GB2508651A

GB2508651A - System for synchronising a renewable power source with mains supply

Info

Publication number: GB2508651A
Application number: GB1222072.9A
Authority: GB
Inventors: Adam Hancock; Safar Miroslav; Martin Dorazil
Original assignee: TORCH SOLAR TECHNOLOGIES Ltd
Current assignee: TORCH SOLAR TECHNOLOGIES Ltd
Priority date: 2012-12-07
Filing date: 2012-12-07
Publication date: 2014-06-11
Anticipated expiration: 2032-12-07
Also published as: GB2508651B

Abstract

A power management system 10 has a control processor 16 with a first power input 20, which may be a mains source, and a second power input 12, which may be a renewable source such as a solar photovoltaic source, and at least one power output 28. The control processor 16 monitors and adjusts the phase of the power supplied at the second power input 12 via an inverter 22 so that it is in phase with the power supplied at the first power input 20. The power to the output 28 may be preferentially supplied by the renewable source 12. Batteries or capacitors 14 may be provided to store power from the renewable source 12. One or more batteries 14 may be removable for use as a stand alone power source.

Description

A Power Management System

Field of the Invention

This invention relates to a power management system, especially to a power management system incorporating a renewable source.

Background to the Invention

There is a known desire for renewable energy to be used more prevalently. However, in domestic settings, the demand for power is unlikely to be met completely by a domestic renewable source of power. Therefore, power is required from multiple sources rather than just from the renewable source. Domestic renewable energy sources are often used instantaneously and there is no way to store the generated power.

In existing systems there is often a flow of power from the renewable source onto the mains grid', during periods when an excess of power is produced than is required locally, for example during the day when people are away from home working, and so are not using as much power. This allows for some of the renewable energy to be sold to the mains by the customer. Conversely, there is often a period where demand exceeds supply from the renewable source, such as in the evening when it's too dark for solar power to be generated. However, a problem occurs when the customer then has to buy energy from the mains at a higher price than they received from the energy company. This results in the customer, who originally generated excess power being penalised for not using their power and being required to pass it to the mains supply. In such systems the renewable power often cannot be used alongside power from another source as they have different characteristics. Therefore, the demand is either met by the renewable energy or the mains cncrgy but not both.

Summary of the Invention

Accordingly, the present invention is directed to a power management system comprising a control processor having a first power input and a second power input and at least one power output, wherein the control processor monitors and adjusts the phase of the power supplied at the second power input so that it is substantially in phase with the power supplied at the first power input.

By adjusting the vohage and the frequency of one of the supplies to match that of the other, both sources of power can be used in combination such that it becomes as a single power source at the output.

It is advantageous that the first power input is a mains supply and that the mains supply is used as a reference for synchronisation of the second power input. By using the mains supply as a reference, the system is able to provide and accept a second power source, adapt it to match the characteristics of the power from the mains supply and then provide that at the output of the system. As a result, devices that are run on a mains supply can be provided with power from a second source without compromising the supply.

Additionally, the risk of power surges from the second supply is reduced as it matches to the mains supply. The system results in a small draw of power, or "trickle", from the mains to provide a rcfcrcncc for thc other input to which the system calibrates thc second source. This reduces the draw on the mains supply, thereby making the system less dependent upon the mains. As a result of using the trickle charge to match the characteristics of the second power input to the supply at the first, the power provided at the sccond power input is transparent to the other supply and any load placed upon the system. The power supplies effectively blend or merge together without any significant difference between them.

Preferably, the demand at the power output is supplied by the second power input and when the power demand at the output exceeds the power supplied by the second power input, the remaining demand is supplied from the mains supply. By providing the bulk of the power from the second source, the draw on the mains is significantly reduced, and often to a level that is required only to provide a calibration reference. However, where the demand for power exceeds the level supplied by the second source, a larger draw on the mains may occur in order that the end-user is not aware of the change of supply.

Because the two sources are in phase with one another, the device(s) running from the system will operate without interruption and there will be no significant change in the supply provided.

Additionally, where one of the power sources fails, the other is able to take over to provide the power. For example, should the mains power supply fail, the secondary supply can be used to provide at least some power to the output. Likewise, should the secondary supply fail, the mains supply can be used to provide a more significant supply to the output.

Advantageously, the second power input is supplied from a renewable source. The use of renewable sources of energy is increasingly more important and more systems are being created for domestic use in the form of solar cells and domestic wind turbines.

Incorporating such renewable sources into the power management system allows the user to manage the use of such energy so that the renewable energy is the primary source of power and mains is a secondary source when the renewable energy cannot provide sufficient power to satisfy the demand.

