A new space vector modulation scheme for three phase four wire inverter for standalone photovoltaic systems

Three phase inverters with unbalanced load have a lot of disadvantages like small utilisation of the DC-link voltage, dependency of the modulation factor of the load current, and the superposition of a DC component with the output AC voltage. The four-phase inverter is able to supply both symmetrical and asymmetrical consumers in the three-phase standalone photovoltaic nets. By the additional half bridge possible to reduce the DC-link voltage by 16% and dc-link capacity by 35%. In this paper a three dimensional space vector modulation for a four leg inverter for standalone photovoltaic systems is presented to solve these problems. A digital control based on a load current observer is implemented according to S. El-Barbari and W. Hofmann (2001), to control the whole system with a microcontroller. Simulation results are presented to verify the performance of the proposed system