Power grid synchronization method based on coupling harmonic observer pre-filtering and electronic equipment

Abstract

The invention relates to the technical field of power grid synchronization, and provides a power grid synchronization method based on pre-filtering of a coupled harmonic observer and electronic equipment, and the method comprises the steps: inputting a target voltage signal into the coupled harmonic observer, and obtaining a fundamental voltage component, state variables of the coupling harmonic observer comprise a fundamental wave voltage component, a direct current component and an orthogonal component of the fundamental wave voltage component in the target voltage signal, a gain coefficient is determined by adopting a pole assignment mode, and a natural frequency of a pole assignment characteristic equation is set as an angular frequency of the fundamental wave voltage component; performing normalization and phase-locked loop operation processing on the fundamental wave voltage component in sequence to obtain an estimated value of a phase and an estimated value of an angular frequency, and calculating a power grid frequency and updating a coupling harmonic observer based on the estimated value of the angular frequency; and performing power grid synchronization based on the phase estimation value and the power grid frequency. The problem that a related method cannot improve the stability of a grid-connected converter under the weak power grid condition while the phase-locked logic is simple is solved.

Description

Technical Field

[0001] This invention relates to the field of power grid synchronization technology, and in particular to a power grid synchronization method and electronic device based on pre-filtering of a coupled harmonic observer. Background Technology

[0002] Due to the high penetration rate of renewable energy sources such as wind and solar power, modern power systems have increasingly stringent requirements for grid synchronization. Renewable energy sources are often connected to the grid using power electronics converters. This not only controls the power delivered to the system but also contributes to grid stability, even maintaining grid voltage and frequency stability during grid faults. However, during grid synchronization of renewable energy sources, grid voltage imbalances and distortions can occur due to grid faults and nonlinear loads. Under these conditions, grid-connected converters should be properly synchronized with the grid to maintain the normal operation of the power generation system.

[0003] While phase-locked loop (PLL)-based grid synchronization methods exhibit good dynamic performance and phase-locking accuracy under ideal grid conditions, their fundamental phase detection accuracy significantly decreases when grid voltage asymmetry or harmonic distortion occurs. This detection error leads to an increase in the harmonic content of the grid-connected current of the three-phase converter, which may, in severe cases, cause control system failure, equipment shutdown, or even more serious system malfunctions.

[0004] There is currently no effective solution to the problem that related methods cannot improve the stability of grid-connected converters under weak grid conditions while maintaining simple phase-locked logic. Summary of the Invention

[0005] The present invention provides a power grid synchronization method and electronic device based on pre-filtering of coupled harmonic observer, which at least solves the problem that related methods cannot improve the stability of grid-connected converters under weak power grid conditions while keeping phase-locked logic simple.

[0006] This invention provides a power grid synchronization method based on pre-filtering of a coupled harmonic observer, comprising: processing a three-phase voltage sampling signal of the power grid into a target voltage signal in a two-phase stationary coordinate system; inputting the target voltage signal into a coupled harmonic observer to obtain a fundamental voltage component, wherein the coupled harmonic observer is constructed based on a Luneburger observer design strategy, and the state variables of the coupled harmonic observer include the fundamental voltage component, the DC component, and the quadrature component of the fundamental voltage component in the target voltage signal; the gain coefficient of the coupled harmonic observer is determined by a pole placement method, and the natural frequency of the pole placement characteristic equation is set as the angular frequency of the fundamental voltage component; performing normalization and phase-locked loop (PLL) operations on the fundamental voltage component sequentially to obtain an estimated value of the phase and an estimated value of the angular frequency; calculating the power grid frequency and updating the coupled harmonic observer based on the estimated value of the angular frequency; and performing power grid synchronization based on the estimated value of the phase and the power grid frequency.

