Single-Phase Seven-Level Grid-Connected Inverter
for Photovoltaic System

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I. INTRODUCTION
THE ever-increasing energy consumption, fossil fuels’
soaring costs and exhaustible nature, and worsening
global environment have created a booming interest in renewable
energy generation systems, one of which is photovoltaic.
Such a system generates electricity by converting the Sun’s energy
directly into electricity. Photovoltaic-generated energy can
be delivered to power system networks through grid-connected
inverters.


II. PROPOSED MULTILEVEL INVERTER TOPOLOGY
The proposed single-phase seven-level inverter was developed
from the five-level inverter in [25]–[29]. It comprises a
single-phase conventional H-bridge inverter, two bidirectional
switches, and a capacitor voltage divider formed by C1, C2,
and C3, as shown in Fig. 1. The modified H-bridge topology
is significantly advantageous over other topologies, i.e., less
power switch, power diodes, and less capacitors for inverters
of the same number of levels.


III. PWM MODULATION
A novel PWM modulation technique was introduced to
generate the PWM switching signals. Three reference signals
(Vref1, Vref2, and Vref3) were compared with a carrier signal
(Vcarrier). The reference signals had the same frequency and
amplitude and were in phase with an offset value that was
equivalent to the amplitude of the carrier signal. The reference
signals were each compared with the carrier signal