monitoring equipment

Abstract

A monitoring device (10) for monitoring a parameter value relating to an AC component of an AC power source or supply device in an electrical distribution network (1), the monitoring device comprising: a sensor device (14) that, in use, is electrically connected to or otherwise monitors the network (1), and a control unit (12) operable to determine an amplitude value at a selected frequency for a voltage using an output of the sensor device (14). The method enables the operation of a device to be controlled in response to a supply from the network without relying on a signal component from a rotating power converter.

Description

[Technical Field]

[0001] The present invention relates to a monitoring apparatus, in particular to a monitoring apparatus for monitoring the condition of a generator or power supply such as a power converter, battery or power bank, etc. More particularly, the present invention relates to an apparatus for in-line monitoring of the condition of a generator or supply for an electrical distribution network, so that information about the condition can be used to control the operation of a load or device. [Background technology]

[0002] Energy supply through an electricity distribution network or power grid is subject to fluctuations due to periods of increased and decreased demand, which typically results in higher demand during peak hours, such as the morning peak hour or the evening peak hour.

[0003] Various methods are under development to measure power demand and thereby control device operation depending on the status of power supplies and generators. For example, delaying or temporarily reducing energy use, such as heating a washing machine or charging an electrical device, may be acceptable or even imperceptible in many scenarios. Thus, such loads may be reduced and / or delayed during peak demand periods and resumed during off-peak periods.

[0004] One method the inventors have explored involves analyzing the frequency variation of the AC component of an AC or voltage signal at a device to derive an indication of excess supply or high demand from the variation. This method recognizes that many types of energy supply use rotating generators, such as turbines. In such cases, changes in rotational frequency can be measured as a frequency variation in the voltage supplied to the device. An increase in frequency can be associated with increased supply, while a decrease in frequency can be associated with decreased supply or relatively higher demand, respectively. This method is less practical for power sources that avoid rotational energy generation. For example, a voltage source converter or inverter, such as a battery or power bank, may operate to provide a substantially constant, sinusoidal AC voltage with little frequency variation.

[0005] The present invention aims to provide an alternative or extension to known methods by reducing or completely avoiding the reliance on the presence of a periodic signal indicative of fluctuations in the rotating generator. Summary of the Invention [Problem to be solved by the invention]

[0006] According to a first aspect of the present invention there is provided a monitoring apparatus as claimed in claim 1 for monitoring a parameter value relating to the AC component of an AC power source or supply device in an electricity distribution network, the monitoring apparatus comprising a sensor apparatus which, in use, is electrically connected to or otherwise monitors the network, and a control unit operable to determine an amplitude value at a selected frequency for a voltage using an output of the sensor apparatus.

[0007] In some embodiments, the control unit is configured to determine an amplitude value of the signal at a predetermined frequency.

[0008] The amplitude value may be determined, for example, via spectral analysis of the voltage signal to extract a component at a particular frequency, for example 50 Hz.

[0009] In some embodiments, the predetermined frequency is a frequency value in the range of 45 Hz to 55 Hz, preferably 50 Hz.

[0010] The frequency value may be greater than 46, 47, 48, or 49 Hz. The frequency value may be less than 54, 53, 52, or 51 Hz.

[0011] In some embodiments, the predetermined frequency is a frequency value in the range of 55 Hz to 65 Hz, preferably 60 Hz.

[0012] The frequency value may be higher than 56, 57, 58, or 59 Hz. The frequency value may be lower than 64, 63, 62, or 61 Hz.

[0013] In some embodiments, the device is configured to derive amplitude values ​​from input values ​​from regions of the waveform being monitored that do not include peak values.

[0014] In some embodiments, the apparatus is configured to determine data points representing at least two slopes of the waveform, determine an intersection between the two slopes, and interpret the slope intersection as an amplitude value.

[0015] The waveform may be a waveform component of a signal at a given frequency.

[0016] In some embodiments, the apparatus is configured to perform a spectral analysis of the waveform to thereby derive the amplitude value.

[0017] As will be appreciated, spectral analysis of the waveform may determine, for example, the shape of a pure sine wave which may have different amplitude values ​​than the measured waveform.

