Research On Novel Resonant Dc-Link Inverter

With the development of convert technique and control theory, dc-ac converter, also known as inverter was extensively studied and much effort has been concentrated on the application. As has long been recognized, a substantial increase in inverter switching frequency is required to satisfy the requirements for an optimal converter, however, higher switching stresses,greater switching losses and EMI result from the increase in switching frequency while power density and circuit performance were improved in conventional hard switching inverter. Soft switching inverter provides a good resolution of these problems.The resonant dc-link inverter(RDCLI) employs resonant network to make the input bus oscillating periodically in order to create the soft switching conditions for the power devices in inverter bridge, the inverter achieve high-frequency operation with reduced switching losses and EMI. Considerable attentions were paid to RDCLI compared with the other two categories of soft inverter by reason of its advantages in topology configuration and efficiency. A substantial number of new topologies has been developed, but there is still much room for improvement, zero-voltage duration dependent on the load current was a major problem with the RDCLI which has not been widely used. A novel resonant dc-link inverter was proposed in this thesis to overcome that problem, the duration of zero-voltage was independent of the load current but determined by calculating the product of the resonant inductor and resonant capacitor values.In the thesis, operating principles of inverter proposed has been explained and its operation under different modes analyzed, design criteria for achieving zero voltage switching were derived from the general mathematical analysis and losses investigation, computer simulation for the inverter was conducted with MATLAB to verify the validity and the innovation of the topology, a summary was made about the theoretical analysis and simulation research, the possibilities on next step was prospected as well.