Balanced charging method for energy storage device, energy storage device and equipment

Abstract

The present application relates to the technical field of energy storage equipment, and discloses a balanced charging method, energy storage device and equipment for energy storage devices, including: pre-charging the energy storage device, and sorting the SoC values ​​of multiple energy storage units on each phase line when the DC side voltage is stable; dynamically cutting off part of the multiple energy storage units on each phase line according to the sorting result, and determining that the energy storage device has completed pre-charging when the SoC values ​​of the remaining energy storage units after cutting off have reached a preset value; connecting the pre-charged energy storage device to the grid for operation, and performing intra-phase balancing control on multiple energy storage units on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, and performing inter-phase balancing control on the energy storage device according to the negative sequence component of the three-phase AC power grid, and quickly charging the energy storage device through a power ring. The present application can avoid overcharging or over-discharging of individual energy storage units, and greatly improve the reliability of the energy storage device.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage equipment, and in particular to a balanced charging method for an energy storage device, an energy storage device and equipment. Background Art

[0002] With the rapid development of renewable energy such as solar energy and wind energy and the corresponding new energy power systems, the importance of energy storage equipment in power systems, transportation and daily life has become increasingly prominent. Energy storage technology usually relies on battery packs, especially lithium-ion capacitors (LIC), which are high-rate energy storage components that can charge and discharge quickly, thus better adapting to the frequently changing power demand and the intermittent and unstable nature of renewable energy generation.

[0003] However, since different battery cells in a battery pack usually have differences in manufacturing process and aging degree, these differences may cause individual battery cells to be overcharged or over-discharged during the charge and discharge process, which will seriously affect the performance and life of the battery pack. Summary of the invention

[0004] The present application provides a balanced charging method, an energy storage device and equipment for an energy storage device, which solves the technical problem that the energy storage device is prone to uneven charging during the rapid charging process. The present application combines battery state of charge (SoC) sorting pre-charging with SoC balancing during grid-connected operation, and uses a power loop to quickly charge the energy storage device after SoC balancing control, thereby effectively balancing the charging state of each energy storage unit, avoiding overcharging or over-discharging of individual energy storage units, and greatly improving the reliability of the energy storage device.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0006] In a first aspect, an embodiment of the present application provides a balanced charging method for an energy storage device, wherein the energy storage device is charged based on a three-phase AC power grid, and each phase line of the energy storage device is cascaded with multiple energy storage units, wherein the balanced charging method includes:

[0007] Pre-charging the energy storage device, and sorting the SoC values ​​of the multiple energy storage units on each phase line when the DC side voltage of each energy storage unit is stable;

[0008] Dynamically partially removing a plurality of the energy storage units on each phase line according to the sorting result, and determining that the energy storage device has completed pre-charging when the SoC values ​​of the remaining energy storage units after the removal all reach a preset value;

[0009] The pre-charged energy storage device is connected to the grid for operation, and multiple energy storage units on each phase are controlled for intra-phase balancing according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, and inter-phase balancing of the energy storage device is controlled according to the negative sequence component of the three-phase AC power grid;

[0010] Determine the overall SoC mean of the energy storage device after completing the balancing control, and when the overall SoC mean is less than a first threshold, control the output power of the three-phase AC power grid through a power loop to quickly charge the energy storage device according to the output power.

[0011] The balanced charging method proposed in the embodiment of the present application pre-charges the energy storage device, and on this basis, sorts the SoC values ​​of multiple energy storage units on each phase line and performs partial dynamic removal, so as to dynamically adjust the charging strategy according to the charging state of each energy storage unit during the pre-charging process. The energy storage device that has completed pre-charging can be connected to the grid for operation, and further use the overall SoC mean and the intra-phase SoC mean to perform intra-phase balancing control on the energy storage units on each phase line. At the same time, the inter-phase balancing control of the energy storage device is achieved with the help of the negative sequence component of the power grid, so as to achieve comprehensive balanced control of the energy storage device in two dimensions, intra-phase and inter-phase. Therefore, the embodiment of the present application can effectively balance the charging state of each energy storage unit, avoid overcharging or over-discharging of individual energy storage units, and greatly improve the reliability of the energy storage device. In addition, the embodiment of the present application adopts a combination of intra-phase balancing control and inter-phase balancing control, which not only realizes voltage balancing between battery cells in each phase, but also makes full use of the negative sequence component of the three-phase AC power grid itself for inter-phase balancing control. Compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, the balancing control strategy is simplified, and the additional hardware requirements are reduced. Not only does it realize inter-phase balanced charging of the energy storage device, but it also reduces the hardware cost of balanced charging. And the embodiment of the present application can use the power ring to control the three-phase AC power grid to provide high-current charging to the energy storage device on the basis of inter-phase and intra-phase balancing control, so as to avoid the energy storage device being in a state of low SoC value for a long time after intra-phase balancing control and inter-phase balancing control. The power ring control can significantly reduce the charging time and increase the charging speed, thereby meeting the user's demand for fast charging.

[0012] Optionally, in some embodiments of the present application, the pre-charging the energy storage device includes:

[0013] A soft-start resistor is connected between the energy storage device and the three-phase AC power grid to perform current-limited charging on the energy storage device, and when the difference between the grid voltage of the three-phase AC power grid and the sum of the bridge arm voltages of all the energy storage units on each phase line is less than a second threshold, the soft-start resistor is removed to perform non-current-limited charging on the energy storage device.

[0014] The embodiment of the present application connects a soft-start resistor between the energy storage device and the three-phase AC power grid to limit the charging current by using the soft-start resistor, which can effectively reduce the current impact when the energy storage device is connected to the power grid, and prevent damage to the energy storage unit or instability of the power grid due to excessive current. In addition, when the difference between the grid voltage of the three-phase AC power grid and the sum of the bridge arm voltages of all energy storage units on each phase line is less than a preset second threshold value, the embodiment of the present application cuts off the soft-start resistor to obtain a larger charging current, thereby increasing the charging speed. Therefore, the embodiment of the present application can control the connection and removal of the soft-start resistor, which not only ensures the safe charging of the energy storage device, but also can flexibly adjust the charging method under different voltage conditions, thereby realizing an efficient and safe pre-charging process.

[0015] Optionally, in some embodiments of the present application, when the DC side voltage of each energy storage unit is stable, sorting the SoC values ​​of the multiple energy storage units on each phase line includes:

[0016] When the difference between the grid voltage of the three-phase AC grid and the sum of the bridge arm voltages of all the energy storage units on each phase line is zero, it is determined that the DC side voltage of each energy storage unit is in a stable state, and the energy storage units are sorted in ascending order according to the SoC value.

[0017] Optionally, in some embodiments of the present application, dynamically removing part of the plurality of energy storage units on each phase line according to the sorting result includes:

[0018] Determining the removable number of the energy storage units according to the rated voltage of the energy storage unit and the grid voltage of the three-phase AC grid, and determining a plurality of third thresholds corresponding to different charging stages according to the removable number;

[0019] The intra-phase SoC average of the energy storage device on each phase line is obtained respectively, and each time the intra-phase SoC average reaches the third threshold of the corresponding charging stage, the energy storage unit with the largest SoC value on each phase line is removed according to the sorting result.

