Method and device for supporting fault voltage of network-forming converter

Abstract

The invention relates to the technical field of power system control, in particular to a fault voltage supporting method and device for a network-building type converter, and the method comprises the steps: collecting the three-phase terminal voltage of the network-building type converter; according to the three-phase terminal voltage, calculating the terminal voltage amplitude of the network-forming converter, and judging whether the terminal voltage amplitude is lower than a preset threshold value or not; and if the terminal voltage amplitude is lower than a preset threshold value, virtual impedance adjustment is started, and the virtual impedance of the network construction type converter is adjusted to carry out fault voltage support. Therefore, the problems that due to the fact that the transient over-current capacity of a network-forming type converter is limited, when a power grid breaks down or voltage drops suddenly, direct current-limiting control is prone to causing loss of the network-forming capacity, and most virtual impedance control strategies are set based on fixed parameters, high in adjustment rigidity and incapable of dynamically adapting to fault characteristics, and consequently the voltage supporting capacity is insufficient are solved.

Description

Technical Field

[0001] This application relates to the field of power system control technology, and in particular to a method and apparatus for supporting fault voltage in a grid-type converter. Background Technology

[0002] As a key component in new power systems, grid-connected converters, by simulating the electrical characteristics of synchronous generators and operating in voltage source mode, can provide services such as inertia compensation, frequency support, and voltage support to the power grid, becoming a crucial technology for enhancing system stability. These converters typically use semiconductor devices as their core, and their transient overcurrent capacity is far lower than that of traditional synchronous generators, usually not exceeding 2 to 3 times the rated current. Therefore, they face relatively stringent current safety constraints under disturbances such as grid faults.

[0003] In related technologies, in order to improve the voltage support capability of grid-type converters during faults, methods such as virtual impedance control and overcurrent protection limiting are usually used to regulate the converter output current and coordinate energy, so as to achieve current limiting control and a certain degree of voltage support during faults.

[0004] However, in related technologies, grid-type converters are limited by their low overcurrent capacity. When there is a grid fault or voltage drop, direct current limiting control can easily lead to the loss of their grid-building capability, making it impossible to continuously provide voltage support to the grid. On the other hand, virtual impedance control strategies mostly use fixed parameter settings and lack the ability to adapt to the dynamic characteristics of the system. They cannot be flexibly adjusted according to factors such as the severity of the fault and changes in network impedance, resulting in insufficient support capability under dynamic operating conditions. This makes it difficult to meet the stable control requirements in complex grid operating environments, and urgently needs to be solved. Summary of the Invention

[0005] This application provides a fault voltage support method and apparatus for grid-connected converters to address the problem in related technologies where, due to the low transient overcurrent capability of grid-connected converters, direct current limiting control can easily lead to the loss of their grid-connecting capability and inability to continuously provide voltage support when a grid fault or voltage drop occurs. Furthermore, virtual impedance control strategies mostly employ fixed parameter settings, resulting in rigid adjustment mechanisms that lack adaptability to system dynamics. They cannot flexibly adjust based on fault severity, grid impedance changes, and other factors, leading to insufficient support capability under dynamic operating conditions and failing to meet the stable control requirements of grid-connected converters in complex grid operating environments, which need to balance current safety and voltage support performance.

[0006] The first aspect of this application provides a fault voltage support method for a grid-type converter, comprising the following steps: acquiring the three-phase terminal voltage of the grid-type converter; calculating the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage, and determining whether the terminal voltage amplitude is lower than a preset threshold; if the terminal voltage amplitude is lower than the preset threshold, initiating virtual impedance adjustment to adjust the virtual impedance of the grid-type converter for fault voltage support.

[0007] Through the above technical means, the embodiments of this application can calculate the terminal voltage amplitude of the grid-type converter by the three-phase terminal voltage, and then start virtual impedance regulation according to the terminal voltage amplitude. This can realize the dynamic current control and voltage support function of the grid-type converter under fault conditions, and enable the converter to flexibly respond to changes in terminal voltage and automatically adjust the amplitude and phase of the output current, thereby improving the voltage support capability, reducing the degree of grid voltage drop, and improving system stability and anti-interference capability.

