Innovation: The innovation in the research is in the phase-locked (PLL) loop developed, which uses a controller that can handle the distortions emanating from grid with unbalanced phase voltage magnitudes and bumps in phase angles. Most conventional PLLs use proportional plus integral (PI) controllers that are not very effective in reading the grid's frequency once the magnitudes of phase voltages are unbalanced. Second harmonics will emanate in the quadrature axis and direct axis transformed voltage quantities due to the unbalanced magnitudes. As such PR controller which has capacity to handle such second harmonic pulsations was used for reading the parameters of the grid.

Sector/Industry Application: ENERGY/POWER

Description: Integration of inverter-based energy resources into distribution grids have been a challenge in Nigeria. The reason for such is mainly attributed to weak nature of the distribution grid where the magnitudes of the phase voltages are unbalanced with bumps in the phase angles. Moreover, sags of above 50% do occur often. Therefore, the conventional phase-locked loop (PLL) may not be effective in reading the frequency and initial angle at such distribution grid. Conventional methods of introducing filters in PLLs to distorted grids will further introduce magnitude and phase distortions if not well compensated. In this research therefore, a method that introduces a proportional plus resonant (PR) controller was developed for determining the phase angle and frequency in distribution grids with significant distortions and sags as applicable in Nigeria. The obtained grid parameters are used for effective synchronization of inverter-based energy resources into Nigerian distribution grid. Since most renewable energy resources are inverter-based resources, the developed synchronization technique will increase penetration of renewables in the energy mix in Nigerian distribution grids. As such, dependence on fossil fuel will reduce which will invariably reduce carbon footprints.

Problem: The research aims at providing an effective grid integration technique for inverter-based energy resources which is sustainable and affordable for emerging economies like Nigeria, where the distribution grids suffer from unbalanced magnitudes in phase voltages and experience bumps in phase angles and more than 50% voltage sag.