Synchronization of Frequency Measurements in Demand Response Systems

Abstract

A method is disclosed for determining a synchronization offset of measurement data for a power supply network. A first and a second data set of measurement data are received from a first source and a second source. Each data set includes measurements of an electrical parameter of the network measured at the respective source together with time information indicating a measurement time of the measurements. A correlation measure is determined for each of a plurality of time shift values, indicating a correlation between a first set of measurements derived from the first data set and a second set of measurements derived from the second data set, one of the first and second sets of measurements being derived under application of a time shift corresponding to the respective time shift value. One of the time shift values ​​is selected in dependence on the correlation measure and is used to provide a synchronization offset. The synchronization offset is used to correct the time information in the measurement data from one of the sources.

Description

[Technical field]

[0001] The present invention relates to a system and method for synchronizing measurement data for an electric power distribution network by determining a synchronization offset for the measurement data and correcting time information using the determined synchronization offset. Certain embodiments apply synchronization to frequency measurement data from demand response assets in a demand response system. [Background technology]

[0002] It has become increasingly challenging for grid operators to manage each aspect of the energy grid, such as balancing electricity supply and demand and accommodating frequency shifts in the electrical grid.

[0003] Generally, grid operators may mandate (or provide financial incentives for) actions of energy producers or energy consumers to ensure a stable and responsive electric grid. For example, a grid operator may purchase regulating capacity from industrial consumers and / or producers of electricity. Consumers or producers offering such services are instructed to reduce or increase their electricity consumption when requested by the grid operator in order to maintain grid stability and quality. Such services are commonly referred to as flexibility services.

[0004] Flexibility services can be provided by large industrial energy assets managed by commercial operators. However, the installation of small private energy assets such as energy storage and generation assets (e.g., solar panels, batteries, heat pumps and boilers) in residential or small commercial installations is becoming more prevalent, and attempts are being made to provide flexibility services by aggregating individual small assets into asset pools and managing services at the pool level, for example by configuring complementary assets to implement aggregate demand response actions.

[0005] In principle, the use of small energy assets such as residential heat pumps, batteries, electric vehicles and boilers to provide flexibility, e.g. frequency or voltage regulation, to the power system requires compliance with strict requirements on the measurement accuracy of local system parameters such as frequency and voltage. For example, the National Grid requires that the reported timestamp of measurements deviate from the actual timestamp by at most 100 milliseconds. In practice, the measurements available for such assets often do not meet these requirements, and it is too costly to install highly accurate local clocks on each asset. While the relative differences between timestamps of cost-effective metering equipment are often quite accurate, the absolute timestamps of the measurements are not. However, deviations in absolute timing can significantly reduce the accuracy of the reported frequency values. For this reason, in principle it would be desirable to incorporate small, low-value energy assets into flexibility systems, but this may be hindered by the limitations of those assets. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention seeks to alleviate some of these problems, allowing assets with poor clock accuracy to be incorporated into demand response systems and provide flexibility services. [Means for solving the problem]

[0007] Therefore, according to a first aspect of the invention, there is provided a method for determining a synchronization offset of measurement data for a power supply network, comprising the steps of: a first dataset of measurement data from a first source and a second dataset of measurement data from a second source, each dataset comprising: A plurality of measurements of electrical parameters of the network measured at each source; and Time information indicating the measurement time receiving a first data set and a second data set, a plurality of correlation measures, each correlation measure being determined for a respective one of a plurality of time shift values; and a first set of measurements derived from the first data set; and a second set of measurements derived from the second data set; determining a plurality of correlation measures indicative of a correlation between one of the first and second sets of measurements derived under application of a time shift corresponding to a respective time shift value; selecting one of the time shift values ​​depending on the correlation measure; determining a synchronization offset based on the selected time shift value; A method is provided that includes:

[0008] Preferably, the method may further comprise correcting timing information in measurement data received from one of the first and second sources using the determined synchronization offset. This may involve correcting data received from one of the first and second sources and / or receiving further measurement data from one of the first and second sources and correcting timing information in the further measurement data using the determined synchronization offset.

[0009] Alternatively (or additionally), the method may include outputting a synchronization offset, preferably by transmitting the synchronization offset to one of the first and second sources, to enable local correction of measurement data at the source. The method may then include receiving (and storing) the synchronization offset at said source, using the synchronization offset to correct timing information in measurement data generated at said source, and transmitting the corrected data (e.g. to a central synchronization controller, a demand response controller, or other system component described below).

