CN110417070A - All-vanadium redox flow battery system, based on group string all-vanadium redox flow battery system a SOC balance circuit and equalization methods - Google Patents

Abstract

The all-vanadium redox flow battery system, the SOC equalization circuit and equalization method based on the string all-vanadium redox flow battery system belong to the field of liquid flow batteries. Multiple battery subsystems are connected in series in the all-vanadium redox flow battery system, and if one or several of the battery subsystems have a higher SOC than the rest of the battery subsystems, then the battery subsystem is used as the power source of the load and put in, the effect is The electric energy is not only consumed to maintain the SOC balance of each electric stack, but also the energy is not wasted, and the electric energy is used to drive the load, thereby realizing energy saving.

Description

All-vanadium redox flow battery system, SOC balance battery system based on string all-vanadium redox flow battery system road and equalization method

technical field

The invention belongs to the field of liquid flow batteries, and relates to an all-vanadium redox flow battery system, a string-based SOC equalization circuit and an equalization method in the system.

Background technique

In recent years, large-scale wind power and photovoltaics have developed rapidly, but their access has also brought new problems to the power system. Energy storage technology is considered to be one of the effective ways to solve these problems. All-vanadium redox flow batteries have a large-scale energy storage Large size, fast response time, good safety, environmental friendliness, deep discharge and other advantages, it is a relatively promising energy storage battery.

Increasing the string voltage or current of the battery system is necessary for the development of large-scale all-vanadium redox flow batteries. Increasing the current of the battery system will greatly increase the cost of the battery system and reduce the economy. Therefore, increasing the string voltage of the battery system is a development An inevitable path for large-scale all-vanadium battery systems.

In order to increase the string voltage of the battery system, a large-scale all-vanadium redox flow battery energy storage power station is usually composed of several battery subsystems connected in series and parallel. Since the characteristics of the stack materials are not completely consistent, the resistance characteristics of the stack are also different, resulting in When charging in series, the state of charge of each battery subsystem is unbalanced, some battery subsystems are overcharged, some battery subsystems are undercharged, and when discharging, some battery subsystems are over-discharged, while some battery subsystems are not fully discharged , due to the short plate effect, the entire battery system is unavailable, which directly affects the efficiency of the all-vanadium redox flow battery. It is very important to realize the large-scale application of the all-vanadium redox flow battery system, prolong its service life, improve the economy, and solve the problem of how to deal with the consistency of the state of charge of multiple battery subsystems connected in series. The current solution is to equalize the SOC through the liquid circuit, which has the following disadvantages: there are many additional devices and the cost is high. Requires downtime for maintenance, complex operation, and reduced system utilization. Energy loss, reducing system efficiency.

Contents of the invention

In order to solve the problem of consistency of state of charge of multiple battery subsystems connected in series, the present invention proposes the following technical solution: a SOC equalization circuit based on a string all-vanadium redox flow battery system, including two-way power supply selection modules and all-vanadium liquid The load of the flow battery system, one of the two power supply selection modules is a battery subsystem power selection module, which is connected to a battery subsystem, and the other is an AC power selection module, which is connected to an AC power supply, and the load is the same For AC drive or DC drive, the power supply selection module is used to select the input power supply, process the output of the corresponding power supply, and output it to the load to drive the load. Multiple battery subsystems are connected in series in the all-vanadium redox flow battery system , and the SOC of one or several battery subsystems is higher than that of the rest of the battery subsystems, the battery subsystem is used as the power source of the load and put into operation.

As a supplement to the technical solution, the load is the circulating pump of the all-vanadium redox flow battery system.

As a supplement to the technical solution, the power selection module is a switching power supply and a DC-DC converter, and the input and cut-off of the power selection module are level-triggered. The cathode of the diode D1 is connected, the DC-DC converter is connected to the electric stack, and the cathode of the diode D2 is connected to the output side, and the common cathode of the diodes D1 and D2 is connected, and the load DC circulation pump is connected to the cathode.

