移相器在电压稳定危机中的作用

分析了电压稳定危机中,进行横向调节的移相器所能起的作用。潮流剧增时在可能率先跳闸的联络线上,动用移相器遏制潮流越限次对保障电压稳定性不致因负荷恶性转移、每相继退而遭到破坏,具有关键使用。     

一款高精度90°移相器实用电路的设计

用RC元件及相应电路设计低频固定频率90°±Δφ移相器是人们常用的方案,然而RC移相器元件的老化、环境(尤其是温度)的变化严重地影响了移相器的稳定性。本文采用了一系列措施:(1)选用低温度系数的精密阻容元件;(2)对阻容元件进行老化处理;(3)分别测量元件的温度系数;(4)用相反温度系数的阻容元件按一定的比例进行补偿等,使RC元件温度系数达到±1ppm/℃以内。对90°±Δφ移相器的温度试验表明,电路的温度系数达到2.88ppm/℃。文中还给出所选用的部分国内外RC元件实测的温度系数,对读者利用RC元件设计某些高稳定性电路(如HPF、BPF、LPF等)有重要的参考价值。     

Transient current analysis of induction generators for wind power generating system

In this paper we present a transient current analysis of induction generators used in a wind power system before and after three‐phase fault conditions. First, the basic equations of an induction generator connected to an infinite bus are developed and then transient current analysis formulas are derived for a three‐phase fault before and after fault clearance. We also determine the initial phase angle for the three‐phase fault or the restoration phase angle of the power supply voltages and the time at which the maximum or minimum transient currents flow in the system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 38–45, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10319     

A low-loss compact six-bit DMTL phase shifter for phased array antenna applications

A phase shifter is one of the main components of radars and phased array systems. In this paper, a novel three-state two-bridge unit cell is presented for a compact low-loss six-bit distributed microelectromechanical systems (MEMS) transmission line (DMTL) phase shifter. The proposed unit cell includes a coplanar waveguide (CPW) transmission line, a MEMS bridge on the signal line, two metal-air-metal (MAM) capacitors on a glass substrate, and two additional electrodes under the MEMS bridge, near the signal line. Using these electrodes, it is possible to generate two different phase states employing the MEMS bridge, and the third state is produced by a metal-air-metal (MAM) bridge. Hence, the designed structure can generate three different phase shifts per unit cell (i.e., 5.625°, 11.25°, and 22.5° phase shifts). The novelty of this design is that the number of unit cells is considerably reduced from 64 in a conventional six-bit phase shifter to only 17 in our design. Therefore, the total length of the six-bit phase shifter and average loss are considerably reduced. The designed structure is calculated and simulated at 32 GHz using MATLAB and ANSOFT HFSS, respectively. According to the calculation and simulation results, the lateral size of the phase shifter is only 8.5 mm, the root mean square (RMS) phase error is 1.38°, and the average loss is 1.1 dB. The feasibility of the proposed design is investigated using the proposed fabrication process. The designed phase shifter can be easily scaled to other frequencies for radar and satellite applications with more bits.     

Control schemes and transient characteristics of a high‐speed phase shifter for power flow control in power transmission systems

In recent years, attention has been paid to the concept of FACTS (Flexible AC Transmission Systems), along with significant progress in power electronic technology. A high‐speed phase shifter, which is one of the most promising devices in the FACTS concept, has the potential of power flow control and/or voltage stability in power transmission systems. In this paper, theory and experiment reveal that conventional high‐speed phase shifters may cause power swings in a transient state as a result of coupling between instantaneous active and reactive power control loops. Thus, two new control schemes for a high‐speed phase shifter are proposed to achieve both power flow control and power swing damping. The second proposed control scheme is based on the control scheme of an already proposed series active filter. Simulated and experimental results agree well with analytical results, not only in steady states but also in transient states. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 74–82, 1999     

利用移相器进行电力系统网损优化控制

提出了一种利用移相器进行电力系统网损化优化控制的统一方法，该方法可以统一优化系统中不同种类的多个移相器的参数以求实现网损最小化的目的。在参数优化过程中，该方法计及了线路潮流的约束和移相器参数约束。算例分析表明，此方法具有通用性强，使用方便的特点，是一种研究移相器及其潮流控制的有效工具。     

Power system stabilizing control by a superconducting magnetic energy storage with a high-speed phase shifter

