CN104734186B - Photovoltaic DC-to-AC converter and its low voltage ride through control method - Google Patents
Photovoltaic DC-to-AC converter and its low voltage ride through control method Download PDFInfo
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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
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- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
This application discloses a kind of photovoltaic DC-to-AC converter and its low voltage ride through control method, this method includes：Judge whether low-voltage crossing occurs, if it is, stopping MPPT maximum power point tracking；Judge whether low-voltage crossing restores, if it is, the busbar voltage of photovoltaic DC-to-AC converter is restored to the first voltage value.The photovoltaic DC-to-AC converter includes inverter module, power controller and master controller.Photovoltaic DC-to-AC converter disclosed in the present application and its low voltage ride through control method pass through after determining low-voltage crossing and restoring; the busbar voltage of inverter is quickly recovered into the first voltage value; shorten the time of low-voltage crossing; requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing can be met, busbar voltage is avoided to be pulled low rear photovoltaic DC-to-AC converter and carries out self-protection.
Description
Technical field
This application involves technical field of photovoltaic power generation, and in particular to a kind of photovoltaic DC-to-AC converter and its low-voltage crossing controlling party
Method.
Background technology
In grid-connected photovoltaic system, photovoltaic DC-to-AC converter main function is the DC conversion for exporting photovoltaic panel
For alternating current, then it is incorporated into power grid.When grid collapses lead to Voltage Drop, photovoltaic DC-to-AC converter can then carry out self
Protection disconnects the connection with power grid.
Low voltage crossing (LVRT, Low Voltage Ride Through) refers to fall in photovoltaic inverter grid-connected point voltage
When falling, photovoltaic DC-to-AC converter can keep grid-connected or even certain reactive power is provided to power grid, support power system restoration, directly
It is normal to power system restoration, so as to " passing through " this low-voltage time (region), at this point, photovoltaic DC-to-AC converter can still be kept simultaneously
Net improves the reliability of power grid power supply.At present, photovoltaic DC-to-AC converter is susceptible to busbar voltage in low-voltage crossing recovery moment and is drawn
Dead situation so as to cause the too low protection of photovoltaic DC-to-AC converter busbar voltage or even more serious causes power grid to pour in down a chimney.National grid
There is strict demand in electric power science and technology institute to the low-voltage crossing ability of grid-connected photovoltaic inverter, it is desirable that its active power is extensive in low-voltage crossing
At least restore the value to failure after multiple with the changed power of 10% rated power/second.This requires photovoltaic DC-to-AC converter can be fast
Detect whether power grid breaks down fastly, and MPPT maximum power point tracking can quickly be adjusted after low-voltage crossing recovery.
However, the response speed of normal MPPT maximum power point tracking is slow, it is extremely difficult to above-mentioned requirements.
Invention content
The application provides a kind of photovoltaic DC-to-AC converter and its low voltage ride through control method, can be carried after low-voltage crossing recovery
The power resume speed of high photovoltaic DC-to-AC converter.
According to the application's in a first aspect, the application provides a kind of low voltage ride through control method of photovoltaic DC-to-AC converter, including：
Judge whether low-voltage crossing occurs according to the variation of network voltage, if it is, stopping MPPT maximum power point tracking.
Judge whether low-voltage crossing restores, if it is, the busbar voltage of photovoltaic DC-to-AC converter is restored to the first work(voltage
Value, the first voltage value be preset value or the first voltage value be low-voltage crossing generation before maximum power point voltage
The average value of the first two more than maximum power point voltage value occurs for value or low-voltage crossing；
The variation according to network voltage judges whether low-voltage crossing occurs or restore, specially：
The three-phase positive sequence voltage of power grid and three-phase negative/positive voltage are obtained, and positive direction rotation is carried out to three-phase positive sequence voltage and is become
Get two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage in return, carrying out negative direction to three-phase negative/positive voltage rotates to obtain three-phase
Two-phase the DC voltage Ud- and Uq- of negative sequence voltage；
It calculatesValue, and by it compared with setting value, if less than
Setting value is then judged as low-voltage crossing, if greater than setting value, is then judged as that low-voltage crossing restores, the setting value is pre-
First set.
