STEPWISE POWER FLOW - A NEW TOOL TO ANALYSE CAPACITY SHORTAGE AND RESERVE REQUIREMENTS

Abstract

Abstract-- Frequency and active power control actions work over a time range from seconds to well over 15 minutes. Few standard computer tools are currently able to analyse slow power system dynamics in the minutes to hours range. This paper describes a new tool called Stepwise Power Flow (SPF), where a regular power flow algorithm is modified to run typically in 5 minute time steps. The tool includes primary (droop) response, secondary control and outages as well as frequency dependent load shedding. The algorithm is developed in an aggregated 18 bus model of the Nordic power system, and is further developed to include multiple synchronous areas, HVDC connections and wind farm dynamics. Testing and verification on a full scale Nordic model with 1257 generators is also shown. The SPF methodology enables the System Operator to assess both provision and activation of spinning reserve in the planning phases. Index Terms-- Frequency control, Active power