[0018] In some embodiments, the control unit uses a recursive discrete Fourier transform (DFT) based technique in analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

[0019] In some embodiments, the control unit uses a Fast Fourier Transform (FFT) based technique in analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

[0020] In some embodiments, the control unit uses a technique based on the fast sine transform (FST) in analyzing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

[0021] In some embodiments, the control unit uses a technique based on fast cosine transform (FCT) in analyzing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

[0022] In some embodiments, the apparatus is configured to control the operation of an electric device, an electric storage device, a smart electric device, and / or an electric heating device such as a heat storage or water heater.

[0023] The device may be used to control the charging or use of a battery or power bank.

[0024] In some embodiments, the apparatus is configured to determine two or more consecutive calculated amplitude values ​​and derive a change in available supply in the power distribution network from the change between the consecutive calculated amplitude values.

[0025] In some embodiments, the control unit is configured to interpret a value indicative of an increase in the amplitude value as indicative of an increase in supply from the electricity distribution network.

[0026] In some embodiments, the control unit is configured to interpret a value indicative of a decrease in the amplitude value as indicative of excess demand from the electricity distribution network.

[0027] In some embodiments, the apparatus is configured to determine the difference between the amplitude value and the measured amplitude value and use the difference to derive an efficiency value indicative of losses in the power distribution network.

[0028] In some embodiments, the control unit is configured to interpret an increase in efficiency as indicative of an increase in supply from the distribution network and / or to interpret a decrease in amplitude value as indicative of excess demand from the distribution network.

[0029] According to a second aspect of the present invention there is provided a method as set forth in claim 18 for monitoring a parameter value relating to an AC component of an AC power supply or feeder in an electrical distribution network, the method comprising using a sensor device electrically connected to or otherwise monitoring the network, using an output of the sensor device to determine an amplitude value for a selected frequency, and controlling operation of a load or device based on the change between successive amplitude values.

[0030] In some embodiments, the method includes using a sensor device to determine amplitude values ​​at frequency values ​​in the range of 45 Hz to 55 Hz and / or in the range of 55 Hz to 65 Hz.

[0031] The frequency values ​​may be 50 Hz or 60 Hz, respectively.

[0032] In some embodiments, the device is configured to derive amplitude values ​​from input values ​​from regions of the waveform being monitored that do not include peak values.

[0033] In some embodiments, the method includes determining data points representing at least two slopes of the waveform, determining an intersection point between the two slopes, and interpreting the intersection point as an amplitude value.

[0034] In some embodiments, the method includes deriving the amplitude value using spectral analysis of the waveform.

[0035] In some embodiments, the method includes controlling the operation of an electric device, an electric storage device, a smart electric device, and / or an electric heating device such as a heat storage or water heater.

[0036] In some embodiments, the method includes repeatedly determining an amplitude value and deriving a change in available supply in the power distribution network from changes in the amplitude value.

[0037] Any one or more of the embodiments described in relation to the first aspect may be combined with any one or more of the embodiments described in relation to the second aspect. Any one or more of the embodiments of the second aspect may comprise one or more steps using any one or more features of the embodiments of the first aspect.

[0038] Exemplary embodiments of the present invention will now be described with reference to the drawings. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram of a grid monitoring device. [Figure 2] FIG. 2 is a diagram of exemplary waveforms for illustrating the present invention. [Figure 3] FIG. 3 is a flow chart illustrating exemplary steps of a method for operating a device. DETAILED DESCRIPTION OF THE INVENTION

[0040] 1 shows a schematic configuration of a monitoring system 10 for a network grid 1 that supplies power from a generator or power source 12 for loads, such as devices 20, connected to and powered or charged via the network grid 1. The monitoring system 10 includes a control unit 16 with one or more sensors 14 constituting a sensor device that measures or records a signal magnitude, such as a voltage magnitude, and provides the output of the sensor 14 as a sensor measurement as an input to the control unit 16. The sensors 14 may be connected to the network grid 1 or otherwise configured to monitor the output of the network grid 1. Suitable sensors or instruments capable of recording voltage signals are known to those skilled in the art and will not be described in detail herein.

