E.J. de Oliveira

A Heuristic Constructive Algorithm for Capacitor Placement on Distribution Systems

This paper presents a heuristic constructive algorithm (HCA) for optimal capacitor placement on distribution systems. This is a nonlinear mixed integer optimization problem. In the proposed approach, the integer variables are represented using sigmoid function, thus interior point optimal power flow formulation can be applied to obtain sensitivity indexes based on Lagrange multipliers, reactive power, and bus voltage. The methodology is applied to two power distribution systems, and the results are compared with those obtained using a genetic algorithm approach.

Transmission system expansion planning using a sigmoid function to handle integer investment variables

Summary form only given. This paper presents an optimum power flow (OPF) modeling algorithm that uses the primal-dual interior point technique to determine the best investment strategy in the transmission line expansion problem. In the proposed method the expansion decision (0 or 1) is mitigated by using a sigmoid function which is incorporated in the OPF problem through the modified DC power flow equations. The investment decision is taken using a new heuristic model based on enhanced sensitivity introduced by the OPF results. Additionally the transmission power losses are considered in the network model. The proposed methodology has been compared with methods available in the literature, using both a test system and an equivalent of the southeastern Brazilian system

Allocation of FACTS devices in hydrothermal systems

This work presents a methodology to represent and analyze the influence of FACTS (flexible AC transmission systems) devices on the multiperiod economic dispatch problem. Two FACTS devices are represented: the series compensator and the phase shifter. The aim is to find the best location of FACTS devices in order to minimize the expected thermal generation costs and the investments on these devices in a prespecified time interval. The methodology handles the operational interdependence between cascade hydro plants which characterize the hydrothermal coordination problem. Transmission losses and circuit capacity variation are also taken into consideration. The approach is tested in a small system and to the system of the southern region of Brazil in order to illustrate the application of the algorithm. Some wheeling transactions are also introduced to investigate their influence on the FACTS location. The results show the robustness of the approach while highlighting the main problems which need be investigated.

Flexible AC transmission system devices: allocation and transmission pricing

The transmission of electricity differs from transportation of any typical commodity by some inherent aspects such as: the production needs to match the consumption at the same time; system control is not an easy task; the electricity flows do not usually follow the economic law. The last aspect is normally observed when transmission systems are included in, for instance, an economic dispatch problem. One way to minimize the operational costs caused by an overloaded transmission system is through the installation of Flexible AC Transmission System (FACTS) devices in the system. They are able to change power flows by modifying the network parameters. This paper focuses on the ability of FACTS devices to change the overall costs of the system and their impact on transmission pricing. The allocation and the determination of the FACTS required are also discussed. Some examples using the IEEE-14 system and the Brazilian electrical system of the Southern region are given to illustrate the concepts introduced in this paper.

Redispatch to Reduce Rotor Shaft Impacts Upon Transmission Loop Closure

This paper describes a novel generation rescheduling method to reduce the generator rotor shaft impacts induced by transmission loop closures. The rotor shaft impact constraints, at the instant of transmission loop closure, are explicitly modeled into an interior point optimal power flow. This method represents a considerable improvement on the conventional redispatch for reducing the standing phase angle of the closing breaker. Optimal power flow and transient stability results are provided for a tutorial four-bus and the IEEE 118-bus test systems.

A new approach for area interchange control modeling

This paper describes a new methodology to evaluate the area interchange control (AIC) in a power flow problem using the Newton-Raphson method. In this methodology, the equations of the AIC are incorporated into the system of equations of the power flow problem. Thus an augmented system of equations, which is linearized and solved, at each iteration, is obtained. The proposed method has been tested and compared with existing methods in the literature using both small and large scale systems. The results presented validate the proposed technique.

Series compensation device allocation under contingency constraints

In this paper the influence of a contingency in the series compensation (SC) device allocation and size is evaluated. The SC placement and size are determined using an optimal power flow (OPF) program via the Benders cut technique to include the contingency influence. This problem is solved in two steps: (i) The SC size and placement are determined as an investment OPF subproblem. The SC cost and energy production cost are included in the objective function; (ii) The operation OPF subproblem is solved considering the specified line and generation outages. The Benders cut are generated according to the outage occurrence probability. In this case the objective function is the minimum load shedding and energy production cost. The OPF subproblems are solved using linear programming technique. The IEEE-14 bus and IEEE-118 bus test systems are used to show the effectiveness of the proposed methodology.

Assessment of the generator remote voltage control through static security regions

This paper describes the use of a static security tool, based on security regions, to evaluate strategies of voltage control in power systems. The remote voltage control technique involving generators and/or synchronous compensators is used as strategy to exploit the system voltage control resources. The proposed tool has been tested using both a 9-bus tutorial system and the 39-bus New England system. The results presented validate and clearly indicate the effectiveness of the proposed method.

Security constraints for wind power operation

This paper presents a model to include a security constraint for wind power plant in a hydrothermal dispatch problem. The proposed Unit Commitment (UC) is an augmented problem to take into account different scenarios of wind speed during the day. The wind farms are represented by a linear model that the generations are considered proportional to the availability of wind. The proposed optimization model uses DC load flow in which transmission system constraints are included. The hydro plants are considered with constant productivity and the times of starting and stopping of thermal generation units are considered as well as ramp deviation. The results using a test system show that the operation of a hydrothermal system is strongly affected by the inclusion of wind farms.

Preliminary analysis of additive noise on outdoor and low voltage electric power grid in Brazil

This work aim at presenting a preliminary analysis of additive noises on outdoor and low voltage electric power grid when the frequency band between 1.7 and 100 MHz is considered. These noises were obtained during a measurement campaign carried out in a Brazilian suburban area comprising a low-income community. The statistical analysis in the time and frequency domains reveal the hardness of such environment for data communication as well as the white holes that can be opportunistic used by PLC systems to operate in the same frequency band of primary users.