Ant Colony Optimized Fuzzy Control Solution for Frequency Oscillation Suppression

This paper presents a novel approach in addressing a critical power system issue, i.e., automatic generation control (AGC) in a smart grid scenario. It proposes the design and implementation of an optimized fuzzy logic controller (FLC) for AGC of interconnected power network. There are three different sources of power generation considered in the two-area interconnected model of power system network. First area is equipped with a single reheat thermal unit and a superconducting magnetic energy storage (SMES) unit, while another area has a hydro-unit with SMES. A multi-stage optimization strategy for the optimal solution of FLC for tie-line and frequency oscillation suppression is proposed in this paper using an ant colony optimization technique. The optimization of FLC is carried out in four different stages. The first stage is the optimization of range of input and output variables; the second stage is the optimization of membership function; the third and fourth stages are the optimization for rule base and rule weight optimization, respectively. The performance of the proposed controller is also compared with another control approaches to stabilize P_tie-line and Δf oscillations; these are the Ziegler–Nichols-tuned proportional–integral–derivative (PID) controller and genetic algorithm optimized PID controller. A comprehensive analysis of the traditional techniques and proposed techniques is presented on the basis of major dynamic performance parameters, i.e., settling time and peak overshoot.     

A fuzzy logic controlled superconducting magnetic energy storage,SMES frequency stabilizer

This paper presents application of fuzzy logic controlled superconducting magnetic energy storage device, SMES to damp the frequency oscillations of interconnected two-area power systems due to load excursions. The system frequency oscillations appear due to load disturbance. To stabilize the system frequency oscillations, the active power can be controlled via superconducting magnetic energy storage device, SMES. The error in the area control and its rate of change is used as controller input signals to the proposed fuzzy logic controller. In order to judge the effect of the proposed fuzzy logic controlled SMES, a comparative study is made between its effect and the effect of the conventional proportional plus integral (PI) controlled SMES. The studied system consists of two-area (thermal–thermal) power system each one equipped with SMES unit. The time simulation results indicate the superiority of the proposed fuzzy logic controlled SMES over the conventional PI SMES in damping the system oscillations and reach quickly to zero frequency deviation. The system is modeled and solved by using MATLAB software.     

超导储能改善并网风电场稳定性的研究

建立了风电机组和超导储能(SMES)装置的数学模型以研究SMES对并网风电场运行稳定性的改善.针对风电系统中经常出现的联络线短路故障和风电场的风速扰动,提出利用SMES安装点的电压偏差作为SMES有功控制器的控制信号的策略.对实例系统进行的仿真计算结果表明,SMES采用该控制策略,不仅可以在网络故障后有效地提高风电场的稳定性,而且能够在快速的风速扰动下平滑风电场的功率输出,降低风电场对电网的冲击.     

超导储能装置应用于风电场平滑功率输出的研究

建立了风电机组和超导储能(superconducting magnetic energy storage,SMES)装置的数学模型以研究SMES对并网风电场运行稳定性的改善。针对风电系统中经常出现的联络线短路故障和风电场的风速扰动,提出利用SMES安装点的电压偏差作为SMES有功控制器的控制信号的策略。并搭建了风电场接入电网后的仿真模型,对实例系统进行的仿真计算结果表明,SMES采用该控制策略,不仅可以在网络故障后有效地提高风电场的稳定性,而且能够在快速的风速扰动下平滑风电场的功率输出,降低风电场对电网的冲击。     

A developed control strategy for mitigating wind power generation transients using superconducting magnetic energy storage with reactive power support

