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

Abstract

The invention 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 steps of collecting a voltage signal and a current signal output by an inverter, performing conversion to obtain a d-axis output current component, a q-axis output current component, a d-axis output voltage component and a q-axis output voltage component, and calculating active power and reactive power; performing droop control based on the active power and the reactive power; comparing the reference reactive power with the calculated reactive power, performing integral adjustment on the generated error, and taking the error as virtual resistance and virtual reactance; calculating a virtual compensation voltage by combining the d-axis output current component and the q-axis output current component; and superposing the virtual compensation voltage on the output of the droop control, and carrying out voltage-current double closed-loop control. According to the invention, the power sharing performance can be accurately realized, and the power sharing performance can be ensured even if the load suddenly changes.

Description

Technical Field

[0001] The present invention belongs to the technical field of microgrid inverters, and in particular relates to a method and a device for adaptive island microgrid power control based on virtual complex impedance. Background Art

[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 grid-connected mode and island mode. In island mode, maintaining accurate power sharing between distributed generation units is the top priority to ensure stable operation. Currently, parallel control technology based on droop control is usually used. Although parallel control technology has been widely used, the mismatch of line impedance will cause inaccurate system reactive power sharing.

[0003] like Figure 1-Figure 2 As shown, the traditional droop controller can be expressed as:

[0004]

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

[0006] like Figure 2 As shown in the figure, by introducing integration, the active power is not affected by the mismatched impedance, and accurate power sharing can be achieved. However, there is no integration in the QU control loop (reactive power-voltage control loop). Therefore, the unmatched feeder impedance between the inverter and PCC (Point of Common Coupling) will lead to different output voltages, thereby reducing the reactive power sharing performance. Summary of the invention

[0007] In order to overcome the problems in the prior art, the present invention proposes an adaptive island microgrid power control method and device based on virtual complex impedance.

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

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

[0010] Step 100: collecting the voltage signal and the current signal output by the inverter, and performing Clarke transformation (Clarke Transformation) and Park transformation (Park Transformation) to obtain a d-axis output current component, a q-axis output current component, a d-axis output voltage component, and a q-axis output voltage component;

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

[0012] Step 300: Compare the reference reactive power with the calculated reactive power, perform integral adjustment on the generated error, and use it as a virtual resistance and a virtual reactance; and calculate a virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component;

[0013] Step 400: superimposing the virtual compensation voltage on the output of the droop control, performing voltage-current dual closed-loop control, and driving the inverter bridge arm switch tube to turn on and off through SVPWM modulation to control the inverter output.

[0014] Furthermore, the step 200 includes:

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

[0016]

[0017] Among them, P i represents the active power of the i-th inverter; Q i represents the reactive power of the i-th inverter; ω c represents the cutoff frequency of the low-pass filter; s represents the complex variable in the Laplace transform; i odi represents the d-axis output current component of the i-th inverter; i oqi represents the q-axis output current component of the i-th inverter; v odi represents the d-axis output voltage component of the i-th inverter; v oqi 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, represents the d-axis component of the reference voltage of the i-th inverter; represents the q-axis component of the reference voltage of the i-th inverter; ω i represents the output frequency of the i-th inverter; ω o Indicates the nominal value of the inverter output frequency; V o Indicates the nominal value of the inverter output voltage; m p 、n q They represent the droop control coefficients respectively.

[0021] Furthermore, the step 300 includes:

[0022] Step 310: Set the reference reactive power Q ref Compared with the calculated reactive power, the resulting error is integrated and adjusted as virtual resistance and virtual reactance:

[0023]

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

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

[0026]

[0027] Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

[0028] Furthermore, the step 400 includes:

[0029] Step 410: superimposing the virtual compensation voltage on the output of the droop control:

[0030]

[0031] Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter;

[0032] Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components, and the reference of the q-axis current loop of the i-th inverter is obtained;

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

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

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

[0036] In a second aspect, the present invention further provides an adaptive island 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 collect the voltage signal and current signal output by the inverter, and perform Clarke transformation and Park transformation to obtain the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and perform droop control based on the active power and the 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 generated error as a virtual resistance and a 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, and after SVPWM modulation, drive the inverter bridge arm switch tube to turn 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 switch tube to turn on and off to control the inverter output.

