WO2022100378A1 - 一种通过扩频载波实现故障诊断的方法 - Google Patents

一种通过扩频载波实现故障诊断的方法 Download PDF

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WO2022100378A1
WO2022100378A1 PCT/CN2021/124646 CN2021124646W WO2022100378A1 WO 2022100378 A1 WO2022100378 A1 WO 2022100378A1 CN 2021124646 W CN2021124646 W CN 2021124646W WO 2022100378 A1 WO2022100378 A1 WO 2022100378A1
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signal
fault
ssplcr
spread spectrum
sequence
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PCT/CN2021/124646
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English (en)
French (fr)
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王莉
陈维佳
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南京航空航天大学
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Priority to US18/005,974 priority Critical patent/US20230327704A1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7087—Carrier synchronisation aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/709—Correlator structure
    • H04B1/7093—Matched filter type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/06—Control of transmission; Equalising by the transmitted signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/46—Monitoring; Testing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines

Definitions

  • the invention relates to a method for realizing the combination of power carrier and fault detection and positioning based on spread spectrum communication, and belongs to the technical field of carrier communication.
  • the aerospace system in order to ensure the high reliability of the system, it is necessary to collect the state parameters of multiple parts of the system for detection and diagnosis of electrical, airborne measurement and control, flight status, atmospheric data and avionics system status. In order to realize the detection and control requirements of the system, it is necessary to collect data from a large number of sensors and control a large number of actuators, and the number of data transmission lines also increases accordingly.
  • the intelligence of the aerospace system the increasing dependence on the engine control and transportation management system, the enrichment of the in-flight entertainment system and the improvement of the passenger service system have put forward high-speed and reliable requirements for information transmission. As a result, the number of cables in the aerospace system increases, the weight increases, and the carrying efficiency is reduced.
  • the power carrier communication technology (Power Line Communication, PLC) was introduced. of high-speed transmission.
  • Information transmission based on the characteristics of the power carrier can reduce the construction cost, overcome the defects of large number of communication lines, complex distribution and crossover, and increased volume and weight brought by traditional communication, improve the carrying efficiency, and fundamentally reduce the number and weight of cables.
  • the working environment of the power line is complex. It is affected by frequent vibration caused by long-term flight, and friction with hard surfaces such as aircraft structure damages the wire insulation layer. , chemical corrosion and other effects, as well as damage during normal use and maintenance.
  • the aging of the power line and the decline of insulation will produce arcs and electromagnetic radiation, which will slowly endanger the conductor layer, resulting in disconnection, grounding, short circuit and other faults of the power line, interrupting the transmission of carrier data, and endangering the normal operation of the avionics system. It may cause power failure of important airborne equipment, cause chain reaction and fatal impact on the entire power system, and even cause serious loss of life and property.
  • Spread Spectrum Time Domain Reflectometry adopts spread spectrum communication technology, referred to as spread spectrum communication technology, and uses the sharp autocorrelation of pseudo-random codes.
  • the positioning accuracy is high, and the anti-interference ability is strong.
  • the influence of the spread spectrum signal on the original power signal is small, so online detection can be realized.
  • Spread spectrum communication modulates the spectrum of the information signal to be transmitted with a pseudo-random code, spreads the spectrum to become a wide-band signal, and then sends it into the channel for transmission; at the receiving end, the same code is used for related synchronization reception, despreading and recovery. transmit information data.
  • the channel bandwidth By increasing the channel bandwidth, even in the case of low signal-to-noise ratio, the channel can still transmit information reliably with the same capacity. In the case where the signal is overwhelmed by noise, reliable communication can be maintained as long as the bandwidth of the transmitted signal is increased accordingly.
  • the spread spectrum communication technology When the spread spectrum communication technology is used for ranging, if the spread spectrum is very wide, it means that the rate of the spread spectrum code used is very high, and the time occupied by each chip is very short.
  • the spread spectrum code sequence When the transmitted spread spectrum signal is reflected back by the measured object, the spread spectrum code sequence is demodulated at the receiving end, and then the phase difference between the two code sequences is compared, and the round-trip time difference of the spread spectrum signal can be accurately measured. Calculate the distance between the two. The narrower the chip, the wider the spread spectrum and the higher the accuracy.
  • a power line carrier-based aircraft power distribution system employs PLC technology and SSTDR fault diagnosis methods to provide critical maintenance functions. Its main contribution is that unlike the traditional aircraft power distribution system, which can only detect and locate the part of the feeder wire before power-on, the invention can realize real-time online fault detection and positioning.
  • the main method is to add the SSTDR fault detection device to the PLC modem, and inject the SSTDR detection signal into the power distribution system through the PLC tap point, so as to realize the online detection and positioning of the power line fault of the aircraft power distribution system.
  • the SSTDR fault detection system injects the detection signal into the power line through the PLC tap point.
  • the carrier communication signal and the fault detection signal coexist in the channel.
  • the two carrier signals have partial spectrum overlap, which reduces their respective signal-to-noise ratios and interferes with each other.
  • the carrier signal is difficult to recover, and the synchronization of the carrier communication function and the fault detection function is affected.
  • the object of the present invention is to propose a method for realizing fault diagnosis through spread spectrum carrier wave, namely Spread Spectrum Power Line Communication Reflectometry (SSPLCR), aiming at the defects and deficiencies existing in the prior art.
  • SSPLCR Spread Spectrum Power Line Communication Reflectometry
  • the source signal of the power carrier is segmented and transformed, and then the transformed source signal is spread by pseudo-random code.
  • the sine wave is used for modulation to generate the SSPLCR signal that can realize fault detection and information transmission.
  • the fault reflection signal is sampled at the transmitting end, the incident signal and the fault reflection signal are synchronized, and a cycle of the incident signal and fault reflection signal after synchronization is intercepted to perform correlation calculation, to determine the fault type and calculate the fault distance;
  • a digital delay-locked loop (Delay-Locked Loop, DLL) is used to finely synchronize the received carrier signal, and then despread and demodulate it through a correlation operation to restore the power carrier signal source signal.
