有效电容可调的单相电容电动机

为了使单相电容电动机具有良好的起动性能和运行性能,与副绕组串联的电容器需要不同的电容量.现在最普遍的作法是配置二只电容器,一只用于改善起动性能, 另一只用于改善运行性能.木文阐述应用电子开关周期性短接电容器,以获得可调的有效电容,从而达到上述目的的原理及方法.该法只需用一只电容器即可同时改善起动和运行性能.在250W 4极电容电动机上试验结果,与应用二只电容器的方法相比较,具有相近的起动性能.     

三绕组并联式单相感应电动机起动方式研究

为了保证三绕组并联式单相感应电动机的起动性能,研究了该种电机的动态特性和起动方式.基于电磁关系,建立动态数学模型,并进行仿真计算.为了验证该模型的正确性和有效性,将仿真结果与试验结果进行对比.利用该仿真模型详细分析电容对该种电机起动性能的影响,并给出结构简单的单电容起动电路.仿真和实验结果表明,选择合适的起动电容和运行电容,可以使三绕组并联式单相感应电动机具有良好的起动性能和稳态运行性能.在实际应用中,使用双起动电容电路可以保证良好的起动性能,选择单电容起动电路,可以简化电路结构,节约成本.     

DC-link电容器在线状态监测方法综述

直流支撑(DC-link)电容器是电力电子变换器的关键器件之一,它的可靠性会影响整个系统的可靠性。状态监测是估计电容器健康状态的一种有效手段,综合分析了电容器的健康状态参数和性能状态参数,针对近年来电容器的在线状态监测研究进行分类,将其分为了传感器法、注入法、电路模型法和智能监测法;介绍每种方法的原理和手段,对比分析各种方法的优缺点,其次,针对研究成果的监测对象和监测参数进行数据统计分析;最后提出电容器状态监测的后续研究方向。     

关于无熔丝电容器和内熔丝电容器优劣的一点看法

本文从理论上、试验情况、生产工艺、适用条件、运行条件要求和国内外运行条件的差异等多方面分析无熔丝电容器与内熔丝电容器的特点,从而得出两种不同结构的电容器具有什么样的适用条件,以及在适用条件下各自具有的优缺点。达到使电容器用户和电容器生产厂家能根据不同的使用条件,正确选择和生产适用结构的电容器产品,从而提高电容器装置使用的安全性和可靠性。     

基于动态规划和遗传算法的配电网电容器优化配置

提出了一种将动态规划与遗传算法相结合的求解配电网无功优化配置问题的方法,该方法首先利用动态规划求解速度快的特点,初步计算出一个次优的规划方案,将此方案作为遗传算法的初始值,再从该点出发,应用遗传算法的全局寻优能力,在整个可行的运营空间中搜索出电容器配置的最佳方案。理论分析及仿真结果均表明:该方法计算速度快,规划精度高,对目标函数的限制较少,是一种可行的、有效的配电网电容器优化配置方法。     

多路高压触发源抗干扰的新方法

提出了一种多路高压触发源抗干扰的新方法,它的特点是各触发电路中的储能电容器并非同时处于充好电的准备状态,而是按预定的实验时序充电并立即放电。因此,当某一火花开关被触发放电并产生电磁干扰,导致其他各路中的开关元件（如晶闸管）误动作时,这几路也不会输出高压触发脉冲（由于它们的储能电容器上电压为０）。该方法被用于电感隔离型重复频率ＭＡＲＸ发生器的触发系统中,取得了很好的结果。     

高压并联电容器在线监测系统灵敏度及可靠性研究

高压并联电容器在长期运行中,由于缺陷、故障较多,而目前电网检修运行方式无法有效实现提前预判设备故障,以致易出现单台电容器故障扩大为整组故障,存在较大的设备安全运行隐患.因此提出了基于对温度值、电容值和不平衡电压进行检测的高压并联电容器在线监测方法,并对其灵敏度及可靠性进行了研究.运行结果表明该系统对提高电容器可靠性及防止发生电容器故障具有重要的实际意义.     