[0041] Although the device 20, the control unit 16, and the sensor 14 are shown separately in FIG. 1 , it will be understood that one or more of the sensors 14 and / or the control unit 16 may be components of the device 20. For example, they may be provided as components on a printed circuit board. Alternatively, or in addition, one or more of the sensors 14 and / or the control unit 16 may be separate devices configured to communicate with the device 20. Suitable communication protocols for wireless or wired communication are known and will not be described in detail herein. Similarly, multiple control units 16 may be configured to affect the operation of one or more common devices 20, and / or one or more devices 20 may be controlled by one or more common control units 16.

[0042] The control unit 16 is configured to control the operation of the device 20, for example, by controlling the operation of the switch 22 in response to output from the one or more sensors 14. The switch 22 should be understood as an example of a configuration that allows the control unit 16 to operate the device 20 in one of two or more different operating modes. Some types of the device 20 may be operated without actuating a physical switch. Several methods of controlling the operation of the device 20 are known to those skilled in the art and will not be described in detail herein. Instead of controlling the operation of the switch 22, the control unit 16 may operate the device 20 in one of several modes, such as switching between a high-performance mode and a low-performance mode, or between a fast-charge mode and a slow-charge mode.

[0043] The monitoring device 10 is configured to analyze signals from the electrical grid 1 and determine, for a predetermined voltage wavelength, an amplitude voltage value representing the amplitude of the voltage signal. The wavelength may be selected by an appropriate wavelength filter. For example, the waveform at the predetermined wavelength may be selected using Fourier transform techniques to extract the sinusoidal waveform component of the voltage signal, for example, at 50 Hz or another wavelength. The present invention is believed to be useful for wavelengths of 50 Hz or 60 Hz, which are the fundamental wavelengths of electrical distribution networks in Europe and North America, respectively. However, the present invention is not necessarily limited to a particular wavelength and may be used with different reference wavelengths. It will be understood that a voltage drop, for example, measuring 48 Hz instead of the expected nominal 50 Hz or measuring 58 Hz instead of the expected nominal 60 Hz, indicates an excess demand on the supply from the power source 12.

[0044] It was a recognition underlying the present invention that the voltage amplitude, when measured directly from the AC voltage signal at device 20, may be lower than the voltage signal amplitude measured at power source 12. This is understood to be the case due to losses 3 (shown here by the dashed rectangle) in grid 1 due to transmission inefficiencies along the power lines and transmission equipment between power source 12 and device 20, as well as due to other effects such as unknown influences and the fluctuating number of other loads being connected and / or disconnected. For purposes of this disclosure, it is assumed that losses 3 may be difficult to quantify.

[0045] Referring to Figure 2, graph 30 shows a waveform that may be obtained by measuring voltage amplitude. It will be understood that the graph shows a full cycle of an AC waveform at a single wavelength and may represent a 50 Hz or 60 Hz waveform as obtained after analysis of the measured voltage signal. In the absence of losses, after extracting the waveform at a given wavelength, such as 50 Hz, with a loss-free amplitude peak 40, the measurement would be expected to yield a perfect or near-perfect sinusoidal waveform 36.

[0046] However, due to the presence of losses 3 (see FIG. 1 ) as indicated by loss waveform 34, the true waveform may have a shape that is “flatter” in the form of actual waveform 32. Actual waveform 32 may be thought of as the difference between a sinusoidal lossless waveform 36 and loss waveform 34. If only the actual AC voltage is measured at device 20 without a separate measurement directly at power supply 12, the shape of loss waveform 34 may be unknown, and therefore the magnitude of losses 3 may be unknown, so lossless amplitude peak 40 of lossless waveform 36 may not be measurable by direct AC voltage measurement near device 20.

[0047] It will be appreciated that if the magnitude of loss 3 is unknown or cannot be derived with the required accuracy and / or cannot be determined with sufficient time resolution, then the magnitude of sinusoidal waveform 36 cannot in fact be determined from measurements of waveform 32 in device 20.

[0048] Thus, while it may be of interest in certain scenarios to measure the amplitude of waveform 32, this may not be the amplitude that would be expected to be measured at power source 1, or in addition, variations in amplitude may be measured that may be affected by varying grid losses 3.

