CN110581666B - Six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method - Google Patents

Six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method Download PDF

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CN110581666B
CN110581666B CN201911049840.6A CN201911049840A CN110581666B CN 110581666 B CN110581666 B CN 110581666B CN 201911049840 A CN201911049840 A CN 201911049840A CN 110581666 B CN110581666 B CN 110581666B
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CN110581666A (en
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邢星
于占东
付莹
于震
梁洪晶
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Bohai University
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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
    • 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
    • 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
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • 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
    • H02M7/4815—Resonant converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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Abstract

A six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method belongs to the technical field of inverters and aims to solve the problems that an existing series resonance type medium-frequency induction heating inversion system with a low quality factor has harmonic components, heat loss of the system can be increased, and electric efficiency of a heating system is reduced. The inversion control method adopts six-pulse wave to control the inverter power supply, eliminates 3-order harmonic waves and 5-order harmonic waves of the inverter system by adjusting the duty ratio or the phase of the six-pulse wave, and adjusts the amplitude of fundamental wave output to realize the output of the inverter power supply for reducing harmonic components. The inversion circuit of the inversion control method adopts a SiC power device, the inversion bridge comprises an A-phase bridge arm and a B-phase bridge arm, the two bridge arms are respectively composed of IGBT modules, and each IGBT module comprises two IGBT units. The inverter is used for an induction heating inverter system.

Description

Six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method
Technical Field
The invention relates to a six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method, and belongs to the technical field of inverters.
Background
The induction heating inverter system is mostly a square wave inverter. According to the Fourier transform, the square wave contains a large number of higher harmonic components, and the energy of the harmonics cannot be applied to heating work and can only be absorbed through the resonant tank circuit.
Although the load series resonance LCR circuit can filter out load higher harmonics, the series resonance filtering function only works when the quality factor of the resonance system is high, and generally, in order to meet the requirement of frequency modulation and power adjustment of an induction heating power supply, the quality factor of the system resonance circuit is not too high (the Q value is less than 5), and the intermediate frequency power supply is particularly suitable. Therefore, the higher harmonics of the square wave inverter induction heating system with low quality factor can increase the heat loss of the system and reduce the electric efficiency of the heating system.
The essence of the specified harmonic cancellation pulse width modulation technique is to remove specified higher order components, which are commonly used in the field of motor traction control, but the application of SHEPWM technique in the field of induction heating has not been reported. This is because induction heating has its particularity compared with electric dragging, which is embodied in several aspects: 1. the frequency band of the fundamental wave is different: the fundamental frequency of the motor inverter system is usually below the power frequency, namely 5 Hz-50 Hz; usually, the fundamental frequency of the medium-frequency induction heating system is between 2kHz and 10kHz and is almost the carrier frequency of a motor inverter system, and the SHEPWM technology is difficult to realize by a traditional method under high frequency; 2. the motor system is 3 phases: the induction heating is a single-phase system, and the 3-phase system has no 3n harmonic component in a phase equilibrium state, but the single-phase system has no such characteristic; 3. the voltage waveforms are different: the frequency of a motor dragging system is low, the period is long, and the voltage waveform on the motor armature is a high-frequency pulse width modulation density wave; the traditional induction heating inversion voltage waveform is a square wave, the frequency is high, and the period is short, so that the number of appointed eliminated harmonics is not too much, otherwise, the realization is difficult; 4. the filtering modes are different: the motor drive system directly inputs voltage waveform into the armature coil, and an electromechanical coupling system formed by a stator and a rotor is utilized for filtering; while the induction heating system utilizes resonant tank circuits in series or parallel for filtering.
Therefore, the harmonic component of the series resonance type intermediate frequency induction heating inverter system with low quality factor can increase the heat loss of the system and reduce the electric efficiency of the heating system.
Disclosure of Invention
The invention aims to solve the problems that the existing series resonance type medium-frequency induction heating inversion system with low quality factor has harmonic components, the heat loss of the system can be increased, and the electric efficiency of the heating system is reduced, and provides a six-pulse-wave series resonance type medium-frequency induction heating inversion control method with low quality factor.
