Online control of AC/AC converter based SHEPWM technique

Conventional online control of AC/AC converter controlled by the selective harmonic elimination pulse width modulation technique (SHEPWM) is based on storing the offline calculated switching angle values in a form of lookup table. Then the required switching pattern of certain modulation index (M) is searched through the lookup table. This methodology suffers from limited system flexibility. This paper introduces a novel implementation scheme based on real-time calculation of the required SHEPWM switching pattern with linear control of the fundamental voltage component magnitude based on curve fitting technique for the exact switching angle trajectories. The accuracy of the derived polynomials is evaluated by calculating converter performance parameters using the approximated switching angles solutions obtained from the introduced method and the exact switching angles solutions. Detail of the introduced methodology is presented. Simulation and experimental results have been carried out to confirm the validity of the introduced algorithm

Particle swarm optimization-based stator resistance observer for speed sensorless induction motor drive

This paper presents a different technique for the online stator resistance estimation using a particle swarm optimization (PSO) based algorithm for rotor flux oriented control schemes of induction motor drives without a rotor speed sensor. First, a conventional proportional-integral controller-based stator resistance estimation technique is used for a speed sensorless control scheme with two different model reference adaptive system (MRAS) concepts. Finally, a novel method for the stator resistance estimation based on the PSO algorithm is presented for the two MRAS-type observers. Simulation results in the Matlab/Simulink environment show good adaptability of the proposed estimation model while the stator resistance is varied to 200% of the nominal value. The results also confirm more accurate stator resistance and rotor speed estimation in comparison with the conventional technique

Assessment of the worthwhileness of efficient driving in railway systems with high-receptivity power supplies

Eco-driving is one of the most important strategies for significantly reducing the energy consumption of railways with low investments. It consists of designing a way of driving a train to fulfil a target running time, consuming the minimum amount of energy. Most eco-driving energy savings come from the substitution of some braking periods with coasting periods. Nowadays, modern trains can use regenerative braking to recover the kinetic energy during deceleration phases. Therefore, if the receptivity of the railway system to regenerate energy is high, a question arises: is it worth designing eco-driving speed profiles? This paper assesses the energy benefits that eco-driving can provide in different scenarios to answer this question. Eco-driving is obtained by means of a multi-objective particle swarm optimization algorithm, combined with a detailed train simulator, to obtain realistic results. Eco-driving speed profiles are compared with a standard driving that performs the same running time. Real data from Spanish high-speed lines have been used to analyze the results in two case studies. Stretches fed by 1 × 25 kV and 2 × 25 kV AC power supply systems have been considered, as they present high receptivity to regenerate energy. Furthermore, the variations of the two most important factors that affect the regenerative energy usage have been studied: train motors efficiency ratio and catenary resistance. Results indicate that the greater the catenary resistance, the more advantageous eco-driving is. Similarly, the lower the motor efficiency, the greater the energy savings provided by efficient driving. Despite the differences observed in energy savings, the main conclusion is that eco-driving always provides significant energy savings, even in the case of the most receptive power supply network. Therefore, this paper has demonstrated that efforts in improving regenerated energy usage must not neglect the role of eco-driving in railway efficiency

Directly driven, low-speed permanent-magnet generators for wind power applications

