Hui-Jen Chuang

Fault detection, isolation and restoration using a multiagent-based Distribution Automation System

A multiagent-based Distribution Automation System (DAS) is developed for service restoration of distribution systems after a fault contingency. In this system, Remote Terminal Unit (RTU) agents, Main Transformer (MTR) agents, Feeder Circuit Breaker (FCB) agents, and Feeder Terminal Unit (FTU) agents of the Multiagent System (MAS) are used to derive the proper restoration plan after the faulted location is identified and isolated. To assure the restoration plan complies with operation regulation, heuristic rules based on standard operation procedures of Taipowers distribution system are included in the best first search of the MAS. For fault contingency during summer peak season when the capacity reserves of supporting feeders and main transformer are not enough to cover the fault restoration, load shedding scheme is derived for the MAS to restore service to as many key customers and loads as possible. A Taipower distribution system with 43 feeders is selected for computer simulation to demonstrate the effectiveness of the proposed methodology. The results show that by applying the proposed multiagent-based DAS, service of distribution systems can be efficiently restored.

Design of optimal coasting speed for saving social cost in Mass Rapid Transit systems

The artificial neural network (ANN) has been proposed in this paper to determine the optimal coasting speed of the train set for a mass rapid transit system to achieve the maximization of social welfare. The energy consumption and the traveling time to complete the journey between stations with various riderships are calculated by executing the train performance simulation to generate the data set for ANN training. The objective function is formulated by considering the cost of energy consumption and the cost of passenger traveling time. The ANN model is obtained after performing the ANN training, which can be applied to solve the optimal coasting speed of train sets according to the distance between stations and the ridership of passengers. To demonstrate the effectiveness of the proposed ANN model, the forecasted annual ridership of train sets for Kaohsiung mass rapid transit (KMRT) system is used to determine the optimal coasting speed of train sets operating between stations for each study years. The corresponding profile of power consumption and the traveling time cost of passengers for the train operation have been solved to illustrate the social cost of MRT systems operation by applying the optimal coasting speed derived.

Artificial Neural Network Based Adaptive Load Shedding for an Industrial Cogeneration Facility

This paper presents the design of adaptive load shedding strategy by executing the artificial neural network (ANN) and transient stability analysis for an Industrial cogeneration facility. To prepare the training data set for ANN, the transient stability analysis has been performed to solve the minimum load shedding for various operation scenarios without causing tripping problem of cogeneration units. Various training algorithms have been adopted and incorporated into the back- propagation learning algorithm for the feed-forward neural networks. By selecting the total power generation, total load demand and frequency decay rate as the input neurons of the ANN, the minimum amount of load shedding is determined to maintain the stability of power system. To demonstrate the effectiveness of the ANN minimum load-shedding scheme, the traditional method and the present load shedding schemes of the selected cogeneration system are also applied for comparison and verification of the proposed methodology.

Design of Optimal Coasting Speed for MRT Systems Using ANN Models

An artificial neural network (ANN) has been proposed in this paper to determine the optimal coasting speed of train operation for the Kaohsiung Mass Rapid Transit (KMRT) system to achieve the cost minimization of energy consumption and passenger traveling time. A train performance simulation (TPS) is applied to solve the energy consumption and the traveling time required to complete the journey between stations with various riderships to create the data set for ANN training. The ANN model for the determination of the optimal coasting speed is then derived by performing the ANN training. To demonstrate the effectiveness of the proposed ANN model, the annual ridership forecast of the KMRT system over the project concession period from 2007 to 2035 has been used to determine the optimal coasting speed of train sets for each study year according to the distance between stations and the passenger ridership. The power consumption profile of train sets and the traveling time of passengers have been solved by TPS to verify the reduction of social cost for KMRT system operation with the optimal coasting speed derived.

Power Quality Assessment of Large Motor Starting and Loading for the Integrated Steel-Making Cogeneration Facility

This paper presents the power quality assessment of large synchronous motor starting and loading in the integrated steel-making cogeneration facility. To execute the transient stability analysis, the proper mathematical models, and the accurate parameters of the cogeneration units, excitation systems, governor systems, load, and static var compensators (SVCs) are investigated in detail. Four case studies with or without considering the connection of the power grid, the installation of autotransformer (AT) starter, and SVC are performed to demonstrate the dynamic responses of system frequency, voltage, and cogeneration units due to motor starting and loading. Also, the voltage sag ride-through curve of sensitivity load has been included, and a power quality index (PQI) due to voltage variation in the assessment period has been proposed to find the impact of motor starting and loading on the power quality of the cogeneration system. It is concluded that the system dynamic responses and PQI values have better performance if the AT starter is applied with either the regulation of the SVC system or connection to the bulk power grid