[0020] The embodiment of the present application sorts the energy storage units in order of SoC values ​​from small to large, and removes the energy storage units with higher SoC values ​​when the SoC mean value in each phase reaches the third threshold value of the corresponding charging stage, so as to avoid overcharging of the energy storage units with higher SoC values, and ensure that the energy storage units with lower SoC values ​​can continue to be charged, so as to effectively balance the SoC values ​​of each energy storage module, thereby improving charging efficiency and safety. In addition, the embodiment of the present application can respond to grid voltage fluctuations in real time by adjusting the charging process according to the difference between the grid voltage and the bridge arm voltage of the energy storage unit, which greatly improves the stability and adaptability of the energy storage device.

[0021] Optionally, in some embodiments of the present application, the step of performing intra-phase balancing control on the multiple energy storage units on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device includes:

[0022] The overall SoC average of all energy storage units in the energy storage device is determined based on the following formula:

[0023] ;

[0024] In the formula, is the overall SoC average of all energy storage units in the energy storage device, N is the total number of energy storage units on each phase line, x represents the three phases A, B, and C of the three-phase AC power grid, x=a, b, c, is the SoC value of the i-th energy storage unit on each phase line;

[0025] The intra-phase SoC mean of the energy storage device is determined based on the following formula:

[0026] ;

[0027] In the formula, is the average SoC value in each phase corresponding to each phase line;

[0028] According to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, the intra-phase SoC correction value corresponding to each phase line is determined based on the following formula:

[0029] ;

[0030] In the formula, is the SoC correction value in each phase corresponding to the line. is the output current of each phase line, is the proportional parameter in the intra-phase balanced control PI parameter, The integral parameter in the intra-phase balance control PI parameter, s represents a complex variable;

[0031] Carrier phase shift modulation is performed on the intra-phase SoC correction value to generate a modulation wave, so as to perform intra-phase balancing control on the multiple energy storage units on each phase line according to the modulation wave.

[0032] The embodiment of the present application calculates an intra-phase SoC correction value based on the overall SoC mean value of the energy storage device and the intra-phase SoC mean value, and dynamically adjusts the SoC value of each energy storage unit according to the intra-phase SoC correction value, thereby ensuring that the SoC values ​​between the energy storage units on each phase line are balanced, avoiding overcharging problems of the energy storage device during grid-connected operation, and is conducive to improving the charging safety of the energy storage device during grid-connected operation.

[0033] Optionally, in some embodiments of the present application, the performing inter-phase balancing control on the energy storage device according to the negative sequence component of the three-phase AC power grid includes:

[0034] According to the intra-phase SoC mean value of the energy storage device, the d-axis negative sequence current reference value of the three-phase AC power grid in the dq rotating coordinate system is determined based on the following formula:

[0035] ;

[0036] In the formula, is the d-axis negative sequence current reference value, is the intra-phase SoC mean value of the energy storage device on the A-phase line, is the intra-phase SoC mean value of the energy storage device on the B phase line, is the intra-phase SoC average of the energy storage device on the C-phase line, is the proportional parameter in the phase balance control PI parameter, is the integral parameter in the phase balance control PI parameter, s represents a complex variable;

[0037] According to the intra-phase SoC average values ​​of the energy storage device on the B-phase line and the C-phase line, the q-axis negative sequence current reference value of the three-phase AC power grid in the dq rotating coordinate system is determined based on the following formula:

[0038] ;

[0039] In the formula, is the q-axis negative sequence current reference value;

[0040] Carrier phase shift modulation is performed on the q-axis negative-sequence current reference value and the q-axis negative-sequence current reference value to generate a modulation wave, so as to perform phase-to-phase balancing control on the multiple energy storage units on each phase line according to the modulation wave.

[0041] The embodiment of the present application utilizes the negative-sequence component of the three-phase AC power grid to effectively realize charging balance control between each phase line. Compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, the embodiment of the present application only needs to perform inter-phase balancing control based on the negative-sequence current existing in the three-phase AC power grid itself, which not only simplifies the balancing control strategy, but also reduces additional hardware requirements. Therefore, there is no need to set up corresponding hardware circuits for injecting zero-sequence voltage. While realizing inter-phase balanced charging of the energy storage device, it also reduces the hardware cost of balanced charging.

[0042] Optionally, in some embodiments of the present application, controlling the output power of the three-phase AC power grid through a power ring to quickly charge the energy storage device according to the output power includes:

[0043] According to the power reference value and the output power of the three-phase AC power grid, the current reference value component of the output current of the three-phase AC power grid in the dq coordinate system is determined based on the following formula:

[0044] ;

[0045] In the formula, is the current reference value component of the output current of the three-phase AC power grid on the d-axis, is the current reference value component of the output current of the three-phase AC power grid on the q-axis, is the active power reference value of the three-phase AC power grid, is the reactive power reference value of the three-phase AC power grid, is the active power output by the three-phase AC power grid, is the reactive power output by the three-phase AC power grid, is the proportional parameter in the active power PI parameter of the power loop, is the integral parameter of the active power PI parameter of the power loop, is the proportional parameter in the reactive power PI parameter of the power loop, is the integral parameter in the reactive power PI parameter of the power loop, and s is a complex variable;

[0046] Carrier phase shift modulation is performed on the current reference value components of the output current of the three-phase AC power grid on the d-axis and the q-axis to generate a modulation wave, so as to control the three-phase AC power grid to quickly charge the energy storage device according to the modulation wave.

[0047] The embodiment of the present application utilizes a power loop to control the active power of a three-phase AC power grid, so as to utilize the current reference value component on the d-axis related to the active power to provide high current charging to the energy storage device, so as to avoid the energy storage device being in a state of low SoC value for a long time after intra-phase balancing control and inter-phase balancing control. The power loop control can significantly reduce the charging time and increase the charging speed, thereby meeting the user's demand for fast charging. In addition, the power loop control not only realizes the fast charging of the energy storage device, but also utilizes the power loop to control the reactive power of the three-phase AC power grid, and provides reactive power compensation to the three-phase AC power grid through the current reference value component on the q-axis related to the reactive power, which is beneficial to maintaining system stability.

[0048] Optionally, in some embodiments of the present application, the energy storage unit includes an H-bridge, and the modulation wave is used to control the on and off of the switch tube in the H-bridge to adjust the charging and discharging mode of the energy storage device.

[0049] In a second aspect, an embodiment of the present application provides an energy storage device, which is charged based on a three-phase AC power grid, and the energy storage device includes:

[0050] Multiple energy storage units cascaded on each phase line;

[0051] A pre-charging module, used to pre-charge the energy storage device, and when the DC side voltage of each energy storage unit is stable, sort the SoC values ​​of the multiple energy storage units on each phase line, and dynamically cut off part of the multiple energy storage units on each phase line according to the sorting result, and determine that the energy storage device has completed pre-charging when the SoC values ​​of the remaining energy storage units after the cut-off all reach a preset value;

[0052] A balancing control module, used for connecting the pre-charged energy storage device to the grid for operation, and performing intra-phase balancing control on a plurality of energy storage units on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, and performing inter-phase balancing control on the energy storage device according to the negative sequence component of the three-phase AC power grid;

[0053] The power ring charging module is used to determine the overall SoC mean value of the energy storage device after completing the balancing control, and when the overall SoC mean value is less than a first threshold value, control the output power of the three-phase AC power grid through the power ring to quickly charge the energy storage device according to the output power.

