Self-adaptive switching control method and system for network construction type converter based on fault identification

Abstract

The invention belongs to the technical field of power supply, and discloses a fault identification-based self-adaptive switching control method and system for a network-building converter, and the method comprises the following steps: S1, carrying out the online identification of the dominant features of a transient fault; s2, selecting a dominant support strategy so as to switch the converter to an operation mode matched with the dominant support strategy; s3, providing optimal support for the transient process; and S4, after the transient fault is cleared, the converter is switched to a conventional operation mode, the system comprises a transient feature identification module, a self-adaptive strategy selection and recombination module and a safe switching and recovery module, and the method has the following beneficial effects: 1, the transient fault response accuracy is improved; 2, the control continuity and safety are guaranteed; and 3, the recovery process is safer and more reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, in particular to a grid-forming converter adaptive switching control method and system based on fault identification. BACKGROUND

[0002] As a key technical equipment to support future power grids, the behavior characteristics of grid-forming (GFM) converters in transient processes directly determine their transient current-carrying capacity, terminal voltage stability level, device operation safety, and support efficiency for power grids. Due to the variable combination of power grid operation modes and the complex and diverse system faults, when a serious power grid fault occurs, the consequences have multi-dimensional characteristics, which are specifically manifested as: it may cause power angle instability or frequency problems due to power imbalance, or it may lead to voltage drop or even collapse due to insufficient reactive power support.

[0003] Since the overcurrent capacity of the GFM converter is much lower than that of the synchronous compensator, in order to avoid damage to the semiconductor devices, the GFM converter needs to implement reactive power priority or active power priority control during a fault to achieve overall current limiting of the current flowing through the semiconductor devices of the converter. In the traditional GFM control strategy, the parameters and priorities of the internal active power-frequency control loop (P-f, used to simulate the inertia of the power grid and provide power angle damping characteristics) and the reactive power-voltage control loop (Q-V, determines the voltage support capability) are usually pre-set and fixed. This fixed "one-size-fits-all" control method lacks robustness in complex transient processes (i.e., it cannot adapt to complex and variable fault scenarios) - it cannot distinguish the current main contradiction, leading to a response behavior that is "off the mark": when the system is on the verge of voltage collapse and urgently needs strong reactive current support to maintain voltage, the controller may still respond to the small frequency deviation, using valuable current capacity to adjust active power, thus missing the best opportunity to support voltage; when the system has severe power angle oscillation and urgently needs strong power angle damping to suppress oscillation, the controller may excessively participate in reactive power regulation and fail to provide critical active power support to suppress oscillation.

[0004] This "mismatch" between the control strategy and the transient demand is the fundamental reason why the transient performance of existing GFM converters cannot reach the theoretical optimum. Therefore, there is an urgent need in the art for a new control method - one that can give the GFM converter "situational awareness" (real-time identification of fault dominant characteristics) and "targeted switching" (directly adjusting the support strategy) capabilities, enabling it to intelligently and adaptively adjust the support strategy during the transient process to match the core needs of different fault scenarios. SUMMARY

[0005] To solve the above problems, the present application provides a grid-forming converter adaptive switching control method and system based on fault identification, which is realized by the following technical scheme.

[0006] A network configuration type converter adaptive switching control method based on fault identification, comprising the following steps: S1, when a transient fault occurs in the power grid to which the converter is connected, real-time acquisition of electrical quantity measurement values at the grid connection point of the converter is performed, and based on the electrical quantity measurement values, dominant characteristics of the transient fault are identified online; S2, according to the dominant characteristics of the transient fault, a dominant support strategy is selected, and the internal control parameters and / or logic of the network configuration type controller of the converter are adjusted to switch the converter to an operating mode matched with the dominant support strategy; S3, closed-loop control is performed according to the adjusted controller to provide optimal support for the transient process, wherein the transient process refers to the process of switching the converter to the operating mode matched with the dominant support strategy; S4, after the transient fault is cleared, the converter is switched to a normal operating mode.

