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Title:
A SYSTEM AND METHOD FOR CONTROLLING DEVICES IN A POWER DISTRIBUTION NETWORK
Document Type and Number:
WIPO Patent Application WO/2019/025775
Kind Code:
A1
Abstract:
Systems and methods for demand-side response management in a power distribution network are provided. The method configured to: respond to requests to supply power by controlling one or more of a first group of a plurality of electrical devices (122-126) to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices (122-136) to draw power from the power distribution network; and maintain each of the first group (122-126) above a first predetermined level of charge.

Inventors:
OAKES GRAHAM (GB)
Application Number:
PCT/GB2018/052165
Publication Date:
February 07, 2019
Filing Date:
July 30, 2018
Export Citation:
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Assignee:
UPSIDE ENERGY LTD (GB)
International Classes:
H02J3/06; H02J3/12; H02J3/28; H02J3/32
Domestic Patent References:
WO2014071459A12014-05-15
Foreign References:
JP2017017908A2017-01-19
US20170103483A12017-04-13
Attorney, Agent or Firm:
WITHERS & ROGERS LLP (GB)
Download PDF:
Claims:
Claims

1. A demand-side response management system for use in a power distribution network, comprising a controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintain each of the first group of batteries above a first predetermined level of charge, and

wherein the controller is configured to control each battery of the first group of batteries to draw power, in a charge mode, when the level of charge in each battery falls below a second predetermined level.

2. A system according to claim 1, wherein the controller is further configured to control one of more of the plurality of electrical devices other than the first group of batteries to draw power from the power distribution network in response to a request to draw power from the network.

3. A system according to claims 1 or 2, wherein the plurality of electrical devices include a plurality of draw-only electrical devices, and the controller is further configured to respond to requests to draw power by controlling one or more of the plurality of draw-only electrical devices to draw power from the power distribution network. 4. A system according to claim 3, wherein the draw-only electrical devices are electrically powered thermal energy stores.

5. A system according to claim 4, wherein the thermal energy stores are one or more of hot water tanks, thermal storage heaters, molten salt storage units, phase change material storage units, refrigeration and air conditioning systems or other thermal energy storage devices.

6. A system according to claim 1, where in the second predetermined level is fully charged. 7. A system according to claim 1, wherein the second predetermined level is less than, or equal to, the first predetermined charge level.

8. A system according to any preceding claim, wherein the first group of batteries comprises two or more battery types, and wherein the first predetermined charge level is set at a different charge level for each of the two or more battery types.

9. A system according to any preceding claim, wherein the first group of batteries comprises two or more battery types, and wherein the second predetermined charge level is set at a different charge level for each of the two or more battery types.

10. A system according to any preceding claim, wherein the controller is further configured to control one of more of the plurality of electrical devices other than the first group of batteries to draw power from the power distribution network when their level of charge falls below a third predetermined level.

11. A system according to claim 10, wherein the plurality of electrical devices other than the first group of batteries comprise two or more electrical device types, and wherein the third predetermined charge level is set at a different charge level for each of the two or more electrical device types.

12. A system of any preceding claim, wherein the first predetermined charge level is greater than 50%.

13. A system according to claim 12, wherein the first predetermined charge level is one of: 60%, 70%, 80%, 90% or fully charged.

14. A system according to any preceding claim, wherein each of the first group of batteries is used to supply power if the level of charge is above the first predetermined charge level.

15. A system according to claim 14, wherein during a request to supply power, the first group of batteries may be controlled to supply power to the power distribution network such that their level of charge drops below the first predetermined level, if the number of batteries having a level of charge above the first predetermined level drops below a first threshold.

16. A system according to any preceding claim, wherein the first predetermined level of charge is determined based on a statistical analysis of parameters of the electrical devices.

17. A system according to any preceding claim, wherein the controller is further configured to control one or more of the plurality of electrical devices presently drawing power from the power distribution network to reduce the power they are drawing from the power distribution network in response to a request to supply power to the network.

18. A system according to any preceding claim, wherein the controller is further configured to adjust the first predetermined charge level based on a received prediction of the future demand on the power distribution network.

19. A system according to any preceding claim, wherein the controller is further configured to reduce the first predetermined charge level to increase local use of the power stored in the first group of batteries. 20. A system according to any preceding claim, wherein the controller is further configured to reduce the first predetermined charge level causing the first group of batteries to partially discharge.

21. A system according to any preceding claim, wherein the controller is further configured to adjust the second predetermined charge level based on a received prediction of the future demand on the power distribution network.

22. A system according to any preceding claim, wherein the controller is further configured to increase the second predetermined charge level to increase the power stored in the first group of batteries.

23. A system according to any preceding claim, wherein the requests to supply power are in response to the frequency of the power distribution network dropping below a first frequency threshold; and the requests to draw power are in response to the frequency of the power distribution network rising above a second frequency threshold.

24. A system according to any preceding claim, wherein each of the first group of batteries may form part of one of: a uninterruptable power supply, an electric vehicle, or an energy storage unit.

