A method, system, device and medium for grid-forming converter control

Abstract

The application discloses a network-constructing converter control method, system, device and medium, and belongs to the technical field of converter control. The method is as follows: determining a reference current according to real-time inductance current and real-time capacitance voltage of a linear virtual oscillator, and active power reference value and reactive power reference value of a target converter; obtaining real-time alternating current of the target converter to determine a given current; obtaining instantaneous inductance current and instantaneous capacitance voltage of the linear virtual oscillator according to the given current to determine a frequency locking direction; obtaining a target capacitance value according to the frequency locking direction and total current of the linear virtual oscillator to obtain adjusted inductance current and adjusted capacitance voltage of the linear virtual oscillator; and obtaining a voltage modulation reference value of the target converter to control the target converter. Therefore, the application can solve the technical problems of complex and unstable network-constructing converter control in the prior art, and realizes efficient control of the converter.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a grid-connected converter control method, system, device and medium. Background Technology

[0002] In modern power systems, the development of renewable energy effectively alleviates the limitations of onshore energy development. However, the integration of power electronic renewable energy will significantly alter the operating state of traditional power systems, posing severe challenges to these systems across multiple time-scale dynamic dimensions. A higher proportion of power electronic renewable energy leads to a decrease in power system inertia and grid strength, posing an instability risk to traditional grid-based control systems in weak grid conditions.

[0003] Existing technologies overcome the risk of synchronous instability under weak interconnection in AC systems by employing grid-based control. However, current grid-based or follow-grid converter control is based on phase and amplitude tracking control in the frequency domain, lacking effective time-domain voltage generation methods, leading to control instability. Furthermore, current time-domain grid-based control strategies are mainly based on virtual oscillation control, resulting in a relative lack of control strategies and involving nonlinear elements, making them relatively complex. Summary of the Invention

[0004] This invention provides a grid-connected converter control method, system, device, and medium, which can solve the technical problems of complex and unstable grid-connected converter control in the prior art and achieve efficient control of the converter.

[0005] To address the aforementioned technical problems, in a first aspect, this invention discloses a grid-connected converter control method applied to a linear virtual oscillator; the linear virtual oscillator includes parallel-connected inductors and capacitors; the grid-connected converter control method includes: The real-time inductor current and real-time capacitor voltage of the linear virtual oscillator are obtained so as to determine the reference current of the linear virtual oscillator based on the active power reference value and reactive power reference value of the target converter. The real-time AC current of the target converter is obtained, and the given current of the linear virtual oscillator is determined based on the real-time AC side current and the reference current. The instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator are obtained based on the given current, so as to obtain the frequency locking direction of the linear virtual oscillator based on the instantaneous inductor current and the instantaneous capacitor voltage; The target capacitance value of the capacitor is obtained based on the frequency locking direction and the total current of the linear virtual oscillator, and the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator are obtained based on the target capacitance value. The voltage modulation reference value of the target converter is obtained based on the adjusted inductor current and the adjusted capacitor voltage. A switching pulse signal of the target converter is generated based on the voltage modulation reference value. The switching pulse signal is used to control the turn-on and turn-off of the target converter.

[0006] This invention discloses a grid-connected converter control method applied to a linear virtual oscillator, which includes parallel inductors and capacitors. This method simplifies the model using linear components, avoiding the complexity of nonlinear elements and providing a foundation for time-domain control. The method acquires the real-time inductor current and capacitor voltage of the linear virtual oscillator and determines a reference current based on the active and reactive power reference values ​​of the target converter. This ensures a close match between the control signal and power demand, providing real-time data support for generating an accurate reference current. The method also acquires the real-time AC side current of the target converter and determines a given current based on the real-time AC side current and the reference current. This method combines actual current feedback to adjust the given current, achieving precise current control and enhancing system stability. Finally, the method acquires the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator based on the given current and obtains the frequency locking direction based on these instantaneous inductor current and instantaneous capacitor voltage. This method dynamically determines the frequency direction using instantaneous parameters, ensuring frequency stability and avoiding the risk of losing synchronization. This method obtains the target capacitance value of the capacitor based on the frequency-locked direction and the total current of the linear virtual oscillator, and then uses this target capacitance value to obtain the adjustment inductor current and adjustment capacitor voltage. This method dynamically adjusts the capacitance value to optimize oscillator performance, adapt to system changes, and improve control efficiency. Furthermore, this method obtains the voltage modulation reference value of the target converter based on the adjustment inductor current and adjustment capacitor voltage, and generates switching pulse signals based on the voltage modulation reference value to control the switching on and off of the target converter. This method directly generates time-domain voltage modulation signals, achieving highly efficient control execution.

[0007] As a preferred example, obtaining the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator to determine the reference current of the linear virtual oscillator based on the active power reference value and reactive power reference value of the target converter includes: The voltage gain coefficient of the linear virtual oscillator is determined based on the real-time inductance value of the inductor and the real-time capacitance value of the capacitor. The first matrix coefficients are constructed based on the product of the voltage gain coefficient, the preset voltage gain, and the real-time inductor current of the linear virtual oscillator. The second matrix coefficients are constructed based on the product of the voltage gain and the real-time capacitor voltage; Construct a current matrix based on the first matrix coefficients, the second matrix coefficients, and the inverse of the second matrix coefficients; The sum of the squared values ​​of the coefficients of the second matrix and the squared values ​​of the coefficients of the first matrix is ​​obtained to obtain the ratio of the current matrix to the sum. Based on the ratio, the active power reference value, and the reactive power reference value, the first reference current vector and the second reference current vector of the linear virtual oscillator in the two-phase coordinate system are obtained.

