Method, system and device for smooth switching control of grid-forming converter mode and medium

Abstract

The application relates to a network-constructing converter mode smooth switching control method, system, device and medium, which comprises the following steps: acquiring grid three-phase voltage and converter three-phase voltage on both sides of a grid-connected switch, performing coordinate transformation and determining phase error and amplitude error; performing phase adjustment based on the phase error to obtain an angular frequency compensation amount; observing converter output voltage amplitude, amplitude change rate and amplitude adjustment total disturbance based on the amplitude error, and obtaining a voltage amplitude compensation amount through state error feedback and disturbance compensation; keeping the network-constructing control mode unchanged, superimposing the angular frequency compensation amount and the voltage amplitude compensation amount into an active-frequency control loop and a reactive-voltage control loop respectively, adjusting the converter output voltage, and executing operation mode switching according to the synchronization state of the converter output voltage and the grid voltage. The application has the effect of improving switching smoothness.

Description

Technical Field

[0001] This invention belongs to the technical field of grid-type converter control, and in particular relates to a method, system, device and medium for smooth mode switching control of grid-type converter. Background Technology

[0002] Currently, with the increasing proportion of new energy power generation units integrated into the power system, grid-connected converters need to switch between grid-connected and islanded operation modes. When a grid-connected converter switches from islanded to grid-connected operation mode, there may be frequency, phase, and amplitude deviations in the voltage across the grid-connected switch. Directly closing the grid-connected switch can easily cause inrush currents and power oscillations, affecting the stable operation of the grid-connected converter and the power system.

[0003] Existing grid-connected converter mode switching control typically pre-synchronizes the phase and amplitude of the converter's output voltage based on the voltage deviation between the two sides of the grid-connected switch. For example, existing technologies have disclosed a scheme that uses the output phase angle of the VSG active power loop as the rotation angle of the dq coordinate system to eliminate the need for a phase-locked loop, and uses a PI regulator to pre-synchronize the phase and amplitude separately. However, in this type of scheme, the amplitude loop uses traditional PI control. Under conditions of grid voltage fluctuations, system parameter changes, or external disturbances, the PI regulator struggles to balance response speed and overshoot suppression, easily leading to voltage amplitude overshoot and oscillation, resulting in excessively large inrush current during grid connection.

[0004] Furthermore, although existing studies have applied active disturbance rejection control to the voltage loop of VSG or used LADRC for the active / frequency channels of grid-connected pre-synchronization, none of these solutions have considered the problem of dynamic response mismatch between the phase loop and the amplitude loop. If both the phase loop and the amplitude loop use fast regulators, they may couple with each other during the pre-synchronization process, causing beat frequency oscillations; if both use slow regulators, the pre-synchronization time will be too long. How to enhance the disturbance rejection capability of the amplitude loop while maintaining the fast response of the phase loop, and how to coordinate the two, is a technical challenge that urgently needs to be solved in the smooth mode switching control of grid-connected converters. Summary of the Invention

[0005] The purpose of this invention is to provide a method, system, device and medium for smooth mode switching control of grid-connected converters, so as to solve the technical problem of grid connection impact caused by disturbances in voltage synchronization regulation during the operation mode switching process of existing grid-connected converters.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for smooth mode switching control of a grid-type converter, the method comprising: Acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The three-phase voltage data of the power grid and the three-phase voltage data of the converter are subjected to coordinate transformation, and the phase error signal and amplitude error signal between the two voltages are determined based on the coordinate transformation result. The phase error signal is input into a proportional-integral controller for phase adjustment to generate angular frequency compensation. The amplitude error signal is input to the active disturbance rejection controller for amplitude compensation adjustment to generate voltage amplitude compensation amount; While keeping the grid control method unchanged, the angular frequency compensation is superimposed on the active-frequency control loop of the grid converter, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop of the grid converter to adjust the output voltage of the grid converter. Based on the synchronization status between the adjusted output voltage and the grid voltage, the grid-connected switch is closed or opened.

[0007] By adopting the above technical solution, and by acquiring the three-phase voltage data of the grid on the grid-connected switch and the three-phase voltage data of the converter on the grid-connected converter side, voltage information of both sides of the grid-connected switch in the same pre-synchronization process can be obtained, thus providing a data basis for the synchronous comparison of the voltages on both sides. By performing coordinate transformation on the two sets of three-phase voltage data and determining the phase error signal and amplitude error signal, the phase deviation and amplitude deviation of the voltages on both sides can be directly characterized, thereby reducing the dynamic lag of deviation detection and improving the real-time performance of pre-synchronization information. By using a proportional-integral controller to adjust the phase error signal, the phase deviation can be targeted to the phase error signal. Phase deviation is insensitive to grid voltage fluctuations and system parameter changes, and its main error source is the accumulation of frequency deviation. This approach achieves zero steady-state error tracking of phase deviation and utilizes the simple structure and fast response of the proportional-integral controller to quickly eliminate phase deviation, thereby shortening the pre-synchronization time. By employing an active disturbance rejection controller to compensate for the amplitude error signal, it can address the vulnerability of amplitude deviation to disturbances such as grid voltage fluctuations, filter parameter perturbations, and load abrupt changes. It performs real-time estimation and active compensation for the total disturbance during amplitude adjustment, thus maintaining the amplitude tracking response speed while suppressing amplitude overshoot and oscillation. To improve the robustness of amplitude tracking under weak grid conditions, the proportional-integral controller (PIC) and active disturbance rejection controller (ADRC) are used for phase and amplitude regulation respectively. This creates an asymmetric combination of fast phase loop response and stable amplitude loop regulation, allowing the two regulation channels to function at different time scales. This avoids beat frequency oscillations that may occur when both the phase and amplitude loops use the same fast regulator, and also avoids excessively long pre-synchronization times caused by using slow regulators in both channels. The asymmetric combination can adapt to the different physical characteristics of phase and amplitude deviations. Furthermore, by maintaining the grid control method unchanged, the angular frequency compensation... The compensation amount and voltage amplitude compensation amount are superimposed on the active-frequency control loop and reactive-voltage control loop respectively. This enables the coordinated adjustment of the output voltage phase and amplitude using the original control loop of the grid-connected converter, thereby avoiding sudden changes in control state caused by switching control architecture. By performing grid-connected switch control based on the synchronization state between the adjusted output voltage and the grid voltage, mode switching can be completed when the voltages on both sides meet the synchronization requirements, and electrical isolation can be maintained when the synchronization requirements are not met. This reduces the inrush current, power oscillation and voltage fluctuation during the mode switching process, and improves the smoothness and safety of the grid-connected converter's operating mode switching.

[0008] In one example, the present invention can be further configured as follows: acquiring the three-phase voltage data of the grid on the grid-connected switch side and the three-phase voltage data of the converter on the grid-connected converter side includes: When the grid-connected converter is in islanded operation mode and the grid-connected switch is in the open state, the three-phase voltage on the grid side of the grid-connected switch and the three-phase voltage on the grid-connected converter side are sampled respectively to obtain the grid-side three-phase voltage sample value and the converter-side three-phase voltage sample value. By matching the sampled values ​​of the three-phase voltage on the grid side and the sampled values ​​of the three-phase voltage on the converter side at the same sampling time, the three-phase voltage data of the grid and the three-phase voltage data of the converter are obtained.

