CN106226623A - A kind of island detection method - Google Patents
A kind of island detection method Download PDFInfo
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- CN106226623A CN106226623A CN201610595060.1A CN201610595060A CN106226623A CN 106226623 A CN106226623 A CN 106226623A CN 201610595060 A CN201610595060 A CN 201610595060A CN 106226623 A CN106226623 A CN 106226623A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
Abstract
The present invention provides a kind of island detection method, comprise the following steps: (1) is when micro-capacitance sensor actual motion, on the output voltage of changer, at least distinguish superposition first frequency harmonic voltage and second frequency harmonic voltage, the first electric current of the junction point of detection micro-capacitance sensor and electrical network and the second electric current；(2) if the first electric current passes through chopper disconnect the connection with electrical network more than or equal to the first detection threshold value and the second electric current more than or equal to the second detection threshold value, micro-capacitance sensor, enter islet operation；Otherwise perform step (1).The island detection method that the present invention provides, the gain of parameter electrical network equiva lent impedance of the transformator of the electrical network accessed according to micro-capacitance sensor, it is achieved the accurate quantification analysis to micro-grid system feature；By the impedance operator of quantitative analysis micro-grid system, accurately select to judge the current detecting threshold values of isolated island；By the addition of multiple interference signals, reduce the impact that isolated island is detected by load end, improve the precision of detection island state.
Description
Technical field
The present invention relates to micro-capacitance sensor protection and control field, be specifically related to a kind of for island detection method.
Background technology
Isolated island is a kind of special total failure of micro-grid system, after entering islet operation, easily to distribution end and user
The equipment of end works the mischief, and even jeopardizes personal safety.
Anti-islanding is the important requirement of micro-capacitance sensor, i.e. can quickly detect island effect and quickly cut off with electrical network, wherein
Difficult point be exactly to detect island phenomenon fast and accurately.
Isolated island detection method include passive means and active method, the former mainly by detection the amplitude of fundamental voltage, frequency,
The quantity of state such as harmonic content, changed power judges, the problem such as have that check frequency is relatively big or the detection time is longer；The latter master
To be judged by detection feedback information by injecting certain interference signal to electrical network, to detect speed, but to lead to
Cross changer to realize.
The micro-capacitance sensor of inversion again after a kind of photovoltaic and energy-storage system outfan parallel connection, its equivalent circuit is as it is shown in figure 1, in figure
The break-make of SW1 represents and net state and island state respectively.Can be seen that micro-capacitance sensor passes through single inverter and electrical network connects, possess
Use the condition of active method detection isolated island.
Actively isolated island detection method adds the disturbing signal such as frequency shift (FS), power disturbance in the output signal of inverter, when
During grid-connected inverters, disturbing signal works hardly；Once entering island state, disturbing signal can make voltage, frequency, phase place
Deng appearance significantly change.But it is easily caused the fluctuation of output, causes output harmonic wave content to increase, easily by load jump
Interference, with the presence of method check frequency, affect speed and the precision of anti-islanding.If adding humorous in the output signal of inverter
Ripple signal, on the basis of this method is typically established at qualitative analysis, detection threshold is not easy to determine, can bring check frequency relatively
Big or result is disturbed bigger problem by electrical network.
Summary of the invention
In view of problems of the prior art, it is an object of the invention to provide a kind of island detection method, by quantitatively
Analyze system features, it is thus achieved that the frequency of harmonic signal and detection threshold, it is possible to detect island state more accurately.
Owing to the equiva lent impedance of low-voltage network is difficult to determine, the parameter of the transformator of the electrical network accessed according to micro-capacitance sensor
Obtain electrical network equiva lent impedance, it is achieved the accurate quantification analysis to micro-grid system feature；By quantitative analysis micro-grid system
Impedance operator, accurately selects to judge the current detecting threshold values of isolated island；By the addition of multiple interference signals, reduce load end to orphan
The impact of island detection, improves the precision of detection island state.
The present invention provides a kind of island detection method, and island detection method comprises the following steps:
(1) when micro-capacitance sensor actual motion, on the output voltage of changer, superposition first frequency harmonic wave electricity the most respectively
Pressure and second frequency harmonic voltage, the first electric current of the junction point of detection micro-capacitance sensor and electrical network and the second electric current；
(2) if the first electric current is more than or equal to the second detection threshold more than or equal to the first detection threshold value and the second electric current
Value, micro-capacitance sensor disconnects the connection with electrical network by chopper, enters islet operation；Otherwise perform step (1).
