Freestanding transportable power generation unit with electrical system

Abstract

There is provided a freestanding transportable power generation unit for powering on-demand devices, comprising: an electrical system (200) configured to convert DC to AC, the electrical system comprising: at least one power generator device (48) configured to output power to the electrical system, first and second power inverters (12) being electrically connected, each configured to convert DC to AC, and a controller (60) operatively configured for selective activation of the first inverter.

Description

[0001] 4911 / 8830 / P / GB

[0002] 1

[0003] Freestanding Unit Electrical System

[0004] The present invention relates to an electrical system unit, particularly (but not exclusively) to a freestanding transportable power generation unit.

[0005] Introduction

[0006] The present invention relates to freestanding transportable units, e.g. for use in remote locations or worksites where mains power is unavailable.

[0007] Freestanding transportable units are used for electric power supply when mains power is unavailable. Such units are typically supplied with power generator devices, i.e. a diesel engine generator, solar-panels etc, to supply off-grid power to the sockets and any electrical appliances connected to the unit, whether the appliances be internal of the unit or externally connected to the unit. It is a typical requirement of a conventional generator set that it is sufficiently powerful to run all of the equipment drawing power from the unit simultaneously.

[0008] The unit comprises a number of electrical components for the operation of supplying electricity to on-demand devices (internal or external devices such as appliances which require power from an external source in order to operate). Examples of the electrical components are power inverters, controllers etc. These components themselves draw electrical power from the unit, i.e., from the power generating devices for operation of the unit. Power consumed by these components therefore cannot be supplied to any of the on-demand devices and therefore affects the efficiency of power supply.

[0009] Furthermore, the power demand from the on-demand devices fluctuates depending on the number of connected devices and other factors such as weather or time of day. Consequently, its often the case that the power demand on the unit is relatively low and so the system's components run ‘overrated’, meaning they operate well below their maximum capacity. Consequently, they consume more 4911 / 8830 / P / GB

[0010] 2 power from the power generator devices than needed for significant periods of time.

[0011] It is the aim of the present invention to eliminate or mitigate one or more of the above-mentioned problems.

[0012] Summary of invention

[0013] According to a first aspect of the invention there is a freestanding transportable power generation unit for powering on-demand devices, comprising an electrical system configured to covert direct current (DC) to alternating current (AC), comprising at least one power generator device configured to output power to the electrical system, first and second power inverters being electrically connected, each configured to convert DC to AC, a controller operatively configured for selective activation of the first inverter.

[0014] According to another aspect of the invention there is a freestanding transportable power generation unit, comprising an electrical system for powering one or more on-demand devices, comprising, internal electrical components for operation of the unit, a power generator device configured to power the on-demand devices and internal electrical components, the internal electrical component comprising first and second components being the same type of component, a logic operator operatively configured for selective activation of the first electrical component.

[0015] According to another aspect of the invention there is an electrical system for powering one or more on-demand devices, comprising, internal electrical 4911 / 8830 / P / GB

[0016] 3 components for operation of the electrical system, a power generator device configured to power the on-demand devices and internal electrical components, the internal electrical component comprising first and second components being the same type of component, a logic operator operatively configured for selective activation of the first electrical component.

[0017] The logic operator may be a controller, processor and / or computer program.

[0018] The power generator device may be any or any combination of: an energy store (e.g. battery / batteries); fuel generator (e.g. diesel / petrol generator); renewable energy generator e.g. solar panel(s) and / or wind turbine(s), and / or hydrogen fuel cells .

[0019] There may be a plurality of power generator devices of the same or different types. For example, there may be diesel generator and solar array (comprising at least one solar panel).

[0020] The maximum power rating of at least one of the inverters is less than the maximum DC output of power generator device(s), such that the inverter is said to be underrated for the electrical system, e.g. the inverter is not configured to convert the maximum power output of the one or more power devices. Optionally, the second inverter is also underrated. Optionally all the inverters are underrated. Optionally one of the inverters may have a power rating substantially equivalent to the combined maximum DC output of the power generator devices.

[0021] The maximum power rating of the first and second inverter may be the same or different. The controller may selectively activate the first and / or second inverter, e.g. in response to one or more sensed condition, such as a power demand.

