中压直挂式供电质量综合提升装置及其负载电压控制策略

为了综合提升中压(10 kV)供电系统的电能质量,满足集中式电力高敏感负载对供电可靠性的要求,提出了一种中压直挂式供电质量综合提升装置及其负载电压控制策略。首先,介绍了该装置的拓扑与工作原理。该装置通过隔离电抗器实现电网与负载间的阻抗隔离,弱化电网电能质量对负载的影响;采用级联H桥型电池储能系统支撑与控制负载电压,实现负载侧持续性高质量供电。其次,分析了装置中关键设备隔离电抗器与并网电抗器对装置运行特性的影响。然后,提出了综合装置并网运行与离网运行的负载电压控制策略,实现对电网注入功率、负载电压频率与幅值的快速控制。最后,通过仿真分析与实验样机测试验证了所提装置及其负载电压控制策略的可行性与有效性,并对比了多种电能质量提升装置的技术性能。     

一种双输入高增益DC-DC变换器

针对光伏发电系统输出电压低、供电稳定性差等问题,提出一种非隔离双输入高增益直流升压变换器,该变换器在2个BOOST变换器的基础上引入了开关电容电路,实现了高电压增益,且两输入源可以单独或同时向负载供电。分析该变换器的电路结构和工作原理,推导出了3种供电模式下变换器的电压增益表达式以及主要开关器件电压应力,给出了两路同时供电时输入电流之间的关系。最后,搭建了一台100W的实验样机,实验验证了该变换器具有电压增益高、开关器件电压应力低、控制简单、可以灵活供电等优点。     

宽电压范围双移相控制多倍压高增益软开关隔离升降压变换器

提出一种适用于宽电压范围、低电压输入应用场合的多倍压高增益软开关隔离升降压变换器及其控制方法。通过将倍压型双有源桥变换器与倍压整流电路相结合,实现了高增益隔离升降压变换。通过采用双移相控制策略,使得一次、二次侧开关管能够在宽电压和宽负载范围内实现软开关,且二极管都可以实现零电流关断、无反向恢复损耗。变压器漏感可以作为能量传输电感的一部分,不存在漏感引起的电压尖峰问题,且一次侧开关器件的电压应力钳位在输入电压,二次侧开关器件的电压应力仅为输出电压的一半,器件电压应力低。详细分析了变换器的工作原理、控制策略和特性,实验验证了所提出拓扑及其控制方法的正确性和有效性。     

一种新型井下架线电机车供电电源设计

提出了一种新型的基于单周期控制的单位功率因数整流器为井下电机车供电。该电源由维也纳整流级和高频隔离DC-DC变换级两级功率变换器级联构成,但控制电路采用一级协调控制。电路控制简单,不需要乘法器和输入电压检测就可以实现单位功率因数运行,且可以降低开关器件一半的电压应力。详细分析了新型整流电路的基本工作原理和双闭环控制策略,并通过仿真和试验对此新型电路拓扑及其相应控制策略的正确性进行了验证。     

产品资讯

PZK-1000Z柱上开关监控装置产品用途:PZK-1000Z柱上开关监控装置(简称PZK-1000Z)用于配电线路柱上开关的监视与控制,称为线路终端单元FTU。它是由核心单元PZK-100配电自动化监控器、开关操作控制回路、控制操作面板、智能充电器、免维护蓄电池以及用户特定的通信装置组成。PZK-1000Z与配电自动化系统主站通信,对配电线路上开关设备运行状态进行监视与控制,实现线路故障检测、隔离及恢复供电等功能。产品特点:(1)完善的SCADA监控、故障检测等功能;(2)使用线路两侧电压互感器或专用变压器输出作为电源输入,双电源自动切换,确保供电…     