[0009] By adopting the above technical solution, when the grid-connected switch is in islanded operation mode and the grid-connected switch is in the open state, the three-phase voltages on both sides of the grid-connected switch are sampled, and the sampled values ​​of the three-phase voltages on both sides are matched according to the same sampling time. This allows for the acquisition of grid three-phase voltage data and converter three-phase voltage data with consistent time reference, thereby reducing the impact of sampling time difference on the calculation results of phase deviation and amplitude deviation.

[0010] In one example, the present invention can be further configured as follows: performing coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determining the phase error signal and amplitude error signal between the voltages on both sides based on the coordinate transformation result, includes: The three-phase voltage data of the power grid and the three-phase voltage data of the converter are subjected to equal amplitude Clarke transformation to obtain the α-axis voltage component of the power grid, the β-axis voltage component of the power grid, the α-axis voltage component of the converter, and the β-axis voltage component of the converter. The grid voltage amplitude is determined based on the α-axis voltage component and the β-axis voltage component on the grid side, and the converter output voltage amplitude is determined based on the α-axis voltage component and the β-axis voltage component on the converter side. The phase error signal is determined based on the α-axis voltage component of the grid side, the β-axis voltage component of the grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side, and the amplitude error signal is determined based on the difference between the grid voltage amplitude and the converter output voltage amplitude.

[0011] By adopting the above technical solution, and by performing equal-amplitude Clarke transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter respectively, the three-phase voltages on both sides can be converted into α-axis voltage components and β-axis voltage components that retain amplitude and phase information, thus facilitating the direct calculation of deviation using instantaneous voltage components. By determining the amplitude of the power grid voltage and the converter output voltage based on the α-axis voltage components and β-axis voltage components on both sides respectively, the amplitude of the voltage vectors on both sides can be obtained, thus providing an accurate feedback basis for amplitude synchronization adjustment. By determining the phase error signal based on the α-axis voltage components and β-axis voltage components on both sides, and determining the amplitude error signal based on the difference between the voltage amplitudes on both sides, the phase deviation and amplitude deviation can be obtained in a unified coordinate system, thereby improving the real-time performance of pre-synchronization deviation detection.

[0012] In one example, the present invention can be further configured as follows: determining the phase error signal based on the grid-side α-axis voltage component, the grid-side β-axis voltage component, the converter-side α-axis voltage component, and the converter-side β-axis voltage component includes: Multiply the α-axis voltage component on the converter side with the β-axis voltage component on the grid side to obtain a first product, and multiply the β-axis voltage component on the converter side with the α-axis voltage component on the grid side to obtain a second product; Calculate the difference between the first product and the second product to obtain the voltage vector cross product result, which characterizes the direction of the deviation between the grid voltage phase and the converter output voltage phase; The phase error signal is obtained by normalizing the voltage vector cross product result using the product of the grid voltage amplitude and the converter output voltage amplitude.

[0013] By employing the above technical solution, and by multiplying the α-axis voltage component on the converter side with the β-axis voltage component on the grid side, as well as the β-axis voltage component on the converter side with the α-axis voltage component on the grid side, a cross product reflecting the relative positional relationship of the voltage vectors on both sides can be formed, thus providing a computational basis for identifying the phase deviation direction. By calculating the difference between the first product and the second product, a voltage vector cross product result containing phase deviation direction information can be obtained, thereby enabling phase adjustment to reduce phase deviation in the corresponding direction. By normalizing the voltage vector cross product result using the product of the voltage amplitudes on both sides, the influence of voltage amplitude changes on the phase error signal can be reduced, thereby improving the consistency of the phase error signal under different voltage amplitude conditions.

[0014] In one example, the present invention can be further configured such that: the active disturbance rejection controller is a second-order linear active disturbance rejection controller; and the step of inputting the amplitude error signal into the active disturbance rejection controller for amplitude compensation adjustment to generate a voltage amplitude compensation amount includes: The second-order linear active disturbance rejection controller takes the amplitude error signal as input and the converter output voltage amplitude as feedback. It observes the converter output voltage amplitude, the rate of change of output voltage amplitude, and the total disturbance during the amplitude adjustment process through a linear extended state observer, and obtains amplitude state observation, amplitude change rate observation, and total disturbance observation. The state error feedback is performed based on the amplitude error signal, the amplitude state observation, and the amplitude change rate observation, and the disturbance compensation is performed based on the total disturbance observation to obtain the voltage amplitude compensation amount.

[0015] By adopting the above technical solutions, and using a second-order linear active disturbance rejection controller to compensate for the amplitude error signal, the dynamic changes in the converter output voltage amplitude and disturbances during the amplitude adjustment process can be incorporated into a unified control process, thereby improving the adaptability of amplitude pre-synchronization control to changes in operating state. By utilizing a linear extended state observer to observe the converter output voltage amplitude, the rate of change of output voltage amplitude, and the total disturbance during the amplitude adjustment process, amplitude state observations, rate of change of amplitude observations, and total disturbance observations can be obtained, providing observational basis for amplitude state feedback and disturbance suppression. By performing state error feedback based on the amplitude error signal, amplitude state observations, and rate of change of amplitude observations, corresponding adjustment actions can be generated in conjunction with amplitude deviation and its dynamic changes, thereby improving the tracking speed of the converter output voltage amplitude to the grid voltage amplitude. By performing disturbance compensation based on the total disturbance observations, the impact of parameter changes, load disturbances, and external voltage fluctuations on the amplitude adjustment process can be weakened, thereby reducing amplitude synchronization errors and improving the immunity and stability of the mode switching process.

[0016] In one example, the present invention can be further configured as follows: while maintaining the grid control mode unchanged, the angular frequency compensation is superimposed on the active-frequency control loop of the grid converter, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop of the grid converter to adjust the output voltage of the grid converter, including: The angular frequency compensation is superimposed with the angular frequency generated by the active-frequency control loop, and the superimposed angular frequency is integrated to obtain the output voltage phase of the grid-type converter. The voltage amplitude compensation is added to the reactive-voltage control loop as an additional voltage setpoint to obtain the voltage amplitude setpoint. A voltage control command is generated based on the given output voltage phase and voltage amplitude, and the output voltage of the grid converter is adjusted according to the voltage control command.

[0017] By adopting the above technical solutions, by superimposing the angular frequency compensation amount with the angular frequency generated by the active-frequency control loop and integrating the superimposed angular frequency, the converter output voltage phase can be corrected while retaining the original active-frequency grid control function, thereby enabling the converter output voltage phase to gradually track the grid voltage phase. By superimposing the voltage amplitude compensation amount as an additional voltage setpoint to the reactive-voltage control loop, the voltage amplitude setpoint can be corrected without changing the original reactive-voltage control structure, thereby enabling the converter output voltage amplitude to gradually approach the grid voltage amplitude. By generating voltage control commands based on the output voltage phase and voltage amplitude setpoint, the phase compensation results and amplitude compensation results can be uniformly converted into the output control target of the grid-type converter, thereby achieving coordinated adjustment of the output voltage phase and amplitude and reducing the impact of pre-synchronization control on the original grid control structure.

