WO2013001395A1

WO2013001395A1 - Active power identification for load monitoring system

Info

Publication number: WO2013001395A1
Application number: PCT/IB2012/052980
Authority: WO
Inventors: Armand Michel Marie Lelkens; Alessio Filippi; Ying Wang
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-06-30
Filing date: 2012-06-13
Publication date: 2013-01-03

Abstract

The present invention relates to a method and apparatus for active identification of devices (120) connected to an electricity network (110). More particularly, application level functions of the devices are used to modulate the power consumption of the devices thus making them recognizable from a central energy monitor system (100). Thereby, already existing application instructions can be used to create an energy identifier.

Description

ACTIVE POWER IDENTIFICATION FOR LOAD MONITORING SYSTEM

FIELD OF THE INVENTION

The invention relates to a load monitoring apparatus, method and system for providing information about a connected type of load in an electrical distribution system. BACKGROUND OF THE INVENTION

Energy monitoring solutions are attracting more and more attention due to the increasing energy awareness and the wish to better understand the energy consumption to avoid useless waste of energy and money

Many methods exist to monitor the energy consumption of buildings. They either include multiple sensors to collect the energy consumption of multiple devices or try to infer the energy consumption of the individual devices by monitoring the overall energy consumption. The latter approach is extremely interesting due to its low cost (only one sensor for multiple devices) and simple installation. It relies on the fact that different devices have different ways to consume energy. By looking at the time evolution of the overall power, signal processing techniques can be applied to identify the unique transient or steady state behaviour, the current distortions or combinations of characteristics that support the identification of the device. One of the first example of these central load monitoring approach is described in Hart, G.W., "Non- intrusive Appliance Load Monitoring", Proc. of IEEE, vol.80, No 12, Dec 1992, pp. 1870-1891. More advanced techniques using the current and voltage are described for example in S.B. Leeb et al "Transient event detection in spectral envelope estimates for nonintrusive load monitoring," IEEE Trans. Power Delivery, vol. 10, no. 3, July 1995, pp. 1200-1210 or in Robert Cox et al, "Transient Event Detection for Nonintrusive Load Monitoring and Demand Side Management Using Voltage

Distortion," IEEE APEC 2006, Page 7. Voltage based techniques use transient sag and swell in voltage (generated due to switching ON/OFF of loads) to establish type of load got connected/disconnected have been also proposed in the scientific literature.

Central monitoring techniques remain however more challenging and suffer from lower reliability since devices with similar energy consumption pattern can be confused. A way to improve the reliability of central monitor solution is to include some sort of active identifiers in the devices to support the central solutions. There are many approaches to do this, but they all include a hardware modification at the power supply level to transmit the identity of the device. As an example, approaches to actively transmit identifiers have been proposed in e.g. the US 7,078,982.

On the one hand, the transmission of identifiers simplifies some aspects of the central monitoring solutions. On the other hand it requires that each device injects a signal via an additional/modified hardware.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved load monitoring system with active identification and less or no hardware modification.

This object is achieved by an apparatus as claimed in claim 1 and 6, by a system as claimed in claim 11, by a method as claimed in claim 12 or 14, and by a computer program product as claimed in claim 15.

Accordingly, different devices or electrical appliances can be identified by using the existing application level interface to modulate the energy consumption. This approach does not require any hardware modification and installation requirements can be significantly reduced. Depending on the type of device, the proposed approach may provide additional support to the central load monitoring solution, e.g., support of disaggregation of the overall energy.

According to a first aspect, the encoder may be adapted to generate the device- specific application level instructions so as to cause the device to perform a predetermined application level function according to the coding pattern. Hence, power consumption of the device can be modulated by selecting an appropriate application level function. According to some non-limiting examples, the predetermined application level function may comprises at least one of a predetermined on-off sequence, a change of the load of a processor, a predetermined number of reboots, a change of a power consumption mode, a temporary switch off or activation of a heating element, a disconnection and reconnection of battery charging, a printing of a special page, and a dimming of a lamp.

