M. Faisal Khan

Selective Maintenance in System Reliability with Random Costs of Repairing and Replacing the Components

In this paper we consider the problem of determining the optimum number of repairable and replaceable components to maximize a systems reliability when both, the cost of repairing the components and the cost of replacement of components by new ones, are random. We formulate it as a problem of non-linear stochastic programming. The solution is obtained through Chance Constrained programming. We also consider the problem of finding the optimal maintenance cost for a given reliability requirement of the system. The solution is then obtained by using Modified E-model. A numerical example is solved for both the formulations.

Self regulating three phase-self excited induction generator for standalone generation

This paper presents a simple and effective method for the voltage control of a three phase self excited induction generator (SEIG). The paper is divided into two sections; first section deals with modeling of self compensated SEIG. In the second section a detailed performance analysis of SEIG without and with compensation is carried out. Each of the two models is subjected to different operating conditions by changing excitation and series capacitances, load etc., for a range of different power factor loads. The mathematical model of SEIG is developed in terms of simple quadratic equation rather than traditional nonlinear equation. Therefore, the implemented method does not require numerical solution of the modeled equations. The simulations are carried out by generating programming codes in MATLAB M-file and the veracity of proposed method is established through experimental tests on a 3 phase, 400 V induction motor. The optimum shunt and series capacitances to achieve best output profile are reported in the paper for present case.

Voltage control of single-phase two winding self excited induction generator for isolated loads

Wind and mini/micro hydro electric generation systems are gaining popularity due to their self sustaining attributes. The Self Excited Induction Generators (SEIGs) are most viable generating machines for such applications due to certain merits of these machines. However, in-spite of carrying excellent fault tolerant and rugged construction, their biggest drawback is an inherently poor voltage regulation. This paper presents a simple method for voltage control of a single phase, capacitor excited induction generator. The voltage control strategy adopted for the modeling is based on series connected static capacitor compensation in the main winding of SEIG. The excitation (shunt) capacitance is accommodated in the auxiliary winding to facilitate voltage buildup of the generator. The simulations are carried out by generating programs in MATLAB M-file to get various performance characteristics of SEIG. In order to verify the optimality of the derived model, experimental verification of results of shunt model is carried out on a 1 hp, 220/230 V, single phase induction motor working as SEIG. Reasonable agreement between simulated and experimental results is observed. The obtained results explicitly exhibit the improved voltage regulation and substantially enhanced steady state loading limit of SEIG.

Analysis of a six-phase self excited induction generator supplying RL load with short shunt connection

Multi-phase self excited induction generators (SEIGs) are increasingly being considered for standalone renewable energy generation due to better fault tolerance and ruggedness offered by them compared to the poly-phase counterparts. This paper presents modeling and analysis of a self voltage regulating, short shunt six-phase SEIG (6Ph-SEIG) supplying RL load. Mathematical model of the 6Ph-SEIG is developed in decoupled dual d-q axes in stationary reference frame. The developed model is then implemented in terms of a simulation model to carry out no-load and on-load analysis of SEIG with a loading of 0.9 lagging power factor. An open stator winding induction machine is integrated with necessary equipments to obtain a 6Ph-SEIG test rig which is used for experimental validation of results. The simulated and experimental results are found to be in good agreement.

Evaluation of excitation capacitance for a single-phase two winding self excited induction generator

Self excited induction generators (SEIGs) are being increasingly called in service for renewable energy applications. They are incapable of generating reactive power and hence their reactive power is invariably supplied by capacitors connected across their magnetizing circuit. Therefore, the foremost design constraint of SEIGs is the evaluation of optimum excitation capacitance which fulfills their reactive power requirements for variable loading conditions. This paper presents a detailed steady state modeling and analysis of a single phase, two winding SEIG to evaluate its optimum excitation capacitance for resistive as well as inductive static loads. The steady state model of SEIG is developed through Matlab M file. Validation of simulation results is carried out through experimental tests on a single phase prime mover driven induction motor operated as SEIG.

Performance analysis of shunt, short shunt and long shunt self excited induction generator: Analysis of shunt, short shunt and long shunt SEIG

This paper presents a simple method for the steady state analysis of a self excited induction generator (SEIG) operating in shunt, short shunt and long shunt configurations. The method is based on solution of nonlinear equations obtained through impedance model of steady state equivalent circuit of a single phase SEIG. The circuit model of SEIG is developed in a generalized manner to accommodate all three modes of operation by changing series capacitance placements. The developed model is used to obtain various performance characteristics of SEIG configurations through computer simulations. For the veracity of proposed method, results of shunt model are validated through experimental investigation on a 1hp, 220/230 volts single phase induction motor. An analysis of results establishes the fact that for optimum SEIG performance it is imperative that shunt and series capacitances are chosen optimally for each configuration. The optimum value of shunt capacitance for shunt and short shunt models comes out to be the same. However, to get optimum values of capacitances for long shunt model a slightly different approach has to be adopted. The optimum values of shunt and series capacitances for each configuration are reported in the paper. Finally, the paper is concluded by comparing performances of three SEIG models operating with optimum parameters.

A comparative analysis of single-phase self-excited induction generator variants under resonating condition

A series compensated short shunt self excited induction generator (SEIG) under goes resonance when supplying low power factor R-L loads. In this paper, two variants of single phase SEIG referred as single winding and double winding are investigated under resonating condition. Approximate equivalent mathematical models for each of the above variants are derived. In order to carry out the study two separate simulation programs are written for each variant of SEIG in the Matlabs M-file utility. All the results obtained through simulation study are verified experimentally on a single phase prime mover driven SEIG.

Fault analysis of wind turbine generator in an isolated network

The paper deals with an HPNSWD (High Penetration No Storage Wind-Diesel) System which consists of a Wind turbine generating electrical energy when wind is available and is accompanied by a Diesel Generator which supplies energy whenever wind is unavailable. In order to implement such a system, outmost care must be taken to design auxiliary circuits and measures to improve the disturbances introduced by the addition of a wind turbine to the system. Disturbances such as change in frequency, Main Load Power, Reactive power, etc. must be checked for stability; otherwise the whole grid may fail.

Performance comparison of single winding and double winding self-excited induction generators

A single phase self excited induction generator (SEIG) can operate in two configurations; single winding and double winding. Their performance analyses have been presented quite extensively by the researchers. However, all of these address each configuration in isolation with no attempt being made thus far to present an integrated comparative performance assessment of the two models. This paper fills this gap on SEIG research by articulating a detailed comparison of the performances of two SEIG constructions operating under steady state condition. The circuit models of both configurations are based on double field revolving theory while the mathematical models are obtained by combining various branch impedances to develop performance equations. The derived performance equations are used to obtain various SEIG characteristics in both operating modes with different operating parameters such as load, speed, capacitances, etc. The simulation programs are developed through MATLAB M-file to obtain various no-load and load characteristics of SEIG models for resistive as well as inductive loads. The results explicitly establish preponderance of double winding SEIG (DWSEIG) over single winding SEIG (SWSEIG) on all counts. This is attributed to the dual winding utilization in DWSEIG unlike SWSEIG in which the load as well as excitation capacitance both are accommodated in main winding leaving auxiliary winding open. The developed method is also verified through experimental tests on a 220/230 V single phase, induction motor. The corresponding simulated and experimental results are reasonably convergent.