A virtual impedance stabilizing control method, system, device and storage medium

Abstract

The application discloses a kind of virtual impedance stabilizing control method, system, equipment and storage medium, bus voltage reference value is multiplied with bus current and divided power difference, then the result is squared operation, obtain compensation factor;Adaptive virtual impedance is calculated, given voltage compensation is obtained;After inductance current reference value is subtracted inductance current value, duty cycle is obtained through current closed loop.The application promotes good interaction of photovoltaic unit and load unit through power calculation link, by introducing self-adaptive compensation factor, virtual impedance can follow load power change, system stable operation can be maintained under various working conditions, to ensure that bus voltage will not appear larger drop, basically can be maintained at given voltage level;The stable control method is conducive to the stability of microgrid in the whole system under the operating condition of multiple working conditions, and will not produce larger bus voltage drop, realize the good interaction of each unit of system.

Description

Technical Field

[0001] This invention belongs to the field of microgrid technology, specifically relating to a virtual impedance stabilization control method, system, device, and storage medium. Background Technology

[0002] Impedance mismatch between converters in a DC microgrid can easily lead to system oscillation and instability, causing significant fluctuations in the DC bus voltage and a sharp decline in power quality.

[0003] To improve the stability of DC microgrids and reduce bus voltage fluctuations, it is crucial to adopt necessary stability control strategies. Most researchers choose active damping control, which adds a virtual impedance to the system control loop to improve the system's phase margin and steady-state performance.

[0004] Existing active damping stability control strategies include: control methods based on virtual RC parallel impedance to compensate for the slow dynamic response of series microgrids and provide dynamic stability in the microgrid; introducing virtual positive resistance to offset the negative incremental resistance of constant power loads; and active damping control strategies using bidirectional DC-DC converter feedback DC current to improve system stability margin. These methods all improve system stability to some extent, but the bus voltage experiences a certain degree of sag. Furthermore, under conditions of significant load power variation, because the virtual impedance remains constant, it cannot effectively adapt to changes in load power, potentially leading to large fluctuations in bus voltage and reduced power quality under certain load conditions.

[0005] Patent publication number CN113224791A, entitled "A Method for Active Damping Control of Virtual Impedance in Grid-Connected Inverters," discloses a method for active damping control of virtual impedance in grid-connected inverters, comprising the following steps: acquiring the hardware parameters of a filter; the grid-side equivalent inductance Lg includes the grid-side filter inductance Lg1 in the hardware topology and the equivalent inductance Lg2 during inverter operation, wherein the value of the equivalent inductance Lg2 during inverter operation is between the maximum and minimum allowable equivalent inductance value of the multi-unit parallel grid-connected inverter (0mH); calculating the resonant frequency fres of the filter based on L1, Cf, and Lg; constructing a virtual damping resistor Rdamp; calculating the virtual capacitor Cdamp based on fres, and obtaining a virtual equivalent RC series branch, wherein the virtual equivalent RC series branch is connected in parallel to the inverter filter capacitor Cf; and combining the three-phase three-level photovoltaic grid-connected inverter control algorithm, superimposing the active damping equivalent transfer function into the control loop to achieve active damping control of virtual impedance in the grid-connected inverter. Although the patent application can achieve active damping, the virtual impedance cannot adapt to changes in load power, resulting in large fluctuations in bus voltage under certain load conditions. Summary of the Invention

[0006] In order to overcome the problems existing in the prior art, the present invention aims to provide a virtual impedance stabilization control method, system, device and storage medium. This control method is beneficial to maintaining the overall stability of the microgrid under multiple operating conditions, and will not produce a large bus voltage drop, which is conducive to good interaction between the various units of the system.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A virtual impedance stabilization control method includes the following steps:

[0009] S1: Transfer the load power P load With the output power P of the photovoltaic unit pv Subtracting the values ​​yields the power difference ΔP; the bus voltage reference value U is then used. ref With bus current i dc Multiply and divide by ΔP, then square the result to obtain the compensation factor ε;

[0010] S2: Perform low-pass filtering on the virtual inductive reactance to obtain the virtual impedance Z. v Multiplying this by the compensation factor ε yields the adaptive virtual impedance Z. va ;

[0011] S3: Convert the bus current i dc Multiply by the adaptive virtual impedance Z va The given voltage compensation is obtained; the voltage reference value U is... ref Subtract the compensation for the given voltage and subtract the bus voltage value u. dc The voltage deviation value Δu is obtained; the obtained voltage deviation value Δu is then processed by a traditional voltage closed-loop PI converter. U Obtain the inductor current reference value i Lref The inductor current reference value i Lref Subtract the inductor current value i L Afterwards, it passes through the current closed-loop PI I Obtain the duty cycle d;

[0012] S4: PWM modulation is applied to the duty cycle d signal to generate a control signal, and the control signal is used to control the switching transistors of the energy storage converter to turn on and off.

