CN104330627A - Automatic power grid resonance detection method based on active injection current - Google Patents

Abstract

The invention discloses an automatic power grid resonance detection method based on active injection current. For the problems of harmonic pollution due to a nonlinear load in a power system and resonance easy occurring when a reactive compensating capacitor is connected in the power system, an active power quality regulating device connected in the power grid in parallel is used for compensating the harmonic, and meanwhile, the active power quality regulating device is used for injecting reactive and harmonic combined current of a specific waveform into the power grid to automatically detect the resonance angular frequency and the damping coefficient of the power grid; for a single-phase system, the rectangular wave current of 180 degrees is injected; for a three-phase system, the rectangular wave current of 120 degrees is injected. According to the automatic power grid resonance detection method based on the active injection current, the resonance detection combined model of the optimal weight algorithm is established according to the harmonic voltage and the harmonic current of the power grid and spectral characteristics of the harmonic power, and then the resonance angular frequency and the damping degree of the power grid can be judged quickly and accurately; as a result, application basis is provided for the damping control of the power grid resonance and the power quality of the power system is further improved.

Description

A kind of electrical network resonance automatic testing method based on active Injection Current

Technical field

The invention belongs to utility power quality control field, more specifically, relate to a kind of electrical network resonance automatic testing method based on active Injection Current.

Background technology

Reactive-load compensation shnt capacitor is a kind of very common power factor correcting method, in industry spot reactive-load compensation field in occupation of leading position.In electric system, usually according to different load levels, the capacitor dropping into respective volume improves the power factor of system, improves the voltage levvl of transmission line of electricity, reduces grid loss simultaneously, eliminates overload.

Along with the widespread use of the nonlinear loads such as all kinds of power electronic equipments, the harmonic current in electrical network increases day by day, and harmonic current flows through in line impedance can produce harmonic voltage pressure drop.Harmonic current and harmonic voltage can make power factor correction electric capacity in parallel produce in parallel or series resonance with electric network impedance, and this situation often occurs in electric system, serious harm shnt capacitor and stability of power system and safe reliability.

The detection of electrical network resonance frequency is the condition precedent suppressing electrical network resonance, detection of grid tuning-points mode conventional is at present: first utilize thyristor switchable capacitor, the methods such as reactor produce harmonic current, in the moment of thyristor switchable capacitor/reactor, can to electrical network harmonic electric current, this harmonic current can produce different impacts at different harmonic frequency place to electrical network, then electrical network Resonance detector instrument is used to carry out waveform recording to harmonic current and voltage, then spectrum analysis is carried out by instrument and wave form analysis, calculate harmonic impedance, thus determine the systematic parameter of electrical network resonance.

But there is the shortcoming that accuracy of detection is poor, detection speed is slower and on-the-spot adaptability is bad in the method for above-mentioned use; And testing process need divide two processes by different checkout equipment complete independentlies, cost is higher, it is more complicated to realize, very flexible, can not meet the demand realizing automatically detecting.First, thyristor switchable capacitor/reactor system is passive impedance switching mode, which utilizes the harmonic current produced in the transient response process of switched capacitor/reactor moment to remove detection of grid tuning-points, and the harmonic current that this mode produces is continuous frequency spectrum, wherein low-frequency harmonics content endangers the normal operation of electric system compared with senior general, and high-frequency harmonic content affects the accurate judgement of electric system resonance frequency compared with young pathbreaker, and affect by the capacitor/reactor impedance magnitude of line voltage and switching, each harmonic content can not be selected flexibly, on-the-spot adaptability is poor.

In addition, current existing electrical network Resonance detector instrument mostly is and uses special checkout equipment, this checkout equipment cost is higher, need to carry out waveform frequency spectrum analysis in conjunction with upper computer software after acquisition mains by harmonics electric current and voltage waveform, whole process operation is complicated, speed is comparatively slow, and dirigibility is poor, can not realize online automatic detection.Electric system is connected to nonlinear load and shnt capacitor at the same time, and load changes when causing parameters of electric power system to change, electrical network resonance frequency is also different, and the passive impedance switching process of conventional resonance detection mode and checkout equipment Algorithm Analysis process are independently carried out, often adaptability is poor, can not realize the demand detected fast and automatically.

Summary of the invention

For the defect of prior art, the object of the present invention is to provide a kind of electrical network resonance automatic testing method based on active Injection Current, be intended to solve the problem that traditional detection method accuracy is not good enough, can not realize online automatic detection function rapidly.

The invention provides a kind of electrical network resonance automatic testing method based on active Injection Current, comprise the steps:

S1: obtain the line voltage of point of common coupling, power network current and power quality adjusting device output current, DC voltage; And angular frequency and the phase theta of line voltage is obtained by digital servo-control link PLL;

Wherein, described point of common coupling refers to the tie point of power quality adjusting device main circuit and electrical network, and output current refers to active power quality regulating device output current;

S2: carry out recursive discrete Fourier transformation respectively to described line voltage and described power network current, obtains electrical network each characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _sh; And according to described characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _shobtain each harmonic first applied power S _h;

S3: the current waveform according to setting obtains the reference current i corresponding with it ^* _ref; And to described reference current i ^* _refcarry out recursive discrete Fourier transformation, obtain each characteristic harmonic current effective value I of reference current ^* _rh;

S4: the feedback regulation described output current being carried out to floating two close cycles, makes active power regulating device inject the output current identical with the current waveform of described setting to electrical network;

S5: when described output current equals the current waveform of described setting, carries out recursive discrete Fourier transformation respectively to the line voltage in this moment and power network current, obtains and injects electrical network each characteristic harmonics voltage effective value V ' after reference current _phand characteristic harmonic current effective value I ' _sh, and according to described characteristic harmonics voltage effective value V ' _phand characteristic harmonic current effective value I ' _shobtain each harmonic second applied power S ' _h;

S6: according to injecting forward and backward electrical network each the characteristic harmonics voltage effective value V of reference current _phwith V ' _ph, characteristic harmonic current effective value I _shwith I ' _sh, characteristic harmonics harmonic wave applied power S _hwith S ' _h, each characteristic harmonic current effective value I of reference current ^* _rh, obtain the system performance parameter for describing electrical network resonance: electrical network resonance angular frequency ω _rand damping coefficientζ.