[0010] The correction preferably involves applying a synchronization offset to timing information in the measurement data from the source, for example by adding or subtracting the synchronization offset to or from timestamps in the measurement data to be corrected.

[0011] Preferably, one or both of the first and second sources include demand response assets configured to implement flexibility services, e.g. by modifying the supply of energy to and / or the use of energy from the electricity supply network in response to locally measured network conditions and / or under the control of a central demand response system. Each source may also include or be associated with an asset controller for executing a demand response control program to control energy flows to and from the network and / or measuring devices for measuring electrical parameters of the network.

[0012] The electrical parameter is preferably one of frequency and voltage.

[0013] The method is preferably performed in a central synchronising controller in communication with the first and second sources over a data network.

[0014] Correlation is preferably determined between measurements derived from the data sets at corresponding time points after shifting the data of the data sets relative to each other by a time shift value.

[0015] For example, the first set of measurements may include measurements from the first data set each associated with a respective first measurement time value in the first data set (e.g., as a measurement timestamp), and the second set of measurements is derived from the second data set based on the second measurement time values, the second measurement time values ​​being obtained by modifying (e.g., adding / subtracting) each of the first measurement time values ​​using a time shift value. The method may then further involve determining a measurement from the second data set (e.g., based on time information such as a timestamp in the second data set) that corresponds to the second measurement time value. This step may use interpolation, as further described below.

[0016] Preferably, a first set of measurements is derived from a first data set over a predetermined time window (e.g. encompassing a particular time period and / or a particular number of measurement samples) and then a second set of measurements is derived from a second data set over a corresponding time window, preferably shifted by a time shift value.

[0017] Deriving at least one of the first and second sets of measurements may include interpolating from measurements of the respective data sets. Preferably, the first set of measurements includes measurements taken from the first data set, each associated with a respective first measurement time value (e.g. measurement timestamp) in the first data set, and deriving the second set of measurements preferably includes interpolating for measurements of the second data set at time points corresponding to the first measurement time values ​​modified by the time shift value. More specifically, the second set of measurements may be obtained by interpolating from the second data set at a plurality of time points determined by applying the time shift value to the timestamps of measurements from the first data set.

[0018] One of the first and second sources preferably corresponds to the source on which the correction is performed, and the other source is a reference source. In the example described herein, the correction can be performed on the first source, and the second source is a reference source. However, the roles of the first and second sources can be reversed. In one embodiment, the first source is an inaccurate measurement source that generates measurement data with timing information based on a first clock to be corrected, and the second source is a reference source that generates measurement data with timing information based on a second clock, and the synchronization offset is used to correct the timing information in the measurement data from the first source, and the timing information based on the first clock is preferably less accurate than the timing information based on the second clock.

[0019] Preferably, the selected time shift value is used as the synchronization offset (i.e., the synchronization offset is the same as the selected time shift value), however, alternatively, post-processing can be applied to the selected time shift value to derive the synchronization offset (e.g., to implement filtering / smoothing of the offset over time when the offset is periodically recalculated).

[0020] The method preferably selects the time shift value associated with the correlation measure that indicates the strongest correlation among the multiple correlation measures. Typically, but not necessarily, this may correspond to the highest correlation value. For example, the correlation measure may be a Pearson correlation measure. The correlation measure may be determined for a predefined set of possible time shift values, configured, for example, as a set of fixed values, or the time shift value to be evaluated may be defined, for example, as a predefined range of time shift values ​​with a predefined step size.

[0021] Preferably, the method includes providing a synchronization offset to a given one of the sources and using the offset to correct a local time reference at the given source for controlling performance of one or more time-dependent actions at the given source.

[0022] The determination of the offset may be repeated one or more times (e.g., periodically) at fixed or variable intervals. In one example, the method may include determining a validity period of the synchronization offset and repeating the determination of the offset upon expiration of the validity period, the validity period being determined depending on the current determined offset, the change in the determined offset over time, the rate of change or stability of the determined offset over time, and one of the types of energy assets of the first or second source. If the correction is performed centrally, the controller may use the calculated offset for the correction until it is recalculated. Similarly, if the correction is performed locally at the source, the source may receive the offset and use it for the correction until it receives an updated offset from the controller.

