Identifying the operation of a specified type of appliance
View Patent ↗A method of identifying the operation of an electrical appliance comprising an induction motor is described. The method comprises identifying the operation of an electrical appliance including an induction motor when a path traced by real power values against corresponding reactive power values over a time period of interest comprises one or more substantially circular arcs. The real power values are related to the total real power supplied to one or more electrical appliances as a function of time, and the reactive power values are related to the total reactive power supplied to the one or more electrical appliances as a function of time. There is also described a related method of identifying the operation of a specified type of appliance, in which the operation of said specified type of appliance is dependent on a supply of at least one utility such as electricity, natural gas or water.
1. A method of identifying the operation of an electrical appliance comprising an induction motor, the method comprising:
electronically receiving, via a computing apparatus, data from a sensor coupled to the computing apparatus, the data including measurements of electrical consumption by a plurality of appliances;
analyzing, via the computing apparatus, the data to characterize the electrical consumption by the plurality of appliances;
providing feedback from the computing apparatus that an electrical appliance comprising an induction motor is in operation at a given time when a path traced by real power values against corresponding reactive power values over a time period of interest comprises one or more substantially circular arcs based on the analysis;
wherein the real power values are related to the total real power supplied to the plurality of appliances as a function of time and the reactive power values are related to the total reactive power supplied to the plurality of appliances as a function of time.
2. The method of claim 1 wherein the real power values and the corresponding reactive power values are determined from measurements of the total current and the total voltage supplied to the plurality of appliances as a function of time.
3. The method of claim 1 further comprising a step of identifying the time period of interest wherein the step of identifying the time period of interest comprises:
detecting a time at which an electrical appliance is switched on from an increase in the total power being supplied to the plurality of appliances as a function of time;
detecting a time at which the electrical appliance reaches a steady state power consumption; and
identifying the time period of interest as being a time period between the detected switch-on time and the detected steady-state time.
4. The method of claim 1 further comprising a step of identifying the time period of interest, wherein the step of identifying the time period of interest comprises identifying a time period during which the total power supplied to the plurality of appliances varies as a function of time.
5. The method of claim 1 comprising fitting the path traced by the real power values against the corresponding reactive power values to a single circle.
6. The method of claim 5 further comprising identifying the operation of an electrical appliance comprising an induction motor when at least one of an angular range of the real and reactive power values around the fitted single circle is greater than a predetermined threshold and the reactive power at the centre of the fitted single circle is greater than one or more of the reactive power values.
7. The method of claim 5 further comprising calculating a single-circle fit parameter representative of a goodness of the fit of the single circle to the path traced by the real power values against the corresponding reactive power values.
8. The method of claim 1 further comprising:
identifying whether the path traced by the real power values against the corresponding reactive power values comprises two consecutive substantially circular arcs;
partitioning the time period of interest into consecutive first and second time periods;
fitting the path traced by the real power values against the corresponding reactive power values over the first time period to a first circle;
fitting the path traced by the real power values against the corresponding reactive power values over the second time period to a second circle; and
calculating a double-circle fit parameter representative of goodness of the combined fit of the first and second circles to the path traced by the real power values against the corresponding reactive power values.
9. The method of claim 8 further comprising:
re-partitioning the time period into different consecutive first and second time periods;
re-fitting the first and second circles in accordance with the re-partitioning;
re-calculating the double-circle fit parameter in accordance with the re-partitioning; and
selecting the best double-circle fit based on the calculated double-circle fit parameters.
10. The method of claim 8 wherein, before the partitioning step, the method further comprises:
fitting the path traced by the real power values against the corresponding reactive power values to a single circle; and
identifying one or more outlying data points in a first portion of the path traced by the real power values against the corresponding reactive power values;
wherein the first time period in the partitioning step corresponds to said first portion of the path which includes the identified outlying data points.
11. The method of claim 1 wherein, having identified the operation of an electrical appliance comprising an induction motor, the method further comprises identifying the electrical appliance based at least partially on the real power values and the corresponding reactive power values.
