High-Precision Calculation Method for SLCC Commutation Overlap Angle Incorporating SVF-LCC Coupling Dynamics

Self-Adaptive STATCOM and Line Commutation Converter (SLCC) utilizes a Static Var & Filter (SVF) to provide dynamic reactive power compensation and harmonic filtering for converter stations. This effectively enhances the inverter station's capability to withstand commutation failure. However, existing research on SLCC primarily focuses on optimizing control strategies. Its fundamental commutation mechanism analysis typically simplifies the receiving-end voltage source and SVF into a single equivalent voltage source within the traditional Line-Commutated Converter (LCC) commutation process model. This approach lacks in-depth analysis of how the SVF compensation current influences the commutation process, resulting in significant deviations between the calculated commutation overlap angle and the actual value, making it difficult to establish an accurate SLCC mathematical model. To address these issues, this paper proposed a high-precision calculation method for SLCC commutation overlap angle incorporating SVF-LCC coupling dynamics. It establishes an equivalent circuit model for the SLCC commutation process by accounting for the coupling effects between the SVF output current/voltage and the LCC at the Point of Common Coupling (PCC). Based on this model, the commutation current characteristics of thyristors under SVF compensation current injection are thoroughly analyzed. A high-precision analytical function relating the SLCC direct current to the commutation overlap angle is derived. Finally, the proposed model and method are validated on the PLECS simulation platform. The results demonstrate that the established equivalent circuit model for the SLCC commutation process better reflects actual operating conditions, and the derived analytical expression for the commutation overlap angle accurately captures the variation pattern of the actual overlap angle with high precision.