CN106026163B - A kind of low voltage traversing control method and system based on MMC photovoltaic combining inverter - Google Patents
A kind of low voltage traversing control method and system based on MMC photovoltaic combining inverter Download PDFInfo
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Abstract
The present invention provides the low voltage traversing control method and system of a kind of photovoltaic combining inverter based on MMC, on the two close cycles vector controlled basis of traditional current inner loop outer voltage, when detecting grid entry point Voltage Drop, referenced reactive current value is redistributed by judging Voltage Drop degreeRealize reactive current injection；And MMC submodule capacitor voltage fluctuation range is adjusted by optimization bridge arm current；New active current command value is re-introduced into limit watt current；Limitation watt current guarantees the operation of photovoltaic safety grid-connection to realize low voltage crossing.This method and system pass through optimization bridge arm loop current suppression voltage fluctuation of capacitor, increase output reactive power, pass through control submodule reference voltage, optimize submodule capacitor voltage fluctuation range, with this, solve the problems, such as that MMC submodule capacitor voltage fluctuates out-of-limit when idle injection, smoothly realizes low voltage crossing.
Description
Technical field
The present invention relates to field of power electronics more particularly to a kind of low voltage crossings of the photovoltaic grid-connected inversion based on MMC
Control field.
Background technique
While with mankind's socio-economic development, the energy is also increasingly asked by necessary for human.However, being on the one hand continuous
The energy demand of rapid growth, on the other hand with the continuous exploitation of limited fossil energy, reserves are constantly reduced and increasingly withered
It exhausts.The energy demand of rapid growth and limited fossil resource ask the dependence of conventional fossil resource and the environment being on the rise
Topic, it would be highly desirable to solve.To realize Sustainable Socioeconomic Development, the mankind to the exploitations of the renewable new energies such as solar energy, wind energy and
Using becoming inevitable choice.Solar energy work is a kind of clean reproducible energy, the attention by various countries.
With quickling increase for photovoltaic power generation specific gravity, photovoltaic electric station grid connection also can bring safety and stability to Operation of Electric Systems
The problem of, especially when system grid connection point, which breaks down, leads to Voltage Drop, low electricity is brought to photovoltaic electric station grid connection
Press crossing problem.This low voltage crossing problem faced now has become the difficult point in new-energy grid-connected technology and grinds
Study carefully hot spot.
Currently, existing domestic and foreign literature is the low voltage crossing technology to the photovoltaic grid-connected inversion based on traditional VSC mostly
It is studied, the patent of a Publication No. CN104734191 discloses a kind of based on the grid-connected inverse of reactive current injection
Become device low-voltage ride-through method, and the low-voltage ride-through method of the photovoltaic DC-to-AC converter based on traditional VSC is studied.
MMC (modular multilevel inverter) has more advantages relative to traditional VSC (voltage source inverter), but because of MMC (mould
Block multilevel converter) submodule capacitor voltage fluctuation influenced by reactive power size.One is reached when MMC issues reactive power
When definite value, submodule capacitor voltage fluctuation can exceed that specified value, so that limiting MMC issues reactive power size.Therefore, exist
When in MMC photovoltaic inverting system using the low voltage traversing control method of reactive power injection, need first to overcome MMC submodule electric
Reactive power ability is issued to improve MMC inverter, stablizes, pacify to realize the problem of holding voltage fluctuation, preventing device failure
Full low voltage crossing.
Summary of the invention
To solve the problems, such as that MMC submodule capacitor voltage fluctuates, the invention proposes a kind of improved low voltage crossing controls
Method processed and corresponding system guarantee the operation of photovoltaic safety grid-connection to realize the photovoltaic inversion low voltage crossing based on MMC.Tool
Body is as follows:
A kind of low voltage traversing control method of the photovoltaic combining inverter based on MMC, in current inner loop outer voltage
On two close cycles vector controlled basis, when detecting grid entry point Voltage Drop, divided again by judging Voltage Drop degree
With referenced reactive current valueRealize reactive current injection；And MMC submodule capacitor voltage is adjusted by optimization bridge arm current
Fluctuation range；New active current command value is re-introduced into limit watt current；Limitation watt current is to realize that low-voltage is worn
More, guarantee the operation of photovoltaic safety grid-connection.
