Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction

IJSRD - International Journal for Scientific Research & Development| Vol. 1, Issue 3, 2013 | ISSN (online): 2321-0613

Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction Motor Drive Ankur P. Desai1 Vijay G. Bhuva2 1 Student 2Assitant Professor 1,2 Shantilal Shah Engineering College, Bhavnagar, Gujarat, India

Abstract— this paper gives idea of comparison of five phase two-level voltage inverter (FPTLVSI) without filter circuit and control scheme and FPTLVSI with filter circuit and PWM control scheme for induction motor drive. The paper demonstrates using mat lab simulations about comparison in term of harmonics analysis for different firing angles and find best angle suitable for output with minimum harmonics for FPTLVSI without filter circuit and control scheme and harmonics analysis of FPTLVSI with filter and PWM control scheme. This paper suggests simulation of comparison of harmonics point of view five phase two-level voltage inverter (FPTLVSI) without filter circuit and control scheme and with filter circuit and PWM control scheme for induction motor drive.

Keywords: Modelling of five phase two-level voltage inverter (FPTLVSI), PWM control scheme for FPTLVSI I. INTRODUCTION RESEARCH interest in the area of multiphase machines has been steadily increasing over the past decade [1].The newest developments are application-driven (marine electric propulsion, electric vehicles (EVs) and hybrid electric vehicles (HEVs), more electric aircraft, locomotive traction, and high-power applications in general) and the consequence of the advantages offered by multiphase machines, when compared to the three-phase equivalents.

These are predominantly related to the possibility of reduction of the converter per-phase rating for the given machine power and to significantly improved fault tolerance, since an n-phase machine can continue to operate with a rotating field as long as no more than (n-3) phases are faulted. A further advantage exists if the multiphase machine is designed with concentrated stator windings, since it then becomes possible to enhance the torque production by injection of the low-order stator current harmonics of an appropriate order. Five phase induction machine drive.

controlled rectifier by varying the conduction angles of the thyristors. The frequency of the fundamental output is controlled from the IGBT based voltage source inverter. The subsequent section describes the implantation issues of control of a five-phase voltage source inverter. The motivation behind choosing this structure lies in the fault tolerant nature of a five-phase drive system. It has been advantage of five phase induction motor drive like reduction in phase current, reliable in faulty conditions, reduction in current ripple.

II. BLOCK DIAGRAM FIVE PHASE TWO LEVEL VOLTAGE SOURCE INVERTER MODEL As shown in fig.2 each switch in the circuit consists of two power semiconductor devices connected in anti-parallel.

One of these is a fully controllable semiconductor, such as a bipolar transistor, MOSFET, or IGBT, while the second is a diode.

Fig. 2: Power Circuit topology of a FPTLVSI The upper and lower power switches of the same leg are complimentary in operation, i.e. if the upper switch is ‘ON’ the lower must be ‘OFF,’ and vice-versa. As shown in fig.3, Dead time is done to avoid shorting the DC supply.

Fig.1: Block diagram of five phase induction motor drive A simple open-loop five-phase drive structure is elaborated in. The dc link voltage is adjusted from the

Fig. 3: Illustration for dead time

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Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction Motor Drive (IJSRD/Vol. 1/Issue 3/2013/0021)

III. HARMONICS ANALYSIS OF FPTLVSI. This section presents the comprehensive analysis of simulation results. The performance of two different conduction modes are elaborated in terms of the harmonic content in the phase voltages, line voltages and the distortion in the ac side line current.

The Fourier series of the phase-to-neutral voltage for 180° conduction mode is obtained as;

1   sin t  3 sin 3t     2 1 1  V  t   V dc sin 7t  sin 9t   … (1) 7   9    1 sin11t  .....  11 

Thus two more conduction states are included when compared to further prove the superiority of control at 120° conduction mode. It is observed that the lowest THD is obtained for 120° conduction mode.

Fig.4 is also mat lab simulation of FPTLVSI with balance resistive load. It can be simulated and analysis for different firing angles and takes measurement of harmonics behavior.

Following Table: 1 shows THD Vs different firing angles for FPTLVSI without any filter circuit.

From above equation (1) it follows that the fundamental component of the output phase-to-neutral voltage has an RMS value equal to

V

1



2



V

dc

 0.45V dc

… (2) The Fourier series of the phase-to-neutral voltage for 120° conduction mode is obtained as;

Fig.4: Matlab/simulink of FPTLVSI

     cos   2n  1  sin   2n  1 t     2 10   V (t )  V dc     n1,2,3,..  2n  1   

Firing angles THD(Total Harmonics Distortion)

… (3) From above equation (3) it follows that the fundamental component of the output phase-to-neutral voltage has an RMS value equal to

  V 1   V dc cos  10   0.428V dc … (4) 2

53.63

110

49.96

115

47.3

118

36.99

120

27.03

125

36.28

126

35.68

130

38.51

144

42.98

180

46.68

Table. 1: Different firing angles and related THD for harmonic analysis of FPTLVSI

Harmonics Analysis of FPTLVSI without Filter Circuit 60 THD

As per the equation of (4) loss in fundamental voltage in 120° conduction mode is of the order of 4.89% compared to 180° conduction mode. This loss will affect the loss of torque in the driven machine and subsequently the load will be affected. However, the drop in the torque is not very significant compared to the benefits obtained due to better harmonic performance.

