CN106972773A - A kind of three level grid-connected inverter constant switching frequency model predictive control methods - Google Patents
A kind of three level grid-connected inverter constant switching frequency model predictive control methods Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
- H02M7/53876—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a kind of three level grid-connected inverters constant switching frequency model predictive control method, comprise the following steps:The first step, three-level space vector modulation method uses three Vector modulations, and object function is determined according to instantaneous power theory and Direct Power forecast Control Algorithm;Second step, according to object function take minimum value determine reference vector where small sector position;3rd step, calculates the difference action time of three vectors in a switch periods;4th step, on off sequence is determined according to neutral point voltage balance.The method of the present invention can greatly reduce the amount of calculation of three level grid-connected inverter Power Controls, reduce combining inverter active power and reactive power ripple, with preferable dynamic and static state performance, while constant switching frequency can be realized, with more preferable harmonic suppression effect.
Description
Technical field
The present invention relates to three level grid-connected inverter fields, more particularly to a kind of constant switch frequency of three level grid-connected inverters
Rate model predictive control method.
Background technology
With developing rapidly for the fields such as distributed power source, energy-storage system, electric automobile, to the quality of power supply and system effectiveness
Requirement also more and more higher.Three-level inverter has that harmonic wave is few compared to traditional two-level inverter, switch tube voltage should
Power is small, high pressure, small electromagnetic interference the advantages of.T-shaped inverter has two compared to other three level neutral-point-clamped type inverters
Main advantage:When it is DC bus-bar voltage and zero to export phase voltage, only one of which switch is switched on, and is reduced open-minded
Loss;The electric current average for flowing through each switching tube is equal, and each switching tube produces identical heat.Therefore, in recent years T-shaped three
Electrical level inverter is by the extensive concern of enterprise and colleges and universities, and prospect is very wide.
However, there is switching frequency with sampling time, load parameter and system mode in traditional direct Power Control method
Change and change, the problem of producing scattered harmonic components, also, prediction algorithm is computationally intensive, occupies substantial amounts of resources of chip.
Therefore, a kind of combining inverter Poewr control method of efficient and superior performance is studied most important.
The content of the invention
The purpose of the present invention exactly in order to overcome above mentioned problem, proposes a kind of three level grid-connected inverters constant switching frequency
Model predictive control method, reduces the amount of calculation of three level grid-connected inverter Power Controls, reduces combining inverter wattful power
Rate and reactive power ripple.
To achieve these goals, the present invention is achieved through the following technical solutions:
A kind of three level grid-connected inverter constant switching frequency model predictive control methods, include following four step:
S1, three-level space vector modulation method use three Vector modulations, pre- according to instantaneous power theory and Direct Power
Survey control method and determine object function;
S2, taken according to object function minimum value determine reference vector where small sector position;
S3, three vectors calculated in a switch periods difference action time;
S4, on off sequence determined according to neutral point voltage balance.
The three level grid-connected inverters constant switching frequency model predictive control method step S1 specific methods are as follows:
The output level of each phase of the T-shaped inverter of three level has three kinds of states:Output voltage be equal to DC bus-bar voltage,
Output voltage is equal to the half of DC bus-bar voltage, output voltage and is equal to 0, is set to P, O, N;Therefore 27 kinds of basis arrows are had
Amount is respectively:NNN、NNO、NNP、NON、NOO、NOP、NPN、NPO、NPP、ONN、ONO、ONP、OON、OOO、OOP、OPN、OPO、
OPP、PNN、PNO、PNP、PON、POO、POP、PPN、PPO、PPP;
The polar plot that 27 basis vectors are constituted is divided into six big sector, and each big sector is divided into four small sectors, each
There are six kinds of resultant vectors big sector, and the sector according to where reference voltage vector selects corresponding resultant vector, specific as follows:
When reference vector is located at the first small sector, resultant vector selection zero vector v0, small vector v1, small vector v2;
When reference vector is located at the second small sector, resultant vector selection small vector v1, middle vector v4, big vector v3;
When reference vector is located at three small sectors, resultant vector selection small vector v1, small vector v2, middle vector v4;
When reference vector is located at four small sectors, resultant vector selection small vector v2, middle vector v4, big vector v5。
Further, negligible resistance R influence, under static α β coordinate systems, can be obtained with reference to instantaneous power theory
Wherein, uα、uβ、iα、iβ、eα、eβRepresent that inverter output phase voltage, phase current and line voltage are quiet in α β respectively
The only value on coordinate system, ω, L are respectively electrical network angular frequency, current-limiting reactor value.