[0007] As a further scheme of the present application, in the step S1, the identification method of the dominant characteristics of the transient fault is: a state phase plane composed of electrical quantity measurement values is constructed in real time; the form feature of the state trajectory of the converter during the transient fault in the state phase plane is analyzed; based on the analysis of the form feature, the dominant characteristics are identified, including a power angle instability dominant type or a voltage collapse dominant type.

[0008] As a further scheme of the present application, the state phase plane includes a V-Q phase plane and a f-P phase plane; and the identification method of the dominant characteristics is: if the state trajectory presents a “falling” form in the V-Q phase plane, the dominant characteristics are the voltage collapse dominant type; if the state trajectory presents a ring or spiral form in the f-P phase plane, the dominant characteristics are the power angle instability dominant type; wherein V is a voltage measurement value; Q is a reactive power measurement value; f is a frequency measurement value; and P is an active power measurement value.

[0009] As a further scheme of the present application, in the step S2, the selection method of the dominant support strategy is: if the identified dominant characteristics are the power angle instability dominant type, a frequency dominant support strategy is selected, and the controller is adjusted to enter a frequency dominant support mode, wherein the frequency dominant support mode of the controller is specifically: increasing the dynamic response gain and / or bandwidth of the active power control loop in the controller, and / or giving a higher allocation priority to the active current component; If the identified dominant characteristic is voltage collapse-dominant, then a voltage-dominant support strategy is selected, and the controller is adjusted to enter the voltage-dominant support mode. Specifically, the voltage-dominant support mode of the controller is to increase the dynamic response gain and / or bandwidth of the reactive power control loop in the controller, and / or assign a higher allocation priority to the reactive current component.

[0010] As a further aspect of the present invention, increasing the dynamic response gain of the active power control loop in the controller specifically involves increasing the proportional gain of the power synchronization loop in the controller, i.e., increasing... The value of D is determined by increasing the active power loop response, i.e., increasing the value of D; the value of D is determined by decreasing the reactive power loop response, i.e., decreasing the reactive power loop response. The possible values ​​of ; in fP is the droop coefficient; D is the active power loop damping coefficient. VQ droop coefficient; Increasing the dynamic response gain of the reactive power control loop in the controller specifically involves: reducing... The value of D; decrease the value of D; increase the value of D. The value of .

[0011] As a further aspect of the present invention, in step S2, when adjusting the internal control parameters and / or logic of the grid-type controller of the converter, a disturbance-free switching technique is adopted to reinitialize the state of the integrator inside the controller at the moment of switching, so as to ensure the continuity of the controller output signal.

[0012] As a further embodiment of the present invention, in step S4, after the transient fault is cleared, the state trajectory in the state phase plane is continuously monitored; when the state trajectory converges to a preset stable region in the state phase plane and remains there for a preset time, the collaborative recovery program is started to restore the internal control parameters and / or logic of the controller to the normal operating mode.

[0013] An adaptive switching control system for a grid-type converter based on fault identification includes: The transient feature identification module is used to acquire electrical quantity measurement values ​​at the grid connection point in real time when a transient fault occurs in the power grid, and to identify the dominant features of the transient fault online based on the morphological characteristics of the state trajectory of the electrical quantity measurement values ​​in a specific state phase plane. The adaptive strategy selection and reconfiguration module is used to adaptively select the dominant support strategy based on the dominant characteristics of transient faults, and generate corresponding control parameters and / or logic adjustment instructions to switch the grid-type controller of the converter to an operating mode that matches the dominant support strategy. The safety switching and recovery module is used to execute adjustment commands to adjust the controller, and after the transient fault is cleared, restore the controller to the normal operating mode according to the preset collaborative recovery program.

[0014] An electronic device comprises a processor, a communication interface, a memory and a communication bus, the processor, the communication interface and the memory complete communication among each other through the communication bus; the memory is used for storing a computer program; when the processor executes the computer program stored on the memory, a fault identification-based adaptive switching control method of a network-forming converter is realized.

[0015] A computer readable storage medium, the computer readable storage medium has a computer program stored therein, the computer program is executed by a processor to realize a fault identification-based adaptive switching control method of a network-forming converter.

