CN114123346B - A general-purpose DFF-SAI phase-locking method in positive sequence rotating coordinate system - Google Patents

Abstract

The present invention relates to the technical field of power grid synchronous tracking, in particular to a general-purpose DFF-SAI phase-locking method under a positive sequence rotating coordinate system to extract three-phase voltages; the three-phase voltages are subjected to Clark transformation and T' transformation to obtain multiple harmonics The d', q' components of the signal; pass the d', q' components through the DFF-SAI unit to obtain the positive sequence multiple harmonic signal; perform Park transformation on the positive sequence multiple harmonic signal to obtain the dq in the positive sequence rotating coordinate system axis component; use the q -axis component to pass through the phase-locking link to obtain the angular frequency and phase angle of the double harmonic signal; the angular frequency of the double harmonic signal is used as the angular frequency given value of the DFF-SAI unit; according to the d -axis component, multiple The frequency and phase angle of the sub-harmonic signal determine the amplitude, frequency and phase angle information of the positive sequence component of the fundamental wave of the power grid; this method realizes the precise locking of the double harmonic signal and the positive sequence component of the fundamental wave. Ideal conditions apply.

Description

A general-purpose DFF-SAI phase-locking method in positive sequence rotating coordinate system

technical field

The invention relates to the technical field of power grid synchronous tracking, in particular to a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system.

Background technique

The grid synchronization technology can track and lock the phase of the AC signal, and when necessary, can also provide synchronization information such as the frequency and amplitude of the signal. It is a key technology for tracking and locking the grid when the converter is connected to the grid. Grid synchronization technology includes zero-crossing detection technology, grid synchronization technology based on discrete Fourier transform, grid synchronization technology based on neural network, recursive weighted least squares estimation algorithm, Kalman filter technology, frequency locking technology and phase locking technology.

At present, the most widely used power grid synchronization technology is phase-locking technology. Phase-locking technology includes open-loop phase-locking method and closed-loop phase-locking method. Because the open-loop phase-locking method has low phase-locking accuracy, slow response speed, and sensitivity to non-ideal power grids, etc. Therefore, in the actual grid-connected application of the converter, the closed-loop phase-locking method is usually adopted. In view of the importance of the closed-loop phase-locked loop, more and more scholars have conducted research on it, and proposed many control and design schemes of the closed-loop phase-locked loop, so that the performance of the phase-locked loop has been continuously improved and promoted.

In the grid balance condition, the most widely used closed-loop phase-locked loop method is the traditional synchronous rotating frame phase-locked loop (synchronous rotating frame phase locked loop, SRF-PLL) method. When the grid is in a balanced condition, the grid voltage only has positive sequence components. At this time, the traditional SRF-PLL can accurately track the synchronization signal of the grid voltage. When the grid is in an unbalanced condition, due to the introduction of negative sequence components, Traditional SRF-PLL is difficult to achieve satisfactory results. In order to deal with unbalanced power grid conditions, many phase-locked loop methods have been proposed, including improved SRF-PLL with filter, enhanced phase-locked loop (Enhanced PLL, EPLL), decoupled dual synchronous reference frame phase-locked loop (Decoupled Double Synchronous Reference Frame PLL, DDSRF-PLL), phase-locked loop (Multiple Reference Frame PLL, MRF-PLL) based on multiple reference coordinate systems, phase-locked loop (Adaptive Notch Filter PLL) based on adaptive notch filter, ANF-PLL), dual second-order generalized integrator-based phase-locked loop (Dual SecondOrder Generalized Integrator PLL, DSOGI-PLL), delayed signal-based phase-locked loop (DelayedSignal Cancellation PLL, DSC-PLL), based on sine amplitude Integrator phase-locked loop (SinusoidalAmplitude Integrator PLL, SAI-PLL), complex filter-based phase-locked loop (Complex CoefficientFilter PLL, CCF-PLL), moving average filter-based phase-locked loop (Moving Average Filters PLL, MAF -PLL), phase-locking method based on Tan-Sun coordinate transformation.

In order to improve the accuracy and rapidity of the phase-locked loop tracking the synchronization signal of the power grid, the present invention proposes a general-purpose DFF-SAI phase-locking method in the positive sequence rotating coordinate system. The method proposed in the present invention is based on the positive sequence rotating coordinate system. The DFF-SAI unit is used to extract the positive-sequence multiple harmonic components, and then to achieve multiple frequency phase-locking. Among them, the DFF-SAI unit uses the angular frequency of the multiple harmonic components obtained in the proposed method as the required angular frequency Compared with the traditional SAI unit, the DFF-SAI unit can quickly and accurately realize the extraction of positive sequence multiple harmonic components. In addition, the method proposed in the present invention can not only quickly and accurately track the synchronization signal of the grid voltage under balanced working conditions, but also can quickly and accurately track the synchronization signal of the grid voltage under the conditions of unbalanced three-phase, voltage single-phase amplitude drop or sudden rise, grid single-phase loss, and phase angle sudden change. Under non-ideal power grid conditions, it can also quickly and accurately obtain the synchronization signal of the grid voltage, which greatly broadens the application range of the phase-locked loop and improves the accuracy and rapidity of tracking the grid synchronization signal.

