CN101980451B - Time-interval-adaptation-based power line power frequency communication system and method - Google Patents

Abstract

The invention discloses a time-interval-adaptation-based power line power frequency communication system and a time-interval-adaptation-based power line power frequency communication method, which relate to the network structure and signal processing of a power system and belong to technical field of power line power frequency communication. The power line power frequency communication system consists of master station equipment which is positioned in a substation and a remote communication terminal which is positioned on a low-voltage side of a distribution transformer, wherein the master station equipment also comprises a downlink signal driving device and an uplink signal demodulation device. In the method, leading information is adopted in the specified power frequency cycle during power frequency signal modulation; during demodulation, the signal-to-noise ratio of a power frequency distortion signal is improved by accumulating a sampling signal in multiple cycles in a time period of the leading information; the time domain of a modulating signal is determined by performing time frequency analysis on the basis of Wigner distribution; and data demodulation is performed in the time domain through a related detection mode. Because an accurate receiving time period and an optimal judgment moment can be obtained for demodulation, the anti-jamming capacity of the power frequency communication is greatly improved, and the system can adapt to various connection modes of the distribution transformers.

Description

Based on adaptive power-frequency communication of electric system and method for period

Technical field

Power-frequency communication of electric technical field of the present invention.Be particularly related to a kind of based on adaptive power-frequency communication of electric system and method for period of power system network structure, communication and signal processing.

Background technology

The power-frequency communication of electric mode realizes the transmission of information by near the voltage the voltage zero-cross, current distortion, because distorted signal belongs to low frequency signal, need not just can realize striding at the high-tension line optional equipment the long Distance Transmission of transformer platform area, compare with the 10KV power line carrier, PLC that adopts the high-frequency signal transmission, equipment cost is much lower, compare with public wireless network, do not have the communication service expense; Therefore, power-frequency communication of electric has important application prospect at the power distribution automation management domain.

Power frequency communication system structural representation as shown in Figure 1 is at the high voltage transmission line of the main transformer secondary of electric substation successively cross-over connection modulation transformer, distribution transformer.Power line is not special communication line, and channel circumstance is undesirable, and the frequency communication mode also is difficult to guarantee the communication performance of industrial electrical network, and basic the kilowatt meter reading-out system in domestic power grid has application; Research emphasis in the past mainly at the noise of industrial electrical network on aspect the impact of power frequency modulation signal, and ignored frequency communication sending and receiving end voltage zero-cross difference constantly, distorted signal as shown in Figure 2 and the sending and receiving end voltage zero-cross time difference, because the factors such as supply line's impedance, transformer connected mode, load, the voltage zero-cross of electric substation and distribution transformer voltage side there are differences constantly, especially in industrial electrical network, mainly be heavy-duty motor with electric loading, voltage zero-cross is poor larger; Traditional frequency communication mode is based on the modulation /demodulation time domain of the local terminal voltage zero-cross moment as frequency communication, can cause the demodulation period of power frequency modulation signal and the time domain that exists of signal to have obvious errors, add the interference of electric network noise, the frequency communication performance is had a strong impact on.

The present invention's design is before the modulation of frequency communication data message, increased the preface information based on pseudorandom sequence coding, separate timing, in the preface information period voltage or current sampling signal are formed composite signal according to pseudorandom order coding, obviously improve the signal to noise ratio of power frequency modulation signal, then utilize Wigner distribution to carry out time frequency analysis and determine power frequency modulation signal place time domain, the voltage zero-cross time difference that obtains according to time frequency analysis when data demodulates is carried out the demodulation computing, because demodulation, the judgement period is accurate, the antijamming capability of frequency communication is obviously strengthened, the abominable channel circumstance of industrial electrical network can be adapted to, the various connected modes of distribution transformer can also be automatically adapted to simultaneously.

