GB2540251A

GB2540251A - Apparatus for providing load response and method

Info

Publication number: GB2540251A
Application number: GB1608230.7A
Authority: GB
Inventors: Robert Linton Howe Andrew
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-05-11
Filing date: 2016-05-11
Publication date: 2017-01-11
Also published as: GB201608230D0; GB201507982D0

Abstract

An apparatus 100 for providing frequency response to an electricity supply network. The apparatus includes an engine 2 with a generator arrangement 3, 6, 7 for providing a first power output, and a battery arrangement 5 for providing a second power output and/or input, wherein the first power output and the second power output are mixed at D.C. to generate a third power output, and wherein the third output is provided via an inverter arrangement 4 to the electricity supply grid. The battery arrangement may include Lithium polymer batteries. The battery may be charged by power from the power grid. A control arrangement may keep the state of charge of the battery 5 in a specific state of charge range.

Description

APPARATUS FOR PROVIDING LOAD RESPONSE AND METHOD Technical Field

The present disclosure relates to apparatus for providing load response, for example for providing load response for assisting to stabilize electric supply networks. Moreover, the present disclosure concerns methods of operating aforementioned apparatus. Moreover, the present disclosure relates a computer program product comprising a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute the aforementioned methods.

Background

Electrical power supply networks are operable to provide power from one or more suppliers to one or more consumers. In operation, electrical power produced by the one or more suppliers is required to match power consumed by the one or more consumers, for maintaining the electrical power supply networks in balance. It is conventional practice to employ hydroelectric or pump-storage generators to inject relatively instantly additional power into the electrical power supply networks to maintain balance, because the one or more suppliers are often not able to adjust their power output instantaneously, for example on account of thermal inertia within their systems.

When the one or more suppliers include renewable energy systems, it is increasingly difficult to maintain the electrical power supply networks in balance when environmental conditions change, for example when a change in wind flow direction or wind velocity occurs in relation to wind turbines configured for electrical power generation. Voltage and frequency of the electrical power supply networks are required to be maintained within certain statutory limits, for safety reasons, as excursion beyond these statutory limits can potentially cause failure of equipment receiving power from the electrical lower supply networks.

In recent years, there has been considerable interest in varying in a dynamic manner power consumed by the one or more consumers in response to changes in power output from the one or more suppliers; such a configuration is often referred to as "smart grid". However, for a variety of reasons, it has been found more technically difficult than originally envisaged to implement a smart grid. Thus, there is now considerable interest in apparatus that can provide a rapid temporal response and is able to supply into the electrical power supply networks additional power when there is excess demand from power by the one or more consumers from the electrical power supply network and/or a sudden change occurs in power output from the one or more suppliers.

However, a contemporary problem is how to provide, in a most cost effective and reliable manner, additional momentary power to ensure that changes in power consumption and/or power supply do not cause a electric power supply networks to fail.

Summary

The present disclosure seeks to provide an improved standby diesel plant to allow provision of frequency response to electrical power distribution networks.

According to a first aspect, there is provided an apparatus for providing frequency response to an electricity supply network, characterized in that the apparatus includes an engine arrangement with a generator arrangement for providing a first power output, and a battery arrangement for providing a second power output and/or input, wherein the first power output and the second power output are mixed at D.C. to generate a third power output, and wherein the third output is provided via an inverter arrangement to the electricity supply grid to provide frequency response thereto.

The present invention is of advantage in that mixing of power in respect of the engine arrangement and the generator arrangement relative to power in respect of the battery arrangement at D.C. enables the apparatus to be implemented in a technically improved manner.

Optionally, in the apparatus, the engine arrangement is operable to function asynchronously in respect of a grid frequency of the electricity supply grid, when the apparatus is in operation.

Optionally, in the apparatus, the battery arrangement includes a configuration including a plurality of mutually connected Lithium polymer rechargeable batteries.

Optionally, ithe apparatus includes a control arrangement for keeping a state of charge (SoC) of the battery arrangement (5) in a range of 30% to 70% of SoC, more optionally in a range of 40% to 60% of SoC, and yet more optionally in a range of 48% to 52% of SoC.

Optionally in the apparatus, the control arrangement is operable to provide state of charge (SoC) balancing between batteries of the battery arrangement.

Optionally, power flows within the apparatus are controlled by adjusting a D.C. voltage of the first power output.

Optionally, in the apparatus, the inverter arrangement is operable to provide for bi-directional power flow therethrough, for charging the battery arrangement from power provided from the electricity supply grid.