[0054] The energy storage device proposed in the embodiment of the present application pre-charges the energy storage device, and on this basis, sorts the SoC values ​​of multiple energy storage units on each phase line and performs partial dynamic removal, so as to dynamically adjust the charging strategy according to the charging state of each energy storage unit during the pre-charging process. The energy storage device that has completed pre-charging can be connected to the grid for operation, and further use the overall SoC mean and the intra-phase SoC mean to perform intra-phase balancing control on the energy storage units on each phase line. At the same time, the inter-phase balancing control of the energy storage device is achieved with the help of the negative sequence component of the power grid, so as to achieve comprehensive balancing control of the energy storage device in two dimensions, intra-phase and inter-phase. Therefore, the embodiment of the present application can effectively balance the charging state of each energy storage unit, avoid overcharging or over-discharging of individual energy storage units, and greatly improve the reliability of the energy storage device. In addition, the embodiment of the present application adopts a combination of intra-phase balancing control and inter-phase balancing control, which not only realizes voltage balancing between battery cells in each phase, but also makes full use of the negative sequence component of the three-phase AC power grid itself for inter-phase balancing control. Compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, it simplifies the balancing control strategy and reduces the additional hardware requirements, which not only improves the balanced charging efficiency of the energy storage device, but also reduces the hardware cost of balanced charging. And the embodiment of the present application can use the power ring to control the three-phase AC power grid to provide high current charging to the energy storage device on the basis of inter-phase and intra-phase balancing control, so as to avoid the energy storage device being in a state of low SoC value for a long time after intra-phase balancing control and inter-phase balancing control. The power ring control can significantly reduce the charging time and increase the charging speed, thereby meeting the user's demand for fast charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 A schematic diagram of the circuit topology of the energy storage device proposed in the embodiment of the present application;

[0057] Figure 2 A schematic diagram of a flow chart of a balanced charging method for an energy storage device proposed in an embodiment of the present application;

[0058] Figure 3 A schematic diagram of the dynamic removal of part of the energy storage unit proposed in an embodiment of the present application;

[0059] FIG4( a) is a schematic diagram of a SoC simulation curve of an energy storage device during a pre-charging process proposed in an embodiment of the present application;

[0060] FIG4( b ) is a voltage simulation curve of the AC side during the pre-charging process proposed in an embodiment of the present application;

[0061] Figure 5 A strategic block diagram of the intra-phase balancing control proposed in an embodiment of the present application;

[0062] Figure 6 A strategic block diagram of the inter-phase balancing control proposed in an embodiment of the present application;

[0063] Figure 7 A strategic block diagram of the power loop control proposed in an embodiment of the present application;

[0064] Figure 8 This is a schematic diagram of the structure of the energy storage device proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0066] With the rapid development of renewable energy such as solar energy, wind energy and corresponding new energy power systems, the importance of energy storage equipment in power systems, transportation and daily life has become increasingly prominent. For example, in electric vehicles, in order to meet users' demand for fast charging of electric vehicles, it is crucial to develop efficient charging methods. It is necessary to significantly reduce the charging time through a fast charging mechanism to improve the user experience. For another example, in the field of renewable energy applications, due to the intermittent and unstable nature of renewable energy generation, fast charging methods can use energy storage equipment to effectively regulate the load of the power grid and improve the flexibility and stability of the power system.

[0067] In some application scenarios, energy storage technology usually relies on battery packs, especially lithium-ion capacitors (LIC). This high-rate energy storage element can charge and discharge quickly, so that it can better adapt to the frequently changing power demand and the intermittent and unstable nature of renewable energy generation.

[0068] However, different battery cells in a battery pack usually have differences in manufacturing process and aging degree. The difference in manufacturing process will lead to different electrochemical characteristics of the battery pack, which will affect the differences in parameters such as capacity and internal resistance of the battery cells, and further affect the charging speed of the battery cells during charging. As the battery pack is used for a longer time, the differences in parameters such as capacity and resistance of the battery cells will also lead to inconsistent aging degrees, and battery cells with more severe aging may not reach the set voltage in time during charging. Therefore, these differences will cause individual battery cells to be overcharged or over-discharged, which will seriously affect the performance and life of the battery pack.

[0069] The balanced charging method provided in this specification can also be applied to an application program running in the above-mentioned power control device.

[0070] In an embodiment of the present application, a balanced charging method for an energy storage device 10 is provided, such as Figure 1 As shown, the balanced charging method can be used in power control devices such as coordinated controllers in distributed energy generation systems such as photovoltaic systems and wind power generation. The energy storage device 10 is charged based on a three-phase AC power grid 20, and multiple energy storage units 11 are cascaded on each phase line of the energy storage device 10, and each energy storage unit 11 includes an H bridge, an LIC capacitor C, an inductor L1 and a battery pack. N energy storage units 11 are cascaded on each phase line to form a commutation chain.

[0071] Among them, Figure 2 As shown, the above-mentioned balanced charging method includes the following steps:

[0072] Step S1 , pre-charge the energy storage device 10 , and when the DC side voltage of each energy storage unit 11 is stable, sort the SoC values ​​of multiple energy storage units 11 on each phase line.

[0073] The embodiment of the present application ensures that the energy storage device 10 has sufficient energy storage before grid-connected operation by precharging the energy storage device 10, and starts the SoC balancing control strategy during the precharging process when the DC side voltage of the energy storage unit 11 is stable.

[0074] Step S3, dynamically cut off part of the multiple energy storage units 11 on each phase line according to the sorting result, and determine that the energy storage device 10 completes pre-charging when the SoC values ​​of the remaining energy storage units 11 after the cut-off reach a preset value.

[0075] The embodiment of the present application controls the removal order of the energy storage units 11 according to the SoC value sorting results to avoid overcharging of the energy storage units 11 with higher SoC values ​​and ensure that the energy storage units 11 with lower SoC values ​​can continue to be charged, thereby effectively balancing the SoC values ​​of each energy storage module.

[0076] It should be noted that, in some embodiments of the present application, the energy storage unit 11 is charged by uncontrolled rectification in both the above steps S1 and S3.

[0077] In step S5, the pre-charged energy storage device 10 is connected to the grid for operation, and multiple energy storage units 11 on each phase line are controlled to balance within the phase according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device 10, and the energy storage device 10 is controlled to balance between phases according to the negative sequence component of the three-phase AC power grid 20.

