Herbert Ho-Ching Iu

Current Sensing Techniques: A Review

This paper provides a thorough review of state-of-the-art current sensing techniques. It catalogues the current sensors according to the underlying physical principle in order to point out their strengths and weaknesses.

Hybrid Particle Swarm Optimization With Wavelet Mutation and Its Industrial Applications

A new hybrid particle swarm optimization (PSO) that incorporates a wavelet-theory-based mutation operation is proposed. It applies the wavelet theory to enhance the PSO in exploring the solution space more effectively for a better solution. A suite of benchmark test functions and three industrial applications (solving the load flow problems, modeling the development of fluid dispensing for electronic packaging, and designing a neural-network-based controller) are employed to evaluate the performance and the applicability of the proposed method. Experimental results empirically show that the proposed method significantly outperforms the existing methods in terms of convergence speed, solution quality, and solution stability.

Improved Hybrid Particle Swarm Optimized Wavelet Neural Network for Modeling the Development of Fluid Dispensing for Electronic Packaging

An improved hybrid particle swarm optimization (PSO)-based wavelet neural network (WNN) for modeling the development of fluid dispensing for electronic packaging (MFD-EP) is presented in this paper. In modeling the fluid dispensing process, it is important to understand the process behavior as well as determine the optimum operating conditions of the process for a high-yield, low-cost, and robust operation. Modeling the fluid dispensing process is a complex nonlinear problem. This kind of problem is suitable to be solved by applying a neural network. Among the different kinds of neural networks, the WNN is a good choice to solve the problem. In the proposed WNN, the translation parameters are variables depending on the network inputs. Due to the variable translation parameters, the network becomes an adaptive one that provides better performance and increased learning ability than conventional WNNs. An improved hybrid PSO is applied to train the parameters of the proposed WNN. The proposed hybrid PSO incorporates a wavelet-theory-based mutation operation. It applies the wavelet theory to enhance the PSO in more effectively exploring the solution space to reach a better solution. A case study of MFD-EP is employed to demonstrate the effectiveness of the proposed method.

A Single-Stage AC/DC Converter With High Power Factor, Regulated Bus Voltage, and Output Voltage

Unlike existing single-stage AC/DC converters with uncontrolled intermediate bus voltage, a new single-stage AC/DC converter achieving power factor correction (PFC), intermediate bus voltage output regulation, and output voltage regulation is proposed. The converter is formed by integrating a boost PFC converter with a two-switch clamped flyback converter into a single power stage circuit. The current stress of the main power switch is reduced due to separated conduction period of the two source currents flowing through the power switch. A dual-loop current mode controller is proposed to achieve PFC, and ensure independent bus voltage and output voltage regulations. Experimental results on a 24-V/100-W hardware prototype are given to confirm the theoretical analysis and performance of the proposed converter.

Hopf bifurcation and chaos in a free-running current-controlled Cuk switching regulator

An autonomous free-running Cuk converter is studied in this paper. Analysis of the describing nonlinear state equations shows that the system loses stability via a supercritical Hopf bifurcation. The boundary of stability is derived and local trajectories of motion studied. Cycle-by-cycle simulations of the actual system reveal the typical bifurcation from a stable equilibrium state to chaos, via limit cycles, and quasi-periodic orbits. Experimental measurements confirm the bifurcation scenarios. The occurrence of such kinds of bifurcation in autonomous dc/dc converters has been rarely known in power electronics.

Quantum-Inspired Particle Swarm Optimization for Power System Operations Considering Wind Power Uncertainty and Carbon Tax in Australia

In this paper, a computational framework for integrating wind power uncertainty and carbon tax in economic dispatch (ED) model is developed. The probability of stochastic wind power based on nonlinear wind power curve and Weibull distribution is included in the model. In order to solve the revised dispatch strategy, quantum-inspired particle swarm optimization (QPSO) is also adopted, which shows stronger search ability and quicker convergence speed. The dispatch model is tested on a modified IEEE benchmark system involving six thermal units and two wind farms using the real wind speed data obtained from two meteorological stations in Australia.

Controlling Chaos in a Memristor Based Circuit Using a Twin-T Notch Filter

After the successful solid state implementation of memristors, a lot of attention has been drawn to the study of memristor based chaotic circuits. In this paper, a systematic study of chaotic behavior in such system is performed with the help of nonlinear tools such as bifurcation diagrams, power spectrum analysis, and Lyapunov exponents. In particular, a Twin-T notch filter feedback controller is designed and employed to control the chaotic behavior in the memristor based chaotic circuit. Both simulation and experiment results validate the proposed control method.

Control of chaos in a PWM current-mode H-bridge inverter using time-delayed feedback

Time-delayed feedback can be used to stabilize unstable periodic orbits (UPOs) in dynamical systems. The technique involves feedback of signals delayed by the orbits period so that the feedback signals vanish on the target orbit and hence the UPO becomes a solution of the original system. An obvious advantage of this method is that it requires only the knowledge of the period of the target UPO. In this brief, a pulsewidth-modulated current-mode H-bridge inverter serves as a subject of investigation. Under certain parameter ranges, it exhibits higher periodic solutions and chaos. A simple time-delay feedback control method is applied to stabilize the UPOs. By using the time-delayed feedback control method, the stability limit and gain range of the system are increased.

Hyperchaos in a memristor-based modified canonical Chua's circuit

After the successful solid state implementation of the memristor, memristor-based circuits have received a lot of attention. In this paper, a memristor with cubic nonlinear characteristics is employed in the modified canonical Chuas circuit. A systematic study of hyperchaotic behavior in this circuit is performed with the help of nonlinear tools such as Lyapunov exponents, phase portraits and bifurcation diagrams. In particular, an imitative memristor circuit is examined to reveal the construction of hyperchaotic attractors.

Fast-scale instability in a PFC boost converter under average current-mode control

This paper investigates the fast-scale instability in a power-factor-correction (PFC) boost converter under a conventional average current-mode control. The converter is operated in continuous mode. Computer simulations and theoretical analysis are performed to study the effects of the time-varying input voltage under the variation of some chosen parameters on the qualitative behaviour of the system. It is found that fast-scale instability may occur during a line cycle, which can cause distortion to the line current and degrade the practical power factor. The results provide useful information for the design of PFC boost converters to avoid distortion due to fast-scale bifurcation. Copyright