There are three vector v in a switch periodsi(i=1,2,3) is acted on respectively, if viDuring effect, the voltage of inverter
For ui(uαi, uβi), uαi, uβiFor uiThe value fastened in α β static coordinates, action time is ti。
And make
Then object function is
Wherein, Pref、QrefThe respectively active power of combining inverter and reactive power set-point, Pj、Qj、TsDifference table
Show current active power value, current reactive power value, switch periods.
The step S2 specific methods of the three level grid-connected inverters constant switching frequency model predictive control method are as follows:
The first step, by 6 combinations point of 2 adjacent long vectors and zero vector in three level grid-connected inverter three dimensional vector diagrams
Object function is not substituted into.By 6 circulations, obtain when J takes the vectorial combination of minimum value, obtain reference vectorThe big fan at place
Zone position.
All small vectorial combinations of sector three in the big sector are substituted into object function, followed by 4 times by second step respectively
Ring, obtains when J takes three vectorial combinations of minimum value, obtains reference vectorThe residing small fan in 3 level space vector figure
Zone position.
The step S3 specific methods of the three level grid-connected inverters constant switching frequency model predictive control method are as follows:
Three vectorial combinations and changed power are substituted into following formula, the difference action time of three vectors is obtained.
Wherein, eq=Pref-Pj、ep=Qref-Qj。
The step S4 specific methods of the three level grid-connected inverters constant switching frequency model predictive control method are as follows:
For the first big sector, there are 4 small sectors, there are 6 vectors, there can be 8 on off sequences;
When inverter output power is just Uc1> Uc2When select p-type on off sequence, increase inverter mid-point voltage;Uc1
< Uc2When select N-type on off sequence, reduce inverter mid-point voltage.
First small sector, Uc1> Uc2Correspondence on off sequence OOO-POO-PPO;Uc1< Uc2Correspondence OOO-OON-ONN;
Second small sector, Uc1> Uc2Correspondence on off sequence PNN-PON-POO;Uc1< Uc2Correspondence PON-PNN-ONN;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-POO-PPO;Uc1< Uc2Correspondence PON-OON-ONN;
4th small sector, Uc1> Uc2Correspondence on off sequence PON-PPN-PPO;Uc1< Uc2Correspondence PPN-PON-OON;
When inverter output power for it is negative when, p-type on off sequence and N-type on off sequence alignment voltage action effect with it is defeated
Go out power for timing on the contrary, Uc1> Uc2When select N-type on off sequence, increase inverter mid-point voltage;Uc1< Uc2When select P
Type on off sequence, reduces the mid-point voltage of inverter.
First small sector, Uc1> Uc2Correspondence on off sequence OOO-OON-ONN;Uc1< Uc2Correspondence OOO-POO-PPO;
Second small sector, Uc1> Uc2Correspondence on off sequence PON-PNN-ONN;Uc1< Uc2Correspondence PNN-PON-POO;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-OON-ONN;Uc1< Uc2Correspondence PON-POO-PPO;
4th small sector, Uc1> Uc2Correspondence on off sequence PPN-PON-OON;Uc1< Uc2Correspondence PON-PPN-PPO;
Wherein, Uc1、Uc2Respectively direct current bus bar holds C1Electric capacity C under the voltage and dc bus at two ends2The electricity at two ends
Pressure.
For other five big sector, by that analogy.
Compared with prior art, the invention has the advantages that and technique effect:
The method of the present invention can substantially reduce the amount of calculation of three level grid-connected inverter Power Controls, it is not necessary to increase
Extra hardware circuit, cost is low;Inverter active power and reactive power ripple can be significantly reduced using the inventive method, together
When can realize constant switching frequency, reduce input harmonics, with good practicality.
Brief description of the drawings
Fig. 1 is T-shaped three level grid-connected inverters structure chart.
Fig. 2 is the three dimensional vector diagram of three level grid-connected inverters.
Fig. 3 is the first big sector division and polar plot.
Fig. 4-1 is the output phase-voltage phase-current simulation waveform using the inventive method.
Fig. 4-2 is the active power simulation waveform using the inventive method.
