Control Method For Wind Turbines Research Articles

A novel higher rotational speed maintaining control for wind power generation systems under unstable wind conditions

This study proposes the Higher Rotational Speed Maintaining (HRSM) control algorithm that is suitable for large wind speed fluctuations. One of the challenges faced by wind generators is operating with significant wind speed oscillations. A wind generator with a large moment of inertia increases the time constant in rotational speed control and delays the tracking of the optimal operating point. This delay could reduce generated power by up to 40% or more. There are numerous regions in Japan’s inland areas where average wind speeds exceed 6.5 m/s. However, frequent fluctuations in wind speeds make wind power generation challenging. Therefore, this paper proposes a control algorithm suitable for wind turbines operating under unstable wind conditions. Higher rotational speeds are required to convert sudden high wind speeds into higher power output, especially when wind speed oscillations are large. Hence, the proposed algorithm focuses on maintaining the rotational speed during periods of unstable wind conditions to improve generation efficiency. The effectiveness of the proposed control method for wind turbines is verified through numerical simulation results. The novel control algorithm aims to promote the spread of wind turbines in areas with unstable wind conditions by overcoming these disadvantages.

Incremental feedforward collective pitch control method for wind turbines

In recent years, wind turbines are becoming larger, which will exacerbate the complexity of loads Complex load change affect the output power quality and wind turbine service life so that must be studied. Pitch control is usually used to reduce wind turbine load. In this paper, based on the Light Detection and Ranging (LiDAR) technology and incremental feedforward control theory, an incremental feedforward collective pitch controller is proposed. The controller can be directly superimposed on the traditional collective pitch controller so that the incremental pitch angle can fully compensate wind influence. The effectiveness of the controller is verified by multi-software platform joint simulation and hardware-in-the-loop experiment. The results show that the controller can effectively reduce the wind turbine power and load fluctuation when the variation trend of wind speed in the rotor plane estimate by LiDAR data is the same as the actual wind speed.

Wind Turbine Fire Prevention System Using Fuzzy Rules and WEKA Data Mining Cluster Analysis

With the rapid expansion of the supply of renewable energy in accordance with the global energy transition policy, the wind power generation industry is attracting attention. Subsequently, various wind turbine control technologies have been widely developed and applied. However, there is a lack of research on optimal pitch control, which detects wind direction and changes the rotation angle of the blade in real time. In areas where the wind speed is not strong, such as South Korea, it is necessary to maintain the optimal angle in real time so that the rotating surface of the blade can face the wind direction. In this study, optimal pitch control was performed through real-time analysis of wind speed, direction, and temperature, which is the core of wind turbine maintenance, using fuzzy rules using FIS (Fuzzy Interface System) and WEKA data mining cluster analysis techniques. In order to prevent fires caused by the over-current of wind turbines, over-current control methods such as VCB (Vacuum Circuit Breaker) utilization, prototype utilization such as a modular MCB (Main Circuit Breaker) incorporating VI (Vacuum Interrupter), and vacuum degree change analysis methods using a PD (Partial Discharge) signal were proposed. The optimal control technique for wind turbine parts and facilities was put forth after judging and predicting the annual average wind distribution suitable for wind power generation using HRWPRM (Korea’s High-Resolution Wind Power Resource Maps). Finally, the various wind turbine control methods carried out in this study were confirmed through computer simulation, such as remote diagnosis and early warning issuance, prediction of power generation increase and decrease situation, and automatic analysis of wind turbine efficiency.

Flexible torque control for wind turbines considering frequency response under wind speed crossing region

The operational range of a wind turbine is typically divided into two regions based on wind speed: below and above the rated wind speed. The turbine switches between these two regions depending on the prevailing wind speed; however, during the transition, the generator may undergo transient shocks in torque, which can negatively impact both the mechanical load of the turbine and the reliability of the power system. This article presents a flexible torque control method for wind turbines, specifically designed to handle the transition between wind speed regions when the turbine is participating in frequency regulation. First, the anomalies in generator torque caused by traditional torque control methods during frequency response scenarios are analyzed. Next, two methods—dynamic deloading and flexible torque control—are developed to address these issues. The developed methods set transition regions based on generator speed, which helps to reduce the impact of transient changes in generator torque. Importantly, the addition of transition regions does not require additional feedback, making the controller easy to implement. The response characteristics of the proposed methods are then analyzed under different deloading factors and wind speeds using model linearization. Simulation studies are presented to verify the effectiveness of the proposed methods. Overall, this study demonstrates the potential value of flexible torque control methods for wind turbines, which can help to mitigate the negative impact of torque shocks and improve the reliability and efficiency of wind power systems.

