Method and system for time synchronization of sensor units

Abstract

Method for time synchronization of sensor units in a distributed system, wherein sensor data are detected by the sensor units and transmitted to a central unit, and a further current value of an internal time unit of the respective sensor unit is stored at the time of detection, at least the value of the internal time unit stored at the time of reception of a characteristic time feature of a characteristic signal, the transmitter identification to which the signal belongs, and the value stored at the time of detection are assigned to the sensor data and transmitted jointly therewith to the central unit, the central unit detects voltage and phase values of at least one phase line of an electrical power supply network, determines therefrom synchronization data for the frequency or the period duration and for the phase position of the voltage of the phase line with respect to the time point of detection of the voltage and phase values of the phase line and transmits them to the sensor units, the respective sensor unit detects the respective sensor data with respect to the synchronization data in the form of current values, which are transmitted to the central unit, and the power is calculated there from the voltage values and the current values.

Description

Technical Field

[0001] The present invention relates to a method and a system for time synchronization of sensor units in a distributed system. Background Technology

[0002] In power distribution infrastructure, such as in smart DC and AC distribution networks, the so-called "smart grid," information about the network status, such as voltage levels, current loads, power flows, and load distribution, is detected and determined through data from multiple distributed sensors.

[0003] To monitor and control the network, sensor data is typically transmitted and centrally evaluated.

[0004] Depending on the type of sensor and the centralized evaluation method of the sensor data, sensor values ​​and detection time points are important for the evaluation, in order to enable, for example, the calculation of active and reactive power based on voltage and current measurements, which can be transmitted by different sensors, which can also be spatially distributed.

[0005] In particular, to determine active power and reactive power or combined apparent power, accurate time points of measurement and, especially, their interrelationships are necessary.

[0006] In the prior art, time synchronization has been solved by wired communication connection between the sensor and the evaluation unit, or the voltage measurement value has been transmitted as an analog measurement value signal to each current measurement sensor by wired connection.

[0007] As a wireless alternative solution, the use of an additional time synchronization source in the case of each sensor is known, which is provided via a radio connection, for example for use by a GPS clock, a radio time standard transmitter (such as the longwave transmitter DCF77), or a central NTP reference time server (Network Time Protocol, abbreviated as NTP).

[0008] The disadvantage of wired communication solutions is the need for data lines, which can lead to increased installation costs and lower user acceptance, and this can be a relevant cost factor and system complexity factor, especially when retrofitting sensors.

[0009] A disadvantage of using a time synchronization source via radio is the limitation on the antenna mounting location.

[0010] Therefore, receiving GPS / DCF77 / mobile radio time signals in enclosed spaces is extremely difficult, even impossible.

[0011] Furthermore, DCF77 or comparable time information services are not accurate enough and are only available in limited, regional areas.

[0012] Furthermore, such a solution introduces undesirable system complexity, unfavorable assembly requirements, and additional costs due to the addition of a radio receiver and its associated antenna.

[0013] Publication EP3993290B1 describes a method for time synchronization of sensor units in a distributed system. This method establishes a time relationship between the sensor data detected by the sensor units in the distributed system. However, it does not take into account the internal signal propagation time during signal detection, which adversely affects the accuracy in determining power consumption in the power distribution network. Summary of the Invention

[0014] Therefore, the objective of this invention is to provide a simpler, more accurate, and more reliable solution for distributed sensor synchronization.

[0015] The objective of the invention is achieved by a method for time synchronization of sensor units in a distributed system, wherein each sensor unit has an internal time unit, and wherein sensor data is detected by the sensor unit and transmitted to a central unit via a radio network, wherein characteristic signals are transmitted in the radio network at regular time intervals, wherein reception of the characteristic signals is monitored in the respective sensor units, wherein the current value of the internal time unit of the respective sensor unit, together with at least one transmitter identifier included in the characteristic signal, is stored when a characteristic time feature of the characteristic signal is received, wherein another current value of the internal time unit of the respective sensor unit is stored when sensor data is detected, and wherein at least the internal time unit value stored when the characteristic time feature of the characteristic signal is received, the transmitter identifier to which the characteristic signal belongs, and the other internal time unit value stored when the sensor data is detected are assigned to the detected sensor data and transmitted to the central unit together with the sensor data. The central unit derives a reference time base based on a transmitter identifier and derives the time relationship of the sensor data transmitted by the corresponding sensor unit relative to the reference time base based on the value stored in the internal time unit of the corresponding sensor unit when receiving the characteristic time feature of the characteristic signal and another value stored in the internal time unit of the corresponding sensor unit when detecting the sensor data. The central unit detects the voltage and phase value of at least one of the three phase lines of the power grid, determines synchronization data from the voltage and phase values ​​for frequency or period duration and for the phase position (Phasenlage) of the voltage of at least one of the three phase lines at the detection time point of the voltage and phase values ​​of the at least one of the three phase lines, and transmits this data to the sensor unit. The corresponding sensor unit detects the corresponding sensor data in the form of current values ​​with respect to the synchronization data. The sensor data is transmitted to the central unit, where power is calculated from the voltage and current values.

[0016] Thus, synchronous power measurement is enabled by radio-based current measurement sensors and a common central voltage detection unit, allowing for flexible and efficient retrofitting and expansion of equipment used for monitoring the distribution network without additional wiring costs.

[0017] Synchronous measurement of the power of electrical systems allows for particularly accurate measurement in a simple manner.

[0018] It is clear that the power calculation in the central unit is performed from the voltage and current values, taking into account their corresponding phase positions.

[0019] This is achieved by measuring the voltage in the power grid at only one location and detecting the current at multiple distributed locations.

[0020] This is actually less expensive than additionally detecting voltage at distributed locations, as it would require higher protection costs and additionally address overvoltage issues.

