CN113809947B - Method and device for optimizing carrier NSPWM (non-synchronous pulse Width modulation) of two-level converter - Google Patents
Method and device for optimizing carrier NSPWM (non-synchronous pulse Width modulation) of two-level converter Download PDFInfo
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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
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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
- H02M7/501—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 sinusoidal output voltages being obtained by the combination of several pulse-voltages having different amplitude and width
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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
- H02M7/53875—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 with analogue control of three-phase output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- 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
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Abstract
The application discloses a carrier NSPWM (non-continuous wave pulse width modulation) method for optimizing a two-level converter. For the two-level converter, the invention superimposes the specific voltage U on the three-phase sine wave in the space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG 1 Superimposing a specific voltage U on the three-phase sine wave in the rest region 2 Obtaining a three-phase modulation wave of an optimized carrier NSPWM; by using an initial value K in the spatial angle region of 330 ° to 30 °, 90 ° to 150 °, 210 ° to 270 ° 1 Uses an initial value of K in the remaining region 2 Obtaining a modulation carrier wave of an optimized carrier NSPWM; and obtaining a switching signal of the optimized carrier NSPWM based on comparison of the three-phase modulation wave and the modulation carrier, thereby realizing the optimized carrier NSPWM. Compared with the traditional NSPWM, the method can prevent overvoltage and eliminate even harmonic while inhibiting common mode voltage and reducing switching frequency, and has the advantages of simple calculation and convenient realization.
Description
Technical Field
The invention relates to the technical field of PWM control, in particular to a carrier NSPWM optimization method and method for a two-level converter.
Background
Fig. 1 is a main circuit topology of a two-level converter. As a key device for electric energy conversion, the two-level converter is widely used in the fields of new energy power generation, motor driving, power reactive compensation and the like.
Defining that the two level states of the two-level converter from high to low output are 1 and 0 and the direct current side voltage is 2E, the space vector of the two-level converter can be summarized in fig. 2. Wherein, the three-phase switch state, vector type and amplitude corresponding to each space vector are listed in table 1.
Table 1 switching states and magnitudes for each space vector of a two-level inverter
The common mode voltage is the reference voltage of the output neutral point of the converter to the ground. The literature "diode clamped three-level inverter common mode voltage suppression" (Wu Keli.[ J ]. Electrical engineering theory, 2015,30 (24): 110-117.) indicates that common mode voltage induces high amplitude shaft voltage on the motor shaft, breaks insulation, and shortens the service life of the motor. In addition, the common mode voltage also can generate high-frequency leakage current, electromagnetic interference is generated, and normal operation of surrounding electrical equipment is affected. In order to reduce the adverse effect of the common-mode voltage without adding additional hardware equipment, the research on the pulse width modulation method for inhibiting the common-mode voltage has important practical significance.
Table 2 lists the common mode voltage magnitudes corresponding to each space vector of the two-level converter. As can be seen from table 2, the non-zero vectors 100, 110, 010, 011, 001, 101 have lower common mode voltage magnitudes than the zero vectors 111 and 000. Thus, the common mode voltage can be reduced by a pulse width modulation method that uses only non-zero vector synthesized reference voltages.
TABLE 2 common mode voltage amplitudes for each space vector
Document A Near state PWM method with reduced switching frequency and reduced common mode voltage for three-phase voltage source inverters (e.un. [ C ]. IEEE International Electric Machines & Drives Conference, 2007:235-240.). An NSPWM (Near-state PWM, NSPWM) is proposed that reduces the common mode voltage amplitude to one sixth of the dc side voltage value by synthesizing the reference voltage using three non-zero vectors closest to the reference voltage. The literature Performance analysis of reduced common-mode voltage PWM methods and comparison with standard PWM methods for three-phase voltage-source inverters (Ahmet M.Hava. [ J ]. IEEE Transactions on Energy Conversion,2009,24 (1): 241-252.) compares the performance of NSPWM, space vector PWM, effective zero vector PWM, and furthest vector PWM, indicating that NSPWM can reduce the three-phase switching frequency while suppressing the common mode voltage, and can achieve better harmonic control in the region with a modulation ratio greater than 0.61. On the basis, the literature (Zhang Xing [ J ]. Power electronics technology, 2015,49 (8): 89-92 ]) proposes an improved NSPWM method capable of reducing the switching loss of a device under the condition of non-unit power factor at the converter side, thereby further improving the NSPWM performance.
While having the advantages of suppressing common mode voltage and reducing switching frequency, NSPWM also has the following drawbacks:
1) Under the NSPWM effect, even harmonic with higher amplitude exists in the output phase voltage of the two-level converter. When the two-level converter is connected with a power grid, the current content of each harmonic on the grid side must be strictly limited within the power grid standard, and the harmonic index of the public power grid has more strict limitation on even harmonics. Therefore, in order to improve the harmonic performance of NSPWM, even harmonic wave under the action of NSPWM needs to be eliminated;
2) Under NSPWM effect, two-level jump exists in the output line voltage of the two-level converter, namely the problem that the line voltage jumps directly between 2E and-2E exists. When the two-level converter is connected with the motor, the overvoltage at the motor end can be caused by the two-level jump of the line voltage, so that the safe operation of the motor is not facilitated. Therefore, in order to improve the reliability of NSPWM, it is necessary to prevent overvoltage.
