风力发电机组的非线性控制——变结构控制与鲁棒控制

风速、风向及负载的随机性、湍流、尾流效应、塔影效应等的影响,使风力发电系统不但要解决最大风能捕获、电能品质控制两类关键问题,还要解决传动链的疲劳负载、叶片的振颤与翦切、塔身的弯曲与抖振等问题,这些问题实际上都可归结为非线性控制的范畴。该文综述了近年来滑模变结构控制、H∞鲁棒控制在风力发电系统稳定,最大风能捕获及调速系统控制等方面应用研究的主要成果与方法,并提出若干需要解决的问题。

直流纳电网技术在波能装置群中的应用

根据波能装置液压发电系统的特性,提出由蓄电池组支撑的直流纳电网技术。波能装置群采用直流并网与传输,可以接受周期波动的波浪能功率,效率、可靠性、电能质量均较高。纳电网蓄电池可解除波能装置群发电功率与纳电网逆变器的馈网功率,各装置负载可简化为纳电网蓄电池,各装置分别向蓄电池充电,互不影响。纳电网逆变器为海岛居民提供稳定的高质量的可控电源。仿真和实践证明波能装置群应用直流纳电网技术的可行性和优势。

PWM逆变器的定向矢量控制策略

针对风力发电并网的优化问题。提出了三相电压源脉冲宽度调制(PWM)逆变器的定向矢量控制技术,并设计了数字控制的变换器-逆变器系统。给出了该变换器和逆变器的数学模型。提出了一种定向矢量控制的方案来实现对风能并网的控制策略。为了检验该系统的动态性能,采用MATLAB7/SIMULINK程序进行了仿真。仿真结果表明,提出的控制系统模型在不同的干扰下都展现出其良好的性能。

Scheduling and control co-design for Networked Wind Energy Conversion Systems

Fieldbus, industrial Ethernet that is simple, reliable, economical, and practical, is widely used in Wind Energy Conversion Systems(WECSs). These techniques belong to the field of networked control systems. Network embedding to Wind Energy Conversion Systems brings many new challenges. Implementing a control system over a communication network causes inevitable time delays that may degrade performance and can even cause instability. This work addresses challenges related to the reliable control of wind energy conversion systems, based on the theoretical framework of networked control systems. A type of WECS with network-induced delay and packet dropout is modeled and adjustable deadbands are explored as a solution to reduce network traffic in WECSs. A method to study the reliable control of WECSs is presented, which takes into account system response as well as the network environment. After detailed theoretical analysis, simulation results are provided, which further demonstrate the feasibility of the proposed scheme.

Event-triggered mechanism based robust fault-tolerant control for networked wind energy conversion system

In this paper,a novel robust fault-tolerant control scheme based on event-triggered communication mechanism for a variable-speed wind energy conversion system(WECS)with sensor and actuator failures is proposed.The nonlinear WECS with event-triggered mechanism is modeled based on the Takagi-Sugeno(T-S)fuzzy model.By Lyapunov stability theory,the parameter expression of the proposed robust fault-tolerant controller with event-triggered mechanisms is proposed based on a feasible solution of linear matrix inequalities.Compared with the existing WECS fault-tolerant control methods,the proposed scheme significantly reduces the pressure of network packet transmission and improves the robustness and reliability of the WECS.Considering a doubly-fed variable speed constant frequency wind turbine,the eventtriggered mechanism based fault-tolerant control for WECS is analyzed considering system model uncertainty.Numerical simulation results demonstrate that the proposed scheme is feasible and effective.

New Robust Energy Management Model for Interconnected Power Networks Using Petri Nets Approach

The problematic of energy management, particularly in terms of resources control and efficiency, has become in the space of a few years an eminently strategic subject. Its implementation is both complex and exciting as the prospects are promising, especially in relation with smart grids technologies. The deregulation of the electricity market, the high cost of storage, and the new laws on energy transition incite some significant users (collectivities, cities, regions, etc.) to form themselves into local producers in order to gain autonomy and reduce their energy bills. Thus, they may have their own sources (classic and/or renewable energy sources) to satisfy their needs and sell their excess production instead of storing it. In this idea, the territorial interconnection principle offers several advantages (energy efficiency, environmental protection, better economic balance). The main challenge of such systems is to ensure good energy management. Therefore, power distribution strategy must be implemented by matching the supply and the demand. Such systems have to be financially viable and environmentally sustainable. This allows among others to reduce the electricity bill and limit the systematic use of the national power network, typically using non-renewable sources, and thereby support sustainable development. This paper presents an original model for aid-decision in terms of grid configurations and control powers exchanged between interconnected territories. The model is based on Petri nets. Therefore, an iterative algorithm for power flow management is based on instantaneous gap between the production capability (photovoltaic, wind) and the demand of each user. So, in order to validate our model, we selected three French regions: the PACA region, the Champagne-Ardenne region and the Lorraine region. Due to their policy, their geographical and climatic features, we opted for two renewable sources: “wind” and “photovoltaic”. The numerical simulations are performed using the instantaneous productions of each region and their energy demand for a typical summer day. A detailed economic analysis is performed for two scenarios (with or without interconnections). The results show that the use of renewable energy in an interconnection context (i.e. pooling), offers serious economic and technical advantages.

