WO2017000708A1

WO2017000708A1 - Cross-band power line frequency recognition method based on fine frequency granularity

Info

Publication number: WO2017000708A1
Application number: PCT/CN2016/083092
Authority: WO
Inventors: 陆阳; 刘伟麟; 李建岐; 安春燕; 高鸿坚; 赵涛; 褚广斌
Original assignee: 全球能源互联网研究院; 国网河北省电力公司; 国家电网公司
Priority date: 2015-06-29
Filing date: 2016-05-24
Publication date: 2017-01-05
Also published as: CN104954112A; CN104954112B

Abstract

The present invention relates to a cross-band power line frequency recognition method based on a fine frequency granularity, comprising: establishing a power line communication (PLC) system model; dividing an operating frequency into a low frequency, an intermediate frequency and a high frequency, and acquiring, according to fine frequency granularity features, a low-frequency fine frequency granularity subband, an intermediate-frequency fine frequency granularity subband and a high-frequency fine frequency granularity subband; measuring power line channel noise of a master station and a slave station; calculating power line channel attenuation of an uplink and a downlink; calculating a link quality indicator (LQI) of the uplink and the downlink; and setting an LQI threshold, acquiring an available fine frequency granularity subband, and performing spectrum aggregation on the available fine frequency granularity subband. The present invention can perform recognition of a fine frequency granularity respectively on different bands of low frequency, intermediate frequency and high frequency by cross-band expansion of PLC frequency resources, so that the PLC can adequately search for a communication frequency and establish a stable communication link under extremely adverse channel conditions.

Description

Cross-band power line carrier frequency cognition method based on fine frequency granularity

Technical field

The present invention relates to the field of power communications, and in particular to a cross-band power line carrier frequency cognition method based on fine frequency granularity.

Background technique

Power Line Communication (PLC) technology is a communication method that uses power lines as a communication medium to transmit data information. Conventional power line communication technology loads modulated high-frequency carrier signals on existing power lines. Communication, therefore, power line communication is commonly referred to as power line carrier communication. According to the voltage level of the carrier communication line, the PLC technology generally includes: a high-voltage power line carrier communication using a high-voltage transmission line of a voltage level of 35 kV and above as a communication medium, and a medium-voltage power line carrier communication using a medium-voltage transmission line of a voltage level of 10 kV as a communication medium. And low-voltage power line carrier communication using a low-voltage transmission line of 380/220V voltage level as a communication medium.

At present, conventional PLC technologies for smart grid applications operate in a pre-specified frequency range, typically 30-500 kHz for narrowband PLCs and 2-30 MHz for wideband PLCs. The traditional narrow-band PLC is easy to implement, but the transmission rate is low and the anti-interference ability is weak; the broadband PLC has a high transmission rate and can carry many services, but often the single-hop communication distance is limited. In fact, power line channel characteristics such as noise and attenuation have significant frequency selectivity characteristics, and are affected by factors such as grid topology, line characteristics and load characteristics, showing geographically relevant differences and unpredictability. The practical application shows that the PLC adopts a single working frequency, which is difficult to achieve full coverage under different channel conditions and application scenarios, which is easy to cause communication blind spots, and its link stability cannot meet the communication requirements of the smart grid service.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides a cross-band power line carrier frequency cognition method based on fine frequency granularity, and performs different frequency bands such as low frequency, intermediate frequency, and high frequency by expanding the cross-band of the PLC communication frequency resource. The recognition of fine frequency granularity enables PLC to fully search for communicable frequencies and establish stable communication links under extremely harsh channel conditions, improving the ability of PLC to flexibly cope with differentiated power line channel environments, and adapting to the future of PLC technology. The direction of development.

