Applied Mechanics and Materials Vol. 787

Abstract: Superconducting magnetic energy storage (SMES) is basically a DC current energy storage technology which stores energy in the form of magnetic field. The DC current flowing through a superconducting coil in a large magnet creates the magnetic field. Because of its fast response during charging and discharging, ability of injecting/absorbing real or reactive power, high storage efficiency, reliability and availability, the SMES technologies are used in power system transmission control and stabilization, and power quality improvement. Generally, an SMES consists of the superconducting coil, the cryogenic system, and the power conversion system. The power conversion system normally uses a power electronic converter as an interface between the coil and AC output. This converter is needed to act as the boost converter during DC side to AC side power flow since the storage suffered from lower input voltage magnitude. On the other hand, the converter is required to work as buck converter during reverse power flow. So the converter must be having bidirectional power flow capability because the need to charge and discharge the coil. The bi-directional Z-source inverter is a new topology, which provides the circuit with bi-directional power flow capacity. This inverter can overcome the limitations of the basic Z-source inverter and be used as an interface between energy storage and utility. A novel modified space vector pulse width modulation (SVPWM) algorithm for bi-directional Z-source inverter is developed in this work, which improves the voltage gain during the boost mode. In the proposed modified SVPWM, four shoot-through states are assigned to each phase within zero state. So zero voltage time period is diminished for generating a shoot-through time, and active states are unchanged. Using MATLAB, the models of the bi-directional Z-source inverter based SMES is established, and the simulation tests are performed to evaluate the system performance.

Abstract: A solar electric vehicle is powered by photovoltaic arrays which allow for direct conversion of solar energy into electrical energy. Since space and weight are very limited with any vehicle, it is desired that the maximum possible amount of energy be obtained from the employed photovoltaic arrays. Every photovoltaic array has an optimum operating point, called the maximum power point (MPP), which varies depending on cell temperature and solar insolation level. This paper is focussed to find the mechanism best suited for employment in a moving vehicle to optimally track this point of maximum efficiency under rapid variation of solar insolation and adjust the operating point of the photovoltaic array accordingly. An integral part of any modern day electric vehicle is power electronic circuits comprising DC-DC converters for conversion and conditioning of electrical power. Recently, Z-source DC-DC converters show promising outcomes when integrated with photovoltaic array compared to conventional DC-DC converters. They provide larger range of output dc voltage, improve reliability and can reduce in-rush and harmonic current. A bi-directional Z-source DC-DC converter with a maximum power point tracking (MPPT) technique suitable for electric vehicle applications is developed to incur high electric power from photovoltaic array. The photovoltaic array output voltage is controlled and the maximum power point tracking is attained by controlling the duty cycle. The well known incremental conductance MPPT algorithm is modified by measuring the power in the middle of the sampling interval to prevent the bewilderedness during rapidly changing insolation condition. Computer simulation and experimental results are provided to establish the performance of the proposed system.

Abstract: In Green Energy technologies like wind energy conversion systems and Domestic applications like SMPS and UPS systems, the input voltage amplitude and input frequency are time varying in nature. Fast-Escalating and extremely challenging high efficiency requirements for AC-DC power supplies for notebooks, desktop computers are to minimize the power losses (Conduction losses). In the conventional rectifiers power losses are more and power factor is poor resulting in loss of efficiency. Normally, the bridgeless topologies, also referred to as dual boost power factor correction (PFC) rectifiers, may reduce the conduction losses by reducing the number of semi-conductor components in the line current path. Power supply units have to make the load compatible with the source. The presence of non-linear load results in poor power factor operation and produces harmonic components in the line. So PFC techniques are necessary to meet harmonic regulations and standards such as IEC 61000-3-2 and IEEE 519. A modified bridgeless topology may be used for such applications. A novel switching controller is developed that regulates the input resistance to a desired value. Hence input power factor is unity and also the total harmonic distortion is controlled to a tolerable limit. In the proposed model, the modified bridgeless boost converter is activated in to a pure resistance mode. Finally the performance of the modified bridgeless boost converter is compared with the existing basic bridgeless boost converter.

Abstract: The paper proposes a comparative analysis of brushless DC (BLDC) motor based photovoltaic (PV) water pumping system with two different controllers namely the proportional-integral (PI) and the fuzzy. The controllers are designed such that the maximum power is extracted from the PV source with the incremental conductance (INC) algorithm. The controlled output is given to the boost converter, which acts as the maximum power point tracker (MPPT). It is followed by the three-phase inverter supplying the BLDC drive system. The constant speed operation is achieved via the spacevector pulsewidth modulation (SVPWM) technique in order to obtain constant throughput from the centrifugal pump. The performance of the system is analyzedwithMatLab/Simulink.It is shown that the fuzzy control provides better response then the PI control.

