Five level diode clapmed inverter 16 September 2018

Inverter: The Inverter is an electrical device which converts direct current (DC) to alternate current (AC). Multilevel Inverter: The multi-level inverter is to synthesize a near sinusoidal voltage from several levels of dc voltages The Multi level inverter is like an inverter and it is used for industrial applications as alternative in high power and medium voltage situations. It has been introduced in 1975 as alternative in high power and medium voltage situations by NABLE ELAL

The need of multilevel converter is to give a high output power from medium voltage source. Multilevel inverters have become more popular over the years in electric high power applications with less disturbances in voltage and the possibility to function at lower switching frequencies than ordinary two level inverter.

ADVANTAGES: Reduced harmonic distortion: Multilevel converters not only can generate the output voltages with very low distortion, but also can reduce the dv/dt stresses; therefore electromagnetic compatibility (EMC) problems can be reduced. Common-mode (CM) voltage: Multilevel converters produce smaller CM voltage; therefore, the stress in the bearings of a motor connected to a multilevel motor drive can be reduced.

3. Input current: Multilevel converters can draw input current with low distortion. 4. Switching frequency: Multilevel converters can operate at both fundamental switching frequency and high switching frequency PWM. It should be noted that lower switching frequency usually means lower switching loss and higher efficiency

TWO LEVEL INVERTER The two level inverter is the simplest type of three-phase voltage source inverter and can be thought of as a six pulse bridge in which the thyristors have been replaced by IGBTs with inverse-parallel diodes, and the DC smoothing reactors have been replaced by DC smoothing capacitors

TYPES OF MODULAR MULTILEVEL INVERTERS Multilevel inverters are three types. Diode clamped or Neutral-Point Clamped type Flying capacitors type Cascaded or H-bridge type

DIODE CLAMPED MULTILEVEL INVERTER This inverter uses diodes and provides the multiple voltage levels through the different phases to the capacitor banks which are in series. A diode transfers a limited amount of voltage, thereby reducing the stress on other electrical devices. The maximum output voltage is half of the input DC voltage.

FLYING CAPACITORS MULTILEVEL INVERTER The main concept of this inverter is to use capacitors. It is of series connection of capacitor clamped switching cells. In this inverter switching states are like in the diode clamped inverter. Clamping diodes are not required in this type of multilevel inverters.

CASCADED H- BRIDGE MULTILEVEL INVERTER Multilevel cascade inverters are used to eliminate the bulky transformer required in case of conventional multi phase inverters, clamping diodes required in case of diode clamped inverters and flying capacitors required in case of flying capacitor inverters. But these require large number of isolated voltages to supply the each cell. The combination of capacitors and switches pair is called an H-bridge and gives the separate input DC voltage for each H-bridge. CASCADED H- BRIDGE MULTILEVEL INVERTER

APPLICATIONS OF MULTILEVEL INVERTER High-voltage and Medium-voltage motor drives High voltage dc transmission Flexible AC transmission system (FACTS) Traction Active filtering Utility interface for renewable energy systems

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