An adaptive switching method, system and storage medium of energy storage converter

Abstract

The present invention provides an adaptive switching method, system and storage medium for an energy storage converter. When the grid connection mode information is a preset first grid connection mode, a first wave generation mode is set; the first wave generation parameter of the first wave generation mode is gradually adjusted, and the first voltage information, the second voltage information and the third voltage information on the three-phase output line are detected at the same time to determine the first zero-sequence voltage information; the grid connection line system is determined according to the first zero-sequence voltage information, and the grid connection line system is automatically identified. In addition, the wave generation mode and the wave generation parameter are adaptively adjusted according to the grid connection line system, so as to improve the simplicity of setting the energy storage converter and improve the user experience.

Description

Technical Field

[0001] The present invention relates to the field of energy storage converters, and more specifically, to an adaptive switching method, system and storage medium of an energy storage converter. Background Art

[0002] With the rapid development of the energy storage industry, energy storage systems have been increasingly used to improve energy efficiency, reduce electricity costs, provide backup power, and participate in auxiliary services in the electricity market. Among them, the energy storage converter is used to complete the bidirectional conversion of energy between the battery and the grid, and is a key device in the energy storage system. The energy storage converter based on unipolar conversion has a high conversion efficiency. The energy storage converter used for three-phase three-wire power grid supports a wider battery voltage range (for example, 615Vdc~950Vdc under 400Vac grid) because of its relatively low uncontrolled rectifier voltage. However, since there is no N-line output, when it is used off-grid with single-phase or unbalanced load, it is necessary to use a transformer to convert the three-phase three-wire into three-phase four-wire, which has the problems of large system volume, high cost and low efficiency. The energy storage converter for three-phase four-wire power grid can be used off-grid with single-phase or unbalanced loads without a transformer, but because its uncontrolled rectifier voltage is relatively high, it only supports a narrow battery voltage range (for example, 680Vdc~950Vdc under 400Vac power grid), which limits its application.

[0003] At present, there are also a few energy storage inverters that can be used for three-phase three-wire power grids or three-phase four-wire power grids, but the applicable power grid must be set manually in advance, and the wiring must be correct, otherwise the system will not be able to operate; in addition, if you want to maximize the adaptation range of its battery voltage, you must set its undervoltage protection point according to the grid line standard, which will increase the complexity of the setting.

[0004] Therefore, there is an urgent need for an adaptive switching technology for energy storage converters that can automatically identify and switch grid types and automatically adjust the battery voltage adaptation range. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide an adaptive switching method, system and storage medium of an energy storage inverter, which can automatically identify the grid connection line system according to the first zero-sequence voltage information obtained by measuring and calculating by adjusting the first wave generation parameters of the first wave generation mode; and adaptively adjust the wave generation mode and wave generation parameters according to the grid connection mode.

[0006] A first aspect of the present invention provides an adaptive switching method for an energy storage converter, the method comprising:

[0007] Obtaining grid connection mode information;

[0008] Determining whether the grid connection mode information is a preset first grid connection mode;

[0009] If not, setting the first wave transmission parameter information to a preset wave transmission parameter threshold;

[0010] If yes, set it to the first wave transmission mode and initialize the first wave transmission parameter information;

[0011] Adjusting the first transmission parameter information;

[0012] Determining whether the first transmission parameter information is lower than a preset transmission parameter threshold;

[0013] If not, the grid connection line system is set to the first connection line system;

[0014] If yes, obtaining the first voltage information, the second voltage information and the third voltage information;

[0015] Obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0016] Determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold;

[0017] If not, adjusting the first transmission parameter information;

[0018] If yes, the grid connection line system is set to the second connection line system.

[0019] This plan also includes:

[0020] When the grid connection mode information is the first grid connection mode;

[0021] Set to the first wave mode;

[0022] Determining whether the grid connection line system is a first connection line system;

[0023] If yes, the first transmission parameter information is set as a preset transmission parameter threshold;

[0024] If not, the first wave parameter information is set to zero.

[0025] This plan also includes:

[0026] When the grid connection mode information is the second grid connection mode;

[0027] Set to the first wave mode;

[0028] The first wave transmission parameter information is set as a preset wave transmission parameter threshold.

[0029] In this solution, the first zero-sequence voltage information is obtained according to the first voltage information, the second voltage information and the third voltage information, specifically:

[0030] Determine first pair of zero voltage information, second pair of zero voltage information and third pair of zero voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0031] calculating the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain a fourth pair of zero voltage information;

[0032] The first zero-sequence voltage information is obtained according to the fourth pair of zero voltage information.

