Water system sodium-ion battery double-closed-loop charging and discharging control method considering abnormal working conditions

Abstract

The invention discloses a water system sodium ion battery double-closed-loop charging and discharging control method considering abnormal working conditions, which is realized through a voltage controller constructed by a PI regulator, a current controller constructed by a PI regulator and an abnormal working condition controller. Double-closed-loop control of the charging process and the discharging process is achieved through the voltage controller and the current controller, and abnormal working condition control is achieved through the abnormal working condition controller. According to the invention, a reasonable and effective charging and discharging control strategy is provided for the water-based sodium-ion battery system, and single control of the energy storage module composed of the water-based sodium-ion battery and the bidirectional DC / DC converter is realized.

Description

Technical Field

[0001] The present invention relates to the field of microgrid sodium ion battery charge and discharge control methods, and in particular to a double closed-loop charge and discharge control method for aqueous sodium ion batteries taking into account abnormal operating conditions. Background Art

[0002] In the microgrid, the sodium ion battery (SIB) as an energy storage unit is connected to the DC bus through a bidirectional DC / DC converter. During the charging process, the external power supply charges the sodium ion battery through the DC bus and the bidirectional DC / DC converter. During the discharging process, the sodium ion battery discharges to the load through the bidirectional DC / DC converter and the DC bus.

[0003] In recent years, aqueous ion batteries that use aqueous solutions as electrolytes have gradually attracted the attention of researchers. They can effectively avoid the flammability problem of traditional organic electrolyte sodium ion batteries. At the same time, aqueous electrolytes have smaller solvent ion sizes, higher ion concentrations, and higher ion conductivity. Therefore, aqueous ion batteries usually have higher power density and cycle stability. In addition, aqueous electrolytes are easy to prepare on a large scale and easy to preserve, while the preparation process of organic system electrolytes is relatively complicated and the introduction of water and oxygen must be avoided. This greatly reduces the preparation cost of aqueous ion batteries and achieves the economy of large-scale energy storage.

[0004] The typical charging and discharging methods of aqueous sodium-ion batteries used in microgrids in the prior art include constant current, constant voltage, and constant power methods. Constant current charging and discharging refers to keeping the current constant during the entire charging or discharging process. Constant voltage charging and discharging refers to keeping the voltage at a constant value, and the current will change during the charging or discharging process. Constant power charging and discharging refers to keeping the output power constant during the charging or discharging process.

[0005] However, the typical charging and discharging methods of aqueous sodium-ion batteries in microgrids used in the prior art have the following problems: the current value of constant current charging and discharging remains unchanged, and the initial current value may appear small, which makes the charging time longer; while the current value appears large at the end, and a large current is still flowing in and out when the battery is almost fully charged or fully discharged, which may cause overcharging or over-discharging. Constant voltage charging and discharging often causes the initial current of SIB charging and discharging to be large, and the final current to be small, and the charging and discharging time is difficult to control. Therefore, in practice, SIB is rarely charged or discharged at a constant voltage for the entire cycle. During constant power charging and discharging, the terminal voltage of SIB is inversely proportional to the trend of the terminal current curve, which places high requirements on the battery management system and requires real-time adjustment of current and voltage. Summary of the invention

