge SOC(t) of the electrolyte at time t. For example, when the depth of charge SOC(t) of the electrolyte is within a predetermined range (10% or more and 90% or less), determination unit 660 determines that the state of charge of the electrolyte is the normal state. Further, when the depth of charge SOC(t) of the electrolyte is smaller than the predetermined range (less than 10%), determination unit 660 determines that the state of charge of the electrolyte is the highly discharged state. When the depth of charge SOC(t) of the electrolyte is, for example, 5% or less, determination unit 660 determines that the state of charge of the electrolyte is the end-of-discharge state. On the other hand, when the state of charge SOC(t) of the electrolyte is greater than the predetermined range (greater than 90%), determination unit 660 determines that the state of charge of the electrolyte is the high state of charge. Furthermore, when the depth of charge SOC(t) of the electrolyte is, for example, 95% or more, determination unit 660 determines that the state of charge of the electrolyte is the end-of-charge state.
Determination unit 660 transmits a signal representing the state of charge of the electrolyte to flow control unit 670 and charge/discharge control unit 680 .

The flow control unit 670 of the control unit 600 controls the flow rates of the positive electrode pump 320a of the positive electrode circulation unit 300a and the negative electrode pump 320c of the negative electrode circulation unit 300c based on the state of charge of the electrolyte. When the state of charge of the electrolytic solution is determined to be the normal state, the flow control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a predetermined first flow rate. Further, when the state of charge of the electrolytic solution is determined to be either a high discharge state or a high charge state, the flow control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a second flow rate that is higher than the first flow rate. do. Further, when the state of charge of the electrolyte is determined to be either the end-of-discharge state or the end-of-charge state, the flow control unit 670 sets the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a third flow rate that is greater than the second flow rate. Control. By controlling the flow rates of the positive electrode pump 320a and the negative electrode pump 320c, overcharging of the electrolyte and overdischarging of the electrolyte can be suppressed.

The charge/discharge control unit 680 of the control unit 600 controls charge/discharge of electric power between the redox flow battery system 10 (that is, the electrolyte of the redox flow battery system 10), the power plant, and the load. For example, when the state of charge of the electrolyte is determined to be the end-of-discharge state, the charge/discharge control unit 680 disconnects the redox flow battery system 10 from the load. Further, when the state of charge of the electrolyte is determined to be the end-of-charge state, the charge/discharge control unit 680 disconnects the redox flow battery system 10 and the power plant. By these controls, overcharging to the electrolyte and overdischarging from the electrolyte can be suppressed.

FIG. 5 shows the hardware configuration of the control unit 600. As shown in FIG. The control unit 600 includes a CPU (Central Processing Unit) 602 , a ROM (Read Only Memory) 604 , a RAM (Random Access Memory) 606 , an input/output interface 608 and a power converter 610 . The CPU 602 executes programs stored in the ROM 604 . A ROM 604 stores programs, data, signals, and the like. RAM 606 stores data. An input/output interface 608 inputs and outputs signals between each unit. The power converter 610 includes an AC/DC converter, a switch connecting the redox flow battery system 10 and the load, a switch connecting the redox flow battery system 10 and the power plant, and the like. The functions of control unit 600 are implemented by executing programs of CPU 602 and the functions of power converter 610 .

Next, a method of operating the redox flow battery system 10 will be described. FIG. 6 is a flow chart showing a method of operating the redox flow battery system 10. As shown in FIG. The operating method of the redox flow battery system 10 includes a measurement step (step S100) of measuring the open-circuit voltage of the battery cell 100, a calculation step (step S200) of obtaining a moving average value of the open-circuit voltage from the measured open-circuit voltage, and a calculation step (step S200). and a control step (S step 300) of controlling charging and discharging of the electrolytic solution based on the moving average value of the open-circuit voltage obtained. Here, as an initial state, the case where the state of charge of the electrolyte is normal (that is, the state of charge SOC is within a predetermined range) and the redox flow battery system 10 is connected to the power plant and the load will be described. do.

In step S100, measurement unit 520 of open-circuit voltage measurement unit 500 measures the open-circuit voltage of monitor cell 510 of open-circuit voltage measurement unit 500, thereby measuring the open-circuit voltage of battery cell 100 indicating the state of charge of the electrolyte. In this embodiment, the open-circuit voltage is measured at intervals of 1 second (measurement interval Δt1=1 sec).

