Dual three-phase permanent magnet synchronous motors suffer from significant stator current harmonics due to inverter nonlinearity

non-sinusoidal back-electromotive force

and external disturbances. Although the conventional extended state observer with resonant terms can effectively observe periodic disturbances

other frequency disturbances suppression performance will be reduced. To address this issue

an optimization method for extended state observer is proposed. First

two disturbance dynamics models are established

based on which conventional resonant extended state observers (ESOs) are systematically classified and modeled. Then

the observer structure is optimized with a notch filter. An effective parameter configuration is proposed to reduce interference among observations of different frequency disturbances and ensure robust suppression over a wide speed range. Additionally

the proposed method can flexibly tune the suppression frequency ranges and strength for periodic disturbances

leading to better performance. Frequency-domain analysis is used to compare the performance of different observers for various frequency disturbance at different speed. Finally

the proposed method is validated on a dual three-phase motor experimental platform. Experimental results show that the proposed method can improve the accuracy of harmonic observation and has good current noise suppression capability.