Virtual Prototyping for Distributed Control of a Fault-Tolerant Modular Multilevel Inverter for Photovoltaics

In this paper, we present virtual prototyping of the distributed control for a modular multilevel inverter used as a grid-tie interface for photovoltaics. Due to the distributed control and inherent redundancy in the system composed of many panels and inverter modules, the system topology exhibits fault-tolerance capabilities that we study through virtual prototyping. The fault-tolerance is enabled by several distributed algorithms, such as services to identify which, if any, agents controlling inverter modules have failed. A distributed identifier algorithm allows the system to keep track of the number of operating panels to appropriately regulate the dc voltage output of the panels using buck-boost converters and determine appropriate switching times for H-bridges in the grid-tie. We evaluate the distributed inverter, its control strategy, and fault-tolerance through thousands of simulation scenarios in Mathworks Simulink/Stateflow. Our virtual prototyping framework allows for generating multilevel inverters composed of many inverter modules, and we evaluate inverters composed of five to dozens of inverter modules. Our analysis suggests the achievable total harmonic distortion of the modular multilevel inverter may allow for operating solar arrays in spite of failures of the power electronics, control software, and other subcomponents.