CN111464057A - Multilevel single-stage DC/AC converter and implementation method thereof - Google Patents
Multilevel single-stage DC/AC converter and implementation method thereof Download PDFInfo
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- CN111464057A CN111464057A CN202010356419.6A CN202010356419A CN111464057A CN 111464057 A CN111464057 A CN 111464057A CN 202010356419 A CN202010356419 A CN 202010356419A CN 111464057 A CN111464057 A CN 111464057A
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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
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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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
Abstract
The invention relates to the technology of a DC/AC converter, in particular to a multi-level single-stage DC/AC converter, which comprises a direct-current power supply, a bidirectional power switch, a multi-tap transformer, a PWM signal and a driving unit, wherein the direct-current power supply is connected with the bidirectional power switch through a power line; the multi-tap transformer is provided with a plurality of taps at the primary side, and the taps of the upper half winding and the turns of the multi-tap transformer are symmetrically distributed with the lower half winding by taking the middle tap as a reference; one end of the bidirectional power switch is connected with the anode of the direct current power supply, the other end of the bidirectional power switch is respectively connected with each tap of the multi-tap transformer, and the cathode of the direct current power supply is connected with the center tap of the multi-tap transformer; and the PWM signal and driving unit is used for generating control signals required by the bidirectional power switch. The DC/AC converter enables different windings of the transformer to be short-circuited to the same direct-current power supply by controlling the on and off of the power switch tube, so that multi-level output voltage is obtained at the output end of the transformer. The power supply has the advantages of low harmonic content of output voltage, small electromagnetic interference, dispersed power loss, high efficiency and the like.
Description
Technical Field
The invention belongs to the technical field of DC/AC converters, and particularly relates to a multi-level single-stage DC/AC converter and an implementation method thereof.
Background
Photovoltaic power generation, fuel cells, UPS and the like are widely used in various fields, wherein a DC/AC converter is a core device, and in most cases, the input of the DC/AC converter is a single low-voltage direct current with a maximum of several hundred volts and a minimum possible voltage of 12V, and the output of the DC/AC converter is an alternating current with a frequency of 50Hz and a voltage of 220V. Generally, a two-stage converter is adopted, low-voltage direct current is converted into high-voltage direct current through a DC/DC converter, then the high-voltage direct current is converted into alternating current through DC/AC, the converter mostly adopts a two-level converter, the harmonic content of output voltage is high, a larger output filter is needed, the size of the filter can be effectively reduced through high frequency, electromagnetic interference is intensified, and large current flows through a power tube at a low-voltage side to cause large loss. While the two-stage conversion increases power consumption.
In order to solve the problem of high output harmonic of a two-level converter, a multi-level converter is generally adopted, and the existing single-input direct-current power converter generally comprises a diode clamping multi-level converter, a flying capacitor multi-level converter and a modular multi-level converter, but when the converters are used in a low-voltage situation, the problems of cost increase, system complexity, control complexity, loss increase and the like are caused. The cascaded H-bridge multilevel converter has wide application in the field of photovoltaic power generation, but the input of the cascaded H-bridge multilevel converter is a plurality of photovoltaic power supplies, and each power supply needs to be isolated, so that the cascaded H-bridge multilevel converter is not suitable for the condition of single power supply input.
The active energy buffer is designed by adopting a flying capacitor technology, a plurality of capacitor voltages are converted into unipolar rectified multi-level voltages, and then the unipolar rectified multi-level voltages are converted into bipolar multi-level voltages through an inverter bridge, the level voltages of the converter depend on the capacitor voltages, ripple waves of the capacitor voltages can influence the accuracy of the levels, and the ripple waves of the capacitor voltages need to be increased when the output power needs to be increased, but the output voltage harmonic waves can be increased.
Disclosure of Invention
The invention aims to provide a multi-level converter based on transformer tap voltage control.
