Alternating current and direct current hybrid micro-grid large signal stability improving method and device based on super-capacitor integral droop control strategy and medium

Abstract

The invention discloses an AC / DC hybrid micro-grid large signal stability improving method and device based on a super capacitor integral droop control strategy and a medium, and belongs to the technical field of power electronic technology and AC / DC hybrid micro-grid system.The AC / DC hybrid micro-grid large signal stability improving method comprises the steps that a super capacitor is connected to a DC bus in parallel, and the super capacitor and a VSC work cooperatively; the supercapacitor employs integral droop control to manage the discharge rate, and the VSC employs voltage-current droop control. And establishing a large-signal nonlinear model of the system and performing stability analysis by using a mixed potential function theory. According to the invention, a voltage source converter adopting traditional U-I droop control and a super capacitor adopting integral droop control work cooperatively: when large disturbances such as constant power load sudden change occur, SC controls a high-frequency component required by instantaneous compensation power through ID by virtue of a quick response characteristic of the SC; and the VSC responds to smooth change of load power and provides low-frequency power support through U-I droop control.

Description

Technical Field

[0001] This invention relates to the fields of power electronics technology and AC / DC hybrid microgrid system technology, specifically to a method, device, and medium for improving the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy. Background Technology

[0002] With the development of renewable energy technologies, AC / DC hybrid microgrid systems have become an important component of future power systems. They offer significant advantages in supporting photovoltaic power generation, wind power, energy storage systems, and smart load integration, and have been widely applied in distributed generation, smart buildings, ship power, rail transit, communication base stations, and data centers.

[0003] Hybrid AC / DC microgrid systems have attracted widespread attention due to their ability to efficiently integrate distributed generation systems (DGS) such as photovoltaics and wind power, providing efficient and reliable power supply for DC loads such as new energy vehicles and LED lighting. However, the highly random nature of DGS and the connection of a large number of constant power loads (CPLs) with negative resistance characteristics pose significant challenges to the stable operation of hybrid AC / DC microgrid systems. In such systems, the DC bus plays a crucial role in multi-source convergence, power coordination, and stable load power supply. Because DC systems lack inherent inertia, the connection of a large number of constant power loads (CPLs) with negative resistance characteristics will cause the DC voltage to become extremely sensitive to disturbances, resulting in severe instability phenomena such as system oscillations, bus voltage dips, and even system collapse.

[0004] Large-signal stability enhancement methods are limited by system structure and complexity, and it remains unclear whether they are applicable to AC / DC hybrid microgrid systems exhibiting "high-frequency, high-intensity, and high-randomness" characteristics. Currently, there are few methods that can effectively improve the large-signal stability of AC / DC hybrid microgrid systems with "high-frequency, high-intensity, and high-randomness" characteristics. Therefore, further research and exploration are needed to enrich and enhance the methods for improving the large-signal stability of AC / DC hybrid microgrid systems. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by this invention is: to address the issue of decreased dynamic stability and increased DC voltage fluctuations in AC / DC hybrid microgrids when faced with large-signal disturbances such as sudden changes in constant power loads. By coordinating the voltage source converter (VSC) with traditional UI droop control and the supercapacitor (SC) with integral droop (ID) control, the SC's ability to quickly respond to high-frequency power demands is used to instantaneously compensate for disturbance power, while the VSC is responsible for responding to smoothly changing low-frequency load power, thereby suppressing DC voltage fluctuations and enhancing the dynamic stability and operational margin of the system under large disturbances.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for improving the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, comprising, An energy storage unit consisting of a supercapacitor and a bidirectional DC / DC converter is connected in parallel to the DC bus. The discharge rate is controlled by the integral droop coefficient of the supercapacitor, forming an integral droop control strategy. The voltage source converter adopts a voltage-current droop control strategy to respond to the low-frequency components in the power demand of the AC / DC hybrid microgrid system, thereby maintaining the steady-state power balance and DC bus voltage stability of the AC / DC hybrid microgrid system. The supercapacitor is controlled by an integral droop control strategy to respond to the high-frequency transient components in the power demand of the AC / DC hybrid microgrid system, thereby suppressing DC bus voltage fluctuations during large disturbances. Through the synergistic effect of the voltage-current droop control strategy and the integral droop control strategy, the total power fluctuation of the AC / DC hybrid microgrid system is automatically decomposed into the low-frequency components borne by the voltage source converter and the high-frequency components borne by the supercapacitor energy storage unit. A large-signal nonlinear mathematical model is constructed based on the supercapacitor and the voltage source converter, and the stability of the AC / DC hybrid microgrid system is evaluated and analyzed using the hybrid potential function theory.

