Three-order VSG voltage active support method and system based on current differential feedforward

Abstract

The application discloses a third-order VSG voltage active support method and system based on current differential feedforward, and the method comprises the following steps: constructing a third-order VSG voltage control mathematical model of an adaptive grid-connected converter; analyzing the armature demagnetization effect of the sharp increase of direct-axis current on internal potential and the limitation of voltage support under the grid fault transient state; introducing a feedforward compensation control strategy based on the differential of direct-axis current to simulate the Lenzie law effect of the damping winding; under the complete compensation state, establishing a closed-loop transfer function between the transient electromotive force of the system and the grid-connected point voltage, and deducing the dynamic performance index; and setting the independently decoupled dynamic performance index parameters in the VSG controller of the grid-connected converter. Without establishing a complex high-order physical model, the application effectively offsets the demagnetization effect by introducing the differential feedforward item related to the direct-axis current, greatly improves the voltage stiffness of the grid-connected converter in the sub-transient time scale, and ensures the smoothness and stability of the voltage recovery process.

Description

Technical Field

[0001] This invention relates to the field of grid-connected control technology for new energy converters, and in particular to a third-order VSG voltage active support method and system based on current differential feedforward. Background Technology

[0002] In the fields of new energy storage and distributed generation, grid-connected converters are widely used to support weak power grids and achieve fault voltage ride-through. Currently, the mainstream active voltage support control methods for grid-connected converters include traditional reactive voltage droop control and virtual synchronous generator (VSG) control based on second- or third-order models. Among them, the third-order VSG, by introducing the transient differential equation of the excitation winding, simulates the voltage inertia characteristics of a synchronous generator and has a natural grid voltage support capability.

[0003] However, existing third-order VSG control schemes have significant drawbacks: during grid fault transients, a sudden drop in voltage at the grid connection point can trigger a sharp increase in stator direct-axis current, resulting in a strong armature demagnetization reaction; constrained by the excitation winding time constant, the transient electromotive force cannot instantaneously rise to offset the demagnetization effect, leading to a large voltage drop depth and insufficient voltage support stiffness at the subtransient scale. Strengthening transient characteristics by building a higher-order synchronous machine model would significantly increase the difficulty of controller parameter tuning and online computational complexity, making engineering implementation difficult.

[0004] Currently, there is no low-cost, low-computation improvement scheme that can offset the demagnetizing effect caused by the instantaneous direct-axis current of a fault without increasing the model order or tuning complexity, while simultaneously achieving independent decoupling adjustment of voltage inertia and damped oscillation performance.

[0005] Therefore, there is an urgent need for a control improvement method that does not rely on higher-order physical models to overcome the demagnetization limitation caused by the surge in transient direct-axis current, thereby further improving the voltage stiffness and active support capability of the third-order virtual synchronous generator on the subtransient time scale. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a third-order VSG voltage active support method and system based on current differential feedforward. By establishing a mathematical model of the third-order VSG voltage control part, the limitations of this model in voltage support under grid fault transients are analyzed. Then, a feedforward compensation control strategy based on current differential is introduced to correct the model and improve the voltage support capability of grid-connected converters.

[0007] To achieve the above objectives, the present invention provides the following solution: A third-order VSG active voltage support method based on current differential feedforward, the method includes the following steps: S1. By combining the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller, a third-order VSG voltage control mathematical model adapted to the grid-type converter is constructed. S2, Analyze the mechanism of direct-axis current surge under transient grid fault conditions, and determine the armature demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support; S3, a transient enhanced feedforward branch is added in parallel between the excitation controller and the third-order VSG body model to simulate the induction characteristics of the magnetic flux change of the synchronous generator damping winding. The feedforward compensation voltage is constructed with the direct-axis current micro-component to correct the excitation voltage control equation and instantly cancel the armature demagnetization effect. S4, substitute the current differential feedforward full compensation condition to simplify the system transfer function, benchmark the standard second-order system model, and define two sets of independent dynamic performance indicators: voltage dynamic characteristic coefficient and voltage oscillation suppression coefficient. S5 establishes a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. Based on the grid operating conditions, it matches the optimal combination of time constants and sets the independent dynamic performance index parameters on the VSG digital controller of the grid converter to complete the online control configuration.

