 Open Access
 Total Downloads : 3793
 Authors : Anand Kumar T, Kannan.C, Ponmanikandan P
 Paper ID : IJERTV2IS50418
 Volume & Issue : Volume 02, Issue 05 (May 2013)
 Published (First Online): 21052013
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
ZSource Based Multi Level Inverter
ZSource Based Multi Level Inverter
Anand kumar T, Kannan.C, Ponmanikandan P
Assistant Professor Assistant Professor
Dr.Mahalingam College of Engineering & Technology
Vol. 2 Issue 5, May – 2013
This paper presents a novel single Zsource based seven level multilevel inverter. In this topology single Zsource impedance network is used to boost up the output voltage using shoot through state control. A new PWM technique is implemented by using three reference signals and a triangular carrier signal which are used to generate the PWM signals for inverter switches, and the shoot through state for Znetwork is achieved by inserting DC reference signal. The advantage of proposed topology makes reduction in number of switches, and this new configuration is suitable for applications working at lower and medium power levels. The performance of proposed topology is validated using MATLAB/SIMULINK software.
Index Terms Zsource inverter, multilevel inverter, renewable energy resource.
I
I

N RECENT years, due to energy crisis, renewable energy resource, such as wind turbine, photovoltaic (PV) cell, and fuel cell are becoming more and more popular in industrial and residential applications [1]. PhotoVoltaic (PV) sources are used today in many applications as they have the advantages of being maintenance and pollution free. Solarelectricenergy demand has grown consistently by 20%25% per annum over the past 20 years, which is mainly due to the decreasing costs and prices. This decline has been driven by the following factors: 1) an increasing efficiency of solar cells 2) manufacturing technology improvements
and 3) economics of scale.
In the conventional PV array systems, the other converter as a DCDC boost chopper is utilized to increase output DC voltage of the PV. In the suggested topology, Zsource inverter is employed instead of DC DC boost chopper. The Zsource inverter utilizes Z impedance network between the DC source and inverter circuitry to achieve boost operation [2]. The voltage boost is achieved by providing a shootthrough state when both switches in the same phase leg are on which is not possible with traditional inverter topology. The Z Source inverters in the comparing of traditional inverters are lower costs, reliable, lower complexity and higher efficiency [34].
Various topologies for multilevel inverters have been proposed over the years. Common ones are diode clamped [5][8], cascaded Hbridge [910], and modified Hbridge multilevel [11][15].
TABLE I
COMPARITION OF MULTILEVEL INVERTER
Multilevel Inverter type
H bridge Auxiliary switch
Diode Clamped
Capacitor Clamped
Asymmetric Cascade
Main switch
4
36
36
36
Required blocking voltage
Vs/2
Vs/7
Vs/7
Vs/7
Anti parallel diodes
8
36
36
36
Auxiliary switches
2
36
–
–
Required blocking voltage
Vs/3
–
–
–
Auxiliary diodes
4
–
–
–
Switches total
6
36
36
36
Diodes total
12
72
36
36
Capacitors
3
7
17
9
Multilevel inverter, which used to convert dc power obtained from PV modules into ac power. Multilevel inverters are promising; they have nearly sinusoidal outputvoltage waveforms, output current with better [1617].
Fig.1. Proposed single Zsource based multilevel inverter
They offer improved output waveforms, smaller filter size, lower EMI and lower total harmonic distortion (THD). This paper recounts the development of a novel modified Hbridge singlephase multilevel inverter that
has two diode embedded bidirectional switches and a novel pulse width modulated (PWM) technique.
It is assumed that average voltage of inductor Vol. 2 Issue 5, May – 2013
is zero so
is zero so
relation between capacitor and output voltage is found as:

V c = V i n
T n s
T n s – Ts h
( 7 )

Zsource network
Fig. 2(a) shows the suggested basic unit for a proposed Zsource topology. This consists of a DC
Where Tsh is the total shootthrough state period and Tns is the total non shootthrough state period during all period of switching. Substituting (8) in to (7) during non shoot through state Vin is obtained as
voltage source, Z impedance with one switch S7 and
V = V d c
( 8 )
Diode DS. It can operate in two modes: non shoot through and shootthrough state. In the shootthrough
i n T
s h
s h
1 – 2
T
1
state, switch S7 is on and diode DS off output voltage of
B =
1 – 2 T s h
( 9 )
znetwork is zero. The shootthrough pulse is generated by comparing a dc reference line with the triangular carrier wave.

