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We need a second nested controller to dictate the current passed to the motor, based on the first controller, which passes a current reference to the nested controller. It then compares it to the current we have running through the motor, and modulates the voltage being applied to the motor phases based on the error between the actual current and desired current.
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It is useful to think of the current as a vector in a polar reference frame (rotation angle and magnitude). The magnitude of the current commanded and the voltage applied are functions of the error terms going into the controllers, and the angle at which they are applied is a function of the orientation of the DQ axis and thus the rotor’s position. These two variables are separately controlled. The magnitude of the vector will be determined by the feedback control loop. Meanwhile, the angle of application will be a function of rotor angle and will be controlled by the chosen method of commutation and PWM to the H-bridge.
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If you were using 6-block commutation with your feedback controller, your current controller would look at the current running through your motor, would then compare it to the reference that has been provided, and then generate the magnitude of the voltage signal to be applied, which would then be used to find the duty cycle to be applied to the MOSFETs of the H-bridge.
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SVM
Just like with sinusoidal modulation, space vector modulation maintains a voltage differential which rotates with the motor angle to stay in line with the Q axis.
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However, it takes full advantage of your supply voltage.
The goal is to create three-phase voltages that are required to drive our PMSM motor, by way of using a three-phase inverter, which takes as an input a constant DC voltage. For properly converting DC to AC power, we need to control the on and off states of the inverter switches along with their switching sequence.
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