Control method and device of inverter power supply system and inverter power supply system

Abstract

The invention provides a control method and device of an inverter power supply system and the inverter power supply system. The inverter power supply system comprises at least two inverters connected in parallel, the direct current end of each inverter is connected with a corresponding direct current source through a corresponding direct current bus, the alternating current end of each inverter jointly supplies power to a load through a parallel connection point, and the method comprises the steps that bus voltage of the direct current buses corresponding to the inverters is obtained; when the bus voltage is greater than a preset voltage threshold value, increasing the intercept of a preset droop curve of the inverter on a frequency axis to obtain a target droop curve; and controlling the inverter to operate at the active power corresponding to the system frequency in the target droop curve. When the inverter operates at the active power corresponding to the system frequency according to the target droop curve, the inverter is more biased to discharge than before the droop curve is adjusted. Therefore, energy flowing towards the direct current side of the inverter can be reduced, the rise of the bus voltage of the direct current bus of the inverter is suppressed, and the risk that the inverter triggers overvoltage protection to stop the inverter is reduced.

Description

Technical Field

[0001] This application relates to the field of power electronics, and more specifically, to a control method, apparatus, and inverter power supply system for an inverter power supply system. Background Technology

[0002] When multiple inverters connected in parallel supply power to a load, the inverter's bidirectional energy flow capability can typically be used to charge and discharge DC sources such as batteries connected to the DC end of the inverter.

[0003] However, when the battery is fully charged, or when only the photovoltaic modules are connected to the DC side of the inverter without connecting the battery, the energy flowing from the inverter to the DC source cannot be consumed by charging the corresponding DC source. In this situation, if the inverter continues to flow energy to the DC side, energy will accumulate on the DC bus. The continuously rising DC bus voltage will trigger the inverter's overvoltage protection, causing the inverter to shut down and affecting the normal operation of the inverter power supply system. Summary of the Invention

[0004] This application provides a control method, device, and inverter power supply system for an inverter power supply system. The various aspects involved in this application will be described below.

[0005] Firstly, a control method for an inverter power supply system is provided. The inverter power supply system includes at least two inverters connected in parallel. The DC terminals of each inverter are connected to a corresponding DC source via a corresponding DC bus. The AC terminals of each inverter supply power to the load through a parallel connection point. The method includes: when each inverter outputs at the system frequency as its output frequency under steady-state conditions, obtaining the bus voltage of the DC bus corresponding to the inverter; when the bus voltage is greater than a preset voltage threshold, increasing the intercept of the preset droop curve of the inverter on the frequency axis to obtain a target droop curve, the droop curve reflecting the negative correlation between active power and frequency; and controlling the inverter to operate at the active power corresponding to the system frequency in the target droop curve.

[0006] In one possible implementation, when the bus voltage is greater than a preset voltage threshold, the intercept of the preset droop curve of the inverter on the frequency axis is increased to obtain the target droop curve. This includes: when the bus voltage is greater than the voltage threshold, determining the corresponding intercept adjustment value of the inverter based on the bus voltage; and increasing the intercept of the preset droop curve of the inverter on the frequency axis based on the intercept adjustment value to obtain the target droop curve.

[0007] In one possible implementation, determining the corresponding intercept adjustment value for the inverter based on the bus voltage includes: determining the intercept adjustment value based on the bus voltage and a voltage threshold.

[0008] In one possible implementation, determining the intercept adjustment value based on the bus voltage and the voltage threshold includes: determining the intercept adjustment value based on the difference between the bus voltage and the voltage threshold.

[0009] In one possible implementation, determining the intercept adjustment value based on the difference between the bus voltage and the voltage threshold includes: determining the intercept adjustment value based on the difference and a preset proportional coefficient.

[0010] In one possible implementation, the proportional coefficient is predetermined based on the control cycle and / or the capacitance of the DC bus.

[0011] In one possible implementation, the voltage threshold is predetermined based on the bus voltage of the DC bus when the inverter is operating normally.

