Off-grid system and power regulation method thereof

Abstract

The application discloses an off-grid system and a power adjusting method thereof, and relates to the technical field of electronic power. The off-grid system comprises an alternating-current bus, a control device and a plurality of inverter devices. The alternating-current bus comprises three phase lines and a neutral line. The plurality of inverter devices connect the alternating-current output ends thereof to corresponding lines of the alternating-current bus based on the output topology types of the inverter devices. The control device determines first power reference information of each phase line based on the output voltage of each phase line of the alternating-current bus. The control device sends the first power reference information of each phase line to each inverter device. Each inverter device processes the first power reference information of each phase line based on the output topology type of the inverter device to obtain second power reference information of each phase of the inverter device. The output power of each phase of the inverter device is adjusted based on the second power reference information of each phase. The application can realize parallel operation of different types of inverters, improve the flexibility of off-grid system configuration, and reduce the system cost.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, and in particular to an off-grid system and its power regulation method. Background Technology

[0002] Currently, based on the output topology type, inverters can be classified into single-phase inverters, three-phase three-wire inverters, and three-phase four-wire inverters. Because different types of inverters have different off-grid power dispatch strategies, the off-grid power dispatch strategy is quite complex when different types of inverters are connected in parallel. Therefore, in existing technologies, the AC output sides of inverters of the same type are usually connected in parallel to supply power to the load. For example, in a three-phase four-wire off-grid scenario, the AC output sides of three-phase four-wire inverters are connected in parallel to directly supply power to the load, or the AC output sides of three-phase three-wire inverters are connected in parallel to a transformer, and the transformer outputs three-phase four-wire power to supply power to the load.

[0003] However, the application scenarios of the scheme of connecting the AC output sides of the same type of inverters in parallel to supply power to the load are limited. When configuring off-grid systems, it has poor flexibility and increases system costs. Summary of the Invention

[0004] This invention provides an off-grid system that enables parallel operation of different types of inverters, improving the flexibility of off-grid system configuration and reducing system costs. The off-grid system includes an AC bus, a control device, and multiple inverters; the AC bus includes three phase lines and one neutral line. The multiple inverters connect their AC output terminals to the corresponding lines of the AC bus based on their own output topology. The control device is used to determine the first power reference information of each phase line based on the output voltage of each phase line of the AC bus; and to send the first power reference information of each phase line to each inverter device. Each inverter is configured to process the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter; and adjust the output power of each phase of the inverter based on the second power reference information of each phase.

[0005] Optionally, the output topology type includes a three-phase four-wire topology, a three-phase three-wire topology, or a single-phase two-wire topology; The inverter device, whose output topology is a three-phase four-wire topology, has its AC output terminal connected to the three phase lines and the neutral line of the AC bus. The inverter device, whose output topology is a three-phase three-wire topology, has its AC output terminal connected to the three phase lines of the AC bus. The inverter is a single-phase two-wire inverter with its output topology type, and its AC output terminal is connected to one of the phase lines and the neutral line of the AC bus.

[0006] Optionally, the control device is further configured to determine the output voltage of each phase of each inverter based on the output topology type of each inverter; and to determine the output voltage of each phase of the AC bus based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus.

[0007] Optionally, the control device determines the output voltage of each phase of each inverter based on the output topology type of each inverter, including: If the output topology is a three-phase four-wire inverter, the phase voltage of each phase of the inverter is determined as the output voltage of each phase. If the output topology is a three-phase three-wire inverter, the output voltage of each phase is determined based on the line voltage of the inverter, wherein the output voltage of each phase is the same. If the output topology type is a single-phase two-wire inverter, the phase voltage of the inverter is determined as the output voltage of the phase to which it is connected, and the output voltage of the other two phases is 0.

[0008] Optionally, the control device determines the output voltage of each phase of the AC bus based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus, including: The average output voltage of each phase is determined based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus. The average output voltage of each phase is determined as the output voltage of each phase line of the AC bus.

[0009] Optionally, each inverter, based on its own output topology, processes the first power reference information of each phase line to obtain the second power reference information of each phase of the inverter, including: If the output topology is a three-phase four-wire inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

[0010] Optionally, the control device is further configured to determine third power reference information based on a preset output voltage frequency of the off-grid system and the rated frequency of the off-grid system; and send the third power reference information to each inverter device. Each of the inverters is further configured to adjust the output power of each phase of the inverter based on the third power reference information and the second power reference information for each phase of the inverter.

[0011] Optionally, each of the inverters adjusts the output power of each phase of the inverter based on the third power reference information and the second power reference information for each phase of the inverter, including: Based on the second power reference information of each phase of the inverter, a voltage regulation signal for each phase is generated; Based on the third power reference information, a frequency adjustment signal is generated; Based on the voltage regulation signal and the frequency regulation signal for each phase, a drive signal for each phase is generated, which is used to drive the power switch of each phase to regulate the output power of each phase.

[0012] Optionally, based on the second power reference information for each phase of the inverter, a voltage regulation signal for each phase is generated, including: The second power reference information of each phase of the inverter is added to the pre-acquired rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal of each phase. Based on the voltage error signal of each phase, a voltage regulation signal for each phase is generated.

[0013] Optionally, before adding the second power reference information of each phase of the inverter to the pre-acquired rated voltage of the off-grid system and subtracting it from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase, the method further includes: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and a preset first gain coefficient, the first power gain of each phase of the inverter is determined. The second power reference information for each phase is adjusted based on the first power gain of each phase of the inverter. The second power reference information of each phase of the inverter is added to the pre-acquired rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase, including: The adjusted second power reference information for each phase is added to the rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase.

[0014] Optionally, based on the third power reference information, a frequency adjustment signal is generated, including: The frequency error is obtained by adding the third power reference information to the rated frequency of the off-grid system and then subtracting it from the output voltage frequency of the inverter. The frequency error is adjusted to obtain a frequency adjustment signal.

