KR20240081212A - Shunt current decreasing apparatus of electrolyte manufacturing facility - Google Patents

Abstract

This specification discloses an electrolyte manufacturing facility capable of reducing shunt current. The electrolyte manufacturing facility according to the present specification includes K unit modules; and an electrolyte tank supplying electrolyte to each of the K unit modules, wherein each unit module includes M unit stacks, and each unit stack includes N anodes, cathodes, and separators. A string may be formed that includes unit redox flow battery (RFB) cells, and unit stacks that do not share an electrolyte among the unit stacks are electrically connected in series.

Description

Shunt current reduction device in electrolyte manufacturing facility {SHUNT CURRENT DECREASING APPARATUS OF ELECTROLYTE MANUFACTURING FACILITY}

The present invention relates to an electrolyte manufacturing facility for a redox flow battery, and more specifically, to a stack configuration and voltage balancing circuit that can prevent loss due to shunt current between a redox flow stack composed of a plurality of redox flow battery cells. It's about.

Currently, various secondary batteries for ESS (Energy Storage System) are being researched. Among secondary batteries, lithium-ion batteries are the most commercialized, but are still imperfect in terms of stability and lifespan. Therefore, the development of other types of secondary batteries, such as redox flow batteries (RFB), is actively underway. RFB uses the oxidation-reduction reaction between two substances, and among them, the zinc-bromine flow battery (Zn-Br flow battery) is a battery based on the oxidation-reduction reaction between zinc and bromine, and has three characteristics: output and capacity autonomy, It has advantages such as price.

Public Patent Publication No. 10-2018-0105937 (2018.10.01)

The purpose of this specification is to provide an electrolyte manufacturing facility capable of reducing shunt current. Furthermore, an additional purpose is to provide a circuit that can efficiently resolve voltage imbalance occurring between redox flow stacks.

The present specification is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

The electrolyte manufacturing facility according to the present specification for solving the above-described problems includes K unit modules; and an electrolyte tank supplying electrolyte to each of the K unit modules, wherein each unit module includes M unit stacks, and among the unit stacks, unit stacks that do not share electrolyte are electrically connected to each other. You can construct strings connected in series.

According to an embodiment of the present specification, the string may be M strings in which each unit stack selected from each unit module is electrically connected in series.

According to an embodiment of the present specification, each string may be composed of a stack having the same location within each unit module.

The electrolyte manufacturing facility according to the present specification may further include a voltage balancing device that controls voltage balancing of each string by measuring the voltage of a unit stack included in each string.

According to an embodiment of the present specification, the voltage balancing device includes an auxiliary power battery; a balancing connection unit electrically connecting the auxiliary power battery and at least one unit stack among K unit stacks included in the string by a balancing control signal; and a balancing control unit that monitors the voltage of the unit stack included in the string and outputs a control signal to the balancing connection unit corresponding to the unit stack requiring voltage balancing.

According to another embodiment of the present specification, the voltage balancing device includes a discharge resistor connected between both ends of a unit stack; a switching element connected between the unit stack and the discharge resistor and operated by a control signal; and a balancing control unit that monitors the voltage of the unit stack included in the string and outputs a control signal to a switching element corresponding to the unit stack requiring voltage balancing.

Other specific details of the invention are included in the detailed description and drawings.

According to one aspect of the present specification, unnecessary energy loss can be prevented by reducing shunt current.

According to another aspect of the present specification, the charging and discharging efficiency of the electrolyte manufacturing facility can be improved by creating a voltage imbalance between the stacks.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

Figure 1 is a reference diagram of the chemical reaction within the stack.
Figure 2 is a reference diagram for cells, stacks, and pipes.
Figure 3 is a reference diagram for electrical wiring when five stacks are connected in series.
Figure 4 is a reference diagram for resistance due to shunt current generation.
Figure 5 is an electrical wiring diagram of an electrolyte manufacturing facility according to the present specification.
Figure 6 is an exemplary diagram briefly showing the physical configuration of an electrolyte manufacturing facility according to the present specification.
Figure 7 is a reference diagram for stack wiring according to the present specification.
Figure 8 is an example circuit diagram of a voltage balancing device.
Figure 9 is a configuration diagram of the experiment module.
Figure 10 is a reference diagram for electrical wiring in an experimental example.
Figure 11 is a reference diagram for the amount of shunt current generated depending on the stack position.
Figure 12 is a reference diagram showing the increase in the amount of electrically connected stack.
Figure 13 is a reference diagram for checking the amount of shunt current according to the stack distance.
Figure 14 is a reference diagram for the electrical wiring in which three stacks are connected.