[0013] Optionally, before step S1, the load power P is collected. load Photovoltaic unit output power P pv Bus voltage reference value U ref Bus current i dc and bus voltage value u dc The data.

[0014] Optionally, in step S1, the formula for calculating the compensation factor ε is:

[0015]

[0016] Where ε is the compensation factor, U ref P is the reference value for bus voltage. load For load power, P pv i represents the output power of the photovoltaic unit. dc This represents the bus current.

[0017] Optionally, in step S2, the virtual impedance includes the virtual resistance R. droop And virtual sense resistance L droop s, giving virtual sense resistance L droop Multiplying s by the low-pass filter transfer function yields the virtual inductive reactance X. droop Virtual resistance R droop Subtract virtual sense resistance X droop Obtain the virtual impedance Z v .

[0018] Optionally, the low-pass filter transfer function is:

[0019] Where ω0 is the cutoff frequency of the low-pass filter, and s is a complex frequency domain variable.

[0020] Optionally, in step S3, the formula for calculating the voltage deviation value Δu is as follows:

[0021] Δu=(U ref -i dc Z va )-u dc

[0022] Among them, U ref i is the reference value for bus voltage. dc Z is the bus current. va For adaptive virtual impedance, u dc This is the bus voltage value.

[0023] A virtual impedance stabilization control device, comprising:

[0024] The power calculation module is used to calculate the load power P. load With the output power P of the photovoltaic unit pv Subtracting the values ​​yields the power difference ΔP; the bus voltage reference value U is then used. ref With bus current i dc Multiply and divide by ΔP, then square the result to obtain the compensation factor ε;

[0025] The virtual impedance calculation module is used to perform low-pass filtering on the virtual inductive reactance to obtain the virtual impedance Z. v Multiplying this by the compensation factor ε yields the adaptive virtual impedance Z.va ;

[0026] The compensation voltage and duty cycle calculation module is used to calculate the bus current i. dc Multiply by the adaptive virtual impedance Z va The given voltage compensation is obtained; the voltage reference value U is... ref Subtract the compensation for the given voltage and subtract the bus voltage value u. dc The voltage deviation value Δu is obtained; the obtained voltage deviation value Δu is then processed by a traditional voltage closed-loop PI converter. U Obtain the inductor current reference value i Lref The inductor current reference value i Lref Subtract the inductor current value i L Afterwards, it passes through the current closed-loop PI I Obtain the duty cycle d;

[0027] The PWM modulation module is used to perform PWM modulation on the duty cycle d signal to generate a control signal, and use the control signal to control the switching transistors of the energy storage converter to turn on and off.

[0028] A virtual impedance stabilization control system includes: a photovoltaic system, a battery, a load, and a DC-DC converter; the DC-DC converter includes a photovoltaic DC-DC converter, an energy storage DC-DC converter, and a load DC-DC converter; the photovoltaic system is connected to a DC bus through the photovoltaic DC-DC converter, the battery is connected to the DC bus through the energy storage DC-DC converter, and the load is connected to the DC bus through the load DC-DC converter; wherein the energy storage DC-DC converter is controlled using the virtual impedance stabilization control method.

[0029] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the virtual impedance stabilization control method.

[0030] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the virtual impedance stabilization control method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention discloses a virtual impedance stabilization control method, system, device, and storage medium. Through power calculation, it promotes good interaction between photovoltaic units and load units. By introducing an adaptively adjustable compensation factor, it enables the virtual impedance to follow changes in load power, maintaining stable system operation under various operating conditions and ensuring that the bus voltage does not experience significant drops, essentially maintaining a given voltage level. In summary, this stabilization control method is beneficial for microgrids to maintain overall system stability under multiple operating conditions without causing significant bus voltage drops, achieving good interaction among system units. Attached Figure Description

[0033] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0034] In the attached diagram:

[0035] Figure 1 A control block diagram is provided for the stable control method of this invention.

[0036] Figure 2 A flowchart of a stable control method for this invention.

[0037] Figure 3 This is a structural diagram of the DC microgrid system used in this invention.

[0038] Among them, 1-power calculation module, 2-virtual impedance calculation module, 3-compensation voltage and duty cycle calculation module, and 4-PWM modulation module. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0040] 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. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. This application can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0043] The present invention will now be described in detail with reference to the accompanying drawings.

