Research on Inter-turn Short-circuit Fault Diagnosis Method Based on High Frequency Voltage Residual for PMSM

Inter-turn fault is a serious stator winding short-circuit fault of permanent magnet synchronous machine(PMSM). Once it occurs, it produces a huge short-circuit current that poses a great risk to the safe operation of PMSM. Thus, an inter-turn short-circuit fault(ITSCF) diagnosis method based on high frequency(HF) voltage residual is proposed in this paper with proper HF signal injection. First, the analytical models of PMSM after the ITSCF are deduced. Based on the model, the voltage residual at low frequency(LF) and HF can be obtained. It is revealed that the HF voltage residual has a stronger ITSCF detection capability compared to the LF voltage residual. To obtain optimal fault signature, a 3-phase symmetrical HF voltage is injected into the machine drive system, and the HF voltage residuals are extracted. The fault indicator is defined as the standard deviation of the 3-phase HF voltage residuals. The effectiveness of the proposed ITSCF diagnosis method is verified by experiments on a triple 3-phase PMSM. It is worth noting that no extra hardware equipment is required to implement the proposed method.

Transient fault identification method for bipolar short-circuit fault on MMC‐HVDC overhead lines based on hybrid HVDC breaker

A bipolar short‐circuit transient fault identification method for overhead transmission lines in modular multi‐level converter‐based high voltage direct current(MMC‐HVDC)grid based on the hybrid HVDC breaker is proposed.The circuit breakers on both sides of the positive and negative overhead transmission lines will trip after a bipolar short‐circuit fault in the MMC‐HVDC grid.In order to identify whether the fault is a transient fault,the isolating switch of the DC breaker on one line side is reclosed first,and the voltage change on this line side in the case of transient and permanent faults is analysed.By comparing the electrical characteristics of the voltage on the line side under transient and permanent faults,a transient fault identification method is proposed,and the calculation method of the setting value of the criterion is obtained.Finally,by building the MMC‐HVDC system model for simulation in power systems computer aided design,the accuracy and effectiveness of the proposed method for transient fault identification are verified.

Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.

Short-circuit fault analysis and isolation strategy for matrix converters

The behavior of matrix converter(MC) drive systems under the condition of MC short-circuit faults is comprehensively investigated. Two isolation strategies using semiconductors and high speed fuses(HSFs) for MC short-circuit faults are examined and their performances are compared. The behavior of MC drive systems during the fuse action time under different operating conditions is explored. The feasibility of fault-tolerant operation during the fuse action time is also studied. The basic selection laws for the HSFs and the requirements for the passive components of the MC drive system from the point view of short-circuit faults are also discussed. Simulation results are used to demonstrate the feasibility of the proposed isolation strategies.

Remedial Phase-Angle Control of a Five-Phase Fault-Tolerant Permanent- Magnet Vernier Machine With Short-Circuit Fault

A fault-tolerant permanent-magnet vernier(FT-PMV)machine incorporates the merits of high fault-tolerant capability and high torque density.In this paper,a remedial phase-angle control(RPAC)strategy is proposed for a five-phase FT-PMV machine with short-circuit fault.Firstly,the proposed strategy can reduce the amount of unknown quantities by structuring the phase-angles of the normal phases.It can simplify the calculation of the remedial currents.Then,in order to obtain the desired torque,only the amplitudes of the remedial currents need to be calculated.Based on the principle of instantaneous electrical input power and mechanical output power balance condition,the real components are used to maintain the torque capability,while the reactive components are limited zero to minimize the torque ripple.Both simulations and experiments are presented to verify the proposed RPAC strategy.

一种用于光隔离IGBT栅极驱动的智能型LED驱动电路

采用双极型工艺设计了一种智能型高速LED驱动电路,可用于光隔离IGBT栅极驱动芯片的输入驱动。该设计采用一种新型逻辑门结构来实现信号传输、故障反馈以及外部置位等功能,同时达到降低信号传输延迟时间的目的。测试结果表明,在常温条件下,LED驱动电路的输入信号传输延迟时间为70 ns,复位信号有效到故障消除的延迟时间为4.59μs。所设计的驱动电路能够满足光耦隔离IGBT栅极驱动芯片的使用要求。

高比例电力电子电力系统过电压(三):直流故障下新能源暂时工频过电压机理

在高比例新能源和大容量直流输电工程大量投运的背景下,电力系统过电压问题日渐凸显,不仅制约直流输电能力,而且可能引发新能源大规模脱网。在新能源占比较高时,与交流设备相比,新能源的工频过电压耐受能力更低,该文针对直流故障引发的送端新能源机端过电压问题进行机理分析。首先,建立直流闭锁和直流多次换相失败后闭锁故障状态下新能源及传统同步机经特高压直流外送系统的等效电路分析模型,基于矢量关系,解析推导直流故障下的暂时工频过电压最大值。然后,分析直流输电功率水平、新能源并网功率、新能源低电压穿越控制参数、同步机至直流换流站电气距离以及新能源至直流换流站电气距离等因素对新能源机端电压最大值的影响。最后,通过PSD-BPA仿真软件在小算例系统和我国西北等值电网中验证理论分析的有效性。

