Shin-Der Chen

A direct Newton–Raphson economic emission dispatch

Abstract In this study, a direct Newton–Raphson method based on an alternative Jacobian matrix is proposed to solve the economic emission dispatch (EED) problem with line flow constraints. The alternative Jacobian matrix is formulated by the incremental transmission loss in terms of the sensitivity factors, line flows, and line resistances. The sensitivity factors are obtained from line flow solutions based on a DC load flow model. The proposed approach is tested on the Taiwan Power Company 288-bus system. Simulation results obtained from the proposed method confirm the advantage of computation rapidity and solution accuracy over that of the AC load flow method and the conventional B-coefficients method, respectively. The comparison confirms the capability of the proposed method in real-time implementation for the EED problem.

Multiobjective power dispatch with line flow constraints using the fast Newton-Raphson method

The fast Newton-Raphson approach based on an alternative Jacobian matrix is proposed to solve the power system multiobjective power dispatch (MPD) problem with line flow constraints. Two conflicting objectives including minimization of fuel cost and environmental impact of emission are considered in this study. The Jacobian matrix is formulated by the incremental transmission loss in terms of the sensitivity factors, line flows and line resistances. The sensitivity factors are obtained from line flow solutions based on a DC load flow model. Moreover, the B-coefficients matrix and the Lagrange function can be shown as convex functions. Therefore, the existence and uniqueness of the solution for the nonlinear equation of the MPD problem can be proven. The proposed approach is tested on the IEEE 14- and 30-bus systems. Simulation results obtained from the proposed method confirm the advantage of computation rapidity and solution accuracy over that of the AC load flow method and the conventional B-coefficients method, respectively. The comparison confirms the capability of the proposed method in real-time implementation for the MPD problem.

An isolated high step-up forward/flyback active-clamp converter with output voltage lift

This paper presents an isolated high step-up forward/flyback active-clamp converter with output voltage lift. In order to obtain high step-up voltage gain, the output voltage lift is adopted. The characteristics of the output voltage lift are similar to the forward converter in the charging mode and the flyback converter in the discharging mode. The active-clamp circuit is employed to recycle the leakage-inductance energy of the forward/flyback transformer and to suppress the voltage stress on the switch. By utilizing the active-clamp circuit, both primary and auxiliary switches can achieve zero-voltage-switching (ZVS), thus improving the efficiency of the proposed converter. Finally, a prototype circuit with 24-V input voltage, 200-V output voltage, and 400-W output power is implemented to verify the performance.

Fast load flow using multiprocessors

Balance loading on all processors is essential to ensure the success of any parallel approach. To achieve this objective, a novel approach involving the factorization tree algorithm is proposed in this study on the basis of calculating the maximum number of fill-in and the degree of every node as the cutset block nodes. Using the proposed approach, the number of nodes in each subnetwork is more uniform and the computation time is saved. Simulation results of the IEEE test systems and the Taiwan Power Company (TPC) 288-bus are presented to demonstrate the performance of the proposed algorithm and its capability to implement parallel computing for the load flow analysis.

Single DC/AC CCFL Inverter for Large Size LCD TV with Burst Control

Currently, dual AC voltage sources are used in the large size LCDTV to drive long and straight CCFLs. These dual AC voltage sources are out-off phase and are applied to the two sides of CCFL to overcome non-uniformity problem. But, higher cost is the penalty of this solution. This paper presents a novel CCFL inverter driver technology for large size LCDTV. The proposed burst control technology is capable to driving 950mm length or even longer CCFL by single voltage source. The luminance of lamp output is above 80% uniformity. Due to the negative incremental resistance of the CCFL, the leakage current flowing through the parasitic capacitor can be efficiently reduced with the proposed control scheme. Finally, a 42-inch LCD TV CCFL inverter is implemented experimentally to demonstrate the high efficacy and uniform luminance of the backlight system

An Experimental Study on the Electrical Properties of Fly Ash in the Grounding System

A good grounding system is the fundamental insurance to keep the safe operation of power systems. The grounding resistance reduction additive-fly ash is proposed in this study. Fly ash is the byproduct of coal-fired power plants. A pulverized coal boiler generates approximately 80% fly ash and only 20% bottom ash. Furthermore, the study of these materials will assume greater importance. Waste utilization is an attractive alternative to disposal in that disposal cost and potential pollution problems are reduced. Extensively used as an additive in Portland cement or as a mineral admixture in concrete in recent years, we have found that fly ash has a low resistivity, and so can be used as an agent for reducing resistance to grounding. Also, an effort is made to investigate the effect of water-to-cement(W/C) and temperature on the resistivity of the test specimens. The grounding resistance reduction agent was determined by considering various proportions of water, cement and salt. Experimental results demonstrate that the proposed approach can effectively reduce the grounding resistance.

A new algorithm based on the Newton -Raphson approach for real-time emission dispatch

Abstract This paper presents a new algorithm based on the Newton-Raphson method with sensitivity factors incorporated to solve real-time emission dispatch. In the economic-emission dispatch approaches, the penalty factor and the incremental losses are always the key points in solution techniques. In this paper, the Jacobian matrix and the B -coefficients have been developed in terms of the generalized generation shift distribution (GGSD) factor, and the solution of emission dispatch can be obtained by an iteration method. Comparing with the results of the conventional method, the proposed method has the same numerical accuracy and very short execution time in demonstration examples, hence, is suitable for emission dispatch in real-time applications.

Design and implementation of a ZCS two-switch forward converter with variable inductor

A zero-current-switching (ZCS) two-switch DC-DC forward converter with variable-inductor is presented in this paper. The quasi-resonant technique is employed to achieve ZCS operation. This variable inductor technique is used to reduce the switching losses and the peak value of the output-diode current. Thus, the conversion efficiency can be improved. Moreover, the voltage across the active switch is clamped at the DC-source input voltage. So, the voltage stress of the active switch is less than that of the conventional DC-DC forward converter. Finally, a prototype circuit is implemented to verify the performance.

Transformer design for reducing the inrush current by asymmetrical winding

Abstract This study proposes a novel approach for designing transformers to reduce the inrush current using asymmetrical winding. Differently from traditional methods, the inrush current was reduced based on increasing the inrush equivalent inductance by changing the proportion of inner layer to outer layer in coil winding. To estimate the distributive ratio of winding, the formulae of the inrush equivalent inductance and the leakage inductance are calculated from the structural parameters of the transformer. By theoretical analyses, an optimum distributive ratio of coil winding is presented. Experimental results confirm that inrush current can be reduced concurrently with appropriate voltage regulation and short‐circuit current in transformer.

An application of the novel network diakoptics algorithm for economic dispatch analysis

Abstract A novel approach involving the network diakoptics technique is proposed in this study to evaluate in parallel the penalty factor term. The transposed Jacobian matrix derived from the load flow equations can be separated into as many independent subnetworks, referred to as a bordered block diagonal (RED) matrix, as the processors of a parallel computer. However, effectively solving the cutset block of a BBD matrix in parallel is a relatively difficult task. To alleviate this limitation, the voltage controlled buses should be selected in any cluster, hence, the penalty factors associated with the cutset block are ones and the computation time is reduced. Simulation results of the IEEE test systems and the Taiwan Power System confirm the feasibility of the proposed approach and its capability for implementation parallel processing for the economic dispatch analysis.