CN106921146B - A kind of the switching overvoltage protective device and method of multilevel photovoltaic grid-connected inverter - Google Patents
A kind of the switching overvoltage protective device and method of multilevel photovoltaic grid-connected inverter Download PDFInfo
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- CN106921146B CN106921146B CN201710165777.7A CN201710165777A CN106921146B CN 106921146 B CN106921146 B CN 106921146B CN 201710165777 A CN201710165777 A CN 201710165777A CN 106921146 B CN106921146 B CN 106921146B
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- 238000000034 method Methods 0.000 title claims abstract description 22
- 230000001681 protective effect Effects 0.000 title claims abstract description 12
- 238000006243 chemical reaction Methods 0.000 claims abstract description 67
- 238000001514 detection method Methods 0.000 claims abstract description 18
- 239000003990 capacitor Substances 0.000 claims description 70
- 230000005611 electricity Effects 0.000 claims description 9
- 238000011897 real-time detection Methods 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000012986 modification Methods 0.000 description 2
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- 238000012545 processing Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
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- H02J3/383—
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
A kind of the switching overvoltage protective device and method of multilevel photovoltaic grid-connected inverter, the device include continuous input cell, multi-level inverse conversion unit, control unit, voltage detection unit and current detecting unit；The output end of continuous input cell is connected with the direct-flow input end of multi-level inverse conversion unit, the ac output end of multi-level inverse conversion unit is connected with power grid by net side switch K but is not limited only to be connected with power grid, the input terminal of voltage detection unit is connected with grid side, the output end of voltage detection unit is connected with the input terminal of control unit, the input terminal of current detecting unit is connected with the ac output end of multi-level inverse conversion unit, the output end of current detecting unit is connected with another input terminal of control unit, the output end of control unit is connected with the driving end of switching tube in multi-level inverse conversion unit；The invention also discloses the control methods of the device；Effectively inversion unit output voltage can be reduced within threshold range, the safety of the outlet side electronic load of protection exchange in time；And system loss is small.
Description
Technical field
The present invention relates to photovoltaic power supply technical fields, and the present invention relates to a kind of switching overvoltage guard methods, especially relate to
And a kind of switching overvoltage protective device and method applied to multilevel photovoltaic grid-connected inverter.
Background technique
The ac output end of photovoltaic combining inverter is directly connected with power grid by points of common connection, while can on port
Other load equipments can be connected, rear port voltage are connect with power grid by power grid clamper, port voltage amplitude is by network voltage size
It determines.When isolated island occurs for power grid, net side switch is disconnected, and inverter and power grid disconnect, and the voltage of net side points of common connection is no longer
By power grid clamper, while inverter still will continue to provide idle function to power grid before detecting that generation isolated island stopping is grid-connected
Rate causes the voltage of inverter ac side points of common connection to rise.In order to prevent the electronic load of inverter ac output end by
To the impact of high voltage, the transient voltage of inverter ac output end is not to be exceeded that " NB/T 32004-2013 photovoltaic power generation is simultaneously
Net inverter technology specification " in required limit value.
For three-phase grid-connected inverter, for problem above present in grid-connected, the prior art is according to three-phase power grid voltage
Orthogonal dq rotating coordinate system is established, by the inverter voltage d axis component or network voltage that calculate three-phase grid-connected inverter
Virtual value judges whether the ac output end of inverter has occurred switching overvoltage.It is past when judging to occur switching overvoltage
Voltage toward grid side has built up, even if stopping is grid-connected at this time, safety capacitor Cx (the usually X of inverter ac output end
Capacitor) both ends voltage it is higher, generally discharged at this time by the internal resistance in inverter.Obvious safety capacitor Cx
The smaller electric discharge of capacitance it is faster, but will affect electromagnetic compatibility (EMC) characteristic of inverter；The resistance value of inverter internal resistance is got over
Small electric discharge is faster, but additional loss can be brought to inverter, increases the cost of inverter.
