GB2467981A

GB2467981A - Smart Responsive Electrical Load

Info

Publication number: GB2467981A
Application number: GB0906500A
Authority: GB
Inventors: Andrew N Dames; Kimon Roussopoulos
Original assignee: RLTEC Ltd
Current assignee: RLTEC Ltd
Priority date: 2009-01-26
Filing date: 2009-04-08
Publication date: 2010-08-25
Also published as: GB0906500D0

Abstract

A smart responsive electrical load 10 is connected to an electricity supply network 20 (e.g. national grid/mains), where the smart responsive electrical load 10 comprises an electrical power consuming device 30 (e.g. a domestic kettle or the battery for an electric vehicle) and a control arrangement 40 for controlling the supply of electrical power from the network 20; the control arrangement 60,110,150,160,170 operates by imposing a variable time delay tpbefore supplying electricity to the device 30 after a request for power to be provided to the device 30 has been sent, the variable time delay tpis a function of a state of the network 20. Preferably a state of the network 20 that variable time delay tpis dependent upon could be the supply frequency f of said network 20.

Description

SMART RESPONSIVE ELECTRICAL LOAD

Field of the invention

The present invention relates to smart responsive electrical loads. Moreover, the invention also concerns methods of providing electrical supply network load control using these smart responsive electrical loads. Furthermore, the present invention relates to electrical supply networks including one or more of these smart responsive electrical loads. Additionally, the present invention relates to software products executable on computing hardware for implementing such methods.

Background of the invention

Devices and methods for providing a smart load for an electricity supply network are described in an earlier published international PCI patent application WO 06/28709A2 which is hereby incorporated by reference. This published patent application describes refrigerators and draws an analogy with pumping water into a tank. However, the application does not consider other types of devices having other operating constraints. Thus, electrical load shedding in response to changes in electrical supply network mains line frequency is known and is based on devices such as water heaters and refrigerators. Moreover, automatic start-up after an electrical black out is also known.

At present, the World consumes circa 80 million barrels of oil per day. A significant portion of this oil is employed for transport, for example for automobiles, trucks, ships and aircraft.

Petroleum represents an extremely concentrated form of energy which is convenient to employ in mobile apparatus, for example automobiles. However, there is a desire to employ electrical power for road transport in the future, wherein the electrical power is ideally generated from renewable energy sources. In practice, the electrical power is more likely to : be derived from burning coal in coal-fired power stations (creating greenhouse gases) and from nuclear reactors (generating dangerous long-lived radioactive waste). Such coal-fired power stations and nuclear power stations are known to be capable of coping with a steady : baseline load but have difficulty coping with rapidly fluctuating demand. Moreover, when a 3r large portion of society employs personal electric transport, it is expected that electricity : ** supply demands will be much greater in future with greater temporal fluctuations in such electrical demand.

I

* S*. ** * * For example, rapid battery chargers for electric vehicles are each expected to consume several kiloWatts (kW) of electrical power from electrical supply networks when charging batteries of these vehicles. Such a magnitude of consumption dwarfs an amount of power consumed by refrigerators and similar appliances. However, methods of controlling heating and cooling in refrigerators are quite inappropriate when charging batteries, for example charging lithium batteries or ultra capacitors, which have very different requirements. For example, a company EEstor Inc. is alleged to have recently developed an ultracapacitor based upon barium titanate material in nano-particle form offering an energy storage density in excess of 300 W/kg with unlimited number of recharge/discharge cycles; if such battery technology can be implemented in an economical form, it represents a major breakthrough in electric road transport paving a way for a transition from combustion engine road transport to electric road transport.

Some processes, for example battery charging processes, are both energy intensive and complex, namely requiring carefully controlled sequences of charging power variation to complete for maintaining optimal battery lifetime. Such charging processes do not fall within constraints appropriate for controlling refrigerators pursuant to the international PCT patent application WO 06/28709A2. In respect of battery charging, electrical supply line-frequency responsive processes that disconnect electrical devices at times of grid stress are undesirable. Similarly, washing machines and dishwashers respond badly to being disconnected for periods from their electrical supply network; for example, dish washers are required to achieve a sufficiently high temperature to ensure that microbes are destroyed during dish washing, and clothes can be damaged if left for unnecessarily prolonged periods at elevated temperatures.