[0008] The above scheme determines the voltage gain coefficient based on the real-time inductance and capacitance values ​​of the inductor and capacitor, respectively. This takes into account the actual circuit parameter variations and avoids gain deviations affecting control accuracy. A first matrix coefficient is constructed based on the voltage gain coefficient, preset voltage gain, and real-time inductor current. Combined with preset values ​​and real-time measurements, dynamic coefficient adjustment is achieved to adapt to the system state. A second matrix coefficient is constructed based on the voltage gain and real-time capacitor voltage. Similarly, the capacitor voltage signal is used to enhance the accuracy of voltage-related calculations. A current matrix is ​​constructed based on the first matrix coefficient, the second matrix coefficient, and the inverse of the second matrix coefficient. The inverse is introduced to handle phase or direction differences, simplifying the negative feedback mechanism. The sum of the squares of the second and first matrix coefficients is obtained to get the ratio of the current matrix to the sum. Normalization is achieved by calculating the sum and ratio, providing a proportional reference. A reference current vector is obtained based on the ratio, active power reference value, and reactive power reference value. A vector in a two-phase coordinate system is directly generated based on power demand, simplifying the control process and improving response efficiency. Overall, these features work together to form a linear computational framework, eliminating nonlinear complexity and improving control stability and accuracy.

[0009] As a preferred example, the step of acquiring the real-time AC side current of the target converter, and determining the given current of the linear virtual oscillator based on the real-time AC side current and the reference current, includes: Obtain the first AC side current vector and the second AC side current vector of the real-time AC side current in the two-phase coordinate system; Obtain the first deviation current vector between the first AC side current vector and the first reference current vector, and the second deviation current vector between the second AC side current vector and the second reference current vector; The given current of the linear virtual oscillator is obtained based on the first deviation current vector, the second deviation current vector, the preset phase angle, and the preset current gain.

[0010] The above scheme obtains the real-time AC side current vector in a two-phase coordinate system. This facilitates the standardization of current data in a specific coordinate system, providing a basis for subsequent deviation calculations and avoiding coordinate system transformation errors. Secondly, the scheme obtains the deviation current vector and quantifies the current error by directly comparing the real-time AC side current vector with the reference current vector, ensuring accurate error identification and providing a basis for adjustment. Finally, the scheme generates a given current based on the deviation vector, preset phase angle, and current gain, and dynamically adjusts it in conjunction with preset parameters to make the given current more closely match actual needs, improving control accuracy and avoiding instability caused by parameter mismatch.

[0011] As a preferred example, the step of obtaining the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator based on the given current, and obtaining the frequency locking direction of the linear virtual oscillator based on the instantaneous inductor current and the instantaneous capacitor voltage, includes: The given current is applied to the linear virtual oscillator to obtain the instantaneous capacitor voltage and instantaneous capacitor current of the capacitor and the instantaneous inductance current of the inductor in the linear virtual oscillator. The instantaneous inductor current and the sum of the instantaneous inductor current and the instantaneous capacitor current are multiplied together, and the resulting product is used as the synchronization feedback signal of the virtual oscillator. The polarity of the synchronization feedback signal is obtained to determine the adjustment direction of the capacitor in the linear virtual oscillator based on the polarity.

[0012] The above scheme applies a given current to a linear virtual oscillator to obtain instantaneous capacitor voltage, instantaneous capacitor current, and instantaneous inductor current. This ensures operation based on real-time dynamic parameters, avoids data lag, and improves response timeliness. Secondly, the instantaneous inductor current and the sum of the two currents are multiplied as a synchronization feedback signal. This combined calculation effectively integrates the instantaneous states of voltage and current, simplifies the synchronization detection process, and enhances the representativeness of the signal. Finally, the polarity of the synchronization feedback signal is obtained to determine the direction of capacitor adjustment. The positive and negative characteristics of the signal are directly used to guide the adjustment, eliminating the need for complex algorithms and improving the efficiency and stability of control decisions.

[0013] As a preferred example, the step of obtaining the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, and then obtaining the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator based on the target capacitance value, includes: The synchronous feedback signal is band-stop filtered, and the filtered synchronous feedback signal is input into a preset proportional-integral controller to obtain the adjustment amount of the capacitor; The capacitor is adjusted to the target capacitance value according to the adjustment amount and the adjustment direction, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator at the target capacitance value.

[0014] The above scheme performs band-stop filtering on the synchronous feedback signal, filtering out specific frequency noise in the signal and ensuring that the total current calculation is based on a clean signal, avoiding the accumulation of errors caused by noise. Next, the above scheme extracts the sum of the instantaneous inductor current and the instantaneous capacitor current from the filtered synchronous feedback signal and inputs it to a proportional-integral controller. The controller's proportional and integral characteristics are used to generate a smooth adjustment amount, preventing abrupt changes or oscillations during the adjustment process and enhancing the continuity of the adjustment. Finally, the above scheme adjusts the capacitor according to the adjustment amount and direction, combining control output and direction information to precisely set the target capacitor value, thereby obtaining optimized adjustment inductor current and capacitor voltage, achieving dynamic optimization of the capacitor value.