[0044] See Figure 1 The present invention provides a virtual impedance stabilization control method, comprising the following steps:

[0045] Power calculation stage: The input is the given bus voltage reference value U. ref By collecting load power P load and the output power P of the photovoltaic unit pv The power difference ΔP is obtained by performing a difference operation, i.e.

[0046] ΔP=P load -P pv

[0047] Then, using the given bus voltage reference value U ref Divide by the power difference ΔP, i.e., U ref / ΔP; Collect bus current i dc Using bus current i dc Multiply by U ref / ΔP yields U ref i dc / ΔP; then squaring it yields the compensation factor ε, i.e.

[0048]

[0049] The compensation factor ε is the output of the power calculation stage;

[0050] Virtual impedance stage: The input to this stage is the compensation factor ε; the virtual impedance is determined by the virtual resistance R.droop And virtual sense resistance L droop The virtual inductive reactance (L) is composed of s. To suppress high-frequency noise, it needs to be low-pass filtered, and the virtual inductive reactance L needs to be given a low-pass filter. droop s multiplied by the low-pass filter transfer function Its function is to filter out high-frequency noise and improve control performance, i.e., virtual X-ray resistance. droop for

[0051]

[0052] In the formula, ω0 is the cutoff frequency of the low-pass filter;

[0053] Thus, the virtual impedance Z is obtained. v for

[0054] Z v =R droop -X droop

[0055] The obtained virtual impedance Z v Multiplying this by the output ε of the power calculation stage yields the adaptive virtual impedance Z. va for

[0056] Z va =εZ v

[0057] Adaptive virtual impedance Z va This is the output quantity of the virtual impedance element;

[0058] Compensation voltage calculation and dual closed-loop control: The input is the adaptive virtual impedance Z. va ; through the collected bus current i dc Multiply by the adaptive virtual impedance Z va As compensation for a given voltage, the voltage reference value U is then used. ref and the collected bus voltage value u dc Calculations are performed to obtain the voltage deviation value Δu, i.e.

[0059] Δu=(U ref -i dc Z va )-u dc

[0060] The obtained voltage deviation value Δu is processed by a traditional voltage closed-loop PI converter. U Obtain the inductor current reference value i Lref It minus the inductor current value i L Afterwards, it passes through the current closed-loop PI I The duty cycle d is obtained, and the duty cycle d is the output of the double closed-loop control loop;

[0061] PWM modulation: The input is the duty cycle d. The control signal is generated by PWM modulation of the duty cycle d signal to control the switching of the energy storage converter transistor.

[0062] See Figure 2 A flowchart of a virtual impedance stabilization control method, including the following steps:

[0063] Step 1: Signal Acquisition: Use voltage and current sensors to acquire the required load output voltage and current, photovoltaic cell output voltage and current, bus voltage, bus current, and energy storage DC-DC converter inductor current; calculate the load output power and photovoltaic cell output power.

[0064] Step 2: Power Calculation: Through power calculation, a compensation factor that can adaptively change with power is introduced, thereby realizing the virtual impedance adaptively changing with power.

[0065] Step 3: Virtual impedance control: Multiply the compensation factor calculated in the above formula with the fixed virtual impedance, and the resulting virtual impedance can be adaptively changed.

[0066] Step 4: Voltage Calculation: Multiply the obtained adaptive virtual impedance by the bus current to obtain a simulated voltage value. Then, introduce the simulated voltage value before the voltage loop and compare it with the voltage loop reference value U. ref Subtract the actual voltage value U after calculating the difference. dc The deviation value Δu is obtained.

[0067] Step 5: Obtain the duty cycle signal through voltage and current dual closed-loop control, obtain the control signal through PWM modulation, and send it to the energy storage DC-DC converter to control the energy storage DC-DC converter.

[0068] See Figure 3 A virtual impedance stabilization control method is applied to Figure 3 The system shown includes a photovoltaic unit consisting of a photovoltaic cell and a DC-DC converter, an energy storage unit consisting of a battery and a DC-DC converter, a load unit consisting of a load and a DC-DC converter, and a DC bus. The photovoltaic cells are connected to the DC bus via a photovoltaic DC-DC converter, the battery is connected to the DC bus via an energy storage DC-DC converter, and the load is connected to the DC bus via a load DC-DC converter.

[0069] This invention is used to control a DC-DC converter for energy storage connected to a battery, enabling the microgrid to maintain overall system stability under multiple operating conditions without causing a large bus voltage drop.

[0070] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0071] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0072] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0073] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0074] Unless otherwise specified, the working methods or control methods involved in the above embodiments are conventional working methods or control methods in the art.

