A grid-connection type photovoltaic inverter parameter setting method and storage medium

Abstract

The application discloses a grid-connection type photovoltaic inverter parameter setting method and a storage medium, and belongs to the technical field of new energy grid-connected inverter control. The method comprises the following steps: acquiring grid parameters and grid-connection type photovoltaic inverter parameters, wherein the grid-connection type photovoltaic inverter parameters comprise constraint parameters and initial control parameters; determining the fluctuation range of grid voltage and impedance according to the constraint parameters; solving a pre-constructed nonlinear dynamic model to obtain a rated steady-state working point; constructing a grid operation condition set and a candidate control parameter set; taking the rated steady-state working point as an initial state, and performing stable checking on each group of parameters in the candidate control parameter set for each condition in the grid operation condition set by using the nonlinear dynamic model; generating a parameter stability domain to obtain the control parameters of the grid-connection type photovoltaic inverter after setting. The application enables the grid-connection type photovoltaic inverter to obtain feasible values of the control parameters in the wide-range grid parameter fluctuation scene, and guarantees the stable operation of the system within the preset condition range.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid-connected inverter control technology, specifically relating to a parameter tuning method and storage medium for a grid-connected photovoltaic inverter. Background Technology

[0002] With the large-scale integration of new energy power generation units such as photovoltaics into the power system, the power system is gradually exhibiting characteristics of high-proportion power electronics. The proportion of traditional synchronous generators continues to decrease, leading to a significant decline in system inertia, damping, and voltage support capabilities. The operating conditions of the power grid are becoming increasingly complex, especially in weak grid scenarios and scenarios with fluctuating grid parameters, where system stability issues are more prominent.

[0003] Grid-mounted photovoltaic (PV) inverters, by simulating the voltage source characteristics, inertia characteristics, and damping characteristics of synchronous generators, can actively establish the amplitude and phase of the output voltage, providing active frequency and voltage support to the grid. Compared with grid-following inverters that rely on grid voltage phase for synchronization, grid-mounted PV inverters have significant application value in scenarios such as weak grids, high proportion of renewable energy integration, and islanded operation.

[0004] The control parameters of a grid-connected photovoltaic inverter directly determine its operational stability. Among them, active power loop parameters, reactive power loop parameters, virtual inertia parameters, damping parameters, and voltage regulation parameters all affect the inverter's dynamic response characteristics of power angle, frequency, and voltage after disturbances. If the parameters are configured improperly, it may lead to a continuous increase in power angle, difficulty in recovering frequency deviation, and drastic fluctuations in voltage amplitude, thereby causing system oscillations or even instability.

[0005] Currently, parameter tuning for grid-connected photovoltaic inverters is typically based on fixed grid parameters, meaning control parameters are selected under specific conditions such as given grid voltage, line impedance, or short-circuit ratio. However, in actual grid-connected scenarios, grid voltage and equivalent impedance usually fluctuate; factors such as operating mode switching, line switching, load level changes, differences in grid connection point location, and grid strength all lead to changes in grid equivalent impedance and voltage levels. If parameter tuning is completed only under a single grid parameter condition, the resulting control parameters are difficult to adapt to the operational requirements under a wide range of grid parameter fluctuations.

[0006] Furthermore, most existing methods directly provide a single set of control parameters, lacking a graphical representation of the parameter stability domain. In engineering applications, if a stability domain for the control parameters can be constructed within a given range of power grid parameter fluctuations, the stable and unstable states corresponding to different parameter combinations can be displayed intuitively, providing designers with a convenient basis for selecting control parameters with sufficient stability margins within the stability domain.

[0007] Therefore, there is an urgent need for a parameter tuning method for grid-connected photovoltaic inverters that can adapt to scenarios with fluctuating grid parameters. Summary of the Invention

[0008] The purpose of this invention is to provide a parameter tuning method and storage medium for a grid-connected photovoltaic inverter, which can quickly determine a stable parameter combination that meets the constraints of power angle, frequency and voltage stability within the entire operating range of grid voltage and grid equivalent impedance fluctuations, thereby effectively improving the adaptability of the grid-connected photovoltaic inverter to weak grid and variable grid environments.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] On one hand, the present invention provides a method for parameter tuning of a grid-connected photovoltaic inverter, comprising:

[0011] Obtain grid parameters and grid-connected photovoltaic inverter parameters, wherein the grid-connected photovoltaic inverter parameters include constraint parameters and initial control parameters;

[0012] Based on the aforementioned constraint parameters, determine the fluctuation range of the grid voltage and impedance;

[0013] Based on the grid parameters, constraint parameters, and initial control parameters, the pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter.

[0014] Based on the fluctuation range of the grid voltage and impedance and the preset value range of the control parameters, a set of grid operating conditions and a set of candidate control parameters are constructed respectively.

[0015] Using the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the nonlinear dynamic model is used to perform stability verification on each group of parameters in the set of candidate control parameters.

