40220130406002

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME

TECHNOLOGY (IJEET)

ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 4, Issue 6, November - December (2013), pp. 14-23
© IAEME: www.iaeme.com/ijeet.asp
Journal Impact Factor (2013): 5.5028 (Calculated by GISI)
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IJEET
©IAEME

DESIGN OF SINGLE PHASE Z SOURCE INVERTER FOR MOTOR DRIVE
AND VARIOUS LOAD
Sattyendrasing A.Seragi 1, Prof. Dr. Pankaj.H. Zope 2
1

2

R.C.Patel Institute of Technology Shirpur, Maharashtra, India
SSBT’S College of Engineering And Technology, Bambhori, Jalgaon, Maharashtra, India

ABSTRACT
In this paper single phase induction motor and various load are studied with the help of single
phase Z-source inverter with ARM-7. The LPC 2148 ARM-7 microcontroller senses the speed’s
feedback signal and consequently provides the pulse width modulated signal (PWM) that sets the gate
voltage of the inverter, which provides the required voltage for desired operation. Also these prototype
models summarize efficiency for various load.
Keywords: LPC-2148 ARM-7 microcontroller, pulse width modulation, single phase induction motor,
Z-source inverter.
INTRODUCTION
The single phase induction motors have been widely used in low power level fields. The speed
control of such motors can be achieved by controlling applied voltage on motor by means of power
electronic devices. The traditional voltage source inverter (VSI) and current source inverters are used for
power control of induction motor. The use of microcontrollers, DSP processors has become very
common to overcome problems like lagging power factor at input side, delay in firing angle over the
past decade. ARM7 LPC-2148 microcontroller has been chosen for implementation. It is used to sense
and control the motor speed by providing pulse width modulated signal for the operation of Z-source
inverter. These papers describe experimental analysis of single phase induction motor and various load
using single phase Z-source inverter.
14


Fig. 1: General Structure of the Z-Source Inverter
II. Z-SOURCE INVERTER:
The Z-source Inverter (ZSI) is a newly proposed power conversion concept that is very
promising in the above mentioned areas of power conditioning especially in alternative energy sources
and distributed generation. To overcome the problems of the traditional voltage source and current
source inverters, in this an impedance-source (or z source) is discussed.
In Fig.1, a two-port network that consists of a split-inductor L1 and L2 and capacitors C1 and C2
and connected in X shape is employed to provide an impedance source (Z-source) coupling the inverter
to the dc source, load or another converter. The dc source or load can be either a voltage or a current
source or load. Therefore, the dc source can be a battery, diode rectifier, thyristor converter, fuel cell, an
inductor, a capacitor, or a combination of those. The inductance and capacitance can be provided
through a split inductor or two separate inductors. The Z-source concept can be applied to all dc-to-ac,
ac-to-dc, ac-to-ac, and dc-to-dc power conversion. Z-source inverter (ZSI) which is based on Z-source
network can buck and boost the output AC voltage, which is not possible using traditional voltage
source or current source inverters. Also the ZSI has the unique ability to allow the dc-link of the inverter
to be shorted which is not possible in the traditional voltage source inverters. This improves the
reliability of the circuit. Actually concept of boosting the input voltage is based on the ratio of “shootthrough” time to the whole switching period. Z-source inverter is shown in Fig.2 where an impedance
network is placed between d.c. link and inverter. Z-source inverter (ZSI) provides a greater voltage than
the d.c. link voltage. It reduces the inrush current & harmonics in the current because of two inductors in
z source network. It forms a second order filter & handles the undesirable voltage sags of the d.c.
voltage source.

15


Fig. 2: Single Phase Z-Source Inverter topology
Fig.2 shows a topology of the single phase Z-source inverter where the impedance network is
placed between the power source and the single phase inverter. The presence of 2 inductors & 2
capacitors in Z-source network, allows both switches of same phase leg ON state simultaneously called
as shoot-through state & gives boosting capability to the inverter without damaging the switching
devices. During shoot through state energy is transferred from capacitor to inductor & hence Z-source
inverter (ZSI) gains the voltage boosting capability. Diode is required to prevent the discharge of
overcharged Capacitor through the source. Table 1: Switching states of single phase Z-source inverter.
As shown in table1, a single phase Z-source inverter has five possible switching states: two active states
(vectors) when the dc voltage is connected across the load, two zero states (vectors) when the load
terminals are shorted through
III. SWITCHING STATES OF A SINGLE PHASE Z-SOURCE INVERTER:
Switching States
Active States
Zero States
Shoot Through States

S1

S2

S3

S4

1
0
1
0
1
S1
1

0
1
0
1
1
S2
1

0
1
1
0
S3
1
1

1
0
0
1
S4
1
1

Output Voltage
Finite Voltage
Zero
Zero

Table 1: Switching states of single phase Z- source inverter
Either the lower or the upper two switches and one shoot through state (vector) when lower
switches of any one leg or two legs. These switching states and their combinations introduce a new
PWM method for the Z- Source inverter. Fig.3 shows the operating states of the single phase Z source
inverter in shoot through states that two switches of one phase leg or two phase legs are turned on
simultaneously.
16