The inversion control method adopts six-pulse wave to control the inverter power supply, eliminates 3-order harmonic waves and 5-order harmonic waves of the inverter system by adjusting the duty ratio or the phase of the six-pulse wave, and adjusts the amplitude of fundamental wave output to realize the output of the inverter power supply for reducing harmonic components.
Preferably, the specific method for eliminating the 3 rd harmonic and the 5 th harmonic of the inverter system by adjusting the phase of the six-pulse wave is as follows:
taking 1/4 periods of the half-cycle three-pulse wave as the origin of the time coordinate, the fourier transform of the voltage pulse wave is expressed as:
Figure BDA0002254098820000021
wherein: k represents the harmonic number, ω1Represents the fundamental angular frequency;
amplitude U of harmonic componentkmComprises the following steps:
Figure BDA0002254098820000022
will UkmAnd (3) expanding an expression:
Figure BDA0002254098820000023
wherein, UDCRepresenting the inverter dc bus voltage;
according to the symmetry of the rectangular wave, the inversion system only has odd harmonics, so k is odd, namely k is 1,3,5, …;
thus:
Figure BDA0002254098820000031
setting a fundamental wave amplitude coefficient A, and eliminating 3-order and 5-order harmonics, namely:
let A be [ sina ]1-sina2+sina3]Then the fundamental amplitude coefficient satisfies:
Figure BDA0002254098820000032
wherein: a e (0.6,0.84), U1mRepresents the amplitude of the 1 st harmonic;
solving an transcendental equation, and removing 3 th harmonic and 5 th harmonic:
Figure BDA0002254098820000033
Figure BDA0002254098820000034
Figure BDA0002254098820000035
a1、a2and a3Is the solution of the transcendental equation,
U3mrepresents the 3 th harmonic amplitude, U5mRepresenting the 5 th harmonic amplitude.
Preferably, the inverter circuit of the inverter control method adopts SiC power devices, the inverter bridge comprises an A-phase bridge arm and a B-phase bridge arm, the two bridge arms are respectively composed of IGBT modules, each IGBT module comprises two IGBT units, the switching devices of the two IGBT units of the A-phase bridge arm are VT1 and VT3, and the switching devices of the two IGBT units of the B-phase bridge arm are VT2 and VT 4;
the implementation method of the six-pulse wave comprises the following steps:
t is a symmetrical triangular wave with a period of 2 pi and a triangular wave center line
Figure BDA0002254098820000041
The up-down symmetric distribution has six comparative values, which are from top to bottom in sequence:
Figure BDA0002254098820000042
α1、α2、α3respectively representing three comparison value variables;
six comparison values are compared with the triangular wave:
for comparison values
Figure BDA0002254098820000043
And
Figure BDA0002254098820000044
when the amplitude of the triangular wave is larger than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are respectively N1、N2And N3Then to N2And N3Performing XOR operation, and comparing the result with N1Performing OR operation to obtain
Figure BDA0002254098820000045
The obtained waveforms are the driving logics of a switching device VT1 of an A-phase bridge arm and a switching device VT4 of a B-phase bridge arm;
for comparison values
Figure BDA0002254098820000046
And
Figure BDA0002254098820000047
when the amplitude of the triangular wave is less than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are B1、B2And B3Then to B2And B3Performing XOR operation, and comparing the result with B1Performing OR operation to obtain
Figure BDA0002254098820000048
The obtained waveform isThe driving logics of a switching device VT2 of the A-phase bridge arm and a switching device VT3 of the B-phase bridge arm;
when adopting
Figure BDA0002254098820000049
The VT1 and the VT4 are driven,
Figure BDA00022540988200000410
drive VT2 and element VT3, inverter output UABIs a six-pulse wave.