Topaz超隔离变压器

通讯系统、数据处理装置、测量和控制仪表以及遥测系统对电源噪声干扰十分敏感,因此要求交流输入电源与市电电网隔离。隔离的装置一般有三种:变压器、电动发电机组、逆变装置。本文介绍的是一种隔离变压器新技术——Topaz超隔离变压器。电源干扰的分类在交流供电中,严格地讲,除了供电频率为50赫(或60赫)的正弦波以外,其它交流成分都是电源干扰。电源干扰原因很多,形式也十分复杂。但大致可分为三类:脉冲干扰(或电压尖峰信号);减幅振荡干扰(主要是供电系统中的补偿电容器引起的干扰,其中也包括某些用电设备的开关操作引     

电压无功自动控制装置在变电站中的作用

利用并联电容器装置和有载调压开关来进行电压、无功的就地平衡,维持较高的电压合格率并保证功率因数,实现经济输电和供电,最后介绍电压无功自动控制装置的控制原理和在变电站中的使用。     

风电潮流优化控制系统的超电容均压策略

超级电容器是风电潮流优化控制系统中的关键储能元件之一,而高效可靠的串联均压策略是其实现中大功率场合应用的前提,为较好地实现均压效果,引入了一种超电容电压均衡控制策略的模型,并在此基础上提出了一种新颖的超电容电压均衡方法—相邻电感储能电压均衡法。该方法实时检测超电容组中各电容器电压,以电感为能量传递媒介,以半导体开关管为控制开关,将电压高的电容器能量转移到电压低的电容器中,实现了各超电容器的电压均衡。在详细介绍了该方法的工作原理后,给出了控制开关占空比的调节规律和电感参数的设计原则。最后,对两组串联超级电容器模块分别进行了仿真和实验,结果表明该方法极大地改善了超电容模块的电压一致性,电压均衡速度快、精度高,在风电潮流优化控制系统中有较高的应用价值。     

PWM-PFM混合控制LCC谐振变换器研究

输入电压和负载宽范围变化时,变频控制LCC谐振变换器的开关频率变化范围宽,而移相控制LCC谐振变换器难以实现宽范围零电压关断(zero voltage switching,ZVS)。为了在较窄开关频率范围内实现LCC谐振变换器的宽范围软开关,该文提出一种脉宽-脉频调制(pulse width modulation-pulse frequency modulation,PWM-PFM)混合控制LCC变换器。通过同时调整LCC变换器原边开关管的导通角与开关频率,在宽输入电压和宽负载变化范围内,提出的PWM-PFM混合控制LCC变换器能在稳压输出的同时保持变换器ZVS软开关工作。此外,PWM-PFM混合控制LCC谐振变换器的开关频率范围较窄,简化了变换器磁性元件的设计。以工作在电容电压连续模式(continuous capacitor voltage mode,CCVM)的LCC谐振变换器为例,利用基波近似法,分析PWM-PFM混合控制LCC谐振变换器的工作原理和控制特性,对谐振元件和控制参数进行设计。最后,通过一台100~200V输入、48V/500W输出的实验样机验证了理论分析的正确性。     

10kV重复频率方波脉冲源的研制

为进行绝缘材料在快前沿高压脉冲作用下的局部放电和绝缘老化的试验研究,研制了1台最高输出电压为10kV的重复频率高压方波脉冲发生器。该方波发生器采用可调直流高压电源和储能电容器作为能源系统,利用半导体固态开关作为主放电开关控制脉冲宽度和重复频率,通过脉冲放电回路在负载上形成所需的电压脉冲。其半导体固态开关采用具有低耦合电容的紧凑型快速高压金属氧化层半导体场效应晶体管(MOSFET)开关,通过复杂可编程逻辑控制器(CPLD)可编程逻辑电路实现开关通断控制。实测结果表明,该脉冲源可以产生脉冲上升沿约为80ns、最小脉冲宽度为320ns的高压准方波脉冲,最高输出幅值达到±10kV,脉冲重复频率的可调范围为1～3kHz,性能指标满足绝缘材料的局部放电以及绝缘老化试验的要求。     

