A method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator and related equipment

Abstract

The present invention discloses a fault ride-through method for a grid-connected inverter based on a virtual synchronous generator and related equipment. The method collects the state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculates the actual active power and actual reactive power when an abnormality occurs in the three-phase grid-connected voltage. The method determines the target voltage positive sequence component based on the actual active power and actual reactive power in combination with a power reference value. A state prediction is performed according to the state variables using a preset continuous-time state-space model to generate multiple future states corresponding to the prediction interval. The target voltage negative sequence component is obtained by minimizing the cost function value of a preset prediction control cost function according to each future state. Space vector pulse width modulation is performed based on the target voltage positive sequence component and the target voltage negative sequence component to generate a switching sequence signal that is output to the grid-connected inverter. This effectively maintains the output power stability of the grid-connected inverter and effectively improves the grid power quality and operational stability.

Description

Technical Field

[0001] The present invention relates to the technical field of inverters, and in particular to a fault ride-through method for a grid-connected inverter based on a virtual synchronous generator and related equipment. Background Art

[0002] As the global energy mix accelerates toward cleaner, lower-carbon energy, large-scale grid integration of distributed renewable energy, represented by wind power and photovoltaics, is becoming mainstream. Virtual synchronous generator grid-connected inverters, by simulating the operating characteristics of traditional synchronous generators, can impart a certain level of inertia and voltage support capabilities to distributed power sources, effectively improving the dynamic stability and anti-interference capabilities of the power grid.

[0003] However, under unbalanced grid conditions caused by asymmetric faults, unbalanced three-phase loads, and other issues, the virtual synchronous generator grid-connected inverter is affected by the negative sequence current generated in the system, causing serious imbalance in the three-phase voltage and current output of the inverter. This imbalance not only causes severe fluctuations in grid-connected power, but also reduces the power quality of the inverter and affects the normal operation of power equipment. Summary of the Invention

[0004] The present invention provides a fault ride-through method and related equipment for a grid-connected inverter based on a virtual synchronous generator, which solves the technical problem that the existing synchronous generator grid-connected inverter is affected by negative sequence current under unbalanced grid conditions, resulting in three-phase voltage and current imbalance, which in turn causes grid-connected power fluctuations and affects the power quality of the inverter and the normal operation of power equipment.

[0005] A first aspect of the present invention provides a method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator, comprising:

[0006] collecting state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid-connected current and the three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage;

[0007] Determining a target voltage positive sequence component according to the actual active power and the actual reactive power in combination with a power reference value;

[0008] Performing state prediction according to the state variables using a preset continuous-time state space model to generate multiple future states corresponding to a prediction interval;

[0009] Minimizing a cost function value of a preset predictive control cost function according to each of the future states to obtain a target voltage negative sequence component;

[0010] Space vector pulse width modulation is performed according to the target voltage positive sequence component and the target voltage negative sequence component to generate a switching sequence signal and output it to the grid-connected inverter.

[0011] Optionally, the power reference value includes a reactive power reference value and an active power reference value; and determining the target voltage positive sequence component according to the actual active power and the actual reactive power in combination with the power reference value includes:

[0012] Performing active frequency adjustment according to the actual active power and the active power reference value to determine a phase angle;

[0013] Performing reactive voltage regulation according to the actual reactive power and the reactive power reference value to determine the voltage amplitude of the virtual synchronous generator;

[0014] Positive sequence components are extracted according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain a target voltage positive sequence component.

[0015] Optionally, the first adjustment formula corresponding to the active frequency adjustment is:

[0016]

[0017]

[0018] in, is the angular frequency, is the rated angular frequency, is the active power reference value, is the actual active power, is the moment of inertia, is the phase angle, is the active power-voltage droop coefficient.

[0019] Optionally, the second regulation formula corresponding to the reactive voltage regulation is:

[0020]

[0021] in, is the reactive power reference value, is the rated voltage effective value, is the actual reactive power, is the actual voltage effective value, is the integration coefficient, is the reactive-voltage droop coefficient, and E is the voltage amplitude of the virtual synchronous generator.

