In the high-frequency (HF) signal injection based position sensorless permanent magnet synchronous motor (PMSM) drives, there is an estimated position error caused by the cross-saturation effect and other factors. In order to suppress the position error, an HF injection angle self-adjustment based online suppression method is proposed in this letter. By tracking the sign of the increment of the absolute back electromotive force in the estimated frame, the criterion of the HF injection angle self-adjustment can be determined online and the position error can be mitigated effectively. This method can avoid the offline measurement or the variation of the operating state, which has a satisfactory suppression effect for the position error under different operating conditions. The effectiveness is verified by experiments on a 2.2-kW PMSM drive platform.

In a position sensorless permanent magnet synchronous motor (PMSM) drive system, parameter mismatch will introduce estimation error in the stator flux and rotor position information. A novel flux observer based on an enhanced second-order generalized integrator (SOGI) with a limit cycle oscillator is proposed to improve the robustness of sensorless PMSM drives. Based on the SOGI structure, the proposed method constructs a nonlinear oscillator with a self-excited oscillation function that can maintain the flux trajectory oscillation even in the absence of the input stator electromotive force. The enhanced observer can converge the stator flux trajectory to its expected state under external disturbances and reduce position estimation error. Moreover, the proposed limit cycle oscillator can improve the harmonic suppression ability of the SOGI-based flux observer. The convergence and robustness of the enhanced observer are both investigated, demonstrating that the proposed method can improve the performance of the flux observer. The effectiveness of this method is verified by experiments on a 2.2-kW PMSM drive platform.

The LC resonance between the line inductor and the DC-link film capacitor is an important concern in the reduced DC-link capacitance interior permanent magnet synchronous motor (IPMSM) drive system. In this paper, an active damping method based on the virtual damping resistor is applied to suppress the LC resonance and improve the drive system stability. The performance of the damping resistor is analyzed in a systematic level, and possible configurations have been analyzed to obtain the optimal solution, which is proved to be the inductor current feedback (ICF) damping method. In order to realize the equivalent damping effect, the DC-link voltage feedback is applied to emulate the ICF-based active damping method by a step-by-step approach. Meanwhile, the grid voltage distortion will stimulate additional harmonics of the grid current in the reduced DC-link capacitance motor drives. Hence a feedforward compensation method is applied to suppress the grid current distortion arising from the distorted grid voltage, which has not been investigated in the previous related researches. Harmonics of the grid current are reduced and requirements of EN61000-3-2 can be satisfied by applying the proposed method. Experiments on a compressor drive platform equipped with reduced DC-link capacitance are performed to verify the effectiveness of the proposed method.

Because of the time-sharing sampling logic, the three-phase currents reconstructed by single DC-link shunt present significant errors in the permanent magnet synchronous motor (PMSM) drives. A traceback-prediction current correction method for sampled currents is proposed in this paper to eliminate the reconstruction errors. According to the analysis of time-sharing sampling errors, the concept of equivalent current change rate during one PWM period is introduced, and the phase current characteristic model based on state observer is established. Both the equivalent and instantaneous current change rates can be obtained by the observer-based calculation method. In order to improve the current reconstruction precision, the ultimate values of three-phase currents can be predicted by adopting the proposed traceback-prediction current correction method, which does not require major computation and is easy to implement with no restrictions on the PWM strategy. The effectiveness of the proposed method is verified by experimental results

Existing online parameter identification methods of permanent magnet synchronous motors (PMSMs) are generally based on the voltage equations, the precision of which is affected by the cross coupling and magnetic saturation effects. In order to deal with this issue, a virtual-rotary-axis high-frequency signal injection based online parameter identification method is proposed in this article, where the cross coupling and magnetic saturation effects on the traditional dq -axis model are analyzed. On this basis, an optimized voltage model under the composite magnetic field rotary axis is introduced. In the proposed method, the cross-coupling angle and the dq -axis inductances can be identified by injecting the high-frequency signal into the constructed virtual rotary axis. In addition, the complex Simpson integral algorithm is adopted to obtain the information of the incremental and apparent inductances. Finally, the permanent magnet flux linkage can be estimated based on the composite magnetic field rotary axis voltage equations. The effectiveness and feasibility of the proposed method are verified by the experiments on a 2.2-kW PMSM drive.

Permanent magnet linear synchronous motor (PMLSM) suffers from inherent thrust ripples, which cause vibration and noise and worsen the control performance. In this article, an iterative learning thrust ripple suppression method based on a proportional resonant internal model extended state observer (PR-IMESO) is proposed for PMLSM drives. A P-type iterative learning controller (PILC) with the forgetting factor is constructed to suppress the detent force which is the main component of thrust ripples and periodic force ripples. On this basis, PR-IMESO is constructed to further suppress the detent force and the residual disturbance in thrust ripples. In addition, the convergence, stability, and parameter sensitivity of the suppression method are analyzed. The proposed PR-IMESO-based PILC suppression method can suppress thrust ripples of PMLSM pertinently according to their characteristics to achieve overall control performance improvement. Finally, the effectiveness of the proposed method is verified on a 750-W PMLSM experimental platform.