串联超级电容器组动态电压均衡试验研究

利用开关电容来实现电池均衡的方法有着广泛的应用,它利用一组电容器在串联电池组相邻电池之间传递电荷,进行能量转移。本文借鉴电池组的开关电容均衡方法,把它用于串联超级电容器组电压均衡上,给出了开关电容法对于串联超级电容器组的参数确定方法和控制策略,并进行了仿真分析和实验验证。     

Optimal capacitor placement in a radial distribution system using Plant Growth Simulation Algorithm

This paper presents a new and efficient approach for capacitor placement in radial distribution systems that determine the optimal locations and size of capacitor with an objective of improving the voltage profile and reduction of power loss. The solution methodology has two parts: in part one the loss sensitivity factors are used to select the candidate locations for the capacitor placement and in part two a new algorithm that employs Plant Growth Simulation Algorithm (PGSA) is used to estimate the optimal size of capacitors at the optimal buses determined in part one. The main advantage of the proposed method is that it does not require any external control parameters. The other advantage is that it handles the objective function and the constraints separately, avoiding the trouble to determine the barrier factors. The proposed method is applied to 10, 34, and 85-bus radial distribution systems. The solutions obtained by the proposed method are compared with other methods. The proposed method has outperformed the other methods in terms of the quality of solution.     

考虑宽负载变化的有源电容等效容值控制与损耗分析

二端口有源电容是一种仅有2个引出端口而无需任何附加电气连接端子的有源电路。然而,基于传统控制方法的有源电容等效容值在理想情况下是无穷大的,这不适用于某些需要精确容值的无源电容应用场合。为此,提出了一种基于二端口有源电容的等效容值控制方法,该方法能根据不同的应用需求实现对有源电容的精准容值控制。首先,对有源电容的阻抗进行建模与分析;然后,通过基于单相整流器的仿真分析,将通过等效容值控制的有源电容与具有相同容值的无源电容进行对比,以验证控制精度;最后,通过与传统有源电容控制方式在功率损耗和动态响应速度方面进行对比,结果验证了所提出等效容值控制方法的有效性。     

Capacitor current imbalance and its suppression method between phase legs for three‐phase inverter

This paper proposes a method to suppress the capacitor current imbalance between the phase legs of a three‐phase inverter circuit. This circuit consists of half‐bridge modules and DC‐link capacitors closely connected to each module. It can be designed for low stray inductance between power semiconductor devices and DC‐link capacitors in each module. However, in the conventional structure, the stray inductance between the phase legs may lead to an imbalance in the capacitor current due to the DC‐side resonance phenomenon under a higher switching frequency condition by using a SiC MOSFET. This paper presents the analyses of the equivalent circuit considering the circuit configuration, which suggests that capacitor current imbalance occurs depending on the stray inductance between phase legs. To suppress the capacitor current imbalance, a delta‐type bus bar connecting phase legs is proposed. The experiment results at 300 V and 4.6 A demonstrate the suppression effectiveness of the proposed method.     

An approximate method for capacitor placement in distribution system using heuristics and greedy search technique

A new method based on heuristics and greedy search technique has been reported in this paper for the placement of capacitors in radial distribution system. Heuristic rules have been developed to determine the probable capacitor locations in a distribution network. A greedy search technique then determines the optimum capacitor locations from these probable locations and the size of capacitors at these locations. The greedy search technique for the determination of the optimum locations and size of capacitors is based on a simple one dimensional search technique called the basic search technique in this paper. This basic search technique has also been used successfully as an additional operator of the genetic search technique to develop a GA based solution of the capacitor placement problem in distribution system.     

Improved “K” type seven-level switched capacitor inverter topology with Self-voltage balancing

This paper proposes an improved “K” type seven-level switched capacitor inverter topology. The proposed topology consists of eight active switches, one floating capacitor, and two dc-link capacitors. The floating capacitors are charged and discharged in each half-cycle to maintain the capacitor voltage with the same value of the input voltage. The floating capacitor voltage is self-balanced, and the output voltage is 1.5 times higher than the input voltage. To prove the superiority of the proposed topology, it is compared with the existing seven-level inverters in terms of maximum voltage stress on the switch and required the number of power components. The simulation and experimental validation are carried out for 1.6 kW, 50 Hz using a laboratory-based setup with a switching frequency of 5 kHz. The results are discussed highlighting the performance of the proposed topology for the dynamic load variations at different modulation indices. Both simulation results and experimental results have good agreement in terms of voltage balancing of flying capacitor.     

