CN105162162A - Phase perturbation based island detection system for distributed gird-connected inverter - Google Patents

Abstract

A phase perturbation based island detection system for a distributed gird-connected inverter is disclosed. The island detection system comprises a voltage controller, a multiplying unit, a summing unit, a current controller and a pulse width modulation generator which are serially connected in sequence, wherein the input ends of the voltage controller, the multiplying unit, the summing unit and the current controller are connected with direct current bus voltage and set direct current bus standard voltage respectively; the pulse width modulation generator is for outputting four paths of triggering pulse signals used for driving a single-phase H bridge inverter of a single-phase distributed gird-connected power generation system; the island detection system also comprises an orthogonal signal generator, a synchronous phase-locking device, a phase perturbation unit and a threshold value judging unit which are serially connected in sequence, wherein the input end of the orthogonal signal generator is connected with the voltage end of a point of common coupling of the single-phase distributed gird-connected power generation system; and the output end of the phase perturbation unit is connected with the input end of the multiplying unit. The phase perturbation based island detection system for the distributed gird-connected inverter has rapidness in island detection, stability of the detection system, and possibility of being used as island detection standard, can satisfy demand on percent of pass of the power quality, and has the important and actual application value in safe operation of the distributed new energy gird-connected power generation system.

Description

A kind of distributed grid-connected inverter alone island detection system based on phase perturbation

Technical field

The present invention relates to a kind of alone island detection system.Particularly relate to a kind of distributed grid-connected inverter alone island detection system based on phase perturbation.

Background technology

Consider many powerful advantages such as novel renewable energy cleanliness without any pollution and rich reserves, the structural adjustment of energy industry is just worldwide extensively risen.The renewable alternative energy source of Development of Novel, improves clean electric power supply, takes a long view, and no matter improves in technology, environmental protection, or all will have substantial promotion meaning in economic development etc.

Set up with leading type regenerative resources such as solar energy, wind energy, biomass energies the distributed generation system grown up to be intended to for user provides high-quality, clean, dynamical electric power resource.Distributed generation system, with its many advantages such as economic, efficient, obtained new development already in renewable electric power energy industry.Island phenomenon in distributed generation system is generally understood as: after main electrical network is because of the reasons such as electric fault, maintenance or misoperation and distributed generation system lost contact, electricity generation system as independent current source by continuation to local load supplying, form independent uncontrollable self-supporting power supply system.According to the relevant regulations of islanding detect standard UL17417 and IEEEStd1547, any distributed grid-connected electricity generation system must have islanding detect function, and completes detection rapidly at the appointed time, blocks inverter in time.

According to the up-to-date criteria for classifying, existing island detection method can be roughly divided into active detection, passive type detects and communicatively detects three major types.Passive type detection method is easy to realize, and can not encroach on the quality of power supply of power distribution network simultaneously, but there is larger islanding detect blind area in the method, thus have a strong impact on the accuracy of detection of self; Although communicatively detection method have real-time, stability is high, to electric energy without outstanding advantages such as infringements, the low profit problems caused by high cost becomes the main cause that self cannot be widely used.Compared with above two kinds of methods, the accuracy of detection that active detection method has advantage that is high, that can reduce even to eliminate check frequency is more applicable for actual commercial Application.

Active detection method adopts the measure certain parameter (as power frequency, current phase, current amplitude, current harmonics and voltage etc.) in inverter control being applied to disturbance usually, observe some parameter at point of common coupling (PCC) place change, judge whether isolated island occurs.The matter of utmost importance of active detection method is the selected of disturbing signal.If disturbing signal frequency is too high, then can amplify the effect of local loaded quality factor, cause the inspection of isolated island difficulty; If adopt even-order harmonic as disturbance, even-order harmonic faced by having to again is difficult to the puzzlement eliminated.Make a general survey of the most of documents and materials relevant to islanding detect, seldom have scholar to propose corresponding islanding detect new method in conjunction with voltage synchronous technology.The key of these class methods is how to ensure that the disturbance applied can not change or affect the position of the synchronous voltage over zero extracted in signal.

Summary of the invention

Technical problem to be solved by this invention is, there is provided a kind of when distributed generation system transfers islet operation to by being incorporated into the power networks, alone island detection system can complete and detect and the timely distributed grid-connected inverter alone island detection system based on phase perturbation blocking inverter within the time short as far as possible.

The technical solution adopted in the present invention is: a kind of distributed grid-connected inverter alone island detection system based on phase perturbation, for controlling single-phase distributed grid-connected electricity generation system, include and be sequentially connected in series: input connects the voltage controller of the DC bus standard voltage value of DC bus-bar voltage and setting respectively, to be multiplied with unitization grid-connected reference current for the reference amplitude of grid-connected current that voltage controller is exported and to obtain the multiplier of grid-connected reference current, the adder that the grid-connected sample rate current getting negative reality for the grid-connected reference current that exported by multiplier and polarity is sued for peace, current controller and the pulse width modulation generator that pulse width modulation exports four road start pulse signals of the single-phase H bridge inverter driven in single-phase distributed grid-connected electricity generation system is carried out to the signal that current controller exports, also include, be sequentially connected in series: input connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling, for generation of the orthogonal signal generator of two-phase quadrature voltage, for obtaining the genlock device at grid phase angle on orthogonal signal generator output signal basis, for generation of the phase perturbation unit of the unitization grid-connected reference current be multiplied with the reference amplitude of grid-connected current and the threshold decision unit based on jump Goertzel filter for carrying out voltage threshold judgement, wherein, the output of described phase perturbation unit connects the input of multiplier.

Described orthogonal signal generator includes the first adder be connected in series successively, first amplifier, second adder and first integrator, wherein, an input of described first adder connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling as the input of orthogonal signal generator, the output of first integrator divides three tunnels: the first via is directly as the first output of orthogonal signal generator, second tunnel polarity is connected with another input of first adder after getting and bearing, the input of the 3rd tunnel connection and all-pass filter, the output of described all-pass filter divides two-way: the first via is directly as the second output of orthogonal signal generator, second tunnel polarity is connected with another input of second adder after getting and bearing.

Described genlock device includes: the 3rd adder be connected in series successively, second amplifier, 3rd multiplier, second integral device and mod arithmetic unit, wherein, the output of described mod arithmetic unit forms the output of genlock device, for exporting grid phase angle, the input of described 3rd adder connects the output of the first multiplier and the second multiplier respectively, an input of described first multiplier directly connects the first via output of orthogonal signal generator, another input of first multiplier connects the first via output of orthogonal signal generator in succession by the first second-order low-pass filter, an input of the second multiplier directly connects the second road output of orthogonal signal generator, another input of second multiplier connects the second road output of orthogonal signal generator in succession by the second second-order low-pass filter, the input of described 3rd multiplier also connects the output of voltage compensator, the input of described voltage compensator connects the output of the first second-order low-pass filter and the output of the second second-order low-pass filter respectively.

