Multi-inverter control method, multi-inverter control device, and electronic apparatus

Abstract

The embodiment of the invention discloses a multi-inverter control method, a multi-inverter control device and electronic equipment, and the main technical scheme comprises the steps: obtaining a common voltage DC component of the output ends of a plurality of parallel inverters, and obtaining a current DC component of a target inverter in the plurality of parallel inverters; based on a preset droop coefficient, the voltage component droop amount of the inverter is determined according to the current direct-current component, and the droop coefficient represents the negative correlation between the current direct-current component and the voltage component droop amount; the common voltage direct current component is adjusted according to the voltage component droop amount, so that the current direct current component is reduced, virtual impedance does not need to be introduced while the current direct current component is effectively suppressed, and then the operation reliability and stability during multi-inverter off-grid parallel connection can be improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for multiple inverters, a control device for multiple inverters, and electronic equipment. Background Technology

[0002] In systems with multiple inverters operating in parallel, even small differences in the DC voltage component between the output voltages of each inverter can lead to a large DC current component. This excessive DC current component can create circulating currents between the parallel inverters, affecting system stability and even damaging the equipment. Traditional suppression methods often involve introducing virtual impedance to regulate the DC voltage component and thus suppress the DC current component. While this reduces the DC current component, the virtual impedance also increases the fundamental voltage drop between inverters, causing the inverter's output voltage to drop and ultimately affecting its normal operation. Summary of the Invention

[0003] This application provides a control method, control device, and electronic equipment for multiple inverters, which suppress the DC component of the inverter current without affecting the fundamental voltage.

[0004] This application provides the following solution:

[0005] According to a first aspect, a control method for multiple inverters is provided, applicable to multiple inverters connected in parallel, wherein the output terminals of the multiple inverters connected in parallel are commonly connected to the same load, the method comprising:

[0006] Obtain the common voltage DC component of the output terminals of the plurality of parallel inverters, and obtain the current DC component of the target inverter among the plurality of parallel inverters;

[0007] Based on a preset droop coefficient, the voltage component droop of the target inverter is determined according to the DC component of the current, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop.

[0008] The common voltage DC component is adjusted according to the voltage component droop.

[0009] As an optional approach, the target inverter is equipped with a PI controller, and the adjustment of the common voltage DC component based on the voltage component droop includes:

[0010] The control command is obtained based on the DC component of the common voltage and the droop of the voltage component.

[0011] The PI controller adjusts the DC component of the common voltage according to the control command.

[0012] As an optional approach, obtaining the control command based on the DC component of the common voltage and the voltage component droop includes:

[0013] The DC component of the common voltage is controlled to zero, and the zero plus the voltage component droop is determined as the control command.

[0014] As an optional approach, adjusting the DC component of the common voltage via the PI controller according to the control command includes:

[0015] The PI controller performs proportional-integral calculations according to the control instructions to generate modulation compensation.

[0016] The modulation compensation amount is superimposed on any instruction link in the control loop of the target inverter to perform instruction modulation on the target inverter. The instruction link includes off-grid voltage instruction, current instruction, or modulation wave instruction.

[0017] As an optional approach, before obtaining the DC component of the common voltage at the output terminals of the plurality of parallel inverters, the method further includes:

[0018] Select any one inverter from the plurality of inverters connected in parallel as the inverter master, and the other inverters as inverter slaves;

[0019] The DC component of the inverter master voltage is obtained and sent to each of the inverter slaves as the common DC component of the output of the multiple parallel inverters.

[0020] As an optional approach, the process of generating the droop coefficient includes:

[0021] Obtain the initial DC component of the target inverter's current;

[0022] A virtual impedance is selected based on the DC component of the initial current, and a droop coefficient is obtained based on the virtual impedance.

[0023] As an optional approach, the step of selecting a virtual impedance based on the DC component of the initial current and obtaining a droop coefficient based on the virtual impedance includes:

[0024] The initial virtual impedance is selected from the historical virtual impedance dataset based on the DC component of the initial current;

[0025] Based on the DC component of the target current corresponding to the virtual impedance, the initial virtual impedance is adjusted within a preset adjustment range to obtain the target virtual impedance;

[0026] The droop coefficient is obtained based on the target virtual impedance.

[0027] Alternatively, the droop coefficient may be less than zero.