The object of the present invention is achieved by the following technical solutions:

A cross-band power line carrier frequency cognition method based on fine frequency granularity, which is improved in that it comprises:

(1) constructing a power line carrier communication system model consisting of a primary station, a secondary station, an uplink, and a downlink;

(2) Dividing the operating frequency into low frequency, intermediate frequency and high frequency;

(3) According to the fine frequency granularity characteristics of low frequency, intermediate frequency and high frequency, the bandwidths of low frequency, intermediate frequency and high frequency are respectively divided in overlapping or non-overlapping manner;

(4) obtaining a low frequency fine frequency granularity subband, an intermediate frequency fine frequency granularity subband, and a high frequency fine frequency granularity subband;

(5) measuring the power line channel noise of the primary station and the secondary station at the current time and the operating frequency, respectively;

(6) calculating the power line channel attenuation of the uplink and the power line channel attenuation of the downlink at the current time and the operating frequency, respectively;

(7) respectively calculating the link quality indication LQI of the uplink and the downlink at the current time and the operating frequency;

(8) setting a link quality indication threshold value, and obtaining a link quality indicator LQI of the uplink and the downlink corresponding to all frequency points of the current time and the fine frequency granularity subband is smaller than the link The quality indicates a threshold frequency of available fine frequency granularity subbands and spectrally aggregates the available fine frequency granularity subbands.

Preferably, in the step (1), the primary station is a PLC device in the PLC system, the secondary station is a PLC device adjacent to the primary station, and the uplink is the slave station to the primary station. The link in the direction, the downlink is the link from the primary station to the secondary station.

Preferably, in the step (2), the low frequency frequency is 30 kHz to 500 kHz, the intermediate frequency frequency is 500 kHz to 1.6 MHz, and the high frequency frequency is 1.6 MHz to 30 MHz.

Preferably, in the step (3), the fine frequency granularity characteristics of the low frequency, the intermediate frequency and the high frequency comprise: the low frequency fine frequency granularity characteristic is a low frequency fine frequency granularity subband width of 1 kHz to 10 kHz, the intermediate frequency fine frequency The granularity is characterized by an intermediate frequency fine frequency granularity sub-band width of 10 kHz to 100 kHz, and a high frequency fine frequency granularity characteristic of a high frequency fine frequency granularity sub-band width of 100 kHz to 1 MHz.

Preferably, in the step (5), the power line channel noise of the primary station and the secondary station at the current time and the operating frequency are respectively measured, including:

The measurement resolution bandwidth is from 1 kHz to 30 kHz, and the power line channel noise formula of the primary station and the secondary station at the current time and the operating frequency is:

In equation (1-1), Noise _ave (t) is the average value of the noise measurement results measured N times at time t, N ∈ (1, 10), and Noise _ave (t-1) is t-1 time N- The average value of the noise measurement results obtained from one measurement, and Noise _meas (t) is the noise power measured at time t.

Preferably, in the step (6), calculating the power line channel attenuation of the downlink at the current time and the operating frequency, including: using the primary station as a transmitting end, the secondary station as a receiving end, the sending The terminal sends the frequency sweep signal to the receiving end; The power line channel attenuation of the downlink is the strength of the swept signal sent by the transmitting end minus the signal strength received by the receiving end.

Preferably, in the step (6), calculating the power line channel attenuation of the uplink at the current time and the operating frequency, including: using the slave station as a transmitting end, the master station as a receiving end, the sending The terminal sends the frequency sweep signal to the receiving end; the power line channel attenuation of the uplink is the strength of the frequency sweep signal sent by the transmitting end minus the signal strength received by the receiving end.

Preferably, in the step (7), the link quality indication LQI of the uplink and the downlink in the current time and the working frequency are respectively calculated, including:

The link quality indication of the uplink is LQI = power line channel noise of the primary station + power line channel attenuation of the uplink;

The link quality indicator for the downlink is LQI = power line channel noise of the slave + power line channel attenuation of the downlink.

Preferably, in the step (8), the link quality indication threshold is: a minimum value of the link quality indicator LQI of the uplink and the downlink in the current time and the operating frequency. Add 5-15dB.

Preferably, in the step (8), spectrum aggregation is performed on the available fine frequency granularity subband, including:

Performing intra-band spectral aggregation on the available fine frequency granularity sub-bands in the low frequency fine frequency granularity subband, the intermediate frequency fine frequency granularity subband, and the high frequency fine frequency granularity subband, respectively;

Performing cross-band spectrum aggregation on the low frequency fine frequency granularity subband and the available fine frequency granularity subband in the intermediate frequency fine frequency granularity subband;

Performing cross-band spectral aggregation on the intermediate frequency fine frequency granularity subband and the available fine frequency granularity subband in the high frequency fine frequency granularity subband.

