MULTI LEVEL INVERTER

• US 20090237962A1
• Filed: 03/19/2009
• Published: 09/24/2009
• Est. Priority Date: 03/20/2008
• Status: Active Grant

• Current Assignee: LS Industrial Systems Company Limited
• Original Assignee: LS Industrial Systems Company Limited
• Inventors: Yun, Hong Min
• Granted Patent: US 8,159,840 B2
• Time in Patent Office: Days
• US Class Current: 363/37
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters

Abstract

The present invention relates to a multilevel inverter comprising: a converter unit converting an inputted AC power source to a direct current (DC) power source; a film capacitor rectifying the DC power source converted by the converter unit; an inverter unit converting the rectified DC power source to a three-phase current in response to a pulse width modulation (PWM) control signal and outputting the current; a current detector detecting a current outputted from the inverter unit; a power cell main controller generating a voltage instruction and a voltage instruction using the detected current; and a PWM controller generating the pulse width modulation (PWM) control signal using the voltage instruction and frequency instruction.

Claims

1. A multilevel inverter, comprising:

a converter unit converting an inputted AC power source to a direct current (DC) power source;

a film capacitor rectifying the DC power source converted by the converter unit;

an inverter unit converting the rectified DC power source to a three-phase current in response to a pulse width modulation (PWM) control signal and outputting the current;

a current detector detecting a current outputted from the inverter unit;

a power cell main controller generating a voltage instruction and a voltage instruction using the detected current; and

a PWM controller generating the pulse width modulation (PWM) control signal using the voltage instruction and frequency instruction.

2. The multilevel inverter of claim 1, further comprising an input transformer, wherein the input transformer has several tabs at a secondary wiring side by way of zigzag connection or an extended delta connection, and an output power source of the input transformer is inputted into the input AC power source.

3. The multilevel inverter of claim 1, wherein the inverter unit includes one of the elements out of metal oxide field effect transistors (MOSFET), insulated gate bipolar transistors (IGBT) and gate turn-off (GTO) thyristors.

4. The multilevel inverter of claim 2, wherein the inverter unit includes one of the elements out of metal oxide field effect transistors (MOSFET), insulated gate bipolar transistors (IGBT) and gate turn-off (GTO) thyristors.

5. The multilevel inverter of claim 1, further comprising a phase shift transformer, where an output power of the phase shift transformer is inputted into the input AC power source.

6. The multilevel inverter of claim 5, wherein the phase shift transformer has a predetermined inductance value, where relation between the inductance value and the capacitance value of the film capacitor is 1:

3.

7. The multilevel inverter of claim 1, wherein a harmonic cut-off frequency by switching at the inverter unit is within a scope of ⅕

to ½

of the switching frequency employed by the inverter unit.

8. The multilevel inverter of claim 7, wherein the harmonic cut-off frequency by the switching at the inverter unit is 200 Hz to 500 Hz when the switching frequency is 1 kHz.