Is there a way of forcing the PV array and the converter (inverter) size to track each other?
HOMER does not give you the ability to link the converter size to the PV array size. If you want to insure that the converter has the same capacity as the PV array, I suggest you model the PV array and the converter as an AC PV array. If you do that, make sure that where you enter the PV capacity in kW, you enter it in terms of AC capacity, after the power has gone through the inverter. And make sure to include the cost of the inverter too.
However, please note that HOMER’s results show that the optimal size of the converter is not the same as the optimal size of the PV array. A smaller converter will reduce the delivery of PV power to the load and therefore increase the generator cost, but it will also save capital cost. HOMER models that cost trade-off and similar ones relating to the other system components in its search for the optimal system configuration.
Of course if the converter can’t handle the full output of the PV array, you will end up throwing away some of the energy the PV array produces. The smaller converter does lead to more excess energy, but the dumped PV energy is a drop in the bucked compared to the dumped diesel energy. The minimum load on the diesel is what leads to all that excess energy. The addition of a battery bank would greatly reduce both the excess diesel energy and the excess PV energy.