Inverter grid connection control method, device, equipment and storage medium

Abstract

The present application provides an inverter grid - connection control method, device, equipment and storage medium. The method includes: obtaining the active power and reactive power output by each of multiple inverters in an inverter circuit; obtaining the angular difference between the active power and reactive power and the phase voltage of the inverter output and the grid - connection phase voltage, and the coupling relationship of the inverter output phase voltage, and obtaining a grid - connection inverter droop control equation according to the coupling relationship; obtaining the voltage at the inverter voltage control point, the reactive power and active power output when the inverter is idling on the grid, and then obtaining the reactive power output when the inverter is fully - loaded and connected to the grid; then obtaining the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient and the reconstructed inverter output active power - actual output angular frequency droop coefficient of the inverter according to the above - obtained parameters; and controlling multiple inverters to be connected to the grid according to the reconstructed droop coefficients. The present application realizes reliable grid - connection between inverters through this control method.

Description

Technical Field

[0001] The present application relates to the field of power technology, and particularly relates to an inverter grid-connected control method, device, equipment, and storage medium. Background Art

[0002] The auxiliary power supply system on rail transit is responsible for supplying power to AC and DC electrical equipment on the vehicle. For AC load power supply, the auxiliary power supply system generally consists of a boost DC module and an inverter. The inverter is responsible for converting DC voltage into AC voltage, maintaining the stability of the output AC voltage amplitude and frequency, and thus transmitting energy to the AC load. Rail transit auxiliary inverters are mainly three-phase inverters. Often, a grid-connected power supply mode without interconnection lines is adopted between multiple inverters. Therefore, to ensure the reliability, safety, and stability of grid connection between three-phase four-wire inverters, a virtual impedance is usually added to the control strategy. The virtual impedance will cancel out a part of the inverter output voltage, resulting in the grid-connected AC bus voltage of multiple inverters being lower than the actual set value and unable to achieve reliable grid-connected operation.

[0003] In view of the above problems, in the prior art, a control strategy of changing the slope of the inverter grid-connected droop curve and a secondary voltage regulation control strategy of the inverter grid-connected droop curve are known to achieve grid-connected operation between multiple inverters.

[0004] However, the inventor found that when using the control strategy of changing the slope of the inverter grid-connected droop curve, when the inverter operates dynamically and at high frequencies, it will affect the equal sharing of active power and reactive power of multiple inverters in grid connection. In severe cases, it will lead to the failure of grid connection of multiple inverters; when using the secondary voltage regulation control strategy of the inverter grid-connected droop curve under the diverse and non-linear requirements of rail transit power supply, it is easy to cause dynamic imbalance of multiple inverters, resulting in grid connection failure. Summary of the Invention

[0005] The present application provides an inverter grid-connected control method, device, equipment, and storage medium to solve the problem of grid connection failure of multiple inverters existing in the prior art.

[0006] In a first aspect, the present application provides an inverter grid-connected control method, including:

[0007] Obtain the output apparent power of multiple inverters in the inverter circuit;

[0008] Obtain the active power and reactive power output by each inverter according to the output apparent power;

[0009] According to the virtual resistance and virtual reactance of inverter grid connection in the inverter circuit, obtain the angle difference between the active power and reactive power and the inverter output phase voltage and grid-connected phase voltage, and the coupling relationship of the inverter output phase voltage;

[0010] Obtain the droop control equation of the grid-connected inverter according to the coupling relationship;

[0011] Set the single-phase maximum load power and load power factor of each grid-connected inverter, and obtain the voltage at the voltage control point of the inverter according to the single-phase maximum load power and load power factor;

[0012] Obtain the reactive power and active power output by the inverter when it is no-load and connected to the grid according to the voltage at the voltage control point of the inverter;

[0013] According to the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter, obtain the reactive power output by the inverter when it is fully loaded and connected to the grid;

[0014] According to the droop control equation of the grid-connected inverter, the voltage at the voltage control point of the inverter, the reactive power and active power output by the inverter when it is no-load and connected to the grid, and the reactive power output by the inverter when it is fully loaded and connected to the grid, obtain the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient;

[0015] Obtain the active power of the inverter circuit when the inverter is fully loaded and connected to the grid;

[0016] According to the reactive power and active power output by the inverter when it is no-load and connected to the grid, and the active power of the inverter when it is fully loaded and connected to the grid, obtain the reconstructed inverter output active power - inverter actual output angular frequency droop coefficient;

[0017] Control multiple inverters to be connected to the grid according to the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient and the reconstructed inverter output active power - inverter actual output angular frequency droop coefficient.

[0018] In a possible design, the apparent power output of each inverter of the inverter circuit is obtained, and the calculation formula is as follows:

[0019]

[0020] Where, i = 1, 2, representing different inverter parameter subscripts; S i represents the apparent power output of the inverter; P i represents the active power output of the inverter; Q i represents the reactive power output of the inverter; V i represents the inverter output phase voltage; V PCC represents the AC bus phase voltage; δ is the angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter connected to the grid; j represents the imaginary number; X represents the equivalent reactance of the inverter connected to the grid; Z LCi represents the inverter filter impedance; ZRi represents the inverter line impedance, Z LRi represents the inverter virtual impedance.

[0021] In a possible design, the active power and reactive power output by each inverter are obtained according to the output apparent power, and the calculation formula is as follows:

[0022]

[0023] where i = 1, 2, representing different subscripts of inverter parameters; P i represents the active power output by the inverter; Q i represents the reactive power output by the inverter; V i represents the phase voltage output by the inverter; V PCC represents the phase voltage of the AC bus; δ is the phase angle difference between the phase voltage output by the inverter and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; X represents the equivalent reactance of the inverter grid connection.

[0024] In a possible design, the coupling relationship between the active power and reactive power and the phase angle difference between the phase voltage output by the inverter and the grid-connected phase voltage and the phase voltage output by the inverter is obtained according to the virtual resistance and virtual reactance of the inverter grid connection in the inverter circuit, and the calculation formula is as follows:

[0025]

[0026] where i = 1, 2, representing different subscripts of inverter parameters; P i represents the active power output by the inverter; Q i represents the reactive power output by the inverter; V i represents the phase voltage output by the inverter; V PCC represents the phase voltage of the AC bus; δ is the phase angle difference between the phase voltage output by the inverter and the grid-connected phase voltage; X represents the equivalent reactance of the inverter grid connection.

[0027] In a possible design, the droop control equation of the grid-connected inverter is obtained according to the coupling relationship, and the calculation formula is as follows:

[0028]

[0029] where i = 1, 2, representing different subscripts of inverter parameters; ω i is the actual output angular frequency of the inverter; ω n is the rated angular frequency of the inverter; P i represents the active power output by the inverter; P0 is the rated value of the active power of the inverter system; k Pi is the droop coefficient of the active power output by the inverter - the actual output angular frequency of the inverter; V PCCiis the actual grid-connected phase voltage of the inverter; Q i represents the output reactive power of the inverter; Q0 is the rated value of the reactive power of the inverter system; k Qi is the droop coefficient of the output reactive power - output phase voltage of the inverter.

[0030] In a possible design, the single-phase maximum load power of each grid-connected inverter is set, and the load power factor is used to obtain the voltage at the voltage control point of the inverter according to the single-phase maximum load power and the load power factor. The calculation formula is as follows:

[0031]

[0032] In the formula, i = 1, 2, representing different inverter parameter subscripts; V SIV-i represents the voltage at the voltage control point of the inverter; V PCC represents the AC bus phase voltage; V PCCi is the actual grid-connected phase voltage of the inverter; Z LRi represents the virtual impedance of the inverter; P Load represents the single-phase maximum load power of each grid-connected inverter; cosθ represents the load power factor.