As a supplement to the technical solution, the power supply selection module is a switch, the backup circuit of the switch is switchably connected to the inverter, the inverter is connected to the stack, and the priority input circuit of the switch is connected to the AC power supply Switchable connection; the switching side of the switch and the load is connected to the frequency converter, and the frequency converter is connected to the load AC circulation pump.

As a supplement to the technical solution, the power supply selection modules are frequency converters and DC-DC converters, and the two power supply selection modules seamlessly switch dual power sources by switching the mode of the frequency converter, and the DC-DC converter is connected to the frequency converter The DC bus, the inverter output is connected to the load AC circulation pump.

An all-vanadium redox flow battery system includes several series-connected battery subsystems and the SOC equalization circuit based on any one of the string-based all-vanadium redox flow battery systems.

An equalization method based on the SOC equalization circuit of the string all-vanadium redox flow battery system. Each battery subsystem and the DC circulation pump have two power sources, one of which is drawn from the AC power source and rectified into DC power through the switching power supply. Level triggering is used for cutting, and the other path is led from the stack of the battery subsystem. Through the DC-DC converter, the voltage of the stack terminal of the battery subsystem is converted to the voltage value available for the DC pump, and the DC-DC converter is switched on and off. Level triggering is adopted, the two DC power supplies use common cathode diodes, the branch with high voltage is prioritized for input, and the DC circulation pump is powered by AC power first; when a battery subsystem is charging, the SOC is higher than that of other battery subsystems due to the internal characteristics of the battery When the battery is activated, the DC-DC converter is triggered, and the circulation pump of the battery subsystem is powered by the battery stack of the battery subsystem. At this time, the battery subsystem operates with load while charging.

A method for equalizing the SOC equalization circuit based on the string all-vanadium redox flow battery system, each battery subsystem and the AC circulating pump have two power sources, one is derived from the AC power source, and the other is derived from the battery subsystem The stack, through the inverter, inverts the stack terminal voltage of the battery subsystem into AC power, and the two AC power sources use dual power sources to switch seamlessly, with the dual power sources being the main and the backup, and the AC branch is given priority by default; when a battery When the subsystem is charging, when the SOC is higher than other battery subsystems due to the internal characteristics of the battery, the inverter is turned on, and the power supply of the circulating pump of the battery subsystem is taken from the battery stack of the battery subsystem. At this time, the battery subsystem Run with load while charging.

A method for equalizing the SOC equalization circuit based on the string all-vanadium redox flow battery system, each battery subsystem and the AC circulating pump have two power sources, one is derived from the AC power source, and the other is derived from the battery subsystem The stack voltage of the battery subsystem is directly connected to the DC bus of the inverter through the DC-DC converter, and the two-way power supply can be switched seamlessly through the switching of the inverter operating mode. The default AC branch is prioritized; when a battery When the subsystem is charging, when the SOC is higher than other battery subsystems due to the internal characteristics of the battery, the inverter switches to the inverter mode, and the circulation pump power supply of the battery subsystem is taken from the DC side of the inverter. At this time, the battery subsystem Run with load while charging.

Beneficial effects: In the equalizing circuit of the present invention, multiple stacks of the battery subsystems are connected in series in the all-vanadium redox flow battery system, and the SOC of one or some of the battery subsystems is higher than that of the rest of the battery subsystems, Then select the battery subsystem as a power source and put it into use, that is, the load in the all-vanadium redox flow battery subsystem is used to consume the power of the battery subsystem with an abnormally high SOC in the battery subsystem in series, thereby reducing the battery subsystem. The SOC of the battery subsystem is balanced with other battery subsystems, and the electricity generated by the battery subsystem due to the high SOC is switched to the all-vanadium redox flow battery system, so that this part of the electricity not only maintains the SOC balance of the battery subsystem, but also Energy is not wasted, and the electricity is used to drive the load of the battery system itself, realizing energy saving.

