Improved DC-Link Voltage Sliding Mode Control for Permanent Magnet Synchronous Generator Systems With Three-Phase AC-DC Converters

Abstract

A conventional proportional-integral (PI) controller is commonly used in the dc-link voltage control outer loop of permanent magnet synchronous generator (PMSG) systems; however, it cannot achieve consistent dc-link voltage control performance across the entire operating range, resulting in poor dynamic response. In contrast, dc-link voltage sliding mode control (SMC) offers faster dynamic performance compared to conventional PI control; nevertheless, stability analysis indicates that SMC may result in voltage tracking errors when the disturbance power is significant. In order to address this issue, a disturbance power observer based on recursive least squares (RLSs) with a forgetting factor is proposed. The RLS-based observer can achieve minimum variance estimation of the total disturbance power, and its convergence speed can be adjusted by tuning the forgetting factor. By feeding forward the RLS-observed power into the SMC (referred to as SMC + RLS method), the dc-link voltage control performance is significantly improved. Experimental results demonstrate that the proposed SMC + RLS method exhibits a faster dynamic response than both conventional PI control and state-of-the-art nonlinear controllers when the operating point changes. The disturbance power can, moreover, be quickly observed by the RLS-based observer, providing the SMC + RLS method with excellent anti-disturbance performance.