A control method and system of a three-phase PWM converter

Abstract

The application discloses a control method and system of a three-phase PWM converter, and belongs to the technical field of converters. The method is: obtaining the operation parameters of the three-phase PWM converter, constructing a voltage dynamic adjustment model and a fixed time disturbance observer, and obtaining a load disturbance estimation value; further obtaining a voltage tracking error and a current tracking error, and combining a pre-obtained nonlinear variable gain to construct a single-loop current constraint variable gain controller; based on the single-loop current constraint variable gain controller, real-time monitoring of grid-connected current is performed, the nonlinear variable gain, the voltage tracking error and the current tracking error are adaptively adjusted, a first control quantity is obtained, and a modulation signal is generated to control the three-phase PWM converter. Therefore, by implementing the application, the grid parameters can be adjusted by using the single-loop structure with the nonlinear variable gain, the load disturbance can be accurately evaluated by combining the disturbance observer, various complex working conditions can be coped with, and the operation stability of the three-phase PWM converter is improved.

Description

Technical Field

[0001] This invention relates to the field of converter technology, and in particular to a control method and system for a three-phase PWM converter. Background Technology

[0002] As a key component in AC-DC conversion, three-phase PWM converters face increasingly stringent performance requirements in applications such as electric vehicle charging systems and energy storage systems, driven by the rapid development of new energy technologies. These converters must be able to quickly adjust and maintain a stable DC output voltage during grid fluctuations or load changes to ensure the safe and stable operation of downstream load devices. However, the pursuit of rapid dynamic response in DC voltage often generates excessive transient AC currents, whose peak values ​​may far exceed the rated current. This severely reduces system safety, affects device lifespan, and can even lead to electrical safety accidents. Therefore, ensuring the more reliable and stable operation of three-phase PWM converters is a crucial issue that requires further research.

[0003] Currently, traditional dual-loop PI control methods are widely used due to their simple structure. However, when load disturbances are large or system parameters change, the limited operating range of the PI controller significantly weakens its control effect, making it difficult to meet the dynamic and static performance requirements under multiple operating conditions. Furthermore, most existing three-phase PWM converter control methods employ a dual-loop cascaded structure with an outer voltage loop and an inner current / power loop, making controller parameter adjustment cumbersome and unsuitable for multi-source operating conditions with frequent load switching. To improve disturbance rejection performance, existing technologies also introduce backstepping control or finite-time control methods, constructing disturbance observers to estimate and compensate for the load disturbance. While these methods address load disturbances, they often have fixed observer bandwidths, resulting in lag in estimating high-frequency interference. Furthermore, the controller parameter adjustment process is complex and heavily reliant on the accurate mathematical model of the system. Other solutions employ command filtering control or multi-mode switching techniques, but they fail to design active suppression mechanisms for load disturbances or theoretically guarantee hard constraints on transient currents at the control law level. Consequently, existing technologies struggle to meet the dynamic and static performance requirements of three-phase PWM converters under various operating conditions, such as large load disturbances, significant parameter changes, or frequent load switching, leading to poor operational stability of the three-phase PWM converter. Summary of the Invention

[0004] This invention proposes a control method and system for a three-phase PWM converter, which solves the problem of poor operational stability caused by the inability of existing technologies to meet the dynamic and static performance requirements of three-phase PWM converters under various operating conditions such as large load disturbances, large parameter changes, or frequent load switching. This invention employs a single-loop structure with nonlinear variable gain to constrain and adjust grid parameters, and combines this with a disturbance observer to accurately assess load disturbances, thereby addressing various complex operating conditions and improving the operational stability of the three-phase PWM converter.

[0005] To achieve the above objectives, embodiments of the present invention provide a control method for a three-phase PWM converter, comprising: acquiring operating parameters of the three-phase PWM converter and constructing a voltage dynamic adjustment model; constructing a fixed-time disturbance observer based on the voltage dynamic adjustment model, and acquiring load disturbance estimates of the three-phase PWM converter according to the fixed-time disturbance observer; acquiring voltage tracking error and current tracking error based on the operating parameters and the load disturbance estimates, and constructing a single-loop current-constrained variable gain controller based on the voltage tracking error, current tracking error, and a pre-acquired nonlinear variable gain; monitoring the grid-connected current of the three-phase PWM converter in real time based on the single-loop current-constrained variable gain controller, and adaptively adjusting the nonlinear variable gain, voltage tracking error, and current tracking error based on the grid-connected current and a preset safety threshold to generate a first control quantity; generating a modulation signal based on the first control quantity, and controlling the three-phase PWM converter through the modulation signal.

[0006] This invention proposes a control method for a three-phase PWM converter. Based on the acquired operating parameters of the three-phase PWM converter, a voltage dynamic adjustment model and a fixed-time disturbance observer are constructed. Load mutations and grid fluctuations are categorized as lumped disturbances. The fixed-time disturbance observer is used to quickly estimate the load disturbance and perform feedforward compensation, improving the converter's immunity to disturbances such as load mutations. Simultaneously, a single-loop current-constrained variable-gain controller is constructed, and a nonlinear variable gain is introduced. The gain is adaptively adjusted based on the relationship between the grid current and the safety threshold to form a current penalty mechanism, strictly constraining the current at the control law level. Therefore, this scheme uses a single-loop structure instead of the traditional double-closed-loop cascaded structure, significantly simplifying the control parameter tuning process. The single-loop structure with nonlinear variable gain constrains and adjusts the grid parameters, and the disturbance observer accurately assesses load disturbances to cope with various complex operating conditions and improve the operational stability of the three-phase PWM converter.

[0007] Furthermore, the step of acquiring the operating parameters of the three-phase PWM converter and constructing a voltage dynamic adjustment model includes: acquiring the operating parameters of the three-phase PWM converter in a three-phase stationary coordinate system, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC-side voltage, and AC-side output voltage; performing coordinate transformation on the three-phase grid voltage, three-phase grid current, and AC-side output voltage to obtain the grid voltage component, grid current component, and AC-side output voltage component in a two-phase synchronous rotating coordinate system; and constructing a voltage dynamic adjustment model based on the grid voltage component, grid current component, DC-side voltage, and AC-side output voltage component.

[0008] In the above scheme, operating parameters in a three-phase stationary coordinate system are collected and transformed. Then, the time-varying parameters on the AC side are converted into DC values ​​in a synchronous rotating coordinate system, providing a data foundation for subsequent model building and control design. Thus, by clearly defining the acquisition range of operating parameters and the coordinate transformation processing method, the accuracy and consistency of the voltage dynamic regulation model are ensured, enabling the model to accurately reflect the dynamic characteristics of the converter. This provides a reliable input data foundation for the construction of a fixed-time disturbance observer and a single-loop variable gain controller.

[0009] Furthermore, based on the grid voltage component, grid current component, DC-side voltage, and AC-side output voltage component, a voltage dynamic adjustment model is constructed, including: squaring the DC-side voltage to obtain a new state variable; constructing a DC-side dynamic model based on the new state variable and the grid current component; constructing an AC-side dynamic model based on preset electrical laws, the grid voltage component, the grid current component, and the AC-side output voltage component; and constructing a voltage dynamic adjustment model based on the DC-side dynamic model and the AC-side dynamic model.