[0008] Further, in step S1, the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller are combined to construct a third-order VSG voltage control mathematical model adapted to the grid-type converter, specifically including: The first-order transient voltage equation of the virtual synchronous generator is expressed as: (1) In the formula, T d0 ′ represents the time constant of the excitation winding of the virtual synchronous generator; E q ′ represents the transient electromotive force; E qe To force no-load electromotive force; I d The current component is the d-axis component; x d For d-axis synchronous reactance; x d ′ represents the d-axis transient reactance; The equivalent resistance and reactance between the converter outlet and the grid connection point are denoted as follows: r T , x T The relationship between the grid connection point voltage and the transient electromotive force is expressed by the grid connection point equivalent impedance voltage coupling equation: (2) In the formula, U d , U q These are the reference values ​​for the d-axis and q-axis voltages at the grid connection point, respectively. I q This refers to the q-axis current component. x dΣ This is the equivalent reactance between the internal potential on the q-axis and the grid connection point; x dΣ ′ represents the equivalent reactance between the internal potential on the d-axis and the grid connection point; The equivalent reactance between the grid connection point voltage and the transient electromotive force is expressed as: (3) Introducing an inertial differential equation for an excitation controller with automatic excitation adjustment characteristics for a virtual synchronous generator: (4) In the formula, U and U ref These are the actual and reference values ​​of the grid connection point voltage, respectively. K e This is the equivalent magnification factor; T e The time constant of the excitation controller; E qe0 This is the initial value of the forced no-load electromotive force.

[0009] Furthermore, in step S2, the mechanism of the surge in direct-axis current under grid fault transients is analyzed, and the armature demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support are determined, specifically including: Ignoring the equivalent resistance of the line, the direct-axis current can be approximated as: (5) Voltage at grid connection point after fault occurs U q A sudden drop, due to T d0 The constraint of ′ E q The inability to change instantaneously leads to a sharp increase in voltage difference, resulting in a rapid increase in direct-axis current. I d According to equation (1), the demagnetizing effect causes the transient electromotive force to... E q The decrease in voltage constitutes a limitation of third-order VSG control in actively supporting grid connection point voltage.

[0010] Furthermore, in step S3, a transient enhanced feedforward branch is added in parallel between the excitation controller and the third-order VSG body model to simulate the flux change induction characteristics of the synchronous generator damping winding. A feedforward compensation voltage is constructed using the direct-axis current differential component to correct the excitation voltage control equation and instantaneously cancel the armature demagnetizing effect. Specifically, this includes: A transient enhancement channel is inserted in parallel between the excitation control stage and the third-order VSG body model. The modified excitation voltage control equation is as follows: (6) In the formula, u d This is the feedforward compensation voltage; The induced electromotive force generated by the damping winding of the synchronous generator E D The rate of change is proportional to the change in magnetic flux, which is also proportional to the change in current. (7) In the formula, L D It is a direct-axis synchronous inductor; ψ For magnetic linkage; The feedforward compensation voltage is expressed as follows: (This is a simulation of the induction characteristics of the magnetic flux change in the damping winding of a synchronous generator.) (8) In the formula, K d This is the differential gain; T d This is the time constant of the low-pass filter.

[0011] Furthermore, in step S4, the system transfer function is simplified by substituting the current differential feedforward complete compensation condition. By benchmarking against the standard second-order system model, two independent sets of dynamic performance indices are defined: the voltage dynamic characteristic coefficient and the voltage oscillation suppression coefficient. Specifically, these include: Under fully compensated conditions, neglecting the direct-axis current term, the transfer function between the transient electromotive force and the grid-connected voltage can be expressed as: (9) In the formula, This represents the deviation of the transient electromotive force. This is the deviation of the voltage at the grid connection point; Compare with the standard second-order system transfer function: (10) In the formula, K is the proportionality coefficient; Obtain the voltage dynamic characteristic coefficients of the third-order VSG system oh n and voltage oscillation suppression coefficient g They are represented as follows: (11) (12) Among them, voltage dynamic characteristic coefficient oh n It reflects the response speed and voltage inertia level of the system voltage loop. oh n The smaller the value, the stronger the voltage inertia of the system; the voltage oscillation suppression coefficient. g It reflects the system's ability to attenuate and suppress transient voltage oscillations, and determines the overshoot and number of oscillations during the dynamic regulation process.

