Performance Study of a Self-Excitation Dual Stator Winding Induction Generator for Renewable Distributed Generation Systems

Renewable power generation is a suitable technology used to deliver energy locally to customers especially in remote regions. Wind energy based on induction generator situates in a foreground position in the total energy produced using renewable sources. In the last few decades, a new self- excitation generator was based on multi-stator induction strongly emerges. This article presents a systematic modelling, a detailed analysis and the performance analysis of self-excitation dual stator winding induction generator (SE-DSWIG). The modelling of the SE-DSWIG was done with taking in account the common mutual leakage inductance between stators and the magnetizing inductance, which played a principal role in the stabilization of the output voltage in the steady state. The generator feeds the end user emulated by an inductive-resistive load. In order to simulate the weather conditions’ variation, a step change of the prime mover speed was applied on the SE-DSWIG. A passive series and shunt compensator was used to mitigate the voltage sag and swell appeared in the power system due to wind variation and the lack of reactive power consumed by the inductive load.

A Reliable and Accurate Calculation of Excitation Capacitance Value for an Induction Generator Based on Interval Computation Technique

A squirrel cage induction generator （SCIG） offers many advantages for wind energy conversion systems but suffers from poor voltage regulation under varying operating conditions. The value of excitation capacitance （C exct ） is very crucial for the selfexcitation and voltage build-up as well as voltage regulation in SCIG. Precise calculation of the value of C exct is, therefore, of considerable practical importance. Most of the existing calculation methods make use of the steady-state model of the SCIG in conjunction with some numerical iterative method to determine the minimum value of C exct . But this results in over estimation, leading to poor transient dynamics. This paper presents a novel method, which can precisely calculate the value of C exct by taking into account the behavior of the magnetizing inductance during saturation. Interval analysis has been used to solve the equations. In the proposed method, a range of magnetizing inductance values in the saturation region are included in the calculation of C exct , required for the self-excitation of a 3-φ induction generator. Mathematical analysis to derive the basic equation and application of interval method is presented. The method also yields the magnetizing inductance value in the saturation region which corresponds to an optimum C exct（min） value. The proposed method is experimentally tested for a 1.1 kW induction generator and has shown improved results.

Genetic Algorithm Based Performance Analysis of Self Excited Induction Generator

This paper investigates the effects of various parameters on the terminal voltage and frequency of self excited induction generator using genetic algorithm. The parameters considered are speed, capacitance, leakage reactance, stator and rotor resistances. Simulated results obtained using genetic algorithm facilitates in exploring the performance of self-excited induction generator. The paper henceforth establishes the application of user friendly genetic algorithm for studying the behaviour of self-excited induction.

Transient Performance of an Isolated Induction Generator under Unbalanced Loading Conditions

This paper presents a new transient model ofa standalone （isolated） self excited induction generator （SEIG）. This model is based on direct phase quantities and is suitable to study the performance of the generator under any balanced or unbalanced conditions. It includes a general load as well as general excitation capacitor model. The model has the advantage of connecting or disconnecting the neutral points of the generator electrical system with both excitation capacitors and load. Furthermore, a more accurate magnetization curve is used. Moreover, the simulation results have been verified experimentally.

Behavior an Induction Generator without and with a Voltage Regulator

During the isolated use of a wind system, the output voltage of the self-excited induction generator depends on the variation characteristic of its parameters: the excitation condensers, the drive speed and the load. Therefore, the regulation of the tension appears to be of great interest. We focused on the use of an analogical regulator of tension, with the aim of controlling the tension at the exit of the self-excited induction generator. So we modelled, implanted and simulated a wind system (Self-excited induction generator, converters (AC/DC, DC/DC) and load it) in the Orcad/Pspice environment. In the first time the behaviour of the asynchronous generator was analyzed when the load, the excitation capacitor and the drive speed vary in the absence of any form of regulation. This analysis was conducted with the aim of defining the limits of the machine exploitation. In the second time the functioning mode is controlled by an analogical control of tension. The results of simulation show the good performances of the system during the application of the proposed voltage regulator.