[0033] In a possible design, the reactive power and active power output by the inverter when the inverter is idling and connected to the grid are obtained according to the voltage at the voltage control point of the inverter. The calculation formula is as follows:

[0034]

[0035] In the formula, i = 1, 2, representing different inverter parameter subscripts; Q 0-min represents the reactive power output by the inverter when the inverter is idling and connected to the grid; P 0-min represents the active power output by the inverter when the inverter is idling and connected to the grid; f0 is the rated frequency of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter.

[0036] In a possible design, the reactive power output by the inverter when the inverter is fully loaded and connected to the grid is obtained according to the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter. The calculation formula is as follows:

[0037]

[0038] In the formula, Q 0-max represents the reactive power output by the inverter when the inverter is fully loaded and connected to the grid; f0 is the rated frequency of the inverter; V PCC represents the AC bus phase voltage; P Load represents the single-phase maximum load power of each grid-connected inverter; C represents the output filter capacitor of the inverter; VSIV-i represents the voltage at the inverter voltage control point; Z m represents the virtual impedance and the total equivalent impedance of the load;

[0039] wherein, the virtual impedance and the total equivalent impedance Z m has the following calculation formula:

[0040]

[0041] In the formula, R represents the equivalent resistance of the inverter connected to the grid; L R represents the output filter inductor of the inverter.

[0042] In a possible design, according to the droop control equation of the grid-connected inverter, the voltage at the inverter voltage control point, the reactive power and active power output by the inverter when the grid is unloaded, and the reactive power output by the inverter when the grid is fully loaded, the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient is obtained, and the calculation formula is as follows:

[0043]

[0044] In the formula, k Qi represents the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient; V SIV_max and V SIV_min respectively represent the maximum and minimum values of the AC bus phase voltage V PCC ; Q 0-min represents the reactive power output by the inverter when the grid is unloaded; Q 0-max represents the reactive power output by the inverter when the grid is fully loaded.

[0045] In a possible design, the active power at the time of full-load grid connection of the inverter is obtained according to the inverter circuit, and the calculation formula is as follows:

[0046]

[0047] In the formula, P 0-max represents the active power at the time of full-load grid connection of the inverter; V PCC-min represents the actual required voltage; P Load represents the single-phase maximum load-carrying power of each grid-connected inverter; V PCC represents the AC bus phase voltage.

[0048] In a possible design, according to the reactive power and active power output by the inverter when the grid is unloaded and the active power at the time of full-load grid connection of the inverter, the reconstructed inverter output active power - inverter actual output angular frequency droop coefficient is obtained, and the calculation formula is as follows:

[0049]

[0050] where k Pi represents the active power output of the reconstructed inverter - the droop coefficient of the actual output angular frequency of the inverter; ω max and ω min are respectively the maximum and minimum values of the AC bus phase voltage ω; P 0-min represents the active power output when the inverter is idling and connected to the grid; P 0-max represents the active power when the inverter is fully loaded and connected to the grid; f max and f min are respectively the maximum and minimum values of the rated frequency f0 of the inverter.

[0051] Second, this application provides an inverter grid - connection control device, including:

[0052] The first acquisition module is used to acquire the output apparent power of multiple inverters in the inverter circuit;

[0053] The second acquisition module is used to obtain the active power and reactive power output by each inverter according to the output apparent power;

[0054] The third acquisition module is used to obtain the angular difference between the active power and reactive power and the grid - connected phase voltage of the inverter output phase voltage and the coupling relationship of the inverter output phase voltage according to the virtual resistance and virtual reactance of the inverter grid - connection in the inverter circuit;

[0055] The fourth acquisition module is used to obtain the droop control equation of the grid - connected inverter according to the coupling relationship;

[0056] The fifth acquisition module is used to set the single - phase maximum load - carrying power and load power factor of each grid - connected inverter, and according to the single - phase maximum load - carrying power and load power factor, to obtain the voltage at the voltage control point of the inverter;

[0057] The sixth acquisition module is used to obtain the reactive power and active power output when the inverter is idling and connected to the grid according to the voltage at the voltage control point of the inverter;

[0058] The seventh acquisition module is used to obtain the reactive power output when the inverter is fully loaded and connected to the grid according to the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter;

[0059] The eighth acquisition module is used to obtain the droop coefficient of the reconstructed inverter output reactive power - inverter output phase voltage according to the droop control equation of the grid - connected inverter, the voltage at the voltage control point of the inverter, the reactive power and active power output when the inverter is idling and connected to the grid, and the reactive power output when the inverter is fully loaded and connected to the grid;

[0060] A ninth acquisition module, configured to acquire the active power of the inverter circuit when the inverter is operating at full load and connected to the grid;

[0061] A tenth acquisition module, configured to obtain a reconstructed active power output of the inverter - the actual output angular frequency droop coefficient of the inverter according to the reactive power and active power output by the inverter when it is idling and connected to the grid, and the active power of the inverter when it is operating at full load and connected to the grid;

[0062] A control module, configured to control multiple inverters to be connected to the grid according to the reconstructed reactive power output of the inverter - the output phase voltage droop coefficient of the inverter and the reconstructed active power output of the inverter - the actual output angular frequency droop coefficient of the inverter.

[0063] In a third aspect, the present application provides a computer device, including: at least one processor and a memory;

[0064] The memory stores computer - executable instructions;

[0065] The at least one processor executes the computer - executable instructions stored in the memory, such that the at least one processor executes the operations described in the first aspect and various possible designs of the first aspect as above.

[0066] In a fourth aspect, the present application provides a computer storage medium, in which computer - executable instructions are stored. When a processor executes the computer - executable instructions, the operations described in the first aspect and various possible designs of the first aspect as above are implemented.

[0067] The inverter grid - connection control method, device, equipment, and storage medium provided by the present application obtain a reconstructed reactive power output of the inverter - the output phase voltage droop coefficient of the inverter by obtaining the grid - connection inverter droop control equation of the inverter circuit, the voltage at the voltage control point of the inverter, the reactive power and active power output by the inverter when it is idling and connected to the grid, and the reactive power output by the inverter when it is operating at full load and connected to the grid; obtain a reconstructed active power output of the inverter - the actual output angular frequency droop coefficient of the inverter by obtaining the reactive power and active power output by the inverter when it is idling and connected to the grid and the active power of the inverter when it is operating at full load and connected to the grid; and control multiple inverters to be connected to the grid according to the reconstructed droop coefficients. The reconstructed droop coefficients reduce the slope of the droop control, making the droop curve more approximate to a straight line, keeping the grid - connected AC bus voltage near the rated value of the AC bus voltage, and realizing reliable grid - connection operation between inverters without interconnection wires. Description of the Drawings

[0068] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0069] Figure 1 Schematic diagram of the connection of the inverter circuit provided by the embodiment of the present application;

[0070] Figure 2 Schematic diagram of the parallel equivalent circuit of the inverter circuit provided by the embodiment of the present application;

[0071] Figure 3 Schematic diagram of the flow of the inverter grid-connected control method provided by the embodiment of the present application Figure 1 ;

[0072] Figure 4 Schematic diagram of the original droop curve and the reconstructed droop curve provided by the embodiment of the present application;

[0073] Figure 5 Schematic diagram of the AC bus voltage waveform after adopting the droop curve reconstruction method provided by the embodiment of the present application;

