This paper investigates open-phase fault modeling and fault tolerant control (FTC) of dual three-phase permanent magnet synchronous machines. A comprehensive fault model that considers both the permanent magnet torque and reluctance torque under the open-phase fault is proposed at first. This model shows that under open-phase fault the average torque of dual three-phase PMSM will decrease, while torque ripple will increase significantly. Then, a novel optimized FTC approach is developed based on the proposed fault model, in which genetic algorithm (GA) is applied to optimize the stator currents to maximize the average torque and minimize the torque ripple under open-phase fault condition. The proposed fault model and GA-based FTC are applicable to both surface-mounted and interior dual three-phase PMSMs. However, existing approaches are only applicable to the surfaced-mounted dual three-phase PMSMs because the reluctance torque has been neglected. Moreover, the proposed approach is simple in implementation as it employs the original control structure, and it is capable of smooth switching between the healthy operation and FTC without inducing noticeable torque pulses. The proposed GA-based FTC is demonstrated with design examples, compared with existing approach and validated with experimental tests on a laboratory interior dual three-phase PMSM.

To develop a high–performance and reliable control for dual three–phase permanent interior magnet synchronous machine (IPMSM), accurate knowledge of machine parameters is of significance. This paper proposes an improved recursive least square (RLS) algorithm and current injection–based parameter estimation method for dual three–phase PMSM with consideration of inverter nonlinearity and magnetic saturation. First, the vector space decomposition (VSD) based dual three–phase PMSM model is established. The inverter nonlinearity model for dual three–phase PMSM is derived, and the cross and self–saturation of DQ1–axis inductances are modeled to improve the estimation accuracy. Finally, the machine parameters including winding resistance, rotor flux linkage, and varying DQ1–axis inductances under different operating conditions are estimated using the proposed current injection-based method with RLS algorithm. Compared with existing methods, the proposed approach can achieve a better estimation performance and is validated on a laboratory dual three–phase interior PMSM under different temperature and operating conditions.

For dual three-phase interior permanent magnet synchronous machines (IPMSMs), open-phase fault can result in significant average torque reduction and harmonics in the output torque and speed, which prevent the machines from reliable and safe operation. Indeed, these adverse effects are mainly due to the significant harmonics in the stator currents caused by the open-phase fault. This paper investigates fault tolerant control (FTC) of dual three-phase IPMSM under open-phase fault and proposes a computation-efficient FTC solution to maximize the average torque and minimize the fault-induced torque and speed ripples. In the proposed FTC, open-phase model is firstly derived, and optimal stator currents are then derived to achieve maximized average torque and minimized fault-induced torque harmonics. The computation efficiency enables the proposed solution the capability of FTC under both the steady-state and transient conditions. Moreover, the proposed FTC can eliminate the harmonic current components in the torque contributing frame and thus reduce the harmonic losses, and nonlinear inductance maps is employed to consider magnetic saturation. The proposed FTC is compared with existing methods and evaluated with experiments on a laboratory dual three-phase IPMSM under various operating conditions.

This paper proposes an optimized current harmonic minimization approach for dual three-phase permanent magnet synchronous machines (PMSMs) with consideration of inverter voltage limit. The current harmonic model is firstly derived to analyze the dominant current harmonic components in dual three-phase PMSM drive. Dual reference frame (DRF) model is then proposed to convert the current harmonics into dc components in the new DRFs, and PI controllers are employed to control voltages to minimize the dc components. This paper will prove that current harmonics can be minimized by using the proposed DRF model. Since current harmonic minimization requires additional voltages, the inverter voltage limit must be considered especially at high-speed conditions. Hence, the inverter voltage limit is considered in the model to derive the theoretical control strategy, in which minimal copper loss is selected as the design objective for current harmonic reduction with limited inverter voltage. The proposed approach is supported by theoretical analysis and proof and it does not require inverter voltage and machine parameters. Moreover, the proposed approach is compared with an existing method to show the performance improvement and evaluated with extensive experiments on a laboratory dual three-phase PMSM under both steady-state and transient conditions.

This paper proposes a current injection-based simultaneous stator winding and permanent magnet (PM) temperature tracking technique for dual three-phase permanent magnet synchronous machines (PMSMs). The estimation models involving winding and PM temperatures are derived for different control strategies with the cancellation of inductances. To improve the tracking performance, a Kalman filter is used for simultaneous winding and PM temperature estimation. Compared with the existing methods, the proposed simultaneous winding and PM temperature estimation technique is independent of the voltage source nonlinearity effect, and is applicable to various machine operating conditions. The main features of the proposed method are underscored by the cancellation of inductance and the elimination of the need for a look-up table. Test results on a laboratory dual three-phase PMSM are used to validate the proposed method under different speed and torque conditions.

A MW class direct-drive vernier motor for the elec-tric ship propulsion is proposed in this paper. The proposed ver-nier motor adopts the homopolar structure and utilizing the high-temperature superconducting wire for electrical excitation. The stator houses the superconducting field winding and the copper armature winding. The rotor consists of iron core without excitation sources. Thus, no cryo-moving components are re-quired. A dual-body Dewar for cooling the pancake HTS field winding is proposed. The motor performance is analyzed and evaluated using the 3-D finite element analysis. Both the brush-less AC (BLAC) and brushless DC (BLDC) operation modes for the proposed motor are assessed and compared.