Medium-voltage ultra-wideband power line carrier coupling system adaptive to wide impedance range of line

Abstract

The invention discloses a medium-voltage ultra-wideband power line carrier coupling system adapting to a wide impedance range of a line, which belongs to the technical field of ultra-wideband medium-voltage carrier communication, and comprises a first Butterworth broadband filter and a second Butterworth broadband filter, the first Butterworth broadband filter is connected with a circulator, and the second Butterworth broadband filter is connected with a second Butterworth broadband filter. And the circulator is connected with the second Butterworth broadband filter, and the circulator is connected with a lantern ring type transmission line transformer. The device can adapt to medium-voltage line wide impedance conversion under ultra-wideband power line carrier communication, the amplitude-frequency and phase characteristics of signals in an OFDM communication mode under the ultra-wideband condition of 1.6-86 Mhz and 54 octave are met, and effective transmission and isolation of the signals in the ultra-wideband power line carrier communication are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-wideband medium-voltage carrier communication, and in particular relates to a medium-voltage ultra-wideband power line carrier coupling system adapting to a wide impedance range of a line. Background Art

[0002] At present, the power line carrier frequency band in the power grid system is divided into narrowband (30kHz-500kHz) and broadband (2MHZ-12MHz) communication. Narrowband power line carrier communication technology is mainly used in scenarios with low transmission rate requirements, such as early power information collection and power grid monitoring; broadband power line carrier is also called high-speed power line carrier (HPLC). Compared with traditional low-speed narrowband power line carrier technology, HPLC communication has the characteristics of wide communication frequency band, high transmission rate and strong anti-interference ability, which increases the communication rate range from hundreds of Kbps to several Mbps. It is suitable for scenarios where the power grid has high requirements for data transmission rate and reliability, such as high-frequency data collection and monitoring, power quality monitoring and regulation, and distribution automation. Compared with distribution automation, the data of the intelligent microgrid with integrated source, grid, load and storage involved in the power grid dominated by new energy in the dual-carbon era has the characteristics of diversity, high speed, high real-time, strong correlation, and large data volume. Millisecond-level and microsecond-level real-time broadband communication is the necessary basis for ensuring the closed-loop measurement and control of microgrids.

[0003] The existing conventional narrowband and broadband medium-low-speed medium-voltage power line carrier communication cannot meet the requirements of fast closed-loop measurement and control of microgrids, and systematic research on ultra-wideband medium-voltage carrier communication technology and equipment has become an issue to be solved. 1.6-86MHz ultra-wideband power line carrier technology (HomePlug AV2) has been widely used in industrial scenarios such as smart home appliances (such as power routers), building elevators, and port terminal cranes in the low-voltage field. This frequency band is distributed in a higher frequency band, effectively avoiding low-frequency interference. At the same time, the ultra-wideband mode is adopted to greatly increase the channel capacity. Its transmission speed is as high as 1000Mbps, and its transmission rate can meet the measurement and control requirements of new power system microgrids.

[0004] Applying 1.6-86MHz ultra-wideband power line carrier technology to the 10kV medium-voltage distribution network system can effectively solve the problems of limited power line carrier communication bandwidth and insufficient channel capacity, greatly improve the communication rate, and meet the needs of new power system construction. However, there are still the following difficulties in applying it to the 10KV medium-voltage distribution network: 1. Feeding 1.6-86MHz signals into kilometer-long lines or extracting carrier signals from lines requires high requirements for coupling equipment. At present, the coupling devices of 10KV medium-voltage distribution networks usually use capacitive couplers or inductive couplers. Capacitive couplers have limited bandwidth due to the influence of frequency response characteristics and parasitic parameters and cannot meet the application requirements of ultra-wideband. Ordinary inductive couplers cannot solve the wide-range impedance matching problem caused by broadband. When the impedance is mismatched, the signal transmitted by the signal transmitter is reflected and fed into the signal receiver, resulting in signal attenuation and even damage to the equipment.

