new multilevel inverter topology
DESCRIPTION
pptTRANSCRIPT
New Multilevel Inverter Topology with reduced number of
Switches
Presentation by,T.Anandkumar.ME (PED) – I Year
120/10/2015
2
Contents
• Introduction• Cascaded H-Bridge Inverters• Multilevel DC Link Inverter • Modulation Strategies Inverter• Carrier based PWM methods• Simulation Results• Conclusions• References
20/10/2015
3
ABSTRACT
• New class of three phase seven level inverter based on a multilevel DC link (MLDCL) and a bridge inverter to reduce the number of switches.
• For voltage levels, the required number of active switches is 2 (m-1) for the existing multilevel inverters, but it is m+3 for the MLDCL inverters.
• The output of proposed MLDCL is synthesized as the staircase wave, whose characteristics are nearer to a desired sinusoidal output.
20/10/2015
4
• Multilevel inverters consist of 3 types named as
i. Diode clamped flying
ii. Capacitor multilevel inverter
iii. Cascaded multilevel inverter• Compared to diode clamped & flying capacitor type
cascaded H-bridge multilevel inverter requires least no. of components to achieve same no of voltage levels
INTRODUCTION
20/10/2015
5
H-BRIDGE INVERTERS
• In single phase inverter, for positive half cycle S1 and s2 will turn on, for negative half cycle S3 and S4 will turn
• Connecting two or more inverter in series than it said to be Multi level inverter.
20/10/2015
6
Cascaded H-Bridge InvertersFor Three Phase
20/10/2015
7
Switching sequence for 1–Ф 7 level cascaded inverter
20/10/2015
8
Output Waveform of H-bridge Inverter
20/10/2015
9
Cascaded H-Bridge Inverters Operation
• An N level Cascaded H bridge inverter consists of series connected (N-1)/2 number of cells in each phase.
• Each cell consists of single phase H bridge inverter with separate dc source.
• There are four active devices in each cell and can produce three levels 0, Vdc/2 and –Vdc/2.
20/10/2015
10
Multilevel DC Link Inverter
• Compared with the existing multi level inverters, the new MLDCL inverters can significantly reduce no. of gate drivers
• And as the no. of voltage levels increases• For a given no.of voltage levels m, the new
inverter requires m+3 active switches
20/10/2015
11
Block diagram for proposed MLDCL Inverter for Single Phase
20/10/2015
12
Multilevel DC Link Inverter
20/10/2015
13
Switching sequence for single phase 7 level MLDCL inverter
20/10/2015
14
Output Waveform of DC Link Inverter
20/10/2015
15
Comparison of the proposed MLDCL inverters and the existing Multilevel Inverters
20/10/2015
16
Modulation Strategies Inverter
• A number of modulation strategies are used in multilevel power conversion applications.
• They can generally be classified into three categories:
• Fundamental Frequency switching strategies
• Space Vector PWM strategies
• Carrier based PWM strategies
20/10/2015
17
Carrier based PWM using Sub-harmonic Methods
• The sub-harmonic pulse-width modulation (SPWM) is commonly used in industrial applications.
• The frequency of reference signals fr determines the inverter output frequency f0.
• Its peak amplitude A controls the modulation index M.
• For a seven level inverter it requires 6 triangular carriers.
20/10/2015
18
Sinusoidal reference with triangular carriers for a 3-phase
20/10/2015
19
Carrier based PWM methods using Modified Space vector PWM
• SPWM scheme for two-level inverters.
• Each reference phase voltage is compared with the triangular carrier and the individual pole voltages are generated.
20/10/2015
20
Modified reference voltages and triangular carriers for a 3-phase
20/10/2015
21
Conclusion
• The cascaded MLDCL inverters are cost less due to the savings from the eliminated gate drivers
• From fewer assembly steps because of the substantially reduced number of components, which also leads to a smaller size and volume.
20/10/2015
22
Thank You
20/10/2015