阅读说明：本技术 一种低压配电网时间同步方法 (Time synchronization method for low-voltage distribution network ) 是由 徐丙垠 王敬华 方善忠 陈文钢 李胜祥 于 2020-06-09 设计创作，主要内容包括：一种低压配电网时间同步方法,属于低压配电技术领域。其特征在于：包括如下步骤：步骤1)沿输电方向给低压配电网划分等级；步骤2)在第一级低压配电网的根节点智能终端P处注入对时特征脉冲信号,并在第一级低压配电网的各组P1~Pn处接收对时特征脉冲信号,完成第一级的级内对时；步骤3)在第一级低压配电网的各组P1~Pn处分别注入对时特征脉冲信号,并在第二级低压配电网中与其相连的子节点智能终端Q处接收信号,完成级间对时；步骤4)按照输电方向依次对每一级低压配电网完成级内对时以及相邻两级低压配电网的级间对时。本低压配电网时间同步方法保证了对时准确,方法成本低,可靠性高,简单易行,便于推广使用。(A time synchronization method for a low-voltage distribution network belongs to the technical field of low-voltage distribution. The method is characterized in that: the method comprises the following steps: step 1) grading a low-voltage distribution network along a power transmission direction; step 2) injecting a time setting characteristic pulse signal at a root node intelligent terminal P of the first-stage low-voltage distribution network, and receiving the time setting characteristic pulse signal at each group P1-Pn of the first-stage low-voltage distribution network to complete the first-stage internal time setting; step 3) time setting characteristic pulse signals are respectively injected into groups P1-Pn of the first-stage low-voltage distribution network, and signals are received at a child node intelligent terminal Q connected with the second-stage low-voltage distribution network in the second-stage low-voltage distribution network to complete inter-stage time setting; and 4) sequentially carrying out intra-stage time synchronization on each stage of low-voltage distribution network and inter-stage time synchronization on two adjacent stages of low-voltage distribution networks according to the power transmission direction. The time synchronization method for the low-voltage distribution network ensures accurate time synchronization, and has the advantages of low cost, high reliability, simplicity, feasibility and convenience in popularization and use.)

1. A time synchronization method for a low-voltage distribution network is characterized by comprising the following steps: the method comprises the following steps:

step 1) grading the low-voltage distribution network along the power transmission direction, wherein the terminal from each transformer terminal or detection terminal to the outgoing line position is one grade, the outgoing line position of each distribution transformer is divided into a plurality of groups, the grade number of the low-voltage distribution network is less than or equal to 10 grades, and the group number of each grade is less than or equal to 5;

step 2) injecting a time setting characteristic pulse signal at a root node intelligent terminal P of the first-stage low-voltage distribution network, and receiving the time setting characteristic pulse signal at each group P1-Pn of the first-stage low-voltage distribution network to complete the first-stage internal time setting;

step 3) time setting characteristic pulse signals are respectively injected into groups P1-Pn of the first-stage low-voltage distribution network, and signals are received at a child node intelligent terminal Q connected with the second-stage low-voltage distribution network in the second-stage low-voltage distribution network to complete inter-stage time setting;

and 4) sequentially carrying out intra-stage time synchronization on each stage of low-voltage distribution network and inter-stage time synchronization on two adjacent stages of low-voltage distribution networks according to the power transmission direction, and completing the time synchronization of the low-voltage distribution networks.

2. The time synchronization method for the low-voltage distribution network according to claim 1, characterized in that: in the step 1), the time slot of each two adjacent low-voltage power distribution networks is 100ms, and the time slot of each two adjacent groups in each first power distribution network is 20 ms.

3. The time synchronization method for the low-voltage distribution network according to claim 1, characterized in that: the time setting characteristic pulse signal in the step 2) or the step 3) is sent out through a signal generating module.

4. The time synchronization method for the low-voltage distribution network according to claim 3, characterized in that: the signal generation module include live wire L1, zero line N, resistance R, electric capacity C and signal generator, live wire L1 connects electric capacity C and resistance R's one end simultaneously, electric capacity C and resistance R's the other end connect signal generator's one end simultaneously, signal generator's the other end connects zero line N.