Further, this method is realized again by adding idle outer ring, 1 three parts of computing module 1 and control logic
Distribute reactive current value instruction valueWherein, idle outer ring is used for when photovoltaic inverting system operates normally；Control logic 1 is used
In judging whether power grid falls, judge that system is to be in failure in normal operating condition by Voltage Drop degree
In the case of subnormal voltage operation state, and switch the corresponding method of operation；Computing module 1 is used for according to grid voltage sags journey
Degree calculates again and distributes new referenced reactive current valueThe corresponding method of operation is, if photovoltaic grid-connected inverting system is just
Often when operation, idle outer ring reactive command value is takenAs output, run with unity power factor；If grid-connected voltage
When falling, it is latched idle outer ring, computing module 1 calculates reactive current value instruction valueMake inverter by injecting reactive current
Reactive power is issued, dynamic reactive enabling capabilities are realized, to realize the low voltage crossing of photovoltaic parallel in system.
The per unit value U of grid-connected voltage is judged by control logic 1TLocating range, to referenced reactive current valueIt is redistributed, distribution method is as follows
In formula, UTIndicate the per unit value of grid-connected voltage, INIndicate the rated current of inverter.
In the case where keeping constant transimission power, submodule capacitance and constant DC voltage, MMC submodule capacitor
Voltage fluctuation is mainly by system power factorIt influences, system power factor issues reactive power with inverter and is inversely proportional.?
During photovoltaic inversion low voltage crossing, reduced by the power factor that reactive current injects after reactive power the system that will lead to, MMC
Submodule capacitor voltage undulate quantity is very big, more than the maximum value of regulation fluctuation, causes to damage device.
Further, two frequency multiplication capacitance voltages are reduced or eliminated by optimization bridge arm circulation to increase MMC inverter hair
Reactive power ability out, and guarantee MMC submodule capacitor voltage undulate quantity within allowed band, it is specific:
In power grid, there are A, B, C three-phase can similarly obtain B, C phase using A phase as representing；Former MMC bridge arm current IcaSize are as follows:
In formula, IdcFor DC side electric current, I2fFor secondary circulation amplitude.
By bridge arm current IcaBy obtaining new bridge arm circulation after formula optimizationOptimize formula are as follows:
In formula, IdcFor DC side electric current, K is voltage modulated coefficient, ImTo export Fundamental-frequency Current amplitude；And after obtaining optimization
MMC submodule capacitor voltage:
In formula,For submodule capacitor voltage in MMC inverter,For lower submodule capacitor voltage, UdcFor DC side
Voltage, PdcFor DC side power, K is voltage modulated coefficient.
In addition, submodule capacitor voltage undulate quantity has following formula in the grid-connected inverting system based on MMC:
In formula, capacitor C；Upper bridge arm voltage fluctuation of capacitor amount is Δ usmc_pa；Upper bridge arm active power is Ppa；
Submodule capacitor voltage is by capacitor reference voltage UcrefWith undulate quantity Δ usmcComposition, by introducing submodule capacitor
Reference voltage UcrefRegulation coefficient λ carrys out adjusting submodule capacitor reference voltage Ucref, further control MMC submodule capacitor voltage
Fluctuation range, the relational expression after introducing are as follows:
λUcref+Δusmc≤umax
In formula, λ is reference voltage regulation coefficient, and value range is 0.9~1.1, umaxFor the capacitance voltage upper limit.Therefore preceding
It states in summary of the invention, adjustment MMC submodule can also be controlled by further controlling MMC submodule capacitor voltage fluctuation range
Voltage fluctuation of capacitor range.
Further, the present invention also passes through addition computing module 2 and control logic 2, limits watt current；Wherein, mould is calculated
Block 2 is used to calculate again new active current command valueControl logic 2 is used to newer active current command valueWith
With outer voltage active current command valueSize, and switch the corresponding method of operation, that is, computing module 2 calculates again new
Active current command valueAfterwards, if control logic 2 judgesIt is less thanThe watt current of outer voltage is taken to instruct
And it is latchedWatt current instruction according toOutput；If control logic 2 judgesIt is more than or equal toWhen, pass through logic control
Molding block judgement after switchover operation mode, watt current instruction according toOutput, blocking voltage outer ring, to realize photovoltaic simultaneously
The low voltage crossing of net system.
