Daniel Brooks

Evaluation of the impact of plug-in electric vehicle loading on distribution system operations

Electric transportation has many attractive features in todays energy environment including decreasing greenhouse gas emissions from the transportation sector, reducing dependence on imported petroleum, and potentially providing consumers a lower cost alternative to gasoline. Plug-in hybrid Electric (PHEV) vehicles represent the most promising approach to electrification of a significant portion of the transportation sector. Electric power utilities recognize this possibility and must analyze the associated impacts to electric system operations. This paper provides details of analytical framework developed to evaluate the impact of PHEV loading on distribution system operations as part of a large, multi-utility collaborative study. This paper also summarizes partial results of the impact of PHEVs on one utility distribution feeder.

Evaluations of plug-in electric vehicle distribution system impacts

With plug-in electric vehicles poised to enter the automotive market this year, a remaining concern for electrical distribution utilities is the potential impact these loads may have on their system and how to account for them in their planning process. In order to address this concern, EPRI has initiated a multi-utility project to quantify the potential impacts across numerous distribution feeders of varying characteristics. As part of this project, an analysis methodology which accounts for PEV spatial and temporal diversities has been developed and used to study these potential impacts. Preliminary findings from some of the initial circuits studied are presented as well as initial insights developed thus far.

Voltage impacts of distributed wind generation on rural distribution feeders

Possible voltage issues are raised when considering interconnecting wind turbines to rural distribution feeders including short-term voltage fluctuations (including flicker) and long-term voltage variations. Detailed computer simulation of representative commercial wind turbine technologies on typical distribution feeders can provide insight into the impact wind generation could have on rural, distribution systems. Due to the relatively slow variation in power fluctuations of wind turbines, frequency-domain system models can be used to quantitatively characterize wind turbine impacts on system voltage. An existing case study is used a basis for an analysis, with results that can provide distribution engineers with a better understanding of how distributed wind generation can impact voltages on typical rural distribution feeders.

Load model parameter derivation using an automated algorithm and measured data

This paper summaries some of the key results achieved in the second phase of a multi-year collaborative load modeling research project. After having identified suitable types of load monitoring devices, actual field data for load model development and validation were collected at appropriate locations for several months to more than a year in three different utilities. This data was post-processed using an automated methodology to filter out events suitable for load model parameter estimation. Two load model structures were then used with an automated parameter estimation algorithm to fit model parameters using the field data collected. The models thus developed were then validated using Siemens PTI PSS/ETM dynamic simulation program. This whole process resulted in some key insights and valuable conclusions for future load modeling research efforts.

Results of residential air conditioner testing in WECC

This paper summarizes the key results of testing work performed by three organizations (EPRI, SCE, and BPA) on a total of twenty seven air conditioning units in order to better understand and thus characterize their behavior for power system simulations. The diversity of the tested air conditioner units included sizes (tonnage), compressor technology (reciprocating and scroll), type of refrigerant (R-22 and R-410A), efficiencies (between 10 and 13 SEER), and vintage (new and old). A common test plan was developed by the three organizations. The tests were then performed independently by each of the three organizations. The EPRI work was sponsored by APS and SRP. This effort was part of the current load modeling effort going on in WECC under the load modeling task force. The key findings of this work are presented here together with a description of the testing methodology. All three organizations found very similar results despite testing a variety of different sizes and manufacturer units. The key results presented are associated with the stalling behavior of the units at different outdoor temperatures, the behavior of thermal overload tripping, contactor dropout, and the behavior of the units in response to different emulated types of system events.

Increasing the value of wind generation through integration with hydroelectric generation

The variability and uncertainty in the output of wind generation reduces wind energys economic value, however, in that wind generation does not lend itself to participation in the control areas economic dispatch process. One promising opportunity to increase the value and soften integration concerns of wind power is to utilize conventional hydroelectric resources. This paper describes a panel discussion of current wind-hydro integration efforts in the Pacific Northwest.

Impact of wind active power control strategies on frequency response of an interconnection

High penetrations of variable generation presents challenges for reliable operation of the power system. Ensuring adequate primary frequency response is one such concern as the generation mix changes with increasing penetration of variable generation and planned retirements of fossil-fired generation. However, inverter-coupled wind generation is capable of contributing to primary frequency response. The focus of the simulation work presented in this paper is to assess the impact of active power control strategies of wind generation on the primary frequency response of an interconnection. All simulations were conducted using the General Electric (GE) PSLF® simulation tool. The base case utilized was developed from the Western Electricity Coordinating Council (WECC) Transmission Expansion Planning Policy Committee (TEPPC) 2022 case with light spring load conditions with approximately 15% wind penetration. The 20, 30 and 40% wind penetration study cases were derived from the base case by strategically replacing thermal units throughout the WECC regions with wind generation. The results presented here are intended to develop a broad understanding of potential impact of changing generation mix and wind generation active power controls on the primary frequency response of an interconnection. The results are not intended to represent actual performance of the WECC since simplifying assumptions are used to serve the study purpose.

Evaluation of Advanced Operation and Control of Distributed Wind Farms to Support Efficiency and Reliability

The integration of increasing penetrations of renewable energy sources is one of the key drivers for the increased deployment of control and optimization on power systems. Much of this wind generation is connected to the distribution system, which presents a range of challenges to the operation of these networks, traditionally utilized solely for power delivery. This paper describes a demonstration program in Ireland which addresses two of the key challenges in delivering high penetrations of wind energy in a cost-effective and efficient manner. First, the paper addresses a trial of the advanced reactive power control capabilities of modern wind turbines, investigating how this resource can be better utilized from a distribution and transmission perspective. The second aspect is measures to improve the efficiency of the distribution system in light of these increasing penetrations of wind energy.

Vulnerability of Large Steam Turbine Generators to Torsional Interactions During Electrical Grid Disturbances

This paper presents a formalized and systematic approach for identifying the zone of vulnerability of a power plant to potentially damaging torsional stress. That is the region of the electrical network surrounding a plant where electrical disturbance may result in significant loss of life at critical rotor locations on the turbine generator. The approach is based on comparing the peak transient torques observed for various network faults and disturbances to the peak transient torque for a machine terminal fault. This is shown to be a useful methodology in the absence of detailed shaft fatigue data. The results of the study provide significant insight into the various factors that influence the level of torsional stress and how one would be able to assess when detailed torsional interaction studies are necessary. Finally, some key general conclusions are drawn with respect to system events that may result in turbine-generator shaft fatigue loss-of-life.

Panel: Standards & interconnection requirements for wind and solar generation NERC Integrating Variable Generation Task Force

Distributed Energy Resources (DERs) are anticipated to play an increasing role in providing energy and ancillary services in the future. Anticipated expansions of DERs encompass distributed solar photovoltaics (PV), demand response, community energy storage, and plug-in electric vehicles. While these resources offer potential reliability improvements to the bulk electric system due to their flexibility and proximity to load, they also represented potential BES concerns as they become a more prevalent portion of the energy and ancillary service mix. Due to the relative size and distributed nature of these resources, the BES has limited to zero visibility and controllability of these resources. Two separate work groups of the NERC IVGTF have been tasked with investigating potential adverse BES reliability impacts of DERs. This panel presentation paper will summarize the potential issues identified by these work groups and status of their relative work.