[0012] Further, in step S5, a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant is established. The optimal time constant combination is matched according to the grid operating conditions, and the independent dynamic performance index parameters are set in the VSG digital controller of the grid converter to complete the online control configuration. Specifically, this includes: Synchronous scaling of virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Both are magnified or reduced by the same factor, and the voltage oscillation suppression coefficient is... g Keep constant, only change the voltage dynamic characteristic coefficient oh n This enables independent voltage inertia adjustment, adapting to grid fault ride-through scenarios; Virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Reverse equal multiple adjustment: The product of the two remains constant, and the voltage dynamic characteristic coefficient oh n Remain unchanged, only the voltage oscillation suppression coefficient is changed. g It enables independent adjustment of damped oscillations, adapting to weak power grids and multi-load disturbance scenarios.

[0013] Furthermore, in step S5, the time constant of the virtual synchronous generator excitation winding is... T d0 ′、Excitation controller inertial time constant T e Differential gain K d and the time constant of the low-pass filter T d The VSG digital controller, embedded in the energy storage grid converter, performs online third-order VSG closed-loop control with direct-axis current differential feedforward compensation.

[0014] This invention also provides a third-order VSG voltage active support system based on current differential feedforward, used to execute the above-described third-order VSG voltage active support method based on current differential feedforward, comprising: The third-order VSG model construction module is used to combine the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller to construct a third-order VSG voltage control mathematical model adapted to the grid-type converter. The fault demagnetization effect analysis module is used to analyze the mechanism of direct-axis current surge under power grid fault transients, and to determine the armature demagnetization effect of direct-axis current on transient electromotive force and the limitations of voltage support. The current differential feedforward compensation control module is connected in parallel to the excitation control loop. It is used to add a transient enhanced feedforward branch in parallel between the excitation controller and the third-order VSG body model to simulate the magnetic flux change induction characteristics of the synchronous generator damping winding. The feedforward compensation voltage is constructed with the direct-axis current differential component to correct the excitation voltage control equation and instantly cancel the armature demagnetization effect. The dynamic index decoupling tuning module is used to simplify the system transfer function by substituting the current differential feedforward full compensation condition, benchmarking the standard second-order system model, and defining two sets of independent dynamic performance indices: voltage dynamic characteristic coefficient and voltage oscillation suppression coefficient. The controller configuration module is used to establish a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. It matches the optimal combination of time constants according to the grid operating conditions and sets the independent dynamic performance index parameters to the VSG digital controller of the grid converter to complete the online control configuration.

[0015] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the third-order VSG active voltage support method based on current differential feedforward as described above.

[0016] According to specific embodiments of the present invention, the third-order VSG voltage active support method and system based on current differential feedforward is used for grid-connected control of new energy grid-connected converters. By adding a direct-axis current differential feedforward branch to simulate the damping winding characteristics of a synchronous generator, the instantaneous armature demagnetization effect during grid faults is offset, and the decoupled independent adjustment of voltage dynamic performance indicators is achieved. Specifically, the following technical effects are disclosed: (1) Low-cost offsetting of the instantaneous armature demagnetization effect during faults, and significantly improved subtransient voltage support stiffness: This invention, without relying on high-order physical models or increasing algorithmic complexity, successfully simulates the Lenz's law effect of the damping winding of a physical synchronous generator by introducing a direct-axis current differential feedforward term, effectively offsetting the armature demagnetizing effect in the early stages of a fault. This method provides instantaneous strong excitation during faults, significantly increasing the transient support current and raising the minimum voltage drop at the grid connection point. Simultaneously, it effectively suppresses transient overvoltages after fault clearance, greatly improving the voltage stiffness of the converter and the system safety under subtransient conditions.

[0017] (2) Voltage dynamic performance is completely decoupled, and engineering parameter tuning is flexible and controllable: This invention separates two sets of uncoupled dynamic indices—voltage inertia and damped oscillation—through mathematical derivation, providing two independent parameter tuning logics: it can separately enhance fault transient voltage inertia or separately eliminate voltage overshoot and low-frequency oscillation; for different operating conditions such as fault ride-through, weak grid, and multiple disturbance loads, it can accurately match the optimal control parameters to ensure smooth and stable system operation, adapt to new energy grid-connected equipment in multiple scenarios, and has extremely strong engineering practical value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0019] Figure 1 This is a flowchart of the third-order VSG active voltage support method based on current differential feedforward according to the present invention; Figure 2 This is a schematic diagram of the main circuit and control system topology for a grid-connected converter in an embodiment of the present invention. Figure 3 The following are comparative response curves of the grid connection point voltage of the conventional third-order VSG and the present invention with differential feedforward control under the condition of a 50% grid voltage drop in an example of the present invention. Among them, (a) is a comparison diagram of the system dynamic response when the grid voltage drops; (b) is a comparison diagram of the system dynamic response when the grid voltage recovers. Figure 4 This is a comparison curve of the dynamic adjustment of the grid connection point voltage under different dynamic index parameters in this invention example, wherein (a) is the change oh n (a) Comparison of voltage and reactive power in the dynamic response of the system; (b) To change g A comparison chart of voltage and reactive power in the dynamic response of the system. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the third-order VSG voltage active support method based on current differential feedforward provided by the present invention includes: Step 1: Establish the mathematical model of the third-order VSG voltage control part; Step 2: Analyze the demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support under power grid fault transient conditions; Step 3: Introduce a feedforward compensation control strategy based on current derivative to correct the excitation voltage equation; Step 4: Establish the closed-loop transfer function of the system under fully compensated conditions and derive the dynamic performance index; Step 5: Set the independently adjustable dynamic performance parameters in the VSG controller of the converter.