[0021] Furthermore, in the case of the aforementioned distributed active and reactive power measurements, additional synchronization sources and additional wiring are not necessary.

[0022] For example, synchronization can be achieved by coordinating the time reference of the master timer in the central unit with the time reference of the corresponding subordinate sensor unit.

[0023] The current flowing through the sensor unit can also be used to power it, which allows for particularly simple and low-maintenance integration into existing systems.

[0024] In the case of characteristic signals, for example, messages, especially synchronization frames for messages to multiple receivers (“multicast”), can be applied.

[0025] In at least one or all of the sensor units, the zero-crossing time of the reference voltage is synchronously determined in the central unit based on the transmitted value for the zero-crossing time point and the optional values ​​for the cycle duration and the zero-crossing for the previous cycle in the current measurement cycle, and a current phasor (Stromzeiger) is first formed for each individual voltage fundamental cycle in the current measurement cycle based on the AC current value.

[0026] In one improved embodiment of the invention, it is specified that the synchronization data relating to the phase position of the voltage of at least one of the three phase lines with respect to the detection time point of the voltage and phase value of the at least one of the three phase lines is formed by the time point of transmission from the central unit to the corresponding sensor unit.

[0027] This allows for the determination and transmission of synchronization data used to compensate for delays in a particularly simple manner.

[0028] In one improved embodiment of the invention, synchronization data is transmitted to the sensor unit by means of a characteristic signal.

[0029] This allows for the transmission of synchronization data for delay compensation in a particularly simple manner, or allows for the calibration of the time reference to be performed within the sensor unit.

[0030] In one improved embodiment of the invention, the synchronization data is determined over more than one period of voltage and phase values ​​of three phases of the power grid, preferably from at least ten periods, and more preferably from at least 100 periods.

[0031] This allows for less load on the radio channel, transmission of less data, and still sufficient accuracy in power measurements within the power grid.

[0032] In an improved embodiment of the invention, the central unit detects the voltage and phase values ​​of the phase lines of the power supply network, as well as first supplementary synchronization data detected in a previous time period for a time delay during the transmission of a characteristic signal, the previous time period being prior to the current time period, the synchronization data being detected in the current time period, and preferably transmits the first supplementary synchronization data to the corresponding sensor unit by means of the characteristic signal, and takes the first supplementary synchronization data into account when detecting the corresponding sensor data through the corresponding sensor unit.

[0033] This allows for a simple way to improve measurement accuracy.

[0034] Furthermore, synchronization data used to compensate for delays can be determined and transmitted in a particularly simple manner.

[0035] The first supplemental synchronization data is the time delay value from the previous measurement period.

[0036] First, the synchronization data, in the form of zero-point crossover time points in the central control device, and the period duration in the phase line are transmitted.

[0037] The detected delay in the transmission of the synchronization frame is then noted retrospectively at the beginning of the next, subsequent measurement cycle.

[0038] The power grid phase conductors mentioned are the selected reference conductors for the three phase conductors, which are used as a reference for the phase positions of the other phase conductors.

[0039] In an improved embodiment of the invention, the central unit further comprises an internal central time unit, the value of which forms second supplementary synchronization data, and the second supplementary synchronization data is preferably transmitted to the corresponding sensor unit by means of the characteristic signal, and the second supplementary synchronization data is taken into account when the corresponding sensor data is detected by the corresponding sensor unit.

[0040] This allows for a simple way to improve measurement accuracy.

[0041] Furthermore, it can determine and transmit synchronization data for delay compensation in a particularly simple manner.

[0042] In one improved embodiment of the invention, the current values ​​of the respective sensor units are aggregated into an aggregated current value, and the aggregated current value is transmitted to the central unit, whereby power is calculated from the voltage value and the aggregated current value in the central unit.

[0043] This reduces the amount of data transmitted from the corresponding sensor units to the central unit, and correspondingly enables efficient use of the transmission channel.

[0044] The task according to the invention is also solved by a distributed system for time synchronization of sensor units, the distributed system further including a central unit, wherein the system is set up to implement the method according to the invention. Attached Figure Description

[0045] The invention is illustrated in more detail below with reference to embodiments. The figures are in: Figure 1 An example of a power distribution network is shown below; Figure 2 The first embodiment of the present invention is shown in block diagram form; Figure 3 The second embodiment of the present invention is shown in block diagram form; Figure 4 The third embodiment of the present invention is shown in block diagram form; Figure 5 A detailed view of the central unit of the present invention is shown in the figure; Figure 6 The image shows an example of a signal change process in a power distribution network. Detailed Implementation

[0046] Figure 1 An example of a distribution network is shown in the form of a "single-wire" circuit diagram. Here, the wires represent 3-wire, 4-wire, or 5-wire connections of individual branches in the low-voltage and medium-voltage areas (common reference numerals are L1, L2, L3, or L1, L2, L3, PEN / E, or L1, L2, L3, N, and PE / E).

[0047] The sensor unit and / or central unit can be installed in each of the listed conductors and also in the medium voltage branch / area.

[0048] In a so-called substation (Ortsnetzstation), high voltage is transferred to the low voltage zone (LV) by means of one or more transformers (TR).

[0049] The central unit is connected to its respective assigned sensor units via corresponding wireless networks N1 and N2, and the wireless networks are controlled by correspondingly assigned network control devices NC1 and NC2.

[0050] The sensor unit is used to detect the current in the phase line of each branch leading to the terminal electrical appliance.

[0051] In a sensor unit installed as an NH fuse group or, for example, in a medium-voltage line / branch, a current phasor, i.e., a complex value of the corresponding current, is detected as a current value or sensor data, wherein an average value is optionally formed for the determined current and the average value is transmitted.