The beneficial effects of the invention:

(1) A cross-band power line carrier frequency cognition method based on fine frequency granularity proposed by the present invention can extend the selection range of PLC operating frequency to a cross-band from tens of kilohertz to several tens of megahertz, covering The low frequency, intermediate frequency and high frequency bands break the narrowing of the traditional PLC operating frequency and the division of the broadband, which improves the frequency utilization and flexibility of selection.

(2) Different frequency bands such as low frequency, intermediate frequency and high frequency are respectively divided into sub-bands that satisfy the characteristics of fine frequency granularity, which realizes finer frequency cognition, so that PLC communication can be guaranteed under extremely severe channel conditions. Access.

(3) Based on the measurement of power line channel noise and attenuation by PLC main station and slave station, link quality indication LQI is introduced as an important parameter indicator of power line carrier frequency cognition, which can objectively reflect channel quality at different frequencies. The principle is simple and easy to implement.

(4) Multi-band parallel transmission is realized by aggregating the available fine frequency granularity sub-bands satisfying the link quality indication LQI threshold, thereby improving the support capability of the PLC for the smart grid service.

(5) Considering the two-way asymmetry of the power line channel, it supports the selection of an appropriate working frequency for the slave station to the primary station uplink and the primary station to the secondary station downlink.

(6) It can be further extended to the scenario of multiple PLC node networking. By selecting the appropriate working frequency for each link, multi-frequency networking can be realized, which effectively improves the coverage performance of the PLC network.

DRAWINGS

1 is a flow chart of a cross-band power line carrier frequency cognition method based on fine frequency granularity according to the present invention;

2 is a schematic structural diagram of a power line carrier communication system;

3 is a schematic diagram of a power line carrier communication system model;

4 is a schematic diagram of a cross-band PLC operating frequency selection range;

5 is a schematic diagram showing the results of sub-bands of fine frequency granularity that satisfy the characteristics of fine frequency granularity without overlapping each other;

Figure 6 is a schematic diagram showing the result of measuring local channel noise;

Figure 7 is a schematic diagram showing measurement channel attenuation results;

8 is a schematic diagram of calculating a link quality indication LQI result;

9 is a schematic diagram of obtaining a sub-band of available fine frequency granularity according to an LQI threshold;

10 is a schematic diagram of spectrum aggregation of available fine frequency granularity sub-bands;

11 is a schematic flow chart of an implementation process of a cross-band power line carrier frequency cognition method based on fine frequency granularity according to the present invention.

detailed description

The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The invention provides a cross-band power line carrier frequency cognition method based on fine frequency granularity, as shown in FIG. 1 , comprising:

Among them, the main station is a PLC device in the PLC system, and the slave station is a PLC device adjacent to the main station, uplink The way is the link from the slave station to the direction of the primary station, and the downlink is the link from the primary station to the secondary station.

For example, as shown in FIG. 2, the power line carrier communication system is composed of a power line carrier communication device and a power line channel. The power line carrier communication device is responsible for the coupling and extraction of the high frequency carrier signal on the power line. The power line channel is a power network composed of a plurality of power lines and various power facilities and electrical equipment, although the actual PLC network structure is relatively complicated, but the phase The neighboring two PLC devices can be regarded as a point-to-point topology, and one of the PLC devices is the master station, and the other PLC device is the slave station. The primary station and the secondary station are connected by a power line channel, and the link from the primary station to the secondary station is called the downlink, and the link from the secondary station to the primary station is called the uplink.

As shown in FIG. 3, the high frequency carrier signal transmitted by the PLC device connected to the power line network is transmitted through the power line channel. The signal will be attenuated when transmitted on the power line channel. At the same time, various noise and interference signals in the power grid will be superimposed on the carrier signal, and the space short-wave radio signal will also be coupled to the asymmetric power line to form narrow-band interference. All of these noises and attenuations are frequency selective and closely related to the topology, line characteristics, load characteristics and other factors of the power grid at different locations, which affects the performance of the PLC system in the traditional fixed operating frequency mode.

Wherein, the low frequency frequency is 30 kHz to 500 kHz, the intermediate frequency frequency is 500 kHz to 1.6 MHz, and the high frequency frequency is 1.6 MHz to 30 MHz.