[0015] Optionally, before adding the third power reference information to the rated frequency of the off-grid system and subtracting it from the output voltage frequency of the inverter to obtain the frequency error, the method further includes: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and a preset second gain coefficient, the second power gain of each phase of the inverter is determined. Based on the second power gain of each phase of the inverter, the third power reference information is adjusted to obtain the fourth power reference information of each phase of the inverter. The frequency error is obtained by adding the third power reference information to the rated frequency of the off-grid system and then subtracting it from the output voltage frequency of the inverter, including: Add the fourth power reference information of each phase of the inverter to the rated frequency of the off-grid system, and then subtract it from the output voltage frequency of the inverter to obtain the frequency error of each phase. Adjusting the frequency error to obtain a frequency adjustment signal includes: The frequency error of each phase is adjusted to obtain the frequency adjustment signal for each phase.

[0016] This invention also provides a power regulation method for achieving power regulation of inverters operating in parallel with different types. This method is applied to the aforementioned off-grid system and includes: The control device determines the first power reference information for each phase line based on the output voltage of each phase line of the AC bus; and sends the first power reference information for each phase line to each inverter device. Each inverter device processes the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter device; and adjusts the output power of each phase of the inverter device based on the second power reference information of each phase.

[0017] Optionally, the output topology type includes a three-phase four-wire topology, a three-phase three-wire topology, or a single-phase two-wire topology; The inverter device, whose output topology is a three-phase four-wire topology, has its AC output terminal connected to the three phase lines and the neutral line of the AC bus. The inverter device, whose output topology is a three-phase three-wire topology, has its AC output terminal connected to the three phase lines of the AC bus. The inverter is a single-phase two-wire inverter with its output topology type, and its AC output terminal is connected to one of the phase lines and the neutral line of the AC bus.

[0018] Optionally, based on its own output topology type, the first power reference information of each phase line is processed to obtain the second power reference information of each phase of the inverter, including: If the output topology is a three-phase four-wire inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

[0019] In this embodiment of the invention, regardless of whether the output topology types of multiple inverters in the off-grid system are the same, the control device sends the same first power reference information for each phase line to each inverter. Upon receiving the same first power reference information for each phase line, each inverter processes the information differently based on its own output topology type to obtain second power reference information. The inverter can then adjust the output power of each phase based on the second power reference information for each phase. This enables off-grid power adjustment when inverters with different output topology types are mixed, allowing for the configuration of mixed inverters with different output topology types in the off-grid system, improving system configuration flexibility and reducing system costs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] In the attached diagram: Figure 1 A structural diagram of an off-grid system provided in an embodiment of the present invention; Figure 2 A flowchart for determining the first power reference information of each phase line based on the output voltage of each phase line of the AC bus, provided in an embodiment of the present invention; Figure 3 A flowchart illustrating how each inverter device processes the first power reference information for each phase line, as provided in an embodiment of the present invention. Figure 4 A flowchart for determining third power reference information based on a preset output voltage frequency and rated frequency of an off-grid system, provided in an embodiment of the present invention; Figure 5 This is a control flowchart of an inverter device provided in an embodiment of the present invention; Figure 6 A structural diagram of another off-grid system provided in an embodiment of the present invention; Figure 7 for Figure 6 The control flowchart of the control device for the off-grid system is shown below; Figure 8 for Figure 6 The control flowcharts for the A-phase power regulation of inverters 1 and 2 in the off-grid system are shown. Figure 9 The flowchart shows the calculation process for the positive-sequence component of the line voltage. Figure 10 This is a flowchart of a power regulation method provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0023] In the description of this specification, the terms "comprising," "including," "having," and "containing" are open-ended terms, meaning that they include but are not limited to. The terms "an embodiment," "a specific embodiment," "some embodiments," and "for example," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. The order of steps involved in the various embodiments is used to illustrate the implementation of this application, and the order of steps is not limited and can be adjusted appropriately as needed.

[0024] In the description of this specification, the terms "first" and "second," etc., are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.

[0025] In the description of this specification, "and / or" is merely a way of describing the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0026] Research has found that in off-grid inverter parallel operation scenarios, the off-grid power dispatch strategy between inverters with different output topologies is quite complex. Therefore, existing technologies usually connect the AC output sides of inverters with the same output topology in parallel to supply power to the load. This results in limited application scenarios, poor flexibility in system configuration, and increased system costs.

[0027] Based on this, embodiments of the present invention provide a scheme for parallel off-grid operation of inverters with different output topologies, so as to improve the flexibility of system configuration and reduce system costs.

[0028] Figure 1 This is a structural diagram of an off-grid system provided in an embodiment of the present invention. (See diagram below.) Figure 1 As shown, the off-grid system may include: an AC bus, a control device, and i inverters (i is a positive integer greater than 1); the AC bus includes three phase lines (i.e., phase A, phase B, and phase C) and one neutral line (N line).

[0029] Among them, i inverters connect their AC output terminals to the corresponding lines of the AC bus based on their own output topology type.

[0030] In one embodiment, the output topology of the inverter may include a three-phase four-wire topology, a three-phase three-wire topology, or a single-phase two-wire topology.

[0031] The inverter has a three-phase four-wire topology, and its AC output terminals are connected to the three phase lines and the neutral line of the AC bus. That is, the A-phase AC output terminal, B-phase AC output terminal, C-phase AC output terminal and N-line AC output terminal of the inverter are respectively connected to the A-phase line, B-phase line, C-phase line and N-line of the AC bus.

[0032] The inverter has a three-phase three-wire topology, and its AC output terminals are connected to the three phase lines of the AC bus. That is, the A-phase AC output terminal, B-phase AC output terminal and C-phase AC output terminal of the inverter are respectively connected to the A-phase line, B-phase line and C-phase line of the AC bus.