[0078] The embodiment of the present application utilizes the overall SoC mean value and the intra-phase SoC mean value of the energy storage device 10 to correct the SoC values ​​of multiple energy storage units 11 on each phase line to ensure that the SoC values ​​between the energy storage units 11 in each phase line remain balanced, and to avoid overcharging of some energy storage units 11 in a single phase during grid-connected operation. In addition, the embodiment of the present application performs inter-phase balancing control on the energy storage device 10 according to the negative sequence component of the three-phase AC power grid 20 to ensure that the SoC values ​​of the energy storage units 11 between the phase lines remain balanced, and to avoid overcharging of the energy storage units 11 in a certain phase.

[0079] Step S7, determining the overall SoC mean of the energy storage device 10 after completing the balancing control, and when the overall SoC mean is less than the first threshold, controlling the output power of the three-phase AC power grid 20 through the power loop to quickly charge the energy storage device 10 according to the output power.

[0080] The embodiment of the present application compares the overall SoC mean with the first threshold value, and can use the power loop to provide high-current charging to the energy storage device based on the balanced control between phases and within phases, so as to avoid the energy storage device being in a state of low SoC value for a long time after the intra-phase balanced control and the inter-phase balanced control.

[0081] The balanced charging method proposed in the embodiment of the present application pre-charges the energy storage device 10, and on this basis, sorts the SoC values ​​of multiple energy storage units 11 on each phase line and performs partial dynamic removal, so as to dynamically adjust the charging strategy according to the charging state of each energy storage unit 11 during the pre-charging process. The energy storage device 10 that has completed pre-charging can be connected to the grid for operation, and further use the overall SoC mean and the intra-phase SoC mean to perform intra-phase balancing control on the energy storage unit 11 on each phase line. At the same time, the inter-phase balancing control of the energy storage device 10 is achieved with the help of the negative sequence component of the power grid, so as to achieve comprehensive balanced control of the energy storage device 10 in two dimensions, intra-phase and inter-phase. Therefore, the embodiment of the present application can effectively balance the charging state of each energy storage unit 11, avoid overcharging or over-discharging of individual energy storage units 11, and greatly improve the reliability of the energy storage device 10. In addition, the embodiment of the present application adopts a combination of intra-phase balancing control and inter-phase balancing control, which not only realizes voltage balancing between battery cells in each phase, but also makes full use of the negative sequence component of the three-phase AC power grid 20 itself for inter-phase balancing control. Compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, the balancing control strategy is simplified, and the additional hardware requirements are reduced. Not only the inter-phase balanced charging of the energy storage device 10 is realized, but also the hardware cost of balanced charging is reduced. And the embodiment of the present application can use the power loop to control the three-phase AC power grid to provide high current charging to the energy storage device on the basis of inter-phase and intra-phase balancing control, so as to avoid the energy storage device being in a state of low SoC value for a long time after the intra-phase balancing control and the inter-phase balancing control. The power loop control can significantly reduce the charging time and increase the charging speed, thereby meeting the user's demand for fast charging.

[0082] In some embodiments of the present application, the above step S1 includes:

[0083] A soft-start resistor R is connected between the energy storage device 10 and the three-phase AC power grid 20. SS , so as to limit the current charging of the energy storage device 10, and when the difference between the grid voltage of the three-phase AC grid 20 and the sum of the bridge arm voltages of all energy storage units 11 on each phase line is less than the second threshold, the soft start resistor R is removed. SS , so as to charge the energy storage device 10 without current limiting.

[0084] Specifically, Figure 1 As shown, in some embodiments of the present application, the three-phase AC power grid 20 is connected to the energy storage device 10 through the isolation transformer 30, the inductor L2, the soft start unit 40, the air switch 50 and the current transformer 60 in sequence, wherein u sa 、u sb and u sc Represent the three-phase AC voltage, i sa 、i sb and isc In the embodiment of the present application, the switch KM1 is first closed to perform the uncontrolled rectification charging stage, at which time the switch KM2 is disconnected, so that the soft-start resistor R SS The current impact at the moment of power-on is reduced in this way, so as to realize current-limited charging of the energy storage device 10.

[0085] The embodiment of the present application is different from the cascade STATCOM sequencing charging strategy in the related art in that, considering the protection of the high-rate LIC energy storage element to prevent it from over-current charging, the embodiment of the present application will not immediately cut off the soft start resistor R during the pre-charging process. SS Instead, when the difference between the grid voltage of the three-phase AC grid 20 and the sum of the bridge arm voltages of all energy storage units 11 on each phase line is less than the second threshold, it is determined that the grid voltage is relatively stable at this time, and then the switch KM2 is closed to make the soft start resistor R SS The short circuit is cut off from the line, so that the energy storage device 10 is charged with a larger charging current without current limiting, thereby increasing the charging speed while ensuring charging safety.

[0086] It should be noted that the DC side voltage of the energy storage unit 11 is the voltage at the connection side of the H bridge and the LIC capacitor C, and the bridge arm voltage of the energy storage unit 11 is the AC voltage of the H bridge.

[0087] In the embodiment of the present application, a soft-start resistor R is connected between the energy storage device 10 and the three-phase AC power grid. SS , to use the soft-start resistor R SS Limiting the charging current can effectively reduce the current impact when the energy storage device 10 is connected to the power grid, and prevent damage to the energy storage unit 11 or instability of the power grid due to excessive current. In addition, in the embodiment of the present application, when the difference between the grid voltage of the three-phase AC grid and the sum of the bridge arm voltages of all energy storage units 11 on each phase line is less than a preset second threshold, the soft start resistor R is cut off. SS To obtain a larger charging current, thereby increasing the charging speed. Therefore, the embodiment of the present application can control the soft start resistor R SS The connection and removal not only ensures the safe charging of the energy storage device 10, but also can flexibly adjust the charging method under different voltage conditions, thereby realizing an efficient and safe pre-charging process.

[0088] In some embodiments of the present application, the above step S1 further includes:

[0089] When the difference between the grid voltage of the three-phase AC grid 20 and the sum of the bridge arm voltages of all the energy storage units 11 on each phase line is zero, it is determined that the DC side voltage of each energy storage unit 11 is in a stable state, and the energy storage units 11 are sorted in ascending order according to the SoC value.

[0090] Furthermore, the above step S3 includes:

[0091] Determine the number of removable energy storage units 11 according to the rated voltage of the energy storage unit 11 and the grid voltage of the three-phase AC grid 20, and determine a plurality of third thresholds corresponding to different charging stages according to the number of removable energy storage units 11;

[0092] The intra-phase SoC average of the energy storage device 10 on each phase line is obtained respectively, and when the intra-phase SoC average reaches the third threshold of the corresponding charging stage each time, the energy storage unit 11 with the largest SoC value on each phase line is removed according to the sorting result.