According to a second aspect which can be combined with the first aspect, the encoder may be adapted to insert the device-specific application level instructions at the beginning and at the end of a working cycle of the device. Thus, the proposed active identification can be used for such devices where continuous modulation of power consumption is not possible.

According to a third aspect which can be combined with at least one of the first and second aspects, the encoder may be adapted to use the coding pattern to encode nominal power consumption of the device. Hence, by detecting and decoding the coding pattern (e.g. power identifier) not only on and off times are obtained but also nominal power consumption of the device.

According to a fourth aspect which can be combined with at least one of the first to third aspects, a code generator or code generating function may be provided for receiving information about monitored devices, for generating coding patterns for the monitored devices, for assigning coding patterns to the monitored devices, and for informing each of the monitored devices of its coding pattern. Thereby, an adaptive coding pattern can be provided so that, as an example, the size of the coding pattern can be adapted to the number of the monitored devices.

According to a fourth aspect which can be combined with at least one of the first to third aspects, the load monitoring apparatus may be adapted to use the identification to support disaggregation of energy in the power distribution system to obtain power consumption of individual devices.

According to a fifth aspect which can be combined with at least one of the first to fourth aspects, a database may be provided for storing data indicating nominal power consumption, wherein the decoder is adapted to derive a nominal power consumption of the device from the detected coding pattern and to store the derived nominal power consumption in the database. This provides the advantage that no further disaggregation is needed.

In a further aspect of the present invention computer programs for performing the above active load identification method and load monitoring method are provided, wherein the computer programs comprise code means for causing an apparatus to carry out the steps of the above methods, when the computer program is run on a computer controlling the apparatus.

It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS In the following drawings:

Fig. 1 shows a schematic block diagram of a load monitoring system for

determining an operational state of appliances according to an embodiment; and

Fig. 2 shows a load monitoring method with active identification according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The following embodiments relate to determination of an operational state, for example the power consumption, of electrical appliances, e.g., lamps, a television and a washing machine, or other devices which consume energy. According to an embodiment a monitor connected to an electrical installation is capable of determining an active

identification of appliances connected to the electrical installation. More specifically, application level instructions are used to modulate energy consumption of the device.

Depending on the particular device the application level instructions can differ significantly. As an additional option, the modulated energy consumption may be used in a central monitoring system to support the disaggregation of the overall energy. To achieve this, different devices are identified by using an existing application level interface to modulate the energy consumption.

Fig. 1 shows an embodiment of a load monitoring system having a load monitoring device 100 for determining an operational state, e.g. power or energy

consumption, of each of a plurality of electrical appliances 120 connected to an electrical installation 110 powered by a power source 111.

The electrical installation 110 is comprised by electrical wiring 110 located between the power source 111 and the load monitoring system 100, and electrical wiring 110 after the load monitoring system 100. The power source 111 may be a utility grid, a local power generator, a solar panel, the battery of an electrical car or other power sources. The appliances 120 are connected to the electrical installation 110 via electrical cables 121 for example using sockets (not shown) of the electrical installation.

The load monitoring device 100 may be connected in series or in parallel with the electrical installation. When the load monitoring device 100 is connected in parallel, the system may simply be connected via a plug to a socket of the electrical installation. When the load monitoring device 100 is connected in series, the system is merely inserted in series with the power source 111 located on one side of the system and the electrical installation 110 located on the other side of the system.

The load monitoring device 100 comprises a voltage sensor 102 connected to the electrical installation 110 for sensing the voltage on the electrical installation.

A modulator or encoder 122 (e.g. a processor) is provided in or at the electrical appliances 120 to use application level instructions to modulate the energy consumption of the electrical appliance 120 so as to insert a power identifier which identifies the electrical appliance 120. Thereby, active identification of the electrical appliance 120 can be achieved by providing and allocating a device specific coding pattern to the electric appliance 120 and generating at the encoder 122 application level instructions to be supplied to an application level interface 123 of said electrical appliance 120.

