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.
- Multi-level inverters
- Scalar and direct vector control
- Three-phase infinite level inverter
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.
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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