Wherein, in step S3, the current waveform of setting is 180 ° of square wave currents or 120 ° of square wave currents.

Wherein, step S4 is specially:

S41: obtain feedback current i according to output current _f; To DC voltage V _dccarry out proportional integral and obtain active current i ^* _dc;

S42: according to described reference current i ^* _ref, feedback current i _fobtain error current with described active current, then error current is carried out Current adjustment, obtain with reference to modulation signal u ^* _r;

Wherein, Current adjustment mode is relevant with the control strategy under different coordinates, the controller of repetition (PI+RP) can be added by adoption rate integration under dq synchronously rotating reference frame, and can the controller of adoption rate resonance (PR) under rest frame.

S43: with reference to modulation signal u ^* _racquisition pwm switching signal is compared with high-frequency carrier signal; Described pwm switching signal is used for the break-make of gauge tap pipe, thus makes active power regulating device inject the output current identical with the current waveform of setting to electrical network.

Wherein, in step S6, according to formula obtain the h subharmonic combination Judging index F after injection h subharmonic current _h, F _hcombine and inject unit and specify the information of the h time mains by harmonics voltage, harmonic current and harmonic power changing value sum after the reference current of waveform, carry out detection of grid resonance than the physical index of employing thrin more accurate; By comparing the comprehensive detection index F of each harmonic _hvalue, obtains F _hbe worth maximum overtone order h _r, so can try to achieve electrical network resonance angular frequency is ω _r=100 π h _r, namely electrical network resonance frequency is f _r=50h _r; Wherein, w _uhfor the weight of voltage detecting index in built-up pattern, w _ihfor the weight of current detecting index in built-up pattern, w _shfor the weight of power detection index model in built-up pattern, for to F _uhcarry out the value after linear nondimensionalization process, for to F _ihcarry out the value after linear nondimensionalization process, for to F _shcarry out the value after linear nondimensionalization process, its computing formula is respectively: , F _uhfor the ratio of mains by harmonics voltage change and harmonic electric current, F _ihfor the ratio of mains by harmonics current variation value and harmonic electric current, F _shfor the ratio of mains by harmonics power change values and harmonic electric current, its computing formula is: $F_{\mathrm{Sh}}=\frac{|S_h-S_h^{\′}|}{{\left(I_{\mathrm{rh}}^{*}\right)}^2}.$

The present invention is owing to only needing the disposable reference current injecting specific waveforms in electrical network, and injection reference current function and tuning-points detection algorithm analytic function all realize at power quality adjusting device, to cooperatively interact step by step by function without the need to multiple testing tool and detect, simple to operate, improve detection speed, and on-the-spot adaptability is stronger; Power quality adjusting device usually accesses in network system for a long time and carries out idle harmonic wave and harmonics restraint, when electrical network resonance frequency changes, enters the online automatic detection that resonant operational pattern can realize electrical network resonance; Simultaneously, reference current signal each the characteristic harmonics content injected is complete, 180 ° of square wave currents contain all 2k+1 characteristic harmonic currents of monophase system, 120 ° of square wave current modes contain all 6k ± 1 time characteristic harmonic current of single three systems (wherein, k is positive integer), after the pulse current injectingt electrical network of therefore described two kinds of waveforms, the voltage and current parameter of network system can be met with a response at different harmonic frequency place, thus the tuning-points of electric system can accurately be detected.

Accompanying drawing explanation

The power quality adjusting device main circuit structure schematic diagram of the automatic detection single-phase/three-phase electrical network resonance that Fig. 1 provides for the embodiment of the present invention.

The power quality adjusting device the being applicable to single-phase/three-phase electric system active Injection Current formula electrical network resonance automatic checkout system control block diagram that Fig. 2 provides for the embodiment of the present invention.

180 ° of square wave reference current output waveform of the active injection of single-phase electrical system power quality adjusting device that Fig. 3 provides for the embodiment of the present invention; The electric current content of 180 ° of square wave currents output waveform (b) each the characteristic frequency wherein injected in (a) monophase system.

120 ° of square wave reference current output waveform of the active injection of three-phase electrical power system quality of power supply tune device that Fig. 4 provides for the embodiment of the present invention; The electric current content of 120 ° of square wave currents output waveform (b) each the characteristic frequency wherein injected in (a) three-phase system.

Electrical network resonance characteristic parameter (the i.e. resonance angular frequency ω that Fig. 5 provides for the embodiment of the present invention _rwith resonance ratio of damping ξ) detection method realization flow figure.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

In view of the traditional detection method accuracy of electrical network resonance is not good enough, can not realize online automatic detection function rapidly, and the shortcoming such as higher, the on-the-spot adaptability of testing tool cost is poor, the invention provides one and utilize active power quality regulating device, by the reference current to the disposable injection specific waveforms of electrical network, and set up detection model according to the spectral characteristic of network system operational factor, realize electrical network resonance frequency and resonance ratio of damping automatic testing method rapidly and accurately.This power quality adjusting device integrates active Injection Current and harmonic analysis algorithm, when electrical network parameter changes, can realize the online automatic detection of electrical network resonance, thus provides basis for the reliable and stable operation of electric system.The present invention for single-phase, three-phase electrical power system is all applicable.

