CN104852378B - Instantaneous virtual reactive power detection-based phase lock method - Google Patents

Abstract

The invention relates to an instantaneous virtual reactive power detection-based phase lock method. The method includes the following steps that: phase-locked loop output voltages are adopted as three-phase alternating-current power source voltages which are connected with three-phase grid voltages through virtual resistors, and the difference values of the alternating-current power source voltages and the three-phase grid voltages are calculated, so that voltage drops on the virtual resistors can be obtained; the voltage drops on the virtual resistors are divided by a virtual resistance value, so that virtual current passing through the virtual resistors can be obtained through calculation; an instantaneous virtual reactive power value outputted by an alternating current power source can be obtained through calculation; the three-phase instantaneous virtual reactive power which is obtained through calculation is inputted into a loop filter; the output of the loop filter and the rated frequency of a power grid are added together, and the addition result is adopted as phase-locked loop output voltage frequency; after the phase-locked loop output voltage frequency passes through a voltage-controlled oscillator, the phase of the phase-locked loop output voltage can be obtained; and the phase-locked loop output voltage of which the phase is changed is fed back to an input end; and the above steps are repeated, so that a closed-loop feedback loop can be formed.

Description

A kind of phase-lock technique based on instantaneous virtual reactive power detection

Technical field:

The invention belongs to PHASE-LOCKED LOOP PLL TECHNIQUE field, be specifically related to a kind of phase-lock technique based on instantaneous virtual reactive power detection.

Background technology:

The systems such as distributed grid-connected inverter, Active Power Filter-APF, static passive compensation device are required to line voltage Phase place, the information such as frequency carry out real-time monitoring, thus the normal table of control system runs.This is accomplished by one and stably may be used The phase-lock technique leaned on the most accurately to obtain electric network voltage phase and the information of frequency change.Software phase-lock loop compares traditional hardware Phaselocked loop, it is possible to overcome the temperature drift phenomenon that analog circuit exists, has higher phase-locked precision and stability.Therefore, soft Part phaselocked loop receives more and more attention at power electronics control field.

Phase-locked loop method based on reference synchronization coordinate system, as existing typical case's three-phase software phlase locking loop technique, needs to introduce synchronizing Reference frame, zero realizes line voltage by controlling line voltage vector being projected as on reference synchronization coordinate system q axle The locking of phase place.As it is shown in figure 1, three-phase power grid voltage blended space vector V_sWith angular frequency₀Rotate, itself and negative the half of β axle Axle clamp angle is θ_*, θ_*Over time with slope ω₀Change.Assuming that reference synchronization dq coordinate system rotates with angular frequency, it is known that its d Axle is θ with the negative semiaxis angle of β axle.V_sd, V_sqIt is respectively line voltage vector V_sOn the d axle and q axle of dq coordinate system Projection.Wherein, V_sqValue reflect line voltage vector with the phase relation of d axle: work as V_sqDuring ＞ 0, the delayed electrical network of d axle Voltage vector；Work as V_sqWhen=0, d axle and line voltage vector homophase；Work as V_sqDuring ＜ 0, d axle advanced line voltage vector.Cause This, be positioned at d axle by phaselocked loop output voltage, with V_sq=0, for controlling target, by pilot angle frequencies omega, can realize d Axle and line voltage same phase, reach phase-locked purpose.

Although phase-locked loop method based on reference synchronization coordinate system can reach follow the tracks of electric network voltage phase requirement, but its need into The a series of coordinate transforms of row, control structure is complex, and the triple-frequency harmonics that cannot be inherently completely eliminated in three phase network is done Disturb.

Summary of the invention:

It is an object of the invention to the defect overcoming above-mentioned prior art to exist, it is provided that a kind of based on the inspection of instantaneous virtual reactive power The phase-lock technique surveyed, this process simplify control structure, and utilizes the feature of three phase network each phase triple-frequency harmonics mutual deviation 360 degree, Inherently eliminated the interference of Triple-Frequency Harmonic in Power System by the calculating of three phase reactive power, improve phase-locked precision.

