Inverter off-grid parallel operation power distribution control method and off-grid parallel operation multi-machine system

Abstract

The invention relates to an inverter off-grid parallel operation power distribution control method and an off-grid parallel operation multi-machine system. The control method is applied to the off-grid parallel operation multi-machine system, the off-grid parallel operation multi-machine system is provided with a plurality of inverter devices, and the control method comprises the following steps: obtaining impedance characteristics of the inverter devices, and obtaining power droop coefficients of the inverter devices according to the impedance characteristics of the inverter devices; and controlling the power output of the inverter equipment during parallel operation according to the power droop coefficient of the inverter equipment. By implementing the method, the phenomenon of parallel operation failure caused by battery power feed of the parallel operation inverter equipment can be prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of off-grid parallel operation, and more particularly to a power distribution control method for an off-grid parallel inverter and an off-grid parallel multi-machine system. Background Art

[0002] Hybrid inverter off-grid paralleling technology is commonly used in industrial, commercial, and residential energy storage inverter products. It is a DC-AC inverter parallel control technology in the power electronics field. During the grid connection process, the output power of the hybrid inverter is limited by the maximum allowable current of the BMS in real time. Achieving coordinated charge and discharge management of multiple parallel units with the BMS, such as flexible power allocation strategies based on the power consumption of each energy storage battery, is a key control process for grid connection. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an off-grid parallel inverter power distribution control method and an off-grid parallel multi-machine system in response to the above-mentioned technical defects of the prior art.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct a power distribution control method for an off-grid parallel inverter, which is applied to an off-grid parallel multi-machine system, wherein the off-grid parallel multi-machine system has multiple inverter devices, and the control method includes the following steps:

[0005] respectively obtaining impedance characteristics of the inverter devices, so as to obtain a power droop coefficient of the inverter devices according to the impedance characteristics of the inverter devices;

[0006] The power output of the inverter device during parallel operation is controlled according to the power droop coefficient of the inverter device.

[0007] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the power droop coefficient of the inverter device according to the impedance characteristics of the inverter device includes:

[0008] When the impedance characteristic of the inverter device is inductive, the active power droop coefficient of the inverter device is obtained according to the frequency parameter of the inverter device.

[0009] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the active power droop coefficient of the inverter device according to the frequency parameter of the inverter device includes: obtaining the active power droop coefficient of the inverter device according to the following formula:

[0010]

[0011] Wherein, m is the active power droop coefficient of the inverter device, f0 is the no-load frequency of the inverter device, f min is the minimum parallel frequency corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device.

[0012] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, the method further includes:

[0013] The minimum allowable output power of the inverter device corresponding to the minimum parallel frequency is obtained, so as to obtain the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power.

[0014] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the minimum allowable output power corresponding to the inverter device and the minimum parallel frequency includes: obtaining the minimum allowable output power P according to the following formula min :

[0015]

[0016] Among them, m max is the maximum active power droop coefficient of the inverter device.

[0017] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, controlling the power output of the inverter device during parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device during parallel operation according to the following droop formula:

[0018]

[0019] Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, which is a preset value obtained according to the off-grid parallel multi-machine system.

[0020] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the power droop coefficient of the inverter device according to the impedance characteristics of the inverter device includes:

[0021] When the impedance characteristic of the inverter is resistive, the active power droop coefficient of the inverter device is obtained according to the voltage parameter of the inverter device.

[0022] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the active power droop coefficient of the inverter device according to the voltage parameter of the inverter device includes obtaining the active power droop coefficient of the inverter device according to the following formula:

[0023]

[0024] Wherein, m is the active power droop coefficient of the inverter device, E0 is the no-load output voltage target value of the inverter device, and E min is the minimum parallel output voltage target value corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device.

[0025] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, the method further includes:

[0026] The minimum allowable output power of the inverter device corresponding to the lowest parallel output voltage target value is obtained, so as to obtain the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power.

[0027] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel output voltage target value includes: obtaining the minimum allowable output power P according to the following formula min :

[0028]

[0029] Among them, m max is the maximum active power droop coefficient of the inverter device.

[0030] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, controlling the power output of the inverter device during parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device during parallel operation according to the following droop formula:

[0031]

[0032] Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, which is a preset value obtained according to the off-grid parallel multi-machine system.

