Cascaded H-bridge Multilevel Inverter Based On Use Of Virtual Synchronous Generator Control

Recently due to lack of fuel for its high cost production and environmental pollution resulting from this process, distribution generators that rely on renewable energies and power electronics inverters have become an optimal option to support power grid.In this thesis a 21-levels cascaded H-bridge multilevel inverter topology based on three-phase voltage source inverter is proposed as a superior replacement for conventional two-level in high voltage applications. The main objective of the proposed circuit is to achieve high number of output voltage levels with low Total Harmonics Distortion (THD). Two control techniques are proposed. The first one is the current controlled active/reactive power controller to control the inverter grid connected. The second is based on the usage of the new technique called virtual synchronous generator (synchronverter) to control a 21-level cascaded H-bridge topology to emulate the dynamic and transient performance of the real synchronous generator, and to make the inverters sharing the load power automatically in proportional of their ratings in case of parallel operation. In this research to validate the performance of the proposed control technique the cascaded H-bridge multilevel inverter tested under different cases with step load. Firstly the system tested for parallel operation of same capacity inverters with local load and different constant inertia, and the second for different capacities inverter to evaluate the proportional load sharing. The two proposed techniques are confirmed by theoretical analysis, simulation experiment by aid of MATLAB/Simulink package.