[0074] Figure 6 Schematic diagram of the power equal sharing waveform of two inverters after adopting the droop curve reconstruction method provided by the embodiment of the present application;

[0075] Figure 7 Schematic diagram of the structure of the inverter grid-connected control device provided by the embodiment of the present application;

[0076] Figure 8 Schematic diagram of the hardware structure provided by the embodiment of the present application. Detailed implementation manners

[0077] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0078] The energy systems on rail transit mainly consist of the traction power supply system and the auxiliary power supply system. The auxiliary power supply equipment undertakes the task of supplying power to AC and DC electrical equipment on the vehicle. For the power supply of AC loads, the auxiliary power supply equipment generally consists of a boost DC module and an inverter. The boost DC module undertakes the function of DC voltage conversion, that is, converting the voltage of the DC power supply or the DC bus into the input voltage level matching the inverter and maintaining it constant. The inverter is responsible for converting the DC voltage into an AC voltage, maintaining the stability of the output AC voltage amplitude and frequency, and thus transmitting the energy to the AC load. The auxiliary inverter on rail transit is mainly a three-phase inverter according to its function. Considering the requirement of the output for the 220V phase voltage, the three-phase inverter usually adopts a four-bridge-arm topology. Due to the installation location of the rail transit auxiliary inverter and the requirement of simplification, a grid-connected power supply mode without interconnection wires is often adopted between multiple inverters. Therefore, to ensure the reliability, safety, and stability of the grid connection between three-phase four-wire inverters, a virtual impedance is usually added to the control strategy, which will cause the virtual impedance to cancel part of the inverter output voltage, resulting in the grid-connected AC bus voltage of multiple inverters being lower than the actual set value.

[0079] To address the above problems, some people in the prior art adopt a control strategy of changing the slope of the inverter grid-connected droop curve. The purpose is to change the slope of the droop curve and formulate a slope change curve of the grid-connected droop curve according to the capacity of the grid-connected load of multiple inverters, so as to dynamically adjust the droop curve and ensure that the grid-connected AC bus of multiple inverters is within the set voltage range. However, this technical solution uses a dynamic droop curve for inverter grid connection, which requires a large number of calculations of the droop curve slope by the controller. When the inverter operates dynamically and at high frequency, it will affect the active power and reactive power sharing of multiple inverters during grid connection. In severe cases, it will lead to the failure of multiple inverters to connect to the grid. Some people in the prior art also adopt a secondary voltage regulation control strategy for the inverter grid-connected droop curve. The purpose is to change the characteristics of the inverter grid-connected droop curve, use part of the inverter output voltage cancelled by the virtual impedance as a compensation amount, and use this compensation amount as the superimposed amount of the inverter output voltage control, so as to change the inverter grid-connected droop control curve and keep the grid-connected AC bus voltage of the inverter near the rated value. However, this technical solution changes the characteristics of the inverter grid-connected droop control curve, cancels the slope of the droop control by means of voltage compensation, and basically changes the droop curve into a straight line, always staying near the rated value of the AC bus voltage. However, this method is applicable to the working conditions of linear loads. Under the diverse and non-linear power supply requirements of rail transit, it is easy to cause dynamic imbalance of multiple inverters, resulting in grid connection failure.

[0080] To solve the above technical problems, the embodiments of the present application propose the following technical solutions: By obtaining the grid-connected inverter droop control equation of the inverter circuit, the voltage at the voltage control point of the inverter, the reactive power and active power output when the inverter is connected to the grid without load, and the reactive power output when the inverter is connected to the grid at full load, the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient is obtained; By obtaining the reactive power and active power output when the inverter is connected to the grid without load and the active power when the inverter is connected to the grid at full load, the reconstructed inverter output active power - actual output angular frequency droop coefficient of the inverter is obtained; And multiple inverters are controlled to be connected to the grid according to the reconstructed droop coefficients.

[0081] Figure 1 The following is a schematic diagram of the parallel connection of the inverter circuits provided by the embodiments of the present application. Specifically, Figure 1 The shown schematic diagram of the parallel connection of the inverter circuits is a connection diagram of two sets of three-phase four-leg inverter circuits for rail transit auxiliary without interconnection lines. In Figure 1 the following are defined:

[0082] V1 and V2 are the positive voltage inputs of the inverter circuit;

[0083] N1 and N2 are the negative voltage inputs of the inverter circuit;

[0084] V in1 = V in2 is the input voltage of the inverter circuit;

[0085] FC1 = FC2 are the input support capacitors of the inverter circuit;

[0086] L 11 = L 12 = L 13 = L 14 = L 21 = L 22 = L 23 = L 24 = L are the output filter inductors of the inverter;

[0087] C 11 = C 12 = C 13 = C 21 = C 22 = C 23 = C are the output filter capacitors of the inverter;

[0088] L R11 = L R12 = L R13 = L R21 = L R22 = L R23 = L R is the virtual inductor for inverter reverse grid connection;

[0089] R 11 = R 12 = R 13 = R 21 = R 22 = R 23 = R b is the virtual resistance for the inverter to be connected to the grid;

[0090] U, V, W, and N are the AC busbars of the inverter respectively.

[0091] Figure 2 provided by the embodiment of the present application Figure 1 schematic diagram of the parallel equivalent circuit of the inverter circuit. Define the following in Figure 2 : Z LC1 represents the inverter filter impedance 1, Z R1 represents the inverter line impedance 1, Z LR1 represents the inverter virtual impedance 1. Z LC2 represents the inverter filter impedance 2; Z R2 represents the inverter line impedance 2, Z LR2 represents the inverter virtual impedance 2.

[0092] Figure 3 Schematic diagram of the flow of the inverter grid connection control method provided by the embodiment of the present application Figure 1 , the execution subject of this embodiment can be a server or other computer devices, and no special limitation is made here in this embodiment. As Figure 1 shown, the method includes:

[0093] S101: Obtain the output apparent power (S i ) of multiple inverters in the inverter circuit.

[0094] In this embodiment, the inverter circuit is Figure 1 and Figure 2 the two - group three - phase four - leg inverter circuit without interconnection lines shown in. The output apparent power (S i ) of multiple inverters in this inverter circuit is calculated as follows:

[0095]

[0096] In the formula, i = 1, 2, representing different subscripts of inverter parameters; S i represents the output apparent power of the inverter; P i represents the output active power of the inverter; Q i represents the output reactive power of the inverter; V i represents the output phase voltage of the inverter; V PCCrepresents the phase voltage of the AC bus; δ is the angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; j represents the imaginary number; X represents the equivalent reactance of the inverter grid connection; Z LCi represents the inverter filter impedance; Z Ri represents the inverter line impedance, Z LRi represents the inverter virtual impedance.

[0097] Specifically, the inverter circuit in this embodiment is Figure 1 the two - group three - phase four - leg inverter circuit for rail transit auxiliary without interconnection line shown in Figure 1 The two - group three - phase four - leg inverter circuit for rail transit auxiliary without interconnection line shown in Figure 2 is shown as follows. From Figure 2 it can be known that the apparent power output by inverter 1 is S1 = P1 + jQ1, and the apparent power output by inverter 2 is S2 = P2 + jQ2.

[0098] S102: Obtain the active power (P i ) and reactive power (Q i ) output by each inverter according to the output apparent power (S i ).

[0099] In this embodiment, the calculation formulas for the active power (P i ) and reactive power (Q i ) output by each inverter are as follows:

[0100]

[0101] In the formula, i = 1, 2, representing the subscripts of different inverter parameters; P i represents the output active power of the inverter; Q i represents the output reactive power of the inverter; V i represents the inverter output phase voltage; V PCC represents the phase voltage of the AC bus; δ is the angle difference between the inverter output phase voltage and the grid - connected phase voltage; R represents the equivalent resistance of the inverter grid connection; X represents the equivalent reactance of the inverter grid connection.