[0008] As a preferred embodiment of the large-signal stability enhancement method for AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy described in this invention, the differential equation of the supercapacitor is expressed as follows: Where R represents the series resistance and C represents the series capacitance. This is expressed as capacitor voltage. This is expressed as the time derivative of the capacitor voltage, where t represents time.

[0009] As a preferred embodiment of the method for improving the large-signal stability of AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy described in this invention, the voltage-current droop control strategy includes: The UI droop of voltage source converters is derived based on VP droop.

[0010] The VP droop is represented as follows: in, This is expressed as the DC bus voltage reference value. This is represented as the output voltage setting value. This represents the droop coefficient when the voltage source converter uses VP droop control. It is represented as the low-frequency component of the equivalent constant power load sudden power change.

[0011] Both VP (Version) and UI (User Interface) drooping exist: in, This is expressed as the UI droop coefficient. It is represented as the d-axis component of the three-phase voltage on the AC side of VSC in the dq coordinate system.

[0012] As a preferred embodiment of the large-signal stability enhancement method for AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy described in this invention, the integral droop control strategy is expressed as follows: in, This is expressed as the DC bus voltage reference value. This is represented as the output voltage setting value. This is expressed as the integral droop coefficient. It is represented as the high-frequency component of the equivalent constant power load sudden power change.

[0013] As a preferred embodiment of the AC / DC hybrid microgrid large-signal stability enhancement method based on a supercapacitor integral droop control strategy described in this invention, wherein: power conservation yields: in, This indicates the power required by the DC system. This is expressed as the equivalent power of an equivalent constant power load. It represents the equivalent power of the energy storage unit, and s represents the Laplace operator.

[0014] As a preferred embodiment of the method for improving the large-signal stability of AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy described in this invention, the large-signal stability criterion of the AC / DC hybrid microgrid system considering supercapacitor integral droop control, obtained through the hybrid potential function theory in the evaluation and analysis of the stability of the AC / DC hybrid microgrid system, is expressed as follows: in, Represented as U - I Sag coefficient, This represents the equivalent resistance on the AC side of the VSC. Indicates the resistance of a DC line. Represented as VSC filter inductor, Indicates the inductance of a DC line. This indicates the introduction of a virtual inductor. This refers to the DC-side filter capacitor. This represents the equivalent capacitance of the DC bus. and These are the proportional and integral coefficients of the outer voltage loop of the VSC converter, respectively. and These are the proportional and integral coefficients of the VSC converter's inner current loop, respectively. and These are the proportional and integral coefficients of the inner loop current of the energy storage unit, respectively. This is represented by the d-axis component of the three-phase AC current on the VSC side after Park transformation. This is represented as the d-axis component of the three-phase AC voltage of the VSC obtained through the Park transform. This is represented as the VSC output voltage. This is represented as the output voltage of the energy storage unit. This represents the power absorbed by the energy storage unit during charging.

[0015] The large-signal stability criterion for AC / DC hybrid microgrid systems is obtained by performing an identity transformation: in, This represents the output power when the energy storage unit discharges.

[0016] As a preferred embodiment of the large-signal stability enhancement method for AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy described in this invention, the large-signal stability criterion based on supercapacitor integral droop control and without supercapacitor integral droop control strategies is expressed as follows: .

[0017] This invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of the method for stabilizing and improving large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy.

[0018] The present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of the method for stabilizing and improving large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy.