There thus arises a need for alternative types of smart responsive electrical loads for electrical supply networks which are able to cope with complex energy consuming processes which employ complex sequences of steps in contradistinction to simple on-off devices, for example refrigerators. * . .

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*::::* Summary of the invention

: The present invention seeks to provide an improved smart responsive electrical load for use with an electrical supply network, the smart load being operable to provide responsive load * ** control for the network whilst also accommodating needs of complex energy consuming processes associated with the smart responsive electrical load.

****** * According to a first aspect of the present invention, there is provided a smart responsive electrical load as claimed in appended claim 1: there is provided a smart responsive electrical load operatively connected to an electricity supply network, the smart responsive electrical load comprising an electrical power-consuming device and a control arrangement for controlling a supply of electrical power from the network to the device, characterized in that the control arrangement is operable to impose a variable time delay (ta) before supplying electrical power to the device after a request for power to be provided to the device, the variable time delay (ta) being a function of a state of the network.

The invention is of advantage in that use of the variable time delay as a function of the state of the network for delaying consumption of electrical power by the device for providing network regulation is capable of coping with needs of complex energy consuming processes.

A smart responsive electrical load as claimed in claim 1, wherein the state of the network is a supply frequency (t) of the network.

Optionally, in respect of the smart responsive electrical load, the control arrangement is operable to supply electrical power in an uninterrupted manner to the device after the variable time delay (ta) has elapsed.

More optionally, in respect of the smart responsive electrical load, the uninterrupted manner is not susceptible to being overridden by user intervention.

Optionally, in respect of the smart responsive electrical load, the control arrangement is operable to apply electrical power to the device in response to the supply frequency (t) exceeding a threshold frequency value, the power being then applied to the device in an uninterrupted manner. * a ** ,*

More optionally, in respect of the smart responsive electrical load, the control arrangement is operable to provide solely low-side response for the supply frequency (1) being lower than a nominal preferred value thereof. * ** S. * *.

*..S. S

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More optionally, in respect of the smart responsive electrical load, the control arrangement is operable to provide solely high-side response for the supply frequency (t) being greater than a nominal preferred value thereof.

More optionally, in respect of the smart responsive electrical load, the control arrangement is operable to provide a combination of high-side response for the supply frequency (! being greater than a nominal preferred value thereof, and low-side response for the supply frequency (f) being lower than the nominal preferred value.

More optionally, in respect of the smart responsive electrical load, the threshold frequency value corresponds to at: (a) a nominal maximum value for the supply frequency (t); or (b) a nominal value for the supply frequency (; or (c) a nominal minimum frequency value for the supply frequency (t).

More optionally, in respect of the smart responsive electrical load, the threshold frequency value is adjustable remotely from the control arrangement. For example, such remote control is implemented via the Internet, via wireless or similar communication media. More optionally, such remote control is determined by an operator of the network.

More optionally, in respect of the smart responsive electrical load, the threshold frequency value is randomly adjustable for enabling a plurality of the smart loads coupled to the network to provide a collectively smoothly changing load characteristic to the network.

Optionally, in respect of the smart responsive electrical load, the state of the network is subject to pre-filtering for defining a threshold value for controlling the variable time delay (tn).

Optionally, in respect of the smart responsive electrical load, the threshold value is varied in response to time-of-day and/or season of year.

Optionally, in respect of the smart responsive electrical load, the device includes at least one of: : (a) a battery; and * (b) a domestic appliance.

3 More optionally, the device includes at least one of: :* (a) an electrical vehicle battery; (b) a washing machine; and (c) a dish washer.

Optionally, in respect of the smart responsive electrical load, the variable time delay (ta) has associated therewith a willingness of the load to switch (WIS) which is susceptible to being adjusted relative to a defined frequency deviation at which the load is operabte to try to maintain the state of the network. Reference is made to FIG. 5 and FIG. 7 in this respect.