[0016] The beneficial effects of the present application are as follows: 1. By constructing a state phase plane, the morphological characteristics of the converter state trajectory are analyzed in real time, the dominant fault characteristics are accurately identified, and according to the identification result, the dominant support strategy is adaptively selected, so as to dynamically adjust the controller parameters and / or logic, and improve the accuracy of transient fault response.

[0017] 2. At the moment of mode switching, the controller integrator state is reinitialized by non-disturbance switching technology, ensuring the continuity and safety of control.

[0018] 3. After the transient fault is cleared, when the state trajectory converges to the preset stable region in the state phase plane and lasts for a preset time, a cooperative recovery program is started to restore the internal control parameters and / or logic of the controller to the normal operation mode, making the recovery process more safe and reliable. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed in the specific implementation manner. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 : The overall function block diagram of the control system of the present application; Figure 2 : Schematic diagram of falling trajectory; Figure 3 : Schematic diagram of ring trajectory; Figure 4 : Logic block diagram of adaptive strategy selection and recombination module of the present application; Figure 5 : Logic flow chart of safety switching and recovery module of the present application; Figure 6 : Schematic diagram of spiral trajectory. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0022] A network configuration type converter adaptive switching control method based on fault identification, comprising the following steps: S1, as shown in the figure, when a transient fault occurs in the power grid to which the converter is connected, the electrical quantity measurement value of the grid connection point of the converter is obtained in real time, and the dominant feature of the transient fault is identified online based on the electrical quantity measurement value. Figure 1

[0023] The identification method of the dominant feature of the transient fault is: a state phase plane composed of the electrical quantity measurement value is constructed in real time; the form feature of the state trajectory of the converter during the transient fault in the state phase plane is analyzed; based on the analysis of the form feature, the dominant feature is identified, and the dominant feature includes a power angle instability dominant type or a voltage collapse dominant type.

[0024] The state phase plane includes a V-Q phase plane and a f-P phase plane; the identification method of the dominant feature is: if the state trajectory presents a "falling type" form in the V-Q phase plane, the dominant feature is the voltage collapse dominant type; if the state trajectory presents a ring or spiral shape in the f-P phase plane, the dominant feature is the power angle instability dominant type; wherein V is the voltage measurement value; Q is the reactive power measurement value; f is the frequency measurement value; and P is the active power measurement value.

[0025] S2, according to the dominant feature of the transient fault, a dominant support strategy is selected, and the internal control parameters and / or logic of the network configuration type controller of the converter are adjusted to switch the converter to the operation mode matched with the dominant support strategy.

[0026] The selection method of the dominant support strategy is: if the identified dominant feature is the power angle instability dominant type, a frequency dominant support strategy is selected, and the controller enters a frequency dominant support mode, and the frequency dominant support mode of the controller is specifically: increasing the dynamic response gain and / or bandwidth of the active power control loop in the controller, and / or giving the active current component a higher distribution priority; ​If the identified dominant feature is voltage collapse dominant type, a voltage dominant support strategy is selected, and the controller is adjusted to enter the voltage dominant support mode. The voltage dominant support mode of the controller is specifically: increasing the dynamic response gain and / or bandwidth of the reactive power control loop in the controller, and / or giving the reactive current component a higher allocation priority.

[0027] Increasing the dynamic response gain of the active power control loop in the controller is specifically: increasing the proportional gain of the power synchronization ring in the controller, that is, increasing the value of Kp; increasing the active ring response, that is, increasing the value of D; reducing the reactive ring response, that is, reducing the value of D. Wherein is the f-P droop coefficient; D is the active ring damping coefficient; is the V-Q droop coefficient; Increasing the dynamic response gain of the reactive power control loop in the controller is specifically: reducing the value of Kp; reducing the value of D; increasing the value of D.

[0028] When adjusting the internal control parameters and / or logic of the grid-forming controller of the converter, a disturbance-free switching technology is adopted to re-initialize the integrator state inside the controller at the switching moment, so as to ensure the continuity of the controller output signal.

[0029] S3, closed-loop control is performed according to the adjusted controller to provide optimal support for the transient process, wherein the transient process refers to the process of switching the converter to the operation mode matched with the dominant support strategy; S4, after the transient fault is cleared, the converter is switched to the normal operation mode.