According to the second aspect of the application, the application provides a kind of photovoltaic DC-to-AC converter, including：
Inverter module, for the busbar voltage that photovoltaic panel exports to be converted to alternating voltage.
Power controller is connect with inverter module, for monitoring and/or controlling the busbar voltage of inverter module.
Master controller is connect respectively with power controller and power grid incoming end, for carrying out MPPT maximum power point tracking, institute
Master controller is stated to be additionally operable to obtain network voltage, and judge whether low-voltage crossing occurs or restore according to the variation of network voltage,
Then stop MPPT maximum power point tracking when the master controller is determined when low-voltage crossing occurs, when determining low-voltage crossing recovery
The busbar voltage of inverter module is then restored to the first voltage value, the first voltage value is preset value or first electricity
Pressure value occurs more than the first two for the maximum power point voltage value before the low-voltage crossing generation of processing unit backup or low-voltage crossing
The average value of maximum power point voltage value；
The master controller includes：
MPPT maximum power point tracking unit, for carrying out MPPT maximum power point tracking；
Judging unit, for obtaining network voltage, and according to the variation of network voltage judge low-voltage crossing whether occur or
Restore；
Processing unit is connect respectively with MPPT maximum power point tracking unit and judging unit, for judging in judging unit
MPPT maximum power point tracking unit is controlled to stop MPPT maximum power point tracking when occurring to low-voltage crossing, low pressure is determined in judging unit
When passing through recovery, the busbar voltage of inverter module is restored to the first voltage value by control MPPT maximum power point tracking unit；
The judging unit judges whether low-voltage crossing occurs or restore according to the variation of network voltage, specially：
Judging unit obtains the three-phase positive sequence voltage of power grid and three-phase negative/positive voltage, and three-phase positive sequence voltage is carried out square
Two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage are obtained to rotation transformation, negative direction rotation is carried out to three-phase negative/positive voltage
Obtain two-phase the DC voltage Ud- and Uq- of three-phase negative/positive voltage；
Judging unit calculatesValue, and by it compared with setting value,
If less than setting value, then it is judged as low-voltage crossing, if greater than setting value, is then judged as that low-voltage crossing restores, it is described
Setting value is pre-set.
The application provide photovoltaic DC-to-AC converter and its low voltage ride through control method by determine low-voltage crossing restore after,
The busbar voltage of photovoltaic DC-to-AC converter is quickly recovered into the first voltage value, can quick-recovery photovoltaic DC-to-AC converter soon output work
Rate shortens the time of low-voltage crossing, can meet requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing, avoids busbar electric
Pressure is pulled low rear photovoltaic DC-to-AC converter and carries out self-protection.
Description of the drawings
Fig. 1 is the structure diagram of photovoltaic DC-to-AC converter in the embodiment of the present application；
Fig. 2 is the module diagram of photovoltaic DC-to-AC converter in the embodiment of the present application；
Fig. 3 is the low voltage ride through control method flow chart of photovoltaic DC-to-AC converter in the embodiment of the present application.
Specific embodiment
The application is described in further detail below by specific embodiment combination attached drawing.
Embodiment one：
Please refer to Fig.1, present embodiments provide a kind of photovoltaic DC-to-AC converter, including master controller 101, power controller 102,
Inverter module 103 and CAN (Controller Area Network, controller local area network) communication bus 104.
Inverter module 103 is used to the DC bus-bar voltage that photovoltaic panel exports being converted to alternating voltage.Power controller
102 connect with inverter module 103, for monitoring and/or controlling the busbar voltage of inverter module 103, realize photovoltaic DC-to-AC converter
Grid-connected hair wave, current control, busbar voltage balance and control.
Master controller 101 is connect with power grid incoming end, and is passed through CAN communication bus 104 and connect with power controller 102.
It please refers to Fig.2, master controller 101 includes MPPT maximum power point tracking unit 1011, judging unit 1012 and processing unit 1013.Always
Controller 101 is connect with power grid incoming end, and is passed through CAN communication bus 104 and connect with power controller 102, specifically, judging
Unit 1012 is connect with power grid incoming end, and MPPT maximum power point tracking unit 1011 and judging unit 1012 pass through CAN communication bus
104 connect with power controller 102.