Description of drawings

Fig. 1 is the structural representation of the all-vanadium redox flow battery system of the first embodiment of the present invention;

Figure 2 is an equivalent impedance diagram inside the resistor;

Fig. 3 is the structural representation of the vanadium redox flow battery system of the second embodiment of the present invention;

Fig. 4 is the structural representation of the all-vanadium redox flow battery system of the second embodiment of the present invention;

FIG. 5 is a flow chart of SOC equalization control.

Detailed ways

Example 1:

An SOC equalization circuit based on a string all-vanadium redox flow battery system. The circuit is composed of multiple sets of battery subsystems connected in series. Each set of battery subsystems uses a DC circulation pump. The DC circulation pump has two power sources, one of which is led The power supply is rectified into direct current through the switching power supply. voltage converter), which converts the stack terminal voltage to the available voltage value of the DC circulation pump, and the DC-DC converter is switched on and off using level triggering. The two-way DC power supply uses a common cathode diode, and the high-voltage branch is automatically switched on first. The DC circulation pump is powered by AC power supply first. When a battery subsystem is charging and the SOC is higher than that of other battery subsystems due to the internal characteristics of the battery, the DC-DC converter is triggered, and the power supply of the circulation pump of the battery subsystem is switched to The stack of the battery subsystem. At this time, the battery subsystem is running with its own load while charging, which is equivalent to the reduction of the battery charging current. After a period of time, the SOC of the battery subsystem and other battery subsystems can be effectively reduced. difference. The detailed strategy is as follows: When the difference between the SOC value of a single battery subsystem and other battery systems is higher than 5% (adjustable), the DC-DC converter is triggered, and the power supply of the DC circulating pump is provided by the stack through the converter. The power of the circulation pump can be adjusted, and the circulation pump is put into operation at the rated power Pe. When the difference between the SOC of the battery subsystem and other systems drops to 4%, the circulation pump operates at 3/4Pe. When the SOC of the battery subsystem is equal to When the difference between other systems drops to 3%, the circulating pump runs at 1/2Pe. When the difference between the SOC of the battery subsystem and other systems drops to 1%, the circulating pump runs at 1/4Pe. When the SOC is lower than other battery system values, and the difference is less than 1%, the DC circulating pump power supply is switched to AC power supply, and the adjustment process ends.

Example 2:

An SOC equalization circuit based on a string all-vanadium redox flow battery system. The circuit is composed of multiple battery subsystems connected in series. Each battery subsystem uses an AC circulation pump. The AC circulation pump has two power sources, one of which is drawn from the ; The other way leads from the stack of the battery subsystem, and through the inverter, the voltage at the stack terminal is inverted into alternating current. The two-way AC power supply is switched by a switch to realize seamless switching of the dual power supply. The dual power supply is one main and one backup. The default AC branch is put into priority. The electric stack, the priority input circuit of the switch is switchably connected to the AC power supply; the switching side of the switch and the load is connected to the frequency converter, and the frequency converter is connected to the load AC circulation pump. When a battery subsystem is charging, the SOC is higher than other battery subsystems due to the internal characteristics of the battery, and the inverter is put into operation. The circulating pump power of this battery subsystem is taken from the battery stack of the battery subsystem. The set of battery subsystems runs with its own load while charging, which is equivalent to reducing the battery charging current. After a period of time, the SOC difference between this set of battery subsystems and other battery subsystems can be effectively reduced. The detailed strategy is as follows: When the difference between the SOC value of a single battery subsystem and other battery subsystems is higher than 5% (adjustable), the dual power supply is switched by remote control, and the inverter branch is switched on. Since the power of the circulating pump can be adjusted , the circulation pump is put into operation at the rated power Pe, when the difference between the SOC of the battery subsystem and other systems drops to 4%, the circulation pump operates at 3/4Pe, when the SOC of the battery subsystem is different from other battery subsystems value drops to 3%, the circulation pump runs at 1/2Pe, when the difference between the SOC of the battery subsystem and other battery subsystems drops to 1%, the circulation pump runs at 1/4Pe, when the SOC ratio of the battery subsystem When the other battery system values are low and the difference is less than 1%, the circulation pump power supply is switched to the AC power supply, and the adjustment process ends.