[0022] Optionally, extracting a positive sequence component according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain a target voltage positive sequence component includes:

[0023] constructing an input signal according to the phase angle and the voltage amplitude of the virtual synchronous generator;

[0024] A second-order generalized integrator is used to construct an orthogonal signal that is orthogonal to the input signal;

[0025] Suppressing the non-fundamental frequency components of the input signal according to the transfer function of the second-order generalized integrator to obtain an input update signal and forming an orthogonal vector with the orthogonal signal;

[0026] The phase angle is used as the phase of the positive-sequence rotating coordinate system, and the orthogonal vector is transformed into a dq synchronous rotating coordinate system to obtain a target voltage positive-sequence component.

[0027] Optionally, the continuous-time state-space model is:

[0028]

[0029] in, is the output voltage of the grid-connected inverter, is the grid current, is the state variable, is the system matrix, is the input matrix, is the interference matrix.

[0030] Optionally, the predictive control cost function is:

[0031]

[0032]

[0033] in, is the suppression weight of negative sequence current, is the suppression weight of negative sequence voltage, is the tracking weight of the positive sequence current, is the tracking weight of the positive sequence voltage, is the input smoothness weight, is the sliding time window discrete quantity, is the component of the negative sequence current at discrete time k in the dq coordinate system, is the component of the negative sequence voltage at discrete time k in the dq coordinate system, is the component of the positive sequence current at discrete time k in the dq coordinate system, is the reference value of positive sequence current, is the component of the positive sequence voltage at discrete time k in the dq coordinate system, is the reference value of the positive sequence voltage, is the output voltage at discrete time k The amount of change, is the output voltage at discrete time k+1, is the output voltage at discrete time k.

[0034] A second aspect of the present invention provides a grid-connected inverter fault ride-through device based on a virtual synchronous generator, comprising:

[0035] a power calculation module for collecting state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid-connected current and the three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage;

[0036] a positive sequence component calculation module, configured to determine a target voltage positive sequence component based on the actual active power and the actual reactive power in combination with a power reference value;

[0037] A state prediction module, configured to perform state prediction according to the state variables using a preset continuous-time state space model, and generate multiple future states corresponding to a prediction interval;

[0038] a negative component calculation module, configured to minimize a cost function value of a preset predictive control cost function according to each of the future states to obtain a target voltage negative sequence component;

[0039] A pulse width modulation module is used to perform space vector pulse width modulation according to the target voltage positive sequence component and the target voltage negative sequence component, generate a switching sequence signal and output it to the grid-connected inverter.

[0040] A third aspect of the present invention provides an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator as described in any one of the first aspects of the present invention.

[0041] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator as described in any one of the first aspects of the present invention.

[0042] It can be seen from the above technical solutions that the present invention has the following advantages:

[0043] The present invention collects state variables, three-phase grid-connected current, and three-phase grid-connected voltage of a grid-connected inverter in real time. When an abnormality occurs in the three-phase grid-connected voltage, the actual active power and actual reactive power are calculated according to the three-phase grid-connected current and voltage. A target voltage positive-sequence component is determined based on the actual active power and reactive power in combination with a power reference value. A state prediction is performed based on the state variables using a preset continuous-time state-space model to generate multiple future states corresponding to the prediction interval. A target voltage negative-sequence component is obtained by minimizing the cost function value of a preset predictive control cost function according to each future state. Space vector pulse width modulation is performed based on the target voltage positive-sequence component and the target voltage negative-sequence component to generate a switching sequence signal that is output to the grid-connected inverter. This effectively maintains the grid-connected power stability of the grid-connected inverter under unbalanced grid conditions, effectively improving the grid power quality and operational stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 A flowchart of a method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator provided by an embodiment of the present invention;

[0046] Figure 2 Schematic diagram of the circuit structure and control process of a grid-connected inverter based on a virtual synchronous generator in an embodiment of the present invention;

[0047] Figure 3 A structural block diagram of a grid-connected inverter fault ride-through device based on a virtual synchronous generator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] An embodiment of the present invention provides a fault ride-through method and related equipment for a grid-connected inverter based on a virtual synchronous generator, which is used to solve the technical problem that the existing synchronous generator grid-connected inverter is affected by negative sequence current under unbalanced grid conditions, resulting in three-phase voltage and current imbalance, which in turn causes grid-connected power fluctuations and affects the power quality of the inverter and the normal operation of power equipment.

