A Simple, Decoupled Control Concept for a Modular DC-DC Converter in ISOP, IPOP, and Back-to-Back Connection

The modularization of power-electronic converters that are made of so-called power-electronic building blocks (PEBBs) is a most relevant trend in power electronics. Whereas modularization is attractive from the hardware point of view, it is challenging from the control perspective, as the interconnection of multiple PEBBs yields cross-coupled systems. Applying control laws to the interconnected system that were previously applied to the individual PEBB is therefore unlikely to result in well-behaved control properties. In this paper, we propose a concept that overcomes this issue by a simple linear transformation of the plant into another coordinate system, in which the cross-couplings are eliminated. Although this concept is not limited to two converters, we discuss it using the example of two 100 kW dc-dc converters that can be interconnected input-parallel-output-parallel (IPOP), input-series-output-parallel (ISOP), or back-to-back (B2B). Software-in-the-loop (SIL) simulations successfully demonstrate the effectiveness of the approach. The proposed decoupling concept has a significant impact to facilitate the control of modular converters and to lay the path for a further modularization of power electronics.