Russell H. Bonn

Determining the relative effectiveness of islanding detection methods using phase criteria and nondetection zones

Islanding of a utility-interactive photovoltaic (UIPV) system occurs if the UIPV system continues to power a section of the utility system after that section has been disconnected from the utility source. Since islanding creates hazards for personnel and equipment, UIPV systems are required to detect and prevent it. It is desirable to have a simplified method of determining which islanding detection methods (IDMs) are most effective. In this paper, a previously described method for finding the nondetection zones (NDZs) of IDMs is experimentally verified. This method is used to determine the NDZs of several common IDMs. These results indicate that, of the IDMs discussed in this paper: (1) Sandia Frequency Shift (SFS) is most effective; and (2) the worst-case loads are low-power loads that are near resonance at the line frequency and have a large capacitance and small inductance (a high value of the quality factor Q).

Development and Testing of an Approach to Anti-Islanding in Utility-Interconnected Photovoltaic Systems

This report documents the development of an inverter control method that detects and avoids islanding in utility-interconnected photovoltaic installations. This method is applicable to single and multiple inverters connected to a single utility distribution line. The anti-islanding approach is described and its performance is demonstrated on both a theoretical basis and with results from tests conducted at Sandia National Laboratories and Ascension Technology, a division of Applied Power Corporation. It has been demonstrated that this approach is effective for single and multiple photovoltaic inverter installations for the special case where the inverter contains a version of anti-islanding software compatible with IEEE Std 929-2000.The report also describes the anti-islanding technique so that it can be incorporated into photovoltaic systems lacking this feature. A test procedure that ascertains whether an anti-islanding capability exists in a PV inverter is also presented. This page intentionally left blank

Removing barriers to utility interconnected photovoltaic inverters

The Million Solar Roofs Initiative has motivated a renewed interest in the development of utility interconnected photovoltaic (UIPV) inverters. Government-sponsored programs (PVMaT, PV:BONUS) and competition among utility interconnected inverter manufacturers have stimulated innovations and improved the performance of existing technologies. With resurgence, Sandia National Laboratories (SNL) developed a program to assist industry initiatives overcome barriers to UIPV inverters. In accordance with newly adopted IEEE Std 929-2000, the interconnected PV inverters are to energizing the utility grid when disturbance occurs or the utility experiences an interruption in service. Compliance with IEEE Std 929-2000 is being widely adopted by utilities as a minimum requirement for utility interconnection. This report summarizes work done at the SNL balance-of-systems laboratory to support the development of IEEE Std 929-2000 and to assist manufacturers in meeting its requirements.

Balance-of-system improvements for photovoltaic applications resulting from the PVMaT Phase 4A1 program

The Photovoltaic Manufacturing Technology Program (PVMaT) began in 1990 as a cost-shared partnership among the photovoltaic industry and the Unites States National Photovoltaic Program. It has been conducted in several phases that were staggered to support technology evolution in the industry. Phase 4A goals broadened the scope of PVMaT resulting in a proposal solicitation that was divided into two parts: (1) Phase 4A1-product-driven system and component technology-with goals to improve system integration, improve component efficiency, and support manufacturing and system or component integration to bring together all elements for a PV product; and (2) Phase 4A2-product-driven PV module manufacturing technology-which addressed PV cell and module manufacturing to maximize the flexibility of applications and to reduce costs for PV products. Of the thirteen awards made in Phase 4A, eight were in 4A1. Developments through these subcontracts include advanced system integration, new and innovative inverter products for a broad range of PV applications and product modifications intended to result in improved reliability and reduced manufacturing costs. This paper summarizes the research, development and progress under phase 4A1.

Inverter testing at Sandia National Laboratories

Inverters are key building blocks of photovoltaic (PV) systems that produce ac power. The balance of systems (BOS) portion of a PV system can account for up to 50% of the system cost, and its reliable operation is essential for a successful PV system. As part of its BOS program, Sandia National Laboratories (SNL) maintains a laboratory wherein accurate electrical measurements of power systems can be made under a variety of conditions. This paper outlines the work that is done in that laboratory.

Sandia National Laboratories photovoltaic balance of systems program

The Sandia National Laboratories photovoltaic balance of system (BOS) program is sponsored by the Department of Energy to increase the reliability and lower the cost of BOS components. Efforts for FY1998 are discussed. Principal efforts include a quality program for inverter manufacturers, a grid-tied anti-islanding program, development of a hybrid inverter, hardware benchmarking program, and a battery evaluation program.

Sandia Smart Anti-Islanding Project; Summer 2001: Task II Investigation of the Impact of Single-Phase Induction Machines in Islanded Loads: Summary of Results

Islanding, the supply of energy to a disconnected portion of the grid, is a phenomenon that could result in personnel hazard, interfere with reclosure, or damage hardware. Considerable effort has been expended on the development of IEEE 929, a document that defines unacceptable islanding and a method for evaluating energy sources. The worst expected loads for an islanded inverter are defined in IEEE 929 as being composed of passive resistance, inductance, and capacitance. However, a controversy continues concerning the possibility that a capacitively compensated, single-phase induction motor with a very lightly damped mechanical load having a large rotational inertia would be a significantly more difficult load to shed during an island. This report documents the result of a study that shows such a motor is not a more severe case, simply a special case of the RLC network.