A power-pulse-modulation control method is applied to a series-resonant converter system with multiple ports for generating synthesized waveforms with reversible power flow. The energy emanates from a source (single of polyphase voltage source generating unipolar of bipolar waveforms), and is transmitted to a network (load) in a specific form (unipolar or bipolar, single or polyphase voltage waveforms). A discussion of the stability of the energy transfer in relation to the excitation voltage leads to a clarifying description of the possibilities for the control of the resonant energy transfer for any conversion ratio. A control strategy is applied to adapt the characteristics of the resonant circuit to the rapidly varying voltages. The results of a simulation program, developed particularly for this class of conversion systems, confirm the processes. >