Development of a synchronverter for a grid connected photovoltaic system

Abstract

As global population has grown exponentially since the past decade, the demand for a sustainable framework for cleaner, greener and stable energy production is becoming more important for a holistic society. Among multiple renewable energy sources, solar power is highly favoured to dominate the market due to improvements in solar energy conversion efficiency and reduction in production cost. Thus, many transmission grids will observe a high penetration of inverters as an interface between solar panels and the AC transmission grid. Consequently, inverter-dominated transmission grid will face issues with maintaining and achieving overall grid stability due to the characteristics of inverters which are composed of mainly solid state devices (SCR, MOSFETS or IGBTs). This is due mainly to the lack of rotational inertia, which is typically contributed and maintained by traditional synchronous generators when the stability of the transmission grid is disturbed. For this reason, conventional inverters can potentially be exploited to mimic the characteristics of synchronous generators to stabilize the transmission grid. Thus, this project is motivated to design a ‘smart’ inverter or synchronverter which can operate on islanded mode while integrated with solar panels. This project focuses on developing and prototyping a working three-phase inverter model using a Raspberry Pi microcontroller with Simulink support. Bipolar Sinusoidal Pulse Width Modulation (SPWM) technique is used to create the sinusoidal output waveform with a fixed frequency of 50Hz. The output waveform will also have a Total Harmonic Distortion (THD) of less than 5%. A Proportional-Integral (PI) controller is also implemented to ensure that amplitude and frequency of output sinusoidal remains constant. In this work, simulation of a three-phase inverter is done using Simulink (MATLAB) to validate the performance of the inverter (hardware prototype). The developed hardware prototype is experimentally tested by integrating with 1000W solar panels.