[0102] Specifically, by arranging the formula (1) in step S101, formula (2) in this embodiment can be obtained from formula (1).

[0103] S103: According to the equivalent resistance (R) and equivalent reactance (X) of the inverter grid connection in the inverter circuit, obtain the coupling relationship between the active power (P i ) and reactive power (Q i ) and the angle difference (δ) between the inverter output phase voltage and the grid - connected phase voltage and the inverter output phase voltage (V i ).

[0104] In this embodiment, the active power (P i ) and the reactive power (Q i ) and the coupling relationship calculation formula of the phase angle difference (δ) between the inverter output phase voltage and the grid-connected phase voltage and the inverter output phase voltage (V i ) are as follows:

[0105]

[0106] In the formula, i = 1, 2, representing different inverter parameter subscripts; P i represents the output active power of the inverter; Q i represents the output reactive power of the inverter; V i represents the inverter output phase voltage; V PCC represents the AC bus phase voltage; δ is the phase angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; X represents the equivalent reactance of the inverter grid connection.

[0107] Specifically, the formula (2) in step S102 is respectively partially derived with respect to the phase angle difference (δ) of the grid-connected phase voltage and the inverter output phase voltage (V i ). Since the phase angle difference (δ) of the grid-connected phase voltage is very small in practice, sinδ = 0 and cosδ = 1 can be set after partial derivation. Due to the effect of the virtual impedance in the grid connection control, X >> R is satisfied in the line. Therefore, the above-mentioned coupling relationship between the active power (P i ) and the reactive power (Q i ) and the phase angle difference (δ) of the grid-connected phase voltage and the inverter output phase voltage (V i ) can be obtained.

[0108] S104: Obtain the droop control equation of the grid-connected inverter according to the coupling relationship.

[0109] In this embodiment, the calculation formula of the droop control equation of the grid-connected inverter is as follows:

[0110]

[0111] In the formula, i = 1, 2, representing different inverter parameter subscripts; ω i is the actual output angular frequency of the inverter; ω n is the rated angular frequency of the inverter; P i represents the output active power of the inverter; P0 is the rated value of the active power of the inverter system; k Pi is the P-ω droop coefficient; V PCCi is the actual grid-connected phase voltage of the inverter; Q i represents the output reactive power of the inverter; Q0 is the rated value of the reactive power of the inverter system; k Qiis the Q-V droop coefficient.

[0112] Specifically, from Equation (3) in Step S103, it can be obtained that finally, only Δδ is used to control the active power P output by the inverter i , and ΔV is used to control the reactive power Q output by the inverter i . Also, since Δδ = Δωt and ω is the angular frequency, the above grid-connected inverter droop control equation can be obtained.

[0113] S105: Set the single-phase maximum load power (P Load ) and load power factor (cosθ) of each grid-connected inverter. According to the single-phase maximum load power (P Load ) and load power factor (cosθ), the voltage (V SIV-i ) at the voltage control point of the inverter is obtained.

[0114] In this embodiment, the calculation formula for the voltage (V SIV-i ) at the voltage control point of the inverter is as follows:

[0115]

[0116] In the formula, i = 1, 2, representing different subscripts of inverter parameters; V SIV-i represents the voltage at the voltage control point of the inverter; V PCC represents the AC bus phase voltage; V PCCi is the actual grid-connected phase voltage of the inverter; Z LRi represents the virtual impedance of the inverter; P Load represents the single-phase maximum load power of each grid-connected inverter; cosθ represents the load power factor.

[0117] Specifically, combining Figure 1 and Equation (4) in Step S104, it can be known that there is an influence of virtual impedance between the voltage control point of the inverter and the actual grid-connected phase voltage V PCCi . Therefore, the actual grid-connected phase voltage V PCCi cannot meet the requirements of the grid-connected AC bus phase voltage and there is a deviation. To accurately achieve the reliability of multi-inverter grid connection without interconnection wires, the grid-connected inverter droop control equation is reconstructed under the influence of virtual impedance. In the inverter grid-connected circuit, the filter impedance Z LCi and the virtual impedance Z LRi are much larger than the line impedance Z Ri between the inverter and the grid-connected AC bus. Therefore, the influence of line impedance on the system will not be considered in the analysis. Set the single-phase maximum load power of each grid-connected inverter to P Load , and the load power factor to cosθ, then the voltage V Figure 1 at the voltage control point of the inverter in SIV-i can be obtained.

[0118] S106: Obtain the reactive power (Q SIV-i ) and active power (P 0-min ) output by the inverter when it is idling and connected to the grid according to the voltage (V 0-min ) at the voltage control point of the inverter.

[0119] In this embodiment, the reactive power (Q 0-min ) and active power (P 0-min ) (Equation 6) output by the inverter when it is idling and connected to the grid are calculated as follows:

[0120]

[0121] In the formula: i = 1, 2, representing different subscripts of inverter parameters; Q 0-min represents the reactive power output by the inverter when it is idling and connected to the grid; P 0-min represents the active power output by the inverter when it is idling and connected to the grid; f0 is the rated frequency of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter.

[0122] Specifically, when the inverter is idling and connected to the grid, its reactive power is mainly determined by the output filter capacitor C, and the active power is approximately 0. At this time, the reactive power and active power output by the inverter satisfy (Equation 6).

[0123] S107: According to the reactive power (Q 0-min ) and active power (P 0-min ) output by the inverter, the virtual impedance and the total equivalent impedance of the load (Z m ), and the output filter capacitor (C) of the inverter, obtain the reactive power (Q 0-max ) output by the inverter when it is fully loaded and connected to the grid.

[0124] In this embodiment, the reactive power (Q 0-max ) output by the inverter when it is fully loaded and connected to the grid is calculated as follows:

[0125]

[0126] In the formula, Q 0-max represents the reactive power output by the inverter when it is fully loaded and connected to the grid; f0 is the rated frequency of the inverter; V PCC represents the phase voltage of the AC bus; P Load represents the maximum single-phase load power of each grid-connected inverter; C represents the output filter capacitor of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter; Z m represents the virtual impedance and the total equivalent impedance of the load;

[0127] Specifically, when the inverter is operating at full load and connected to the grid, its reactive power is jointly determined by the output filter capacitor C, the virtual impedance, and the load. At this time, the total equivalent impedance Z of the virtual impedance and the load m is calculated by the following formula:

[0128]

[0129] In the formula, R represents the virtual resistance of the inverter connected to the grid; L R represents the output filter inductor of the inverter.

[0130] S108: According to the droop control equation of the grid-connected inverter, at the voltage control point of the inverter (V SIV-i ), the reactive power (Q 0-min ) and active power P 0-min output by the inverter when it is connected to the grid with no load, and the reactive power (Q 0-max ) output by the inverter when it is connected to the grid at full load, the reconstructed reactive power (Q) - droop coefficient (k Qi ) of the inverter output voltage (V) is obtained.

[0131] In this embodiment, the calculation formula of the reconstructed reactive power (Q) - droop coefficient (k Qi ) of the inverter output voltage (V) is as follows:

[0132]

[0133] In the formula: k Qi represents the reconstructed Q-V droop coefficient; V SIV_max , V SIV_min respectively represent the maximum and minimum values of the AC bus phase voltage V PCC ; Q 0-min represents the reactive power output by the inverter when it is connected to the grid with no load; Q 0-max represents the reactive power output by the inverter when it is connected to the grid at full load.