Very different solutions for power modulation based on application level instructions or commands exist depending on the device type. In the following a list of electrical appliances 120 is provided and possible approaches to insert the power identifier using the application level interface 123.

• In a dish washer, the application level instruction may include switching on the

heating element, or switching on the pump to discharge the water. The identifier of the dish washer could consist of modulating the ON-OFF sequence of the heating element in a unique way (i.e. according to a predetermined coding pattern) e.g. at the beginning and at the end of the cycle.

• In a personal computer (PC), the application level instructions can be used by any software program. To modulate the power consumption of the PC, a software program could change the load of a processor of the PC thus changing the power consumption (i.e. according to a predetermined coding pattern). In another way, it could simply reboot the PC a predetermined number of times (i.e. according to a predetermined coding pattern) thus identifying the presence of the PC rather than its power profile.

• A television (TV) screen could modulate the power consumption by changing its power consumption mode in a pre-determined sequence (i.e. according to a predetermined coding pattern).

• A water kettle with an electronic interface could switch off for very short time its heating element (i.e. according to a predetermined coding pattern). • A laptop could have a software program that disconnect the battery charging and reconnect it in a predetermined sequence (i.e. according to a predetermined coding pattern).

• A printer could have dedicated software installed that prints a special page or activate the heating element (usually a halogen lamp in laser printers) in a predetermined sequence (i.e. according to a predetermined coding pattern).

• A dimmable lamp which belongs to a centrally controlled system could be dimmed in a predetermined sequence (i.e. according to a predetermined coding pattern) that makes the lamp identifiable.

For some of the electrical appliances 120, the continuous modulation of the power consumption may not be possible. In those cases, the pre-determined sequences according to the coding pattern might only be inserted by the encoder 122 via the application level interface 123 at the beginning and at the end of some cycles (e.g. the washing cycle of a washing machine) of the respective electrical appliance 120 thus identifying the ON and OFF events or states.

By inserting the power identifiers, e.g. at the beginning and at the end of the appliance's working cycle, a reliable event detection can be achieved at the load monitoring device 100, i.e., knowing accurately the time when some appliances are turned "ON" or "OFF". Then a disaggregation can be applied to obtain the power consumption of individual appliances (e.g., using steady-state current signature based disaggregation). Energy or power disaggregation is understood as the task of taking a whole-home or office energy or power consumption signal and separating it into its component appliances.

A conventional event detector monitors the total power consumption, and declares an "ON" or "OFF" event when the power's change is within a given range . It may fail in many cases, e.g., appliances with multi-stage power consumption, appliances with long duration of ON/OFF transients. Given the power identifier sequence according to the present embodiments, a much more robust event detection can be achieved, which is critical for further disaggregation. First, the output event can be used to trigger the disaggregation. The disaggregation usually requires more intensive computation, which should be performed only when necessary. Second, the output event can reduce the search space for

disaggregation, e.g., only newly activated appliances have to be disaggregated instead of all activated appliances.

As a further option, the power identifier inserted by the encoder 122 may be used for embedding power consumption information or encoding the appliance's nominal power consumption. By detecting and decoding the power identifier at the load monitoring device 100, not only the "ON" and "OFF" time can be obtained, but also the nominal power consumption of an appliance. No further disaggregation is needed. Optionally, a database 104 of the nominal power consumption of all the electrical appliances 120 can be maintained. The length of the power identifier sequence thus depends on the number of electrical appliances 120 to be distinguished in the database 104, depending on the encoding scheme.

The load monitoring device 100 further comprises a state detector 101 which is connected with the electrical installation 110 for detecting, extracting and decoding power identifiers of the electrical appliances 120. The state detector 101 is arranged to measure electrical values on the supply connectors of the electrical installation 110. The state detector 101 may obtain the power identifiers directly from the measurements. More specifically, the modulated individual device-specific power identifiers of the electrical appliances 120 can be obtained by the state detector 101 at the load monitoring device 100 from measurements of electrical values on the electrical supply cables 121, e.g. current or voltage values. Thus, during the operation of the electrical appliances 120, electrical values, for example any changes on the supply cables 121 are monitored or recorded by a pattern detector 105 provided at the state detector 101 in order to detect the appliance specific power identifiers (i.e. coding patterns) by which power consumption of the electrical appliances has been modulated.