25. A system according to any preceding claim, wherein the controller is further arranged to:

determine, based on aggregated power and/or energy data regarding the plurality of electrical devices, and received requests, one or more parameters defining properties of electrical devices to be controlled in response to the request; and

instruct one or more of the plurality electrical devices based on the determined parameters.

26. A system of any preceding claim, wherein the controller is further arranged to:

receive status updates from the plurality of electrical devices; and instruct each electrical device in response to receiving a status update from that device.

27. A system of claim 26, wherein the received status updates include the total capacity and the present capacity of the first group of batteries.

28. A system of any of claims 25 to 27, wherein the controller is further arranged to generate said aggregated power and/or energy data based on status updates received within a first time period.

29. A power distribution network, comprising :

a plurality of electrical devices including a first group of batteries; and a demand-side response management system according to any of claims 1 to 28.

30. A power distribution network, comprising :

a plurality of batteries configured to supply power to the power distribution network;

a plurality of draw-only electrical devices configured to draw power from the power distribution network;

a demand-side response controller configured to receive requests to supply power to or draw power from the network, the controller configured to:

in response to a request to draw power from the power distribution network, control one or more of the plurality of draw-only electrical devices to draw power;

in response to a request to supply power to the power distribution network, control one or more of the plurality of batteries to supply power to the power distribution network. 31. A power distribution network, comprising : a plurality of electrically controlled thermal stores, a plurality of batteries and a controller, the controller configured to control the plurality of electrically controlled thermal stores and the plurality of batteries in response to request to supply power to, and draw power from, the power distribution network, in order to maintain the plurality of batteries above a predetermined level of charge, and wherein the controller is configured to control each battery of the plurality of batteries to draw power, in a charge mode, when the level of charge in each battery falls below a second predetermined level.

32. A network according to any of claims 29, 30 or 31, further comprising a frequency monitor configured to monitor grid frequency and provide the controller with grid frequency data, wherein the requests to supply power are in response to the frequency of the power distribution network dropping below a first frequency threshold; and the requests to draw power are in response to the frequency of the power distribution network rising above a second frequency threshold.

33. A controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; maintain each of the first group of batteries above a first predetermined level of charge; and control each battery of the first group of batteries to draw power, in a charge mode, when the level of charge in each battery falls below a second predetermined level.

34. A method of controlling electrical devices in a power distribution network, the method comprising :

receiving requests to supply power to, or draw power from, a power distribution network;

responding to requests to supply power by controlling one or more of a first group of batteries to supply power to the power distribution network;

responding to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; maintaining each of the first group of batteries above a first predetermined level of charge; and

controlling each battery of the first group of batteries to draw power, in a charge mode, when the level of charge in each battery falls below a second predetermined level. 35. A method of controlling a plurality of power units in a power distribution network (PDN), the plurality of power units comprising thermal storage units and electrical storage units, the method comprising :

a) receiving a request to draw power from, or supply power to, the PDN ; b) instructing one or more of the thermal storage units to increase the power they draw from the PDN if the request is to draw power from the PDN ; and c) instructing one or more of the electrical storage units to increase the power they supply to the PDN if the request is to supply power to the PDN .

36. A server arranged to carry out the method of claim 35.

Description:
A System and Method for Controlling Devices in a Power Distribution Network The present application relates to a system, a method, a network and a controller for controlling devices in a power distribution network.

Background to the Invention Supply and demand for energy in a power distribution network must be kept in constant balance. Imbalances in supply and demand become apparent as real time variations from the nominal frequency of the power distribution network. The nominal frequency of the United Kingdom's power distribution network is 50Hz. The frequency decreases from 50 Hz when demand exceeds supply, and increases from 50 Hz when supply exceeds demand. If the imbalance in supply and demand becomes too large, then the power distribution network can become unstable. Such imbalances also have negative economic consequences for energy suppliers and other parties. For example, by exposing them to penalty payments to compensate for imbalances between the energy they buy in the market and that which they sell on to their customers. Moreover, if this imbalance is not quickly corrected, generation equipment and connected consumer devices may be damaged or trip- out causing wide-spread blackouts.

Such imbalances are traditionally corrected by adjusting the amount of energy generated by power stations in order to match demand. However, this can have large economic and environmental costs. For example, to enable power stations to be able to quickly increase supply, they must be run at part load. This is because increasing the output of an operating power station is significantly quicker than bringing cold power generation equipment online. However, power stations run at part load are relatively inefficient, causing an increase in the consumption of fuel per MW/Hr.

These additional economic and environmental costs can be avoided by offsetting some or all of this imbalance through demand-side response. Demand-side response is where demand for energy is adjusted in order to match the available supply. For example, when demand exceeds supply, and hence grid frequency drops, equipment in households, offices and factories can be turned down or off in order to reduce demand. Conversely, when supply exceeds demand, e.g. due to production of large amounts of solar or wind generation, equipment can be turned on to use this excess supply. Typically, demand-side response is provided by large battery-based storage units which are capable of both drawing power from the power distribution network and supplying power to the power distribution network. However, in order to provide this functionality, these battery based storage units must be maintained at a nominal partial-charge state (for example kept at 50% of charge) to allow both additional charging and discharging. Keeping batteries at partial charge can negatively affect the long-term ability of a battery to store power. Moreover, partially charged batteries are not desirable to the owner of the batteries, who may wish to use the batteries to provide local power in an emergency. There is additionally a higher economic and environmental cost of using partially charged batteries to provide a given level of demand-side response, as more partially- charged batteries will be required than otherwise would be needed if fully charged batteries could be used.

