Abstract: Among various active filters, shunt active filter is a
viable solution for reactive power and harmonics compensation. In
this paper, the SRF plan is used to generate current reference for
compensation and conventional PI controllers were used as the
controller to compensate the reactive power. The design of the closed
loop controllers is reserved simple by modeling them as first order
systems. Computationally uncomplicated and efficient SVM system
is used in the present work for better utilization of dc bus voltage.
The rating of shunt active filter has been finalized based on the
reactive power demand of the selected reactive load. The proposed
control and SVM technique are validated by simulating in MATLAB
software.
Abstract: Nonlinear and unbalance loads in three phase
networks create harmonics and losses. Active and passive filters are
used for elimination or reduction of these effects. Passive filters have
some limitations. For example, they are designed only for a specific
frequency and they may cause to resonance in the network at the
point of common coupling. The other drawback of a passive filter is
that the sizes of required elements are normally large. The active
filter can improve some of limitations of passive filter for example;
they can eliminate more than one harmonic and don't cause resonance
in the network. In this paper inverter analysis have been done
simultaneously in three phase and the RL impedance of the line have
been considered. A sliding mode control based on energy feedback of
capacitors is employed in the design with this method, the dynamic
speed of the filter is improved effectively and harmonics and load
unbalance is compensating quickly.
Abstract: This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMD-s) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 12-pulse rectified output voltage is accomplished via two paralleled six-pulse ac-dc converters each of them consisting of three-phase diode bridge rectifier. An autotransformer is designed to supply the rectifiers. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 24 pulses. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6- pulse, 12-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 5% for the proposed topology at various loads.