Step S200 includes a step of acquiring a measured value of the open-circuit voltage (step S210), a step of obtaining a moving average value OCV(t) of the open-circuit voltage at time t from the measured value of the open-circuit voltage (step S220), and and a step of determining the depth of charge SOC(t) of the electrolytic solution at time t from the moving average value OCV(t) of the open-circuit voltage (step S230).

In step S<b>210 , acquisition section 620 of control section 600 acquires the measured value of the open-circuit voltage from measurement section 520 . Acquisition unit 620 then transmits a signal representing the measured value of the open-circuit voltage to storage unit 630 and calculation unit 650 of control unit 600 .

In step S220, the calculation unit 650 of the control unit 600 calculates the moving average value OCV(t) of the open-circuit voltage at time t based on the conditions set by the setting unit 640 of the control unit 600 from the open-circuit voltage measurement value. Ask. In the present embodiment, as the initial state, the state of charge of the electrolyte is the normal state (the depth of charge SOC is within a predetermined range). It is set to S1 (S1=60×Δt1, Δt1=1 sec). Therefore, the calculator 650 obtains the moving average value OCV(t) of the open-circuit voltage at the time t under the conditions of the first period S1. By obtaining the moving average value OCV(t) of the open-circuit voltage, it is possible to correct variations in the measured values of the open-circuit voltage.

In step S230, calculation unit 650 obtains the state of charge SOC(t) of the electrolytic solution at time t based on the moving average value OCV(t) of the open-circuit voltage. For example, the electrolyte charging depth SOC(t) is obtained from the correlation between the electrolyte charging depth and the open-circuit voltage. In the present embodiment, since the state of charge SOC(t) of the electrolyte is obtained from the moving average value OCV(t) of the open-circuit voltage without variations, the state of charge of the electrolyte can be accurately grasped.
Calculation unit 650 transmits to setting unit 640 and determination unit 660 a signal representing the calculated depth of charge SOC(t) of the electrolytic solution.

Note that setting unit 640 sets period S for obtaining the moving average value of the open-circuit voltage based on the signal representing the state of charge SOC(t) of the electrolytic solution. That is, when the received depth of charge SOC(t) of the electrolytic solution is within a predetermined range, setting unit 640 sets the moving average value of open-circuit voltage A period S for obtaining OCV(t) is set to the first period S1. Further, when the electrolyte charging depth SOC(t) is smaller than the predetermined range and when the received electrolyte charging depth SOC(t) is greater than the predetermined range, for example, the setting unit 640 changes the open-circuit voltage. A period S for obtaining the average value OCV(t) is set to a second period S2 (S2=5×Δt1, Δt1=1 sec). When the depth of charge of the electrolyte is smaller than the predetermined range and when it is greater than the predetermined range, the setting unit 640 shortens the period S for obtaining the moving average value of the open-circuit voltage. It is possible to quickly respond to changes in the depth of charge and realize stable operation of the redox flow battery system 10 .

Step S300 includes a step of determining the state of charge of the electrolyte (step S310) and a step of controlling the flow rate of the electrolyte and charging/discharging between the power plant and the load (step S320).

In step S310, the determination unit 660 of the control unit 600 determines the state of charge of the electrolyte from the depth of charge SOC(t) of the electrolyte obtained based on the moving average value OCV(t) of the open-circuit voltage. In the present embodiment, as described above, the determination unit 660 determines whether the state of charge of the electrolytic solution is normal (SOC(t): 10% or more and 90% or less) and the high discharge state (SOC(t): 10%). less than), an end-of-discharge state (SOC(t): 5% or less), a high-charge state (SOC(t): greater than 90%), and an end-of-charge state (SOC(t): 95% or more). Judge either. Determination unit 660 transmits a signal representing the state of charge of the electrolyte to flow control unit 670 and charge/discharge control unit 680 of control unit 600 .

In step S320, the flow control section 670 of the control section 600 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c based on the state of charge of the electrolyte. Also, the charge/discharge control unit 680 of the control unit 600 controls charge/discharge of the redox flow battery system 10, the power plant, and the load based on the state of charge of the electrolyte.

