single-phase seven-level grid-connected inverter (1)

7/29/2019 Single-Phase Seven-Level Grid-Connected Inverter (1)

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By

P.V.N.Reddy

11011D4903

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With Worsening Global Environment, RenewableEnergy Generation Systems such as Photo voltaic

System gained Superior Interest.

Photovoltaic-generated energy can be delivered topower system networks through grid-connected

inverters.

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A Modified H-bridge 1Ph multilevel inverter that has

two diode embedded bidirectional switches along with

a pulse width modulated (PWM) technique is proposed.

This Topology Shall be applied to a grid-connected

photovoltaic system with considerations for a

maximum-power-point tracker (MPPT) and a current-

control algorithm.

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The proposed 1Ph 7L Inverter was developed from the

5L inverter.

It comprises a 1Ph conventional H-bridge inverter, twobidirectional switches, and a capacitor voltage divider

formed by C1, C2, and C3.

A filtering inductanceLfwas used to filter the currentinjected into the grid.

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Proper switching of the inverter can produce seven

output-voltage levels (Vdc, 2Vdc /3, Vdc/3,

0,Vdc,2Vdc/3,Vdc/3) from the dc supply voltage.

Fig. (a), (d), and (g) shows a conventional inverters

operational states in sequence, while Fig. (b), (c), (e),

and (f) shows additional states in the proposed inverter

synthesizing one- and two-third levels of the dc-busvoltage.

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1) Maximum positive output (Vdc):

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2) Two-third positive output (2Vdc/3):

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3) One-third positive output (Vdc/3):

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4) Zero output:

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5) One-thirdnegative output (Vdc/3):

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6) Two-thirdnegative output (2Vdc/3):

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7) Maximumnegative output (Vdc):

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A Novel PWM modulation Technique Shall be

introduced where 3 reference signals (Vref1, Vref2, and

Vref3) are compared with a carrier signal (Vcarrier) togenerate the PWM switching signals

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The phase angle depends on modulation indexMa

Since the proposed 7L PWM inverter utilizes 3 carrier

signals, the modulation index is defined to be

whereAcis the peak-to-peak value of the carrier signal

andAmis the peak value of the voltage reference signal

Vref

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The 2 main tasks of the control system are

o Maximization of the energy transferred from the PV

arrays to the grid

o Generation of a sinusoidal current with minimum

harmonic distortion, also under the presence of grid

voltage harmonics.

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The behavior of the proposed multilevel inverter Shall

analyzed in detail.

By controlling the modulation index, the desirednumber of levels of the inverters output voltage shall

be achieved.

The less THD in the 7L inverter compared with that inthe 5L & 3L inverters Shall be an attractive solutionfor grid-connected PV inverters.

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single-phase seven-level grid-connected inverter (1)

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