CN108429476A - A kind of control method and controller of Cascade H bridge inverter - Google Patents
A kind of control method and controller of Cascade H bridge inverter Download PDFInfo
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- CN108429476A CN108429476A CN201810265670.4A CN201810265670A CN108429476A CN 108429476 A CN108429476 A CN 108429476A CN 201810265670 A CN201810265670 A CN 201810265670A CN 108429476 A CN108429476 A CN 108429476A
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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
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
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Abstract
The present invention provides a kind of control method of Cascade H bridge inverter, since it is used to compensate the second harmonic of the modulating wave of normal module, with the first harmonic of the amplitude limit modulating wave for compensating ovennodulation module, the two homogeneous, amplitude be identical and opposite in phase, therefore it can ensure that the total output voltage of exchange of Cascade H bridge module is free of the harmonic wave compensated, and compensation range can be expanded, and then the range of operation of system can be expanded.The present invention also provides a kind of controllers of Cascade H bridge inverter, and the range of operation of system is expanded using identical technological means.
Description
Technical field
The present invention relates to technical field of photovoltaic power generation, more particularly to the control method of a kind of Cascade H bridge inverter and control
Device.
Background technology
In field of photovoltaic power generation, the system structure of Cascade H bridge inverter as shown in Figure 1, each H bridge modules input terminal
One piece of photovoltaic module (as shown in Figure 1) either at least one photovoltaic string formation or can also to increase other straight can be separately connected
Rheology exchange device.When the power that uneven illumination is even or other conditions cause an even several H bridge modules input terminals to receive is serious
When decline, grid-connected current is can decline to a great extent；Since the input power of other H bridge modules is almost unchanged, modulation degree meeting
Increase.And ovennodulation can make the increase of grid current harmonic content or even system irregular operation.Therefore, when each H bridges mould
Between block when input power imbalance, it is necessary to take certain measure to avoid H bridge module ovennodulations, to expand the operation of system
Range.
A kind of triple-frequency harmonics compensation policy exists in the prior art, the modulation degree of H bridge modules can be extended to 1.155,
H bridge module ovennodulations are avoided in a certain range.Meanwhile this method also ensure system run under unity power factor and
DC capacitor voltage fluctuation is smaller.However, when the uneven degree of input power between each H bridge modules is heavier, this method
The modulation degree of lower part H bridge modules may be more than 1.155, even if compensation triple-frequency harmonics, is not avoided that certain H bridges moulds still
Block ovennodulation.
Invention content
The present invention provides a kind of control method and controller of Cascade H bridge inverter, to expand the range of operation of system.
To achieve the above object, technical solution provided by the present application is as follows：
A kind of control method of Cascade H bridge inverter is applied in the controller of Cascade H bridge inverter, the Cascade H
The main circuit of bridge inverter includes multiple cascade H bridge modules；The control method of the Cascade H bridge inverter includes：
The modulation degree of each H bridge modules is calculated；
Correspondence and the modulation degree are preset according to the ovennodulation between modulation degree and modulation wave amplitude, was obtained
The amplitude limit modulating wave of modulation module；
According to the amplitude limit modulating wave of ovennodulation module and the modulation degree, the amplitude limit modulation of ovennodulation module is calculated
The first harmonic compensated needed for wave；
According to the first harmonic and the modulation degree, the modulating wave of normal module and its required compensation is calculated
Second harmonic；The second harmonic is identical as the first harmonic homogeneous, amplitude and opposite in phase；
It is generated according to the amplitude limit modulating wave of ovennodulation module, the modulating wave of normal module and phase-shifting carrier wave modulation strategy
The corresponding drive signal of each H bridge modules.
Preferably, the modulation degree that each H bridge modules are calculated, used formula are：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor whole H bridge modules
General power, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is of H bridge modules
Number.
Preferably, the ovennodulation according between modulation degree and modulation wave amplitude presets correspondence and the tune
System obtains the amplitude limit modulating wave of ovennodulation module, including：
Correspondence and the modulation degree are preset according to the ovennodulation, obtains the modulation wave amplitude of ovennodulation module；
The ovennodulation presets correspondenceWherein, S is H bridge modules
Modulation degree and fundamental voltage amplitude, M be ovennodulation module modulation wave amplitude；
According to the modulation wave amplitude of ovennodulation module, using formula
The amplitude limit modulating wave of ovennodulation module is calculated；Wherein,For the amplitude limit modulating wave of i-th of ovennodulation module, L is indicated
Positive and negative 1 slicing operation,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage, x is toning molding
The number of block.