[0008] Optionally, in one embodiment of this application, the step of calculating the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage includes: performing a Parker transformation on the three-phase terminal voltage to convert it into a dq-axis voltage; and calculating the terminal voltage amplitude based on the dq-axis voltage.

[0009] Through the above technical means, the embodiments of this application can perform Parker transformation on the three-phase terminal voltage to convert it into dq-axis voltage, and then calculate the terminal voltage amplitude. This can effectively simplify the voltage characteristic analysis process of grid-type converters, improve control accuracy and real-time performance, help to accurately judge the grid status, promptly activate the virtual impedance adjustment mechanism, and dynamically adjust the virtual resistance and / or virtual reactance values, thereby achieving effective control of the output current.

[0010] Optionally, in one embodiment of this application, the formula for calculating the terminal voltage amplitude is:

[0011] U=(U d 2 +U q 2 ) 1 / 2 ,

[0012] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0013] Through the above technical means, the embodiments of this application can quantify the terminal voltage amplitude, which can more intuitively reflect the current voltage state of the grid-type converter. This helps to accurately determine whether the power grid is in an abnormal operating condition such as a fault or voltage drop, thereby triggering the virtual impedance regulation mechanism in a timely manner and improving the system's rapid response capability and adaptability to power grid disturbances.

[0014] Optionally, in one embodiment of this application, adjusting the virtual impedance of the grid converter includes: calculating the virtual impedance of the grid converter; and adjusting the virtual impedance according to the virtual impedance so that the current phase of the grid converter lags behind the voltage by 90 degrees.

[0015] Through the above technical means, the embodiments of this application can adjust the virtual impedance through feedback control using virtual impedance parameters, so that the phase of the output current of the grid-type converter lags behind the terminal voltage by 90 degrees, thereby achieving maximum reactive power support and enhancing the stability and recovery capability of the power grid under voltage drop and fault conditions.

[0016] Optionally, in one embodiment of this application, the formula for calculating the virtual impedance is:

[0017]

[0018] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0019] Through the above technical means, the embodiments of this application calculate the virtual impedance based on the dq axis voltage and current components to intuitively reflect the equivalent output characteristics of the grid-type converter. This helps to accurately judge the operating status of the converter and the grid voltage status, thereby achieving timely and effective virtual impedance adjustment and improving the voltage support capability and dynamic stability of the system.

[0020] A second aspect of this application provides a fault voltage support device for a grid-type converter, comprising: a data acquisition module for acquiring the three-phase terminal voltage of the grid-type converter; a judgment module for calculating the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage and judging whether the terminal voltage amplitude is lower than a preset threshold; and a support module for initiating virtual impedance adjustment and adjusting the virtual impedance of the grid-type converter to support the fault voltage if the terminal voltage amplitude is lower than the preset threshold.

[0021] Through the above technical means, the embodiments of this application can calculate the terminal voltage amplitude of the grid-type converter by the three-phase terminal voltage, and then start virtual impedance regulation according to the terminal voltage amplitude. This can realize the dynamic current control and voltage support function of the grid-type converter under fault conditions, and enable the converter to flexibly respond to changes in terminal voltage and automatically adjust the amplitude and phase of the output current, thereby improving the voltage support capability, reducing the degree of grid voltage drop, and improving system stability and anti-interference capability.

[0022] Optionally, in one embodiment of this application, the determination module includes: a conversion unit for performing Parker transformation on the three-phase terminal voltage to convert it into a dq-axis voltage; and a first calculation unit for calculating the terminal voltage amplitude based on the dq-axis voltage.

[0023] Through the above technical means, the embodiments of this application can calculate the terminal voltage amplitude of the grid-type converter by the three-phase terminal voltage, and then start virtual impedance regulation according to the terminal voltage amplitude. This can realize the dynamic current control and voltage support function of the grid-type converter under fault conditions, and enable the converter to flexibly respond to changes in terminal voltage and automatically adjust the amplitude and phase of the output current, thereby improving the voltage support capability, reducing the degree of grid voltage drop, and improving system stability and anti-interference capability.