5. The time synchronization method for a low-voltage distribution network according to claim 3 or 4, characterized in that: the signal sending method of the signal generating module comprises the following steps:

step 1001, start;

step 1002, judging whether the task time is reached, if so, executing step 1002, and if not, continuing to wait until the cycle task time is reached;

step 1003, calibrating the starting time;

step 1004, generating a pair pulse code;

step 1005, sending out a disturbance signal in the equipment distribution time slot;

and step 1006, ending.

6. The time synchronization method for a low-voltage distribution network according to claim 1 or 3, characterized in that: the time setting characteristic pulse signal is received by the signal receiving module.

7. The time synchronization method for the low-voltage distribution network according to claim 6, characterized in that: the signal receiving module comprises a band-pass filtering module, a level detection module, an A/D conversion module and a CPU, wherein a signal input end of the band-pass filtering module receives a time synchronization characteristic pulse signal, a signal output end of the band-pass filtering module is connected with input ends of the level detection module and the A/D conversion module at the same time, and output ends of the level detection module and the A/D conversion module are connected with the CPU.

8. The time synchronization method for the low-voltage distribution network according to claim 6, characterized in that: the signal receiving method of the signal receiving module comprises the following steps:

step 2001, start;

step 2002, band-pass filtering;

step 2003, judging whether the level is triggered, if so, executing step 2004, and otherwise, executing step 2002;

step 2004, recording the triggering time and the wave recording process;

step 2005, identifying the pulse, checking the code;

step 2006, judging whether the verification passes, if so, executing step 2007, and if not, executing step 2002;

step 2007, starting a timing process;

step 2008, end.

9. The time synchronization method for a low-voltage distribution network according to claim 1 or 3, characterized in that: the time setting characteristic pulse signal sequentially comprises a lead code, a mark code, data and a CRC check code from front to back.

10. The time synchronization method for the low-voltage distribution network according to claim 9, characterized in that: the time synchronization method in the step 2) or the step 3) comprises the following steps:

code discrimination, intercepting plus or minus 20us of the first 1 position of the lead code as a reference, sliding by taking a pulse width time window as a unit, calculating a correlation coefficient once when sliding a pulse width, recording as K, finishing the identification of the whole data by taking K >0.8 as 1 and K <0.5 as 0,

wherein, the calculation formula of the correlation coefficient is as follows:

，

wherein the content of the first and second substances,Cov（X，Y) Is composed ofXAndYthe covariance of (a) of (b),Var[X]is composed ofXThe variance of (a) is determined,Var[Y]is composed ofYThe variance of (a);

checking, namely checking the validity of the data by CRC;

and finishing time synchronization operation.

Technical Field

A time synchronization method for a low-voltage distribution network belongs to the technical field of low-voltage distribution.

Background

The time synchronization of the low-voltage distribution network is a supporting technology for a plurality of applications such as fault detection, instantaneous line loss and the like, and a simple and reliable time synchronization method is lacked for a long time. The low-voltage power distribution internet of things generally adopts wireless communication and HPLC (high performance liquid chromatography) broadband carrier communication, the time delay of the two communication modes is difficult to determine, accurate time synchronization cannot be realized, accurate time synchronization can be realized by adopting satellite synchronization modes such as GPS (global positioning system) and the like, but the low-voltage power distribution internet of things is high in cost, and is difficult to popularize and apply due to signal shielding in buildings.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method overcomes the defects of the prior art, and is low in cost, high in reliability, simple and easy to implement.