[0018] In one example, the present invention can be further configured such that: the step of closing or opening the grid-connected switch based on the synchronization state between the adjusted output voltage and the grid voltage includes: Determine the frequency deviation, phase deviation, and amplitude deviation between the regulated output voltage and the mains voltage; The frequency deviation, the phase deviation, and the amplitude deviation are compared with the corresponding synchronization determination ranges to obtain the synchronization determination results. When the synchronization determination result indicates that the frequency deviation, the phase deviation, and the amplitude deviation are all within the corresponding synchronization determination range, it is determined that the synchronization state meets the grid connection conditions, and the grid connection switch is controlled to close, so that the grid-type converter switches from islanded operation mode to grid-connected operation mode. When the synchronization determination result indicates that the frequency deviation, phase deviation, or amplitude deviation exceeds the corresponding synchronization determination range, it is determined that the synchronization state does not meet the grid connection conditions, and the grid connection switch is controlled to remain open.

[0019] By adopting the above technical solution, and by determining the frequency deviation, phase deviation, and amplitude deviation between the regulated output voltage and the grid voltage, the matching degree of the voltages on both sides of the grid-connected switch can be characterized from multiple synchronization dimensions, thereby avoiding misjudgments caused by judging the grid connection timing based solely on a single voltage parameter. By comparing the frequency deviation, phase deviation, and amplitude deviation with the corresponding synchronization judgment ranges respectively, a synchronization judgment result with clear judgment criteria can be formed, thereby improving the accuracy and feasibility of grid connection condition identification. By controlling the grid-connected switch to close when the frequency deviation, phase deviation, and amplitude deviation are all within the corresponding synchronization judgment range, the grid-connected converter can be switched from islanded operation mode to grid-connected operation mode after the voltages on both sides meet the synchronization requirements, thereby reducing the inrush current, power surge, and voltage fluctuation at the moment of closing. By controlling the grid-connected switch to remain open when any deviation exceeds the corresponding synchronization judgment range, the grid-connected converter can be prevented from connecting to the grid before the synchronization conditions are met, thereby reducing the risk of asynchronous closing and improving the safety of the mode switching process.

[0020] In a second aspect, the present invention provides a mode smoothing switching control system for a grid-type converter, the system comprising: The voltage acquisition module is used to acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The error determination module is used to perform coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determine the phase error signal and amplitude error signal between the two voltages based on the coordinate transformation result. The phase adjustment module is used to input the phase error signal into the proportional-integral controller for phase adjustment and generate angular frequency compensation. An amplitude adjustment module is used to input the amplitude error signal into an active disturbance rejection controller for amplitude compensation adjustment, thereby generating a voltage amplitude compensation amount; The voltage regulation module is used to add the angular frequency compensation to the active-frequency control loop of the grid-type converter and add the voltage amplitude compensation to the reactive-voltage control loop of the grid-type converter while keeping the grid control mode unchanged, so as to regulate the output voltage of the grid-type converter. The mode switching module is used to close or open the grid-connected switch according to the synchronization state between the adjusted output voltage and the grid voltage.

[0021] By adopting the above technical solution, and by acquiring the three-phase voltage data of the grid on the grid-connected switch and the three-phase voltage data of the converter on the grid-connected converter side, voltage information of both sides of the grid-connected switch in the same pre-synchronization process can be obtained, thus providing a data basis for the synchronous comparison of the voltages on both sides. By performing coordinate transformation on the two sets of three-phase voltage data and determining the phase error signal and amplitude error signal, the phase deviation and amplitude deviation of the voltages on both sides can be directly characterized, thereby reducing the dynamic lag of deviation detection and improving the real-time performance of pre-synchronization information. By using a proportional-integral controller to adjust the phase error signal, the phase deviation can be targeted to the phase error signal. Phase deviation is insensitive to grid voltage fluctuations and system parameter changes, and its main error source is the accumulation of frequency deviation. This approach achieves zero steady-state error tracking of phase deviation and utilizes the simple structure and fast response of the proportional-integral controller to quickly eliminate phase deviation, thereby shortening the pre-synchronization time. By employing an active disturbance rejection controller to compensate for the amplitude error signal, it can address the vulnerability of amplitude deviation to disturbances such as grid voltage fluctuations, filter parameter perturbations, and load abrupt changes. It performs real-time estimation and active compensation for the total disturbance during amplitude adjustment, thus maintaining the amplitude tracking response speed while suppressing amplitude overshoot and oscillation. To improve the robustness of amplitude tracking under weak grid conditions, the proportional-integral controller (PIC) and active disturbance rejection controller (ADRC) are used for phase and amplitude regulation respectively. This creates an asymmetric combination of fast phase loop response and stable amplitude loop regulation, allowing the two regulation channels to function at different time scales. This avoids beat frequency oscillations that may occur when both the phase and amplitude loops use the same fast regulator, and also avoids excessively long pre-synchronization times caused by using slow regulators in both channels. The asymmetric combination can adapt to the different physical characteristics of phase and amplitude deviations. Furthermore, by maintaining the grid control method unchanged, the angular frequency compensation... The compensation amount and voltage amplitude compensation amount are superimposed on the active-frequency control loop and reactive-voltage control loop respectively. This enables the coordinated adjustment of the output voltage phase and amplitude using the original control loop of the grid-connected converter, thereby avoiding sudden changes in control state caused by switching control architecture. By performing grid-connected switch control based on the synchronization state between the adjusted output voltage and the grid voltage, mode switching can be completed when the voltages on both sides meet the synchronization requirements, and electrical isolation can be maintained when the synchronization requirements are not met. This reduces the inrush current, power oscillation and voltage fluctuation during the mode switching process, and improves the smoothness and safety of the grid-connected converter's operating mode switching.

[0022] In a third aspect, the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned grid-type converter mode smooth switching control method.

[0023] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the aforementioned grid-type converter mode smooth switching control method. Attached Figure Description

[0024] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of a mode smooth switching control method for a grid-type converter in an embodiment of the present invention; Figure 2 This is a vector diagram of the converter output voltage and the grid voltage in an embodiment of the present invention; Figure 3 This is a block diagram of the pre-synchronization control without phase-locked loop in an embodiment of the present invention; Figure 4 This is a schematic diagram of voltage pre-synchronization based on LADRC in an embodiment of the present invention; Figure 5 This is a block diagram of the LADRC control in an embodiment of the present invention; Figure 6 This is a voltage waveform diagram of off-grid to on-grid switching in an embodiment of the present invention; Figure 7 This is a current waveform diagram of off-grid to on-grid switching in an embodiment of the present invention; Figure 8 This is a voltage waveform diagram of grid connection and grid disconnection in an embodiment of the present invention; Figure 9 This is a current waveform diagram of grid connection and disconnection in an embodiment of the present invention; Figure 10 This is a structural block diagram of the grid-type converter mode smooth switching control system in an embodiment of the present invention; Figure 11 This is a structural block diagram of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0026] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0027] Example 1 like Figure 1 As shown, this invention discloses a method for smooth mode switching control of a grid-type converter, specifically including the following steps: S10: Obtain the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side.