For example, the 2-fold frequency phase-locking method disclosed in Chinese invention patent CN201510050220.X is based on two band-pass filters to extract the 2-fold frequency AC quantity and then realize 2-fold frequency phase-locking, which is different from the DFF- The basic principles of the multiplication and phase-locking method of the SAI unit are different.

Another example, the 2-fold frequency phase-locking method disclosed in the paper "2-fold frequency grid synchronization phase-locking method based on second-order generalized integrator SOGI when the power grid voltage is unbalanced" is based on the optimized SOGI-QSG for 2-fold frequency AC The basic principle of extracting and then realizing phase locking is different from the frequency multiplication phase locking method using DFF-SAI unit proposed by the present invention.

Another example, in the paper "A New Double Frequency Phase Locking Technology Based on Sine Amplitude Integrator", the disclosed double frequency phase lock method is based on the negative rotating coordinate system, and the cascaded SOGI and SAI are used to complete the double frequency lock However, the phase-locking method proposed by the present invention is based on the positive-sequence rotating coordinate system, and only uses the DFF-SAI positive and negative sequence separation and extraction links to complete frequency multiplication phase-locking. The basic principles of the two are different, and The method proposed in this patent has simple structure and good rapidity.

The positive-sequence rotating coordinate system, SAI unit, and positive-negative sequence separation and extraction of the present invention are common knowledge in the field of phase-locking technology. The present invention does not apply for protection of these individual links, but applies for protection of these links and is composed of these links The basic principle of the multiplier phase-locked loop method proposed by the present invention is different from other traditional phase-locked loop methods, and also different from the basic principle of the above-mentioned disclosed phase-locked method.

Contents of the invention

The purpose of the present invention is to provide an ideal and non-ideal power grid common to grid voltage balance, grid voltage unbalance, grid voltage single-phase amplitude drop or sudden rise, grid voltage single-phase loss and phase angle sudden change based on positive sequence The rotating coordinate system adopts the frequency multiplication phase-locked loop method of the DFF-SAI unit, which can quickly and accurately track the synchronization signal of the grid voltage and realize phase synchronization with the grid voltage.

To achieve the above object, the present invention provides the following technical solutions:

A general-purpose DFF-SAI phase-locking method under a positive-sequence rotating coordinate system, comprising the following steps:

Step 1: Obtain the voltage signal of the three-phase grid;

Step 2: Obtain the double harmonic component signal, construct a new transformation matrix T' and construct a new coordinate system dq' coordinate system to realize the acquisition of the double harmonic signal, use the transformation matrix T', according to the three-phase The grid voltage is transformed from the three-phase static abc coordinate system to the dq' coordinate system, and the d' axis voltage component v _d ' and the q' axis voltage component v _q ' including the harmonic component of the multiple are obtained, and the transformation matrix T' is

Step 3: Extract the positive sequence multiple harmonic component signal; according to the d' axis voltage component v _d ' and the q' axis voltage component v _q ' containing the multiple harmonic component, use DFF-SAI and positive and negative sequence separation extraction units , to separate and extract positive sequence multiple harmonic components;

Step 4: Obtain the positive-sequence dq-axis components in the positive-sequence rotating coordinate system; according to the positive-sequence multiple harmonic components, after Park transformation, the d-axis voltage component v _d and the q-axis voltage component in the positive-sequence dq rotating coordinate system are obtained _vq ;

Step 5: Obtain the angular frequency of the double harmonic and the phase synchronization information corresponding to the double harmonic, and use the phase-locked loop to lock the double harmonic according to the q-axis voltage component v _q in the positive sequence dq rotating coordinate system The angular frequency and the phase angle synchronization information corresponding to the double harmonic can realize the tracking and locking of the double harmonic component; the double harmonic angular frequency is used as the angular frequency required by the DFF-SAI unit; the double harmonic frequency The corresponding phase angle is the transformation angle, which is used as the transformation angle for Park transformation when obtaining the positive sequence dq axis components;

Step 6: Obtain the synchronization information of the amplitude, phase and frequency of the positive sequence component of the fundamental wave of the power grid; according to the d-axis voltage component v _d in the positive sequence dq rotating coordinate system, the synchronization information of the amplitude of the positive sequence component of the fundamental wave of the power grid can be obtained ;According to the double harmonic angular frequency and the phase angle corresponding to the double harmonic frequency, the synchronization information of the frequency and phase angle of the fundamental positive sequence component of the power grid can be obtained; the phase angle of the positive sequence component of the fundamental wave of the power grid is used to determine the multiple harmonic The transformation angle of the d' axis voltage component v _d ' and the q' axis voltage component v _q ' of the signal; that is, the transformation angle of the transformation matrix T'; according to the amplitude, phase and frequency of the positive sequence component of the fundamental wave of the power grid Synchronization information to realize the tracking and locking of the positive sequence component of the fundamental wave, so as to realize the signal synchronization of ideal and non-ideal power grids.

