Xiaochen Ma

For dual three-phase (DTP) permanent-magnet synchronous machine (PMSM), vector space decomposition (VSD) is a classical modeling method that can separate the main harmonic (5th and 7th) currents from the fundamental current. However, the 5th and 7th harmonics in VSD model are still coupled. Conventional methods use filters to decouple harmonics of different orders, yet this inevitably affects control performance. Considering this issue, this paper proposes a new method to decouple the harmonic currents of DTP PMSM without using filters. First, through Park transform, the original harmonic subspace of VSD model is converted into the rotating coordinate system (RCS). Consequently, the 5th and 7th harmonic current vectors become two vectors with the same rotation speed and opposite rotation directions. On this basis, two reconstructed harmonic subspaces are proposed by performing time-shifting and axes-rotation operations on the harmonic subspace under RCS. By arranging the two reconstructed harmonic subspaces appropriately, natural decoupling of 5th and 7th harmonic currents can be achieved through vector operations. In light of such decoupling features, the corresponding harmonic regulation scheme has been further designed. Experimental results validate the correctness of the proposed method and demonstrate its advantages over existing methods in terms of harmonic control performance and computational burden.

Considering the local magnetic characteristics of surface‐mounted permanent magnet (SPM) motors, the paper proposes an adaptive connecting equivalent magnetic network (ACEMN) model to accurately predict SPM motor performance. First, for modeling the magnetic field at the inclined boundary of the stator pole shoe, a diagonal hybrid permeance element covering two materials is developed. And considering the parallel magnetization of PMs, a branching calculation of the magnetomotive force source is performed inside a cross‐shaped permeance of a fan‐shaped mesh. Then, by analyzing the phenomenon of magnetic field line deflection at the air gap boundary, an air gap node connecting way based on adaptive conversion of connecting permeances is built. Thereby, the rotating magnetic field of the air gap can be accurately described using the different connecting permeances with variable size. To accelerate the nonlinear solution for saturated element permeability, a hybrid iterative method is used. The validity of this modeling method is verified by finite element analysis (FEA) and prototype experiments, which allows a satisfactory compromise between accuracy and calculation speed.

This study proposes a new modeling and control scheme for dual three-phase permanent-magnet synchronous machine with harmonic current regulation requirements. Compared with existing schemes, the proposed scheme further considers the situation where two sub-three-phase winding sets of the machine are in an unbalanced power sharing state. In such case, classical vector space decomposition (VSD) will no longer be able to decouple the fundamental and main harmonic (5th and 7th) currents into the fundamental and harmonic subspaces, respectively. Consequently, both subspaces need more filters to separate the fundamental and harmonic current components, thereby affecting control performance. For this reason, this article first analyzes the specific coupling mechanism of fundamental and harmonic currents in VSD model under unbalanced power sharing. Subsequently, based on common-mode and differential-mode concept, two virtual balanced systems are proposed to decouple the coupling of fundamental and harmonics caused by power unbalance. Owing to the natural decoupling features of the proposed scheme, the dynamic and steady-state performance of current regulation under unbalanced power sharing can be improved. Finally, the effectiveness and advantages of the proposed scheme are verified by experiments.

In this article, a new space vector pulsewidth modulation (SVPWM) strategy is proposed for dual three-phase (DTP) machine drives. The proposed strategy is based on vector space decomposition (VSD) and mainly targets the scenario where power of the two subthree-phase winding sets of the machine is unequal. In the basic VSD-based SVPWM strategies, the constraints of non-negative dwell time of the basic vectors result in zero linear modulation range when the DTP machine is under unbalanced power sharing conditions. Different from them, this article investigates the maximum linear modulation capability of VSD-based SVPWM under power sharing by removing the dwell time constraints of the basic vectors. In this regard, only the physical limitations of the dwell time of each phase need to be guaranteed. According to this principle, a two-step-based design procedure of the proposed modulation strategy is presented in detail, followed by a numerical analysis regarding its linear modulation boundary. Moreover, the performance comparisons with many other typical VSD-based SVPWM strategies are also conducted. It has been theoretically and experimentally proven that the proposed SVPWM solution can obtain maximum linear modulation range when the DTP machine is under unbalanced power sharing.