[0033] Optionally, in an embodiment of the inverter off-grid parallel power distribution control method of the present invention, obtaining the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power includes: obtaining the real-time maximum allowable output power P1 of the inverter device according to the following formula:

[0034]

[0035] The present invention also provides an off-grid parallel multi-machine system, comprising a plurality of inverter devices and a controller; the controller is used to execute the inverter off-grid parallel power distribution control method as described above.

[0036] The off-grid parallel inverter power distribution control method and off-grid parallel multi-machine system of the present invention have the following beneficial effects: they can prevent the parallel inverter equipment battery power feeding caused by the parallel failure phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0038] Figure 1 This is a flowchart of an embodiment of a method for controlling power distribution of an off-grid parallel inverter according to the present invention;

[0039] Figure 2 This is a flowchart of another embodiment of the inverter off-grid parallel power distribution control method of the present invention;

[0040] Figure 3 yes Figure 2 Schematic diagram of the control principle corresponding to the embodiment;

[0041] Figure 4 This is a flowchart of another embodiment of the inverter off-grid parallel power distribution control method of the present invention;

[0042] Figure 5 yes Figure 4 Schematic diagram of the control principle corresponding to the embodiment. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0044] like Figure 1 FIG. 1 shows an embodiment of the inverter off-grid parallel power distribution control method of the present invention. Figure 1In the illustrated embodiment of the present invention, the power distribution control method for off-grid parallel inverters is primarily applied to an off-grid parallel multi-machine system, wherein the off-grid parallel multi-machine system comprises multiple inverter devices, i.e., a system network formed by coupling the AC terminals of the multiple inverter devices. The method achieves the final power output of the parallel multi-machine system by controlling the power output of the inverter devices. The method includes the following steps: S1. Obtaining the impedance characteristics of each inverter device to determine the power droop coefficient of the inverter device based on the impedance characteristics of the inverter device; S2. Controlling the power output of the inverter devices during parallel operation based on the power droop coefficient of the inverter device.

[0045] Specifically, during the grid connection process, the impedance characteristics of the inverter device are evaluated. Inverters with different impedance characteristics will have different impacts on the operation of the parallel system when connected to an off-grid multi-machine parallel system. Therefore, different power droop coefficients need to be set to control the inverter device's output power during parallel operation.

[0046] The impedance characteristics of an inverter are determined by the inverter filter parameters, the inverter loop design, and its parameters. Generally speaking, once the hardware and software loop designs are complete, the impedance characteristics of the inverter, whether they are primarily inductive or resistive, can be determined accordingly.

[0047] In one embodiment, if Figure 2 As shown, obtaining the power droop coefficient of the inverter device based on the impedance characteristics of the inverter device includes: S11, when the impedance characteristics of the inverter device are inductive, obtaining the active power droop coefficient of the inverter device based on the frequency parameters of the inverter device. Specifically, when the impedance characteristics of the inverter device are inductive, the operating frequency of the inverter device has a significant impact on the power output of the inverter device. That is, the active power droop coefficient of the inverter device can be obtained based on the frequency parameters of the inverter device to perform a specific power droop control process.

[0048] Optionally, obtaining the active power droop coefficient of the inverter device according to the frequency parameter of the inverter device includes: obtaining the active power droop coefficient of the inverter device according to the following formula:

[0049]

[0050] Wherein, m is the active power droop coefficient of the inverter device, f0 is the no-load frequency of the inverter device, and f minis the minimum parallel frequency corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device. Specifically, the active power droop coefficient of the inverter device is obtained by the above formula, where f min This parameter is determined by regulatory requirements for the frequency operating range of off-grid, parallel multi-machine systems. It can be considered a known value determined by the system. During specific calculations, it can be pre-set based on system requirements. P1 is determined by the inverter's operating status and is used to limit the inverter's maximum output power at the current moment.

[0051] In one embodiment, the real-time maximum allowable output power of the inverter device can be obtained by the following steps: obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel frequency, so as to obtain the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power. In a specific embodiment, obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel frequency includes: obtaining the minimum allowable output power P according to the following formula min :

[0052]

[0053] Among them, m max is the maximum active power droop coefficient of the inverter device. It can be understood that m max This is the maximum active power droop factor of the inverter. It is determined based on the stability of the inverter's droop control loop and after loop debugging. This parameter is a known parameter that can be set as needed.