Specifically, when the state of charge of the electrolytic solution is the normal state, the flow rate control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a predetermined first flow rate, and the connection control unit 680 controls the redox flow battery. Maintain the operational status of the system 10 and the plant and loads. When the state of charge of the electrolytic solution is either the high discharge state or the high charge state, the flow control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a second flow rate that is larger than the first flow rate, thereby charging and discharging. The control unit 680 maintains the operational states of the redox flow battery system 10, the power plant, and the load. Further, when the state of charge of the electrolytic solution is in the end-of-discharge state, the flow rate control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a third flow rate that is greater than the second flow rate, and the charge/discharge control unit 680 Disconnect the redox flow battery system 10 from the load. Further, when the state of charge of the electrolytic solution is in the end-of-charge state, the flow rate control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a third flow rate that is larger than the second flow rate, and the charge/discharge control unit 680 controls the redox flow rate. Disconnect the flow battery system 10 from the power plant. By these controls, overcharging to the electrolyte and overdischarging from the electrolyte can be suppressed.

After step S320, if no operation stop instruction is input to the control unit 600 (step S322: NO), the operation of the redox flow battery system 10 returns to step S100. When the operation stop instruction is input to the control unit 600 (step S322: YES), the operation of the redox flow battery system 10 is terminated.

As described above, by obtaining the moving average value of the open-circuit voltage, it is possible to correct the variation in the measured value of the open-circuit voltage and accurately grasp the charging depth of the electrolytic solution. Since the control unit 600 obtains the moving average value of the open-circuit voltage according to the charging depth of the electrolytic solution, and controls the charging and discharging of the electrolytic solution based on the obtained moving average value of the open-circuit voltage, the charging depth of the electrolytic solution changes. can be quickly dealt with, and stable operation of the redox flow battery system 10 can be realized.

Furthermore, since the depth of charge of the electrolyte can be accurately grasped, fluctuations in power generation output at renewable energy power plants can be leveled out. Since the depth of charge of the electrolyte can be accurately grasped, it is possible to easily estimate the optimum capacity when increasing the electrolyte capacity, and to easily control power distribution according to load priority in the event of a disaster.

<Embodiment 2>
In Embodiment 1, the charging and discharging of the electrolytic solution is controlled based on the moving average value of the open-circuit voltage. You may control charge/discharge of a liquid. The configurations of the battery cell 100, the circulation unit 300, and the open-circuit voltage measurement unit 500 of the redox flow battery system 10 of the present embodiment are the same as those of the first embodiment. explain.
As with the control unit 600 of the first embodiment, the control unit 600 of the present embodiment includes an acquisition unit 620, a storage unit 630, a setting unit 640, a calculation unit 650, a determination unit 660, and a flow rate control unit 670. , and a charge/discharge control unit 680 .

The acquiring unit 620 of the present embodiment acquires the measured value of the open-circuit voltage measured by the measuring unit 520 of the open-circuit voltage measuring unit 500, like the acquiring unit 620 of the first embodiment. Also, the acquisition unit 620 of the present embodiment acquires the power generation amount from the renewable energy power plant. The acquisition unit 620 of the present embodiment transmits the acquired signal representing the open-circuit voltage measurement value and the acquired signal representing the power generation amount to the storage unit 630 and the calculation unit 650 .
The storage unit 630 of the present embodiment stores programs, data, open-circuit voltage measurement values, and the like, like the storage unit 630 of the first embodiment.

The setting unit 640 of the present embodiment sets conditions for the calculation unit 650 to obtain the moving average value of the open-circuit voltage and the moving average value of the power generation amount. In this embodiment, as in the first embodiment, the interval Δt1 for calculating the moving average value is set to 1 second (Δt1=1 sec). Further, when the depth of charge of the electrolytic solution is within the predetermined range, the setting unit 640 of the present embodiment sets the period S for obtaining the moving average value to a predetermined first period S1=60 seconds. When the depth of charge of the electrolyte is smaller than the predetermined range and when the depth of charge of the electrolyte is greater than the predetermined range, the setting unit 640 of the present embodiment sets the period S for obtaining the moving average value to a predetermined first A predetermined second period S2=5 seconds shorter than the period S1 is set (S2=5×Δt1, n=5). The setting unit 640 of this embodiment transmits a signal representing the set conditions to the calculation unit 650 .

