DESIGN PHOTOVOLTAIC SYSTEM FOR GREATER RATHNAPURA WATER

DESIGN AND ANALYZING OF OPTIMIZED SOLAR PHOTOVOLTAIC SYSTEM FOR GREATER RATHNAPURA WATER TREATMENT PLANT D. L.

K. S. KUMARIM.Sc.Eng.

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2018DESIGN AND ANALYZING OF OPTIMIZED SOLAR PHOTOVOLTAIC SYSTEM FOR GREATER RATHNAPURA WATER TREATMENT PLANT D. L. K. S. KUMARIM.Sc.

Eng. Thesis Department of Electrical and Electronic EngineeringFaculty of EngineeringUniversity of PeradeniyaPeradeniya, Sri Lanka 2018This thesis has been submitted to the University of Peradeniya as a partial fulfillment of the requirements for the degree of Master of the Science of Engineering. DECLARATIONI do hereby declare that the work reported in this thesis was exclusively carried out by me under the supervision of Dr.

Prabath J.Binduhewa. It describes the results of my own independent research except where due reference has been made in the text. No part of this thesis has been submitted earlier or concurrently for the same or any other degree. Date:………………………. ……………………………………… Signature of the Candidate Certified by: 1.

Supervisor (Name): Dr. Prabath J.Binduhewa Date:……………………………(Signature): …………………………………ACKNOWLEDGMENT First I would like to express my sincere thanks to my supervisor, Dr. Prabath J.Binduhewa for his passionate instruction and guidance throughout the period. Next I would like to thank my loving mother and specially my loving sister, for providing me with love, support, and encouragement to move ahead during this period.

Further I would like to thank to everyone who help me to gather power consumption data of the Greater Rathnapura Water treatment plant.I also want to acknowledge my colleagues namely Miss. M.

P.P Mithila (Electrical Engineer, International construction consortium (pvt) ltd), who helped me with finding information and the support given to resolve problems encountered during this research work.I also wish acknowledgment to the people who give support direct or indirectly to the research and during the thesis writing.

Once again, thank you very much.ABSTRACTThis thesis “Design and analyzing of optimized solar photovoltaic system for greater Rathnapura water treatment plant” has been submitted to the University of Peradeniya as a partial fulfillment of the requirements for the degree of Master of the Science of Engineering in “Power, High voltage and Energy systems” by Kumari D.L.

K.S (PG/EE/14/MSc/29).Energy generation using photovoltaic panels is increasing rapidly in Sri Lanka.

The government and non-governmental organizations have tried to contribute to more efficient and reliable integration to the industry to address the problem of energy. As per the project “Surya Bala Sangramaya” launched by the Ministry of power and Renewable Energy in collaboration with Sri Lanka Sustainable Energy Authority (SLSEA) Ceylon Electricity Board (CEB) , Lanka Electricity Company (Private) Limited (LECO) PV market is spreading widely in Sri Lanka. The purpose of this work is to provide an algorithm for the design and analyzing of an optimized solar photovoltaic system for grid-connected photovoltaic system.In addition, data of average hourly solar irradiance and environmental temperature in Ratnapura, as well as energy consumption pattern of Greater Ratnapura Water treatment plant were analyzed and implement a tool for design and optimize the system with the commercially available solar panel.

Simulation results are analyzed to validate the proposed system. Finally, the estimated local load demands, as well as simulation results are extracted and analyzed.TABLE OF CONTENTLIST OF TABLESLIST OF FIGURESLIST OF ABBREVIATIONS1.0 IntroductionINTRODUCTIONThe early development of solar technology was started in the 1860s. The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies.

Between 1970 and 1983 installations of photovoltaic systems grew rapidly, but falling oil prices in the early 1980s moderated the growth of photovoltaic from 1984 to 1996. In the mid-1990s, development of both, residential and commercial rooftop solar as well as utility-scale photovoltaic power stations. Worldwide growth of solar PV was driven by European deployment, but has since shifted to Asia, especially China and Japan, and to a growing number of countries and regions all over the world, including, but not limited to, Australia, Canada, Chile, India, Israel, Mexico, South Africa, South Korea, Thailand, and the United States. Worldwide growth of photovoltaic has averaged 40% per year since 2000 and total installed capacity reached 139 GW at the end of 2013 with Germany having the most cumulative installations (35.7 GW) and Italy has the highest percentage of electricity generated by solar PV (7.