Fig. 4-3 is the reactive power simulation waveform using the inventive method.
Embodiment
The embodiment of the present invention is elaborated with example below in conjunction with the accompanying drawings.
Fig. 1 gives T-shaped three-level inverter structure chart, including three bridge arms in parallel, and two strings are included per phase bridge arm
The IGBT switching tubes of connection, the IGBT that the midpoint side series connection both direction of each phase bridge arm is different is managed, and opposite side is connected with power network;
Each bridge arm in parallel is terminated into same direct voltage source;The midpoint connection of input voltage source two neutral point clamp electric capacity in parallel
One end of the different IGBT pipes of the both direction of each phase bridge arm;Each IGBT pipe is by control circuit drives.
Three level grid-connected inverter constant switching frequency model predictive control methods, embodiment includes four steps
Suddenly:The first step, three-level space vector modulation method uses three Vector modulations, according to instantaneous power theory and direct Power Control
Method determines object function;Second step, according to object function take minimum value determine reference vector where small sector position;3rd
Step, calculates the difference action time of three vectors in a switch periods;4th step, determines to switch according to neutral point voltage balance
Sequence.
Synthesized in the first step using the Vector Modulation of 3 level space vector three and determine the implementation process of object function
For:The output level of each phase of the T-shaped inverter of three level has three kinds of states:Output voltage is equal to DC bus-bar voltage, output
Voltage is equal to the half of DC bus-bar voltage, output voltage and is equal to 0, is set to P, O, N;Therefore 27 kinds of basis vectors point are had
It is not:NNN、NNO、NNP、NON、NOO、NOP、NPN、NPO、NPP、ONN、ONO、ONP、OON、OOO、OOP、OPN、OPO、OPP、
PNN、PNO、PNP、PON、POO、POP、PPN、PPO、PPP;
Fig. 2 is the polar plot that 27 basis vectors are constituted, and is divided into six big sector, and each big sector can be divided into four small again
There are six kinds of resultant vectors sector, each big sector, and Fig. 3 is the polar plot of the first big sector, is fanned according to where reference voltage vector
Area selects corresponding resultant vector, specific as follows:
When reference vector is located at the first small sector, resultant vector selection zero vector v0, small vector v1, small vector v2;
When reference vector is located at the second small sector, resultant vector selection small vector v1, middle vector v4, big vector v3;
When reference vector is located at three small sectors, resultant vector selection small vector v1, small vector v2, middle vector v4;
When reference vector is located at four small sectors, resultant vector selection small vector v2, middle vector v4, big vector v5。
The object function determines method, specific as follows:
Negligible resistance R influence, under static α β coordinate systems, can be obtained with reference to instantaneous power theory
Wherein, uα、uβ、iα、iβ、eα、eβRepresent that inverter output phase voltage, phase current and line voltage are quiet in α β respectively
The only value on coordinate system, ω, L are respectively electrical network angular frequency, current-limiting reactor value.
There are three vector v in a switch periodsi(i=1,2,3) is acted on respectively, if viDuring effect, the voltage of inverter
For ui(uαi, uβi), uαi, uβiFor uiThe value fastened in α β static coordinates, action time is ti。
And make
Then after a switch periods, the transformation relation of active power and reactive power is
Then object function is
Wherein, Pref、QrefThe respectively active power of combining inverter and reactive power set-point, Pj、Qj、TsDifference table
Show current active power value, current reactive power value, switch periods;Pj+1、Qj+1Respectively represent subsequent time active power value,
The reactive power value of subsequent time.
In the second step according to object function take minimum value determine reference vector where small sector position implementation
Journey is divided into two steps:
The first step, by 6 combinations point of 2 adjacent long vectors and zero vector in three level grid-connected inverter three dimensional vector diagrams
Object function is not substituted into.By 6 circulations, obtain when J takes the vectorial combination of minimum value, obtain reference vectorThe big fan at place
Zone position.
All small vectorial combinations of sector three in the big sector are substituted into object function, followed by 4 times by second step respectively
Ring, obtains when J takes three vectorial combinations of minimum value, obtains reference vectorThe residing small fan in 3 level space vector figure
Zone position.
The implementation process of difference action time that three vectors in a switch periods are calculated in 3rd step is:
Three vectorial combinations and changed power are substituted into following formula, the difference action time of three vectors is obtained.
