Direct torque control motor controller with transient current limiter

A control system coupled to an AC motor via a power inverter, comprising:

• a primary A/D converter, wherein said primary A/D converter converts a measured analog stator current to a first digital stator current during a primary computational step, wherein said primary computational step is one of a plurality of primary computational steps, wherein initiation of each primary computational step of said plurality of primary computational steps is determined by a primary loop counter operating at a primary sampling frequency;
• a flux and torque estimator coupled to a voltage sensor and to said primary A/D converter, wherein said flux and torque estimator outputs an estimated stator flux and an estimated output torque;
• a flux error estimator, said flux error estimator comparing said estimated stator flux and a reference stator flux and outputting an estimated flux error;
• a torque error estimator, said torque error estimator comparing said estimated output torque and a reference torque and outputting an estimated torque error;
• a flux hysteresis comparator coupled to said flux error estimator, said flux hysteresis comparator outputting a flux error status;
• a torque hysteresis comparator coupled to said torque error estimator, said torque hysteresis comparator outputting a torque error status based on said estimated torque error relative to a primary torque error band;
• a sector evaluator outputting a spatial sector;
• a first device containing a vector selection table, wherein said first device is coupled to said flux hysteresis comparator and to said torque hysteresis comparator and to said sector evaluator, wherein said first device outputs a voltage vector based on said torque error status and said flux error status, wherein said voltage vector determines a set of inverter switching variables, and wherein said first device delays outputting said voltage vector until initiation of a subsequent primary computational step;
• a secondary A/D converter, wherein said secondary A/D converter converts a measured phase current to a measured digital phase current during a secondary computational step, wherein said secondary computational step is one of a plurality of secondary computational steps, wherein initiation of each secondary computational step of said plurality of secondary computational steps is determined by a secondary loop counter operating at a secondary sampling frequency, wherein said secondary sampling frequency is at least two times faster than said primary sampling frequency;
• a pulse-width-modulation (PWM) controller coupled to said first device and to said secondary A/D converter and to said voltage sensor and to said power inverter, wherein said PWM controller compares said measured digital phase current to a preset current limit, and wherein said PWM controller sets said voltage vector to a null voltage vector whenever said measured digital phase current exceeds said preset current limit.