阅读说明：本技术 一种单相频率自适应锁相环 (Single-phase frequency self-adaptive phase-locked loop ) 是由 杨仁增 张良 肖迎群 于 2020-05-14 设计创作，主要内容包括：本发明公开的一种单相频率自适应锁相环,包括消除直流偏置模块、正交信号生成模块、正序基波信号分离模块、正序基波信号锁相模块,所述消除直流偏置模块、正交信号生成模块、正序基波信号分离模块、正序基波信号锁相模块基于采用广义二阶积分器设计的频率自适应滤波器,可从谐波畸变严重的两路正交电网信号中分离出电网基波正序分量,并抑制两路正交信号可能的不平衡问题对锁相环相角与频率检测误差的影响,滤波器参数的整定简洁方便,可提高锁相环的相角检测精度,可消除电网及并网变流器中不易解决的直流偏置问题。(The invention discloses a single-phase frequency self-adaptive phase-locked loop, which comprises a direct current bias eliminating module, an orthogonal signal generating module, a positive sequence fundamental wave signal separating module and a positive sequence fundamental wave signal phase-locked module, wherein the direct current bias eliminating module, the orthogonal signal generating module, the positive sequence fundamental wave signal separating module and the positive sequence fundamental wave signal phase-locked module are based on a frequency self-adaptive filter designed by adopting a generalized second-order integrator, can separate a power grid fundamental wave positive sequence component from two paths of orthogonal power grid signals with serious harmonic distortion, and inhibit the influence of the possible unbalance problem of the two paths of orthogonal signals on phase-locked loop phase angle and frequency detection errors, the setting of filter parameters is simple and convenient, the phase angle detection precision of the phase-locked loop can be improved, and the direct current bias problem which is difficult to solve in a power grid and grid-.)

1. A single-phase frequency adaptive phase-locked loop, characterized by: the device comprises a direct current bias eliminating module, an orthogonal signal generating module, a positive sequence fundamental wave signal separating module and a positive sequence fundamental wave signal phase locking module, wherein the direct current bias eliminating module, the orthogonal signal generating module, the positive sequence fundamental wave signal separating module and the positive sequence fundamental wave signal phase locking module are based on a frequency self-adaptive filter designed by adopting a generalized second-order integrator;

according to the signal processing flow, the direct current offset elimination module, the orthogonal signal generation module, the positive sequence fundamental wave signal separation module and the positive sequence fundamental wave signal phase locking module are sequentially connected.

2. A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the frequency self-adaptive filter comprises a second-order generalized integrator module SOGI and a frequency locking module FLL, wherein an input signal u can output two paths of signals u through the second-order generalized integrator module SOGI_dAnd u_qThe frequency-locked loop module FLL may output a frequency signal ω' tracking the input signal u, followed by a self-frequency-locked loopThe parameters of the adaptive filter are discussed:

a1, a second-order generalized integrator module SOGI state space equation of the frequency self-adaptive filter is as follows:

a2, frequency-locking module FLL frequency tracking equation of the frequency self-adaptive filter is:

the transfer functions of the output two paths of signals of the A3 and the second-order generalized integrator module SOGI are respectively as follows:

a4, the second-order generalized integrator module SOGI is connected to the input signal u (t) ═ Vsin (ω t), and the corresponding output signal time domain expression is:

a5, the second-order generalized integrator module SOGI is connected to an input signal u (t) Vsin (ω t) + a containing dc offset a, and the corresponding output signal time domain expression is:

a6 dynamic adjustment time t of second-order generalized integrator module SOGI_s(SOGI)Can be set by the following formula:

a7, frequency locking module FLL corresponding to A6 dynamically adjusts time t_s(FLL)Comprises the following steps:

in the formula, a filter constant omega c is the angular frequency of the fundamental wave of the power grid, parameters k and η are filter parameters needing to be set, and β is 0.5[4-k ]²]^1/2。

3. A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the direct current bias eliminating module is a second-order generalized integrator module SOGI1, and the input end of the direct current bias eliminating module receives a single-phase power grid signal u_aA filter central frequency signal omega' provided by an orthogonal signal generating module, and a second-order generalized integrator module SOGI1 outputting a power grid signal u_a1。

4. A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the orthogonal signal generation module is a frequency self-adaptive filter SOGI-FLL1, and the input end of the orthogonal signal generation module receives a power grid signal u output by the direct current bias elimination module_a1And the output end outputs two orthogonal power grid signals u_α2And u_βAnd outputs a tracking grid signal u_a2Of the fundamental frequency signal ω.