When the grid-connected voltage of photovoltaic parallel in system is fallen, it is specified that grid entry point electric current i is no more than rated current IN
1.5 times, calculate new watt current value instruction valueFormula is as follows:
Wherein, idIndicate watt current, iqIndicate reactive current, INIndicate rated current.
On this basis, the invention also provides the photovoltaic combining inverter low voltage ride through control system based on MMC, should
System includes photovoltaic array PV, Boost chopper circuit, MMC inverter；Wherein, photovoltaic array PV uses perturbation observation method, realizes
Maximum power output；Boost chopper circuit is for boosting photovoltaic output voltage；MMC inverter is used for DC inversion
At exchange；This system uses above-mentioned photovoltaic combining inverter low voltage traversing control method, realizes low voltage crossing control.
The utility model has the advantages that
1) by optimization bridge arm loop current suppression voltage fluctuation of capacitor, increase output reactive power, efficiently solving will be idle
The low-voltage ride-through method of injection is applied to MMC submodule capacitor voltage and fluctuates out-of-limit problem；
2) by control submodule reference voltage, optimize submodule capacitor voltage fluctuation range, keep MMC submodule capacitor electric
Pressure fluctuation range is further controlled, to further prevent the fluctuation of MMC submodule capacitor voltage out-of-limit；
3) optimize the two methods of bridge arm circulation and submodule reference voltage or combinations thereof method to reduce submodule capacitor
Voltage fluctuation, method is simple and effective, Yi Shixian, and does not need to increase additional outer power equipment, at low cost；
4) by adding new active current command valueTo redistribute active current command value to limit idle injection
When watt current, guarantee system operational safety；
5) it on the basis of the two close cycles vector control system of traditional current inner loop outer voltage, is infused by reactive current
The method for entering, limiting watt current and adjusting MMC submodule capacitor voltage fluctuation range, without increasing additional outer power equipment
Device can be achieved with the low voltage crossing of the photovoltaic inverting system based on MMC, guarantee the operation of photovoltaic safety grid-connection.
Detailed description of the invention
The low voltage ride through system block diagram of photovoltaic combining inverter of the Fig. 1 based on MMC
Low-voltage control module block diagram in low voltage ride through system of the Fig. 2 based on the photovoltaic combining inverter of MMC
The flow chart of the low-voltage ride-through method of photovoltaic combining inverter of the Fig. 3 based on MMC
Grid-connected voltage analogous diagram of the Fig. 4-1 based on MMC
Fig. 4-2 uses the output current simulations figure of the MMC inverter of low voltage traversing control method of the invention
Fig. 4-3 reactive current actual value and instruction value analogous diagram
The reactive power analogous diagram that Fig. 4-4 is exported based on the photovoltaic combining inverter of MMC
Fig. 4-5 is not optimised submodule capacitor voltage analogous diagram
Submodule capacitor voltage fluctuates analogous diagram after Fig. 4-6 optimization
Embodiment
This hair provides the low voltage traversing control method and system of a kind of photovoltaic combining inverter, in traditional current inner loop
On the two close cycles vector controlled basis of outer voltage, when detecting grid entry point Voltage Drop, pass through reactive current injection, control
The mode that system module capacitance scope range of the fluctuation of voltage and limitation watt current combine, realizes low voltage crossing, guarantees photovoltaic safety
It is incorporated into the power networks.Specific embodiment is as follows:
When detecting grid entry point Voltage Drop, by redistributing referenced reactive current valueTo realize reactive current
Injection；By adding new active current command valueTo redistribute watt current value instruction value to limit watt current；And
MMC submodule capacitor voltage fluctuation range is adjusted by optimization bridge arm current and/or control submodule reference voltage method；To
It realizes low voltage crossing, guarantees the operation of photovoltaic safety grid-connection.