[0041] Furthermore, the droop control unit comprises:

[0042] The three-phase current output by the acquisition inverter is transformed into the d-axis output current component and the q-axis output current component through Clarke and Park;

[0043] The three-phase voltage output by the acquisition inverter is transformed into d-axis output voltage component and q-axis output voltage component through Clarke and Park;

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

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

[0046]

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

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

[0049]

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

[0051] Furthermore, the virtual compensation unit includes:

[0052] The reference reactive power Q refCompared with the reactive power calculated by the droop control unit, the resulting error is integrated and regulated as a virtual resistance and virtual reactance:

[0053]

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

[0055] Based on the virtual resistor R vi and virtual reactance X vi , and 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] Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

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

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

[0060]

[0061] Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter;

[0062] Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components, and the reference of the q-axis current loop of the i-th inverter is obtained;

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

[0064] The q-axis component of the reference current and the 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 q-axis controller output of the i-th inverter.

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

[0066] The present invention can accurately achieve power sharing performance, and ensure power sharing performance even if the load changes suddenly. Virtual resistance and virtual inductance are taken into account, and no additional measurement of line impedance is required. Integration into the local controller can reduce the impact of communication delay. Even if communication is interrupted, the controller can operate normally at the last value of virtual impedance, thereby ensuring the accuracy of power sharing. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

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

[0071] Figure 4 The adaptive virtual complex impedance control strategy of the present invention;

[0072] Figure 5 It is a voltage-current dual closed-loop controller of the present invention;

[0073] Figure 6 A comparison chart of system power performance before and after the invention control strategy is added;

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

[0075] Figure 8 This is the output performance diagram when communication is interrupted. DETAILED DESCRIPTION

[0076] In order to further explain the technical means and effects taken by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the technical solutions proposed by the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments. The 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 those commonly understood by technicians in the technical field of the present invention.

[0077] In one embodiment of the present invention, referring to Figure 3-Figure 5 , provides an adaptive island microgrid power control method based on virtual complex impedance, comprising the following steps:

[0078] Step 100: collecting the voltage signal and current signal output by the inverter, and performing Clarke transformation and Park transformation to obtain a d-axis output current component, a q-axis output current component, a d-axis output voltage component, and a q-axis output voltage component;

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

[0080] Step 300: Compare the reference reactive power with the calculated reactive power, perform integral adjustment on the generated error, and use it as a virtual resistance and a virtual reactance; and calculate a virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component;

[0081] Step 400: superimposing the virtual compensation voltage on the output of the droop control, performing voltage-current dual closed-loop control, and driving the inverter bridge arm switch tube to turn on and off through SVPWM modulation to control the inverter output.

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

[0083] Step 100: collecting the voltage signal and current signal output by the inverter, and performing Clarke transformation and Park transformation 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 by the i-th inverter oai 、i obi and i oci After Clarke and Park transformation, it becomes the d-axis output current component i odi and the q-axis output current component i oqi ;

[0085] Collect the three-phase voltage v output by the i-th inverter oai 、v obi and v oci After Clarke and Park transformation, it becomes the d-axis output voltage component v odi and the q-axis output voltage component v oqi ;

[0086] Collect the inductor current i output by the i-th inverter Lai 、i Lbi and i Lci After Clarke and Park transformation, it becomes the d-axis inductor current component i Ldi and the q-axis inductor current component i Lqi .

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

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

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

[0090]

[0091] Among them, P i represents the active power of the i-th inverter; Q i represents the reactive power of the i-th inverter; ω c represents the cutoff frequency of the low-pass filter; s represents the complex variable in the Laplace transform; i odi represents the d-axis output current component of the i-th inverter; i oqi represents the q-axis output current component of the i-th inverter; v odi represents the d-axis output voltage component of the i-th inverter; v oqi 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, represents the d-axis component of the reference voltage of the i-th inverter; represents the q-axis component of the reference voltage of the i-th inverter; ω i represents the output frequency of the i-th inverter; ωo Indicates the nominal value of the inverter output frequency; V o Indicates the nominal value of the inverter output voltage; m p 、n q They represent the droop control coefficients respectively.

