PWM controlled neutral point clamped multilevel converter

Patent metadata

Field	Value
Publication number	US-9755546-B2
Application number	US-201214646465-A
Country	US
Kind code	B2
Filing date	Nov 21, 2012
Priority date	Nov 21, 2012
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A neutral point clamped, multilevel level converter includes a DC voltage link; a first capacitor coupling one side of the DC link to a neutral point; a second capacitor coupling another side of the DC link to the neutral point; a plurality of phase legs, each phase leg including switches, each phase leg coupled to an AC node; a current sensor associated with each AC node; and a controller generating a PWM signal to control the switches, the controller generating a current zero sequence component in response to current sensed at each of the current sensors, the controller adjusting a modulation index signal in response to the current zero sequence component to produce the PWM signal.

First claim

The invention claimed is:

1. A neutral point clamped, multilevel level converter, comprising:
a DC voltage link;
a first capacitor coupling one side of the DC link to a neutral point;
a second capacitor coupling another side of the DC link to the neutral point;
a plurality of phase legs, each phase leg including switches, each phase leg coupled to an AC node;
a current sensor associated with each AC node; and
a controller generating a PWM signal to control the switches, the controller generating a current zero sequence component in response to current sensed at each of the current sensors, the controller adjusting a modulation index signal in response to the current zero sequence component to produce the PWM signal;
wherein generating the current zero sequence component includes inverting current sensed at each of the current sensors to produce inverted current for each AC node.

2. The neutral point clamped, multilevel level converter of claim 1 , wherein:
generating the current zero sequence component includes selecting a maximum and minimum of the inverted current for each AC node.

3. The neutral point clamped, multilevel level converter of claim 2 , wherein:
generating the current zero sequence component includes obtaining a difference between the maximum and minimum of the inverted current for each AC node.

4. The neutral point clamped, multilevel level converter of claim 3 , wherein:
generating the current zero sequence component includes scaling the difference between the maximum and minimum of the inverted current for each AC node.

5. A neutral point clamped, multilevel level converter, comprising:
a DC voltage link;
a first capacitor coupling one side of the DC link to a neutral point;
a second capacitor coupling another side of the DC link to the neutral point;
a plurality of phase legs, each phase leg including switches, each phase leg coupled to an AC node;
a current sensor associated with each AC node; and
a controller generating a PWM signal to control the switches, the controller generating a current zero sequence component in response to current sensed at each of the current sensors, the controller adjusting a modulation index signal in response to the current zero sequence component to produce the PWM signal;
wherein the controller combines the current zero sequence component with a voltage zero sequence component to provide a combined zero sequence component, the controller adjusting the modulation index signal in response to the combined zero sequence component to produce the PWM signal.

6. The neutral point clamped, multilevel level converter of claim 5 , wherein:
the controller changes a sign of the combined zero sequence component in response to an operating mode of the converter.

7. A neutral point clamped, multilevel level converter, comprising:
a DC voltage link;
a first capacitor coupling one side of the DC link to a neutral point;
a second capacitor coupling another side of the DC link to the neutral point;
a plurality of phase legs, each phase leg including switches, each phase leg coupled to an AC node;
a current sensor associated with each AC node; and
a controller generating a PWM signal to control the switches, the controller generating a current zero sequence component in response to current sensed at each of the current sensors, the controller adjusting a modulation index signal in response to the current zero sequence component to produce the PWM signal;
wherein the controller changes a sign of the current zero sequence component in response to an operating mode of the converter.

Assignees

• Otis Elevator Co
• Otis Elecator Company

Inventors

• Arnedo Luis
• Kovacic Marinko
• Wang Yang
• Krishnamurthy Shashank

Classifications

• H02M7/487 Primary

  Neutral point clamped inverters · CPC title

• H02M7/537 Primary

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title