Preferably, the amplitude limit modulating wave according to ovennodulation module and the modulation degree, are calculated ovennodulation module
Amplitude limit modulating wave needed for the first harmonic that compensates, used formula is：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,It is i-th
The amplitude limit modulating wave of a ovennodulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For network voltage
Phase angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
Preferably, described according to the first harmonic and the modulation degree, be calculated normal module modulating wave and its
The second harmonic of required compensation, including：
According to the first harmonic, using formulaNormal module is calculated to need to mend
The total harmonic voltage repaidWherein,First compensated needed for amplitude limit modulating wave for i-th of ovennodulation module is humorous
Wave, x are the number of ovennodulation module, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
The total harmonic voltage for needing to compensate according to normal moduleUsing formulaIt is humorous that second compensated needed for the modulating wave of normal module is calculated
Wave, wherein Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, Vdci(max)Allow the maximum of compensation by i-th of normal module
Positive voltage amplitude, VdciFor the DC capacitor voltage of i-th of normal module, SiFor the modulation degree and fundamental wave of i-th of normal module
Amplitude；Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, Vdcj(max)Allow the maximum positive electricity of compensation by j-th of normal module
Pressure amplitude value, VdcjFor the DC capacitor voltage of j-th of normal module, SjFor the modulation degree and fundamental wave width of j-th of normal module
Value；N-x is the number of normal module,The second harmonic compensated needed for modulating wave for i-th of normal module；
According to the second harmonic and the modulation degree compensated needed for the modulating wave of normal module, using formulaThe modulating wave of normal module is calculated；Wherein,It is
The modulating wave of i normal modules, SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage.
A kind of controller of Cascade H bridge inverter, with each cascade H bridges mould in the cascaded H-bridges converter main circuit
Block is connected；The controller of the Cascade H bridge inverter includes：
First computing unit, the modulation degree for each H bridge modules to be calculated；
Second computing unit, for according to modulation degree and modulation wave amplitude between ovennodulation preset correspondence and
The modulation degree obtains the amplitude limit modulating wave of ovennodulation module；
Third computing unit is used for the amplitude limit modulating wave according to ovennodulation module and the modulation degree, toning is calculated
The first harmonic compensated needed for the amplitude limit modulating wave of molding block；
4th computing unit, for according to the first harmonic and the modulation degree, the modulation of normal module to be calculated
Involve its required second harmonic compensated；The second harmonic is identical as the first harmonic homogeneous, amplitude and opposite in phase；
Signal generation unit, for the modulating wave and carrier wave according to the amplitude limit modulating wave of ovennodulation module, normal module
The corresponding drive signal of each H bridge modules of phase shift modulation strategy generating.
Preferably, when the modulation degree of each H bridge modules is calculated in first computing unit, used public affairs
Formula is：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor whole H bridge modules
General power, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is of H bridge modules
Number.
Preferably, second computing unit includes：
First module obtains ovennodulation module for presetting correspondence and the modulation degree according to the ovennodulation
Modulation wave amplitude；The ovennodulation presets correspondenceIts
In, S is the modulation degree and fundamental voltage amplitude of H bridge modules, and M is the modulation wave amplitude of ovennodulation module；
Second module, for the modulation wave amplitude according to ovennodulation module, using formulai
=1, the amplitude limit modulating wave of ovennodulation module is calculated in 2 ..., x；Wherein,For the amplitude limit of i-th of ovennodulation module
Modulating wave, L indicate positive and negative 1 slicing operation,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage,
X is the number of ovennodulation module.
Preferably, amplitude limit modulating wave and the modulation degree of the third computing unit according to ovennodulation module, calculates
The first harmonic compensated needed for amplitude limit modulating wave to ovennodulation module, used formula are：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,It is i-th
The amplitude limit modulating wave of a ovennodulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For network voltage phase
Parallactic angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
Preferably, the 4th computing unit includes：
Third module is used for according to the first harmonic, using formulaIt is calculated just
Norm block needs the total harmonic voltage compensatedWherein,For the amplitude limit modulating wave institute of i-th of ovennodulation module
The first harmonic that need to be compensated, x are the number of ovennodulation module, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
4th module, total harmonic voltage for needing to compensate according to normal moduleUsing formulaIt is humorous that second compensated needed for the modulating wave of normal module is calculated
Wave, wherein Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, Vdci(max)Allow the maximum of compensation by i-th of normal module
Positive voltage amplitude, VdciFor the DC capacitor voltage of i-th of normal module, SiFor the modulation degree and fundamental wave of i-th of normal module
Amplitude；Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, Vdcj(max)Allow the maximum positive electricity of compensation by j-th of normal module
Pressure amplitude value, VdcjFor the DC capacitor voltage of j-th of normal module, SjFor the modulation degree and fundamental wave width of j-th of normal module
Value；N-x is the number of normal module,The second harmonic compensated needed for modulating wave for i-th of normal module；
5th module, the second harmonic for being compensated needed for the modulating wave according to normal module and the modulation degree use
FormulaThe modulating wave of normal module is calculated；Wherein,
For the modulating wave of i-th of normal module, SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module,For electric network voltage phase
Angle,For the angle of total modulation voltage and network voltage.
