CN103713211B - The single-phase, two-phase island detection method of a kind of three-phase grid-connected inverter and device - Google Patents
The single-phase, two-phase island detection method of a kind of three-phase grid-connected inverter and device Download PDFInfo
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Abstract
The invention discloses the single-phase, two-phase island detection method of a kind of three-phase grid-connected inverter and device.Method includes: periodic injecting reactive current on the output electric current of inverter；Respectively moving average calculate the three-phase power grid voltage of positive axis and negative semiaxis often biphase between phase angle；Calculate when half front axle and a upper semiaxis often biphase between the variable quantity at phase angle；Calculate described when the variable quantity of half front axle with the reactive current of a described upper semiaxis；Judge when half front axle and a upper semiaxis often biphase between the variable quantity at phase angle whether meet the variable quantity at first phase angle and be directly proportional to the variable quantity of reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity of reactive current, and the variable quantity at the 3rd phase angle is not by the impact of reactive current；If meeting, it is determined that isolated island occurs.By present invention achieves detection island state quick, accurate, non-blind area, and reduce the impact of the quality of power supply in electrical network.
Description
Technical field
The present invention relates to isolated island detection field, particularly relate to single-phase, two-phase island detection method and the device of a kind of three-phase grid-connected inverter based on reactive disturbance.
Background technology
During the new energy grid-connected power system access public electric wire nets such as solar energy, wind energy, fuel cell, public electric wire net stop power supply after the existence of the new energy grid-connected power system such as solar energy, wind energy, fuel cell, the part circuit making grid power blackout district still maintains electriferous state, forms the isolated island of self-supporting power supply supply.Under island state, Utilities Electric Co. just loses the control to line voltage distribution, frequency, and then can bring a series of potential safety hazard and accident dispute.
For this reason, it may be necessary to island state is detected fast and effectively, to eliminate the issuable harm of unplanned islet operation.At present, the detection of island state mainly has active alone island detection and passive type isolated island detection two ways to protect.Passive type isolated island detection mode detects island effect by detecting the exception of inverter ac output end voltage or frequency.But after isolated island occurs, the relation between the power that the frequency of system points of common connection and voltage magnitude change are provided by load power demand and inverter in system is determined, during isolated island, the frequency of system is finally stable at resonant frequency place.If the resonant frequency now between load inductance and electric capacity and the electric voltage frequency of common node be (namely during isolated island detection, the bound of frequency sets threshold value) in the fluctuation range that electrical network rated frequency normally allows, then isolated island can not get detection.Namely there is check frequency in passive type isolated island detection mode.
Existing active detection mode is all one disturbance quantity of injection in electrical network, judges island state by the change of disturbance quantity.But Active frequency drift formula and the disturbance that actively phase shift island detection method introduces can cause the decline of the quality of power supply.
Accordingly, it would be desirable to a kind of new island detection method solves prior art Problems existing.
Summary of the invention
It is an object of the invention to provide the single-phase, two-phase island detection method of a kind of three-phase grid-connected inverter and device, to detect island state fast and accurately.
Based on above-mentioned purpose, embodiments provide the single-phase, two-phase island detection method of a kind of three-phase grid-connected inverter, including:
Periodic injecting reactive current on the output electric current of inverter；
Respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle；
Calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle；
Calculate described when the variable quantity of half front axle with the reactive current of a described upper semiaxis；
Judge when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle whether meet the variable quantity at first phase angle and be directly proportional to the variable quantity of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity of described reactive current, and the variable quantity at the 3rd phase angle is not by the impact of described reactive current；
If meeting, it is determined that isolated island occurs.
Preferably, described method also includes:
After determining generation isolated island, if determining the variable quantity of described first-phase parallactic angle: the variable quantity=1:1 of described reactive current and the variable quantity of described second-phase parallactic angle: the variable quantity=-1:1 of described reactive current, be then one-phase island, and isolated island phase place to be that described first-phase parallactic angle and described second-phase parallactic angle are each corresponding biphase own phase together；
If determining the variable quantity of described first-phase parallactic angle: the variable quantity=2:1 of described reactive current and the variable quantity of described second-phase parallactic angle: the variable quantity=-2:1 of described reactive current, be then biphase isolated island, and isolated island phase place be described first-phase parallactic angle and described second-phase parallactic angle each corresponding biphase own together beyond mutually other are biphase.
