November 12, 2024
Emiliano Bellini

An Iraqi-Lebanese research team has proposed using a series active 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 for current harmonics and voltage unbalance.

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

The driving 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 delivered to the loads or to the overhead grid, which is why the “Use of filters in these systems has increased,” the researchers said.

In their article, “Improve power quality and stability of grid-connected PV system using 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 bar and operates through a conventional controller.

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

“The principle of the proposed filter on the DC side of photovoltaic systems is to reduce the amount of high-frequency electromagnetic interference (EMI) that can damage sensitive electronic components,” the academics 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 voltage peaks 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. Researchers say the active filter significantly reduces harmonic distortion, reducing total harmonic distortion by 2.8% for voltage and 9.58% for current.

“The addition of the filter improves the transient response and stability of the system. This is demonstrated by a 50% reduction in maximum overshoot when subjected to test input signals,” the researchers said. “By prioritizing 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 its maximum overshoot value compared to the test input signals.

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