MPPT maximum power point tracking unit 1011 is used to carry out MPPT maximum power point tracking.MPPT maximum power point tracking (MPPT,
Maximum Power Point Tracking) refer to the hair of MPPT maximum power point tracking circuit detecting real-time photovoltaic panel
Piezoelectric voltage, and ceiling voltage current value (VI) is tracked, it is applied in solar energy photovoltaic system, for coordinating solar cell
Plate, accumulator, the work loaded, make photovoltaic DC-to-AC converter Maximum Power Output.The pre- fixed step size of MPPT maximum power point tracking generally use
Adjust busbar voltage or electric current and the method for gradually approaching peak power output.When carrying out MPPT maximum power point tracking, to busbar
Voltage is disturbed to some direction, by the way that the output power of the present output power detected and previous moment is compared,
If present output power is larger, busbar voltage is continued to disturb to the same direction, it is right if present output power is smaller
Busbar voltage disturbs round about, so that it is determined that maximum power point.
Judging unit 1012 is used to obtain network voltage, and judge whether low-voltage crossing occurs according to the variation of network voltage
Or restore.Processing unit 1013 is connect respectively with MPPT maximum power point tracking unit 1011 and judging unit 1012, for judging
Unit 1012 determines control MPPT maximum power point tracking unit 1011 when low-voltage crossing occurs and stops MPPT maximum power point tracking, is sentencing
When disconnected unit 1012 determines low-voltage crossing recovery, MPPT maximum power point tracking unit 1011 is controlled by the busbar of inverter module 103
Voltage is restored to the first voltage value, and the first voltage value preset value or the first voltage value are the low pressure that processing unit 1013 backs up
The average value of the first two more than maximum power point voltage value occurs for the maximum power point voltage value or low-voltage crossing passed through before occurring.
In the present embodiment, judging unit 1012 judges whether low-voltage crossing occurs or restore according to the variation of network voltage,
Specially：
Judging unit 1012 obtains the three-phase positive sequence voltage of power grid and three-phase negative/positive voltage, and three-phase positive sequence voltage is carried out
Positive direction rotation transformation obtains two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage, and negative direction is carried out to three-phase negative/positive voltage
Rotation obtains two-phase the DC voltage Ud- and Uq- of three-phase negative/positive voltage.
Judging unit 1012 carries out positive direction rotation transformation to three-phase positive sequence voltage can be according to formula：
Ud+=Ua+*cos (theta)+Ub+*cos (theta-120)+Uc+*cos (theta+120) and
Uq+=Ua+*sin (theta)+Ub+*sin (theta-120)+Uc+*sin (theta+120) is carried out.
Ua+, Ub+, Uc+ are three-phase positive sequence voltage, and theta is the angle of power grid A phases, and Ud+ represents power grid positive sequence voltage
The mould of vector, Uq+ represent power grid positive sequence voltage rotating vector and the difference of A phase angles, and three-phase positive sequence voltage is converted by this
The DC quantity of two-phase stabilization is converted to after formula.
Judging unit 1012 carries out negative direction rotation transformation to three-phase negative/positive voltage can be according to formula：
Ud-=Ua-*cos (theta)+Ub-*cos (theta+120)+Uc-*cos (theta-120) and
Uq-=Ua-*sin (theta)+Ub-*sin (theta+120)+Uc-*sin (theta-120) is carried out.
Ua-, Ub-, Uc- are three-phase negative/positive voltage, and theta is the angle of power grid A phases, and Ud- represents electrical network negative phase-sequence voltage
The mould of vector, Uq- represent electrical network negative phase-sequence voltage rotating vector and the difference of A phase angles, and three-phase negative/positive voltage is converted by this
The DC quantity of two-phase stabilization is converted to after formula.
When power grid is normal, Uq+, Ud-, Uq- are the mould that zero, Ud+ is power grid three-phase voltage resultant vector, in three-phase
After exception occurs in network voltage, Uq+, Ud-, Uq- will be not zero, thus judging unit 1012 by judge Ud+, Uq+, Ud-,
The situation of change of Uq- may determine that the abnormal conditions of power grid, that is, judge whether low-voltage crossing occurs or restore.
Later, judging unit 1012 is first filtered Ud+, Uq+, Ud-, Uq-, then acquires formulaValue, judged according to obtained absolute value with preset value
Whether power grid there is exception, that is, judges whether low-voltage crossing occurs or restore, if its value is less than preset value, sentences
Break and occur for low-voltage crossing, if greater than preset value, be then judged as that low-voltage crossing restores.