[0023] The specific scheme for step 1 is as follows: By simultaneously establishing the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller, a third-order VSG voltage control mathematical model adapted to the grid-type converter is constructed. Specifically, this includes: The first-order transient voltage equation of the virtual synchronous generator is expressed as: (1) In the formula, T d0 ′ represents the time constant of the excitation winding of the virtual synchronous generator; E q ′ represents the transient electromotive force; E qe To force no-load electromotive force; I d The current component is the d-axis component; x d For d-axis synchronous reactance; x d ′ represents the d-axis transient reactance; The equivalent resistance and reactance between the converter outlet and the grid connection point are denoted as follows: r T , x TThe relationship between the grid connection point voltage and the transient electromotive force is expressed by the grid connection point equivalent impedance voltage coupling equation: (2) In the formula, U d , U q These are the reference values ​​for the d-axis and q-axis voltages at the grid connection point, respectively. I q This refers to the q-axis current component. x dΣ This is the equivalent reactance between the internal potential on the q-axis and the grid connection point; x dΣ ′ represents the equivalent reactance between the internal potential on the d-axis and the grid connection point; The equivalent reactance between the grid connection point voltage and the transient electromotive force is expressed as: (3) Introducing an inertial differential equation for an excitation controller with automatic excitation adjustment characteristics for a virtual synchronous generator: (4) In the formula, U and U ref These are the actual and reference values ​​of the grid connection point voltage, respectively. K e This is the equivalent magnification factor; T e The time constant of the excitation controller; E qe0 This is the initial value of the forced no-load electromotive force.

[0024] Step 2 involves analyzing the mechanism of the surge in direct-axis current under transient grid fault conditions, and determining the armature demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support. Specifically, this includes: Ignoring the equivalent resistance of the line, the direct-axis current can be approximated as: (5) Voltage at grid connection point after fault occurs U q A sudden drop, due to T d0 The constraint of ′ E q The inability to change instantaneously leads to a sharp increase in voltage difference, resulting in a rapid increase in direct-axis current. I d According to equation (1), the demagnetizing effect causes the transient electromotive force to... E q The decrease in voltage constitutes a limitation of third-order VSG control in actively supporting grid connection point voltage.

[0025] The specific scheme for step 3 is as follows: A transient enhanced feedforward branch is added in parallel between the excitation controller and the third-order VSG body model to simulate the flux change induction characteristics of the synchronous generator damping winding. A feedforward compensation voltage is constructed using the direct-axis current differential component to correct the excitation voltage control equation and instantaneously cancel the armature demagnetizing effect. Specifically, this includes: A transient enhancement channel is inserted in parallel between the excitation control stage and the third-order VSG body model. The modified excitation voltage control equation is as follows: (6) In the formula, u d This is the feedforward compensation voltage; The induced electromotive force generated by the damping winding of the synchronous generator E D The rate of change is proportional to the change in magnetic flux, which is also proportional to the change in current. (7) In the formula, L D It is a direct-axis synchronous inductor; ψ It is a magnetic flux.

[0026] The feedforward compensation voltage is expressed as follows: (This is a simulation of the induction characteristics of the magnetic flux change in the damping winding of a synchronous generator.) (8) In the formula, K d This is the differential gain; T d This is the time constant of the low-pass filter.