Electric power demand has increased rapidly and this is expected to continue. Undamped power swings with low frequency tend to occur in large power systems with complex configuration. Therefore, several stabilizing control schemes, e.g., a power system stabilizer (PSS), have already been investigated. On the other hand, superconducting magnetic energy storage (SMES) is expected to be an effective apparatus in power systems since any SMES located in power systems is capable of leveling load demand, compensating for load changes, maintaining bus voltages and stabilizing power swings. The effectiveness of each function, however, depends upon the location of the SMES in the power system because output power from the SMES is distributed according to the impedance ratio of the transmission line at the SMES location. Therefore, it is difficult for SMES to serve two different purposes simultaneously. This paper proposes a combination of SMES with a high-speed phase shifter (HSPS). The HSPS, which consists of a phase shift transformer and a set of power converters, is capable of controlling the power flow of the transmission line by adjusting the phase angle of a phase shift transformer. Therefore, it is expected that the combination of SMES and HSPS can realize a highly effective controller independent of its location. Numerical examples demonstrate that the proposed apparatus located far from a generator in a long distance bulk power transmission system is capable of stabilizing the power swing as effectively as the SMES located at a generator terminal. In addition, the effectiveness of both load change compensation and power system stabilization is confirmed numerically.     

Power system security enhancement by OPF with phase shifter

This paper presents an integrated optimal power flow (OPF) with phase shifter approach to enhance power system security. The general OPF calculations are hourly based and the control variables of OPF are continuous. However, the calculations of phase shifter are daily based, and the variables related to phase shifter are discrete. Therefore, the general OPF cannot be directly used to solve this problem. The paper develops the rule-based OPF with phase shifter scheme to bridge the problems. In order to effectively alleviate the line overloads, the ranking of phase shifter locations is conducted based on contingency analysis and sensitivity analysis. The best phase shifter sites are identified and selected into a rule-based system accordingly. The handshaking procedure between the adjustment of the selected phase shifters and OPF calculation is proposed using a rule-based method. The hourly-based OPF problem is solved by the extended quadratic interior point method. The IEEE 30-bus system is used to test the proposed scheme     

采用分布系数和相角匹配分析的电磁环网潮流监控形式

针对切机措施下电磁环网的潮流控制形式和主要监控支路的识别问题,提出了一种采用分布系数和相角匹配分析的电磁环网潮流监控形式。该监控形式以常规分布系数法为基础,通过发电转移因子来消除被切机组出力对电磁环网潮流监控的影响;根据直流潮流的观点,利用高电压等级线路和低电压等级线路的电压相角匹配程度来识别主要监控线路。对南方某省500 k V/220 k V电磁环网的实例分析结果表明:所提方法能确保电磁环网高电压等级线路断开,并采取安全措施切除机组后,低电压等级线路不过载,从而在确保系统安全的前提下充分发挥电磁环网的输送能力。同时,所提方法不需要大量计算,仅依靠相角匹配分析就能准确识别出电磁环网的主要监控线路,有效减轻了调度监控的工作量,具有较高的安全预警性能。     

基于多桥脉冲宽度调制(PWM)交流控制技术的静止移相器

介绍一种基于脉冲宽度调制（ＰＷＭ）交流控制技术的新型静 相器。对单桥ＰＷＭ移相器在１个开关周期中的３种工作模式进行了理论分析,推导了旁路电容及吸收电阻的参数设计公式;采用多桥叠加结构的交流控制器抑制大容量ＰＷＭ移相器的自身谐波发生量、降低装置开关频率及开关损耗;是出了多桥ＰＷＭ交流控制器的电压转移函数以及多桥移相器的线路注入电压表达式;通过计算机仿真分析及物理模型实验,验证了理论推导结果的正确性。     

Optimum Reflection-Type Phase Shifter Using (Ba,Sr)TiO3 Thin Film

In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate (Ba,Sr)TiO₃ [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB 90° branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper.     

750 kV同塔双回不换位线路电流不平衡度研究

在线路走廊特别紧张的地区,部分线路可能没有条件采用完全换位的方式架设,而同塔多回线路采用不换位架设将导致电气三相参数不对称。针对这个问题,对同塔双回不换位线路不平衡度计算进行了推导,并应用PSCAD/EMTDC软件从杆塔类型、相序排列方式、回间距离、线路长度几个方面对750 kV同塔双回不换位线路进行了仿真分析。仿真结果表明,输电线路较短时采用同塔同窗逆相序方式架设并适当调整回间距离,电流不平衡度能控制在一定的范围之内。输电线路较长时则需进行换位,避免对系统造成不良影响。     