Therefore, there exists a need for improved systems and methods for providing demand-side response in a power distribution network.

Summary of the Invention

In a first aspect, the present invention provides a demand-side response management system for use in a power distribution network, comprising a controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintain each of the first group of batteries above a first predetermined level of charge.

In a second aspect, the present invention provides a power distribution network, Comprising a plurality of batteries configured to supply power to the power distribution network; a plurality of draw-only electrical devices configured to draw power from the power distribution network; a demand-side response controller configured to receive requests to supply power to or draw power from the network, the controller configured to: in response to a request to draw power from the power distribution network, control one or more of the plurality of draw-only electrical devices to draw power; in response to a request to supply power to the power distribution network, control one or more of the plurality of batteries to supply power to the power distribution network.

In a third aspect, the present invention provides a controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintain each of the first group of batteries above a first predetermined level of charge.

In a fourth aspect, the present invention providesa method of controlling electrical devices in a power distribution network, the method comprising : receiving requests to supply power to, or draw power from, a power distribution network responding to requests to supply power by controlling one or more of a first group of batteries to supply power to the power distribution network; responding to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintaining each of the first group of batteries above a first predetermined level of charge.

In a fifth aspect, the present invention provides a method of controlling a plurality of power units in a power distribution network (PDN), the plurality of power units comprising thermal storage units and electrical storage units, the method comprising : a) receiving a request to draw power from, or supply power to, the PDN; b) instructing one or more of the thermal storage units to increase the power they draw from the PDN if the request is to draw power from the PDN; and c) instructing one or more of the electrical storage units to increase the power they supply to the PDN if the request is to supply power to the PDN. Further features of the invention are defined in the appended dependent claims. Brief Description of the Drawings

By way of example only, the present invention will now be described with reference to the drawings, in which :

Figure 1 shows a demand-side response management system for use in a power distribution network;

Figure 2 is a flow-chart showing a method of operation of the demand-side response management system for use in a power distribution network; Figure 3 shows a method of determining which electrical devices to control in response to a request to draw power from a power distribution network;

Figure 4 is a flow-chart showing a method of operation of the demand-side response management system for use in a power distribution network;

Figure 5 shows a method of determining which electrical devices to control in response to a request to supply power to a power distribution network;

Figure 6 shows a method of controlling electrical devices for demand-side response management system use in a power distribution network;

Figure 7 shows a method of controlling electrical devices for demand-side response management system use in a power distribution network. Detailed Description of Embodiments

Systems, methods, networks and controllers suitable for controlling devices in a power distribution network are described. They are directed to balancing load in a demand-side response management system, comprising a plurality of batteries and a plurality of thermal stores. The thermal stores are used to place demand onto the power distribution network. The use of the thermal stores to place demand on to the power distribution network enables the batteries in the system to be maintained at a higher charge level. This improves the long term health of the batteries and maximises the amount of energy available to be supplied to the power distribution network upon request. The present invention provides an improved means of providing demand side response. In the present invention, local energy storage systems, such as batteries and/or thermal energy stores are integrated into demand-side response systems and methods. In the present invention, excess load can be diverted from the power distribution network to the local energy store when there is excess demand on the grid ; or additional load can be placed onto the power distribution network in order to recharge the local energy store when supply exceeds demand. This allows equipment to run uninterrupted, while simultaneously balancing supply and demand without the need for additional generation capacity. However, such local energy storage can be expensive. Thus it is important to optimise the utilisation of this storage so as to maximise the amount of balancing it can provide for a given level of investment.

A first embodiment of the present invention will now be described with reference to Figure 1. Figure 1 shows a demand-side response management system 100 for use in a power distribution network.

The demand-side response management system 100 comprises a plurality of electrical devices 110. For ease of understanding, only six devices are shown in Figure 1. In practice, there may be thousands, if not millions of devices forming part of the demand-side response management system 100. The precise number is not relevant to the understanding of this embodiment. Each of the plurality of electrical devices 110 is connected to the power distribution network (not shown). The power distribution network is an electricity distribution grid, such as the UK's National Grid. The amount of power drawn from the power distribution network by the plurality of electrical devices 110 can be controlled. In addition to this, a subset of the plurality of electrical devices 110 can supply power to the power distribution network. As such, the demand-side response management system 100 may be controlled to increase or decrease the demand on the power distribution network, or to increase or decrease the amount of power supplied to the power distribution network. In Figure 1, the plurality of electrical devices 110 have been separated into two groups 120, 130. The first group 120 of the plurality of electrical devices 110 is made up of batteries 122, 124 and 126. The batteries 122, 124 and 126 are capable of being controlled to both supply power, and draw power, from the power distribution network. The batteries may be stand-alone battery banks or form part of an uninterruptable power supply, an electric vehicle, or an energy storage unit.

