CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA
Combined voltage space vector locations of a dual five-level inverter fed open-end winding IM drive (a nine-level inverter) 217 Combined Voltage Vectors Triangular Sectors 15,625 Switching State Combinations Shaded voltage vectors generate zero common-mode voltage CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Common-mode voltage of the dual five-level inverter fed open-end winding IM drive Common-mode voltage generated by individual five-level inverters (Inverter-A or Inverter-A’) Inverter-A Inverter-A’ Common-mode voltage in the phase voltage of induction motor with the proposed dual five-level inverter fed drive CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Groups of common-mode voltage generated by individual five-level inverter
Switching state of the five-level inverter (Inv.-A or Inv.-A’) VCM 1 222 Vdc/4 2 122, 212, 221 5Vdc/24 3 022, 112, 121, 202, 211, 220 Vdc/6 4 012, 021, 102, 111, 120, 201, 210, 22-1, 2-12, -122 Vdc/8 5 002, 011, 020, 101, 110, 12-1, 1-12, 200, 21-1, 22-2, 2-11, 2-22, -112, , -222 Vdc/12 6 001, 010, 02-1, 0-12, 100, 11-1, 12-2, 1-11, 1-22, 20-1, 21-2, 2-10, , -102, -111, -120, -212, -221 Vdc/24 7 000, 01-1, 02-2, 0-11, 0-22, 10-1, 11-2, 1-10, 1-21, 20-2, 2-1-1, 2-20, , -110, -12-1, -1-12, -202, -211, -220 8 00-1, 01-2, 0-10, 0-21, 10-2, 1-1-1, 1-20, 2-1-2, 2-2-1, -100, -11-1, , -1-11, -1-22, -201, -210, -22-1, -2-12 -Vdc/24 9 00-2, 0-1-1, 0-20, 1-1-2, 1-2-1, 2-2-2, -10-1, -11-2, -1-10, -1-21, -200, , -22-2, -2-11, -2-22, -Vdc/12 10 0-1-2, 0-2-1, 1-2-2, -10-2, , -1-20, -20-1, -21-2, -2-10, -2-21 -Vdc/8 11 0-2-2, , , -20-2, , -2-20 -Vdc/6 12 -1-2-2, , -5Vdc/24 13 -2-2-2 -Vdc/4 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Voltage vectors and corresponding switching states resulting into zero common-mode voltage in individual five-level inverter (Inv.-A or Inv.-A’) 19 Voltage Vectors 24 Triangular Sectors 19 Switching States All the shaded switching states belong to the Group-7,which generate zero common-mode voltage at the inverter poles

Achieved when individual five-level inverters (Inv.-A
Combined voltage space phasor locations resulting into zero common-mode voltage (a five-level inverter voltage space phasor structure) Combined Voltage Vectors Triangular Sectors 361 Switching State Combinations Achieved when individual five-level inverters (Inv.-A and Inv.-A’) are switched using the switching states belonging to the Group-7 only.

Number of redundant switching states available for each voltage vectors of the five-level inverter with zero common-mode voltage Combined Voltage Vectors Triangular Sectors 361 Switching Stats Combinations Achieved when individual five-level inverters (Inv.-A and Inv.-A’) are switched using the switching states belonging to the Group-7 only.

Some of the voltage vectors and their redundant switching states for five-level inverter with zero common-mode voltage Voltage Vector Redundant switching state combinations (switching state of Inverter-A, switching state of Inverter-A’) 1 (000,000), (0-22,0-22), (1-21,1-21), (0-11,0-11), (1-10,1-10), (2-20,2-20), (11-2,11-2), (2-1-1,2-1-1), (-12-1,-12-1), (20-2,20-2), (-110,-110), (-211,-211), (-101,-101), (-202,-202), (-220,-220), (-1-12,-1-12), (02-2,02-2), (01-1,01-1), (10-1,10-1) 9 (000,-101), (0-11,-1-12), (02-2,-12-1), (11-2,01-1), (10-1,000), (1-21,0-22), (1-10,0-11), (2-1-1,1-10), (20-2,10-1), (2-20,1-21), (-110,-211), (-101,-202), (01-1,-110), (-12-1,-220) 11 (000,-202), (1-10,-1-12), (01-1,-211), (2-1-1,0-11), (02-2,-220), (11-2,-110), (20-2,000), (2-20,0-22), (10-1,-101) 28 (000,-1-12), (1-10,0-22), (01-1,-101), (2-1-1,1-21), (02-2,-110), (-12-1,-211), (11-2,000), (20-2,1-10), (-110,-202), (10-1,0-11) 95 (10-1,-202), (11-2,-211), (2-1-1,-1-12), (20-2,-101) 66 (01-1,-202), (02-2,-211), (10-1,-1-12), (11-2,-101), (20-2,0-11), (2-1-1,0-22) 174 (20-2,-202) 133 (11-2,-202), (20-2,-1-12) 98 (02-2,-202), (11-2,-1-12), (20-2,0-22) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Amplitude of maximum reference space vector possible in linear range of modulation without boost in the DC-link of the proposed inverter CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