[0028] Specifically, during the pre-synchronization phase when the grid-connected converter switches from islanded operation mode to grid-connected operation mode, the grid-connected switch remains open. The three-phase instantaneous voltages on the grid side and the grid-connected converter side are acquired at the same sampling time, so that the two sets of three-phase voltage data have a consistent time reference, providing input data for the direct comparison of voltage amplitude and phase on both sides.

[0029] S20: Perform coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determine the phase error signal and amplitude error signal between the voltages on both sides based on the coordinate transformation result.

[0030] Specifically, the three-phase voltage data of the power grid and the three-phase voltage data of the converter are mapped to the αβ coordinate system respectively. Based on the voltage components of the voltages on both sides in the αβ coordinate system, the amplitude of the power grid voltage, the amplitude of the converter output voltage, and the amplitude error signal of both are calculated. The phase error signal is calculated by using the cross product relationship between the voltage vectors on both sides. The amplitude error signal and the phase error signal are obtained by algebraic operation of the instantaneous sampled values. The calculation process does not introduce a phase-locked loop.

[0031] S30: Input the phase error signal into the proportional-integral controller for phase adjustment to generate angular frequency compensation.

[0032] Specifically, such as Figure 3 The block diagram of the phase-locked loop-free pre-synchronization control shown uses the phase error signal as the input of the proportional-integral regulator. The proportional regulation generates a corresponding regulation component based on the current phase error signal, and the integral regulation generates a corresponding regulation component based on the cumulative result of the phase error signal over time. The two regulation components together constitute the angular frequency compensation, so that the phase error signal gradually approaches zero. The frequency and phase synchronization channels maintain their original regulation structure during the pre-synchronization period.

[0033] S40: Input the amplitude error signal into the active disturbance rejection controller for amplitude compensation adjustment to generate voltage amplitude compensation amount.

[0034] Specifically, the amplitude error signal is used as the input for amplitude compensation regulation. The active disturbance rejection controller processes the amplitude deviation of the grid-connected converter's output voltage and the disturbances encountered during amplitude regulation to generate a voltage amplitude compensation amount used to correct the output voltage amplitude, thereby ensuring that the grid-connected converter's output voltage amplitude tracks the grid voltage amplitude.

[0035] S50: While keeping the grid control mode unchanged, the angular frequency compensation is superimposed on the active-frequency control loop of the grid converter, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop of the grid converter to adjust the output voltage of the grid converter.

[0036] Specifically, without changing the original control method of the grid-type converter, the output of the active-frequency control loop is corrected by using angular frequency compensation, and the output of the reactive-voltage control loop is corrected by using voltage amplitude compensation. This allows the output voltage phase and output voltage amplitude of the grid-type converter to gradually track the grid voltage phase and grid voltage amplitude, thereby reducing the difference between the output voltage of the grid-type converter and the grid voltage.

[0037] S60: Based on the synchronization status between the regulated output voltage and the grid voltage, execute the closing or opening of the grid-connected switch.

[0038] Specifically, the synchronization status of the output voltage of the grid-connected converter with the grid voltage is determined, and the grid-connected switch is controlled according to the synchronization status and the operating mode of the grid-connected converter. When the output voltage and the grid voltage reach the synchronization status required for grid connection, the grid-connected switch is closed to connect the grid-connected converter to the grid. When the grid-connected converter needs to disconnect from the grid, the grid-connected switch is opened to disconnect the grid-connected converter from the grid. The grid-connected control mode remains unchanged during the closing or opening of the grid-connected switch.

[0039] In one embodiment, step S10, namely acquiring the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side, includes: S11: When the grid-connected converter is in islanded operation mode and the grid-connected switch is in the open state, the three-phase voltage on the grid side of the grid-connected switch and the three-phase voltage on the grid-connected converter side are sampled respectively to obtain the sampled values ​​of the three-phase voltage on the grid side and the three-phase voltage on the converter side.

[0040] Specifically, in islanded operation mode, the grid-type converter independently establishes voltage and frequency references for the local load. After receiving the grid connection command, it keeps the grid connection switch open and starts the pre-synchronization process. It collects the three-phase grid voltage on the grid side of the grid connection switch and the three-phase output voltage on the grid-type converter side to obtain the grid-side three-phase voltage sampling values ​​and the converter-side three-phase voltage sampling values ​​corresponding to the same pre-synchronization process.

[0041] S12: Match the sampled values ​​of the three-phase voltage on the grid side and the three-phase voltage on the converter side at the same sampling time to obtain the grid three-phase voltage data and the converter three-phase voltage data.

[0042] Specifically, the three-phase voltage sampling values ​​on the grid side and the converter side are time-correlated according to each sampling time. The grid side A-phase, B-phase, and C-phase voltage sampling values ​​at the same sampling time are combined to form the grid three-phase voltage data, and the converter side A-phase, B-phase, and C-phase voltage sampling values ​​at the same sampling time are combined to form the converter three-phase voltage data. This allows the two sets of three-phase voltage data to be coordinate transformed and deviation calculated under the same time reference.

[0043] In one embodiment, step S20 involves performing coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determining the phase error signal and amplitude error signal between the two voltages based on the coordinate transformation result, including: S21: Perform equal-amplitude Clarke transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter respectively to obtain the α-axis voltage component of the power grid side, the β-axis voltage component of the power grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side.

[0044] Specifically, the three-phase voltage on any side is denoted as... The three-phase voltages are mapped to the αβ coordinate system using the constant amplitude Clarke transform, and the transformation relationship is as follows: , where u a u b and u c These represent the instantaneous values ​​of phase A, phase B, and phase C of the three-phase voltage, respectively. α and u β Representing the voltage components of the three-phase voltage on the α and β axes respectively, substituting the grid three-phase voltage data and the converter three-phase voltage data into this transformation relationship, we obtain u. gα u gβ u vα and u vβ In this transformation, the subscript g represents the grid side and the subscript v represents the grid-type converter side. This transformation is a linear orthogonal transformation and retains the amplitude and phase information of the three-phase voltage.

[0045] S22: Determine the grid voltage amplitude based on the α-axis voltage component and β-axis voltage component on the grid side, and determine the converter output voltage amplitude based on the α-axis voltage component and β-axis voltage component on the converter side.

