New Trends in Grid Integration of Solar Photovoltaic Energy Systems

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New Trends in Grid Integration of Solar Photovoltaic Energy Systems Professor Saifur Rahman Virginia Tech Advanced Research Institute Virginia, USA

1 New Trends in Grid Integration of Solar Photovoltaic Energy Systems Professor Saifur Rahman Virginia Tech Advanced Research Institute Virginia, USA PVES Workshop Cairo, Egypt 12 July 2015 Virginia Tech Research Center Arlington, Virginia, USA PPT slides will be available at

In 2012, the 100 GW mark was reached and by 2013, almost 138.

2 Global PV Cumulative Installed Capacity Top 13 countries (2013) At the end of 2009, the world s cumulative installed PV capacity was more than 23 GW. One year later it was 40.3 GW and at the end of 2011 it was 70.5 GW. In 2012, the 100 GW mark was reached and by 2013, almost GW of PV had been installed globally an amount capable of producing at least 160 terawatt hours (TWh) of electricity every year. This is also the equivalent of the electricity produced by 32 large coal power plants. (Source: Global Market Outlook http 2

3 Europe remains the world s leading region in terms of cumulative installed capacity, with 81.5 GW as of This represents about 59% of the world s cumulative PV capacity, down from 70% in 2012 and about 75% of the world s capacity in Asia Pacific countries are growing fast, with 40.6 GW now installed. Next in the rankings are the Americas (13.7 GW). (Source: Global Market Outlook http Global PV Cumulative Installed Capacity (Source: European Photovoltaic Industry Association, Global Market Outlook

Growth of Global PV Cumulative Capacity (2003-2013) (Source: International Energy Agency Renewable Energy Medium Term Report Outlo PV

4 Growth of Global PV Cumulative Capacity ( ) (Source: International Energy Agency Renewable Energy Medium Term Report Outlo PV Annual Capacity Additions, GW (Source: International Energy Agency Renewable Energy Medium Term Report Outlook for Solar PV Deployment to

Projected Growth of Global PV Market, Cumulative Capacity

0 8,000.0 6,000.0 4,000.0 2,000.0 0.0 U.S.

Cumula8ve Capacity (MW) (Source: Lawrence Berkeley

5 Projected Growth of Global PV Market, Cumulative Capacity ( ) (Source: International Energy Agency Solar Photovoltaic Roadmap Foldout U.S. Grid-connected PV Capacity , , , , , , U.S. Annual Capacity Addi8ons (MW) U.S. Cumula8ve Capacity (MW) (Source: Lawrence Berkeley National Laboratory & US DOE Sunshot Program An Historical Summary of the Installed Price of PV in the United States,1998 to 2013) 5

6 Map of Direct Normal Irradiance (DNI) and Utility-Scale Solar Project Locations in the U.S. (Source: Lawrence Berkeley National Laboratory (LBNL) & US DOE Sunshot Program - Utility-Scale Solar 2013: An Empirical Analysis of Project Cost, Performance, and Pricing Trends in the US) (Source: Solar Energy Industries Association (SEIA)- SOLAR ENERGY FACTS: 2014 YEAR IN REVIEW) 6

Price Drop Of Utility-scale Solar PV Projects (Source: Energy.Gov- http://energy.

7 Price Drop Of Utility-scale Solar PV Projects (Source: Energy.Gov- Evolutionary Utility-scale (1-axis Tracking) PV System Price Reductions & DOE Target, * (Source: NREL - Residential, Commercial, and Utility-Scale Photovoltaic (PV) System Prices in the United States: Current Drivers and Cost-Reduction Opportunities) 7

8 Large Scale Deployment Challenges Variability Flexibility Dispatchability T&D losses O&M costs Regulatory constraints Technical Solutions Storage Smart inverter Demand response Revised codes and standards (Source: EPIA.org: Connecting the Sun: SOLAR PHOTOVOLTAICS ON THE ROAD TO LARGE/SCALE GRID INTEGRATION) Electrical Design Of a Utility-scale PV Project DC - Module array(s) - Inverters - DC cabling (module, string and main cable) and connectors (plugs and sockets) - Junction boxes/combiners - Disconnects/switches - Protection devices - Earthing AC - AC cabling - Switchgear - Transformer - Substation - Earthing and surge protection (Source: International Finance Corporation (A World Bank group)- Utility Scale Solar Power Plants: A Guide For Developers and Investors) 8

9 Inverter Manufacturer Market Share (2009) Others 18% Siemens (Germany) 5% Power-One (USA) 6% SMA (Germany) 49% Fronius (Austria) 10% KACO new energy (Germany) 12% (Source: International Finance Corporation (A World Bank group)- Utility Scale Solar Power Plants: A Guide For Developers and Investors) Global Average Sale Prices For Different Types Of Inverters($/Wac) (Source: GTM research: The Global PV Inverter Landscape 2015: Technologies, Markets and Prices) 9

Smart Inverter: Common Functions Low/High Voltage Ride-Through (L/HVRT) L/HVRT functionalities are to be implemented with user-configurable X (duration)-y (voltage parameter) arrays.