[0012] Secondly, a control device for an inverter power supply system is provided. The inverter power supply system includes at least two inverters connected in parallel. The DC terminals of each inverter are connected to a corresponding DC source via a corresponding DC bus. The AC terminals of each inverter supply power to the load through a parallel connection point. The device includes: a processing module, used to obtain the bus voltage of the DC bus corresponding to the inverter when each inverter outputs at the system frequency as the output frequency under steady-state conditions; when the bus voltage is greater than a preset voltage threshold, increasing the intercept of the preset droop curve of the inverter on the frequency axis to obtain a target droop curve, the droop curve reflecting the negative correlation between active power and frequency; and a control module, used to control the inverter to operate at the active power corresponding to the system frequency in the target droop curve.

[0013] In one possible implementation, the processing module is specifically used to determine the corresponding intercept adjustment value of the inverter based on the bus voltage when the bus voltage is greater than the voltage threshold; and to increase the intercept of the inverter's preset droop curve on the frequency axis based on the intercept adjustment value to obtain the target droop curve.

[0014] In one possible implementation, the processing module is specifically configured to determine the intercept adjustment value based on the bus voltage and the voltage threshold.

[0015] In one possible implementation, the processing module is specifically configured to determine the intercept adjustment value based on the difference between the bus voltage and the voltage threshold.

[0016] In one possible implementation, the processing module is specifically configured to determine the intercept adjustment value based on the difference and a preset scaling factor.

[0017] In one possible implementation, the proportional coefficient is predetermined based on the control cycle and / or the capacitance of the DC bus.

[0018] In one possible implementation, the voltage threshold is predetermined based on the bus voltage of the DC bus when the inverter is operating normally.

[0019] Thirdly, an inverter power supply system is provided, comprising: at least two inverters connected in parallel, wherein the DC terminal of each inverter is connected to a corresponding DC source through a corresponding DC bus, and the AC terminal of each inverter supplies power to the load through a parallel connection point, and further comprising a controller for executing the method described in the first aspect or any possible implementation thereof.

[0020] Fourthly, a computer-readable storage medium is provided having a computer program stored thereon, the computer program including program instructions that, when executed by a controller of an inverter power supply system, perform the method described in the first aspect or any possible implementation thereof.

[0021] In this embodiment, during the process where the inverter power supply system enters steady state and each inverter outputs using the same system frequency, the intercept of the preset droop curve (active power-frequency droop curve) on the frequency axis of the corresponding inverter is increased when the bus voltage of the DC bus of each inverter exceeds a preset voltage threshold, based on the bus voltage of the DC bus of each inverter. This results in a target droop curve, allowing the inverter to operate according to the active power corresponding to the system frequency in the target droop curve. Since the intercept of the target droop curve is larger than that of the preset droop curve, the active power corresponding to the target droop curve will be greater than that corresponding to the preset droop curve at the same frequency. Therefore, when the inverter operates at the active power corresponding to the system frequency according to the target droop curve, the inverter will be more inclined to discharge (i.e., energy will flow more towards the AC side) compared to before the droop curve adjustment. This reduces the flow of energy to the DC side of the inverter, suppresses the rise of the DC bus voltage of the inverter, reduces the risk of the inverter triggering overvoltage protection and shutting down, and improves the stability of the inverter power supply system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the inverter power supply system provided in the embodiments of this application;

[0024] Figure 2 This is a flowchart illustrating the control method of the inverter power supply system provided in the embodiments of this application;

[0025] Figure 3 This is a schematic diagram of the preset droop curve and the target droop curve provided in the embodiments of this application;

[0026] Figure 4 This is a schematic diagram of the control device of the inverter power supply system provided in the embodiments of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0028] When multiple inverters connected in parallel supply power to a load, the inverter's bidirectional energy flow capability can typically be used to charge and discharge DC sources such as batteries connected to the DC end of the inverter.

[0029] However, when the battery is fully charged, or when only the photovoltaic modules are connected to the DC side of the inverter without connecting the battery, the energy flowing from the inverter to the DC source cannot be consumed by charging the corresponding DC source. In this situation, if the inverter continues to flow energy to the DC side, energy will accumulate on the DC bus. The continuously rising DC bus voltage will trigger the inverter's overvoltage protection, causing the inverter to shut down and affecting the normal operation of the inverter power supply system.