Based on the conditions set by the setting unit 640, the calculation unit 650 of the present embodiment calculates the moving average value OCV(t) of the open-circuit voltage at time t and the depth of charge of the electrolyte at time t from the measured value of the open-circuit voltage. Obtain SOC(t). The moving average value OCV(t) of the open-circuit voltage and the depth of charge SOC(t) of the electrolyte are obtained in the same manner as in the first embodiment. Calculation unit 650 of the present embodiment transmits a signal representing the calculated depth of charge SOC(t) of the electrolytic solution to setting unit 640 and determination unit 660 .

Further, the calculation unit 650 of the present embodiment calculates the moving average value REP(t) of the power generation amount at time t from the acquired power generation amount based on the conditions set by the setting unit 640, and A difference Δp between the calculated power generation amount and the moving average value REP(t) is calculated. The moving average value REP(t) of the power generation amount at time t is obtained in the same manner as the moving average value OCV(t) of the open-circuit voltage. The calculator 650 of the present embodiment transmits a signal representing the obtained difference Δp to the charge/discharge controller 680 .

As with the determination unit 660 of the first embodiment, the determination unit 660 of the present embodiment determines the state of charge of the electrolyte based on the depth of charge SOC(t) of the electrolyte at time t. Further, the determination unit 660 of the present embodiment transmits a signal indicating the state of charge of the electrolyte to the flow control unit 670 and the charge/discharge control unit 680 .

Similar to the flow control unit 670 of the first embodiment, the flow control unit 670 of the present embodiment controls the flow rate of the positive electrode pump 320a of the positive electrode circulation unit 300a and the negative electrode pump 320c of the negative electrode circulation unit 300c based on the state of charge of the electrolytic solution. to control. Control of the flow rates of the positive electrode pump 320a and the negative electrode pump 320c is the same as the control of the first embodiment.

The charge/discharge control unit 680 of the present embodiment controls charge/discharge of electric power between the redox flow battery system 10, the power plant, and the load, similarly to the charge/discharge control unit 680 of the first embodiment. Control of charging and discharging of electric power is the same as the control of the first embodiment.

Further, the charging/discharging control unit 680 of the present embodiment controls the charging/discharging of the electrolytic solution based on the obtained moving average value REP(t) of the power generation amount. Specifically, when the difference Δp between the amount of power generation and the moving average value REP(t) of the amount of power generation is positive (that is, when the amount of power generation is greater than the moving average value REP(t) of the amount of power generation), this The charge/discharge control unit 680 of the embodiment charges the electrolytic solution by the difference Δp of the power generation amount of the power plant. On the other hand, if the difference Δp between the amount of power generation and the moving average value REP(t) of the amount of power generation is negative (that is, if the amount of power generation is smaller than the moving average value REP(t) of the amount of power generation), The charge/discharge control unit 680 discharges the electrolyte by the difference Δp. Further, when the difference Δp between the power generation amount and the moving average value REP(t) of the power generation amount is zero, the charge/discharge control unit 680 of the present embodiment neither charges nor discharges. This makes it possible to absorb instantaneous output fluctuations of renewable energy power generation that are influenced by nature. FIG. 7 shows an example of the relationship between the amount of solar power generation, the charge/discharge power from the redox flow battery system 10, and the solar power output after charge/discharge control (result of absorption of fluctuations in the amount of solar power generation). In FIG. 7, the moving average value REP(t) of the amount of solar power generation is temporarily set to 3 kW. As shown in FIG. 7, based on the moving average value REP(t) of the power generation amount, by controlling the charging and discharging of the redox flow battery system 10 (the electrolyte of the redox flow battery system 10), the renewable energy power plant power generation fluctuations can be leveled in real time.

