CN104917518A - SVG single-phase phase-locked loop method - Google Patents

Abstract

The present invention discloses an SVG single-phase phase-locked loop method. Through analyzing the single-phase grid phase lock principle, a DTF algorithm is proposed, a phase angle is dynamically adjusted by using the closed-loop phase control of phase, and the phase lock of the fixed sampling point number of a single-phase grid is realized. Based on the single-phase digital phase-locked closed loop of the fixed sampling point number of the DTF algorithm, even a synchronous signal contains harmonics, multiple zero-crossing points, imbalance and other cases, the synchronous signal is still able to work normally, the precision and rapidity are high, and the problem of tracking power grid voltage synchronization signal frequency and phase by a power electronic device in the single-phase grid is solved.

Description

A kind of SVG single-phase phase-locked loop method

Technical field

The present invention relates to a kind of SVG single-phase phase-locked loop method, even if still can normally run containing during the multiple situations such as harmonic wave, multiple zero crossing, imbalance in synchronizing signal, there is higher precision and rapidity.

Background technology

On the basis that power electronics, automatically control progressively develop, power electronic equipment, its performance depends on the follow-up control of its phase-locked loop for single-phase mains voltage synchronous signal frequency and phase place to a certain extent.When conventional discrete Fourier transform (DFT) is for calculating amplitude and the phase place of electrical network, if the cycle of DFT sampling window and grid cycle inconsistent, then result of calculation has phase difference.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides a kind of SVG single-phase phase-locked loop method, the multiple situations such as harmonic wave, multiple zero crossing, imbalance are contained in the synchronizing signal of single-phase electrical network, the methods such as fixed sample is counted by adopting, DFT computing, closed-loop control, the problem such as overcome pll phase and there is error, cannot lock, solve the tracking problem for line voltage synchronous signal frequency and phase place of power electronic equipment in single-phase electrical network, there is higher precision and rapidity; Also solve in engineering the problem being convenient to digitized processing simultaneously.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

A kind of SVG single-phase phase-locked loop method, by analyzing the phase-locked principle of single-phase electrical network, propose a kind of based on DTF algorithm, utilize and dynamic adjustments phase angle come to the closed-loop control of phase place, thus realize to the fixed sample of single-phase electrical network count phase-locked; Specifically comprise the steps:

Step one: set single-phase input signal as u (t), following first-harmonic Fourier transform is carried out to input signal u (t):

$\left\{\begin{array}{c}{u}_{1x}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×sin\left(\mathrm{\ω}t\right)dt\\ u_{1y}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×cos\left(\mathrm{\ω}t\right)dt\\ \mathrm{\θ}=arctan\left(\frac{u_{1y}}{u_{1x}}\right)\end{array}\right.$

Wherein: T is power frequency period, ω is angular frequency; u _1x+ u _1y× j is the first-harmonic vector of input signal u (t), and first-harmonic vector is θ with the angle with reference to sinusoidal vector;

Step 2: with u _1yas the error signal of phase-locked loop closed-loop adjustment, obtain analog domain closed control loop;

Step 3: single-phase phase-locked loop: according to input signal u (t), reference frequency f ₀, feedback signal sin θ and cos θ, obtain u through first-harmonic Fourier transformation operation _1y, to u _1ynegate obtains error signal △ θ=-u _1y, using △ θ as the input signal of scattered controller D (s) and obtain control export T _x, obtain phase angle through computing trigonometric function is carried out to θ and calculates feedback signal sin θ and cos θ, the closed loop that final formation one is complete.

The filter design procedure that in the method, scattered controller D (s) input stage of closed-loop control relates to is as follows:

(1) in order to solve discrete sampling, causing the 100Hz of positive sequence, negative phase-sequence to fluctuate, designing the filtering of a 50Hz at the output of filter, the fluctuation that filtering causes because of digitlization;

(2) designing second-order low-pass filter is ω _n=100 π, S are complex variable in complex frequency domain; Through Analysis of Magnitude-Frequency Characteristic, be 1 (undamped) in 50Hz place amplitude, after phase place 90 °, decay rapidly more than amplitude after 50Hz, the effect of filtering and phase shift can be played simultaneously.

Beneficial effect: SVG single-phase phase-locked loop method provided by the invention, cycle and the inconsistent problem causing result of calculation to there is phase difference of grid cycle of DFT sampling window can be overcome, can solve zero passage phase discriminator causes phase-locked failed problem in synchronizing signal because causing multiple zero crossing containing harmonic wave simultaneously, phase-locked loop periodic adjustment can also be realized, there is higher precision and rapidity, solve the tracking problem for line voltage synchronous signal frequency and phase place of power electronic equipment in single-phase electrical network.

Accompanying drawing explanation

Fig. 1 is the phase-locked closed-loop block diagram based on scattered Fourier transform of the present invention;

Fig. 2 is second-order low-pass filter amplitude-frequency characteristic of the present invention;

Fig. 3 is the phase-locked loop simulation model based on Fourier transform of the present invention;

External synchronization signal when Fig. 4 is first-harmonic of the present invention and inter-sync signal phase;

External synchronization signal when Fig. 5 is harmonic wave of the present invention and inter-sync signal phase.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

Be illustrated in figure 1 a kind of SVG single-phase phase-locked loop method, by analyzing the phase-locked principle of single-phase electrical network, propose a kind of based on DTF algorithm, utilize and dynamic adjustments phase angle come to the closed-loop control of phase place, thus realize to the fixed sample of single-phase electrical network count phase-locked; Specifically comprise the steps:

Step one: set single-phase input signal as u (t), following first-harmonic Fourier transform is carried out to input signal u (t):

$\left\{\begin{array}{c}{u}_{1x}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×sin\left(\mathrm{\ω}t\right)dt\\ u_{1y}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×cos\left(\mathrm{\ω}t\right)dt\\ \mathrm{\θ}=arctan\left(\frac{u_{1y}}{u_{1x}}\right)\end{array}\right.$

Wherein: T is power frequency period, ω is angular frequency; u _1x+ u _1y× j is the first-harmonic vector of input signal u (t), and first-harmonic vector is θ with the angle with reference to sinusoidal vector;

Step 2: with u _1yas the error signal of phase-locked loop closed-loop adjustment, obtain analog domain closed control loop;

Step 3: single-phase phase-locked loop: according to input signal u (t), reference frequency f ₀, feedback signal sin θ and cos θ, obtain u through first-harmonic Fourier transformation operation _1y, to u _1ynegate obtains error signal △ θ=-u _1y, using △ θ as the input signal of scattered controller D (s) and obtain control export T _x, obtain phase angle through computing trigonometric function is carried out to θ and calculates feedback signal sin θ and cos θ, the closed loop that final formation one is complete.

As shown in Figure 2, the amplitude-frequency characteristic of the filter that scattered controller D (s) input stage for closed-loop control in this method relates to, the design process of this filter is as follows:

(1) in order to solve discrete sampling, causing the 100Hz of positive sequence, negative phase-sequence to fluctuate, designing the filtering of a 50Hz at the output of filter, the fluctuation that filtering causes because of digitlization;

(2) designing second-order low-pass filter is ω _n=100 π, S are complex variable in complex frequency domain; Through Analysis of Magnitude-Frequency Characteristic, be 1 (undamped) in 50Hz place amplitude, after phase place 90 °, decay rapidly more than amplitude after 50Hz, the effect of filtering and phase shift can be played simultaneously.

Fig. 2 is Bode diagram (the Bode Diagram of filter, also known as amplitude-frequency response and phase-frequency response curve chart), the frequency response of system can be found out, transverse axis is frequency (Frequency, Hz) represent with logarithmic scale (log scale), amplitude-frequency (Magnitude, DB), phase frequency (Phase, Deg) the upper and lower hurdle of the corresponding longitudinal axis of characteristic difference, amplitude frequency diagram represents the change of decibel value to frequency of frequency response gain, and phase frequency figure is then the change of the phase versus frequency of frequency response.Concrete property is: be 1 (undamped) in 50Hz place amplitude, after phase place 90 °, decays rapidly, can play the effect of filtering and phase shift simultaneously more than amplitude after 50Hz.

Fig. 3 is the phase-locked loop simulation model based on Fourier transform, builds according to Fig. 1 Control loop, comprises analog signal, controlling unit, output signal etc., mainly in order to verify its feasibility, performance.

External synchronization signal when Fig. 4 is simulation waveform figure-first-harmonic and inter-sync signal phase, transverse axis is time t, in the longitudinal axis: solid line is external synchronization signal-be also input signal, dotted line is inter-sync signal; Both real-time trackings, phase difference keep zero.

External synchronization signal when Fig. 5 is simulation waveform figure-harmonic wave and inter-sync signal phase, transverse axis is time t, in the longitudinal axis: solid line is external synchronization signal-be also input signal, some broken string is inter-sync signal, dotted line is for reference to fundamental signal; Though have multiple zero crossing, harmonic wave, both same real-time trackings, phase difference keep zero.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (2)

1. a SVG single-phase phase-locked loop method, is characterized in that: by analyzing the phase-locked principle of single-phase electrical network, propose a kind of based on DTF algorithm, utilize and dynamic adjustments phase angle come to the closed-loop control of phase place, thus realize to the fixed sample of single-phase electrical network count phase-locked; Specifically comprise the steps:

Step one: set single-phase input signal as u (t), following first-harmonic Fourier transform is carried out to input signal u (t):

$\left\{\begin{array}{c}{u}_{1x}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×sin\left(\mathrm{\ω}t\right)dt\\ u_{1y}=\frac{2}{T}{\∫}_0^{T}u\left(t\right)\×cos\left(\mathrm{\ω}t\right)dt\\ \mathrm{\θ}=arctan\left(\frac{u_{1y}}{u_{1x}}\right)\end{array}\right.$

Wherein: T is power frequency period, ω is angular frequency; u _1x+ u _1y× j is the first-harmonic vector of input signal u (t), and first-harmonic vector is θ with the angle with reference to sinusoidal vector;

Step 2: with u _1yas the error signal of phase-locked loop closed-loop adjustment, obtain analog domain closed control loop;

Step 3: single-phase phase-locked loop: according to input signal u (t), reference frequency f ₀, feedback signal sin θ and cos θ, obtain u through first-harmonic Fourier transformation operation _1y, to u _1ynegate obtains error signal △ θ=-u _1y, using △ θ as the input signal of scattered controller D (s) and obtain control export T _x, obtain phase angle through computing trigonometric function is carried out to θ and calculates feedback signal sin θ and cos θ, the closed loop that final formation one is complete.

2. SVG single-phase phase-locked loop method according to claim 1, is characterized in that: the filter design procedure that in the method, scattered controller D (s) input stage of closed-loop control relates to is as follows:

(1) filtering of a 50Hz is designed at the output of filter;

(2) designing second-order low-pass filter is ω _n=100 π, S are complex variable in complex frequency domain.