Electrical network resonance automatic testing method based on active Injection Current provided by the invention, comprise the active power quality regulating device by utilizing access electric system, the real-time operational factor such as detection of grid voltage and power network current on the one hand, calculated the effective value of electrical network each characteristic harmonics voltage and electric current again by RDFT algorithm, and calculate electrical network each characteristic harmonics applied power thus in real time; On the other hand, to the reference current of the disposable injection specific waveforms of electrical network, relatively inject the difference of the harmonic energy spectral characteristic of mains by harmonics voltage, harmonic current and correspondence before and after reference current, set up the Resonance detector built-up pattern of best initial weights algorithm, thus automatically detect electrical network resonance frequency and ratio of damping quickly and accurately, damping for electrical network resonance controls to provide application foundation, improves the quality of power supply of electric system further, improves stability of power system.

Power quality adjusting device is active electric power electronic on-off-type compensation system, by controlling the break-make of electronic power switch device in main circuit, can export to floating the reference current of specific waveforms.

Power quality adjusting device has line voltage, power network current and self output electric current measure module, detects in real time the operational factor of whole electric system.Power quality adjusting device central control unit has higher data operation and processing power, and peripheral circuit possesses communication and display module simultaneously, operation of power networks parameter and Resonance detector result can be sent into panel and show.

Power quality adjusting device has two kinds of mode of operations, i.e. harmonic compensation pattern and Resonance detector pattern.When being operated in harmonic compensation pattern, extracting each characteristic harmonics respectively by RDFT algorithm, can realize specifying the floating of subharmonic to compensate; When being operated in Resonance detector pattern, the disposable reference current injecting specific waveforms in electrical network, can realize electrical network resonance frequency quickly and accurately and ratio of damping detects automatically.

The reference current injection mode of specific waveforms comprises: adopt injection 180 ° of square wave current modes for monophase system, adopts injection 120 ° of square wave current modes for three-phase system.In the Injection Current of described two kinds of different wave, first-harmonic is reactive current, thus the DC bus-bar voltage of power quality adjusting device can be kept to stablize, and each time characteristic harmonics content is complete, controlled flexibly, therefore can determine electrical network tuning-points quickly and accurately.

The tracing control of reference current adopts the feedback control strategy of floating two close cycles, and outer voltage control mode can the FEEDBACK CONTROL that regulates of adoption rate integration (PI); Current inner loop control mode is relevant with the control strategy under different coordinates, the controller of repetition (PI+RP) can be added by adoption rate integration under dq synchronously rotating reference frame, and can the controller of adoption rate resonance (PR) under rest frame.

For achieving the above object, the invention provides and be a kind ofly applicable to the electrical network resonance automatic testing method based on active Injection Current that is single-phase and three-phase electrical power system.The described power quality adjusting device main circuit automatically detected for the electrical network resonance of monophase system is: be connected to the single-phase bridge converters between single-phase electrical network and single-phase nonlinear load with parallel way.The described power quality adjusting device main circuit automatically detected for the electrical network resonance of three-phase system is: be connected to the three-phase bridge converters between three phase network and three-phase nonlinear load with parallel way.

The present invention is applicable to the electrical network resonance automatic testing method based on active Injection Current of single-phase/three-phase electric system, comprises the steps:

S1: obtain the line voltage of point of common coupling (i.e. Point of Common Coupling, PPC point), power network current and active power quality regulating device output current, DC voltage; And angular frequency and the phase theta of line voltage is obtained by digital servo-control link PLL.

Wherein, step S1 is specially:

S11: carry out AD conversion in real time, obtains the line voltage instantaneous value v of point of common coupling _p, power network current instantaneous value i _sand active power quality regulating device output current instantaneous value i _c, DC voltage instantaneous value V _dc; In embodiments of the present invention, point of common coupling refers to the tie point of power quality adjusting device main circuit and electrical network.

S12: the angular frequency and the phase theta that are obtained described line voltage by digital servo-control link PLL.

S2: to line voltage instantaneous value v _pwith power network current instantaneous value i _scarry out recursive discrete Fourier transformation (Recursive Discrete Fourier Transform, RDFT) respectively, obtain electrical network each characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _sh; And according to V _phand I _shobtain each harmonic applied power S _h; Wherein, h is overtone order, and for monophase system h=2k+1, for three-phase system h=6k ± 1, k is positive integer, k=1,2 ...

S3: obtain the reference current i corresponding with it according to the current waveform of specifying ^* _ref; And to reference current i ^* _refcarry out recursive discrete Fourier transformation, obtain each characteristic harmonic current effective value I of reference current ^* _rh.Wherein, for monophase system reference current i ^* _refwith the current waveform of 180 ° of square wave currents for specifying, for three-phase system reference current i ^* _refwith the current waveform of 120 ° of square wave currents for specifying.

S4: feedback regulation power quality adjusting device output current being carried out to floating two close cycles, makes active power regulating device inject the output current identical with specified current flow waveform to electrical network.

Wherein, step S4 is specially:

S41: by output current instantaneous value i _cobtain feedback current i _f; To DC voltage instantaneous value V _dccarry out proportional integral (PI) and obtain active current i ^* _dc.