Summary of the invention

The purpose of this invention is to provide based on adaptive power-frequency communication of electric detection method of period and system, it is characterized in that, describedly be comprised of the main website equipment that is positioned at electric substation and the telecommunication terminal that is positioned at the distribution transformer low-pressure side based on adaptive power-frequency communication of electric detection system of period, described master station device comprises again downstream signal drive unit and upward signal demodulating equipment; The downstream signal drive unit is connected on the ultra-high-tension power transmission line by the house transformer in the electric substation, A/D converter is connected on the ultra-high-tension power transmission line by voltage transformer pt summation current transformer CT, and the voltage and current signal that PT, CT are gathered is converted to the digital quantity that can supply DSP to process; Dsp processor, downstream signal drive unit and A/D converter composition control module; The power frequency component terminal is connected on the ultra-high-tension power transmission line by voltage transformer pt and distribution transformer;

Described downstream signal drive unit connects respectively the circuits for triggering of bidirectional triode thyristor, positive and negative comparison circuit and Max485 by microprocessor CPU; Bidirectional triode thyristor is connected with inductance L by protective circuit, and positive and negative comparison circuit connects signal conditioning circuit and consists of; Signal conditioning circuit is connected to the house transformer secondary by voltage transformer pt; Inductance L is connected to the house transformer secondary; Industrial computer is connected with Max485;

Described upward signal demodulating equipment connects to form with dsp processor and 16 A/D converters, and dsp processor is connected with house transformer by positive and negative comparison circuit, voltage transformer pt; 16 A/D converters by modulate circuit respectively be connected to A, B, C phase line on three secondary current instrument transformer CT be connected; Described telecommunication terminal comprises by dsp processor and 16 A/D converters and connects to form processing module, dsp processor connects circuits for triggering, circuits for triggering connect the control utmost point of bidirectional triode thyristor by protective circuit, the drain electrode of bidirectional triode thyristor is by inductance L ground connection, and source electrode connects distribution transformer 380V end; Distribution transformer 380V end connects respectively signal conditioning circuit and positive and negative comparison circuit by voltage transformer pt, and signal conditioning circuit connects 16 A/D converters again, and positive and negative comparison circuit connects dsp processor again.The function of telecommunication terminal is that the demodulation of descending voltage distorted signal, communication protocol are processed, the ascending current modulation, and these functions all are to finish take the DSP calculation process as core; DSP gathers, processes voltage signal by 16 A/D, at first according to the definite descending voltage distortion information place time domain from electric substation of preface information, then carries out data demodulates in conjunction with the sending and receiving end voltage zero-cross time difference, and antijamming capability strengthens greatly,

Described downstream signal drive unit produces the low-pressure side that the voltage distortion signal transfers to distribution transformer by modulation transformer or electric substation with becoming near voltage zero-cross, telecommunication terminal receives, processes downstream signal based on the period adaptive mode; When frequency communication terminal loopback uplink information, communication terminal passes through distribution transformer generation current distorted signal near voltage zero-cross, the upward signal demodulating equipment of electric substation also is based on the period adaptive mode and realizes uplink demodulation by the current signal of transducer collection 10KV circuit.Owing to possess period adaptive reception characteristics, power frequency communication system of the present invention can the Adaptive Modulation transformer and the various connected modes of distribution transformer when modulation /demodulation.

A kind ofly it is characterized in that based on adaptive power-frequency communication of electric detection method of period, comprise following part:

1) determines based on the signal time domain of preface information

At first according to the synthetic sampled signal of modulating-coding, can obviously improve like this signal to noise ratio of power frequency distorted signal, then according to the spectrum modulation signal scope composite signal being carried out time frequency analysis calculates, time frequency analysis adopts based on the Wigner distribution of short time discrete Fourier transform as window function, very high time frequency resolution can be obtained, interference effect can be suppressed to intersect again; The most concentrated time domain of Energy distribution namely is judged as the power frequency distorted signal place period, and the time difference of definite frequency communication sending and receiving end voltage zero-cross; Before the uplink and downlink Data Modulation of power frequency communication system, all add preface information; Preface information realizes modulation by N sequence chip by 2N power frequency period, each chip represents with the front and back of voltage, current distortion signal location in two power frequency periods, its chip coded system adopts false noise coding, N is larger, the time domain of modulation signal is determined more accurate, but time overhead also increases, and selecting then, N is 7 or 11;

At receiving terminal, by the coding consistent with transmitting terminal the sampled signal of 2N power frequency period is passed through difference, coding ranking operation generation composite signal, weighted coding is consistent with the transmitting terminal coding.