[0033] This plan also includes:

[0034] Neutral relay;

[0035] Determining whether the grid connection mode information is a preset second grid connection mode;

[0036] If so, the neutral phase relay is driven to disconnect;

[0037] If not, the neutral relay is driven to close.

[0038] This plan also includes:

[0039] Three inverter inductors, three filter capacitors and three grid-side inductors;

[0040] The energy storage converter includes a three-phase output, and each phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor.

[0041] A second aspect of the present invention provides an adaptive switching system for an energy storage converter, including an adaptive switching method program for an energy storage converter, wherein the adaptive switching method program for the energy storage converter implements the following steps when executed by the processor:

[0042] Obtaining grid connection mode information;

[0043] Determining whether the grid connection mode information is a preset first grid connection mode;

[0044] If yes, set it to the first wave transmission mode and initialize the first wave transmission parameter information;

[0045] Adjusting the first transmission parameter information;

[0046] Determining whether the first transmission parameter information is lower than a preset transmission parameter threshold;

[0047] If not, the grid connection line system is set to the first connection line system;

[0048] If yes, obtaining the first voltage information, the second voltage information and the third voltage information;

[0049] Obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0050] Determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold;

[0051] If not, adjusting the first transmission parameter information;

[0052] If yes, the grid connection line system is set to the second connection line system.

[0053] This plan also includes:

[0054] When the grid connection mode information is the first grid connection mode;

[0055] Set to the first wave mode;

[0056] Determining whether the grid connection line system is a first connection line system;

[0057] If yes, the first transmission parameter information is set as a preset transmission parameter threshold;

[0058] If not, the first wave parameter information is set to zero.

[0059] This plan also includes:

[0060] When the grid connection mode information is the second grid connection mode;

[0061] Set to the first wave mode;

[0062] The first wave transmission parameter information is set as a preset wave transmission parameter threshold.

[0063] A third aspect of the present invention provides a computer-readable storage medium, which includes an adaptive switching method program for an energy storage inverter. When the adaptive switching method program for the energy storage inverter is executed by a processor, the steps of the adaptive switching method for the energy storage inverter as described in any one of the above items are implemented.

[0064] The present invention provides an adaptive switching method, system and storage medium for an energy storage converter. When the grid connection mode information is a preset first grid connection mode, a first wave generation mode is set; the first wave generation parameter of the first wave generation mode is gradually adjusted, and the first voltage information, the second voltage information and the third voltage information on the three-phase output line are detected at the same time to determine the first zero-sequence voltage information; the grid connection line system is determined according to the first zero-sequence voltage information, and the grid connection line system is automatically identified. In addition, the wave generation mode and the wave generation parameter are adaptively adjusted according to the grid connection line system, so as to improve the simplicity of setting the energy storage converter and improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope.

[0066] Figure 1 A flow chart showing an adaptive switching method of an energy storage converter according to the present invention is shown;

[0067] Figure 2 A flow chart showing the adjustment of the wave generation mode and wave generation parameters in the first grid connection mode is shown;

[0068] Figure 3 A flow chart showing the adjustment of the wave generation mode and wave generation parameters in the second grid connection mode is shown;

[0069] Figure 4 A block diagram of an adaptive switching system for an energy storage converter according to the present invention is shown. DETAILED DESCRIPTION

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] Unless otherwise defined, all terms (including technical and scientific terms) used in the embodiments of the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless the embodiments of the present invention are explicitly defined in this way.

[0072] The words "first", "second" and similar words used in the embodiments of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "one", "an" or "the" and similar words do not indicate a quantity limitation, but indicate the existence of at least one. Similarly, words such as "include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The steps before or after the method of the embodiment of the present invention are not necessarily carried out in precise order. On the contrary, various steps can be processed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or more steps can be removed from these processes.

[0073] In addition, the functional modules in the various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0074] Figure 1 A flow chart of an adaptive switching method for an energy storage converter according to the present invention is shown.