[0049] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] See also Figure 1 , Figure 1 A flowchart of the steps of a fault ride-through method for a grid-connected inverter based on a virtual synchronous generator is provided in an embodiment of the present invention.

[0051] The present invention provides a fault ride-through method for a grid-connected inverter based on a virtual synchronous generator, comprising:

[0052] Step 101: collecting state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid-connected current and the three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage;

[0053] like Figure 2 As shown, Figure 2 The circuit structure and control process diagram of the grid-connected inverter based on the virtual synchronous generator in the embodiment of the present invention are shown.

[0054] In the embodiment of the present invention, the grid-connected inverter adopts a three-phase two-level voltage source inverter (VSI), and the DC side is connected to the bus capacitor C dc (voltage is U dc） , after filtering inductor L fa , L fb and L fc And the filter capacitor C f The filter outputs three-phase grid-connected voltage u a ,u b ,u c and the filtered current i La ,i Lb ,i Lc Incorporated into the grid, the equivalent resistance on the grid side is R g , the equivalent inductance is L g In addition, current sensors and voltage sensors can be set at the grid connection point to obtain the three-phase grid connection voltage u ga ,u gb ,u gc and three-phase grid current i ga ,i gb ,i gcWhen an abnormality is detected in the three-phase grid voltage, that is, when the three-phase grid voltage drops below a first specific value or exceeds a second specific value, the fault ride-through control is started, and the three-phase grid current and three-phase grid voltage are used to calculate the actual active power. and actual reactive power Calculation.

[0055] Specifically, the three-phase grid-connected current and the three-phase grid-connected voltage can be converted to a two-phase stationary coordinate system through Clarke transformation to obtain the voltage component and the current component, which are then calculated according to the following formula:

[0056]

[0057]

[0058] in, and is the voltage component, and is the current component.

[0059] At the same time, the state variables corresponding to the grid-connected inverter are obtained as the data input for the subsequent model predictive control. The state variables include the positive and negative sequence components of the inductor current and capacitor voltage. In the dual synchronous rotating coordinate system (positive sequence dq + and negative sequence dq - ), specifically:

[0060]

[0061] in, and is the positive sequence inductor current, and is the positive sequence capacitor voltage, and is the negative sequence inductor current, and is the negative sequence capacitor voltage.

[0062] It should be noted that the grid-connected inverter can be used in photovoltaic power stations.

[0063] Step 102, determining a target voltage positive sequence component based on the actual active power and the actual reactive power in combination with a power reference value;

[0064] In this embodiment, a hierarchical control structure is adopted. The upper layer simulates the motion equation of the synchronous generator rotor to provide inertia and damping. After obtaining the actual active power and actual reactive power, the power deviation between the two and the reference value is determined in combination with the power reference value. The power deviation is further used to perform frequency adjustment to obtain the virtual synchronous generator voltage amplitude and phase angle. According to the virtual synchronous generator voltage amplitude and phase angle, a second-order generalized integrator is combined to generate the target voltage positive sequence component.

[0065] In one example of the present invention, the power reference value includes a reactive power reference value and an active power reference value; step 102 may include the following sub-steps S11-S13:

[0066] S11. Adjust the active frequency according to the actual active power and the active power reference value to determine the phase angle;

[0067] Optionally, a first adjustment formula corresponding to active frequency adjustment is:

[0068]

[0069]

[0070] in, is the angular frequency, is the rated angular frequency, is the active power reference value, is the actual active power, is the moment of inertia, is the phase angle, is the active power-voltage droop coefficient.

