Armando Salazar

A Measurement-Based Framework for Dynamic Equivalencing of Large Power Systems Using Wide-Area Phasor Measurements

Wide-area analysis and control of large-scale electric power systems are highly dependent on the idea of aggregation. For example, one often hears power system operators mentioning how northern Washington oscillates against southern California in response to various disturbance events. The main question here is whether we can analytically construct dynamic electromechanical models for these conceptual, aggregated generators representing Washington and California, which in reality are some hypothetical combinations of thousands of actual generators. In this paper we address this problem, and present a concise overview of several new results on how to construct simplified interarea models of large power networks by using dynamic measurements available from phasor measurement units (PMUs) installed at specific points on the transmission line. Our examples of study are motivated by widely encountered power transfer paths in the Western Electricity Coordinating Council (WECC), namely, a two-area radial system representing the WA-MT flow, and a star-connected three-area system resembling the Pacific AC Intertie.

Synchronized Phasor Data Based Energy Function Analysis of Dominant Power Transfer Paths in Large Power Systems

Many large interconnected power systems such as the U.S. eastern interconnection and the U.S. western power system are characterized by many power transfer paths or interfaces with high loading. Disruptions of these transfer paths frequently lead to increased loading on neighboring transfer paths, which themselves will become less secure and could cause further disruptions. State estimators have limited performance under large system disruptions, because of low sampling rates and potentially poor solution quality due to topology errors. Furthermore, disruptions in external power systems cannot be readily seen by control room operators because most state estimators only use reduced models for external systems. A system of well-placed phasor measurement units (PMUs) that provide voltage and current magnitude and phase at a high sampling rate can provide useful system dynamic security information. In this paper we apply energy function analysis using phasor data to monitor the dynamic status of power transfer paths. The ideas will be illustrated using actual data captured by several PMUs in the U.S. western power system

Voltage Stability Analysis of a Multiple-Infeed Load Center Using Phasor Measurement Data

Voltage stability is a security concern for modern power systems. It can be analyzed using detailed or equivalent models. In this paper a new approach is presented for voltage stability analysis using synchronized phasor measurement data. Simple equivalent models of the interconnected system and load side at a measurement point are estimated from the data, and then used for calculating PV curves and predicting the stability limit. Two different models are proposed, and compared based on the analyses performed on the event recordings from US western power system. Minimal modeling and formulation makes the method suitable for online calculations. The models are continuously updated to reflect the effects of different system components and changes

See It Fast to Keep Calm: Real-Time Voltage Control Under Stressed Conditions

As the electrical utility industry addresses energy and environmental needs through greater use of renewable energy, storage, and other technologies, power systems are becoming more complex and stressed. Increased dynamic changes that require improvements in real-time monitoring, protection, and control increase the complexity of managing modern grids. In an effort to ensure the secure operation of power systems, more attention is being given to voltage management. Voltage management includes addressing voltage stability and fault-induced delayed voltage recovery (FIDVR) phenomena. Deployment of phasor measurement unit (PMU) technology, in combination with recently developed methodologies for tracking voltage behavior, has resulted in improved real-time voltage monitoring, protection, and control.

Use of Synchronized Phasor Measurement system for monitoring power system stability and system dynamics in real-time

This paper / presentation is discussing the use of Synchronized Phasor Measurement Technology, which is now being used for monitoring power system status and dynamic transient event recording at Southern California Edison (SCE)off-line and in Real-time. This real time monitoring system is expected to enhance the Transmission system reliability and provide wide area visibility of the WECC system. The SPMS can enable SCE to monitor AC-DC power transmission system reliability and improve reliability by monitoring the phase angles and oscillations at several substations and two remote DC terminals. The system could be used for real-time control in future. SCE has been working aggressively on this Synchronized Phasor Measurement technology for over last twelve years and has installed a network of Phasor Measurement Units (PMUs), obtains data from eighteen Phasor Measurement Units (PMUs) and has installed two Phasor Data Concentrators (PDC) on its system. The data from the PMUs/PDCs is now being collected and being used for monitoring and analysis of the system events.

