Search

The rapid depletion of fossil fuels, increased electricity consumption, and global environmental concerns have led to shift electricity generation from non-renewable to renewable energy sources. Solar photovoltaic (PV) technology is increasing with significant land requirement. To conserve this valuable land and water evaporation, PV panels are being installed on water bodies such as irrigation canals, lakes and dams. Researchers have found that hybrid power generation systems are more efficient than single power generating system, thus by covering canals with solar panels and harnessing the kinetic energy of flowing water using hydrokinetic turbines (HKT), a massive amount of electricity can be generated. The Hybrid Optimization of Multiple Energy Resources (HOMER) software is used in this study to stimulate and acquire the best results and configuration for a hybrid PV/hydrokinetic system in district Sanghar of Sindh province in Pakistan. Model is designed by covering the 1 km canal surface with PV and the hydrokinetic turbines along with it. The overall potential for 1 km length of canal for both PV/hydrokinetic turbine system is found around 2.8 MW with payback period in 5.7 years and by saving 324.58 million cubic meters of water in terms of evaporation with annual saving in GHG emissions of 416,451.74 kg/yr.

Solar-energy is a clean source of energy and photovoltaic (PV) panels are constructed from solar cells (SC) which convert energy of light into electricity without any environmental effect. The researchers and policy makers focus on the huge scale adoption of solar panels due to its cleaner production. However, there is non-linear behavior in current-voltage characteristics of solar panels and shortage of data in manufacturer’s datasheet. In order to enhance the efficiency of solar panels it is mandatory to develop the PV panels scheme accurately by extracting the basic parameters. In this research study a mathematical model of two different solar cell models is used such as Single Diode Model (SDM) and Double Diode Model (DDM). The Particle Swarm Optimization (PSO) is used to extract the five and seven unknown parameters of SDM and DDM. The algorithm runs with one thousand iterations to minimize the Root Mean Square Error (RMSE) where the RMSE is the vector of five unknown parameters for SDM and seven for DDM. The superiority of proposed PSO algorithm is proved by the optimized results of unrevealed parameters with minimized RMSE of up to 10-3. Optimum parameter values for the solar cell models are applied on the real time data of a 55 mm diameter commercial RTC-France SC. Finally, the results reveal that P-V and I-V curves exhibit smallest deviation between estimated and real time values. The results reveal that the proposed PSO converges to optimal solution with least number of iterations compared to the existing metaheuristic algorithms.

Switched Reluctance Machine (SRM) is the advanced version of the stepper motor and since last decade, it is of high interest among researchers and industrial applications. Modelling an SRM relies on accurate data and proper selection of parameters. The next step is the performance analysis of the machine for which losses determination is indispensable. Previous studies have shown losses calculation only at a particular instant of switching of the machine (i.e., conduction angle). Therefore, the impact of losses in a motoring region cannot be justified. This paper investigates the impact of varying conduction angle on the performance of machines for a set of switch-on angle. Losses are calculated and predicted through simulating motor operating parameters carried out in MATLAB environment and accuracy of results are compared with experimental results.

An appropriate numerical computational method and simplest model captures the performance of Switched Reluctance Machines (SRMs). Several papers and computer software-based simulation models are reported in the literature. Each model has its own merits and demerits. This paper proposes a mathematical model, based on a combination of voltage and mechanical equations, suitable for the transient running of a switched reluctance machine. The simulation results of current, torque and speed profile of SRM are produced under current chopping control and voltage pulse width modulation control. The proposed work has used experimental data of flux linkage and static torque in the mathematical model for best performance and control of the machine. The obtained simulation results are verified with experimental results. This model can be extended to a range of rotor position where the machine can be switched at decreased and increased inductance region which gives motoring and generating operation mode.

The adoption of renewable energy sources, particularly wind energy, has seen remarkable growth in recent years. Wind energy generation requires efficient and reliable generators that can convert wind energy into usable electrical energy. Switched Reluctance Generators (SRGs) have been gaining popularity in wind energy applications due to their high efficiency, reliability, and low maintenance requirements. The multiphase switched reluctance generators are used especially in wind power plants due to their ability to operate in variable speed ranges. In this paper, a MATLAB/SIMULINK based model of Switched Reluctance Generator (SRG) is presented. The obtained results show good agreement under different operating conditions. The obtained results (current, voltage, torque, speed, flux, and angle of generator) are shown in graphs.

The increasing environmental repercussions and depletion of nonrenewable energy resources have cautioned and enabled researchers to incorporate renewable energy systems. Amongst the renewable energy resources, the solar energy system has been utilized in most parts of the world due to cheaper, reliable, robust and sustainable energy resource than other resources. The Maximum Power Point Tracking (MPPT) techniques are used for increasing the power output of PV array. The Perturb and Observe (P&O) technique is widely used MPPT technique due to higher efficiency and ease in implementation. The proposed “Perturb and Observe (P&O)” MPPT technique is incorporated through Matlab Simulation software on PV arrays of various companies. The results are then compared through comparative analysis and optimum results are recommended for the manufacturing companies.

