CN105629087A - Improved inverter anti-island detection method - Google Patents
Improved inverter anti-island detection method Download PDFInfo
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Abstract
The invention provides an improved inverter anti-island detection method comprising the following steps: the resonance frequency of an RLC load is adjusted to different intervals under the condition that the quality factor and fundamental wave current meet the existing initial conditions; and the time for inverter anti-island detection at different resonance frequencies of the RLC load is recorded by an oscilloscope. The system introduces the resonance frequency of the RLC load as a key quantity of test to perform inverter anti-island detection for the first time. On the basis of taking into full consideration factors like quality factor and fundamental wave current specified in the existing standard, the influence of the resonance frequency of the RLC load on the result of anti-island detection is also taken into consideration. The improved inverter anti-island detection method is more accurate than the existing detection method.
Description
Technical field
A kind of method that the present invention relates to photovoltaic combining inverter detection field, in particular to the anti-island detection method of inverter of a kind of improvement.
Background technology
When public electric wire net is stopped power supply suddenly, the distributed photovoltaic power generation system being connected with electrical network fails to detect that the power down mode of electrical network continues to work in time, thus forming a self-energizing isolated island. The grid-connected photovoltaic system being in island operation state can produce serious consequence, and voltage and frequency in isolated island are uncontrollable, it is possible to the equipment of user can be caused damage; Circuit in isolated island is still charged, it is possible to the life security of entail dangers to maintainer; Moreover, the action sequence of network system protection switch can also be affected; When Utilities Electric Co. restores electricity, due to problems such as the dash currents that the asynchronous generation of phase place is big. For this, prior art discloses corresponding anti-isolated island examination criteria and testing process.
IEEE1547.1 specifies, the inverter run to the 33% of rated power, 66% and 100% is carried out anti-isolated island test respectively. Test device is RLC load, regulating load quality factor qf=1.0 �� 0.05, and flow through the fundamental current of grid-connected switch less than the 2% of equipment under test rated current, disconnect grid-connected switch, record the anti-isolated island detection time; Subsequently with 1% rate adaptation perception or capacitive reactive power load, and according to whether anti-isolated island testing time Trend judgement increases test.
VDE0126 specifies, inverter when running to the 25% of rated power, 50% and 100% is carried out anti-isolated island test respectively. Adjust loaded quality factor Qf> 2, the fundamental current flowing through grid-connected switch is little as much as possible, disconnects grid-connected switch, records the anti-isolated island detection time. After completing benchmark test, selected parameter L or C respectively, the parameter value with 1% is adjusted for step-length, and whole knots modification is less than �� 5%, then retests.
Test to the anti-isolated island performance of inverter in Q/GDW618, inverter output power is not made regulation, only after regulation inverter stable operation, regulating test fixture prime factor is 1 �� 0.2, and flow through the fundamental current of grid-connected switch less than the 5% of tested inverter output current, disconnect grid-connected switch, record the anti-isolated island detection time.
The prior art of anti-isolated island detection only accounts for fundamental current size in initial testing conditions, and fundamental current is not presented respectively resistive, perceptual and three kinds of situations of capacitive and further specifies, the observation of the present inventor, research, analysis find: test result is had and significantly affects by resistive, perceptual and three kinds of fundamental currents of capacitive sizes, and whether fundamental current presents resistive, capacitive and perception is determined by load resonant frequency.
Accordingly, it is desirable to provide the anti-island detection method of the inverter of a kind of improvement.
Summary of the invention
For overcoming above-mentioned the deficiencies in the prior art, the present invention provides the anti-island detection method of inverter of a kind of improvement.
Realizing the solution that above-mentioned purpose adopts is:
A kind of inverter anti-island detection method of improvement, the system of described inverter anti-isolated island detection includes the grid-connected switch for connecting power distribution network and photovoltaic DC-to-AC converter, it is connected RLC load by load switch K1 between described grid-connected switch and described photovoltaic DC-to-AC converter, it is connected oscillograph between described grid-connected switch and described photovoltaic DC-to-AC converter, between described grid-connected switch and described power distribution network, is connected device for testing power; It thes improvement is that: described detection method includes: meet in initial condition situation in quality factor and fundamental current, it is different interval that described RLC load resonant frequency is adjusted to, determines the described RLC load anti-isolated island detection time of the described inverter when different resonant frequency interval respectively.
