CN107196491B - A kind of double buck gird-connected inverter half period current distortion inhibition system and method - Google Patents
A kind of double buck gird-connected inverter half period current distortion inhibition system and method Download PDFInfo
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- CN107196491B CN107196491B CN201710479415.5A CN201710479415A CN107196491B CN 107196491 B CN107196491 B CN 107196491B CN 201710479415 A CN201710479415 A CN 201710479415A CN 107196491 B CN107196491 B CN 107196491B
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Classifications
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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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
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/123—Suppression of common mode voltage or current
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Abstract
The invention discloses a kind of double buck gird-connected inverter half period operating current distortion to inhibit system and method, the present invention passes through the analysis to buck unit half period working condition in double buck topologys, buck cell operation is established in the different sections of continuous current mode and discontinuous conduct mode, and establishes that electric current is continuous and the corresponding relationship of discontinuous mode switching moment and grid current amplitude.Under discontinuous conduct mode, according to the non-linear relation between the gain of buck cell voltage and duty ratio, it is modulated the amendment of wave equivalent linearization to the output of electric current loop adjuster, makes that adjuster is output to the gain of bridge arm voltage and electric current consecutive hours is consistent.The present invention reduces current ripples and current lead-through time by reducing duty ratio, it avoids in Traditional control because of inductive current ripple bring current distortion problem, the double buck inverters not only high efficient and reliable for making the half period work, it realizes grid current low harmony wave simultaneously, is more advantageous to double buck topologys and applies in gird-connected inverter.
Description
Technical field
The present invention relates to DC-AC grid-connection converter technical fields, and in particular to one kind is applied to double buck gird-connected inverters
In half period current over-zero distortion inhibit system and method.
Background technique
Global energy consumption is in cumulative year after year trend, and traditional fossil energy is increasingly depleted, while bringing serious environment dirty
Dye problem, generation of electricity by new energy is at important channel to solve this problem.The distributed hair that the new energy such as wind energy, solar energy rely on
Electric system occupies increasingly consequence in AC network.New energy have dispersibility, timesharing, regionality, by nature
The features such as condition is affected is caused extensively based on generation of electricity by new energy with the micro-capacitance sensor structure of bulk power grid interaction in recent years
General concern.As the key interface between distributed power generation and power grid and load, the research of DC-AC gird-connected inverter has important meaning
Justice.
Traditional bridge-type inverter topology bridge arm switching tube is directly connected on DC bus, it is contemplated that switching tube is open-minded
Turn-off time and driving delay etc., up and down there is straight-through hidden danger in switching tube to bridge arm, makes dc-side short-circuit, damages switching tube.
Dead zone would generally be added between down tube driving signal on the bridge arm that complementation is opened in order to avoid straight-through, dead time is by power tube
The influence of switching speed and driving delay.Afterflow is carried out by diode in dead time, will affect the distribution of generating positive and negative voltage pulse,
Fundamental wave error and low-frequency harmonics are introduced in the bridge arm voltage of output, while also will affect grid current quality.Bridge arm switching tube
When using IGBT, because body diode is not present in this body structure of IGBT device, additional anti-and diode is needed to flow through reverse current.
When bridge arm switching tube uses MOSFET, electric current flows through body diode in dead time, and body diode characteristic is generally poor, reversed
The problems such as the problems such as recovery, can bring loss to increase.
A kind of alternative topology of double buck topologys as conventional bridge topology, each phase is by positive and negative two buck unit group
It closes, has the ability of to and fro flow of power.Positive and negative buck unit is all three ends being made of switching tube, diode, inductance
Structure, and be connected three endpoint sides.Switching tube and Diode series on DC bus, wherein diode Opposite direction connection to
Block straight circuit, midpoint and the extraction of inductance connection to switching tube and diode bridge arm.Every phase is positive and negative in double buck topologys
Buck unit works in electric current positive-negative half-cycle respectively, leads directly to problem there is no bridge arm switching tube and compares tool with conventional bridge topology
There is higher reliability.And compared with using the conventional bridge topology of IGBT, the quantity of switching device does not increase.
