Design of 50 MW Grid Connected Solar Power Plant

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Design of 50 MW Grid Connected Solar Power Plant

Krunal Hindocha1 B.TECH Electrical Engineering Indus University, Ahmedabad

Gujarat, India

Dr. Sweta Shap

Asst. Professor

Indus University, Ahmedabad Gujarat, India

Abstract-This paper aimed at developing a convectional procedure for the design of large-scale (50MW) on-grid solar PV systems using the PVSYST Software and AutoCAD. The output of the 50MW grid-connected solar PV system was also simulated using PVsyst software and design of plant layout and Substation to transmit it to 132Kv Busbar using AutoCAD was done with all standard measures. The project began with a collection of databases of various renewable energy systems components from different producers. In this paper the standard procedure developed was affirm in the design of a 50MW grid connected solar PV. This paper contains the different diagrams and single line diagrams that are required for the design of 50MW grid connect solar power plant.

Key words: Solar power plant, power system, Plant Layout, Substation, Substation design, AutoCAD Design, PVsyst performance prediction.

  1. INTRODUCTION

    Now days conventional sources are rapidly depleting. Moreover, the cost of energy is rising and therefore solar energy is one of the most economical and exploitable renewable sources of energy that can be harnessed for generation of power. There are several advantages of using solar energy like low establishment period, no raw material expenses, non-polluting and renewable form of energy, etc. India has very good conditions for the development of photovoltaic solar power systems due mainly the geographical location and it receives solar radiation almost throughout the year, which amounts to 3000 h of sunshine. This is equal to more than 5000 trillion kW h. Almost all parts of India receive 47 kW h of solar radiation per sq meters. The country's solar installed capacity reached 34.045 GW as of 31 January 2020. The Indian government had an initial target of 20 GW capacity for 2022, which was achieved four years ahead of schedule. In 2015 the target was raised to 100 GW of solar capacity (including 40 GW from rooftop solar) by 2022, targeting an investment of US$100 billion. India has established nearly 42 solar parks to make land available to the promoters of solar plants. Photovoltaic modules or panels are made of semiconductors that allow sunlight to be converted directly into electricity. These modules can provide you with a safe, reliable, maintenance-free and environmentally friendly source of power for a very long time. A successful

    implementation of solar PV system involves knowledge on their operational performance under varying climatic condition and also the adequate knowledge of overall plant

    layout design and design of substation with an appropriate rating of all the equipment used in the plant.

    1.1 SYSTEM DESIGN AND OBJECTIVE

    A study was conducted for optimise Design of 50MW solar power plant considering all Electrical regulation and standards. The general objective in designing a Solar Power Plant to adequately match the capabilities to the load requirements of the consumer, at a minimum cost of the system to the consumer. In order to accomplish this, the designer will need to know the following types of questions about the system.

    (1) Power Requirements, (2)Solar Data Availability, (3)Type and Size of Solar Power Plant Required, (4) Cost of Energy Produced, (5) Solar Power Viability, (6) System Characteristics, (7) System Requirement, (8) Evaluation Criteria, (9) Design Optimization, (10) Economic Viability and (11) Prospects of Cost Reduction.

  2. DESCRIPTION OF SOLAR- PV GRID SYSTEM Photovoltaic (PV) refers to the direct conversion of sunlight into electrical energy. PV finds application in varying fields such as Off-grid domestic, Off-grid non-domestic, grid connected distributed PV and grid-connected centralised PV. The proposed 50Mw AC is a utility scale grid interactive PV plant.

    Fig 2.1 Overview of typical Solar PV project

    Fig 2.1 Overview of typical Solar PV project

    2.1 SOLAR PLANT DC COMPONENTS

    • Solar PV modules

      A PV cell is the principal building block of a solar PV plant. Basically, a semi-conductor, PV cells convert sunlight into useful Direct Current (DC) electrical energy. PV cells are small in size and capable of generating only a few Watts (W) of energy. However, PV plants are highly modular (i.e.) modules can be combined together to generate power ranging from a few watts (W) to tens of megawatts (MW). Due to the electrical properties of PV cells, their manufacturing is restricted to a handful of raw materials. Each material has its unique characteristics which impact PV module performance, manufacturing process and cost. PV cells may be based on either wafer (manufactured by cutting wafers from a solid ingot block of material) or thin film material (which is deposited onto low-cost substrates).Module Structures allow PV modules to be securely attached to the ground at a fixed tilt angle, or on sun-tracking frames which orient sun. PV cells can further be characterised according to the long-range structure of the semiconductor material used:

