The company JEMA has delivered to the Joint European Torus (JET facility in Culham) two High Voltage Switching Mode Power Supplies (HVSMPS), each rated 130kVdc and 130A. One HVSMPS feeds the grids of two PINI loads. This paper describes the main control issues and the algorithms developed for the project. The most demanding requirements, from the control point of view is an absolute accuracy of +/- 1300V and the possibility of performing up to 255 re-applications of the high voltage during a 20 second pulse. Keeping the output voltage ripple to the specified tolerance has been a major achievement of the control system. Since the output stage is formed of several modules (120) connected in series, their stray capacity to ground significantly influences the individual contribution of each single module to the global output voltage. Two complementary techniques have been used to balance the effects of the stray capacities. The fast re-applications requirement has a significant impact on the intermediate DC Link. This section is composed of a capacity of 0.83 Farad, which feeds the 120 invertor modules The DC Link is fed by a 12 pulse SCR rectifier, whose matching transformers are connected to the 36kV Grid. Every re-application and every voltage shutdown supposes a quasiinstantaneous power step of 17MWatt. Fast open loop algorithms have been implemented in order to keep the DC Link voltage within acceptable margins. Moreover, the HVSMPS output characteristics have to be maintained during the rapid and important voltage fluctuations of the 36kV mains (28kV ­ 37kV). The general control system is based on a Simatic S7 PLC, and a SCADA user interface. Up to 1000 signals are considered. The control system has demonstrated to allow for a rapid and accurate identification of faults and their origin.