voltage inverter with 2n+1 voltage levels

摘要

#CMT# #/CMT# The system has a control unit (121) for controlling switching of first and second switching cells (112, 120) according to a corresponding control law, where the control law is implemented such that current flows through a capacitor (116) at a given value of alternating output voltage in a direction during a first phase and in another direction during a second phase. The first cells are connected between each other by an intermediate point (114). The first cells are connected between an output terminal (108) and a mid-point (118). #CMT#USE : #/CMT# System i.e. five-level voltage inverter, for use in a three-phase electric motor for converting input direct voltage into periodic output alternating voltage, for supplying the converted output alternating voltage to the electric motor. #CMT#ADVANTAGE : #/CMT# The control law is implemented such that current flows through the capacitor at a given value of the alternating output voltage in a direction during the first phase and in the other direction during the second phase, so that the average value of the current passing through the capacitor is null at balancing period, thus reducing risks of unbalance of the voltage in the mid-point regardless of the alternating voltage and current supplied by the converting system, without requiring additional voltage balancing units at terminals of the capacitor. The design of the converting system reduces harmonic distortion of the output alternating voltage, and decreases insulation constraints at the level of the electric motor to be supplied by the converting system. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a circuit diagram of a converting system. 108 : Output terminal 112, 120 : Switching cells 114 : Intermediate point 116 : Capacitor 118 : Mid-point 121 : Control unit.