ABSTRACT:
The
design and performance analysis of an open-ended three-phase induction motor,
driven by an Infinite Level Inverter (ILI) with its speed control using scalar
and direct vector control techniques are presented in this paper. The ILI
belongs to an Active-Front-End (AFE) Reduced-Device-Count (RDC) Multi-level
Inverter (MLI) topology. The fundamental structure of this inverter topology is
a dc-to-dc buck converter followed by an H-bridge. This topology performs a
high-quality power conversion without any shoot-through issues and reverse
recovery problems. The performance of the proposed topology is validated using
a resistive load. The THD of output voltage waveform obtained is 1.2%.
Moreover, this topology has exhibited a high degree of dc-source voltage
utilization. ILI considerably reduces the switching and conduction losses,
since only one switch per phase is operated at high frequency, and other
switches are operated at power frequency. The overall efficiency of the
inverter is 98%. The speed control performance of the ILI topology using
three-phase open-ended induction motor has been further validated through
scalar and direct vector control techniques. Results obtained from simulation
studies are verified experimentally.
KEYWORDS:
1. Active-front-end
2. Multi-level
inverters
3. Reduced-device-count
4. Scalar
and direct vector control
5. Three-phase infinite level inverter
SOFTWARE: MATLAB/SIMULINK
SCHEMATIC DIAGRAM:
Figure 1. Three Phase Infinite Level Inverter Topology. Basic Structure Of The Proposed Topology Is A Buck Converter (Afe Converter) Followed By An H-Bridge. This Topology Consists Of One High-Frequency Operated Switch For Every Buck Circuit And Four Low-Frequency Operated Switches For Every H-Bridge; Hence, One Inductor And One Capacitor Per Phase.
EXPECTED SIMULATION RESULTS:
Figure 2. Simulated Waveforms Of Ili. (A) High
Frequency, (B,C) Low Frequency Switching Pulses.
Figure 3. Simulated Waveforms Of Ili Using
Resistive Load. Voltage And Current Wave Forms Across The Afe Converter
Components. (A,B) High Frequency Switch, (C,D) Diode,(E,F) Inductor, (G,H)
Capacitor,(I,J) Voltage Across Low Frequency Operating Switches.
Figure 4. Simulated Waveforms Of Ili Using
Resistive Load. (A) Voltage Waveforms Across
The
Buck Capacitor, (B) Voltage ,(C) current Wave Form Across The Load Resistance.
Figure5. Simulated Waveforms Of Ili Using
Resistive Load. (A) Three-Phase Output Voltage Waveforms Across
The
Buck Capacitor, (B) Three-Phase Output Voltage Wave Form Across The Load
Resistance.
Figure 6. Simulated Waveforms Of (A) Third
Harmonic Injection Pwm Control Implementation Logic, (B) Phase Voltage Waveform
Of The Ili Using Resistive Load.
Figure 7. The Dynamic Responses Of The Simulated
Output Voltage Waveforms Using V/F Control. (A) Voltage Waveform Across The
Buck Capacitor, (B) Line-To-Line Voltage Across The Load.
Figure 8. The Dynamic Responses Of The Simulated
Output Voltage Waveforms Using Direct Vector Control. (A,C) Voltage Waveform
Across The Buck Capacitor, (B,D) Line-To-Line Voltage Across The Load.
Figure 9. The Simulated Output Voltage Waveforms
Using Resistive Load (A) Conventional 2-Level H-Bridge Inverter, (B) 3-Level
H-Bridge Inverter, (C) 5-Level Cascaded H-Bridge Mli, (D) Proposed Topology.
CONCLUSION:
Design and analysis of the performance of an infinite level inverter driven induction motor have been discussed in this paper. ILI has been found to impart better performance to an induction motor drive. The ILI which belongs to an AFERDC- MLI topology has been tested with a resistive load and found to possess very good quality voltage and current waveforms in terms of THD. While conventional inverter topologies contain tens of percentage of THD, the topology mentioned in this paper contains a THD as low as 1.2%. Moreover, the dc- voltage requirement for generating a fixed ac-voltage output has been found to be much less than that required by other similar topologies, making the dc-source utilization better with this topology. While it is required to have a dc-voltage requirement of 677V in a conventional inverter working in sine PWM mode, the requirement of dc-voltage in the new inverter is only 338V. Use of third harmonic injection modulation scheme has also been performed using this inverter and found that the dc-source utilization can be improved further. Efficiency of inverter has also been found to be better, since only one switch per phase is operated at high frequency. All the switches in conventional inverters are operated at high frequency. Scalar and vector control of induction motor have also been performed using this topology. It has been found that the dynamic performance is better with this topology. This has been validated by accelerating and decelerating the machine with different reference speeds. Since the harmonic content in current has been very less, torque pulsations experienced by the motor would be negligible. Requirement of de-rating associated with induction motors fed by conventional inverters is not present in this case. Since there is no shoot-through menace, the chances of the inverter getting damaged is less, which results in better life and reliability of the drive system.
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