AU2014265107A1

AU2014265107A1 - Apparatus for controlling power output

Info

Publication number: AU2014265107A1
Application number: AU2014265107A
Authority: AU
Inventors: Marcus Black; David Burns; Duane Stapleton; Christopher Taylor; Jacob Truloff
Original assignee: Dbs Ind Qld Pty Ltd
Current assignee: Dbs Industries (qld) Pty Ltd
Priority date: 2014-11-21
Filing date: 2014-11-21
Publication date: 2016-06-09

Abstract

An apparatus (100) for controlling power output comprising: a controller (120) configured to adjust a power output of an inverter (14, 214, 215) of a power 5 generation system (200) which comprises a load (17) to which the power output (16, 216, 217) of the inverter is connected, said power generation system (200) being connected (18) to an electricity supply grid; and a detector (110) for providing input to the controller (120), the detector being adapted to detect the input (at 22) of the electricity supply grid to the power generation system (200); 10 wherein the controller (120) is adapted to adjust the power output of the inverter (14, 214, 215) downwards when the detected input power of the electricity supply grid to the power generation system is below a first, lower, predetermined threshold and to adjust the power output of the inverter upwards when the detected power input of the electricity supply grid to the power generation system 15 is above a second, higher, predetermined threshold. Figure 2 for publication System Power Turns On 1.Ceking Building Power Usage Inverter Disconnected 30 seconds elapsed while N imported flow >03kW disconnects 2lInverter Startup Period n 20 -mins Inverter Connected, Ye~s Raped t o minue lc .outu 60 seconds elapsed 5 seconds elapsed after inverter ramped to minimum 3 agtBn output. 3 agtBn No change to inverter output. Net export flow Net import flow >0kW 0.3kW Net export flow Net import flow <=OkW >= 0.3kW 4. Exported Power > 0 S.imported Pwr > 03kW Ramp inverter output Ramp inverter output UP DOWN at 20%/sec at 3%/sec .Fault -(:nverter Disconnected (Requires Power Cycle)

Description

Apparatus for Controlling Power Output

Field

The present disclosure relates to an apparatus for controlling power output and especially, but not exclusively, to an apparatus for controlling power output from solar electricity generation apparatus.

Definition

In the specification the term “comprising” shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

Background

In recent years it has become increasingly common to provide small scale or local electricity generation systems at or close to a location where power is used. Local generation may be provided by various types of generation, such as wind turbines and the like. An increasingly common form of local electricity generation involves the use of solar photovoltaic (PV) systems.

Solar PV electricity generation systems employ PV panels to generate electricity from solar radiation. A photovoltaic system may comprise one or more arrays of solar panels, with each solar panel comprising interconnected solar cells. Solar radiation incident on the solar panels is used to generate direct current. Most PV systems use an inverter to convert direct current generated by the solar panels to alternating current suitable for use by an electrical system adapted to use electrical power provided by a power grid. The output of the inverter may be controlled to meet requirements. Conventional PV systems may provide power delivery to a load and provide excess power to a power grid. Provision of power to the grid is sometimes known as feed in.

While feed in of locally generated power to the grid has historically been considered desirable, the proliferation of local electricity generation systems has led to concerns that the power grid may be adversely affected by excessive feed in. Accordingly it is often desirable, and in some cases mandated, that feed in to the grid be limited or eliminated. Where the power generated exceeds the local load, one way of limiting or eliminating power feed in to the grid is to reduce the power provided by the PV system. This may be achieved by turning off one or more inverters. The present inventor has discerned that improvements in apparatus for controlling inverter output are desirable.

The reference to prior art or other technological background in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the referenced prior art or other background forms part of the common general knowledge in Australia or in any other country

Summary

According to a first aspect of the present disclosure there is provided an apparatus for controlling power output comprising: a controller configured to adjust a power output of an inverter of a power generation system which comprises a load to which the power output of the inverter is connected, said power generation system being connected to an electricity supply grid; and a detector for providing input to the controller, the detector being adapted to detect the input of the electricity supply grid to the power generation system; wherein the controller is adapted to adjust the power output of the inverter downwards when the detected input power of the electricity supply grid to the power generation system is below a first, lower, predetermined threshold and to adjust the power output of the inverter upwards when the detected power input of the electricity supply grid to the power generation system is above a second, higher, predetermined threshold.

In an embodiment the apparatus is for use with a power generation system which includes one or more solar panels.

In an embodiment the first, lower, predetermined threshold is substantially zero or negative detected power input of the electricity supply grid to the power generation system.

