JPH0542209B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a synchronization method in a communication device used to compare values sampled simultaneously at remote locations, such as a sampling signal synchronization method used in a protective relay device for a power transmission line. [Prior Art] Digital protective relay devices (carrier relays) that measure current at two remote points on a power transmission line and compare the results to check for abnormalities have come into use. In this type of comparative protective relay device,
After sampling the instantaneous values of current at two points on a power transmission line at regular intervals and converting them into A/D (analog/digital), they are transmitted to each other's device using a microwave line, for example, and each device's own System failures in power transmission lines are monitored by comparing the value with the received value from the other device. In this case, the sampling timing in both devices must be the same time, and the time from sending data to receiving it by the other device,
That is, the transmission delay time is usually longer than the sampling period and several times that period. Therefore, it is necessary to assign a series of repetition numbers to the sampling timing, and to transmit the same number to data sampled at the same time by both devices, to ensure comparison and verification. In this type of protective relay device,
A means of synchronizing timing and sampling numbers has become a very important issue. As this type of signal synchronization method, for example, Japanese Patent Application Laid-open No. 49645/1983 has been proposed. This will be briefly explained below. FIGS. 4a and 4b are explanatory diagrams of the principle of the invention disclosed in Japanese Patent Application Laid-Open No. 50-49645. Hereinafter, the device that takes the initiative in synchronization will be called the master station, and the device that will perform slave synchronization will be called the slave station.The data of a specific sampling number to be sent from the master station to the slave station will be sent to _S1 , and from the slave station to the master station. Let the thing to be sent be _S2 . Figure 4 shows the temporal relationship regarding the transmission and reception of data with a specific sampling number, and shows the time it takes for S ₁ from the master station to arrive at the slave station, and the time for S ₂ from the slave station to reach the master station. There is only a negligible difference in the time it takes to arrive.
Assume that they are equal to each other, and define this as the transmission delay time Td
shall be. (In this way, a transmission line with equal transmission delay time in both directions can actually be constructed.) Also, S ₁ and S ₂
The transmission period T should be at least twice the maximum value of Td, taking into account fluctuations. In Fig. 4, the time from the transmission of S ₁ to the reception of S ₂ at the master station is defined as T ₁ , and this time is measured at the master station, while the time from the transmission of S ₂ to the reception of S ₁ at the slave station is Assuming that the time is _T2 , the slave station measures this time _T2 . And the main station is at the above time
_T1 is loaded onto the data transmission format and sent to the slave station, which receives this _T1 . Conversely, the slave station sends the time _T2 to the master station, and the master station receives it. At this time, FIG. 4a shows a case where the downward diagonal line indicating the transmission of S ₁ from the master station and the upward diagonal line indicating the transmission of S ₂ from the slave station intersect with each other, and T ₁
The time relationship is shown when the relationship +T ₂ = 2Td holds. Further, FIG. 4b shows the time relationship when the diagonal lines S ₁ and S ₂ do not intersect and the relationship T ₁ +T ₂ >2Td holds. Figure 4a shows a case where the transmission of S ₂ from the slave station is delayed in time from the transmission of S ₁ from the master station, and as is clear from the figure, the slave station must It is necessary to slightly advance the phase (timing) of the clock pulse of the transmitter and move the entire transmission from the slave station to the left as indicated by the white arrow in the figure. That is, if T ₁ > T ₂ , the transmission from the slave station must be accelerated, and conversely, if T ₁ <T ₂ , the transmission from the slave station must be delayed. Then, the clock pulse phase is controlled in either the main station, the slave station, or both so that T ₁ =T ₂ . If T ₁ = T ₂ , S ₁ and S ₂ will be transmitted at exactly the same time, and therefore all operations, including the generation of data for other sampling numbers, will be performed by the main station. It becomes possible to perform sampling at the same time with the slave station, and the synchronization of the sampling signals becomes complete. Moreover, FIG. 5b shows the case where the diagonal lines indicating the transmission do not intersect closely, and in this case, T ₁ + T ₂
=T+2Td always holds true. It is clear that in the case of FIG. 5b, the slave station's _S2 transmission can reach the synchronized state more quickly if it is moved to the left as indicated by the white arrow in the figure. What should be noted here is that in the case of Figure 5 a,
In the case of b in the same figure, the transmission of slave station S ₂ is moved to the left when T ₁ > T ₂ and to the right when T ₁ < T ₂ .
It must be moved to the left when T ₁ < T ₂ and to the right when T ₁ > T ₂ . However, this problem can be easily solved by the above-mentioned preconditions. That is, in figure a, T ₁ + T ₂ =
From 2Td, T ₁ +T ₂ <T, and in the same figure b, T ₁
Since _{T 1 +} T ₂ >T from +T 2 =T+2Td, the control conditions may be reversed using an exclusive OR circuit. [Problem to be solved by the invention] Now, in the above method, the transmission timing of the data S ₁ and S ₂ of the same predetermined sampling number, and therefore the main station that should be synchronized with this,
Match the sampling timing of slave stations. At this time, in order to match the sampling timing at either the main station or the slave station, the phase of the clock pulse is advanced or delayed, but the adjustment time width is
This is the maximum time of 1/2 of the transmission period T of data S ₁ and S ₂ of a specific sampling number. If the time difference between the sampling timings of both stations is shifted at once to adjust the timing consistency, the data transmission timing will change suddenly, which will cause a received data error at the receiving end, so it is not practical in practice. The desired adjustment is made by repeating the process of shifting the sampling timing by a very short period of time within a range that does not cause a received data error several times. For this reason, it took a long time to synchronize the sampling signals. In particular, since the adjustment time span extends to T/2, it may take an extremely long time to complete the adjustment. Also, the time required to synchronize the sampling signals, that is, after the own station transmits data S ₁ or S ₂ of a specific sampling number, it receives data S ₂ or S ₁ of the same sampling number from the other station. In order to measure the time up to that point, it is necessary to be able to measure the time period T during which data of a specific sampling number is transmitted. Although it depends on the time measurement accuracy, a time measurement counter with a relatively large number of bits is required. Therefore, the number of bits of the time data (T ₁ or T ₂ ) to be transmitted to the partner station is large, and there is a disadvantage that the data occupies a large number of bits on the transmission