The further improvement of the technical solution of the present invention lies in: in step 2, a novel matrix T' is constructed, which can convert the positive-sequence component of the unbalanced three-phase voltage into a positive-sequence frequency-doubled AC quantity, that is, a positive-sequence doubled harmonic component; Specifically include:

The three-phase grid voltage signal [v _a v _b v _c ] ^T is multiplied by the T _abc/αβ matrix to the left, and the three-phase grid voltage vector is transformed from the three-phase static abc coordinate system to the two-phase static αβ coordinate system, and the αβ coordinate system is obtained The two-phase AC voltage v _α and v _β ;

Taking the phase angle of the positive sequence component of the fundamental wave of the power grid as the transformation angle, T' transformation is performed on the two-phase AC voltage v _α and v _β in the αβ coordinate system to obtain the d' axis voltage component v _d ' containing the multiple harmonic component and q' axis voltage component v _q ';

The transformation matrix T _abc/αβ of the three-phase stationary abc coordinate system to the two-phase stationary αβ coordinate system is

The further improvement of the technical solution of the present invention lies in: in step 3, the positive-sequence multiple harmonic component is extracted to complete frequency-multiplication phase-locking. After the voltage of the three-phase grid is transformed by T', the positive-sequence component including the voltage positive-sequence component can be obtained. The two-phase voltage v' _d and v' _q of the DC component converted into the double harmonic component and the negative sequence component of the voltage, in order to extract the positive sequence component double harmonic component, the v' _d and v' _q are passed through the DFF -SAI positive and negative sequence extraction and separation unit is enough, and then use the positive sequence component multiple harmonic components to complete phase locking; specifically include:

The d' axis voltage component v _d ' and the q' axis voltage component v _q ' containing the multiple harmonic components are used as the input signal of the DFF-SAI unit, and the AC quantities v _dt ' and v _qt ' are output through the DFF-SAI unit, The AC quantities v _dt ' and v _qt ' include: the same AC component as the input AC component and a DC component linearly related to the input DC component, and the DFF-SAI unit makes full use of the angular frequency of the obtained double harmonic signal, The angular frequency is used as the given amount of the angular frequency required by the DFF-SAI unit, so that the DFF-SAI unit can quickly and accurately realize the extraction of positive sequence multiple harmonic components;

Take the alternating current v _dt ' and v _qt ' as the input of the positive and negative sequence separation and extraction unit, and output the alternating current v _dac ' and v _qac ' and the direct current v _ddc ' and v _qdc ' through the positive and negative sequence separation and extraction unit , AC quantities v _dac ' and v _qac ' are positive-sequence multiple harmonic components, and DC quantities v _ddc ' and v _qdc ' are negative-sequence DC components.

The further improvement of the technical solution of the present invention lies in: in step 5, for the tracking and locking of the multiplier harmonic signal, according to the q-axis voltage component v _q , the phase-locked loop can be used to lock the angle of the multiplier harmonic The phase angle synchronization information corresponding to the frequency and the multiple harmonics realizes the tracking and locking of the multiple harmonic components; specifically includes:

The q-axis voltage component v _q under the positive sequence dq rotating coordinate system is used as the input signal, and after passing through the PI regulator, it is added to 200π to determine the angular frequency of the double harmonic component;

After the multiple harmonic angular frequency is integrated, the remainder is processed with 2π to determine the phase angle corresponding to the multiple harmonic frequency.

The further improvement of the technical solution of the present invention lies in: in step 6, the tracking and locked multiplier phase-locking of the fundamental wave positive sequence component of the power grid, and obtaining the synchronous information of the amplitude of the fundamental positive sequence component of the power grid according to the d-axis voltage component v _d , according to the multiple harmonic angular frequency and the phase angle corresponding to the multiple harmonic frequency, the synchronization information of the frequency and phase angle of the positive sequence component of the fundamental wave of the power grid can be obtained; specifically include:

According to the d-axis voltage component v _d in the positive sequence dq rotating coordinate system as the output signal, the amplitude information of v _d can represent the amplitude information of the positive sequence component of the fundamental wave of the power grid, that is, the amplitude of the output signal v _d can achieve tracking The purpose of synchronizing information on the magnitude of the positive sequence component of the fundamental wave of the power grid;

After the angular frequency of the double harmonic is calculated by 1/2, the angular frequency information of the positive sequence component of the fundamental wave of the power grid is determined;

After the angular frequency of the positive sequence component of the fundamental wave of the power grid is integrated, it is processed with 2π to determine the phase angle information of the positive sequence component of the fundamental wave of the power grid.