On the basis of original current inner loop outer voltage, by adding idle outer ring, computing module 1 and control logic 1
Three parts, which are realized, redistributes reactive current value instruction valueWherein, idle outer ring in photovoltaic inverting system for normally transporting
When row；Control logic 1 judges that system is in normal operation for judging whether power grid falls, by Voltage Drop degree
State is in the subnormal voltage operation state under fault condition, and switches the corresponding method of operation；Computing module 1 is used for basis
Grid voltage sags degree calculates again and distributes new referenced reactive current value
When power grid operates normally, idle outer ring reactive command value is takenAs output, reactive power command value at this time
QrefIt is set as 0, to realize that MMC inverter unity power factor is run；When power grid falls, redistribute new idle
Current instruction valueReactive current injection is realized, for making MMC inverter issue corresponding reactive power；1 part of control logic
It is mainly used to judge whether power grid falls, and the corresponding method of operation is switched to according to judgement.
Such as Fig. 2, carrying out practically mode are as follows: when the photovoltaic grid-connected inverting system of MMC operates normally, pass through Logic control module
Switch 1 is connected with switch 2 after judgement, takes idle outer ring reactive command valueAs output, existing MMC inverter unit power because
Number operation.When grid-connected Voltage Drop, switchover operation mode after being judged by logic control 1, switch 1 is connected with switch 3,
It is latched idle outer ring, and according to new referenced reactive current valueMMC is set to issue reactive power by injecting reactive current, it is real
Existing dynamic reactive enabling capabilities, to realize the low voltage crossing of photovoltaic parallel in system.
Power system technology provision discussion is accessed in view of photo-voltaic power generation station, grid-connected point electricity is judged by control logic 1
The per unit value U of pressureTLocating range, to referenced reactive current valueIt is redistributed, distribution method is as follows:
In formula, UTThat indicate is the per unit value of grid-connected voltage, INWhat is indicated is the rated current of MMC inverter.
Relative to traditional VSC, there are more advantages, but because the fluctuation of MMC submodule capacitor voltage is big vulnerable to reactive power
Small influence, when MMC, which issues reactive power, reaches certain value, submodule capacitor voltage fluctuation may be more than specified value, thus
It limits MMC and issues reactive power size.Therefore in Voltage Drop, when MMC issues reactive power, submodule capacitor electricity should be reduced
Pressure can generate fluctuation, and MMC is made to issue more reactive powers.For this purpose, the present invention provides two methods, i.e., optimization bridge arm current and
The method of control submodule reference voltage, or MMC submodule capacitor voltage fluctuation range is adjusted by a combination thereof, to guarantee nothing
The normal sending of function power, advanced optimizes on this basis, to ensure to export OPTIMAL REACTIVE POWER current instruction valueSpecifically such as
Under:
Embodiment 1 optimizes the method for bridge arm current:
In power grid, there are A, B, the respective formula and respective value of B, C phase similarly can be obtained using A phase as representing in C three-phase；
MMC submodule capacitor voltage size are as follows:
In formula, UcpaTo optimize submodule capacitor voltage in preceding A phase, UcnaTo optimize submodule capacitor voltage under preceding A phase, Udc
For DC voltage, PdcFor DC side power, K is voltage modulated coefficient,For power factor.
It is analyzed by above formula it is found that keeping the situation that transimission power is constant, submodule capacitance and DC voltage are constant
Under, submodule capacitor voltage fluctuates mainly by power factorIt influences, the smaller expression MMC of power factor issues reactive power and gets over
Greatly, then the fundamental frequency of submodule capacitor voltage and two frequency multiplication voltage fluctuation of capacitor are bigger.During photovoltaic inversion low voltage crossing,
MMC inverter needs to issue reactive power, and the power factor that will lead to system reduces, so that submodule capacitor voltage undulate quantity is very
Greatly, the maximum value that can exceed that regulation fluctuation causes to damage device, so must during the low voltage crossing of photovoltaic parallel in system
It must keep submodule capacitor voltage fluctuation within prescribed limit, meet the requirement for being less than submodule capacitor reference voltage 10%.
A phase original MMC bridge arm current IcaSize are as follows:
In formula, IdcFor DC side electric current, I2fFor secondary circulation amplitude.