[0022] The controller may selectively operate one or more inverters by switching it off and on, for example via actuation of a switch, for example a power switch, or diverting a DC input, for example circuit switches such as a relay. 4911 / 8830 / P / GB

[0023] 4

[0024] The controller dynamically sets the inverter power rating by activation of the appropriate inverter to handle the real-time or predicted DC input. Inverter activation may be logic based. The activation may be based on the current or predicted load demand. Based on real-time voltage or current demand. The electrical system may comprise a power meter to measure demand. The system may activate one or more appropriate inverter(s) based on predicted future demand, for example, based on a schedule or monitor the weather conditions and estimating the power demand.

[0025] By dynamically controlling the inverter rating of the electrical system the power waste is minimised by ensuring that the system is not operating an overrated inverter, by ensuring that an electrical system has appropriate total inverter power rating for the operation of DC to AC conversion.

[0026] The electrical system may have two, three, four, or five inverters. Optionally between 2-10 inverters. The inverters may be selectively activatable in turn and / or in different combinations. The plurality of inverters may be referred to as an inverter cascade.

[0027] The inverters may be arranged in series or in parallel.

[0028] Alternatively or additionally, the power rating of other electrical components of the electrical system may be dynamically adjusted. For example, controllers, batteries, battery chargers, rectifiers, wireless transmitters / receivers, or on-demand devices.

[0029] The power generator device may be operatively connected to each of the inverters to provide a supply of power for operation, eg to power the inverters. The controller may selectively operate a power switch for supplying power to the component.

[0030] According to another aspect of the invention there is a method of dynamically controlling the power rating of inverters for a freestanding transportable power generation unit, comprising the steps of: 4911 / 8830 / P / GB

[0031] 5 determining whether the number of activated inverters is sufficient to meet the power demand on the inverters by on-demand devices, selectively activating one or more inverters such that the combined power rating of the activated inverters is greater than the power demand.

[0032] The controller may selectively deactivate one or more inverters when the power demand of the remaining activated inverters is sufficient to meet the power demand on the inverters.

[0033] The method may involve determining the power demand by measuring the current, or voltage or power of the on-demand devices and may involve using a power meter.

[0034] The method may use a controller, eg, a logic controller for performing operation of the method.

[0035] The method may involve determining the minimum power consumption of inverters in order to meet the required power rating. For example, it may be determined that the total number of inverters in operation is greater than the power demand on the unit and therefore unnecessary.

[0036] The controller may selectively activate one or more inverters such that the power rating thereof exceeds the power demand by as small a margin as available.

[0037] The controller may selectively operate the appropriate inverter or combination of inverters according to the maximum efficiency (eg the highest efficiency achievable) of the inverters to minimize energy wastage. For example, it may use the peak efficiency of one or a combination of inverters. The required power demand may be used as an input variable in a calculation to determine which combination of power inverters should be activated or deactivated to achieve the highest efficiency ratings, e.g., peak efficiency. The controller then sends an activation or deactivation signal accordingly. 4911 / 8830 / P / GB

[0038] 6

[0039] According to another aspect of the invention there is a method of dynamically controlling the power rating of inverters, the power generator device being an AC generator, and the controller being configured to selectively actuate the electrical system to provide power from AC generator to the demand devices without using the inverters.

[0040] According to another aspect of the invention there is a method of dynamically controlling the power rating of inverters for a freestanding transportable power generation unit, comprising the steps of: a controller determining the power output % of a deactivated inverter by calculating the power demand of on-demand devices over the max power rating on the inverter, and selectively activating the inverter if the power output is above a preselected power output value %.

[0041] The power output may be determined by dividing the power demand of the on- demand devices by the power rating of a given inverter.

[0042] Optionally, the controller may selectively deactivate an inverter if the power output % of the inverter is below the preselected power output value %.

[0043] The controller may determine the power output value of each inverter before activating or deactivating any (eg any combination) or all of the inverters. The controller may determine which of the inverters (or combination of inverters) is the most efficient to handle the on-demand power, then activates those inverters and may deactivate the other inverters. Where one or more of the most efficient inverters is already activated, the controller maintains said inverter in operation by not sending a deactivation signal.