2) in conjunction with the data demodulates mode of the voltage zero-cross time difference, coding characteristic according to data message, the modulation signal waveform of reflection data message can determine that in advance data demodulates is the judgement of waveform direction, and calculates the accurate time domain that can determine modulation waveform by time frequency analysis; Adopt the cross-correlation mode to carry out data demodulates, its demodulation computing, judgement are determined in conjunction with the time frequency analysis resulting sending and receiving end voltage zero-cross time difference constantly by the test side voltage zero-cross constantly; Because electric network noise is strong, the uplink and downlink transfer of data all is the direction reflection by the power frequency modulation signal in the power frequency communication system, the modulation system of data message, it is consistent with traditional power frequency communication system to encode, the downlink data modulation adopts per 2 power frequency periods to carry a data message, front and back by voltage distortion signal position represent, and the current distortion signal of each upstream data by 4 power frequency periods represents.

Described Wigner distribution (WVD) has very high time frequency resolution, very suitablely determine the distortion current transmitting time by time-frequency distributions, but Wigner distribution belongs to nonlinear transformation, for composite signal, obtain accurately time-frequency situation of change by the Wigner distribution conversion, also the essential intersection that suppresses between the unlike signal is disturbed; To be combined with Wigner distribution and can either obtain good time-frequency distributions characteristic based on the window function of certainly composing of short time discrete Fourier transform, and can reduce again and intersect the impact of disturbing.

The Wigner distribution of preface information composite signal s (t) is:

$W(t,\mathrm{\ω})=\underset{-\∞}{\overset{+\∞}{\∫}}s(t+\mathrm{\τ}/2)s*(t-\mathrm{\τ}/2)\exp (-\mathrm{j\ω\τ})\mathrm{d\τ}$

Be expressed as from the spectrum window function:

$Q(t,\mathrm{\ω})={\left|\mathrm{STFT}(t,\mathrm{\ω})\right|}^2={\left|\underset{-\∞}{\overset{+\∞}{\∫}}s\left(\mathrm{\τ}\right)h(\mathrm{\τ}-t)\exp (-\mathrm{j\ω\τ})\mathrm{d\τ}\right|}^2$

Wherein, h (t) is the window function of short time discrete Fourier transform, and this patent is chosen as rectangular window.

Like this, the Wigner distribution of inhibition cross influence is: W (t, ω) ^▽=W (t, ω) Q (t, ω)

The operand of Wigner distribution is very large, for the real-time of calculating, only analyze the time-frequency distributions situation that meets the frequency modulating signal scope in the composite signal, consider that the odd harmonic interference ratio is more serious in the electrical network, this patent adopts the Wigner distribution of 208.3HZ, 312.5HZ, near the frequency of these 4 even-order harmonics of 416.6HZ, 520.8HZ to reflect the energy distribution state of modulation signal.

Like this, the energy distribution function W (n) that meets power frequency modulation signal frequency domain scope is: Wherein, n is the discrete time of sampled signal, ω _iAbove 4 radio-frequency components have been represented; The peak value that receiving terminal can access power frequency modulation signal Energy distribution by W (n) parameter constantly, this is constantly very little and substantially fixing with the voltage zero-cross time difference of transmitting terminal, so just can calculate the voltage zero-cross time difference of frequency communication sending and receiving end.

The invention has the beneficial effects as follows with traditional frequency communication mode and compare, this method can improve the frequency communication performance, and can automatically adapt to the various connected modes of distribution transformer, even since the transformer variable star angle cause also can guaranteeing communication quality under the large operating mode of the sending and receiving end voltage zero-cross time difference.

Description of drawings

Fig. 1 is the power frequency communication system structural representation.

Fig. 2 is distorted signal and sending and receiving end voltage zero-cross time difference map.

Fig. 3 is power frequency communication system equipment schematic diagram.

Fig. 4 is downlink drive device schematic diagram.

Fig. 5 is the telecommunication terminal structural representation.

Fig. 6 is up modulation circuit schematic diagram.

Fig. 7 is uplink demodulation apparatus structure schematic diagram.

Embodiment

The invention provides based on adaptive power-frequency communication of electric detection method of period and system.Be explained below in conjunction with accompanying drawing.