By bridge arm circulation IcaIt is rounded definite value and obtains new bridge arm circulationAre as follows:
The corresponding submodule capacitor voltage being derived by after optimization:
It is analyzed by above formula it is found that by the bridge arm circulation after optimizationSo that being free of two frequency multiplication waves in submodule capacitor voltage
It is dynamic, and fundamental frequency fluctuation also corresponding reduction, although producing frequency tripling fluctuation, numerical value is at least below original capacitance voltage two
The 1/3 of double-frequency fluctuation amount.Therefore submodule capacitor voltage fluctuation can be effectively reduced after the optimization of bridge arm circulation.
Embodiment 2, the method for control submodule reference voltage:
When the submodule quantity of MMC reaches certain amount, there is following formula for submodule capacitor voltage undulate quantity:
In formula, bridge arm submodule number, U in N expressioncrefIndicate submodule reference voltage, C is capacitor, Δ usmc_paIn expression
Bridge arm voltage fluctuation of capacitor amount, PpaBridge arm active power in expression.
It is analyzed from above formula it is found that submodule reference voltage is U in one timing of upper bridge arm submodule number, capacitor and powercref
Change can shadow rise voltage fluctuation of capacitor, that is, submodule reference voltage UcrefBecome larger, then voltage fluctuation of capacitor Δ usmc_paReduce；
Submodule reference voltage UcrefBecome smaller, then voltage fluctuation of capacitor Δ usmc_paBecome larger.Submodule capacitor voltage is by capacitor reference voltage
UcrefWith undulate quantity Δ usmcComposition, i.e. Ucref+Δusmc.Therefore, control submodule capacitor reference voltage U can also be passed throughcrefTo control
Undulate quantity Δ u processedsmc, to guarantee submodule capacitor voltage in the reasonable scope.
For this purpose, the present invention controls capacitance voltage reference value size by introducing reference voltage regulation coefficient λ, obtain with public affairs
Formula:
λUcref+Δusmc≤umax
In formula, λ is reference voltage regulation coefficient；umaxFor the capacitance voltage upper limit；It by analysis and simulates, λ value is in 0.9-
Between 1.1.
Embodiment 3, the combination of two methods:
That is, optimization bridge arm current and control submodule reference voltage method are used in combination with, to control MMC submodule
Voltage fluctuation of capacitor range smoothly realizes low voltage crossing to guarantee the normal sending of reactive power.
Further, when the grid entry point voltage using MMC photovoltaic grid-connected inverting system is there is no falling, grid entry point electricity
Stream can be expressed with following formula:
In formula, idIndicate watt current, iqIndicate reactive current.
When grid entry point voltage falls, provide grid entry point electric current no more than rated current I according to the usage of tradeN's
1.5 again.Further, it is limited and is formed with function current value, the present invention is by addition computing module 2, for calculating new watt current
Instruction valueCalculation formula is as follows:
In formula, INIndicate rated current,For referenced reactive current value.
Equally, on the basis of original current inner loop outer voltage, then new computing module 2 and 2 liang of control logic are added
A part.Limit active current command valueIt can be by grid entry point current limit in 1.5 times of rated current INWithin, to guarantee light
Overhead utility is securely and reliably grid-connected；Control logic 2 is mainly used to compare active current command valueRefer to outer voltage watt current
Enable valueSize, to judge grid entry point electric current whether more than 1.5IN, thus switch to the corresponding method of operation.
Such as Fig. 2, carrying out practically mode are as follows: acquisition active current command valueAnd according to referenced reactive current valueMeter
New active current command valueIf control logic 2 compares new active current command valueWith the active electricity of outer voltage
Flow instruction valueSize, and switch the corresponding method of operation；That is, calculating watt current value instruction valueAfterwards, if new has
Function current instruction valueGreater than the active current command value of connection outer voltageSwitch 5 is connected with switch 4, takes voltage
The watt current of outer ring instructsAnd it is latchedWatt current instruction according toOutput；If control logic judgement is new to be had
Function current instruction valueLess than or equal to the active current command value of connection outer voltageWhen, switch 5 is connected with switch 6,
And new active current command valueAs output, blocking voltage outer ring, to realize grid entry point current limit in 1.5INWithin,
To realize the low voltage ride-through function of photovoltaic parallel in system.
In conclusion control bridge arm loop current suppression voltage fluctuation of capacitor, increases output reactive power, change submodule capacitor
Mainly for optimizing submodule capacitor voltage fluctuation range, both methods united application exports MMC more reference voltage
Reactive power have preferable effect.
