Evaluation of 3-Level 4-Leg inverter with harmonic injection for smart grid regulator

As the amount of decentralized generation is continuously increasing the controlling and maintaining of grid stability becomes more complex. This is caused by a change of production capacities from the high voltage area into the distribution network. In order to ensure stability of future smart grids a new 3-Level 4-Leg inverter as a part of a power electronic regulator is introduced. This topology is compared to a 3-Leg 4-Wire (3L4W) operation mode with focus on harmonic injection method. The difference between THD and efficiency is evaluated. As a result the 4L4W operation with harmonic injection can increase efficiency in most operation points. The THD is reduced in all test cases compared to the 3L4W operation. Additionally the overall flexibility is increased by an increased DC-Link voltage operation range.