The fast variations of wind speed during extreme wind gusts result in fluctuations in both generated power and the voltage of power systems connected to wind energy conversion system (WECS). This paper presents a control strategy which has been tested out using two scenarios of wind gusts. The strategy is based on active and reactive powers controls of superconducting magnetic energy storage (SMES). The WECS includes squirrel cage induction generator (SCIG) with shunt connected capacitor bank to improve the power factor. The SMES system consists of step down transformer, power conditioning unit, DC–DC chopper, and large inductance superconducting coil. The WECS and SMES are connected at the point of common coupling (PCC). Fuzzy logic controller (FLC) is used with the DC–DC chopper to control the power transfer between the grid and SMES coil. The FLC is designed so that the SMES can absorb/deliver active power from/to the power system. Moreover, reactive power is controlled to regulate the voltage profile of PCC. Two inputs are applied to the FLC; the wind speed and SMES current to control the amount active and reactive power generated by SMES. The proposed strategy is simulated in MATLAB/Simulink®. The proposed control strategy of SMES is robust, as it successfully controlled the PCC voltage, active and reactive powers during normal wind speeds and for different scenarios of wind gusts. The PCC voltage was regulated at 1.0 pu for the two studied scenarios of wind gusts. The fluctuation ranges of real power delivered to the grid were decreased by 53.1% for Scenario #1 and 56.53% for Scenario #2. The average reactive power supplied by the grid to the wind farm were decreased by 27.45% for Scenario #1 and 31.13% for Scenario #2.     

非线性PID控制器在超导磁储能装置中的应用研究

非线性比例-积分-微分(Nonlinear Proportion-Integral-Differential,NLPID)控制是一种利用非线性跟踪-微分器和非线性组合方法对线性PID控制进行改进的新型控制策略,它具有不依赖于被控系统模型的特点.作者设计了用于电力系统超导磁储能(Superconducting Magnetic Energy Storage,SMES)装置的NLPID控制器,该控制器通过对由跟踪-微分器提取的转子角速度和机端电压的偏差及其微分和积分信号分别进行适当非线性组合,产生用于协调控制SMES和系统之间的有功和无功功率交换的控制信号.仿真结果表明该NLPID控制器具有较好的适应性和鲁棒性,且改善了系统的阻尼特性,提高了系统电压的稳定性.     

超导储能单元在并网型风力发电系统的应用

风力发电系统发展的趋势是将风力发电机组直接与高压电网相连（简称并网型风力发电系统）。但风速变化造成风力涡轮机械功率变化,会使发电机输出的有功和无功产生波动,从而使电网的电能质量下降。该文提出使用超导储能SMES（super conducting magnetic energy storage system）单元使风力发电机组输出的电压和频率稳定。文中详细介绍了SEMS的调节原理及其最优控制方法,建立了SEMS模型和加入SMES后系统的线性化仿真模型,采用基因算法求最优反馈矩阵,并借助MATLAB软件包设计控制器,仿真结果表明SMES单元对并网型风力发电系统中风力发电机的输出稳定具有极大的改善作用。     

Augmentation of transient stability using a superconducting coiland adaptive nonlinear control

The very nonlinear nature of the generator and system behaviour following a severe disturbance precludes the use of classical linear control techniques. In this paper, a nonlinear adaptive excitation and a thyristor-controlled superconducting magnetic energy storage (SMES) unit is proposed to enhance the transient stability of a power system with unknown or varying parameters like equivalent reactances of the transmission lines. The SMES unit is located near the generator bus terminal in a power system. A nonlinear feedback control law is found which linearizes and decouples the power system. An adaptive control law is used to design the controller for the generator excitation and SMES system. Simulation results demonstrate that the proposed controller can ensure transient stability of a single-machine-infinite-bus system under a large sudden fault which may occur near the generator bus terminal     

集成SMES和CS-SGSC的双馈型风力发电系统

双馈型风力发电机面临能量输出不稳定和低电压穿越能力弱2个主要问题。为了同时解决这2个问题,提出了一种集成超导储能系统和电流型串联网侧变流器的双馈型风力发电系统。该系统利用超导磁体作为能量储存和缓冲环节,提高了能量输出的稳定性;利用电流型串联网侧变流器实现了对定子电压的保护,提升了双馈型风力发电机的低电压穿越能力。仿真结果证明了该拓扑结构及其控制策略的有效性。     

超导磁储能系统抑制风力发电功率波动的研究

建立含超导磁储能装置(SMES)的单机无穷大系统的Phillips-Heffron模型,导出含SMES电力系统总的电磁转矩表达式,从理论上分析SMES对增强系统阻尼的作用.并设计了SMES非线性比例积分微分控制器,数字仿真结果验证了SMES阻尼系统功率振荡的特性,同时表明该控制器具有较好的鲁棒性.     

