The electric distribution network in Finland has normally voltage levels of 20 kV and 400 V. First the electric power is transferred near the customers with 20 kV and then transformed down to 400 V. The problem in this case is that the amount of transformers is big at rural areas, because they must be placed close to the users. An alternative for this could be DC distribution, where the RMS value of the voltage would be bigger. In this case electrical power could be transferred for longer distances without the need of 20kV lines for one or a few customers. This again leads to a need for a DC/AC converter to each user.

The converter presented in this work is designed to convert a power of 1 kVA from 750 VDC to mains voltage (230 VRMS, 50 Hz). The device is optimized to have a good efficiency and to separate the output galvanically from the input.

The converter uses a primary resonant converter, which turns the DC voltage in high frequency AC. This is then fed to a high frequency transformer, which creates the galvanic separation. The transformer feeds a cycloconverer that forms the mains voltage using pulse density modulation. After this the voltage is filtered with an LC- filter to get the output distortion to match standard levels.

The device is split into 3 pieces, which each are separately simulated and their function explained. At the end the whole system is simulated as one peace. The efficiency was roughly estimated to be 94 % and the final results show, that the development of a prototype could be worth an effort.