      Fig 2.2 Classification of PV Technology

      Fig 2.2 Classification of PV Technology

    • Inverter

    Inverters are solid state electronic devices. They convert DC electricity generated by the PV modules into AC electricity. Inverters can also perform a variety of functions to maximise the output of the plant. These range from optimising the voltage across the strings and monitoring string performance to logging data, and providing protection and isolation in case of irregularities in the grid or with the PV modules.

    There are two broad classes of inverters:

    1. String Inverters ii) Central Inverter

      Considering all the losses in inverter from DC to AC, in cables and other transmission losses Solar plant will be designed with 45% overloading of inverter

  3. GENERAL LAYOUT AND DESIGN OF DC PART OF

    50MW SOLAR PLANT

    • Before Making layout of the Solar power plant, study and analysis is done of the given land.

    • study of the proposed site through satellite images to assess the suitability of the site for development of a 50MWAC solar PV plant is done. Also, by the help of PVsyst software all land analysis and generation prediction are done of the given land.

    • Thus, by all the analysis and study it was concluded that for Design of 50Mw Solar plant components to be used are:

      1. 0Wp Solar Module

      2. 0Kw String Inverter (with 45%overloading)

    • Array of Module that is a set of Table is of 2×16

    • Approximately 250 Acers of land will be used to place a 50Mw Solar power plant.

      • As mentioned above per Module is of 330wp, and each table have such 32 modules so per Table capacity=10.56K

      • For 50 Mw plant, one Block of 858 tables having capacity of 6.25Mw is selected. So, total such 8 blocks

        are required to reach 50Mw AC

      • As mentioned above 160Kw inverter is used in this 50Mw plant. But overloading of 45% is considered so per Inverter capacity would be 160*1.45= 232 DC

      • Number of inverters for 50Mw plant = 312 units

      • Total inverter capacity of plant: 312*232=72384Mw DC

      • AS per table is of 10.56 Mw, total number of tables in 50Mw plant will be 6864 units

      • As mentioned above per Module is of 330wp, and each table have such 32 modues so per Table capacity=10.56K

      • For 50 Mw plant, one Block of 858 tables having capacity of 6.25Mw is selected. So, total such 8 blocks

        are required to reach 50Mw AC

      • As mentioned above 160Kw inverter is used in this 50Mw plant. But overloading of 45% is considered so per Inverter capacity would be 160*1.45= 232 DC

      • Number of inverters for 50Mw plant = 312 units

      • Total inverter capacity of plant: 312*232=72384Mw DC

      • AS per table is of 10.56 Mw, total number of tables in 50Mw plant will be 6864 units

      • Layout of the tables on the given land is done with a standard measurement. Such that shadows are avoided of the surrounding tables or other structure.

        Horizontal distance between 2 tables = 0.100m Vertical distance between 2 table = 3.5860m Pitch = 7.500m

          1. STUDY OF ONE BLOCK OF 6.25 MW:

            Each block consists of total 858 tables and 39 inverters. So, for per inverter 22 tables are connected. The grouping of tables is done 22 table in one group connected to one inverter. Total such 8 blocks are made for 50Mw plant.

            Per block – 6.25Mw

            Inverter – 160Kw(45%overloading)

            Therefore, 6.25 / 0.160 = 39 Number of inverters per block Per Inverter capacity 22 tables

            So, for total 39 inverters in one block and total tables in one block 858 units

            Per block – 6.25Mw

            Inverter – 160Kw(45%overloading)

            Therefore, 6.25 / 0.160 = 39 Number of inverters per block Per Inverter capacity 22 tables