[0024] Optionally, in one embodiment of this application, the formula for calculating the terminal voltage amplitude is:

[0025] U=(U d 2 +U q 2 ) 1 / 2 ,

[0026] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0027] Through the above technical means, the embodiments of this application can quantify the terminal voltage amplitude, which can more intuitively reflect the current voltage state of the grid-type converter. This helps to accurately determine whether the power grid is in an abnormal operating condition such as a fault or voltage drop, thereby triggering the virtual impedance regulation mechanism in a timely manner and improving the system's rapid response capability and adaptability to power grid disturbances.

[0028] Optionally, in one embodiment of this application, the support module includes: a second calculation unit for calculating the virtual impedance of the grid converter; and an adjustment unit for adjusting the virtual impedance according to the virtual impedance so that the current phase of the grid converter lags behind the voltage by 90 degrees.

[0029] Through the above technical means, the embodiments of this application can adjust the virtual impedance through feedback control using virtual impedance parameters, so that the phase of the output current of the grid-type converter lags behind the terminal voltage by 90 degrees, thereby achieving maximum reactive power support and enhancing the stability and recovery capability of the power grid under voltage drop and fault conditions.

[0030] Optionally, in one embodiment of this application, the formula for calculating the virtual impedance is:

[0031]

[0032] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0033] Through the above technical means, the embodiments of this application calculate the virtual impedance based on the dq axis voltage and current components to intuitively reflect the equivalent output characteristics of the grid-type converter. This helps to accurately judge the operating status of the converter and the grid voltage status, thereby achieving timely and effective virtual impedance adjustment and improving the voltage support capability and dynamic stability of the system.

[0034] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the grid-type converter fault voltage support method as described in the above embodiments.

[0035] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described grid-type converter fault voltage support method.

[0036] A fifth aspect of this application provides a computer program product, including a computer program that, when executed, is used to implement the above-described grid-type converter fault voltage support method.

[0037] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0038] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 This is a schematic diagram of the fault voltage support structure of a grid-type converter according to an embodiment of this application;

[0040] Figure 2 This is a flowchart of a fault voltage support method for a grid-type converter according to an embodiment of this application;

[0041] Figure 3 This is a flowchart illustrating a fault voltage support method for a grid-type converter according to an embodiment of this application.

[0042] Figure 4 This is a block diagram of a fault voltage support device for a grid-type converter according to an embodiment of this application;

[0043] Figure 5 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application.

[0044] Figure label:

[0045] 101-Power calculation stage, 102-Active power-frequency outer loop, 103-Voltage amplitude calculation stage, 104-Start-up judgment stage, 105-Virtual impedance calculation stage, 106-Virtual impedance control, 107-Current inner loop, 108-PWM (Pulse Width Modulation); 10-Grid-type converter fault voltage support device; 100-Acquisition module, 200-Judgment module, 300-Support module; 501-Memory, 502-Processor, 503-Communication interface. Detailed Implementation

[0046] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0047] The following description, with reference to the accompanying drawings, illustrates a method and apparatus for supporting fault voltage in a grid-type converter according to embodiments of this application. To address the technical problems mentioned in the background, such as the low transient overcurrent capability of grid-connected converters leading to loss of grid-connected capability and inability to continuously provide voltage support when direct current limiting control is used during grid faults or voltage drops, and the rigidity of virtual impedance control strategies due to fixed parameter settings, which lack adaptability to system dynamics and cannot be flexibly adjusted according to fault severity or grid impedance changes, resulting in insufficient support capability under dynamic conditions, this application provides a fault voltage support method for grid-connected converters. This method calculates the terminal voltage amplitude of the grid-connected converter based on the three-phase terminal voltage and then dynamically adjusts the virtual impedance parameters to achieve fault voltage support. This allows the converter to flexibly adjust the phase and amplitude of the output current according to real-time voltage changes, improving fault voltage support capability, effectively mitigating voltage dips, and enhancing the stability and robustness of the converter under faults and dynamic disturbances. Furthermore, it can adapt to complex grid conditions, monitor the terminal voltage amplitude in real time, and perform feedback control, making it suitable for grid-connected systems where new energy sources and induction motors coexist. This solves the problems that, due to the limited transient overcurrent capacity of grid-type converters, direct current limiting control can easily lead to the loss of grid-type capacity during grid faults or voltage drops, and that virtual impedance control strategies are mostly based on fixed parameter settings, resulting in rigid adjustment and inability to dynamically adapt to fault characteristics, leading to insufficient voltage support capacity.

