Synchronous SVPMW modulation strategy digital realizing method based on switching angle
An implementation method and technology of switching angle, which can be used in control systems, control generators, vector control systems, etc., and can solve problems such as the decrease of motor current control effect and the discontinuous change of modulation calculation frequency.
Active Publication Date: 2018-08-28
BEIJING JIAOTONG UNIV
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[0055] (2) In the synchronous SVPWM modulation strategy based on the space vector implementation method, when switching between different modulation modes, the carrier ratio changes, and the modulation calculation frequency changes discontinuously, which leads to the problem that the motor current control effect decreases during the switching process
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[0130] The following is attached Figure 1-16 The present invention is described in further detail.
[0131] Let's take 11 frequency division BBCS SVPWM as an example, according to its vector action sequence, you can get the pulse waveform within a fundamental cycle, taking the A-phase pulse waveform as an example, as follows Figure 7 shown, from Figure 7 It can be seen that the A-phase pulse waveform has 1 / 2 cycle even symmetry and 1 / 4 cycle odd symmetry, so the concept of switching angle proposed in SHEPWM (Specific Harmonic Elimination Pulse Width Modulation) modulation can be used, according to each The switching angle within 1 / 4 cycle is deduced at the switching action moment of a small sector, and then the pulse of the entire fundamental wave cycle can be obtained according to the vector action sequence, and the switching angle and A-phase pulse are drawn in the same graph, as follows Figure 7 .
[0132] Figure 7 It is the overmodulation process of 11-frequency s...
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The invention relates to a synchronous SVPWM modulation strategy digital realizing method based on a switching angle. The method comprises the steps of S1, dividing a voltage vector complex plane intosix 60-DEG I-VI large sectors by the SVPWM by means of six basic voltage vectors which correspond with six switch devices and two zero vectors, equally dividing each 60-DEG large sector into five small sectors, setting a sampling point at the midpoint of each small sector, synthesizing an instruction voltage vector according to a vector action sequence; S2, calculating m according to a current instruction voltage amplitude, obtaining action time of two basic voltage vectors and action time of a zero vector according to a volt-second balance principle; S3, calculating five switching angles alpha1, alpha2, alpha3, alpha4 and alpha5 in a quarter period according to a current modulation ratio; S4, calculating a duty ratio by means of the switching angle, furthermore calculating comparing values A and B, comparing the counted value of a counter with the comparing values A and B, when the counted value is higher than the comparing value A, setting to a high grade, and when the counted valueis higher than the comparing value B, setting to a low grade, thereby obtaining an A-phase pulse waveform; and S5, obtaining a B-phase pulse waveform and a C-phase pulse waveform according to three-phase symmetry.
Description
technical field [0001] The invention relates to the field of power electronics and electric transmission, in particular to a digital implementation method of a synchronous SVPWM modulation strategy based on switching angles. Background technique [0002] figure 1 It is a circuit diagram of a two-level voltage source inverter widely used in high-power AC drive control systems. Space vector pulse width modulation (SVPWM) starts from the macroscopic point of view of motor control, and its purpose is to make the three-phase two-level inverter The 3 bridge arms and 6 switching devices generate the final modulation wave according to the specific switching mode, so that the output current waveform is as close as possible to the ideal sinusoidal waveform, and the three-phase synthetic rotating magnetic field is close to a circle. [0003] SVPWM uses 8 voltage vectors corresponding to 6 switching devices (6 basic voltage vectors, 2 zero vectors), and divides the voltage vector compl...
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Login to View More IPC IPC(8): H02P21/22H02P27/08
CPCH02P27/08
Inventor 杨中平林飞方晓春朱龙胜李华孙湖
Owner BEIJING JIAOTONG UNIV