应用于电力系统中的电流保护

本文针对于在电力系统中装设的电流保护——定时限过电流保护、反时限过电流保护、电流速断保护、限时电流速断保护、三段式电流保护和零序电流保护做了介绍,分析了其保护特点和动作参数。     

配网中自适应电流速断保护的应用

在阐述传统电流速断保护和自适应电流速断保护构成原理及特点的基础上,对自适应式电流速断保护在单端电源条件下发生在正、反方向故障时的动作性能进行了分析。结果表明,自适应电流速断保护性能比传统电流保护具有明显的优越性及适用条件。     

智能配电网保护控制的设计与研究

面对配电网供电需求的增大、配电网连接复杂度的增高以及可再生能源接入等问题,研究和发展突出自愈功能的智能配电网成为电力系统发展的必然选择和趋势。本文以智能配电网为研究对象,首先针对智能配电网继电保护方式的选取问题进行了简要分析,进而详细研究了电流差动保护与电流速断保护这两个方面入手,针对智能配电网中的保护判据形式做出了详细说明,最后以结合实际案例的方式,论证了面向智能配电网保护与控制的重要意义,希望引起关注与重视。     

浅谈10kV配电系统继电保护

文章介绍了电网10kV配电系统在电力系统中的重要位置及电网10kV配电系统继电保护的基本类型,着重介绍了几种目前国内常用的电流保护：反时限过电流保护,定时限过电流保护、电流速断保护,并分析了各类保护装置的基本构成,保护范围．动作原理、配合方法．优缺点。     

城市电网10kv配电系统继电保护的分析探讨

文章介绍了城市电网10kV配电系统在电力系统中的重要位置及城市电网10kV配电系统继电保护的基本类型,着重介绍了几种目前国内常用的电流保护：反时限过电流保护、定时限过电流保护、电流速断保护,并分析了各类保护装置的基本构成、保护范围、动作原理、配合方法、优缺点,给出了详细的整定计算过程。     

基于零序电流分布的自耦变压器电流保护分析

文中基于自耦变压器零序电流的分布特点,探讨了自耦变压器零序电流保护的构成及整定原则,重点分析了自耦变压器零序差动保护。     

低压成套开关设备保护电路的连续性分析

阐述低压成套开关设备的特点，低压成套开关设备保护电路的应用，低压成套开关设备保护电路的连续性分析，包括附加直流电保护、零序电流保护、零序功率方向保护、漏电故障保护。     

一种矿用漏电保护器的设计

介绍了一种适用于矿井T380V、660V、1140V供电系统的漏电保护系统的设计方法.该漏电保护系统以单片机为核心,在总开关处使用附加直流源检测原理,并在分开关处采用零序功率选择性漏电保护原理,使得该保护器可以达到漏电保护的选择性和准确性.     

异步电动机缺相及定子电压不对称的保护

三相异步电动机由于缺相损坏的比例在工业企业中的所占约８０％以上，而三相电压严重不平衡造成断相、严重过热而损坏的电机也占相当比例，本文初步探讨了负序电压系数与零序电压的关系，并介绍了缺相与定子电压不对称的保护方案。     

变压器零序过电流保护动作原因浅析

在中性点直接接地的高压电网中,针对主变压器配置的两段零序过流保护在不同故障点时的动作情况,提出相应的对策措施：对于一般接地点,主变装设两段零序过电流保护,可满足要求;但当接地点发生在主变110 kV侧TA与隔离开关之间时,该两段保护不能满足要求,必须添加一个独立时限跳母联断路器,可为主变零序过流保护提供参考和借鉴。     

Dual-Modulator Compensation Technique for Parallel Inverters Using Space-Vector Modulation

In common dc-link parallel-inverter systems, the amplitudes and the phase angles of three-phase inverters can be separately adjusted to control power sharing. However, when the space-vector modulation technique is used in a parallel-inverter system without the output transformers, the zero-sequence circulating current will occur. This paper provides detailed analysis of the zero-sequence circulating current and proposes a novel dual-modulator compensation technique for eliminating the zero-sequence circulating current caused by power-sharing control systems. Results obtained from both simulation and experiments confirmed the performance and the effectiveness of the proposed compensation method.      