A novel step-up topology for multilevel power conversion

Renewable energy sources employ a power conditioning unit for injecting power into the grid. Such resources of small capacity are characterized by low generated voltage and thus require a high voltage boost at the inversion stage. This paper proposes a novel transformer-less, single-phase grid-connected, 13-level inverter to yield the voltage boost. The presented topology is realized through 12 unidirectional switches, 2 diodes, and 3 capacitors. A single-stage circuit synthesizes 13 levels with a single input source and yielding an overall voltage gain of six. The adapted modulation technique is robust enough to keep the capacitors self-balanced for all values of the modulation index. The proposed topology is modular and cost-effective in comparison to other similar typologies due to reduced device count and space requirement. The presented topology is validated experimentally with satisfactory operation in yielding input voltage boost by a factor of six.     

Predicting harmonic problems resulting from customer capacitoradditions for demand-side management

The use of capacitors to correct for poor power factor is a well-established and cost-effective means of reducing demand and system losses. Utilities routinely apply capacitors on transmission and distribution systems. Additional gains may be made by installing capacitors in customer facilities and many utilities are encouraging such installations for demand-side management (DSM) purposes. Unfortunately, many industrial customers have serious problems with capacitor installations because of interactions with harmonic distortion from plant loads. Capacitors may cause one or more harmonics to be accentuated through resonance. The capacitors themselves may be damaged or the resulting voltage distortion may make it impossible to operate some process equipment. It is often difficult to predict which capacitor installations will be troublesome, particularly when there are numerous capacitors and harmonic-producing loads scattered over a plant's power system. A simplified approach that depends on less input data is described. The method is based on the voltage distortion at the main bus and the currents in the capacitors. Two test cases are presented     

Harmonic disturbance identification in electrical systems with capacitor banks

The identification of distortion sources in a power system is an unsolved topic. The problem is difficult to solve because there are elements in the system that do not produce harmonics but amplify those already present in the electrical network. The most common of these elements is the capacitor, which is widely used to compensate for the power factor at the fundamental frequency. The capacitor behaviour makes the indices proposed up until now to identify distortion sources fail in the presence of this element. This paper presents a new index: the load characterization index. Besides using an extended equivalent circuit to represent the load, this index calculates the distortion introduced by the load, evaluating, in addition to the current distortion at its input, the voltage distortion at its terminals. The introduction of voltage assessment makes the index suitable for identifying the linear and non-linear loads in the power system even in the presence of capacitors and from only the voltage and current measured at the point of common coupling.     

中压配电网的线路分段开关优化规划

介绍了确定中压配电网分段开关位置的实用计算方法。分段开关是为了提高供电可靠性而装设，所设开关应尽可能保护它所在位置的电源侧用户免受开关负荷侧故障的影响。通过采用以最小停电费用为目标函数，以供电可靠性为约束条件的枚举法来求解。此方法可使分段开关安装位置的选择更合理。     

输入并联输出串联变换器系统的控制策略

将多个直流变换器模块在输入侧并联和输出侧串联,得到输入并联输出串联直流变换器,它可以降低开关管的电流应力和输出整流二极管的电压应力,适用于高输出电压、大功率的场合.为了保证该变换器的可靠工作,必须确保各模块的输出电压均衡.本文从能量守恒的角度出发,揭示了该变换器中各模块的输出均压和输入均流之间的关系,指出可以直接控制各模块的输出电压以使它们均衡,也可以采用输入均流控制来实现输出均压.提出一种新的输出均压的控制方法,它对系统输出电压控制闭环没有影响.同时采用交错控制,可以有效减小输入滤波电容和输出电容.论文最后给出了仿真和实验结果,验证了该方法的有效性.     