[0054] In one embodiment, obtaining the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power includes: obtaining the real-time maximum allowable output power P1 of the inverter device according to the following formula:

[0055]

[0056] That is, when P1 <P min , that is, the maximum power allowed to be output by the inverter at the current moment is less than the minimum power allowed to be output at the minimum frequency point of the inverter. At this time, at the lowest frequency f min You can only choose to output P min To ensure loop stability, because P min I was affected by max Limitation of the maximum droop coefficient.

[0057] At the same time, P1 can also be defined by the following formula:

[0058] P bms =I bms U bat ;

[0059] P1=min(P bms ,P max );

[0060] P bms is the maximum power allowed by the BMS in the inverter equipment, I bms is the maximum current allowed by the BMS, U bat P is the battery voltage of the inverter device. max The maximum power that the inverter can bear is determined by the maximum discharge power P allowed by the BMS. bms and P max The smaller value determines

[0061] In one embodiment, controlling the power output of the inverter device during parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device during parallel operation according to the following droop formula:

[0062]

[0063] Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, where n can be understood as a preset value obtained according to the off-grid parallel multi-machine system. That is, after obtaining the droop formula, power distribution control can be performed on the inverter devices in the off-grid parallel multi-machine system. The final droop control principle diagram is shown as follows: Figure 3 shown.

[0064] Take an off-grid parallel multi-machine system consisting of two inverter devices as an example. The two inverter devices are defined as prototype 1 and prototype 2. The active power droop coefficient of prototype 1 is defined as m. sample1 , define the maximum power that prototype 1 can output at the current moment as P 1_sample1 ;

[0065] in,

[0066] Define the active power droop coefficient of prototype 2 as m sample2 , define the maximum power that prototype 2 can output at the current moment as P 1_sample2 ;

[0067] in,

[0068] Substituting the droop coefficients of prototype 1 and prototype 2 into the droop formula, the droop formula of prototype 1 is obtained as follows:

[0069]

[0070] The droop formula of prototype 2 is obtained as follows:

[0071]

[0072] Because prototype 1 and prototype 2 are off-grid and connected in parallel, that is, the AC output terminals are connected together, the AC voltage and frequency of the two prototypes are equal, that is, f sample1 =f sample2 , where f sample1 is the operating frequency of prototype 1, f sample2 is the operating frequency of prototype 2, E sample1 is the output voltage target value of prototype 1, E sample2 is the output voltage target value of prototype 2, P sample1 is the average active power of prototype 1, P sample2 is the average active power of prototype 2, Q sample1 is the average reactive power of prototype 1, Q sample2 is the average reactive power of prototype 2.

[0073] Then we get m sample1 P sample1 =m sample2 P sample2 ;

[0074] Finally got

[0075] That is, the real-time active power ratio of prototype 1 and prototype 2 = the real-time maximum power ratio allowed to be output by prototype 1 and prototype 2, and the real-time maximum power ratio allowed to be output by prototype 1 and prototype 2 will be controlled by the maximum power ratio allowed to be output by BMS (BMS maximum allowable current). This is linked to the maximum allowable current of BMS to prevent the parallel failure caused by the battery power feeding of the parallel inverter equipment, and can realize the BMS charging and discharging coordinated management strategy of multiple parallel machines, such as allocating power proportion according to the power proportion of each energy storage battery and other flexible power allocation strategies.

[0076] In one embodiment, if Figure 4As shown, obtaining the power droop coefficient of the inverter device based on the impedance characteristics of the inverter device includes: when the impedance characteristics of the inverter device are resistive, obtaining the active power droop coefficient of the inverter device based on the voltage parameters of the inverter device. Specifically, when the impedance characteristics of the inverter device are resistive, the voltage parameters of the inverter device have a significant impact on the power output of the inverter device. That is, the active power droop coefficient of the inverter device can be obtained based on the voltage parameters of the inverter device to perform a specific power droop control process.

[0077] Optionally, acquiring the active power droop coefficient of the inverter device according to the voltage parameter of the inverter device includes: acquiring the active power droop coefficient of the inverter device according to the following formula:

[0078]

[0079] Wherein, m is the active power droop coefficient of the inverter device, E0 is the no-load output voltage target value of the inverter device, and E min is the minimum parallel output voltage target value corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device. Specifically, the active power droop coefficient of the inverter device is obtained by the above formula, where E min This parameter is determined by the voltage operating range regulations for off-grid, parallel multi-machine systems. It can be understood as a known value determined by the system. During specific calculations, it can be pre-set based on system requirements. P1 is determined by the inverter's operating status and is used to limit the inverter's maximum output power at the current moment.