0%).Solar power is the conversion of energy in sunlight into electricity. Remote homes can be powered by an off-grid rooftop Photovoltaic (PV) system.  The number of grid-connected solar PV systems has grown into the millions.

PV is rapidly becoming an economically feasible, requiring a relatively low maintenance, low-carbon technology to harness renewable energy from the Sun. The PV systems can be operated in both stand-alone and grid-connected. A stand-alone PV system is an autonomous system that can operate without any connection to the grid and satisfy the design load. These systems are ideal when the grid is either not available or the cost of electricity is too high.

Grid-tie and hybrid systems make up the majority of PV systems currently installed and operating. Hybrid systems allow the addition of batteries for either back-up in case of utility failure, or for demand control such as peak -shaving rates.In Sri Lanka, solar powers have been used for lighting purposes using DC power in small islands. However, during the last decade, Net metering system has become popular. Advances in power electronics industry have also contributed to more efficient and reliable integration of these renewable resources into electric power grids. The electric energy industry introduction of the concept of a smart grid has also led to new technologies such as distributed energy resources (DER) and distributed generation (DG).

As per the project “Surya Bala Sangramaya” launched by the Ministry of power and Renewable Energy in collaboration with Sri Lanka Sustainable Energy Authority (SLSEA) Ceylon Electricity Board (CEB), Lanka Electricity Company (Private) Limited (LECO).The aim of the project is to reduce the Carbon dioxide emissions from thermal power plants by 150000 metric tons per year after 2020.It is expected to add 200 MW of solar electricity to the national grid by 2020 and 1000 MW by the year 2025. In parallel with the above project, reducing prices, solar leasing and other innovative financing methods PV market are spreading widely in Sri Lanka. Three connecting schemes were introduced with above project by CEB and LECO such as net metering, Net accounting, and net plus.

The advantage of solar electricity is that the capital investment can be recovered within 5-9 years depending on the capacity. The power consumption of the Greater Ratnapura Water Treatment Plant (GRWTP) is very high since there are large motors are operating. Installing a PV system would decrease the dependency from the utility supply and will reduce the cost of electricity.PSCAD is software used in this research to integrates and model the proposed PV system. The aim of this research is to design a photovoltaic system for GRWTP while analyzing the cost benefits of the proposed system and to find out the payback time.

2.0 LITERATURE REVIEW 2.1 SOLAR ENERGY2.1.

1: OFF-GRID VS GRID-TIED PV SYSTEMCurrently most of the PV systems are installed in islands which have very little chance of getting connected to the national grid. Off grid systems details installed in Sri Lanka is shown in below.Table N0.2.

1: System capacity of Solar Off grid systems Location System Capacity(kW) Battalangunduwa12Kalpitiya6Euwathiv40 Typical configuration of a rural off grid system is shown in figure 1.Figure 2. SEQ Figure * ARABIC 1: Typical configuration of a rural off grid systemTo reach the goal of “Surya Bala Sangramaya” we need to follow the technology trend of developed PV systems in this regard.

90% of the European PV systems are Grid connected. Following to the world trend of grid tied PV market, country like Sri Lanka have high potential to utilize the solar energy through grid –tied PV systems. System capacity improvement of the provinces of before and after “Surya Bala Sangramaya” is shown in below.Table N0.

2.2: System capacity improvement of Solar PV roof top systems with “Surya Bala Sangramaya” Province Before(kW) After(kW)western 23322 31355.4Southern 3571 6506.6Central 471 5369Sabaragamuwa1187 6869North Western 978 1782North Central 772 861Nothern872 1364Uva243 1652Eastern 410 585Graph N0.2.

1: System capacity improvement of Solar PV roof top systems with “Surya Bala Sangramaya”Table N0.2.3: Ground Mounted Solar PV systems details District Capacity (MW)Hambanthota 31.237 Polonnaruwa 10.000 Vauniya 10.000 Anuradhapura 0.