[0095] Step 300: Compare the reference reactive power with the calculated reactive power, perform integral adjustment on the generated 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, this 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 and adjusted as virtual resistance and virtual reactance.

[0098]

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

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

[0101]

[0102] Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

[0103] Step 400: superimposing the virtual compensation voltage on the output of the droop control, performing voltage-current dual closed-loop control, and driving the inverter bridge arm switch tube to turn on and off through SVPWM modulation to control the inverter output.

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

[0105] Step 410: superimposing the virtual compensation voltage on the output of the droop control:

[0106]

[0107] Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter;

[0108] Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components to obtain the reference of 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 passed through the current loop controller, and the q-axis voltage coupling component is subtracted to obtain the d-axis controller output of the i-th inverter. In order to enhance the regulation speed of the inner loop, the d-axis current inner loop controller can be proportional control;

[0110] The q-axis component of the reference current and the q-axis inductor current component i Lqi The difference is passed through the current loop controller, and the d-axis voltage coupling component is superimposed to obtain the q-axis controller output of the i-th inverter. In order to enhance the regulation 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 switch tube on and off to control the inverter output.

[0112] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0113] Based on the same inventive concept, the embodiment of the present application also provides an adaptive island microgrid power control device based on virtual complex impedance for implementing the adaptive island microgrid power control method based on virtual complex impedance mentioned above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more system embodiments provided below can refer to the limitations of an adaptive island microgrid power control method based on virtual complex impedance above, and will not be repeated here.

[0114] In one embodiment, a virtual complex impedance-based adaptive island microgrid power control device is provided, the device comprising: 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 collect the voltage signal and current signal output by the inverter, and perform Clarke transformation and Park transformation to obtain the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and perform droop control based on the active power and the reactive power.

[0116] Specifically, the three-phase current i output by the i-th inverter is collected oai 、i obi and i oci After Clarke and Park transformation, it becomes the d-axis output current component i odi and the q-axis output current component i oqi ;

[0117] Collect the three-phase voltage v output by the i-th inverter oai 、v obi and v oci After Clarke and Park transformation, it becomes the d-axis output voltage component v odi and the q-axis output voltage component v oqi ;

[0118] Collect the inductor current i output by the i-th inverter Lai 、i Lbi and i Lci After Clarke and Park transformation, it becomes the d-axis inductor current component i Ldi and the q-axis inductor current component i Lqi .

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

[0120]

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

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

[0123]

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

[0125] The virtual compensation unit is used to compare the reference reactive power with the calculated reactive power, and to integrate and adjust the generated error as a virtual resistance and a 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 is ref The error is compared with the reactive power calculated by the droop control unit and integrated and adjusted as virtual resistance and virtual reactance.

[0127]

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

[0129] Based on the virtual resistor Rvi and virtual reactance X vi , and 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] Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

[0132] 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, and after SVPWM modulation, drive the inverter bridge arm switch tube to turn 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] Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter;

[0136] Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components to obtain the reference of 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 passed through the current loop controller, and the q-axis voltage coupling component is subtracted to obtain the d-axis controller output of the i-th inverter. In order to enhance the regulation speed of the inner loop, the d-axis current inner loop controller can be proportional control;

[0138] The q-axis component of the reference current and the 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 q-axis controller output of the i-th inverter. In order to enhance the regulation 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 switch tube to turn on and off to control the inverter output.

[0140] The following is a simulation comparing the power performance of this embodiment and the traditional droop controller.

[0141] Simulation 1: Initially, the microgrid is running with a traditional controller. Figure 6 It shows that the active power sharing is accurate, while the reactive power sharing performs poorly (ΔQerr is about 12.2%). When the proposed scheme is adopted at t=6s, the reactive power tends to be evenly distributed and the reactive power sharing error ΔQerr drops to 0.18%.