考虑瞬时功率特性的高压直流电网双极短路故障识别技术

高压直流电网运行过程中,由于受到负载特性和电压波动等因素影响,电容电流及谐波等瞬时功率特性较为复杂,增加了对电网系统故障的识别难度。为此,提出考虑瞬时功率特性的高压直流电网双极短路故障识别技术。通过建立高压直流电网拓扑结构模型,分析高压直流电网的双极短路故障;结合高压直流电网端点的瞬时功率特性判断出双极短路故障发生区域。利用双端故障电流最大值定位法获取双极短路故障定位,完成对高压直流电网双极短路的故障识别。实验结果表明,所提方法对高压直流电网双极短路故障定位识别精度较高,提升了故障识别效率。

受端电网故障下真双极柔性直流输电系统电压协同控制方法

盈余功率积累可能诱发基于模块化多电平换流器的高压柔性直流输电系统(high-voltage direct current based on the modular multilevel converter,MMC-HVDC)过压闭锁,乃至引发海上风电场机组失步或受端电网低频减载。现有降压或升频等直流电压控制方法仅针对伪双极接线,缺乏讨论不同控制模式的换流器间协同原则;且控制参考值未能自适应受端电网的故障严重程度,导致海上风电场有功功率调节过量。该文基于受端电网故障下MMC-HVDC平均值模型,解析了海上正负极换流器和风电场的功率耦合特性,提出了交流母线电压控制极换流器平衡换流站间有功功率,有功和无功功率控制极换流站抑制极间不平衡的协同原理。通过解析海上风电场在交流母线电压控制极换流器降压作用下的功率外特性,提出了恰好避免直流电压越限的临界交流母线电压计算方法。通过解析使得受端换流站有功电流受限的交流母线电压作为启动门槛,提出了受端电网故障下真双极MMC-HVDC电压协同控制方法。理论分析和仿真结果表明,所提方法令海上正负极换流器分别运行于临界交流母线电压和抑制极间不平衡的有功功率,可在避免直流电压越限的前提下,最大限度提升MMC-HVDC在受端电网故障工况下的有功功率传输能力。

Design and Optimization of Dual-Winding Fault-Tolerant Permanent Magnet Motor

To improve the performance of the traditional fault-tolerant permanent magnet(PM)motor,the design and optimal schemes of dual-winding fault-tolerant permanent magnet motor(DWFT-PMM)are proposed and investigated.In order to obtain small cogging torque ripple and inhibiting the short-circuit current,the air gap surface shape of the PM and the anti short-circuits reactance parameters are designed and optimized.According to the actual design requirements of an aircraft electrical actuation system,the parameters,finite element analysis and experimental verification of the DWFT-PMM after optimal design are presented.The research results show that the optimized DWFT-PMM owns the merits of strong magnetic isolation,physics isolation,inhibiting the short circuit current,small cogging torque ripple and high fault tolerance.

Placement optimization of Multi-Type fault current limiters based on genetic algorithm

The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.

Single-phase earth fault current distribution between optical fiber composite overhead ground wire and ordinary ground wire in transmission system

It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.

New “Intellectual Networks” (Smart Grid) for Detecting Electrical Equipment Faults, Defects and Weaknesses

The most important elements of “intellectual networks” (Smart Grid) are the systems of monitoring the parameters of electrical equipment. Information-measuring systems (IMS), which described in this paper, were proposed to use together with rapid digital protection against short-circuit regimes in transformer windings. This paper presents an application’s experience of LVI-testing, some results of the use of Frequency Response Analysis (FRA) to check the condition of transformer windings and infra-red control results of electrical equipment. The LVI method and short-circuit inductive reactance measurements are sensitive for detecting such faults as radial, axial winding deformations, a twisting of low-voltage or regulating winding, a losing of winding’s pressing and others.

基于拉依达准则的MMC子模块开路故障定位

模块化多电平换流器(modular multilevel converter,MMC)凭借模块化结构等优点,被广泛应用于高压大功率输电领域。MMC含有大量子模块(submodule,SM),SM的开关器件故障是影响MMC可靠性的关键问题之一。其中SM开路故障不易及时检测,威胁系统正常运行,为此提出一种基于拉依达准则的SM开路故障定位方法。首先,对SM开路故障进行故障特性分析,根据SM开路故障会引起SM电容电压的异常变化,应用拉依达准则进行判别。其次,计算同桥臂内SM电容电压的均值和3倍标准偏差来构造一个置信区间,通过判断SM电容电压是否超出置信区间且持续一定时间来检测并定位发生开路故障的SM。该方法不需要额外传感器,不用建立精确数学模型,不用手动设置经验阈值,算法较为简单。最后,在PSCAD/EMTDC中搭建三相MMC系统仿真,并在实验室搭建单相MMC实验平台对该方法进行验证。仿真和实验结果表明,基于拉依达准则的SM开路故障定位方法能够快速有效地定位出发生开路故障的SM。