S42: to i ^* _ref,-i _fwith i ^* _dcsummation, obtains error current, then error current is carried out Current adjustment, obtains with reference to modulation signal u ^* _r.

S43: by described with reference to modulation signal u ^* _racquisition pwm switching signal is compared with high-frequency carrier signal; By the break-make of pwm switching signal gauge tap pipe, active power regulating device is made to inject the output current identical with specified current flow waveform to electrical network.

According to sinusoidal pulse width modulation principle, or high-frequency carrier signal is sawtooth wave triangle carrier signal, and amplitude is 1; In a carrier cycle, as reference modulation signal u ^* _rwhen being greater than high-frequency carrier signal, export the pwm signal of high level; As reference modulation signal u ^* _rwhen being less than high-frequency carrier signal, the pwm signal of output low level.

S5: through the regulating action repeatedly of step S4, active power regulating device, by electric current identical with the current waveform of specifying for stable output, now passes through RDFT computing, electrical network each characteristic harmonics voltage effective value V ' after acquisition injection reference current _phand characteristic harmonic current effective value I ' _sh, and calculate each harmonic applied power S ' _h.

S6: will electrical network each the characteristic harmonics voltage effective value V before and after reference current be injected _phwith V ' _ph, characteristic harmonic current effective value I _shwith I ' _sh, characteristic harmonics harmonic wave applied power S _hwith S ' _h, each characteristic harmonic current effective value I of reference current ^* _rh, substitute into Resonance detector built-up pattern as input, carry out calculation process, thus draw electrical network resonance angular frequency ω _rwith damping coefficientζ, ω _rthe system performance parameter describing electrical network resonance is with ζ.

In embodiments of the present invention, in step S4, the tracing control of reference current adopts the feedback control strategy of floating two close cycles, the FEEDBACK CONTROL of outer voltage control mode adoption rate integration; Current inner loop control mode is relevant with the control strategy under different coordinates, the control mode of repetition (PI+RP) can be added by adoption rate integration under dq synchronously rotating reference frame, and can the control mode of adoption rate resonance (PR) under rest frame.

In step S6, best initial weights algorithm is specially: first to harmonic voltage effective value V _phwith V ' _ph, harmonic current effective value I _shwith I ' _shcarry out synchronous accumulation filtering, namely to harmonic voltage, harmonic current effective value averaged that continuous several times detects; Then, harmonic wave applied power S is calculated _hwith S ' _h, harmonic voltage changing value Δ V before and after the reference current of calculating injection appointment waveform _ph, harmonic current changing value Δ I _sh, harmonic wave applied power variation delta S _h; Then, each harmonic voltage, harmonic current and the exporting change amount of harmonic wave applied power and the ratio F of the harmonic magnitude of current is calculated _uh, F _ihwith F _sh.Finally according to the spectral characteristic of harmonic voltage, electric current and power, judge electrical network resonance angular frequency ω _rwith damping coefficientζ.

The above step to single-phase, three-phase system is all applicable, and is all the FEEDBACK CONTROL of floating two close cycles to the control strategy that the tracing control of reference current is taked; Difference is that the specified current flow waveform of described reference current is different with the number of phases, and three-phase system need generate the reference current i of three-phase 120 ° of square waves ^* _refa, i ^* _refb, i ^* _refc, wherein i ^* _refathe advanced i of phase place ^* _refb120 °, phase place, i ^* _refbthe advanced i of phase place ^* _refc120 °, phase place, and monophase system only need generate the reference current i of a phase 180 ° of square waves ^* _ref.

The invention provides a kind of automatic testing method realizing electrical network resonance frequency and resonance ratio of damping based on active Injection Current, utilize single-phase, three-phase electric energy quality regulator all can realize described automatic detection function, therefore all applicable in single-phase, three-phase electrical power system.Described method integrates active injection reference current and harmonic analysis algorithm, only need the disposable reference current injecting specific waveforms in electrical network, just can realize the online automatic detection function of electrical network resonance frequency and ratio of damping quickly and accurately, thus guarantee electric system efficient stable reliability service.Because injection instruction harmonic current function and tuning-points detection algorithm analytic function all realize at power quality adjusting device, to cooperatively interact step by step by function without the need to multiple testing tool and detect, simple to operate, improve detection speed, and on-the-spot adaptability is stronger; Power quality adjusting device usually accesses in network system for a long time and carries out idle harmonic wave and harmonics restraint, when electrical network resonance frequency changes, enters the online automatic detection that resonant operational pattern can realize electrical network resonance; Simultaneously, reference current each the characteristic harmonics content injected is complete, 180 ° of square wave currents contain all 2k+1 characteristic harmonic currents of monophase system, 120 ° of square wave current modes contain all 6k ± 1 time characteristic harmonic current of single three systems (wherein, k is positive integer), after the pulse current injectingt electrical network of therefore described two kinds of waveforms, the voltage and current parameter of network system can be met with a response at different harmonic frequency place, thus electrical network resonance frequency and the damping degree of electric system can accurately be detected.

Below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

The power quality adjusting device circuit structure that the active pouring-in electrical network resonance being applicable to single-phase/three-phase electric system that Fig. 1 shows the embodiment of the present invention to be provided detects automatically, for convenience of explanation, illustrate only the part relevant to the embodiment of the present invention.

