Model-Free Adaptive Control of STATCOM for SSO Mitigation in DFIG-Based Wind Farm

As the wind-integrated power system is a strongly nonlinear system with uncertain operating conditions that vary with time, it is difficult to guarantee the effectiveness of the conventional model-based sub-synchronous damping control (SSDC). To solve this problem, a model-free adaptive control (MFAC) method for static synchronous compensator (STATCOM) is proposed to realize sub-synchronous oscillation (SSO) mitigation. The method is driven by a limited number of online input/output (I/O) data rather than full technical and operational details of the system. First, the structure of the proposed MFAC is described in detail with control algorithms of all modules. Particularly, a new form of one-step-ahead weighted predictive control algorithm of MFAC for SSO mitigation is proposed. Then, the convergence of tracking error along with the stability of the closed-loop system with the improved MFAC are analyzed. Finally, the performance of the proposed MFAC for STATCOM is demonstrated and compared with that of the conventional SSDC under various operating conditions. Time domain simulation results validate the effectiveness of the proposed MFAC and demonstrate its better adaptability than the conventional SSDC.