CN116053532A - Flow battery pile control device and control method, flow battery pile and energy storage system - Google Patents
Flow battery pile control device and control method, flow battery pile and energy storage system Download PDFInfo
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
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- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
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- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
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- H—ELECTRICITY
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- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
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Abstract
The application provides a control device and a control method for a flow battery stack, the flow battery stack and an energy storage system. The device comprises a detection circuit, a plurality of compensation circuits and a controller. The flow battery stack comprises a plurality of single batteries connected in series. The detection circuit detects the voltage of the single cells, and when the voltage value of one or more single cells deviates from the voltage balance reference value, the controller instructs the compensation circuit to adjust the voltage value of the single cells so as to maintain the voltage consistency of the flow battery stack. When the voltage of the single cell in the flow battery stack or the voltage of the flow battery stack exceeds the upper voltage limit value or is smaller than the lower voltage limit value, the failed single cell or the whole flow battery stack is bypassed. In addition, the device and the control method can also realize accurate measurement of the voltage and the SOC of the flow battery and realize intelligent management of the flow battery stack.
Description
Technical Field
The application relates to the field of energy storage, in particular to a flow battery pile device, a control method and an energy storage system.
Background
The energy structure of China is fast to adjust, and new energy gradually replaces traditional fossil energy. The Chinese operators are wide, have rich solar energy and wind energy resources, but the natural energy has the characteristics of intermittence, volatility and the like, and can be directly integrated into a power grid with great difficulty, and the natural energy must be subjected to smoothing treatment. Meanwhile, the power supply and demand often have a mismatch in time and space, and exhibit a peak Gu Boduan, and an imbalance in area, etc. The important way to solve the problems is an energy storage technology, especially electrochemical energy storage has the advantages of high efficiency, high response speed, flexible configuration, no limitation of geographical environment, environmental friendliness, low life cycle and the like, is suitable for smooth treatment of wind-solar power generation, energy storage of a power grid side and electric energy management of a demand side.
Energy storage technology is a technology that stores energy in different forms through a specific device or physical medium in different ways for later use when needed. According to the specific mode, the method is divided into physical energy storage, electrochemical energy storage and chemical energy storage technologies. The physical energy storage means that the medium for storing energy achieves the purpose of energy storage through the change of physical forms of the medium, and the physical energy storage comprises the energy storage technologies such as pumped storage, compressed air energy storage, flywheel energy storage, superconducting energy storage, super capacitor energy storage, heat storage, cold storage and the like. Chemical energy storage refers to the purpose of storing energy by manufacturing or generating new chemical substances, including modes of electro-hydrogen production, electro-chemical production and the like. Electrochemical energy storage refers to the energy storage technology of lead-acid batteries, lithium ion batteries, flow batteries, sodium-sulfur batteries, nickel-hydrogen batteries, electrochemical capacitors, metal-air batteries and the like, wherein the purpose of energy storage is achieved through electrochemical change of an energy storage medium. Compared with other electrochemical energy storage technologies, the flow battery has the characteristics of high safety and ultra-long cycle life, and is particularly suitable for large-scale energy storage power stations.
The flow battery is a liquid-phase electrochemical energy storage device, active substances of the flow battery are completely dissolved in electrolyte, and energy storage and release are realized through oxidation valence state change of active elements, so that the flow battery belongs to a redox battery. In general, a flow battery needs two redox couples to form an anode and a cathode, and oxidation valence states (potentials) of active elements of the anode and the cathode change correspondingly along with the charge and discharge processes of the battery.
Flow batteries are one of the mainstream energy storage technology routes, and recently global flow batteries store energy into a rapid development channel. The flow battery stack is a core component of an energy storage system and is a place where energy conversion occurs. Flow cell stacks are composed of tens to hundreds of single cells in series, and a single flow cell stack is typically composed of thousands of components, which presents a significant challenge for cell uniformity within the flow cell stack. The consistency of the cells in the flow battery pile is improved, the reliability and the service life of the pile can be improved, and the LCOS (Levelized Cost of Storage energy storage sharing cost) is reduced, so that the flow battery pile is a key technology development field and industry development direction. The flow battery pile is an aggregate of 'materials-structures-processes', and is also a coupling body of 'reaction-multiphase-electric field-heat', and is the most complex key device in a flow battery system. The flow battery pile is easy to generate battery series mismatch, so that a wooden barrel effect is caused, the whole pile cannot work, serious economic loss is caused, and the operation and maintenance difficulty is high. In addition, the performance of the electric pile is poor, the detection of the SOC (state of charge) of the battery is inaccurate, and great SOC deviation among the batteries also brings great challenges for the development of the flow battery technology.
Disclosure of Invention
The application provides a control device and a control method for a flow battery, which can maintain the voltage consistency of the flow battery pile, when a single cell in the flow battery pile breaks down, the broken single cell can be bypassed, and when the whole flow battery pile breaks down, the whole flow battery pile is bypassed, and the normal operation of other single cells or battery piles is not influenced. In addition, the device and the control method can also realize accurate measurement of the end voltage and the SOC of the flow battery and realize intelligent management of the flow battery stack.
In a first aspect, the present application provides a control device for a flow battery stack, where the flow battery stack includes a plurality of unit cells connected in series, the device includes a detection circuit, a compensation circuit, and a controller, the detection circuit includes a plurality of first branches, each first branch is used for being connected with one unit cell, the first branch is used for detecting a voltage value of the unit cell, the compensation circuit includes a plurality of second branches, each second branch is connected in parallel with one unit cell or one unit cell group, where the one unit cell group includes at least two unit cells, and when a difference between a voltage value of one unit cell and a voltage balance reference value is greater than a voltage deviation threshold, the controller is used for instructing the compensation circuit to adjust that a difference between the voltage value of the unit cell and the voltage balance reference value is less than the voltage deviation threshold.
The device realizes accurate measurement of the terminal voltage of each single cell in the flow cell pile through the detection circuit, the controller compares the obtained terminal voltage value of each single cell with the voltage balance reference value, and controls the compensation circuit to adjust the voltage value of the single cell according to the comparison result, so that the automatic adjustment of the flow cell pile is realized, the voltage consistency of the flow cell pile is ensured, and the normal operation of the flow cell pile is ensured.
In a possible implementation, the apparatus includes a plurality of first switching circuits, each for being connected in parallel with one single cell or in parallel with each single cell group; wherein each cell group comprises at least two cells; when the voltage of the single cell is greater than the upper limit value of the single cell voltage or less than the lower limit value of the single cell voltage, the controller is used for indicating the first switch circuit to bypass the single cell with the fault or the single cell group where the single cell with the fault is located.
The first switching circuit skips the failed cell. The first switch circuit can also be a part of the detection circuit, the first switch circuit is connected with the fault battery in parallel, and is regarded as a parallel branch, other single batteries are connected with the fault battery in series, when the fault battery breaks down, the first switch circuit works, the fault battery is placed on the shelf, the working of other batteries is not influenced, and the operation and maintenance cost of the flow battery pile and the energy storage system is reduced.
In a possible implementation manner, each second branch includes a switch and a variable resistor, and when the difference between the voltage value of the single cell and the balance reference value is greater than the voltage deviation threshold, the controller is configured to instruct the compensation circuit to adjust the resistance value of the variable resistor. The second branch circuit adjusts the resistance value of the variable resistor to achieve the purpose of adjusting the internal resistance of the flow battery, and the adjustment of the voltage value of the single battery in the flow battery stack is achieved, so that the difference value between the voltage value of the single battery and the voltage balance reference value is smaller than the voltage deviation threshold value, the voltage consistency of the flow battery stack is ensured, and the normal operation of the flow battery stack is ensured.
In a possible implementation manner, each second branch includes a capacitor circuit, each capacitor circuit is connected in parallel with each single cell group, the capacitor circuit includes a capacitor and a switch, when the difference between the voltage value of a single cell and the balance reference value is greater than the voltage deviation threshold, the controller is used for indicating the capacitor circuit to close the switch, so that the adjacent single cell performs voltage compensation on the single cell, and the voltage value of the corresponding connected single cell is adjusted, so that the difference between the voltage value of the single cell and the voltage balance reference value is less than the voltage deviation threshold, the voltage consistency of the flow cell stack is ensured, and the normal operation of the flow cell stack is ensured.
In a possible implementation manner, each second branch includes a DC/DC circuit, each DC/DC circuit is connected in parallel with each single cell, and when the difference between the voltage value of the single cell and the balance reference value is greater than the voltage deviation threshold value, the controller is configured to instruct the DC/DC circuit to adjust the voltage value of the correspondingly connected single cell so that the difference between the voltage value of the single cell and the balance reference value is less than the voltage deviation threshold value. The DC/DC circuit directly adjusts the voltage of a single cell in the flow battery pile, so that the voltage consistency of the flow battery pile is ensured, and the normal operation of the flow battery pile is ensured.
