Integrating Voltage Source Converter to Weak Grids

Abstract

A new control scheme is presented to permit effective integration of voltage source converters (VSCs) in very weak grids. The proposed controller consist of two main parts. The first part is a linear controller that automatically synchronizes a VSC to a grid by providing damping and synchronizing power components, and provides effective full power injection during islanded and grid connected mode. The controller has three cascaded loops namely angle, frequency and power loops for frequency and angle regulation. The angle and frequency loops generate synchronization and damping power components that can track frequency and angle deviations of the grid and automatically synchronizes itself with the grid. Even though the linear controller provides stable and smooth operation in many cases, it cannot guarantee system stability in weak grids where there is sudden large disturbances. To overcome this problem, a supplementary nonlinear controller is developed to support the linear controller and enhance system performance under large-signal disturbances. The controller performance analyzed through MATLAB/SIMULINK software.