磁控式并联电抗器（MCSR）可实现无功功率的大范围平滑调节,但现有研究中MCSR容量调节暂态特性及其对保护的影响尚不清晰。因此,该文对MCSR容量调节过程展开研究,首先分析了磁控式并联电抗器的稳态运行特性,引入磁饱和度概念,在此基础上,对其容量调节暂态过程特性展开讨论。调容暂态过程中,由于心柱间磁饱和度的差异,三相控制绕组电流及控制绕组总电流的基波分量将会增加,导致基于控制绕组总电流基波分量的匝间保护误动。为解决该问题,根据MCSR调容过程中三相控制绕组电流基波分量平均值近似相等的特点,利用三相控制绕组电流基波分量差异度,可以准确识别出容量调节过程,从而有效解决了MCSR容量调节过程中匝间保护误动的问题。基于Matlab/Simulink的仿真及1.5kV MCSR样品的动模实验,验证了所提方案的正确性。

实际工程中对于特高压磁控式并联电抗器（MCSR）控制绕组接地故障配置直流母线过压保护,然而发生控制绕组端部接地故障时,母线极对地电压无交流过电压特征,导致保护无法识别该故障。针对该问题,分析了控制绕组接地故障及稳态运行、2种方式合闸、区外故障工况下母线极对地电压变化情况,基于此提出一种基于直流母线不平衡电压的控制绕组接地保护方案。该方案利用正、负极直流母线电压之和构造直流母线不平衡电压,基于故障下直流母线不平衡电压明显上升的特征识别故障。方案原理简单、易于实现,解决了现有保护无法识别控制绕组端部接地故障问题。在MATLAB/Simulink软件中搭建了750 kV三相MCSR仿真模型,大量仿真结果验证了该保护方案的有效性。

磁控式并联电抗器（MCSR）作为电网中十分重要的无功补偿设备,具有平滑调节容量,消除操作过电压和潜供电流的作用。文中利用Ansoft Maxwell软件搭建了二维有限元模型,并使用外电路编辑器作为有限元激励源,通过仿真网侧绕组接地故障、网侧绕组匝间故障、控制绕组接地故障、控制绕组匝间故障,分析了在这4种不同故障情况下磁控式并联电抗器的工作特性。

Converter transformers are vital devices in line-commutated-converter (LCC) high-voltage direct-current (HVDC) systems. This paper introduces a new inrush current induced by a valve-side asymmetric ground fault on a converter transformer. It is defined as a "fault-induced inrush current (FIIC)." Taking a valve-side single-phaseto-ground (VSSPG) fault on a rectifier-side converter transformer as an example, the FIIC induced by this fault and its characteristics are first analyzed. Subsequently, the differences of the FIICs caused by the VSSPG faults occurring at the transformers in wye-grounded-wye (Y-0/Y) and wye-grounded-delta (Y-0/Delta) connections are discussed. After that, the effect of HVDC control and protection (C&P) on the characteristics of FIICs is considered. Finally, the impact of the FIIC on the transformer differential protection is analyzed. It is concluded that the transformer differential protection has a risk of being inappropriately blocked because of the FIIC. A suggestion for the HVDC C&P to apply a shorter protection action delay is proposed to reduce the risk. The theoretical analysis is verified through simulations performed in PSCAD/EMTDC. This study will be valuable for the research of inrush currents of converter transformers.

In the actual project, the DC bus overvoltage protection is configured for the control winding grounding fault of the extra-high voltage MCSR(Magnetically Controlled Shunt Reactor). However, under the condition of grounding fault occurring in the end part of control winding, the DC bus does not exhibit AC overvoltage characteristic, which causes the protection to fail to identify the fault. To solve this problem, the characteristics of DC bus pole-to-ground voltage under different conditions, such as control winding groun-ding fault, steady-state operation, two ways of energizing and external faults, are analyzed. Based on this, a protection scheme based on DC bus unbalanced voltage is proposed, which uses the sum of the positive and negative DC bus voltages to construct an unbalanced voltage of DC bus, and identifies the fault based on the characteristic that the DC bus unbalanced voltage rises obviously during control winding grounding fault. The principle of the protection scheme is simple and easy to implement, which overcomes the problem that the conventional protection cannot identify the control winding end part grounding fault. A large number of simulative results based on MATLAB/Simulink verify the effectiveness of the proposed protection scheme. © 2021, Electric Power Automation Equipment Press. All right reserved.