The rotor of a typical wind turbine rotates at a speed of 20-200 rpm. In conventional wind power plants the generator is coupled to the turbine via a gear so that it can typically rotate at a speed of 1000 or 1500 rpm. The wind power plant can be simplified by eliminating the gear and by using a low-speed generator, the rotor of which rotates at the same speed as the rotor of the turbine. The hypothesis in this work is that the typical generator-gear solution in the wind power plant can be replaced by a low-speed PM synchronous generator. This thesis deals with the electromagnetic design and the optimisation of two types of low-speed generators for gearless wind turbines. The generators designed are radial-flux permanent-magnet synchronous machines excited by NdFeB magnets. The machines have different kinds of stator windings. The first machine has a conventional three-phase, diamond winding. The second machine has a three-phase, unconventional single-coil winding consisting of coils which are placed in slots around every second tooth. The electromagnetic optimisation of the machine is done by the finite element method and by a genetic algorithm combined with the finite element method. The rated powers of the machines optimised are 500 kW, 10 kW and 5.5 kW. Two prototype machines were built and tested. The optimisation of the machines shows that the cost of active materials is smaller and the pull-out torque per the cost of active materials higher in the conventional machines than in the single-coil winding machines. The torque ripple can be reduced to a low level by choosing a suitable magnet and stator slot shape in both the designs. The demagnetisation of permanent magnets is easier to avoid in the single-coil winding machines than in the conventional designs. The investigation of various rotor designs shows that the rotor equipped with curved surface-mounted magnets has various advantages compared with the other rotor designs, for instance pole shoe versions. The analysis of the machines also shows that the load capacity of the machine is lower in a diode rectifier load than that when connected directly to a sinusoidal grid. According to the analysis, a typical generator-gear solution of the wind power plant can be replaced by a multipole radial-flux PM synchronous machine. The conventional diamond winding machine is a better choice for the design of a directly driven wind turbine generator but the single-coil winding machine is also suitable because of its simplicity.reviewe

Advances in power quality analysis techniques for electrical machines and drives: a review

The electric machines are the elements most used at an industry level, and they represent the major power consumption of the productive processes. Particularly speaking, among all electric machines, the motors and their drives play a key role since they literally allow the motion interchange in the industrial processes; it could be said that they are the medullar column for moving the rest of the mechanical parts. Hence, their proper operation must be guaranteed in order to raise, as much as possible, their efficiency, and, as consequence, bring out the economic benefits. This review presents a general overview of the reported works that address the efficiency topic in motors and drives and in the power quality of the electric grid. This study speaks about the relationship existing between the motors and drives that induces electric disturbances into the grid, affecting its power quality, and also how these power disturbances present in the electrical network adversely affect, in turn, the motors and drives. In addition, the reported techniques that tackle the detection, classification, and mitigations of power quality disturbances are discussed. Additionally, several works are reviewed in order to present the panorama that show the evolution and advances in the techniques and tendencies in both senses: motors and drives affecting the power source quality and the power quality disturbances affecting the efficiency of motors and drives. A discussion of trends in techniques and future work about power quality analysis from the motors and drives efficiency viewpoint is provided. Finally, some prompts are made about alternative methods that could help in overcome the gaps until now detected in the reported approaches referring to the detection, classification and mitigation of power disturbances with views toward the improvement of the efficiency of motors and drives.Peer ReviewedPostprint (published version

Solar Photovoltaic Power with Control Strategies and Applications: A Review

Growing concerns about environment issues, photovoltaic (PV) power is widely gaining importance all over the world. Use of this solar electric power is increasing day by day in many countries. This paper presents a review on applications of solar photovoltaic power for domestic purposes, irrigation purposes as well as for the grid purposes. Solar photovoltaic (PV) system works under variable solar irradiations and thus various control strategies to utilize this solar power in an efficient manner are also reviewed in this paper

Design optimization of Halbach array permanent magnet motor to achieve sensorless performance using genetic algorithm

Purpose The purpose of this paper is to investigate Halbach array effects in surface mounted permanent magnet machine (SMPM) in terms of both self-sensing and torque capabilities. A comparison between a conventional SMPM, which has radially magnetized rotor, and a Halbach machine has been carried out. Design/methodology/approach The geometric parameters of the two machines have been optimized using genetic algorithm (GA) with looking Pareto. The performance of the machines’ geometry has been calculated by finite element analysis (FEA) software, and two parametric machine models have been realized in Matlab coupled with the FEA and GA toolboxes. Outer volume of the machine, thus copper loss per volume has been kept constant. The Pareto front approach, which simultaneously considers looks two aims, has been used to provide the trade-off between the torque and sensorless performances. Findings The two machines’ results have been compared separately for each loading condition. According to the results, the superiority of the Halbach machine has been shown in terms of sensorless capability compromising torque performance. Additionally, this paper shows that the self-sensing properties of a SMPM machine should be considered at the design stage of the machine. Originality/value A Halbach machine design optimization has been presented using Pareto optimal set which provides a trade-off comparison between two aims without using weightings. These are sensorless performance and torque capability. There is no such a work about sensorless capability of the Halbach type SMPM in the literature