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.     

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.     

Enhancement of transient stability by fuzzy logic-controlled SMES considering communication delay

This paper presents a fuzzy logic-controlled superconducting magnetic energy storage (SMES) for the enhancement of transient stability in a multi-machine power system. The control scheme of SMES is based on a pulse width modulation (PWM) voltage source converter (VSC) and a two-quadrant DC–DC chopper using gate-turn-off (GTO) thyristor. Total kinetic energy deviation (TKED) of the synchronous generators is used as the fuzzy input for SMES control. Communication delays introduced in online calculation of the TKED are considered for the actual analysis of transient stability. Global positioning system (GPS) is proposed for the practical implementation of the calculation of the TKED. Simulation results of balanced fault at different points in a multi-machine power system show that the proposed fuzzy logic-controlled SMES is an effective device for transient stability enhancement of multi-machine power system. Moreover, the transient stability performance is effected by the communication delay.     

A unified approach for the solution of power flows in electric power systems including wind farms

This paper proposes a solution approach of the power flow problem to assess the steady-state condition of power systems with wind farms in a single frame of reference, in which the state variables of the wind generators are combined with the nodal voltage magnitudes and angles of the entire network for a unified iterative solution through the Newton-Raphson method. Different wind energy conversion systems (WECS) are mathematically derived from the steady-state representation of the induction generator. Suitable strategies for initializing the state variables of the wind generators are also proposed in this paper. Lastly, three numerical examples are presented to numerically illustrate the applicability of the proposed approach.     

超导储能装置用于改善暂态电压稳定性的研究

建立了超导储能装置(SMES)在暂态电压稳定性分析中的简化数学模型.SMES经双桥系统的电流源型换流电路与电力系统相连.研究了具有快速响应特性的SMES在提高电力系统暂态电压稳定性方面的作用和其无功控制策略,以及采用不等触发角控制时的控制原则.在Matlab平台上编制了暂态仿真程序,对典型3机10母线系统进行了仿真计算.仿真结果表明,超导储能装置安装在动态负荷处,采用无功-电压控制方式能够有效地提高系统的暂态电压稳定性.     

Improvement of Dynamic Stability in a Multimachine Power System via SMES with Active Power Modulation Controlled by Frequency Deviation

With the recent increase in demand, power systems have become large and complex and generation plants are located far from the load center. As a result, power system instability has become more serious. On the other hand, the active and reactive powers am controlled rapidly and flexibly by the superconducting magnetic energy storage (SMES) system. This paper proposes a practical method to suppress power oscillation in a multimachine power system by using SMES wherein its active power is controlled by the signal derived from a bus frequency deviation. This controlled scheme is conducted easily only by detecting the frequency deviation on the site. The proposed method is examined on a 4-machine miniature power system connecting a I-MJ SMES as well as another digital simulation using the same model. The effectiveness of the proposed method is shown.     

Influence of magnetic linkage between coils of a modular SMES

To scale up the capacity of an SMES for a practical application, it is necessary to adopt a high-voltage system, a large current system or a modular system. The first system is difficult because of the very low withstanding voltage of a superconducting coil and the second also involves difficulties such as multiple connections of many convertors on the dc side and large current conductors in the superconducting coil. The third system, composed of several modules with small-scale convertor units and element coils, might be a solution of the above difficulties. In this modular system, the module coils have magnetic linkage with one another. In this paper, the influence of magnetic linkage between coils of a modular SMES is investigated by computer simulation. The magnetic linkage varies with the number of modules and the type of connection of the coils. By the effect of this magnetic linkage, each module's coil current is different at the same power. The current and energy transfer characteristics are determined for discharge from one or more of 6 modules, consisting of 18 coils. The discussion deals with the case in which there is an unused module when quenching occurs. The transfer with the same current in all modules is shown by control of convertor power of the current feedback. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 1–9, 1997     

Enhancement of Output Power Smoothing and Transient Stability of DFIG-Based Wind Energy Conversion System Using Optimized Controllers Parameters

In this paper, an attempt is made to tune the controllers of a doubly fed induction generator (DFIG)–based wind energy conversion system (WECS). The procedure is optimized to improve the performance of the WECS under both normal and transient operating conditions. It is shown that under normal operating conditions, the outer control loop of the rotor side converter, i.e., speed controller, affects the quality and quantity of output power. Therefore, to extract the maximum available power and smooth the power injected to the grid, this controller is tuned. On the other hand, other controllers affect the response of the DFIG during transient conditions. Thus, to improve the transient stability of the DFIG, the parameters of these controllers are tuned based on the eigenvalue analysis. To verify the performance of the proposed tuning method, comparisons between the proposed and conventional pole placement methods, under normal and fault operating conditions, are presented.     