[0048] Before describing the fault voltage support method for grid-type converters in the embodiments of this application, the system structure and application scenarios involved in the embodiments of this application will be illustrated with examples.

[0049] like Figure 1 As shown, the structure of a grid-type converter for voltage regulation may include, but is not limited to: power calculation stage 101, active power-frequency outer loop 102, voltage amplitude calculation stage 103, start-up judgment stage 104, virtual impedance calculation stage 105, virtual impedance control 106, current inner loop 107, PWM 108, etc.

[0050] Among them, the power calculation link 101 is usually based on the collected three-phase voltage and current signals, and performs coordinate transformation (such as abc→dq) to calculate the active power and reactive power output of the converter in real time, which can provide a basis for subsequent active frequency regulation and reactive voltage regulation.

[0051] The active-frequency outer loop 102 can adjust the output frequency according to the change of active power to achieve active power control. It is usually suitable for Pf (Power-Frequency) droop control and can provide support when the system frequency deviates to maintain frequency stability.

[0052] The voltage amplitude calculation step 103 can calculate the voltage amplitude in the dq coordinate system (such as the terminal voltage amplitude), which can provide a reference index for voltage regulation and virtual impedance regulation.

[0053] The start judgment step 104 can determine whether to enter the voltage support state or trigger the virtual impedance adjustment mechanism based on the degree of bus voltage drop, current amplitude or frequency deviation, so as to avoid erroneously triggering the support mechanism during normal operation.

[0054] The virtual impedance calculation stage 105 can dynamically calculate the virtual resistance and virtual reactance values ​​based on the real-time operating status (such as voltage amplitude, dq component, etc.), thereby adjusting the converter output impedance and improving system damping and stability.

[0055] The virtual impedance control 106 can be used to dynamically adjust the output virtual impedance parameters, thereby controlling the amplitude and phase of the output current.

[0056] The inner current loop 107 can quickly adjust the converter output current and achieve rapid tracking of the command current. It commonly uses control methods such as PI (Proportional-Integral) controller, feedforward control, and MPC (Model Predictive Control) to improve system response speed and prevent current over-limit.

[0057] PWM modulation 108 can convert the control quantity calculated by the inner current loop into a specific drive signal to control the switching of power devices. Commonly used methods include sinusoidal PWM and SVPWM (Space Vector Pulse Width Modulation) to complete the final execution from control quantity to actual output.

[0058] This application embodiment can dynamically identify and support the transient voltage stability problem in a system where new energy power sources and induction motors coexist. By real-time detection and analysis of key operating parameters in the system (such as terminal voltage, current amplitude, frequency deviation, etc.), it can quickly identify transient voltage instability. Combined with strategies such as virtual impedance control and voltage / frequency droop control, it can dynamically adjust its output characteristics, thereby achieving effective support for system transient voltage and improvement of power quality, and enhancing the robustness and stability of system operation.

[0059] The system structure and application scenarios proposed in the above embodiments can realize the fault voltage support method for grid-type converters proposed in this application. The fault voltage support method for grid-type converters will be described in detail below.

[0060] Specifically, Figure 2This is a flowchart illustrating a fault voltage support method for a grid-type converter provided in an embodiment of this application.

[0061] like Figure 2 As shown, the fault voltage support method for this grid-type converter includes the following steps:

[0062] In step S201, the three-phase terminal voltage of the grid-type converter is collected.

[0063] Among them, grid-connected converters are typically power interface devices capable of actively establishing AC voltage and frequency, which can be used to enhance the grid support capacity of renewable energy systems. Three-phase terminal voltage usually refers to the three-phase voltage value at the device's terminals, reflecting the voltage applied or received by the device. It is an important reference quantity for voltage control, power calculation, fault diagnosis, and other related processes, and is usually expressed in μ. a u b u c express.