Overview of Various Voltage Control Technologies for Wind Turbines and AC/DC Connection Systems

Wind power generation is one of the mainstream renewable energy resources. Voltage stability is as important as the frequency stability of a power system with a high penetration of wind power generation. The advantages of high-voltage direct current (HVDC) transmission systems become more significant with the increase of both installed capacity and transmission distance in offshore wind farms. Therefore, this study discusses various voltage control methods for wind turbines and HVDC transmission systems. First, various voltage control methods of a wind farm were introduced, and they include QV control and voltage droop control. The reactive power of a wind turbine varies with active power, while the active power from each wind turbine may be different owing to wake effects. Thus, QV and voltage droop control with varying gain values are also discussed in this paper. Next, the voltage control methods for an HVDC transmission system, such as power factor control, voltage control, and Vac-Q control, are also summarized and tested in this study. When a three-phase short circuit fault occurs or a sudden reactive power load increases, the system voltage would drop immediately. Thus, various voltage control methods for wind turbines or HVDC can make the system’s transient response more stable. Therefore, this study implemented the simulation scenarios, including a three-phase short circuit fault at the point of common coupling (PCC) or a sudden increase of reactive power load, and adopted various voltage control methods, which aim to verify whether additional voltage control methods are effective to improve the performance of transient voltage. The voltage control method has been implemented in PSCAD/EMTDC, and the simulation results show that the QV control performs better than the droop control. In addition, when applying the voltage control technique during a three-phase fault, transient voltage nadir can be improved through either an HVDC transmission system or an AC transmission system.

Current Harmonic Control Method of Wind Turbine Based on PIR Controller

Wind power equipment technology is the basis for the development of wind power generation. Aiming at the problem that the traditional PI controller is difficult to control the AC component of the current in the DQ axis, resulting in a large number of current harmonics in the process of power generation, which seriously affects the efficiency of power generation. This paper proposes a current harmonic control method for wind turbines based on a PIR controller. The mathematical model of wind power generation is constructed based on the synchronous rotating coordinate system. The current harmonic components are calculated according to the DQ rotor speed, shaft component, and other parameters. The PIR current harmonic controller is established by improving the ordinary PI controller to track and control the AC current signal. And finally, a current harmonic control target value is obtained according to different main control targets, and a specific harmonic component is eliminated. The experimental results show that the harmonic content is 3.12%, 2.06%, 1.17%, and 1. 02%, respectively, when the harmonic current order is 5, 7, 11, and 13. It is better than the comparison method. Therefore, this method can greatly reduce the harmonic content of the current in the process of different current orders, reduce the harmonic loss, and improve the generating efficiency of the unit.

Comparison of primary frequency control methods for wind turbines based on the doubly fed induction generator

The penetration of large levels of wind energy leads to technical problems affecting the frequency stability of the power system. Naturally, a wind power plant does not provide an inertial response nor does it regulate the system frequency in case of generation-demand imbalance due to the decoupling between the rotor speed and the grid frequency through the electronic converter (AC/DC/AC). This paper reviews, analysis and compares the performance of four control methods based on the modification of the electromagnetic torque set point and one of the mechanical torque. These methods allow that activation of the wind turbine inertia when a frequency deviation occurs, contributing to the regulation of the system frequency similarly to a conventional synchronous generator. However, wind turbines only change their operating point for a limited time and not permanently.

Wind turbine LIDAR-assisted control: Power improvement, wind coherence and loads reduction

This paper aims to firstly review various LIDAR-assisted wind turbine control methods proposed in the past ten years for improving power production in the below rated wind speed region in order to clarify their performance and quantify the potential benefits and drawbacks of LIDAR-assisted control. Secondly, a new LIDAR-assisted control algorithm based on Extremum Seeking Control (ESC) using LIDAR preview information for tracking the optimal power coefficient value is presented and compared to the traditional control strategy. The results show that the newly proposed LIDAR-assisted control strategy is beneficial in the below rated wind speed region when the aerodynamic properties of blades are changed largely compared to the original design. Lastly, the effects of the wind field coherence between the LIDAR measured points and the rotor plane on the LIDAR-assisted control for loads reduction in above rated region is discussed. An important conclusion is that the major benefit of LIDAR-assisted wind turbine control is to improve collective pitch control for reducing fatigue loads in above rated region, when the coherence bandwidth between the LIDAR measured wind speed and the rotor effective wind speed is high.

New perspectives on maximum wind energy extraction of variable-speed wind turbines using previewed wind speeds

Maximum wind energy extraction remains a challenge for the large-scale wind turbines due to their increasing moment of inertia. In this study, a novel nonlinear predictive control method using previewed wind speeds is proposed to address the issue of maximum wind energy extraction for variable-speed wind turbines. Different from the conventional structure, the proposed nonlinear predictive control is based on the discrete prediction model established by a large time step. By doing so, the number of time discrete points is significantly reduced and the quantity of the solution set becomes numerable. As a result, the implementation complexity and computational burden are able to be relieved, and the real-time implementation becomes practical and easy to carry out. The proposed method is demonstrated on two models of wind turbines with different scales, and its performance is compared with the industrial controller. Comparison results show that the increased energy extraction efficiency gained by the proposed method is more than 1% on the two turbine models under different wind conditions, and thus the superior capability in extracting wind energy promises potential industrial applications. Meanwhile, the expense is the considerable increment of torque variation, which can be relieved by revising the control parameters. The presented method provides new insights into the design of the control methods for wind turbines equipped with advanced measurement devices.