Extending the selection range of PLC operating frequency to cross-band from tens of kilohertz to tens of megahertz, covering different frequency bands such as low frequency, intermediate frequency and high frequency, thus breaking the traditional PLC narrowband and wideband frequency division, improving the available Communication frequency resource utilization, and flexibility in frequency selection;

For example, as shown in Figure 4, the cross-band PLC operating frequency selection range from 150 kHz to 11.6 MHz covers the low frequency band from 150 kHz to 500 kHz, the IF band from 500 kHz to 1.6 MHz, and the high frequency band from 1.6 MHz to 11.6 MHz. .

Wherein the low frequency, intermediate frequency and high frequency fine frequency granularity characteristics include: low frequency fine frequency granularity characteristic is low frequency fine frequency granularity sub-band width is 1 kHz to 10 kHz, medium frequency fine frequency granularity characteristic is intermediate frequency fine frequency granularity The sub-band width is 10 kHz to 100 kHz, and the high-frequency fine-frequency granularity is characterized by a high-frequency fine-frequency granularity sub-band width of 100 kHz to 1 MHz.

Considering the differences in bandwidth, channel characteristics, and applicable environment of the low-frequency, intermediate-frequency, and high-frequency bands of the power line channel, different frequency bands such as low-frequency, intermediate-frequency, and high-frequency are respectively divided into sub-bands that satisfy fine-frequency granularity characteristics, wherein The divided sub-bands may overlap each other or may not overlap each other;

For example, as shown in FIG. 5, a low frequency band of 350 kHz to 500 kHz with a total bandwidth of 350 kHz is divided into a low frequency fine frequency granularity sub-band width of 10 kHz with a total of 35 low frequency fine frequency granular sub-bands; The intermediate frequency band with a total bandwidth of 1.1 MHz of 1.6 MHz is divided into 55 kHz as the intermediate frequency fine frequency granularity sub-band width, and a total of 20 intermediate frequency fine frequency granular sub-bands; a total of 10 MHz bandwidth from 1.6 MHz to 11.6 MHz The high-frequency frequency bands are divided into sub-band widths of 500 kHz as high-frequency fine-frequency granularity without overlapping, and a total of 20 high-frequency fine-frequency granularity sub-bands.

Specifically, the power line channel noise of the primary station and the secondary station at the current time and the operating frequency are respectively measured, including:

In equation (1-1), Noise _ave (t) is the average value of the noise measurement results measured N times at time t, N is the number of measurements, N ∈ (1, 10), and Noise _ave (t-1) is t -1 The average value of the noise measurement results measured at N-1 times, and Noise _meas (t) is the noise power measured at time t.

For example, the primary station and the secondary station measure the local channel noise of low frequency (150-500 kHz), intermediate frequency (500 kHz-1.6 MHz) and high frequency (1.6-11.6 MHz) according to the order from low frequency to high frequency, according to the formula. (1-1) With 10 kHz Resolution Band-Width (RBW), and using multiple measurements to average the method to improve the accuracy of the measurement results, PLC slave noise measurement results shown in Figure 6;

The calculating the downlink power line channel attenuation at the current time and the working frequency includes: using the primary station as a transmitting end, the secondary station serving as a receiving end, and the sending end sending the frequency sweeping signal to the receiving end The power line channel attenuation of the downlink is the strength of the swept signal sent by the transmitting end minus the signal strength received by the receiving end.

Calculating the power line channel attenuation of the uplink in the current time and the working frequency, comprising: using the slave station as a transmitting end, the primary station as a receiving end, and the sending end sending the frequency sweeping signal to the receiving end; The power line channel attenuation of the uplink is the strength of the swept signal sent by the transmitting end minus the signal strength received by the receiving end.

