7. simulation of single phase inverter using psim software for solar p.v. system give constant...

Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah 26

International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569) Vol. 4, Issue. 1, June-2013

Simulation of Single Phase Inverter using PSIMSoftware for Solar P.V. System give ConstantOutput Voltage at Different Solar Radiation

Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah

Abstract:This study investigated the detail function ofinverterin small scale distributed power generation, itsmodelling and related simulation on P-SIM software. Thismodel can be used for photovoltaic application or especially forparticular AC module. In this paper work on three basicrequirements for Inverter Modelling Amplification, Inversionand Voltage regulation under change in atmospheric condition.

1. IntroductionThe overview of single phase inverters developed for

small distributed power generators. The functions ofinverters in distributed power generation (DG) systemsinclude dc–ac conversion, output power quality assurance,various protection mechanisms, and system controls. Uniquerequirements for small distributed power generation systemsinclude low cost, high efficiency and tolerance for anextremely wide range of input voltage variations. Theserequirementshavedriven the inverter development towardsimpler topologies and structures, lower component counts,and tighter modular design. Both single-stage and multiple-stage inverters have been developed for power conversion inDG systems. Single-stage inverters offer simple structureand low cost, but suffer from a limited range of inputvoltage variations and are often characterized bycompromised system performance. On the other hand,multiple-stage inverters accept a wide range of input voltagevariations, but suffer from high cost, complicated structureand low efficiency [1]. Various circuit topologies arepresented, compared, and evaluated against the requirementsof power decoupling and dual-grounding, the capabilities forgrid-connected or/and stand-alone operations [2].and thesimulation of two stage inverter saw a variation in inverteroutput power when there is a small variation in input supplyor variation in solar panel power output due to change insolar radiation during the day. And result discussion.

Brijesh M. Patel is working as Assistant Professor, ADIT, New VallabhVidyanagar, India, [email protected], Kalpesh J.Chudasma and HardikA.Shah are working as Associate Professor, ADIT, New VallabhVidyanagar, India,

2 Discussion on different possible powerconversion topology for PV system or DG system

2.1 Topology of single-phase inverters

DG systems are usually small modular devicesclose to electricity users, including wind turbines, solarenergy systems, fuel cells, micro gas turbines, and smallhydro systems, as well as the relevant controlling/ managingand energy storage systems. Such systems commonly needdc–ac converters or inverters as interfaces between theirsingle-phase loads and sources as shown in Fig. 1[7],which depicts a typical renewable DG system usingphotovoltaic (PV) as energy source. DG inverters oftenexperience a wide range of input voltage variations due tothe fluctuations of energy sources, which impose stringentrequirements for inverter topologies and controls. Functionsof inverters for small DG systems can be summarized asfollow [2, 12].

Fig. 1. Block diagram of a photovoltaic system. [19]

1) Power conversion from variable dc voltage into fixed acvoltage for stand-alone applications or ac current outputfollowing the grid voltage and frequency for grid-connectedapplications. The variable dc voltage can be higher or lowerthan the ac voltage in one system, which is observednormally in a wind-turbine energy system.

2) Output power quality assurance with low total harmonicdistortion (THD), voltage and frequency deviation, andflickering.

3) Protections of DG generators and electric power systemsfrom abnormal voltage, current, frequency and temperatureconditions, with additional functions such as anti islanding



protection and electrical isolation if necessary.

4) Control of DG systems and accomplishment ofcertain objectives such as maximum power extraction fromwind energy, maximum power point tracking (MPPT) ofPV modules, optimum efficiency for fuel cell systems,optimal energy flow control [5], etc.

Based on the electrical isolation between the inputand output, inverters can be classified as isolated invertersor non isolated inverters. While electrical isolation isnormally achieved using transformers, a choice can bemade between using line-frequency transformers as in Fig.2or high-frequency transformers as in Fig. 3. The dc-linkvoltage of inverters for DG systems may vary over a widerange. Depending on the input dc voltage range incomparison to the output ac voltage, inverters can be buckinverters, boost inverters, or buck-boost inverters. It shouldbe noted that although the inverters in Fig. 2 and Fig. 3 arebuck inverters by themselves, the whole topologies actuallyrepresent boost or buck-boost inverters due to PWMoperations and voltage step-up in either low frequency orhigh frequency.