[0023] The method may include performing, for each of a plurality of sources, a method for determining a synchronization offset to determine a respective synchronization offset for each source based on measurement data received from the respective source, and preferably using the respective synchronization offset to correct the measurement data received from the respective source or to transmit the offset to the respective source for local time correction at the source. The synchronization offset for each of the sources for which correction is performed (e.g. corresponding to a first source) is preferably determined using measurement data from the same reference source (e.g. a second source). The method may include associating a respective validity period with each synchronization offset, and recalculating the offset after expiry of the respective validity period, for example as described above.

[0024] The method may include selecting one of a number of available sources as a reference source (e.g., the second source) and using measurement data from the selected source in the method, the selection preferably being made depending on the proximity of the available source to the source (e.g., the first source) for which the correction is to be made. The method may select as the reference source the source that is closest in the network (e.g., geographically or topologically) to the source for which the correction is to be made.

[0025] The method preferably includes transmitting corrected measurement data having timing information corrected using a synchronization offset to a demand response control system, and preferably further includes, in the control system, performing demand response control based on the corrected measurement data.

[0026] In a further aspect, the present invention provides a system comprising: Synchronous control device, a first source including a demand response asset connected to an electricity supply network and configured to implement flexibility services by modifying the supply of energy to and / or the use of energy from the network, the first source configured to generate a first measurement data set and transmit it to a synchronization controller; Preferably, a second source including a second demand response asset connected to the electricity supply network, the second source configured to generate a second measurement data set and transmit it to the synchronization controller. each of the first and second measurement data sets comprising: A plurality of measurements of electrical parameters of the power supply network measured at each source; and Time information indicating the measurement time The synchronous control device includes: Receiving first and second data sets; a plurality of correlation measures, each correlation measure being determined for a respective one of a plurality of time shift values; and a first set of measurements derived from the first data set; and a second set of measurements derived from the second data set; determining a plurality of correlation measures indicative of a correlation between one of the first and second sets of measurements derived under application of a time shift corresponding to a respective time shift value; selecting one of the time shift values ​​in dependence on the correlation measure; determining a synchronization offset based on the selected time shift value; Using the determined synchronization offset, correcting time information in the measurement data received from the first (or second) source and outputting the corrected measurement data; Transmitting a synchronization offset to the first (or second) source to enable local correction of time information at the first (or second) source; and The present invention provides a system configured to:

[0027] The invention also provides a computer program, computer program product or tangible computer readable medium comprising software code adapted to perform any of the methods described herein when executed on a data processing apparatus.

[0028] The present invention also provides a system or synchronization controller having means for performing any of the methods described herein, optionally in the form of one or more processing devices with associated memory.

[0029] Any feature of one aspect of the invention may be applied to other aspects of the invention in any appropriate combination, in particular method aspects may be applied to apparatus and computer program aspects and vice versa.

[0030] Furthermore, features implemented in hardware may generally be implemented in software and vice versa, and any references herein to software features and hardware features shall be construed accordingly.

[0031] Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0032] [Figure 1] 1 illustrates an overview of a synchronization system for a demand response system. [Diagram 2] 1 illustrates a synchronization method. [Diagram 3] 1 illustrates a frequency measurement data set from an imprecise asset and a frequency measurement data set from a reference source. [Figure 4] 1 illustrates a computing device for implementing the techniques described above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] overview The present disclosure relates to a demand response system that uses energy assets to provide flexibility services on a distribution grid. The term "asset" or "energy asset" preferably refers to any device, machine, or other equipment (or collection of such entities) that is arranged to supply energy to or use energy from a distribution grid. A flexibility asset or demand response asset is an asset that is configured or capable of participating in a demand response system by modifying the energy flow between the asset and the grid on demand, for example, based on local grid conditions (such as grid frequency) and / or central commands. Energy flow encompasses both flows from the asset to the grid (supplying energy to the grid) and flows from the grid to the asset (using energy from the grid).

