Optimizing PWM modulation method capable of restraining harmonic wave
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A modulation method and harmonic technology, which are used in control systems, AC motor control, output power conversion devices, etc.
Inactive Publication Date: 2010-06-02
NORTHWESTERN POLYTECHNICAL UNIV
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The feature of this method is that it can be realized by programming. It not only solves the problem of the calculation amount of the SHEPWM method or the storage amount of the look-up table, but also uses the synthesized voltage vector to approximate the circular trajectory of the flux linkage, which helps to reduce the torque ripple. And complete the task of selecting harmonic cancellation
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Embodiment 1
[0099] 1. For the one-phase output PWM pulse function expression of the inverter is the following formula, that is, formula (4),
[0100] U km = 2 U d Kπ [ 1 + 2 Σ i = 1 N ( - 1 ) i cos ( K α i ) ] , ( n = 1 , 3 , 5 , . . . )
[0101] According to the variable voltage variable frequency strategy (such as VVVF control, etc.), the reference voltage vector V * , and determine the deg...
Embodiment 2
[0116] Still use formula (4) as the one-phase output PWM pulse function expression of the inverter. A feasible implementation step is:
[0117] 1~7 steps are with embodiment one;
[0118] 8. When k is an even number, it is the working stage of the up counter, and when k is an odd number, it is the working stage of the down counter. Determine the state of the switching angle, and output the PWM level according to the comparison rule in Table 5;
[0119] Steps 9 to 10 are the same as in Embodiment 1.
Embodiment 3
[0121] Still use formula (4) as the one-phase output PWM pulse function expression of the inverter. A feasible implementation step is:
[0122] 1,2 steps are with embodiment one;
[0123] 3. Start from any area between area II~VI, from k=1 to k max =N+1, according to the parity of k value, determine the basic voltage vector that works in this area;
[0124] Steps 4 to 10 are the same as those in Embodiment 1, and the three-phase output PWM pulse waveform of the inverter can still be obtained with the same effect.
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Abstract
The invention discloses a modulating method for the optimized PWM of restrainable harmonic waves, which utilizes the combination of space voltage vectors (SVPWM) to realize the elimination of 'm' ('m'equals to 6 multiplied 'j' and plus or minus1; 'j' equals to 1, 2, ellipsis) times of harmonic wave, wherein, 'm' refers to a certain odd number which is not divisible by 3 and comprises 5, 7, 11, 13, etc. The method of the invention is characterized in that the method can be realized by programming, thereby not only solving the problem of calculated amount or look-up table memory capacity existing in a SHEPWM method, using the combined voltage vector to approach the circular trace of a flux linkage, and helping to reduce torque pulsation, but also fulfilling the task of selectively eliminating the harmonic wave.
Description
technical field [0001] The invention relates to a PWM modulation method, which is used to realize the control of a three-phase voltage type inverter to drive a three-phase AC motor to run. Background technique [0002] Three-phase voltage source inverters can be used in AC motor drive and inverter power supply, and the corresponding pulse width modulation (Pulsewidth modulation, PWM) technology, especially the voltage space vector PWM (space vector pulse width modulation, SVPWM) technology has gradually become One of the most widely used modulation techniques. [0003] The basic principle of SVPWM technology is: using figure 1 The 8 switching states of the inverter in the shown main circuit are used to synthesize the space voltage vector and send out PWM waves. figure 1 In , if 1 is used to represent the conduction state of the switching device of the upper arm of each phase of the inverter, and 0 is the conduction state of the switching device of the lower arm of the inve...
Claims
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