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INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Subramanian K. et al., Vol. 2, Special Issue , pp. 12-19, 2014

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Simulation Study of Nine-Level Inverter Fed 1-Ø Induction Motor Drive

Subramanian K.,* Poovarasan P., Saraswathi M. and Uthra M.

Power Electronics and Drives Division, School of Electrical Engineering, VIT University, Vellore, Tamil Nadu, India

*Corresponding author: [email protected]

Abstract—At present nine-level PWM inverters are introduced in industrial drives, for interconnecting the renewable energy sources into the grid supply and traction motor drives, where the high and medium voltage levels. This paper presents an attempt made to evaluate the performance of 9-level cascaded inverter supplying power to a 1-Ø induction motor using computer simulation. Mathematical modeling of the system derived using equivalent circuit and the device operations. MATLAB/ Simulink based performance study completed. A novel technique used for modulation process to generates the pulses. These are applying to the gate circuit of the solid-state switches are used to configure the nine -level inverter. Simulation study completed using ODE 23 solver and results are presented.

Index Terms—PWM inverter, nine -level, 1-Ø induction motor

I. INTRODUCTION

Multi-level inverters (MLI), in particular three-level inverter fed AC drives employed in industries and electric traction for high voltage, power and efficiency of energy conversion process. Many utility companies nowadays provide cash incentive programs for energy saving. This encourages the use of large power PWM AC drives which are typically rated from several hundred to thousands horsepower. The advantages of this scheme are

Avoid series connections because the voltage of the

switching device is

It shifts the first group of voltage harmonics to a frequency band, which centers at two times the modulation frequency

To reduces the switching losses

It re u es the v ⁄ t on the motor win ings.

High voltage power conversion using conventional series connected voltage source inverter, techniques is compared and reviewed shows series connection of switches is essential [1] - [2]. D.C voltage is the input for the high voltage level PWM inverter obtained from a.c source using rectifier. At present, renewable source like, wind, solar etc. gives the energy in d.c form those are supplying energy to the MLI; during energy conversion, process voltage across dc source change abruptly. Therefore, voltage unbalancing will exist. A novel dc voltage charge balance control discussed by C.C. Hua et al [3].

A single-phase n-level multilevel inverter needs (n-1) voltage levels, recently 9-level hybridized cascade multi-level inverter presented [4] with different dc voltage level using diodes and controlled switches, though it gives better power quality but input power factor of this drives is an important task.

At present, the utility of MLIs increases to connect the non-conventional energy sources to the utility grid or employed for water pumping applications in isolated mode [5]- [8]. The aim of this work is develop the mathematical model of a single-phase 9-level PWM inverter supplying power to a single-phase induction motor drive. The simulation study completed using built-in libraries of power system toolbox in MATLAB / SIMULINK software [9] and presented.

The subsequent section-II, describes the system configuration. A deadbeat control is used to gives the d.c voltage to the inverter with different voltage levels. Single-phase 9-level cascaded PWM multi-level cascaded inverter operation presented. Modulating technique for pulse generation discussed. In section-III, mathematical model of the system explained. Simulation presented in section-IV, results and conclusion discussed in sections V and VI respectively.

II. SYSTEM CONFIGURATION

A. D. C. Supply System for Inverter

Figure 1. Connection diagram of D.C supply for the inverter


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Figure 1 depicted the dc voltage sources for the 9-Level inverter .Deadbeat control technique [10] used to control the state of the switch and and voltage level of the inverter.

B. 9-Level Cascaded Inverter

The multilevel inverter (MLI) structure can eliminates the need for step-up transformer and reduced the harmonics generated by the inverter. Figure 3 shows the nine-level cascaded

inverter. The voltage stress on the switch is s

.

Each of the two cell comprises a single-phase conventional H-bridge inverter. One bi-directional switch connected to the centre tap of two dc sources. By making appropriate switching (Table-1) of the inverter will gives nine level of the output

voltage. i.e, - - - - . In general, the maximum number of voltage level obtainable by adding number of 5-level inverter is

Figure 2. Circuit connection of 9-level inverter supplying power to R load

For positive half-cycle, the output voltage of obtain by the switches are turned on, then the current flowing as:

o - . In case of , the switches are turned ON, The current flowing as: o For , the switches and are turned ON, the current flowing as: o

. For , the switches and are turned ON, the current flowing as: o . For zero output voltage, the switches

n are turned on, then no current flowing, since circuit is open. It is common for negative half-cycle also.

For negative half-cycle, the output voltage of -

obtain by

the switches are turned on, then the current

flowing as: o - . In

case of -

, the switches are turned ON, The

current flowing as: o For

-

, the switches and are turned ON, the

current flowing as: o . For

-

, the switches and are turned ON, the

current flowing as: o .