[0030] After the transient fault is cleared, the state trajectory in the state phase plane is continuously monitored; when the state trajectory converges to a preset stable region in the state phase plane and lasts for a preset time, a collaborative recovery program is started to restore the internal control parameters and / or logic of the controller to the normal operation mode.

[0031] A grid-forming converter adaptive switching control system based on fault identification, comprising: A transient feature identification module is configured to, when a transient fault occurs in a power grid, acquire electrical quantity measurement values of a grid-connected point in real time, and identify the dominant feature of the transient fault based on the morphological features of the state trajectory of the electrical quantity measurement values in a specific state phase plane.

[0032] 1. Implementation process of the transient feature identification module 1.1 Data acquisition and state phase plane construction ​​​​Data source and sampling rate: The controller collects the three-phase voltage ( ) and three-phase current ( ) at the output of the converter in real time through its analog-to-digital converter (ADC) at a sampling rate of no less than 20 kHz (the switching frequency of the GFM converter is usually 2-10 kHz, and a sampling rate of 20 kHz is more than twice the switching frequency, which can avoid transient signal aliasing and ensure that transient electrical quantities are collected without distortion).

[0033] Coordinate transformation and filtering: A high-bandwidth phase-locked loop (PLL) is used to track the phase angle θ and angular frequency ω of the grid point (PCC) voltage in real time.

[0034] Through Park transformation, ( ) and ( ) are converted to ( , ) and ( ) in the synchronous rotating coordinate system (d-q coordinate system), the d-axis (direct axis) in the d-q coordinate system aligns with the direction of the grid voltage vector, and the q-axis (quadrature axis) lags the d-axis by 90 degrees, the d-component ( ) represents the active part, and the q-component ( ) represents the reactive part, and the specific formula of Park transformation is as follows:

[0035]

[0036] Where:

[0037]

[0038] Based on the calculated ( , ) and ( ), the active power and the reactive power are calculated in real time.

[0039] To suppress high-frequency noise, all calculated electrical quantities are filtered through a filter with a cutoff frequency of 100 Hz before being used for identification, and the filter is a "second-order Butterworth low-pass filter".

[0040] Where the actual voltage amplitude of the grid point (PCC) is calculated as:

[0041] V is the "line voltage / phase voltage effective value amplitude" commonly said in power systems, usually in "p.u.(per unit)" or "kV", which is the core index reflecting the voltage level of the power grid. V is the basis for subsequent construction of "V-Q phase plane" (used for identifying voltage collapse faults), judgment of voltage drop (such as the pre-warning threshold of "V_pre_alert_th=0.85 p.u.").

[0042] Phase plane construction: the controller opens two buffer zones in memory, respectively for storing the V-Q state pairs (V[k], Q[k]) and f-P state pairs (f[k], P[k]) of the last N sampling points (where f=ω / 2π). These two buffer zones constitute the data basis for trajectory morphology analysis, where N=2000 (corresponding to a 100 ms data window, covering the complete transient process of typical grid faults (100 ms), ensuring that there is no omission in trajectory morphology analysis).

[0043] 1.2 Quantitative identification criteria and algorithm implementation based on "trajectory morphology" As shown in Figure 2 , voltage collapse dominant feature identification ("drop type" trajectory) Core criterion: when the last N_confirm_V sampling points simultaneously satisfy V<V_pre_alert_th and v_r_avg<v_th, it is determined to be voltage collapse dominant.

[0044] For example, if v_r_avg is lower than -0.5 p.u. / ms in the last 50 points and V<0.85 p.u., it is determined to be voltage collapse dominant.

[0045] Quantitative index: sliding average of radial velocity of V-Q plane state point v_r_avg.

[0046] At each control period k, calculate the instantaneous radial position: .

[0047] Calculate the instantaneous radial velocity: , is the control period.

[0048] Calculate the sliding average of v_r[k] in the last M sampling points (e.g. M=20, corresponding to 1 ms) to filter out transient disturbances.

[0049] Parameter setting example: V_pre_alert_th (voltage pre-warning threshold): 0.85 p.u. (indicating that the voltage has deviated significantly from the normal range).

