Performance Analysis of Type-1 and Type-2 FLC based Shunt Active Filter Control Strategies for Power Quality Improvement

Abstract

In recent years electrical power quality has been an important and growing problem
because of the proliferation of nonlinear loads such as power electronic converters in typical
power distribution systems. Particularly, voltage harmonics and power distribution equipment
problems result from current harmonics produced by nonlinear loads. The electronic
equipments like; computers, battery chargers, electronic ballasts, variable frequency drives,
and switch mode power supplies, generate perilous harmonics and cause enormous economic
loss every year. Problems caused by power quality have great adverse economic impact on
the utilities and customers. Due to that both power suppliers and power consumers are
concerned about the power quality problems and compensation techniques.
Issue of harmonics are of a greater concern to engineers and building designers because
harmonics can do more than distort voltage waveforms, they can overheat the building
wiring, causes nuisance tripping, overheat transformer units, and cause random end-user
equipment failures. Thus power quality (PQ) has become more and more serious with each
passing day. As a result active power filter (APF) gains much more attention due to excellent
harmonic and reactive power compensation in two-wire (single phase), three-wire (threephase
without neutral), and four-wire (three-phase with neutral) ac power networks with
nonlinear loads. The APF technology has been under research and development for providing
compensation for harmonics, reactive power, and/or neutral current in ac networks. Current
harmonics are one of the most common power quality problems and are usually resolved by
the use of shunt active filters.
In this research work, the performance of the shunt active filter control strategies has been
evaluated in terms of harmonic mitigation and DC link voltage regulation. Three-phase
reference current waveforms generated by proposed scheme are tracked by the three-phase
voltage source converter in a hysteresis band control scheme. This research presents different
topologies and controllers with enhanced performance of shunt active filter for power quality
improvement by mitigating the harmonics and maintaining dc link voltage constant.
For extracting the three-phase reference currents for shunt active power filters, we have
developed shunt active filter Instantaneous active and reactive power “p-q” and
Instantaneous active and reactive current “Id-Iq” control strategies. For regulating and
maintaining the DC link capacitor voltage constant, the active power flowing into the active
filter needs to be controlled. In order to maintain DC link voltage constant and to generate the
compensating reference currents, we have developed PI Controller, Type-1 and Type-2 Fuzzy
logic controller with different Fuzzy MFs (Trapezoidal, Triangular and Gaussian). The
proposed APF is verified through MATLAB/SIMULINK. The detailed real-time results using
Real-time digital simulator are presented to support the feasibility of proposed control
strategy.