For reaching above-mentioned purpose, the present invention is to be achieved through the following technical solutions:

A kind of phase-lock technique based on instantaneous virtual reactive power detection, comprises the steps:

1) using phaselocked loop output voltage as three-phase alternating-current supply voltage U_af、U_bf、U_cf, it passes through virtual resistance R and three-phase Line voltage U_ar、U_br、U_crConnect, calculate three-phase alternating-current supply voltage U_af、U_bf、U_cfWith three-phase power grid voltage U_ar、U_br、 U_crDifference obtain the pressure drop U on virtual resistance R_ae、U_be、U_ce；

2) by the pressure drop U on virtual resistance R_ae、U_be、U_ceDivided by virtual resistance value R, it is calculated and flows through virtual resistance R Virtual current i_a、i_b、i_c；

3) according to the instantaneous reactive power computing formula (1) of three-phase circuit, it is calculated the instantaneous virtual idle of alternating current power supply output Performance number Q；

$Q=\frac{1}{\sqrt{3}}[(U_{\mathrm{bf}}-U_{\mathrm{cf}})i_a+(U_{\mathrm{cf}}-U_{\mathrm{af}})i_b+(U_{\mathrm{af}}-U_{\mathrm{bf}})i_c]---\left(1\right)$

4) instantaneous for calculated three-phase virtual reactive power Q is inputted to loop filter；

5) by rated frequency ω of the output Δ ω of loop filter Yu electrical network_nIt is added as phaselocked loop output voltage frequency ω；

6) phaselocked loop output voltage frequency ω obtains the phase theta of phaselocked loop output voltage after voltage controlled oscillator；

7) step 6 is utilized) phase theta of phaselocked loop output voltage that obtains is by virtual dq shaft voltage U_dq0Through PARK inverse transformation, The phaselocked loop output voltage U ' after phase place it is changed after CLARKE inverse transformation_af、U′_bf、U′_cf, phase-locked by change after phase place Ring output voltage U '_af、U′_bf、U′_cfFeed back to input, repeat the above steps 1 again) to step 6), form closed loop feedback ring Road.

The present invention is further improved by, step 1) in, virtual resistance value R is 1 ohm.

The present invention is further improved by, step 4) in, using proportional integral link as loop filter.

The present invention is further improved by, step 6) in, using integrator as voltage controlled oscillator.

The present invention is further improved by, step 7) in, virtual dq shaft voltage U_dq0For [1 0 0].

Relative to prior art, the method have the advantages that

A kind of phase-lock technique based on instantaneous virtual reactive power detection of the present invention, instantaneous virtual reactive power is examined by this phase-lock technique Surveying the module phase discriminator as phaselocked loop, the instantaneous virtual reactive power Q of output is as the input of loop filter；At phaselocked loop Loop filter output on plus electrical network rated frequency ω_n, thus obtain phaselocked loop output voltage frequency ω；Phaselocked loop exports Electric voltage frequency ω obtains the phase theta of phaselocked loop output voltage after voltage controlled oscillator；Change the phaselocked loop output voltage after phase place Feed back to instantaneous virtual reactive power detection module again, thus form closed feedback loop.

In sum, the present invention, by simulating the generation principle of three-phase circuit instantaneous reactive power, detects three-phase instantaneous reactive in real time Power, its phase-demodulating principle is simple, simplifies control structure, and phase-locked speed is fast.

Additionally, utilize the feature of three phase network each phase triple-frequency harmonics mutual deviation 360 degree, by the calculating of three phase reactive power from essence The interference of upper elimination Triple-Frequency Harmonic in Power System, improves phase-locked precision.

Accompanying drawing illustrates:

Fig. 1 is α β and the voltage vector-diagram under dq coordinate system；

Fig. 2 is virtual grid-connected three-phase circuit figure；

Fig. 3 is three-phase circuit phasor diagram；

Fig. 4 is the control principle drawing of phaselocked loop of the present invention；

Fig. 5 (a) is three-phase power grid voltage fundamental frequency analogous diagram, and Fig. 5 (b) adds the voltage waveform analogous diagram of triple-frequency harmonics；

Fig. 6 (a) is phase-lock-ring output frequency analogous diagram, Fig. 6 (b) output voltage waveforms simulation result figure；

Fig. 7 is the simulation result figure of the phase-lock-ring output frequency near 0.03s after abscissa amplification.

Detailed description of the invention:

The present invention is described in further detail with embodiment below in conjunction with the accompanying drawings, described in be explanation of the invention rather than limit Fixed.

