A control method and device of a network-forming converter, a terminal device, and a storage medium

Abstract

The application discloses a kind of network type converter control method, device, terminal equipment and storage medium, belong to the field of converter control, method includes: in each control cycle, extraction obtains positive and negative sequence voltage component and current component;Based on positive sequence voltage, current component and power reference value, obtain positive sequence voltage reference value;Based on negative sequence voltage component, obtain negative sequence voltage total amplitude;In the case where negative sequence voltage total amplitude is less than threshold value, positive sequence voltage reference value is used as modulation voltage reference value;In the case where negative sequence voltage total amplitude is greater than or equal to threshold value, construct and solve double-frequency active fluctuation component equation set;Based on negative sequence current component reference value and negative sequence current, voltage component, obtain negative sequence voltage component reference value;Based on positive sequence voltage reference value and negative sequence voltage component reference value, obtain modulation voltage reference value and control converter accordingly, the present application can solve the problem that the control method of network type converter in prior art is poor in operating stability.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a control method, device, terminal equipment and storage medium for a grid-type converter. Background Technology

[0002] In modern power systems, grid-connected converters are core equipment for new energy grid connection and power quality regulation. Their operational stability and control precision directly affect the safe and efficient operation of the entire power system.

[0003] Most existing control methods for grid-connected converters focus solely on symmetrical operating conditions. The core control logic and parameter settings are based on the ideal assumption of grid voltage and current symmetry, which means that the total amplitude of the negative sequence voltage is always below a preset threshold. They do not consider the imbalance problems that easily occur in grid voltage and current in actual engineering projects, nor do they design corresponding control strategies for such imbalance problems. Therefore, the existing control methods for grid-connected converters suffer from poor operational stability. Summary of the Invention

[0004] This invention provides a control method, device, terminal equipment, and storage medium for a grid-type converter, which can solve the problem of poor operational stability in the existing control methods for grid-type converters.

[0005] The control method for a grid-type converter provided by the present invention includes: During each control cycle of the grid-connected converter, the real-time port voltage and real-time port current of the current control cycle are collected. Based on real-time port voltage and real-time port current, positive sequence voltage component, positive sequence current component, negative sequence voltage component and negative sequence current component are extracted; Based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value, the positive sequence voltage reference value is obtained; Based on the negative sequence voltage components, the total amplitude of the negative sequence voltage is obtained; If the total amplitude of the negative sequence voltage is less than the preset amplitude threshold, the positive sequence voltage reference value will be used as the modulation voltage reference value for the current control cycle. When the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component and negative sequence voltage component, with the cosine component amplitude of the second harmonic active power fluctuation equal to the first preset value and the sine component amplitude of the second harmonic active power fluctuation equal to the second preset value, the equation system of the second harmonic active power fluctuation component is constructed and solved to obtain the reference value of the negative sequence current component. Based on the reference value of the negative sequence current component, the negative sequence current component, and the negative sequence voltage component, the reference value of the negative sequence voltage component is obtained; Based on the positive sequence voltage reference value and the negative sequence voltage component reference value, the modulation voltage reference value for the current control cycle is obtained; The grid-type converter is controlled within the control cycle based on the modulation voltage reference value.

[0006] Furthermore, based on the real-time port voltage and real-time port current, the positive-sequence voltage component, positive-sequence current component, negative-sequence voltage component, and negative-sequence current component are extracted, including: Perform a Clarke transform on the real-time port voltage to obtain the result. The first stationary component of the voltage on the axis and in The second stationary component of the voltage on the axis; The first and second static components of the voltage are input into a second-order generalized integral structure to generate... The first static component of the positive sequence voltage on the axis, The first static component of the negative sequence voltage on the axis, The second static component of the positive sequence voltage on the axis and in The second stationary component of the negative sequence voltage on the axis; Performing a Clarke transform on the real-time port current yields the result. The first static component of the current on the shaft and in The second static component of the current on the shaft; The first and second static components of the current are input into a second-order generalized integrator structure so that the output of the second-order generalized integrator structure is... The first static component of the positive sequence current on the axis, The first static component of the negative sequence current on the axis, The second static component of the positive sequence current on the axis and in The second stationary component of the negative sequence current on the axis; The first stationary component and the second stationary component of the positive sequence voltage are connected to a synchronous rotating phase-locked loop so that the synchronous rotating phase-locked loop can calculate the positive sequence synchronization angle; based on the positive sequence synchronization angle, the negative sequence reverse synchronization angle is obtained. Based on the positive sequence synchronization angle, Park transform is performed on the first static component of positive sequence voltage, the second static component of positive sequence voltage, the first static component of positive sequence current, and the second static component of positive sequence current to obtain the first component of positive sequence voltage on the d-axis, the second component of positive sequence voltage on the q-axis, the first component of positive sequence current on the d-axis, and the second component of positive sequence current on the q-axis. Based on the negative sequence reverse synchronization angle, Park transform is performed on the first stationary component of negative sequence voltage, the second stationary component of negative sequence voltage, the first stationary component of negative sequence current, and the second stationary component of negative sequence current to obtain the first component of negative sequence voltage on the d-axis, the second component of negative sequence voltage on the q-axis, the first component of negative sequence current on the d-axis, and the second component of negative sequence current on the q-axis. The first and second components of the positive-sequence voltage are taken as positive-sequence voltage components; the first and second components of the positive-sequence current are taken as positive-sequence current components; the first and second components of the negative-sequence voltage are taken as negative-sequence voltage components; and the first and second components of the negative-sequence current are taken as negative-sequence current components.

[0007] Furthermore, the preset power reference value includes a preset reactive power reference value and a preset active power reference value; Based on the positive-sequence voltage component, the positive-sequence current component, and a preset power reference value, a positive-sequence voltage reference value is obtained, including: The product of the first component of positive sequence voltage and the first component of positive sequence current is taken as the first active power component of positive sequence; the product of the second component of positive sequence voltage and the second component of positive sequence current is taken as the second active power component of positive sequence. The product of the second component of positive-sequence voltage and the first component of positive-sequence current is taken as the first component of positive-sequence reactive power; the second component of positive-sequence reactive power is obtained based on the product of the first component of positive-sequence voltage and the second component of positive-sequence current. The measured active power is obtained based on the first positive-sequence active power component and the second positive-sequence active power component; the measured reactive power is obtained based on the first positive-sequence reactive power component and the second positive-sequence reactive power component. The frequency deviation command is obtained based on the measured active power, the preset active power reference value, and the preset active power droop coefficient. The voltage outer loop reference value is calculated based on the measured reactive power, the preset reactive power reference value, and the preset reactive power droop coefficient. Based on the frequency deviation command, the outer voltage reference value, the first component of the positive sequence voltage, and the second component of the positive sequence voltage, the inner current reference value is obtained. Based on the current inner loop reference value, the first component of the positive sequence current and the second component of the positive sequence current, the reference values ​​of the first component of the positive sequence voltage and the reference values ​​of the second component of the positive sequence voltage are obtained. The reference values ​​of the first component and the second component of the positive sequence voltage are used as the reference values ​​for the positive sequence voltage.

[0008] Furthermore, based on the negative sequence voltage components, the total amplitude of the negative sequence voltage is obtained, including: The square of the first component of the negative sequence voltage is taken as the first square term of the negative sequence voltage. The square of the second component of the negative sequence voltage is taken as the second square term of the negative sequence voltage. The total amplitude of the negative sequence voltage is obtained based on the first square term and the second square term of the negative sequence voltage.