Further, first frequency comprises the following steps with the system of selection of second frequency:
(11) equivalent circuit of micro-grid system is set up；
(12) according to equivalent circuit, it is thus achieved that and the transmission function of net state and island state；
(13) electric current span more than the also electric current of net state of island state is obtained；
(14) described first frequency and described second frequency select from span.
Further, step (13) comprises the following steps:
(131) for the load set, obtain respectively and net state amplitude-frequency response, island state amplitude-frequency response
And its intersecting area, intersecting area is span.
Further, step (13) comprises the following steps:
(132) for different loads, obtain respectively and net state amplitude-frequency response, island state amplitude-frequency response
And its intersecting area；
(133) obtaining the public territory of the intersecting area for different loads, public territory is span.
Further, the method for the equivalent circuit that step (11) sets up micro-grid system comprises the following steps:
(111) changer being considered as voltage source, load end includes filter circuit, load and electrical network equiva lent impedance；
(112) transformer parameter of the electrical network accessed according to micro-capacitance sensor, calculates the equiva lent impedance of electrical network；
(113) by equivalent with RLC parallel circuit to micro-capacitance sensor load and the network load accessed.
Further, the system of selection of the first detection threshold value comprises the following steps:
(21) emulation tool is utilized to set up the phantom of micro-capacitance sensor；
(22) for different loads, on the output voltage of changer, superposition first frequency harmonic voltage, obtain respectively
Micro-capacitance sensor and the junction point of electrical network that accessed and the electric current of electric current and island state of net state；
(23) selecting the first detection threshold value, the first detection threshold value is more than all and electric current of net state and less than all isolated islands
The electric current of state.
Further, island detection method is for the micro-capacitance sensor being connected with electrical network by single changer.
Compared with prior art, the island detection method that the present invention provides, have the advantages that
(1) the gain of parameter electrical network equiva lent impedance of the transformator of the electrical network accessed according to micro-capacitance sensor, it is achieved to micro-capacitance sensor
The accurate quantification analysis of system features；
(2) by the impedance operator of quantitative analysis micro-grid system, accurately select to judge the current detecting threshold values of isolated island；
(3) by the addition of multiple interference signals, reduce the impact that isolated island is detected by load end, improve detection island shape
The precision of state.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of integrated photovoltaic micro-capacitance sensor；
Fig. 2 is the equivalent circuit that micro-capacitance sensor accesses the transformator of electrical network；
Fig. 3 is leakage reactance, copper loss to be converted low-pressure side and omit the transformer equivalent circuit of exciting impedance；
Fig. 4 is the amplitude-frequency response of Ipcc/Vinv；
Fig. 5 is the schematic diagram of the system of selection of the Ipcc threshold values judging isolated island.
Detailed description of the invention
The island detection method of one embodiment of the present of invention, island detection method comprises the following steps:
(1) when micro-capacitance sensor actual motion, on the output voltage of changer, superposition first frequency harmonic wave electricity the most respectively
Pressure and second frequency harmonic voltage, the first electric current of the junction point of detection micro-capacitance sensor and electrical network and the second electric current；
(2) if the first electric current is more than or equal to the second detection threshold more than or equal to the first detection threshold value and the second electric current
Value, micro-capacitance sensor disconnects the connection with electrical network by chopper, enters islet operation；Otherwise perform step (1).
First frequency comprises the following steps with the system of selection of second frequency:
(11) equivalent circuit of micro-grid system is set up；
(12) according to equivalent circuit, it is thus achieved that and the transmission function of net state and island state；
(13) electric current span more than the also electric current of net state of island state is obtained；
(14) described first frequency and described second frequency select from span.
Micro-capacitance sensor in the present embodiment is integrated photovoltaic micro-capacitance sensor, and its circuit diagram is as it is shown in figure 1, for can from Fig. 1
To find out, it is connected with electrical network by single changer, possesses the condition of the island detection method using the present embodiment.
The method of the equivalent circuit that step (11) sets up micro-grid system comprises the following steps:
(111) changer being considered as voltage source, load end includes filter circuit, load and electrical network equiva lent impedance；
(112) transformer parameter of the electrical network accessed according to micro-capacitance sensor, calculates the equiva lent impedance of electrical network；
(113) by equivalent with RLC parallel circuit to micro-capacitance sensor load and the network load accessed.
Wherein, L1, R1, Cf, Rf, L2, R2 are the filter circuit in step (111), and Rl, Cl, Ll parallel circuit is step
(113) equivalent circuit of the network load that the micro-capacitance sensor in loads and accessed, Rl is determined by active loss, Ll and Cl is according to product
Prime factor (Qf) determines；The transformator of the Tr electrical network by being accessed, Vs is the line voltage accessed.