[0080] In one embodiment, obtaining the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power includes: obtaining the real-time maximum allowable output power P1 of the inverter device according to the following formula:

[0081]

[0082] When P1 <P min , that is, the maximum power allowed to be output by the inverter at the current moment is less than the minimum power allowed to be output at the minimum frequency point of the inverter. At this time, at the lowest voltage E min You can only choose to output P min To ensure loop stability, because P min I was affected by max Limitation of the maximum droop coefficient.

[0083] At the same time, P1 can also be defined by the following formula:

[0084] P bms =I bms U bat ;

[0085] P1=min(P bms ,P max );

[0086] P bms is the maximum power allowed by the BMS in the inverter equipment, I bms is the maximum current allowed by the BMS, U bat P is the battery voltage of the inverter device. max The maximum power that the inverter can bear is determined by the maximum discharge power P allowed by the BMS. bms and P max The smaller value of .

[0087] In one embodiment, the real-time maximum allowable output power of the inverter device can be obtained by the following steps: obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel output voltage target value, so as to obtain the real-time maximum allowable output power of the inverter device based on the real-time allowable output power of the inverter device and the minimum allowable output power. Wherein, obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel output voltage target value includes: obtaining the minimum allowable output power P according to the following formula min :

[0088]

[0089] Among them, m max is the maximum active power droop coefficient of the inverter device. It can be understood that m max This is the maximum active power droop factor of the inverter. It is determined based on the stability of the inverter's droop control loop and after loop debugging. This parameter is a known parameter that can be set as needed.

[0090] In one embodiment, controlling the power output of the inverter device during parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device during parallel operation according to the following droop formula:

[0091]

[0092] Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, wherein n can be understood as a preset value obtained according to the off-grid parallel multi-machine system. That is, after obtaining the droop formula, the power distribution control of the inverter device in the off-grid parallel multi-machine system can be performed. The final droop control principle diagram is shown as follows: Figure 5 shown.

[0093] Take an off-grid parallel multi-machine system consisting of two inverter devices as an example. The two inverter devices are defined as prototype 1 and prototype 2. The droop coefficient of prototype 1 is defined as m. sample1 , define the maximum power that prototype 1 can output at the current moment as P 1_sample1 ;

[0094]

[0095] Define the droop coefficient of prototype 2 as m sample2 , define the maximum power that prototype 2 can output at the current moment as P 1_sample2 ;

[0096]

[0097] Substituting the droop coefficients of prototype 1 and prototype 2 into the droop formula, the droop formula of prototype 1 is obtained as follows:

[0098]

[0099] The droop formula of prototype 2 is obtained as follows:

[0100]

[0101] Because prototype 1 and prototype 2 are off-grid and in parallel, that is, the AC output terminals are connected together, the AC voltage and frequency of the two prototypes are equal, that is, E sample1 =E sample2 , where f sample1 is the operating frequency of prototype 1, f sample2 is the operating frequency of prototype 2, E sample1 is the output voltage target value of prototype 1, E sample2 is the output voltage target value of prototype 2, P sample1 is the average active power of prototype 1, P sample2 is the average active power of prototype 2, Q sample1 is the average reactive power of prototype 1, Q sample2 is the average reactive power of prototype 2.

[0102] Then we get msample1 P sample1 =m sample2 P sample2 ;

[0103] Finally got

[0104] That is, the real-time active power ratio of prototype 1 and prototype 2 = the real-time maximum power ratio allowed to be output by prototype 1 and prototype 2, and the real-time maximum power ratio allowed to be output by prototype 1 and prototype 2 will be controlled by the maximum power ratio allowed to be output by BMS (BMS maximum allowable current). This is linked to the maximum allowable current of BMS to prevent the parallel failure caused by the battery power feeding of the parallel inverter unit, and can realize the BMS charging and discharging coordinated management strategy of multiple parallel machines, such as allocating power proportion according to the power proportion of each energy storage battery, and other flexible power allocation strategies.

[0105] Furthermore, the present invention provides an off-grid parallel multi-machine system comprising several inverter devices and a controller; the controller is configured to execute the inverter off-grid parallel power distribution control method described in the above embodiments. Specifically, in an off-grid parallel multi-machine system, the control method is used to distribute power to each inverter device, thereby preventing parallel failures caused by battery power feeding from the parallel inverter devices. This allows for coordinated charge-discharge management strategies for multiple parallel BMSs, such as flexible power distribution strategies such as allocating power based on the power share of each energy storage battery.

