Observations on Dynamic Transient and Small Signal Analyses Report

The report highlights several key areas for improvement, including the tuning of existing Power System Stabilizers (PSSs) on Thermal Power Plants (TPPs) and Hydroelectric Power Plants (HPPs. The report emphasizes that even marginal improvements in PSS performance at low frequencies can result in significant differences in damping, particularly in challenging operating regimes such as the N-1 and changed flow cases. The selected parameters for the existing PSSs can be improved, but there is still room for improvement. This measure can be implemented quickly and can support a limited exchange scenario based on simulation results. The report also discusses the use of Power Electronic Devices (PEDs) to improve grid stability. Current-controlled PEDs, such as STATCOM and HVDC with modulation, are capable of providing additional damping. Modulation of reactive power has an indirect effect on active power, and it would be beneficial to see the impact of 200MVAR on active power in the simulation results. In addition to PEDs, the report considers alternative solutions, including battery storage and breaking resistors. Battery storage systems with a capacity of 5-20MW (with 1-4MWh energy storage) are expected to have a similar impact on damping as they directly modulate active power. Breaking resistors can also be considered as a fast and economic solution. The report proposes several countermeasures to be implemented before parallel operation with limited exchange levels. The first step involves retuning PSSs on HPPs and TPPs to improve damping. The second step involves retuning existing AVR-SD settings and considering a reduction in AVR gain for Nuclear Power Plants (NPPs). The report also suggests that adding PSS to the AVR-SD structure may not provide significant benefits due to limitations in field implementation. The report was prepared by Tetra Tech ES, Inc. under the USAID Energy Security Project (ESP) contract 72011118C00003. The contents of the report are the sole responsibility of Tetra Tech ES, Inc. and do not necessarily reflect the views of USAID or the United States Government.