[0142] Simulation 2: To test the dynamic performance, load 1 (75kW, 40kVar) is connected to the microgrid system at t=2 and disconnected from the microgrid at t=2; load 2 (75kW, 40kVar) is connected to the microgrid system at t=4 and disconnected from the microgrid at t=6. This embodiment is started at t=0s, and the simulation waveform is as follows: Figure 7 It is found that the power distribution performance is not affected even under load variations. In addition, the proposed scheme shows smaller oscillations and smoother transient performance compared to the controllers in the conventional literature.

[0143] Simulation 3: When the communication is interrupted at t=2s, due to the integral action of the controller, the virtual impedance remains at the last value before the fault occurs. According to the previous theoretical analysis, the system still achieves accurate power sharing performance at this time. When the load step increases at t=4, the virtual impedance cannot be adaptively adjusted according to the current load condition. The compensation voltage generated at this time increases ΔQerr to 1.26%. It was not until t=6 that the communication was restored and the reactive power sharing performance was restored. Figure 8 shown.

[0144] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An adaptive island microgrid power control method based on virtual complex impedance, characterized in that: The following steps are involved: Step 100: collecting the voltage signal and current signal output by the inverter, and performing Clarke transformation and Park transformation to obtain a d-axis output current component, a q-axis output current component, a d-axis output voltage component, and a q-axis output voltage component; Step 200: Calculate active power and reactive power based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component, and the q-axis output voltage component; Performing droop control based on the active power and the reactive power; Step 300: Compare the reference reactive power with the calculated reactive power, and perform integral adjustment on the generated error to serve as virtual resistance and virtual reactance; and calculating a virtual compensation voltage in combination with the d-axis output current component and the q-axis output current component; Step 400: superimposing the virtual compensation voltage on the output of the droop control, performing voltage-current dual closed-loop control, and driving the inverter bridge arm switch tube to turn on and off through SVPWM modulation to control the inverter output.

2. The method for adaptive island microgrid power control based on virtual complex impedance according to claim 1 is characterized in that: The step 200 comprises: Step 210: Calculate active power and reactive power based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component, and the q-axis output voltage component: Among them, P i represents the active power of the i-th inverter; Q i represents the reactive power of the i-th inverter; ω c represents the cutoff frequency of the low-pass filter; s represents the complex variable in the Laplace transform; i odi represents the d-axis output current component of the i-th inverter; i oqi represents the q-axis output current component of the i-th inverter; v odi represents the d-axis output voltage component of the i-th inverter; v oqi represents the q-axis output voltage component of the i-th inverter; Step 220: Perform droop control based on the active power and reactive power: in, represents the d-axis component of the reference voltage of the i-th inverter; represents the q-axis component of the reference voltage of the i-th inverter; ω i represents the output frequency of the i-th inverter; ω o Indicates the nominal value of the inverter output frequency; V o Indicates the nominal value of the inverter output voltage; m p 、n q They represent the droop control coefficients respectively.

3. The method for adaptive island microgrid power control based on virtual complex impedance according to claim 2 is characterized in that: The step 300 includes: Step 310: Set the reference reactive power Q ref Compared with the calculated reactive power, the resulting error is integrated and adjusted as virtual resistance and virtual reactance: Among them, R vi represents the virtual resistance of the i-th inverter; X vi represents the virtual reactance of the i-th inverter; k r Indicates the virtual resistance integral coefficient; k x represents the virtual reactance integral coefficient; Step 320: Based on the virtual resistance R vi and virtual reactance X vi , and calculate the virtual compensation voltage by combining the d-axis output current component and the q-axis output current component: Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

4. The method for adaptive island microgrid power control based on virtual complex impedance according to claim 3 is characterized in that: The step 400 includes: Step 410: superimposing the virtual compensation voltage on the output of the droop control: Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter; Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components, and the reference of the q-axis current loop of the i-th inverter is obtained; The d-axis component of the reference current and the d-axis inductor current component i Ldi The difference is passed through the current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the d-axis controller output of the i-th inverter; The q-axis component of the reference current and the q-axis inductor current component i Lqi The difference is passed through the current loop proportional controller, and the d-axis voltage coupling component is superimposed to obtain the q-axis controller output of the i-th inverter; The outputs of the d-axis controller and the q-axis controller are modulated by SVPWM to drive the inverter bridge arm switch tube on and off to control the inverter output.