If the quality of power supply adjusts device automatically to detect for the electrical network resonance of single-phase electrical system, main circuit comprises: be connected to the single-phase bridge converters between single-phase electrical network and single-phase nonlinear load with parallel way, the first dc-link capacitance C ₁and the first AC reactor L _f; First dc-link capacitance C ₁be connected in parallel on the DC terminal of single-phase bridge converters, the first AC reactor L _fbe connected between single-phase electrical network and single-phase bridge converters AC.If described power quality adjusting device detects automatically for the electrical network resonance of three-phase electrical power system, main circuit is: be connected to the three-phase bridge converters between three phase network and three-phase nonlinear load with parallel way, the first dc-link capacitance C ₁and the first AC reactor group L _f; First dc-link capacitance C ₁be connected in parallel on the DC terminal of three-phase bridge converters, the first AC reactor group L _fbe connected between three phase network and three-phase bridge converters AC.

As shown in Figure 2, for realizing the above-mentioned Systematical control block diagram being applicable to the electrical network resonance automatic testing method based on active Injection Current of single-phase/three-phase electric system, power quality adjusting device is connected in parallel on AC network PCC point, it is the control system of power quality adjusting device in dotted line frame, peripheral function comprises harmonic voltage detection, Harmonic currents detection, load harmonic detection, output electric current measure and PWM and drives, and is respectively used to detection of grid harmonic voltage v _p, mains by harmonics current i _s, load harmonic current i _l, output current i _cand drive the break-make of main circuit converter module switching tube; Control core practical function comprises the phase-locked PLL of line voltage, the RDFT of peripheral each detection signal, mode of operation is selected (to comprise switch controlling signal and S ₁two parts), specify time load harmonic to compensate (realizing by specifying subharmonic compensatory control unit), the electric current of specific waveforms generates (being realized by appointment waveform-shaped current instruction generation unit), the Resonance detector analysis (being realized by ordering calculation and Resonance detector Schema control, best initial weights algorithm combination model two parts) of best initial weights algorithm and floating double-closed-loop control (comprising outer voltage to control and current inner loop zero steady state error control two parts).When power quality adjusting device is operated in Resonance detector pattern, ordering calculation and Resonance detector mode control module output switching signal, make S by switch control rule ₁invest reference current end, start to carry out the detection of electrical network tuning-points.Specify waveform-shaped current directive generation module to export reference current on the one hand, compare with power quality adjusting device output current, and carry out the FEEDBACK CONTROL of floating two close cycles, thus output pwm signal controls main circuit switch pipe break-make; On the other hand, ordering calculation and Resonance detector mode control module extract the harmonic components of current-order, with each the characteristic harmonics voltage effective value of the electrical network before and after Injection Current, characteristic harmonic current effective value and each harmonic applied power effective value jointly as preprocessed data, carry out the analysis of electrical network tuning-points by best initial weights algorithm combination model, and identify electrical network resonance angular frequency ω _rwith damping coefficientζ.

In the embodiment of the present invention, the reference current waveform of the active injection of single-phase electrical system is adopted to the mode of injection 180 ° of square wave currents, the reference current waveform for the active injection of three-phase electrical power system adopts the mode of injection 120 ° of square wave currents; Outer voltage control mode adopts the FEEDBACK CONTROL of pi regulator; Current inner loop controls the floating Closed-loop Control Strategy under control strategy employing dq coordinate axis, by carrying out dq coordinate transform to reference current, taking out lower employing PI+RP control strategy at dq coordinate, can realize the injection of specifying square wave current preferably.

Fig. 5 shows the electrical network resonance characteristic parameter that the embodiment of the present invention provides, i.e. electrical network resonance angular frequency ω _rdetection method realization flow figure with resonance ratio of damping ξ, specifically comprises the steps:

S1: obtain the line voltage of PPC point, power network current and active power quality regulating device output current, DC voltage; And angular frequency and the phase theta of line voltage is obtained by digital servo-control link PLL.

S11: carry out AD conversion in real time, obtains the line voltage instantaneous value v of point of common coupling _p, power network current instantaneous value i _sand active power quality regulating device output current instantaneous value i _c, DC voltage instantaneous value V _dc; In embodiments of the present invention, point of common coupling refers to the tie point of power quality adjusting device main circuit and electrical network.

S12: the angular frequency and the phase theta that are obtained described line voltage by digital servo-control link PLL;

S2: to line voltage instantaneous value v _pwith power network current instantaneous value i _scarry out recursive discrete Fourier transformation respectively, obtain electrical network each characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _sh; And according to V _phand I _shobtain each harmonic applied power S _h.Wherein, h is overtone order, and for monophase system h=2k+1, for three-phase system h=6k ± 1, k is positive integer, k=1,2 ...

S3: according to specifying the current waveform and amplitude thereof that inject, generate corresponding reference current i ^* _ref.In monophase system, using 180 ° of square waves as Injection Current waveform, generate corresponding reference current i ^* _ref, can be through Fourier decomposition:

$i_{\mathrm{ref}}^{*}=\frac{{4I}_s}{\mathrm{\π}}[\sin (\mathrm{\ωt}+\frac{\mathrm{\π}}{2})+\frac{1}{3}\sin (3\mathrm{\ωt}+3\·\frac{\mathrm{\π}}{2})+...+\frac{1}{n}\sin (\mathrm{n\ωt}+n\·\frac{\mathrm{\π}}{2})+...]---\left(1\right)$

Wherein, I _sfor current effective value, n=2k+1, k are positive integer.Containing all odd harmonic components in visible 180 ° of square wave currents.