Further, put into and meet initial condition and RLC load that resonant frequency is 49.9Hz��50.1Hz, disconnect described grid-connected switch, carry out anti-isolated island detection;
Record and described grid-connected switch off the moment to tested inverter time t1 out of service, if described time t1 is more than 2s, detection terminates, anti-isolated island ability is defective, if described time t1 is less than 2s, then when initial condition is constant, first time regulates RLC load resonant frequency, disconnects described grid-connected switch, carries out anti-isolated island detection;
Record and described grid-connected switch off the moment to tested inverter time t2 out of service, if described time t2 is more than 2s, detection of end, anti-isolated island ability is defective, if described time t2 is less than 2s, then when initial condition is constant, second time regulates RLC load resonant frequency, disconnects described grid-connected switch, carries out anti-isolated island detection;
Recording described grid-connected switch K2 and disconnect the moment to tested inverter time t3 out of service, if described time t3 is more than 2s, detection terminates, and anti-isolated island ability is defective, if described time t2 is less than 2s, then anti-isolated island ability is qualified, detection of end.
Further, described initial condition includes:
Active power that the active power that reactive power that the reactive power that LC consumes sends equal to tested inverter, RLC consume sends equal to tested inverter, the quality factor of RLC load are 1 �� 0.2 and flow through the fundamental current of grid-connected switch K2 less than the 5% of tested inverter output current.
Further, described first time regulates RLC load resonant frequency for described resonant frequency is adjusted to 50.1Hz��50.2Hz.
Further, described second time regulates RLC load resonant frequency for described resonant frequency is adjusted to 49.5Hz��49.9Hz.
Compared with prior art, the method have the advantages that
1, in the anti-island detection method of inverter provided by the invention, the fundamental current characteristic proposing to flow through grid-connected switch is relevant with RLC load characteristic, RLC load characteristic is determined by load resonant frequency simultaneously, needs to consider the load resonant frequency impact on anti-island detection method during test.
2, in the anti-island detection method of inverter provided by the invention, it is firstly introduced RLC load resonant frequency to detect as the anti-isolated island of inverter that carries out testing critical quantity, in taking into full account existing standard on the basis of the factor such as the quality factor of defined, fundamental current size, also take into full account the impact on anti-isolated island testing result of the RLC load resonant frequency.
When 3, inverter being carried out anti-isolated island Site Detection according to existing anti-island detection method, there will be identical two inverters of model only because the nuance of RLC load resonant frequency and cause that anti-isolated island testing result is different, even occurring that a detection is qualified, one is detected underproof situation. Found by the research of the present inventor: in the equal-sized situation of the fundamental current flowing through grid-connected switch, the difference of RLC load resonant frequency causes that fundamental current is likely to be rendered as perception, capacitive and resistive three kinds of situations, and fundamental current is when presenting perception or capacitive, may result in the inverter anti-isolated island detection time less than normal, namely occur that the probability that testing result is qualified is bigger, for the inverter of same model, this occurs that different testing results is inequitable, the detection of this anti-isolated island can not embody the anti-isolated island performance of inverter objectively. And in the anti-island detection method of inverter provided by the invention, when in considering Q/GDW617 " photovoltaic plant accesses electric power network technique and specifies ", regulation photovoltaic DC-to-AC converter is properly functioning, grid-connected dot frequency ranges on the basis of 49.5Hz��50.2Hz, load resonant frequency is respectively set to 49.5Hz��49.9Hz, 49.9Hz��50.1Hz and 50.1Hz��50.2Hz tri-interval, in each interval, carry out the detection of anti-isolated island one by one, effectively evade the generation of above-mentioned erroneous judgement situation.
4, anti-island detection method provided by the invention, original only consider loaded quality factor and flow through grid-connected switch fundamental current size basis on, the impact that anti-isolated island is detected by the load resonant frequency also taken into full account, more objectively and fairly embody the anti-isolated island testing result of inverter, will effectively enrich and improve existing domestic and international anti-isolated island detection field Correlative Standard System
Accompanying drawing explanation
Fig. 1 is the anti-alone island detection system schematic diagram of inverter in the present invention;
Detailed description of the invention
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
As shown in Figure 1, Fig. 1 is the anti-alone island detection system schematic diagram of inverter in the present invention, this system includes: by the grid-connected switch K2 photovoltaic DC-to-AC converter being connected with power distribution network, it is connected RLC load by load switch K1 between grid-connected switch K2 and photovoltaic DC-to-AC converter, it is connected oscillograph between described grid-connected switch K2 and photovoltaic DC-to-AC converter, being connected device for testing power between described grid-connected switch K2 and described power distribution network, active power and the reactive power of described grid-connected switch K2 is flow through in power detection device measurement.