Preferably, using described when half front axle and a described upper semiaxis often biphase between the positive feedback of reactive current that to inject as next disturbance cycle in the described disturbance cycle when half front axle place of the variable quantity at phase angle.
Preferably, described reactive current is the 1% of the output electric current of described inverter.
Preferably, described method is interrupted by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, with calculate often biphase between phase angle.
The embodiment of the present invention additionally provides the single-phase, two-phase isolated island detecting device of a kind of three-phase grid-connected inverter, including:
Reactive current injection unit, for injecting reactive current periodic on the output electric current of inverter；
Phase angle computing unit, for respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle；
Phase angle variations amount computing unit, for calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle；
Reactive current variable quantity computing unit, described when the variable quantity of half front axle with the reactive current of a described upper semiaxis for calculating；
Isolated island judging unit, for when determine when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle meet the variable quantity at first phase angle and be directly proportional to the variable quantity of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity of described reactive current, the variable quantity at the 3rd phase angle is not by when affecting of described reactive current, it is determined that isolated island occurs.
Preferably, described isolated island judging unit is used for,
After there is isolated island, variable quantity determining described first-phase parallactic angle: the variable quantity=1:1 of described reactive current and the variable quantity of described second-phase parallactic angle: during the variable quantity=-1:1 of described reactive current, be defined as one-phase island, and isolated island phase place to be that described first-phase parallactic angle and described second-phase parallactic angle are each corresponding biphase own phase together；
Variable quantity determining described first-phase parallactic angle: the variable quantity=2:1 of described reactive current and the variable quantity of described second-phase parallactic angle: during the variable quantity=-2:1 of described reactive current, be defined as biphase isolated island, and isolated island phase place be described first-phase parallactic angle and described second-phase parallactic angle each corresponding biphase own together beyond mutually other are biphase.
Preferably, described reactive current injection unit, for using described when half front axle and a described upper semiaxis often biphase between the positive feedback of reactive current that to inject as next disturbance cycle in the described disturbance cycle when half front axle place of the variable quantity at phase angle.
Preferably, described phase angle computing unit is for interrupting by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, calculate often biphase between phase angle.
Preferably,
Described reactive current injection unit includes control signal transmitting element, for sending control signal to inverter, it is achieved Setting signal superposition in actual current waveform.
The invention has the beneficial effects as follows:
The present invention adopts the mode of injecting reactive current, and which is only small on the impact of system output current harmonic component, and in normal also network process, owing to utility grid clamps down on effect so that system only has minimum idle change.With in current techniques based on compared with frequency disturbance mode, injecting reactive current of the present invention reduces active alone island and detects the current distortion rate brought, and improves isolated island detection speed, and is fully able to the requirement meeting the detection of system isolated island.
Accompanying drawing explanation
Fig. 1 is the inventive method embodiment flow chart；
Fig. 2 is the reactive current schematic diagram injected in the cycle；
RST three-phase voltage current phase diagram when Fig. 3 is that isolated island does not occur；
Fig. 4 is voltage current phase figure during T-phase isolated island；
Fig. 5 is under reactive disturbance, and voltage current phase figure during isolated island does not occur；
Fig. 6 is under reactive disturbance, voltage current phase figure during T-phase generation isolated island；
Fig. 7 is apparatus of the present invention example structure figure；
Fig. 8 is the actual loading test oscillogram of one-phase island；
Fig. 9 is the actual loading test oscillogram of biphase isolated island.
Detailed description of the invention
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under not making creative work premise, broadly fall into the scope of protection of the invention.
For making the present invention clearly, first principles of the invention is illustrated below.