based five-level inverter
Generation of same maximum peak fundamental amplitude of the phase voltage equivalent to that of a conventional SVPWM based five-level inverter A boost of 15% in the dc-link of the proposed drive is required to generate the maximum peak fundamental amplitude of the phase voltage equivalent to that of a conventional SVPWM based five-level inverter. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Voltage space vector locations for proposed five-level inverter with common-mode voltage elimination (with dc-link boost) Combined Voltage Vectors Triangular Sectors 361 Switching Stats Combinations CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Switching state combination selected to generate the voltage space phasors of five-level inverter with zero CMV Combined Voltage Vectors Triangular Sectors 61 Switching Stats Combinations CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Power scheme of the proposed five-level inverter with CME
CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental results Pole voltage (VAO) Two-level operation
Y-axis: 1 div. = 50 V X-axis: 1 div. = 10 ms Phase voltage (VA’A) Pole voltage (VA’O) Pole voltage FFT (two-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic Phase voltage FFT (two-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental results (contd…)
Pole voltage (VAO) Three-level operation Y-axis: 1 div. = 40 V X-axis: 1 div. = 10 ms Phase voltage (VA’A) Pole voltage (VA’O) Pole voltage FFT (three-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic Phase voltage FFT (three-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Pole voltage (VAO) Four-level operation Y-axis: 1 div. = 70 V X-axis: 1 div. = 5 ms Phase voltage (VA’A) Pole voltage (VA’O) Pole voltage FFT (four-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic Phase voltage FFT (four-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Pole voltage (VAO) Five-level operation Y-axis: 1 div. = 75 V X-axis: 1 div. = 5 ms Phase voltage (VA’A) Pole voltage (VA’O) Pole voltage FFT (five-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic Phase voltage FFT (five-level operation) Y-axis: Normalized amplitude X-axis: Order of harmonic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Pole voltage (VAO) Over-modulation operation Y-axis: 1 div. = 80 V X-axis: 1 div. = 5 ms Phase voltage (VA’A) Pole voltage (VA’O) Pole voltage FFT (over-modulation operation) Y-axis: Normalized amplitude X-axis: Order of harmonic Phase voltage FFT (over-modulation operation) Y-axis: Normalized amplitude X-axis: Order of harmonic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Phase voltage (VA’A) Y-axis: 1 div. = 50 V Four-level operation X-axis: 1 div. = 5 ms Phase current Y-axis: 1 div. = 1 A Phase voltage (VA’A) Y-axis: 1 div. = 50 V Five-level operation X-axis: 1 div. = 5 ms Phase current Y-axis: 1 div. = 1 A CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Salient features of the proposed common-mode elimination scheme for multilevel inverter fed drive
A dual five-level inverter fed open-end winding induction motor drive with elimination of common-mode voltage in the entire operating range. Each five-level inverter of the proposed drive is formed by cascading two conventional two-level inverters and a conventional three-level NPC inverter. Hence, the proposed drive offers simple power-bus structure compared to the five-level NPC inverter fed drive. There is no alternating common-mode voltage in the inverter poles as well as at the phase windings of the induction machine. CEDT, Indian Institute of Science CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Salient features of proposed common-mode elimination scheme for multilevel inverter fed drive (contd…) A common DC-link is used at both the ends of the open-end winding induction machine, for both the five-level inverters. The DC-link voltage requirement of proposed open-end winding IM drive is nearly half as compared to that of a single five-level inverter fed conventional IM drive. Hence, the voltage stress on the devices is reduced and devices with lower voltage blocking capability can be used, which makes the proposed drive scheme suitable for high power applications. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