Example 3:

An SOC equalization circuit based on a string all-vanadium redox flow battery system. The circuit is composed of multiple battery subsystems connected in series. Each battery subsystem uses an AC circulation pump. The AC circulation pump has two power sources, one of which is drawn from the The other one is from the electric stack of the battery subsystem, and the electric stack voltage is directly connected to the DC bus of the inverter through the DC-DC booster, and the seamless switching between the two power sources is realized through the switching of the working mode of the inverter. By default, the AC branch is put into priority. When a battery subsystem is charging, the SOC of the battery subsystem is higher than that of other battery subsystems due to the internal characteristics of the battery, and the inverter switches to the inverter mode. At this time, the set of battery subsystems is running with load while charging, which is equivalent to the reduction of battery charging current. After a period of time, the SOC difference between this set of battery subsystems and other battery subsystems can be effectively reduced. The detailed strategy is as follows: When the difference between the SOC value of a single battery subsystem and other battery subsystems is higher than 5% (adjustable), switch the working mode of the inverter, and the inverter works in the inverter mode. When the difference between the SOC of this set of battery subsystems and other battery subsystems drops to 4%, the circulation pump operates at 3/4Pe, when the SOC of this set of battery subsystems and other battery subsystems When the difference value of the battery subsystem drops to 3%, the circulating pump runs at 1/2Pe. When the difference between the SOC of the battery subsystem and other battery subsystems drops to 1%, the circulating pump runs at 1/4Pe. The SOC of the battery subsystem is lower than that of other battery subsystems. When the differential pressure value is less than 1%, the inverter switches to AC power supply, and the circulating pump power supply switches to AC power supply, that is, the inverter adjustment process ends.

Example 4:

An all-vanadium redox flow battery system, including a battery control system, several battery subsystems connected in series, and an SOC equalization circuit based on any one of the above-mentioned string-based all-vanadium redox flow battery systems, each battery subsystem has N battery The battery subsystem is composed of stacks and series, and different battery subsystems are connected in series. The battery subsystem adopts a speed-regulating pump, and the maximum power accounts for about 1/4 of the battery subsystem; the power of the pump can be adjusted. By adjusting the power of the pump of each battery subsystem and switching The pump supplies power to adjust the SOC of each battery subsystem. During the charging or discharging process, the circulating pump of the battery subsystem is powered by AC first. When the SOC of a certain battery subsystem is high, the circulating pump of the battery subsystem is switched to the battery system for power supply. By adjusting the power of the pump in real time online, that is, adjusting the charging and discharging current of the battery can ensure that the SOC difference of each battery subsystem connected in series during the charging and discharging process is less than 1%. The system effectively solves the SOC balance problem of subsystems connected in series with multiple vanadium redox flow batteries. Among them, the equalization circuit and the all-vanadium redox flow battery system involved have the following effects: save equipment, reduce costs; increase battery system utilization rate; connect batteries in series, increase battery system voltage, reduce battery system current, reduce system loss, and improve battery system efficiency .

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope of the disclosure of the present invention, according to the present invention Any equivalent replacement or change of the created technical solution and its inventive concept shall be covered within the scope of protection of the present invention.

Claims (9)

