CN112271943A - NPC two-level inverter random AZSPWM1 method - Google Patents

NPC two-level inverter random AZSPWM1 method Download PDF

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CN112271943A
CN112271943A CN202011115598.0A CN202011115598A CN112271943A CN 112271943 A CN112271943 A CN 112271943A CN 202011115598 A CN202011115598 A CN 202011115598A CN 112271943 A CN112271943 A CN 112271943A
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azspwm1
random
segment
theta
reference vector
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张晓�
高捷
李昌易
宋明轩
张辉
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China University of Mining and Technology CUMT
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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • 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

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Abstract

The invention discloses a random AZSPWM1 method for an NPC two-level inverter, and belongs to the field of power electronics and power transmission. Firstly, obtaining a sector where a reference vector is located, an active vector used for synthesizing the reference vector, corresponding time T0, T1 and T2 of the active vector, and a 7-segment switch sequence by using a traditional AZSPWM1 method; then determining the duration of each segment in the 7-segment switch sequence to be T0/4, T1/2, T2/2, T0/2, T2/2, T1/2 and T0/4; then multiplying the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence by three different parameters P0, P1 and P2 which are randomly changed within 0-1 and the variants (1-P0), (1-P1) and (1-P2) thereof; and finally obtaining new 7-segment switching time T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2, thereby realizing randomization of the switching pulse position of the inverter and realizing random AZSPWM 1. The invention realizes the spectrum diffusion of harmonic voltage and reduces the amplitude of harmonic wave of output voltage under the condition of not increasing hardware cost and not reducing the modulation performance of AZSPWM1, thereby reducing the electromagnetic interference generated by the harmonic wave.

Description

NPC two-level inverter random AZSPWM1 method
Technical Field
The invention relates to a random PWM (pulse-width modulation) method for an inverter, in particular to a random AZSPWM1 method based on an NPC (neutral point clamped) two-level inverter, belonging to the field of power electronics and power transmission.
Background
The traditional three-phase two-level AZSPWM1 method not only realizes the control of the amplitude and the frequency of fundamental voltage, but also reduces common-mode voltage. However, when the waveform of the line voltage is analyzed by the FFT, the waveform contains abundant higher harmonics, which are mainly concentrated at the switching frequency and its multiple. These harmonics with very high amplitude not only cause electromagnetic vibration of the motor, excite annoying noise, increase motor losses but also cause severe electromagnetic interference, affecting the safe operation of other electronic devices in the inverter system. Therefore, it is necessary to reduce the amplitude and harmonic suppression of harmonics in the line voltage waveform output by the inverter.
For the inverter to reduce the amplitude of the output voltage harmonic, there are two main methods in current practice: the method is characterized in that hardware suppression is realized, the inverter output level number is increased by changing the topology structure of the inverter, so that harmonic waves are reduced along with the increase of the level number, or a filter is used for filtering part of high-frequency harmonic waves. This approach not only increases the cost, but also makes the inverter modulation method more complex. And secondly, software inhibition is carried out, harmonic waves are inhibited through a special harmonic wave inhibition PWM modulation method, but the modulation performance of reducing common-mode voltage by the original AZSPWM1 modulation method cannot be realized, or the switching frequency of the inverter is increased to reduce the harmonic waves and reduce the amplitude of the harmonic waves, but the switching loss of the inverter is obviously increased.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a random AZSPWM1 method for an NPC two-level inverter, which realizes harmonic voltage spectrum diffusion and reduces the amplitude of output voltage harmonics under the conditions of not increasing hardware cost and not reducing AZSPWM1 modulation performance.
