Shunt active power filter is the preeminent solution
against nonlinear loads, current harmonics and power quality problems. APF
topologies for harmonic compensation use numerous high-power rating components
and are therefore disadvantageous. Hybrid topologies combining low-power rating
APF with passive filters are used to reduce the power rating of voltage source
inverter. Hybrid APF topologies for high-power rating systems use a transformer
with large numbers of passive components. In this paper, a novel four-switch
two-leg VSI topology for a three-phase SAPF is proposed for reducing the system
cost and size. The proposed topology comprises a two-arm bridge structure, four
switches, coupling inductors, and sets of LC PFs. The third leg of the
three-phase VSI is removed by eliminating the set of power switching devices,
thereby directly connecting the phase with the negative terminals of the
dc-link capacitor. The proposed topology enhances the harmonic compensation
capability and provides complete reactive power compensation compared with
conventional APF topologies. The new experimental prototype is tested in the
laboratory to verify the results in terms of total harmonic distortion,
balanced supply current, and harmonic compensation, following the IEEE-519 standard.
KEYWORDS:
1. Harmonics
2. hybrid topology
3. nonlinear load
4. power quality (PQ)
5. Transformerless inverter
6. Grid-connected system
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Proposed transformerless APF system
EXPECTED SIMULATION RESULTS:
Fig.
2. Steady state operation of the proposed SAPF a) Utility voltage (THDv=4%)
b) Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d)
Compensating filter current.
Fig.
3. a) DC voltage (50V/div). b) Filter current (100A/div) at filter switched ON
(t=0.15).
Fig.
4. Starting performance of the proposed SAPF. a) Utility voltage (THDv=4%) b)
Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d) Compensating
current at switched ON
Fig.
5. a) On-state and Off-state APF operations. b) Zoom image of utility line
current (𝒊𝑺𝒂𝒃𝒄)
at 5th and 7th order harmonics.
Fig. 6. Dynamic performance with the R-L load step-change waveforms of
the proposed SAPF.
CONCLUSION:
In this paper, a
novel three-phase reduced switch count and transformer-less APF circuit,
operating with the function of active filtering and enhanced reactive power
compensation. The main point of the proposed APF circuit topology, which uses a
two-leg bridge structure and only four IGBT power devices in the three-phase
power converter. Compared with the other existing topologies, the elimination
of the transformer and minimum active and passive component contributes to a
significant reduction in the manufacturing cost, volumetric size and weight.
The proposed APF system is more robust, efficient and stable to improve the
feasibility and harmonic propagation of the power distribution system. A detail
analysis of the both the active filter inverter and passive filter, including
the reactive power capability and filtering characteristics has been presented.
The series LC tuned PF at the 5th and 7th order harmonic frequencies improves
the harmonic mitigation performance. However, the series ac coupling inductors
can overcome the fixed reactive power compensation caused by the defined value
of the LC filter. The control algorithm can ensure the regulated sinusoidal
voltage, phase amplitude, and low THD in the power distribution system, along
with dc-link voltage control. The experimental and simulation results have
verified the feasibility of the proposed APF topology and its excellent
performance in terms of both transient and steady states responses to
compensate selectively either the reactive power compensation, as well as in
damping out the current harmonic distortion. Furthermore, the proposed APF
system based on transformerless and power switching device reduced count
configuration could be used in extensive applications, such as the
grid-connected power converters, grid interfaced distributed energy sources,
and so on.
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