ABSTRACT:
Motor
drive systems based on diode-rectifier are utilised in many industrial and
commercial applications due to their cost-effectiveness and simple topology.
However, these diode rectifier-based systems can be affected by power quality
and harmonics in distribution networks. Thus, this paper investigates the
impact of grid voltage harmonics on the operation of power converters with
three-phase diode rectifier using mathematical formulation of the drive voltage
and current harmonics based on grid voltage harmonics. Simulation analysis and
practical tests have been then carried out to validate the mathematical
equations and the impact of grid voltage harmonics on the power converter
harmonics. The results illustrate that even a small amount of grid voltage harmonics
(around 4%) could significantly impact the input current harmonic contents of
the three-phase diode rectifier. It is also shown that the phase-angle of grid
voltage harmonics plays a crucial role to improve or deteriorate the input
current harmonics of the power converters. In the next step, the optimum
condition of grid voltage harmonics to minimise the input current harmonics has
been evaluated and verified based on different grid codes. Finally, a harmonic
mitigation technique in multi-drive systems using Electronic Inductor is
proposed to mitigate the current harmonics at the PCC.
KEYWORDS:
1. Distorted
grid
2. Distribution
networks
3. Total
harmonic distortion
4. Three-phase rectifier
Voltage harmonics
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Figure 1. Simulink Model For The
Tested Asd Under The Presence Of Voltage Harmonics At The Pcc.
EXPECTED SIMULATION RESULTS:
Figure 2. Simulation Results Of The Three-Phase
Input Currents And Vrec
In
Case: (A) 1, (B) 2, And (C) 3.
Figure 3. Practical Measurements Of The
Three-Phase Input Currents And Vrec In Cases: (A) 1, (B) 2, And (C) 3.
Figure 4. Simulation Results Of The Three-Phase
Input Currents And Vrec
In
Cases: (A) Ieee-Min, (B) Ieee-Max.
Figure 5. Practical Measurements Of The
Three-Phase Input Currents
And
Vrec In Cases: (A) Ieee-Min, (B) Ieee-Max.
Figure 6. Simulation Results For Phase ``A''
Current When U1 Mitigates
Harmonics
Generated By U2: (A) Case 3, (B) Ieee-Max Case.
Figure 7. Simulation Results For Output Voltage
(Vo), Inductor Current, And Phase ``A'' Inverter Side Current Of U1.
CONCLUSION:
In
this paper, the impact of grid voltage distortion on power converter current
harmonics emission has been investigated. For that aim, ASDs with conventional
diode rectifier has been considered to represent the power electronic system. A
mathematical formulation of the rectified voltage, inductor current, and input
currents of a three-phase diode rectifier is derived under the presence of
voltage harmonics at the PCC. Different cases of voltage harmonics are then
considered in the analysis to investigate the behaviour of the rectified voltage
and the input current harmonics. The results show that the presence of even a
small level of voltage harmonics (4%) at the PCC can change the current THDi by
up to 30%. Furthermore, it has been shown that the phase-angle of the voltage
harmonics can have a significant impact on the input current harmonics.
Depending on the voltage harmonic phase-angle, the same amount of voltage
harmonics could improve or deteriorate the rectified voltage ripple and the
input current THDi. Moreover, the voltage harmonic phase-angle could create a
phase delay (1) in the diodes conduction time. A positive 1 impacts the
displacement power factor negatively, whereas a negative 1 improves that factor.
Finally, a harmonic mitigation technique to compensate the high level of
current harmonics using Electronic Inductor (EI) is presented.
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[3]
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