[0033] An inverter with a single-phase two-wire topology has its AC output terminals connected to one of the phase lines and the neutral line of the AC bus. Specifically, the phase line AC output terminals of the inverter are connected to any one of the A-phase, B-phase, or C-phase lines of the AC bus, and the N-line AC output terminals of the inverter are connected to the N-line of the AC bus.

[0034] In specific implementation, the aforementioned i inverter devices can be of the same output topology type or different output topology types; the output topology type of each inverter device can be any one of three-phase four-wire topology, three-phase three-wire topology, and single-phase two-wire topology. Therefore, the off-grid system provided in this embodiment of the invention can realize the parallel connection of inverter devices with different output topology types, for example, Figure 1 In the above, inverter 1 is a three-phase three-wire system, inverter 2 is a single-phase two-wire system, and inverter i is a three-phase four-wire system. The AC output terminals of these inverters are connected in parallel to supply power to the load through the A-phase line, B-phase line, and C-phase line of the AC bus.

[0035] based on Figure 1 The off-grid system shown includes a control device used to determine the first power reference information for each phase line based on the output voltage of each phase line of the AC bus; and to send the first power reference information for each phase line to each inverter device. Each inverter is used to process the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter; and to adjust the output power of each phase of the inverter based on the second power reference information of each phase.

[0036] In specific implementation, in order to achieve power distribution during the operation of the off-grid system, the present invention implements system-level control through a control device and inverter-level control through each inverter device.

[0037] Specifically, the control device can determine the first power reference information for each phase line based on the output voltage of each phase line of the AC bus, where the output voltage of each phase line of the AC bus is the output voltage of each phase line of the off-grid system; and the first power reference information for each phase line is the first power reference information for each phase line of the off-grid system. Then, the control device sends the same three-phase power reference command, i.e., the first power reference information for each phase line, to each inverter.

[0038] Each inverter can process the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter; based on the second power reference information of each phase, the output power of each phase of the inverter can be adjusted.

[0039] Therefore, in this embodiment of the invention, regardless of whether the output topology types of multiple inverters in the off-grid system are the same, the control device issues the same three-phase power reference command to each inverter. Upon receiving the same three-phase power reference command, each inverter processes the command differently based on its own output topology type to obtain the required three-phase power reference command, i.e., the second power reference information. The inverter can then adjust the output power of each phase based on the second power reference information for each phase. This enables off-grid power adjustment when inverters with different output topology types are mixed, allowing for the configuration of mixed inverters with different output topology types in the off-grid system, improving system configuration flexibility and reducing system costs.

[0040] In one embodiment, the control device determines first power reference information for each phase line based on the output voltage of each phase line of the AC bus, which may specifically include: The control device determines the first power reference information for each phase line based on the output voltage of each phase line of the AC bus and the pre-acquired rated voltage of the off-grid system.

[0041] In specific implementation, such as Figure 2 The diagram shows a flowchart illustrating the process of determining the first power reference information for each phase line based on the output voltage of each phase line of the AC bus in an embodiment of the present invention. First, the output voltage of each phase line... U fdb_n (The effective value or voltage amplitude of the output voltage) and the rated voltage U of the off-grid system N The difference between the effective value of the rated voltage and the voltage amplitude is used to obtain the first power reference information after adjustment by the voltage controller G(S) at the system level. P ref_n ,in, P ref_n , U fdb_n middle,n Indicates phase A, phase B, or phase C, for example, P ref_A This provides the first power reference information for phase A. U fdb_A G(S) is the output voltage of phase A; G(S) can be a PI controller.

[0042] It should be noted that the first power reference information P ref_n Used to control the effective value or amplitude of the output voltage of each phase, the first power reference information can be an active power dispatch command when the off-grid system exhibits low voltage resistive characteristics, and a reactive power dispatch command when the off-grid system exhibits high voltage inductive characteristics.

[0043] In one embodiment, the output voltage of each phase line U fdb_n The control device can determine this based on the output voltage of all inverters in that phase. Specifically, it can be determined in the following ways: The control device can also be used to determine the output voltage of each phase of each inverter based on the output topology type of each inverter; and to determine the output voltage of each phase of the AC bus based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus.

[0044] In practice, the control device can determine the average output voltage of each phase based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus; the average output voltage of each phase is then defined as the output voltage of each phase of the AC bus. U fdb_n It can be calculated using formula (1): in, V fdb ( m,n () represents the output voltage of phase n of the m-th inverter, for example, V fdb (1 , A) represents the output voltage of phase A of the first inverter; V fdb (1 , B) represents the output voltage of phase B of the first inverter unit; V fdb (1 , C) represents the output voltage of phase C of the first inverter.

[0045] j nThis indicates the number of inverters connected to n phases of the off-grid system, for example... j A This indicates the number of inverters connected to phase A of the off-grid system; j B This indicates the number of inverters connected to phase B of the off-grid system. j C This indicates the number of inverters connected to phase C of the off-grid system.

[0046] Based on the above formula (1), firstly, it is necessary to determine the output voltage of each phase of each inverter according to the output topology type of each inverter. V fdb ( m,n ).

[0047] Specifically, for an inverter with a three-phase four-wire topology, the phase voltage (effective value or amplitude of the phase voltage) of each phase is determined as the output voltage of each phase. In other words, for a three-phase four-wire inverter, the phase voltage of each phase is the output voltage of that phase, and the phase voltage can be obtained by measurement.

[0048] If the output topology of the inverter is a three-phase three-wire topology, the output voltage of each phase is determined based on the line voltage of the inverter, where the output voltage of each phase is the same. That is to say, for a three-phase three-wire inverter, since there is no neutral line, the phase voltage cannot be directly measured, and only the line voltage between the phase lines can be measured. However, the actual measured three-phase line voltages may be unbalanced. Therefore, the positive sequence component can be obtained from the three-phase line voltage by DQ transformation, and then the output voltage of each phase can be determined based on the amplitude or effective value of the positive sequence component of the three-phase line voltage. Specifically, this can be achieved by the following formula (2): in, V fdb_pos This represents the amplitude or effective value of the positive sequence component of the line voltage of a three-phase three-wire inverter.

