Frequency-locked loop control method and control system based on double-second-order generalized integrator

Abstract

The invention relates to the technical field of power systems, in particular to a frequency-locked loop control method and system based on a double-second-order generalized integrator. According to the method, a traditional phase-locked loop is replaced by a frequency-locked loop to provide center frequency for the bisecond-order generalized integrator, and high-precision and high-response-speed real-time tracking of power grid frequency is achieved. And based on a DSOGI-FLL structure, parallel processing is carried out on the axis signal and the axis signal after Clark transformation, an orthogonal signal is generated, a positive sequence component and a negative sequence component are decoupled, and frequency doubling fluctuation under the asymmetric working condition of the power grid is eliminated. A phase angle of a positive sequence component is locked by combining a single synchronous coordinate system phase-locked loop, a positive sequence dq-axis component and a negative sequence dq-axis component are output through dq conversion, and a power grid synchronizing signal is rapidly obtained when voltage drops, frequency abrupt changes and three-phase faults occur. According to the method, the dynamic response speed and the detection precision can be remarkably improved, additional parameter compensation calculation is avoided, the universality of the method is enhanced, and a high-reliability synchronization reference is provided for fault ride-through of the power electronic converter.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to a frequency-locked loop control method and control system based on a dual second-order generalized integrator. Background Technology

[0002] With the continuous maturation of distributed generation technology, traditional power systems are gradually transforming into new power systems dominated by new energy sources. Power electronic converters, as one of the key devices in distributed generation systems, have been widely applied in these new power systems. Rapidly and accurately acquiring grid synchronization signals is one of the key technologies to ensure the stable operation of power electronic converters. Obtaining grid synchronization signals is relatively easy under ideal grid conditions; however, during power system operation, voltage dips, frequency surges, and three-phase asymmetry faults occur frequently. In the event of grid faults, to ensure the continuous operation of the power electronic converter, the converter control system needs to be able to quickly and accurately detect the phase and frequency of the grid voltage, as well as the positive and negative sequence components of the grid voltage.

[0003] The invention patent with publication number CN110224442A discloses a single-phase phase-locked loop control method based on a second-order generalized integrator. However, this scheme still uses a phase-locked loop structure with a PI (Proportional-Integral) controller, which suffers from slow dynamic response and long settling time when the grid frequency fluctuates greatly. It cannot achieve high-precision, high-response real-time tracking of the grid frequency. Furthermore, it only provides an implementation of a single-phase phase-locked loop based on a second-order generalized integrator, without further explanation on how to handle the more common three-phase signals in practical applications. The invention patent with publication number CN117559421A discloses a phase-shifting phase-locked loop method and system based on a second-order generalized integrator. However, this scheme requires calculating the compensation angle at the output of the phase-shifting phase-locked loop based on target parameters such as the AC electromotive force, AC output power, and estimated resistance and inductance values ​​of the weak grid side, which increases the computational load of the system. Moreover, it requires re-acquiring the grid target parameters according to different application scenarios, and it lacks universality. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a frequency-locked loop control method and control system based on dual second-order generalized integrators, so as to solve the problems of slow dynamic response, large computational load and poor versatility of the existing phase-locked loop control method.

[0005] This invention discloses a frequency-locked loop control method based on dual second-order generalized integrators, comprising: Acquire the three-phase voltage signals of the power grid; The three-phase voltage signal is transformed into a two-phase stationary coordinate system. Axis signals and Axis signals; Regarding the Axis signals and the The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; The orthogonal signals obtained are calculated and acquired respectively. Axis signals and the Positive and negative sequence components of the axis signal; According to the above Axis signal, the The axis signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the second-order generalized integral is dynamically adjusted. Based on the positive sequence component obtained from the second-order generalized integral after center frequency adjustment, the signal phase is locked using a single synchronous coordinate system phase-locked loop, the current phase angle is obtained, and the sine and cosine values ​​of the current phase angle are calculated. Based on the sine and cosine values ​​of the current phase angle, the... Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; The generated positive-sequence dq-axis components and negative-sequence dq-axis components are used to output a power grid synchronization signal.

[0006] Optionally, the transformation of the three-phase voltage signal into a two-phase stationary coordinate system... Axis signals and Axis signals, including: The three-phase voltage signal is converted into the [missing information] using Clark transform. Axis signals and the The Clark transform function expression for the shaft signal is:

[0007] In the formula, In a two-phase stationary coordinate system Axis signal, In a two-phase stationary coordinate system Axis signal, This is the voltage signal of phase A. This is the B-phase voltage signal. This is the C-phase voltage signal.

[0008] Optionally, the above refers to the Axis signals and the The axis signals are subjected to second-order generalized integration to obtain two sets of orthogonal signals, including: Regarding the Axis signals and the The two axes signals are respectively subjected to second-order improper integrals to obtain two sets of orthogonal signals. The functional expression of the second-order improper integral is as follows:

[0009] In the formula, For in-phase signals in a stationary coordinate system, These are orthogonal signals of phase signal in stationary coordinate system. The damping coefficient is... For the center frequency, The signal variable is in a stationary coordinate system.

