ISO New England Net Load Analysis with High Penetration Distributed PV October 12, 2015 | Chicago, il ISO New England Net Load Analysis with High Penetration Distributed PV CIGRE USNC Grid of the Future Symposium Jon Black Lead engineer

Introduction Installed AC nameplate capacity of distribution-connected PV resources in New England is growing rapidly From 44 MW in 2010 to more than 1,000 MW by mid 2015 This growth is expected to continue ISO-NE forecasts that PV capacity will total almost 2,500 MW by 2024 Analysis of net load profiles in high PV penetration scenarios can assist in identifying key future system characteristics important to system operators and planners Net load profiles were developed and analyzed to help identify the system impacts of distributed PV, including higher-than-forecasted amounts Analysis and key results of net load simulations for ISO New England with up to 8 GW of distributed PV are discussed

Background There is a growing body of both real-world experience and study results regarding high penetration PV scenarios and the range of potential impacts they could have on system planning and system operations (some which are listed below) System operations Short-term load forecasting Allocation of sufficient reserves & ramping capabilities Disturbance tolerance & voltage support System planning Long-term load forecasting Determining future system needs (i.e., generation and/or transmission) Overall operability of systems with very high penetrations (frequency response and transient stability)

Methodology Future net load scenarios are based on coincident, historical hourly load and PV production data for the years 2012-2014 Top plot illustrates the spatial distribution of PV capacity deployed in the region at the end of 2014 PV production data accessed via Solectria Renewables’ SolrenView web-based monitoring system* 665 PV sites totaling 82 MWac (locations shown in bottom plot) Normalized PV profiles developed for each New England state, blended into a regional profile which was then “upscaled” to each PV scenario Existing PV system design and technology trends are not anticipated to change significantly over the next decade. It is therefore assumed that the upscaling of these profiles yields a reasonable estimate of future profiles associated with larger PV fleets that is adequate for simulation purposes *Accessed via http://www.solrenview.com/

Summer Season Net Load Profile Friday, July 19, 2013 Fourth highest ISO-NE peak load day ever As PV penetrations become higher: The timing of peak net loads (blue dots) becomes later in afternoon/evening Each successively larger PV scenario contributes less to serving summer peak net loads (which now occur later in the day), due to the setting of the sun

Winter Season Net Load Profile Tuesday, January 7, 2014 PV does not reduce winter peak Load reductions from PV can be significant during midday hours on sunny winter days High PV penetrations will increase the need for ramping capability throughout sunlight hours

Shoulder Season Net Load Profile Sunday, April 20, 2014 Profile sometimes referred to as the “Duck Curve” Lowest loads often occur on weekend days during spring/autumn and low demand for heating/cooling Increased PV will displace significant amounts of synchronous generation Potential minimum generation emergency events during midday hours (minimum load hours are shown in green)

Timing and Magnitude of Daily Summer Peaks Scenarios Shown: No PV, 1 GW PV, 2 GW PV, 4 GW PV, 6 GW PV, 8 GW PV

Hourly Net Load Ramp Rates April/May Non-Holiday Weekends Boxplot shows the distribution of hourly net load ramps without PV (red boxes), with 4 GW PV (green boxes), and with 8 GW PV (blue boxes) Large amounts of distributed PV cause increased net load ramping and a higher frequency of larger magnitude ramps, especially on days exhibiting both high irradiance and low load

Conclusions Results highlight significant changes to the overall system and some of the accompanying challenges that would need to be addressed in order to efficiently and reliably integrate the amounts of PV evaluated: Understanding the effect on the timing and magnitude of summer peak loads; Ensuring there is sufficient ramping/cycling capability among non-PV resources to serve the increasingly volatile net loads; The need to mitigate potential reliability issues associated with significant displacement of synchronous generation and increased potential for minimum generation events Similar analyses on sub-hourly data could yield additional insights, such as potential impacts on regulation requirements