[0028] According to a second aspect, a control device for multiple inverters is provided, applicable to multiple inverters connected in parallel, wherein the output terminals of the multiple inverters connected in parallel are commonly connected to the same load, the device comprising:

[0029] The voltage acquisition module is configured to acquire the common DC component of the output voltage of the plurality of parallel inverters, and to acquire the DC component of the current of the target inverter among the plurality of parallel inverters.

[0030] The droop acquisition module is configured to determine the voltage component droop of the target inverter based on the DC component of the current according to a preset droop coefficient, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop.

[0031] The component adjustment module is configured to adjust the common voltage DC component according to the voltage component droop.

[0032] According to a third aspect, an electronic device is provided, comprising:

[0033] The controller and multiple inverters connected in parallel, the outputs of which are all connected to the same load;

[0034] The controller is used to perform the steps of the method as described in any one of the first aspects.

[0035] According to the specific embodiments provided in this application, the following technical effects are disclosed:

[0036] The solution provided in this application determines the negative correlation between the droop of the DC current component and the voltage component based on a preset droop coefficient. The DC current component then determines the voltage component droop of the target inverter based on this negative correlation. This allows for the adjustment of the common voltage DC component, reducing the DC current component to the target DC current component. This effectively suppresses excessive DC current components to avoid circulating current affecting system stability or damaging equipment. Furthermore, it eliminates the need for virtual impedance, thus avoiding the problems of increased fundamental voltage drop, output voltage slump, and interference with inverter operation caused by virtual impedance in traditional methods. This effectively improves the operational reliability and stability of multiple inverters connected in parallel off-grid.

[0037] Of course, any product implementing this application does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0039] Figure 1 This is a circuit architecture diagram applicable to the embodiments of this application;

[0040] Figure 2 A flowchart of a control method for multiple inverters provided in an embodiment of this application;

[0041] Figure 3 A schematic diagram of the DC component module in the control method for multiple inverters provided in the embodiments of this application;

[0042] Figure 4 A schematic diagram of the droop curve in the control method for multiple inverters provided in the embodiments of this application;

[0043] Figure 5 In the control method for multiple inverters provided in the embodiments of this application, a control block diagram for generating modulation compensation amount is included;

[0044] Figure 6 A control block diagram for command modulation in the control method for multiple inverters provided in the embodiments of this application;

[0045] Figure 7 A schematic block diagram of a control device for a multi-inverter provided in an embodiment of this application. Detailed Implementation

[0046] 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, and not all embodiments. 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.

[0047] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0048] It should be understood that the term "and / or" used 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, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0049] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0050] In existing technologies, when multiple inverters operate in parallel, differences in the DC component of their output voltage can lead to excessive DC current, forming circulating current and affecting system stability or even damaging the equipment. Traditional methods introduce virtual impedance to regulate the DC voltage component and suppress the DC current component. However, virtual impedance increases the fundamental voltage drop of the inverter, causing a voltage slump in the output voltage and affecting normal inverter operation. For example, in photovoltaic power generation systems, when multiple inverters are connected to the grid in parallel, differences in line impedance can cause DC voltage differences. While traditional virtual impedance regulation can reduce circulating current, it leads to a decrease in output voltage quality.

[0051] To address the aforementioned issues, this application proposes a control method for multiple inverters connected in parallel with their outputs connected to the same load. By establishing a negative correlation between the DC component of the current and the droop of the voltage component, the voltage component is dynamically adjusted to indirectly control the current component, achieving current component control without relying on virtual impedance.

[0052] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0053] Figure 1 This is a system architecture diagram applicable to the embodiments of this application; such as Figure 1 As shown, Figure 1 This circuit architecture diagram, applicable to embodiments of this application, illustrates the basic topology of a multi-inverter parallel system. The system can include one master inverter and several slave inverters (e.g., slave 1, slave 2, etc.), both of which are inverters. The master and slave inverters interact via CAN communication, and the outputs of all inverters are connected to the same load. This architecture, through the communication mechanism between the master and slave inverters, ensures that each inverter performs droop control based on unified DC component voltage data, solving the problem of voltage differences easily generated by independent sampling by multiple inverters, and providing a hardware foundation for subsequent suppression of DC circulating current.