[0010] Optionally, the step of calculating and obtaining the orthogonal signals respectively... Axis signals and the The positive and negative sequence components of the axis signal include: The Axis signals and the The orthogonal signals of the axis signals are used to calculate the positive and negative sequence components of the grid voltage. The functional expression for the positive and negative sequence calculation is as follows:

[0011]

[0012] In the formula, For the The positive sequence component corresponding to the axis signal. For the The positive sequence component corresponding to the axis signal. For the The negative sequence component corresponding to the axis signal For the The negative sequence component corresponding to the axis signal For the The orthogonal signal corresponding to the axis signal For the The orthogonal signal corresponding to the axis signal.

[0013] Optionally, the method according to the Axis signal, the The shaft signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the frequency-locked loop is dynamically adjusted, including: According to the above Axis signal, the The frequency-locked loop is used to calculate the signal error for both the axis signal and the orthogonal signal. The functional expression for calculating the signal error is as follows:

[0014] In the formula, For signal error; The instantaneous power grid frequency is obtained based on the signal error. The functional expression for obtaining the instantaneous power grid frequency is:

[0015]

[0016] In the formula, This is the instantaneous power grid frequency gain. For adaptive gain coefficients, The instantaneous grid frequency after gain. The sampling time interval is the power grid frequency; The center frequency of the second-order generalized integral is dynamically adjusted based on the instantaneous grid frequency after the gain is obtained from the frequency-locked loop.

[0017] Optionally, the step of dynamically adjusting the center frequency of the second-order generalized integral based on the instantaneous grid frequency obtained by the frequency-locked loop includes: Based on the instantaneous grid frequency after gain is obtained from the frequency-locked loop, discretized parameters are generated using the bilinear transform method. The instantaneous grid frequency after extracting the gain from the discretized parameters is used as the center frequency after adjustment by the second-order generalized integral.

[0018] Optionally, the positive-sequence component obtained based on the second-order generalized integral after center frequency adjustment, using a single-synchronous coordinate system phase-locked loop to lock the signal phase, obtaining the current phase angle and calculating the sine and cosine values ​​of the current phase angle, includes: Based on the positive-sequence component obtained from the second-order generalized integral after center frequency adjustment, the... Axis signals and the The positive-sequence component of the axis signal is mapped from the stationary coordinate system to the rotating coordinate system through the Park transform. The functional expression for the positive-sequence component mapping is as follows:

[0019] In the formula, For the d-axis component mapped to the rotated coordinate system, For the q-axis component mapped to the rotated coordinate system, The sine value of the phase angle. The value is the cosine of the phase angle; Based on the q-axis component after positive sequence component transformation, the angular frequency is obtained using a single synchronous coordinate system phase-locked loop, and the phase angle is generated by integrating the obtained angular frequency over time. The phase angle at the current moment is obtained by discrete-domain calculation of the phase angle generated by integration. The functional expression for calculating the phase angle at the current moment is:

[0020] In the formula, The phase angle at the current moment. The phase angle at the previous moment. Angular frequency; Based on the calculated current phase angle, calculate and obtain the sine and cosine values ​​of the current phase angle.

[0021] Optionally, the will of the Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components, including: The Axis signals and the The positive-sequence component corresponding to the axis signal is transformed into a positive-sequence dq axis component through a positive-sequence dq transform. The functional expression of the positive-sequence dq transform is:

[0022] In the formula, For positive-order d-axis components, These are the positive-order q-axis components; The Axis signals and the The negative-sequence component corresponding to the axis signal is transformed into a negative-sequence dq axis component through a negative-sequence dq transform. The functional expression of the negative-sequence dq transform is:

[0023] In the formula, For negative d-axis components, These are the negative-order q-axis components.

[0024] This invention also discloses a control system employing the aforementioned frequency-locked loop control method based on dual second-order generalized integrators. The control system includes: The voltage signal acquisition module is used to acquire the three-phase voltage signals of the power grid; The Clark transform module is used to transform the three-phase voltage signal into a two-phase stationary coordinate system. Axis signals and Axis signals; The orthogonal signal generation module is used to generate the... Axis signals and the The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; The positive and negative order calculation module is used to calculate and obtain the positive and negative order based on the obtained orthogonal signals. Axis signals and the Positive and negative sequence components of the axis signal; Frequency-locked loop module, used according to the Axis signal, the The axis signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the second-order generalized integral is dynamically adjusted. The phase-locked loop module is used to obtain the positive-sequence component based on the second-order generalized integral after center frequency adjustment. It uses a single-synchronous coordinate system phase-locked loop to lock the signal phase, obtain the current phase angle, and calculate the sine and cosine values ​​of the current phase angle. The dp transformation module is used to transform the current phase angle based on the sine and cosine values. Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; The power grid signal output module is used to output a power grid synchronization signal based on the generated positive-sequence dq-axis components and negative-sequence dq-axis components.