[0030] Therefore, to address the aforementioned problems, this application provides a control method for an inverter power supply system. During the process where the inverter power supply system enters a steady state and each inverter outputs at the same system frequency, the intercept of the preset droop curve (active power-frequency droop curve) on the frequency axis is increased based on the bus voltage of each inverter's DC bus. When the bus voltage exceeds a preset voltage threshold, the intercept is increased to obtain a target droop curve (active power-frequency droop curve). This allows the inverter to operate according to the active power corresponding to the system frequency in the target droop curve. Since the intercept of the target droop curve is larger than that of the preset droop curve, the active power corresponding to the target droop curve will be greater than that corresponding to the preset droop curve at the same frequency. Therefore, when the inverter operates at the active power corresponding to the system frequency according to the target droop curve, the inverter will be more inclined to discharge (i.e., energy will flow more towards AC) compared to before the droop curve adjustment. Furthermore, it can reduce the flow of energy to the DC side of the inverter, suppress the rise of the DC bus voltage of the inverter, reduce the risk of the inverter triggering overvoltage protection and shutting down, and improve the stability of the inverter power supply system.

[0031] The droop curve (active power-frequency droop curve) illustrates the negative correlation between active power and frequency, and can be used to implement droop control for inverters. In inverter power supply systems with multiple inverters operating in parallel, droop control based on the active power-frequency droop curve can automatically allocate the active power of each inverter according to its droop characteristics, achieving power balance in the system. For example, when the inverter power supply system is in steady state, the active power of each inverter can be determined according to the system frequency based on the active power-frequency droop curve.

[0032] In this embodiment, the control method for the inverter power supply system can be applied to a corresponding inverter power supply system. This inverter power supply system may include at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding DC source via a corresponding DC bus, and the AC terminals of each inverter supply power to the load through a parallel connection point. The DC source may include various forms of DC sources such as batteries and photovoltaic modules, and is not limited here.

[0033] For example, taking an inverter power supply system consisting of two inverters as an example, such as Figure 1 As shown, the inverter power supply system may include a first inverter and a second inverter connected in parallel. The first inverter and the second inverter jointly supply power to the load. The first inverter can be connected to a DC source such as a first battery or a first photovoltaic module, and the second inverter can be connected to a DC source such as a second battery or a second photovoltaic module. When the first inverter allows energy to flow to its DC side, a portion of the energy output from the second inverter can flow to the DC side of the first inverter. Similarly, when the second inverter is operating with energy flowing to its DC side, a portion of the energy output from the first inverter can flow to the DC side of the second inverter.

[0034] It should be noted that in practical applications, inverter power supply systems may also include other necessary or required devices besides those listed above, and there are no restrictions here.

[0035] For example, the inverter power supply system may further include a controller for executing the control method of the inverter power supply system provided in the embodiments of this application. This controller may be an independently configured controller for controlling each inverter separately, or it may be a controller integrated into each inverter for controlling its own operation; no limitation is made here. When the controller is an independent controller for each inverter, the control method of the inverter power supply system provided in the embodiments of this application can be applied to each inverter separately, with each inverter's own controller executing the method of this application to control the corresponding inverter. When the controller is an independently configured controller for controlling each inverter, the control method of the inverter power supply system provided in the embodiments of this application can be executed by this independently configured controller, thereby controlling each inverter separately according to the method of this application.

[0036] The control method of an inverter power supply system provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0037] like Figure 2 As shown, when each inverter outputs at the system frequency as the output frequency under steady-state conditions, the control method of an inverter power supply system provided in this application embodiment may include the following S201-S203.

[0038] S201. Obtain the bus voltage of the DC bus corresponding to the inverter.

[0039] For example, the DC bus voltage can be detected by setting up a corresponding voltage detection device, thereby obtaining the DC bus voltage through the voltage detection device. The voltage detection device can be any device capable of detecting voltage values, such as an energy metering chip, etc., and there are no limitations here.

[0040] S202. When the bus voltage is greater than the preset voltage threshold, increase the intercept of the preset droop curve of the inverter on the frequency axis to obtain the target droop curve.

