Space vector modulation (SVM)-based on the explicit control of converter switching states-is not the most suitable approach for the modulation of modular power electronics systems due to its apparent lack of modeling flexibility. This paper addresses this issue by presenting a new analytical standpoint for the analysis of SVM in modular power conversion systems, namely power electronics building blocks (PEBB)-based systems. Specifically, the paper presents a mathematically and physically sound modulation technique for PEBB-based converters developed by means of a three-dimensional (3D) space-vector representation. As a result, a processing efficient three-dimensional space-vector modulation algorithm is proposed (3D-SVM). The algorithm itself rests on the well-known carrier-based pulse width modulation technique, therefore it does not require any trigonometric calculations, definitions of optimal sequences, and direct control over the switching states of the three-phase converter. The proposed 3D-SVM technique is verified by simulation and experimental results obtained with a three-phase power converter using 33 kW IGBT-based PEBB modules.