PERFORMANCE ANALYSIS OF FRACTIONAL ORDER SLIDING MODE CONTROL FOR VOLTAGE REGULATION IN HYBRID VSHG & PV SYSTEM IN ISLANDED MICRO-GRID

Abstract

There are many isolated communities which couldn’t be supplied by main grid due to uninvited reasons but have the potential to facilitate themselves using isolated grid. The environmental issues have the same importance as electricity, so renewable energies are one of the most important method to reduce environmental effects and reducing the fossil fuel consumption. Renewable Energies (RE’s) like solar and/or wind can be used as power sources in such communities if suitable conditions are met but due to intermittence property of these renewable energies, some stable power source will also be needed. That’s why, depending only in renewable energy source is impractical solution. Communities are transitioning to renewables from fossil fuels and Hydro Power Plants (HPP) have an important role in the amalgamation of huge quantities of mutable sources in the power system, such as solar and/or wind. So, the hybrid system is one of the practical solutions which comprises of RE’s with HPP as stable power provider. In addition, some power storage is compulsory to overcome the fluctuations of these renewables during load change periods. Hydro power is one of the most suitable integration with these renewables. Variable Speed Hydro Generator (VSHG) is used in this study with Superconducting Magnetic Energy Storage (SMES). This amalgamation is used to deliver stable power supply to the grid in islanding mode. For this purpose, many linear and non-linear controllers are used in the context of power control system. In this proposed research work, a non-linear controller, Fractional Order Sliding Mode Control (FOSMC) is used which is most reliable and robust control method. This control theory is basically derived from switched control concept which is known as variable structure control. In this control firstly non integer surfaces (called sliding surfaces) are chosen according to system dynamics than based on these dynamics control laws formulated. Non integer dynamics gives the chattering free control which allows the system output to be stable under bounded external disturbances. FOSMC gives us robust control of Voltage Source Inverter (VSI) by maintaining the voltages and frequency according to Institute of Electrical & Electronics Engineers (IEEE) standards and improves steady state and transient response of the system. Simulations of this system are carried out using Simulink-MATLAB (version R2018b) software and results are obtained by considering three phase active linear and nonlinear loads with different VSHG models.