Indian Institute of Technology Gandhinagar, India Integration of Distributed S olar PV Generations into S econdary Distribution Grid Dr. N M Pindoriya Assistant Professor Electrical Engineering IIT Gandhinagar, Gujarat Email: naran@iitgn.ac.in Cable Modeling Load Modeling Load Pattern SPV Data Loggers Data DPF Intermittent SPVs Compensation Load variation Unbalancing Voltage/Current Profile Losses Energy statistics SPV Impact Results
Electricity Market Operation in India NHPC NTPC NPCIL DISCOMS IPPs Open access CPPs Reliance TATA consumers Adani DISCOMs DISCOMS Traders Retails/large consumers CPPs Open access consumers State Gens. Long Term Market Medium Term Market Bilateral Transaction Short Term Open Access Collective Transaction Day Ahead Transaction Contingency Transaction 12-25 Yr 3months -3 Years 3 month ahead Day Ahead ahead After Clearance of PX On the day of operation System DISC operation Injections/drawals adjustment OMS Balancing Market ( UI ) ( Real Time Operation ) 1
Motivation: ABT Capacity Charges Fixed costs comprising of interest on loan and working capital, return on equity, O&M expenses, insurance, taxes and depreciation Dependent on the availability of the plant Variable Charges Energy charge charged as per the fuel consumption Dependent on the schedule of the day and not on the actual generation Charges of Deviation (COD) Payment for deviations from schedule Dependent on system frequency Generators declare capability Distributors submit requisition Participants can revise schedules New schedule comes into application 1: am 11: am 3: pm 5: pm 1: pm 11: pm 12: am RLDCs communicate RLDCs prepare RLDCs issue respective shares to schedules final schedules the distributors 2
Motivation: UI/Charges of Deviation Known as Unscheduled Interchange (UI) Charges till 17 th Feb 214 Varies inversely with system frequency No over drawl is allowed. Overdrawl @ 16.48 Rs / KWh i.e. 1% additional charge of Freq 49.7 Hz Frequency range 49.7 49.75 49.8 49.85 49.9 49.95 5. 5.5 5.1 Rate in Rs per KWh 8.24 6.99 5.94 4.9 3.86 2.82 1.78.. Under drawl / over injection Penalty @ 1.78 per KWh 3
Power Scenario in India All India Power Installed Capacity (as on 31 st July 214) Nuclear; 478; 2% Hydro; 4799; 16% Waste to Power, 17, % Solar Power, 2753, 9% Bio Power, 446, 12% Thermal; 172986; 69% RES; 32424; 13% Small Hydro Power, 3826, 12% Wind Power, 21693, 67%
Power from Renewable Energy Sources RE based power generation : ~ 2% growth in last 5 years Wind energy (21,132 MW) continues to dominate - 67 % of total RE Solar power : 2,647 MW As on 31 st March 214
Wind and Solar Energy Sources Projection: ~ 5 GW at 2% land availability Goal of 2 GW by 222
Cumulative capacity (MW) Cumulative Capacity Addition of Solar Power NSM Phase I, Batch 1, Projects under Gujarat Solar Policy NSM Phase I, Batch 2, Solar REC based Projects 3 25 2 15 1 5 2.11 2.12 2.12 1.28 35.15 941.24 1645.61 2631.9 26-7 27-8 28-9 29-1 21-11 211-12 212-13 213-14 (up to 23rd April 214) Installed Sr. States Capacity No. (MW) 1 Andhra Pradesh 131.84 2 Arunachal Pradesh.25 3 Chhattisgarh 7.1 4 Delhi 5.15 5 Goa & UT 8.66 6 Gujarat 916.4 7 Haryana 1.3 8 Jharkhand 16 9 Karnataka 31 1 Kerela.25 11 Madhya Pradesh 347.17 12 Maharashtra 249.25 13 Odisha 3.5 14 Punjab 16.85 15 Rajasthan 73.1 16 Tamil Nadu 98.36 17 Uttarakhand 5.5 18 Uttar Pradesh 21.75 19 West Bengal 7.5 Total 2631.88
