Ching Lien Huang

A new neural networks approach to on-line fault section estimation using information of protective relays and circuit breakers

This paper proposes a new neural network diagnostic system for online power system fault section estimation using information of relays and circuit breakers. This system has a similar profile of an expert system, but can be constructed much more easily from elemental samples. These samples associate fault section with its primary, local and/or remote protective relays and breakers. The diagnostic system can be applicable to the power system control center for single or multiple fault sections estimation, even in the cases of failure operation of relays and breakers, or error-existent data transmission. The proposed approach has been practically verified by testing on a model power system. The test results, although preliminary, suggest this system can be implemented by various electric utilities with relatively low customization effort. >

A parallel genetic algorithm approach to solving the unit commitment problem: implementation on the transputer networks

Through a constraint handling technique, this paper proposes a parallel genetic algorithm (GA) approach to solving the thermal unit commitment (UC) problem. The developed algorithm is implemented on an eight-processor transputer network, processors of which are arranged in master-slave and dual-direction ring structures, respectively. The proposed approach has been tested on a 38-unit thermal power system over a 24-hour period. Speed-up and efficiency for each topology with different number of processor are compared to those of the sequential GA approach. The proposed topology of dual-direction ring is shown to be well amenable to parallel implementation of the GA for the UC problem.

Solving the unit commitment problem with a genetic algorithm through a constraint satisfaction technique

This paper proposes a genetic algorithm (GA) in conjunction with constraint handling techniques to solve the thermal unit commitment problem. To deal effectively with the constraints of the problem and prune the search space of the GA in advance, the difficult minimum up- and down-time constraints are embedded in the binary strings that are coded to represent the on-off states of the generating units. The other constraints are handled by integrating penalty factors into the cost function within an enhanced economic dispatch program. The proposed GA approach has been tested on a practical Taiwan Power (Taipower) thermal system over a 24-hour period for different utility factors and GA control parameters. Test results reveal that the features of easy implementation, fast convergence, and a highly near-optimal solution in solving the UC problem can be achieved by the proposed GA approach.

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.

A new model for transformer saturation characteristics by including hysteresis loops

A simplified analytical expression in polynomial form to determine the transformer saturation and hysteresis characteristics without field test data is presented. Higher-order approximations are simulated for comparison with transformers of various capacities. The results are compared with experiments and simulations and show very good agreement. It is possible to determine accurate transformer saturation and hysteresis characteristics with this simplified procedure. >

A new intelligent hierarchical fault diagnosis system [for power networks]

As a part of a substation-level decision support system, a new intelligent hierarchical fault diagnosis system for the online fault diagnosis of power systems is presented in this paper. The proposed diagnosis system divides the fault diagnosis process into two phases. Using time-stamped information of relays and breakers, phase I identifies the possible fault sections through the group method of data handling (GMDH) networks, and phase II recognizes the types and detailed situations of the faults identified in phase I by using a fast bit-operation logical inference mechanism. The diagnosis system has been practically verified by testing on a typical Taiwan power secondary transmission system. Test results show that rapid and accurate diagnosis can be obtained with flexibility and portability for fault diagnosis purpose of diverse substations.

Power substation magnetic field measurement using digital signal processing techniques

In this paper, a method is presented for measurement of power frequency magnetic fields due to distorted sinusoidal currents in power systems. The proposed method is an integral approach and consists of a multi-rate digital signal processor, an adaptive filter and an overlap processor. In field test, actual test results are accomplished by a standard area-type measurement setup to identify and characterize magnetic fields distribution of a 69 kV SF/sub 6/-gas insulated substation (GIS) using the proposed method.

Suggested power definition and measurement due to harmonic load

Abstract This paper resolves conventional power content into incident, reflected, and transmitted power components that can be measured in relation to power factor compensation and harmonic elimination problems in power distribution systems. Simultaneously, the proposed concept can successfully overcome the drawbacks of Budeanu reactive and distortion power. From the power engineer’s viewpoint, the proposed reactive and distortion powers possess the attributes of non-sinusoidal waveforms in power systems, and provide the information necessary for compensation of both reactive power and harmonics. An analytical method is proposed in this paper, and examples and case studies illustrate the physical and engineering significance of active, reactive and distortion power. Finally, this paper proposes a concept of ‘reflected power loss factor’, also termed as ‘Γ-factor,’ for harmonic loads. It represents a figure of merit in defining the power transfer capability of a harmonic load.

Investigation of fuzzy real power flow modeling with probabilistic—heuristic based information

A conceptual possibilistic framework is proposed to manage the input uncertainties encountered in steady-state real power flow analysis. This study is devoted to building the robust input framework of the possibilistic load flow (POLF) algorithm under an uncertain environment. Three probability density functions are transformed consistently into the corresponding possibilistic representations. Under the possibilistic framework, a compromise between transformation consistency and human updating experience can be satisfied. The possibility distribution function (podf) derived yields both a mean interval and a reasonable spread interval. Compared with the results of probabilistic load flow (PLF) analysis, the spread interval of the compromise line flow podf can be derived to cover only the reasonable output region and its mean interval contains most of the significant probability information. Numerical simulations for three extreme line flows in the IEEE 25-bus system indicate the feasibility of the proposed approach.

Hybrid filter application for power quality improvement

The passive power filter in power system applications has problems that source impedance and may strongly affect the filtering characteristics and cause system resonance. These disadvantages can be improved by introducing a combination of active and passive power filters with appropriate coordination in operations. Harmonics generating from nonlinear loads are characterized by varying frequency and fixed frequency components. The proposed idea applies the active and passive power filters for such characteristics. This provides good harmonic compensation over the entire operation range for dynamic nonlinear loads. In addition, this arrangement can suppress parallel and series resonances. In this paper, the operation and control strategy for proposed hybrid filter is analyzed and simulated.