[0041] The droop curve can be an active power-frequency droop curve, where the frequency decreases as the active power increases. The preset droop curve can be a droop curve pre-set for each inverter in the inverter power supply system. Each inverter operates using the preset droop curve by default.

[0042] In this embodiment, the intercept of a preset droop curve on the frequency axis can be increased based on the bus voltage of the DC bus to obtain the target droop curve. For example, a corresponding intercept adjustment value can be determined based on the bus voltage, and then the intercept of the preset droop curve on the frequency axis can be increased based on the intercept adjustment value to obtain the target droop curve. This can be achieved by establishing a functional relationship between the bus voltage and the intercept adjustment value, thus determining the corresponding intercept adjustment value based on the bus voltage. In this embodiment, the functional relationship is not limited, as long as it establishes a positive proportional relationship between the bus voltage and the intercept adjustment value, such that a larger bus voltage results in a larger intercept adjustment value.

[0043] For example, the aforementioned voltage threshold can be used as a parameter in the functional relationship between bus voltage and the intercept adjustment value to better correlate and associate the bus voltage and the intercept adjustment value. That is, the intercept adjustment value can be determined based on the bus voltage and the voltage threshold.

[0044] For example, the intercept adjustment value can be determined based on the difference between the bus voltage and the voltage threshold. This allows the intercept adjustment value to increase with the increase of the bus voltage, thereby further increasing the intercept of the preset droop curve when the bus voltage increases. This achieves a more significant suppression of energy flowing to the DC side of the inverter by the control method of the inverter power supply system provided in this application when the bus voltage is higher, thus regulating the bus voltage to a greater extent and avoiding overvoltage of the DC bus due to energy accumulation.

[0045] Of course, in some possible implementations, the intercept adjustment value can be further determined based on the difference and a preset proportional coefficient. This allows for the regulation of the correspondence between the difference between the bus voltage and the voltage threshold and the intercept adjustment value through the proportional coefficient. This prevents the determined intercept adjustment value from changing too small or too large when the bus voltage changes, thereby avoiding the final adjustment of the inverter's active power being too small or too large. This reduces the likelihood of a significant rise in bus voltage due to an under-adjustment of the inverter's active power, and the occurrence of bus voltage oscillations due to overshoot caused by an over-adjustment of the inverter's active power.

[0046] For example, taking the determination of the intercept adjustment value based on the difference between the bus voltage and the voltage threshold and a preset proportional coefficient as an example, the aforementioned functional relationship between the bus voltage and the intercept adjustment value can be:

[0047] fb = k × (Vbus - VbusStand)

[0048] Where fb is the intercept adjustment value, k is the preset proportional coefficient, Vbus is the obtained DC bus voltage, and VbusStand is the preset voltage threshold.

[0049] In some possible implementations, the preset proportional coefficient can be predetermined based on the capacitance of the DC bus. In practical applications, the intercept of the preset droop curve of the inverter on the frequency axis can be adjusted periodically according to the method provided in this application based on a preset control cycle, as required. Therefore, the preset proportional coefficient can also be predetermined based on the control cycle and / or the capacitance of the DC bus.

[0050] In the embodiments of this application, the aforementioned voltage threshold can be predetermined based on the DC bus voltage of the inverter when it is operating normally. For example, the DC bus voltage of the inverter when it is operating normally can be directly used as the voltage threshold, or any voltage value of the DC bus voltage of the inverter when it is operating normally within the error range can be used as the voltage threshold, etc., without limitation.

[0051] S203. Control the inverter to operate at the active power corresponding to the system frequency in the target droop curve.

[0052] Since the inverter power supply system is in a steady state, all inverters in the system operate at the same output frequency (i.e., the system frequency). Therefore, after the inverter's droop curve is adjusted to the target droop curve, the inverter can operate according to the active power corresponding to the system frequency in the target droop curve. This allows for adjustment of the inverter's operating power by adjusting the droop curve, thereby regulating the amount of energy flowing to the inverter's DC side and ultimately controlling the bus voltage of its DC bus.