[0044] Any of the optional or essential features defined in relation to any one aspect of the invention above may be applied to any further aspect, wherever practicable. Those optional feature combinations have not been explicitly repeated only for conciseness.

[0045] For example, the invention is described in explicit detail towards inverters, however, the principle of dynamically controlling the power rating of a system of 4911 / 8830 / P / GB

[0046] 7 inverters is equally applicable to other electrical components of the unit, eg controllers, and optional features described by way of the inverters are also applicable to the other electrical components. Workable embodiments of the invention are described in further detail below, by way of example only, with reference to the accompanying drawings, of which:

[0047] Figure 1 shows an example schematic electrical system for a unit;

[0048] Figure 2 shows an example schematic of the control arrangement for a unit; Figure 3 shows an example schematic of power generation unit.

[0049] Figure 4 shows a further example schematic electrical system for a unit;

[0050] Figure 5 shows a plot of the power out% of an inverter against efficiency.

[0051] 4911 / 8830 / P / GB

[0052] 8

[0053] Detailed

[0054] The present invention is related to a free-standing transportable power generation unit or cabin, such as a welfare cabin, comprising on board power generation means. The freestanding unit / cabin can be provided in any suitable location, for example, in locations without connection to mains electricity.

[0055] A preferred use of the unit is on construction sites or the like, for powering welfare cabins, worksite equipment / appliances, vehicles and other devices that draw electrical power. However, the unit is mobile and can be deployed in any location as desired. In particularly, it is envisaged that the unit will be deployed in locations where mains electricity is unavailable or limited. In some examples, the power generation unit could itself form part of a cabin, e.g. as a power generation cabin or as part of a welfare unit having an on-board power generation / supply system.

[0056] The unit is therefore typically solely reliant on producing electricity via the on-board power generating devices for providing electricity on-demand (although the unit could be hooked up to a mains / external power connection if available). The power generator devices are therefore also responsible for powering the electrical components within the unit, i.e. controllers, inverters and other power drawing components. Since power used by these components cannot be made available to the on-demand devices, this power is deemed as waste and should ideally be minimised.

[0057] The unit dynamically adjusts the combined power rating of one or more components in order to more efficiently manage the power consumption of the onboard electrical components. In the preferred embodiment as shown in figure 1 , the total power rating of the unit for the inverters can be set according to the power demand of the on-demand devices. The unit comprises a plurality of inverters for converting a DC input to an AC output.

[0058] Since the AC load 14 is dependent on the on-demand devices connected, which can change rapidly, the controller adjusts the combined power rating of the 4911 / 8830 / P / GB

[0059] 9 inverters of the unit by selectively activating individual inverters until the combined power rating of the active inverters is sufficient to meet the demand of the AC load.

[0060] As shown in the embodiment in figure 1 , there may be a plurality of inverters 12, each having their own power rating. The total power rating of the unit is the sum of all the individual inverters. For example, where each of the four inverters has an equal output power rating of 2kW of AC, the combined maximum power rating is 8kW of AC from the inverters for the on-demand devices 14. Where the demand on the unit is low, for example at night, eg less than 2kW, then only one of the inverters needs to be operative to meet the demand. The controller 60 deactivates three of the inverters by switching them off or putting them into a stand-by mode.

[0061] These deactivated inverters draw no (or little) power when compared to being active and idle. Hence the power demand of the on-board devices 14 is reduced and the power burden on the power generating devices 46, 48, 49, 50 is also reduced. The overall effect on the unit is that more power can be made available to the on-demand devices, improving efficiency and performance. The service life of the unit 102 is also increased as the electrical components usage is reduced.

[0062] Another benefit of the current system is to provide contingency modes during outages or maintenance. For example, where an inverter is being serviced or replaced, the unit can continue operating via the other inverters while being serviced.

[0063] The on-demand devices include (but not limited to) devices that require power to operate. This includes amenity devices or appliances, eg kettles, microwaves, toasters, heating, lighting, worksite equipment etc, but could also include electric vehicles, welfare cabins, data servers, buildings (schools, hospitals etc) connected to the device for power delivery.