[0025] The present invention also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the above-described frequency-locked loop control method based on a dual second-order generalized integrator.

[0026] Compared with the prior art, the frequency-locked loop control method and control system based on dual second-order generalized integrators provided in this invention have the following advantages: By replacing the traditional phase-locked loop with a frequency-locked loop (PLL), a center frequency is provided for the dual second-order generalized integrator, enabling high-precision, high-response-speed real-time tracking of the power grid frequency. Furthermore, the Clark transform is applied based on the DSOGI-FLL structure. Axis signals and Parallel processing of axis signals generates orthogonal signals and decouples the positive-sequence and negative-sequence components, eliminating second-harmonic fluctuations under asymmetrical grid conditions. By combining a single-synchronous coordinate system phase-locked loop to lock the phase angle of the positive-sequence component, and outputting the positive-sequence and negative-sequence dq-axis components through dq transformation, the system can quickly acquire grid synchronization signals (phase, frequency, positive / negative sequence components) during voltage dips, frequency abrupt changes, and three-phase faults. This significantly improves dynamic response speed and detection accuracy, while avoiding additional parameter compensation calculations, enhancing the method's versatility, and providing a highly reliable synchronization reference for fault ride-through in power electronic converters. Attached Figure Description

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic block diagram illustrating the overall steps of the frequency-locked loop control method provided in an embodiment of the present invention; Figure 2 This is a control principle diagram of the frequency locking loop control method provided in an embodiment of the present invention; Figure 3The control principle diagram of the dual second-order generalized integral-frequency-locked loop provided in the embodiment of the present invention. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] This invention discloses a frequency-locked loop control method based on dual second-order generalized integrators, such as... Figures 1-3 As shown, it includes: S1. Obtain the three-phase voltage signal of the power grid; S2. Transform the three-phase voltage signal into a two-phase stationary coordinate system. Axis signals and Axis signals; S3, to Axis signals and The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; S4. Calculate and obtain the results based on the obtained orthogonal signals. Axis signals and Positive and negative sequence components of the axis signal; S5, according to Axis signals, For both axial and quadrature signals, a frequency-locked loop is used to track the signal frequency, and the center frequency of the second-order generalized integral is dynamically adjusted. S6. Based on the positive sequence component obtained from the second-order generalized integral after center frequency adjustment, the signal phase is locked using a single synchronous coordinate system phase-locked loop, the current phase angle is obtained, and the sine and cosine values ​​of the current phase angle are calculated. S7. Based on the sine and cosine values ​​of the current phase angle, Axis signals and The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; S8. Output the power grid synchronization signal based on the generated positive-sequence dq-axis components and negative-sequence dq-axis components.

[0030] Through the implementation of the above-described frequency-locked loop control method, a frequency-locked loop (FLL) is used to replace the traditional phase-locked loop (PLL) to provide the center frequency for the second-order generalized integrator-quadrature signal generator (SOGI-QSG) in the dual second-order generalized integrator (DSOGI). This achieves high-precision, high-response-speed real-time tracking of the power grid frequency, solving the problems of slow dynamic response and long settling time caused by the PI controller structure in existing technologies. Based on the DSOGI-FLL (Dual second-order generalized integrator frequency-locked loop) structure, the Clark Transform (two-phase to three-phase transformation) is applied. Axis signals and The axis signals are processed in parallel using second-order generalized integration to generate four orthogonal signals. In-phase / quadrature signals (In-phase / quadrature signals), decoupled by positive and negative sequence calculation. / The positive and negative sequence components in the coordinate system eliminate the second harmonic fluctuation component under asymmetrical grid conditions, overcoming the detection distortion of traditional schemes during voltage dips, frequency abrupt changes, and three-phase asymmetrical faults. A single synchronous reference frame (SRF-PLL) is used to lock the phase angle of the positive sequence component. Combined with a sine and cosine calculation module, real-time phase sine and cosine values ​​are output. Positive and negative sequence dq axis components are generated through positive and negative sequence dq transformations, providing a complete output of the grid synchronization signal (phase angle, frequency, positive sequence dq component, and negative sequence dq component). This embodiment of the invention achieves frequency-phase co-optimization through a modular DSOGI-FLL structure, avoiding the complex calculation of compensation angles in phase-shifting PLLs, significantly reducing system computation. It does not rely on scenario-specific variables such as grid AC electromotive force, output power, or weak grid parameters, exhibiting strong versatility. It provides a highly reliable synchronization reference for power electronic converters under fault ride-through conditions, ensuring the stable operation of new energy equipment in new power systems.