In a possible implementation manner, when the voltage of the single cell is greater than the upper limit value of the voltage of the single cell or less than the lower limit value of the voltage of the single cell, the first switch circuit bypasses the single cell, and the DC/DC circuit is further used for generating the same voltage as that generated when the single cell normally works, so that the output power of the whole flow battery stack is the same as that before the fault occurs, and the normal operation of the whole flow battery stack is ensured.
In one possible implementation, a flow battery stack includes a positive current collector plate and a negative current collector plate, the current collector plates including a plurality of interfaces for connecting a detection circuit and a controller. The positive current collecting plate and the negative current collecting plate are used for collecting the current of each single cell, and an interface on the current collecting plate is connected with an external circuit to realize the communication between the flow cell stack and the external circuit. The device comprises a second switch circuit, wherein a first end of the second switch circuit is connected with a positive current collecting plate, a second end of the second switch circuit is connected with a negative current collecting plate, a detection circuit is used for detecting faults of the flow battery pile, and when the voltage of the flow battery pile is larger than the upper voltage limit value or smaller than the lower voltage limit value, the controller is used for indicating the second switch circuit to bypass the failed flow battery pile. The device has the function of skipping the fault pile, when the detection circuit finds that a plurality of single cells are in fault or the pile is in fault as a whole, the controller starts the second switching circuit to skip the fault flow battery pile, the problems of system fault shutdown, downtime and the like are avoided, stable operation of the system is ensured, intelligent management of the system is realized, skipping of the fault pile can be realized from the system level, and operation and maintenance cost is reduced.
In a possible implementation manner, the controller is further configured to calculate an SOC value of the battery cell according to the voltage value of the battery cell detected by the detection circuit, and when the SOC value of the battery cell is greater than or equal to the upper limit value of the battery cell SOC, the controller is configured to instruct the compensation circuit to adjust the voltage value of the battery cell to be less than a first voltage threshold value, and when the SOC value of the battery cell is less than or equal to the lower limit value of the battery cell SOC, the controller is configured to instruct the compensation circuit to adjust the voltage of the battery cell to be greater than a second voltage threshold value, where the second voltage threshold value is less than the first voltage threshold value. According to the SOC state of the flow battery, the voltage value of the flow battery is adjusted, the SOC working range of the flow battery is optimized, the polarization loss of the flow battery in the charge-discharge process is effectively reduced, the side reaction of the battery at the end of charge-discharge is avoided, the performance of the flow battery is improved, the reliability of the flow battery is improved, the service life of the flow battery is prolonged, and the operation and maintenance cost of the flow battery is reduced.
In a second aspect, the present application provides a method for controlling a flow battery stack, where the method includes: detecting the voltage value of each single cell in the flow battery pile, and when the difference value between the voltage value of the single cell and the voltage balance reference value is larger than the voltage deviation threshold value, adjusting the difference value between the voltage value of the single cell and the voltage balance reference value to be smaller than the voltage deviation threshold value.
In one possible implementation, the method includes: when the voltage of the single cell is larger than the upper limit value of the voltage of the single cell or smaller than the lower limit value of the voltage of the single cell, the single cell is bypassed, the fault cell is put aside, the work of other cells is not influenced, and the operation and maintenance cost of the flow cell stack is reduced.
In one possible implementation, the method includes: and when the voltage of the flow battery pile is larger than the upper limit value of the voltage of the flow battery pile or smaller than the lower limit value of the voltage of the flow battery pile, bypassing the flow battery pile. The fault flow battery pile is skipped, the problems of fault shutdown, downtime and the like of a pile system are avoided, the stable operation of the system is ensured, the intelligent management of the system is realized, the skip of the fault pile can be realized from the system level, and the operation and maintenance cost of the flow battery pile is reduced.
In one possible implementation, the method includes: and calculating the SOC value of the single cell according to the voltage value of the single cell. The sensing and processing of the information of the single cells in the pile with small granularity, the precise processing of the SOC and the fault adjustment and processing of the single cells are realized by accurately judging the SOC state of the battery in real time, so that the intelligent function of the pile level is realized. When the SOC value of the single cell is larger than or equal to the upper limit value of the single cell SOC, the voltage of the single cell is adjusted to be smaller than a first voltage threshold value; when the SOC value of the single cell is smaller than or equal to the lower limit value of the single cell SOC, the voltage of the single cell is adjusted to be larger than a second voltage threshold value, and the second voltage threshold value is smaller than the first voltage threshold value. The problem that the flow battery is easy to generate side reaction under the high SOC condition and the capacity of the flow battery is attenuated due to long-time high SOC charging is avoided, and meanwhile, the charging amount can be increased by increasing the upper limit of the charging voltage under the low SOC condition.
The control method provided by the application can solve the problem of consistency of the voltage of the single cells in the flow battery pile, realize optimal charging and discharging, isolate the fault single cells or the fault pile, not influence the operation of other single cells in the flow battery pile, and can measure the SOC of the single cells in the pile according to the terminal voltage of the measured single cells so as to realize intelligent sensing and control of the pile. The high-efficiency, high-power density and high-capacity input/output of the galvanic pile are realized, and the high-stability operation and long-service-life operation of the galvanic pile of the flow battery are ensured.
In a third aspect, the present application provides a flow battery stack, including a plurality of single cells, an anode current collecting plate, a cathode current collecting plate, and a control device provided in the first aspect, where the control device is connected to each single cell, and the control device is connected to the anode current collecting plate and the cathode current collecting plate.
In a fourth aspect, the present application provides an energy storage system, where the energy storage system includes a plurality of flow battery stacks provided in the third aspect, a control device provided in the first aspect, a battery management system, and a power conversion unit, where the power conversion unit is used to control charging and discharging of the energy storage system.
In a fifth aspect, the present application provides an energy storage system, where the energy storage system includes a plurality of flow battery stacks provided in the third aspect, a control device provided in the first aspect, a battery management system, and a power conversion unit, where the plurality of flow battery stacks are connected in series or in parallel, the battery management system is used for communicating with the control device, for obtaining information of the control device, and the power conversion unit is used for controlling charging and discharging of the energy storage system.
Drawings
Fig. 1 is a schematic structural diagram of a flow battery stack control device according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of another flow battery stack control device according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a compensation circuit provided in an embodiment of the present application;
FIG. 4 is another schematic diagram of a compensation circuit provided by an embodiment of the present application;
FIG. 5 is a schematic diagram of a compensation circuit according to an embodiment of the present disclosure;
fig. 6 is a schematic structural diagram of another flow battery stack control device according to an embodiment of the present disclosure;
fig. 7 is a graph of terminal voltage versus SOC of a single cell according to an embodiment of the present disclosure;
fig. 8 is a first flowchart of a control method of a flow battery stack according to an embodiment of the present application;
fig. 9 is a second flowchart of a control method of a flow battery stack according to an embodiment of the present application;
fig. 10 is a third flowchart of a control method of a flow battery stack according to an embodiment of the present application;
fig. 11 is a fourth flowchart of a control method of a flow battery stack according to an embodiment of the present disclosure;
fig. 12 is a fifth flowchart of a control method of a flow battery stack according to an embodiment of the present disclosure;
Fig. 13 is a sixth flowchart of a control method of a flow battery stack according to an embodiment of the present disclosure;
fig. 14 is a seventh flowchart of a control method of a flow battery stack provided in an embodiment of the present application;
fig. 15 is a schematic structural diagram of an energy storage system according to an embodiment of the present application.
Reference numerals illustrate:
a flow battery stack; 200-control device 200;
101-single cells 101;
201-a detection circuit; 202-a compensation circuit; 203-a first switching circuit; 204-a second switching circuit; 205-controller.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail with reference to the accompanying drawings. However, the example embodiments may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The same reference numerals in the drawings denote the same or similar structures, and thus a repetitive description thereof will be omitted. The words expressing positions and directions described in the embodiments of the present application are illustrated by way of example in the drawings, but may be changed according to the needs, and all the changes are included in the protection scope of the present application. The drawings of the embodiments of the present application are merely schematic for relative positional relationships and are not representative of true proportions.
It is noted that in the following description, specific details are set forth in order to provide an understanding of the present application. This application may be carried out in a variety of other ways than those herein set forth, and similar generalizations may be made by those skilled in the art without departing from the spirit of the application. Therefore, the present application is not limited by the specific embodiments disclosed below.
In the present embodiments, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
For ease of understanding, the terms involved in the embodiments of the present application are explained first.
And/or: merely one association relationship describing the associated object, the representation may have three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone.
A plurality of: refers to two or more.
