Adaptive island micro-grid power control method and device based on virtual complex impedance

Abstract

The application belongs to the technical field of micro-grid inverters, and particularly relates to a self-adaptive island micro-grid power control method and device based on virtual complex impedance. The method comprises the following steps: collecting voltage signals and current signals output by an inverter, transforming the voltage signals and the current signals to obtain d-axis output current components, q-axis output current components, d-axis output voltage components and q-axis output voltage components, and calculating active power and reactive power; performing droop control based on the active power and the reactive power; comparing a reference reactive power with the calculated reactive power, integrating and adjusting an error generated in the comparison to obtain a virtual resistance and a virtual reactance; calculating a virtual compensation voltage in combination with the d-axis output current components and the q-axis output current components; and superimposing the virtual compensation voltage on an output of the droop control to perform voltage-current double closed-loop control. The application can accurately realize power sharing performance, and can ensure power sharing performance even if a load suddenly changes.

Description

Technical Field

[0001] This invention belongs to the field of microgrid inverter technology, specifically relating to an adaptive islanded microgrid power control method and device based on virtual complex impedance. Background Technology

[0002] Currently, microgrids have become an effective way to coordinate distributed generation (DGs) to achieve energy integration and complementarity. Compared with traditional transmission systems, microgrids can operate in both grid-connected and islanded modes. In islanded mode, maintaining accurate power sharing among distributed generation units is the primary task to ensure stable operation, and parallel control technology based on droop control is commonly used. Although parallel control technology is widely used, inaccurate reactive power distribution in the system can occur due to line impedance mismatch.

[0003] like Figures 1-2 As shown, a traditional droop controller can be represented as:

[0004]

[0005] Where i is the index of the i-th inverter; ω i For the output frequency, U i For the output voltage, ω o U is the nominal value of the output frequency. o P is the nominal value of the output voltage. i The active power is calculated using a low-pass filter; Q i The reactive power is calculated using a low-pass filter.

[0006] like Figure 2 As shown, by introducing integration, active power is unaffected by mismatched impedance, enabling precise power sharing. However, there is no integration in the QU control loop (reactive power-voltage control loop). Therefore, the mismatched feed impedance between the inverter and the PCC (Point of Common Coupling) leads to different output voltages, thus reducing reactive power sharing performance. Summary of the Invention

[0007] To overcome the problems in the prior art, this invention proposes an adaptive islanded microgrid power control method and device based on virtual complex impedance.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0009] In a first aspect, the present invention provides an adaptive power control method for islanded microgrids based on virtual complex impedance, comprising the following steps:

[0010] Step 100: Acquire the voltage and current signals output by the inverter, and perform Clarke Transform and Park Transform to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component.

[0011] Step 200: Calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; perform droop control based on the active power and reactive power.

[0012] Step 300: Compare the reference reactive power with the calculated reactive power, integrate the resulting error and adjust it as virtual resistance and virtual reactance; and calculate the virtual compensation voltage by combining the d-axis output current component and the q-axis output current component.

[0013] Step 400: The virtual compensation voltage is superimposed on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, the inverter bridge arm switching transistors are driven to switch on and off to control the inverter output.

[0014] Further, step 200 includes:

[0015] Step 210: Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, calculate the active power and reactive power:

[0016]

[0017] Among them, P i Q represents the active power of the i-th inverter; i ω represents the reactive power of the i-th inverter; c The cutoff frequency of the low-pass filter is represented by s; s represents the complex variable in the Laplace transform; i odi This represents the d-axis output current component of the i-th inverter; i oqi v represents the q-axis output current component of the i-th inverter; odi V represents the d-axis output voltage component of the i-th inverter; oqi This represents the q-axis output voltage component of the i-th inverter;

[0018] Step 220: Perform droop control based on the active power and reactive power:

[0019]

[0020] in, This represents the d-axis component of the reference voltage of the i-th inverter; ω represents the q-axis component of the reference voltage of the i-th inverter; i ω represents the output frequency of the i-th inverter; o Indicates the nominal output frequency of the inverter; V o Indicates the nominal value of the inverter output voltage; m p n q These represent the droop control coefficients.

[0021] Further, step 300 includes:

[0022] Step 310: The reference reactive power Q... ref The error is compared with the calculated reactive power and integrated to form virtual resistance and virtual reactance.