CONCLUSION In the implemented scheme, the rotor flux position is estimated from the motor phase current ripples During the low speed region of operation, the current ripple during the zero vector periods are used for rotor flux position estimation During the high speed region of operation, the current ripple during the active vector periods are used for rotor flux position estimation The scheme is implemented for a three phase motor, but the scheme can be extended to any multi phase motor and also with open-end winding structure CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Linearization of the Multi-level SVPWM in Over-modulation Region
By R. S. Kanchan, P. N. Tekwani, and K. Gopakumar Centre for Electronic Design and Technology, Indian Institute of Science Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Linearization of the Multi-level SVPWM in the Over-Modulation Region
Conventional two-level Sine-Triangle PWM Reference signals and carrier (wt) v AN BN CN 0.5 -0.5 V a0 b0 c0 dc /2 -V Vt π/2 π 3 π/2 2 π The fundamental component in the output PWM waveform is equal to k = (peak amplitude of the sinusoidal reference) / (height of the triangular carrier signal) Three sinusoidal (1200 phase shifted) reference signals are compared with triangular carrier The PWM signals are generated for three phases The pole voltage is clamped to +ve DC link bus if Vref >Vt else to –ve DC link bus CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Conventional Sine-Triangle PWM: Over-Modulation Range π/2 π 3 π/2 2 π (wt) V a0 b0 c0 -V dc /2 CN BN AN When ref signal is greater than carrier, the pole voltages are clamped to the DC link bus voltage The fundamental component in output PWM waveform is not given by But there is reduction in the fundamental component in the output voltage CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Conventional Sine-Triangle PWM: Over-Modulation Range 0.5 wt 00 π/2 π Reduction in the output fundamental is proportional to the shaded area CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Conventional Sine-Triangle PWM MI k Linear range Over-modulation 0.50 0.637 0.7854 Non-linear characteristic The voltage transfer characteristics i.e the ratio between the output fundamental and the reference signal amplitude is non-linear in the over-modulation region CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Carrier based Space-Vector PWM (SVPWM) 200 400 600 800 1000 1200 1400 1600 1800 Reference signals and carrier V a0 b0 c0 1 (wt) v*AN v*BN v*CN dc /2 -V π/2 π 3 π/2 2 π 0.5 -0.5 The reference signals are added with an offset voffset1 The resultant PWM is a Space Vector PWM CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Carrier based Space-Vector PWM (SVPWM) 0.5 wt 00 π/6 π/3 π/2 2π/3 π Again when ref signal is greater than carrier, the pole voltages are clamped to the DC link bus voltage There is reduction in the fundamental component in the output voltage Reduction in the output fundamental is proportional to the shaded area CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Output voltage (per unit w.r.t Vdc ) Linear range Over-modulation 0.5 0.637 0.785 0.577 0.866 SPWM SVPWM Non-linear characteristic The extended linear region in SVPWM as compared to SPWM The voltage transfer characteristics is again non-linear in the over-modulation region similar to SPWM Ideal requirement for the PWM modulator : Linear voltage transfer characteristics CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

In the Proposed Work An over-modulation scheme with the linear voltage transfer characteristics for a general n-level SVPWM signal generation Reference signal to the PWM modulator is pre-scaled in over-modulation region such that The fundamental component of the original and the modified reference signal is same The modified reference signal is always within carrier region Thus voltage transfer characteristic is a linear function of the modulation index both in the linear-modulation as well as in the over-modulation region The inverter leg switching times are directly obtained with a simple algorithm using only the sampled amplitudes of the reference phase voltages CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of linearization: when k=0.637 i.e. six step mode k=0.637 F1, the original reference signal in six step mode ( f1 (pk)=0.637) goes above the carrier (0.5) The output voltage will be less, if f1 is used for PWM generation f2 is a rectangular signal such that fundamental component of f2 is equal to f1, the original reference signal in six step mode i.e. F2 (1)=0.637 Therefore, f2 can be used for PWM generation instead of f1 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of linearization: when 0.5 < k < 0.637 θ π-θ 2π-θ π +θ π/2 π 3 π/2 2 π -1 1 f 2 -0.5 0.5 modified ref. signal Reference A part of original reference signal is clamped The fundamental component of the modified reference signal is same as original reference signal This requires that the fundamental component of rectangular pulse f2 is equal to fundamental component of part of the original reference signal f1 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fundamental component of part of the original reference signal f1 = θ π-θ 2π-θ π +θ π/2 π 3 π/2 2 π -1 1 f 2 -0.5 0.5 modified ref. signal Reference Fundamental component of rectangular pulse f2 = CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

The relationship between modulation index MI and clamping angle q 10 20 30 40 50 60 70 80 90 0.7854 0.8168 0.8482 0.8796 0.9111 0.9524 0.9739 1 q MI Thus if MI is known, the clamping angle q can be determined The modified reference signal is clamped for the angle q to π-θ and π+θ to 2π-θ CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of the proposed SVPWM in the over-modulation region 0.5 wt 00 π/6 π/3 π/2 2π/3 π Modified reference signal Reference signal goes out of the carrier two times in the positive half cycle CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of the proposed SVPWM in the over-modulation region The reference signal is clamped to 0.5 twice in +ve half cycle Again the fundamental component of the modified reference signal is same as original reference signal 0.5 wt θ0 00 π/6 π/3 π/2 (2π/3- θ)0 2π/3 π CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of the proposed SVPWM in the over-modulation The fundamental component of the original reference signal f1 between q to 2π/3-θ 0.5 θ0 (2π/3- θ)0 The fundamental component of rectangular pulse f2 between q to 2π/3-θ 0.5 For the fundamental component of the modified reference signal to be same as original signal, θ0 (2π/3- θ)0 00 π/6 π/3 π/2 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

