有源滤波器多目标检测策略建模研究

针对有源滤波器多个控制目标的趋势,本文采用一种能在不对称和电网电压存在畸变条件下准确提取电网中谐波或无功电流的检测方法,并搭建了PSCAD仿真模型。该模型从矢量分析角度出发,通过对三相电网电压和电流矢量在d-q坐标系下进行投影变换,实现了谐波和无功电流任意组合的提取。仿真结果验证了多目标检测策略的检测精度,该多目标检测策略也大大简化了对多目标有源滤波器的控制策略设计,模型具有很强的实用价值。     

分布式电网参数监测系统的设计

介绍了分布式电网参数监测系统的结构以及下位机的硬件设计,给出了利用该系统实时检测电网三相电压,电流等运行参数以及通过DFT检测有功功率,无功功率和电网中电压,电流各类谐波成分参量的测量原理,以及计算电网负载大小及非线性度的计算方法。     

有源电力滤波器的谐波检测方法研究

针对基于FFT的谐波检测和ip-iq法的不足，详细分析并实现了有源滤波器基于旋转坐标系下进行坐标变换的谐波检测方法。该方法在电网电压存在不对称情况下均能很好地检测和补偿电网中的谐波电流和无功电流，根据需要，还可以检测和补偿任意次谐波电流。理论分析和实验结果验证所提出的控制方法的有效性，基于旋转坐标系下进行坐标变换的谐波检测方法的有源电力滤波器具有良好的工作性能。     

谐波和无功电流检测方法分析

谐波、无功和负序电流的准确与快速检测是决定配电网静止同步补偿器性能的关键因素之一。文章对p-q法、ip-iq法、改进ip-iq法的检测性能进行了理论和仿真分析,并在TMS320LF2407A实验系统中对它们进行了实验研究。结果表明,只有当三相电压对称无畸变时,p-q法才能准确检测谐波、无功和负序电流分量;不管电网电压是否对称畸变,改进的ip-iq法都能精确检测正序基波有功电流,但计算量大;即使电网电压不对称且畸变,ip-iq法也能准确检测谐波电流,而对谐波、无功和负序电流的检测精度取决于锁相环对正序基波电压相位的检测精度,但该法的计算量小,更易于数字化实现。     

双线电压调制MC输入/输出特性的仿真研究

在深入分析双线电压调制矩阵式变换器工作原理的基础上,采用理论推导和仿真实验相结合的方法研究了对称/不对称电网电压对矩阵式变换器输出电压及输入电流特性的影响。结果表明,无论电网电压对称与否,矩阵式变换器的输出电压均能达到期望值,但其输入电流在电网电压不对称条件下产生严重的畸变。文中结论对于改善矩阵式变换器的输入/输出特性具有一定的指导意义。     

电气测量技术及仪器

TM93 00051595钢琴琴键排列平整性的测里/陈兴梧,刘鸣,陈本智,方清莉(夭津大学精密仪器与光电子工程学院)11电子技术应用.一20()O,26(1)一35一37介绍一种非接触扫描法测量钢琴琴键平整性的方法,讨论了建立测量基准的两种方法以及测量系统的基本组成.图6参6(金),王昊,易颂文(华南理工大学)11华南理工大学学报.一2000,28(1)一70一75发展了一种电网电流的检测方法,在考虑电网电压畸变和基波电压初始相角的情况下,只需通过检测一相线路的电流、电压,就能有效地检测出电网基波有功、无功电流和任意次数的谐波电流,适用于电网无功功率补偿、谐波…     

基于重复控制的风力发电不平衡控制策略

针对风电场电网接入点电压不平衡问题,文章对双馈风力发电机组在不平衡电网条件下的控制策略进行了研究设计,提出了基于内模的重复控制器应用于双馈风力发电机转子变流器的控制。控制器通过对负序电流的有效控制,使得双馈发电机输出定子电流平衡。并通过风场实际应用证明,这种控制方法可以有效控制电网电压负序引起的风力发电机组输出的三相电流不平衡问题。     

基于DSP的电能质量检测技术与无功补偿测控方法

针对目前电能质量检测技术检测精度低,无功补偿效果随着电网电压降低而降低的问题,基于DSP研究了一种新的电能质量检测技术与无功补偿测控方法。通过DSP处理器对电能质量进行检测,确定复序列,在DSP内部对复序列进行转换,通过电压传感器采样,使用空闲线多处理器模式实现串口通信。利用STATCOM实时追踪电流变化,STATCOM以并联的方式连接于电网之中,内部发送的无功电流会跟随电网负荷变化而快速变化,实现功率的自动补偿,确保电网在动态的模式下实现无功补偿。实验结果表明,基于DSP的电能质量检测技术与无功补偿测控方法的测量精度为0.027 3%,满足电网要求,补偿过程不会受到电网电压影响,始终保持在恒定水平。     