[0052] So-called time-synchronized current phasors can be applied, which are detected synchronously with voltage phasors at a specific point in time.

[0053] In the case of current, the average value of the current phasor, the current magnitude / amplitude, or the effective value of the current can be used because the average value of alternating current is often close to zero.

[0054] In the central unit, voltage phasors, i.e., complex values ​​of the corresponding voltages, are detected as voltage values, wherein an average value is optionally formed for the determined voltage.

[0055] So-called time-synchronized voltage phasors can be applied, which are detected synchronously with current phasors at a specific point in time.

[0056] In the case of voltage, the average value of the voltage phasor, the voltage magnitude / amplitude, or the effective value of the voltage can be used, because the average value of AC voltage is often close to zero.

[0057] In the central unit, averaged current phasors are received from one or more sensor units via short-range radio communication (such as "Zigbee" or Bluetooth).

[0058] Taking into account the averaged voltage phasors, the active and reactive power P and Q in the corresponding phase line are calculated in the central unit.

[0059] A phasor (Zeiger) for current or voltage is understood as the corresponding complex value, that is, the magnitude and phase value of the current or voltage.

[0060] Figure 2 The first embodiment of the present invention is shown in block diagram form.

[0061] The central unit (CU) includes means for performing a reference phase position transmission (PHU), said means for: • Identify zero crossings during voltage changes; • Calculate the voltage, i.e., the voltage phasor, which has both magnitude and phase position information; • The corresponding reference voltage U selected from the grid voltages u1, u2, and u3 REF_H1The measurement period p is used for counting, and the grid voltage is preferably a phase voltage; • Determine the reference conductor LREF from the power grid phase lines L1, L2, and L3; • Voltage phasor of grid voltage U 1. U 2. U The phase sequence of the grid voltages u1, u2, and u3 is determined by the form 3.

[0062] The measurement period p can be considered as a period that can last for more than one grid voltage cycle, and this period can also be called the voltage fundamental period, which is then counted accordingly.

[0063] The fundamental voltage frequency is often referred to as the first harmonic or simply "H1" of the grid voltage.

[0064] Data from the device used for reference phase position transmission (PHU) is distributed in the central unit (CU) to the high-frequency module (RF_M) via a transmitter or receiver (UART) or an internal interface, such as a serial interface.

[0065] For reference voltage U REF_H1 The zero-crossing interrupt signal IS is provided to the reference signal transmitter REF_TX within the high-frequency module RF_M, which in turn obtains information about the time delay Δt from the central oscillator OSC1 and the connected command counter device LC. EGS Information.

[0066] The time delay Δt at the start of measurement period p EGS It activates the interrupt signal IS, which is for the reference voltage U. REF_H1 The zero-crossing time point t0 EGSp The time point t when the synchronization frame MAC_SYNCF is sent to the corresponding sensor unit SU EGS_SYNCp The delay between them.

[0067] These two time points t0 EGSp and t EGS_SYNCp and delay Δt EGS In the high-frequency module RF_M, the timing information t is based on the oscillator OSC1 and the connected command counter device LC. EGS It has been confirmed.

[0068] In the synchronization frame MAC_SYNCF, the dominant counter LC transmits the following information as a value: the information pertains to the period duration T. p-1That is, the estimated current voltage period determined based on the last, for example, 10 to 30 voltage periods of the previous measurement period p-1, and the time delay Δt determined at the beginning of the previous measurement period p-1 but after the issuance of the synchronization frame MAC_SYNCF. EGSp-1 And activate the interrupt signal IS, i.e., for the reference voltage U. REF_H1 The zero-crossing time point t0 EGSp .

[0069] The start of sending a SYNC frame implicitly corresponds to a specific point in time. .

[0070] In this embodiment, regarding the time delay Δt EGSp The information is generated only after the synchronization frame MAC_SYNCF is sent, and is transmitted to the corresponding sensor unit SU along with the next synchronization frame MAC_SYNCF at the beginning of the measurement period p+1.

[0071] Only at this time, i.e., one measurement period later, with respect to the time delay Δt for measurement period p. EGSp Only then is compensation possible.

[0072] The high-frequency module RF_M also provides a calculation device CALC for calculating active and reactive power P and Q from the corresponding voltage / voltage phasor and current / current phasor.

[0073] The wireless transmission of synchronization information to one or more sensor units SU and the transmission of detected sensor data from sensor units SU to central unit CU via high-frequency transmission link RF_L, for example in the form of “unicast” data transmission UC_D, are described in further detail below.

[0074] The sensor units SU are local control devices used for data detection via corresponding sensor devices.

[0075] The high-frequency transmission link RF_L can transmit the synchronization frame MAC_SYNC via a MAC-layer-based "multicast" of the synchronization frame.

[0076] The sensor unit SU has a time delay Δt for use in the high-frequency transmission link RF_L. RF_L The compensation device DCOMP, along with the local oscillator OSC2 and the connected slave counter device FC, provide time information t. 3NA .

[0077] Time delay Δt RF_L The time delay in the sensor unit SU up to the compensation device DCOMP in the receiver is also taken into consideration.

[0078] Time t 3NA It is the local value of the slave counter FC in the local control device, i.e., the sensor unit SU.

[0079] The current phasor is detected in the sensor unit SU and the reference voltage U in the central unit CU. REF_H1 Zero-crossing synchronization.

[0080] After compensating for the time delay of the high-frequency transmission link RF_L in the compensation device DCOMP, at the reception time point t0 of the synchronization frame MAC_SYNCF at the beginning of measurement periods p and p+1. 3NAp and t0 3NAp+1 Corresponding to the corresponding transmission time point t in the central unit CU EGS_SYNCp and t EGS_SYNCp+1 .