[0064] It can be noted that the acquisition method may include, but is not limited to, using a resistor divider, voltage transformer or isolation amplifier circuit, etc., to convert the three-phase AC voltage into a low-voltage signal suitable for the analog-to-digital converter input; after the acquisition result is input to the controller, it is filtered and processed by coordinate transformation to extract the voltage component and voltage amplitude in the dq coordinate system, which can be used as parameter input for modules such as power calculation, virtual impedance adjustment, and voltage control.

[0065] In step S202, the terminal voltage amplitude of the grid-type converter is calculated based on the three-phase terminal voltage, and it is determined whether the terminal voltage amplitude is lower than a preset threshold.

[0066] Among them, the terminal voltage amplitude refers to the overall voltage magnitude of the three-phase AC terminal output voltage, which can reflect the strength of the voltage provided by the converter. It is often used in control links such as voltage regulation and virtual impedance regulation.

[0067] It should be noted that in the embodiments of this application, when the voltage drop reaches 10% to 15%, it can be regarded as a voltage disturbance. Therefore, the preset threshold can be 0.9 pu or 0.85 pu, which can be set by those skilled in the art according to the actual situation, and no specific limitation is made here.

[0068] Optionally, in one embodiment of this application, calculating the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage includes: performing a Parker transformation on the three-phase terminal voltage to convert it into a dq-axis voltage; and calculating the terminal voltage amplitude based on the dq-axis voltage.

[0069] The Parker transformation, also known as the dq transformation, is a commonly used coordinate transformation method in power electronics and motor control. It can transform three-phase AC variables (a, b, c) into DC variables in a rotating coordinate system (d-axis, q-axis), thereby simplifying the design of the controller.

[0070] As a specific example, the embodiments of this application can perform Park transformation on the collected three-phase terminal voltages of the grid-type converter to convert them into dq-axis voltages. The square root of the sum of the squares of the dq-axis voltages can then be calculated and used as the terminal voltage amplitude.

[0071] Optionally, in one embodiment of this application, the formula for calculating the terminal voltage amplitude can be expressed as:

[0072] U=(U d 2 +U q 2 ) 1 / 2 ,

[0073] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0074] Furthermore, in this embodiment of the application, a judgment threshold can be set according to system operation requirements or standard voltage level. When the terminal voltage amplitude of the grid-type converter is lower than the threshold, the virtual impedance adjustment mechanism can be activated. By adjusting the value of virtual resistance and / or virtual reactance, the converter's ability to support fault voltage can be enhanced, thereby improving system stability and voltage recovery performance during voltage sag.

[0075] In step S203, if the terminal voltage amplitude is lower than a preset threshold, virtual impedance adjustment is initiated to adjust the virtual impedance of the grid-type converter in order to support the fault voltage.

[0076] Virtual impedance regulation typically refers to introducing a set of adjustable equivalent impedance parameters, including virtual resistance and / or virtual reactance, into the converter control system and dynamically adjusting them according to the system operating status, thereby improving system stability and dynamic response capability.

[0077] As one possible implementation, embodiments of this application may set the threshold value for judging the terminal voltage amplitude to 0.9 pu and set a judgment signal Flag to indicate whether the fault voltage support state has been entered.

[0078] In the embodiments of this application, when the terminal voltage amplitude U is lower than 0.9pu, a judgment signal Flag can be output as 1, indicating a voltage drop, thus triggering the dynamic adjustment process of the virtual impedance; conversely, when U is not lower than 0.9pu, the judgment signal Flag is 0, and the system maintains normal operation. The embodiments of this application can be represented as follows:

[0079]

[0080] Furthermore, embodiments of this application can calculate and dynamically adjust the virtual impedance in real time based on the current operating state, such as the terminal voltage amplitude, voltage components in the dq coordinate system, and judgment signals, thereby optimizing the output impedance characteristics of the grid-type converter and improving the system's stability and fault support capability.