[0049] If the inverter's output topology is a single-phase two-wire topology, the phase voltage (effective value or amplitude of the phase voltage) is determined as the output voltage of the phase to which the inverter is connected, while the output voltage of the other two phases is 0. In other words, a single-phase two-wire inverter can be virtually treated as a three-phase four-wire inverter with two phases having no output. For example, if the phase wire of a single-phase two-wire inverter is connected to phase A of the AC bus, then... V fdb ( m,A () represents the phase voltage of the inverter. V fdb ( m,B) = 0, V fdb ( m,C =0.

[0050] As can be seen, in this embodiment of the invention, all inverters of all output topology types are virtualized as a three-phase four-wire inverter, single-phase two-wire inverters are virtualized as three-phase four-wire inverters with no output in two phases, and three-phase three-wire inverters are virtualized as three-phase four-wire inverters where each phase can only output the same power, so as to facilitate power regulation of the off-grid system.

[0051] After obtaining the output voltage of each phase of each inverter device V fdb ( m,n After that, based on the above formula (1), the output voltage of each phase line can be calculated. U fdb_n .

[0052] Based on the above description, the control device can obtain P ref_A , P ref_B , P ref_C ;Will P ref_A , P ref_B , P ref_C Send to each inverter unit.

[0053] In one embodiment, each inverter processes the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter, which may specifically include: If the output topology is a three-phase four-wire topology inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire topology inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

[0054] In practical implementation, each inverter can be connected via, for example... Figure 3 The flowchart shown processes the first power reference information for each phase line. (Reference) Figure 3Each inverter receives the same first power reference information for phases A, B, and C from the control device, i.e. P ref_A , P ref_B , P ref_C First, the inverter determines its own output topology type. If it is a three-phase four-wire inverter, then formula (3) is executed. Formula (3) is shown below: In other words, for a three-phase four-wire inverter, the control device sends... P ref_A , P ref_B , P ref_C The second power reference information for each phase of the three-phase four-wire inverter was determined, namely... P ref ( i , A ), P ref ( i , B ), P ref ( i , C ).

[0055] Next, if it is not a three-phase four-wire inverter, then determine whether it is a three-phase three-wire inverter. If it is, then execute formula (4), which is shown below: In other words, P ref_A , P ref_B , P ref_C The minimum value in the range is determined as the second power reference information for each phase of the three-phase three-wire inverter, and P ref ( i , A )= P ref ( i , B )= P ref ( i , C ).

[0056] If it is not a three-phase three-wire inverter, then determine whether it is a single-phase two-wire inverter. If so, execute formula (5), which is shown below: in, l A , l B , l C This represents the power reference gain of each phase of a single-phase two-wire inverter. If the phase output of the single-phase two-wire inverter is connected to phase A of the off-grid system, then... l A =1, l B =0, l C =0, thus, the second power reference information of phase A of this single-phase two-wire inverter is... P ref ( i , A )= P ref_A , P ref ( i , B )= P ref ( i , C =0. If the phase output terminal of a single-phase two-wire inverter is connected to other phase lines of an off-grid system, the power reference information gain and the second power reference information of each phase can be deduced in the same way, which will not be elaborated here.

[0057] Based on the above processing results, the second power reference information for each phase of each inverter device is obtained. P ref ( i , A ), P ref ( i , B ), P ref ( i , C It adjusts the output power of each phase.

[0058] Thus, in this embodiment of the invention, even if inverters of different output topologies are connected in parallel, off-grid power can be evenly distributed. Moreover, the adjustment strategy is simple and can be responded to and implemented quickly.

[0059] In addition, during off-grid power regulation, the aforementioned first power reference information and second power reference information are used to control the effective value (or amplitude) of the output voltage. However, in practical applications, the frequency of the output voltage is also controlled. Power regulation of the off-grid system is achieved by controlling both the effective value (or amplitude) and frequency of the output voltage.

[0060] Therefore, in this embodiment of the invention, the control device is further configured to determine third power reference information based on a preset output voltage frequency of the off-grid system and the rated frequency of the off-grid system; and send the third power reference information to each inverter device. Each inverter is also used to adjust the output power of each phase of the inverter based on the third power reference information and the second power reference information of each phase of the inverter.

[0061] In specific implementation, refer to Figure 4 This is a flowchart illustrating how, in this embodiment of the invention, third power reference information is determined based on a preset output voltage frequency and rated frequency of the off-grid system. First, the output voltage frequency of the off-grid system... w fdb and the rated frequency of the off-grid system w N The difference is calculated, and the difference is adjusted by the system-level frequency controller R(S) to obtain the third power reference information. Q ref Where R(S) can be a PI controller.

[0062] It should be noted that the third power reference information Q ref Used to control the output voltage frequency of each phase, the third power reference information can be a reactive power dispatch command when the off-grid system exhibits low voltage resistive characteristics, and an active power dispatch command when the off-grid system exhibits high voltage inductive characteristics.

[0063] In practice, the control device can provide the first power reference information for each phase line. P ref_n and third power reference information Q ref This information is sent to each inverter. Each inverter can first determine the power reference information based on the first power reference information. P ref_n Based on its own output topology type, the second power reference information for each phase of the inverter is determined. P ref ( i , n This process has been described in detail in the above embodiments and will not be repeated here; then, based on the second power reference information of each phase of the inverter... Pref ( i , n ) and third power reference information Q ref Adjust the output power of each phase of the inverter.