[0007] Preferably, the state variable equation of the coupled harmonic observer is: ; In the formula, Represents the fundamental voltage component. Represents the orthogonal component of the fundamental voltage component. Represents the DC component , This represents the amplitude of the fundamental voltage component. Represents angular frequency. Indicates time, Indicates the initial phase.

[0008] Preferably, the formula for the coupled harmonic observer is expressed as: ; In the formula, Represents the observed value of the fundamental voltage component. The observed values ​​represent the orthogonal components. The observed values ​​represent the DC component. Represents the Laplace operator. This represents the gain coefficient of the coupled harmonic observer. This represents the voltage signal input to the coupled harmonic observer.

[0009] Preferably, the target voltage signal is input into the coupled harmonic observer, and the formula for obtaining the fundamental voltage component is expressed as: ; In the formula, Represents the fundamental voltage component. This represents an estimated value of the angular frequency. This represents the target voltage signal in a two-phase stationary coordinate system.

[0010] Preferably, the step of normalizing the fundamental voltage component includes: normalizing the fundamental voltage component. of and Multiply by respectively .

[0011] Preferably, the fundamental voltage component is subjected to normalization processing and phase-locked loop (PLL) operation processing in sequence to obtain the estimated value of phase and the estimated value of angular frequency, including: normalizing the fundamental voltage component to obtain a normalized component; and using a proportional-integral (PI) controller to perform PLL operation processing on the normalized component to obtain the estimated value of phase and the estimated value of angular frequency.

[0012] Preferably, after synchronizing the power grid based on the estimated phase value and the power grid frequency, the above method further includes: calculating the phase deviation between the estimated phase value and the actual grid-connected phase; if the phase deviation exceeds a preset threshold, adjusting the proportional coefficient of the proportional-integral regulator based on the phase deviation to obtain a new proportional-integral regulator; re-processing the normalized component with phase-locked loop based on the new proportional-integral regulator to obtain a first phase and a first angular frequency; calculating a first power grid frequency based on the first angular frequency; and synchronizing the power grid based on the first phase and the first power grid frequency.

[0013] Preferably, when the phase deviation exceeds a preset threshold, the above method further includes: performing a moving average filter on the fundamental voltage component to obtain a new fundamental voltage component; normalizing the new fundamental voltage component to obtain a new normalized component; performing a phase-locked loop operation on the new normalized component based on a new proportional-integral regulator to obtain a second phase and a second angular frequency; calculating a second grid frequency based on the second angular frequency; and performing grid synchronization based on the second phase and the second grid frequency.

[0014] Preferably, before synchronizing the power grid based on the phase estimate and the power grid frequency, the method further includes: dividing the estimated angular frequency by twice pi to obtain the power grid frequency.

[0015] An embodiment of the present invention provides an electronic device comprising: a processor, and a memory storing a program, the program including instructions which, when executed by the processor, cause the processor to perform any of the methods described above.

[0016] This invention provides a power grid synchronization method and electronic device based on pre-filtering using a coupled harmonic observer. By pre-filtering the phase-locked loop (PLL) with a coupled harmonic observer, it achieves accurate observation and harmonic suppression of the fundamental voltage component and eliminates the negative impact of DC components on PLL frequency and phase estimation, thus improving estimation accuracy under grid disturbances. The gain coefficient selection rule for the coupled harmonic observer is clarified through pole configuration, ensuring that the optimal gain coefficient is used for PLL pre-filtering. The introduction of fundamental voltage component normalization avoids abrupt changes in PLL bandwidth due to grid voltage amplitude and frequency fluctuations, ensuring accurate estimation of grid frequency and phase under complex operating conditions. This improves the accuracy and stability of the PLL under conditions such as grid voltage imbalance, frequency jumps, and voltage abrupt changes, making it suitable for grid synchronization under complex conditions of weak grids. It addresses the problem that related methods cannot improve the stability of grid-connected converters under weak grid conditions while maintaining simple PLL logic. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the steps of a power grid synchronization method based on pre-filtering of a coupled harmonic observer, as described in an embodiment of the present invention.