Preferably, the comparison value variable α1、α2、α3The acquisition method comprises the following steps:
solution a from transcendental equation1、a2And a3Finding alpha1、α2、α3：
Figure BDA00022540988200000411
Preferably, the method for acquiring the six comparison values comprises the following steps:
are respectively according to a1、a2And a3Finding alpha1、α2And alpha3Will be alpha1、α2And alpha3The values of (a) are stored in a processor, and then six comparison values are calculated according to a set inversion frequency f:
Figure BDA00022540988200000412
Figure BDA0002254098820000051
Figure BDA0002254098820000052
Figure BDA0002254098820000053
Figure BDA0002254098820000054
Figure BDA0002254098820000055
the invention has the advantages that: the inversion method provided by the invention is applied to a medium-frequency induction heating power supply, the inversion frequency is 2 kHz-10 kHz, the quality factor of an inversion tank circuit is not high due to low inversion frequency, the power supply is a low-quality-factor inversion power supply, and the quality factor is not more than 5, so that the component of high-order harmonic waves in a resonance tank circuit is high. Therefore, a designated harmonic elimination pulse width modulation technology (SHEPWM) is adopted to eliminate low-order harmonics with larger energy on a frequency spectrum, and because the energy of higher-order harmonics is smaller, the resonant tank circuit has larger impedance to the higher-order harmonics, so that the higher-order harmonics are easy to filter, and meanwhile, the heating brought to the resonant tank circuit is smaller and can be ignored.
Has the advantages that:
1. harmonic components of an induction heating inversion system are reduced, and the efficiency of an induction heating power supply is improved;
2. the amplitude of the fundamental wave can be adjusted, so that the power of the inverter system is controlled, and impedance matching and power control are conveniently carried out.
Drawings
FIG. 1 is a schematic block diagram of a six-pulse-wave low-Q series resonant medium-frequency induction heating inverter system;
FIG. 2 is a waveform diagram of a control method for eliminating the 3 rd harmonic and the 5 th harmonic of an inverter system by adjusting the phase of a six-pulse wave;
FIG. 3 is a timing diagram of a six pulse wave inversion;
fig. 4 is a graph of the relative intensity effect for the 24 fundamental amplitude coefficients in table 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
The first embodiment is as follows: the present embodiment will be described with reference to fig. 1, and the six-pulse-wave low-quality-factor series resonance type intermediate frequency induction heating inversion control method according to the present embodiment controls the inverter power supply using the six-pulse wave, and by adjusting the duty ratio or phase of the six-pulse wave, eliminates the 3 rd order harmonic and the 5 th order harmonic of the inverter system, and adjusts the amplitude of the fundamental wave output, thereby realizing output of the inverter power supply with reduced harmonic components.
In the present embodiment, as shown in fig. 1, the six-pulse-wave low-quality-factor series resonance type intermediate frequency induction heating inverter system specifically includes: the device comprises a three-phase bridge type uncontrolled rectifier, a Buck chopper voltage regulating unit based on an IGBT, a single-phase bridge type inversion unit based on a SiC power device, a resonant load circuit (comprising an electric heating coil, an isolation transformer, a compensation capacitor and the like) and the like.
Further, as shown in fig. 2, a rectangular wave group (solid line) is a voltage pulse waveform in one inversion period, the rectangular wave group is a half-period three-pulse wave, and a sine wave (broken line) is a fundamental component of the inversion waveform.
The specific method for eliminating the 3 rd harmonic and the 5 th harmonic of the inverter system by adjusting the phase of the six-pulse wave comprises the following steps:
taking 1/4 periods of the half-cycle three-pulse wave as the origin of the time coordinate, the fourier transform of the voltage pulse wave is expressed as:
Figure BDA0002254098820000061
wherein: k represents the harmonic number, ω1Represents the fundamental angular frequency;
amplitude U of harmonic componentkmComprises the following steps:
Figure BDA0002254098820000062
will UkmAnd (3) expanding an expression:
Figure BDA0002254098820000063
wherein, UDCRepresenting the inverter dc bus voltage;
according to the symmetry of the rectangular wave, the inversion system only has odd harmonics, so k is odd, namely k is 1,3,5, …;
thus:
Figure BDA0002254098820000071
setting a fundamental wave amplitude coefficient A, and eliminating 3-order and 5-order harmonics, namely:
let A be [ sina ]1-sina2+sina3]Then the fundamental amplitude coefficient satisfies:
Figure BDA0002254098820000072
wherein: a e (0.6,0.84), U1mRepresents the amplitude of the 1 st harmonic;
solving an transcendental equation, and removing 3 th harmonic and 5 th harmonic:
Figure BDA0002254098820000073
Figure BDA0002254098820000074
Figure BDA0002254098820000075
a1、a2and a3Is the solution of the transcendental equation,
U3mrepresents the 3 th harmonic amplitude, U5mRepresenting the 5 th harmonic amplitude.