[0016] Based on the results of the stability verification, a parameter stability domain is generated, and the control parameters of the grid-type photovoltaic inverter after tuning are obtained based on the parameter stability domain.

[0017] The above technical solutions incorporate grid parameter fluctuations into the parameter tuning process of grid-connected photovoltaic inverters by obtaining the fluctuation range of grid voltage and grid equivalent impedance. By establishing a nonlinear dynamic model with power angle, frequency deviation, and grid-connected photovoltaic inverter output voltage amplitude as state variables, the dynamic response of grid-connected photovoltaic inverters under different grid operating conditions can be reflected. By performing stability verification on candidate control parameters and generating parameter stability domains, the distribution of stable and unstable parameter combinations can be intuitively given, providing a basis for the feasible values ​​of grid-connected photovoltaic inverter control parameters.

[0018] Optionally, the grid parameters include the grid rated voltage, rated angular frequency, and initial grid equivalent impedance, wherein the grid equivalent impedance includes the grid equivalent resistance and grid equivalent reactance; the constraint parameters include the grid-connected photovoltaic inverter rated voltage, rated capacity, DC side voltage, output current limit, filter parameters, and power reference value; and the control parameters include the virtual inertia coefficient, active power loop damping coefficient, reactive power loop droop coefficient, and reactive power loop integral coefficient.

[0019] Optionally, based on the constraint parameters, the fluctuation range of the grid voltage and impedance is determined, including:

[0020] Based on the constraint parameters, the grid connection point voltage phasor and output current phasor are obtained at the preset sampling time using the power perturbation method;

[0021] The equivalent impedance of the power grid is calculated based on the voltage phasor and output current phasor at the grid connection point.

[0022] Based on the grid connection point voltage phasors and grid equivalent impedance at multiple sampling times, the fluctuation range of grid voltage and impedance is determined respectively.

[0023] The sampling time is during the stable operation period of the system or during the period after the system enters a quasi-steady state following a disturbance.

[0024] The above technical solutions, without affecting the normal operation of the power grid, utilize the measurement information of the grid-connected photovoltaic inverter itself to achieve online, accurate, and safe acquisition of the fluctuation range of grid voltage and grid equivalent impedance, thereby providing a comprehensive operating condition basis for the subsequent stable verification of control parameters; the specific implementation of the power disturbance method is existing technology and will not be described in detail here.

[0025] Optionally, the nonlinear dynamic model uses the power angle, frequency deviation, and output voltage amplitude of the grid-connected photovoltaic inverter as state variables, and its state equation is expressed as:

[0026] ,

[0027] in, Represents the state vector. This represents the first derivative of the state vector with respect to time. This represents the power angle between the output voltage of a grid-connected photovoltaic inverter and the grid voltage. This indicates the frequency deviation of the actual output angular frequency of the grid-connected photovoltaic inverter relative to the rated angular frequency of the power grid. This indicates the output voltage amplitude of a grid-connected photovoltaic inverter; This refers to the internal parameter set, which is the inherent attribute parameters of the grid-type photovoltaic inverter itself or the controller setting parameters; This refers to the set of external parameters, which are the parameters of the external power grid to which the grid-connected photovoltaic inverter is connected.

[0028] The state equation is specifically expressed as follows:

[0029]

[0030] in, This represents the first derivative of the work angle with respect to time. This represents the first derivative of the frequency deviation with respect to time. This represents the first derivative of the output voltage amplitude of the grid-connected photovoltaic inverter with respect to time. This indicates the actual output angular frequency of the grid-connected photovoltaic inverter. Indicates the rated angular frequency of the power grid. This represents the active power loop damping coefficient. This represents the reactive power loop droop coefficient. Represents the virtual inertia coefficient. This represents the reference value for active power. Indicates the grid voltage. Represents the equivalent reactance of the power grid. This indicates the rated voltage of the grid-connected photovoltaic inverter. Indicates the reactive power loop integral coefficient. This indicates the reference value for reactive power.

[0031] Optionally, based on the grid parameters, constraint parameters, and initial control parameters, a pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter, including:

[0032] Under rated power grid operating conditions, let the first derivative of each state variable in the nonlinear dynamic model be zero, i.e. The steady-state equation is obtained. ;in, This represents the values ​​of each state variable under the rated steady state. This represents the set of internal parameters under rated steady state, including the initial virtual inertia coefficient, the initial active power loop damping coefficient, the initial reactive power loop integral coefficient, the initial reactive power loop droop coefficient, the rated voltage of the grid-type photovoltaic inverter, the active power reference value, and the reactive power reference value. This represents the set of external parameters under rated steady-state conditions, including the grid rated voltage and the initial grid equivalent reactance.

[0033] Solving the steady-state equation yields the rated steady-state operating point: , serving as a reference for parameter tuning; where, superscript Indicates transpose. Indicates the rated steady-state power angle. This indicates the output voltage amplitude of a grid-type photovoltaic inverter under rated steady-state conditions.