More optionally, in respect of the smart responsive electrical load, a characteristic of the willingness to switch (WTS) is arranged to provide the network with a linearly-varying load response when a plurality of the loads are coupled to the network in operation. Reference is made to FIG. 7 in this respect.

According to a second aspect of the present invention, there is provided a method as claimed in appended claim 18: there is provided a method of operating a smart responsive electrical load operatively connected to an electricity supply network, the smart responsive electrical load comprising an electrical power-consuming device and a control arrangement for controlling a supply of electrical power from the network to the device, characterized in that said method includes: (a) receiving a request for power to be provided to the device; (b) controlling using the control arrangement delivery of electrical power to the device by imposing a variable time delay (tn) before supplying electrical power to the device after receiving the request for power to be provided to the device, the variable time delay (t,,) being a function of a state of the network.

According to a third aspect of the invention, there is provided a smart load system as claimed in appended claim 19: there is provided a smart load system for providing a responsive load to an electrical supply network, the smart load system including a plurality of smart loads pursuant to the first aspect of the invention.

It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention. * ** * * * S...

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Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein: FIG. I is an illustration of a smart responsive electrical load pursuant to the present invention coupled to an electrical supply network; FIG. 2a to FIG. 2d are example illustrations of various response characteristics provided in operation by the smart responsive electrical load of FIG. 1; FIG. 3 is an example illustration of the smart responsive load being triggered by a change in a state of the network of FIG. 1 wherein the smart responsive load is operable to provide both high-side and low-side response; FIG. 4 is an example illustration of the smart responsive load being triggered by a change in a state of the network of FIG. 1 wherein the smart responsive load is operable to provide low-side response; FIG. 5 is an illustration of willingness-to-switch (WTS) characteristics for a plurality of the smart loads of FIG. 1; FIG. 6 is an illustration of a response regulation characteristic provided by the plurality of smart loads having characteristics as depicted in FIG. 5; and FIG. 7 is an illustration of alternative willingness-to-switch (WTS) characteristics for a plurality of the smart loads of FIG. 1.

3D.. In the accompanying diagrams, an underlined number is employed to represent an item over * which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non- underlined number to the item. When a number is non-underlined and accompanied by an :. associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing. * S. * * S

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Description of embodiments of the invention

The present invention is concerned with automated responsive loads which are operable to delay their start-up pursuant to an algorithm which attempts to find an optimal balance between reducing likely start-up delay, and providing useful electrical supply network responsive load response as a function of electrical supply frequency and/or electrical supply voltage magnitude. The loads are beneficially arranged so that their power-consuming behaviour is not interrupted or significantly modified once started. Issues related to unwanted consequences of interruption do not thereby arise. Moreover, electrical supply network load response is beneficially provided using numerous smart responsive electrical loads implemented pursuant to the present invention, such responsive electrical loads employing energy consuming processes which hitherto would have been considered unsuitable for providing load control of electrical supply networks. The present invention is contrasted from "cold start assistance", also known as "black start assistance", which is concerned with allowing a time delay before starting loads after a electrical supply network recovers after being shut down.

Referring to FIG. 1, there is shown an illustration of a smart responsive electrical load pursuant to the present invention; the smart load is indicated generally by 10. The smart load 10 includes an electrical load 30 which is coupled via a control arrangement 40 to an electrical supply network 20. The control arrangement 40 includes a main power switch 50 connected in series with a latching contactor 60 between the electrical load 30 and the supply network 20. For example, the main power switch 50 is beneficially implemented to be user-operable, for example implemented as an ON/OFF switch or a plug/socket connector.

A control input 100 of the latching contactor 60 is coupled to an output of a comparator 110.

The comparator 110 includes a non-inverting input 120 and an inverting input 130. The comparator 110 is operable to compare a first signal Si provided at the non-inverting input :. 120 with a second signal S2 provided at the inverting input 130. When the first signal Si **exceeds the second signal S2, the comparator 110 is operable to activate the latching contactor 60. Once the latching contactor 60 energized, it remains latched to provide power : from the supply network 20 to the electrical load 30. *... S..