In this embodiment, the solution a of the transcendental equation1、a2And a3The three angle components are adopted, and the distance between the three angles is not too small, so that the switching frequency of the power device is not too high and is difficult to realize. Also, the value of the fundamental amplitude coefficient a should not be too low from the viewpoint of the inversion efficiency, and therefore, the fundamental amplitude system is usually set to a e (0.6, 0.83). If 0.83 is taken as the fundamental voltage coefficient at the time of full power output, the system power adjustment range is 0.832÷0.62At 0.5, the power adjustment range is about 50%.
In the embodiment, 3-order and 5-order harmonics are removed, meanwhile, the amplitude of the fundamental wave can be adjusted according to needs, and the purpose of power adjustment can be achieved, but power adjustment gears need to be preset, solutions of transcendental equations under different fundamental wave amplitude constraints are solved in advance and stored in the processor. The solution of the transcendental equation can be realized by off-line calculation of special calculation software. The solutions of the transcendental equation under different fundamental amplitude coefficients are shown in the table:
TABLE 1 solution of transcendental equation for different fundamental amplitude coefficients
Figure BDA0002254098820000081
Figure BDA0002254098820000091
Wherein: when A is 0.84, a3Has exceeded 90And, therefore, should discard the set of parameters.
Still further, as shown in fig. 3, a timing diagram of the inversion of six-pulse wave is shown.
The inverter circuit of the inversion control method adopts SiC power devices, the inverter bridge comprises an A-phase bridge arm and a B-phase bridge arm, the two bridge arms are respectively composed of IGBT modules, each IGBT module comprises two IGBT units, the switching devices of the two IGBT units of the A-phase bridge arm are VT1 and VT3, and the switching devices of the two IGBT units of the B-phase bridge arm are VT2 and VT 4;
the implementation method of the six-pulse wave comprises the following steps:
t is a symmetrical triangular wave with a period of 2 pi and a triangular wave center line
Figure BDA0002254098820000092
The up-down symmetric distribution has six comparative values, which are from top to bottom in sequence:
Figure BDA0002254098820000093
α1、α2、α3respectively representing three comparison value variables;
six comparison values are compared with the triangular wave:
for comparison values
Figure BDA0002254098820000094
And
Figure BDA0002254098820000095
when the amplitude of the triangular wave is larger than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are respectively N1、N2And N3Then to N2And N3Performing XOR operation, and comparing the result with N1Performing OR operation to obtain
Figure BDA0002254098820000096
The obtained waveforms are the driving logics of a switching device VT1 of an A-phase bridge arm and a switching device VT4 of a B-phase bridge arm;
to ratioComparison value
Figure BDA0002254098820000097
And
Figure BDA0002254098820000098
when the amplitude of the triangular wave is less than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are B1、B2And B3Then to B2And B3Performing XOR operation, and comparing the result with B1Performing OR operation to obtain
Figure BDA0002254098820000099
The obtained waveforms are the driving logics of a switching device VT2 of an A-phase bridge arm and a switching device VT3 of a B-phase bridge arm;
when adopting
Figure BDA0002254098820000101
The VT1 and the VT4 are driven,
Figure BDA0002254098820000102
drive VT2 and element VT3, inverter output UABIs a six-pulse wave.
