Gustavo Valverde

Wide-Area Monitoring, Protection, and Control of Future Electric Power Networks

Wide-area monitoring, protection, and control (WAMPAC) involves the use of system-wide information and the communication of selected local information to a remote location to counteract the propagation of large disturbances. Synchronized measurement technology (SMT) is an important element and enabler of WAMPAC. It is expected that WAMPAC systems will in the future reduce the number of catastrophic blackouts and generally improve the reliability and security of energy production, transmission, and distribution, particularly in power networks with a high level of operational uncertainties. In this paper, the technological and application issues are addressed. Several key monitoring, protection, and control applications are described and discussed. A strategy for developing a WAMPAC system in the United Kingdom is given as well.

Model Predictive Control of Voltages in Active Distribution Networks

This paper presents a centralized control scheme to regulate distribution network voltages in the presence of high penetration of distributed generation. The approach is inspired of Model Predictive Control in order to compensate for modeling inaccuracies and measurement noise. The control actions, calculated from a multi-step optimization, are updated and corrected by real-time measurements. The proposed controller uses a linear model to predict the behavior of the system and the optimization is solved using quadratic programming. The proposed corrective control has been tested in a 11-kV distribution network including 75 nodes and hosting 22 distributed generating units.

A Constrained Formulation for Hybrid State Estimation

This paper presents a new hybrid constrained power system state estimator. The conventional and synchrophasor measurements are simultaneously incorporated in the estimation problem without using any transformation of measurements. This constrained formulation makes it possible to take advantage of information from phasor measurement unit (PMU) branch current and voltage measurements, improving the accuracy of the existing estimators. The methodology is applied on the IEEE 14-, 57-, and 118-bus test systems, and its performance is compared with other hybrid estimators.

Nonlinear Estimation of Synchronous Machine Parameters Using Operating Data

This paper presents a nonlinear parameter estimator for synchronous machines based on the unscented Kalman filter. The proposed methodology uses voltages and current signals recorded from the stator and the field winding to update the parameters of the classical model of the synchronous machine for stability studies. The methodology can be applied without interrupting the normal operation of the generator. Parks Transformation is included in the estimation process to relate the stator measurements (in abc components) to the nonlinear voltage equations in the qd0 reference frame. The proposed robust methodology has been validated using real and simulated data to estimate the model parameters of a 483-MVA round rotor machine.

State estimation including synchronized measurements

The paper presents a methodology to include measurements from phasor measurement units (PMUs) as well as conventional measurements in a state estimator. A comprehensive strategy to combine conventional measurements, such as the power flow and power injection measurements, with the direct and pseudo-voltage measurements by the PMUs in a weighted least square (WLS) formulation of the state estimation problem is demonstrated. The proposed state estimator is applied on the IEEE 14-bus test system, and the simulation results are presented.

Stochastic Monitoring of Distribution Networks Including Correlated Input Variables

The evolving complexity of distribution networks with higher levels of uncertainties is a new challenge faced by system operators. This paper introduces the use of Gaussian mixtures models as input variables in stochastic power flow studies and state estimation of distribution networks. These studies are relevant for the efficient exploitation of renewable energy sources and the secure operation of network assets.

Control of dispersed generation to regulate distribution and support transmission voltages

This paper presents an on-line centralized controller based on Model Predictive Control concepts to regulate distribution network voltages, and possibly support transmission network. It computes and applies a sequence of changes of the distributed generators power outputs to progressively meet a set of operation constraints at distribution, and possibly transmission level. An 11-kV, 75-bus test system with 22 distributed generators is used to illustrate the performance of the proposed controller when transmission system support is requested. Comparisons with single-step open-loop control are also provided.

Enhanced state estimation with real-time updated network parameters using SMT

This paper presents a brief explanation how Synchronized Measurement Technology (SMT) and WAMPAC architecture can support State Estimation and it discusses the existing correlation between each other. Additionally, it is presented a practical implementation of Phasor Measurement Units for updating network parameter data bases to improve the performance of state estimators. The methodology presented can be implemented only when full observability of the network parameters is available. The performance of the enhanced state estimator is assessed for different types of measurements and parameter errors. It is shown how the proposed solution delivers a more reliable estimation, especially when parameter errors are difficult to detect.

PMU-based multi-area state estimation with low data exchange

The paper proposes a novel multi-area state estimator based on wide area measurements where only boundary buses are considered in the coordination level. The power injection measurements are not used during the coordination level reducing the number of states and therefore size of the problem. Instead, a set of pseudo-measurements are included whenever a power injection measurement is available in boundary buses. The proposed method was validated using the IEEE 300 bus system split into 7 different areas.

Optimal placement of Phasor Measurement Units to Improve Parallel Power System Restoration

This paper proposes a new method for optimal placement of Phasor Measurement Units (PMUs) across the weak areas of the power system to monitor the status of the boundary buses during Parallel Power System Restoration (PPSR). The proposed PMU placement method is based on an Integer Linear Programming (ILP) methodology. For validation purposes, the proposed method is implemented across the weak areas of the following two test systems: New England 39-bus test system and IEEE 118-bus test system.