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When the microgrid operates in grid-tied mode, the voltage ride-through (VRT) capability presents a challenge in its inverter controller design. This letter proposes an effective method to support the VRT capability of an inverter-based grid-tied microgrid during grid fault. In addition, the inverter control is implemented by a combined method to mitigate its output current harmonics under normal or faulty grid conditions, even if the grid voltage is distorted. Simulations are performed using Matlab/Simulink and implemented in a real-time simulator with a hardware setup to validate the usefulness of the proposed method.

It is well known that the performance of the (industry standard) field-oriented control (FOC) for induction motors is highly sensitive to uncertainties in the rotor resistance. In this paper we describe how to use supervisory control to obtain an adaptive implementation of FOC for current-fed machines. The unknown rotor resistance is assumed to belong to a discrete set, while the uncertain load torque ranges in a given compact set. Even though no restrictions are a priori imposed on the size of these sets, their definitions reflect the prior knowledge of the designer, which is effectively incorporated in the supervisory control algorithm. The supervisor selects from these sets values for the parameters to be applied to the FOC, a choice that is made by continuously comparing suitably defined performance signals. We prove that the proposed supervisor achieves global stabilization of the system when the load torque is known to belong to a given finite set of values. Apparently, this is the first globally convergent adaptive algorithm for current-fed machines which simply adds adaptation to the widely popular FOC and is not a radically new complicated controller, hence it is more likely to be adopted by practitioners. Some simulation results illustrate the properties of the algorithm. Copyright © 2001 John Wiley & Sons, Ltd.

It is well known that the performance of the (industry standard) field‐oriented control (FOC) for induction motors is highly sensitive to uncertainties in the rotor resistance. In this paper we describe how to use supervisory control to obtain an adaptive implementation of FOC for current‐fed machines. The unknown rotor resistance is assumed to belong to a discrete set, while the uncertain load torque ranges in a given compact set. Even though no restrictions are a prioriimposed on the size of these sets, their definitions reflect the prior knowledge of the designer, which is effectively incorporated in the supervisory control algorithm. The supervisor selects from these sets values for the parameters to be applied to the FOC, a choice that is made by continuously comparing suitably defined performance signals. We prove that the proposed supervisor achieves global stabilizationof the system when the load torque is known to belong to a given finite set of values. Apparently, this is the first globally convergent adaptive algorithm for current‐fed machines which simply adds adaptation to the widely popular FOC and is not a radically new complicated controller, hence it is more likely to be adopted by practitioners. Some simulation results illustrate the properties of the algorithm. Copyright © 2001 John Wiley & Sons, Ltd.

A series of cells representing normal, non-tumorigenic cell lines, as well as differentiating neoplastic and undifferentiated neoplastic rat tracheal epithelial cell populations were evaluated for their ability to establish homologous and/or heterologous cell-cell gap junction communication in culture. Gap junction communication was evaluated by flow cytometric quantitation of the transfer of the fluorescent dye calcein from a donor to a recipient cell population via gap junctions. The data indicate that normal primary cultures of rat tracheal epithelial cells, as well as non-tumorigenic cell lines and squamous cell carcinomas cell populations, retain the ability to establish both homologous and heterologous gap junction communication. In all cases an average of >48% of recipient cells had acquired calcein label during a 5-h interval of co-culture of donor and recipient cells at confluent densities. Cells harvested directly from squamous cell carcinoma tumors exhibited similar levels of cell-cell communication. In contrast, cells giving rise to undifferentiated carcinomas, as well as cells harvested from undifferentiated carcinomas, exhibited very low levels or no homologous or heterologous cell-cell communication. Cell populations exhibiting distinctly different communication phenotypes were evaluated by Northern blot analysis for expression of connexins (Cx 26, 32 and 43) and E-cadherin. Neither communicating nor non-communicating cells expressed connexin 32. Those cell populations, which established functional gap junctions, expressed E-cadherin as well as connexin 26 and/or 43. In contrast, those cell populations that lacked the ability to communicate universally lacked expression of E-cadherin, and a quarter also lacked expression of detectable levels of connexin.

We report an electro-optic Bragg modulator using a periodically poled lithium niobate (PPLN) crystal. We measured a half-wave voltage of 160 V when transmitting a 1064 nm laser through a 14.2 mm long, 780 μm thick, 20.13 μm period PPLN crystal at the Bragg angle. We also demonstrated a Q-switched Nd:YVO_4 laser using such a PPLN Bragg modulator as its Q-switch, producing 7.8 ns, 201 μJ pulses at a 10 kHz repetition rate when pumped by a 19.35 W diode laser at 808 nm.