In the present embodiment, α is determined by calculation3The values should be noted in relation to the dead time, and should not be too small. If α is3If the value of (A) is too small, the upper and lower switching tubes of the same bridge arm are simultaneously conducted. The dead time of the upper and lower bridge arms is related to the inversion period and the characteristics of a switching device, the dead time is not less than 1 mu s for a SiC switching tube, and the dead time is between 2 and 3 mu s for an IGBT switching tube.
Still further, the comparison value variable α1、α2、α3The acquisition method comprises the following steps:
solution a from transcendental equation1、a2And a3Finding alpha1、α2、α3：
Figure BDA0002254098820000103
Still further, the method for acquiring the six comparison values comprises the following steps:
are respectively according to a1、a2And a3Finding alpha1、α2And alpha3Will be alpha1、α2And alpha3The values of (a) are stored in a processor, and then six comparison values are calculated according to a set inversion frequency f:
Figure BDA0002254098820000104
Figure BDA0002254098820000105
Figure BDA0002254098820000106
Figure BDA0002254098820000107
Figure BDA0002254098820000108
Figure BDA0002254098820000109
in the invention, six pulse waves are adopted, and 3-order and 5-order harmonics which possibly generate heat loss in an inverter system are eliminated by adjusting the duty ratio or the phase of the pulse waves to eliminate designated harmonics, so that the heat loss caused by the harmonics of a resonant tank circuit of the medium-frequency power supply is reduced, and the improvement of the overall efficiency of the heating power supply is finally realized.
In the invention, a calculation method for adjusting the duty ratio or the phase of the three-pulse wave is provided, and an transcendental equation to be solved is provided. The transcendental equation, although not shown as an analytical solution, may be numerically calculated by a computer to obtain a numerical solution. In practice, the calculation can be performed off-line, and the calculation result can be stored in the inverter system processor.
In the invention, the adjustment of the system power is carried out by adjusting the amplitude coefficient of the fundamental wave, and different amplitude coefficients of the fundamental wave and values of corresponding phase angles are provided. The power regulating method provided by the invention can enable the inverter system to be in the medium frequency range, eliminate 3-order and 5-order harmonic waves and enable the power regulating range to reach 50%.
In the invention, a six-pulse wave implementation mode is provided, namely, a value obtained by solving an transcendental equation is converted into 6 comparison values, the comparison values are compared with a symmetrical triangular wave with a set frequency, logic operation is carried out as shown in fig. 3, a driving pulse of a power device is obtained, and then an inversion waveform of a system is obtained.
The six-pulse wave inverter harmonic elimination effect is as follows:
the indexes for measuring harmonic components are as follows: harmonic relative intensity and total harmonic distortion. The relative intensity of the harmonics is defined as CnThe ratio of the amplitude of each harmonic to the amplitude of the fundamental wave. The total harmonic distortion is defined as:
Figure BDA0002254098820000111
as shown in fig. 4 and table 1, fig. 4 is a graph of relative intensity effect of the half-cycle tripulse waveform corresponding to the 24 fundamental wave amplitude coefficients in table 1, and considering only the effect and realizability of harmonic cancellation, the solution when a is 0.8 is preferable, and under this condition, the fundamental wave amplitude and the harmonic cancellation effect of the system can be compatible. When the actual power regulation is considered, the values in table 1 may be stored in the processor in advance, and the parameter switching may be performed according to the requirement of the actual power regulation.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims (3)

1. The inversion control method adopts six pulse waves to control an inverter power supply, eliminates 3-order harmonic waves and 5-order harmonic waves of the inverter system by adjusting the duty ratio or the phase of the six pulse waves, and adjusts the amplitude of fundamental wave output to realize the output of the inverter power supply for reducing harmonic components;