[0031] Furthermore, the three-phase voltage signal is transformed into a two-phase stationary coordinate system. Axis signals and Axis signals, including: The three-phase voltage signal is converted using the Clark transform. Axis signals and The Clark transform function expression for the shaft signal is:

[0032] In the formula, In a two-phase stationary coordinate system Axis signal, In a two-phase stationary coordinate system Axis signal, This is the voltage signal of phase A. This is the B-phase voltage signal. This is the C-phase voltage signal.

[0033] Through the implementation of the above frequency-locked loop control method embodiment, the three-phase voltage signal is accurately converted into a two-phase stationary coordinate system using Clark transformation. Axis signal and Axis signal This lays the core foundation for subsequent synchronization signal detection. The core effects of this transformation are: (1) by reducing the dimension, the three-phase AC quantities are transformed into two mutually orthogonal stationary coordinate signals, which significantly simplifies the complexity of subsequent signal processing and provides structurally compatible input conditions for the parallel processing of the dual second-order generalized integrator (DSOGI); (2) by strictly maintaining the integrity of the amplitude and phase information of the original three-phase voltage, making Axis signal With β-axis signal It can equivalently characterize the instantaneous state of the three-phase voltage of the power grid; (3) Through the specific design of the coefficient matrix, it ensures that the transformed orthogonal signals have a strict 90-degree phase difference relationship, which provides a key guarantee for generating accurate transformation pairs and realizing the function of the orthogonal signal generator (QSG). It not only eliminates the redundant information of the three-phase system, but also directly constructs a standardized two-dimensional signal processing channel suitable for frequency-locked loop (FLL) and phase-locked loop (PLL), which is an indispensable pre-technical link for subsequent realization of high-precision frequency tracking, fast phase locking and positive and negative sequence component separation.

[0034] Furthermore, on Axis signals and The axis signals are subjected to second-order generalized integration to obtain two sets of orthogonal signals, including: right Axis signals and The two axes signals are respectively subjected to second-order improper integrals to obtain two sets of orthogonal signals. The functional expression of the second-order improper integral is as follows:

[0035] In the formula, For in-phase signals in a stationary coordinate system, These are orthogonal signals of phase signal in stationary coordinate system. The damping coefficient is... For the center frequency, The signal variable is in a stationary coordinate system.

[0036] By implementing the frequency-locked loop control method described above, identical second-order generalized integrators (SOGI) are applied to both the α-axis and β-axis signals to generate two sets of orthogonal signals in the stationary coordinate system. and The core technical effect of this processing is: (1) For each input signal (α-axis or β-axis), the in-phase component of the original signal is generated simultaneously through a rigorously designed second-order transfer function. and its precise orthogonal components The two components are at a specified center frequency. The nearby components have a strict 90-degree phase difference relationship, which constructs a complete orthogonal signal pair, providing the necessary signal basis for subsequent accurate separation of positive and negative sequence components; (2) by adjusting the damping coefficient The bandwidth and damping characteristics of the filter can be flexibly controlled, ensuring high-precision extraction of specific frequency signals while effectively suppressing high-frequency noise and harmonic interference, thus improving the system's anti-interference capability; (3) center frequency As a key adjustable parameter, its dynamic adjustment capability (updated in real time by the frequency-locked loop FLL) enables the quadrature signal generator to adaptively track actual grid frequency changes, ensuring that it can maintain its frequency even when the grid frequency fluctuates. and The orthogonality and amplitude accuracy; (4) The processing is completely symmetrical and independently executed on the α-axis and β-axis channels, forming a parallel structure of dual second-order generalized integrators (DSOGI). This not only avoids the complexity caused by the coupling of the three-phase system, but also significantly suppresses the inherent second harmonic fluctuation component of the single-channel SOGI through dual-channel collaboration, greatly improving the detection accuracy and dynamic stability of the system under non-ideal power grid conditions (such as three-phase imbalance). This orthogonal signal generation link is a prerequisite for the frequency-locking loop to quickly track the frequency, achieve high-precision positive and negative sequence component separation and phase locking. Its robustness and adaptability directly determine the performance of the entire synchronization signal detection system.

[0037] Furthermore, based on the obtained orthogonal signals, calculations are performed to obtain... Axis signals and The positive and negative sequence components of the axis signal include: Will Axis signals and The orthogonal signals of the axis signals are used to calculate the positive and negative sequence components of the grid voltage. The functional expression for the positive and negative sequence calculation is as follows:

[0038]

[0039] In the formula, for The positive sequence component corresponding to the axis signal. for The positive sequence component corresponding to the axis signal. for The negative sequence component corresponding to the axis signal for The negative sequence component corresponding to the axis signal for The orthogonal signal corresponding to the axis signal for The orthogonal signal corresponding to the axis signal.