[0027] Step 4 involves: substituting the current differential feedforward complete compensation condition to simplify the system transfer function; benchmarking against the standard second-order system model; and defining two independent sets of dynamic performance indices: the voltage dynamic characteristic coefficient and the voltage oscillation suppression coefficient. Specifically, this includes: Under fully compensated conditions, neglecting the direct-axis current term, the transfer function between the transient electromotive force and the grid-connected voltage can be expressed as: (9) In the formula, This represents the deviation of the transient electromotive force. This is the deviation of the voltage at the grid connection point.

[0028] Compare with the standard second-order system transfer function: (10) In the formula, K is the proportionality coefficient.

[0029] Obtain the voltage dynamic characteristic coefficients of the third-order VSG system oh n and voltage oscillation suppression coefficient g They are represented as follows: (11) (12) Among them, voltage dynamic characteristic coefficient oh n It reflects the response speed and voltage inertia level of the system voltage loop. oh n The smaller the value, the stronger the system's voltage inertia, and the less likely the transient electromotive force is to change with the voltage at the grid connection point when facing grid disturbances, thus providing stronger transient voltage support; however, if the value is too small... oh n This can lead to slower system recovery; voltage oscillation suppression coefficient g This reflects the system's ability to attenuate and suppress transient voltage oscillations, determining the overshoot and number of oscillations during dynamic voltage regulation. A reasonable... g It can effectively suppress voltage fluctuations during and after a fault is cleared.

[0030] Step 5 involves establishing a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. Based on the grid operating conditions, the optimal time constant combination is matched, and the independent dynamic performance index parameters are set in the VSG digital controller of the grid converter to complete the online control configuration. Specifically, this includes: Synchronous scaling of virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Both are magnified or reduced by the same factor, and the voltage oscillation suppression coefficient is... g Keep constant, only change the voltage dynamic characteristic coefficient oh n This enables independent voltage inertia adjustment, adapting to grid fault ride-through scenarios; Virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Reverse equal multiple adjustment: The product of the two remains constant, and the voltage dynamic characteristic coefficient oh n Remain unchanged, only the voltage oscillation suppression coefficient is changed. g It enables independent adjustment of damped oscillations, adapting to weak power grids and multi-load disturbance scenarios.

[0031] In step 5, the parameters Td0 ′、 T e , K d as well as T d The VSG digital controller, embedded in the energy storage grid converter, performs online third-order VSG closed-loop control with direct-axis current differential feedforward compensation.

[0032] Virtual synchronous generator excitation time constant T d0 ′ and excitation controller time constant T e They made the decision together. oh n and g Two indicators. By synchronously adjusting these two time parameters according to a specific proportional relationship, targeted control of a single indicator can be achieved. The specific mechanism is as follows: When two time constants are magnified or reduced by the same factor, their sum and the square root of their product are also magnified or reduced by the same factor. Because g This is determined by dividing these two factors; the scaling factors cancel each other out completely during the calculation, thus keeping the system's damping and overshoot characteristics absolutely unchanged. Meanwhile, because... oh n It is inversely proportional only to the square root of the product, so it changes with proportional adjustment, thereby enabling independent adjustment of the system voltage response speed and inertia.

[0033] When one time constant is magnified by a certain factor, and another time constant is reduced by the same factor, the product of the two time constants remains constant. Because... oh n This is entirely determined by this product, so the system's voltage inertia and overall response bandwidth remain unchanged. However, this adjustment of increasing and decreasing will inevitably change the sum of the two time constants, thus causing a change in the numerator term that determines the damping magnitude, thereby achieving the desired effect. g Independent adjustments.

[0034] Based on the above decoupling and regulation principles, in practical engineering, the optimal combination of time constants can be flexibly derived according to the specific requirements of the power grid conditions (such as the need for strong inertia during fault ride-through or strong damping in weak grid environments). By directly configuring this set of optimized parameters into the VSG controller of the grid-type converter, the limitation of the unadjustable physical parameters of traditional synchronous generators can be overcome, giving the system a highly customized active support and regulation capability for the power grid.

[0035] To verify the control effect of the grid-connected converter structure and the third-order virtual synchronous generator voltage active support method based on current differential feedforward, this invention utilizes MATLAB / Simulink to build a system as follows: Figure 2 The simulation system shown has a main circuit structure including an energy storage battery, a grid-type converter, an external power grid G, and line impedance, etc. The virtual reactance of the grid-type energy storage in this structure is represented by... x d The control strategy adopted is a third-order virtual synchronous generator control based on current differential feedforward. The current differential feedforward gain is adjusted according to the grid voltage support requirements. K d It can control the minimum voltage drop under fault transients; it can configure the time constant of virtual synchronization control. T d0 'and T e It can achieve dynamic control effects such as rapid adjustment, no overshoot, and oscillation suppression.