The second group 130 of the plurality of electrical devices 110 is made up of draw- only electrical devices 132, 134 and 136. Draw-only electrical devices are electrical devices which are either configured to only draw power, or are only able to draw power, from the power distribution network. Therefore, the draw-only electrical devices 132, 134 and 136 are capable of being controlled to only draw power from the power distribution network. The draw-only electrical devices 132, 134 and 136 may be electrically powered thermal energy stores, such as hot water tanks, thermal storage heaters, molten salt storage units, phase change material storage units, refrigeration and air conditioning systems or other thermal energy storage devices.

The demand-side response management system 100 also comprises a controller 140. The controller 140 is arranged to send to, and receive data from, all of the electrical devices 110. In particular, the controller 140 is arranged to receive information indicative of the current state of the electrical devices 110 and, when necessary, to send instruction messages to tell the electrical devices 110 to increase or decrease the amount of power they draw or supply to the power distribution network. To achieve this, the electrical devices 110 include a communications module (not shown) enabling two-way communication with the controller 140. The communications modules may use any suitable communications technology, such as a modem or a cellular phone. In Figure 1, the electrical devices 110 are shown as directly linked to the controller 140. In practice, the electrical devices 110 may be linked to the controller 140 by an intermediate network (not shown), such as the Internet. In this manner, each electrical device 110 may exchange information with the controller 140 through the intermediate network, without the need for a direct connection. The controller 140 may also use information received from the electrical devices 110 to construct a statistical overview of the electrical devices 110. In particular, this may include:

• The number of electrical devices 110 in communication with the controller 140;

• The total rated power and energy capacity of these electrical devices 110;

• The total current available power and energy capacity of these electrical devices 110;

• Measures of the distribution of rated and current power and energy capacity of these electrical devices 110, such as the mean and median capacity, skewness of the distribution of capacities, and histograms of the distribution of capacities;

• The number of electrical devices 110 drawing or supplying power to the power distribution network;

• The amount of power being drawn or supplied by the electrical devices 110;

• The current power and energy capacity of each of the electrical devices 110; and

• Measures of the distribution of power being drawn or supplied by the electrical devices 110, such as the mean and median power being drawn or supplied, skewness of the distribution of power being drawn or supplied, and histograms of the power being drawn or supplied.

As discussed previously, the controller 140 may control each of the electrical devices 110 via their respective communication modules (not shown). The controller 140 can instruct each of the electrical devices 110 stop, increase or decrease the amount of power drawn (and for some electrical devices, the amount of power supplied) to the power distribution network by sending a control message to each device.

The controller 140 is also arranged to receive to requests to supply power to, or draw power from the power distribution network. The request may be a frequency response request, such as a Demand Response Event Notice (DREN), issued by the operator of the power distribution network. DRENs are requests from the power distribution network for systems, such as the one described here, to reduce or increase demand on the power distribution network. Such requests typically include an amount of power to be supplied to, or drawn from, the power distribution network and/or a response time within which the request must be fulfilled.

The demand-side response management system 100 may also comprise a frequency monitor (not shown) configured to monitor frequency of the power distribution network, i.e. the "grid frequency". The frequency monitor is configured to provide the controller 140 with data indicative of the grid frequency. The frequency monitor may form part of the controller 140, or it may be a separate component in data communication with the controller 140.

The frequency monitor may itself generate requests to draw power or supply to the power distribution network. Requests to supply power may be generated in response to the frequency of the power distribution network dropping below a first frequency threshold. For example, if the nominal frequency of the power distribution network is 50 Hz, a request to supply power may be generated if the frequency falls below 49.5 Hz. Additionally, the requests to draw power may be generated in response to the frequency of the power distribution network rising above a second frequency threshold. For example, if the nominal frequency of the power distribution network is 50 Hz, a request to draw power may be generated if the frequency rises above 50.5 Hz.

The operation of the demand-side response management system 100 will now be described in more detail, with reference to Figure 2. Figure 2 is a flow-chart showing the operation of the demand-side response management system 100 in response to receiving a request to draw power from the power distribution network.

At step S201, the controller 140 receives one or more requests to draw power from the power distribution network. At step S202, the controller 140 determines, which of the electrical devices 110 to control in order to fulfil the one or more received requests. How the controller makes this determination will be discussed in greater detail below with reference to Figure 3. At step S203, the controller 140 controls one or more of the electrical devices in accordance with the determination made in step S202, thereby fulfilling the one or more received requests.

