An adaptive switching method for network mode support of a network-type converter

Abstract

The application discloses a self-adaptive switching method for grid-connection mode support of a grid-connection type converter in the field of new energy power generation, and aims to solve the technical problem that a large number of grid-connection type converters in an existing power grid cannot actively provide voltage and frequency support. The method comprises the following steps: acquiring rated parameters and circuit information of the grid-connection type converter; judging a disturbance level of the power grid according to the circuit information; determining whether to start a converter control mode switching based on the disturbance level; if the disturbance level is no disturbance or small disturbance, maintaining a grid-connection mode of the grid-connection type converter; and if the disturbance level is large disturbance, judging whether the grid-connection type converter has spare capacity, if yes, starting smooth switching to a grid-connection mode, otherwise, maintaining the grid-connection mode. The application is applied to a power system, can make full use of idle capacity of the existing grid-connection type converter, and enables the grid-connection type converter to autonomously switch to the grid-connection mode when a power grid fault occurs, so as to provide voltage and frequency support for the power grid.

Description

Technical Field

[0001] This invention relates to an adaptive switching method for grid-connected converters to support grid-connected modes, belonging to the field of new energy power generation technology. Background Technology

[0002] With the large-scale development and grid connection of wind energy, especially offshore wind power, a large number of wind farms have been put into operation. These wind farms generally use direct-drive wind turbines and are connected to the grid through full-power converters (inverters). Currently, most of these converters adopt grid-following control strategies. Their core working principle is to rely on phase-locked loops (PLLs) to track the phase and frequency of the grid voltage, thereby achieving precise power tracking and injection in the form of a controlled current source.

[0003] However, this high proportion of wind power integration, primarily using grid-connected line converters (GFLs), has significantly negatively impacted the safe and stable operation of the power system. Lacking active support capabilities, GFL converters essentially rely on the grid for stable voltage and frequency. They lack the ability to autonomously establish and regulate grid voltage / frequency, nor can they provide similar dynamic support. When the grid encounters large disturbances, the system requires rapid voltage and frequency support to maintain stability. The passive nature of GFL converters results in poor grid stability under large disturbances. This problem is particularly severe in regions with weak grid strength.

[0004] To enhance grid stability, particularly addressing the challenges posed by the integration of high proportions of power electronic equipment, grid-connected converter (GFM) technology has been proposed and experimentally validated. GFM converters mimic the core characteristics of synchronous generators; their internal control algorithms (such as Virtual Synchronous Generator (VSG) and droop control) can autonomously generate stable voltage and frequency reference values, functioning as a controlled voltage source. Therefore, GFM converters are considered a key technology for improving the safety and stability of new power systems. However, the large-scale application of GFM converters faces significant challenges: High cost: The design and manufacture of GFM converters typically require higher initial costs compared to standard GFL converters. High operating losses: To achieve its active support function, the GFM control strategy often needs to maintain a certain energy buffer under normal operating conditions, resulting in relatively high operating losses. Limited quantity: Due to cost and losses, the number of dedicated GFM converters deployed in actual power grids is currently very limited, and their support capacity coverage is far from meeting system requirements.

[0005] Currently, dedicated GFM converters typically possess backward compatibility and can operate in GFL mode. However, the vast number of conventional GFL converters, due to limitations in their hardware design and control architecture, are generally considered difficult or even impossible to operate directly in standard GFM mode. How to enable the massive existing number of GFL converters to possess GFM functionality has not yet been fully explored or effectively resolved in research and engineering applications. Summary of the Invention

[0006] The purpose of this invention is to provide an adaptive switching method for grid-connected converters to support grid-connected modes, which can make full use of existing grid-connected converters and enable the improved grid-connected converters to achieve grid-connected mode switching.

