Multi-Area Automatic Generation Control Scheme Considering Frequency Quality in Southwest China Grid: Challenges and Solutions

Abstract

Southwest China Grid (SCG) is one of the hydropower-rich power grids around the world. SCG has recently been into asynchronous operation mode, it is expected to face challenges in low inertia and frequency stability issues caused by the hydraulic turbine governing system (HTGS), which brings profound changes to the validity and stability for the multi-area automatic generation control (AGC) power systems. This paper analyzes the frequency control problems of SCG according to the operation data from asynchronous operation tests. To overcome the large overshoot and reverse regulation for external disturbances, frequency-based segment values of frequency bias for areas under TBC mode are developed considering multi-deadband effects, and a switching method of control modes for supporting largedisturbance recovery is proposed. Based on the complex and nonlinear of AGC systems, a fuzzy PD+I controller is proposed to reduce the excessively large overshoot. Furthermore, the rule for tuning D gain is established by the sign of change of area control error (ACE), and flexible I-part is applied to the control process based on the relationship between ACE and frequency. Then, we also provide filter-based control strategies with adaptive parameters to effectively coordinate hydropower and thermal power generators. The filter coefficients are computed considering various delays within AGC systems. Some case studies and actual operating conditions demonstrate the efficiency and accuracy of the proposed ideas compared with current control strategies.INDEX TERMS Automatic generation control, hydroelectric power generation, frequency response characteristic, full dynamic simulation. NOMENCLATURE Abbreviations AAL Area control error alarm limit. ACE Area control error. ADI Area control error diversity interchange. AEL Area control error emergency limit. AFC Additional frequency controller. AGC Automatic generation control. ANL Area control error normal limit. AUTOR Automatic base-point with regulation. BAAL Balancing authority area control error limit. CA Control area. CCS Coordinated control system. CG Conventional generator. CPS Control performance standard. D Derivative. DC Direct current. DFT Discrete Fourier Transform. DSA Dynamic Stability Assistant.

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