Experimental Validation of an Advanced Load-Shift System Operating as Shunt Active Power Filter

This paper presents a load-shift system with advanced functionalities for the power grid. When compared with the conventional approach, an advanced load-shift system allows the compensation of power quality problems on the power grid side, namely problems related to current harmonics, current imbalances, and low power factor. The advanced load-shift system is composed by a bidirectional ac-dc converter to interface the power grid and by a bidirectional dc-dc converter to interface an energy storage system. Since the main innovation is related with the power grid interface, the focus of this work is on the analysis of the ac-dc converter, which is based on a three-phase four-leg voltage source converter. A theoretical study and the details concerning the control algorithm are presented and discussed along the paper. A laboratory prototype of the advanced load-shift system was developed, and the main details of implementation are described in the paper. Experimental results obtained with the developed prototype prove that the advanced load-shift system contributes for the technology progress in this area, validating a new operation concept concerning the power quality on the power grid side. For all the operation modes, the system operates with high power factor and the currents on the power grid side are balanced with a low total harmonic distortion and in phase with the respective power grid voltages