Disclosure of Invention
In order to solve the problems of overvoltage and even harmonic existing in the traditional NSPWM, the invention provides a method for optimizing carrier NSPWM of a two-level converter. Compared with the traditional NSPWM, the method can prevent overvoltage and eliminate even harmonic while inhibiting common-mode voltage amplitude and changing frequency and reducing switching loss, so that the method has better harmonic performance and higher reliability. In addition, the method directly obtains the switching signals of the switching devices according to the comparison result of the modulation wave and the modulation carrier wave, and the method does not need to calculate the space vector action time, so the method also has the advantages of simple calculation and convenient realization.
The invention discloses a two-level converter optimized carrier NSPWM method, which is characterized in that a first specific voltage is superposed on a three-phase sine wave in a first preset space angle area, a second preset space angle area and a third preset space angle area, and a second specific voltage is superposed on the three-phase sine wave in a fourth preset space angle area, a fifth preset space angle area and a sixth preset space angle area, so that a three-phase modulation wave of an optimized carrier NSPWM is obtained; the method comprises the steps that rising carriers with initial values of a first preset value are used in the first preset space angle area, the second preset space angle area and the third preset space angle area, and falling carriers with initial values of a second preset value are used in the fourth preset space angle area, the fifth preset space angle area and the sixth preset space angle area, so that modulation carriers of optimized carrier NSPWM are obtained; based on the comparison of the three-phase modulated wave and the modulated carrier wave, the step of obtaining the three-phase modulated wave of the optimized carrier NSPWM by superposing a first specific voltage on the three-phase sine wave in a first preset space angle area, a second preset space angle area and a third preset space angle area, and superposing a second specific voltage on the three-phase sine wave in a fourth preset space angle area, a fifth preset space angle area and a sixth preset space angle area, specifically includes:
in the first preset space angle area, let U am ＝U as +U 1 ，U bm ＝-U bs -U 1 ，U cm ＝U cs +U 1 ；
In the fourth preset space angle area, let U am ＝-U as -U 2 ，U bm ＝U bs +U 2 ，U cm ＝U cs +U 2 ；
In the second preset space angle area, let U am ＝U as +U 1 ，U bm ＝U bs +U 1 ，U cm ＝-U cs -U 1 ；
In the fifth preset space angle area, let U am ＝U as +U 2 ，U bm ＝-U bs -U 2 ，U cm ＝U cs +U 2 ；
In the third preset space angle area, let U am ＝-U as -U 1 ，U bm ＝U bs +U 1 ，U cm ＝U cs +U 1 ；
In the sixth preset space angle area, let U am ＝U as +U 2 ，U bm ＝U bs +U 2 ，U cm ＝-U cs -U 2 ；
Wherein the three-phase sine wave is a three-phase sine wave with the maximum peak value in the linear modulation ratio region being the difference between the second preset value and the first preset value, U 1 Represents the first specific voltage, U 2 Representing the second specific voltage, U as 、U bs 、U cs A phase A sine wave, a phase B sine wave and a phase C sine wave respectively representing the three-phase sine wave, U am 、U bm 、U cm Representing an a-phase modulated wave, a B-phase modulated wave and a C-phase modulated wave of the three-phase modulated wave, respectively.
Preferably, the first specific voltage is defined as follows:
U 1 ＝K 2 -max(U as ,U bs ,U cs )
in the above, K 2 Represents said second preset value, max (U as ,U bs ,U cs ) Represents U as 、U bs 、U cs Maximum value of (2);
the second specific voltage is defined as follows:
U 2 ＝K 1 -min(U as ,U bs ,U cs )
in the above, K 1 Represents the first preset value, min (U as ，U bs ，U cs ) Represents U as 、U bs 、U cs Is the minimum value of (a).
Preferably, the obtaining the modulated carrier of the optimized carrier NSPWM by using rising carriers with initial values of a first preset value in the first preset spatial angle region, the second preset spatial angle region, and the third preset spatial angle region, and using falling carriers with initial values of a second preset value in the fourth preset spatial angle region, the fifth preset spatial angle region, and the sixth preset spatial angle region specifically includes:
setting U in the first preset spatial angle area, the second preset spatial angle area and the third preset spatial angle area carrier ＝UP carrier ；
Setting U in the fourth preset spatial angle area, the fifth preset spatial angle area and the sixth preset spatial angle area carrier ＝DN carrier ；
Wherein U is carrier Modulated carrier representing optimized carrier NSPWM, UP carrier The DN represents the rising carrier with the initial value being the first preset value carrier Representing the falling carrier with the initial value being the second preset value.
Preferably, when 0.ltoreq.t run ＜t sample In the time-course of which the first and second contact surfaces,
the definition of the rising carrier with the initial value being the first preset value is as follows:
the definition of the descending carrier with the initial value being the second preset value is as follows:
when t sample ≤t run ＜2t sample In the time-course of which the first and second contact surfaces,
the definition of the rising carrier with the initial value being the first preset value is as follows:
the definition of the descending carrier with the initial value being the second preset value is as follows:
wherein K is 1 Represents the first preset value, K 2 Representing the second preset value, t sample Represents the sampling period, t run For a value of 0 to 2t sample Time-run variable that varies cyclically between.