Fig. 3: Operating Modes of a Single Phase Z-Source Inverter (a) Shoot through Zero State (b) Non
Shoot through states
In Fig.3.a, a diode placed at the input side is reversing biased and the capacitors charge the
inductors and the voltage across the inductors is:
VL1 = VC1, VL2 =VC2

… (1)

With the assumption of symmetric impedance network (C1= C2=C and L1=L2=L), it can be observed
that
VL1 = VL2 = VL and IL1 = IL2 =IL and the DC-link voltage across the inverter bridge during a shoot
through interval (To) is:
Vi = 0

… (2)

Fig.3.b shows the Z-source inverter in the traditional active and null states and due to a symmetric Znetwork, inductors current (IL1, IL2) and capacitors current (IC1, IC2) are equal. The diode at the input side
is turned on and the voltage across the inductors is
VL = Vdc- VC

… (3)

The DC-link voltage across the inverter bridge during a non shoot
Through interval (Ti) is:
Vi = Vc -VL = 2VC- Vdc

… (4)

Therefore the average DC-link voltage across the inverter bridge over one switching cycle (T) is:
To+To(2Vc – Vdc)

Vi =

T1.Vdc
=

T

… (5)
T1-To

17


By applying T1= T -TO in Eq.5
Vi =

1- To
T (Vdc)
1-2To
T

=

(1-Do) Vdc
1-2Do

…(6)

Where Do is the shoot through duty cycle and Vd, is the input voltage source.
IV. METHODOLOGIES
The block diagram of single phase Z- inverter using ARM7 for speed control of induction
motor is shown in fig.4 It contain following main section Z-source inverter, ARM7 processor, driver
section, triggering circuit, speed control circuit. The Z source inverter is utilized to realize inversion and
boost function. The ARM7 LPC-2148 has been programmed to vary the PWM signal of inverter.

Fig.4: Block diagram of single phase Z-source inverter using ARM7
TRIGRRING CIRCUIT: For turning on the MOSFET, it required gate triggering method. Triggering
circuit provides triggering pulse to gate of the MOSFET. Turning on/off the MOSFET by gate triggering
is simple, reliable and most efficient, so it is most useful method of triggering MOSFET.
DRIVER CIRCUIT: In a controllable power semiconductor switch, its switching speeds and on-state
losses depend on how it is controlled. Therefore, for a proper converter design, it is important to design
the proper drive circuit for the gate of MOSFET. Driver circuit provides current required to gate
terminal of MOSFET.

18


Fig 5: Circuit diagram of Driver circuit
ARM 7: The ARM7 is part of the Advanced RISC Machines (ARM) family of general purpose 32-bit
microprocessors which offer very low power consumption and price for high performance devices. The
architecture is based on Reduced Instruction Set Computer (RISC) principles and the instruction set and
related decode mechanism are much simpler in comparison with micro programmed Complex
Instruction Set Computers.
Key features: 16-bit/32-bit ARM7TDMI-S microcontroller in a tiny LQFP64 package. 8 kB to 40 kB of
on-chip static RAM and 32 kB to 512 kB of on-chip flash memory. 128-bit wide interface/accelerator
enables high-speed 60MHz operation. In-System Programming/In-Application Programming (ISP/IAP)
via on-chip boot loader Software. Single flash sector or full chip erase in 400 ms and programming of
256 bytes in 1 ms.. Embedded ICE RT and Embedded Trace interfaces offer real-time debugging with
the on-chip Real Monitor software and high-speed tracing of instruction execution.USB 2.0 Full-speed
compliant device controller with 2kB of endpoint RAM. In addition, the LPC2146/48 provides 8 kB of
on-chip RAM accessible to USB by DMA. One or two (LPC2141/42 vs. LPC2144/46/48) 10-bit ADCs
provide a total of 6/14analog inputs, with conversion times as low as 2.44 µs per channel.
Single 10-bit DAC provides variable analog output (LPC2142/44/46/48 only). Two 32-bit
timers/external event counters (with four capture and four compare channels each) PWM unit (six
outputs) and watchdog.
IMPEDANCE NETWORK: The lattice networks are used in filter sections and are also used as
attenuators. Lattice networks are sometimes used in preference to ladder structure in some special
applications. This lattice network L1 and L2 are series arms inductances C1 and C2 are diagonal
capacitances. This is a two-port network that consists of split inductors L1 and L2 and capacitors C1 and
C2 connected in X-shape