One of the aims of the present invention is to maintain, as far as possible, the first group 120 of the plurality of electrical devices 110 at, or above, a first predetermined level of charge. The first predetermined charge level may be greater than 50%, the first predetermined charge level may also be set at any of: 60%, 70%, 80%, 90% or fully charged. The above levels of charge are not meant to be limiting, any and all intermediates are also within the scope of the present invention. Preferably, the first predetermined charge level is set at a level where the capacity of the electrical devices is not damaged by prolonged maintenance at this charge level. Thus, preferably, the first predetermined charge level is set at a level of 80% or above. This is the preferred charge level at which the electrical devices are maintained. The first predetermined level of charge may further be determined based on the statistical overview of the electrical devices 110. The statistical overview of the electrical devices enables the controller to monitor the total power of the connected electrical devices 110 and the statuses of the electrical devices 110. The controller 140 may adjust the first predetermined charge level to maintain one or more of the statistical measures at a constant level, for example, to ensure there is always a set level of power available to be supplied to the power distribution network and/or a set capacity of power demand available to draw power from the power distribution network. In use, the electrical devices may have been asked to supply power such that they are presently at a charge level below the first pre-determined charge level. Over short time frames, this is allowable and indeed will be necessary to respond to some response requests. As well as a preferred maintenance level of charge (the first predetermined charge level), there is also a level of charge above which the electrical device must be maintained if they are to be able to respond to any local demands on the electrical device and/or avoid damage. This mandatory level of charge will be further referred to as the "second predetermined level of charge", where the second predetermined level of charge is lower than the first predetermined level of charge.

The second predetermined level of charge may further be determined based on the statistical overview of the electrical devices 110. The controller 140 may adjust the second predetermined charge level to maintain one or more of the statistical measures at a constant level, for example, to ensure there is always a set level of power available to be supplied to the power distribution network and/or a set capacity of power demand available to draw power from the power distribution network.

Figure 3 is a flow chart 300 illustrating a first algorithm for determining which of the electrical devices 110 to control in order to fulfil the one or more received requests to draw power from the power distribution network. As stated above, one of the aims of the present invention is to ensure that all of the first group of electrical devices 120 are maintained above the second predetermined level and then, preferably, the first predetermined level. Hence, when the algorithm starts 302 the controller 140 is arranged to first determine 304 whether any of the first group of electrical devices 120 are at a charge level below the second predetermined level. If any of the first group of electrical devices 120 are at a charge level below the second predetermined level, they are preferentially controlled 306 to draw power from the power distribution network.

If none of the first group of electrical devices 120 are below the second predetermined level, the controller 140 is arranged to determine 308 whether any of the first group of electrical devices 120 are at a charge level above the second predetermined level but below the first predetermined level. If any of the first group of electrical devices 120 are at this charge level, they are preferentially controlled 306 to draw power from the power distribution network.

If none of the first group of electrical devices 120 are below the second predetermined charge level or the first predetermined charge level (i.e. all of the first group of electrical devices are above the first predetermined charge level), the controller 140 is arranged to control 314 one or more of the second group of electrical devices 130 to draw power from the power distribution network. At this point, it is presumed sufficient devices from the second group of devices are available, and hence the process ends 316.

Returning to step 306, once the controller 140 has controlled one or more of the first group of electrical devices to draw power, the controller is arranged to determine 310 if this has resulted in sufficient electrical devices 110 being instructed to meet the received one or more requests. If sufficient devices have been controlled, the process ends 312. If insufficient devices have been identified, the controller next looks 308 at any devices in the first group of electrical devices at a charge level above the second predetermined level but below the first predetermined level, and then subsequently 314 at the second group of electrical devices 130, until the request is fulfilled.

This above described determination preferentially ensures that the first group of electrical devices 120 are maintained at high charge levels, when responding to requests to draw power from the power distribution network.

In the above described method, the predetermined charge levels are all applied equally to all devices in each group 120, 130. In some circumstances however it may be preferable to adapt the method shown in Figures 3 and 5 to apply different predetermined levels to different classes of device within each group. For example, uninterruptible power supplies with lead acid batteries and electric vehicles with lithium ion batteries may each form separate classes in the first group of devices, where the first predetermined charge level is set to 100% for the uninterruptible power supplies and to 90% of the electric vehicles. Likewise, the second predetermined charge level might be set to 80% for the uninterruptible power supplies and 60% for the electric vehicles. Similarly, different predetermined charge levels might be set to different classes of device in the second group. The algorithms shown in Figures 3 and 5 can then be simply adapted to apply the appropriate predetermined level to each device based on the class it belongs to. This can be further extended to apply different predetermined charge levels to each individual device based on its capabilities, operating characteristics and intended local usage profile. In the above described method, the charge state of the second group of electrical devices 130 is not taken into account. In some circumstances however, it may be preferable to further adapt the method shown in Figure 3 to take into account the charge state of the second group of electrical devices 130. This can be simply achieved by defining a third predetermined charge level for the first group of electrical devices 120, wherein the third predetermined charge level is between the first and second predetermined charge level. Additionally, a predetermined charge level for the second group of electrical devices 130 should be defined, for clarity this will be referred to as the "fourth predetermined charge level". The controller 140 may then be further arranged to preferentially control one or more of the second group of electrical devices 130 to draw power if all of the first group of electrical devices 120 are above the third predetermined charge level and one or more of the second group of electrical devices 130 are at a charge level below the fourth predetermined charge level.

The operation of the demand-side response management system 100 will now be described in further detail, with reference to Figure 4. Figure 4 is a flow-chart showing the operation of the demand-side response management system 100 in response to receiving a request to supply power to the power distribution network.

