Performance Evaluation of Different Fuzzy Logic Controllers for E-STATCOM

Abstract

This paper investigates the performance of three different Fuzzy Logic Controllers (FLCs) for an Enhanced Static Synchronous Compensator (E-STATCOM) for reactive power compensation and voltage stability improvement in power systems. The E-STATCOM is a keydevice in modern power system, ensuring efficient power flow and dynamic voltage regulation. Traditional control methods like Proportional and Integral (PI) Controllers often face drawbackslike inadaptability and robustness under varying load conditions. To address these challenges, three distinct FLCsare implemented and their transient response is compared. The study assess the controllers\' effectiveness in dynamic response. Simulation results, conducted in MATLAB/Simulink, demonstrate that fuzzy logic controller designed with a smaller number of membership functions can provide better transient response. This comparative analysis highlights the potential of intelligent control strategies in enhancing E-STATCOM performance.

Introduction

Background and Motivation:

• The integration of large-scale renewable energy sources (like wind and solar) into the grid has increased due to:

  • A fourfold rise in electricity demand.

  • Supportive government policies.

  • Rising fossil fuel prices.

• These sources are inherently variable and primarily integrated at the transmission level, reducing grid inertia and stability.

???? Role of Power Electronics and FACTS Devices:

• Power electronic converters manage variable outputs from renewable sources.

• STATCOMs (Static Synchronous Compensators) support voltage regulation and reactive power at the Point of Common Coupling (PCC).

• However, conventional converters lack capacity to meet all grid code requirements.

• To address this, an Energy Storage-STATCOM (E-STATCOM) is used, combining:

  • STATCOM for voltage and reactive power support.

  • Energy Storage System (ESS) for active power injection.

???? Proposed Fuzzy Logic Controllers for E-STATCOM:

To improve control performance, three fuzzy logic controllers (FLCs) are evaluated as replacements for the traditional PI controller:

1. FLC-1 (F-1):

   • Based on [10]-[12], uses two inputs, five membership functions, 25 fuzzy rules.

   • Quick response but higher steady-state error.

2. FLC-2 (F-2):

   • Based on [13]-[14], two inputs with seven equidistant Gaussian membership functions, and 49 fuzzy rules.

   • Best performance, offering quick response and minimal steady-state error.

3. FLC-3 (F-3):

   • Based on [15]-[18], uses non-equidistant Gaussian membership functions and 49 rules.

   • Slower response and higher steady-state error.

???? Control Strategy and Simulation:

• E-STATCOM operates in the synchronous dq-frame:

  • Id controls DC-link voltage.

  • Iq manages reactive power.

• Simulation introduces step changes in DC-link voltage (1650V → 1750V and 1750V → 650V) to test controller responses.

Conclusion

In this paper the performance of three different fuzzy logic controllers for E-STATCOM are compared for a step change. All controllers effectively regulated the voltage and reactive power during steady state. But the transient performance of F-2 controller is observed to be superior than other controllers which gives low rise time, low peak time and less steady state error than the other controllers. Fuzzy-2 demonstrated superior performance in terms of response time and accuracy.

References

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Copyright

Copyright © 2025 Srinu Bhukya, T. Murali Krishna, G. Mallesham, Ch. Anilbharadwaj. 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.