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Several Control Ways of AC Motor II

Update:25-04-2020
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SVPWM Control Method SVPWM (Space Vector Pulse Width Mo […]

SVPWM Control Method

SVPWM (Space Vector Pulse Width Modulatlon, space vector pulse width modulation) control method is a relatively new control method developed in recent years. It is a pulse width generated by a characteristic switching mode composed of six power switching elements of a three-phase power inverter and can make the current waveform of the book as close as possible to the ideal sine waveform. The space voltage vector PWM is different from the traditional sinusoidal PWM. It starts from the overall effect of the three-phase output voltage and focuses on how to make the AC motor obtain the ideal circular flux linkage trajectory. Compared with SPWM, the SVPWM technology has smaller harmonic components of the winding current waveform. The torque ripple of the electric vehicle AC motor is reduced, the rotating magnetic field is closer to a circle, and the utilization rate of the DC bus voltage is greatly improved, and it is easier Digitization.

SVPWM combines basic voltage vectors within one switching cycle to make its average value equal to a given voltage vector. At a certain moment, the voltage vector rotates into a certain area, which can be obtained by different combinations of two adjacent non-zero vectors and zero vectors constituting this area in practice. It is applied multiple times in the cycle to control the action time of each voltage vector, so that the voltage space vector rotates close to a circular trajectory. The actual magnetic flux generated by the different switching states of the inverter approaches the magnetic flux source in the village, and the comparison between the two determines the switching state of the inverter, thereby forming a PWM waveform.

Suppose the voltage on the DC bus side is Udc, and the three-phase phase voltages output by the inverter are Uu, Uv, Uw, which are respectively sandwiched on a three-phase plane static coordinate system with a spatial difference of 120 °, and three voltage space vectors can be defined Uu (t), Uv (t), Uw (t), their direction is always on the axis of each phase, and the size changes with time according to the sine law, and the time and phase are different from each other by 120 °.

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