Jose M. Lozano-Garcia

Practical implementation of a VSC-HVDC in WLS-based state estimation

This paper proposes a practical approach to incorporate a High Voltage Direct-current (HVDC) link in a state estimation algorithm based on the technique Weighted Least Squares (WLS). The power measurements of the HVDC are directly appended to traditional measurements to estimate the equilibrium point of the power system. The proposed approach simultaneously upgrades the estimated values of the state variables of the HVDC controllers and the state variables of the rest of the electric network, to obtain a unified solution in a single-frame of reference. Results are presented to demonstrate the effectiveness of the proposed approach to assess the estimation of the system state and to set the parameters of the HVDC controllers for given control specifications.

Computational development of a practical educational tool for state estimation of power systems using the MATLAB optimization toolbox

State estimation is one of the most important processes to perform a reliable monitoring and control of the steady-state operating condition of modern electric power systems; thus, it is currently a fundamental part in the development of research to enhance the monitoring and security of the smart grids operation. This important topic is taught in advanced courses of operation and control of power systems, for graduate and undergraduate power engineering students. However, the most used software packages for simulation and analysis of power systems by researchers, students, and educators have put little attention on the state estimation module. Due to this fact, this paper proposes an approach to develop the computational implementation of a practical educational tool for state estimation of electric power systems using the MATLAB optimization toolbox. In this proposal, the formulation of the state estimation problem consists of developing a general digital code to implement an objective function based on the weighted least squares method. While the lsqnonlin function of the MATLAB optimization toolbox solves the formulated state estimation problem. Simplifying both research and educational processes, this tool helps graduate and undergraduate students to improve learning, understanding, and the times of implementation and development of research in state estimation. Simulations of an equivalent model of the Mexican interconnected power system consisting of 190 buses and 46 machines are used to test and validate the proposal performance.

Directional Derivative-Based Transient Stability-Constrained Optimal Power Flow

This paper proposes a novel active power redispatch sequential approach to solve the transient stability-constrained optimal power flow (TSC-OPF) problem for the preventive control of transient stability. Based on an independent transient stability assessment of the power system for a given contingency scenario, two proposed power redispatch constraints are formulated and embedded into a conventional OPF formulation. Since these two new constraints only depend on steady-state variables, the dimension of the resulting TSC-OPF model is similar to that of a conventional OPF model and can be solved by standard optimization methods to perform a nonheuristic active power redispatch. The stabilization process is performed by sequentially solving the optimization and the transient stability problems until a suitable generation dispatch that provides a transiently stable equilibrium point is assessed. The validity and the effectiveness of the proposed method are numerically demonstrated in the WSCC three-machine, nine-bus system and an equivalent model of the Mexican power system.

A novel sequential transient stability constrained optimal power flow

A different approach for formulating the sequential TSC-OPF problem is proposed in this paper, where only two power re-dispatch constraints are added to a conventional OPF model to formulate the proposed TSC-OPF model. These two constraints are derived from a proposed best direction vector that provides the power re-dispatch direction in which the rotor angular deviations at the time to instability decrease at the maximum rate of change. In this way, the resulting TSC-OPF model forces the magnitude and direction of the power re-dispatch in order to steer the power system operation state to a transiently stable equilibrium point. The effectiveness of the proposed method is numerically demonstrated in the WSCC 3-machine, 9-bus system.

Analysis and Implementation of an 84-Pulse STATCOM

This chapter describes the use of STATCOM for the reactive power compensation and the power quality improvement. The assembling of a Voltage Source Converter (VSC) that meets the IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems (IEEE Std. 519-1992) is emphasized. The low Total Harmonic Distortion (THD) that this VSC generates, qualifies this power conditioner to be considered for its use on stringent applications. The reinjection principle is used, that makes this proposal be considered as an affordable solution to the sinusoidal synthesis due to the reduced number of switches. The reinjection transformer is one of the most important elements in this configuration, and it can have a wide turn ratio variation without leading out the special application standards. Conventional Proportional-Integral (PI) controllers are applied to hold the output voltage of the STATCOM around nominal conditions. The followed strategy employs the error and its variation to break down the control action into smaller sections that can be selected according to simple rules.