Methods, systems, circuits, and devices for power-packet-switching power converters using bidirectional bipolar transistors for switching. Loads are aggregated into a virtual load by maximizing a global value function. The invention further concerns an antimicrobial andor cytotoxic method for treating plants. By providing a single cover for each model of golf club, in combination with a plurality of weights that are interchangeable between golf club models, the total number of balance weights that must be maintained in inventory is significantly reduced.