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The fault-tolerant control method of dual three-phase permanent-magnet synchronous motor (PMSM) drives has gained more and more attention in some applications, such as aircraft system and offshore wind energy system. In this letter, the reason for the torque ripple caused by the standard control method has been investigated in view of the frequency domain after the occurrence of a single open-phase fault. Based on the theoretical analysis, a universal control scheme has been proposed for the dual three-phase PMSM drives with two isolated neutral points, which can be implemented under either healthy condition or fault condition. The key is to modify with a closed-loop controller on harmonic subspace with the notch filter. The proposed method not only realizes the seamless transition between two operation conditions without fault diagnosis but also avoids the reconfiguration of the control structure. Moreover, the system optimization of the minimum copper loss under postfault condition has been integrated into the proposed method. The experimental results are presented to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The rotor flux linkage of permanent-magnet synchronous motor (PMSM) is of great importance for monitoring and high-performance control. However, most of the existing online estimation methods need prior knowledge of other PMSM parameters such as stator resistance and dq axis inductance, which are difficult to realize in the rank-deficient models of electrical machines. This article proposes a simple online estimation method of rotor flux linkage for the dual three-phase surface-mounted PMSM (SPMSM) drives with the assistance of injected position offset. The independent estimation model has been developed for the rotor flux linkage by appropriate setting of positon offset between two sets of three-phase windings of dual three-phase SPMSM drives. The proposed method not only has little influence on the output torque and high signal-to-noise ratio for observation, but also offers the superior performance in estimation accuracy irrespective of the influence of VSI nonlinearity. In addition, the proposed position-offset-based method is suitable for the full-speed region including the field-weakening operation. Finally, comprehensive experimental results are presented to verify validity of the proposed method under different working conditions. [ABSTRACT FROM AUTHOR]

In standalone brushless doubly-fed induction generator (BDFIG) power generation systems, unbalanced and nonlinear loads can produce distorted power winding (PW) voltage, and consequently affects the normal operation of other loads and degrades the performance of the power generation system. Although the negative-sequence and harmonic components of the PW voltage can be eliminated by the conventional control methods implemented in either machine-side converter (MSC) or load-side converter (LSC), it causes higher voltage rating of converters and needs more current sensors. In this article, the detailed analysis for the impact of conventional control methods on the voltage rating of the two converters is presented. And then, an improved collaborative control method considering the power converter voltage rating is proposed, in which the MSC can be employed to eliminate the seventh-harmonic voltage of PW, and the LSC can be used to reject the negative-sequence and fifth-harmonic components of PW voltage without extra current sensors. The proportional-integral-resonant controller is applied to the current control loops in both MSC and LSC so as to obtain good current track ability. Comprehensive experimental results based on a 30-kVA BDFIG demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes an improved coordinated control of standalone brushless doubly fed induction generator (BDFIG) supplying nonlinear loads. Due to the existence of nonlinear loads, the voltage at the point of common coupling becomes distorted with a large number of low-order harmonics, which severely degrades the performance of power generation systems. In order to eliminate the included low-order harmonics, a coordinated control method of harmonic mitigation has been presented in this paper for the control of both machine side and load side converters. Then, a weight factor is introduced to the proposed control method for distributing the contribution of harmonic mitigation between the two converters. Comprehensive experimental results on a 30 kVA BDFIG are presented to verify the proposed control method. [ABSTRACT FROM AUTHOR]

In this article, the control strategy is studied for the neutral-point-clamped three-level inverter-fed dual three-phase permanent-magnet synchronous motor (PMSM) drive with low switching frequencies. An interleaved finite-control-set model predictive control (MPC) scheme is proposed, where a two-layer MPC is designed to solve the multiobjective optimization problem. The two sets of windings in PMSM are sampled and controlled in an interleaved way so that the control delay and the prediction horizon of the drive system are reduced by half. Moreover, the proposed interleaved control scheme increases the equivalent sampling and control frequency from the perspective of the whole drive system, and thus provides better steady-state performance and dynamic performance. With the switching states of one inverter remaining unchanged, the cross traversal of vector candidate sets between two sets of windings is avoided, and the computational burden can be reduced effectively. Experimental results are given to verify the validity and effectiveness of the proposed interleaved control scheme. [ABSTRACT FROM AUTHOR]

The brushless doubly-fed machine (BDFM) without a brush and slip ring has some advantages of high operation reliability and less maintenance cost, which is very suitable for the ship shaft power generation. In this application, the BDFM mainly works on the stand-alone state, in which the power winding (PW) voltage should be controlled directly. The unbalanced load is a typical working state, which mostly results in the unbalance of PW voltage and affects the normal operation of loads severely. The sensorless control strategy can enhance the operation safety under extreme environment and cut down the cost effectively, which is highly desired to be applied in the BDFM-based ship shaft power generation. In this paper, an improved sensorless phase control strategy is proposed, which can work effectively under the unbalanced load condition. First, the sensorless operation is achieved by controlling the $q$ -component of PW voltage, which can realize the phase control simultaneously. Then, the unbalanced compensation is designed in details. Finally, both simulation and experiments have demonstrated that, by the proposed method, the PW voltage phase can be controlled precisely and the voltage unbalance factor is lower than the permissible level. [ABSTRACT FROM AUTHOR]