In order to achieve the purpose, the invention adopts the technical scheme that: a multi-level single-stage DC/AC converter comprises a DC power supply, a bidirectional power switch, a multi-tap transformer and a PWM signal and drive unit; the multi-tap transformer is provided with a plurality of taps at the primary side, and the taps of the upper half winding and the turns of the multi-tap transformer are symmetrically distributed with the lower half winding by taking the middle tap as a reference; one end of the bidirectional power switch is connected with the anode of the direct current power supply, the other end of the bidirectional power switch is respectively connected with each tap of the multi-tap transformer, and the cathode of the direct current power supply is connected with the center tap of the multi-tap transformer; and the PWM signal and driving unit is used for generating control signals required by the bidirectional power switch.
A method for realizing a multilevel single-stage DC/AC converter comprises the following steps:
step 2, the power switch tubes connected with the transformer taps work in turn according to the change of the modulation signals, and the working states of the positive and negative winding switch tubes are symmetrical;
and 3, changing the amplitude and the frequency of the modulation signal so as to change the amplitude and the frequency of the output signal.
In the method for implementing the multi-level single-stage DC/AC converter, the number of the output levels is increased or decreased by increasing or decreasing the number of taps of the multi-tap transformer and the power switch branches connected correspondingly.
In the method for implementing the multi-level single-stage DC/AC converter, only one power branch is allowed to participate in energy exchange between the input and the output at a time by controlling the power switch.
In the method for implementing the multi-level single-stage DC/AC converter, the high-voltage tap is connected in series to the center tap of the multi-tap transformer through a power switch tube and a diode, and when the output level is 0, the branch power tube is turned on to provide a path for the feedback current.
The invention has the beneficial effects that: the multi-level output is obtained through the control of the tap voltage of the transformer, so that the harmonic content of the output voltage is greatly reduced under the same switching frequency.
The whole transformation process only has one transformation, and no intermediate link exists; only a maximum of two power tubes are in current flow at any time; because of the output multi-level, a lower switching frequency can be adopted; when the PWM works, the voltage born by the switching tube is very low. These features greatly reduce system losses.
Because each power branch works in turn, the system loss is distributed in each branch, and the system heat dissipation is facilitated.
Drawings
FIG. 1(a) is a schematic diagram of a multilevel single-stage DC/AC converter circuit configuration according to an embodiment of the present invention;
FIG. 1(b) is an output waveform of a multi-level single-stage DC/AC converter according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a 9-level converter circuit configuration for a multilevel single-stage DC/AC converter in accordance with an embodiment of the present invention;
fig. 3 is a schematic diagram of the multilevel single-stage DC/AC converter 9 level converter switching tube control waveform generation of one embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
In the embodiment, a multi-tap transformer is adopted, and the voltage of each tap of the transformer is controlled, so that multi-level output is completed through one-time conversion, and the output level can be expanded by adding the taps of the transformer. The method is suitable for the fields of DC/AC converters with lower input direct-current voltage, such as photovoltaic power generation, fuel cells, UPS and the like.
The embodiment is realized by the technical scheme that the multi-level single-stage DC/AC converter comprises a direct-current power supply, a bidirectional power switch, a multi-tap transformer and a PWM signal generating and driving unit. The primary side of the transformer is provided with a plurality of taps, and the taps of the upper half winding and the turns of the upper half winding are symmetrically distributed with the lower half winding by taking the middle tap as a reference; one end of the bidirectional power switch is connected with the anode of the input direct-current power supply, the other end of the bidirectional power switch is respectively connected with each tap of the transformer, and the cathode of the direct-current power supply is connected with the center tap of the transformer; and the PWM signal generating and driving unit is used for generating control signals required by the power switch.
The method for realizing the multilevel single-stage DC/AC converter comprises the following steps: firstly, different windings of the transformer are short-circuited to the same direct-current power supply by controlling the on and off of the power switch tube, so that multi-level output voltage is obtained at the output end of the transformer through one-time conversion.
And secondly, the power switch tubes connected with the transformer taps work in turn according to the height change of the modulation signal, and the working states of the positive and negative winding switch tubes are symmetrical.
And thirdly, changing the amplitude and the frequency of the modulation signal changes the amplitude and the frequency of the output signal.