[0064] Unit circuit

[0065] A schematical representation of the power circuit is shown in figure 1 . 4911 / 8830 / P / GB

[0066] 10

[0067] The unit 102 comprises both DC and AC power generator devices. Specifically, an optional DC fuel cell 49, DC solar panels 46 and an AC generator 48, e.g. in the form of a diesel generator set. However, other embodiments may comprise different power generator devices, for example petrol generator(s) or renewable energy generators, such as wind turbines. In some embodiments, the unit 102 may only provide renewable energy, eg, not have any fossil fuel-based generators. In some embodiments there may be a DC diesel / petrol generator instead of (or additionally) to the AC generator. A plurality of generators of the same type could be used e.g. with generators being selectively activatable on demand.

[0068] The electrical system 100 comprises an energy store in the form of a battery bank 50 comprising one or a plurality of batteries. The battery bank may comprise a voltage between 12V and 60V. The battery bank may comprise a voltage of 48V. The battery bank may comprise a capacity between 5kWh and 500kWh, e.g. Between 20kWh and 100kWh. The battery bank may comprise a capacity of 40kWh. Alternatively, another conventional electrical energy store could be used.

[0069] The fuel cell 49 and / or solar panel(s) 46 are operatively connected to the battery bank via a battery charger 66 responsible for managing the charge on the battery. Specifically, determining the current charge level of the bank and determine which of the renewable energy devices should be activated and which of the batteries in the bank should be charged.

[0070] The 230V AC generator 48 can provide direct power to the AC load when there is an immediate need for high power levels, and the controller 60 determines that the battery's charge state is insufficient to meet this demand.

[0071] The generator 48 can also be used to charge the battery bank through the rectifier that converts the generators AC to DC. 4911 / 8830 / P / GB

[0072] 11

[0073] While using a rectifier 16 to first convert AC to DC then converting back to AC through the inverters may seem counter-intuitive (i.e. instead of simply using a DC generator), it allows power to be supplied from the AC generator 48 to the AC load directly in times of high demand. This is done through a second electrical circuit 18 which is independent from the circuit comprising the inverters (which defines a first circuit). The controller 60 can selectively control the supply of power to the on- demand devices 14 through either the first or second 18 circuits. It can provide power using the first and second circuits simultaneously when there is high demand.

[0074] The electrical system 100 comprises four inverters 12, however, some embodiments may comprise only two inverters, or three inverters, or five inverters. The electrical system may have between 2-10 inverters.

[0075] The power rating of each inverter 12 may be such that it is sufficient to run the most power intensive component in the system. The power rating of the / each inverter may be greater than or equal 5kW, 10kW or 12kW.

[0076] The power rating of the / each inverter may be less than or equal to 12kW, 15kW or 20kW.

[0077] In some embodiments one inverter 12 may remain constantly activated, eg. is not selectively operated by the controller such that there is always at least one inverter in operation / activated. The inverter may be a ‘trickle’ or underrated inverter suitable for low power loads such as lighting or in times of low energy use, for example, at night or a standby mode. The other inverters 12 may be selectively activatable as described above, and have (combined) power rating suitable to convert any DC power being supplied by the power generator device(s). Hence the trickle inverter may have a lower power rating than the other inverter(s). For example, the trickle inverter may have power a rating between 50-2000W, optionally between 100-500W. The second inverter may have a power rating between 2-20kW. Optionally some or all the inverters may have the same power 4911 / 8830 / P / GB

[0078] 12 rating. The combined power rating of the inverters may be 10kW or more, 15kW or more, or 20kW or more, or 40kW or more.

[0079] The ability to provide inverters of different ratings has been found to be beneficial since it may offer different options for combinations of inverters to be activated by the controller to meet a power demand more closely. That is to say, if the inverters are each of equal power rating, the controller may simply sum the inverters in sequence to achieve a desired overall power rating. However, where the inverters are of different power ratings, the controller may select different combinations to achieve the required current power rating for power delivery. The controller could switch off one (smaller) inverter in favour of another (larger) inverter. Additionally or alternatively, the controller could apply different combinations of activated inverters (e.g. the first and third inverter or the second and fourth inverter) to achieve different total power rating.