[0053] Based on the aforementioned control method for the inverter power supply system, during the process where the inverter power supply system enters steady state and each inverter outputs at the same system frequency, the intercept of the preset droop curve (active power-frequency droop curve) on the frequency axis of the corresponding inverter is increased according to the bus voltage of the DC bus of each inverter. When the bus voltage is greater than a preset voltage threshold, the intercept of the preset droop curve (active power-frequency droop curve) on the frequency axis is increased to obtain the target droop curve. This allows the inverter to operate according to the active power corresponding to the system frequency in the target droop curve. Since the intercept of the target droop curve is larger than that of the preset droop curve, the active power corresponding to the target droop curve will be greater than that corresponding to the preset droop curve at the same frequency. Therefore, when the inverter operates at the active power corresponding to the system frequency according to the target droop curve, the inverter will be more inclined to discharge (i.e., energy will flow more towards the AC side) compared to before the droop curve adjustment. Furthermore, it can reduce the flow of energy to the DC side of the inverter, suppress the rise of the DC bus voltage of the inverter, reduce the risk of the inverter triggering overvoltage protection and shutting down, and improve the stability of the inverter power supply system.

[0054] For example, assuming an inverter operates at system frequency f2, its preset droop curve is f = K × P + 50 (where f is the inverter output frequency, P is the inverter active power, K is the curve slope, and 50 is the rated frequency). If the adjusted target droop curve is f = K × P + 50 + fb, then... Figure 3 As shown in the figure, the dashed line represents the preset droop curve of the inverter, and the solid line represents the target droop curve. The active power corresponding to the negative half-axis of the droop curve represents the power that the inverter is allowed to charge (i.e., allowed to flow to the DC side), and the active power corresponding to the positive half-axis represents the power that the inverter discharges (i.e., flows to the AC side).

[0055] Since the inverter is currently operating at a system frequency of f2, when the inverter is controlled according to the preset droop curve, the corresponding active power during operation is P1 on the negative half-axis of the preset droop curve. That is, at this time, the inverter allows energy corresponding to the power of P1 to flow to its DC side. Therefore, when the DC source connected to the DC side of the inverter cannot charge to consume this energy, the bus voltage of its DC bus will increase due to energy accumulation.

[0056] According to the method provided in this application, a target droop curve is obtained through adjustment. After the inverter is controlled according to the target droop curve, the active power corresponding to the inverter during operation is the active power corresponding to the system frequency f2 in the target droop curve. Since the intercept of the target droop curve on the frequency axis is increased compared to the preset droop curve, the active power corresponding to the system frequency f2 in the target droop curve is greater than the corresponding P1 in the preset droop curve. That is, after the inverter is controlled according to the target droop curve, it is more inclined to discharge (i.e., energy flows to the AC side), thereby reducing the amount of energy flowing to the DC side of the inverter, suppressing the rise in bus voltage caused by energy accumulation on the DC bus, reducing the risk of the inverter triggering overvoltage protection and shutting down, and improving the stability of the inverter power supply system.

[0057] The method embodiments of this application have been described in detail above with reference to the accompanying drawings. The apparatus embodiments of this application will now be described in detail. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any parts not described in detail can be referred to the foregoing method embodiments.

[0058] This application also provides a control device for an inverter power supply system. The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding DC source via a corresponding DC bus. The AC terminals of each inverter supply power to the load through a parallel connection point. (Refer to...) Figure 4As shown, the device includes: a processing module 401, used to obtain the bus voltage of the DC bus corresponding to the inverter when each inverter outputs at the system frequency as the output frequency under steady-state system conditions; when the bus voltage is greater than a preset voltage threshold, increasing the intercept of the preset droop curve of the inverter on the frequency axis to obtain a target droop curve, the droop curve reflecting the negative correlation between active power and frequency; and a control module 402, used to control the inverter to operate at the active power corresponding to the system frequency in the target droop curve.

[0059] In one possible implementation, the processing module 401 is specifically used to determine the corresponding intercept adjustment value of the inverter based on the bus voltage when the bus voltage is greater than the voltage threshold; and to increase the intercept of the inverter's preset droop curve on the frequency axis based on the intercept adjustment value to obtain the target droop curve.

[0060] In one possible implementation, the processing module 401 is specifically configured to determine the intercept adjustment value based on the bus voltage and the voltage threshold.