[0005] 2. The operating frequency of the ultra-wideband carrier communication system ranges from 1.6MHz to 86MHz, reaching 54 times the frequency band. The system uses OFDM technology to divide the high-speed data stream into multiple low-speed sub-streams and distribute them to multiple carriers for transmission. If the in-band amplitude-frequency characteristics of the combined filter are not good, it will cause distortion and interference between sub-carriers, thereby affecting the performance of the carrier system. The phase-frequency characteristics of the combined filter will also affect the orthogonality of the sub-carriers, thereby affecting the amplitude-frequency consistency within the full bandwidth of the ultra-wideband power line carrier. The combined filter used in the current 10kV medium-voltage power line carrier is difficult to meet the ultra-wideband power line carrier communication application.

[0006] 3. The current application distance of HomePlug AV in low-voltage systems is about 200 meters, and the power line impedance changes relatively normally. The maximum power supply distance of the 10kV medium-voltage distribution network is 25km. The line is long, there are many branches along the way, and the power load impedance changes dramatically. The input impedance along the line changes dramatically with the frequency at each point in the entire communication frequency band. The impedance value at different times and locations can change from more than ten ohms to hundreds of ohms. In the 1.6-86MHz passband, the medium-voltage line carrier impedance changes greatly, and the amplitude-frequency characteristics deteriorate due to group delay, which will cause nonlinear attenuation of the signal in the passband, seriously affecting the quality of the QAM signals of different sub-bands of OFDM in ultra-wideband power line carrier communication, resulting in a high system bit error rate. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a medium voltage ultra-wideband power line carrier coupling system that adapts to a wide impedance range of the line, which can meet the ultra-wideband signal coupling requirements and at the same time achieve wide range impedance matching adaptation during ultra-wideband power line carrier medium voltage communication.

[0008] The object of the present invention is achieved in that: A medium voltage ultra-wideband power line carrier coupling system adapted to a wide impedance range of a line includes a first Butterworth broadband filter and a second Butterworth broadband filter, wherein the first Butterworth broadband filter is connected to a circulator, and the circulator is connected to the second Butterworth broadband filter, and the circulator is connected to a sleeve-type transmission line transformer. The working principle of the first Butterworth broadband filter and the second Butterworth broadband filter is to achieve a specific frequency response by adjusting the pole position and order of the filter, and in the design of the filter, the cutoff frequency, bandwidth, phase-frequency characteristics and amplitude-frequency characteristics of the attenuation degree of the filter are determined by setting the pole position and the order.

[0009] Specifically, the design goal of the Butterworth broadband filter is to achieve maximum flatness within the passband, that is, the frequency response curve is kept as horizontal as possible in this area without fluctuations. In order to achieve this goal, the Butterworth broadband filter adopts the design idea that the pole positions are evenly distributed on the unit circle. This design makes the frequency response of the filter have the maximum flatness within the passband, while achieving a gradually decreasing attenuation characteristic in the stopband. In the implementation process, the filtering effect can be improved by increasing the order of the filter. In practical applications, the appropriate order can be selected according to specific needs.

[0010] The advantages of Butterworth broadband filter are: 1. The frequency response of Butterworth filter in the passband is flat, so it will not introduce amplitude distortion or phase distortion. 2. The stopband part has a very high suppression ratio, which can effectively filter out-of-band noise and clutter.

[0011] Furthermore, the first Butterworth broadband filter is connected to the circulator via a high-frequency cable, the second Butterworth broadband filter is connected to the circulator via a high-frequency cable, and the sleeve-type transmission line transformer is connected to the circulator via a high-frequency cable. The circulator is used to ensure that the signal is transmitted in a given direction to ensure the unidirectional circulation transmission of the signal, isolate the reverse signal, have a wide working bandwidth, and have a small insertion loss for broadband applications, so as to realize the effective transmission and isolation of signals in ultra-wideband power line carrier communication.