Summary of the invention
In order to solve the above technical problems, the present invention provides a kind of operations applied to multilevel photovoltaic grid-connected inverter
Voltage protection and method, the device mainly detect network voltage by detection unit, by whether detecting network voltage
Isolated island occurs, inverter is controlled by control unit and switches to the working condition that switching overvoltage is protected from grid-connected working condition,
Until the ac output voltage of inverter drops to given voltage, whole operation overvoltage protection process just terminates, at inverter
In standby mode, wait again grid-connected；The device and guard method use simple circuit structure, and combination controlling method,
When isolated island occurs for power grid, first inverter and power grid are disconnected and quickly being disconnected, inverter ac output voltage is then reduced to mark
Within the scope of required by quasi-, the electronic equipment that inverter ac side is connected is effectively protected.
In order to achieve the above object, the present invention adopts the following technical scheme:
A kind of switching overvoltage protective device of multilevel photovoltaic grid-connected inverter, the device include continuous input cell,
Multi-level inverse conversion unit, control unit, voltage detection unit and current detecting unit；The output end of the continuous input cell with
The direct-flow input end of multi-level inverse conversion unit is connected, and the ac output end of the multi-level inverse conversion unit passes through net side switch K
It is connected with power grid but is not limited only to be connected with power grid, the input terminal of the voltage detection unit is connected with grid side, uses
In detection network voltage, the output end of the voltage detection unit is connected with the input terminal of control unit, the current detecting
The input terminal of unit is connected with the ac output end of multi-level inverse conversion unit, the output end of the current detecting unit and control
Another input terminal of unit is connected, the driving end phase of the output end of described control unit and switching tube in multi-level inverse conversion unit
Connection, for controlling the working condition of multi-level inverse conversion unit switch pipe.
The multi-level inverse conversion unit is single-phase or three-phase；Multi-level inverse conversion unit by DC bus module, inverter bridge leg,
Ac filter module is sequentially connected in series composition, and the DC bus module is that n-1 bus capacitor is in series, and n is level
Number；The multi-level inverse conversion bridge arm includes " zero " level switch group, " just " level switch group and " negative " level switch group, described
" zero " level switch group is connected in series between bus capacitor midpoint and " just " level switch group and " negative " level switch group, described
Ac filter module is by filter inductance L and filter capacitor CinvComposition, one end of the filter inductance L and the output of inverter bridge leg
It is connected, the other end is the positive output end of multi-level inverse conversion unit, the filter capacitor CinvOne end and multi-level inverse conversion unit
Positive output end be connected, filter capacitor CinvThe other end be connected with bus capacitor midpoint as multi-level inverse conversion unit
Negative output terminal.
The control method of the switching overvoltage protective device:
Step 1: voltage detection unit real-time detection network voltage, and the voltage that will test is given control unit and is counted
According to processing；
Step 2: control unit handles the voltage data sent, when detecting network voltage virtual value VaveIt is less than
The given threshold value V of systemGWhen, control unit control multi-level inverse conversion unit keeps grid-connected working condition；When detecting electricity
Net voltage effective value VaveThe threshold value V given greater than systemGWhen, control unit issues control signal, makes multi-level inverse conversion unit institute
There is switching tube disconnection, while multi-level inverse conversion unit is immediately switched to switching overvoltage guard mode from grid connection state, waits to be controlled
Unit processed re-emits control signal；
Step 3: carrying out switching overvoltage guard mode, i.e. control unit gives zero level switching group to issue control letter again
Number, make zero level switching group ON operation, forms current loop inside multi-level inverse conversion unit, exchange multi-level inverse conversion unit
Output end voltage is fed back in the DC bus module of inversion unit direct-flow input end；
Step 4: when multi-level inverse conversion unit ac output end voltage value V is greater than corresponding safe voltage value VsafeIt is (described
Safe voltage value VsafeIt is the inverter safety value required when carrying out switching overvoltage), then it continues to execute step 3 and is grasped
Make overvoltage protection；When multi-level inverse conversion unit ac output end voltage V is less than safe voltage value Vsafe, control unit will sending
Signal is controlled, zero level switching group is turned off, switching overvoltage guard mode stops, and net side switch K is disconnected, multi-level inverse conversion list
Member is in standby, and switching overvoltage protection process terminates.