[0010] In the above scheme, the DC-side voltage is squared to obtain new state variables, transforming the original nonlinear model into a linear form that is easier to control design, thus simplifying the complexity of the subsequent fixed-time disturbance observer design. By constructing DC-side dynamic models and AC-side dynamic models separately, and integrating them to obtain a complete voltage dynamic regulation model, the model can accurately describe the coupling relationship between the AC and DC sides simultaneously, providing an accurate mathematical description for the subsequent disturbance observer design, thereby improving the accuracy of subsequent disturbance estimation and helping to improve the operational stability of the three-phase PWM converter.

[0011] Furthermore, a fixed-time disturbance observer is constructed based on the voltage dynamic adjustment model, and the load disturbance estimate of the three-phase PWM converter is obtained according to the fixed-time disturbance observer. This includes: constructing a load disturbance based on a new state variable in the voltage dynamic adjustment model; using the new state variable and the load disturbance as observation objects to construct a fixed-time disturbance observer; inputting the new state variable into the fixed-time disturbance observer to calculate the state estimate; and adjusting the parameters of the fixed-time disturbance observer based on the state estimate so that the observation error between the state estimate and the load disturbance converges to zero within a preset time to obtain the load disturbance estimate of the three-phase PWM converter.

[0012] In the above scheme, a fixed-time disturbance observer is constructed using a voltage dynamic regulation model. New state variables and load disturbances in the voltage dynamic regulation model are taken as observation objects. Utilizing the observer's fast convergence characteristic, the observation error converges to zero within a fixed time, independent of the initial state. Therefore, compared to traditional nonlinear disturbance observers and finite-time disturbance observers, the fixed-time observer proposed in this embodiment has a faster estimation speed and stronger robustness. It can accurately estimate the lumped disturbances caused by input voltage fluctuations and load abrupt changes, and feed the estimated values ​​forward to compensate the controller. This allows the three-phase PWM converter to respond to DC voltage output fluctuations before they occur, improving the dynamic response speed and disturbance rejection capability of the three-phase PWM converter.

[0013] Furthermore, based on the operating parameters and the estimated load disturbance, voltage tracking error and current tracking error are obtained. A single-loop current-constrained variable-gain controller is constructed based on the voltage tracking error, current tracking error, and a pre-acquired nonlinear variable gain. This includes: calculating the voltage tracking error based on the DC-side voltage in the operating parameters and the new state variable; calculating the current tracking error based on the grid current component and the estimated load disturbance; constructing an error dynamic model with the voltage tracking error and current tracking error as state variables based on preset control parameters; and adding the pre-acquired nonlinear variable gain to the error dynamic model to obtain the single-loop current-constrained variable-gain controller.

[0014] In the above scheme, voltage tracking error and current tracking error are specifically defined, transforming the DC voltage regulation problem into an error convergence problem, providing a clear objective for the design of the control law. By converting the physical constraint of the grid-connected current into an equivalent constraint on the current tracking error, a theoretical basis is provided for the mathematical processing of the current constraint. By constructing an error dynamic model with voltage tracking error and current tracking error as state variables and introducing a nonlinear variable gain, voltage regulation and current constraint are unified within a single-loop control framework. This avoids the parameter decoupling problem between the outer voltage loop and the inner current loop in traditional dual-loop control, simplifies the control structure, and helps improve the operational stability of the three-phase PWM converter.

[0015] Furthermore, based on the single-loop current-constrained variable gain controller, the grid-connected current of the three-phase PWM converter is monitored in real time. Based on the grid-connected current and a preset safety threshold, the nonlinear variable gain, voltage tracking error, and current tracking error are adaptively adjusted to generate a first control quantity. This includes: inputting the voltage tracking error, the current tracking error, and the estimated load disturbance value into the single-loop current-constrained variable gain controller; monitoring the grid-connected current of the three-phase PWM converter in real time through the single-loop current-constrained variable gain controller; when the grid-connected current increases, adaptively increasing the nonlinear variable gain according to the preset safety threshold to obtain a target gain value; and adjusting the control parameter weights of the voltage tracking error and current tracking error based on the target gain value to generate the first control quantity.

[0016] In the above scheme, the voltage tracking error, current tracking error, and load disturbance estimate are input into a single-loop current-constrained variable gain controller. When the grid-connected current increases and approaches the safety threshold, the nonlinear variable gain increases adaptively, penalizing the weight of the current tracking error in the control law and forcing the current to pull back. This adaptive penalty mechanism strictly ensures from the control theory level that the transient grid-connected current will not exceed the preset safety threshold, effectively avoiding the risk of equipment protection shutdown or hardware damage caused by overcurrent, and helps to improve the operating stability of the three-phase PWM converter.

[0017] Furthermore, generating a modulation signal based on the first control quantity and controlling the three-phase PWM converter through the modulation signal includes: generating a second control quantity based on the AC side output voltage component; combining the first control quantity and the second control quantity to obtain a comprehensive control quantity in a two-phase synchronous rotating coordinate system; performing an inverse coordinate transformation on the comprehensive control quantity to generate a modulation signal in a two-phase stationary coordinate system; inputting the modulation signal into a preset PWM modulator to generate a corresponding switching transistor drive signal, and controlling the three-phase PWM converter based on the switching transistor drive signal.

[0018] In the above scheme, the first control quantity and the second control quantity output by the single-loop current-constrained variable gain controller are combined to obtain the comprehensive control quantity in the two-phase synchronous rotating coordinate system. Then, the control quantity in the synchronous rotating coordinate system is converted back to the modulation signal in the two-phase stationary coordinate system through coordinate inverse transformation. The signal is then generated as a switching transistor drive signal through PWM modulation, completing the complete conversion from control algorithm to power device execution command. This ensures the accurate execution of control commands and enables the designed voltage regulation and current constraint functions to be realized in the actual converter system, which helps to improve the operating stability of the three-phase PWM converter.

[0019] This invention also provides a control system for a three-phase PWM converter, including a model building module, a load disturbance estimation module, a single-loop current-constrained variable gain controller building module, a first control quantity generation module, and a converter control module; wherein: the model building module is used to acquire the operating parameters of the three-phase PWM converter and build a voltage dynamic adjustment model; the load disturbance estimation module is used to build a fixed-time disturbance observer based on the voltage dynamic adjustment model and acquire the load disturbance estimation value of the three-phase PWM converter according to the fixed-time disturbance observer; the single-loop current-constrained variable gain controller building module is used to acquire the load disturbance estimation value of the three-phase PWM converter based on the operating parameters. The voltage tracking error and current tracking error are obtained from the estimated load disturbance value, and a single-loop current-constrained variable gain controller is constructed based on the voltage tracking error, current tracking error, and pre-acquired nonlinear variable gain. The first control quantity generation module is used to monitor the grid-connected current of the three-phase PWM converter in real time based on the single-loop current-constrained variable gain controller, and adaptively adjust the nonlinear variable gain, voltage tracking error, and current tracking error based on the grid-connected current and a preset safety threshold to generate a first control quantity. The converter control module is used to generate a modulation signal based on the first control quantity, and control the three-phase PWM converter through the modulation signal.