For conventional bridge topology, bridge arm output electric current, that is, bridge arm side inductive current works in entire section to be connected in electric current
Discontinuous Conduction mode, when average value direction of the electric current in a switch periods changes, because of the presence of ripple current, in electric current
Average value absolute value is less than in the switch periods of current ripples half, and the stage that the existing electric current of bridge arm current is positive also has the electric current to be
The negative stage.And for double buck topologys, because of the presence of diode, positive/negative buck unit is only capable of flowing through unidirectional current, when it
Time-sharing work is when electric current positive-negative half-cycle, the minimum value of average value absolute value of the bridge arm current of output in a switch periods
The as half of ripple current.When using bipolar modulation strategy, bridge arm switching tube duty ratio is 0.5 near current over-zero
Left and right, current ripples at this time are maximum, and bridge arm, which exports average value of the electric current in a switch periods, can not be reduced to zero.?
Current reference value absolute value was less than in the stage of ripple current half, and bridge arm output electric current cannot be changed by reference current, that is, went out
Existing half period current over-zero distortion.Three-phase current is mutually coupled, and a phase current zero-acrross ing moment is distorted mutually can also go out at other
6 distortion will occur in existing current distortion, each periodic current.
Bridge arm output current distortion can introduce distortion in current on line side, increase the total harmonic distortion of grid current, increase
Filter size.Current distortion also results in current effective value and becomes larger, and increases the loss of switching device and magnetic device.Cause
This, inhibiting the distortion of half period current over-zero is that double buck topologys are applied to DC-AC grid-connection converter institute is to be solved important to be asked
Topic.
Summary of the invention
Goal of the invention: technical problem solved by the invention is the deficiency for above-mentioned background technique, provides a kind of inhibition
The system and its control method of the topological half period operating current Zero-crossing Distortion of double buck improve double buck topologys and are applied to DC-AC
Output performance and working efficiency when grid-connection converter.
Technical solution:
A kind of double buck gird-connected inverter half period operating current distortion inhibition systems, including the double buck inverter masters of three-phase
Circuit and its control system；
The double buck converter main circuits of the three-phase include including DC bus capacitor, the double buck bridge arms of three-phase and three-phase
LCL filter；Two interface is separately connected DC source and power grid；The double buck bridge arms of the three-phase are by three single-phase double buck bridges
Arm is formed in parallel；Each single-phase double buck bridge arms are composed of positive and negative two buck units, and positive/negative buck unit is opened by one
Guan Guan, a diode and an inductance are constituted；
The control system includes sample circuit, DSP control unit and driving circuit；The sample circuit includes three-phase electricity
Net voltage sample, the sampling of three-phase grid current, DC voltage sampling, DC side current sample；
The DSP control unit is by locking phase, current regulator, modulating wave shaping link and half-cycle driving logical link structure
At；The control system sampling three-phase network voltage simultaneously extracts voltage phase angle by the locking phase, the phase angle benchmark as electric current；
The magnitude references of electric current are determined that the phase angle benchmark and magnitude references of electric current constitute current reference by power；The system is by electric current
The error of benchmark and the three-phase grid current of sampling feedback is sent into current regulator, and the closed loop for carrying out power network current is adjusted, described
The output of current regulator is sent into modulating wave shaping link and generates modulating wave；The modulating wave shaping link judges that current buck is mono-
Whether member works in discontinuous conduct mode, and carries out the equivalent linearization amendment of modulating wave；Inverter bridge when according to interrupter duty
The relationship of gain and duty ratio, duty ratio and modulating wave after equivalent linearization is calculated, modulating wave are sent into half-cycle driving
Logical link；The half-cycle driving logical link compares modulating wave and carrier wave, exports the switching signal of IGBT, and shields
Buck unit does not work the driving signal of half cycle；The switching drive signal that the driving circuit exports the DSP control unit
After carrying out power amplification and isolated from power, six IGBT switching tubes of three-phase bridge arm are driven.