Compared to the prior art, the present invention has following advantage:
1. apparatus of the present invention, when inversion unit output voltage exceeds threshold value, inversion unit effectively can be exported electricity by system
Pressure is reduced within threshold range, the safety of the outlet side electronic load of protection exchange in time.
2. the protective device and method are will to exchange the electric energy feedback that exceeds of output to DC bus, rather than pass through system
Internal resistance is consumed, so system loss is small.
Detailed description of the invention
Fig. 1 switching overvoltage protective device block diagram.
Fig. 2 multi-level inverse conversion element circuit block diagram.
Fig. 3 switching overvoltage guard method control flow chart.
Fig. 4 is single-phase T-type three-level inverter.
Fig. 5 is that four operation modes after switching overvoltage occur for single-phase T-type three-level inverter, and wherein Fig. 5 (a) is
[0, D × Ts] period filter capacitor is transferred to the circuit working state in filter inductance L, and Fig. 5 (b) is the filter of [D × Ts, Ts] period
The energy of wave inductance is fed to the circuit working state of DC bus module, and Fig. 5 (c) is [0, D × Ts] period filter capacitor
Circuit working state of the energy transfer into filter inductance L., Fig. 5 (d) is the energy of [D × Ts, Ts] period filter inductance
It is fed to the circuit working state of DC bus module.
Fig. 6 is three-phase T-type three-level inverter.
Fig. 7 is single-phase I type three-level inverter.
Fig. 8 is that four operation modes after switching overvoltage occur for single-phase I type three-level inverter, and wherein Fig. 8 (a) is
[0, D × Ts] period filter capacitor is transferred to the circuit working state in filter inductance L, and Fig. 8 (b) is the filter of [D × Ts, Ts] period
The energy of wave inductance is fed to the circuit working state of DC bus module, and Fig. 8 (c) is [0, D × Ts] period filter capacitor
Circuit working state of the energy transfer into filter inductance L, Fig. 8 (d) are that the energy of [D × Ts, Ts] period filter inductance is fed
To the circuit working state of DC bus module.
Fig. 9 is three-phase I type three-level inverter.
Figure 10 is three-phase I type five-electrical level inverter.
Specific embodiment
The invention will be further described for embodiment shown in reference to the accompanying drawing.
Fig. 1 is switching overvoltage protective device block diagram, as shown, a kind of applied to multilevel photovoltaic grid-connected inverter
Switching overvoltage protective device and method, the device include continuous input cell, multi-level inverse conversion unit, control unit, voltage
Detection unit and current detecting unit.The direct-flow input end phase of the output end of the continuous input cell and multi-level inverse conversion unit
Connection, the ac output end of the multi-level inverse conversion unit is connected by net side switch K with power grid, while the exchange of inversion unit
Output end can also be connected to other electronic loads, and the input terminal of the voltage detection unit is connected with grid side, for detecting electricity
Net voltage, the output end of the voltage detection unit are connected with the input terminal of control unit, the current detecting unit it is defeated
Enter end to be connected with the ac output end of multi-level inverse conversion unit, the output end of the current detecting unit and control unit it is another
One input terminal is connected, and the output end of described control unit is connected with the driving end of switching tube in multi-level inverse conversion unit, uses
In the working condition of control multi-level inverse conversion unit switch pipe.
Fig. 2 is multi-level inverse conversion element circuit block diagram, as shown, the multi-level inverse conversion unit is single-phase or three-phase.
