超导储能用大功率换流器及其控制技术

根据超导储能系统的研制现状,阐述了超导储能系统中大功率换流器技术的发展,比较了近年来采用的电压型大功率变换流电路的优缺点以及控制方式,并在此基础上分析了基于载波调制的相移PWM技术和基于非载波PWM的滑模控制技术的不同控制特点。分析表明,级联型换变流电路拓扑的工作特性及灵活性优于其它常用的电路拓扑,易于构成大功率高性能的超导储能用换变流电路;用于级联型电路的控制策略具有简单可靠等优点。     

超导储能用级联型大功率换流器控制系统设计

在超导储能系统中换流器与电网相连,使超导储能磁体能够通过换流器与电网进行能量交换,从而实现电网谐波抑制、有功无功补偿等功能.根据超导储能用换流器的特点,结合目前大功率电力电子器件以及电路拓扑的发展趋势,设计了一种结构灵活的换流器控制系统.该控制系统采用数字信号处理器(DSP)与复杂可编程逻辑器件(CPLD)相结合的分离模块式构架设计,在功能上实现了控制系统的算法部分与控制信号产生部分分离、系统的模拟部分与数字部分分离,从而大大提高了控制系统的电气稳定性及系统灵活性.该控制系统还可适用于多种大功率换流设备,因而具有较强的拓展性及通用性.     

超导电力磁储能系统研究进展(一)——超导储能装置

交介绍了超导磁储能装置（SMES）的基本原理、系统组成和发展状,阐述了具有高效、快速响应、能与系统独立进行四象限交换有功和无功功率等特性的SMES在电力系统中应的重要意义,概述了SMES的应用前景和需要进一步解决的若干问题。并针对我国SMES研究的现状提出了一些建设性意见。     

电压型超导储能系统统一非线性控制策略

传统的电压型超导储能系统采用电压型换流器和斩波器分别进行建模和控制的方法,这种控制方式未考虑两者之间的相互影响,协调性能较差.文中建立了电压型超导储能系统的整体数学模型,并在此基础上提出了基于李亚普诺夫直接法的统一非线性控制方法.这种控制方法使得系统在大信号干扰下的稳定性大大提高,同时由于将电压型换流器和斩波器视为一个整体进行控制,两者的协调性得以加强,因此可以采用更小的直流连接电容连接.在斩波器的脉宽调制控制中,采用了载波移相法,提高了等效开关频率,有利于开关管功率的平均分配.系统仿真证明了该控制策略的有效性.     

用于超导储能系统的多电平电流调节器

电压型超导储能系统中的直流变换器用于实现对超导磁体的快速充放电。传统的直流变换器存在软开关难以实现、直流母线电压难以平衡的问题。为解决这一问题,提出一种用于超导储能的多电平电流调节器,它实现了高频变压器原边器件的零电压开关和副边器件的零电流开关,并能实现电压侧各直流母线电压的自动平衡。采用改变晶闸管移相角,进而控制超导磁体上的平均电压大小的方法来调节超导磁体充放电功率。在实现方法上,采用了基于数字信号处理器（DSP）和复杂可编程逻辑器件（CPLD）的综合控制方法。实验结果证明了这种多电平电流调节器的良好性能。     

级联多电平换流器的高效仿真模型

级联多电平换流器是目前在柔性交直流输配电领域极具发展潜力的换流器拓扑,然而由于其拓扑中有大量独立的开关器件支路,如果在EMTP类仿真软件(如PSCAD/EMTDC)中采用器件模型直接建模将使得仿真计算极其缓慢,给研究及工程应用带来障碍。提出一种基于Dommel等值计算原理的级联多电平换流器仿真等值计算模型,可有效地解决仿真计算缓慢的问题,具有建模原理明确、计算结果可靠的优点。使用PSCAD/EMTDC软件对所提仿真模型进行仿真验证,结果表明,所提仿真计算模型与详细器件模型在暂态仿真中的响应高度一致,并且在仿真计算时间上具有明显的优势。     

基于模块化多电平换流器的电池储能系统控制策略

针对基于模块化多电平换流器的电池储能系统,提出了电网电压对称运行和电网电压不对称运行情况的通用控制策略。其控制策略主要包括输出功率控制、电池荷电状态(SOC)均衡控制以及并网电流直流分量抑制。SOC均衡控制分为相间SOC均衡、桥臂间SOC均衡以及桥臂内SOC均衡。通过控制环流实现相间SOC均衡和桥臂间SOC均衡;通过调节各个子模块输出电压工频分量,实现桥臂内各子模块的SOC均衡。首先对基于模块化多电平换流器的电池储能系统的模型进行了详细分析;基于等效模型,提出了相应的控制策略。最后,通过仿真以及实验对所提出的控制策略进行了验证。     