Described phase perturbation unit includes the 3rd amplifier, sine operation device, the 4th amplifier, the 4th adder and the cos operation device that are connected in series successively, wherein, input and another input of the 4th adder of described 3rd amplifier are connected the output of genlock device jointly, and the output of the output formation phase perturbation unit of described cos operation device connects an input of described multiplier.

Described islanding detect realizes unit and includes the sample circuit and jump Goertzel filter that connect successively, wherein, the input of described sample circuit connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling, the output voltage of described jump Goertzel filter is as the detection voltage of single-phase distributed grid-connected electricity generation system, contrast with the voltage threshold set, when output voltage is more than or equal to the voltage threshold of setting, pulse width modulation generator does not export four road start pulse signals, single-phase H bridge inverter in single-phase distributed grid-connected electricity generation system does not work, when output voltage is less than the voltage threshold of setting, pulse width modulation generator exports four road start pulse signals, single-phase H bridge inverter work in single-phase distributed grid-connected electricity generation system.

Described jump Goertzel filter includes: the comb filter be connected in series successively, slender acanthopanax musical instruments used in a Buddhist or Taoist mass, 5th amplifier and the 6th adder, wherein, the output of slender acanthopanax musical instruments used in a Buddhist or Taoist mass is divided into three tunnels again after the first delay cell: the first via connects an input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass by the 6th amplifier, second tunnel by after the second delay cell again polarity get another input of negative connection slender acanthopanax musical instruments used in a Buddhist or Taoist mass, the 3rd direct polarity in tunnel gets negative rear another input connecting the 6th adder, the input of described comb filter connects the output of sample circuit, the output of described 6th adder forms the output voltage of jump Goertzel filter.

Described comb filter includes the 7th adder, an input of described 7th adder directly connects the output of sample circuit, another input of 7th adder connects the output of sample circuit by the 3rd delay cell, the output of described 7th adder connects the input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass.

A kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention, possesses following advantage: one is the rapidity of islanding detect, and the realization of rapidity needs to rely on the data processing algorithm with less operand usually; Another is should the stability of ensuring method self and the possibility as islanding detect standard, simultaneously the method also should meet the requirement to quality of power supply qualification rate simultaneously, thus provides important actual application value and theory directive significance for the safe operation of distributed new grid-connected system.The present invention has following technique effect:

(1) the genlock device under the single-phase grid-connected system adopted, the structure from single-phase mains voltage to two-phase quadrature voltage can be realized fast, connected by all-pass filter each harmonic to identical gain between the two-phase quadrature voltage simultaneously built, therefore containing identical total harmonic distortion factor, this just eliminates the phase-locked precision problem brought because harmonic wave is uneven in two-phase quadrature voltage.

(2) the genlock device under the single-phase grid-connected system adopted, can obtain the phase information of electrical network rapidly and accurately, and this phase locking unit also has the rapidity to the electrical network parameter stronger robustness of sudden change and frequency adjustment simultaneously.

(3) the phase perturbation injection method adopted, can ensure that the phase perturbation injected can not change the position of grid phase information voltage over zero, this ensures that there distributed new grid-connected system and can run with unity power factor under grid-connect mode.

(4) by the reasonable choosing value to phase perturbation coefficient, the controllability to the change of grid-connected current total harmonic distortion factor can be realized, thus effectively can control the extent of damage of the program to the quality of power supply.

(5) the harmonic component extraction algorithm for islanding detect has lower data operation quantity, ensure that whole alone island detection system can complete islanding detect rapidly in a short period of time.

(6) because total harmonic distortion factor in the program is controlled, the harmonic component extraction algorithm of employing is stable, and therefore, whole alone island detection system is also reliable, and the possibility as a kind of islanding detect standard is very high.

Accompanying drawing explanation

Fig. 1 is single-phase distributed grid-connected electricity generation system block diagram, wherein,

V _dc: inverter DC bus side voltage, because magnitude of voltage is higher, is also called DC bus high pressure;

Single-phase H bridge inverter A: input termination DC bus high pressure, exports termination LC filter (high fdrequency component in filtering inverter output current); Four switching tubes in single-phase H bridge inverter A select IGBT, and the gate pole of switching tube drives by PWM trigger impulse;

V _pCCand i _invbe respectively the voltage at point of common coupling place, grid-connected current (variable is explained and is applicable to Fig. 2);

Local load: form RLC shunt load by resistance, inductance and Capacitance parallel connection, be mainly used in islanding detect;

Fig. 2 is the distributed grid-connected inverter alone island detection system entire block diagram that the present invention is based on phase perturbation, wherein,

V _dc: DC bus high pressure V _{dc_ref}: the DC bus high voltage standard value of setting

I ^* _inv: grid-connected current magnitude references cos θ _inv ^*: unitization grid-connected reference current

I ^* _inv: grid-connected reference current θ _g: the angle of grid phase accurately obtained by PLL

θ _inv ^*: the phase reference angle that grid-connected inverters controls, by θ _gbe formed by stacking with the phase perturbation amount injected;

Fig. 3 is novel orthogonal signal generator block diagram of the present invention;

Fig. 4 is the structured flowchart of genlock device of the present invention;

Fig. 5 is the phase perturbation cellular construction block diagram in the present invention;

Fig. 6 is that disturbance phase place in the present invention is to the analogous diagram of genlock Influence on test result;

Fig. 7 is the analogous diagram that the disturbance phase place in the present invention affects grid-connected current;

Fig. 8 is the simplified electrical circuit diagram of distributed grid-connected electricity generation system used in the present invention;

Fig. 9 is that the present invention jumps the structured flowchart of Goertzel filter;

Figure 10 is line voltage analogous diagram;

Figure 11 is the two-phase quadrature voltage v built by orthogonal signal generator of the present invention _αand v _βanalogous diagram;

Figure 12 is the frequency self-adaption adjustment dynamic response curve figure of genlock device;

Figure 13 is the v detected when local load is pure resistor load in the present invention _pCCoscillogram;

Figure 14 is that the present invention works as the grid-connected inverters current i detected when local load is pure resistor load _invoscillogram;

Figure 15 is the oscillogram of the point of common coupling place third harmonic voltage adopting jump Goertzel filter detection to arrive in the present invention when local load is pure resistor load;

Figure 16 is the v detected when local load is RLC shunt load in the present invention _pCCoscillogram;

Figure 17 is the grid-connected inverters current i detected when local load is RLC shunt load in the present invention _invoscillogram;

Figure 18 is the oscillogram of the point of common coupling place third harmonic voltage adopting jump Goertzel filter detection to arrive in the present invention when local load is RLC shunt load.