Fig. 3 is power frequency communication system equipment schematic diagram.Describedly be comprised of the main website equipment that is positioned at electric substation and the telecommunication terminal that is positioned at the distribution transformer low-pressure side based on adaptive power-frequency communication of electric detection system of period, described master station device comprises again downstream signal drive unit and upward signal demodulating equipment; The downstream signal drive unit is connected on the ultra-high-tension power transmission line by house transformer, A/D converter is connected on the ultra-high-tension power transmission line by voltage transformer pt summation current transformer CT, and the voltage and current signal that PT, CT are gathered is converted to the digital quantity that can supply DSP to process; Dsp processor, downstream signal drive unit and A/D converter composition control module; The power frequency component terminal is connected on the ultra-high-tension power transmission line by voltage transformer pt and distribution transformer.Shown in Figure 4, the downstream signal drive unit connects respectively the circuits for triggering of bidirectional triode thyristor, positive and negative comparison circuit and Max485 by microprocessor CPU; Bidirectional triode thyristor is connected with inductance L by protective circuit, and positive and negative comparison circuit connects signal conditioning circuit and consists of; Signal conditioning circuit is connected to used change secondary by voltage transformer pt; Inductance L also is connected to used change secondary; Industrial computer is connected with Max485.The downstream signal drive unit is installed used low pressure side, the output of the low pressure of modulation transformer forms square wave behind voltage sensor PT and signal conditioning circuit, positive and negative comparison circuit, microprocessor in the downstream signal drive unit just can be judged voltage zero-cross constantly by square wave, thereby can modulate front about 30 ° of voltage zero-cross.

When needs send descending frequency communication information, for security consideration, prevent mistake and drive, microprocessor forms logical signal by 8 I/O interfaces by decoding circuit and modulates through the low-voltage output that circuits for triggering drive the SCR control modulation transformer.

The present invention selects inductance as driving element, and in identical voltage distortion amplitude situation, the shared time domain of voltage distortion signal that produces is wider than resistance type of drive, and is favourable to descending demodulation.

In order to comprise device security; the downstream signal drive unit also has protective circuit; protective circuit is comprised of air switch and fast acting fuse; when the device short circuit occurring; when modulated current strengthened suddenly, protective circuit can be cut off rapidly and drive the loop, can not damage device; after fault is got rid of, can conveniently recover.

Described downstream signal drive unit is in the downstream signal modulated process, downlink command formation control coding is driven by microprocessor according to the coded system that is fit to oilfield electric net, this patent must add the frequency communication terminal that is modulated to of preface information and determine that voltage distortion signal time domain provides raw information before Data Modulation, preface information and data encoding mode are as previously mentioned.

Because this patent can be realized period adaptive reception, described downstream signal drive unit can carry out the modulation of voltage distortion by phase ground mode at modulation transformer any, need not consider whether the modulation transformer of electric substation exists variable star angle.

Described downstream signal drive unit microprocessor is selected Atmega8.The downstream signal drive unit produces the low-pressure side that the voltage distortion signal transfers to distribution transformer by modulation transformer or electric substation with becoming near voltage zero-cross, telecommunication terminal receives, processes downstream signal based on the period adaptive mode; When frequency communication terminal loopback uplink information, communication terminal passes through distribution transformer generation current distorted signal near voltage zero-cross, the upward signal demodulating equipment of electric substation also is based on the period adaptive mode and realizes the upward signal demodulation by the current signal of transducer collection 10KV circuit.Owing to possess period adaptive reception characteristics, power frequency communication system of the present invention can the Adaptive Modulation transformer and the various connected modes of distribution transformer when modulation /demodulation.

Figure 5 shows that the telecommunication terminal structural representation.This telecommunication terminal comprises by dsp processor and 16 A/D converters and connects to form processing module, dsp processor connects circuits for triggering, circuits for triggering connect the control utmost point of bidirectional triode thyristor by protective circuit, the drain electrode of bidirectional triode thyristor is by inductance L ground connection, and source electrode connects distribution transformer 380V end; Distribution transformer 380V end connects respectively signal conditioning circuit and positive and negative comparison circuit by voltage transformer pt, and signal conditioning circuit connects 16 A/D converters again, and positive and negative comparison circuit connects dsp processor again.Upward signal demodulating equipment shown in Fig. 6,7 connects to form with dsp processor and 16 A/D converters, and dsp processor is connected with used change by positive and negative comparison circuit, voltage transformer pt; 16 A/D converters by modulate circuit respectively be connected to A, B, C phase line on three secondary current instrument transformer CT be connected; The function of telecommunication terminal is that the demodulation of descending voltage distorted signal, communication protocol are processed and the upward signal current-modulation; These functions all are to finish take the DSP calculation process as core; DSP gathers, processes voltage signal by 16 A/D, at first according to the definite descending voltage distortion information place time domain from electric substation of preface information, then carries out data demodulates in conjunction with the sending and receiving end voltage zero-cross time difference, and antijamming capability strengthens greatly,