[0050] - v_th (radial velocity threshold): -0.5 p.u. / ms (indicating that the voltage drop speed is extremely fast).

[0051] N_confirm_V (confirmation count): 50 (corresponding to 2.5 ms of continuous deterioration to avoid misjudgment).

[0052] As shown in Figure 3 and Figure 6 , the dominant feature of angle instability recognition ("circular / spiral" trajectory) Core criterion: the state point (f[k], P[k]) in the f-P phase plane exhibits periodic reciprocating movement (circular trajectory), and the frequency deviation peak of adjacent oscillation periods does not decrease (amplitude does not attenuate), or even increases (divergent spiral trajectory) - this feature corresponds to continuous fluctuations in the power angle difference of the power grid, which will lead to power angle instability (such as converter off-grid) if not intervened.

[0053] Quantitative indicators: Core indicator 1: frequency of zero-crossing events of f-P plane state point speed deviation (reflecting the persistence of oscillation); Core indicator 2: trend of frequency deviation peak in each half cycle (reflecting whether the amplitude is attenuated).

[0054] ① Calculate the frequency deviation First, the actual frequency f[k] of the power grid is derived based on the voltage phase angle 0 of the grid connection point (PCC) (f[k]=w[k] / 2π, where w[k]=d0[k] / dt is the angular frequency, which is tracked in real time by a phase-locked loop (PLL)); Then calculate the frequency deviation: .

[0055] In the formula: is the frequency deviation of the kth control period (unit: Hz); is the rated frequency of the power grid (such as the power frequency of 50 Hz in China, with a default value of 50 Hz); is the actual frequency of the power grid in the kth control period (unit: Hz).

[0056] ②Detect the frequency deviation zero-crossing event The zero-crossing event is defined as "the signs of the frequency deviations of two consecutive control periods are opposite", that is, it satisfies: ; Anti-shake processing: to avoid false detection caused by high-frequency noise, the sign change must be detected in two consecutive control periods (sampling rate > 20 kHz, corresponding to ≤0.1 ms) to determine 1 valid zero-crossing event; Half-cycle division: take the "effective zero-crossing event" as the boundary, the time interval between two adjacent zero-crossing events is defined as a "half-cycle". If the previous zero-crossing event is "△f from positive to negative", then this half-cycle is "negative half-cycle" (△f is negative); if the previous zero-crossing event is "△f from negative to positive", then this half-cycle is "positive half-cycle" (△f is positive).

[0057] ③Record the frequency deviation peak value Peak_f in the half-cycle From the moment of the first effective zero-crossing event (denoted as k0) to the moment of the next effective zero-crossing event (denoted as k1), in this half-cycle (ke∈[k0,k1]), the absolute value maximum of is tracked in real time, denoted as the frequency deviation peak value Peak_f of this half-cycle.

[0058] Compare the peak value Peak_f[n] of the current half-cycle with the peak value Peak_f[n-1] of the previous half-cycle.

[0059] Parameter setting example: Peak_f_th (frequency deviation peak threshold value): 0.5 Hz (indicating that the oscillation amplitude is already very large).

[0060] N_confirm_F_persist (confirmation number of persistent oscillation): 3 (detecting 3 consecutive half-waves of large amplitude oscillation), if Peak_f> Peak_f_th, then it indicates that this half-cycle belongs to the half-wave of large amplitude oscillation.

[0061] N_confirm_F_div (confirmation number of divergent oscillation): 2 (detecting 2 consecutive half-waves of increasing amplitude), if Peak_f[n]-Peak_f[n-1]>0, then it indicates that this half-cycle belongs to divergent oscillation.

[0062] Decision logic: in a fault process, the above two discriminators run in parallel. The fault type corresponding to the first triggered discriminator is determined as the current dominant feature. Once determined, the diagnosis result will be locked until the end of the whole transient process and enters the recovery stage, to avoid frequent mode switching due to the interweaving of the two phenomena in the process.

[0063] Adaptive strategy selection and reorganization module, for adaptively selecting the dominant support strategy according to the dominant feature of the transient fault, and generating corresponding control parameters and / or logic adjustment instructions, to switch the network configuration controller of the converter to the operation mode matched with the dominant support strategy.