[0054] It should be noted that the method used in this application is not limited to... Figure 1 The master-slave division in this architecture allows for adaptation to the DC voltage component acquisition and droop control logic of this application when the system adopts a distributed parallel topology (without explicit master-slave division, and each inverter communicates peer-to-peer) or a hybrid topology (partial master-slave, partial peer-to-peer). This can be achieved through dynamic election of temporary masters and multi-machine collaborative sampling, ensuring DC circulating current suppression under different parallel topologies. This architecture, through flexible communication and control mechanisms, provides support for unified execution of DC voltage component regulation in multi-topology scenarios.

[0055] Figure 2 A flowchart of the control method for a multi-inverter provided in the embodiments of this application; such as Figure 2 As shown, this application provides a control method for multiple inverters, which can be applied to... Figure 1 A method involving multiple inverters connected in parallel, with the outputs of these inverters all connected to the same load, may include at least the following steps:

[0056] Step 201: Obtain the DC component of the common voltage at the output terminals of multiple parallel inverters, and obtain the DC component of the current of the target inverter among the multiple parallel inverters.

[0057] Step 202: Based on the preset droop coefficient, determine the voltage component droop of the target inverter according to the DC component of the current, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop.

[0058] Step 203: Adjust the DC component of the common voltage according to the voltage component droop.

[0059] The solution provided in this application determines the negative correlation between the droop of the DC current component and the voltage component based on a preset droop coefficient. The DC current component then determines the voltage component droop of the target inverter based on this negative correlation. This allows for the adjustment of the common voltage DC component, reducing the DC current component to the target DC current component. This effectively suppresses excessive DC current components to avoid circulating current affecting system stability or damaging equipment. Furthermore, it eliminates the need for virtual impedance, thus avoiding the problems of increased fundamental voltage drop, output voltage slump, and interference with inverter operation caused by virtual impedance in traditional methods. This effectively improves the operational reliability and stability of multiple inverters connected in parallel off-grid.

[0060] The target inverter is at least one of multiple inverters connected in parallel. The common voltage DC component is the DC voltage component at the common connection point of the parallel inverter outputs. It can be sampled and measured at the parallel outputs by a voltage sensor. It's understood that the outputs of the parallel inverters are all connected together, and each inverter acquires the common voltage DC component. However, due to sampling deviations, there may be numerical differences. Therefore, the main inverter can broadcast its sampled values ​​for other inverters to unify the common voltage DC component. The droop coefficient is the proportional parameter between the current DC component and the voltage component droop. It can be preset or dynamically adjusted according to the system impedance characteristics to establish the quantitative relationship between the two. The voltage component droop is the adjustment amount to be applied to the common voltage DC component, which can be determined by the product of the target current DC component and the droop coefficient.

[0061] Furthermore, there is a corresponding relationship between the droop coefficient and the target current DC component. The target current DC component is the desired current DC component, which can be calculated by multiplying the droop coefficient by the voltage difference. It is used to guide the adjustment direction of the voltage component. For example, in this application, the droop coefficient is less than zero, so the voltage component droop is the value that the voltage DC component needs to be reduced. Thus, by adjusting the common voltage DC component according to the voltage component droop, the excessive current DC component can be effectively suppressed.

[0062] refer to Figure 3 , Figure 3 The schematic diagram of the DC component in the control method for multiple inverters provided in this application embodiment shows the DC current distribution when two inverters are connected in parallel. In the diagram, DCV1 and DCV2 are the DC components of the inverter output voltage, Idc1 and Idc2 are the DC components of the current in the corresponding branches, and DCVC at the common connection point AN is the DC component of the common voltage.

[0063] Understandably, when multiple inverters are connected in parallel to the DC bus, this application can obtain the DC voltage component output by each inverter using a voltage sensor, and select the DC voltage component of any inverter as the common DC voltage component. The DC voltage component of the inverter is affected by the line impedance, which is the equivalent impedance from the inverter output terminal to the common connection point, reflecting the current transmission path loss characteristics. For example, if the DC voltage component output by inverter 1 is the common DC voltage component, and we assume that the common DC voltage component corresponding to inverter 1 is 1mV, then with a line impedance of 0.002Ω, the Idc1 of inverter 1 is 500mA. Obviously, 500mA is an excessively large DC current component. Therefore, this application needs to determine the voltage component droop based on the droop coefficient, and reduce the DC current component to the target DC current component based on the voltage component droop.