Wherein, eq=Pref-Pj、ep=Qref-Qj。
Determine that the implementation process of on off sequence is according to neutral point voltage balance in 4th step:
For the first big sector, there are 4 small sectors, there are 6 vectors, there can be 8 on off sequences;
When inverter output power is just Uc1> Uc2When select p-type on off sequence, increase inverter mid-point voltage;Uc1
< Uc2When select N-type on off sequence, reduce inverter mid-point voltage.
First small sector, Uc1> Uc2Correspondence on off sequence OOO-POO-PPO;Uc1< Uc2Correspondence OOO-OON-ONN;
Second small sector, Uc1> Uc2Correspondence on off sequence PNN-PON-POO;Uc1< Uc2Correspondence PON-PNN-ONN;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-POO-PPO;Uc1< Uc2Correspondence PON-OON-ONN;
4th small sector, Uc1> Uc2Correspondence on off sequence PON-PPN-PPO;Uc1< Uc2Correspondence PPN-PON-OON;
When inverter output power for it is negative when, p-type on off sequence and N-type on off sequence alignment voltage action effect with it is defeated
Go out power for timing on the contrary, Uc1> Uc2When select N-type on off sequence, increase inverter mid-point voltage;Uc1< Uc2When select P
Type on off sequence, reduces the mid-point voltage of inverter.
First small sector, Uc1> Uc2Correspondence on off sequence OOO-OON-ONN;Uc1< Uc2Correspondence OOO-POO-PPO;
Second small sector, Uc1> Uc2Correspondence on off sequence PON-PNN-ONN;Uc1< Uc2Correspondence PNN-PON-POO;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-OON-ONN;Uc1< Uc2Correspondence PON-POO-PPO;
4th small sector, Uc1> Uc2Correspondence on off sequence PPN-PON-OON;Uc1< Uc2Correspondence PON-PPN-PPO;
Wherein, Uc1、Uc2Respectively direct current bus bar holds C1Electric capacity C under the voltage and dc bus at two ends2The electricity at two ends
Pressure.
For other five big sector, by that analogy.
Fig. 4-1,4-2,4-3 are the three level grid-connected inverter constant switching frequency Model Predictive Control sides using the present invention
Simulation waveform during method, started control after 0.1 second, and wherein Fig. 4-1 is to export phase voltage and phase current waveform figure, and Fig. 4-
2 be active power oscillogram, and Fig. 4-3 is reactive power oscillogram, simulation result:Output voltage current harmonics is small, with preferable
Harmonic restraining function, combining inverter active power and reactive power ripple be small, with preferable dynamic and static state performance, fully card
Understand the practicality of the present invention.
Above-described embodiment is preferably embodiment, but embodiments of the present invention are not by above-described embodiment of the invention
Limitation, other any Spirit Essences without departing from the present invention and the change made under principle, modification, replacement, combine, simplification,
Equivalent substitute mode is should be, is included within protection scope of the present invention.
Claims (5)
1. a kind of three level grid-connected inverters constant switching frequency model predictive control method, it is characterised in that include following step
Suddenly:
S1, three-level space vector modulation method use three Vector modulations, according to instantaneous power theory and the pre- observing and controlling of Direct Power
Method processed determines object function;
S2, taken according to object function minimum value determine reference vector where small sector position;
S3, three vectors calculated in a switch periods difference action time;
S4, on off sequence determined according to neutral point voltage balance.
