Introduction of a hybrid multi-converter system and its control strategy

A hybrid converter system aiming at a higher voltage higher capacity higher efficiency converter system having fewer harmonics in its output is proposed. The system consists of a GTO inverter operating in a square-wave mode and a neutral-point-clamped IGBT inverter operating in a PWM mode. The former produces a base part of the resultant output. The latter produces an additional part of the resultant output as well as eliminates the harmonic components generated by the GTO inverter. A basic control strategy for both inverter and rectifier operation of the system is proposed. Furthermore, an attainable output capacity, device losses, and current THD of the hybrid system, when available devices in the market are used, are estimated. It is concluded that the hybrid system has an advantage over the others in terms of efficiency and harmonic distortion.