November 12, 2024
Emiliano Bellini

An Iraqi-Lebanese research team has proposed the use of an active series filter on the DC side of grid-connected photovoltaic systems to improve power quality.

Active power filters are increasingly used in photovoltaic systems to simultaneously compensate current harmonics and voltage unbalance.

“The use of filters in systems has increased due to the significant improvement in power quality at the output of the inverter and the power delivered to loads or the grid as a result of the reduction of the ripple factor on the DC side,” the researchers explained.

The ripple factor is the peak-to-peak value of the AC component of the current at the inverter input divided by the nominal DC input.

“Reducing the ripple factor on the DC side has a significant impact on improving the power quality at the inverter output, the power supplied to loads or the overhead grid, so the use of filters in these systems has increased,” the researchers said.

In their work, “Improve the power quality and stability of the grid-connected PV system by using the series filter,” recently published in Heliyon, Researchers describe an active filter designed to reduce voltage and current fluctuations on the DC side of a photovoltaic system. The proposed filter, consisting of an inductor, two capacitors and four transistor-diode pairs, connects to the DC bus and operates through a conventional controller.

The filter is controlled by a sinusoidal pulse width modulation (SPWM), which is common switching technique of power switching converters. Determines the frequency and nature of the converter’s output AC voltage.

“The principle of the proposed filter on the DC side of PV systems is to reduce the amount of high-frequency electromagnetic interference (EMI) that can damage sensitive electronics,” the researchers explained. “Series filters work by creating an impedance match between the source and the load to ensure that the voltage across both remains the same. This equalization reduces any voltage spikes that may occur and prevents them from damaging downstream equipment.”

The proposed filter reduces the noise generated by the switching of the inverter and other system components, thereby increasing the overall efficiency and reliability of PV systems. The researchers claim that the active filter lowers harmonic distortion significantly, reducing total harmonic distortion by 2.8% for voltage and 9.58% for current.

“Adding the filter improves the transient response and stability of the system. This is demonstrated by a 50% reduction in peak overshoot when subjected to test input signals,” the researchers said. “By prioritizing the transient response and using SPWM, the method goes beyond basic harmonic reduction to address dynamic system performance.”

The researchers also noted that the active filter improved the transient response of the PV system by reducing the peak overshoot with respect to the test input signals.

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