CN110543093A

CN110543093A - Power distribution terminal time synchronization method using power grid frequency value comparison

Info

Publication number: CN110543093A
Application number: CN201910981468.6A
Authority: CN
Inventors: 韩国政; 剧晶晶; 赵文青
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2019-07-05
Filing date: 2019-10-16
Publication date: 2019-12-06

Abstract

A method for carrying out time synchronization by using a power frequency value of a power grid voltage as a reference quantity can improve the time synchronization precision between different power distribution terminals on a power distribution line, and is characterized in that: the power frequency value of the power grid is changed in real time, the frequency values acquired and calculated at different places are the same, and by utilizing the characteristic, clock synchronization is realized through frequency value comparison, and the error of clock synchronization is reduced. By the method and the device, the time synchronization precision between different power distribution terminals on the same distribution line can be improved.

Description

Power distribution terminal time synchronization method using power grid frequency value comparison

Technical Field

A method for comparing power grid frequency values and calculating clock deviation to achieve clock consistency between power distribution terminals belongs to the field of power system automation. The method is suitable for keeping clock synchronization among all power distribution terminals on the same power distribution line or power distribution terminals on different power distribution lines on the same bus.

Background

Feeder automation is an important component of distribution automation, and by means of a distribution automation terminal (short for a distribution terminal, FTU) installed on a distribution line (feeder), the states of a feeder section switch and a tie switch and the conditions of feeder current and voltage are monitored in real time under a normal state, so that remote or local switching-on and switching-off operations of the line switch are realized. When the fault occurs, the fault record is obtained, the fault section of the feeder line can be automatically distinguished and isolated, and the power supply can be rapidly recovered to the non-fault area. The method has the advantages that fault positioning, isolation and automatic recovery are significant to improving the reliability of power supply and shortening the power failure time of a non-fault area, and the method is a main function of feed automation. The basic principle is as follows: the power distribution network line of the open-loop operation of the ring network structure is divided into a plurality of power supply sections by the section switches, when a permanent fault occurs in a feeder line, the fault is automatically positioned, and fault isolation is realized through the sequential action of the switch equipment; the load transfer is realized in the power distribution network with the looped network operation or the looped network structure but the open loop operation, and the power supply is recovered. When a transient fault occurs, the fault current is normally cut off, and the fault automatically disappears, so that the breaker automatically closes and the power supply to the load can be restored. Therefore, the power failure range is reduced, the power failure time is shortened, and the power supply reliability is improved. In order to realize feeder automation, a distribution terminal device is required to be installed at a section switch on a distribution line (feeder), the current and voltage conditions of the feeder are monitored, and the remote control of opening and closing of the section switch is realized. Therefore, the clocks of different power distribution terminals are kept consistent, and the method has important influence on fault judgment, isolation and power supply recovery of the power distribution line.

In order to keep the clocks of the distribution terminals on the same distribution line consistent, a common method is to install a GPS or beidou clock in a substation to provide a standard clock signal, the distribution terminal of the substation is responsible for clock synchronization of the terminals on the distribution line, the standard clock signal is sent to the distribution terminal on the feeder line, and the distribution terminal on the distribution line adjusts the local clock according to the received standard clock. Common time synchronization methods include IEC 60870-5-101/104 time synchronization method, simple network time protocol SNTP, IEEE 1588 time synchronization protocol and the like. When the time setting command of IEC 60870-5-101/104 is adopted to time the power distribution terminal, the network delay is difficult to calculate, and the time setting error is large, usually in the order of seconds. The SNTP protocol adopts a client/server working mode, the server receives GPS signals as the time reference of the system, and the client acquires accurate time information by regularly accessing the time service provided by the server and adjusts the system clock of the client to achieve the aim of network clock synchronization. In a feeder-automated network environment, the SNTP time tick error exceeds 10 ms. IEC 61588 uses hardware and software to cooperate at the same time, more accurate timing synchronization is obtained, and microsecond-level time synchronization accuracy can be realized. However, IEC 61588 requires the support of routers and switches, and is difficult to implement in a feeder-automated network environment.

Disclosure of Invention

The invention aims to provide a time synchronization method, which utilizes the characteristics that the frequency values of a power grid are changed at different times and the frequency values of the power grid at different places and the same time are the same, and takes the frequency values of the power grid as the reference quantity for adjusting the clock of a power distribution terminal, thereby improving the time synchronization precision of the power distribution terminal and realizing that the time synchronization error between the power distribution terminals is less than 1 ms.

The purpose of the invention can be realized by the following technical scheme.

A time synchronization method for a power distribution terminal by using a frequency value of a grid voltage as a reference quantity is realized by a system comprising a power distribution terminal (FTU) and a communication system on the same distribution line, as shown in figure 1. The power distribution terminals exchange information through the communication system.

The distribution terminal (FTU) comprises an FTU positioned at a substation bus and an FTU positioned at a section switch on a distribution line. And monitoring the voltage information of the substation bus by the FTU at the substation bus. FTU on the distribution lines monitors and collects the current and voltage information of the operation of the distribution lines and the on-off action information of the switches, and the line fault is judged according to the collected line information. And receiving time tick information and adjusting the local clock of the FTU.

The communication system provides channels for communication among the FTUs of the power distribution terminals.