[0007] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0008] On one hand, the present invention provides an adaptive switching method for grid-connected converters to support grid configuration modes, comprising:

[0009] Obtain the rated parameters and circuit information of the grid-connected converter;

[0010] Based on the circuit information, determine the level of disturbance to the power grid;

[0011] Based on the disturbance level, determine whether to initiate converter control mode switching: if the disturbance level is no disturbance or a small disturbance, maintain the grid-connected converter's grid-connected mode; if the disturbance level is a large disturbance, determine whether the grid-connected converter has spare capacity; wherein, the process of determining whether the grid-connected converter has spare capacity includes:

[0012] Based on the rated parameters and circuit information, calculate the power margin and current margin of the grid-connected converter;

[0013] Based on the power margin and current margin, it is determined whether the grid-connected converter has spare capacity. If both the power margin and current margin are greater than the preset margin threshold, the grid-connected converter has spare capacity and a smooth switch to grid-connected mode is initiated; otherwise, the grid-connected mode is maintained.

[0014] In conjunction with the first aspect, the process for determining the disturbance level further includes:

[0015] Based on the circuit information, calculate the voltage and frequency changes of the power grid;

[0016] Disturbance levels are classified according to the deviation range of voltage and frequency from their reference values, and the disturbance levels satisfy the following conditions:

[0017] When there is no disturbance:

[0018] and ;

[0019] For small perturbations:

[0020] or ;

[0021] During large disturbances:

[0022] or ;

[0023] Where V represents the voltage of the grid-connected converter; Indicates a reference value for the mains voltage; Indicates the real-time detected power grid frequency; This indicates the rated frequency of the power grid.

[0024] In conjunction with the first aspect, the expressions for the power margin and current margin of the grid-connected converter are as follows:

[0025] Power margin:

[0026] ;

[0027] ;

[0028] in, Indicates active power margin; This indicates the active power output during grid-connected operation. Indicates the rated active power; Indicates reactive power margin; This indicates the reactive power during grid-connected operation. Indicates the rated reactive power;

[0029] Current margin:

[0030] ;

[0031] in, Indicates current margin; Indicates the maximum allowable current; This represents the current flowing through the converter.

[0032] In conjunction with the first aspect, the smooth transition to the network construction mode includes:

[0033] When a large disturbance is detected and the grid-connected converter has spare capacity, the grid-connected converter smoothly switches the grid mode through a hierarchical phase amplitude control loop, resulting in a grid mode that switches from constant power control to virtual synchronous machine control.

[0034] In conjunction with the first aspect, the smooth switching of the network configuration mode through the hierarchical phase amplitude control link further includes:

[0035] The grid-type converter receives a switching mode command triggered by the disturbance level and margin judgment results;

[0036] According to the switching mode command, the phase-locked loop control of the grid-connected converter is released to break away from the tracking of the grid phase;

[0037] After the grid phase is disconnected from tracking, the active / reactive power value is reduced from the rated active / reactive power value before the switch according to the preset slope steepness to obtain the reduced active / reactive power reference value.

[0038] Based on the reduced active / reactive power reference values, a virtual voltage source capable of automatically generating phase and amplitude is constructed.

[0039] The phase and amplitude generated by the virtual voltage source are used as a reference, and pre-synchronization control is performed with the current operating state of the grid-connected mode to eliminate the phase angle difference and voltage difference at the moment of mode switching.

[0040] Once the pre-synchronization control is completed, the grid-connected converter controlled by constant power is switched to virtual synchronous machine control with the virtual voltage as the core, thereby smoothly completing the transition to the grid-connected mode.

[0041] In conjunction with the first aspect, the expression for the reduced active / reactive power reference value is further as follows:

[0042] ;

[0043] ;

[0044] in, This represents the reference value of the active power of the grid-connected converter at time t. Indicates the rated active power; Indicates the steepness of the slope; Indicates time; This represents the reference value of reactive power of the grid-connected converter at time t; This indicates the rated reactive power.

[0045] In conjunction with the first aspect, the phase and amplitude expressions generated by the virtual voltage source are as follows:

[0046] ;

[0047] ;

[0048] in, The amplitude of the virtual voltage source; Indicates the grid voltage before the switch; Indicates the reactive power droop coefficient; This indicates the reactive power reference value for the grid-type converter; Indicates the rated reactive power; For virtual voltage source phase values; Indicates the rated frequency; Active power-frequency coefficient; This indicates the active power reference value for the grid-type converter; This indicates the rated active power.