The state detector 101 further comprises a decoder 103 (e.g. a processor) for comparing a detected modulation pattern with the available power identifiers allocated to the electrical appliances 120. The decoder 103 may be part of the state detector 101 or may be a separate device, e.g. a computer, located elsewhere. The appliance power identifiers may have been stored previously in a storage of the load monitoring device 100, provided for example at the state detector 101 or the decoder 103.

If a detected modulation pattern matches a power identifier during the comparison, an operational state, e.g. power or energy consumption, may be assigned to the respective electrical appliance. Also, a plurality of possibly different operational states may be assigned to a plurality of different appliances.

The assignment of the operational state may be performed by a processor comprised by the load monitoring device 100, for example the decoder 103 or a different processor. Thus, the actual assignment is performed depending on the result of the comparison of the detected modulation pattern with the appliance power identifiers. The load monitoring system 100 may further comprise a user interface (not shown) for enabling a user to see results of assignments of operational states.

The state detector 101, the pattern detector 105 and possibly the decoder 103 may be seen as a load monitoring apparatus which may be fixedly or detachably connected to the electrical installation 110.

The modulation patterns may comprise any electrical value which may be determined from measurements of the current in the supply wires 121 and/or the voltage over the supply wires. Such measurements enable determination of changes in current, power, phase difference between voltage and current, appliance impedance or appliance admittance due to a modulation pattern obtained by controlling an application function of an electrical appliance 120. Any of these modulation patterns may be determined as real, imaginary or complex values.

The operational state of an appliance may be the current ON or OFF state, the current power or energy consumption, or other operational states or electrical values. Once an operational state has been attributed to an appliance the energy usage per appliance can be determined. The determination of the energy usage may be achieved by the state detector 101, or other processing means. For example, when ON and OFF switching states have been attributed to different appliances together with time information of the power identifiers, then the energy usage can be determined from knowledge of the real power consumption between ON/OFF transitions. These power consumptions may have been determined from

measurements of the current or the current harmonics. Alternatively, the power consumption may have been manually entered by a user via the user interface. For example, the power consumption of lamps may be entered manually as an alternative to measure the

consumption.

Fig. 2 shows a flow diagram of a load monitoring procedure which can be applied in the load monitoring device 100 of the above embodiment.

In step 201, the voltage or current on the electrical installation 110 is monitored, e.g. by the pattern detector 105, and analog-to-digital (A/D) converted for subsequent processing in the digital domain. Then, in step 202, time dependent changes of the monitored output voltage or current are evaluated with regard to their patterns to extract code sequences. In step 203, predetermined change patterns (frequencies, transients or steady state changes) which correspond to coding patterns of power identifiers as defined above are detected and decoded, e.g. by the decoder 103, to derive the corresponding appliance. Then, in step 204 disaggregation can be applied for the derived appliance. Optionally, if a nominal power consumption of the specific electrical appliance is additionally encoded in the power identifier, the nominal power consumption of the determined appliance can be updated in the database 104 in step 205.

According to an alternative embodiment, besides or instead of the predetermined coding patterns, also adaptive coding patterns could be provided. Then, at the central monitoring device, a code generator or the like could be added, which is adapted to receive information about the appliances under monitoring, e.g., appliance type, number of appliances of each type etc., to generate coding patterns for appliances, to assign coding patterns to appliances, and to inform each appliance of its coding pattern. The coding patterns can be designed adaptive to the appliances under monitoring. For example, if only a few appliances are provided, then simple coding patterns or short power identifier sequences could be used.