In addition, the present invention also provides be directed to the corresponding photovoltaic grid-connected inversion low voltage crossing based on MMC of the above method
System, as shown in Figure 1, the system includes photovoltaic array PV, Boost chopper circuit, MMC inverter；Wherein, photovoltaic array PV is adopted
With perturbation observation method, maximum power output is realized；Boost chopper circuit is for boosting photovoltaic output voltage；The MMC change of current
Device is used for DC inversion into exchange；This system uses above-mentioned photovoltaic combining inverter low voltage traversing control method, realizes low
Voltage ride-through control.
According to method described in above-described embodiment 3, the low voltage crossing built in Matlab/Simulink simulation software
Control system, parameter such as the following table 1, emulation use MMC photovoltaic parallel in system such as Fig. 1,
| Photovoltaic array parameter name | Numerical value | MMC parameter name | Numerical value |
| Intensity of illumination | 25℃ | DC bus voltage rating | 800V |
| Temperature | 1000W/m3 | AC network voltage rating | 380V |
| Open-circuit voltage | 44.5V | MMC bridge arm submodule number | 4 |
| Short circuit current | 8.2A | The voltage rating of submodule | 200V |
| Maximum power point voltage | 35V | Carrier frequency | 3kHz |
| Maximum power point electric current | 7.86A | Submodule capacitance | 1mF |
| Photovoltaic array series connection number | 16 | Bridge arm inductance value | 5mH |
| Photovoltaic array parallel connection number | 114 | Connect reactance value | 2mH |
| Rated capacity | 50kW | Equivalent resistance | 0.01Ω |
Table 1 emulates major parameter
In 1.3s three phase short circuit fault, 1.925s failure vanishes, when the failure of system maintains occur for networked system grid entry point
Between be 0.625s, the fault resstance size of setting is 0.0013 Ω, and ground resistance size is 0.001 Ω, and three-phase voltage is down to volume
20% or so, the 1.925s three-phase voltage of constant voltage starts to restore.This system rated current is 80A.
By Fig. 4-1 and Fig. 4-2, grid entry point voltage, electric current restore normal, and photovoltaic plant realizes low voltage crossing.And by
For Fig. 4-2 it is found that grid entry point electric current is successfully limited in 1.5 times of rated current, i.e. 120A guarantees photovoltaic system safe operation.Figure
4-3 is that reactive current actual value and instruction value calculate reactive command value in grid voltage sags, wherein dotted line in Fig. 4-3
Referenced reactive current value is represented, solid line represents reactive current actual value, and as can be seen from the figure reactive current actual value can be quasi-
True trace command value, reactive current value become 80A from 0A during normal operation, successfully the injection of realization reactive current, and by
Fig. 4-4 is it is found that it is about 8.5kvar that MMC inverter, which issues reactive power,.It is analyzed by Fig. 4-5 it is found that issuing reactive power in MMC
Period, no optimization submodule capacitor voltage fluctuation range is about 22.5%, is far longer than the specified value of MMC inverter 10%, by
It is found that after using submodule capacitor voltage fluctuation after optimization, submodule fluctuation range is about 7.5%, meets MMC for Fig. 4-6 analysis
Inverter, which operates normally, to be required.
The above examples only illustrate the technical idea of the present invention, and this does not limit the scope of protection of the present invention, all
According to the technical idea provided by the invention, any changes made on the basis of the technical scheme each falls within the scope of the present invention
Within.
