Patent ID: 9209735
Filing Date: 2015-12-08
Classification: H02P

Abstract:
1. A control system for an electric three-phase variable speed motor having a stator and rotor, the control system comprising an inverter for providing power to the electric motor, a scalar based control arrangement for controlling said inverter, and current sensors configured to repeatedly detect currents of the motor, wherein the control arrangement comprises: a d and q axis currents determining module configured to repeatedly determine d and q axis currents based on the detected currents; a filter block for repeatedly filtering the determined q axis current, thereby generating a reference q axis current; an MTPA (maximum torque per ampere) control block for repeatedly generating a reference d axis current based on said determined d and q axis currents and a ratio value such that the ratio of the d and q axis currents is equal to said ratio value, wherein said ratio value is unity, and a switching signal generation module configured to repeatedly generate switching signals to control said inverter based on said reference d and q axis currents characterized in that the control arrangement comprises a fine adjustment module which is configured to calculate a magnitude of a current or power of the motor and to determine an optimum compensation ratio value based on the calculated magnitude of a current or power of the motor, which optimum compensation ratio value is added to the ratio value to form an adjusted ratio value, which adjusted ratio value when being used by the MTPA control block would cause the motor to operate in a condition wherein the magnitude of a current or power of the motor is minimized, wherein the MTPA control block is configured to repeatedly generate an adjusted reference d axis current based on said determined d and q axis currents and said adjusted ratio value such that the ratio of the d and q axis currents is equal to said adjusted ratio value; and the switching signal generation module is configured to repeatedly generate switching signals to control said inverter based on said adjusted reference d axis current.