Direct Harmonic Compensation for Grid-Connected DC/AC Converter

Abstract:
An auxiliary circuit for 2-level PWM DC/AC converters is presented, which allows a partial compensation of the funda-mental oscillation of the ripple current, so that at D = 0.5 the ripple current becomes zero. This enables the same power quality to be achieved with little additional effort as is otherwise only possible with 3-level circuits or 2-phase interleaving operation. This allows the sine filter to be reduced for a given target ripple current. It is also possible to retrofit existing DC/AC converters. A transfer of the principle to multi-level circuits is possible. The new circuit is compared with the application of a non-linear smoothing choke for the same purpose