K.W.E. Cheng

General Study for using LED to replace traditional lighting devices

High power LED provides a high luminous and high efficient for using as a lighting source. Because of the advent for LED as lighting device, LED lighting becomes one of the new trends in the lighting industry. In this paper, the power circuit design based on the constant current flyback and the heat distribution matter are discussed. The aims of the work are provide a solution for using LED to replace the traditional lighting device.

Virtual laboratory development for teaching power electronics

Distance learning has been promoted across the whole education sector as more people educate themselves after work or as part of their professional development. Web-based teaching is therefore emerging rapidly because of the need and the development in the Internet and information technology. The hardware experiments can therefore be redesigned such that they also can be accessed via the web. The proposed virtual laboratory is not a web-based simulation. It is a real power electronics experiment conducted in the laboratory by remote control and monitoring by web-based tools. The facility is useful for todays requirement of teaching via the Internet. The paper demonstrates how a power electronics experiment is programmed in a remotely controlled laboratory setup. From there students can conduct the experiment without any limitation of time and space. Feedback from the students is also very positive and it can also give an alternative solution for conducting a hardware laboratory when distance learning is used.

Exploring the power conditioning system for fuel cell

This paper presents an analysis of various fuel cells (proton exchange membrane, solid oxide, molten carbonate, phosphoric acid, and aqueous alkaline)and their characteristics. A range of power conditioning systems including the inverter and DC/DC converter for the fuel cell is then proposed. Experimental results are used to support the analysis.

A Novel Detection Method for Voltage Sags

Determining the start and end of the voltage sag event is very important for sag analysis and mitigation. There are several detection methods for voltage sags in which sag voltages are usually expressed in the terms of RMS. The RMS method represents one cycle historical average value, not instantaneous value which may lead to long detection time when voltage sag has occurred. This paper will proposed a novel voltage sag detection method based on miss voltage technique. Proper dead-band and hysteresis are used in the method. The actual instantaneous voltage is compared with certain percentage of desired grid voltage and certain percentage of the amplitude of the grid voltage. Through instantaneous value comparison, low instantaneous value of the grid is shielded which overcome the mishandling turnover of voltage sags. The approach is fully described, and the results are compared with other methods for marking the beginning and end of sag, such as RMS value evaluation method and Peak-value method and simulation result provides that the method is efficient and fast and can be used to determine the initiation and recovery of voltage sags accompanied by missing voltage technique.

A survey of distributed power system — AC versus DC distributed power system

The history of the centralized and distributed power system is introduced far away from the power system being first built by Edison, which started the first confrontation between ac and dc power system. Although ac power system has dominated for a long century because of easy transmission and some other benefits, dc power system has still gave some good performances and attracted more attention during the past three decades. This paper will discuss the current developing stage of dc distributed power system by the following contents: the basic structure and characteristics; the benefits of the dc distribution system; the development of current techniques adopted in DPS and its analysis of protection and system interaction. In additional, the comparisons between dc and ac distributed power system are presented in detail, and finally, the challenge in future is also summarized.

A self-training numerical method to calculate the magnetic characteristics for switched reluctance motor drives

Based on the two-dimensional (2-D) least squares method, this paper presents a novel numerical method to calculate the magnetic characteristics for switched reluctance motor drives. In this method, the 2-D orthogonal polynomials are used to model the magnetic characteristics. The coefficients in these polynomials are determined by the 2-D least squares method. These coefficients can be computed off line and can also be trained on line. The computed results agree well with the experimental results. In addition, the effect of the order number of the polynomials on the computation errors is discussed. The proposed method is very helpful in torque prediction, simulation studies and development of sensorless control of switched reluctance motor drives.

Switched Reluctance Generators with Hybrid Magnetic Paths for Wind Power Generation

The novel switched reluctance generator (SRG) with hybrid magnetic paths is developed for wind power generation in this paper. For the proposed SRG, there is no mutual coupling between phase windings. The proposed SRG has the longitudinal magnetic structure at the completely aligned position. However, it has the transverse and longitudinal magnetic structure at the unaligned position. Thus, three-dimensional finite element computation is needed in the design. The computed results based on three-dimensional finite-element analysis (FEA) are shown in the paper. Furthermore, the experimental results of the prototype demonstrate that the proposed SRG is feasible and effective.

Longitudinal and Transversal End-Effects Analysis of Linear Switched Reluctance Motor

An accurate estimation of flux linkage characteristics is very important during the preliminary design stage and high-performance control of linear switched reluctance motor (LSRM). In this paper, longitudinal and transversal end-effects of a double-side LSRM are studied using analytical method and finite element analysis (FEA). The estimation discrepancy introduced by both end-effects is presented respectively by investigating their sensitivities to machine parameters, such as excitation level, translator position, and stack length.

Genetic Algorithm-Based RBF Neural Network Load Forecasting Model

To overcome the limitation of the traditional load forecasting method, a new load forecasting system basing on radial basis Gaussian kernel function (RBF) neural network is proposed in this paper. Genetic algorithm adopting the real coding, crossover probability and mutation probability was applied to optimize the parameters of the neural network, and a faster convergence rate was reached. Theoretical analysis and simulations prove that this load forecasting model is more practical and has more precision than the traditional one.

Trigonometry-Based Numerical Method to Compute Nonlinear Magnetic Characteristics in Switched Reluctance Motors

Based on two-dimensional (2-D) trigonometry, a new numerical method is presented to compute the nonlinear magnetic and electromagnetic torque characteristics in switched reluctance motors (SRMs). In the proposed method, the mathematical model is composed of the 2-D truncated Fourier series. The coefficients can be determined from a small amount of given magnetic or torque data acquired by experiment or finite-element (FE) analysis. The computed and experimental results demonstrate that the proposed method can be used to precisely compute the nonlinear magnetic and torque characteristics in SRMs. Hence, this paper provides a valuable approach for performance prediction, design, simulation, and control of SRMs