[0023]

[0024] Among them, R vi X represents the virtual resistance of the i-th inverter; vi k represents the virtual reactance of the i-th inverter; r Indicates the integral coefficient of the virtual resistance; k x Indicates the virtual reactance integral coefficient;

[0025] Step 320: Based on virtual resistance R vi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component.

[0026]

[0027] Where, δv di Represents the virtual compensation voltage along the d-axis; δv qi This represents the virtual compensation voltage along the q-axis.

[0028] Further, step 400 includes:

[0029] Step 410: Superimpose the virtual compensation voltage onto the output of the droop control:

[0030]

[0031] d-axis component of reference voltage With d-axis output voltage component v odi The difference is passed through the voltage loop proportional-integral controller, superimposed with the d-axis current feedforward, and the q-axis current coupling component is subtracted to obtain the reference of the d-axis current loop of the i-th inverter.

[0032] q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through the voltage loop proportional-integral controller, and the q-axis current feedforward and d-axis current coupling components are superimposed to obtain the reference of the q-axis current loop of the i-th inverter.

[0033] Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by the current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the output of the d-axis controller of the i-th inverter;

[0034] Reference current q-axis component and q-axis inductor current component i Lqi The difference is passed through the current loop proportional controller and superimposed with the d-axis voltage coupling component to obtain the output of the q-axis controller of the i-th inverter;

[0035] The outputs of the d-axis controller and q-axis controller are modulated by SVPWM (Space Vector Pulse Width Modulation) to drive the inverter bridge arm switching transistors to turn on and off to control the inverter output.

[0036] Secondly, the present invention also provides an adaptive islanded microgrid power control device based on virtual complex impedance, the device comprising: a droop control unit, a virtual compensation unit, a voltage-current dual closed-loop control unit, and a PWM unit;

[0037] The droop control unit is used to acquire the voltage and current signals output by the inverter, and perform Clarke and Park transforms to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and perform droop control based on the active power and reactive power.

[0038] The virtual compensation unit is used to compare the reference reactive power with the calculated reactive power, and to integrate and adjust the resulting error as a virtual resistance and virtual reactance; and to calculate the virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component.

[0039] The voltage-current dual closed-loop control unit is used to superimpose the virtual compensation voltage on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, it drives the inverter bridge arm switching transistor to switch on and off to control the inverter output.

[0040] The PWM unit is used to perform SVPWM modulation on the voltage output by the voltage-current dual closed-loop control unit, and drive the inverter bridge arm switching transistors to switch on and off to control the inverter output.

[0041] Furthermore, the droop control unit includes:

[0042] The three-phase current output from the inverter is collected and transformed into d-axis and q-axis output current components by Clarke and Park.

[0043] The three-phase voltage output from the inverter is collected and transformed into d-axis and q-axis output voltage components by Clarke and Park.

[0044] The inductor current output from the inverter is collected and transformed into d-axis and q-axis inductor current components by Clarke and Park.

[0045] Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, the active power and reactive power are calculated:

[0046]

[0047] Among them, P i Q represents the active power of the i-th inverter; i ω represents the reactive power of the i-th inverter; c The cutoff frequency of the low-pass filter is represented by s; s represents the complex variable in the Laplace transform; i odi This represents the d-axis output current component of the i-th inverter; i oqi v represents the q-axis output current component of the i-th inverter; odi V represents the d-axis output voltage component of the i-th inverter; oqi This represents the q-axis output voltage component of the i-th inverter;

[0048] Droop control is performed based on the aforementioned active and reactive power:

[0049]

[0050] in, This represents the d-axis component of the reference voltage of the i-th inverter; ω represents the q-axis component of the reference voltage of the i-th inverter; i ω represents the output frequency of the i-th inverter; o Indicates the nominal output frequency of the inverter; V o Indicates the nominal value of the inverter output voltage; m p n q These represent the droop control coefficients.

[0051] Furthermore, the virtual compensation unit includes:

[0052] Reference reactive power Q refThe reactive power is compared with that calculated by the droop control unit, and the resulting error is integrated and adjusted as a virtual resistance and virtual reactance.