Preferably, the method for obtaining the switching signal of the optimized carrier NSPWM based on the comparison between the three-phase modulated wave and the modulated carrier wave, thereby implementing the optimized carrier NSPWM is as follows:
in the first preset spatial angle area and the fifth preset spatial angle area, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is XO, and when U bm ＜U carrier When the B phase switch signal is OX; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
in the fourth preset spatial angle area and the third preset spatial angle area, when U am ≥U carrier When the phase A switch signal is XO, and when U am ＜U carrier When the phase A switch signal is made to be OX; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
in the second preset space angle region and the sixth preset space angle region, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier When the C phase switch signal is XO, and when U cm ＜U carrier When the C phase switch signal is OX;
wherein U is am 、U bm 、U cm A phase A modulated wave, a phase B modulated wave and a phase C modulated wave respectively representing the three-phase modulated waves, U carrier Representing the modulation carrier of the optimized carrier NSPWM, XO represents that the upper bridge arm switching device of the corresponding phase is turned off, the lower bridge arm switching device is turned on, and OX represents that the upper bridge arm switching device of the corresponding phase is turned on and the lower bridge arm switching device of the corresponding phase is turned off.
Preferably, the first preset value is-1, and the second preset value is 1.
The invention also provides a device for optimizing carrier NSPWM of the two-level converter, which comprises:
a three-phase modulated wave acquisition module for superposing a first special on the three-phase sine wave in the first preset space angle region, the second preset space angle region and the third preset space angle regionConstant voltage U 1 Superposing a second specific voltage on the three-phase sine wave in a fourth preset space angle area, a fifth preset space angle area and a sixth preset space angle area to obtain a three-phase modulation wave of an optimized carrier NSPWM;
a modulated carrier acquisition module, configured to use rising carriers with initial values of a first preset value in the first preset spatial angle area, the second preset spatial angle area, and the third preset spatial angle area, and use falling carriers with initial values of a second preset value in the fourth preset spatial angle area, the fifth preset spatial angle area, and the sixth preset spatial angle area, so as to obtain modulated carriers of an optimized carrier NSPWM;
and the switching signal acquisition module is used for comparing the three-phase modulation wave with the modulation carrier wave to obtain a switching signal of the optimized carrier NSPWM, thereby realizing the optimized carrier NSPWM.
The device for optimizing the carrier NSPWM of the two-level converter has the same beneficial effects as the method for optimizing the carrier NSPWM of the two-level converter.
Drawings
Fig. 1 is a schematic diagram of a two-level converter main circuit topology according to the related art;
fig. 2 is a space vector diagram of a two-level converter according to the background art;
fig. 3 is a flowchart of a method for optimizing carrier NSPWM of a two-level converter according to an embodiment of the present invention;
FIG. 4 illustrates the phase voltage, line voltage and common mode voltage of a two-level converter under SVPWM according to an embodiment of the present invention;
fig. 5a, 5b, and 5c are simulation results of conventional NSPWM, wherein: fig. 5a is a phase voltage, a line voltage and a common mode voltage of the two-level converter under the function of the conventional NSPWM, fig. 5b is a result of analyzing amplitude of each subharmonic of the phase voltage of the conventional NSPWM, and fig. 5c is an output line voltage of the two-level converter under the function of the conventional NSPWM;
fig. 6a, fig. 6b, fig. 6c, fig. 6d are simulation results of the method of the present invention for optimizing carrier NSPWM, wherein: fig. 6a is a phase voltage, a line voltage and a common-mode voltage of the two-level converter under the function of the optimized carrier NSPWM, fig. 6b is a result of analysis of amplitude of each subharmonic of the phase voltage of the optimized carrier NSPWM, fig. 6c is an output line voltage of the two-level converter under the function of the optimized carrier NSPWM, and fig. 6d is a simulation result of obtaining a switching signal of the three-phase device by the optimized carrier NSPWM based on comparison of the three-phase modulation wave and the modulation carrier;
fig. 7a and fig. 7b are simulation results of the method of the present invention for optimizing carrier NSPWM at different fundamental frequencies, different carrier frequencies, and different modulation ratios, wherein: fig. 7a is a phase voltage, line voltage, common mode voltage and modulation wave of the optimized carrier NSPWM at different fundamental frequencies, different carrier frequencies and different modulation ratios, and fig. 7b is a result of analysis of amplitude of each subharmonic of the phase voltage of the optimized carrier NSPWM at different fundamental frequencies, different carrier frequencies and different modulation ratios.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order to solve the problems of overvoltage and even harmonic existing in the traditional NSPWM, the invention provides a two-level converter optimized carrier NSPWM method, which is characterized in that a specific voltage U is superposed on a three-phase sine wave in a space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG 1 Superimposing a specific voltage U on the three-phase sine wave in the rest region 2 Obtaining a three-phase modulation wave of an optimized carrier NSPWM; by using an initial value K in the spatial angle region of 330 ° to 30 °, 90 ° to 150 °, 210 ° to 270 ° 1 Uses an initial value of K in the remaining region 2 The invention obtains the modulated carrier of the optimized carrier NSPWM; based on the comparison of the three-phase modulation wave and the modulation carrier wave, the invention obtains the switching signal of the optimized carrier NSPWM, thereby realizing the optimized carrier NSPWM. Compared with the traditional NSPWM, the method of the invention can inhibit commonThe mode voltage amplitude and the change frequency can prevent overvoltage and eliminate even harmonic while reducing the switching loss, so that the device has better harmonic performance and higher reliability. In addition, the method directly obtains the switching signals of the switching devices according to the comparison result of the modulation wave and the modulation carrier wave, and the method does not need to calculate the space vector action time, so the method also has the advantages of simple calculation and convenient realization. A carrier NSPWM method for two-level converter optimization, the concrete implementation flow is as follows:
step 1, obtaining a three-phase modulation wave of an optimized carrier NSPWM:
in this embodiment, the first preset spatial angle region is set to 330 ° to 30 °, the second preset spatial angle region is set to 90 ° to 150 °, the third preset spatial angle region is set to 210 ° to 270 °, the fourth preset spatial angle region is set to 30 ° to 90 °, the fifth preset spatial angle region is set to 150 ° to 210 °, and the sixth preset spatial angle region is set to 270 ° to 330 °.