At step S401, the controller 140 receives one or more requests to supply power to the power distribution network. At step S402, the controller 140 determines, which of the electrical devices 110 to control in order to fulfil the one or more received requests. How the controller makes this determination will be discussed in greater detail below with reference to Figure 5. At step S403, the controller 140 controls one or more of the electrical devices in accordance with the determination made in step S402, thereby fulfilling the one or more received requests.

Figure 5 is a flow chart 500 illustrating a second algorithm for determining which of the electrical devices 110 to control in order to fulfil one or more received requests to supply power to the power distribution network. As discussed previously, only some of the electrical devices are able to supply power to the power distribution network (the remaining devices being demand-only devices). To aid understanding, the devices able to supply power to the power distribution network have been grouped into the first group of electrical devices 120. However, the demand-only devices, those in the second group of electrical devices 130, can contribute to requests for supplying power to the power distribution network, in that they may be controlled to reduce the amount of power they are drawing from the power distribution network, which produces a net surplus in the amount of power available to the power distribution network. When this algorithm 500 starts 502 the controller 140 is arranged to first determine 504 whether any electrical devices 110 are presently drawing power and if they are, whether any of these devices can reduce the amount of power they draw. If any of the identified electrical devices 120 can reduce the amount of power they draw, one or more of these devices are controlled 506 to reduce the amount of power they draw from the power distribution network. If none of the electrical devices 110 are drawing power, or can reduce the power they are drawing, the controller 140 is arranged to next determine 508 whether any of the first group of electrical devices 120 are at a charge level above the first predetermined level. If any of the first group of electrical devices 120 are above the first charge level, they are controlled 510 to supply power to the power distribution network.

If none of the first group of electrical devices 120 are above the first predetermined charge level, the controller 140 is arranged to determine 512 whether any of the first group of electrical devices 120 are at a charge level above the second predetermined level but below the first predetermined level. If any of the first group of electrical devices 120 are at this charge level, they are controlled 510 to supply power to the power distribution network. If none of the first group of electrical devices are at a charge level above the second predetermined level but below the first predetermined level, the controller 140 is arranged to control 514 any of the first group of electrical devices 120 to supply power from the power distribution network to fulfil the request. At this point, the process ends 516. Preferably at this step, the controller 140 is arranged to preferentially control the first group of electrical devices 120 in order of the highest charge level to the lowest charge level.

Returning to step 506, once the controller 140 has controlled one or more of the electrical devices 110 to reduce the power they draw, the controller is arranged to determine 518 if this has resulted in sufficient electrical devices 110 being instructed to meet the received one or more requests. If sufficient devices have been controlled, the process ends 520. If insufficient devices have been identified, the controller next looks 508 at any devices in the first group of electrical devices at a charge level above the first predetermined level, then follows steps 512 and if necessary, 514, until the request is fulfilled.

Returning to step 510, once the controller 140 has controlled one or more of the electrical devices 110 to supply power, the controller is arranged to again determine 518 if this has resulted in sufficient electrical devices 110 being instructed to meet the received one or more requests. If sufficient devices have been controlled, the process ends 520. If insufficient devices have been identified, the controller next follows steps 512 and 514, until the request is fulfilled. The following description relates to further methods for determining which of the electrical devices 110 to control in order to fulfil the one or more received requests to draw power from, or supply power to, the power distribution network. These further methods enable the controller 140 to make use of received predictions of the future demand on the power distribution network.

The received predictions may include any information from which the future demands on the power distribution network, may be ascertained either directly or indirectly. This information may be, for example, the scheduling of the power generation systems supplying power to the grid, scheduling of upcoming servicing of power generation systems, weather reports, scheduling of large sporting events, sunset and sunrise times, or a measure of the predicted carbon intensity of the grid. This information can essentially be split into two categories, information indicative of a likely excess or a likely deficit of power in the power distribution network.

For example, long sunny days, days with higher than average wind speeds and days having relatively cooler weather, are all indicative of likely lower demand from households and an increase in supply from renewable energy generation. All of these events indicate a likely future decrease in requests to supply power to the power distribution network, and/or a likely increase in demands to draw power from the power distribution network. Identification of these trends enables the controller 140 to pre-emptively control all electrical devices 110 to decrease their level of charge. Decreasing their level of charge enables future requests to draw power to be easily met, and enables electrical devices 110 to make use of future lower energy costs which coincide with excess supply in the power distribution network.

Conversely, servicing of power generation systems leads to a loss in power generation capacity, hot weather leads to an increase in demand from cooling systems, large sporting events may lead to an increase in demand from households watching the events. All of these events indicate a likely future increase in requests to supply power to the power distribution network. Identification of this likely increase enables the controller 140 to pre-emptively control electrical devices in the first group of electrical devices 120 to increase their level of charge. This will then enable the system to better meet future requests to supply power to the power distribution network. The present invention advantageously enables the controller 140 to easily adapt to these predicted events by adjusting the predetermined charge levels applied to the electrical devices 110. Figure 6 illustrates this process in the situation that the controller predicts an increase in requests to draw power from the power distribution network.

