Python Code For Modifying Power System Files To Represent Water Level In Pss/e

Abstract

Bulk power systems span large geographic areas and are hence contained in large software files for simulation for industrial and research purposes. These files contain generator, transmission and load data along with many other assets that facilitate the reliable operation of power systems. The generator data in these files are collected by engineers that test these facilities in the field. Among these generators are hydropower generators that have associated reservoirs with them and whose maximum power output is a direct function of its reservoir water level. These files are snapshots of the system representing one instant, and hence the maximum power output levels captured by these files at one reservoir level are not representative of the power output levels at a different instant with a different water level. These files (or snapshots) are of two types: a) steady-state data and b) dynamic data. Given a desired water level, the designed code modifies both types of files corresponding to this water level in the format corresponding to PSS/E – a commercial software for power system simulation. In the stead-state files (used for load flow analysis and optimal power flow analysis), it modifies the maximum power output and in the dynamic data file (used for transient stability analysis in response to a contingency and/or grid disturbance) it modifies the water level directly. To reflect the impact of reduced water head in power system files, the maximum power generation parameter is changed according to a given water head. PyRAPSS provides the user with two alternate methods for calculating maximum power generation parameter. The first method (Method A) requires less information (i.e., maximum power which can be obtained from the steady-state file itself) but is also less accurate, whereas the second method (Method B) requires more information (i.e., maximum power from the steady-state data file, turbine MVA rating from the dynamic data file, as well as governor parameter data from the dynamic data file) but is more accurate. When both steady- state and dynamic data are available, Method B can be used, otherwise Method A can be used to obtain a reasonable estimate of the maximum power generation parameter. Once the modification of files (representation of hydropower under a different water level condition) is completed, the designed code ensures that the modified system model (or new file) is stable by performing a load flow. It then saves the changes and generates new steady-state and dynamic files that reflect the reservoir water level and are ready for the user to perform desired analysis.