  • DLL Digital delay-locked loop
  • the first step is to determine the center frequency and sequence length of the fault detection spreading code, and generate m-sequence and sinusoidal signals that meet the requirements as the SSPLCR signal spreading code and the SSPLCR signal modulation code;
  • the second step is to set the fault detection period
  • the third step is to convert the source signal carrying the carrier information into a binary sequence, and segment the binary sequence of the source signal according to the set fault detection period. From the start bit of the binary sequence to the end, at the segment Insert the same binary sequence containing only 0 or 1 to form a new binary sequence of the source signal;
  • the fourth step is to periodically spread and modulate the binary sequence of the new signal source signal with the generated m-sequence and sine wave to generate the SSPLCR signal;
  • the fifth step when the cable is working normally, sample the SSPLCR signal transmitted through the cable at the receiving end, perform synchronization processing with the locally generated PN code, and restore the power carrier information carried by it through despreading and demodulation to realize data transmission;
  • the SSPLCR fault reflection signal is sampled at the transmitting end, and the SSPLCR fault reflection signal is processed synchronously with the incident signal, and the phase of the SSPLCR fault reflection signal is adjusted and optimized, and then the correlation operation and normalization are performed with the incident signal to determine the type and location of the cable fault.
  • the method for determining the center frequency and sequence length of the SSPLCR spreading code in the first step includes:
  • n-order spread spectrum code ranging is where v is the transmission rate of the signal in the cable.
  • the method for setting the fault detection time gap in the second step includes:
  • the n-order m-sequence is determined and selected as the spread spectrum code, n ⁇ 5, the number of bits of the m-sequence is 2 n -1, as the spread spectrum detection sequence S 1 , and the frequency is f 1 ; Source sequence S 2 , frequency f 2 . Satisfy that the bit length of the source signal symbol is a times the period length of the m sequence, that is,
  • the fault detection interval time t 10 should be k times a(2 n-1 )/f 2 , and the requirements for the frequency of fault diagnosis are considered comprehensively. and interval time requirements, k should take an integer not less than 10, and set the fault detection time interval t 10 .
  • the method for forming a new source signal binary sequence S3 in the third step includes:
  • the size of the fault detection interval t 10 determined in the second step that is, k times the duration of a symbol of the binary sequence S 2 of the source signal, from the start bit of the binary source sequence to the end, every k codes
  • the meta-insertion only contains a binary sequence of 0 or 1 to form a new source signal binary sequence S 3 , whose frequency is f 2 , which is consistent with the original source signal binary sequence.
  • the method for forming the SSPLCR signal in the fourth step includes:
  • Step 1 use the m sequence generated in the first step as a spreading code, and perform periodic spreading processing on the binary sequence of the new source signal;
  • Step 2 Modulate the periodic spread spectrum signal obtained in Step 1, select BPSK as the modulation method, and the frequency of the modulated sine wave is f 1 , which is the same as the frequency of the m-sequence chip, and the SSPLCR signal is obtained after modulation; the signal has a power line carrier wave. Communication function and power line fault detection and positioning ability, use it as a detection signal, perform digital-to-analog conversion, signal conditioning, and couple it into the power line for information transmission and fault diagnosis;
  • the SSPLCR signal sampled by the receiver and the method for synchronous processing of the locally generated PN code include:
  • Step 1 Create a local PN code generator at the receiving end to generate an m-sequence, which is consistent with the m-sequence frequency, series and primitive polynomial generated at the transmitting end;
  • Step 2 Use the sliding synchronization module to perform rough synchronization on the received signal: Input the product of the local PN code and the received signal into the integral decision subsystem, perform integral operation, and compare the obtained integral value with the set threshold to determine whether the two signals are synchronized. , output the synchronization signal; in this process, the phase search control module always controls the PN code generation module to adjust the chip phase according to the synchronization signal, if the output value of the integrator at a certain moment exceeds the threshold, it is regarded as successful capture;
  • Step 3 Use a digital delay-locked loop to finely synchronize the received signal.
  • the method for despreading and demodulating the synchronization signal at the receiving end includes:
  • Step 1 The synchronized local PN code is multiplied by the received signal, filtered by an intermediate frequency filter, the carrier frequency of the modulated signal is removed, and the fundamental frequency signal is retained.
  • Step 2 Make zero judgment on the output signal of the intermediate frequency filter, the output value is greater than 0 and judged as 1, otherwise it is judged as 0. Add a counting and judgment module to make 2 n -1 zero-crossing judgments in a chip period, where n is the number of stages of the local PN code; when the detected zero-crossing times are greater than or equal to 2 n-1 times, it is considered that in this The source signal is 1 in the chip period; otherwise, it is determined that the source signal is 0 in this chip period.
  • the method for determining the type and location of the cable fault in the fifth step includes:
  • Step 1 The start time is the same as the start time of the SSPLCR signal transmission, and the fault detection time interval t 10 is used as the period to sample the fault reflection signal at the receiving end, and the sampling length is twice the chip period.
  • Step 2 Perform phase calibration on the sampled fault signal and the sent SSPLCR sequence.
  • the correlation operation is performed to calculate the size of the primary reflected wave peak, and the obtained primary reflected wave peak size is sorted. Combined with the spectral energy value, a comprehensive analysis is carried out to select the number m of delay chips that can reflect the fault information and amplify the fault peak.
  • Step 3 From the moment of m chips, intercept the sampled signal with a period length of 1 chip from the sampled fault signal, perform correlation operation with the 1-period spread spectrum code and perform normalization processing, extract the fault peak, and determine the fault. type and locate the distance to fault.
  • the method firstly transforms the source signal and inserts a specific detection sequence code, which can realize the sampling of the incident and reflected sequences at a certain period during the long-sequence data transmission process.
  • a specific detection sequence code samples the reflected signal at the same time, and the reconstructed source signal contains the power carrier information while ensuring the efficiency and frequency of fault detection.
