A method and computer program product are provided for selecting switching cells for voltage contribution in a phase arm of a multilevel converter, a cell selecting control device for a multilevel converter and a multilevel converter. The operating portion is pivotally connected to the display portion, and includes a casing and a touch unit located inside the casing. The duty-cycle adjustment circuit is configured to generate a divider output signal with a 50% duty cycle in response to a periodic signal generated by the half-integer frequency divider. The housing has a lead-in member at least at one end in order to allow passage through an EDS more easily and provide accurate CT calibrating.