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1. 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) www.jifactor.com 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME 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
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 6, November - December (2013), © IAEME VIII. REFERENCES             T. Chandrashekhar , M. Veerachary “Control of Single-Phase Z-source Inverter for a Grid Connected System”, 2009 Third International Conference on Power Systems, Kharagpur, INDIA December 27-29 P. H. Zope, A. J. Patil, Ajay Somkuwar,” Performance and Simulation Analysis of Single-Phase Grid Connected PV System Based on Z-Source Inverter”, 2010, IEEE Conference PEDES-2010Power India, Digital Object Identifier: 10.1109/PEDES.2010.5712436, Print ISBN: 978-1-42447782-1 P. H. Zope , K. S. Patil, Prashant Sonare, « Development of Single Phase Z-source Inverter Using ARM7 for Speed Control of Induction Motor”, Second International Conference on Control, Communication and Power Engineering 2011-CCPE Nov-2011, Proc. Published by Springer, V.V. Das and N. Thankachan (Eds.): CIIT 2011, CCIS 250, pp. 440–443, 2011, © Springer-Verlag Berlin Heidelberg 2011. M. Shen, F. Z. Peng "Operating modes and characteristics of the Z-source inverter with small inductance" In proc. EEE IAS, 2005. P. C. Loh, D. M. Vilathgamuwa, Y. S. Lai , G. T. Chua, et al, “Pulse-width modulation of Zsource inverters,” IEEE Trans. on Power Electronics, vol. 20, no. 6, pp. 1346-1355, November 2005. X. P. Fang,Z. M. Qian and F. Z. Peng, “Single-phase ZSource PWM AC-AC converters,” IEEE Power Electronics Letters, vol.3, no.4, pp.121-124, December 2005. P.C. Loh, D. M. Vilathgamuwa, Y. S. Lai, G. T. Lai, Y. Li, "Pulse- Width Modulation of ZSource Inverters", In proc.EEE IAS'04, 2004. F. Z. Peng, M. Shen, Z- Qian, "Maximum Boost Control of ZSource Inverter", In Proc. of EEE PESC 2004. F. Z. Peng, "Z- Source Inverter for Motor Drives", in proc, of EEE PESC 2004. F. Z. Peng, “Z-source inverter,” IEEE Trans. on Industry Applications, vol. 39, no. 2, pp. 504510, March/April 2003. P.H. Zope and Ajay Somkuwar, “Design and Simulation of Single Phase Z-Source Inverter for Utility Interface”, International Journal of Electrical Engineering & Technology (IJEET), Volume 1, Issue 1, 2010, pp. 127 - 143, ISSN Print : 0976-6545, ISSN Online: 0976-6553. P.H. Zope, Prashant Sonare, Avnish Bora and Rashmi Kalla, “Simulation and Implementation of Control Strategy for Z-Source Inverter in the Speed Control of Induction Motor”, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 1, 2012, pp. 21 - 30, ISSN Print : 0976-6545, ISSN Online: 0976-6553. B.Sivaprasad, O.Felix, K.Suresh, G.Pradeep Kumar Reddy and E.Mahesh, “A New Control Methods for Offshore Grid Connected Wind Energy Conversion System using Doubly FedInduction Generator and Z-Source Inverter”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 2, 2013, pp. 305 - 323, ISSN Print : 0976-6545, ISSN Online: 0976-6553. 23