Performance of an OVT inverter reliant on the switching frequency of the filtering inverter
Keywords:Active power filter, space vector, vector orthogonality, three-phase inverter, spectrum, THD factor
The paper presents an inverter based on the orthogonal space vectors theory (OVT inverter) and its performance. The OVT inverter consists of two constituent twolevel 3-phase inverters: the main inverter (MI) and the auxiliary one (AI). The MI is controlled in a simple way to generate the stepped output voltage and the AI works as an active filter limiting the higher harmonics in the OVT output voltage. The filtering process is formed by the use of the orthogonal space vector theory. The output voltage of the OVT inverter takes the shape of a stepped voltage comparable to the voltage generated by multilevel inverters. The AI operates as a very effective active power filter (APF) of the OVT inverter output voltage. The AI power is significantly lower in comparison to the MI power nevertheless its switching frequency affects the OVT performance. The article describes studies in which the impact of changes in the switching frequency filter inverter on the operation of the orthogonal inverter and the output voltage THD. Increasing the filter inverter switching frequency improved performance and reduced the transformer size, which acts as a summing node.