10 Smart Inverter: Common Functions Low/High Voltage Ride-Through (L/HVRT) L/HVRT functionalities are to be implemented with user-configurable X (duration)-y (voltage parameter) arrays. L/HVRT function is defined with two curves- Must Disconnect (in blue: LM1-LM5 or HM1-HM5), and Must Remain Connected (in orange: LC1-LC6 or HC1-HC4) Must Disconnect curves are assumed to extend downward or upward from the first point (LM1 or HM1) and horizontally to the right from the last point (LM5/HM5). Must Remain Connected curves are assumed to extend horizontally to the left below the first point (LC1 or HC1) in the array and to the right from the last point (LC6 or HC4) (Source: EPRI- Common Functions for Smart Inverters, Version 3) Smart Inverter: Common Functions Maximum Generation Limit Time window is used to define the duration over which a new setting would take effect Ramp time expresses the duration over which the inverter linearly places the new limit into effect Read & Set Maximum Generation Level command is used to set the maximum generation level as a percent of peak generation (in Watts) (Source: EPRI- Common Functions for Smart Inverters, Version 3) 10

Smart Inverter: Common Functions Volt-VAR function An array of voltage points (% of reference voltage) and VAR levels (% of available VARs) are used to define piece-wise linear curve of the desired

The VAR level is assumed to remain constant for voltages below P1 output (at the Q1 level) and above the highest voltage point for P4 (at Q4) At least two points (P2, V2 and P3, V3) are required to

Energy Sources Act, 2014 For PV plants connected to LV grid or less than 100 kw of nominal power connected to MV grid VDE-AR-N 4105 (effective since January 1, 2012) Relevant requirements: Phase

11 Smart Inverter: Common Functions Volt-VAR function An array of voltage points (% of reference voltage) and VAR levels (% of available VARs) are used to define piece-wise linear curve of the desired Volt-VAR behavior Available VARs implies the reactive injection level the inverter is capable of providing at the moment, without compromising its Watt output. The VAR level is assumed to remain constant for voltages below P1 output (at the Q1 level) and above the highest voltage point for P4 (at Q4) At least two points (P2, V2 and P3, V3) are required to set up the ramping functions (Source: EPRI- Common Functions for Smart Inverters, Version 3) Three directives in Germany The BDEW medium voltage directive The VDE code of practice The Renewable Energy Sources Act, 2014 For PV plants connected to LV grid or less than 100 kw of nominal power connected to MV grid VDE-AR-N 4105 (effective since January 1, 2012) Relevant requirements: Phase balancing Frequency-based power reduction Reactive power control Inverter reconnection conditions Output power control BDEW: Bundesverband der Energie- und Wasserwirtschaft (German Association of Energy and Water Industries) VDE: Verband der Elektrotechnik, Elektronik und Informationstechnik (The Association for Electrical, Electronic & Information Technologies) Sources: VDE-AR-N 4105 Generators connected to the low-voltage ( SolarEdge Inverter Compliance with New German Grid Code ( SMA- PV grid integration ( 11

Frequency-based Power Reduction P m = Instantaneously available power P= Power reduction f network = Network frequency Figure: Active power reduction of renewables- based generating units in the case

5 Hz, PV systems should in future lower (in the event of a rise in frequency) or increase (in the event of a reduction in frequency) the currently generated active power P m with a gradient of 40 %

12 Frequency-based Power Reduction P m = Instantaneously available power P= Power reduction f network = Network frequency Figure: Active power reduction of renewables- based generating units in the case of over- frequency Frequency requirements to be met by PV systems or other controllable generators (VDE- AR- N 4105) In the frequency range between 50.2 Hz and 51.5 Hz, PV systems should in future lower (in the event of a rise in frequency) or increase (in the event of a reduction in frequency) the currently generated active power P m with a gradient of 40 % of P m per Hz At mains frequencies > 51.5 Hz, the PV systems must disconnect immediately from the network (safety shutdown) The PV system may only be connected or re- connected to the network if the mains voltage is within the tolerance range of 85 % to 110 % of nominal voltage and the mains frequency is within the tolerance range of 47.5 Hz to Hz for a period of at least 60 seconds Sources: VDE, Transmissioncode 2007 ( The 50.2 Hz problem ( 10 MW Plant near Carlsbad, New Mexico, USA System Owner: SunEdison Utility: Xcel Energy System Integrator: SunEdison System Size: 9.9 MWdc (arrays with tracking system) Network Type: Radial, Dedicated Feeder for PV Plant Special Interconnection Requirements: Fixed power factor to avoid high voltages Inverters required to energize incrementally (Source: NREL: High Penetration Photovoltaic Case Study Report, 2013) 12

Colorado State University Foothills Campus, Fort Collins, Colorado, USA System Owner: Colorado State Univ. Utility: Xcel Energy, Public Service Company of Colorado System Size: 5.

13 Colorado State University Foothills Campus, Fort Collins, Colorado, USA System Owner: Colorado State Univ. Utility: Xcel Energy, Public Service Company of Colorado System Size: 5.2 MWac (single axis tracking and fixed-axis arrays) Network Type: Radial Special Interconnection Requirements: Inverters required to energize incrementally Required to set inverters to absorb 100 kvar or 150 kvar at utility request to avoid high voltages (Source: NREL: High Penetration Photovoltaic Case Study Report, 2013) Thank You Professor Saifur Rahman Virginia Tech Advanced Research Institute Virginia, USA 13

Issues and Best Practices in Grid Integration of Solar Photovoltaic Power Plants

Issues and Best Practices in Grid Integration of Solar Photovoltaic Power Plants Professor Saifur Rahman Virginia Tech Advanced Research Institute Virginia, USA University of Manchester Manchester, England