[0036] The external grid voltage is set to drop by 50% at 1 second and return to normal at 1.5 seconds. This is used to induce a sudden drop in the grid connection point voltage and to mitigate overvoltage after fault clearance. Figure 3 As shown, (a) characterizes the voltage drop at the grid connection point caused by a sudden drop in the external grid voltage at 1 s, and (b) characterizes the overvoltage process at the grid connection point caused by fault clearance at 1.5 s. Figure 3 In subplots (a) and (b), the black curves represent the uncompensated operating condition using conventional third-order VSG control, while the red curves represent the compensated operating condition with current differential feedforward compensation introduced on the basis of third-order VSG control. Observation Figure 3 As shown in the curves, after introducing compensation, the minimum voltage drop at the grid connection point during a fault increased by approximately 14V, and the peak overvoltage caused by fault clearing decreased by approximately 17V. Therefore, by introducing current differential feedforward compensation and appropriately setting the compensation amount, the safety and stability of the grid connection point voltage can be improved.

[0037] A sudden increase in reactive load is introduced at a certain point in time to observe the dynamic adjustment process of the system under different indicators. For example... Figure 4 As shown, two operating conditions are set: Operating condition 1 is as follows. Figure 4 As shown in (a), the holding voltage oscillation suppression coefficient is characterized. g Keeping the two time parameters constant and adjusting them proportionally to change the voltage dynamic characteristic coefficient oh n The dynamic response process of the system. The black curve represents... oh n The system response at 4.47 is represented by the red curve. oh nThe system response when the value is increased to 44.72; combining the curves, it can be seen that when... oh n When the voltage rises, the time for the system to reach stability through dynamic adjustment is shortened by approximately 100ms, the minimum voltage drop at the grid connection point increases by approximately 16V, and the system can provide more reactive power support in the early stages of a fault; Condition 2, as... Figure 4 As shown in (b), the holding voltage dynamic characteristic coefficient is characterized. oh n Keeping them unchanged, the two time parameters are adjusted by a ratio that is their reciprocal to change the voltage oscillation suppression coefficient. g The dynamic response process of the system; where the red curve represents g The system response at 1.34 is represented by the black curve. g The system response when the value is increased to 11.2. Combining the curves, it can be seen that when... g When the voltage rises, the overshoot of system voltage and reactive power is completely eliminated, and low-frequency oscillations are also suppressed, allowing the system to smoothly return to a steady state. Therefore, by independently configuring the time parameters... T d0 'and T e It can decouple and regulate the voltage dynamic characteristic coefficient of the system. oh n and voltage oscillation suppression coefficient g The indicators ultimately improve the dynamic adjustment performance of the system.

[0038] This invention also provides a third-order VSG voltage active support system based on current differential feedforward, used to execute the above-described third-order VSG voltage active support method based on current differential feedforward, comprising: The third-order VSG model construction module is used to combine the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller to construct a third-order VSG voltage control mathematical model adapted to the grid-type converter. The fault demagnetization effect analysis module is used to analyze the mechanism of direct-axis current surge under power grid fault transients, and to determine the armature demagnetization effect of direct-axis current on transient electromotive force and the limitations of voltage support. The current differential feedforward compensation control module is connected in parallel to the excitation control loop. It is used to add a transient enhanced feedforward branch in parallel between the excitation controller and the third-order VSG body model to simulate the magnetic flux change induction characteristics of the synchronous generator damping winding. The feedforward compensation voltage is constructed with the direct-axis current differential component to correct the excitation voltage control equation and instantly cancel the armature demagnetization effect. The dynamic index decoupling tuning module is used to simplify the system transfer function by substituting the current differential feedforward full compensation condition, benchmarking the standard second-order system model, and defining two sets of independent dynamic performance indices: voltage dynamic characteristic coefficient and voltage oscillation suppression coefficient. The controller configuration module is used to establish a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. It matches the optimal combination of time constants according to the grid operating conditions and sets the independent dynamic performance index parameters to the VSG digital controller of the grid converter to complete the online control configuration.

[0039] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the third-order VSG active voltage support method based on current differential feedforward as described above.

[0040] The present invention also provides an electronic device including one or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the third-order VSG voltage active support method based on current differential feedforward as described above.