[0020] This invention proposes a control system for a three-phase PWM converter. Based on the acquired operating parameters of the three-phase PWM converter, a voltage dynamic adjustment model and a fixed-time disturbance observer are constructed. Load abrupt changes and grid fluctuations are categorized as lumped disturbances. The fixed-time disturbance observer is used to quickly estimate the load disturbance and perform feedforward compensation, improving the converter's immunity to disturbances such as load abrupt changes. Simultaneously, a single-loop current-constrained variable-gain controller is constructed, introducing a nonlinear variable gain. The gain is adaptively adjusted based on the relationship between the grid current and the safety threshold to form a current penalty mechanism, strictly constraining the current at the control law level. Therefore, this scheme uses a single-loop structure instead of the traditional double-closed-loop cascaded structure, significantly simplifying the control parameter tuning process. The single-loop structure with nonlinear variable gain constrains and adjusts the grid parameters, and the disturbance observer accurately assesses load disturbances to cope with various complex operating conditions, improving the operational stability of the three-phase PWM converter.

[0021] Furthermore, the model building module includes a data acquisition unit, a coordinate transformation unit, and a voltage dynamic adjustment model building unit; wherein: the data acquisition unit is used to acquire the operating parameters of the three-phase PWM converter in a three-phase stationary coordinate system, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC side voltage, and AC side output voltage; the coordinate transformation unit is used to perform coordinate transformation on the three-phase grid voltage, three-phase grid current, and AC side output voltage to obtain the grid voltage component, grid current component, and AC side output voltage component in a two-phase synchronous rotating coordinate system; the voltage dynamic adjustment model building unit is used to construct a voltage dynamic adjustment model based on the grid voltage component, grid current component, DC side voltage, and AC side output voltage component.

[0022] Furthermore, the load disturbance estimation module includes a fixed-time disturbance observer construction unit, a state estimation calculation unit, and a fixed-time disturbance observer adjustment unit; wherein: the fixed-time disturbance observer construction unit is used to construct a load disturbance based on the new state variables in the voltage dynamic regulation model, and uses the new state variables and the load disturbance as observation objects to construct a fixed-time disturbance observer; the state estimation calculation unit is used to input the new state variables into the fixed-time disturbance observer and calculate the state estimation value; the fixed-time disturbance observer adjustment unit is used to adjust the parameters of the fixed-time disturbance observer based on the state estimation value so that the observation error between the state estimation value and the load disturbance converges to zero within a preset time, thereby obtaining the load disturbance estimation value of the three-phase PWM converter. 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 1 A flowchart illustrating the steps of a control method for a three-phase PWM converter according to a certain embodiment of the present invention; Figure 2 A block diagram illustrating a control method for a three-phase PWM converter according to a certain embodiment of the present invention; Figure 3 A flowchart illustrating a control method for a three-phase PWM converter according to a certain embodiment of the present invention; Figure 4 A DC voltage waveform diagram of a control method for a three-phase PWM converter under DC voltage tracking conditions, provided in a certain embodiment of the present invention; Figure 5 A DC voltage tracking current waveform diagram of a control method for a three-phase PWM converter provided in a certain embodiment of the present invention; Figure 6 A DC voltage waveform diagram under load disturbance conditions for a control method of a three-phase PWM converter provided in a certain embodiment of the present invention; Figure 7 A load disturbance condition d-axis current waveform diagram of a control method for a three-phase PWM converter provided in a certain embodiment of the present invention; Figure 8 This is a schematic diagram of the module structure of a control system for a three-phase PWM converter provided in a certain 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 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.

[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] To address the issue of poor operational stability in three-phase PWM converters due to their inability to meet dynamic and static performance requirements under various operating conditions such as large load disturbances, significant parameter changes, or frequent load switching, please refer to [reference needed]. Figure 1 , Figure 1 This is a flowchart illustrating the steps of a control method for a three-phase PWM converter according to a certain embodiment of the present invention. Figure 1 As shown in the figure, this embodiment of the invention proposes a control method for a three-phase PWM converter, including steps 101 to 105, each step of which is as follows: Step 101: Obtain the operating parameters of the three-phase PWM converter and construct a voltage dynamic adjustment model; Step 102: Construct a fixed-time disturbance observer based on the voltage dynamic adjustment model, and obtain the load disturbance estimate of the three-phase PWM converter according to the fixed-time disturbance observer; Step 103: Based on the operating parameters and the estimated load disturbance, obtain the voltage tracking error and the current tracking error, and construct a single-loop current-constrained variable gain controller according to the voltage tracking error, the current tracking error and the pre-acquired nonlinear variable gain. Step 104: Based on the single-loop current-constrained variable gain controller, monitor the grid-connected current of the three-phase PWM converter in real time, and based on the grid-connected current and the preset safety threshold, adaptively adjust the nonlinear variable gain, voltage tracking error and current tracking error to generate the first control quantity; Step 105: Generate a modulation signal based on the first control quantity, and control the three-phase PWM converter through the modulation signal.

[0033] One possible implementation involves first acquiring the operating parameters of the three-phase PWM converter, including three-phase grid voltage, three-phase grid current, DC-side voltage, and AC-side output voltage. A voltage dynamic adjustment model is then constructed based on the power conservation law and Kirchhoff's laws, which classifies output voltage fluctuations and load abrupt changes as lumped disturbances. Next, a fixed-time disturbance observer is built based on the voltage dynamic adjustment model. This observer processes the output load disturbance estimate, which quickly and accurately reflects the disturbance experienced by the system. Finally, voltage tracking is calculated based on the operating parameters and the load disturbance estimate. Error and current tracking error are identified, and a single-loop current-constrained variable gain controller with nonlinear variable gain is constructed accordingly. The single-loop current-constrained variable gain controller unifies voltage regulation and current constraint within a single-loop structure. Then, the grid-connected current is monitored in real time through the single-loop current-constrained variable gain controller. When the grid-connected current approaches a preset safety threshold, the nonlinear variable gain is adaptively adjusted to generate a first control quantity that includes current constraint penalty. Finally, a modulation signal is generated based on the first control quantity, and the switching action of the three-phase PWM converter is controlled through the modulation signal to achieve rapid and stable regulation of DC voltage and accurate constraint of grid-connected current.

[0034] For example, see Figure 2 , Figure 2 A block diagram illustrating the implementation of a control method for a three-phase PWM converter according to a certain embodiment of the present invention; as shown below. Figure 2 As shown, the single-loop current-constrained variable gain control strategy for a three-phase PWM converter mainly consists of two parts: a fixed-time disturbance observer and a single-loop current-constrained variable gain controller. The fixed-time disturbance observer accurately estimates input voltage fluctuations and load abrupt changes and feeds these disturbances forward to the controller. The single-loop current-constrained controller adaptively adjusts the nonlinear gain to limit the grid current within a safe threshold and achieves stable DC voltage control. The output of the single-loop current-constrained variable gain controller... Transform into The modulation wave is generated by PWM modulation to control the three-phase PWM converter.