And (3) connection: refers to an electrical connection, and two electrical component connections may be direct or indirect connections between two electrical components. For example, a may be directly connected to B, or indirectly connected to B through one or more other electrical components, for example, a may be directly connected to B, or directly connected to C, and C may be directly connected to B, where a and B are connected through C.
And (3) a switch: the switch in the embodiments of the present application may be one or more of various types of switching devices such as a relay, a metal oxide semiconductor field effect transistor (metal oxide semiconductor field effect transistor, MOSFET), a bipolar junction transistor (bipolar junction transistor, BJT), an insulated gate bipolar transistor (insulated gate bipolar transistor, IGBT), a silicon carbide (SiC) power transistor, and the like, which are not further listed in the embodiments of the present application. Each switching device may include a first electrode, a second electrode, and a control electrode for controlling the on or off of the switch. When the switch is closed, current can be transmitted between the first electrode and the second electrode of the switch, and when the switch is opened, current cannot be transmitted between the first electrode and the second electrode of the switch. Taking a MOSFET as an example, the control electrode of the switch is a gate, the first electrode of the switch may be the source of the switching device, the second electrode may be the drain of the switching device, or the first electrode may be the drain of the switch, and the second electrode may be the source of the switch.
Bypass: the single cells at two sides of a single cell or two ends of a flow battery pile are connected through a circuit, so that the current originally flowing through the single cell flows through the connecting circuit, and the fault single cell or the fault flow battery pile is bypassed.
Unlike conventional lithium ion batteries, lead acid batteries, flow batteries store their energy not within the battery but in an electrolyte separate from the battery. Such a battery structure allows independent configuration of the power unit and the energy unit by making the power output and the energy storage independent of each other. Since flow batteries are independent stacks and electrolytes, and lithium ion batteries are single cells, this makes them fundamentally different from lithium ion battery energy storage systems in many aspects of battery control methods, energy storage systems, and the like. The flow battery comprises a battery pile, an electrolyte storage tank and a circulating pump, wherein the flow battery pile is a power unit and consists of anode and cathode materials, a diaphragm and a battery shell. The electrolyte storage tank is an energy unit and consists of independent positive and negative electrolyte and independent positive and negative storage tanks. The circulating pump enables electrolyte to circulate between the anode and the cathode. The main working principle of the flow battery is as follows: when the battery pile works, under the drive of the circulating pump, positive electrolyte and negative electrolyte respectively stored in the positive storage tank and the negative storage tank are respectively conveyed to inlet public pipelines of the positive electrode and the negative electrode of the pile through corresponding pipelines, enter positive pipelines and negative pipelines of single cells communicated with the positive pipelines and the negative pipelines after passing through the public pipelines of the positive electrode and the negative pipelines, are both positioned in a plate frame structure, encircle the positive electrode, or the negative electrode, and the electrolyte passing through the pipelines enters the electrode. The electrode is made of porous materials, electrolyte undergoes oxidation reaction or reduction reaction at an electrode interface, the electrolyte after reaction enters an outlet of the positive electrode pipeline and an outlet of the negative electrode pipeline, then enters an outlet positive electrode and a negative electrode common pipeline, and then is conveyed back to a corresponding positive electrode storage tank and a corresponding negative electrode storage tank through an external pipeline. The current is transmitted to an external load through an external circuit by the current collector, and energy conversion between chemical energy and electric energy is completed. The flow battery has the advantages of decoupling power and energy and flexible design, can meet the requirement of energy storage capacity by changing the amount of positive and negative electrolyte, and can meet different power requirements by changing the serial-parallel number and the effective acting area of single cells in a galvanic pile.
The battery core of the lithium ion battery energy storage system is a single battery, the battery core of the lithium ion battery comprises an anode, a cathode, a diaphragm, electrolyte, a component and the like, and the electrode and the electrolyte of the lithium ion battery cannot be separated and are positioned in the same battery core. Therefore, in the lithium ion battery, energy conversion and energy storage of charge and discharge thereof are simultaneously reacted in one single cell. The flow battery reaction and the energy storage space are decoupled, the redox reaction occurs in the galvanic pile, the energy is stored in the electrolyte, and the electrolyte is stored in a separate storage tank. When the battery works, electrolyte is conveyed into the electric pile, and oxidation-reduction reaction occurs at the anode and the cathode. The main characteristics of the flow battery include:
(1) The safety is good, the reliability is high, the flow battery generally uses aqueous solution to store energy, potential safety hazards such as fire burning and the like are avoided, and the flow battery is particularly suitable for places with higher requirements on safety level, such as a coal mine standby power supply;
(2) The energy storage time is long and can reach 4 to 8 hours, and the energy storage device is particularly suitable for the energy storage requirements of new energy stations such as wind power generation and the like;
(3) The energy storage capacity is large, and the maximum energy storage capacity can reach GW.h scale;
(4) The output power is high, and the maximum output power can reach the GW scale;
(5) The cycle times are more, the service life is long, the cycle times reach 15,000-20,000 times, and the service life can reach 15-25 years;
(6) The full life cycle has low electricity cost which is less than 0.2 yuan/kWh;
(7) The power and the capacity can be independently designed, the device is suitable for large-scale energy storage, the power is determined by the performance and the volume of a single cell or a cell stack, the capacity is determined by the concentration and the volume of electrolyte, and the design can be customized;
(8) The starting and response speed is high, and the charging and discharging switching is in millisecond level, so that the method is suitable for frequency modulation;
(9) The energy efficiency is relatively high, and the efficiency is between 70 and 80 percent;
(10) The maintenance is free, deep discharge can be realized, and phase change and battery damage can not occur in the deep discharge;
(11) The working condition is mild, and the working is carried out at normal temperature and normal pressure;
(12) The recycling property is high, and the key materials can be recycled and are environment-friendly.
Therefore, the flow battery is particularly suitable for large and medium-sized energy storage scenes, however, since the large-sized energy storage system comprises thousands of flow battery stacks, each flow battery stack comprises a plurality of single cells, and the problem of non-uniformity of the voltages of the single cells can be generated due to the reasons of material manufacturing process, preparation process of the stacks, distribution characteristics of electrolyte, electrolyte concentration and internal resistance variation of each single cell and the like. Meanwhile, problems such as electrode material failure, solid phase deposition, diaphragm perforation, electrolyte bias flow and the like can occur in the working process of the single cell, so that the single cell is in fault, and a plurality of single cells are in fault to cause a galvanic pile to be in fault.
To solve the above problems, embodiments of the present application provide a control device 200 and a control method for a flow battery stack.
Fig. 1 is a schematic structural diagram of a flow battery stack device provided in an embodiment of the present application, where the flow battery stack includes a plurality of unit cells 101, and the unit cells 101 are connected in series. The device comprises a detection circuit 201, a compensation circuit 202 and a controller 205, wherein the detection circuit 201 comprises a plurality of first branches, each first branch is used for being connected with each single cell 101, the first branches are used for detecting the voltage value of each single cell 101, the compensation circuit 202 comprises a plurality of second branches, each second branch is used for being connected with one single cell 101 or one single cell group in parallel, the single cell group comprises at least two single cells, the controller 205 is respectively connected with the detection circuit 201 and the compensation circuit 202, and when the difference value between the voltage value of each single cell 101 and the voltage balance reference value is larger than a voltage deviation threshold value, the controller 205 is used for instructing the compensation circuit 202 to adjust the voltage value of each single cell 101 so that the deviation value between the voltage value of each single cell 101 and the voltage balance reference value is smaller than the voltage deviation threshold value.
The flow battery pile is formed by connecting a plurality of single cells 101 in series, and the pile is a place where the flow battery carries out electrochemical reaction, so that the power characteristic of the system is determined, and the performance of the pile can directly influence the overall performance of the system. The single cell 101 includes a bipolar plate, a positive electrode, a separator, and a negative electrode. The electrode of the flow battery does not participate in electrochemical reaction, but is only used as a reaction place, and the active substance obtains or loses electrons on the surface of the electrode to perform reduction reaction or oxidation reaction so as to realize the mutual conversion between electric energy and chemical energy. The membrane is an ion conducting membrane, is positioned in the center of each single cell 101 and is used for separating positive and negative electrolyte inside the single cell 101, so that active substances are prevented from being mixed with each other to generate 'liquid-bouncing' to self discharge, and meanwhile, selective transmission of specific ions is allowed to ensure that the internal circuit of the cell is conducted. The bipolar plate is a conductive separator plate, which is tightly attached to the positive and negative electrodes of the flow battery, is used for separating the positive and negative electrolytes of two adjacent single cells 101, collecting current, and supporting the electrodes, so that the series connection of a plurality of single cells 101 is realized inside the electric pile. The bipolar plate is communicated with the electronic circuits of two adjacent batteries, electrons reacted by the electrodes are collected to form current, and meanwhile, the ion circuits of the two adjacent batteries are isolated, so that the normal operation of the electric pile is ensured. The anode and the cathode of the pile are respectively provided with a current collecting plate of the pile, and the current collecting plates are used for collecting the current of the whole pile.