Micro-capacitance sensor accesses the equivalent circuit of the transformator Tr of electrical network, as in figure 2 it is shown, R1, L1 are high-pressure side copper loss and leakage reactance,
R2, L2 are low-pressure side copper loss and leakage reactance, and Rm, Lm are exciting impedance.
Leakage reactance R1, copper loss L1 are converted low-pressure side, and omit exciting impedance Rm, Lm, transformator Tr equivalent circuit such as Fig. 3
Shown in, wherein:
Rs=R1 (N2/N1)2+ R2,
Ls=L1 (N2/N1)2+ L2,
The equivalent resistance of the Rs electrical network by being accessed, the equivalent inductance of the Ls electrical network by being accessed, Vs (N2/N1) is by being connect
The electrical network equivalent voltage entered.
Step (12) is according to equivalent circuit, it is thus achieved that and the transmission function of net state and island state, specifically, take changer
Output voltage Vinv as input, the electric current Ipcc of micro-capacitance sensor and the junction point PCC of the electrical network accessed is as output, permissible
Obtain and net state and the transmission function of island state, as follows:
Wherein:
Zs=Rs+s Ls.
Step (13) obtains the electric current span more than the also electric current of net state of island state.
Step (13) comprises the following steps:
(131) for the load set, obtain respectively and net state amplitude-frequency response, island state amplitude-frequency response
And its intersecting area, intersecting area is span.
Specifically, under certain loading condition, such as, the output of changer is set to rated value, it is thus achieved that amplitude-frequency response is bent
Line, as it is shown on figure 3, solid line represents that dotted line represents the amplitude-frequency response of island state at the amplitude-frequency response of also net state.
The intersecting area of the two--dash area represents that voltage magnitude is more than at the region of also net state, namely Vinv at island state
Time identical, the Ipcc of island state is more than the Ipcc of also net state.
Different loads can affect amplitude-frequency response, and this is also to detect the result of island state in prior art by electrical network
Disturb bigger reason.In order to reduce the different load impact for the result of detection island state, step (13) include with
Lower step:
(132) for different loads, obtain respectively and net state amplitude-frequency response, island state amplitude-frequency response
And its intersecting area；
(133) obtaining the public territory of the intersecting area for different loads, public territory is span.
Obtain the public territory of intersecting area for different loads, so, further reduce different loads to the
The impact that one frequency and second frequency are chosen, improves the precision of detection island state.
Step (14) first frequency and second frequency select from span.
Specifically, arranging quality factor is 2.5, and the nominal load power using 5%, as step-length, from the beginning of zero load, takes
20 kinds of load states, draw under every kind of load state and net state and the amplitude-frequency response of island state and intersection thereof
Between, the common portion in crossing interval takes two Frequency points, i.e. first frequency and second frequency.
Island detection method in the present embodiment, obtains and net state and the transmission letter of island state according to equivalent circuit
Number, then obtain the electric current span more than the also electric current of net state of island state, therefrom choose first frequency and the second frequency
Rate, namely by quantified system analysis feature, it is thus achieved that the frequency of harmonic signal, it is possible to detect island state more accurately.
The system of selection of the first detection threshold value comprises the following steps:
(21) emulation tool is utilized to set up the phantom of micro-capacitance sensor；
(22) for different loads, on the output voltage of changer, superposition first frequency harmonic voltage, obtain respectively
Micro-capacitance sensor and the junction point of electrical network that accessed and the electric current of electric current and island state of net state；
(23) selecting the first detection threshold value, the first detection threshold value is more than all and electric current of net state and less than all isolated islands
The electric current of state.
Specifically, according to also net state and the transmission function of island state, emulation tool is utilized to set up the emulation of micro-capacitance sensor
Model, for different loads, on the output voltage of changer, superposition first frequency harmonic voltage, obtain micro-capacitance sensor respectively
With the junction point of the electrical network accessed and the electric current of electric current and island state of net state；As shown in Figure 4, state 1,2,3 ...
N represents different loads state, such as the output of changer is respectively set to rated value, the 80% of rated value, rated value
50% and the 20% of rated value, from figure 5 it can be seen that the electric current Ipcc of island state is above, and the electricity of net state
Stream Ipcc is positioned at lower section, and the electric current Ipcc of two states is the most non-intersect, therefore the current threshold that isolated island detects can be located at two
Between group current value, thus judge island state exactly.