The advantages and features of the invention disclosed in this specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present specification is not limited to the embodiments disclosed below and may be implemented in various different forms, and the present embodiments are merely intended to ensure that the disclosure of the present specification is complete and to provide a general understanding of the technical field to which the present specification pertains. It is provided to fully inform those skilled in the art of the scope of this specification, and the scope of rights of this specification is only defined by the scope of the claims.

The terms used in this specification are for describing embodiments and are not intended to limit the scope of this specification. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other elements in addition to the mentioned elements. Like reference numerals refer to like elements throughout the specification, and “and/or” includes each and every combination of one or more of the referenced elements. Although “first”, “second”, etc. are used to describe various components, these components are of course not limited by these terms. These terms are merely used to distinguish one component from another. Therefore, it goes without saying that the first component mentioned below may also be a second component within the technical spirit of the present invention.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with meanings commonly understood by those skilled in the art to which this specification pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless clearly specifically defined.

Spatially relative terms such as “below”, “beneath”, “lower”, “above”, “upper”, etc. are used as a single term as shown in the drawing. It can be used to easily describe the correlation between a component and other components. Spatially relative terms should be understood as terms that include different directions of components during use or operation in addition to the directions shown in the drawings. For example, if you flip a component shown in a drawing, a component described as "below" or "beneath" another component will be placed "above" the other component. You can. Accordingly, the illustrative term “down” may include both downward and upward directions. Components can also be oriented in other directions, so spatially relative terms can be interpreted according to orientation.

Currently, various batteries for ESS are being studied. Although LiB Battery is close to commercialization, complete verification in terms of stability and lifespan has not yet been achieved. Therefore, development of other types of batteries, such as Redox flow batteries, is actively underway. RFB uses the chemical reaction of the Redox couple, and among them, the Vanadium flow battery is a battery based on the chemical reaction within the stack and has advantages such as output, capacity autonomy, and price.

However, during the reaction, the shunt current flowing through the electrolyte in the stack and pipe is unbalanced, resulting in loss of energy in the stack. To solve this phenomenon, we analyze the structure of shunt current generation within the stack and try to minimize its occurrence. The purpose of this development is to analyze the process and extent of such shunt current generation and to minimize the occurrence by differentiating the electrical wiring between stacks that share electrolyte.

Figure 1 is a reference diagram of the chemical reaction within the stack.

Referring to Figure 1, in a zinc-bromine flow battery, a chemical reaction occurs at the anode (anode electrolyte) and the cathode (cathode electrolyte) as shown in the reaction equation below with a separator in between.

Cathode: Zn ²⁺ + 2e ^- ↔ Zn (-0.77V)

Anode: 2Br ^- ↔ Br ₂ + 2e ^- (+1.08V)

The unit cell where the reaction occurs generates a voltage of approximately 1.2 to 1.85 V depending on the charging and discharging state. To obtain the required voltage, a stack is formed by connecting multiple unit cells in series. The stack can have about 60 to 100 unit cells connected in series to obtain an output voltage of about 100 to 120 V. Additionally, to configure a large-capacity ESS, the required high voltage can be obtained by connecting the stacks again in series.

Meanwhile, shunt current is indispensable in RFB, which is based on the chemical reaction of an electrolyte through which current can flow. The tendency of the shunt current varies depending on the path through which the electrolyte flows. The electrolyte passes through a path called a channel inside the cell, a manifold, which is an inflow path created when cells are fused in series, and a pipe connected to the stack. do.

Figure 2 is a reference diagram for cells, stacks, and pipes.