In order to achieve the purpose, the technical solution of the invention is as follows: a NPC two-level inverter random AZSPWM1 method comprises the following steps:
(1) obtaining a sector where a reference vector is located, an active vector used for synthesizing the reference vector and corresponding time T0, T1, T2 and 7-segment switching sequences by using a traditional AZSPWM1 method;
(2) determining the duration of each segment in the 7-segment switching sequence to be T0/4, T1/2, T2/2, T0/2, T2/2, T1/2 and T0/4 respectively;
(3) three different parameters P0, P1 and P2, which vary randomly within 0-1, are generated, as well as the deformation parameters (1-P0), (1-P1), (1-P2) thereof;
Figure BDA0002730051500000021
where the function rand () is a random function for generating random numbers, and rand (1) represents the generation of a random arbitrary real number in the range of 0-1. Thus, in each switching cycle of the two-level inverter, random P0, P1, and P2 values within 0-1 are generated.
(4) Obtaining new 7-segment switching time of T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2 by multiplying the parameter which is randomly changed in 0-1 in the step (3) and the deformation thereof by the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence in the step (2), thereby realizing the randomization of the positions of the switching pulses of the inverter and realizing the random of the pulse width with AZSPWM 1;
the reference vector in the step (1) above
Figure BDA0002730051500000022
The number of located sectors N is obtained as follows: firstly, dividing a plane into six sectors, wherein the angle of each sector is pi/3; then using clack transformation, i.e. three-phase voltage Ua、UbAnd UcIs converted into Uα、UβReuse of space vector definition formula
Figure BDA0002730051500000023
Reference vectors can be derived
Figure BDA0002730051500000024
Angle of (theta) is a reference vector
Figure BDA0002730051500000025
Angle with alpha axis) of
Figure BDA0002730051500000026
Finally, the reference vector can be known by the size of theta
Figure BDA0002730051500000027
Number of located sectors N
Figure BDA0002730051500000028
Figure BDA0002730051500000031
The above step (1) uses the conventional AZSPWM1 active vector selection method and switching sequence to select the random AZSPWM1 active vector and switching sequence as follows:
number of sectors Active vectors used and switching sequences therefor
1 OPO-PPO-POO-POP-POO-PPO-OPO
2 OPP-OPO-PPO-POO-PPO-OPO-OPP
3 OOP-OPP-OPO-PPO-OPO-OPP-OOP
4 POP-OOP-OPP-OPO-OPP-OOP-POP
5 POO-POP-OOP-OPP-OOP-POP-POO
6 PPO-POO-POP-OOP-POP-POO-PPO
Wherein, the switching state P indicates that one bridge arm upper tube in the two-level inverter is conducted, so that the output voltage of the inverter is + Udc/2, and the switching state O indicates that one bridge arm lower tube in the two-level inverter is conducted, so that the output voltage of the inverter is 0.
The step (1) utilizes the 'volt-second balance' principle and the traditional AZSPWM1 active voltage vector selection principle to calculate a synthetic reference vector
Figure BDA0002730051500000032
All active vectors
Figure BDA0002730051500000033
Are expressed as times T0, T1, and T2
Figure BDA0002730051500000034
Wherein Ts is a sampling period, and T1, T2 and T0 are vectors respectively
Figure BDA0002730051500000035
With theta ═ theta '- (N-1) pi/3, theta' being a reference vector
Figure BDA0002730051500000041
Included angle with alpha axis, N being reference vector
Figure BDA0002730051500000042
Number of sectors
In the step (4), the parameters randomly changed in the step (3) and the deformation thereof are multiplied by the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence in the step (2), and finally, new 7-segment switching time is obtained, namely T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2, so that the position randomization of the inverter switching pulse is realized, and the random AZSPWM1 is realized.
Compared with the prior art, the invention has the following beneficial effects:
1. the method is changed on the basis of the traditional AZSPWM1 modulation method, hardware does not need to be added, the operation cost is low, and the flexibility is strong;
2. only 6 segments of duration time which is symmetrical about the center in a 7-segment switching sequence in the traditional AZSPWM1 modulation method is randomized, switching loss is not increased, and harmonic voltage spectrum diffusion, amplitude of output voltage harmonic and harmonic suppression are obviously realized while the performance of reducing common-mode voltage by AZSPWM1 is not reduced.