In three-phase system, using 120 ° of square waves as Injection Current waveform, generate corresponding three-phase current instruction i ^* _refa, i ^* _refb, i ^* _refc, wherein i ^* _refathe advanced i of phase place ^* _refb120 °, i ^* _refbthe advanced i of phase place ^* _refc120 °.Now 120 ° of square wave currents can be through Fourier decomposition:

$i_{\mathrm{ref}}^{*}=\frac{2\sqrt{3}{I}_s}{\mathrm{\π}}[\sin (\mathrm{\ωt}+\frac{\mathrm{\π}}{2})-\frac{1}{5}\sin (5\mathrm{\ωt}+5\·\frac{\mathrm{\π}}{2})-\frac{1}{7}\sin (7\mathrm{\ωt}+7\·\frac{\mathrm{\π}}{2})+...]---\left(2\right)$

Wherein, I _sfor current effective value, visible 120 ° of square wave currents contain all h=6k ± 1 order harmonic components.

S4: feedback regulation power quality adjusting device output current being carried out to floating two close cycles, makes active power regulating device inject the output current identical with specified current flow waveform to electrical network.

S41: by output current instantaneous value i _cobtain feedback current i _f; To DC voltage instantaneous value V _dccarry out proportional integral (PI) and obtain active current i ^* _dc.To i ^* _ref,-i _fwith i ^* _dcsummation, obtains error current.In monophase system, single-phase error electric current is i ^* _er; In three-phase system error current, three-phase error current is i ^* _era, i ^* _erb, i ^* _erc.

S42: for monophase system, by single-phase error current i ^* _erbe transformed to the current i in α β rest frame ^* _α, i ^* _β, shown in (2), then by first order dq conversion by current signal stream i ^* _α, i ^* _βthe harmonic signal of middle different frequency is converted into the signal i in dq coordinate system ^* _d, i ^* _q, shown in (3).

$\left[\begin{array}{c}{i}_{\mathrm{\α}}^{*}\\ i_{\mathrm{\β}}^{*}\end{array}\right]=\left[\begin{array}{c}{i}_{\mathrm{er}}^{*}\left(t\right)\\ i_{\mathrm{er}}^{*}(t-T/4)\end{array}\right]---\left(3\right)$

$\left[\begin{array}{c}{i}_d^{*}\\ i_q^{*}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ \cos \mathrm{\ωt}& \sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}^{*}\\ i_{\mathrm{\β}}^{*}\end{array}\right]---\left(4\right)$

For three-phase system, be i by three-phase error current ^* _era, i ^* _erb, i ^* _ercconverted by dq, the command signal i in dq coordinate system can be converted into _d ^*, i _q ^*, shown in (5).

$\left[\begin{array}{c}{i}_d^{*}\\ i_q^{*}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\ωt}+\frac{2\mathrm{\π}}{3})\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{era}}^{*}\\ i_{\mathrm{erb}}^{*}\\ i_{\mathrm{erc}}^{*}\end{array}\right]---\left(5\right)$

S43: in dq coordinate system, to signal i _d ^*, i _q ^*carry out PI+RP control, obtain with reference to modulation signal u ^* _dand u ^* _q, and with reference to modulation signal u ^* _dand u ^* _qcarry out dq inverse transformation, obtain final reference modulation signal u ^* _r, it and high-frequency carrier signal compare, and produce pwm signal with the break-make of gauge tap pipe according to sinusoidal pulse width modulation principle, thus make active power regulating device inject the output current i identical with reference current waveform to electrical network _c.

As one embodiment of the present of invention, the control mode of adoption rate resonance under rest frame: (monophase system error current is i first to obtain error current by S41 ^* _er; Three-phase system error current is i ^* _era, i ^* _erb, i ^* _erc.), then error current is carried out the adjustment of ratio resonant feedback, wherein, the transport function for the accurate ratio resonant controller of feedback regulation is:

$G\left(s\right)=K_p+\frac{{2K}_R{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}_0^2}---\left(6\right)$

K in formula _pfor proportional coefficient, K _rfor resonance term coefficient, ω _cfor the bandwidth of controller, ω ₀for the frequency of controller gain maximum point.Final reference modulation signal u is obtained after above-mentioned feedback regulation ^* _r, it and high-frequency carrier signal compare and produce pwm signal with the break-make of gauge tap pipe, thus make active power regulating device inject the output current i identical with reference current waveform to electrical network _c.

Be illustrated in figure 3 the 180 ° of square-wave current waveform being applicable to monophase system of generation, be illustrated in figure 4 the 120 ° of square-wave current waveform being applicable to monophase system of generation.After electrical network harmonic electric current, the described Resonance detector built-up pattern based on best initial weights algorithm need be adopted to carry out the judgement of electrical network tuning-points.

S5: by RDFT computing, electrical network each characteristic harmonics voltage effective value V ' after acquisition injection reference current _phand characteristic harmonic current effective value I ' _sh, and calculate each harmonic applied power S ' _h.And to reference current i ^* _refcarry out RDFT computing, calculate each characteristic harmonic current effective value I of reference current ^* _rh.

S6: to harmonic voltage V _phwith V ' _ph, harmonic current effective value I _shwith I ' _sh, harmonic wave applied power S _hwith S ' _hcarry out synchronous accumulation filtering, the harmonic voltage, harmonic current and the harmonic wave applied power effective value that namely measure according to continuous several times are averaged to its cumulative summation again, and computing formula is:

$X_{\mathrm{so}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{T}_{\mathrm{si}}=n\·\frac{1}{n}\·[X_{s1}+X_{s2}+...+X_{\mathrm{sn}}]=n{\stackrel{\‾}{X}}_s---\left(7\right)$

In formula: for the same signal averaging of repetitive measurement, X _siit is the signal effective value measured for i-th time.

