Frequency-locked phase-locked loop method

Abstract

The invention provides a frequency-locked phase-locked loop method, which is based on a synchronous rotating coordinate system, and adopts an angular frequency error and a phase angle error to carry out frequency locking and phase locking. According to the technology, a low-pass filter is adopted to observe a power grid voltage synchronous rotating coordinate system component udq to obtain an observation error edq and an observation value # imgabs0 #, the conjugate # imgabs1 # of the observation value is calculated, and the observation error edq is multiplied by the conjugate # imgabs2 # of the observation value to obtain an expression containing angular frequency error information; multiplying an imaginary part xaI containing an angular frequency error information expression by a normalization coefficient gamma and a transfer function f (s) for pole-zero cancellation to obtain an angular frequency error omega e, multiplying an actually measured value of a direct-axis component or a quadrature-axis component of the power grid voltage by a proportionality coefficient K, or multiplying an observed value by the proportionality coefficients K and f (s) to serve as a phase angle control signal epsilon, and calculating the phase angle of the power grid voltage according to the phase angle control signal epsilon. And after the added value is input into the integrator with the transfer function of # imgabs3 #, an angular frequency observation value # imgabs4 # is output, after the angular frequency observation value # imgabs5 # is input into the integrator with the transfer function of # imgabs6 #, a phase angle observation value # imgabs7 # is output, and finally frequency locking and phase locking are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed power generation, and in particular to a frequency-locked phase-locked loop method, which is applicable to situations of conventional grid voltage, grid voltage imbalance and harmonic distortion. Background Art

[0002] When distributed power sources are connected to the large power grid through grid-connected converters, the grid-connected converter control requires grid synchronization technology to accurately estimate the amplitude and phase information of the grid fundamental positive-sequence voltage. Currently, the most widely used grid synchronization technologies are mainly phase-locked loops based on synchronous rotating coordinate systems, frequency-locked loops based on stationary coordinate systems, frequency-locked phase-locked loops based on synchronous and stationary dual coordinate systems, and frequency-locked phase-locked loops based on stationary coordinate systems. The phase-locked loop technology based on the synchronous rotating coordinate system has the problem of not being able to quickly detect the grid voltage angular frequency when the grid voltage angular frequency jumps because it does not have an independent angular frequency loop; the frequency-locked loop technology based on the stationary coordinate system has the problem of not being able to accurately estimate the grid voltage amplitude and phase information because it does not have an independent phase-locked loop; the existing frequency-locked phase-locked loop technology has the problems of inconsistent system coordinate system architecture, difficulty in establishing a system small signal model in a stationary coordinate system, complex system parameter design, unclear relationship between loop response and parameters, etc., and cannot provide guidance for the system design and optimization process; currently there is still a lack of a frequency-locked phase-locked loop technology constructed in a synchronous rotating coordinate system, which can more conveniently and quickly establish a system small signal model and design system parameters, clarify the relationship between loop response and parameters, provide guidance for the system design and optimization process, and is suitable for conventional grid voltage, grid voltage imbalance and harmonic distortion occasions. Summary of the invention

[0003] The embodiment of the present invention provides a frequency-locked phase-locked loop method, which is used to solve the technical problems existing in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme.

[0005] A frequency-locked phase-locked loop method, comprising:

[0006] S1 transforms the grid voltage from a three-phase stationary coordinate system to a two-phase stationary coordinate system through Clark transformation;

[0007] S2 transforms the grid voltage from a two-phase stationary coordinate system to a two-phase rotating coordinate system through Park transformation;

[0008] S3 obtains the observation error and observation value of the grid voltage by observing the grid voltage in the two-phase rotating coordinate system, and calculates the conjugate of the observation value;

[0009] S4 multiplies the observed error by the conjugate of the observed value to obtain an expression containing angular frequency error information, and multiplies the imaginary part of the expression containing angular frequency error information by the normalization coefficient γ and the zero-pole cancellation transfer function to obtain the angular frequency error;

[0010] S5, based on the condition that the direct-axis component of the grid voltage and the quadrature-axis component of the grid voltage include phase angle error information, multiplying the direct-axis component of the grid voltage or the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller as the phase angle control signal, or multiplying the observed value of the direct-axis component of the grid voltage or the observed value of the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller and the zero-pole cancellation transfer function as the phase angle control signal;

[0011] S6 adds the angular frequency error to the phase angle control signal and inputs the added value into the transfer function: The integrator of The output value of the integrator is added to the rated angular frequency of the power grid to obtain the angular frequency observation value. The angular frequency observation value is input into the transfer function: The integrator outputs the phase angle observation value to complete the frequency-locked phase-locked process; in this step, d is the proportional coefficient of the inner frequency-locked loop integral controller;

[0012] The execution result of step S6 is used to construct or optimize the frequency-locked phase-locked loop system structure and / or control the grid-connected converter.

[0013] Preferably, there is also a design process of control parameters for implementing the method, specifically including:

[0014] Set the phase-locked loop to the outer loop and the frequency-locked loop to the inner loop;

[0015] The phase-locked loop of the outer loop adopts a proportional controller with a coefficient of K. The input of the phase-locked loop of the outer loop is a direct-axis component of the grid voltage or a quadrature-axis component of the grid voltage containing grid voltage phase angle error information. The output of the phase-locked loop of the outer loop is a phase angle control signal ε.