123 Typical configuration of a grid tied system is shown in figure 2.Figure 2. SEQ Figure * ARABIC 2: Typical configuration of a grid tied system2.1.2 NET METERING, NET ACCOUNTING AND NET PLUSFigure 2.

3: Schematic diagram of a solar systemFigure No: 2.3 shows a schematic diagram of a solar system. Detail about the Net metering, Net accounting and net plus system is given below.Normal Power supply from the grid (CEB) remains as usual.The inverter converts solar current (DC) into AC and make it compatible with normal grid electricity.

Smart meter or Import-Export meter record monthly energy generation (Export) by the solar system and the amount consumed from the grid (Import).No need to change the existing house wiring.No effect to Electrical equipment you are using now.Net metering Net accounting Net plusIf the export is greater than import Excess credited to account Not paying for excessElectricity bill will be rental For the excess CEB and LECO will be paid according to the table 01 For the export CEB and LECO will be paid according to the table 01For the import electricity will be as usualIf the import is greater than export Electricity bill will be deference Electricity bill will be deference Table N0.2.4: Method of paying for the excess electricity Time Period Rs/kWhFor the 1st seven years 22.

00For the 8 – 20 years 15.50-7720627349300However any KVA charges will have to be paid.left233920Figure 2.

4: Electrical layout of Net Metering,Net Accounting InstallationsFigure 2.4: Electrical layout of Net Metering,Net Accounting Installations138454905800604820186150Figure 2.5: Electrical layout of Net Plus Installations0Figure 2.5: Electrical layout of Net Plus Installations2.

1.3 Electricity sector in Sri LankaIn Sri Lanka, Maximum contribution to the electricity generation given by the thermal power plant. Coal power generation about 900 MW from CEB and Oil fired power generation about 1000 MW from CEB and Independent power producers. Total Hydro power generation was 1350 MW from CEB.

Non-Conventional Renewable Energy Capacity (Approximately) is mentioned below.Mini hydro – 293 MWWind – 124 MWBiomass – 23 MWSolar- 1 MWElectricity production using thermal power plant has become a huge environmental issue in the world. It emits Nox, So2 while producing the energy and causes to the green house effects. Electricity production using Solar has low carbon emission, no noise or air pollution. Solar is an environmental friendly and low maintenance, energy production method. Energy sector depend on fossil fuel.

Using solar power it can be reduced. Solar electric power systems can be easily sited at the point of use with no environmental impact. Solar power produces no greenhouse gases, so it does not contribute to global warming.

2.2: OVERVIEW OF GRWTP2.2.1 Location and OrientationGreater Ratnapura Water Treatment Plant (GRWTP) of NWS&DB is located at Rathnapura near to the Rathnapura town. The location map of the Plant is shown in Figure No: 07.

The roof top plan is given in Figure No: 08.center13264Figure 2.6: Location Map of the GRWTP00Figure 2.

6: Location Map of the GRWTP2.2.2 Electricity loads and electricity usage patternLoad pattern of the plant10096511176004738039113085003004185113030001301778111870002437765191770Lighting-1%00Lighting-1%845820182880Motor-45%0Motor-45%4281805186055Other-54%0Other-54%Electricity usage pattern of the GRWTP studied and consumed energy pattern shown in following graph.Graph N0.2.2: Energy consumption pattern of the plant2.

3 PV installation capacityAvailability of solarGraph N0.2.3: Lowest, Medium Peak and Average Irradiance Data Temperature variationGraph N0.2.4: Lowest, Medium Peak and Average Ambient Temperature DataArea(1873.4m2)-203200100965001125220739140Figure 2.

7: Roof top plan of the GRWTP 00Figure 2.7: Roof top plan of the GRWTP 3.0 PV SYSTEM SIZING3.

1 Array Placement schemeFor the system layout the determination of gap between rows is essential to avoid shading from each other. This location Latitude and Longitude was 6.7055o N and 80.

3847o E and Declination angle change -23.45 to + 23.45 throughout the year.

Maximum solar elevation angle can be calculated using the equation (3.1)9334563500DL-DELD00DL-DELD-7810510795Maximum Solar Elevation Angle (E) = 90o+L-D (3.1)E = 120.1555o00Maximum Solar Elevation Angle (E) = 90o+L-D (3.

