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Induction Motor Drives Based on Multilevel Dodecagonal and Octadecagonal Voltage Space Vectors

Induction Motor Drives Based on Multilevel Dodecagonal and Octadecagonal Voltage Space Vectors. Mathew K. Research Advisors: Prof. K Gopakumar and Prof. L Umanand Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore-560012, INDIA.

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Induction Motor Drives Based on Multilevel Dodecagonal and Octadecagonal Voltage Space Vectors

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  1. DESE, Indian Institute of Science Bangalore • Induction Motor Drives Based on • Multilevel Dodecagonal and • Octadecagonal Voltage • Space Vectors Mathew K. Research Advisors: Prof. K Gopakumar and Prof. L Umanand Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore-560012, INDIA

  2. DESE, Indian Institute of Science Bangalore Overview of the presentation • Evolution of multilevel space vector structures • Comparison of Hexagonal, Dodecagonal and Octadecagonal Space-vector Switching • Multilevel Dodecagonal Voltage Space-vector Generation using Cascaded H-bridges • Multilevel Dodecagonal Voltage Space-vector Generation using 2-level and 3-level Inverters • Multilevel Octadecagonal Voltage Space-vector Generation for Induction Motor Drives • Conclusion

  3. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) 2-level

  4. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 3-level 2-level

  5. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 5-level 3-level 2-level

  6. DESE, Indian Institute of Science Bangalore Evolution of spce vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 5-level 3-level 2-level 12-sided polygonal space vectors.

  7. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 5-level 3-level 2-level 12-sided polygonal space vectors.

  8. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 5-level 3-level 2-level 12-sided polygonal space vectors. 18-sided polygonal space vectors.

  9. DESE, Indian Institute of Science Bangalore Evolution of space vector structures (Hexagonal,12-sided and 18-sided) Hexagonal space vectors. 5-level 3-level 2-level 12-sided polygonal space vectors. 18-sided polygonal space vectors.

  10. DESE, Indian Institute of Science Bangalore Advantages of multilevel inverter • Output wave shape is more closer to sine wave in the entire modulation range • Size of the filters are reduced • Low voltage ratings are sufficient for the switching devices • Low electromagnetic interference due to lower dv/dt in the output waveform • It is possible to eliminate common mode voltage

  11. DESE, Indian Institute of Science Bangalore Harmonics for hexagonal switching Hexagonal switching points Phase voltage waveform harmonic amplitude Harmonics present present for hexagonal switching are 5,7,11,13,17,19, ... Normalized harmonic spectrum of phase voltage Harmonic order

  12. DESE, Indian Institute of Science Bangalore Harmonics for dodecagonal switching Dodecagonal switching points Phase voltage waveform harmonics are completely absent Harmonics present present for dodecagonal switching are 11,13,23,25, ... Waveform has less dv/dt and less Harmonic distortion compared to hexagonal switching harmonic amplitude Normalized harmonic spectrum of phase voltage Harmonic order

  13. DESE, Indian Institute of Science Bangalore Determination of pole voltages for dodecagonal switching

  14. DESE, Indian Institute of Science Bangalore Harmonics for Octadecagonal switching Dodecagonal switching points Phase voltage waveform 5th, 7th, 11th, 13th harmonics are completely absent Harmonics present present for dodecagonal switching are 17,19,35,37... Waveform has less dv/dt and less Harmonic distortion compared with dodecagonal switching harmonic amplitude Normalized harmonic spectrum of phase voltage Harmonic order

  15. DESE, Indian Institute of Science Bangalore Determination of pole voltages for Octadecagonal switching

  16. DESE, Indian Institute of Science Bangalore Multilevel Dodecagonal Voltage Space-vector Generation Using Cascaded H-bridges

  17. DESE, Indian Institute of Science Bangalore Schematic Each phase voltage is the sum of the output voltages of two H bridges Six isolated sources are required to power the H-bridges The output of CELL-1 can be +kVdc, 0, -kVdc The output of CELL-2 can be +0.366kVdc, 0, -0.366kVdc 24 IGBTs are required for the construction The series connection of H bridges results in a 9-level inverter