[0080] Each inverter 12 may be a combined inverter and charger. The inverter may accept two AC inputs. In this example, the inverter may also accept two AC inputs and automatically connect to the running generator. In the event of one of the generators failing, the inverter takes over the supply to the connected loads. This happens at a speed such that any electronic equipment connected to the outlets will continue to operate without disruption.

[0081] The inverters 12 are arranged in electrical series such that incoming DC from the battery 50 or generator (46, 48 49) is channelled through successive inverters. Each inverter 12 comprises an AC output line for directing the AC power to the AC Load (on-demand devices) 14.

[0082] The electrical system 100 may comprise bypasses (e.g. transfer switch) for directing DC to each of the inverters. For example where the DC being supplied to one inverter is greater than its power rating, the bypass ensures that current is directed to an inverter that has the required capacity. Whilst an inverter unit may have an on-board transfer switch (bypass) for passthrough current, the rating of the inverter may limit the passthrough capacity. As such, separate transfer 4911 / 8830 / P / GB

[0083] 13 switches (bypasses) have been implemented that are capable of a greater passthrough than the rating of the inverter, e.g. being external of the individual inverter units and / or capable of passthrough for up to the maximum power demand for the electrical system.

[0084] In alternative embodiments the inverters 12 may be arranged in parallel or in combination of series and parallel where there are multiple inverters.

[0085] The electrical system 100 comprises a power meter 20 for measuring the real-time power demand of the AC devices. Specifically, the power meter can measure the power, current or voltage demand. An additional power meter may be located between the generator 48 and AC load 14, i.e on the second circuit 18. As described below, the controller 60 can selectively operate the electrical components of the electrical system based on the measurements of the power meter(s).

[0086] There are a plurality of outlet sockets for connecting to the AC on-demand devices. The sockets enable different devices to selectively engage with the unit, specifically the electrical system thereof to receive an AC current. The sockets will comprise standard 3-pin adaptors for appliances, and 32A 2P+E sockets. The sockets may be located to be externally accessible such that users are not required to enter the unit (i.e. internally) to access the sockets. The sockets may be mounted in an external wall of the unit and / or may be substantially flush with the external wall. The sockets may be recessed or located in a recess to provide some weather protection. The sockets may be extendible, i.e. on retractable cables such that the on-demand AC devices need not be directly adjacent the unit (for example 2-20m long cables).

[0087] The plurality of outlet sockets may comprise different current outputs. The plurality of outlets sockets may comprise at least one 32A socket, at least one 16A socket and / or at least one 63A socket. There may be nine outlets sockets. The nine outlet sockets may comprise six 32A sockets and three 16A sockets. 4911 / 8830 / P / GB

[0088] 14

[0089] The unit 102 provides electrical power to appliances independently from the mains. Specifically, the unit provides UK voltage alternating current (AC) eg, 230V, from direct current power generating devices. The voltage may be fixed and the current may be monitored, e.g. in determining the demand.

[0090] The inverters 12 may be used to convert DC power from the batteries 50, renewable energy generator 46,49 and / or electrical energy store 50.

[0091] The electrical system comprises one or more relays or switches for selectively activating the electrical components, eg., individual inverters 12. The relays may be used to provide electrical bypasses for pathing DC from certain electrical components, for example deactivated inverters. The switches may provide the passthrough / bypass functionality for individual inverters discussed above.

[0092] The electrical system 100 may comprise wireless transmitters for sending and receiving instructions or data, for example receiving instructions from an input device such as a smart phone. The transmitter may provide status updates to the user to be displayed on a device. The transmitter may receive and transmit signals to the electrical components, for example, selective activation of the inverters, relays switches, or receiving power readings from the power meters.

[0093] In this example, the electrical system 100 may comprise a plurality of fossil fuel generators 48, for example, two, three, four or five generators. There may be DC or AC generators or a combination thereof.

