Fractional-order PI based STATCOM and UPFC controller to diminish subsynchronous resonance

Area of Science:

• Electrical Engineering
• Control Systems
• Power Systems

Background:

• Subsynchronous resonance (SSR) causes harmful oscillations in turbine-generator shafts.
• Flexible AC transmission system (FACTS) devices like STATCOM and UPFC can interact with SSR.
• Existing controllers may not fully mitigate these oscillations.

Purpose of the Study:

• To propose a powerful fractional-order PI controller for mitigating subsynchronous oscillations.
• To enhance network damping near the turbine-generator shaft's torsional mode frequency.
• To validate the controller's effectiveness with FACTS devices.

Main Methods:

• Implementing a fractional-order PI controller in the control scheme.
• Injecting subsynchronous frequency components of current and voltage into the transmission line.
• Utilizing STATCOM and UPFC for shunt current and simultaneous current/voltage injection.
• Testing on the IEEE first benchmark model using MATLAB-Simulink.

Main Results:

• Subsynchronous oscillations reduced by 92% with STATCOM and 98% with UPFC.
• Achieved 14% greater reduction compared to conventional PI controllers.
• Demonstrated precision and robustness of the proposed controller.
• Effectively minimized subsynchronous currents, the primary cause of oscillations.

Conclusions:

• The fractional-order PI controller is highly effective in mitigating SSR-induced subsynchronous oscillations.
• The proposed method significantly improves power system stability and generator protection.
• The controller offers superior performance over conventional PI controllers in damping network oscillations.