5. A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the positive sequence fundamental wave signal separation module comprises a second-order generalized integrator module SOGI2 and a second-order generalized integratorThe module SOGI3, the mathematical operation module and the second-order generalized integrator module SOGI2 receive the power grid signal u output by the orthogonal signal generation module_α2The second-order generalized integrator module SOGI2 outputs two orthogonal network signals u_α3、qu_α(ii) a The second-order generalized integrator module SOGI3 receives the power grid signal u output by the orthogonal signal generation module_βOutputting two orthogonal electric network signals u_β1、qu_βThe input ends of a second-order generalized integrator module SOGI2 and a second-order generalized integrator module SOGI3 receive a central frequency signal omega and a power grid signal u provided by a positive-sequence fundamental wave signal phase-locking module_α3、qu_α、u_β1、qu_βTwo paths of power grid fundamental wave positive sequence signals are separated by 4 modulesAndthe corresponding mathematical operation formula is:

in the formula: is a time domain phase shift operator.

6. A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the positive sequence fundamental wave signal phase locking module comprises a frequency self-adaptive filter SOGI-FLL2 and an inverse trigonometric function operation atan2 module, wherein the input end of the frequency self-adaptive filter SOGI-FLL2 receives the grid fundamental wave positive sequence signal output by the positive sequence fundamental wave signal separation moduleThe frequency self-adaptive filter SOGI-FLL2 outputs a positive sequence signal for tracking the fundamental wave of the power gridThe frequency signal omega of the frequency, the input end of the atan2 module for inverse trigonometric function operation receives the positive sequence signal of the fundamental wave of the power gridAndthe anti-trigonometric function operation atan2 module outputs a phase angle signal of a fundamental wave positive sequence signal of the power grid;

the phase angle calculation formula of the power grid fundamental wave positive sequence signal corresponding to the range of [ -pi, pi ] is as follows:

Technical Field

The invention relates to a single-phase frequency self-adaptive phase-locked loop system.

Background

The key problem of the grid-connected operation of the distributed power supply is that the output voltage of a converter of the distributed power supply can be accurately synchronized with the voltage at a public connection point of a power grid, a phase-locked loop is a main technology for detecting the frequency and the phase of a fundamental wave signal of the voltage of the power grid to form a synchronous signal of the power grid, harmonic pollution generated by nonlinear power loads such as a grid-connected inverter and an active filter which are widely applied in the power grid and abnormal conditions such as power grid voltage fluctuation and flicker caused by impact loads bring great difficulty to the phase-locked loop for accurately detecting the synchronous signal of the power grid, and therefore the electric energy quality of the grid-connected.

The synchronous signal detection of the single-phase grid-connected system usually adopts zero crossing point detection to obtain the period and phase information of the power grid voltage, thereby completing the phase locking of the power grid voltage. Because each power frequency period can be adjusted at most twice, the zero crossing point detection method cannot track the phase change quickly, and the phase detection precision is poor when the voltage of the power grid is distorted. In addition, a two-Phase orthogonal Signal is constructed by a single-Phase input Signal through an orthogonal Signal Generator (QSG), and a Synchronous Reference Frame Phase-Locked-Loop (SRF-PLL) suitable for a three-Phase circuit is adopted to obtain a Synchronous detection Signal with higher precision. However, when the input grid voltage signal has direct current bias and harmonic distortion, the two paths of orthogonal signals output by the QSG contain direct current components and harmonic components, and the frequency and phase angle detection precision of the SOGI-FLL are affected.