A kind of double buck gird-connected inverter half period operating current distortion suppressing methods, comprising steps of
Step 1: in conjunction with system parameter, including IGBT switching frequency, filter inductance value, DC voltage and modulation ratio,
It solves at rated power and the following power of rated power, positive buck unit and is born in double buck topology of half period work
Two critical angles of the buck cell operation in continuous current mode divide the continuous and interrupted workspace of buck cell current
Between；
Step 2: meeting linear close in electric current continuum, between the voltage gain and duty cycle of switching of buck unit
System, by current regulator linear convergent rate directly as modulating wave；
Step 3: being nonlinear dependence between the voltage gain and duty cycle of switching of buck unit in discontinuous current section
System, seeks modulating wave according to duty ratio under discontinuous conduct mode, exports electric current according to buck unit and seeks under discontinuous conduct mode
Duty ratio；The corresponding relationship between discontinuous conduct mode modulated wave and current regulator output is established, and by current regulator
Output obtains modulating wave；
Step 4: the modulating wave according to obtained in step 2 and step 3 synthesizes entire section modulating wave, inputs half-cycle driving
Logical link exports the switching signal of IGBT, and six IGBT switching tubes of three-phase bridge arm are driven by driving circuit.
The utility model has the advantages that joined modulating wave shaping link in control loop, it is double when control reference current absolute value is smaller
The work of buck bridge arm reduces bridge arm output current ripple, makes positive and negative buck unit in a switch periods in discontinuous conduct mode
The current average of interior output can track reference current and change to zero.Inverter bridge gain and duty ratio are under discontinuous conduct mode
Non-linear relation, for the Unified Model of inverter bridge, i.e., the equivalent gain in whole region is constant, needs to carry out modulating wave
Equivalent linearization transformation, according to gain under discontinuous mode and duty cycle relationship be calculated it is equivalent after duty ratio and modulating wave.
The method of the topological half period current over-zero distortion of the double buck of inhibition of the invention, does not need to add additional sensor
Or circuit, can be easier to realize by the way that DSP is digital control, by using discontinuous current operating mode reduce current ripples and from
The generation for substantially inhibiting current distortion, improves the quality of grid current, reduces switching tube and magnetic device loss, improves
Inverter efficiency, while reducing filter size.
Detailed description of the invention
Attached drawing 1 is the structural schematic diagram of the double buck grid-connected inverter systems of three-phase of the present invention；
Attached drawing 2 is the double buck LCL synchronization inverter main circuit topology figures of three-phase of the present invention；
Attached drawing 3 is the topological phase bridge arm structure figure of double buck of the present invention.
Attached drawing 4 is that the positive and negative buck cell current of the topological phase bridge arm of double buck of the present invention and bridge arm export current wave
Shape schematic diagram；
Attached drawing 5 is output external characteristic figure of the positive and negative buck cell voltage gain of the present invention to electric current；
Attached drawing 6 is that equivalent linearization of the present invention compensates preceding and compensated modulating wave waveform diagram；
Attached drawing 7 is using the grid current waveform diagram before and after Zero-crossing Distortion suppressing method of the present invention.
Wherein, 1 is DC source, and 2 be double buck inverters, and 3 be power grid, and 4 be sample circuit, and 5 be DSP control unit, and 6 are
Driving circuit, 7 be locking phase, and 8 be current regulator, and 9 be modulating wave shaping link, and 10 be half-cycle driving logical link；
Primary symbols title in the figures above: CdcDC bus capacitor；S1-S6: IGBT；D1-D6: it is fast to restore two pole of power
Pipe；La1/La2: positive/negative buck unit inductance；C: ac filter capacitor；Lg: net side filter inductance；idc: DC side input current；
ia1/ia2: positive/negative buck cell current；ia/b/ci: bridge arm exports electric current；ia/b/cg: current on line side；P: DC bus anode；N:
DC bus negative terminal；A1/A2: positive/negative buck unit bridge arm midpoint；A0: double buck bridge arms midpoint；Positive/negative buck unit
Switch periods average current；The a reference value of bridge arm output electric current；Uo/Uin: buck unit output voltage to input voltage increases
Benefit；D:buck unit duty ratio；Io/IGmax: the ratio of buck cell current and critical continuous mode electric current；CCM: continuous current mode；
DCM: discontinuous current mode；umod: modulating wave after equivalent linearization compensation；u'mod: modulating wave before compensating.