[0049] In conjunction with the first aspect, further, the elimination of phase angle difference and voltage difference at the moment of mode switching includes:

[0050] Obtain the first phase angle output by the phase-locked loop control and the second phase angle output by the network configuration mode control loop, and calculate the phase angle difference between the first phase angle and the second phase angle;

[0051] The phase angle difference is input into the PI controller to obtain the phase compensation amount, and the phase compensation amount is fed back to the network configuration mode control loop to adjust the phase output of the network configuration mode control loop;

[0052] Obtain the voltage component of the power grid and the reference value of the power grid voltage during grid-following mode control operation, and calculate the voltage difference between the voltage component of the power grid and the reference value of the power grid voltage;

[0053] The voltage difference is input to the PI regulator to obtain the voltage compensation amount, and the voltage compensation amount is fed back to the network mode control loop to adjust the voltage amplitude output of the network mode control loop.

[0054] Based on the adjusted phase output and voltage amplitude output, the phase angle difference and voltage difference at the moment of converter control mode switching are eliminated.

[0055] In conjunction with the first aspect, it further includes:

[0056] Obtain the circuit information of the grid-connected converter after the switching is completed;

[0057] Determine whether the difference in circuit information after the switch is completed within a preset time is within a preset safety range:

[0058] If the change is within the safe range, the switch is considered successful and the grid connection mode is maintained; if the change difference exceeds the preset safe range, the converter control mode is forcibly restored to the grid connection mode.

[0059] In conjunction with the first aspect, further,

[0060] The smooth transition from startup to network construction mode also includes:

[0061] The circuit information of the grid-connected converter is collected before switching.

[0062] Based on the collected circuit information, the risk index R of the power grid is calculated;

[0063] Based on the risk index R, the hysteresis width H(t) of the mode switching judgment step during the smooth switching process is dynamically adjusted. The dynamic adjustment of the hysteresis width H(t) satisfies the following condition:

[0064] ;

[0065] in, H represents the hysteresis width; R represents the initial hysteresis width; A represents the hazard index; B represents the loop expansion gain; and C represents the loop contraction gain.

[0066] The Black Swan algorithm is used to optimize the expanding loop gain, shrinking loop gain, and risk index factor to obtain a set of optimal hysteresis widths and risk indices.

[0067] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0068] This invention establishes an intelligent and reliable automatic decision-making mechanism by real-time monitoring of the power grid status and the operating status of the grid-connected converter. Its primary benefit lies in its ability to accurately identify the level of power grid disturbance, ensuring that the converter only initiates mode switching when a large disturbance occurs in the grid and genuine support is required. During periods of no or minor disturbance, it maintains efficient grid-connected operation, thus avoiding unnecessary mode switching and the resulting energy loss and control complexity. Furthermore, before deciding to switch, this method introduces a spare capacity judgment step based on power and current margins, ensuring that the grid-connected converter only switches to grid-connected mode when it has sufficient capacity. This fundamentally prevents equipment damage due to overload and greatly improves the safety and reliability of the switching process.

[0069] In summary, this series of condition judgment processes enables a large number of low-cost conventional grid converters to selectively and intelligently play the role of grid converters during grid emergencies, while ensuring their own safety. This significantly improves the dynamic stability and disturbance resistance of the power grid in an economical and efficient manner. Attached Figure Description

[0070] Figure 1 The diagram shown is a flowchart of the grid-connected converter switching process provided in an embodiment of the present invention;

[0071] Figure 2 The diagram shows the main flow of adaptive switching control for grid-connected converters provided in an embodiment of the present invention.