[0071] like Figure 2 As shown, after obtaining the actual active power and active power reference value, combined with the rated angular frequency According to the first adjustment formula above, the active frequency is adjusted to obtain the angular frequency , through the proportional link diagonal frequency After processing, the phase angle is obtained .

[0072] S12, performing reactive voltage regulation according to the actual reactive power and the reactive power reference value, and determining the voltage amplitude of the virtual synchronous generator;

[0073] In this embodiment, the actual reactive power and the reactive power reference value are used in combination with the actual voltage effective value to perform reactive voltage regulation to determine the voltage amplitude of the virtual synchronous generator.

[0074] Optionally, the second regulation formula corresponding to reactive voltage regulation is:

[0075]

[0076] in, is the reactive power reference value, is the rated voltage effective value, is the actual reactive power, is the actual voltage effective value, is the integration coefficient, is the reactive-voltage droop coefficient, and E is the voltage amplitude of the virtual synchronous generator.

[0077] like Figure 2 As shown in the figure, after obtaining the actual reactive power and reactive power reference values, reactive voltage regulation is performed by combining the integral coefficient, the actual voltage RMS value, and the rated voltage RMS value to determine the corresponding virtual synchronous generator voltage amplitude. The actual voltage RMS value refers to the actual voltage RMS value at the grid connection point.

[0078] S13. Extract the positive sequence component according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain the target voltage positive sequence component.

[0079] Furthermore, S13 may include the following sub-steps:

[0080] Constructing an input signal according to the phase angle and the voltage amplitude of the virtual synchronous generator;

[0081] A second-order generalized integrator is used to construct a quadrature signal that is orthogonal to the input signal;

[0082] According to the transfer function of the second-order generalized integrator, the non-fundamental frequency components of the input signal are suppressed to obtain the input update signal and form an orthogonal vector with the orthogonal signal;

[0083] The phase angle is used as the phase of the positive-sequence rotating coordinate system, and the orthogonal vector is transformed into the dq synchronous rotating coordinate system to obtain the target voltage positive-sequence component.

[0084] In this embodiment, after obtaining the phase angle and the voltage amplitude of the virtual synchronous generator, the input signal e = Esinθ is constructed. The orthogonal signal generation characteristic of the second-order generalized integrator (SOGI) is used to generate a signal e that is orthogonal to it. q =Ecosθ.

[0085] According to the transfer function of the second-order generalized integrator, the non-fundamental frequency components of the input signal are suppressed, that is, through the transfer function Perform frequency filtering on the input signal, where ω0 is the fundamental angular frequency and k is the damping coefficient. Suppress non-fundamental frequency components (such as harmonics, negative sequence components, etc.) and retain only the fundamental frequency components to obtain the input update signal and form an orthogonal vector (e,eq ).

[0086] Then, the phase angle θ is used as the phase of the positive sequence rotation coordinate system, and the orthogonal vector (e,e q ) is converted to the dq synchronous rotating coordinate system through Park transformation to obtain the target voltage positive sequence component :

[0087]

[0088] Since SOGI has filtered out non-fundamental and negative sequence components, the transformed and That is the target voltage positive sequence component.

[0089] Step 103: Perform state prediction according to the state variables using a preset continuous-time state space model to generate multiple future states corresponding to the prediction interval;

[0090] In this embodiment, a state prediction is performed based on the state variables at the current moment using a continuous-time state space model to determine N future states corresponding to the prediction interval.

[0091] After obtaining the state variables, in the positive sequence coordinate system, the inductor current equation is:

[0092]

[0093] Where, 、 is the positive sequence current of the d and q axis inductors, 、 is the negative sequence component of the target voltage on the d and q axis inverter side, 、 is the positive sequence voltage of the d and q axis capacitors. L is the filter inductance (that is, Figure 2 L in f ), R is the parasitic resistance of the filter.