This paper presents a proposed model of a multi-stack slotted stator axial-flux type permanent magnet synchronous machine (AFPMSM) specifically for reducing torque ripple. The proposed AFPMSM model uses pentagon-shaped permanent magnets (PMs). It has a low value of cogging torque and torque ripples compared to the conventional model with a trapezoidal magnet shape. Additionally, it has increased internal generated voltage (Ef) as compared to the conventional model. To further enhance Ef phases and minimize cogging torque of the proposed model, the proposed AFPMSM model was optimized by varying different sides of PMs using a genetic algorithm (GA). A time-stepped three-dimensional (3D) finite element analysis (FEA) was performed for the comparative analysis of conventional, proposed, and optimized AFPMSM models. From this comparative performance analysis, it is observed that torque ripples and cogging torque of the optimized AFPMSM are significantly decreased, while output average torque is appreciably increased. Ef and output power are also enhanced.

Switched reluctance motor (SRM) is an energy efficient machine, which receives electrical energy from the power source and returns part of the stored magnetic energy back to the supply, during each cycle of the machine operation. Characteristically, the SRM possesses nonlinear characteristics due to dual saliency and magnetic saturation. The exertion is realized in developing a mathematical model of the machine in presence of huge input data tables, famously, known as static characteristics. These data tables are required for mathematical modeling of the machine in a single pulse, steady state and transient performances separately. This paper presents a simple and flexible mathematical model of a switched reluctance machine in MATLAB/Simulink environment. In Simulink, based on graphical coding environment, the proposed model uses fewer data tables and less simulation time. Furthermore, with less addition to the same proposed model, another operating mode of the machine is possible, under the same operating conditions. A similar model in MATLAB, based on test code environment is also proposed, using the same operating conditions as in the Simulink based model to see the difference. The obtained results are validated by comparing the results of both the models, and with the experimentally obtained results, under single pulse, steady-state, and dynamic modes of the machine operation. The proposed model can handle the measured or computed data of the flux linkage and static torque, respectively.

The modeling and simulation of Switched Reluctance (SR) machine and drives is challenging for its dual pole salient structure and magnetic saturation. This paper presents the input data in form of experimentally obtained magnetization characteristics. This data was used for computer simulation based model of SR machine, “Selecting Best Interpolation Technique for Simulation Modeling of Switched Reluctance Machine” [1], “Modeling of Static Characteristics of Switched Reluctance Motor” [2]. This data is primary source of other data tables of co energy and static torque which are also among the required data essential for the simulation and can be derived from this data. The procedure and experimental setup for collection of the data is presented in detail.

This paper proposes a novel brushless excitation topology for a three-phase synchronous machine based on a customary current-controlled voltage source inverter (VSI). The inverter employs a simple hysteresis-controller-based current control scheme that enables it to inject a three-phase armature current to the stator winding which contains a dc offset. This dc offset generates an additional air gap magneto-motive force (MMF). On the rotor side, an additional harmonic winding is mounted to harness the harmonic power from the air gap flux. Since a third harmonic flux is generated in this type of topology, the machine structure is also modified to accommodate the third harmonic rotor winding to have a voltage induced as the rotor rotates at synchronous speed. Specifically, four-pole armature and field winding patterns are used, whereas the harmonic winding is configured for a twelve-pole pattern. A diode rectifier is also mounted on the rotor between the harmonic and field windings. Therefore, the generated voltage on the harmonic winding feeds the current to the field winding for excitation. A 2D-finite element analysis (FEA) in JMAG-Designer was carried out for performance evaluation and verification of the topology. The simulation results are consistent with the proposed theory. The topology could reduce the cost and stator winding volume compared to a conventional brushless machine, with good potential for various applications.

Pakistan is facing a severe energy crisis of its time with significant generation deficit in recent years. The future plan shows hydro and thermal coal generation as major contributor and Wind power to replace Thermal-oil generation in long run. This paper proposes a Super grid model for the transfer of bulk power from generation station to the load centres, which can provide efficient transmission between generation and load centres and is also adaptive to deal with variations in power from renewable generations. A dynamic simulation analysis is performed on six-terminal MTDC (Multi-Terminal High Voltage Direct Current) system VSC (Voltage Source Converter) based MTDC meshed grid with different control operations. The results show that the proposed super grid model can provide efficient transmission between generation and load centres and it is also adaptive to deal with variation in power from renewable generation.

The main objective of suspension system is to reduce the motions of the vehicle body with respect to road disturbances. The conventional suspension systems in road vehicles use passive elements such as springs and dampers to suppress the vibrations induced by the irregularities in the road. But these conventional suspension systems can suppress vibrations to a certain limit. This paper presents a novel idea to improve the ride quality of roads vehicles without compromising vehicle?s stability. The paper proposes the use of primary and secondary suspension to suppress the vibrations more effectively.