[0072] Figure 3 The diagram shows a flowchart of the parameter optimization process of the Black Swan algorithm provided in an embodiment of the present invention. Detailed Implementation

[0073] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0074] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0075] Example 1

[0076] See Figure 1 This embodiment introduces an adaptive switching method for grid-type converters to support grid configuration modes, including:

[0077] Real-time acquisition of rated parameters and operating circuit information of grid-connected converters;

[0078] Based on the circuit information, accurately determine the disturbance level of the power grid;

[0079] Based on this disturbance level, determine whether to initiate converter control mode switching:

[0080] If the grid disturbance level is in a state of no disturbance or small disturbance, it indicates that the grid is operating stably and no additional support is needed. Therefore, it is sufficient to maintain the grid-following mode operation of the grid-following converter to avoid losses and control complexity caused by unnecessary mode switching.

[0081] Once a large disturbance level is detected in the power grid, it indicates that the grid stability is threatened and active support is required. At this point, it is necessary to further determine whether the grid-connected converter itself has the ability to provide support. Determining whether there is spare capacity is an important step, and the determination process is as follows:

[0082] Calculate the power margin and current margin of the grid-connected converter based on the rated parameters and circuit information;

[0083] Based on the comparison between the power margin and current margin and the preset margin threshold, it is determined whether the grid-connected converter has spare capacity, thereby assessing whether the grid-connected converter has the potential to undertake grid-connection function. Only when the converter does have sufficient spare capacity (i.e. all margins are greater than the threshold) will a smooth switch to grid-connection mode be initiated; otherwise, the grid-connected mode will be maintained.

[0084] In summary, this invention utilizes the potential capacity of the existing large-scale grid-connected converters, intelligently transforming them into virtual synchronous machines with voltage and frequency support capabilities only in emergency situations where the power grid truly needs support. This significantly enhances the power grid's ability to withstand disturbances and restore stability, maximizing the efficiency of existing resources and solving the problems of high cost and limited quantity of grid-connected converters, which hinder their large-scale application.

[0085] Example 2

[0086] Step 1: Monitor the grid-connected converter in real time to obtain its rated parameters and operating circuit information; the rated parameters of the grid-connected converter include rated apparent power. Rated active power Rated reactive power Maximum permissible current Rated voltage ;

[0087] Circuit information includes the grid voltage before the switch. Grid current The rated frequency of the power grid Current flowing through the converter , Switching phase angle Active power during operation The reactive power Q during operation.

[0088] Furthermore, detect any abnormalities in the power grid, i.e., disturbances, and assess the severity of the disturbances, as in step 2 below.

[0089] Step 2: Based on the circuit information, determine the disturbance level of the power grid. The process of determining the disturbance level includes:

[0090] Step S21: Calculate the voltage and frequency changes of the power grid based on the circuit information;

[0091] Step S22: Classify the disturbance level according to the deviation range of voltage and frequency from their reference values.

[0092] The classification of disturbance levels satisfies the following conditions:

[0093] a. When the power grid disturbance level is in a state of no disturbance or small disturbance, its expression is as follows:

[0094] and (1)

[0095] b. When the power grid disturbance level is small:

[0096] or (2)

[0097] c. When the power grid is experiencing a large disturbance:

[0098] or (3)

[0099] Where V represents the voltage of the grid-connected converter; Indicates a reference value for the mains voltage; Indicates the real-time detected power grid frequency; Indicates the rated frequency of the power grid; Indicates the voltage deviation value; This indicates the frequency deviation value.

[0100] Step 3: Based on the disturbance level, determine whether to initiate the converter control mode switching, that is, smoothly switch from the grid-following mode to the grid-connecting mode.

[0101] Specifically, if the disturbance level is no disturbance or a small disturbance, the grid-connected converter maintains its grid-connected mode; if the disturbance level is a large disturbance, it is determined whether the grid-connected converter has spare capacity. The process for determining whether the grid-connected converter has spare capacity includes:

[0102] Step S31: Calculate the power margin and current margin of the grid-connected converter based on the rated parameters and circuit information; the expressions for the power margin and current margin are as follows:

[0103] Power margin:

[0104] (4)

[0105] (5)

[0106] in, Indicates active power margin; This indicates the active power output during grid-connected operation. Indicates the rated active power; Indicates reactive power margin; This indicates the reactive power during grid-connected operation. Indicates the rated reactive power;

[0107] Current margin:

[0108] (6)

[0109] in, Indicates current margin; Indicates the maximum allowable current; This represents the current flowing through the converter.