[0134] Specifically, V SIV_max , V SIV_min respectively represent the maximum and minimum values of the AC bus phase voltage V PCC , corresponding to the maximum and minimum values of the voltage at the voltage control point of the inverter obtained by formula (5). The droop curve represented by the reconstructed reactive power (Q) - droop coefficient (k Qi ) of the inverter output voltage (V) is as shown in the right figure of Figure 4 .

[0135] S109: Obtain the active power (P 0-max ) of the inverter circuit when the inverter is connected to the grid at full load.

[0136] In this embodiment, when the inverter is operating at full load and connected to the grid, the formula for the active power (P 0-max ) is as follows:

[0137]

[0138] In the formula, P 0-max represents the active power when the inverter is operating at full load and connected to the grid; V PCC-min represents the actual required voltage; P Load represents the maximum single-phase load power of each grid-connected inverter; V PCC represents the AC bus phase voltage.

[0139] Specifically, when the inverter is operating at full load and connected to the grid, its active power is approximately equal to the active power required by the load. Therefore, the active power when the inverter is operating at full load and connected to the grid as shown in Equation (10) can be obtained.

[0140] S110: Based on the reactive power (Q 0-min ) and active power (P 0-min ) output by the inverter when it is idling and connected to the grid, and the active power (P 0-max ) when the inverter is operating at full load and connected to the grid, obtain the droop coefficient (k Pi ) of the reconstructed active power (P) - the actual output angular frequency (ω) of the inverter.

[0141] In this embodiment, the formula for the droop coefficient (k Pi ) of the reconstructed active power (P) - the actual output angular frequency (ω) of the inverter is as follows:

[0142]

[0143] In the formula, k Pi represents the droop coefficient of the reconstructed P-ω; ω max , ω min are respectively the maximum and minimum values of the AC bus phase voltage ω; P 0-min represents the active power output by the inverter when it is idling and connected to the grid; P 0-max represents the active power when the inverter is operating at full load and connected to the grid; f max , f min are respectively the maximum and minimum values of the rated frequency f0 of the inverter.

[0144] Specifically, by combining Equation (4) in step S104, Equation (6) in step S106, Equation (10) in step S109, and ω = 2πf, the droop coefficient (k Pi ) of the reconstructed active power (P) - the actual output angular frequency (ω) of the inverter can be obtained. The droop curve represented by this droop coefficient is as shown in the left figure in Figure 4 .

[0145] S111: Control multiple inverters to be connected to the grid according to the droop coefficient (k Qi ) of the reactive power (Q) output by the reconstructed inverter - the phase voltage (V) of the inverter output and the droop coefficient (k Pi ) of the active power (P) output by the reconstructed inverter - the actual output angular frequency (ω) of the inverter.

[0146] In this embodiment, Figure 4 is a schematic diagram of the original droop curve and the reconstructed droop curve provided by the embodiment of the present application. Figure 4 The left figure in Pi is the droop coefficient (k Figure 1 and Figure 4 of the active power (P) output by the reconstructed inverter - the actual output angular frequency (ω) of the inverter. The right figure is the droop coefficient of the reactive power (Q) output by the reconstructed inverter - the phase voltage (V) of the inverter output. Combining PCC min . It can be seen that when the output voltage is controlled according to the original droop curve at the voltage control point of the inverter, the virtual impedance will share a part of the output voltage, resulting in the AC bus voltage of the inverter being lower than the actual required voltage V PCC min . By using Figure 4 the droop coefficient (k Qi ) of the reactive power (Q) output by the reconstructed inverter - the phase voltage (V) of the inverter output and the droop coefficient of the active power (P) output by the reconstructed inverter - the actual output angular frequency (ω) of the inverter to control multiple inverters to be connected to the grid, effective grid connection of multiple inverters without interconnection lines can be achieved, and the grid-connected AC bus voltage can also meet the design requirements.

[0147] In summary, the inverter grid connection control method provided by this embodiment obtains the droop control equation of the grid-connected inverter of the inverter circuit, the voltage at the voltage control point of the inverter, the reactive power and active power output when the inverter is unloaded and connected to the grid, and the reactive power output when the inverter is fully loaded and connected to the grid, and obtains the droop coefficient of the reactive power output by the reconstructed inverter - the phase voltage of the inverter output; by obtaining the reactive power and active power output when the inverter is unloaded and connected to the grid and the active power when the inverter is fully loaded and connected to the grid, the droop coefficient of the active power output by the reconstructed inverter - the actual output angular frequency of the inverter is obtained; and multiple inverters are controlled to be connected to the grid according to the reconstructed droop coefficient. The reconstructed droop coefficient reduces the slope of the droop control, making the droop curve closer to a straight line, keeping the grid-connected AC bus voltage near the rated value of the AC bus voltage, and realizing reliable grid connection operation between inverters without interconnection lines.

[0148] According to Figure 1In the embodiments shown below, the specific implementation of this application will be further described in conjunction with the accompanying drawings and simulation examples. The system parameters of the simulation design of the auxiliary two - group three - phase four - leg inverter circuit without interconnection lines are shown in Table 1 below.

[0149] Table 1 Simulation System Parameter Settings

[0150]

[0151] According to the inverter grid - connection control method in Embodiment 1, the droop - curve parameters and controller parameters are designed, and a three - phase four - leg dual - machine grid - connection model is established, where the three - phase four - leg inverter adopts the 3D - SVM control algorithm.

[0152] At this time, when the whole system is running, the waveforms are as Figure 5 and Figure 6 shown. From 0 to 1 s, the two three - phase four - leg inverters are running without load. At this time, the grid - connected AC bus voltage is maintained by the first inverter, and the peak value of the phase voltage is 326.5 V. At 1 s, the second inverter is connected to the grid and runs without load together with the first inverter. At this time, the grid - connected AC bus voltage is borne by the two inverters together, and the peak value of the phase voltage is still 326.5 V. At 2 s, a 120 kVA load is switched on, and the two inverters jointly provide energy for the load. At this time, the peak value of the grid - connected AC bus phase voltage is 312 V. At 4 s, a 240 kVA load is switched on, and the two inverters jointly provide energy for the load. At this time, the peak value of the grid - connected AC bus phase voltage is 295.8 V.

[0153] In summary, for the inverter grid - connection control method provided in this embodiment, after adopting the inverter grid - connection control method in Embodiment 1, the inverter can still be effectively grid - connected, the AC bus voltage has good consistency with the set upper and lower limits, and the two inverters can achieve effective sharing of active power and reactive power.

[0154] Figure 7 This is the structural schematic diagram of the inverter grid - connection control device provided in the embodiments of this application. As Figure 7 shown, the inverter grid - connection control device includes: a first acquisition module 701, a second acquisition module 702, a third acquisition module 703, a fourth acquisition module 704, a fifth acquisition module 705, a sixth acquisition module 706, a seventh acquisition module 707, an eighth acquisition module 708, a ninth acquisition module 709, a tenth acquisition module 710, and a control module 711.

[0155] The first acquisition module 701 is used to acquire the output apparent power of multiple inverters in the inverter circuit.

[0156] The second acquisition module 702 is used to obtain the active power and reactive power output by each inverter according to the output apparent power.

[0157] The third acquisition module 703 is configured to obtain the coupling relationship between the active power and the reactive power and the output phase voltage of the inverter and the grid-connected phase voltage according to the virtual resistance and the virtual reactance of the inverter for grid connection in the inverter circuit.

[0158] The fourth acquisition module 704 is configured to obtain the droop control equation of the grid-connected inverter according to the coupling relationship.