Generally, it can also judge whether low-voltage crossing occurs or restore by the virtual value of network voltage, specially：
The virtual value of the network voltage in each period is calculated, which is compared with setting value, if less than setting value,
Then illustrate that exception occurs in power grid, that is, be judged as low-voltage crossing.However, the method judge low-voltage crossing whether occur or
Recovery needs the time of a cycle, takes longer.In the present embodiment, judging unit 1012 by the positive and negative sequence voltage of three-phase come
Judge whether power grid exception occurs, it is only necessary to which 1/4 period can be completed, with the shorter response time, in addition, also having
Higher sensitivity.
In the present embodiment, processing unit 1013 determines when low-voltage crossing occurs in judging unit 1012 and controls maximum power
After point tracking cell 1011 stops MPPT maximum power point tracking, processing unit 1013 also controls power controller 102 to reduce inversion mould
The given value of current that block 103 exports to improve busbar voltage, avoids being unlikely in power system restoration drawing DC bus-bar voltage dead.
Processing unit 1013 controls MPPT maximum power point tracking unit 1011 that the busbar voltage of inverter module 103 is restored to the first voltage value
Afterwards, processing unit 1013 also controls MPPT maximum power point tracking unit 1011 to open MPPT maximum power point tracking.
Processing unit 1013 controls MPPT maximum power point tracking unit 1011 that the busbar voltage of inverter module 103 is restored to the
During one voltage value, PI (proportional integration) coefficient can be improved, specifically, PI coefficients can be increased to a preset value, to improve light
Lie prostrate power resume speed of the inverter in low-voltage crossing.Later, in order to ensure 1011 maximum work of MPPT maximum power point tracking unit
The accuracy of rate point tracking after the busbar voltage of inverter module 103 is restored to the first voltage value, PI coefficient adjustments is returned normal
Value.
In order to illustrate the communication of master controller 101 and power controller 102, in the present embodiment, master controller 101 can be with
The communication unit to communicate including being used for master controller 101 with power controller 102.Master controller 101 passes through CAN by communication unit
Communication bus 104 receives the processing signal of its return to 102 broadcast current set-point of power controller, is returned when detecting
Processing signal it is incorrect or when being not received by the processing signal of return, then send out stopping signal.In the present embodiment, communication
Unit is communicated by the CAN communication bus of two-way independence with power controller 102, can be in certain failure that communicates all the way
When, it is contacted by another way with power controller 102.Wherein CAN communication bus is mainly used for current signal all the way
Given, emergency cutoff order has faster response speed.Another way CAN communication bus is used for transmission power controller 102
Status information.
It should be appreciated that in the present embodiment, master controller 101 can be used for controlling one or more power controller and inversion mould
Block.
In power grid after abnormal restoring, if making the output work of photovoltaic DC-to-AC converter by normal MPPT maximum power point tracking
Rate is restored, and resume speed is slower, is extremely difficult to requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing.The present embodiment provides
Photovoltaic DC-to-AC converter can judge the generation and recovery of low-voltage crossing within the shorter time, first by busbar after power system restoration
Voltage is quickly adjusted to the first voltage value, is carried out MPPT maximum power point tracking again later, is shortened the time of low-voltage crossing, Neng Goufu
Requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing is closed, busbar voltage is avoided to be pulled low rear photovoltaic DC-to-AC converter and carries out self guarantor
Shield.
Embodiment two：
It please refers to Fig.3, present embodiments provides a kind of low voltage ride through control method of photovoltaic DC-to-AC converter, including：
Step 201：Judge whether low-voltage crossing occurs, if do not occurred, go to step 202, if it happens, then turn
To step 203.In general, the generation of low-voltage crossing represents that power grid is abnormal, it therefore, can be by judging the effective of network voltage
Value judges whether low-voltage crossing occurs, specially：Calculate the virtual value of the network voltage in each period, by the virtual value with
Setting value is compared, and if less than setting value, is then illustrated that exception occurs in power grid, that is, is judged as low-voltage crossing, together
Sample may determine that whether low-voltage crossing restores using the above method.However, the method judges whether low-voltage crossing needs
The time of a cycle takes longer.