[0081] Optionally, in one embodiment of this application, adjusting the virtual impedance of the grid converter includes: calculating the virtual impedance of the grid converter; and adjusting the virtual impedance according to the virtual impedance so that the current phase of the grid converter lags behind the voltage by 90 degrees.

[0082] It is understood that the embodiments of this application can calculate the current virtual impedance parameters of the grid-connected converter and dynamically adjust parameters such as the magnitude and phase of the virtual impedance based on these parameters and the operating status to optimize the output performance of the converter. In the embodiments of this application, the regulating current of the grid-connected converter lags behind the voltage by 90 degrees, which can provide reactive power support and help maintain grid voltage stability, especially playing an important role during voltage dips or faults.

[0083] The following examples illustrate the calculation and adjustment methods of the virtual impedance of the grid converter in this application.

[0084] In the embodiments of this application, when U d When >0, the terminal voltage phase can be expressed as:

[0085]

[0086] Where θ is the phase of the terminal voltage of the grid converter; δ is the phase of the internal potential of the grid converter.

[0087] WhenU d When <0, the terminal voltage phase can be expressed as:

[0088]

[0089] WhenU d When = 0, with the d-axis leading the q-axis as the positive direction, the phase of the terminal voltage can be expressed as:

[0090]

[0091] Right now

[0092]

[0093] Furthermore, based on the aforementioned phase information of the terminal voltage, in this embodiment of the application, to ensure that the phase of the output current of the grid-connected converter lags behind the terminal voltage by 90 degrees, i.e., θ-π / 2, in order to provide maximum reactive power support, the internal potential amplitude of the grid-connected converter can be set to a constant value of 1pu, serving as a reference for voltage support. Based on this, this embodiment of the application can further calculate the virtual impedance parameters required to satisfy the aforementioned phase relationship, thereby achieving phase adjustment of the output current and improving reactive power support capability.

[0094] In actual implementation, based on the set internal potential amplitude and combined with the amplitude and phase information of the terminal voltage, the embodiments of this application can calculate and dynamically adjust the virtual resistance value. At this time, the formula for calculating the virtual resistance value can be expressed as:

[0095]

[0096] Among them, R v This represents the virtual resistance value for a grid-type converter.

[0097] The embodiments of this application can suppress system oscillations to a certain extent and improve the damping characteristics of converter current control by dynamically adjusting the virtual resistance value, thereby enhancing its dynamic response capability and stability under fault disturbances.

[0098] Furthermore, in the embodiments of this application, the virtual reactance value can be adjusted according to the desired current phase relationship, for example, by making the phase of the converter output current lag behind the phase of the terminal voltage by 90 degrees, thereby achieving precise control of the current phase and dynamic support of reactive power.

[0099] It should be noted that, ideally, a current phase lagging by 90° corresponds to a purely inductive current. In this case, the virtual impedance only needs to introduce a purely reactive component, that is, set the virtual resistance to zero, and the required current phase control can be achieved simply by adjusting the virtual reactance.

[0100] Optionally, in one embodiment of this application, the formula for calculating virtual impedance can be expressed as:

[0101]

[0102] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0103] The embodiments of this application can adjust the virtual impedance parameters of the grid-type converter so that the phase of the output current lags behind the phase of the terminal voltage by 90 degrees, thereby simulating the characteristics of a purely inductive power source. This provides maximum reactive power support when the grid experiences disturbances such as voltage drops, and improves the voltage stability and dynamic response capability of the system.

[0104] like Figure 3 As shown below, a specific example is used to illustrate the flow of the fault voltage support method for a grid-type converter according to an embodiment of this application. Embodiments of this application may include:

[0105] In step S301, the adjustment process begins;

[0106] In step S302, the voltage signals of the three-phase ports of the converter are acquired to provide raw data for subsequent processing;

[0107] In step S303, a Parker transformation is performed to convert the acquired three-phase terminal voltage signal from the abc stationary coordinate system to the dq rotating coordinate system to facilitate subsequent amplitude and phase calculations.

[0108] In step S304, the terminal voltage amplitude is calculated based on the dq component, which can be used to determine the voltage state.

