Design and Control of LowVoltage Dynamic Voltage Restorers employing Semi-Z-Source Inverters

Abstract

Industries have attained tremendous growth rate in recent years with the advent of computers, sensitive equipment and control systems. Most of the processes involving these devices are disturbed and sometimes damaged by the voltage quality problems. Dynamic Voltage Restorer (DVR) is a power electronic converter based device that protects the sensitive loads from experiencing the power quality problems. The main objective of the research work is to find an alternative to the commonly used Full-Bridge (FB) inverter in the DVR structure. The research work here presents two novel topologies of constant dc-link type DVR based on a) semi-Z-source inverter and b) differential semiZ-source inverter. The semi-Z-source inverter offers the same output voltage range as the FB inverter with reduced number of switches. The differential semi-Z-source inverter gives double the output voltage range with four semi-conductor switches compared to the FB inverter. The Modified Sinusoidal Pulse Width Modulation Technique (MSPWM) is used for generating the switching pulses for the semi-Z-source inverter and differential semi-Z-source inverter. The two DVR topologies proposed effectively mitigate the voltage sag by employing feed-forward control and modified feed-back control. The numerical simulations of the proposed DVR topologies for different voltage disturbances are carried out in MATLAB/ Simulink environment. The application of semi-Z-source inverter and differential semi-Z-source inverter as DVR inverter is validated by the results obtained from the laboratory prototype. The MSPWM for the independent inverter operation, rms voltage method for voltage sag detection and DVR inverter control are implemented in Xilinx-Basys-3 FPGA. The voltage sag generation is implemented using Solid State Relays, transformers and PIC microcontroller. The experimental results of voltage sag compensation by proposed DVR approves the application of semi-Z-source inverter as DVR inverter.