A certain in three-phase grid-connected inverter, it is assumed that this phase point of common coupling voltage is:
Wherein VgFor voltage effective value, ω is voltage angle frequency.Then inverter output power network current can be expressed as:
Wherein IpFor watt current virtual value, IqFor reactive current virtual value, the setting reactive current reference value I ' when grid-connected inverters runsqIt is zero.By the effect of inverter phaselocked loop and power control loop, the reactive current of inverter output may be controlled to zero.Now the output electric current of inverter is:
Now, in isolated island, the modulus value of load can be expressed as:
Its phase angle is zero, so this impedance can be expressed as:
Now, isolated island algorithm is to one reactive disturbance of superposition in the output reactive current of inverter, and perturbation amplitude is:
Iq=Κ*Ip(6)
After adding disturbance, inverter output current is:
Wherein it is changed to owing to reactive current changes the given current amplitude caused:
The given current phase caused owing to reactive current changes is changed to:
This function of current is after load Z, and the voltage of point of common coupling is:
Visible by above-mentioned analysis, when changing the reactive current value injecting inverter, the phase place of its output electric current has transition, the PCC point (commoncoupling when line voltage is normal;Commoncoupled, point of common coupling) voltage has the clamped effect of line voltage, therefore the amplitude of PCC point voltage and phase place remain unchanged, when under the state that electrical network is in power-off, when namely there is isolated island, PCC point voltage phase place with follow given reactive disturbance change and change (now electrical network this phase disconnect, therefore the voltage of this phase it doesn't matter with line voltage).By checking after adding reactive current disturbance that the Changing Pattern of PCC point voltage phase place can then determine whether isolated island.
The embodiment of the present invention one provides the island detection method of a kind of three-phase grid-connected inverter, as it is shown in figure 1, the method includes:
S11, on the output electric current of inverter periodic injecting reactive current.
System adopts injecting reactive current, and which is only small on the impact of system output current harmonic component, and in normal also network process, owing to utility grid clamps down on effect so that system only has minimum idle change.With in current techniques based on compared with frequency disturbance mode, injecting reactive current of the present invention reduces active alone island and detects the current distortion rate brought, and improves isolated island detection speed, and is fully able to the requirement meeting the detection of system isolated island.
And be the impact reducing the reactive current introduced further to the electrical network quality of power supply, the present invention adopts periodic reactive current injection mode, and the variable quantity of the voltage phase angle of point of common coupling is introduced in the positive feedback of function of reactive current disturbance, generate the reactive current that next cycle to inject, thus accelerating the deviation of electric voltage frequency under island state, shorten the detection time of isolated island.Periodically and by the reactive current injection mode of positive feedback, it is possible to what the reactive current initially injected limited is smaller, to ensure the impact of reactive current that the performance of system do not injected.
In the present invention, reactive current is the 1% of the output electric current of inverter.
Fig. 2 shows the reactive current injected in the disturbance cycle, and within a cycle, its positive and negative semiaxis is alternately.
S12, respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle.
Concrete, can be interrupted by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, with calculate often biphase between phase angle.
S13, calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle.
The concrete half front axle that deserves is likely to be at the same disturbance cycle with a upper semiaxis, it is also possible to be respectively in two disturbance cycles.
S14, the described variable quantity working as half front axle and the reactive current of a described upper semiaxis of calculating.
S15, judge when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle whether meet the variable quantity at first phase angle and be directly proportional to the variable quantity size of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity size of described reactive current, and the variable quantity at the 3rd phase angle is not by the impact of described reactive current；If meeting, it is determined that isolated island occurs.
Above-mentioned variable quantity is a vector, has two attributes of size and Orientation.
The order that above-mentioned steps limits as the inventive method enforcement order one.But present invention additionally comprises its other orders limited with word.Such as the order of step S13, S14 can be exchanged.
In the present invention, concrete when at least determine a three-phase power grid voltage when half front axle and a upper semiaxis often biphase between the variable quantity at phase angle meet above-mentioned condition time, it is determined that there is isolated island.
For more accurate, a numerical value can be set so that determine the three-phase power grid voltage when half front axle and a upper semiaxis that has more than this numerical value often biphase between the variable quantity at phase angle when meeting above-mentioned condition, it is determined that there is isolated island.
Such as can arrange continue to exceed three times, six times or nine times determine when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle meet above-mentioned condition time, it is determined that there is isolated island.
The present invention can be determine for continuous three times when half front axle and on a semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle time, in the way of above-mentioned positive feedback, calculate the reactive current that will inject.
In the specific embodiment of the invention, the disturbance cycle is 500ms, positive and negative half period is 250ms, meet above-mentioned isolated island according to continuous 3 half period and judge rule, amplify isolated island disturbance quantity, continuous 3 half period meet isolated island and judge rule again, again amplify isolated island disturbance, it is determined that the mode of isolated island fault.Then isolated island judges that the cycle is as 250ms*3*3=2.25s, meets current safety code requirement time 5s.