  18. DESE, Indian Institute of Science Bangalore Switching states and Pole voltage levels Nine pole voltage levels are possible at the output The levels are numbered from 4 to -4

  19. DESE, Indian Institute of Science Bangalore Space vector diagram The total number of combinations for a 3-phase, 9-level inverter is 9 x 9 x 9 = 729 Some switching points are on the vertices of 12-sided polygons Out of the 7 available 12 sided polygons, 6 are used for switching Three polygons have vertex on the ABC-axis Other three polygons are rotated by 15 degrees Other than zero vector, there are 72 switching points Point Va Vb Vc 61 1.366 -0.634 -1.366 62 1.366 0.634 -1.366 63 0.634 1.366 -1.366

  20. DESE, Indian Institute of Science Bangalore Space-vector locations and switching states

  21. DESE, Indian Institute of Science Bangalore Triangular regions in the space-vector diagram Vertices of adjacent 12 sided polygons can be joined to form triangles There are 120 isosceles triangular regions in the vector diagram The legs of all the triangles are same but there are 6 different base lengths There are two types of triangles: Type 1 triangles are within angles n*30 to (n+1)*30 degrees, Type 2 triangles are within angles (n+0.5)*30 to (n+1.5)*30 degrees Where n = 0,1,2,3,... If the tip of a reference vector is inside a triangle, the reference vector can be realized by switching between the vertices of the triangle keeping volt-second balancing

  22. DESE, Indian Institute of Science Bangalore Calculation of switching times Tip of reference vector is inside the triangle region formed by P1, P2, P3 Volt-second balancing is done to realize the reference vector Switching triangle should be identified Timings T1,T2,T3 should be calculated Proper devices should be activated to generate the vectors P1, P2, P3 for the calculated time

  23. DESE, Indian Institute of Science Bangalore Timing calculation procedure Find timings for the outermost hexagon from the sampled references of Va,Vb,Vc Convert these timings to outermost dodecagon Again convert these timings to outermost dodecagon, which is rotated by 15 degrees Identify the sector (1 to 24) in which the reference vector lies Calculate the timings of the switching triangle from the dodecagon timings

  24. DESE, Indian Institute of Science Bangalore Switching times for the hexagon For odd numbered sectors For even numbered sectors Sector identification logic

  25. DESE, Indian Institute of Science Bangalore Switching times for dodecagon - case 1 The basis vectors for hexagonal switching are V1,V2 The new basis vectors are V1' & V2' Need to find the matrix for the change of basis The standard basis in two dimension The basis for the hexagonal vectors V1,V2 The basis for the dodecagonal vectors V1',V2' The new timings are

  26. DESE, Indian Institute of Science Bangalore Switching times for dodecagon - case 2 The basis for the hexagonal vectors V1,V2 The basis for the dodecagonal vectors V1',V2‘ The new timings are

  27. DESE, Indian Institute of Science Bangalore Switching times for the triangular region The previous timing calculations are for the outermost dodecagons with zero pivot vector The system requires nonzero pivot vectors and smaller active vectors Switching times of the internal triangular region can be found by volt second balancing The calculated timings for the inner triangle are

  28. DESE, Indian Institute of Science Bangalore Finding the exact triangular region To find the exact triangle of operation a searching algorithm may be used There are 10 triangles in which searching should be performed The searching can be stopped when the calculated values of timings are all positive If Ts/2 >T0, the given order of searching will be efficient For larger values of T0, reverse order may be used

  29. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  30. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  31. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  32. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  33. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  34. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  35. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  36. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  37. DESE, Indian Institute of Science Bangalore Finding the exact triangular region

  38. DESE, Indian Institute of Science Bangalore Alternate timing computation method Each hexagonal sector is divided into 4 sub-sectors Each sub-sector spans 15 degrees The reference vector can be brought to sub-sector 1 of sector 1, using linear transformation

