Bharat Singh

Reactive Capability Limitations of Doubly-fed Induction Generators

Abstract In the new electricity grid code, reactive power generation by wind farms, which must operate similarly to other conventional power plants, is a major concern during both steady-state and fault conditions. This article presents the reactive power capability of a doubly-fed induction generator through the use of performance capability curves. First, three steady-state models of doubly-fed induction generators are derived in terms of (i) stator and rotor voltage (V S and V R), (ii) stator voltage and rotor current (V S and I R), and (iii) stator voltage and stator current (V S and I S), to derive the limitations in the reactive power production caused by the rotor voltage, rotor current, and stator current limits, respectively. Second, the reactive power capability of the grid-side converter is included. Finally, a complete capability curve of doubly-fed induction generators for stator voltages is developed by optimization of rotor speed employing the maximum power point tracking algorithm. It is established that the total reactive power production is limited by the rotor voltage limit for large slips and then by rotor current limit, and the total reactive power consumption is limited by the stator current limit for the entire operating region of the optimized slip. The capability curve of the unified doubly-fed induction generator scheme is also presented in this article.

Renewable energy generation in india: Present scenario and future prospects

The development of Renewable Energy Sources (RES) is necessary for the sustainable development of any country due to depleting fossil fuel level, climbing fossil fuel prices across the world and more recently pressure for reduction emission level. In India, several schemes and policies are launched by the government to support the use of RES to achieve energy security and self-sufficiency. This paper discusses the present scenario and future prospects of RES in India. Various schemes such as financial assistance, tax holiday etc for promoting RESs development and utilization are also discussed. The present situation is seen to be very promising and favorable for RES in India.

Reactive power capability of unified DFIG for wind power generation

This paper, first, develops the reactive power capabilities of wind power generator and then discusses reactive power ancillary services issues related to the wind farms in the electricity market. Presently, the doubly fed induction generator (DFIG) system, with partial rated power electronic converters in the rotor circuit, is the most popular and widely used for the wind power generation due to its several advantages. The strength of the conventional DFIG in power processing, namely direct connection of the stator windings to the PCC, turns out to be a source of weakness in regards to tolerating PCC voltage disturbances. Utilizing, an additional series grid-side converter (SGSC) connected in series with stator winding of DFIG, it is possible to inject voltage into the grid for necessary compensation. This configuration is known as unified DFIG. A complete reactive power capability of unified DFIG is presented in this paper. The various key issues in providing the reactive power ancillary service are discussed.

Performance evaluation of series and parallel connected grid side converters of DFIG

With the increased penetration of wind power in the system having new electricity grid code, it is required for the wind power generator to fulfill the same requirements as conventional power plants. In this paper, series and parallel connected grid side converters with conventional doubly fed induction generator (DFIG) scheme is explored to suit the Grid Code Requirements (GCRs) during static and dynamic conditions. A dynamic model and control structure for the series architecture are developed and the performance of the system is analyzed with three-phase fault, voltage sag and step response to reactive power injection. The reactive power capability curves of conventional and modified DFIG schemes through the use of performance capability curves has been developed.

Intelligent control of grid connected unified doubly-fed induction generator

A nonlinear adaptive neuro-fuzzy inference system (ANFIS) based controller is proposed for power electronic systems (PES) of grid connected unified doubly-fed induction generators (DFIG). The unified DFIG utilizes an additional series grid-side converter (SGSC) connected in series with the stator winding of the DFIG to inject voltage into the grid for compensation purposes. The SGSC is useful in tolerating voltage disturbances at the point of common coupling, compared to the conventional DFIG. The conventional proportional integrator (PI) controller of the PES of a unified DFIG is replaced with a nonlinear adaptive neuro-fuzzy inference system (ANFIS) based controller applied for adaptive, fast, and efficient control of power electronic systems. The performance of the conventional PI and ANFIS based controllers are compared on a test system. The transient response of ANFIS based controllers is found to be better compared to the conventional PI controllers.

Performance Evaluation of New Series Connected Grid-Side Converter of Doubly-Fed Induction Generator

Increasing penetration of the large wind farm in the system has forced the power system policy makers to develop new electricity grid codes which are required for the wind power generator to fulfill the same requirements as conventional power plants. In this paper, a series connected grid side converters with conventional doubly-fed induction generator (DFIG) scheme is explored to suit the grid code requirements (GCRs) during static and dynamic conditions. A dynamic model and control structure for the series architecture are developed and the performance of the system along with the controller is analyzed for voltage sag condition. Reactive power support capability of series converter during steady state condition is also demonstrated.

Technical and economical practices for Alternative Energy in India

The development of Alternative Energy Sources (AES) is necessary for the sustainable development of any country due to depleting fossil fuel level, climbing fossil fuel prices across the world and more recently pressure for reduction in emission level form electric power generation. In India, several schemes and policies are launched by the government to support the use of AES to achieve energy security and self-sufficiency. This paper discusses the present status, technical and economical practices for AES in India. Various schemes such as financial assistance, tax holiday, energy certificates, etc. for promoting AESs development and utilization are also discussed. The present situation is seen to be very promising and favorable for AES in India.

Intelligent Control of Power Electronic Systems for Wind Turbines

Electric power generation from wind is becoming a major contributing energy source in the power systems around the world. Modern variable-speed wind turbines (WTs) systems that process power through power-electronic systems (PESs) have found better acceptance and have captured most of the market share. PES technologies enhance the controllability of WTs substantially. The PES employed in the wind power generation (WPG) system can effectively face the challenges of grid connection requirements (GCRs). Computational intelligence (CI) techniques, such as fuzzy logic (FL), artificial neural network (ANN), evolutionary computation (EC), etc. are recently proposed and utilized for the control of power electronics systems. Overall, the dynamic performance of a wind turbine system can be substantially improved by the intelligent control of the PESs that are used in WPG systems.