Rachid Cherkaoui

Optimal Location of Multi-Type FACTS Devices in a Power System by Means of Genetic Algorithms

This paper presents a genetic algorithm to seek the optimal location of multi-type FACTS devices in a power system. The optimizations are performed on three parameters: the location of the devices, their types, and their values. The system loadability is applied as a measure of power system performance. Four different kinds of FACTS controllers are used and modeled for steady-state studies: TCSC, TCPST, TCVR, and SVC. Simulations are done on a 118-bus power system for several numbers of devices. Results show the difference of efficiency of the devices used in this context. They also show that the simultaneous use of several kinds of controllers is the most efficient solution to increase the loadability of the system. In all the cases (single-and multi-type FACTS devices), we observe a maximum number of devices beyond which this loadability cannot be improved.

Optimizing a Battery Energy Storage System for Frequency Control Application in an Isolated Power System

This paper presents a method for optimal sizing and operation of a battery energy storage system (BESS) used for spinning reserve in a small isolated power system. Numerical simulations are performed on a load-frequency control (LFC) dynamic simulator of the isolated network. A novel control algorithm using adjustable state of charge limits is implemented and tested on a BESS dynamic model. An optimal sizing procedure of the BESS is developed for an isolated power system in order to achieve highest expected profitability of the device. The BESS can increase significantly the power system stability, the grid security, and the planning flexibility for a small isolated power system with low grid inertia. Meanwhile, it fulfills the frequency control requirements with a high expected economic profitability.

Sizing and Optimal Operation of Battery Energy Storage System for Peak Shaving Application

This paper presents a sizing methodology and optimal operating strategy for a battery energy storage system (BESS) to provide a peak load shaving. The sizing methodology is used to maximize a customers economic benefit by reducing the power demand payment with a BESS of a minimum capacity, i.e. a system with a lowest cost. The BESS optimal operating strategy is based on dynamic programming and is aimed to minimize the energy cost while satisfying battery physical constraints.

Optimal Allocation of Dispersed Energy Storage Systems in Active Distribution Networks for Energy Balance and Grid Support

Dispersed storage systems (DSSs) can represent an important near-term solution for supporting the operation and control of active distribution networks (ADNs). Indeed, they have the capability to support ADNs by providing ancillary services in addition to energy balance capabilities. Within this context, this paper focuses on the optimal allocation of DSSs in ADNs by defining a multi-objective optimization problem aiming at finding the optimal trade-off between technical and economical goals. In particular, the proposed procedure accounts for: network voltage deviations; feeders/lines congestions; network losses; cost of supplying loads (from external grid or local producers) together with the cost of DSS investment/maintenance; load curtailment; and stochasticity of loads and renewables productions. The DSSs are suitably modeled to consider their ability to support the network by both active and reactive powers. A convex formulation of ac optimal power flow problem is used to define a mixed integer second-order cone programming problem to optimally site and size the DSSs in the network. A test case referring to IEEE 34 bus distribution test feeder is used to demonstrate and discuss the effectiveness of the proposed methodology.

Optimal location of FACTS devices to enhance power system security

This paper compares three heuristic methods (SA, TS and GA) applied to the optimal location of FACTS devices in a power system. The optimizations are made on three parameters: the location of the devices, their types and their sizes. The FACTS devices are located in order to enhance the system security. Five types of FACTS controllers are modeled for steady-state studies: TCSC, TCVR, TCPST, SVC and UPFC. Simulations are performed on an IEEE 118-bus power system for several numbers of devices. Results show that the three algorithms converge to similar optimal solutions. The security margin of the system may be increased with the use of FACTS devices, but some limitations are observed. The locations of the devices and their influence areas are analyzed.

Approaches for analog VLSI simulation of the transient stability of large power networks

This paper suggests several approaches for determining the transient stability of a power network by using an analog VLSI chip for simulating the system behavior. The main advantages of using this method are the much shorter computation time and lower complexity compared to the currently used methods, which are based on numerical calculations or discrete analog emulators.

Multi-Area Energy and Reserve Dispatch Under Wind Uncertainty and Equipment Failures

The cross-border trading among electricity markets in an interconnected multi-area system (e.g., in central Europe) and the integration of renewable resources (e.g., wind energy) have remarkably increased in recent years. To efficiently operate such system, a proper coordination among different areas is required. Within this context, a decentralized algorithm for market clearing is proposed in this paper to dispatch simultaneously energy and reserve under wind generation uncertainty and equipment failures. The proposed technique does not require a central operator but just a moderate interchange of information among neighboring areas. Additionally, the benefit of cross-border trading is studied.

Multi-Area Unit Scheduling and Reserve Allocation Under Wind Power Uncertainty

This paper proposes a decentralized methodology to optimally schedule generating units while simultaneously determining the geographical allocation of the required reserve. We consider an interconnected multi-area power system with cross-border trading in the presence of wind power uncertainty. The multi-area market-clearing model is represented as a two-stage stochastic programming model. The proposed decentralized procedure relies on an augmented Lagrangian algorithm that requires no central operator intervention but just moderate interchanges of information among neighboring regions. The methodology proposed is illustrated using an example and a realistic case study.

State estimation of Active Distribution Networks: Comparison between WLS and iterated kalman-filter algorithm integrating PMUs

One of the challenging tasks related to the realtime control of Active Distribution Networks (ADNs) is represented by the development of fast (i.e. sub-second) state estimation (SE) processes. As known, the problem of SE of power networks links the measurements performed in the network with a set of non-linear equations representing the links between the network node voltage phasors (i.e. the system states) and measured quantities. The calculation of these voltages is accomplished by the solution of a minimization problem by using, for instance, Weighted Least Squares (WLS) or Kalman filter (KF) methods. The availability of phasor measurement units (PMUs), characterized by high accuracy and able to directly measure node voltage phasors, allows, in principle, a simplification of the SE problem. Within this framework, the paper has two aims. The first is to propose a procedure based on the use of the Iterated KF (IKF) aiming at making achievable, in a straightforward manner, the SE of ADNs integrating PMU measurements. The second goal is to present a sensitivity analysis of the performances of WLS vs IKF methods as a function of the measurements and process covariance matrices.

Improvement of Dynamic Modeling of Supercapacitor by Residual Charge Effect Estimation

This paper presents a set of experimental investigations related to the dynamic behavior of supercapacitors (SCs). The experimentally observed results are then used as inputs for the development of an improved version of one of the most common SC RC-equivalent circuit models. The key improvement concerns the accurate modeling of the diffusion phenomenon of the SC residual charge during charging/discharging and rest phases. The experimental procedure needed for evaluating the parameters of the proposed model is also given. The accuracy of the obtained model is then experimentally validated for different cycles characterized by different dynamics.