[0019] Figure 2 This is a block diagram of the operational structure of a power grid synchronization method based on pre-filtering of a coupled harmonic observer, as described in an embodiment of the present invention.

[0020] Figure 3 This is a block diagram of the operational structure of a coupled harmonic observer in an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0022] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0023] Grid synchronization technology is very important in the control of grid-connected power converters because rapid and accurate detection of grid voltage parameters is essential for implementing stable control strategies under normal grid conditions.

[0024] While phase-locked loop (PLL)-based grid synchronization methods exhibit good dynamic performance and phase-locking accuracy under ideal grid conditions, their fundamental phase detection accuracy significantly decreases when grid voltage asymmetry or harmonic distortion occurs. This detection error leads to an increase in the harmonic content of the grid-connected current of the three-phase converter, which may, in severe cases, cause control system failure, equipment shutdown, or even more serious system malfunctions.

[0025] Therefore, please refer to Figure 1 As shown, the present invention provides a power grid synchronization method based on pre-filtering of a coupled harmonic observer, including steps S101 to S104.

[0026] Step S101: Process the three-phase voltage sampling signal of the power grid into a target voltage signal in a two-phase stationary coordinate system.

[0027] Step S102: Input the target voltage signal into the coupled harmonic observer to obtain the fundamental voltage component. The coupled harmonic observer is constructed based on the Luneburg observer design strategy. The state variables of the coupled harmonic observer include the fundamental voltage component in the target voltage signal, the DC component in the target voltage signal, and the quadrature component of the fundamental voltage component. The gain coefficient of the coupled harmonic observer is determined by pole placement. The natural frequency of the pole placement characteristic equation is set as the angular frequency of the fundamental voltage component.

[0028] Step S103: Normalize the fundamental voltage component and perform phase-locked loop (PLL) operation sequentially to obtain the estimated values ​​of phase and angular frequency. The grid frequency is calculated and the coupled harmonic observer is updated based on the estimated angular frequency.

[0029] Step S104: Perform grid synchronization based on the phase estimate and grid frequency.

[0030] In an ideal three-phase AC system, the voltage is undistorted, and its fundamental voltage component is a pure sine signal.

[0031] The aforementioned three-phase voltage sampling signals from the power grid are not ideal voltage signals, and the effects of analog-to-digital conversion, power grid faults, and DC component injection from distributed generation systems must be considered. The method for obtaining these three-phase voltage sampling signals is existing technology and will not be described further in this embodiment.

[0032] The Luenberger observer can perform state estimation for linear systems. Its design logic is based on observability, and it configures poles through error feedback to achieve asymptotic state tracking.

[0033] Please combine Figure 2 As shown in the figure, the following embodiments of the present invention will specifically explain the above-mentioned power grid synchronization method based on pre-filtering of coupled harmonic observers through formulas.

[0034] The three-phase voltages of the power grid are sampled to obtain the three-phase voltages in a three-phase stationary coordinate system (abc axis system). , , After a stationary coordinate transformation (Clark transformation), a two-phase stationary coordinate system is obtained. Target voltage signal under shaft system , .

[0035] The target voltage signal in the two-phase stationary coordinate system , The input coupled harmonic observer is pre-filtered to obtain the fundamental voltage component in the two-phase stationary coordinate system. , .

[0036] The fundamental voltage component obtained by pre-filtering , Voltage normalization is performed, that is, the fundamental voltage component is normalized. , Multiply by respectively .

[0037] The normalized fundamental voltage component is used as the input to the phase-locked loop (PLL), and the estimated angular frequency is obtained through PLL arithmetic. and the estimated value of the phase .

[0038] The estimated value of angular frequency Divide by twice pi Obtain the power grid frequency .

[0039] The estimated angular frequency obtained from phase-locked loop arithmetic. Feedback is sent to the coupled harmonic observer to achieve frequency adaptation.

