Electronic Load Controller for a Parallel Operated Isolated Asynchronous Generator Feeding Various Loads

This paper presents an investigation on a voltage and frequency controller (VFC), which functions as an improved elec-tronic load controller (IELC) for parallel operated isolated asynchronous generators (IAGs) in an autonomous hydro power generation system. In such type of hydro scheme whole generating system is isolated from the grid and supply electricity to the remote communities. The single point operation of these generators is realized, in such a manner that excitation capacitors, speeds, load, voltage, currents of generators remain constant under various operating conditions. The proposed controller consists of a 3-leg IGBT (Insulated Gate Bipolar Transistor) based voltage source converter (VSC) and a DC chopper with an auxiliary load at the DC bus of the VSC. The IELC controls the reactive and active powers simultaneously for controlling the voltage and frequency under varying consumer loads. Along with voltage and frequency control through single point operation of IAGs driven by uncontrolled pico hydro turbines, the IELC meets the power quality standard an IEEE-519 and it keeps the total harmonic distortion (THD) of the terminal voltage and currents within the limit of 5%. Here the proposed electrical system along with its controller is modeled in MATLAB along with Simulink and PSB (Power System Block-set) toolboxes. Simulation results are presented to demonstrate the capability of proposed controller for an isolated generating system.

Probabilistic Load Flow Algorithm with the Power Performance of Double-Fed Induction Generators

Probabilistic load flow(PLF)algorithm has been regained attention,because the large-scale wind power integration into the grid has increased the uncertainty of the stable and safe operation of the power system.The PLF algorithm is improved with introducing the power performance of double-fed induction generators(DFIGs)for wind turbines(WTs)under the constant power factor control and the constant voltage control in this paper.Firstly,the conventional Jacobian matrix of the alternating current(AC)load flow model is modified,and the probability distributions of the active and reactive powers of the DFIGs are derived by combining the power performance of the DFIGs and the Weibull distribution of wind speed.Then,the cumulants of the state variables in power grid are obtained by improved PLF model and more accurate power probability distributions.In order to generate the probability density function(PDF)of the nodal voltage,Gram-Charlier,Edgeworth and Cornish-Fisher expansions based on the cumulants are applied.Finally,the effectiveness and accuracy of the improved PLF algorithm is demonstrated in the IEEE 14-RTS system with wind power integration,compared with the results of Monte Carlo(MC)simulation using deterministic load flow calculation.

Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.

发电机失磁保护定值整定的讨论--对2007年版《IEEE Guide for AC Generator Protection》的斟酌

对2007年版《IEEE Guide for AC Generator Protection》中失磁保护定值整定的几个问题提出不同意见。明确指出:发电机失磁故障必有滑差(s),其平均异步阻抗Xd(js)Xd(s=0),失磁保护中的阻抗元件下端定值为-Xd,已有足够余度,不应该是-(1.1～1.25)Xd;在P-Q坐标与R-X坐标的转换公式中,U值应由"失磁保护动作滞后于低励限制线(UEL)"原则来确定,不应主观选择0.95UN。

Steady State Analysis of a Doubly Fed Induction Generator

In this paper, we present the steady state analysis of a double-fed induction generator (DFIG) adopted for wind power generation. The three-phase induction machine connected to the network, to work as a generator for wind farms, is excited on the rotor circuit by a slip-frequency current injected to the rotor, from an exciter mounted on the same shaft of the machine. The resulting rotating magnetic field rotates at synchronous speed;as such the generated power has a constant frequency independent of the shaft speed. Effects of the excitation voltage magnitude and phase angle on the active and reactive power are studied, when the machine runs at constant speed. It has been shown that by controlling the excitation voltage magnitude and phase angle would control the mode of operation of the machine;motor mode or generator mode. Furthermore, the effects of the shaft speed on the active and reactive power at constant excitation voltage magnitude and constant phase angle are also investigated.

Influence of dc Component during Inadvertent Operation of the High Voltage Generator Circuit Breaker during Mis-Synchronization

This paper analyses the synchronization problem of a generator onto power system without satisfying synchronization condition. The main focus of the paper is on the impact of the dc component of the current in the high voltage circuit breaker during its close-open operating cycle. Using real time measurements of currents/voltages and angles during the close-opening cycle of high voltage generator circuit breaker and the impact of the dc component of current in context of interrupting large magnitude of current from the circuit breaker. In addition, the paper describes a study case model and the results of simulations performed using the software EMTP-ATP of an actual incident that occurred during the inadvertent synchronization of a large 339 MW, 24 kV generator to the grid.

