 Open Access
 Total Downloads : 416
 Authors : C. Saravanan, Dr. M. A. Panneerselvam, Dr. K. Srinivasan
 Paper ID : IJERTV2IS110929
 Volume & Issue : Volume 02, Issue 11 (November 2013)
 Published (First Online): 22112013
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Analysis on Photovoltaic Based Cost Effective Four Switch Three Phase Inverter Driven Water Pumping System
inverters have few drawbacks, like switching losses of the six switches as well as the complexity of the
inverters have few drawbacks, like switching losses of the six switches as well as the complexity of the
C. Saravanan 1, Dr. M. A. Panneerselvam 2,Dr. K. Srinivasan3
Assistant Professor1, Professor2,Professor3 Tagore Engineering College, Chennai.
Abstract
This paper presents the analysis of a Photo Voltaic (PV) based Four Switch ThreePhase Inverter (FSTPI) fed induction motor driven water pump. The cost effective FSTPI uses a SPWM technique for producing three phase voltage output and this output is used to drive 3 phase induction motor driving a pump load. Advantages of the FSTP inverter over the conventional six switch three phase inverter such as, reduced price because of reduction in the switches, low switching losses and less interface circuits to supply pulse signals for the switches, simpler control algorithms to generate pulses, damaging of the switches due to the lesser interaction between switches and less realtime computational burden. The Power quality improves by reducing the order of harmonics. The complete model is simulated in MATLAB/SIMULINK and validates the theoretical considerations.
Keywords Four switch threephase inverter (FSTPI), Induction motor drive, Photovoltaic array (PV), Pump load.

Introduction
Solar photovoltaic (PV) system generates electricity and it has advantages as like pollution, noise and wear tear etc., Solar water pumping system is an rapid growth accepted means of obtaining water in remote areas where national grid connection is not viable [1]. There are numerous photovoltaic power systems ranging from 100 W to several megawatts [2]. PV cells are generated dc power, and further feed into the power controlling unit. Consecutively to maintain the frequency and Voltage level of inverter to be connected in the load. The Main cause in inverter is to eliminate harmonics, and this draw back has been concentrated by researcher over many years.
Traditionally, Six Switch Three Phase (SSTP) inverters have been widely utilized for variable speed induction motor (IM) drives [4], [5]. These
control algorithm and interface circuits to generate control algorithms and interface circuits to generate six PWM logic signals. Some efforts have been made on the application of Four Switches Three Phase (FSTP) inverter for uninterruptible power supply and variablespeed drives. Advantages of the FSTP inverter over the conventional SSTP inverter such as, low cost, number of switches, switching losses and number of interface circuits to supply logic signals for the switches, simpler control algorithms to generate logic signals, fewer chances of destroying the switches due to lesser interaction among switches and less realtime computational burden.
This four switch threephase inverter connected to a threephase induction motor. The use of induction motor gives many advantages as the comparison to DC motor. [5] In this paper, an analysis has been made on FSTPI supplying induction motor driven a water pump for irrigation purpose.

System Description
The Complete system is divided into three major parts a) Photovoltaic system, b) cost effective four switch threephase inverter, c) Induction motor fed water pump drive system. The Various mechanism of system are described as,
The Schematic diagram of complete system is shown in fig1. In it solar PV dc power output is feed to four switch threephase inverter. The Pump load is driven by induction motor, which draws power from FSTPI.

Photovoltaic system
The PV cell characteristics are strongly nonlinear in nature; its most referred equivalent circuit [1] is shown in fig2. The expression for fig. 2. is given in equation (1) [1] as follows:
As shown in the fig2, IPV stands for PV short circuits current, Id is a diode current, Rs means the series resistance of photovoltaic cells, Rsh represents the photovoltaic battery parallel resistance, the internal value is less than 1 .[2]
The performance of photovoltaic cell is expressed as in below equation,(1)
q V IR V IR
Where:
Va,, Vb,, Vc= Inverter output voltages
Vdc =Be the voltage across the dclink capacitors
Sa, Sb =The switching functions for each phase leg
In matrix form, the above equations can be written as:
a
a
Va 4 2 1
b 3 S
b 3 S
V V dc 2 4 S 1
V 2 2 b 2
V 2 2 b 2
c (8)
For a balanced capacitor voltage, the four switching combinations lead to four voltage
I I

I exp
S 1 S
reactors. Table 1 shows the different modes of
pv o
Where,
KTa
RSh
—(1)
operation and the corresponding output voltage vector of the inverter.
IPV= Photogenerated current (A) I= Cell output current (A) I0=Diode Saturation Current (A) V=Cell Output Voltage (V) Rs=Series Resistor ()
e= Electron Charge 1.6Ã—1019 (coul)
K=Boltzman Constant (j/K) T=cell temperature
For ease the dc battery is used instead of PV in this paper.