Preferably, the present embodiment judges whether low-voltage crossing occurs or restore by following method.
The three-phase positive sequence voltage of power grid and three-phase negative/positive voltage are obtained, and positive direction rotation is carried out to three-phase positive sequence voltage and is become
Get two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage in return, carrying out negative direction to three-phase negative/positive voltage rotates to obtain three-phase
Two-phase the DC voltage Ud- and Uq- of negative sequence voltage.
Carrying out positive direction rotation transformation to three-phase positive sequence voltage can be according to formula：
Ud+=Ua+*cos (theta)+Ub+*cos (theta-120)+Uc+*cos (theta+120) and
Uq+=Ua+*sin (theta)+Ub+*sin (theta-120)+Uc+*sin (theta+120) is carried out.
Ua+, Ub+, Uc+ are three-phase positive sequence voltage, and theta is the angle of power grid A phases, and Ud+ represents power grid positive sequence voltage
The mould of vector, Uq+ represent power grid positive sequence voltage rotating vector and the difference of A phase angles, and three-phase positive sequence voltage is converted by this
The DC quantity of two-phase stabilization is converted to after formula.
Carrying out negative direction rotation transformation to three-phase negative/positive voltage can be according to formula：
Ud-=Ua-*cos (theta)+Ub-*cos (theta+120)+Uc-*cos (theta-120) and
Uq-=Ua-*sin (theta)+Ub-*sin (theta+120)+Uc-*sin (theta-120) is carried out.
Ua-, Ub-, Uc- are three-phase negative/positive voltage, and theta is the angle of power grid A phases, and Ud- represents electrical network negative phase-sequence voltage
The mould of vector, Uq- represent electrical network negative phase-sequence voltage rotating vector and the difference of A phase angles, and three-phase negative/positive voltage is converted by this
The DC quantity of two-phase stabilization is converted to after formula.
When power grid is normal, Uq+, Ud-, Uq- are the mould that zero, Ud+ is power grid three-phase voltage resultant vector, in three-phase
After exception occurs in network voltage, Uq+, Ud-, Uq- will not all be zero, so the variation feelings by judging Ud+, Uq+, Ud-, Uq-
Condition may determine that the abnormal conditions of power grid.
In the present embodiment, first Ud+, Uq+, Ud-, Uq- are filtered, then acquire formulaValue, judged according to obtained absolute value with preset value
Whether power grid there is exception, that is, judges whether low-voltage crossing occurs, if its value is less than preset value, is judged as low
It presses to wear and more occurs, if greater than preset value, be then judged as that low-voltage crossing restores.
The judgment method that low-voltage crossing provided in this embodiment occurs or restores no longer needs a complete period, only needs
1/4 period is wanted, with the shorter response time, in addition, also having higher sensitivity.
Step 202：The maximum power point voltage value for backing up in realtime current when power grid is normal or current maximum power point
Voltage value and the average value of multiple maximum power point voltage values closed on before.The value of the backup is supplied to as the first voltage value
Step 206 uses.It should be appreciated that the first voltage value can also be by the pre-set preset value of user.
Step 203：It is judged as low-voltage crossing in step 201, then stops MPPT maximum power point tracking.
Step 204：After stopping MPPT maximum power point tracking, photovoltaic DC-to-AC converter actively reduces given value of current, to improve busbar electricity
Pressure avoids being unlikely in power system restoration drawing DC bus-bar voltage dead.
Step 205：Whether real-time judge low-voltage crossing restores, if restored, continues to step 206.
Step 206：Busbar voltage is restored to the first voltage value, i.e., the voltage value that step 202 backs up by photovoltaic DC-to-AC converter.This
In embodiment, photovoltaic DC-to-AC converter can first improve PI (proportional integration) coefficient, to improve photovoltaic inversion when restoring the first voltage value
Power resume speed of the device in low-voltage crossing.Later, in order to ensure the accuracy of photovoltaic DC-to-AC converter MPPT maximum power point tracking,
After the busbar voltage of photovoltaic DC-to-AC converter is restored to the first voltage value, PI coefficient adjustments are returned into normal value.
Step 207：Judge whether the busbar voltage of photovoltaic DC-to-AC converter is restored to the first voltage value, if it is, going to step
Rapid 208.