[0046] Specifically, based on the α-axis voltage component u on the grid side gα and grid-side β-axis voltage component u gβ Calculate the voltage amplitude of the power grid According to the α-axis voltage component u on the converter side vα and the converter-side β-axis voltage component u vβ Calculate the output voltage amplitude of the converter Among them, U gU represents the magnitude of the grid voltage vector. v This represents the magnitude of the output voltage vector of the grid-type converter. The magnitude calculation depends only on the α-axis voltage component and the β-axis voltage component at the same sampling time.

[0047] S23: Determine the phase error signal based on the α-axis voltage component of the grid side, the β-axis voltage component of the grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side, and determine the amplitude error signal based on the difference between the grid voltage amplitude and the converter output voltage amplitude.

[0048] Specifically, such as Figure 2 The converter output voltage versus grid voltage vector diagram shown below represents the grid voltage vector as follows: The output voltage vector of the grid converter is expressed as , where θ g θ represents the phase of the grid voltage. v The phase error signal is determined by the cross product of the voltage vectors on both sides in the αβ coordinate system, and the amplitude error signal is determined by the difference between the grid voltage amplitude and the converter output voltage amplitude. , where ΔU represents the amplitude error signal of the grid voltage amplitude relative to the converter output voltage amplitude.

[0049] In one embodiment, step S23, namely determining the phase error signal based on the grid-side α-axis voltage component, the grid-side β-axis voltage component, the converter-side α-axis voltage component, and the converter-side β-axis voltage component, includes: S231: Multiply the α-axis voltage component on the converter side with the β-axis voltage component on the grid side to obtain the first product, and multiply the β-axis voltage component on the converter side with the α-axis voltage component on the grid side to obtain the second product.

[0050] Specifically, the α-axis voltage component u on the grid side gα With the converter-side β-axis voltage component u vβ Multiply, and combine the β-axis voltage component u on the grid side. gβ With the converter side α-axis voltage component u vα The two products represent the cross-product relationship between the voltage vectors on both sides along the α-axis and β-axis, respectively, providing a basis for forming the voltage vector cross-product result with phase deviation direction information.

[0051] S232: Calculate the difference between the first product and the second product to obtain the voltage vector cross product result, which characterizes the direction of the deviation between the grid voltage phase and the converter output voltage phase.

[0052] Specifically, such as Figure 2The converter output voltage versus grid voltage vector diagram shown is composed of the grid voltage vector and the converter output voltage vector, respectively, synthesized from the corresponding α-axis voltage components and β-axis voltage components. Calculate the cross product of the voltage vectors on both sides, where u gα and u gβ Let u represent the α-axis voltage component and β-axis voltage component on the grid side, respectively. vα and u vβ U represents the α-axis voltage component and β-axis voltage component on the converter side, respectively. g U represents the magnitude of the grid voltage. v θ represents the output voltage amplitude of the converter. g θ represents the phase of the grid voltage. v Indicates the phase of the converter output voltage. This indicates the phase deviation between the voltages on both sides.

[0053] S233: The phase error signal is obtained by normalizing the voltage vector cross product by multiplying the grid voltage amplitude and the converter output voltage amplitude.

[0054] Specifically, such as Figure 2 The converter output voltage and grid voltage vector diagram shown indicates that at the start of pre-synchronization, there is a phase deviation Δθ between the grid voltage vector and the converter output voltage vector. As the phase adjustment process progresses, the two voltage vectors gradually coincide. When the phase deviation enters a small angle range, the desired phase is achieved. Using the grid voltage amplitude U g With the converter output voltage amplitude U v The product of the voltage vector cross product is normalized to obtain the result. The normalized result is used as the phase error signal input to the phase adjustment channel. This calculation does not require calling the arctangent function, and the phase error signal is obtained through multiplication, subtraction and division operations of instantaneous sampled values.

[0055] In one embodiment, in step S40, where the active disturbance rejection controller is a second-order linear active disturbance rejection controller, the amplitude error signal is input to the active disturbance rejection controller for amplitude compensation adjustment to generate a voltage amplitude compensation amount, including: S41: The second-order linear active disturbance rejection controller takes the amplitude error signal as input and the converter output voltage amplitude as feedback. It observes the converter output voltage amplitude, the rate of change of output voltage amplitude, and the total disturbance during the amplitude regulation process through a linear extended state observer, and obtains the amplitude state observation, amplitude change rate observation, and total disturbance observation.

[0056] Specifically, such as Figure 5The LADRC control block diagram shown treats the voltage amplitude regulation process of the grid-type converter as the controlled object G(s). The input to the controlled object is the control quantity u after disturbance compensation, and the output of the controlled object is the converter output voltage amplitude U. v The amplitude adjustment process is described as a second-order system. Where y represents the output of the second-order system and corresponds to the output voltage amplitude of the strain gauge. The first rate of change of the output voltage amplitude of the converter. The second rate of change of the converter output voltage amplitude is represented by , where u represents the control quantity and the corresponding amplitude correction quantity. Let represent the total disturbance including internal unmodeled dynamics, parameter perturbations, and external voltage disturbances, where t represents time and b0 represents an approximate estimate of the control gain. The total disturbance is then expanded into a new state variable and defined. , , The state equations are obtained. Where z1 represents the output voltage amplitude state, z2 represents the output voltage amplitude change rate state, and z3 represents the total disturbance state. This represents the rate of change of the total disturbance; The amplitude y of the converter output voltage output from the controlled object G(s) and the actual control quantity u are input into a linearly extended state observer, and the amplitude state observation is obtained through three integrators. Observation of amplitude change rate Total disturbance observations The observation process satisfies Where β1, β2, and β3 represent the gains of the three observers, and the observation error is... The bandwidth tuning method is used to uniformly configure the observer poles within the observer bandwidth ω. o At this point, the characteristic polynomial of the observer is and in accordance with Configure the observer gain, where s represents the complex frequency domain variable, ω o This represents the observer bandwidth and determines the speed at which the linearly extended state observer tracks the total disturbance.

[0057] S42: Perform state error feedback based on the amplitude error signal, amplitude state observation, and amplitude change rate observation, and perform disturbance compensation based on the total disturbance observation to obtain the voltage amplitude compensation amount.

[0058] Specifically, such as Figure 5 The LADRC control block diagram shown will control the grid voltage amplitude U. g As a reference input, the amplitude state observation As a feedback quantity, the difference between the reference input and the amplitude state observation is calculated, and this difference is passed through a gain k.p Processing, the observed amplitude change rate Gain k d The two processing results are combined to obtain... Where v represents the reference input and corresponds to the amplitude deviation setpoint ΔU ref , The observed state quantity representing the output voltage amplitude of the converter. The observed state variable represents the rate of change of the converter output voltage amplitude, u0 represents the virtual control variable without total disturbance compensation, and k p and k d Let the proportional gain and derivative gain of the state error feedback controller be respectively, and let the closed-loop characteristic polynomial be... = and take , where ω c The controller bandwidth is represented and determines the amplitude adjustment response speed; ξ represents the damping ratio, with a typical value of ξ = 0.707. Based on total disturbance observations Feedforward compensation is performed on the state error feedback control quantity u0, according to... Calculate the actual control quantity, where u represents the voltage amplitude compensation after total disturbance compensation, and u0 represents the state error feedback control quantity. Let represent the total disturbance observation obtained by the linearly extended state observer, b0 represent the approximate estimate of the control gain, and the observer bandwidth ω. o The controller bandwidth ω is taken according to a fixed ratio. c This is three to five times faster, allowing the observer to track the total disturbance faster than the amplitude control response speed.