Four Switch Three Phase Inverter topology
In the analysis, the inverter switches are considered as ideal power switches and it is assumed that the conduction state of the power switches is associated with binary variables S01 to S04[4]. Therefore, a binary 1 will indicate a closed state, while 0 will indicate the open state. Pairs S01 to S03 and S02 to S04 are complementary and as a sequence:
S03 = 1 S01 (2)
S04 = 1 S02 (3)
Also, it will be assumed that a stiff voltage is available across the two dclink capacitors and:
VC1= VC2=/2 (4)
where, corresponds to a stiff dcbus voltage, i.e., the actual value of the dcbus voltage is equal to . The phase voltage equations of the motor can be written as a function of the switching logic of the switches and the dclink voltage and given by [5]:
S01
S02
Va
Vb
Vc
0
0
Uc/6
Uc/6
Uc/3
1
0
Uc/2
Uc/2
0
0
1
Uc/6
Uc/6
Uc/3
1
1
Uc/2
Uc/2
0
However, the basic problem with four switch three phase inverter lies in the control of the third phase for maintaining balanced output in all the three phases of the inverter. Existing modulation schemes are employed for controlling q1q4 switches, such that the fundamental frequency component of the reduced switch three phase inverter output
Va = Vdc(4Sa2Sb1)/3 (5)
Vb = Vdc(2Sa+4Sb1)/3 (6)
Vc = Vdc(2Sa2Sb+2)/3 (7)
voltages has a 600 phase difference. Thus, the fundamental components of the three
phase voltages are a balanced set with 1200 phase difference a shown in Figure 4.
T=1.0407320.24422+0.022 (9)
The Complete simulation model based on Matlab/Simulink is shown in fig6, which contains three major sections. First one is inverter section, second section is induction
motor, and third one is pump load. A three phase squirrel cage 220V, The Complete simulation model based on Matlab/Simulink is shown in fig6, which contains three
motor, and third one is pump load. A three phase squirrel cage 220V, The Complete simulation model based on Matlab/Simulink is shown in fig6, which contains three
In this paper three phase induction motor is driving a water pump system. The starting torque required by a water pump is shown Fig5. In order to overcome the static friction torque, 10% of fullload torque is allowed at standstill as there is no gland friction. When the pump fails to meet the line of torque, then torque taken by water pump is proportional to square of speed. The speedtorque characteristic of pump load is expressed in Eq. (7), where quantities are expressed in p.u.
major sections. First one is inverter section, second section is induction motor, and third one is pump load. A three phase squirrel cage 220V, 60Hz induction motor is used. The induction motor is run by PV based cost effective FSTPI and it is used for driving a water pump load.


Results and Discussion
The Performance analysis of the system is studied using various system quantities such as voltage generated, torque, rotor current, stator current, Speed, water pump power V/s speed curve, THD analysis Following investigations are carried out on the system to verify the system model.

Analysis of four switch three phase inverter output for induction motorpump load system
Transients in stator and rotor currents are there for short span of time that is, it settles quickly as shown in Figures 12 15. The starting current is high but within the steady state value. Steady state value of stator current is equal to 10.6 Ampere. Steady state value of rotor current is equal to 10.10 Ampere. The result of speed estimation is shown in Figure 14. It can be observed that speed reaches at steady state value that is 1535 rpm within 0.5 seconds when motor is subjected to constant load of 11.9 Nm. So when the motor is fed by FSTP inverter then its speed increases and settling time decreases and it is due to voltage after inverter circuit which boosted by FSTP inverter. The electromagnetic torque waveform of the induction motor is shown in Figure 15. It is also observed that the cost effective four switch inverter performance is much closer to that of the conventional inverter from Figures 8 and 9 respectively. The efficiency of induction motor for this system is nearly about 80%.

Power quality analysis
The FFT analysis of lineline voltage Vab has been carried out for one cycle after study state is shown in fig11. The performance of the four switch three phase inverter fed induction motor drive is compared with the six switches three phase inverter fed drive on the basis of THD of stator current and speed response under identical operating conditions. The total harmonic distortion of the four switch three phase inverter was found to be 1.31 % as against the standard value of 5% which proves the effectiveness of the proposed topology.


Conclusion
In this paper, the analysis on four switch three phase inverter fed induction motor pump load system is studied. The proposed cost effective four switch three phase inverter produce low harmonic distortion and power quality is enhanced. The proposed FSTPI also has less complex control circuit in comparison to the traditional three phase inverter topology. The complete system is designed in MATLAB/ SIMULINK. The system performance is found to be satisfactory for induction motorpump load system which thereby validating the system model.

References
[6]. Cruise,R.J.,C.F. Landy and M.D. McCulloch, 1999. Evaluation of a reduced topology phaseconverter operating a threephase induction motor. Proceeding of the IEEE International Electric Machines and Drives Conference Seattle, WA., pp: 466468.
[7]. X. Zhou, D. Song, Y. Ma, and D. Cheng, "The simulation and design for MPPT of PV system Based on Incremental Conductance Method," in Information Engineering (ICIE), 2010 WASE International Conference on, Vol:2, pp. 314317, 2010. [8]. Zhou De jia , Zhao Zhengming, WU Libo. Analysis characteristics of photovoltaic arrays using simulation. J T singhua Univ (Sci & Tech), 47(7):11091117, 2007. [9]. K.Srinivasan and S.S. Dash Performance Analysis of a Reduced Switch ZSource Inverter fed IM Drives IJCEE, Vol. 2, No. 4, August, 2010,PP:17938163.