Shootthrough state:
The equivalent circuit of shoottrough state is shown in Fig. 2(b). With the analysis of circuits 2(b) it can be expressed as:
T
Where T is period of switching and B is boost factor and it is clear that B 1.
TABLE II
SWITCHES STATES AND Vo VALUE
State
Output Voltage(V0)
Switches
1
Vin(Non Shootthrough)
S7 OFF, DS ON
2
0(Shootthrough)
S7 ON, DS OFF
V L = V c
( 1 )


Multilevel inverter topology
V i n
= 0 ( 2 )

Non Shootthrough state:
The equivalent circuit in non shootthrough state is shown in Fig. 2(c). Inductors voltage and output of LC network can be calculated as:
The proposed singlephase sevenlevel inverter was developed from the fivelevel inverter in [11][12]. It consist of a singlephase conventional Hbridge inverter, two bidirectional switches, and a capacitor
voltage divider formed by C1, C2, and C3, as shown in
V L = V d c
– V c
( 3 )
(Fig. 1). The modified Hbridge topology is significantly
Vin
= Vc – VL
( 4 )
advantageous over other topologies, i.e., less power
V i n
= 2 V c
– V d c
( 5 )
switch, power diodes, and less capacitors or inverters of the same number of levels. Photovoltaic (PV) arrays were connected to the inverter via a single zsource converter. Proper switching of the inverter can produce seven outputvoltage levels (Vdc, 2Vdc/3, Vdc/3, 0, Vdc,
2Vdc/3, Vdc/3) from the dc supply voltage.
TABLEIII
SWITCHING STATES OF PROPOSED INVERTER
(a)
(b)
(c)
Fig.2 Circuit diagram of (a) single phase proposed basic unit, (b) basic unit in shoot through state, (c) basic unit in non shoot through state.
S1
V0
S2
S3
S4
S5
S6
Vdc
On
Off
Off
On
Off
Off
2Vdc/3
Off
Off
Off
On
On
Off
Vdc/3
Off
Off
Off
On
Off
On
0
Off
Off
On
On
Off
Off
0*
On
On
Off
Off
Off
Off
Vdc/3
Off
On
Off
Off
On
Off
–
2Vdc/3
Off
On
Off
Off
Off
On
Vdc
Off
On
On
Off
Off
Off


PWM switching signals are generated by a novel PWM modulation technique. 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. If Vref1 had exceeded the peak amplitude of Vcarrier, Vref2 was compared with Vcarrier until it had exceeded the peak amplitude of Vcarrier. Then, onward, Vref3 would take charge and would be compared with Vcarrier until it reached zero. Once Vref3 had reached zero, Vref2 would be compared until it reached zero. Then, onward, Vref1 would be compared with Vcarrier. The shootthrough pulse for Zsource network is generated by comparing dc reference line with the carrier signal. Shootthrough time varies depending on the magnitude level of dc reference line as compared with Vcarrier.
Fig.5 (a) PWM signal for S1
Fig.5 (b) PWM signal for S2
Vol. 2 Issue 5, May – 2013
Fig.3 Proposed PWM Technique

The PWM switching patterns were generated by comparing three reference signals (Vref1, Vref2, and Vref3) against a triangular carrier signal (see Fig. 4). One leg of the inverter operated at a high switching rate that was equivalent to the frequency of the carrier signal, while the other leg operated at the rate of the fundamental frequency (i.e., 50 Hz). Switches S5 and S6 also operated at the rate of the carrier signal. The shootthrough pulse is shown in fig.5 (g).
TABLE IV
ZSource Network
Parameters
Value
L1,L2
1mH
C1,C2
2600uH
Simulation result of 7 Level Multilevel Inverter at switching frequency 3 kHz, 230V, 4A, 720W were shown in fig (6 & 7). The sevenlevel inverter produces lowest THD value (0.42%) as compared with five and threelevel inverter with filter shown in fig (9).
Fig .4 Proposed PWM switching pattern
Fig.5 (c) PWM signal for S3
Fig.5 (d) PWM signal for S4
Fig.5 (e) PWM signal for S5
Fig.5 (f) PWM signal for S6
Fig.5 (g) ShootThrough pulse for S7
Fig.6 Inverter output voltage (Vout)
Fig.7 Harmonic analysis for output Voltage (without filter)
Fig.8 Harmonic analysis for output Voltage (with filter)
In this paper the modeling and simulation of novel single Zsource based multilevel inverter have been shown. The PWM switching signals are generated by comparing three reference signals against a triangular carrier signal. The voltage level of the PV panel is improved using Zsource network & multilevel inverter. The proposed multilevel inverter is to reduce both voltage & current THD of the inverter .The proposed topology has minimum number of switches compare than other configuration.