Isolated island is likely one-phase island or biphase isolated island, it is sometimes necessary to determines that one-phase island still exposes isolated island, and determines the phase that isolated island occurs.
Finding by analysis, in one-phase island process, if reactive current variable quantity is Δ Iq, the variable quantity of first-phase parallactic angle is 2arctan (Iq/Id).In biphase isolated island process, if reactive current variable quantity is Δ Iq, because Δ Iq is biphase with what disconnect by effect, can be obtained by resolution of vectors, the variable quantity of its first-phase parallactic angle is 2arctan (2Iq/Id).Because IqMuch smaller than Id, therefore arctan (2Iq/Id) 2arctan (I can be approximatelyq/Id), namely in biphase isolated island process, when reactive current variable quantity is Δ Iq, the variable quantity of first-phase parallactic angle is approximately 4arctan (Iq/Id).Wherein Δ IqInfinitely it is similar to 2arctan (Iq/Id), therefore when there is one-phase island, the variable quantity of first-phase parallactic angle: reactive current variable quantity is approximately 1, when there is biphase isolated island, the variable quantity of first-phase parallactic angle: reactive current variable quantity is approximately 2.For convenience of judging, ratio herein all takes approximation.
Therefore for further determining that island state, can after determining generation isolated island, if determining the variable quantity of described first-phase parallactic angle: the variable quantity=1:1 of described reactive current and the variable quantity of described second-phase parallactic angle: the variable quantity=-1:1 of described reactive current, be then one-phase island, and isolated island phase place to be that described first-phase parallactic angle and described second-phase parallactic angle are each corresponding biphase own phase together.If determining the variable quantity of described first-phase parallactic angle: the variable quantity=2:1 of described reactive current and the variable quantity of described second-phase parallactic angle: the variable quantity=-2:1 of described reactive current, be then biphase isolated island, and isolated island phase place be described first-phase parallactic angle and described second-phase parallactic angle each corresponding biphase own together beyond mutually other are biphase.
Fig. 2-6 shows a concrete application scenarios in the present invention.
Wherein Fig. 2 is the reactive current being injected in inverter in the disturbance cycle, and its positive and negative semiaxis within a cycle hands over the phase, and the average current on two-semiaxle is equal in magnitude, in opposite direction.
In Fig. 3, RST represents line voltage situation, and dotted line RTSi represents grid-connected current situation, between voltage and electric current, phase contrast is θ, due in reality network process, the connect loading condition difference of three-phase, therefore phase difference θ just can be, can also be negative, can also be 0 equally, think that at this place this value can be any situation, under normal circumstances, voltage current phase difference is in system allowed band, and this scope is determined by product safety specification.Wherein Ti1 is cycle given certain semiaxis maximum of disturbance, Ti2 gives other semiaxis maximum the cycle, analyze description for convenience, assuming that the actual current situation in the Ti1 maximum reactive power disturbance situation that is positive axis, then, Ti2 is the actual current situation in the negative maximum reactive power disturbance situation of semiaxis, owing to disturbance quantity is consistent, in platform situation not change situation, identical sized by the phase place of both relative voltage T, symbol is contrary.
When system generation island state, currently assuming system T-phase generation isolated island, system generation resonance, T-phase voltage will be followed actual grid-connected current and be changed, and obtain the voltage current phase figure shown in Fig. 4, can analyze isolated island algorithm with regard to above-mentioned phase diagram below.
In three-phase power grid voltage, between two phase voltages, phase relation is as shown in Figure 5 under normal circumstances.Due to the clamped effect of line voltage, so θRS、θSTWith θTRPhase relation will not change with reactive disturbance, phase relation between line voltage will be kept biphase.