[0059] In one embodiment, in step S50, while keeping the grid control mode unchanged, the angular frequency compensation is superimposed on the active-frequency control loop of the grid converter, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop of the grid converter to adjust the output voltage of the grid converter, including: S51: The angular frequency compensation is superimposed with the angular frequency generated by the active-frequency control loop, and the superimposed angular frequency is integrated to obtain the output voltage phase of the grid converter.

[0060] Specifically, the angular frequency compensation output by the proportional-integral regulator is superimposed on the angular frequency reference value generated by the active-frequency control loop. The superimposed angular frequency is used to adjust the output voltage frequency of the grid-type converter. The superimposed angular frequency is integrated over time to obtain the output voltage phase of the grid-type converter, so that the output voltage phase gradually tracks the grid voltage phase according to the phase error signal.

[0061] S52: The voltage amplitude compensation is added to the reactive-voltage control loop as an additional voltage setpoint to obtain the voltage amplitude setpoint.

[0062] Specifically, such as Figure 4 The diagram shown illustrates voltage pre-synchronization based on LADRC. It uses the voltage amplitude compensation output from the second-order linear active disturbance rejection controller as the amplitude correction value, and compares it with the original voltage amplitude reference value U of the reactive power-voltage control loop. ref0 By superimposing the values, the given voltage amplitude U is obtained. ref , among which, U ref0 This represents the reference voltage amplitude value without the pre-synchronization amplitude correction. The voltage amplitude compensation represents the additional adjustment amount generated based on the amplitude error signal, state observation results, and total disturbance observation results. The voltage amplitude setpoint U ref Used to adjust the output voltage amplitude of a grid-type converter.

[0063] S53: Generates voltage control commands based on the output voltage phase and voltage amplitude, and adjusts the output voltage of the grid converter according to the voltage control commands.

[0064] Specifically, the output voltage of the grid-connected converter is generated based on the output voltage phase and voltage amplitude. The frequency, phase, and amplitude of the adjusted output voltage are continuously compared with the grid voltage to obtain the frequency deviation, phase deviation, and amplitude deviation, respectively. When the amplitude adjustment process is affected by filter phase shift, line impedance change, grid voltage fluctuation, or load change, the amplitude deviation is brought close to zero by amplitude adjustment, and the phase deviation is brought close to zero by phase adjustment. The synchronization state is determined based on whether the three types of deviations meet the grid connection requirements.

[0065] In one embodiment, step S60, namely, closing or opening the grid-connected switch according to the synchronization state between the regulated output voltage and the grid voltage, includes: S61: Determine the frequency deviation, phase deviation, and amplitude deviation between the regulated output voltage and the grid voltage.

[0066] Specifically, the output voltage of the grid-connected converter and the grid voltage on the grid side of the grid-connected switch are continuously acquired after adjustment. The frequency, phase, and amplitude of the output voltage and the grid voltage are compared to obtain the frequency deviation, phase deviation, and amplitude deviation, respectively. The output voltage frequency and phase are adjusted using angular frequency compensation to make the output voltage frequency and phase track the grid voltage frequency and phase. The output voltage amplitude is adjusted using voltage amplitude compensation. When the amplitude adjustment is affected by filter phase shift, line impedance change, grid voltage fluctuation, or load change, the total disturbance observation is used for compensation to make the output voltage amplitude track the grid voltage amplitude.

[0067] S62: Compare the frequency deviation, phase deviation, and amplitude deviation with the corresponding synchronization determination ranges to obtain the synchronization determination results.

[0068] Specifically, the frequency deviation is compared with the frequency synchronization judgment range, the phase deviation is compared with the phase synchronization judgment range, and the amplitude deviation is compared with the amplitude synchronization judgment range. Based on whether the frequency deviation, phase deviation, and amplitude deviation are respectively within the corresponding synchronization judgment range, a joint judgment is made to obtain the synchronization judgment result used to characterize whether the synchronization state between the regulated output voltage and the grid voltage meets the grid connection conditions.

[0069] S63: When the synchronization judgment result shows that the frequency deviation, phase deviation and amplitude deviation are all within the corresponding synchronization judgment range, it is determined that the synchronization state meets the grid connection conditions, and the grid connection switch is closed to switch the grid-connected converter from islanded operation mode to grid-connected operation mode.

[0070] Specifically, when the frequency deviation, phase deviation, and amplitude deviation are all within the corresponding synchronization judgment range, it is determined that the adjusted output voltage and the grid voltage have reached a synchronized state. A grid-connected switch closing command is generated, controlling the grid-connected switch to close, thus switching the grid-type converter from islanded operation mode to grid-connected operation mode while maintaining the grid-connected control mode unchanged. The grid-type converter enters islanded operation mode at 0 s, receives a pre-synchronization signal and starts pre-synchronization control at 0.2 s, and closes the grid-connected switch at 0.5 s. Figure 6 The voltage waveform diagram for off-grid to grid switching shown indicates that before the pre-synchronization control is started, there is a phase deviation between the output voltage and the grid voltage. After the pre-synchronization control is started, the voltage phases on both sides gradually approach each other and achieve phase coincidence after about 0.015 seconds. Figure 7 The current waveform diagram shown shows that the output current maintains a continuous periodic change during the pre-synchronization stage. When the grid connection switch is closed, only a small instantaneous amplitude disturbance occurs, and there is no continuous current oscillation. After closing the switch, the output current returns to stability.

[0071] S64: When the synchronization determination result indicates that the frequency deviation, phase deviation, or amplitude deviation exceeds the corresponding synchronization determination range, it is determined that the synchronization state does not meet the grid connection conditions, and the grid connection switch is kept open.

[0072] Specifically, when at least one of the frequency deviation, phase deviation, or amplitude deviation exceeds the corresponding synchronization judgment range, it is determined that the adjusted output voltage and the grid voltage have not reached synchronization. The grid-connected switch is kept open, allowing the grid-type converter to continue operating in islanded mode, and the output voltage continues to be adjusted using angular frequency compensation and voltage amplitude compensation. When the grid-type converter is in grid-connected mode and the grid-connected switch is open, it switches to islanded mode while maintaining the grid-connected control method unchanged. Figure 8The voltage waveform diagrams shown are for grid connection and grid disconnection. Figure 9 The current waveform diagrams shown in the grid-connected and grid-off diagrams indicate that when the grid-connected switch is disconnected at 0.8 s, the output voltage waveform and output current waveform remain continuous before and after the grid-connected switch is disconnected, without any obvious amplitude abrupt changes or continuous oscillations.