35' The first signal Si as generated by a frequency function 150 is representative of electric :.. supply frequency f of the supply network 20. Moreover, the second signal S2 is generated by a response function 160 whose input X is connected via a timer function 170 to an electrical side Y of the power switch 50 remote from the supply network 20 as illustrated.

The timer function 170 is operable to provide a time delay t from a time instance t = 0 that the power switch 50 is switched from an OFF state to an ON state.

In operation, when the power switch 50 is user-activated, the comparator compares the first signals SI with the signal S2. When the first signal SI exceeds the second signal S2, the latching contactor 60 is activated and connects the electrical load 30 to the supply network 20. A nature of the signals SI, S2 will now be elucidated in greater detail.

The timer function 170 is capable of being implemented to provide: (a) a major high-side response as depicted in FIG. 2a; (b) a major low-side response as depicted in FIG. 2b; (C) a comprehensive major low-side and major high-side response as depicted in FIG. 2c; or (d) a combination of minor low-side response and major high-side response as depicted in FIG. 2d.

Moreover, the timer function 170 is driven by two parameters, namely whether or not the power switch 50 is in its ON state and the frequency f of electricity provided from the supply network 20. The time delay t is a function of the frequency f as depicted in FIG. 2a to FIG. 2d, depending upon which control regime is employed in the smart load 10. Optionally, the control regime is dependent upon at least one of: (a) time of day, for example night time in contrast to evening; (b) period of year, for example season of year; and (b) signals received at the smart load 20 which control its function, for example a wireless or Internet directive from an operator of the supply network 20.

In FIG. 2a to FIG. 2d, the frequency f= 50.0 Hz is a nominal desired operating frequency for the supply network 20.

In FIG. 2a, the time delay t,, is 0 second when the frequency f is greater than 50.5 Hz. The Q.. time delay t increases progressively from 0 seconds when the frequency f is 50.5 Hz to a *::. limit t,maxl when the frequency f is 50.0 Hz. For the frequency f being lower than 50.0 Hz, the time delay t is limited to t,axl as illustrated. S. S. S...

In FIG. 2b, the time delay t isO seconds when the frequency f is greater than 50.0 Hz. The time delay t increases progressively to t1,,ax2 for the frequency f decreasing from 50.0 Hz to 49.5 Hz. When the frequency f is less than 49.5 Hz, the time delay t remains at a value tpm2.

In FIG. 2c, the time delay t is 0 seconds when the frequency f is greater than 50.5 Hz. The time delay t increases progressively from 0 seconds to tpmax3 when the frequency f varies from 50.5 Hz to 49.5 Hz. When the frequency f is less than 49.5 Hz, the time delay t,, remains at tpmax3.

In FIG. 2d, the time delay t is 0 seconds when the frequency f is greater than 50.5 Hz. The time delay t increases progressively from 0 seconds to a value tpmax4a when the frequency f varies from 50.5 Hz to 50.0 Hz. Moreover, the time delay t increases progressively from tpmax4a to tpmax4b when the frequency f varies from 50.0 Hz to 49,5 Hz. When the frequency f is less than 49.5 Hz, the time delay t remains at a value tpmax4b.

The timer function 170 is capable of being implemented with other types of characteristics to those illustrated in FIG. 2a to FIG. 2d which are intended to be illustrative examples.

In operation, the smart load 10 tends to delay longer before engaging the latching contactor when the frequency f is reduced due to heavier load on the supply network 20. FIG. 2a to FIG. 2d illustrate different regimes to implement the delay t as a function of the frequency f at an instance when the power switch 50 is engaged. Optionally, the smart load 10 is operable to consider a previous average of the frequency f for a sampling period before an instance f 0 seconds when the power switch 50 is changed from its OFF state to its ON state; such consideration of a previous average is an example of pre-filtering. Yet more optionally, the frequency f is sampled for a period before the power switch 50 is engaged to model a temporal variation in the frequency f, the time delay t,, is a function of a future anticipated extrapolated value for the frequency f.