[0041] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A third-order VSG active voltage support method based on current differential feedforward, characterized in that, Includes the following steps: S1. By combining the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller, a third-order VSG voltage control mathematical model adapted to the grid-type converter is constructed. S2, Analyze the mechanism of direct-axis current surge under transient grid fault conditions, and determine the armature demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support; S3, a transient enhanced feedforward branch is added in parallel between the excitation controller and the third-order VSG body model to simulate the induction characteristics of the magnetic flux change of the synchronous generator damping winding. The feedforward compensation voltage is constructed with the direct-axis current micro-component to correct the excitation voltage control equation and instantly cancel the armature demagnetization effect. S4, substitute the current differential feedforward full compensation condition to simplify the system transfer function, benchmark the standard second-order system model, and define two sets of independent dynamic performance indicators: voltage dynamic characteristic coefficient and voltage oscillation suppression coefficient. S5 establishes a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. Based on the grid operating conditions, it matches the optimal combination of time constants and sets the independent dynamic performance index parameters on the VSG digital controller of the grid converter to complete the online control configuration.

2. The third-order VSG voltage active support method based on current differential feedforward according to claim 1, characterized in that, In step S1, the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller are combined to construct a third-order VSG voltage control mathematical model adapted to the grid-type converter, specifically including: The first-order transient voltage equation of the virtual synchronous generator is expressed as: （1） In the formula, T d0 ′ represents the time constant of the excitation winding of the virtual synchronous generator; E q ′ represents the transient electromotive force; E qe To force no-load electromotive force; I d The current component is the d-axis component; x d For d-axis synchronous reactance; x d ′ represents the d-axis transient reactance; The equivalent resistance and reactance between the converter outlet and the grid connection point are denoted as follows: r T , x T The relationship between the grid connection point voltage and the transient electromotive force is expressed by the grid connection point equivalent impedance voltage coupling equation: （2） In the formula, U d , U q These are the reference values ​​for the d-axis and q-axis voltages at the grid connection point, respectively. I q This refers to the q-axis current component. x dΣ This is the equivalent reactance between the internal potential on the q-axis and the grid connection point; x dΣ ′ represents the equivalent reactance between the internal potential on the d-axis and the grid connection point; The equivalent reactance between the grid connection point voltage and the transient electromotive force is expressed as: （3） Introducing an inertial differential equation for an excitation controller with automatic excitation adjustment characteristics to a virtual synchronous generator: （4） In the formula, U and U ref These are the actual and reference values ​​of the grid connection point voltage, respectively. K e This is the equivalent magnification factor; T e The time constant of the excitation controller; E qe0 This is the initial value of the forced no-load electromotive force.

3. The third-order VSG voltage active support method based on current differential feedforward according to claim 2, characterized in that, In step S2, the mechanism of the surge in direct-axis current under transient grid fault conditions is analyzed, and the armature demagnetizing effect of direct-axis current on transient electromotive force and the limitations of voltage support are determined. Specifically, this includes: Ignoring the equivalent resistance of the line, the direct-axis current can be approximated as: （5） Voltage at grid connection point after fault occurrence U q A sudden drop, due to T d0 The constraint of ′ E q The inability to change instantaneously leads to a sharp increase in voltage difference, resulting in a rapid increase in direct-axis current. I d According to equation (1), the demagnetizing effect causes the transient electromotive force to... E q The decrease in voltage constitutes a limitation of third-order VSG control in actively supporting grid connection point voltage.

4. The third-order VSG voltage active support method based on current differential feedforward according to claim 2, characterized in that, In step S3, a transient enhanced feedforward branch is added in parallel between the excitation controller and the third-order VSG body model to simulate the flux change induction characteristics of the synchronous generator damping winding. A feedforward compensation voltage is constructed using the direct-axis current differential component to correct the excitation voltage control equation and instantaneously cancel the armature demagnetizing effect. Specifically, this includes: A transient enhancement channel is inserted in parallel between the excitation control loop and the third-order VSG body model. The modified excitation voltage control equation is as follows: （6） In the formula, u d This is the feedforward compensation voltage; The induced electromotive force generated by the damping winding of the synchronous generator E D The rate of change is proportional to the change in magnetic flux, which is also proportional to the change in current. （7） In the formula, L D It is a direct-axis synchronous inductor; ψ For magnetic linkage; The feedforward compensation voltage is expressed as follows: (This is a simulation of the induction characteristics of the magnetic flux change in the damping winding of a synchronous generator.) （8） In the formula, K d This is the differential gain; T d This is the time constant of the low-pass filter.

