Stacked modular isolated dynamic current source converters for medium voltage applications

Techniques for operating at medium voltage using semiconductor devices of lower rating are well known in the industry and academia. These techniques range from device to converter stacking. Dynamic current (Dyna-C) topologies are a new class of converters that is able to provide fast dynamic control with bi-directional power flow and galvanic isolation. These converters can interface with dc, single-phase ac, and/or three-phase ac systems. Scaling to medium voltage can be achieved via modular stacking of lower voltage cells. However, voltage and power balancing between the cells is challenging and complex due to the differences in control dynamics and low energy inertia of each cells. This paper presents a control strategy to provide stable and well regulated voltage across each of the cells in a stacked Dyna-C configuration. Simulation results are provided to verify the control strategy.