Cascade H-bridge energy storage interphase SOC fast equalization method and cascade H-bridge energy storage system

Abstract

The invention relates to the technical field of electrochemical energy storage, and discloses a cascade H-bridge energy storage inter-phase SOC rapid equalization method and a cascade H-bridge energy storage system.The equalization method comprises the steps that when the inter-phase residual electric quantity deviation is larger than a preset value, the A / B / C three-phase residual electric quantity is calculated, and the average value of the A / B / C three-phase residual electric quantity is calculated; a switch between a first phase and a second phase is closed, the first phase is controlled to charge the second phase through a carrier phase-shifting modulation method, the first phase is the phase with the residual electric quantity larger than the average value, and the second phase is the phase with the residual electric quantity smaller than the average value; and after the three-phase cascaded H-bridge system completes inter-phase SOC equalization, normal operation is recovered. Two groups of switches are additionally arranged on the energy storage network side of the cascaded H bridge, so that direct parallel connection of three-phase cascaded modules of the cascaded H bridge can be realized, and then the charging and discharging power among the three-phase cascaded modules can be controlled by controlling the output voltage of each phase, so that the inter-phase SOC balance can be quickly realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly relates to a method for quickly balancing the inter-phase SOC of a cascaded H-bridge energy storage and a cascaded H-bridge energy storage system. Background Art

[0002] The development of large-capacity battery energy storage technology is beneficial to improving the installed capacity of wind and solar power sources and promoting the transformation of the energy structure. Conventional energy storage systems are limited by technologies such as battery materials, battery grouping, and battery management systems, and the single-unit capacity generally does not exceed 0.5 MW. Conventional large-capacity energy storage power stations generally operate multiple such energy storage systems in parallel on the low-voltage AC side and are connected to the high-voltage power grid through step-up transformers step by step. However, energy storage power stations based on conventional architectures have problems such as low energy cycle efficiency, obvious cask effect, low battery utilization rate, and poor safety. The high-voltage direct-connected energy storage system based on the cascaded H-bridge converter has a highly modular structure, and its single-unit equipment has a large capacity. Compared with traditional energy storage systems, the high-voltage direct-connected energy storage realizes large single-unit capacity, and at the same time meets the requirements of high efficiency, high reliability, economy, and safety.

[0003] However, during the normal charge and discharge operation of the high-voltage direct-connected energy storage system based on the cascaded H-bridge converter, there will be a phenomenon of excessive deviation of the inter-phase SOC (State Of Charge). Especially for the cascaded H-bridge energy storage used for frequency modulation, since the frequency modulation working condition is generally in the shallow charge and discharge operation range of the battery, after the frequency modulation energy storage operates for a long time, there will be a deviation in the measurement of SOC. If the SOC calibration of full charge and full discharge is not performed for a long time, the inter-phase SOC deviation will become larger and larger, and finally the inter-phase SOC deviation will be too large and the alarm will stop operation. After the phenomenon of excessive inter-phase SOC deviation occurs, it is necessary to perform balanced operation and maintenance on the inter-phase SOC of the cascaded H-bridge energy storage. However, there is currently a lack of relevant operation and maintenance methods. Summary of the Invention

[0004] In view of this, the present invention provides a method for quickly balancing the inter-phase SOC of a cascaded H-bridge energy storage and a cascaded H-bridge energy storage system to solve the problem that there is currently a lack of an SOC balanced operation and maintenance solution.

[0005] In a first aspect, the present invention provides a method for quickly balancing the inter-phase SOC of a cascaded H-bridge energy storage. The method is based on a cascaded H-bridge energy storage system, and a set of switches is arranged between every two phases on the grid side of the cascaded H-bridge energy storage system. The method includes:

[0006] When the deviation of the remaining charge between phases is greater than a preset value, calculate the remaining charge of the A / B / C three phases respectively, and calculate the average value of the remaining charge of the A / B / C three phases;

[0007] Close the switch between the first phase and the second phase, and control the charging from the first phase to the second phase by means of carrier phase-shifted modulation. The first phase is the phase with the remaining power greater than the average value, and the second phase is the phase with the remaining power less than the average value;

[0008] After the three-phase cascaded H-bridge system completes the inter-phase SOC balancing, it resumes normal operation.