The tune of each H bridge modules is calculated in the control method of Cascade H bridge inverter provided by the invention first
System；Then correspondence and the modulation degree are preset according to the ovennodulation between modulation degree and modulation wave amplitude, obtained
The amplitude limit modulating wave of modulation module；Amplitude limit modulating wave further according to ovennodulation module and the modulation degree, are calculated ovennodulation
The first harmonic compensated needed for the amplitude limit modulating wave of module；By the first harmonic and the modulation degree, can be calculated just
The second harmonic compensated needed for the modulating wave of norm block, and then the modulating wave of normal module can be calculated；Finally according to mistake
The amplitude limit modulating wave of modulation module, the modulating wave of normal module and phase-shifting carrier wave modulation strategy, you can generate each H bridges mould
The drive signal of block.Since it is used to compensate the second harmonic of the modulating wave of normal module, and for compensating ovennodulation module
The first harmonic of amplitude limit modulating wave, the two homogeneous, amplitude be identical and opposite in phase, therefore can ensure the friendship of Cascade H bridge module
It flows total output voltage and is free of the harmonic wave compensated, and compensation range can be expanded, and then the operation model of system can be expanded
It encloses.
Description of the drawings
Technical solution in order to illustrate the embodiments of the present invention more clearly or in the prior art, below will to embodiment or
Attached drawing needed to be used in the description of the prior art is briefly described, it should be apparent that, interior attached drawing, which is described below, is only
Some embodiments of the present invention, for those of ordinary skill in the art, without creative efforts, also
It can be obtain other attached drawings according to these attached drawings.
Fig. 1 is the system construction drawing for the Cascade H bridge inverter that the prior art provides；
Fig. 2 is the flow chart of the control method of Cascade H bridge inverter provided in an embodiment of the present invention；
Fig. 3 a are the normal modulation wave oscillograms of H bridge modules provided in an embodiment of the present invention；
Fig. 3 b are the amplitude limit modulating wave oscillograms of ovennodulation module provided in an embodiment of the present invention；
Fig. 3 c are that the ovennodulation between modulation degree provided in an embodiment of the present invention and modulation wave amplitude presets correspondence song
Line chart；
Fig. 4 is the partial process view of the control method of Cascade H bridge inverter provided in an embodiment of the present invention；
Fig. 5 a are the input power oscillograms for four H bridge modules that another embodiment of the present invention provides；
Fig. 5 b are the modulation degree oscillograms for four H bridge modules that another embodiment of the present invention provides；
Fig. 5 c are the modulating wave oscillograms for four H bridge modules that another embodiment of the present invention provides；
Fig. 5 d are the network voltage and power network current oscillogram that another embodiment of the present invention provides；
Fig. 5 e are the DC capacitor voltage oscillograms for first H bridge module that another embodiment of the present invention provides；
Fig. 5 f are the network voltage and power network current oscillogram that the prior art provides；
Fig. 6 is the structural schematic diagram of the controller of Cascade H bridge inverter provided in an embodiment of the present invention.
Specific implementation mode
Below in conjunction with the attached drawing in the embodiment of the present application, technical solutions in the embodiments of the present application carries out clear, complete
Site preparation describes, it is clear that described embodiments are only a part of embodiments of the present application, instead of all the embodiments.It is based on
Embodiment in the application, those of ordinary skill in the art obtained without creative efforts it is all its
His embodiment, shall fall in the protection scope of this application.
The present invention provides a kind of control method of Cascade H bridge inverter, to expand the range of operation of system.
The control method of Cascade H bridge inverter is applied in the controller of Cascade H bridge inverter；As shown in Figure 1, the grade
The main circuit for joining H bridge inverters includes multiple cascade H bridge modules；Referring to Fig. 2, the control method of the Cascade H bridge inverter
Including：
S101, the modulation degree that each H bridge modules are calculated；
The modulation degree of each H bridge modules is calculated, used formula is specially：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor whole H bridge modules
General power, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is of H bridge modules
Number.
It is calculated according to the modulation degree of each H bridge modules as a result, each H bridge modules can be divided into ovennodulation module and just
Norm block, wherein：H bridge module of the modulation degree less than or equal to 1 is normal module, and modulation degree is more than 1 and the H bridges less than or equal to 4/ π
Module is ovennodulation module.
