Predictive current control method for a six-phase induction motor

A predictive current control method for a six-phase induction motor driven by a six-phase inverter, comprising:

• initializing the six-phase inverter at a present control sample comprising a present switching state corresponding to a present voltage vector, wherein the six-phase inverter employs the present control sample for converting a DC input voltage to a set of six-phase outputs for an operation of the six-phase induction motor;
• measuring a stator current and a rotor speed of the six-phase induction motor;
• transforming the measured stator current to a set of orthogonal subspace current values, wherein the set of orthogonal subspace current values comprising a set of current values in αβ and xy frames;
• estimating a set of rotor variables of the six-phase induction motor using a difference between the measured rotor speed and a reference rotor speed, wherein the set of rotor variables comprising a pair of current values in αβ frame and xy frame;
• calculating a future stator current for a future control sample of the six-phase inverter based on the transformed set of orthogonal subspace current values, estimated set of rotor variables, and the measured rotor speed;
• selecting four candidate voltage vectors from sixty-four voltage vectors mapped to αβ and xy frames corresponding to sixty-four possible switching states of the six-phase inverter, comprising:
• predefining a lookup table representing a correlation between twelve possible non-zero voltage vectors and twelve corresponding groups of voltage vectors, wherein the twelve possible non-zero voltage vectors are twelve possible switching states of the six-phase inverter with on state for at least one of but not all of the set of six phase outputs, wherein each group of the twelve corresponding groups of voltage vectors comprising four voltage vectors;
• selecting a non-zero voltage vector from at least one of the present voltage vector if the present voltage vector is non-zero and a last appeared nonzero voltage vector from the lookup table;
• and
• identifying a group of voltage vectors from the lookup table corresponding to the selected non-zero voltage vector, wherein the identified group of voltage vectors corresponds to the four candidate voltage vectors;
• implementing a cost function to calculate a squared error between the predicted future stator current and a reference stator current, wherein a weighing factor is applied to the cost function;
• calculating a plurality of cost function results corresponding to each of the four candidate voltage vectors;
• identifying a future voltage vector providing a minimum of the calculated plurality of cost function results for the future control sample;
• saving the future voltage vector as an input to the lookup table for a successive control sample;
• and
• controlling a plurality of current values in αβ and xy frames of the six-phase induction motor by applying the future control sample as a switching state of the six-phase inverter.