Voltage Balancing Control for Single-Phase 5-Level Cascaded H- Bridge Inverter in Performing Harmonic Mitigation

Rising usage of technological products which are the major source of current harmonics has caused serious issues such as overheating, power failure and power loss. Hence, a shunt active power filter (SAPF) based on 5-level cascaded H-bridge (CHB) inverter is utilised to mitigate harmonics due to its superior performance. However, CHB multilevel inverter suffer from notable voltage unbalance issue due to different charging and discharging rates of each connected H-bridge. Without proper control, the unbalanced voltage will deteriorate quality of the output voltage and potentially cause power failure. Thus, in this work, a voltage balancing algorithm based on the concept of equal distribution control is integrated to achieve voltage balance across the individual H-bridges. MATLAB/Simulink software is used to build and perform simulations on the CHB inverter model and the proposed algorithm. The CHB inverter with the proposed algorithm is tested under steady-state and dynamic-state conditions, involving two highly nonlinear rectifier loads, and both ideal and distorted grids. From the findings, the resulted waveform of the source current regains its sinusoidal shape with the THD recorded between 1.97 % to 3.04 % in all tested conditions, thereby satisfies the IEEE 519–2014 standard. Additionally, implementation of the proposed voltage balancing algorithm has found to effectively minimize the voltage unbalance issue thus providing a more stabilised DC-link voltage.