For ovennodulation module, it is assumed that its modulating wave is sine wave as shown in Figure 3a, and the expression formula of the sine wave is f
(x)=Msin (x), M ＞, 1M modulate wave amplitude for it.
In order to make this ovennodulation module modulation wave amplitude be not more than 1, need to carry out slicing operation to it, so obtain as
Amplitude limit modulating wave shown in Fig. 3 b, the expression formula of the amplitude limit modulating wave are
NamelyWherein, θ=arcsin (1/M).
Then, Fourier expansion is carried out to function g (x), expression formula is：
Wherein,
Therefore, fundamental wave h (x) expression formulas of function g (x) are h (x)=a1cosx+b1Sinx=Ssin (x)；
Wherein,This formula namely modulation degree and modulation wave amplitude
Between ovennodulation preset correspondence；
It can be obtained by above formulaThat is, for the fundamental frequency sine wave that amplitude is M, it is carried out non-
After linear slicing operation, fundamental voltage amplitude is reduced to the relation curve of S, S and M referring to Fig. 3 c.
S102, correspondence and modulation degree are preset according to the ovennodulation between modulation degree and modulation wave amplitude, obtained
The amplitude limit modulating wave of modulation module；
Preferably, can correspondence and modulation degree be preset according to ovennodulation first, obtains the modulation of ovennodulation module
Wave amplitude；Then, further according to the modulation wave amplitude of ovennodulation module, the amplitude limit modulating wave of ovennodulation module is calculated.
Specifically, the ovennodulation presets correspondence as described above, in specific practical application, it can direct basisIt is calculated, S can also be drawn by relation curve shown in c according to fig. 3
With the one-to-one correspondence table of M, using tabling look-up to obtain corresponding M；It does not limit herein, depending on its concrete application environment,
Within the scope of protection of this application.
The amplitude limit modulating wave of ovennodulation module, used public affairs are calculated according to the modulating wave amplitude of ovennodulation module
Formula isAs shown in the above,Fundamental wave component amplitude etc.
In modulation degree Si；Wherein,For the amplitude limit modulating wave of i-th of ovennodulation module, L indicates positive and negative 1 slicing operation,For electricity
Net voltage phase angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
The amplitude limit modulation of ovennodulation module is calculated in S103, amplitude limit modulating wave and modulation degree according to ovennodulation module
The first harmonic compensated needed for wave；
Used formula is：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,It is i-th
The amplitude limit modulating wave of a ovennodulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For network voltage phase
Parallactic angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
S104, according to first harmonic and modulation degree, be calculated normal module modulating wave and its required compensation second
Harmonic wave；
Specifically, step S104 includes shown in Fig. 4：
S201, total harmonic voltage that normal module needs compensate is calculated according to first harmonic
Total harmonic voltage that ovennodulation module is compensatedFor：
In order to which the total output voltage for making each H bridge modules cascade exchange side is free of the harmonic voltage compensated, normal mode
Block needs the total harmonic voltage compensatedFor：
Namely
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module, x are ovennodulation
The number of module, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
S202, the total harmonic voltage for needing to compensate according to normal moduleThe modulating wave of normal module is calculated
The second harmonic of required compensation；
Used formula is：
Wherein, Vdci(max)The maximum positive voltage amplitude for allowing to compensate by i-th of normal module, calculation formula are
Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, VdciFor the DC capacitor voltage of i-th of normal module, SiJust for i-th
The modulation degree and fundamental voltage amplitude of norm block；Vdcj(max)Allow the maximum positive voltage amplitude of compensation by j-th of normal module,
Calculation formula is Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, VdcjFor the DC capacitor voltage of j-th of normal module,
SjFor the modulation degree and fundamental voltage amplitude of j-th of normal module；N-x is the number of normal module,For i-th normal module
Modulating wave needed for compensate second harmonic；
By above-mentioned calculating process, obtained second harmonic is identical as first harmonic homogeneous, amplitude and opposite in phase.
The second harmonic and modulation degree compensated needed for S203, the modulating wave according to normal module, is calculated normal module
Modulating wave；
Used formula is：
Wherein,For the modulating wave of i-th of normal module, SiFor the modulation degree and fundamental wave width of i-th of normal module
Value,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage.
S105, according to the amplitude limit modulating wave of ovennodulation module, the modulating wave of normal module and phase-shifting carrier wave modulation strategy
Generate the drive signal of each H bridge modules.
As shown in the above, as the modulation degree S of H bridge modulesiWhen in 1~4/ π, corresponding compensation system can be found
Number modulates wave amplitude Mi, it can be made to modulate wave amplitude MiNo more than 1.Therefore, the method can be the line of H bridge modules
Property modulation range is expanded to 4/ π.
