Question 1

How do I solve a unit commitment problem online for free?

Accepted Answer

Open the ED/UC Simulator at https://tool.adjiebrotots.com/ed-uc-simulator/, draw the buses, lines, generators and loads, give each unit its cost, minimum output, start-up cost and minimum up and down times, and press Run dispatch. It builds the same mixed-integer problem PyPSA builds and solves it with HiGHS in your browser.

Question 2

How are the nodal prices (LMP) worked out?

Accepted Answer

Each price is the cost of serving one more MW at that bus in that hour, the dual of its power balance in a DC optimal power flow. A unit commitment has no duals, so it is solved again as a linear problem with the commitment held as found, the way electricity markets price it. The PJM 5-bus Quick Start reproduces the published prices.

Question 3

What is the difference between economic dispatch and unit commitment?

Accepted Answer

Economic dispatch shares the load among units that are all available, cheapest first, within their limits. Unit commitment also decides which units run in each hour, so it weighs start-up costs, minimum stable output and minimum up and down times. The simulator solves both on the same network so you can compare them.

ED/UC Simulator

Single-line diagram

Dispatch

Nodal prices

Commitment

Storage

Results by element

What this assumes