[0040] Through the implementation of the above frequency-locked loop control method embodiment, matrix operations are used to... Orthogonal signals of axis signals Orthogonal signals to the β-axis signal As a key input, a cross-coupling and decoupling structure for the α-axis and β-axis channels was constructed, in which the positive-order component calculation matrix... The generation depends on both the direct path of the original orthogonal signal along the α-axis and the orthogonal signal along the β-axis. The negative compensation path, and The generation is achieved by using the original orthogonal signal along the β-axis and the orthogonal signal along the α-axis. The positive coupling is implemented, while the negative order component matrix is ​​calculated using a sign-flipping strategy (such as...). Introduced in calculation Symmetrical decoupling is achieved through forward coupling. This method fully utilizes the 90-degree phase difference characteristic of orthogonal signal pairs at the output, and ensures that the positive-sequence component is completed without distortion by using a 1 / 2 scaling coefficient. , With negative order components , Instantaneous and precise separation in a stationary coordinate system. This allows for positive-sequence matrix output under any power grid operating condition (including three-phase asymmetrical faults). and It only carries the positive-sequence characteristic information of the grid voltage, while outputting the negative-sequence matrix. and The negative sequence characteristics of the grid voltage are independently represented, and the two components are completely decoupled in both the time and frequency domains. This process requires no coordinate transformation or complex filtering, significantly reducing computational complexity, and achieving sub-cycle-level dynamic response speed by avoiding iterative calculations. The separation result is directly output as a standard orthogonal stationary coordinate system component, providing a clean and synchronized sequence component signal source for subsequent frequency tracking by frequency-locked loop (FLL) and phase locking by phase-locked loop (PLL), fundamentally ensuring the accuracy and real-time performance of grid synchronization signal detection.

[0041] Furthermore, according to Axis signals, For both axial and quadrature signals, a frequency-locked loop (LLL) is used to track the signal frequency and dynamically adjust the LLL's center frequency, including: according to Axis signals, For both axial and quadrature signals, a frequency-locked loop (LLL) is used to calculate the signal error. The functional expression for signal error calculation is as follows:

[0042] In the formula, For signal error; The instantaneous power grid frequency is obtained based on the signal error. The functional expression for obtaining the instantaneous power grid frequency is:

[0043]

[0044] In the formula, This is the instantaneous power grid frequency gain. For adaptive gain coefficients, The instantaneous grid frequency after gain. The sampling time interval is the power grid frequency; The center frequency of the second-order generalized integral is dynamically adjusted based on the instantaneous grid frequency after the gain is obtained from the frequency-locked loop.

[0045] Furthermore, the center frequency of the second-order generalized integral is dynamically adjusted based on the instantaneous grid frequency obtained from the frequency-locked loop, including: Based on the instantaneous grid frequency after gain acquisition by the frequency-locked loop, discretized parameters are generated using the bilinear transform method. The instantaneous grid frequency after extracting the gain from the discretized parameters is used as the center frequency after adjustment by the second-order generalized integral.

[0046] Through the implementation of the above-described frequency-locked loop control method, the key error quantities of the power grid status are obtained by calculating the signal error using the frequency-locked loop, and the original α-axis signal is utilized. Orthogonal signals β-axis raw signal Orthogonal signals The product and construction error signal Its technical advantages are: (1) It fully utilizes the strict orthogonality of the output of the quadrature signal generator. When the grid frequency is consistent with the SOGI center frequency, the product of the original signal and its orthogonal components approaches zero; while when the frequency shifts, the error signal... The amplitude and polarity can directly characterize the deviation between the actual power grid frequency and the set center frequency ω, generating a highly sensitive unbiased error signal; (2) a dual-channel (α-axis and β-axis) error superposition strategy is adopted to significantly suppress single-phase measurement noise interference, while enhancing the robustness of the error signal under three-phase unbalanced conditions. Furthermore, based on the error amount, the frequency correction amount is precisely quantified by the instantaneous power grid frequency gain to ensure the consistency of system stability and convergence speed over a wide frequency range: when the error signal When the frequency deviation increases, the gain automatically increases to accelerate tracking, while in the near-synchronous state (error signal) the gain decreases. Gain attenuation (approaching zero) avoids overshoot. This adaptive mechanism effectively suppresses the risk of misadjustment caused by high-frequency disturbances while ensuring dynamic response speed. The frequency closed-loop update is ultimately completed using the instantaneous grid frequency after gain. This forms a highly dynamic adaptive frequency tracking closed loop by feeding back the instantaneous grid frequency after gain to the center frequency parameter of the dual second-order generalized integrator (DSOGI) in real time. This frequency-locked loop structure completely avoids the inherent phase margin and bandwidth contradiction of the PI controller in traditional phase-locked loops (PLLs). Under complex operating conditions such as sudden grid frequency changes and three-phase voltage distortion, it still achieves zero steady-state error tracking of the center frequency to the real grid frequency with a sub-cycle-level response speed, providing a precise frequency reference for subsequent quadrature signal generation and positive-negative sequence separation, fundamentally solving the bottleneck problems of slow dynamic response and weak anti-interference capability.

