R.K. Nema

Pre-feasibility study of PV-solar / Wind Hybrid Energy System for GSM type mobile telephony base station in Central India

This paper proposes the most feasible configuration of a stand alone PV/Wind Hybrid Energy System with diesel generator as a backup for cellular mobile telephony base station site in isolated areas of Central India. It is expected that the newly developed and installed system will provide very good opportunities for mobile telephony base station in near future. The meteorological data of Solar Insolation, hourly wind speed, are taken for Bhopal, Central India and the pattern of load consumption of mobile base station are studied and suitably modeled for pre-feasibility study of the hybrid energy system. This system is more cost effective and environmental friendly over the conventional diesel generator. It should reduced approximate Seventy to Eighty percent fuel cost over conventional diesel generator and also reduced the emission of Carbon dioxide and other harmful gasses in environments.

Switching Losses and Harmonic Investigations in Multilevel Inverters

Abstract Use of conventional two-level pulse width modulation (PWM) inverters provide less distorted current and voltage but at the cost of higher switching losses due to high switching frequencies. Multilevel inverters are emerging as a viable alternative for high power, medium voltage applications. This paper compares total harmonic distortion and switching losses in conventional two-level inverters with multilevel inverters (three-level and five-level) at different switching frequencies. An optimized switching frequency has been obtained for a lower level of total harmonic distortion and switching losses. Diode-clamped, three-phase topology is considered for study. A sinusoidal PWM technique is used to control the switches of the inverter. Simulation study confirms the reduction in harmonic distortion and switching losses as the number of the levels increases.

Selection of TCSC parameters: Capacitor and inductor

Thyristor controlled series compensator (TCSC) device is a series compensator to govern the power flow by compensating the reactance of the transmission line. Both capacitive and inductive reactance compensations are possible by proper selection of capacitor and inductor values of the TCSC device which can be realized through reactance equation. This paper presents a conceptual study to adopt an apt value for the capacitor and inductor of a TCSC device. Degree of Series compensation (K) brings an idea of selecting the TCSC capacitor. The Reactance characteristic curve is analyzed with resonant point for different values of ‘ω’ which defines the square root of ratio between capacitive and inductive reactance. The study is helpful in selecting an appropriate value for TCSC inductor which has influence on multi resonance point in TCSC device. Additionally, power flows in the transmission line are discussed with tabulation to realize the operating span of the TCSC for various values of ‘ω’. While designing, TCSC parameters can also be selected as per requirement on end side demands and for safe operating span of a TCSC.

Adaptive Control Schemes for Improving the Control System Dynamics: A Review

ABSTRACT Adaptive control involves modifying the control law used by the controller to cope with the fact that the parameters of the system being controlled change drastically owing to change in environmental conditions or in the system itself. The adaptive control process continuously and automatically measures the dynamic behaviour of plant, compares it with the desired output and uses the difference to vary adjustable system parameters or to generate an actuating signal in such a way that optimal performance can be maintained regardless of system changes. This paper deals with the application of different adaptive schemes in the control system and provides a detailed comparison between the schemes on the basis of their approach to deal with the control problem. A comparative analysis is presented to show the effectiveness of adaptive control techniques during transients in the area of power quality improvement with a shunt active power filter. A classified list of more than 90 publications on this topic is also given for quick reference.

Inverter topologies and control structure in photovoltaic applications: A review

The inverter is an integral component of the power conditioning unit of a photovoltaic power system and employs various dc/ac converter topologies and control structure. It has to meet various international standards before it can be put in commercial use. The function of inverter in distributed power generation system on top of photovoltaic generation includes dc-ac conversion, output power quality assurance, various protection mechanisms, and system controls. The requirements in terms of low cost, high efficiency, high reliability, and tolerance over wide range of input voltage variations have driven the inverter development toward simpler topologies, lower component counts, and tighter modular design. Historically, the inverters employed in PV technology may be classified based on number of power processing stages, type of power decoupling, types of interconnection between the stages, and types of grid interface. Based on power processing stage, the inverter may be classified as single stage and multip...