Specific embodiment
The present invention will be further explained with reference to the accompanying drawing.
The double buck grid-connected inverter systems of three-phase as shown in Figure 1 are by the double buck converter main circuits of three-phase and its control
System processed is constituted.Main circuit part is double buck inverters 2, including the double buck bridge arms of DC bus capacitor, three-phase, three-phase LCL filter
Wave device, two interface are DC source 1 and power grid 3.The double buck bridge arms of three-phase are formed in parallel by three single-phase double buck bridge arms, such as
Shown in Fig. 2.Each single-phase double buck bridge arms are composed of positive and negative two buck units, and positive/negative buck unit is switched by one
Pipe, a diode and an inductance are constituted, as shown in Figure 3.
Control system includes sample circuit 4, DSP control unit 5 and driving circuit 6.Sample circuit 4 includes three phase network electricity
Pressure sampling, the sampling of three-phase grid current, DC voltage sampling, DC side current sample.DSP control unit 5 is by locking phase 7, electricity
Throttle regulator 8, modulating wave shaping link 9 and half-cycle driving logical link 10 are constituted.Sampling three-phase network voltage simultaneously passes through lock
Phase 7 extracts voltage phase angle, and as the phase angle benchmark of electric current loop, the magnitude references of current regulator 8 are determined by power.Network voltage
The locking phase of phase angle controls, and is to realize that locking phase angle is as coordinate transform by the closed-loop control of q shaft voltage under synchronous rotating frame
Angle.The error of sampling three-phase grid current and current reference is sent into current regulator 8, carries out the closed-loop control of power network current, electricity
The output of throttle regulator 8 is sent into modulating wave shaping link 9 and generates modulating wave.Modulating wave shaping link 9 is according to current reference value, nothing
Function current value, buck unit inductance value, DC voltage, network voltage, switching frequency etc. judge current buck unit whether work
Make in discontinuous conduct mode, and carries out the equivalent linearization amendment of modulating wave；It inverter bridge gain when according to interrupter duty and accounts for
The relationship of empty ratio, duty ratio and modulating wave after equivalent linearization is calculated, modulating wave are sent into half-cycle driving logical link
10.Half-cycle driving logical link 10 compares modulating wave and carrier wave, exports the switching signal of IGBT, and shields buck unit not
The driving signal of work half cycle.Driving circuit 6 carries out power amplification and electricity to the switching drive signal that DSP control unit 5 exports
After the isolation of source, six IGBT switching tubes of three-phase bridge arm are driven.
Shown in Fig. 2 is the double buck LCL synchronization inverter main circuit topologies of three-phase, the double buck bridge arms of three-phase and DC side
Capacitor is connected in parallel on DC bus, and the inductance in buck unit is used as the current transformer side filter inductance of LCL filter, cascade simultaneously
It is connected after LCL filter with three phase network.
Fig. 3 is the topological phase bridge arm structure figure of double buck, is made of positive and negative two buck units.Wherein, switching tube S1, two
Pole pipe D2, inductance La1Constitute positive buck unit；Switching tube S2, diode D1, inductance La2Negative buck unit is constituted, positive and negative buck is mono-
Three ends of member, which are connected, becomes the double buck bridge arms of a phase.Bridge arm current iaiThe half cycle being positive, only positive buck cell operation, electric current ia1
Electric current needed for providing；Bridge arm current iaiWhen being negative, only negative buck cell operation, electric current ia2Electric current needed for providing.
Fig. 4 is positive and negative buck cell current and bridge arm output current wave, and be from left to right successively positive buck cell current
ia1And its switch periods average valueNegative buck cell current-ia2And its switch periods average valueBridge arm exports electric current iai
And its switch periods average valueAnd a reference valueBecause the presence of diode in buck unit, is only capable of flowing through unidirectional current,
Buck cell currentWith0 cannot be dropped to, when its work is in electric current critical continuous modeMinimum value is ripple current
Half.Therefore, bridge arm exports electric currentAnd a reference valueIt compares, distorts near current over-zero.