Analysis and control of wind-driven self-excited induction generators connected to the grid through power converters

The analysis of the wind-driven self-excited induction generators （SEIGs） connected to the grid through power converters has been developed in this paper. For this analysis, a method of representing the grid power as equivalent load resistance in the steady-state equivalent circuit of SEIG has been formulated. The technique of genetic algorithm （GA） has been adopted for making the analysis of the proposed system simple and straightfor- ward. The control of SEIG is attempted by connecting an uncontrolled diode bridge rectifier （DBR） and a line commutated inverter （LCI） between the generator term- inals and three-phase utility grid. A simple control technique for maximum power point tracking （MPPT） in wind energy conversion systems （WECS）, in which the firing angle of the LCI alone needs to be controlled by sensing the rotor speed of the generator has been proposed. The effectiveness of the proposed method of MPPT and method of analysis of this wind-driven SEIG-converter system connected to the grid through power converters has been demonstrated by experiments and simulation. These experimental and simulated results confirm the usefulness and successful working of the proposed system and its analysis.

自激振荡射流微通道换热特性及热力学分析

该文对自激振荡射流微通道内流体换热性能进行模拟研究,结果表明在不同入口质量流量(1.0~6.0 g/s)条件下,自激振荡器内高压区域的移动造成了微通道散热器内射流的偏转,形成射流周期性循环摆动的同时强化了流体区域的扰动。此外,经对比分析后发现相较射流微通道内流体区域其冲击范围更广,因此其均温性能也优于射流微通道。与此同时,该文运用热力学原理分析评价自激振荡技术对射流微通道内流体流动换热性能的影响,发现自激振荡器所产生的振荡射流可以减小射流微通道内流体对流换热过程中的不可逆损失,其热能传输效率高达到98.48%。

基于自激振荡原理的双线圈磨粒检测技术研究

为满足实际工业应用的需要,基于LC自激振荡,提出双线圈式磨粒检测技术。首先建立了等效电路模型,其次引入磁场均匀度系数的概念并利用COMSOL Multiphysics仿真软件研究了管道域中的磁场分布及金属颗粒通过线圈时的输出响应,最后制作传感器进行试验。结果显示,该传感器管道域的磁场均匀度系数达0.91以上,可通过检测电压、频率的变化获取磨粒信息。研究结果为电感式磨损传感器研发提供一种新思路。

基于扰动观测器-Lyapunov理论的稳压控制策略

针对小型风力自励异步发电机(SEICG)机端电压在投切负载时产生电压跌落的问题,通过并联静止无功补偿器(STATCOM)提高异SEIG的机端特性,改善电能质量。提出一种基于扰动观测器(DOB)的Lyapunov(DOB-Lyapunov)控制策略,通过数学模型构造Lyapunov函数,将误差跟踪问题转换成求解Lyapunov函数在平衡点全局渐近稳定问题;针对线路电感测量误差及摄动对控制策略造成影响,内环加入DOB,使得整个控制器在鲁棒性、静态稳定性方面得到提升。结果表明:所提DOB-Lyapunov方法可以在线路阻抗发生变化时仍有较好的控制性能,电压平方外环结构实现了线性化电压控制,在响应速度以及总谐波畸变率(THD)方面均优于传统方法。

1.3 GHz连续波超导射频腔的数字低电平射频系统和腔模拟器设计及测试

1.3 GHz连续波超导射频腔需要高精度低电平射频(LLRF)系统来稳定超导腔的电磁场。但由于1.3 GHz CW射频腔的高负载品质因数和宽电磁频段,射频腔在频域中的电磁带宽较小。射频功率源与射频腔体之间的微小电磁频率差异易造成发生器驱动谐振器控制系统的不稳定,最终导致腔体电磁场的变化。开发了一种自激环控制系统,以防止“有质”不稳定性的发生,并补偿微噪声的影响。此外,还开发了数字1.3 GHz射频腔体模拟器,用于验证LLRF系统的设计算法。测试表明,即使在射频腔失谐5 Hz时,自激励控制系统也能确保腔场的稳定性。经过对比,验证了1.3 GHz射频腔体模拟器是测试新算法的可靠平台。

