Sharif Digital Repository

Brushless doubly fed machine (BDFM) shows promising results for wind power and adjustable-speed drive applications. Due to poor rotor magnetic coupling and relatively high value of slip, core loss is more emphasized in this machine than the conventional machines. By now, there are few comprehensive researches on core loss effect on performance characteristics of BDFM in the literature. In this paper, based on the derived relations and by applying suitable rules for transformation of parameters from one winding to another one, the steady state equivalent circuit model of BDFM referred to power winding stator side is obtained. Comparison between simulation and experimental results verifies the... 

A short circuit fault in an AC railway supply system could have undesired consequences; including high-amplitude current flow in the power path, the rail potential rise in the fault vicinity. This paper studies the problem of the rail voltage rise in Tehran-Karaj railway system by the use of a steady state circuit model for the AC autotransformer during a phase-to-ground fault. By using this model, all the currents and voltages of the system can be easily calculated for all possible short circuit fault locations. With the help of the derived analytical model, one can also predict the possible fault locations which may cause the protection system to operate. The estimation of the system... 

This paper considers the modeling and control of a tubular fixed bed reactor with recycle stream for dimethyl ether (DME) production. For simulation purposes, a pseudo homogeneous model has been developed. By reactor simulation under steady state condition, effects of parameters such as feed rate, pressure and shell temperature are investigated. Using the steady state model, an optimizer that maximizes the reactor yield has been developed. For cooling the reactor, a steam drum that uses heat of reactions to produce steam was coupled with the reactor. Through dynamic simulation, system open loop response was obtained and two control loops were considered for controlling the reactor... 

A variable air volume (VAV) air handling system can significantly reduce fan power under partial load conditions. The focus of this study is developing a modeling program to predict the potential energy saving by the secondary HVAC system strategies. Comprehensive steady-state models are established to describe the energy performance of different control strategies for secondary HVAC systems. With building loads, minimum fresh air flow rate, pressure losses, supply air temperature control, dampers control and coil characteristic as inputs, the objectives were to develop a simulation model to evaluate performance of an air handling system. The potential energy savings of constant air volume... 

The performance of a vertical ground source heat pump system (GSHPS) largely depends on the fluid temperature leaving the borehole heat exchanger (BHE) that may be affected by the short-term behavior of the BHE. Although considerable research has been carried out to analyze the short-term transient response of the BHEs, few studies have investigated its impact on dynamic simulation of GSHPS. Therefore, this paper presents a numerical approach based on a transient BHE model to evaluate the performance of a residential GSHPS over short and long timescales. The numerical results are compared with the results of EnergyPlus software. It is shown that the proposed model can appropriately predict... 

this paper presents two new methods for power flow calculation of power systems in presence of Dynamic Flow Controller (DFC), which is a new member of FACTS controllers. In first method A new steady state model of DFC is introduced for the implementation of the device in the conventional Newton-Raphson power flow algorithm. The impact of DFC on power flow is accommodated by adding new entries and modifying some existing ones in the linearized Jacobian equations of the same system without DFC. The focus of second method is on the discrete nature of the DFC and including its effects on power flow. This method is based on Nabavi model for FACTS devices. A case study on a power system located in... 

A variable air volume (VAV) air handling system can significantly reduce fan power under partial load conditions. The focus of this study is developing a modeling program to predict the potential energy saving by the secondary HVAC system strategies. Comprehensive steady-state models are established to describe the energy performance of different control strategies for secondary HVAC systems. With building loads, minimum fresh air flow rate, pressure losses, supply air temperature control, dampers control and coil characteristic as inputs, the objectives were to develop a simulation model to evaluate performance of an air handling system. The potential energy savings of constant air volume...