Compared with the prior art, the invention provides a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system, which has the following beneficial effects:

1. The present invention provides a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system. Under the positive-sequence rotating coordinate system, the double harmonic signal is obtained by constructing a transformation matrix T', and the DFF-SAI positive The sequence negative separation and extraction unit can extract the positive sequence double harmonic signal, and use the phase locking link to realize the acquisition of the frequency and phase angle information of the double harmonic signal, and realize the tracking and locking of the double harmonic signal; In this process, by tracking the multiple harmonic signal, the synchronization information of the amplitude, frequency and phase of the positive sequence fundamental component of the power grid can be obtained, and the tracking and locking of the positive sequence fundamental component of the power grid can be realized to achieve phase synchronization with the grid voltage the goal of.

2. The present invention provides a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system. The phase-locked loop method is based on double-order harmonic signals to perform frequency phase-locking to track and lock the grid voltage, which is different from traditional Compared with the phase-locking method based on the fundamental frequency signal, this method has fast transient response and good accuracy; the phase-locking method adopts DFF-SAI positive and negative sequence separation and extraction in the positive sequence rotating coordinate system The unit obtains the positive-sequence multiple harmonic signal to realize frequency multiple phase-locking. This method has simple results and a small amount of calculation.

3. The present invention provides a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system. This method is not only suitable for ideal grid conditions, but also suitable for grid voltage imbalance, single-phase amplitude drop or sudden rise of grid voltage , single-phase loss of grid voltage and non-ideal grid conditions with sudden phase angle changes. Quickly and accurately obtain the synchronization information of the grid voltage to achieve phase synchronization with the grid voltage.

4. The present invention provides a general-purpose DFF-SAI phase-locking method in a positive-sequence rotating coordinate system. This method generates frequency-multiplied AC volumes after coordinate transformation of unbalanced three-phase voltages, that is, double-order harmonic components. Traditional phase-locked The method is to filter out or discard the multiple harmonic components, but the present invention uses the multiple harmonic components to complete frequency phase locking, and quickly and accurately lock the multiple harmonic angular frequency and fundamental wave of the grid voltage. Angular frequency, to obtain the synchronous information of the amplitude, frequency and phase of the grid voltage, to achieve phase synchronization with the grid voltage; this method is not only applicable to non-ideal grid conditions, but also to ideal grid conditions, including grid voltage balance, grid Voltage imbalance, grid voltage single-phase amplitude drop or sudden rise, grid single-phase loss and phase angle jump working conditions.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a structural block diagram of the frequency multiplication phase-locking method proposed in the present invention.

Fig. 2 is the structural block diagram of traditional SRF-PLL.

Fig. 3 is a structural block diagram of the double-frequency phase-locking method based on optimized SOGI-QSG.

FIG. 4 is a structural block diagram of a 2-fold frequency phase-locking method based on cascaded SOGI and SAI.

Fig. 5 is a structural block diagram of the DFF-SAI unit in the method proposed by the present invention.

Fig. 6 is a structural block diagram of the positive and negative sequence extraction and separation unit in the method proposed by the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below through specific embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

As shown in Figure 1, the overall structure diagram of the frequency multiplication phase-locking method of the present invention is provided, and the main steps are the extraction of the three-phase grid voltage, Clark transformation, T' transformation, DFF-SAI unit, positive and negative sequence separation and extraction links, Park transformation, phase-locking link. Among them, the phase-locking link obtains the frequency of the double harmonic signal as the frequency information required by the DFF-SAI unit, and the double harmonic frequency is integrated to obtain the corresponding phase angle of the double harmonic as the transformation angle of the Park transform. The frequency of the wave signal is multiplied by 1/2 to obtain the frequency information of the positive sequence component of the fundamental wave of the power grid, and the frequency of the positive sequence component of the fundamental wave is integrated to obtain its corresponding phase angle as the transformation angle of the T' transformation.

A general-purpose DFF-SAI phase-locking method under a positive-sequence rotating coordinate system, comprising the following steps:

Step 1: Obtain the voltage signal of the three-phase grid;

传统的获取倍次谐波分量的方法包括傅里叶分解方法以及快速傅里叶分解方法。Step 2: Obtain the double harmonic component signal; different from the traditional method of obtaining the double harmonic component, a new transformation matrix T' and a new coordinate system dq' coordinate system are used to realize the double harmonic Wave signal acquisition. Using the transformation matrix T', according to the three-phase grid voltage, transform from the three-phase static abc coordinate system to the dq' coordinate system, and obtain the d' axis voltage component v _d ' and the q' axis voltage component v _q including the multiple harmonic components ', the transformation matrix T' is

Traditional methods for obtaining multiple harmonic components include Fourier decomposition methods and fast Fourier decomposition methods.

