added a research item
Distributed Energy Resources (DER) is emerging as the future of the electrical grid commonly known as Smart Grid or Micro grid. The electrical infrastructure of the power grid is under changes, in a sense that more and more independent power producers will supply power to the network of users that could or could not be connected to the main grid. The Micro grids are connected to the main power system grid through power electronic interface for flexible control so that the Micro grid will be crucial towards a well-functioning network. However, at the same time, the interface domain will be under high stress due to non-linear behaviour of power electronic components. Also, the use of non-linear loads at the consumers end in the form of power electronic converters, UPS, electric arc furnaces, and growing use of adjustable speed motor drives is increasing day by day. The power electronic based interface and loads inject harmonic current and reactive power into the supply grid having a significant impact on voltage and power quality, thus polluting the electric distribution network. With a network then dominated by nonlinear components (power electronics coupling for generators, and non-linear loads connected to distribution system), non-sinusoidal regimes will be a common situation. On the other hand, there is a high degree of demand for premium electric power because of the high number of sensitive loads, which can malfunction if the supply has bad power quality. The paper suggests potential solution to the harmonic current and reactive power problems under unbalanced and distorted regimes using shunt active power filter (SAPF) with control based on Instantaneous active and reactive (p-q) power Theory.