[0110] Step S32: Based on the power margin and current margin, determine whether the grid-connected converter has spare capacity. If both the power margin and current margin are greater than a preset margin threshold, in this embodiment of the invention, the margin threshold is 10% of the calculated margin value itself. That is, when both the power margin and current margin are greater than 10% of their calculated margin values, it is determined that the grid-connected converter has spare capacity (spare margin), and a smooth switch to grid-connected mode is initiated; otherwise, the grid-connected mode is maintained. The initiation of the smooth switch to grid-connected mode includes:

[0111] When a large disturbance is detected and the grid-connected converter has spare capacity, the grid-connected converter smoothly switches the grid mode through the hierarchical phase amplitude control loop, resulting in a grid mode that switches from constant power control to virtual synchronous machine control.

[0112] Specifically, the smooth switching of the grid configuration mode with the grid-type converter through hierarchical phase amplitude control includes the following steps:

[0113] Step S321: The grid-connected converter receives a switching mode command triggered by the disturbance level and margin judgment result;

[0114] Step S322: According to the switching mode command, release the phase-locked loop (PLL) control of the grid-connected converter to break away from tracking the grid phase;

[0115] To prevent damage to the device caused by sudden power changes during switching, the power is reduced using the following step S323.

[0116] Step S323: After the grid phase disconnects from tracking, the active / reactive power value decreases from the pre-switching rated active / reactive power value according to a preset slope steepness to obtain the decreased active / reactive power reference value. The expression for this decreased active / reactive power reference value is:

[0117] (7)

[0118] (8)

[0119] in, This represents the reference value of the active power of the grid-connected converter at time t. Indicates the steepness of the slope; Indicates time; This represents the reference value of reactive power of the grid-connected converter at time t.

[0120] Since the grid-connected converter is actually a P and Q output, if it is to be converted to a constant internal potential output, a virtual voltage source as described in step S324 is required to ensure that the grid-connected converter can achieve the function of grid mode after switching.

[0121] Step S324: Based on the reduced active / reactive power reference values, construct a virtual voltage source with specific autonomous phase and amplitude generation capabilities. The phase and amplitude expressions generated by this virtual voltage source are as follows:

[0122] (9)

[0123] (10)

[0124] in, The amplitude of the virtual voltage source; Indicates the grid voltage before the switch; Indicates the reactive power droop coefficient; This indicates the reactive power reference value for the grid-type converter; For virtual voltage source phase values; Indicates the rated frequency; Active power-frequency coefficient; This indicates the active power reference value for the grid converter.

[0125] Step S325: Based on the phase and amplitude values ​​generated by the virtual voltage source, perform pre-synchronization control with the current operating state of the grid-connected mode to eliminate the phase angle difference and voltage difference at the moment of mode switching;

[0126] The pre-synchronization control includes two processes: phase pre-alignment and amplitude pre-matching, as detailed below:

[0127] Phase pre-alignment:

[0128] Obtain the first phase angle output by the phase-locked loop control. The second phase angle output by the network configuration control loop At this point, there is a certain difference in the phase angles generated by the two control methods; that is, the phase angle difference between the first phase angle and the second phase angle is calculated. ;

[0129] The phase angle difference is input into the PI controller to obtain the phase compensation amount, and the phase compensation amount is fed back to the meshing mode control loop to adjust the phase output of the meshing mode control loop, thereby eliminating the phase angle difference that may occur during the flower cutting process.

[0130] The PI controller is derived from a set of PI controllers included in the GFM voltage control module.

[0131] Amplitude pre-matching:

[0132] Since the GFM voltage control module also includes a set of PI regulators, it is difficult to guarantee consistency before and after switching the converter control mode directly. Therefore, it is necessary to calculate the voltage components of the power grid. Grid voltage reference value during grid-following mode control operation Calculate the voltage difference between the voltage components of the power grid and the reference voltage value of the power grid. ;

[0133] The voltage difference is input into the PI regulator to obtain the voltage compensation amount, and the voltage compensation amount is fed back to the grid mode control loop to adjust the voltage amplitude output of the grid mode control loop, thereby achieving smooth switching of the port voltage.