FTU0 is the distribution terminal of monitoring transformer substation busbar voltage, installs at the transformer substation, and FTU0 links to each other with the GPS or the beidou system of transformer substation, as standard clock source. FTU11, FTU12, FTU13 are power distribution terminals installed at section switches on the distribution line 1 (feeder 1), and FTU11, FTU12, FTU13 are clocked in line with FTU 0.

All the power distribution terminals can collect the same-phase voltage power frequency signals (taking AB line voltage as an example).

The time stamp of the time tick is composed of 64-bit unsigned floating point numbers, the integer part is the first 32 bits, the decimal part is the last 32 bits, the unit is second, and the time is 1 month, 1 day and zero point corresponding to 1900 years. The frequency value of the cycle is expressed by 32-bit unsigned integer, and the number is divided by 1000 to obtain the true value of the frequency, and the unit is Hz.

The flow of the whole system time setting is shown in fig. 2: the FTU0 sends broadcast messages to all the power distribution terminals (FTU 11, FTU12 and FTU 13) on the same distribution line, and informs the FTU0 of being a standard clock source of the local area, and the power distribution terminals (FTU 11, FTU12 and FTU 13) on the line carry out clock synchronization by taking the FTU0 as the standard clock.

FTU11 sends a time tick request command to FTU0, while FTU11 starts collecting voltage (for example, AB line voltage) signals and calculates frequency values, once per cycle, recording the time and frequency values at which the cycle starts.

After receiving the time synchronization request command, the FTU0 starts to collect voltage (for example, AB line voltage) signals of the power grid and calculates frequency values, each cycle is calculated once, and the time T0 when the 1 st cycle starts (phase of 0 °) and 5 consecutive frequency values are recorded. And after 5 cycles, stopping frequency calculation.

After the frequency values of 5 consecutive cycles are calculated, the FTU0 sends a time response command to the FTU11, where the command information includes the start time of the 1 st cycle and the frequency values of 5 consecutive cycles.

And after receiving the time-setting response command sent by the FTU0, the FTU11 stops frequency calculation.

f ₁₁FTU11 begins to perform frequency value comparisons. If the frequency values of N cycles are recorded in the FTU11 from the beginning of sending the time synchronization request to the time synchronization response, the comparison is performed from the 1 st frequency value f11 to the N-5 th frequency value, and the following are calculated:

f1 _(i+k) f0 _(i+1) k k k ρ kin the above formula, f1(i + k) represents the frequency value recorded by the FTU11, f0(i +1) represents the frequency value recorded by the FTU0, k represents the kth frequency value recorded by the FTU11, and k starts from 1. And selecting k corresponding to the minimum rho value, wherein the time T1k-1 corresponding to the beginning of the kth cycle of the FTU11 is the same as the time T0 returned by the FTU0, and the clock deviation is Toffset = T0-T1 k-1.

FTU11 performs clock correction: t = T + Toffset

The time setting process of other FTUs such as the FTU12 and the like is the same as that of the FTU11, and the steps are the same as [0013] to [0018 ].

Drawings

Fig. 1 is a block diagram of a feeder automation system; fig. 2 is a diagram of a power distribution terminal versus time communication process.

Detailed Description

The specific embodiment of the present invention is shown in fig. 2, but is not limited to this example.

FTU0 is the FTU located at the feeder line outlet switch of the substation, and the substation GPS provides a standard clock for FTU 0. FTU0 serves as a standard clock for FTU11, FTU12, etc. on the feeder line. FTU11 is the FTU at the section switch on the feeder line, and FTU11 needs to be clocked in line with FTU 0.

FTUs 0, 11, and the like have a function of detecting voltage and current on a feeder line.

FTU0, FTU11, etc. are connected via a communication network.

Claims

1. A distribution terminal time synchronization method using a power grid frequency value as a reference quantity is characterized in that a distribution terminal at a bus of a transformer substation is used as a standard clock source, and time difference between distribution terminals is calculated through frequency value comparison by utilizing the characteristics that the power grid frequency value changes constantly and the power grid frequency values detected by different distribution terminals at the same moment are the same, so that time synchronization precision is improved.

2. The method of claim 1, wherein the power distribution terminal at the standard clock source power distribution terminal of the substation and the power distribution terminal at the section switch on the power distribution line select voltage power frequency signals of the same phase (such as AB line) for collecting and calculating the power grid frequency, and the starting time of each cycle is the time when the power grid voltage phase angle is 0 °.

3. A method according to claim 1, 2, characterized in that the power distribution terminal (slave clock) on the line, after sending the time synchronization request command, starts the frequency calculation of the voltage signal immediately and records the starting time and frequency value of each cycle.

4. The method of claim 1 or 2, wherein the distribution terminal (master clock) of the substation, after receiving the time synchronization request command, starts the frequency calculation of the voltage signal, records the starting time of the 1 st cycle and the frequency value of 5 consecutive cycles, and sends the time synchronization response command, wherein the command information includes the starting time of the 1 st cycle and the frequency value of 5 consecutive cycles.

5. The method as claimed in claims 1, 2, 3 and 4, wherein the master clock and the slave clock are compared by frequency value to find out the cycle corresponding relationship of the master clock and the slave clock and calculate the clock deviation.