Asynchronous Observer Design for Switched Linear Systems: A Tube-Based Approach

This paper proposes a tube-based method for the asynchronous observation problem of discrete-time switched linear systems in the presence of amplitude-bounded disturbances.Sufficient stability conditions of the nominal observer error system under mode-dependent persistent dwell-time(MPDT)switching are first established. Taking the disturbances into account, a novel asynchronous MPDT robust positive invariant(RPI) set and an asynchronous MPDT generalized RPI(GRPI)set are determined for the difference system between the nominal and disturbed observer error systems. Further, the global uniform asymptotical stability of the observer error system is established in the sense of converging to the asynchronous MPDT GRPI set, i.e., the cross section of the tube of the observer error system. Finally, the proposed results are validated on a space robot manipulator example.

High Efficiency Double–Fed Induction Generator Applied to Wind Power Generator Technical Analyses

High efficiency Double-Fed Induction Generator applies new power electronic technology, and utilizes vector control to fix the magnetic direction of the stator to the vertical axis. Adjusting the input current of rotor via an inverter can separately control the cross axis and vertical axis current of real power and reactive power of a generator. Traditionally, rotating speed affects frequency and the output is unstable. This study concentrates on high efficiency Double-Fed Induction Generators and Traditional Generators from mathematic model to derive and control the characteristics simulation and comparison than get an output of high efficiency Double-Fed Industrial Generators. This study utilizes the simulation software MATLAB/Simulink to simulate the response characteristics of vector control of a Double-Fed Industrial Generator. The operating and control functions are better than those of a traditional generator.

Steady State Analysis of an Isolated Self-Excited Dual Three-Phase Induction Generator for Renewable Energy

In this paper modelling and analysis in autonomous mode of dual three-phase induction generator (DTPIG) with a new algorithm have been done. We develop the steady state model of a dual three-phase self-excited induction generator for stand-alone renewable generation dispensing with the segregating real and imaginary components of the complex impedance of the induction generator. The obtained admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Steady state performances and characteristics of different configurations are clearly examined and compared. The analytical results are found to be in good agreement with experimental results.

High Frequency Charging Techniques—Grid Connected Power Generation Using Switched Reluctance Generator

Power generation becomes the need of developed, developing and under developed countries to meet their increasing power requirements. When affordability increases their requirement of power increases, this happens when increased per capita consumption. The existing power scenario states that highest power is produced using firing of coals called thermal energy. A high efficiency Switched Reluctance Generator (SRG) based high frequency switching scheme to enhance the output for grid connectivity is designed, fabricated and evaluated. This proposed method generates the output for the low wind speed. It provides output at low speed because of multi-level DC-DC converter and storage system. It is an efficient solution for low wind power generation. The real time readings and results are discussed.

基于转子铜耗的异步机运行状态分类

提出一个关于异步机运行状态的新的分类方法:转子铜耗法。按此法,异步机运行状态可分为两个:差能态、和能态。差能态包含电动、发电两个态;和能态对应电制态。转子铜耗分类法对学习和巩固异步机制动知识点尤其有帮助。

双馈异步风力发电机转子匝间短路故障振动特性分析

针对双馈异步风力发电机转子匝间短路的故障振动机理尚不明确且无法为故障诊断提供理论依据的问题,开展了双馈异步风力发电机转子匝间短路故障振动特性分析.首先,结合有限元仿真及解析推导,分析转子匝间短路下双馈异步风力发电机的气隙磁密规律,得到转子所受的不平衡磁拉力;然后,考虑转子不平衡磁拉力的情况下构建双馈异步风力发电机转子-轴承系统非线性动力学模型,利用非线性动力学仿真获取转子匝间短路故障下系统的振动仿真信号;最后,在双馈异步风力发电机故障模拟实验台上进行转子匝间短路故障实验,利用实验分析验证非线性动力学仿真结果的有效性.非线性动力学仿真及实验分析结果均表明,转子匝间短路故障下双馈异步风力发电机转子-轴承系统振动信号的频谱存在转频的谐波成分,通过检测转频的谐波分量可诊断双馈异步风力发电机转子匝间短路故障,有效揭示了双馈异步风力发电机转子匝间短路的故障振动机理.

