Improvement Issues on the Input Filter Design for PWM-CSR that are SHE Modulated

Abstract

PWM current-source rectifiers that are modulated with selective harmonic elimination techniques are frequently used in medium voltage/high power AC drives. The AC filter requirements are usually satisfied using a low-pass LC network including a damping resistor. This is connected in the capacitive branch to avoid two unwanted oscillation sources, (a) the transient response of the filter to a sharply sloping edge in the rectifier-input current and (b) the amplification of non-characteristic harmonics - present in the rectifier input currents - that near the filter-resonant frequency. As a result of including resistors, it is necessary to increase the filter size in order to keep the harmonic attenuation which degrades the dynamic system response and increases the filter cost. The proposed solution is to modify the capacitive branch to obtain a smaller filter than using the standard topology. Practical considerations and necessary equations are shown in a detailed procedure to design the proposed filter. Simulated and experimental results are presented to validate the theoretical considerations