The three-phase grid voltage signal [v _a v _b v _c ] ^T is multiplied by the T _abc/αβ matrix to the left, and the three-phase grid voltage vector is transformed from the three-phase static abc coordinate system to the two-phase static αβ coordinate system, and the αβ coordinate system is obtained The two-phase AC voltage v _α and v _β , where _Tabc/αβ is

变换角度/>

为电网基波正序分量对应的相角。T' transformation is performed on the two-phase AC voltages v _α and v _β in the αβ coordinate system, that is, [v _α v _β ] ^T is multiplied by the T' matrix to the left, and the d' axis voltage component v _d ' containing the double harmonic component is obtained and q'-axis voltage component v _q ', where T' is

change angle />

is the phase angle corresponding to the positive sequence component of the fundamental wave of the power grid.

Step 3: Extract the positive sequence multiple harmonic component signal; according to the d' axis voltage component v _d ' and the q' axis voltage component v _q ' containing the multiple harmonic component, use DFF-SAI and positive and negative sequence separation extraction units , to separate and extract positive sequence multiple harmonic components.

The d' axis voltage component v _d ' and the q' axis voltage component v _q ' containing the multiple harmonic components are used as the input signal of the DFF-SAI unit, and the AC quantities v _dt ' and v _qt ' are output through the DFF-SAI unit, The AC quantities v _dt ' and v _qt ' include: an AC component identical to the input AC component and a DC component linearly related to the input DC component;

Take the alternating current v _dt ' and v _qt ' as the input of the positive and negative sequence separation and extraction unit, and output the alternating current v _dac ' and v _qac ' and the direct current v _ddc ' and v _qdc ' through the positive and negative sequence separation and extraction unit , AC quantities v _dac ' and v _qac ' are positive-sequence multiple harmonic components, and DC quantities v _ddc ' and v _qdc ' are negative-sequence DC components.

Step 4: Obtain the positive-sequence dq-axis components in the positive-sequence rotating coordinate system; according to the positive-sequence multiple harmonic components, after Park transformation, the d-axis voltage component v _d and q-axis voltage in the positive-sequence dq rotating coordinate system can be obtained Component v _q .

变换角度/>

为倍次谐波信号对应的相角。Take the positive sequence multiple harmonic components v _dac ' and v _qac ' as input signals, after Park transformation, that is, the positive sequence multiple harmonic component [v _dac 'v _qac '] ^T left multiplied T _αβ/dq matrix , to obtain the d-axis voltage component v _d and the q-axis voltage component v _q in the positive sequence dq rotating coordinate system, the T _αβ/dq matrix is

Transform angle />

is the phase angle corresponding to the double harmonic signal.

Step 5: Obtain the angular frequency of the double harmonic and the phase synchronization information corresponding to the double harmonic; according to the q-axis voltage component v _q in the positive sequence dq rotating coordinate system, the double harmonic can be locked by using the phase-locked loop The angular frequency and the phase angle synchronization information corresponding to the double harmonic can realize the tracking and locking of the double harmonic component; the double harmonic angular frequency is used as the angular frequency required by the DFF-SAI unit; the double harmonic frequency The corresponding phase angle is the transformation angle, which is used as the transformation angle for Park transformation when obtaining the positive sequence dq axis components.

The q-axis voltage component v _q under the positive sequence dq rotating coordinate system is used as the input signal, and after passing through the PI regulator, it is added to 200π to determine the angular frequency of the double harmonic component;

After the multiple harmonic angular frequency is integrated, it is processed with 2π to determine the phase angle corresponding to the multiple harmonic frequency;

Step 6: Obtain the synchronization information of the amplitude, phase and frequency of the positive sequence component of the fundamental wave of the power grid; according to the d-axis voltage component v _d in the positive sequence dq rotating coordinate system, the synchronization information of the amplitude of the positive sequence component of the fundamental wave of the power grid can be obtained ;According to the double harmonic angular frequency and the phase angle corresponding to the double harmonic frequency, the synchronization information of the frequency and phase angle of the fundamental positive sequence component of the power grid can be obtained; the phase angle of the positive sequence component of the fundamental wave of the power grid is used to determine the multiple harmonic The transformation angle of the d' axis voltage component v _d ' and the q' axis voltage component v _q ' of the signal; according to the synchronization information of the amplitude, phase and frequency of the fundamental positive sequence component of the power grid, the positive sequence of the fundamental wave can be realized component tracking and locking; according to the d-axis voltage component v _d in the positive sequence dq rotating coordinate system as the output signal, the amplitude information of v _d can represent the amplitude information of the positive sequence component of the fundamental wave of the power grid, that is, through the output signal v The amplitude of _d can achieve the purpose of tracking the synchronization information of the magnitude of the positive sequence component of the fundamental wave of the power grid; after the angular frequency of the double harmonic is calculated by 1/2, the angular frequency information of the positive sequence component of the fundamental wave of the power grid can be determined; After the angular frequency of the positive sequence component of the fundamental wave of the power grid is integrated, it is processed with 2π to determine the phase angle information of the positive sequence component of the fundamental wave of the power grid.