[0061] In one possible implementation, the processing module 401 is specifically configured to determine the intercept adjustment value based on the difference between the bus voltage and the voltage threshold.

[0062] In one possible implementation, the processing module 401 is specifically configured to determine the intercept adjustment value based on the difference and a preset scaling factor.

[0063] In one possible implementation, the proportional coefficient is predetermined based on the control cycle and / or the capacitance of the DC bus.

[0064] In one possible implementation, the voltage threshold is predetermined based on the bus voltage of the DC bus when the inverter is operating normally.

[0065] This application also provides an inverter power supply system, including: at least two inverters connected in parallel, the DC terminals of each inverter being connected to a corresponding DC source through a corresponding DC bus, the AC terminals of each inverter supplying power to the load through a parallel connection point, and a controller for executing the method described in any of the preceding embodiments.

[0066] This application also provides a computer-readable storage medium storing a computer program thereon. The computer program includes program instructions, which, when executed by the controller of the inverter power supply system, perform the methods described in any of the preceding embodiments.

[0067] It should be understood that, in the embodiments of this application, determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0068] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0069] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0070] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0071] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0072] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0073] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0074] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can read or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs, DVDs) or semiconductor media (e.g., solid-state disks, SSDs), etc.

[0075] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for an inverter power supply system, characterized in that, The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding DC source via a corresponding DC bus. The AC terminals of each inverter supply power to the load through a parallel connection point. The method includes: When each inverter outputs at the system frequency under steady-state conditions, the bus voltage of the DC bus corresponding to the inverter is obtained. When the bus voltage is greater than the preset voltage threshold, the intercept of the preset droop curve of the inverter on the frequency axis is increased to obtain the target droop curve. The droop curve reflects the negative correlation between active power and frequency. The inverter is controlled to operate at the active power corresponding to the system frequency in the target droop curve.

2. The method according to claim 1, characterized in that, When the bus voltage is greater than a preset voltage threshold, the intercept of the preset droop curve of the inverter on the frequency axis is increased to obtain the target droop curve, including: When the bus voltage is greater than the voltage threshold, the intercept adjustment value of the inverter is determined based on the bus voltage. The target droop curve is obtained by increasing the intercept of the inverter's preset droop curve on the frequency axis according to the intercept adjustment value.

3. The method according to claim 2, characterized in that, Determining the intercept adjustment value of the inverter based on the bus voltage includes: The intercept adjustment value is determined based on the bus voltage and the voltage threshold.

4. The method according to claim 3, characterized in that, Determining the intercept adjustment value based on the bus voltage and the voltage threshold includes: The intercept adjustment value is determined based on the difference between the bus voltage and the voltage threshold.

5. The method according to claim 4, characterized in that, Determining the intercept adjustment value based on the difference between the bus voltage and the voltage threshold includes: The intercept adjustment value is determined based on the difference and a preset proportional coefficient.

6. The method according to claim 5, characterized in that, The proportional coefficient is predetermined based on the control cycle and / or the capacitance of the DC bus.

7. The method according to any one of claims 1-6, characterized in that, The voltage threshold is predetermined based on the bus voltage of the DC bus when the inverter is operating normally.

8. A control device for an inverter power supply system, characterized in that, The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding DC source via a corresponding DC bus. The AC terminals of each inverter supply power to the load through a parallel connection point. The device includes: The processing module is used to obtain the bus voltage of the DC bus corresponding to each inverter when each inverter outputs at the system frequency as the output frequency under steady state of the system; when the bus voltage is greater than a preset voltage threshold, the intercept of the preset droop curve of the inverter on the frequency axis is increased to obtain the target droop curve, which reflects the negative correlation between active power and frequency. The control module is used to control the inverter to operate at the active power corresponding to the system frequency in the target droop curve.

9. An inverter power supply system, characterized in that, The method includes at least two inverters connected in parallel, wherein the DC terminals of each inverter are connected to a corresponding DC source via a corresponding DC bus, and the AC terminals of each inverter supply power to the load through a parallel connection point. The method also includes a controller for performing the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program, which includes program instructions that, when executed by the controller of the inverter power supply system, perform the method as described in any one of claims 1 to 7.

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