[0064] refer to Figure 4 The schematic diagram of the droop curve in the control method for multi-inverters provided in this application embodiment shows the linear relationship between the voltage droop Dcv and the DC current Idc. The voltage droop Dcv and the DC current Idc are negatively correlated, that is, they conform to the formula Dcv=K×Idc, where K is the droop coefficient, and K is less than 0. Figure 4 The slope of the curve is determined by K. Figure 4 The I on the X-axis can be understood as the DC component of the current, Idc. Figure 4 V on the Y-axis can be understood as Dcv, and the physical meaning of K can be equivalent to the virtual impedance of the DC component. By establishing the relationship between the current and voltage adjustment through the droop coefficient, the DC component of the current can be suppressed.

[0065] Understandably, if the droop factor K of this application is -0.2 when the Idc1 of the inverter 1 is 500mA, it means that a 0.2 ohm impedance is introduced only for the DC component of the current. It is worth noting that the droop factor is a proportional parameter of the droop of the DC component of the current and the voltage component, which is obtained through experimental calibration or dynamic adjustment. The droop factor can be zero minus the corresponding virtual impedance. The sum of the virtual impedance corresponding to the droop factor and the line impedance can be used as the impedance coefficient of the target inverter. The DC component of the voltage of the target inverter divided by the impedance coefficient is the DC component of the current of the target inverter. Therefore, under steady state, the DC component of the current is 1 / (0.2+0.002)=4.95mA. The voltage droop corresponding to 4.95mA is 0.99mV. Therefore, it is necessary to reduce the value of DCV1 of inverter 1 from 1mV to 0.01mV through software control. 0.01mV / 0.002Ω=5mA≈4.95mA, so that the DC component of the inverter current is reduced from 500mA to the target DC component of 4.95mA. In engineering practice, due to the limitation of effective bit accuracy, the parameters in the theoretical derivation are assumed to have infinite accuracy. In actual systems, due to sensor resolution, AD conversion bit number, etc., there will be a slight deviation between the calculated value and the theoretical value.

[0066] It's worth noting that conventional virtual impedance introduces virtual impedance for current across all frequency bands. A larger virtual impedance results in better DC component suppression, but also a larger voltage drop caused by the fundamental current. For example, if the expected output voltage for off-grid operation is 230V, increasing the load might cause it to drop to 200V, which is unacceptable. Therefore, conventional virtual impedance schemes often require a trade-off between fundamental voltage drop and DC component suppression. This application, however, sets the droop coefficient K instead of the virtual impedance itself. It inherits the virtual impedance mathematically, and based on the droop coefficient K, the droop control generates DC offset, modifying only the DC offset of the output voltage without affecting the fundamental amplitude / phase, thus not impacting the inverter's normal operation.

[0067] Figure 5 In the control method for multiple inverters provided in the embodiments of this application, a control block diagram for generating modulation compensation amounts is presented, exhibiting closed-loop control logic for the DC voltage component; (Refer to...) Figure 5 This application further proposes that when a PI controller is installed on the target inverter, the common voltage DC component is adjusted according to the voltage component droop, including: obtaining a control command based on the common voltage DC component and the voltage component droop; and adjusting the common voltage DC component according to the control command through the PI controller.

[0068] The PI controller is used to implement proportional-integral control. It can employ operational amplifier circuits or built-in algorithms of digital signal processors to dynamically adjust based on the input voltage difference signal. The control command is to modify the DC offset of the output voltage. The DC offset is a reference quantity used to correct the voltage component. It can be generated by controlling the common voltage DC component to zero and adding the voltage component droop to zero. Therefore, the DC offset is defined as the control command, and the PI controller can adjust the common voltage DC component of the target inverter according to the control command. The above command modulation process can be an adjustment operation on the output waveform of the target inverter, which can employ pulse width modulation or space vector modulation techniques to change the output voltage by adjusting the on-time of the switching devices.

[0069] In some embodiments, adjusting the DC component of the common voltage by a PI controller according to a control command includes: performing proportional-integral calculations by the PI controller according to the control command to generate a modulation compensation amount; and superimposing the modulation compensation amount onto any command link in the control loop of the target inverter to perform command modulation on the target inverter, wherein the command link includes an off-grid voltage command, a current command, or a modulation wave command.

[0070] like Figure 5 As shown, this application can control the DC component of the common voltage DCVC to zero, add the voltage droop DCV to zero and subtract the DC component of the common voltage DCVC as the feedback quantity as the input of the PI controller, so that the PI controller outputs the modulation compensation quantity VrefDcv.