The above embodiments can be applied in any load monitoring system for smart energy monitoring and control applications designed for energy savings and occupant comfort in homes, offices, hotels and buildings, such as for example in products for lighting and lifestyle.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

To summarize, the present invention relates to a method and apparatus for active identification of devices connected to an electricity network. More particularly, application level functions of the devices are used to modulate the power consumption of the devices thus making them recognizable from a central energy monitor system. Thereby, already existing application instructions can be used to create an energy identifier.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope. The above steps 201 to 205 of Fig. 2 can be performed by a single unit or by any other number of different units. Any calculations, processing and/or control functions of the described load monitoring can be implemented as program code means of a computer program and/or as dedicated hardware.

The computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. An ap aratus for providing active load identification in a power distribution system, said apparatus comprising:

- an encoder (122) for providing a coding pattern as an identification for a device (120) connected to said power distribution system and for generating device-specific application level instructions according to said coding pattern; and

an application level interface (123) for receiving said device-specific application level instructions at said device (120) and modulating energy consumption of said device (120) in accordance with said application level instructions.

2. The apparatus according to claim 1, wherein said encoder (122) is adapted to generate said device-specific application level instructions so as to cause said device (120) to perform a predetermined application level function according to said coding pattern.

3. The apparatus according to claim 2, wherein said power predetermined application level function comprises at least one of a predetermined on-off sequence, a change of the load of a processor, a predetermined number of reboots, a change of a power consumption mode, a temporary switch off or activation of a heating element, a

disconnection and reconnection of battery charging, a printing of a special page, and a dimming of a lamp.

4. The apparatus according to any one of the preceding claims, wherein said encoder (122) is adapted to insert said device-specific application level instructions at the beginning and at the end of a working cycle of said device (120).

5. The apparatus according to claim 1, wherein said encoder (122) is adapted to use said coding pattern to encode nominal power consumption of said device (120).

6. The apparatus according to claim 1, further comprising a code generator for receiving information about monitored devices (120), for generating coding patterns for said monitored devices (120), for assigning coding patterns to said monitored devices (120), and for informing each of said monitored devices (120) of its coding pattern.

7. The apparatus according to claim 6, wherein said code generator is configured to adapt the size of said coding pattern to the number of said monitored devices (120).

8. An apparatus for monitoring load in a power distribution system, said apparatus (100) comprising:

a pattern detector (105) for detecting a coding pattern from one or more measurements on an electrical installation powered by said power distribution system; and

a decoder (103) for decoding said detected coding pattern in order to derive an identification of a device (120) powered by said power distribution system and to attribute an operational state to said device (120).

9. The apparatus according to claim 8, wherein said apparatus (100) is adapted to use said identification to support disaggregation of energy in said power distribution system to obtain power consumption of individual devices.

10. The apparatus according to claim 8 or 9, further comprising a database (104) for storing data indicating nominal power consumption, wherein said decoder (103) is adapted to derive a nominal power consumption of said device (120) from said detected coding pattern and to store said derived nominal power consumption in said database (104).

11. A system for providing load information in a power distribution system, said system comprising:

at least two apparatuses according to claim 1 connected to respective devices (120) powered by said power distribution system; and

at least one apparatus according to claim 6.

12. A method for active load identification in a power distribution system, said method comprising:

- providing a coding pattern as an identification for a device (120) connected to said power distribution system;

generating device-specific application level instructions according to said coding pattern; receiving said device-specific application level instructions at said device (120) and modulating energy consumption of said device (120) in accordance with said application level instructions.

13. The method of claim 12, further comprising receiving information about monitored devices (120), generating coding patterns for said monitored devices (120), assigning coding patterns to said monitored devices (120), and informing each of said monitored devices (120) of its coding pattern

14. A method for monitoring load in a power distribution system, said method comprising:

detecting a coding pattern from one or more measurements on an electrical installation powered by said power distribution system; and

decoding said detected coding pattern in order to derive an

identification of a device (120) powered by said power distribution system and to attribute an operational state to said electrical appliance.

15. A computer program product comprising code means for producing the steps of method claim 12 or 14 when run on a computing device.