The specific materials of the bipolar plate, the positive electrode, the separator and the negative electrode are not limited in the embodiments of the present application. For example, common electrode materials include metal electrodes including elemental metals such as gold, lead, and titanium, and alloy materials such as titanium-based platinum and titanium-based iridium oxide, and carbon-based electrode materials such as graphite, glassy carbon, carbon felt, graphite felt, carbon cloth, and carbon fiber. Common bipolar plates include graphite bipolar plates, metallic bipolar plates, composite bipolar plates, and the like. Common cation exchange membrane materials comprise perfluorinated sulfonic acid resin, benzenesulfonyl modified ETFE and sulfonated polyaryletherketone, common anion exchange membranes comprise quaternized polyaryletherketone and the like, and common porous ion conducting membranes comprise porous polybenzimidazole and the like.
Note that, the number of the single cells 101 is not limited in the embodiment of the present application, and for example, the number of the single cells 101 connected in series may be 20 to 100.
It should be noted that, the embodiments of the present application are not limited to the type of the flow battery, and the flow battery may be, for example, a zinc-bromine flow battery, an all-vanadium flow battery, a sodium polysulfide-bromine battery, or the like.
The detection circuit 201 is connected to the positive bipolar plate and the negative bipolar plate of each single cell 101 for detecting the voltage value V of each single cell 101 i . The voltage value of the unit cell 101 is obtained by detection by the detection circuit 201, and since the current flowing through the unit cell 101 is equal to the current of the cell stack (the unit cells 101 in the stack are connected in series, and the current flowing through each unit cell 101 is equal to the current of the stack according to ohm's law), the resistance value of the unit cell 101 is obtained by dividing the voltage value of the unit cell 101 by the current value. In one embodiment, the detection circuit 201 includes a voltage sensor that detects the voltage of the single cell 101 and outputs a signal, and the voltage sensor is further connected to the controller 205 to transmit the voltage signal to the controller 205, and the controller 205 determines the single cellIf the voltage value of the battery 101 deviates from the voltage balance reference value, if the difference between the voltage value of the battery cell 101 and the voltage balance reference value is greater than the voltage deviation threshold value, the controller 205 is configured to instruct the compensation circuit 202 to adjust the voltage value of the battery cell 101 so that the difference between the voltage of the battery cell and the voltage balance reference value is less than the threshold value.
It should be noted that, in the embodiments of the present application, the position of the voltage sensor is not limited, for example, the voltage sensor of the detection circuit 201 may be preset in the bipolar plate of the cell 101, or the interface of the detection circuit 201 may be preset in the bipolar plate of the cell 101, and the detection circuit 201 may be connected to the interface.
The controller 205 is used for analyzing, processing and issuing instructions on the voltage value detected by the detection circuit 201. When the electric pile is in operation, the detection circuit 201 detects the voltage V of the single cell 101 in real time i When the controller 205 determines the voltage V of the single cell 101, the controller 205 acquires the voltage information of the single cell 101 detected by the detection circuit 201 i >V set +DeltaV or V i ＜V set at-DeltaV (where V set For the voltage balance reference value, Δv is a voltage deviation threshold value of the single cell 101), the controller 205 is configured to instruct the compensation circuit 202 to adjust the voltage value of the single cell 101 to control the voltage value of the single cell 101 within a range allowed by voltage uniformity, that is, V set Within +/-DeltaV.
V set Can be a factory set value of a flow battery stack, and in an ideal state, the terminal voltage V of each single battery 101 i And V is equal to set The values are the same, but due to the variation in the electrolyte concentration, internal resistance of the individual cells 101, the terminal voltage V of each cell 101 i And V is equal to set Deviations in the values occur. When the deviation value is too large, firstly, the wooden barrel effect is caused, the voltage consistency of the flow battery pile is reduced, the pile efficiency is reduced, and the system efficiency is reduced. Second, when the voltage of the plurality of single cells 101 is too low, the system capacity decreases. Finally, damage to the unit cells 101 (breakdown, short circuit, electrode blockage, etc.) may also occur, and the unit cells 101 cannot operate normally, which in turn leads to failure of each flow cell stack. Pre-preparation First, a voltage deviation threshold DeltaV is set, when the terminal voltage of a certain single cell 101 is equal to V set When the difference of (a) is greater than Δv, the controller 205 is configured to instruct the compensation circuit 202 to perform voltage adjustment on the single cell 101. The embodiment of the application does not limit V set With the specific value of DeltaV, the person skilled in the art can determine V according to the application scene requirement, the pile characteristics, the safety and other factors set And DeltaV.
Fig. 2 is a schematic structural diagram of another flow battery stack control device 200 according to an embodiment of the present disclosure. In one implementation, the apparatus includes a detection circuit 201, a first switching circuit 203, and a controller 205. A flow cell stack is connected to the device, the flow cell stack comprising a plurality of single cells 101 connected in series. Each first switching circuit 203 is connected in parallel with each cell 101 or with each cell group, each cell group comprising at least two cells 101, the first switching circuit 203 also being connected to the controller 205. When the detection circuit 201 finds that the voltage of the cell 101 is greater than the cell voltage upper limit value or less than the cell voltage lower limit value, the controller 205 is configured to instruct the first switch circuit 203 to bypass the failed cell 101 or the cell group where the failed cell 101 is located, and skip the failed cell 101.
For example, the first switch circuit 203 may also be a part of the detection circuit 201, which is connected in parallel with the faulty single cell, and is regarded as a parallel branch, and other single cells are connected in series with the faulty single cell.
V HE Is the upper voltage limit value of the single cell 101, V LE Is the cell 101 voltage lower limit value. The controller 205 determines whether the cell 101 has failed based on the information provided by the detector, when the voltage V of the cell 101 i ＞V HE When the single cell overvoltage faults are formed. When V is i ＜V LE When the single cell voltage-loss fault is formed, the controller 205 instructs the first switch circuit 203 to bypass the faulty single cell 101, and the current originally flowing through the faulty single cell 101 is no longer usedFlows through the single cell 101, and flows through the first switching circuit 203. The embodiment of the application does not limit V HE And V is equal to LE The specific numerical values of (2) can be determined by a person skilled in the art according to the application scene requirements, pile characteristics, safety and other factors HE And V is equal to LE Specific values of (2).
The implementation mode for realizing the consistency of the stack voltage of the flow battery is not limited by the embodiment of the application. For example, maintaining the voltage uniformity of the flow battery stack may be achieved by adjusting the resistance value of the cell 101, or adjusting the terminal voltage of the cell 101, or by a capacitive circuit.
The internal resistance of the flow battery stack is essentially different from that of the solid-state battery, because the internal resistance of the flow battery is not constant, but can be dynamically changed according to the different working processes of the current stack, the internal resistance of the flow battery can be dynamically changed along with the change of the charge state, the temperature and the charge-discharge state of the flow battery, and the voltage of each single battery 101 is different due to the different internal resistances, so that the voltage can be adjusted by adjusting the resistance of the battery, and the voltage consistency of the flow battery stack is improved.