[0064] In one embodiment, each inverter adjusts the output power of each phase of the inverter based on the third power reference information and the second power reference information for each phase of the inverter, which may specifically include: Based on the second power reference information of each phase of the inverter, a voltage regulation signal for each phase is generated; A frequency adjustment signal is generated based on the third power reference information; Based on the voltage regulation signal and the frequency regulation signal of each phase, a drive signal for each phase is generated. The drive signal is used to drive the power switch of each phase to regulate the output power of each phase.

[0065] Furthermore, based on the second power reference information of each phase of the inverter, a voltage regulation signal for each phase is generated, which may specifically include: The second power reference information of each phase of the inverter is added to the pre-acquired rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal of each phase. Based on the voltage error signal of each phase, a voltage regulation signal for each phase is generated.

[0066] Furthermore, before adding the second power reference information of each phase of the inverter to the pre-acquired rated voltage of the off-grid system, and then subtracting it from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase, the process may further include: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and the preset first gain coefficient, the first power gain of each phase of the inverter is determined. The second power reference information for each phase is adjusted based on the first power gain of each phase of the inverter. The adjusted second power reference information for each phase is added to the rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase.

[0067] Furthermore, the generation of the frequency adjustment signal based on the third power reference information can specifically include: The frequency error is obtained by adding the third power reference information to the rated frequency of the off-grid system and then subtracting it from the output voltage frequency of the inverter. The frequency error is adjusted to obtain the frequency adjustment signal.

[0068] Furthermore, before adding the third power reference information to the rated frequency of the off-grid system and subtracting it from the output voltage frequency of the inverter to obtain the frequency error, the process may further include: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and a preset second gain coefficient, the second power gain of each phase of the inverter is determined. Based on the second power gain of each phase of the inverter, the third power reference information is adjusted to obtain the fourth power reference information of each phase of the inverter. Add the fourth power reference information of each phase of the inverter to the rated frequency of the off-grid system, and then subtract it from the output voltage frequency of the inverter to obtain the frequency error of each phase. The frequency error of each phase is adjusted to obtain the frequency adjustment signal for each phase.

[0069] In specific implementation, such as Figure 5 The diagram shown is a control flowchart of an inverter device provided in an embodiment of the present invention. Figure 5 The following section describes a scenario where an off-grid system exhibits low-voltage resistive characteristics. The control process includes adjusting the output voltage (RMS value or amplitude) and adjusting the output voltage frequency. P ref_n This is an active power dispatch command. Q ref This is a reactive power dispatch command. First, in the stage of adjusting the output voltage (RMS value or amplitude), the inverter uses a MUX (multiplexing) stage to process the first power reference information. P ref_n Processing is performed to generate second power reference information. P ref ( i , n The process has been described in detail in the above embodiments and will not be repeated here.

[0070] The following section focuses on the second power reference information for each phase of each inverter. P ref ( i , n ) and third power reference information Q ref The process of adjusting the output power of each phase of the inverter is explained.

[0071] In the process of adjusting the output voltage (RMS value or amplitude), K ( i , n ) indicates the first iThe first power gain of the n phases of the inverter, the first power gain being related to the first... i The output capacity of each inverter's n-phase is related to the total input capacity of the off-grid system's n-phase, and therefore can be determined by the following formula (6). K ( i , n ): in, S ( i , n ) indicates the first i The maximum output power of an n-phase inverter; kp The first gain coefficient is an adjustable coefficient. kp It only affects the response speed of the effective voltage value or amplitude of the off-grid system.

[0072] In practice, the maximum output power of each phase of the inverter can be a parameter during the inverter design, and therefore can be obtained in advance through the inverter design data; however, in the embodiments of the present invention, the maximum output power of each phase of each inverter is different based on different output topology types.

[0073] For example, if the inverter is a three-phase four-wire system, the maximum output power of each phase can be designed separately. Therefore, the maximum output power of each phase can be obtained from the design data.

[0074] If the inverter is a three-phase three-wire system, the maximum output power of each phase is not specified in the design data; the design data only contains the total maximum output power S of the three-phase three-wire inverter. Therefore, the maximum output power of each phase can be calculated from the total maximum output power S. S ( i , A )= S ( i , B )= S ( i , C =S / 3.

[0075] If the inverter is a single-phase two-wire system and its AC output terminal is connected to phase A of the off-grid system, then the maximum output power of phase A of the inverter is the maximum output power in the design data, and the maximum output power of the other two phases is 0.

[0076] Based on the above description, the output voltage (RMS or amplitude) regulation of each phase of the inverter includes: second power reference information. P ref ( i , n After the first power gain K (i , n After adjustment, the adjusted P ref ( i , n The voltage U of the off-grid system is connected through an adder. N The values ​​are added together, and then subtracted from each phase's output voltage of the inverter. V fdb ( i,n Subtracting the two, we get the voltage error. V 1. Voltage error signal V 1. After adjustment by the voltage controller H(S) of the inverter, the voltage regulation signal of each phase is obtained. V 2.

[0077] Here, the output voltage of each phase of the inverter is... V fdb ( i,n That is, the above. V fdb ( m,n ), representing the first i The output voltage of n phases of an inverter (i=m) is therefore... V fdb ( i,n The process of obtaining the voltage controller H(S) can be referred to the description in the above embodiments, and will not be repeated here. In addition, the voltage controller H(S) can be a PI controller.

[0078] In the process of adjusting the output voltage frequency, J ( i , n ) indicates the first i The frequency gain (i.e., the second power gain) of the n-phase inverter is related to the frequency gain of the n-phase inverter. i The output capacity of each inverter's n-phase is related to the total input capacity of the off-grid system's n-phase, and therefore can be determined by the following formula (7). J ( i , n ): in, S ( i , n ) indicates the first i The maximum output power of an n-phase inverter; kq This is the second gain coefficient, which is an adjustable coefficient. kq It only affects the frequency response speed of the off-grid system.