Magnetically controlled shunt reactor (MCSR) is one of the key equipments applied in EHV/UHV transmission systems for reactive power compensation and voltage control. Due to its special core structure and winding connection mode, the probability of occurrence of turn-to-turn faults is high and the detection is still a challenge. The existing protection schemes have problems of low reliability and sensitivity the maloperation may happen when MCSR is pre-excited energized, and the fault with less short-circuited turns is difficult to detect. To solve these problems, a novel protection scheme based on equivalent magnetizing inductance (EMI) is proposed. The definition and calculation of EMIs of MCSR are introduced. Based on the parameters of 750 kV MCSR applied in Northwest China, a simulation model in MATLAB/Simulink is built. The variation of EMIs in different scenarios is analyzed through theoretical and simulation and an EMI-based protection is proposed through calculating unbalance level of EMIs of limb p and q (ULEMI) and average values of EMIs. The novel protection scheme provides an effective method for turn-to-turn fault detection and will not be affected by energization, which is of great significance for practical engineering application.

磁控式并联电抗器（MCSR）可实现容量大范围平滑调节,是解决超/特高压输电系统无功及电压控制难题的有效措施。匝间短路是MCSR的一种常见故障,由于其特殊的铁心结构以及绕组联结方式,故障绕组和非故障绕组之间存在复杂的电磁耦合关系,MCSR匝间故障的准确判别具有一定挑战性。针对该问题,提出一种基于等效漏电感参数辨识的MCSR匝间故障保护方案。基于MCSR网侧与控制侧、补偿侧的电压回路等效电路,推导得到相应的等效漏电感参数辨识模型,通过递推最小二乘法实时辨识等效漏电感参数,利用其在匝间故障时变化明显以及故障相与非故障相的差异特征,构建基于等效漏电感参数变化率和三相差异度的匝间保护方案。此外,该方案还可以根据故障后等效漏电感参数的大小关系,进一步实现故障绕组的判别,最后基于Matlab/Simulink的大量仿真,验证了该方案的有效性。

Based on an actual project, the main structure and working principle of EHV magnetically controlled shunt reactor (MCSR) is presented. The generation mechanism of fundamental component in total control current during pre-excitation closing is analyzed. It is illustrated that maloperation may happen due to applying the protection scheme based on fundamental component in total control current in pre-excitation closing situation. Further analysis find out that generation of the fundamental component is not a unique phenomenon when fault occurs on control winding and it is derived from the fault phase control winding during internal fault. Under pre-excitation closing condition, the fundamental component is derived from three-phase control winding currents and its proportion is related to closing angle. An improved MCSR protection scheme is proposed, applying the ratio between the fundamental component of the winding current and total control current. This scheme is not affected by pre-excitation closing, and highly sensitive in the case of light turn-to-turn faults. Simulation results demonstrate effectiveness of the improved scheme.
© 2019, Power System Technology Press. All right reserved.

基于实际工程介绍了一种超/特高压磁控式并联电抗器的本体结构及其工作原理,分析了预励磁合闸时控制绕组三相电流之和（简称总控电流）的基频分量产生机理,结合MATLAB/Simulink仿真结果以及动模实验结果,说明预励磁合闸可能会导致基于总控电流基频分量的控制绕组保护方案误动。深入分析发现,总控电流基频分量的产生并不是控制绕组发生匝间故障时的特有现象,内部故障时总控电流基频分量主要来源于相应的故障相控制绕组;预励磁合闸时,总控电流基频分量来源于三相控制绕组电流分相电流基频分量之和,且各相占比与合闸角有关。基于此,提出以分相控制绕组电流基频分量与总控电流基频分量比值为判据的MCSR保护改进方案,该方案不受预励磁合闸影响,在控制绕组轻微匝间故障时仍具有很高的灵敏度,仿真结果验证了新原理的有效性。