The field-weakening scheme is generally adopted for traction motors to achieve a wider speed range where the common proportional and integration compensator is needed to regulate the flux-producing current. However, the regulator performance deteriorates due to dc-link voltage disturbances and motor parameter nonlinearities in the different speed regions. To solve this issue, a model predictive control (MPC) based field-weakening algorithm is proposed for a traction electric vehicle using a low-voltage induction motor. The augmented prediction state relationship between stator voltage and flux-producing current is established for motor current control. The steady-state error can be eliminated with an integrator embedded within the augmented equation. The overall closed-loop control is presented where the system eigenvalues are adjusted in real time for various speed regions, and accordingly, the controller performance can be evaluated with the amplitude of the eigenvalues. Moreover, the weight coefficient in the cost function can be adjusted corresponding to speed variation for guaranteed motor control performance. The simulation and experimental results are provided to verify the proposed MPC-based field-weakening algorithm.

The port harmonic features of the single-phase single-stage high-frequency isolated dc–ac converter is not analyzed so far and the corresponding theoretical basis for improving the current quality is still a research gap. In this article, a linear model in frequency domain of the single-stage high-frequency isolated dc–ac converter is originally derived based on the combined harmonic state-space and extended description function modeling technique. The systematic modeling process is analyzed and the accuracy of the modeling is verified by the simulation results. Combined with the model analysis, the harmonic coupling characteristics between the ac side and the dc side are clearly presented. On this basis, this article proposes a closed-loop control strategy to reduce the decrease of the dc-side and ac-side current quality caused by the harmonic coupling at the control level. Furthermore, this article constructs the compound controllers based on the p-type iterative learning to suppress the harmonic currents of the dc side and the ac side, respectively. The composite controller does not distinguish the harmonic frequency. Hence, the proposed controller achieves the effective suppression of the harmonic currents in real time. The effectiveness and feasibility of the proposed control strategy are verified by the experiments.

In order to further improve the integration of the ac grid-connected hybrid energy storage system, a novel three-phase single-stage three-port high-frequency isolated dc-ac converter is proposed in this paper. This converter connects two dc ports and one ac port via a three-winding transformer, saving one ac-side port. The ac-side port uses the matrix converter and the dc-side ports use the interleaved parallel boost converter, which has the advantages of low dc-side current ripple and wide voltage range. The proposed converter achieves galvanic isolation and bidirectional power conversion with the single-stage structure to improve the integration of the converter. A hybrid PWM plus space vector phase shift modulation is proposed to achieve the direct control of the ac side current synthesizing vector and thus ensures the sinusoidal three-phase currents. On this basis, the relationship between the control freedoms is constrained with the optimization objective of minimizing the root-mean-square value of the transformer resonant current, thus the efficiency of the converter is improved. The correctness and the effectiveness of the proposed converter and the corresponding modulation are verified by the detailed experimental results.

In the LCC-LCC wireless power transfer system (WPT) with the secondary buck converter, the overvoltage and overcurrent faults occur when the secondary buck converter is shut down suddenly. In order to ensure the safety, this issue is analyzed at the transient level and the dual-side indirect closed-loop control strategy is proposed to achieve the closed-loop control of the terminal voltage and the secondary dc bus voltage. The secondary dc bus voltage is under the indirect control by the closed-loop control of the primary inverter current and this conclusion is proven in the transient level. Under the dual-side closed-loop control strategy, the two-stage WPT system forms a cascade system and there is the instability problem. The integrated design criteria of the dual-side controller parameters based on the cascade system stability theory is given. The feasibility and practicability of the proposed control strategy and parameter design method are verified by the experiments.

Existing parameter identification methods often neglect the AC losses effect on impedance parameters and exhibit incomplete compensation for low-current-region voltage source inverter (VSI) nonlinearity. As a result, identification failures or inaccuracies occur in low-impedance motors. To address these challenges, this paper presents an impedance-based parameter self-learning method for dual three-phase permanent magnet synchronous motors (DTP-PMSMs). The proposed method utilizes a hybrid current injection sequence that combines xy plane bias current with test-axis sinusoidal current to account for the AC losses effect. The xy bias current saturates the terminal voltage errors, which is then eliminated by differencing the proposed injection states, thereby eliminating the VSI nonlinearity. Additionally, a time-division multiplexed parameter estimation method based on signal processing and recursive least squares (RLS) is introduced to enhance signal-to-noise ratio and identification accuracy. Finally, experiments are carried out on a high-speed, low-impedance DTP-PMSM to verify the proposed method.

This letter elaborates an accurate online parameter identification method for dual three-phase permanent magnet synchronous motors. For resistance and inductance identification, sinusoidal currents are strategically injected into the dq-/xy-planes. Second-order generalized integrator-based quadrature signal generators perform the extraction and differentiation of signals. These techniques eliminate identification errors and instabilities caused by nonideal back electromotive force and inverter nonlinearity. In addition, for the identification of permanent magnet flux linkage, dc current is injected into the d -axis to eliminates q -axis voltage errors caused by inverter nonlinearity, ensuring high accuracy. Experiments have been conducted to validate the effectiveness of the proposed method.