[0064] 2. Detailed implementation of the dominant support function dynamic reorganization module Detailed description of the switching process As​Figure 4 is shown.

[0065] Switch to frequency dominant support mode (F-Support): Call the seamless switching procedure: Firstly, switch from 0.08 p.u. / Hz to 0.2 p.u. / Hz, and then switch from 0.2 p.u. / Hz to 0.4 p.u. / Hz; Switch from 1.0 to 3.0, where is the per-unit value based on rated power; Reduce the PI gain of the reactive power loop, i.e. reduce the value of from 8.0 p.u. / kV to 4.0 p.u. / kV; Send a flag to the current loop to enable the "d-axis priority" current limiting logic. This means that even if the voltage deviates, the controller will prioritize the output of the active current that stabilizes the power angle, and only use the "surplus" to support the voltage.

[0066] The specific meaning of the "d-axis priority" current limiting logic is that the output current of the converter is limited by the overcurrent capability of the semiconductor devices (such as the maximum current is 1.5 times the rated current I rated ), and "d-axis priority" means that the output of the d-axis current (active component) is prioritized under the premise that the total current amplitude does not exceed the limit, and the specific logic is as follows: 1. Current limit constraint: ( is the maximum allowed current of the converter); 2. Priority processing: when the active command increases to increase the demand, which may cause the total current to approach , the controller will: prioritize the command value of (ensure active power output, stabilize frequency and power angle).

[0067] limit the increase of (even if the voltage deviation still needs reactive power support, the command value of will be reduced).

[0068] Switch to voltage dominant support mode (V-Support): Call the seamless switching procedure: Firstly, ​Switch from 0.08 p.u. / Hz to 0.02 p.u. / Hz - this adjustment can reduce the active loop's response sensitivity to frequency deviation by 75%, equivalent to increasing the GFM power inertia to 4 times the normal value, making it relatively sluggish to transient power oscillation; meanwhile, the 0.02 p.u. / Hz Active support ≥ 0.01 p.u. can be provided when the frequency deviation ≤ 0.5 Hz to avoid frequency collapse, thus ensuring the basic stability of the grid frequency while "giving up control ability and current capacity to voltage control"; Switch from 3.0 to 1.0, where is the rated power-based per-unit value; Switch from 3.0 to 1.0, where is the rated power-based per-unit value; Increase the PI gain of the reactive loop, i.e., increase the value of from 4.0 p.u. / kV to 8.0 p.u. / kV.

[0069] Send a flag bit to the current loop to enable "q-axis priority" logic, and the converter will try to (even temporarily reduce active output) to prioritize the reactive current command required to support voltage.

[0070] The meaning of "q-axis priority" logic is: contrary to "d-axis priority", "q-axis priority" is to prioritize the output of q-axis current (reactive component) under the premise that the total current amplitude does not exceed the limit value, the specific logic is as follows: 1. Current limit constraint: ; 2. Priority processing: when the active command increases, causing demand to increase, which may cause the total current to approach , the controller will: Prioritize the command value of (ensure reactive output, support grid point voltage).

[0071] Limit the increase of (decrease the command value of ).

[0072] The safety switching and recovery module is used to execute adjustment instructions to adjust the controller, and after the transient fault is cleared, the controller is restored to the normal operation mode according to the preset coordinated recovery program.

[0073] 3. Detailed implementation of the safety switching and coordinated recovery module as shown in Figure 5 .

[0074] 3.1 Activation mechanism Primary trigger (fast response): based on traditional fault signature detection, i.e. current amplitude out of limit (I_mag > 1.1 p.u.) or ROCOA out of limit (|ROCOA| > 8 rad / s). This trigger initiates the parallel recognition procedure of TSI module immediately.

[0075] Secondary confirmation (precise activation): only when TSI module explicitly outputs a non-“normal” diagnosis result (i.e. one of “power angle instability” or “voltage collapse”) within a preset recognition window (e.g. 40 ms), the mode switching of SODS module will be finally executed. This “secondary confirmation” mechanism effectively prevents unnecessary mode switching for small disturbances which are self-recoverable and non-threatening, and may even deteriorate the control performance.