Three-phase induction motor operating from single-phase supply with an electronically controlled capacitor

In this paper the performance of a three-phase induction motor operating from single-phase supply with a new electronically controlled capacitor using an electronic switch in series with a fixed capacitor to achieve a minimum unbalance of the motor phase voltages at all loading conditions is proposed. No mechanical or centrifugal switch is used here. Basic system operation, theoretical analysis, simulated and experimental results in comparison with conventional operation using one and two fixed capacitors are presented in this paper. The optimum effective capacitor value can be on-line adjusted at any operating speed by periodically changing the duty cycle of the controlled switch to achieve minimum unbalance in phase voltages to improve the motor performance at different speeds.     

Advances in Capacitor Starting

An 8000-hp motor at the LOCAP Pipeline Clovelly Station is brought on line with three step capacitor starting and is protected from resonant overvoltage by a large metal oxide voltage limiter. Three-step starting is required to stay within the utility requirement of a maximum of ±1.5 percent primary voltage fluctuation during the entire starting operation. Cycle timers are utilized to obtain critical breaker sequencing as well as protect the system from breaker failure. Should the utility power fail while the motor is accelerating, the starting capacitor may cause severe motor overvoltage. Zinc oxide limiters are sized to absorb 1 MJ over a period of ten cycles allowing the breakers to clear the motor and capacitors.     

并联电容器装置的参数优化

提出了以抑制谐波为目标的并联电容器装置参数优化选择方法,构建了以满足并联电容器装置的连续运行条件和抑制各次谐波放大为约束,以各次谐波放大倍数平方和最小为目标函数的并联电容器装置参数优化模型。模型综合考虑电网谐波响应特性和各种影响因素,包括频率偏差、电抗偏差和电容偏差对并联电容器装置谐波特性的影响。运用粒子群优化算法求解优化模型,给出了具体实现方法。针对工程实例进行了比较和分析。     

变电站投切电容器组过电压研究

投切补偿电容器组电力系统最常发生的内部过电压,以贵州某变电站为原型,建立了仿真计算模型。操作过电压仿真研究中,断路器模型起着关键性作用,在分析了真空断路器开断时交流电弧物理过程的基础上建立了断路器的仿真模型,大大提高了仿真精度。仿真计算结果表明：投、切电容器组过程中电容器上承受的过电压幅值较小,不会对电容器造成威胁,但会在电容器入口端产生较高的对地过电压;在切除电容器组过程中发生断路器两相重燃时,由于断路器相间电压较高,将会在重燃相产生上千安的涌流,对电容器组的通流能力要求较高。     

一起串联补偿电容器复杂故障的分析

结合某500 kV线路的串联补偿(简称串补)电容器发生的一起多重转换性故障,分析了故障时线路保护和串补保护的动作行为,结果与动作报告及录波数据相符,分析表明故障时火花间隙动作出现异常.通过分析火花间隙的动作原理可知,电容器在短时间内大面积损坏是火花间隙未触发的主要原因.分析了电容器组的接线方式及耐爆容量,表明两并或三并...     

A hybrid optimization approach for distribution capacitor allocation considering varying load conditions

This work presents a new algorithm based on a combination of fuzzy (FUZ), Forward Update (FWD), and Genetic Algorithm (GA) approaches for capacitor allocation in distribution feeders. The problem formulation considers three distinct objectives related to total cost of energy loss and total cost of capacitors including the purchase and installation costs and one term related to total cost of produced power under peak load condition. The novel formulation is a multi-objective and non-differentiable optimization problem. The proposed methodology of this article uses an iterative optimization technique based on Forward Update approach which is embedded in a Genetic Algorithm framework. The fuzzy reasoning supported by the fuzzy set theory is used for sitting of capacitors and the GA is employed for finding the optimum shape of membership functions. The proposed method has been implemented in a software package and its effectiveness has been verified through a 9-bus radial distribution feeder along with a 34-bus radial distribution feeder for the sake of conclusions supports. A comparison has been done among the proposed method of this paper and similar methods in other research works that shows the effectiveness of the proposed method of this paper for solving optimum capacitor planning problem.     

一种新的电力电容器连续调容方法研究

提出了一种新的电力电容器调容方法,该方法基于PWM控制原理,用电力电子开关控制两组电容器的投切,通过调节控制脉冲的占空比连续调节电容.该方法克服了目前无功补偿装置中分组投切电容器时电容有级差的缺点,同时减少了补偿所需电容器组的数量.采用MATLAB中的PowerSimSyetems对该方法进行仿真分析,仿真结果与理论值一致.