In one implementation, each second branch includes a switch and a variable resistor, and each second branch is connected in parallel with one single cell 101, and when the voltage value of one or more single cells 101 deviates from the voltage balance reference value, the controller 205 is configured to instruct the compensation circuit 202 to adjust the resistance value of the variable resistor to adjust the voltage of the single cell 101, so as to maintain the consistency of the flow battery stack. Fig. 3 is a schematic diagram of a compensation circuit 202 according to an embodiment of the present application, and according to the embodiment shown in fig. 3, a single cell B of a flow battery stack 1 、B 2 、B 3 ···B n In parallel with an adjustable resistive component comprising a switch S 1 、S 2 、···S n And a variable resistor R 1 、R 2 、···R n . The switch is closed to enable the adjustable resistance component to be connected into a corresponding parallel circuit in a charging or discharging state of the flow battery stack. The flow battery stack comprises a plurality of single cells 101 connected in series, and each single cell 101 is connected in series according to ohm's lawThe current flowing is uniform, and when the resistance values are the same, the voltages are the same. Therefore, uniformity of voltages among the respective cells can be ensured by adjusting the resistance of the single cells 101. For example, the internal resistance value of the n single cells 101 is R 01 、R 02 、R 03 、···、R 0n The resistance value of the n variable resistors connected in parallel with the resistor is R 1 、R 2 、R 3 ···R n The calculation formula of the resistance value of each single cell 101 and the resistor after parallel connection is 1/R Total 1 ＝1/R 01+ 1/R 1 ,1/R Total 2 ＝1/R 02+ 1/R 2 ,1/R Total 3 ＝1/R 03+ 1/R 3 ，···，1/R Total n ＝1/R 0n+ 1/R n Wherein 1/R Total 1 、R Total 2 、/R Total 3 、···、R Total n The total resistance values of the n single cells 101 and the variable resistor connected in parallel are respectively. From this, the resistance of the total resistance of each single cell 101 is smaller than that of any one of the branch resistances, and the larger the branch resistance is, the smaller the current is. By connecting a variable resistor with the single cell 101 in parallel, the resistance value of which is far greater than the internal resistance of the single cell, the controller 205 sends an instruction to the compensation circuit 202 according to the voltage value detected by the detection circuit 201, and the instruction is used for instructing the compensation circuit 202 to adjust the resistance value of the adjustable resistance component, so that the voltage value difference between the single cell 101 with abnormal current voltage and other single cells is smaller than DeltaV. When the detection circuit 201 detects one or several single cells 101 voltage V i >V set At +Δv, the controller 205 instructs the compensation circuit 202 to adjust the resistance of the adjustable resistive component, for example, to adjust the resistance in a decreasing manner, so as to adjust the voltage of the unit cells 101 such that the resistances of the unit cells 101 are uniform or such that the resistance difference of the unit cells 101 is within a Δr range, where Δr=Δv/I (I is the current flowing through the unit cell 101). When the detection circuit 201 detects one or several single cells 101 voltage V i ＜V set At ΔV, the controller 205 is configured to instruct the compensation circuit 202 to adjust the resistance of the adjustable resistive component, e.g., to adjust the resistance incrementally to adjust the voltage of the cells 101 such that the resistances of the cells 101 are uniform or such that the resistance of the cells 101 are differentThe value is within the Δr range where Δr=Δv/I (I is the current flowing through the cell 101). The voltage value V of each single cell 101 is made by adjusting the resistance value of each single cell 101 after the parallel resistors to be the same resistance value or within a certain deviation value so that the difference value between the voltage value of the single cell 101 and the voltage balance reference value is smaller than the voltage deviation threshold value i And V is equal to set The difference of (a) is within the range of the voltage deviation threshold Δv.
Optionally, the minimum resistance of the variable resistor is at least N times the internal resistance of the single cell 101, and N is greater than or equal to 100. For example, if the single cell 101R 0 When the internal resistance of the resistor is 20mΩ, at least a minimum resistance of 2Ω is required. This is because from the above 1/R Total n ＝1/R 0n+ 1/R n It can be known that the resistance of the parallel resistor of each single cell 101 is smaller than the resistance of any branch, if the resistance of the variable resistor is far greater than the internal resistance of the single cell 101, the resistance of the parallel resistor can be approximately changed along with the resistance of the variable resistor, and when the detection circuit 201 finds the voltage V of one or more single cells 101 i >V set +DeltaV or V i ＜V set At- Δv, the detection circuit 201 can ensure that the voltages of the stacks are kept consistent by adjusting the resistance values of the variable resistors connected in parallel to the two ends of the single cell 101, and meanwhile, the current values of the parallel paths are very small due to the fact that the resistance values of the variable resistors are far greater than the internal resistance of the single cell 101, and the corresponding resistance power consumption is very small, so that the problem of power consumption increase caused by introduction of the adjustable resistance component is effectively solved.
Fig. 4 is a schematic diagram of a compensation circuit 202 according to an embodiment of the present application, where each second branch includes a capacitor circuit connected in parallel with each cell group, and each cell group includes at least two cells, for example, each cell group includes two cells. When the detection circuit 201 detects the voltage V of the single cell 101 i >Vset+DeltaV or V i ＜V set at-DeltaV, the controller 205 is configured to instruct the capacitive circuit to close the switch, the capacitor may store electrical energy, by closing S n-1 And S is n So that adjacent cells voltage compensate the faulty cell (whichWhere n is an integer of 2 or more), the voltage values of the single cells 101 are adjusted so that the voltage value V of each single cell 101 is set to i And V is equal to set The difference of (a) is within the range of the voltage deviation threshold Δv.
FIG. 5 is another schematic diagram of a compensation circuit 202 according to an embodiment of the present application, in one possible implementation, each second branch includes a DC/DC circuit, which is coupled to each cell B 1 、B 2 、B 3 ···B n And are connected in parallel. When the detection circuit 201 detects the voltage V of the single cell 101 i >At vset+Δv, the controller 205 instructs the DC/DC circuit to reduce the voltage of the cell 101 so that the voltage value V of the cell 101 i ’＜V set +Δv; when the detection circuit 201 generates a voltage V of one or more single cells 101 i ＜V set at-DeltaV, the controller 205 is configured to instruct the DC/DC circuit to increase the voltage of the cell 101 such that the voltage value V of the cell i ’＞V set Δv, so that the voltage value V of each single cell 101 i And V is equal to set The difference of (a) is within the range of the voltage deviation threshold Δv.
In one implementation, each second branch includes a DC/DC circuit, each DC/DC circuit is connected in parallel with each cell 101, and the primary function of the first switch circuit 203 is to bypass the faulty cell 101 and ensure normal operation of the stack. When the voltage of the cell 101 is greater than the cell voltage upper limit value or less than the cell voltage lower limit value, the first switch circuit 203 bypasses the cell 101, and at this time, the stack operates at a new power point, which is generally less than the power of the previous stack. The DC/DC circuit can generate the same voltage as that of the single cell 101 connected in parallel with the DC/DC circuit during normal operation, when the single cell 101 fails and loses voltage, the voltage generated by the DC/DC circuit replaces the voltage of the failed single cell 101, the voltage of the whole electric pile is ensured to be unchanged, the voltage supporting function of the electric pile is realized, and the new power point of the flow battery electric pile is ensured to be the same as the original power point. In the charge and discharge process, due to uneven distribution of the electrolyte and uneven distribution of the voltage, the voltage of one or more single cells 101 may be higher than the voltage of other single cells 101, and at this time, the DC/DC circuit may adjust the voltage of the single cell 101 to be consistent with the voltage of other single cells 101, so as to keep the new power point consistent with the original power point. The operation of the energy storage system is ensured, and the downtime, energy loss and economic loss of the system caused by the failure of individual single cells 101 in the system are reduced.
The above-described voltage supporting function is mainly realized by an external device communicating with the controller 205. The communication mode between the controller 205 and the detection circuit 201 and the external device is not particularly limited, and the communication mode includes wired and wireless communication modes, and the controller 205 and the detection circuit 201 and the external device may communicate based on an RS-485 bus or a CAN (Controller Area Network, controller 205 local area network) protocol.
Optionally, the external device includes a battery management system BMS (Battery Management System). The BMS is one of core subsystems of the battery energy storage system and is responsible for monitoring the running state of each battery in the battery energy storage unit, so that the safe and reliable running of the energy storage unit is ensured. The BMS can monitor and collect state parameters (including but not limited to single battery voltage, battery post temperature, battery loop current, battery pack terminal voltage, battery system insulation resistance and the like) of the energy storage battery in real time, performs necessary analysis and calculation on relevant state parameters to obtain more system state evaluation parameters, and realizes effective management and control on the energy storage battery body according to a specific protection control strategy so as to ensure safe and reliable operation of the whole battery energy storage unit. Meanwhile, the BMS can carry out information interaction with other external equipment (PCS, EMS, fire-fighting system and the like) through a communication interface and an analog/digital input interface of the BMS, so that linkage control of all subsystems in the whole energy storage system is formed, and safe, reliable and efficient grid-connected operation of the power station is ensured. The BMS communicates with the control device 200 of the flow cell stack. The BMS may obtain the voltage value detected by each flow cell stack detection circuit 201, and if the detection circuit 201 detects that the voltage of a certain flow cell stack is abnormal, the BMS communicates with the controller 205, and the controller 205 is configured to instruct the second switch circuit 204 to skip the failed flow cell stack.
In particular implementations, the controller 205 may be a general purpose central processing unit (central processing unit, CPU), a general purpose processor, digital signal processing (digital signal processing, DSP), application specific integrated circuit (application specific integrated circuits, ASIC), field programmable gate array (field programmable gate array, FPGA) or other programmable logic device, transistor logic device, hardware components, or any combination thereof. The above-described processors may also be a combination of computing functions. For example, the controller 205 may include one or more microprocessor combinations, a combination of a DSP and a microprocessor, or the like.
