Three-phase shunt active power filter systems for high-power applications

Shunt active power filters are considered effective and practical solutions for the ever growing problem of power quality. However, the ability of a converter to perform effectively as an active filter is limited by the power and the frequency distribution of the distortion for which it must compensate. This research provides comprehensive and practical active filter systems for high power applications in general and the development of efficient control schemes for these systems in particular. It addresses both control and application aspects related to shunt active power filters. Two solutions are presented: a hierarchical multiple-converter and hybrid single-converter shunt active filter systems.; A multiple shunt active power filter system is designed with a view toward identifying ways to separate the filtering task among different filters. The control of such an interconnected system is more complicated than the control of a single converter, so an appropriate control formulation is needed to support a multiple converter filter system that enforces the appropriate sharing of the filtering responsibilities.; In this thesis a progressive approach for developing a frequency partitioned control strategy is described. It starts with the design of a single-phase shunt active power filter based on a sliding-mode control law (SMC). The equivalent control concept of sliding-mode control is shown to be a useful tool in designing the power circuit of the active filter. The application of sliding-mode control is then extended to a dual active filter system that facilitates the proposed hierarchical configuration of a multiple active filter system. The objective is to prove the concept of using multiple converters to realize high performance active power filters based on distortion bandwidth partitioning approach.; A more practical solution for extending the compensation capability of active power filters is the use of a hybrid series passive/shunt active filter system. This system is comprised of a three-phase shunt active filter and a series ac line smoothing reactance installed in front of the target load. The passive element limits the slope of the falling and rising edges of the load current, whereas the active filter suppresses the residual harmonic currents to the recommended limits. Hence, the filter bandwidth requirement is reduced by the reduction of the load current bandwidth through the smoothing process performed by the series reactance. The proposed system can solve the problem inherent in using only a single or multiple shunt active filter system. A Space-Vector PWM (VPWM) control is developed based on dead-beat control. The two challenging tasks associated with this control are model reduction and an efficient control algorithm implementation.; A 7.5 kVA/208 V laboratory prototype of the proposed hybrid series passive/shunt active filter system is built. A single microcontroller board is used to implement the proposed digital VPWM current regulator. An analytical approach to compute the lookup table index is proven to be effective in saving a considerable amount of the processor time. Experimental results demonstrate that the proposed hybrid system is successful in meeting the IEEE519-1992 recommended harmonic standard limits with relatively low bandwidth.