According to a second aspect, there is provided a method of operating an apparatus for providing frequency response to an electricity supply network, characterized in that the method includes arranging for the apparatus to includes an engine arrangement with a generator arrangement for providing a first power output, and a battery arrangement for providing a second power output and/or input, wherein method further includes mixing at D.C. the first power output and the second power output to generate a third power output, and providing the third output via an inverter arrangement to the electricity supply grid to provide frequency response thereto.

Optionally, the method includes operating the engine arrangement to function asynchronously in respect of a grid frequency of the electricity supply grid, when the apparatus is in operation.

Optionally, the method includes arranging for the battery arrangement to include a configuration including a plurality of mutually connected Lithium polymer rechargeable batteries.

Optionally, the method includes arranging for the apparatus to include a control arrangement for keeping a state of charge (SoC) of the battery arrangement in a range of 30% to 70% of SoC, more optionally in a range of 40% to 60% of SoC, and yet more optionally in a range of 48% to 52% of SoC.

Optionally, the method includes arranging for the control arrangement to be operable to provide state of charge (SoC) balancing between batteries of the battery arrangement.

Optionally, the method includes controlling power flows within the apparatus by adjusting a D.C. voltage of the first power output.

Optionally, the method includes arranging for the inverter arrangement (4) to be operable to provide for bi-directional power flow therethrough, for charging the battery arrangement from power provided from the electricity supply grid.

According to a third aspect, there is provided a computer program product comprising a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute a method of the second aspect.

It will be appreciated that features of the invention are susceptible to being combined in various combinations without departing from the scope of the invention as defined by the appended claims.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein: FIG. 1 is a schematic illustration of a block diagram of apparatus for providing frequency response for assisting to stabilize in operation electrical power supply networks.

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

Description of embodiments

In overview, embodiments of the present disclosure seek to provide an apparatus that is operable to provide frequency response to an electricity supply network that conveys electrical power from one or more suppliers to one or more consumers. The apparatus is conveniently implemented, for example, as a diesel generator arrangement that is augmented with a battery arrangement for providing such frequency response. Such a synergistic arrangement is beneficial in that the diesel generator itself is not capable of providing an instantaneous frequency response, on account of momentum within its moving component parts, when in operation, but the battery arrangement via solid-state power converters is capable of providing a substantially instantaneous frequency response to fluctuations in balance of the electricity supply network. Such synergy is made possible by mixing power from the diesel generator and the battery arrangement at direct current (D.C.), as will be described in greater detail later.

Referring to FIG. 1, there is shown an illustration of an apparatus pursuant to the present disclosure; the apparatus is indicated generally by 100. The apparatus 100 includes a conventional diesel plant 1 including a diesel engine arrangement 2 whose output drive shaft is coupled to drive an alternator 3; the alternator 3 is operable to provide alternating current (A.C.) power via a rectifying arrangement 7 and a D.C./D.C. converter 6 to provide D.C. power, then via an inverter 4 to provide A.C. power via a transformer 9 onto an electricity supply grid (not shown), wherein the electricity supply grid is operable to provide power to one or more consumers. The apparatus 100 further includes a battery storage plant including the inverter 4, and a battery 5; the inverter 4 and the battery 5 are coupled via the transformer 9 to provide power to the electrical supply grid, as aforementioned. The battery 5 is beneficially implemented as a rechargeable battery, for example as a Lead acid accumulator arrangement, a flow-cell battery, a rechargeable Lithium polymer battery arrangement or similar. However, it will be appreciated that a state-of-charge (SoC) of the battery 5 is important to monitor and control, otherwise a risk of damaging the battery 5 by over-charging or over discharging can potentially arise in operation.

By adding such battery storage using the battery 5 and inverter 4, together with an associated rectifier 7 and D.C./D.C. convertor 6, to a conventional diesel generation plant, it is feasible to provide nearly instantaneous availability of power for assisting to stabilize operation of the electricity supply grid. Moreover, by optimally controlling the apparatus 100 by using a controller 8, it is feasible to modulate the power available to the electricity supply grid in a temporally highly responsive manner. Furthermore, it is not necessary in the apparatus 100 to synchronise an A.C. output from the generator 3 to a frequency of operation of the electricity supply grid. Thus, the apparatus 100 of FIG. 1 includes the generator 3 that does not need to be synchronized to the frequency of operation of the electricity supply grid. Such non-synchronous operation provides two important advantages: (i) a start-up time for the apparatus 100 of FIG. 1 to reach full power is reduced; and (ii) the engine 2 can be run at a higher rotations per minute (r.p.m.) (namely, frequency of rotation of its output shaft), namely in an operating regime whereat the engine 2 can output more electrical power for a given engine size for the engine 2, for example the size relating to a "cc" rating for one or more combustion cylinders of the engine 2.

