IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 10, 2015 | ISSN (online): 2321-0613
Close Loop Control of Induction Motor Using Z-Source Inverter Vijay joshi1 Prof. Jitendra Singh Shakya2 1,2 Samrat Ashok Technological Institue, Vidisha (M.P) Abstract— In this paper a new closed loop control of induction motor fed by a Z – source inverter based on the vector control or field oriented control strategy is presented. Induction motor is supplied by Z – source inverter, in the Z – source inverter the term Z denotes impedance which means a combination of L & C element which are cross connected. The Z-source inverter consists of a unique impedance network (or circuit) to couple the inverter main circuit to the power supply, hence providing great features that cannot be observed in the conventional voltage-source inverter and current-source inverters in which capacitor and inductor are used, respectively.In the field oriented control method or vector control method speed of the induction motor, torque & 3 phase stator current is given to the field oriented controller and gate pulses for the inverter is generated to obtain the desired operation of the induction motor. Key words: FOC method, Z-source inverter, MATLAB simulation I. INTRODUCTION The main aim of this paper is the close loop control of Induction Motor by field oriented control (FOC) method using Z-source inverter. In this paper indirect field-oriented control (IFOC) method has been used to carry out the control the induction motor because of its simplicity. The close loop control of induction motor is carried out with the help of MATLAB SIMULATION[1]. II. Z-SOURCE INVERTER Z-Source Inverters are used to overcome the limitations and barriers of traditional Voltage Source Inverters and Current Source Inverters[2]. Fig. 1 shows the Z source inverter circuit diagram[5]. It consists of a unique impedance network to link the inverter main circuit to the power supply, load, or additional converter circuit, for providing unique features that cannot be observed in the conventional Voltage Source and Current Source Inverters in which a capacitor and inductor are employed respectively. A splitinductor L1 and L2 and capacitors C1 and C2 are cross connected or connected in X shape is used to offer an impedance source (Z-Source) pairing the inverter to the DC supply, load, or additional converter. The DC supply or load may be either a voltage source or a current source or it may be the load. Therefore, the DC supply can be a battery, diode rectifier, thyristor converter, an inductor, a capacitor, or a arrangement of those. Switches employed in the converter can be a arrangement of switching devices and diodes like the antiparallel combination or the series combination etc. The inductance L1 and L2 can be used as a a split inductor or two separate inductors.
A. Circuit Diagram of Z-Source Inverter:
Fig. 1: Z- source inverter circuit diagram III. FIELD ORIENTED CONTROL This type of control is achieved,[4] Firstly, by converting AC motor dynamics into dq synchronous frame under certain conditions. Secondly, by aligning the flux of the machine to the reference frame. Depending upon the alignment of flux, the system categorized into two different schemes.If the reference frame is aligned to the stator field then it is called as stator field oriented control and if it is to the rotor flux then referred as rotor field oriented scheme. The decoupled control can be achieved by rotor field oriented control like in separately excited DC machine. However, calculation of the rotor flux is carried in two different ways. Direct Field Oriented Control (DFOC) Indirect Field Oriented Control (IFOC) A. Direct Field Oriented Control (DFOC) If flux is measured directly by using sensors then it is called Direct Field Oriented Control (DFOC). In direct field oriented scheme, the rotor flux measures from hall effect sensors. The installation of flux sensors is difficult due to limitations of air gap space, armature reaction, noise, etc. Due to these limitations the rotor flux is calculated indirectly from stator currents that are measured using current sensors. using the stator flux and currents ,and the second is from slip information IV. MATLAB SIMULATION OF CLOSED LOOP CONTROL OF INDUCTION MOTOR:
All rights reserved by www.ijsrd.com
260
Close Loop Control of Induction Motor Using Z-Source Inverter (IJSRD/Vol. 3/Issue 10/2015/062)
Fig. 2: Simulink model of closed loop control of induction motor The rotor flux angle can be measured by integrating the proportional to the slip. The two currents , are to be synchronous speed which is shown in eq.(1) used for the control of Induction machine[10]. θ= = (1) V. SIMULATION RESULTS = slip speed in r/s The speed evaluated by field oriented control method or = rotor speed in r/s vector control method is 160 r/s.When the motor starts its speed increases gradually from zero speed and finally settles s down to a constant speed ie. 160 r/s speed /time graph From = we find id which is used to generate A. Torque Versus Time rotor flux
Where inductance,
= rotor flux along d axis,
= mutual
= stator current along d axis,
rotor time constant stator current along q axis
= is
All rights reserved by www.ijsrd.com
261
Close Loop Control of Induction Motor Using Z-Source Inverter (IJSRD/Vol. 3/Issue 10/2015/062)
B. Stator Current /Time Graph
[7] Gopal K. Dubey, “Fundamental Of Electrical Drives”, Narosa Publication House, Second Edition, 2011 [8] P. S. Bimbhra “ Power Electronics” Khanna Publishers 4th edition 2009 [9] P. S. Bimbhra “Generalized Theory of Electrical Machine.
VI. CONCLUSION Fast response of vector control compared to scalar control make it better than other method of speed control of induction motor, by using this method we achieve maximum response in minimum time. The vector control method or the d-q axes model leads to a simpler analysis of an induction motor. A d-q axes model with the d-axis aligned along the synchronously rotating rotor frame, leads to the decoupled analysis where the torque and the flux components can be independently controlled just like in case of a dc motor. Speed can be controlled by varying parameters of motor, load torque, load limit value. VII. FUTURE SCOPE A new closed loop control of induction motor fed by a Z – source inverter based on the vector control or field oriented control strategy can be applied to the induction motors of different ratings of desired application. A hardware model of this proposed scheme can be implemented REFERENCES [1] Omar Ellabban, Joeri Van Mierlo and Philippe Lataire „‟A new Closed Loop Speed Control of Induction Motor Fed by A High Performance Z-Source Inverter‟‟ 2010 IEEE Electrical Power & Energy Conference 978-1-4244-8188-0/10 [2] Fang Zheng Peng, “Z-Source Inverter”, IEEE Transaction Industrial Application. Vol.-39, No.-2, Page: 504-510, 2003 [3] Hiren M. Patel, Pankit T. Shah, Hemangini V. Patel “Field Oriented Control of Induction Motor using Matlab Simulink” Volume -01, Issue – 02, Nov. 10 to Oct.11 [4] Sandeep Goyat , Rajesh Kr. Ahuja “Speed control of induction motor using vector or field oriented control” International Journal of Advances in Engineering & Technology, July 2012 [5] Mohit Tyagi, Atul Kushwaha, Shubra Goel, Amit Kumar, Manoj Saini„‟ Modelling and Simulation of PWM based Z source inverter using Matlab/Simulink‟‟ IJEEE, Vol. No.6, Issue No. 02, July-Dec., 2014 [6] Habeeb Fatima, Dr. S. Tara Kalyani “Performance Analysis of Z – source Inverter for Speed Control of Induction Motor using Wind Energy Conversion System” IJERT Vol.3 Issue 8 August- 2014 .
All rights reserved by www.ijsrd.com
262