[0073] Example 2 like Figure 10 As shown, based on the same inventive concept as the above embodiments, the present invention also provides a grid-type converter mode smooth switching control system, including: The voltage acquisition module is used to acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The error determination module is used to perform coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determine the phase error signal and amplitude error signal between the two voltages based on the coordinate transformation result. The phase adjustment module is used to input the phase error signal into the proportional-integral controller for phase adjustment and generate angular frequency compensation. The amplitude adjustment module is used to input the amplitude error signal into the active disturbance rejection controller for amplitude compensation adjustment, and generate the voltage amplitude compensation amount; The voltage regulation module is used to add the angular frequency compensation to the active-frequency control loop of the grid-type converter and the voltage amplitude compensation to the reactive-voltage control loop of the grid-type converter while keeping the grid control mode unchanged, so as to regulate the output voltage of the grid-type converter. The mode switching module is used to close or open the grid-connected switch according to the synchronization status between the regulated output voltage and the grid voltage.

[0074] Optionally, the voltage acquisition module includes: The synchronous sampling submodule is used to sample the three-phase voltage on the grid side of the grid-connected switch and the three-phase voltage on the grid-connected switch side when the grid-connected converter is in islanded operation mode and the grid-connected switch is in the open state, so as to obtain the grid-side three-phase voltage sampling value and the converter-side three-phase voltage sampling value. The data correspondence submodule is used to correspond the sampled values ​​of the three-phase voltage on the grid side and the sampled values ​​of the three-phase voltage on the converter side according to the same sampling time, so as to obtain the grid three-phase voltage data and the converter three-phase voltage data.

[0075] Optionally, the error determination module includes: The coordinate transformation submodule is used to perform equal-amplitude Clarke transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter respectively, to obtain the α-axis voltage component of the power grid side, the β-axis voltage component of the power grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side. The amplitude determination submodule is used to determine the grid voltage amplitude based on the grid-side α-axis voltage component and the grid-side β-axis voltage component, and to determine the converter output voltage amplitude based on the converter-side α-axis voltage component and the converter-side β-axis voltage component; The error calculation submodule is used to determine the phase error signal based on the α-axis voltage component of the grid side, the β-axis voltage component of the grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side, and to determine the amplitude error signal based on the difference between the grid voltage amplitude and the converter output voltage amplitude.

[0076] Optionally, the error calculation submodule includes: The product calculation unit is used to multiply the α-axis voltage component on the converter side with the β-axis voltage component on the grid side to obtain a first product, and to multiply the β-axis voltage component on the converter side with the α-axis voltage component on the grid side to obtain a second product; The cross product determination unit is used to calculate the difference between the first product and the second product to obtain the voltage vector cross product result, which characterizes the direction of the deviation between the grid voltage phase and the converter output voltage phase. The normalization processing unit is used to normalize the voltage vector cross product result by using the product of the grid voltage amplitude and the converter output voltage amplitude to obtain the phase error signal.

[0077] Optionally, the amplitude adjustment module includes: The state observation submodule is used by the second-order linear active disturbance rejection controller to take the amplitude error signal as input and the converter output voltage amplitude as feedback. It observes the converter output voltage amplitude, the rate of change of output voltage amplitude, and the total disturbance during the amplitude regulation process through a linear extended state observer, and obtains the amplitude state observation, amplitude change rate observation, and total disturbance observation. The disturbance compensation submodule is used to perform state error feedback based on the amplitude error signal, amplitude state observation and amplitude change rate observation, and to perform disturbance compensation based on the total disturbance observation to obtain the voltage amplitude compensation amount.

[0078] Optionally, the voltage regulation module includes: The phase generation submodule is used to superimpose the angular frequency compensation amount with the angular frequency generated by the active-frequency control loop, and integrate the superimposed angular frequency to obtain the output voltage phase of the grid converter. The amplitude setting submodule is used to add the voltage amplitude compensation amount as an additional voltage setting amount to the reactive-voltage control loop to obtain the voltage amplitude setting. The command regulation submodule is used to generate voltage control commands based on the given output voltage phase and voltage amplitude, and to regulate the output voltage of the grid converter according to the voltage control commands.

[0079] Optionally, the mode switching module includes: The synchronization deviation submodule is used to determine the frequency deviation, phase deviation, and amplitude deviation between the regulated output voltage and the grid voltage; The synchronization determination submodule is used to compare the frequency deviation, phase deviation, and amplitude deviation with the corresponding synchronization determination range to obtain the synchronization determination result. The grid-connected control submodule is used to determine that the synchronization state meets the grid-connection conditions when the synchronization judgment results show that the frequency deviation, phase deviation and amplitude deviation are all within the corresponding synchronization judgment range. It then controls the grid-connection switch to close, so that the grid-type converter can switch from islanded operation mode to grid-connected operation mode. The disconnect holding submodule is used to determine that the synchronization state does not meet the grid connection conditions when the synchronization judgment result shows that the frequency deviation, phase deviation or amplitude deviation exceeds the corresponding synchronization judgment range, and to control the grid connection switch to remain disconnected.

[0080] Example 3 like Figure 11 As shown, the present invention also provides an electronic device 100 for implementing a mode smooth switching control method for a grid-type converter; The electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on at least one processor 102, and at least one communication bus 104.

[0081] The memory 101 can be used to store the computer program 103. The processor 102 implements the steps of the grid-type converter mode smooth switching control method of Embodiment 1 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101.

[0082] The memory 101 may primarily include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created based on the use of the electronic device 100 (such as audio data), etc. In addition, the memory 101 may include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0083] At least one processor 102 may 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. Processor 102 may be a microprocessor or any conventional processor. Processor 102 is the control center of electronic device 100, connecting various parts of electronic device 100 via various interfaces and lines.

[0084] The memory 101 in the electronic device 100 stores multiple instructions to implement a smooth switching control method for a grid-type converter mode, and the processor 102 can execute multiple instructions to achieve the following: Acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The three-phase voltage data of the power grid and the three-phase voltage data of the converter are transformed by coordinate, and the phase error signal and amplitude error signal between the two voltages are determined based on the coordinate transformation results. Phase adjustment is performed based on the phase error signal to obtain the angular frequency compensation amount. Based on the amplitude error signal, the output voltage amplitude of the converter, the rate of change of the output voltage amplitude, and the total disturbance during the amplitude adjustment process are observed. Based on the observation results, state error feedback and disturbance compensation are performed to obtain the voltage amplitude compensation amount. While keeping the grid-connected control mode unchanged, the angular frequency compensation is superimposed on the active-frequency control loop, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop to adjust the output voltage of the grid-connected converter. The operating mode is switched according to the synchronization state between the adjusted output voltage and the grid voltage corresponding to the three-phase grid voltage data.

[0085] Example 4 If the modules / units integrated in the electronic device 100 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of 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 system capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, and read-only memory (ROM).

[0086] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0087] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A system that specifies functions in one or more boxes.