[0081] Based on the time point t0 transmitted at the beginning of the measurement period p EGSp and the time point t0 transmitted at the beginning of measurement period p+1 EGSp+1 And regarding the time delay Δt EGSp and period duration T p In the sensor unit SU, the reference voltage U is first... REF_H1 The zero-crossing time point t0 EGSp+1 Estimated time point This time point corresponds to time point t0 in the central unit CU. EGSp+1 The estimated value of the slave counter FC in the sensor unit SU at that time.

[0082] Then, the reference voltage U REF_H1 The zero-crossing time point of the next cycle is determined as time. .

[0083] The time with index * indicates the estimated value and corresponds to the slave counter FC.

[0084] The time with index 3NA corresponds to the time in the sensor unit SU and is formed by the slave counter FC.

[0085] The time with index EGS corresponds to the time in the central unit CU and is formed by the dominant counter LC.

[0086] The actual current measurement or current phasor determination in the measurement period p+1 is performed in the sensor unit SU from time point t0. 3NAi+101 start.

[0087] Sensor data SD is detected, processed, and calculated as a current phasor value by sensor unit SU in the form of current value I, and is then optionally delivered to aggregation unit AGG for processing.

[0088] Sensor data SD can be, for example, the AC current value of the primary current in the power grid.

[0089] Aggregation can be understood, for example, as forming an average value over multiple measurements, such as multiple alternating current cycles within a measurement cycle, where other statistical methods for mapping the measurements may also be applied.

[0090] In the synchronization frame or frame MAC_SYNCF, information about its transmission time is expressed as the difference Δt between counter readings. EGSp The voltage change process U from the previous cycle p-1 is transmitted to the sensor unit SU via "multicast" transmission. REF_H1 The duration of the period T p-1 And activate the interrupt signal IS, i.e., for the reference voltage U REF_H1 The zero-crossing time point t0 EGSp The value t0 of the dominant counter LC EGSp .

[0091] From the sensor unit SU, data is transmitted via "unicast," either as a single value or as an aggregated value, depending on the implementation, to the complex current phasor for a period with index p. I H1p The values ​​and current phasors I H1p The information about the detected sensor data SD is transmitted to the central unit CU in the form of [data source name].

[0092] In the central unit CU, voltage phasors are formed for each cycle i of the fundamental AC voltages u1, u2, and u3 of the three-phase power grid. U1 i , U2 i and U3 i .

[0093] Voltage phasors can also be optionally aggregated.

[0094] Voltages u1, u2, and u3 can be, for example, the voltages at phase lines L1, L2, and L3 of the power supply network.

[0095] One of the voltages, such as u1, is selected as the reference voltage U. REF_H1 .

[0096] For example, including the reference voltage U REF_H1For each measurement period p of 100 fundamental frequency cycles, the reference voltage U is determined. REF_H1 Zero-point crossing time point t0 EGSp The zero-point crossover time is relative to the reference voltage U. REF_H1 The first phase of the fundamental period is synchronized with the beginning of the phase, and is related to the phase with time t. EGS The dominant counter, in LC form, is related to the microsecond counter present in the central unit CU.

[0097] Zero-point crossing time point t0 EGSp This involves the current time point in the central control unit, while the zero-point crossing time point t0 EGSp-1 This involves the first zero-point crossover time point of the previous measurement cycle.

[0098] Additionally, determine the duration T of the current grid voltage cycle. p .

[0099] As additional information, the counter reading Δt from the previous measurement period p-1 can also be obtained using the characteristic signal, namely the so-called SYNC frame MAC_SYNCF. EGSp-2 and period duration T p-2 The value (not shown in the figure) is transmitted to the sensor unit SU, and then the difference Δt between the counter readings is used. EGSp-1 The time point is determined in the form of [the method].

[0100] Time point Δt EGSp-1 Used to correct the time synchronization between the central unit CU and at least one sensor unit SU in the current measurement cycle p.

[0101] Except for the zero-point intersection time point t0 EGSp Duration of the period T p and optional counter reading difference Δt EGSp-1 In addition, the synchronization frame or "SYNC frame" MAC_SYNCF that introduces the start of the measurement period p also contains the number of the measurement period p itself, and the reference voltage U in that measurement period. REF_H1 The first fundamental cycle number i and the central unit CU network source address used as the transmitter identifier in the SYNC frame MAC_SYNCF.

[0102] The measurement period is specified based on the fundamental frequency counter, for example, in units of time.

[0103] In at least one, or all, of the sensor units SU, the measurement period p is based on the zero-crossing time point t0 used in the central control unit CU. EGSp and t0 EGSp-1 The transmitted value, the current cycle duration T p and time delay ΔtEGSp-1 The selectable time points of the deviation are used to synchronously determine the reference voltage U in the central unit CU. REF_H1 The zero-point crossing time points, where these time points correspond to the values ​​of the corresponding master counter LC.

[0104] Based on sensor data SD presented as alternating current values, a current phasor is formed for each individual harmonic cycle i within the measurement period p. I H1 i And either individually or as a current phasor aggregated over the measurement period p. I H1 p The current phasor is transmitted to the central unit CU in a sensor data frame containing sensor data SD.

[0105] For example, the same sensor data frame may also contain the timestamp t of the corresponding sensor unit SU. 3NA Reference voltage U during measurement period p REF_H1 The number i of the first fundamental period and optionally, the numbering of the current measurement period p and / or the previous measurement periods p-1, p-2.

[0106] After receiving sensor data SD in the central unit CU, the synchronously detected voltage and current phasors are used to calculate the active and reactive power values ​​P. p and Q p .