[0009] A method for rapid inter-phase SOC balancing of a cascaded H-bridge energy storage provided by the present invention can realize the direct parallel connection of the three-phase cascaded modules of the cascaded H-bridge by adding two groups of switches on the grid side of the cascaded H-bridge energy storage. Then, by controlling the output voltage of each phase, the charge and discharge power between the three-phase cascaded modules can be controlled, so as to rapidly realize the inter-phase SOC balancing.

[0010] In an optional embodiment, the step of closing the switch between the first phase and the second phase and controlling the charging from the first phase to the second phase by means of carrier phase-shifted modulation includes:

[0011] Sort the remaining power of the three phases A / B / C to generate a sorting sequence;

[0012] Compare the median value of the sorting sequence with the average value to determine the first phase and the second phase.

[0013] In an optional embodiment, the step of comparing the median value of the sorting sequence with the average value to determine the first phase and the second phase includes:

[0014] When the median value is greater than the average value, determine that the first phase is the phase corresponding to the median value and the phase corresponding to the maximum value of the sorting sequence, and determine that the second phase is the phase corresponding to the minimum value of the sorting sequence.

[0015] In an optional embodiment, the step of comparing the median value of the sorting sequence with the average value to determine the first phase and the second phase further includes:

[0016] When the median value is not greater than the average value, determine that the first phase is the phase corresponding to the maximum value of the sorting sequence, and determine that the second phase is the phase corresponding to the median value and the phase corresponding to the minimum value of the sorting sequence.

[0017] In an optional embodiment, the step of closing the switch between the first phase and the second phase and controlling the charging from the first phase to the second phase by means of carrier phase-shifted modulation further includes:

[0018] Close the switch between the two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value;

[0019] Adopt the method of carrier phase-shifted modulation of cascaded H-bridge modules, respectively perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the minimum value, establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the minimum value.

[0020] In an alternative embodiment, closing the switch between the first phase and the second phase, and controlling the first phase to charge the second phase by the method of carrier phase-shifted modulation, further includes:

[0021] Closing the switch between two phases, and the two phases are the phase corresponding to the intermediate value and the phase corresponding to the minimum value;

[0022] Adopt the method of carrier phase-shifted modulation of cascaded H-bridge modules, respectively perform open-loop control on the phase corresponding to the intermediate value and the phase corresponding to the minimum value, establish an AC voltage, and control the phase corresponding to the intermediate value to charge the phase corresponding to the minimum value.

[0023] In an alternative embodiment, the angle by which the phase of the output voltage of phase x leads the phase of the output voltage of phase z is calculated by the following formula:

[0024]

[0025] The angle by which the phase of the output voltage of phase y leads the phase of the output voltage of phase z is calculated by the following formula:

[0026]

[0027] where Δδ1 is the angle by which the phase of the output voltage of phase x leads the phase of the output voltage of phase z, Δδ2 is the angle by which the phase of the output voltage of phase y leads the phase of the output voltage of phase z, S is the total capacity of the three-phase cascaded H-bridge energy storage, ω is the angular frequency of the AC voltage, L is the grid-connected inductance value of each phase of the three-phase cascaded H-bridge, T is the charge and discharge time of this stage.

[0028] In an alternative embodiment, closing the switch between the first phase and the second phase, and controlling the first phase to charge the second phase by the method of carrier phase-shifted modulation, further includes:

[0029] Closing the switch between two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the intermediate value;

[0030] Adopt the method of carrier phase-shifted modulation of cascaded H-bridge modules, respectively perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the intermediate value, establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the intermediate value.

[0031] In an alternative embodiment, closing the switch between the first phase and the second phase to control the charging from the first phase to the second phase by means of carrier phase-shifted modulation further includes:

[0032] Closing the switch between the two phases, where the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value;

[0033] Adopting the method of carrier phase-shifted modulation of cascaded H-bridge modules to perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the minimum value respectively, establishing an AC voltage, and controlling the charging from the phase corresponding to the maximum value to the phase corresponding to the minimum value.