In figure

A: single-phase H bridge inverter B:LC filter

C: local load D: circuit breaker

E: electrical network 1: voltage controller

2: multiplier 3: adder

4: current controller 5: pulse width modulation generator

6: orthogonal signal generator 7: genlock device

8: phase perturbation unit 9: islanding detect realizes unit

61: first adder 62: the first amplifier

63: second adder 64: first integrator

65: all-pass filter 71: the first second-order low-pass filter

72: the first multiplier 73: the second second-order low-pass filters

74: the second multiplier 75: the three adders

76: the second amplifiers 77: voltage compensator

78: the three multipliers 79: second integral device

710:mod arithmetic unit 81: the three amplifier

82: sine operation device 83: the four amplifier

84: the four adders 85: cos operation device

91: sample circuit 92: jump Goertzel filter

921: comb filter 922: the slender acanthopanax musical instruments used in a Buddhist or Taoist mass

923: the five amplifier 924: the six adders

925: the first delay cell 926: the six amplifiers

927: the second delay cell 9211: the seven adders

9212: the three delay cells

Embodiment

Below in conjunction with embodiment and accompanying drawing, a kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention is described in detail.

Because a kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention proposes and sets up on phase perturbation basis, therefore, the prerequisite that whole alone island detection system can effectively realize is the accurate fast Acquisition of this system to grid phase information; Although active alone island detection method can inevitably be injected a small amount of harmonic wave and then affect total harmonic distortion factor (THD) in power distribution network, should make every effort to accomplish the controllability to total harmonic distortion factor change in the specific implementation of method; When distributed generation system transfers islet operation to by being incorporated into the power networks, alone island detection system should complete and detects and block inverter in time within the time short as far as possible, and this just requires to comprise as far as possible few data operation quantity in proposed islanding detect algorithm.Therefore, solve emphatically in the present invention and realize following problem:

(1) the genlock device under the single-phase grid-connected system adopted, the structure from single-phase mains voltage to two-phase quadrature voltage should be realized fast, the two-phase quadrature voltage built should have identical total harmonic distortion factor, eliminates the phase-locked precision problem brought because harmonic wave is uneven in two-phase quadrature voltage.

(2) the genlock device under the single-phase grid-connected system adopted, should have the ability obtaining grid phase information rapidly and accurately, possesses the rapidity to the electrical network parameter stronger robustness of sudden change and frequency adjustment simultaneously.

(3) injection of the phase perturbation adopted realizes, and should balance the relation of phase perturbation amount and grid phase information, ensures that the phase perturbation amount injected can not change or affect the position of grid phase information voltage over zero.

(4) in order to reduce the extent of damage to the quality of power supply, the grid-connected current total harmonic distortion factor brought by disturbance phase place should be controlled.

(5) algorithm for islanding detect should have lower data operation quantity, thus ensures that whole alone island detection system can complete islanding detect rapidly within the shorter time, to maintain the reliability service of distributed new grid-connected system.

Single-phase distributed grid-connected electricity generation system corresponding to a kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention as shown in Figure 1, for the AC network of 220V, the DC bus-bar voltage V of inverter direct-flow side in distributed grid-connected electricity generation system _dcbe chosen to be 400V.What inverter adopted is realize the controlled single-phase H bridge topology of grid-connected current by single-polarity PWM modulated energy, and inverter output current is through the filter action of LC filter, and inner high frequency harmonic components is effectively eliminated.When breaker closing in Fig. 1, inverter output current injects electrical network; When circuit breaker disconnects, inverter output current can be used for local RLC load supplying.

As shown in Figure 2, a kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention, for controlling single-phase distributed grid-connected electricity generation system, mainly to set up on the basis of Grid-connected Control Strategy, include and be sequentially connected in series: input connects DC bus-bar voltage V respectively _dcwith the DC bus standard voltage value V of setting _{dc_ref}voltage controller 1, the reference amplitude I of grid-connected current for voltage controller 1 is exported ^* _invwith unitization grid-connected reference current cos θ _inv ^*be multiplied and obtain grid-connected reference current i ^* _invmultiplier 2, grid-connected reference current i for multiplier 2 is exported ^* _invthe grid-connected sample rate current i of negative reality is got with polarity ^* _invthe adder 3 of summation, the current controller 4 and pulse width modulation generator 5 that pulse width modulation exports the four road start pulse signal PWM1 ~ PWM4 of the single-phase H bridge inverter A driven in single-phase distributed grid-connected electricity generation system is carried out to the signal that current controller 4 exports, also include, be sequentially connected in series: input connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling PCC, for generation of the orthogonal signal generator 6 of two-phase quadrature voltage, for outputing signal the genlock device 7 basis obtaining grid phase angle at orthogonal signal generator 6, for generation of the reference amplitude I with grid-connected current ^* _invthe unitization grid-connected reference current cos θ be multiplied _inv ^*phase perturbation unit 8 and the threshold decision unit 9 based on jump Goertzel filter for carrying out voltage threshold judgement, wherein, the output of described phase perturbation unit 8 connects the input of multiplier 2.

The main operational principle of a kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention is: by the DC bus-bar voltage V of input _dc, setting DC bus-bar voltage standard value V _{dc_ref}be input to voltage controller, the output of voltage controller is as the magnitude references I of grid-connected current ^* _inv, this magnitude references and unitization grid-connected reference current cos θ _inv ^*be multiplied, obtain grid-connected reference current i ^* _inv, this grid-connected reference current and actual grid-connected sample rate current i ^* _invdiffer from, its difference is transported to current controller, the output of current controller is transported to PWM generator, the four road trigger impulse PWM1 ~ PWM4 produced by PWM generator drive four switching tubes in the single-phase H bridge inverter shown in Fig. 1, realize from direct current to the reversals exchanged, the LC filter of output current in Fig. 1 of inverter, injects electrical network after obtaining the grid-connected current with line voltage with frequency homophase.

Distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention on specific algorithm with Grid-connected Control Strategy interdependence, indivisible.Specifically, the voltage v at point of common coupling PCC place _pCCafter the QSG (orthogonal signal generator) that proposes in the present invention and PLL (phase-locked loop), obtain grid phase angle θ accurately _g, this phase angle superposes with the phase perturbation amount of injection, the phase reference angle θ that its result controls as grid-connected inverters _inv ^*, this phase reference angle, after cos operation, obtains unitization grid-connected reference current cos θ _inv ^*, this result again with the magnitude references I of grid-connected current ^* _invbe multiplied, product is as grid-connected reference current i ^* _inv, participate in the cutting-in control of inverter.Because the phase perturbation injected can produce a certain amount of triple harmonic current component in grid-connected current, this triple harmonic current component will produce corresponding third harmonic voltage component at point of common coupling PCC place.In islanding detect algorithm, the jump Goertzel filter designed in the present invention is adopted to extract third harmonic voltage component.When the mode of operation of distributed generation system transfers islet operation to by being incorporated into the power networks, if the third harmonic voltage component at the point of common coupling PCC place detected has exceeded the Islanding detection threshold values preset in islanding detect algorithm, control system completes islanding detect rapidly, blocks inverter in time.

As shown in Figure 3, described orthogonal signal generator 6 includes first adder 61, first amplifier 62, second adder 63 and the first integrator 64 that are connected in series successively, wherein, an input of described first adder 61 connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling PCC as the input of orthogonal signal generator 6, and the output of first integrator 64 divides three tunnels: the first via is directly as the first output v of orthogonal signal generator 6 _α, the second tunnel polarity is connected with another input of first adder 61 after getting and bearing, and the 3rd tunnel connects the input of all-pass filter 65, and the output of described all-pass filter 65 divides two-way: the first via is directly as the second output v of orthogonal signal generator 6 _β, the second tunnel polarity is connected with another input of second adder 63 after getting and bearing.

In the present invention, by the novel orthogonal signal generator shown in Fig. 3, according to the single-phase mains voltage signal of input, the two-phase quadrature voltage v needed for genlock device can be produced _αand v _β.Such orthogonal signal generator can provide the output signal with identical percent harmonic distortion (THD), i.e. v _αand v _β, prevent the phase-locked precision problem brought because contained harmonic wave is different.In Fig. 3, the transfer function of orthogonal signal generator is

$\left\{\begin{array}{c}\frac{V_{\mathrm{\α}}\left(s\right)}{V_g\left(s\right)}=\frac{{\mathrm{k\ω}}_o\left({\mathrm{\ω}}_o+s\right)}{s^2+{\mathrm{k\ω}}_{o}s+\left(1+k\right){\mathrm{\ω}}_o^2}\\ \frac{V_{\mathrm{\β}}\left(s\right)}{V_g\left(s\right)}=\frac{{\mathrm{k\ω}}_o\left({\mathrm{\ω}}_o-s\right)}{s^2+{\mathrm{k\ω}}_{o}s+\left(1+k\right){\mathrm{\ω}}_o^2}\end{array}\right.---\left(1\right)$

In formula, ω _orepresent the electrical network fundamental frequency estimated, k represents the gain of orthogonal signal generator.

Do not considering, under the prerequisite that mains by harmonics affects, to suppose that single-phase mains voltage signal can be expressed as v _g=Vcos ω t, wherein V and ω is respectively the amplitude of line voltage and actual electrical network fundamental frequency, then when the electrical network fundamental frequency estimated equals actual electrical network fundamental frequency, i.e. ω _o=ω, after the orthogonal signal generator shown in Fig. 3, the two-phase output voltage obtaining any time is respectively

$\{\begin{array}{c}{v}_{\mathrm{\α}}\left(t\right)=V\cos \mathrm{\ω}t-{\mathrm{Ve}}^{-\frac{k\mathrm{\ω}}{2}t}\[{\mathrm{cosh\ξ}}_d\mathrm{\ω}t-\frac{{\mathrm{ksinh\ξ}}_d\mathrm{\ω}t}{\sqrt{2}{\mathrm{\ξ}}_d}\]\\ v_{\mathrm{\β}}\left(t\right)=V\sin \mathrm{\ω}t-\frac{1+k}{{\mathrm{\ξ}}_d}{\mathrm{Ve}}^{-\frac{k\mathrm{\ω}}{2}t}{\mathrm{sinh\ξ}}_d\mathrm{\ω}t\end{array}---\left(2\right)$

In formula, ${\mathrm{\ξ}}_d=\sqrt{1+k-\frac{1}{4}{k}^2}.$

Under limit, two-phase output voltage can be expressed as

$\left\{\begin{array}{c}{v}_{\mathrm{\α}}=V\cos \mathrm{\ω}t\\ v_{\mathrm{\β}}=V\sin \mathrm{\ω}t\end{array}\right.---\left(3\right)$

Can find from formula (3), under being in limit, the two-phase output voltage v that orthogonal signal generator as shown in Figure 3 obtains _αand v _βit is strict orthogonal.

For second-order system, available setting time t _s=4.6 τ roughly estimate setting time.In formula (2), timeconstantτ=2/k ω, therefore, for given setting time t _s, the gain k of the orthogonal signal generator shown in Fig. 3 can be calculated as follows:

$k=\frac{9.2}{t_s\mathrm{\ω}}---\left(4\right)$

As shown in Figure 4, described genlock device 7 includes: the 3rd adder 75, second amplifier 76, the 3rd multiplier 78, second integral device 79 and the mod arithmetic unit 710 that are connected in series successively, wherein, the output of described mod arithmetic unit 710 forms the output of genlock device 7, for exporting grid phase angle θ _g, the input of described 3rd adder 75 connects the output of the first multiplier 72 and the second multiplier 74 respectively, and an input of described first multiplier 72 directly connects the first via output v of orthogonal signal generator 6 _α, another input of the first multiplier 72 meets the first via output v of orthogonal signal generator 6 in succession by the first second-order low-pass filter 71 _α, an input of the second multiplier 74 directly connects the second road output v of orthogonal signal generator 6 _β, another input of the second multiplier 74 meets the second road output v of orthogonal signal generator 6 in succession by the second second-order low-pass filter 73 _β, the input of described 3rd multiplier 78 also connects the output of voltage compensator 77, and the input of described voltage compensator 77 connects the output v of the first second-order low-pass filter 71 respectively _{α L}and the second output v of second-order low-pass filter 73 _{β L}.

If consider the harmonic disturbance under actual electric network background, so under steady state conditions, a reactor by v that orthogonal signal generator produces _αand v _βin can be mixed into a certain amount of harmonic component equally, in order to effectively weaken these harmonic components, realize in block diagram at the genlock device shown in Fig. 4, special to introduce such as formula (5) described second-order low-pass filter.

