A new medium voltage drive system based on ANPC-5L technology

A new medium voltage drive has been developed based on the active neutral-point clamped 5-level (ANPC-5L) topology. In the last decade three-level neutral-point clamped (NPC) converters have become the industry standard in MV Drives. This configuration has proved very successful for applications where high power and high performance requirements necessitated the use of inverter grade motors and the associated costs. On the other hand, there is an increasing demand by industry for drives which can be used to increase the efficiency of standard, low cost direct online (DOL) machines. The problems of high harmonic content, high dv/dt and common mode voltage have been significantly improved in this new drive solution. The structure of the converter will be described with explanation of the multiple levels of redundancy available. The necessary conditions for regulating the neutral-point and phase (or floating) capacitor voltages will be illustrated. The highly dynamic direct torque control (DTC) method has been chosen the inverter control. The synchronous frame current regulator used for rectifier control allows for full four-quadrant operation on the network side. The mechanical design philosophy will be displayed along with the salient technical features: rectifier and inverter operating waveforms, protection concept, and ride through behavior. Finally experience in pilot installations will be reviewed.