[0034] In an alternative embodiment, the angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage is calculated by the following formula:

[0035]

[0036] The angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage is calculated by the following formula:

[0037]

[0038] Where Δδ3 is the angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage, and Δδ4 is the angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage.

[0039] In a second aspect, the present invention provides a cascaded H-bridge energy storage system, the system includes: A / B / C three-phase branches, where each phase branch is composed of a plurality of cascaded H-bridge energy storage sub-modules, and a set of switches is provided between every two phases on the grid side of the cascaded H-bridge energy storage system;

[0040] When the remaining charge deviation between phases is greater than a preset value, calculate the remaining charge of A / B / C three phases respectively, and calculate the average value of the remaining charge of A / B / C three phases;

[0041] Close the switch between the first phase and the second phase, and control the charging from the first phase to the second phase by means of carrier phase-shifted modulation, where the first phase is the phase with the remaining charge greater than the average value, and the second phase is the phase with the remaining charge less than the average value for charging.

[0042] The cascaded H-bridge energy storage system provided by the present invention can realize the direct parallel connection of the cascaded H-bridge three-phase cascaded modules by adding two sets of switches on the grid side of the cascaded H-bridge energy storage, and then by controlling the output voltage of each phase, the charging and discharging power between the three-phase cascaded modules can be controlled, so as to quickly achieve the balance of the SOC between phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0044] Figure 1 is the topology diagram of the cascaded H-bridge energy storage system according to an embodiment of the present invention;

[0045] Figure 2 is the flow schematic diagram of the method for rapid SOC equalization between phases of the cascaded H-bridge energy storage according to an embodiment of the present invention. Specific Embodiments

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0047] According to an embodiment of the present invention, an embodiment of a method for rapid SOC equalization between phases of a cascaded H-bridge energy storage is provided. It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0048] In this embodiment, a method for rapid SOC equalization between phases of a cascaded H-bridge energy storage is provided. This method is based on the cascaded H-bridge energy storage system as shown in Figure 1 shown, Figure 2 is the flowchart of the method for rapid SOC equalization between phases of the cascaded H-bridge energy storage according to an embodiment of the present invention. As shown in Figure 2 shown, this process includes the following steps:

[0049] Step S1, when the deviation of the remaining power between phases is greater than a preset value, calculate the remaining power of phases A / B / C respectively, and calculate the average value of the remaining power of phases A / B / C.

[0050] Specifically, as shown in Figure 1As shown in the figure, the cascaded H-bridge energy storage system includes: A / B / C three-phase branches, where each phase branch is composed of multiple cascaded H-bridge energy storage sub-modules SM. A set of switches K1 / K2 / K3 is provided for each phase branch, and a set of switches T1 / T2 / T3 is provided between every two phases on the grid side of the cascaded H-bridge energy storage system. When the cascaded H-bridge energy storage system is operating normally, K1, K2, and K3 are closed, and T1, T2, and T3 are open; when the SOC deviation between phases is too large (i.e., the remaining power deviation between phases is greater than the preset value), the cascaded H-bridge energy storage system stops connecting to the grid, and K1, K2, and K3 are open. Among them, the preset value is determined according to the actual situation.

[0051] Further, calculate the average SOC_A, SOC_B, and SOC_C of the three phases respectively, as well as the average value of the three-phase SOC. Among them, the calculation formula for the average value of the three-phase SOC is as follows:

[0052]

[0053] Among them, SOC_avg is the average value of the three-phase SOC.

[0054] Step S2, close the switch between the first phase and the second phase, and control the first phase to charge the second phase through the method of carrier phase-shifted modulation. The first phase is the phase with the remaining power greater than the average value, and the second phase is the phase with the remaining power less than the average value.