This is referred as over-modulation Mode-I (0.577<k <0.60337)
Linearization of the Multi-level SVPWM in the Over-Modulation Region Principle of the proposed SVPWM in the over-modulation The relationship between modulation index MI and clamping angle q Thus if MI is known, the clamping angle θ can be determined Clamping of the modulating signal starts when 0.5 and clamping angle θ is equal to π/3 When clamping angle = π/6, k = Thus the clamping scheme can be used only in the range 0.577<k < as the clamping starts at an angle less than π/6, where modulating wave is (3/2)ksin(wt) instead of θ0 This is referred as over-modulation Mode-I (0.577<k < ) (2π/3- θ)0 π/6 π/3 π/2 00 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of the proposed SVPWM in the over-modulation MODE-II The reference signal is clamped to 0.5 for θ < wt < π- θ Again the fundamental component of the modified reference signal is same as original reference signal (dotted line) The MI range greater than , angle θ at which clamping starts is less than π/3 . 0.5 θ0 (π -θ)0 π/6 π/3 π π/2 2π/3 00 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Principle of the proposed SVPWM in the over-modulation MODE-II 0.5 wt θ0 (π -θ)0 00 π/6 π/3 π/2 2π/3 π . 5π/6 The relationship between θ and k can be derived similarly CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Summary: The relationship between θ and k
Linearization of the Multi-level SVPWM in the Over-Modulation Region Principle of the proposed SVPWM in the over-modulation MODE-II Summary: The relationship between θ and k Over-modulation Mode-I (0.577<k < ) & clamping angle π/3<θ< π/6 Over-modulation Mode-II ( <k <0.637) & clamping angle 0<θ< π/3 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

The relationship between θ and k (MI) for SPWM and SVPWM Mode-I Mode-II Steps Read Modulation Index MI Determine clamping angle θ Clamp the reference signal to 0.5 appropriately The implementation needs instantaneous angle information CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Modified reference voltages and triangular carriers for a five-level SVPWM scheme n-level SPWM scheme uses n-1 level shifted carrier waves Sinusoidal reference signals are added with offset which centers them within carrier region CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross , Tb_cross and Tc_cross during switching interval TS (When reference voltages are spanning the inner carrier region, MI < 0.433) Ta_cross , Tb_cross and Tc_cross : the time duration from the start of switching interval when the reference phase - A, B and C cross the carrier CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross , Tb_cross and Tc_cross during switching interval TS (When reference voltages are spanning the inner carrier region, MI < 0.433) Carrier- C1 Carrier- C2 Carrier- C2 T*as , T*bs and T*cs : Time equivalents of the modified reference signal amplitudes CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross , Tb_cross and Tc_cross during switching interval TS (When reference voltages are spanning the entire carrier region, 0.433<MI < 0.866) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages SUMMARY: Ta_cross , Tb_cross and Tc_cross for various carrier regions to bring the reference within a carrier region CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross: Represent the carriers and ref. signals in terms of time equivalents using relationship 3600 1800 900 2700 00 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross: Shift the ref. signal into one carrier region (first +ve carrier) by adding proper offset 3600 1800 900 2700 00 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Determination of the Ta_cross 3600 1800 900 2700 00 wt CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Equivalence to Conventional SVPWM The reference signals in carrier based SVPWM are shifted to one carrier region The outer sub-hexagon in the conventional SVPWM are shifted to central sub-hexagon in conventional SVPWM The reference signal shifting in carrier based SVPWM is equivalent to sub-hexagonal shifting in the conventional SVPWM 1800 900 00 1800 900 00 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Algorithm for inverter leg switching time calculation: Tfirst_cross , Tsecond_cross and Tthird_cross : the time duration from the start of switching interval when the reference phases cross the carrier for first, second and third time respectively. , x= a, b, c Inverter leg switching times CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Tgfirst_cross , Tgsecond_cross and Tgthird_cross : the inverter leg switching time for the reference phases which cross the carrier for first, second and third time respectively. The traces of Tgfirst_cross , Tgsecond_cross and Tgthird_cross showing centered time duration for middle vectors CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Space Vector PWM signal generation for multi-level inverters using only the sampled amplitudes of reference phase voltages Schematic representation of the Multi-level SVPWM Inverter Gating Signals Ta_cross, Tb_cross Tc_cross Gating Signals Tgx PWM Compa- rators VAN Time Equivalents Txs + VBN + VCN Toffset1 Toffset2 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Implementation of the Multi-level SVPWM with Linear Transfer Characteristics in Over-Modulation In overmodulation, clamps the reference signals appropriately MI Vs Inverter Gating Signals Ta_cross, Tb_cross Tc_cross Gating Signals Tgx PWM Compa- rators Pre- scaler VAN Time Equivalents Txs + VBN Toffset2 + VCN Toffset1 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Implementation of the Multi-level SVPWM with Linear Transfer Characteristics in Over-Modulation Pre-scaler: Read Modulation Index MI Determine clamping angle θ and then Clamping level ‘A’ Clamp the reference signal if it is greater than ‘A’ 0.5 wt 00 π/2 π A SVPWM MODE-I, (θ> π/6) SVPWM MODE-II, (θ< π/6) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

