Enhanced Control of Generators within a Marine Electrical Power System

摘要

With the move towards integrated electric propulsion systems even greater demands will be placed on marine electrical power systems of the future. This paper reports that the stability of power systems on ships could be enhanced if more robust control methods were to be applied. Electric generator sets within power systems on ships are subject to large variations in demand. The ratio of rated capacity of a single generator to total system capacity is much greater than that found within terrestrial power systems. Conventional control of a generator considers the control of the real and reactive power to be decoupled, with the governor controlling the frequency and the Automatic Voltage Regulator (AVR) controlling the voltage. Whilst this may be an acceptable approximation for a single generator operating in isolation, it can lead to stability problems when generators are operated in parallel. This paper reports an investigation into the stability of a marine electrical power system which uses conventional decoupled control. The investigation is performed by analysis of a validated software simulation. The control system is then augmented with a Power System Stabiliser (PSS), which provides a link between the governor control loop and the AVR control loop. In addition, Multi-Variable Control (MVC) techniques, as developed for use in the aerospace industry, are employed to create an MVC controller to improve the stability of a single governor/AVR pair. Finally MVC design of a system-wide integrated controller is demonstrated and evaluated. The robustness of each of these control strategies is evaluated and compared quantitatively. The PSS and MVC controllers have been demonstrated to improve the stability of the power system investigated, and are found to be more robust to system parameter uncertainties than the conventional controllers.