[0159] The fifth acquisition module 705 is configured to set the single-phase maximum load power and the load power factor of each grid-connected inverter, and obtain the voltage at the voltage control point of the inverter according to the single-phase maximum load power and the load power factor.

[0160] The sixth acquisition module 706 is configured to obtain the reactive power and the active power output by the inverter when the inverter is open-circuited according to the voltage at the voltage control point of the inverter.

[0161] The seventh acquisition module 707 is configured to obtain the reactive power output by the inverter when the inverter is fully loaded and grid-connected according to the reactive power and the active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter.

[0162] The eighth acquisition module 708 is configured to obtain the droop coefficient of the reactive power output by the reconstructed inverter - the output phase voltage of the inverter according to the droop control equation of the grid-connected inverter, the voltage at the voltage control point of the inverter, the reactive power and the active power output by the inverter when the inverter is open-circuited, and the reactive power output by the inverter when the inverter is fully loaded and grid-connected.

[0163] The ninth acquisition module 709 is configured to obtain the active power of the inverter circuit when the inverter is fully loaded and grid-connected.

[0164] The tenth acquisition module 710 is configured to obtain the droop coefficient of the active power output by the reconstructed inverter - the actual output angular frequency of the inverter according to the reactive power and the active power output by the inverter when the inverter is open-circuited and the active power of the inverter when the inverter is fully loaded and grid-connected.

[0165] The control module 711 is configured to control multiple inverters to be grid-connected according to the droop coefficient of the reactive power output by the reconstructed inverter - the output phase voltage of the inverter and the droop coefficient of the active power output by the reconstructed inverter - the actual output angular frequency of the inverter.

[0166] In a possible implementation manner, the first acquisition module 701 is configured to obtain the calculation formula for the apparent power output by multiple inverters of the inverter circuit as follows:

[0167]

[0168] In the formula, i = 1, 2, representing different subscripts of inverter parameters; S iRepresents the apparent power of the inverter output; P i Represents the active power of the inverter output; Q i Represents the reactive power of the inverter output; V i Represents the phase voltage of the inverter output; V PCC Represents the phase voltage of the AC bus; δ is the angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the virtual equivalent resistance of the inverter grid connection; j represents the imaginary number; X represents the virtual equivalent reactance of the inverter grid connection; Z LCi Represents the impedance of the inverter filter; Z Ri Represents the line impedance of the inverter, Z LRi Represents the virtual impedance of the inverter.

[0169] In a possible implementation, the second acquisition module 702 is used to obtain the calculation formulas for the active power and reactive power output by each inverter according to the output apparent power as follows:

[0170]

[0171] In the formula, i = 1, 2, representing different inverter parameter subscripts; P i Represents the active power of the inverter output; Q i Represents the reactive power of the inverter output; V i Represents the phase voltage of the inverter output; V PCC Represents the phase voltage of the AC bus; δ is the angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; X represents the equivalent reactance of the inverter grid connection.

[0172] In a possible implementation, the third acquisition module 703 is used to obtain the calculation formulas for the coupling relationship between the active power and reactive power and the angle difference between the inverter output phase voltage and the grid-connected phase voltage and the inverter output phase voltage according to the virtual resistance and virtual reactance of the inverter grid connection in the inverter circuit as follows:

[0173]

[0174] In the formula, i = 1, 2, representing different inverter parameter subscripts; P i Represents the active power of the inverter output; Q i Represents the reactive power of the inverter output; V i Represents the phase voltage of the inverter output; V PCC Represents the phase voltage of the AC bus; δ is the angle difference between the inverter output phase voltage and the grid-connected phase voltage; X represents the equivalent reactance of the inverter grid connection.

[0175] In a possible implementation, the fourth acquisition module 704 is used to obtain the calculation formula for the droop control equation of the grid-connected inverter according to the coupling relationship as follows:

[0176]

[0177] Wherein, i = 1, 2, representing different subscripts of inverter parameters; ω i is the actual output angular frequency of the inverter; ω n is the rated angular frequency of the inverter; P i represents the output active power of the inverter; P0 is the rated value of the active power of the inverter system; k Pi is the droop coefficient of the output active power of the inverter - the actual output angular frequency of the inverter; V PCCi is the actual grid-connected phase voltage of the inverter; Q i represents the output reactive power of the inverter; Q0 is the rated value of the reactive power of the inverter system; k Qi is the droop coefficient of the output reactive power of the inverter - the output phase voltage of the inverter.

[0178] In a possible implementation manner, the fifth acquisition module 705 is configured to set the single-phase maximum load power and the load power factor of each grid-connected inverter, and obtain the following calculation formula for the voltage at the voltage control point of the inverter according to the single-phase maximum load power and the load power factor:

[0179]

[0180] Wherein, i = 1, 2, representing different subscripts of inverter parameters; V SIV-i represents the voltage at the voltage control point of the inverter; V PCC represents the phase voltage of the AC bus; V PCCi is the actual grid-connected phase voltage of the inverter; Z LRi represents the virtual impedance of the inverter; P Load represents the single-phase maximum load power of each grid-connected inverter; cosθ represents the load power factor.

[0181] In a possible implementation manner, the sixth acquisition module 706 is configured to obtain the following calculation formulas for the reactive power and active power output by the inverter when it is connected to the grid without load according to the voltage at the voltage control point of the inverter:

[0182]

[0183] Wherein, i = 1, 2, representing different subscripts of inverter parameters; Q 0-min represents the reactive power output by the inverter when it is connected to the grid without load; P 0-min represents the active power output by the inverter when it is connected to the grid without load; f0 is the rated frequency of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter.

[0184] In a possible implementation, the seventh acquisition module 707 is configured to obtain the calculation formula for the reactive power output by the inverter when it is fully loaded and connected to the grid based on the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter as follows:

[0185]

[0186] In the formula, Q 0-max represents the reactive power output by the inverter when it is fully loaded and connected to the grid; f0 is the rated frequency of the inverter; V PCC represents the phase voltage of the AC bus; P Load represents the maximum single-phase load power of each grid-connected inverter; C represents the output filter capacitor of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter; Z m represents the virtual impedance and the total equivalent impedance of the load;

[0187] Among them, the calculation formula for the virtual impedance and the total equivalent impedance Z m is as follows:

[0188]

[0189] In the formula, R represents the virtual resistance of the inverter for grid connection; L R represents the output filter inductor of the inverter.

[0190] In a possible implementation, the eighth acquisition module 708 is configured to obtain the calculation formula for the reconstructed reactive power output of the inverter - the droop coefficient of the inverter output phase voltage based on the droop control equation of the grid-connected inverter, the voltage at the voltage control point of the inverter, the reactive power and active power output by the inverter when it is unloaded and connected to the grid, and the reactive power output by the inverter when it is fully loaded and connected to the grid as follows:

[0191]

[0192] In the formula, k Qi represents the reconstructed reactive power output of the inverter - the droop coefficient of the inverter output phase voltage; V SIV_max and V SIV_min respectively represent the maximum value and the minimum value of the phase voltage V PCC of the AC bus; Q 0-min represents the reactive power output by the inverter when it is unloaded and connected to the grid; Q 0-max represents the reactive power output by the inverter when it is fully loaded and connected to the grid.

[0193] In a possible implementation, the ninth acquisition module 709 is configured to obtain the calculation formula for the active power of the inverter circuit when the inverter is fully loaded and connected to the grid as follows:

[0194]

[0195] In the formula, P 0-max represents the active power when the inverter is connected to the grid at full load; V PCC-min represents the actual required voltage; P Load represents the maximum single-phase load power of each grid-connected inverter; V PCC represents the phase voltage of the AC bus.