[0055] Specifically, compare the average SOC_A, SOC_B, and SOC_C of the three phases with the average value SOC_avg of the three-phase SOC to determine the phase with SOC greater than SOC_avg and the phase with SOC less than SOC_avg. Close the switch between the phase with SOC greater than SOC_avg and the phase with SOC less than SOC_avg, and control the phase with SOC greater than SOC_avg to charge the phase with SOC less than SOC_avg through the method of carrier phase-shifted modulation, that is, control the charging and discharging power of the three-phase cascaded module through the voltage source control of one phase and the current source control of the other two phases, so as to quickly achieve the balance of the SOC between phases.

[0056] In an optional implementation manner, step S2 includes:

[0057] Step S201, sort the remaining power of the A / B / C three phases to generate a sorting sequence.

[0058] Step S202, compare the intermediate value of the sorting sequence with the average value to determine the first phase and the second phase.

[0059] Specifically, compare the magnitudes of SOC_A, SOC_B, and SOC_C and sort them to generate a sorting sequence SOC_x > SOC_y > SOC_z, and the corresponding phase - interval switches are defined as Tx, Ty, and Tz. When the middle value SOC_y in the sorting sequence is greater than the average value SOC_avg, determine the first phase as the y - phase corresponding to the middle value and the x - phase corresponding to the maximum value in the sorting sequence, and determine the second phase as the z - phase corresponding to the minimum value in the sorting sequence. When the middle value SOC_y is not greater than the average value SOC_avg, determine the first phase as the x - phase corresponding to the maximum value in the sorting sequence, and determine the second phase as the y - phase corresponding to the middle value and the z - phase corresponding to the minimum value in the sorting sequence.

[0060] In this embodiment, compare SOC_y with SOC_avg. If SOC_y > SOC_avg, then determine the phase (x / y phase) with SOC greater than SOC_avg as the first phase, and determine the phase (z phase) with SOC less than SOC_avg as the second phase. For example, if the sorting sequence is SOC_A > SOC_B > SOC_C and SOC_B > SOC_avg, then determine the A / B phase with SOC greater than SOC_avg as the first phase, and determine the C phase with SOC less than SOC_avg as the second phase.

[0061] Similarly, compare SOC_y with SOC_avg. If SOC_y ≤ SOC_avg, then determine the phase (x phase) with SOC greater than SOC_avg as the first phase, and determine the phase (y / z phase) with SOC less than SOC_avg as the second phase. For example, if the sorting sequence is SOC_A > SOC_B > SOC_C and SOC_B ≤ SOC_avg, then determine the A phase with SOC greater than SOC_avg as the first phase, and determine the B / C phase with SOC less than SOC_avg as the second phase.

[0062] In an alternative embodiment, step S2 further includes:

[0063] Step S203: Close the switch between two phases, where the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value.

[0064] Step S204: Adopt the method of carrier - phase - shifted modulation of the cascaded H - bridge module to perform open - loop control on the phase corresponding to the maximum value and the phase corresponding to the minimum value respectively, establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the minimum value.

[0065] Step S205: Close the switch between two phases, where the two phases are the phase corresponding to the middle value and the phase corresponding to the minimum value.

[0066] Step S206: Using the method of carrier phase shift modulation of the cascaded H-bridge module, perform open-loop control on the phase corresponding to the intermediate value and the phase corresponding to the minimum value respectively to establish an AC voltage, and control the phase corresponding to the intermediate value to charge the phase corresponding to the minimum value.

[0067] Specifically, from steps S201 - S202, it can be known that the phase corresponding to the maximum value SOC_x of the sorting sequence is the x-phase, the phase corresponding to the intermediate value SOC_y is the y-phase, and the phase corresponding to the minimum value SOC_z is the z-phase. If the intermediate value SOC_y of the sorting sequence > the average value SOC_avg, then first close Tx and Tz, and then perform open-loop control on the x-phase and z-phase through the method of carrier phase shift modulation of their respective cascaded H-bridge modules to establish an AC voltage with a fundamental wave amplitude of U_1 and a frequency of 50 Hz, where U_1 can be taken as 0.8 times the rated value under normal operation. At the same time, the angle by which the output voltage phase of the x-phase leads the output voltage phase of the z-phase is calculated by the following formula:

[0068]

[0069] where, Δδ1 is the angle by which the output voltage phase of the x-phase leads the output voltage phase of the z-phase, S is the total capacity of the three-phase cascaded H-bridge energy storage, ω is the angular frequency of the AC voltage, L is the grid-connected inductance value of each phase of the three-phase cascaded H-bridge, T is the charge and discharge time at this stage.