[0079] In practical implementation, the maximum output power of each phase of the inverter can be achieved with reference to the above embodiments, and will not be elaborated further here.

[0080] Based on the above description, the output voltage frequency regulation of each phase of the inverter includes: third power reference information. Q ref After the second power gain J ( i , n After adjustment, the fourth power reference information is obtained. This fourth power reference information is then multiplied by an adder and compared with the rated frequency of the off-grid system. w N Add them together, and then subtract them from the output voltage frequency of the inverter. w fdbi Subtracting them gives the frequency error. W 1. Frequency error W 1. After adjustment by the frequency controller L(S) of the inverter, the frequency adjustment signal of each phase is obtained. W 2.

[0081] in, w fdbi Let L(S) be the output voltage frequency of the i-th inverter. The output voltage frequency of each inverter is a parameter preset for that inverter. The frequency controller L(S) can be a PI controller.

[0082] In summary, the voltage regulation signal of each phase of this inverter can be... V 2 and frequency adjustment signal W 2. Combining these, a modulation wave duty(i,n) for each phase is generated. duty(i,n) is the modulation wave of the nth phase of the i-th inverter. Finally, a drive signal PWM(i,n) for each phase is generated based on duty(i,n). PWM(i,n) is the PWM drive signal for the nth phase of the i-th inverter. PWM(i,n) drives the power switching transistors of the nth phase of the i-th inverter to perform voltage inversion in order to adjust the output power of each phase.

[0083] It should be noted that in scenarios where off-grid systems exhibit high-voltage inductive characteristics, the control process also includes adjusting the effective value or amplitude of the output voltage and adjusting the frequency of the output voltage. P ref_n This is a reactive power dispatch command. Q ref This is an active power dispatch command. For the specific control flow, please refer to [reference needed]. Figure 5 The description is omitted here.

[0084] Based on the above description, the off-grid power regulation can be achieved when inverters with different output topologies are mixed in the above-mentioned off-grid system.

[0085] To clearly understand the off-grid system provided in the embodiments of the present invention, a specific example is given below.

[0086] like Figure 6 The off-grid system shown has inverter 1 as a three-phase three-wire system with no N-phase output; inverter 2 as a three-phase four-wire system with N-phase output; the three-phase four-wire inverter and the three-phase three-wire inverter are connected in parallel for off-grid operation.

[0087] Figure 7 for Figure 6 The control flowchart of the off-grid system's control device is shown. (Reference) Figure 7 The effective value of the output voltage of phase A line in the off-grid system can be used as a reference. U fdbA Rated voltage effective value U of off-grid system N The difference is calculated, and the difference is adjusted by a PI controller to obtain the first power reference information for phase A. P refA Similarly, using the same method, based on the effective value of the output voltage of phase B in the off-grid system... U fdbB The effective value of the output voltage of phase C line U fdbC The first power reference information of phase B can be obtained. P refB First power reference information for phase C line P refC .

[0088] Since the power regulation control process of each phase of inverter 1 and inverter 2 is the same, the following explanation will take phase A as an example. Figure 8 for Figure 6 The control flowcharts for the A-phase power regulation of inverters 1 and 2 in the off-grid system are shown.

[0089] refer to Figures 6 to 8 Because inverter 1 is a three-phase three-wire system, the A-phase output voltage of inverter 1... V fdb1 for: v d This represents the effective value of the positive sequence component of the line voltage.

[0090] in, Figure 9 This is a flowchart for calculating the positive-sequence component of line voltage. (Example:) Figure 9 As shown, v a1 , v b1 , vc1 These are the three-phase line voltages of inverter 1. v d , v q These are the d-axis and q-axis components of the three-phase line voltage after DQ transformation, respectively, where PLL is a three-phase phase-locked loop.

[0091] Because inverter 2 is a three-phase four-wire system, the A-phase output voltage of inverter 2 is... V fdb2 This is the A-phase voltage of inverter 2, which is the effective value of the off-grid output voltage of inverter 2.

[0092] based on V fdb1 and V fdb2 The effective value of the output voltage of phase A of the off-grid system can be obtained. U fdbA for: Figure 8 In the diagram, K1 is the active power gain (i.e., the first power gain) of inverter 1; K2 is the active power gain (i.e., the first power gain) of inverter 2.

[0093] Wherein, S1 is the maximum output power of phase A of inverter 1, and S2 is the maximum output power of phase A of inverter 2.

[0094] J1 is the reactive power gain (i.e., the second power gain) of inverter 1; J2 is the reactive power gain (i.e., the second power gain) of inverter 2.

[0095] w N The rated frequency of the off-grid system. w fdb1 The frequency of the output voltage of inverter 1. w fdb2 The frequency of the output voltage of inverter 2.

[0096] The control process for A-phase power regulation in inverter 1 and inverter 2 is described below: Both inverter 1 and inverter 2 receive signals from the control device. P refA , P refB , P refC and reactive power reference information Q ref(Third power reference information). Inverter 1 and Inverter 2 each determine their respective second power reference information for phase A through their respective MUX circuits, i.e. p ref1 and p ref2 .

[0097] Inverter 1 will p ref1 After adjustment by the active power gain K1, it is compared with the rated voltage U of the off-grid system. N Add them together, and then combine them with the output voltage of phase 1A of the inverter. V fdb1 The difference is processed by a PI controller to generate the reference signal (i.e., voltage regulation signal) of the effective value of phase A voltage of inverter 1.

[0098] Inverter 1 will display reactive power reference information. Q ref After adjustment by reactive power gain J1, the frequency is the same as the rated frequency of the off-grid system. w N Add them together, and then add them to the output voltage frequency of inverter 1. w fdb1 The difference is processed by a PI controller to generate the A-phase voltage frequency reference signal (i.e., frequency adjustment signal) of inverter 1.

