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Brushless Harmonic current injection to the stator windings is one of the most effective methods for torque ripple reduction of brushless DC motors. Because of multi harmonic contents of the stator currents, the conventional methods based on rotational reference frame cannot be used to calculate the voltage references for voltage source inverter. sliding mode control (SMC), which has high dynamic response to track a time varying command, can be used to force the arbitrary reference current to the stator windings without transfer the motor currents to the rotational reference frame. However, the main disadvantage of SMC is that the system states cannot reach the equilibrium point in infinite time as well as has a major chattering problem. In this paper, a new control method called integral terminal sliding mode control (ITSMC) is used to overcome these drawbacks. In order to show the robustness and performance of the proposed method, this method is compared with a SMC by some simulation and experimental tests. It is concluded that the dynamic response and robustness of the proposed ITSMC method is higher than SMC and ITSMC is an appropriate method to inject the arbitrary reference current to the motor windings. [ABSTRACT FROM AUTHOR]

In this study, a Z-source alternating current-to-alternating current (AC-AC) converter with a specific topology, which can provide both buck and boost modes, is investigated. This converter, which can be implemented easily, utilizes only two switches with complemented commands. A comparison between the Z-source AC-AC converter and a conventional thyristor voltage controlled one is presented here, and it shows that in the most areas, the Z-source converter provides a faster response and lower total harmonic distortion of the output currents than the conventional one. Moreover, the Z-source converter is also extended to the multiphase systems. In addition, a new arrangement of this converter is proposed here to remove the isolated single-phase sources. Furthermore, an open-loop method is proposed for soft-starting applications. Finally, a closed-loop control system is also suggested for a three-phase Z-source converter to soft start and control the speed of an induction motor. Computer simulations show the validity and effectiveness of the proposed schemes. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This paper proposes a modified switching strategy for hybrid flow controller (HFC) as a power flow controller. The current strategies for HFC are suitable only for specific situations and generally are not applicable. The modified strategy is implemented by using the logical operators as a classical controller. Simulation results on two situations, representing all the possible states of the HFC, verify its performance. The fluctuations of the transferred active power caused by switching the HFC might have an adverse effect on the decision of the controller as well as the stability of the system. To mitigate the fluctuations, a fuzzy logic controller is designed, and also a comparison with the classical controller is provided. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, a well-known adaptive input-output feedback-linearization (AIOFL) technique is used for speed and torque-tracking control of synchronous reluctance motor drive. This controller is capable of estimating motor two-axis inductances (Ld, Lq) simultaneously. The overall stability of the proposed control and the persistency of excitation condition are proved based on Lyapunov theory. In addition, the maximum rate of change of torque control scheme is applied to generate the motor dand q-axis reference currents which are needed for AIOFL controllers. Another contribution of this paper is to estimate the rotor speed and position. For low-speed estimation, we have to eliminate the current and voltage sensors' dc offsets, detect the stator resistance, and take into account the voltage drop of the inverter power switches. We solve these problems by using a simple technique for eliminating the voltage sensors and a simple method for online estimation of the stator resistance and modeling the voltage drop of the inverter power switches. It is worthwhile to mention that the current sensors' dc offsets, seen on the measured currents, are negligible. Finally, the validity of the proposed method is verified by experimental results. [ABSTRACT FROM AUTHOR]