The D.C./D.C. convertor 6 provides an arrangement for connecting and regulating the output power from the generator 3. Moreover, monitoring the battery 5 power is achieved by using an ammeter 10 or a power meter, thereby allowing the control system 8 to provide constant electrical power to the electricity supply grid, while the engine 2 starts and runs up to full mechanical output power. It will be appreciated that the engine 2 is optionally implemented as a cluster of a plurality of individual smaller engines. Moreover, it will be appreciated that the smaller engines are beneficially diesel engines, although other types of engines are optionally alternatively or additionally employed, for example LNG engines, petrol engines, and similar hydrocarbon-burning engines or turbines.

Alternative approaches to controlling the apparatus 100 of FIG. 1 are possible. The D.C./D.C. convertor 6 optionally includes a part of the inverter 4, for example. Control of power into (charging) the battery 5 is possible by choosing an output voltage that the D.C./D.C. convertor 6 generates when in operation. Alternatively, the inverter 4 ("invertor") optionally includes a D.C./D.C. inverter for charging the battery 5 from grid electricity provided from the electricity supply grid.

In a desired application, the battery 5 stores energy to cover for, namely to compensate for, the engine start and run-up time. Optimally, high capacity (C) rating batteries are used for implementing the battery 5, for example Lithium polymer batteries, although other types of battery are feasible to use, for example Lead acid accumulators, NiMH batteries and similar. For example, a capacity rating of C = 40 with a proprietary 180S battery (providing approximately 600 volts D.C. output) provides 30 seconds of stored energy at full power, when using a 33% state of charge (SoC) for the battery 5, and a linear ramp over a next 90 seconds (namely, circa 2 minutes from start) to zero uses another 50% SoC. A fully charged battery reaches 17% SoC in such an operating scenario.

In one example embodiment of the apparatus 100 of FIG. 1, the inverter 6 has a 500 kW performance rating, and the generator set 1 has a 500 kW performance rating. The battery 5 has a performance rating of 500 kW at 600 volts, and is thus capable of delivering a current of approximately ~1000 A; the battery 5 optionally comprises a battery arrangement including a plurality of mutually interconnected smaller 5 Ah capacity batteries. The smaller 5 Ah batteries are, for example, coupled together as five parallel groups, wherein each parallel group includes 180 smaller 5 Ah capacity batteries coupled in series. Each such smaller 5 Ah battery provides an output voltage of around 4.2 volts in operation when charged, and approximately ~3.lv at a 20% SoC. The battery 5 optionally incorporates electronic circuits to provide fault protection to the battery 5, and to provide battery management, namely load balancing between the plurality of smaller 5 Ah batteries employed.

The apparatus 100 of FIG. 1 provides frequency response in operation, as described in the foregoing, and the controller 8 measures grid frequency and provides an appropriate response power to a defined droop characteristic. Moreover, the apparatus 100 of FIG. 1 has a power meter on a high voltage (H.V.) as well as on a low voltage (L.V.) part of its circuit. Solar sites employing an array of photoelectric panels are susceptible to being similarly modified by including a battery 5 in combination therewith, in a similar manner to the diesel engine 2 and its generator 3, thereby providing an advantage of being ramp rate controlled.

The apparatus 100 of FIG. 1 provides only low response to the electricity supply grid. Optionally, the apparatus 100 is operable to provide bi-directional response, namely both to absorb power from the electricity supply grid and well as providing power to the electricity supply grid. Optionally, the apparatus 100 of FIG. 1 is switched at 49.8 Hz, providing thereby potentially near maximum power for the electricity supply grid. The apparatus 100 of FIG. 1 optionally includes a plurality of 500 kW units, for example typically twenty or more.

It will be appreciated that the apparatus 100 of FIG. 1 is operable to mix net energy from the diesel engine 2 with power provided from or to the battery 5. On account of mixing power at D.C., it is feasible to operate the diesel engine 2 and its generator 3 asynchronously relative to the frequency of the electricity supply grid. When the diesel engine 5 includes a plurality of smaller diesel engines, the plurality of smaller diesel engines are beneficially operated mutually synchronously.

Beneficially, the apparatus 100 of FIG. 1 employs control algorithms in the control system 8 to provide a load provided by the diesel engine 2 in cooperation with the battery 5, wherein the control system 8 is operable to keep the battery 5 in a range of 30% to 70% of SoC when in operation, more optionally in a range of 40% to 60% of SoC when in operation, and yet more optionally in a range of 48% to 52% of SoC in operation (namely substantially 50% of SoC). A 100% SoC corresponds to the battery 5 being fully charged, whereas a 0% SoC corresponds to the battery 5 being fully discharged. Employing a substantially 50% SoC enables the apparatus 100 of FIG. 1 to address a random walk, namely a random variation, of frequency response to the electricity supply network.