In order to gives, the required output voltage magnitude of the nine-level inverter, the switches are triggering properly. In order to get the pulse the signals are modulated, Fig.4. For the continuous operation of the inverter, the switches are sequentially gated, Table-1. The state of the switches and the output voltage of the nine-level inverter is Table-1. In Table-1, zero indicates OFF and one indicates ON of the concerned switches.

Table 1. Switching logic of 9-level inverter

Vo S1 S2 S3 S4 S5 S6 S7 S8 SA SB

Vdc 0 1 0 0 0 1 0 0 1 0

2Vdc 1 1 0 0 0 1 0 0 0 0

3Vdc 1 1 0 0 0 1 0 0 0 0

4Vdc 1 1 0 0 1 1 0 0 0 0

+0 0 1 0 0 0 1 0 0 0 0

- 0 0 0 0 1 0 0 0 1 0 0

-Vdc 0 0 1 1 0 0 1 0 1 0

-2Vdc 0 0 1 1 0 0 1 0 0 0

-3Vdc 0 0 1 1 0 0 1 0 0 1

-4Vdc 0 0 1 1 0 0 1 1 0 0

C. Proposed 1-Ø Induction Motor Drive System

The proposed 9-level inverter fed single-phase induction motor drive is shown in Fig.3, comprises the induction motor as a load, LC filter with their internal resistances r n r and d.c supply system. Performance of the motor characteristics is studied using computer simulation. The d.c source is the equivalent of power extracted from either solar or other renewable energy source like photovoltaic, biomass etc.


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The aim of this work is to develop an isolated water pump driven by the non-conventional energy sources. Therefore, the system is suggest and implemented in computer simulation

level with 230V input dc level in particular household applications.

Figure 3. Circuit connection of 9-level inverter fed 1-ØInduction motor drives

III. MATHEMATICAL MODEL OF THE PROPOSED SYSTEM

A. Modeling of 1-Ø Induction motor

A single-phase induction motor with balanced stator

windings are represented stationary reference frame in q-d

axis equivalent circuit, Figs.4 (a) & (b) [11].

Figure 4. q-d Axis equivalent circuit of single –phase induction motor

From Fig.6, the d-q axis voltage equations of are:

Where ωb is the b se spee p

t, the flux linkage

equations are

(

)

(

)

These equations (8) – (15) are writing matrix form as:


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[

]

[

]

[

]

Where, p is equal to d/dt and n is the turn ratio of stator to

rotor. The equation (10) describes the dynamic characteristics

of single-phase induction motor.

The developed electromagnetic torque is

(

) (

) [

]

B. Modeling of Single-Phase Inverter

Figure 2 shows the inverter system with LC filter and load resistance R, In Fig.2, r and r represents the equivalent series resistance of inductor and capacitor. The state equations describing linear model of PWM inverter system is given as:

[

]

[

]

[

] [

]

[

] [

]

IV. MATLAB/SIMULINK BASED SIMULATION

The proposed single-phase induction motor drive simulated for 3 seconds, Fig.6, using the built-in libraries.


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Figure 5. Simulink Connection of the proposed 9-level inverter fed 1-Ø induction motor drive.


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Figure 6. Simulink connection of Modulating blocks

blocks of power system tool box in MATLAB/SIMULINK software. Ode 25 solver used to solve the equations, which are describing the system dynamics. Fig.7 shows the modulation block developed in Matlab [10]. A 1-Ø, 110V, induction motor is considered as load and its parameter as shown in Table-1.

Table 2. Induction motor parameters

Phase Single-phase

Rating 1Hp

Type Split phase

voltage 220V

Frequency 50Hz

Pole 4

Main winding resistance 36Ω

Main winding inductance 32.07mH

Main winding mutual inductance 50.9mH

Auxiliary winding resistance 36Ω

Auxiliary winding inductance 32.07mH

Friction factor 0

Inertia 0.005kg-m2

V. RESULTS AND DISCUSSION

The simulated results are shows in Figs.7 to 9. The extracted current and voltage waveforms are shown Fig. (7). It clearly shows the needs of reactive volt-ampere (VAr) to improve the power factor. An external connected capacitor across the main winding will improve the power factor by injecting leading VAr to mitigate the lagging VAr required by the motor.

Figure 7. Load voltage and current waveforms

Figure 8 illustrates the simulated gate signals (g to g ) of the

solid-state switches. It gated the switches at appropriate time intervals will get the required output voltage level


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Figure 8. Gate pulses of the proposed triggering modulation

The 9-level inverter output voltage and current values (rms) are shown in Fig.9. In order to make the clarity of current magnitude is magnified with ten times the actual value In Fig.9. Both values are attains their steady state value after 0.02 seconds, Fig.9.