More optionally, the delay t is a function of a change in the frequency f during the delay period t,. For example in FIG. 3, actuation of the latching contactor 60 to supply power to the electrical load 30 is also a function of a rate of increase in the frequency f. Moreover, for SQ.. example in FIG. 4, actuation of the latching contactor 60 to supply power to the electrical * load 30 is a function of a temporal rate of decrease of the frequency f being below a threshold value. S...

:. Optionally, switching characteristics as illustrated in FIG. 2a to 2d are combined with switching characteristics as depicted in FIG. 3 and/or FIG. 4 to provide a degree of hybrid ::. control from a Request Start (RS) when the power switch 50 is set to its ON state to an actual start time (ST) for high-side and low-side response respectively. The response function 160 is beneficially operable to provide this additional control over a basic timing delay function provided by the timer function 170.

A first situation will now be described wherein the smart load 10 is providing a high-side response for assisting to stabilize the supply network 20; "high-side response" corresponds to providing power stabilizing response from the smart load 10 for electrical supply frequencies f from supply network 20 which are greater than 50.0 Hz, namely above a nominal operating frequency for the network 20. Many smart loads 10 are beneficially coupled to the supply network 20 so as to provide a smoothly varying collective load to the network 20 which is responsive to stabilize the network 20 towards operating at substantially f = 50.0 Hz. A best stabilization response for the network 20 is beneficially provided without causing undue user inconvenience. Electrical loads 30 with a slow ramp up when initially energized usually attain full power operation within 10 seconds; a start-up delay of circa 10 seconds is generally not noticeable to the user. Longer delays, for example less than 30 minutes, enable a greater degree of stabilization of the network 20. Yet longer delays, for example several hours or even several days may be necessary in a situation when the network 20 is very severely overloaded.

For example, the electrical load 30 is a battery charger for charging a battery at a rate of 3 kW, wherein the battery has a full energy capacity of 10 kWh. On account of the battery typically being only partially discharged in use before being recharged, a charging cycle of the battery involves storing circa 7 kWh energy. Assuming that a consumption of 3 kW occurs during a first 30 minutes of charging the battery when the frequency f is 50.5 Hz, and charging occurs after 2 hours delay when the frequency f is 50 Hz, a high side response of around 86 W is possible to achieve for assisting to stabilize the supply network 20.

A second situation will now be described wherein the smart load 10 is providing low-side response for assisting to stabilize the supply network 20; "low-side response" corresponds to providing power stabilizing response from the smart load 10 for electrical supply frequencies D.. I from the supply network 20 which are less than 50.0 Hz, namely below a nominal operating *,* frequency for the network 20. In other words, low-side response amounts to delaying starting the electrical load 30 that would otherwise have started if it had been directly : connected to the supply network 20 when the frequency f is less than 50.0 Hz. To obtain low-side response that reacts in 10 seconds of less, only those smart loads 10 which would have reacted in less than 10 second are relevant. Similarly, to obtain low-side response : .. reacting in 30 seconds or more, only those smart loads 10 which would have reacted in 30 seconds or more are relevant. In practice, for purposes of assisting to stabilize the network 20, fast-reacting low-side is best provided by high power loads 30 which are susceptible to many starts where a short nominal delay is anticipated by users.

For example, the load 30 is a domestic kettle which consumes 2.7 kW when in operation and requires 2 minutes to heat water within the kettle for the user. In an event that the kettle is used 10 times each day, a total daily power consumption associated with the kettle is 0.9 kWh, or an average of 37.5 W over a 24-hour period. When the start delay t,, varies in a range of 0 seconds for f = 50.0 Hz to 30 seconds for f = 49.5 Hz, a low-side regulation response from the kettle of (2.7 kWh x 30 seconds) / 2.4 hrs = 9.5 W throughout the 24 hour period is possible to achieve. In practice, such regulation provided by the kettle operating as the smart load 10 would be biased towards times of day when kettles are most often used.