[0009] Furthermore, the negative sequence current component reference value includes a first negative sequence current component reference value and a second negative sequence current component reference value; The equation set for the second harmonic active power fluctuation component is as follows: in, This represents the amplitude of the cosine component of the second-harmonic active power oscillation. This is the first component of the positive sequence voltage. This is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence voltage. This is the first component of the positive sequence current. This is the second component of the negative sequence voltage. Let be the second component of the positive sequence current, 'a' be the first set value (a is a preset control target value), and 'b' be the second set value (b is a preset control target value). This represents the amplitude of the sinusoidal component of the second harmonic active power fluctuation. This is the reference value for the second component of the negative sequence current.

[0010] Furthermore, based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component, the negative sequence voltage component reference value is obtained, including: Based on the reference value of the negative sequence current component, the negative sequence current component, and the negative sequence voltage component, the reference value of the negative sequence voltage component is obtained according to the complex frequency domain equation of the inner loop of the negative sequence current. The complex frequency domain equation for the inner loop of the negative sequence current is: in, This is the reference value for the first component of the negative sequence voltage. The preset proportional gain, The preset integral coefficient, It is the Laplace operator. It is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence current. The preset fundamental angular frequency of the power grid. The preset filter inductor, This is the second component of the negative sequence current. This is the first component of the negative sequence voltage. This is the reference value for the second component of the negative sequence voltage. This is the reference value for the second component of the negative sequence current. This is the second component of the negative sequence voltage; The reference values ​​of the first and second components of the negative sequence voltage are used as the reference values ​​for the negative sequence voltage components.

[0011] Furthermore, based on the positive-sequence voltage reference value and the negative-sequence voltage component reference value, the modulation voltage reference value for the current control cycle is obtained, including: By performing Parker inverse transform on the reference values ​​of the first component and the second component of the positive sequence voltage, respectively, reference values ​​of the first static component and the second static component of the positive sequence voltage are obtained. By performing inverse Park transform on the reference values ​​of the first component and the second component of the negative sequence voltage, the reference values ​​of the first static component and the second static component of the negative sequence voltage are obtained. Based on the reference values ​​of the first static component of the positive sequence voltage and the first static component of the negative sequence voltage, the first static component of the total voltage is obtained; Based on the reference values ​​of the second static component of the positive sequence voltage and the second static component of the negative sequence voltage, the second static component of the total voltage is obtained; Based on the first static component and the second static component of the total voltage, the reference value of the modulation voltage for the current control cycle is obtained.

[0012] Another embodiment of the present invention provides a control device for a grid-type converter, comprising: a data acquisition module, a component extraction module, a positive sequence voltage reference value determination module, a negative sequence voltage total amplitude determination module, a first reference value determination module, a negative sequence current component reference value determination module, a negative sequence voltage component reference value determination module, a second reference value determination module, and a converter control module; The data acquisition module is used to acquire the real-time port voltage and real-time port current of the current control cycle during each control cycle of the grid-connected converter during grid-connected operation. The component extraction module is used to extract positive sequence voltage components, positive sequence current components, negative sequence voltage components, and negative sequence current components based on real-time port voltage and real-time port current. The positive sequence voltage reference value determination module is used to obtain the positive sequence voltage reference value based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value. The negative sequence voltage total amplitude determination module is used to obtain the total amplitude of the negative sequence voltage based on the negative sequence voltage components; The first reference value determination module is used to use the positive sequence voltage reference value as the modulation voltage reference value of the current control cycle when the total amplitude of the negative sequence voltage is less than the preset amplitude threshold. The negative sequence current component reference value determination module is used to construct and solve the equation system of the second harmonic active power fluctuation component when the total amplitude of the negative sequence voltage is greater than or equal to a preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component, and negative sequence voltage component, with the cosine component amplitude of the second harmonic active power fluctuation equal to a first preset value and the sine component amplitude of the second harmonic active power fluctuation equal to a second preset value, to obtain the reference value of the negative sequence current component. The negative sequence voltage component reference value determination module is used to obtain the negative sequence voltage component reference value based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component. The second reference value determination module is used to obtain the modulation voltage reference value of the current control cycle based on the positive sequence voltage reference value and the negative sequence voltage component reference value. The converter control module is used to control the grid-type converter within a control cycle based on the modulated voltage reference value.

[0013] Another embodiment of the present invention provides a terminal device, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the steps of the control method for a grid-type converter as provided by the present invention.

[0014] Another embodiment of the present invention also provides a computer-readable storage medium item, including: a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located executes the control method of the grid-type converter provided by the present invention.

[0015] The present invention provides the following beneficial effects: It offers a control method, apparatus, terminal equipment, and storage medium for a grid-connected converter. The method includes: during each control cycle of the grid-connected converter's operation, acquiring the real-time port voltage and real-time port current of the current control cycle; extracting positive-sequence voltage components, positive-sequence current components, negative-sequence voltage components, and negative-sequence current components based on the real-time port voltage and current; obtaining a positive-sequence voltage reference value based on the positive-sequence voltage components, positive-sequence current components, and a preset power reference value; obtaining the total amplitude of the negative-sequence voltage based on the negative-sequence voltage components; and using the positive-sequence voltage reference value as the modulation voltage for the current control cycle when the total amplitude of the negative-sequence voltage is less than a preset amplitude threshold. The system calculates and solves a set of equations for the active power fluctuation components based on the positive-sequence voltage component, positive-sequence current component, and negative-sequence voltage component, with the cosine component amplitude of the second-harmonic active power fluctuation equal to a first set value and the sine component amplitude of the second-harmonic active power fluctuation equal to a second set value. This yields a reference value for the negative-sequence current component. Based on the reference values ​​for the negative-sequence current component, negative-sequence current component, and negative-sequence voltage component, a reference value for the negative-sequence voltage component is obtained. Based on the reference values ​​for the positive-sequence voltage and negative-sequence voltage components, a reference value for the modulation voltage of the current control cycle is obtained. Based on the reference value for the modulation voltage, the grid-type converter is controlled within the control cycle. Compared with existing technologies, this invention no longer controls the grid-connected converter based on the ideal assumption of grid voltage and current symmetry. Instead, when the total amplitude of the negative sequence voltage is less than a preset amplitude threshold (indicating a slight imbalance or symmetrical operation of the grid voltage and current, requiring no triggering correction), it directly uses the positive sequence voltage reference value obtained using existing conventional methods as the modulation voltage reference value for the current control cycle. When the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold (indicating an unbalanced grid operation), based on the known positive sequence voltage component, positive sequence current component, and negative sequence voltage component, it uses the cosine component amplitude of the second harmonic active power fluctuation equal to a first set value and the second harmonic active power... The goal is to make the amplitude of the sinusoidal component of the fluctuation equal to the second set value. A set of equations for the active power fluctuation component of the second harmonic frequency is constructed and solved to obtain the reference value of the negative sequence current component. Then, based on the reference value of the negative sequence current component, the reference value of the negative sequence voltage component is obtained. Based on the reference values ​​of the positive sequence voltage component and the negative sequence voltage component, the reference value of the modulation voltage for the current control cycle is obtained and used for the control of the grid-type converter. Since this invention does not assume that the voltage and current of the grid are symmetrical, but fully considers the situation of unbalanced grid operation, it specifically suppresses the active power fluctuation of the second harmonic frequency, ensuring that the final obtained reference value of the modulation voltage can effectively avoid power pulsation and improve the stability of the grid-type converter operation. Attached Figure Description

[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a control method for a grid-type converter according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the effect of a control method for a grid-type converter provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the effect of a control method for a grid-type converter provided in another embodiment of the present invention; Figure 4 This is a schematic diagram of the control device for a grid-type converter provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0024] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0025] See Figure 1 To address the problem of poor operational stability in existing control methods for grid-type converters, an embodiment of the present invention provides a control method for a grid-type converter, comprising: S101: During each control cycle of the grid-connected converter, collect the real-time port voltage and real-time port current of the current control cycle.