[0034] Optionally, taking the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the stability verification of each set of parameters in the candidate control parameter set is performed using the nonlinear dynamic model, including:

[0035] Taking the rated steady-state operating point as the initial state, each set of candidate control parameters and each set of grid operating conditions are combined and substituted into the nonlinear dynamic model for numerical solution to obtain the dynamic response of the corresponding power angle, frequency deviation and output voltage amplitude of the grid-type photovoltaic inverter.

[0036] Based on the preset stability requirements, the dynamic response is used to determine whether each set of candidate control parameters is stable under the corresponding power grid operating conditions.

[0037] The above technical solutions, through quantitative judgment of preset stability requirements, ensure that the selected combination of control parameters meets stability constraints across the entire operating range, thereby improving the reliability of control parameter tuning for grid-connected photovoltaic inverters.

[0038] Optionally, the stability requirements include at least one of the following: the power angle does not continue to diverge; the frequency deviation recovers to within a preset threshold; the output voltage amplitude of the grid-type photovoltaic inverter remains within the preset allowable voltage amplitude range; and each state variable converges to the stable operating region after disturbance.

[0039] It should be noted that the non-continuous divergence of the power angle can be determined by whether it is less than or equal to the power angle of the unstable equilibrium point. The power angle of the unstable equilibrium point is obtained by solving the steady-state equation or the power angle-power relationship. If the power angle is less than or equal to the power angle of the unstable equilibrium point, and all state variables of the system converge to the stable operating region, then the control parameters are determined to be stable under the corresponding power grid operating conditions. If the power angle is greater than the power angle of the unstable equilibrium point, or any state variable continues to diverge, then the control parameters are determined to be unstable under the corresponding power grid operating conditions.

[0040] Optionally, based on preset stability requirements, the dynamic response is used to determine whether each set of candidate control parameters is stable under the corresponding power grid operating conditions, including:

[0041] If a set of candidate control parameters does not meet the stability requirements under a certain power grid operating condition, it is marked as unstable; otherwise, it is marked as stable.

[0042] If a set of candidate control parameters meets the stability requirement under all operating conditions in the power grid operating condition set, it is marked as a stable parameter combination; if a set of candidate control parameters does not meet the stability requirement under any power grid operating condition, it is marked as an unstable parameter combination.

[0043] Optionally, a parameter stability domain is generated based on the stability verification result, and the control parameters of the grid-type photovoltaic inverter after tuning are obtained based on the parameter stability domain, including:

[0044] The stable parameter combination and the unstable parameter combination are mapped onto the parameter plane or parameter space to generate a graphical parameter stability domain, and the stable control parameter combination is determined based on the graphical parameter stability domain.

[0045] On the other hand, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the grid-type photovoltaic inverter parameter tuning method as described in the first aspect.

[0046] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0047] This invention achieves quantitative characterization of power grid parameter fluctuation scenarios by determining the fluctuation range of power grid voltage and power grid equivalent impedance, thereby improving the adaptability of control parameters to changes in power grid impedance.

[0048] Meanwhile, this invention obtains the rated steady-state operating point by solving the nonlinear dynamic model of the grid-type photovoltaic inverter, and constructs a mathematical model that can accurately reflect the dynamic coupling relationship between power angle, frequency and voltage, providing an accurate benchmark reference for subsequent stability verification, and providing a clear basis for control parameter tuning;

[0049] Furthermore, this invention generates a parameter stability domain and determines a stable parameter combination by performing parameter scanning and stability verification within the range of grid parameter fluctuations and control parameter values. This transforms complex nonlinear stability constraints into intuitive visual boundaries, simplifies the parameter tuning process, and significantly improves the operational stability of grid-connected photovoltaic inverters under weak and fluctuating grid conditions. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the parameter tuning method for a grid-type photovoltaic inverter according to an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of the equivalent structure of a grid-connected photovoltaic inverter system according to an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of the control structure of a grid-type photovoltaic inverter according to an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram of the impedance identification waveform using the power perturbation method according to an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the parameter stability domain generation process in an embodiment of the present invention;

[0055] Figure 6 This is a schematic diagram of the graphical parameter stability region according to an embodiment of the present invention;

[0056] Figure 7 The graph shows the response curves of the grid connection point voltage and output current under a stable parameter combination according to an embodiment of the present invention.

[0057] Figure 8 This is a graph showing the response curves of grid connection point voltage and output current under the combination of instability parameters in an embodiment of the present invention. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment describes a parameter tuning method for a grid-type photovoltaic inverter, referring to... Figure 1 It includes:

[0061] Obtain grid parameters and grid-connected photovoltaic inverter parameters, wherein the grid-connected photovoltaic inverter parameters include constraint parameters and initial control parameters;

[0062] Based on the aforementioned constraint parameters, determine the fluctuation range of the grid voltage and impedance;

[0063] Based on the grid parameters, constraint parameters, and initial control parameters, the pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter.