B. K. Bose, Energy, environment, and advances in power electronics, IEEE Trans. Power Electron., vol. 15, no. 4, pp. 688701, Jul. 2000.

Miaosen Shen, Stefan Hodek, Fang Z.Peng, "Control of the ZSource Inverter for FCHEV with the battery Connected to the Motor Neutral Point", Power Electronics Specialists Conference, pp. 14851490,2007 .

Amitava Das, Debasish Lahiri, A.K.Dhakar , Residential Solar Power Systems Using ZSource Inverter", TENCON, IEEE Regional 10 Conference, 2008.

Jin Wang, Fang Z. Peng, Leon M. Tolbert, Donald J. Adams, "Maximum Constant Boost Control of the Z Source Inverter " , Industry Application Conference, 39 th Annual meeting Conference Record, Vol.1,2004.

J. RodrÃguez, J. S. Lai, and F. Z. Peng, Multilevel inverters: A survey of topologies, controls, and applications, IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724738, Aug. 2002.

J. Rodriguez, S. Bernet, B. Wu, J. O. Pontt, and S. Kouro, Multilevel voltagesourceconverter topologies for industrial mediumvoltage drives, IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 29302945,Dec. 2007.

M. M. Renge and H. M. Suryawanshi, Fivelevel diode clamped inverter to eliminate common mode voltage and reduce dv/dt in medium voltage rating induction motor drives, IEEE Trans. Power Electron., vol. 23, no. 4, pp. 15981160, Jul. 2008.

E. Ozdemir, S. Ozdemir, and L. M. Tolbert, Fundamental frequency modulated sixlevel diodeclamped multilevel inverter for threephase standalone photovoltaic system, IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 44074415, Nov. 2009.

E. Villanueva, P. Correa, J. RodrÃguez, andM. Pacas, Control of a single phase cascaded Hbridge multilevel inverter for gridconnected photovoltaic systems, IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 43994406, Nov. 2009.

K. A. Corzine, M. W. Wielebski, F. Z. Peng, and J. Wang, Control of cascaded multilevel inverters, IEEE Trans. Power Electron., vol. 19, no. 3, pp. 732738, May 2004.

G. Ceglia, V. Guzman, C. Sanchez, F. Ibanez,Vol. 2 Issue 5, May – 2013
J. Walter,
J. Walter,
and M. I. Gimanez, A new simplified multilevel inverter topology for DCAC conversion, IEEE Trans. Power Electron., vol. 21, no. 5, pp. 13111319, Sep. 2006.

V. G. Agelidis, D. M. Baker, W. B. Lawrance, and C. V. Nayar , A multilevel PWMinverter topology for photovoltaic applications, in Proc. IEEE ISIE, GuimÃ¤es, Portugal, 1997, pp. 589594.

S. J. Park, F. S. Kang,M.H.Lee, and C. U. Kim, Anewsinglephase fivelevel PWM inverter employing a deadbeat control scheme, IEEE Trans. Power Electron., vol. 18, no. 3, pp. 831843, May 2003.

J. Selvaraj and N. A. Rahim, Multilevel inverter for grid connected PV system employing digital PI controller, IEEE Trans. Ind. Electron.,vol. 56, no. 1, pp. 149158, Jan. 2009.

N. A. Rahim and J. Selvaraj, Multistring fivelevel inverter with novel PWM control scheme for PV application, IEEE Trans. Ind. Electron., vol. 57, no. 6, pp. 21112121, Jun. 2010.

Y. Cheng, C. Qian, M. L. Crow, S. Pekarek, and S. Atcitty, A comparison of diodeclamped and cascaded multilevel converters for a STATCOM with energy storage, IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 15121521, Oct. 2006.

Nasrudin A. Rahim, Senior Member, IEEE, Krismadinata Chaniago, Student Member, IEEE, and Jeyraj Selvaraj ,Single Phase SevenLevel GridConnected Inverterfor Photovoltaic System, IEEE Trans. Ind. Electron., vol. 58, no. 6, pp. 2345 2443, June. 2011