[0134] In summary, to achieve smooth switching of converter control modes, the core lies in utilizing a PI controller to proactively adjust the internal state of the grid-type control loop to be taken over before switching. Through phase pre-alignment and amplitude pre-matching mechanisms, the grid-type control loop synchronizes its phase angle and voltage amplitude to the stable operating point corresponding to the current grid-type operation in the background. When the actual switching occurs, since the grid-type control loop has pre-established correct phase and voltage control references, the switching process can achieve a bumpless transition, thereby effectively eliminating phase angle and voltage differences at the moment of switching, and significantly reducing or even eliminating phase angle abrupt changes and voltage fluctuations.

[0135] Step S326: After the pre-synchronization control is completed, the grid-connected converter controlled by constant power will be switched to virtual synchronous machine control with virtual voltage as the core, thereby smoothly completing the transition to the grid-connected mode.

[0136] In addition, dynamic hysteresis control is introduced during the process of judging the disturbance level of the power grid and initiating a smooth switching. The hysteresis width of the mode switching is adaptively adjusted according to the risk index calculated in real time to prevent frequent mode switching and optimize switching stability.

[0137] Specifically, circuit information of the grid-connected converter is collected before switching; the collected circuit information includes the voltage V, current i, and time t of the grid-connected converter before switching.

[0138] Based on the collected circuit information, the risk index R of the power grid is calculated. This risk index R is used to assess the current stability of the power grid, and it is mainly divided into two types of risks: voltage collapse risk and frequency collapse risk, and their expressions are as follows:

[0139] (11)

[0140] (12)

[0141] in, Indicates the risk of voltage collapse; V represents the voltage of the grid-connected converter; Indicates a reference value for the mains voltage; This indicates a risk of frequency collapse; This indicates the frequency of the power grid being monitored in real time. This indicates the rated frequency of the power grid.

[0142] According to formulas (11) and (12), 0.1pu is a preset voltage deviation threshold, which means that when the voltage deviation is less than or equal to this value, the system voltage is considered stable. Similarly, 0.5Hz is a preset frequency deviation threshold, which means that when the frequency deviation is less than or equal to this value, the system frequency is considered stable.

[0143] Based on the overall risk index R ( + ), dynamically adjust the hysteresis width H(t) of the mode switching judgment link during the smooth switching process;

[0144] The dynamic adjustment of the hysteresis width H(t) must meet the following conditions:

[0145] (13)

[0146] in, H represents the hysteresis width; R represents the initial hysteresis width; A represents the hazard index; B represents the loop expansion gain; and C represents the loop contraction gain.

[0147] According to formula (13), when the total risk index R is greater than 0.25, the system is considered to be in the fault expansion condition, and the hysteresis width needs to be expanded to enhance the stability of the system; when the total risk index R is less than or equal to 0.25, the system is considered to be in the stable shrinkage condition, and the hysteresis width can be reduced to improve the response speed of the system.

[0148] It should be noted that, see Figure 3 In the process of optimizing the extended-loop gain, contracted-loop gain, and risk index factor using the Black Swan (BSA) algorithm, the optimization goal is to improve the dynamic performance of the switching process, specifically in terms of voltage overshoot. and recovery stabilization time Therefore, the optimization process is actually about finding an optimal set of hysteresis widths and risk indices that maximizes these two performance metrics.

[0149] This voltage overshoot and recovery stabilization time The minimization process includes:

[0150] Initialize a particle swarm, where each particle swarm represents a parameter combination to be optimized, X=[A, B, c]. At the same time, construct a disturbance scenario library for various typical power grid disturbances; where A represents the expanding loop gain; B represents the shrinking loop gain; and c represents the risk index factor.