Among Fig. 7, because 1 primary current instrument transformer CT of 10KV circuit is output as about 5A, this signal can't directly be processed by MCU and metering circuit, must can processedly use by 2 conversion, 2 CT in the upward signal demodulating equipment from the 10KV of electric substation or 6KV circuit 1 primary current instrument transformer CT obtain current signal; 2 primary current instrument transformer CT will be converted to from 1 primary current instrument transformer CT signal of high-tension line the weak electric signal of 0～5V, and signal conditioning circuit will carry out filtering, matching treatment from the signal of No. 2 transducers, suppress wherein useless to electrical energy parameter High-frequency Interference.

Voltage transformer pt obtains voltage signal from the 220V output of used change, by converting 50hz power-frequency voltage signal to square-wave signal behind the positive and negative comparison circuit, so that DSP can access the local terminal voltage zero-cross constantly.

After current signal is gathered by dsp processor by 16 A/D converters, according to the upward signal modulated current place time domain of determining from the preface information of each frequency communication terminal from this terminal, then carry out data demodulates according to the upward signal modulating-coding, because the data demodulates time domain is accurate, antijamming capability strengthens greatly.

The present invention is based on adaptive power-frequency communication of electric detection method of period, comprise following part:

1. determine based on the signal time domain of preface information

Before the uplink and downlink Data Modulation of power frequency communication system, all add preface information; Preface information realizes modulation by N sequence chip by 2N power frequency period, each chip represents with the front and back of voltage, current distortion signal location in two power frequency periods, its chip coded system this patent adopts false noise coding, N is larger, the time domain of modulation signal is determined more accurate, but time overhead also increases, and this patent selects then that N is 7 or 11.

At receiving terminal, by the coding consistent with transmitting terminal the sampled signal of 2N power frequency period is passed through difference, coding ranking operation generation composite signal, weighted coding is consistent with the transmitting terminal coding.

Except modulation signal, comprise that first-harmonic remaining after the difference, harmonic signal and various electrical network disturb in the composite signal; Because the characteristics of false noise coding, the modulation signal composition can access N enhancing doubly in the composite signal, and electric network noise does not almost strengthen, and the signal to noise ratio of power frequency modulation signal is improved greatly, provides the foundation for determine power frequency modulation signal place time domain by time frequency analysis.

In the power frequency communication system, the frequency range of descending voltage distorted signal is between 150HZ to 600HZ, and the ascending current distorted signal is between 200HZ to 500HZ; In the composite signal of preface information period, because the modulation signal composition strengthens greatly, there is the period at the power frequency modulation signal, other periods of energy Ratios in corresponding frequency range have obvious advantage, therefore, Energy distribution situation by corresponding frequencies scope in the time frequency analysis calculating composite signal just can access the voltage zero-cross time difference between each distribution transformer low-pressure side and the electric substation.

Wigner distribution (WVD) has very high time frequency resolution, very suitablely determine the distortion current transmitting time by time-frequency distributions, but Wigner distribution belongs to nonlinear transformation, for composite signal, obtain accurately time-frequency situation of change by the Wigner distribution conversion, also the essential intersection that suppresses between the unlike signal is disturbed; To be combined with Wigner distribution and can either obtain good time-frequency distributions characteristic based on the window function of certainly composing of short time discrete Fourier transform, and can reduce again and intersect the impact of disturbing.

The Wigner distribution of preface information composite signal s (t) is:

$W(t,\mathrm{\ω})=\underset{-\∞}{\overset{+\∞}{\∫}}s(t+\mathrm{\τ}/2)s*(t-\mathrm{\τ}/2)\exp (-\mathrm{j\ω\τ})\mathrm{d\τ}$

Be expressed as from the spectrum window function:

$Q(t,\mathrm{\ω})={\left|\mathrm{STFT}(t,\mathrm{\ω})\right|}^2={\left|\underset{-\∞}{\overset{+\∞}{\∫}}s\left(\mathrm{\τ}\right)h(\mathrm{\τ}-t)\exp (-\mathrm{j\ω\τ})\mathrm{d\τ}\right|}^2$

Wherein, h (t) is the window function of short time discrete Fourier transform, and this patent is chosen as rectangular window.