Multi-level inverse conversion unit is sequentially connected in series and is formed by DC bus module, inverter bridge leg, ac filter module.The direct current is female
Wire module is that (n-1) a bus capacitor is in series, and n is level number；The multi-level inverse conversion bridge arm includes " zero " level switch
Group, " just " level switch group and " negative " level switch group, " zero " the level switch group be connected in series in bus capacitor midpoint with
" just " between level switch group and " negative " level switch group, the ac filter module is by filter inductance L and filter capacitor C group
At one end of the filter inductance L is connected with the output of multi-level inverse conversion bridge arm, and other end is the just defeated of inversion unit
Outlet, the filter capacitor CinvOne end be connected with the output end of multi-level inverse conversion unit, filter capacitor CinvThe other end
It is connected with bus capacitor midpoint and is connected in the negative output terminal of multi-level inverse conversion unit.
Fig. 3 is switching overvoltage guard method software control flow chart, the controlling party of the switching overvoltage protective device
Method:
Step 1: voltage detection unit real-time detection network voltage V, and the voltage that will test gives control unit progress
Data processing；
Step 2: control unit handles the voltage data sent, when detecting network voltage virtual value VaveIt is less than
The given threshold value V of systemGWhen, control unit control multi-level inverse conversion unit keeps grid-connected working condition；When detecting electricity
Net voltage effective value is greater than the threshold value V that system givesGWhen, control unit issues control signal, keeps multi-level inverse conversion unit all
Switching tube disconnects, while multi-level inverse conversion unit is immediately switched to switching overvoltage guard mode from grid connection state, waits to be controlled
Unit re-emits control signal；
Step 3: carrying out switching overvoltage guard mode, i.e. control unit gives zero level switching group to issue control letter again
Number, make zero level switching group ON operation, forms current loop inside multi-level inverse conversion unit, exchange multi-level inverse conversion unit
Output end voltage is fed back in the DC bus module of inversion unit direct-flow input end.
Step 4: when multi-level inverse conversion unit ac output end voltage value V is greater than safe voltage value Vsafe(the safety electricity
Pressure value VsafeIt is the inverter safety value required when carrying out switching overvoltage), then it continues to execute step 3 and was operated electricity
Pressure protection；When multi-level inverse conversion unit ac output end voltage V is less than safe voltage value Vsafe, control unit, which will issue to control, to be believed
Number, turn off zero level switching group, switching overvoltage guard mode stops, and net side switch K is disconnected, and multi-level inverse conversion unit is in
Standby mode, switching overvoltage protection process terminate.
Fig. 4 is single-phase T-type three-level inverter, as shown, dc-link capacitance is by first capacitor C1 and the second capacitor
C2 is connected in series, and zero level switch is connected between the midpoint of first capacitor C1 and the second capacitor C2 and the midpoint of inverter bridge leg,
Zero level switch is connected in series by the first zero level switching tube S2 and the second zero level switching tube S3, the first zero level switch
The collector of pipe S2 is connected with the midpoint of first capacitor C1 and the second capacitor C2, the current collection of the second zero level switching tube S3
Pole is connected with the midpoint of inverter bridge leg, the emitter-base bandgap grading of the first zero level switching tube S2 and the second zero level switching tube S3 emitter-base bandgap grading
It is connected.The collector of the positive level switch S1 is connected with the anode of first capacitor C1, the emitter-base bandgap grading of positive level switch S1 with
The collector of negative level switch S4 is connected, and the emitter-base bandgap grading of negative level switch S4 is connected with the cathode of the second capacitor C2.Inductance L's
One end is connected with the midpoint of inverter bridge leg, the other end and filter capacitor C of the inductance LinvOne end be connected, the filter
Wave capacitor CinvThe other end be connected with the midpoint of first capacitor C1 and the second capacitor C2.