[0075] like Figure 1 As shown, the present invention discloses an adaptive switching method for an energy storage converter, the method comprising:

[0076] S102, obtaining grid connection mode information;

[0077] S104, determining whether the grid connection mode information is a preset first grid connection mode;

[0078] S106, if yes, set to the first wave transmission mode, and initialize the first wave transmission parameter information;

[0079] S108, adjusting the first transmission parameter information;

[0080] S110, determining whether the first transmission parameter information is lower than a preset transmission parameter threshold;

[0081] S112, if not, setting the grid connection line system to the first connection line system;

[0082] S114, if yes, obtaining first voltage information, second voltage information and third voltage information;

[0083] S116, obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0084] S118, determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold;

[0085] S108, if not, adjusting the first transmission parameter information;

[0086] S120: If yes, set the grid connection line system to the second connection line system.

[0087] It should be noted that the grid connection mode information is the connection mode between the energy storage converter and the external grid, including the off-grid mode and the grid-connected mode; the first grid connection mode is the mode in which the energy storage converter is not connected to the public grid, that is, the off-grid mode; the first wave generation mode is the SPWM wave generation mode, wherein the sinusoidal pulse width modulation method (SPWM) is to perform natural or regular width modulation on multiple pulses in each sinusoidal cycle, so that it sequentially modulates a pulse sequence with a phase angle and an area equivalent to a sinusoidal wave equivalent to the value of a sinusoidal function, thereby forming a sinusoidal current output with equal amplitude and unequal width; the first wave generation parameter information is the weight parameter for adjusting the third harmonic of the SPWM; the first connection line system is a three-phase three-wire output line; the second connection line system is a three-phase four-wire output line; the first voltage information is the AC voltage value measured on the A phase in the output line; the second voltage information is the AC voltage value measured on the B phase in the output line; the third voltage information is the AC voltage value measured on the C phase in the output line; the first zero-sequence voltage information is the relative voltage value on the N line in the output line.

[0088] Usually, three-phase three-wire can use SPWM wave generation, but there are problems such as low DC utilization and narrow battery voltage range; therefore, the method of injecting third harmonics through SPWM wave generation can improve DC utilization and widen the battery voltage range when the third harmonic injection amplitude is appropriate. However, since the three-phase four-wire system is in a grid-connected state, the N line needs a return current. If the third harmonic is injected when using SPWM wave generation, the energy storage inverter will have the problem of too large N line current and cannot work. According to the above characteristics, the following method is adopted to realize automatic identification and switching of the output line system of the energy storage inverter:

[0089] When the energy storage converter is connected to the public power grid, that is, in the grid-connected mode, the first wave parameter information is set according to the preset wave parameter threshold. When the energy storage converter is not connected to the public power grid, that is, in the off-grid mode, first, the wave mode of the energy storage converter is set to SPWM wave generation, and the first wave parameter information is adjusted, that is, the injection amplitude of the third harmonic is adjusted. Secondly, the AC voltage of each phase line of the three-phase output is collected through the differential operational amplifier circuit to obtain the first voltage information, the second voltage information and the third voltage information, and the first zero-sequence voltage information of the N line is obtained according to the preset calculation method. Then, it is determined whether the first zero-sequence voltage information exceeds the preset zero-sequence voltage threshold; if so, it indicates that the grid line system connected to the energy storage converter is a three-phase four-wire system; if not, the injection amplitude of the third harmonic is continuously increased, and the AC voltage collection of each phase line and the calculation step of the first zero-sequence voltage information of the N line are performed again to determine whether it exceeds the preset zero-sequence voltage threshold; until the injection amplitude of the third harmonic reaches the preset amplitude, that is, when the first wave parameter information reaches the preset wave parameter threshold, if the first zero-sequence voltage information still does not exceed the preset zero-sequence voltage threshold, it indicates that the grid line system connected to the energy storage converter is a three-phase three-wire system. Finally, the output line system of the energy storage converter is switched by driving the state of the neutral line relay, and the injection amplitude of the third harmonic of the SPWM wave is adjusted, so as to achieve the effects of high DC utilization and wide battery voltage range.

[0090] Figure 2 A flow chart of adjusting the wave generation mode and wave generation parameters in the first grid connection mode is shown.

[0091] According to an embodiment of the present invention, Figure 2 As shown, it also includes:

[0092] S202, when the grid connection mode information is the first grid connection mode;

[0093] S204, setting to the first wave transmission mode;

[0094] S206, determining whether the grid connection line system is a first connection line system;

[0095] S208, if yes, setting the first transmission parameter information as a preset transmission parameter threshold;

[0096] S210: If not, the first wave transmission parameter information is set to zero.