[0049] To determine the amplitude value, the present disclosure suggests measuring the slope of waveform 32, i.e., one ascending slope and one descending slope, by measuring multiple points 38a, 38b (here, two points on the decreasing slope) and 39a, 39b (here, two points on the ascending slope) and determining the intersection of two adjacent slopes (i.e., an upward and a downward slope) as the lossless amplitude peak 40, i.e., the amplitude value location indicating the amplitude value of the waveform if measured without losses. This allows the calculated amplitude value to be used as a value indicating the lossless amplitude value predicted from direct measurement at power supply 1. The locations of points 38a, 38b, 39a, 39b may be dynamically determined with reference to the peak of actual waveform 32 and / or with reference to a baseline, e.g., at 30% and 50% of the amplitude of actual waveform 32, or other suitable values. For a sine wave, the region between approximately 35% and 50% of the amplitude can be assumed to be within the relatively linear region of the sinusoidal waveform. In this region, the points on the sine wave are closer to the base and off the peak, and therefore less susceptible to peak flattening or other loss effects.

[0050] Calculation of the lossless calculated amplitude values ​​can be effectively performed via only five calculation steps: two steps to determine two data points 39b, 39a for one slope, two steps to determine two data points 38a, 38b for the return slope, and a fifth calculation step to calculate the intersection point of the two slopes 40. It will be appreciated that fewer calculation steps allows for more lossless amplitudes to be calculated in a given period of time, thus increasing the time resolution of such measurements.

[0051] In scenarios where the wave signal can be assumed to be symmetric, the computational effort can be further reduced. If it is understood that the locations of the two slope data points 38a, 38b are symmetric with respect to data points 39a, 39b, the calculation may be reduced to two steps: determining two data points (e.g., 38a, 38b) and then determining the intersection point 40 from data points 38a, 38b and their corresponding mirrored / inverted values.

[0052] Alternatively, or in addition, the waveform may be processed by spectral analysis to determine the peak amplitude of a pure sine wave at a given wavelength, e.g., 50 Hz or 60 Hz, as will be appreciated. It will be appreciated that using two data points may mathematically yield multiple possible results, and that a clear value can be determined by comparison with an expected wavelength, e.g., 50 Hz, and / or by comparison with successive measurements. Suitable spectral analysis methods are known and include recursive discrete Fourier transforms (DFTs), fast Fourier transforms (FFTs), fast sine transforms (FSTs), fast cosine transforms (FCTs), and other suitable techniques.

[0053] As mentioned above, the underlying waveform can be assumed to follow a sinusoidal curve. Therefore, by periodically sampling the measurable waveform 32, data points closer to the base, in a region approximately 30%-50% of the peak amplitude, can be used to determine data points from regions off the peak. As an example, the linear region of a sine wave can be derived from a first-order approximation from a Taylor series expansion, where the first-order expansion is linear. Depending on the desired level of accuracy, other suitable methods can be used. In this manner, spectral analysis can be used instead of or in addition to geometric analysis. In other words, spectral analysis can be performed using data from regions off the peak amplitude, typically approximately 30%-50% of the peak amplitude, typically the linear or near-linear region of the sinusoidal waveform function, as input to calculate amplitude values ​​representing the lossless peak amplitude. This eliminates the need to use data points from the measured peak amplitude.

[0054] By measuring and comparing successive amplitude values ​​that represent the calculated, lossless amplitude, the apparatus can determine fluctuations in voltage amplitude in the power supply 1 using an arrangement of sensors 14 near, at, or within the device 20. It will be appreciated that the monitoring system may obtain measurements at regular intervals, which may be hundreds or thousands of times per second, or at shorter or longer intervals, for example, once per minute, or once every few minutes, for example, every five minutes. It will be appreciated that this allows for a correspondingly higher time resolution for determining fluctuations in supply and demand, and therefore allows for the operation of the device 20 to be controlled at shorter intervals.