[0034] An asset may be an energy supplying asset, an energy using asset, or both. An energy using asset may be considered as a receiver (or consumer) of energy from the grid and may be, for example, a factory or machine, an industrial load such as a charging point for electric vehicles, a domestic electricity supply point or a domestic load, an energy storage device that is partially or fully discharged and needs to be recharged, etc. An energy supplying asset may be, for example, an energy storage device such as a generator (e.g., a gasoline generator, a wind turbine, a solar panel, etc.) or a battery. Multiple individual energy using devices and / or energy supplying devices may be operated together as a single asset (e.g., turbines of a wind farm, various machines and systems in a factory). In some cases, an asset may be capable of both supplying energy to the grid and receiving energy from the grid (e.g., a factory with an on-site generator that uses excess energy from the grid and supplies excess generating capacity to the grid at various times, or a battery that can store power drawn from the grid and later supply this stored power back to the grid).

[0035] An asset may provide demand response services by increasing or decreasing its energy use (in the case of an energy-using asset) or increasing or decreasing its supply (in the case of an energy-supplying asset). For example, an asset may change its use / supply to counter frequency instabilities on the grid and keep the grid frequency within standard tolerances of a nominal frequency (e.g., 50 Hz in Europe or 60 Hz in the United States). An asset may measure local grid conditions, such as frequency and / or voltage, and use those measurements to control local demand response and / or report such measurements to a central demand response control system or other assets, etc.

[0036] An embodiment of the present invention provides a process for correcting measurement data from energy assets with limited clock accuracy. This may typically be applied to small, low-value assets that may be installed, for example, in residential or commercial facilities. One class of such assets is networked to report frequency measurements and enable communication with a central Demand Response (DR) control system for the purpose of implementing DR control actions. Such assets are also referred to herein as Internet of Things (IoT) assets. However, while the description herein focuses on this class of assets, it should be understood that the technique may be used with any asset or other measurement source where some correction of timing information in the reported measurement data may be desirable.

[0037] To improve the measurement accuracy of IoT assets and make it easier to incorporate them into pools to provide flexibility, embodiments of the present invention provide a synchronization process that allows for improved accuracy of an IoT asset's reported absolute timestamp by using frequency values ​​of neighboring assets whose frequency measurements are more accurate, both in terms of absolute time reporting and frequency values.

[0038] A demand response system implementing a synchronization process for frequency regulation applications is illustrated in schematic form in Figure 1. The diagram shows two measurement sources: an imprecise source 102 and a reference source 110. Typically, the different sources represent the respective flexibility assets connected to the power grid 100 to participate in the provision of flexibility / demand response services.

[0039] The inaccuracy source 102 includes a first energy asset 104, an asset controller 106, and a frequency measurement device 108. Similarly, the reference source 110 includes a second energy asset 112, an asset controller 114, and a frequency measurement device 116. The assets 104 and 112 are energy assets that actually provide flexibility services, such as variable power usage from a power grid (for loads and storage devices, e.g., batteries) or variable power supply to a power grid (for generators and storage devices, e.g., batteries). It should be noted that components such as the asset, the asset controller, and the frequency measurement device may be separate components or may be integrated into fewer devices. For example, the frequency measurement device and / or the asset controller may be embedded in the energy asset, or instead the frequency measurement device may be integrated into a separate asset controller.

[0040] The asset controllers 106 / 114 are control devices that implement control logic to take some demand response action based on the locally measured frequency. The frequency measurement devices 108 and 116 measure the frequency of the power grid at each asset. The frequency measurement device 108 at the inaccurate source 102 generates its measurement data based on an inaccurate clock source 103 (e.g., a cheap local oscillator), while the reference source 110 uses a more accurate clock source 111, e.g., an accurate local clock synchronized to a remote atomic clock.

[0041] More specifically, the frequency measurement device 108 receives a data tuple

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[0042] The frequency measurement device 116 also

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[0043] Thus, differences in accuracy between clock sources may result in a timestamp accompanying a frequency measurement generated by an inaccurate source 102.

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[0044] The central controller 118 implements a synchronization algorithm to correct timing information in the frequency data received from the inaccurate source and provides the corrected data stream to the DR control system 120 for further processing.

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[0045] Synchronization Process The synchronization algorithm relies on an optimization formulation that identifies, with adequate accuracy, an absolute timestamp for each imprecise source based on an underlying statistical correlation analysis. The algorithm relies on the assumption that the frequency measured at the reference source is strongly correlated with the frequency measured at the imprecise source (hence the shape of the frequency signal will match). Given the physics behind power systems, this is a generally reasonable assumption.

