Pseudo-coevolutionary genetic algorithms for power electronic circuits optimization

In this paper, an orthogonal local search genetic algorithm (OLSGA) is proposed for the design and optimization of power electronic circuits. The genetic algorithm is accelerated with a fast local search operator that automatically adjusts the search direction and the step size. An experimental design method called orthogonal design is used to determine the most promising direction of the potential region in the local search. In each generation, the step size is adaptively expanded or shrunk according to whether there is a newly improvement in the given local region. As a result, with proper direction and step size, the local search operator is able to stride forward and provide better exploitation ability to speed up the convergence rate of the genetic algorithm. The proposed method is applied to design and optimize a buck regulator. The results in comparison with other published results indicate that our proposed algorithm is effective and efficient.

Techniques for reconstructing or estimating unmeasured circuit variables and parameters in power electronic circuits are investigated. In numerous applications in power electronic systems, measurements of circuit variables are required for closed-loop control purposes or for diagnostic purposes, but are expensive or impossible to obtain directly. The method for state estimation relies on observer theory and is based on an intrinsic Lyapunov function, termed the energy in the increment. For cases where circuit parameters are not completely known, an adaptive estimation algorithm is developed for estimating the unknown circuit parameters along with the unmeasured circuit variables. The exponential stability of the combined parameter and state estimation scheme is established using averaging and singular perturbation analysis. Averaging analysis is used in off-line calculations to determine the feasibility of estimating certain parameters and to determine a basis from which to choose parameter update gains. Examples with an up-down converter illustrate the results. A hardware implementation of the state estimation scheme is also documented along with a description of a hardware implementation for parameter estimation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In recent years, designed experiments and response surface methods of analysis have been used in the design and optimization of electronic circuits. The key to this statistical approach is to build a set of accurate response models of the circuit performances. This paper introduces the class of Generalized Linear Models (GLMs), which extend classical linear regression models and often provide better-fitting surfaces for the description of circuit performance. GLMs have not so far been applied to electronic circuit design. A circuit design example is given.

Permanent Magnet Synchronous Generators are an emerging technology in wind power applications. A simplified Thevenin equivalent simulation model of a wind generator has been developed in the ATPDraw environment and validated by comparing its dynamics with that of a Matlab/Simulink detailed model. The simplified model includes also power electronic circuits, for interfacing the generator to a MV primary distribution grid, and their controls. A 2,5 MVA wind generator was simulated in ATPDraw in order to assess flicker severity dependence upon different grid and circuit parameters. Simulation results show a strong flicker severity dependence on grid short circuit power and X/R line characteristics, in particular when generator supplies reactive power to the grid, as required by some National standards.

The issues related to integrating these systems into the grids continue to gain importance with the increasing use and importance of renewable energy sources. Therefore, the importance of power distribution transformers is increasing. Besides, these power distribution transformers are connected to the grid with power electronics circuits and inverters. Considering the modular inverter structures, ease of maintenance, and connection, three-level T-type inverters are chosen for this study. The secondary output voltage of the power transformer is estimated by using circuit parameters such as the dead time of the inverter circuit, PWM switching frequency, and modulation rate. Based on the finite element analysis analysis according to the selected parameters, 810 data are obtained with time-dependent parametric analysis. The adaptive neuro-fuzzy inference system model is constructed by considering the simulation data to estimate the secondary output of the power transformer of these parameters. In the training phase of the model, 648 randomly selected data from 810 data obtained by ANSYS-Electronics/Simplorer are used. The remaining 162 data are used in the testing process to measure system performance. As a result of the analysis made by ANFIS, the Root Mean Square Error (RMSE) error is found as 2.475%. Since the values obtained in the estimation process of the study are very close to the simulation values, the ANFIS method can be used as an estimation method that will give accurate results during the design phase.