[0016] The frequency-locked loop of the inner loop uses an integral controller with a proportional coefficient of d, and its transfer function is The input of the inner frequency-locked loop is the phase angle control signal ε plus the grid voltage angle frequency error signal ω e , where the grid voltage angular frequency error signal ω e Equal to the actual value of the grid voltage angular frequency ω minus the observed value of the grid voltage angular frequency The output of the inner frequency-locked loop is the observed value of the grid voltage angular frequency The angular frequency error ω e Add the phase angle control signal ε and input the added value into the inner loop of the frequency-locked loop transfer function: The integral controller is used to compare the output value of the integrator with the rated angular frequency ω of the power grid. 0 Add up to get the angular frequency observation value Rated angular frequency of the power grid ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount is used to improve the dynamic performance of the frequency-locked phase-locked loop response;

[0017] Based on the angular frequency observations obtained The angular frequency observation The input transfer function is The integrator outputs the phase angle observation value The phase angle observation Multiplying by the amplitude U of the fundamental positive sequence component of the grid phase voltage, the grid voltage direct axis component or grid voltage quadrature axis component is obtained;

[0018] Based on the principle of inner loop first and outer loop later, the open-loop transfer function of the inner frequency-locked loop is set as The closed-loop transfer function is calculated as By adjusting the parameter d of the inner frequency-locked loop integral controller, the bandwidth and phase angle stability domain of the inner frequency-locked loop closed-loop transfer function are changed, and then the loop response characteristics of the inner frequency-locked loop are designed; by setting the open-loop transfer function of the outer phase-locked loop to The closed-loop transfer function is calculated as By adjusting the parameter K of the outer phase-locked loop proportional controller, the bandwidth and phase angle stability domain of the outer phase-locked loop closed-loop transfer function are changed, and then the loop response characteristics of the outer phase-locked loop are designed.

[0019] It can be seen from the technical solutions provided by the above embodiments of the present invention that the present invention provides a frequency-locked phase-locked loop method, which is based on a synchronous rotating coordinate system and uses angular frequency error and phase angle error to perform frequency-locked phase locking. The technology uses a low-pass filter to perform frequency-locked phase locking on the synchronous rotating coordinate system component u of the grid voltage. dq Observe and obtain the observation error e dq and observations Calculate the conjugate of the observation The observation error e dq Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the transfer function f(s) for zero-pole cancellation gives the angular frequency error ω e , multiply the measured value of the direct-axis component of the grid voltage or the quadrature-axis component of the grid voltage by the proportional coefficient K, or multiply the observed value by the proportional coefficient K and f(s) as the phase angle control signal ε, and compare it with the angular frequency error ω e Add the added value and input it into the transfer function as The integrator outputs the angular frequency observation value The angular frequency observation The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 It is a technical framework diagram of a frequency-locked phase-locked loop method provided by the present invention;

[0023] Figure 2 It is a framework diagram of one mode of an embodiment of a frequency-locked phase-locked loop method provided by the present invention that is applicable to conventional power grid voltage;

[0024] Figure 3 It is a framework diagram of another embodiment of a frequency-locked phase-locked loop method provided by the present invention that is applicable to conventional power grid voltage;

[0025] Figure 4 It is a framework diagram of an embodiment of a frequency-locked phase-locked loop method provided by the present invention, which is applicable to unbalanced and harmonically distorted power grid voltage;

[0026] Figure 5 It is a framework diagram of an embodiment of a frequency-locked phase-locked loop method provided by the present invention based on an unbalanced and harmonically distorted power grid voltage connected in series with a notch filter;

[0027] Figure 6 It is a framework diagram of an embodiment of a frequency-locked phase-locked loop method provided by the present invention based on an unbalanced and harmonically distorted power grid voltage connected in series with a notch filter;

[0028] Figure 7 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a second-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0029] Figure 8 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a second-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0030] Fig. 9 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a reduced-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0031] Fig.10 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a reduced-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0032] Fig.11 It is a framework diagram of an embodiment of a frequency-locked phase-locked loop method provided by the present invention, which is applicable to unbalanced and harmonically distorted power grid voltage;

[0033] Fig.12 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a second-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0034] Fig.13 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a second-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0035] Fig.14 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a reduced-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0036] Fig.15 It is a framework diagram of an embodiment of an unbalanced and harmonically distorted grid voltage based on a reduced-order generalized integrator of a frequency-locked phase-locked loop method provided by the present invention;

[0037] Fig.16 It is a schematic diagram of a small signal model of a frequency-locked phase-locked loop method provided by the present invention. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0039] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0040] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0041] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0042] See also Figure 1 The present invention provides a frequency-locked phase-locked loop method, which uses an angular frequency error and a phase angle error to perform frequency-locked phase-locking based on a synchronous rotating coordinate system, and includes the following steps:

[0043] S1 transforms the grid voltage from a three-phase stationary coordinate system to a two-phase stationary coordinate system through Clark transformation;

[0044] S2 transforms the grid voltage from a two-phase stationary coordinate system to a two-phase rotating coordinate system through Park transformation;

[0045] S3 obtains the observation error and observation value of the grid voltage by observing the grid voltage of the two-phase rotating coordinate system, and calculates the conjugate of the observation value;

[0046] S4 multiplies the observed error by the conjugate of the observed value to obtain an expression containing angular frequency error information, and multiplies the imaginary part of the expression containing angular frequency error information by the normalization coefficient γ and the zero-pole cancellation transfer function to obtain the angular frequency error;

[0047] S5, based on the condition that the direct-axis component of the grid voltage and the quadrature-axis component of the grid voltage include phase angle error information, multiplying the direct-axis component of the grid voltage or the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller as the phase angle control signal, or multiplying the observed value of the direct-axis component of the grid voltage or the observed value of the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller and the zero-pole cancellation transfer function as the phase angle control signal;

[0048] S6 adds the angular frequency error to the phase angle control signal and inputs the added value into the transfer function: The integrator of The output value of the integrator is added to the rated angular frequency of the power grid to obtain the angular frequency observation value. The angular frequency observation value is input into the transfer function: The phase angle observation value is output after the integrator. The obtained angular frequency observation value and phase angle observation value both meet the observation error requirements of the grid voltage angular frequency and phase angle, that is, the frequency and phase locking of the grid are achieved. In this step, d is the proportional coefficient of the inner loop frequency lock loop integral controller.