[0046] To identify the correct absolute timestamp (the "correct" time in this case is the time given by the reference source clock), the optimization identifies the delay between a frequency measurement of an inaccurate source and a frequency measurement with an accurate absolute timestamp received from a reference source.

[0047] For example, the process performed by synchronization controller 118 of FIG. 1 is illustrated in FIG.

[0048] In step 202, a first frequency data set is received at the controller from an imprecise source, such as source 102 of Figure 1. In step 204, a second frequency data set is received at the controller from a reference source, such as source 110 of Figure 1. The data set includes a time series of frequency measurements with associated measurement timestamps, as described above. The data set may be received as a bulk download, but more commonly the controller receives a continuous stream of frequency data from the source over a data network.

[0049] In step 206, a correlation time window is determined. For example, this can be a window of fixed duration starting at or centered around some reference time (e.g., the time the synchronization process is running). Alternatively, the window can be defined as including a fixed number of consecutive samples of measurement data from an imprecise source. In one example, a window size of 400 to 10,000 samples can be used (e.g., this range can be appropriate for 1 minute resolution data, but for higher resolution data, e.g., 1 second resolution data, even smaller window sizes can be used). Thus, the window size will typically depend on the sample resolution of the data set, and shorter or longer window sizes than the above ranges can be used depending on the data. In step 208, a set of candidate time shifts to be evaluated is obtained. This can be a fixed, pre-configured set of time shift values ​​configured by the operator, and can be defined (determining the resolution), for example, as an array or range of time shift values ​​(e.g., minimum and maximum values) and a step size. For example, a time shift of -1 second to +1 second can be evaluated with a step size of 10 milliseconds.

[0050] In step 210, a correlation value is then calculated for each candidate time shift value over the defined time window, indicating the correlation between a time-shifted version of the second data set (from the reference source) shifted by the candidate time shift value and the first data set (to be corrected) over the entire window. In practice, this step may typically be implemented as a loop, stepping through a series of time shift values ​​and calculating the correlation at each time shift. However, correlations for different time shift values ​​may also be calculated in parallel (e.g., by parallel processes processing subranges of the time shift values).

[0051] The correlation is the time point from the inaccurate source (over a defined window) for the time shift τ being evaluated.

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[0052] In step 212, the process then selects the time shift value that results in the strongest correlation (e.g., the maximum correlation value depending on the correlation measure used) as the optimal time shift value, and this value is then adopted as the synchronization offset.

[0053] In step 214, a correction of the timestamps of the inaccurate data set is then performed using the determined synchronization offset. This is done by correcting the timestamps of each frequency sample from the inaccurate source.

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[0054] The search for the optimal synchronization offset is summarized by the following equation:

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[0055] As mentioned above,

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[0056] Imprecise frequency measurements often have varying resolution and / or may have a lower resolution than the reference frequency measurement. As an example, FIG. 3 shows frequency measurements of two assets with 1 second resolution.

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[0057] In equation (1), f (g) (.)teeth,

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[0058] Any suitable correlation measure can be used for p. In one embodiment, the Pearson correlation measure is used, more specifically the Pearson product-moment correlation coefficient, which can be calculated as follows:

number

[0059] where X and Y are vectors of frequency values ​​over the window over which the correlation is being calculated, E(.) is a function that calculates the expectation of a vector of values, and Var(.) is a function that calculates the variance of a vector of values.

[0060] The correlation is evaluated by searching over a maximum window size of possible time shift values. In a typical example, the window size is on the order of a few seconds to a few minutes. The value of the time offset τ is evaluated at fixed time increments over the maximum window size. In a typical example, the time resolution is on the order of 1 to 10 milliseconds. The window size and the time resolution within that window define the values ​​of τ that are iteratively evaluated. For example, the process may be repeated in 10 millisecond increments with τ ranging from -60 to +60 seconds.

[0061] This process is summarized in the following pseudocode: 1. One-dimensional interpolation function f for measuring a reference frequency with an accurate clock (g) Create a (.). 2. Define an array τ of possible shifts to be tested. 3. Loop with an iterator q through the array τ of possible shifts. a. Tested time shift τ q Shift the inaccurate clock instants from τ using

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[0062] It should be noted that, although in the above examples the process is described as assessing correlation by time-shifting the reference source, the process could instead time-shift the imprecise measurement (similarly, interpolation could be applied to the imprecise measurement rather than the reference measurement).The described approach is preferred because the reference source measurement is assumed to be provided with a fixed time resolution and higher resolution than the imprecise measurement, although the approach may vary depending on the nature of the data source.

