Closed Loop Control of a Cascaded Multi-Level Converter to Minimize Harmonic Distortion

As the United States Navy moves toward the all-electric ship, the need for a robust, high fidelity inverter for propulsion motors becomes mandatory. Military vessels require high power converters capable of producing nearly sinusoidal outputs to prevent torque pulsations and electrical noise that can compromise the mission location. This thesis presents a hybrid pulse-width-modulated controller for a 3x3 Cascaded Multi-Level Converter (CMLC). Ancil-lary results include a simple technique for extracting the reference sine wave from an inde-pendent bulk converter and implementing a synchronization technique that coordinates a space vector modulation controller with the switching pattern of a bulk inverter. The algorithms were tested on CMLC hardware that resides in the Naval Postgraduate School Power Systems Labo-ratory, and the results were compared with a sine-triangle pulse width modulation algorithm. The controller and converter were used to power a quarter-horsepower three-phase induction motor.