[0035] This invention proposes a control method for a three-phase PWM converter. Based on the acquired operating parameters of the three-phase PWM converter, a voltage dynamic adjustment model and a fixed-time disturbance observer are constructed. Load mutations and grid fluctuations are categorized as lumped disturbances. The fixed-time disturbance observer is used to quickly estimate the load disturbance and perform feedforward compensation, improving the converter's immunity to disturbances such as load mutations. Simultaneously, a single-loop current-constrained variable-gain controller is constructed, and a nonlinear variable gain is introduced. The gain is adaptively adjusted based on the relationship between the grid current and the safety threshold to form a current penalty mechanism, strictly constraining the current at the control law level. Therefore, this scheme uses a single-loop structure instead of the traditional double-closed-loop cascaded structure, significantly simplifying the control parameter tuning process. The single-loop structure with nonlinear variable gain constrains and adjusts the grid parameters, and the disturbance observer accurately assesses load disturbances to cope with various complex operating conditions and improve the operational stability of the three-phase PWM converter.

[0036] In a preferred embodiment, the step of acquiring the operating parameters of the three-phase PWM converter and constructing a voltage dynamic adjustment model includes: acquiring the operating parameters of the three-phase PWM converter in a three-phase stationary coordinate system, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC-side voltage, and AC-side output voltage; performing coordinate transformation on the three-phase grid voltage, three-phase grid current, and AC-side output voltage to obtain grid voltage components, grid current components, and AC-side output voltage components in a two-phase synchronous rotating coordinate system; and constructing a voltage dynamic adjustment model based on the grid voltage components, grid current components, DC-side voltage, and AC-side output voltage components.

[0037] For example, such as Figure 2 As shown, the operating parameters of the three-phase PWM converter in the three-phase stationary coordinate system are first collected using voltage and current sensors, including the three-phase grid voltage. Three-phase power grid current DC side voltage and AC side output voltage It is worth mentioning that the three-phase power grid voltage include , and Three-phase power grid current include , and AC side output voltage include , and These raw operating parameters reflect the actual operating state of the converter in the physical coordinate system. Then, a Park coordinate transformation is performed on these raw operating parameters to transform them from a three-phase stationary coordinate system to a two-phase synchronous rotating coordinate system, thus obtaining the d-axis grid voltage component. and q-axis grid voltage component d-axis grid current component and q-axis grid current component and the AC output voltage component of the d-axis. and q-axis AC side output voltage component The purpose of coordinate transformation is to convert the time-varying AC quantities on the AC side into DC quantities, which facilitates the design of the subsequent controller. Finally, based on the grid voltage component, grid current component, DC side voltage and AC side output voltage component obtained after transformation, a voltage dynamic adjustment model is constructed. This model can accurately describe the dynamic characteristics of the DC side voltage of the converter, laying a mathematical foundation for subsequent disturbance observation and control design.

[0038] In the above scheme, operating parameters in a three-phase stationary coordinate system are collected and transformed. Then, the time-varying parameters on the AC side are converted into DC values ​​in a synchronous rotating coordinate system, providing a data foundation for subsequent model building and control design. Thus, by clearly defining the acquisition range of operating parameters and the coordinate transformation processing method, the accuracy and consistency of the voltage dynamic regulation model are ensured, enabling the model to accurately reflect the dynamic characteristics of the converter. This provides a reliable input data foundation for the construction of a fixed-time disturbance observer and a single-loop variable gain controller.

[0039] A preferred embodiment involves constructing a voltage dynamic adjustment model based on the grid voltage component, grid current component, DC-side voltage, and AC-side output voltage component. This includes: squaring the DC-side voltage to obtain a new state variable; constructing a DC-side dynamic model based on the new state variable and the grid current component; constructing an AC-side dynamic model based on preset electrical laws, the grid voltage component, the grid current component, and the AC-side output voltage component; and constructing a voltage dynamic adjustment model based on the DC-side dynamic model and the AC-side dynamic model.

[0040] For example, first, the DC side voltage Perform the squaring operation and define a new state variable. This transformation simplifies the subsequently derived model into a linear form, facilitating controller design; then, based on the d-axis grid current component... and d-axis grid voltage component Combined with DC side capacitor C A dynamic model of the DC side is constructed, which describes the relationship between DC side voltage and active power, specifically as follows: ; In the formula, The line's equivalent load resistance; Then based on the new state variables The above DC-side dynamic model can be simplified as follows: ; Meanwhile, based on the preset electrical law, namely Kirchhoff's voltage law, the d-axis grid voltage component is utilized. and q-axis grid voltage component d-axis grid current component and q-axis grid current component and the AC output voltage component of the d-axis. and q-axis AC side output voltage component And the filter inductance L and the line equivalent load resistance A dynamic model for the AC side is constructed, which describes the relationship between AC side current and voltage, specifically as follows: ; In the formula, The angular frequency of the three-phase voltage; Finally, due to the control in the three-phase PWM converter system To achieve unity power factor, the amplitude of the grid-connected current is therefore determined by... Decisions need to be limited. To prevent excessive grid current, the DC-side dynamic model and the AC-side dynamic model are combined to eliminate intermediate variables, resulting in a simplified voltage dynamic regulation model. This model summarizes factors such as load mutations and grid fluctuations as lumped disturbances, expressed as: ; In the formula, the control objective is to Adjust to its DC side voltage reference value ; The angular frequency of the three-phase voltage; The equivalent load resistance of the line is used to achieve rapid and precise DC voltage regulation, while the d-axis current must meet the constraints. To ensure the safe operation of the three-phase PWM converter, It is the safe threshold for grid current, which is usually selected as 1.5 to 2 times the rated current.

[0041] In the above scheme, the DC-side voltage is squared to obtain new state variables, transforming the original nonlinear model into a linear form that is easier to control design, thus simplifying the complexity of the subsequent fixed-time disturbance observer design. By constructing DC-side dynamic models and AC-side dynamic models separately, and integrating them to obtain a complete voltage dynamic regulation model, the model can accurately describe the coupling relationship between the AC and DC sides simultaneously, providing an accurate mathematical description for the subsequent disturbance observer design, thereby improving the accuracy of subsequent disturbance estimation and helping to improve the operational stability of the three-phase PWM converter.

[0042] A preferred embodiment involves constructing a fixed-time disturbance observer based on the voltage dynamic regulation model, and obtaining the load disturbance estimate of the three-phase PWM converter based on the fixed-time disturbance observer. This includes: constructing a load disturbance based on a new state variable in the voltage dynamic regulation model; using the new state variable and the load disturbance as observation objects to construct a fixed-time disturbance observer; inputting the new state variable into the fixed-time disturbance observer to calculate a state estimate; and adjusting the parameters of the fixed-time disturbance observer based on the state estimate to make the observation error between the state estimate and the load disturbance converge to zero within a preset time, thereby obtaining the load disturbance estimate of the three-phase PWM converter.