Further, in this step, a specific voltage U is superimposed on the three-phase sine wave in a space angle region of 330 ° to 30 °, 90 ° to 150 °, 210 ° to 270 ° 1 Superimposing a specific voltage U on the three-phase sine wave in the rest region 2 The method for obtaining the three-phase modulation wave of the optimized carrier NSPWM comprises the following steps:
1) When in the space angle region of 330 DEG to 30 DEG, let U am ＝U as +U 1 ，U bm ＝-U bs -U 1 ，U cm ＝U cs +U 1 ；
2) When in the space angle region of 30 DEG to 90 DEG, let U am ＝-U as -U 2 ，U bm ＝U bs +U 2 ，U cm ＝U cs +U 2 ；
3) When in the space angle region of 90 DEG to 150 DEG, let U am ＝U as +U 1 ，U bm ＝U bs +U 1 ，U cm ＝-U cs -U 1 ；
4) When in the space angle area of 150 DEG to 210 DEG, let U am ＝U as +U 2 ，U bm ＝-U bs -U 2 ，U cm ＝U cs +U 2 ；
5) When in the space angle region of 210 DEG to 270 DEG, let U am ＝-U as -U 1 ，U bm ＝U bs +U 1 ，U cm ＝U cs +U 1 ；
6) When in the spatial angle region of 270 DEG to 330 DEG, let U am ＝U as +U 2 ，U bm ＝U bs +U 2 ，U cm ＝-U cs -U 2 。
In the three-phase modulation wave method for obtaining the optimized carrier NSPWM, U as 、U bs 、U cs Represents the maximum peak-to-peak value in the linear modulation ratio region as (K 2 -K 1 ) Three-phase sine wave of U am 、U bm 、U cm Representing a three-phase modulated wave of optimized carrier NSPWM, wherein a specific voltage U 1 The calculation method of (2) is as shown in formula (1):
U 1 ＝K 2 -max(U as ,U bs ,U cs ) (1)
in formula (1), max (U as ,U bs ,U cs ) Representing the maximum value of a three-phase sine wave;
specific voltage U 2 The calculation method of (2) is as follows:
U 2 ＝K 1 -min(U as ,U bs ,U cs ) (2)
in the formula (2), min (U as ,U bs ,U cs ) Representing the minimum of a three-phase sine wave.
Step 2, obtaining a modulation carrier wave of an optimized carrier NSPWM:
the invention uses the initial value K in the space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG 1 Uses an initial value of K in the remaining region 2 The method for obtaining the modulated carrier of the optimized carrier NSPWM is as follows:
1) In the spatial angular region of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG,set U carrier ＝UP carrier ；
2) U is arranged in the spatial angle area of 30 DEG to 90 DEG, 150 DEG to 210 DEG, 270 DEG to 330 DEG carrier ＝DN carrier 。
In the above carrier modulation method for obtaining the optimized carrier NSPWM, U carrier Modulated carrier representing optimized carrier NSPWM, UP carrier Representing an initial value of K 1 Rising carrier of DN carrier Representing an initial value of K 2 Is a carrier of the carrier-down signal. Wherein the initial value is K 1 The setup method of the rising carrier of (2) is as follows:
in the formula (3), t sample Represents the sampling period, t run For a value of 0 to 2t sample A time-running variable that varies cyclically between;
initial value of K 2 The setting method of the descending carrier of (2) is as follows:
in the formula (4), t sample Represents the sampling period, t run For a value of 0 to 2t sample Time-run variable that varies cyclically between.
Step 3, obtaining a switching signal of the optimized carrier NSPWM:
based on the comparison of the three-phase modulation wave and the modulation carrier wave, the invention obtains the switching signal of the optimized carrier NSPWM, thereby realizing the method for optimizing the carrier NSPWM as follows:
1) In the spatial angle region of 330 DEG to 30 DEG and 150 DEG to 210 DEG, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is XO, and when U bm ＜U carrier When the B phase switch signal is OX; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
2) In the spatial angle region of 30 DEG to 90 DEG and 210 DEG to 270 DEG, when U am ≥U carrier When the phase A switch signal is XO, and when U am ＜U carrier When the phase A switch signal is made to be OX; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
3) In the spatial angle region of 90 DEG to 150 DEG and 270 DEG to 330 DEG, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier When the C phase switch signal is XO, and when U cm ＜U carrier Let the C-phase switch signal be OX.
In the above method for obtaining the switching signal of the optimized carrier NSPWM, XO represents that the upper bridge arm switching device of the corresponding phase is turned off and the lower bridge arm switching device is turned on, and OX represents that the upper bridge arm switching device of the corresponding phase is turned on and the lower bridge arm switching device of the corresponding phase is turned off.