[0015] As a preferred example, obtaining the voltage modulation reference value of the target converter based on the adjusted inductor current and the adjusted capacitor voltage includes: The real-time voltage gain coefficient is determined based on the target capacitance value and the inductance value of the inductor. The first voltage modulation matrix coefficient is determined based on the real-time voltage gain coefficient and the preset voltage gain, and the voltage gain is used as the second voltage modulation matrix coefficient to obtain a two-dimensional voltage modulation matrix. A one-dimensional voltage modulation matrix is ​​constructed based on the adjusted inductor current and the adjusted capacitor voltage. The product of the one-dimensional voltage modulation matrix and the two-dimensional voltage modulation matrix is ​​obtained to obtain the first voltage modulation vector and the second voltage modulation vector in the two-phase coordinate system.

[0016] The above scheme determines the real-time voltage gain coefficient based on the target capacitance and inductance values. This step considers the actual parameter changes of the capacitor and inductor, ensuring that the gain coefficient dynamically reflects the system state and avoids error accumulation caused by using fixed values, providing an accurate basis for subsequent calculations. Next, the scheme determines the first voltage modulation matrix coefficients based on the real-time voltage gain coefficients and a preset voltage gain, and uses the voltage gain as the second voltage modulation matrix coefficients to obtain a two-dimensional voltage modulation matrix. This process, by combining the real-time gain and the preset gain to construct a standardized matrix, achieves uniformity and simplification of the calculation process, reduces nonlinear interference, and enhances the robustness of the system. Then, the scheme constructs a one-dimensional voltage modulation matrix by adjusting the inductor current and capacitor voltage, directly using the adjusted current and voltage values ​​as input, ensuring the real-time nature and accuracy of the data source, providing reliable support for matrix operations, and avoiding the complexity of additional conversion steps. Finally, the above scheme obtains the product of the one-dimensional voltage modulation matrix and the two-dimensional voltage modulation matrix to obtain the first voltage modulation vector and the second voltage modulation vector in the two-phase coordinate system. By efficiently integrating one-dimensional and two-dimensional data through matrix multiplication, the vector in the coordinate system is directly generated, which simplifies the conversion logic, reduces the consumption of computing resources, and improves the generation accuracy of the voltage modulation reference value, thereby supporting the stable generation of subsequent switching pulse signals.

[0017] As a preferred example, the step of generating a switching pulse signal for the target converter based on the voltage modulation reference value, and controlling the switching on and off of the target converter according to the switching pulse signal, includes: The first voltage modulation vector and the second voltage modulation vector are transformed in coordinate system to obtain the three-phase voltage reference values; The three-phase voltage reference values ​​are subjected to pulse width modulation processing to obtain the switching pulse signal of the target converter.

[0018] The above scheme performs coordinate transformation on the first and second voltage modulation vectors to obtain the three-phase voltage reference values. This step maps the modulation signal in the two-phase coordinate system to the reference voltage of the three-phase system, ensuring the compatibility and accuracy of the signal conversion and avoiding phase distortion or system mismatch that may be caused by directly using the two-phase signals. Next, the above scheme performs pulse width modulation processing on the three-phase voltage reference values ​​to obtain the switching pulse signal of the target converter. This processing uses standardized modulation technology to generate high-precision switching timing, simplifies the control process, reduces the computational burden, and enhances the reliability and response speed of the switching signal, ultimately achieving efficient control of the converter's turn-on and turn-off.

[0019] Secondly, the present invention discloses a grid-connected converter control system applied to a linear virtual oscillator; the linear virtual oscillator includes parallel inductors and capacitors; the grid-connected converter control system includes a reference current module, an oscillation modulation module, a frequency locking module, a capacitor adjustment module, and a pulse control module; The reference current module is used to obtain the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator, so as to determine the reference current of the linear virtual oscillator according to the active power reference value and reactive power reference value of the target converter. The oscillation modulation module is used to acquire the real-time AC side current of the target converter, so as to determine the given current of the linear virtual oscillator based on the real-time AC side current and the reference current. The frequency locking module is used to obtain the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator according to the given current, so as to obtain the frequency locking direction of the linear virtual oscillator according to the instantaneous inductor current and the instantaneous capacitor voltage; The capacitor adjustment module is used to obtain the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator based on the target capacitance value; The pulse control module is used to obtain the voltage modulation reference value of the target converter based on the adjustment inductor current and the adjustment capacitor voltage, generate the switching pulse signal of the target converter based on the voltage modulation reference value, and control the switching on and off of the target converter based on the switching pulse signal.