the specific method for eliminating the 3 rd harmonic and the 5 th harmonic of the inverter system by adjusting the phase of the six-pulse wave comprises the following steps:
taking 1/4 periods of the half-cycle three-pulse wave as the origin of the time coordinate, the fourier transform of the voltage pulse wave is expressed as:
Figure FDA0003241196380000011
wherein: k represents the harmonic number, ω1Represents the fundamental angular frequency;
amplitude U of harmonic componentkmComprises the following steps:
Figure FDA0003241196380000012
will UkmAnd (3) expanding an expression:
Figure FDA0003241196380000013
wherein, UDCRepresenting the inverter dc bus voltage;
according to the symmetry of the rectangular wave, the inversion system only has odd harmonics, so k is odd, namely k is 1,3,5, …;
thus:
Figure FDA0003241196380000021
setting a fundamental wave amplitude coefficient A, and eliminating 3-order and 5-order harmonics, namely:
let A be [ sina ]1-sina2+sina3]Then the fundamental amplitude coefficient satisfies:
Figure FDA0003241196380000022
wherein: a e (0.6,0.84), U1mRepresents the amplitude of the 1 st harmonic;
solving an transcendental equation, and removing 3 th harmonic and 5 th harmonic:
Figure FDA0003241196380000023
Figure FDA0003241196380000024
Figure FDA0003241196380000025
a1、a2and a3Is the solution of the transcendental equation,
U3mrepresents the 3 th harmonic amplitude, U5mRepresents the 5 th harmonic amplitude;
the inverter circuit of the inversion control method adopts SiC power devices, the inverter bridge comprises an A-phase bridge arm and a B-phase bridge arm, the two bridge arms are respectively composed of IGBT modules, each IGBT module comprises two IGBT units, the switching devices of the two IGBT units of the A-phase bridge arm are VT1 and VT3, and the switching devices of the two IGBT units of the B-phase bridge arm are VT2 and VT 4;
the method for realizing the six-pulse wave is characterized by comprising the following steps:
t is a symmetrical triangular wave with a period of 2 pi and a triangular wave center line
Figure FDA0003241196380000031
The up-down symmetric distribution has six comparative values, which are from top to bottom in sequence:
Figure FDA0003241196380000032
α1、α2、α3respectively representing three comparison value variables;
six comparison values are compared with the triangular wave:
for comparison values
Figure FDA0003241196380000033
And
Figure FDA0003241196380000034
when the amplitude of the triangular wave is larger than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are respectively N1、N2And N3Then to N2And N3Performing XOR operation, and comparing the result with N1Performing OR operation to obtain
Figure FDA0003241196380000035
The obtained waveforms are the driving logics of a switching device VT1 of an A-phase bridge arm and a switching device VT4 of a B-phase bridge arm;
for comparison values
Figure FDA0003241196380000036
And
Figure FDA0003241196380000037
when the amplitude of the triangular wave is less than the comparison value, a high level is generated, otherwise, a low level is generated, and the waveforms generated by the three comparison values are B1、B2And B3Then to B2And B3Performing XOR operation, and comparing the result with B1Performing OR operation to obtain
Figure FDA0003241196380000038
The obtained waveforms are the driving logics of a switching device VT2 of an A-phase bridge arm and a switching device VT3 of a B-phase bridge arm;
when adopting
Figure FDA0003241196380000039
The VT1 and the VT4 are driven,
Figure FDA00032411963800000310
drive VT2 and element VT3, inverter output UABIs a six-pulse wave.
2. The inverter control method for six-pulse-wave low-Q series resonance type medium-frequency induction heating according to claim 1, wherein the comparison value variable α is1、α2、α3The acquisition method comprises the following steps:
solution a from transcendental equation1、a2And a3Finding alpha1、α2、α3：
Figure FDA00032411963800000311
3. The six-pulse-wave low-quality-factor series resonance type medium-frequency induction heating inversion control method according to claim 1, wherein the six comparison values are obtained by:
are respectively according to a1、a2And a3Finding alpha1、α2And alpha3Will be alpha1、α2And alpha3The values of (a) are stored in a processor, and then six comparison values are calculated according to a set inversion frequency f:
Figure FDA0003241196380000041
Figure FDA0003241196380000042
Figure FDA0003241196380000043
Figure FDA0003241196380000044
Figure FDA0003241196380000045
Figure FDA0003241196380000046
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