On the search for expanded grid control capabilities: Discrete control on emerging power technologies

This letter proposes discrete changes in the power output of emerging power technologies (EPT) for controlling oscillations and frequency excursions. For the former, a new perspective is proposed that connects oscillations with the transient shift of the system equilibrium point. This is transformative as discrete control can be applied to multi-modal systems for the first time, without any model aggregation. For the latter, new insights are provided in regard to the nature of the discrete actions. Applications to a 2-bus, 9-bus and 39-bus test systems are presented. Through the proposed scheme, EPT can be enabled with controls that recognize their characteristics, while expanding grid dynamic capabilities with the addition of new effective controllers

Oscillation energy based sensitivity analysis and control for multi-mode oscillation systems

This paper describes a novel approach to analyze and control systems with multi-mode oscillation problems. Traditional single dominant mode analysis fails to provide effective control actions when several modes have similar low damping ratios. This work addresses this problem by considering all modes in the formulation of the system kinetic oscillation energy. The integral of energy over time defines the total action as a measure of dynamic performance, and its sensitivity allows comparing the performance of different actuators/locations in the system to select the most effective one to damp the oscillation energy. Time domain simulations in the IEEE 9-bus system and IEEE 39-bus system verify the findings obtained by the oscillation energy based analysis. Applications of the proposed method in control and system planning are discussed.Comment: Conference paper, IEEE PESGM 201

Wind farm model for power system stability analysis

In this thesis, the modeling of wind farms based on type-C wind power generators (WTGs) is studied. Based on time scale decomposition, two detailed dynamic models are presented. In both models, a rotor speed controller, a reactive power controller and a pitch angle controller are considered. The turbine's aerodynamic is represented by an static model and a single-mass model is assumed. With respect to the controllers, the speed controller is designed to extract maximum power from the wind for a given wind speed. The reactive power controller is designed to follow a reference. The pitch angle controller is designed to limit the maximum active power output. All controllers use proportional and integral control. Modal and bifurcation analysis is performed revealing that WTG's variables do not exhibit major oscillatory behavior when the system is perturbed. Moreover, WTG's variables do not participate in unstable modes and they do not change the system stability structure. In general, the most important interaction between WTGs and the system is the interchange of power. An aggregated model is proposed for wind farms. This model is characterized by a single equivalent WTG and an equivalent wind speed. Moreover, the order of the aggregated model is reduced by using selective modal analysis. This technique focusses on the most relevant modes and most relevant variables. Irrelevant variables are expressed in terms of the relevant ones which allows reducing the model order. Replacing either a two-axis or zero-axis model of a WTG for the reduced order model neither considerably alters the original system dynamics nor modifies the system variables. An important reduction of simulation time and model complexity is obtained. In the largest case, it is shown that two wind farms that in total are represented by 500 differential equations and 800 algebraic equations can be represented by just 4 differential equations