[0107] In other words, in Figure 5 In the embodiment, the transmission time of the SYNC frame MAC_SYNCF is provided by the reference signal transmitter REF_TX as the start of the SYNC frame “header” MAC_SYNCF and additionally as the counter reading (difference) of the counter LC of the central unit CU, preferably corresponding to a time resolution in the microsecond range.

[0108] Therefore, zero-point crossing t0 is transmitted in the following synchronization frame MAC_SYNCF. EGSp As the start of the synchronization frame MAC_SYNCF and as the time point t0 at the zero crossing. EGSp The difference Δt between the current counter reading at the current time and the counter reading between the previous reference zero crossing and the previous transmission time point. EGSp-1 .

[0109] In this embodiment, the signal propagation time is therefore corrected in the corresponding sensor unit SU at the beginning of the current measurement period p by taking the zero-point crossover t0 from the previous SYNC frame MAC_SYNCF of the measurement period p-1. EGSp-1 And the zero-crossing t0 from the current measurement period p is taken from the currently received SYNC frame MAC_SYNCF.EGSp and transmission delay Δt EGSp-1 .

[0110] When using DCOMP compensation, a time delay Δt can be considered. RF_L However, the time delay is very small and can be ignored for simplicity.

[0111] Therefore, in this case, two consecutive SYNC frames are always necessary in order to determine the reference voltage U in the sensor unit SU. REF_H1 The zero-point crossing.

[0112] Therefore, the first embodiment can also be described using the following terms.

[0113] A method for time synchronization of sensor units in a distributed system is used to determine reactive and active power in the central unit CU by utilizing at least one sensor unit SU and based on the synchronization of zero-point crossover of reference voltages between the central unit CU and the sensor unit SU, i.e., between the first, dominant counter LC and the first, central oscillator OSC1 of the central unit CU and the second, subordinate counter FC and the second, local oscillator OSC2 of the corresponding sensor unit SU.

[0114] Here, the starting time point and subsequent time change process of the current phasor used to calculate the sensor unit SU are synchronized with the zero crossing time point of the voltage fundamental wave.

[0115] This corresponds to the time synchronization between the central unit CU and the sensor unit SU, that is, the time reference t of the master timer or counter LC within the central unit CU. EGS The time base t of the dominant counter FC inside the corresponding subordinate sensor unit SU 3NA Coordination between them.

[0116] This does not have to be absolute clock time, but can involve the fundamental period of each voltage and / or the clock period of the corresponding counters LC, FC.

[0117] Sensor units SU each have an internal time unit FC, wherein these internal counters serve as the time unit, the time unit being based on numbered grid voltage cycles and / or in microsecond-based time units (t). 3NA (This generates a time base.)

[0118] Sensor data SD is periodically detected by sensor unit SU in the form of current phasors with a pre-given time resolution of, for example, 1 microsecond, and / or with grid voltage cycle numbering, and transmitted to central unit CU via radio network RL_L.

[0119] In a radio network or on a high-frequency transmission link RF_L, characteristic signals are transmitted at regular time intervals, such as a SYNC frame MAC_SYNCF sent from the central unit CU to the corresponding sensor unit SU every two seconds.

[0120] The reception of the characteristic signal SYNC frame MAC_SYNCF is monitored in the corresponding sensor unit SU.

[0121] When receiving the characteristic time features of the characteristic signal, the current value of the internal time unit FC of the corresponding sensor unit SU is stored together with at least one transmitter identifier contained in the characteristic signal, i.e., the data contained therein, such as the source address and / or authentication data of the RF module RF_M in the central unit CU, the characteristic time information contained therein, such as timestamps, time delay information, the number of the corresponding grid voltage cycle, etc., and the current value of the corresponding sensor unit SU's own time unit, such as the received timestamp from the SYNC frame MAC_SYNCF.

[0122] When detecting sensor data SD, the other current values ​​of the internal time unit FC of the corresponding sensor unit SU are stored. For example, the current timestamp of the time unit of the corresponding sensor unit SU and the number of the corresponding power grid voltage cycle are assigned and stored together with these sensor data SD.

[0123] Therefore, zero crossover should be synchronized with the local time unit in the sensor, where the zero crossover in the sensor should be reproduced as accurately as possible, and correlation with the time unit in the central unit is not necessary.

[0124] At least the value of the internal time unit FC stored when receiving the characteristic time features of the characteristic signal, the transmitter identifier to which the characteristic signal MAC_SYNCF belongs, and the additional value of the internal time unit stored when detecting the sensor data SD are assigned to the detected sensor data SD and transmitted together with the sensor data SD to the central unit CU.

[0125] This can be done via a data telegram sent from the corresponding sensor unit SU to the central unit CU, the data telegram containing the grid voltage cycle number to which the measurement data pertains, the address to which the central unit CU to which the measurement data is sent, i.e., the transmitter identifier of the characteristic signal, and the current timestamp of the corresponding sensor unit SU's time unit assigned when the data is detected.

[0126] Based on the transmitter identifier, for example, based on the corresponding grid cycle number and / or the timestamp contained in the received data telegram, the reference time base is derived, and the time relationship of the sensor data SD transmitted by the corresponding sensor unit SU relative to the reference time base is derived based on the value of the internal time unit FC of the corresponding sensor unit SU stored when receiving the characteristic time features of the characteristic signal and another value of the internal time unit FC of the corresponding sensor unit SU stored when detecting the sensor data SD.

[0127] The central unit (CU) detects the voltage and phase value of at least one of the three phase lines of the power supply network, and determines synchronization data t0 from the voltage and phase values, relating to the frequency or period duration and the phase position of the voltage of at least one of the three phase lines with respect to the detection time point of the voltage and phase values ​​of the at least one of the three phase lines. EGSp And Tp and transmit to the sensor unit SU.

