Active power reserves are needed for the proper operation of an electrical system. These reserves are continuously regulated in order to match the generation and consumption in the system and thus, to maintain a constant electrical frequency. They are usually provided by synchronized conventional generating units such as hydraulic or thermal power plants. With the progressive displacement of these generating plants by non-synchronized renewable-based power plants (e.g. wind and solar) the net level of synchronous power reserves in the system becomes reduced. Therefore, wind power plants are required, according to some European Grid Codes, to also provide power reserves like conventional generating units do. This paper focuses not only on the review of the requirements set by Grid Codes, but also on control methods of wind turbines for their participation in primary frequency control and synthetic inertia.

Participation of wind power plants in system frequency control: Review of grid code requirements and control methods

In this paper we propose two modeling procedures for wind speed simulation. These procedures could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems. The evolution of a horizontal wind speed has been synthesized taking into account two components. The medium- and long-term component is described by a power spectrum associated to a specific site. The turbulence component is assumed to be dependent on the medium- and long-term wind speed evolution. It is considered as a nonstationary process. Two simulation methods for this component, using rational and nonrational filters are proposed. In both procedures, the turbulence model is defined by two parameters, which are either obtained experimentally, or adopted a priori, according to information from the considered site. Numerical results and implementation aspects are also discussed.

https://ieeexplore.ieee.org/iel5/8949/28458/01270996.pdf

Large band simulation of the wind speed for real time wind turbine simulators

Prediction, operations, and condition monitoring in wind energy

Robust control of the variable speed wind turbines in the presence of uncertainties: A comparison between H∞ and PID controllers

Model predictive control with finite control set for variable-speed wind turbines

This paper focuses on the design of Linear Quadratic Gaussian (LQG) controllers for variable-speed horizontal axis Wind Turbines (WT). These turbines use blade pitch angle and electromagnetic torque control variables to meet specified objectives for Full Load (FL) zone. The main control objectives are to reduce structural dynamic loads and to regulate the power of the WT. The controllers are designed in order to optimize a trade-off between several control objectives. Four different LQG using Individual Pitch Control (IPC) are designed, with Wireless-Sensors (WS) placed at the end of the blades for the last one. Their control model is progressively more complex. The first one takes into account a rigid simple behavior, the second control model considers the first mode of the drive-train flexibility, the third model takes into account the drive-train and tower flexibilities and the fourth that of the blades. Likewise, their optimization criteria consider for each controller a new control objective to alleviate fatigue loads in the drive-train, then, also in the tower and finally also in the blades. The evaluation of the fatigue loads affecting the WT components are based on a Rainflow Counting Algorithm (RFC) and the Miner's rule. The results indicate a significant reduction of fatigue loads especially in the drive-train and the blades when its flexibility is taken into account in the control models.

Comparison of wind turbine LQG controllers using Individual Pitch Control to alleviate fatigue loads

Control of wind turbines for fatigue loads reduction and contribution to the grid primary frequency regulation

This study aims to analyse different linear quadratic Gaussian (LQG) controllers' performances in terms of reducing the fatigue load of wind turbines' (WT) most costly components caused by the spatial turbulence of wind speed. Five LQGs with increasing control model complexity and a greater number of objectives are designed, the first four with collective pitch control (CPC), and the fifth with individual pitch control (IPC). In the design of the controllers, firstly a linear control model is obtained in the operating point corresponding to a wind speed of 18 m/s. Then, the Kalman filter (KF) and the rest of the controller are tuned with simulations in order to obtain the lowest possible fatigue loads while respecting certain generator power and speed variation limits. Finally, the five controllers are tested with processor-in-the-loop (PIL). Fatigue loads are evaluated by rainflow counting algorithm and then applying the Palmgren'Miner rule. Tests results show that drive-train loads are significantly reduced from LQG1_CPC, that the complexity of the controllers does not have a significant influence on the reduction of tower loads, and that LQG3_IPC allows fatigue loads on blades to be alleviated considerably.

Comparison of an island wind turbine collective and individual pitch LQG controllers designed to alleviate fatigue loads

This paper focuses on the design of Linear Quadratic Gaussian (LQG) controllers for variable-speed horizontal axis Wind Turbines (WTs). Those turbines use blades pitch angle and electromagnetic torque control variables to meet specified objectives for Full Load (FL) zone. The main control objectives are to reduce the structural dynamic loads and to regulate the power of the WT. The controllers are designed in order to optimize a trade-off between several control objectives. Four different LQG controllers are designed. Their control model is progressively more complex. The first one takes into account a rigid simple behavior, the second control model considers the first mode of flexibility of the drive train, the third model takes into account the tower flexibilities and the fourth that of the blades. In the same manner, their optimization criteria considers for each controller a new control objective to alleviate fatigue loads in the drive train, then, also in the tower and finally also in the blades. The evaluation of the fatigue loads affecting the WT components are based on a Rainflow Counting Algorithm and the Miner's rule (RFC). The results indicate a significant reduction of fatigue loads in the drive-train when its flexibility is taken into account in the control model.

Comparison of wind turbine LQG controllers designed to alleviate fatigue loads

The objectives of this work have been to design and analyze a discrete LQG controller which contributes to the primary frequency control of the grid and to the reduction of the drive-train fatigue loads of a Wind Turbine (WT). The WT rotational speed and electrical power are controlled using the electromagnetic torque and the pitch angle as control variables. The rotational speed and electrical power references are generated in a higher control level depending on the wind speed and a frequency droop. The controller has been designed in Matlab® and has been simulated in Simulink®, in some linear simulation models corresponding to different operating points. These linear models have been obtained from a 5MW WT model implemented in Bladed commercial wind turbine simulation tool. The results validate the efficiency of the designed controller, in comparison with another discrete LQG controller which has not been designed to reduce drive-train fatigue loads.

Said Nourdine

Papers

Comparison of wind turbine LQG controllers using Individual Pitch Control to alleviate fatigue loads

Control of wind turbines for fatigue loads reduction and contribution to the grid primary frequency regulation

Comparison of an island wind turbine collective and individual pitch LQG controllers designed to alleviate fatigue loads

Comparison of wind turbine LQG controllers designed to alleviate fatigue loads

Control of wind turbines for frequency regulation and fatigue loads reduction