Patent ID: 9444384
Filing Date: 2016-09-13
CPC Classification: H02P

Claim Text:
1. A method of controlling an AC motor, wherein said AC motor is coupled to a power inverter, the method comprising the steps of: estimating an instantaneous output torque at a primary sampling frequency; estimating an instantaneous stator flux at said primary sampling frequency; comparing said instantaneous output torque and a reference torque to determine an estimated torque error; providing said estimated torque error to a torque hysteresis comparator, wherein said torque hysteresis comparator outputs a torque error status based on whether the estimated torque error falls within a primary torque error band or exceeds either a primary upper torque error limit or a primary lower torque error limit, wherein said primary upper torque error limit and said primary lower torque error limit correspond to said primary torque error band; comparing said instantaneous stator flux and a reference stator flux to determine an estimated flux error; providing said estimated flux error to a flux hysteresis comparator, wherein said flux hysteresis comparator outputs a flux error status; selecting and applying 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 for said power inverter coupled to said AC motor measuring a phase current at a secondary sampling frequency, wherein said secondary sampling frequency is at least two times faster than said primary sampling frequency; providing said phase current to a pulse-width-modulation (PWM) controller, wherein said PWM controller compares said phase current to a current limit; leaving said voltage vector selected based on said torque error status and said flux error status unchanged when said phase current does not exceed said current limit; and selecting a null voltage vector when said phase current exceeds said current limit.