This paper presents a gate driver circuit for the switching devices used in the asymmetrical converter for a switched reluctance machine with reduced number of isolated dc/dc converters. Isolation required in the gate driver circuit of switching devices is indispensable. For the purpose of isolation different arrangements may be used such as pulse transformers. The dc/dc converter for isolation and powering the gate drive circuits is suitable, cheaper in cost and simple to implement. It is also significant that required number of isolation converters is much less than the switches used in converter. In addition, a simple logic circuit has been presented for producing the gate signals at correct phase sequence which is compared with the gated signals directly obtained from the encoder of an existing machine.

In this paper the actuation properties of two NiTi (Nickel Titanium) SMA (Shape Memory Alloy) actuators available under the commercial names of Flexinol ® and Biometal ® are investigated and compared with each other. Both actuators have diameter of 0.15mm and transformation temperature of 70 o C. The diameter of 0.15mm is selected because of best combination of force and cooling time. An experimental test rig specially designed and developed by the first author was used to conduct tests on the actuators. Both actuators were tested by supplying actuation voltages of 5 and 5.5V. Actuators were thermomechanically loaded for 100 cycles and their strains were recorded. The results of the tests show that 5.5V actuation resulted in greater strain. It was found from the test results that Biometal ® actuators produced more strain as compared to Flexinol ® actuators for both the actuation voltages. However, the drift results showed that higher strains in Biometal ® are due the permanent deformation of the same. This shows that Flexinol ® actuators possess better actuation characteristics as compared to Biometal ® actuators.

To investigate the running characteristics of a switched reluctance motor, the static characteristics and related input data tables are required. The static characteristics comprise of flux linkage, co-energy and static torque characteristics. The co-energy and static torque are calculated once data of magnetization characteristics is available. The data of co-energy is required for the calculation of static torque characteristics. The simulation model includes the data of static characteristics for prediction of the instantaneous and steady state performance of the motor. In this research a computer based procedure of experiments is carried out for measurement of the magnetization characteristics. For every set of measurements, the removal of eddy current is carefully addressed. The experiments are carried out on an existing 8/6 pole rotary switched reluctance motor. Additionally, the instantaneous phase current, instantaneous torque and flux waveforms are produced by using linear, which is by default and spline data interpolation separately. The information obtained from theses simulation results will help in an improved simulation model for predicting the performance of the machine.

Condition changes at the rail surface due to the fallen tree leaves and/or other contaminations can cause the low adhesion levels which present a serious challenge for the traction/braking control systems to avoid the problem of wheel slip/slide. This paper presents a multiple model based method for the identification of the adhesion limit to overcome the problem of the wheel slip/slide in poor contact conditions. The proposed scheme is an indirect method that exploits the dynamic properties of the conventional solid axle wheelset in response to changes in contact condition at the wheel-rail interface avoiding difficult and expensive measurement requirements. A nonlinear model of lateral and yaw dynamics of a conventional solid axle wheelset is used for the study. The non-linearity and changes in the interaction with the rail are modelled by using a set of non-linear creep/slip curves. The scheme consists of a bank of Kalman filters based on the linearized wheelset models. Each Kalman filter in the filter bank is optimally tuned to operate in a specific contact condition. Normalized root mean square values from the residual of each filter calculated using time moving windows are assessed to identify the operating condition of the wheelset.

In this paper the hardware implementation of producing the voltage pulses of variable duty cycle which are applied at the gate driver terminal of the switching devices used in the converter of a switched reluctance motor have been presented. These voltage gated pulses which corresponds to phase excitation sequence of the motor are necessary to run the motor. The proposed counter was tested in the laboratory with the 8/6 poles drive, and operation of the machine at variable conduction angles was found to be excellent. The implemented method of producing the variable conduction angles is simple, cheaper and easy to implement and does not require prior knowledge of programming.

The incorporation of wind energy as a non-conventional energy source has received a lot of attention. The selection of wind turbine (WT) prototypes and their installation based on assessment and analysis is considered as a major problem. This paper focuses on addressing the aforementioned issues through a Weibull distribution technique based on five different methods. The accurate results are obtained by considering the real-time data of a particular site located in the coastal zone of Pakistan. Based on the computations, it is observed that the proposed site has most suitable wind characteristics, low turbulence intensity, wind shear exponent located in a safe region, adequate generation with the most adequate capacity factor and wind potential. The wind potential of the proposed site is explicitly evaluated with the support of wind rose diagrams at different heights. The energy generated by ten different prototypes will suggest the most optimum and implausible WT models. Correspondingly, the most capricious as well as optimal methods are also classified among the five Weibull parameters. Moreover, this study provides a meaningful course of action for the selection of a suitable site, WT prototype and parameters evaluation based on the real-time data for powering local communities.