[0097] It should be noted that when the energy storage inverter is not connected to the public power grid, that is, in off-grid mode, the wave generation mode is set to SPWM wave generation. Then, the output line system of the energy storage inverter is determined; when the output line system of the energy storage inverter is a three-phase three-wire system, the third harmonic injection amplitude is adjusted to the preset wave generation parameter threshold. Usually, in practical applications, the wave generation parameter threshold is the maximum value of the third harmonic injection amplitude, which is used to improve the DC utilization rate of the energy storage inverter and widen the battery voltage range; when the output line system of the energy storage inverter is a three-phase four-wire system, the third harmonic injection amplitude is adjusted to zero to avoid excessive current in the N line of the three-wire four-wire system.

[0098] Figure 3 A flow chart of adjusting the wave generation mode and wave generation parameters in the second grid connection mode is shown.

[0099] According to an embodiment of the present invention, Figure 3 As shown, it also includes:

[0100] S302, when the grid connection mode information is a second grid connection mode;

[0101] S304, setting to the first wave transmission mode;

[0102] S306: Set the first wave transmission parameter information as a preset wave transmission parameter threshold.

[0103] It should be noted that when the energy storage inverter is connected to the public power grid, that is, in the grid-connected mode, since the N line of the three-phase four-wire system in the grid-connected mode does not need to flow with current, in order to improve the DC utilization rate of the energy storage inverter and widen the battery voltage range, the third harmonic injection amplitude of the SPWM wave of the energy storage inverter is adjusted to a preset amplitude threshold. Usually, in practical applications, the preset amplitude threshold is the maximum value of the third harmonic injection amplitude.

[0104] According to an embodiment of the present invention, the first zero-sequence voltage information is obtained according to the first voltage information, the second voltage information and the third voltage information, specifically:

[0105] Determine first pair of zero voltage information, second pair of zero voltage information and third pair of zero voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0106] calculating the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain a fourth pair of zero voltage information;

[0107] The first zero-sequence voltage information is obtained according to the fourth pair of zero voltage information.

[0108] It should be noted that the first zero-sequence voltage information satisfies the following calculation formula:

[0109] ;

[0110] Where:

[0111] V_A is the first voltage information; V_B is the second voltage information; V_C is the third voltage information; V0 is the first zero-sequence voltage information.

[0112] Since the first voltage information, the second voltage information and the third voltage information are respectively the AC voltage values ​​measured by the A phase, the B phase and the C phase in the three-phase output line, when used to calculate the first zero-sequence voltage information, they need to be converted into voltage effective values. Therefore, the first voltage information, the second voltage information and the third voltage information are processed according to the voltage effective value calculation rule, that is, divided by , obtain the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information. Then, calculate the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain the fourth pair of zero voltage information; finally, process the fourth pair of zero voltage information according to the zero-sequence voltage calculation rule, that is, divide by 3 to obtain the first zero-sequence voltage information. The magnitude of the first zero-sequence voltage information can be used to represent the magnitude of the N-line current.

[0113] According to an embodiment of the present invention, it also includes:

[0114] Neutral relay;

[0115] Determining whether the grid connection mode information is a preset second grid connection mode;

[0116] If so, the neutral phase relay is driven to disconnect;

[0117] If not, the neutral relay is driven to close.

[0118] It should be noted that the second grid connection mode is a mode in which the energy storage inverter is connected to the public power grid, that is, the grid-connected mode; wherein, since the N line does not need to flow current in the grid-connected mode, the N line connection state of the energy storage inverter can be disconnected to avoid erroneous operations such as false touches. A zero line relay is provided on the N line of the energy storage inverter, and the closed and open states of the zero line relay are switched by sending preset drive information to the zero line relay. Determine the grid connection mode of the energy storage inverter; when it is in the grid-connected mode, the zero line relay is driven to be disconnected, that is, the N line output of the energy storage inverter is disconnected; when it is in the off-grid mode, the zero line relay is driven to be closed, that is, the N line output of the energy storage inverter is turned on.

[0119] According to an embodiment of the present invention, it also includes:

[0120] Three inverter inductors, three filter capacitors and three grid-side inductors;

[0121] The energy storage converter includes a three-phase output, and each phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor.

