Investigation of the Impact of Load Tap Changers and Automatic Generation Control on Cascading Events

Abstract

This paper presents an assessment of the impact of control mechanisms, specifically load tap changers (LTCs) and automatic generation control (AGC), on cascading events in power systems with renewable generation. In order to identify the impact of these voltage and frequency related mechanisms, a large number of dynamic RMS simulations for various operating conditions is performed taking into consideration renewable generation, system loading and the action of protection devices. The sequences in which the cascading events appear are analysed, and each cascading event is described by the component that trips, the time and the reason for tripping. The number and reason of cascading events, the average load loss and the time between consecutive events are used as metrics to quantify the impact of LTCs and AGC. The study is demonstrated on a modified version of the IEEE-39 bus model with renewable generation and protection devices.

A Method for Variance-Based Sensitivity Analysis of Cascading Failures

“…In [13], a modified version of the IEEE 39 bus model is extended with: demand transformers and tap changers; automatic generation control; the addition of some wind farms; and the addition of protection relays. The modified model is then used to generate power system cascading failures via dynamic simulations including relay modelling whilst considering input power system operational scenarios and three-phase fault location.…”

“…The modified model is then used to generate power system cascading failures via dynamic simulations including relay modelling whilst considering input power system operational scenarios and three-phase fault location. The contribution of [13] are descriptive statistics results of observed power system relay operations during cascading failures which show: firstly, inclusion of demand transformer tap changers in dynamic simulations decreases the number of cascading failures, and secondly; inclusion of automatic generation control decreases the number of UFLS operations. Ref.…”

“…Ref. [13] only provides descriptive statistics results of observed power system relay operations during cascading failures which highlight the impact of relevant mechanisms (tap changers and automatic generation control) to the number of cascading failures and relay trips. Our proposed method is demonstrated in this paper using the power system model developed and used within [13].…”

“…[13] only provides descriptive statistics results of observed power system relay operations during cascading failures which highlight the impact of relevant mechanisms (tap changers and automatic generation control) to the number of cascading failures and relay trips. Our proposed method is demonstrated in this paper using the power system model developed and used within [13]. However, [13] does not allow for quantitative assessment to enable the linking of observed cascading failure relay operations with input power system operational scenarios and disturbance locations in a manner which could detect the relative importance of those input variables with respect to cascading failure propagation.…”

“…Our proposed method is demonstrated in this paper using the power system model developed and used within [13]. However, [13] does not allow for quantitative assessment to enable the linking of observed cascading failure relay operations with input power system operational scenarios and disturbance locations in a manner which could detect the relative importance of those input variables with respect to cascading failure propagation. Here lies the difference between the contributions of [13] and our paper's contributions: we propose a method which can be used to perform variance based sensitivity analysis which allows ranking of input variables importance with respect to cascading failure propagation.…”