  • a specific chip since a specific chip is inserted into the source signal, it avoids the change of the autocorrelation and cross-correlation characteristics of the incident sequence after the spread spectrum modulation due to the constant change of the phase of the randomly changing source signal, which is caused by the correlation operation of fault detection. Negative Effects.
  • This method generates SSPLCR incident signals that can simultaneously realize power carrier and fault detection and location, avoiding the traditional method of simultaneously injecting two signals into the cable in order to realize power carrier communication and fault detection at the same time, which interferes with each other due to overlapping spectrums Caused by the problem that the source information cannot be recovered.
  • the method organically combines the power carrier communication function and the fault detection function, and does not need to implement the two functions separately through the fault diagnosis device and the power carrier device, reduces the size, weight and cost of the device, and can realize the miniaturization and low cost of the hardware device. , Low power consumption design, can effectively improve the reliability and maintainability of power transmission and communication systems, which is conducive to market promotion.
  • this method proposes to apply the digital delay-locked loop to the despreading of the spread spectrum power carrier, and combine with the sliding synchronization acquisition module to synchronize the local synchronization PN code and the received signal to reduce the synchronization error. to within 0.1 chip. It solves the problem of fractional time delay caused by the signal in the process of cable transmission, and improves the accuracy of the power carrier.
  • This method proposes a phase calibration method in determining the fault type and locating the fault distance, which solves the problem of multiple peaks in fault detection by performing correlation operations between the sampled multi-period fault reflected spread spectrum carrier signal and the incident spread spectrum carrier signal. Selecting a periodic reflection signal that is finally correlated with the spread spectrum code, compared with the traditional method using a single cycle sampling reflected signal and the spread spectrum code for correlation operation, it can amplify the fault peak and increase the longest fault detection distance. Compared with the traditional SSTDR system, the SSPLCR system can realize the fault detection function of the same performance while carrying the power carrier information.
  • the technical scheme of the present invention can be widely applied to low-voltage and high-voltage power systems of aircraft, ships and electric vehicles.
  • Fig. 1 is the flow chart of spread spectrum power carrier SSPLCR method of the present invention
  • Fig. 2 is the principle block diagram of the spread spectrum power carrier SSPLCR method of the present invention
  • FIG. 3 is a schematic diagram of a method for generating an SSPLCR incident signal
  • FIG. 4 is a flow chart of a method for adjusting the phase of a spread spectrum signal at a receiving end
  • Figure 5 is the source data transmission waveform of the transmitting end and the receiving end of the SSPLCR system.
  • Figure 6 is a comparison diagram of the power line fault information curve obtained by the SSPLCR method for fault diagnosis and the SSTDR method;
  • the method for implementing fault diagnosis through a spread spectrum carrier includes the following steps:
  • S101 Determine the transmission parameters of the SSPLCR signal, and segment and transform the power carrier signal source signal.
  • S104 Synchronize, despread and demodulate the spread spectrum carrier signal at the receiving end, and recover the information carried by the spread spectrum carrier signal.
  • S105 extract the fault reflection signal at the transmitting end, and obtain the cable fault type and location through correlation operation.
  • the method realizes the integration of power transmission, data transmission and fault diagnosis, and improves the reliability and maintainability of the power transmission and communication systems.
  • the transmission parameters of the incident signal in the time-frequency domain are determined, and the center frequency and series of the spreading code are determined.
  • the interval time of fault detection is determined, and the source sequence is segmented and transformed.
  • the new source code is spread and modulated to generate the SSPLCR incident signal with power carrier and fault detection functions.
  • the time-frequency domain incident signal is digital-to-analog converted and injected into the cable, and a sampling module is set at the transmitting end.
  • impedance mismatch occurs at the fault point, and the incident signal is reflected at the fault point.
  • the reflected signal is sampled at the transmitting end, the phase of the sampled reflected signal is adjusted, and the correlation operation is performed with the spread spectrum code to determine the fault type and location;
  • the SSPLCR signal transmitted through the cable is sampled, and is synchronized with the locally generated PN code.
  • the synchronized received signal is despread and demodulated to restore the source signal and realize the high-speed data transmission of the power carrier.
  • the method for determining the transmission parameters of an incident signal in the time-frequency domain is as follows:
  • the frequency bandwidth of the operating voltage of the cable to be tested determine the minimum value of the spectrum starting value of the spreading code, and determine the frequency f 1 of the spreading code.
  • n of the spread spectrum code determines the order n of the spread spectrum code, and the maximum distance of the n-order spread spectrum code range is: where v is the transmission rate of the signal in the cable.
  • the n-order m sequence is selected as the spreading code, n ⁇ 5, the number of bits of the m sequence is 2 n -1, and the binary sequence S 1 of the detection signal is used, and the frequency is f 1 .
  • the binary sequence S 2 of the source signal carrying the power carrier information, and the frequency f 2 of the source signal is determined: it satisfies that the bit length of the binary sequence symbol of the source signal is a times the period length of the m sequence, that is,
  • the fault detection interval time t 10 should be k times of a(2 n-1 )/f 2. Considering the requirements for fault diagnosis frequency and interval time, k should be an integer not less than 10.
  • every k symbol insertion only contains
  • the binary sequence of 0 or 1 forms a new binary sequence S 3 of the source signal, and its frequency is f 2 , which is consistent with the binary sequence of the original source signal.
  • 2 Modulate the periodic spread spectrum signal obtained in the previous step, select BPSK as the modulation method, and modulate the frequency of the sine wave as f 1 , which is the same as the frequency of the m-sequence chip, and obtain the SSPLCR signal; this signal has the power line carrier communication function and the power line The ability to detect and locate faults, use it as a detection signal, perform digital-to-analog conversion, signal conditioning, and couple it into the power line for information transmission and fault diagnosis.
  • FIG. 3 is a schematic diagram of a method for generating an incident signal with a fault detection function carried by a spread spectrum carrier.
  • a 00 sequence is inserted as a detection sequence.
  • the reconstructed source signal is spread spectrum with m sequence.
  • the spread spectrum sequence is BPSK modulated with a sine wave.