[0122] It should be noted that each phase line of the three-phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor. Taking phase A as an example, the phase A output port of the energy storage converter is connected to the first end of the inverter inductor; the second end of the inverter inductor is simultaneously connected to the first end of the filter capacitor and the first end of the grid-side inductor; the second end of the filter capacitor is connected to the N line; and the second end of the grid-side inductor is connected to the grid-connected phase A interface. An inverter inductor, a filter capacitor and a grid-side inductor together form an LCL filter circuit, which converts the AC voltage with a sinusoidal duty cycle output by the first-stage conversion in the energy storage converter into a smooth sinusoidal voltage.

[0123] It is worth mentioning that it also includes:

[0124] When the grid connection mode information is the first grid connection mode;

[0125] Get battery voltage information;

[0126] Determining off-grid output voltage information according to the battery voltage information;

[0127] Determine whether the off-grid output voltage information is lower than a preset off-grid output voltage threshold;

[0128] If yes, stop the first wave mode.

[0129] It should be noted that when the energy storage inverter is not connected to the public power grid, that is, in off-grid mode, if the connection line system of the energy storage inverter is set to a three-phase four-wire system, there is a situation where the battery voltage cannot meet the normal operation of the load after being converted by the energy storage inverter. Therefore, the battery voltage value is monitored in real time, and the off-grid output voltage information is obtained according to the preset calculation rules; wherein the off-grid output voltage information and the battery voltage value satisfy the following relationship:

[0130] ;

[0131] Where:

[0132] Vac is the off-grid output voltage information; Vbat is the battery voltage information.

[0133] When the off-grid output voltage information is lower than the preset off-grid output voltage threshold, that is, when the off-grid output voltage information is lower than the minimum low voltage required for normal operation of the load, the SPWM wave generation of the energy storage inverter is stopped, that is, the energy storage inverter is stopped from outputting three-phase AC power.

[0134] Figure 4A block diagram of an adaptive switching system for an energy storage converter according to the present invention is shown.

[0135] like Figure 4 As shown, the present invention discloses an adaptive switching system 4 of an energy storage converter, comprising a memory 41 and a processor 42, wherein the memory comprises an adaptive switching method program of the energy storage converter, and when the adaptive switching method program of the energy storage converter is executed by the processor, the following steps are implemented:

[0136] Obtaining grid connection mode information;

[0137] Determining whether the grid connection mode information is a preset first grid connection mode;

[0138] If yes, set it to the first wave transmission mode and initialize the first wave transmission parameter information;

[0139] Adjusting the first transmission parameter information;

[0140] Determining whether the first transmission parameter information is lower than a preset transmission parameter threshold;

[0141] If not, the grid connection line system is set to the first connection line system;

[0142] If yes, obtaining the first voltage information, the second voltage information and the third voltage information;

[0143] Obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0144] Determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold;

[0145] If not, adjusting the first transmission parameter information;

[0146] If yes, the grid connection line system is set to the second connection line system.

[0147] It should be noted that the grid connection mode information is the connection mode between the energy storage converter and the external grid, including the off-grid mode and the grid-connected mode; the first grid connection mode is the mode in which the energy storage converter is not connected to the public grid, that is, the off-grid mode; the first wave generation mode is the SPWM wave generation mode, wherein the sinusoidal pulse width modulation method (SPWM) is to perform natural or regular width modulation on multiple pulses in each sinusoidal cycle, so that it sequentially modulates a pulse sequence with a phase angle and an area equivalent to a sinusoidal wave equivalent to the value of a sinusoidal function, thereby forming a sinusoidal current output with equal amplitude and unequal width; the first wave generation parameter information is the weight parameter for adjusting the third harmonic of the SPWM; the first connection line system is a three-phase three-wire output line; the second connection line system is a three-phase four-wire output line; the first voltage information is the AC voltage value measured on the A phase in the output line; the second voltage information is the AC voltage value measured on the B phase in the output line; the third voltage information is the AC voltage value measured on the C phase in the output line; the first zero-sequence voltage information is the relative voltage value on the N line in the output line.