[0020] This invention discloses a grid-connected converter control system applied to a linear virtual oscillator, which includes parallel inductors and capacitors. The system simplifies the model using linear components, avoiding the complexity of nonlinear elements and providing a foundation for time-domain control. The system acquires the real-time inductor current and capacitor voltage of the linear virtual oscillator and determines a reference current based on the active and reactive power reference values ​​of the target converter. This method ensures a close match between the control signal and power demand, providing real-time data support for generating an accurate reference current. The system acquires the real-time AC side current of the target converter and determines a given current based on the real-time AC side current and the reference current. The system adjusts the given current using actual current feedback to achieve precise current control and enhance system stability. The system acquires the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator based on the given current and obtains the frequency locking direction based on these instantaneous inductor current and instantaneous capacitor voltage. This method dynamically determines the frequency direction using instantaneous parameters, ensuring frequency stability and avoiding the risk of losing synchronization. This system obtains the target capacitance value of the capacitor based on the frequency-locked direction and the total current of the linear virtual oscillator. It then uses this target capacitance value to adjust the inductor current and capacitor voltage. This method dynamically adjusts the capacitance value to optimize oscillator performance, adapt to system changes, and improve control efficiency. The system also obtains the voltage modulation reference value of the target converter based on the adjusted inductor current and capacitor voltage. Using this voltage modulation reference value, it generates switching pulse signals to control the switching on and off of the target converter. This system directly generates time-domain voltage modulation signals, achieving highly efficient control execution.

[0021] 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 a grid converter control method as described in the first aspect.

[0022] Another embodiment of the present invention also provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform the steps of a grid converter control method as described in the first aspect. Attached Figure Description

[0023] 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.

[0024] Figure 1This is a flowchart illustrating a grid converter control method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the circuit structure of a linear virtual oscillator provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the control flow of a linear virtual oscillator provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a transformer control based on a linear virtual oscillator provided by an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the control effect test of a linear virtual oscillator provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a grid converter control system provided in an embodiment of the present invention. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] 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.

[0030] 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).

[0031] 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.

[0032] See Figure 1 To address the complex and unstable control issues of existing grid-connected converters, an embodiment of the present invention provides a grid-connected converter control method applied to a linear virtual oscillator. The linear virtual oscillator comprises parallel inductors and capacitors, achieving stable operation of the transformer under a wide range of short-circuit ratios. Specifically, the method includes: S1: Obtain the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator to determine the reference current of the linear virtual oscillator based on the active power reference value and reactive power reference value of the target converter; S2: Obtain the real-time AC side current of the target converter, and determine the given current of the linear virtual oscillator based on the real-time AC side current and the reference current; S3: Obtain the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator according to the given current, so as to obtain the frequency locking direction of the linear virtual oscillator according to the instantaneous inductor current and the instantaneous capacitor voltage; S4: Obtain the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, and obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator based on the target capacitance value; S5: Obtain the voltage modulation reference value of the target converter based on the adjusted inductor current and the adjusted capacitor voltage, generate the switching pulse signal of the target converter based on the voltage modulation reference value, and control the switching on and off of the target converter based on the switching pulse signal.

[0033] In this embodiment, refer to Figure 2 As shown in the diagram, the linear virtual oscillator includes an inductor L and a capacitor C connected in parallel. To achieve grid frequency locking via the linear virtual oscillator, the terminals of the inductor L and the capacitor C are respectively connected to a preset current source, so that a given current is output through the current source. The linear virtual oscillator achieves frequency locking. It's important to note that in the linear virtual oscillator controller composed of inductor L and capacitor C, the inductor value is constant, while the capacitor is adjustable. The characteristic oscillation of the linear virtual oscillator controller... Where ω is the characteristic frequency. It should be noted that, referring to... Figure 2 As shown in the linear virtual oscillator, in order to control the target converter in real time, the given current source and the linear virtual oscillator can be controlled synchronously to achieve synchronous output of the given current, the adjusting inductor current, and the adjusting capacitor voltage.

[0034] In this embodiment, step S1 includes: S11: Determine the voltage gain coefficient of the linear virtual oscillator based on the real-time inductance value of the inductor and the real-time capacitance value of the capacitor; S12: Construct the first matrix coefficients based on the product of the voltage gain coefficient, the preset voltage gain, and the real-time inductor current of the linear virtual oscillator; S13: Construct the second matrix coefficients based on the product of the voltage gain and the real-time capacitor voltage; S13: Construct a current matrix based on the first matrix coefficients, the second matrix coefficients, and the inverse of the second matrix coefficients; S14: Obtain the sum of the squared values ​​of the coefficients of the second matrix and the squared values ​​of the coefficients of the first matrix to obtain the ratio of the current matrix to the sum. S15: Based on the ratio, the active power reference value, and the reactive power reference value, obtain the first reference current vector and the second reference current vector of the linear virtual oscillator in the two-phase coordinate system.

[0035] In this embodiment, refer to Figure 3As shown in the control flow diagram of the linear virtual oscillator, when the linear virtual oscillator achieves frequency locking with the power grid, L and C resonate, and its input current is 0. At this time, a parallel controlled current source is introduced. This ensures that the controlled current source is always zero, thereby achieving current tracking control.

[0036] Specifically, the given current output of the controlled current source is calculated from the reference current of the linear virtual oscillator and the real-time AC side current of the target converter. A dot product operation is used to convert the vector current deviation to a scalar current deviation.

[0037] Specifically, from Figure 3 It can be seen that the first reference current vector in the reference current... and the second reference current vector It can be obtained from the active power reference value Reactive power reference value The real-time state values ​​of the linear virtual oscillator during the current period, such as the real-time voltage value of the capacitor. Real-time current value of inductor Calculated. Specifically, the first reference current vector. and the second reference current vector The calculation process is as follows: Among them, the Voltage gain; , representing the voltage gain coefficient.

[0038] Preferably, the reference current can also be calculated by directly specifying the phase. The formula for calculating the reference current is as follows: Among them, the Represents a preset alternating current; the This represents the phase of the target converter.

