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diagram for the overall control system components. While
section VI include the MATLAB simulation and modeling of
the system. Finally, section VII include the conclusion from
this work.
II. FIVE-LEVEL POWER SUPPLY INVERTER
TOPOLOGY
A multilevel inverter (MLI) is an electronic power supply con-
verter that produces multiple voltage levels. It is employed in
applications with medium and high voltages [27, 28]. Multi-
level inverters are important because of their power quality,
harmonic amplitude reduction, and ability to provide an output
voltage that is as close to a sinewave as possible. Multilevel
resonant inverter topologies have experienced a substantial
expansion in industrial applications in recent years due to the
capability to deliver a voltage waveform of outstanding qual-
ity and reduce the current and voltage ratings of the power
switches [29].
A reduced switches five-levels resonant inverter had been
utilized as a power supply inverter for induction heating sys-
tem. The configuration of the series resonant multilevel in-
verter explained with detailed in [30].
The general layout of the conducted power supply inverter
for the induction heating system (reduced switches 5-level
inverter) consists of two classical parts: the cascade H bridge
MLI and the neutral point clamped MLI. The proposed topol-
ogy of 5-level power supply inverter circuit diagram is shown
in Fig. 1
Fig. 1. Five Level Inverter Power Supply Model
As it clear in Figure (1), the inverter consists of six MOS-
FETs switching devices and two power diodes D1 and D2.
The input DC voltage source is divided by connecting two
identical capacitors C1 and C2 across the source. The split
voltage is delivered to the H-bridge through two MOSFET
switches SW1 and SW2 and two power diodes D1 and D2.
The five operation modes are clarified in Fig. 2
Al-Jrew, Mahmood & Ali
Fig. 2. Switching modes of five level power supply inverter
(a) Vo=+Vdc (b) Vo=+0.5Vdc (c) Vo=0 (d) Vo= -0.5Vdc (e) Vo=
-Vdc
III. PWM FOR THE USED POWER SUPPLY
INVERTER
The multicarrier PWM techniques have been used in this study.
These techniques have two categories phase shift and level
shift. All carrier waves used in the multicarrier modulation
technique known as phase shift modulation have a phase shift
from one carrier to another. The number of carriers is associ-
ated with the number of voltage levels. The same frequency
and peak-to-peak amplitude should be used for all carriers.
The relationship between voltage levels and the number
of carriers in the level shift PWM technique is similar to
that of phase shift. The difference between level shift and
phase shift can be noticed in the disposition of the triangular
carrier. The phase shift and the level shift multicarrier PWM
techniques have a similar relationship between the levels of
voltage and carrier number. The level shift PWM approach
for the employed five level inverter was the subject of this
work.
IV. THE MATHEMATICAL MODEL
DESCRIPTION
The adopted mathematical model described with details in [1]
has been used to build the modified control system for a five
level series resonant inverter in the next section. The phase
angle between the inverter voltage vinv and capacitor voltage
vc has been adjusted to achieve the PLL concept. The phase
difference error between the inverter and capacitor voltages is
described as:
e(k) = x f (k) - 1 (1)
2