[0019] The beneficial effects of this invention: The main objective of this invention is to propose a control method that enhances the dynamic stability of AC / DC hybrid microgrid systems under large-signal disturbances, effectively improving the system's rapid response capability and operational stability margin. This invention utilizes the coordinated control of a traditional UI-drooping VSC and an ID-drooping SC. High-frequency components of power demand under large disturbance conditions such as sudden CPL changes can be instantaneously compensated by the ID-based SC, while the UI-drooping VSC responds to smooth changes in load power. The rapid discharge response characteristics of the SC are used to reduce the impact of large-signal disturbances on the DC voltage of the AC / DC hybrid microgrid system. The core idea is to introduce a set of supercapacitors based on integral droop control into the system as a rapid power supply source for transient high-frequency disturbances, while retaining the low-frequency power regulation function of the existing VSC using a U-I droop strategy, thus achieving dual-control coordination in the dynamic frequency domain. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0021] Figure 1 This is a flowchart illustrating a method for improving the stability of large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy, as provided in one embodiment of the present invention.

[0022] Figure 2 This invention provides an illustrative circuit and characteristic curves for a method to improve the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, as an embodiment of the present invention.

[0023] Figure 3 This is a control system diagram of an SC converter for a method to improve the stability of large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy, as provided in an embodiment of the present invention.

[0024] Figure 4 This invention provides a method for improving the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, and includes a large signal model diagram of an AC / DC hybrid microgrid system considering large SC integral droop.

[0025] Figure 5 The figure shows the influence of the SC integral droop control strategy on the large signal stability of the AC / DC hybrid microgrid system, which is a method for improving the large signal stability of AC / DC hybrid microgrids based on the supercapacitor integral droop control strategy provided in an embodiment of the present invention.

[0026] Figure 6 This diagram illustrates an embodiment of the present invention that provides a method for improving the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, specifically an SC integral droop control strategy to expand the stable operating range of the AC / DC hybrid microgrid system.

[0027] Figure 7 The figure shows simulation results for different power jump conditions of a method for improving the stability of large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy, which is provided as an embodiment of the present invention.

[0028] Figure 8 The diagram illustrates the improvement of instability in an AC / DC hybrid microgrid system when the grid voltage drops to 49%, based on a supercapacitor integral droop control strategy, as provided in one embodiment of the present invention. Figure 9 The image shows the DC voltage and constant power load step waveforms of a method for stabilizing large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy, as provided in an embodiment of the present invention. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0030] Example 1, referring to Figures 1-5 This is one embodiment of the present invention, which provides a method for improving the large-signal stability of AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, including: S1. Connect an energy storage unit consisting of a supercapacitor and a bidirectional DC / DC converter in parallel on the DC bus. Control the discharge rate through the integral droop coefficient of the supercapacitor to form an integral droop control strategy.

[0031] like Figure 2 The SC illustrative circuit and characteristic curves are shown, illustrating the voltage and current characteristics of the SC. Figure 2The SC discharge condition shown follows Kirchhoff's Voltage Law (KVL), and the differential equation for SC is: (1) Where R represents the series resistance and C represents the series capacitance. Indicates the capacitor voltage. This is expressed as the time derivative of the capacitor voltage, where t represents time. Then, by solving formula (1), the time-domain descriptions of the SC voltage and current are obtained, expressed as follows: (2) in, This represents the initial voltage across the capacitor. Represented as a time-domain function, Represented as, This is expressed as capacitor voltage. Represented as a series resistor, It is represented as a series capacitor.

[0032] and The general relationship between them can be summarized as follows: (3) in, =1 / C represents the constant of the discharge rate. Figure 2 The diagram also shows the corresponding voltage and current distributions as indicated by formula (2). The capacitor tends to provide a burst of power at the instant the switch is opened, and the power drops exponentially to zero at the end of the discharge process. According to... Figure 2 The characteristics of the capacitor current shown are used to design a new droop controller (ID) with the same format as formula (3), as shown below: (4) in, This is expressed as the DC bus voltage reference value. This is represented as the output voltage setting value. This is expressed as the integral droop coefficient. The high-frequency component is represented as the ECPL mutation power.

[0033] S2. The voltage source converter adopts a voltage-current droop control strategy to respond to the low-frequency components in the power demand of the AC / DC hybrid microgrid system, so as to maintain the steady-state power balance and DC bus voltage stability of the AC / DC hybrid microgrid system.