Island detection method in the present embodiment, obtains and net state and the transmission letter of island state according to equivalent circuit
Number, then for different loads, on the output voltage of changer, superposition first frequency harmonic voltage, obtain micro-capacitance sensor respectively
With the junction point of the electrical network accessed and the electric current of electric current and island state of net state；Namely pass through quantified system analysis
Feature, it is thus achieved that the current threshold of isolated island detection, it is possible to detect island state more accurately.
Second detection threshold value uses same method to obtain.
The harmonic signal of plural frequency can certainly be used, such as three, in span, select three
Frequency point, and select three detection threshold values accordingly, it is possible to detect island state exactly.
The present invention takes full advantage of the transmission characteristic of micro-grid system itself, and the injection of interference harmonic wave more meets electric network impedance
Characteristic, the setting of detection threshold is more accurate, and can reach the effect of detection non-blind area；Owing to tested measurement is harmonic current, inspection
The survey time can be controlled in a power frequency cycle, and method of other detection first-harmonic content, the detection time is more than 1 cycle more；
Owing to have employed multiple test point, reduce the electrical network interference impact on testing result.Accuracy of detection and the raising of speed, to guarantor
Barrier Electrical Safety, promotes the application of distributed generation system to have positive effect.
The preferred embodiment of the present invention described in detail above.Should be appreciated that those of ordinary skill in the art without
Need creative work just can make many modifications and variations according to the design of the present invention.Therefore, all technology in the art
Personnel are available by logical analysis, reasoning, or a limited experiment the most on the basis of existing technology
Technical scheme, all should be in the protection domain being defined in the patent claims.
Claims (7)
1. an island detection method, it is characterised in that described island detection method comprises the following steps:
(1) when micro-capacitance sensor actual motion, on the output voltage of changer, the most respectively superposition first frequency harmonic voltage with
Second frequency harmonic voltage, the first electric current of the junction point of detection micro-capacitance sensor and electrical network and the second electric current；
(2) if the first electric current detects threshold value more than or equal to the first detection threshold value and the second electric current more than or equal to second, micro-
Electrical network disconnects the connection with electrical network by chopper, enters islet operation；Otherwise perform step (1).
2. island detection method as claimed in claim 1, it is characterised in that described first frequency and the choosing of described second frequency
Selection method comprises the following steps:
(11) equivalent circuit of micro-grid system is set up；
(12) according to equivalent circuit, it is thus achieved that and the transmission function of net state and island state；
(13) electric current span more than the also electric current of net state of island state is obtained；
(14) described first frequency and described second frequency select from described span.
3. island detection method as claimed in claim 2, it is characterised in that step (13) comprises the following steps: (131) for
The load set, obtains and net state amplitude-frequency response, island state amplitude-frequency response and its intersecting area, institute respectively
Stating intersecting area is described span.
4. island detection method as claimed in claim 2, it is characterised in that step (13) is the most further comprising the steps of: (132)
For different loads, obtain respectively and net state amplitude-frequency response, island state amplitude-frequency response and its intersection
Territory；
(133) obtaining the public territory of the intersecting area for different loads, described public territory is described span.
5. island detection method as claimed in claim 2, it is characterised in that step (11) sets up the equivalent electric of micro-grid system
The method on road comprises the following steps:
(111) changer being considered as voltage source, load end includes filter circuit, load and electrical network equiva lent impedance；
(112) transformer parameter of the electrical network accessed according to micro-capacitance sensor, calculates the equiva lent impedance of electrical network；
(113) by equivalent with RLC parallel circuit to micro-capacitance sensor load and the network load accessed.
6. island detection method as claimed in claim 1, it is characterised in that the system of selection of described first detection threshold value includes
Following steps:
(21) emulation tool is utilized to set up the phantom of micro-capacitance sensor；
(22) for different loads, on the output voltage of changer, superposition first frequency harmonic voltage, obtain micro-electricity respectively
Net and the junction point of electrical network that accessed and the electric current of electric current and island state of net state；
(23) selecting described first detection threshold value, described first detection threshold value is more than all and electric current of net state and less than all
The electric current of island state.
7. island detection method as claimed in claim 1, it is characterised in that described island detection method is for by single change
The micro-capacitance sensor that parallel operation is connected with electrical network.
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| CN110546844A (en) * | 2017-04-24 | 2019-12-06 | 乌本产权有限公司 | method for detecting islanding grid formation |
| CN110612650A (en) * | 2017-06-28 | 2019-12-24 | 艾思玛太阳能技术股份公司 | Method for operating an islanded grid and islanded grid |
| CN115629277A (en) * | 2022-12-06 | 2023-01-20 | 深圳市首航新能源股份有限公司 | Weak power grid island detection method and device and electronic equipment |
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