Traditional full-bridge buck inverters are used inmany existing high power applications with bulky andheavy line-frequency transformers. However, modern powerelectronic converters tend to use “more silicon and lessiron.” This leads to the pursuance of compact designs withwide input voltage ranges and improved overall efficiency[3].

A multiple-stage inverter is defined as an inverter with morethan one stage of power conversion, in which mostly one ormore stages accomplish voltage step-up or step-down orelectrical isolation, and the last stage performs dc–acconversion.

1) dc–dc–ac topologies;

2) dc–ac–dc–ac topologies;

3) dc–ac–ac topologies.

These topologies will also be discussed regarding thecapabilities to meet certain challenging requirements of DGresource and ac utility [3,8].

Fig. 2. Traditional buck inverter and line-frequencytransformer[17]

Fig. 3 Multiple-stage inverter with a high frequencytransformer.

2.2 Two-Level PWM Control techniquefor H bridge inverter control

The H-bridge topology inverter is the most popular single-phase converter in various applications, especially inhigher power rating applications. It consists of two armsfig4 and outputs a single-phase AC output voltage, V outto the load. Pulse Width Modulation (PWM) techniques areused to control the switching devices on and off. During lastfew years, PWM technique has been the subject of intensiveresearch and a large variety of PWM control schemes havebeen discussed. Sinusoidal PWM (SPWM) approach is oftenused in single-phase applications.

Fig.4 single-phase H-bridge inverter

Three different sinusoidal PWM switchingschemes are used commonly for two-level single-phaseinverter. They are bipolar PWM scheme, unipolar PWMscheme and modified unipolar PWM scheme [3] Figure 5below shows the bipolar PWM modulation scheme. In



order to generate a sinusoidal AC output with desiredamplitude Vm and frequency f, a sinusoidal controlsignal Vcontrol at a desired frequency f1 is comparedwith a continuous triangular waveform Vcarrier as shown inFigure 5[13,16]

Fig.5 bipolar PWM modulation scheme

When Vcontrol is greater than Vcarrier, the PWMoutput is positive; otherwise the PWM output is negative.The frequency of carrier waveform Vcarrier establishesthe switching frequency s f of the inverter. The modulationindex i m is defined as

where Vcm is the peak amplitude of the control signal,while Vcrp is the peak amplitude of the triangle signal(carrier).

the modulation ratio is defined as:

where f carrier is the carrier frequency.

A unipolar PWM modulation scheme is shown inFigure 6 where the two switch pairs in H-bridgeinverter are not always switched simultaneously as in thebipolar scheme. Instead, the switching of the two arms iscontrolled by two control signals. Therefore, the outputvoltage changes between 0 and +Vd or between 0 and - Vdin half fundamental period. Two control reference signalsare used in this scheme. The output voltage from the bipolarPWM scheme does not have zero state, which means theoutput voltage of the inverter only changes between +Vdand - Vd. This scheme requires only one control referencesignal, but the performance is poor[14]

Fig. 6 unipolar PWM modulation scheme

2.3 Overview of Solar Power ConversionSystem

The power conversion subsystem for a solar powersystem has two main tasks: one is to control the inputterminal conditions to make photovoltaic (PV) modulesoperate at a maximum power point (MPP) and to capturethe maximum power for the sun [7]. The other is toconvert the output dc voltage from solar modules to asuitable ac voltage and meet the utility requirements [5]Therefore, most of the solar power conversion systemsapply two-stage topology. The most common two-stagesystems [6] consist of a dc-dc solar module-connectedconverter and dc-ac PWM inverters as shown in Figure 7[9,15].