Interarea Model Estimation for Radial Power System Transfer Paths With Intermediate Voltage Control Using Synchronized Phasor Measurements

In this paper we develop measurement-based methods for estimating a two-machine reduced model to represent the interarea dynamics of a radial, two-area power system with intermediate dynamic voltage control. Two types of voltage control equipment are considered, namely, a static VAr compensator (SVC), and a synchronous condenser. The methods use synchronized bus voltage phasor data at several buses including the voltage control bus, and the line currents on the power transfer path.

Generic Model Structures for Simulating Static Var Systems in Power System Studies—A WECC Task Force Effort

This paper describes three models developed through the Western Electricity Coordinating Council (WECC) SVC Task Force, to represent static Var systems (SVS) for power-flow and time-domain stability simulations. The goal was to develop a set of model structures that are generic, and can be easily parameterized to represent a variety of SVS systems. The term generic is used to imply a model structure that is not specific to a given vendor or equipment, and that is non-proprietary and public. These models have been implemented by several software vendors, and may soon be adopted by others. These models offer: 1) a suitable non-proprietary, not vendor specific set of models that can be used to evaluate SVS solution options for planning studies, and 2) the means to move away from the proliferation of user-written models that are becoming hard to manage in large interconnected power system models such as the WECC. The dissemination of the models and modeling documentation helps provide guidance to power system planners and operators about the latest SVS technologies and their application.

A measurement-based framework for dynamic equivalencing of large power systems using WAMS

Wide-area analysis and control of large-scale electric power systems are highly dependent on the idea of aggregation. For example, one often hears power system operators mentioning how ‘Northern Washington’ oscillates against ‘Southern California’ in response to various disturbance events. The main question here is whether we can analytically construct dynamic electromechanical models for these conceptual, aggregated generators representing Washington and California, which in reality are some hypothetical combinations of thousands of actual generators. In this paper we address this problem, and present several new results on how to construct simplified inter-area models of large power networks by using dynamic measurements available from phasor measurement units (PMUs) installed at specific points on the transmission line. Our examples of study are motivated by widely encountered power transfer paths in the Western Electricity Coordinating Council (WECC), namely a two-area radial system, a two-area system with intermediate voltage control, and a star-connected three-area system.

Developing generic static Var system models - a WECC Task Force effort

This paper describes the current status of the work being conducted by the Western Electricity Coordinating Council (WECC) SVC Task Force to develop generic power flow and time-domain stability models to represent all existing and future (modern) static Var systems (SVS) in the Western Interconnection. The intent is to have these models implemented by software vendors such as GE, Siemens PTI, Powertech Labs and others so that these models are then available to users in WECC (and worldwide) for their use in system planning studies. The value of this exercise is three fold: (i) it provides suitable non-proprietary, non-vendor specific models that can be used to evaluate SVS solution options for planning studies, (ii) it helps to move away from the proliferation of user-written models that are becoming hard to manage in large interconnected power system models such as the WECC, and (iii) the dissemination of the models and modeling documentation helps to educate power system planners and operators about the latest SVS technologies and their application.

Identification and Predictive Analysis of a Multi-Area WECC Power System Model Using Synchrophasors

This paper describes the construction of a reduced-order five-machine dynamic equivalent electro-mechanical model of the Western Electricity Coordinating Council (WECC) 500 kV power system network using slow mode oscillations of power flows derived from phasor measurement unit data. We first extract the slow oscillations using modal decomposition, and use them to estimate four key parameters of the reduced-order system, namely, the inter-area transmission line impedances, intra-area Thevenin reactances, rotational inertia, and damping of the aggregated synchronous generators. The resulting five-machine equivalent model is validated using different ranges of contingencies such as generation loss and line loss, and thereafter used for accurate prediction of oscillation mode frequencies and their damping factors. Finally, we present an algorithm by which this reduced-order model can be used to determine the criticality of line loss events within any area based on the divergence of load flow. The conclusions are drawn with the possible applications of the model for transient stability assessment, and prediction of stability limits needed to sustain increasing wind power penetration in the WECC.