[0076] 3.2 Smooth switching execution At the moment of mode switching, i.e. parameters are switched to , the integrator state of the adjusted PI controller will be immediately recalculated and loaded:

[0077] where, is the new state of integrator; is the total output of controller at the moment before switching; is the new control parameter after switching; is the error signal at current time; this guarantees and absolute smoothness.

[0078] To achieve “smooth switching”, i.e. the controller output never experiences abrupt change at the moment of mode switching (from normal mode to transient mode, or vice versa), avoiding the jump of converter output power, voltage or current, and ensuring the safety of equipment and stability of power grid.

[0079] Specific logic derivation (combined with the principle of PI controller output): The output formula of PI controller is: (proportional term + integral term); Substitute formula into the above formula, we get: ; That is, the output u after switching is exactly equal to the output u at the moment before switching, realizing “zero jump” smooth switching.

[0080] 3.3 Adaptive exit recovery based on state convergence Exit Condition Judgment: After fault clearance, continuously monitor two conditions: 1. Trajectory Convergence: The state trajectory points in the VQ plane and fP plane must remain within a radius of [missing value] around the steady-state equilibrium point for N consecutive control cycles (e.g., N=5000, corresponding to 250ms). Within the "attraction domain". 2. Trigger reset: All primary trigger signals (current, ROCOA) have returned to normal. Co-fade-Out procedure: Once the exit condition is met, the controller does not use an instantaneous "shutdown" method, but instead starts a "co-fade-out" procedure. In the following T_fade time window (e.g., 300ms), all adjusted parameters ( , (PI gain, etc.) will gradually recover from the transient mode value to the normal mode value according to a smooth cosine function curve.

[0081]

[0082] in: For time The changing output value is used to smoothly adjust parameters during the transition period, avoiding system instability caused by sudden changes; This is the stable value (target value) under normal conditions, which is the normal value that the system ultimately needs to recover to; The initial value after a transient or disturbance indicates the temporary state of the system after being disturbed or malfunctioning, which needs to be gradually restored to normal. The total duration of the transition process controls the speed of the recovery process, ensuring that within time... A smooth transition is achieved within the system; Used for the current time. Dynamically calculate the transition progress within the scope; This is a transition factor used to generate a smooth curve from 1 to 0 over time. when At this time, the transition factor is 1. .

[0083] when At this time, the transition factor is 0. .

[0084] Nonlinear transitions are achieved using cosine functions to avoid the shocks that may be caused by linear switching.

[0085] Robustness: This kind of "state confirmation" based, rather than "fixed time delay", and "progressive, collaborative" exit mechanism, completely eliminate the risk of secondary oscillation may be caused by premature or too fast to remove the control support, to ensure the high robustness and safety of the control system.

[0086] An electronic device includes a processor, a communication interface, a memory and a communication bus, the processor, the communication interface and the memory complete the communication among each other through the communication bus; the memory is used for storing a computer program; when the processor executes the computer program stored on the memory, a network-forming type converter adaptive switching control method based on fault identification is realized.

[0087] A computer readable storage medium, the computer readable storage medium stores a computer program, the computer program is executed by a processor to realize a network-forming type converter adaptive switching control method based on fault identification.

[0088] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments. Obviously, many modifications and variations can be made according to the content of the specification. The specification selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application.

Claims

1. An adaptive switching control method for a grid-type converter based on fault identification, characterized in that, Includes the following steps: S1. When a transient fault occurs in the power grid to which the converter is connected, the electrical quantity measurement values ​​at the converter's grid connection point are acquired in real time, and the dominant characteristics of the transient fault are identified online based on the electrical quantity measurement values. S2, based on the dominant characteristics of the transient fault, select the dominant support strategy and adjust the internal control parameters and / or logic of the grid-type controller of the converter to switch the converter to an operating mode that matches the dominant support strategy; S3, perform closed-loop control based on the adjusted controller to provide optimal support for transient processes, where transient processes refer to the process by which the converter switches to an operating mode that matches the dominant support strategy; S4. After the transient fault is cleared, the converter is switched to normal operating mode.