[0094] The capacitor voltage equation is:

[0095]

[0096] Where, 、 is the positive sequence current of the d and q axis inductors, 、 is the positive sequence current on the d and q axis grid side (i.e. Figure 2 i in ga 、i gb 、i gc ), 、 is the positive sequence voltage of the d and q axis capacitors. C is the filter capacitor (that is, Figure 2 C in f ), R is the parasitic resistance of the filter.

[0097] In the negative sequence coordinate system, the inductor current equation is:

[0098]

[0099] Where, 、 is the negative sequence current of the d and q axis inductors, 、 is the negative sequence component of the target voltage on the d and q axis inverter side, 、 is the negative sequence voltage of the d and q axis capacitors. L is the filter inductance (also known as L in the figure). f ), R is the parasitic resistance of the filter.

[0100] The capacitor voltage equation is:

[0101]

[0102] Where, 、 is the negative sequence current of the d and q axis inductors, 、 is the negative sequence current on the grid side of the d and q axes (that is, Figure 2 i in ga 、i gb 、i gc ), 、 is the negative sequence voltage of the d and q axis capacitors. C is the filter capacitor (that is, Figure 2 C in f ), R is the parasitic resistance of the filter.

[0103] In one example of the present invention, by integrating the capacitor voltage equation and the inductor current equation in the positive-sequence coordinate system and the negative-sequence coordinate system, a continuous-time state-space model is obtained:

[0104]

[0105] in, is the output voltage of the grid-connected inverter, is the grid current, is the state variable, is the system matrix, is the input matrix, is the interference matrix.

[0106] In this embodiment, the system matrix Specifically:

[0107]

[0108] Input Matrix for:

[0109]

[0110] Interference Matrix for:

[0111]

[0112] Among them, C is the inverter filter capacitor, that is, Figure 2 C in f ; L is the inverter inductance, that is Figure 2 L in f . R is the parasitic resistance.

[0113] Step 104 , minimizing the cost function value of the preset predictive control cost function according to each future state to obtain the target voltage negative sequence component;

[0114] In this embodiment, the model predictive control cost function is optimized by minimizing the negative sequence current and voltage, tracking the positive sequence reference current and voltage, and limiting the rate of change of the inverter output voltage to obtain the target voltage negative sequence component.

[0115] In one example of the present invention, the predictive control cost function is:

[0116]

[0117]

[0118] in, is the suppression weight of negative sequence current, is the suppression weight of negative sequence voltage, is the tracking weight of the positive sequence current, is the tracking weight of the positive sequence voltage, is the input smoothness weight, is the sliding time window discrete quantity, is the component of the negative sequence current at discrete time k in the dq coordinate system, is the component of the negative sequence voltage at discrete time k in the dq coordinate system, is the component of the positive sequence current at discrete time k in the dq coordinate system, is the reference value of positive sequence current, is the component of the positive sequence voltage at discrete time k in the dq coordinate system, is the reference value of the positive sequence voltage, is the system input at discrete time k The amount of change, is the system input at discrete time k+1, is the system input at discrete time k.

[0119] In this embodiment, the model predictive controller uses the quadratic programming (QP) problem transformation to solve the target voltage negative sequence component U, U=[ 、 ].

[0120] The quadratic programming solution method can be, for example, to first solve the continuous-time state space model Discretize it and get , and then substitute the discretized model into the predictive control cost function, and expand the quadratic form , where U=[ 、 is the input sequence.

[0121] pass ,have to , find the optimal input sequence U.

[0122] Step 105 : Perform space vector pulse width modulation according to the target voltage positive sequence component and the target voltage negative sequence component to generate a switching sequence signal and output it to the grid-connected inverter.

[0123] SVPWM is a pulse width modulation technology used in inverters. By controlling the on and off of the inverter power switches, it synthesizes the desired voltage vector, making the inverter output voltage closer to a sine wave, thereby improving power quality and system efficiency.