Power oscillation damping by superconducting magnetic energy (SMES) storage unit

With the increase in the size and capacity of electric power systems and the growth of widespread interconnections, the problem of power oscillations due to the reduced system damping has become increasingly serious. Since a Superconducting Magnetic Energy Storage (SMES) unit with a self-commutated converter is capable of controlling both the active (P) and reactive (Q) power simultaneously and quickly, increasing attention has been focused recently on power system stabilization by SMES control. This paper describes the effects of SMES control on the damping of power oscillations. By examining the case of a single generator connected to an infinite bus through both theoretical analyses and experimental tests (performed with a SMES unit with maximum stored energy of 16 kJ and an artificial model system), the difference in the effects between P and Q control of SMES is clarified as follows:

• 1 In the case of P control, as the SMES unit is placed closer to the terminal of the generator, the power oscillations will decay more rapidly.
• 2 In the case of Q control, it is most effective to install the SMES unit near the midpoint of the system.
• 3 By comparing the P control with Q control, the former is more effective than the latter based on the conditions that the SMES unit location and the control gain are the same.

     

Performance of a grid-connected wind generation system with a robust susceptance controller

Wind turbine driven induction generators are vulnerable to transient disturbances like wind gusts and low voltages on the system. The fixed capacitor at the generator terminal or the limited support from the grid may not be able to provide the requisite reactive power under these abnormal conditions. This paper presents a susceptance control strategy for a variable speed wound-rotor induction generator which can cater for the reactive power requirement. The susceptance is adjusted through a robust feedback controller included in the terminal voltage driven automatic excitation control circuit. The fixed parameter robust controller design is carried out in frequency domain using multiplicative uncertainty modeling and H_∞ norms. The robustness of the controller has been evaluated through optimally tuned PID controllers. Simulation results show that the robust controller can effectively restore normal operation following emergencies like sudden load changes, wind gusts and low voltage conditions. The proposed robust controller has been shown to have adequate fault ride through capabilities in order to be able to meet connection requirements defined by transmission system operators.     

非线性PID控制器在超导磁储能装置中的应用

基于非线性比例积分微分PID(Proportional Integration Differential)控制器在设计上具有不依赖于被控系统数学模型的特点,设计了用于电力系统的超导磁储能装置SMES(Superconducting Magnetic Energy Storage)的非线性PID控制器。概述了非线性PID控制器利用“跟踪-微分器”非线性结构产生控制所需的比例、积分、微分信号的原理。介绍了含SMES的电力系统模型及非线性PID控制器的设计。数字仿真结果验证了所设计的控制器是可行的,同时表明该控制器结构简单、易实现。     

Improvement of Wind-Generator Stability by Fuzzy-Logic-Controlled SMES

This paper proposes a fuzzy-logic-controlled superconducting magnetic energy storage (SMES) scheme for the stabilization of grid-connected wind-generator systems. The control scheme of SMES is based on a sinusoidal pulsewidth-modulation voltage-source converter and a two-quadrant dc–dc chopper using an insulated-gate bipolar transistor. A comparative study is carried out between the proposed fuzzy-logic-controlled SMES and the fuzzy-logic-based pitch controller to improve the wind-generator stability. Simulation results demonstrate that the performance of the proposed fuzzy-logic-controlled SMES is better than that of the fuzzy-logic-based pitch controller in order to stabilize the wind generator.      

分散励磁与超导储能装置的干扰抑制控制

提出了一种新的设计多机电力系统中励磁和超导储能装置的分散L₂增益干扰抑制控制器的方法。文中首先建立了含超导储能装置的多机电力系统的动态模型，继而利用递推方法设计励磁和超导储能装置的增益干扰抑制控制器，所得控制器可以利用本地测量量实现。计算机仿真结果说明了所设计的控制器可以提高系统的暂态稳定性，显著改善系统的动态性能。     

无刷双馈风力发电机组的模糊自适应控制

针对变桨距并网型风力发电机组的最大功率跟踪及改善电能质量问题，采用新型无刷双馈电机构成风力发电机组．基于DSP控制的电力电子装置来改变无刷双馈电机控制绕组电流的频率、幅值、相位，设计了模糊控制器，使得额定风速以下时，根据风速变化，控制电机转速获得最佳叶尖速比，实现最大功率跟踪和变速恒频;额定风速及以上时，控制风轮的桨距角及风力机转速，调节叶尖速比，实现风力发电机组的恒功率输出及频率恒定。仿真结果表明，比传统PID控制器能更有效地减少振荡，较快地达到稳态，提高了风能转换系统的效率和质量。     