q Linearization of the Multi-level SVPWM in the Over-Modulation Region
The clamping angle information is converted into a level signal ‘A’ Prescaler: A simple look-up table of MI vs A 10 20 30 40 50 60 q 0.9 0.92 0.94 0.96 0.98 1 0.1 0.2 0.3 0.4 0.5 Modulation Index 'MI' Clamping level 'A' θ A CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Linear-Modulation Region Pre- scaler Time Equivalents Txs VAN VBN VCN MI Toffset1 Vs PWM Compa- rators Gating Signals Tgx Ta_cross, Tb_cross Tc_cross Toffset2 + No clamping of Tas in linear range of modulation Pre-scaler is inactive in linear modulation range (wt) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 0.92) (wt) Clamping of Tas in over-modulation (Mode-I) Pre-scaler is active in over-modulation range CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 0.94) (wt) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 0.95) (wt) Clamping of Tas in over-modulation (Mode-II) Pre-scaler is active in over-modulation range CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 0.96) (wt) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 0.98 ) (wt) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation Results: Over-Modulation Region (MI: 1.00) (wt) Square-wave switching mode CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental verification: Five-level inverter fed IM drive configuration CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Five-level inverter fed IM drive configuration Inverter-A + Inv1 Inv2 - Each three-level inverter configuration by cascading two two-level inverters The pole voltage can attain three levels:Vdc/2, 0 , -Vdc/2 Ref: V. T. Somasekhar, K. Gopakumar, “Three - level inverter configuration cascading two 2-level inverters”, IEE Proc. – EPA, Vol. 150, No. 3, May 2003, pp CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Five-level inverter fed IM drive configuration + Inv1 Inv2 - Inv3 Inv4 Induction motor Ref: M. R. Baiju, K. K. Mohapatra, V. T. Somasekhar, K. Gopakumar and L. Umanand, “A five-level inverter voltage space phasor generation for an open-end winding induction motor drive”, IEE Proc. EPA, Vol. 150, No. 5, Sept 2003, pp: Five-level space phasor generation across induction motor windings : Vdc/2,Vdc/4, 0 , -Vdc/4, or -Vdc/2 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces of pre-scaler output T*as and inverter leg switching time Tga Linear-Modulation Region (MI: 0.906) T*as Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces of pre-scaler output T*as and inverter leg switching time Tga Over-Modulation Region (MI: 0.92) T*as Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces of pre-scaler output T*as and inverter leg switching time Tga Square wave switching mode (MI: 1.00) T*as Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces machine phase voltage and inverter leg switching time Tga Linear modulation region (MI: 0.906) Phase voltage Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces machine phase voltage and inverter leg switching time Tga Over-Modulation Region (MI: 0.926) Phase voltage Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces machine phase voltage and inverter leg switching time Tga Square wave switching mode (MI: 1.00) Phase voltage Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces machine phase voltage and phase current Linear-Modulation Region (MI: 0.906) Phase voltage Phase current CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: The traces machine phase voltage and phase current Square wave switching mode (MI: 1.00) Phase voltage Phase current CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: Transition from Linear to square wave switching mode Top Trace: time equivalent of modified reference signals T*as Bottom Trace: Inverter gate switching time Tga CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental Results: Transition from Linear to six-step mode Top Trace: Phase voltage, Bottom Trace: Phase current CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fundamental output voltage as a function of modulation index-MI
10 20 30 40 50 60 70 80 90 100 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 MI (%) V fund (P.U.) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Harmonic components in the output waveform in the over-modulation region 90 92 94 96 98 100 0.05 0.1 0.15 0.2 0.25 MI (%) n th Harmonic (P.U.) 5 7 11 13 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

SUMMARY: A simple n-level PWM signal generation with linear voltage transfer characteristics throughout the modulation range, up to six-step mode of operation Linear voltage transfer characteristics in the over-modulation region is achieved by modifying the reference signal such that the modified reference signal has the same fundamental component as the original reference signal modified reference signals are always within the carrier region Inverter leg switching times are directly obtained from the sampled amplitudes of reference phase voltages signals Does not require any sector identification, sine look-up tables for switching vector identification Does not use sector mapping or complex timing calculations CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Twelve-sided polygonal voltage space vector based multilevel inverter for induction motors.