The present invention provides the anti-island detection method of a kind of improvement, the method is a kind of anti-island detection method considering load resonant frequency, for Q/GDW617 " photovoltaic plant accesses power system technology regulation ", when quality factor and fundamental current are constant, adjust described RLC load resonant frequency, inverter anti-isolated island detection when carrying out RLC load for different resonant frequency.
Detection starts, and first puts into the RLC load meeting following condition, disconnects described grid-connected switch K2, carries out anti-isolated island detection; Condition includes:
1) reactive power that the reactive power that LC consumes sends equal to tested inverter;
2) active power that the active power that RLC consumes sends equal to tested inverter;
3) quality factor of RLC load are 1 �� 0.2;
4) fundamental current of K2 is flow through less than the 5% of tested inverter output current;
5) RLC load resonant frequency is 49.9Hz��50.1Hz.
Then, record grid-connected switch K2 and disconnect the moment to tested inverter time t1 out of service, it is the anti-isolated island detection time of tested inverter, it is judged that whether time t1 is more than 2s, if described time t1 is more than 2s, detection terminates, anti-isolated island ability is defective, if described time t1 is less than 2s, then when other initial condition are constant, first time regulates RLC load resonant frequency, disconnect described grid-connected switch K2, carry out anti-isolated island detection;
Record described grid-connected switch K2 and disconnect the moment to tested inverter time t2 out of service, if described time t2 is more than 2s, detection terminates, anti-isolated island ability is defective, if described time t2 is less than 2s, then when initial condition is constant, second time regulates RLC load resonant frequency, disconnects described grid-connected switch K2, carries out anti-isolated island detection;
Recording described grid-connected switch K2 and disconnect the moment to tested inverter time t3 out of service, if described time t3 is more than 2s, detection terminates, and anti-isolated island ability is defective, if described operation time t2 is less than 2s, then anti-isolated island ability is qualified, terminates test.
First time regulates RLC load resonant frequency for described resonant frequency is adjusted to 50.1Hz��50.2Hz.
Second time regulates RLC load resonant frequency for described resonant frequency is adjusted to 49.5Hz��49.9Hz.
In the present embodiment, it is believed that the anti-isolated island ability of inverter is defective refers to that the anti-isolated island ability of this inverter does not meet Q/GDW617 " photovoltaic plant accesses power system technology regulation ".
Carrying out the emulation detection of anti-isolated island under Matlab/Simulink environment for certain type 100kW photovoltaic DC-to-AC converter, detection system is as shown in Figure 1.
When acquisition RLC load is resistive, inverter anti-isolated island testing result is as shown in table 1 below, when RLC load is in perception, inverter anti-isolated island testing result is as shown in table 2 below, when RLC load presents capacitive, inverter anti-isolated island testing result is as shown in table 3 below, and table 1��table 3 embodies the fundamental current flowing through grid-connected switch K2 respectively and varies in size and during RLC load characteristic difference, the inverter anti-isolated island detection time.
Table 1
Being found by table 1, when RLC load presents resistive, resonant frequency is 50Hz, flows through the fundamental current of grid-connected switch K2 less than when exporting electric current 5%, and the anti-isolated island of inverter is detected the time substantially without impact by the fundamental current size flowing through grid-connected switch K2.
Found by table 2, when RLC load presents perception, resonant frequency, less than 50Hz, flows through the fundamental current of grid-connected switch K2 less than when exporting electric current 5%, and the fundamental current flowing through grid-connected switch K2 is more big, deviation 50Hz is more remote for resonant frequency, the 49.5Hz even specify beyond standard, and resonant frequency between 49.5Hz��50Hz time, the anti-isolated island detection time constantly reduces with resonant frequency deviation 50Hz, when resonant frequency is less than 49.5Hz, the inverter anti-isolated island detection time is basically unchanged.