[0053]

[0054] Among them, R vi X represents the virtual resistance of the i-th inverter; vi k represents the virtual reactance of the i-th inverter; r Indicates the integral coefficient of the virtual resistance; k x Indicates the virtual reactance integral coefficient;

[0055] Based on virtual resistance R vi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component calculated by the droop control unit.

[0056]

[0057] Where, δv di Represents the virtual compensation voltage along the d-axis; δv qi This represents the virtual compensation voltage along the q-axis.

[0058] Furthermore, the voltage-current dual closed-loop control unit includes:

[0059] The virtual compensation voltage calculated by the virtual compensation unit is superimposed on the output of the droop control:

[0060]

[0061] d-axis component of reference voltage With d-axis output voltage component v odi The difference is passed through the voltage loop proportional-integral controller, superimposed with the d-axis current feedforward, and the q-axis current coupling component is subtracted to obtain the reference of the d-axis current loop of the i-th inverter.

[0062] q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through the voltage loop proportional-integral controller, and the q-axis current feedforward and d-axis current coupling components are superimposed to obtain the reference of the q-axis current loop of the i-th inverter.

[0063] Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by the current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the output of the d-axis controller of the i-th inverter;

[0064] Reference current q-axis component and q-axis inductor current component i LqiThe difference is passed through the current loop proportional controller and superimposed with the d-axis voltage coupling component to obtain the output of the q-axis controller of the i-th inverter.

[0065] Compared with the prior art, the present invention has the following technical effects:

[0066] This invention accurately achieves power sharing performance, ensuring power sharing even with sudden load changes. It considers virtual resistance and virtual inductance, eliminating the need for additional line impedance measurements. Integration with a local controller reduces the impact of communication latency; even if communication is interrupted, the controller continues to operate at the latest value of the virtual impedance, thus ensuring accurate power sharing. Attached Figure Description

[0067] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 For a parallel system with two three-phase voltage source inverters (VSI);

[0069] Figure 2 This is a schematic diagram of a traditional droop controller;

[0070] Figure 3 This is a block diagram of the adaptive islanded microgrid power control based on virtual complex impedance according to the present invention;

[0071] Figure 4 This invention relates to an adaptive virtual complex impedance control strategy;

[0072] Figure 5 This invention relates to a voltage-current dual closed-loop controller;

[0073] Figure 6 To illustrate the invention of the control strategy, a comparison chart of the system power performance before and after the invention was added.

[0074] Figure 7 This is a dynamic performance diagram of the control system;

[0075] Figure 8 This is a graph showing the output performance when communication is interrupted. Detailed Implementation

[0076] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, structures, features, and effects of the technical solutions proposed according to the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments. Specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0077] In one embodiment of the present invention, reference is made to... Figures 3-5 An adaptive power control method for islanded microgrids based on virtual complex impedance is provided, comprising the following steps:

[0078] Step 100: Acquire the voltage and current signals output by the inverter, and perform Clarke and Park transformations to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component.

[0079] Step 200: Calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; perform droop control based on the active power and reactive power.

[0080] Step 300: Compare the reference reactive power with the calculated reactive power, integrate the resulting error and adjust it as virtual resistance and virtual reactance; and calculate the virtual compensation voltage by combining the d-axis output current component and the q-axis output current component.

[0081] Step 400: The virtual compensation voltage is superimposed on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, the inverter bridge arm switching transistors are driven to switch on and off to control the inverter output.

[0082] The following is a detailed explanation of each of the above steps:

[0083] Step 100: Acquire the voltage and current signals output by the inverter, and perform Clarke and Park transformations to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component.

[0084] Collect the three-phase current i output from the i-th inverter oai i obi and i oci After Clarke and Park transformations, the d-axis output current component i is obtained. odi and q-axis output current component i oqi ;

[0085] Collect the three-phase voltage v output from the i-th inverter oai v obi and v oci After Clarke and Park transformations, the output voltage component v is converted to the d-axis. odi and q-axis output voltage component v oqi ;

[0086] Collect the inductor current i output from the i-th inverter Lai i Lbi and i Lci After Clarke and Park transformations, the d-axis inductor current component i is obtained. Ldi and q-axis inductor current component i Lqi .

[0087] Step 200: Calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; perform droop control based on the active power and reactive power.

