The Analysis of HVDC Over-Modulation Technique of Three-Phase CSR

This paper introduces an over-modulation technique, a continuous extension of space vector PWM (SVPWM) linear control scheme for the HVDC three-phase current source rectifier (CSR). By judging the magnitude of active current vectors durations, this technique can select the current vectors in sectors and modify their active durations. It is neither necessary to store a lot of data in advance nor needs complex calculation strategy, which is very suitable to a digital implementation based on field programmable gate array (FPGA). The over-modulation scheme can extend the DC output voltage range of three-phase CSR, useful in improving the dynamic response and fulfilling the specific load demands. The simulations and experiments prove that the produced scheme not only has good dynamic and static performances, but also can keep the power factor at unity in a wide range of output DC voltage and the input current harmonic THD is very low.