In an embodiment the first, lower, predetermined threshold is substantially zero detected power input of the electricity supply grid to the power generation system.

In an embodiment the second, higher, predetermined threshold is less than one kilowatt greater than the first, lower, predetermined threshold.

In an embodiment the second, higher, predetermined threshold is less than half a kilowatt greater than the first, lower, predetermined threshold.

In an embodiment the adjustment of the power output of the inverter downwards is an incremental adjustment.

In an embodiment the adjustment of the power output of the inverter upwards is an incremental adjustment.

In an embodiment the controller is adapted to adjust the power output of the inverter upwards at a predetermined ramping rate.

In an embodiment the controller is adapted to adjust the power output of the inverter downwards at a predetermined ramping rate.

In an embodiment the or each predetermined ramping rate comprises a percentage of the maximum power output of the inverter per unit time.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is different to the predetermined ramping rate for adjustment of the power output of the inverter upwards.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than the predetermined ramping rate for adjustment of the power output of the inverter upwards.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than five percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than ten percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is less than eighty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is less than fifty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter downwards is approximately twenty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is greater than one percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is greater than two percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than eighty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than fifty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than twenty percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than ten percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than five percent of the maximum power output of the inverter per second.

In an embodiment the predetermined ramping rate for adjustment of the power output of the inverter upwards is approximately three percent of the maximum power output of the inverter per second.

In an embodiment the detector comprises a power meter.

In an embodiment the controller comprises a microprocessor.

In an embodiment the controller comprises a programmable logic controller.

In an embodiment the controller is adapted to adjust the output of the inverter by providing control signals.

In an embodiment the controller is adapted to adjust the output of the inverter by providing control signals via a network interface.

In an embodiment the network interface comprises a network cable.

In an embodiment the network interface comprises a USB or RS485 network cable.

In an embodiment the apparatus comprises a translation module for providing control instructions to the inverter in a control protocol suitable for controlling the inverter.

In an embodiment the apparatus comprises a translation module for providing control instructions to the inverter in a digitally communicated control protocol suitable for controlling the inverter.

In an embodiment the translation module is provided by a component distinct from the controller.

In an embodiment the translation module is provided by a component adapted to convert control signals from the controller into a control protocol suitable for controlling the inverter.

In an embodiment the translation module is provided by a component adapted to convert control signals from the controller into a digital control protocol suitable for controlling the inverter.

In an embodiment the translation module is provided by a component adapted to convert analogue control signals from the controller into a digital control protocol suitable for controlling the inverter.

In an embodiment the apparatus is preconfigured, prior to installation in a power generation system, to: detect, using the detector, the power input of a electricity supply grid into a system, based on input from one or more power detectors associated with one or more respective mains cables of the system; transmit signals indicative of the detected power input from the detector to the controller; provide control instructions, based on the power input detected by the detector, to adjust the power output of the inverter, in a control protocol suitable for controlling the inverter.

In an embodiment the apparatus comprises a housing.

In an embodiment the apparatus is provided, prior to installation in a power generation system, with at least the detector and the controller provided within the housing.

In an embodiment the apparatus is provided, prior to installation in a power generation system, with at least the detector, the controller and the translation module provided within the housing.

In an embodiment the apparatus is provided, prior to installation in a power generation system, with at least the detector, the controller and the translation module provided within the housing, the detector being electrically connected to the controller, the controller being electrically connected to the translation module, the apparatus providing at least one input connection to the detector adapted for connection of the detector to one or more power detectors associated with one or more respective mains cables of the system, the apparatus providing at least one output connection from the translation module adapted for connection to one or more inverters, and wherein the translation module is preconfigured to convert control signals from the controller into a digital control protocol suitable for controlling the inverter of the system.

In an embodiment substantially all electrical and/or electronic components of the apparatus are arranged within the housing, prior to installation.

In an embodiment the housing is suitable for mounting on a wall.

In an embodiment the housing has at least one access part for allowing access to an interior of the housing.

In an embodiment the housing is such that the apparatus is suitable for mounting on an external wall.

In an embodiment the housing is compliant with an IP code IP54.

In an embodiment the apparatus comprises a system status display which displays information relating to the operating state of the apparatus.

In an embodiment the apparatus comprises an inverter status display which displays information relating to the operating state of the inverter.

It will be appreciated that the apparatus may be for controlling more than one inverter of the power generation system, and references to inverter in the singular are intended to include this.