Fig. 5 is that four operation modes after switching overvoltage occur for single-phase T-type three-level inverter, as shown, " zero "
Level switch pipe includes the first zero level switching tube S2 and the second zero level switching tube S3.When digital controller senses are to having occurred
After switching overvoltage, digitial controller sends the driving signal of duty ratio D (0 < D < 1), switch periods to " zero " level switch pipe
For Ts, while forbidding the work of rest switch pipe.At this time when " zero " level switch pipe is opened or turned off, inverter shares four
A operation mode:
Mode 1: equivalent circuit such as Fig. 5 (a) is shown, at this time filter capacitor CinvBoth end voltage is greater than zero, in switch periods
[0, D × Ts] period, the first zero level switching tube S2 in " zero " level switch are connected with the second zero level switching tube S3, other
Power switch tube shutdown.Filter capacitor CinvEnergy transfer into filter inductance L；
Mode 2: equivalent circuit such as Fig. 5 (b) is shown, at this time filter capacitor CinvBoth end voltage is greater than zero, in switch periods
[D × Ts, Ts] period, all switching tube shutdowns.Filter inductance L electric current passes through positive level switching tube S1Body diode afterflow,
The energy of filter inductance is fed to DC bus module；
Mode 3: equivalent circuit such as Fig. 5 (c) is shown, at this time filter capacitor CinvBoth end voltage is less than zero, in switch periods
[0, D × Ts] period, the first zero level switching tube S2 in " zero " level switch are connected with the second zero level switching tube S3, other
Power switch tube shutdown.Filter capacitor CinvEnergy transfer into filter inductance L；
Mode 4: equivalent circuit such as Fig. 5 (d) is shown, at this time filter capacitor CinvBoth end voltage is less than zero, in switch periods
[D × Ts, Ts] period, all switching tube shutdowns.Filter inductance electric current passes through negative level switching tube S4Body diode afterflow, filter
The energy of wave inductance L is fed to DC bus module；
Fig. 6 is three-phase T-type three-level inverter.As shown, dc-link capacitance is by first capacitor C1 and the second capacitor
C2 is connected in series, and the zero level switching group of a phase is connected in the midpoint and inverter bridge leg of first capacitor C1 and the second capacitor C2
Between point, zero level switch is connected in series by the first zero level switching tube S2a and the second zero level switching tube S3a respectively, described
The collector of first zero level switching tube S2a is connected with the midpoint of first capacitor C1 and the second capacitor C2, the 2nd 0 electricity
The collector of flat switching tube S3a is connected with the midpoint of inverter bridge leg, the emitter-base bandgap grading and second of the first zero level switching tube S2a
Zero level switching tube S3a emitter-base bandgap grading is connected.The collector of the positive level switch S1a is connected with the anode of first capacitor C1,
The emitter-base bandgap grading of positive level switch S1a is connected with the collector of negative level switch S4a, the emitter-base bandgap grading of the negative level switch S4a and
The cathode of two capacitor C2a is connected.The output of a phase terminates ac filter module.The circuit of the b phase and c phase and a phase phase
Together, details are not described herein again.The switching overvoltage protection operation mode of the circuit is identical as single-phase T-type three-level inverter simultaneously.
Fig. 7 is single-phase I type three-level inverter.As shown, single-phase I type tri-level circuit is by four with inverse parallel
The switching tube of diode is connected in series, and positive level switching tube S1Drain electrode be connected with the anode of first capacitor C1, positive level
Switching tube S1Source electrode and the first zero level switching tube S2Drain series connection, the first zero level switching tube S2Source electrode and
Two zero level switching tube S3Drain series connection, the second zero level switching tube S3Source electrode and negative level switching tube S4Drain electrode
It is connected in series, negative level switching tube S4Source electrode be connected with the cathode of the second capacitor C2.The power supply positive and negative and between go here and there
It is associated with first capacitor C1 and the second capacitor C2, the positive level switching tube S1With the first zero level switching tube S2Series connection point and first
Zero level first diode D is connected between capacitor C1 and the series connection point N of the second capacitor C21, zero level first diode D1Sun
Pole is connected with N point, zero level first diode D1Cathode and positive level switching tube S1With zero level first switch tube S2String
Connection point is connected.The zero level second switch S3With negative level switching tube S4Series connection point and first capacitor C1 and the second capacitor
The second diode of zero level D is connected between the series connection point N of C22, the second diode of zero level D2Cathode be connected with N point, zero
Two diode D of level monitoring2Anode and zero level second switch S3With negative level switching tube S4Series connection point be connected, it is described
Zero level first switch tube S2With zero level second switch S3Series connection point connect a filter inductance L, the filter inductance L's
A filter capacitor C is connected between the other end and first capacitor C1 and the second capacitor C2 midpoint Ninv, filter capacitor CinvBoth ends are in parallel
There is a load resistance R.