The technical scheme adopted by the invention for solving the technical problems is as follows: the time synchronization method for the low-voltage distribution network is characterized by comprising the following steps: the method comprises the following steps:

step 1) grading the low-voltage distribution network along the power transmission direction, wherein the terminal from each transformer terminal or detection terminal to the outgoing line position is one grade, the outgoing line position of each distribution transformer is divided into a plurality of groups, the grade number of the low-voltage distribution network is less than or equal to 10 grades, and the group number of each grade is less than or equal to 5;

step 2) injecting a time setting characteristic pulse signal at a root node intelligent terminal P of the first-stage low-voltage distribution network, and receiving the time setting characteristic pulse signal at each group P1-Pn of the first-stage low-voltage distribution network to complete the first-stage internal time setting;

step 3) time setting characteristic pulse signals are respectively injected into groups P1-Pn of the first-stage low-voltage distribution network, and signals are received at a child node intelligent terminal Q connected with the second-stage low-voltage distribution network in the second-stage low-voltage distribution network to complete inter-stage time setting;

and 4) sequentially carrying out intra-stage time synchronization on each stage of low-voltage distribution network and inter-stage time synchronization on two adjacent stages of low-voltage distribution networks according to the power transmission direction, and completing the time synchronization of the low-voltage distribution networks.

Preferably, the time slot of each two adjacent low-voltage distribution networks in the step 1) is 100ms, and the time slot of each two adjacent groups in each first distribution network is 20 ms.

Preferably, the time tick characteristic pulse signal in step 2) or step 3) is sent out by a signal generation module.

Preferably, the signal generating module includes a live wire L1, a neutral wire N, a resistor R, a capacitor C and a signal generator, the live wire L1 is connected to one end of the capacitor C and one end of the resistor R, the other end of the capacitor C and the other end of the resistor R are connected to one end of the signal generator, and the other end of the signal generator is connected to the neutral wire N.

Preferably, the signal sending method of the signal generating module includes the following steps:

step 1001, start;

step 1002, judging whether the task time is reached, if so, executing step 1002, and if not, continuing to wait until the cycle task time is reached;

step 1003, calibrating the starting time;

step 1004, generating a pair pulse code;

step 1005, sending out a disturbance signal in the equipment distribution time slot;

and step 1006, ending.

Preferably, the time tick characteristic pulse signal is received by a signal receiving module.

Preferably, the signal receiving module comprises a band-pass filtering module, a level detecting module, an a/D converting module and a CPU, a signal input end of the band-pass filtering module receives the time tick feature pulse signal, a signal output end of the band-pass filtering module is connected with input ends of the level detecting module and the a/D converting module at the same time, and output ends of the level detecting module and the a/D converting module are connected with the CPU.

Preferably, the signal receiving method of the signal receiving module is as follows:

step 2001, start;

step 2002, band-pass filtering;

step 2003, judging whether the level is triggered, if so, executing step 2004, and otherwise, executing step 2002;

step 2004, recording the triggering time and the wave recording process;

step 2005, identifying the pulse, checking the code;

step 2006, judging whether the verification passes, if so, executing step 2007, and if not, executing step 2002;

step 2007, starting a timing process;

step 2008, end.

Preferably, the time tick signature pulse signal sequentially includes a preamble, a flag code, data, and a CRC check code from front to back.

Preferably, the time synchronization method in step 2) or step 3) includes the following steps:

code discrimination, intercepting plus or minus 20us of the first 1 position of the lead code as a reference, sliding by taking a pulse width time window as a unit, calculating a correlation coefficient once when sliding a pulse width, recording as K, finishing the identification of the whole data by taking K >0.8 as 1 and K <0.5 as 0,

wherein, the calculation formula of the correlation coefficient is as follows:

，

wherein the content of the first and second substances,Cov（X，Y) Is composed ofXAndYthe covariance of (a) of (b),Var[X]is composed ofXThe variance of (a) is determined,Var[Y]is composed ofYThe variance of (a);

checking, namely checking the validity of the data by CRC;

and finishing time synchronization operation.

Compared with the prior art, the invention has the beneficial effects that:

1. the time synchronization method for the low-voltage distribution network utilizes the distribution Internet of things terminal and the HPLC communication network, ensures that the system clock error is within 20us, ensures that the time synchronization is accurate, and signals are not shielded by buildings, has low cost, high reliability, simplicity and feasibility, is convenient to popularize and use, ensures that the number of stages of the low-voltage distribution network is less than or equal to 10, and the number of groups of each stage is less than or equal to 5, thereby ensuring the time synchronization precision, assumes that the maximum error of one-stage time synchronization is 4us, ensures that the common low-voltage distribution line does not exceed five stages, and ensures that the system clock error is within 20 us.