Techniques for reconstructing or estimating unmeasured circuit variables and parameters in power electronic circuits are investigated. In numerous applications in power electronic systems, measurements of circuit variables (currents and voltages) are required for closed-loop control purposes or for diagnostic purposes, but are expensive or impossible to obtain directly. Examples are certain inductor currents, voltage at high-impedance nodes where probes cannot be applied or circuit variables in electrically isolated portions of a circuit. The approach taken is based on observer theory, and so the resulting algorithms may be implemented in real time. A natural scheme for implementing an observer is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photovoltaic (PV) systems are gradually becoming the key renewable source of electrical energy. But the nonlinear characteristics of the PV module require special techniques to harvest maximum power. The techniques used to track the Maximum Power Point (MPP) from the nonlinear I-V characteristics through power electronic circuits are known as Maximum Power Point Tracking (MPPT) techniques. Although enormous MPPT techniques have been anticipated in literature, each endures its own advantages and disadvantages. This paper proposes a novel hybrid technique to enhance the performance of Incremental conductance (InC) technique. Our proposed technique removes the limitations of InC under rapid changing environmental condition. It improves the efficiency and reduces the oscillation power loss under steady state. A hybrid combination of variable-step sized Incremental Conductance with Fractional Short Circuit Current (FSCC) technique is proposed in this research work. Initially, the FSCC forces the PV system to work near MPP and then InC technique track the exact peak. Matlab/Simulink software is used to implement the proposed hybrid technique. Finally, the results verify its superior performance under rapidly changing environmental conditions.

In order to improve the optimization of middle and large-scale logic circuits, a heuristic inspired traversal method of circuit polarities called the least operation traversal method (LOTM) is proposed. Firstly, the polarity traversal sequence problem of fixed-polarity RM circuits is analyzed and a mathematical model of the problem is given and discussed; Secondly, the detailed realization of the LOTM is explained; finally, the method embedded in genetic algorithm is tested by 10 circuits from MCNC Benchmark. The results show that the method can significantly improve the efficiency of genetic algorithm for circuit optimization, especially for circuits with a number of inputs or complex structure1.

Europe rushes to externalize its migration management. To ease the migratory pressure on European borders, the European Union and its single members seek to integrate countries of origin and transit into an extended concept of border and migration control. However, the diplomatic negotiations and the efforts to establish migration control in Africa confront Europeans not only with diverging geostrategic interests, but also with colonial legacies, strong cultures of migration and everyday strategies to undermine foreign domination. On different levels, these forces mold the places where Europe bundles its efforts to establish new rules of migration. The Malian Capital Bamako is an example how, despite all imbalances of power, African societies deal with the renewed European interest in confining their freedom of movement. The chapter explores how France, the former colonial power, but also Spain and the European Commission promote a number of activities in Bamako, and how with each single step they have to deal with the particularities of the place and the political cultures that mold it.

Yield optimization of nonlinear microwave circuits operating in the steady state under large-signal periodic excitations is studied. Two novel high-speed methods of gradient calculation, the integrated gradient approximation technique (IGAT) and the feasible adjoint sensitivity technique (FAST) are introduced. IGAT utilizes the Broyden formula with special iterations of Powell to update the approximate gradients. FAST combines the efficiency and accuracy of the adjoint sensitivity technique with the simplicity of the perturbation technique. IGAT and FAST are compared with the simple perturbation approximate sensitivity technique (PAST) on the one extreme and the theoretical exact adjoint sensitivity technique (EAST) on the other. A FET frequency doubler example treats statistics of both linear elements and nonlinear device parameters. This design has six optimizable variables, including input power and bias conditions, and 34 statistical parameters. Using either IGAT or FAST, yield is driven from 40% to 70%. FAST exhibits superior efficiency.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A computer-oriented approach for transient and steady-state analysis of power electronics circuits is presented. The switching elements are extracted in a time-variable two-port, which is defined by its nodal equations. A set of modified nodal equations for describing the overall transient of the circuit is obtained. No small-signal approximations are required. The analytical expressions of the network waveforms are found accurately for each switching stage. The transient computation is based on a cyclical use of these expressions together with the threshold conditions. The general method is then applied to simulation of current-mode quasi-resonant converters. Transients due to large-signal changes in the line voltage and load are studied. The influence of the load value on transient peaks is pointed out. The voltage conversion ratio versus switching frequency is studied for both the half-wave and full-wave mode operation. A computer program for time-domain simulation of power electronics converters is developed based on this approach. >