            So, for total 39 inverters in one block and total tables in one block 858 units

            Fig 3.1 Single Block layout

            Fig 3.1 Single Block layout

            EQUIPMENTS

            QUANTITY

            TABLES

            6864 UNITS

            INVERTERS

            312 UNITS

            IDT STATION

            8

            BLOCKS

            8

            EQUIPMENTS

            QUANTITY

            TABLES

            6864 UNITS

            INVERTERS

            312 UNITS

            IDT STATION

            8

            BLOCKS

            8

          2. OVERALL DESIGN OF 50MW SOLAR POWER PLANT

            132/33Kv substation

            132/33Kv substation

            Fig 3.2 50MW Solar plant Block layout

            BLOCK

            COLOR IDENTIFICATION

            BLOCK 1

            ORANGE

            BLOCK 2

            YELLOW

            BLOCK 3

            BLUE

            BLOCK 4

            GREEN

            BLOCK 5

            LIGHT BLUE

            BLOCK 6

            PURPLE

            BLOCK 7

            RED

            BLOCK 8

            LIGHT BLUE

            • Hence, by standard dimension and land allocated all the tables, Inverter and IDT (Inverter Duty Transformer) are place. Now DC cables are to be placed from every inverter to IDT in an optimise way in which minimum cable are stretched so as to set minimum DC cable losses and minimum digging work.

            • In Inverter DC power from solar generation is inverted to AC power which is collected and pass to the Inverter Duty Transformer. By the help of LT cable power from inverter to IDT is transferred where power is stepped up by the transformer. After step up using HT cable it is passed to 33kv switchgear.

    HT CABLES

    HT CABLES

    33KV SWITCHYARD

    33KV SWITCHYARD

    INVERTER DUTY TRANSFORMER

    5/6.25 MVA,

    33KV/0.800KV/0800KV

    LT CABLES

    INVERTER DUTY TRANSFORMER

    5/6.25 MVA,

    33KV/0.800KV/0800KV

    LT CABLES

    Fig 3.3 Inverter duty transformer layout

    Fig 3.3 Inverter duty transformer layout

      1. STRING INVERTER CONNECTION

        For 160kw inverter, Huawei 185kTL is selected. (Datasheet of this inverter is provided at the end) As input capacity of this inverter is 18, 4 Y connectors will be used to connect the connection of 22 tables with an Inverter.

        For 160kw inverter, Huawei 185kTL is selected. (Datasheet of this inverter is provided at the end) As input capacity of this inverter is 18, 4 Y connectors will be used to connect the connection of 22 tables with an Inverter.

        Fig 3.4 String Inverter Connection diagram

        Fig 3.4 String Inverter Connection diagram

      2. INVERTER TO IDT CONNECTION DIAGRAM

    Fig 3.5 String inverter to IDT connection diagram

    Fig 3.5 String inverter to IDT connection diagram

    Equipment

    Ratings and Type

    Inverter Duty Transformer (IDT)

    5/6.25 MVA

    33kv / 0.800kv/0800kv Dy11y11 ONAN /ONAF type

    MCCB

    400A ,3P ,30kA@800v AND 32A,3P,30kA

    Auxiliary Transformer

    10kVA, 800/415V, DYn11

    Cable

    1.9/3.3kv, 1Rx3Cx120 sq mm

    1.9/3.3kv, 1Rx3Cx300 sq mm

    19/33kV, 1Rx3C185 sq mm

  4. DESIGN OF AC PART OF 50MW SOLAR POWER PLANT

    Up till now, DC portion of plant was discussed that is up to IDT. After inverting the power from DC to AC power it is to be step up so as to meet the voltage level and frequency of the line grid where the generated power is to be transferred. In AC portion of plant voltage level is quite higher so lots of protecting systems are required. In the power plant most important and costliest equipment is transformer which is to be protected first.

    Following are the electrical equipment used in the substation for protecting and metering purpose:

    1. MV Switchgear

    2. Bus-Bar Schemes

    3. Switchyard

    4. Circuit Breakers

    5. Isolators

    6. Instrument Transformers

    7. Surge Arresters

    8. Insulators

    9. Metering

    10. Earthing System

    11. Lightning Protection

  5. SINGLE LINE DIAGRAM (SLD)

      1. SLD OF 33KV PANEL

        Power in IDT after step up to 33Kv it is passed to 33Kv switchgear panel. Here power is pass through the protecting system before transferring to 132kv Substation. Below SLD shows the flow of power in 33kv panel.