[0109] In step S305, the terminal voltage amplitude is calculated. If the terminal voltage amplitude is less than 0.9pu, step S306 is executed. If the terminal voltage amplitude is not less than 0.9pu, step S309 is executed.

[0110] In step S306, the system enters a dynamic adjustment state and adjusts the virtual impedance parameters based on voltage and current information.

[0111] In step S307, the virtual resistance value is adjusted according to the control algorithm to improve system stability and current damping;

[0112] In step S308, the virtual reactance value is adjusted according to the desired current phase control target to achieve dynamic reactive power support;

[0113] In step S309, the adjustment process is terminated.

[0114] The embodiments of this application can achieve flexible control of the output impedance characteristics of the grid-type converter by adjusting the virtual resistance and / or virtual reactance, so that the phase and amplitude of the converter output current can be dynamically adjusted according to the changes in the terminal voltage, thereby enhancing the fault voltage support capability.

[0115] The fault voltage support method for grid-connected converters proposed in this application calculates the terminal voltage amplitude of the grid-connected converter through the three-phase terminal voltage, and then dynamically adjusts the virtual impedance parameters to achieve fault voltage support for the grid-connected converter. This allows the converter to flexibly adjust the phase and amplitude of the output current according to real-time voltage changes, improves the fault voltage support capability, effectively alleviates voltage drop problems, and enhances the stability and robustness of the converter under faults and dynamic disturbances. At the same time, it can adapt to complex power grid conditions, monitor the terminal voltage amplitude in real time, and perform feedback control, making it suitable for grid-connected systems where new energy sources and induction motors coexist.

[0116] Next, referring to the accompanying drawings, the fault voltage support device for a grid-type converter proposed according to an embodiment of this application is described.

[0117] Figure 4 This is a block diagram of a grid-type converter fault voltage support device according to an embodiment of this application.

[0118] like Figure 4 As shown, the fault voltage support device 10 for the grid-type converter includes: a data acquisition module 100, a judgment module 200, and a support module 300.

[0119] Among them, the acquisition module 100 is used to acquire the three-phase terminal voltage of the grid-type converter.

[0120] The judgment module 200 is used to calculate the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage and to determine whether the terminal voltage amplitude is lower than a preset threshold.

[0121] The support module 300 is used to activate virtual impedance regulation if the terminal voltage amplitude is lower than a preset threshold, and adjust the virtual impedance of the grid-type converter to provide fault voltage support.

[0122] Optionally, in one embodiment of this application, the determination module 200 includes a conversion unit and a first calculation unit.

[0123] The conversion unit is used to perform Parker transformation on the three-phase terminal voltages to convert them into dq-axis voltages.

[0124] The first calculation unit is used to calculate the terminal voltage amplitude based on the dq axis voltage.

[0125] Optionally, in one embodiment of this application, the formula for calculating the terminal voltage amplitude is:

[0126] U=(U d 2 +U q 2 ) 1 / 2 ,

[0127] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0128] Optionally, in one embodiment of this application, the support module 300 includes: a second calculation unit and an adjustment unit.

[0129] The second calculation unit is used to calculate the virtual impedance of the grid-type converter.

[0130] The regulating unit is used to adjust the virtual impedance according to the virtual impedance so that the current phase of the grid converter lags the voltage by 90 degrees.

[0131] Optionally, in one embodiment of this application, the formula for calculating virtual impedance is:

[0132]

[0133] Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

[0134] It should be noted that the foregoing explanation of the fault voltage support method embodiment for grid-type converters also applies to the fault voltage support device for grid-type converters in this embodiment, and will not be repeated here.

[0135] The fault voltage support device for grid-type converters proposed in this application calculates the terminal voltage amplitude of the grid-type converter through the three-phase terminal voltage, and then dynamically adjusts the virtual impedance parameters to achieve fault voltage support for the grid-type converter. This allows the converter to flexibly adjust the phase and amplitude of the output current according to real-time voltage changes, improves the fault voltage support capability, effectively alleviates voltage drop problems, and enhances the stability and robustness of the converter under faults and dynamic disturbances. At the same time, it can adapt to complex grid conditions, monitor the terminal voltage amplitude in real time and perform feedback control, and is suitable for grid-type systems where new energy sources and induction motors coexist.