[0012] Furthermore, the first Butterworth broadband filter is connected to a carrier transmitter via a high-frequency cable, and the second Butterworth broadband filter is connected to a carrier receiver via a high-frequency cable. The sleeve-type transmission line transformer is sleeved on a medium-voltage line, and the circuit of the medium-voltage line is connected to a wave arrester. When the line impedance changes, the sleeve-type transmission line transformer transmits communication signals, realizes electrical insulation, and reduces the mismatch between the power line impedance and the circulator impedance through magnetic coupling. The reflected signal generated by the impedance mismatch can be isolated by the circulator to prevent the reflected signal from affecting the filter and the transmitter. These devices work together to achieve medium-voltage line wide impedance transformation under ultra-wideband power line carrier communication.

[0013] When transmitting information: the 1.6MHz-86MHz signal transmitted by the carrier transmitter passes through the first Butterworth broadband filter to filter out-of-band harmonics, enters the circulator port 1, is sent to the ring-type transmission line transformer through the high-frequency cable through the circulator port 2, is fed into the medium-voltage line through the ring-type transmission line transformer, and is sent to other similar communication devices on the line through the medium-voltage line. When receiving information: the signal transmitted by the medium-voltage line passes through the coupling effect of the ring-type transmission line transformer, enters the circulator through port 2, enters the second Butterworth broadband filter from port 3 under the right-handed effect of the circulator magnetic field, and enters the receiver demodulation signal after filtering out-of-band interference.

[0014] When the line impedance changes, the ring-type transmission line transformer reduces the impedance mismatch between the signal and the line through the magnetic coupling characteristics. The reflected signal generated by the impedance mismatch enters the circulator through the ring-type transmission line transformer. (1) The reflected signal is isolated by the circulator and cannot be transmitted from port 2 to port 1, which prevents the reflected signal from being superimposed on the transmitted signal, causing signal attenuation and overvoltage, and causing the transmitter to be broken down and damaged; (2) The reflected signal is transmitted from port 2 to port 3 and enters the receiving filter 2. At this time, there are two types of working states and disposal measures: ① When working at the same frequency, time division duplexing is used. At this time, the receiver does not respond because it cannot work; ② When working at different frequencies, the working modes of the transceivers at a and b are: the transmitter at a transmits a signal with a frequency band of f1, and the receiver receives a signal with a frequency band of f2 from the transceiver at b, while the transmitter at b transmits a signal with a frequency band of f2, and the receiver receives a signal with a frequency band of f1 from the transceiver at a. The frequency band of the reflected signal is different from that of the receiver and is filtered out. This system uses the magnetic coupling of the ring-type transmission line transformer to reduce the impedance mismatch caused by line impedance transformation, and uses the circulator to isolate the reflected waves generated by the impedance mismatch, thereby achieving stable OFDM mode QAM modulation communication when the medium voltage line impedance changes.

[0015] A medium voltage ultra-wideband power line carrier coupling method adapting to a wide impedance range of a line comprises connecting a first Butterworth broadband filter, a second Butterworth broadband filter, a circulator, a sleeve transmission line transformer, a carrier transmitter and a carrier receiver through a high-frequency cable.

[0016] Furthermore, the first port of the circulator is connected to the first Butterworth broadband filter, the second port of the circulator is connected to the sleeve-type transmission line transformer, and the third port of the circulator is connected to the second Butterworth broadband filter.

[0017] Beneficial effects of the present invention: During the operation of the system, the ring-type transmission line transformer, circulator, and Butterworth filter all have wide bandwidth characteristics, and can therefore adapt to ultra-wideband application scenarios. When the line impedance changes, the ring-type transmission line transformer reduces the mismatch between the power line impedance and the circulator impedance through magnetic coupling. The reflected signal generated by the impedance mismatch can be isolated by the circulator to prevent the reflected signal from affecting the filter and transmitter. These devices work together to achieve wide impedance transformation of medium-voltage lines under ultra-wideband power line carrier communications. It meets the application requirements of ultra-wideband and solves the wide-range impedance matching problem caused by the wide band.

[0018] The impedance mismatch caused by line impedance transformation is weakened by the magnetic coupling effect of the ring-type transmission line transformer, and the reflected wave generated by the impedance mismatch is isolated by the circulator, so that when the medium-voltage line impedance changes, the system can stably realize OFDM mode QAM modulation communication.

