Performance Evaluation of New Cascaded VSC Arranged Megawatt-Scale Nine-Level Converter in Intermittent Solar and Grid-Voltage Fluctuations

This work presents a new medium voltage nine-level solar converter, which uniquely connects the three-leg converters. The output terminal connects the voltage source converter (VSC) to the upper switch of the next VSC. Moreover, photovoltaic (PV) arrays are connected in series with a negative terminal connected to the positive dc rail of next VSC. This approach utilizes a common PV array for a three-phase system, which reduces the installation and maintenance cost on the PV side. To deliver same amount of megawatt power in a nine-level line voltage, a cascaded H-bridge requires six PV arrays (two in each phase). However, this converter utilizes only four PV arrays with nine levels of line voltage at the same power rating. The maximum power point tracking and proportional integral voltage regulators are reduced in this configuration, making the controller simple to tune in closed loop. The intermittent solar and grid voltage fluctuations are considered for testing the system's performance. The economic aspects of the presented topology are discussed with a cost function. Moreover, test results validate the operation of a new high-power solar multilevel converter with excellent dynamic performance.