[0071] refer to Figure 6 , Figure 6 The control block diagram for command modulation in the control method for multiple inverters provided in the embodiments of this application; such as Figure 6As shown, the command modulation process can be further implemented through a dual closed-loop control structure, specifically including a voltage outer loop and a current inner loop: The voltage outer loop uses the superposition value (Vref+VrefDcv) of the off-grid voltage command Vref and the modulation compensation amount VrefDcv as the voltage reference command, and compares it with the actual output voltage Vinv of the inverter to generate a voltage error signal. After processing by the voltage loop PI controller, this voltage error signal outputs a current reference command Iinvref, so that the current inner loop uses the current reference command Invref as a reference and compares it with the actual output current Iinv of the inverter to generate a current error signal. Further, after processing by the current loop PI controller, this current error signal generates a modulation wave command Vmodulation, which is used to control the switching action of the inverter bridge arm, thereby controlling the inverter output voltage and current.

[0072] Understandably, in a dual-loop control structure, the outer voltage loop is primarily responsible for ensuring the stability and tracking performance of the inverter's output voltage, while the inner current loop is used to improve the system's dynamic response speed and anti-interference capability. By superimposing the modulation compensation amount VrefDcv onto the off-grid voltage command Vref, closed-loop control of the DC component of the common voltage can be achieved to reduce the DC current component, thereby effectively solving the DC circulating current problem in multi-inverter parallel systems.

[0073] It is worth noting that, compared with the traditional method, this solution uses a PI controller for closed-loop control, which does not require additional virtual impedance components. Therefore, it can avoid the additional voltage drop of the fundamental voltage and eliminate the DC voltage difference in the parallel system without affecting the AC output voltage amplitude of the target inverter, thereby improving system stability.

[0074] Furthermore, regarding the communication and sampling mechanism for multiple parallel inverters, this application proposes the following: before acquiring the common DC voltage component of the output terminals of the multiple parallel inverters, the method further includes: selecting any one inverter from the multiple parallel inverters as the inverter master and the other inverters as inverter slaves; acquiring the DC voltage component of the inverter master and sending the DC voltage component of the inverter master to each inverter slave to serve as the common DC voltage component of the output terminals of the multiple parallel inverters. The inverter master is the main control unit of the parallel system, which can be determined through communication protocol priority determination or random selection, and is used to uniformly collect and distribute DC voltage component data; the inverter slaves achieve synchronization by receiving voltage data sent by the master, avoiding the accumulation of errors from independent acquisition; the communication connection can adopt a CAN bus, Ethernet, or wireless communication module to ensure real-time data interaction between the master and slave. Specifically, the parallel inverter system can determine the master inverter through a preset communication protocol or dynamic election mechanism, such as prioritizing based on device ID. The master inverter can measure its own output DC voltage component using sensors and transmit it to all slave inverters via the communication link. The slave inverters can then use this data as their own DC voltage component input to the control algorithm, replacing their local measurements. Thus, all inverters perform droop control calculations based on the same data source, obtaining a unified common DC voltage component. This eliminates voltage differences in the DC voltage component caused by variations in sensor accuracy or environmental interference. Compared to traditional methods where each inverter independently measures the DC voltage component, leading to data inconsistencies due to hardware differences or measurement noise and generating additional DC current components, this solution eliminates data voltage differences at the source through a unified data source, reducing control errors, simplifying system complexity, avoiding resource waste from independent measurements by multiple nodes, and improving circulating current suppression and system stability.

[0075] Furthermore, regarding the determination of the droop of the target current DC component and voltage component, this application proposes: obtaining the initial current DC component of the target inverter; selecting a virtual impedance based on the initial current DC component; and obtaining the droop coefficient based on the virtual impedance. Here, the initial current DC component is the output current DC component of the inverter before droop coefficient adjustment, which can be obtained through sensor sampling; the virtual impedance is an equivalent impedance parameter simulating the actual line impedance characteristics, which can be implemented using an impedance simulation circuit or an impedance algorithm in a digital controller, used to adjust the correspondence between the droop coefficient and the current DC component; the target virtual impedance is the optimal impedance value after debugging that balances the DC component suppression effect and the fundamental voltage stability, obtained through iterative optimization using a preset impedance adjustment step size combined with current feedback signals.