The communication mode between the controller 205 and the detection circuit 201 is not particularly limited, and the communication mode includes wired and wireless communication modes, and the controller 205 and the detection circuit 201 may communicate based on an RS-485 bus or a CAN (Controller Area Network, controller 205 local area network) protocol. In other embodiments, the communication may also be performed based on other communication methods, which is not limited in this application.
In one implementation, the flow cell stack includes a positive current collector plate and a negative current collector plate, each including a plurality of interfaces that interface with the detection circuit 201 and the controller 205 to communicate the flow cell stack with the controller 205. The positive and negative current collector plates also serve to collect and transmit current to an external load.
Fig. 6 is a schematic structural diagram of yet another flow battery stack control device 200 provided in an embodiment of the present application, and in one implementation, the embodiment of the present application provides a control device for a flow battery stack, where the device includes a detection circuit 201, a compensation circuit 202, a switching circuit, a second switching circuit 204, and a controller 205. The detection circuit 201 is connected to each single cell 101 in a stack, which is connected to the device, and which comprises a plurality of single cells 101 connected in series. A switching circuit is connected in parallel with each unit cell 101, the switching circuit is connected in parallel with the controller 205, and the second switching circuit 204 is connected with the positive electrode collector plate and the negative electrode collector plate of the stack. According to the flow battery pile device, the function of skipping the fault pile is achieved, when the detection circuit 201 finds that a plurality of single cells 101 break down, or the pile integrally breaks down, the controller 205 is used for indicating the second switch circuit 204 to bypass the broken down flow battery pile, the broken down flow battery pile is skipped, at the moment, the energy storage circuit and the energy storage system work at another power point, the problems of system fault shutdown, downtime and the like are avoided, stable operation of the system is guaranteed, intelligent management of the system is achieved, skipping of the broken down pile can be achieved from a system level, and operation and maintenance costs are reduced.
V SHE Is the upper voltage limit value of the flow battery pile, V SLE Is the lower voltage limit of the flow battery stack. The controller 205 determines whether the single cell 101 has a fault according to the voltage value of the single cell 101 detected by the detection circuit 201, and when the output voltage V of the flow battery stack is S >V SHE When the flow battery pile is in overvoltage fault, when V S <V SLE When a flow cell stack voltage loss fault is formed, the controller 205 is configured to instruct the second switch circuit 204 to bypass the failed cell stack, and the current originally flowing through the corresponding flow cell stack no longer flows through the flow cell stack, but flows through the second switch circuit 204. The embodiment of the application does not limit V SHE And V is equal to SLE The specific numerical values of (2) can be determined by a person skilled in the art according to the application scene requirements, pile characteristics, safety and other factors SHE And V is equal to SLE Specific values of (2).
In one implementation, the controller 205 is further configured to calculate an SOC value of the single cell 101 or the flow battery stack according to the voltage value obtained by the detection circuit 201. SOC refers to the state of charge of the battery, typically 0% -100% SOC, which is one of the most important parameters of the state of the stack. The calculation formula of SOC is soc=residual capacity/battery capacity, and the following relationship exists between the open circuit voltage of the flow battery cell and the SOC of the battery cell: v (V) Open circuit voltage ＝E Positive electrode -A*log((1/SOC-1) 2 *(1/C cc ) 2 )(V Open circuit voltage Refers to the open circuit voltage, E, of a single cell Positive electrode Refers to the positive electrode potential of a single cell, A refers to a constant, C cc Refers to the concentration of the electrolyte).
The battery stably operates and needs to accurately sense the SOC, and the traditional method cannot directly sense the SOCThe voltage value of the single cell 101 is measured, and a small single cell is additionally connected between the positive electrode storage tank and the negative electrode storage tank of the system, so that the voltage of the single cell is measured, and the SOC of the flow battery is obtained, and is deviated from the SOC value of the cell in the cell stack after the cell reacts within a certain time, has hysteresis, cannot reflect the instant cell state, and influences the accuracy of the cell. Redox reaction occurs in the flow battery, reactants are continuously consumed, the concentration of electrolyte is continuously changed, the capacity of the flow battery is changed, the SOC of the flow battery is changed, and different SOC states correspond to different voltage values. The control device provided by the embodiment of the application includes a detection circuit 201, the detection circuit 201 is connected with a flow battery stack, the detection circuit 201 includes a voltage sensor, the voltage sensor can read the voltage of each single battery 101 in the stack in the battery system in real time, and the detection circuit 201 obtains that the voltage value of the single battery is V i The controller 205 obtains V i FIG. 7 is a graph of terminal voltage and SOC value of the single cell 101 according to the embodiment of the present application, by comparing V with a curve of the relation between the preset voltage V in the controller 205 and the State-of-Charge (SOC) i And comparing the obtained value with the curve to obtain a real-time SOC value of the single cell 101. The device can obtain the SOC value of each single cell 101 in the electric pile on line in real time, improves the accuracy, timeliness and high precision of SOC detection, and provides a data base for intelligent management of the electric pile and an energy storage system. By accurately judging the SOC state of the single cell in real time, the sensing and processing of the information of the single cell 101 in the pile with small granularity, the accurate processing of the SOC and the fault adjustment and processing of the single cell 101 are realized, and the intelligent control of the pile level is realized.
The controller 205 is further configured to control a voltage value of the battery cell according to the SOC value of the battery cell 101, where the controller 205 is configured to instruct the compensation circuit 202 to adjust the voltage of the flow battery to be less than a first voltage threshold when the SOC value of the battery cell 101 is equal to or greater than an upper limit value of the battery cell SOC, and instruct the compensation circuit 202 to adjust the voltage of the flow battery to be greater than a second voltage threshold when the SOC value of the battery cell 101 is equal to or less than a lower limit value of the battery cell SOC. Wherein the second voltage threshold is less than the first voltage threshold. The problem that the flow battery is easy to generate side reaction under the high SOC condition and the capacity of the flow battery is attenuated due to long-time high SOC charging is avoided, and meanwhile, the charging amount can be increased by increasing the upper limit of the charging voltage under the low SOC condition.
The concentration polarization is increased at the end of charge and discharge of the flow battery, the risk of side reaction is greatly increased, the active substances, supporting electrolyte or solvent of the flow battery can be irreversibly changed, the capacity of the flow battery is irreversibly attenuated, the long-term operation life and stability of the flow battery are affected, and the control device provided by the embodiment of the application can control charge and discharge according to the SOC value of the flow battery, so that the energy efficiency and the capacity performance of the flow battery are maximally improved.
For example, the lower limit value of the SOC of the unit cell is 15%, the upper limit value of the SOC of the unit cell is 90%, the first voltage threshold is 1.7v×m, and the second voltage threshold is 1v×m, where m is the number of unit cells 101 included in the flow battery stack. According to the method and the device, the upper limit of the voltage of the flow battery can be configured according to the specific condition of the SOC of the flow battery, and the problem that the capacity of the flow battery is irreversibly attenuated due to the fact that the flow battery is charged under the high SOC condition for a long time due to side reaction is avoided. In this embodiment of the present application, the SOC upper limit value, the SOC lower limit value, the first voltage threshold value, and the second voltage threshold value of the single battery are not specifically limited, and may be set by a person skilled in the art according to an actual application scenario.
In a second aspect, the embodiments of the present application further provide a method for controlling a flow battery stack, where the structure of the flow battery stack may refer to the description of the foregoing embodiments, and the description is not repeated here. The control method comprises the following steps: detecting a voltage value of each single cell 101 in the flow battery stack, and adjusting the voltage of the single cell 101 to be smaller than a voltage deviation threshold value when the difference value between the voltage value of the single cell 101 and the voltage balance reference value is larger than the voltage deviation threshold value.
Referring to fig. 8, fig. 8 is a first flowchart of a control method of a flow battery stack according to an embodiment of the present application, and in one implementation, the control method may include the following steps:
step H101, detecting the voltage V of each single cell 101 in the flow battery stack i ；
Step H102, when the cell 101 voltage V i And the equilibrium voltage reference value V set Is greater than the voltage deviation threshold DeltaV, i.e. V i >V set +DeltaV or V i ＜V set at-DeltaV, the controller 205 instructs the compensation circuit 202 to adjust the voltage value of the single cell 101 to V i ’；
Step H103, when V i ’>V set +DeltaV or V i ’＜V set -at Δv, step H102 is performed, otherwise the execution of the action is terminated.
Referring to fig. 9, fig. 9 is a second flowchart of a control method of a flow battery stack according to an embodiment of the present application, where in one implementation, the control method may include the following steps:
Step S101, detecting the voltage V of each single cell 101 in the flow battery stack i ；
Step S102, when the cell 101 voltage V i And the equilibrium voltage reference value V set Is greater than the voltage deviation threshold DeltaV, i.e. V i >V set +DeltaV or V i ＜V set At- Δv, the controller 205 instructs the compensation circuit 202 to adjust the resistance of the variable resistor connected in parallel with the cell 101, and the voltage value of the adjusted cell 101 is V i ’；
Step S103, when V i ’>V set +DeltaV or V i ’＜V set -at Δv, step S102 is performed, otherwise the execution of the action is terminated.
