Power Quality Enhancement titles
The proliferation of non-linear loads and the increasing penetration of Distributed Energy Resources (D ER) in Medium-Voltage (M V) and Low-Voltage (L V) 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 (TH D V ) in residential electrical grids.
manuscript proposes a modification for PFC controllers by adapting the operation mode depending on the measured TH D V . As a result, the PF Cs operate either in a low current Total Harmonic Distortion (TH DI ) mode or in the conventional resistor emulator mode and contribute to the regulation of the TH D V and the PF at the distribution feeders. To prove the concept, the modification is applied to a current sensor less Non-Linear Controller (N LC) applied to a single-phase Boost rectifier. Experimental results show its performance in a PFC front-end stage operating in Continuous Conduction Mode (CC M) connected to the grid with different TH D V.
Fig. 1. Residential L V grid with household appliances feed through conventional AC/DC stages (without the proposed operation mode selector) and the proposed P Q E controller.
EXPECTED SIMULATION RESULTS:
Fig. 2. Experimental results of P Q E PFC at 50 Hz. Voltage and current wave forms 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 P Q E PFC at 60 Hz. Voltage and current wave forms 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 P Q E PFC at 400 Hz. Voltage and current wave forms in a) resistor emulator mode (k = 0), b) sinusoidal current mode (k = 1) and c) measured spectra in both operation modes.
The consequence on the electrical power quality of connecting household appliances to the grid through PFC stages has been assessed considering different TH D V scenarios. As has been shown in (17) and (23), there are conditions under which sinusoidal current consumption results in better PF at the PC C than with resistor emulator behavior, commonly assumed to be ideal for PFC stages. A modification of the carrier signal of N LC 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 N LC 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.
P Q E controller
The P Q E 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 TH D V , without extra circuitry. The user or a TH D V threshold detection selects the convenient behavior (either resistor emulator or pure sinusoidal current). Experimental results obtained with high TH D V (above 5 %) confirm the feasibility of the P Q E controller in both sinusoidal current and resist i v e emulator modes.
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