For such a kettle, high-side response is also susceptible to being added as depicted in FIG. 2c, wherein the time delay t,, increases progressively as the frequency I reduces from 50.5 Hz to 49.5 Hz. If a nominal delay of 30 seconds were used for enabling the smart load 10 including the kettle to provide more load regulation for the network 20, both high-side and low-side response can be provided wherein the smart load 10 including the kettle provides an intermediate amount of time delay t when the frequency f is 50.0 Hz, the time delay t reducing as the frequency f increases to approach 50.5 Hz corresponding to light loading of the network 20, and the time delay t,, delay increasing as the frequency f decreases to approach 49.5 Hz corresponding to heavy loading of the network 20.

In a situation of a battery charger for the electrical load 30 of the smart load 10, a response characteristic as depicted in FIG. 2d is especially desirable, namely providing strong high-end response and relatively weaker low-end response such that tpmax4b << (2 X tpmax4a) subject to tpmax4b> tpmax4a. The time delay tpmax4a is beneficially 2 hours when the frequency f 50.0 Hz. However, due to relatively infrequency of battery recharging in comparison to repeated use of a kettle for heating water, an amount of low-side regulation response for the network provided by the smart load 10 implemented as a battery charger is relatively small, estimated to be 0.7 W for a 30-second time delay or 0.24 W for a 10-second reaction delay.

Clearly, longer time delays of at least minutes or even hours is thus highly desirable for providing more significant response load control for the network 20. S... *5*

* In the foregoing, the smart load 10 exhibits from a user's viewpoint a characteristic of "willingness to switch" (WTS) which is a function of the frequency f of electrical power :::5. provided from the supply network 20. The "willingness to switch" (WTS) is beneficially : implemented as a two-part function in a manner akin to FIG. 2d which provides regulation for -12 -both sides of a nominal operating frequency f of 50.0 Hz for the network 20. When many smart loads 10 are provided for coupling to the network 20 and also providing regulation for the network 20, the smart loads 10 are beneficially provided with mutually different "willingness to switch" (WTS) characteristics, namely effectively nominally different preferred target frequencies about which their low-side and high-side responses are implemented.

Such mutually different WTS provides a smoother regulation response for the network 20 which assists to reduce regulation control oscillations and potential operating instabilities in respect of the network 20.

Referring to FIG. 5, there is illustrated a collection of response of ten smart loads 10 denoted by SLI to SLIO. An abscissa axis denotes "willingness to switch" (WTS) and an ordinate axis denotes deviation from nominal switching frequency, namely f 50.0 Hz. A target frequency for each smart load 10 (SL) is denoted by a circle 200 in FIG. 5. There is thus provided a plurality of smart loads 10 with mutually different target frequencies about which their high-side and low-side response is arranged. Optionally, the smart loads 10 are each operable to randomly adopt amongst the characteristics depicted in FIG. 5 regarding which "willingness to switch" to employ. Such adoption is beneficially a function of behaviour of the network 20; for example, a tendency of the network 20 to operate at frequencies flower than 50.0 Hz causes the smart loads 10 to automatically adopt a regime wherein they provide greater low-end response. When such operation of the smart loads 10 is employed, an operating characteristic for loading the network 20 as depicted in FIG. 6 is obtained, wherein an abscissa axis NFD corresponds to normalized frequency deviation, and an ordinate axis PD corresponds to a fraction of smart loads 10 turned to ON status. A curve 300 corresponds to a response characteristic for the smart loads 10 when a linear regulation response is employed in the smart loads 10, for example as depicted in FIG. 2b, and a curve 310 corresponds to a collection of mutually different response for the smart loads 10 as depicted in FIG. 5. From FIG. 6, it will be appreciated that the smart loads 10 initially turn on more quickly for the curve 310 in comparison to the smart loads 10 being all similar as pertains for the curve 300. Qa.

improved characteristic is obtainable from a plurality of the smart loads 10 (SL) implemented to provide mutually different load regulation characteristics for stabilizing the network 20 is obtained when the smart loads 10 (SL) are arranged to provide characteristics :. as depicted in FIG. 7, namely each smart load 10 is assigned a "target WTS" instead of a target frequency. A distribution of "target WTS" within a groups of smart loads 10 (SL) is :. beneficially uniformly distributed as depicted in FIG. 7. Moreover, the smart loads 10 are : susceptible to having their "target WTS" modified at random and/or in response to S * instructions communicated to the smart loads 10, for example via Internet and/or wireless communication from an operator of the supply network 20.