[0148] Usually, three-phase three-wire can use SPWM wave generation, but there are problems such as low DC utilization and narrow battery voltage range; therefore, the method of injecting third harmonics through SPWM wave generation can improve DC utilization and widen the battery voltage range when the third harmonic injection amplitude is appropriate. However, since the three-phase four-wire system is in a grid-connected state, the N line needs a return current. If the third harmonic is injected when using SPWM wave generation, the energy storage inverter will have the problem of too large N line current and cannot work. According to the above characteristics, the following method is adopted to realize automatic identification and switching of the output line system of the energy storage inverter:

[0149] When the energy storage converter is connected to the public power grid, that is, in the grid-connected mode, the first wave parameter information is set according to the preset wave parameter threshold. When the energy storage converter is not connected to the public power grid, that is, in the off-grid mode, first, the wave mode of the energy storage converter is set to SPWM wave generation, and the first wave parameter information is adjusted, that is, the injection amplitude of the third harmonic is adjusted. Secondly, the AC voltage of each phase line of the three-phase output is collected through the differential operational amplifier circuit to obtain the first voltage information, the second voltage information and the third voltage information, and the first zero-sequence voltage information of the N line is obtained according to the preset calculation method. Then, it is determined whether the first zero-sequence voltage information exceeds the preset zero-sequence voltage threshold; if so, it indicates that the grid line system connected to the energy storage converter is a three-phase four-wire system; if not, the injection amplitude of the third harmonic is continuously increased, and the AC voltage collection of each phase line and the calculation step of the first zero-sequence voltage information of the N line are performed again to determine whether it exceeds the preset zero-sequence voltage threshold; until the injection amplitude of the third harmonic reaches the preset amplitude, that is, when the first wave parameter information reaches the preset wave parameter threshold, if the first zero-sequence voltage information still does not exceed the preset zero-sequence voltage threshold, it indicates that the grid line system connected to the energy storage converter is a three-phase three-wire system. Finally, the output line system of the energy storage converter is switched by driving the state of the neutral line relay, and the injection amplitude of the third harmonic of the SPWM wave is adjusted, so as to achieve the effects of high DC utilization and wide battery voltage range.

[0150] According to an embodiment of the present invention, it also includes:

[0151] When the grid connection mode information is the first grid connection mode;

[0152] Set to the first wave mode;

[0153] Determining whether the grid connection line system is a first connection line system;

[0154] If yes, the first transmission parameter information is set as a preset transmission parameter threshold;

[0155] If not, the first wave parameter information is set to zero.

[0156] It should be noted that when the energy storage inverter is not connected to the public power grid, that is, in off-grid mode, the wave generation mode is set to SPWM wave generation. Then, the output line system of the energy storage inverter is determined; when the output line system of the energy storage inverter is a three-phase three-wire system, the third harmonic injection amplitude is adjusted to the preset wave generation parameter threshold. Usually, in practical applications, the wave generation parameter threshold is the maximum value of the third harmonic injection amplitude, which is used to improve the DC utilization rate of the energy storage inverter and widen the battery voltage range; when the output line system of the energy storage inverter is a three-phase four-wire system, the third harmonic injection amplitude is adjusted to zero to avoid excessive current in the N line of the three-wire four-wire system.

[0157] According to an embodiment of the present invention, it also includes:

[0158] When the grid connection mode information is the second grid connection mode;

[0159] Set to the first wave mode;

[0160] The first wave transmission parameter information is set as a preset wave transmission parameter threshold.

[0161] It should be noted that when the energy storage inverter is connected to the public power grid, that is, in the grid-connected mode, since the N line of the three-phase four-wire system in the grid-connected mode does not need to flow with current, in order to improve the DC utilization rate of the energy storage inverter and widen the battery voltage range, the third harmonic injection amplitude of the SPWM wave of the energy storage inverter is adjusted to a preset amplitude threshold. Usually, in practical applications, the preset amplitude threshold is the maximum value of the third harmonic injection amplitude.

[0162] According to an embodiment of the present invention, the first zero-sequence voltage information is obtained according to the first voltage information, the second voltage information and the third voltage information, specifically:

[0163] Determine first pair of zero voltage information, second pair of zero voltage information and third pair of zero voltage information according to the first voltage information, the second voltage information and the third voltage information;

[0164] calculating the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain a fourth pair of zero voltage information;

[0165] The first zero-sequence voltage information is obtained according to the fourth pair of zero voltage information.

[0166] It should be noted that the first zero-sequence voltage information satisfies the following calculation formula:

[0167] ;

[0168] Where:

[0169] V_A is the first voltage information; V_B is the second voltage information; V_C is the third voltage information; V0 is the first zero-sequence voltage information.

[0170] Since the first voltage information, the second voltage information and the third voltage information are respectively the AC voltage values ​​measured by the A phase, the B phase and the C phase in the three-phase output line, when used to calculate the first zero-sequence voltage information, they need to be converted into voltage effective values. Therefore, the first voltage information, the second voltage information and the third voltage information are processed according to the voltage effective value calculation rule, that is, divided by , obtain the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information. Then, calculate the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain the fourth pair of zero voltage information; finally, process the fourth pair of zero voltage information according to the zero-sequence voltage calculation rule, that is, divide by 3 to obtain the first zero-sequence voltage information. The magnitude of the first zero-sequence voltage information can be used to represent the magnitude of the N-line current.