[0043] For example, the new state variable U and load disturbance in the voltage dynamic regulation model are... As the object of observation, define The estimated value is The goal is to reduce the observation error. Converging to zero in a bounded, fixed-time period, construct a fixed-time perturbation observer containing a sign function. The fixed-time perturbation observer is designed as follows: Figure 2 The differential equation with fixed-time convergence is specifically represented as follows: ; In the formula, yes The estimated value; yes The first derivative; yes The first derivative; function , correspond , , and ; and For fixed-time observer parameters, , , and For exponential parameters and , , and .

[0044] By inputting the new state variable U into the fixed-time disturbance observer, the fixed-time disturbance observer calculates the state estimate using its internal algorithm. Then, by adjusting the parameters of the fixed-time perturbation observer, including the gain parameter and the exponential parameter, the observation error between the state estimate and the actual value can converge to zero within a preset fixed time. Big enough Converging to zero, Therefore, the fixed-time disturbance observer outputs a load disturbance estimate. In this embodiment, the load disturbance estimate is... Adding a feedforward compensation term to the current-constrained variable gain controller allows the system to respond to DC voltage output fluctuations before they occur, thus improving the system's dynamic response speed and robustness.

[0045] In the above scheme, a fixed-time disturbance observer is constructed using a voltage dynamic regulation model. New state variables and load disturbances in the voltage dynamic regulation model are taken as observation objects. Utilizing the observer's fast convergence characteristic, the observation error converges to zero within a fixed time, independent of the initial state. Therefore, compared to traditional nonlinear disturbance observers and finite-time disturbance observers, the fixed-time observer proposed in this embodiment has a faster estimation speed and stronger robustness. It can accurately estimate the lumped disturbances caused by input voltage fluctuations and load abrupt changes, and feed the estimated values ​​forward to compensate the controller. This allows the three-phase PWM converter to respond to DC voltage output fluctuations before they occur, improving the dynamic response speed and disturbance rejection capability of the three-phase PWM converter.

[0046] A preferred embodiment involves obtaining voltage tracking error and current tracking error based on the operating parameters and the estimated load disturbance, and constructing a single-loop current-constrained variable-gain controller based on the voltage tracking error, current tracking error, and a pre-acquired nonlinear variable gain. This includes: calculating the voltage tracking error based on the DC-side voltage in the operating parameters and the new state variable; calculating the current tracking error based on the grid current component and the estimated load disturbance; constructing an error dynamic model with the voltage tracking error and current tracking error as state variables based on preset control parameters; and adding a pre-acquired nonlinear variable gain to the error dynamic model to obtain the single-loop current-constrained variable-gain controller.

[0047] For example, firstly based on the DC-side voltage reference value in the operating parameters. The new state variable U and the grid current component in the operating parameters Calculate voltage tracking error and current tracking error Specifically, it is expressed as: ; in, Load disturbance estimates can be generated based on fixed-time disturbance observers. And obtain the new state variable U, then... Taking the derivative, we get: ; Based on the definition of current tracking error, the problem of constraining grid-connected current can be transformed into a problem of constraining current tracking error. Specifically, based on current tracking error, the grid-connected current limit is equivalent to: ; In the formula, ; Among them, based on voltage tracking error Current tracking error Voltage tracking error after differentiation The current tracking error after differentiation And with instantaneous power theory, we obtain This is the steady-state value of the d-axis current, therefore we obtain... and Therefore, the control objective is transformed into designing a single-loop current-constrained variable-gain controller. ,make Approaching zero, at the same time To meet the current constraints, an error dynamic model is constructed, and a nonlinear variable gain is introduced into the error dynamic model. , construct as Figure 2 The single-loop current-constrained variable-gain controller shown is specifically represented as follows: ; In the formula, These are control parameters, serving as a penalty mechanism for grid-connected current. Approaching the safety threshold At this time, this nonlinear gain will adaptively increase to limit the current within a safe threshold.

[0048] In the above scheme, voltage tracking error and current tracking error are specifically defined, transforming the DC voltage regulation problem into an error convergence problem, providing a clear objective for the design of the control law. By converting the physical constraint of the grid-connected current into an equivalent constraint on the current tracking error, a theoretical basis is provided for the mathematical processing of the current constraint. By constructing an error dynamic model with voltage tracking error and current tracking error as state variables and introducing a nonlinear variable gain, voltage regulation and current constraint are unified within a single-loop control framework. This avoids the parameter decoupling problem between the outer voltage loop and the inner current loop in traditional dual-loop control, simplifies the control structure, and helps improve the operational stability of the three-phase PWM converter.

[0049] In a preferred embodiment, based on the single-loop current-constrained variable gain controller, the grid-connected current of the three-phase PWM converter is monitored in real time. Based on the grid-connected current and a preset safety threshold, the nonlinear variable gain, voltage tracking error, and current tracking error are adaptively adjusted to generate a first control quantity. This includes: inputting the voltage tracking error, the current tracking error, and the estimated load disturbance value into the single-loop current-constrained variable gain controller; monitoring the grid-connected current of the three-phase PWM converter in real time through the single-loop current-constrained variable gain controller; when the grid-connected current increases, adaptively increasing the nonlinear variable gain according to the preset safety threshold to obtain a target gain value; and adjusting the control parameter weights of the voltage tracking error and current tracking error based on the target gain value to generate the first control quantity.

[0050] For example, such as Figure 2 As shown, the calculated voltage tracking error is first... Current tracking error and the load disturbance estimate output by the fixed-time disturbance observer The input is fed into a single-loop current-constrained variable gain controller, which monitors the grid-connected current of the three-phase PWM converter in real time, specifically by monitoring the d-axis current component. ,when Increase and approach the preset safety threshold At that time, the nonlinear variable gain in the controller The gain value will increase adaptively to achieve the increased target gain value. This adaptive mechanism is essentially the controller's proactive response to the risk of current exceeding limits. Finally, based on the target gain value, the controller adjusts the control parameter weights for voltage tracking error and current tracking error. Specifically, this is manifested in increasing the penalty coefficient for current tracking error in the control law, thereby generating a first control variable that can strongly constrain the current while regulating the voltage. This control quantity includes both the feedforward compensation required for voltage regulation and the penalty term to prevent current overruns.

[0051] In the above scheme, the voltage tracking error, current tracking error, and load disturbance estimate are input into a single-loop current-constrained variable gain controller. When the grid-connected current increases and approaches the safety threshold, the nonlinear variable gain increases adaptively, penalizing the weight of the current tracking error in the control law and forcing the current to pull back. This adaptive penalty mechanism strictly ensures from the control theory level that the transient grid-connected current will not exceed the preset safety threshold, effectively avoiding the risk of equipment protection shutdown or hardware damage caused by overcurrent, and helps to improve the operating stability of the three-phase PWM converter.