[0076] Furthermore, the process of selecting the virtual impedance and obtaining the droop coefficient based on the initial current DC component can also include: selecting the initial virtual impedance from the historical virtual impedance dataset based on the initial current DC component; adjusting the initial virtual impedance within a preset adjustment range based on the target current DC component corresponding to the virtual impedance to obtain the target virtual impedance; and obtaining the droop coefficient based on the target virtual impedance. The historical virtual impedance dataset stores virtual impedance values ​​corresponding to different initial current DC components, established through experimental testing or historical operating data, and is used to quickly match the initial virtual impedance to improve computational efficiency. The virtual impedance can be derived through the mathematical relationship between the droop coefficient and the line impedance, and is used to adjust the droop coefficient to balance the suppression of the current DC component and the stability of the fundamental voltage. The preset adjustment range is a virtual impedance adjustment interval set according to the maximum allowable fundamental voltage drop value of the system, determined through system parameters or empirical values, constraining the virtual impedance adjustment amplitude to avoid abnormal output voltage. Specifically, this application can gradually adjust the virtual impedance value by matching the initial virtual impedance value from a preset virtual impedance database based on the magnitude of the initial current DC component (e.g., when the initial current DC component is 100mA to 1A, the initial virtual impedance is selected from 0.05 to 0.5Ω) through closed-loop control until the target current DC component reaches the preset threshold range; the optimized target virtual impedance is substituted into the droop coefficient calculation formula to generate a droop coefficient that matches the actual working condition, so that the droop coefficient adaptively matches the current working condition.

[0077] It is worth noting that the process of gradually adjusting the virtual impedance value through closed-loop control in this application is essentially a process of setting the droop coefficient K through software, and does not actually set the virtual impedance of the inverter. Furthermore, the process of setting the droop coefficient K through software can be understood as a process of modifying the control loop parameters of the DC-V loop of the PI controller and the filter parameters of the inverter. The droop coefficient K can be changed in real time according to the actual application scenario while being less than zero, so as to adjust the suppression effect on the DC component of the inverter current.

[0078] refer to Figure 7 , Figure 7 A schematic block diagram of a control device for multiple inverters provided in embodiments of this application; in some embodiments, this application provides a control device 700 for multiple inverters connected in parallel, wherein the output terminals of the multiple inverters connected in parallel are connected to the same load, and the device includes:

[0079] The voltage acquisition module 701 is configured to acquire the common DC component of the output voltage of multiple inverters connected in parallel, and to acquire the DC component of the current of the target inverter among the multiple inverters connected in parallel.

[0080] The droop acquisition module 702 is configured to determine the voltage component droop of the target inverter based on the DC component of the current according to a preset droop coefficient, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop.

[0081] The component adjustment module 703 is configured to adjust the common voltage DC component according to the voltage component droop.

[0082] As an optional approach, the target inverter is equipped with a PI controller. When the component adjustment module 703 performs the adjustment of the common voltage DC component based on the common voltage component droop, it is also configured to: obtain control commands based on the common voltage DC component and the voltage component droop; and adjust the common voltage DC component according to the control commands through the PI controller.

[0083] As an optional approach, when the component adjustment module 703 executes the control command obtained based on the common voltage DC component and the voltage component droop, it is also configured to: control the common voltage DC component to zero, and add the zero to the voltage component droop to determine the control command.

[0084] As an optional approach, when the component adjustment module 703 adjusts the DC component of the common voltage according to the control command via the PI controller, it is also configured to: perform proportional-integral calculations via the PI controller according to the control command to generate a modulation compensation amount; and superimpose the modulation compensation amount onto any command link in the control loop of the target inverter to perform command modulation on the target inverter, wherein the command link includes off-grid voltage command, current command, or modulation wave command.

[0085] As an optional approach, multiple inverters are connected in parallel. Before acquiring the common DC voltage component of the output terminals of the multiple parallel inverters, the voltage acquisition module 701 is further configured to: select any one inverter from the multiple parallel inverters as the inverter master and the other inverters as inverter slaves; acquire the DC voltage component of the inverter master and send the DC voltage component of the inverter master to each inverter slave as the common DC voltage component of the output terminals of the multiple parallel inverters.

[0086] As an optional approach, the process of generating the droop coefficient in the droop acquisition module 702 includes: acquiring the initial current DC component of the target inverter; selecting a virtual impedance based on the initial current DC component; and obtaining the droop coefficient based on the virtual impedance.