燃气轮发电机同期回路加装闭锁继电器的研究与应用

某些燃气轮发电机同期回路未配置闭锁继电器,存在非同期并网的安全隐患。为解决此问题,对某电厂燃气轮发电机同期回路进行研究,提出了在其同期回路中加装闭锁继电器的方案,进行闭锁继电器和中间继电器选型。现场试验证明,该方案能够提高燃气轮发电机同期并列的可靠性,达到了消除非同期并列安全隐患的目的,可为同类型燃气轮发电机同期回路加装闭锁继电器提供借鉴。

不同阶段的背靠背直流输电系统异步互联调度优化方法

异步互联调度优化可以保证背靠背直流输电系统的稳定运行,但不同调度时段会影响调度优化的均衡性和稳定性,由此,提出不同阶段的背靠背直流输电系统异步互联调度优化方法。在分析背靠背直流输电系统等值电路的基础上,根据整流器等值电路计算整流器输出的电压值,构建背靠背直流输电系统的出力模型;在发电阶段和电能输送阶段,设定异步互联调度的约束条件,设计直流输电系统异步互联调度优化算法,实现直流输电系统异步互联调度优化。实验结果表明,直流输电系统输出的功率始终稳定在20~42 kW,可以稳定提高均衡性和稳定性。

不平衡电网电压下风力发电机网侧变流器控制策略

针对不平衡电网中负序分量对风力发电机的正常运行造成巨大影响,以风力发电机中的双馈风力发电机为例,提出了在网侧变流器中通过双闭环控制和滑模变结构控制共同作用的控制策略。通过空中管制中心和网络自抗扰控制器控制组成双闭环控制,可维持变流器电压的稳定。通过与滑模变结构控制相结合,消除负序分量对系统产生的影响。通过试验仿真验证了双闭环控制策略可使电压波形输出为与电网电压一致的正弦波。提出的控制策略对单相短路故障上出现的危害有很好的抑制作用。

基于深度学习的异步风力发电机组功率振荡抑制方法

由于引起异步风力发电机组功率振荡的因素较多,难以保障功率振荡抑制的效果,为此,提出基于深度学习的异步风力发电机组功率振荡抑制方法的研究。从风力机动态特性、发电机组动态特性以及传动链动态特性3个角度分析了异步风力发电机组功率振荡状态,借助长短期记忆网络实现对振荡的有效抑制。在测试结果中,设计的振荡抑制方法应用效果不仅更高效,且对于基础振荡幅度的控制效果更好。

双馈风电机组双模并网控制策略

当前,我国陆上风电场大多采用双馈机组,虽然其变流器容量小、成本低,但是通常只能在±30%的转差率范围内运行,在低转速下无法正常并网。为了提高低转速工况下双馈风电机组的发电量,文章提出一种双模并网控制方案。其建立了双馈电机定子短接的异步数学模型,以确定最终短接电阻的取值范围;提出了双模柔性切换策略,即在转速较低时机组以异步模式运行,转速升高后机组以常规的双馈模式运行,从而实现低转速也能发电运行。仿真结果表明,低转速下,异步模式相较双馈模式,转子电流畸变率最大可降低55%,功率控制精度也更高(功率波动幅值可控制在3 kW以内);且采用柔性切换策略后,暂态冲击电流减小36%以上,仅150 ms就可达到新稳态,验证了风电机组双模并网控制策略的有效性和可行性。

异步机状态的能量观及其对同步发电机不对称短路的启示

从能量(功率)的角度,详尽分析了异步机全部五种状态的特征。特别值得强调的是制动状态的特征:从定子和转子两个方向汲取功率,用于转子绕组的铜耗。该铜耗转化为热能,导致转子绕组过热,甚至被烧毁。从中得到对同步发电机不对称短路的启示:负序猛于虎,千万要当心。

虚拟同步发电机对系统低频振荡的影响及抑制方法综述

为梳理虚拟同步发电机接入后对系统低频振荡的影响,进一步发掘其在提供阻尼和惯量方面的潜力和应用,开展相关梳理和研究工作。首先,归纳和总结电力系统低频振荡的研究现状;然后,对非同步发电机电源并网后对系统低频振荡的影响进行概括和分析;最后,综述伴随非同步发电机电源接入的虚拟同步发电机对系统低频振荡的影响和抑制方法,并针对虚拟同步发电机在新型电力系统应用过程中亟需解决的关键问题提出进一步的思考和展望。

Design and implementation of control system for superconducting RSFQ circuit

The superconducting rapid single flux quantum(RSFQ)integrated circuit is a promising solu-tion for overcoming speed and power bottlenecks in high-performance computing systems in the post-Moore era.This paper presents an architecture designed to improve the speed and power limitations of high-performance computing systems using superconducting technology.Since superconducting microprocessors,which operate at cryogenic temperatures,require support from semiconductor cir-cuits,the proposed design utilizes the von Neumann architecture with a superconducting RSFQ mi-croprocessor,cryogenic semiconductor memory,a room temperature field programmable gate array(FPGA)controller,and a host computer for input/output.Additionally,the paper introduces two key circuit designs:a start/stop controllable superconducting clock generator and an asynchronous communication interface between the RSFQ and semiconductor chips used to implement the control system.Experimental results demonstrate that the proposed design is feasible and effective,provi-ding valuable insights for future superconducting computer systems.