[0052] A preferred embodiment, which generates a modulation signal based on the first control quantity and controls the three-phase PWM converter through the modulation signal, includes: generating a second control quantity based on the AC side output voltage component; combining the first control quantity and the second control quantity to obtain a comprehensive control quantity in a two-phase synchronous rotating coordinate system; performing an inverse coordinate transformation on the comprehensive control quantity to generate a modulation signal in a two-phase stationary coordinate system; inputting the modulation signal into a preset PWM modulator to generate a corresponding switching transistor drive signal; and controlling the three-phase PWM converter based on the switching transistor drive signal.

[0053] For example, such as Figure 2 As shown, firstly based on the AC side output voltage component The second control quantity is obtained through PI control processing. This second control quantity is used to adjust reactive power or achieve unity power factor control. Then, the first control quantity generated by the single-loop current-constrained variable gain controller is... With the second control quantity The control quantities are combined to obtain the integrated control quantity in the two-phase synchronous rotating coordinate system. Then, a Park inverse transform is performed on this integrated control quantity to convert it back to the modulation voltage in the two-phase stationary coordinate system. Finally, the modulation signal is input to a preset PWM modulator. The PWM modulator generates corresponding switching transistor drive signals based on the modulation voltage. These drive signals act on the power switching devices of the three-phase PWM converter to control their on and off states, thereby achieving precise control of the converter's output voltage and current, completing the entire process from control algorithm to physical execution.

[0054] In the above scheme, the first control quantity and the second control quantity output by the single-loop current-constrained variable gain controller are combined to obtain the comprehensive control quantity in the two-phase synchronous rotating coordinate system. Then, the control quantity in the synchronous rotating coordinate system is converted back to the modulation signal in the two-phase stationary coordinate system through coordinate inverse transformation. The signal is then generated as a switching transistor drive signal through PWM modulation, completing the complete conversion from control algorithm to power device execution command. This ensures the accurate execution of control commands and enables the designed voltage regulation and current constraint functions to be realized in the actual converter system, which helps to improve the operating stability of the three-phase PWM converter.

[0055] For a specific explanation, see Figure 3 , Figure 3 A flowchart illustrating a control method for a three-phase PWM converter according to a certain embodiment of the present invention is shown below; Figure 3 As shown, the operating parameters of the three-phase PWM converter in the three-phase stationary coordinate system are first collected using voltage and current sensors, including the three-phase grid voltage. Three-phase power grid current DC side voltage and AC side output voltage Then, these raw operating parameters reflect the actual operating state of the converter in the physical coordinate system; next, Park coordinate transformation is performed on these raw operating parameters to transform them from a three-phase stationary coordinate system to a two-phase synchronous rotating coordinate system, obtaining the grid voltage components corresponding to the d-axis and q-axis. The grid current components corresponding to the d-axis and q-axis And the corresponding AC output voltage components on the d-axis and q-axis. When defining a new state variable Then, a dynamic voltage regulation model for a three-phase PWM converter was established, and the data was then processed. The output is fed to a fixed-time disturbance observer and a single-loop current-constrained variable-gain controller, where the input to the fixed-time disturbance observer is... The output load disturbance estimate is processed by the fixed-time disturbance observer. To a single-loop current-constrained variable gain controller, and simultaneously The input is a single-loop current-constrained variable-gain controller, which processes the data and outputs the first control quantity. Then, the second control quantity output by the existing q-axis current PI control is... With the first control quantity Perform inverse Park coordinate transformation to generate modulation voltage. Modulation voltage The modulation wave is generated through the PWM modulation stage to realize the control of the three-phase PWM converter.

[0056] Furthermore, this embodiment of the invention also proposes a stability theory analysis section to ensure reliable control performance. Specifically, it first considers any given initial value of the tracking error. ,in, and These are voltage tracking errors. and current tracking error The initial state, It is the safe operating range for tracking errors. It is the set of real numbers. Define the time interval [0, T) as such that... The maximum time interval that holds true, where T is a positive number or infinity; at time... t When the time interval is [0, T), the voltage tracking error is calculated by substituting the calculation formula of the single-loop current-constrained variable gain controller into the derivative. and current tracking error Specifically, it is expressed as: ; In the formula, These are control parameters; C For DC side capacitors; L is the equivalent load resistance of the line; L is the filter inductance. This is a safety threshold; Then, candidate Lyapunov functions are selected. V for: Differentiating the candidate Lyapunov function at time t ∈ [0, T) yields the following results: ; In the formula, These are control parameters; From the formula, we can see that... and Therefore, we can conclude that: ; in, It is a candidate function of Lyapunov function. V Initial values; let positive constants be used. Therefore, we can conclude that if ,but ; Then, define a constant. and constant For time ,if Then we have: ; as well as: ; In the formula, These are control parameters; From the two expressions above, it can be seen that at time... and hour, ; Redefining constants For time We can obtain: ; as well as: ; In the formula, These are control parameters; From the two expressions above, it can be seen that at time... and hour, ; This proves that the tracking error For any given According to the continuation theorem of solutions and the definition of the time interval [0, T), we can derive This ensures current constraint. Meanwhile, theoretical analysis proves that the closed-loop system is asymptotically stable, meaning the DC voltage tracking error converges exponentially to zero.

[0057] In one preferred implementation, to further illustrate the effectiveness of the proposed single-loop current-constrained variable gain control method for three-phase PWM converters, a system simulation model is built in existing simulation software. In the main circuit parameter settings of the system simulation model, the three-phase grid voltage amplitude is set to... The filter inductor is set to The equivalent resistance of the line is set to The load resistance is set to The three-phase angular frequency is set to The DC-side capacitor is set to The switching frequency is set to The DC side voltage reference value is set to In addition, the control parameters are set to Meanwhile, the control method for a three-phase PWM converter proposed in this embodiment of the invention is compared with the traditional dual-loop PI method. The dual-loop PI method uses two sets of parameters: one set is a high-gain parameter to achieve fast dynamic performance; the other set is a conservative gain parameter to ensure current constraint conditions. In addition, the control method for a three-phase PWM converter proposed in this embodiment of the invention is characterized as a current constraint control method.

[0058] See Figure 4 and Figure 5 , Figure 4A DC voltage waveform diagram of a control method for a three-phase PWM converter under DC voltage tracking condition, provided in a certain embodiment of the present invention; Figure 5 The d-axis current waveform diagram of a control method for a three-phase PWM converter according to a certain embodiment of the present invention is shown below, under DC voltage tracking conditions. Figure 4 and Figure 5 As shown, in order to evaluate the dynamic response performance of the control method of the three-phase PWM converter proposed in this embodiment of the invention and the PI control of the traditional dual closed-loop PI method in DC voltage regulation, test 1 was designed. The specific test results are as follows: when the DC voltage is adjusted from 320V to 350V, Figure 4 and Figure 5 The response performance of different control methods is shown. Both the high-gain PI method and the current-constrained control method proposed in this embodiment exhibit fast dynamic response to DC voltage and a settling time of less than 8ms. However, the transient d-axis current of the high-gain PI method exceeds the safety threshold. Figure 5 As shown, this can cause the device to shut down due to overcurrent protection, leading to hardware damage. In contrast, the current constraint control method proposed in this embodiment effectively limits the current amplitude and provides a fast voltage response; as... Figure 4 As shown, the conservative gain PI method significantly reduces the dynamic response of DC voltage, with a settling time of 30ms.

