Chin E. Lin

Hierarchical Economic Dispatch for Piecewise Quadratic Cost Functions

This paper presents a method to solve the economic power dispatch problem with piecewise quadratic cost functions. The solution approach is hierarchical, which allows for decentral i zed computations. An advantage of this approach is the capability to optimize over a greater variety of operating conditions. Traditionally, one cost function for each generator is assumed. In this formulation multiple intersecting cost functions are assumed. This method has appl ication to fossil generation units capable of burning gas and oil , as well as other problems which result in multiple intersecting cost curves for a particular unit. The results show that the solution method is practical and valid for real-time application. The motivation for this research stems from the actual operational and planning problems of a large Southwestern Utility.

A direct Newton-Raphson economic dispatch

The authors present a method to solve the real-time economic dispatch problem using an alternative Jacobian matrix considering system constraints. The transmission loss is approximately expressed in terms of generating powers and the generalized generation shift distribution factor. Based on this expression, a set of simultaneous equations of the Jacobian matrix are formulated and solved by the Newton-Raphson method. The proposed method eliminates the penalty factor calculation and solves the economic dispatch directly. The method resulted in a very fast solution speed and maintained good accuracy in test examples. It is a good approach to solve the economic dispatch problem. >

Reactive and harmonic current compensation for unbalanced three-phase systems using the synchronous detection method

Abstract This paper presents the application of the synchronous detection method for reactive and harmonic current compensation in an unbalanced three-phase power system. When the instantaneous power theory is applied, a balanced three-phase voltage source is required. However, in practical distribution systems, it is difficult to maintain balanced three-phase voltage along the feeder lines. To handle the reactive and harmonic current compensation in an unbalanced voltage source, the synchronous detection method is applied by per-phase calculation to obtain proper compensating components. Three different approaches using equal power, equal line current, and equal load resistance concepts in the synchronous detection method are discussed. Formulations and calculation algorithms are derived for each approach. By simulation, it is proved that the synchronous detection method is effective in unbalanced system compensation and gives a better performance than the instantaneous power theory. In this paper, preliminary results from simulations are obtained. Using the different approaches of the synchronous detection method, the line loss after compensation can also be minimized.

Investigation of magnetizing inrush current in transformers. I. Numerical simulation

A simple method for simulating magnetizing inrush currents in power transformers using real-time measurements is proposed. The method is based on a simplified model for representing the inrush current under different loading conditions. A digital simulation method using a PC-AT microcomputer is also proposed. Transformer operating conditions, including transformer loading power factors, switching-on angles, and remanent flux, are included. The simulation result show very good agreement with experiment results. >

Economic analysis for demand-side hybrid photovoltaic and battery energy storage system

This paper examines the cost analysis of a hybrid photovoltaic and battery energy storage system (PV-BESS) for demand-side applications in Southern Taiwan. The forms of input data and output data for three different invest plans are proposed and discussed. A sensitivity analysis to understand those affecting parameters to the investment is also investigated. The analysis results can support the users with a trade-off among economic, operational and environmental factors. This paper establishes a potential and practical tool for cost analysis of most energy conversion applications.

Fuzzy approach for generator maintenance scheduling

Abstract A new approach using fuzzy dynamic programming for generator maintenance scheduling in power systems is proposed. In this paper, multiple objectives and soft constraints are expressed by fuzzy sets. The process of solution formulation is discussed. A practical example chosen from Taiwan Power Company is tested and demonstrated in this paper. Operation experts are consulted for the determination of membership functions. Test solutions prove the capability and effectiveness of this approach to solve the generator maintenance scheduling problem.

A hybrid-control approach for pendulum-car control

A hybrid-control approach for operation of a pendulum-car mechanical system that improves the unstable control phenomenon within a limited length of car position is presented. The proposed hybrid-control approach combines a fuzzy logic control approach and a linear state-feedback control approach to obtain the desired performance. The experimental system has been designed and its control system implemented into a 16-b personal computer with successful operation from a downward stable position to an upright holding position. >

A new method for representation of hysteresis loops

The i- phi hysteresis characteristic of a transformer is modeled and simulated by a curve-fitting technique, including a consuming function for representing hysteresis loss. The method is established on the basis of measured hysteresis data and allows direct calculation of hysteresis losses. The analytical expression also exhibits the property of increasing the loop area with increment of operating frequency. The simulation results are compared with experiments, and good agreement is shown. The approach can be adapted to determine an accurate transformer hysteresis characteristic by a simplified procedure. >

Investigation of magnetizing inrush current in transformers. II. Harmonic analysis

For pt.I see ibid., vol.8, no.1, p.246-54. Simulation data for the magnetizing inrush current generated by power transformers, obtained in part one, are used for harmonic analysis. The simulation results show very good agreement with experiment results. The relationship of the harmonics to all parameters is discussed. The results establish a guideline for eliminating harmonics due to inrush current, and provide reference for system design. >

Power frequency harmonic measurement using integer periodic extension method

Abstract Reduced frequency resolution and spectral leakage are the two major defects on the Fourier spectrum resulting from a data window function and fast Fourier transform (FFT) in power system harmonic measurement. In this paper a novel method, termed the integer periodic extension (IPE) method, is proposed to overcome the noted problems. The proposed method simplifies measurement process and increases measurement accuracy. Finally, five cases from practical demand-side power systems are demonstrated with improved performance.