Past Issue

The paper develops a duty cycle control for the fly back boost converter using fuzzy based MPPT method. The photovoltaic (PV) systems exhibits nonlinear I-V characteristics and the maximum power point varies in accordance with solar radiation or insolation and temperature. The intermediate high frequency switched dc - dc converter increases the efficiency of the system by providing impedance matching between the PV system and the load. The innate nature of fuzzy principles introduces a reasoning theory to facilitate the operation of the PV cell arrays at their maximum power point.

This paper represents dynamic modeling and simulation of variable speed wind turbine (VSWT) with grid and without grid connection using MATLAB/SIMULINK, a widely used power system analysis and dynamic tool. The variable speed wind turbine with single fed induction generator (IG) and power electronic converter, controller is modeled for dynamic analysis. Component model and equations are represented and implemented in MATLAB/SIMULINK.

Renewable energy sources which are considered to be a promising alternative energy source, brings new challenges when connected to the power grid. Due to the environmental conditions the generated power from renewable energy source such as wind mill, keeps on fluctuating. The Fluctuating nature of the wind increases the uncertainty, thus challenges the power system security during wind power injection into an electric grid. The uncontrollable power flow in the power system may cause bottlenecks in the power system such as angle and voltage instability.

In recent years, the renewable energy markets, industries, and policy frameworks have evolved rapidly. Solar and wind energy generation across the globe has increased substantially during past few years and shares a significant proportion of the total generation in the grid. These renewable generation is concentrated only in a few states in India marginally, to a extent and serious thought needs to be given to balance the variability of such generation.

With the conventional resources of energy striving hard to meet the demands of the growing population, the renewable resources are landing as the remedy to meet the major part of the energy consumption. The advent of newer technologies has made it a cakewalk for the renewable energy sources to capture the market. In this paper, we emphasize about the need for a smoother shift of energy from the conventional towards the renewable energy resources and developing an in-built consciousness about the necessity for a change of energy in the upcoming future.

In this paper the output voltage regulation in response to the perturbation of input voltage by means of varying insolation condition with reference to the perturb and observe maximum power point tracking algorithm was presented and a battery charging for stand-alone photovoltaic (PV) applications was presented for varying illumination condition. The essential work of modeling, control and regulation of output voltage for battery application due to varying input voltage by means of varying insolation condition was carried out.

The general function of a multilevel inverter is to synthesize a desired output voltage from several levels of dc voltages as inputs. In order to increase the steps in the output voltage, a new H- bridge topology is recommended which benefits from a series connection of several sub-multilevel inverters. In addition, for producing an output voltage with a constant number of steps, there are different configurations with a different number of components.

Multilevel inverters (MLI) have been a suitable alternate to three level inverters in medium/high power applications due to reduced voltage distortion, lesser voltage stress, lower electromagnetic interference (EMI) and improved power quality. The MLI have the distinctive advantage of increased voltage level with reduced switching stress while it suffers from increased power components. In this paper, a new MLI is proposed to nurture the power component count while increasing the number of voltage levels.

Inverter is a power electronic circuit that converts DC supply into AC supply of desired frequency and voltage. Based on the voltage levels at the output, inverters are classified as two level voltage source inverter and multilevel inverter. Advantages of multilevel inverters over two level inverters are less harmonic distortion and reduced electromagnetic interference. Because of these advantages, multilevel inverters are widely employed for active power filtering, reactive power compensation and speed control of electrical machine drives.

In this paper various new hybrid PWM strategies for sine-trapezoidal reference with triangular carrier PWM signals are analyzed with the new symmetrical nine level inverter topology. This new multilevel level inverter uses only ten switches rather than conventional multilevel inverter uses sixteen switches for the same nine level output. The topology has many advantages of less switching losses, converter cost and installation cost.