GRD Journals- Global Research and Development Journal for Engineering | Volume 1 | Issue 4 | March 2016 ISSN: 2455-5703
Simulation of Impedance Source Inverter Driven Single Phase Induction Motor Aachal V. Jaiswal UG Student Department of Electrical Engineering Smt. Rajshree Mulak College of Engineering for Women, Nagpur
Bhesheshwari N. Nimje UG Student Department of Electrical Engineering Smt. Rajshree Mulak College of Engineering for Women, Nagpur
Aarti N. Jaiswal UG Student Department of Electrical Engineering Smt. Rajshree Mulak College of Engineering for Women, Nagpur
Miss. Sneha Barapatre Assistant Professor Department of Electrical Engineering Smt. Rajshree Mulak College of Engineering for Women, Nagpur
Abstract This work presents an alternative power conversion topology that can buck or boost the input voltage or current with linear and non-linear load depending upon duty ratio and modulation index in single stage conversion with the help of Impedance source passive Network (L&C), which is usually known as Z-Source. The objective of this paper is to demonstrate a low-cost, efficient, and reliable inverter for various loads. The simulation and the performance of single-phase induction motor are studied with the control of single phase Z-source inverter. The unique features of Z-source network is it acts as filter which reduces the line harmonics and shoot-through duty cycle, extends the output ac voltage range of inverter, improves power factor and increases reliability. Keywords- Z-source inverter (ZSI), Voltage source inverter (VSI), Current source inverter (CSI), pulse width modulation generator, Single phase induction motor, Modulation Index
I. INTRODUCTION This report focuses on DC to AC power inverters, which aim to efficiently transform a DC power source to a high voltage AC source, similar to power that would be available at an electrical wall outlet. Inverters are used for many applications, as in situations where low voltage DC sources such as batteries, solar panels or fuel cells must be converted so that devices can run off of AC power. Z-source inverter can boost dc input voltage with no requirement of dc-dc boost converter or step up transformer, hence overcoming output voltage limitation of traditional voltage source inverter as well as lower its cost. A comparison among conventional PWM inverter, dc-dc boosted PWM inverter, and Z-source inverter shows that Z-source inverter needs lowest semiconductors and control circuit cost, which are the main costs of a power electronics system. This results in increasing attention on Z-source inverter. The main advantage of this approach is that it adopts a consistent strategy for the entire range of modulation index i.e. it does not require any mode change and also causes exactly same number of switching per cycle. The control strategy of Z-source inverter is simulated in MATLAB environment and implemented using Simple Boost Controller. It is used to sense and control the motor speed. The simple boost pulse width modulated signal are applied to the control operation of ZSI. Z-Source inverter is used for power control of single phase induction motor as compared to the traditional voltage source inverter (VSI) and current source inverter (CSI) inverters. In traditional voltage source inverter (VSI), the DC voltage source connected at the input side across a large capacitor DC link voltage produced across this capacitor feeds the main bridge. In traditional current-source inverter (CSI), the DC current source is formed by a large dc Inductor fed by a voltage source such as a battery or fuel-cell stack or diode rectifier or converter etc. The Z-source inverter comprises of a pair of both inductor and capacitor Connected as X connection. The main advantage of this approach is that it adopts a consistent strategy for the entire range of modulation index i.e. it does not require any mode change and also causes exactly same number of switching per cycle. The well-known Traditional inverter VSI and CSI have also some limitation as below: 1) The two switches can’t be gated on simultaneously which can damage the inverter. 2) Buck and Boost both phenomenon can’t be take from single topology. 3) The cost of circuit increases as high generating semiconductor devices are required. 4) The newly proposed inverter had overcome the problems which were occurred in traditional inverter.
All rights reserved by www.grdjournals.com
14
Simulation of Impedance Source Inverter Driven Single Phase Induction Motor (GRDJE/ Volume 1 / Issue 4 / 003)
II. Z-SOURCE INVERTER The main objective of static power converters is to produce an AC output waveform from a DC power supply. Switches used in the converter can be a combination of switching devices and diodes such as the anti-parallel combination or the series combination etc. It consists of 2 identical inductors and 2 identical capacitors which are composed to form a unique impedance network to avoid short circuit when the devices are conducting, a diode to block reverse current, and a three phase bridge as in traditional inverter. The inductor and capacitor pair as shown in fig.1 forms a second order filter and the values of both the inductor and capacitor are equal.
