No abstract

No abstract

No abstract

No abstract

Summary This article investigates a modified circuit for multilevel converter based on cascaded basic units. The proposed circuit can be operated in both symmetrical and asymmetrical source configuration. The magnitudes of two dc source in basic units can be adopted for symmetrical and asymmetrical configuration. In the symmetrical configuration, the magnitude of the dc voltage source is identical for each unit. On the other hand, the values of the dc voltage source for basic units are unequal in asymmetrical configuration. In order to generate a large number of voltage levels with less number of components, several methods are suggested for determining the magnitude of dc voltage source. Comparison analysis proves that the suggested circuit needs less number of components, reduces power loss, and improves the efficiency of the inverter. Moreover, the standing voltage across the switches is acceptable compared with contemporary topologies. Simulation and experimental results for 15‐, 17‐, 23‐, and 31‐level inverters are analysed to validate the performance of investigated topology.

Photovoltaic (PV) module parameters act an important task in PV system design and simulation. Most popularly used single diode R_sh model has five unknown electrical parameters such as series resistance (R_se), shunt resistance (R_sh), diode quality factor (a), photo-generated current (I_pg) and dark saturation current (I_s) in the mathematical model of PV module. The PV module output voltage and current relationship is represented by a transcendental equation and is not possible to solve analytically. This paper proposes nonlinear least square (NLS) technique to extract five unknown parameters. The proposed technique is compared with other two popular techniques available in the literature such as Villalva’s comprehensive technique and modified Newton-Raphson (N-R) technique. Only two parameters R_se and R_sh are estimated by Villalva’s technique, but all single diode unknown electrical parameters can be estimated by the NLS technique. The accuracy of different estimation techniques is compared in terms of absolute percentage errors at MPP and is found the minimum for the proposed technique. The elapsed time for parameter estimation for NLS technique is minimum and much less compared to other two techniques. Extracted parameters of polycrystalline ELDORA-40 PV panel by the proposed technique have been validated through simulation and experimental current-voltage (I-V) and power-voltage (P-V) characteristics.

Abstract-The aim of this paper is to present the complete modeling and simulation of wind turbine driven doubly-fed induction generator which feeds ac power to the utility grid. For that, two pulse width modulated voltage source converters are connected back to back between the rotor terminals and utility grid via common dc link. The grid side converter controls the power flow between the DC bus and the AC side and allows the system to be operated in sub-synchronous and super synchronous mode of operation. The proper rotor excitation is provided by the machine side converter. The complete system is modeled and simulated in the MATLAB Simulink environment in such a way that it can be suited for modeling of all types of induction generator configurations. The model makes use of rotor reference frame using dynamic vector approach for machine model. Index Terms-doubly-fed induction generator (DFIG), pulse width modulation (PWM), dynamic vector approach, utility grid, wind energy conversion systems,

No abstract