The control method of Cascade H bridge inverter provided in this embodiment, since it is used to compensate the modulating wave of normal module
Second harmonic, the first harmonic with the amplitude limit modulating wave for compensating ovennodulation module, the two homogeneous, amplitude be identical and phase
Therefore position is on the contrary, can ensure that the total output voltage of exchange of Cascade H bridge module is free of the harmonic wave compensated, and can expand
Compensation range, and then the range of operation of system can be expanded.
It is illustrated by taking four cascade systems of H bridge modules as an example, it is assumed that the peak value that power grid presses is 100V, four H bridges
The photovoltaic module peak power output of module prime is 260W, then：
When system is initially run, the intensity of illumination of four photovoltaic modulies is respectively：1000W/m2、 1000W/m2、
850W/m2 and 700W/m2；When t=0.5s, the intensity of illumination of third and fourth photovoltaic module become respectively 350W/m2 and
The input power (P1~P4) of 400W/m2, four H bridges are as shown in Figure 5 a.
The input power of system is uneven, and first and second H bridge modules are since input power is compared with conference ovennodulation, and four
The modulation degree (S1~S4) of a H bridge modules is as shown in Figure 5 b.
According to the control method for the Cascade H bridge inverter that above-described embodiment is proposed, the modulating wave of four H bridge modules
(m1~m4) will be as shown in Figure 5 c, network voltage vgWith power network current igAs fig 5d, DC capacitor voltage VdclSuch as Fig. 5 e
Shown, the difference Δ u of upper and lower amplitude becomes 0.8V from 1V.
As can be seen that the waveform of power network current is preferable, power factor PF=1, although due to module imbalance degree
Increase, the waveform of phase-shifting carrier wave modulation strategy synthesis can be undesirable, and two times of switching frequency harmonic components increase, and lead to its THD
(Total Harmonic Distortion, total harmonic distortion) increase, but compared with the prior art employed in three times
Harmonic compensation strategy, referring to the oscillogram of network voltage and power network current shown in Fig. 5 f, it can be found that due to first and second
The modulation degree of a H bridges was about 1.2 (being more than 1.155), and the THD of power network current reaches 8.36%, inverse much larger than this cascaded H-bridges
Become the control method of device can be realized 3.49%.
Therefore, the control method of this Cascade H bridge inverter compared with the prior art in triple-frequency harmonics compensation policy,
Under conditions of not dropping volume operation, the maximum linear modulation range of each H bridge modules can be expanded to 4/ π；Also, work as H bridge moulds
When block power is uneven in a certain range (i.e. modulation degree is between 1~4/ π), THD is relatively low, DC voltage fluctuation is smaller,
It can realize unity power factor, and then can ensure system normal operation.
It is worth noting that there is also a kind of modulation of low-frequency square-wave and high frequency sinusoidal pulse width tune in the prior art
Make hybrid control strategy, a kind of modified MPPT (Maximum Power Point Tracking, the maximum power point being combined
Tracking) control strategy and a kind of the control of reactive power compensating strategy；Specifically：
The hybrid control strategy is to improve H bridge DC side voltages the characteristics of utilizing square wave maximum percentage modulation to be 4/ π and utilize
Rate.However, the strategy is to distribute each H bridge modules according to system running state to carry out charge or discharge, it is not to DC side
Capacitance voltage accurately controls, therefore the fluctuation of DC capacitor voltage can be caused larger；The fluctuation of DC voltage makes light
It lies prostrate component and deviates maximum power point operation, reduce the average generated energy of photovoltaic module.Further, since hybrid modulation stratgy is straight
The capacitance voltage control for flowing side is that have static difference, therefore MPPT is less efficient.
Modified MPPT control strategies are moved back when intermodule unbalanced power by the H modules for keeping output power larger
Go out maximum power point operation, operates in the voltage source region of I-V characteristic curve, the input power between balance module is carried out with this.So
And the strategy can reduce the generated energy of system.
The control of reactive power compensating strategy, by compensating certain reactive power, when the output power of each H bridge modules is tight
Weight can still ensure that all H bridge modules all will not ovennodulation when uneven.However, the strategy can reduce the power of inverter
Factor.
The advantage and disadvantage of the various prior arts are summarized, content shown in table 1 can be obtained：
1 prior art advantage and disadvantage of table are summarized
As shown in the above, hybrid modulation stratgy DC capacitor voltage irregular fluctuation, influence system generated energy and
MPPT efficiency, thus it is unsuitable applied to field of photovoltaic power generation.Although modified MPPT control strategies largely can
The input power of H bridge modules is enough balanced, but drop volume is needed to run, reduces system generated energy.The control of reactive power compensating strategy can
H bridge module ovennodulations are largely avoided, but the power factor of system can decline, and may limit its application.Three times
Although harmonic compensation strategy has been compromised the advantage and disadvantage of above several algorithms, it can expand the operation of system to a certain extent
Range, while ensureing that DC voltage fluctuation is smaller and system unit power factor is run, also, this method is maximum
Linear modulation range is expanded to 1.155 from 1, and the uneven scene coped with is limited.