Topology of a multilevel inverter for generation of 12-side polygonal voltage space vectors for induction motor drives. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Generation of voltage space vectors CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

‘Va’ positive ‘Vb-Vc’ positive: 1st quadrant ‘Va’ negative ‘Vb-Vc’ positive: 2nd quadrant ‘Va’ negative ‘Vb-Vc’ negative: 3rd quadrant ‘Va’ positive ‘Vb-Vc’ negative: 4th quadrant CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

If in quadrant 1: If |Vb-Vc|<=|Va|.√3.tan150 then sector 1 else If |Vb-Vc|<=|Va|.√3.tan450 then sector 2 else If |Vb-Vc|<=|Va|.√3.tan750 then sector 3 else sector 4 If in quadrant 2: If |Vb-Vc|<=|Va|.√3.tan150 then sector 7 else If |Vb-Vc|<=|Va|.√3.tan450 then sector 6 else If |Vb-Vc|<=|Va|.√3.tan750 then sector 5 else sector 4 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

If in quadrant 3: If |Vb-Vc|<=|Va|.√3.tan150 then sector 7 else If |Vb-Vc|<=|Va|.√3.tan450 then sector 8 else If |Vb-Vc|<=|Va|.√3.tan750 then sector 9 else sector 10 If in quadrant 4: If |Vb-Vc|<=|Va|.√3.tan150 then sector 1 else If |Vb-Vc|<=|Va|.√3.tan450 then sector 12 else If |Vb-Vc|<=|Va|.√3.tan750 then sector 11 else sector 10 CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

V/f scheme for the drive CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Comparison to obtain time durations CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Pole voltage at 30Hz. Voltage levels at 0.366Vdc, 1.0Vdc and 1.366Vdc are observed. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Phase voltage at 30Hz. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Pole voltage at 50Hz. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Phase voltage at 50Hz. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 14a: Phase voltage and motor current at 15Hz. (X-axis: 1div=20ms, Y-axis: 1div=100V) Fig. 14b: Pole voltage at 15Hz. (X-axis: 1div=20ms, Y-axis:1div=50V) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 15a: Phase voltage and motor current at 30Hz. (X-axis: 1div=10ms, Y-axis: 1div=50V) Fig. 15b: Pole voltage and motor current at 30Hz. (X-axis: 1div=5ms, Y-axis: 1div=50V) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 16a: Phase voltage and motor current at 45Hz. (X-axis: 1div=10ms, Y-axis: 1div=100V) Fig. 16b: Pole voltage at 45Hz. (X-axis: 1div=10ms, Y-axis: 1div=50V) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 17b: Pole voltage at 50Hz. (X-axis: 1div=5ms, Y-axis:1div=50V) Fig. 17a: Phase voltage and motor current at 50Hz. (X-axis: 1div=5ms, Y-axis: 1div=100V) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 18: Harmonics at 15Hz operation. (X-axis: nth harmonic, Y-axis: Relative amplitude) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 19: Harmonics in 30Hz operation. . (X-axis: nth harmonic, Y-axis: Relative amplitude) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 20: Harmonics in 45Hz operation. (X-axis: nth harmonic, Y-axis: Relative amplitude) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Fig. 21: Harmonics in 50Hz operation. . (X-axis: nth harmonic, Y-axis: Relative amplitude) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Control of Switching Frequency Variation in
Hysteresis Controller for IM Drives Using Variable Parabolic Bands for Current Error Space Phasor CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Problem of Switching Frequency Variation
Common problems associated with the conventional, as well as current error space phasor based hysteresis controllers with fixed bands (boundaries), are the wide variation of switching frequency in a fundamental output cycle and variation of switching frequency with the variation in the speed of the load motor. These problems cause increased switching looses in the inverter, non-optimum current ripple, and excess harmonics in the load current, which leads to additional heating in the motor. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Two-Level VSI fed IM Drive
Voltage Space Phasor Structure Power Schematic CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Directions of Current Error Space Phasor When Different Voltage Vectors are Switched for Different Positions of Vm in Sector-1 Start of the Sector Middle of the Sector End of the Sector

Factors Influencing the Switching Frequency Variation
Leakage inductance of the machine (L) Machine voltage vector (Vm) (dominated by the back emf vector Vb) DC-link voltage (as amplitude of Vk is decided by dc-link voltage) Current error space phasor ripple ((i)) CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Variation of Switching Frequency in
Hysteresis Current Controller Over a fundamental period, the position of Vm varies with respect to the inverter voltage vectors of space phasor structure. Also, the selected inverter voltage vector Vk (V1, …, V8) keeps on changing in a fundamental cycle during hysteresis PWM current control. Therefore, either the inverter switching frequency or/and the current error space phasor ripple will vary over a fundamental inverter period. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Variation of Switching Frequency in Hysteresis
Current Controller (Contd…) For the given operating speed, if the shape of the fixed boundary of the current error space phasor is not properly selected, the switching frequency of inverter will vary over a fundamental cycle. Further to this, if the same boundary of current error space phasor is maintained at different operating speeds of the machine (for different fundamental values of the machine back emf) then also the inverter switching frequency will vary. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Investigation of Current Error Space Phasor in
VC-SVPWM based VSI fed IM Drives Typical SVPWM switching pattern of the inverter voltage vectors for two consecutive PWM switching intervals CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Switching times for inverter voltage vectors in a switching interval
Investigation of Current Error Space Phasor in VC-SVPWM based VSI fed IM Drives (Contd…) Switching times for inverter voltage vectors in a switching interval