[0124] In this embodiment, the target voltage positive-sequence component and target voltage negative-sequence component are superimposed on the d-axis and q-axis, respectively. These superimposed components are then input into the SVPWM module. Using the space vector pulse width modulation algorithm, the superimposed components in the dq coordinate system are converted to a three-phase stationary coordinate system. The action time of each space vector is calculated to generate a pulse width modulation sequence, or switching sequence signal. This switching sequence signal is then output to the grid-connected inverter to control the on and off of the inverter's switches. This ensures that the inverter's output voltage waveform approaches the reference voltage obtained by combining the positive and negative sequence components, achieving precise control of the output power. This ensures that the system tracks the positive-sequence reference while effectively suppressing negative-sequence disturbances, thereby improving grid-connected power quality and operational stability.

[0125] In an embodiment of the present invention, by collecting state variables, three-phase grid current, and three-phase grid voltage of a grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid current and three-phase grid voltage when an abnormality occurs in the three-phase grid voltage, a target voltage positive sequence component is determined based on the actual active power and actual reactive power in combination with a power reference value, a state prediction is performed according to the state variables using a preset continuous-time state-space model to generate multiple future states corresponding to the prediction interval, a cost function value of a preset predictive control cost function is minimized according to each future state, and a target voltage negative sequence component is obtained, and space vector pulse width modulation is performed according to the target voltage positive sequence component and the target voltage negative sequence component to generate a switching sequence signal that is output to the grid-connected inverter. This effectively maintains the grid-connected power stability of the grid-connected inverter under unbalanced grid conditions, effectively improving the grid power quality and operational stability.

[0126] See also Figure 3 , Figure 3 The present invention shows a structural block diagram of a grid-connected inverter fault ride-through device based on a virtual synchronous generator.

[0127] An embodiment of the present invention provides a grid-connected inverter fault ride-through device based on a virtual synchronous generator, comprising:

[0128] The power calculation module 301 is used to collect the state variables, three-phase grid-connected current and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculate the actual active power and actual reactive power according to the three-phase grid-connected current and three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage;

[0129] The positive sequence component calculation module 302 is used to determine the target voltage positive sequence component according to the actual active power and the actual reactive power in combination with the power reference value;

[0130] The state prediction module 303 is used to perform state prediction according to the state variables using a preset continuous-time state space model to generate multiple future states corresponding to the prediction interval;

[0131] A negative component calculation module 304 is configured to minimize a cost function value of a preset predictive control cost function according to each future state to obtain a target voltage negative sequence component;

[0132] The pulse width modulation module 305 is used to perform space vector pulse width modulation according to the target voltage positive sequence component and the target voltage negative sequence component, generate a switching sequence signal, and output it to the grid-connected inverter.

[0133] Optionally, the power reference value includes a reactive power reference value and an active power reference value; the positive sequence component calculation module 302 includes:

[0134] Phase determination submodule, used to adjust the active frequency according to the actual active power and the active power reference value and determine the phase angle;

[0135] The voltage amplitude submodule is used to adjust the reactive voltage according to the actual reactive power and the reactive power reference value, and determine the voltage amplitude of the virtual synchronous generator;

[0136] The positive sequence component determination submodule is used to extract the positive sequence component according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain the target voltage positive sequence component.

[0137] Optionally, a first adjustment formula corresponding to active frequency adjustment is:

[0138]

[0139]

[0140] in, is the angular frequency, is the rated angular frequency, is the active power reference value, is the actual active power, is the moment of inertia, is the phase angle, is the active power-voltage droop coefficient.

[0141] Optionally, the second regulation formula corresponding to reactive voltage regulation is:

[0142]

[0143] in, is the reactive power reference value, is the rated voltage effective value, is the actual reactive power, is the actual voltage effective value, is the integration coefficient, is the reactive-voltage droop coefficient, and E is the voltage amplitude of the virtual synchronous generator.