[0006] The present invention provides a dual closed-loop charge and discharge control method for an aqueous sodium ion battery taking into account abnormal operating conditions, so as to solve the problems existing in the charge and discharge method for an aqueous sodium ion battery in a microgrid in the prior art.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A dual closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal working conditions, wherein the sodium ion battery is connected to a DC bus through a bidirectional DC / DC converter, a voltage controller is constructed with a PI regulator, and a current controller is constructed with a PI regulator, including a charging process and a discharging process, wherein the charging process is as follows: The voltage controller obtains the actual input voltage of the sodium ion battery U d , and set the sodium ion battery input voltage to The actual input voltage U d The difference is used as input for proportional integration to obtain the input current reference value ; The current controller obtains the actual input current of the sodium ion battery i L And the current reference value output by the voltage controller , and the current reference value output by the voltage controller and the actual input current of the sodium ion battery i L The difference is used as input for proportional integration to obtain the duty cycle D to control the bidirectional DC / DC converter; when charging, the actual input current of the sodium ion battery is i L When the actual input current of the sodium ion battery increases i L Increase to the input current reference value At the same time, constant current charging is achieved. At this time, the duty cycle D remains constant, and the actual input voltage of the sodium ion battery is U d When the actual input voltage of the sodium ion battery U d Increase to equal the sodium ion battery input voltage setting value Constant voltage charging is achieved when the sodium ion battery actually outputs current i L Gradually decrease until the sodium ion battery is fully charged, thereby forming a double closed-loop charging process of current closed loop and voltage closed loop; The discharge process is as follows: The voltage controller obtains the actual voltage of the DC bus U o , and set the DC bus voltage to The actual DC bus voltage U o The difference is used as input for proportional integration to obtain the current reference value ; The current controller obtains the actual output current of the sodium ion battery i L And the current reference value output by the voltage controller , and the current reference value output by the voltage controller and the actual output current of the sodium ion battery i L The difference is used as input for proportional integration to obtain the duty cycle D to control the bidirectional DC / DC converter; when discharging, the actual output current of the sodium ion battery is i L When the actual output current of the sodium ion battery increases i L Increase to the current reference value At the same time, constant current discharge is achieved. At this time, the duty cycle D remains constant and the actual voltage of the DC bus U o When the actual voltage of the DC bus increases U o Increase to equal to the DC bus voltage setting value The output voltage is consistent with the DC bus voltage, thus forming a double closed-loop discharge process of current closed loop and voltage closed loop.

[0008] Furthermore, the proportional-integral formula of the voltage controller is as follows: , in, K P2 is the proportional coefficient of the voltage controller, K I2 is the integral coefficient of the voltage controller.

[0009] Furthermore, the proportional-integral formula of the current controller is as follows: , in, K P1 is the proportional coefficient of the current controller; K I1 is the integral coefficient of the current controller; The output current setting value of the sodium ion battery is based on the current reference value output by the voltage controller As the output current setting value of the sodium ion battery, that is .

[0010] Furthermore, it also includes an abnormal operating condition controller, the output of which is used to control the battery charge and discharge current setting value. During the charging and discharging process, the abnormal operating condition controller obtains the temperature of the sodium ion battery and compares the temperature of the sodium ion battery with the set upper limit of the battery temperature. When the temperature of the sodium ion battery is greater than the upper limit of the battery temperature, the abnormal operating condition controller Switch to 0.

[0011] Furthermore, during the charging and discharging process, the abnormal operating condition controller obtains the actual output current of the sodium ion battery i L , and the actual output current of the sodium ion battery i L Compared with the set output current upper limit, when the actual output current of the sodium ion battery is i L When the output current is greater than the upper limit, the abnormal condition controller will Switch to 0.

[0012] Furthermore, during the charging and discharging process, the abnormal condition controller obtains the actual output voltage of the sodium ion battery U d , and the actual output voltage of the sodium-ion battery U d Compared with the set output voltage upper limit, when the actual output voltage of the sodium ion battery U d When the output voltage is greater than the upper limit, the abnormal condition controller will Switch to 0.

[0013] The present invention determines the goal of mainly using aqueous sodium-ion batteries when exchanging energy with a DC power grid and mainly using the load when supplying power to the load. Taking into account abnormal parameters such as battery temperature, output voltage and output current, a reasonable and effective charge and discharge control strategy is proposed for the aqueous sodium-ion battery system, thereby realizing single-cell control of an energy storage module composed of an aqueous sodium-ion battery and a bidirectional DC / DC converter.

[0014] Compared with the prior art, the present invention has the following advantages: 1. Improve charging and discharging efficiency: By dividing the charging and discharging process into multiple stages, the optimal charging current and voltage can be used for different stages to improve the overall charging efficiency.

[0015] 2. Extend battery life: Staged charging and discharging can effectively control the battery's temperature, voltage and current, reduce the stress of the battery during the charging and discharging process, and thus extend the battery's cycle life.

[0016] 3. Optimize performance: By optimizing the charging and discharging at different stages, the overall performance of the battery can be improved, including energy density, power density, etc.

[0017] 4. Improve energy utilization: The staged charging and discharging strategy can more effectively utilize the battery's energy storage capacity, reduce energy loss, and thus improve energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the charging process of an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the discharge process of an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] This embodiment discloses a dual closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions. The sodium ion battery is connected to the DC bus through a bidirectional DC / DC converter. When charging, the external power supply charges the sodium ion battery through the DC bus and the bidirectional DC / DC converter. When discharging, the sodium ion battery discharges to the load through the bidirectional DC / DC converter and the DC bus. This embodiment is implemented based on a voltage controller constructed by a PI regulator, a current controller constructed by a PI regulator, and an abnormal operating condition controller constructed by three comparators, including a charging process and a discharging process.