format. The present invention has been made to solve these problems, and it allows the sampling timing and sampling numbers of the master station and the slave station to match in a short time, and also allows time measurement to be performed in a short time, reducing the number of bits of time data. The purpose of the present invention is to provide a sampling signal synchronization method that can shorten the transmission efficiency and improve transmission efficiency. [Means for solving the problem] The present invention calculates the time difference between the reception time of a signal emitted by one station at another station and the immediately preceding transmission time or sampling timing at the other station, and transmits this time difference to the one station. Based on this reply information and the reception timing of this reply information at that one station, that is, the time difference from the previous transmission time or sampling timing, the sampling number at the reception time, etc., one of the stations first performs sampling. This method performs fine adjustment control to match the timing, and then performs coarse adjustment control to correct the sampling number. [Operation] A station transmits a signal, another station receives the signal, and returns the time difference between the reception time and the previous transmission time at the other station together with data reporting the reception. Using this reply information, the time difference between the time of receiving the reply information and the previous transmission time or sampling timing, and the sampling number at the time of receiving the reply information, first fine control is performed to match the sampling timing, and then the sampling number Coarse adjustment control is performed to approximately match the values. The time difference is measured for a period shorter than the sampling period. [Examples] The present invention will be described in detail below based on drawings showing examples thereof. FIG. 1 is a timing chart showing the transmission and reception status between master station A and slave station B. Master station A and slave station B generate sampling numbers with a period of T, and here the power system frequency (50Hz or
60Hz) (equivalent to 360 electrical degrees)
It is. T ₀ is the sampling timing period, which is assumed to be 30 electrical degrees here. Therefore T=12
×T ₀ , and the sampling number changes from 0, 1, 2...11 at each sampling timing. Furthermore, for convenience of explanation, the sampling timing and the transmission timing are assumed to be the same. Then, the data of a specific sampling number is
The data is transmitted and received between the slave stations, but here it is assumed that the transmission is from the master station A to the slave station B, and this is referred to as _S1 . In FIG. 1, the specific sampling number is set to "0". Since the time it takes for data _S1 sent from master station A to arrive at slave station B and the time it takes for data sent out from slave station B to arrive at the master station are practically negligible, Let these be equal to each other, and let this be the transmission delay time Td. Under the condition shown in FIG. 1 in which both stations are out of synchronization, the sampling numbers of both stations differ by, for example, 6, and the sampling timings differ by ΔT. Next, the system of the present invention will be explained with reference to FIG. 1 and a flowchart in FIG. 2 showing the transmission/reception and data processing procedures of master station A and slave station B. Data S ₁ with a specific sampling number "0" is transmitted from the main station A at regular intervals (T=12×T ₀ ). _S1 sent from main station A is the transmission delay time
After Td, the call arrives at slave station B. At this time, slave station B measures the time from the sampling timing immediately before receiving S ₁ to receiving S ₁ at each sampling timing as Ts. This can be accomplished by counting appropriate clocks using a counter that is reset at each sampling timing, and stopping counting upon reception. When slave station B receives S ₁ from master station A, it always sends S ₁ to the transmission data to master station A at the next sampling timing.
It is transmitted with the flag F1 indicating reception and the above Ts. In this example, slave station B transmits data with sampling number "10" to master station A with flags F1 and Ts added thereto. Master station A receives flag F1 and measurement time Ts from slave station B. The main station A receives its own sampling number SA2, which is "7" here.
is specified and stored, and the time from the sampling timing immediately before the arrival of data from slave station B to the reception of the data is measured as TM among each sampling timing. This measuring means is similar to the Ts measuring means of slave station B. First, the master station performs fine adjustment control to match the sampling timings of the master station and the slave station. As is clear from FIG. 1, the following relationship always holds between the transmission delay time Td, measurement time TM, and Ts. Td + ΔT = nT ₀ + Ts … (1) Td = mT ₀ + TM + ΔT … (2) However, n is the number of sampling cycles from the sampling timing of the nearby slave station at the time of _S1 transmission to the sampling timing of the Ts time measurement reference m is the number of sampling periods at the time of F1 transmission Number of sampling cycles from the sampling timing of the nearby main station to the sampling timing of the TM timekeeping reference Calculating ΔT from equations (1) and (2): ΔT = (n-m)/2T ₀ + (Ts-TM)/2 …(3) The insulation value of the sampling timing difference ΔT is T ₀ /
Since it is within 2, (n-m) of the first term on the right side of equation (3)
can only take a value of 0 or ±1. Therefore, in order to make the sampling timing difference ΔT zero in equation (3), Ts=TM (for n-m=0)...(4) T ₀ +Ts=TM (for n-m=1) )...(5) T ₀ +TM=Ts (n-m=-1)...(6) If the sampling timing of the main station is controlled in advance or delay so as to satisfy any of the equations, the synchronization will be removed. Which of equations (4) to (6) is used to control the sampling timing is determined by n and m. That is, the following relationship holds between n and m. (a) SA2: For odd numbers, m = SA2-1/2, n = SA2-1/2 (b) SA2: For even numbers, m = SA2/2, n = SA2/2-1 (TM>Ts) m = SA2/2-1, n = SA2/2 (TM<Ts) Since the main station has data of SA2, TM, and Ts, use this to calculate n-m and determine the sampling timing when ΔT = 0. Performs advance/delay control. In this example, SA2 = 7, so m = n = 3, so nm = 0, and as fine control, equation (4)
Phase control of the sampling timing of the main station is performed so that Ts=TM. Its speed and slowness are Ts
It may be determined based on the magnitude relationship of TM, and in this example, since Ts>TM, the sampling timing of the main station is advanced. The above fine adjustment control causes the sampling timings to match at both stations. Next, coarse adjustment control is performed to match the sampling numbers at both stations. FIG. 3 shows the state after the above-mentioned fine adjustment control. The main station is flag F1
Sampling number RA of the data loaded
1 (“10” in this example). It is also recognized that the data carrying this flag F1 was received at sampling number SA2 ("7" in this example). Using these SA2 and RA1, the delay ε of the sampling number of the master station with respect to the slave station can be expressed by the following equation (7). ε=RA1-SA2+1/2 (7) In this example, ε=10-(7+1)/2=6, meaning that the master station is behind the slave station by 6 sampling numbers. Table 1 shows the relationship between the value of ε and the difference between the sampling numbers of the main and slave stations.

