Modelling, simulation and analysis of variable speed constant frequency wind energy conversion scheme using self excited induction generator

Abstract

Canada SELF EYCIIED POUER -INDUCIION e COHUERSIOH PRlnE IIOUER CEHLRIIOR L I N KAIlSTRACT: This paper presents the dynamic modelling of variable speed constant frequency [VSCF] wind energy conversion scheme [WECS], employing self excited induction generator, connected to the utility grid through an AC-DC-AC converter scheme with Uncontrolled rectilier and PWM inverter. The proposed scheme for regulating the flow of power through the link ensures reduced reactive power burden on the self excitation capacitor banks, reduced harmonic injection into the host power utility grid and efficient utili7ation of available wind energy. Modelling of the subsystems and simulation of the unified system with pulse width modulated [PWM] inverter control, to reduce harmonics iiijected into the utility grid are also presented. nt U T I L I T Y GRID I INTRODUCTION:Variable speed constant frequency [VSCF] wind energy conversion schemes generally use synchonous or wound rotor induction niachincs along with an asynchronous AC-DC-AC link, to obtain constant frequency power generation, even in presence of prime mover speed fluctuations. Further, on account of its simplicity, ease of implementation, and low cost, the self excited induction generator finds wide application in power generation using non-conventional energy sources such as wind [I-41. Due to the stochastic nature of wind, the speed fluctuation, in cases where wind turbine is used as a prime mover, is substantial. This has to be countered by constant speed gear train mechanism, mechanical pitch control and excitation control of synchronous generator, to ensure constant frequencyholtage power generation [SI. The constant speed gear train mechanism is complex and requires a lot of maintenance. On the other hand, an induction machine once synchronised with the utility grid will generate fixed frequency power, with speed variation of wind turbine, being countered by change in the machine slip (which in case of operation as a generator is negative). However, the terminal voltage will he fluctuating with the speed and requires a direct power conversion link (asynchronous link) as shown in Fig:l(a), to alleviate problems of voltage fluctuations, flickering and generation of harmonicshb-harmonics, associated with the pulsating torque, characteristic of wind turbine (prime mover) driving the induction generator which is directly interfaced to the utility grid [6]. Generally, the asynchronous DC link utilizes a phase controlled rectifier and line commutated inverter [5,7], as shown in Fig:l(b) which imposes certain restriction on the operating range based on i) KVAR requirement of Self excited Induction machine.0094-2898/91/0000/0033$01 .OO 0 1991 IEEE ii) Reactive power requirements of the controlled rectifier unit. iii) Reactive power to be supplied by host power system to the inverter stage. iv) Constraints imposed to ensure reliable commutation of inverter devices. v) Harmonics injected into the host power system grid. (b) Figure:l(a) DC power conversion link for variable speed pr...

Aerodynamic model of wind turbine considering yaw error

“…It can modify the blade's pitch through variable propeller pitch mounting inside the hub, thus change the size of wind energy absorbed [1][2][3].Therefore, the research on the turbine model is not only related to the load of wind turbine and structure design [4],but also has significant sense of complete machine design [5], power quality and wind power output prediction [6].…”

A rule-based fuzzy logic controller for a PWM inverter in a stand alone wind energy conversion scheme

“…IND energy conversionhnterface scheme (WECS) using a wind turbine driven self-excited induction generator and line commutatedPWM inverter have been modeled, analyzed, and implemented [ 11- [4]. In remote locations where the utility grid does not exist, stand alone wind energy conversion scheme (SAWESCS) can be used to feed the local electrical load.…”

“…Hence, the variable magnitude, variable frequency voltage at the self-excited induction generator terminal is first rectified and the dc power is then transferred to the local load through a PWM inverter. It has been shown that the power available from a WES can be approximated as a cubic function of the wind veloci1,y [4], [ 5 ] . To ensure complete utilization of available wind energy under varying wind velocities, most of the schemes reported use a PID controller to track and extract maximum energy.…”