Asynchronous AC systems interconnection with DC-bus capacitor-less VSC back-to-back topology

The bulky electrolytic capacitors that are typically used at the dc-bus of back-to-back topologies limit the reliability of the system and their elimination can benefit the reliability and operational life of a power electronics converter. This paper presents the interconnection of two ac systems through a dc-bus capacitor-less back-to-back converter topology. The back-to-back topology consists of two voltage source converters; one fundamental frequency switched at the input and one high frequency switched at the output. The lack of energy storage at the dc-bus results in non-constant dc-bus voltage and couples the input and output stages, making the use of input ac filters necessary. However, it is shown through simulations that the topology under investigation is capable of controlling the power flow between two asynchronous ac systems despite the absence of the dc-bus capacitor.