Performance comparison in terms of harmonic content in output phase voltage, for different conduction modes are presented in fig.10 to 11. It is clearly seen that the harmonic content reduces significantly with reduction in conduction angle. The harmonic content is largest in 180 degree conduction mode and it is least in 120 degree conduction mode. However, the best utilization of available dc link voltage is possible with conventional ten step mode (180 degree conduction mode). It can thus be concluded that a trade-off exist between the loss in fundamental and corresponding gain in terms of lower harmonic content in output waveform is obtained by using 120 degree conduction mode.

A comparison of total harmonic distortion in the output phase voltages of five-phase voltage source inverter for different conduction angle is presented. The conduction angles considered are 180°, 162°, 144°, 126°, and 108°.

108

40 20 0

Series1 0

100 200 Firing Angle of FPTLVSI without Filter circuit

Fig.5 curve of different firing angles and related THD for harmonic analysis of FPTLVSI

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Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction Motor Drive (IJSRD/Vol. 1/Issue 3/2013/0021)

IV. THE CARRIER-BASED PULSE WIDTH MODULATION (PWM) TECHNIQUE FOR FIVE PHASE INDUCTION MOTOR DRIVE

the modulating technique (higher values of ma leads to over modulation); (b) for odd values of the normalized carrier frequency

m

f

the harmonics in the ac output voltage

appear at normalized frequencies

m

f

f

h

centred around and

its multiples, specifically,

h  lm f  k

l  1, 2,3,.....

Where For And

Fig. 6: Single phase half –bridge VSI As mentioned earlier, it is desired that the ac output

k  2, 4,6,...

… (4)

l  1,3,5,..... k  1,3,5,...



voltage, v o v aN follow a given waveform (e.g. sinusoidal) on a continuous basis by properly switching the power valves. The carrier-based PWM technique fulfils such a requirement as it defines the on- and off-states of the switches of one leg of a VSI by comparing a modulating signal

v

c

(desired ac output voltage) and a triangular

waveform  (carrier signal). In practice, when v c v  the switch S+ is on and the switch S− is off; similarly, when v c < v  the switch S+ is off and the switch S− is on.

A special case is when the modulating signal v

v

c

is a sinusoidal at frequency f

v

triangular signal

v





c

and amplitude v c , and the

is at frequency f



and amplitude

. This is the sinusoidal PWM (SPWM) scheme. In this

case, the modulation index m a (also known as the amplitude-modulation ratio) is defined as

m

a



v v

c 

… (1)

And the normalized carrier frequency the frequency-modulation ratio) is

m

f

f f



m

f

(also known as Fig. 7: The half-bridge VSI. Ideal waveforms for the SPWM



m

c … (2) Figure 7 clearly shows that the ac output voltage

v v 0

aN

is

basically

a

sinusoidal

waveform

plus

harmonics, which features: (a) the amplitude of the fundamental component of the ac output voltage satisfying the following expression:

v

01

 v aN 1 for

m

a

v

v

01

m

f a = 0.8, ( = 9): (a) carrier and modulating signals; (b) switch S+ state;(c) switch S− state; (d) ac output voltage; (e) ac output voltage spectrum; (f) ac output current; (g) dc current; (h) dc current spectrum; (i) switch S+ current; and (j) diode D+ current.

for l = 2, 4, 6,…; the amplitude of the ac output voltage harmonics is a function of the modulation index

m

a

and is independent of the normalized carrier frequency

m

i

2

m

a

…(3)

≤ 1, which is called the linear region of

f for m f > 9; (d) the harmonics in the dc link current (due to the modulation) appear at normalized frequencies f p centered around the normalized carrier frequency m and its multiples, specifically, f

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Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction Motor Drive (IJSRD/Vol. 1/Issue 3/2013/0021)

p  l m f  k  1 l  1, 2,3,.....

(5) Where For And

DC Link Voltage Vdc=200 V before running simulation given in command prompt.

Freq=50 Hz running simulation given in command prompt.

k  2, 4,6,... l  1,3,5,..... k  1,3,5,...

l = 2, 4, 6, … Additional important issues are: (a) for small values of

m

v

v



and the signal

c

f

( m f < 21), the carrier signal should be synchronized to each

other ( m

f integer), which is required to hold the previous features; if this is not the case, sub harmonics will be present in the ac output voltage.

