Slide 1

RiversidePublicUtilities.com Arts & Innovation RiversidePublicUtilities.com Challenges and Solutions for Large-Scale PV Integration on RPUs Distribution System Ed Cortez, Principal Electrical Engineer In collaboration with Dr. Emma Stewart, Lawrence Berkeley National Laboratories

Slide 2

RiversidePublicUtilities.com Electric System Publicly Owned Electric and Water Utility Population - 311,896 Service Area - 82 square miles Substations 14 Transmission Lines 91 Circuit Miles Distribution Lines 1,323 Circuit Miles Electric Meters 107,500 Record peak demand of 612 MW on 9/14/2014 2014 Total of 13 MW installed PV 2015 Anticipating >10 MW of new PV

Slide 3

RiversidePublicUtilities.com Commercial PV Sites

Slide 4

RiversidePublicUtilities.com PV Interconnection Requirements RPU Rule 22 (CA Rule 21) Point of Interconnection Interconnection Equipment Generating Capacity Voltage Operating Range Protective Functions

Slide 5

RiversidePublicUtilities.com PV Interconnection RPU Rule 22 Interconnection requirements Point of Interconnection Point of Interconnection Primary 12kV Interconnection Equipment Interconnection Equipment - RPU providing primary switchgear Generating Capacity Generating Capacity 7.5 MW (AC) Voltage Operating Range Voltage Operating Range - SEL 351 Relay 59/27 implemented Overvoltage/Undervoltage Protection Functions Protection Functions Inverter is compliant with IEEE 1547/UL 1741 IEEE 1547 - Trips automatically during voltage and frequency excursion UL 1741 Islanding detection Fault Detection Fault Detection (Supplemental requirement)

Slide 6

RiversidePublicUtilities.com PV Interconnection Barriers From a distribution planning view, there are three barriers to the integration of large PV systems Inadequate tools that simulate high-penetration levels Inaccurate models, due to limited availability of data Limited accuracy of measured data sources

Slide 7

RiversidePublicUtilities.com PV Studies - Data Comprehensive model ESRI-based distribution network SCADA circuit load and voltage Summer Peak Winter Peak Hourly Minutes

Slide 8

RiversidePublicUtilities.com PV Studies Steady-State Analysis utilizing Synergi Electric Modeling, Power flow, Voltage, Volt/VAR, Fault, Distribution Protection

Slide 9

RiversidePublicUtilities.com PV Studies - Modeling Modeling Distribution model typically constructed assuming traditional power flow (one direction) Distribution voltage usually represented by the blue line In reality it looks like the red line

Slide 10

RiversidePublicUtilities.com PV Studies Power flow Reverse power flow/high voltage During off-peak daytime loads (winter), the 7.5 MW PV exceeds load on the circuit Reverse power flow from the distribution system through the substation transformer RPU Solution Currently improving the existing distribution infrastructure to limit the effects Reconductor, transfer loads, relocate capacitor banks

Slide 11

RiversidePublicUtilities.com PV Studies Protection Feeder relay / PV relay / short circuit current

Slide 12

RiversidePublicUtilities.com Analysis and Software Options

Slide 13

RiversidePublicUtilities.com Enhanced Modeling & Analysis LBNL and RPU collaborating to conduct dynamic and transient studies Evaluate additional infrastructure improvements Install PMUs at RPU Use PMUs as calibration and validation inputs to improve accuracy of the models

Slide 14

RiversidePublicUtilities.com Next Steps Model and simulate events to plan for future changes Simulate events to provide intelligence in reacting to outages and emergency conditions Utilize a combination of GIS, distribution planning tools and measured data to achieve objectives

Slide 15

RiversidePublicUtilities.com Conclusion No single software can achieve all analysis objectives Model data accuracy and standardization is essential Measured data is critical for validation Analyze in both steady-state and dynamic simulation