Proc. of Int. Conf. on Control, Communication and Power Engineering 2010
Automatic Power Generation Control of Grid Connected 3-Ø Asynchronous Generator Using Electronic Controller in the Rotor Circuit 1
K. Subramanian* and K. Hari Prasad2
*Power Electronics Division, School of Electrical Engineering VIT University Vellore, Tamil Nadu, India, 632 014 1 Email id: ksubramanian@vit.ac.in ; 2Email id: hari_sekhar18@yahoo.co.in generator over a wide range of wind speeds is proposed in this paper. Constant stator power output control involves keeping the shaft torque constant as the wind speed changes. Torque control is achieved by electronically varying the rotor resistance of the induction generator. The control system monitors the difference between the actual and the desired stator power output and adjusts the external resistance in the generator rotor circuit so as to reduce the differential to zero.
Abstract— This paper explains the power generation control of wind driven grid connected 3-Ø self-excited asynchronous generator. Power semiconductor switch based Electronic controller has been used to change the rotor resistance value. The changes in the resistance could be change the rotor power which is fed to the grid in double fed induction generators. The proposed control technique is either addition or deletion (remove) the external resistance to the rotor circuit. Wind turbine characteristics are derived and simulated. Simulation of the proposed system has been done using power system tools box in MATLAB / Simulink. Results are presented.
I.
The proposed scheme consists of wind driven grid connected self-excited asynchronous generator (SEASG), rectifier and Electronic controller shown in Fig.1. In this configuration wind turbine and rotor of the generator is mechanically coupled. The external resistance (effective resistance) is to be connected to the rotor circuit using the electronic controller.
Index Terms—grid connected asynchronous generator, electronic controller wind characteristic
I. INTRODUCTION The increasing rate of depletion of conventional energy resources has revived worldwide interest in wind turbine generators. For small and isolated communities where electricity is generated using diesel fuel, this interest is largely due to the economic benefits associated with the reduction in diesel fuel consumption. However, integration of wind power with a small isolated power grid is not straightforward because the system voltage, frequency, and performance of other diesel generators connected to the grid depend on the amount of the wind power penetration [1]. During gust periods, a wind turbine is subjected to rapid changes in wind velocity and hence violent fluctuations in input power. By adjusting the turbine blades, it is possible to regulate the energy that a wind turbine is extracting from the wind at a given instant. But mechanical regulation of power involves considerable capital cost and usually complicates the system at the expense of reliability. The simplicity and flexibility exhibited by the induction machine in providing electromechanical energy conversion make it the most favored choice for wind powered systems operating in parallel with an existing power grid [2]. Although not as common as the squirrelcage induction machine, the wound-rotor type has several attractive features in providing constant-frequency ac power when driven from a variable-speed source such as a wind turbine.A scheme for scheduling a desired output power from a wind-driven wound-rotor induction
Fig.1 Schematic arrangement of proposed wind energy conversion scheme
Since the stator terminals of the slip ring induction motor are connected to the grid, if the wind velocity is sufficient to drive the rotor above the synchronous speed it generates power. The amount of power generation depends on the wind velocity and system efficiency. This scheme describes the constant power generation irrespective of wind velocity.
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