$SOLF\left(s\right)=\frac{{\mathrm{\ω}}_o^2}{s^2+\sqrt{2}{\mathrm{\ω}}_{o}s+{\mathrm{\ω}}_o^2}---\left(5\right)$

The magnitude-phase characteristics equation of formula (5) described second-order low-pass filter is

$\left\{\begin{array}{c}H=\left|SOLF\left(j\mathrm{\ω}\right)\right|=\frac{{\mathrm{\ω}}_o^2}{\sqrt{{\left(\sqrt{2}{\mathrm{\ω\ω}}_o\right)}^2+{\left({\mathrm{\ω}}^2+{{\mathrm{\ω}}_o}^2\right)}^2}}\\ P=\∠SOLF\left(j\mathrm{\ω}\right)=-\arccos \frac{{{\mathrm{\ω}}_o}^2-{\mathrm{\ω}}^2}{\sqrt{{\left(\sqrt{2}{\mathrm{\ω\ω}}_o\right)}^2+{\left({\mathrm{\ω}}^2+{{\mathrm{\ω}}_o}^2\right)}^2}}\end{array}\right.---\left(6\right)$

As the output voltage v of orthogonal signal generator _αand v _βeach via (as shown in Figure 4) after second-order low-pass filter filtering, the response obtained exports and can be expressed as

$\{\begin{array}{c}{v}_{\mathrm{\α}L}=HV\cos \left(\mathrm{\ω}t+P\right)\\ v_{\mathrm{\β}L}=HV\sin \left(\mathrm{\ω}t+P\right)\end{array}---\left(7\right)$

The frequency self-adaption controller designed in genlock device is restrained according to the adjustment shown in formula (8).

${\stackrel{\·}{\mathrm{\ω}}}_o=-\mathrm{\δ}\·\frac{v_{\mathrm{\α}L}{v}_{\mathrm{\α}}+v_{\mathrm{\β}L}{v}_{\mathrm{\β}}}{v_{\mathrm{\α}L}^2+v_{\mathrm{\β}L}^2}---\left(8\right)$

In formula, δ is frequency self-adaption regulation coefficient.

Formula (3) and formula (7) are substituted into formula (8), and when the electrical network fundamental frequency estimated is approximately equal to actual electrical network fundamental frequency, abbreviation obtains

${\stackrel{\·}{\mathrm{\ω}}}_o=2\mathrm{\δ}\frac{\mathrm{\ω}-{\mathrm{\ω}}_o}{\mathrm{\ω}}---\left(9\right)$

The dynamic adjustment process of the frequency self-adaption adjustment rule shown in formula (9) is: as ω > ω _otime, automatically can adjust ω _oit is made linearly to increase; As ω < ω _otime, ω can be adjusted in time again _oit is made linearly to reduce; Work as ω _oω is equaled, ω through self-adaptative adjustment _oremain unchanged.The process of frequency self-adaption adjustment is again the process that phase locking unit exports grid phase self-adjusting simultaneously.Again through mod computing after frequency self-adaption adjustment acquisition electrical network fundamental frequency, the phase angle θ of electrical network can be obtained _g.

The value of frequency self-adaption regulation coefficient δ, according to formula (10), can try to achieve according to given time constant η.Time constant η is desirable power frequency period, i.e. a 20ms usually.

$\mathrm{\&delta;}=\frac{\mathrm{\&omega;}}{2\mathrm{\&eta;}}---\left(10\right)$

It should be noted that, the impact of frequency self-adaption regulation coefficient δ shown in formula (10) not by grid voltage amplitude in value, therefore in the frequency self-adaption adjustment process shown in formula (9), even if there is voltage fluctuation, also the fast Acquisition of genlock device to mains frequency and grid phase can not be affected, therefore, the frequency-tracking scheme described in formula (8) has good robustness to electrical network amplitude fluctuations.

As shown in Figure 5, described phase perturbation unit 8 includes the 3rd amplifier 81, sine operation device 82, the 4th amplifier 83, the 4th adder 84 and the cos operation device 85 that are connected in series successively, wherein, input and another input of the 4th adder 84 of described 3rd amplifier 81 are connected the output θ of genlock device 7 jointly _g, the output of described cos operation device 85 forms the output cos θ of phase perturbation unit 8 _inv ^*connect an input of described multiplier 2.

The principle of grid phase signal voltage over zero position can not be changed, the disturbance quantity σ determined by SIN function in scheme according to the phase perturbation of foregoing injection _injbe injected into current electric grid lock phase angle theta _gin, as the phase reference angle in distributed generation system cutting-in control.Specific implementation block diagram as shown in Figure 5.

In Fig. 5, the phase perturbation amount of injection is

σ _inj＝μsin2θ _g(11)

In formula, μ is for phase perturbation coefficient during islanding detect.

Now, the phase reference containing disturbance is such as formula shown in (12):

${\mathrm{\&theta;}}_{inv}^{*}={\mathrm{\&theta;}}_g+{\mathrm{\&sigma;}}_{inj}={\mathrm{\&theta;}}_g+\mathrm{\&mu;}sin2{\mathrm{\&theta;}}_g---\left(12\right)$

Fig. 6 shows the disturbance phase place that adds to the impact of genlock result.In Fig. 6, solid line represents the phase angle θ after adding disturbance _inv ^*, the phase reference value namely in cutting-in control; Dotted line represents the undisturbed phase angle θ that phase-locked loop exports when not adding disturbance quantity _g.With the phase angle θ exported during undisturbed _gcompare, the disturbance quantity added does not affect the phase place at zero crossing and peak value place, but then can produce phase deviation to a certain extent in other positions.

Convolution (12), can obtain grid-connected reference current is

$I_{inv}^{*}{\mathrm{cos\&theta;}}_{inv}^{*}=I_{inv}^{*}cos({\mathrm{\&theta;}}_g+\mathrm{\&mu;}sin2{\mathrm{\&theta;}}_g)---\left(13\right)$

5kW combining inverter emulates, the grid-connected reference current i obtained ^* _invwaveform as shown in Figure 7.As can be seen from Fig. 7, at zero crossing and the peak value place of reference current waveshape, the impact not by external disturbance phase place in phase place.