[0026] In one possible implementation, before acquiring the real-time port voltage and real-time port current of the current control cycle during each control cycle of the grid-connected converter, the following steps are also included: Initially, the initial active power output, initial reactive power output, initial port voltage, initial port current, and initial internal phase angle of the grid-connected converter are acquired. Based on these initial parameters, the initial grid-connected pre-synchronization and parameter initialization of the grid-connected converter are completed. Once the grid-connected converter reaches a stable grid-connected operating state, the periodic real-time sampling and control process begins.

[0027] It should be noted that the control cycle is a fixed time interval preset by the control system, which is the minimum time unit to complete a single complete control process. The system continuously cycles based on this duration.

[0028] It should be noted that real-time port voltage and real-time port current refer to the instantaneous voltage and current electrical quantities at the grid-connected interface of the grid-connected converter. These electrical quantities change dynamically with the grid operating conditions and are used as raw sampled data for subsequent calculations.

[0029] S102: Based on the real-time port current, extract the positive sequence voltage component, positive sequence current component, negative sequence voltage component, and negative sequence current component; Based on real-time port voltage and real-time port current, positive-sequence voltage components, positive-sequence current components, negative-sequence voltage components, and negative-sequence current components are extracted, including: Perform a Clarke transform on the real-time port voltage to obtain the result. The first stationary component of the voltage on the axis and in The second stationary component of the voltage on the axis; The first and second static components of the voltage are input into a second-order generalized integral structure to generate... The first static component of the positive sequence voltage on the axis, The first static component of the negative sequence voltage on the axis, The second static component of the positive sequence voltage on the axis and in The second stationary component of the negative sequence voltage on the axis; Performing a Clarke transform on the real-time port current yields the result. The first static component of the current on the shaft and in The second static component of the current on the shaft; The first and second static components of the current are input into a second-order generalized integrator structure so that the output of the second-order generalized integrator structure is... The first static component of the positive sequence current on the axis, The first static component of the negative sequence current on the axis, The second static component of the positive sequence current on the axis and in The second stationary component of the negative sequence current on the axis; The first stationary component and the second stationary component of the positive sequence voltage are connected to a synchronous rotating phase-locked loop so that the synchronous rotating phase-locked loop can calculate the positive sequence synchronization angle; based on the positive sequence synchronization angle, the negative sequence reverse synchronization angle is obtained. Based on the positive sequence synchronization angle, Park transform is performed on the first static component of positive sequence voltage, the second static component of positive sequence voltage, the first static component of positive sequence current, and the second static component of positive sequence current to obtain the first component of positive sequence voltage on the d-axis, the second component of positive sequence voltage on the q-axis, the first component of positive sequence current on the d-axis, and the second component of positive sequence current on the q-axis. Based on the negative sequence reverse synchronization angle, Park transform is performed on the first stationary component of negative sequence voltage, the second stationary component of negative sequence voltage, the first stationary component of negative sequence current, and the second stationary component of negative sequence current to obtain the first component of negative sequence voltage on the d-axis, the second component of negative sequence voltage on the q-axis, the first component of negative sequence current on the d-axis, and the second component of negative sequence current on the q-axis. The first and second components of the positive-sequence voltage are taken as positive-sequence voltage components; the first and second components of the positive-sequence current are taken as positive-sequence current components; the first and second components of the negative-sequence voltage are taken as negative-sequence voltage components; and the first and second components of the negative-sequence current are taken as negative-sequence current components.

[0030] Specifically, for the real-time port voltage, this step involves transforming the real-time port voltage in the three-phase coordinate system using Clarke transformation to obtain the voltage in the three-phase coordinate system. First static component of voltage on the shaft and in Second static component of voltage on the shaft Then and Input to a second-order generalized integral structure so that the second-order generalized integral structure is... and Perform filtering and symmetric component operations to decompose and obtain the result. First static component of positive sequence voltage on the axis ,exist First static component of negative sequence voltage on the axis ,exist The second static component of the positive sequence voltage on the axis and in Second static component of negative sequence voltage on the axis ; Specifically, for real-time port current, this step involves transforming the real-time port current in the three-phase coordinate system using Clarke transformation to obtain the current in the three-phase coordinate system. First static component of current on the shaft and in Second static component of current on the shaft Then and Input to a second-order generalized integral structure so that the second-order generalized integral structure is... and Perform filtering and symmetric component operations to decompose and obtain the result. First static component of positive sequence current on the axis ,exist First static component of negative sequence current on the axis ,exist The second static component of the positive sequence current on the axis and in Second static component of negative sequence current on the axis ; Preferably, the second-order generalized integral structure is a dual second-order generalized integrator DSOGI, specifically composed of two independent second-order generalized integrator units. It can perform fundamental filtering on two-phase stationary axis electrical signals and, in conjunction with the symmetrical component operation rules, accurately separate the positive-sequence and negative-sequence independent sequence components from the original stationary components containing harmonics and asymmetrical disturbances, while retaining the orthogonal axis information of each sequence component.

[0031] Preferably, the internal processing of the dual second-order generalized integrator DSOGI is as follows: For in First static component of current on the shaft and in Second static component of current on the shaft The dual second-order generalized integrator DSOGI will respectively... and Each is configured with a second-order generalized integrator SOGI, whose transfer function is: (1) in, Let be the transfer function of the second-order generalized integrator. It is a preset damping coefficient, preferably , For the Laplace operator, The preset system angular frequency (fundamental angular frequency), for example, 50Hz power frequency corresponds to The second-order generalized integrator SOGI performs bandpass filtering and orthogonal signal generation on the input signal; subsequently, based on the obtained orthogonal signals after filtering, the positive and negative order of the α-axis and β-axis components is separated using the symmetric component method, thereby obtaining the signal in... First static component of positive sequence current on the axis ,exist First static component of negative sequence current on the axis ,exist The second static component of the positive sequence current on the axis and in Second static component of negative sequence current on the axis .

[0032] In obtaining , , , , Then, the first static component of the positive sequence voltage needs to be... and the second static component of positive sequence voltage The input is fed into a synchronous rotating phase-locked loop (PLL) to enable the PLL to track the phase change of the positive-sequence voltage in real time. By continuously comparing the signal phase with a reference, the real-time phase angle of the current power grid is calculated, and this angle is the positive-sequence synchronization angle. It is used to match the phase rotation of the positive sequence component.

[0033] In one possible implementation, "obtaining the negative-sequence reverse synchronization angle based on the positive-sequence synchronization angle" includes: using the calculated positive-sequence synchronization angle... Using the angle as a reference, the negative sequence reverse synchronization angle can be obtained by inverting the angle. .

[0034] In one possible implementation, "performing Parker transformation on the first quiescent component of positive-sequence voltage, the second quiescent component of positive-sequence voltage, the first quiescent component of positive-sequence current, and the second quiescent component of positive-sequence current based on the positive-sequence synchronization angle" includes: using the calculated positive-sequence synchronization angle... Using the rotation reference angle, the alternating positive-sequence voltage and current stationary components are substituted into the Parker transform formula to complete the calculation, converting the AC signal in the two-phase stationary coordinate system into the DC component in the d-q rotating coordinate system. Specifically, the first component of the positive-sequence voltage on the d-axis... The second component of the positive sequence voltage on the q-axis The first component of the positive sequence current on the d-axis and the second component of the positive sequence current on the q-axis To adapt to subsequent steady-state control calculations, it should be noted that the Parker transformation formula is a classic conversion relationship from a two-phase stationary coordinate system to a two-phase rotating coordinate system, which belongs to the conventional and universal coordinate transformation algorithm in the field of power converter control.