[0019] Advantages of the invention: 1. To meet the requirements of the power line carrier communication rate and data capacity of the source-grid-load-storage integrated microgrid, it is proposed to apply the 1.6Mhz-86Mhz ultra-wideband to the power line carrier communication system of the medium-voltage distribution network, greatly improving the channel capacity and rate of the power line carrier system.

[0020] 2. By utilizing the frequency flatness of the signal within the Butterworth broadband filter, the amplitude-frequency and phase-frequency characteristics of the signal within 1.6-86Mhz are improved, and the phase group delay of the signal transmission is reduced.

[0021] 3. The magnetic coupling characteristics of the ring-type transmission line transformer and the unidirectional transmission isolation of the circulator are utilized, and the two are combined and applied in the ultra-wideband power line carrier system to improve its adaptability to medium-voltage line impedance transformation.

[0022] 4. The filter, circulator and sleeve-type transmission line transformer used in the invention are all wide-band devices, which are connected to each other through high-frequency cables, thus avoiding the influence of external factors on system impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] In the figure: 1, a first Butterworth broadband filter 2, a second Butterworth broadband filter 3, a circulator 4, a sleeve-type transmission line transformer 5, a carrier transmitter 6, a carrier receiver 7, a medium voltage line 8, a wave trap 9, and a coupling system. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below in conjunction with the accompanying drawings. It should be pointed out that all directional words such as up, down, front, back, left, and right appearing in the present invention do not limit the present invention, but are only for clearer description and explanation of the present invention. Example

[0026] like Figure 1 As shown, this embodiment discloses a medium voltage ultra-wideband power line carrier coupling system adapting to a wide impedance range of a line, which includes a first Butterworth broadband filter 1 and a second Butterworth broadband filter 2, wherein the first Butterworth broadband filter 1 is connected to a circulator 3, and the circulator 3 is connected to the second Butterworth broadband filter 2, and the circulator 3 is connected to a sleeve-type transmission line transformer 4. The working principle of the first Butterworth broadband filter 1 and the second Butterworth broadband filter 2 is to achieve a specific frequency response by adjusting the pole position and order of the filter. In the design of the filter, the cutoff frequency, bandwidth, phase-frequency characteristics, and amplitude-frequency characteristics of the attenuation degree of the filter are determined by setting the pole position and the order.

[0027] Specifically, the design goal of the Butterworth broadband filter is to achieve maximum flatness within the passband, that is, the frequency response curve is kept as horizontal as possible in this area without ups and downs. In order to achieve this goal, the Butterworth broadband filter adopts the design idea that the pole positions are evenly distributed on the unit circle. This design makes the frequency response of the filter have the maximum flatness within the passband, while achieving a gradually decreasing attenuation characteristic in the stopband. In the implementation process, the filtering effect can be improved by increasing the order of the filter. In practical applications, the appropriate order is selected according to specific needs. The advantages of the Butterworth broadband filter are: 1. The frequency response of the Butterworth filter within the passband is flat, so it will not introduce amplitude distortion or phase distortion. 2. The stopband part has a very high suppression ratio, which can effectively filter out-band noise and clutter. Example

[0028] like Figure 1 As shown, this embodiment discloses a medium voltage ultra-wideband power line carrier coupling system adapted to a wide impedance range of the line. In this embodiment, based on the embodiment 1, for better effect, the first Butterworth broadband filter 1 is connected to the circulator 3 through a high-frequency cable, the second Butterworth broadband filter 2 is connected to the circulator 3 through a high-frequency cable, and the sleeve transmission line transformer 4 is connected to the circulator 3 through a high-frequency cable. The circulator 3 is used to ensure that the signal is transmitted in a given direction to ensure the unidirectional circulation transmission of the signal, isolate the reverse signal, the working bandwidth, and the broadband application has a small insertion loss, so as to achieve effective transmission and isolation of the signal in the ultra-wideband power line carrier communication.