III. PROBLEM FORMULATION The equivalent circuit of the impedance network is shown in fig.1. L1
IL1
+
+
V0 Vd
+ VC2
+ C2
_
_
Vi
C1 _ VC1
_ _
IL2
L2
Fig.1: Equivalent Circuit of Impedance Network
For simplicity, assuming that the inductors L1 and L2 and capacitorsC1 and C2 have the same inductance and capacitance respectively, the Z-source network become symmetrical. From the symmetry and the equivalent circuits, we have VC1=VC2 (1) VL1=VL2 =VL (2) Now consider that the inverter bridge is in one of the non-shoot-through states for an interval of T1, during the switching cycle. From the equivalent circuit, Fig. 1, one has VL=V0-VC
(3) Vd=V0 Vi=VC-VL=VC-(V0-VC ) Vi=2VC-V0 (4) Where Vo is the DC source voltage and T=T0+T1 (5) The average voltage of the inductor over one switching period should be zero in steady state, thus, We have VL=(T0-T1)VC / T + (T1V0)/T VC/V0=T1/T1-T0 (6) Similarly the average DC link voltage across the inverter bridge can be found as follows. From equation 4: Vi= ( T0*0+T1(2VC-V0) )/T Vi=(2VC.T1/T)-(T1V0/T) 2VC=V0 (7) From equation 6: VC=V0.T1/(T1-T0) The peak DC-link voltage across the inverter bridge is Vi=VC-VL=2VC-V0=0 =T/(T1-T0).V0=B.V0 (8) B=T/(T1-T0)>=1 B is a boost factor The output peak phase voltage from the inverter Vout=M.Vi/2 (9) All rights reserved by www.grdjournals.com
15
Simulation of Impedance Source Inverter Driven Single Phase Induction Motor (GRDJE/ Volume 1 / Issue 4 / 003)
Where M is the modulation index In this source Vout=M.B.V0/2 (10) The output voltage can be stepped up and down by choosing an appropriate buck - boost factor ‘B*’ B*= B.M (it varies from 0 to α) (11) The capacitor voltage can be expressed as VC=VC2=VC1=(1-T0/T).V0/(1-2T0/T) The boost factor B is determined by the modulation index M. 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 produces the same zero voltage to the load terminal, the available shoot- through period is limited by the modulation index.
IV. SIMULATION OF IMPEDANCE SOURCE INVERTER DRIVEN SINGLE PHASE INDUCTION MOTOR The Simulink model of Z-Source Inverter is shown in Fig.2 the switching signals which are applied to all the four switches so that the output of the Z-Source Inverter is according to the requirement. For the simulation purpose we have kept the modulation index 0.6.
Fig. 2: Simulation of impedance source inverter driven single phase induction motor.
Fig. 3: Output voltage of ZSI
All rights reserved by www.grdjournals.com
16
Simulation of Impedance Source Inverter Driven Single Phase Induction Motor (GRDJE/ Volume 1 / Issue 4 / 003)
The output voltage waveform of Z- source inverter is shown in fig.3.The output voltage of Z- source inverter is boosted to 230V which is available at the commercial wall outlets.
Fig. 4: Rotor speed.
The rotor speed of the induction motor increases gradually until it attains its synchronous speed i.e 1500rpm (4 pole motor) and the synchronous speed is attained at 0.06s.
Fig. 5: Electromagnetic torque.
The electromagnetic torque during the starting of the motor produces some transients which are died out once the motor starts running at the synchronous speed. When the motor attains synchronism the electromagnetic torque becomes stable.
V. CONCLUSION The theoretical analysis and design of Z-source inverter is studied. The Z-source inverter employs a unique impedance network to couple the inverter main circuit to the power source and thus providing unique feature. The control methods with the insertion of shoot-through states of Z-source inverter have been studied. The proposed scheme under simple boost control is simulated with the help of MATLAB/SIMULINK and the simulation results are obtained for different values of modulation indices. The simulation results shows that by varying Modulation index (M) or Boost factor (B) we can control the speed of the motor.
ACKNOWLEDGEMENT This completion of project on “Simulation of impedance source inverter driven single phase induction motor� has given us immense pleasure and knowledge. We are over whelmed by a profound of gratitude to our guide Miss. Sneha Barapatre for showing
All rights reserved by www.grdjournals.com
17
Simulation of Impedance Source Inverter Driven Single Phase Induction Motor (GRDJE/ Volume 1 / Issue 4 / 003)
interest in the work and extended their valuable time, guidance expertise critics, moral support and expedition in completion to this dissertation work. Our special thanks to all teaching and non–teaching staff in Electrical Engineering department of Smt. Rajshree Mulak College of Engineering for Women, Nagpur for expending moral support.
REFERENCES [1] [2] [3] [4] [5]
Vrushali Suresh Neve, P.H. Zope, S.R. Suralkar, “Analysis And Simulation Of Z-Source Inverter Fed To Single Phase Induction Motor Drive” in Jan 2013. Sattyendrasing A. Seragi,” Review on Z-Source Inverter”, International Journal of Computer Applications (0975 – 8887). Suresh L., G.R.S. Naga Kumar, M.V. Sudarsan&K.Rajesh,”Simulation of Z-Source Inverter Using Maximum Boost Control PWM Technique”,IJSS,Vol.7 No.2 July-December 2013, pp.49-59. Penchalababu. V, Chandrakala. B, Gopal Krishna, ”A Survey on Modified PWM Techniques for Z-Source Inverter”, International Journal of Engineering and Advanced Technology,5 June 2012 Volume No.1. J.B. Gupta “Theory and performance of electrical machines”, S.K. Kataria and Sons, publisher of engineering and computer books.
All rights reserved by www.grdjournals.com
18