In the above method, K 1 And K 2 Any value can be taken as long as K is satisfied 1 Less than K 2 By, for example, K 1 Take the value of 0, K 2 Take a value of 2, or K 1 Take the value of-1, K 2 Take on a value of 1, etc., below by K 1 Take the value of-1, K 2 When the value is 1, the effect of the invention will be described as an embodiment of the invention.
The two-level converter carrier NSPWM optimizing method is shown in fig. 3, and the implementation flow is as follows:
by a range of 330 DEG to 30 DEGThe three-phase sine wave is superimposed with a specific voltage U in the spatial angle region of 90 DEG to 150 DEG, 210 DEG to 270 DEG 1 Superimposing a specific voltage U on the three-phase sine wave in the rest region 2 Obtaining a three-phase modulation wave of an optimized carrier NSPWM; by using rising carriers with initial values of-1 in the spatial angle areas of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG and using falling carriers with initial values of 1 in the other areas, the invention obtains the modulation carrier of the optimized carrier NSPWM; based on the comparison of the three-phase modulation wave and the modulation carrier wave, the invention obtains the switching signal of the optimized carrier NSPWM, thereby realizing the optimized carrier NSPWM.
1. Three-phase modulation wave for obtaining optimized carrier NSPWM
A specific voltage U is superimposed on the three-phase sine wave in the space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG 1 Superimposing a specific voltage U on the three-phase sine wave in the rest region 2 The method for obtaining the three-phase modulation wave of the optimized carrier NSPWM comprises the following steps:
1) When in the space angle region of 330 DEG to 30 DEG, let U am ＝U as +U 1 ，U bm ＝-U bs -U 1 ，U cm ＝U cs +U 1 ；
2) When in the space angle region of 30 DEG to 90 DEG, let U am ＝-U as -U 2 ，U bm ＝U bs +U 2 ，U cm ＝U cs +U 2 ；
3) When in the space angle region of 90 DEG to 150 DEG, let U am ＝U as +U 1 ，U bm ＝U bs +U 1 ，U cm ＝-U cs -U 1 ；
4) When in the space angle area of 150 DEG to 210 DEG, let U am ＝U as +U 2 ，U bm ＝-U bs -U 2 ，U cm ＝U cs +U 2 ；
5) When in the space angle region of 210 DEG to 270 DEG, let U am ＝-U as -U 1 ，U bm ＝U bs +U 1 ，U cm ＝U cs +U 1 ；
6) When in the spatial angle region of 270 DEG to 330 DEG, let U am ＝U as +U 2 ，U bm ＝U bs +U 2 ，U cm ＝-U cs -U 2 。
In the three-phase modulation wave method for obtaining the optimized carrier NSPWM, U am 、U bm 、U cm Three-phase modulated wave representing optimized carrier NSPWM, U as 、U bs 、U cs Representing a three-phase sine wave in which a specific voltage U 1 The calculation method of (2) is as shown in formula (5):
U 1 ＝1-max(U as ,U bs ,U cs ) (5)
in formula (5), max (U as ,U bs ,U cs ) Representing the maximum value of a three-phase sine wave;
specific voltage U 2 The calculation method of (2) is as shown in formula (6):
U 2 ＝-1-min(U as ,U bs ,U cs ) (6)
in formula (6), min (U) as ,U bs ,U cs ) Representing the minimum of a three-phase sine wave.
2. Modulated carrier wave for obtaining optimized carrier NSPWM
The invention uses ascending carrier with initial value of-1 in the space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG and uses descending carrier with initial value of 1 in the other areas, the method for obtaining the modulation carrier of the optimized carrier NSPWM is as follows:
1) U is arranged in the space angle area of 330 DEG to 30 DEG, 90 DEG to 150 DEG, 210 DEG to 270 DEG carrier ＝UP carrier ；
2) U is arranged in the spatial angle area of 30 DEG to 90 DEG, 150 DEG to 210 DEG, 270 DEG to 330 DEG carrier ＝DN carrier 。
In the above carrier modulation method for obtaining the optimized carrier NSPWM, U carrier Modulated carrier representing optimized carrier NSPWM, UP carrier Represents the rising carrier with initial value of-1, DN carrier Representing a falling carrier with an initial value of 1. Wherein, the setting method of the rising carrier with the initial value of-1 is as followsFormula (7):
in formula (7), t sample Represents the sampling period, t run For a value of 0 to 2t sample A time-running variable that varies cyclically between;
the setting method of the descending carrier with the initial value of 1 is as shown in the formula (8):
3. obtaining the switching signal of the optimized carrier NSPWM
Based on the comparison of the three-phase modulation wave and the modulation carrier wave, the invention obtains the switching signal of the optimized carrier NSPWM, thereby realizing the method for optimizing the carrier NSPWM as follows:
1) In the spatial angle region of 330 DEG to 30 DEG and 150 DEG to 210 DEG, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is XO, and when U bm ＜U carrier When the B phase switch signal is OX; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
2) In the spatial angle region of 30 DEG to 90 DEG and 210 DEG to 270 DEG, when U am ≥U carrier When the phase A switch signal is XO, and when U am ＜U carrier When the phase A switch signal is made to be OX; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
3) In the spatial angular region of 90 DEG to 150 DEG and 270 DEG to 330 DEGWhen U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier When the C phase switch signal is XO, and when U cm ＜U carrier Let the C-phase switch signal be OX.