  39. DESE, Indian Institute of Science Bangalore Sub-sector identification The ratio between the active vectors can be used to identify the sub-sector location At sub-sector 1, sub-sector 2 boundary, At sub-sector 2, sub-sector 3 boundary, At sub-sector 3, sub-sector 4 boundary,

  40. DESE, Indian Institute of Science Bangalore Ten possible locations of the reference vector in sub-sub sector 1

  41. DESE, Indian Institute of Science Bangalore Calculation of timings for the inner sub-sector 5 For the outer hexagonal vectors For inner sub-sector 5 Equating

  42. DESE, Indian Institute of Science Bangalore Calculation of timings for the inner sub-sector 5 Resolving along alpha and beta axis The timings for inner subsector 5 is The general equation for the timings

  43. DESE, Indian Institute of Science Bangalore Block diagram of the experimental setup Motor specifications Rated power: 3.7kW Rated line-to-line voltage: 400V AC Rated frequency: 50Hz Number of poles: 4 stator resistance Rs : 2.08Ω Rotor resistance Rr : 4.19Ω Stator self inductance Ls : 0.28H Rotor self inductance Lr : 0.28H Magnetizing inductance M : 0.272H Moment of inertia J :0.1kg.m2 Waveforms are taken for the motor under steady state operation and during acceleration The waveforms taken are 1. Pole voltages of individual H bridges 2. Phase voltage 3. Phase current

  44. DESE, Indian Institute of Science Bangalore Experimental results at 10 Hz operation harmonic amplitude Phase voltage (100 V/div) Normalized harmonic spectrum of voltage CELL-1 voltage (100 V/div) Harmonic order harmonic amplitude CELL-2 voltage (100 V/div) Normalized harmonic spectrum of current Phase current (2 A/div) Time (20 ms/div) Harmonic order

  45. DESE, Indian Institute of Science Bangalore Experimental results at 24.5 Hz operation harmonic amplitude Phase voltage (200 V/div) Normalized harmonic spectrum of voltage CELL-1 voltage (100 V/div) Harmonic order harmonic amplitude CELL-2 voltage (100 V/div) Normalized harmonic spectrum of current Phase current (2 A/div) Harmonic order Time (10 ms/div)

  46. DESE, Indian Institute of Science Bangalore Experimental results at 40 Hz operation harmonic amplitude Phase voltage (200 V/div) Normalized harmonic spectrum of voltage CELL-1 voltage (100 V/div) Harmonic order harmonic amplitude CELL-2 voltage (100 V/div) Normalized harmonic spectrum of current Phase current (2 A/div) Harmonic order Time (5 ms/div)

  47. DESE, Indian Institute of Science Bangalore Experimental results at 49.9 Hz operation harmonic amplitude Phase voltage (200 V/div) Normalized harmonic spectrum of voltage CELL-1 voltage (100 V/div) Harmonic order harmonic amplitude CELL-2 voltage (100 V/div) Normalized harmonic spectrum of current Phase current (2 A/div) Harmonic order Time (5 ms/div)

  48. DESE, Indian Institute of Science Bangalore Experimental results at 50 Hz operation harmonic amplitude Phase voltage (200 V/div) Normalized harmonic spectrum of voltage CELL-1 voltage (100 V/div) Harmonic order harmonic amplitude CELL-2 voltage (100 V/div) Normalized harmonic spectrum of current Phase current (2 A/div) Harmonic order Time (5 ms/div)

  49. DESE, Indian Institute of Science Bangalore Transient performance (10 Hz to 30 Hz) Phase voltage (200 V/div) Phase current (2 A/div) Time (1 s/div)

  50. DESE, Indian Institute of Science Bangalore Summary of the work A new inverter power circuit has been proposed that consists of cascaded connection of two H-bridge cells. The circuit is capable of generating six concentric dodecagonal voltage space-vectors and there are 120 triangular regions. Under all operating conditions, switches of the high and low voltage cells have a maximum switching frequency of 500 Hz and 1.5 kHz respectively. Total elimination of harmonics from the phase voltage is possible with increased linear modulation range. Fourier analysis of the phase voltage and phase current shows very low magnitudes for the harmonics.

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