基于DSP的光伏并网技术的研究与实现

在光伏并网发电系统中,为了避免所发电能并入电网后造成电网污染,必须使用锁相环（PLL--Phase-Locked Loop）技术,保证并网电流和电网电压严格同频同相。文中针对软件锁相环技术,提出了一种基于电网电压过零检测硬件电路的新方法,并在CCS3.3软件中编写程序,以DSP芯片TMS320F2812为控制芯片进行了实验验证。实验结果表明此锁相环方案可以快速准确地使并网电流跟踪电网电压。     

电网不平衡条件下PWM整流控制策略的研究

通常情况下由于各种原因三相电网电压是不完全平衡的.这就使得常规的PWM整流器整流效率较低,为了提高电网不平衡条件下PWM整流器的整流效率,本文讨论了一种在电网不平衡条件下PWM整流的控制方法,在分析不平衡电网数学模型的基础上,建立了正、负序双电流控制策略的数学模型,利用Simplorer7.0对系统进行了仿真,通过对不平衡条件下常规的PWM整流器和不平衡条件下正、负序双电流控制的仿真结果进行对比,表明正、负序双电流控制可以提高网侧功率因数,改善系统的动态性能,同时得到较平稳的整流输出电压,有利于提高系统整体的运行效率。     

不平衡负载条件下三相四桥臂逆变器的控制

三相四桥臂逆变器具备外接三相不平衡负载的能力。为改善逆变器系统在严重不平衡负载情况下输出电压的对称性,文中提出一种新颖的控制策略——旋转坐标系下的PIR-P双环控制。当系统接不平衡负载时,电压外环的PI控制器保证系统的动态性能,谐振控制器保证其稳态精度。最后在旋转坐标系下对系统分别采用PI-P和PIR-P两种双闭环控制器情形作对比仿真。结果表明系统在严重不平衡负载情况下,输出电压负序不平衡度由2.41%减小到0.129%,零序不平衡度由2.25%减小到0.032%。     

DC harmonic distortion minimization of thyristor converters underunbalanced voltage supply using asymmetrical firing angle

Noncharacteristic harmonics of significant magnitude are produced at the output and input terminals of phase-controlled power converters under unbalanced voltage supply conditions. The concept of switching functions has been proposed before to evaluate the harmonics produced by a phase-controlled six-pulse power converter under both balanced and unbalanced power supply conditions. This paper extends the switching-functions approach to establish analytical equations for the DC output voltage harmonics produced by 12-, 18-, and 24-pulse power converters. The problem is approached from the standpoint of symmetrical voltage components. The increase in distortion under unbalance is caused by the appearance of a second harmonic component. A method, based on an asymmetrical firing angle, to cancel the second harmonic at the power converter output under unbalanced voltage supply is also presented. Cancellation of the second harmonic improves power converter DC output voltage quality     

输入电压不平衡时三相脉冲阻塞式交交变频研究

为充分体现交交变频调速性能的优势,文中在传统电压平衡情况下脉冲阻塞式交交变频原理的基础上,提出了一种输入电压不平衡时的三相脉冲阻塞式交-交变频系统。通过对阻塞后斩波控制的理论分析,采用全控型功率器件,根据面积等效原理推导出了每个区间对应的占空比表达式。文中实现了输入电压不平衡情况下输出电压的变频调幅,使变频调速系统达到平衡状态时的运行效果。最后,搭建了输入电压不平衡时的三相脉冲阻塞式变频调速系统数学模型,设计了半实物仿真平台。仿真结果与平衡条件下的结果一致,证明了理论分析的可行性。     

Control of a Cascade STATCOM With Star Configuration Under Unbalanced Conditions

A control scheme for star-connected cascade static synchronous compensators (STATCOMs) operating under unbalanced conditions is proposed. The STATCOM is assumed to be connected to an equivalent three-phase star-connected power supply. By selecting the line-to-neutral voltages of the equivalent power supply, zero average active power in each phase can be obtained under unbalanced compensation currents or unbalanced supply voltages. Furthermore, to implement a separate control for the three-phase dc-link voltages, the average active power in each phase can also be adjusted to a target value determined by the dc-link voltage control loop. Then, by forcing the converter neutral voltage to be equal to the counterpart of the equivalent power supply, the STATCOM can be decoupled into three single-phase systems and the line-to-neutral voltage of the equivalent power supply can be used as the input voltage to the corresponding phase leg. Accordingly, reference current tracking and dc-link voltage maintaining can be simultaneously achieved under unbalanced conditions. The valid operating range of the star-connected cascade STATCOM under unbalanced conditions is also analyzed. The proposed control scheme has been tested using the power systems computer-aided design/electromagnetic transient in dc system (EMTDC) simulation results and the experimental results based on a 30-kVAr cascade STATCOM laboratory prototype are proposed.      