[0144] Optionally, the positive sequence component determination submodule is specifically configured to:

[0145] Constructing an input signal according to the phase angle and the voltage amplitude of the virtual synchronous generator;

[0146] A second-order generalized integrator is used to construct a quadrature signal that is orthogonal to the input signal;

[0147] According to the transfer function of the second-order generalized integrator, the non-fundamental frequency components of the input signal are suppressed to obtain the input update signal and form an orthogonal vector with the orthogonal signal;

[0148] The phase angle is used as the phase of the positive-sequence rotating coordinate system, and the orthogonal vector is transformed into the dq synchronous rotating coordinate system to obtain the target voltage positive-sequence component.

[0149] Optionally, the continuous-time state-space model is:

[0150]

[0151] in, is the output voltage of the grid-connected inverter, is the grid current, is the state variable, is the system matrix, is the input matrix, is the interference matrix.

[0152] Optionally, the predictive control cost function is:

[0153]

[0154]

[0155] in, is the suppression weight of negative sequence current, is the suppression weight of negative sequence voltage, is the tracking weight of the positive sequence current, is the tracking weight of the positive sequence voltage, is the input smoothness weight, is the sliding time window discrete quantity, is the component of the negative sequence current at discrete time k in the dq coordinate system, is the component of the negative sequence voltage at discrete time k in the dq coordinate system, is the component of the positive sequence current at discrete time k in the dq coordinate system, is the reference value of positive sequence current, is the component of the positive sequence voltage at discrete time k in the dq coordinate system, is the reference value of the positive sequence voltage, is the output voltage at discrete time k The amount of change, is the output voltage at discrete time k+1, is the output voltage at discrete time k.

[0156] An embodiment of the present invention provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory. When the computer program is executed by the processor, the processor performs the steps of the fault ride-through method for a grid-connected inverter based on a virtual synchronous generator as described in any embodiment of the present invention.

[0157] An embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the method for fault ride-through of a grid-connected inverter based on a virtual synchronous generator as described in any embodiment of the present invention is implemented.

[0158] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices, modules and sub-modules can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0159] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0160] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected to achieve the purpose of the present embodiment according to actual needs.

[0161] In addition, the functional modules in various embodiments of the present invention may be integrated into a single processing module, or each module may exist physically separately, or two or more modules may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or software functional modules.

[0162] If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing an electronic device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0163] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault ride-through method for a grid-connected inverter based on a virtual synchronous generator, characterized in that: include: collecting state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid-connected current and the three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage; Determining a target voltage positive sequence component according to the actual active power and the actual reactive power in combination with a power reference value; Performing state prediction according to the state variables using a preset continuous-time state space model to generate multiple future states corresponding to a prediction interval; Minimizing a cost function value of a preset predictive control cost function according to each of the future states to obtain a target voltage negative sequence component; Performing space vector pulse width modulation according to the target voltage positive sequence component and the target voltage negative sequence component to generate a switching sequence signal and output it to the grid-connected inverter; The predictive control cost function is: Among them, λ1 is the suppression weight of negative sequence current, λ2 is the suppression weight of negative sequence voltage, λ3 is the tracking weight of positive sequence current, λ4 is the tracking weight of positive sequence voltage, γ is the input smoothness weight, N p is the sliding time window discrete quantity, is the component of the negative sequence current at discrete time k in the dq coordinate system, is the component of the negative sequence voltage at discrete time k in the dq coordinate system, is the component of the positive sequence current at discrete time k in the dq coordinate system, is the reference value of positive sequence current, is the component of the positive sequence voltage at discrete time k in the dq coordinate system, is the reference value of the positive sequence voltage, Δu[k] is the change of the output voltage u at discrete time k, u[k+1] is the output voltage at discrete time k+1, and u[k] is the output voltage at discrete time k.

2. The method according to claim 1, characterized in that The power reference value includes a reactive power reference value and an active power reference value; The determining of a target voltage positive sequence component according to the actual active power and the actual reactive power in combination with a power reference value includes: Performing active frequency adjustment according to the actual active power and the active power reference value to determine a phase angle; Performing reactive voltage regulation according to the actual reactive power and the reactive power reference value to determine the voltage amplitude of the virtual synchronous generator; Positive sequence components are extracted according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain a target voltage positive sequence component.