[0151] Based on a perturbation scenario library, iterative optimization of the Black Swan algorithm is performed:

[0152] (1) For each parameter combination X in the current particle swarm, simulate the switching process in the perturbation scenario library;

[0153] (2) Calculate the voltage overshoot corresponding to the set of parameters based on the dynamic response curve obtained from the simulation. With time to recovery and stabilization ;

[0154] (3) Construct a multi-objective fitness function F(X) and calculate the fitness value of each particle;

[0155] Specifically, this multi-objective fitness function combines the above two performance metrics ( and The fitness function F(X) is synthesized into a single scalar to evaluate the merits of each parameter combination X. The multi-objective fitness function F(X) is defined as follows:

[0156] ;

[0157] In the formula, and It refers to the voltage overshoot and recovery time obtained by simulation or actual measurement under the parameter combination X (hysteresis width, risk index coefficient). and These are weighting coefficients used to balance the importance of the two optimization objectives.

[0158] (4) Based on the fitness value of the particles, update the individual optimal solution of each particle and the global optimal solution of the entire population;

[0159] (5) According to the iteration rules of the Black Swan algorithm, update the position and velocity of each particle in the entire particle swarm, thereby generating a new generation of particle swarm;

[0160] (6) Repeat steps (1) to (5) until the algorithm converges and outputs a set of optimal controller parameters.

[0161] Finally, see Figure 2During the actual operation of the inverter, real-time circuit data (voltage, current, frequency, etc.) is continuously collected, and the real-time risk index R is calculated. If the real-time risk index R does not exceed the set safety threshold, the current optimal controller parameters continue to be used. If the real-time risk index R exceeds the safety threshold, it indicates that the power grid system has exceeded the typical scenario of online rolling optimization, and the Black Swan (BSA) fine-tuning mechanism is activated. This mechanism uses the current optimal controller parameters as the starting point and performs a local, fast particle swarm optimization based on the latest real-time data to quickly find new parameters that are more suitable for the current operating conditions. Subsequently, the power grid system updates the controller parameters to the results of this fine-tuning.

[0162] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. An adaptive switching method for supporting grid-type converter network configuration modes, characterized in that, include: Obtain the rated parameters and circuit information of the grid-connected converter; Based on the circuit information, the disturbance level of the power grid is determined. The process of determining the disturbance level includes: Based on the circuit information, calculate the voltage and frequency changes of the power grid; Disturbance levels are classified according to the deviation range of voltage and frequency from their reference values, and the disturbance levels meet the following conditions: No disturbance: and ; For small perturbations: or ; During large disturbances: or ; Where V represents the voltage of the grid-connected converter; Indicates a reference value for the mains voltage; Indicates the real-time detected power grid frequency; Indicates the rated frequency of the power grid; Based on the disturbance level, determine whether to initiate converter control mode switching: if the disturbance level is no disturbance or a small disturbance, maintain the grid-connected converter's grid-connected mode; if the disturbance level is a large disturbance, determine whether the grid-connected converter has spare capacity; wherein, the process of determining whether the grid-connected converter has spare capacity includes: Based on the rated parameters and circuit information, calculate the power margin and current margin of the grid-connected converter; Based on the power margin and current margin, it is determined whether the grid-connected converter has spare capacity. If both the power margin and current margin are greater than the preset margin threshold, the grid-connected converter has spare capacity and a smooth switch to grid-connected mode is initiated; otherwise, the grid-connected mode is maintained.

2. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 1, characterized in that, The expressions for the power margin and current margin of the grid-connected converter are as follows: Power margin: ； ； in, Indicates active power margin; This indicates the active power output during grid-connected operation. Indicates the rated active power; Indicates reactive power margin; This indicates the reactive power during grid-connected operation. Indicates the rated reactive power; Current margin: ； in, Indicates current margin; Indicates the maximum allowable current; This represents the current flowing through the converter.

3. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 1, characterized in that, The smooth transition from startup to network construction mode includes: When a large disturbance is detected and the grid-connected converter has spare capacity, the grid-connected converter smoothly switches the grid mode through a hierarchical phase amplitude control loop, resulting in a grid mode that switches from constant power control to virtual synchronous machine control.

4. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 3, characterized in that, The smooth switching of network configuration modes through the hierarchical phase amplitude control stage includes: The grid-type converter receives a switching mode command triggered by the disturbance level and margin judgment results; According to the switching mode command, the phase-locked loop control of the grid-connected converter is released to break away from the tracking of the grid phase; After the grid phase is disconnected from tracking, the active / reactive power value is reduced from the rated active / reactive power value before the switch according to the preset slope steepness to obtain the reduced active / reactive power reference value. Based on the reduced active / reactive power reference values, a virtual voltage source capable of automatically generating phase and amplitude is constructed. The phase and amplitude generated by the virtual voltage source are used as a reference, and pre-synchronization control is performed with the current operating state of the grid-connected mode to eliminate the phase angle difference and voltage difference at the moment of mode switching. Once the pre-synchronization control is completed, the grid-connected converter controlled by constant power is switched to virtual synchronous machine control with the virtual voltage as the core, thereby smoothly completing the transition to the grid-connected mode.

5. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 4, characterized in that, The expression for the reduced active / reactive power reference value is: ； ； in, This represents the reference value of the active power of the grid-connected converter at time t. Indicates the rated active power; Indicates the steepness of the slope; Indicates time; This represents the reference value of reactive power of the grid-connected converter at time t; This indicates the rated reactive power.

6. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 4, characterized in that, The phase and amplitude expressions generated by the virtual voltage source are as follows: ； ； in, The amplitude of the virtual voltage source; Indicates the grid voltage before the switch; Indicates the reactive power droop coefficient; This indicates the reactive power reference value for the grid-type converter; Indicates the rated reactive power; For virtual voltage source phase values; Indicates the rated frequency; Active power-frequency coefficient; This indicates the active power reference value for the grid-type converter; This indicates the rated active power.

7. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 4, characterized in that, The elimination of phase angle difference and voltage difference at the moment of mode switching includes: Obtain the first phase angle output by the phase-locked loop control and the second phase angle output by the network configuration mode control loop, and calculate the phase angle difference between the first phase angle and the second phase angle; The phase angle difference is input into the PI controller to obtain the phase compensation amount, and the phase compensation amount is fed back to the network configuration mode control loop to adjust the phase output of the network configuration mode control loop; Obtain the voltage component of the power grid and the reference value of the power grid voltage during grid-following mode control operation, and calculate the voltage difference between the voltage component of the power grid and the reference value of the power grid voltage; The voltage difference is input to the PI regulator to obtain the voltage compensation amount, and the voltage compensation amount is fed back to the network mode control loop to adjust the voltage amplitude output of the network mode control loop. Based on the adjusted phase output and voltage amplitude output, the phase angle difference and voltage difference at the moment of converter control mode switching are eliminated.

8. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 1, characterized in that, Also includes: Obtain the circuit information of the grid-connected converter after the switching is completed; Determine whether the difference in circuit information after the switch is completed within a preset time is within a preset safety range: If the change is within the safe range, the switch is considered successful and the grid connection mode is maintained; if the change difference exceeds the preset safe range, the converter control mode is forcibly restored to the grid connection mode.

9. The adaptive switching method for grid-connected converters supporting grid configuration modes according to claim 3, characterized in that, The smooth transition to network construction mode during startup also includes: The circuit information of the grid-connected converter is collected before switching. Based on the collected circuit information, the risk index R of the power grid is calculated; Based on the risk index R, the hysteresis width H(t) of the mode switching judgment step during the smooth switching process is dynamically adjusted. The dynamic adjustment of the hysteresis width H(t) satisfies the following condition: ； in, H represents the hysteresis width; R represents the initial hysteresis width; A represents the hazard index; B represents the loop expansion gain; and C represents the loop contraction gain. The Black Swan algorithm is used to optimize the expanding loop gain, shrinking loop gain, and risk index factor to obtain a set of optimal hysteresis widths and risk indices.

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