基于灭磁理论的双馈风机高电压穿越策略

针对双馈异步风力发电机(doubly-fed induction generator,DFIG)转子侧变流器的传统灭磁控制策略存在精确观测定子磁链和加大变流器输出端电压的问题,基于经典的定子磁场定向、功率解耦控制系统进行研究,提出了一种改进高电压穿越控制策略。首先,利用定子电流暂态分量获取转子灭磁电流指令值和转子侧变流器输出端电压补偿项,避免对定子磁链的精确测量。然后,将灭磁控制与前馈电压控制相结合,加快定子暂态磁链衰减,抑制转子过电流。最后,仿真结果验证了所提策略可以有效拓宽DFIG故障穿越范围,提升其穿越性能。

基于前馈补偿的双馈感应发电机励磁控制研究

针对双馈感应电机在发生低电压故障时定转子产生瞬时暂态振荡电流及传统Crowbar电路保护方式,将使其消耗较大无功而降低可控性的问题,提出一种转子电流前馈补偿的励磁控制方案。根据双馈电机的数学模型及等效电路结构,分析其定子侧电网发生低电压故障时的电磁暂态特性,归纳定转子暂态电流的变化规律。再通过电网电压与转子电流对定子电流的控制传递函数,分析电网电压跌落对定子暂态电流振荡的作用机理,并提出由控制转子电流对定子电流进行前馈补偿的故障穿越方案,经仿真分析证明了其有效性。

一种感应式角度传感器的激励信号产生方法

针对基于印制板谐振感应式角位移传感器感应信号弱,现有感应式角度传感器单端、低压高频方波激励信号强度低,抗干扰能力差的问题,提出一种感应式角度传感器的激励信号产生方法。通过反向电路、自举升压电路和驱动电路等硬件电路设计和优化,将单端、低压的高频方波激磁信号转换为高频、高压的差分正弦激磁信号,有效解决感应式角度传感器谐振信号强度低、高次谐波占比大的问题。此方法不仅可以提高感应式角度传感器磁场的强度,减小高次谐波占比,提升模拟信号的抗干扰能力,还可以提升感应式角度传感器的输出精度。

Enhancing the Stability of SEIG Connected Distribution System Using Reactive Power Control Capabilities of DFIG under Varying Wind Speeds

The increased level of penetration of wind generators into modern power system has significant effect on network operation. The time varying nature of wind speed has significant effect on performance of wind generator, therefore efficient mechanism for stabilizing the output of the wind generator is very much needed. Self-excited induction generators （SEIG） already existing in the network are sensitive to wind speeds. In this paper, a new method for voltage control of SEIG utilizing reactive power enhancing capabilities of doubly-fed induction generator （DFIG） is simulated and its effect on the network is analyzed for varying wind speeds. The choice of placing DFIG adjacent to SEIG or at another bus is also addressed in this paper with simulation results. The results show that this method of utilizing the reactive power capabilities of DFIG enhances voltage stability of SEIG as well as system stability.

12/3相双绕组感应发电机励磁系统的控制方法和动态特性的研究

12/3相双绕组感应发电机是为了实现适合于原动机高速运行特性而设计的一种特殊电机。系统在电机上增设了一个励磁绕组,使用静止励磁装置对电机进行励磁控制。该文对励磁装置的电路原理进行了分析,对控制原理进行了讨论,给出了系统动态等效模型。最后给出了仿真和试验研究结果。