Analysis of dynamic load behavior for electrified mass rapid transit systems

This paper investigates the dynamic load flow behavior of an electrified mass rapid transit (MRT) system. Because the power consumption of an MRT system varies with train operation mode and system route gradient, curvature, etc., the motion equation of train sets has been applied to find the mechanical power required for train operation. The electrical input power to the car borne VVVF inverters for the driving of induction motors are solved by the simulation of power electronics. The impedance matrix of the DC power network is then modified for each study snapshot based on the train location and the corresponding resistance change of the conducting 3rd rail and train running rail. The DC and AC load flow analyses have been performed for a practical MRT line in Taipei by considering the operation timetable and actual ridership to demonstrate the effectiveness of the proposed computer simulation methodology. The power consumption of the MRT is solved and the energy conservation by electric regenerative braking when the train set approaches the next station is also determined. The variation of traction transformer loading factors with train operation are calculated for the evaluation of power system operation efficiency. It is concluded that the power flow analysis does provide a very useful tool for the proper capacity planning of traction substations during the design stage of an MRT system.

Optimization of inverter placement for mass rapid transit systems using genetic algorithm

This paper has presented a methodology to solve the optimal planning of inverter substations for an electrified mass rapid transit (MRT) system by using the genetic algorithm (GA). The mathematical models of power converters in traction substations have been derived for different operation modes. With the variation of power demand of train sets along the main line, the AC/DC load flow analysis has been performed to find the energy consumption and braking regeneration restoration at each power converting substation for system peak and off peak operation over the study period. The overall cost of power consumption, inverter investment, and service reliability are included in the objective function, and each feasible solution is expressed as a chromosome in the GA simulation process. The fitness is then enhanced by considering the diversity of chromosomes so that the global optimization during the solution process can be obtained. It is found that the energy regeneration, which has been resulted from braking operation of train sets approaching the next station, can be restored effectively by the optimal planning of inverters using the proposed genetic algorithm

Identification of customers served by distribution transformer using power line carrier technology

In this paper, a narrow-band power line carrier (PLC) based identifier has been designed and developed to support the on line identification of customers served by each distribution transformer. To investigate the transmission characteristics of power line carrier signal over low voltage distribution lines, the mathematical model of distribution components such as transformers, low voltage conductors, customer appliances, etc. at PLC carrier frequency are derived and included in the computer simulation. The two port network is used to represent the low voltage distribution systems and Matlab/Simulink is applied for the analysis of PLC signal attenuation from the secondary side of transformer to the customer locations. After completing the development of PLC based identifier, the field test of a commercial building has been executed. The PLC signal strength and the noise level have been measured to verify the effectiveness of the identifier to determine the connectivity of distribution transformer and the customers served without requiring power service interruption.

Optimal Expansion Planning of Traction Substations for an Electrified Mass Rapid Transit System

This paper is to investigate the proper expansion planning of traction substations (TSS) for an electrified mass rapid transit (MRT) system. The motion equation of train sets is used to solve the mechanical power consumption at each time snapshot according to the operation timetable, the passenger ridership and various types of operation resistance. The mathematical models of power converters in traction substations for different operation modes have been derived. With all train sets operated along the main line, the AC/DC load flow analysis is performed to find power demand of all traction substations for annual system peak operation over the study period. The objective function is formulated by considering both the voltage drop of train sets and investment cost of traction substations as the equivalent cost of all feasible states of each year. By performing the dynamic programming (DP) to minimize the objection function, the expansion planning of traction substations to achieve the minimum overall cost has been obtained by identifying the optimal capacity and locations of new traction substations to be committed at each year.

Design of Undervoltage Relay Setting for an Industrial Plant With Cogeneration Units to Enhance Power Quality of Critical Loads

This paper presents the design of undervoltage relay settings for an industrial plant with cogeneration units to prevent critical loads from tripping due to voltage sags. The critical loads that are sensitive to voltage sags in the plant have been identified from actual system fault contingencies. The power quality of these loads is enhanced by quickly islanding the subsystem with cogeneration units before tie line tripping with an external Taipower system. According to the transient stability analysis of the rest of the industrial power system near a Taipower network, the critical loads that are nonsensitive to voltage sags are disconnected from external system faults in time to restore the system stability with the execution of proper load shedding. To ensure the normal operation of critical and voltage-sensitive loads by considering the voltage tolerance curves, the proper relay settings for tie line tripping of the internal subsystem has been determined. This way, the critical loads and cogeneration units in the industrial power systems can be survived from system faults to mitigate the production loss of industrial customers.