[0034] Furthermore, since SC only compensates for the transient component of the ECPL's sudden power surge, it needs to be coordinated with the UI droop of VSC to achieve SC compensation for high-frequency transient power and VSC smooth response to the low-frequency portion. Ignoring the voltage loss from VSC to the DC bus, for ease of subsequent derivation, the UI droop of VSC is temporarily written as VP droop, and its control equation is: (5) in, This represents the droop coefficient when the voltage source converter uses VP droop control. The low-frequency component of the transient power of the equivalent constant power load (ECPL) has a conversion relationship with the droop coefficient of the VSC using UI droop, as shown in formula (6).

[0035] (6) in, This is expressed as the UI droop coefficient. It is represented as the d-axis component of the three-phase voltage on the AC side of VSC in the dq coordinate system.

[0036] From the law of conservation of power, we can obtain: (7) in, This indicates the power required by the DC system. This is expressed as the equivalent power of an equivalent constant power load. It represents the equivalent power of the energy storage unit, and s represents the Laplace operator.

[0037] It can be used express and The expression is: (8) S3. The supercapacitor adopts an integral droop control strategy to respond to the high-frequency transient components in the power demand of the AC / DC hybrid microgrid system, and to suppress DC bus voltage fluctuations during large disturbances.

[0038] Next, a reasonable integral droop control coefficient will be designed, and the time-domain representation of formula (8) will be expressed. and Transformed into the step response expression shown in formula (9): (9) and The dynamic power distribution is mainly determined by Determine, find the answer in formula (9) The derivatives are: (10) in, The rate of change of the equivalent constant power load over time should be less than or equal to the maximum value of the response rate of the voltage source converter. .

[0039] To ensure the system can operate stably under large disturbances, the value of formula (10) should be less than or equal to the maximum value of the VSC response rate. Then the droop coefficient of the SC integral can be obtained from formula (11): (11) In formula (11), VSC is adopted as the droop coefficient of VP droop. Converted to the UI droop coefficient used in this article have: (12) S4. Through the synergistic effect of voltage-current droop control strategy and integral droop control strategy, the total power fluctuation of the AC / DC hybrid microgrid system is automatically decomposed into low-frequency components undertaken by the voltage source converter and high-frequency components undertaken by the supercapacitor energy storage unit.

[0040] Figure 3 The diagram shows the control system of the SC converter of this invention. Since the SC only provides rapid power support to the system during disturbances, it does not participate in the operation of the AC / DC hybrid microgrid system under stable operating conditions. Therefore, a control structure using ID control and DC voltage outer loop control is employed to determine the magnitude of the secondary-side output current.

[0041] S5. A large-signal nonlinear mathematical model is constructed based on supercapacitors and voltage source converters, and the stability of the AC / DC hybrid microgrid system is evaluated and analyzed using the hybrid potential function theory.

[0042] Figure 4 The diagram shows the large-signal model of the AC / DC hybrid microgrid system considering the large integral droop of the SC (Signal Center) in this invention. To reduce model and computational complexity, the SC and its converter are represented as current sources, and the energy storage is set to be in charging mode. Based on the large-signal nonlinear model of the AC / DC hybrid microgrid system considering SC integral droop control, the stability criterion for the large-signal system considering SC integral droop control is obtained through the hybrid potential function: (13) Among them, among them, among them Represented as U - I Sag coefficient, This represents the equivalent resistance on the AC side of the VSC. Indicates the resistance of a DC line. Represented as VSC filter inductor, Indicates the inductance of a DC line. This indicates the introduction of a virtual inductor. This refers to the DC-side filter capacitor. This represents the equivalent capacitance of the DC bus. and These are the proportional and integral coefficients of the outer voltage loop of the VSC converter, respectively. and These are the proportional and integral coefficients of the VSC converter's inner current loop, respectively. and These are the proportional and integral coefficients of the inner loop current of the energy storage unit, respectively. This is represented by the d-axis component of the three-phase AC current on the VSC side after Park transformation. This is represented as the d-axis component of the three-phase AC voltage of the VSC obtained through the Park transform. This is represented as the VSC output voltage. This is represented as the output voltage of the energy storage unit. This represents the power absorbed by the energy storage unit during charging.

