A DSP controlled resonant active filter for current harmonic mitigation in three-phase power systems

Power quality has become an important concern to both electric utilities and end users due to the increased use of non-linear loads in modern power systems over the past decade. Nonlinear loads inject harmonics into the power system and thus may lead to poor power quality and lower power factor. Current and voltage harmonics can adversely affect the operation of sensitive devices.; A common remedial solution to reduce the effects of harmonic distortion in a power system is filtering. Passive and active filters are two common types of harmonic filters. An active filter, in general, is a controllable current source that injects current at the same magnitude and opposite phase to that of the harmonic current. For this thesis work, a DSP-controlled active filter to cancel lower order (5th, 7th, 11th, and 13th) harmonics in a three-phase, three-wire power system is designed. The proposed active filter employs a series LC tank tuned to a high frequency, along with a pulse-width modulated (PWM) converter topology. The PWM control of the active filter is implemented in a TMS320F240 DSP. The DSP implementation enhances the performance of the filter in real-time and enables the filter to compensate for varying loads. Additionally, the use of DSP-control reduces the number of components and therefore reduces the cost and improves the reliability of the overall system. The uniqueness of the filter is in its ability to control each harmonic separately. A laboratory prototype of the proposed active filter has been built and tested to verify the performance of the active filter.