The Analysis and Control of Zero-Sequence Components in a Transformerless Back-To-Back (BTB) System Using Modular Multilevel Cascade Converters for Power Distribution Systems
This paper provides an intensive discussion on analysis and simulation of a back-to-back (BTB) system based on double-star chopper cells (MMCCs-DSCCs). It is installed between two 6.6-kV power distribution feeders. It is also referred to as the so-called “loop power flow controller.” A three-phase 200-V, 10-kW, 50-Hz BTB transformerless system is simulated to verify its operating principles, modelling, and performance of zero-sequence current control using combination between a simple PI controller and a common-mode choke. The simulation results show that the zero-sequence current circulating between the two feeders can be suppressed as small as 10 mA (0.03%) in rms, which is within acceptable value and small enough to negligible.