储能型模块化多电平换流器的分析与控制方法

电池储能是目前最有前景的储能技术之一,模块化多电平换流器(MMC)广泛应用于柔性直流输电领域。将电池储能与MMC相结合,构成储能型MMC。由于其具有电池系统、交流电网与直流电网间功率交换的功能,导致与传统MMC的控制方法不同。分析了储能型MMC的结构与工作原理,研究了多种运行工况下换流器功率解耦控制方法,搭建了仿真与实验样机,验证了所提控制方法的正确性和有效性。     

基于级联多电平换流器的两级式储能系统控制策略

储能技术是构建以新能源为主体的新型电力系统的关键技术和维持微网可靠稳定运行的重要保证。国内外现有理论研究及示范工程主要集中于单级式链式储能系统,功率模块与电池系统之间无源连接,结构简单但控制自由度不高。同时,针对基于链式储能的电池荷电状态(state of charge,SOC)不均衡问题,现有的相内SOC均衡控制策略存在不同负载率适应性不足、极度不均衡时可能过调制等缺点,为此,文中基于两级式链式储能系统,研究其总体控制策略,对相间、相内SOC均衡策略进行分析,并提出一种自适应的相内SOC均衡策略,详细说明均衡控制参数的设计原则。该策略能有效地改善链式储能系统在轻载、重载等不同工况下的适应性和均衡效果。最终通过仿真验证了所提控制策略的可行性和有效性,从而为工程实施提供理论储备和技术支撑。     

具有储能功能的模块化多电平换流器的控制方法

研究具有储能功能的模块化多电平换流器的控制方法,将模块化多电平换流器与电池储能系统相结合,适用于离岸风电场接入电力系统等柔性直流输电应用。系统在模块化多电平换流器的基础上,在子模块直流侧加入蓄电池实现储能。换流器两侧均可等效为受控电压源,可在储能容量范围内对直流侧馈入功率起到平滑作用。运行时,换流器交流侧有功无功电流解耦控制实现交流功率控制,换流器直流侧直流电流控制实现直流功率控制,给出子模块SOC控制方法和子模块组SOC控制方法实现系统中大量蓄电池SOC的平衡控制。计算机仿真分析表明,提出的系统可实现交直流功率控制和储能功能。     

电压型高温超导储能系统变流器设计与试验

为提高电力系统动态稳定性,实现高温超导储能系统对电网电压跌落的有效补偿,采用三单相H桥型拓扑结构,搭建了一个电压型高温超导储能系统功率变换器.对控制系统、信号调理系统、功率和驱动保护电路进行了设计;基于SPWM脉冲触发方式,应用TMS320F2812型DSP实现了动态电压瞬时跌落补偿的全数字闭环控制,给出了相关的软件程...     

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.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

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.     

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.     

Neural-network-controlled superconducting magnetic energy storage for power system stabilization

It has been clarified that a superconducting magnetic energy storage (SMES) is very effective for power system stabilization. The control methods proposed for power system stabilization by SMES are the pole assignment, the optimal control, and so on, each of which, however, has its drawbacks. This paper is concerned with the power system stabilization by neural network control of the active power of SMES. First, the optimal stabilizing control of the SMES power for the model power system is calculated for various power system operating conditions and fault conditions. Then these optimal controls are used as training data for the neural network. The neural network used is a multilayer type with a feedback from the output layer to the input layer. The trained neural network is examined by untrained operating conditions and faults.     

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.

     

Measurement of the damping coefficient of an electric power system by use of a superconducting magnet energy storage system

In this paper, a new application of superconducting magnetic energy storage (SMES) for diagnosis of power systems is proposed. Basic experiments for measurement of damping coefficient of power systems by use of SMES are carried out in an experimental system with a small generator, artificial transmission lines, and a small SMES. The SMES produces small power disturbances in the power system without affecting its operating conditions. The small power oscillations in the power system due to continuous power disturbances generated by SMES are observed. The relations among the damping coefficient, the power disturbances, and the power change of SMES are discussed for a one-machine infinite-bus system. The damping coefficients of the power system are obtained by investigating the oscillations due to the sinusoidal power changes of the SMES. The possibility of estimation of the steady-state power system stability by monitoring the damping coefficients of an operating power system by the use of SMES can be shown experimentally. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 40–48, 1997     

基于超导储能装置的电磁合环环流抑制技术研究

当线路检修或设备故障时,合环是解决不断电倒负荷的重要手段。目前对于合环的操作,调度都是基于经验法进行操控,往往因为合环两侧的电压差,相位差等造成馈线中出现较大的合环电流,影响负荷的正常工作,严重的甚至引起停电故障。为解决合环线路中的环流问题,提出一种基于超导储能装置(Superconducting Magnetic Energy Storage,SMES)的电磁合环环流抑制方案,并在PSCAD中搭建了仿真模型,分别验证了SMES在合环两侧负荷不同和变压器参数设置不同情况下,SMES对合环后馈线中电磁环流的抑制效果,最后仿真验证了所提方案的可实施性。