3. The method according to claim 2, characterized in that The first adjustment formula corresponding to the active frequency adjustment is: θ=ω / s Where ω is the angular frequency, ω n is the rated angular frequency, P set is the active power reference value, P e is the actual active power, J is the moment of inertia, θ is the phase angle, D p is the active power-voltage droop coefficient, and s is the Laplace operator.

4. The method according to claim 2, characterized in that The second regulation formula corresponding to the reactive voltage regulation is: Among them, Q set is the reactive power reference value, u n is the rated voltage effective value, Q e is the actual reactive power, u is the actual voltage effective value, k is the integral coefficient, D q is the reactive-voltage droop coefficient, and E is the voltage amplitude of the virtual synchronous generator.

5. The method according to claim 2, characterized in that The extracting the positive sequence component according to the phase angle and the voltage amplitude of the virtual synchronous generator to obtain the target voltage positive sequence component includes: constructing an input signal according to the phase angle and the voltage amplitude of the virtual synchronous generator; A second-order generalized integrator is used to construct an orthogonal signal that is orthogonal to the input signal; Suppressing the non-fundamental frequency components of the input signal according to the transfer function of the second-order generalized integrator to obtain an input update signal and forming an orthogonal vector with the orthogonal signal; The phase angle is used as the phase of the positive-sequence rotating coordinate system, and the orthogonal vector is transformed into a dq synchronous rotating coordinate system to obtain a target voltage positive-sequence component.

6. The method according to claim 1, characterized in that The continuous-time state-space model is: Among them, u is the output voltage of the grid-connected inverter, w is the grid current, x is the state variable, A c is the system matrix, B c is the input matrix, C c is the interference matrix.

7. A grid-connected inverter fault ride-through device based on a virtual synchronous generator, characterized in that: include: a power calculation module for collecting state variables, three-phase grid-connected current, and three-phase grid-connected voltage of the grid-connected inverter in real time, and calculating actual active power and actual reactive power according to the three-phase grid-connected current and the three-phase grid-connected voltage when an abnormality occurs in the three-phase grid-connected voltage; a positive sequence component calculation module, configured to determine a target voltage positive sequence component based on the actual active power and the actual reactive power in combination with a power reference value; A state prediction module, configured to perform state prediction according to the state variables using a preset continuous-time state space model, and generate multiple future states corresponding to a prediction interval; a negative sequence component calculation module, configured to minimize a cost function value of a preset predictive control cost function according to each of the future states to obtain a target voltage negative sequence component; a pulse width modulation module, configured to perform space vector pulse width modulation according to the target voltage positive sequence component and the target voltage negative sequence component, generate a switching sequence signal, and output the signal to the grid-connected inverter; The predictive control cost function is: Δu[k]=u[k+1]-u[k] Among them, λ1 is the suppression weight of negative sequence current, λ2 is the suppression weight of negative sequence voltage, λ3 is the tracking weight of positive sequence current, λ4 is the tracking weight of positive sequence voltage, γ is the input smoothness weight, N p is the sliding time window discrete quantity, is the component of the negative sequence current at discrete time k in the dq coordinate system, is the component of the negative sequence voltage at discrete time k in the dq coordinate system, is the component of the positive sequence current at discrete time k in the dq coordinate system, is the reference value of positive sequence current, is the component of the positive sequence voltage at discrete time k in the dq coordinate system, is the reference value of the positive sequence voltage, Δu[k] is the change of the output voltage u at discrete time k, u[k+1] is the output voltage at discrete time k+1, and u[k] is the output voltage at discrete time k.

8. An electronic device, characterized in that: It includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor performs the steps of the fault ride-through method of a grid-connected inverter based on a virtual synchronous generator according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the fault ride-through method for a grid-connected inverter based on a virtual synchronous generator according to any one of claims 1 to 6 is implemented.

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