Five-phase permanent-magnet synchronous motor (PMSM) has the ability of fault-tolerant operation, which is beneficial for high reliability occasions. A fault-tolerant current vector control strategy based on five-phase six-leg inverter is proposed for open-circuit fault in this article. It deals with single-, double-, and triple-phase fault conditions. First, the overall control scheme is established based on the mathematical model of five-phase surface-mounted PMSM. To release more control degrees of freedom, the constraint for the sum of fault-tolerant phase currents is removed, and the control variates method is used to calculate the optimal fault-tolerant currents. Furthermore, to achieve the current tracking, the corresponding reduced-order current transformation matrices are derived, and the corresponding main power topology, the five-phase six-leg voltage source inverter (VSI), is established. The unbalanced operation of the topology is investigated, the equivalence to the full-bridge VSI is proved, and the voltage utilization and voltage unbalance of five phase half-bridge, full-bridge, and six-leg inverter are compared. Then, the corresponding carrier-based PWM control strategy based on zero-sequence injection has been proposed, which is equivalent with the three-dimensional space vector PWM algorithm and is computationally efficient. The experimental results confirm the effectiveness of the proposed fault-tolerant control strategy.

This paper presents a new soft switching high voltage gain interleaved dc-dc converter with a three-windings coupled inductor for a fuel cell vehicle. Two interleaved and intercoupled boost cells are connected by the input parallel and output series (IPOS) configuration, realizing low input current ripple and high voltage gain simultaneously. All power switches can operate under soft switching conditions by only adding a simple auxiliary circuit composed of one auxiliary inductor and one power switch. Besides, the auxiliary inductor is coupled with the main inductors, which results in a rapid zero convergence of the auxiliary current and a small conduction loss of the auxiliary circuit. The operating principle, steady state characteristic, comparison with other converters, and parameter design are analyzed in this paper. Finally, the main characteristics of the proposed converter are verified by a 1-kW laboratory prototype.

In this article, a novel bidirectional dc-dc converter (BDC) consisting of an active switched-inductor (A-SL) cell, a zero current ripple cell and an auxiliary capacitor cell is proposed for the battery energy storage system. The proposed BDC integrates with the advantages of high voltage conversion ratio, low power switch voltage stresses, zero ripple current on the low voltage side (LVS), and constant potential difference between the grounds of LVS and high voltage side. Thanks to the use of synchronous rectification technology, the efficiency of the proposed BDC is increased. The operating principles, the characteristics analysis and the parameter design of the proposed BDC are given. In addition, to show the merits of the proposed BDC, a comparison study involves the proposed converter and other BDCs is demonstrated. Finally, some experimental results obtained using a 1000 W prototype are presented to valid the effectiveness of the proposed BDC. 96.43% and 96.67% maximum conversion efficiencies can be achieved in the step-up and step-down modes, respectively.

In this paper, a bidirectional inductor-inductor-capacitor-inductor (LLCL) resonant dc-dc converter is presented. Compared with the conventional LLC, a parallel-connected inductors structure is employed into the resonant tank. By virtue of this unique resonant tank, LLCL exhibits the following desirable features: 1) good voltage gain regulation capability in bidirectional power flow applications; 2) zero-voltage-switching turn-on of the power switches in a wide load range; 3) compared with the other bidirectional LLC-type resonant converters, lower resonant tank currents and lower resonant capacitor voltage stress are achieved under the same working conditions. The topology derivation and operating principles of LLCL are shown, and the vital characteristics of LLCL are especially discussed. Moreover, based on battery applications in energy storage systems, in order to make the voltage gain range of LLCL meet the requirements while minimizing the resonant tank currents, a parameter design method is conducted. Finally, a 500-W prototype is established to verify the operating principles and design effects of the proposed converter.