[0094] Each of the plurality of generators are installed within the unit. Each of the generators are underrated for the maximum possible power demand of the unit. The maximum possible power demand will vary depending on the purpose of the unit and its working requirements. In this example, the generator has a power of 20kW. The controller can selectively activate the generators depending on the load of the on-demand devices.

[0095] The electrical system comprises AC and DC systems / circuits. The AC system 4911 / 8830 / P / GB

[0096] 15 comprises the generator set, the inverters and the AC outlet sockets, general, AC power is provided by the generator. The unit may be configured to be connected to an external main source, for powering the appliances.

[0097] The renewable energy source 46, 49 and the energy store are connected to the DC circuit. DC power is thus generally provided by the energy store. The DC output of the renewable energy source can thus be used to charge the energy store.

[0098] The AC voltage can be adjusted as desired, for example to 120V, 240V, 230V

[0099] While the embodiment describes the process of dynamically controlling the power rating of the inverters 12, the method of adjusting the power rating can be applied to any electrical component within the unit. For example, the unit may comprise a plurality of controllers, where one or more the controllers is selectively operable depending on the processing power required in order for operation of the unit.

[0100] Logic control

[0101] A schematical representation of the control and electrical system 200 is shown in figure 2. It shows four inverters 12 arranged electrically in series, all being operatively connected to a generator 48, a controller and a battery pack 50.

[0102] As mentioned, each of the inverters 12 has an individual power rating, the combined power rating being the sum of all the inverters. The active inverter rating equates to the total power rating of the active inverters, for example where the power rating of each of the four inverters is 5kW, the maximum combined rating is 20kW and the active power rating for when 1 inverter is active is 5kW, 2 active inverters is 10kW and so on.

[0103] Each activated inverter 12 draws power from the batteries in order to operate. The amount of power consumed by each of the inverters may correlate with their power ratings, eg, a larger inverter requires more power to operate. 4911 / 8830 / P / GB

[0104] 16

[0105] The inverters 12 are arranged in series, although there may be plurality of series wiring between adjacent inverters, i.e there may be two series connections between adjacent inverters, one for providing DC and another wire for providing AC (i.e. a bypass). The inverters may receive an AC input and DC input from the previous inverter.

[0106] When the AC load is measured, the controller 60 activates an appropriate number of inverters to ensure the active power rating is sufficient to meet the demand. For example where the AC load is 14kW and each inverter has a power rating of 5kW, the controller will activate three of the inverters. If the fourth inverter is already activated, it is considered redundant and therefore unnecessarily consuming power as the other inverters would be sufficient to meet the demand. The controller sends a deactivation signal to the fourth inverter to turn it off. AC current is then bypassed to the AC load, either through the deactivated inverters or through a separate bypass.

[0107] The power rating of the inverters 12 may be different. For example, the respective power ratings of the four inverters may be 1 kW, 4kW, 8kW and 20kW. The controller 60 may selectively activate the appropriate inverters based on which configuration draws the least amount of power from the batteries to meet the demand of the AC load. In most applications, this may mean minimising the number of active inverters.

[0108] The controller 60 may activate inverters based on the number of sockets engage used and / or type of socket used. For example, if only 1 of the 9 sockets are in use, only one and / or a low power rated inverter may be activated.

[0109] The controller 60 may follow a schedule of which inverters 12 to activate / deactivate. For example, a preferred order of activation. The schedule may activate inverters 12 based on expected / predicted demand to ensure uninterrupted supply of AC. There may be a log of previous usage over a time period, for example a day or week, and so the controller can anticipate future 4911 / 8830 / P / GB

[0110] 17 demand and active / deactivate the appropriate number of inverters. Additionally or alternatively a schedule of intended operation may be manually set by an operator or cabin manager. Additionally or alternatively a default or base schedule may be applied, e.g. to accommodate normal daytime / nighttime peaks / troughs in power demand and / or a normal working week.

[0111] The inverters 12 may send a signal to the controller 60 once they reach capacity, the controller 60 will then activate an additional inverter.

