Scientists use series active filter to improve power quality of grid-connected PV – pv magazine International

12 November 2024
Emiliano Bellini

An Iraqi-Lebanese research team proposed using a series of active filters on the DC side of grid-connected PV systems to improve power quality.

Active power filters are increasingly used in PV systems to simultaneously compensate for current harmonics and voltage imbalance.

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

Ripple factor 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, power supplied to the loads or the overhead network, hence the increased use of filters in these systems,” the researchers said.

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

The filter is controlled by the widely used sinusoidal pulse width modulation (SPWM). Switching technique for power switching converters. The converter determines the frequency and nature of the 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 academics said. “Series filters work by creating an impedance match between the source and load to ensure the voltage at both ends remains the same. This balancing reduces voltage spikes that may occur and prevents them from damaging downstream equipment.”

The proposed filter reportedly improves the overall efficiency and reliability of PV systems by reducing noise generated by inverter switching and other system components. Researchers claim that 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 increases the transient response and stability of the system. The researchers noted that this was evidenced by a 50% reduction in maximum overshoot when exposed to test input signals. “By prioritizing the transient response and using SPWM, the method uses fundamental harmonics to address the dynamic performance of the system. It goes beyond reduction.”

The researchers also noted that the active filter improved the transient response of the PV system by reducing the maximum overshoot value relative to the test input signals.

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