Abstract: In this paper, two solar Photovoltaic (PV) systems are considered; one in the department with capacity of 100 kW and the other in the hostel with capacity of 200 kW. Each one has battery and load. The capital cost and energy savings by conventional methods are compared and it is proved that the energy dependency from grid is reduced in solar micro-grid element, operating in distributed environment. In the smart grid frame work, the grid energy consumption is further reduced by optimal scheduling of the battery, using Reinforcement Learning. Individual unit optimization is done by a model free reinforcement learning method, called Q-Learning and it is compared with distributed operations of solar micro-grid using a Multi Agent Reinforcement Learning method, called Joint Q-Learning. The energy planning is designed according to the prediction of solar PV energy production and observed load pattern of department and the hostel. A simulation model was developed using Python programming.

Abstract: In this paper, various power quality issues that occur while driving an industrial motor drive such as voltage sag, swell, interruptions are discussed. A solution for such issues is proposed drives during various conditions of power quality issues is discussed in detail and a comparison with traditional Z-source inverter is made. The results are validated for mathematically modelled using Multicell Z-source inverter. By controlling shoot-through duty cycle using various techniques such as Simple boost control, Maximum boost control, constant boost control these issues are addressed. Multicell Z-source inverter has come as a replacement for traditional Z-source inverter due to its less EMI noise; increased voltage level with increase in cell as well as reduced voltage stress makes it more advantages than traditional one. In this paper, control of industrial system of 3 kW induction drive in MATLAB/Simulink environment and the results are summarised.

Abstract: In this paper Switched reluctance motors are proposed for high temperature automotive applications due to the absence of magnets in comparison to conventional DC or brushless DC motors. The improvement in converter efficiency by the use of a current source converter in the front end simplifies the current control strategy that is otherwise required to be implemented in each phase coil winding. The analysis of the converter will be supported with simulation and the results for converter efficiency will be calculated. The proposed strategy will be suitable for implementation using a microcontroller based control mechanism for position control in an automotive application such as throttle control.

Abstract: Partial shading is the major contributing factor for reduced energy harvest in building integrated or rooftop photovoltaic (PV) systems. The architecture of the PV array is altered dynamically in accordance with shade intensity to alleviate the impact of partial shading. However, this technique demands more number of sensors, switches and a sophisticated control algorithm. In small urban residential installations, the shade is often caused by trees and structures in the same or nearby buildings and is inevitable due to space limitations. The shape and intensity of the shade does not vary rapidly in these cases and hence dynamic reconfiguration is not necessary. The paper addresses the issue by proposing a simple tailored architecture to enhance the output under shaded conditions without using additional sensors and switches. The location of the panels in an array is predetermined in the proposed work in such a way that the shade is evenly distributed all over the array. This reduces the mismatch losses and enhances the output. For utility purposes, asymmetric multilevel inverter controlled by FPGA (Field Programmable Gate Array) is employed and the results are presented.

Abstract: Electricity demand is a major concern in the world today. To meet this demand, a number of natural sources are used for electricity production. The produced electrical energy from these natural sources will be given to consumers after going through a lot of conversion stages. So losses mostly occur in these conversion stages. In this paper the four existing converters CUK, SEPIC, Self-lift CUK and Self-lift SEPIC performances are separately compared and analyzed with each other. The voltage-lift (VL) technique is a popular method that is widely applied in electronic circuit design. This technique overcomes the effects of parasitic elements and increases the output voltage effectively along with high power efficiency and high power density with a simple structure. The operating principles of these converters are discussed and Simulation results are provided to verify and compare the feasibility of each systemwith solar photo-voltaic panel incorporated maximum power point tracking (MPPT).

Abstract: Flux switching motor (FSM) is one of the classification of brushless DC motor. The major drawback of the conventional DC machine is presence of brushes and commutator. This makes conventional DC machines not suitable to operate in hazardous conditions. FSM is a type of brushless DC motor without commutator and rotor windings, which has the advantages of both conventional DC and switched reluctance machines. Here a step by step electromagnetic design of FSM using the basic reluctance principle. The designed parameters are verified using two dimensional finite element analysis (FEA). Finally, the analytical results are compared with the simulated results.