Performance Evaluation of Adjustable Speed Drives Using Multilevel Inverter Based STATCOM

Adjustable speed drives (ASD) employing induction motors are widely used in the industrials and process control in the form of varied applications such as fans, compressors, pumps etc. They are energy efficient and can result in substantial energy saving when properly installed. However, they inject high harmonic content into current drawn from the ac system. This paper deals with the application of a STATCOM for compensation of such loads. The MATLAB / Simulink based models are developed for adjustable speed drive loads. The analysis is carried out with and without STATCOM. The results shown in the paper prove that STATCOM can be used as a good harmonic filter. Cascaded multi-level converter based STATCOM (CMCSTATCOM), with a topology of modular-cascaded structure, has a wide prospect of applications in both transmission and distribution system. Under the background of application of STATCOM in high voltage power grid, there are many advantages of CMC-STATCOM compared with other kinds of STATCOM. On the basis of mathematical model of main topology, the states feedback decoupled reactive power control strategy based on the d-q coordinate system is studied in this paper, together with the application principle of carrier phase shift PWM modulation method in CMC. The balance of DC bus voltage is a key factor to the stable operation of devices In this paper, the hierarchical control method is used to achieve a balance of DC bus voltage, and it involves the DC bus voltage overall control and individual control of each cascade module. Keywords-Cas caded H-Bridge, Multilevel Converter, STATCOM, Drives.