In FIG. 7, each line represents a smart load 10 having a particular target WTS represented by a circle 350 for each line. The smart loads 10 will each switch when the frequency f of the network 20 deviates to a magnitude comparable to a switching frequency associated with its own WTS state. Each smart load's (SL) target WTS is a WTS value at a mid-frequency excursion, namely at a turning point for the smart load 10.

The inventors have appreciated, both by simulation and calculation, that if the target WTS of a population of the smart loads 10 are evenly distributed over a range of possible WTS, and the actual WTS of the smart loads 10 vary linearly with time and are independent, then the population will respond linearly to a frequency excursion of the frequency f away from its nominal desired value, for example 50.0 Hz; such linear response is to be understood to represent the number of smart loads 10 turning ON and OFF as a function of frequency. For a small population of the smart loads 10, such switching will be subject to quantization coarseness but is observed to be averaged to a smooth response for a large population of the smart loads 10.

In order to obtain a useful linear response from the population of smart loads 10 implemented pursuant to FIG. 7, it is not necessary that the target WTS are distributed evenly. It is sufficient that a numerical mean of the WTS target values is substantially equal to a mid-WTS value, for example 0.5 in a range of 0 to 1. Optionally, a half-sine distribution, a triangular distribution or even an asymmetrical distribution of WTS target values can be beneficially employed to provide smart load stabilization of the network 20. FIG. 7 does not represent a unique solution for providing a linear response to frequency deviations occurring within the network 20 based upon employing a time delay t, before coupling a load to the network 20. However, a basic requirement is that an average gradient of all the WTS frequency curves for all devices considered in aggregate must be substantially constant as a function of the frequency f. S...

* The control arrangement 40 illustrated in FIG. 1 is optionally implemented as a retrofit to : existing electrical loads 30. Alternatively, the control arrangement 40 is susceptible to being S...

:. integrally incorporated into new devices for coupling to the network 20. Optionally, the control arrangement is implemented, at least in part, using computing hardware operable to ::::. executed one or more software products for implementing the present invention. Yet : alternatively, the control arrangement 40 is susceptible to being implemented in hard-wired

S -14-

electronic circuits, for example in application specific integrated circuits (ASICs), custom integrated circuits and similar.

The present invention is highly desirable for future plug-in electric vehicles which are recharged via electricity supply networks where it is desirable avoid periodic overloading of such supply networks.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims.

Although embodiments of the invention has been described in the foregoing in respect of frequency f of the supply network 20, it will be appreciated that the present invention is similarly applicable where supply voltage magnitude V is a parameter employed for varying and controlling the time delay t,, via the control arrangement 40. Yet alternatively, the control arrangement 40 is operable to vary and control the time delay t via a composite parameter which is both a function of the frequency f and the supply voltage magnitude V. Expressions such as "including", "comprising", "incorporating", "consisting of", "have", "is" used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims. *... * * * ** * 4 * Sb, S..' S*5S