At step 601, the controller 140 receives one or more predictions that indicated a likely increase in requests from the power distribution network to draw power from the power distribution network.

At step 602, the controller 140 decides to respond to the received predictions by reducing the first predetermined charge level. For example, this may be by reducing the first predetermined charge level from 90% of charge capacity to 80%. Referring back to Figure 3, this reduction in charge level will mean fewer electrical devices from the first group of devices 120 will be identified in step 308. Therefore, when requests to draw power from the power distribution network are dealt with by the controller 140, fewer electrical devices 120 will be used to respond to the requests to draw power. Over time, when electrical devices 120 respond to local loads and subsequent demands to supply power, the average charge level of the first group of electrical devices will be reduced.

Figure 7 illustrates this process of the controller 140 reacting to an indication of a likely future increase in requests to supply power to the power distribution network

At step 701, the controller 140 receives one or more predictions that indicated a likely future increase in requests to supply power to the power distribution network.

At step 702, the controller 140 decides to respond to the received predictions by increasing the second predetermined charge level. For example, this may be by increasing the second predetermined charge level from 50% of charge capacity to 70%. Referring back to Figure 3, when dealing with requests to draw power, this increase in the second predetermined charge level will mean more electrical devices from the first group of devices 120 will be identified in step 304. Therefore, when requests to draw power from the power distribution network are dealt with by the controller 140, more electrical devices 120 will be used to initially respond to the requests to draw power. Therefore, over time, when electrical devices 120 respond to subsequent demands to supply power, the average charge level of the first group of electrical devices will be increased.

The above description refers to the controller 140 "controlling" one or more electrical devices. The specific details of this control are not necessary for the skilled person to understand the present invention. However, in brief, the controller 140 may send one or more control messages to identified electrical devices 110. The control messages comprise an instruction to increase, decrease or stop supplying or drawing power from the power distribution network. These control message may comprise further commands or instructions, such as a time to start any action and a time to stop any action.

The controller 140 may be arranged to determine, based on the statistical overview, using data such as the aggregated power and/or energy data regarding the plurality of electrical devices, and the received requests, one or more parameters defining properties of electrical devices 110 to be controlled in response to the request.

The control messages may be sent upon identification of a suitable electrical device 110 fitting the determined parameters. That is, the controller 140 may then instruct one or more of the plurality electrical devices based on the determined parameters. Alternatively, the control messages may be sent upon receipt of a status update from an electrical device 110 fitting the determined parameters.

Features of the present invention are defined in the appended claims. While particular combinations of features have been presented in the claims, it will be appreciated that other combinations, such as those provided above, may be used.

The above embodiments describe one way of implementing the present invention. It will be appreciated that modifications of the features of the above embodiments are possible within the scope of the independent claims. Clauses

There follows a list of numbered clauses defining particular embodiments of the invention. Where a numbered clause refers to an earlier numbered feature then those clauses may be considered in combination.

1. A demand-side response management system for use in a power distribution network, comprising a controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintain each of the first group of batteries above a first predetermined level of charge.

2. A system according to clause 1, wherein the controller is further configured to control one of more of the plurality of electrical devices other than the first group of batteries to draw power from the power distribution network in response to a request to draw power from the network.

3. A system according to clauses 1 or 2, wherein the plurality of electrical devices include a plurality of draw-only electrical devices, and the controller is further configured to respond to requests to draw power by controlling one or more of the plurality of draw-only electrical devices to draw power from the power distribution network.

4. A system according to clause 3, wherein the draw-only electrical devices are electrically powered thermal energy stores.

5. A system according to clause 4, wherein the thermal energy stores are one or more of hot water tanks, thermal storage heaters, molten salt storage units, phase change material storage units, refrigeration and air conditioning systems or other thermal energy storage devices. 6. A system according to any preceding clause, wherein the controller is configured to control each battery of the first group of batteries to draw power, in a charge mode, when the level of charge in each battery falls below a second predetermined level.

7. A system according to clause 6, where in the second predetermined level is fully charged.

8. A system according to clause 6, wherein the second predetermined level is less than, or equal to, the first predetermined charge level.

9. A system according to any preceding clause, wherein the first group of batteries comprises two or more battery types, and wherein the first predetermined charge level is set at a different charge level for each of the two or more battery types.

10. A system according to any of clauses 6 to 9, wherein the first group of batteries comprises two or more battery types, and wherein the second predetermined charge level is set at a different charge level for each of the two or more battery types.

11. A system according to any preceding clause, wherein the controller is further configured to control one of more of the plurality of electrical devices other than the first group of batteries to draw power from the power distribution network when their level of charge falls below a third predetermined level.

12. A system according to clause 11, wherein the plurality of electrical devices other than the first group of batteries comprise two or more electrical device types, and wherein the third predetermined charge level is set at a different charge level for each of the two or more electrical device types.

