Taking the Mystery out of Choosing Electrostatic Precipitator (ESP) Power Supplies for MATS PM Control

Presented at the Power Plant Pollutant Control “MEGA” Symposium
August 19-22, 2014
Baltimore, MD

David F. Johnston1, John A. Knapik1, and John Walker2; 1Babcock & Wilcox, Barberton, Ohio, 2Duke Energy, Wabash River Station, W. Terre Haute, Indiana


Many coal-fired power plants will upgrade their aging electrostatic precipitators (ESPs) to meet the particulate matter (PM) emissions requirements established by the Mercury and Air Toxics Standards (MATS) established by the U.S. Environmental Protection Agency (EPA). Many of those upgrades will likely entail the replacement of existing conventional power supplies [transformer rectifier (TR) sets].

While the conventional single-phase power supplies have been the norm for more than 60 years, in large part due to a stellar reliability record, new types have been introduced into the marketplace. The high frequency switch mode power supply (SMPS) was launched in the 1990s. During its early stages, the SMPS was plagued with a high rate of failure which has improved, but has not achieved the reliability of single-phase. An even newer introduction, especially popular in Europe, is the 3-phase rectified power supply, which inherited many of the reliability benefits of its single-phase predecessor. Not much has been reported on the development and performance of the 3-phase low frequency power supply.

In this paper, the results of ESP power supply modeling and laboratory testing will be presented for multiple types of precipitator power supplies. In addition, the results of field testing of a single-phase and a low frequency 3-phase power supply are presented. This paper highlights the key features, advantages, and disadvantages of each device, with the intent to help the end user in the technology selection process. Several factors that affect this decision will be discussed, including the amount of ripple in the secondary voltage waveform, increased power in the precipitator field, harmonic distortion, equipment size, weight and footprint, cost, and reliability.

The results imply that low ripple power supplies hold a distinct advantage over the conventional single-phase power supply because of their ability to apply more power to the precipitator field. The results further indicate that the 3-phase power supply (a low frequency design) has an advantage over other types of low ripple power supplies because of its higher reliability and lower cost, albeit in a larger, heavier package.

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