[0088] As an example, step 200 may include:

[0089] Step 210: Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, calculate the active power and reactive power:

[0090]

[0091] Among them, P i Q represents the active power of the i-th inverter; i ω represents the reactive power of the i-th inverter; c The cutoff frequency of the low-pass filter is represented by s; s represents the complex variable in the Laplace transform; i odi This represents the d-axis output current component of the i-th inverter; i oqi v represents the q-axis output current component of the i-th inverter; odi V represents the d-axis output voltage component of the i-th inverter; oqi This represents the q-axis output voltage component of the i-th inverter.

[0092] Step 220: Perform droop control based on the active power and reactive power:

[0093]

[0094] in, This represents the d-axis component of the reference voltage of the i-th inverter; ω represents the q-axis component of the reference voltage of the i-th inverter; i ω represents the output frequency of the i-th inverter;o Indicates the nominal output frequency of the inverter; V o Indicates the nominal value of the inverter output voltage; m p n q These represent the droop control coefficients.

[0095] Step 300: Compare the reference reactive power with the calculated reactive power, integrate and adjust the resulting error as virtual resistance and virtual reactance; and calculate the virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component.

[0096] As an example, step 300 may include:

[0097] Step 310: The reference reactive power Q calculated by the MGCC (Microgrid Central Controller) ref The error is compared with the reactive power of the machine and integrated to adjust the virtual resistance and virtual reactance.

[0098]

[0099] Among them, R vi X represents the virtual resistance of the i-th inverter; vi k represents the virtual reactance of the i-th inverter; r Indicates the integral coefficient of the virtual resistance; k x This represents the virtual reactance integral coefficient. Preferably, k r =0.8e-3,k x =4.86e-3.

[0100] Step 320: Based on virtual resistance R vi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component.

[0101]

[0102] Where, δv di Represents the virtual compensation voltage along the d-axis; δv qi This represents the virtual compensation voltage along the q-axis.

[0103] Step 400: The virtual compensation voltage is superimposed on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, the inverter bridge arm switching transistors are driven to switch on and off to control the inverter output.

[0104] As an example, step 400 may include:

[0105] Step 410: Superimpose the virtual compensation voltage onto the output of the droop control:

[0106]

[0107] d-axis component of reference voltage With d-axis output voltage component v odi The difference is passed through the voltage loop proportional-integral controller, superimposed with the d-axis current feedforward, and the q-axis current coupling component is subtracted to obtain the reference of the d-axis current loop of the i-th inverter.

[0108] q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through the voltage loop proportional-integral controller, and the q-axis current feedforward and d-axis current coupling components are superimposed to obtain the reference for the q-axis current loop of the i-th inverter.

[0109] Step 420: Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by the current loop controller, and the q-axis voltage coupling component is subtracted to obtain the output of the d-axis controller of the i-th inverter. In order to enhance the adjustment speed of the inner loop, the d-axis current inner loop controller can be proportional control.

[0110] Reference current q-axis component and q-axis inductor current component i Lqi The difference is passed through the current loop controller and superimposed with the d-axis voltage coupling component to obtain the output of the q-axis controller of the i-th inverter. In order to enhance the adjustment speed of the inner loop, the q-axis current inner loop controller can be proportional control.

[0111] The outputs of the d and q axis controllers are modulated by SVPWM to drive the inverter bridge arm switching transistors to switch on and off to control the inverter output.

[0112] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0113] Based on the same inventive concept, this application also provides an adaptive islanded microgrid power control device based on virtual complex impedance for implementing the aforementioned adaptive islanded microgrid power control method based on virtual complex impedance. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more system embodiments provided below can be found in the above-described limitations of the adaptive islanded microgrid power control method based on virtual complex impedance, and will not be repeated here.

[0114] In one embodiment, an adaptive islanded microgrid power control device based on virtual complex impedance is provided. The device includes: a droop control unit, a virtual compensation unit, a voltage-current dual closed-loop control unit, and a PWM unit.

[0115] The droop control unit is used to acquire the voltage and current signals output by the inverter, and perform Clarke and Park transformations to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and perform droop control based on the active power and reactive power.