[0047] Furthermore, based on the positive-sequence component obtained from the second-order generalized integral after center frequency adjustment, the signal phase is locked using a single-synchronous coordinate system phase-locked loop, the current phase angle is obtained, and the sine and cosine values ​​of the current phase angle are calculated, including: The positive-sequence component obtained based on the second-order generalized integral after center frequency adjustment will be... Axis signals and The positive-sequence component of the axis signal is mapped from the stationary coordinate system to the rotating coordinate system through the Park transform. The functional expression for the positive-sequence component mapping is as follows:

[0048] In the formula, For the d-axis component mapped to the rotated coordinate system, For the q-axis component mapped to the rotated coordinate system, The sine value of the phase angle. The value is the cosine of the phase angle; Based on the q-axis component after positive sequence component transformation, the angular frequency is obtained using a single synchronous coordinate system phase-locked loop, and the phase angle is generated by integrating the obtained angular frequency over time. The phase angle at the current moment is obtained by discrete-domain calculation of the phase angle generated by integration. The functional expression for calculating the phase angle at the current moment is:

[0049] In the formula, The phase angle at the current moment. The phase angle at the previous moment. Angular frequency; Based on the calculated current phase angle, calculate and obtain the sine and cosine values ​​of the current phase angle.

[0050] By implementing the above-described frequency-locked loop control method embodiment, the stationary coordinate system positive sequence component of the second-order generalized integral output after center frequency adjustment is obtained. and Based on the rotation mapping matrix, it is converted in real time into the d-axis components of the rotating coordinate system. With q-axis components Here, cosθ and sinθ represent the cosine and sine values ​​of the current phase angle, respectively. This transformation achieves a decoupled expression of the fundamental positive-sequence component—the d-axis component—by projecting the stationary orthogonal signal onto a synchronously rotating coordinate axis. Physically representing voltage amplitude information, while the q-axis component... This approach directly quantifies the phase tracking deviation. Its core effect lies in directly utilizing the q-axis component as the error feedback quantity for the single-synchronous-coordinate-system phase-locked loop (PLL). The PLL's built-in control loop calculates the grid angular frequency in real time. This angular frequency generates a phase angle sequence through discrete integration iteration, where the sampling time interval determines the discretization step size of the phase update, ensuring that the phase angle continuously converges to the true grid phase at a sub-periodic speed. Simultaneously, based on the real-time updated phase angle, its sine and cosine values ​​are calculated immediately. These parameters not only provide closed-loop feedback to the Park transformation matrix to achieve self-synchronous adjustment of the rotating coordinate system, but also provide a phase reference for the subsequent accurate decoupling of positive and negative sequence components in the rotating coordinate system (i.e., the generation of positive and negative dq-axis components). This design eliminates the cascaded filtering stage in traditional schemes, achieving a balance between dynamic response speed and steady-state accuracy in phase tracking during grid frequency fluctuations or phase jumps. Furthermore, by directly processing the separated pure positive sequence component, it significantly enhances the anti-interference capability of the PLL under grid distortion conditions.

[0051] Furthermore, Axis signals and The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components, including: Will Axis signals and The positive-sequence component corresponding to the axis signal is transformed into a positive-sequence dq axis component through a positive-sequence dq transform. The functional expression of the positive-sequence dq transform is:

[0052] In the formula, For positive-order d-axis components, These are the positive-order q-axis components; Will Axis signals and The negative-sequence component corresponding to the axis signal is transformed into a negative-sequence dq axis component through a negative-sequence dq transform. The functional expression of the negative-sequence dq transform is:

[0053] In the formula, For negative d-axis components, These are the negative-order q-axis components.

[0054] By implementing the frequency-locked loop control method described above, the exact same two-dimensional rotation transformation matrix structure is used to precisely separate the positive-sequence components in the stationary coordinate system. , With negative order components , Independently mapped to a synchronously rotating coordinate system, generating positive-sequence d-axis components with clear physical meaning. Positive sequence q-axis components and negative d-axis components Negative q-axis components The core advantage of this process is that: (1) it uses a unified phase angle (provided in real time by the phase-locked loop) as the rotation transformation reference, ensuring that the positive and negative sequence components complete the rotation coordinate mapping on the same time scale, so that... and It rigorously characterizes the amplitude and phase deviation information of the fundamental positive sequence voltage, while and (1) Independently quantize the amplitude and phase characteristics of the fundamental negative sequence voltage to achieve complete decoupling of the dual-sequence components in the rotating coordinate system; (2) The positive sequence dq transform converts the orthogonal stationary signal into the direct-axis component in the rotating coordinate system through a linear combination of cosθ and sinθ. (Characterizing voltage amplitude) and cross-axis components (Characterizing phase tracking error), providing directly usable positive sequence amplitude and phase control variables for converter control; (3) Negative sequence dq transformation uses fully symmetric matrix operations to transform , Independent conversion , This allows the negative-order component to also obtain the amplitude-phase decoupling expression in the rotating coordinate system, providing accurate negative-order state quantities for unbalanced compensation control; (4) The two transformation processes share the real-time phase angle, avoiding additional coupling errors introduced by the inconsistent phase reference of the order components, and there is no need to design an inverse rotation matrix for the negative-order component, significantly reducing computational complexity and memory overhead; (5) The generated rotating coordinate system components , , , It can directly output the core element as a grid synchronization signal, fully meeting the high-precision control requirements of power electronic converters for positive sequence phase frequency tracking, negative sequence suppression and imbalance compensation under grid fault conditions. At the same time, it has strong versatility and engineering applicability due to its simple structure.