[0088] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including an instruction set implemented in a process. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0089] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0090] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for smooth mode switching control of a grid-type converter, characterized in that, The method includes: Acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The three-phase voltage data of the power grid and the three-phase voltage data of the converter are subjected to coordinate transformation, and the phase error signal and amplitude error signal between the two voltages are determined based on the coordinate transformation result. The phase error signal is input into a proportional-integral controller for phase adjustment to generate angular frequency compensation. The amplitude error signal is input to the active disturbance rejection controller for amplitude compensation adjustment to generate voltage amplitude compensation amount; While keeping the grid control method unchanged, the angular frequency compensation is superimposed on the active-frequency control loop of the grid converter, and the voltage amplitude compensation is superimposed on the reactive-voltage control loop of the grid converter to adjust the output voltage of the grid converter. Based on the synchronization status between the adjusted output voltage and the grid voltage, the grid-connected switch is closed or opened.

2. The method for smooth mode switching control of a grid-type converter according to claim 1, characterized in that, The acquisition of three-phase voltage data of the grid on the grid-connected switch side and three-phase voltage data of the converter on the grid-connected converter side includes: When the grid-connected converter is in islanded operation mode and the grid-connected switch is in the open state, the three-phase voltage on the grid side of the grid-connected switch and the three-phase voltage on the grid-connected converter side are sampled respectively to obtain the grid-side three-phase voltage sample value and the converter-side three-phase voltage sample value. By matching the sampled values ​​of the three-phase voltage on the grid side and the sampled values ​​of the three-phase voltage on the converter side at the same sampling time, the three-phase voltage data of the grid and the three-phase voltage data of the converter are obtained.

3. The method for smooth mode switching control of a grid-type converter according to claim 1, characterized in that, The step of performing coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determining the phase error signal and amplitude error signal between the two voltages based on the coordinate transformation result, includes: The three-phase voltage data of the power grid and the three-phase voltage data of the converter are subjected to equal amplitude Clarke transformation to obtain the α-axis voltage component of the power grid, the β-axis voltage component of the power grid, the α-axis voltage component of the converter, and the β-axis voltage component of the converter. The grid voltage amplitude is determined based on the α-axis voltage component and the β-axis voltage component on the grid side, and the converter output voltage amplitude is determined based on the α-axis voltage component and the β-axis voltage component on the converter side. The phase error signal is determined based on the α-axis voltage component of the grid side, the β-axis voltage component of the grid side, the α-axis voltage component of the converter side, and the β-axis voltage component of the converter side, and the amplitude error signal is determined based on the difference between the grid voltage amplitude and the converter output voltage amplitude.

4. The method for smooth mode switching control of a grid-type converter according to claim 3, characterized in that, The step of determining the phase error signal based on the grid-side α-axis voltage component, the grid-side β-axis voltage component, the converter-side α-axis voltage component, and the converter-side β-axis voltage component includes: Multiply the α-axis voltage component on the converter side with the β-axis voltage component on the grid side to obtain a first product, and multiply the β-axis voltage component on the converter side with the α-axis voltage component on the grid side to obtain a second product; Calculate the difference between the first product and the second product to obtain the voltage vector cross product result, which characterizes the direction of the deviation between the grid voltage phase and the converter output voltage phase; The phase error signal is obtained by normalizing the voltage vector cross product result using the product of the grid voltage amplitude and the converter output voltage amplitude.

5. The method for smooth mode switching control of a grid-type converter according to claim 1, characterized in that, The active disturbance rejection controller is a second-order linear active disturbance rejection controller. The step of inputting the amplitude error signal into the active disturbance rejection controller for amplitude compensation adjustment to generate a voltage amplitude compensation amount includes: The second-order linear active disturbance rejection controller takes the amplitude error signal as input and the converter output voltage amplitude as feedback. It observes the converter output voltage amplitude, the rate of change of output voltage amplitude, and the total disturbance during the amplitude adjustment process through a linear extended state observer, and obtains amplitude state observation, amplitude change rate observation, and total disturbance observation. The state error feedback is performed based on the amplitude error signal, the amplitude state observation, and the amplitude change rate observation, and the disturbance compensation is performed based on the total disturbance observation to obtain the voltage amplitude compensation amount.

6. The method for smooth mode switching control of a grid-type converter according to claim 1, characterized in that, The method of adjusting the output voltage of the grid-type converter by adding the angular frequency compensation to the active-frequency control loop and the voltage amplitude compensation to the reactive-voltage control loop while keeping the grid control mode unchanged includes: The angular frequency compensation is superimposed with the angular frequency generated by the active-frequency control loop, and the superimposed angular frequency is integrated to obtain the output voltage phase of the grid converter. The voltage amplitude compensation is added to the reactive-voltage control loop as an additional voltage setpoint to obtain the voltage amplitude setpoint. A voltage control command is generated based on the given output voltage phase and voltage amplitude, and the output voltage of the grid converter is adjusted according to the voltage control command.

7. The method for smooth mode switching control of a grid-type converter according to claim 1, characterized in that, The step of closing or opening the grid-connected switch based on the synchronization state between the adjusted output voltage and the grid voltage includes: Determine the frequency deviation, phase deviation, and amplitude deviation between the regulated output voltage and the mains voltage; The frequency deviation, the phase deviation, and the amplitude deviation are compared with the corresponding synchronization determination ranges to obtain the synchronization determination results. When the synchronization determination result indicates that the frequency deviation, the phase deviation, and the amplitude deviation are all within the corresponding synchronization determination range, it is determined that the synchronization state meets the grid connection conditions, and the grid connection switch is closed to switch the grid-connected converter from islanded operation mode to grid-connected operation mode. When the synchronization determination result indicates that the frequency deviation, phase deviation, or amplitude deviation exceeds the corresponding synchronization determination range, it is determined that the synchronization state does not meet the grid connection conditions, and the grid connection switch is controlled to remain open.

8. A mode-smoothing control system for a grid-type converter, characterized in that, The system includes: The voltage acquisition module is used to acquire the three-phase voltage data of the grid on the grid-connected switch grid side and the three-phase voltage data of the converter on the grid-connected converter side; The error determination module is used to perform coordinate transformation on the three-phase voltage data of the power grid and the three-phase voltage data of the converter, and determine the phase error signal and amplitude error signal between the two voltages based on the coordinate transformation result. The phase adjustment module is used to input the phase error signal into the proportional-integral controller for phase adjustment and generate angular frequency compensation. An amplitude adjustment module is used to input the amplitude error signal into an active disturbance rejection controller for amplitude compensation adjustment, thereby generating a voltage amplitude compensation amount; The voltage regulation module is used to add the angular frequency compensation to the active-frequency control loop of the grid-type converter and add the voltage amplitude compensation to the reactive-voltage control loop of the grid-type converter while keeping the grid control mode unchanged, so as to regulate the output voltage of the grid-type converter. The mode switching module is used to close or open the grid-connected switch according to the synchronization state between the adjusted output voltage and the grid voltage.

9. An electronic device, characterized in that, It includes a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the grid-type converter mode smooth switching control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction, which, when executed by a processor, implements the grid-type converter mode smooth switching control method as described in any one of claims 1 to 7.

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