Mitigating Voltage Sag and Swell for Improved Power Quality in Non-Linear Load Systems via Series Active Filtering

Abstract

The power quality enhancement is mandatory with the newer generation load equipment, whose performance is very sensitive to power quality disturbances especially with voltage sag, Harmonics and Interruption. The power electronic based power conditioning devices can be the effective solution to enhance the quality of the power supplied to the power distribution system. The series connected Series Active Filter is one of the effective solution to mitigate power quality problems in the distribution system. In a control, theory of the Series active filters main consideration includes detection of the start and finish of the sag, voltage reference generation, transient and steady state control of the injected voltage, and protection of the system. In this work, the simulation model of nonlinear load connected power distribution system is implement for checking the effect of non-linear load on the entire system in the MATLAB/Simulink. In this case, we simulate three voltage sag, voltage swell and effect of non-linear load and check the THD with series active filter or without.

Introduction

Electrical energy is a versatile and easily controlled form of energy that must maintain quality and continuity for economic operation. A power system consists of generation, transmission, and distribution, with the distribution network playing a critical role in power quality and reliability. Failures in distribution cause about 90% of customer interruptions. Modern power quality challenges—such as voltage sags, swells, interruptions, transients, and harmonics—are increasingly common due to the widespread use of power electronics.

Voltage sags are particularly severe disturbances. To mitigate these, Series Active Power Filters (SAPFs) are employed, connecting in series with the distribution line to stabilize voltage and protect sensitive loads. SAPFs work by injecting compensating voltages that isolate harmonic disturbances caused by nonlinear loads, ensuring a clean sinusoidal voltage waveform.

The series APF operates as a controlled voltage source, showing zero impedance at fundamental frequencies but high impedance at harmonic frequencies, effectively blocking harmonic currents from affecting the source. This protects equipment and improves power quality, especially in distribution systems with nonlinear loads.

A MATLAB/Simulink model simulates the SAPF’s performance under steady and transient conditions, using components like injection transformers, voltage source inverters (VSI), LC filters, and energy storage. The model demonstrates the filter’s ability to reduce voltage distortions caused by nonlinear loads such as rectifiers, thereby preventing damage to transformers and improving overall system stability and efficiency.

Conclusion

This research work addresses power quality concerns and proposes a series active power filter (SAPF) to minimize voltage sags, swells, and harmonics. The SAPF aims to improve overall system performance. To display its effectiveness in reducing voltage sags, a simple distribution network is simulated using MATLAB. Results from the simulation demonstrate the benefits of using the SAPF. This work contributes to enhancing power quality in electrical systems. Power quality issues are increasingly causing problems in various sectors, including urban areas, industries, and hospitals, especially where power electronic devices or non-linear loads are used. These non-linear loads create harmonics, as well as voltage sags and swells, leading to distortion and imbalance in the system. This work focuses on improving power quality using a series active power filter (SAPF). The SAPF injects voltage into the distribution system to balance the voltage and smooth out the waveforms of voltage and current. A controller manages the voltage and frequency. This approach is a modern solution using power electronics to address harmonic pollution. This simulates a series active power filter (SAPF) to address power quality challenges such as voltage sags, voltage swells, and their combined effects using MATLAB. Afterward, non-linear loads are added to the distribution system to analyze their impact on performance. It is found that these non-linear loads negatively affect the system and generate harmonics. The series active power filter helps reduce these harmonics, and the total harmonic distortion (THD) is also analyzed in this work.

References

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Copyright

Copyright © 2025 Komal Harsh, Dr. M. K. Bhaskar, Manish Parihar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.