Promoting the adoption of RE resources by encouraging private sector investment and mandating the use of RE generation Ample opportunities for the establishment of landbased RE generation as well as for offshore wind farms Government support Vast untapped potential Energy security concerns Key drivers of renewable energy in India India ranks 4 th and 6 th globally as the largest importer of oil, and of petroleum products and LNG, respectively. The increased use of indigenous renewable resources is expected to reduce India s dependence on expensive imported fossil fuels. Climate change Increasing cost competitive ness of RE technology NAPCC promoting the understanding, adaption and mitigation of climate change, energy efficiency and resource conservation Distributed electricity demand RE is distributed and scalable resource, making it well suited to meet the need for power in remote areas, which lack grid and road infrastructure
Power Distribution Network of IITGN-VGEC Campus 1 kw Multi-crystalline PV plant, 25 kva x 4 inverters, ABB 1 kw Multi-crystalline Installed by GEDA, Gandhinagar 1 kw Thinfilm Installed by NTT Facilities, Inc., Japan
1 kw p Solar PV (Thin-film, CIS) System Pyranometer and Irradiance sensors with module temperature sensor Pyranometer Ambient temperature sensor Installed by NTT Facilities, Inc., Japan Total 64 PV modules (Thin-film, CIS) Thermocouple PV Inverter (REFUsol 1K) PV module Manufacturer Type Nominal value (http://www.solar-frontier.com) Installation conditions Inclined angle : 25 Orientation : South : Solar Frontier, Japan : CIS (SF15-L) : 15 W p Inverter & Data logger Data logger (Solar-Log 2) 2.1 79 V, 1.9 A Installed in January 212 String junction box with surge protection 11
Electricity Generation (kwh) Capacity Factor (%) 1 kw p Solar PV (Thin-film, CIS) System Solar PV system performance from January to May & June to December in 212 6 5 Energy (kwh) CUF 25 2 4 3 2 1 15 1 5 1.6.12 1.7.12 31.7.12 3.8.12 29.9.12 29.1.12 28.11.12 28.12.12
7:: 8:: 9:: 1:: 11:: 12:: 13:: 14:: 15:: 16:: 17:: 18:: PV Output Power (W) (AC) Ambient Temperature (C), Module Temperature (C) 7:: 8:: 9:: 1:: 11:: 12:: 13:: 14:: 15:: 16:: 17:: 18:: PV Outut Power (W) (AC) Ambient Tmp (C), Module Tmp (C) 1 kw p Solar PV (Thin-film, CIS) System 1 9 8 24th Feb 213 PV Power 7 6 Solar PV Profile over a day 7 Module Temperature 5 6 5 4 3 2 1 Time 1 9 8 7 6 3rd March 214 Ambient Temperature Solar Irradiance (W/m2) PV Power Module Temperature 4 3 2 1 7 6 5 4 Date Time Pac (W) Energy (Wh) Pdc (W) Vdc (V) Vac (Vph) SolIrr (W/m2) Tmp Mod Tmp Amb DaySumIrr (Wh/m2) 24.2.13 13:35: 9246 395 9373 628 248 19 57 29 3998 24.2.13 13:3: 9323 387 9449 628 249 118 57 29 3923 24.2.13 13:25: 9328 379 9453 627 249 122 57 29 3846 24.2.13 13:2: 9321 372 945 627 249 121 57 29 377 24.2.13 13:15: 942 364 9531 628 248 131 55 29 3694 24.2.13 13:1: 9471 356 9599 63 249 135 55 29 3616 24.2.13 13:5: 9545 348 9674 63 25 146 57 28 3538 24.2.13 13:: 9432 34 9558 628 249 137 58 28 346 24.2.13 12:55: 945 332 9579 628 248 143 58 29 3382 24.2.13 12:5: 9533 324 9667 632 248 142 55 28 335 24.2.13 12:45: 9537 317 9674 634 247 14 54 28 3226 24.2.13 12:4: 9554 39 972 634 247 142 54 28 3148 24.2.13 12:35: 9568 31 9712 636 248 141 54 28 369 24.2.13 12:3: 9485 293 9627 637 247 132 54 28 299 24.2.13 12:25: 9522 285 9679 64 247 134 53 28 2912 24.2.13 12:2: 943 277 9545 637 247 124 54 27 2834 24.2.13 12:15: 9481 269 9621 636 247 137 55 27 2756 24.2.13 12:1: 9288 264 9427 634 246 118 55 27 2679 5 4 3 3 Ambient Temperature 2 2 1 Solar Irradiance (W/m2) 1 Time
