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The least cell state-of-charge (SOC) in a battery pack directly determines the left runtime of the total battery pack. Hence, an equalizing strategy is often needed to balance the battery cells, especially for lithium-ion batteries. In this paper, it is shown that this can be achieved with a simple equalizing circuit, which only needs a power semiconductor switch and an inductor for each cell. To avoid the intensive requirement on the processing power of existing control algorithms, two simple control schemes are proposed to obtain better modular performance. First, the operating modes under different switching states are illustrated with a four-cell battery module. After that, the required duty cycles to operate the switches are obtained by comparing the SOC of the relevant cells and the average SOC of all cells. By fixing the maximum of the duty cycle of the highest SOC cell, the inductor can be easily designed and the rated currents of switches and cells can also be regulated. Moreover, the multilayer and modular concept is developed to speed up the balancing process and modularize the design of equalizing circuits. Finally, experiments were completed to demonstrate the proposed scheme. [ABSTRACT FROM AUTHOR]

Electrical excitation doubly salient (EEDS) machines and electrical excitation flux-switching (EEFS) machines, both of which have simple and robust rotor structure and good flux regulation capability, are suitable for use as generators in dc power systems that need high reliability and good constant-power operating capability. In this paper, the basic design dimensions and electromagnetic performance of the EEFS machines are analyzed and those of the EEDS machines are also given for comparison. Compared with the EEDS machine, the EEFS machine exhibits bipolar stator flux-linkage and sinusoidal back-EMF waveforms as well as larger torque density. Then, control schemes of the two machines for voltage regulation of dc power systems are discussed, and in order to improve the steady state and dynamic performance of the EEFS generator dc power system, an improved direct torque control scheme is presented. It develops the strictly linear relationship between the torque and sinusoidal value of the torque angle, and can regulate the instantaneous torque directly and smoothly without current loop. Besides, the flux weakening control of the proposed scheme is also studied. The EEFS generator dc power system with excellent dynamic performance and lower flux and torque ripple has been achieved experimentally. [ABSTRACT FROM AUTHOR]

A position sensorless method for direct torque control with space vector modulation (DTC–SVM) of hybrid excitation flux-switching generator (HEFS) is presented. Based on the synchronous angular frequency acquired by a m-order low-pass filter, a programmable first-order low-pass filter together with a band pass filter and a coordinate transformation is used to estimate the stator flux-linkages without magnitude and phase angle errors. Thus, the instantaneous torque and the rotor position can be accurately estimated based on the precise stator flux-linkages. The DTC–SVM scheme of the HEFS using the proposed position sensorless method exhibits good steady-state and dynamic performance, which is verified by experimental results. [ABSTRACT FROM AUTHOR]

The fault-tolerant control of bearingless motors is vital for their safe and robust operation. In this paper, the operation of current-controlled multiphase slice permanent-magnet bearingless motors (PMBMs) with different open-circuited faulty phases is analyzed, and their fault-tolerant controllability in the general case is investigated. As an example, the feasibility of fault-tolerant control with arbitrary single, double, or triple open-circuited faulty phase(s) for a six-phase slice PMBM is discussed in detail. Simulation results from finite-element analysis are presented to demonstrate the operation of the motor under the proposed fault-tolerant control strategy. Moreover, experimental results are also provided to further verify the theoretical development. [ABSTRACT FROM PUBLISHER]