ABSTRACT:
The proliferation of non-linear loads and the increasing
penetration of Distributed Energy Resources (DER) in Medium-Voltage (MV) and
Low-Voltage (LV) distribution grids, make it more difficult to maintain the
power quality levels in residential electrical grids, especially in the case of
weak grids. Most household appliances contain a conventional Power Factor
Corrector (PFC) rectifier, which maximizes the load Power Factor (PF) but does not
contribute to the regulation of the voltage Total Harmonic Distortion (THDV
) in residential electrical grids. This
manuscript proposes a modification for PFC controllers by adapting the
operation mode depending on the measured THDV . As a result, the PFCs operate either in a low current Total Harmonic
Distortion (THDI ) mode or in the
conventional resistor emulator mode and contribute to the regulation of the THDV
and the PF at the distribution feeders. To prove the
concept, the modification is applied to a current sensorless Non-Linear
Controller (NLC) applied to a single-phase Boost rectifier. Experimental
results show its performance in a PFC front-end stage operating in Continuous Conduction
Mode (CCM) connected to the grid with different THDV .
KEYWORDS:
1.
Harmonic
distortion
2.
Non-linear
carrier control
3.
Power factor
correction
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Residential LV grid with household appliances feed through conventional
AC/DC stages (without the proposed operation mode selector) and the proposed
PQE controller.
EXPECTED SIMULATION RESULTS:
Fig.
2. Experimental results of PQE PFC at 50 Hz. Voltage and current waveforms in
a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c)
measured spectra in both operation modes.
Fig.
3. Experimental results of PQE PFC at 60 Hz. Voltage and current waveforms in
a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c)
measured spectra in both operation modes.
Fig.
4. Experimental results of PQE PFC at 400 Hz. Voltage and current waveforms in
a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c)
measured spectra in both operation modes.
CONCLUSION:
The
consequence on the electrical power quality of connecting household appliances
to the grid through PFC stages has been assessed considering different THDV
scenarios. As has been shown in (17) and (23), there are conditions under which
sinusoidal current consumption results in better PF at the PCC than with
resistor emulator behavior, commonly assumed to be ideal for PFC stages. A
modification of the carrier signal of NLC controllers applied to PFC stages is
designed to impress sinusoidal input current despite the input voltage
distortion. The line current estimation with no interaction with the power stage
implements the NLC with high noise immunity. The digital implementation of the
non-linear controller is appropriate to define the carrier and to include
additional reduction of the current distortion depending on the application.
The PQE controller can be applied to mitigate the effect of nonlinear loads
within household appliances on residential electrical grids. The operation mode
of the digital controller can be autonomously adjusted through the locally
measured THDV , without extra circuitry. The user or a THDV threshold detection
selects the convenient behavior (either resistor emulator or pure sinusoidal
current). Experimental results obtained with high THDV (above 5 %) confirm the
feasibility of the PQE controller in both sinusoidal current and resistive
emulator modes.
REFERENCES:
[1]
IEEE Std. 519-2014 (Revision of IEEE Std. 519-1992), IEEE Recommended Practice
and Requirements for Harmonic Control in ElectricPower Systems, DOI
10.1109/IEEESTD.2014.6826459, pp. 1–29, Jun. 2014.
[2]
Y. J. Wang, R. M. O’Connell, and G. Brownfield, “Modeling and prediction of
distribution system voltage distortion caused by nonlinear residential loads,”
IEEE Trans. Power Del., vol. 16, DOI 10.1109/61.956765, no. 4, pp. 744–751,
Oct. 2001.
[3]
H. Oraee, “A quantitative approach to estimate the life expectancy of motor
insulation systems,” IEEE Trans. Dielectr. Electr. Insul., vol. 7, DOI
10.1109/94.891990, no. 6, pp. 790–796, Dec. 2000.
[4]
D. Fabiani and G. C. Montanari, “The effect of voltage distortion on ageing
acceleration of insulation systems under partial discharge activity,” IEEE
Electr. Insul. Mag., vol. 17, DOI 10.1109/57.925300, no. 3, pp. 24–33, May.
2001.
[5]
T. J. Dionise and V. Lorch, “Harmonic filter analysis and redesign for a modern
steel facility with two melt furnaces using dedicated capacitor banks,” in IEEE
IAS Annual Meeting, vol. 1, DOI 10.1109/IAS.2006.256496, pp. 137–143, Oct.
2006.