[0029] The first Butterworth broadband filter 1 is connected to a carrier transmitter 5 via a high-frequency cable, and the second Butterworth broadband filter 2 is connected to a carrier receiver 6 via a high-frequency cable. The sleeve-type transmission line transformer 4 is sleeved on a medium-voltage line 7, and the circuit of the medium-voltage line 7 is connected to a wave arrester 8. When the line impedance changes, the sleeve-type transmission line transformer 4 transmits communication signals, realizes electrical insulation, and reduces the mismatch between the power line impedance and the circulator 3 impedance through magnetic coupling. The reflected signal generated by the impedance mismatch can be isolated by the circulator 3 to prevent the reflected signal from affecting the filter and the transmitter. These devices work together to achieve the wide impedance transformation of the medium-voltage line 7 under ultra-wideband power line carrier communication.

[0030] When transmitting information: the 1.6MHz-86MHz signal transmitted by the carrier transmitter 5 passes through the first Butterworth broadband filter 1 to filter out the out-of-band harmonics, enters the port 1 of the circulator 3, is sent to the sleeve transmission line transformer 4 by the high-frequency cable through the sleeve transmission line transformer 4, is fed into the medium voltage line 7 through the sleeve transmission line transformer 4, and is sent to other similar communication devices on the line through the medium voltage line 7. When receiving information: the signal transmitted by the medium voltage line 7 passes through the coupling effect of the sleeve transmission line transformer 4, enters the circulator 3 through the port 2, enters the second Butterworth broadband filter 2 from the port 3 under the right-handed effect of the magnetic field of the circulator 3, and enters the receiver demodulation signal after filtering out the out-of-band interference.

[0031] When the line impedance changes, the ring-type transmission line transformer 4 reduces the impedance mismatch between the signal and the line through the magnetic coupling characteristics. The reflected signal generated by the impedance mismatch enters the circulator 3 through the ring-type transmission line transformer 4. (1) The reflected signal is isolated by the circulator 3 and cannot be transmitted from port 2 to port 1, thereby avoiding the superposition of the reflected signal and the transmitted signal, causing signal attenuation and overvoltage, and causing the transmitter to break down and be damaged; (2) The reflected signal is transmitted from port 2 to port 3 and enters the receiving filter 2. At this time, there are two types of working states and disposal measures: ① When working at the same frequency, time division duplexing is adopted. At this time, the receiver does not respond because it cannot work; ② When working at different frequencies, the working modes of the transceivers at a and b are: the transmitter at a transmits a signal with a frequency band of f1, and the receiver receives a signal with a frequency band of f2 from the transceiver at b, while the transmitter at b transmits a signal with a frequency band of f2, and the receiver receives a signal with a frequency band of f1 from the transceiver at a. The frequency band of the reflected signal is different from that of the receiver and is filtered out. The system reduces the impedance mismatch caused by line impedance transformation through the magnetic coupling effect of the ring-type transmission line transformer 4, and uses the circulator 3 to isolate the reflected waves generated by the impedance mismatch, thereby achieving stable OFDM mode QAM modulation communication when the impedance of the medium voltage line 7 changes.

[0032] A medium voltage ultra-wideband power line carrier coupling method adapting to a wide impedance range of a line comprises connecting a first Butterworth broadband filter 1, a second Butterworth broadband filter 2, a circulator 3, a sleeve-type transmission line transformer 4, a carrier transmitter 5 and a carrier receiver 6 through a high-frequency cable. Example

[0033] like Figure 1 As shown, this embodiment discloses a medium voltage ultra-wideband power line carrier coupling system that adapts to a wide impedance range of the line. In order to achieve better results based on Example 2, this embodiment connects the first port of the circulator 3 to the first Butterworth broadband filter 1, the second port of the circulator 3 to the sleeve-type transmission line transformer 4, and the third port of the circulator 3 to the second Butterworth broadband filter 2.