[0022] Among them, Figure 1 As shown, the charging process is described as follows: The voltage controller obtains the actual input voltage of the sodium ion battery U d , and set the sodium ion battery input voltage to The actual input voltage U d The difference As input, proportional integration is performed to obtain the input current reference value , the proportional-integral formula of the voltage controller is as follows: , in, K P2 is the proportional coefficient of the voltage controller; K I2 is the integral coefficient of the voltage controller.

[0023] The current controller obtains the actual input current of the sodium ion battery i L And the current reference value output by the voltage controller , and the current reference value output by the voltage controller and the actual input current of the sodium ion battery i L The difference As input for proportional integration, the duty cycle D is obtained to control the bidirectional DC / DC converter. The proportional integral formula of the current controller is as follows: , in, K P1 is the proportional coefficient of the current controller; K I1 is the integral coefficient of the current controller; is the output current setting value of the sodium ion battery. In this embodiment, the current reference value output by the voltage controller is As the output current setting value of the sodium ion battery, that is .

[0024] When charging, the actual input current of the sodium ion battery is i L When the actual input current of the sodium ion battery increases i L Increase to the input current reference value At the same time, constant current charging is achieved. At this time, the duty cycle D remains constant, and the actual input voltage of the sodium ion battery is U d When the actual input voltage of the sodium ion battery U d Increase to equal the sodium ion battery input voltage setting value Constant voltage charging is achieved when the sodium ion battery actually outputs current i L It gradually decreases until the sodium-ion battery is fully charged, thus forming a dual closed-loop charging process of current closed loop and voltage closed loop.

[0025] like Figure 2 As shown, the discharge process is as follows: The voltage controller obtains the actual voltage of the DC bus U o , and set the DC bus voltage to The actual DC bus voltage U o The difference is used as input for proportional integration to obtain the current reference value ; The current controller obtains the actual output current of the sodium ion battery i L And the current reference value output by the voltage controller , and the current reference value output by the voltage controller and the actual output current of the sodium ion battery i LThe difference is used as input for proportional integration to obtain the duty cycle D to control the bidirectional DC / DC converter; when discharging, the actual output current of the sodium ion battery is i L When the actual output current of the sodium ion battery increases i L Increase to the current reference value At the same time, constant current charging is achieved. At this time, the duty cycle D remains constant and the actual voltage of the DC bus U o When the actual voltage of the DC bus increases U o Increase to equal to the DC bus voltage setting value The output voltage is consistent with the DC bus voltage, thus forming a double closed-loop discharge process of current closed loop and voltage closed loop.

[0026] The output of the abnormal condition controller is used to control the battery charge and discharge current setting value During the charging process, the abnormal condition controller obtains the sodium ion battery temperature T and the actual output current of the sodium ion battery i L , the actual output voltage of the sodium ion battery U d , and make abnormal working condition judgments, where the abnormal working condition judgment under temperature parameters is taken as the first priority, the abnormal working condition judgment result under current parameters is taken as the second priority, and the abnormal working condition judgment result under voltage parameters is taken as the third priority. In the actual execution order, the first priority is higher than the second priority, and the second priority is higher than the third priority, where: The abnormal condition controller compares the sodium ion battery temperature T with the set battery temperature upper limit T up For comparison, when the sodium ion battery temperature T is greater than the upper limit of the battery temperature T up When the abnormal condition controller Switch to 0.

[0027] The abnormal condition controller converts the actual output current of the sodium ion battery i L The output current upper limit is set i Lup For comparison, when the sodium ion battery actually outputs current i L Greater than the output current upper limit i Lup When the abnormal condition controller Switch to 0.

[0028] The abnormal condition controller converts the actual output voltage of the sodium ion batteryU d The output voltage upper limit is set U dup When compared with the actual output voltage of the sodium ion battery U d Greater than the output voltage upper limit U dup When the abnormal condition controller Switch to 0.