In specific implementation, as shown in fig. 1(a), the primary side of the transformer is formed by connecting 2N windings in series, so as to form a 2N +1 total taps of a 1-aN, a1 '-aN' and a0, a0 is a center tap, N windings are symmetrically distributed up and down with a0 as a center, the turn ratios of the N windings relative to the secondary winding are N1 and N2 … … nN, the upper half winding is called a positive winding, and the lower half winding is called a negative winding. The input DC power voltage is VDC, and the output voltage is Vo. One end of each of the 2N switches is connected with 2N taps of the primary side of the transformer, the other end of each switch is connected with the positive pole of the input direct-current power supply, and the negative pole of the power supply is connected with a center tap a0 of the primary winding of the transformer.
FIG. 1(b) shows a multi-level output principle waveform, where the output voltage is 0 when all switches are turned off, and when the input voltage is applied between taps an and a0 after switch Sun is turned on, the output voltage is
Kn is nN + N2+ … … + nN, if it is S L N (N is 1, 2, … N), the output voltage is
Because different switches are connected with different winding taps, different levels can be obtained by controlling the on and off of the different switches, and if the switches are sequentially turned on according to a sine rule, step sine waveform voltage can be obtained. It is apparent that 2N windings can output 2N +1 levels. The positive and negative windings are symmetrical, so the output level is positive and negative symmetrical.
As shown in FIG. 2, the 9-level topological circuit diagram designed according to the above concept is that a power tube (including a switching tube and a diode) connected with a positive winding is called a positive winding power tube, a power tube connected with a negative winding is called a negative winding power tube, power tubes Sun1 and Sun2 and S L n1 and S L n2(n is 1 …) form a bidirectional switch, energy bidirectional flow is ensured, Sun1 and S L n1 are forward switching tubes, Sun2 and S L n2 are reverse switching tubes, a Sun 02 and S3502 branches are respectively connected with a positive and negative highest voltage winding tap and a common tap, and are switched on when 0 level is output to provide an energy feedback path, DU01 and D L are used for defining an energy flow direction, in FIG. 2, i 0-i 4 and i0 '46i' are respectively positive and negative power direct current, and ic is input power supply current.
As shown in fig. 3, the method for generating the control waveform of the 9-level converter connected with the positive winding switching tube includes that the modulation wave is a half-wave sine, the carrier wave is 4 overlapped triangular waves, the amplitude is sequentially increased by one level, and if the output level intervals are equal, the amplitude difference between adjacent triangular waves is the same. And 4 triangular waves and the same half-wave sine are compared to obtain a control signal which is used as a reference signal of the control signal of the positive winding switching tube. The control signal obtained by the lowest triangular wave comparator is the control signal GU11 of the switching tube SU11, and the control signal GU02 is the control signal GU02 of Su02 after the inversion (in FIG. 3,/GU 02 to/GU 32 are the inverse signals of GU02 to GU32 respectively). The generation process of the control signal of the negative half-winding switch tube is completely the same as that of the control signal of the switch tube in the figure 3, except that the phase of the modulation signal (half-wave sine) needs to be shifted by 180 degrees. When the device works, the positive and negative half-cycle switching tubes work in turn to respectively generate positive and negative half cycles of output signals.
As shown in fig. 3, at the starting time of a half-wave sine, all forward switching tubes are turned off, all reverse switching tubes are turned on, the highest winding tap a1 is shorted to a common point, the output voltage is 0, at this time, if a feedback current exists, a current flows in the transformer winding, when the modulated wave voltage is in the first triangular wave interval, the switching tubes SU11 and SU02 are in a PWM state, the two switching tubes work complementarily, and since the other forward switching tubes are in a cut-off state, energy flows only in the SU11 branch and the SU02 branch in turn.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
Although specific embodiments of the present invention have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that these are merely illustrative and that various changes or modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is only limited by the appended claims.