全桥配网柔直双极短路故障穿越策略研究

中压柔性直流配电网在新能源平滑接入、直流负荷高效供电等方面具备突出的优势,是配电网重要发展方向之一。双极短路故障作为最严重的直流系统故障,其故障发展速度快,短路电流冲击大,研究该场景下中压柔性直流配网如何故障穿越并实现快速故障恢复,对于提高中压柔直配网的供电可靠性与运行安全性具有重要的意义。针对中压柔性直流配电网中配网全桥柔直换流器,提出了故障穿越的控制方法和故障穿越的逻辑设计原则。最后,仿真与现场试验结果证明了所提中压柔直配网全桥换流器双极短路故障穿越方法的可行性和有效性。

Intelligent System Design for Stator Windings Faults Diagnosis:Suitable for Maintenance Work

The short circuit is a severe fault that occurs in the stator windings. Therefore, it is very important to diagnose this type of failure in its beginning before it causes unscheduled stop and the machine loss. In this context, the Support Vector Machine (SVM) is a tool of considerable importance for standard classification. From some training data, it can diagnose whether or not there is a short circuit beginning, and which is important for predictive maintenance. This work proposes a technique for early detection of a short circuit between the turns aiming at its implementation in a real plant. The paper shows simulation and experimental results, and validates the proposed technique.

Validation of Full-Converter Wind Power Plant Generic Model Based on Actual Fault Ride-Through Measurements

Modeling and validation of full power converter wind turbine models with field measurement data are rarely reported in papers. In this paper an aggregated generic dynamic model of the wind farm consisting of full power converter wind turbines is composed and the model validation based on actual field measurements is performed. The paper is based on the measurements obtained from the real short circuit test applied to connection point of observed wind farm. The presented approach for validating the composed model and fault ride-through （FRT） capability for the whole wind park is unique in overall practice and its significance and importance is described and analyzed.

随机森林模型在IGBT器件状态监测中的应用

针对绝缘栅双极型晶体管(IGBT)模块老化故障频发的问题,这里将优化随机森林模型应用于IGBT老化故障诊断系统中以实现IGBT器件的状态监测和老化故障预测。首先选定老化故障特征参数并进行数据预处理,建立老化故障诊断数据集。其次,建立传统随机森林模型,并在此基础上通过基评估器参数寻优、模型框架参数寻优及袋装法的处理方法对传统随机森林模型进行优化,形成优化随机森林模型。在交叉验证的基础上完成模型训练,最后通过多种评估指标对所提模型和其他模型在IGBT老化故障诊断数据集上的预测效果进行评估,最终优化后的模型拟合情况较好,训练集曲线和测试集曲线之间的误差为1.19%,在测试集上的预测精度可达98.81%,验证了优化随机森林模型应用于IGBT状态监测系统中的可行性和精确性。

基于MPCC的永磁同步电机驱动系统逆变器IGBT开路故障诊断方法

针对永磁同步电机(PMSM)驱动系统逆变器绝缘栅双极晶体管(IGBT)开路故障诊断过程中电流检测法检测时间较长的问题,研究了一种基于模型预测电流控制(MPCC)的误差电流极性法,通过将MPCC中代价函数的变化和电流检测法相结合,可有效缩短故障检测时间。然而,MPCC容易受到电机参数变化的影响,负载转矩、转速的变化可能导致电机参数变化或不匹配,进而影响代价函数的输出,导致误诊。针对该问题,在基于MPCC的误差电流极性法中对故障检测指标进行了归一化处理并加入了计数法,进一步提高了故障诊断的鲁棒性能。

半桥型MMC直流侧故障恢复过程过流机理及抑制方法

直流侧发生短路故障后,半桥型模块化多电平换流器(MMC)易闭锁,故障恢复期间不当解锁导致桥臂过流,MMC存在连续闭锁风险,引发系统性安全问题。针对该问题,文中理论分析了故障恢复期间绝缘栅双极型晶体管(IGBT)的解锁过流机理,并提出了一种新的故障恢复控制。首先,指出欠阻尼状态的故障回路必然导致IGBT闭锁。其次,揭示了故障恢复期间IGBT解锁过流的根源是直流侧和交流侧的压差。进一步,提出了故障恢复控制,在闭锁期间切除功率外环,抬高交流侧调制波以减少压差,抑制桥臂电流。计及闭锁期间子模块电容电压和重合闸时序,构建了自适应外环参考值曲线,解决功率盈余造成的过压问题。结果表明,和现有串联交流侧启动电阻方法相比,在不同工况下所提故障恢复控制最低可将桥臂电流峰值由1.57 p.u.降至0.79 p.u.,解锁后调控功率侧MMC直流电压为额定值,有助于加快故障恢复。