Torque ripple suppression of permanent magnet synchronous machines by minimal harmonic current injection

Reducing torque ripples in a permanent magnet (PM) synchronous machine (PMSM) system has been an essential requirement in some high‐performance applications. To suppress the torque ripples caused by time harmonics and spatial harmonics, an approach based on injecting minimum harmonic currents is proposed here. The proposed method extracts torque ripples from speed fluctuations, and the gradient descent optimisation (GDO) is utilised to determine the injected harmonic currents which are the commands of the harmonic current regulators. Using the torque ripple minimisation and the injected harmonic current minimisation as the two objectives, the GDO not only minimises the torque ripples of the PMSM system but also guarantees that the magnitude of the injected harmonic currents is minimal. The proposed method is simple to implement in the hardware and does not require complex computation. Its effectiveness is verified by experimental results.