Drawings
FIG. 1 is a flow chart of a NPC two-level inverter random AZSPWM1 method of the present invention;
FIG. 2 is a main circuit topology of a NPC two-level inverter random AZSPWM1 method of the present invention;
FIG. 3 is a sector division and space vector diagram of the NPC two-level inverter random AZSPWM1 method of the present invention;
FIG. 4 shows a reference vector of a NPC two-level inverter random AZSPWM1 method
Figure BDA0002730051500000043
A switching pulse schematic diagram in a second sector;
FIG. 5A is an FFT analysis graph of the output line voltage Uab of the conventional AZSPWM1 method;
fig. 5B is a graph of FFT analysis of a random AZSPWM1 method output line voltage Uab.
FIG. 6 is a graph of the common mode voltage of a conventional AZSPWM1 method;
fig. 7 is a graph of the common mode voltage of the random AZSPWM1 method.
Detailed Description
The following describes in detail an NPC two-level inverter random AZSPWM1 method according to the present invention with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are not to precise scale, and are only used for conveniently and clearly assisting in explaining the technical scheme of the embodiment of the invention.
As shown in the flow chart of the method in fig. 1, the method of the NPC two-level inverter random AZSPWM1 includes the steps of:
(1) obtaining a sector where a reference vector is located, an active vector used for synthesizing the reference vector and corresponding time T0, T1, T2 and 7-segment switching sequences by using a traditional AZSPWM1 method;
(2) determining the duration of each segment in the 7-segment switching sequence to be T0/4, T1/2, T2/2, T0/2, T2/2, T1/2 and T0/4 respectively;
(3) three different parameters P0, P1 and P2, which vary randomly within 0-1, are generated, as well as the deformation parameters (1-P0), (1-P1), (1-P2) thereof;
(4) obtaining new 7-segment switching time of T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2 by multiplying the parameter which is randomly changed in 0-1 in the step (3) and the deformation thereof by the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence in the step (2), thereby realizing the randomization of the positions of the switching pulses of the inverter and realizing the random of the pulse width with AZSPWM 1;
the main circuit topology structure of the NPC two-level AZSPWM1 inverter of this embodiment is shown in fig. 2, the neutral-point-clamped three-phase two-level inverter includes A, B, C three-phase bridge arms, each phase of bridge arm is composed of 2 IGBT switching tubes and 2 freewheeling diodes, point O in the figure represents the neutral point of the dc bus, point n represents the neutral point of the star-connected resistive-inductive load, and the voltage difference between point n and point O is called the common-mode voltage Uno, S1、S 42 switching tubes of phase A are shown. Is a common three-phase two-level NPC circuit.
First, there are 8 possible switching state combinations for the two-level inverter, as shown in table 1 below. And then the clack transformation and the definition of the space vector are utilized, so that a space vector diagram of the two-level inverter shown in the figure 3 can be obtained.
TABLE 1 definition of switching states of two-level inverter
Figure BDA0002730051500000051
Figure BDA0002730051500000061
The space vector is usually defined in terms of two-phase voltages in an alpha-beta coordinate system
Figure BDA0002730051500000062
Thus using the clack transformation, i.e. three-phase voltage Ua、UbAnd UcIs converted into Uα、UβReuse of space vector definition formula
Figure BDA0002730051500000063
Reference vectors can be derived
Figure BDA0002730051500000064
Angle of (theta) is a reference vector
Figure BDA0002730051500000065
Angle with alpha axis) of
Figure BDA0002730051500000066
Finally, the reference vector can be known by the size of theta
Figure BDA0002730051500000067
Number of located sectors N
Figure BDA0002730051500000068
Secondly, a synthetic reference vector is obtained by utilizing the 'volt-second balance' principle and the traditional AZSPWM1 active voltage vector selection principle
Figure BDA0002730051500000069
All active vectors
Figure BDA00027300515000000610
Are expressed as times T0, T1, and T2
Figure BDA00027300515000000611
Wherein Ts is a sampling period, and T1, T2 and T0 are vectors respectively
Figure BDA00027300515000000612
With theta ═ theta '- (N-1) pi/3, theta' being a reference vector
Figure BDA0002730051500000071
Included angle with alpha axis, N being reference vector
Figure BDA0002730051500000072
Number of sectors
Next, the duration of each segment in the 7-segment switching sequence is determined to be T0/4, T1/2, T2/2, T0/2, T2/2, T1/2, T0/4.