In the above method for obtaining the switching signal of the optimized carrier NSPWM, XO represents that the upper bridge arm switching device of the corresponding phase is turned off and the lower bridge arm switching device is turned on, and OX represents that the upper bridge arm switching device of the corresponding phase is turned on and the lower bridge arm switching device of the corresponding phase is turned off.
The following describes the effects of the present invention with reference to the drawings.
According to the embodiment of the invention, a two-level inverter model is built by PSIM software, and the effectiveness of the carrier NSPWM method of the two-level converter for preventing overvoltage and eliminating even harmonic is verified by simulation. The example simulation conditions were: the direct-current side voltage is 2000V, the output fundamental wave frequency is 50Hz, the carrier frequency is 1000Hz, the modulation ratio is 0.8, and the simulation step size is 2us.
Fig. 4 shows the phase voltage, line voltage and common mode voltage of the two-level converter under SVPWM in the embodiment. As can be seen from analysis of fig. 4, under the SVPWM effect, the amplitude of the common-mode voltage of the two-level inverter reaches one half of the dc-side voltage value, that is, as can be seen from fig. 4, the amplitude of the common-mode voltage of the present embodiment is only 1000V, and the variation frequency of the common-mode voltage is three times the sampling frequency. The high-amplitude and high-frequency common-mode voltage can influence the service life of a motor and the communication of equipment, and the common-mode voltage needs to be restrained in order to improve the safety and the reliability of a system.
Fig. 5a, 5b, and 5c are simulation results of conventional NSPWM in the embodiment, wherein: fig. 5a is a phase voltage, a line voltage and a common mode voltage of the two-level converter under the effect of the conventional NSPWM, fig. 5b is a result of analysis of amplitude of each subharmonic of the phase voltage of the conventional NSPWM, and fig. 5c is an output line voltage of the two-level converter under the effect of the conventional NSPWM. From this, it can be seen that:
1) In contrast to fig. 4 and 5a, compared to SVPWM, under the conventional NSPWM effect, the common-mode voltage amplitude of the two-level inverter is reduced to one sixth of the dc-side voltage value, and the variation frequency of the common-mode voltage is reduced to twice the sampling frequency. Therefore, the traditional NSPWM can effectively inhibit the amplitude and the change frequency of the common-mode voltage;
2) In contrast to fig. 4 and 5a, conventional NSPWM reduces the switching frequency by one third by clamping the phase voltage to a specific level state, as compared to SVPWM. Therefore, the traditional NSPWM can effectively reduce the switching loss;
3) Analysis of fig. 5b, under the effect of conventional NSPWM, the output phase voltage of the two-level converter contains both odd harmonics and even harmonics of higher amplitude. When the two-level converter is connected with a power grid, the current content of each harmonic on the grid side must be strictly limited within the power grid standard, and the harmonic index of the public power grid has more strict limitation on even harmonics. Therefore, in order to improve the harmonic performance of the traditional NSPWM, even harmonic wave under the action of the traditional NSPWM needs to be eliminated;
4) Analysis of fig. 5C, under the conventional NSPWM effect, the a-phase and B-phase line voltages of the two-level converter have two-level jumps when entering the space angle region of 30 ° to 90 ° or 270 ° to 330 °, the B-phase and C-phase line voltages have two-level jumps when entering the space angle region of 30 ° to 90 ° or 330 ° to 30 °, and the C-phase and a-phase line voltages have two-level jumps when entering the space angle region of 270 ° to 330 ° or 330 ° to 30 °. When the two-level converter is connected with the motor, the overvoltage at the motor end can be caused by the two-level jump of the line voltage, so that the safe operation of the motor is not facilitated. Therefore, in order to improve the reliability of the conventional NSPWM, it is necessary to try to prevent the overvoltage.
Fig. 6a, fig. 6b, fig. 6c, fig. 6d are simulation results of the method of the present invention optimizing carrier NSPWM in the embodiment, wherein: fig. 6a is a phase voltage, a line voltage and a common-mode voltage of the two-level converter under the function of the optimized carrier NSPWM, fig. 6b is a result of analysis of amplitude of each subharmonic of the phase voltage of the optimized carrier NSPWM, fig. 6c is an output line voltage of the two-level converter under the function of the optimized carrier NSPWM, and fig. 6d is a simulation result of obtaining a switching signal of the three-phase device by the optimized carrier NSPWM based on comparison of the three-phase modulation wave and the modulation carrier. Analysis shows that:
1) Comparing fig. 4 and fig. 6a, compared with SVPWM, under the effect of the optimized carrier NSPWM of the present invention, the common-mode voltage amplitude of the two-level inverter is reduced to one sixth of the dc-side voltage value, and the variation frequency of the common-mode voltage is reduced to twice the sampling frequency. Therefore, the amplitude and the change frequency of the common-mode voltage can be effectively restrained by optimizing the carrier NSPWM;
2) Compared with SVPWM in FIG. 4 and FIG. 6a, the optimized carrier NSPWM of the invention reduces the switching frequency by one third by clamping the phase voltage to a specific level state. Therefore, optimizing carrier NSPWM can effectively reduce switching loss;
3) Compared with the traditional NSPWM, the output phase voltage harmonic component of the two-level converter only contains odd harmonic components under the function of optimizing carrier NSPWM in comparison with the traditional NSPWM in fig. 5b and 6 b. Therefore, the optimized carrier NSPWM can effectively eliminate even harmonics, so that the harmonic performance is better;
4) Compared with the traditional NSPWM, the optimized carrier NSPWM of the invention uses the rising carrier with the initial value of-1 in the space angle area of 330 degrees to 30 degrees, 90 degrees to 150 degrees and 210 degrees to 270 degrees, and uses the falling carrier with the initial value of 1 in the rest areas, thereby ensuring that the output line voltage of the two-level converter does not have two-level jump. Therefore, the optimized carrier NSPWM can effectively prevent overvoltage, so that the carrier NSPWM has higher reliability;
5) Analyzing fig. 6d, the optimized carrier NSPWM of the present invention obtains the switching signal of the three-phase device based on the comparison of the three-phase modulated wave and the modulated carrier, and does not need to calculate the action time of the space vector, so the present invention has the advantages of simple operation and easy realization. (marking which is the three-phase modulation wave and which is the three-phase carrier wave)
For example, in the spatial angular region of 270 ° to 330 °, the comparison method is: when U is am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier When the C phase switch signal is XO, and when U cm ＜U carrier Let the C-phase switch signal be OX.
