CN107888105B - Space vector modulation method for three-phase three-level converter - Google Patents
Space vector modulation method for three-phase three-level converter Download PDFInfo
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- CN107888105B CN107888105B CN201711207875.9A CN201711207875A CN107888105B CN 107888105 B CN107888105 B CN 107888105B CN 201711207875 A CN201711207875 A CN 201711207875A CN 107888105 B CN107888105 B CN 107888105B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
Abstract
A three-phase three-level converter space vector modulation method comprises the following steps: step 1: dividing each sector of the space voltage vector of the three-phase three-level converter into two intervals; step 2: calculating the angle of a space voltage vector according to three-phase sinusoidal voltage required to be output by the three-phase three-level converter; and step 3: determining a modulation mode and a modulation interval which need to be adopted according to the interval of the space voltage vector angle; and 4, step 4: and modulating according to the determined modulation mode and the sector to which the modulation mode belongs. The invention reduces the fluctuation of the midpoint potential by dividing different modulation modes and the length of the vector action time in the modulation interval adjustment, and realizes the balance control of the midpoint potential on the basis of reducing the switching loss.
Description
Technical Field
The invention belongs to the field of power electronics, and particularly relates to a space vector modulation method for a three-phase three-level converter.
Background
At present, the three-phase three-level converter is more and more widely applied in many occasions due to the advantages of low voltage bearing of a switching device, smaller output filter and the like. However, the three-phase three-level converter has inherent problems of midpoint potential fluctuation and offset, and the balance control of the midpoint potential needs to be realized through additional hardware circuits or software control. In many applications, higher demands are also made on the reduction of losses in the pursuit of higher efficiency.
When the three-phase three-level converter adopts a space vector modulation method, the control of the neutral point potential balance is generally realized by adjusting the action time of the redundant small vector, namely, the conventional seven-segment modulation. In order to further reduce the switching loss and improve the efficiency of the three-level converter, five-segment modulation can be adopted to reduce the switching action times, but the scheme abandons part of small vectors and does not have the capability of controlling the neutral point potential balance.
Therefore, how to reduce the switching loss of the three-phase three-level converter and realize the balance control of the midpoint potential becomes a problem to be solved urgently in the application of the circuit.
Disclosure of Invention
The present invention is directed to solve the above problems in the prior art, and an object of the present invention is to provide a space vector modulation method for a three-phase three-level converter, which reduces the switching loss of the three-phase three-level converter and simultaneously realizes the balance control of the midpoint potential within the operating range.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
step 1: dividing each sector of the space voltage vector of the three-phase three-level converter into two intervals;
step 2: calculating the angle of a space voltage vector according to three-phase sinusoidal voltage required to be output by the three-phase three-level converter;
and step 3: determining a modulation mode and a modulation interval which need to be adopted according to the interval of the space voltage vector angle;
and 4, step 4: and modulating according to the determined modulation mode and the sector to which the modulation mode belongs.
In the step 1, for a sector with 60 degrees, 0-15 degrees and 45-60 degrees are divided into one interval, and 15-45 degrees are divided into another interval.
The method for calculating the space voltage vector angle comprises the following steps that three-phase sinusoidal voltage required to be output by the three-phase three-level converter is converted into an αβ coordinate system through CLARKE, and the conversion formula is as follows:
wherein: u. ofA、uB、uCAre respectively three-phase sinusoidal voltages uα、uβαβ axis voltage after CLARKE transformation;
then, the angle of the space voltage vector is calculated as follows:
the atan2 function is adopted in the C language function, and the calculation formula of the space voltage vector angle is simplified by the following formula:
ω＝atan2(uβ,uα)
the modulation mode of the step 3 comprises the following steps: five-segment modulation capable of reducing switching loss but not controlling neutral point potential balance, and seven-segment modulation capable of controlling neutral point potential balance; the five-segment modulation and the seven-segment modulation are respectively corresponding to two intervals of sector division.
In the full modulation range, the interval of five-segment modulation and seven-segment modulation is crosswise arranged on the space voltage vector of the three-phase three-level converter.
Compared with the prior art, the invention has the following beneficial effects: because the fluctuation of the middle vector to the neutral potential is greatly influenced, each sector of the space voltage vector of the three-phase three-level converter is divided into different intervals, the angle of the space voltage vector is calculated according to the three-phase sinusoidal voltage required to be output by the three-phase three-level converter, the modulation mode and the modulation interval which need to be adopted are determined according to the interval where the angle of the space voltage vector is located, and the acting time of the middle vector is adjusted by dividing different modulation modes and modulation intervals, so that the fluctuation of the neutral potential is reduced, and the balance control of the neutral potential is realized on the basis of reducing the switching loss.