笼型异步风电机组串联耦合补偿低电压穿越研究

随着我国风电装机容量不断扩大,风电场具备低电压穿越能力已成为其并网发电的必要条件。而传统笼型异步发电机组本身并不具备低电压穿越能力,因此提出了一种串联耦合补偿(series coupled compensation,SCC)新型低电压穿越方案,SCC 通过变压器串联接在发电机定子与公共连接点之间,配合双向晶闸管进行投切。在PSCAD/EMTDC建立了750 kW异步发电机组的串联补偿系统,仿真结果表明在各种电压故障下SCC能有效提高机组低电压穿越能力,同时减小电磁转矩振荡。     

Superconducting Magnetic Energy Storage Integrated Current-source DC/DC Converter for Voltage Stabilization and Power Regulation in DFIG-based DC Power Systems

Unpredictable power fluctuation and fault ridethrough capability attract increased attention as two uncertain major factors in doubly-fed induction generators（DFIGs） integrated DC power system. Present solutions usually require complicated cooperation comprising multiple modules of energy storage, current control, and voltage stabilizer. To overcome the drawbacks of existing solutions, this paper proposes a superconducting magnetic energy storage（SMES） integrated currentsource DC/DC converter（CSDC）. It is mainly composed of a current-source back-to-back converter, and the SMES is tactfully embedded in series with the intermediate DC link. The proposed SMES-CSDC is installed in front of the DC-DFIG to carry out its dual abilities of load voltage stabilization under multifarious transient disturbances and power regulation under wind speed variations. Compared with the existing DC protection devices, the SMES-CSDC is designed on the basis of unique current-type energy storage. It has the advantages of fast response, extensive compensation range, concise hardware structure, and straightforward control strategy. The feasibility of the SMESCSDC is implemented via a scaled-down experiment, and its effectiveness for DC-DFIG protection is verified by a large-scale DC power system simulation.     

A fuzzy logic supervisor for active and reactive power control of a fixed speed wind energy conversion system

In this paper, we present the design of a fuzzy logic supervisor for the control of active and reactive power which is generated by fixed speed wind energy conversion systems (WECS). First, the modelling of a three-phase induction generator driven by a horizontal axis wind turbine is described. An adjustable capacitor bank is plugged at the connection point with a Static Var Compensator (SVC), which is controlled to regulate the rms voltage. The obtained model is reduced by taking into consideration the dynamics of the system. A fuzzy logic-based supervisor is proposed in order to minimize variations of the generated active power and the stator voltage. The regulation of the rms voltage is performed while imposing a reactive power reference. The pitch angle of the turbine blades is set to obtain the maximum wind power. The obtained performances of the proposed supervisor are then presented.     

自适应控制和微分几何控制在风力发电系统中的应用

本文综述了近年来自适应控制、微分几何控制在风能转换系统稳定、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。     

Minimization of shaft oscillations by fuzzy controlled SMES considering time delay

This paper analyzes the effect of fuzzy logic-controlled superconductive magnetic energy storage (SMES) on minimizing shaft torsional oscillations of synchronous generators in a multi-machine power system. The proposed fuzzy logic controller has been designed in a very simple way considering only one input variable and one output variable. The time derivative of the total kinetic energy deviation (TKED) of the synchronous generators is used as the global input to the fuzzy controller for SMES switching. The influence of time delay associated with the global input calculation of the fuzzy controller on minimizing shaft torsional oscillations is investigated. Global positioning system (GPS) is proposed for the practical implementation of the calculation of the global input to the fuzzy controller. Simulation results of a balanced fault at different points in a multi-machine power system show that the proposed SMES can minimize the shaft torsional oscillations of synchronous generators well. Moreover, the time delay has an influence on the performance of fuzzy controlled SMES to minimize shaft torsional oscillations. However, even though the performance of fuzzy controlled SMES is somewhat effected by the communication delay, it is clear from the simulation responses that the fuzzy logic-controlled SMES considering typical communication delays can minimize the shaft torsional oscillations of synchronous generators well.     

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.     

双馈风电场等值阻抗模型在高频振荡研究中的适用性分析与评价

以双馈风力发电系统(doubly-fed induction generator based wind energy conversion system,DFIG-based WECS)为例,利用小信号分析法推导出由风机、双质量块传动链构成的动力与传动系统通用传递函数方程。动力与传动系统传递函数的零极点位置、稳定性与系统参数及系统运行工作点相关。该传递函数可进一步分解为扭转分量和非扭转分量。传动链参数仅对扭转分量造成影响。在此基础上,建立了考虑动力传动、电机、变流器、控制等环节的风力发电系统传递函数模型。模型综合了各环节参数,可直观反映系统参数对系统响应的影响,有助于深入了解系统动态行为。算例及时域仿真结果证明了所提出传递函数模型的准确性和高效性,可为系统参数设计研究提供理论依据。

     

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.     

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.

     

20 kJ/15 kW可控超导储能实验装置

介绍了一套可控超导储能(SMES)实验装置.该装置可作为可控超导储能在电力系统中应用的实验研究平台.它包括一个储能量为20 kJ的低温超导磁体和一个15 kW的基于绝缘栅双极晶体管(IGBT)的电流型变流装置.为了减少冷却系统的漏热,超导磁体通过Bi-2223带材制成的高温超导电流引线同变流装置连接.变流装置采用双桥型拓扑和PWM开关策略以减少其输出电流中的谐波成分.为了可以执行高速和高精度的控制算法,变流装置的控制系统采用双DSP的控制器.文中还介绍了该实验装置各部分的结构和工作原理,并给出了初步的实验结果.