Fuzzy logic average current-mode control for DC-DC converters using an inexpensive 8-bit microcontroller

This paper describes the design and implementation of a microcontroller-based fuzzy logic average current-mode control (ACMC) for dc-dc converters. A fuzzy logic ACMC boost converter operating in the continuous conduction mode has been designed using a PIC16C782 microcontroller. Design procedures and implementation issues are discussed. No complex algorithm is required to estimate the controlled current because of the on-board peripherals of the microcontroller. By using lookup tables and other techniques, the fuzzy logic algorithm is implemented on the microcontroller successfully. Experimental results are presented and encouragingly demonstrate the performance that a fuzzy logic ACMC dc-dc converter can achieve.     

An improved fault analysis algorithm for unbalanced multi-phasepower distribution systems

The results of an improved method for fault calculations in unbalanced multi-phase power distribution systems containing nonutility generators and large induction motor loads are presented in this paper. The method utilizes a combined time- and frequency-domain analysis approach to produce results that are superior to those obtained in “classical” fault analysis without the large increase in computer time with complete time-domain solutions. Sources and loads can be represented by either classical frequency-domain models or detailed differential equation models. The potentially unbalanced power distribution system is represented by an admittance matrix formed using a linear graph-based application of AC circuit theory. The time-domain differential equation source and load models are interfaced with the frequency-domain distribution system model using time series analyses to estimate equivalent voltage and current phasors from discrete data sets     

Simulation of AC spacecraft power systems

A technique is presented for modeling and simulating AC spacecraft power systems by combining all component models into an overall system model. Each component in the spacecraft power system is treated as a two-port network. A state model is written for each two-port network with the port voltages as the inputs. Each component state model is solved independently using the state transition matrix approach and assuming that its inputs are constant. The inputs to all components are then calculated using network analysis principles. As an example, a 20 kHz system is simulated using this approach, and the results are compared with those of a SPICE2 simulation     

Database Publishing: Applications, examples, and fundamental concepts

Database publishing is one of microcomputing's lates buzzwords. This paper offers a definition for this activity and suggests major classifications for database publishing. Advantages of database publishing are discussed and an overview of software approaches for IBM and Macintosh environments is provided. A features check list for database publishing is advanced and the development and operation of the Georgia Electronic Economic Profile System is described. Finally, predictions for the future of database publishing are formulated.     

A capacitor charging power supply utilizing a Ward converter

A prototype capacitor-charging power supply (CCPS) that utilizes a Ward converter is presented. This converter is a member of the family of resonant converters and is capable of zero-current switching. It is applicable to capacitor charging because of its inherent short-circuit protection and its insensitivity to the value of the load capacitance. The converter is controlled using a constant on-time constant frequency scheme that allows the utilization of zero-current switching techniques. The prototype CCPS is capable of charging various values of load capacitors up to 1000 V DC. Waveforms that show single- and repetitive-charge operation of the CCPS are presented     

A capacitor-charging power supply using a series-resonant topology,constant on-time/variable frequency control, and zero-current switching

A power supply specifically designed for capacitor-charging applications that uses a series-resonant circuit topology, a constant on-time/variable frequency control scheme, and zero-current switching techniques has been developed. The performance of this capacitor-charging power supply (CCPS) has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. The CCPS has charged a 1 μF capacitor from 0 to 1500 V DC in 750 μs, exhibiting a charging power of 1500 J/s. This operation has been repeated at a rate of 800 charges per second, which corresponds to an average power output of 900 W. A 10 μF capacitor has been charged from 0-1500 V DC in 8 ms. These results indicate that this design is feasible for use in capacitor-charging applications     

Equivalent circuit elements for PSpice simulation of PEM stacks at pulse load

The PEFC stack in a commercial power system was operated with room air and pure hydrogen. After the system reached a steady temperature, an ac impedance test was conducted on the fuel cell power system. The impedance data were real-time response generated by the ac sinusoidal excitation. Data for a single PEM stack and PEM stacks operating in parallel and series were collected with or without an embedded system controller board and electronic devices. The equivalent circuit model with three time constants and the non-linear least square fitting program (NLLS) were applied for fitting the stack impedance spectrum. The Levenberg–Marquardt algorithm utilized in the NLLS fitting process automatically adjusted the parameter values of the physical elements in the model to find the best fit result. From the preliminary results, data interpretation and the equivalent circuit model identified the physical elements, the related electrochemical processes, and the phenomenon inside the fuel cells or stacks. Losses from ohmic conduction, anode activation, cathode activation, and mass transfer were separated and analyzed. Further PSpice simulation curves using these equivalent circuit elements demonstrate good agreement with the pulse testing data measured from the PEFC power system.     

Alteration of N-terminal phosphoesterase signature motifs inactivates Saccharomyces cerevisiae Mre11

Saccharomyces cerevisiae Mre11, Rad50, and Xrs2 function in a protein complex that is important for nonhomologous recombination. Null mutants of MRE11, RAD50, and XRS2 are characterized by ionizing radiation sensitivity and mitotic interhomologue hyperrecombination. We mutagenized the four highly conserved phosphoesterase signature motifs of Mre11 to create mre11-11, mre11-2, mre11-3, and mre11-4 and assessed the functional consequences of these mutant alleles with respect to mitotic interhomologue recombination, chromosome loss, ionizing radiation sensitivity, double-strand break repair, and protein interaction. We found that mre11 mutants that behaved as the null were sensitive to ionizing radiation and deficient in double-strand break repair. We also observed that these null mutants exhibited a hyperrecombination phenotype in mitotic cells, consistent with previous reports, but did not exhibit an increased frequency of chromosome loss. Differential ionizing radiation sensitivities among the hypomorphic mre11 alleles correlated with the trends observed in the other phenotypes examined. Two-hybrid interaction testing showed that all but one of the mre11 mutations disrupted the Mre11-Rad50 interaction. Mutagenesis of the phosphoesterase signatures in Mre11 thus demonstrated the importance of these conserved motifs for recombinational DNA repair.