When enough hour of phase perturbation coefficient μ value, formula (13) can abbreviation further, obtains

$\begin{array}{c}{I}_{inv}^{*}{\mathrm{cos\&theta;}}_{inv}^{*}=I_{inv}^{*}\left(1-\frac{\mathrm{\&mu;}}{2}\right){\mathrm{cos\&theta;}}_g+I_{inv}^{*}\frac{\mathrm{\&mu;}}{2}\cos 3{\mathrm{\&theta;}}_g\\ \&ap;I_{inv}^{*}{\mathrm{cos\&theta;}}_g+I_{inv}^{*}\frac{\mathrm{\&mu;}}{2}\cos 3{\mathrm{\&theta;}}_g\end{array}---\left(14\right)$

Triple harmonic current component in formula (14) can be expressed as independently

$i_{inv\_150Hz}=I_{inv}^{*}\frac{\mathrm{\&mu;}}{2}cos3{\mathrm{\&theta;}}_g---\left(15\right)$

Phase perturbation amount σ described by formula (11) _injcreate such as formula the triple harmonic current component described in (15) in the reference current that grid-connected inverters controls.The total harmonic distortion factor of grid-connected current and the percentage of triple harmonic current component can be determined according to phase perturbation coefficient μ.Therefore, the total harmonic distortion factor in grid-connected current and triple harmonic current component are controlled.In different μ value situation, the percentage of corresponding total harmonic distortion factor and triple-frequency harmonics content is as shown in table 1.

The THD of grid-connected current and triple-frequency harmonics content during table 1 different μ value

According to can not more than 5% to the grid-connected current total harmonic distortion factor specified in combining inverter quality of power supply relevant criterion, and the triple harmonic current injecting electrical network must lower than the technical requirement of 4%, according to the data that table 1 provides, if adopt the phase perturbation injection method carried to carry out islanding detect herein, need to consider the power quality problem that combining inverter causes and access electrical network background harmonics, so the value upper limit of coefficient of disturbance μ lower than 0.08, and specifically should should provide according to Practical Project condition.

As shown in Figure 2, described islanding detect realizes unit 9 and includes the sample circuit 91 and jump Goertzel filter 92 that connect successively, wherein, the input of described sample circuit 91 connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling PCC, the output voltage v of described jump Goertzel filter 92 _mn (), as the detection voltage of single-phase distributed grid-connected electricity generation system, contrasts with the voltage threshold set, as output voltage v _mwhen () is more than or equal to the voltage threshold of setting n, pulse width modulation generator 5 does not export four road start pulse signal PWM1 ~ PWM4, and the single-phase H bridge inverter A in single-phase distributed grid-connected electricity generation system does not work, as output voltage v _mwhen () is less than the voltage threshold of setting n, pulse width modulation generator 5 exports four road start pulse signal PWM1 ~ PWM4, and the single-phase H bridge inverter A in single-phase distributed grid-connected electricity generation system works.

About the setting of Islanding detection threshold values.When distributed generation system works in grid-connect mode and island mode respectively, the complex impedance at point of common coupling place is different, causes the also corresponding difference of third harmonic voltage herein.This point can be used for the foundation setting Islanding detection threshold values.For ease of analyzing and statement, Fig. 8 gives the simplification circuit of single-phase distributed grid-connected electricity generation system.

When distributed generation system works in grid-connect mode, what the complex impedance at point of common coupling place was local load complex impedance with electrical network complex impedance is in parallel, and research finds, under normal conditions, the resistance value when resistance value of triple-frequency harmonics is far smaller than local load corresponding triple-frequency harmonics in electrical network, namely | Z _{g_150Hz}|| Z _{l_150Hz}|, now, the third harmonic voltage vector at point of common coupling place can be expressed as

$\begin{array}{c}{\stackrel{\&CenterDot;}{V}}_{PCC\_150Hz}=\left({\stackrel{\&CenterDot;}{Z}}_{L\_150Hz}\left|\right|{\stackrel{\&CenterDot;}{Z}}_{g\_150Hz}\right)\&CenterDot;{\stackrel{\&CenterDot;}{I}}_{inv\_150Hz}\\ \&ap;{\stackrel{\&CenterDot;}{Z}}_{g\_150Hz}\&CenterDot;I_{inv\_150Hz}\end{array}---\left(16\right)$

When distributed generation system works in island mode, the complex impedance at point of common coupling place is the complex impedance of local load, and therefore, the third harmonic voltage vector expression at point of common coupling place is

${\stackrel{\&CenterDot;}{V}}_{PCC\_150Hz}={\stackrel{\&CenterDot;}{Z}}_{L\_150Hz}\&CenterDot;{\stackrel{\&CenterDot;}{I}}_{inv\_150Hz}---\left(17\right)$

The impedance of local RLC load can be tried to achieve according to formula (18).

$\left|{\stackrel{\&CenterDot;}{Z}}_{L\_150Hz}\right|=\frac{1}{\sqrt{{\left(\frac{1}{R}\right)}^2+{\left(2\mathrm{\&pi;}\&CenterDot;150C-\frac{1}{2\mathrm{\&pi;}\&CenterDot;150L}\right)}^2}}---\left(18\right)$

In formula (18), the resistance R in local RLC load, inductance L and electric capacity C are usually according to formula (19) value.

$\left\{\begin{array}{c}R=\frac{V^2}{P}\\ L=\frac{V^2}{2{\mathrm{\&pi;f}}_r{\mathrm{PQ}}_f}\\ C=\frac{{\mathrm{PQ}}_f}{2{\mathrm{\&pi;f}}_r{V}^2}\end{array}\right.---\left(19\right)$

In formula (19), V is the effective value of line voltage, the active power that P provides for combining inverter, f _rfor the resonance frequency of RLC load, Q _ffor the quality factor of RLC load.When doing islanding detect, f _r, Q _fusually value is 50Hz and 2.5 respectively.

Because | Z _{g_150Hz}|| Z _{l_150Hz}|, so when distributed generation system produces island effect, v _pCCin third-harmonic component can become large, therefore, with this, the voltage effective value that can be calculated by formula (16), as the threshold value of islanding detect, judges whether distributed generation system is in islet operation.

(2), the extraction of point of common coupling place third-harmonic component

When carrying out continuous sampling to real number signal and calculating DFT frequency spectrum, sliding-type DFT filter described in formula (20) obtains extensive concern because having less operand, but when carrying out numerical approximation computing to filter coefficient, the truncated error of getting very easily causes the instability of oneself boundary.In order to there is less operand equally when ensureing spectrum analysis, safeguard the stability of self simultaneously, effective measures do the conversion of shape such as formula (21) to the z territory transfer function of the sliding-type DFT filter described by formula (20), forms novel jump Goertzel filter thus.