〔effect〕

As described above, according to the present invention, not only the sampling timing is adjusted but also the sampling number is quickly corrected. That is, the measurement time for sampling timing synchronization can be set to time data that is less than or equal to the minimum sampling interval _T0 , the number of bits of the time measurement data is reduced, and the number of circuits for measuring time can be reduced. Furthermore, the number of mutually transmitted time data bits can be reduced, and the efficiency of data transmission can be improved. Furthermore, the flag F1 sent back to the other station when receiving a specific sampling number can be composed of a single bit, which also improves transmission efficiency. Since the synchronization control is divided into coarse adjustment and fine adjustment, the time required to match the sampling timing between the master station and the slave station can be significantly shortened, and synchronization can be quickly achieved.

[Brief explanation of the drawing]

Fig. 1 is a time chart for explaining the synchronization method of the present invention, Fig. 2 is a flowchart showing the transmission/reception of the main station and slave stations, and data processing procedures, and Fig. 3 is for explaining the coarse adjustment control and fine adjustment control. time chart,
FIG. 4 is an explanatory diagram of the principle of the conventional method. A...Main station, B...Slave station.

Claims (1)

[Claims] 1. Sampling signals obtained by sampling at equal intervals in each of the two devices are changed at the same intervals,
In addition, in a synchronization method in a communication system in which data is transmitted and received between two devices at the same period as sampling using a common transmission format that includes sampling numbers that occur repeatedly, the repetition period of the sampling number is set to the transmission delay time between the two devices. When a signal is transmitted from one device and received by another device, the time Ts between the reception time and the immediately previous signal transmission time of the other device is measuring, the other device transmitting data reporting the reception and the measured value Ts of the time to the one device; the one device transmitting the signal at the time of receiving the transmission signal from the other device and immediately before transmitting the signal; measuring the time TM between the two devices, and zeroing out the time difference ΔT between sampling timings in each device based on the measured time TM and the time measurement Ts transmitted from the other device. The sampling timing of the one device or the other device is adjusted in order to A sampling signal characterized by comprising correcting the sampling number of the one device or the other device based on the formula ε=RA1−SA2−1/2 in order to match the sampling numbers generated by both devices based on SA2. Synchronous method.