Partitioning approach for large wind farms: active power control for optimizing power reserve

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Nowadays, large wind farms are expected to guarantee stability of the electrical grid contributing with ancillary services, such as frequency support. To this end, wind farm controllers must set the power generation of each turbine to compensate generation and demand imbalances. With the aim of optimizing primary frequency support, this paper proposes a partitioning approach to split large wind farms into several disjoint subsets of turbines according to the wake propagations through the wind farm. The partitioning problem is solved as a mixed-integer multi-objective optimization problem stated to maximize the strength of the coupling among the turbines due to the wake effect. Thus, no additional information sharing related to the wake propagations needs to be considered between the subsets. Different control tasks are assigned to the local controller of each subset, such that the total power generated meets the power demanded by the grid while the power reserve for enhancing primary frequency support is maximized. Finally, as an application of the proposed model, a decentralized wind farm control strategy is designed and compared with a centralized approach.Peer ReviewedPostprint (author's final draft

Optimization of constant power control of wind turbines to provide power reserves

In several countries, the wind power penetration increased tremendously in the last years. As the current wind turbines do not participate in frequency control nor reserve provision, this may compromise the proper functioning of the primary control and the provision of power reserves. If no actions are taken, increasing levels of wind penetration may result in serious problems concerning the stable operation of the power system. This paper focuses on the provision of power reserves by wind turbines. For this service, the constant power control strategy is chosen as control strategy, as it gives a constant power output and has the ability to provide power reserves. In this way, the wind turbine behaves more like a conventional power plant. The choice of the power reference value is crucial as it determines whether or not a stable operation of the wind turbine is possible and power reserves can be provided. In this paper, an algorithm is proposed to obtain the range of possible reference values. By means of simulations, the optimal reference value to provide power reserves with a single wind turbine is obtained. Also, reserve provision in a wind farm is investigated. It is shown that the provision of power reserves with wind turbines using the constant power strategy is possible, especially in wind farms

Model Predictive Control for Enhancing Wind Farms Participation in Ancillary Services

The increasing penetration of Renewable Energy (RE) systems into the electric grid is creating new challenges into the power system. The unpredictable and variable nature of renewable power generation is increasing the imbalances between generation and demand. For this reason, wind farms, which are the main source of RE in Europe, are required nowadays to support the grid, providing services of voltage and frequency regulation. To be able to increase their power production during a frequency event, Wind Power Plants (WPPs) need to work below their maximum generation capacity, keeping an additional amount of power, called power reserve, that can be injected into the grid when required. The power reserve of a wind farm strongly depends on the interaction among the wind turbines. The wake effect produced by the upstreams turbines affects the wind condition that each turbine faces and reduces their maximum available power. This study aims to present the effects of different distribution of the Wind turbines (WTs) individual power contribution on the power reserve. Three control strategies, based on Model Predictive Control (MPC), are tested on a fifteen turbines wind farm under different wind conditions. Simulation results show that, in almost all cases, prioritizing the power contribution of the most downstream turbines and deloading the upstream ones, leads to a maximization of the wind farm power reserve. Furthermore, an additional MPC strategy aiming to combine active and reactive power control, for providing both frequency and voltage regulation at the Point of Common Coupling (PCC), is presented. The advantage of a combined active and reactive power control is the possibility of improve the voltage support capability of the WPPs, by controlling the active power set-points. The MPC is also tested on a fifteen turbines wind farm, in order to validate the performances of the controller while solving the multi-objective problem. The ability of the controller to handle simultaneously the different requirements is proven

Wind farm power optimization and fault ride-through under inter-turn short-circuit fault

Inter-Turn Short Circuit (ITSC) fault in stator winding is a common fault in Doubly-Fed Induction Generator (DFIG)-based Wind Turbines (WTs). Improper measures in the ITSC fault affect the safety of the faulty WT and the power output of the Wind Farm (WF). This paper combines derating WTs and the power optimization of the WF to diminish the fault effect. At the turbine level, switching the derating strategy and the ITSC Fault Ride-Through (FRT) strategy is adopted to ensure that WTs safely operate under fault. At the farm level, the Particle Swarm Optimization (PSO)-based active power dispatch strategy is used to address proper power references in all of the WTs. The simulation results demonstrate the effectiveness of the proposed method. Switching the derating strategy can increase the power limit of the faulty WT, and the ITSC FRT strategy can ensure that the WT operates without excessive faulty current. The PSO-based power optimization can improve the power of the WF to compensate for the power loss caused by the faulty WT. With the proposed method, the competitiveness and the operational capacity of offshore WFs can be upgraded