1)E = 120.1555o-89052128175L = Latitude (+ve for the northern hemisphere and -ve for the southern hemisphere)D = Declination AngleE = Sun Elevation Angle 00L = Latitude (+ve for the northern hemisphere and -ve for the southern hemisphere)D = Declination AngleE = Sun Elevation Angle The resulting gap requirement is shown on below.Tilt AngleIf the Latitude below the 25o, use the latitude times 0.

87.With the solar panel (1.56m × 1.05m) and tilt angle 6o.G = 0.

29 m and H = 0.17m, since the span of the panel is 1.56m.3.

2 Irradiance levelUsing the data for irradiation for the one year, it can be approximated per unit area the irradiance level. For this purpose, by taking lowest, Average and highest irradiance values for each hour (In table 3.1) an estimation of the power being produced per hour is obtained (Please refer appendices for details). Lowest, mean and highest Temperature values with respect to the irradiance for each hour are taken for calculation (In table 3.

2).Table N0.3.1: Irradiance (Lowest, Peak and Average)  Time Lowest Peak Average12-1 AM 0.

00 0.00 01-2 AM 0.00 0.00 02-3 AM 0.00 0.

00 03-4 AM 0.00 0.00 04-5 AM 0.

00 0.00 05-6 AM 0.00 0.00 06-7 AM 26.03 43.67 29.