[0039] This embodiment determines the voltage gain coefficient based on the real-time inductance and capacitance values ​​of the inductor and capacitor, respectively. This takes into account changes in actual circuit parameters and avoids gain deviations affecting control accuracy. A first matrix coefficient is constructed based on the voltage gain coefficient, a preset voltage gain, and the real-time inductor current. Combined with preset values ​​and real-time measurements, dynamic coefficient adjustment is achieved to adapt to the system state. A second matrix coefficient is constructed based on the voltage gain and the real-time capacitor voltage, similarly utilizing the capacitor voltage signal to enhance the accuracy of voltage-related calculations. A current matrix is ​​constructed based on the first matrix coefficient, the second matrix coefficient, and the inverse of the second matrix coefficient. The inverse is introduced to handle phase or direction differences, simplifying the negative feedback mechanism. The sum of the squares of the second and first matrix coefficients is obtained to get the ratio of the current matrix to the sum. Normalization is achieved by calculating the sum and ratio, providing a proportional reference. A reference current vector is obtained based on the ratio, active power reference value, and reactive power reference value. A vector in a two-phase coordinate system is directly generated based on power demand, simplifying the control process and improving response efficiency. Overall, these features work synergistically to form a linear calculation framework, eliminating nonlinear complexity and improving control stability and accuracy.

[0040] In this embodiment, step S2 includes: S21: Obtain the first AC side current vector and the second AC side current vector of the real-time AC side current in the two-phase coordinate system; S22: Obtain the first deviation current vector between the first AC side current vector and the first reference current vector, and the second deviation current vector between the second AC side current vector and the second reference current vector; S23: Based on the first deviation current vector, the second deviation current vector, the preset phase angle, and the preset current gain, the given current of the linear virtual oscillator is obtained.

[0041] In this embodiment, from Figure 3 It can be seen that the given current output of the controlled current source is calculated based on the reference current and the real-time AC side current of the target converter. From Figure 3 It can be seen that the controller input is the real-time AC side current of the target converter, which is obtained first. and the above Perform three-phase coordinate system abc to Coordinate transformation between two coordinate systems to obtain The first AC side current vector in the two-phase coordinate system Second AC side current vector Next, based on the first deviation current vector obtained between the first AC side current vector and the first reference current vector... and the second deviation current vector between the second AC side current vector and the second reference current vector The formula for calculating the given current based on the aforementioned deviation current vector is as follows: in, For gain, It is the phase angle.

[0042] This embodiment acquires the real-time AC side current vector in a two-phase coordinate system. This facilitates the standardization of current data in a specific coordinate system, providing a basis for subsequent deviation calculations and avoiding coordinate system transformation errors. Secondly, this embodiment acquires the deviation current vector and quantifies the current error by directly comparing the real-time AC side current vector with the reference current vector, ensuring accurate error identification and providing a basis for adjustment. Finally, this embodiment generates a given current based on the deviation vector, preset phase angle, and current gain, and dynamically adjusts it in conjunction with preset parameters to make the given current more closely match actual needs, improve control accuracy, and avoid instability caused by parameter mismatch.

[0043] In this embodiment, step S3 includes: S31: Apply the given current to the linear virtual oscillator to obtain the instantaneous capacitor voltage and instantaneous capacitor current of the capacitor and the instantaneous inductance current of the inductor in the linear virtual oscillator. S32: Multiply the instantaneous inductor current and the sum of the instantaneous inductor current and the instantaneous capacitor current, and use the resulting product as the synchronization feedback signal of the virtual oscillator. S33: Obtain the polarity of the synchronization feedback signal to determine the adjustment direction of the capacitor in the linear virtual oscillator based on the polarity.

[0044] In this embodiment, from Figure 3 It can be seen that a virtual oscillator is used, employing the feedback effect of the inductor-capacitor current and the product of the inductor current, to achieve frequency locking through virtual capacitance adjustment. Specifically, as shown below, where... For the power grid frequency, and These are the capacitor current and the inductor current, respectively. = + Let be the total current flowing into the LC virtual oscillator. From the following equation, it can be seen that, since the square of the voltage is non-negative, when the characteristic frequency of the virtual oscillator... Less than the grid frequency When C is too large, the product becomes negative, thus reducing C, and vice versa, thereby achieving frequency locking.

[0045] Specifically, the frequency locking formula for the virtual oscillator is as follows: Among them, the This represents the real-time voltage value of the capacitor in the virtual oscillator.

[0046] This embodiment applies a given current to a linear virtual oscillator to obtain instantaneous capacitor voltage, instantaneous capacitor current, and instantaneous inductor current. This ensures operation based on real-time dynamic parameters, avoids data lag, and improves response timeliness. Secondly, this embodiment multiplies the square of the instantaneous capacitor voltage, the instantaneous inductor current, and the sum of the two currents to generate a synchronization feedback signal. This combined calculation effectively integrates the instantaneous states of voltage and current, simplifies the synchronization detection process, and enhances the representativeness of the signal. Finally, this embodiment obtains the polarity of the synchronization feedback signal to determine the direction of capacitor adjustment. Directly utilizing the positive and negative characteristics of the signal to guide the adjustment eliminates the need for complex algorithms and improves the efficiency and stability of control decisions.