[0035] In one possible implementation, "performing Parker transformation on the first stationary component of negative-sequence voltage, the second stationary component of negative-sequence voltage, the first stationary component of negative-sequence current, and the second stationary component of negative-sequence current based on the negative-sequence reverse synchronization angle" specifically includes: using the obtained negative-sequence reverse synchronization angle... As a reference angle for transformation, for Negative sequence voltage and current stationary components of the shaft 、 , By applying the Parker transform formula to perform matrix operations and matching the reverse rotation characteristic of the negative sequence component, the AC fluctuation is transformed into a DC component in the d-q rotating coordinate system: the first component of the negative sequence voltage on the d-axis. The second component of the negative sequence voltage on the q-axis The first component of the negative sequence current on the d-axis and the second component of the negative sequence current on the q-axis This facilitates subsequent negative sequence operating condition analysis and control adjustment.

[0036] Specifically, the first component of the positive sequence voltage and the second component of positive sequence voltage That is, the positive sequence voltage component. The first component of the positive sequence current and the second component of the positive sequence current As the positive sequence current component The first component of negative sequence voltage and the second component of negative sequence voltage That is, the negative sequence voltage component. The first component of the negative sequence current and the second component of negative sequence current That is, the negative sequence current component. .

[0037] S103: Based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value, obtain the positive sequence voltage reference value; Furthermore, the preset power reference value includes a preset reactive power reference value and a preset active power reference value; Based on the positive-sequence voltage component, the positive-sequence current component, and a preset power reference value, a positive-sequence voltage reference value is obtained, including: The product of the first component of positive sequence voltage and the first component of positive sequence current is taken as the first active power component of positive sequence; the product of the second component of positive sequence voltage and the second component of positive sequence current is taken as the second active power component of positive sequence. The product of the second component of the positive-sequence voltage and the first component of the positive-sequence current is taken as the first positive-sequence reactive power component; the product of the first component of the positive-sequence voltage and the second component of the positive-sequence current is taken as the second positive-sequence reactive power component. The measured active power is obtained based on the first positive-sequence active power component and the second positive-sequence active power component; the measured reactive power is obtained based on the first positive-sequence reactive power component and the second positive-sequence reactive power component. The frequency deviation command is obtained based on the measured active power, the preset active power reference value, and the preset active power droop coefficient. The voltage outer loop reference value is calculated based on the measured reactive power, the preset reactive power reference value, and the preset reactive power droop coefficient. Based on the frequency deviation command, the outer voltage reference value, the first component of the positive sequence voltage, and the second component of the positive sequence voltage, the inner current reference value is obtained. Based on the current inner loop reference value, the first component of the positive sequence current and the second component of the positive sequence current, the reference values ​​of the first component of the positive sequence voltage and the reference values ​​of the second component of the positive sequence voltage are obtained. The reference values ​​of the first component and the second component of the positive sequence voltage are used as the reference values ​​for the positive sequence voltage.

[0038] In one possible implementation, the formula for "taking the product of the first component of the positive-sequence voltage and the first component of the positive-sequence current as the first component of the positive-sequence active power" is as follows: (2) in, This is the first active power component in positive sequence. This is the first component of the positive sequence voltage. This is the first component of the positive sequence current.

[0039] In one possible implementation, the formula for "taking the product of the second component of the positive-sequence voltage and the second component of the positive-sequence current as the second component of the positive-sequence active power" is as follows: (3) in, It is the second active power component in the positive sequence. This is the second component of the positive-sequence voltage. This is the second component of the positive sequence current.

[0040] In one possible implementation, the formula for "taking the product of the second component of the positive-sequence voltage and the first component of the positive-sequence current as the first component of the positive-sequence reactive power" is as follows: (4) in, This is the first reactive power component in positive sequence. This is the second component of the positive-sequence voltage. This is the first component of the positive sequence current.

[0041] In one possible implementation, the formula for "obtaining the positive-sequence second reactive power component based on the product of the first component of positive-sequence voltage and the second component of positive-sequence current" is expressed as: (5) in, It is the second reactive power component in positive sequence. This is the first component of the positive sequence voltage. This is the second component of the positive sequence current.

[0042] In one possible implementation, the formula for "obtaining the measured active power based on the first positive-sequence active power component and the second positive-sequence active power component" is: (6) in, To measure the active power, This is the first active power component in positive sequence. It is the second active power component in the positive sequence.

[0043] In one possible implementation, the formula for "obtaining the measured reactive power based on the positive-sequence first reactive power component and the positive-sequence second reactive power component" is: (7) in, To measure reactive power, This is the first reactive power component in positive sequence. It is the second reactive power component in the positive sequence.

[0044] In one possible implementation, the formula for "obtaining the frequency deviation command based on measured active power, a preset active power reference value, and a preset active power droop coefficient" is expressed as follows: (8) in, It is a frequency deviation command. It is the preset active power droop coefficient. It is a preset active power reference value. It is the measured active power.

[0045] In one possible implementation, the formula for "calculating the voltage outer loop reference value based on measured reactive power, a preset reactive power reference value, and a preset reactive power droop coefficient" is as follows: (9) in, This is the outer loop reference value for voltage. The preset reactive power droop coefficient, The preset reactive power reference value, This is the measured reactive power.

[0046] In one possible implementation, "obtaining the current inner loop reference value based on the frequency deviation command, the outer voltage loop reference value, the first component of the positive sequence voltage, and the second component of the positive sequence voltage" includes: First, based on the first and second components of the positive-sequence voltage, the measured amplitude of the current positive-sequence voltage is calculated using the following formula: (10) in, This is the currently measured positive sequence voltage amplitude. It is the first component of the positive sequence voltage. It is the second component of the positive sequence voltage.

[0047] Next, the reference value of the inner loop of the d-axis current is calculated using the following formula: (11) in, This is the reference value for the inner loop of the d-axis current. The preset positive-sequence steady-state initial d-axis current, The preset frequency-to-current conversion coefficient, This is a frequency deviation command.

[0048] Next, based on the outer voltage loop reference value and the current measured positive sequence voltage amplitude, the q-axis current inner loop reference value is calculated using the following formula: (12) in, This is the reference value for the inner loop of the q-axis current. This is the outer loop reference value for voltage. This represents the current measured positive sequence voltage amplitude. This refers to the operation of a PI controller. A PI controller is a common proportional-integral controller in the control field. It is a mature closed-loop control device / algorithm. Its basic operating principle is a well-known technology, and those skilled in the art can directly implement it using standard proportional-integral control logic.

[0049] In one possible implementation, the specific steps for "obtaining the reference values ​​for the first and second components of the positive-sequence voltage based on the inner current loop reference value, the first component of the positive-sequence current, and the second component of the positive-sequence current" are as follows: First, the current errors along the d and q axes are calculated using the following formulas: (13) in, For the current error along the d-axis, This represents the current error along the q-axis. This is the reference value for the inner loop of the d-axis current. This is the first component of the positive sequence current. This is the reference value for the inner loop of the q-axis current. This is the second component of the positive sequence current.

[0050] Next, the current errors of the d and q axes are input to the inner-loop PI controller, enabling it to perform proportional-integral closed-loop control. This involves proportional amplification and integral calculation of the d-axis and q-axis current error signals, respectively. The proportional element rapidly suppresses the current deviation, while the integral element eliminates the steady-state error of the current control, yielding the reference value of the first component of the positive-sequence voltage. and the reference value of the second component of the positive sequence voltage It should be noted that the processing of the current inner loop PI regulator is a conventional technique in this field and will not be elaborated here.

[0051] S104: Based on the negative sequence voltage components, obtain the total amplitude of the negative sequence voltage; Furthermore, based on the negative sequence voltage components, the total amplitude of the negative sequence voltage is obtained, including: The square of the first component of the negative sequence voltage is taken as the first square term of the negative sequence voltage. The square of the second component of the negative sequence voltage is taken as the second square term of the negative sequence voltage. The total amplitude of the negative sequence voltage is obtained based on the first square term and the second square term of the negative sequence voltage.

