**4.2. Study statement**

The two most stringent configurations will be presented and discussed further below. The first one relates to the study of the 11th harmonic order when the ship is travelling at full speed with three diesel engine generators running (configuration A). The second one involves the study of the fifth harmonic order when the ship is on berth with only one diesel engine generator operating (configuration B). Given the harmonic currents introduced by the non-linear loads of the electrical system as mentioned in the table 9 of the appendix, the simulation of the power system for the both configurations above shows the results of the table 2 and the table 3 respectively. It can be appreciated that the resulting voltage levels for the 11th harmonic order extend far beyond the limits set by the requirements. When simulating the harmonic voltages for the 5th order when the ship is in dock, the specified limits are not exceeded on the 690V busbar only. A filtering schedule is however required on the other busbars. The choice of the most suitable placement is then questioned: is it better to plan filtering on the 400V busbar or on the 230V busbar? The proposed optimisation procedure makes it possible to get answers to that critical question.

As displayed in figure 3, the electrical system shows six nodes and thus offers six possible placements for active or passive filters. With six possible locations, the number of filters can vary from one to six. A complete analysis to determine the most suitable placement(s) to select requires sixty-three case studies. With the support of the implemented software, all the combinations are examined in 9.3 seconds of CPU time with a personal computer fitted out with an Intel© CoreDuo T8100, 2.1GHz processor. Among the list of the possible filtering solutions, the most relevant ones will be presented and argued in the following section.

In order to ensure that the optimisation procedure works well, several variables have been saved at each temperature of the SA process as the search for the optimal solution moves forward. The progress of the filtering power and the nodal voltages is then reported at the end of the computation procedure in order to control the performance of the convergence towards the global optimal solution.