Figure 9. RMS value of load voltage and current

Figure 10. Electromagnetic torque and speed

The electromagnetic torque developed by the motor and its speed is shown in Fig.10.

VI. CONCLUSION

The simulated results of the 9-level inverter fed 1-Ø induction motor shows its capability of the drives. The problems encountered single-phase multi-level inverter is absorbed that, it need dc voltage level is twice the peak value of the inverter output voltage. If it is from a renewable energy sources, will needs intermediate stage either boost or buck operation of d.c to converter

ACKNOWLEDGMENT

The authors acknowledge the Management of Vellore

Institute of Technology University, Vellore, India, 632014 and

Dean School of Electrical Engineering, for the support and

keen interest in promoting the research and development in

the division by providing the facilities and time.

REFERENCES

[1] T. A. Meyn r n H. Fo h “Mu ti-level conversion: High voltage choppers and voltage–sour e inverter” IEEE conference proceeding, 1993, pp 397- 403.

[2] I h mi o k Ers n K b i n m z n yin ir “ eview of multilevel voltage inverter topologies and control s hemes” International Journal of energy conversion and Management, Science direct –articled in press.

[3] C. C. Hu .W. Wu n .W. hu ng “ Novel d.c voltage h rge b n e ontro or s e Inverter” IET Transactions Power Electronics, Vol.3, Iss.2, 2009,pp 147-155.


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[4] h r es I. O eh mi n . Nun i “ ing e-phase 9-level hybri ize s e mu ti eve inverter’, IET Transactions On Power Electronics, Vol.6, Issu. 3, 2013, pp 468-477.

[5] Mariusz Malinowski, K. Gopakumar, Jose Rodriguez and M r e o . Perez “ urvey On s e Mu ti eve inverters” IEEE Transactions On Industrial Electronics, Vol.57,No.7, July 2010, pp 2197-2206.

[6] Biying Ren, Xiangdong Sun, Schaoliang An, Xiangui Cao, Qi Zh ng “ n ysis n esign o n Fi ter or the Three-Level Grid- onne te Inverter” IEEE

th International

Power Electronics and Motion control Conference-ECCE Asia, June 2-5,2012,harbin,China, pp 2023-2027.

[7] E u r Muj i “P W ter pumping with Pe k- power tracker using a simple six step square- w ve Inverter” IEEE Transactions On Industrial Electronics, Vol.33,No.3, May 1997, pp 714 -721.

[8] Y ser n gresh “Per orm n e o ing e-phase induction motor rive e by photovo t i Energy system” IEEE international conference JPEC 2010, 31 August, 3

rd

September 2010.

[9] Mat lab/Simulink Software Version.9.0

[10] [10] Sung-Jun Park, Feel-Soon Kang, Man Hyung Lee and Cheul-U Kim, “Single–Phase Five-level PWM Employing a Deadbeat Control Scheme” IEEE Transactions On Power Electronics,Vol.18,No.3, March 2003, pp. 831 -843.

[11] P. . Kr use O eg W syn zuk n ott . u ho “ n ysis o E e tri M hinery n rive system” IEEE Power engineering Society, A John Wiley & Sons, Inc, Publication, 2002.

Dr. K. Subramanian received B.E degree in Electrical and Electronics Engineering and M.E degree in Power System from National Institute of Technology (Formerly Regional

Engineering College), Thiruchirappalli-15 in 1994 and 1998 and Ph.D degree from VIT Uuniversity, Vellore, India,2013.His research interest is Induction Generator Voltage/ Var Control, Electrical Machines Drives, Modeling & Simulation, Power Electronics and drives, Application in Reactive Power Control.

P.Poovarasan received B.E degree in Electrical and Electronics Engineering from Saveetha Engineering College, Chennai affliated to Anna University, Chennai, Tamil Nadu, India and Persuing M.Tech in VIT University, Vellore, Tamil Nadu, India,632014. He is interested in power electronics and drives.

M.Saraswathi received B.E degree in Electronics and Communication Engineering from Priyadharshini Engineering College, Vaniyambadi, affliated to Anna University, Chennai, Tamil Nadu, India and Persuing M.Tech in VIT University, Vellore, Tamil Nadu, India,632014. She is interested in power electronics and drives.

M.Uthra received B.E degree in Electrical and E e troni s Engineering rom t.Joseph’s College of Engineering, Chennai, affliated to Anna University, Chennai, Tamil Nadu, India and Persuing M.Tech in VIT University, Vellore, Tamil Nadu, India,632014. She is interested in

power electronics and drives.

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