5. An adaptive island microgrid power control device based on virtual complex impedance, characterized in that: The device comprises: 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 collect the voltage signal and current signal output by the inverter, and perform Clarke transformation and Park transformation to obtain the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and calculate the active power and reactive power based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component; and perform droop control based on the active power and the 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 generated error as a virtual resistance and a 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 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, and after SVPWM modulation, drive the inverter bridge arm switch tube to turn 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 switch tube to turn on and off to control the inverter output.

6. The adaptive island microgrid power control device based on virtual complex impedance according to claim 5, characterized in that: The droop control unit comprises: The three-phase current output by the acquisition inverter is transformed into the d-axis output current component and the q-axis output current component through Clarke and Park; The three-phase voltage output by the acquisition inverter is transformed into d-axis output voltage component and q-axis output voltage component through Clarke and Park; The inductor current output by the collected inverter is transformed into the d-axis inductor current component and the q-axis inductor current component by Clarke and Park; Based on the d-axis output current component, the q-axis output current component, the d-axis output voltage component and the q-axis output voltage component, the active power and the reactive power are calculated: Among them, P i represents the active power of the i-th inverter; Q i represents the reactive power of the i-th inverter; ω c represents the cutoff frequency of the low-pass filter; s represents the complex variable in the Laplace transform; i odi represents the d-axis output current component of the i-th inverter; i oqi represents the q-axis output current component of the i-th inverter; v odi represents the d-axis output voltage component of the i-th inverter; v oqi represents the q-axis output voltage component of the i-th inverter; Droop control is performed based on the active power and reactive power: in, represents the d-axis component of the reference voltage of the i-th inverter; represents the q-axis component of the reference voltage of the i-th inverter; ω i represents the output frequency of the i-th inverter; ω o Indicates the nominal value of the inverter output frequency; V o Indicates the nominal value of the inverter output voltage; m p 、n q They represent the droop control coefficients respectively.

7. The adaptive island microgrid power control device based on virtual complex impedance according to claim 6 is characterized in that: The virtual compensation unit comprises: The reference reactive power Q ref Compared with the reactive power calculated by the droop control unit, the resulting error is integrated and regulated as a virtual resistance and virtual reactance: Among them, R vi represents the virtual resistance of the i-th inverter; X vi represents the virtual reactance of the i-th inverter; k r Indicates the virtual resistance integral coefficient; k x represents the virtual reactance integral coefficient; Based on the virtual resistor R vi and virtual reactance X vi , and 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: Among them, δv di Indicates the d-axis virtual compensation voltage; δv qi Represents the q-axis virtual compensation voltage.

8. The adaptive island microgrid power control device based on virtual complex impedance according to claim 7, characterized in that: The voltage-current dual closed-loop control unit comprises: The virtual compensation voltage calculated by the virtual compensation unit is superimposed on the output of the droop control: Reference voltage d-axis component The d-axis output voltage component v odi The difference passes through the voltage loop proportional-integral controller, superimposes the d-axis current feedforward, and subtracts the q-axis current coupling component to obtain the reference of the d-axis current loop of the i-th inverter; Reference voltage q-axis component The q-axis output voltage component v oqi The difference passes through the voltage loop proportional-integral controller, superimposed with the q-axis current feedforward and d-axis current coupling components, and the reference of the q-axis current loop of the i-th inverter is obtained; The d-axis component of the reference current and the d-axis inductor current component i Ldi The difference is passed through the current loop proportional controller, and the q-axis voltage coupling component is subtracted to obtain the d-axis controller output of the i-th inverter; The q-axis component of the reference current and the q-axis inductor current component i Lqi The difference is passed through the current proportional loop controller and superimposed with the d-axis voltage coupling component to obtain the q-axis controller output of the i-th inverter.

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