High-power drive system with advanced power circuitry and improved digital control

A drive system featuring a three-level inverter (which is also known as a neutral-point-clamped inverter) and offering new features is introduced. The circuit concept not only makes it possible to expand the power range without connecting GTOs directly in series or parallel, but it also greatly improves the voltage and current waveforms, enhances control properties, and reduces losses. In addition, this drive system features a self-commutated GTO converter on the line side. It permits free energy exchange in both directions without reactive power and with a low harmonic content of the line current. Digital, signal-processor-based vector control and new PWM methods for both convertors are ideally suited for steady-state operation as well as for conditions demanding high dynamic performance. The results of a system test in the megawatt range underscore the qualities of this drive system