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:
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