Table 2
Table 3
Found by table 3, when RLC load presents capacitive, resonant frequency, more than 50Hz, flows through the fundamental current of grid-connected switch K2 less than when exporting electric current 5%, and fundamental current is more big, deviation 50Hz is more remote for resonant frequency, the 50.2Hz even specify beyond standard, and resonant frequency between 50Hz��50.2Hz time, the anti-isolated island detection time constantly reduces with resonant frequency deviation 50Hz, when resonant frequency is more than 50.2Hz, the inverter anti-isolated island detection time is basically unchanged.
Contrasted by table 1��table 3 it appeared that, in the anti-isolated island ability detection process of this model inverter, the fundamental current flowing through grid-connected switch K2 whether meets " less than equipment rated current 2% " of regulation in IEEE1547.1 standard, still " less than output electric current 5% " of Q/GDW617 standard regulation is met, fundamental current for formed objects, all there is following phenomenon: when resonant frequency is 50Hz, the anti-isolated island detection time is the longest, deviation 50Hz is more remote for resonant frequency, the detection time is more short, and this testing result does not more have objectivity.
Therefore, except reaching standard-required except quality factor, fundamental current during test, also take into full account the system resonance frequencies impact on anti-isolated island testing result. Test condition is pressed load resonant frequency respectively three intervals of 49.9 to 50.1Hz, 49.5 to 49.9Hz and 50.1 to 50.2Hz, assesses the anti-isolated island protective value of inverter more exactly.
Finally should be noted that: above example is merely to illustrate the technical scheme of the application but not the restriction to its protection domain; although with reference to above-described embodiment to present application has been detailed description; those of ordinary skill in the field are it is understood that the detailed description of the invention of application still can be carried out all changes, amendment or equivalent replacement by those skilled in the art after reading the application; but these change, revise or equivalent replacement, all within the claims that application is awaited the reply.
Claims (5)
1. the anti-island detection method of inverter improved, the system of described inverter anti-isolated island detection includes the grid-connected switch for connecting power distribution network and photovoltaic DC-to-AC converter, it is connected RLC load by load switch K1 between described grid-connected switch and described photovoltaic DC-to-AC converter, it is connected oscillograph between described grid-connected switch and described photovoltaic DC-to-AC converter, between described grid-connected switch and described power distribution network, is connected device for testing power; It is characterized in that: described detection method includes: meet in initial condition situation in quality factor and fundamental current, it is different interval that described RLC load resonant frequency is adjusted to, determines the described RLC load anti-isolated island detection time of the described inverter when different resonant frequency interval respectively.
2. the as claimed in claim 1 anti-island detection method of inverter, it is characterised in that: put into and meet initial condition and RLC load that resonant frequency is 49.9Hz��50.1Hz, disconnect described grid-connected switch, carry out anti-isolated island detection;
Record and described grid-connected switch off the moment to tested inverter time t1 out of service, if described time t1 is more than 2s, detection terminates, anti-isolated island ability is defective, if described time t1 is less than 2s, then when initial condition is constant, first time regulates RLC load resonant frequency, disconnects described grid-connected switch, carries out anti-isolated island detection;
Record and described grid-connected switch off the moment to tested inverter time t2 out of service, if described time t2 is more than 2s, detection of end, anti-isolated island ability is defective, if described time t2 is less than 2s, then when initial condition is constant, second time regulates RLC load resonant frequency, disconnects described grid-connected switch, carries out anti-isolated island detection;
Recording described grid-connected switch K2 and disconnect the moment to tested inverter time t3 out of service, if described time t3 is more than 2s, detection terminates, and anti-isolated island ability is defective, if described time t2 is less than 2s, then anti-isolated island ability is qualified, detection of end.
3. the anti-island detection method of inverter as claimed in claim 1, it is characterised in that: described initial condition includes:
Active power that the active power that reactive power that the reactive power that LC consumes sends equal to tested inverter, RLC consume sends equal to tested inverter, the quality factor of RLC load are 1 �� 0.2 and flow through the fundamental current of grid-connected switch K2 less than the 5% of tested inverter output current.
4. the anti-island detection method of inverter as claimed in claim 1, it is characterised in that: described first time regulates RLC load resonant frequency for described resonant frequency is adjusted to 50.1Hz��50.2Hz.
5. the anti-island detection method of inverter as claimed in claim 1, it is characterised in that: described second time regulates RLC load resonant frequency for described resonant frequency is adjusted to 49.5Hz��49.9Hz.
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