[0128] The corresponding sensor unit SU regarding the synchronization data t0 EGSp and T p The corresponding sensor data SD is detected in the form of current value, and the sensor data is transmitted to the central unit CU.

[0129] In the central unit (CU), power, especially active and reactive power, is calculated from voltage and current values.

[0130] Synchronization data t0 involving the phase position of the voltage of at least one of the three phase lines at the detection time point with respect to the voltage and phase value of said at least one of the three phase lines. EGSp It is formed by the time point when the SYNC frame MAC_SYNCF is transmitted from the central unit CU to the corresponding sensor unit SU.

[0131] Synchronize data t0 EGSp T p It can be transmitted to the sensor unit SU by means of the characteristic signal MAC_SYNCF.

[0132] Synchronize data t0 EGSp T p The voltage and phase values ​​can be determined over more than one period of three phases of the power grid, preferably from at least ten periods, and particularly preferably from at least 100 periods.

[0133] In addition, the central unit (CU) can detect the voltage and phase values ​​of the phase lines of the power supply network, as well as the first supplementary synchronization data Δt detected in the previous time period. EGSp-1， The previous time period is before the current time period, and the synchronized data t0 EGSp Tp It was detected during the current time period.

[0134] Preferably, the first supplementary synchronization data Δt can be transmitted using the characteristic signal MAC_SYNCF. EGSp-1 The signal is transmitted to the corresponding sensor unit (SU).

[0135] When detecting the corresponding sensor data SD through the corresponding sensor unit SU, the first supplementary synchronization data Δt can be considered. EGSp-1 .

[0136] In order to use the counter reading difference Δt EGSp-1 Periodic synchronization is clearly necessary.

[0137] Figure 3 A second embodiment of the present invention is shown in block diagram form.

[0138] In this embodiment, the counter reading difference Δt is not transmitted in the SYNC frame MAC_SYNCF of the measurement period p. EGSp-1 Information.

[0139] Assumption: In the central unit CU, and specifically in the transmitter REF_TX, a SYNC frame MAC_SYNCF is transmitted with reference voltage U. REF_H1 The zero-point crossing time is synchronized, and the propagation time correction for the reception of the SYNC frame MAC_SYNCF is performed only in the sensor unit SU in order to establish time synchronization between the central unit CU and the corresponding sensor unit SU.

[0140] In this embodiment, a counter reading is delivered when the reference signal transmitter REF_TX of the central unit CU is transmitted, which should begin from the issuance of the SYNC frame header MAC_SYNCF.

[0141] Compared to the first embodiment, at the beginning of the measurement period p, the interrupt signal IS is activated, i.e., for the reference voltage U. REF_H1 The zero-crossing time point t0 EGSp The time point t when the synchronization frame MAC_SYNCF is sent to the corresponding sensor unit SU EGS_SYNCp The time delay Δt between EGSp It is negligible and therefore does not need to be transmitted.

[0142] The synchronization frame MAC_SYNCF only transmits information about the period duration T. p-1 Information such as the estimated current voltage cycle determined, for example, based on the last 10 to 30 voltage cycles of the previous measurement cycle p-1.

[0143] Due to the delay Δt EGSpThe values ​​of most of them are negligible, so the start of the SYNC frame MAC_SYNCF transmission implicitly corresponds to a specific time point. .

[0144] This means that compensation for the time delay of the SYNC frame MAC_SYNCF on the receiving side for the same measurement period p is performed immediately at the start of the measurement period p, as well as synchronization between the central unit CU and the corresponding sensor unit SU.

[0145] Exactly the same as the reference voltage U REF_H1 Synchronously at the zero-point crossover time point, a SYNC frame MAC_SYNCF is sent from the central unit CU to delay by one fundamental frequency cycle.

[0146] With the issuance of the SYNC frame MAC_SYNCF, information about time point t0 is implicitly transmitted. EGSp Information.

[0147] In this example, it is not necessary to transmit additional counter readings of the central unit CU in the SYNC frame MAC_SYNCF.

[0148] The RF receiving unit in the sensor unit SU provides a counter reading for use at the time point of receiving the SYNC frame header MAC_SYNCF.

[0149] time At the corresponding sensor unit time point t0 EGSp The corresponding MAC_SYNCF of the SYNC frame is received at that time.

[0150] In this embodiment, the signal propagation time on the high-frequency transmission link RF_L is corrected in the corresponding sensor unit SU by directly using the reference voltage U. REF_H1 The zero-point crossover time is used as the corrected reception time point of the SYNC frame header.

[0151] In this method, the reference voltage U can be determined from each SYNC frame MAC_SYNCF in the sensor unit SU. REF_H1 The zero-point crossing time point.

[0152] Figure 4 The third embodiment of the invention is shown in block diagram form, wherein the time value t of the counter in the central unit CU is shown. EGS The time is transmitted to the sensor unit SU via a separate time synchronization frame and the value t is transmitted through the time reference of the central unit CU. EGS For the time reference t in the sensor unit SU 3NA It was adopted after propagation time correction.

[0153] It can be achieved The correction is performed by pre-preparing a separate time synchronization frame in the central unit CU and sending the time synchronization frame to the sensor unit SU at the time point contained in the frame.

[0154] This allows the previously described SYNC frame MAC_SYNCF to be not synchronized with the reference voltage U at the beginning of each measurement cycle p in the central unit CU. REF_H1 Zero-point crossing time point t0 EGSp Instead of being transmitted synchronously, it is transmitted at a reference voltage U. REF_H1 It is sent within the first cycle because information about the zero-point crossover time is included in the value t0. EGSp In this context, the value refers not only to time t EGS Furthermore, the time reference t involved in the continuous synchronization of the sensor unit SU 3NA .