Then, three different parameters P0, P1 and P2 were generated, which varied randomly within 0-1, as shown in the following formula, and their variants (1-P0), (1-P1), (1-P2)
Figure BDA0002730051500000073
In the formula, the rand (1) function is a random function for generating random numbers, and rand (1) means that a random arbitrary real number is generated in the range of 0-1. Thus, in each switching cycle of the two-level inverter, random P0, P1, and P2 values within 0-1 are generated.
Finally, multiplying the parameters randomly changed within 0-1 and the deformation thereof by the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence to finally obtain the new 7-segment switching time of T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2, thereby comparing with the triangular carrier waves which are changed periodically to obtain the switching time of the inverter, realizing the position randomization of the switching pulse of the inverter, and realizing the position randomization of the switching pulse of the inverterRandom AZSPWM1 with reference vector
Figure BDA0002730051500000074
Located in the second sector, for example, as shown in fig. 4.
Simulation parameters: DC side voltage Udc250V, a switching frequency of 10khz, a modulation index of 0.69, and star-connected resistance-inductance load parameters of 8 omega and 23 mh.
FIGS. 5A and 5B are graphs comparing the harmonic FFT analysis plots of the output line voltage Uab of the conventional AZSPWM1 method and the random AZSPWM1 method, respectively; wherein, fig. 5A is a graph of FFT analysis of the output line voltage Uab of the conventional AZSPWM1 method, and fig. 5B is a graph of FFT analysis of the output line voltage Uab of the random AZSPWM1 method. The results are obvious when the two figures are compared. The harmonic peak amplitude is reduced from 70 to 45 and, in addition, the diffusion of the high amplitude harmonic into other low amplitude harmonics is evident in fig. 5B. Referring to FIGS. 6 and 7, both the conventional AZSPWM1 method and the random AZSPWM1 method limit the common mode voltage to + -UdcIn/6, it is clear from the above description that the modulation performance of the present invention is hardly degraded. Therefore, the random AZSPWM1 method realizes harmonic voltage spectrum diffusion and reduces the amplitude of suppressing output voltage harmonics under the conditions of not increasing hardware cost and not reducing AZSPWM1 modulation performance, and proves the correctness and the effectiveness of the method.
The invention is not the best known technology.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose of the present invention is to make the contents of the present invention clearly understood and implemented by those skilled in the art, and the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (5)

1. A NPC two-level inverter random AZSPWM1 method is characterized in that: the method comprises the following steps:
(1) deriving reference vectors using the conventional AZSPWM1 method
Figure FDA0002730051490000011
The sector and the synthesized reference vector
Figure FDA0002730051490000012
All active vectors and their corresponding time T0, T1, T2 and 7-segment switching sequences;
(2) determining the duration of each segment in the 7-segment switching sequence in step 1 to be T0/4, T1/2, T2/2, T0/2, T2/2, T1/2 and T0/4;
(3) three different parameters P0, P1 and P2, which vary randomly within 0-1, are generated, as well as the deformation parameters (1-P0), (1-P1), (1-P2) thereof;
Figure FDA0002730051490000013
wherein, the rand (1) function is a random function for generating random numbers, and the rand (1) represents a random arbitrary real number generated in the range of 0-1; thus, in each switching cycle of the two-level inverter, random P0, P1, and P2 values within 0-1 are generated;
(4) and multiplying the parameter randomly changed within 0-1 and the deformation thereof by the 6-segment duration time which is symmetrical according to the center in the original 7-segment switching sequence to obtain new 7-segment switching time T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2, thereby realizing the position randomization of the inverter switching pulse and realizing the random AZWM SPWM 1.
