This paper addresses a transformerless medium-voltage adjustable-speed motor drive consisting of two five-level diode-clamped PWM converters connected back-to-back. It is followed by designing, constructing, and testing a 200-V downscaled model to verify the validity and effectiveness of the medium-voltage motor drive. This downscaled model has four split DC capacitors equipped with a voltage-balancing circuit using two bidirectional buck-boost choppers. The two five-level converters are based on sinusoidal pulsewidth modulation with a carrier frequency of 3 kHz. The motor tested in this paper is a three-phase four-pole induction motor rated at 200 V, 5.5 kW, and 60 Hz. Experimental waveforms show that the four split dc-capacitor voltages are well balanced in any operating conditions and that the total harmonic distortion values of the input line current and the output motor current are 3.9% and 3.5%, respectively.

Five-Level Diode-Clamped PWM Converters Connected Back-to-Back for Motor Drives

The object of this paper is to proposes a method for induction motors with adjustable-speed drive consisting of two five level diode-clamped converter connected back-to-back with transformer less configuration in medium voltage application. This paper delivers a remedy for the voltage stabilizing problem which occurs during the implementation of split dc capacitors. This problem has been reduced by using suitable switching technique in the proposed configuration. Multi carrier pulse width modulation technique has been dropped back behind the advanced Space vector PWM technique. The voltage and current harmonic values of the induction motor output were reduced by using the space vector PWM switching technique.

Performance characteristics of five level diode clamped multilevel inverter for induction motor drives

This paper outlines the approach taken in the development of a new medium voltage variable frequency drive. It examines the existing medium voltage drive formats, their advantages and disadvantages. It also outlines new standards implemented overseas to limit the effect of harmonics on the electricity supply system, and how these limits impacted on the design of the new generation VSDs. It further examines the effect that advances in microprocessors and electronic power devices has had in the design of the new drive topology.

M.S. Baker

Papers

New approach to medium voltage variable speed drives