Campus Facilities Load Shedding Design

=Introduction=

Background
The project aims to design a microgrid load shed algorithm to balance power on the University of Idaho island when Avista undergoes a blackout event. We will determine which campus buildings get power and the priority of the buildings. The loads will be grouped in a logical way to effectively reduce overloading on University of Idaho microgrid generation. The overall UI microgrid scope includes the entire campus, with a total of 143 floors, excluding Northern farms. Currently, 12% of the campus load is expected to come from the Steam Plant turbines, of which 3% must provide electricity for the Steam Plant. The remaining 9% of annual power production has been allocated for our load shed product. Our project scope includes designing the load shed algorithm for the following campus buildings: McClure, CNR, GJL, BEL. The current microgrid generation considered for this project includes the steam turbines in the Steam Plant and solar panels to be placed on the roof of IRIC. We will aim to design a module load shed scheme that can be scaled when more generation sources are determined for the UI microgrid.

Problem Definition
1.The UI does not have a systematic control system to control microgrid loads.

2. A load shed algorithm is required to efficiently regulate microgrid power.

Project Goals
1. Load shed algorithm to allocate the Steam Plant and IRIC power generation efficiently and safely a. Load prioritization for McClure, CNR, BEL, and GJL b. Algorithm to include user input, time of day/year, and to be easily modifiable c. Determination of switchgear required to implement the system 2. Load shed system to be modularized to allow for microgrid expansion, system testing, and verification with Real Time Digital Power System Simulator (RTDS) and SEL equipment

3. Economic analysis for the required load shed system equipment investment

=Microgrid Design=

Specifications
Our goal is to utilize SEL equipment to implement an efficient system to allocate power from the UI Steam Plant to local campus buildings during Avista blackouts. SEL equipment has functions such as automatic bus synchronism, trip/close commands to remote enabled breakers and so on. This equipment from SEL will contribute significantly to student development in this Capstone project and in projects to come. Furthermore, this hands-on experience with state of the art equipment from SEL will provide students with an invaluable education that is of interest to SEL.

System Overview
This figure illustrates the microgrid one-line for the University of Idaho. The generation in this microgrid includes the Steam Plant turbines and IRIC solar. The loads include many buildings that will not be included in the load-shed scheme as well as the four priority buildings. The last two relays in this system will include two tie relays on either side of the microgrid. These tie relays will be responsible for islanding the system as well as returning to the utility. This figure showcases the system we plan on testing using a Real Time Power System Digital Simulator (RTDS) in Dr. Johnson’s lab. We plan to use nine SEL-751 relays and an SEL Real Time Automation Controller (RTAC). The relays included will be the two tie relays, two relays on the microgrid generation, four priority buildings, and one non-priority building.

Communications


The 18 SEL relays in this network represent two tie relays, one relay on the Steam Plant, one relay on IRIC, four relays on the load shed buildings, and the remaining ten relays on the non-load shed buildings. These smart devices must communicate to the RTAC in order for power to be balanced and for the system to respond to utility events appropriately. We decided to use a primary and redundant IEC 61850 GOOSE communication network to pass information to/from the RTAC and relays. The redundant network helps limit the chance of information being dropped in the Ethernet-based communication scheme. Additionally, this network should have a software-defined switch (SDN) to facilitate network communication. The switch on the network will greatly increase the system security because any messages not recognized by the switch will be dropped.



This figure shows the inputs and outputs from the RTAC. Ideally, this controller would be centrally located at the Steam Plant. The controller is to take information from the relays on the system and issue the appropriate commands to operate the microgrid system. The utility ties will communicate their breaker status to the RTAC as well as the power flow into the system. Additionally, the RTAC will send a maintenance mode to the tie relays so when the Steam Plant is not operational, the system is not islanded. The Steam Plant relays will communicate the power generation (real and reactive) as well as the frequency. Frequency is included here because if the frequency of the system begins to drop, that is a sign that there is too much load. The IRIC relay will communicate its breaker status and power generation. The breaker status is included because, under normal conditions, the IRIC solar panels will not be providing enough to power IRIC, itself. In this case, the relay will keep the breaker open in the island so no power will be provided to the microgrid network from the solar panels. The priority buildings will communicate their power consumption (real and reactive) as well as voltage. Like frequency, if the voltage begins to drop at the load, that is a sign the system is overloaded. The priority buildings will receive open/close commands from the RTAC. The last relay type included in our network is the non-priority building relays. These relays will send power consumption (real and reactive) and receive open/close commands from the RTAC.

RTAC Algorithm
Our RTAC algorithm begins with islanding. The UI system will island when the voltage drops for a set amount of time on the Avista bus. This logic will be done in the tie relays and their breaker status will be shared with the controller so the RTAC can implement the appropriate decisions for balance power in the island. This represents the first box in the figure above. The controller will receive power from the Steam Plant, tie relays, and IRIC and will use this information to calculate how much power will need to be shed when the tie breakers are opened. Once this event occurs, the calculated load shed required will be used to trip campus buildings based on priority. Once the microgrid is in island mode, the power must be constantly balanced within the system. Our team is using two schemes to balance power. The first is contingency load shedding. A contingent load shed scheme compares the power generation to the power consumption and adds or removes load based on this comparison. The second scheme is frequency/voltage-based load shedding. The frequency of the steam turbines and the voltage of the loads will be monitored in the microgrid system. If either the frequency or voltage begins to drop, load will be shed to restore the power balance. The last action the RTAC must implement is returning the microgrid system to the Avista grid. The tie relays implement most of this logic. When the voltage returns to the Avista bus for a certain amount of time, the tie relays begin a synchronism check. This synch check verifies the voltage, frequency, and phase on the Avista bus and the UI microgrid match. Once the synch check is complete, the UI microgrid is connected back to the grid. The breaker status from the tie relays is then sent to the RTAC which then closes all of the UI microgrid campus buildings back into the grid.

=Simulation Process=

=Validation=

=Team Information=

=Additional Documentation=
 * Timeline Schedule


 * Meeting Agendas


 * Meeting Minutes


 * Snapshot Poster1


 * Design Review1