And the control method of Cascade H bridge inverter provided in this embodiment, due to being based on PWM (Pulse Width
Modulation, pulse width modulation), it is relatively high so to may make that DC capacitor voltage fluctuates smaller and MPPT efficiency.
Also, by giving ovennodulation module to inject a certain amount of harmonic wave, it can be reduced and modulate wave amplitude, avoid ovennodulation；In addition,
This method also by compensation to ovennodulation module with normal module homogeneous, amplitude identical and opposite in phase harmonic wave, and then not
Under conditions of the operation of drop volume, the maximum linear modulation range of each H bridge modules is expanded to 4/ π, while can ensure system list
Position power factor operation, is conducive to application.
Another embodiment of the present invention additionally provides a kind of controller of Cascade H bridge inverter, with Cascade H bridge inverter master
Each cascade H bridge modules are connected in circuit；Controller referring to Fig. 6, the Cascade H bridge inverter includes：
First computing unit 101, the modulation degree for each H bridge modules to be calculated；
Second computing unit 102, for according to modulation degree and modulation wave amplitude between ovennodulation preset correspondence with
And modulation degree, obtain the amplitude limit modulating wave of ovennodulation module；
Toning is calculated for the amplitude limit modulating wave and modulation degree according to ovennodulation module in third computing unit 103
The first harmonic compensated needed for the amplitude limit modulating wave of molding block；
4th computing unit 104, for according to first harmonic and modulation degree, the modulation that normal module is calculated to involve
The second harmonic compensated needed for it；Second harmonic is identical as first harmonic homogeneous, amplitude and opposite in phase；
Signal generation unit 105, for according to the amplitude limit modulating wave of ovennodulation module, the modulating wave of normal module and
Phase-shifting carrier wave modulation strategy generates the drive signal of each H bridge modules.
Preferably, when the modulation degree of each H bridge modules is calculated in the first computing unit 101, used formula is：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor whole H bridge modules
General power, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is of H bridge modules
Number.
Preferably, the second computing unit 102 includes：
First module obtains the amplitude limit tune of ovennodulation module for presetting correspondence and modulation degree according to ovennodulation
Wave amplitude processed；Ovennodulation presets correspondenceWherein, S is H bridges
The modulation degree and fundamental voltage amplitude of module, M are the modulation wave amplitude of H bridge modules；
Second module, for modulating wave amplitude according to the amplitude limit of ovennodulation module, using formula
The amplitude limit modulating wave of ovennodulation module is calculated in i=1,2 ..., x；Wherein,For the amplitude limit of i-th of ovennodulation module
Modulating wave, L indicate positive and negative 1 slicing operation,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage,
X is the number of ovennodulation module.
Preferably, third computing unit 103 was calculated according to the amplitude limit modulating wave and modulation degree of ovennodulation module
The first harmonic compensated needed for the amplitude limit modulating wave of modulation module, used formula are：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,It is i-th
The amplitude limit modulating wave of a ovennodulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For network voltage
Phase angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
Preferably, the 4th computing unit 104 includes：
Third module is used for according to first harmonic, using formulaNormal mode is calculated
Block needs the total harmonic voltage compensatedWherein,It is compensated needed for amplitude limit modulating wave for i-th of ovennodulation module
First harmonic, x be ovennodulation module number, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
4th module, total harmonic voltage for needing to compensate according to normal moduleUsing formulaIt is humorous that second compensated needed for the modulating wave of normal module is calculated
Wave, wherein Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, Vdci(max)For
I-th of normal module allows the maximum positive voltage amplitude of compensation, VdciFor the DC capacitor voltage of i-th of normal module,
SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module, Vdcj(max)The maximum of compensation is being allowed just by j-th of normal module
Voltage magnitude, VdcjFor the DC capacitor voltage of j-th of normal module, SjFor the modulation degree and fundamental wave of j-th of normal module
Amplitude, n-x are the number of normal module,The second harmonic compensated needed for modulating wave for i-th of normal module；
5th module, the second harmonic for being compensated needed for the modulating wave according to normal module and modulation degree, using formulaThe modulating wave of normal module is calculated；Wherein,For
The modulating wave of i-th of normal module, SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage.
Remaining principle is same as the previously described embodiments, no longer repeats one by one herein.
Each embodiment is described by the way of progressive in the present invention, the highlights of each of the examples are with other
The difference of embodiment, just to refer each other for identical similar portion between each embodiment.For device disclosed in embodiment
For, since it is corresponded to the methods disclosed in the examples, so description is fairly simple, related place is referring to method part
Explanation.