[0093] Specifically, Figure 3 As shown, when the difference between the grid voltage of the three-phase AC grid 20 and the sum of the bridge arm voltages of all energy storage units 11 on each phase line is zero, it means that the bridge arm voltage on the AC side of the H bridge is in a stable state, and then the DC side voltage of each energy storage unit 11 is determined to be in a stable state, and the energy storage units 11 are sorted in order from small to large according to the SoC value. For example, 7 energy storage units 11 are cascaded in the A phase line, and the SoC values ​​of these 7 energy storage units 11 are SoC a1 、SoC a2 、SoC a3 、SoC a4 、SoC a5 、SoC a6 and SoC a7 . Sorting is performed according to the current SoC value, and the sorting result is shown in the following formula (1):

[0094] SoC a1 SoC a3 SoC a5 SoC a6 SoC a4 SoC a7 SoC a2 Formula (1)

[0095] In one example of the embodiment of the present application, the rated voltage of the energy storage unit 11 is 40V, and the grid voltage of the three-phase AC grid 20 is 245V. Each phase line is composed of multiple energy storage units 11 connected in series, and the total voltage of each phase line is the sum of the rated voltages of all series energy storage units. In the embodiment of the present application, it is necessary to make the total voltage of each phase line as close to the grid voltage as possible, and it is allowed to fluctuate within the error range. For example, in this example, the error range of the total voltage of each phase line is the grid voltage. 20%, that is, the error range is 196V to 294V. If the number of cut-offs is greater than 2, for example, 3 energy storage units 11 are cut off, then the total voltage that the remaining 4 energy storage units 11 can provide is only 160V, which exceeds the above error range. Therefore, it is determined that the number of energy storage units 11 that can be cut off is 2, and therefore 2 third thresholds are set correspondingly, which are 70% and 81% respectively.

[0096] When the average SoC of all energy storage units 11 on the A phase line reaches 70%, the SoC a2 is the maximum value, indicating that SoC a2 The corresponding energy storage unit 11 is charged faster. If it continues to be charged with other energy storage units 11, overcharging may occur. a2 The corresponding energy storage unit 11 is removed from the A phase line, and the remaining other energy storage units 11 continue to charge and continuously update the sorting results. When the average intra-phase SoC of all energy storage units 11 on the A phase line reaches 81%, if the sorting result at this time is as shown in the following formula (2):

[0097] SoC a1 SoC a3 SoC a5 SoC a6 SoC a7 SoC a4 Formula (2)

[0098] Similarly, at this time SoC a4 is the maximum value, so the SoC a4 The corresponding energy storage unit 11 is cut off from the A-phase line, and the other energy storage units 11 continue to charge until the remaining energy storage units 11 are charged to the maximum SoC value, that is, the remaining energy storage units 11 are fully charged.

[0099] It should be noted that, in the embodiment of the present application, the removed energy storage unit 11 enters a locking mode to ensure that the bridge arm voltage remains balanced.

[0100] Figures 4(a) and 4(b) show the simulation results of the above dynamic removal. The initial SoC value of each energy storage unit 11 is set to 55%. First, uncontrolled rectification charging is performed. When the DC side voltage is stable, SoC sorting and balancing are started, and the simulation runs for 500s. The average SoC value of the energy storage unit 11 on the A phase line is shown in Figure 4(a), and the AC side current of the energy storage unit 11 is shown in Figure 4(b). Uncontrolled rectification charging is performed within 170s of the start of charging. When the SoC value of each energy storage unit 11 is smoothly increased to 70%, the first energy storage unit 11, that is, SoC a2 The corresponding energy storage unit 11 makes the SoC value of the energy storage unit 11 continue to rise to 81%, and the second energy storage unit 11 is removed, that is, SoC a4 The corresponding energy storage unit 11 is charged, and the SoC value of the remaining energy storage unit 11 continues to increase to the set value, thereby completing the pre-charging.

[0101] The embodiment of the present application sorts the energy storage units 11 in order of the SoC values ​​from small to large, and removes the energy storage units 11 with higher SoC values ​​when the SoC mean value in each phase reaches the third threshold value of the corresponding charging stage, so as to avoid overcharging of the energy storage units 11 with higher SoC values, and ensure that the energy storage units 11 with lower SoC values ​​can continue to be charged, so as to effectively balance the SoC values ​​of each energy storage module, thereby improving charging efficiency and safety. In addition, the embodiment of the present application adjusts the charging process according to the difference between the grid voltage and the bridge arm voltage of the energy storage unit 11, and can respond to grid voltage fluctuations in real time, greatly improving the stability and adaptability of the energy storage device 10.

[0102] In the embodiment of the present application, the energy storage device that has completed pre-charging will start grid-connected operation. During the grid-connected operation, the energy storage device will charge or discharge according to the energy demand of the three-phase AC power grid. The embodiment of the present application performs intra-phase balancing control and inter-phase balancing control for the charging process of the energy storage device in grid-connected operation.

[0103] In the embodiment of the present application, the energy storage device 10 that has completed pre-charging will start grid-connected operation. During the grid-connected operation, the energy storage device 10 will be charged or discharged according to the energy demand of the three-phase AC power grid 20. The embodiment of the present application performs intra-phase balancing control and inter-phase balancing control for the charging process of the energy storage device 10 in grid-connected operation.

[0104] In some embodiments of the present application, the above step S5 includes:

[0105] Based on the following formula (3), the overall inter-phase SoC average of all energy storage units 11 in the energy storage device 10 is determined as:

[0106] Formula (3)

[0107] In the formula, is the overall SoC average of all energy storage units 11 in the energy storage device 10, N is the total number of energy storage units 11 on each phase line, x represents the three phases A, B, and C of the three-phase AC power grid 20, x=a, b, c, is the SoC value of the i-th energy storage unit 11 on each phase line;

[0108] The intra-phase SoC mean of the energy storage device 10 is determined based on the following formula (4):

[0109] Formula (4)

[0110] In the formula, is the average SoC value in each phase corresponding to each phase line;

[0111] According to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device 10, the intra-phase SoC correction value corresponding to each phase line is determined based on the following formula (5):

[0112] Formula (5)

[0113] In the formula, is the SoC correction value in each phase corresponding to the line. is the output current of each phase line, is the proportional parameter in the intra-phase balanced control PI parameter, is the integral parameter in the intra-phase balanced control PI parameter, s represents a complex variable;

[0114] The intra-phase SoC correction value is subjected to carrier phase shift modulation to generate a modulation wave, so as to perform intra-phase balancing control on multiple energy storage units 11 on each phase line according to the modulation wave.

[0115] Specifically, the intra-phase balancing control strategy proposed in the embodiment of the present application is as follows: Figure 5 As shown in the figure, the average SoC value within the phase of phase A is Compared with the overall SoC average After being calculated by the subtractor, it is sent to the PI controller, and then the output result of the PI controller is compared with the output current of the A phase line. Perform multiplication operation to finally obtain the phase SoC correction value corresponding to phase A line Similarly, the intra-phase SoC average of phase B is Compared with the overall SoC average After being calculated by the subtractor, it is sent to the PI controller, and then the output result of the PI controller is compared with the output current of the B phase line. Perform multiplication operation to finally obtain the phase SoC correction value corresponding to the B phase line SoC average value within phase C line Compared with the overall SoC average After being calculated by the subtractor, it is sent to the PI controller, and then the output result of the PI controller is compared with the output current of the C phase line. Perform multiplication operation to finally obtain the phase SoC correction value corresponding to the C phase line .