A comprehensive assessment of maximum power point tracking techniques under uniform and non-uniform irradiance and its impact on photovoltaic systems: A review

Under shading condition, the power–voltage characteristics of the photovoltaic (PV) modules exhibit complexity with multiple numbers of peaks. Existence of multiple peaks leads to additional difficulties in tracking maximum power point (MPP) and shall mar efficiency of PV arrays under shading, if appropriate measures are not taken. It is due to the nonlinear characteristics of PV cell, maximum power can be extracted under particular weather condition. Maximum power point tracking (MPPT) techniques are used to maximize PV array output power continuously, by tracking MPP, the location of which depends on atmospheric temperature and solar insolation. The major drawbacks of traditional MPPT techniques are that they are unable to track global peak under non-uniform irradiance/insolation. Numerous techniques are reported in literature to find MPP in both under uniform insolation and partial shading condition. This paper presents a comprehensive review of various MPPT techniques under uniform and non-uniform irr...

Comparative analysis of maximum power point (MPP) tracking techniques for solar PV application using MATLAB simulink

The renewable energy sources such as PV cells, fuel cells or energy storage devices are most popular. Among which photovoltaic energy is becoming one of the main power suppliers. This paper presents a comparative analysis between Perturb & Observe (P&O) and Incremental Conductance (Inc-Cond) algorithm for extracting the maximum power from photovoltaic Array. Because of the nonlinear characteristics of PV cell, the maximum power can be extracted under particular whether condition. Therefore, maximum power point tracking (MPPT) techniques are used to maximize the output power of PV array, continuously to track the maximum power point (MPP), which depends on atmospheric temperature and solar insolation. This paper addresses the comparison between of the existing maximum power point tracking (MPPT) techniques used in photovoltaic systems as reported in literature by using MATLAB/Simulink and PSPICE.

Performance of installed TCSC projects

This paper presents brief investigations on performance of Installed Thyristor Controlled Series Compensator (TCSC) projects world around. The main and basic objective of TCSCs in power system is to enhance power flow and improve system stability. The deployment of TCSC in transmission line also improves SSR mitigation, Power Oscillation Damping (POD) and Transient Stability (TS). The paper intends to discuss some important TCSC projects installed world around and highlights the benefits derived in terms of enhancing power networks. Test results of installed TCSC projects are reviewed from published research works. The authors use technical data of these installed projects to investigate the reactance characteristic, the factor ‘ω’, the resonance region and possible capacitive operating range. The paper also investigates the maximum power transfers on lossless symmetrical transmission line with Fixed Series Capacitors (FSC) and TCSC device installed with possible power improvement at these locations are calculated and tabulated. The simulated results show the working performance of Installed Thyristor Controlled Series Compensator (TCSC) projects manifestly.

Development of photovoltaic (PV) cell/module/array and non-uniform irradiance effect based on two-diode model by using PSPICE simulator

Need of alternate electrical energy resource and compatibility with grid connection has revived the interest in PV system. To study the interaction with converters an accurate modeling approach is required which should be able to define precisely the electrical behavior with changes in the surrounding temperature and insolation level. This paper proposes a PSPICE based model utilizing two diode based cell contributing higher accuracy at low irradiance level and allowing better analysis of PV system performance. Also to analyze partial shading effect a model is put forward with the utilization of two diode based PV cell. Temperature and insolation levels are kept as variables to plot the VI and PV characteristics. In order to study the interfacing with MPPT algorithms and converters PV array and module simulation are performed. PSPISE simulator is a platform to deal with non-linear devices such as diodes and transistors availed with a number of parameter to achieve numerical convergence.

A two-stage power electronic interface for fuel cell-based power supply system

The increasing energy demands, insufficient availability of power generation and increasing global environmental problems, need alternate/green power sources. Among the different green power technologies such as wind power, photovoltaic, gas turbine and fuel cell, the fuel cell-based distributed generation is considered as one of the most promising solutions for stand-alone/grid applications due to its cleanliness, modularity and higher potential capability. The selection of a power conditioning unit plays an important role to maintain the stability of the system and to improve the performance of fuel cell system. While using a single-stage DC/AC inverter with step up transformer for stand-alone/gird applications, the major issue is high current flow through the inverter and primary side of the transformer. This paper presents a two-stage power conditioning unit, a DC/DC boost converter combined with a DC/AC inverter for fuel cell system to reduce the current level at the DC/AC inverter.