Fig. 5 is output external characteristic figure of the buck cell voltage gain to electric current, when output electric current is greater than critical continuous mode electric current,
Buck cell operation is in continuous current mode, and voltage gain and duty ratio meet linear relationship at this time；Electric current is exported less than critical
When continuous current, buck cell operation is non-linear relation between voltage gain and duty ratio at this time in discontinuous conduct mode.Cause
This, when bridge arm output current reference is smaller, buck unit should work in discontinuous conduct mode to provide bridge arm output electric current
Track benchmark.It is non-linear relation between duty ratio at this time and voltage gain, in order to guarantee that voltage gain relationship is constant, it should
Correspondingly change the value of duty ratio, i.e. change modulating wave.
In linear region, directly as modulating wave, the transmission function to bridge arm voltage can be with for the output of current regulator
Approximate Equivalent is a ratio enlargement link, equal to the ratio of DC voltage and carrier wave peak-to-peak value.And in nonlinear area, modulation
Wave is to being non-linear relation between bridge arm voltage, if directlying adopt current regulator output is used as modulating wave, current regulator
Not only to contain fundametal compoment in output, also to include the harmonic component of a large amount of compensating non-linears.In practice by electric current loop band
The limitation of gain in wide and bandwidth, current regulator cannot be without modulating waves required for poorly exporting.
Modulating wave shaping link is added between current regulator and PWM modulation, in the continuous linear region of electric current, directly
It regard current regulator output as modulating wave；In the inelastic region of discontinuous current, current regulator output is that have with bridge arm voltage
The fundametal compoment of wired sexual intercourse, is sent to nonlinear calculator, actually required in conjunction with current reference and circuit parameter calculation
Modulating wave is sent into PWM modulation link.It directly sees that current regulator is output to the gain of bridge arm fundamental voltage at this time, is still one
Equivalent linear element, current regulator output in do not contain non-linear introducing harmonic component.Therefore, modulating wave shaping link
It is the process of an equivalent linearization.
It all will be DCM → CCM → DCM handoff procedure in the half cycle of each buck cell operation, corresponding there are two switchings
Point θ1And θ2.The switch periods of discontinuous conduct mode are switched to from continuous current mode in buck unit, it is believed that electric current is critical
Continuously, ripple current value is exactly 2 times of corresponding periodic current benchmark, can determine θ according to the relationship1And θ2。
Bridge arm output voltage period average is equal to the sum of network voltage and inductive drop, DC bus-bar voltage Udc, account for
Sky is than being d, network voltage UgSin θ, electrical network angular frequency ω, j are imaginary unit's operator, and buck unit inductance value is L1, net
Side filter inductance value is L2, grid current IgSin θ and the same phase of network voltage ignore capacitance current on buck unit inductance
Pressure drop has
The switch periods of electric current critical continuous mode, ripple current value are exactly 2 times of corresponding periodic current benchmark, bridge arm side electricity
Flow benchmark Ig' sin (θ+φ) is equal to current on line side and capacitor reactive current vector sum, wherein φ is generator rotor angle.Switch periods are Ts,
Modulation ratio m=Ug/(1/2Udc)。
According to formula (1) and (2) available binary quadratic equation about sin θ and cos θ, in conjunction between sin θ and cos θ
Unit orthogonality relation can acquire θ, and non trivial solution is related with the value of coefficient, i.e., with DC voltage Udc, switch periods Ts, be adjusted to compare
M, inductance L1And L2, current amplitude Ig, generator rotor angle φ it is related.When stable state, above each parameter value be it is certain, i.e., non trivial solution is
Fixed.When the variation of network access power/current benchmark, rear two IgIt can change with φ, wherein φ is with IgChange and changes
, therefore non trivial solution and current amplitude have a function corresponding relationship.
A biquadratic equation is equivalent to according to unit orthogonality relation formula (3) between sin θ and cos θ
sin2θ+cos2θ=1 (4)
Non trivial solution in formula (3) is analyzed, when current reference amplitude is greater than maximum ripple 1/2, must exist and
There is only two different switching point θ1And θ2, therefore there are two biquadratic equation qualified real solutions.Solve sin θ and
Real solution of the value of cos θ in [- 1,1] section is effective solution, can further be solved according to the value of sin θ and cos θ [0,2 π) area
Between upper θ two values.