[0040] Specifically, considering analog-to-digital conversion, grid faults, and DC component injection from distributed generation systems, the desired fundamental sinusoidal component will be superimposed with DC disturbances, i.e., the input voltage signal. Described as: ; In the formula, It represents the voltage amplitude (the amplitude of the fundamental voltage component). Indicates the angular frequency of the power grid. Indicates time, This represents the initial phase angle (initial phase). This represents the DC component.

[0041] In order to separate and extract the fundamental component from the input voltage signal, a first state variable (fundamental voltage component) is defined. for: ; The first state variable (fundamental voltage component). Construct an orthogonal component as the second state variable That is, the first state variable With the second state variable The following relationship must be satisfied: ; In the formula, Describes the differential operator. , This represents an antisymmetric matrix, also known as a commutative matrix or a rotational differential operator matrix.

[0042] To separate and extract the DC component from the input voltage signal, the DC component Defined as a third state variable .

[0043] Therefore, the state equation is established as follows: ; The state variable equations of the coupled harmonic observer are: ; Please continue, in conjunction with Figure 3 As shown, the present invention will now provide a detailed description of the coupled harmonic observer. Figure 3 middle, This represents the difference between the input voltage signal and the feedback signal. This represents the observed value output by the coupled harmonic observer.

[0044] Based on the Luenberger observer design strategy, the state observer is established as follows: ; In the formula, Represents the first state variable The observed values, Represents the second state variable The observed values, Represents the third state variable The observed values.

[0045] Based on modern control theory, the transfer function of the observed values ​​of each state variable relative to the input voltage signal can be obtained as follows: ; In the formula, Represents the observation value of the first state variable. Relative to the input voltage signal The transfer function, Represents the observation value of the second state variable Relative to the input voltage signal The transfer function, Represents the observation value of the third state variable Relative to the input voltage signal The transfer function, Represents the Laplace operator. Represents the observation value of the first state variable. The corresponding observer gain, Represents the observation value of the second state variable The corresponding observer gain, Represents the observation value of the third state variable The corresponding observer gain.

[0046] The characteristic equation of pole placement for the third-order system with the above transfer function for: ; In the formula, and Represents the natural frequency of a third-order system. This indicates the damping ratio.

[0047] Therefore, we have: ; To reduce the complexity of the observer design, in the method provided in the embodiments of this invention, the natural frequency of the third-order system is set as the angular frequency of the fundamental component of the grid voltage. ,Right now .

[0048] Subsequently, through pole placement, the observer gain can be tuned as follows: ; Therefore, we have: ; To distinguish the damping ratio of a third-order system Parameters, the observer gain coefficient defined in this invention embodiment That is, the transfer function for extracting the fundamental voltage component by the coupled harmonic observer is modified to: ; Thus, this invention has created a coupled harmonic observer for extracting sampled three-phase grid voltages in a two-phase stationary coordinate system. The fundamental component under the axis system.

[0049] The formula for the coupled harmonic observer is expressed as: ; In the formula, The observed value represents the fundamental voltage component. The observed values ​​represent the orthogonal components. The observed values ​​represent the DC component. Represents the Laplace operator. This represents the gain coefficient of the coupled harmonic observer. This represents the voltage signal input to the coupled harmonic observer.

[0050] The formula for obtaining the fundamental voltage component by inputting the target voltage signal into the coupled harmonic observer is as follows: ; In the formula, Represents the fundamental voltage component. This represents an estimated value of the angular frequency. This represents the target voltage signal in a two-phase stationary coordinate system.