        In the given panel surge arrester is connected to protect from any short period surge power. Next comes CT for metering and protection. Then circuit breaker is placed to break the circuit in case of fault. Further on PT is placed to measuring and protection. From this power is transferred to main 33Kv panel.

        Fig 5.1 33Kv panel Single line diagram

        Fig 5.1 33Kv panel Single line diagram

      2. GENERAL SUBSTATION SLD

        As discussed above, substation is equipped with the rated and fast responding protection equipment to make the smooth flow of power without any breakdown due to faults.

        Fig 5.2 Substation general Single line Diagram

        Fig 5.2 Substation general Single line Diagram

      3. 132 KV / 33KV POOLING SUBSTATION

        Fig 5.2 132Kv/33Kv pooling substation SLD with

        Metering M1

        Fig 5.2 132Kv/33Kv pooling substation SLD with

        Metering M1

      4. 132 KV SUBSTATION SLD

    Fig 5.4 Symbols and Abbreviations

    Fig 5.4 Symbols and Abbreviations

    Fig 5.3 132Kv substation SLD with Metering M2

    Fig 5.3 132Kv substation SLD with Metering M2

    M1 = Energy values in ABT Meter at 132kv plant end. M2 = Energy values in ABT Meter at 132kv Remote end. Total Losses (L) = M1-M2

  6. SIMULATION USING PV SYST SIMULATION SOFTWARE

    Data obtained for irradiation on collector plane, PV modue and inverter specifications and plant configuration are input into the PV modelling software PV Syst to calculate DC energy generated from the modules in hourly time steps throughout the year. This direct current is converted to AC in the inverter. A number of losses occur during the process

    of converting irradiated solar energy into AC electricity fed into the grid. The losses may be described as a yield loss factor. They are calculated within the PV modelling software and calculated from the cable dimensions.

      1. MONTH-WISE ENERGY YIELD PREDICTION (P50)

        Table: Month-wise breakup of P50 energy yield

        Month

        50 MW

        Project Total MWh Generation

        January

        6,872

        February

        9,142

        March

        11,923

        April

        11,927

        May

        11,624

        June

        9,510

        July

        8,064

        August

        9,182

        September

        9,426

        October

        10,030

        November

        8,387

        December

        7,440

        Total Estimated MWh Generation

        1,13,527

      2. GENERATION AND CAPACITY UTILISATION FACTOR (CUF)

        The Capacity Utilization Factor (CUF) also known as Plant Load Factor (PLF) of a PV power plant (usually expressed as a percentage) is the ratio of the actual output over the period of a year and its output if it had operated at nominal power the entire year, as described in the formula below.

        CUF(AC)= Energy Generated per annum (MWh) / (8760 x Installed AC Capacity in MW)

        The Year 1 Generation and aggregate CUF (AC) on cumulative project capacity is as below:

      3. PERFORMANCE RATIO

    The quality of a PV power plant may be described by its Performance Ratio (PR). Usually expressed as a percentage, can be used to compare PV systems independent of size and solar resource.

    The PR is expressed as:

    % PR = (Energy generated per annum x 100%) / (Installed Capacity x Plane of Array Irradiation)

    By normalising with respect to irradiation at Standard Temperature Conditions (STC), the PR quantifies the overall effect of losses on the rated output and allows a comparison between PV plants.

    Expected Performance Ratio (PR)

    50 MW

    Project Total

    % PR of Year 1

    80.70 %

    Year 1 Generation and CUF

    50 MW

    Project Total

    P90 Generation

    107,596 MWh

    P90 % CUF (AC)

    24.56 %

    P75 Generation

    102,246 MWh

    P75 % CUF (AC)

    23.34 %

    P50 Generation

    113,527 MWh

    P50 % CUF (AC)

    25.92 %

    Fig 6.1 Normalized production per installed kwh

    Fig 6.1 Normalized production per installed kwh

    Fig 6.2 Performance ration Pr

    Fig 6.2 Performance ration Pr

  7. CONCLUSION

    Hence a study was concluded for 50MW on grid Solar power plant. Concluding the overview of solar plant with all the necessary components of DC as well as for AC. With all this analysis a design of 50MW on grid solar power plant was done using AutoCAD. Designs included the plant layout and all the electrical diagrams with electrical standard measures. Also, using PVsyst software plant efficiency and generation prediction was calculated which comes out to be 80.70% for 1 year.