As shown in Figure 2 and Figure 4, a kind of phase-lock technique based on instantaneous virtual reactive power detection of the present invention, comprise the steps:

1) using phaselocked loop output voltage as three-phase alternating-current supply voltage U_af、U_bf、U_cf, it passes through virtual resistance R and three-phase Line voltage U_ar、U_br、U_crConnect, calculate three-phase alternating-current supply voltage U_af、U_bf、U_cfWith three-phase power grid voltage U_ar、U_br、 U_crDifference obtain the pressure drop U on virtual resistance R_ae、U_be、U_ce；Wherein, virtual resistance value R is 1 ohm；

2) by the pressure drop U on virtual resistance R_ae、U_be、U_ceDivided by virtual resistance value R, it is calculated and flows through virtual resistance R Virtual current i_a、i_b、i_c；

3) according to the instantaneous reactive power computing formula (1) of three-phase circuit, it is calculated the instantaneous virtual idle of alternating current power supply output Performance number Q；

$Q=\frac{1}{\sqrt{3}}[(U_{\mathrm{bf}}-U_{\mathrm{cf}})i_a+(U_{\mathrm{cf}}-U_{\mathrm{af}})i_b+(U_{\mathrm{af}}-U_{\mathrm{bf}})i_c]---\left(1\right)$

4) using proportional integral link as loop filter, instantaneous for calculated three-phase virtual reactive power Q is inputted to loop Wave filter；

5) by rated frequency ω of the output Δ ω of loop filter Yu electrical network_nIt is added as phaselocked loop output voltage frequency ω；

6) using integrator as voltage controlled oscillator, phaselocked loop output voltage frequency ω obtains phaselocked loop output after voltage controlled oscillator The phase theta of voltage；

7) step 6 is utilized) obtain the phase theta of phaselocked loop output voltage by virtual dq shaft voltage U_dq0Through PARK inverse transformation, The phaselocked loop output voltage U ' after phase place it is changed after CLARKE inverse transformation_af、U′_bf、U′_cf, phase-locked by change after phase place Ring output voltage U '_af、U′_bf、U′_cfFeed back to input, repeat the above steps 1 again) to step 6), form closed loop feedback ring Road；Wherein, virtual dq shaft voltage U_dq0For [1 0 0].

As in figure 2 it is shown, the present invention simulates the transmitting procedure of three-phase circuit instantaneous reactive power in the controller: phaselocked loop is exported Voltage is as three-phase alternating voltage U_af、U_bf、U_cf, it is connected with three phase network by the virtual resistance R that resistance is m.When The output voltage of the alternating-current voltage source i.e. phase place of phaselocked loop output voltage and three-phase power grid voltage U_ar、U_br、U_crPhase place difference time, Alternating-current voltage source sends reactive power to load.

Phaselocked loop output voltage carries out making difference and compares the pressure drop obtained on virtual resistance R, by it divided by virtual resistance with line voltage Resistance m obtains flowing through the electric current i of virtual resistance_a、i_b、i_c, i.e. the output electric current of alternating-current voltage source.By three-phase alternating current potential source It is calculated three-phase instantaneous reactive power according to formula (1) with three-phase output electric current.Taking virtual resistance resistance is 1 ohm, such as figure Shown in 3, as phaselocked loop output voltage U_af1、U_bf1、U_cf1Phase place advanced line voltage U_ar、U_br、U_crAngle beTime, The pressure drop produced on virtual resistance is U_ae1、U_be1、U_ce1, the electric current that three-phase resistance flows through is i_a1、i_b1、i_c1, accordingly Reactive current is i_aq1、i_bq1、i_cq1, the instantaneous virtual reactive power of three-phase be on the occasion of, i.e. three-phase alternating-current supply sends perception to electrical network Reactive power；As phaselocked loop output voltage U_af2、U_bf2、U_cf2Delayed line voltage U_ar、U_br、U_crPhase placeVirtual The pressure drop produced on resistance is U_ae2、U_be2、U_ce2, the electric current that three-phase resistance flows through is i_a2、i_b2、i_c2, the most idle Electric current is i_aq2、i_bq2、i_cq2, the instantaneous virtual reactive power of three-phase is that negative value, i.e. three-phase alternating-current supply send capacitive reactive power to electrical network Power；As phaselocked loop output voltage U_af、U_bf、U_cfWith line voltage U_ar、U_br、U_crDuring same phase, three-phase is instantaneous virtual Reactive power is zero.Therefore, can realize phase place is differentiated by detection three-phase instantaneous reactive power.During stable state, three-phase is instantaneous Reactive power is zero, now phaselocked loop output voltage and line voltage same phase.