[0070] After the above steps are completed, disconnect Tx and Tz, close Ty and Tz, and perform open-loop control on the y-phase and z-phase through the method of carrier phase shift modulation of their respective cascaded H-bridge modules to establish an AC voltage with a fundamental wave amplitude of U_1 and a frequency of 50 Hz, where U_1 can be taken as 0.8 times the rated value under normal operation. At the same time, the angle by which the output voltage phase of the y-phase leads the output voltage phase of the z-phase is calculated by the following formula:

[0071]

[0072] where, Δδ2 is the angle by which the output voltage phase of the y-phase leads the output voltage phase of the z-phase.

[0073] In this embodiment, the closing sequence of the switches can also be adjusted. For example, first close Ty and Tz to control the y-phase to charge the z-phase, and then close Tx and Tz to control the x-phase to charge the z-phase, so as to quickly achieve the balance of the SOC between phases.

[0074] In an alternative embodiment, step S2 further includes:

[0075] Step S207: Close the switch between two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the intermediate value.

[0076] Step S208: By using the method of carrier phase-shifted modulation of the cascaded H-bridge module, perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the intermediate value respectively to establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the intermediate value.

[0077] Step S209: Close the switch between the two phases, where the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value.

[0078] Step S210: By using the method of carrier phase-shifted modulation of the cascaded H-bridge module, perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the minimum value respectively to establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the minimum value.

[0079] Specifically, it can be known from Steps S201 - S202 that the phase corresponding to the maximum value SOC_x in the sorting sequence is the x-phase, the phase corresponding to the intermediate value SOC_y is the y-phase, and the phase corresponding to the minimum value SOC_z is the z-phase. If the intermediate value SOC_y of the sorting sequence ≤ SOC_avg, then after closing Tx and Ty first, open-loop control is performed on the x-phase and y-phase through the method of carrier phase-shifted modulation of their respective cascaded H-bridge modules to establish an AC voltage with a fundamental wave amplitude of U_1 and a frequency of 50 Hz, where U_1 can be taken as 0.8 times the rated value under normal operation. At the same time, the angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage is calculated by the following formula:

[0080]

[0081] where, Δδ3 is the angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage.

[0082] After the above steps are completed, disconnect Tx and Ty, close Tx and Tz, and open-loop control is performed on the x-phase and z-phase through the method of carrier phase-shifted modulation of their respective cascaded H-bridge modules to establish an AC voltage with a fundamental wave amplitude of U_1 and a frequency of 50 Hz, where U_1 can be taken as 0.8 times the rated value under normal operation. At the same time, the angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage is calculated by the following formula:

[0083]

[0084] where, Δδ4 is the angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage.

[0085] In this embodiment, the closing sequence of the switches can also be adjusted. For example, first close Tx and Tz, control the x-phase to charge the z-phase, and then close Tx and Ty, control the x-phase to charge the y-phase, so as to quickly achieve the balance of the SOC between phases.

[0086] In an alternative embodiment, the cascaded H-bridge energy storage inter-phase SOC fast equalization method further includes: Step S3, after the three-phase cascaded H-bridge system completes the inter-phase SOC equalization, it resumes normal operation.

[0087] Specifically, after the three-phase cascaded H-bridge completes the SOC equalization, T1, T2, and T3 are disconnected, and K1, K2, and K3 are closed, and the three-phase cascaded H-bridge energy storage is put into normal operation.

[0088] A cascaded H-bridge energy storage inter-phase SOC fast equalization method provided by the present invention can realize the direct parallel connection of three-phase cascaded modules of a cascaded H-bridge by adding two groups of switches on the grid side of the cascaded H-bridge energy storage. Then, by controlling the output voltage of each phase, the charge and discharge power between the three-phase cascaded modules can be controlled, so as to quickly realize the equalization of the inter-phase SOC, effectively reducing the outage time of the cascaded H-bridge energy storage.