[0116] Finally, , and It is sent to the carrier phase-shift modulator, and the switch tube of the H bridge in each energy storage unit 11 is controlled according to the output modulation wave. By adjusting the on and off states of the switch tube in the H bridge, the charge and discharge state of the energy storage unit 11 is controlled, so that the SoC value of each energy storage unit 11 in the energy storage device 10 reaches intra-phase balance.

[0117] Therefore, the embodiment of the present application implements intra-phase SoC balancing control based on mean calculation. Specifically, the intra-phase SoC correction value is calculated based on the overall SoC mean of the energy storage device 10 and the intra-phase SoC mean, and the SoC value of each energy storage unit 11 is dynamically adjusted according to the intra-phase SoC correction value, thereby ensuring that the SoC values ​​between the energy storage units 11 on each phase line are balanced, avoiding overcharging problems of the energy storage device 10 during grid-connected operation, and is conducive to improving the charging safety of the energy storage device 10 during grid-connected operation.

[0118] In some embodiments of the present application, the above step S5 further includes:

[0119] According to the intra-phase SoC mean value of the energy storage device 10, the d-axis negative sequence current reference value of the three-phase AC power grid 20 in the dq rotating coordinate system is determined based on the following formula (6):

[0120] Formula (6)

[0121] In the formula, is the d-axis negative sequence current reference value, is the average intra-phase SoC of the energy storage device 10 on the A phase line, is the average intra-phase SoC of the energy storage device 10 on the B phase line, is the intra-phase SoC average of the energy storage device 10 on the C phase line, is the proportional parameter in the phase balance control PI parameter, is the integral parameter in the phase balance control PI parameter, s represents a complex variable;

[0122] According to the intra-phase SoC average values ​​of the energy storage device 10 on the B phase line and the C phase line, the q-axis negative sequence current reference value of the three-phase AC power grid 20 in the dq rotating coordinate system is determined based on the following formula (7):

[0123] Formula (7)

[0124] In the formula, is the reference value of the q-axis negative sequence current;

[0125] Carrier phase shift modulation is performed on the q-axis negative-sequence current reference value and the q-axis negative-sequence current reference value to generate a modulation wave, so as to perform phase-to-phase balancing control on multiple energy storage units 11 on each phase line according to the modulation wave.

[0126] Specifically, the embodiment of the present application studies the power exchange law of the converter under the action of negative sequence current, and determines the three-phase power according to the following formula (8):

[0127] Formula (8)

[0128] In the formula, n represents negative sequence, , and are the active powers of phase A, phase B and phase C respectively, is the three-phase negative sequence current, is the voltage amplitude on the AC side, It is the negative sequence initial phase.

[0129] Then, the relationship between the exchange power and each phase voltage is determined according to the following formula (9):

[0130] Formula (9)

[0131] The component of the negative sequence current component in the dq rotating coordinate system is determined according to the following formula (10):

[0132] Formula (10)

[0133] Substituting formula (10) into formula (9), the relationship between the active power and the negative sequence current component in the dq rotating coordinate system can be obtained according to the following formula (11):

[0134] Formula (11)

[0135] At the same time, the active power of each phase is proportional to the AC voltage, and further proportional to the DC side voltage and the energy storage SoC, and the following formula (12) can be obtained:

[0136] Formula (12)

[0137] In the formula, , and are respectively the DC side voltages of the energy storage unit 11 corresponding to each phase line.

[0138] Therefore, the inter-phase balancing control strategy proposed in the embodiment of the present application is as follows: Figure 6 As shown in the figure, the average SoC value of the phase B line is The average SoC value within the phase of the C phase line After being sent to the adder, it undergoes proportional operation and the proportional operation result is compared with the phase SoC mean value of the A phase line. After being calculated by the subtractor, it is sent to the PI controller to obtain the d-axis negative sequence current reference value. At the same time, the SoC mean value within the phase of the B phase line is calculated. The average SoC value within the phase of the C phase line It is sent to the subtractor, and after proportional operation and PI controller, the q-axis negative sequence current reference value is obtained.

[0139] Finally, and The power is sent to the carrier phase-shift modulator, and the switch tube of the H bridge in each energy storage unit 11 is controlled according to the output modulation wave. The charge and discharge state of the energy storage unit 11 is controlled by adjusting the on and off state of the switch tube in the H bridge, so that the SoC value of each energy storage unit 11 in the energy storage device 10 reaches phase balance.

[0140] Therefore, the embodiment of the present application utilizes the negative-sequence component of the three-phase AC power grid 20 to effectively realize charging balance control between each phase line, and compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, the embodiment of the present application only needs to perform inter-phase balancing control based on the negative-sequence current existing in the three-phase AC power grid 20 itself, which not only simplifies the balancing control strategy, but also reduces additional hardware requirements. Therefore, there is no need to set up additional corresponding hardware circuits for injecting zero-sequence voltage. While realizing inter-phase balanced charging of the energy storage device 10, it also reduces the hardware cost of balanced charging.

[0141] In some embodiments of the present application, after the above step S5, the balanced charging method further includes:

[0142] When the overall SoC mean value of the energy storage device 10 is less than the first threshold, the output power of the three-phase AC power grid 20 is controlled by the power loop to quickly charge the energy storage device 10 according to the output power.

[0143] Furthermore, the output power of the three-phase AC power grid 20 is controlled by a power loop to quickly charge the energy storage device 10 according to the output power, including:

[0144] According to the power reference value and the output power of the three-phase AC power grid 20, the current reference value component of the output current of the three-phase AC power grid 20 in the dq coordinate system is determined based on the following formula (13):

[0145] Formula (13)

[0146] In the formula, is the current reference value component of the output current of the three-phase AC power grid 20 on the d-axis, is the current reference value component of the output current of the three-phase AC power grid 20 on the q axis, is the active power reference value of the three-phase AC power grid 20, is the reactive power reference value of the three-phase AC power grid 20, is the active power output by the three-phase AC power grid 20, is the reactive power output by the three-phase AC power grid 20, is the proportional parameter in the active power PI parameter of the power loop, is the integral parameter of the active power PI parameter of the power loop, is the proportional parameter in the reactive power PI parameter of the power loop, is the integral parameter in the reactive power PI parameter of the power loop, and s is a complex variable;

[0147] The current reference value components of the output current of the three-phase AC grid 20 on the d-axis and q-axis are subjected to carrier phase shift modulation to generate a modulation wave, so as to control the three-phase AC grid 20 to quickly charge the energy storage device 10 according to the modulation wave.

[0148] After adding the high-rate energy storage element LIC, the energy storage device 10 has the ability to output active power, but it is necessary to effectively manage the energy storage unit 11 in the energy storage device 10 according to the circuit topology to improve the energy utilization efficiency, extend the service life of the energy storage unit 11, and ensure that the energy storage device 10 can operate safely and stably. Since the energy storage unit 11 in the embodiment of the present application adopts the topology of passive filtering connected to the H bridge, the charging process of the energy storage unit 11 depends entirely on the power / energy demand on the AC side. This part adopts power loop control to obtain energy from the power grid and charges the high-rate LIC energy storage unit 11 during operation.