[0087] As an optional approach, the process of selecting a virtual impedance based on the DC component of the initial current and obtaining a droop coefficient in the droop acquisition module 702 may include: selecting an initial virtual impedance from a historical virtual impedance dataset based on the DC component of the initial current; adjusting the initial virtual impedance within a preset adjustment range based on the target DC component of the virtual impedance to obtain a target virtual impedance; and obtaining a droop coefficient based on the target virtual impedance, wherein the droop coefficient is less than zero.

[0088] In addition, embodiments of this application also provide a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of any of the methods in the foregoing method embodiments.

[0089] And an electronic device, comprising:

[0090] The controller and multiple inverters connected in parallel, with the outputs of the multiple inverters connected in parallel all connected to the same load;

[0091] The controller is used to execute the steps of the method as described in any of the foregoing method embodiments.

[0092] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of any of the methods in the foregoing method embodiments.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method of controlling a multi-inverter, characterized by, A method applicable to multiple inverters connected in parallel, wherein the outputs of the multiple inverters are all connected to the same load, the method includes: Obtain the common voltage DC component of the output terminals of the plurality of parallel inverters, and obtain the current DC component of the target inverter among the plurality of parallel inverters; Based on a preset droop coefficient, the voltage component droop of the target inverter is determined according to the DC component of the current, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop. The common voltage DC component is adjusted according to the voltage component droop.

2. The method of claim 1, wherein, The target inverter is equipped with a PI controller, and the adjustment of the common voltage DC component according to the voltage component droop includes: The control command is obtained based on the DC component of the common voltage and the droop of the voltage component. The PI controller adjusts the DC component of the common voltage according to the control command.

3. The method according to claim 2, characterized in that, The step of obtaining control commands based on the DC component of the common voltage and the voltage component droop includes: The DC component of the common voltage is controlled to zero, and the zero plus the voltage component droop is determined as the control command.

4. The method according to claim 2, characterized in that, The step of adjusting the DC component of the common voltage via the PI controller according to the control command includes: The PI controller performs proportional-integral calculations according to the control instructions to generate modulation compensation amounts. The modulation compensation amount is superimposed on any instruction link in the control loop of the target inverter to perform instruction modulation on the target inverter. The instruction link includes off-grid voltage instruction, current instruction, or modulation wave instruction.

5. The method according to any one of claims 1 to 4, characterized in that, Before obtaining the common DC component of the output voltage of the plurality of parallel inverters, the method further includes: Select any one inverter from the plurality of inverters connected in parallel as the inverter master, and the other inverters as inverter slaves; The DC component of the inverter master voltage is obtained and sent to each of the inverter slaves as the common DC component of the output terminals of the multiple parallel inverters.

6. The method according to any one of claims 1 to 4, characterized in that, The process of generating the droop coefficient includes: Obtain the initial DC component of the target inverter's current; A virtual impedance is selected based on the DC component of the initial current, and a droop coefficient is obtained based on the virtual impedance.

7. The method according to claim 6, characterized in that, The step of selecting a virtual impedance based on the DC component of the initial current and obtaining a droop coefficient based on the virtual impedance includes: The initial virtual impedance is selected from the historical virtual impedance dataset based on the DC component of the initial current; Based on the DC component of the target current corresponding to the virtual impedance, the initial virtual impedance is adjusted within a preset adjustment range to obtain the target virtual impedance; The droop coefficient is obtained based on the target virtual impedance.

8. The method according to claim 7, characterized in that, The droop coefficient is less than zero.

9. A control device for multiple inverters, characterized in that, A device for use with multiple inverters connected in parallel, wherein the outputs of the multiple inverters are all connected to the same load, the device comprising: The voltage acquisition module is configured to acquire the common DC component of the output voltage of the plurality of parallel inverters, and to acquire the DC component of the current of the target inverter among the plurality of parallel inverters. The droop acquisition module is configured to determine the voltage component droop of the target inverter based on the DC component of the current according to a preset droop coefficient, wherein the droop coefficient represents the negative correlation between the DC component of the current and the voltage component droop. The component adjustment module is configured to adjust the common voltage DC component according to the voltage component droop.

10. An electronic device, characterized in that, include: The controller and multiple inverters connected in parallel, the outputs of which are all connected to the same load; The controller is used to perform the method as described in any one of claims 1 to 8.

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