In this paper we propose two novel approaches for solving constrained multi-objective optimization problems using steady state GAs. These methods are intended for solving real-world application problems that have many constraints and very small feasible regions. One method called Objective Exchange Genetic Algorithm for Design Optimization (OEGADO) runs several GAs concurrently with each GA optimizing one objective and exchanging information about its objective with the others. The other method called Objective Switching Genetic Algorithm for Design Optimization (OSGADO) runs each objective sequentially with a common population for all objectives. Empirical results in benchmark and engineering design domains are presented. A comparison between our methods and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) shows that our methods performed better than NSGA-II for difficult problems and found Pareto-optimal solutions in fewer objective evaluations. The results suggest that our methods are better applicable for solving real-world application problems wherein the objective computation time is large.

Traditional optoelectronic manufacturing of butterfly packages involves laser welding of a fiber mount followed by a tedious realignment procedure to reverse thermally induced distortions commonly referred to as Post Weld Shift (PWS). An alternative PWS compensation technique, Laser Hammering, entails manipulation of the fiber to light alignment through deformation of the fiber housing with high precision laser beams. The goal of this study is to predict and understand fiber displacements for butterfly packages subjected to the laser hammering process using finite element analysis. A standardized, two-dimensional fiber mounting/ferrule geometry is employed in a simulation case study. Various laser waveforms are applied to focus spot diameters of 50 and 200 μm over a range of applied heat fluxes (10 to 1000 W/mm2). The primary investigation focused on the degree to which a steady state (SS) model can predict the final state of a transient response (asymptotic steady state) subjected to a periodic laser excitation. Effects of laser energy deposition location and resolution, as well as the use of multiple lasers were also studied. The results obtained to date show that the steady state solution is in good agreement with the asymptotic transient response (ATR) for the center horizontal fiber displacement and the center fiber temperature. The focus spot region surface temperature predictions of steady state and asymptotic transient simulations were also found to be in reasonable agreement. However, the vertical fiber displacement tends to be over predicted by the steady state solution, sometimes by as much as an order of magnitude. The causes, both physical and computational, of this disagreement are discussed in the paper.

The rapidity and accuracy of the initial alignment influence the performance of the Strapdown Inertial Navigation System (SINS), compass alignment is one of the most important methods for initial alignment. The selection of the parameters of the compass alignment loop directly affects the result of alignment. Nevertheless, the optimal parameters of the compass loop of different SINS are also different. Traditionally, the alignment parameters are determined by experience and trial-and-error, thus it cannot ensure that the parameters are optimal. In this paper, the Genetic Algorithm-Particle Swarm optimization (GA-PSO) algorithm is proposed to optimize the compass alignment parameters so as to improve the performance of the initial alignment of strapdown gyrocompass. The experiment results showed that the GA-PSO algorithm can find out the optimal parameters of the compass alignment circuit quickly and accurately and proved the effectiveness of the proposed method.

A hybrid time-domain simulation technique for pulse-width-modulated (PWM) switching regulators is presented. The methodology integrates the advantages of the simulation concepts for switched and nonswitched networks. A regulator is decoupled into dual-analysis components, namely, the power conversion stage (PCS) and feedback network (FN). The former component is simulated by a time-domain digital integration technique with stepwise analysis of the switches' state and automatic determination of correct topological configuration in the PCS operation while the latter one is analyzed by formulating a modified system difference equation and defining at each switching period with second-order extrapolations and corrections of the PCS and error amplifier outputs. Other superior features of this approach include: (1) elegant numerical method of determining the gate signals from the PWM modulator; (2) simple manipulations of numeric and algebraic equations; and (3) applicability to simulate regulators with multiple parameters feedback from PCS. The proposed methodology is illustrated with several examples. The simulated steady-state and large-signal transient waveforms are favorably verified with experimental measurements and available literature.