Step 208：After the busbar voltage of photovoltaic DC-to-AC converter is restored to the first voltage value, reopen maximum power point with
Track, to obtain the maximum power point of photovoltaic DC-to-AC converter reality.
In power grid after abnormal restoring, if making the output work of photovoltaic DC-to-AC converter by normal MPPT maximum power point tracking
Rate is restored, and resume speed is slower, is extremely difficult to requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing.The present embodiment provides
Photovoltaic DC-to-AC converter low voltage ride through control method, can judge the generation and recovery of low-voltage crossing within the shorter time,
Busbar voltage is quickly first adjusted into the first voltage value after power system restoration, MPPT maximum power point tracking is carried out again later, shortens
The time of low-voltage crossing can meet requirement of the national standard to photovoltaic DC-to-AC converter low-voltage crossing, busbar voltage is avoided to be pulled low
Photovoltaic DC-to-AC converter carries out self-protection afterwards.
It will be understood by those skilled in the art that all or part of step of various methods can pass through in the above embodiment
Program instructs related hardware to complete, which can be stored in a computer readable storage medium, storage medium can wrap
It includes：Read-only memory, random access memory, disk or CD etc..
The foregoing is a further detailed description of the present application in conjunction with specific implementation manners, it is impossible to assert this Shen
Specific implementation please is confined to these explanations.For those of ordinary skill in the art to which this application belongs, it is not taking off
Under the premise of conceiving from the application, several simple deduction or replace can also be made.
Claims (7)
1. a kind of low voltage ride through control method of photovoltaic DC-to-AC converter, which is characterized in that including：
Judge whether low-voltage crossing occurs according to the variation of network voltage, if it is, stopping MPPT maximum power point tracking；
Judge whether low-voltage crossing restores, if it is, the busbar voltage of photovoltaic DC-to-AC converter is restored to the first voltage value, it is described
The first voltage value is the maximum power point voltage value or low pressure before preset value or the first voltage value occur for low-voltage crossing
Pass through the average value that the first two more than maximum power point voltage value occurs；
The variation according to network voltage judges whether low-voltage crossing occurs or restore, specially：
The three-phase positive sequence voltage of power grid and three-phase negative/positive voltage are obtained, and positive direction rotation transformation is carried out to three-phase positive sequence voltage and is obtained
To two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage, negative direction is carried out to three-phase negative/positive voltage and rotates to obtain three-phase negative/positive
Two-phase the DC voltage Ud- and Uq- of voltage；
It calculatesValue, and by it compared with setting value, if less than setting
Value, then be judged as low-voltage crossing, if greater than setting value, is then judged as that low-voltage crossing restores, the setting value is set in advance
It puts.
2. the method as described in claim 1, which is characterized in that determining low-voltage crossing, stop maximum power point with
After track, further include：Reduce the given value of current of photovoltaic DC-to-AC converter output.
3. method as claimed in claim 2, which is characterized in that be restored to the first voltage value in the busbar voltage of photovoltaic DC-to-AC converter
Afterwards, unlatching MPPT maximum power point tracking is further included.
4. a kind of photovoltaic DC-to-AC converter, which is characterized in that including：
Inverter module, for the busbar voltage that photovoltaic panel exports to be converted to alternating voltage；
Power controller is connect with inverter module, for monitoring and/or controlling the busbar voltage of inverter module；
Master controller is connect respectively with power controller and power grid incoming end, described total for carrying out MPPT maximum power point tracking
Controller is additionally operable to obtain network voltage, and judge whether low-voltage crossing occurs or restore according to the variation of network voltage, works as institute
State master controller determine low-voltage crossing occur when then stop MPPT maximum power point tracking, when determine low-voltage crossing restore when then will
The busbar voltage of inverter module is restored to the first voltage value, and the first voltage value is preset value or the first voltage value
The first two more than maximum power point voltage occurs for the maximum power point voltage value or low-voltage crossing backed up before occurring for low-voltage crossing
The average value of value；
The master controller includes：
MPPT maximum power point tracking unit, for carrying out MPPT maximum power point tracking；
Judging unit for obtaining network voltage, and judges whether low-voltage crossing occurs or restore according to the variation of network voltage；
Processing unit is connect respectively with MPPT maximum power point tracking unit and judging unit, low for being determined in judging unit
It presses to wear and the stopping MPPT maximum power point tracking of time control MPPT maximum power point tracking unit more occurs, low-voltage crossing is determined in judging unit
During recovery, the busbar voltage of inverter module is restored to the first voltage value by control MPPT maximum power point tracking unit；
The judging unit judges whether low-voltage crossing occurs or restore according to the variation of network voltage, specially：
Judging unit obtains the three-phase positive sequence voltage of power grid and three-phase negative/positive voltage, and carries out positive direction rotation to three-phase positive sequence voltage
Two-phase the DC voltage Ud+ and Uq+ of three-phase positive sequence voltage are got in transformation in return, and carrying out negative direction to three-phase negative/positive voltage rotates to obtain
Two-phase the DC voltage Ud- and Uq- of three-phase negative/positive voltage；
Judging unit calculatesValue, and by it compared with setting value, if
Less than setting value, then it is judged as low-voltage crossing, if greater than setting value, is then judged as that low-voltage crossing restores, the setting
Value is pre-set.