In a redox flow battery, which is based on the chemical reaction of an electrolyte that allows current to flow, shunt current is indispensable. The tendency of the shunt current varies depending on the path through which the electrolyte flows. The electrolyte flows through a path called a channel inside a cell and a manifold, which is an inflow path created when cells are fused in series. It passes through a pipe connected to the stack. Accordingly, the types of shunt current and resistance can be defined as the three types mentioned above. Therefore, energy loss occurs due to the shunt current, and there is a need to reduce it.

Figure 3 is a reference diagram for electrical wiring when five stacks are connected in series.

Referring to Figure 3, when connected in ideal series, the current between stacks, which can be confirmed by electrical wiring, is the same. This means that there is no internal shunt current generation, which means there is no loss. However, in the actual experiment, it was confirmed that the current generated in the wiring between stacks and the current in the output terminal connected to DC-Link are different. This means that shunt current occurs inside the stack. In particular, in a no-load state, the current at the output stage is 0A, but it was confirmed that the internal current flows at 2~3A.

Figure 4 is a reference diagram for resistance due to shunt current generation.

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

Figure 5 is an electrical wiring diagram of an electrolyte manufacturing facility according to the present specification.

The electrolyte manufacturing facility 100 according to the present specification may include K unit modules 110 and an electrolyte tank 112 that supplies electrolyte to each of the K unit modules.

Each unit module 110 may include M unit stacks 111.

Each unit stack 111 may include N unit redox flow battery (RFB) cells including an anode, a cathode, and a separator.

The redox flow battery cell has been described with reference to FIG. 1, and since it is a technology widely known to those skilled in the art, detailed description will be omitted.

The K, M, and N are natural numbers, and the K, M, and N can be set in various ways depending on the required charge/discharge capacity, output voltage, etc. In this specification, for convenience of explanation, a unit module is composed of 10 unit stacks, and the description will focus on an electrolyte manufacturing facility composed of 8 unit modules. However, it is emphasized once again that the present invention is not limited to the examples described herein and that various changes and settings are possible.

Figure 6 is an exemplary diagram briefly showing the physical configuration of an electrolyte manufacturing facility according to the present specification.

Referring to Figure 6, 'A to J' are symbols for distinguishing the unit stack 111 included in each unit module 110, and '1 to 8' are unit modules included in the electrolyte manufacturing facility 100. This is a symbol to distinguish (110). Therefore, the symbol 'A1' means the first unit stack included in unit module 1. And 'Tank 1~ Tank 8' refers to electrolyte tanks that supply electrolyte to unit modules 1 through 8, respectively. That is, each unit module 110 included in the electrolyte manufacturing facility 100 according to the present specification receives electrolyte from separate electrolyte tanks.

The electrolyte manufacturing facility 100 according to the present specification may configure a string in which unit stacks that do not share electrolyte among the unit stacks are electrically connected in series to reduce shunt current.

Figure 7 is a reference diagram for stack wiring according to the present specification.

Referring to Figure 7, parallel connection of the stack within the module, serial connection of the bus-bar between modules, and connection of one DC/DC converter at both ends are possible. By connecting all stacks in the module in parallel to maintain the same potential, shunt current can be prevented and self-balancing can be maintained. In addition, by connecting modules in series, the voltage can be boosted and a constant current can be maintained to maintain an appropriate level of current applied to the converter. Through this, converter power conversion losses can be minimized by operating at high voltage.

The string may be M strings in which each unit stack selected from each unit module 110 is electrically connected in series. In other words, one stack is included in only one string and is not connected to two or more strings.

At this time, each string may be configured as a stack with the same location within each unit module. That is, as shown in FIG. 6, the first string is a string composed only of the 'A'th stack included in each module 110. The second string is a string composed only of the 'B'th stack included in each module 110, the third string is a string composed only of the 'C'th stack included in each module 110, and the fourth string is a string composed of only the 'C'th stack included in each module 110. It is a string composed only of the 'D'th stack included in each module 110, the fifth string is a string composed only of the 'E'th stack included in each module 110, and the sixth string is a string composed of only the 'E'th stack included in each module 110. ), the 7th string is a string composed only of the 'G'th stack included in each module 110, and the 8th string is a string composed of only the 'G'th stack included in each module 110. The 9th string is a string composed only of the 'H'th stack, the 9th string is a string composed of only the 'I'th stack included in each module 110, and the 10th string is a string composed of only the 'J'th stack included in each module 110. It is a string composed only of a stack.