Like this, the Wigner distribution of inhibition cross influence is: W (t, ω) ^▽=W (t, ω) Q (t, ω)

The operand of Wigner distribution is very large, for the real-time of calculating, this patent is only analyzed the time-frequency distributions situation that meets the frequency modulating signal scope in the composite signal, consider that the odd harmonic interference ratio is more serious in the electrical network, this patent adopts the Wigner distribution of 208.3HZ, 312.5HZ, near the frequency of these 4 even-order harmonics of 416.6HZ, 520.8HZ to reflect the energy distribution state of modulation signal.

Like this, the energy distribution function W (n) that meets power frequency modulation signal frequency domain scope is:

Wherein, n is the discrete time of sampled signal, ω _iAbove 4 radio-frequency components have been represented; The peak value that receiving terminal can access power frequency modulation signal Energy distribution by W (n) parameter constantly, this is constantly very little and substantially fixing with the voltage zero-cross time difference of transmitting terminal, so just can calculate the voltage zero-cross time difference of frequency communication sending and receiving end.

2. in conjunction with the data demodulates of the voltage zero-cross time difference

Because electric network noise is strong, the uplink and downlink transfer of data all is the direction reflection by the power frequency modulation signal in the power frequency communication system, the modulation system of data message is consistent with coding and traditional power frequency communication system, the downlink data modulation adopts per 2 power frequency periods to carry a data message, front and back by voltage distortion signal position represent, and the current distortion signal of each upstream data by 4 power frequency periods represents.

Consider that from cost and signal distortion effect this patent adopts the resistance modulation at uplink communication, downlink communication adopts the reactance modulation; Because the waveform of modulation signal can be determined in advance, data demodulates is the judgement of waveform direction, so thereby receiving terminal carries out the direction realization power frequency data demodulates that computing cross-correlation just can be judged the actual modulated signal with reference signal after sampled signal is removed most of the interference by computings such as difference again.

In power frequency communication system, the downlink communication voltage modulated, uplink communication adopts current-modulation, and the modulation signal waveform is different, so reference signal is also different.

In downlink communication, long-range frequency communication terminal gathers voltage signal, be y (t) at corresponding power frequency period according to the composite signal that data encoding forms, in the remote terminal in advance the reference signal of storage be v (t), by the cross-correlation parameters R between them _YvThe positive and negative direction that just can reflect modulation signal (τ), the cross-correlation parameter is:

$R_{\mathrm{sv}}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}y\left(t\right)v(t+\mathrm{\τ})h(t+\mathrm{\τ})\mathrm{dt}$

Wherein, y (t) is the data composite signal, and τ is the relevant time delay take the receiving-end voltage zero passage as benchmark, and h (t+ τ) is rectangular window function, and the data composite signal can further be expressed as:

y(t)＝f(i)v(t+Δ)+n(t)

Wherein, f (i) is ambipolar data message, and Δ is the voltage zero-cross time difference of sending and receiving end, and n (t) disturbs for electrical network, and substitution cross-correlation calculation of parameter can get:

$R_{\mathrm{sv}}\left(\mathrm{\τ}\right)=f\left(i\right)\underset{-\∞}{\overset{+\∞}{\∫}}v(t+\mathrm{\Δ})v(t+\mathrm{\τ})\mathrm{dt}+\underset{-\∞}{\overset{+\∞}{\∫}}n\left(t\right)v(t+\mathrm{\τ})\mathrm{dt}$

R _SvBoth comprised the cross-correlation composition between modulation signal and the electric network noise (τ), and also comprised the auto-correlation composition of modulation signal, and be independent of each other between electric network noise and the modulation signal, noise is subject to the inhibition of certain degree; Owing to can calculate the voltage zero-cross time difference Δ of sending and receiving end by time frequency analysis, power frequency modulation signal time of occurrence can determine, when relevant time delay τ equals Δ, and auto-correlation coefficient maximum and for just, R _Sv(τ) positive and negative main just determined by data message f (i), therefore just can realize data demodulates by the positive and negative of judgement cross-correlation parameter.