[0089] As Figure 1 shown, the present invention also provides a cascaded H-bridge energy storage system, including: A / B / C three-phase branches, where each phase branch is composed of multiple cascaded H-bridge energy storage sub-modules SM. A set of switches K1 / K2 / K3 is provided for each phase branch, and a set of switches T1 / T2 / T3 is provided between every two phases on the grid side of the cascaded H-bridge energy storage system. When the cascaded H-bridge energy storage system is operating normally, K1, K2, and K3 are closed, and T1, T2, and T3 are disconnected. When the inter-phase SOC deviation is too large (i.e., the deviation of the remaining charge between phases is greater than the preset value), the cascaded H-bridge energy storage system stops operating in parallel with the grid, and K1, K2, and K3 are disconnected.

[0090] Further, calculate the average SOC_A, SOC_B, and SOC_C of each of the three phases, as well as the average value of the three-phase SOC. Compare the average SOC_A, SOC_B, and SOC_C of each of the three phases with the average value SOC_avg of the three-phase SOC to determine the phase with SOC greater than SOC_avg and the phase with SOC less than SOC_avg. Close the switch between the phase with SOC greater than SOC_avg and the phase with SOC less than SOC_avg, and by means of carrier phase-shifted modulation, control the phase with SOC greater than SOC_avg to charge the phase with SOC less than SOC_avg, that is, through the voltage source control of one phase and the current source control of the other two phases, and then control the charge and discharge power of the three-phase cascaded modules, so as to quickly realize the equalization of the inter-phase SOC.

[0091] A cascaded H-bridge energy storage system provided by the present invention can realize the direct parallel connection of three-phase cascaded modules of a cascaded H-bridge by adding two groups of switches on the grid side of the cascaded H-bridge energy storage. Then, by controlling the output voltage of each phase, the charge and discharge power between the three-phase cascaded modules can be controlled, so as to quickly realize the equalization of the inter-phase SOC.

[0092] While embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A cascaded H-bridge energy storage inter-phase SOC fast equalization method, characterized in that, The method is based on a cascaded H-bridge energy storage system, and a set of switches is arranged between every two phases on the grid side of the cascaded H-bridge energy storage system. The method includes: When the remaining power deviation between phases is greater than a preset value, calculate the remaining power of phases A / B / C respectively, and calculate the average value of the remaining power of phases A / B / C; Close the switch between the first phase and the second phase, and control the first phase to charge the second phase by means of carrier phase-shifted modulation. The first phase is the phase with remaining power greater than the average value, and the second phase is the phase with remaining power less than the average value; After the three-phase cascaded H-bridge system completes the SOC balance between phases, resume normal operation.

2. The cascade H-bridge energy storage inter-phase SOC fast equalization method according to claim 1, characterized in that The step of closing the switch between the first phase and the second phase and controlling the first phase to charge the second phase by means of carrier phase-shifted modulation includes: Sort the remaining power of phases A / B / C to generate a sorting sequence; Compare the middle value of the sorting sequence with the average value to determine the first phase and the second phase.

3. The cascaded H-bridge energy storage inter-phase SOC fast equalization method according to claim 2, characterized in that, The step of comparing the middle value of the sorting sequence with the average value to determine the first phase and the second phase includes: When the middle value is greater than the average value, determine that the first phase is the phase corresponding to the middle value and the phase corresponding to the maximum value of the sorting sequence, and determine that the second phase is the phase corresponding to the minimum value of the sorting sequence.

4. The cascaded H-bridge energy storage phase-interphase SOC fast equalization method according to claim 2, wherein The step of comparing the middle value of the sorting sequence with the average value to determine the first phase and the second phase further includes: When the middle value is not greater than the average value, determine that the first phase is the phase corresponding to the maximum value of the sorting sequence, and determine that the second phase is the phase corresponding to the middle value and the phase corresponding to the minimum value of the sorting sequence.