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Claims

CLAIMS1. A smart responsive electrical load (10) operatively connected to an electricity supply network (20), said smart responsive electrical load (10) comprising an electrical power-consuming device (30) and a control arrangement (40) for controlling a supply of electrical power from the network (20) to the device (30), characterized in that said control arrangement (60, 110, 150, 160, 170) is operable to impose a variable time delay (tn) before supplying electrical power to the device (30) after a request for power to be provided to the device (30), said variable time delay (ta) being a function of a state of said network (20).
2. A smart responsive electrical load (10) as claimed in claim 1, wherein said state of said network (20) is a supply frequency (t) of said network (20).
3. A smart responsive electrical load (10) as claimed in claim 1, wherein said control arrangement (60, 110, 150, 160) is operable to supply electrical power in an uninterrupted manner to said device (30) after said variable time delay (ta) has elapsed.
4. A smart responsive electrical load (10) as claimed in claim 3, wherein said uninterrupted manner is not susceptible to being overridden by user intervention.
5. A smart responsive electrical load (10) as claimed in claim 2, wherein said control arrangement (60, 110, 150, 160, 170) is operable to apply electrical power to said device (30) in response to said supply frequency (t) exceeding a threshold frequency value, said :: power being then applied to the device (30) in an uninterrupted manner. *I..
6. A smart responsive electrical load (10) as claimed in claim 5, wherein said control :" arrangement (60, 110, 150, 160, 170) is operable to provide solely low-side response for the , supply frequency (t) being lower than a nominal preferred value thereof. * ** * r -16-
7. A smart responsive electrical load (10) as claimed in claim 5, wherein said control arrangement (60, 110, 150, 160, 170) is operable to provide solely high-side response for the supply frequency (t) being greater than a nominal preferred value thereof.
8. A smart responsive electrical load (10) as claimed in claim 5, wherein said control arrangement (60, 11, 150, 160, 170) is operable to provide a combination of high-side response for the supply frequency (1) being greater than a nominal preferred value thereof, and low-side response for the supply frequency (f) being lower than the nominal preferred value.
9. A smart responsive electrical load (10) as claimed in claim 5, wherein said threshold frequency value corresponds to at: (a) a nominal maximum value for the supply frequency (f); or (b) a nominal value for the supply frequency (1); or (c) a nominal minimum frequency value for the supply frequency (1.
10. A smart responsive electrical load (10) as claimed in claim 5, wherein said threshold frequency value is adjustable remotely from said control arrangement (40).
11. A smart responsive electrical load (10) as claimed in claim 5, wherein said threshold frequency value is randomly adjustable for enabling a plurality of said smart loads (10) coupled to the network (20) to provide a collectively smoothly changing load characteristic to said network (20).
12. A smart responsive electrical load (10) as claimed in claim 1, where said state of said network (20) is subject to pre-filtering for defining a threshold value for controlling said variable time delay (tn).

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13. A smart responsive electrical load (10) as claimed in claim 5, wherein said threshold *3i: value is varied in response to time-of-day and/or season of year. * S *S.S
14. A smart responsive electrical load (10) as claimed in claim 1, wherein said device (30) I...includes at least one of: * (a) a battery; and : (b) a domestic appliance. * 0Ss * S

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15. A smart responsive electrical load (10) as claimed in claim 14, wherein said device (30) includes at least one of: (a) an electrical vehicle battery; (b) a washing machine; and (c) a dish washer.
16. A smart responsive electrical load (10) as claimed in claim 1, wherein said variable time delay (ti,) has associated therewith a willingness of said load (10) to switch (VVTS) which is susceptible to being adjusted relative to a defined frequency deviation at which said load (10) is operable to try to maintain said state of said network (20).
17. A smart responsive electrical load (10) as claimed in claim 16, wherein a characteristic of said willingness to switch (WTS) is arranged to provide the network (10) with a linear-varying load response when a plurality of said loads (10) are coupled to the network (20) in operation.
18. A method of operating a smart responsive electrical load (10) operatively connected to an electricity supply network (20), said smart responsive electrical load (10) comprising an electrical power-consuming device (30) and a control arrangement (40) for controlling a supply of electrical power from the network (20) to the device (30), characterized in that said method includes: (a) receiving a request for power to be provided to said device (30); (b) controlling using said control arrangement (60, 110, 150, 160, 170) delivery of electrical power to the device (30) by imposing a variable time delay (tn) before supplying electrical power to the device (30) after receiving said request for power to be provided to the device (30), said variable time delay (t,) being a function of a state of said network (20).* S. * * . *SS*
19. A smart load system for providing a responsive load to an electrical supply network (20), said smart load system including a plurality of smart load (10) pursuant to any one of S..claims ito 17. : . S...IS.,... * S