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Current-source inverter (CSI) is considered as a prospective solution for modern machine drives, for its higher reliability and superior harmonic suppression. The open-circuit fault-tolerant control for five-phase CSI-fed permanent magnet synchronous machine drive with pentagon winding connection is investigated. The switch open-circuit fault and winding open-circuit fault are studied. For the switch open fault, three cases are discussed including single-phase, adjacent two-phase, and nonadjacent two-phase faults. It is indicated that in pentagon circuit, despite the switch of fault phase is disabled, the corresponding phase winding is still connected in the end-to-end power circuit and contributes for torque generation. The new sets of coordinate transformation are proposed, and the mathematical modeling is presented. The fault-tolerant space vector modulation techniques are proposed based on the reconstructed vector planes. In addition, the single winding open fault is studied, which is a specific fault case and breaks off the closed pentagon connection. An important conclusion is derived that the pentagon winding connected CSI gains inherent fault-tolerant capability against the single winding open circuit. The control algorithm even does not need to be switched during this typical fault. Experiments are performed on verifying the proposed schemes.

Free-piston linear generators (FPLGs) without a crank mechanism are promising to be used in hybrid vehicles due to their unique operation characteristics. However, the FPLG currently still faces challenges in the start-up and piston control. In this article, the start-up and operation process of FPLG are analyzed deeply and the improved thrust control strategies for the linear electric machine are presented accordingly. First, the mechanism that the vibration center shifts under the general constant thrust resonance starting method is revealed, considering the asymmetric potential energy caused by nonlinear compression spring effect in the combustion chamber. Then, a compensation thrust iteratively adjusted by the vibration offset is added to stabilize the swing center during start-up. Next, the coupling effect between the dead centers under single-stroke independent thrust control method is analyzed by modeling the piston motion from the aspect of energy flow. Accordingly, an improved thrust control method for coupling suppression is presented to enhance the accuracy and robustness of piston motion. Finally, the performance of the proposed method is verified by controlling a permanent-magnet linear synchronous machine in experiments and simulations.

Free-piston linear generator (FPLG) is considered as a potential technology in the field of hybrid vehicles due to its unique operation characteristics. However, the special structure of no crank-link also leads to the difficulty of piston control. In the presence of frequent combustion variations, the stable operation of FPLG is the biggest challenge it currently faces. In this respect, this article presents a robust piston control method by progressively updating thrust-position trajectory (PUT-PT) of permanent-magnet linear synchronous machine (PMLSM) in FPLG. According to the target points and desired speed, the required motor thrust is obtained based on the energy balance relationship. The calculation of thrust is repeated with a certain position interval in the whole target stroke, so as to obtain the updating thrust-position trajectory. A high-order fast terminal sliding-mode load force observer (HOFTSM-LFO) is designed to estimate the combustion work of an engine based on thermodynamics. Finally, a thrust compensation mechanism is added to the control scheme to counteract modeling errors to maintain high-precision dead centers positions. A sufficient theoretical analysis is provided with an emphasis on thrust calculation and observer design. The performance of the PUT-PT is successfully verified on an 18 kW PMLSM motion platform and a simulated single-cylinder FPLG.