For example, a frequency-adaptive single-phase-locked loop based on a virtual three-phase algorithm, which is disclosed as CN109547016A, constructs other two-phase signals of a single-phase signal based on the virtual three-phase algorithm, performs positive-sequence dq transformation after forming a symmetrical three-phase signal, controls the obtained q-axis component to be zero through closed-loop control, and outputs a variable quantity for adjusting a locking phase to realize network voltage phase locking. In order to eliminate the influence of the frequency change of an input signal on the precision of a phase-locked loop, closed-loop control of a q-axis component obtained based on negative sequence dq conversion is introduced, and the frequency change of the grid voltage is adapted by adjusting related fundamental frequency parameters of a virtual three-phase algorithm through the closed-loop control. The system only considers the harmonic distortion problem of the power grid voltage, does not consider the direct current bias problem of the distributed power supply and the signal sampling process, and cannot effectively inhibit the influence of the power grid harmonic distortion and the voltage unbalance on the SRF-PLL steady-state detection precision when the control parameters are not adjusted properly. Therefore, the anti-interference capability of the single-phase frequency self-adaptive phase-locked loop is not strong enough, and the phase-locking effect is not ideal.

Disclosure of Invention

In order to solve the technical problem, the invention provides a single-phase frequency self-adaptive phase-locked loop system.

The invention is realized by the following technical scheme.

The invention provides a single-phase frequency self-adaptive phase-locked loop, which comprises a direct current bias eliminating module, an orthogonal signal generating module, a positive sequence fundamental wave signal separating module and a positive sequence fundamental wave signal phase-locked module, wherein the direct current bias eliminating module, the orthogonal signal generating module, the positive sequence fundamental wave signal separating module and the positive sequence fundamental wave signal phase-locked module are based on a frequency self-adaptive filter designed by adopting a generalized second-order integrator;

according to the signal processing flow, the direct current offset elimination module, the orthogonal signal generation module, the positive sequence fundamental wave signal separation module and the positive sequence fundamental wave signal phase locking module are sequentially connected.

The frequency self-adaptive filter comprises a second-order generalized integrator module SOGI and a frequency locking module FLL, wherein an input signal u can output two paths of signals u through the second-order generalized integrator module SOGI_dAnd u_qIn conjunction with the frequency locking module FLL, the frequency signal ω' tracking the input signal u may be output, and then parameters of the frequency adaptive filter are discussed:

a1, a second-order generalized integrator module SOGI state space equation of the frequency self-adaptive filter is as follows:

a2, frequency-locking module FLL frequency tracking equation of the frequency self-adaptive filter is:

the transfer functions of the output two paths of signals of the A3 and the second-order generalized integrator module SOGI are respectively as follows:

a4, the second-order generalized integrator module SOGI is connected to the input signal u (t) ═ Vsin (ω t), and the corresponding output signal time domain expression is:

a5, the second-order generalized integrator module SOGI is connected to an input signal u (t) Vsin (ω t) + a containing dc offset a, and the corresponding output signal time domain expression is:

a6 dynamic adjustment time t of second-order generalized integrator module SOGI_s(SOGI)Can be set by the following formula:

a7, frequency locking module FLL corresponding to A6 dynamically adjusts time t_s(FLL)Comprises the following steps:

in the formula, a filter constant omega c is the angular frequency of the fundamental wave of the power grid, parameters k and η are filter parameters needing to be set, and β is 0.5[4-k ]²]^1/2；。

The direct current bias eliminating module is a second-order generalized integrator module SOGI1, and the input end of the direct current bias eliminating module receives a single-phase power grid signal u_aA filter central frequency signal omega' provided by an orthogonal signal generating module, and a second-order generalized integrator module SOGI1 outputting a power grid signal u_a1。

The orthogonal signal generating module is frequency adaptiveThe input end of the filter SOGI-FLL1 receives the power grid signal u output by the DC offset elimination module_a1And the output end outputs two orthogonal power grid signals u_α2And u_βAnd outputs a tracking grid signal u_a2Of the fundamental frequency signal ω.

