P. S. Kulkarni

A Robust Method of Tuning the Feedback Gains of a Variable Structure Load Frequency Controller Using Genetic Algorithm Optimization

Abstract In this article, the tuning of feedback gains of a variable structure load frequency controller by genetic algorithm optimization of selected performance indices is presented. The load frequency control of a single- and multi-area power system has been carried out. The effect of generator rate constraints has been studied. The system performance against step load variations has been simulated and compared with the conventional trial-and-error method. The results show that the system dynamic performance has been improved, the control effort has been reduced, the controller is robust against large disturbances, and the system is insensitive to wide parameter variations.

A new simplified multilevel inverter topology for grid-connected application

Multilevel inverter performance is high compared to the conventional two level inverters due to their reduced harmonic distortion, lower electromagnetic interference. However the main drawback of multilevel inverter is increased number of switches, complex pulse width modulation control and balancing of capacitor voltages. This paper proposes a single phase seven level inverter for grid connected system. The proposed inverter topology consists of fewer components with low complexity gate drives and control signals. An LC filter is used to limit the switching current ripple by providing high attenuation of harmonic and high dynamic performance. This paper also presents the most relevant control and modulation methods by a new reference/carrier based PWM scheme employing three similar reference signals with an offset of magnitude equal to the amplitude of the carrier signal. The entire system is numerically simulated using MATLAB/SIMULINK and the simulation results are presented.

Generator System Reliability Analysis Including Wind Generators Using Hourly Mean Wind Speed

Abstract The aim of the article is to study the generator system reliability analysis with wind energy penetration in the conventional grid. It presents the reliability evaluation process, which has accurately modeled the intermittent nature of wind resource. A stochastic model with hourly mean wind speed (HMWS), standard deviation and sequential Monte Carlo simulation is used for reliability analysis. Case studies based on Roy Billinton Test System (RBTS) test system are presented using wind data from two sites in Maharashtra and one Gujarat state of India. The proposed HMWS method offers advantages, such as fast convergence of the reliability indices and high efficiency, over the Weibull method.

A comparison of seven-level inverter topologies for multilevel DC-AC power conversion

Multilevel inverter (MLI) performance is high compared to the conventional two level inverters since they offer high power capability, associated with lower output harmonics and lower commutation losses. However the main drawback of MLI is their increased number of power devices, passive components, complex pulse width modulation control and balancing of capacitor voltages. In this paper the most popular topologies like diode-clamped inverter (neutral-point clamped), cascaded multicell with separate dc sources, and transistor clamped H-Bridge inverter are discussed. A simplified multilevel inverter (Switched Transistor MLI) is proposed and its performance is compared with the above said topologies. Component count and the % total harmonic distortion (THD) of the output voltage are considered as the indexes of the comparative performance. The operating principle of each topology, the most relevant modulation method of all the topologies and the detailed analysis of the proposed Switched Transistor MLI is included. The selection of topology and control techniques depends and varies according to power demands of inverter. Simulation study of all the topologies considered is carried out on MATLAB/SIMULINK platform and the performance of the proposed topology is verified experimentally by the tests performed on a scaled laboratory prototype.

Design of a constant current solar charge controller with microcontroller based soft switching buck converter for solar home lighting system

This paper describes the design of a solar charge controller with microcontroller based soft switching buck converter. Zero current switching technique is used for buck converter design. Atmega 16 microcontroller is used for generating the necessary PWM switching signal. The output voltage of the solar panel is reduced to 15 V and it is applied to a charge controller circuit. The overcharge protection and under charge alarm is available in the charge controller circuit. The settings of these protection circuits are adjustable through potentiometers. Win AVR software is used as a compiler for the generation of necessary hex file.12V, 45 Ah lead acid battery is used for charging purpose.

A Robust Method of Tuning a Decentralized Proportional-Integral Load Frequency Controller in a Deregulated Environment Using Genetic Algorithms

Abstract In this article, load frequency control of an interconnected power system is achieved by two methods. The first is based on the classical h∞ control method and is subjected to linear matrix inequalities. The second uses a proportional-integral controller that is tuned by genetic algorithm optimization and is also subjected to the same linear matrix inequalities in order to obtain robustness against disturbances. Both controllers are tested on a two-area power system with three scenarios of load disturbances, as well as on power systems in a deregulated environment to demonstrate their robust performances.