$H_{SDFT}\left(z\right)=\frac{1-z^{-N}}{1-e^{j2\mathrm{\&pi;}m/N}{z}^{-1}}---\left(20\right)$

$\begin{array}{c}{H}_{HG}\left(z\right)=\frac{e^{j2\mathrm{\&pi;}m/N}\left(1-e^{-j2\mathrm{\&pi;}m/N}{z}^{-1}\right)\left(1-z^{-N}\right)}{\left(1-e^{-j2\mathrm{\&pi;}m/N}{z}^{-1}\right)\left(1-e^{j2\mathrm{\&pi;}m/N}{z}^{-1}\right)}\\ =\frac{\left(e^{j2\mathrm{\&pi;}m/N}-z^{-1}\right)\left(1-z^{-N}\right)}{1-2\cos \left(2\mathrm{\&pi;}m/N\right)z^{-1}+z^{-1}}\end{array}---\left(21\right)$

In formula (20) and formula (21), N is sampling number total in power frequency period, and m is the specific frequency corresponding with forcing frequency.If forcing frequency, sample frequency and electrical network fundamental frequency are expressed as f _dist, f _samand f _g, then N and m can carry out value according to formula (22).

$\{\begin{array}{c}N=f_{sam}/f_g\\ m=f_{dist}/f_{sam}\end{array}---\left(22\right)$

The design carrying out jump Goertzel filter according to formula (21) realizes.As shown in Figure 9, described jump Goertzel filter 92 includes: the comb filter 921 be connected in series successively, slender acanthopanax musical instruments used in a Buddhist or Taoist mass 922, 5th amplifier 923 and the 6th adder 924, wherein, the output of slender acanthopanax musical instruments used in a Buddhist or Taoist mass 922 is divided into three tunnels again after the first delay cell 925: the first via connects an input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass 922 by the 6th amplifier 926, second tunnel by after the second delay cell 927 again polarity get another input of negative connection slender acanthopanax musical instruments used in a Buddhist or Taoist mass 922, the 3rd direct polarity in tunnel gets negative rear another input connecting the 6th adder 924, the input of described comb filter 921 connects the output of sample circuit 91, the output of described 6th adder 924 forms the output voltage v of jump Goertzel filter 92 _m(n).

Described comb filter 921 includes the 7th adder 9211, an input of described 7th adder 9211 directly connects the output of sample circuit 91, another input of 7th adder 9211 connects the output of sample circuit 91 by the 3rd delay cell 9212, the output of described 7th adder 9211 connects the input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass 922.

In Fig. 9, intermediate variable w _m(n) and output variable v _mn the numerical operation relation of () is such as formula shown in (23) and formula (24).

$\begin{array}{c}{w}_m\left(n\right)=2w_m\left(n-1\right)\&CenterDot;\cos \frac{2\mathrm{\&pi;}m}{N}-w_m\left(n-2\right)\\ +v_{PCC}\left(n\right)-v_{PCC}\left(n-N\right)\end{array}---\left(23\right)$

$v_m\left(n\right)=w_m\left(n\right)e^{j2\mathrm{\&pi;}m/N}-w_m(n-1)---\left(24\right)$

Formula (24) is launched, has

$v_m\left(n\right)=w_m\left(n\right)cos\frac{2\mathrm{\&pi;}m}{N}-w_m(n-1)+{\mathrm{jw}}_m\left(n\right)sin\frac{2\mathrm{\&pi;}m}{N}---\left(25\right)$

As can be seen from formula (25): according to the spectrum value of n moment and n-1 moment intermediate variable, after 2 real additions and 1 complex addition operations, just can obtain the spectrum value of n moment harmonic voltage, sliding DFT filter then needs 6 real multiplications and 3 complex addition operations just can obtain same result.Therefore, adopt jump Goertzel filter to calculate the spectrum value of n moment harmonic voltage, greatly will reduce operand.M spectrum value of n instance sample value can be calculated by formula (26) tries to achieve.

$\left|v_m\left(n\right)\right|=\sqrt{{(w_m\left(n\right)\&CenterDot;cos\frac{2\mathrm{\&pi;}m}{N}-w_m(n-1))}^2+{(w_m\left(n\right)\&CenterDot;sin\frac{2\mathrm{\&pi;}m}{N})}^2}---\left(26\right)$

Through type (26) tries to achieve third harmonic voltage value, itself and the Islanding detection threshold values determined by formula (16) is made comparisons, can judge whether distributed generation system isolated island occurs.

A kind of distributed grid-connected inverter alone island detection system based on phase perturbation of the present invention:

(1) two-phase quadrature voltage v is produced at structure orthogonal signal generator _αand v _βin process, can ensure the rapidity of dynamic response, the two-phase quadrature voltage simultaneously built contains identical total harmonic distortion factor, this obviates the phase-locked precision problem brought because harmonic wave is uneven in two-phase quadrature voltage.According to the design in the present invention, necessary simulating, verifying is carried out to the mains voltage signal of 220V/50Hz.The gain k of orthogonal signal generator according to formula (4) with setting time t _s=10ms value, the simulation result shown in Figure 10 and Figure 11 shows, through the setting time of 10ms, can realize the structure of two-phase quadrature voltage.

(2) in Fig. 5, the frequency self-adaption controller of genlock device eliminates the impact of electrical network amplitude change on frequency adjustment dynamic responding speed.Reason is that the design of controller with the addition of voltage compensator in realizing.According to the design shown in Fig. 4, necessary emulation is carried out to the mains voltage signal of 220V/50Hz.In simulation process, setting voltage amplitude drops to 249V in the t=0.02s moment by 311V, and in the t=0.04s moment, electrical network fundamental frequency reduces to 45Hz by 50Hz, and time constant η is set as 20ms, and simulation result as shown in figure 12.As can be seen from simulation result, the frequency self-adaption controller in design can ensure that the dynamic response time that frequency self-adaption adjusts can break away from the impact that electrical network amplitude changes generation, therefore has response speed faster.

(3) the disturbance phase place injected is on the impact of phase-locked output and grid-connected current.According to the scheme that the present invention proposes, the simulating, verifying of being correlated with, simulation result respectively as shown in Figure 6 and Figure 7.Simulation result shown in Fig. 6 and Fig. 7 all demonstrates the phase perturbation amount that adds can not the phase place at modified zero point and peak value place, but the phase deviation that then can produce in other positions to a certain degree, thus ensure that distributed generation system is under the pattern of being incorporated into the power networks, even if by the impact of disturbance phase place, still can with unity power factor stable operation.This point, can observe out intuitively from the simulation result shown in Fig. 7.