[0034] Case 1: The length of a medium-voltage distribution network line is about 2 kilometers. When constructing a UPLC (ultra-wideband power carrier communication) medium-voltage power carrier channel, it is necessary to install a power broadband wave blocker 8, a sleeve transmission line transformer 4, a 50-ohm communication cable, and a broadband combination filter in the three-phase line of the transformer offline of the medium-voltage distribution network line. There are circulators 3 and Butterworth broadband filters in the box of the broadband combination filter, and then decompose the transceiver of the broadband power carrier machine. Among them, the broadband wave blocker 8 can isolate the carrier signal within the bandwidth of 1.6-86MHz by 20db, the working frequency band of the circulator 3 is 1.6-86MHz, the port isolation is 24db, the working frequency band of the Butterworth filter is 1.6-86MHz, the out-of-band attenuation is 18db / octave, the amplitude-frequency characteristic fluctuation within the band is less than 0.5db, the distortion frequency point in the closed-loop group delay characteristic of the line is measured, and the OFDM sub-band is closed in a targeted manner to reduce the influence of signal distortion. After field communication verification, it is ensured that the standing wave ratio of each link is less than 1.3 to meet the requirements of high-reliability broadband high-speed digital communication.

[0035] Case 2: The length of a medium-voltage distribution network line is about 10 kilometers. When constructing a UPLC medium-voltage power carrier channel, it is necessary to install a power broadband wave arrester 8, a ring-type transmission line transformer 4, and a broadband combined filter in the three-phase line downstream of the transformer of the medium-voltage distribution network line. The broadband combined filter box contains a circulator 3 and a Butterworth broadband filter, and then decomposes the transceiver of the broadband power carrier machine. As the communication distance increases, the loss increases, and a high-power power carrier machine is used. The broadband wave blocker 8 used can isolate the carrier signal to 32db within the bandwidth of 1.6-86MHz. The operating frequency band of the circulator 3 is 1.6-86MHz, the port isolation is 24db, the operating frequency band of the Butterworth filter is 1.6-86MHz, the out-of-band attenuation is 24db / octave, the in-band amplitude-frequency characteristic fluctuation is less than 0.5db, the distortion frequency point in the closed-loop group delay characteristic of the line is measured, and the OFDM sub-band is closed in a targeted manner to reduce the impact of signal distortion. It has been verified through on-site communication that the standing wave ratio of each link is less than 1.3 to meet the requirements of high-reliability broadband and high-speed digital communication.

[0036] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A medium voltage ultra-wideband power line carrier coupling system adapted to a wide impedance range of a line, comprising a first Butterworth broadband filter and a second Butterworth broadband filter, characterized in that: The first Butterworth broadband filter is connected to a circulator, and the circulator is connected to the second Butterworth broadband filter, and the circulator is connected to a sleeve-type transmission line transformer.

2. The medium voltage ultra-wideband power line carrier coupling system adapted to a wide line impedance range according to claim 1 is characterized in that: The first Butterworth broadband filter is connected to the circulator via a high-frequency cable, the second Butterworth broadband filter is connected to the circulator via a high-frequency cable, and the sleeve-type transmission line transformer is connected to the circulator via a high-frequency cable.

3. The medium voltage ultra-wideband power line carrier coupling system adapting to a wide line impedance range according to claim 2 is characterized in that: The first Butterworth broadband filter is connected to a carrier transmitter via a high-frequency cable, and the second Butterworth broadband filter is connected to a carrier receiver via a high-frequency cable.

4. The medium voltage ultra-wideband power line carrier coupling system adapting to a wide line impedance range according to claim 3 is characterized in that: The sleeve-type transmission line transformer is sleeved on a medium-voltage line, and a wave arrester is connected to the circuit of the medium-voltage line.

5. A medium voltage ultra-wideband power line carrier coupling method adapted to a wide impedance range of a line, characterized in that: The method comprises connecting a first Butterworth broadband filter, a second Butterworth broadband filter, a circulator, a sleeve-type transmission line transformer, a carrier transmitter and a carrier receiver through a high-frequency cable.

6. The medium voltage ultra-wideband power line carrier coupling method adapted to a wide line impedance range according to claim 5, characterized in that: The first port of the circulator is connected to the first Butterworth broadband filter, the second port of the circulator is connected to the sleeve-type transmission line transformer, and the third port of the circulator is connected to the second Butterworth broadband filter.

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