Voltage stability in large marine integrated electrical and electronic power systems

Offshore oil and gas vessels operating in deep and ultradeep waters demand larger and more sophisticated power and control systems. This tendency brings new system design and integration challenges of the electrical distribution plant especially for platforms requiring marine dynamic positioning and power system redundancy. Voltage stability with continuously changing loads demands and with a limited power generation is essential for islanded integrated power systems, such as the marine systems with increasing presence of power electronic converters to feed variable frequency drives and other electronic equipment. Most of these present a controlled front-end, whose control can affect network voltage with a destabilizing effect. Such a behavior, which is well assessed and studied in traditional land power systems, deserves special attention if the quota of power electronics loads on the total installed power assumes very high values (up to the 85% for new large all electric ships). This work will initially introduce the well-known Constant Power Loads voltage instability issue. Some different system models will be presented, and then will be proposed a methodology to assess the voltage stability at design stage (rather than facing them with equipment retrofits during vessel building or commissioning). Finally, some case study will be discussed, and the solutions to overcome the instability will be presented.