[0149] In the embodiment of the present application, the intra-phase balancing control and the inter-phase balancing control are to ensure that the SoC value of the energy storage unit 11 is as consistent as possible between each phase and each energy storage unit 11, so as to prevent the problem of overcharging or over-discharging of individual energy storage units 11. And the goal of the balancing process is to balance the SoC of each energy storage unit 11 by adjusting the energy flow between different phases or energy storage units 11, thereby ensuring the safe and stable operation of the system. However, since some energy storage units 11 may need to discharge to achieve balance during the process of intra-phase balancing and inter-phase balancing, this may cause the SoC value of the energy storage unit 11 of the balancing controller to decrease, or even cause the SoC to be too low.

[0150] When the SoC value of the energy storage unit 11 is detected, the embodiment of the present application uses the power ring to quickly charge the energy storage device 10 to ensure the charging efficiency of the energy storage unit 11. Specifically, the power ring control strategy proposed in the embodiment of the present application is as follows: Figure 7 As shown, first, according to the three-phase AC voltage amplitude and the three-phase AC current amplitude of the three-phase AC power grid 20, the active power and reactive power are calculated based on the following formula (14):

[0151] Formula (14)

[0152] In the formula, is the active power, is the reactive power, , and are the three-phase AC voltage amplitudes, , and are the three-phase AC current amplitudes respectively.

[0153] Then, the current reference value components of the output current of the three-phase AC power grid 20 on the d-axis and q-axis are calculated respectively, and the The actual current component of the output current on the d-axis Make a difference, and The actual current component of the output current on the q axis The difference is then generated through the PI controller and the carrier phase shift modulator (CPS-PWM) in sequence to generate a modulation wave. The power loop adjusts the active power output by the three-phase AC power grid 20 according to the output modulation wave to achieve fast charging of the energy storage device 10 by the three-phase AC power grid 20.

[0154] It should be noted that the embodiments of the present application introduce The three-phase AC power grid 20 is regulated to quickly charge the energy storage device 10. Realizing reactive power compensation for the three-phase AC power grid 20 is beneficial to improving system stability.

[0155] Therefore, the embodiment of the present application utilizes a power loop to control the active power of the three-phase AC power grid 20, so as to utilize the current reference value component on the d-axis related to the active power to provide high-current charging to the energy storage device 10, so as to avoid the energy storage device 10 being in a state of low SoC value for a long time after intra-phase balancing control and inter-phase balancing control. The power loop control can significantly reduce the charging time and increase the charging speed, thereby meeting the user's demand for fast charging. In addition, the power loop control not only realizes the fast charging of the energy storage device 10, but also utilizes the power loop to control the reactive power of the three-phase AC power grid 20, and provides reactive power compensation to the three-phase AC power grid 20 through the current reference value component on the q-axis related to the reactive power, which is beneficial to maintaining system stability.

[0156] Accordingly, please refer to Figure 8 The embodiment of the present application further provides an energy storage device 10, which is charged based on a three-phase AC power grid 20, and includes:

[0157] A plurality of energy storage units 11 are cascaded on each phase line;

[0158] The pre-charging module 12 is used to pre-charge the energy storage device 10, and when the DC side voltage of each energy storage unit 11 is stable, sort the SoC values ​​of the multiple energy storage units 11 on each phase line, and dynamically remove part of the multiple energy storage units 11 on each phase line according to the sorting result, and determine that the energy storage device 10 has completed pre-charging when the SoC values ​​of the remaining energy storage units 11 after removal reach a preset value;

[0159] A balancing control module 13 is used to connect the pre-charged energy storage device 10 to the grid for operation, and to perform intra-phase balancing control on multiple energy storage units 11 on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device 10, and to perform inter-phase balancing control on the energy storage device 10 according to the negative sequence component of the three-phase AC power grid 20;

[0160] The power ring charging module 14 is used to determine the overall SoC mean of the energy storage device 10 after completing the balancing control, and when the overall SoC mean is less than the first threshold, control the output power of the three-phase AC power grid 20 through the power ring to quickly charge the energy storage device 10 according to the output power.

[0161] The specific configuration of each of the above modules and units and further functional description are the same as those of the above corresponding embodiments and will not be repeated here.

[0162] The energy storage device proposed in the embodiment of the present application pre-charges the energy storage device, and on this basis, sorts the SoC values ​​of multiple energy storage units on each phase line and performs partial dynamic removal, so as to dynamically adjust the charging strategy according to the charging state of each energy storage unit during the pre-charging process. The energy storage device that has completed pre-charging can be connected to the grid for operation, and further use the overall SoC mean and the intra-phase SoC mean to perform intra-phase balancing control on the energy storage units on each phase line. At the same time, the inter-phase balancing control of the energy storage device is achieved with the help of the negative sequence component of the power grid, so as to achieve comprehensive balancing control of the energy storage device in two dimensions, intra-phase and inter-phase. Therefore, the embodiment of the present application can effectively balance the charging state of each energy storage unit, avoid overcharging or over-discharging of individual energy storage units, and greatly improve the reliability of the energy storage device. In addition, the embodiment of the present application adopts a combination of intra-phase balancing control and inter-phase balancing control, which not only realizes voltage balancing between battery cells in each phase, but also makes full use of the negative sequence component of the three-phase AC power grid itself to perform inter-phase balancing control. Compared with the inter-phase balancing technology of injecting zero-sequence voltage in the related art, it simplifies the balancing control strategy and reduces additional hardware requirements, which not only improves the balanced charging efficiency of the energy storage device, but also reduces the hardware cost of balanced charging.

[0163] The embodiment of the present application also provides a computer-readable storage medium. The above method according to the embodiment of the present application can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0164] The embodiment of the present application provides a computer program product, which includes computer instructions, which are stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the method of any embodiment of the present application.

[0165] Although the embodiments of the present application are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations fall within the scope defined by the appended claims. For the convenience of description, the above device is described separately by function into various units. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0166] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, devices, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0167] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0168] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0169] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0170] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0171] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0172] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0173] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A balanced charging method for an energy storage device, characterized in that: The energy storage device is charged based on a three-phase AC power grid, and a plurality of energy storage units are cascaded on each phase line of the energy storage device, wherein the balanced charging method includes: Pre-charging the energy storage device, and sorting the SoC values ​​of the multiple energy storage units on each phase line when the DC side voltage of each energy storage unit is stable; Dynamically partially removing a plurality of the energy storage units on each phase line according to the sorting result, and determining that the energy storage device has completed pre-charging when the SoC values ​​of the remaining energy storage units after the removal all reach a preset value; The pre-charged energy storage device is connected to the grid for operation, and multiple energy storage units on each phase are controlled for intra-phase balancing according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, and inter-phase balancing of the energy storage device is controlled according to the negative sequence component of the three-phase AC power grid; Determine an overall SoC mean value of the energy storage device after completing the balancing control, and when the overall SoC mean value is less than a first threshold value, control the output power of the three-phase AC power grid through a power loop to quickly charge the energy storage device according to the output power; The step of performing intra-phase balancing control on the multiple energy storage units on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device includes: The overall SoC average of all energy storage units in the energy storage device is determined based on the following formula: ； In the formula, is the overall SoC average of all energy storage units in the energy storage device, N is the total number of energy storage units on each phase line, x represents the three phases A, B, and C of the three-phase AC power grid, x=a, b, c, is the SoC value of the i-th energy storage unit on each phase line; The intra-phase SoC mean of the energy storage device is determined based on the following formula: ； In the formula, is the average SoC value in each phase corresponding to each phase line; According to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, the intra-phase SoC correction value corresponding to each phase line is determined based on the following formula: ； In the formula, is the SoC correction value in each phase corresponding to the line. is the output current of each phase line, is the proportional parameter in the intra-phase balanced control PI parameter, is the integral parameter in the intra-phase balanced control PI parameter, s represents a complex variable; Carrier phase shift modulation is performed on the intra-phase SoC correction value to generate a modulation wave, so as to perform intra-phase balancing control on the multiple energy storage units on each phase line according to the modulation wave.