1.1.14 4.1.14 7.1.14 1.1.14 13.1.14 16.1.14 19.1.14 22.1.14 25.1.14 28.1.14 31.1.14 3.2.14 6.2.14 9.2.14 12.2.14 15.2.14 18.2.14 21.2.14 24.2.14 27.2.14 2.3.14 5.3.14 8.3.14 11.3.14 14.3.14 17.3.14 2.3.14 23.3.14 26.3.14 29.3.14 1.4.14 4.4.14 7.4.14 1.4.14 13.4.14 16.4.14 19.4.14 22.4.14 25.4.14 28.4.14 7:: 8:: 9:: 1:: 11:: 12:: 13:: 14:: 15:: 16:: 17:: 18:: PV Outut Power (W) (AC) Ambient Temperature (C), Module Temperature (C) 1 kw p Solar PV (Thin-film, CIS) System 1 9 8 7 5th May 214 Module Temperature PV Power 7 6 5 6 5 4 3 Ambient Temperature 4 3 2 Statistical (Average) performance (so far in 214) 2 1 Solar Irradiance 1 Energy: 54 kwh/day Sun Energy: 5.5 kwh/m 2 /day Time CUF: 22.5 75 65 Energy (kwh) CUF Sun Energy kwh/m2 8 7 55 45 35 25 15 5 6 5 4 3 2 Sun Energy (kwh/m2)
Generation (kwh) 1 kw p Solar PV (Thin-film, CIS) System 2 16 212 213 214 Rain started in June month in 213 whereas it was started in July in 212 12 8 4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec It has been observed that winter season is most favorable weather condition for solar PV power generation Energy generation in March month is the highest across the year The performance in rainy season (July-Sept) is so much intermittent which essentially drops the total power generation in this season
PV Inverter (REFUsol 1K) Pyranometer and Irradiance sensors with module temperature sensor 1 kw p Solar PV (Multicrystalline Silicon) System Installed by Gujarat Energy Development Agency (GEDA), Gandhinagar Total 44 PV modules (Multicrystalline Silicon) PV module Manufacturer Type Nominal value Installation conditions Inclined angle : 21 Orientation : South : Jain Photovoltaic : JJ M66 : 23 W p (http://www.jains.com/solar/jain%2jyot/mod els%2-%21%2to%223%2watt.htm) Installed in February 212 Anemometer (Madgetech, 11A) P max V mpp I mpp 23 W p 3.26 V 7.55 A V oc 36.35 I sc 8.15
Electricity Generation (kwh) Capacity Factor (%) 1 kw p Solar PV (Multicrystalline Silicon) Rooftop System Solar PV system performance from May to December in 212 6 5 Maintenance for first 2 days & then mal operation of Inverter (Total 8 days) Energy (kwh) CUF 25 2 4 15 3 2 1 1 5 5/1/212 : 6/1/212 : 7/1/212 : 8/1/212 : 9/1/212 : 1/1/212 : 11/1/212 : 12/1/212 : Operational failure sometimes happened because of unstable distribution grid conditions
Generation (kwh) 1 kw p Solar PV (Multicrystalline Silicon) System 2 212 213 214 16 12 8 4 Jan Feb March April May June July Aug Sept Oct Nov Dec Energy generation in March month is the highest across the year The performance in rainy season (July-Sept) is so much intermittent which essentially drops the total power generation in this season
Steady state operational analysis SOLAR PV INTEGRATION Anti-islanding protection and risk assessment Impact investigation
The Impact Investigation Exercise Cable Modeling Load Modeling Load Pattern SPV Data Loggers Data DPF Intermittent SPVs Compensation Load variation Unbalancing Voltage/Current Profile Losses Energy statistics SPV Impact Results Node Lighting Loads Air Conditioners Single Phase Motors Electronic Loads 3 4% 82% 9% 5% 7 5% 86% 6% 3% 9 6% 78% 4% 11% 13 12% 65% 1% 13% 14 25% 57% 8% 1% 15 8% 72% 7% 12% 17 5% 88% 6% 1% 18 9% 78% 8% 5% 2 6% 74% 5% 15% 21 25% 54% 11% 1% Kalpesh Joshi and N.M. Pindoriya, Impact Investigation of Rooftop Solar PV System: A Case Study in India, 212 3rd IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe), Berlin, October 14-17, 212, pp. 1-8.