[0075] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A virtual impedance stabilization control method, characterized in that, Includes the following steps: S1: Load power P load With photovoltaic unit output power P pv Subtraction yields the power difference ΔP; bus voltage reference value U ref With bus current i dc Multiplication and division ΔP Then, square the result to obtain the compensation factor. ; S2: Perform low-pass filtering on the virtual inductive reactance to obtain the virtual impedance. Z v Multiply by the compensation factor To obtain the adaptive virtual impedance Z va ; S3: Bus current i dc Multiply by adaptive virtual impedance Z va To obtain the given voltage compensation; the voltage reference value is then used. U ref Subtract the compensation for the given voltage and subtract the bus voltage value. u dc Obtain voltage deviation value Δu The obtained voltage deviation value Δu After traditional voltage closed loop PI U Obtain the inductor current reference value i Lref The inductor current reference value i Lref Subtract the inductor current value i L Then, through the current closed loop PI I Get the duty cycle d ; S4: PWM modulation of the duty cycle d signal generates a control signal, and the control signal is used to control the switching transistors of the energy storage converter to turn on and off. In step S2, the virtual impedance includes the virtual resistance. R droop and virtual sensory resistance L droop s, to give virtual resistance L droop Multiplying s by the low-pass filter transfer function yields the virtual inductive reactance. X droop Virtual resistance R droop Subtract virtual sensory resistance X droop Obtain virtual impedance Z v ; The low-pass filter transfer function is: in, is the cutoff frequency of the low-pass filter, and s is a complex frequency domain variable.

2. The virtual impedance stabilization control method according to claim 1, characterized in that, Before step S1, collect the load power. P load Photovoltaic unit output power P pv 、 Bus voltage reference value U ref 、 bus current i dc and bus voltage value u dc The data.

3. The virtual impedance stabilization control method according to claim 1, characterized in that, In step S1, the compensation factor The calculation formula is: in, As a compensation factor, U ref This is the reference value for bus voltage. P load For load power, P pv For the output power of the photovoltaic unit, i dc This represents the bus current.

4. The virtual impedance stabilization control method according to claim 1, characterized in that, In step S3, the voltage deviation value Δu The calculation formula is in, U ref This is the reference value for bus voltage. i dc Bus current, Z va For adaptive virtual impedance, u dc This is the bus voltage value.

5. A virtual impedance stabilization control device, characterized in that, include: The power calculation module (1) is used to calculate the load power. P load With photovoltaic unit output power P pv Subtraction yields the power difference ΔP; bus voltage reference value U ref With bus current i dc Multiplication and division ΔP Then, square the result to obtain the compensation factor. ; The virtual impedance calculation module (2) is used to perform low-pass filtering on the virtual inductive reactance to obtain the virtual impedance. Z v Multiply by the compensation factor To obtain the adaptive virtual impedance Z va Virtual impedance includes virtual resistance. R droop and virtual sensory resistance L droop s, to give virtual resistance L droop Multiplying s by the low-pass filter transfer function yields the virtual inductive reactance. X droop Virtual resistance R droop Subtract virtual sensory resistance X droop Obtain virtual impedance Z v The low-pass filter transfer function is: ;in, is the cutoff frequency of the low-pass filter, and s is a complex frequency domain variable; The compensation voltage and duty cycle calculation module (3) is used to calculate the bus current. i dc Multiply by adaptive virtual impedance Z va To obtain the given voltage compensation; the voltage reference value is then used. U ref Subtract the compensation for the given voltage and subtract the bus voltage value. u dc Obtain voltage deviation value Δ u The obtained voltage deviation value Δu After traditional voltage closed loop PI U Obtain the inductor current reference value i Lref The inductor current reference value i Lref Subtract the inductor current value i L Then, through the current closed loop PI I Get the duty cycle d ; The PWM modulation module (4) is used to generate a control signal by PWM modulation of the duty cycle d signal, and to control the switching of the energy storage converter transistor by the control signal.

6. A virtual impedance stabilization control system, characterized in that, include: The system comprises a photovoltaic system, a battery, a load, and a DC-DC converter; the DC-DC converter includes a photovoltaic DC-DC converter, an energy storage DC-DC converter, and a load DC-DC converter; the photovoltaic system is connected to a DC bus through the photovoltaic DC-DC converter, the battery is connected to the DC bus through the energy storage DC-DC converter, and the load is connected to the DC bus through the load DC-DC converter; wherein the energy storage DC-DC converter is controlled using the virtual impedance stabilization control method described in any one of claims 1-4.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the virtual impedance stabilization control method according to any one of claims 1-4.

8. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the virtual impedance stabilization control method according to any one of claims 1-4.

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