[0106] It is understandable that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for controlling power distribution of off-grid and parallel inverters, characterized in that: Applied to an off-grid parallel multi-machine system, wherein the off-grid parallel multi-machine system includes multiple inverter devices, the control method includes the following steps: respectively obtaining impedance characteristics of the inverter devices, so as to obtain a power droop coefficient of the inverter devices according to the impedance characteristics of the inverter devices; The power output of the inverter device during parallel operation is controlled according to the power droop coefficient of the inverter device.

2. The inverter off-grid parallel power distribution control method according to claim 1, characterized in that: The step of obtaining a power droop coefficient of the inverter device according to the impedance characteristics of the inverter device comprises: When the impedance characteristic of the inverter device is inductive, the active power droop coefficient of the inverter device is obtained according to the frequency parameter of the inverter device.

3. The inverter off-grid parallel power distribution control method according to claim 2, characterized in that: The acquiring the active power droop coefficient of the inverter device according to the frequency parameter of the inverter device includes: acquiring the active power droop coefficient of the inverter device according to the following formula: Wherein, m is the active power droop coefficient of the inverter device, f0 is the no-load frequency of the inverter device, and f min is the minimum parallel frequency corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device.

4. The inverter off-grid parallel power distribution control method according to claim 3, characterized in that: The method further comprises: The minimum allowable output power of the inverter device corresponding to the minimum parallel frequency is obtained, so as to obtain the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power.

5. The inverter off-grid parallel power distribution control method according to claim 4, characterized in that: The obtaining of the minimum allowable output power of the inverter device corresponding to the minimum parallel frequency includes: obtaining the minimum allowable output power P according to the following formula min : Among them, m max is the maximum active power droop coefficient of the inverter device.

6. The off-grid parallel inverter power distribution control method according to claim 3, characterized in that: The controlling the power output of the inverter device when the inverters are in parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device when the inverters are in parallel operation according to the following droop formula: Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, which is a preset value obtained according to the off-grid parallel multi-machine system.

7. The inverter off-grid parallel power distribution control method according to claim 1, characterized in that: The step of obtaining a power droop coefficient of the inverter device according to the impedance characteristics of the inverter device comprises: When the impedance characteristic of the inverter is resistive, the active power droop coefficient of the inverter device is obtained according to the voltage parameter of the inverter device.

8. The off-grid parallel inverter power distribution control method according to claim 7, characterized in that: The acquiring the active power droop coefficient of the inverter device according to the voltage parameter of the inverter device includes acquiring the active power droop coefficient of the inverter device according to the following formula: Wherein, m is the active power droop coefficient of the inverter device, E0 is the no-load output voltage target value of the inverter device, and E min is the minimum parallel output voltage target value corresponding to the off-grid parallel multi-machine system, and P1 is the real-time maximum allowable output power of the inverter device.

9. The off-grid parallel inverter power distribution control method according to claim 8, characterized in that: The method further comprises: The minimum allowable output power of the inverter device corresponding to the lowest parallel output voltage target value is obtained, so as to obtain the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power.

10. The inverter off-grid parallel power distribution control method according to claim 9, characterized in that: The step of obtaining the minimum allowable output power of the inverter device corresponding to the minimum parallel output voltage target value includes: obtaining the minimum allowable output power P according to the following formula: min : Among them, m max is the maximum active power droop coefficient of the inverter device.

11. The inverter off-grid parallel power distribution control method according to claim 10, characterized in that: The controlling the power output of the inverter device when the inverters are in parallel operation according to the power droop coefficient of the inverter device includes: controlling the power output of the inverter device when the inverters are in parallel operation according to the following droop formula: Among them, f is the output frequency of the inverter device, E is the output voltage target value of the inverter device, P is the average active power of the inverter device, Q is the average reactive power of the inverter device, and n is the reactive power droop coefficient of the inverter device, which is a preset value obtained according to the off-grid parallel multi-machine system.

12. The inverter off-grid parallel power distribution control method according to claim 5 or 10, characterized in that: The acquiring the real-time maximum allowable output power of the inverter device according to the real-time allowable output power of the inverter device and the minimum allowable output power includes: acquiring the real-time maximum allowable output power P1 of the inverter device according to the following formula:

13. An off-grid parallel multi-machine system, characterized in that: It includes several inverter devices and a controller; the controller is used to execute the inverter off-grid parallel power distribution control method according to any one of claims 1 to 12.

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