Whereas in fig. 6d, in the spatial angular region of 270 deg. to 330 deg. (specifically illustrated)
Changing the fundamental wave frequency from 50Hz to 100Hz, changing the carrier wave frequency from 1000Hz to 4000Hz, changing the modulation ratio from 0.8 to 0.95, and optimizing simulation results of the carrier NSPWM under different fundamental wave frequencies, different carrier wave frequencies and different modulation ratios by the method in the embodiment shown in FIG. 7a and FIG. 7b, wherein: fig. 7a is a phase voltage, line voltage, common mode voltage and modulation wave of the optimized carrier NSPWM at different fundamental frequencies, different carrier frequencies and different modulation ratios, and fig. 7b is a result of analysis of amplitude of each subharmonic of the phase voltage of the optimized carrier NSPWM at different fundamental frequencies, different carrier frequencies and different modulation ratios. As can be seen from fig. 7a and 7b, when the fundamental frequency, the carrier frequency and the modulation ratio are changed, the optimized carrier NSPWM of the present invention can still effectively suppress the common mode voltage, reduce the switching frequency, prevent the overvoltage and eliminate the even harmonic.
As shown in fig. 4 to 7b, the results of the embodiment verify the effectiveness of a two-level converter optimized carrier NSPWM method of the present invention that prevents overvoltage and eliminates even harmonics. Compared with the traditional NSPWM, the method can prevent overvoltage and eliminate even harmonic while inhibiting common-mode voltage amplitude and changing frequency and reducing switching loss, so that the method has better harmonic performance and higher reliability. In addition, the method directly obtains the switching signals of the switching devices according to the comparison result of the modulation wave and the modulation carrier wave, and the method does not need to calculate the space vector action time, so the method also has the advantages of simple calculation and convenient realization.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The two-level converter optimized carrier NSPWM method provided by the invention is described in detail, and specific examples are applied to illustrate the principle and implementation of the invention, and the description of the above examples is only used for helping to understand the method and core ideas of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (8)
1. A two-level converter optimized carrier NSPWM method, comprising:
superposing a first specific voltage on the three-phase sine wave in a first preset space angle area, a second preset space angle area and a third preset space angle area, and superposing a second specific voltage on the three-phase sine wave in a fourth preset space angle area, a fifth preset space angle area and a sixth preset space angle area to obtain a three-phase modulation wave of optimized carrier NSPWM;
the method comprises the steps that rising carriers with initial values of a first preset value are used in the first preset space angle area, the second preset space angle area and the third preset space angle area, and falling carriers with initial values of a second preset value are used in the fourth preset space angle area, the fifth preset space angle area and the sixth preset space angle area, so that modulation carriers of optimized carrier NSPWM are obtained;
and comparing the three-phase modulation wave with the modulation carrier wave to obtain a switching signal of the optimized carrier NSPWM, thereby realizing the optimized carrier NSPWM.
2. The method for optimizing carrier NSPWM according to claim 1, wherein the step of obtaining the three-phase modulated wave of the optimized carrier NSPWM by superposing a first specific voltage on the three-phase sine wave in a first preset space angle region, a second preset space angle region, and a third preset space angle region, and superposing a second specific voltage on the three-phase sine wave in a fourth preset space angle region, a fifth preset space angle region, and a sixth preset space angle region specifically comprises:
in the first preset space angle area, let U am ＝U as +U 1 ，U bm ＝-U bs -U 1 ，U cm ＝U cs +U 1 ；
In the fourth preset space angle area, let U am ＝-U as -U 2 ，U bm ＝U bs +U 2 ，U cm ＝U cs +U 2 ；
In the second preset space angle area, let U am ＝U as +U 1 ，U bm ＝U bs +U 1 ，U cm ＝-U cs -U 1 ；
In the fifth preset space angle area, let U am ＝U as +U 2 ，U bm ＝-U bs -U 2 ，U cm ＝U cs +U 2 ；
In the third preset space angle area, let U am ＝-U as -U 1 ，U bm ＝U bs +U 1 ，U cm ＝U cs +U 1 ；
In the sixth preset space angle area, let U am ＝U as +U 2 ，U bm ＝U bs +U 2 ，U cm ＝-U cs -U 2 ；
Wherein the three-phase sine wave is a three-phase sine wave with the maximum peak value in the linear modulation ratio region being the difference between the second preset value and the first preset value, U 1 Represents the first specific voltage, U 2 Representing the second specific voltage, U as 、U bs 、U cs A phase A sine wave, a phase B sine wave and a phase C sine wave respectively representing the three-phase sine wave, U am 、U bm 、U cm Representing an a-phase modulated wave, a B-phase modulated wave and a C-phase modulated wave of the three-phase modulated wave, respectively.
