Drive control enhances thruster performance

The fleet, owned by Petroleum Geophysical Services (PGS) of Norway, has had its original analogue load commutated inverter (LCI) drive systems upgraded to a digital control platform. The upgrade delivers active dynamic load reduction to the vessels propulsion systems, while improving the efficiency and utilisation of the generators and the ships power management system.

The upgrade vastly improves the effectiveness and local ability of the shipboard maintenance teams, with the added reassurance of optional remote support engineering from Dynamotive, via a secure internet connection. The remote engineering tool provides support to vessels anywhere in the world, providing clients with more assured business continuity via rapid monitoring, protection and diagnostic display of machines, transformers, choke temperatures, system currents, voltages and alarms.

The overall project upgrade delivers a high performance, robust and reliable propulsion drive system with an extended lifecycle and with vastly reduced overall project costs. By retaining and re-using components from the original LCI drive system, such as power thyristors and Brush manufactured synchronous machines, the ship’s infrastructure faced minimum intrusion and disruption, saving money and reducing downtime.

Dynamotive’s upgrade system features the high speed ABB AC 800PEC controller which forms the heart of the digital front end (DFE) design. The DFE brings a faster and more dynamic response to the propulsion system relative to available ship power. This leads to cost savings and improved operational efficiency.

The AC 800PEC is a high performance process control system that provides the control and management of the thyristor power devices. It combines high speed control capability for dynamic load management with low speed process control and information tasks usually carried out by separate PLC units.

The DFE upgrade was installed and commissioned during a 30 day drydock period alongside other essential vessel maintenance and upgrade works.

“The old analogue drives are, by design, slower to react and, as such, the generators were not fully loaded and utilised to protect against potential black outs on the vessel, explained David Bates, commercial and marketing director of Dynamotive. “The upgrade has allowed the client to better optimise the generator loading, improving the vessel efficiency and performance while bringing significant energy saving and associated carbon dioxide emission reductions.”

Using its proof of concept test rig at its UK facility, Dynamotive designed and tested the digital control system prior to vessel installation. Client and maritime classification tests were conducted at the facility.

Complex retrofits face significant challenges when integrating new design components into retained elements of an existing installation. Dynamotive overcame these challenges, such as restricted access, by supplying a mix of new control cabinets and technologies deployed on chassis plates. This way all components could be integrated seamlessly into the retained elements of the vessel’s control system. This flexible approach added complexity to the deployment, but saved the client money and downtime.