Optionally, the diesel engine 2 and its associated load can be simultaneously connected and running to correct battery SoC as individual 500 kW sections running to achieve an output from the apparatus 100 of FIG. 1 of 20 MW. However, it will be appreciated that other power ratings are potentially feasible for the apparatus 100, for example depending upon choice of the diesel engine 2, the generator 3 and the battery 5.

It will be appreciated that the apparatus 100 of FIG. 1 can be built for mobile deployment. Alternatively, the apparatus 100 of FIG. 1 is intended to be for fixed installation use.

The control system 8 is beneficially implemented using computing hardware that is operable to execute computing instructions. However, it will be appreciated that the control system 8 is operationally implemented, at least in part, using hardwired logic circuits.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "consisting of", "have", "is" used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims

CLAIMS We claim:

1. An apparatus (100) for providing frequency response to an electricity supply network, characterized in that the apparatus (100) includes an engine arrangement (2) with a generator arrangement (3, 6, 7) for providing a first power output, and a battery arrangement (5) for providing a second power output and/or input, wherein the first power output and the second power output are mixed at D.C. to generate a third power output, and wherein the third output is provided via an inverter arrangement (4) to the electricity supply grid to provide frequency response thereto.

2. An apparatus (100) of claim 1, characterized in that the engine arrangement (2) is operable to function asynchronously in respect of a grid frequency of the electricity supply grid, when the apparatus (100) is in operation.

3. An apparatus (100) of claim 1 or 2, characterized in that the battery arrangement (5) includes a configuration including a plurality of mutually connected Lithium polymer rechargeable batteries.

4. An apparatus (100) of claim 1, 2 or 3, characterized in that the apparatus (100) includes a control arrangement (8) for keeping a state of charge (SoC) of the battery arrangement (5) in a range of 30% to 70% of SoC, more optionally in a range of 40% to 60% of SoC, and yet more optionally in a range of 48% to 52% of SoC.

5. An apparatus (100) of claim 4, characterized in that the control arrangement (8) is operable to provide state of charge (SoC) balancing between batteries of the battery arrangement (5).

6. An apparatus (100) of any one of the preceding claims, characterized in that power flows within the apparatus (100) are controlled by adjusting a D.C. voltage of the first power output.

7. An apparatus (100) of any one of the preceding claims, characterized in that the inverter arrangement (4) is operable to provide for bi-directional power flow therethrough, for charging the battery arrangement (5) from power provided from the electricity supply grid.

8. A method of operating an apparatus (100) for providing frequency response to an electricity supply network, characterized in that the method includes arranging for the apparatus (100) to includes an engine arrangement (2) with a generator arrangement (3, 6, 7) for providing a first power output, and a battery arrangement (5) for providing a second power output and/or input, wherein method further includes mixing at D.C. the first power output and the second power output to generate a third power output, and providing the third output via an inverter arrangement (4) to the electricity supply grid to provide frequency response thereto.

9. A method of claim 8, characterized in that the method includes operating the engine arrangement (2) to function asynchronously in respect of a grid frequency of the electricity supply grid, when the apparatus (100) is in operation.

10. A method of claim 8 or 9, characterized in that the method includes arranging for the battery arrangement (5) to include a configuration including a plurality of mutually connected Lithium polymer rechargeable batteries.

11. A method of claim 8, 9 or 10, characterized in that the method includes arranging for the apparatus (100) to include a control arrangement (8) for keeping a state of charge (SoC) of the battery arrangement (5) in a range of 30% to 70% of SoC, more optionally in a range of 40% to 60% of SoC, and yet more optionally in a range of 48% to 52% of SoC.

12. A method of claim 11, characterized in that the method includes arranging for the control arrangement (8) to be operable to provide state of charge (SoC) balancing between batteries of the battery arrangement (5).

13. A method of any one of claims 8 to 12, characterized in that the method includes controlling power flows within the apparatus (100) by adjusting a D.C. voltage of the first power output.

14. A method of any one of claims 8 to 13, characterized in that the method includes arranging for the inverter arrangement (4) to be operable to provide for bi-directional power flow therethrough, for charging the battery arrangement (5) from power provided from the electricity supply grid.

15. A computer program product comprising a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute a method as claimed in any one of claims 8 to 14.