5. photovoltaic DC-to-AC converter as claimed in claim 4, which is characterized in that the processing unit determines low pressure in judging unit
When passing through recovery, the busbar voltage of inverter module is restored to the first voltage value by control MPPT maximum power point tracking unit, specially：
The processing unit control MPPT maximum power point tracking unit improves PI coefficients to preset value, controls MPPT maximum power point tracking list later
The busbar voltage of inverter module is restored to the first voltage value by member；MPPT maximum power point tracking unit is by the busbar voltage of inverter module
After being restored to the first voltage value, processing unit controls MPPT maximum power point tracking unit that PI coefficient adjustments are returned normal value.
6. photovoltaic DC-to-AC converter as described in claim 4 or 5, which is characterized in that the processing unit is determined in judging unit
After control MPPT maximum power point tracking unit stops MPPT maximum power point tracking when low-voltage crossing occurs, further include：Processing unit controls
Power controller reduces the given value of current of inverter module output.
7. photovoltaic DC-to-AC converter as claimed in claim 6, which is characterized in that the processing unit controls MPPT maximum power point tracking list
After the busbar voltage of inverter module is restored to the first voltage value by member, further include：Processing unit controls MPPT maximum power point tracking list
Member opens MPPT maximum power point tracking.
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| JP2007239599A (en) * | 2006-03-08 | 2007-09-20 | Mitsubishi Heavy Ind Ltd | Wind power generation system and method of supplying emergency power for wind power generation system |
| CN101841188A (en) * | 2010-02-08 | 2010-09-22 | 哈尔滨工业大学 | Hybrid power supply uninterruptible inverted power supply of power feedback type optical network |
| CN201805236U (en) * | 2010-05-17 | 2011-04-20 | 东南大学 | Series type LVRT (low voltage ride through) control device of wind generating set |
| CN102088191A (en) * | 2010-12-22 | 2011-06-08 | 阳光电源股份有限公司 | Method and system for cooperatively controlling low voltage ride through of full-power fan converter |
| CN102664427A (en) * | 2012-05-25 | 2012-09-12 | 华北电力大学（保定） | Active and reactive coordination control method for permanent-magnet direct-driven wind turbines in low-voltage ride-through process |
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| JP2007239599A (en) * | 2006-03-08 | 2007-09-20 | Mitsubishi Heavy Ind Ltd | Wind power generation system and method of supplying emergency power for wind power generation system |
| CN101841188A (en) * | 2010-02-08 | 2010-09-22 | 哈尔滨工业大学 | Hybrid power supply uninterruptible inverted power supply of power feedback type optical network |
| CN201805236U (en) * | 2010-05-17 | 2011-04-20 | 东南大学 | Series type LVRT (low voltage ride through) control device of wind generating set |
| CN102088191A (en) * | 2010-12-22 | 2011-06-08 | 阳光电源股份有限公司 | Method and system for cooperatively controlling low voltage ride through of full-power fan converter |
| CN102664427A (en) * | 2012-05-25 | 2012-09-12 | 华北电力大学（保定） | Active and reactive coordination control method for permanent-magnet direct-driven wind turbines in low-voltage ride-through process |
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