2. three level grid-connected inverter constant switching frequency model predictive control method according to claim 1, its feature exists
In the step S1 is specific as follows:
The output level of each phase of the T-shaped inverter of three level has three kinds of states:Output voltage is equal to DC bus-bar voltage, output
Voltage is equal to the half of DC bus-bar voltage, output voltage and is equal to 0, is set to P, O, N;Therefore 27 kinds of basis vectors point are had
It is not:NNN、NNO、NNP、NON、NOO、NOP、NPN、NPO、NPP、ONN、ONO、ONP、OON、OOO、OOP、OPN、OPO、OPP、
PNN、PNO、PNP、PON、POO、POP、PPN、PPO、PPP;
The polar plot that 27 basis vectors are constituted is divided into six big sector, and each big sector is divided into four small sectors, each big fan
Qu Youliu kind resultant vectors, the sector according to where reference voltage vector selects corresponding resultant vector, specific as follows:
When reference vector is located at the first small sector, resultant vector selection zero vector v0, small vector v1, small vector v2;
When reference vector is located at the second small sector, resultant vector selection small vector v1, middle vector v4, big vector v3;
When reference vector is located at three small sectors, resultant vector selection small vector v1, small vector v2, middle vector v4;
When reference vector is located at four small sectors, resultant vector selection small vector v2, middle vector v4, big vector v5;
Negligible resistance R influence, under static α β coordinate systems, can be obtained with reference to instantaneous power theory
Wherein, (uα, uβ)、(iα, iβ)、(eα, eβ) represent that inverter output phase voltage, phase current, line voltage are quiet in α β respectively
The only coordinate on coordinate system;ω, L are respectively electrical network angular frequency, current-limiting reactor value;To carry out differential to active-power P,To carry out differential to active power Q;
In a switch periods TsInside there are three vector viAct on respectively, wherein i=1,2,3;If viDuring effect, the electricity of inverter
Press as ui, (uαi,uβi) it is uiThe coordinate fastened in α β static coordinates, action time is ti;
And make
Then object function J is
Wherein, Pref、QrefThe respectively active power of combining inverter and reactive power set-point, Pj、Qj、TsRepresent to work as respectively
Preceding active power value, current reactive power value, switch periods.
3. three level grid-connected inverter constant switching frequency model predictive control method according to claim 2, its feature exists
In the step S2 is specific as follows:
The first step, generation respectively is combined by 6 of 2 adjacent long vectors and zero vector in three level grid-connected inverter three dimensional vector diagrams
Enter object function;By 6 circulations, obtain when J takes the vectorial combination of minimum value, obtain reference vectorThe big sector position at place
Put;
All small vectorial combinations of sector three in the big sector are substituted into object function by second step respectively, by 4 circulations, are asked
Go out when J takes three vectorial combinations of minimum value, obtain reference vectorThe residing small sector position in 3 level space vector figure
Put.
4. three level grid-connected inverter constant switching frequency model predictive control method according to claim 3, its feature exists
In the step S3 is specific as follows:
Three vectorial combinations and changed power are substituted into following formula, the difference action time t of three vectors is obtained1、t2、t3:
Wherein, eq=Pref-Pj、ep=Qref-Qj。
5. three level grid-connected inverter constant switching frequency model predictive control method according to claim 4, its feature exists
In the step S4 is specific as follows:
For the first big sector, there are 4 small sectors, there are 6 vectors, there can be 8 on off sequences;
When inverter output power is just Uc1> Uc2When select p-type on off sequence, increase inverter mid-point voltage;Uc1< Uc2
When select N-type on off sequence, reduce inverter mid-point voltage;
First small sector, Uc1> Uc2Correspondence on off sequence OOO-POO-PPO;Uc1< Uc2Correspondence OOO-OON-ONN;
Second small sector, Uc1> Uc2Correspondence on off sequence PNN-PON-POO;Uc1< Uc2Correspondence PON-PNN-ONN;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-POO-PPO;Uc1< Uc2Correspondence PON-OON-ONN;
4th small sector, Uc1> Uc2Correspondence on off sequence PON-PPN-PPO;Uc1< Uc2Correspondence PPN-PON-OON;
When inverter output power is bears, p-type on off sequence and N-type on off sequence alignment voltage action effect and output work
Rate is timing on the contrary, Uc1> Uc2When select N-type on off sequence, increase inverter mid-point voltage;Uc1< Uc2When selection p-type open
Sequence is closed, reduces the mid-point voltage of inverter;
First small sector, Uc1> Uc2Correspondence on off sequence OOO-OON-ONN;Uc1< Uc2Correspondence OOO-POO-PPO;
Second small sector, Uc1> Uc2Correspondence on off sequence PON-PNN-ONN;Uc1< Uc2Correspondence PNN-PON-POO;
3rd small sector, Uc1> Uc2Correspondence on off sequence PON-OON-ONN;Uc1< Uc2Correspondence PON-POO-PPO;
4th small sector, Uc1> Uc2Correspondence on off sequence PPN-PON-OON;Uc1< Uc2Correspondence PON-PPN-PPO;
Wherein, Uc1、Uc2Respectively direct current bus bar holds C1Electric capacity C under the voltage and dc bus at two ends2The voltage at two ends;
For other five big sector, by that analogy.
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