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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. Index Terms--Cogeneration, motor starting, power quality.

This paper presents the influence of the large motor starting and the large rolling mill operation on the isolated integrated steel cogeneration facility by executing the transient stability analysis. The system configuration of the steel facility will be introduced first. Furthermore, the proper mathematical models and the accurate parameters of the cogeneration units, excitation systems, and governor systems are investigated in detail. Both the static and dynamic load models are applied in this paper. To reduce the starting current of large motors, the conventional step-down voltage method by adjusting the suitable tap position of the autotransformer and the constant magnetic flux control method by using the variable-voltage and variable-frequency inverter are considered in the computer simulations. Also, the system voltage and frequency fluctuations due to the operation of the rolling mill will he observed and investigated carefully to verify that the isolated cogeneration can be operated well and safely. Index Terms--Cogeneration, motor starting, transient stability.

This paper presents the proper design of protective relay settings for tie-line tripping and load shedding of a cogeneration system in a high-tech science-based industrial park in Taiwan, R.O.C. To improve the power service quality for the industrial customers, two 161/161-kV transformers with tap changers have been designed to be in series with the tie line. According to the transient stability analysis, the voltage levels at the customer buses can be significantly improved during the time interval of utility fault. The reduction of the voltage drop at the cogeneration bus can also benefit the critical clearing time to restore the stable operation of the cogeneration units after system disturbance. To comply with the fault interruption capacity of the circuit breakers of other industrial customers served by the same utility substation, the series transformers can effectively reduce the fault current magnitude supplied by the cogeneration units. It is found that the application of the series transformers and the cogeneration system with proper protective relay settings can enhance the power service quality of high-tech industrial customers by providing better voltage control and transient stability. Index Terms--Cogeneration, relay design, Science-Based Industrial Park.

To enhance the outage quality of a distribution system with a high penetration of photovoltaic (PV) renewable energy, this paper proposes a coordinating control strategy for an on-load tap changer (OLTC) of the main transformer in a distribution substation and PV smart inverters. The voltages at the end points of all distribution feeders that are served by the main transformer and the power generation of each PV system are collected using a SCADA system. The hourly tap position of the OLTC is then derived from the daily profiles of feeder voltage and the injected power that is generated by all PV systems along the feeder. Thereafter, the PV smart inverters perform autonomous control of reactive power compensation so that the voltage at the point of common coupling can be fixed at the specified voltage level. To demonstrate the effectiveness of the proposed voltage-control strategy, a main transformer, which serves six feeders of the Taiwan Power Company(Taipower) with high PV penetration, was considered in a case study. The proposed coordinating control of the OLTC and PV smart inverters dramatically improved the voltage quality of the distribution feeder and enabled the effective mitigation of the impact of large PV integration in the distribution system. [ABSTRACT FROM AUTHOR]

This paper presents the proper underfrequency relay settings to enhance the operation of industrial power systems with cogeneration facilities. A cogeneration unit was installed in the plant in 1996 to supply the power demand of the plant. The cogeneration unit always faces the shutdown problem when a severe fault occurs on the nearby Taipower network. It is, therefore, necessary to investigate the plant protective relay settings to prevent a whole plant blackout when the contingency occurs. The transient stability analysis has been performed by considering both the detailed models of the cogenerators with the governor and exciter control systems and the external utility power system. The underfrequency relay settings for tie line tripping and load shedding are designed to prevent the tripping of the cogeneration units so that the electricity service to the critical loads of the industrial customer can be maintained in case serious external disturbances such as short circuit faults occur. In this study, the scheme of underfrequency relay settings has been developed for the power system of a large synthetic rubber manufacturer with a large cogeneration unit. Three study cases have been selected for the transient stability analysis to verify the effectiveness of the proposed protective relay setting. Index Terms--Load-shedding scheme, transient stability.

This paper presents the dispatch of reactive power compensation and real power curtailment of photovoltaic (PV) systems to prevent the overvoltage violation when load transfer between distribution feeders is executed. The voltage sensitivity factors of reactive power injection at all PV buses are derived according to the configuration of the distribution network. The advanced distribution automation system issues the control command to each PV inverter for adjustment of PV power generation, according to the sensitivity coefficients and PV installation capacity, so that the ancillary service of voltage support can be provided by all PV systems in a fairer manner. The practical Taiwan Power Company (Taipower) distribution feeders are selected for computer simulation, to verify the effectiveness of the proposed control method to mitigate the voltage violation problem for the operation of load transfer between distribution feeders with high penetration of PV installation. [ABSTRACT FROM AUTHOR]