[0116] Specifically, the three-phase current i output from the i-th inverter is collected. oai i obi and i oci After Clarke and Park transformations, the d-axis output current component i is obtained. odi and q-axis output current component i oqi ;

[0117] Collect the three-phase voltage v output from the i-th inverter oai v obi and v oci After Clarke and Park transformations, the output voltage component v is converted to the d-axis. odi and q-axis output voltage component v oqi ;

[0118] Collect the inductor current i output from the i-th inverter Lai i Lbi and i Lci After Clarke and Park transformations, the d-axis inductor current component i is obtained. Ldi and q-axis inductor current component i Lqi .

[0119] Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, the active power and reactive power are calculated:

[0120]

[0121] Among them, P i Q represents the active power of the i-th inverter; i ω represents the reactive power of the i-th inverter; c The cutoff frequency of the low-pass filter is represented by s; s represents the complex variable in the Laplace transform; i odi This represents the d-axis output current component of the i-th inverter; i oqi v represents the q-axis output current component of the i-th inverter; odi V represents the d-axis output voltage component of the i-th inverter; oqi This represents the q-axis output voltage component of the i-th inverter.

[0122] Droop control is performed based on the aforementioned active and reactive power:

[0123]

[0124] in, This represents the d-axis component of the reference voltage of the i-th inverter; ω represents the q-axis component of the reference voltage of the i-th inverter; i ω represents the output frequency of the i-th inverter; o Indicates the nominal output frequency of the inverter; V o Indicates the nominal value of the inverter output voltage; m p n q These represent the droop control coefficients.

[0125] The virtual compensation unit is used to compare the reference reactive power with the calculated reactive power, and to integrate and adjust the resulting error as a virtual resistance and virtual reactance; and to calculate the virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component.

[0126] Specifically, the reference reactive power Q calculated by MGCC ref The reactive power is compared with that calculated by the droop control unit, and the resulting error is integrated and adjusted as virtual resistance and virtual reactance.

[0127]

[0128] Among them, R vi X represents the virtual resistance of the i-th inverter; vi k represents the virtual reactance of the i-th inverter; r Indicates the integral coefficient of the virtual resistance; k x This represents the virtual reactance integral coefficient.

[0129] Based on virtual resistance Rvi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component calculated by the droop control unit.

[0130]

[0131] Where, δv di Represents the virtual compensation voltage along the d-axis; δv qi This represents the virtual compensation voltage along the q-axis.

[0132] The voltage-current dual closed-loop control unit is used to superimpose the virtual compensation voltage onto the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, it drives the inverter bridge arm switching transistors to switch on and off to control the inverter output.

[0133] Specifically, the virtual compensation voltage calculated by the virtual compensation unit is superimposed on the output of the droop control:

[0134]

[0135] d-axis component of reference voltage With d-axis output voltage component v odi The difference is passed through the voltage loop proportional-integral controller, superimposed with the d-axis current feedforward, and the q-axis current coupling component is subtracted to obtain the reference of the d-axis current loop of the i-th inverter.

[0136] q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through the voltage loop proportional-integral controller, and the q-axis current feedforward and d-axis current coupling components are superimposed to obtain the reference for the q-axis current loop of the i-th inverter.

[0137] Step 420: Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by the current loop controller, and the q-axis voltage coupling component is subtracted to obtain the output of the d-axis controller of the i-th inverter. In order to enhance the adjustment speed of the inner loop, the d-axis current inner loop controller can be proportional control.

[0138] Reference current q-axis component and q-axis inductor current component i Lqi The difference is passed through the current loop controller and superimposed with the d-axis voltage coupling component to obtain the output of the q-axis controller of the i-th inverter. In order to enhance the adjustment speed of the inner loop, the q-axis current inner loop controller can be proportional control.

[0139] The PWM unit is used to perform SVPWM modulation on the voltage output by the voltage-current dual closed-loop control unit, and drive the inverter bridge arm switching transistors to switch on and off to control the inverter output.

[0140] The following is a simulation comparison of the power performance of this embodiment with that of a traditional droop controller.

[0141] Simulation 1: Initially, when the microgrid was running using a conventional controller, Figure 6 The results showed accurate active power sharing, but poor reactive power sharing (ΔQerr approximately 12.2%). When the proposed scheme was applied at t=6s, reactive power tended to be evenly distributed, and the reactive power distribution error ΔQerr decreased to 0.18%.