Claims (6)
1. a kind of low voltage traversing control method based on MMC photovoltaic combining inverter, it is characterised in that: in current inner loop voltage
On the two close cycles vector controlleds basis of outer ring, when detecting grid entry point Voltage Drop, by judge Voltage Drop degree come
Redistribute referenced reactive current valueTo realize that reactive current is injected, and MMC submodule is adjusted by optimization bridge arm current
Voltage fluctuation of capacitor range, and new active current command value is re-introduced into limit watt current；
By adding idle outer ring, 1 three parts of computing module 1 and control logic are realized and redistribute reactive current value instruction valueWherein, output setting when idle outer ring is operated normally for photovoltaic inverting system；Control logic 1 is for judging that power grid is
It is no to fall, judge that system is the low electricity being under fault condition in normal operating condition by Voltage Drop degree
Operating status is pressed, and switches the corresponding method of operation；Computing module 1 is used to be calculated again simultaneously according to grid voltage sags degree
Distribute new referenced reactive current valueThe corresponding method of operation is if photovoltaic grid-connected inverting system operates normally, to take nothing
Function outer ring reactive command valueAs output, run with unity power factor；If when grid-connected Voltage Drop, being latched nothing
Function outer ring, computing module 1 calculate reactive current value instruction valueInverter is set to issue reactive power by injecting reactive current,
Realize dynamic reactive support；
In the case where keeping constant transimission power, submodule capacitance and constant DC voltage, MMC submodule capacitor voltage
Fluctuation is mainly by system power factorIt influences, system power factor issues reactive power with inverter and is inversely proportional, in photovoltaic
During inversion low voltage crossing, reactive power is injected, the power factor that will lead to system reduces, MMC submodule capacitor voltage wave
Momentum is very big, more than the maximum value of regulation fluctuation, causes to damage device；Two frequencys multiplication are reduced or eliminated by optimization bridge arm circulation
Capacitance voltage issues reactive power ability to increase MMC inverter, and guarantees that MMC submodule capacitor voltage undulate quantity is allowing model
It is specific within enclosing:
In power grid, there are A, B, C three-phase can similarly obtain B, C phase using A phase as representing；Former MMC bridge arm current IcaSize are as follows:
In formula, IdcFor DC side electric current, I2fFor secondary circulation amplitude,
By bridge arm current IcaBy obtaining new bridge arm circulation after formula optimizationOptimize formula are as follows:
In formula, IdcFor DC side electric current, K is voltage modulated coefficient, ImTo export Fundamental-frequency Current amplitude；
And the MMC submodule capacitor voltage after being optimized:
In formula,For submodule capacitor voltage in MMC inverter,For lower submodule capacitor voltage, UdcFor DC voltage,
PdcFor DC side power, K is voltage modulated coefficient；
By addition computing module 2 and control logic 2, watt current is limited；Wherein, computing module 2 is used to calculate new active
Current instruction valueControl logic 2 is used to newer active current command valueIt is instructed with outer voltage watt current
ValueSize, and switch the corresponding method of operation；That is, calculating watt current value instruction valueAfterwards, if control logic 2 judgesIt is less thanBe latched computing module 2, active current command value according to outer voltage active current command valueOutput；If
Control logic 2 judgesIt is more than or equal toWhen, watt current is instructed according to new active current command valueOutput, locking
Outer voltage.
2. low voltage traversing control method according to claim 1, it is characterised in that: by judging grid-connected voltage
Per unit value UTLocating range, to referenced reactive current valueIt is redistributed, distribution method is as follows:
In formula, UTIndicate the per unit value of grid-connected voltage, INIndicate the rated current of inverter.
3. low voltage traversing control method according to claim 1, it is characterised in that: submodule capacitor voltage undulate quantity has
Following formula:
In formula, capacitor C；Upper bridge arm voltage fluctuation of capacitor amount is Δ usmc_pa；Upper bridge arm active power is Ppa；
Submodule capacitor voltage is by capacitor reference voltage UcrefWith undulate quantity Δ usmcComposition, by introducing submodule capacitor with reference to electricity
Press UcrefRegulation coefficient λ carrys out adjusting submodule capacitor reference voltage Ucref, further control MMC submodule capacitor voltage and fluctuate model
It encloses, the relational expression after introducing is as follows:
λUcref+Δusmc≤umax
In formula, λ is reference voltage regulation coefficient, umaxFor the capacitance voltage upper limit.
4. low voltage traversing control method according to claim 3, it is characterised in that: reference voltage regulation coefficient λ's takes
Being worth range is 0.9~1.1.
5. low voltage traversing control method according to claim 1, it is characterised in that: when the grid-connected electricity of photovoltaic parallel in system
, it is specified that grid entry point electric current i is no more than rated current I when pressure life is fallenN1.5 times, new watt current value instruction value
Calculation formula is as follows:
In formula, idIndicate watt current, iqIndicate reactive current, INIndicate rated current.