[0055] A determination can be made whether there is an increase in voltage amplitude or a decrease in voltage amplitude by comparing the voltage amplitude value to one or more preceding lossless amplitude peaks 40. Additionally, voltage amplitude performance over time may be determined, allowing the voltage amplitude to be mapped to hours of the day, weekdays, hours within each weekday, etc.

[0056] Alternatively, or in addition, the monitoring system 10 may be configured to measure an efficiency value or a loss value, respectively, as the difference between a calculated loss-free voltage amplitude and an actual measured voltage amplitude. The efficiency value or loss value may be understood as an indication of losses in the power distribution network. The monitoring system 10 may be configured to determine whether losses 3 are increasing or decreasing, for example, by comparing changes in successive efficiency or loss values.

[0057] Alternatively, or in addition, the monitoring system 10 may compare the loss-free amplitude value with the loss value. The monitoring system 10 may derive a loss ratio as the ratio between the loss value and the calculated (loss-free) voltage amplitude. The monitoring system 10 may be configured to determine whether the loss factor is increasing or decreasing, for example, by comparing the change in successive loss factor values.

[0058] If the lossless voltage swing increases, this may be interpreted as an indication of an oversupply. If the lossless voltage swing decreases, this may be interpreted as an increased demand on power supply 12. Control unit 16 may control the operation of device 20 depending on the determination made by control unit 20 about the state of power supply 12.

[0059] Referring to FIG. 3, this illustrates exemplary steps of a method 50 for monitoring parameter values ​​associated with AC power devices in an electrical distribution network. The parameter may be a value representing the lossless amplitude or peak value of the AC signal. In step 52, a sensor device is provided for monitoring the AC signal in the electrical distribution network. The sensor device may be configured to determine the waveform of the AC signal at a predetermined wavelength, e.g., 50 Hz or 60 Hz. In optional step 54, this method is used to determine the amplitude of the measured AC signal or waveform at the predetermined wavelength. It will be appreciated that, in the absence of further information, the amplitude of the measured AC signal may be lower than the lossless amplitude that the signal would have if it were lossless. In step 56, a calculated amplitude value is determined. The calculated amplitude value may be considered indicative of the lossless amplitude value. Step 56 may include or be provided by step 58, in which the lossless amplitude value is determined based on the intersection between two slopes, in the manner described above in connection with FIG. 2. Step 56 may include or be provided by step 60, in which a lossless amplitude value is determined using spectral analysis, such as a Fourier transform-based technique, which may be a discrete Fourier transform (DFT), fast Fourier transform (FFT), fast sine transform (FST), fast cosine transform (FCT), or other suitable technique. Steps 58 and 60 may be performed simultaneously or sequentially, or only one of steps 58 and 60 may be performed. The input for steps 58 and / or 60 may be a waveform region outside the peak amplitude of the measured AC signal, e.g., a waveform region obtained from the linear region of a sinusoidal waveform. In optional step 62, a loss value may be determined as the difference between the measured amplitude value obtained in optional step 54 and the calculated amplitude value obtained in steps 56, 58, and / or 60. In step 64, a further calculated amplitude value is determined and / or a further loss value is determined. In step 66, the successively calculated amplitude values ​​are compared to a reference value. The reference value may be a baseline reference, for example a zero baseline value, or one or more preceding calculated amplitude values.In step 66, it is determined whether the change between the calculated amplitude and / or loss values ​​is positive or negative, i.e., whether it indicates an increase in peak amplitude or a decrease in peak amplitude and / or an increase in loss value or a decrease in loss value.

[0060] In step 68, the operation of a load or device is controlled based on the changes determined in step 66. As an example, in step 68 the operation of an electrical storage device, a battery and / or power bank, or a smart electrical device, or an electrical heating device such as a heat storage or water heater may be controlled.

[0061] While particular embodiments of the present invention have been described herein, it will be understood that a wide range of modifications and variations can be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. 1. A monitoring apparatus for monitoring a parameter value relating to an AC component of an AC power source or supply in an electrical power distribution network, the monitoring apparatus comprising: a sensor apparatus that, in use, is electrically connected to or otherwise monitors the network; and a control unit operable to determine an amplitude value at a selected frequency for a voltage using the output of the sensor apparatus.