[0063] 1 shows a single imprecision source, the controller 118 may receive frequency measurements from multiple different imprecision sources and apply the above process to generate a respective synchronization offset for each source, which can be used to correct the data stream from (and / or transmitted to) that source. Frequency data from multiple sources may be corrected in this manner using a single reference source 110.

[0064] In some cases, multiple reference sources with accurate clocks may be available in a grid. In that case, the central controller may select a particular reference source for correction of data from a given inaccurate source. Typically, the closest reference source (e.g., in terms of network topological or geographical distance) may be selected based on the assumption that assets located close to each other on the network will show the highest correlation between frequency measurements. However, for frequency measurements where the frequencies can be assumed to be generally similar across the network, any suitable reference source (with a sufficiently accurate clock) may be selected.

[0065] 1, a central controller calculates a synchronization offset for the inaccurate source 102, then uses the offset to correct the timestamps of frequency measurement data received from the inaccurate source, and provides the corrected data to the DR control system 120 or any other system that uses the measurement data therein. In a preferred embodiment, the controller may recalculate the offset periodically, for example at a fixed or variable interval, and then apply this updated offset to subsequently received data.

[0066] However, in an alternative configuration, the controller can transmit the calculated offset to the inaccurate source, which then performs the correction itself on the acquired measurement data, resulting in a time-corrected data stream sent from the source to the controller. In that case, the central controller can still periodically repeat the synchronization algorithm (taking into account that the received measurements already include some correction) and generate and send updated corrections as necessary to the inaccurate source. The inaccurate source applies the correction using the received offset until such time as an updated offset is received from the controller.

[0067] In either case (centralized correction at the controller or providing offsets to the source for local correction), the controller may run the synchronization algorithm with a fixed update interval, or may instead determine when to dynamically update the synchronization offset based on, for example, the type of asset, the received measurement data, the calculated offset, and / or conditions within the grid. In one example, the controller may determine the amount / speed at which the synchronization offset is changing (e.g., by tracking the rate of change of the synchronization offset or by monitoring the absolute difference between successive values ​​of the offset) and use that to determine the next update interval. For example, if the rate of change of the offset or the change in the offset between the most recent offset and the currently calculated offset exceeds some threshold, the offset may be deemed unstable and therefore require more frequent recalculation, so the controller may set the next update interval shorter. On the other hand, if the offset is relatively stable (e.g., little change / low rate of change over successive calculations), a longer update interval may be set to avoid unnecessary calculations and communication traffic with the inaccurate source.

[0068] Thus, when calculating an offset for each source of inaccuracy, the process may also determine the validity time of the offset based on current conditions (e.g., using criteria such as offset stability discussed above and / or other criteria such as asset type). Upon expiration of the validity time of the offset calculated for a given asset, the controller repeats the synchronization process to calculate a new offset for that asset. As a result, the validity times, and therefore the frequency of synchronization, for different assets may also differ.

[0069] This approach allows the system to efficiently handle situations where the offset changes over time (e.g., gradual clock drift), as long as the offset remains stable long enough to provide enough data for the synchronization algorithm to operate.

[0070] 1, the reference source is another demand response asset, but any source of frequency measurement with an accurate clock may be used as a reference source. For example, a stand-alone frequency measurement device that measures frequency on the grid may be used.

[0071] The corrected data may be used by the DR control system 120 of Figure 1 to, for example, determine whether or to what extent a DR asset is delivering a required control response, or to make adjustments to the DR control (e.g., as part of settlement with a DR service provider). If the control system determines that a response from an asset is insufficient, it may send modified control instructions to the asset, disable the provision of DR from the asset, and / or identify and configure alternative / additional assets to provide the required DR services.

[0072] More generally, the corrected data can be used for any other process where high time accuracy measurement data is needed, including implementing time-dependent actions (such as changing billing rates for smart energy tariffs), whether by the central controller 118 / DR control system 120 or the inaccurate source 102. The offset can be provided to the inaccurate source 102 to allow for local clock correction for any time-dependent actions, not just correction of frequency data. For example, the source's asset controller 106 can use the time offset as a global clock correction to correct time information used in control processes, network communications with other systems, etc.