Because this patent is determined the voltage zero-cross time difference Δ of signal transmitting and receiving end by time frequency analysis, the auto-correlation composition absolute value that can guarantee modulation signal in the calculating of cross-correlation parameter is maximum, and obtain optimal judgement constantly, thereby improved the antijamming capability of data demodulates, Δ is larger, and effect is more obvious, after Δ surpasses certain numerical value, even it is very little that electrical network disturbs, traditional power frequency demodulation mode also mistake can occur.

The process of up frequency communication is basically identical with appeal uplink communication process, so difference is being taken a sample to current signal, the coded system that forms composite signal is different, form 1 composite signal at 4 power frequency periods, and it is not identical with reference to the waveform of modulation signal yet, be stored in advance in the uplink demodulation device in the electric substation, also be in conjunction with determining that by the preface information time frequency analysis voltage zero-cross time difference Δ of signal transmitting and receiving end carries out computing cross-correlation and realizes demodulation, its communication performance can strengthen greatly, the voltage zero-cross time difference of sending and receiving end is larger, and effect is more obvious.

Claims (4)

1. one kind based on adaptive power-frequency communication of electric detection system of period, it is characterized in that, describedly be comprised of the main website equipment that is positioned at electric substation and the telecommunication terminal that is positioned at the distribution transformer low-pressure side based on adaptive power-frequency communication of electric detection system of period, described main website equipment comprises again downstream signal drive unit and upward signal demodulating equipment; The downstream signal drive unit is connected on the ultra-high-tension power transmission line by the house transformer that is positioned at electric substation, A/D converter is connected on the ultra-high-tension power transmission line by voltage transformer pt summation current transformer CT, and the voltage and current signal that PT, CT are gathered is converted to the digital quantity that can supply DSP to process; Dsp processor, downstream signal drive unit and A/D converter composition control module; The frequency communication terminal is connected on the ultra-high-tension power transmission line by voltage transformer pt and distribution transformer;

Described downstream signal drive unit connects respectively the circuits for triggering of bidirectional triode thyristor, positive and negative comparison circuit and Max485 by microprocessor CPU; Bidirectional triode thyristor is connected with inductance L by protective circuit, and positive and negative comparison circuit connects signal conditioning circuit and consists of; Signal conditioning circuit is connected to the secondary of house transformer by voltage transformer pt; Inductance L is connected to the secondary of house transformer; Industrial computer is connected with Max485;

Described upward signal demodulating equipment connects to form with dsp processor and 16 A/D converters, and dsp processor is connected with house transformer by positive and negative comparison circuit, voltage transformer pt; 16 A/D converters by modulate circuit respectively be connected to A, B, C phase line on three secondary current instrument transformer CT be connected;

Described telecommunication terminal comprises by dsp processor and 16 A/D converters and connects to form processing module, dsp processor connects circuits for triggering, circuits for triggering connect the control utmost point of bidirectional triode thyristor by protective circuit, the drain electrode of bidirectional triode thyristor is by inductance L ground connection, and source electrode connects distribution transformer 380V end; Distribution transformer 380V end connects respectively signal conditioning circuit and positive and negative comparison circuit by voltage transformer pt, and signal conditioning circuit connects 16 A/D converters again, and positive and negative comparison circuit connects dsp processor again; The function of telecommunication terminal is that the demodulation of descending voltage distorted signal, communication protocol are processed, the ascending current modulation, and these functions all are to finish take the DSP calculation process as core; DSP gathers, processes voltage signal by 16 A/D, at first according to the definite descending voltage distortion information place time domain from electric substation of preface information, then carries out data demodulates in conjunction with the sending and receiving end voltage zero-cross time difference, and antijamming capability strengthens greatly.

2. described based on adaptive power-frequency communication of electric detection system of period according to claim 1, it is characterized in that, described downstream signal drive unit produces the low-pressure side that the voltage distortion signal transfers to distribution transformer by modulation transformer or electric substation with becoming near voltage zero-cross, telecommunication terminal receives, processes downstream signal based on the period adaptive mode; When frequency communication terminal loopback uplink information, the frequency communication terminal is passed through distribution transformer generation current distorted signal near voltage zero-cross, the upward signal demodulating equipment of electric substation also is based on the period adaptive mode and realizes uplink demodulation by the current signal of transducer collection 10KV circuit; Owing to possess period adaptive reception characteristics, power frequency communication system can the Adaptive Modulation transformer and the various connected modes of distribution transformer when modulation /demodulation.