[0099] Finally, based on the effective value reference signal and voltage frequency reference signal of phase A voltage of inverter 1, the modulation wave duty1 of phase A of inverter 1 is generated, and the drive signal PWM1 for driving phase A of inverter 1 is generated based on duty1.

[0100] Inverter 2 will p ref2 After adjustment by the active power gain K2, it is compared with the rated voltage U of the off-grid system. N Add them together, and then combine them with the output voltage of phase A of inverter 2. V fdb2 The difference is processed by a PI controller to generate the reference signal (i.e., voltage regulation signal) of the effective value of phase A voltage of inverter 2.

[0101] Inverter 2 will display reactive power reference information. Q ref After reactive power gain adjustment J2, the frequency is consistent with the rated frequency of the off-grid system. w N Add them together, and then add them to the output voltage frequency of inverter 2. w fdb2 The difference is processed by a PI controller to generate the A-phase voltage frequency reference signal (i.e., frequency adjustment signal) of inverter 2.

[0102] Finally, based on the effective value reference signal and voltage frequency reference signal of phase A voltage of inverter 2, the modulation wave duty2 of phase A of inverter 2 is generated, and the drive signal PWM2 for driving phase A of inverter 2 is generated based on duty2.

[0103] Ultimately, inverter 1 and inverter 2 can achieve an equal distribution of active and reactive power.

[0104] In summary, the off-grid system provided by this invention can connect inverters with different output topologies in parallel and virtualize all inverters with different output topologies as a single three-phase four-wire inverter. For example, a single-phase two-wire inverter can be virtualized as a three-phase four-wire inverter with no output on two phases, and a three-phase three-wire inverter can be virtualized as a three-phase four-wire inverter where each phase can only output the same power. In this way, the control device can issue the same three-phase power reference command to each inverter. When each inverter receives the same three-phase power reference command, it processes the command differently based on its own output topology to obtain the required three-phase power reference command, i.e., the second power reference information. Based on the second power reference information for each phase, the inverter can adjust the output power of each phase, achieving off-grid power adjustment when inverters with different output topologies are mixed. This allows for the configuration of mixed-connection of inverters with different output topologies in the off-grid system, improving system configuration flexibility and reducing system costs.

[0105] This invention also provides a power regulation method, as described in the following embodiments. Since the principle behind this power regulation method is similar to that of the off-grid system described above, its implementation can be found in the implementation of the off-grid system; repeated details will not be elaborated further.

[0106] like Figure 10 The diagram shows a flowchart of a power regulation method provided by an embodiment of the present invention. This method is applied to the aforementioned off-grid system and may include: Step 101: The control device determines the first power reference information of each phase line based on the output voltage of each phase line of the AC bus; and sends the first power reference information of each phase line to each inverter. Step 102: Each inverter processes the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter; based on the second power reference information of each phase, the output power of each phase of the inverter is adjusted.

[0107] In one embodiment, the output topology type includes a three-phase four-wire topology, a three-phase three-wire topology, or a single-phase two-wire topology; The inverter device, whose output topology is a three-phase four-wire topology, has its AC output terminal connected to the three phase lines and the neutral line of the AC bus. The inverter device, whose output topology is a three-phase three-wire topology, has its AC output terminal connected to the three phase lines of the AC bus. The inverter is a single-phase two-wire inverter with its output topology type, and its AC output terminal is connected to one of the phase lines and the neutral line of the AC bus.

[0108] In one embodiment, step 102 involves processing the first power reference information of each phase line based on its own output topology type to obtain the second power reference information of each phase of the inverter, which may specifically include: If the output topology is a three-phase four-wire inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

[0109] This invention also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the power regulation method described above.

[0110] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the power regulation method described above.

[0111] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements the power regulation method described above.

[0112] The power regulation method provided in this invention virtualizes all inverters of different output topologies as a single three-phase four-wire inverter. For example, a single-phase two-wire inverter is virtualized as a three-phase four-wire inverter with no output in two phases, and a three-phase three-wire inverter is virtualized as a three-phase four-wire inverter where each phase can only output the same power. Thus, when each inverter receives the same three-phase power reference command from the control device, it can process the command differently based on its own output topology to obtain the specific three-phase power reference command required by the inverter itself—the second power reference information. Based on this second power reference information, the inverter can then adjust the output power of each phase, achieving off-grid power regulation when inverters of different output topologies are mixed. This allows for the configuration of mixed inverters of different output topologies in off-grid systems, improving system configuration flexibility and reducing system costs.

[0113] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0115] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0116] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0117] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An off-grid system, characterized in that, include: The system includes an AC busbar, a control unit, and multiple inverters; the AC busbar comprises three phase lines and one neutral line. The multiple inverters connect their AC output terminals to the corresponding lines of the AC bus based on their own output topology. The control device is used to determine the first power reference information of each phase line based on the output voltage of each phase line of the AC bus; and to send the first power reference information of each phase line to each inverter device. Each inverter is configured to process the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter; and adjust the output power of each phase of the inverter based on the second power reference information of each phase.

2. The off-grid system as described in claim 1, characterized in that, The output topology types include three-phase four-wire topology, three-phase three-wire topology, or single-phase two-wire topology; The inverter device, whose output topology is a three-phase four-wire topology, has its AC output terminal connected to the three phase lines and the neutral line of the AC bus. The inverter device, whose output topology is a three-phase three-wire topology, has its AC output terminal connected to the three phase lines of the AC bus. The inverter is a single-phase two-wire inverter with its output topology type, and its AC output terminal is connected to one of the phase lines and the neutral line of the AC bus.

3. The off-grid system as described in claim 2, characterized in that, The control device is further configured to determine the output voltage of each phase of each inverter based on the output topology type of each inverter; and to determine the output voltage of each phase of the AC bus based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus.