Fig 7 two-stage solar power conversion system [11]

2.4 Simulation of single phase inverter

topology

Linear regulator often plays important role in implementingpower supply capable of constant voltage/current control. Italways provides lost of advantage such as low ripplenoise, low EMI, good regulation, easy control strategy.However due to bulky size, low efficiency switch modetechnique has become inevitable development trend forraising the power density, power efficiency and dynamic



F

performance. The full bridge converter is one of the isolatedconverter topology that use in high power rating. The blockdiagram of it is shown in fig 8. The feedback signal ofvoltage is given to control circuit using PI-controllerblock for control and protection purpose.

Fig. 8 Single Phase Inverter Topology with p-sim software

2.5 Closed loop converter control system

Control system should be able to adjust duty cycle in timein order to regulate the output voltage with input voltageand load variation. Voltage mode and current control modecontrol technique adapted to design switching powersupply. As the speed of the processors increase and largeload changes frequently encountered in system transitionfrom one sleep mode to active mode, the faster transientresponse of DC-DC power supply has been moreimportant. The transient response of voltage mode controltechnique, when the input voltage is changing because it hasonly one feedback loop. The input voltage varying after thevariation of output voltage occurs. In fact, the transientresponse of voltage mode control is slow for any variationof power stage. The basic principle of followingcircuits in the boosting up the voltage are, charging &discharging reactive component into a load, controlling thelevel of charge & consequently output voltage by switchingthe DC supply in & out of the circuit at very highfrequencies. They include a freewheeling diode to protectthe switch from inductor’s very reverse current and this alsoensures that the generated inductor energy is applied toload capacitor are connected in parallel with load, to filterthe voltage ripple & to maintain constant output voltage.Inductor is used in series with the load to filter the currentripple.

2.6 Converter control scheme usingPI-controllerThe control scheme essentially consisting ofonly one sensor with simple structure when compared withclassical boost converter which requires both voltage andcurrent sensors. Here, DC voltage of load is fed back andcompared with Vdc reference voltage. If, there is reduced dcvoltage then there is difference between ref. voltage & O/Pvoltage. This difference is in the form of error, which isgiven to PI-Controller. PI- controller stabilizes this error andgive the modulated single output for PWM scheme. Signalsfrom PI- controller is compared with high frequency signalreference signal as shown in fig9[2]

Fig 9 Comparison between Pi Output Signal and Carrier signal

Fig 10 Converter output 230v DC

To set the gain and time-constant there are threemethods given below:

(i) Analytical method(ii) Empirical method(iii) Trial and error method

PI-controller is designed by trial and error method forline and load regulation. Most of industries used this methodfor tuning of PI-controller. PI-proportional integral, whereintegral term yields zero steady- state error in tracingconstant set point & proportional term yields output isproportional to input. Integral control filters higherfrequency sensor noise; it is slow in response to currenterror. On the other hand, the proportional term respondsimmediately to the current error, yet it cannot achievewithout an unacceptably large gain. PI controllerreduces very high transient error. PWM technique is used



for generating gate pulses of IGBTs. The duty cycle isvaried according to output voltage. To increase the outputvoltage increases the duty ratio. Main drawback of thissystem is slow transient response of output voltage. Ifinput voltage changes from 20v to 17v due to solar radiationas shown in table, the output voltage of the converter willalso changes and error will generated accordingly thecontrol circuit and this error signal after comparing withtriangular wave is used for triggering the four IGBT and itwill maintain the output voltage of converter to 230v dcconstant. Now this 230v dc is converted to 230v AC with Aunipolar PWM modulation scheme is shown in Figure6.4where the two switch pairs in H-bridge inverter are notalways switched simultaneously as in the bipolar scheme.Instead, the switching of the two arms in Fig.12 iscontrolled by two control signals. Therefore, the outputvoltage changes between 0 and +230 or between 0 and -230 in half fundamental period as shown in fig13. Twocontrol reference signals are used in this scheme as shownin fig11. and also in table show the variation in outputvoltage and power using this control topology when theinput supply voltage changes due to variation in solarradiation.

