Analysis and Modelling of a MultilevelInverter in Distribution System with FACTSCapability

Abstract

This paper presents the design of a multi-level inverter with Flexible AC transmission systems (FACTS) capability for small to medium size (10–20kW) permanent-magnet wind applications using modular multi-level converter (MMC) topology. The aim of the paper is to design a new type of inverter with Distribution static synchronous compensator (D-STATCOM) option to provide utilities with more control on active and reactive power transfer of distribution lines. The proposed inverter is placed between the renewable energy source, specifically a wind turbine, and the distribution grid in order to fix the power factor (PF) of the grid at a target value, regardless of wind speed, by regulating active and reactive power required by the grid. The D-STATCOM inverter is capable of controlling active and reactive power by controlling the phase angle (𝛿) and modulation index (m), respectively. The unique contribution of the proposed work is to combine the two concepts of inverter and D-STATCOM using a voltage source converter (VSC) multi-level topology in a single unit without additional cost. Simulations of the proposed inverter, with 11 levels, have been conducted in MATLAB/Simulink. The main function of the proposed inverter is to transfer the active power to the grid as well as keeping the powerfactor (PF) of the local power lines constant at a target PF regardless of the incoming active power from the wind turbine.