[0052] In one possible implementation, the formula for calculating the total magnitude of the negative-sequence voltage is: (14) in, This represents the total amplitude of the negative sequence voltage. This is the first component of the negative sequence voltage. This is the second component of the negative sequence voltage. This is the first squared term of the negative sequence voltage. This is the second square term of the negative sequence voltage.

[0053] S105: When the total amplitude of the negative sequence voltage is less than the preset amplitude threshold, the positive sequence voltage reference value is used as the modulation voltage reference value for the current control cycle. It should be noted that when the total amplitude of the negative sequence voltage is less than the preset amplitude threshold, the three-phase voltage of the system is determined to be in a balanced state, the influence of the negative sequence component can be ignored, no additional negative sequence control compensation is required, and the positive sequence voltage reference value is directly used as the modulation voltage reference value of the current control cycle and input into the subsequent modulation stage to generate the drive signal.

[0054] S106: When the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component and negative sequence voltage component, with the goal of the amplitude of the cosine component of the second harmonic active power fluctuation being equal to the first set value and the amplitude of the sine component of the second harmonic active power fluctuation being equal to the second set value, construct the equation system of the second harmonic active power fluctuation component and solve the equation system of the second harmonic active power fluctuation component to obtain the reference value of the negative sequence current component. Furthermore, the negative sequence current component reference value includes a first negative sequence current component reference value and a second negative sequence current component reference value; The equation set for the second harmonic active power fluctuation component is as follows: (15) in, This represents the amplitude of the cosine component of the second-harmonic active power oscillation. This is the first component of the positive sequence voltage. This is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence voltage. This is the first component of the positive sequence current. This is the second component of the negative sequence voltage. Let be the second component of the positive sequence current, 'a' be the first set value (a is a preset control target value), and 'b' be the second set value (b is a preset control target value). This represents the amplitude of the sinusoidal component of the second harmonic active power fluctuation. This is the reference value for the second component of the negative sequence current.

[0055] In one possible implementation, the first setting value is 0, the second setting value is 0, and a preset amplitude threshold is used. , The unit is per unit, which is the ratio of the actual physical quantity to the reference value. In this embodiment, the system rated voltage is used as the reference value. Therefore, 0.1 pu means that the negative sequence voltage amplitude reaches 10% of the rated voltage.

[0056] It should be noted that, when the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold, the theoretical basis for constructing and solving the equations for the second harmonic active power fluctuation component is: under asymmetrical fault conditions (the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold), the positive sequence d-axis is aligned ( The instantaneous active power of the three phases can be decomposed into the sum of the DC component and the second harmonic component: (16) in, It is the three-phase instantaneous active power (the instantaneous value that changes with time). It is the DC component / average value of active power. It is the amplitude of the sinusoidal component of the second harmonic active power fluctuation. It is the fundamental angular frequency of the power grid. It is the amplitude of the cosine component of the second harmonic active power oscillation.

[0057] It should be noted that, It is a known quantity calculated based on the real-time port voltage and real-time port current. It is the average value extracted from the three-phase instantaneous active power through a low-pass filter. It is determined by the rated frequency of the power grid, under the power frequency. ,exist The speed is approximately 314 rad / s.

[0058] Among them, the amplitude of the cosine component of the second harmonic active power oscillation The relationship with other known quantities and control target values ​​can be represented by the following formula: (17) in, It is the first component of the positive sequence voltage. This is the reference value for the first component of the negative sequence current. The reference value for the first component of the negative sequence current is the control target value of the negative sequence current on the d-axis, and it is the only adjustable variable within the current control cycle. It is the first component of the negative sequence voltage. It is the first component of the positive sequence current. This is the second component of the negative sequence voltage. This is the second component of the positive sequence current. The second harmonic active power fluctuation component will continuously feed back to the system's frequency control loop through the active power-frequency droop control loop, causing the frequency adjustment command to fluctuate periodically with the second harmonic component. This leads to continuous power oscillations in the system after a fault, which is the main reason why the system cannot operate stably under fault conditions. Formula (17) explains that the amplitude of the cosine component of the second harmonic active power fluctuation is determined by the reference values ​​of the first component of positive sequence voltage, the first component of negative sequence voltage, the first component of positive sequence current, the second component of negative sequence voltage, the second component of positive sequence current, and the first component of negative sequence current. In the current control cycle, the first component of positive sequence voltage, the first component of negative sequence voltage, the first component of positive sequence current, the second component of negative sequence voltage, and the second component of positive sequence current are all known quantities that have been collected or calculated. Therefore, the amplitude of the cosine component of the second harmonic active power fluctuation is only a single variable function of the reference value of the first component of negative sequence current. Therefore, in order to make the amplitude of the cosine component of the second harmonic active power fluctuation 0, only by adjusting the reference value of the first component of negative sequence current can the second harmonic active power fluctuation component generated by the coupling of voltage and current components be offset, so as to achieve a stable output of active power.

[0059] The relationship between the amplitude of the sinusoidal component of the second-harmonic active power fluctuation and other known quantities and control target values ​​can be characterized by the following formula: (18) in, This represents the amplitude of the sinusoidal component of the second harmonic active power fluctuation. This is the first component of the positive sequence voltage. This is the reference value for the second component of the negative sequence current. This is the second component of the negative sequence voltage. This is the first component of the positive sequence current. This is the first component of the negative sequence voltage. The second component of the positive sequence current. As can be seen from formula (18), the amplitude of the sinusoidal component of the second harmonic active power fluctuation is jointly determined by the reference values ​​of the first component of the positive sequence voltage, the second component of the negative sequence voltage, the first component of the positive sequence current, the first component of the negative sequence voltage, the second component of the positive sequence current, and the second component of the negative sequence current. Among them, the first component of the positive sequence voltage, the second component of the negative sequence voltage, the first component of the positive sequence current, the first component of the negative sequence voltage, and the second component of the positive sequence current are all known values ​​that have been collected or calculated within the current control cycle. Therefore, the amplitude of the sinusoidal component of the second harmonic active power fluctuation is uniquely determined by the reference value of the second component of the negative sequence current.

[0060] To address the issue of continuous system oscillation caused by second-harmonic active power fluctuations through the active-frequency droop loop under three-phase unbalanced conditions, it is necessary to ensure that both the sinusoidal and cosine amplitudes of the second-harmonic active power fluctuations are zero. According to the aforementioned formula, the cosine amplitude of the second-harmonic active power fluctuation is mainly determined by the reference value of the first component of the negative-sequence current, and the sinusoidal amplitude is mainly determined by the reference value of the second component of the negative-sequence current. Therefore, it is necessary to solve for the reference values ​​of the first and second components of the negative-sequence current when both the sinusoidal and cosine amplitudes of the second-harmonic active power fluctuations are zero, serving as the control targets for the inner loop of the negative-sequence current.

[0061] Preferably, by constructing the matrix form of the equation set of the second harmonic active power fluctuation components and performing inversion operation based on the invertible matrix formed by the positive sequence voltage components, the unique solution of the reference values ​​of the first negative sequence current component and the second negative sequence current component that make the amplitudes of both the cosine and sine components of the second harmonic active power fluctuation zero can be obtained.