Fig. 8 is that four operation modes after switching overvoltage occur for single-phase I type three-level inverter, as shown, " zero "
Level switch pipe includes power switch tube zero level first switch S2With zero level second switch S3.When digital controller senses arrive
After switching overvoltage has occurred, digitial controller sends the driving signal of duty ratio D (0 < D < 1) to " zero " level switch pipe, opens
The pass period is Ts, while forbidding the work of rest switch pipe.At this time when " zero " level switch pipe is opened or turned off, inverter
There are four operation modes altogether:
Mode 1: equivalent circuit such as Fig. 8 (a) is shown, at this time filter capacitor CinvBoth end voltage is greater than zero, in switch periods
[0, D × Ts] period, the first zero level switching tube S2 and the second zero level switching tube S in " zero " level switch3Conducting, other
Power switch tube shutdown.Filter capacitor CinvEnergy transfer into filter inductance L；
Mode 2: equivalent circuit such as Fig. 8 (b) is shown, at this time filter capacitor CinvBoth end voltage is greater than zero, in switch periods
[D × Ts, Ts] period, all switching tube shutdowns.Filter inductance L electric current closes pipe S by opening positive level1Body diode and zero electricity
Flat switching tube S2Body diode afterflow, the energy of filter inductance L is fed to DC bus module；
Mode 3: equivalent circuit such as Fig. 8 (c) is shown, at this time filter capacitor CinvBoth end voltage is less than zero, in switch periods
[0, D × Ts] period, the first zero level switching tube S in " zero " level switch2It is connected with the second zero level switching tube S3, other
Power switch tube shutdown.The energy transfer of filter capacitor Cin is into filter inductance L；
Mode 4: equivalent circuit such as Fig. 8 (d) is shown, at this time filter capacitor CinvBoth end voltage is less than zero, in switch periods
[D × Ts, Ts] period, all switching tube shutdowns.Filter capacitor CinvFor both end voltage less than zero, inversion inductor electric current passes through second
Zero level switching tube S3Body diode and negative level switching tube S4Body diode afterflow, the energy of filter inductance L is fed to directly
Flow bus；
Fig. 9 is three-phase I type three-level inverter.As shown, the circuit is combined by three single-phase I type tri-level circuits
's.Operation mode is close with the single-phase I type three-level inverter of embodiment, and details are not described herein again.
Figure 10 is three-phase I type five-electrical level inverter, as shown, the circuit is by three single-phase five level circuit groups of I type
It closes, operation mode is close with the single-phase I type three-level inverter of embodiment, and details are not described herein again.
By the various embodiments described above as can be seen that the applicable multi-level inverter circuit of this programme can there are many modification, when
When switching overvoltage occurs, as long as control " zero " level switch pipe turns on and off, remaining power switch tube is held off, just
It can satisfy the guard time requirement of switching overvoltage.This programme is not under the premise of increasing extra hardware expense, by simple
Control method can satisfy switching overvoltage protection needs.
Above-described embodiment only illustrates technical concepts and features of the invention, and its object is to allow person skilled in the art
Scholar cans understand the content of the present invention and implement it accordingly, and it is not intended to limit the scope of the present invention.It is all according to the present invention
Equivalent change or modification made by Spirit Essence, should be covered by the protection scope of the present invention.
