Investigation of a Family of Power Conditioners Integrated into a Utility Grid, Phase II. Period Covered: January 1, 1981 to December 31, 1981

摘要

Category II, intermediate size, power conditioners for solar photovoltaic (SPV) arrays in the range 30 kW to 600 kW are investigated. These systems interface with three-phase utility distributions at low voltage, below 1000 V. It is concluded that a family of designs based on the programmed-wave voltage-sourced dc-to-ac converter will best serve the needs of the application. The designs are modular in nature, with a three-phase six-pulse bridge as the basic power circuit building block. Two bridge designs, at 30 kW and 150 kW rating, are needed to cover the range. State-of-the-art baseline designs use impulse-commutated thyristor bridges with front-end dc-to-dc converters. They cannot meet cost goals, by quite a margin, or efficiency goals, though they are much closer to the latter than the former. Advanced concept designs use gate turn-off devices (GTOs) for the lower power range. These nearly meet the long range efficiency goals, but fail to meet long range cost goals. The higher power units are still thyristor based. Sufficiently large GTOs are not yet available at a reasonable price, nor are they expected to be for quite some time. When large GTOs do enter the marketplace, they can be substituted for thyristors in the 100 kW to 600 kW range with some cost and efficiency gains; however, the thyristors designs meet both long range cost and efficiency goals. In both power ranges, the advanced designs dispense with a dc-to-dc converter and use a multi-pattern programmed-wave approach as opposed to the fixed pattern, regulated dc link approach of the baseline designs. This technique, by avoiding processing the power twice, is largely responsible for the cost and efficiency gains observed.