2. 100ms time slots are distributed to the same-level low-voltage distribution network, the time slots of two adjacent groups in each-level low-voltage distribution network are 20ms, and each terminal sends 2 time synchronization pulses from the first power frequency peak-valley point in the belonged time slot, so that the accuracy of time synchronization is guaranteed.

3. The signal generator is a square wave signal generator, and the signal generator is coupled between one phase in the line and the ground, so that signal transmission is realized.

4. The time synchronization characteristic pulse signal sequentially comprises a lead code, a mark code, data and a CRC (cyclic redundancy check) code from front to back, so that the signal is conveniently identified, processed and checked, the signal transmission stability is ensured, and the time synchronization is more accurate.

5. A binary data string can be obtained through the code discrimination, so that the identification and processing of signals are facilitated.

Drawings

Fig. 1 is a flowchart of a time synchronization method for a low-voltage distribution network.

Fig. 2 is a circuit diagram of the signal generating module.

Fig. 3 is a circuit block diagram of a signal receiving module.

Fig. 4 is a transmission flow chart of the signal generation module.

Fig. 5 is a receiving flow chart of the signal receiving module.

Detailed Description

Fig. 1 to 5 are preferred embodiments of the present invention, and the present invention will be further described with reference to fig. 1 to 5.

As shown in fig. 1: a time synchronization method for a low-voltage distribution network comprises the following steps:

step 1) grading the low-voltage distribution network along the power transmission direction, wherein the terminal from each transformer terminal or detection terminal to the outgoing line position is a first stage, the outgoing line position of each distribution transformer is divided into a plurality of groups, the grade number of the low-voltage distribution network is less than or equal to 10 grades, and the time slot number of each stage is less than or equal to 5;

the time synchronization needs to know the network topology structure of a low-voltage system, the low-voltage distribution network is divided according to the topology structure, generally, a terminal (a fusion terminal or an intelligent gateway) at a distribution transformer is a first stage, a terminal at an outgoing line is a second stage, and so on, the longitudinal direction can be divided into 10 stages at most, and the width of each stage of time slot is 100 ms.

The same stage distributes 100ms time slots, each time slot is 20ms, each stage of low-voltage distribution network is divided into a plurality of groups, and the requirements of practical application are met. The transverse time slot is 20ms, and 2 power frequency voltage peak-valley points exist. And each terminal sends 2 time synchronization pulses from the first power frequency peak-valley point in the time slot to which the terminal belongs, and the time synchronization process is started after the receiving terminal detects the preamble signal of the time synchronization pulse.

In this embodiment, the low-voltage distribution network is divided into four levels in sequence from top to bottom.

Step 2) injecting a time setting characteristic pulse signal at a root node intelligent terminal P of the first-stage low-voltage distribution network, and receiving the time setting characteristic pulse signal at each group P1-Pn of the first-stage low-voltage distribution network to complete the first-stage internal time setting;

in this embodiment, the root node intelligent terminal P of the first-level low-voltage distribution network is used as a reference clock, and the clock is used as a reference to clock the whole low-voltage distribution network.

Injecting a time setting characteristic pulse signal at a root node intelligent terminal P of the first-stage low-voltage distribution network, receiving the time setting characteristic pulse signal at each group P1-Pn of the first-stage low-voltage distribution network by using a Rogowski coil, and completing the first-stage internal time setting. Wherein n is a positive integer and n is less than or equal to 5.

Step 3) time setting characteristic pulse signals are respectively injected into groups P1-Pn of the first-stage low-voltage power distribution network, and signals are received at a child node intelligent terminal Q of the second-stage low-voltage power distribution network to complete inter-stage time setting;

in this embodiment, the child node intelligent terminal Q of the second-stage low-voltage distribution network is connected to the group P1 of the first-stage low-voltage distribution network, that is, a time synchronization characteristic pulse signal is injected at the group P1 of the first-stage low-voltage distribution network, and a signal is received at the child node intelligent terminal Q connected to the second-stage low-voltage distribution network in the second-stage low-voltage distribution network, so that inter-stage time synchronization is completed.

