Modular Multilevel Converter based STATCOM with Hybrid Energy Storage System Considering Unbalanced Loading Condition

Abstract

A new configuration of STATCOM with hybrid energy storage system using Modular Multilevel Converter (MMC) is proposed in this paper. The configuration is capable to provide both active and reactive powers simultaneously. Battery and ultracapacitors (UC) are employed to form the hybrid energy storage system (HSS), which they are distributed at the dc-bus of MMC through dc-dc converters. The proposed topology is suitable for higher power level. It offers higher redundancy, modularity and lower losses compared to two-level or three-level converter based approaches. A negative sequence current controller is incorporated to perform under unbalance loading condition. A super-twisting sliding mode technique has been employed for the control of dc-dc converters at the dc-link to overcome the limitations of conventional PI controllers. The effectiveness of the proposed configuration as E-STATCOM (STATCOM + Energy storage) is verified for a grid connected wind power generation system. A PSCAD model of the complete system along with control techniques are developed in PSCAD and the results show satisfactory performance.