Referring to fig. 10, fig. 10 is a third flowchart of a control method of a flow battery stack according to an embodiment of the present application, and in one implementation, the control method may include the following steps:
step P101, detecting the voltage V of each single cell 101 in the flow battery stack i ；
Step P102, when the cell 101 voltage Vi is equal to the voltage reference value V set Is greater than the voltage deviation threshold DeltaV, i.e. Vi>V set +DeltaV or Vi < V set At- Δv, the controller 205 instructs the capacitive circuit to close the switch, adjusting the voltage value of the cell 101 to Vi';
step P103, when Vi'>V set +DeltaV or Vi' < V set -at Δv, step P102 is performed, otherwise the execution of the action is terminated.
Referring to fig. 11, fig. 11 is a fourth flowchart of a control method of a flow battery stack according to an embodiment of the present application, where in one implementation, the control method includes the following steps:
Step R101, detecting the voltage V of each single cell 101 in the flow battery stack i ；
Step R102, when one or more single cells 101 voltage Vi and equalizing voltage reference value V set Is greater than the voltage deviation threshold DeltaV, i.e. Vi>V set +DeltaV or Vi < V set At- Δv, the controller 205 instructs the DC/DC circuit to adjust the voltage value of the single cell 101 to Vi';
step R103, when V i ’>V set +DeltaV or V i ’＜V set -at Δv, step R102 is performed, otherwise the execution of the action is terminated.
Referring to fig. 12, fig. 12 is a fifth flowchart of a control method of a flow battery stack according to an embodiment of the present application, where in one implementation, the control method includes, when one or more of the single cells 101 has a voltage fault, bypassing the faulty single cell 101. The control method may include the steps of:
step Q101, detecting each cell 101 voltage V in the flow battery stack i ；
Step Q102, when the voltage V of the single cell 101 i Higher voltage upper limit V of unit cell 101 HE Or V i < lower voltage limit V of single cell 101 LE When the battery cell is in the failure state, the switching circuit bypasses the failure battery cell or the battery cell group.
Referring to fig. 13, fig. 13 is a sixth flowchart of a control method of a flow battery stack according to an embodiment of the present application, where in one implementation manner, the control method includes, when a voltage failure exists in the flow battery stack, bypassing the failed flow battery stack. The control method may include the steps of:
Step Y101, detecting the voltage V of each flow battery stack S ；
Step Y102, when the voltage V of the flow battery stack S Higher voltage limit V of flow battery stack SHE Or V S < lower limit V of voltage of flow battery stack SLE And when the fault flow battery pile is in the fault state, the switching circuit bypasses the fault flow battery pile.
In one implementation manner, the control method includes: when a voltage fault exists in the plurality of flow battery stacks, the BMS sends out a command to bypass the failed flow battery stack. The BMS communicates with the controller 205 of the flow cell stack. The BMS may obtain the voltage value detected by each flow cell stack detection circuit 201, and if the detection circuit 201 detects that the voltages of the plurality of flow cell stacks are abnormal, the BMS communicates with the controller 205, and the controller 205 is configured to instruct the second switch circuit 204 to skip the failed stack.
Referring to fig. 14, fig. 14 is a seventh flowchart of a control method of a flow battery stack according to an embodiment of the present application, and in one implementation manner, the control method further includes: calculating the SOC value of the single cell 101 according to the voltage value of the single cell 101; when the SOC value of the single cell 101 is larger than or equal to the single cell SOC upper limit value, the voltage of the liquid flow single cell 101 is adjusted to be smaller than a first voltage threshold value; when the SOC value of the single cell 101 is smaller than or equal to the single cell SOC lower limit value, the voltage of the liquid flow single cell 101 is adjusted to be larger than a second voltage threshold value; wherein the second voltage threshold is less than the first voltage threshold. The control method comprises the following steps:
Step X101, detecting the voltage V of each single cell 101 in the flow battery stack i ；
Step X102, according to the voltage V of the cell 101 i Calculating the SOC value of the single cell 101;
step X103, when the SOC value of the single cell 101 is greater than or equal to the upper limit value of the single cell SOC, adjusting the voltage of the single cell to be smaller than the first voltage threshold V u The method comprises the steps of carrying out a first treatment on the surface of the When the SOC value of the single cell 101 is less than or equal to the single cell SOC lower limit value, the voltage of the single cell is adjusted to be greater than the second voltage threshold V d Wherein the second voltage threshold V d Less than the first voltage threshold V u 。
It should be noted that the embodiments of the present application do not limit V u And V is equal to d The specific numerical values of (2) can be determined by a person skilled in the art according to the application scene requirements, pile characteristics, safety and other factors u And V is equal to d Specific values of (2).
According to the method, the voltage of the flow battery is controlled according to the charge state of the flow battery, and the SOC use interval of the flow battery is optimized, so that the reaction polarization of the flow battery at the end of charge and discharge is greatly reduced, the performance and the service life of the flow battery are improved, the side reaction of the flow battery is reduced, and the capacity attenuation problem caused by the running of the flow battery under high SOC is solved.
Based on the same technical conception, the embodiment of the application also provides a flow battery stack comprising the device. The flow battery pile comprises a plurality of single cells 101, an anode current collecting plate, a cathode current collecting plate, at least one anode electrolyte inlet, at least one anode electrolyte outlet, at least one cathode electrolyte inlet and at least one cathode electrolyte outlet, wherein the single cells 101 comprise an anode, a cathode, an electrode frame, a bipolar plate, a diaphragm, a pile fastener and the control device for the flow battery pile; the plurality of single cells 101 are connected in series, and a positive electrode and a negative electrode are respectively arranged in the electrode frame; the electrode frame is provided with a plurality of inlets and a plurality of outlets, and the inlets and the outlets are respectively connected with the corresponding flow channels.
Firstly, the flow battery stack can measure the terminal voltage of the single battery 101 on line in real time, and when the voltage value of the single battery 101 deviates from a voltage balance reference value, the voltage of the single battery 101 is adjusted to ensure that the deviation of the voltage of the single battery 101 and the voltage balance reference value is within a voltage deviation threshold value, so that the voltage consistency of the flow battery stack is maintained. Secondly, according to the measured voltage value of the single cell 101, the flow cell stack can timely find out whether the single cell 101 has a voltage loss or an overvoltage fault or not, and bypass the single cell 101 with the fault. Finally, the flow battery pile can also realize fault skip of pile level, when the overall flow battery pile has overvoltage or voltage loss fault, the failed flow battery pile is bypassed, and the normal operation of other flow battery piles is not influenced.
Based on the same technical concept, the embodiments of the present application further provide an energy storage system including the flow battery stack, where the structure of the flow battery stack may refer to the description in the foregoing embodiments, and the description is not repeated here.
The energy storage system comprises the flow battery pile, the energy unit, the electrolyte transmission unit, the Battery Management System (BMS) and the power conversion unit (PCS). The flow battery pile is a place for converting electric energy and chemical energy, and realizes the conversion of the electric energy and the chemical energy. The power conversion includes a plurality of flow cell stacks connected in parallel or in series in a particular manner. The energy unit of the flow battery comprises an electrolyte storage tank and electrolyte, and the electrolyte transmission unit comprises a pipeline, a pump valve, a sensor and the like. Electrolyte of the flow battery is an energy storage place, and the electrolyte is subjected to electrochemical reaction in a galvanic pile to realize energy storage and release. The flow battery pile determines the power of the energy storage system, and the energy unit determines the capacity of the energy storage system, which are independent of each other.
A Battery Management System (BMS) is a collection of electronic devices for monitoring, evaluating and protecting the operation state of a battery, and functions include: monitoring and transmitting running state information of the battery, the battery pack and the battery system unit, wherein the information comprises battery voltage, current, temperature and the like; evaluating and calculating the state of charge (SOC) of the battery; protecting the safety of the battery, etc. A power conversion unit (PCS) controls the power bidirectional flow of the energy storage system according to the instruction; the system is also used for protecting the energy storage system and the power grid to enable the energy storage system and the power grid to meet grid connection requirements, and is used for carrying out direct current and alternating current conversion and connecting the power grid and the energy storage system. The PCS can control the charging and discharging processes of the storage battery to perform alternating current-direct current conversion, and can directly supply power to an alternating current load under the condition of no power grid. The PCS communicates with the BMS through the CAN interface to acquire the state information of the battery pack, so that the battery CAN be charged and discharged in a protective manner, and the operation safety of the battery is ensured.