[0043] Note that in formula (13) The magnitude has changed. Before the SC integral droop was connected, the power was balanced by the VSC converter when the system experienced disturbances. After the SC integral droop was connected, the disturbance power was automatically distributed according to formula (8). A more intuitive large-signal stability criterion can be obtained by performing an identity transformation on formula (13): (14) S4. When a large disturbance occurs, the supercapacitor provides high-frequency transient power support, and the voltage source converter provides low-frequency power through traditional UI droop control to achieve dynamic stability of the DC bus voltage.

[0044] Figure 5 This is a diagram illustrating the impact of the SC integral droop control strategy of this invention on the large-signal stability of the system. The influence of system parameters on stability can be plotted using the large-signal stability criterion formula (14) for AC / DC hybrid microgrid systems with and without the SC integral droop control strategy, respectively. Figure 5 As shown in the figure, it is clear that after introducing the SC integral droop control strategy, the amplitude of the large-signal stability criterion μ1+μ2 of the AC / DC hybrid microgrid system is improved across the entire range. In other words, the system's ability to withstand large disturbances is enhanced after introducing the SC integral droop control strategy. Figure 5This paper only theoretically demonstrates that introducing SC integral droop control can improve the system stability margin. Further verification of this strategy through time-domain simulation is needed, along with an analysis of the mechanism by which the proposed SC integral droop control affects the stability of the AC / DC hybrid microgrid system under large-signal disturbances.

[0045] (15) Example 2, refer to Figures 6-9 This invention provides a method for stabilizing and improving large-signal performance in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy. To verify the beneficial effects of this invention, scientific demonstration is conducted through experiments.

[0046] The effectiveness of the method proposed in this invention will be verified and analyzed through simulation: The time-domain switching circuit of the AC / DC hybrid microgrid system and the simulation circuit based on the RLC equivalent circuit model of the control system were built using Matlab / Simulink software. The main circuit parameters of the system are shown in Table 1, and the control parameters and the calculated equivalent circuit model parameters are shown in Table 2.

[0047] Table 1. Main circuit parameters of AC / DC hybrid microgrid system

[0048] Table 2 Simulation control parameters of AC / DC hybrid microgrid system

[0049] In Table 2, This is represented as the VSC voltage outer loop proportional coefficient. This is represented as the VSC voltage outer loop integral coefficient. This is represented as the VSC UI droop coefficient. Represented as equivalent resistance, Represented as equivalent resistance, It is represented as the equivalent inductance.

[0050] Simulation 1: Load Sudden Disturbance Condition: Figure 6 This diagram illustrates the expansion of the stable operating range of the system using the SC integral droop control strategy of the present invention (system instability condition without the SC integral droop control strategy). The ID control droop coefficient is set to 0.007. The dynamic response of the DC bus voltage, the SC discharge current response, and the output power response of SC and VSC after incorporating the SC integral droop control strategy are shown below. Figure 6As shown, before the SC integral droop control strategy is implemented, when the CPL load changes abruptly, the VSC cannot quickly respond to the required power, leading to a bus voltage dip and eventually a bus voltage collapse. After introducing the SC integral droop control strategy proposed in this invention, with the sudden change in CPL, the SC controlled by ID discharges rapidly, mitigating the bus voltage change and preventing bus voltage collapse caused by the VSC's inability to respond quickly. Figure 6 In the medium power variation curve, the SC with ID control quickly releases the high-frequency transient power required by the load to prevent the bus voltage from collapsing, while the VSC with UI droop control slowly provides low-frequency power to maintain the system power balance and keep the bus voltage constant during the system steady state.

[0051] Using the system main circuit parameters shown in Table 1, the control parameters shown in Table 2, and their calculated equivalent circuit model parameters, two sets of power switching conditions are designed as shown in Table 3. The corresponding simulation results are as follows. Figure 7 As shown.

[0052] Table 3 Two sets of power jump values ​​with SC integral droop introduced

[0053] In the table, This represents the maximum value of a constant power load.