  • the SSPLCR signal sampled by the receiving end and the locally generated PN code are synchronized as follows:
  • Step 1 create a local PN code generator at the receiving end to generate an m sequence, which is consistent with the frequency, series and primitive polynomial of the m sequence (that is, the detection signal binary sequence S 1 ) generated at the transmitting end;
  • Step 2 Use the sliding synchronization module to coarsely synchronize the received signal:
  • the product of the local PN code and the received signal is input into the integral decision subsystem, and the integral operation is carried out, and the integral value of the gained is compared with the set threshold value, and it is judged whether the two signals reach synchronization, and output the synchronization signal;
  • the phase search control module always controls the PN code generation module to adjust the chip phase according to the synchronization signal. If the output value of the integrator exceeds the threshold at a certain moment, it is regarded as successful acquisition;
  • Step 3 Use a digital delay-locked loop to finely synchronize the received signal.
  • the method for despreading and demodulating the synchronization signal at the receiving end is as follows:
  • Step 1 The synchronized local PN code is multiplied by the received signal, filtered by an intermediate frequency filter, the carrier frequency of the modulated signal is removed, and the fundamental frequency signal is retained.
  • Step 2 Make zero judgment on the output signal of the intermediate frequency filter, the output value is greater than 0 and judged as 1, otherwise it is judged as 0. Add a counting and judgment module to make 2 n -1 zero-crossing judgments in a chip period, where n is the number of stages of the local PN code; when the detected zero-crossing times are greater than or equal to 2 n-1 times, it is considered that in this The source signal is 1 in the chip period; otherwise, it is determined that the source signal is 0 in this chip period.
  • the method for fault diagnosis and location provided by the embodiment of the present invention is as follows:
  • the start time is the same as the start time of the SSPLCR signal transmission, and the fault detection period t 10 is used as the period to sample the fault reflection signal at the receiving end, and the sampling length is twice the chip period.
  • the correlation operation is performed to calculate the size of the primary reflected wave peak, and the obtained primary reflected wave peak size is sorted. Combined with the spectral energy value, a comprehensive analysis is performed to select the delay chip number k that can reflect the fault information and magnify the fault peak most obviously.
  • the SSPLCR system is simulated on the Matlab/Simulink platform.
  • Build the incident signal generation module, isolation coupling module, cable module, carrier signal despreading and demodulation module and fault information extraction module set the center frequency of the incident signal to 62.5MHz, and the frequency of the power carrier to 0.492MHz.