A single-phase frequency adaptive phase-locked loop as claimed in claim 1, wherein: the positive sequence fundamental wave signal separation module comprises a second-order generalized integrator module SOGI2, a second-order generalized integrator module SOGI3 and a mathematical operation module, wherein the second-order generalized integrator module SOGI2 receives a power grid signal u output by the orthogonal signal generation module_α2The second-order generalized integrator module SOGI2 outputs two orthogonal network signals u_α3、qu_α(ii) a The second-order generalized integrator module SOGI3 receives the power grid signal u output by the orthogonal signal generation module_βOutputting two orthogonal electric network signals u_β1、qu_βThe input ends of a second-order generalized integrator module SOGI2 and a second-order generalized integrator module SOGI3 receive a central frequency signal omega and a power grid signal u provided by a positive-sequence fundamental wave signal phase-locking module_α3、qu_α、u_β1、qu_βTwo paths of power grid fundamental wave positive sequence signals are separated by 4 modulesAndthe corresponding mathematical operation formula is:

in the formula:is a time domain phase shift operator.

The positive sequence fundamental wave signal phase locking module comprises a frequency self-adaptive filter SOGI-FLL2 and an inverse trigonometric function operation atan2 module, wherein the input end of the frequency self-adaptive filter SOGI-FLL2 receives the power grid output by the positive sequence fundamental wave signal separation moduleFundamental positive sequence signalThe frequency self-adaptive filter SOGI-FLL2 outputs a positive sequence signal for tracking the fundamental wave of the power gridThe frequency signal omega of the frequency, the input end of the atan2 module for inverse trigonometric function operation receives the positive sequence signal of the fundamental wave of the power gridAndthe anti-trigonometric function operation atan2 module outputs a phase angle signal of a fundamental wave positive sequence signal of the power grid;

the phase angle calculation formula of the power grid fundamental wave positive sequence signal corresponding to the range of [ -pi, pi ] is as follows:

the invention has the beneficial effects that: under the condition of considering direct current bias and harmonic distortion, the constructed single-phase power grid frequency self-adaptive phase-locked loop can eliminate direct current bias components in single-phase power grid sampling signals, construct two orthogonal power grid signals without direct current bias components, separate power grid fundamental wave positive sequence components from two orthogonal power grid signals with serious harmonic distortion, and inhibit the influence of possible unbalance problems of the two orthogonal signals on phase-locked loop phase angle and frequency detection errors.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

FIG. 2 is a schematic diagram of a frequency adaptive filter of a second order generalized integrator design of the present invention;

fig. 3 is a simulation waveform of the phase locking effect of the present invention.

Detailed Description

The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

A single-phase frequency self-adaptive phase-locked loop for eliminating direct current bias and inhibiting harmonic distortion adopts a generalized second-order integrator to design a frequency self-adaptive filter, and a direct current bias eliminating module, an orthogonal signal generating module, a positive sequence fundamental wave signal separating module and a positive sequence fundamental wave signal phase-locked module are respectively constructed on the basis of the frequency self-adaptive filter. The whole single-phase frequency self-adaptive phase-locked loop is formed by sequentially connecting a direct current offset eliminating module, an orthogonal signal generating module, a positive sequence fundamental wave signal separating module and a positive sequence fundamental wave signal phase-locked module according to a signal processing flow.

The input end of the direct current bias eliminating module inputs a single-phase power grid signal, the single-phase power grid signal is subjected to frequency self-adaptive filtering, and the single-phase power grid signal subjected to direct current bias elimination is output to the orthogonal signal generating module.

The orthogonal signal generating module constructs an orthogonal two-phase power grid signal from the input single-phase power grid signal without direct current bias, and transmits two paths of orthogonal power grid signals to the positive sequence fundamental wave signal separating module.

The positive sequence fundamental wave signal separation module is used for separating positive sequence fundamental wave power grid signals in the two-phase static coordinate system from the two paths of input orthogonal power grid signals and transmitting output signals to the positive sequence fundamental wave signal phase locking module.

The positive sequence fundamental wave signal phase locking module performs mathematical operation on the positive sequence fundamental wave power grid signal and outputs accurate frequency and phase angle of the power grid positive sequence signal.

