Turbine Governor Modeling and Scripting in an Open Source Simulation Software

Turbine governors have been included in power system studies to assess their effects on power system stability. Each type of the TGs is different from one another, thus requires different modeling. For example, time delays in the steam TG model are due to steam chest and inlet piping, re-heaters, and crossover piping while, in the hydro TG model, they are due to transient droop compensation, pilot valves and gate servomotors. Moreover, the effects of water inertia in hydro turbines significantly influence the governors’ requirements and must be compensated by a rate feedback in the modeling whereas steam TG are more influenced by time delays occurring between valve movement and change in steam flows.

Power System Analysis Toolbox (PSAT) is an educational open source software for power system analysis studies [3]. The software is Matlab-based and is freely distributed online [4]. PSAT is currently being used for power system stability analysis of the Nordic power system by the Electric Power Systems Division at KTH. Main features of the software are as follows:

1) PSAT has user-friendly graphical user interfaces (GUI) as well as a Simulink-based toolbox;
2) PSAT can cover a wide scale of test systems; from small to medium size.
3) PSAT covers several important packages for power system studies such as the power flow (PF), the optimal power flow (OPF), and the small signal stability analysis (SSA).
4) PSAT is flexible; being Matlab-based enables PSAT to run on common operating systems including Windows, Mac OS X, UNIX, and Linux. PSAT also runs on GNU/Octave. It also allows data file conversion from and to other formats.

Dynamic models of TGs, as well as static models, are incorporated within PSAT. However, the PSAT’s TG models do not offer different types of governors, for example, hydraulic governors which are important in the study of the Nordic system are not provided in PSAT. With properly modeled TG systems, study on the small-signal stability analysis of power systems could be accurately carried out.

This thesis will focus on developing the turbine governor models for PSAT implementation.