Three-phase AC-DC Converter for Direct-drive PMSG-based Wind Energy Conversion System

In this paper,a wind energy conversion system(WECS)is presented for the electrification of rural areas with wind energy availability.A three-phase AC-DC converter based on a bridgeless Cuk converter is used for power extraction from the permanent magnet synchronous generator(PMSG).The bridgeless topology enables the elimination of the front-end diode bridge rectifier(DBR).Moreover,the converter has fewer components,simple control,and high efficiency,making it suitable for a small-scale WECS.A squirrel cage induction motor(SCIM)is used to emulate a MOD-2 wind turbine to implement the PMSG-based WECS.A direct-drive eight-pole PMSG is used in this study;thus,a low-input-voltage system is designed.The converter is designed to operate in the discontinuous inductor current mode(DICM)for inherent power factor correction(PFC)and the maximum power point tracking(MPPT)is achieved through the tip-speed ratio(TSR)following.The performance of the developed system is analyzed through simulation,and a 500 W hardware prototype is developed and tested in different wind speed conditions.

A Novel Modified Fuzzy-predictive Control of Permanent Magnet Synchronous Generator Based Wind Energy Conversion System

A wind energy conversion system(WECS)based on a permanent magnet synchronous generator(PMSG)is an effective solution for renewable energy generation in modern power systems.The main advantages of PMSG include high performance at high and low speeds,minimal control effort owing to lower rotor inertia,self-excitation,high reliability,and simplicity of structure compared with induction generators.However,the intermittent nature of wind energy implies that maximum efficiency is not obtained from this system.Accordingly,maximum power point tracking(MPPT)in wind turbine systems has been proposed to address this problem.Traditional MPPT strategies suffer from severe output power fluctuations,low efficiency,and significant ripples in turbine rotation speed.This paper presents a novel MPPT control strategy based on fuzzy logic control(FLC)and model predictive control(MPC)to extract the maximum power from a PMSG-WECS and control the machine-side and grid-side converters.The simulation results obtained from Matlab/Simulink confirm the superiority of the control model in eliminating the output power fluctuations of the wind generators and accurately tracking the maximum power point.A comparative study between conventional MPPT and control methods is also conducted.

仿射线性结果T-S模糊建模及其应用

为了改善风能转换系统(WECS)非线性模型的线性化水平,本文以其为研究对象,围绕工况点且基于一阶泰勒展开提出了一种结果部分为仿射线性结构的Takagi-Sugeno(T-S)模糊建模方法;然后利用该方法处理WECS模型中的非线性,给出了具体的T-S模糊建模步骤并得到了高精度的WECS线性控制设计模型;最后,基于模糊逻辑工具箱对该T-S模糊模型进行了模型验证。仿真结果显示,该T-S模糊建模方法具有任意精度的非线性模型及动态特性逼近能力。

Ferroresonance Overvoltage Mitigation Using STATCOM for Grid-connected Wind Energy Conversion Systems

We present the ferroresonance overvoltage mitigation concerning the power systems of the grid-connectcd wind energy conversion systems(WECSs).WECS is considered based on a doubly-fed induction generator(DFIG).Ferroresonance overvoltage associated with a single-pole outage of the line breaker is mitigated by fast regulating the reactive power using the static compensator(STATCOM).STATCOM controller is introduced,in which t>\o incorporated proportional-integral(PI)controllers are optimally tuned using a modified flow-er pollination algorithm(MFPA)as an optimization technique.To show the capability of the proposed STATCOM controller in mitigating the ferroresonance overvoltage,two test cases are introduced,which are based on the interconnection status of the power transformer used with the grid-connected DFIGs.The results show that the ferroresonance disturbance can occur for the power transformers installed in the wind farms although the transformer terminals are interconnected,and neither side of the transformer is isolated.Furthermore,as a mitigation method of ferroresonance overvoltage,the proposed STATCOM controller succeeds in improving the system voltage profile and speed profile of the wind turbine as well as protecting the system components against the ferroresonance overvoltage.