As shown in Figure 2, it is a traditional SRF-PLL structure diagram. The main steps are to extract the three-phase grid voltage, and transform the three-phase voltage vector from the three-phase stationary abc coordinate system to the two-phase rotating dq through Clark transformation and Park transformation In the coordinate system, the d-axis voltage component and the q-axis voltage component are obtained. The output of the q-axis passes through the PI regulator to obtain the frequency information of the grid voltage. Voltage tracking and locking. The phase-locking method shown in Figure 2 uses the fundamental frequency signal to complete the phase-locking, while the method proposed in this patent obtains the double harmonic signal by constructing the transformation matrix T' and performs frequency-multiple phase-locking based on the double harmonic signal , and finally realize the tracking and locking of the positive sequence fundamental wave component of the grid voltage, the two are quite different. Compared with the traditional SRF-PLL, the method proposed in this patent has fast transient response speed, good accuracy, and wide application range. It is not only suitable for ideal grid conditions, but also suitable for grid voltage unbalance and single-phase amplitude drop of grid voltage. Non-ideal grid conditions such as sudden rise, grid voltage single-phase loss, and phase angle mutation conditions.

As shown in Figure 3, it is a structural block diagram of the 2-fold frequency phase-locking method based on the optimized SOGI-QSG. The main steps are to extract the three-phase voltage and perform Clark transformation to obtain the two-phase AC voltage v _α and v _β in the αβ coordinate system; Then perform T' ₊ transformation to obtain two-phase voltages v' _d and v' _q containing double harmonic components; after optimized SOGI-QSG processing, two perfectly orthogonal double harmonic signals are obtained, and then Park Transform to obtain the dq-axis voltage component in the dq coordinate system. At this time, the output of the q-axis passes through the PI regulator to obtain the angular frequency information of the double harmonic, and then perform integral operations to obtain the phase angle corresponding to the double harmonic signal information, and after 1/2 processing, the phase angle information of the positive sequence component of the fundamental wave of the power grid can be obtained. The 2-fold frequency phase-locking method shown in Figure 3 belongs to the research results of this research group. It is based on the 2-fold frequency phase-locking idea and method proposed based on the multiple harmonic signal. The phase-locking method proposed in this patent is also based on the multiple The frequency multiplication phase-locking method proposed by the harmonic signal, however, the method shown in Figure 3 is proposed based on the optimized SOGI-QSG, and the method proposed in this patent is to use the DFF-SAI positive and negative sequence separation and extraction unit to extract the positive sequence multiple harmonic wave component and complete phase-locking, which is different from the basic principle of the method shown in Figure 3; in addition, compared with the method shown in Figure 3, the method proposed in this patent has a wide range of applications, not only for ideal grid conditions, but also It is suitable for non-ideal grid conditions such as grid voltage unbalance, grid voltage single-phase amplitude drop or sudden rise, grid voltage single-phase loss, and phase angle sudden change.

As shown in Figure 4, it is a structural block diagram of the 2-fold frequency phase-locking method based on cascaded SOGI and SAI. The main steps are to extract the three-phase voltage and perform Clark transformation to obtain the two-phase AC voltage v _α and v in the αβ coordinate system _β ; filter v _α and v _β through cascaded SOGI to obtain relatively pure two-phase AC quantities v' _α and v'_β; then transform v' _α and v' _β through negative sequence rotation coordinates to obtain negative sequence The dq axis voltage components v' _d and v' _q in the dq rotating coordinate system, where v' _d and v' _q contain multiple harmonic components; then v' _d and v' _q are separated and extracted by SAI positive and negative sequences The unit obtains the positive sequence components v _dac and v _qac and the negative sequence components v _ddc and v _qdc ; finally, the phase locking link is used to track and lock the multiple harmonic components and the positive sequence components of the fundamental wave of the grid. The double-frequency phase-locking method shown in Figure 4 belongs to the research results of this research group. It is based on the idea and method of double-frequency phase-locking proposed based on the double-order harmonic signal. The phase-locking method proposed in this patent is also based on the double-order The frequency multiplication phase-locking method proposed by the harmonic signal, however, the method shown in Figure 4 is based on the cascaded SOGI and SAI positive and negative sequence separation and extraction units in the negative sequence rotating coordinate system. The method proposed in this patent is based on The positive sequence rotating coordinate system only uses the DFF-SAI positive and negative sequence separation and extraction unit to extract positive sequence multiple harmonic components and complete phase locking, which is different from the basic principle of the method proposed in Figure 4; Compared with the method shown in the patent, the method proposed in this patent has a simple and compact structure, a small amount of calculation, and a fast transient response.