5. The third-order VSG voltage active support method based on current differential feedforward according to claim 2, characterized in that, In step S4, the system transfer function is simplified by substituting the current differential feedforward complete compensation condition. By benchmarking against the standard second-order system model, two independent sets of dynamic performance indices are defined: the voltage dynamic characteristic coefficient and the voltage oscillation suppression coefficient. Specifically, these include: Under fully compensated conditions, neglecting the direct-axis current term, the transfer function between the transient electromotive force and the grid connection point voltage can be expressed as: （9） In the formula, This represents the deviation of the transient electromotive force. This is the deviation of the voltage at the grid connection point; Compare with the standard second-order system transfer function: （10） In the formula, K is the proportionality coefficient; Obtain the voltage dynamic characteristic coefficients of the third-order VSG system ω n and voltage oscillation suppression coefficient ζ They are represented as follows: （11） （12） Among them, voltage dynamic characteristic coefficient ω n It reflects the response speed and voltage inertia level of the system voltage loop. ω n The smaller the value, the stronger the voltage inertia of the system; the voltage oscillation suppression coefficient. ζ It reflects the system's ability to attenuate and suppress transient voltage oscillations, and determines the overshoot and number of oscillations during the dynamic regulation process.

6. The third-order VSG voltage active support method based on current differential feedforward according to claim 5, characterized in that, In step S5, a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant is established. The optimal time constant combination is matched according to the grid operating conditions, and the independent dynamic performance index parameters are set in the VSG digital controller of the grid converter to complete the online control configuration. Specifically, this includes: Synchronous scaling of virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Both are magnified or reduced by the same factor, and the voltage oscillation suppression coefficient is... ζ Keep constant, only change the voltage dynamic characteristic coefficient ω n This enables independent voltage inertia adjustment, adapting to grid fault ride-through scenarios; Virtual synchronous generator excitation winding time constant T d0 ′ and excitation controller inertial time constant T e Reverse equal multiple adjustment: The product of the two remains constant, and the voltage dynamic characteristic coefficient ω n Remain unchanged, only the voltage oscillation suppression coefficient is changed. ζ It enables independent adjustment of damped oscillations, adapting to weak power grids and multi-load disturbance scenarios.

7. The third-order VSG voltage active support method based on current differential feedforward according to claim 5, characterized in that, In step S5, the time constant of the virtual synchronous generator excitation winding is... T d0 ′、Excitation controller inertial time constant T e Differential gain K d and the time constant of the low-pass filter T d The VSG digital controller, embedded in the energy storage grid converter, performs online third-order VSG closed-loop control with direct-axis current differential feedforward compensation.

8. A third-order VSG active voltage support system based on current differential feedforward, characterized in that, The method for implementing the third-order VSG active voltage support method based on current differential feedforward as described in any one of claims 1 to 7 includes: The third-order VSG model construction module is used to combine the first-order transient voltage equation of the virtual synchronous generator, the voltage coupling equation of the equivalent impedance at the grid connection point, and the inertial differential equation of the excitation controller to construct a third-order VSG voltage control mathematical model adapted to the grid-type converter. The fault demagnetization effect analysis module is used to analyze the mechanism of direct-axis current surge under power grid fault transients, and to determine the armature demagnetization effect of direct-axis current on transient electromotive force and the limitations of voltage support. The current differential feedforward compensation control module is connected in parallel to the excitation control loop. It is used to add a transient enhanced feedforward branch in parallel between the excitation controller and the third-order VSG body model to simulate the magnetic flux change induction characteristics of the synchronous generator damping winding. The feedforward compensation voltage is constructed with the direct-axis current differential component to correct the excitation voltage control equation and instantly cancel the armature demagnetization effect. The dynamic index decoupling tuning module is used to simplify the system transfer function by substituting the current differential feedforward full compensation condition, benchmarking the standard second-order system model, and defining two sets of independent dynamic performance indices: voltage dynamic characteristic coefficient and voltage oscillation suppression coefficient. The controller configuration module is used to establish a two-dimensional decoupled adjustment logic for the excitation winding time constant and the excitation controller inertial time constant. It matches the optimal combination of time constants according to the grid operating conditions and sets the independent dynamic performance index parameters to the VSG digital controller of the grid converter to complete the online control configuration.

9. A non-transitory 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 third-order VSG active voltage support method based on current differential feedforward as described in any one of claims 1 to 7.

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