[0112] Unit construction

[0113] A free-standing transportable power generation unit according to an example of the present invention is shown schematically in Figure 3 and generally designated 102. The unit 102 comprises an enclosure 104, e.g. in the form of a housing or container (i.e. the system is self-contained). The enclosure 104 may comprise a steel shell, for example, the unit may comprise a structure similar to an ISO container, e.g. albeit smaller.

[0114] The unit 102 is mobile and may be selectively deployable, i.e between transport condition and deployed condition. In the deployed state, the solar panels may be deployed to maximise surface area.

[0115] The unit is mobile and may comprise wheels 106, towbar and / or a forklift hooks for mobility.

[0116] The unit is not intended to be a living space and so may not be habitable (eg not to provide a sleeping space). The unit may or may not have doors sufficient size to allow a person to enter, or windows. The unit may have an access closure for maintenance, etc of components within the interior.

[0117] The shell of the unit is exposed to the weather and so is waterproof, i.e. the internal components are shielded from the weather. The shell may be made from metal, eg, steel alloy or aluminium. 4911 / 8830 / P / GB

[0118] 18

[0119] The unit 102 is not an independent vehicle meaning it requires another vehicle to move it around.

[0120] Figure 4 shows a further example of the electrical system of a unit including connections between the relevant components / modules disclosed herein.

[0121] Figure 5 shows a plot of how the efficiency of a power inverter can vary with power output. The efficiency of the inverter increases between 0-30% power output, with a steep efficiency increase between 5-15% before levelling off at a peak efficiency around 30%, and a steady decline thereafter. It should be understood that these numbers are provided as examples and will vary from inverter to inverter, e.g., by models, brands, or different power-rated units. The graph highlights the poor efficiency of an inverter when run underrated, particularly when used below 15% power output. Hence it is desirable not to run inverters substantially underrated. Each inverter therefore has its own efficiency distributions which may be the same or different.

[0122] The controller may selectively activate inverters based on the power rating (e.g., the number of inverters required to meet the power demand), the optimal efficiency rating, or a combination of both. The controller may use control logic to determine the optimum combination of inverters to activate.

[0123] In a simple embodiment, the controller can determine whether the power demand (e.g., power output) is below a preselected value of a given inverter and send an activation / deactivation signal to the appropriate inverters accordingly. For example, the preselected value may be set at the peak efficiency. Where the power demand is below peak efficiency of that inverter, the controller may deactivate said inverter and activate a more appropriate one (e.g., with a lower power rating). In an example where the efficiency curve of a 10kW rated inverter is represented by the plot shown in figure 5, if the power demand is less than 3kW (e.g., less than 30% power output) the controller can deactivate the inverter and activate an inverter with a lower power rating, e.g., a 5kW rated inverter 4911 / 8830 / P / GB

[0124] 19 corresponding to 60% power output. Since the lower rated inverter is more utilised, it has a comparatively higher power output% and therefore is more efficient.

[0125] The preselected power output value will be set appropriately for each inverter, and may be the peak efficiency rating of that inverter, or a set given value, for example, below 40%, or below 35%, or below 30%, or below 25%, or below 20%, or below 15%, or below 10%.

[0126] In some embodiments, the controller may maintain activation a given inverter if the power output% is above the preselected value, or within range, for example 20%- 50%.

[0127] Where there is a plurality of inverters with different power ratings, the controller determines which inverter (or combination of inverters) would run more efficiently and activates / deactivates the appropriate inverters.

[0128] In an example comprising three or more 10kW rated inverters and a power demand of 10kW, while one inverter may be sufficient to meet the demand, the controller can determine whether activating more inverters would be more efficient. To do this, the controller determines whether the compounded energy loss (calculated from the efficiency %) would be less by running fewer inverters.

[0129] For example, running three of the inverters so that the output power on each inverter is around 33% (e.g., closer to the peak efficiency). Where the inverters have efficiency curves like those shown in figure 5, the efficiency of running an inverter at 33% corresponds to an efficiency of about 97% or a 3% loss. This power loss for this efficiency can be calculated, e.g., in kW, and multiplied by three to determine the power loss for running three inverters. If the energy loss for running a single inverter at the maximum power rating is more than running three inverters, the controller selectively activates the three inverters accordingly.