[0064] Based on the fluctuation range of the grid voltage and impedance and the preset value range of the control parameters, a set of grid operating conditions and a set of candidate control parameters are constructed respectively.

[0065] Using the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the nonlinear dynamic model is used to perform stability verification on each group of parameters in the set of candidate control parameters.

[0066] Based on the results of the stability verification, a parameter stability domain is generated, and the control parameters of the grid-type photovoltaic inverter after tuning are obtained based on the parameter stability domain.

[0067] By acquiring the fluctuation range of grid voltage and impedance, grid parameter fluctuations are incorporated into the parameter tuning process of grid-connected photovoltaic inverters. By establishing a nonlinear dynamic model with power angle, frequency deviation, and output voltage amplitude of the grid-connected photovoltaic inverter as state variables, the dynamic response of the grid-connected photovoltaic inverter under different grid operating conditions can be reflected. By performing stability verification on candidate control parameters and generating parameter stability domains, the distribution of stable and unstable parameter combinations can be intuitively given, providing a basis for the tuning of control parameters of grid-connected photovoltaic inverters.

[0068] refer to Figure 2 The external power grid is equivalent to the grid voltage. Equivalent impedance to power grid Series connection; where the equivalent impedance of the power grid is... Represented as , Represents the equivalent resistance of the power grid. Represents the equivalent reactance of the power grid. The imaginary unit is used; the equivalent reactance of the power grid is expressed as... , Indicates the rated angular frequency of the power grid. This represents the equivalent inductance of the power grid. If the equivalent impedance of the power grid... If it is mainly characterized by sensory qualities, then adopt Provide an approximate description.

[0069] The specific implementation of the method in this embodiment mainly involves the following parts:

[0070] I. Parameter Acquisition

[0071] The power grid parameters include the rated voltage and rated angular frequency of the power grid. And the initial grid equivalent impedance, wherein the grid equivalent impedance includes grid equivalent resistance and grid equivalent reactance;

[0072] The constraint parameters include the rated voltage of the grid-type photovoltaic inverter. Rated capacity DC side voltage, output current limit, filter parameters and Power reference value and The control parameters include the virtual inertia coefficient. Active circuit damping coefficient droop coefficient of reactive power loop and reactive power loop integral coefficient It is used to construct nonlinear dynamic models and determine initial operating conditions;

[0073] In this embodiment, the rated capacity of the grid-type photovoltaic inverter is... For a 100kVA grid with a rated frequency of 50Hz, the corresponding rated angular frequency is... The value is 314.16 rad / s, and the rated voltage of the power grid is 380V.

[0074] II. Determining the Parameter Range

[0075] Based on the aforementioned constraint parameters, combined with engineering experience and the controller's allowable range, the virtual inertia coefficient is determined. Active circuit damping coefficient droop coefficient of reactive power loop and reactive power loop integral coefficient The range of values ​​for .

[0076] In some possible embodiments, determining the fluctuation range of the grid voltage and impedance based on the constraint parameters includes:

[0077] Based on the rated capacity of the grid-type photovoltaic inverter At a preset sampling time, the voltage phasor at the grid connection point is obtained using the power perturbation method. and output current phasor According to the voltage phasor at the grid connection point and output current phasor The equivalent impedance of the power grid was calculated. The power disturbance method is as follows: sequentially adjusting the active power reference value of the grid-connected photovoltaic inverter. and reactive power reference value A small disturbance is applied to transition the system from its pre-disturbance operating point to its post-disturbance operating point. The voltage phasor at the grid connection point is then collected at both operating points. and output current phasor ;

[0078] refer to Figure 4 The diagram shows the actual power response waveform and voltage / current waveform after a disturbance is applied according to an embodiment of the present invention. Specifically:

[0079] During the stable grid-connected operation of the grid-connected photovoltaic inverter, the voltage phasor at the grid connection point before the disturbance is collected. and output current phasor ;

[0080] Small disturbances are applied sequentially to the active power reference value and the reactive power reference value to satisfy the following:

[0081] ,

[0082] ,

[0083] in, and These represent the reference values ​​of active power and reactive power before the disturbance, respectively. and These represent the reference values ​​for active power and reactive power after the disturbance, respectively. and These represent active power disturbance and reactive power disturbance, respectively, used to generate observable voltage and current responses without changing the steady-state operating point of the grid-type photovoltaic inverter. and These represent the active power disturbance coefficient and the reactive power disturbance coefficient, respectively. In this embodiment, ; This indicates the rated capacity of the grid-type photovoltaic inverter;

[0084] Collect the grid connection point voltage phasor after disturbance and output current phasor ;

[0085] Based on the phasor difference of the grid connection point voltage and the phasor difference of the output current before and after the disturbance, the equivalent impedance of the power grid is obtained. The calculation formula is as follows:

[0086] ,

[0087] Based on the grid connection point voltage phasors and grid equivalent impedance at multiple sampling times, the fluctuation ranges of grid voltage and impedance are determined respectively, which are used to subsequently construct a set of grid operating conditions as external operating condition inputs for control parameter stability verification; the fluctuation range is expressed as: , , , In this embodiment, , .