Claims (1)
1. a kind of control method of the switching overvoltage protective device of multilevel photovoltaic grid-connected inverter, switching overvoltage protection
Device includes continuous input cell, multi-level inverse conversion unit, control unit, voltage detection unit and current detecting unit；It is described
The output end of continuous input cell is connected with the direct-flow input end of multi-level inverse conversion unit, the friendship of the multi-level inverse conversion unit
Stream output end be connected by net side switch K with power grid but be not limited only to be connected with power grid, the voltage detection unit it is defeated
Enter end to be connected with grid side, for detecting network voltage, the output end of the voltage detection unit and the input of control unit
End is connected, and the input terminal of the current detecting unit is connected with the ac output end of multi-level inverse conversion unit, the electric current
The output end of detection unit is connected with another input terminal of control unit, the output end and multi-level inverse conversion of described control unit
The driving end of switching tube is connected in unit, for controlling the working condition of multi-level inverse conversion unit switch pipe；
The multi-level inverse conversion unit is single-phase or three-phase；Multi-level inverse conversion unit is by DC bus module, inverter bridge leg, exchange
Filter module is sequentially connected in series composition, and the DC bus module is that n-1 bus capacitor is in series, and n is level number；Institute
Stating inverter bridge leg includes " zero " level switch group, " just " level switch group and " negative " level switch group, " zero " level switch
Group is connected in series between bus capacitor midpoint and " just " level switch group and " negative " level switch group, the ac filter module
By filter inductance L and filter capacitor CinvComposition, one end of the filter inductance L are connected with the output of inverter bridge leg, the other end
For the positive output end of multi-level inverse conversion unit, the filter capacitor CinvOne end and the positive output end phase of multi-level inverse conversion unit
Connection, filter capacitor CinvThe negative output terminal that is connected with bus capacitor midpoint as multi-level inverse conversion unit of the other end；
It is characterized by: the control method includes the following steps:
Step 1: voltage detection unit real-time detection network voltage, and the voltage that will test is given control unit and is carried out at data
Reason；
Step 2: control unit handles the voltage data sent, when detecting network voltage virtual value VaveLess than system
Given threshold value VGWhen, control unit control multi-level inverse conversion unit keeps grid-connected working condition；When detect power grid electricity
It is pressed with valid value VaveThe threshold value V given greater than systemGWhen, control unit issues control signal, makes multi-level inverse conversion unit is all to open
It closes pipe to disconnect, while multi-level inverse conversion unit is immediately switched to switching overvoltage guard mode from grid connection state, waits list to be controlled
Member re-emits control signal；
Step 3: carry out switching overvoltage guard mode, i.e. control unit gives " zero " level switch group to issue control signal again,
Make " zero " level switch group ON operation, forms current loop inside multi-level inverse conversion unit, exchange multi-level inverse conversion unit
Output end voltage is fed back in the DC bus module of multi-level inverse conversion unit direct-flow input end；
Step 4: when multi-level inverse conversion unit ac output end voltage value V is greater than corresponding safe voltage value Vsafe, then continue to execute
Step 3 carries out switching overvoltage protection；When multi-level inverse conversion unit ac output end voltage V is less than safe voltage value Vsafe, control
Unit processed will issue and control signal, turn off " zero " level switch group, and switching overvoltage guard mode stops, and net side switch K is disconnected
It opens, multi-level inverse conversion unit is in standby, and switching overvoltage protection process terminates.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710165777.7A CN106921146B (en) | 2017-03-20 | 2017-03-20 | A kind of the switching overvoltage protective device and method of multilevel photovoltaic grid-connected inverter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710165777.7A CN106921146B (en) | 2017-03-20 | 2017-03-20 | A kind of the switching overvoltage protective device and method of multilevel photovoltaic grid-connected inverter |
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