The order between stacks connected in series within each string takes into account the physical distance where each stack is located so that adjacent stacks are connected in order.

Through the configuration of the string according to the present specification, the shunt current generated through the manifold and pipe can be minimized. In other words, electrical connection between unit stacks using the same electrolyte supplied from each electrolyte tank can be avoided to minimize the occurrence of shunt current caused by electrolyte sharing.

However, since stacks selected from different unit stacks according to the present specification form a string, voltage imbalance between stacks within the string may worsen.

Therefore, the electrolyte manufacturing facility 100 according to the present specification may further include a voltage balancing device that controls voltage balancing of each string by measuring the voltage of the unit stack included in each string.

The voltage balancing device can adjust voltage balancing in two ways. One method is to increase the voltage of a stack that is relatively lower than the voltage of other stacks (Active Balancing), and the other method is to lower the voltage of a stack that is relatively higher than the voltage of other stacks (Passive Balancing).

8 is an example circuit diagram of a voltage balancing device.

According to an embodiment of the present specification, the voltage balancing device electrically connects the auxiliary power battery and at least one unit stack among the K unit stacks included in the string by a balancing control signal. It may further include a balancing control unit that monitors the voltage of the connection unit and the unit stack included in the string, and outputs a control signal to the balancing connection unit corresponding to the unit stack requiring voltage balancing. The voltage balancing device can be used in standby mode, charging mode, and discharging mode of an electrolyte manufacturing facility.

According to another embodiment of the present specification, the voltage balancing device includes a discharge resistor connected between both ends of a unit stack, a switching element connected between the unit stack and the discharge resistor and operated by a control signal, and a unit included in the string. It may further include a balancing control unit that monitors the voltage of the stack and outputs a control signal to a switching element corresponding to a unit stack requiring voltage balancing. The voltage balancing device can be used in standby mode and charging mode. For example, in the voltage balancing, the balancing control unit detects the voltage of each stack, and when the voltage of the other stack differs by more than 1V based on the lowest voltage among the stacks included in the string, the control signal is output to discharge. Resistance allows current to flow. In addition, the balancing control unit may output the control signal to prevent current from flowing through the discharge resistor when the voltage of the other stacks is 100 mV or less based on the lowest voltage among the stacks included in the string.

The balancing control unit may include a processor, an application-specific integrated circuit (ASIC), other chipsets, logic circuits, registers, communication modems, data processing devices, etc. known in the art to calculate and execute various control logic. You can. Additionally, when the above-described control logic is implemented as software, the control unit 140 may be implemented as a set of program modules. At this time, the program module may be stored in the memory unit and executed by the processor.

The above-mentioned computer program is C/C++, C#, JAVA that the processor (CPU) of the computer can read through the device interface of the computer in order for the computer to read the program and execute the methods implemented in the program. , may include code coded in computer languages such as Python and machine language. These codes may include functional codes related to functions that define the necessary functions for executing the methods, and include control codes related to execution procedures necessary for the computer's processor to execute the functions according to predetermined procedures. can do. In addition, these codes may further include memory reference-related codes that indicate at which location (address address) in the computer's internal or external memory additional information or media required for the computer's processor to execute the above functions should be referenced. there is. In addition, if the computer's processor needs to communicate with any other remote computer or server in order to execute the above functions, the code uses the computer's communication module to determine how to communicate with any other remote computer or server. It may further include communication-related codes regarding whether communication should be performed and what information or media should be transmitted and received during communication.

The storage medium refers to a medium that stores data semi-permanently and can be read by a device, rather than a medium that stores data for a short period of time, such as a register, cache, or memory. Specifically, examples of the storage medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc., but are not limited thereto. That is, the program may be stored in various recording media on various servers that the computer can access or on various recording media on the user's computer. Additionally, the medium may be distributed to computer systems connected to a network, and computer-readable code may be stored in a distributed manner.

<Experimental example>

Figure 9 is a configuration diagram of the experiment module.