1. A SOC equalization circuit based on a string all-vanadium redox flow battery system, characterized in that it comprises two power supply selection modules and the load of the all-vanadium redox flow battery system, and one of the two power supply selection modules is a battery Subsystem power selection module, which is connected to a battery subsystem, and the other is an AC power selection module, which is connected to an AC power supply, and the loads are both AC driven or DC driven, and the power selection module is used to select input power, and The output processing of its corresponding power supply is output to the load to drive the load. Multiple battery subsystems are connected in series in the all-vanadium redox flow battery system, and one or several battery subsystems have higher SOC than the rest of the battery subsystems, then The battery subsystem is used as the power source of the load and put into operation. 2. The SOC equalization circuit based on the string all-vanadium redox flow battery system according to claim 1, wherein the load is a circulation pump of the all-vanadium redox flow battery system. 3. The SOC equalization circuit based on the group string all-vanadium redox flow battery system as claimed in claim 1, wherein the power selection module is respectively a switching power supply and a DC-DC converter, and the input of the power selection module and Cut off as a level trigger, the switching power supply is connected to the AC power supply, and the cathode of the diode D1 is connected on its output side, and the DC-DC converter is connected to the stack, and the cathode of the diode D2 is connected on the output side of the diode. D1 and D2 have a common cathode, and a load DC circulation pump is connected to the cathode. 4. The SOC equalization circuit based on the string all-vanadium redox flow battery system as claimed in claim 1, wherein the power supply selection module is a switch, and the backup circuit of the switch and the inverter can be switched connection, the inverter is connected to the stack, and the priority input circuit of the switch is switchably connected to the AC power supply; the connection side of the switch and the load is connected to the frequency converter, and the frequency converter is connected to the load AC circulation pump. 5. The SOC equalization circuit based on the group string all-vanadium redox flow battery system as claimed in claim 1, wherein the power selection modules are frequency converters and DC-DC converters respectively, and the two power supply selection modules are The inverter mode switches to seamlessly switch dual power supplies, and the DC-DC converter is connected to the DC bus of the inverter, and the output of the inverter is connected to the load AC circulation pump. 6. An all-vanadium redox flow battery system, characterized in that it comprises several series-connected battery subsystems and the SOC equalization circuit based on the string-based all-vanadium redox flow battery system according to any one of claims 1-5. 7. A balancing method based on the SOC balancing circuit of the group string all-vanadium redox flow battery system according to claim 3, characterized in that, each battery subsystem, the DC circulation pump has two power supplies, one of which is drawn from the AC power supply , the switching power supply is rectified into direct current, the switch power input and cut-off adopt level trigger, and the other one is led from the stack of the battery subsystem, through the DC-DC converter, the voltage of the stack terminal of the battery subsystem is converted to the DC pump. The DC-DC converter is switched on and off using level triggering, the two DC power supplies use common cathode diodes, the branch with high voltage is prioritized to be switched on, and the DC circulating pump is powered by AC power first; when a battery subsystem is charging, When the SOC is higher than that of other battery subsystems due to the internal characteristics of the battery, the DC-DC converter is triggered, and the power supply of the circulating pump of the battery subsystem is taken from the battery stack of the battery subsystem. At this time, the battery subsystem is in Run with load while charging. 8. An equalization method based on the SOC equalization circuit of the group string all-vanadium redox flow battery system according to claim 4, characterized in that, each battery subsystem, the AC circulation pump has two power sources, one of which is drawn from the AC power source , the other one is from the stack of the battery subsystem, through the inverter, the voltage of the stack terminal of the battery subsystem is inverted into AC power, and the two AC power sources are seamlessly switched by dual power sources. The AC branch is put into priority; when a certain battery subsystem is charging, when the SOC is higher than that of other battery subsystems due to the internal characteristics of the battery, the inverter is turned on, and the power supply of the circulation pump of the battery subsystem is taken from the power supply of the battery subsystem. Stack, at this time, the battery subsystem is running with load while charging. 9. An equalization method based on the SOC equalization circuit of the group string all-vanadium redox flow battery system according to claim 5, characterized in that, for each battery subsystem, the AC circulating pump has two power sources, one of which is drawn from the AC power source , the other one is from the stack of the battery subsystem, the stack voltage of the battery subsystem is directly connected to the DC bus of the inverter through the DC-DC converter, and the seamless switching between the two power sources is realized by switching the working mode of the inverter. The AC branch is put into priority; when a battery subsystem is charging, when the SOC is higher than other battery subsystems due to the internal characteristics of the battery, the inverter switches to the inverter mode, and the circulation pump power of the battery subsystem is taken from the DC side of the inverter , at this time, the battery subsystem is running with load while charging.