The following describes an implementation example of a single-phase frequency adaptive phase-locked loop for eliminating dc offset and suppressing harmonic distortion according to the present invention with reference to the accompanying drawings:

referring to fig. 1, fig. 1 is a schematic diagram of an exemplary single-phase frequency-adaptive phase-locked loop for dc offset cancellation and harmonic distortion suppression, which includes a dc offset cancellation module, an orthogonal signal generation module, a positive-sequence fundamental wave signal separation module, and a positive-sequence fundamental wave signal phase-locked module. The direct current bias eliminating module, the orthogonal signal generating module, the positive sequence fundamental wave signal separating module and the like are obtained by cascading one or two frequency self-adaptive filters (including simplified variants thereof).

In fig. 2, the frequency adaptive filter is composed of a second-order generalized integrator module SOGI and a frequency-locking module FLL, and an input signal u can output two paths of signals u through the SOGI_dAnd u_qThe frequency signal ω' of the tracking input signal u can be output by matching with the frequency locking module FLL, and the filter constant ω is_cEqual to the angular frequency of the fundamental wave of the power grid, and the parameters k and η are filter parameters needing to be adjusted.

The state space equation of the frequency adaptive filter SOGI module is as follows:

the frequency tracking equation of the frequency adaptive filter FLL module is:

the transfer functions of the two paths of output signals of the SOGI module are respectively as follows:

the SOGI module receives an input signal u (t) ═ Vsin (ω t), and the corresponding output signal time domain expression is:

wherein β ═ 0.5[4-k ]²]^1/2。

The SOGI module receives an input signal u (t) including a dc offset a, Vsin (ω t) + a, and outputs a corresponding signal time domain expression as:

dynamic adjustment time t of SOGI module_s(SOGI)Can be set by the following formula

Frequency locking module FLL, take η ═ k/V²Omega' is set to a first order system

Corresponding frequency locking module dynamic regulation time t_s(FLL)Is composed of

The DC offset elimination module consists of an SOGI module simplified into a band-pass filter, and the input of the SOGI module is a single-phase power grid signal u_aAnd the required filter center frequency signal omega' is provided by a post-stage module, so that the direct current bias of the input power grid signal can be eliminated, and harmonic signals in the input power grid signal can be suppressed.

The orthogonal signal generating module consists of a complete frequency self-adaptive filter, and the input signal is the eliminating straight output by the former-stage moduleCurrent-biased grid signal u_aOutputting two orthogonal electric network signals u_αAnd u_βAnd outputs tracking power grid signal u_aOf the fundamental frequency signal ω.

The positive sequence fundamental wave signal separation module is composed of two complete SOGI modules and 4 mathematical operation modules, and the input signal of one SOGI module is the electric network signal u output by the former-stage module_αOutputting two orthogonal electric network signals u_αAnd qu_α(ii) a The input signal of another SOGI module is the power grid signal u output by the former-stage module_βOutputting two orthogonal electric network signals u_βAnd qu_β. The center frequency signals omega required by the two SOGI modules are provided by the latter module. Four-way intermediate signal u_α、qu_α、u_β、qu_βThen simple mathematical operation is carried out by 4 mathematical operation modules. Finally, the positive sequence fundamental wave signal separation module inhibits harmonic distortion of the input signal and separates two paths of grid fundamental wave positive sequence signalsAnd

the separation of the fundamental wave positive sequence signal of the power grid corresponds to a mathematical operation formula of

In the formula (I), the compound is shown in the specification,and performing q operation on the signal in the static coordinate for a time domain phase shift operator to obtain an orthogonal signal with pi/2 phase angle lag.

The positive sequence fundamental wave signal phase locking module consists of a frequency self-adaptive filter and an inverse trigonometric function operation atan2 module, wherein the frequency self-adaptive filter inputs the grid fundamental wave positive sequence signal output by the former-stage moduleOutputting tracking power grid fundamental wave positive sequence signalThe frequency signal omega of the frequency, inverse trigonometric function operation atan2 module inputs two paths of power grid fundamental wave positive sequence signalsAndand obtaining a phase angle signal of the fundamental wave positive sequence signal of the power grid.

The phase locking of the fundamental positive sequence signal of the power grid, the phase angle calculation formula corresponding to the range of [ -pi, pi ] is