一种新型的六位数字移相器的设计

针对传统的数字移相器插入损耗高和相位精度低等性能的不足,提出了一种新型的加匹配线的开关式移相器设计技术。包括固定长λ/2主线以及在主线边缘长λ/8的平行短路和开路短截线,克服了传统数字移相器设计中端口驻波比高,插入损耗大的缺点,而且在相位精度上也有提高。在设计中,用加匹配线的方法对45°,90°和180°移相器进行设计,并将相位为5.625°,11.25°,22.5°,45°,90°及180°6个二态移相器电路组合起来,构成六位数字式移相器,通过二进制代码控制各个PIN二极管,从而得到64个相移状态,实现了输出频率范围为400～450MHz的低插入损耗,高相移精度的六位数字移相器,通过实际测试得到整个六位数字移相器插入损耗低于5.3dB,相移精度小于3°,驻波比小于1.5的较好实验结果,具有比传统设计方法更优良性能。     

同塔双回不换位线路电压不平衡度研究

在线路走廊特别紧张的地区,部分线路可能没有条件采用完全换位,而同塔多回输电线路中采用不换位架设将导致电力系统三相参数不对称。针对这个问题,以某地区一条750 kV同塔双回线路为例,对该线路不平衡度计算进行了理论推导,并应用PSCAD/EMTDC软件从杆塔类型、相序排列方式、回间距离、线路长度几个方面对线路不平衡度进行了仿真分析。仿真结果表明,输电线路较短时采用同塔同窗逆相序方式架设并适当调整回间距离,能将电压不平衡度控制在一定范围内。输电线路过长时则需采取换位措施,避免对系统造成不良影响。     

可控移相器对系统不对称短路电流的影响研究

以可控移相器在电力系统中得到广泛应用为研究背景,以研究可控移相器接入系统后对不对称短路电流的影响为目标,提出了基于可控移相器的不对称短路电流实用计算方法。首先根据可控移相器的结构与原理建立其正序、负序以及零序模型。然后基于对称分量法建立含可控移相器系统的各序分量网络方程,进而提出含可控移相器系统的各类型不对称短路电流实用计算方法,并分析影响短路电流的因素。最后基于三机九节点系统,运用上述实用计算方法进行不对称短路电流计算,算例仿真结果表明该方法具备有效性。通过对比分析可知移相器的移相角和短路点位置是影响短路电流的因素,而影响情况需通过具体计算得出。     

铁氧体移相器差相移一致性浅析

以X波段背脊式非互易移相器为研究对象,从磁芯、应力、激励器等多方面对影响铁氧体移相器差相移一致性的因素进行了分析和讨论.为了使这种一致性达到要求,在移相器的设计、加工、装配等过程中,首先力求将各种不利因素的影响程度降到最低;然后采用数理统计等方法对同批移相器的差相移进行统计和分析,淘汰不合格品.     

A variable structure static phase shifting transformer for power system stabilization

A variable structure sliding mode control system for controlling a static phase shifter is developed. The static phase shifter aims at introducing voltage phase shift between the terminals of transmission line. The voltage phase shift is controlled by adding to the voltage of one end of transmission line a quadrature voltage component. The thyristor switches is used to regulate that quadrature component, whereupon, the phase shift is changed. A sample power system model used for digital simulation is linearzied to design the variable structure control algorithm. To validate the power and robustness of the proposed controller for enhancing power system stability, the studied power system is subjected to different disturbances such as tie line power, frequency or synchronous machine speed disturbances. The power system dynamic responses for the above disturbances prove the effectiveness and superiority of the variable structure control system in terms of fast damping response with less settling time.     

相位角表法的分析与应用

针对互感器极性错误时,会使线电压和相电流夹角直接发生变化,从而影响到功率表达式的计算,在介绍三相三线两元件电能计量装置接法的前提下,分别分析了电压互感器极性正确与错误时的向量图,对应给出了不同的相位角表,可不用画向量图直接列出功率表达式。     

Study of phase current measurement by the whole conductors clamping method for three‐phase cable

This paper describes a new measuring method for the phase current in a high‐voltage three‐phase cable. Twenty‐four pieces of independent coils wound around the coreless bobbins are used to make a CT sensor. The primary phase current may be calculated based on the output voltage of each coil. The certain correlation between the output voltage and primary phase current is observed by the experimental data. This new CT sensor enables the measurement of the phase current using the whole conductors clamping method for a three‐phase cable. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(2): 9–20, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20753     

基于移相器统一特性的潮流控制

本文根据移相器的共同性质，在保持原始网络节点导纳矩阵对称性的条件下，推导了节点等效附加注入电流和功率的统一表达式，并将此式用于修正移相器参数的选代过程中。实例分析表明，本文方法能统一地分析多个不同种类的移相器对潮流控制的作用，具有适应性强的特点。