12. The method of claim 11 wherein the step of identifying the electrical appliance comprises:
determining one or more parameters of the one or more substantially circular arcs; and
identifying the electrical appliance based at least partially on the one or more arc parameters:
wherein the one or more arc parameters include one or more of arc radius, arc length, and arc location.
13. The method of claim 12 wherein the step of identifying the electrical appliance comprises:
comparing the one or more arc parameters of the electrical appliance to corresponding arc parameters in a database of known electrical appliances; and
calculating the value of
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where { a } α denotes the real power values and the corresponding reactive power values for the electrical appliance α; ρ α denotes the one or more arc parameters for the electrical appliance α; { a } β denotes the real power values and the corresponding reactive power values for a known electrical appliance β in the database of known electrical appliances; ρ β denotes the one or more arc parameters for the known electrical appliance β in the database of known electrical appliances; and f({ a } p ,ρ q ) is a function which provides an indication of a goodness of the fit between the real power values and corresponding reactive power values for an electrical appliance p and the one or more arc parameters for an electrical appliance q;
comparing the value of C to a predetermined threshold value.
14. The method of claim 1 wherein, having identified the operation of an electrical appliance comprising an induction motor, the method further comprises determining the load on the induction motor at a specified time by comparing the location of the real power value and the corresponding reactive power value on the circular arc at the specified time to the real power value and the corresponding reactive power value at the start location of the arc.
15. A method of identifying the operation of a specified type of appliance, the operation of said specified type of appliance being dependent on a supply of at least one utility including electricity, natural gas or water, the method comprising:
electronically receiving, via a computing apparatus, data from a sensor coupled to the computing apparatus, the data including measurements of electrical consumption by a plurality of appliances;
analyzing, via the computing apparatus, the data to characterize the electrical consumption by the plurality of appliances;
providing feedback from the computing apparatus that a specified type of appliance is in operation when a path traced by data points in an n-dimensional space substantially corresponds to a predetermined path type associated with that specified type of appliance based on the analysis;
wherein each dimension of the n-dimensional space represents a respective utility variable derived from the total supply of that utility to the plurality of appliances;
wherein the data points in the n-dimensional space represent values of the utility variables; and
wherein n>1.
16. The method of claim 15 further comprising:
fitting a function representative of the predetermined path type to the path traced by the data points;
calculating a fit parameter representative of a goodness of the fit of the function to the path traced by the data points; and
identifying the operation of the specified type of appliance by comparing the fit parameter to a predetermined threshold value.
17. The method of claim 15 wherein:
n=2;
the specified type of appliance is an electrical appliance comprising an induction motor;
the utility variable represented by the first dimension of the n-dimensional space is the total real power supplied to the plurality of appliances;
the utility variable represented by the second dimension of the n-dimensional space is the total reactive power supplied to the plurality of appliances; and
the predetermined path type comprises one or more substantially circular arcs.
18. An apparatus for identifying the operation of an electrical appliance comprising an induction motor, the apparatus comprising:
an input section arranged to receive data representative of the total supply of electrical power to a plurality of appliances as a function of time; and
a processing section arranged to identify the operation of an electrical appliance comprising an induction motor when a path traced by real power values against corresponding reactive power values over a time period of interest comprises one or more substantially circular arcs;
wherein the real power values are related to the total real power supplied to the plurality of appliances as a function of time and the reactive power values are related to the total reactive power supplied to the plurality of appliances as a function of time.
19. An apparatus for identifying the operation of a specified type of appliance, the operation of said specified type of appliance being dependent on a supply of at least one utility including electricity, natural gas or water, the apparatus comprising:
an input section arranged to receive data representative of the total supply of at least one utility to a plurality of appliances as a function of time;
an analysis section arranged to analyse the received data and to determine a time series of data points in an n-dimensional space, each dimension of the n-dimensional space representing a respective utility variable derived from the total supply of that utility to the plurality of appliances, the data points representing the received data, wherein n>1; and
a processing section arranged to identify the operation of a specified type of appliance when a path traced by the data points in the n-dimensional space substantially corresponds to a predetermined path type associated with that specified type of appliance.