Fig 11 switching of the two arms using unipolar PWMmodulation scheme

Fig. 11Switching signal of the two arms of PWM modulation scheme

Table 1 variation in inverter o/p power when there is aSmall variation in input supply

Fig 12 output current and voltage waveform of inverter in p-sim software

2.7 Simulation result and discussion

In fig 12 and table 1 show the simulation result ofinverter with above topology so we can see the variation ininverter output power when there is a small variation ininput supply or variation in solar panel power outputdue to change in solar radiation during the day.

3. Conclusion

These inverter topologies can be used forphotovoltaic applications and particular inverters for theAC-Module. The task for such an inverter is to amplifythe photovoltaic-module low voltage up to the higher-levelvoltage of the grid and to convert it from DC into AC. andmaintain it constant as there is a variation in atmospheric

Vin

D.C

Volt

Delta

Vin

Volt

Vinverter

A.C Volt

IL

Amp

Power

(watt)

Delta

Vinverter

%

Delta

P

%

22 10 % 259.7 1.29 335.01 12.09 25

21.5 7.5 % 252 1.26 317.52 8.87 19

21 5 % 245 1.22 298.9 5.8 12

20.5 2.5 % 237.08 1.18 280.72 2.8 5.6

19.5 2.5 % 230.39 1.15 264.94 0.0462 0.26

19 5% 229.7 1.148 263.69 0.39 0.73

18.5 7.5% 229.35 1.146 262.83 0.54 1.06

18 10 % 230.45 1.152 265.48 0.43 0.06



condition or in solar radiation during the whole day.

4. References[1] Inverters for Single-phase Grid Connected Photovoltaic

Systems - An Overview, Martina Calais, Johanna Myrzik,Vassilios G, School of Engineering, Murdoch University,Murdoch WA 6150, Australia Technical University ofEindhoven, The Netherlands

[2] Muhammad h. Rashid, “power electronics handbook”,academic press, USA

[3] Billy M. T. Ho and Henry Shu-Hung Chung, “An IntegratedInverter with Maximum Power Tracking for Grid- ConnectedPV Systems”, IEEE, china

[4] Liuchen Chang, “Design Of A 400w Single-Phase Buck-Boost Inveter for PV Applications”, Liuchen Chang, Canada

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[6] Mihai Ciobotaru, Remus Teodorescu and Frede Blaabjerg,“Control of single-stage single-phase PV inverter”, Denmark.

[7] A Low Cost Utility Interactive Inverter for Residential PowerGeneration Sangmin Jung, Youngsang Bae, Sewan ChoiHyosung Kim Seoul National University ofTechnology,Dept.of Control and Instrumentation Eng. 172Kongneung-Dong, Nowon-Ku, Seoul 139-743, Korea

[8] Topologies of Single-Phase Inverters for Small DistributedPower Generators: An Overview Yaosuo Xue, StudentMember, IEEE, Liuchen Chang, Senior Member, IEEE,Søren Bækhøj Kjær, Member, IEEE, IEEETRANSACTIONS ON POWER ELECTRONICS, VOL. 19,NO. 5, SEPTEMBER 2004

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[1]Mr. B.M. Patel was born in visnagar, India, in 1986. He received his B.E. degree from L.C.I.T. Bhandu, and M.E. from B.V.M College V.V.Nagar under S.P. University. Presently he is working asAssistant Professorin A.D. Patel institute of technology New V.V Nagar

[2]Mr.H.A.Shah was born in umreth, India, in 1979. He received his B. E.degree from B.V.M, V.V. Nagar, and M.E. from M.S. University,baroda.Presently he is working as Associate Professor in A.D. Patel institute oftechnology New V.V Nagar

[3] Mr.K.J Chudasma was born in umreth, India, in 1974. He received hisB. E. degree from B.V.M, V.V. Nagar, and M.E. from B.V.M. CollegeV.V.Nagar under S.P. University. Presently he is working as AssociateProfessor in A.D. Patel institute of technology New V.V Nagar

7. simulation of single phase inverter using psim software for solar p.v. system give constant...

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