When certain phase generation isolated island, it is assumed that T-phase generation isolated island, as shown in Figure 6, when reactive disturbance to Ti2, calculate and obtain θRS2、θST2 and θTR2 phase relations, when reactive disturbance to Ti1, calculate and obtain θRS1、θST1 and θTR1 phase relation, from the above, it can be seen that line voltage R, S will occur phase place to change because of reactive disturbance, so θRS2=θRS1, there is reactive disturbance phase place change θ at isolated island phase TST2-θST=θ t, and θTR1-θTR=-θt；Isolated island disturbance upper half cycle θST2-θST=-θ t, and θTR1-θTR=θ t, it is assumed that isolated island algorithm calculates the cycle at Ti2 cycle semiaxis, say, that in the upper cycle semiaxis of Ti1, adopts θRS’=θRS2-θRS1、θST’=θST2-θST1 and θTR’=θTR2-θTR1.Ti2 can be obtained for when half front axle cycle stage from above-mentioned rule:
θRS’=0
θST’=2θt
θTR’=-2θt
At subsequent time, transfer to Ti1 for when half front axle cycle stage:
θRS’=0
θST’=-2θt
θTR’=2θt
As can be seen from the above results, the given disturbance of reactive current is in different semiaxis situations, phase contrast between biphase calculates phase contrast situation of change it would appear that disturbance rule at different cycles semiaxis, its rule is: certain θ ' and reactive disturbance direction and big Theravada's direct ratio thereof, an other θ ' and reactive disturbance direction are inversely proportional to, with big Theravada's direct ratio, also a θ ' does not change with reactive disturbance, carrys out interpreting system isolated island fault by this rule.Consistent with one-phase island principle for biphase isolated island accident analysis principle, only in biphase isolated island situation, civil power is biphase will follow reactive power disturbance and change.
Fig. 8, Fig. 9 respectively one-phase island, biphase isolated island actual loading test oscillogram.
Corresponding said method, the embodiment of the present invention additionally provides the isolated island detecting device of a kind of three-phase grid-connected inverter, and referring to Fig. 7, this device specifically includes:
Reactive current injection unit 11, for injecting reactive current periodic on the output electric current of inverter.
Concrete, reactive current injection unit, for the positive feedback of the reactive current that the variable quantity at the phase angle between often biphase when half front axle and a upper semiaxis to inject as next disturbance cycle in the described disturbance cycle when half front axle place.
Reactive current injection unit 11 includes control signal transmitting element, for sending control signal to inverter, it is achieved Setting signal superposition in actual current waveform.
Phase angle computing unit 12, for respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle.
Phase angle computing unit 12 can be interrupted by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, calculate often biphase between phase angle.
Phase angle variations amount computing unit 13, for calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle；
Reactive current variable quantity computing unit 14, described when the variable quantity of half front axle with the reactive current of a described upper semiaxis for calculating；
Isolated island judging unit 15, for when determine when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle meet the variable quantity at first phase angle and be directly proportional to the variable quantity of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity of described reactive current, the variable quantity at the 3rd phase angle is not by when affecting of described reactive current, it is determined that isolated island occurs.
Wherein, isolated island judging unit 15 is used for, after there is isolated island, variable quantity determining the phase angle being directly proportional to the variable quantity of described reactive current: the variable quantity=1:1 of described reactive current, it it is then one-phase island, and isolated island phase place is this biphase phase of owning together, and for after there is isolated island, variable quantity determining the phase angle being directly proportional to the variable quantity of described reactive current: the variable quantity=2:1 of described reactive current, it is then biphase isolated island, and isolated island phase place is that these biphase other of phase owned together are biphase.
Apparatus of the present invention specifically can be made up of digital signal processor (DSP), and it is specifically realized the detection of electric network voltage phase by sampling unit, voltage modulate circuit, then pass through phase angle computing unit calculate often biphase between phase angle.
The voltage gathered can also be modified by the digital signal processor of the present invention, controls PWM output.
Digital signal processor realizes the basic thought of the present invention: realized isolated island detection by algorithm controls with detection inverter output.When implementing, electrical network bus bar side output voltage is exchange, and sampling unit uses voltage sensor device to detect the voltage of electrical network bus bar side.Owing to using dsp chip, the A/D converter that its sheet carries is unipolar, can only receive the voltage signal of 0～3.0V, and therefore gathering voltage needs to change, and so could be connected with DSP.Realize improving the photovoltaic DC-to-AC converter isolated island detection algorithm of the quality of power supply in dsp, control inverter output with combining with photovoltaic maximal power tracing algorithm, it is achieved isolated island detects.
It should be noted that the method and apparatus in the present invention is only used for judging single-phase, two-phase island state.
Apparatus and method of the present invention embodiment is corresponding, and relevant portion can reference mutually.
Above specific embodiment, the purpose of the present invention, technical scheme and beneficial effect have been further described, be it should be noted, these are only the present invention a specific embodiment, the present invention can be carried out various change and modification without deviating from the spirit and scope of the present invention by those skilled in the art.So, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.