2. The apparatus of claim 1 , wherein the control unit is configured to determine an amplitude value of the signal at a predetermined frequency.

3. 3. The device according to claim 2, wherein the predetermined frequency is a frequency value in the range of 45 Hz to 55 Hz, preferably 50 Hz.

4. 3. The device according to claim 2, wherein the predetermined frequency is a frequency value in the range of 55 Hz to 65 Hz, preferably 60 Hz.

5. 10. Apparatus according to any one of the preceding claims, configured to derive the amplitude values ​​from input values ​​from regions of the waveform being monitored that do not include peak values.

6. 10. An apparatus according to any one of the preceding claims, configured to determine data points representing at least two slopes of a waveform, determine an intersection between two slopes, and interpret the intersection of the slopes as the amplitude value.

7. 10. Apparatus according to any one of the preceding claims, configured to perform a spectral analysis of the waveform and thereby derive the amplitude value.

8. 10. The apparatus of any one of the preceding claims, wherein the control unit uses a recursive Discrete Fourier Transform (DFT) based technique in analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

9. 10. The apparatus of any one of the preceding claims, wherein the control unit uses a Fast Fourier Transform (FFT) based technique in analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

10. 10. The apparatus of any one of the preceding claims, wherein the control unit uses a Fast Sine Transform (FST) based technique in analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

11. 10. The apparatus of any one of the preceding claims, wherein the control unit uses a Fast Cosine Transform (FCT) based technique when analysing the waveform of the AC signal or a predetermined wavelength thereof, thereby deriving the amplitude value.

12. 10. An apparatus according to any one of the preceding claims, configured to control the operation of an electric device, an electric storage device, a smart electric device, and / or an electric heating device such as a heat storage or water heater.

13. 10. Apparatus according to any one of the preceding claims, configured to successively determine two or more successive calculated amplitude values ​​and to derive a change in supply available in the electricity distribution network from the change between successive calculated amplitude values.

14. 10. Apparatus according to any one of the preceding claims, wherein the control unit is configured to interpret a value indicative of an increase in the amplitude value as indicative of an increase in supply from the power distribution network.

15. 10. Apparatus according to any one of the preceding claims, wherein the control unit is configured to interpret a value indicative of a decrease in the amplitude value as indicative of excess demand from the electricity distribution network.

16. 10. Apparatus according to any one of the preceding claims, configured to determine a difference between the amplitude value and a measured amplitude value, and to use the difference to derive an efficiency value indicative of losses in the power distribution network.

17. 16. The apparatus of claim 15, wherein the control unit is configured to interpret an increase in efficiency value as indicative of an increase in supply from the power distribution network and / or to interpret a decrease in the amplitude value as indicative of excess demand from the power distribution network.

18. 1. A method of monitoring a parameter value associated with an AC component of an AC power source or supply in an electrical distribution network, the method comprising: using a sensor device electrically connected to or otherwise monitoring the network; using an output of the sensor device to determine amplitude values ​​for selected frequencies; and controlling operation of a load or device based on the variation between successive amplitude values.

19. 19. The method of claim 18, comprising using the sensor device to determine amplitude values ​​at frequency values ​​in the range of 45 Hz to 55 Hz and / or in the range of 55 Hz to 65 Hz, respectively, preferably at a frequency value of 50 Hz or 60 Hz, respectively.

20. 20. Apparatus according to claim 18 or 19, configured to derive the amplitude values ​​from input values ​​from regions of the waveform being monitored that do not include peak values.

21. 21. A method according to any one of claims 18 to 20, comprising determining data points representing at least two slopes of a waveform, determining an intersection point between the two slopes, and interpreting the intersection point as the amplitude value.

22. A method according to any one of claims 18 to 21, comprising deriving the amplitude value using spectral analysis of the waveform.

23. 23. The method of any one of claims 18 to 22, comprising controlling the operation of an electric device, an electric storage device, a smart electric device, and / or an electric heating device such as a heat storage or water heater.

24. A method according to any one of claims 18 to 23, comprising repeatedly determining the amplitude value and deriving a change in the supply available in the electricity distribution network from changes in the amplitude value.

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