Research On Control Strategy Of The Shunt Active Power Filter

In a modern power system, the power conversion units and the power electronicequipments have become more and more popular. However, the nonlinear characteristics ofthese equipments are responsible for harmonic pollution of the power system. The harmoniccurrents are the source of adverse effects such as: malfunction of protection equipment, lowpower factor, interference with precision instruments and communication equipment. Activepower filters are being considered as a potential candidate for solving harmonic problems.The main contents include:(1) A new reference current computation method suitable for shunt active power filter controlunder distorted voltage condition is proposed. The active power filter control is based onthe use of self-tuning filters (STF) for the reference current generation. The use of STFinstead of classical extraction filters allows extraction directly the voltage and currentfundamental components in the α-β axis without phase locked loop (PLL). Theperformances are good even under distorted voltage conditions.(2) Contributes a comprehensive analysis of designing a passive LCL-filter for the shuntactive filter that is modulated by using variable switching frequency techniques.Designing an LCL-filter is not simple because of high compensating bandwidth andvariable frequency modulations involved in active filter. This paper examines variouseffective conditions on designing this kind of passive LCL-filters. Then it will proposed acomprehensive design procedure in which about the outcomes of the active filters,resonance and stability and other possible consequences. An example of LCL-filter designhas been realized and tested. The experimental results demonstrate the goodness of thedesign procedure the LCL-filter.(3) The main difficulties in controlling Three-phase active power filter (APF) arise from theirhybrid nature, and stability analysis for systems under state constraints. A novel approachto the modeling and regulation problem of APF is presented from the combinedperspective of switched system and stability of systems with saturation constraints. Firstly,the three-phase APF is built as switched affine system model. Based on the sufficientcondition for quadratic stability of convex combination, the common Lyapunov function was selected. Meanwhile, the switched rules are put forward by this function. Then,investigate the problem of feedback control for the switched systems with saturatednonlinear constraint; a sufficient global asymptotic stability condition is obtained. Thetheoretical results are applied to three-leg split-capacitor shunt active power filter andfour-leg shunt active power filter.(4)50A rated current active power filter is designed. Firstly, structure and parameters of theactive power filter are being designed. The compensation current references calculationalgorithm are based on the proposed p-q theory. The saturation switched control for activepower filter is given. Later, the proposed control technique has been simulatedMatlab/Simulink and tested under thyristor bridge rectifier load condition, and validatedwith a380V experimental prototype based on Digital Signal Processor(DSP)TMS320F2812+FPGA. Experimental test results demonstrate the performance of theproposed method.