Considering the asymmetry between the downlink of the master station and the downlink of the slave station and the uplink of the slave station, the two-way channel attenuation is measured. The channel attenuation measurement result is obtained by the method of averaging multiple measurements, and the PLC master station to the slave station is down. Link channel attenuation measurement The result is shown in Figure 7;

The link quality indication LQI of the uplink and the downlink in the current time and the working frequency are respectively calculated, including:

Further, the link quality indicator LQI indicates the transmit signal power required by the transmitting end at the frequency when the receiving end reaches a 0 dB signal to noise ratio according to the current resolution bandwidth at a certain frequency. The smaller the LQI is, the better the channel quality is at this frequency, and the LQI is independent of the transmitted signal power of the transmitting end. It can objectively reflect the power line carrier channel quality at different frequencies, and is an important parameter indicator for realizing the power line carrier frequency awareness. At the same time, the signal-to-noise ratio of the receiving end can be obtained by subtracting the LQI from the actual transmitted signal power of the transmitting end at the frequency, as shown in FIG. 8;

The link quality indication threshold is: a minimum value of the link quality indicator LQI of the uplink and the downlink at the current time and the operating frequency plus 5-15 dB.

For the uplink LQI of the uplink station, the secondary station sets an appropriate LQI threshold for the LQI of the downlink, and selects the fine frequency granularity of the uplink and downlink respectively according to whether the LQI threshold is satisfied. Subband, if the LQI of all frequency points in a subband is less than the LQI threshold, the subband is the preferred fine frequency granularity available subband. Calculating the LQI of the downlink according to the power line channel noise and attenuation measurement results of FIG. 6 and FIG. 7, and obtaining the available fine frequency granularity sub-band according to the LQI threshold, as shown in FIG. 9;

The primary station and the secondary station respectively aggregate the preferred fine frequency granularity available sub-bands by spectrum aggregation technology to construct a multi-band parallel transmission channel, thereby effectively improving the spectrum utilization rate, communication rate, and bandwidth configuration flexibility of the PLC. Meet the transmission requirements of smart grid services with high real-time requirements. At the same time, considering the difference between the low-frequency, intermediate-frequency, and high-frequency bands in their respective fine-frequency granularity sub-band bandwidths, channel characteristics, and applicable environments, it is prescribed to perform spectrum aggregation on the available fine-frequency granular sub-bands, as shown in the figure. 10, including:

According to the steps (1) to (8), the implementation process of the cross-band power line carrier frequency cognition method based on the fine frequency granularity provided by the embodiment, as shown in FIG. 11, includes:

The primary station actively initiates a frequency cognition process, and sends a noise measurement frame to specify a time for measuring local channel noise. After the station completes the noise measurement, it sends an ACK confirmation to the primary station, and the primary station starts local channel noise measurement until completion;

The primary station transmits an attenuation measurement frame to initiate downlink attenuation measurement, the secondary station sends an ACK acknowledgement to the primary station, and the primary station receives the ACK signal and performs downlink attenuation measurement. After the measurement is completed, the slave station transmits the attenuation measurement frame to start the uplink attenuation measurement, the primary station sends an ACK confirmation to the slave station, and the slave station receives the ACK signal and performs uplink attenuation measurement.

After the noise and attenuation measurements are completed, the secondary station performs downlink LQI calculation, preferably selects the available fine frequency granularity sub-band of the downlink, completes spectrum aggregation, and finally feeds back the determined downlink operating frequency information to the primary station. After receiving the information, the primary station performs uplink LQI calculation, preferably obtains the available fine frequency granularity sub-band of the uplink, completes spectrum aggregation, and finally feeds back the determined uplink working frequency information to the secondary station. After receiving the information, the slave station sends an ACK confirmation to the master station, thereby completing the frequency awareness of the PLC master station and the slave station.

Finally, it should be noted that the above embodiments are only for explaining the technical solutions of the present invention and are not limited thereto, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be It is intended that the present invention cover the modifications and equivalents of the invention.