  • the power carrier information is extracted at 25m, and the open circuit fault is set at 30m.
  • Figure 5 shows a schematic diagram of the transmission waveforms of the transmitter and the receiver of the SSPLCR system when the carrier communication system works normally. As can be seen from the figure, due to the delay caused by the signal transmission in the cable, after a period of synchronization, the received signal is synchronized with the transmitted signal, and accurate transmission is achieved.
  • Figure 6 shows the comparison of the power line fault information curve obtained by the spread spectrum power carrier reflection method to achieve fault diagnosis and the traditional SSTDR method under the open circuit fault.
  • Both fault diagnosis methods can diagnose the type of fault, the fault location distance is 30.4m, and the relative error is 1.3%.
  • the spread spectrum power carrier reflection method can amplify the fault peak and reduce the difficulty of fault point identification to a certain extent.

Abstract

本发明公开一种通过扩频载波实现故障诊断的方法，步骤如下：设计入射信号参数，选取用于故障检测的扩频序列，确定扩频码的中心频率和序列长度，对电力载波信源信号分段和改造；以故障检测扩频序列作为载波扩频码，对改造后的电力载波信源信号进行扩频调制，生成SSPLCR序列；将SSPLCR序列耦合至待测线缆中，线缆正常工作未发生故障时，SSPLCR信号经线缆传输到达接收端；线缆故障时，SSPLCR信号发生反射返回发送端；在接收端对SSPLCR信号进行同步、解扩解调，恢复其携带的电力载波信息；在发送端提取SSPLCR故障反射信号，通过相关运算得到电缆故障类型和位置。该方法实现电能输送、数据传输、故障诊断一体化，提升了电能输送和通信系统的可靠性和可维护性。

Description

一种通过扩频载波实现故障诊断的方法 技术领域
本发明涉及一种基于扩频通信实现电力载波与故障检测定位结合的方法，属于载波通信技术领域。
背景技术
在航空航天系统中，为了保证系统的高可靠工作，需要对系统多个部位的状态参数进行采集，以进行电气、机载测控、飞行状态、大气数据和航电系统状态的检测和诊断。为实现对系统的检测和控制要求，需要对大量的传感器进行数据采集，并对大量的作动器进行控制，数据传输线的数量也相应增多。与此同时，航天系统的智能化，对发动机控制和运载管理系统的依赖程度不断增加，机载娱乐系统的丰富和客运服务系统的完善都对信息传输提出了高速、可靠的要求，不可避免的导致航空航天系统中电缆数量增多，重量增加，降低运载效率。为了解决这一现状，引入电力载波通信技术(Power Line Communication,PLC)，其最大特点是利用电力线路作为传输信息的通道，不需要额外铺设通信线路，在不影响供电质量的前提下，实现信息的高速传输。基于电力载波特性进行信息传输，可以降低建设成本，克服传统通信带来的通讯线数量大、分布交叉复杂、体积重量增大的缺陷，提升运载效率，从根本上减少了电缆的数量和重量，大大地降低通信成本，避免二次布线的施工困难。因此在汽车，飞机，宇宙飞船等领域得到了广泛地研究与应用。
在航空航天系统中，电力线工作环境复杂，受到长时间飞行引起的频繁振动的影响，与飞机结构等硬表面摩擦，破坏导线绝缘层；同时飞机内部导线会因为机龄，受水、辐射、高温、化学腐蚀等影响，以及在正常使用和维修期间所受的应力而损伤。电力线的老化、绝缘性下降会产生电弧和电磁辐射，慢慢地危及导体层，导致电力线发生断线、接地、短路等故障，中断了载波数据的传输，危及航电系统的正常工作。可能造成重要机载设备断电，对整个电源系统造成连锁反应和致命影响，甚至造成严重的生命财产损失。而飞机电缆布线的空间和线路非常有限，排除故障困难，修复时间长，例行维修会造成飞机停场，更换电线系统成本高昂。因此，降低飞机电线故障维修成本的关键在于对电线故障进行快速准确的故障识别和定位。
在各种关于故障检测和精确定位的方法中，扩展频谱时域反射法(Spread Spectrum Time Domain Reflectometry,SSTDR)采用了扩展频谱通信技术，简称扩频通信技术，利用伪随机码尖锐的自相关性，对故障进行识别和定位，其定位精度高，抗干扰能力强。同时由于伪随机码的中心频率高、频带宽，扩频信号对原有电源信号的影响小，因此可实现在线检测。
将扩频通信应用于电力载波，可以获得抗人为干扰、抗窄带干扰、抗多径干扰的能力。扩频通信通过将待传输信息信号的频谱用伪随机码调制，扩展频谱后成为宽频带信号，然后送入信道中传输；在接收端则用同样的码进行相关同步接收、解扩及恢复所传信息数据。通过增加信道带宽，即使在低信噪比的情况下，信道仍可以用相同的容量来可靠的传输信息。在信号被噪声淹没的情况下，只要相应的增加传输信号的带宽就能保持可靠的通信。
扩频通信技术用于测距时，如果扩展频谱很宽，则意味着所采用的扩频码速率很高，每个码片占用的时间就很短。当发射出去的扩频信号在被测量物体反射回来后，在接收端解调出扩频码序列，然后比较收发两个码序列相位之差，就可以精确测出扩频信号往返的时间差，从而算出两者之间的距离。码片越窄，扩展的频谱越宽，精度越高。