并网型双馈电机风力发电系统建模与仿真

双馈电机已成为变速恒频风力发电系统的主流电机。文中介绍了交流励磁变速恒频双馈电机运行的基本原理,推导了风力机模型和交流励磁双馈电机动态数学模型。交流励磁变速恒频双馈电机风力发电系统空载运行和发电运行由于涉及并网时刻状态转移导致建模复杂,故提出用S函数描述双馈电机的数学模型,结合MATLAB中Simulink环境建立完备的系统仿真模型。由仿真结果可看出,所提系统实现了最大风能追踪控制,且动态响应快,双馈电机可运行于不同转差频率下亚同步和超同步状态,同时稳态时转子侧和定子侧注入电网谐波基本为零。

带整流桥负载的定子双绕组感应发电机系统宽转速运行时的稳态特性

针对带整流桥负载的定子双绕组感应发电机(dual stator-winding induction generator,DWIG)系统在宽转速范围内运行时的稳态运行特性进行了研究。建立了带电容滤波的整流桥负载的DWIG系统数学模型,指出整流桥负载是具有容性的非线性负载,提出了采用数学仿真的方法进行励磁电容的选取以降低变换器容量。采用控制绕组端电压定向的控制策略,对一台18kW、270V带整流桥负载的DWIG系统在变速时稳态规律进行了仿真和实验研究,结果表明发电机系统能够在4000-8000r/min宽转速范围内稳定运行,控制绕组最大功率为功率绕组额定输出功率的37%,控制绕组电流的最大有效值为功率绕组电流额定值的21%,与输出功率比较,实现了大幅度降低控制侧变换器容量的目的。

基于模糊自调整PID控制的同步发电机励磁研究

随着发电机单机容量和电网规模的增大,发电机组及电力系统对励磁控制在可靠性和动态品质等方面提出了越来越高的要求。在日益复杂的被控过程面前,由于不可能得到过程的精确数学模型,传统的基于精确模型的常规PID控制模型已不能满足系统的动态和静态运行性能要求;为了克服这个缺点,设计了一种新型的基于模糊自调整PID的控制系统。运用Simulink对传统PID与模糊自调整PID在励磁控制过程中进行仿真比较,并比较了在加入干扰信号情况下两者的性能,结果表明模糊自调整PID具有明显动态运行性能和抗干扰能力优势。

一种新型混合励磁同步发电机的两级式无刷励磁方法

针对切向/径向混合励磁同步发电机(tangential/radialhybrid excitation synchronous generators,T/R-HESG),提出了一种两级式无刷化自励方法。根据切向/径向混合励磁同步发电机的结构特点和磁路特性设计了两级式无刷化方法,实现了完全自励。同时,完成了励磁机的设计,通过对空载特性以及旋转整流器换相重叠角的研究,结合有限元仿真,优化了其结构,以保证励磁机与主发电机的匹配。对两级式无刷系统进行建模,通过整体仿真验证了该种方案的正确性。加工了一台基于T/R-HESG的两级式无刷励磁样机,测试了励磁机的电流放大特性、两级式无刷励磁系统的静态特性和动态特性,结果表明该两级式无刷发电机具有良好的工作性能。在航空航天、风力发电等领域有广阔的应用前景。

低电压穿越过程中双馈风电机组虚拟电感暂态自灭磁控制

双馈式感应发电机(DFIG)由于其定子直接与电网相耦合,电网故障将引起定子磁链暂态,并会在转子侧产生电压和电流冲击。传统基于Crowbar的低电压穿越(LVRT)解决方案不仅没能充分利用变流器对DFIG的控制灵活性,而且也难以较好地适应当今不断提升的并网要求。而当前基于灭磁控制的暂态补偿策略多依赖于磁链观测技术,不仅算法较为复杂而且对电机参数具有较强的依赖性。对电网电压发生跌落故障时定、转子电磁暂态过程进行了深入分析和讨论,并依据其暂态电磁特性,提出了一种基于虚拟电感暂态自灭磁算法的LVRT控制策略。该策略不仅能够较好地抑制转子暂态电压冲击,最大限度地拓展可穿越的故障范围,充分发挥DFIG的控制灵活性,而且无需暂态磁链观测,简化了算法,具有较好的快速性和鲁棒性。11kW模拟机组的仿真和实验,验证了所提出的分析和设计的正确性和可行性。