[0130] It should be understood that the number of inverters, power ratings, efficiency curves discussed above are provided as examples to demonstrate how the system works and may vary from embodiment to embodiment.

Claims

4911 / 8830 / P / GB20Claims1 . A freestanding transportable power generation unit for powering on-demand devices, comprising an electrical system configured to covert direct current (DC) to alternating current (AC), comprising at least one power generator device configured to output power to the electrical system, first and second power inverters being electrically connected, each configured to convert DC to AC, a controller operatively configured for selective activation of the first inverter.

2. A freestanding transportable power generation unit according to claim 1 , where the maximum power rating of at least one inverter is below the combined maximum power rating of all the power generator devices.

3. A freestanding transportable power generation unit according to claims 1 or2, where one inverter has a power rating substantially equal to the combined maximum power rating of all power generator devices, preferably within + / - 1 kW range.

4. A freestanding transportable power generation unit according to claim 1 , where there are n inverters, where is n any integer between 2-10.

5. A freestanding transportable power generation unit according to claim 4, where at least n-1 inverters are selectively activatable by the controller.

6. A freestanding transportable power generation unit according to claims 4 or 5, where there are four inverters.

7. A freestanding transportable power generation unit according to claim 1 , the inverters are arranged electrically in series.4911 / 8830 / P / GB218. A freestanding transportable power generation unit according to claim 1 , where at least one inverter comprises an AC bypass for providing AC to on- demand devices.

9. A freestanding transportable power generation unit according to any of claims 4-6, where at least two inverters have different power ratings.

10. A freestanding transportable power generation unit according to claim 9, where one inverter has a power rating 1 kW or less.

11. A freestanding transportable power generation unit according to claim 10, where one inverter has a power rating of 10kW or more.

12. A freestanding transportable power generation unit according to any of claims 4-6, where at least two inverters have the same power rating.

13. A freestanding transportable power generation unit according to claim 12, where all inverters have the same power rating.

14. A freestanding transportable power generation unit according to claim 1 , the power generator devices comprising a renewable energy generator.

15. A freestanding transportable power generation unit according to claim 1 , the power generator devices comprising a fossil fuel generator.

16. A freestanding transportable power generation unit according to claim 15, where the fossil fuel generator is an AC generator.

17. A freestanding transportable power generation unit according to claim 16, the electrical system comprising a second electrical circuit being electrically independent from the circuit comprising the inverters, the second circuit configured to supply power from the AC generator to the on-demand devices.4911 / 8830 / P / GB2218. A freestanding transportable power generation unit according to claim 1 , the unit comprising electrical sockets for selective engagement with the on- demand devices.

19. A freestanding transportable power generation unit according to claim 18, the sockets being externally accessible.

20. An electrical system for powering one or more on-demand devices, comprising, internal electrical components for operation of the electrical system, a power generator device configured to power the on-demand devices and internal electrical components, the internal electrical component comprising first and second components being the same type of component, a logic operator operatively configured for selective activation of the first electrical component.21 . A method of dynamically controlling the power rating of inverters for a freestanding transportable power generation unit, comprising the steps of: determining whether the number of activated inverters is sufficient to meet the power demand of on-demand devices, using a controller to selectively activate one or more inverters such that the combined power rating of the activated inverters is greater than the power demand of the on-demand devices supply power from a power generator device to the on-demand devices using the activated inverters.

22. A method of dynamically controlling the power rating of inverters according to claim 21 , deactivating one of the inverters if the power rating of the remaining activated inverters is greater than the power demand of the on- demand devices.4911 / 8830 / P / GB2323. A method of dynamically controlling the power rating of inverters according to claims 21 or 22, where selective activation of the inverters is based on the real-time demand of the on-demand devices.

24. A method of dynamically controlling the power rating of inverters according to claims 21 or 22, where the selective activation of the inverters is based on the predicted demand of the on-demand devices.

25. A method of dynamically controlling the power rating of inverters for a freestanding transportable power generation unit, comprising the steps of: a controller determining the power output % of a deactivated inverter by calculating the power demand of on-demand devices over the max power rating of the inverter, and selectively activating the inverter if the power output % is above a preselected power output value %.

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