[0073] Although described above with respect to frequency measurements, the same approach may be used to correct timing information for measurements of other electrical grid operating characteristics, particularly voltage measurements. Voltage may generally be less consistent across an electrical distribution network than frequency, and therefore for voltage measurements it may be preferable to use a reference source that is located relatively close in the network to the inaccurate source that needs to be corrected.

[0074] Additionally, although the synchronization process for demand response assets in particular has been described with respect to measurements on the electric grid, the principles described may be applied to situations where measurement data measuring a physical property of any other physical system is obtained from two sources, where the measurements from the sources are expected to be closely correlated, but one of the sources has a less accurate clock than the other.

[0075] System Architecture 4 illustrates an example of a computing device for implementing the synchronization controller 118. The controller includes one or more processors 404 along with volatile / random access memory 402 for storing temporary data and running software code.

[0076] A network interface 406 is provided for communicating with other system components (e.g., the inaccurate source 102, the reference source 110, and the DR control system 120) via one or more networks 400 (e.g., a local area network or a wide area network including the Internet).

[0077] Persistent storage 408 (e.g., in the form of hard disk storage, optical storage, etc.) persistently stores control software for implementing the functions of the controller, including a synchronization process 410 for performing the described synchronization and determining a synchronization offset, and a correction process 412 for correcting the received frequency data stream using the determined synchronization offset. The persistent storage also includes other software and data (not shown), such as an operating system for the controller.

[0078] The controller may be implemented using conventional computer server hardware and includes other conventional hardware and software components known to those skilled in the art.

[0079] Although a specific architecture is shown as an example, the controller may be implemented using any suitable hardware / software architecture.

[0080] Additionally, functional components shown as separate may be combined or vice versa. For example, the synchronization process 410 and the correction process 412 may be executed on the same controller (e.g., in parallel), or the processes may be executed on separate processing devices. In either case, the processing may be split across multiple controllers, e.g., to provide separate controllers corresponding to different subpopulations of source / DR assets for which corrections are being made. The functionality of the controllers may also be incorporated into the DR control system 120 or one of the sources 102 / 110.

[0081] It will be understood that the invention has been described above purely by way of example and that modifications of detail can be made within the scope of the invention.

Claims

1. 1. A method for determining a synchronization offset of measurement data for an electricity supply network, comprising: a first dataset of measurement data from a first source and a second dataset of measurement data from a second source, each dataset comprising: a plurality of measurements of the electrical parameters of the network measured at the respective sources; and Time information indicating the measurement time of the measurement receiving a first data set and a second data set, a plurality of correlation measures, each correlation measure being determined for a respective one of a plurality of time shift values; and a first set of measurements derived from the first data set; and a second set of measurements derived from the second data set; and determining a plurality of correlation measures indicative of a correlation between one of the first and second sets of measurements derived under application of a time shift corresponding to the respective time shift value; selecting one of the time shift values ​​in dependence on the correlation measure; determining a synchronization offset based on the selected time shift value; The method includes:

2. 2. The method of claim 1, comprising using the determined synchronization offset to correct timing information in measurement data received from one of the first and second sources.

3. 3. The method of claim 1, further comprising transmitting the synchronization offset to one of the first and second sources to enable local correction of measurement data at the source.

4. 4. The method of claim 1, wherein one or both of the first and second sources comprise demand response assets configured to implement flexibility services by modifying the supply of energy to and / or the use of energy from the electricity supply network.

5. The electrical parameters are: Frequency, and Voltage The method according to any one of claims 1 to 4, wherein the method is one of the following:

6. A method according to any one of claims 1 to 5, performed in a central synchronisation controller in communication with the first and second sources via a data network.

7. 7. The method of claim 1, wherein the first set of measurement values ​​comprises measurements from the first data set, each associated with a respective first measurement time value in the first data set, and the second set of measurement values ​​is derived from the second data set based on second measurement time values, the second measurement time values ​​being obtained by correcting each of the first measurement time values ​​using the time shift value.

8. 8. The method according to claim 1, wherein the first set of measurements is derived from the first data set over a predetermined time window, and preferably the second set of measurements is derived from the second data set over a corresponding time window shifted by the time shift value.