[0062] In one possible implementation, solving the equations for the second harmonic active wave component yields the following unique solution: (19) in, This is the reference value for the first component of the negative sequence current. This is the reference value for the second component of the negative sequence current. This is the first component of the positive sequence voltage. This is the second component of the positive-sequence voltage. This is the first component of the negative sequence voltage. This is the second component of the negative sequence voltage. This is the first component of the positive sequence current after low-pass filtering. This is the second component of the positive-sequence current after low-pass filtering. It should be noted that the reason for low-pass filtering the first and second components of the positive-sequence current is that under three-phase unbalanced conditions, the positive-sequence current component will be superimposed with a second-harmonic AC fluctuation component generated by the coupling of negative-sequence voltage and negative-sequence current. This fluctuation component is a high-frequency interference signal and is not the fundamental positive-sequence current component required by the system. Direct use would introduce additional errors into the calculated negative-sequence current reference value, failing to achieve accurate suppression of the second-harmonic active power fluctuation. By removing the second-harmonic and higher-frequency fluctuation components through low-pass filtering, a stable average value of the fundamental positive-sequence current can be extracted, thereby ensuring the accuracy of the negative-sequence current reference value calculation and the stability of the control.

[0063] Preferably, the positive-sequence dq frame of the grid-type converter adopts positive-sequence voltage-oriented control, aligning the d-axis with the positive-sequence voltage vector of the grid, so that... 0、 It should be noted that this invention only utilizes... 0、 This approximation eliminates redundant terms, simplifies complex matrix solutions into simple algebraic expressions, reduces computational load, meets real-time control requirements, and will not cause [further issues] in actual numerical calculations. 0、 With the help of 0、 After eliminating redundant terms from this approximation relationship, the following solution results are obtained: (20) in, This is the reference value for the first component of the negative sequence current. This is the reference value for the second component of the negative sequence current. This is the first component of the positive sequence voltage. This is the first component of the negative sequence voltage. This is the second component of the negative sequence voltage. This is the first component of the positive sequence current after low-pass filtering. This is the second component of the positive sequence current after low-pass filtering.

[0064] S107: Based on the negative sequence current component reference value, negative sequence current component, and negative sequence voltage component, obtain the negative sequence voltage component reference value; Furthermore, based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component, the negative sequence voltage component reference value is obtained, including: Based on the reference value of the negative sequence current component, the negative sequence current component, and the negative sequence voltage component, the reference value of the negative sequence voltage component is obtained according to the complex frequency domain equation of the inner loop of the negative sequence current. The complex frequency domain equation for the inner loop of the negative sequence current is: (twenty one) in, This is the reference value for the first component of the negative sequence voltage. The preset proportional gain, The preset integral coefficient, It is the Laplace operator. It is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence current. The preset fundamental angular frequency of the power grid. The preset filter inductor, This is the second component of the negative sequence current. This is the first component of the negative sequence voltage. This is the reference value for the second component of the negative sequence voltage. This is the reference value for the second component of the negative sequence current. This is the second component of the negative sequence voltage; The reference values ​​of the first and second components of the negative sequence voltage are used as the reference values ​​for the negative sequence voltage components.

[0065] S108: Based on the positive sequence voltage reference value and the negative sequence voltage component reference value, obtain the modulation voltage reference value for the current control cycle; Based on the positive-sequence voltage reference value and the negative-sequence voltage component reference value, the modulation voltage reference value for the current control cycle is obtained, including: By performing Parker inverse transform on the reference values ​​of the first component and the second component of the positive sequence voltage, respectively, reference values ​​of the first static component and the second static component of the positive sequence voltage are obtained. By performing inverse Park transform on the reference values ​​of the first component and the second component of the negative sequence voltage, the reference values ​​of the first static component and the second static component of the negative sequence voltage are obtained. Based on the reference values ​​of the first static component of the positive sequence voltage and the first static component of the negative sequence voltage, the first static component of the total voltage is obtained; Based on the reference values ​​of the second static component of the positive sequence voltage and the second static component of the negative sequence voltage, the second static component of the total voltage is obtained; Based on the first static component and the second static component of the total voltage, the reference value of the modulation voltage for the current control cycle is obtained.

[0066] It should be noted that the reference value for the first component of the positive sequence voltage and the reference value of the second component of the positive sequence voltage It is a control command in a rotating coordinate system (d, q axes), while SVPWM modulation requires a stationary coordinate system ( The function of the inverse Park transform (inverse Park transform) is to convert the commands on the d and q axes back to reference values ​​in the three-phase stationary coordinate system, thus obtaining the reference value of the first stationary component of the positive sequence voltage. and the reference value of the second static component of the positive sequence voltage Similarly, the reference value of the first component of the negative sequence voltage. and the reference value of the second component of the negative sequence voltage It is also necessary to convert to reference values ​​in a three-phase stationary coordinate system to obtain the reference value of the first stationary component of the negative sequence voltage. and the reference value of the second static component of the negative sequence voltage .

[0067] In one possible implementation, the specific steps for "obtaining the first static component of the total voltage based on the reference values ​​of the first static component of the positive-sequence voltage and the first static component of the negative-sequence voltage" are as follows: Since in the stationary coordinate system... On the axis (first component), positive sequence voltage reference value and negative sequence voltage reference value They are in phase and can be directly superimposed; therefore, the first stationary component of the total voltage is... It is the algebraic sum of the two. Similarly, "based on the reference values ​​of the second static component of the positive-sequence voltage and the second static component of the negative-sequence voltage, the second static component of the total voltage is obtained" specifically, in the stationary coordinate system. On the axis (second component), positive sequence voltage reference value and negative sequence voltage reference value They are in phase and can be directly superimposed. The second stationary component of the total voltage. It is the algebraic sum of the two.

[0068] "Obtaining the modulation voltage reference value for the current control cycle based on the first and second static components of the total voltage" specifically includes: , Perform an inverse Clarke transform to obtain the modulation voltage reference value in the three-phase stationary coordinate system. , , .

[0069] S109: Controls the grid-type converter within the control cycle based on the modulation voltage reference value.

[0070] Based on the modulation voltage reference value, PWM drive pulses are generated, and the switching transistors of the grid-type converter are adjusted according to the control cycle to make the converter output voltage match the target command, thus completing the grid voltage support and power regulation.

[0071] To demonstrate the effectiveness of this invention, a simulation example is provided. The control methods of the grid-connected converter (hereinafter referred to as the "invention method") and the traditional negative-sequence current PI control method (hereinafter referred to as "traditional negative-sequence current PI control") from the embodiments of this invention are used to simulate the control effects of the two models. To ensure a fair comparison, both models use the same external network parameters, the same steady-state operating point, and the same fault disturbance scenario. It should be noted that the fault disturbance scenario is not a necessary condition for the model to take effect. The fault disturbance scenario is set in this simulation only to highlight the performance differences between the two control strategies under severe grid imbalance conditions. Even without fault disturbances, under the slight imbalance conditions of three-phase load asymmetry and line parameter inequality present in daily operation, this invention can still effectively suppress active power frequency double-harmonic fluctuations and ensure stable system operation. The simulation results are as follows: Figure 2 As shown, Figure 2 This is a schematic diagram illustrating the effect of a control method for a grid-type converter provided in an embodiment of the present invention; see also Figure 2As can be seen, the blue curve represents the active power response under the method of this invention, the red curve represents the active power response under the traditional negative-sequence current PI control, and the gray shaded area represents the fault duration. It can be observed that before the fault disturbance is set (t<3s): the active power of the grid-type converter is stable at a steady-state value of approximately 5MW, with no significant fluctuations, indicating that both control methods can achieve good steady-state control effects under symmetrical operating conditions. During the fault duration (t=3.0~3.5s), under the three-phase imbalance of the power grid caused by a single-phase ground fault in phase A, the active power under both control methods exhibits typical 100Hz second harmonic fluctuations. Among them, the control effect of the method of this invention (blue curve) is comparable to that of the traditional negative-sequence current PI control (red curve), both able to maintain basic system operation, and the active power fluctuation amplitude under the method of this invention is slightly smaller than that of the traditional scheme. After the fault is cleared (t>3.5s): the performance difference between the two control methods becomes significantly more pronounced. Under traditional negative-sequence current PI control (red curve), the active power exhibited continuous and large-amplitude second-harmonic oscillations, with a peak value reaching 9.19 MW and a peak-to-valley difference of 7.54 MW, preventing the system from quickly recovering to stability. However, under the method of this invention (blue curve), the peak active power decreased to 6.97 MW (a reduction of approximately 24%), the peak-to-valley difference narrowed to 4.26 MW (a reduction of approximately 43%), the oscillation amplitude was significantly reduced, and the system quickly converged to a steady-state value, resulting in a significantly faster system recovery speed. These results demonstrate that the method of this invention can fundamentally suppress active power second-harmonic fluctuations caused by three-phase voltage imbalance in the power grid, especially effectively avoiding continuous power oscillations under traditional control methods during transient recovery after fault clearance, and significantly improving the transient stability of the system.