It is preferable that an inverter is provided to convert power supplied from the renewable source to an AC power supply, and that the inverter is phased to the mains supply.

Renewable energy is generally produced in the form of DC power supply and the use of an invcrtcr allows for the supply to be converted to an AC supply prior to being supplied to the power management system. By phasing the inverter to the mains, the renewable power supplied is substantially in phase with, and has similar characteristics to, the supply from the mains.

In one embodiment, the renewable source is supplied via an accumulator to allow power from the renewable source to be stored until it is required. The use of an accumulator, for example a battery or capacitor, allows for the storage of energy produced during times when supply exceeds demand. Solar energy may be used in the system of the present invention, but during the night the supply of solar energy will be significantly reduced.

Therefore, storing excess energy produced during the day allows for that energy to be used in periods where demand outstrips supply, more especially renewable supply where applicable.

In a preferred configuration, a plurality of accumulators are provided and the accumulators arc connected in parallel and charged in parallel, and advantageously, at least one individual accumulator can be readily removed from the system without disconnecting or interrupting the associated power input or power output. Using a bank of batteries that are individually readily removable, allows a user to disconnect one or more of the batteries and use it as a stand-alone power source. Additionally, with the use of the invcrtcr, the power can be stored as DC in the accumulators and then converted to AC as and when required. The power can then be drawn from the bank of accumulators when required. By charging the batteries in parallel the cells can be balanced.

Furthermore, when one cell is removed from the system, the power within that cell should be substantially similar to that of the other cells. This prevents the removal ofa cell that might contain the majority of the power, thereby leaving the system unable to meet demand from the renewable source and having to rely upon mains power. Balancing may be undertaking by natural balancing, passive balancing or active balancing. Where a plurality of accumulators are used, for example a number of batteries connected in parallel to form a daisy chain', it may be advantageous that one or more units can be removed from the daisy chain circuit and used as a power source where none exists, for example in a caravan or boat.

Preferably, the renewable power supply is provided by way of solar power. The usc of solar power is particular suited to domestic applications as it can be fitted to the roof of a home or outbuilding. Alternatively, or additionally, the renewable power source may comprise wind power, water power or thermal power, including geothermal power. As the efficiency of renewable power devices increases, it may be desirable to change the source of the renewable power over time or to add a further source of renewable power where demand increases.

In a preferred construction, power provided from either power input cannot be supplied to the other power input. Such an arrangement prevents flow of the energy created using the renewable power source from entering the mains supply. This prevents the system from feeding the mains grid, thereby preventing outflow of the renewable power away from the system. Whilst it may be desirable in some applications to provide a link to supply the mains, the use of accumulators reduces the need for such a supply to the grid and preserves power generated by the system for use when the demand increases.

The invention extends to a power management device comprising at least two inlets and at least one outlet adapted to manage the system as described herein. The device, which can be used in the system, is provided for aligning the second power source to the first power source. It may be retrofitted to existing power management systems.

The invention further extends to an electrical inverter comprising at least one power input and one power output, wherein the inverter is provided with a reference, including a reference frequency and reference voltage, and the power arriving at the power input is converted to match the reference frequency and voltage. The inverter uses an AC reference signal to align the DC power received at the inlet with the AC signal during inversion. This allows the inverted AC power to be used alongside an AC power supply.

Preferably, the phase of the output power is matched to the phase of the reference. By matching the phase of the reference signal, the usc of the inverted power along side a source for which the reference is provided is less likely to cause integration problems.

Advantageously, the reference comprises a connection to a mains source. Using a mains source as the reference and converting a renewable source using the invcrter allows usc of both sources together in accordance with the system disclosed herein.

The invention also extends to a building incorporating such a power management system.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a diagram showing one possible arrangement of a control system in accordance with the present invention; Figure 2 is a diagram showing a first arrangement of a power management system for use in a home; Figure 3 is a diagram showing a second arrangement of a power management system for use in a home; and Figure 4 is a diagram showing a third arrangement of a power management system for usc in a home.

Detailed Description of Exemplary Embodiments

Figure 1 shows a system 10 comprising a solar source 12, comprising four 150 Watt photovoltaic modules, and a battery connected to an accumulator 14 in the form of a one-kilowatt hour LiFe P04 battery. The accumulator 14 feeds into a control box 16, which comprises a processor and two powers inputs 18; a first power input I 8b being connected to a mains supply 20; the second power input iSa being the accumulator 14.