157-8 AM 143.71 340.3 146.838-9 AM 208.95 600.61 355.329-10 AM 260.34 883.78 520.5610-11 AM 206.06 1025.63 655.5011-12 PM 296.92 1065.93 765.8012-1 PM 247.40 931.57 791.281-2 PM 201.17 887.35 680.532-3 PM 100.01 700.96 488.213-4 PM 93.95 435.23 329.124-5 PM 8.45 164.21 129.765-6 PM 0.00 26.80 13.896-7 PM 0.00 0.00 07-8 PM 0.00 0.00 08-9 PM 0.00 0.00 09-10 PM 0.00 0.00 010-11 PM 0.00 0.00 011-12 AM 0.00 0.00 03.3 Cell TemperatureCell temperature can be calculated using the equation 3.2TCell=TAir+NOCT-20800xS (3.2)TCell = Cell Temperature (oC)TAir =Air Temperature (oC)NOCT =Nominal Operating Cell Temperature (oC)S=Irradiance (mW/cm2)Table N0.3.2: Air Temperature (Lowest, Peak and Average) Time Lowest Peak Average12-1 AM 22.41 24.29 22.271-2 AM 22.59 23.82 22.092-3 AM 22.46 23.44 21.593-4 AM 22.40 21.24 21.204-5 AM 22.20 20.30 20.855-6 AM 21.53 20.00 20.466-7 AM 21.55 19.65 20.127-8 AM 22.19 23.17 20.098-9 AM 23.05 27.20 22.229-10 AM 25.07 28.76 25.0610-11 AM 25.08 29.72 27.2411-12 PM 25.03 29.41 28.4812-1 PM 25.40 30.24 29.151-2 PM 25.93 31.82 29.482-3 PM 25.05 31.40 29.783-4 PM 24.81 30.89 29.484-5 PM 24.25 28.93 28.795-6 PM 24.27 27.68 27.696-7 PM 22.61 26.72 26.267-8 PM 22.10 26.45 25.208-9 PM 21.95 26.16 24.519-10 PM 21.65 26.23 23.9410-11 PM 21.04 25.70 23.5011-12 AM 22.89 24.59 23.013.4 System output in the environmentThe output power of a cell is dependent on the temperature and the irradiance (G). Their effects are related to the photocurrent (Iph) and open circuit voltage (Voc) as given in equations 3.3 and 3.4.Photocurrent is highly dependent on cell temperature and irradiance and hence it is modeled using (3.3).ISC= ISC/STC X G 1 + a (Tcell-TSTC) (3.3) ISC= Photo Generated Current (A)G = Irradiance (kW/m²)TCell= Cell Temperature (oC)TSTC= Cell Temperature in Standard Test Condition (25 oC) a = Manufacturer Specified Temperature Coefficient of IscISC/STC= Short Circuit Current (A) in Standard Test Condition In open circuit condition the whole photo current flows through the diode. Therefore, open circuit voltage with respect to the temperature and irradiance modeled using (3.4).VOC=VOC/STC + b (Tcell-TSTC) (3.4)VOC= Open Circuit Voltage (V)VOC/STC= Open Circuit Voltage (V) in Standard Test Conditionb = Manufacturer Specified Temperature Coefficient of VocThe voltage based MPPT technique is based on the fact that the PV array voltage corresponding to the maximum power exhibits a linear dependence with respect to the array open circuit voltage for different irradiation and temperature levels.Vmpp = Kv.VOC(3.5)Vmpp = Maximum Power Point VoltageVOC= Open Circuit VoltageKv= Voltage FactorThe short circuit current algorithm is the simplest MPPT control method. This technique is also known as constant current method. ISC is the Short circuit current of the PV panel. ISC depends on the property of the solar cells. This relationship can be described by equation 3.6.Impp = KI.I SC(3.6)Impp = Maximum Power Point CurrentI SC= Short Circuit Current KI= Current FactorFill factor can be calculated equation 3.7.FF = KV x KI(3.7)FF = Fill factorThe generated power in the PV system can be calculated using equation 3.8.Power Output = VOC x ISC x FF(3.8)Moving from one module to an array of modules also affects the output power. This is especially true as there exists a mismatch in the performance of the modules in an array strung in series. It is to be noted that when considering an entire array of modules the module with the lowest current Imp will dominate the string. Let us consider an array of n modules indexed as 1, 2, . . . ,n . Module i ?{ 1, 2, . . . ,n} delivers voltage Vimp and current Iimp.Then total power output of an n module array can be calculated using equation 3.9.229362097155min Impii=1nVmpi1?i?n00min Impii=1nVmpi1?i?nTotal power of an n module array = (3.9)The performance of an array is not just affected by module performance mismatch and actual irradiance, temperature effects. Several other factors also determine the performance of a PV system. Panel orientation, panel tilt, dust on the panels, aging of the panels, installation location, electrical losses, soiling losses, inverter efficiency, transmission losses, and module degradation are some of the many factors that determine the performance of a PV system. Total output of the system can be calculated using the equation 3.10.Total power output of the system = Power Output x ?Invx (1- ?loss)(3.10)?Inv = Efficiency of the Inverter (%)?loss= loss Factor for