[0072] To better illustrate the effects of the present invention, another simulation example is provided. The control methods of the grid-type converter of this embodiment (hereinafter referred to as the PSCAD fine-grained model to distinguish it from the first simulation example) and the control methods of the traditional DSP electromechanical transient simulation model (hereinafter referred to as the DSP electromechanical transient model) are used to simulate the control effects of the two models. To ensure a fair comparison, both models use the same external network parameters, the same steady-state operating point, and the same fault disturbance scenario. It should be noted that the DSP electromechanical transient model maintains consistency with the method of this invention in positive-sequence control, that is, it also adopts the control logic shown in step S103 of this invention (this logic is also a common technical means in this field); the core difference lies in the negative-sequence control stage. The method of this invention completely preserves the positive and negative sequence separation of DSOGI, Key steps such as optimal negative-sequence reference calculation and the inner-loop complex frequency domain equation for negative-sequence current enable refined active control of the negative-sequence component, while the traditional DSP electromechanical transient model significantly simplifies the negative-sequence dynamic control process. Please refer to [link / reference]. Figure 3 , Figure 3This is a schematic diagram illustrating the effect of a control method for a grid-type converter provided in another embodiment of the present invention; see also Figure 3 As can be seen, the red curve represents the active power response under the traditional DSP electromechanical transient model, the blue curve represents the active power response under the PSCAD fine-grained model of this invention, and the gray shaded area represents the fault duration (t=3.0s~3.5s). It can be seen that during the fault period (t=3.0~3.5s): under the three-phase imbalance of the power grid caused by a single-phase ground fault in phase A, the traditional DSP electromechanical transient model (red curve) only presents a smooth, approximately linear change in active power, failing to capture the 100Hz second harmonic active power fluctuation generated by negative sequence voltage excitation, and losing key details of negative sequence control and system dynamic interaction; while the PSCAD fine-grained model of this invention (blue curve) clearly reproduces the high-frequency second harmonic oscillation process of active power during the fault, truly restoring the dynamic interaction of positive and negative sequence components and the response process of the control loop. The transient characterization capability of this application is significantly better than the traditional model.

[0073] like Figure 4 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided; An embodiment of the present invention provides a control device for a grid-type converter, comprising: a data acquisition module, a component extraction module, a positive sequence voltage reference value determination module, a negative sequence voltage total amplitude determination module, a first reference value determination module, a negative sequence current component reference value determination module, a negative sequence voltage component reference value determination module, a second reference value determination module, and a converter control module; The data acquisition module is used to acquire the real-time port voltage and real-time port current of the current control cycle during each control cycle of the grid-connected converter during grid-connected operation. The component extraction module is used to extract positive sequence voltage components, positive sequence current components, negative sequence voltage components, and negative sequence current components based on real-time port voltage and real-time port current. The positive sequence voltage reference value determination module is used to obtain the positive sequence voltage reference value based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value. The negative sequence voltage total amplitude determination module is used to obtain the total amplitude of the negative sequence voltage based on the negative sequence voltage components; The first reference value determination module is used to use the positive sequence voltage reference value as the modulation voltage reference value of the current control cycle when the total amplitude of the negative sequence voltage is less than the preset amplitude threshold. The negative sequence current component reference value determination module is used to construct and solve the equation system of the second harmonic active power fluctuation component when the total amplitude of the negative sequence voltage is greater than or equal to a preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component, and negative sequence voltage component, with the cosine component amplitude of the second harmonic active power fluctuation equal to a first preset value and the sine component amplitude of the second harmonic active power fluctuation equal to a second preset value, to obtain the reference value of the negative sequence current component. The negative sequence voltage component reference value determination module is used to obtain the negative sequence voltage component reference value based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component. The second reference value determination module is used to obtain the modulation voltage reference value of the current control cycle based on the positive sequence voltage reference value and the negative sequence voltage component reference value. The converter control module is used to control the grid-type converter within a control cycle based on the modulated voltage reference value.

[0074] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can implement the control method of the grid-type converter provided by any of the above-described method embodiments of the present invention.

[0075] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0076] Based on the above-described embodiments of the control method for grid-type converters, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the control method for grid-type converters of any embodiment of the present invention.

[0077] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0078] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0079] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0080] Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the control method of the grid-type converter described in any of the above-described method embodiments of the present invention.

[0081] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0082] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A control method for a grid-type converter, characterized in that, include: During each control cycle of the grid-connected converter, the real-time port voltage and real-time port current of the current control cycle are collected. Based on real-time port voltage and real-time port current, positive sequence voltage component, positive sequence current component, negative sequence voltage component and negative sequence current component are extracted; Based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value, the positive sequence voltage reference value is obtained; Based on the negative sequence voltage components, the total amplitude of the negative sequence voltage is obtained; If the total amplitude of the negative sequence voltage is less than the preset amplitude threshold, the positive sequence voltage reference value will be used as the modulation voltage reference value for the current control cycle. When the total amplitude of the negative sequence voltage is greater than or equal to the preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component and negative sequence voltage component, with the cosine component amplitude of the second harmonic active power fluctuation equal to the first preset value and the sine component amplitude of the second harmonic active power fluctuation equal to the second preset value, the equation system of the second harmonic active power fluctuation component is constructed and solved to obtain the reference value of the negative sequence current component. Based on the reference value of the negative sequence current component, the negative sequence current component, and the negative sequence voltage component, the reference value of the negative sequence voltage component is obtained; Based on the positive sequence voltage reference value and the negative sequence voltage component reference value, the modulation voltage reference value for the current control cycle is obtained; The grid-type converter is controlled within the control cycle based on the modulation voltage reference value.

2. The control method for a grid-type converter as described in claim 1, characterized in that, Based on real-time port voltage and real-time port current, positive-sequence voltage components, positive-sequence current components, negative-sequence voltage components, and negative-sequence current components are extracted, including: Perform a Clarke transform on the real-time port voltage to obtain the result. The first static component of the voltage on the axis and in The second stationary component of the voltage on the axis; The first and second static components of the voltage are input into a second-order generalized integral structure to generate... The first static component of the positive sequence voltage on the axis, The first static component of the negative sequence voltage on the axis, The second static component of the positive sequence voltage on the axis and in The second stationary component of the negative sequence voltage on the axis; Performing a Clarke transform on the real-time port current yields the result. The first static component of the current on the shaft and in The second static component of the current on the shaft; The first and second static components of the current are input into a second-order generalized integrator structure so that the output of the second-order generalized integrator structure is... The first static component of the positive sequence current on the axis, The first static component of the negative sequence current on the axis, The second static component of the positive sequence current on the axis and in The second stationary component of the negative sequence current on the axis; The first stationary component and the second stationary component of the positive sequence voltage are connected to a synchronous rotating phase-locked loop so that the synchronous rotating phase-locked loop can calculate the positive sequence synchronization angle; based on the positive sequence synchronization angle, the negative sequence reverse synchronization angle is obtained. Based on the positive sequence synchronization angle, Park transform is performed on the first static component of positive sequence voltage, the second static component of positive sequence voltage, the first static component of positive sequence current, and the second static component of positive sequence current to obtain the first component of positive sequence voltage on the d-axis, the second component of positive sequence voltage on the q-axis, the first component of positive sequence current on the d-axis, and the second component of positive sequence current on the q-axis. Based on the negative sequence reverse synchronization angle, Park transform is performed on the first stationary component of negative sequence voltage, the second stationary component of negative sequence voltage, the first stationary component of negative sequence current, and the second stationary component of negative sequence current to obtain the first component of negative sequence voltage on the d-axis, the second component of negative sequence voltage on the q-axis, the first component of negative sequence current on the d-axis, and the second component of negative sequence current on the q-axis. The first and second components of the positive-sequence voltage are taken as positive-sequence voltage components; the first and second components of the positive-sequence current are taken as positive-sequence current components; the first and second components of the negative-sequence voltage are taken as negative-sequence voltage components; and the first and second components of the negative-sequence current are taken as negative-sequence current components.