And 4) sequentially carrying out intra-stage time synchronization on each stage of low-voltage distribution network and inter-stage time synchronization on two adjacent stages of low-voltage distribution networks according to the power transmission direction, and completing the time synchronization of the low-voltage distribution networks.

Time setting characteristic pulse signals are injected into the Q position of the sub-node intelligent terminal of the second-stage low-voltage distribution network, the time setting characteristic pulse signals are received by utilizing Rogowski coils at the Q1-Qm positions of each group of the second-stage low-voltage distribution network, and the second-stage internal time setting is completed. Wherein m is a positive integer and m is less than or equal to 5.

In this embodiment, the child node intelligent terminal S of the third-level low-voltage distribution network is connected to the group Qm of the second-level low-voltage distribution network, that is, a time synchronization characteristic pulse signal is injected into the group Qm of the second-level low-voltage distribution network, and a signal is received at the child node intelligent terminal S of the third-level low-voltage distribution network, so that inter-stage time synchronization is completed.

Time setting characteristic pulse signals are injected into the position of a child node intelligent terminal S of the third-level low-voltage power distribution network, the time setting characteristic pulse signals are received by utilizing Rogowski coils at the positions of all groups S1-Sa of the third-level low-voltage power distribution network, and the third-level internal time setting is completed. Wherein a is a positive integer and a is less than or equal to 5.

In this embodiment, the child node intelligent terminal T1 of the fourth-stage low-voltage distribution network is connected to the group Q1 of the second-stage low-voltage distribution network, the child node intelligent terminal T2 of the fourth-stage low-voltage distribution network is connected to the group Q3 of the second-stage low-voltage distribution network, the child node intelligent terminal T3 of the fourth-stage low-voltage distribution network is connected to the group S1 of the third-stage low-voltage distribution network, and the child node intelligent terminal of the fourth-stage low-voltage distribution network is connected to the group Sa of the third-stage low-voltage distribution. Wherein b is a positive integer, and b is less than or equal to 5. Sub-node intelligent terminal T1~ Tb of fourth level low voltage distribution network connects user's table case respectively.

Injecting time-setting characteristic pulse signals at a group Q1 of the second-stage low-voltage distribution network, and receiving the time-setting characteristic pulse signals at a sub-node intelligent terminal T1 of the fourth-stage low-voltage distribution network; injecting time-setting characteristic pulse signals at a group Q3 of the second-stage low-voltage distribution network, and receiving the time-setting characteristic pulse signals at a sub-node intelligent terminal T2 of the fourth-stage low-voltage distribution network; injecting time-setting characteristic pulse signals at a group S1 of the third-level low-voltage distribution network, and receiving the time-setting characteristic pulse signals at a child node intelligent terminal T3 of the fourth-level low-voltage distribution network; and injecting a time synchronization characteristic pulse signal at the group Sa of the third-level low-voltage distribution network, and receiving the time synchronization characteristic pulse signal at the sub-node intelligent terminal Tb of the fourth-level low-voltage distribution network, thereby completing the interstage time synchronization.

When the intelligent gateway and the low-voltage terminal carry out communication time synchronization according to the stipulation, the time synchronization error is larger due to different differences of channels, HPLC communication is generally adopted in a low-voltage system, the average network delay is less than 30ms according to the requirements of 'interconnection and intercommunication technical specification of low-voltage power line broadband carrier communication' (Q/GDW 11612.1-2016), the time calibration error can be generally controlled within 1s in consideration of extreme conditions, and the maximum allowable error of the scheme is 1 s. In order to compress the amount of data as much as possible, it is recommended to use a 2-level time-tick scheme, namely: the method comprises two modes of millisecond-level time synchronization (hereinafter referred to as coarse time synchronization) and microsecond-level time synchronization (hereinafter referred to as fine time synchronization).