Each phase triple-frequency harmonics mutual deviation 360 degree in three-phase circuit, by the formula (1) calculating to three-phase instantaneous reactive power, by The reactive power summation that each phase triple-frequency harmonics produces is zero, inherently eliminates Triple-Frequency Harmonic in Power System component and does phase demodulation link Disturb.

Embodiment:

Seeing Fig. 5, Fig. 5 (a) is three-phase power grid voltage fundamental frequency analogous diagram, and Fig. 5 (b) adds the voltage wave of triple-frequency harmonics Shape analogous diagram, wherein adds the triple-frequency harmonics that amplitude is 1 in three-phase power grid voltage, the three-phase power grid voltage first-harmonic when 0.03 second Frequency is sported 45Hz by 50Hz.Seeing Fig. 6, Fig. 6 (a) is phase-lock-ring output frequency analogous diagram, and Fig. 6 (b) exports electricity Corrugating simulation result figure, does not wherein contain Triple-Frequency Harmonic in Power System component in the output voltage of phaselocked loop, demonstrates the present invention and possess The advantage eliminating Triple-Frequency Harmonic in Power System.Due to the phase-locked speed of the phaselocked loop of the present invention quickly, it is impossible to observe phase-locked from Fig. 6 Process and time.Therefore, see Fig. 7, the waveform of phase-lock-ring output frequency is amplified near 0.03, it appeared that phase-locked mistake The time of journey is about 1 microsecond, demonstrates the present invention and possesses quick phase locking process.

Claims (5)

1. a phase-lock technique based on instantaneous virtual reactive power detection, it is characterised in that comprise the steps:

1) using phaselocked loop output voltage as three-phase alternating-current supply voltage U_af、U_bf、U_cf, it passes through virtual resistance R and three-phase Line voltage U_ar、U_br、U_crConnect, calculate three-phase alternating-current supply voltage U_af、U_bf、U_cfWith three-phase power grid voltage U_ar、U_br、 U_crDifference obtain the pressure drop U on virtual resistance R_ae、U_be、U_ce；

2) by the pressure drop U on virtual resistance R_ae、U_be、U_ceDivided by virtual resistance value R, it is calculated and flows through virtual resistance R Virtual current i_a、i_b、i_c；

3) according to the instantaneous reactive power computing formula (1) of three-phase circuit, it is calculated the instantaneous virtual idle of alternating current power supply output Performance number Q；

$Q=\frac{1}{\sqrt{3}}\[(U_{bf}-U_{cf})i_a+(U_{cf}-U_{af})i_b+(U_{af}-U_{bf})i_c\]---\left(1\right)$

4) instantaneous for calculated three-phase virtual reactive power Q is inputted to loop filter；

5) by rated frequency ω of the output Δ ω of loop filter Yu electrical network_nIt is added as phaselocked loop output voltage frequency ω；

6) phaselocked loop output voltage frequency ω obtains the phase theta of phaselocked loop output voltage after voltage controlled oscillator；

7) step 6 is utilized) phase theta of phaselocked loop output voltage that obtains is by virtual dq shaft voltage U_dq0Through PARK inverse transformation, The phaselocked loop output voltage U' after phase place it is changed after CLARKE inverse transformation_af、U′_bf、U′_cf, phase-locked by change after phase place Ring output voltage U'_af、U′_bf、U′_cfFeed back to input, repeat the above steps 1 again) to step 6), form closed loop feedback ring Road.

A kind of phase-lock technique based on instantaneous virtual reactive power detection the most according to claim 1, it is characterised in that step Rapid 1), in, virtual resistance value R is 1 ohm.

A kind of phase-lock technique based on instantaneous virtual reactive power detection the most according to claim 1, it is characterised in that step Rapid 4) in, using proportional integral link as loop filter.

A kind of phase-lock technique based on instantaneous virtual reactive power detection the most according to claim 1, it is characterised in that step Rapid 6) in, using integrator as voltage controlled oscillator.

A kind of phase-lock technique based on instantaneous virtual reactive power detection the most according to claim 1, it is characterised in that step Rapid 7) in, virtual dq shaft voltage U_dq0For [1 0 0], the d shaft voltage of the most virtual dq shaft voltage is unit voltage 1, q axle and 0 Shaft voltage is zero.