在Honeywell公司的专利U.S.Pat NO 7,868,621 B2，Liu et al.中介绍了一种方法，基于电力线载波的飞机配电系统采用PLC技术和SSTDR故障诊断方法来提供关键的维护功能。其主要贡献在于不同于传统的飞机配电系统只能对通电前的馈电导线部分进行检测定位，该发明可以实现实时在线故障检测定位。主要方法是将SSTDR故障检测装置添加至PLC调制解调器，通过PLC抽头点将SSTDR检测信号注入配电系统，以实现飞机配电系统电力线故障的在线检测定位。
但是该专利仍然存在以下几个方面的问题：
(1)将SSTDR故障检测模块添加至PLC系统的同时，增加了配电系统故障检测装置的体积、重量和成本；
(2)SSTDR故障检测系统通过PLC抽头点向电力线注入检测信号，载波通信信号与故障检测信号在信道中并存，两股载波信号存在部分频谱重叠，降低了各自的信噪比，相互干扰，使载波信号恢复困难，载波通信功能与故障检测功能同步受到影响。
发明内容
本发明的目的在于针对现有技术存在的缺陷和不足，提出一种通过扩频载波实现故障诊断的方法，即扩频电力载波反射法(Spread Spectrum Power Line Communication Reflectometry，SSPLCR)。该方法通过对电力载波的信源信号进行分段和改造，再用伪随机码对改造后的信源信号进行扩频，最后采用正弦波进行调制，生成能够实现故障检测和信息传输的SSPLCR信号，从根本上解决SSTDR故障检测和PLC系统两套设备并存带来的装置增加和信号串扰问题，减少了外接硬件检测设备，降低了硬件装置的体积、成本，实现硬件装置的小型化、低成本、低功耗设计。线缆故障时，在发射端对故障反射信号进行采样，对入射信号和故障反射信号进行同步，截取同步后的一周期入射信号和故障反射信号进行相关运算，判断故障 类型并计算故障距离；在接收端，通过数字延迟锁相环(Delay-Locked Loop，DLL)对载波接收信号进行精同步，然后通过相关运算进行解扩解调，恢复电力载波信源信号。
本发明所述一种通过扩频载波实现故障诊断的方法，其特征在于包括以下步骤：
第一步，确定故障检测扩频码的中心频率和序列长度，生成符合要求的m序列和正弦信号作为SSPLCR信号扩频码和SSPLCR信号调制码；
第二步，设定故障检测周期；
第三步，将携带载波信息的信源信号转换为二进制序列，依据设定的故障检测周期对信源信号二进制序列分段处理，自该二进制序列的起始位始至结束，在分段处插入相同的只包含0或1的二进制序列，形成新的信源信号二进制序列；
第四步，用已生成的m序列和正弦波对新的信源信号二进制序列进行周期性扩频和调制，生成SSPLCR信号；
第五步，线缆正常工作时，在接收端采样经过线缆传输的SSPLCR信号，与本地生成的PN码做同步处理，经过解扩解调恢复其携带的电力载波信息，实现数据传输；线缆故障时，在发送端采样SSPLCR故障反射信号，与入射信号做同步处理，对SSPLCR故障反射信号进行相位调整与优选，再与入射信号做相关运算和归一化处理，判定电缆故障类型和位置。
进一步，第一步中确定SSPLCR扩频码的中心频率和序列长度的方法，包括：
根据待测电缆的运行电压的频带宽度，确定扩频码频谱起始值的最小值，因此可以得到扩频码的频率f 1；根据待测电缆的长度，确定扩频码的阶数n，n阶扩频码测距的最大距离为
Figure PCTCN2021124646-appb-000001
其中v是信号在线缆中的传输速率。
进一步，第二步中设定故障检测时间间隙的方法，包括：
在第一步中确定并选取了n阶m序列作为扩频码，n≥5，m序列位数为2 n-1，作为扩频检测序列S 1，频率为f 1；携带电力载波信息的信源序列S 2，频率为f 2。满足信源信号码元位长是m序列周期长的a倍，即
Figure PCTCN2021124646-appb-000002
每隔时间t 10，做一次故障检测，在接收端进行一次故障诊断，故障检测间隔时间t 10大小应为a(2 n-1)/f 2的k倍，综合考虑对故障诊断频率的要求和间隔时间的要求，k应取不小于10的整数，设定故障检测时间间隔t 10。
进一步，第三步中形成新的信源信号二进制序列S 3的方法，包括：
由第二步中确定的故障检测间隔时间t 10大小，即信源信号二进制序列S 2一个码元时长的k倍，自该二进制信源序列的起始位始至结束，每隔k个码元插入只包含0或1的二进制序 列，形成新的信源信号二进制序列S 3，其频率为f 2，与原信源二进制序列保持一致。
进一步，第四步中形成SSPLCR信号的方法，包括：
步骤1：将第一步中生成的m序列作为扩频码，对新的信源信号二进制序列进行周期性扩频处理；
步骤2：对步骤1得到的周期性扩频信号进行调制处理，调制方式选取BPSK，调制正弦波的频率为f 1，与m序列码片频率相同，调制后得到SSPLCR信号；该信号具备电力线载波通信功能和电力线故障检测定位的能力，将其作为检测信号，进行数模转换、信号调理并耦合入电力线进行信息的传输及故障诊断；
进一步，第五步中接收端采样的SSPLCR信号与本地生成的PN码做同步处理的方法，包括：
步骤1：在接收端创建本地PN码发生器，产生m序列，与发射端产生的m序列频率、级数以及本原多项式一致；
步骤2：使用滑动同步模块对接收信号进行粗同步：将本地PN码与接收信号的乘积输入积分判决子系统，进行积分运算，所得的积分值与设定阈值进行比较，判断两信号是否达到同步，输出同步信号；在此过程中相位搜索控制模块始终根据同步信号，控制PN码生成模块进行码片相位的调整，若积分器在某一刻的输出值超过阈值，则视为捕获成功；
步骤3：使用数字延迟锁相环对接收信号进行精同步。
进一步，第五步中接收端同步信号解扩解调的方法，包括：
步骤1：同步过后的本地PN码与接收信号相乘，经过中频滤波器滤波，去掉调制信号的载频，保留基频信号。
步骤2：对中频滤波器的输出信号做过零判断，输出数值大于0判定为1，反之判定为0。加入计数判决模块，在一个码片周期内做2 n-1次过零判断，其中n为本地PN码的级数；当检测到的过零次数大于等于2 n-1次时，认为在这个码片周期内信源信号为1；反之，判定在这个码片周期内信源信号为0。
进一步，第五步中判定线缆故障类型和位置的方法，包括：
步骤1：起始时刻与SSPLCR信号发送起始时间相同，以故障检测时间间隔t 10为周期，对接收端的故障反射信号采样，采样长度为码片周期的两倍。
步骤2：对采样得到的故障信号与发送的SSPLCR序列进行相位校准。对采样信号，从0码片、1码片...n码片时刻开始，进行截取，截取采样点的时长为1码片周期长度；将截取到的采样信号分别与1周期扩频码进行相关运算并计算一次反射波峰的大小，对得到的一次反射波峰值大小进行排序，结合频谱能量值进行综合分析，选出能够反映故障信息并对故障波 峰放大最明显的延迟码片数m。
步骤3：从m码片时刻开始，对采样得到的故障信号，截取1码片周期长度的采样信号，与1周期扩频码进行相关性运算并进行归一化处理，提取故障波峰，判断故障类型并定位故障距离。
本发明的有益效果是：