[0049] The above-mentioned angular frequency observation value and phase angle observation value are the output results of the frequency-locked phase-locked loop method for locking the frequency and phase of the power grid voltage.

[0050] When the distributed power source is connected to the large power grid through the grid-connected converter, the grid-connected converter is controlled to execute the frequency-locked phase-locked loop method provided by the present invention to estimate the amplitude and phase information of the fundamental positive-sequence component of the power grid and thus realize grid synchronization. As a key component of the control of the grid-connected converter, the frequency-locked phase-locked method has a faster dynamic response characteristic to the angular frequency change of the power grid voltage compared to the phase-locked loop in the synchronous rotating coordinate system. It can enable the grid-connected converter to adjust the active power and simulate the inertial behavior more quickly and accurately when facing frequency fluctuations, further improving its inertia support capacity and active power support capacity for the power grid, which is crucial to improving the frequency stability of the power grid and adapting to rapidly changing load demands; compared to the frequency-locked loop in the two-phase stationary coordinate system, the frequency-locked phase-locked method can quickly detect the phase angle change of the power grid voltage, making up for the two-phase static The frequency-locked loop in the stationary coordinate system cannot detect the amplitude and phase information of the fundamental positive-sequence component of the grid voltage; compared with the existing frequency-locked phase-locked loop method, the frequency-locked phase-locked method is implemented in a synchronous rotating coordinate system, which can more conveniently and quickly establish a system small signal model and design system parameters, clarify the relationship between loop response and parameters, and provide guidance for system design and optimization process. In addition, this method uses a multi-frequency adaptive filter to suppress grid imbalance and harmonic interference, and is suitable for various occasions such as conventional grid voltage, grid voltage imbalance and harmonic distortion, which makes the frequency-locked phase-locked method have a broader application prospect in grid-connected converter control.

[0051] Several preferred embodiments are provided below to specifically illustrate the execution process of each step.

[0052] Embodiment 1:

[0053] like Figure 2 , 3 As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop of a conventional grid voltage. First, the grid voltage is converted from a three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ , and then use Park transformation to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq ,

[0054] Then, the grid voltage u in the synchronous rotating coordinate system is filtered through a first-order low-pass filter. dq Observe and obtain the observation error e dq and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter and s is the Laplace operator; calculate the conjugate of the observed value

[0055] The observation error e dq Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e , where the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0056] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage The phase angle control signal ε is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s), where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0057] After obtaining the phase angle control signal ε, the angular frequency error ω eAdded to the phase angle control signal ε, the added value is input into the transfer function: The integrator of

[0058] The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0059] Among them, when considering the influence of the low-pass filter on the loop response characteristics, the transfer function f(s) and the low-pass filter contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the low-pass filter on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct-axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The low-pass filter contained in the circuit performs zero-pole cancellation to eliminate the influence of the low-pass filter on the response characteristics of the phase-locked loop. When the influence of the low-pass filter on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aI Multiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the grid voltage direct axis d or the grid voltage quadrature axis component multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0060] Embodiment 2:

[0061] like Figure 5 , 6 As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop for grid voltage imbalance and harmonic distortion. First, the grid voltage is converted from the three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ .

[0062] Then Park transformation is used to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq .

[0063] Then, a negative sequence and harmonic component filter composed of multiple angular frequency adaptive notch filters connected in series is used to filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and obtain the fundamental positive sequence component of the grid voltage. Since the gain of the angular frequency adaptive notch filter at its center angular frequency is close to zero, the negative sequence or harmonic components at its center angular frequency can be filtered out; in the synchronous rotating coordinate system, the fundamental positive sequence component of the grid voltage is a DC quantity, and the gain of the angular frequency adaptive notch filter for DC quantities is close to one, and the fundamental positive sequence component of the grid voltage can pass through the angular frequency adaptive notch filter almost without attenuation; in the synchronous rotating coordinate system, the frequency of the negative sequence component of the grid voltage is 2ω, and the frequencies of the harmonic components are 6ω, 12ω, ..., 6nω, where n is an integer and ω is the actual angular frequency of the grid, so multiple angular frequency adaptive notch filters with different center angular frequencies are connected in series to filter out the grid voltage u in the synchronous rotating coordinate system. dq The negative sequence and harmonic components contained in it are used to obtain its fundamental positive sequence component The central angular frequency of each angular frequency adaptive notch filter is The observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function expression of the angular frequency adaptive notch filter is: Where s is the Laplace operator, ±ω n is the center angular frequency of the angular frequency adaptive notch filter, ω b is the bandwidth of the angular frequency adaptive notch filter, and the grid voltage u is obtained dq The fundamental positive sequence component contained After that, the fundamental positive sequence component of the grid voltage is filtered through a first-order low-pass filter. Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter and s is the Laplace operator; calculate the conjugate of the observed value

[0064] The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e , where the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0065] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage The phase angle control signal ε is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s), where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0066] After obtaining the phase angle control signal ε, the angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0067] Among them, when considering the influence of the low-pass filter on the loop response characteristics, the transfer function f(s) and the low-pass filter contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the low-pass filter on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct-axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The low-pass filter contained in the circuit performs zero-pole cancellation to eliminate the influence of the low-pass filter on the response characteristics of the phase-locked loop. When the influence of the low-pass filter on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aI Multiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the direct axis or quadrature axis component of the grid voltage multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0068] Embodiment three:

[0069] like Figure 7 , 8 As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop for grid voltage imbalance and harmonic distortion. First, the grid voltage is converted from the three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ .

[0070] Then Park transformation is used to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq .

[0071] Then, the negative sequence and harmonic component filter composed of multiple second-order generalized integrators SOGI is used to filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system to obtain the fundamental positive sequence component of the grid voltage. Since the second-order generalized integrator SOGI has a very high gain at its center angular frequency, the frequency of the negative sequence component of the grid voltage in the synchronous rotating coordinate system is 2ω, and the frequencies of the harmonic components are 6ω, 12ω, ..., 6nω, where n is an integer and ω is the actual angular frequency of the grid, multiple center angular frequencies are used. The second-order generalized integrator SOGI observes the negative sequence and harmonic components contained in the grid voltage, where: is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function of the second-order generalized integrator SOGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the second-order generalized integrator SOGI for observing each harmonic component are: Its output is the observed value of each harmonic component of the grid voltage in the synchronous rotating coordinate system Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence and each harmonic component to obtain the fundamental positive sequence component Fundamental positive sequence component As the input of each second-order generalized integrator SOGI, the negative sequence and harmonic component filter composed of multiple second-order generalized integrators SOGI can observe and filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and obtain its fundamental positive sequence component The transfer function of the second-order generalized integrator SOGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the second-order generalized integrator SOGI, ω b is the bandwidth of the second-order generalized integrator SOGI, and the grid voltage u is obtained dq The fundamental positive sequence component contained After that, the fundamental positive sequence component of the grid voltage is filtered through a first-order low-pass filter. Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter and s is the Laplace operator; calculate the conjugate of the observed value

[0072] The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e , where the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0073] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage Multiply the proportional coefficient K and the zero-pole cancellation transfer function f(s) as the phase angle control signal ε, where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0074] After obtaining the phase angle control signal ε, the angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0075] Among them, when considering the influence of the low-pass filter on the loop response characteristics, the transfer function f(s) and the low-pass filter contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the low-pass filter on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct-axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The low-pass filter contained in the circuit performs zero-pole cancellation to eliminate the influence of the low-pass filter on the response characteristics of the phase-locked loop. When the influence of the low-pass filter on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aI Multiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the direct axis or quadrature axis component of the grid voltage multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0076] Embodiment 4:

[0077] like Fig. 9 , 10 As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop for grid voltage imbalance and harmonic distortion. First, the grid voltage is converted from the three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ .

[0078] Then Park transformation is used to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq .

[0079] Then, the negative sequence and harmonic component filter composed of multiple reduced-order generalized integrators ROGI is used to filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and the fundamental positive sequence component of the grid voltage is obtained.

[0080] Since the reduced-order generalized integrator ROGI has a very high gain at its center angular frequency, the frequency of the negative sequence component of the grid voltage in the synchronous rotating coordinate system is 2ω, and the frequencies of the harmonic components are 6ω, 12ω, ..., 6nω, where n is an integer and ω is the actual angular frequency of the grid, multiple center angular frequencies are used. The reduced-order generalized integrator ROGI observes the negative sequence and harmonic components contained in the grid voltage, where: is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function of the reduced-order generalized integrator ROGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the reduced-order generalized integrator ROGI for observing each harmonic component are: Its output is the observed value of the harmonic component of the grid voltage in the synchronous rotating coordinate system Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence and each harmonic component to obtain the fundamental positive sequence component Fundamental positive sequence component As the input of each reduced-order generalized integrator ROGI, the negative-sequence and harmonic component filter composed of multiple reduced-order generalized integrators ROGI can observe and filter out the negative-sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and obtain its fundamental positive-sequence component The transfer function of the reduced-order generalized integrator ROGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the reduced-order generalized integrator ROGI, ω b is the bandwidth of the reduced-order generalized integrator ROGI, and the grid voltage u is obtained dq The fundamental positive sequence component of After that, the fundamental positive sequence component of the grid voltage in the synchronous rotating coordinate system is filtered through a first-order low-pass filter. Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter and s is the Laplace operator; calculate the conjugate of the observed value

[0081] The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e , where the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0082] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage The phase angle control signal ε is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s), where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0083] After obtaining the phase angle control signal ε, the angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0084] Among them, when considering the influence of the low-pass filter on the loop response characteristics, the transfer function f(s) and the low-pass filter contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the low-pass filter on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct-axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The low-pass filter contained in the circuit performs zero-pole cancellation to eliminate the influence of the low-pass filter on the response characteristics of the phase-locked loop. When the influence of the low-pass filter on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aI Multiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the direct axis or quadrature axis component of the grid voltage multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0085] Embodiment five:

[0086] like Fig.12 , 13As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop for grid voltage imbalance and harmonic distortion. First, the grid voltage is converted from the three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ .

[0087] Then Park transformation is used to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq .

[0088] Then through multiple second-order generalized integrators SOGI and the transfer function is The grid voltage fundamental positive sequence component and error observer composed of the integrator are obtained to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. Its observation error Since the second-order generalized integrator SOGI has a very high gain at its center angular frequency, the transfer function is The integrator has a high gain for the DC component. In the synchronous rotating coordinate system, the fundamental positive sequence component of the grid voltage is a DC quantity. In the synchronous rotating coordinate system, the frequency of the negative sequence component of the grid voltage is 2ω, and the frequencies of the harmonic components are 6ω, 12ω, ..., 6nω, where n is an integer and ω is the actual angular frequency of the grid. Therefore, multiple central angular frequencies are used. The second-order generalized integrator SOGI observes the negative sequence and harmonic components contained in the grid voltage, and adopts the transfer function The integrator observes the fundamental positive sequence component contained in the grid voltage, where: is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, k is the proportional coefficient of the integrator, and s is the Laplace operator; the transfer function of the second-order generalized integrator SOGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the second-order generalized integrator SOGI for observing each harmonic component are: Its output is the observed value of each harmonic component of the grid voltage in the synchronous rotating coordinate system The integrator transfer function for observing the fundamental positive sequence component of the grid voltage is: Its output is the observed value of the fundamental positive sequence component of the grid voltage Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence, each harmonic and the fundamental positive sequence component to obtain the observed error of the fundamental positive sequence component Observation error of fundamental positive sequence component As each second-order generalized integrator SOGI and transfer function is The integrator input, multiple second-order generalized integrator SOGI and transfer function are The grid voltage fundamental positive sequence component and error observer composed of the integrator can observe the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. and its observation error The transfer function of the second-order generalized integrator SOGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the second-order generalized integrator SOGI, ω b is the bandwidth of the second-order generalized integrator SOGI; the observed value of the fundamental positive sequence component is obtained and observation error Afterwards, the conjugate of this observation is calculated

[0089] The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e Among them, the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0090] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage The phase angle control signal ε is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s), where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0091] After obtaining the phase angle control signal ε, the angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0092] Among them, when considering the influence of the fundamental positive sequence component observer on the loop response characteristics, the transfer function f(s) and the fundamental positive sequence component observer contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the fundamental positive sequence component observer on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The fundamental positive sequence component observer contained in the circuit performs zero-pole cancellation to eliminate the influence of the fundamental positive sequence component observer on the response characteristics of the phase-locked loop. When the influence of the fundamental positive sequence component observer on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aI Multiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the direct axis or quadrature axis component of the grid voltage multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0093] Embodiment six:

[0094] like Fig.14 , 15 As shown, the solution of this embodiment is applicable to the construction of a frequency-locked phase-locked loop for grid voltage imbalance and harmonic distortion. First, the grid voltage is converted from the three-phase stationary coordinate system u abc Transform to the two-phase stationary coordinate system u αβ .

[0095] Then Park transformation is used to transform the grid voltage from the two-phase stationary coordinate system u αβ Transform to the two-phase rotating coordinate system u dq .

[0096] Then through multiple reduced-order generalized integrators ROGI and transfer functions are The grid voltage fundamental positive sequence component and error observer composed of the integrator are obtained to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. Its observation error Since the reduced-order generalized integrator ROGI has a very high gain at its center angular frequency, the transfer function is The integrator has a high gain for the DC component. In the synchronous rotating coordinate system, the fundamental positive sequence component of the grid voltage is a DC quantity, the frequency of the negative sequence component of the grid voltage is 2ω, and the frequencies of the harmonic components are 6ω, 12ω, ..., 6nω, where n is an integer and ω is the actual angular frequency of the grid; therefore, multiple central angular frequencies are used. The reduced-order generalized integrator ROGI observes the negative sequence and harmonic components contained in the grid voltage, and adopts the transfer function The integrator observes the fundamental positive sequence component contained in the grid voltage. Among them, is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, k is the proportional coefficient of the integrator, and s is the Laplace operator; the transfer function of the reduced-order generalized integrator ROGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the reduced-order generalized integrator ROGI for observing each harmonic component are: Its output is the observed value of the harmonic component of the grid voltage in the synchronous rotating coordinate system The integrator transfer function for observing the fundamental positive sequence component is Its output is the observed value of the fundamental positive sequence component of the grid voltage in the synchronous rotating coordinate system Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence, each harmonic and the fundamental positive sequence component to obtain the observed error of the fundamental positive sequence component Observation error of fundamental positive sequence component As each reduced-order generalized integrator ROGI and transfer function are The input of the integrator, multiple reduced-order generalized integrators ROGI and the transfer function are The grid voltage fundamental positive sequence component and error observer composed of the integrator can observe the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. and its observation error The transfer function of the reduced-order generalized integrator ROGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the reduced-order generalized integrator ROGI, ω b is the bandwidth of the reduced-order generalized integrator ROGI; the observed value of the fundamental positive sequence component is obtained and observation error Afterwards, the conjugate of this observation is calculated

[0097] The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e , where the imaginary part x of the expression containing the angular frequency error information is aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

[0098] Since the direct-axis and quadrature-axis components of the grid voltage contain phase angle error information, the direct-axis component of the grid voltage u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage The phase angle control signal ε is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s), where K is the proportional coefficient of the outer loop phase-locked loop proportional controller.

[0099] After obtaining the phase angle control signal ε, the angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is related to the rated angular frequency ω of the power grid 0 Add up to get the angular frequency observation value Where d is the proportional coefficient of the integral controller of the inner frequency-locked loop, and the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0100] Among them, when considering the influence of the fundamental positive sequence component observer on the loop response characteristics, the transfer function f(s) and the fundamental positive sequence component observer contained in the angular frequency error information expression are zero-pole canceled to eliminate the influence of the fundamental positive sequence component observer on the frequency-locked loop response characteristics. The transfer function f(s) and the observed value of the direct axis component of the grid voltage are Or the observed value of the quadrature axis component of the grid voltage The fundamental positive sequence component observer contained in the circuit performs zero-pole cancellation to eliminate the influence of the fundamental positive sequence component observer on the response characteristics of the phase-locked loop. When the influence of the fundamental positive sequence component observer on the loop response characteristics is not considered, the angular frequency error ω e Equal to the imaginary part x of the expression containing the angular frequency error information aIMultiplied by the normalization coefficient γ, the phase angle control signal ε is equal to the actual value or observed value of the direct axis or quadrature axis component of the grid voltage multiplied by the proportional coefficient K; the grid rated angular frequency ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response. The proportional coefficients d and K provide two degrees of freedom for the design of the frequency-locked phase-locked loop response. The loop responses of the frequency-locked loop and the phase-locked loop can be designed respectively through the proportional coefficients d and K.