(4) the quick realization of islanding detect.In order to assess the performance of islanding detect better, at light current net (pure inductance electric network impedance, L _g=1.8mH) carry out emulation testing under condition.Testing time, to be 0.3s, 0.11s moment inverter operating state instantaneously switched to islet operation by being incorporated into the power networks.Simulation parameter arranges as follows: DC voltage is 400V, electrical network parameter is 220V/50Hz, anti-1.8mH in electrical network, LC filter parameter is 5mH/47nF, the switching frequency of switching tube is 20kHz, sample frequency is 1kHz, and phase perturbation coefficient μ is 0.06, and it is δ=7850 that frequency self-adaption regulation coefficient δ carries out exploitation according to formula (10).Following test result is that pure resistor load (R=17.48 Ω) and RLC shunt load two kinds of situations provide successively according to local load, the resonance frequency of local RLC shunt load is set to 50Hz, the quality factor q of load is that 2.5 (relevant parameter is set to R=174.8 Ω, L=220mH, C=45 μ F).Simulation result in two kinds of test load situations is respectively as shown in Figure 13, Figure 14, Figure 15 and Figure 16, Figure 17, Figure 18.As can be seen from analogous diagram, under pure resistor load and RLC shunt load situation, islanding detect algorithm in the present invention can complete islanding detect rapidly respectively in 70ms and 50ms, and blocks inverter, and the detection blocking time under above two kinds of load situation all meets IEEE929-2000 standard.

Claims (7)

1. based on a distributed grid-connected inverter alone island detection system for phase perturbation, for controlling single-phase distributed grid-connected electricity generation system, including and being sequentially connected in series: input connects DC bus-bar voltage (V respectively _dc) and setting DC bus standard voltage value (V _{dc_ref}) voltage controller (1), the reference amplitude (I of grid-connected current for voltage controller (1) is exported ^* _inv) with unitization grid-connected reference current (cos θ _inv ^*) being multiplied obtains grid-connected reference current (i ^* _inv) multiplier (2), grid-connected reference current (i for multiplier (2) is exported ^* _inv) get the grid-connected sample rate current (i of negative reality with polarity ^* _inv) adder (3) of suing for peace, current controller (4) and the pulse width modulation generator (5) that pulse width modulation exports four road start pulse signals (PWM1 ~ PWM4) of the single-phase H bridge inverter (A) driven in single-phase distributed grid-connected electricity generation system is carried out to the signal that current controller (4) exports, it is characterized in that, also include, be sequentially connected in series: input connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC), for generation of the orthogonal signal generator (6) of two-phase quadrature voltage, for the genlock device (7) at upper acquisition grid phase angle, orthogonal signal generator (6) output signal basis, for generation of the reference amplitude (I with grid-connected current ^* _inv) unitization grid-connected reference current (the cos θ that is multiplied _inv ^*) phase perturbation unit (8) and the threshold decision unit (9) based on jump Goertzel filter for carrying out voltage threshold judgement, wherein, the output of described phase perturbation unit (8) connects the input of multiplier (2).

2. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described orthogonal signal generator (6) includes the first adder (61) be connected in series successively, first amplifier (62), second adder (63) and first integrator (64), wherein, an input of described first adder (61) connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC) as the input of orthogonal signal generator (6), the output of first integrator (64) divides three tunnels: the first via is directly as the first output (v of orthogonal signal generator (6) _α), second tunnel polarity is connected with another input of first adder (61) after getting and bearing, the input of the 3rd tunnel connection and all-pass filter (65), the output of described all-pass filter (65) divides two-way: the first via is directly as the second output (v of orthogonal signal generator (6) _β), the second tunnel polarity is connected with another input of second adder (63) after getting and bearing.

3. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described genlock device (7) includes: the 3rd adder (75) be connected in series successively, the second amplifier (76), the 3rd multiplier (78), second integral device (79) and mod arithmetic unit (710), wherein, the output of described mod arithmetic unit (710) forms the output of genlock device (7), for exporting grid phase angle (θ _g), the input of described 3rd adder (75) connects the output of the first multiplier (72) and the second multiplier (74) respectively, and an input of described first multiplier (72) directly connects the first via output (v of orthogonal signal generator (6) _α), another input of the first multiplier (72) meets the first via output (v of orthogonal signal generator (6) in succession by the first second-order low-pass filter (71) _α), an input of the second multiplier (74) directly connects the second road output (v of orthogonal signal generator (6) _β), another input of the second multiplier (74) meets the second road output (v of orthogonal signal generator (6) in succession by the second second-order low-pass filter (73) _β), the input of described 3rd multiplier (78) also connects the output of voltage compensator (77), and the input of described voltage compensator (77) connects the output (v of the first second-order low-pass filter (71) respectively _{α L}) and the output (v of the second second-order low-pass filter (73) _{β L}).

4. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described phase perturbation unit (8) includes the 3rd amplifier (81), sine operation device (82), the 4th amplifier (83), the 4th adder (84) and the cos operation device (85) that are connected in series successively, wherein, input and another input of the 4th adder (84) of described 3rd amplifier (81) are connected the output (θ of genlock device (7) jointly _g), the output of described cos operation device (85) forms output (the cos θ of phase perturbation unit (8) _inv ^*) connect an input of described multiplier (2).

5. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described islanding detect realizes unit (9) and includes the sample circuit (91) and jump Goertzel filter (92) that connect successively, wherein, the input of described sample circuit (91) connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC), the output voltage (v of described jump Goertzel filter (92) _m(n)) as the detection voltage of single-phase distributed grid-connected electricity generation system, contrast with the voltage threshold set, as output voltage (v _m(n)) when being more than or equal to the voltage threshold of setting, pulse width modulation generator (5) does not export four road start pulse signals (PWM1 ~ PWM4), single-phase H bridge inverter (A) in single-phase distributed grid-connected electricity generation system does not work, as output voltage (v _m(n)) when being less than the voltage threshold of setting, pulse width modulation generator (5) exports four road start pulse signals (PWM1 ~ PWM4), single-phase H bridge inverter (A) work in single-phase distributed grid-connected electricity generation system.

6. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 5, it is characterized in that, described jump Goertzel filter (92) includes: the comb filter (921) be connected in series successively, slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922), 5th amplifier (923) and the 6th adder (924), wherein, the output of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922) is divided into three tunnels again after the first delay cell (925): the first via connects an input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922) by the 6th amplifier (926), second tunnel by after the second delay cell (927) again polarity get another input of negative connection slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922), the 3rd direct polarity in tunnel gets negative rear another input connecting the 6th adder (924), the input of described comb filter (921) connects the output of sample circuit (91), the output of described 6th adder (924) forms the output voltage (v of jump Goertzel filter (92) _m(n)).

7. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 6, it is characterized in that, described comb filter (921) includes the 7th adder (9211), an input of described 7th adder (9211) directly connects the output of sample circuit (91), another input of 7th adder (9211) connects the output of sample circuit (91) by the 3rd delay cell (9212), the output of described 7th adder (9211) connects the input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922).