1、该方法首先对信源信号进行改造，插入特定检测序列码，能够实现在长序列数据传输过程中，以一定的周期对入射和反射序列的采样，相比于SSTDR系统在注入检测扩频码同时对反射信号采样，改造后的信源信号在包含电力载波信息的基础上，同时保证了故障检测的效率和频率。同时，由于在信源信号中插入特定码片，规避了随机变化的信源信号由于相位的不断变化，导致扩频调制后的入射序列自相关互相关特性改变，对故障检测的相关运算造成的不利影响。
2、该方法生成能够同时实现电力载波与故障检测定位的SSPLCR入射信号，避免了传统方法中为了同时实现电力载波通信和故障检测，将两股信号同时注入线缆中，由于频谱重叠而互相干扰导致的无法恢复信源信息的问题。同时该方法将电力载波通信功能和故障检测功能有机结合，无需通过故障诊断装置和电力载波装置分别实现两种功能，减少了装置的体积、重量和成本，能够实现硬件装置的小型化、低成本、低功耗设计，可有效提升电力输送和通信系统的可靠性和可维护性，有利于市场推广。
3、该方法在恢复和提取载波信号时，提出将数字延迟锁相环应用于扩频电力载波解扩中，结合滑动同步捕获模块，对本地同步PN码与接收信号进行同步，实现同步误差缩小至0.1码片以内。解决了信号在线缆传输过程中产生的小数倍延时问题，提高了电力载波的准确率。
4、该方法在确定故障类型、定位故障距离中提出相位校准法，解决了采样多周期故障反射扩频载波信号与入射扩频载波信号做相关运算进行故障检测出现多个波峰的问题，通过算法选取最终与扩频码进行相关运算的一个周期反射信号，对比传统方法中使用单周期采样反射信号与扩频码进行相关运算，能够实现放大故障波峰，增大了故障最长检测距离。对比传统的SSTDR系统，SSPLCR系统能够在携带电力载波信息的同时，实现同样性能的故障检测功能。
本发明的技术方案可广泛应用于飞机、船舶、电动汽车的低压和高压电力系统。
附图说明
图1是本发明所述扩频电力载波SSPLCR方法的流程图；
图2是本发明所述扩频电力载波SSPLCR方法的原理框图；
图3是SSPLCR入射信号生成方法示意图；
图4是接收端扩频信号相位调整方法的流程图；
图5是SSPLCR系统发射端与接收端信源数据传输波形。
图6是SSPLCR方法实现故障诊断与SSTDR方法得到的电力线故障信息曲线的对比图；
具体实施方式
下面结合附图详细介绍本发明所涉及的一些关键技术，以支持权利要求部分。
如图1所示，本发明实施例提供的通过扩频载波实现故障诊断的方法包括以下步骤：
S101、确定SSPLCR信号的传输参数，对电力载波信源信号分段和改造。
S102、以故障检测序列作为扩频码,对改造后的电力载波信源信号进行扩频与调制，生成能够同时满足电力载波与故障检测定位要求的SSPLCR序列。
S103、将该SSPLCR扩频序列耦合至待测线缆中，线缆正常工作未发生故障时，该信号经线缆传输到达接收端；线缆故障时，由于故障点阻抗发生变化，扩频信号发生反射返回接收端。
S104、在接收端对扩频载波信号进行同步、解扩解调，恢复其携带的信息。
S105、在发送端提取故障反射信号，通过相关运算得到电缆故障类型和位置。该方法实现电能输送、数据传输、故障诊断一体化，提升了电能输送和通信系统的可靠性和可维护性。
本发明实施例中提供的通过扩频载波实现故障诊断的方法，其实现原理如图2所示：
在信号发射端，根据待测电缆的物理特性，确定时频域入射信号的传输参数，确定扩频码的中心频率和级数。根据故障检测的时效性的要求，确定故障检测的间隔时间，对信源序列进行分段和改造。对新的信源码进行扩频和调制，生成具有电力载波和故障检测功能的SSPLCR入射信号。对该时频域入射信号进行数模转换后注入电缆，并在发射端设置采样模块，当线缆发生故障时，在故障点产生阻抗不匹配，入射信号在故障点发生反射。在发射端对反射信号进行采样，对采样到的反射信号做相位调整，与扩频码进行相关运算判定故障类型和位置；
在信号接收端，对经过线缆传输的SSPLCR信号进行采样，与本地生成PN码做同步处理，同步后的接收信号经过解扩解调，恢复信源信号，实现电力载波高速数据传输。
下面结合具体实施例对本发明作进一步描述。
作为优选实施例，本发明实施例提供的确定时频域入射信号的传输参数的方法如下：
根据待测电缆运行电压的频带宽度，确定扩频码频谱起始值的最小值，确定扩频码的频率f 1。
根据待测电缆的长度，确定扩频码的阶数n，n阶扩频码测距的最大距离为
Figure PCTCN2021124646-appb-000003
其中v是信号在线缆中的传输速率。
选取n阶m序列作为扩频码，n≥5，该m序列位数为2 n-1，作为检测信号二进制序列S 1，频率为f 1。
本发明实施例提供的对电力载波信源信号分段和改造的方法如下：
1)携带电力载波信息的信源信号二进制序列S 2，确定信源信号频率f 2：满足信源信号二进制序列码元位长是m序列周期长的a倍，即
Figure PCTCN2021124646-appb-000004
2)设定故障检测周期t 10，每隔时间间隔t 10，做一次故障检测，在接收端进行一次故障诊断。故障检测间隔时间t 10大小应为a(2 n-1)/f 2的k倍，综合考虑对故障诊断频率的要求和间隔时间的要求，k应取不小于10的整数。
3)根据故障检测间隔时间t 10大小，即信源信号二进制序列S 2一个码元时长的k倍,自该二进制信源序列的起始位始至结束，每隔k个码元插入只包含0或1的二进制序列，形成新的信源信号二进制序列S 3，其频率为f 2，与原信源信号二进制序列保持一致。
本发明实施例提供的生成时SSPLCR入射信号的方法如下：
①以检测信号二进制序列S 1为扩频码，对新生成的信源信号二进制序列S 3进行周期性扩频处理。
②对上一步得到的周期性扩频信号进行调制处理，调制方式选取BPSK，调制正弦波的频率为f 1，与m序列码片频率相同，得到SSPLCR信号；该信号具备电力线载波通信功能和电力线故障检测定位的能力，将其作为检测信号，进行数模转换、信号调理并耦合入电力线进行信息的传输及故障诊断。
图3为扩频载波携带故障检测功能的入射信号生成方法示意图，首先，在信源序列中，每隔十个字节，插入一个00序列作为检测序列。其次，用m序列对改造后的信源信号进行扩频。最后，对扩频后的序列用正弦波进行BPSK调制。
作为优选实施例，本发明实施例中接收端采样的SSPLCR信号与本地生成的PN码做同步处理的方法如下：
步骤1：在接收端创建本地PN码发生器，产生m序列，与发射端产生的m序列(即检测信号二进制序列S 1)的频率、级数以及本原多项式一致；
步骤2：使用滑动同步模块对接收信号进行粗同步：
将本地PN码与接收信号的乘积输入积分判决子系统，进行积分运算，所得的积分值与 设定阈值进行比较，判断两信号是否达到同步，输出同步信号；
在此过程中相位搜索控制模块始终根据同步信号，控制PN码生成模块进行码片相位的调整，若积分器在某一刻的输出值超过阈值，则视为捕获成功；
步骤3：使用数字延迟锁相环对接收信号进行精同步。
作为优选实施例，本发明实施例提供的接收端同步信号解扩解调的方法如下：
步骤1：同步过后的本地PN码与接收信号相乘，经过中频滤波器滤波，去掉调制信号的载频，保留基频信号。