[0051] In summary, the method provided by the embodiments of this invention achieves accurate observation and harmonic suppression of the fundamental voltage component by pre-filtering the phase-locked loop (PLL) using a coupled harmonic observer, and eliminates the negative impact of DC components on the PLL frequency and phase estimation, thus improving the estimation accuracy when the power grid is disturbed. The pole configuration clarifies the selection rule for the gain coefficient of the coupled harmonic observer, ensuring that the optimal gain coefficient is used for PLL pre-filtering. The introduction of fundamental voltage component normalization avoids abrupt changes in the PLL bandwidth due to fluctuations in power grid voltage amplitude and frequency, ensuring that the PLL can accurately estimate the frequency and phase of the power grid under complex operating conditions.

[0052] The method provided by the embodiments of this invention can improve the accuracy and stability of phase-locked loops (PLLs) under conditions such as grid voltage imbalance, frequency jumps, and voltage surges, and is suitable for grid synchronization under complex conditions of weak grids. This solves the problem that related methods cannot improve the stability of grid-connected converters under weak grid conditions while maintaining simple PLL logic.

[0053] Preferably, step S103 involves performing normalization and phase-locked loop (PLL) operations on the fundamental voltage component sequentially to obtain estimated phase and estimated angular frequency values. This includes: normalizing the fundamental voltage component to obtain a normalized component; and performing PLL operations on the normalized component using a proportional-integral (PI) controller to obtain estimated phase and estimated angular frequency values.

[0054] Normalizing the fundamental voltage component can eliminate the impact of voltage amplitude fluctuations on the phase-locked loop (PLL), avoid sudden changes in PLL bandwidth, and ensure that the PLL can still operate stably when the grid voltage amplitude changes.

[0055] Using a proportional-integral (PI) controller for phase-locked loop (PLL) operations can quickly correct phase errors in the normalized component. The proportional element of the PI controller responds to errors instantly, while the integral element eliminates steady-state deviations, improving both the speed and accuracy of PLL operations.

[0056] Furthermore, after synchronizing the grid based on the estimated phase value and the grid frequency, the above method further includes: calculating the phase deviation between the estimated phase value and the actual grid-connected phase. If the phase deviation exceeds a preset threshold, the proportional-integral (PI) regulator's proportional coefficient is adjusted based on the phase deviation to obtain a new PPI regulator. The normalized components are then reprocessed using a phase-locked loop (PLL) based on the new PPI regulator to obtain the first phase and the first angular frequency. The first grid frequency is calculated based on the first angular frequency; grid synchronization is then performed based on the first phase and the first grid frequency.

[0057] The preset threshold is determined by those skilled in the art based on grid connection standards, equipment tolerance limits, and control performance objectives. For example, the preset threshold is 0.5°.

[0058] By calculating the deviation between the phase estimate and the actual grid-connected phase, a real-time feedback mechanism for synchronization accuracy is established. This mechanism can instantly capture deviations between the phase-locked loop output and the actual grid state, such as phase shifts caused by grid disturbances. It can also prevent the accumulation of deviations from causing synchronization failures, such as excessive grid-connected current harmonics or converter control instability, thus providing a basis for subsequent parameter adjustments.

[0059] When the phase deviation exceeds the preset threshold, the proportional coefficient can be increased. By utilizing the characteristic of the proportional element of the PI controller to respond to errors instantly, the correction speed of phase and angular frequency can be accelerated, the deviation convergence time can be reduced, and long-term synchronization inaccuracy can be avoided.

[0060] When the phase deviation is less than or equal to the preset threshold, the proportional coefficient can be reduced / maintained to prevent system oscillation caused by an excessively large proportional coefficient, thus ensuring the steady-state stability of the phase-locked loop.

[0061] Furthermore, when the phase deviation exceeds a preset threshold, the above method further includes: performing a moving average filter on the fundamental voltage component to obtain a new fundamental voltage component; normalizing the new fundamental voltage component to obtain a new normalized component; performing a phase-locked loop operation on the new normalized component based on a new proportional-integral regulator to obtain a second phase and a second angular frequency; calculating a second grid frequency based on the second angular frequency; and performing grid synchronization based on the second phase and the second grid frequency.