Current error space phasor during switching of various voltage vectors
Investigation of Current Error Space Phasor in VC-SVPWM based VSI fed IM Drives (Contd…) Current error space phasor during switching of various voltage vectors Specific form for Sector-1

Movement of current error space phasor (on - plane) in a few sampling intervals of VC-SVPWM based two-level VSI fed IM drive [Y-axis And X-axis: Current In Amperes] Vm at start of the sector ( varies from 0 to 7) Vm at middle of the sector ( varies from 27 to 33) Vm at end of the sector ( varies from 54 to 60)

Approximate theoretical boundary of i for VC-SVPWM based two-level VSI fed IM drive for position of Vm in Sector-1 [Y-axis And X-axis: Current In Amperes] 10 Hz 20 Hz 30 Hz 40 Hz

Simulation results for VC-SVPWM based two-level VSI fed IM drive
10 Hz Operation

20 Hz Operation

30 Hz Operation

35 Hz Operation

41 Hz Operation

Theoretical Simulation
Comparison of boundary obtained by theoretical calculations and simulation studies for VC-SVPWM based two-level VSI fed IM drive Theoretical 10 Hz 0.1 A/div. 20 Hz 0.2 A/div. 30 Hz 0.2 A/div. 40 Hz 0.5 A/div. Simulation

Establishing variable boundary for proposed hysteresis controller
The parabola is defined as the locus of a point which moves so that it is always at the same distance from a fixed point (called the focus) and a given line (called the directrix). Formula for a vertical parabola (having Y-axis as axis of symmetry) with the vertex on (h, k), is: (x-h)2=4p(y-k). Formula for a horizontal parabola (having X-axis as axis of symmetry) with the vertex on (h, k), is: (y-k)2=4p(x-h). Here, p is the distance between vertex and focus of the parabola.

Equivalent new X-axis and Y-axis for the parabolas of current error space phasor boundary in different sectors Sectors X-axis Y-axis 1, 4 B-axis jB-axis 2, 5 A-axis jA-axis 3, 6 C-axis jC-axis CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Generalized Technique (Matlab Program) Developed in Proposed Work
Generalized technique to find the parameters of the boundary defining parabolas for given induction motor (x, y), (h, k), p For boundary defining parabolas for operating frequency from 1 Hz to 45 Hz with the resolution of 1 Hz Vdc, Base_freq, L, TS, Generalized Technique (Matlab Program) Developed in Proposed Work input output CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Boundary for proposed hysteresis controller with new reference axis

Parameters of boundary defining parabolas
for proposed hysteresis controller CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Output of the generalized technique in terms of parameters of boundary defining parabolas

[conventional Y-axis and X-axis: 1div.=0.5 A]
Output of the generalized technique in terms of the current error space phasor boundary for different operating frequencies [conventional Y-axis and X-axis: 1div.=0.5 A]

Voltage vector selection in Sector-1 for forward as well as reverse
direction of rotation of machine Present vector “ON” Conditions to be satisfied and next vector to be switched “ON” (y2-4p1 (x-h1))  0 up to 24 Hz operation (x2-4(p2 (y-k2)))  0 25 Hz onwards operation (x2-4(p2 (y-k2)))  0 (y2-4(p3 (x-h3)))  0 (x2-4(p4(y-k4)))  0 (x2-4(p4(y-k4)))  0 ijC  0 & ijA  0 ijA  0 & ijB  0 ijC0 & ijA0 ijC  0 & ijA  0 ijC  0 & ijA  0 V1 - V2 V7 V8 CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Sector changed detection using outer parabolic boundary
[Y-axis: 1div.=0.2 A and X-axis: 1div.=0.5 A]

Sector change detection logic (based on outer parabolic bands)
for forward rotation of machine From sector Present vector “ON” Condition to be satisfied for the sector change and next sector to be considered as new sector (y2-4(p3_outer(x-h3_outer)))  0 (y2-4(p1_outer(y-h1_outer)))  0 ijA < 0 & ijB < 0 ijB < 0 & ijC < 0 ijC < 0 & ijA < 0 ijC  0 & ijA  0 ijA  0 & ijB  0 ijB  0 & ijC  0 1 V2 or V7 or V8 2 * V3 or V7 or V8 3 V4 or V7 or V8 4 V5 or V7 or V8 5 V6 or V7 or V8 6 V1 or V7 or V8 (‘*’ means continue with the same sector) CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Simulation results of proposed hysteresis controller
10 Hz Operation

