Thomas Basso

IEEE 1547 series of standards: interconnection issues

IEEE 1547 2003 standard for interconnecting distributed resources with electric power systems is the first in the 1547 series of planned interconnection standards. Major issues and a wealth of constructive dialogue arose during 1547 development. There was also a perceived increased vitality in updating complementary IEEE standards and developing additional standards to accommodate modern electrical and electronics systems and improved grid communications and operations. Power engineers and other stakeholders looking to the future are poised to incorporate 1547 into their knowledge base to help transform our nations aging distribution systems while alleviating some of the burden on existing transmission systems.

Microgrid standards and technologies

Microgrids are intentional islands formed at a facility or in an electrical distribution system that contain at least one distributed energy resource and associated loads. Microgrids that operate both electrical generation and loads in a coordinated manner can offer benefits to the customer and the local utility. The loads and energy sources in a microgrid can be disconnected from and reconnected to the utility system with minimal disruption, thereby improving reliability. Any time a microgrid is implemented in an electrical distribution system, it must be well planned to avoid problems. This paper discusses current microgrid technologies and standards that are being developed to address implementation of microgrids.

Cell shunt resistance and photovoltaic module performance

The shunt resistance of solar cells in photovoltaic modules can affect module power output and could indicate flawed manufacturing processes and reliability problems. The authors describe a two-terminal diagnostic method to directly measure the shunt resistance of individual cells in a series-connected module nonintrusively, without de-encapsulation. Peak power efficiency vs. light intensity was measured on a 12-cell, series-connected, single crystalline PV module having relatively high cell shunt resistances. The module was remeasured with 0.5-, 1-, and 2-ohm resistors attached across each cell to simulate shunt resistances of several emerging technologies. Peak power efficiencies decreased dramatically at lower light levels. Using the PSpice circuit simulator, the authors verified that cell shunt and series resistances can indeed be responsible for the observed peak power efficiency vs. intensity behavior. They discuss the effect of basic cell diode parameters, i.e., shunt resistance, series resistance, and recombination losses, on PV module performance as a function of light intensity.

Microgrid Standards and Technology Development

Distributed resources can provide power to local loads in the electric distribution system as well as benefits such as improved reliability. Microgrids are intentional islands formed at a facility or in an electrical distribution system that contain at least one distributed resource and associated loads. Microgrids that operate both electrical generation and loads in a coordinated manner can offer additional benefits to the customer and local utility. The loads and energy sources can be disconnected from and reconnected to the area or local utility with minimal disruption to the local loads, thereby improving reliability. This paper describes research being conducted in microgrid standards, technologies, and applications to allow successful implementation of this concept.

High-penetration, grid-connected photovoltaic technology codes and standards

This paper reports the interim status in identifying and reviewing photovoltaic (PV) codes and standards (C&S) and related electrical activities for grid-connected, high-penetration PV systems with a focus on U.S. electric utility distribution grid interconnection. That includes identifying topics and concerns not yet in the scope of existing C&S documents, identifying C&S-related ongoing work and approaches, and providing recommendations related to C&S needs. This paper also addresses certain technical concerns, e.g., monitoring, information exchange, and control pertaining to business models, tariffs, and economics governed by policy and regulatory mandates. However, the policy, regulatory, and business concerns are not this papers direct focus. Rather, the primary focus is on systems engineering-based C&S technical concerns for high-penetration PV systems in U.S. utility distribution grids.

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.

IEEE P1547-series of standards for interconnection

The IEEE P1547 Standard For Interconnecting Distributed Resources With Electric Power Systems is the first in the P1547-series of planned interconnection standards, and, there are additional standards needed. There are major issues and obstacles to an orderly transition to using and integrating distributed power resources with electric power systems (grid or utility grid). The lack of uniform national interconnection standards and tests for interconnection operation and certification, as well as the lack of uniform national building, electrical, and safety codes, are understood, and, resolving that needs reasonable lead time to develop and promulgate consensus. The P1547 standard is a benchmark milestone for the IEEE standards consensus process and successfully demonstrates a model for ongoing success in developing further national standards and for moving forward in modernizing our nations electric power system.

A power hardware-in-the-loop framework for advanced grid-interactive inverter testing

This paper presents a power hardware-in-the-loop (PHIL) framework for testing advanced inverter features such as voltage regulation and frequency response that interact dynamically with the electric grid. The PHIL model simulates grid voltage dynamics using a simplified Thévenin-based model and simulates grid frequency dynamics using a turbine-governor model including droop, inertia, and damping. Also presented are a statistical analysis of short-circuit impedances in the IEEE 8500-node test feeder, and analytical justification for approximating Thévenin impedances at inverter connection points as short-circuit impedances. Test results are presented for two inverters performing volt-VAr control, high-frequency power curtailment, voltage and frequency ride-through, and abnormal voltage disconnection while connected to the PHIL system. Results confirm advanced grid support functions have the desired effects when performing voltage regulation and high-frequency power curtailment while riding through large voltage and frequency transients. Some PHIL tests presented here replicate IEEE 1547.1-style conformance tests; no evidence is seen that grid dynamic response emulation affects the results of such conformance tests.

Deploying high penetration photovoltaic systems — A case study

Photovoltaic (PV) system capacity penetration, or simply “penetration,” is often defined as the rated power output of the aggregate PV systems on a distribution circuit segment divided by the peak load of that circuit segment. Industry experts agree that a single value defining high penetration is not universally applicable. However, it is generally agreed that a conservative value to designate high penetration is the condition when the ratio of aggregate PV systems ratings to peak load exceeds 15%. This case study illustrates the case of a distribution feeder which is able to accommodate a traditional capacity penetration level of 47%, and perhaps more. New maximum penetration levels need to be defined and verified and enhanced definitions for penetration on a distribution circuit need to be developed. The new penetration definitions and studies will help utility engineers, system developers, and regulatory agencies better agree what levels of PV deployment can be attained without jeopardizing the reliability and power quality of a circuit.

Evaluating future standards and codes with a focus on high penetration photovoltaic (HPPV) system deployment

High-penetration photovoltaic (PV) system deployment is becoming a reality in several regions of the United States and the trend toward high penetration levels will continue to rise due to decreasing PV system costs in concert with increasing electric utility rates and societal deliberations. New standards and codes for high-penetration PV deployment must be developed, while some existing standards and codes will need to be revised to accommodate increasing levels of PV deployment.