Seasonal performance The Impact Investigation Exercise Case 1 Base case study Balance load, without capacitor compensation and solar PV generation Case 2 With capacitor compensation Balance load, without solar PV generation Case 3 With solar PV generation Balance load, without capacitor compensation Case 4 With capacitor compensation & solar PV generation Balance load Case 5 Unbalance load With capacitor compensation & solar PV generation 1.4 1.2 1..8.6.4.2. -.2 8 kw 15 kw Winter peak Summer peak Winter off-peak 28 kw Summer off-peak Winter off-peak Summer off-peak Winter peak Summer peak 45 kw Source Current Profile in pu Case 1 Case 2 Case 3 case 4 -.4
The Impact Investigation Exercise
Technical issues in solar PV integration with utility distribution grid Power Quality Voltage Flicker Protection Islanding protection Waveform Distortion Nuisance Tripping THD Reconnect after disturbance Frequency and Power Factor Correction Grounding IEEE Recommended Practice for Utility Interface of PV systems, IEEE Standard 929-2
Power Quality Constraints Islanding Condition
Risk Assessment of Unintentional Islanding Exercise What is Unintentional Islanding??? 14 12 Winter - Nonworking days 11 12 12 Process of elimination and identification of probable scenarios for unintended islanding 1 8 6 4 5 7 8 6 9 2 Allowable mismatch in powers Power balance check with DPF Permissible deviations in V & f 14 12 1 8 6 9 1 11 12 13 14 15 16 Time of Day Offpeak - Nonworking days 8 11 13 1 9 6 Most Probable Days and Time of Day (ToD) for formation of island 4 2 2 3 9 1 11 12 13 14 15 16 Time of Day
Goals for successful grid integration Detection of islanding and disconnection of the PV system from the utility, regardless of the initial state of the system, perturbations, composition of the load Detection of islanding which is sufficiently fast to guarantee safety and safeguard the reliability and integrity of the utility and PV systems Disconnection of the PV system only when islanding is actually occurring (no nuisance trips)
Anti-Islanding Protection P > Under voltage relay P < Over voltage relay Q > Over frequency relay Q < Under frequency relay Non-detection Zone
Anti-Islanding Protection
Anti-Islanding Protection Real time digital simulation
An underground cable-fed actual spot network in India with 3 roof-top PV plants 21 Node Network, 4 V, small & spot network
(IITGN-VGEC) Daily peak demand with and without PV generation maximum reduction in peak demand occurs in the months of February and March. However, the year-round net reduction in peak demand is found to be 68.75 kw.
Demand (kw or kvar) Power factor (IITGN-VGEC) average power factor consistently stays below.9 (lagging) during the months of February, March and partly April in the year 212 3 1 The drop in average power factor is shown expanded for a typical day (February 27, 212). 25 2 15.8.6 The real power demand sinks during sunshine hours due to real power injection from RPVs. Inverters of all RPVs are set to operate at unity power factor. 1 5-5 2 4 6 8 1 12 14 16 18 2 22 24 Time of Day (Hour).4.2 Demand W/o PV Net Demand Reactive Power PF
Renewable Energy Trading Cost of electricity through RE generation Cost equivalent to conventional resources Cost for GREEN Attributes Unbundling of REC from electrical energy REC Option Solar PV Solar Thermal Wind 12-15 Rs/kWh for first 12 years 3-5 Rs/kWh for next 13 years 9-11 Rs/kWh for first 12 years 3-4 Rs/kWh for next 13 years 3-5 Rs/kWh Feed-in-Tariff (FiT) Electricity Green attributes Electricity sale at market price Sale of electricity to obligated entities at price average price REC (Solar and non-solar) Sale of REC at PXs Sale of electricity to obligated entities (DISCOMs, CPPs, OA consumers) at preferential tariff
Operational Framework for REC Source: MNRE
No. of REC (Non-solar) traded MCP (Rs/REC) Non-solar REC Trading 7, 6, MCV@PXIL MCV@IEX MCP@IEX MCP@PXIL 25 2 5, Floor price 15 4, 15 3, 1 2, 1, 5 Non-Solar REC (Rs/REC) Forbearance Price Floor Price 33 15
No. of REC (Solar) traded MCP (Rs/REC) Solar REC Trading 12 1 MCV@PXIL MCV@IEX MCP@IEX MCP@PXIL 16 14 12 8 Floor price 93 1 6 8 4 2 6 4 2 Solar REC (Rs/REC) Forbearance Price Floor Price 13,4 93
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