A system comprises an electric submersible pump (ESP) motor electrically coupled to a variable speed drive (VSD) that outputs voltage to the ESP motor. The system comprises a magnet on a shaft of the ESP motor and a downhole sensor coupled to the magnet, wherein the downhole sensor is to measure a magnetic flux of the magnet. The system comprises a VSD controller to control the VSD, wherein the VSD controller comprises a processor and a non-transitory memory storage having instructions stored thereon that are executable by the processor to perform operations comprising: obtaining a measurement of at least one pump performance variable and a motor current for a first period of time to establish a first data set and making a first adjustment to a voltage output from the VSD to the ESP motor, the first adjustment having a first adjustment type.