[0055] This invention also discloses a control system that employs the aforementioned frequency-locked loop control method based on dual second-order generalized integrators. The control system includes: The voltage signal acquisition module is used to acquire the three-phase voltage signals of the power grid; The Clark transform module is used to transform three-phase voltage signals into two-phase stationary coordinates. Axis signals and Axis signals; Orthogonal signal generation module, used for... Axis signals and The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; The positive and negative order calculation module is used to calculate and obtain the positive and negative order based on the obtained orthogonal signals. Axis signals and Positive and negative sequence components of the axis signal; Frequency-locked loop module, used to... Axis signals, For both axial and quadrature signals, a frequency-locked loop is used to track the signal frequency, and the center frequency of the second-order generalized integral is dynamically adjusted. The phase-locked loop module is used to obtain the positive-sequence component based on the second-order generalized integral after center frequency adjustment. It uses a single-synchronous coordinate system phase-locked loop to lock the signal phase, obtain the current phase angle, and calculate the sine and cosine values ​​of the current phase angle. The dp transformation module is used to transform the current phase angle based on its sine and cosine values. Axis signals and The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; The power grid signal output module is used to output a power grid synchronization signal based on the generated positive-sequence dq-axis components and negative-sequence dq-axis components.

[0056] The present invention also discloses a computer-readable storage medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, implements the above-described frequency-locked loop control method based on a dual second-order generalized integrator.

[0057] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the above-described frequency-locked loop control method based on a dual second-order generalized integrator when executing the computer program.

[0058] This invention is described based on flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to specific embodiments. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts 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 device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the flowcharts and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0059] 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 instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0060] 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.

[0061] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the present invention.

Claims

1. A frequency-locked loop control method based on a dual second-order generalized integrator, characterized in that, The frequency-locked loop control method includes: Acquire the three-phase voltage signals of the power grid; The three-phase voltage signal is transformed into a two-phase stationary coordinate system. Axis signals and Axis signals; Regarding the Axis signals and the The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; The orthogonal signals obtained are calculated and acquired respectively. Axis signals and the Positive and negative sequence components of the axis signal; According to the above Axis signal, the The axis signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the second-order generalized integral is dynamically adjusted. Based on the positive sequence component obtained from the second-order generalized integral after center frequency adjustment, the signal phase is locked using a single synchronous coordinate system phase-locked loop, the current phase angle is obtained, and the sine and cosine values ​​of the current phase angle are calculated. Based on the sine and cosine values ​​of the current phase angle, the... Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; The generated positive-sequence dq-axis components and negative-sequence dq-axis components are used to output a power grid synchronization signal.

2. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 1, characterized in that, The transformation of the three-phase voltage signal into a two-phase stationary coordinate system Axis signals and Axis signals, including: The three-phase voltage signal is converted into the [missing information] using Clark transform. Axis signals and the The Clark transform function expression for the shaft signal is: In the formula, In a two-phase stationary coordinate system Axis signal, In a two-phase stationary coordinate system Axis signal, This is the voltage signal of phase A. This is the B-phase voltage signal. This is the C-phase voltage signal.

3. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 2, characterized in that, The above Axis signals and the The axis signals are subjected to second-order generalized integration to obtain two sets of orthogonal signals, including: Regarding the Axis signals and the The two axes signals are respectively subjected to second-order improper integrals to obtain two sets of orthogonal signals. The functional expression of the second-order improper integral is as follows: In the formula, For in-phase signals in a stationary coordinate system, These are orthogonal signals of phase signal in stationary coordinate system. The damping coefficient is... For the center frequency, The signal variable is in a stationary coordinate system.

4. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 3, characterized in that, The method of calculating and obtaining the orthogonal signals respectively Axis signals and the The positive and negative sequence components of the axis signal include: The Axis signals and the The orthogonal signals of the axis signals are used to calculate the positive and negative sequence components of the grid voltage. The functional expression for the positive and negative sequence calculation is as follows: In the formula, For the The positive sequence component corresponding to the axis signal. For the The positive sequence component corresponding to the axis signal. For the The negative sequence component corresponding to the axis signal For the The negative sequence component corresponding to the axis signal For the The orthogonal signal corresponding to the axis signal For the The orthogonal signal corresponding to the axis signal.

5. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 4, characterized in that, According to the Axis signal, the The shaft signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the frequency-locked loop is dynamically adjusted, including: According to the above Axis signal, the The frequency-locked loop is used to calculate the signal error for both the axis signal and the orthogonal signal. The functional expression for calculating the signal error is as follows: In the formula, For signal error; The instantaneous power grid frequency is obtained based on the signal error. The functional expression for obtaining the instantaneous power grid frequency is: In the formula, This is the instantaneous power grid frequency gain. For adaptive gain coefficients, The instantaneous grid frequency after gain. The sampling time interval is the power grid frequency; The center frequency of the second-order generalized integral is dynamically adjusted based on the instantaneous grid frequency after the gain is obtained from the frequency-locked loop.

6. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 5, characterized in that, The step of dynamically adjusting the center frequency of the second-order generalized integral based on the instantaneous grid frequency obtained by the frequency-locked loop includes: Based on the instantaneous grid frequency after gain is obtained from the frequency-locked loop, discretized parameters are generated using the bilinear transform method. The instantaneous grid frequency after extracting the gain from the discretized parameters is used as the center frequency after adjustment by the second-order generalized integral.

7. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 5, characterized in that, The positive-sequence component obtained based on the second-order generalized integral after center frequency adjustment is used to lock the signal phase using a single-synchronous coordinate system phase-locked loop, obtain the current phase angle, and calculate the sine and cosine values ​​of the current phase angle, including: The positive-sequence component obtained based on the second-order generalized integral after center frequency adjustment will be... Axis signals and the The positive-sequence component of the axis signal is mapped from the stationary coordinate system to the rotating coordinate system through the Park transform. The functional expression for the positive-sequence component mapping is as follows: In the formula, For the d-axis component mapped to the rotated coordinate system, For the q-axis component mapped to the rotated coordinate system, The sine value of the phase angle. This is the cosine value of the phase angle; Based on the q-axis component after positive sequence component transformation, the angular frequency is obtained using a single synchronous coordinate system phase-locked loop, and the phase angle is generated by integrating the obtained angular frequency over time. The phase angle at the current moment is obtained by discrete-domain calculation of the phase angle generated by integration. The functional expression for calculating the phase angle at the current moment is: In the formula, The phase angle at the current moment. The phase angle at the previous moment. Angular frequency; Based on the calculated current phase angle, calculate and obtain the sine and cosine values ​​of the current phase angle.

8. The frequency-locked loop control method based on a dual second-order generalized integrator according to claim 7, characterized in that, The Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components, including: The Axis signals and the The positive-sequence component corresponding to the axis signal is transformed into a positive-sequence dq axis component through a positive-sequence dq transform. The functional expression of the positive-sequence dq transform is: In the formula, For positive-order d-axis components, These are the positive-order q-axis components; The Axis signals and the The negative-sequence component corresponding to the axis signal is transformed into a negative-sequence dq axis component through a negative-sequence dq transform. The functional expression of the negative-sequence dq transform is: In the formula, For negative d-axis components, These are the negative-order q-axis components.

9. A control system employing the frequency-locked loop control method based on a dual second-order generalized integrator as described in any one of claims 1-8, characterized in that, The control system includes: The voltage signal acquisition module is used to acquire the three-phase voltage signals of the power grid; The Clark transform module is used to transform the three-phase voltage signal into a two-phase stationary coordinate system. Axis signals and Axis signals; The orthogonal signal generation module is used for the... Axis signals and the The axis signals are respectively subjected to second-order generalized integrals to obtain two sets of orthogonal signals; The positive and negative order calculation module is used to calculate and obtain the positive and negative order based on the obtained orthogonal signals. Axis signals and the Positive and negative sequence components of the axis signal; Frequency-locked loop module, used according to the Axis signal, the The axis signal and the orthogonal signal are tracked using a frequency-locked loop, and the center frequency of the second-order generalized integral is dynamically adjusted. The phase-locked loop module is used to obtain the positive-sequence component based on the second-order generalized integral after center frequency adjustment. It uses a single-synchronous coordinate system phase-locked loop to lock the signal phase, obtain the current phase angle, and calculate the sine and cosine values ​​of the current phase angle. The dp transformation module is used to transform the current phase angle based on the sine and cosine values. Axis signals and the The positive and negative sequence components corresponding to the axis signal are transformed by dq transformation to generate positive sequence dq axis components and negative sequence dq axis components; The power grid signal output module is used to output a power grid synchronization signal based on the generated positive-sequence dq-axis components and negative-sequence dq-axis components.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the frequency-locked loop control method based on a dual second-order generalized integrator as described in any one of claims 1-8.

Images