In this embodiment, the charge/discharge control unit 680 controls charge/discharge of the electrolytic solution based on the moving average value of the power generation amount, and the flow rate control unit 670 controls the positive electrode pump 320a and the negative electrode pump 320a based on the moving average value of the open circuit voltage. Controls the flow rate of pump 320c. Since the moving average value of the power generation amount of the renewable energy power plant represents the short-term or long-term trend of the power generation amount of the renewable energy power plant, the redox flow battery system 10 can monitor the power generation fluctuation of the renewable energy power plant in real time. can be leveled. Furthermore, as in Embodiment 1, overcharging of the electrolyte and overdischarging of the electrolyte can be suppressed, changes in the charging depth of the electrolyte can be quickly handled, and the redox flow battery system 10 can be operated stably. can be realized.

<Modification>
Although the embodiments have been described above, the present disclosure can be modified in various ways without departing from the gist of the present disclosure.

For example, the active materials of the positive electrode electrolyte PL and the negative electrode electrolyte NL are not limited to vanadium ions. The active materials of the positive electrode electrolyte PL and the negative electrode electrolyte NL may be iron ions and chromium ions, respectively.

In the first embodiment, when the depth of charge of the electrolyte is within a predetermined range, the setting unit 640 sets the period S for obtaining the moving average value of the open-circuit voltage to a predetermined first period S1, and the depth of charge of the electrolyte is outside the predetermined range, the period S for obtaining the moving average value of the open-circuit voltage is set to a predetermined second period S2 shorter than the predetermined first period S1. The setting unit 640 may set the period S for obtaining the moving average value of the open-circuit voltage to a third period S3 (for example, S3=120×Δt1, n=120) longer than the predetermined first period S1.

For example, when the depth of charge of the electrolytic solution is within a predetermined range, the setting unit 640 sets the period S for obtaining the moving average value of the open-circuit voltage to a predetermined first period S1 and a third period S3. The calculation unit 650 obtains the moving average value of the open-circuit voltage in the first period S1 and the moving average value of the open-circuit voltage in the third period S3, and further calculates the depth of charge of the electrolytic solution in the first period S1 and the third period S1. The charging depth of the electrolytic solution in the period S3 is obtained. If the difference between the depth of charge of the electrolyte in the first period S1 and the depth of charge of the electrolyte in the third period S3 is within a predetermined range, determination unit 660 determines that the state of charge of the electrolyte is stable. do. When it is determined that the state of charge of the electrolyte is stable, the flow control unit 670 controls the flow rates of the positive electrode pump 320a and the negative electrode pump 320c to a third flow rate that is smaller than the predetermined first flow rate. Thereby, the redox flow battery system 10 can be operated with power saving.

The measurement interval (Δt0) of the open-circuit voltage of the battery cell 100, the interval (Δt1) for obtaining the moving average value of the open-circuit voltage, and the period S (S1 to S3) for obtaining the moving average value of the open-circuit voltage are arbitrary.

In the first and second embodiments, the determination unit 640 determines the state of charge of the electrolyte from the state of charge SOC(t) of the electrolyte obtained based on the moving average value OCV(t) of the open-circuit voltage. there is Determination unit 640 may directly determine the state of charge of the electrolyte from the moving average value OCV(t) of the open-circuit voltage without using the state of charge SOC(t) of the electrolyte. Since there is a correlation between the depth of charge of the electrolyte and the open-circuit voltage of the battery cell 100, the determination unit 640 determines the electrolyte from the moving average value OCV(t) of the open-circuit voltage based on the previously obtained correlation. may be determined. In this case, calculation unit 650 does not have to obtain the depth of charge SOC(t) of the electrolytic solution. Moreover, the setting unit 640 sets conditions for obtaining the moving average value based on the obtained moving average value OCV(t) of the open-circuit voltage.

In the second embodiment, the moving average value OCV(t) of the open-circuit voltage and the moving average value REP(t) of the power generation amount are obtained. It is preferable that the period S for obtaining the moving average value OCV(t) of the open-circuit voltage and the moving average value REP(t) of the power generation amount be equal.

The control unit 600 may include dedicated hardware such as, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and a control circuit. In this case, each of the processes may be performed by separate hardware. Also, each of the processes may be collectively executed by a single piece of hardware. Part of the processing may be performed by dedicated hardware, and another part of the processing may be performed by software or firmware.

