Applied Mechanics and Materials Vol. 573

Abstract: The extraction of solar energy will be higher using the multijunction solar cells instead of single junction solar cell by splitting the solar spectrum. This work proposes a detailed study to identify the optimum interconnection method for various multijunction solar cells. An effective power electronic circuit could substantially enhance the efficiency and utilization of a photovoltaic (PV) power system constructed from multijunction solar cells. The multiple input dc-dc non-inverting buck-boost converter is used to demonstrate the advantage of the proposed interconnection technique, which can maintain a constant output voltage by performing both the buck and boost mode of operation. In order to ensure maximum power point (MPP) operation, a particle swarm optimization (PSO) algorithm is applied which needs only one MPP control for multiple solar modules resulting reduction in cost and complexity. The PSO algorithm has the ability to track the global maxima of the system even under complex illumination situations.

Abstract: Nowadays the number of non linear loads in power systems is increasing dramatically. These non linear loads inject harmonic currents and voltage which makes the supply currents non-sinusoidal. These harmonics are eliminated via an active power filter. The reference currents are generated by shunt active filter which is provided to compensate harmonic currents demanded by the load. Different current control strategies are implemented to improve the performance of shunt active power filter. These techniques are useful in making the supply currents sinusoidal. The performance of the current control techniques are different from each other. The %THD can be reduced with the aid of shunt active power filter. In this paper, different current control schemes are analyzed and their outputs are compared to determine the effectiveness. The most effective current controller generates less %THD. The power quality of the system is improved with the reduction of %THD. The different current controllers which are compared in this paper are GA controller and PI-VPI controller.Under analysis, the PI-VPI controller is found to be effective.

Abstract: The Unified Power Flow Controller (UPFC) is accepted as the versatile Power Flow Controller between electrical power nodes or power sources many times referred to as the buses. Regulation of real and reactive power flow between power nodes can be achieved in the desired manner using the UPFC. In this paper it is demonstrated how additional real power sources like Wind and Photo Voltaic Solar power sources can be augmented into the DC link of the UPFC and supplementing the seamless performance of the UPFC. Fuzzy Logic has been chosen to be the controller as it is moderately robust and its usefulness in this application is compared and contrasted against traditional PI controller. MATLAB / SIMULINK based simulation environment has been used for demonstrating the validity of the proposed schemes.

Abstract: This paper proposes the single phase ac-dc three-level boost converter with controller circuit such as sliding mode controller, proportional integral controller and employs three-level pulse width modulation technique. Solid state switched mode three-level boost converter along with the control methods achieve unity power factor, high efficiency, precisely regulated dc output in boost converter, reduced output voltage ripple and less than 5% of total harmonic distortion with unidirectional power flow. The outstanding feature of proposed control scheme is line current is driven to follow sinusoidal reference current command which is in phase with sinusoidal input voltage and guaranteeing dc-link capacitor voltage balance in every switching cycle. Comparative analysis of PI controller and sliding mode controller is carried out. The performances of converter under load variation, unbalanced load condition and sudden change in load condition for various control strategies were verified.

Abstract: This paper explores the level of conducted EMI in a buck boost converter under a non linear load condition based on the CISPR 11 / Class A EMC standard. Here, the buck boost converter was designed to produce a constant output voltage irrespective of load conditions. The closed loop control is designed using dsPIC controller. Three different randomization firing schemes are adopted and the EMI analysis in each mode is done experimentally. Also, the results are compared with normal PWM scheme. The experimental result shows that in RPWM scheme the emission levels are comparatively low.

Abstract: The interest toward the application of fuel cells is increasing in the last years mainly due to the possibility of highly efficient decentralized clean energy generation. The output voltage of fuel-cell stacks is generally below 50 V. Consequently, low-power applications with high output voltage require a high gain for proper operation. A zero-voltage-switching (ZVS) dc–dc converter with high voltage gain is proposed for fuel cell as a front-end converter. It consists of a ZVS boost converter stage and a ZVS half-bridge converter stage and two stages are merged into a single stage. The ZVS boost converter stage provides a continuous input current and ZVS operation of the power switches. The ZVS half-bridge converter stage provides a high voltage gain. The principle of operation and system analysis are presented. Theoretical analysis and simulation result of the proposed converter were verified.

Abstract: Maximum power point tracking techniques play an important role in solar photovoltaic systems to achieve the desired output power. These techniques track maximum power from the solar panel under varying solar irradiation and cell temperature. Among these techniques, Perturb & Observe (P&O) is used by many researchers. Due to the ease of realization and Incremental conductance (INC) algorithm is widely used because of reduced oscillations around maximum power point. In this paper, MATLAB/SIMULINK tool has been used to evaluate the performance of 125W solar PV panel by using these algorithms. The performance comparison of P&O and INC techniques is made and the results exhibit the maximum power tracking from solar PV panel and well regulated output voltage across the load is achieved.

Abstract: The main work of this paper is to control the speed of a four switch inverter fed three phas s Brushless DC motor drive based on the concept of switching functions. The advantage of this inverter that uses of four switches instead of using six switches are lesser switching losses, lower electromagnetic interference (EMI), less complexity of control algorithms and reduced interface circuits. This drive system consists of a Buck Boost converter, four switch inverter and BLDC motor. Here current and torque ripples could be reduced based on controlled dc link voltage according to the motor speed. This proposed scheme is compared with conventional BLDC motor drive system. Simulation and Experimental works are carried out and results presented to demonstrate the feasibility of the proposed four switch inverter method.

Abstract: Converter plays a vital role in modern transferable electronic devices and systems. In the battery operated transferable devices, the battery supplies an input voltage to the converter which in turn converts into the desired voltage. Buck-boost, Cuk, SEPIC and Zeta converter are meeting the operational requirements of DC-DC converters. The DC-DC converters are used in both buck function as well as boost function. But the advantage of Zeta converter is that, it does not suffer the polarity reversal problem. The aim of the proposed work is to design a Zeta converter which can be used to drive the Permanent Magnet Brushless Direct Current Motor. The proposed Zeta converter is suggested to control the speed of the Permanent Magnet Brushless Direct Current Motor, according to the generated switching sequence. The proposed work is generally used for low power applications and occasionally used for medium power applications.

Abstract: Power electronic devices with front-end rectifier are widely used in industry, commerce and transportation, which result in low power factor. Though there are several proposed solutions to this, Single Ended Primary Inductance Converter (SEPIC) converter was the most successful one. But the conventional SEPIC converters suffer from high switching losses. Hence in this paper, a modified SEPIC converter is used to improve the power factor at the mains side. This paper presents the simulation and analysis of single phase single-switch, converter topologies of AC-DC SEPIC converter and modified SEPIC converter for Continuous Conduction Mode (CCM) of operation with 48V, 100W output power. The results of SEPIC converter and modified SEPIC converter are compared for closed loop analysis in simulation which is done in PSIM. It is found that modified SEPIC converter has high regulated output voltage and high power factor.