Firstly, the energy storage system can measure the voltage of the single cell 101 on line in real time, compare the measured voltage value with a voltage balance reference value, and adjust the voltage of the single cell 101 when the voltage value of the single cell 101 deviates from the voltage balance reference value, so that the deviation of the voltage value of the single cell 101 and the voltage balance reference value is within a threshold value, thereby maintaining the voltage consistency of the flow battery stack. Secondly, according to the measured voltage value of the single cell 101, the flow cell stack can timely find out whether the single cell 101 has a voltage loss or an overvoltage fault or not, and bypass the single cell 101 with the fault. Finally, the flow battery pile can also realize fault skip of a pile level, and when the overall flow battery pile has overvoltage or voltage loss faults, the failed flow battery pile is bypassed.
Based on the same technical concept, the embodiment of the application also provides an energy storage system including the control device, referring to fig. 15, the energy storage system further includes a plurality of flow battery stacks, a battery management system and a power conversion unit, and the plurality of flow battery stacks are connected in series or in parallel; the battery management system is used for communicating with the control device, and the power conversion unit is used for controlling the charging and discharging of the energy storage system.
Firstly, the energy storage system can measure the voltage of the single cell 101 on line in real time, compare the measured voltage value with a voltage balance reference value, and adjust the voltage value of the single cell 101 when the voltage value of the single cell 101 deviates from the voltage balance reference value, so that the deviation of the voltage value of the single cell 101 and the voltage balance reference value is within a threshold value, thereby maintaining the voltage consistency of the flow battery stack. Secondly, according to the measured voltage value of the single cell 101, the flow cell stack can timely find out whether the single cell 101 has a voltage loss or an overvoltage fault or not, and bypass the single cell 101 with the fault. Finally, the flow battery pile can also realize fault skip of a pile level, and when the overall flow battery pile has overvoltage or voltage loss faults, the failed flow battery pile is bypassed.
Based on the above embodiments, the present application further provides an apparatus, which includes a processor and a memory, where the memory stores a computer program capable of being executed by the processor, and the processor is capable of executing the method provided in the above embodiments.
Based on the above embodiments, the present application further provides a computer-readable storage medium having a computer program stored therein, which when executed by a computer, causes the computer to implement the method provided in the above embodiments. Wherein a storage medium may be any available medium that can be accessed by a computer. Taking this as an example but not limited to: the computer readable medium may include RAM, read-only memory (ROM), electrically erasable programmable read-only memory (electrically erasable programmable read-only memory, EEPROM 1), CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.
The technical solution provided in the embodiments of the present application may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions in accordance with embodiments of the present application are produced in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, an access network device, a terminal device, or other programmable apparatus. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another, for example, by wired (e.g., coaxial cable, fiber optic, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means from one website, computer, server, or data center. Computer readable storage media can be any available media that can be accessed by a computer or data storage devices, such as servers, data centers, etc. that contain an integration of one or more available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (digital video disc, DVD)), or a semiconductor medium, etc.
The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present application, and the changes or substitutions are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (15)
1. A control device for a flow battery stack comprising a plurality of single cells connected in series, characterized in that the control device comprises a detection circuit, a compensation circuit and a controller;
the detection circuit comprises a plurality of first branches, wherein each first branch is used for being connected with one single cell and detecting the voltage value of the corresponding connected single cell;
the compensation circuit comprises a plurality of second branches, wherein each second branch is used for being connected with one single cell or one single cell group in parallel, and one single cell group at least comprises two single cells;
when the difference value between the voltage value of the single cell and the voltage balance reference value is larger than a voltage deviation threshold value, the controller is used for indicating the compensation circuit to adjust that the difference value between the voltage value of the single cell and the voltage balance reference value is smaller than the voltage deviation threshold value.
2. The apparatus of claim 1, further comprising a plurality of first switching circuits;
each of the first switch circuits is used for being connected with one single cell or one single cell group in parallel;
and when the voltage of the single cell is larger than the upper limit value of the single cell voltage or smaller than the lower limit value of the single cell voltage, the controller is used for indicating the first switch circuit to bypass the single cell or the single cell group where the single cell is located.
3. The apparatus of claim 1 or 2, wherein each of the second branches comprises a switch and a variable resistor;
the second branch is used for adjusting the voltage value of the single cells connected in parallel correspondingly by adjusting the resistance value of the variable resistor.
4. The apparatus of claim 1 or 2, wherein each of said second branches comprises a capacitive circuit;
the capacitive circuit comprises a capacitor and a switch;
the capacitor circuit is used for adjusting the voltage value of the single cells which are connected in parallel correspondingly.
5. The apparatus of claim 1 or 2, wherein each of said second branches comprises a DC/DC circuit;
the DC/DC circuit is used for adjusting the voltage value of the single cells which are connected in parallel correspondingly.
6. The apparatus of claim 5, wherein the DC/DC circuit is further configured to: when a cell connected in parallel therewith is bypassed, the same voltage as when the bypassed cell is operating normally is generated.
7. The apparatus of any one of claims 1-6, wherein the apparatus further comprises a second switching circuit;
the first end of the second switch circuit is used for being connected with a positive current collecting plate of the flow battery stack, and the second end of the second switch circuit is used for being connected with a negative current collecting plate of the flow battery stack;
and when the voltage of the flow battery pile is larger than the upper limit value of the voltage of the flow battery pile or smaller than the lower limit value of the voltage of the flow battery pile, the controller is used for indicating the second switch circuit to bypass the flow battery pile.
8. The apparatus according to any one of claims 1 to 7, wherein the controller is further configured to calculate an SOC value of the single cell from the voltage value acquired by the detection circuit;
when the SOC value of the single cell is greater than or equal to the upper limit value of the single cell SOC, the controller is used for indicating the compensation circuit to adjust the voltage value of the single cell to be smaller than a first voltage threshold value;
When the SOC value of the single cell is smaller than or equal to the lower limit value of the single cell SOC, the controller is used for indicating the compensation circuit to adjust the voltage value of the single cell to be larger than a second voltage threshold value;
the second voltage threshold is less than the first voltage threshold.
9. A control method of a flow battery stack, wherein the flow battery stack includes a plurality of single cells connected in series, the method comprising:
detecting a voltage value of each single cell in the flow battery stack;
and when the difference value between the voltage value of the single cell and the voltage balance reference value is larger than a voltage deviation threshold value, adjusting the difference value between the voltage of the single cell and the voltage balance reference value to be smaller than the voltage deviation threshold value.
10. The control method according to claim 9, characterized in that the method further comprises: and when the voltage value of the single cell is larger than the upper limit value of the single cell voltage or smaller than the lower limit value of the single cell voltage, bypassing the single cell or the single cell group where the single cell is positioned.
11. The control method according to claim 9 or 10, characterized in that the method further comprises: and when the voltage value of the flow battery pile is larger than the upper limit value of the voltage of the flow battery pile or smaller than the lower limit value of the voltage of the flow battery pile, bypassing the flow battery pile.
12. The control method according to any one of claims 9 to 11, characterized in that the control method further comprises: calculating the SOC value of the single cell according to the voltage value of the single cell;
when the SOC value of the single cell is larger than or equal to the upper limit value of the single cell SOC, the voltage value of the single cell is adjusted to be smaller than a first voltage threshold value;
when the SOC value of the single cell is smaller than or equal to the lower limit value of the single cell SOC, adjusting the voltage value of the single cell to be larger than a second voltage threshold value;
the second voltage threshold is less than the first voltage threshold.
13. A flow battery stack comprising a positive current collector plate, a negative current collector plate, a plurality of single cells, and a control device according to any one of claims 1-8;
a plurality of the single cells are connected in series;
the control device is connected with each single cell;
the control device is connected with the positive current collecting plate and the negative current collecting plate.
14. An energy storage system comprising a plurality of flow cell stacks of claim 13, a battery management system, and a power conversion unit;
a plurality of flow battery stacks are connected in series or in parallel;
the battery management system is used for communicating with the control device;
The power conversion unit is used for controlling the charging and discharging of the energy storage system.
15. An energy storage system, characterized in that the energy storage system comprises a plurality of flow battery stacks, a control device according to any of claims 1-8, a battery management system and a power conversion unit;
a plurality of flow battery stacks are connected in series or in parallel;
the battery management system is used for communicating with the control device;
the power conversion unit is used for controlling the charging and discharging of the energy storage system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310074833.1A CN116053532A (en) | 2023-01-12 | 2023-01-12 | Flow battery pile control device and control method, flow battery pile and energy storage system |
Applications Claiming Priority (1)
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| CN116742057A (en) * | 2023-08-11 | 2023-09-12 | 福建星云电子股份有限公司 | Pile controller and method |
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