2. The adaptive switching control method for a grid-type converter based on fault identification according to claim 1, characterized in that, In step S1, the method for identifying the dominant features of transient faults is as follows: Real-time construction of the state phase plane composed of electrical quantity measurements; Analyze the morphological characteristics of the converter's state trajectory in the state phase plane during transient faults; Based on the analysis of morphological characteristics, the dominant features are identified, including power angle instability-dominant type or voltage collapse-dominant type.

3. The adaptive switching control method for a grid-type converter based on fault identification according to claim 2, characterized in that, The state phase plane includes the VQ phase plane and the fP phase plane; The method for identifying dominant features is as follows: If the state trajectory exhibits a "drop-type" shape within the VQ phase plane, then the dominant characteristic is voltage collapse-dominated. If the state trajectory is circular or spiral in the fP phase plane, the dominant characteristic is power angle instability. Where V is the voltage measurement value; Q is the reactive power measurement value; f is the frequency measurement value; and P is the active power measurement value.

4. The adaptive switching control method for a grid-type converter based on fault identification according to claim 2, characterized in that, In step S2, the method for selecting the dominant support strategy is as follows: If the identified dominant characteristic is power angle instability, then select the frequency-dominant support strategy and adjust the controller to enter the frequency-dominant support mode. The frequency-dominant support mode of the controller is specifically: increase the dynamic response gain and / or bandwidth of the active power control loop in the controller, and / or give the active current component a higher allocation priority. If the identified dominant characteristic is voltage collapse-dominant, then a voltage-dominant support strategy is selected, and the controller is adjusted to enter the voltage-dominant support mode. Specifically, the voltage-dominant support mode of the controller is to increase the dynamic response gain and / or bandwidth of the reactive power control loop in the controller, and / or assign a higher allocation priority to the reactive current component.

5. The adaptive switching control method for a grid-type converter based on fault identification according to claim 4, characterized in that, Increasing the dynamic response gain of the active power control loop in the controller specifically involves increasing the proportional gain of the power synchronization loop in the controller, i.e., increasing... The value of D is determined by increasing the active power loop response, i.e., increasing the value of D; the value of D is determined by decreasing the reactive power loop response, i.e., decreasing the reactive power loop response. The possible values ​​of ; in fP is the droop coefficient; D is the active power loop damping coefficient. VQ droop coefficient; Increasing the dynamic response gain of the reactive power control loop in the controller specifically involves: reducing... The value of D; decrease the value of D; increase the value of D. The value of .

6. The adaptive switching control method for a grid-type converter based on fault identification according to claim 1, characterized in that, In step S2, when adjusting the internal control parameters and / or logic of the grid-type controller of the converter, a disturbance-free switching technique is adopted to reinitialize the state of the integrator inside the controller at the moment of switching, so as to ensure the continuity of the controller output signal.

7. The adaptive switching control method for a grid-type converter based on fault identification according to claim 3, characterized in that, In step S4, after the transient fault is cleared, the state trajectory in the state phase plane is continuously monitored; when the state trajectory converges to the preset stable region in the state phase plane and remains there for a preset time, the collaborative recovery program is started to restore the internal control parameters and / or logic of the controller to the normal operating mode.

8. A fault-identification-based adaptive switching control system for a grid-type converter, used to implement the method as described in any one of claims 1-7, characterized in that, include: The transient feature identification module is used to acquire electrical quantity measurement values ​​at the grid connection point in real time when a transient fault occurs in the power grid, and to identify the dominant features of the transient fault online based on the morphological characteristics of the state trajectory of the electrical quantity measurement values ​​in a specific state phase plane. The adaptive strategy selection and reconfiguration module is used to adaptively select the dominant support strategy based on the dominant characteristics of transient faults, and generate corresponding control parameters and / or logic adjustment instructions to switch the grid-type controller of the converter to an operating mode that matches the dominant support strategy. The safety switching and recovery module is used to execute adjustment commands to adjust the controller, and after the transient fault is cleared, restore the controller to the normal operating mode according to the preset collaborative recovery program.

9. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other through the communication bus. The memory is used to store computer programs. When the processor executes the computer program stored in the memory, it implements the method described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method described in any one of claims 1-7.

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