[0047] In this embodiment, step S4 includes: S41: Perform band-stop filtering on the synchronous feedback signal, and input the filtered synchronous feedback signal into a preset proportional-integral controller to obtain the adjustment amount of the capacitor; S42: Adjust the capacitor to the target capacitance value according to the adjustment amount and the adjustment direction, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator at the target capacitance value.

[0048] In this embodiment, as Figure 3 As shown, to further remove the second harmonic of the product control quantity, a second-order band-stop filter is introduced. Simultaneously, to further eliminate frequency tracking error, proportional-integral (PI) control is introduced to adjust the capacitor. The capacitor adjustment formula is as follows: Where s is the Laplace operator; G is the gain; The rated frequency is set to the rated frequency of the power grid; ζ is the damping coefficient. and These are the proportional-integral coefficients, used to achieve frequency tracking of the power grid frequency without deviation; the... This represents the adjustment amount of capacitor C.

[0049] This embodiment performs band-stop filtering on the synchronous feedback signal to filter out specific frequency noise, ensuring that the total current calculation is based on a clean signal and avoiding error accumulation caused by noise. Next, this embodiment inputs the total current into a proportional-integral controller (PIC), utilizing the controller's proportional and integral characteristics to generate a smooth adjustment amount, preventing abrupt changes or oscillations during the adjustment process and enhancing the continuity of the adjustment. Finally, this embodiment adjusts the capacitor based on the adjustment amount and direction, combining control output and direction information to precisely set the target capacitor value, thereby obtaining optimized adjustment inductor current and capacitor voltage, achieving dynamic optimization of the capacitor value.

[0050] In this embodiment, step S5 includes: S51: Determine the real-time voltage gain coefficient based on the target capacitance value and the inductance value of the inductor; S52: Determine the first voltage modulation matrix coefficients based on the real-time voltage gain coefficients and the preset voltage gain, and use the voltage gain as the second voltage modulation matrix coefficients to obtain a two-dimensional voltage modulation matrix; S53: Construct a one-dimensional voltage modulation matrix based on the adjusted inductor current and the adjusted capacitor voltage; S54: Obtain the product of the one-dimensional voltage modulation matrix and the two-dimensional voltage modulation matrix to obtain the first voltage modulation vector and the second voltage modulation vector in the two-phase coordinate system.

[0051] S55: Perform coordinate system transformation on the first voltage modulation vector and the second voltage modulation vector to obtain the three-phase voltage reference value; S56: Perform pulse width modulation processing on the three-phase voltage reference value to obtain the switching pulse signal of the target converter.

[0052] In this embodiment, the voltage reference is obtained through the capacitor voltage and capacitor current of the virtual oscillator, and can be expressed as the following expression: in For voltage gain, , and This is the reference value for voltage modulation.

[0053] In this embodiment, as Figure 4 As shown, the voltage reference described above is ultimately transformed from αβ to abc to obtain the three-phase voltage reference e, which is then modulated by PWM to obtain the switching signal of the converter. Specifically, as... Figure 4 As shown, after PWM modulation and the output of the linear LC virtual oscillator, the switching pulse signal is input to the converter connected to the main circuit; from Figure 4 It can be seen that the DC side of the converter is connected to a DC power supply. As energy input, the AC side of the converter uses a filter inductor. The common connection point connected to the main circuit has a voltage denoted as . and further related to grid voltage Connected. The main circuit also includes mains current. Measured values ​​used for feedback control, such as... Figure 4 As shown, the output power of the converter and The voltage and current values ​​of the power grid indicate that the main circuit where the converter is located is a typical grid-connected structure. Therefore, from... Figure 4 It can be seen that the converter is connected to the main circuit by connecting the AC output terminal of the converter to the power grid through a filter inductor to achieve power exchange.

[0054] In this embodiment, coordinate system transformation is performed on the first and second voltage modulation vectors to obtain the three-phase voltage reference values. This step maps the modulation signal in the two-phase coordinate system to the reference voltage of the three-phase system, ensuring the compatibility and accuracy of the signal conversion and avoiding phase distortion or system mismatch that may be caused by directly using the two-phase signals. Next, the three-phase voltage reference values ​​are processed by pulse width modulation to obtain the switching pulse signal of the target converter. This processing uses standardized modulation technology to generate high-precision switching timing, which simplifies the control process, reduces the computational burden, and enhances the reliability and response speed of the switching signal, ultimately achieving efficient control of the converter's turn-on and turn-off.

[0055] In this embodiment, Figure 1 The method shown is applicable to all grid-type converters and can effectively achieve converter current control. Based on the above control, a DC voltage or AC voltage control loop can be added to the outer loop to achieve both DC and AC voltage control.

[0056] In this first embodiment, to verify the effectiveness of the above control strategy, a traditional two-level VSC is used, with an ideal voltage source connected to the DC side and an AC system connected to the AC side. The grid strength varies from 1.5 to ∞. The detailed system parameters are shown in the table below: Taking a grid-connected inverter as an example, in a 0.69kV AC, 1.5kV DC system with a line impedance angle of 85°, and selecting SCR=1.5 and ∞, the test results for power references of 3MW+2Mvar and 3MW+2Mvar are as follows: Figure 5 As shown. Among them, Figure 5This includes time-varying curves for a grid strength of 1.5 (active power / SC = 1.5 and reactive power / SC = 1.5), and also time-varying curves for a grid strength of ∞ (active power / SC = ∞ and reactive power / SC = ∞). Note that the topology of the voltage-equalizing converter here is not limited to the traditional three-phase two-level topology; other topologies can also be used. Furthermore, other control strategies can also be employed. Figure 5 The curves showing the changes in active power and reactive power over time demonstrate that the system operates stably before 5 seconds. At 5 seconds, the system's active power reference increases to 5MW, and the system continues to operate stably. This indicates that the proposed control method can operate stably across a wide range of short-circuit ratios. Note that because the converter output voltage reference is used as the reference value, the simulated power value is the power at the grid common point, and therefore deviates slightly from the reference power value.