3. The control method for a grid-type converter as described in claim 2, characterized in that, The preset power reference value includes a preset reactive power reference value and a preset active power reference value. Based on the positive-sequence voltage component, the positive-sequence current component, and a preset power reference value, a positive-sequence voltage reference value is obtained, including: The product of the first component of positive sequence voltage and the first component of positive sequence current is taken as the first active power component of positive sequence; the product of the second component of positive sequence voltage and the second component of positive sequence current is taken as the second active power component of positive sequence. The product of the second component of positive-sequence voltage and the first component of positive-sequence current is taken as the first component of positive-sequence reactive power; the second component of positive-sequence reactive power is obtained based on the product of the first component of positive-sequence voltage and the second component of positive-sequence current. The measured active power is obtained based on the first positive-sequence active power component and the second positive-sequence active power component; the measured reactive power is obtained based on the first positive-sequence reactive power component and the second positive-sequence reactive power component. The frequency deviation command is obtained based on the measured active power, the preset active power reference value, and the preset active power droop coefficient. The voltage outer loop reference value is calculated based on the measured reactive power, the preset reactive power reference value, and the preset reactive power droop coefficient. Based on the frequency deviation command, the outer voltage reference value, the first component of the positive sequence voltage, and the second component of the positive sequence voltage, the inner current reference value is obtained. Based on the current inner loop reference value, the first component of the positive sequence current and the second component of the positive sequence current, the reference values ​​of the first component of the positive sequence voltage and the reference values ​​of the second component of the positive sequence voltage are obtained. The reference values ​​of the first component and the second component of the positive sequence voltage are used as the reference values ​​for the positive sequence voltage.

4. The control method for a grid-type converter as described in claim 3, characterized in that, Based on the negative sequence voltage components, the total amplitude of the negative sequence voltage is obtained, including: The square of the first component of the negative sequence voltage is taken as the first square term of the negative sequence voltage. The square of the second component of the negative sequence voltage is taken as the second square term of the negative sequence voltage. The total amplitude of the negative sequence voltage is obtained based on the first square term and the second square term of the negative sequence voltage.

5. The control method for a grid-type converter as described in claim 4, characterized in that, The negative sequence current component reference value includes the negative sequence current first component reference value and the negative sequence current second component reference value; The equation set for the second harmonic active power fluctuation component is as follows: in, This represents the amplitude of the cosine component of the second-harmonic active power oscillation. This is the first component of the positive sequence voltage. This is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence voltage. This is the first component of the positive sequence current. This is the second component of the negative sequence voltage. Let be the second component of the positive sequence current, 'a' be the first set value (a is a preset control target value), and 'b' be the second set value (b is a preset control target value). This represents the amplitude of the sinusoidal component of the second harmonic active power fluctuation. This is the reference value for the second component of the negative sequence current.

6. The control method for a grid-type converter as described in claim 5, wherein the negative sequence voltage component reference value is obtained based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component, includes: Based on the reference value of the negative sequence current component, the negative sequence current component, and the negative sequence voltage component, the reference value of the negative sequence voltage component is obtained according to the complex frequency domain equation of the inner loop of the negative sequence current. The complex frequency domain equation for the inner loop of the negative sequence current is: in, This is the reference value for the first component of the negative sequence voltage. The preset proportional gain, The preset integral coefficient, It is the Laplace operator. It is the reference value for the first component of the negative sequence current. This is the first component of the negative sequence current. The preset fundamental angular frequency of the power grid. The preset filter inductor, This is the second component of the negative sequence current. This is the first component of the negative sequence voltage. This is the reference value for the second component of the negative sequence voltage. This is the reference value for the second component of the negative sequence current. This is the second component of the negative sequence voltage; The reference values ​​of the first and second components of the negative sequence voltage are used as the reference values ​​for the negative sequence voltage components.

7. The control method for a grid-type converter as described in claim 6, characterized in that, Based on the positive-sequence voltage reference value and the negative-sequence voltage component reference value, the modulation voltage reference value for the current control cycle is obtained, including: By performing Parker inverse transform on the reference values ​​of the first component and the second component of the positive sequence voltage, respectively, reference values ​​of the first static component and the second static component of the positive sequence voltage are obtained. By performing inverse Park transform on the reference values ​​of the first component and the second component of the negative sequence voltage, the reference values ​​of the first static component and the second static component of the negative sequence voltage are obtained. Based on the reference values ​​of the first static component of the positive sequence voltage and the first static component of the negative sequence voltage, the first static component of the total voltage is obtained; Based on the reference values ​​of the second static component of the positive sequence voltage and the second static component of the negative sequence voltage, the second static component of the total voltage is obtained; Based on the first static component and the second static component of the total voltage, the reference value of the modulation voltage for the current control cycle is obtained.

8. A control device for a grid-type converter, characterized in that, include: The system includes a data acquisition module, a component extraction module, a positive sequence voltage reference value determination module, a negative sequence voltage total amplitude determination module, a first reference value determination module, a negative sequence current component reference value determination module, a negative sequence voltage component reference value determination module, a second reference value determination module, and a converter control module. The data acquisition module is used to acquire the real-time port voltage and real-time port current of the current control cycle during each control cycle of the grid-connected converter during grid-connected operation. The component extraction module is used to extract positive sequence voltage components, positive sequence current components, negative sequence voltage components, and negative sequence current components based on real-time port voltage and real-time port current. The positive sequence voltage reference value determination module is used to obtain the positive sequence voltage reference value based on the positive sequence voltage component, the positive sequence current component, and the preset power reference value. The negative sequence voltage total amplitude determination module is used to obtain the total amplitude of the negative sequence voltage based on the negative sequence voltage components; The first reference value determination module is used to use the positive sequence voltage reference value as the modulation voltage reference value of the current control cycle when the total amplitude of the negative sequence voltage is less than the preset amplitude threshold. The negative sequence current component reference value determination module is used to construct and solve the equation system of the second harmonic active power fluctuation component when the total amplitude of the negative sequence voltage is greater than or equal to a preset amplitude threshold, based on the positive sequence voltage component, positive sequence current component, and negative sequence voltage component, with the cosine component amplitude of the second harmonic active power fluctuation equal to a first preset value and the sine component amplitude of the second harmonic active power fluctuation equal to a second preset value, to obtain the reference value of the negative sequence current component. The negative sequence voltage component reference value determination module is used to obtain the negative sequence voltage component reference value based on the negative sequence current component reference value, the negative sequence current component, and the negative sequence voltage component. The second reference value determination module is used to obtain the modulation voltage reference value of the current control cycle based on the positive sequence voltage reference value and the negative sequence voltage component reference value. The converter control module is used to control the grid-type converter within a control cycle based on the modulated voltage reference value.

9. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the control method for a grid-type converter as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform the control method for a grid-type converter as described in any one of claims 1-7.

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