Capacitance and inductance selection of the modular multilevel converter

Abstract

The paper presents a proposal for capacitance and inductance selection procedure of the modular multilevel converter. Two analysis criteria are taken into consideration, the circulating current and voltage ripple across submodule capacitors. Results are obtained numerically by using the converter averaged model based on state equations. In the modular multilevel converter operating under a direct modulation method, based on sinusoidal modulating signals, circulating currents flows through the converter arms. These currents are strongly dependant on the component parameters of the converter, such as: submodule DC-link capacitor capacitance and arm inductor inductance. Both components form a series resonance circuit in each converter arm. Resonance that occurs in the converter arm has to be avoided and therefore it is important to properly select component parameters while taking into account all possible resonances. Such components selection should be carried out at an early stage of the converter design.