2. The balanced charging method according to claim 1, characterized in that: The pre-charging of the energy storage device comprises: A soft-start resistor is connected between the energy storage device and the three-phase AC power grid to perform current-limited charging on the energy storage device, and when the difference between the grid voltage of the three-phase AC power grid and the sum of the bridge arm voltages of all the energy storage units on each phase line is less than a second threshold, the soft-start resistor is removed to perform non-current-limited charging on the energy storage device.

3. The balanced charging method according to claim 2, characterized in that: When the DC side voltage of each energy storage unit is stable, sorting the SoC values ​​of the multiple energy storage units on each phase line includes: When the difference between the grid voltage of the three-phase AC grid and the sum of the bridge arm voltages of all the energy storage units on each phase line is zero, it is determined that the DC side voltage of each energy storage unit is in a stable state, and the energy storage units are sorted in ascending order according to the SoC value.

4. The balanced charging method according to claim 1, characterized in that: The dynamically removing part of the plurality of energy storage units on each phase line according to the sorting result comprises: Determining the removable number of the energy storage units according to the rated voltage of the energy storage unit and the grid voltage of the three-phase AC grid, and determining a plurality of third thresholds corresponding to different charging stages according to the removable number; The intra-phase SoC average of the energy storage device on each phase line is obtained respectively, and each time the intra-phase SoC average reaches the third threshold of the corresponding charging stage, the energy storage unit with the largest SoC value on each phase line is removed according to the sorting result.

5. The balanced charging method according to claim 1, characterized in that: The step of performing inter-phase balancing control on the energy storage device according to the negative sequence component of the three-phase AC power grid comprises: According to the intra-phase SoC mean value of the energy storage device, the d-axis negative sequence current reference value of the three-phase AC power grid in the dq rotating coordinate system is determined based on the following formula: ； In the formula, is the d-axis negative sequence current reference value, is the intra-phase SoC mean value of the energy storage device on the A-phase line, is the intra-phase SoC mean value of the energy storage device on the B phase line, is the intra-phase SoC average of the energy storage device on the C-phase line, is the proportional parameter in the phase balance control PI parameter, is the integral parameter in the phase balance control PI parameter, s represents a complex variable; According to the intra-phase SoC average values ​​of the energy storage device on the B-phase line and the C-phase line, the q-axis negative sequence current reference value of the three-phase AC power grid in the dq rotating coordinate system is determined based on the following formula: ； In the formula, is the q-axis negative sequence current reference value; Carrier phase shift modulation is performed on the q-axis negative-sequence current reference value and the q-axis negative-sequence current reference value to generate a modulation wave, so as to perform phase-to-phase balancing control on the multiple energy storage units on each phase line according to the modulation wave.

6. The balanced charging method according to claim 1, characterized in that: The controlling the output power of the three-phase AC power grid through a power ring to quickly charge the energy storage device according to the output power includes: According to the power reference value and the output power of the three-phase AC power grid, the current reference value component of the output current of the three-phase AC power grid in the dq coordinate system is determined based on the following formula: ； In the formula, is the current reference value component of the output current of the three-phase AC power grid on the d-axis, is the current reference value component of the output current of the three-phase AC power grid on the q-axis, is the active power reference value of the three-phase AC power grid, is the reactive power reference value of the three-phase AC power grid, is the active power output by the three-phase AC power grid, is the reactive power output by the three-phase AC power grid, is the proportional parameter in the active power PI parameter of the power loop, is the integral parameter of the active power PI parameter of the power loop, is the proportional parameter in the reactive power PI parameter of the power loop, is the integral parameter in the reactive power PI parameter of the power loop, and s is a complex variable; Carrier phase shift modulation is performed on the current reference value components of the output current of the three-phase AC power grid on the d-axis and the q-axis to generate a modulation wave, so as to control the three-phase AC power grid to quickly charge the energy storage device according to the modulation wave.

7. The balanced charging method according to claim 5 or 6, characterized in that: The energy storage unit includes an H-bridge, and the modulation wave is used to control the on and off of the switch tube in the H-bridge to adjust the charging and discharging mode of the energy storage device.

8. An energy storage device, characterized in that: The energy storage device is charged based on a three-phase AC power grid, and the energy storage device includes: Multiple energy storage units cascaded on each phase line; A pre-charging module, used to pre-charge the energy storage device, and when the DC side voltage of each energy storage unit is stable, sort the SoC values ​​of the multiple energy storage units on each phase line, and dynamically cut off part of the multiple energy storage units on each phase line according to the sorting result, and determine that the energy storage device has completed pre-charging when the SoC values ​​of the remaining energy storage units after the cut-off all reach a preset value; A balancing control module, used for connecting the pre-charged energy storage device to the grid for operation, and performing intra-phase balancing control on a plurality of energy storage units on each phase line according to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, and performing inter-phase balancing control on the energy storage device according to the negative sequence component of the three-phase AC power grid; A power ring charging module, used to determine the overall SoC mean value of the energy storage device after completing the balancing control, and when the overall SoC mean value is less than a first threshold value, control the output power of the three-phase AC power grid through the power ring to quickly charge the energy storage device according to the output power; The balancing control module is also used for: The overall SoC average of all energy storage units in the energy storage device is determined based on the following formula: ； In the formula, is the overall SoC average of all energy storage units in the energy storage device, N is the total number of energy storage units on each phase line, x represents the three phases A, B, and C of the three-phase AC power grid, x=a, b, c, is the SoC value of the i-th energy storage unit on each phase line; The intra-phase SoC mean of the energy storage device is determined based on the following formula: ； In the formula, is the average SoC value in each phase corresponding to each phase line; According to the overall SoC mean value and the intra-phase SoC mean value of the energy storage device, the intra-phase SoC correction value corresponding to each phase line is determined based on the following formula: ； In the formula, is the SoC correction value in each phase corresponding to the line. is the output current of each phase line, is the proportional parameter in the intra-phase balanced control PI parameter, is the integral parameter in the intra-phase balanced control PI parameter, s represents a complex variable; Carrier phase shift modulation is performed on the intra-phase SoC correction value to generate a modulation wave, so as to perform intra-phase balancing control on the multiple energy storage units on each phase line according to the modulation wave.

9. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the balanced charging method according to any one of claims 1 to 7 by executing the computer instructions.

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