[0054] Figure 7 The following are simulation results for different power switching conditions according to the present invention. Figure 7 (a) It can be seen from the L1 time period that when the CPL jumps from 10kW to 1.5kW... At kW, due to the droop coefficient of the SC integral. Under this disturbance, the system still possesses a sufficient response rate to allow the DC bus voltage to decrease slowly until the system stabilizes. And when the CPL jumps from 10kW to 1.625kW... hour, ,Depend on Figure 7 The simulation results shown in (b) indicate that the bus voltage can still decrease slowly during time period L2. However, as the SC discharge decays, it can no longer provide the transient power required for the disturbance, and the DC bus voltage begins to collapse. With a further decrease in bus voltage (time period L3), the integral output of the SC integral droop control cannot be reset to 0, causing the SC to discharge further to maintain a constant bus voltage. However, at this point, the transient power release rate of the SC is much lower than the rate of decrease in bus voltage, ultimately leading to a collapse of the DC bus voltage and system instability. Finally, through comparison... Figure 9 and Figure 7 The simulation results shown in (a) show that after introducing the SC integral droop control strategy, the maximum CPL power boundary of the system is increased by 50%, which verifies that the SC integral droop control improves the stability margin of the system.

[0055] Simulation 2: Grid voltage sag disturbance condition: This invention is based on For example, among which It is 35kW. It is 5kW. The main circuit parameters of the AC / DC hybrid microgrid system shown in Table 1, the control parameters shown in Table 2, and the calculated equivalent circuit model parameters were used for simulation verification.

[0056] Table 4 shows a comparison of the stability analysis of the AC / DC hybrid microgrid system before and after the introduction of the SC integral droop control strategy. The simulation results are as follows: Figure 8 As shown.

[0057] Table 4. Grid voltage sag operation results with and without SC integral droop.

[0058] Figure 8 This diagram illustrates the improvement in system instability caused by a grid voltage drop of 49% according to the present invention. Figure 8 The results showed that at t=0.3s, the grid voltage dropped to 49%. Similar to load surges, the SC (Supercharger) provides transient current through rapid ID control, mitigating the impact of large-signal disturbances on the system and maintaining dynamic stability of the bus voltage. Due to the SC's rapid response characteristics, the SC integral droop control strategy can stabilize initially unstable operating conditions (grid voltage temporarily dropping to 49% of rated value). This verifies the effectiveness of the SC integral droop control strategy in enhancing system stability under large-signal conditions.

[0059] This invention addresses the problem of instability in AC / DC hybrid microgrid systems under large disturbance conditions such as CPL surges and grid voltage dips. The source converter (DC-DC & VSC) struggles to quickly respond to provide the high-frequency components required for the large disturbances, leading to positive feedback voltage collapse on the DC bus and subsequent instability. This invention presents a method for improving large-signal stability in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy. Through coordinated control of the traditional UI-drooping VSC and ID-drooping SC, the high-frequency components of power demand under large disturbance conditions such as CPL surges can be instantaneously compensated by the ID-drooping SC, while the UI-drooping VSC responds to smooth changes in load power. The ID control coefficient can be rationally selected based on the magnitude of the disturbance to achieve rapid response to support the power required for the disturbance, prevent bus voltage collapse, and improve the system's large-disturbance stability margin.

[0060] This embodiment also provides an electronic device applicable to a method for stabilizing and enhancing large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the method for stabilizing and enhancing large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy proposed in the above embodiment.

[0061] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a method for stabilizing and improving large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, as proposed in the above embodiment.