5. The cascaded H-bridge energy storage inter-phase SOC fast equalization method according to claim 3, wherein, The step of closing the switch between the first phase and the second phase and controlling the first phase to charge the second phase by means of carrier phase-shifted modulation further includes: Close the switch between two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value; Adopt the method of carrier phase-shifted modulation of the cascaded H-bridge module to perform open-loop control on the phase corresponding to the maximum value and the phase corresponding to the minimum value respectively, establish an AC voltage, and control the phase corresponding to the maximum value to charge the phase corresponding to the minimum value.

6. The cascaded H-bridge energy storage inter-phase SOC rapid equalization method according to claim 5, characterized in that, The step of closing the switch between the first phase and the second phase and controlling the first phase to charge the second phase by means of carrier phase-shifted modulation further includes: Close the switch between two phases, and the two phases are the phase corresponding to the middle value and the phase corresponding to the minimum value; Adopt the method of carrier phase-shifted modulation of the cascaded H-bridge module to perform open-loop control on the phase corresponding to the middle value and the phase corresponding to the minimum value respectively, establish an AC voltage, and control the phase corresponding to the middle value to charge the phase corresponding to the minimum value.

7. The method for rapid SOC balance between phases of a cascaded H-bridge energy storage according to claim 6, wherein The angle by which the output voltage phase of phase x leads the output voltage phase of phase z is calculated by the following formula: The angle by which the output voltage phase of phase y leads the output voltage phase of phase z is calculated by the following formula: Among them, Δδ 1 is the angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage, Δδ 2 is the angle by which the phase of the y-phase output voltage leads the phase of the z-phase output voltage, S is the total capacity of the three-phase cascaded H-bridge energy storage, ω is the angular frequency of the AC voltage, L is the grid-connected inductance value of each phase of the three-phase cascaded H-bridge, T is the charge and discharge time of this stage.

8. The cascaded H-bridge energy storage phase-interphase SOC fast equalization method according to claim 4, characterized in that The step of closing the switch between the first phase and the second phase and controlling the first phase to charge the second phase by means of carrier phase-shifted modulation further includes: Close the switch between two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the middle value; By using the method of carrier phase-shifted modulation of cascaded H-bridge modules, open-loop control is respectively performed on the phase corresponding to the maximum value and the phase corresponding to the intermediate value to establish an AC voltage, and the phase corresponding to the maximum value is controlled to charge the phase corresponding to the intermediate value.

9. The cascaded H-bridge energy storage phase-interphase SOC fast equalization method according to claim 8, wherein Closing the switch between the first phase and the second phase, and controlling the first phase to charge the second phase by using the method of carrier phase-shifted modulation, further includes: Closing the switch between two phases, and the two phases are the phase corresponding to the maximum value and the phase corresponding to the minimum value; By using the method of carrier phase-shifted modulation of cascaded H-bridge modules, open-loop control is respectively performed on the phase corresponding to the maximum value and the phase corresponding to the minimum value to establish an AC voltage, and the phase corresponding to the maximum value is controlled to charge the phase corresponding to the minimum value.

10. The cascaded H-bridge energy storage phase-interphase SOC fast equalization method according to claim 9, characterized in that The angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage is calculated by the following formula: The angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage is calculated by the following formula: Among them, Δδ 3 is the angle by which the phase of the x-phase output voltage leads the phase of the y-phase output voltage, Δδ 4 is the angle by which the phase of the x-phase output voltage leads the phase of the z-phase output voltage.

11. A cascaded H-bridge energy storage system, characterized in that, The system includes: A / B / C three-phase branches, where each phase branch is composed of multiple cascaded H-bridge energy storage sub-modules, and a set of switches is arranged between every two phases on the grid side of the cascaded H-bridge energy storage system; When the remaining power deviation between phases is greater than a preset value, calculate the remaining power of A / B / C three phases respectively, and calculate the average value of the remaining power of A / B / C three phases; Closing the switch between the first phase and the second phase, and controlling the first phase to charge the second phase by using the method of carrier phase-shifted modulation, where the first phase is the phase with remaining power greater than the average value, and the second phase is the phase with remaining power less than the average value.

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