Drawings
FIG. 1 is an overall flow diagram of the modulation method of the present invention;
FIG. 2 is a prior art three-phase three-level converter topology;
fig. 3 is a voltage space vector distribution diagram of the conventional three-phase three-level converter;
FIG. 4 is a voltage space vector interval division diagram of the present invention;
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1-3, the implementation steps of the space vector modulation method of the three-phase three-level converter of the invention are as follows:
step 1: dividing each large sector of the space voltage vector of the three-phase three-level converter into two intervals;
step 2: calculating the angle of a space voltage vector according to three-phase sinusoidal voltage required to be output by the three-phase three-level converter;
and step 3: determining an interval adopting seven-segment modulation and an interval adopting five-segment modulation according to the interval where the space voltage vector angle is positioned;
and 4, step 4: and modulating according to the determined debugging mode and the sector to which the debugging mode belongs.
In step 1, in a space voltage vector of the three-phase three-level converter, a dividing method for dividing each large sector into two intervals is shown in fig. 4, and in each 60-degree large sector, 0-15 degrees and 45-60 degrees are one interval, and 15-45 degrees are the other interval.
In step 2, the three-phase sinusoidal voltage required to be output by the three-phase three-level converter is firstly converted into αβ coordinate system through CLARKE, and the conversion formula is as follows:
wherein: u. ofA、uB、uCAre respectively three-phase sinusoidal voltages uα、uβIs αβ axle voltage after CLARKE conversion.
The formula for calculating the vector angle of the space voltage is as follows:
to simplify the calculation, the atan2 function can be directly used in the C language function, and the calculation formula is:
ω＝atan2(uβ,uα)
in step 3, according to the divided intervals shown in fig. 4, five-segment modulation is adopted in the shaded interval, and seven-segment modulation is adopted in other intervals.
In summary, each large sector of the space vector distribution diagram of the three-phase three-level converter is divided into two intervals according to the angle, and in one interval, five-segment modulation which can reduce the switching loss but does not have the neutral point potential balance control capability is adopted; in the other interval, seven-segment modulation capable of controlling the neutral point potential balance is adopted. By adopting the method, the action time of the neutral point potential balance control can be ensured in the full modulation degree range, so that the neutral point potential balance control is realized; meanwhile, the switching loss of the three-phase three-level converter is reduced to a certain extent, and the efficiency is improved.
The above-mentioned way of interval division and determining the five-segment modulation and the seven-segment modulation interval according to the divided intervals belongs to an embodiment of the present invention, and according to this way, without inventive improvement, only the way of changing the interval division and determining the five-segment modulation and the seven-segment modulation interval according to the divided intervals also belongs to the protection scope of the present invention patent.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (3)
1. A space vector modulation method of a three-phase three-level converter is characterized by comprising the following steps:
step 1: dividing each sector of the space voltage vector of the three-phase three-level converter into two intervals;
for a sector with 60 degrees, dividing 0-15 degrees and 45-60 degrees into one interval, and dividing 15-45 degrees into another interval;
step 2: calculating the angle of a space voltage vector according to three-phase sinusoidal voltage required to be output by the three-phase three-level converter;
and step 3: determining a modulation mode and a modulation interval which need to be adopted according to the interval of the space voltage vector angle;
the modulation method comprises the following steps: five-segment modulation capable of reducing switching loss but not controlling neutral point potential balance, and seven-segment modulation capable of controlling neutral point potential balance; the five-segment modulation and the seven-segment modulation are respectively corresponding to two intervals of sector division;
in the full modulation degree range, sequentially dividing 360-degree sectors at intervals of 15 degrees and 30 degrees according to the 60-degree sector division mode, adopting five-segment modulation in each 15-degree sector, adopting seven-segment modulation in each 30-degree sector, and crosswise setting intervals of the five-segment modulation and the seven-segment modulation on a space voltage vector of the three-phase three-level converter;
and 4, step 4: and modulating according to the determined modulation mode and the sector to which the modulation mode belongs.
2. The space vector modulation method of the three-phase three-level converter according to claim 1, wherein the method for calculating the space voltage vector angle in step 2 comprises:
the three-phase sinusoidal voltage required to be output by the three-phase three-level converter is firstly converted into αβ coordinate system through CLARKE, and the conversion formula is as follows:
wherein: u. ofA、uB、uCAre respectively three-phase sinusoidal voltages uα、uβIs a warpαβ axis voltage after CLARKE conversion;
then, the angle of the space voltage vector is calculated as follows:
3. the three-phase three-level converter space vector modulation method according to claim 2, characterized in that: the atan2 function is adopted in the C language function, and the calculation formula of the space voltage vector angle is simplified by the following formula:
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| CN1299426C (en) * | 2003-08-01 | 2007-02-07 | 清华大学 | Method for reducing three-level frequency converter swithcing loss |
| US8649195B2 (en) * | 2010-04-08 | 2014-02-11 | Arizona Board Of Regents For And On Behalf Of Arizona State University | Hybrid space vector PWM schemes for interleaved three-phase converters |
| CN104617804A (en) * | 2015-01-19 | 2015-05-13 | 云南电网有限责任公司电力科学研究院 | Space vector pulse width modulation method |
| CN104578870B (en) * | 2015-01-23 | 2018-04-10 | 阳光电源股份有限公司 | A kind of three-phase tri-level inverter space vector width pulse modulation method and modulator |
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