The PWM technique allows an ace output voltage to be generated that tracks a given modulating signal. A special case is the SPWM technique (the modulating signal is a sinusoidal) that provides, in the linear region, an ac output voltage that varies linearly as a function of the modulation index, and the harmonics are at well-defined frequencies and amplitudes. These features simplify the design of filtering components. Unfortunately, the

Fig. 9: Matlab/simulation results for output phase voltages of Three phase two-level voltage source inverter and five phase two-level voltage source

maximum amplitude of the fundamental ac voltage is v i /2 in this operating mode. Higher voltages are obtained by using the over modulation region ( m a > 1); however, loworder harmonics appear in the ac output voltage. Very large values of the modulation index ( m a > 3.24) lead to a totally square ac output voltage that is considered as the square-wave modulating technique

 Matlab simulink model of five phase two-level voltage source inverter with PWM technique

Fig. 10: Matlab/simulation results for output load currents of three phase two-level voltage source inverter and five phase two-level voltage source

Fig. 8: Matlab/simulink model for PWM Method of five phase induction motor drive V. RESULTS Matlab/simulation results of three phase two-level voltage source inverter and five phase two-level voltage source Simulation results of for TPTLVSI and FPTLVSI the operating conditions given below are shown in Fig.7 to fig.11. Simulation results show output phase voltages, line voltage currents, gate triggering, load current, harmonics analysis for five phase two level voltage inverter.

Operating condition: Simulation time: 0.02 sec

Fig.11: Matlab/simulation results for Input signal, carrier signal and PWM method

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Analysis Approach for Five Phase Two-Level Voltage Source Inverter with PWM Technique for Induction Motor Drive (IJSRD/Vol. 1/Issue 3/2013/0021)

Harmonic analysis of output line voltages of one of the phase of FPTLVSI without any control scheme and filter is carried out with different firing angle of gating circuit of FPTLVSI and result is obtained that at 120 0 optimal value of THD of line voltage of 27.03.

Harmonic analysis of output line voltages of one of the phase of FPTLVSI with PWM control scheme and filter is carried out and result is obtained that THD of of output line voltages of one of the phase of FPTLVSI is reduced greatly with value of 3.65.

This paper has reviewed analytical approach for five phases two level voltage inverter used in application of induction motor drive.

REFERENCES Fig. 12: Matlab/simulation results for output voltages (without filter) of five phase two-level VSI

Fig. 13: Matlab/simulation results for output voltages (with filter and PWM control scheme) of five phase two-level VSI

Fig.14: Matlab/simulation results for FFT analysis output voltages (with filter and PWM control scheme) of five phase two-level VSI

[1] E. Levi, R. Bojoi, F. Profumo, H. A. Toliyat, and S. Williamson, “Multiphase induction motor drives—A technology status review,” IET Electr. Power Appl., vol.

1, no. 4, pp. 489–516, 2007.

[2] Grandi, G. Serra, and A. Tani, “General analysis of multi-phase systems based on space vector approach,” in Proc. Int. Power Electr. Motion Control Conf. (EPEPEMC), Portoroz, Slovenia, 2006, pp. 834– 840.

[3] Y. Zhao and T. A. Lipo, “Space vector PWM control of dual three-phase induction machine using vector space decomposition,” IEEE Trans. Ind.Appl., vol. 31, no. 5, pp. 1100–1109, Sep./Oct. 1995.

[4] P. S. N. de Silva, J. E. Fletcher, and B. W. Williams, “Development of space vector modulation strategies for five-phase voltage source inverters,” in Proc. Inst. Electr.

Eng. Power Electr. Mach. Drives Conf. (PEMD), Edinburgh, U.K., 2004, pp. 650–655.

[5] D. Dujic, E. Levi,M. Jones, G. Grandi, G. Serra, and A. Tani, “Continuous PWM techniques for sinusoidal voltage generation with seven-phase voltage source inverters,” in Proc. IEEE Power Electr. Spec. Conf.

(PESC), Orlando, FL, 2007, pp. 47–52.

[6] G. Grandi, G. Serra, and A. Tani, “Space vector modulation of a seven phase voltage source inverter,” in Proc. Int. Symp. Power Electron. Electr. Drives, Autom.

Motion (SPEEDAM), Taormina, Italy, 2006, pp. 1149– 1156.

[7] D. Dujic, M. Jones, and E. Levi, “Space-vector PWM for nine-phase VSI with sinusoidal output voltage generation,” in Proc. IEEE Ind. Electron.Soc. Annu.

Meeting (IECON), Taipei, Taiwan, 2007, pp. 1324– 1329.

VI. CONCLUSION A comparison of total harmonic distortion in the output phase voltages of five-phase voltage source inverter for different conduction angle is presented. The conduction angles considered are 180°, 162°, 144°, 126°, and 108°.

Thus two more conduction states are included when compared to further prove the superiority of control at 120° conduction mode. It is observed that the lowest THD is obtained for 120° conduction mode.

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