[0171] According to an embodiment of the present invention, it also includes:

[0172] Neutral relay;

[0173] Determining whether the grid connection mode information is a preset second grid connection mode;

[0174] If so, the neutral phase relay is driven to disconnect;

[0175] If not, the neutral relay is driven to close.

[0176] It should be noted that the second grid connection mode is a mode in which the energy storage inverter is connected to the public power grid, that is, the grid-connected mode; wherein, since the N line does not need to flow current in the grid-connected mode, the N line connection state of the energy storage inverter can be disconnected to avoid erroneous operations such as false touches. A zero line relay is provided on the N line of the energy storage inverter, and the closed and open states of the zero line relay are switched by sending preset drive information to the zero line relay. Determine the grid connection mode of the energy storage inverter; when it is in the grid-connected mode, the zero line relay is driven to be disconnected, that is, the N line output of the energy storage inverter is disconnected; when it is in the off-grid mode, the zero line relay is driven to be closed, that is, the N line output of the energy storage inverter is turned on.

[0177] According to an embodiment of the present invention, it also includes:

[0178] Three inverter inductors, three filter capacitors and three grid-side inductors;

[0179] The energy storage converter includes a three-phase output, and each phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor.

[0180] It should be noted that each phase line of the three-phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor. Taking phase A as an example, the phase A output port of the energy storage converter is connected to the first end of the inverter inductor; the second end of the inverter inductor is simultaneously connected to the first end of the filter capacitor and the first end of the grid-side inductor; the second end of the filter capacitor is connected to the N line; and the second end of the grid-side inductor is connected to the grid-connected phase A interface. An inverter inductor, a filter capacitor and a grid-side inductor together form an LCL filter circuit, which converts the AC voltage with a sinusoidal duty cycle output by the first-stage conversion in the energy storage converter into a smooth sinusoidal voltage.

[0181] It is worth mentioning that it also includes:

[0182] When the grid connection mode information is the first grid connection mode;

[0183] Get battery voltage information;

[0184] Determining off-grid output voltage information according to the battery voltage information;

[0185] Determine whether the off-grid output voltage information is lower than a preset off-grid output voltage threshold;

[0186] If yes, stop the first wave mode.

[0187] It should be noted that when the energy storage inverter is not connected to the public power grid, that is, in off-grid mode, if the connection line system of the energy storage inverter is set to a three-phase four-wire system, there is a situation where the battery voltage cannot meet the normal operation of the load after being converted by the energy storage inverter. Therefore, the battery voltage value is monitored in real time, and the off-grid output voltage information is obtained according to the preset calculation rules; wherein the off-grid output voltage information and the battery voltage value satisfy the following relationship:

[0188] ;

[0189] Where:

[0190] Vac is the off-grid output voltage information; Vbat is the battery voltage information.

[0191] When the off-grid output voltage information is lower than the preset off-grid output voltage threshold, that is, when the off-grid output voltage information is lower than the minimum low voltage required for normal operation of the load, the SPWM wave generation of the energy storage inverter is stopped, that is, the energy storage inverter is stopped from outputting three-phase AC power.

[0192] A third aspect of the present invention provides a computer-readable storage medium, which includes an adaptive switching method program for an energy storage inverter. When the adaptive switching method program for the energy storage inverter is executed by a processor, the steps of the adaptive switching method for the energy storage inverter as described in any one of the above items are implemented.

[0193] The present invention provides an adaptive switching method, system and storage medium for an energy storage converter. When the grid connection mode information is a preset first grid connection mode, a first wave generation mode is set; the first wave generation parameter of the first wave generation mode is gradually adjusted, and the first voltage information, the second voltage information and the third voltage information on the three-phase output line are detected at the same time to determine the first zero-sequence voltage information; the grid connection line system is determined according to the first zero-sequence voltage information, and the grid connection line system is automatically identified. In addition, the wave generation mode and the wave generation parameter are adaptively adjusted according to the grid connection line system, so as to improve the simplicity of setting the energy storage converter and improve the user experience.