[0062] Moving average filtering effectively smooths high-frequency noise and instantaneous fluctuations by weighting the fundamental voltage component across multiple time points. For example, if the fundamental voltage component experiences a spike fluctuation of ±0.3V due to a short-term disturbance in the power grid, a moving average over five sampling periods can reduce the fluctuation amplitude to within ±0.05V, making the new fundamental voltage component closer to the actual waveform of the fundamental signal.

[0063] Combining moving average filtering with coupled harmonic observers to suppress harmonics and eliminate DC components creates a complementary effect: the coupled harmonic observers address the large interference from harmonics and DC components, while the moving average filtering addresses the small residuals of high-frequency noise and transient disturbances. Together, they provide a cleaner signal source for subsequent processing and improve the output accuracy of the phase-locked loop operation.

[0064] The present invention also provides a non-transitory machine-readable medium storing a computer program, wherein the computer program, when executed by a computer's processor, is used to cause the computer to perform a method according to an embodiment of the present invention.

[0065] The present invention also provides a computer program product, including a computer program, wherein the computer program, when executed by a computer's processor, is used to cause the computer to perform the method of the embodiments of the present invention.

[0066] This invention also provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor, which, when executed by the at least one processor, causes the electronic device to perform the method of this invention.

[0067] refer to Figure 4This is a structural block diagram of an electronic device, either a server or a client, according to an embodiment of the present invention. It is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0068] like Figure 4 As shown, the electronic device includes a computing unit 401, which can perform various appropriate actions and processes based on a computer program stored in a read-only memory (ROM) 402 or a computer program loaded from a storage unit 408 into a random access memory (RAM) 403. The RAM 403 may also store various programs and data required for the operation of the electronic device. The computing unit 401, the ROM 402, and the RAM 403 are interconnected via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0069] Multiple components in the electronic device are connected to I / O interface 405, including: input unit 406, output unit 407, storage unit 408, and communication unit 409. Input unit 406 can be any type of device capable of inputting information into the electronic device. Input unit 406 can receive input digital or character information and generate key signal inputs related to user settings and / or function control of the electronic device. Output unit 407 can be any type of device capable of presenting information and may include, but is not limited to, a display, speaker, video / audio output terminal, vibrator, and / or printer. Storage unit 408 may include, but is not limited to, disks and optical discs. Communication unit 409 allows the electronic device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks, and may include, but is not limited to, modems, network cards, infrared communication devices, and / or wireless communication transceivers, such as Bluetooth devices, WiFi devices, WiMax devices, cellular communication devices, and / or the like.

[0070] The computing unit 401 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 401 include, but are not limited to, CPUs, graphics processing units (GPUs), various special-purpose artificial intelligence (AI) computing units, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. The computing unit 401 performs the various methods and processes described above. For example, in some embodiments, the method embodiments of the present invention can be implemented as computer programs tangibly contained in a machine-readable medium, such as storage unit 408. In some embodiments, part or all of the computer program can be loaded and / or installed on an electronic device via ROM 402 and / or communication unit 409. In some embodiments, the computing unit 401 can be configured to perform the methods described above by any other suitable means (e.g., by means of firmware).

[0071] Computer programs for implementing the methods of embodiments of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0072] In the context of embodiments of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, or infrared systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0073] It should be noted that the term "comprising" and its variations used in the embodiments of this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of this invention are illustrative and not restrictive, and those skilled in the art should understand that unless explicitly indicated otherwise in the context, they should be understood as "one or more". The descriptions of terms such as "first", "second", etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features.

[0074] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of this invention are all information and data authorized by the user or fully authorized by all parties.