13. A system of any preceding clause, wherein the first predetermined charge level is greater than 50%.

14. A system according to clause 13, wherein the first predetermined charge level is one of: 60%, 70%, 80%, 90% or fully charged. 15. A system according to any preceding clause, wherein each of the first group of batteries is used to supply power if the level of charge is above the first predetermined charge level. 16. A system according to clause 15, wherein during a request to supply power, the first group of batteries may be controlled to supply power to the power distribution network such that their level of charge drops below the first predetermined level, if the number of batteries having a level of charge above the first predetermined level drops below a first threshold.

17. A system according to any preceding clause, wherein the first predetermined level of charge is determined based on a statistical analysis of parameters of the electrical devices. 18. A system according to any preceding clause, wherein the controller is further configured to control one or more of the plurality of electrical devices presently drawing power from the power distribution network to reduce the power they are drawing from the power distribution network in response to a request to supply power to the network.

19. A system according to any preceding clause, wherein the controller is further configured to adjust the first predetermined charge level based on a received prediction of the future demand on the power distribution network. 20. A system according to any preceding clause, wherein the controller is further configured to reduce the first predetermined charge level to increase local use of the power stored in the first group of batteries.

21. A system according to any preceding clause, wherein the controller is further configured to reduce the first predetermined charge level causing the first group of batteries to partially discharge.

22. A system according to any of clauses 6 to 21, wherein the controller is further configured to adjust the second predetermined charge level based on a received prediction of the future demand on the power distribution network. 23. A system according to any of clauses 6 to 22, wherein the controller is further configured to increase the second predetermined charge level to increase the power stored in the first group of batteries. 24. A system according to any preceding clause, wherein the requests to supply power are in response to the frequency of the power distribution network dropping below a first frequency threshold; and the requests to draw power are in response to the frequency of the power distribution network rising above a second frequency threshold.

25. A system according to any preceding clause, wherein each of the first group of batteries may form part of one of: a uninterruptable power supply, an electric vehicle, or an energy storage unit. 26. A system according to any preceding clause, wherein the controller is further arranged to:

determine, based on aggregated power and/or energy data regarding the plurality of electrical devices, and received requests, one or more parameters defining properties of electrical devices to be controlled in response to the request; and

instruct one or more of the plurality electrical devices based on the determined parameters.

27. A system of any preceding clause, wherein the controller is further arranged to:

receive status updates from the plurality of electrical devices; and instruct each electrical device in response to receiving a status update from that device. 28. A system of clause 21, wherein the received status updates include the total capacity and the present capacity of the first group of batteries.

29. A system of any of clauses 26 to 28, wherein the controller is further arranged to generate said aggregated power and/or energy data based on status updates received within a first time period.

30. A power distribution network, comprising : a plurality of electrical devices including a first group of batteries; and a demand-side response management system according to any of clauses 1 to 29.

31. A power distribution network, comprising :

a plurality of batteries configured to supply power to the power distribution network;

a plurality of draw-only electrical devices configured to draw power from the power distribution network;

a demand-side response controller configured to receive requests to supply power to or draw power from the network, the controller configured to:

in response to a request to draw power from the power distribution network, control one or more of the plurality of draw-only electrical devices to draw power;

in response to a request to supply power to the power distribution network, control one or more of the plurality of batteries to supply power to the power distribution network.

32. A power distribution network, comprising : a plurality of electrically controlled thermal stores, a plurality of batteries and a controller, the controller configured to control the plurality of electrically controlled thermal stores and the plurality of batteries in response to request to supply power to, and draw power from, the power distribution network, in order to maintain the plurality of batteries above a predetermined level of charge.

33. A network according to any of clauses 30, 31 or 32, further comprising a frequency monitor configured to monitor grid frequency and provide the controller with grid frequency data, wherein the requests to supply power are in response to the frequency of the power distribution network dropping below a first frequency threshold; and the requests to draw power are in response to the frequency of the power distribution network rising above a second frequency threshold.

34. A controller configured to respond to requests to supply power to, or draw power from, a power distribution network by controlling a plurality of electrical devices to supply power to or draw power from the network, wherein the plurality of electrical devices comprise a first group of batteries, and the controller is further configured to: respond to requests to supply power by controlling one or more of the first group of batteries to supply power to the power distribution network; respond to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and maintain each of the first group of batteries above a first predetermined level of charge.

35. A method of controlling electrical devices in a power distribution network, the method comprising :

receiving requests to supply power to, or draw power from, a power distribution network;

responding to requests to supply power by controlling one or more of a first group of batteries to supply power to the power distribution network;

responding to requests to draw power by controlling one or more of the plurality of electrical devices to draw power from the power distribution network; and

maintaining each of the first group of batteries above a first predetermined level of charge.

36. A method of controlling a plurality of power units in a power distribution network (PDN), the plurality of power units comprising thermal storage units and electrical storage units, the method comprising :

a) receiving a request to draw power from, or supply power to, the PDN ; b) instructing one or more of the thermal storage units to increase the power they draw from the PDN if the request is to draw power from the PDN ; and c) instructing one or more of the electrical storage units to increase the power they supply to the PDN if the request is to supply power to the PDN .

37. A server arranged to carry out the method of clause 36.