[0057] On the other hand, refer to Figure 6 This embodiment also provides a grid-connected converter control system applied to a linear virtual oscillator; the linear virtual oscillator includes parallel inductors and capacitors; the grid-connected converter control system includes a reference current module 1, an oscillation modulation module 2, a frequency locking module 3, a capacitor adjustment module 4, and a pulse control module 5; The reference current module 1 is used to obtain the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator, so as to determine the reference current of the linear virtual oscillator according to the active power reference value and reactive power reference value of the target converter. The oscillation modulation module 2 is used to acquire the real-time AC side current of the target converter, so as to determine the given current of the linear virtual oscillator based on the real-time AC side current and the reference current. The frequency locking module 3 is used to obtain the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator according to the given current, so as to obtain the frequency locking direction of the linear virtual oscillator according to the instantaneous inductor current and the instantaneous capacitor voltage; The capacitor adjustment module 4 is used to obtain the target capacitance value of the capacitor according to the frequency locking direction and the total current of the linear virtual oscillator, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator according to the target capacitance value; The pulse control module 5 is used to obtain the voltage modulation reference value of the target converter based on the adjustment inductor current and the adjustment capacitor voltage, generate the switching pulse signal of the target converter based on the voltage modulation reference value, and control the switching on and off of the target converter based on the switching pulse signal.

[0058] It should be noted that the system 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 system embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0059] Based on the above-described embodiment of a grid-connected converter control method, 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 a grid-connected converter control method according to any embodiment of the present invention.

[0060] 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.

[0061] 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.

[0062] 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 various parts of the terminal device via various interfaces and lines.

[0063] 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 a grid converter control method as described in any of the above-described method embodiments of the present invention.

[0064] 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.

[0065] This embodiment discloses a grid-connected converter control method, system, device, and medium. It proposes a grid-connected control method based on a linear LC oscillator, analyzes the detailed implementation of its power control, and discusses its DC / AC voltage control. It can operate stably under a wide range of short-circuit ratios and has strong scalability. Specifically, the control method is applied to a linear virtual oscillator, which includes parallel inductors and capacitors. This method simplifies the model using linear components, avoiding the complexity of nonlinear elements and providing a foundation for time-domain control. The control method obtains the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator and determines the reference current based on the active power reference value and reactive power reference value of the target converter. This method ensures a close match between the control signal and power demand, providing real-time data support for generating an accurate reference current. The control method obtains the real-time AC side current of the target converter and determines the given current based on the real-time AC side current and the reference current. This method combines actual current feedback to adjust the given current, achieving precise current control and enhancing system stability. The control method obtains the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator based on a given current, and then obtains the frequency locking direction based on these instantaneous inductor current and instantaneous capacitor voltage. This method dynamically determines the frequency direction using instantaneous parameters, ensuring frequency stability and avoiding the risk of losing synchronization. The control method obtains the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, and then obtains the adjustment inductor current and adjustment capacitor voltage based on the target capacitance value. This method dynamically adjusts the capacitance value to optimize oscillator performance, adapt to system changes, and improve control efficiency. The control method obtains the voltage modulation reference value of the target converter based on the adjustment inductor current and adjustment capacitor voltage, and generates a switching pulse signal based on the voltage modulation reference value to control the switching on and off of the target converter. This method directly generates a time-domain voltage modulation signal, achieving efficient control execution.

[0066] 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 grid-connected converter control method, characterized in that, Applied to linear virtual oscillators; The linear virtual oscillator includes inductors and capacitors connected in parallel; the grid converter control method includes: The real-time inductor current and real-time capacitor voltage of the linear virtual oscillator are obtained so as to determine the reference current of the linear virtual oscillator based on the active power reference value and reactive power reference value of the target converter. The real-time AC side current of the target converter is obtained, and the given current of the linear virtual oscillator is determined based on the real-time AC side current and the reference current. The instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator are obtained based on the given current, so as to obtain the frequency locking direction of the linear virtual oscillator based on the instantaneous inductor current and the instantaneous capacitor voltage; The target capacitance value of the capacitor is obtained based on the frequency locking direction and the total current of the linear virtual oscillator, and the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator are obtained based on the target capacitance value. The voltage modulation reference value of the target converter is obtained based on the adjusted inductor current and the adjusted capacitor voltage. A switching pulse signal of the target converter is generated based on the voltage modulation reference value. The switching pulse signal is used to control the turn-on and turn-off of the target converter.