[0194] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0195] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An adaptive switching method for an energy storage converter, characterized in that: The method comprises: Obtaining grid connection mode information; Determining whether the grid connection mode information is a preset first grid connection mode; If yes, set it to the first wave transmission mode and initialize the first wave transmission parameter information; Adjusting the first transmission parameter information; Determining whether the first transmission parameter information is lower than a preset transmission parameter threshold; If not, the grid connection line system is set to the first connection line system; If yes, obtaining the first voltage information, the second voltage information and the third voltage information; Obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information; Determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold; If not, adjusting the first transmission parameter information; If yes, then set the grid connection line system to the second connection line system; The first voltage information is the AC voltage value measured at phase A in the output circuit; the second voltage information is the AC voltage value measured at phase B in the output circuit; and the third voltage information is the AC voltage value measured at phase C in the output circuit.

2. The adaptive switching method of an energy storage converter according to claim 1, characterized in that: Also includes: When the grid connection mode information is the first grid connection mode; Set to the first wave mode; Determining whether the grid connection line system is a first connection line system; If yes, the first transmission parameter information is set as a preset transmission parameter threshold; If not, the first wave parameter information is set to zero.

3. The adaptive switching method of an energy storage converter according to claim 1, characterized in that: Also includes: When the grid connection mode information is the second grid connection mode; Set to the first wave mode; The first wave transmission parameter information is set as a preset wave transmission parameter threshold.

4. The adaptive switching method of an energy storage converter according to claim 1, characterized in that: The first zero-sequence voltage information is obtained according to the first voltage information, the second voltage information and the third voltage information, specifically: Determine first pair of zero voltage information, second pair of zero voltage information and third pair of zero voltage information according to the first voltage information, the second voltage information and the third voltage information; calculating the sum of the first pair of zero voltage information, the second pair of zero voltage information and the third pair of zero voltage information to obtain a fourth pair of zero voltage information; The first zero-sequence voltage information is obtained according to the fourth pair of zero voltage information.

5. The adaptive switching method of an energy storage converter according to claim 1, characterized in that: Also includes: Neutral relay; Determining whether the grid connection mode information is a preset second grid connection mode; If so, the neutral relay is driven to disconnect; If not, the neutral relay is driven to close.

6. The adaptive switching method of an energy storage converter according to claim 1, characterized in that: Also includes: Three inverter inductors, three filter capacitors and three grid-side inductors; The energy storage converter includes a three-phase output, and each phase output is connected to an inverter inductor, a filter capacitor and a grid-side inductor.

7. An adaptive switching system for an energy storage converter, characterized in that: The system includes a memory and a processor, wherein the memory includes an adaptive switching method program of an energy storage converter, and when the adaptive switching method program of the energy storage converter is executed by the processor, the following steps are implemented: Obtaining grid connection mode information; Determining whether the grid connection mode information is a preset first grid connection mode; If yes, set it to the first wave transmission mode and initialize the first wave transmission parameter information; Adjusting the first transmission parameter information; Determining whether the first transmission parameter information is lower than a preset transmission parameter threshold; If not, the grid connection line system is set to the first connection line system; If yes, obtaining the first voltage information, the second voltage information and the third voltage information; Obtaining first zero-sequence voltage information according to the first voltage information, the second voltage information and the third voltage information; Determining whether the first zero-sequence voltage information exceeds a preset zero-sequence voltage threshold; If not, adjusting the first transmission parameter information; If yes, then set the grid connection line system to the second connection line system; The first voltage information is the AC voltage value measured at phase A in the output circuit; The second voltage information is the AC voltage value measured at phase B in the output circuit; The third voltage information is the AC voltage value measured at phase C in the output circuit.

8. The adaptive switching system of an energy storage converter according to claim 7, characterized in that: Also includes: When the grid connection mode information is the first grid connection mode; Set to the first wave mode; Determining whether the grid connection line system is a first connection line system; If yes, the first transmission parameter information is set as a preset transmission parameter threshold; If not, the first wave parameter information is set to zero.

9. The adaptive switching system of an energy storage converter according to claim 7, characterized in that: Also includes: When the grid connection mode information is the second grid connection mode; Set to the first wave mode; The first wave transmission parameter information is set as a preset wave transmission parameter threshold.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer-readable storage medium includes an adaptive switching method program for an energy storage converter. When the adaptive switching method program for the energy storage converter is executed by a processor, the steps of the adaptive switching method for the energy storage converter as described in any one of claims 1 to 6 are implemented.

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