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A three-phase soft-switched DC-DC resonant converter with variable frequency to perform the output voltage control is proposed. The open delta-wye connection provides a double output voltage reducing the primary current stress, turns ratio, weight and volume of high-frequency transformer. To achieve high efficiency, an LLC resonant tank is designed so that all switches can perform zero-voltage switching for the entire power range. In order to verify the operating principle of the converter, a design example is described, with the following converter specifications: input voltage 96 V, output voltage 380 V and a switching frequency up to 120 kHz. The feasibility and practicality of the proposed converter are confirmed by experimental results with a 1.5 kW prototype.

This paper describes a voltage impulse generator, which is utilized in the commissioning of an electrical grounding system. Unlike the Marx generator with spark gap switches, this converter uses semiconductor devices, which have a long life, better efficiency, and it can operate at high frequencies. The generator's topology uses a boost converter array operating in Discontinuous Conduction Mode (DCM). Therefore, it is responsible to inject an impulse voltage signal similar to a lightning stroke into the installed grounding system. Furthermore, one acquisition subsystem is responsible to acquire the response signals (voltage and current) at a high sample rate, and a developed software extracts the features from the transient signals. In this work, four grounding system configurations which are widely used by electricity companies are exploited, and the results are discussed.