Anew concept of Naval Support Ship, the Mobile Landing Platform (MLP) is a type of amphibious assault/expeditionary ship with the first ship (USNS Montford Point) entered service in United States Navy in 2013. Currently, there are three MLP vessels in service. The first two ships are part of the Maritime Prepositioning Force, where as the third ship (entered into service in June 2015), an Afloat Forward Staging Base (AFSB) variant, and two more AFSB variants are underway. The ships are designed primarily to support military hovercraft (such as the Landing Craft Air Cushion), to serve as floating bases for amphibious operations, and operate as a transfer point between large ships and small landing craft. Another role of the MLP platform would be a seagoing pier for friendly forces in case accessibility to onshore bases are denied. The MLPs can also be deployed in wide range of operations, including humanitarian assistance, disaster relief, counter-piracy, maritime security, amphibious and other combat missions.
Powered by a diesel-electric main propulsion scheme, the ships utilize an integrated power system which supplies the electric power, propulsion and vessel automation system. The system includes the tandem propulsion motor powered by variable frequency drives, as well as the harmonic filters, generators, high voltage switchboards, transformers, automation, an azimuth thruster that can be swiveled for dynamic positioning, and the associated thruster drive and motor.
The power quality of distributed service power, which powers the vessel’s navigation, alarm, communications, and information technology equipment has high levels of harmonic content and significant voltage excursions during variable frequency drive actuation. The problem is amplified by the distribution system having a limited number of parallel branch distribution circuits. This has resulted in a power quality level that is not able to support reliable operation of the Vessel’s communications, operational management systems and other mission-critical equipment.
US Naval Sea Systems Command (NAVSEA) attempted to alleviate the situation by adding a line-interactive Uninterruptable Power Supply (UPS) to provide power conditioning for the critical equipment. The line-interactive UPS did not have the ability to condition either the voltage excursions or correct the harmonic content. This forced the line-interactive UPS to continually run from battery. The batteries were unable to sustain the critical equipment. This resulted in the line-interactive UPS shutting down and to operate in a by-pass mode, leaving the powered systems subject to the full voltage excursions and harmonic content of the distributed power, causing the equipment to shut down and restart at various times. An example of the line-interactive UPS output power waveform is shown in Figure 1.
In order to come up with an optimal solution in order to remedy those power quality problems, NAVSEA consulted NOVA Power Solutions for a close collaboration with participation of MLP program design engineers. The adopted approach for an optimal solution for this power issue was to employ a power conditioner and battery back-up with a wide input range, capable of correcting for a full range of power quality conditions. For this purpose a number of products from different manufactures were put on various test and trials. NOVA Power Solutions was able to provide this system from their highly customizable product offerings. Throughout extensive field testing, harbor and finally sea trials, only the NOVA Power Solutions systems were capable of consistent and reliable operation across the full range of tested power quality conditions and meeting NAVSEA’s all requirements.
An example of the clear signal output power of a NOVA Power Solutions true online UPS system is shown in Figure 2. As a result of those comprehensive tests and trials and tests, a NOVA Power Solutions rugged shipboard tactical power conditioner was selected to meet this specific application and fully satisfy the MLP program extreme requirements. This solution allowed NAVSEA to restore the mission-critical equipment to full operating capacity.
Upon the NAVSEA’s decision on employing NOVA Power products on board MLP ships, “We are extremely pleased with our close collaboration with NAVSEA design engineers and ship crew to come up with an optimal solution for MLP platform.” stated Mr. Steve Ziff, President and CEO, NOVA Power Solutions, Inc. “As a result of this successful work, we had a chance to offer the best solution to this specific application and NOVA Power solutions truly stood apart from competitors. I believe, in this decision of NAVSEA, not only the specific performance of NOVA Power during these tests played an important role; but the knowledge and expertise to successfully offer and support our customers with best-in-class power protection solutions for more than 25 years with a large installed base of over 40,000 UPS systems deployed, our range of products that are highly customizable to meet customer program specific requirements, a deep understanding of logistics and supply chain management and post-sale support throughout the equipment life cycle were also taken into account.”