In order to analyze the trend of shunt current, a test bed consisting of 10 stacks of 5 in series and 2 sets was prepared. The internal flow path of the cell is designated as a fixed variable that cannot be changed (channelt shunt), and the shunt current trend is determined according to the number of stacks connected in series (manifold shunt) or the distance of the pipe (pipe shunt). I experimented to find out.

Figure 10 is a reference diagram for electrical wiring in an experimental example.

When five stacks sharing the electrolyte mentioned in FIGS. 9 and 10 are electrically connected in series, the estimated experimental results are shown in Table 1.

<Table 1>

The shunt current estimated from the above results is shown in Table 2.

<Table 2>

Figure 11 is a reference diagram for the amount of shunt current generated depending on the stack position.

Referring to FIG. 11, the amount of shunt current generated increased toward the center of the stack, and the amount of shunt current generated in the loaded state and unloaded state was similar at approximately 2 to 4 A.

Figure 12 is a reference diagram showing the increase in the amount of electrically connected stack.

As shown in FIG. 12, the increase in shunt current as the number of stacks electrically connected in series increases can be seen in Table 3.

<Table 3>

It was confirmed that the serial connection stack increased by approximately 1A per unit. Next, to determine the trend of shunt current at each position when two stacks are connected in series, the wiring was changed and tested as follows.

Figure 13 is a reference diagram for checking the amount of shunt current according to the stack distance.

As shown in Figure 13, the results of checking the amount of shunt current according to the stack distance can be found in Table 4.

<Table 4>

As a result of the experiment, 1.2~1.3A was generated based on connecting two adjacent stacks in series. When one stack was skipped and connected, there was a tendency for the power to decrease by approximately 0.1A per stack. This can be inferred from the result that when the stack shares electrolyte in series, the shunt current decreases when the manifold is spaced apart.

Figure 14 is a reference diagram for the electrical wiring in which three stacks are connected.

Referring to FIG. 14, you can see an example where three adjacent stacks are electrically connected and an example where three stacks that are separated from each other are electrically connected. The measured values in each case are shown in Table 5.

<Table 5>

Based on connecting three adjacent stacks in series, a shunt current of 2.08A was generated at no load, but when the distance between the stacks was increased, 1.75A was generated, a decrease of approximately 0.33A. Compared to the experiment by distance when connecting the previous two stacks in series, it was confirmed that 1A increased due to the addition of one stack, but that approximately 0.1 to 0.15A was reduced due to the distance of one stack.

An experiment was conducted to determine the tendency of the shunt current generated by the electrolyte in the pipe as shown below, but the difference was not significant (△A=0.09). It was confirmed that when the distance between stacks was extremely large, a slightly greater shunt current occurred.

Although the embodiments of the present specification have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features. You will be able to understand it. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.

Claims (6)

K unit modules; and
An electrolyte manufacturing facility comprising an electrolyte tank that supplies electrolyte to each of the K unit modules,
Each unit module includes M unit stacks,
An electrolyte manufacturing facility comprising a string in which unit stacks that do not share an electrolyte among the unit stacks are electrically connected in series. In claim 1,
The string is an electrolyte manufacturing facility, characterized in that M strings are electrically connected in series to each unit stack selected from each unit module. In claim 1,
An electrolyte manufacturing facility, characterized in that each string is composed of a stack having the same position within each unit module. In claim 1,
An electrolyte manufacturing facility further comprising a voltage balancing device that controls the voltage balancing of each string by measuring the voltage of the unit stack included in each string. In claim 4,
The voltage balancing device,
Auxiliary power battery;
a balancing connection unit electrically connecting the auxiliary power battery and at least one unit stack among K unit stacks included in the string by a balancing control signal; and
An electrolyte manufacturing facility further comprising a balancing control unit that monitors the voltage of the unit stack included in the string and outputs a control signal to the balancing connection unit corresponding to the unit stack requiring voltage balancing. In claim 5,
The voltage balancing device,
A discharge resistor connected between both ends of the unit stack;
a switching element connected between the unit stack and the discharge resistor and operated by a control signal; and
An electrolyte manufacturing facility further comprising a balancing control unit that monitors the voltage of the unit stack included in the string and outputs a control signal to the switching element corresponding to the unit stack requiring voltage balancing.