RESEARCH ON HYBRID MODULATION STRATEGIES ON THE H-BRIDGE TOPOLOGY OF MULTILEVEL INVERTER

PROJECT MEMBERS

S.Amanullah 50408105005

R.Balamurugan 50408105013

A.Manivasagan 50408105045

M.Sai natarajan 50408105071

GUIDED BY: Mr.C.R.Balamurugan, Senior Lecturer(EEE)

Main Applications of MLI

Active Power Filters Static Var Compensator Machine Drives for Sine wave Current

Applications HEV Solar PV modules

Advantages

Devices of lower rating can be used thereby enabling the schemes to be used for high voltage applications.

Reduced total harmonic distortion (THD). Better Performance Less dv/dt Stresses Less Stresses in the Bearings of the Motor Lower switching frequencies can be used

and hence reduction in switching losses.

Disadvantages

Switching devices required is proportional to Number of Levels

Control strategy is difficult When the number of levels Increases design is

Complicated The number of isolated DC-links are more

compared to a two-level inverter. Power bus structure and hence the control

schemes become complex as the number of levels increases.

Decrease in Reliability

Objective

To Perform Hybrid Modulation Strategies on the H-Bridge Topology and Hybrid Topology of the Multilevel Inverter

To Analyze the Different Modulation techniques In MATLAB and to Choose the technique which is Efficient for Hardware Implementation

Operation of MLI by Switch

Conventional MLI topologies

DCMLI(MPC or NPC) FCMLI Cascaded H Bridge

DCMLI

The extension of a bridge inverter circuit to multiple voltage levels with diodes used to constrain the maximum voltage across the power switches to safe operating levels was first proposed independently by Baker

The general class of these multilevel inverters are referred to as diode-clamped or multipoint-clamped inverters

Schematic of 5 level dcmli for a phase

Advantages of DCMLI

When the Level of Inverter Increases the Harmonic content Decreases

Efficiency is high because of Inverters are Switching at Fundamental Switching Frequency

Control scheme is simple

Disadvantages

Excessive Clamping diodes required when the level is high

Difficult to control the Real Power flow of the Individual Converter In MLI

FCMLI

The capacitor-clamped multilevel converter is an alternative topology where the clamping diodes are removed and floating capacitors are used instead to clamp the node voltages in the series connected power switches.

The single flying capacitor converter was first proposed by Simon and Bronner whereas Present interest in the circuit as a multilevel converter stems from the work of Meynard and Foch who applied the basic switched capacitor bridge principle to enable voltage clamping in multiple level power converters

Schematic of 5 level FCMLI for a phase

Advantages

Capacitor provides Capabilities during Power Outages

Inverter provides Switching combination Redundancy for balancing Different voltage levels

Real and Reactive power flow can be controlled

Disadvantages

Excess Capacitor and Expensive Control Complicate Switching Frequency and Switching

losses high for Real power Transmission

Cascaded H-Bridge

The 5 Level circuit features two conventional full-bridges serially connected together with their power rails connected to separate isolated dc voltage supplies.

Number of DC sources required can be calculated as S=3(m-1)/2

Main Features

The H-bridge inverter eliminates the excessively large number of Bulky transformers required by

conventional inverters Clamping diodes required by multilevel

diode-clamped inverters Flying capacitors required by multilevel

flying-capacitor inverter.

Schematic of 5 level H-Bridge for a phase

Switching Pattern

1Hv

2Hv

21S

11S

41S

31S

22S42S

32S12S

E

E

A

H1

H2 N

3 Phase 5 Level Topology

Advantages

Less Components compared with FCMLI and DCMLI

Optimized Circuit layout and Extra Clamping

Disadvantages

Need of Separate DC Sources

Topology Comparison

Modulation Strategies

SPWM Modulation

Switching Pulses are produced by comparing the Reference wave and the Carrier wave

Reference wave Sine Wave Carrier Wave Triangular wave or

Hybrid carrier signal

Project work

Simulation

Hardware Module

Matlab Simulation

Design Analysis

Design

Power Circuit Design Switching sequence Design

Power circuit Design Per Phase

Switching Sequence Design Per Phase

Analysis

Factors considered during Analysis Modulation Technique Analysis Operation of Inverter in R , RL and

Induction Motor Loads

Parameters Chosen for Simulation• DC source Voltage 220 V

• Modulation Index 1 to 0.6

• Carrier Frequency 2000 Hz

• Rated Output Frequency 50 Hz

Factors Considered during Analysis THD DF Vrms

Vpeak

Form Factor Crest Factor

Modulation Technique Analysis

HYBRID 1

HYBRID 2

HYBRID 3

Operation of Inverter in R , RL and Induction Motor Loads

To analyze the operation of Inverter under different conditions the Inverter circuit designed in Matlab is analyzed with different loads 1) R Load 2) RL Load 3) Induction Motor load

OUTPUT VOLTAGE and FFT Analysis

HYBRID 1

HYBRID 2

HYBRID 3

HYBRID 4

HYBRID 5

HYBRID 6

HYBRID 7

HYBRID 8

SIMULATION RESULTS FOR RL LOAD

THD

Vpeak and Vrms

Distortion Factor and Crest Factor

SIMULATION RESULTS FOR INDUCTION MOTOR LOAD

Hardware Module

FPGA Module H Bridge (PC01 Module) DC Sources

FPGA Module

FPGA Module is used for Generating switching pulses for triggering the IGBT’s

FPGA Module is programmed by using xilinx IDE or Libero IDE

FPGA Module consists of 100,000-gate Xilinx Spartan-3E XC3S100E FPGA in a 144-Thin Quad Flat Pack package (XC3S100E-TQ144)

FPGA Module Block Diagram

H Bridge Module

H Bridge module consists of MOSFET’s , Power diodes, di/dt protection devices ,dv/dt protection devices.. etc

We are using 6 H bridge module for a 3 ph ,5 level inverter

(S=3(M-1)/2)

S-No of Sources; M-No of Levels.

MOSFET Specification

We are using 8A, 500V, 0.850 Ohm, N-Channel Power MOSFET Features 8A, 500V Rds(ON)= 0.850Ω Single Pulse Avalanche Energy Rated SOA is Power Dissipation Limited Nanosecond Switching Speeds Linear Transfer Characteristics High Input Impedance

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