[0136] Figure 5 A schematic diagram of the structure of an electronic device provided in an embodiment of this application. The electronic device may include:

[0137] The memory 501, the processor 502, and the computer program stored on the memory 501 and capable of running on the processor 502.

[0138] When the processor 502 executes the program, it implements the fault voltage support method for grid-type converters provided in the above embodiments.

[0139] Furthermore, electronic devices also include:

[0140] Communication interface 503 is used for communication between memory 501 and processor 502.

[0141] The memory 501 is used to store computer programs that can run on the processor 502.

[0142] The memory 501 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0143] If the memory 501, processor 502, and communication interface 503 are implemented independently, then the communication interface 503, memory 501, and processor 502 can be interconnected via a bus to complete communication between them. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 5 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0144] Optionally, in a specific implementation, if the memory 501, processor 502, and communication interface 503 are integrated on a single chip, then the memory 501, processor 502, and communication interface 503 can communicate with each other through an internal interface.

[0145] Processor 502 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0146] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described grid-type converter fault voltage support method.

[0147] This application also provides a computer program product, including a computer program that can run computer instructions. When the computer instructions are executed by a processor, they implement the grid-type converter fault voltage support method provided in this application.

[0148] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0149] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "N" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0150] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing a custom logical function or process step, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed in a different order than shown or discussed, including performing functions in a substantially simultaneous manner or in a reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0151] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0152] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, it can be implemented using any one or more of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0153] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0154] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0155] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for supporting fault voltage in a grid-type converter, characterized in that, Includes the following steps: Collect the three-phase terminal voltage of the grid-type converter; Calculate the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage, and determine whether the terminal voltage amplitude is lower than a preset threshold. If the terminal voltage amplitude is lower than the preset threshold, virtual impedance adjustment is initiated to adjust the virtual impedance of the grid-type converter in order to support the fault voltage.

2. The method according to claim 1, characterized in that, The calculation of the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage includes: The three-phase terminal voltages are subjected to Parker transformation to convert them into dq-axis voltages; The terminal voltage amplitude is calculated based on the dq axis voltage.

3. The method according to claim 2, characterized in that, The formula for calculating the terminal voltage amplitude is: U=(U d 2 +U q 2 ) 1 / 2 , Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

4. The method according to claim 1, characterized in that, The adjustment of the virtual impedance of the grid converter includes: Calculate the virtual impedance of the grid-type converter; The virtual impedance is adjusted according to the virtual impedance so that the current phase of the grid converter lags the voltage phase by 90 degrees.

5. The method according to any one of claims 1-4, characterized in that, The formula for calculating the virtual impedance is: Where U is the amplitude of the terminal voltage of the grid-connected converter; U d and U q These are the d-axis and q-axis components of the grid-type converter terminal voltage after Parker transformation, respectively.

6. A fault voltage support device for a grid-type converter, characterized in that, include: The acquisition module is used to acquire the three-phase terminal voltage of the grid-type converter; The judgment module is used to calculate the terminal voltage amplitude of the grid-type converter based on the three-phase terminal voltage, and to determine whether the terminal voltage amplitude is lower than a preset threshold. The support module is used to activate virtual impedance adjustment if the terminal voltage amplitude is lower than the preset threshold, thereby adjusting the virtual impedance of the grid-type converter to provide fault voltage support.

7. The apparatus according to claim 6, characterized in that, The judgment module includes: A conversion unit is used to perform Parker transformation on the three-phase terminal voltages to convert them into dq-axis voltages; The first calculation unit is used to calculate the terminal voltage amplitude based on the dq axis voltage.

8. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the grid-type converter fault voltage support method as described in any one of claims 1-5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to implement the fault voltage support method for grid-type converters as described in any one of claims 1-5.

10. A computer program product, comprising a computer program, characterized in that, The computer program is executed to implement the fault voltage support method for grid-type converters as described in any one of claims 1-5.

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