[0101] Embodiment seven:

[0102] like Fig.16 As shown in the figure, the frequency-locked phase-locked loop parameter design method constructs a frequency-locked phase-locked double closed-loop small signal model based on the small signal analysis method, wherein the phase-locked loop is the outer loop and the frequency-locked loop is the inner loop; the outer loop phase-locked loop adopts a proportional controller with a coefficient of K, and the input of the outer loop phase-locked loop is the grid voltage direct axis or grid voltage quadrature axis component containing grid voltage phase angle error information, and the output is the phase angle control signal ε; the inner loop adopts an integral controller with a proportional coefficient of d, and its transfer function is Where s is the Laplace operator, and the input of the inner frequency-locked loop is the phase angle control signal ε plus the grid voltage angle frequency error signal ω e , where the grid voltage angular frequency error signal ω e Equal to the actual value of the grid voltage angular frequency ω minus the observed value of the grid voltage angular frequency The output of the inner frequency-locked loop is the observed value of the grid voltage angular frequency The angular frequency error ω e Add the phase angle control signal ε, and input the added value into the transfer function of the inner loop frequency locked loop: The integral controller is used to compare the output value of the integral controller with the rated angular frequency ω of the power grid. 0 Add up to get the angular frequency observation value Rated angular frequency of the power grid ω 0 is the observed value of the frequency-locked loop angular frequency The feedforward amount improves the dynamic performance of the frequency-locked phase-locked loop response and obtains the angular frequency observation value Then, the angular frequency observation value The input transfer function is The integrator outputs the phase angle observation value The phase angle observation Multiplying by the amplitude U of the fundamental positive sequence component of the grid phase voltage, the grid voltage direct axis or grid voltage quadrature axis component is obtained; the frequency-locked phase-locked loop parameter design method follows the principle of inner loop first and outer loop later, and the open-loop transfer function of the inner loop frequency-locked loop is: The closed-loop transfer function is calculated as By adjusting the parameter d of the inner frequency-locked loop integral controller, the bandwidth and phase angle stability domain of the inner frequency-locked loop closed-loop transfer function are changed, and the loop response characteristics of the inner frequency-locked loop are designed; the open-loop transfer function of the outer phase-locked loop is The closed-loop transfer function is calculated as By adjusting the parameter K of the outer phase-locked loop proportional controller, the bandwidth and phase angle stability domain of the outer phase-locked loop closed-loop transfer function are changed, and then the loop response characteristics of the outer phase-locked loop are designed.

[0103] In summary, the present invention provides a frequency-locked phase-locked loop method, which is based on a synchronous rotating coordinate system and uses angular frequency error and phase angle error to perform frequency-locked phase locking. This technology uses a low-pass filter to perform frequency-locked phase locking on the synchronous rotating coordinate system component u of the grid voltage. dq Observe and obtain the observation error e dq and observations Calculate the conjugate of the observation The observation error e dq Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the transfer function f(s) for zero-pole cancellation gives the angular frequency error ω e , the measured value of the direct-axis or quadrature-axis component of the grid voltage is multiplied by the proportional coefficient K, or the observed value is multiplied by the proportional coefficient K and the zero-pole cancellation transfer function f(s) as the phase angle control signal ε, and is compared with the angular frequency error ω e Add the added value and input it into the transfer function as The integrator outputs the angular frequency observation value The angular frequency observation The input transfer function is The integrator outputs the phase angle observation value Finally, frequency and phase locking are achieved.

[0104] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0105] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A frequency-locked phase-locked loop method, characterized in that: include: S1 transforms the grid voltage from a three-phase stationary coordinate system to a two-phase stationary coordinate system through Clark transformation; S2 transforms the grid voltage from a two-phase stationary coordinate system to a two-phase rotating coordinate system through Park transformation; S3 obtains the observation error and observation value of the grid voltage by observing the grid voltage in the two-phase rotating coordinate system, and calculates the conjugate of the observation value; S4 multiplies the observed error by the conjugate of the observed value to obtain an expression containing angular frequency error information, and multiplies the imaginary part of the expression containing angular frequency error information by the normalization coefficient γ and the zero-pole cancellation transfer function to obtain the angular frequency error; S5, based on the condition that the direct-axis component of the grid voltage and the quadrature-axis component of the grid voltage include phase angle error information, multiplying the direct-axis component of the grid voltage or the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller as the phase angle control signal, or multiplying the observed value of the direct-axis component of the grid voltage or the observed value of the quadrature-axis component of the grid voltage by the proportional coefficient K of the outer-loop phase-locked loop proportional controller and the zero-pole cancellation transfer function as the phase angle control signal; S6 adds the angular frequency error to the phase angle control signal and inputs the added value into the transfer function: The integrator of The output value of the integrator is added to the rated angular frequency of the power grid to obtain the angular frequency observation value. The angular frequency observation value is input into the transfer function: The phase angle observation value is output after the integrator of the frequency-locked loop to complete the frequency-locked phase-locked process; in this step, d is the proportional coefficient of the integral controller of the inner frequency-locked loop; The execution result of step S6 is used to construct or optimize the frequency-locked phase-locked loop system structure and / or control the grid-connected converter.