According to bridge arm side current reference Ig' sin (θ+φ), it may be determined that the section of positive and negative buck cell operation is respectively electricity
Pressure phase angle is located at the region of [- φ, π-φ] and [π-φ, 2 π-φ].For positive buck unit, when voltage phase angle is located at [θ1,θ2]
In section, buck cell operation is exported in continuous current mode, current regulator directly as modulating wave；When voltage phase angle is located at
[-φ,θ1] and [θ2, π-φ] and in section, buck cell operation is needed in discontinuous conduct mode, current regulator output by whole
Modulating wave after obtaining equivalent linearization after shape.Similarly available negative buck cell operation situation.
By taking positive buck unit as an example, when its work is in discontinuous conduct mode, each switch periods can be divided into three ranks
Section: 1) d1Ts: switching tube S1Conducting, electric current rise；2): d2Ts: diode D2Conducting, electric current decline；3)d3Ts: switching tube S1With
Diode D2It is turned off, electric current 0.
Current average and bridge arm output current reference value should be equal in one switch periods
The expression formula of switching tube duty when corresponding modulating wave can be solved according to formula (5) and (6)
Continuous current mode lower switch pipe duty ratio and modulating wave expression formula are under corresponding situation
According to the expression formula of formula (7) and (8) available modulating wave nonlinear calculator
Wherein u 'modFor the modulating wave of the equivalent linearization of current regulator output, umodTo be ultimately delivered to PWM modulation link
Modulating wave.The similarly modulating wave reforming process of available negative buck unit.
Fig. 6 is the modulating wave u ' of equivalent linearization compensation front and backmodAnd umodIn the waveform of an ac cycle, abscissa is
Voltage phase angle θ.When θ is located in [- φ, π-φ] range, positive buck cell operation provides electric current needed for bridge arm.θ is located at [θ1,
θ2] when, positive buck cell operation is linear relationship between modulating wave and bridge arm voltage at this time in continuous current mode, therefore umod
And u 'modWaveform is identical.θ is located at [- φ, θ1] and [θ2, π-φ] when, positive buck cell operation is adjusted at this time in discontinuous conduct mode
It is non-linear relation between wave and bridge arm voltage processed, connects to maintain current regulator to be output to approximate current between bridge arm voltage
Linear relationship when Discontinuous Conduction mode, compensates modulating wave.As θ=- φ or π-φ, compensated modulating wave is reduced to most
Small, duty ratio is 0 at this time, is 0 equal with current reference according to formula (6) electric current of buck unit output at this time.
Fig. 7 is that the double buck gird-connected inverters of three-phase traditional half period current simulations waveform and use equivalent linear in semi-load
Change the comparison of the half period current simulations waveform of modulating wave.At the current over-zero moment in the presence of obvious abnormal in traditional half period electric current
Become, and three-phase system three-phase current is mutually coupled, mutually also will appear current distortion, therefore each period in other phases in the same time
6 distortion will occur in electric current.Current distortion can introduce a large amount of harmonic wave distribution in current spectrum, and electric current THD is larger.Emulate wave
Traditional half period electric current THD about 7.1% in shape, using the half period electric current THD about 2.8% of equivalent linearization modulating wave.Therefore
Half period current distortion can be effectively eliminated using method proposed by the invention, improve current waveform, reduce electric current THD.
The above is only a preferred embodiment of the present invention, it should be pointed out that: for the ordinary skill people of the art
For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered
It is considered as protection scope of the present invention.