[0088] In the above technical solution, the power disturbance identification is performed at a preset sampling time or under typical operating conditions. The preset sampling time is the period when the system is running stably or when it enters a quasi-steady state after a disturbance. The typical operating conditions include representative operating states of the power grid operation mode, line impedance, and voltage level. Each disturbance identification includes three stages: pre-disturbance sampling, application of a small power disturbance, and post-disturbance quasi-steady-state sampling. The sampling window must avoid the transient process at the moment of the disturbance to ensure that the collected data truly reflects the system parameters.

[0089] III. Obtaining the rated steady-state operating point

[0090] refer to Figure 3A grid-connected photovoltaic inverter connects to the power grid via photovoltaic modules (PV), a power converter, filters, and a PCC point. Its control structure includes a coordinate transformation module, a power calculation module, an active power loop, a reactive power loop, an inner voltage and current loop, and a PWM modulation module.

[0091] Specifically, the coordinate transformation module is used to convert between the abc coordinate system and the dq coordinate system; the power calculation module is used to calculate the active power based on the grid connection point voltage and output current. and reactive power The active power loop is used to determine the active power. With active power reference value The deviation generates the frequency and power angle; the reactive power loop is used to determine the reactive power. Reactive power reference value The deviation generates a voltage amplitude reference; the voltage-current inner loop is used to generate a d-axis voltage reference value based on the voltage amplitude reference. and q-axis voltage reference value And based on the d-axis current feedback value q-axis current feedback value d-axis voltage feedback value and q-axis voltage feedback value Tracking control is performed; the PWM modulation module is used to generate a grid-type photovoltaic inverter switching control signal based on the output of the voltage and current inner loop.

[0092] For a grid with inductive impedance, the active power output of a grid-connected photovoltaic inverter... and reactive power They are represented as follows: , ,

[0093] in, This indicates the output voltage of a grid-connected photovoltaic inverter. Indicates the grid voltage. Represents the equivalent reactance of the power grid. This represents the power angle between the output voltage of a grid-connected photovoltaic inverter and the grid voltage.

[0094] In some possible embodiments, the nonlinear dynamic model uses the power angle, frequency deviation, and output voltage amplitude of the grid-connected photovoltaic inverter as state variables, and its state equation is expressed as:

[0095] ,

[0096] in, Represents the state vector. This represents the first derivative of the state vector with respect to time. This represents the power angle between the output voltage of a grid-connected photovoltaic inverter and the grid voltage. This indicates the frequency deviation of the actual output angular frequency of the grid-connected photovoltaic inverter relative to the rated angular frequency of the power grid. This indicates the output voltage amplitude of a grid-connected photovoltaic inverter; For the internal parameter set, that is, the inherent attribute parameters of the grid-type photovoltaic inverter itself or the parameters set by the controller; This refers to the set of external parameters, which are the parameters of the external power grid to which the grid-connected photovoltaic inverter is connected.

[0097] The state equation is specifically expressed as follows:

[0098]

[0099] in, This represents the first derivative of the work angle with respect to time. This represents the first derivative of the frequency deviation with respect to time. This represents the first derivative of the output voltage amplitude of the grid-connected photovoltaic inverter with respect to time. This indicates the actual output angular frequency of the grid-connected photovoltaic inverter. Indicates the rated angular frequency of the power grid. This represents the active power loop damping coefficient. This represents the reactive power loop droop coefficient. Represents the virtual inertia coefficient. This represents the reference value for active power. The grid voltage is represented by the three-phase voltage at the grid connection point, obtained through coordinate transformation, positive sequence component extraction, or effective value calculation. Represents the equivalent reactance of the power grid. This indicates the rated voltage of the grid-connected photovoltaic inverter. Indicates the reactive power loop integral coefficient. This indicates the reference value for reactive power.

[0100] The above technical solution incorporates grid parameters and grid-connected photovoltaic inverter parameters into a unified analysis framework. By solving the nonlinear dynamic model, the power angle, frequency deviation, and output voltage amplitude response of the grid-connected photovoltaic inverter under different grid operating conditions and different combinations of control parameters are obtained.

[0101] In some possible embodiments, based on the grid parameters, constraint parameters, and initial control parameters, a pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter, including:

[0102] Under rated power grid operating conditions, let the first derivative of each state variable in the nonlinear dynamic model be zero, i.e. The steady-state equation is obtained. ;in, This represents the values ​​of each state variable under the rated steady state. It represents the set of internal parameters under rated steady state, including the initial virtual inertia coefficient, the initial active power loop damping coefficient, the initial reactive power loop integral coefficient, the initial reactive power loop droop coefficient, the inverter rated voltage, the active power reference value, and the reactive power reference value. This represents the set of external parameters under rated steady-state conditions, including the grid rated voltage and the initial grid equivalent reactance.