[0059] See Figure 6 and Figure 7 , Figure 6 A DC voltage waveform diagram under load disturbance conditions for a control method of a three-phase PWM converter provided in a certain embodiment of the present invention; Figure 7 A load disturbance condition d-axis current waveform diagram of a control method for a three-phase PWM converter provided in a certain embodiment of the present invention; as shown. Figure 6 and Figure 7 As shown, in order to evaluate the dynamic response performance of the control method of a three-phase PWM converter proposed in this embodiment of the invention and the PI control of the traditional dual closed-loop PI method under load disturbance, test two was designed, and the specific test results are as follows: When the load from Become hour, Figure 6 and Figure 7 The response waveforms of DC voltage and d-axis current are displayed separately. All three methods adjust the DC voltage to the reference value after a load disturbance, but exhibit significantly different dynamic responses. For example... Figure 6 and Figure 7 As shown, compared with the high-gain and conservative-gain PI methods, the current constraint control method proposed in this embodiment of the invention exhibits a faster dynamic response speed, while also effectively limiting the current amplitude.

[0060] Based on the above method embodiments, corresponding apparatus embodiments are provided; see [link to apparatus embodiments]. Figure 8 , Figure 8 This is a schematic diagram of the module structure of a control system for a three-phase PWM converter according to a certain embodiment of the present invention. Figure 8 As shown, this embodiment of the invention also provides a control system for a three-phase PWM converter, including: a model building module 201, a load disturbance estimation module 202, a single-loop current-constrained variable gain controller building module 203, a first control quantity generation module 204, and a converter control module 205; wherein: the model building module 201 is used to acquire the operating parameters of the three-phase PWM converter and build a voltage dynamic adjustment model; the load disturbance estimation module 202 is used to build a fixed-time disturbance observer based on the voltage dynamic adjustment model, and acquire the load disturbance estimation value of the three-phase PWM converter according to the fixed-time disturbance observer; the single-loop current-constrained variable gain controller building module 203 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the single-loop current-constrained variable gain controller building module 204 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the model building module 201 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the load disturbance estimation value acquisition module 202 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the load disturbance estimation value acquisition module 202 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the load disturbance estimation value acquisition module 203 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the load disturbance estimation value acquisition module 204 is used to acquire the load disturbance estimation value of the three-phase PWM converter; the load disturbance estimation value acquisition module 205 ... 3 is used to obtain voltage tracking error and current tracking error based on the operating parameters and the estimated load disturbance, and to construct a single-loop current-constrained variable gain controller based on the voltage tracking error, current tracking error and pre-acquired nonlinear variable gain; the first control quantity generation module 204 is used to monitor the grid-connected current of the three-phase PWM converter in real time based on the single-loop current-constrained variable gain controller, and adaptively adjust the nonlinear variable gain, voltage tracking error and current tracking error based on the grid-connected current and a preset safety threshold to generate a first control quantity; the converter control module 205 is used to generate a modulation signal based on the first control quantity, and control the three-phase PWM converter through the modulation signal.

[0061] This invention proposes a control system for a three-phase PWM converter. Based on the acquired operating parameters of the three-phase PWM converter, a voltage dynamic adjustment model and a fixed-time disturbance observer are constructed. Load abrupt changes and grid fluctuations are categorized as lumped disturbances. The fixed-time disturbance observer is used to quickly estimate the load disturbance and perform feedforward compensation, improving the converter's immunity to disturbances such as load abrupt changes. Simultaneously, a single-loop current-constrained variable-gain controller is constructed, introducing a nonlinear variable gain. The gain is adaptively adjusted based on the relationship between the grid current and the safety threshold to form a current penalty mechanism, strictly constraining the current at the control law level. Therefore, this scheme uses a single-loop structure instead of the traditional double-closed-loop cascaded structure, significantly simplifying the control parameter tuning process. The single-loop structure with nonlinear variable gain constrains and adjusts the grid parameters, and the disturbance observer accurately assesses load disturbances to cope with various complex operating conditions, improving the operational stability of the three-phase PWM converter.

[0062] Furthermore, the model building module 201 is used to acquire the operating parameters of the three-phase PWM converter and build a voltage dynamic adjustment model, including a data acquisition unit 301, a coordinate transformation unit 302, and a voltage dynamic adjustment model building unit 303; wherein: the data acquisition unit 301 is used to acquire the operating parameters of the three-phase PWM converter in a three-phase stationary coordinate system, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC side voltage, and AC side output voltage; the coordinate transformation unit 302 is used to perform coordinate transformation on the three-phase grid voltage, three-phase grid current, and AC side output voltage to obtain the grid voltage component, grid current component, and AC side output voltage component in a two-phase synchronous rotating coordinate system; the voltage dynamic adjustment model building unit 303 is used to build a voltage dynamic adjustment model based on the grid voltage component, grid current component, DC side voltage, and AC side output voltage component.

[0063] Furthermore, the load disturbance estimation module 202 includes a fixed-time disturbance observer construction unit 401, a state estimation calculation unit 402, and a fixed-time disturbance observer adjustment unit 403; wherein: the fixed-time disturbance observer construction unit 401 is used to construct a load disturbance based on the new state variables in the voltage dynamic regulation model, and to construct a fixed-time disturbance observer by taking the new state variables and the load disturbance as observation objects; the state estimation calculation unit 402 is used to input the new state variables into the fixed-time disturbance observer and calculate the state estimation value; the fixed-time disturbance observer adjustment unit 403 is used to adjust the parameters of the fixed-time disturbance observer based on the state estimation value so that the observation error between the state estimation value and the load disturbance converges to zero within a preset time, thereby obtaining the load disturbance estimation value of the three-phase PWM converter.

[0064] 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 a three-phase PWM converter provided by any of the above-described method embodiments of the present invention.

[0065] 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.

[0066] Based on the above-described embodiment of a control method for a three-phase PWM converter, 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 control method for a three-phase PWM converter according to any embodiment of the present invention.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 a three-phase PWM converter described in any of the above-described method embodiments of the present invention.

[0071] 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.

[0072] 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 three-phase PWM converter, characterized in that, include: Obtain the operating parameters of the three-phase PWM converter and construct a dynamic voltage regulation model; A fixed-time disturbance observer is constructed based on the voltage dynamic regulation model, and the load disturbance estimate of the three-phase PWM converter is obtained based on the fixed-time disturbance observer. Based on the operating parameters and the estimated load disturbance, the voltage tracking error and current tracking error are obtained, and a single-loop current-constrained variable gain controller is constructed according to the voltage tracking error, current tracking error and pre-acquired nonlinear variable gain. Based on the single-loop current-constrained variable gain controller, the grid-connected current of the three-phase PWM converter is monitored in real time. Based on the grid-connected current and a preset safety threshold, the nonlinear variable gain, voltage tracking error and current tracking error are adaptively adjusted to generate the first control quantity. A modulation signal is generated based on the first control quantity, and the three-phase PWM converter is controlled by the modulation signal.