[0142] Simulation 2: To verify dynamic performance, load 1 (75kW, 40kVar) was connected to the microgrid system at t=2 and disconnected from the microgrid at t=2; load 2 (75kW, 40kVar) was connected to the microgrid system at t=4 and disconnected from the microgrid at t=6. This embodiment starts at t=0s, and the simulation waveform is as follows. Figure 7 As shown in the figure. The results show that the power distribution performance is not affected even under load variations. Furthermore, compared with controllers in traditional literature, the proposed scheme exhibits smaller oscillations and smoother transient performance.

[0143] Simulation 3: When communication is interrupted at t=2s, the virtual impedance remains at its last value before the fault due to the integral action of the controller. Based on the previous theoretical analysis, the system still achieves accurate power sharing performance at this time. When the load increases dramatically at t=4, the virtual impedance cannot adaptively adjust to the current load condition. The resulting compensation voltage increases ΔQerr to 1.26%. The reactive power sharing performance is restored only when communication is restored at t=6. Figure 8 As shown.

[0144] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An adaptive islanded microgrid power control method based on virtual complex impedance, characterized in that, Includes the following steps: Step 100: Acquire the voltage and current signals output by the inverter, and perform Clarke and Park transformations to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component. Step 200: Calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component and q-axis output voltage component; Droop control is performed based on the active power and reactive power. Step 300: Compare the reference reactive power with the calculated reactive power, and integrate the resulting error to form virtual resistance and virtual reactance; The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component, including: Step 310: Reference reactive power Q ref The error is compared with the calculated reactive power and integrated to form virtual resistance and virtual reactance. ； in, Indicates the first i Virtual resistor of the inverter; Indicates the first i Taiwan inverter virtual reactance; Indicates the integral coefficient of the virtual resistance; Indicates the virtual reactance integral coefficient; Indicates the first i Reactive power of the inverter; Step 320: Based on virtual resistance R vi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component. ； in, Indicates the virtual compensation voltage along the d-axis; Indicates the virtual compensation voltage along the q-axis; i odi Indicates the first i The d-axis output current component of the inverter; i oqi Indicates the first i The q-axis output current component of the inverter; Step 400: The virtual compensation voltage is superimposed on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, the inverter bridge arm switching transistors are driven to switch on and off to control the inverter output.

2. The adaptive islanded microgrid power control method based on virtual complex impedance according to claim 1, characterized in that, Step 200 includes: Step 210: Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, calculate the active power and reactive power: ； in, Indicates the first i Active power of the inverter; This indicates the cutoff frequency of the low-pass filter; Represent the complex variables in the Laplace transform; v odi Indicates the first i The d-axis output voltage component of the inverter; v oqi Indicates the first i The q-axis output voltage component of the inverter; Step 220: Perform droop control based on the active power and reactive power: ； in, Indicates the first i The d-axis component of the inverter reference voltage; Indicates the first i The q-axis component of the inverter reference voltage; Indicates the first i The inverter's output frequency; This indicates the nominal value of the inverter's output frequency; This indicates the nominal value of the inverter's output voltage; , These represent the droop control coefficients.

3. The adaptive islanded microgrid power control method based on virtual complex impedance according to claim 2, characterized in that, Step 400 includes: Step 410: Superimpose the virtual compensation voltage onto the output of the droop control: ； d-axis component of reference voltage With d-axis output voltage component v odi The difference is processed by a voltage loop proportional-integral controller, superimposed with d-axis current feedforward, and subtracted from the q-axis current coupling component to obtain the first... i Reference for the d-axis current loop of the inverter; q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through a voltage loop proportional-integral controller, and superimposed with the q-axis current feedforward and d-axis current coupling components to obtain the first... i Reference for the q-axis current loop of the inverter; Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by a current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the first... i Output of the inverter's d-axis controller; Reference current q-axis component and q-axis inductor current component i Lqi The difference is passed through a current loop proportional controller, and superimposed with the d-axis voltage coupling component to obtain the first... i Output of the inverter's q-axis controller; The outputs of the d-axis controller and q-axis controller are modulated by SVPWM to drive the inverter bridge arm switching transistors to switch on and off to control the inverter output.

