Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Electrical and Computer Engineering

Supervisor

Pearce, Dr Joshua M.

Abstract

Decreasing cost of green energy producing solar panels has significantly boosted their popularity. Despite this, the power electronics associated with PV systems remain closed-source, expensive, and not easily compatible or expandable. This limits accessibility, especially for low-power applications. This research addresses these issues by adopting and analyzing DC nanogrid technology, converting it into a modular, open-source hardware system that users can easily assemble and expand. Detailed small signal analysis of the DC nanogrid was conducted, followed by the design of controllers and an effective energy management system. The system's stability was also thoroughly analyzed. Subsequently, hardware was developed and tested to ensure adaptability and modularity. The resulting system offers higher efficiency by serving most loads in DC, eliminating the need for AC conversion and concomitant conversion losses. This technology is particularly suitable for applications in ambulances, mini clinics, tents, expedition vehicles, houses, and camps where grid power is unreliable or unavailable.

Summary for Lay Audience

The cost of solar photovoltaic (PV) panels has been decreasing steadily, but the associated power electronics, such as converters, maximum power point trackers, and inverters, have not seen similar reductions. This discrepancy limits the accessibility and potential of solar power. The goal of this research was to develop an alternative PV system solution that is more accessible for the general users. The aim was to create a system that people can easily replicate, assemble, and use to power small-scale setups with solar energy. To achieve this, various microgrid technologies and topologies were explored. DC nanogrids were identified as the most promising alternative to conventional PV systems. This research focused on making the nanogrid modular by examining converter topologies and control methodologies. It was determined that three different converters—dedicated for PV, battery, and load—were necessary. The system's operation was first simulated, and then the system was mathematically modeled to check the stability of the bus under various conditions, ensuring it could handle additional PV units, batteries, or loads without issues. The results confirmed the system's stability under different disturbances.

Next hardware was designed. Initially, a prototype was created on a protoboard, later a final hardware of modular nanogrid was developed incorporating a hybrid control technique. In this setup, local converters manage their operations while a master controller oversees the entire nanogrid, making critical decisions such as managing excess loads and controlling power generation. The master controller also handles data logging and monitoring, sending information to a Raspberry Pi display equipped with a graphical user interface to show the system's performance.

The research identified ambulances and mini clinics as ideal candidates for adopting this hardware, given that most of their equipment can operate on battery power or directly from 6V or 12V supplies. By using two buck converters, along with PV and battery converters, these vehicles can be powered throughout the year. The PV and battery sizes were optimized through simulations. While there is room for further development, this system introduces a novel approach to PV systems and DC grids, making it accessible for general users to adopt and implement.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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