Claims (10)
1. the single-phase, two-phase island detection method of a three-phase grid-connected inverter, it is characterised in that described method includes:
Periodic injecting reactive current on the output electric current of inverter；
Respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle；
Calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle；
Calculate described when the variable quantity of half front axle with the reactive current of a described upper semiaxis；
Judge when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle whether meet the variable quantity at first phase angle and be directly proportional to the variable quantity size of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity size of described reactive current, and the variable quantity at the 3rd phase angle is not by the impact of described reactive current；
If meeting, it is determined that isolated island occurs.
2. island detection method as claimed in claim 1, it is characterised in that described method also includes:
After determining generation isolated island, if determining the variable quantity at described first phase angle: the variable quantity=1:1 of described reactive current and the variable quantity at described second phase angle: the variable quantity=-1:1 of described reactive current, it is then one-phase island, and isolated island self-corresponding biphase owns phase together for described first phase angle and described second phase angle are each mutually；
If determining the variable quantity at described first phase angle: the variable quantity=2:1 of described reactive current and the variable quantity at described second phase angle: the variable quantity=-2:1 of described reactive current, be then biphase isolated island, and isolated island mutually for described first phase angle and described second phase angle each self-corresponding biphase own together beyond mutually other are biphase.
3. island detection method as claimed in claim 1, it is characterized in that, using described when half front axle and a described upper semiaxis often biphase between the positive feedback of reactive current that to inject as next disturbance cycle in the described disturbance cycle when half front axle place of the variable quantity at phase angle.
4. island detection method as claimed in claim 1, it is characterised in that described reactive current is the 1% of the output electric current of described inverter.
5. island detection method as claimed in claim 1, it is characterised in that described method is interrupted by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, with calculate often biphase between phase angle.
6. the single-phase, two-phase isolated island detecting device of a three-phase grid-connected inverter, it is characterised in that described device includes:
Reactive current injection unit, for injecting reactive current periodic on the output electric current of inverter；
Phase angle computing unit, for respectively moving average calculate the positive axis in each disturbance cycle and the three-phase power grid voltage of negative semiaxis often biphase between phase angle；
Phase angle variations amount computing unit, for calculate when half front axle and a upper semiaxis three-phase power grid voltage often biphase between the variable quantity at phase angle；
Reactive current variable quantity computing unit, described when the variable quantity of half front axle with the reactive current of a described upper semiaxis for calculating；
Isolated island judging unit, for when determine when half front axle and the three-phase power grid voltage of a upper semiaxis often biphase between the variable quantity at phase angle meet the variable quantity at first phase angle and be directly proportional to the variable quantity size of described reactive current and direction is identical, the variable quantity at second phase angle is directly proportional and in opposite direction to the variable quantity size of described reactive current, the variable quantity at the 3rd phase angle is not by when affecting of described reactive current, it is determined that isolated island occurs.
7. isolated island detecting device as claimed in claim 6, it is characterised in that described isolated island judging unit is used for,
After there is isolated island, variable quantity determining described first phase angle: the variable quantity=1:1 of described reactive current and the variable quantity at described second phase angle: during the variable quantity=-1:1 of described reactive current, it is defined as one-phase island, and isolated island self-corresponding biphase owns phase together for described first phase angle and described second phase angle are each mutually；
Variable quantity determining described first phase angle: the variable quantity=2:1 of described reactive current and the variable quantity at described second phase angle: during the variable quantity=-2:1 of described reactive current, be defined as biphase isolated island, and isolated island mutually for described first phase angle and described second phase angle each self-corresponding biphase own together beyond mutually other are biphase.
8. isolated island detecting device as claimed in claim 6, it is characterized in that, described reactive current injection unit, for using described when half front axle and a described upper semiaxis often biphase between the positive feedback of reactive current that to inject as next disturbance cycle in the described disturbance cycle when half front axle place of the variable quantity at phase angle.
9. isolated island detecting device as claimed in claim 6, it is characterised in that described phase angle computing unit is for interrupting by system zero crossing, it is achieved the phase capturing of every phase voltage of three-phase power grid voltage, calculate often biphase between phase angle.
10. isolated island detecting device as claimed in claim 6, it is characterised in that
Described reactive current injection unit includes control signal transmitting element, for sending control signal to inverter, it is achieved Setting signal superposition in actual current waveform.
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