6. a kind of photovoltaic combining inverter low voltage ride through control system based on MMC, it is characterised in that: the system includes photovoltaic
Array PV, Boost chopper circuit, MMC inverter；Wherein, photovoltaic array PV uses perturbation observation method, realizes that maximum power is defeated
Out；Boost chopper circuit is for boosting photovoltaic output voltage；MMC inverter is used for DC inversion into exchange；This is
System realizes that low-voltage is worn using any one photovoltaic combining inverter low voltage traversing control method described in claim 1 to 5
More control.
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| CN108809132B (en) * | 2018-06-26 | 2020-04-17 | 西安端怡科技有限公司 | Hybrid MMC half-bridge submodule capacitor voltage balancing method |
| CN110233501A (en) * | 2019-06-25 | 2019-09-13 | 福州大学 | A kind of three-phase photovoltaic grid-connected electricity generation system low voltage traversing control method of two-stage |
| CN110323781A (en) * | 2019-07-03 | 2019-10-11 | 国网江苏省电力有限公司电力科学研究院 | A kind of low voltage traversing control method of modular multilevel electric power electric transformer |
| CN111064233B (en) * | 2019-12-04 | 2022-10-04 | 中国电力科学研究院有限公司 | Method and system for distributing active and reactive current proportion of inverter |
| CN111082471B (en) * | 2019-12-04 | 2022-09-09 | 中国电力科学研究院有限公司 | Inverter active and reactive current dynamic distribution method and system under steady state |
| CN111030105B (en) * | 2019-12-25 | 2022-01-14 | 重庆涪陵电力实业股份有限公司 | Low-voltage ride through method of photovoltaic power generation system based on three-phase cascade H bridge |
| CN111510009B (en) * | 2020-05-20 | 2021-07-30 | 上海海事大学 | Photovoltaic inverter without leakage current and control method thereof |
| CN114204586A (en) * | 2021-12-03 | 2022-03-18 | 华北电力大学 | Second harmonic injection method for inhibiting voltage fluctuation of MMC capacitor and suitable for multiple working conditions |
| CN117375075A (en) * | 2023-10-11 | 2024-01-09 | 国网宁夏电力有限公司经济技术研究院 | Active voltage support control method, medium and system for optical storage integrated converter |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103441512A (en) * | 2013-08-13 | 2013-12-11 | 上海交通大学 | Reactive compensation (MMC-STATCOM) method based on modular multi-level converter |
| WO2014001079A1 (en) * | 2012-06-28 | 2014-01-03 | Siemens Aktiengesellschaft | Power converter and operating method for converting voltages |
| CN104269878A (en) * | 2014-07-29 | 2015-01-07 | 西安交通大学 | Low-voltage ride through control method for grid-connected photovoltaic power generation system capable of providing reactive support |
| CN104917415A (en) * | 2014-03-13 | 2015-09-16 | 国家电网公司 | DC fault ride-through control method for hybrid modular multilevel converter |
-
2016
- 2016-05-27 CN CN201610365691.4A patent/CN106026163B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014001079A1 (en) * | 2012-06-28 | 2014-01-03 | Siemens Aktiengesellschaft | Power converter and operating method for converting voltages |
| CN103441512A (en) * | 2013-08-13 | 2013-12-11 | 上海交通大学 | Reactive compensation (MMC-STATCOM) method based on modular multi-level converter |
| CN104917415A (en) * | 2014-03-13 | 2015-09-16 | 国家电网公司 | DC fault ride-through control method for hybrid modular multilevel converter |
| CN104269878A (en) * | 2014-07-29 | 2015-01-07 | 西安交通大学 | Low-voltage ride through control method for grid-connected photovoltaic power generation system capable of providing reactive support |
Non-Patent Citations (2)
| Title |
|---|
| Operating Region of Modular Multilevel Converter for HVDC With Controlled Second-Order Harmonic Circulating Current: Elaborating P-Q Capability;Kim H等;《IEEE TRANSACTIONS ON POWER DELIVERY》;20160430;第31卷(第2期);493-502 |
| 三电平光伏并网逆变器的模块化控制研究;邵章平;《中国博士学位论文全文数据库 工程科技Ⅱ辑》;20160515(第5期);C042-14 |
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