[0196] In a possible implementation, the tenth acquisition module 710 is configured to obtain the calculation formula of the reconstructed active power output by the inverter - the actual output angular frequency droop coefficient of the inverter according to the reactive power and active power output by the inverter when it is connected to the grid without load and the active power when the inverter is connected to the grid at full load, as follows:

[0197]

[0198] In the formula, k Pi represents the reconstructed active power output by the inverter - the actual output angular frequency droop coefficient of the inverter; ω max , ω min are respectively the maximum value and the minimum value of the phase voltage ω of the AC bus; P 0-min represents the active power output by the inverter when it is connected to the grid without load; P 0-max represents the active power when the inverter is connected to the grid at full load; f max , f min are respectively the maximum value and the minimum value of the rated frequency f0 of the inverter.

[0199] The device provided in this embodiment can be used to execute the technical solutions of the above method embodiments. The implementation principles and technical effects are similar, and will not be elaborated here in this embodiment.

[0200] Figure 8 is a schematic hardware structure diagram of the computer device provided in the embodiment of the present application. As Figure 8 shown, the computer device 80 in this embodiment includes: a processor 801 and a memory 802; wherein

[0201] The memory 802 is used to store computer execution instructions;

[0202] The processor 801 is configured to execute the computer execution instructions stored in the memory to implement the respective steps executed by the computer device in the above embodiments. Specifically, reference can be made to the relevant descriptions in the foregoing method embodiments.

[0203] Optionally, the memory 802 can be either independent or integrated with the processor 801.

[0204] When the memory 802 is independently provided, the computer device further includes a bus 803 for connecting the memory 802 and the processor 801.

[0205] An embodiment of the present application further provides a computer storage medium, in which computer-executable instructions are stored. When a processor executes the computer-executable instructions, the inverter grid-connection control method as described above is implemented.

[0206] An embodiment of the present application further provides a computer program product, including a computer program. When the computer program is executed by a processor, the inverter grid-connection control method as described above is implemented. An embodiment of the present application further provides a computer program product, including a computer program. When the computer program is executed by a processor, the inverter grid-connection control method as described above is implemented.

[0207] In several embodiments provided by the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces, and the indirect coupling or communication connection of devices or modules can be in an electrical, mechanical or other form.

[0208] The modules described as separate components may or may not be physically separated. The components displayed as modules may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to implement the solution of this embodiment.

[0209] In addition, in each embodiment of the present application, the functional modules can be integrated in a processing unit, or each module can exist physically alone, or two or more modules can be integrated in one unit. The unit formed by the above modules can be implemented in the form of hardware, or in the form of a hardware plus software functional unit.

[0210] The integrated modules implemented in the form of software functional modules can be stored in a computer-readable storage medium. The above software functional modules are stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute some steps of the methods described in each embodiment of the present application.

[0211] It should be understood that the above-mentioned processor may be a Central Processing Unit (CPU), or it may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the method disclosed in combination with the invention can be directly implemented by a hardware processor, or can be implemented by a combination of hardware and software modules in the processor.

[0212] The memory may include high-speed RAM memory, and may also include non-volatile storage NVM, such as at least one disk memory, and can also be a USB flash drive, a mobile hard disk, a read-only memory, a magnetic disk, or an optical disc, etc.

[0213] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, the bus in the attached drawings of this application is not limited to only one bus or one type of bus.

[0214] The above storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic memory, flash memory, magnetic disk or optical disc. The storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0215] An exemplary storage medium is coupled to the processor, so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an Application Specific Integrated Circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in an electronic device or a master control device.

[0216] Those of ordinary skill in the art will understand that all or part of the steps for implementing the above method embodiments can be completed by hardware related to program instructions. The foregoing program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps including those of the above method embodiments; and the foregoing storage medium includes: various media such as ROM, RAM, magnetic disk, or optical disk that can store program code.

[0217] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A grid-connected control method for an inverter, characterized in that, Including: Obtaining the output apparent power of multiple inverters in the inverter circuit; Obtaining the active power and reactive power output by each inverter according to the output apparent power; According to the virtual grid-connected resistance and virtual grid-connected reactance of the inverter in the inverter circuit, obtaining the angle difference between the active power and reactive power and the grid-connected phase voltage of the inverter output phase voltage and the coupling relationship of the inverter output phase voltage; Obtaining the droop control equation of the grid-connected inverter according to the coupling relationship; Setting the single-phase maximum load power and load power factor of each grid-connected inverter, and obtaining the voltage at the inverter voltage control point according to the single-phase maximum load power and load power factor; Obtaining the reactive power and active power output by the inverter when the inverter is idling and connected to the grid according to the voltage at the inverter voltage control point; According to the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter, obtaining the reactive power output by the inverter when it is fully loaded and connected to the grid; According to the droop control equation of the grid-connected inverter, the voltage at the inverter voltage control point, the reactive power and active power output by the inverter when the inverter is idling and connected to the grid, and the reactive power output by the inverter when it is fully loaded and connected to the grid, obtaining the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient; the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient, the calculation formula is as follows: ； In the formula, represents the droop coefficient of the reactive power output by the reconstructed inverter - the phase voltage of the inverter output; V SIV_max and V SIV_min respectively represent the maximum and minimum values of the phase voltage V PCC of the AC bus; Q 0-min represents the reactive power output by the inverter when the grid is open; Q 0-max represents the reactive power output by the inverter when it is fully loaded and connected to the grid; Obtaining the active power of the inverter circuit when the inverter is fully loaded and connected to the grid; According to the reactive power and active power output by the inverter when the inverter is idling and connected to the grid, and the active power when the inverter is fully loaded and connected to the grid, obtaining the reconstructed inverter output active power - actual output angular frequency droop coefficient of the inverter; the reconstructed inverter output active power - actual output angular frequency droop coefficient of the inverter, the calculation formula is as follows: Wherein, represents the droop coefficient of the active power output by the reconstructed inverter - the actual output angular frequency of the inverter; and are respectively the maximum value and the minimum value of the AC bus phase voltage ; P 0-min represents the active power output by the inverter when it is open-circuited; P 0-max represents the active power of the inverter when it is fully loaded and grid-connected; f max , f min are respectively the maximum value and the minimum value of the rated frequency f0 of the inverter; Controlling multiple inverters to be connected to the grid according to the reconstructed inverter output reactive power - inverter output phase voltage droop coefficient and the reconstructed inverter output active power - actual output angular frequency droop coefficient of the inverter.

2. The method according to claim 1, wherein The calculation formula for obtaining the output apparent power of each inverter in the inverter circuit is as follows: ； Where \(i = 1, 2\), representing different subscripts of inverter parameters; \(S\) i represents the output apparent power of the inverter; P i represents the active power output of the inverter; Q i represents the output reactive power of the inverter; V i represents the inverter output phase voltage; V PCC represents the AC bus phase voltage; is the phase angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; j represents the imaginary number; X represents the equivalent reactance of the inverter grid connection; Z LCi represents the impedance of the inverter filter; Z Ri represents the inverter line impedance, Z LRi represents the inverter virtual impedance.

3. The method according to claim 1, wherein The calculation formula for obtaining the active power and reactive power output by each inverter according to the output apparent power is as follows: ； where \(i = 1, 2\), representing different subscripts of inverter parameters; \(P\) i represents the output active power of the inverter; Q i represents the output reactive power of the inverter; V i represents the inverter output phase voltage; V PCC represents the AC bus phase voltage; is the phase angle difference between the inverter output phase voltage and the grid-connected phase voltage; R represents the equivalent resistance of the inverter grid connection; X represents the equivalent reactance of the inverter grid connection.