用可再生能源充电的SMES装置在系统调频中的应用

受自然条件限制,可再生能源发电具有很大的随机性,直接并入电网会对系统造成一定的冲击,增加系统不稳定的因素。文中以风能为例,提出将风能等可再生能源作为超导磁储能（SMES）装置的充电电源,为可再生能源的使用提出一个新的思路。SMES装置具有转换效率高且动作快速的特点,能够与系统独立进行有功、无功的交换。因此,SMES装置可以根据系统负荷变化快速调整出力来稳定系统频率及减少不必要的联络线功率流动。仿真结果证明,SMES装置的投入可以有效改善系统频率,解决旋转备用不足的问题。     

Neuro-fuzzy controller for gas turbine in biomass-based electric power plant

Biomass gasification is a technology that transforms solid biomass into syngas. The gas turbine controller regulates both the gas turbine and the gas turbine generator. Two fuzzy logic controllers have been developed using speed and mechanical power deviations, and a neural network has been designed to tune the gains of the fuzzy logic controllers based on the operating conditions of the biomass-based electric power plant. It is shown that by tuning the fuzzy logic controllers, optimal time domain performance of the system can be achieved in a wide range of operating conditions compared to fixed parameter fuzzy logic controllers and PID controllers.     

Matching wind turbine generators with wind regime in Egypt

This paper presents a novel method of matching wind turbine generators to a site using turbine performance index (TPI) in conjunction with minimum deviation ratio (DR) between rated speed of wind turbine generator (WTG) and optimal speed and resulting in minimum cost of energy (COE). The methodology allows yielding higher energy production at higher capacity factor and minimum cost of energy. The wind speeds are parameterized using cubic mean cube-root and statistically modeled using Weibull probability density function. Normalized power (P_N) and capacity factor (CF) are expressed entirely in normalized rated speed. The plots of P_N, CF and TPI versus normalized rated wind speed are drawn for known values of Weibull parameters of a site. The proposed methodology for identifying optimum wind turbine generator parameters for two sites with installed WTG and two candidate locations for installation of WTG in Egypt are examined. The cost of energy (COE) and capital cost of WTG under different tower heights at the sites are also determined. The proposed methodology, if used at the planning and development stages of wind power stations, will serve as useful tool to make a judicious choice of a wind turbine generator that yields higher energy at higher capacity factor.     

Load frequency control of an autonomous hybrid power system by quasi-oppositional harmony search algorithm

This paper deals with a novel quasi-oppositional harmony search algorithm (QOHSA) based design of load frequency controller for an autonomous hybrid power system model (HPSM) consisting of multiple power generating units and energy storage units. QOHSA is a novel improved version of music inspired harmony search algorithm for obtaining the best solution vectors and faster convergence rate. In this paper, the efficacy of the proposed QOHSA is adjudged for optimized load frequency control (LFC) of an autonomous HPSM. The studied HPSM consists of renewable/non-renewable energy based generating units such as wind turbine generator, solar photovoltaic, solar thermal power generator, diesel engine generator, fuel cell with aqua-electrolyzer while energy storage units consists of battery energy storage system, flywheel energy storage system and ultra-capacitor. Gains of the conventional controllers such as integral (I) controller, proportional–integral (PI) controller and proportional–integral–derivative (PID) controller (installed as frequency controller one at a time in the proposed HPSM) is optimized using QOHSA to mitigate any frequency deviation owing to sudden generation/load change. In order to corroborate the efficacy of QOHSA, performance of QOHSA to design optimal LFC is compared with that of other well-established technique such as teaching learning based optimization algorithm (TLBOA). The comparative performances of the HPSM under the action of QOHSA/TLBOA based optimized conventional controllers (I or PI or PID) are investigated and compared in the present work. It is found that the QOHSA tuned frequency controllers improves the overall dynamic response in terms of settling time, overshoot and undershoot in the profile of frequency deviation and power deviation of the studied HPSM.