As shown in Figure 5, it is a structural block diagram of the DFF-SAI unit in the method proposed by the present invention. In this method, after the three-phase voltage is transformed by T', the two-phase AC voltage v' _d and v containing the double harmonic signal are obtained. ' _q , using v' _d and v' _q as the input signal of the DFF-SAI unit can realize no static error tracking of positive sequence multiple harmonic components, and achieve positive sequence multiple harmonic components and negative sequence DC components purpose of extraction. In addition, the DFF-SAI unit makes full use of the angular frequency of the double harmonic signal obtained in the method proposed in this patent, and uses the angular frequency as the given amount of the angular frequency required by the DFF-SAI unit. Compared with the traditional SAI unit, The DFF-SAI unit can quickly and accurately realize the extraction of positive sequence multiple harmonic components.

As shown in Figure 6, it is a structural block diagram of the positive and negative sequence separation and extraction unit in the method proposed by the present invention. In the proposed method, the positive sequence of the two-phase voltages v' _d and v' _q can be multiplied by the positive and negative sequence separation and extraction unit. The sub-harmonic component is separated from the negative-sequence DC component, and the positive-sequence multiple harmonic components v _dac ' and v _qac ' and the negative-sequence DC components v _ddc ' and v _qdc ' are obtained, so that the positive sequence multiple harmonic components can be further utilized Perform multiplier phase lock.

The above-mentioned embodiments are only descriptions of preferred implementations of the present invention, and are not intended to limit the scope of the present invention. All these variations and improvements should fall within the scope of protection defined by the claims of the device of the present invention.

Claims (5)

1. The universal DFF-SAI phase locking method under the positive sequence rotation coordinate system is characterized by comprising the following steps:

step 1: acquiring a three-phase power grid voltage signal;

step 2: acquiring a harmonic component signal; constructing a new transformation matrix T ' and a new coordinate system dq ' to acquire the harmonic signals, and transforming the transformation matrix T ' from a three-phase static abc coordinate system to the dq ' coordinate system according to the three-phase grid voltage to obtain a d ' axis voltage component v containing the harmonic components _d 'and q' axis voltage component v _q 'transform matrix T' is

Step 3: extracting positive sequence multiple harmonic component signals; according to the d' axis voltage component v containing the harmonic component _d 'and q' axis voltage component v _q ' separating and extracting positive sequence multiple harmonic components by using a DFF-SAI and a positive and negative sequence separation and extraction unit;

step 4: acquiring a positive sequence dq axis component under a positive sequence rotation coordinate system; according to the positive order multiple harmonic component, obtaining a d-axis voltage component v under a positive order dq rotating coordinate system through Park transformation _d And q-axis voltage component v _q ；

Step 5: acquiring phase synchronization information corresponding to the angular frequency of the harmonic wave; the q-axis voltage component v in the coordinate system is rotated according to the positive sequence dq _q The phase-locked loop can be used for locking the angular frequency of the harmonic wave and the phase angle synchronous information corresponding to the harmonic wave, so that the tracking and locking of the harmonic wave component are realized; the harmonic angular frequency is used as the angular frequency required by the DFF-SAI unit; the phase angle corresponding to the multiple harmonic frequency is a transformation angle, and the transformation angle is used for Park transformation when the positive sequence dq axis component is acquired;

step 6: acquiring the synchronous information of the amplitude, the phase and the frequency of the fundamental wave positive sequence component of the power grid; according to the positive sequenced-axis voltage component v in dq rotation coordinate system _d The synchronous information of the amplitude of the fundamental wave positive sequence component of the power grid can be obtained; according to the frequency of the harmonic wave angle and the phase angle corresponding to the harmonic wave frequency, the synchronous information of the frequency and the phase angle of the positive sequence component of the fundamental wave of the power grid can be obtained; phase angle of positive sequence component of fundamental wave of power grid as d' axis voltage component v of determined subharmonic signal _d 'and q' axis voltage component v _q ' transformation angle at time; i.e. the transformation angle of the transformation matrix T'; according to the obtained synchronous information of the amplitude, the phase and the frequency of the fundamental wave positive sequence component of the power grid, the tracking and the locking of the fundamental wave positive sequence component are realized, and therefore the signal synchronization of an ideal power grid and a non-ideal power grid is realized.