2. The method according to claim 1, characterized in that: Step S3 includes any one of the following multiple groups of sub-steps: S31a uses a first-order low-pass filter to filter the grid voltage u in the synchronous rotating coordinate system. dq Observe and obtain the observation error e dq and observations Calculate the conjugate of the observation The transfer function of the first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter, and s is the Laplace operator; S31b uses a negative sequence and harmonic component filter composed of multiple angular frequency adaptive notch filters in series to filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and obtain the fundamental positive sequence component of the grid voltage. S32b uses multiple angular frequency adaptive notch filters with different central angular frequencies in series to filter out the grid voltage u in the synchronous rotating coordinate system. dq The negative sequence and harmonic components contained in it are used to obtain its fundamental positive sequence component In this sub-step, the central angular frequency of each angular frequency adaptive notch filter is The observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function expression of the angular frequency adaptive notch filter is: Where s is the Laplace operator, ±ω n is the center angular frequency of the angular frequency adaptive notch filter, ω b is the bandwidth of the angular frequency adaptive notch filter; S33b uses a first-order low-pass filter to filter the fundamental positive sequence component of the grid voltage Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter, and s is the Laplace operator; S34b calculates the observed value Conjugation S31c uses a negative sequence and harmonic component filter composed of multiple second-order generalized integrators SOGI to filter out the negative sequence and harmonic components contained in the grid voltage in the synchronous rotating coordinate system, and obtain the fundamental positive sequence component of the grid voltage. S32c uses multiple center angular frequencies The second-order generalized integrator SOGI observes the negative sequence and harmonic components contained in the grid voltage; in this sub-step, is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function of the second-order generalized integrator SOGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the second-order generalized integrator SOGI for observing each harmonic component are: Its output is the observed value of each harmonic component of the grid voltage in the synchronous rotating coordinate system S33c utilizes the grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence and each harmonic component to obtain the fundamental positive sequence component Fundamental positive sequence component It is used as the input of each second-order generalized integrator SOGI. The transfer function of the second-order generalized integrator SOGI is: Where s is the Laplace operator, ±ω n is the central angular frequency of the second-order generalized integrator SOGI, ω b is the bandwidth of the second-order generalized integrator SOGI; S34c uses a first-order low-pass filter to filter the fundamental positive sequence component of the grid voltage. Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter, and s is the Laplace operator; S35c calculates the observed value Conjugation S31d uses multiple center angular frequencies The reduced-order generalized integrator ROGI observes the negative sequence and harmonic components contained in the grid voltage; in this sub-step, is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, and the transfer function of the reduced-order generalized integrator ROGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the reduced-order generalized integrator ROGI for observing each harmonic component are: Its output is the observed value of the harmonic component of the grid voltage in the synchronous rotating coordinate system S32d utilizes the grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence and each harmonic component to obtain the fundamental positive sequence component Fundamental positive sequence component It is used as the input of each reduced-order generalized integrator ROGI. The transfer function of the reduced-order generalized integrator ROGI is: Where s is the Laplace operator, ±ω n is the central angular frequency of the reduced-order generalized integrator ROGI, ω b is the bandwidth of the reduced-order generalized integrator ROGI; S33d uses a first-order low-pass filter to filter the fundamental positive sequence component of the grid voltage in the synchronous rotating coordinate system. Observe and obtain its observation error and observations The transfer function of this first-order low-pass filter is Where k is the cutoff frequency of the first-order low-pass filter, and s is the Laplace operator; S34d Calculate the observed value Conjugation S31e is implemented through multiple second-order generalized integrators SOGI and the transfer function is The grid voltage fundamental positive sequence component and error observer composed of the integrator are obtained to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. Its observation error Specifically include: Using multiple center angular frequencies The second-order generalized integrator SOGI observes the negative sequence and harmonic components contained in the grid voltage, and adopts the transfer function The integrator observes the fundamental positive sequence component contained in the grid voltage; in this sub-step, is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, k is the proportional coefficient of the integrator, and s is the Laplace operator; the transfer function of the second-order generalized integrator SOGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the second-order generalized integrator SOGI for observing each harmonic component are: Its output is the observed value of each harmonic component of the grid voltage in the synchronous rotating coordinate system The integrator transfer function for observing the fundamental positive sequence component of the grid voltage is: Its output is the observed value of the fundamental positive sequence component of the grid voltage Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence, each harmonic and the fundamental positive sequence component to obtain the observed error of the fundamental positive sequence component Observation error of fundamental positive sequence component For each second-order generalized integrator SOGI, the transfer function is The input of the integrator passes through multiple second-order generalized integrators SOGI and the transfer function is The grid voltage fundamental positive sequence component and error observer formed by the integrator of the grid voltage are observed to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. and its observation error The transfer function of the second-order generalized integrator SOGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the second-order generalized integrator SOGI, ω b is the bandwidth of the second-order generalized integrator SOGI; S32e calculates the observed value Conjugation S31f is implemented through multiple reduced-order generalized integrators ROGI and the transfer function is The grid voltage fundamental positive sequence component and error observer composed of the integrator are obtained to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. Its observation error Specifically include: Using multiple center angular frequencies The reduced-order generalized integrator ROGI observes the negative sequence and harmonic components contained in the grid voltage, and adopts the transfer function The integrator observes the fundamental positive sequence component contained in the grid voltage, where: is the observed angular frequency of the fundamental positive sequence component of the grid voltage obtained by the frequency-locked loop, k is the proportional coefficient of the integrator, and s is the Laplace operator; the transfer function of the reduced-order generalized integrator ROGI for observing the negative sequence component is Its output is the observed value of the negative sequence component of the grid voltage in the synchronous rotating coordinate system The transfer functions of the reduced-order generalized integrator ROGI for observing each harmonic component are: Its output is the observed value of the harmonic component of the grid voltage in the synchronous rotating coordinate system The integrator transfer function for observing the fundamental positive sequence component is Its output is the observed value of the fundamental positive sequence component of the grid voltage in the synchronous rotating coordinate system Using grid voltage u dq Subtract the sum of the observed values ​​of the negative sequence, each harmonic and the fundamental positive sequence component to obtain the observed error of the fundamental positive sequence component Observation error of fundamental positive sequence component For each reduced-order generalized integrator ROGI, the transfer function is The input of the integrator passes through multiple reduced-order generalized integrators ROGI and the transfer function is The grid voltage fundamental positive sequence component and error observer formed by the integrator of the grid voltage are observed to obtain the grid voltage fundamental positive sequence component observation value in the synchronous rotating coordinate system. and its observation error The transfer function of the reduced-order generalized integrator ROGI is Where s is the Laplace operator, ±ω n is the central angular frequency of the reduced-order generalized integrator ROGI, ω b is the bandwidth of the reduced-order generalized integrator ROGI; S32f calculates the observed value Conjugation 3. The method according to claim 2, characterized in that When sub-step S31a is executed, step S4 specifically includes: S41a will observe the error e dq Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e ; In this sub-step, the imaginary part x of the expression containing the angular frequency error information aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage; When sub-steps S31b to S34b, S31c to S35c, S31d to S34d, S31e and S32e, and S31f and S32f are executed, step S4 specifically includes: The observation error Multiply by the conjugate of the observation Get the expression containing the angular frequency error information, and replace the imaginary part x aI Multiplying with the normalization coefficient γ and the zero-pole cancellation transfer function f(s) yields the angular frequency error ω e ; In this sub-step, the imaginary part x of the expression containing the angular frequency error information aI equal The normalization coefficient γ is The transfer function f(s) used for zero-pole cancellation is U is the amplitude of the fundamental positive sequence component of the grid phase voltage.