The time setting characteristic pulse signal sequentially comprises a lead code, a mark code, data and a CRC check code from front to back.

The data length of the preamble code is 2 bits, including 11 and 10, where 11 is a coarse time pair, 10 is a fine time pair, and the first bit "1" of the preamble code is used as a time reference time. The data length of the mark code is 4 bits, and is used for identifying the time tick source level, namely the level number. The length of the data is 10 bits, wherein the data meaning during coarse time setting is a deviation value of the whole second, each bit is 1ms, and the maximum length is 999 ms; the fine-time data means a deviation value of a whole millisecond, 1us per bit, and the maximum is 999 us. The data length of the CRC check code is 8 bits.

The time setting characteristic pulse signal is sent by the signal generating module and received by the signal receiving module. The root node intelligent terminal refers to a transformer terminal or a detection terminal of a low-voltage outgoing line main switch, and the sub-node intelligent terminal refers to a low-voltage detection terminal of each node on a line.

As shown in fig. 2: the signal generation module comprises a live wire L1, a zero line N, a resistor R, a capacitor C and a signal generator, wherein the live wire L1 is connected with one ends of the capacitor C and the resistor R, the other ends of the capacitor C and the resistor R are connected with one end of the signal generator, and the other end of the signal generator is connected with the zero line N.

As shown in fig. 3: the signal receiving module comprises a band-pass filtering module, a level detection module, an A/D conversion module and a CPU, wherein a signal input end of the band-pass filtering module receives a time synchronization characteristic pulse signal, a signal output end of the band-pass filtering module is connected with input ends of the level detection module and the A/D conversion module at the same time, and output ends of the level detection module and the A/D conversion module are connected with the CPU. The band-pass filter module is a band-pass filter, the level detection module is a level detector, the A/D conversion module is an A/D converter, and the CPU is a processor.

After the time tick characteristic pulse signal triggers the receiving circuit, the pulse wave recording process is started, the whole time tick pulse is subjected to high-speed sampling (the sampling frequency is temporarily set to be 1 MHz) wave recording, and data needs to be identified after the wave recording is finished, wherein the method comprises the following steps:

code discrimination, intercepting plus or minus 20us of the first 1 position of the lead code as a reference, sliding by taking a pulse width time window as a unit, calculating a correlation coefficient once when sliding a pulse width, recording as K, finishing the identification of the whole data by taking K >0.8 as 1 and K <0.5 as 0,

wherein, the calculation formula of the correlation coefficient is as follows:

，

wherein Cov (X, Y) is the covariance of X and Y, Var [ X ] is the variance of X, and Var [ Y ] is the variance of Y;

checking, namely checking the validity of the data by CRC;

and finishing time synchronization operation.

As shown in fig. 4: the intelligent gateway configures a time synchronization flag bit list for all terminals in the jurisdiction, automatically sets the time synchronization flag bit list to be invalid after timeout, the terminal performs time synchronization as a circular task, sends time synchronization success information to the intelligent gateway after the time synchronization is successful, and refreshes the time synchronization flag bit.

The signal sending method of the signal generating module comprises the following steps:

step 1001, start;

step 1002, judging whether the task time is reached, if so, executing step 1002, and if not, continuing to wait until the cycle task time is reached;

step 1003, calibrating the starting time;

step 1004, generating a pair pulse code;

step 1005, sending out a disturbance signal in the equipment distribution time slot;

and step 1006, ending.

As shown in fig. 5: the signal receiving method of the signal receiving module comprises the following steps:

step 2001, start;

step 2002, band-pass filtering;

step 2003, judging whether the level is triggered, if so, executing step 2004, and otherwise, executing step 2002;

step 2004, recording the triggering time and the wave recording process;

step 2005, identifying the pulse, checking the code;

step 2006, judging whether the verification passes, if so, executing step 2007, and if not, executing step 2002;

step 2007, starting a timing process;

step 2008, end.

The synchronization precision of the time synchronization method for the low-voltage power distribution network can reach 4us, and the method is low in cost, high in reliability, simple and easy to implement by using the power distribution internet of things terminal and the HPLC communication network.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.