2. The method for phase locking of a universal DFF-SAI in a positive rotation coordinate system according to claim 1, wherein: in the step 2, a novel matrix T' is constructed, and the matrix can convert the unbalanced three-phase voltage positive sequence component into positive sequence frequency multiplication alternating current quantity, namely positive sequence subharmonic component; the method specifically comprises the following steps:

by means of a three-phase network voltage signal v _a v _b v _c ] ^T Left-hand T _abc/αβ Matrix, transforming the three-phase power grid voltage vector from the three-phase static abc coordinate system to the two-phase static alpha beta coordinate system to obtain the two-phase alternating voltage v under the alpha beta coordinate system _α And v _β ；

The phase angle of the positive sequence component of the fundamental wave of the power grid is used as a transformation angle for the two-phase alternating current voltage v under an alpha beta coordinate system _α And v _β T 'transforming to obtain d' axis voltage component v containing multiple harmonic component _d 'and q' axis voltage component v _q '；

Transformation matrix T for transforming three-phase static abc coordinate system into two-phase static alpha beta coordinate system _abc/αβ Is that

3. The method for phase locking of universal DFF-SAI in a positive rotation coordinate system as recited in claim 1, wherein the method comprises the steps of: in step 3, positive sequence harmonic components are extracted to complete frequency multiplication phase locking, and after the three-phase power grid voltage is subjected to T ' transformation, a two-phase voltage v ' containing positive sequence harmonic components converted from voltage positive sequence components and direct current components converted from voltage negative sequence components is obtained ' _d And v' _q To extract the positive sequence component and the subharmonic component, v 'is calculated' _d And v' _q The phase locking is finished by using the positive sequence component and the negative sequence component of the DFF-SAI through a positive sequence extraction and separation unit; the method specifically comprises the following steps:

the d' axis voltage component v containing the harmonic component _d 'and q' axis voltage component v _q ' as an input signal to the DFF-SAI unit, an alternating current quantity v is output through the DFF-SAI unit _dt ' and v _qt ' AC quantity v _dt ' and v _qt ' comprising: the DFF-SAI unit fully utilizes the angular frequency of the obtained multiple harmonic signal, and takes the angular frequency as a given quantity of the angular frequency required by the DFF-SAI unit, so that the DFF-SAI unit can rapidly and accurately extract the positive sequence multiple harmonic component;

traffic volume v _dt ' and v _qt ' as input quantity of positive and negative sequence separation and extraction unit, output alternating current quantity v through positive and negative sequence separation and extraction unit _dac ' and v _qac ' and DC quantity v _ddc ' and v _qdc ' AC quantity v _dac ' and v _qac ' is positive order multiple harmonic component, DC quantity v _ddc ' and v _qdc ' is a negative sequence direct current component.

4. The method for phase locking of a universal DFF-SAI in a positive rotation coordinate system according to claim 1, wherein: in step 5, the tracking and locking of the harmonic signal are frequency-doubled and phase-locked according to the q-axis voltage component v _q The phase-locked loop can be used for locking the angular frequency of the harmonic wave and the phase angle synchronous information corresponding to the harmonic wave, so that the tracking and locking of the harmonic wave component are realized; the method specifically comprises the following steps:

the q-axis voltage component v in the positive sequence dq rotation coordinate system _q As input signal, through PI regulator, adding with 200 PI to determine angular frequency of harmonic component;

and (3) integrating the harmonic angular frequency, then performing remainder processing with 2 pi, and determining a phase angle corresponding to the harmonic frequency.

5. The method for phase locking of a universal DFF-SAI in a positive rotation coordinate system according to claim 1, wherein: in step 6, tracking and locking the positive sequence component of the fundamental wave of the power grid are locked by frequency multiplication according to the voltage component v of the d axis _d The synchronous information of the amplitude of the positive sequence component of the fundamental wave of the power grid is obtained, and the synchronous information of the frequency and the phase angle of the positive sequence component of the fundamental wave of the power grid can be obtained according to the angular frequency of the harmonic wave and the phase angle corresponding to the frequency of the harmonic wave; the method specifically comprises the following steps:

the d-axis voltage component v in the coordinate system is rotated according to the positive sequence dq _d As an output signal v _d Is representative of the amplitude information of the positive sequence component of the fundamental wave of the network, i.e. by the output signal v _d The amplitude of the positive sequence component of the fundamental wave of the power grid is tracked;

after 1/2 operation is carried out on the angular frequency of the multiple harmonic wave, determining the angular frequency information of the positive sequence component of the fundamental wave of the power grid;

and (3) carrying out integral operation on the angular frequency of the positive sequence component of the fundamental wave of the power grid, and then carrying out remainder taking processing on the angular frequency and 2 pi, so as to determine the phase angle information of the positive sequence component of the fundamental wave of the power grid.

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