[0155] Therefore, the transmission delay Δt is transmitted in the SYNC frame MAC_SYNCF. EGSp-1 The point-in-time value is not necessary, and Figure 3 In the first embodiment, at the beginning of the measurement period p and at t0 so far... EGSp-1 The time interval between time reference points is shortened to t0 EGSp Reference point.

[0156] In other words, the central unit CU may also have an internal, central time unit LC, the value of which forms a second supplementary synchronization data t. EGS Furthermore, the second supplementary synchronization data can preferably be transmitted to the corresponding sensor unit SU via the characteristic signal MAC_SYNCF, and the second supplementary synchronization data t can be considered when detecting the corresponding sensor data SD through the corresponding sensor unit SU. EGS .

[0157] The current value of the corresponding sensor unit SU can be aggregated into an aggregated current phasor. I H1p And can polymerize current phasors I H1p Transmitted to the central unit CU, and can be obtained from the voltage value and aggregated current phasor in the central unit CU. I H1p Calculate the power.

[0158] Figure 5 A detailed view of the central unit CU of the present invention is shown.

[0159] If the central unit CU and at least one sensor unit SU communicate directly or through multiple nodes / hops via a wired connection, such as in the case of an Ethernet-based "daisy-chain", then all three listed embodiments can be used.

[0160] Here, propagation time correction should be performed on the side of the corresponding sensor unit SU when receiving the SYNC frame MAC_SYNCF, based on the position of the sensor unit SU in the daisy chain.

[0161] The propagation time correction value is preferably determined for each sensor unit SU during the periodic propagation time correction value determination or at the start of communication, i.e., for example by sending periodic propagation time measurement frames.

[0162] The analog data detection device AFE samples voltages U2, U2, and U3.

[0163] Zero Crossover Identification Device (ZCD) identifies reference voltage U REF_H1 Zero crossings during the time-varying process and counting the voltage cycles of the corresponding voltage.

[0164] The high-frequency module RF_M can be formed, for example, through the "Zigbee" module ZB_M and the "Zigbee" application ZB_APP, where the latter provides the results RES for current, voltage, and power.

[0165] The computing device CALC1 is used to calculate active power P and reactive power Q from the corresponding voltage and current or from the voltage and current phasors.

[0166] The CALC2 computing device is used for: • Calculate the voltage value from the magnitude and phase position information, where the count point corresponds to the last previous count point; • Provides the reference voltage U counted in the zero-crossing identification device ZCD. REF_H1 The measurement cycle; • Determine the reference line LREF for the power grid phase lines L1, L2, and L3; • Determine the minimum voltage U MIN At the minimum voltage, voltage zero crossings are not determined or counted in order to improve fault susceptibility. • Optionally, the voltage phasor of the grid voltage can be used. U 1. U 2. U The phase sequence of the grid voltages u1, u2, and u3 is determined by the form 3; • Determine the voltage phasors from the grid voltages u1, u2, and u3. U 1. U 2. U 3.

[0167] The calculations of the computing device CALC2 are periodically checked by the corresponding verification device VAL during the measurement cycle, particularly in terms of the consistency of the voltage and current cycle numbers.

[0168] Data from the device used to transmit the reference phase position PHU is distributed to the high-frequency module RF_M via a transmitter or receiver UART in the central unit CU.

[0169] For reference voltage U REF_H1 The zero-crossing interrupt signal IS is provided to the reference signal transmitter REF_TX within the high-frequency module RF_M, which in turn obtains a zero-crossing t0 with respect to the reference voltage. EGS The zero-point crossing and the time delay Δt of the central oscillator OSC1 and the command counter device LC when the SYNC frame MAC_SNCF is sent. EGS Information.

[0170] Using minimum voltage U MIN This ensures that only the minimum allowable voltage is considered in subsequent evaluations of power calculations, thereby improving fault susceptibility.

[0171] Figure 6 An example of a signal change process in a power distribution network is shown, illustrating the time flow of data detection from sensor data SD.

[0172] The time ranges ALL_A, ALL_B, and ALL_C indicate that all sensor units SU transmit the corresponding current to the central unit CU for the measurement periods p-1, p, p+1, and p+2.

[0173] The time ranges CALC_A, CALC_B, CALC_C, and CALC_D show the aggregate current calculated by the sensor unit SU for the measurement periods p-1, p, p+1, and p+2 respectively.

[0174] The time ranges ADJ_A and ADJ_B indicate the corresponding SYNC frame SF, which is generally referred to as SYNC frame MAC_SYNCF. p-1 SF p SF p+1 SF p+2 The time unit of the corresponding sensor unit SU is calibrated in the synchronous data.

[0175] The SYNC frame SF is not shown in the diagram. p-1 .