wires, mismatch, dust, Transmission (%)3.5 System CapacityConsidering the collected data of energy consumption of the plant, Irradiance and Air temperature in recent year (2017), Peak energy consumption considered and Average Irradiance data and relevant temperature considered for calculations (see Appendix 01).To the fulfill per day peak energy consumption of the plant (784.83 kWh) PV system capacity would be 170kW (energy generation per day will be 785.2 kWh).To calculate the system capacity developed the solar sizing tool (Figure 3.1). Figure 3. SEQ Figure * ARABIC 1: Developed solar sizing tool Hourly estimated energy that will be produced per day of the plant correlated with the averaged irradiance and relevant temperature values from 170 kW PV system and Peak energy demand (per day) of the plant compare in Graph 3.1.Graph N0.3.1: Peak Energy consumption pattern of the plant and Energy generation pattern using Average irradiance dataMonthly to be forcast3.6 Proposed system3.6.1 System configurationAs figure 3.2 illustrates, the propose system will consist of PV arrays, 17 no of step down DC-DC converter and a grid tie inverter. Buck converter Step down array voltage to a lower voltage and connect to the common DC bus. The GTI inverts the DC power produced by the PV array into AC power aligned with the voltage and power quality requirement of the utility grid.-190536195Control System10kW x 17 No of DC/DC Buck ConvertersGridLC FilterT/FDC/AC InverterDC/DC Buck ConverterPV Arrays00Control System10kW x 17 No of DC/DC Buck ConvertersGridLC FilterT/FDC/AC InverterDC/DC Buck ConverterPV ArraysFigure 3.2: Configuration of the proposed solar system3.6.2 System componentThis system is a grid tied; being in this position the system does not need many components as a stand-alone application. Starting with the most important the Solar panels, the Inverter and the wiring, for installation a specially made brackets are need these will be made to give a tilt angel of 6 degrees.Solar PanelsSun Power systems provide the highest efficient cells in the Market, they have rated a 21% extra power gaining capability from there panels, these panels are 20.3% efficient, for further clarifications the assumed Solar panel data sheet is attached in appendices. A survey carried out by ENF (2007) shows that average of directors in companies they surveyed said SunPower was of the highest quality among others. The panel is well protected and it has a lower temperature coefficient making it suitable for the high temperature summer months. The product warranty of 10 years is a market common, but the 25 years Power warranty is a good choice for long term operation. The panels are certified by IEC 61215, Safety tested IEC 61730.Figure 3.3: Energy production in 25 year comparison with conventional solar panelsThe characteristics of a panel are as follows.Measured at Standard Test ConditionsNominal Power (+5/-0%) 230 WRated Voltage (Vmp)42.8 VRated Current (Imp) 5.84 AOpen Circuit Voltage (Voc)50.9 VShort Circuit Current (Isc)6.2 AMaximum System Voltage IEC, UL 1000 V, 600 VTemperature CoefficientsPower(Pmpp)–0.30% /°CVoltage (Voc) –125.6 mV/°CCurrent (Isc)3.5 mA/°CSeries Fuse Rating20 AWeight 15 kg, 33 lbsSolar Cells 72 Monocrystalline Maxeon Gen III Cells Front Glass High Transmission Tempered Anti-Reflective Junction Box IP-65 rated Frame Class 1 black anodized, highest AAMA RatingTemperature – 40°F to +185°F (– 40°C to +85°C)Solar panel connecting arrangement1504953175040 no of PV Module-series in 1 array 0040 no of PV Module-series in 1 array 345567019367524841203460752274570155575172212015557511696701555756076951555755524515557531127701270019316701714513792201714581724517145264795171452626995142557517 no of array connect to an Inverter0017 no of array connect to an Inverter15049536182301504952818130457203175635457203937635255270412750059817039376358077204127500116014539376351369695412750017125953937635192214541275002265045393763524745954128135310324541230553446145397573534556702337435311277024847552484120248983522745702299335193167024892001722120229933513792202489200116967022993358172452489200607695229933526479524892005524522993353455670176593531127701913255248412019183352274570172783519316701917700172212017278351379220191770011696701727835817245191770060769517278352647951917700552451727835345567012325353112770137985524841201384935227457011944351931670138430017221201194435137922013843001169670119443581724513843006076951194435264795138430055245119443534556706515103112770798830248412080391022745706134101931670803275172212061341013792208032751169670613410817245803275607695613410264795803275552456134103455670609603112770208280248412021336022745702286019316702127251722120228601379220212725116967022860817245212725607695228602647952127255524522860Figure 