3. The method for optimizing carrier NSPWM of a two-level converter according to claim 2, characterized in that,
the first specific voltage is defined as follows:
U 1 ＝K 2 -max(U as ,U bs ,U cs )
in the above, K 2 Represents said second preset value, max (U as ,U bs ,U cs ) Represents U as 、U bs 、U cs Maximum value of (2);
the second specific voltage is defined as follows:
U 2 ＝K 1 -min(U as ,U bs ,U cs )
in the above, K 1 Represents the first preset value, min (U as ，U bs ，U cs ) Represents U as 、U bs 、U cs Is the minimum value of (a).
4. The method for optimizing carrier NSPWM according to claim 1, wherein the obtaining the modulated carrier of the optimized carrier NSPWM by using rising carriers with initial values of a first preset value in the first preset spatial angle region, the second preset spatial angle region, and the third preset spatial angle region, and using falling carriers with initial values of a second preset value in the fourth preset spatial angle region, the fifth preset spatial angle region, and the sixth preset spatial angle region specifically includes:
setting U in the first preset spatial angle area, the second preset spatial angle area and the third preset spatial angle area carrier ＝UP carrier ；
Setting U in the fourth preset spatial angle area, the fifth preset spatial angle area and the sixth preset spatial angle area carrier ＝DN carrier ；
Wherein U is carrier Modulated carrier representing optimized carrier NSPWM, UP carrier The DN represents the rising carrier with the initial value being the first preset value carrier Representing the falling carrier with the initial value being the second preset value.
5. The method for optimizing carrier NSPWM of a two-level converter according to claim 4, characterized in that,
when 0 is less than or equal to t run ＜t sample In the time-course of which the first and second contact surfaces,
the definition of the rising carrier with the initial value being the first preset value is as follows:
the definition of the descending carrier with the initial value being the second preset value is as follows:
when t sample ≤t run ＜2t sample In the time-course of which the first and second contact surfaces,
the definition of the rising carrier with the initial value being the first preset value is as follows:
the definition of the descending carrier with the initial value being the second preset value is as follows:
wherein K is 1 Represents the first preset value, K 2 Representing the second preset value, t sample Represents the sampling period, t run For a value of 0 to 2t sample Time-run variable that varies cyclically between.
6. The method for optimizing carrier NSPWM of a two-level converter according to claim 1, wherein the method for optimizing carrier NSPWM based on comparing the three-phase modulated wave with the modulated carrier wave to obtain a switching signal of the optimized carrier NSPWM is as follows:
in the first preset spatial angle area and the fifth preset spatial angle area, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is XO, and when U bm ＜U carrier When the B phase switch signal is OX; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
in the fourth preset spatial angle area and the third preset spatial angle area, when U am ≥U carrier When the phase A switch signal is XO, and when U am ＜U carrier When the phase A switch signal is made to be OX; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier When the phase B switch signal is XO; when U is cm ≥U carrier Let the C-phase switch signal be OX, and let U be cm ＜U carrier When the phase C switch signal is XO;
in the second preset space angle region and the sixth preset space angle region, when U am ≥U carrier When the phase A switch signal is OX, and when U am ＜U carrier When the phase A switch signal is made to be XO; when U is bm ≥U carrier When the B phase switch signal is OX, and when U bm ＜U carrier At the time, make phase B openThe off signal is XO; when U is cm ≥U carrier When the C phase switch signal is XO, and when U cm ＜U carrier When the C phase switch signal is OX;
wherein U is am 、U bm 、U cm A phase A modulated wave, a phase B modulated wave and a phase C modulated wave respectively representing the three-phase modulated waves, U carrier Representing the modulation carrier of the optimized carrier NSPWM, XO represents that the upper bridge arm switching device of the corresponding phase is turned off, the lower bridge arm switching device is turned on, and OX represents that the upper bridge arm switching device of the corresponding phase is turned on and the lower bridge arm switching device of the corresponding phase is turned off.
7. The method for optimizing carrier NSPWM of a two-level current transformer according to claim 1, wherein the first preset value is-1 and the second preset value is 1.
8. A device for optimizing carrier NSPWM for a two-level converter, comprising:
a three-phase modulated wave acquisition module for superposing a first specific voltage U on the three-phase sine wave in a first preset spatial angle region, a second preset spatial angle region and a third preset spatial angle region 1 Superposing a second specific voltage on the three-phase sine wave in a fourth preset space angle area, a fifth preset space angle area and a sixth preset space angle area to obtain a three-phase modulation wave of an optimized carrier NSPWM;
a modulated carrier acquisition module, configured to use rising carriers with initial values of a first preset value in the first preset spatial angle area, the second preset spatial angle area, and the third preset spatial angle area, and use falling carriers with initial values of a second preset value in the fourth preset spatial angle area, the fifth preset spatial angle area, and the sixth preset spatial angle area, so as to obtain modulated carriers of an optimized carrier NSPWM;
and the switching signal acquisition module is used for comparing the three-phase modulation wave with the modulation carrier wave to obtain a switching signal of the optimized carrier NSPWM, thereby realizing the optimized carrier NSPWM.
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