2. The NPC two-level inverter random AZSPWM1 method of claim 1, wherein: the reference vector in step (1)
Figure FDA0002730051490000014
The number of located sectors N is obtained as follows: firstly, dividing a plane into six sectors, wherein the angle of each sector is pi/3; then using clack transformation, i.e. three-phase voltage Ua、UbAnd UcIs converted into Uα、UβReuse of space vector definition formula
Figure FDA0002730051490000015
Deriving reference vectors
Figure FDA0002730051490000016
With the argument theta, theta being the reference vector
Figure FDA0002730051490000017
Angle with alpha axis, theta being of magnitude
Figure FDA0002730051490000018
Finally, the reference vector can be known by the size of theta
Figure FDA0002730051490000019
Number of located sectors N:
reference vector with theta more than 0 and less than or equal to pi/3
Figure FDA0002730051490000021
Located in sector one
Reference vector with phi/3 < theta < 2 pi/3
Figure FDA0002730051490000022
Located in sector two
Reference vector with 2 pi/3 < theta ≦ pi
Figure FDA0002730051490000023
Located sector three
Reference vector with pi < theta and less than or equal to 4 pi/3
Figure FDA0002730051490000024
Located sector four
Reference vector with 4 pi/3 < theta ≦ 5 pi/3
Figure FDA0002730051490000025
Located sector five
Reference vector with the value of theta being more than 5 pi/3 and less than or equal to 2 pi
Figure FDA0002730051490000026
Located in sector six.
3. The NPC two-level inverter random AZSPWM1 method of claim 1, wherein: the step (1) selects an active vector and a switching sequence used by a random AZSPWM1 method synthetic reference vector by using an active vector selection method and a switching sequence of a traditional AZSPWM1, and comprises the following steps:
Figure FDA0002730051490000027
wherein, the switching state P indicates that a certain bridge arm of the two-level inverter is conducted, so that the output voltage of the inverter is + Udc/2, and the switching state O indicates that a certain bridge arm of the two-level inverter is conducted, so that the output voltage of the inverter is 0.
4. The NPC two-level inverter random AZSPWM1 method of claim 1, wherein: the step (1) utilizes the volt-second balance and the traditional AZSPWM1 active voltage vector selection principle to calculate a synthetic reference vector
Figure FDA0002730051490000028
All active vectors
Figure FDA0002730051490000029
Are expressed as times T0, T1, and T2
Figure FDA0002730051490000031
Wherein Ts is a sampling period, and T1, T2 and T0 are vectors respectively
Figure FDA0002730051490000032
With theta ═ theta '- (N-1) pi/3, theta' being a reference vector
Figure FDA0002730051490000033
Included angle with alpha axis, N being reference vector
Figure FDA0002730051490000034
The number of sectors.
5. The NPC two-level inverter random AZSPWM1 method of claim 1, wherein: and (4) multiplying the parameters and the deformation thereof which are randomly changed in the step (3) by the 6-segment duration time which is centrosymmetric in the original 7-segment switching sequence in the step (2) to obtain new 7-segment switching times which are respectively T0P0/2, T1P1, T2P2, T0/2, T2(1-P2), T1(1-P1) and T0(1-P0)/2, thereby realizing the randomization of the switching pulse positions of the inverter and realizing the random AZSPWM 1.
CN202011115598.0A 2020-10-19 2020-10-19 NPC two-level inverter random AZSPWM1 method Pending CN112271943A (en)

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