Enhancement of Transient Reactive Power Compensation Capability for STATCOM Based on Power Balance Phase-Locked Strategy

Abstract

When a fault occurs in transmission lines, the voltage at the point of common coupling of renewable energy stations can drop drastically. This causes the phase-locked loop (PLL) performance to degrade, reducing the transient voltage support capability of the STATCOM in the station. To address this issue, this paper proposes a novel phase-locked method for STATCOM based on power balance (PB) theory. First, the paper establishes a mathematical model of the traditional STATCOM to identify the causes of PLL performance degradation during transient events. Next, the paper introduces the PB phase-locked strategy: this strategy adjusts the power exchange between the grid and STATCOM, simulating the synchronization process of a synchronous condenser. Finally, the paper uses PSCAD/EMTDC to build simulation models and verify the performance of the proposed scheme. The simulation results show that overvoltage and overcurrent are reduced by 16.5% and 20.1%, respectively, compared to traditional SRF-PLL. The proposed strategy provides sufficient transient voltage support even when the traditional PLL fails.