S7: according to the spectral characteristic of harmonic voltage, electric current and energy, sets up Resonance detector model, identifies electrical network resonance angular frequency ω _r.The ratio F of the h subharmonic current of system h subharmonic voltage changing value and injection before and after the reference current of calculating injection appointment waveform _uh:

$F_{\mathrm{uh}}=\frac{{\mathrm{\ΔV}}_{\mathrm{ph}}}{I_{\mathrm{rh}}^{*}}=\frac{|V_{\mathrm{ph}}-V_{\mathrm{ph}}^{\′}|}{I_{\mathrm{rh}}^{*}}---\left(8\right)$

The ratio F of the h subharmonic current of computing system h subharmonic current changing value and injection _ih:

$F_{\mathrm{Ih}}=\frac{{\mathrm{\ΔI}}_{\mathrm{sh}}}{I_{\mathrm{rh}}^{*}}=\frac{|I_{\mathrm{sh}}-I_{\mathrm{sh}}^{\′}|}{I_{\mathrm{rh}}^{*}}---\left(9\right)$

The ratio F of the h subharmonic current of computing system h subharmonic applied power changing value and injection _sh:

$F_{\mathrm{Sh}}=\frac{{\mathrm{\ΔS}}_h}{{\left(I_{\mathrm{rh}}^{*}\right)}^2}=\frac{|S_h-S_h^{\′}|}{{\left(I_{\mathrm{rh}}^{*}\right)}^2}---\left(10\right)$

Obtain F _uh, F _ihwith F _shafter, utilize normalization processing method, to F _uh, F _ihwith F _shcarry out linear nondimensionalization process, computing formula is:

$F_{\mathrm{Yh}}^{*}=\frac{F_{\mathrm{Yh}}}{\underset{h=h\left(k\right)}{\overset{n}{\mathrm{\Σ}}}{F}_{\mathrm{Yh}}}---\left(11\right)$

Wherein Y represents voltage u, electric current I or applied power S, and for monophase system h=2k+1, for three-phase system h=6k ± 1, k is positive integer.Result after normalized is substituted into detection model weighted sum again, and computing formula is:

$F_h=F_{\mathrm{uh}}^{*}{w}_{\mathrm{uh}}+F_{\mathrm{Ih}}^{*}{w}_{\mathrm{Ih}}+F_{\mathrm{Sh}}^{*}{w}_{\mathrm{Sh}}---\left(12\right)$

Wherein, w _uhfor the weight of voltage detecting index in built-up pattern, w _ihfor the weight of current detecting index in built-up pattern, w _shfor the weight of power detection index model in built-up pattern.F _hfor injecting the combination of the h subharmonic after h subharmonic current Judging index, electrical network resonance angular frequency ω can be judged thus _r.F _hfor injecting the combination of the h subharmonic after h subharmonic current Judging index, by comparing the combination Judging index F of each harmonic _hvalue, obtains F _hbe worth maximum overtone order h _r, electrical network resonance angular frequency ω can be judged _rfor ω _r=100 π h _r, i.e. electrical network resonance frequency f _rfor f _r=50h _r.Weighted value w _uh, w _ih, w _shthe impedance magnitude chosen with the AD accuracy of detection of network system parameter, load and electrical network relevant.If line voltage AD accuracy of detection is higher than power network current accuracy of detection, then w _uhvalue compares w _ihgreatly, on the contrary w _ihvalue compares w _uhgreatly; When the AD accuracy of detection of line voltage electric current is all higher, because power Judging index is the product of voltage Judging index and electric current Judging index, its spectrum curve is more precipitous, differentiates that electrical network tuning-points is more accurate, now w with power Judging index _shdesirable relatively larger value, but when AD accuracy of detection is lower, power Judging index error is maximum, now w _shvalue should be relatively little; When network load is larger, the spectrum curve of voltage Judging index and electric current Judging index is comparatively mild, but now power Judging index spectrum curve is still more precipitous, w _shdesirable relatively larger value; When electric network impedance is larger, voltage Judging index is more precipitous than the spectrum curve of electric current Judging index, and now weights are followed successively by w by order of successively decreasing _sh, w _uh, w _ihotherwise weights are followed successively by w by order of successively decreasing _sh, w _ih, w _uh.

S8: connecing in loaded electric system, make Z=L _sLs+R _sLfor the equiva lent impedance sum of electric network impedance and loaded impedance, C is electrical network shnt capacitor, due to the equivalent resistance R of network system _sLvery little, then the resonance angular frequency of network system is close to its undamped resonance angular frequency, and so electrical network resonance angular frequency is power network current I _swith load current I _lsum is I _sL, so I _sLwith the electric current I injecting electrical network _ctransport function be:

$\frac{I_{\mathrm{SL}}}{I_C}=\frac{1}{L_{\mathrm{SL}}{\mathrm{Cs}}^2+R_{\mathrm{SL}}\mathrm{Cs}+1}---\left(13\right)$

As s=j ω _rtime, make I _{c ω r}for the effective value of power network current is injected at resonance frequency place, I _{sL ω r}for resonance

Frequency place electrical network and load current sum.The amplitude-frequency response at electrical network resonance frequency place can be obtained:

$\left|\frac{I_{{\mathrm{SL\ω}}_r}}{I_{{\mathrm{C\ω}}_r}}\right|={\left|\frac{{\mathrm{\ω}}_r^2}{s^2+2{\mathrm{\ζ\ω}}_{r}s+{\mathrm{\ω}}_r^2}\right|}_{s=j{\mathrm{\ω}}_r}=\frac{1}{2\mathrm{\ζ}}---\left(14\right)$