3.4: Solar panel connecting arrangementII Grid tried InverterThe major component of grid tried PV system is the GTI which along with regulating the voltage and current received from solar panels ensures that the power supply is in phase with the grid power and which allows the system to be connected to the grid. The inverter is controlled using the terminal quantities. The controller of the inverter is responsible for keeping voltage and frequency within the given limits. It keeps the sinusoidal output synchronized to the grid frequency (nominally 50Hz).A transformer is then used to remove any residual dc current injection. The voltage of the inverter output needs to be variable and a touch higher than the grid voltage to enable current to supply excess power to the utility.Grid voltage range=400?3?6%Grid voltage range=217.1-244.7Inverter output voltage range= Grid voltage X 1.2 =260.52 – 293.64Following equation (3.11) gives the line-to-line output voltage of an inverter (VLL,rms) and DC link voltage (Vd), where ma is the modulation index 6.VLL,rms = 0.612 ma Vd(ma?1)(3.11)In this equation the modulation index is considered (ma = 1).For the Lowest inverter output voltageMaximum DC link voltage would be = 260.52 x ?3.612 = 737.3v.For the Highest inverter output voltageMaximum DC link voltage would be= 293.64 x ?3 .612 = 831v.If the DC link voltage consider as the 737.3v, Then for the Highest inverter output voltage ma = 1.127. If the DC link voltage consider as the 831v, Then for the Lowest inverter output voltage ma = 0.887.Modulation index (ma ) shall be ?1.6So, DC link voltage select as 831v.As the simplified schematic diagram in figure 3.5, the operation principle of a grid tied inverter with three power stages.Figure 3.4: schematic diagram of grid tied inverterAt the first stage, the DC input voltage is step down by the buck converter by a combination of Pulse Width Modulation circuit, Insulated Gate Bipolar Transistor (IGBT) switch input capacitor Cin, output capacitor Cout, Inductor L and free-wheel diode D1 as shown in figure 3.5.Voc of the panel = 50.9 VThere are 40 no of series connected PV panels in one array. 17 no of arrays connecting to the 170 kW inverter in parallel. The PV panels connect as figure 3.4.DC-DC Buck ConverterThe relationship between the input voltage ,output voltage and duty ratio given in equation (3.12).Duty Ratio, D=VoutVin (3.12)Duty ratio would be 0.41.Table N0.3.3: Buck converter specificationParameter ValuePower/(kW) 10Output Voltage/(V) 831Inductor current ripple in terms of average inductor current/(%) 30Input voltage/(V) 1385-2077.5Switching frequency/(kHz) 10,400khzOutput voltage ripple in terms of output voltage/(%) 2%,10mv,50mvInput Voltage, Vin=2036VThe inductor value and its peak current are determined based on the specified maximum inductor current ripple.We can obtain inductor value using equation 3.13. 2L=Vo1-Dfs?iind(3.13)L=831×1-0.4110×103×3.61L=13.6x 10-3HVo=Output voltage of the buck converter (V)D= Duty Ratiofs=Switching frequency (Hz)?iind= Inductor current ripple in terms of average inductor currentInductor current is 12.034A. The switching frequency is selected at 10 kHz and the current ripple will be limited at 30 % of maximum load. Then ripple current would be 3.61 A. The inductor peak current is then:Ipk=Iout+?Iind2(3.14)Ipk=Iout+30% x Iout 2=1.15 x Iout=1.15 x10000 831=13.839AIpk=Inductor Peak current (A)Iout =Output Current (A)Inductor must sustain a peak current of 14A without showing saturation.Using equation 3.13 and using the data given in Table 3.3 the inductor value should be 13.6mH. Practically a 13mH inductor will have to be chosen.Inductor L provides a smooth continuous output current waveform to the load on the output side. The input current of the buck converter is varied in large range and switched current emits noise to the system. For the overcome those problems, Cin. capacitor value design so that to reduce the ripple voltage amplitude to acceptable levels.Cin(min)=D x 1-DIout fs x ?vout(3.15)=0.577 x 1-0.577 x17.3310x103x .02=21.15mFCin (min) = Required Minimum Input Capacitance (F)fs= Switching Frequency (Hz)Iout =Output Current (A)?vout= Output Voltage Ripple