4. The method according to claim 1, characterized in that Step S5 specifically includes: Based on the condition that the direct-axis component and quadrature-axis component of the grid voltage include phase angle error information, the direct-axis component u d Or the quadrature axis component u of the grid voltage q Multiply the proportional coefficient K of the outer phase-locked loop proportional controller as the phase angle control signal ε, or take the observed value of the direct axis component of the grid voltage Or the observed value of the quadrature axis component of the grid voltage Multiply the proportional coefficient K of the outer loop phase-locked loop proportional controller and the zero-pole cancellation transfer function f(s) as the phase angle control signal ε.

5. The method according to claim 1, characterized in that: Step S6 specifically includes: The angular frequency error ω e Added to the phase angle control signal ε, the added value is input into the transfer function: The integrator of The output value of the integrator is added to the rated angular frequency ω0 of the power grid to obtain the angular frequency observation value The angular frequency observation The input transfer function is The integrator outputs the phase angle observation value 6. The method according to claim 1, characterized in that There is also a design process of control parameters for implementing the method, which specifically includes: Set the phase-locked loop to the outer loop and the frequency-locked loop to the inner loop; The phase-locked loop of the outer loop adopts a proportional controller with a coefficient of K. The input of the phase-locked loop of the outer loop is a direct-axis component of the grid voltage or a quadrature-axis component of the grid voltage containing grid voltage phase angle error information. The output of the phase-locked loop of the outer loop is a phase angle control signal ε. The frequency-locked loop of the inner loop uses an integral controller with a proportional coefficient of d, and its transfer function is The input of the inner frequency-locked loop is the phase angle control signal ε plus the grid voltage angle frequency error signal ω e , where the grid voltage angular frequency error signal ω e Equal to the actual value of the grid voltage angular frequency ω minus the observed value of the grid voltage angular frequency The output of the inner frequency-locked loop is the observed value of the grid voltage angular frequency The angular frequency error ω e Add the phase angle control signal ε and input the added value into the inner loop of the frequency-locked loop transfer function: The integral controller is used to add the output value of the integrator to the rated angular frequency ω0 of the power grid to obtain the angular frequency observation value The rated angular frequency of the power grid ω0 is the observed value of the angular frequency of the frequency-locked loop The feedforward amount is used to improve the dynamic performance of the frequency-locked phase-locked loop response; Based on the angular frequency observations obtained The angular frequency observation The input transfer function is The integrator outputs the phase angle observation value The phase angle observation Multiplying by the amplitude U of the fundamental positive sequence component of the grid phase voltage, the grid voltage direct axis component or grid voltage quadrature axis component is obtained; Based on the principle of inner loop first and outer loop later, the open-loop transfer function of the inner frequency-locked loop is set as The closed-loop transfer function is calculated as By adjusting the parameter d of the inner frequency-locked loop integral controller, the bandwidth and phase angle stability domain of the inner frequency-locked loop closed-loop transfer function are changed, and then the loop response characteristics of the inner frequency-locked loop are designed; by setting the open-loop transfer function of the outer phase-locked loop to The closed-loop transfer function is calculated as By adjusting the parameter K of the outer phase-locked loop proportional controller, the bandwidth and phase angle stability domain of the outer phase-locked loop closed-loop transfer function are changed, and then the loop response characteristics of the outer phase-locked loop are designed.

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