Single-phase grid-connected photovoltaic system based on ripple correlation control maximum power point tracking

This work presents a comparison of ripple correlation control maximum power point tracking (MPPT) technique and the modified version of the same MPPT applied to single-phase, single-stage, grid-connected photovoltaic (PV) system, as the technique is fast and suitable for fast changing environmental conditions. Both the techniques are compared on the basis of the time taken to reach (track) the MPP, operating point oscillations about MPP and the dependence of the algorithms, if any, on array configuration and parameters. An LCL-Filter based grid connected inverter with proportional-resonant (PR) current controller is suggested to provide power to the line with unity power factor and the inverter offers much less total harmonic distortion. The focus is on presenting a systematic design procedure for AC current, DC voltage controllers for the VSI and low complexity grid synchronization method. The complete system is numerically simulated in MATLAB and the results are presented for rapidly changing irradiation levels.

Energy Analysis of Solar Home Lighting System With Microcontroller-Based Charge Controller

In this paper, a solar powered home lighting system in the Electrical Engineering Department of Visvesvaraya National Institute of Technology (VNIT), Nagpur is analyzed for energy using a personal computer simulation program with integrated circuit emphasis (circuit simulation software, PSpice 9.1). The home lighting system consists of a solar panel of 37 Wp, a 45 Ah battery, a solar charge controller, dc loads of two 9 W compact fluorescent lamps (CFLs), and a dc fan of 14 W. Through the solar panel, the battery is charged during day time. In the night, when solar power is not available, the battery provides power as a backup to the dc load consisting of two CFLs and a dc fan. The aim of the paper is to analyze the solar home lighting system for energy gain/loss with a microcontroller-based charge controller. From the analysis, it is concluded that the solar home lighting system is not designed for continuous energy gain as per manufacturers specifications. The design needs to be modified to have energy gain in the system for Nagpur, India. A designed microcontroller-based charge controller is also analyzed. The advantages of a microcontroller 89C2051-based charge controller are its simple design, low cost, logic change facility with change of programming of microcontroller, presence of liquid crystal display (LCD) with battery charge status, and display of different messages. Ride software is used as an assembler for generating the required hex file of program and it is used for burning in the microcontroller IC with the help of Vegarobokit (a microcontroller programmer developer) to make a microcontroller programmer.

Analysis and design of ZVS-PWM active clamping DC-to-DC Cuk converter based PV generation system

This paper presents the application of the “ripple correlation control (RCC)” maximum power point tracking (MPPT) algorithm for Stand-Alone photovoltaic (PV) system employing dc-dc Cuk converter to maximize the output power of PV module. The combination of auxiliary switch, clamp capacitor and resonant inductor is used to exploit the advantage of minimum voltage stress across the semiconductors at switching transitions due to clamping action. RCC technique uses the high frequency signal ripple, which is inherent in power converters to converge asymptotically to the maximum power point independent of module configuration and parameters. The operating modes of converter for different switching time intervals are analyzed and design considerations are presented. To evaluate the feasibility of ZVS Cuk converter with MPPT, simulation is carried out using MATLAB/SIMULINK platform for an 87 Wp solar PV system and the simulated performance results are presented.

Asymmetric H-Bridge Single-Phase Seven-Level Inverter Topology with Proportional Resonant Controller

ABSTRACT This paper presents an asymmetrical H-bridge single-phase seven-level inverter topology with modified gating scheme for reducing the number of high-frequency switches. Due to shortcomings like steady-state error and problems in removing low-order harmonics associated with proportional integral controller, proportional resonant controller is used for grid-connected converter current control. A practical application of proportional resonant current controller is developed using a low-cost dsPIC33EP256MC202 microcontroller to keep the current injected in to the grid. The validity of proposed inverter and control scheme is verified through simulation and implemented for low-voltage laboratory prototype.