4. An adaptive islanded microgrid power control device based on virtual complex impedance, characterized in that, The device includes: a droop control unit, a virtual compensation unit, a voltage-current dual closed-loop control unit, and a PWM unit; The droop control unit is used to acquire the voltage and current signals output by the inverter, and perform Clarke and Park transforms to obtain the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component; and perform droop control based on the active power and reactive power. The virtual compensation unit is used to compare the reference reactive power with the calculated reactive power, and to integrate and adjust the resulting error as a virtual resistance and virtual reactance; and to calculate the virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component. The virtual compensation unit includes: Reference reactive power Q ref The reactive power is compared with that calculated by the droop control unit, and the resulting error is integrated and adjusted as a virtual resistance and virtual reactance. ； in, Indicates the first i Virtual resistor of the inverter; Indicates the first i Taiwan inverter virtual reactance; Indicates the integral coefficient of the virtual resistance; Indicates the virtual reactance integral coefficient; Indicates the first i Reactive power of the inverter; Based on virtual resistance R vi and virtual reactance X vi The virtual compensation voltage is calculated by combining the d-axis output current component and the q-axis output current component calculated by the droop control unit. ； in, Indicates the virtual compensation voltage along the d-axis; Indicates the virtual compensation voltage along the q-axis; i odi Indicates the first i The d-axis output current component of the inverter; i oqi Indicates the first i The q-axis output current component of the inverter; The voltage-current dual closed-loop control unit is used to superimpose the virtual compensation voltage on the output of the droop control to perform voltage-current dual closed-loop control. After SVPWM modulation, it drives the inverter bridge arm switching transistor to switch on and off to control the inverter output. The PWM unit is used to perform SVPWM modulation on the voltage output by the voltage-current dual closed-loop control unit, and drive the inverter bridge arm switching transistors to switch on and off to control the inverter output.

5. The adaptive islanded microgrid power control device based on virtual complex impedance according to claim 4, characterized in that, The droop control unit includes: The three-phase current output from the inverter is collected and transformed into d-axis and q-axis output current components by Clarke and Park. The three-phase voltage output from the inverter is collected and transformed into d-axis and q-axis output voltage components by Clarke and Park. The inductor current output from the inverter is collected and transformed into d-axis and q-axis inductor current components by Clarke and Park. Based on the d-axis output current component, q-axis output current component, d-axis output voltage component, and q-axis output voltage component, the active power and reactive power are calculated: ； in, Indicates the first i Active power of the inverter; Indicates the first i Reactive power of the inverter; This indicates the cutoff frequency of the low-pass filter; Represent the complex variables in the Laplace transform; v odi Indicates the first i The d-axis output voltage component of the inverter; v oqi Indicates the first i The q-axis output voltage component of the inverter; Droop control is performed based on the aforementioned active and reactive power: ； in, Indicates the first i The d-axis component of the inverter reference voltage; Indicates the first i The q-axis component of the inverter reference voltage; Indicates the first i The inverter's output frequency; This indicates the nominal value of the inverter's output frequency; This indicates the nominal value of the inverter's output voltage; , These represent the droop control coefficients.

6. The adaptive islanded microgrid power control device based on virtual complex impedance according to claim 5, characterized in that, The voltage-current dual closed-loop control unit includes: The virtual compensation voltage calculated by the virtual compensation unit is superimposed on the output of the droop control: ； d-axis component of reference voltage With d-axis output voltage component v odi The difference is processed by a voltage loop proportional-integral controller, superimposed with d-axis current feedforward, and subtracted from the q-axis current coupling component to obtain the first... i Reference for the d-axis current loop of the inverter; q-axis component of reference voltage With q-axis output voltage component v oqi The difference is passed through a voltage loop proportional-integral controller, and superimposed with the q-axis current feedforward and d-axis current coupling components to obtain the first... i Reference for the q-axis current loop of the inverter; Reference current d-axis component and d-axis inductor current component i Ldi The difference is processed by a current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the first... i Output of the inverter's d-axis controller; Reference current q-axis component and q-axis inductor current component i Lqi The difference is passed through a current proportional loop controller, and superimposed with the d-axis voltage coupling component to obtain the first... i Output of the inverter's q-axis controller.

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