A novel wind speed estimator-integrated pitch control method for wind turbines with global-power regulation

The increasing penetration of wind power has led to a growing interest in that wind turbines (WTs) are operated with global-power regulation, which refers to de-rating and rated power regulation. In this study, the conventional control method is introduced and analyzed. The analysis results show that the conventional control methods may not provide sufficient performance when the WTs are operated along different operating trajectories during the global-power regulation. Accordingly, this study proposes a novel pitch control method that integrates a non-standard extended Kalman filter-based estimator. In this method, a cascade control structure is developed for the pitch controller, which receives the speed reference from a power-speed scheduler. To improve the cascade controller design, the nonlinearities in the WT should be removed by utilizing the information provided by the estimator. By doing so, the proposed controller provides a consistent optimal performance under the global-power regulation while avoiding wind measurement. Finally, the proposed method is validated on a real industrial 1.5 MW WT. The comparative experimental results demonstrate the significant improvements made using the proposed method in maintaining the speed and pitch-actuator usage for global-power regulation of the WTs compared to the conventional method.

MODEL-BASED CONTROL OF UTILITY-SCALE WIND TURBINES

As wind turbine size increases, small increases in efficiency can lead to significant monetary and lifespan improvements. As utility scale wind turbines approach structural efficiency limits, control systems have become the primary means of improving power efficiency and reducing fatigue. In variable speed turbines, collective or individual blade pitch control is one of the most common control schemes for above-rated speed operation. This paper presents the design and implementation of a model-based controller for jointly controlling the wind turbines power and blade loading reduction. First, a high-fidelity simulation model of a 3MW wind turbine is devel-oped followed by the control development using a computationally efficient version of model predictive control which benefits from short-term wind speed forecasts. The proposed controller is com-prehensively tested under multiple practical scenarios and compared with conventional wind turbine control methods.

Probability Density Function Characterization for Aggregated Large-Scale Wind Power Based on Weibull Mixtures

The Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even greater for aggregated wind power generation in power systems with high wind penetration. Consequently, models based on one-Weibull component can provide poor characterizations for aggregated wind power generation. With this aim, the present paper focuses on discussing Weibull mixtures to characterize the probability density function (PDF) for aggregated wind power generation. PDFs of wind power data are firstly classified attending to hourly and seasonal patterns. The selection of the number of components in the mixture is analyzed through two well-known different criteria: the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Finally, the optimal number of Weibull components for maximum likelihood is explored for the defined patterns, including the estimated weight, scale, and shape parameters. Results show that multi-Weibull models are more suitable to characterize aggregated wind power data due to the impact of distributed generation, variety of wind speed values and wind power curtailment.

A bio-inspired approach to enhancing wind power conversion

The primary objective of this investigation is to develop a new control method for wind turbines that can increase their wind energy capture efficiency. Since the resultant wind turbine system dynamics are profoundly nonlinear and coupled with significant uncertainties, traditional model-based control is found to be not only structurally complex but also computationally expensive. Here, we explore two sets of control algorithms to enhance wind to electrical energy conversion. The first accounts for system nonlinearities and external disturbances by integrating variable structure control with adaptive control. The second accommodates the nonlinearities arising from rotor aerodynamics and pitch (actuation) dynamics, as well as external disturbances, through a method inspired by a 1st order human memory/learning model. The second method allows direct maximum power coefficient tracking for winds under the rated speed and ensures rated power output for winds over the rated speed. Basically, it uses the system current and most recent memorized responses, together with past control experience, to generate new control actions. Both rotor dynamics and actuation (pitch) dynamics are reflected indirectly through the observed/measured system response at each instant, and are embedded within the control mechanism. Thus, there is no need for detailed information on the system model or system parameters in the control’s design and implementation. The efficacy of both proposed approaches is analyzed through numerical simulations.

난류풍속에 대한 MW급 풍력터빈의 토크제어 방법에 따른 응답 특성 비교

풍력터빈의 토크제어는 정격풍속 이하에서 매우 중요하다. 토크제어의 주된 목적은 바람이 가진 공기역학적 파워로부터 최대의 파워를 얻도록 하는 것이다. 풍력터빈의 토크제어 방법은 토크모드 제어와 속도모드 제어로 크게 두 경우로 구분된다. 토크모드 제어는 풍력터빈에서 잘 알려지고 전통적으로 사용되는 방법으로 발전기 회전속도의 제곱에 비례하도록 발전기의 토크크기를 발생시킨다. 속도모드 제어에서는 발전기의 토크크기를 발생하기 위하여 PI 제어기를 사용한다. 본 논문에서는 실제 풍속이 난류인 점을 고려하여 2.75 ㎿ 풍력터빈을 대상으로 두 토크제어 방법을 적용한 수치실험 결과를 제시하고 응답특성을 비교한다.