4. The method according to claim 1, wherein The calculation formula for obtaining the angle difference between the active power and reactive power and the grid-connected phase voltage of the inverter output phase voltage and the coupling relationship of the inverter output phase voltage according to the virtual grid-connected resistance and virtual grid-connected reactance of the inverter in the inverter circuit is as follows: ； Where \(i = 1, 2\), representing different subscripts of inverter parameters; \(P\) i represents the output active power of the inverter; Q i represents the output reactive power of the inverter; V i represents the inverter output phase voltage; V PCC represents the AC bus phase voltage; is the phase angle difference between the inverter output phase voltage and the grid-connected phase voltage; X represents the equivalent reactance of the inverter grid connection.

5. The method according to claim 1, characterized in that, The calculation formula for obtaining the droop control equation of the grid-connected inverter according to the coupling relationship is as follows: ； Where \(i = 1, 2\), representing the subscripts of different inverter parameters; is the actual output angular frequency of the inverter; is the rated angular frequency of the inverter; \(P\) i represents the output active power of the inverter; \(P_0\) is the rated value of the active power of the inverter system; is the droop coefficient of the output active power - actual output angular frequency of the inverter; \(V\) PCCi is the actual grid-connected phase voltage of the inverter; Q i represents the output reactive power of the inverter; Q0 is the rated reactive power of the inverter system; is the droop coefficient of the output reactive power of the inverter - the output phase voltage of the inverter.

6. The method according to any one of claims 1 to 5, characterized in that The calculation formula for setting the single-phase maximum load power and load power factor of each grid-connected inverter and obtaining the voltage at the inverter voltage control point according to the single-phase maximum load power and load power factor is as follows: ； where \(i = 1, 2\), representing different subscripts of inverter parameters; \(V\) SIV-i represents the voltage at the voltage control point of the inverter; \(V\) PCC represents the phase voltage of the AC bus; \(V\) PCCi is the actual grid-connected phase voltage of the inverter; Z LRi represents the inverter virtual impedance; P Load represents the single-phase maximum load power of each grid-connected inverter; represents the load power factor.

7. The method according to any one of claims 1 to 5, characterized in that The calculation formula for obtaining the reactive power and active power output by the inverter when the inverter is idling and connected to the grid according to the voltage at the inverter voltage control point is as follows: ； where \(i = 1, 2\), representing different subscripts of inverter parameters; \(Q\) 0-min represents the reactive power output by the inverter when it is open-circuited; \(P\) 0-min represents the active power output by the inverter when it is open-circuited; \(f_0\) is the rated frequency of the inverter; \(V\) SIV-i represents the voltage at the voltage control point of the inverter.

8. The method according to any one of claims 1 to 5, characterized in that The reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter are used to obtain the reactive power output when the inverter is fully loaded and connected to the grid. The calculation formula is as follows: ； Where Q 0-max represents the reactive power output when the inverter is connected to the grid at full load; f0 is the rated frequency of the inverter; V PCC represents the phase voltage of the AC bus; P Load represents the maximum single-phase load power of each grid-connected inverter; C represents the output filter capacitor of the inverter; V SIV-i represents the voltage at the voltage control point of the inverter; Z m represents the virtual impedance and the total equivalent impedance of the load; Among them, the virtual impedance and the total equivalent impedance Z of the load m are calculated by the following formula: ； Wherein, R represents the equivalent resistance of the inverter connected to the grid; L R represents the output filter inductor of the inverter.

9. The method according to any one of claims 1 to 5, characterized in that, The active power at the time when the inverter is fully loaded and connected to the grid is obtained according to the inverter circuit. The calculation formula is as follows: ； Wherein, P 0-max represents the active power when the inverter is connected to the grid at full load; V PCC-min represents the actual required voltage; P Load represents the maximum single-phase load power of each grid-connected inverter; V PCC represents the AC bus phase voltage.

10. An inverter grid-connected control device, characterized in that, Including: The first acquisition module is used to acquire the output apparent power of multiple inverters in the inverter circuit; The second acquisition module is used to obtain the active power and reactive power output by each inverter according to the output apparent power; The third acquisition module is used to obtain the phase angle difference between the active power and reactive power and the grid-connected phase voltage of the inverter output and the coupling relationship of the inverter output phase voltage according to the virtual resistance and virtual reactance of the inverter grid connection in the inverter circuit; The fourth acquisition module is used to obtain the droop control equation of the grid-connected inverter according to the coupling relationship; The fifth acquisition module is used to set the single-phase maximum load power and load power factor of each grid-connected inverter, and obtain the voltage at the voltage control point of the inverter according to the single-phase maximum load power and load power factor; The sixth acquisition module is used to obtain the reactive power and active power output by the inverter when it is connected to the grid without load according to the voltage at the voltage control point of the inverter; The seventh acquisition module is used to obtain the reactive power output when the inverter is fully loaded and connected to the grid according to the reactive power and active power output by the inverter, the virtual impedance and the total equivalent impedance of the load, and the output filter capacitor of the inverter; The eighth acquisition module is used to obtain the droop coefficient of the reconstructed inverter output reactive power - inverter output phase voltage according to the droop control equation of the grid-connected inverter, the voltage at the voltage control point of the inverter, the reactive power and active power output by the inverter when it is connected to the grid without load, and the reactive power output by the inverter when it is fully loaded and connected to the grid. The calculation formula of the droop coefficient of the reconstructed inverter output reactive power - inverter output phase voltage is as follows: ； In the formula, represents the droop coefficient of the reactive power output by the reconstructed inverter - the phase voltage of the inverter output; V SIV_max and V SIV_min respectively represent the maximum and minimum values of the phase voltage V PCC of the AC bus; Q 0-min represents the reactive power output by the inverter when the grid is empty; Q 0-max represents the reactive power output by the inverter when it is fully loaded and connected to the grid; The ninth acquisition module is used to acquire the active power of the inverter circuit when the inverter is fully loaded and connected to the grid; The tenth acquisition module is used to obtain the droop coefficient of the reconstructed inverter output active power - actual output angular frequency of the inverter according to the reactive power and active power output by the inverter when it is connected to the grid without load and the active power of the inverter when it is fully loaded and connected to the grid. The calculation formula of the droop coefficient of the reconstructed inverter output active power - actual output angular frequency of the inverter is as follows: Wherein, represents the active power droop coefficient of the reconstructed inverter output - the actual output angular frequency of the inverter; and are respectively the maximum and minimum values of the AC bus phase voltage ; P 0-min represents the active power output by the inverter when it is idling and connected to the grid; P 0-max represents the active power of the inverter when it is fully loaded and connected to the grid; f max and f min are respectively the maximum and minimum values of the rated frequency f0 of the inverter; The control module is used to control multiple inverters to be connected to the grid according to the droop coefficient of the reconstructed inverter output reactive power - inverter output phase voltage and the droop coefficient of the reconstructed inverter output active power - actual output angular frequency of the inverter.

11. A computer device, characterized in that, Including: A processor and a memory; The memory stores computer execution instructions; The processor executes the computer execution instructions stored in the memory, so that the processor executes the inverter grid connection control method according to any one of claims 1 to 9.

12. A computer storage medium, characterized in that, The computer storage medium stores computer execution instructions, and when the processor executes the computer execution instructions, the inverter grid connection control method according to any one of claims 1 to 9 is realized.

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