RTDS Simulation of PV Inverters in a Small Power System

The goal of the project is to develop a model of a small power system with multiple photovoltaic (PV) inverters. We will then implement external controls to coordinate real and reactive power output from the inverters.​ Finally, we will condense our findings into a lab exercise for future engineering students.​

=Problem Definition= As renewable energy sources become more and more prevalent in our society's power infrastructure there is a growing need for engineers with an understanding of how inverter based renewable energy sources affect the power grid.

Background
Appropriate power system models are a necessity for effective engineering in the power field. With the rise of inverter based renewable resources, the need for accurate working models is greater than ever, both for working professionals in the field as well as the future power engineers in the classroom.

Deliverables
Our goal is to create a basic distribution model that incorporates photovoltaic inverters and provides a hands on look at how this technology affects larger power system stability. We will also incorporate an automation scheme that can, in real time, regulate power flow to maintain stability for our small system. Ultimately, we will package our creation into a laboratory procedure so that students after us can learn first hand about inverter based resources in a larger distribution system.

Specifications
The model we will create will be based on the IEEE 13 bus system using a Real Time Digital Simulator (RTDS) and implemented with RSCAD software. It will incorporate three separate PV inverters with controls for each. We will also create a control scheme using an SEL Real Time Automation Controller (RTAC) to control real and reactive power output from the PV inverters based on specified grid parameters. A human-machine interface (HMI) will then be developed for real-time manipulation of the RTAC controls. When the model is working properly with the controls in place we will create a lab procedure document so future engineering students can experiment with small power systems with integrated PV inverters.

=Design Considerations= One of the major considerations for our project design was which model to base it on. We had a few different choices. We could have used a model built from scratch that had any number of busses, loads, sources, etc. There were also two pre-made model options, one was the IEEE 13 bus system and the other was the IEEE 34 bus system. Ultimately we decided that since all of the team members were new to RSCAD and working with the RTDS we probably shouldn't try to build a model from scratch as it would be too time consuming. We also decided that a 34 bus system would be too complex considering the goals of the project. The IEEE 13 bus system was the model we chose to base our project on.

We also had to decide how many inverters we wanted to integrate into the system. Dr. Johnson, our client, recommended two or three. We decided to include three PV inverters. This would make the results of the simulation results variable enough to give a good idea as to how the grid behaves based on different power outputs from the inverters. It was also recommended to connect the inverters at the weakest busses. This meant finding which busses had the lowest power factor, or ratio of real power to total apparent power. We could find this by running the IEEE 13 bus system on the RTDS and finding the power factor of each bus.

=Project Learning= Our main need for learning at the beginning of this project was to learn how to use RSCAD to build models to run on the RTDS. There is a fairly steep learning curve for this software. After finding a PV inverter model that would be suitable for integration in the IEEE 13 bus system, we found it difficult to find how to make the system register the effects of the inverter.

=Final Design=

=Validation= The Design Validation Plan can be found in the image to the right. It shows the major project requirements and how the will be tested to make sure they meet specifications. As the project progresses and certain requirements are met and tested, the table will be updated to reflect the status of the project.

=Team Members=

=Additional Documentation=

Project Schedule



Milestones



Presentations



Reference Materials