Joshua Hambrick

Steady-State Analysis of Maximum Photovoltaic Penetration Levels on Typical Distribution Feeders

This paper presents simulation results for a taxonomy of typical distribution feeders with various levels of photovoltaic (PV) penetration. For each of the 16 feeders simulated, the maximum PV penetration that did not result in a steady-state voltage or current violation is presented for several PV location scenarios: clustered near the feeder source, clustered near the midpoint of the feeder, clustered near the end of the feeder, randomly located, and evenly distributed. In addition, the maximum level of PV is presented for single, large PV systems at each location. Maximum PV penetration was determined by requiring that feeder voltages stay within ANSI Range A and that feeder currents stay within the ranges determined by overcurrent protection devices. Generation ramp rates, protection and coordination, and other factors that may impact maximum PV penetrations are not considered here. Simulations were run in GridLAB-D using hourly time steps over a year with randomized load profiles based on utility data and typical meteorological year weather data. For 86% of the 336 cases simulated, maximum PV penetration was at least 30% of peak load.

Evaluation of DER adoption in the presence of new load growth and energy storage technologies

This study considers potential system effects from the addition of Plug-in Electric Vehicle (PEV) load to individually metered residential customers together with a concurrent market adoption of Distributed Energy Resources (DER) and energy storage technologies to offset the associated load growth. To evaluate various renewable energy source conditions, a prototypical circuit is evaluated in Detroit, Los Angeles, and Orlando locations for both summer and winter loading conditions. Various load adoption scenarios are simulated by randomly assigning specified loading to target customer classes on the circuit.

Photovoltaic (PV) Impact Assessment for Very High Penetration Levels

This paper describes a granular approach for investigating the impacts of very high photovoltaic (PV) generation penetration. Studies on two real-world distribution feeders connected to PV plants are presented. The studies include both steady-state and time-series power flow analyses, which include the effects of solar variability. The goal of the study is to predict the effects of increasing levels of PV generation as it reaches very high penetration levels. The loss and return of generation with and without regulation is simulated to capture short-term problems such as voltage fluctuations. Impact results from the analyses are described along with potential mitigations.

Configurable, Hierarchical, Model-Based Control of Electrical Distribution Circuits

Grid modernization strategies often focus on replacing aging distribution control equipment with state-of-the-art devices capable of remote monitoring, communication, and control. However, wholesale replacement of the existing distribution infrastructure may not be practical or economical. Additionally, even with improved capabilities, “smart” devices may still be ignorant of changes in circuit topology. This paper presents a model-based distribution control scheme that is independent of circuit topology and integrates legacy and modern control equipment. Simulation results indicate the proposed method can improve circuit performance under both normal and abnormal conditions.

DSR design fundamentals: Power flow control

The electrical power sector is facing a crucial issue which is the need to analyse and determine the adequacy of the transmission capacity, and the need for new techniques to increase the capability of transmission systems. Distributed Series Reactance (DSR) control is a new smart grid technology that is primarily being applied to control flows in the transmission system. This paper investigates the use of DSRs to make best use of the additional capacity already existing in long transmission lines. An experiment using 230 kV, 345 kV and 500 kV three parallel transmission lines is performed to determine the fundamentals of DSR design. Several case studies were adopted, in which the three long transmission lines are variously modeled to investigate different line models, and impedance models impact. Observations are highlighted and design considerations are suggested.

High-penetration PV deployment in the Arizona Public Service System, Phase 1 update

In an effort to better understand the impacts of high penetrations of photovoltaic generators on distribution systems, Arizona Public Service and its partners have begun work on a multi-year project to develop the tools and knowledge-base needed to safely and reliably integrate high penetrations of utility- and residential-scale photovoltaics (PV). Building upon the APS Community Power Project - Flagstaff Pilot, this project will analyze the impact of PV on a representative feeder in northeast Flagstaff. To quantify and catalog the effects of the estimated 1.3 MW of PV that will be installed on the feeder (both smaller units at homes as well as large, centrally located systems), high-speed weather and electrical data acquisition systems and digital “smart” meters are being designed and installed to facilitate monitoring and to build and validate comprehensive, high-resolution models of the distribution system. These models will be used to analyze the impacts of the PV on distribution circuit protection systems (including anti-islanding), predict voltage regulation and phase balance issues, and develop volt/var control schemes. This paper continues from a paper presented at the 2011 IEEE PVSC conference that introduces the project and describes some of the preliminary consideration, as well as project plans and early results. This paper gives a status update of the project and presents selected results from Phase 2 of the project. It discusses baseline feeder modeling, load allocation, data acquisition, utility-scale PV integration, preliminary model validation, and plans for future phases.

Advantages of Integrated System Model-Based Control for Electrical Distribution System Automation

Abstract Integrated system models based upon the generic programming paradigm and which include all fundamental problem domain objects are applied to electrical distribution system automation and control. The control architecture resulting from this approach is reviewed. Flexibility of design, topology independence, fail-safe operation, and robustness of algorithms are considered.

NREL Smart Grid projects

Summary form only given. Although implementing Smart Grid projects at the distribution level provides many advantages and opportunities for advanced operation and control, a number of significant challenges must be overcome to maintain the high level of safety and reliability that the modern grid must provide. For example, while distributed generation (DG) promises to provide opportunities to increase reliability and efficiency and may provide grid support services such as volt / var control, the presence of DG can impact distribution operation and protection schemes. Additionally, the intermittent nature of many DG energy sources such as photovoltaics (PV) can present a number of challenges to voltage regulation, etc. This presentation provides an overview a number of Smart Grid projects being performed by the National Renewable Energy Laboratory (NREL) along with utility, industry, and academic partners. These projects include modeling and analysis of high penetration PV scenarios (with and without energy storage), development and testing of interconnection and microgrid equipment, as well as the development and implementation of advanced instrumentation and data acquisition used to analyze the impacts of intermittent renewable resources. Additionally, standards development associated with DG interconnection and analysis as well as Smart Grid interoperability will be discussed.

Model-based DG control as an economic solution to load growth

At the distribution level distributed generators (DGs) can sometimes provide more economic solutions to load growth than building new substations and lines. In such cases a DG can be controlled to eliminate cable overloads or low voltages due to load growth. A model that accurately estimates conditions throughout the circuit can make the DG solution even more economically attractive, and in some cases with underground cables, feasible. The use of the model can avoid the cost of installing new instrumentation and communication equipment for the control function throughout the circuit, which can spread out over many square miles. DGs also provide benefits in system reliability and operating costs, especially near system peak. These benefits can increase significantly when circuits are interconnected. This paper addresses control architecture, field validation of models, economics, and field experience with model-based DG control.

PV impact assessment for very high penetration levels

This paper describes a granular approach for investigating the impacts of very high PV generation penetration. Studies on two real-world distribution feeders connected to PV plants are presented. The studies include both steady-state and time series power flow analyses, which include the effects of solar variability. The goal of the study is to predict the effects of increasing levels of PV generation as it reaches very high penetration levels. Impact results from the analyses are described along with potential mitigations.