Terminal Characteristics Measurements and Analysis of the Three-Phase Active Front End Converter Building Block

The safe and reliable operation of modern power system imposes the need to describe and estimate the system stability through impedance-admittance measurement and identification. The integration and operation of medium voltage equipment in existing infrastructure requires impedance-admittance measurement devices which are currently few in numbers and often limited in output voltage level and output bandwidth. The four-quadrant Cascaded H-Bridge topology, featuring a three-phase Active Front End and a single-phase H-Bridge inverter presents itself as a potential solution to this problem. To support the development of the Cascaded H-Bridge topology the Active Front End hardware and control platforms require implementation and testing. The testing aspect of the process additionally includes the measurement of terminal characteristics such as the input admittance and the output impedance. The complexity of the Cascaded H-Bridge converter and its increased number of power electronics building blocks requires the use of industrial control platforms. This paper defines the hardware implementation and control principle of the three-phase Active Front End of a Cascaded H-Bridge converter as well as the system for measuring its terminal characteristics. The results obtained show that the proposed system can be successfully used to measure the input admittance and output impedance of the Active Front End upon which the development of the Cascaded H-Bridge is based.