The second power input 18a leads on to an inverter 22, which is provided with a trickle of power 24 from the mains supply 20 via the first power inlet I8b. This trickle of power 24, which is a one-way connection and prevents flow of power to the first input 18b from the inverter 22, provides the inverter 22 with a reference of the characteristics of the mains supply 20, including the frequency, voltage and phase of the power supplied to the first power input 18b.

The inyerter 22 and the first power input 18b are both connected to a switch box 26, which is connected to a power output 28. The switch box 26 comprises a mechanical link to control the flow of power from the inverter 22 and the mains inlet lSb to the power outlet 28.

Whcn in use, thc solar sourcc 12 provides powcr to thc accumulator 14 in thc form of a direct current supply. The accumulator 14 charges such that it holds and/or stores the power created by the solar source 12. As power is required at the power output 28, the control box 26 draws power from the accumulator 14 via the inverter 22. As the power passes through the inverter 22, it converts the direct current supplied from the accumulator 14 to alternating current, which is supplied to the switch box 26. In converting the power from direct current to alternating current, the inverter 22 substantially matches the characteristics of the converted alternating power to the characteristics of the mains power supplied to the control box 16. This is done by the trickle of power 24 that flows from the first powcr inlet 18b to the inverter 22. The trickle of power 24 is used as a reference for converting the direct current to alternating current.

As a result of the inverter 22 matching the characteristics of the power supplied at the second inlet I 8a to the power supplied at the first inlet I 8b, the power reaching the switch box 26 from the two sources is substantially the same.

The switch box 26 monitors the demand at the power output 28 and draws power from the two sources to match that demand. The switch box 26 preferentially draws power from the inyerter 22, and therefore from the accumulator 14, which ensures that power is provided at the power outlet 28 primarily from the renewable source 12. Where the demand at the power output 28 is in excess of the supply provided from the inverter 22, the switch box 26 allows the extra energy to be provided by the mains supply 20.

Because the power supplied from the two sources 12 and 20 is substantially the same, the power supplied to the power output 28 is substantially the same, regardless of its source.

Therefore, the power from each source can be used to provide power to the power outlet 28 with the mains supply being used to top-up' the supply from the renewable source 12, when required.

No power is able to flow from the first power inlet I 8b to the second power inlet I 8a, nor can any power flow from the second power inlet iSa to the first power inlet lSb.

Therefore, the accumulator 14 cannot be charged by the mains power 20, and the solar source 12 cannot send power to the mains supply 20.

Figures 2 to 4 show potential arrangements for distributing power within a domestic home using the present invention.

Figure 2 shows an arrangement 110 wherein the system comprises a solar array 112 connected to an accumulator 114 that incorporates an inverter. A mains supply 120 is provided to the home and connected to the ifise box 116 in a traditional fashion. The mains supply 120 feeds upstairs lighting 130, an upstairs ring mains 132, downstairs lighting 134, a downstairs ring mains 136 and fixed appliances 138, for example an oven and/or burglar alarm, as indicated by the solid line. The accumulator is provided with a trickle feed from the mains supply 120 to usc as a reference in order that the inverter can provide power with substantially the same characteristics as, and in phase with, the mains power 120. The feed from the accumulator 114 is used to power an extension cable box 140, as indicated by the dashed line, into which further devices may be connected. The renewable energy is used only for the farther devices and the mains power supplies the lighting, sockets and fixed appliance(s).

Figure 3 shows a further arrangement 210 wherein the system comprises a solar array 212 connected to an accumulator that comprises an inverter 214. The accumulator 214 feeds into a control box 216, which is also supplied by a mains power supply 220. The accumulator is connected to the upstairs lighting 230 and the downstairs lighting 234, as indicated by the dashed line. The mains power supply 220 is used to power the upstairs mains ring 232 and the downstairs mains ring 236 and the fixed appliances 238, along with an extension cable box 240, as indicated by the solid line. The renewable source is thus used to supply power to the lighting, thereby reducing the reliance upon the mains supply 220 of a major use of power within the building.

Figure 4 shows yet a further arrangement 310, wherein the system comprising a plurality of solar arrays 312a to 3 12c connected to an accumulator 314, which is in turn connected to a control box 316. The control box 316 is also provided with a mains supply 320. The accumulator 314 is used to provide power to the upstairs lighting 330, an upstairs ring mains 332, downstairs lighting 334, a downstairs ring mains 336 and fixed appliances 338, as indicated by the dashed line. This arrangement reduces the demand on the mains supply 320 by relying upon the renewable source 312 for most, if not all, of the required power. In such a system, the mains supply 320 is used as a reference for inverting the renewable source and also as a back-up system should the renewable source 312 be unable to supply the required demand on the system.