Implementation of a Three-Phase Capacitor-Clamped Active Power Filter Under Unbalanced Condition

A capacitor-clamped voltage-source inverter for active power filter operation under balanced and unbalanced conditions is proposed to suppress current harmonics and compensate the reactive power generated from the nonlinear loads. The adopted voltage-source inverter is based on a three-level capacitor-clamped topology to reduce the voltage stress of power semiconductors. Two control loops are used in the control scheme to achieve harmonic and reactive currents compensation and to regulate the inverter dc side voltage. In the adopted inverter, the neutral point voltage is compensated by a voltage compensator to obtain the balanced capacitor voltages on the dc side. In order to control the flying capacitor voltages, two redundant states in each inverter leg can be selected to compensate the flying capacitor to obtain a better voltage waveform with low harmonic contents on the ac terminals. The balanced and sinusoidal line currents are drawn from the ac source under the balanced and unbalanced conditions. The feasibility of the proposed scheme is confirmed through experimental results     

A bipolar four-quadrant analog quarter-square multiplier consistingof unbalanced emitter-coupled pairs and expansions of its input ranges

A bipolar four-quadrant analog multiplier based on the quarter-square technique, which is constituted from unbalanced emitter-coupled pairs, and some methods for extending the input voltage range, are described. The building blocks for the circuit consist of an unbalanced emitter-coupled pair with different emitter areas, an emitter-coupled pair with an input bias offset, and an unbalanced emitter-coupled pair with unbalanced emitter degeneration. A basic squaring circuit is realized from two identical unbalanced emitter-coupled pairs with emitter area ratio K and cross-coupled inputs and parallel-connected outputs. The quarter-square multipliers proposed in this paper can operate under low supply voltage (typically <3 V, and a minimum of 1 V). Therefore, the Gilbert multiplier, which has been the most popular analog multiplier in bipolar technology over the past few decades, can be replaced     

Coordinated Control of DFIG's Rotor and Grid Side Converters During Network Unbalance

This paper proposes a coordinated control of the rotor side converters (RSCs) and grid side converters (GSCs) of doubly-fed induction generator (DFIG) based wind generation systems under unbalanced voltage conditions. System behaviors and operations of the RSC and GSC under unbalanced voltage are illustrated. To provide enhanced operation, the RSC is controlled to eliminate the torque oscillations at double supply frequency under unbalanced stator supply. The oscillation of the stator output active power is then cancelled by the active power output from the GSC, to ensure constant active power output from the overall DFIG generation system. To provide the required positive and negative sequence currents control for the RSC and GSC, a current control strategy containing a main controller and an auxiliary controller is analyzed. The main controller is implemented in the positive (dq)⁺ frame without involving positive/negative sequence decomposition whereas the auxiliary controller is implemented in the negative sequence (dq)^- frame with negative sequence current extracted. Simulation results using EMTDC/PSCAD are presented for a 2 MW DFIG wind generation system to validate the proposed control scheme and to show the enhanced system operation during unbalanced voltage supply.     

含负荷不平衡补偿的SVC复合控制方法研究

该文提出了一种通过加装带滤波器的静止无功补偿器（SVC）,使负序引起的不平衡功率和谐波功率流入SVC,最终达到平衡系统目的的方法;提出基于前馈-反馈复合控制的SVC不平衡负荷补偿方法,将电压闭环控制与三相不平衡控制相结合、功率因数闭环控制与三相不平衡控制相结合,以达到适应各种工况的需求。最后,该文在SVC相关理论研究的基础上搭建了仿真模型,仿真结果表明该文提出控制方法的正确性和可行性。     

New control scheme of three-phase PWM AC/DC converter without phase angle detection under the unbalanced input voltage conditions

In general, three-phase PWM AC/DC power converters have been implemented in the synchronous frame model to eliminate steady state errors effectively and to obtain fast transient response characteristics. However, controllers designed in such way would have input current harmonics and DC-link voltage ripples under the unbalanced input voltage conditions due to the assumption of the balanced input voltage conditions. This paper describes a new control scheme to minimize harmonic distortions of the input current and DC-link voltage in the converter under the unbalanced input voltage. conditions. The synchronous frame input voltage, which is considered as the input side back-EMF component, is regulated pertinently according to the input voltage conditions. The current command is selected to eliminate the reactive power and the second order harmonic component of active power. In this case, the analysis of the input voltage is implemented in the synchronous frame without detecting the phase angle and magnitude of each phase voltage. The proposed control scheme is simple and effectively minimizing the harmonic distortions in the input and output system under the unbalanced input voltage conditions.