Control of circulating current in two parallel three-phase boost rectifiers

One unique feature in parallel three-phase converters is a potential zero-sequence circulating current. To avoid the circulating current, most present technology uses an isolation approach, such as transformers or separate power supplies. This paper proposes a parallel system where individual converters connect both AC and DC sides directly without additional passive components to reduce size and cost of the overall parallel system. In this case, the control of the circulating current becomes an important objective in the converter design. This paper: (1) develops an averaged model of the parallel converters based on a phase-leg averaging technique; (2) a zero-sequence model is then developed to predict the dynamics of the zero-sequence current; (3) based on the zero-sequence model, this paper introduces a new control variable, which is associated with space-vector modulation; (4) a strong zero-sequence current control loop is designed to suppress the circulating current; and (5) simulation and experimental results validate the developed model and the proposed control scheme.     

Interleaved PWM with discontinuous space-vector modulation

This paper describes the effect of interleaved discontinuous space-vector modulation (SVM) in paralleled three-phase systems using three-phase pulsewidth modulation (PWM) rectifiers as an example. At the discontinuous point of the SVM, the phase shift between the switching signals of the paralleled modules generates a zero-sequence excitation to the system. Because the conventional control in a balanced three-phase system with only dq channels cannot reject this disturbance, a beat-frequency circulating current will develop on the zero axis. Based on this observation, a SVM without using zero vectors is used to eliminate the cause of pure zero-sequence current for parallel operation. Using this SVM, the circulating current is observable in dq channels. It can be suppressed dynamically by strong current loops of power-factor-correction (PFC) circuits. The concept is verified experimentally on a breadboard system     

Comparisons Between the p--q and p--q--r Theories in Three-Phase Four-Wire Systems

This paper presents a comparative analysis between results from applications of the p-q and the p-q-r theories in shunt active power filters for three-phase four-wire systems, discussing aspects related to the influence of the system voltage in the control methods that calculate the compensating currents. It is shown that in some cases, a preprocessing of the system voltage is required if the goal is to achieve sinusoidal compensated currents. On the other hand, when the goal is to compensate zero-sequence current, the need of energy storage elements in the active filter is discussed. In this case, if zero-sequence components are present simultaneously in the system voltage and load current, they produce zero-sequence power flow, and the control methods based on both theories must contain additional calculations to allow the elimination of energy storage elements in the active filter. A control strategy based on the p-q theory is proposed to eliminate the neutral current without the need of energy storage elements, with the advantage of avoiding the extra transformation from alphabeta0 to pqr coordinates that is needed in the p-q-r theory. Simulation results are presented for the purpose of comparing the performance of both control methods.     

三相四线制系统新型中线滤波装置研究

三相四线制电路中由于非线性负载的大量使用,使得中线上累加了大量的零序谐波电流,给电网的安全运行带来隐患。为此本文提出了一种新的中线零序谐波治理方案,即采用Zigzag变压器与有源电力滤波器（Active Power Filter,APF）相结合的方法。Zigzag变压器因其接线简单、性价比高而在中线谐波治理方面倍受青睐。两者的结合使得目标装置具有较高的性价比和广阔的市场应用前景。经仿真验证,此方案滤波效果在三相负载对称和不对称时均较好,是解决目前日益严重的中线零序谐波污染问题的一种切实可行的方案。     

Harmonic and reactive power compensation based on the generalizedinstantaneous reactive power theory for three-phase four-wire systems

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented     

10kV配电网故障定位系统取电与零序电流计算

配电网故障指示器已成为国内外研究的热点,其中,其高压侧取电及零序电流的获取与计算是设计的重点与难点。该文介绍了一种带气隙的多绕组的磁芯结合电力电子技术,来获取高压侧电源与零序电流的提取。并通过实验验证了此方法的可行性。     

基于绝缘在线监测原理的矿井低压电网漏电保护选线方法研究

分析了煤矿井下供电系统漏电故障模型及系统各条支路零序电流的逻辑关系,阐述了以此逻辑关系为基础,结合低频信号附加法,进而提出基于绝缘在线检测原理的漏电保护选线方法。该漏电故障选线方法对于各种结构和规模的供电系统具有较强适应性,特别是能够有效解决小规模供电系统中选择性漏电保护灵敏度低、可靠性差的技术难题。仿真结果表明此漏电选线保护方法能够有效进行漏电故障选线判断。     

一种全数字控制的工业激光器驱动电源

介绍了一种全数字控制半导体激光器驱动电源方案.方案采用高速数字信号处理器产生高频率高分辨率的数字调制PWM直接驱动功率回路,完全采用软件实现闭环的控制,结合高精度AD采样,使得输出电流具有高精度、低纹波和高动态响应速度的特点.系统还提供六种保护功能,具有故障锁定及故障自诊断功能,具有数字化的远程通讯接口.