[0075] The steps described in the method embodiments provided by the present invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0076] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0077] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A grid synchronization method based on coupled harmonic observer pre-filtering, characterized in that, The method comprises the following steps: sampling three-phase voltage signals of a power grid to obtain target voltage signals in a two-phase stationary coordinate system; inputting the target voltage signals into a coupled harmonic observer to obtain a fundamental voltage component, wherein the coupled harmonic observer is constructed based on a design strategy of a Luenberger observer, state variables of the coupled harmonic observer include a fundamental voltage component in the target voltage signals, a direct current component in the target voltage signals, and a quadrature component of the fundamental voltage component, gain coefficients of the coupled harmonic observer are determined in a manner of pole placement, and a natural frequency of a pole placement characteristic equation is set as an angular frequency of the fundamental voltage component; sequentially performing normalization processing and phase-locked loop operation processing on the fundamental voltage component to obtain an estimated value of a phase and an estimated value of the angular frequency, wherein a power grid frequency is calculated based on the estimated value of the angular frequency, and the coupled harmonic observer is updated; performing power grid synchronization based on the estimated value of the phase and the power grid frequency.

2. The method of claim 1, wherein, The state variable equation of the coupled harmonic observer is: ； wherein denotes the fundamental voltage component, denotes the quadrature component of the fundamental voltage component, denotes the DC component , denotes the amplitude of the fundamental voltage component, denotes the angular frequency, denotes time, denotes the initial phase.

3. The method of claim 2, wherein, The formula of the coupled harmonic observer is: ； wherein denotes the observation of the fundamental voltage component, denotes the observation of the quadrature component, denotes the observation of the direct current component, denotes the Laplace operator, denotes the gain coefficient of the coupled harmonic observer, denotes the voltage signal input to the coupled harmonic observer.

4. The method of claim 3, wherein, The formula of inputting the target voltage signals into the coupled harmonic observer to obtain the fundamental voltage component is: ； wherein denotes the fundamental voltage component, denotes an estimate of the angular frequency, denotes the target voltage signal in two-phase stationary coordinate system.

5. The method of claim 4, wherein, The step of performing normalization processing on the fundamental voltage component comprises: The fundamental voltage component of and is multiplied by respectively.

6. The method of claim 1, wherein, The step of sequentially performing normalization processing and phase-locked loop operation processing on the fundamental voltage component to obtain the estimated value of the phase and the estimated value of the angular frequency comprises: performing normalization processing on the fundamental voltage component to obtain a normalized component; performing phase-locked loop operation processing on the normalized component by using a proportional-integral regulator to obtain the estimated value of the phase and the estimated value of the angular frequency.

7. The method of claim 6, wherein, After performing power grid synchronization based on the estimated value of the phase and the power grid frequency, the method further comprises: calculating a phase deviation between the estimated value of the phase and an actual grid-connected phase; in a case where the phase deviation exceeds a preset threshold, adjusting a proportional coefficient of the proportional-integral regulator based on the phase deviation to obtain a new proportional-integral regulator; re-performing phase-locked loop operation processing on the normalized component based on the new proportional-integral regulator to obtain a first phase and a first angular frequency; calculating a first power grid frequency based on the first angular frequency; performing power grid synchronization based on the first phase and the first power grid frequency.

8. The method of claim 7, wherein, In a case where the phase deviation exceeds the preset threshold, the method further comprises: performing sliding average filtering on the fundamental voltage component to obtain a new fundamental voltage component; performing normalization processing on the new fundamental voltage component to obtain a new normalized component; performing phase-locked loop operation processing on the new normalized component based on the new proportional-integral regulator to obtain a second phase and a second angular frequency; calculating a second power grid frequency based on the second angular frequency; performing power grid synchronization based on the second phase and the second power grid frequency.

9. The method of claim 1, wherein, Before performing power grid synchronization based on the estimated value of the phase and the power grid frequency, the method further comprises: dividing the estimated value of the angular frequency by twice a circular constant to obtain the power grid frequency.

10. An electronic device comprising: A processor, and a memory storing a program, the program comprising instructions which, when executed by the processor, cause the processor to carry out the method according to any one of claims 1 to 9.

Images