[0103] Solving the steady-state equation yields the rated steady-state operating point: , where superscript Indicates transpose. Indicates the rated steady-state power angle. This indicates the output voltage amplitude of a grid-type photovoltaic inverter under rated steady-state conditions.

[0104] By using the rated steady-state operating point, the initial power angle, frequency deviation, and output voltage amplitude of the grid-type photovoltaic inverter under rated operating conditions can be determined, providing a reliable initial state reference for subsequent full-condition stability verification and ensuring the accuracy of parameter scanning results and the effectiveness of stability criteria.

[0105] IV. Parameter Scanning and Stability Verification

[0106] According to the grid voltage Equivalent impedance of the power grid The fluctuation range is used to construct a set of power grid operating conditions. This set consists of interval endpoints, equally spaced sampling points, or typical engineering operating points. For example, low, rated, and high values ​​of the power grid voltage, as well as low, intermediate, and high values ​​of the power grid equivalent impedance, can be selected and combined to obtain multiple sets of power grid operating conditions. The set of power grid operating conditions is represented as follows: Each Corresponding to a set of grid voltages and grid equivalent impedances, This represents the total number of combinations.

[0107] A set of candidate control parameters is generated based on the preset value range of the control parameters; in this embodiment, the control parameters within the preset value range include the virtual inertia coefficient. Active circuit damping coefficient droop coefficient of reactive power loop reactive power loop integral coefficient At least one of them, the candidate control parameter set is represented as: , Indicates the first Group of candidate control parameter combinations, This represents the total number of combinations.

[0108] In some possible embodiments, taking the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the nonlinear dynamic model is used to perform stability verification on each set of parameters in the candidate control parameter set, including:

[0109] Using the rated steady-state operating point as the initial state, each set of candidate control parameters is combined with each set of power grid operating conditions, and substituted into the nonlinear dynamic model for numerical solution to obtain the corresponding power angle. Frequency deviation Output voltage amplitude of grid-connected photovoltaic inverter Dynamic response;

[0110] Based on the preset stability requirements, the dynamic response is used to determine whether each set of candidate control parameters is stable under the corresponding power grid operating conditions.

[0111] By quantitatively determining the preset stability requirements, the selected combination of control parameters is ensured to meet stability constraints across the entire operating range, thereby improving the reliability of control parameter tuning for grid-connected photovoltaic inverters.

[0112] In some possible embodiments, reference Figure 5 Input grid parameters and grid-connected photovoltaic inverter parameters to construct state variable and nonlinear dynamic models; select two control parameters to be verified. and As input variables, their value range and calculation step size are set respectively. , Solve the nonlinear dynamic model under various working conditions and judge the stability based on the preset requirements. and Whether it is stable under the corresponding power grid operating conditions, and finally generate The corresponding feasible region of stable parameters. Among them, and Select according to actual needs; for example, the reactive power loop integral coefficient can be chosen. and reactive power droop coefficient The virtual inertia coefficient can also be used as an input variable. and active circuit damping coefficient As input variables, by adjusting different combinations of input parameters, stability region results can be obtained under different parameter planes or parameter spaces.

[0113] In some possible embodiments, the stability requirement includes at least one of the following: work angle Discontinuous divergence; frequency deviation The output voltage amplitude of the grid-connected photovoltaic inverter has recovered to within the preset threshold. The voltage amplitude remains within the preset allowable range; all state variables converge to the stable operating region after disturbance; wherein, the frequency deviation... The preset threshold, i.e., within the preset stabilization time. Post-satisfaction The preset voltage amplitude allowable range is set to ,in, , and Determined based on grid connection specifications, equipment operation constraints, or simulation verification requirements.

[0114] It should be noted that the aforementioned power angle Non-continuous divergence can be assessed by whether its work angle is less than or equal to the unstable equilibrium point. Determine the work angle of the unstable equilibrium point. It is obtained by solving the steady-state equation or the power angle-power relationship; if the power angle Less than or equal to the work angle at the unstable equilibrium point If all system state variables converge to the stable operating region, then the control parameters are determined to be stable under the corresponding power grid operating conditions; if the power angle greater than the work angle of the unstable equilibrium point If any state variable continues to diverge, then it is determined to be unstable.

[0115] In some possible embodiments, based on the preset stability requirements, determining whether each set of candidate control parameters is stable under the corresponding power grid operating conditions based on the dynamic response includes:

[0116] If a set of candidate control parameters does not meet the stability requirements under a certain power grid operating condition, it is marked as unstable; otherwise, it is marked as stable.

[0117] If a set of candidate control parameters meets the stability requirement under all operating conditions in the power grid operating condition set, it is marked as a stable parameter combination; if a set of candidate control parameters does not meet the stability requirement under any power grid operating condition, it is marked as an unstable parameter combination.

[0118] It should be noted that the instability parameter combination is not the final recommended parameter output, but it is not directly deleted; in this embodiment, it is used to mark the instability region and help form a graphical parameter stability domain boundary. The final parameter selection is only performed within the stable parameter combination or stability domain.

