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This paper deals with the reduction of torque ripple in a PMSM (permanent magnet synchronous motor) drive using disturbance observer based control. The current ripple is periodically synchronized to the position of the rotor in the form of distorted back-EMF voltage. Therefore, the current ripple is concentrated on the rotation frequency and integral multiples in the frequency domain. In this paper, a method is introduced to reduce the current ripple while maintaining reference tracking performance without a significant change of the controller by intensively increasing the disturbance suppression performance of the frequency band corresponding to the current ripple. The proposed method is verified that a steady-state 58% ripple reduction in 500W SPMSM in the experiments.

This study exhibits a self-tuning speed control scheme for the surface-mounted permanent magnet synchronous motor (SPMSM) against the parameter variations through the multivariable approach. The proposed method has two novelties. The first one is to combine the adaptive controller with the self-tuning algorithm so as to make the decay ratio of the tracking errors higher in the transient period. The second one is to provide a systematical way to find a robust stabilizing control gain corresponding the speed and current tracking errors by solving an optimization problem. The efficacy of the proposed method was experimentally investigated using a 3- kW SPMSM.

This paper presents a cascade output voltage control law adopting the self-tuning adaptive inner and outer-loop controllers for a AC/DC converter modelled as a nonlinear system. The first contribution is to design the inner and outer-loop controllers updating their control gains to enhance the closed-loop performance, estimating unknown parameters. The second one is to show that the proposed inner-loop controller stabilizes not only current error dynamics but also output voltage dynamics viewed as internal dynamics. The effectiveness of proposed method is shown by performing experiments using a 3-kW AC/DC converter.

In this paper, an offset-free model predictive control (MPC) method is suggested for regulating the output voltage of a three-phase inverter for an uninterruptible power supply (UPS) application through the multivariable design approach. A reference state, which satisfies the control objective of output voltage regulation, is derived. In addition, a one-step-ahead cost index penalizing the state tracking error is used by the proposed MPC. A disturbance observer (DOB) is used to compensate for the errors caused by uncertainties. Online optimization considering the input constraint of the inverter system is very simple, and no numerical method is required. It is shown that the proposed MPC makes the closed-loop system globally asymptotically stable in the presence of input constraints. The closed-loop performance is experimentally evaluated when resistive and resistive–inductive loads are used.

This paper proposes an offset-free model predictive control (MPC) method for output voltage regulation of the three phase inverter for an uninterruptible power supply (UPS) application. A use of a disturbance observer (DOB) is made to estimate the unknown disturbance caused by the load current and a plant-model mismatch. The proposed MPC optimizes the one step ahead cost function. The online computation considering the input constraint of the inverter system is very simple. It is shown that the closed-loop system is globally asymptotically stable in the presence of input constraints and that the integral action in the DOB eliminates the steady state errors caused by a plant-model mismatch. The effectiveness of the closed-loop system is experimentally shown under a use of resistive load.