The above described is only a preferred embodiment of the present invention, being not intended to limit the present invention in any form.
Although the present invention has been disclosed as a preferred embodiment, however, it is not intended to limit the invention.Any technology for being familiar with this field
Personnel, without departing from the scope of the technical proposal of the invention, all using the methods and technical content of the disclosure above to this hair
Bright technical solution makes many possible changes and modifications, or is revised as the equivalent embodiment of equivalent variations.Therefore, it is every not
Be detached from technical solution of the present invention content, according to the technical essence of the invention it is made to the above embodiment it is any it is simple modification,
Equivalent variations and modification, still fall within technical solution of the present invention protection in the range of.
Claims (10)
1. a kind of control method of Cascade H bridge inverter, which is characterized in that be applied in the controller of Cascade H bridge inverter, institute
The main circuit for stating Cascade H bridge inverter includes multiple cascade H bridge modules；The control method packet of the Cascade H bridge inverter
It includes：
The modulation degree of each H bridge modules is calculated；
Correspondence and the modulation degree are preset according to the ovennodulation between modulation degree and modulation wave amplitude, obtains toning molding
The amplitude limit modulating wave of block；
According to the amplitude limit modulating wave of ovennodulation module and the modulation degree, it is calculated needed for the amplitude limit modulating wave of ovennodulation module
The first harmonic of compensation；
According to the first harmonic and the modulation degree, be calculated normal module modulating wave and its required compensation it is second humorous
Wave；The second harmonic is identical as the first harmonic homogeneous, amplitude and opposite in phase；
Each H is generated according to the amplitude limit modulating wave of ovennodulation module, the modulating wave of normal module and phase-shifting carrier wave modulation strategy
The corresponding drive signal of bridge module.
2. the control method of Cascade H bridge inverter according to claim 1, which is characterized in that it is described be calculated it is each
The modulation degree of the H bridge modules, used formula are：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor the total work of whole H bridge modules
Rate, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is the number of H bridge modules.
3. the control method of Cascade H bridge inverter according to claim 1, which is characterized in that it is described according to modulation degree with
The ovennodulation modulated between wave amplitude presets correspondence and the modulation degree, obtains the amplitude limit modulating wave of ovennodulation module,
Including：
Correspondence and the modulation degree are preset according to the ovennodulation, obtains the modulation wave amplitude of ovennodulation module；It is described
Ovennodulation presets correspondenceWherein, S is the modulation of H bridge modules
Degree and fundamental voltage amplitude, M are the modulation wave amplitude of ovennodulation module；
According to the modulation wave amplitude of ovennodulation module, using formulaIt calculates
Obtain the amplitude limit modulating wave of ovennodulation module；Wherein,For the amplitude limit modulating wave of i-th of ovennodulation module, L indicates positive and negative 1
Slicing operation,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage, x is of ovennodulation module
Number.
4. the control method of Cascade H bridge inverter according to claim 1, which is characterized in that described according to toning molding
The first harmonic compensated needed for the amplitude limit modulating wave of ovennodulation module is calculated in the amplitude limit modulating wave of block and the modulation degree,
Used formula is：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,For i-th of mistake
The amplitude limit modulating wave of modulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For electric network voltage phase
Angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
5. the control method of Cascade H bridge inverter according to claim 1, which is characterized in that described according to described first
The modulating wave of normal module and its second harmonic of required compensation is calculated in harmonic wave and the modulation degree, including：
According to the first harmonic, using formulaBe calculated normal module needs compensate it is total
Harmonic voltageWherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module, x are
The number of ovennodulation module, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
The total harmonic voltage for needing to compensate according to normal moduleUsing formulaIt is humorous that second compensated needed for the modulating wave of normal module is calculated
Wave, wherein Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, Vdci(max)The maximum of compensation is being allowed just by i-th of normal module
Voltage magnitude, VdciFor the DC capacitor voltage of i-th of normal module, SiFor the modulation degree and fundamental wave width of i-th of normal module
Value；Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, Vdcj(max)Allow the maximum positive voltage of compensation by j-th of normal module
Amplitude, VdcjFor the DC capacitor voltage of j-th of normal module, SjFor the modulation degree and fundamental voltage amplitude of j-th of normal module；
N-x is the number of normal module,The second harmonic compensated needed for modulating wave for i-th of normal module；
According to the second harmonic and the modulation degree compensated needed for the modulating wave of normal module, using formulaThe modulating wave of normal module is calculated；Wherein,It is i-th
The modulating wave of a normal module, SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module,For electric network voltage phase angle,For
The angle of total modulation voltage and network voltage.