Can calculate resonance ratio of damping is thus: $\mathrm{\ζ}=\left|\frac{I_{{\mathrm{C\ω}}_r}}{2I_{{\mathrm{SL\ω}}_r}}\right|---\left(15\right)$

Adopt the mode of injection 180 ° of square wave currents to detect single-phase electrical network tuning-points in the embodiment of the present invention, adopt the mode of injection 120 ° of square wave currents to detect three phase network tuning-points.Containing all odd characteristic harmonics that may occur in single-phase circuit in 180 ° of square wave currents, containing all (6k ± 1) subharmonic that may occur in three-phase three-line system in 120 ° of square wave currents, higher to the accuracy of mains by harmonics Resonance detector; In addition, the function realizing active injection reference current and harmonic analysis algorithm is all integrated on power quality adjusting device, simple to operation, the online automatic detection function of electrical network resonance can be realized quickly and accurately, thus guarantee power system stability reliability service.

Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (4)

1., based on an electrical network resonance automatic testing method for active Injection Current, it is characterized in that, comprise the steps:

S1: obtain the line voltage of point of common coupling, power network current and power quality adjusting device output current, DC voltage; And angular frequency and the phase theta of line voltage is obtained by digital servo-control link PLL;

Wherein, described point of common coupling refers to the tie point of power quality adjusting device main circuit and electrical network, and output current refers to active power quality regulating device output current i _c;

S2: carry out recursive discrete Fourier transformation respectively to described line voltage and described power network current, obtains electrical network each characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _sh; And according to described characteristic harmonics voltage effective value V _phwith characteristic harmonic current effective value I _shobtain each harmonic first applied power S _h;

S3: the current waveform according to setting obtains the reference current i corresponding with it ^* _ref; And to described reference current i ^* _refcarry out recursive discrete Fourier transformation, obtain each characteristic harmonic current effective value I of reference current ^* _rh;

S4: the feedback regulation described output current being carried out to floating two close cycles, makes active power regulating device inject the output current identical with the current waveform of described setting to electrical network;

S5: when described output current equals the current waveform of described setting, carries out recursive discrete Fourier transformation respectively to the line voltage in this moment and power network current, obtains and injects electrical network each characteristic harmonics voltage effective value V ' after reference current _phand characteristic harmonic current effective value I ' _sh, and according to described characteristic harmonics voltage effective value V ' _phand characteristic harmonic current effective value I ' _shobtain each harmonic second applied power S ' _h;

S6: according to injecting forward and backward electrical network each the characteristic harmonics voltage effective value V of reference current _phwith V ' _ph, characteristic harmonic current effective value I _shwith I ' _sh, characteristic harmonics harmonic wave applied power S _hwith S ' _h, each characteristic harmonic current effective value I of reference current ^* _rh, obtain the system performance parameter for describing electrical network resonance: electrical network resonance angular frequency ω _rand damping coefficientζ.

2. electrical network resonance automatic testing method as claimed in claim 1, it is characterized in that, in step S3, the current waveform of described setting is 180 ° of square wave currents or 120 ° of square wave currents.

3. electrical network resonance automatic testing method as claimed in claim 1, it is characterized in that, step S4 is specially:

S41: obtain feedback current i according to output current _f; To DC voltage V _dccarry out proportional integral and obtain active current i ^* _dc;

S42: according to described reference current i ^* _ref, feedback current i _fobtain error current with described active current, then error current is carried out Current adjustment, obtain with reference to modulation signal u ^* _r;

S43: by described with reference to modulation signal u ^* _racquisition pwm switching signal is compared with high-frequency carrier signal; Described pwm switching signal is used for the break-make of gauge tap pipe, thus makes active power regulating device inject the output current identical with the current waveform of setting to electrical network.

4. electrical network resonance automatic testing method as claimed in claim 1, is characterized in that, in step S6, according to formula obtain the h subharmonic combination Judging index F after injection h subharmonic current _h, by comparing the comprehensive detection index F of each harmonic _hvalue obtains F _hbe worth maximum overtone order h _r, and according to overtone order h _robtain electrical network resonance angular frequency ω _r=100 π h _r, namely electrical network resonance frequency is f _r=50h _r;

Wherein, w _uhfor the weight of voltage detecting index in built-up pattern, w _ihfor the weight of current detecting index in built-up pattern, w _shfor the weight of power detection index model in built-up pattern; F ^* _uhfor to F _uhcarry out the value after linear nondimensionalization process, F ^* _ihfor to F _ihcarry out the value after linear nondimensionalization process, F ^* _shfor to F _shcarry out the value after linear nondimensionalization process, wherein, f _uhfor the ratio of the h subharmonic current of electrical network h subharmonic voltage changing value and injection, F _ihfor the ratio of the h subharmonic current of electrical network h subharmonic current changing value and injection, F _shfor the ratio of the h subharmonic current of electrical network h subharmonic power change values and injection, wherein, $F_{\mathrm{uh}}=\frac{|V_{\mathrm{ph}}-V_{\mathrm{ph}}^{\′}|}{I_{\mathrm{rh}}^{*}},F_{\mathrm{Ih}}=\frac{|I_{\mathrm{sh}}-I_{\mathrm{sh}}^{\′}|}{I_{\mathrm{rh}}^{*}},F_{\mathrm{Sh}}=\frac{|S_h-S_h^{\′}|}{{\left(I_{\mathrm{rh}}^{*}\right)}^2}.$