A Novel, PWM-Inverter Scheme for Grid Connected WEGS for Power Quality Measure

Abstract

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and their power quality are determined on the basis of measurements, and according to the guideline specified in International Electro-technical Commission , IEC 61400-21.The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national / international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. The pulse width modulation (PWM) inverter scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. Due to improvement in technologies, the wind turbine is expected to support the grid and therefore the wind turbine has to control the reactive power over a wide range, and also to deliver the reactive power, in case of voltage drop and can remain connected during short-term voltage drop. Hence to ensure its fulfillments, the power quality measure is specified in IEC 61400- 21.The development in the grid co-ordination rule and the scheme for improvement in power quality has been presented in the paper. Keywords-component; International Electro-technical Commission (IEC), power quality, Wind Generating System (WES) I. INTRODUCTION The power quality is an essential customer-focused measure and is greatly affected by the operation of a distribution and transmission network. The issue of power quality is of great importance to the wind turbine. The individual units can be of large capacity, up to 2 MW, feeding into distribution network with high source impedance, particularly with customers connected in close proximity (1). In case of fixed-speed wind turbine operation, all the fluctuation in the wind speed are transmitted as fluctuations in the mechanical torque , electrical power on the grid and leads to large voltage fluctuations. Thus the network needs to manage, the excessive voltage transients which are to be avoided. Today in the variable-speed wind turbine designs, the uses of power electronic converters are mostly used. During the normal operation, wind turbine produces a continuous variable output power. These power variations are mainly caused by the effect of turbulence, wind shear, and tower-shadow and of control system in the power system. Thus the power quality issues can be viewed with respect to the wind generation, transmission and distribution network can cause the variation in voltage to which the wind turbine is connected, such as voltage sag, swells, etc. However the wind generator introduces disturbances into the distribution network. Today the PWM inverter control technology has been developed and it can technically manage to control the power level associates with the commercial wind turbines. The wind turbine and their quality are assessed according to the national and international guidelines, and so it is important to evaluate the grid connection with wind generating system.