2. The control method for a three-phase PWM converter as described in claim 1, characterized in that, The process of acquiring the operating parameters of the three-phase PWM converter and constructing a dynamic voltage regulation model includes: The operating parameters of the three-phase PWM converter in the three-phase stationary coordinate system are collected, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC side voltage and AC side output voltage; The three-phase grid voltage, three-phase grid current and AC side output voltage are transformed by coordinate transformation to obtain the grid voltage component, grid current component and AC side output voltage component in a two-phase synchronous rotating coordinate system. A voltage dynamic adjustment model is constructed based on the grid voltage component, grid current component, DC side voltage, and AC side output voltage component.

3. The control method for a three-phase PWM converter as described in claim 2, characterized in that, Based on the grid voltage component, grid current component, DC side voltage, and AC side output voltage component, a voltage dynamic regulation model is constructed, including: The DC-side voltage is squared to obtain a new state variable; Based on the new state variables and the grid current components, a DC-side dynamic model is constructed; Based on the preset electrical laws, the grid voltage component, the grid current component, and the AC side output voltage component, an AC side dynamic model is constructed. Based on the DC-side dynamic model and the AC-side dynamic model, a voltage dynamic adjustment model is constructed.

4. The control method for a three-phase PWM converter as described in claim 3, characterized in that, A fixed-time disturbance observer is constructed based on the voltage dynamic regulation model, and the load disturbance estimate of the three-phase PWM converter is obtained according to the fixed-time disturbance observer, including: Based on the new state variables in the voltage dynamic regulation model, a load disturbance is constructed, and the new state variables and the load disturbance are used as observation objects to construct a fixed-time disturbance observer. The new state variable is input into the fixed-time disturbance observer to calculate the state estimate. Based on the state estimate, the parameters of the fixed-time disturbance observer are adjusted so that the observation error between the state estimate and the load disturbance converges to zero within a preset time, thereby obtaining the load disturbance estimate of the three-phase PWM converter.

5. The control method for a three-phase PWM converter as described in claim 3, characterized in that, Based on the operating parameters and the estimated load disturbance, voltage tracking error and current tracking error are obtained. Then, based on the voltage tracking error, current tracking error, and the pre-acquired nonlinear variable gain, a single-loop current-constrained variable gain controller is constructed, including: The voltage tracking error is calculated based on the DC-side voltage in the operating parameters and the new state variable; The current tracking error is calculated based on the grid current component and the estimated load disturbance. Based on preset control parameters, an error dynamic model is constructed with the voltage tracking error and the current tracking error as state variables. A pre-acquired nonlinear variable gain is added to the error dynamic model to obtain a single-loop current-constrained variable gain controller.

6. The control method for a three-phase PWM converter as described in claim 5, characterized in that, Based on the single-loop current-constrained variable gain controller, the grid-connected current of the three-phase PWM converter is monitored in real time. Based on the grid-connected current and a preset safety threshold, the nonlinear variable gain, voltage tracking error, and current tracking error are adaptively adjusted to generate a first control quantity, including: The voltage tracking error, the current tracking error, and the load disturbance estimate are input into the single-loop current-constrained variable-gain controller. The grid-connected current of the three-phase PWM converter is monitored in real time by the single-loop current-constrained variable gain controller. When the grid-connected current increases, the nonlinear variable gain is adaptively increased according to the preset safety threshold to obtain the target gain value. Based on the target gain value, the control parameter weights of the voltage tracking error and current tracking error are adjusted to generate a first control quantity.

7. The control method for a three-phase PWM converter as described in claim 6, characterized in that, Based on the first control quantity, a modulation signal is generated, and the three-phase PWM converter is controlled by the modulation signal, including: A second control quantity is generated based on the AC side output voltage component; The first control quantity and the second control quantity are combined to obtain the comprehensive control quantity in the two-phase synchronous rotating coordinate system; Perform an inverse coordinate transformation on the integrated control quantity to generate a modulation signal in a two-phase stationary coordinate system; The modulation signal is input to a preset PWM modulator to generate a corresponding switching transistor drive signal, and the three-phase PWM converter is controlled based on the switching transistor drive signal.

8. A control system for a three-phase PWM converter, characterized in that, It includes a model building module, a load disturbance estimation module, a single-loop current-constrained variable-gain controller construction module, a first control quantity generation module, and a converter control module; wherein: The model building module is used to obtain the operating parameters of the three-phase PWM converter and build a voltage dynamic adjustment model; The load disturbance estimation module is used to construct a fixed-time disturbance observer based on the voltage dynamic adjustment model, and obtain the load disturbance estimation value of the three-phase PWM converter according to the fixed-time disturbance observer; The single-loop current-constrained variable gain controller construction module is used to obtain voltage tracking error and current tracking error based on the operating parameters and the estimated load disturbance, and to construct a single-loop current-constrained variable gain controller based on the voltage tracking error, current tracking error and pre-acquired nonlinear variable gain. The first control quantity generation module is used to monitor the grid-connected current of the three-phase PWM converter in real time based on the single-loop current-constrained variable gain controller, and adaptively adjust the nonlinear variable gain, voltage tracking error and current tracking error based on the grid-connected current and a preset safety threshold to generate the first control quantity; The converter control module is used to generate a modulation signal based on the first control quantity, and control the three-phase PWM converter through the modulation signal.

9. The control system for a three-phase PWM converter as described in claim 8, characterized in that, The model building module includes a data acquisition unit, a coordinate transformation unit, and a voltage dynamic adjustment model building unit; wherein: The data acquisition unit is used to acquire the operating parameters of the three-phase PWM converter in the three-phase stationary coordinate system, wherein the operating parameters include three-phase grid voltage, three-phase grid current, DC side voltage and AC side output voltage; The coordinate transformation unit is used to perform coordinate transformation on the three-phase grid voltage, three-phase grid current and AC side output voltage to obtain the grid voltage component, grid current component and AC side output voltage component in a two-phase synchronous rotating coordinate system. The voltage dynamic adjustment model construction unit is used to construct a voltage dynamic adjustment model based on the grid voltage component, grid current component, DC side voltage and AC side output voltage component.

10. The control system for a three-phase PWM converter as described in claim 8, characterized in that, The load disturbance estimation module includes a fixed-time disturbance observer construction unit, a state estimation calculation unit, and a fixed-time disturbance observer adjustment unit; wherein: The fixed-time disturbance observer construction unit is used to construct load disturbances based on the new state variables in the voltage dynamic regulation model, and to construct a fixed-time disturbance observer by taking the new state variables and the load disturbances as observation objects. The state estimation calculation unit is used to input the new state variable into the fixed-time disturbance observer and calculate the state estimation value. The fixed-time disturbance observer adjustment unit is used to adjust the parameters of the fixed-time disturbance observer based on the state estimate, so that the observation error between the state estimate and the load disturbance converges to zero within a preset time, thereby obtaining the load disturbance estimate of the three-phase PWM converter.

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