[0029] This embodiment adopts a dual closed-loop structure of a voltage loop and a current loop, and both the voltage outer loop and the current inner loop adopt a PI regulator with amplitude limiting. i L The negative feedback of the current controller increases continuously until , maintain constant current discharge; U o The negative feedback of the voltage controller increases to , keep the output voltage consistent with the DC bus voltage. When abnormal conditions such as high battery temperature, high output voltage, and high output current occur, the switch makes the battery output current set value When the DC-DC is 0, the battery is no longer discharged through the DC-DC.

[0030] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction, and such combinations should also be regarded as the contents disclosed in the present disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0031] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by technical personnel in this field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A dual closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions, wherein the sodium ion battery is connected to a DC bus via a bidirectional DC / DC converter, characterized in that: A voltage controller is constructed with a PI regulator, and a current controller is constructed with a PI regulator. During the charging process, the voltage controller sets the input voltage setting value of the sodium ion battery. The actual input voltage U d The difference is used as input for proportional integration to obtain the input current reference value ; The current controller sets the current reference value and the actual input current of the sodium ion battery i L The difference is used as input for proportional integration to obtain a duty cycle D to control the bidirectional DC / DC converter; forming a dual closed-loop charging process of current closed loop and voltage closed loop; During the discharge process, the voltage controller sets the DC bus voltage to The actual voltage of the DC bus U o The difference is used as input for proportional integration to obtain the current reference value ; The current controller sets the current reference value and the actual output current of the sodium ion battery i L The difference between the input and the output is used for proportional integration to obtain a duty cycle D to control the bidirectional DC / DC converter; A double closed-loop discharge process of current closed loop and voltage closed loop is formed.

2. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 1, characterized in that: During the charging process, the actual input current of the sodium ion battery is i L When the actual input current of the sodium ion battery increases i L Increase to the input current reference value At the same time, constant current charging is achieved. At this time, the duty cycle D remains constant, and the actual input voltage of the sodium ion battery is U d When the actual input voltage of the sodium ion battery U d Increase to equal the sodium ion battery input voltage setting value Constant voltage charging is achieved when the sodium ion battery actually outputs current i L It gradually decreases until the sodium-ion battery is fully charged, thus forming a dual closed-loop charging process of current closed loop and voltage closed loop.

3. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 1, characterized in that: During the discharge process, the sodium ion battery actually outputs current i L When the actual output current of the sodium ion battery increases i L Increase to the current reference value At the same time, constant current discharge is achieved. At this time, the duty cycle D remains constant and the actual voltage of the DC bus U o When the actual voltage of the DC bus increases U o Increase to equal to the DC bus voltage setting value The output voltage is consistent with the DC bus voltage, thus forming a double closed-loop discharge process of current closed loop and voltage closed loop.

4. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 1, characterized in that: The proportional-integral formula of the voltage controller is as follows: ， in, K P2 is the proportional coefficient of the voltage controller, K I2 is the integral coefficient of the voltage controller.

5. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 1, characterized in that: The proportional-integral formula of the current controller is as follows: , in, K P1 is the proportional coefficient of the current controller; K I1 is the integral coefficient of the current controller; The output current setting value of the sodium ion battery is based on the current reference value output by the voltage controller As the output current setting value of the sodium ion battery, that is .

6. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to any one of claims 1 to 5, characterized in that: It also includes an abnormal operating condition controller, the output of which is used to control the battery charge and discharge current setting value During the charging and discharging process, the abnormal operating condition controller obtains the temperature of the sodium ion battery and compares the temperature of the sodium ion battery with the set upper limit of the battery temperature. When the temperature of the sodium ion battery is greater than the upper limit of the battery temperature, the abnormal operating condition controller Switch to 0.

7. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 6, characterized in that: During the charging and discharging process, the abnormal condition controller obtains the actual output current of the sodium ion battery i L , and the actual output current of the sodium ion battery i L Compared with the set output current upper limit, when the actual output current of the sodium ion battery is i L When the output current is greater than the upper limit, the abnormal condition controller will Switch to 0.

8. The double closed-loop charge and discharge control method for aqueous sodium ion batteries considering abnormal operating conditions according to claim 6, characterized in that: During the charging and discharging process, the abnormal condition controller obtains the actual output voltage of the sodium ion battery U d , and the actual output voltage of the sodium-ion battery U d Compared with the set output voltage upper limit, when the actual output voltage of the sodium ion battery U d When the output voltage is greater than the upper limit, the abnormal condition controller will Switch to 0.

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