19


Fig 6: Equivalent circuit of Impedance network.
Assume the inductors (L1&L2) and capacitors (C1 &C2) have the same inductance and capacitance
values respectively. From the above equivalent circuit
Vc1 = Vc2 =Vc
(1)
(2)
VL1=VL2=VL
VL= Vc, Vd = 2V
Vi=0; During the switching cycle
VL=Vo-Vc
(3)
Vd = Vo
Vi= Vc -VL Vc-(Vo-Vc)
Vi= 2Vc -Vo
(4)
Where, Vo is the dc source voltage and T=To +T1
(5)
The average voltage of the inductors over one switching period (T) should be zero in steady state
VL = To .Vc +T1 (Vo-Vc)/T = 0
VL = (To .Vc +Vo.T1- Vc.T1)/T=0
VL= (To-Tc) Vc/T + (T1.Vo)/T
Vc/Vo=T1/T1-T0

(6)

Similarly the average dc link voltage across the inverter bridge can be found as follows. From
equation 4:
Vi=Vi = (To .0+T1.(2Vc-Vo))/T
Vi = (2Vc. T1/T)-(T1Vo/T)
2Vc=Vo From equation 6
T1.Vo/(T1-To)=2Vc.T1/(T1-To)
Vc=Vo.T1/(T1-To)

(7)

20


The peak dc-link voltage across the inverter bridge is
Vi = Vc-V l = 2Vc-Vo =T/(T1-To).Vo=B.Vo

(8)

Where B=T/(T1-To)i.e. ≥1 B is a boost factor The output peak phase voltage from the inverter
Vac=M.vi/2

(9)

Where M is the modulation index in this source
Vac=M.B.Vo/2

(10)

In the traditional sources Vac = M.Vo/2 For Z-Source Vac = M.B.Vo/2 The output voltage can
be stepped up and down by choosing an appropriate buck - boost factor BB
(11)

BB= B.M (it varies from 0 to α)

The capacitor voltage can be expressed as Vc1=Vc2=Vc= (1-To/T).Vo/ (1-2To/T) The boost
factor BB is determined by the modulation index m and the boost factor B. The boost factor B can be
controlled by duty cycle of the shoot through zero state over the non-shoot through states of the PWM
inverter. The shoot through zero state does not affect PWM control of the inverter. Because it
equivalently produce the same zero voltage to the load terminal. The available shoot through period is
limited by the zero state periods that is determined by the modulation index.
V. OPERATION
In this prototype system of inverter main function block is ARM7 LPC2148 which is
programmed to generate the PWM this generated PWM signal is used to control the MOSFET Bridge.
The PWM output is of very low voltage value of 3v only. The power for the ARM7 is generated from
the battery of 12v,7AH and next a power supply of 5 v is used where regulator IC7805 is used to supply
the voltage in the power supply diode which is conducting in forward direction and filter capacitors used
such as electrolytic capacitor and ceramic capacitors reduce ripples of low and high freq respectively.
The output from ARM7 is PWM is in voltage form and some current level, the triggering circuit build
around the IC3524 which also wave shapes the signal appropriate enough for the MOSFET driving
level. The output is available on pin 11,13 of the IC. The further gate voltage level is amplified using the
driver stage. In this circuit the transistor two stage ckt is used this complementary stage switch on and
off alternately. Switching the MOSFET on and off of the bridge alternately in the bridge. The MOSFET
Bridge is supplied through the z source circuit from the dc voltage battery. The output of the MOSFET
bridge is coupled to the step up transformer and the output of the transformer is applied to the filter
circuit wired around the capacitor and inductor of the secondary of the transformer forms series
resonant circuit. The output is then used to drive the Induction motor and various load. As shown in
fig. 7

21


Fig 7: Experimental set-up for motor drive and various load
VI. RESULT

Sr.
No.
1
2
3

Load
Watt
No Load
5
20

Vdc V

Idc A

Pdc=Vdc*Idc

Vac

Iac

Pac

12.5
12.5
12.5

7.4
7.4
7

92.5
92.5
87.5

262
244
235

0
0.2
0.3

0
48.8
70.5

Eff. = Pac/Pdc in
(%)
0
52.75
80.57

4
5
6

27
32
40

12.5
12.5
12.5

7.8
8.2
7.8

97.5
102.5
97.5

115
90
117

0.6
0.8
0.5

69
72
58.5

70.76
70.24
60

Table 2: Experimental results for various load

VII. CONCLUSION
In this paper the single phase induction motor and various load are successfully driven and
motors speed can be adjusted using proposed drive system using ARM-7. Due to the shoot through
switching states in the Z-source inverter, the simple boost control modulation is suitable for a single
phase Z-source inverter. Also the experimental result shows efficiency for various load, and this
prototype model provides maximum efficiency of 80.57% for 20Watt load.
22


VIII. REFERENCES
[1]

[2]

[3]

[4]
[5]

[6]
[7]
[8]
[10]
[11]

[12]

[13]

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