2. The grid converter control method according to claim 1, characterized in that, The step of acquiring the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator, and determining the reference current of the linear virtual oscillator based on the active power reference value and reactive power reference value of the target converter, includes: The voltage gain coefficient of the linear virtual oscillator is determined based on the real-time inductance value of the inductor and the real-time capacitance value of the capacitor. The first matrix coefficients are constructed based on the product of the voltage gain coefficient, the preset voltage gain, and the real-time inductor current of the linear virtual oscillator. The second matrix coefficients are constructed based on the product of the voltage gain and the real-time capacitor voltage; Construct a current matrix based on the first matrix coefficients, the second matrix coefficients, and the inverse of the second matrix coefficients; The sum of the squared values ​​of the coefficients of the second matrix and the squared values ​​of the coefficients of the first matrix is ​​obtained to obtain the ratio of the current matrix to the sum. Based on the ratio, the active power reference value, and the reactive power reference value, the first reference current vector and the second reference current vector of the linear virtual oscillator in the two-phase coordinate system are obtained.

3. The grid converter control method according to claim 2, characterized in that, The step of acquiring the real-time AC side current of the target converter, and determining the given current of the linear virtual oscillator based on the real-time AC side current and the reference current, includes: Obtain the first AC side current vector and the second AC side current vector of the real-time AC side current in the two-phase coordinate system; Obtain the first deviation current vector between the first AC side current vector and the first reference current vector, and the second deviation current vector between the second AC side current vector and the second reference current vector; The given current of the linear virtual oscillator is obtained based on the first deviation current vector, the second deviation current vector, the preset phase angle, and the preset current gain.

4. The grid converter control method according to claim 1, characterized in that, The step of obtaining the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator based on the given current, and obtaining the frequency locking direction of the linear virtual oscillator based on the instantaneous inductor current and the instantaneous capacitor voltage, includes: The given current is applied to the linear virtual oscillator to obtain the instantaneous capacitor voltage and instantaneous capacitor current of the capacitor and the instantaneous inductance current of the inductor in the linear virtual oscillator. The instantaneous inductor current and the sum of the instantaneous inductor current and the instantaneous capacitor current are multiplied together, and the resulting product is used as the synchronization feedback signal of the virtual oscillator. The polarity of the synchronization feedback signal is obtained to determine the adjustment direction of the capacitor in the linear virtual oscillator based on the polarity.

5. The grid converter control method according to claim 4, characterized in that, The step of obtaining the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, and then obtaining the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator based on the target capacitance value, includes: The synchronous feedback signal is band-stop filtered, and the filtered synchronous feedback signal is input into a preset proportional-integral controller to obtain the adjustment amount of the capacitor; The capacitor is adjusted to the target capacitance value according to the adjustment amount and the adjustment direction, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator at the target capacitance value.

6. The grid converter control method according to claim 1, characterized in that, The step of obtaining the voltage modulation reference value of the target converter based on the adjusted inductor current and the adjusted capacitor voltage includes: The real-time voltage gain coefficient is determined based on the target capacitance value and the inductance value of the inductor. The first voltage modulation matrix coefficient is determined based on the real-time voltage gain coefficient and the preset voltage gain, and the voltage gain is used as the second voltage modulation matrix coefficient to obtain a two-dimensional voltage modulation matrix. A one-dimensional voltage modulation matrix is ​​constructed based on the adjusted inductor current and the adjusted capacitor voltage. The product of the one-dimensional voltage modulation matrix and the two-dimensional voltage modulation matrix is ​​obtained to obtain the first voltage modulation vector and the second voltage modulation vector in the two-phase coordinate system.

7. The grid converter control method according to claim 6, characterized in that, The step of generating a switching pulse signal for the target converter based on the voltage modulation reference value, and controlling the switching on and off of the target converter based on the switching pulse signal, includes: The first voltage modulation vector and the second voltage modulation vector are transformed in coordinate system to obtain the three-phase voltage reference values; The three-phase voltage reference values ​​are subjected to pulse width modulation processing to obtain the switching pulse signal of the target converter.

8. A grid-connected converter control system, characterized in that, It is applied to a linear virtual oscillator; the linear virtual oscillator includes parallel inductors and capacitors; the grid converter control system includes a reference current module, an oscillation modulation module, a frequency lock module, a capacitor adjustment module, and a pulse control module; The reference current module is used to obtain the real-time inductor current and real-time capacitor voltage of the linear virtual oscillator, so as to determine the reference current of the linear virtual oscillator according to the active power reference value and reactive power reference value of the target converter. The oscillation modulation module is used to acquire the real-time AC side current of the target converter, so as to determine the given current of the linear virtual oscillator based on the real-time AC side current and the reference current. The frequency locking module is used to obtain the instantaneous inductor current and instantaneous capacitor voltage of the linear virtual oscillator according to the given current, so as to obtain the frequency locking direction of the linear virtual oscillator according to the instantaneous inductor current and the instantaneous capacitor voltage; The capacitor adjustment module is used to obtain the target capacitance value of the capacitor based on the frequency locking direction and the total current of the linear virtual oscillator, so as to obtain the adjustment inductor current and adjustment capacitor voltage of the linear virtual oscillator based on the target capacitance value; The pulse control module is used to obtain the voltage modulation reference value of the target converter based on the adjustment inductor current and the adjustment capacitor voltage, generate the switching pulse signal of the target converter based on the voltage modulation reference value, and control the switching on and off of the target converter based on the switching pulse signal.

9. A terminal device, characterized in that, The method 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 a grid converter control method 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 where the computer-readable storage medium is located to perform a grid converter control method as described in any one of claims 1-7.

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