[0176] List of reference numerals ADJ_A and ADJ_B are used for the process of calibrating time units. AFE (Analog Frontend) AGG polymerization unit ALL_A, ALL_B, and ALL_C are used to transmit current information. CALC_A, CALC_B, CALC_C, and CALC_D are used to calculate the polymerization current. CU Central Control Unit Δt EGSp-1 , Δt EGSp The value of the time delay in the measurement period p-1 or p DCOMP is a time delay compensation device used in high-frequency transmission links. FC (Follower Clock) I Current I H1 Complex current phasor I H1p (Polymerized) Complex Current Phasor IS is an interrupt signal for zero crossover of the reference voltage. L1, L2, L3 power grid phase lines L REF Reference wire LC (Leader Clock) LV Low Voltage Area MAC_SYNCF, SF p-1 SF p SF p+1 SF p+2 Synchronization frames using MAC layer-based "multicast" at the synchronization layer N1 and N2 networks NC1 and NC2 network control devices OSC1 and OSC2 oscillators p Measurement period Pp is the (aggregate) active power within measurement period p. PHU is a device used for transmitting reference phase position. Qp is the (aggregate) reactive power within measurement period p. REF_TX reference signal transmitter RES is used for results of current, voltage, and power. RF_L stands for "radio frequency link". RF_M high-frequency module SD sensor data, such as for primary current (x n The current phasor I of the alternating current value H1p SU local control device, sensor device SF p-1 SF p SF p+1 SF p+2 t0 EGSp Zero-point crossover time point in the central control unit t0 EGSp-1 Zero-point crossing time point in previous measurement period p-1 t 3NA The counter value of the locally determined grid voltage cycle duration in the local control device t EGS Time provided by counter LC T p Current cycle duration of grid voltage TR Transformer The time-varying process of the grid voltage at the inputs u1, u2, and u3 of the central unit. U1 , U2 , U3 Voltage phasor of grid voltage U MIN Minimum values ​​of voltages u1, u2, and u3 U REF Reference voltage UART transmitter / receiver (English: "Universal Asynchronous Receiver Transmitter") UC_D "Unicast" data transmission Periodic verification of VAL measurement cycle x, y coordinate axes ZB_APP Zigbee application ZB_M Zigbee module ZCD (Zero Crossing Detection)

Claims

1. A method for time synchronization of sensor units (SUs) in a distributed system, wherein each sensor unit (SU) has an internal time unit (FC), and wherein sensor data (SD) is detected by the sensor unit (SU) and transmitted to a central unit (CU) via a radio network, and The radio network transmits characteristic signals (MAC_SYNCF) at regular time intervals. The monitoring involves receiving the characteristic signal (MAC_SYNCF) in the corresponding sensor unit (SU). When receiving the characteristic time features of the characteristic signal (MAC_SYNCF), the current value of the internal time unit (FC) of the corresponding sensor unit (SU) is stored together with at least one transmitter identifier included in the characteristic signal. When detecting sensor data (SD), the system stores an additional current value of the internal time unit (FC) of the corresponding sensor unit (SU). The value stored in the internal time unit when receiving the characteristic time feature of the characteristic signal, the transmitter identifier to which the characteristic signal belongs, and the additional value stored in the internal time unit (FC) when detecting the sensor data (SD) are assigned to the detected sensor data (SD) and transmitted together with the sensor data (SD) to the central unit (CU). The reference time base is derived based on the transmitter identifier, and the time relationship of the sensor data (SD) transmitted by the corresponding sensor unit (SU) relative to the reference time base is derived based on the value of the internal time unit (FC) of the corresponding sensor unit (SU) stored when receiving the characteristic time features of the characteristic signal and another value of the internal time unit (FC) of the corresponding sensor unit (SU) stored when detecting the sensor data (SD), characterized in that, The central unit (CU) detects the voltage and phase value of at least one of the three phase lines of the power supply network, and determines from the voltage and phase value synchronization data (t0) regarding the frequency or period duration and the phase position of the voltage of at least one of the three phase lines with respect to the detection time point of the voltage and phase value of the at least one of the three phase lines. EGSp T p And transmit it to the sensor unit (SU), and The corresponding sensor unit (SU) with respect to the synchronization data (t0) EGSp T p The corresponding sensor data (SD) is detected in the form of a current value, the sensor data (SD) is transmitted to the central unit (CU), and the power is calculated from the voltage and current values ​​in the central unit (CU).

2. The method of claim 1, wherein the synchronization data (t0) relates to the phase position of the voltage of at least one of the three phase lines with respect to the detection time point of the voltage and phase value of the at least one of the three phase lines. EGSp This is formed by the timing of the transmission from the central unit (CU) to the corresponding sensor unit (SU).

3. The method according to any one of the preceding claims, wherein the synchronization data (t0) is transmitted by means of the characteristic signal (MAC_SYNCF). EGSp T p The signal is transmitted to the sensor unit (SU).

4. The method according to any one of the preceding claims, wherein the synchronization data (t0) EGSp T p The voltage and phase values ​​of the three phases of the power supply network are determined over more than one period, preferably from at least ten periods, and particularly preferably from at least 100 periods.

5. The method according to any one of the preceding claims, wherein the central unit (CU) detects the voltage and phase values ​​of the phase lines of the power supply network and a first supplementary synchronization data (Δt) detected in a previous time period for the time delay at the transmit characteristic signal (MAC_SYNCF). EGSp-1 ) ， The previous time period is before the current time period, the synchronization data (t0) EGSp T p The first supplementary synchronization data (Δt) is detected during the current time period and preferably transmitted via the characteristic signal (MAC_SYNCF). EGSp-1 The data is transmitted to the corresponding sensor unit (SU), and the first supplementary synchronization data (Δt) is considered when the corresponding sensor data (SD) is detected by the corresponding sensor unit (SU). EGSp-1 ).

6. The method according to any one of the preceding claims, wherein the central unit (CU) further has an internal central time unit, the value of which forms a second supplementary synchronization data (t). EGS The second supplementary synchronization data is preferably transmitted to the corresponding sensor unit (SU) by means of the characteristic signal (MAC_SYNCF), and the second supplementary synchronization data is taken into account when the corresponding sensor data (SD) is detected by the corresponding sensor unit (SU). EGS ).

7. The method according to any one of the preceding claims, wherein the current values ​​of the respective sensor units (SU) are aggregated into aggregated current phasors (...). I H1p ), and the polymer current phasor ( I H1p The voltage value and the aggregated current phasor are transmitted to the central unit (CU), and in the central unit (CU) the voltage value and the aggregated current phasor are transmitted to the central unit (CU). I H1p Calculate the power.

8. A distributed system for time synchronization of a sensor unit (SU), the distributed system comprising a central unit (CU), wherein the system is configured to implement the method according to any one of the preceding claims.

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