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New VFD Technologies in Harmonic Mitigation – Part 5: Practical Benefits of Three-Level Active Front End Drives

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Schneider Electric
Low harmonic, three-level, active rectification VFD technologies, inside and out.

Authors: Garrett Abbott-Frey, US Process Drive Offer Manager – Industry Business, Schneider Electric, and Jack Creamer, Market Segment Manager, Pumping Equipment – Industry Business, Schneider Electric

 

Harmonics in electrical systems have been a major concern for engineers and designers since the invention of inverter technologies. In the previous articles in this series, we have worked to explain the advances in harmonic mitigation technologies in variable frequency drives (VFDs) over the years. Today, VFDs must fulfill many requirements and, as resources and energy are limited, the efficient use of them becomes increasingly important.

We have shown the engineering behind the new three-level, active front end drive technology and the advantages it poses over existing or older technologies.  Now, we will explore the practical benefits they provide to two very different fields – Water/Wastewater and Oil & Gas.

Focus on Water/Wastewater

A major metropolitan district was facing the need to upgrade the VFD’s running the larger centrifugal pumps on site at a water treatment facility. The project included 11 drives ranging from 400HP and larger therefore, minimizing the harmonic content was a critical aspect to consider. The older drives being replaced relied on 18-pulse technology to keep the harmonic generation at a low level, but the decision was made to move to the newer technology of 3-level Active Front End harmonic mitigation and the Altivar Process ATV680 drives were selected.

The benefits from the update projects realized by the customer were immediate and focused on two areas.  First, the ease of planning the upgrade. The replacement AFE drives were considerably smaller, allowing for easy planning of the staged drives replacement, without allocation of additional space in the electrical room. The second benefit was a reduced purchase price for the drives – always appreciated by the customer in a project!

Longer term expectations for the drives include a reduced energy consumption from a combination of the higher efficiency of the AFE-based drives and additional energy savings that can be realized from implementation of drive functions, such as Stop-And-Go, cutting energy consumption during non-run intervals. In addition, the modular construction of the drives allowed for a reduced range of spare parts required to support the long-term operation and maintenance of the drives.

Focus on Oil & Gas

In upstream Oil and Gas, specifically Artificial Lift, there are numerous techniques for bringing fluid to the surface. One common example is SRP or Sucker Rod Pumping. In a recent project, an Oil & Gas OEM located in the mid-west was faced with producer request for a regenerative drive system solution capable of running on both utility power or by a standby generator during phase loss from the grid. This producer also wanted to avoid the extra cost and time associated with installing breaking resisters (often requiring mounting outside the E-house).

The innovative harmonic mitigation technology paired with the regenerative capabilities of the Altivar Process 980 made it the ideal solution for the OEM. The full regenerative capabilities allow the ATV980 solution to be adaptable to various Oil and Gas Applications, while delivering the THDi of 2.3% harmonic mitigation required by the end user (without additional input or motor output filtering). The ATV980 can regenerate 120% nameplate current, which makes it ideal for some high demand pumping applications, such as SRPs. This regeneration capability can also be suppressed when a generator power supply is being used.

Further, this OEM integrated the well site’s automation PLC and HMI in an additional cabinet section connected to the main drive system enclosure. The ability to add control systems into the drive enclosure allowed him great flexibility when fine tuning these solutions the producer’s specific application requirements.

Conclusion

It is the responsibility of the specifying engineer – whether their focus is Water/Wastewater, Oil & Gas, or another industry – to understand the technologies available and make the decision that best fits their individual projects.  New technologies, like the three-level, active front end drives, force those specifying engineers to continue to educate themselves on innovations so they can share them with their customers and incorporate the best products available for their projects.

The introduction of this new solution for addressing the challenge of harmonics ushers in a new chapter in power conversion devices. These low harmonic drive systems improve reliability and efficiency in generator applications by maintaining a power factor near unity down to 20% of VFD rated full load amps. This high efficiency, combined with the high input current quality, small size, and significant reduction of high-frequency CM voltage caused by the active bridge, make this three-level low harmonic offer a smart technology selection for a drive system with low harmonic requirements – with or without power line, regenerative capabilities – for any industry or application that requires a compact, low harmonic solution.

This article is part of a five-part series looking at new technologies in harmonic mitigation – including the industry’s first three-level low-harmonic drive – designed to uniquely address the harmonics issue.  For more information, please visit: goo.gl/zFuMXf.

About the Authors

Garrett Abbott-Frey is the U.S. Process Drive Offer Manager in the Industry Business of Schneider Electric. Based in Raleigh, North Carolina, Garrett brings nearly 5 years of professional experience to the role drawing from previous positions in OEM Machine Design and Electric Motor and Drives validation and testing. He currently focuses on Enclosed Drive Systems targeting the upstream Oil & Gas industry to support production process optimization for customer Artificial Lift applications. Garrett has led numerous training sessions on harmonics, drives commissioning, and other drives-related topics as well as recently publishing the whitepaper, “Transformation from Six-Pulse to Low Harmonic, Three-Level, Active Rectification Technologies.” He has a bachelor’s in Mechanical Engineering from North Carolina State University with a focus on Physics and Environmental Science.

Jack Creamer is Schneider Electric Segment Marketing Manager – Pumping Equipment, based in the United States. Mr. Creamer has more than 30 years in the Electrical Industry, and has been involved for 10 years in the Pumping Industry. He is involved in key industry organizations such as the Hydraulic Institute and Submersible Wastewater Pump Association, where he holds both Committee Chair and Board level positions. In his time in the Pump industry, he has help Schneider create numerous solutions that both enhance pumping efficiency and address issues such as maintenance and downtime.

 

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