Three-Phase Four-Wire Active Power Conditioners for Weak Grids

A micro-grid is a weak electrical grid, which can be easily subject to disturbances because it includes a variety of intermittent power sources, single-phase, three-phase and nonlinear loads, which can have a dynamic impact on power quality. The unbalance and the harmonic components in current and voltage waveforms are the most important among these. In this paper, the topologies and the control strategy of two Active Power Conditioners (APC) have been investigated in order to improve the operation of a micro-grid. The APC topologies presented in this paper act as an interface between renewable energy sources and the AC bus of a micro-grid. They also use an improved control strategy, which makes possible to inject energy in the micro-grid, compensate the current harmonics and correct the power factor. Moreover, the proposed control strategy allows the line current at the point of common coupling (PCC) to be balanced and sinusoidal even when the load is unbalanced. Consequently, the voltage at the PPC becomes balanced. The validity of the innovative control strategy has been proved in simulation using Matlab/Simulink environment.