Claims

A cross-band power line carrier frequency cognition method based on fine frequency granularity, comprising the following steps:

(1) constructing a power line carrier communication system model consisting of a primary station, a secondary station, an uplink, and a downlink;

(2) Dividing the operating frequency into low frequency, intermediate frequency and high frequency;

(3) According to the fine frequency granularity characteristics of low frequency, intermediate frequency and high frequency, the bandwidths of low frequency, intermediate frequency and high frequency are respectively divided in overlapping or non-overlapping manner;

(4) obtaining a low frequency fine frequency granularity subband, an intermediate frequency fine frequency granularity subband, and a high frequency fine frequency granularity subband;

(5) measuring the power line channel noise of the primary station and the secondary station at the current time and the operating frequency, respectively;

(6) calculating the power line channel attenuation of the uplink and the power line channel attenuation of the downlink at the current time and the operating frequency, respectively;

(7) respectively calculating the link quality indication LQI of the uplink and the downlink at the current time and the operating frequency;

(8) setting a link quality indication threshold value, and obtaining a link quality indicator LQI of the uplink and the downlink corresponding to all frequency points of the current time and the fine frequency granularity subband is smaller than the link The quality indicates a threshold frequency of available fine frequency granularity subbands and spectrally aggregates the available fine frequency granularity subbands.
The method according to claim 1, wherein in the step (1), the primary station is a PLC device in the PLC system, and the secondary station is a PLC device adjacent to the primary station, and the uplink is uplink. For the link from the slave station to the primary station, the downlink is the link from the primary station to the secondary station.
The method according to claim 1, wherein in said step (2), said low frequency is from 30 kHz to 500 kHz, said intermediate frequency is from 500 kHz to 1.6 MHz, and said high frequency is from 1.6 MHz to 30 MHz. .
The method according to claim 1, wherein in the step (3), the low frequency fine frequency granularity characteristic is a low frequency fine frequency granularity sub-band width of 1 kHz to 10 kHz, and the intermediate frequency fine frequency granularity The intermediate frequency fine frequency granularity sub-band width is 10 kHz to 100 kHz, and the high frequency fine frequency granularity is characterized by a high frequency fine frequency granularity sub-band width of 100 kHz to 1 MHz.
The method according to claim 1, wherein in the step (5), the power line channel noise of the primary station and the secondary station at the current time and the operating frequency are respectively measured, including:

The measurement resolution bandwidth is from 1 kHz to 30 kHz, and the power line channel noise formula of the primary station and the secondary station at the current time and the operating frequency is:

In equation (1-1), Noise ave (t) is the average value of the noise measurement results measured N times at time t, N ∈ (1, 10), and Noise ave (t-1) is t-1 time N- The average value of the noise measurement results obtained from one measurement, and Noise meas (t) is the noise power measured at time t.
The method according to claim 1, wherein in the step (6), calculating the downlink power line channel attenuation at the current time and the operating frequency comprises: using the primary station as a transmitting end, The slave station is a receiving end, and the transmitting end sends the frequency sweep signal to the receiving end; the power line channel attenuation of the downlink is the strength of the frequency sweep signal sent by the transmitting end minus the signal strength received by the receiving end.
The method according to claim 1, wherein in the step (6), calculating the power line channel attenuation of the uplink at the current time and the operating frequency comprises: using the slave station as a transmitting end, The primary station serves as a receiving end, and the transmitting end sends the frequency sweeping signal to the receiving end; the power line channel attenuation of the uplink is the strength of the frequency sweeping signal sent by the transmitting end minus the signal strength received by the receiving end.
The method according to claim 1, wherein in the step (7), the link quality indication LQI of the uplink and the downlink in the current time and the operating frequency are respectively calculated, including:

The link quality indication of the uplink is LQI = power line channel noise of the primary station + power line channel attenuation of the uplink;

The link quality indicator for the downlink is LQI = power line channel noise of the slave + power line channel attenuation of the downlink.
The method according to claim 1, wherein in the step (8), the link quality indication threshold is: the uplink and the downlink in the current time and the operating frequency. The link quality of the road indicates the minimum value of LQI plus 5-15dB.
The method according to claim 1, wherein in the step (8), spectrally aggregating the available fine frequency granular subbands comprises:

Performing intra-band spectral aggregation on the available fine frequency granularity sub-bands in the low frequency fine frequency granularity subband, the intermediate frequency fine frequency granularity subband, and the high frequency fine frequency granularity subband, respectively;

Performing cross-band spectrum aggregation on the low frequency fine frequency granularity subband and the available fine frequency granularity subband in the intermediate frequency fine frequency granularity subband;

Performing cross-band spectral aggregation on the intermediate frequency fine frequency granularity subband and the available fine frequency granularity subband in the high frequency fine frequency granularity subband.