3. one kind based on adaptive power-frequency communication of electric detection method of period, it is characterized in that, comprises following part:

1) determines based on the signal time domain of preface information

At first according to the synthetic sampled signal of modulating-coding, can obviously improve like this signal to noise ratio of power frequency distorted signal, then according to the spectrum modulation signal scope composite signal being carried out time frequency analysis calculates, time frequency analysis adopts based on the Wigner distribution of short time discrete Fourier transform as window function, very high time frequency resolution can be obtained, interference effect can be suppressed to intersect again; The most concentrated time domain of Energy distribution namely is judged as the power frequency distorted signal place period, and the time difference of definite frequency communication sending and receiving end voltage zero-cross; Before the uplink and downlink Data Modulation of power frequency communication system, all add preface information; Preface information realizes modulation by N sequence chip by 2N power frequency period, each chip represents with the front and back of voltage, current distortion signal location in two power frequency periods, its chip coded system adopts false noise coding, N is larger, the time domain of modulation signal is determined more accurate, but time overhead also increases, and selecting then, N is 7 or 11;

At receiving terminal, by the coding consistent with transmitting terminal the sampled signal of 2N power frequency period is passed through difference, coding ranking operation generation composite signal, weighted coding is consistent with the transmitting terminal coding;

2) in conjunction with the data demodulates mode of the voltage zero-cross time difference, coding characteristic according to data message, the modulation signal waveform of reflection data message can determine that in advance data demodulates is the judgement of waveform direction, and calculates the accurate time domain that can determine modulation waveform by time frequency analysis; Adopt the cross-correlation mode to carry out data demodulates, its demodulation computing, judgement are determined in conjunction with the time frequency analysis resulting sending and receiving end voltage zero-cross time difference constantly by the test side voltage zero-cross constantly; Because electric network noise is strong, the uplink and downlink transfer of data all is the direction reflection by the power frequency modulation signal in the power frequency communication system, the modulation system of data message, it is consistent with traditional power frequency communication system to encode, the downlink data modulation adopts per 2 power frequency periods to carry a data message, front and back by voltage distortion signal position represent, and the current distortion signal of each upstream data by 4 power frequency periods represents.

4. described based on adaptive power-frequency communication of electric detection method of period according to claim 3, it is characterized in that, described Wigner distribution has very high time frequency resolution, very suitablely determine the distortion current transmitting time by time-frequency distributions, but Wigner distribution belongs to nonlinear transformation, for composite signal, obtain accurately time-frequency situation of change by the Wigner distribution conversion, also the essential intersection that suppresses between the unlike signal is disturbed; To be combined with Wigner distribution and can either obtain good time-frequency distributions characteristic based on the window function of certainly composing of short time discrete Fourier transform, and can reduce again and intersect the impact of disturbing,

The Wigner distribution of preface information composite signal s (t) is:

Be expressed as from the spectrum window function:

Wherein, h (t) is the window function of short time discrete Fourier transform, is chosen as rectangular window;

Like this, the Wigner distribution of inhibition cross influence is:

The operand of Wigner distribution is very large, for the real-time of calculating, only analyze the time-frequency distributions situation that meets the frequency modulating signal scope in the composite signal, consider that the odd harmonic interference ratio is more serious in the electrical network, adopt the Wigner distribution of 208.3HZ, 312.5HZ, near the frequency of these 4 even-order harmonics of 416.6HZ, 520.8HZ to reflect the energy distribution state of modulation signal;

Like this, the energy distribution function W (n) that meets power frequency modulation signal frequency domain scope is:

Wherein, n is the discrete time of sampled signal, ω _iAbove 4 radio-frequency components have been represented; The peak value that receiving terminal can access power frequency modulation signal Energy distribution by W (n) parameter constantly, this is constantly very little and substantially fixing with the voltage zero-cross time difference of transmitting terminal, so just can calculate the voltage zero-cross time difference of frequency communication sending and receiving end.

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