Claims (2)
- The inhibition system 1. a kind of double buck gird-connected inverter half period operating currents distort, it is characterised in that: double including three-phase Buck converter main circuit and its control system；The double buck converter main circuits of the three-phase include DC bus capacitor, the double buck bridge arms of three-phase and three-phase LCL filter； Two interface is separately connected DC source (1) and power grid (3)；The double buck bridge arms of the three-phase by three single-phase double buck bridge arms simultaneously Join；Each single-phase double buck bridge arms are composed of positive and negative two buck units, and positive/negative buck unit is opened by an IGBT Guan Guan, a diode and an inductance are constituted；The control system includes sample circuit (4), DSP control unit (5) and driving circuit (6)；Sample circuit (4) packet Include three-phase power grid voltage sampling, the sampling of three-phase grid current, DC voltage sampling, DC side current sample；The DSP control unit (5) is patrolled by locking phase (7), current regulator (8), modulating wave shaping link (9) and half-cycle driving Link (10) are collected to constitute；The control system sampling three-phase network voltage simultaneously extracts voltage phase angle by the locking phase (7), as The phase angle benchmark of electric current；The magnitude references of electric current are determined that the phase angle benchmark and magnitude references of electric current constitute current reference by power； The error that current reference and the three-phase grid current of sampling are fed back is sent into current regulator (8) by the system, carries out power grid electricity The closed loop of stream is adjusted, and the output of the current regulator (8) is sent into modulating wave shaping link (9) and generates modulating wave；The modulation Wave shaping link (9) judges whether current buck unit works in discontinuous conduct mode, and carries out the equivalent linearization of modulating wave Amendment；The relationship of inverter bridge gain and duty ratio when according to interrupter duty, duty ratio after equivalent linearization is calculated and Modulating wave, modulating wave are sent into half-cycle driving logical link (10)；The half-cycle driving logical link (10) by modulating wave and Carrier wave compares, and exports the switching signal of IGBT, and shields buck unit and do not work the driving signal of half cycle；The driving circuit (6) after carrying out power amplification and isolated from power to the switching drive signal of the DSP control unit (5) output, three-phase bridge is driven Six IGBT switching tubes of arm.
- 2. a kind of inhibition using double buck gird-connected inverter half period operating current distortion inhibition systems described in claim 1 Method, it is characterised in that: comprising steps ofStep 1: in conjunction with system parameter, including IGBT switching frequency, filter inductance value, DC voltage and modulation ratio, solving Out at rated power and the following power of rated power, just buck unit and negative buck is mono- in double buck topology of half period work Two critical angles of the member work in continuous current mode, divide the continuous and interrupted operation interval of buck cell current；Step 2: in electric current continuum, meet linear relationship between the voltage gain and duty cycle of switching of buck unit, it will Current regulator linear convergent rate is directly as modulating wave；Step 3: being non-linear relation, root between the voltage gain and duty cycle of switching of buck unit in discontinuous current section Modulating wave is sought according to duty ratio under discontinuous conduct mode, electric current is exported according to buck unit and seeks duty under discontinuous conduct mode Than；The corresponding relationship between discontinuous conduct mode modulated wave and current regulator output is established, and is exported by current regulator Obtain modulating wave；Step 4: the modulating wave according to obtained in step 2 and step 3 synthesizes entire section modulating wave, inputs half-cycle driving logic Link exports the switching signal of IGBT, and six IGBT switching tubes of three-phase bridge arm are driven by driving circuit.
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| CN110995044B (en) * | 2019-12-25 | 2020-11-17 | 深圳第三代半导体研究院 | Nonlinear correction device for power switch device |
| US11742750B2 (en) | 2021-10-11 | 2023-08-29 | Halo Microelectronics International | Boost converter apparatus and control method |
| CN114156890B (en) * | 2021-12-09 | 2024-03-29 | 西安理工大学 | LCL type grid-connected inverter current control method with double inductance current changes |
| CN113972839B (en) * | 2021-12-27 | 2022-03-11 | 广东希荻微电子股份有限公司 | Control method and controller of boost converter and power conversion device |
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| CN102223101A (en) * | 2011-06-21 | 2011-10-19 | 盐城工学院 | Control method for dual-bucking full-bridge grid-connected inverter |
| US8629668B2 (en) * | 2011-09-19 | 2014-01-14 | Eta Semiconductor Inc. | Multi-phase synthetic ripple power converter |
| CN102624277B (en) * | 2012-04-18 | 2014-06-25 | 南京航空航天大学 | Dead-zone-free three-phase AC/DC converter with high-frequency rectifier bridge |
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