Contrôle vectoriel des machines synchrones à aimants permanents : identification des paramètres et minimisation des ondulations de couple

Not availableLe présent travail apporte des solutions aux problèmes que pose le contrôle du couple des machines synchrones à aimants permanents alimentées par un onduleur triphasé. La première contribution concerne l'identification en ligne des constantes de temps électriques des machines synchrones à répartition sinusoïdales des conducteurs: celle-ci améliore l'efficacité de l'algorithme de découplage du contrôle des courants direct et en quadrature et permet d'imposer des courants optimaux même en régime transitoire. La seconde partie traite des machines synchrones à rotor lisse et à répartition non sinusoïdale des conducteurs, dans lesquelles on annule les ondulations du couple par une modulation appropriée des courants. Une méthode simple et efficace consiste à annuler le courant direct et à imposer un courant en quadrature inversement proportionnel à la F.E.M. correspondante. Enfin une troisième partie est consacrée à l'autopilotage des machines synchrones à aimants sans capteur de position mécanique. Cet autopilotage est effectué simplement à partir des grandeurs externes de la machine en utilisant le fait que la composante directe de la F.E.M. induite est null

Power systems wide-area voltage stability assessment considering dissimilar load variations and credible contingencies

Abstract This paper reveals that the existing techniques have some deficiencies in the proper estimation of voltage stability margin (VSM) when applied to a power system with different load change scenarios. The problem gets worse when credible contingencies occur. This paper proposes a real-time wide-area approach to estimate VSM of power systems with different possible load change scenarios under normal and contingency operating conditions. The new method is based on an artificial neural network (ANN) whose inputs are bus voltage phasors captured by phasor measurement units (PMUs) and rates of change of active power loads. A new input feature is also accommodated to overcome the inability of trained ANN in prediction of VSM under N−1 and N−2 contingencies. With a new algorithm, the number of contingencies is reduced for the effective training of ANN. Robustness of the proposed technique is assured through adding a random noise to input variables. To deal with systems with a limited number of PMUs, a search algorithm is accomplished to identify the optimal placement of PMUs. The proposed method is examined on the IEEE 6-bus and the New England 39-bus test system. Results show that the VSM could be predicted with less than 1% error

A comprehensive stochastic energy management system in reconfigurable microgrids

This paper addresses the joint stochastic energy and reserve scheduling problem in microgrids (MGs). The established approach proposes a novel high-performance energy management system (EMS) making use of automatically controlled switches (ACSs). Accordingly, besides the optimal scheduling of active elements namely distributed generations (DGs) and responsive loads (RLs), the optimal topology of the network for each of the scheduling intervals is determined as well. Likewise, the effects of the reconfiguration process in probable variations of the scheduled energy patterns in DGs, RLs, and grid purchases are thoroughly assessed to highlight the alterations in unallocated capacities of these resources. Moreover, the uncertainties associated with both the load and wind speed forecasting errors are suitably accommodated through the reserve allocations. The proposed optimization procedure is formulated as a mixed-integer non-linear problem and resolved using a genetic algorithm (GA). The effectiveness of the projected framework is verified utilizing a typical MG, and the obtained numerical results are discussed in depth. Copyright © 2016 John Wiley & Sons, Ltd

Coordination of generators and existing Energy Storage Systems with wind farms in order to reduce the transient effects

In order to keep the power system equilibrium, system supply needs to be equal to the load demand continually. The existing synchronous generators are mostly capable to keep the system balance in traditional power system. However, in power systems with wind power penetration, due to random nature of wind energy, keeping electricity supply-demand balancing has been got more difficult. Such systems may be faced with many difficulties in dealing with transient phenomena. In this study, Energy Storage System is utilized with wind farm to modulate the wind farm power output fluctuations, and also to improve the response of synchronous generators to transient variations such as sudden load changes. Energy storage system has been utilized to reduce the transient effects in power systems. As it is shown, with applying a suitable coordination control method to energy storage systems, the transient effects will be reduced and wind farm power output fluctuations will be compensated as well. The simulations are performed using PSCAD software, with a 9 bus system. © 2012 IEEE

A new long term load management model for asset governance of electrical distribution systems

Long term load management (LTLM) is one of the key factors in making decisions regarding new investments in distribution systems. However, none of the previous studies have investigated the effect of external factors such as governance, urban planning and social behavior factors on LTLM. In this paper, a new LTLM model is proposed to determine the influence of external factors on LTLM. Distribution system development indices have been used to obtain asset governance targets; these indices can help Distribution Companies (DISCOs) compromise between reliability and running the system economically. Capacity utilization and the number of maneuver points are used here to do LTLM and improve asset governance. Numerical studies on a real distribution system (city with population about 200,000) have been conducted and sensitivity analysis of maneuver points and capacity utilization level with respect to external factors is studied and analyzed. The results show the feasibility of the proposed LTLM to obtain higher efficiency from the viewpoint of cost and quality service compared to conventional LTLM.Long term load management Social behavior Urban planning Neural network Distribution system Asset governance