This paper proposes a novel voltage estimation scheme for the modular multilevel converter (MMC) based on model predictive control (MPC). The developed strategy is presented by combining a disturbance observer (DOB) with an adaptive neural network (ANN) for voltage estimation in the MMC. Firstly, the ac-side and dc bus voltages are estimated as the disturbance items of the DOB which acts as the cost function during each control cycle and ensures the minimal computational cost. Then, the submodule (SM) capacitor voltage estimation is achieved based on the ANN with the estimated ac-side and dc bus voltages. The proposed method requires only one current sensor per arm and has a simple structure with three weights to be adjusted. Comprehensive simulation studies and experiments are presented to demonstrate its effectiveness and feasibility. The results indicate that the proposed method has a high accuracy, a fast dynamic response, and no effects on the original MPC performance.

This article proposes an improved tubular single-phase permanent magnet linear oscillation actuator (SP-PMLOA) considering eliminating detent force for direct drive compressor applications. First, the flux tube method and Maxwell stress tensor are used to derive the end force and cogging force formulations based on the magnetic flux leakage of the magnet rings. Then, a novel model with minimum detent force is presented by finite element parametric sweeping. Finally, the electromagnetic performance of the three SP-PMLOAs is compared using 2-D finite element analysis (FEA), whose merits are evaluated, and the thermal distribution of the optimal PMLOA is analyzed using 3-D FEA. The predicted results show that the proposed structure not only can significantly reduce the detent force and the mover axial length but also can increase the thrust force-moving magnet mass ratio.

Tubular permanent magnet linear oscillation actuator (TPMLOA), with the simple structure and convenient control, has been paid extensive attention in the field of compressors and industry applications. In this paper, an electromagnetic calculation method of the TPMLOA is proposed. Firstly, an improved topology of the TPMLOA is introduced. Then, based on the radially laminated stator and equivalent magnetic circuit method, the actual air gap length is derived, and the total corrected factor is given. Finally, the electromagnetic characteristic of the TPMLOA is analyzed by 2-D finite-element analysis (FEA) considering the corrected air gap permeance, and the results are compared with normal 2-D FEA and 3-D FEA results. Additionally, a prototype of the TPMLOA is manufactured and tested to verify the accuracy of the calculated results. The comparison results show that the proposed method can quickly and accurately calculate the electromagnetic performance.

Single-phase permanent magnet linear oscillation actuators (SP-PMLOAs) have been paid extensive attention in the field of compressors and industry applications. However, the detent force of SP-PMLOA limits the effective stroke and affects the control accuracy of the system. The purpose of this paper is to present a novel C-core SP-PMLOA with double stators arc-teeth and auxiliary slots to reduce detent force. Firstly, the basic structure and dynamic equation of the traditional linear oscillation actuator are introduced. Then, considering the magnetic flux leakage, the detent force formulation is derived by the flux tube method, and a novel structure is presented to reduce detent force and increase the effective stroke by the parametric scan. In addition, the traditional and presented structures of C-core SP-PMLOA are analyzed by 2-D finite element analysis (FEA) mothed. Finally, a prototype is built and tested to verify the results of FEA and calculations. The experimental results show that the presented structure can significantly reduce the detent force and increase the effective stroke.

In this paper, a thermal analysis method of electric motor based on the magnetic equivalent circuit method and the ensemble thermal network method is proposed, which is convenient for modelling, fast for calculation, and is able to obtain the accurate temperature distribution of the motor quickly. Firstly, on the basis of the proposed unitary magnetic circuit model, all kinds of losses of the electric motor are analyzed and calculated. Subsequently, a thermal network model is established, and multilayered modelling is carried out on the rotor and the stator part in order to obtain more accurate calculation results. In the thermal network solution, the two cases of temperature affecting only the copper resistance and temperature affecting the working performance of permanent magnets at the same time are considered, respectively, and the calculation results in the two cases are compared with the finite element temperature field calculation results, which verifies the validity of the calculation method proposed in this paper.