    Also, after studying whole plant and its procedure to develop it, some of the research study was done along with this design which can be helpful in future to increase the efficiency of any solar plant. Firstly, using the Black silicon in manufacturing of PV module will increase the module efficiency as black silicon trap and hold maximum solar radiations. And other idea can be implemented in future of Agro Solar plant which include the agriculture of herbs on a cultivated land also can fix solar plant both simultaneously

    which is said to be Agrosolar plant. Also updating a technology in software used in designing the plant which can reduce man-work and software can calculate and design its own plant design by knowing land coordinates and plant capacity required.

  8. REFERENCES

    1. https://en.wikipedia.org/wiki/Solar_power_in_India

    2. Vasanth Kumar, Dr. S. Kumarappa, Dr. H. Naganagouda Design and Development of 5MW Solar PV Grid Connected Power Plant Using PVsyst.

    3. Performance evaluation of 10 MW grid connected solar photovoltaic power plant in India (B. Shiva Kumar, K. Sudhakar)

    4. Elhodeiby, A.S., Metwally, H.M.B., Farahat, M.A., 2011. Performance analysis of3.6 kW Rooftop grid connected photovoltaic system Egypt. In: InternationalConference on Energy Systems and Technologies, Cairo, Egypt, CEST 2011,1114 March. Goura, R., 2015. Analyzing the on-field performance of a 1-641 megawatt-grid -tied PV system in South India. Int. J. Sustainable Energy 34, 19.

    5. IEEE Standard Definitions of Terms for Solar Cells, 1999.

    6. H.Mithavachan,Anandhi Gokhale and J.Srinivasan performance assessment of 3MW scale grid connected solar plant at kolar,Karnataka.August 2011

    7. Design on AutoCAD

    8. Output performance on PVsyst

  9. TECHNICAL DATASHEET

    1. SOLAR MODULE DATASHEET

      Type

      String

      Max. Input Voltage

      1500V

      Max. current per MPPT

      26A

      Max. Short circuit current per MPPT

      40A

      Start voltage

      550V

      MPPT operating voltage range

      500V-1500V

      Nominal input voltage

      1080V

      Number of inputs

      18

      Number of MPP trackers

      9

      Nominal Ac Active power

      175kw @ 40°C

      160kw @50°C

      Max. AC Active power

      185kw

      Nominal Output voltage

      800V

      Nominal output current

      126.3 @ 40°C

      115.5 @50°C

      Max. Output current

      134.9A

      Max. total Harmonic Distortion

      < 3%

      Dimension

      1035x700x365mm

      Weight

      84kg

      Operating Temp. Range

      -25°C ~ 60°C

      Type

      String

      Max. Input Voltage

      1500V

      Max. current per MPPT

      26A

      Max. Short circuit current per MPPT

      40A

      Start voltage

      550V

      MPPT operating voltage range

      500V-1500V

      Nominal input voltage

      1080V

      Number of inputs

      18

      Number of MPP trackers

      9

      Nominal Ac Active power

      175kw @ 40°C

      160kw @50°C

      Max. AC Active power

      185kw

      Nominal Output voltage

      800V

      Nominal output current

      126.3 @ 40°C

      115.5 @50°C

      Max.Output current

      134.9A

      Max. total Harmonic Distortion

      < 3%

      Dimension

      1035x700x365mm

      Weight

      84kg

      Operating Temp. Range

      -25°C ~ 60°C

    2. STRING INVERTER DATASHEET

Characteristics

Value

Type

Polycrystalline

Nominal Power (PMPP)

330Wp

Voltage at Pmax (VMPP)

37.71V

Current at PMax (IMPP)

8.75A

Open Circuit Voltage (VOC)

46.40V

Short Circuit Current (ISC)

9.24A

Module Efficiency

16.8%

Temperature range

40°C to +85°C

Dimensions Module Area Weight

1,956mm x 992mm x 40mm 1.94m2

26.5kg

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