[0062] The storage medium proposed in this embodiment belongs to the same inventive concept as the method for stabilizing and improving large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0063] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0064] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the stability of large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy, characterized in that: include, An energy storage unit consisting of a supercapacitor and a bidirectional DC / DC converter is connected in parallel to the DC bus. The discharge rate is controlled by the integral droop coefficient of the supercapacitor, forming an integral droop control strategy. Voltage source converters employ a voltage-current droop control strategy to respond to the low-frequency components in the power demand of AC / DC hybrid microgrid systems, thereby maintaining the steady-state power balance and DC bus voltage stability of the AC / DC hybrid microgrid system. The supercapacitor employs an integral droop control strategy to respond to high-frequency transient components in the power demand of the AC / DC hybrid microgrid system, thereby suppressing DC bus voltage fluctuations during periods of large disturbances. Through the synergistic effect of voltage-current droop control strategy and integral droop control strategy, the total power fluctuation of the AC / DC hybrid microgrid system is automatically decomposed into low-frequency components handled by the voltage source converter and high-frequency components handled by the supercapacitor energy storage unit. A large-signal nonlinear mathematical model is constructed based on supercapacitors and voltage source converters, and the stability of the AC / DC hybrid microgrid system is evaluated and analyzed using the hybrid potential function theory.

2. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on supercapacitor integral droop control strategy as described in claim 1, characterized in that: The differential equation for the supercapacitor is expressed as: in, Indicates series resistance. Indicates a series capacitor. This is expressed as capacitor voltage. This is expressed as the time derivative of the capacitor voltage, where t represents time.

3. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on supercapacitor integral droop control strategy as described in claim 2, characterized in that: The voltage-current droop control strategy includes... Based on VP droop, UI droop of voltage source converter is derived; The VP droop is represented as follows: in, This is expressed as the DC bus voltage reference value. This is represented as the output voltage setting value. This represents the droop coefficient when the voltage source converter uses VP droop control. The low-frequency component is represented as the alternating power of the equivalent constant power load. Both VP (Version) and UI (User Interface) drooping exist: in, This is expressed as the UI droop coefficient. It is represented as the d-axis component of the three-phase voltage on the AC side of VSC in the dq coordinate system.

4. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy as described in claim 3, characterized in that: The integral droop control strategy is expressed as follows: in, This is expressed as the DC bus voltage reference value. This is represented as the output voltage setting value. This is expressed as the integral droop coefficient. It is represented as the high-frequency component of the equivalent constant power load sudden power change.

5. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on supercapacitor integral droop control strategy as described in claim 4, characterized in that: From the law of conservation of power: in, This indicates the power required by the DC system. This is expressed as the equivalent power of an equivalent constant power load. It represents the equivalent power of the energy storage unit, and s represents the Laplace operator.

6. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on supercapacitor integral droop control strategy as described in claim 5, characterized in that: The large-signal stability criterion for AC / DC hybrid microgrid systems, which takes into account supercapacitor integral droop control and is obtained through the hybrid potential function theory in the evaluation and analysis of the stability of AC / DC hybrid microgrid systems, is expressed as follows: in, Represented as U - I Sag coefficient, This represents the equivalent resistance on the AC side of the VSC. Indicates the resistance of a DC line. Represented as VSC filter inductor, Indicates the inductance of a DC line. This indicates the introduction of a virtual inductor. This refers to the DC-side filter capacitor. This represents the equivalent capacitance of the DC bus. and These are the proportional and integral coefficients of the outer voltage loop of the VSC converter, respectively. and These are the proportional and integral coefficients of the VSC converter's inner current loop, respectively. and These are the proportional and integral coefficients of the inner loop current of the energy storage unit, respectively. This is represented by the d-axis component of the three-phase AC current on the VSC side after Park transformation. This is represented as the d-axis component of the three-phase AC voltage of the VSC obtained through the Park transform. This is represented as the VSC output voltage. This is represented as the output voltage of the energy storage unit. This represents the power absorbed by the energy storage unit during charging. The large-signal stability criterion for AC / DC hybrid microgrid systems is obtained by performing an identity transformation: in, This represents the output power when the energy storage unit discharges.

7. The method for large-signal stability enhancement of AC / DC hybrid microgrids based on supercapacitor integral droop control strategy as described in claim 6, characterized in that: The large-signal stability criterion based on supercapacitor integral droop control and without supercapacitor integral droop control strategies is expressed as follows: 。 8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of any one of the claims 1 to 7: a method for stabilizing and improving large signals in an AC / DC hybrid microgrid based on a supercapacitor integral droop control strategy.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of any one of the claims 1 to 7 for the method of stabilizing and improving large signals in AC / DC hybrid microgrids based on a supercapacitor integral droop control strategy.

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