Harmonics and transient overvoltages due to capacitor switching

This work presents a study of the steady-state and transient effects of power factor correction capacitors on the utility and on the customer. In the presence of harmonic-producing loads, capacitors used for power factor correction can cause parallel or series resonance problems which tend to increase the total harmonic distortion (THD) of the voltage and current waveforms. The cases studied in this work considers the addition of a power factor correction capacitor, in the presence of downstream harmonic loads and at the harmonic load site. In both cases the resonance created by the addition of the capacitor caused the harmonic distortion of the voltage and current waveforms to increase. Another problem is transient overvoltages created by switching the capacitor. A case study is reported where the operation of a semiconductor controlled motor drive is effected by transient overvoltages     

Improvement of power system stability by on-off discrete control of series capacitors

Application of controlled series capacitors with anti-parallel thyristor combination across the capacitor segment is one of the new and promising countermeasures for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors, hence, it is very effective to apply the capacitors for damping power system disturbances. In this paper, we describe the following. (1) The design method of control system for the segmented series capacitors with thyristor switches is proposed. (2) The effectiveness of the controlled capacitors proposed for power system stabilization is shown with the results of EMTP analysis. (3) The possibility of zero passing missing phenomena of capacitor voltage is indicated by EMTP simulation, and a countermeasure is proposed in order to avoid the phenomena. The effects of the countermeasure is indicated by the results of EMTP simulation.     

Efficiency improvement of high‐frequency inverter for wireless power transfer system using series compensator

This paper proposes a wireless power transfer system using a series compensator GCSC (gate‐controlled series capacitor) as a primary side capacitor. The GCSC is a circuit module that functions as a series variable capacitor by controlling semiconductor switches. The advantage of applying the GCSC to the primary side capacitor is that it provides controllability of the output power factor for a high‐frequency inverter. Therefore, optimum operation of the high‐frequency inverter can be achieved irrespective of the coil parameters by controlling the output power factor. Experimental results with a 1 kW laboratory prototype confirmed that the proposed system can achieve optimum operation and high efficiencies of the high‐frequency inverter.     

A new parallel ZVS converter with less power switches and low current stress components

A new direct current (DC)/DC converter with parallel circuits is presented for medium voltage and power applications. There are five pulse‐width modulation circuits in the proposed converter to reduce current stress at low voltage side for high output current applications. These five circuits share the same power switches in order to reduce switch counts. To reduce the converter size, conduction loss, and voltage stress of power semiconductors, the series connections of power metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with high switching frequency instead of insulated gate bipolar transistor (IGBT) with low switching frequency are adopted. Thus, the voltage stress of MOSFETs is clamped at half of input voltage. The switched capacitor circuit is adopted to balance input split capacitor voltages. Asymmetric pulse‐width modulation scheme is adopted to generate the necessary switching signals of MOSFETs and regulate output voltage. Based on the resonant behavior at the transition interval of power switches, all MOSFETs are turned on under zero voltage switching from 50% load to 100% load. The circuit configuration, operation principle, converter performance, and design example are discussed in detail. Finally, experimental verifications with a 1.92 kW prototype are provided to verify the performance of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.     

Step-up Transformerless Seven-level DC-AC Hybrid Topology for Interconnection of Renewable-based DC Sources to Microgrids

This article introduces a new step-up transformerless multi-level DC-AC hybrid topology for interconnecting renewable DC sources to loads or microgrids. This enabling technology incorporates the best characteristics of three modified basic topologies—a DC-DC multi-level boost converter, a DC-DC multi-level buck converter, and an H-bridge—to obtain a seven-level step-up DC-AC hybrid structure using only one DC input and nine power switches for a single-phase output with field-programmable gate array based control. The advantages of the step-up seven-level structure compared to other proposals are higher efficiency, a reduced number of power switches, and high power density associated with transformerless characteristic. Furthermore, in contrast to conventional topologies, the proposed design does not require voltage/current monitoring of the capacitors or a capacitor-balancing control scheme, and only one DC source input is used. Consequently, a high-performance configuration is obtained. The laboratory results demonstrate the validity of the design and the performance of the prototype.