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Space vector pulse width modulation (SVPWM)-Nooyi

Author: ComeFrom: Date:2017-12-15 11:53:24 Hits:585
SVPWM:SVPWM is the abbreviation of Space Vector Pulse Width Modulation.

Working principle:

The main idea of SVPWM is based on the three-phase symmetrical sine wave voltage three-phase motor stator ideal flux circle as the reference standard, with three-phase inverter (inverter) of different switching mode for proper switching, thereby forming a PWM wave, the actual flux vector formed to track its accurate flux circle. The traditional SPWM method from the supply point of view, to generate a frequency modulated voltage sine wave power supply, and the SVPWM method of the inverter (inverter) and asynchronous motor system as a whole to consider, the model is relatively simple, but also facilitate the real-time control of microprocessor.

A common three phase full bridge is a three half bridge consisting of six switch devices. The six switch devices are combined (opposite the upper and lower half bridges of the same arm), and there are 8 safe switching states. Of these, 000, 111 (here are the switching states of the three upper bridge arms), the two switching states do not produce an effective current in the motor drive. So it is called a zero vector. The other 6 switching states are six effective vectors, respectively. They divide the voltage space of 360 degrees into 60 degrees, a sector and six sectors. Using these six basic effective vectors and two zeros, we can synthesize any vector within 360 degrees.

When we want to synthesize a vector, we decompose the vector into the two basic vectors nearest to it, then use these two basic vectors to represent, and the action size of each basic vector is represented by the action time. Voltage vectors are synthesized by voltage vectors at different time proportions. This ensures that the generated voltage waveform is approximate to the sine wave.

When the variable frequency power is driven, the vector direction changes continuously, so we need to continuously calculate the time of the action of the vector. For the convenience of computer processing, it is usually timed to calculate (for example, once per 0.1ms) during the synthesis. So we can just figure out the time that two basic vectors are acting in 0.1ms. The sum of two time calculated may not be 0.1ms (smaller than this), and that the rest of the time to insert the appropriate zero vector. The synthetic drive waveform is similar to that of PWM because of this quantity. So we call it PWM, and because this PWM is based on the voltage space vector, it is called SVPWM.

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