9. A method according to any preceding claim, wherein deriving at least one of the first and second sets of measurements comprises interpolating from the measurements of the respective data sets.

10. 10. The method of claim 9, wherein the first set of measurements includes measurements taken from the first data set each associated with a respective first measurement time value in the first data set, and deriving the second set of measurements includes performing interpolation on measurements of the second data set at time points corresponding to the first measurement time values ​​corrected by the time shift value.

11. 11. The method of claim 1, wherein the first source is an inaccurate measurement source generating measurement data having timing information based on a first clock to be corrected, and the second source is a reference source generating measurement data having timing information based on a second clock, and the synchronization offset is used to correct the timing information in the measurement data from the first source.

12. The method of claim 11 , wherein the timing information based on the first clock is less accurate than the timing information based on the second clock.

13. A method according to any preceding claim, comprising using the selected time shift value as the synchronization offset.

14. A method according to any preceding claim, comprising selecting the time shift value associated with the correlation measure of the plurality of correlation measures that indicates the strongest correlation.

15. 15. A method according to any one of claims 1 to 14, comprising providing the synchronization offset to a given one of the sources, and using the offset to correct a local time reference at the given source for controlling performance of one or more time-dependent actions at the given source.

16. A method according to any preceding claim, comprising repeating the determination of the offset at fixed or variable intervals.

17. determining a validity period for the synchronization offset; and repeating the determination of the offset upon expiration of the validity period, the validity period being: the currently determined offset, the change in the determined offset over time; the rate of change or stability of the determined offset over time; and The type of energy asset of the first or second source The method according to any one of claims 1 to 16, wherein the method is determined depending on one of the following:

18. 18. A method according to any one of claims 1 to 17, comprising performing the method for determining a synchronization offset for each of a plurality of sources to determine a respective synchronization offset for each source based on measurement data received from the respective source, and preferably using the respective synchronization offset to correct measurement data received from the respective source or transmitting the offset to the respective source for local time correction at the source.

19. The method of claim 18 , wherein the synchronization offset for each of the sources is determined using measurement data from a same reference source.

20. 20. A method according to claim 18 or 19, comprising associating a respective validity period with each synchronization offset, and recalculating the offset after expiry of the respective validity period.

21. A method according to any one of claims 1 to 20, comprising selecting one of a plurality of available sources as a reference source (e.g. the second source) and using measurement data from the selected source in the method, the selection preferably being made depending on the proximity of the available source to the source (e.g. the first source) for which correction is to be made.

22. 22. The method of any one of claims 1 to 21, comprising transmitting corrected measurement data having timing information corrected using the synchronization offset to a demand response control system, and preferably further comprising in the control system performing demand response control based on the corrected measurement data.

23. A computer program, computer program product or tangible computer readable medium comprising software code adapted to perform the method according to any one of claims 1 to 22, when said computer program, computer program product or tangible computer readable medium comprises software code adapted to perform the method according to any one of claims 1 to 22, when said computer program, computer program product or tangible computer readable medium,

24. A system having means for performing the method of any one of claims 1 to 22, optionally in the form of one or more processing devices with associated memory.

25. 1. A system comprising: Synchronous control device, a first source including a demand response asset connected to an electricity supply network and configured to implement flexibility services by modifying the supply of energy to and / or the use of energy from the network, the first source configured to generate a first measurement data set and transmit it to the synchronization controller; Preferably, a second source including a second demand response asset connected to the electricity supply network, the second source configured to generate a second measurement data set and transmit it to the synchronization controller. each of the first and second measurement data sets comprising: a plurality of measurements of electrical parameters of the power delivery network measured at each of the sources; and Time information indicating the measurement time of the measurement The synchronous control device includes: receiving the first and second data sets; a plurality of correlation measures, each correlation measure being determined for a respective one of a plurality of time shift values; and a first set of measurements derived from the first data set; and a second set of measurements derived from the second data set; and determining a plurality of correlation measures indicative of a correlation between one of the first and second sets of measurements derived under application of a time shift corresponding to the respective time shift value; selecting one of the time shift values ​​in dependence on the correlation measure; determining a synchronization offset based on the selected time shift value; using said determined synchronization offset; correcting time information in measurement data received from the first source and outputting the corrected measurement data; transmitting the synchronization offset to the first source to enable local correction of time information at the first source; and A system configured to:

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