6. a kind of controller of Cascade H bridge inverter, which is characterized in that with each grade in the cascaded H-bridges converter main circuit
The H bridge modules of connection are connected；The controller of the Cascade H bridge inverter includes：
First computing unit, the modulation degree for each H bridge modules to be calculated；
Second computing unit, for presetting correspondence and the tune according to the ovennodulation between modulation degree and modulation wave amplitude
System obtains the amplitude limit modulating wave of ovennodulation module；
Third computing unit is used for the amplitude limit modulating wave according to ovennodulation module and the modulation degree, toning molding is calculated
The first harmonic compensated needed for the amplitude limit modulating wave of block；
4th computing unit, for according to the first harmonic and the modulation degree, the modulation that normal module is calculated to involve
The second harmonic compensated needed for it；The second harmonic is identical as the first harmonic homogeneous, amplitude and opposite in phase；
Signal generation unit, for the modulating wave and phase-shifting carrier wave according to the amplitude limit modulating wave of ovennodulation module, normal module
Modulation strategy generates the corresponding drive signal of each H bridge modules.
7. the controller of Cascade H bridge inverter according to claim 6, which is characterized in that the first computing unit meter
When calculation obtains the modulation degree of each H bridge modules, used formula is：
Wherein, SiFor the modulation degree of i-th of H bridge module, PiFor the power of i-th of H bridge module, PTFor the total work of whole H bridge modules
Rate, VrFor the amplitude of total modulation voltage, VdciFor the DC capacitor voltage of i-th of H bridge module, n is the number of H bridge modules.
8. the controller of Cascade H bridge inverter according to claim 6, which is characterized in that the second computing unit packet
It includes：
First module obtains the tune of ovennodulation module for presetting correspondence and the modulation degree according to the ovennodulation
Wave amplitude processed；The ovennodulation presets correspondenceWherein, S is
The modulation degree and fundamental voltage amplitude of H bridge modules, M are the modulation wave amplitude of ovennodulation module；
Second module, for the modulation wave amplitude according to ovennodulation module, using formulaThe amplitude limit modulating wave of ovennodulation module is calculated；Wherein,For
The amplitude limit modulating wave of i-th of ovennodulation module, L indicate positive and negative 1 slicing operation,For electric network voltage phase angle,Always to modulate
The angle of voltage and network voltage, x are the number of ovennodulation module.
9. the controller of Cascade H bridge inverter according to claim 6, which is characterized in that the third computing unit root
Compensation needed for the amplitude limit modulating wave of ovennodulation module is calculated in amplitude limit modulating wave according to ovennodulation module and the modulation degree
First harmonic, used formula are：
Wherein,The first harmonic compensated needed for amplitude limit modulating wave for i-th of ovennodulation module,For i-th of mistake
The amplitude limit modulating wave of modulation module, SiFor the modulation degree and fundamental voltage amplitude of i-th of ovennodulation module,For electric network voltage phase angle,For the angle of total modulation voltage and network voltage, x is the number of ovennodulation module.
10. the controller of Cascade H bridge inverter according to claim 6, which is characterized in that the 4th computing unit packet
It includes：
Third module is used for according to the first harmonic, using formulaNormal module is calculated
Need the total harmonic voltage compensatedWherein,It is compensated needed for amplitude limit modulating wave for i-th of ovennodulation module
First harmonic, x are the number of ovennodulation module, VdciFor the DC capacitor voltage of i-th of ovennodulation module；
4th module, total harmonic voltage for needing to compensate according to normal moduleUsing formulaIt is humorous that second compensated needed for the modulating wave of normal module is calculated
Wave, wherein Vdci(max)=(1-Si)Vdci, i=1 ..., n-x, Vdci(max)The maximum of compensation is being allowed just by i-th of normal module
Voltage magnitude, VdciFor the DC capacitor voltage of i-th of normal module, SiFor the modulation degree and fundamental wave width of i-th of normal module
Value；Vdcj(max)=(1-Sj)Vdcj, j=1 ..., n-x, Vdcj(max)Allow the maximum positive voltage of compensation by j-th of normal module
Amplitude, VdcjFor the DC capacitor voltage of j-th of normal module, SjFor the modulation degree and fundamental voltage amplitude of j-th of normal module；
N-x is the number of normal module,The second harmonic compensated needed for modulating wave for i-th of normal module；
5th module, the second harmonic for being compensated needed for the modulating wave according to normal module and the modulation degree, using formulaThe modulating wave of normal module is calculated；Wherein,It is
The modulating wave of i normal modules, SiFor the modulation degree and fundamental voltage amplitude of i-th of normal module,For electric network voltage phase angle,
For the angle of total modulation voltage and network voltage.
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