20 Hz Operation

30 Hz Operation

30 Hz Operation CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

35 Hz Operation

40 Hz Operation

Proposed Hysteresis Controller Simulation
Comparison of boundary obtained by theoretical calculations and simulation studies for VC-SVPWM based two-level VSI fed IM drive SVPWM Simulation 10 Hz 30 Hz 35 Hz 40 Hz Proposed Hysteresis Controller Simulation

Six-Step Mode of Operation

Block schematic of experimental set-up used for proposed
hysteresis controller CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Experimental results of proposed hysteresis controller
vAN, 130 V/div. i, 0.2 A/div. iA, 1.3 A/div. 10 Hz Operation i, Sector-1 i, Sector-2 i, Sector-3

iA*, 1.3 A/div. i, 1 A/div. iA, 1.3 A/div. 10 Hz Operation CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

vAN, 130 V/div. iA, 1.3 A/div. i, 0.35 A/div. 20 Hz Operation i, Sector-1 i, Sector-2 i, Sector-3

iA*, 1.3 A/div. i, 1 A/div. iA, 1.3 A/div. 20 Hz Operation iA, 1.3 A/div. iA*, 1.3 A/div.

vAN, 135 V/div. iA, 1.3 A/div. i, 0.45 A/div. 30 Hz Operation i, Sector-1 i, Sector-2 i, Sector-3

iA*, 1.3 A/div. iA, 1.3 A/div. i, Sector-3, 0.45 A/div. 30 Hz Operation iA, 1.3 A/div. iA*, 1.3 A/div. i, 1 A/div.

vAN, 130 V/div. iA, 1.3 A/div. i, 0.55 A/div. 35 Hz Operation i, Sector-2, 0.55 A/div. i, Sector-3, 0.55 A/div. i, Sector-3-4, 0.55 A/div.

iA*, 1.3 A/div. iA, 1.3 A/div. iA*, 1.3 A/div. iA, 1.3 A/div. 35 Hz Operation CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

vAN, 130 V/div. iA, 1.3 A/div. i, 0.6 A/div. 40 Hz Operation i, Sector-1, 0.6 A/div. i, Sector-2, 0.6 A/div. i, Sector-3, 0.6 A/div.

iA*, 1.3 A/div. i, Sector-4-5, 0.6 A/div. iA, 1.3 A/div. 40 Hz Operation iA, 1.3 A/div. iA*, 1.3 A/div.

vAN, 130 V/div. iA, 1.3 A/div. i, 0.6 A/div. 45 Hz Operation CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

vAN, 130 V/div. iA, 1.3 A/div. i, 0.5 A/div. 47 Hz Operation CEDT, Indian Institute of Science, Bangalore, INDIA CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

vAN, 130 V/div. 50 Hz Operation (Six-Step Mode) iA, 1.3 A/div. i, 0.65 A/div. i, 1.4 A/div.

vAN, 130 V/div. Acceleration Transients iA, 1.3 A/div.

speed, 910 rpm//div. Starting Operation iA, 1.3 A/div. vAN, 160 V/div. iA*, 1.5 A/div. iA, 1.5 A/div. iA, 1.7 A/div.

speed, 910 rpm//div. Starting Operation iA, 1.3 A/div. iA*, 1.5 A/div. vAN, 160 V/div. iA, 1.5 A/div. iA, 1.7 A/div.

speed, 910 rpm//div. Speed Reversal iA, 1.1 A/div. iA*, 1.35 A/div. vAN, 130 V/div. iA, 1.5 A/div. iA, 1.35 A/div.

speed, 910 rpm//div. Speed Reversal iA, 1.1 A/div. iA*, 1.5 A/div. vAN, 130 V/div. iA, 1.65 A/div. iA, 1.5 A/div.

Salient features of the proposed hysteresis controller
Current error space phasor based simple hysteresis controller Controls the switching frequency variation in a two-level VSI fed IM drive Based on the novel concept of on-line variation of hysteresis band, depending upon the speed of the machine Uses parabolic boundary for the current error space phasor Obtains switching frequency spectrum in the output voltage similar to that of the constant switching frequency VC-SVPWM based VSI fed IM drive. CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Salient features of the proposed hysteresis controller
(Contd…) Performance of the proposed controller is independent of the load machine parameters The unique parabolic boundary for different operating speeds for any given induction motor is determined using generalized technique (Matlab program) developed in proposed work Calculation of machine back emf vector is not needed Sector change logic is self-adaptive and is capable of taking the drive up to six-step mode of operation, if needed Controller always selects the adjacent inverter voltage vectors, forming a sector, in which the tip of the machine voltage vector lies CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

Multimotor drive setup

Inverter setup for multilevel structure

CEDT, INDIAN INSTITUTE OF SCIENCE, BANGALORE, INDIA

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