步骤2：对中频滤波器的输出信号做过零判断，输出数值大于0判定为1，反之判定为0。加入计数判决模块，在一个码片周期内做2 n-1次过零判断，其中n为本地PN码的级数；当检测到的过零次数大于等于2 n-1次时，认为在这个码片周期内信源信号为1；反之，判定在这个码片周期内信源信号为0。
如图4所示，作为优选实施例，本发明实施例提供的故障诊断和定位的方法如下：
ⅰ.起始时刻与SSPLCR信号发送起始时间相同，以故障检测周期t 10为周期，对接收端的故障反射信号采样，采样长度为码片周期的两倍。
ⅱ.对采样得到的故障信号与发送的SSPLCR序列进行相位校准。
对采样信号，从0码片、1码片...n码片时刻开始，进行截取，截取采样点的时长为1码片周期长度；将截取到的采样信号分别与1周期扩频码进行相关运算并计算一次反射波峰的大小，对得到的一次反射波峰值大小进行排序，结合频谱能量值进行综合分析，选出能够反映故障信息并对故障波峰放大最明显的延迟码片数k。
ⅲ.从k码片时刻开始，对采样得到的故障信号，截取1码片周期长度的采样信号，与1周期扩频码进行相关性运算并进行归一化处理，提取故障波峰，判断故障类型并定位故障距离。
本实施例中，在Matlab/Simulink平台对SSPLCR系统进行仿真。搭建入射信号生成模块、隔离耦合模块、电缆模块、载波信号解扩解调模块以及故障信息提取模块，设置入射信号的中心频率62.5MHz，电力载波的频率为0.492MHz，在电缆模块中设置其在25m处提取电力载波信息，在30m处设置开路故障。
图5所示为载波通信系统正常工作时，SSPLCR系统的发射端与接收端传输波形示意图。从图中可以看出，由于信号在线缆中传输导致延时，经过一段时间的同步后，接收信号与发送信号同步，实现了准确传输。
图6所示为开路故障下，扩频电力载波反射法实现故障诊断与传统SSTDR方法得到的电力线故障信息曲线的对比图。两种故障诊断方法都能诊断故障类型，定位故障距离30.4m， 相对误差为1.3％。扩频电力载波反射法相比传统SSTDR方法，能够放大故障波峰，一定程度上降低了故障点识别的难度。
综上所述，尽管本发明的基本结构、原理、方法通过上述实施例予以具体阐述，在不脱离本发明要旨的前提下，根据以上所述的启发，本领域普通技术人员可以不需要付出创造性劳动即可实施变换/替代形式或组合均落入本发明保护范围。

Claims (7)

  1. 一种通过扩频载波实现故障诊断的方法，其特征在于包括以下步骤：
    第一步，确定故障检测扩频码的中心频率和序列长度，生成符合要求的m序列和正弦信号作为SSPLCR信号扩频码和SSPLCR信号调制码；
    第二步，设定故障检测周期；
    第三步，将携带载波信息的信源信号转换为二进制序列，依据设定的故障检测周期对信源信号二进制序列分段处理，自该二进制序列的起始位始至结束，在分段处插入相同的只包含0或1的二进制序列，形成新的信源信号二进制序列；
    第四步，用已生成的m序列和正弦波对新的信源信号二进制序列进行周期性扩频和调制，生成SSPLCR信号；
    第五步，线缆正常工作时，在接收端采样经过线缆传输的SSPLCR信号，与本地生成的PN码做同步处理，经过解扩解调恢复其携带的电力载波信息，实现数据传输；线缆故障时，在发送端采样SSPLCR故障反射信号，与入射信号做同步处理，对SSPLCR故障反射信号进行相位调整与优选，再与入射信号做相关运算和归一化处理，判定电缆故障类型和位置。
  2. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于第二步中设定故障检测时间间隔的方法如下：
    综合考虑对故障诊断频率的要求和间隔时间的要求设定故障检测周期，故障检测周期时长为信源信号二进制序列一个码元时长的k倍，k取不小于10的整数。
  3. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于新的信源信号二进制序列频率与原信源信号二进制序列保持一致。
  4. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于第四步中生成SSPLCR信号的方法，包括：
    步骤1：将第一步中生成的m序列作为扩频码，对新的信源信号二进制序列进行周期性扩频处理；
    步骤2：对步骤1得到的周期性扩频信号进行调制处理，调制方式选取BPSK，调制正弦波的频率与m序列码片频率相同，调制后得到SSPLCR信号；该信号具备电力线载波通信功能和电力线故障检测定位的能力，将其作为检测信号，进行数模转换、信号调理并耦合入电力线进行信息的传输及故障诊断。
  5. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于第五步中接收端采样的SSPLCR信号与本地生成的PN码做同步处理的方法，包括：
    步骤1：在接收端创建本地PN码发生器，产生m序列，与发射端产生的m序列频率、 级数以及本原多项式一致；
    步骤2：使用滑动同步模块对接收信号进行粗同步：将本地PN码与接收信号的乘积输入积分判决子系统，进行积分运算，所得的积分值与设定阈值进行比较，判断两信号是否达到同步，输出同步信号；在此过程中相位搜索控制模块始终根据同步信号，控制PN码生成模块进行码片相位的调整，若积分器在某一刻的输出值超过阈值，则视为捕获成功；
    步骤3：使用数字延迟锁相环对接收信号进行精同步。
  6. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于第五步中接收端同步信号解扩解调的方法，包括：
    步骤1：同步过后的本地PN码与接收信号相乘，经过中频滤波器滤波，去掉调制信号的载频，保留基频信号；
    步骤2：对中频滤波器的输出信号做过零判断，输出数值大于0判定为1，反之判定为0；加入计数判决模块，在一个码片周期内做2 n-1次过零判断，其中n为本地PN码的级数；当检测到的过零次数大于等于2 n-1次时，认为在这个码片周期内信源信号为1；反之，判定在这个码片周期内信源信号为0。
  7. 如权利要求1所述的基于扩频通信实现电力载波与故障检测定位结合的方法，其特征在于第五步中判定线缆故障类型和位置的方法，包括：
    步骤1：起始时刻与SSPLCR信号发送起始时间相同，按照设定的故障检测周期对接收端的故障反射信号采样，采样长度为码片周期的两倍；
    步骤2：对采样得到的故障信号与发送的SSPLCR序列进行相位校准；对采样信号，从0码片、1码片...n码片时刻开始，进行截取，截取采样点的时长为1码片周期长度；将截取到的采样信号分别与1周期扩频码进行相关运算并计算一次反射波峰的大小，对得到的一次反射波峰值大小进行排序，结合频谱能量值进行综合分析，选出能够反映故障信息并对故障波峰放大最明显的延迟码片数m；
    步骤3：从第m码片时刻开始，对采样得到的故障信号，截取1码片周期长度的采样信号，与1周期扩频码进行相关性运算并进行归一化处理，提取故障波峰，判断故障类型并定位故障距离。
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