Synchronous transfer control of medium voltage pump in water treatment: A multilevel cascaded H-bridge inverter-based solution

Abstract

In large-scale pump stations, medium-voltage three-phase induction motors are commonly used to drive pumps. Conventional soft starters enable smooth motor startup and facilitate grid connection to reduce energy losses; however, they lack speed control capabilities, which are essential for regulating flow or pressure. On the other hand, traditional inverters provide effective speed regulation but do not support seamless motor transfer to the grid. This research proposes a novel synchronous-transfer control scheme as an extended function of variable frequency drives. By applying advanced control strategies, the inverter's output voltage is precisely synchronized with the grid in terms of magnitude, frequency, and phase angle. And hence allowing the motor to be smoothly transferred to the grid when needed. The effectiveness of the proposed solution is demonstrated through comprehensive numerical simulations utilizing multilevel cascaded H-bridge inverters as the primary drive system.