4. The off-grid system as described in claim 3, characterized in that, The control device determines the output voltage of each phase of each inverter based on the output topology type of each inverter, including: If the output topology is a three-phase four-wire inverter, the phase voltage of each phase of the inverter is determined as the output voltage of each phase. If the output topology is a three-phase three-wire inverter, the output voltage of each phase is determined based on the line voltage of the inverter, wherein the output voltage of each phase is the same. If the output topology type is a single-phase two-wire inverter, the phase voltage of the inverter is determined as the output voltage of the phase to which it is connected, and the output voltage of the other two phases is 0.

5. The off-grid system as described in claim 3, characterized in that, The control device determines the output voltage of each phase of the AC bus based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus, including: The average output voltage of each phase is determined based on the output voltage of each phase of each inverter and the number of inverters connected to each phase of the AC bus. The average output voltage of each phase is determined as the output voltage of each phase line of the AC bus.

6. The off-grid system as described in claim 2, characterized in that, Each inverter, based on its own output topology, processes the first power reference information of each phase line to obtain the second power reference information of each phase of the inverter, including: If the output topology is a three-phase four-wire inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

7. The off-grid system as described in claim 1, characterized in that, The control device is further configured to determine third power reference information based on the preset output voltage frequency of the off-grid system and the rated frequency of the off-grid system; and send the third power reference information to each inverter device. Each of the inverters is further configured to adjust the output power of each phase of the inverter based on the third power reference information and the second power reference information for each phase of the inverter.

8. The off-grid system as described in claim 7, characterized in that, Each inverter adjusts the output power of each phase of the inverter based on the third power reference information and the second power reference information for each phase of the inverter, including: Based on the second power reference information of each phase of the inverter, a voltage regulation signal for each phase is generated; Based on the third power reference information, a frequency adjustment signal is generated; Based on the voltage regulation signal and the frequency regulation signal for each phase, a drive signal for each phase is generated, which is used to drive the power switch of each phase to regulate the output power of each phase.

9. The off-grid system as described in claim 8, characterized in that, Based on the second power reference information of each phase of the inverter, a voltage regulation signal for each phase is generated, including: The second power reference information of each phase of the inverter is added to the pre-acquired rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal of each phase. Based on the voltage error signal of each phase, a voltage regulation signal for each phase is generated.

10. The off-grid system as described in claim 9, characterized in that, Before adding the second power reference information of each phase of the inverter to the pre-acquired rated voltage of the off-grid system, and then subtracting it from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase, the process further includes: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and a preset first gain coefficient, the first power gain of each phase of the inverter is determined. The second power reference information for each phase is adjusted based on the first power gain of each phase of the inverter. The second power reference information of each phase of the inverter is added to the pre-acquired rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase, including: The adjusted second power reference information for each phase is added to the rated voltage of the off-grid system, and then subtracted from the output voltage of each phase of the inverter to obtain the voltage error signal for each phase.

11. The off-grid system as described in claim 8, characterized in that, Based on the third power reference information, a frequency adjustment signal is generated, including: The frequency error is obtained by adding the third power reference information to the rated frequency of the off-grid system and then subtracting it from the output voltage frequency of the inverter. The frequency error is adjusted to obtain a frequency adjustment signal.

12. The off-grid system as described in claim 11, characterized in that, Before adding the third power reference information to the rated frequency of the off-grid system and subtracting it from the output voltage frequency of the inverter to obtain the frequency error, the process further includes: Based on the proportion of the maximum output power of each phase of the inverter to the sum of the maximum output power of multiple inverters connected to that phase in the off-grid system, and a preset second gain coefficient, the second power gain of each phase of the inverter is determined. Based on the second power gain of each phase of the inverter, the third power reference information is adjusted to obtain the fourth power reference information of each phase of the inverter. The frequency error is obtained by adding the third power reference information to the rated frequency of the off-grid system and then subtracting it from the output voltage frequency of the inverter, including: Add the fourth power reference information of each phase of the inverter to the rated frequency of the off-grid system, and then subtract it from the output voltage frequency of the inverter to obtain the frequency error of each phase. Adjusting the frequency error to obtain a frequency adjustment signal includes: The frequency error of each phase is adjusted to obtain the frequency adjustment signal for each phase.

13. A power regulation method, characterized in that, This invention is applied to an off-grid system, which includes an AC bus, a control device, and multiple inverters. The AC bus includes three phase lines and one neutral line. The multiple inverters connect their AC output terminals to the corresponding lines of the AC bus based on their own output topology. The method includes: The control device determines the first power reference information for each phase line based on the output voltage of each phase line of the AC bus; and sends the first power reference information for each phase line to each inverter device. Each inverter device processes the first power reference information of each phase line based on its own output topology to obtain the second power reference information of each phase of the inverter device; and adjusts the output power of each phase of the inverter device based on the second power reference information of each phase.

14. The method as described in claim 13, characterized in that, The output topology types include three-phase four-wire topology, three-phase three-wire topology, or single-phase two-wire topology; The inverter device, whose output topology is a three-phase four-wire topology, has its AC output terminal connected to the three phase lines and the neutral line of the AC bus. The inverter device, whose output topology is a three-phase three-wire topology, has its AC output terminal connected to the three phase lines of the AC bus. The inverter is a single-phase two-wire inverter with its output topology type, and its AC output terminal is connected to one of the phase lines and the neutral line of the AC bus.

15. The method as described in claim 14, characterized in that, Based on its own output topology type, the first power reference information of each phase line is processed to obtain the second power reference information of each phase of the inverter, including: If the output topology is a three-phase four-wire inverter, the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter. If the output topology is a three-phase three-wire topology inverter, the minimum value in the first power reference information of each phase line is determined as the second power reference information of each phase of the inverter, wherein the second power reference information of each phase of the inverter is the same. If the output topology is a single-phase two-wire inverter, the first power reference information of the phase connected to the inverter is determined as the second power reference information of that phase of the inverter, and the second power reference information of the other two phases is 0.

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