An effort to formulate frequency modulation constraints in ship-electrical systems with pulsed loads

One of the most significant power supply quality problems in ship electric networks is `frequency modulation`. This is a phenomenon most frequently met in extensively electrified ships and it is caused by the operation of certain electric loads, known as `pulsed loads`, which require high power repeated on a regular or random basis. To the best of the authors` knowledge, no well-based theoretical analysis of the phenomenon exists in the literature, although any existing constraints limiting the operation of pulsed loads are not properly explained in the respective standards. Hence, in this study, an effort is made, first to establish a theoretical explanation of the modulation phenomenon via an analytical mathematical expression comprising all the critical parameters that affect it, and then highlight the appropriate procedure of setting limits via standards. In this way, the frequency modulation is expressed as a function of several parameters of the ship electric system. Furthermore, using the obtained expression, a sensitivity analysis of the particular effect of each of these system parameters is made. The proposed method is a useful design tool for ship electric power systems enabling the assessment of acceptable pulsed loading level without the need of complicated simulation models comprising many parameters usually not readily available.