[0119] V. Generation of Parameter Stability Region

[0120] In some possible embodiments, a parameter stability region is generated based on the result of the stability verification, and the control parameters of the grid-type photovoltaic inverter after tuning are obtained based on the parameter stability region, including:

[0121] The stable parameter combination and the unstable parameter combination are mapped onto a parameter plane or parameter space to generate a graphical parameter stability region, and the stability control parameter combination is determined based on the graphical parameter stability region; the graphical parameter stability region is represented as follows: .

[0122] If there are two control parameters to be verified, the stable and unstable regions are plotted on a two-dimensional parameter plane. If the influence of grid voltage or grid equivalent impedance fluctuations is further considered, a parameter stability region is constructed in a three-dimensional parameter space. Based on the graphical parameter stability region... You can directly select a combination of control parameters that meet the stability requirements within the domain.

[0123] In some possible embodiments, the location in the stable region is preferred. Parameter points that are internal and have a certain margin from the boundary are selected to enhance the robustness of grid-connected photovoltaic inverters in scenarios with fluctuating grid parameters.

[0124] In some possible embodiments, the parameter stability region may be represented in the form of a data list or mathematical constraints.

[0125] Example 2

[0126] Based on the same inventive concept as Embodiment 1, this embodiment introduces a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the grid-type photovoltaic inverter parameter tuning method as described in Embodiment 1.

[0127] To verify the effectiveness of the method of the present invention, simulation verification was performed. Figure 6 This is a graphical representation of the stability region of parameters according to an embodiment of the present invention, using the reactive power loop integral coefficient K and the reactive power loop droop coefficient. For the parameter plane, introduce the grid voltage. As a representation of power grid parameter fluctuations, the figure uses an arc-shaped curve as a boundary. The selectable region above the curve represents the set of control parameters that meet the preset stability requirements, while the unstable region below the curve represents the set of control parameters that do not meet the preset stability requirements. Two representative sets of control parameter combinations are selected from outside and inside the stability region for comparison. Case 1 represents the control parameter combination inside the stability region. Figure 7 The results of stable operation are in Case 1; Case 2 is the combination of control parameters outside the stability region or close to the instability region, corresponding to... Figure 8The results of oscillation and instability are as follows: Within the fluctuation range of grid voltage and grid equivalent impedance, some control parameter combinations can only remain stable under specific grid operating conditions and cannot adapt to all grid parameter fluctuation scenarios; while control parameter combinations within the stability region can meet the preset stability requirements under all grid operating conditions. In practical applications, control parameter combinations within the selectable region can be preferentially selected.

[0128] Figure 7 This is the response curve of the grid connection point voltage and output current under a stable parameter combination according to an embodiment of the present invention. Figure 8 The figures show the response curves of the grid connection point voltage and output current under the combination of instability parameters in an embodiment of the present invention. Figure 7 In the above scenario, after a fluctuation in grid voltage, the system's grid connection point voltage and output current recover to a stable operating state after a brief transition; however, under the same grid voltage fluctuation scenario, Figure 8 In the middle, because the control parameters are outside the stable region, the grid-connected voltage and output current of the system oscillate significantly and gradually diverge and become unstable.

[0129] In summary, by constructing a parameter stability domain, this invention can intuitively reflect the impact of control parameters on system stability and guide the selection of optimal control parameter combinations within the stability domain under grid parameter fluctuation scenarios, thereby effectively improving the stability and robustness of grid-connected photovoltaic inverters under all operating conditions.

[0130] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0131] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0132] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement flow in a process. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0133] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0134] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above, which are merely illustrative and not restrictive. Those skilled in the art, under the guidance of the present invention, can make many modifications without departing from the spirit and scope of the claims, and all such modifications are within the protection scope of the present invention.

Claims

1. A method for parameter tuning of a grid-connected photovoltaic inverter, characterized in that it includes: Obtain grid parameters and grid-connected photovoltaic inverter parameters, wherein the grid-connected photovoltaic inverter parameters include constraint parameters and initial control parameters; Based on the aforementioned constraint parameters, determine the fluctuation range of the grid voltage and impedance; Based on the grid parameters, constraint parameters, and initial control parameters, the pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter. Based on the fluctuation range of the grid voltage and impedance and the preset value range of the control parameters, a set of grid operating conditions and a set of candidate control parameters are constructed respectively. Using the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the nonlinear dynamic model is used to perform stability verification on each group of parameters in the set of candidate control parameters. Based on the results of the stability verification, a parameter stability domain is generated, and the control parameters of the grid-type photovoltaic inverter after tuning are obtained based on the parameter stability domain.

2. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, The grid parameters include the grid rated voltage, rated angular frequency, and initial grid equivalent impedance, wherein the grid equivalent impedance includes the grid equivalent resistance and grid equivalent reactance; the constraint parameters include the grid-connected photovoltaic inverter rated voltage, rated capacity, DC side voltage, output current limit, filter parameters, and power reference value; the control parameters include the virtual inertia coefficient, active power loop damping coefficient, reactive power loop droop coefficient, and reactive power loop integral coefficient.

3. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, Based on the aforementioned constraint parameters, the fluctuation range of the grid voltage and impedance is determined, including: Based on the constraint parameters, the grid connection point voltage phasor and output current phasor are obtained at the preset sampling time using the power perturbation method; The equivalent impedance of the power grid is calculated based on the voltage phasor and output current phasor at the grid connection point. Based on the grid connection point voltage phasors and grid equivalent impedance at multiple sampling times, the fluctuation range of grid voltage and impedance is determined respectively. The sampling time is during the stable operation period of the system or during the period after the system enters a quasi-steady state following a disturbance.

4. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, The nonlinear dynamic model uses the power angle, frequency deviation, and output voltage amplitude of the grid-connected photovoltaic inverter as state variables, and its state equation is expressed as: ， in, Represents the state vector. This represents the first derivative of the state vector with respect to time. This represents the power angle between the output voltage of a grid-connected photovoltaic inverter and the grid voltage. This indicates the frequency deviation of the actual output angular frequency of the grid-connected photovoltaic inverter relative to the rated angular frequency of the power grid. This indicates the output voltage amplitude of a grid-connected photovoltaic inverter. Represents the set of internal parameters. Represents the set of external parameters; The state equation is specifically expressed as follows: in, This represents the first derivative of the work angle with respect to time. This represents the first derivative of the frequency deviation with respect to time. This represents the first derivative of the output voltage amplitude of the grid-connected photovoltaic inverter with respect to time. This indicates the actual output angular frequency of the grid-connected photovoltaic inverter. Indicates the rated angular frequency of the power grid. This represents the active power loop damping coefficient. This represents the reactive power loop droop coefficient. Represents the virtual inertia coefficient. This represents the reference value for active power. Indicates the grid voltage. Represents the equivalent reactance of the power grid. This indicates the rated voltage of the grid-connected photovoltaic inverter. Indicates the reactive power loop integral coefficient. This indicates the reference value for reactive power.

5. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, Based on the grid parameters, constraint parameters, and initial control parameters, a pre-constructed nonlinear dynamic model is solved to obtain the rated steady-state operating point of the grid-connected photovoltaic inverter, including: Under rated power grid operating conditions, let the first derivative of each state variable in the nonlinear dynamic model be zero, i.e. The steady-state equation is obtained. ,in, This represents the values ​​of each state variable under the rated steady state. and These represent the internal parameter set and external parameter set under rated steady state, respectively. Solving the steady-state equation yields the rated steady-state operating point: , where superscript Indicates transpose. Indicates the rated steady-state power angle. This indicates the output voltage amplitude of a grid-type photovoltaic inverter under rated steady-state conditions.

6. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, Using the rated steady-state operating point as the initial state, for each operating condition in the set of power grid operating conditions, the stability verification of each set of parameters in the candidate control parameter set is performed using the nonlinear dynamic model, including: Taking the rated steady-state operating point as the initial state, each set of candidate control parameters and each set of grid operating conditions are combined and substituted into the nonlinear dynamic model for numerical solution to obtain the dynamic response of the corresponding power angle, frequency deviation and output voltage amplitude of the grid-type photovoltaic inverter. Based on the preset stability requirements, the dynamic response is used to determine whether each set of candidate control parameters is stable under the corresponding power grid operating conditions.

7. The parameter tuning method for a grid-type photovoltaic inverter according to claim 6, characterized in that, The stability requirement includes at least one of the following: the power angle does not continuously diverge; The frequency deviation recovers to within the preset threshold; the output voltage amplitude of the grid-type photovoltaic inverter remains within the preset allowable voltage amplitude range; and all state variables converge to the stable operating region after the disturbance.

8. The parameter tuning method for a grid-type photovoltaic inverter according to claim 6, characterized in that, Based on preset stability requirements, the dynamic response is used to determine whether each set of candidate control parameters is stable under the corresponding power grid operating conditions, including: If a set of candidate control parameters does not meet the stability requirements under a certain power grid operating condition, it is marked as unstable; otherwise, it is marked as stable. If a set of candidate control parameters meets the stability requirement under all operating conditions in the power grid operating condition set, it is marked as a stable parameter combination; if a set of candidate control parameters does not meet the stability requirement under any power grid operating condition, it is marked as an unstable parameter combination.

9. The parameter tuning method for a grid-type photovoltaic inverter according to claim 1, characterized in that, Based on the results of the stability verification, a parameter stability domain is generated, and based on the parameter stability domain, the control parameters of the grid-type photovoltaic inverter after tuning are obtained, including: The stable parameter combination and the unstable parameter combination are mapped onto the parameter plane or parameter space to generate a graphical parameter stability domain, and the stable control parameter combination is determined based on the graphical parameter stability domain.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the parameter tuning method for a grid-type photovoltaic inverter as described in any one of claims 1-9.

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