in terms of Output Voltage (%)Diode (D1) is selected to avoid reverse voltage of the capacitor and as it can dissipate the power.This power can be calculated using equation 3.16.Pdiode=(1-D) x Iout x VD(3.16)VD =Voltage drop across the Diode, 0.3v for Schottky diode and 0.7v for silicon diode MOSFET is selected to minimize the power dissipation and temperature rise. Switching losses is main reason of the power dissipation. Switching losses occurs due to on/off transition.Output capacitance (Cout) is selected to minimize the overshoots and voltage ripple in the output. Cout can be calculated using the equation 3.17.Cout=Vout 1-Dfsw 2x 8 x ?vout x L(3.17)=1-0.41×831104 x 104 x 8 x .02x 13.6 x10-3 =2.26 mFThree Phase InverterTransformerTransformers in grid connected PV systems act as galvanic isolation and can be used for voltage adjustment if required. Most commonly used method for galvanic isolation is using the conventional low frequency transformer. But this has some disadvantages like high weight, high cost, additional losses and non-unity power factor, especially at low load conditions. One way to omit the bulky transformer is to use high frequency transformers. Another emerging topology is the transformer-less inverter which has less overall losses, lighter in weight and it is cheaper than conventional grid frequency transformer topology. In addition, topology without transformer increases the control over the system voltage and power since transformer limits the control of the grid current. One way to omit the bulky transformer is to use high frequency transformers. Another emerging topology is the transformer-less inverter which has less overall losses, lighter in weight and it is cheaper than conventional grid frequency transformer topology. In addition, topology without transformer increases the control over the system voltage and power since transformer limits the control of the grid current.AC FilterGridControl algorithmPv converter control-4DC-DC converter is used for Maximum Power Point Tracking (MPPT) by controlling the voltage across the DC link capacitor and the PV array. This is achieved by first creating a reference voltage that is then supplied to a PI controller which creates switching signals that force the voltage across the PV array to follow the reference voltage.These two stages are discussed next.2) DC-DC Converter ControlThree phase InverterTransformerUtility grid8.0 APPENDICES APPENDIX ATime T ambirradiance (W/m2)-G TC IscVOC power output from panel power output from the system in a day-kWh ?InvInverter output (kWh) Power output after losses Output in a month Output in a year 96% 4% 30 days  12-1 AM 22.27 0 22.274 0.00 51.24 0.0000 0.00 0.0 0.0 – – 1-2 AM 22.09 0 22.088 0.00 51.27 0.0000 0.00   0.0 0.0 – – 2-3 AM 21.59 0 21.592 0.00 51.33 0.0000 0.00   0.0 0.0 – – 3-4 AM 21.20 0 21.204 0.00 51.38 0.0000 0.00   0.0 0.0 – – 4-5 AM 20.85 0 20.849 0.00 51.42 0.0000 0.00   0.0 0.0 – – 5-6 AM 20.46 0 20.461 0.00 51.47 0.0000 0.00   0.0 0.0 – – 6-7 AM 20.12 29.15 20.958 0.18 51.41 7.2538 4.93   4.7 4.6 137.09 1,645.03 7-8 AM 20.09 146.83 24.307 0.91 50.99 36.6734 24.94   23.9 23.1 693.07 8,316.90 8-9 AM 22.22 355.32 32.431 2.26 49.97 89.4530 60.83   58.4 56.4 1,690.53 20,286.39 9-10 AM 25.06 520.56 40.027 3.40 49.01 131.8797 89.68   86.1 83.1 2,492.34 29,908.05 10-11 AM 27.24 655.50 46.088 4.36 48.25 166.7821 113.41   108.9 105.1 3,151.94 37,823.29 11-12 PM 28.48 765.80 50.500 5.17 47.70 195.3792 132.86   127.5 123.1 3,692.38 44,308.62 12-1 PM 29.15 791.28 51.900 5.37 47.52 202.0396 137.39   131.9 127.3 3,818.26 45,819.10 1-2 PM 29.48 680.53 49.045 4.57 47.88 173.4733 117.96   113.2 109.3 3,278.40 39,340.76 2-3 PM 29.78 488.21 43.815 3.23 48.54 124.0278 84.34   81.0 78.1 2,343.95 28,127.35 3-4 PM 29.48 329.12 38.938 2.14 49.15 83.3101 56.65   54.4 52.5 1,574.44 18,893.29 4-5 PM 28.79 129.76 32.525 0.83 49.95 32.6689 22.21   21.3 20.6 617.40 7,408.75 5-6 PM 27.69 13.89 28.087 0.09 50.51 3.4831 2.37   2.3 2.2 65.82 789.90 6-7 PM 26.26 0 26.256 0.00 50.74 0.0000 0.00   0.0 0.0 – – 7-8 PM 25.20 0 25.197 0.00 50.88 0.0000 0.00   0.0 0.0 – – 8-9 PM 24.51 0 24.508 0.00 50.96 0.0000 0.00   0.0 0.0 – – 9-10 PM 23.94 0 23.941 0.00 51.03 0.0000 0.00   0.0 0.0 – – 10-11 PM 23.50 0 23.504 0.00 51.09 0.0000 0.00   0.0 0.0 – – 11-12 AM 23.01 0 23.006 0.00 51.15 0.0000 0.00   0.0 0.0 – – 785.2 23,555.62 282,667.41 Low Peak Ave required kwh per day 534.72 784.83 643.96

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