Examples

1. An appliance with the input power 100W is connected to the power output. The control device is set such that the inverter has a set-up output power 100W.

Therefore, no power is taken from the mains supply beyond that required for the inverter reference.

2. No appliance is connected to the output. The inverter is phased to the grid via the reference trickle but no power is drawn from the accumulator as there is no demand to be met.

3. An appliance with the input power 700W is connected to the output. The inverter draws the maximum available possible power from the accumulator, for example 500W. The remaining 200W required to meet the demands on the system is supplied from the mains.

4. Mains power failure. The control system will supply limited power drawn from the renewable source to meet as much of the output demand as possible until the power is restored or the accumulated and stored energy is used. The circuits within the building may be prioritized so that some appliances are powered for as long as possible, for example the freezer or burglar alarm.

The system may comprise a plurality of renewable sources such that it is formed from a number of similar systems, for example a plurality of solar panels may be used together, or a plurality of wind turbines. Alternatively, there may be mix of renewable sources, such as wind, solar and water power to all be used together to supply the accumulators, thereby reducing any reliance on a single source of power.

It is envisaged that such a system could use an inverter with a 500 Watt maximum power output and galvanic isolatcd 48 volt DC input. Additionally, it could comprisc 485 interface connections for configuration and reading of operating parameters. The inverter may be a stand-alone part or it may be built into any of the equipment as required.

Therefore, it may be part of the accumulator, part of the control box or could be built into a rack into which the accumu'ators may be connected. The invertcr, when phased into the mains power supply may, for example, provide power at 23OVolt and 50 Hertz from a 48Volt accumulator device or array.

The inverter draws energy from the accumulator according to the instant requirements at thc power output. Therefore, the energy can be stored as DC and used as AC as and when required. The inverter works as a controlled AC power source. Additionally, the control system may comprise "anti-islanding" protection and so is shutdown from the supply in the case of under/over voltage or under/over frequency and it will reconnect once the conditions that causes the shutdown are removed; the limits being predetermined. This means that the device can deal appropriately with any surge currents.

The system may be disconnected from the mains supply, either intentionally or by way of a power failure and the accumulators can still provide power to the output(s) via the inverter. The inverter can be programmed to have a default setting so that it reverts to supplying a 230V/SOHz supply in the event of the mains being disconnected, or it may record the most recently supplied mains characteristics and use them for further conversion of the DC supplied by the accumulators to AC. In such a situation, the inverter may automatically shutdown if the output is overloaded and it may reconnect automatically once the overload is removed. This can be set using the 485 communication lines.

The input to the invcrtcr may be 38V to 68V of direct current with galvanic isolation for the C side. The output AC sine wave may be 230V/50Hz ± 15%, TDH less than 3% variable to the supply, although this maybe varied according to the application, for example to 1 1OV!6OHz. The interconnection AC-in to AC-out can be sized for a maximum 32 Amps, although a larger current, for example 60 Amps, may be required in some situations. The operating temperature is intended to be -20 degrees Celsius to +40 degrees with an inverter efficiency of 90%. The maximum output may be limited to 500W. There may bc a plurality of accumulators feeding thc system and the limit per accumulator may be 500W.

The system comprises a microchip that is programmed to act as a firewall' between the system and the househokl mains power input. This fircwafl enables the renewable source of power to supply all or part of the power required, with an option to top-up the supply from a different source, such as a mains power supply, where the demand cannot be met by the renewable source alone. Lithium-iron cells may be used as the accumulator and these are balanced to give an efficient and even charge to all of the cells in the accumulator array. This maintains the maximum capacity of the whole array as much as possible. Additional accumulators may be added to the system in order to increase its capacity and to assist with meeting the demand of the building.

Some of the accumulator units may be disconnected from the rest of the accumulator units in order to be used elsewhere. This allows a user to use a portable power supply' elsewhere whilst leaving some units in place to continue to power the building. For example, a user may take one or more units from the system to power a caravan whilst on holiday, leaving the remaining units in place to keep the fridge, freezer and burglar alarm running on renewable power rather than the mains power supply. The system acts as a charging system to these removable accumulator units, using renewable energy to recharge them as required.

The system, and more specifically the management microchip, can be retrofitted into existing renewable systems. This allows for the storage of energy produced in existing systems, thereby reducing the reliance on a mains supply in times of reduced supply, for example at night for solar systems. Additionally, the user can store the energy rather than supplying it to the mains grid and buying it back therefrom at a later time.