Claims (5)
1. A multilevel single-stage DC/AC converter is characterized by comprising a direct current power supply, a bidirectional power switch, a multi-tap transformer and a PWM signal and drive unit; the multi-tap transformer is provided with a plurality of taps at the primary side, and the taps of the upper half winding and the turns of the multi-tap transformer are symmetrically distributed with the lower half winding by taking the middle tap as a reference; one end of the bidirectional power switch is connected with the anode of the direct current power supply, the other end of the bidirectional power switch is respectively connected with each tap of the multi-tap transformer, and the cathode of the direct current power supply is connected with the center tap of the multi-tap transformer; and the PWM signal and driving unit is used for generating control signals required by the bidirectional power switch.
2. The method of claim 1, further comprising the steps of:
step 1, by controlling the on and off of a power switch tube, different windings of a multi-tap transformer are short-circuited to the same direct-current power supply, so that multi-level output voltage is obtained at the output end of the multi-tap transformer through one-time conversion;
step 2, the power switch tubes connected with the transformer taps work in turn according to the change of the modulation signals, and the working states of the positive and negative winding switch tubes are symmetrical;
and 3, changing the amplitude and the frequency of the modulation signal so as to change the amplitude and the frequency of the output signal.
3. The method of claim 2, wherein the increase or decrease in the number of output levels is achieved by increasing or decreasing the number of multi-tap transformer taps and associated power switch legs.
4. The method of claim 2 wherein only one power branch is allowed to participate in the energy exchange between the input and output at a time by controlling the power switches.
5. The method of claim 2 wherein the high voltage tap is connected in series to the center tap of the multi-tap transformer through a power switch and diode, and wherein the branch power transistor opens to provide a path for the feedback current when the output level is 0.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112910425A (en) * | 2021-01-28 | 2021-06-04 | 武汉大学 | High-efficiency high-capacity piecewise linear power amplifier based on multi-tap transformer |
| CN115940672A (en) * | 2023-03-14 | 2023-04-07 | 成都英格利科技有限公司 | Electrolytic hydrogen production rectifier with rapid voltage regulation capability and control method thereof |
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| CN101030737A (en) * | 2007-03-26 | 2007-09-05 | 浙江大学 | High-power factor and low-harmonic wave controllable commutator based on transistor |
| CN101150286A (en) * | 2007-04-04 | 2008-03-26 | 南京理工大学 | AC-AC three level AC-AC converter based on positive converter |
| CN104980028A (en) * | 2014-04-10 | 2015-10-14 | 通用电气能源能量变换技术有限公司 | Power Converters |
| CN106849663A (en) * | 2015-12-03 | 2017-06-13 | 中国航空工业集团公司雷华电子技术研究所 | A kind of three level power electronic transformer circuit structures |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050024027A1 (en) * | 2003-06-20 | 2005-02-03 | Mcvicar Randy W. | Voltage control system |
| CN101030737A (en) * | 2007-03-26 | 2007-09-05 | 浙江大学 | High-power factor and low-harmonic wave controllable commutator based on transistor |
| CN101150286A (en) * | 2007-04-04 | 2008-03-26 | 南京理工大学 | AC-AC three level AC-AC converter based on positive converter |
| CN104980028A (en) * | 2014-04-10 | 2015-10-14 | 通用电气能源能量变换技术有限公司 | Power Converters |
| CN106849663A (en) * | 2015-12-03 | 2017-06-13 | 中国航空工业集团公司雷华电子技术研究所 | A kind of three level power electronic transformer circuit structures |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112910425A (en) * | 2021-01-28 | 2021-06-04 | 武汉大学 | High-efficiency high-capacity piecewise linear power amplifier based on multi-tap transformer |
| CN112910425B (en) * | 2021-01-28 | 2022-07-19 | 武汉大学 | High-efficiency high-capacity piecewise linear power amplifier based on multi-tap transformer |
| CN115940672A (en) * | 2023-03-14 | 2023-04-07 | 成都英格利科技有限公司 | Electrolytic hydrogen production rectifier with rapid voltage regulation capability and control method thereof |
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| CN111464057B (en) | 2021-08-03 |
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