Alvaro Giusto

Using synchrophasors for controlled islanding - A prospective application for the Uruguayan power system

Summary form only given. This paper describes two Wide-Area Protection schemes for controlled islanding of the Uruguayan electrical power system. The first scheme relies only on local signals available for distance protection relays, whereas the second scheme is based both on local and remote synchrophasor measurements. The paper compares results in terms of load shedding amount necessary to maintain system integrity, with and without the proposed protection schemes. The investigation is based on comprehensive transient stability studies using actual dynamical models. Past occurrences that led the system to widespread blackouts have motivated the investigations presented in this paper.

Modal analysis of the Uruguayan electrical power system

The Uruguayan electric power system is facing deep challenges in the near future. The plans for 2015 include a significant expansion of generation based on renewable sources (wind, biomass) and a new HVDC international interconnection. These plans and the opening to multiple, distributed private generators pose significant challenges to the system operation and planning. This work describes the modal analysis of the Uruguayan Power System by considering a base 2004 scenario and two 2010 scenarios. These scenarios include conventional-thermal and hydro synchronous generation-and constitute a reference for a set of ongoing studies associated with the new expansion plans. The system comprises a relatively small electrical network with important hydroelectrical generation and highly interconnected with the neighboring countries. The main oscillation modes, which exhibit a poorly damped behavior, are analyzed in detail. The results were validated through simulations of the systemss response for different contingencies. The study includes the selection of appropriate machines to damp the oscillations and the tuning of Power System Stabilizers, PSS. The effects of this control action are then assessed via the modal analysis and validated via complete non linear simulation of transient response.

An investigation of controlled power system separation of the Uruguayan network

The Uruguayan power system is highly dependent on two 500 kV transmission lines connecting the largest generation site (Salto Grande) and the Argentinean interconnection in the North, to the largest loading area in the South. Actual occurrences, where both 500 kV lines tripped, lead the system to widespread blackouts including the critical area of Montevideo, the nations capital district. This paper presents an investigation of a controlled separation of the Uruguayan network into two stable islands, using power swing blocking (PSB) and out-of-step tripping (OST) protection functions.

Assessment of power swing blocking functions of line protective relays for a near scenario of the Uruguayan system

During normal operation of an electrical power system, there will be some conditions like faults or other disturbances which may cause loss of synchronism between areas. When loss of synchronism takes place, asynchronous areas should be separated to avoid equipment damaged or extensive outages. This paper describes the assessment of the protection system of a part of the Uruguayan power system. The focus is on the incorporation of a big consumer with generation capacity. The involved added apparent power generation is about 10% of the maximum historical Uruguayan load. The article describes a set of studies on the protective system associated to transmission lines feeding the new consumer. Particular attention is paid to blocking power swing functions of the involved relays. Power system simulations and relay tests have been performed, to evaluate the performance of the relays under power swing conditions. The foreknowledge makes possible to avoid undesired operation.

Performance evaluation of power swing blocking function and islanding protection - A case study on the Uruguayan network

The Uruguayan electric power system is facing deep challenges. The current and near scenarios include a significant expansion of generation based on renewable sources (wind, biomass) and the opening to multiple, distributed private generators. This paper describes the performance assessment of the protection scheme of a subsystem of the Uruguayan network directly associated to the connection of a big industrial cogenerator involving about 10% of the maximum historical Uruguayan load. The protective scheme contemplates the islanding of this generator when significant, unstable disturbances are present. The focus is on power swings blocking and out-of-step tripping functions of the involved protective relays. The analysis involves time domain simulations and laboratory tests on the relays, to evaluate its performance under power swing conditions.

Using synchrophasors for controlled islanding - a prospective application for the Uruguayan power system

This paper describes two wide-area protection schemes for controlled islanding of the Uruguayan electrical power system. The first scheme relies only on local signals available for distance protection relays, whereas the second scheme is based both on local and remote synchrophasor measurements. The paper compares results in terms of load shedding amount necessary to maintain system integrity, with and without the proposed protection schemes. The investigation is based on comprehensive transient stability studies using actual dynamical models. Past occurrences that led the system to widespread blackouts have motivated the investigations presented in this paper.

Design of power system stabilizers in variable speed wind generators using remote signals

This work aims the description, modeling and simulation of the incorporation of a power system stabilizer (PSS) in variable speed wind turbines in order to dampen oscillation in power grids. The proposed PSS aims to alter the nature of the electric power injected by the wind farms to, in some sense, mimic the oscillatory behavior of synchronous generators and allows dampening these transient oscillations. The main advantage of this stabilizing action lies in the fact that the wind turbines, by decoupling the electrical frequency of the network respect its rotational speed by the inclusion of power electronic converters, allows the injection of oscillating power without risk of suffering stability issues. This allows to improve the oscillation damping between different synchronous generators.The proposed PSS has been analyzed in a grid of three areas: an area comprises the infinite bus; the second one a synchronous generator and the third one contains a synchronous generator and a wind farm. The PSS takes as reference the active power injected by the synchronous generator of the third area using synchrophasors. Finally, it is studied the performance of the PSS for a particular case of the Uruguayan power grid. In this scenario, the second area is composed by the hydro power plant Baygorria; the third area is comprised by the hydro power plant Terra and the wind farms Palmatir and Agua Leguas; finally, the first area is the rest of the power system.

Dynamic characterization of wind farms and their impact in power systems oscillations

This paper has two main objectives: to explain the dynamic characterization of wind farms as part of their integration in power systems using modal analysis and to present a qualitative development for understanding the main factors that impact on the damping of the oscillation modes by incorporating wind farms based on variable speed wind turbines. Moreover, such developments are validated by performing simulations on a 2017 peak scenario for the Uruguayan electrical system, showing a strong interaction between the hydroelectrics power plants located on the Río Negro and future wind farms Palmatir and Agua Leguas.

Online prediction of power system trajectories from noisy data by penalized least-squares minimization

This paper advances a new method to predict trajectories of rotor angles and bus voltages in dynamic power systems, with data collected by phasor measurement units. The predictor incorporates real time data adaptively, leveraging the algebraic differential equations describing the system, while being able to accommodate model inaccuracies. Numerical tests on a one machine infinite bus system are carried out to illustrate the predictor properties. Then, further results are presented on a classical networked testbed of nine buses and three generators.

Power network state estimation algorithms and their use with synchrophasors

This article studies an algorithm for state estimation in electric power networks, adding information from phasor measurement units (PMU) to the classical SCADA data. This work describes the implementation in MatLab of one of the algorithms found in the literature and the migration of the code to C++ in order to test its time performance. The algorithm was tested on the 39 bus IEEE case study. A good tracking of the waveforms was achieved even in cases of three phase short-circuits or drastic load changes. Execution times obtained in C++ in regular desk computers where short enough to predict a suitable real time performance.