Where the accumulators are connected in parallel, only one of the accumulators needs to be connected to the mains reference. The other accumulators can reference the one accumulator that is connected to the mains reference. The accumulators can thus be easily and quickly removed from the system without complicated connections. They can then be transported using a trolley or back pack.

Various accumulators may be provided and the use of a LiFe P04 battery is an example of one possible accumulator.

Claims

Claims 1. A power management system comprising a control processor having a first power input and a second power input and at least one power output, wherein the control processor monitors and adjusts the phase of the power supplied at the second power input so that it is substantially in phase with the power supplied at the first power input.
2. A power management system according to claim 1, wherein the first power input is a mains supply and wherein the mains supply is used as a reference for synchronisation of the second power input.
3. A power management system according to claim 2, wherein the demand at the power output is supplied by the second power input and wherein when the power demand at the output exceeds the power supplied by the second power input, the remaining demand is supplied from the mains supply.
4. A power management system according to claim 2 or claim 3, wherein the second power input is supplied from a renewable source.
5. A power management system according to claim 4, wherein an inverter is provided to convert power supplied from the renewable source to an AC power supply, and wherein the inverter is phased to the mains supply.
6. A power management system according to claim 4 or claim 5, wherein the renewable source is supplied via an accumulator to allow power from the renewable source to be stored until it is required.
7. A power management system according to claim 6, wherein a plurality of accumulators are provided and wherein the accumulators are connected in parallel and charged in parallel.
8. A power management system according to claim 7, wherein at least one individual accumulator can be readily removed from the system without interrupting the associated power input or at least one power output.
9. A power management system according to claim 4 or any claim depending thereupon, wherein the renewable power supply is provided by way of solar power.
10. A power management system according to any preceding claim, wherein power provided from either power input cannot be supplied to the other power input.
11. A power management device comprising at least two inlets and at least one outlet adapted to manage the system of any preceding claim.
12. An electrical inverter comprising at least one power input and one power output, wherein the inverter is provided with a reference, including a reference frequency and vohage, and the power arriving at the power input is converted to match the reference frequency and voltage.
13. An electrical invcrtcr according to claim 12, wherein the phase of the output power is matched to the phase of the reference.
14. An electrical inverter according to claim 12 or claim 13, wherein the reference comprises a connection to a mains source.
15. A building comprising an electrical supply from a renewable source of power and an electrical supply from a mains source of power, wherein the building power is managed by a power management system as defined in any one of claims I to 10 and/or incorporates a device according to any one of claims 11 to 14.Amendments to the claims have been made as follows: Claims 1. A power management system comprising a control processor having a first power input and a second power input in the form of a renewable energy source and at least one power output, wherein the control processor monitors and adjusts the phase of the power supplied at the second power input so that it is substantially in phase with the power supplied at the first power input, wherein the demand at the power output is supplied by the second power input and wherein when the power demand at the output exceeds the power supplied by the second power input, the remaining demand is supplied from the first power input, wherein the second power input is supplied via at least two accumulators to allow power from the renewable source to be stored until it is required and wherein at least one individual accumulator can be readily removed from the system without interrupting the associated power input or at least one power output.2. A power management system according to claim 1, wherein the first power input is a mains supply and wherein the mains supply is used as a reference for synchronisation of the second power input.3. A power management system according to claim 2, wherein an inverter is provided to convert power supplied from the renewable source to an AC power supply, and wherein the inverter is phased to the mains supply.4. A power management system according to any preceding claim, wherein a plurality of accumulators are provided and wherein the accumulators are connected in parallel and charged in parallel.5. A power management system according to any preceding claim, wherein the renewable power supply is provided by way of solar power.* ***** * . 6. A power management system according to any preceding claim, wherein power provided **.*.* . . * * from either power input cannot be supplied to the other power input. * *7. A power management device comprising at least two inlets and at least one outlet adapted * to manage the system of any preceding claim. * *8. An electrical inverter comprising at least one power input and one power output, wherein the inverter is provided with a reference, including a reference frequency and voltage, and the power arriving at the power input is converted to match the reference frequency and voltage.9. An electrical inverter according to claim 9, wherein the phase of the output power is matched to the phase of the reference.10. An electrical inverter according to claim 9 or claim 10, wherein the reference comprises a connection to a mains source.11. A building comprising an electrical supply from a renewable source of power and an electrical supply from a mains source of power, wherein the building power is managed by a power management system as defined in any one of claims ito 6 and/or incorporates a device according to any one of claims 7 to 10. *.e.S..... * . * * .S *...*....,S