10 redox flow battery system, 100 battery cell, 105a positive electrode, 105c negative electrode, 110a positive electrode chamber, 110c negative electrode chamber, 120 diaphragm, 300 circulation unit, 300a positive electrode circulation unit, 300c negative electrode circulation unit, 310a positive electrode electrolyte storage tank, 320a positive electrode Pump 322a Positive electrode supply pipe 324a Supply branch pipe 326a First positive electrode recovery pipe 328a Second positive electrode recovery pipe 310c Negative electrode electrolyte reservoir 320c Negative electrode pump 322c Negative electrode supply pipe 324c Supply branch pipe 326c First first positive electrode recovery pipe Negative electrode recovery tube 328c Second negative electrode recovery tube 500 Open circuit voltage measurement unit 510 Monitor cell 520 Measurement unit 600 Control unit 602 CPU 604 ROM 606 RAM 608 Input/output interface 610 Power converter 620 Acquisition Part 630 Storage Part 640 Setting Part 650 Calculation Part 660 Determination Part 670 Flow Control Part 680 Charge/Discharge Control Part PL Positive Electrolyte Solution NL Negative Electrolyte Solution

Claims (7)

a battery cell having a positive electrode chamber in which a positive electrode is arranged, a negative electrode chamber in which a negative electrode is arranged, and a diaphragm separating the positive electrode chamber and the negative electrode chamber;
a circulation unit that circulates a positive electrode electrolyte in the positive electrode chamber and circulates a negative electrode electrolyte in the negative electrode chamber;
an open-circuit voltage measuring unit that measures the open-circuit voltage of the battery cell;
A moving average value of the open-circuit voltage measured by the open-circuit voltage measuring unit is obtained according to the charge depth of the positive electrode electrolyte and the negative electrode electrolyte, and based on the obtained moving average value of the open-circuit voltage, the A control unit that controls charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte,
Redox flow battery system. The control unit obtains a moving average value of the open-circuit voltage in a predetermined first period and a moving average value of the open-circuit voltage in a predetermined second period shorter than the predetermined first period,
When the depths of charge of the positive electrode electrolyte and the negative electrode electrolyte are within a predetermined range, the controller controls the positive electrode electrolyte and the negative electrode electrolyte based on the moving average value of the open-circuit voltage in the predetermined first period. Control the charging and discharging of the negative electrode electrolyte,
When the depths of charge of the positive electrolyte and the negative electrolyte are smaller than the predetermined range and when the depths of charge of the positive electrolyte and the negative electrolyte are greater than the predetermined range, the control unit , controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte based on the moving average value of the open-circuit voltage in the predetermined second period;
The redox flow battery system of claim 1. The control unit obtains a moving average value of the open-circuit voltage in a predetermined third period longer than the predetermined first period, and obtains a moving average value of the open-circuit voltage in the predetermined third period and the predetermined third period. controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte based on the difference between the moving average value of the open circuit voltage in one period;
The redox flow battery system according to claim 2. The control unit obtains a moving average value of the open-circuit voltage in a predetermined first period and a moving average value of the open-circuit voltage in a predetermined third period longer than the predetermined first period. controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte based on the difference between the moving average value of the open circuit voltage in the three periods and the moving average value of the open circuit voltage in the predetermined first period;
The redox flow battery system of claim 1. The control unit controls charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte by controlling the flow rates of the positive electrode electrolyte and the negative electrode electrolyte.
The redox flow battery system according to any one of claims 1-4. The control unit obtains a power generation amount of a renewable energy power plant connected to the battery cell, obtains a moving average value of the power generation amount, and calculates the positive electrode based on the obtained moving average value of the power generation amount. controlling charging and discharging of the electrolyte and the negative electrode electrolyte;
The redox flow battery system according to any one of claims 1-5. a measuring step of measuring the open-circuit voltage of the battery cell;
From the measured open-circuit voltage, a moving average value of the open-circuit voltage is calculated according to the charge depth of the positive electrode electrolyte supplied to the positive electrode chamber of the battery cell and the negative electrode electrolyte supplied to the negative electrode chamber of the battery cell. a desired calculation process;
a control step of controlling charging and discharging of the positive electrode electrolyte and the negative electrode electrolyte based on the obtained moving average value of the open-circuit voltage;
A method of operating a redox flow battery system.

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