According to a second aspect of the present disclosure there is provided a method of controlling power output of an inverter of a power generation system which comprises a load to which the power output of the inverter is connected, said power generation system being connected to an electricity supply grid, comprising: detecting the input of the electricity supply grid to the power generation system; adjusting the power output of the inverter downwards when the detected input power of the electricity supply grid to the power generation system is below a first, lower, predetermined threshold, and adjusting the power output of the inverter upwards when the detected power input of the electricity supply grid to the power generation system is above a second, higher, predetermined threshold.

In an embodiment the method comprises providing a controller to adjust the power output of an inverter.

In an embodiment the method comprises providing a detector to detect the input of the electricity supply grid to the power generation system.

In an embodiment the method comprises adjusting the output of the inverter by providing control signals to the inverter.

In an embodiment the method comprises adjusting the output of the inverter by providing control signals via a network interface.

In an embodiment the method comprises providing control instructions to the inverter in a control protocol suitable for controlling the inverter.

In an embodiment the method comprises providing control instructions to the inverter in a digitally communicated control protocol suitable for controlling the inverter.

In an embodiment the method comprises providing a translation module for providing control instructions to the inverter.

In an embodiment the method comprises converting control signals from the controller into a control protocol suitable for controlling the inverter.

In an embodiment the control protocol suitable for controlling the inverter is a digital control protocol suitable for controlling the inverter.

In an embodiment converting control signals from the controller into a control protocol suitable for controlling the inverter comprises converting analogue control signals from the controller into a digital control protocol suitable for controlling the inverter.

In an embodiment the method comprises providing an apparatus in accordance with the first aspect.

It will be appreciated that statements relating to features or characteristics of embodiments of the first aspect are also applicable to the second aspect. Unless context or logic require otherwise statements relating to features or characteristics of embodiments of the first aspect should be regarded as applicable to the second aspect without necessarily requiring the limitations of the first aspect as recited above.

According to a third aspect of the present disclosure there is provided a method of providing an apparatus for controlling power output in accordance with the first aspect, comprising: providing the apparatus, prior to installation in a power generation system, with at least the detector and the controller provided within a housing, the detector being electrically connected to the controller, the apparatus providing at least one input connection to the detector adapted for connection of the detector to one or more power detectors associated with one or more respective mains cables of the system, the apparatus providing at least one output connection adapted for connection to one or more inverters of the system, and wherein the apparatus is preconfigured to provide instructions in a digital control protocol suitable for controlling the one or more inverters of the system of the system.

Brief description of the drawings

Embodiments will be described below, in detail, with reference to accompanying drawings. The primary purpose of this detailed description is to instruct persons having an interest in the subject matter of the invention how to carry the invention into practical effect. However, it is to be clearly understood that the specific nature of the detailed description of embodiments does not supersede the generality of the preceding broad description in the Summary. In the accompanying diagrammatic drawings:

Fig. 1 is a schematic representation of a very simple grid-connected local electricity generating system including an embodiment of an apparatus for controlling power output in accordance with the present disclosure;

Fig. 2 is a schematic representation of further simple grid-connected local electricity generating system including an embodiment of an apparatus for controlling power output in accordance with the present disclosure;

Fig. 3 is a schematic representation of the embodiment of an apparatus for controlling power output illustrated in Fig. 2;

Fig. 4 is a conceptual representation of three levels of detected power flow which result in different operational states of an apparatus for controlling power output in accordance with the present disclosure;

Fig. 5 is a simple block diagram illustrating the different operational states of an apparatus for controlling power output in accordance with the present disclosure;

Fig. 6 is a state model illustrating a number of states of an embodiment of an apparatus for controlling power output in accordance with the present disclosure;

Fig. 7 is a diagrammatic representation of an embodiment of apparatus for controlling power output in accordance with the present disclosure in a grid-connected local electricity generation system;

Fig. 8 is a detailed diagrammatic representation of an embodiment of apparatus for controlling power output in accordance with the present disclosure in a grid-connected local electricity generation system, including connections to the rest of the system;

Fig. 9 is a schematic illustration of a physical embodiment of apparatus for controlling power output in accordance with the present disclosure, showing internal components;

Fig. 10 is a schematic illustration of the physical embodiment of Fig. 9 with covers attached;

Fig. 11 is an enlarged representation of an electrical connection assembly of the embodiment of Fig. 9; and

Figs. 12(a) and 12(b) are schematic illustrations of embodiments of power flow detectors which may be used in embodiments of apparatus for controlling power output in accordance with the present disclosure.

Detailed description of embodiments

With reference to the accompanying drawings embodiments of apparatus for controlling power output in accordance with the present disclosure will be described.

Fig. 1 is a schematic representation of a very simple grid-connected local electricity system, generally designated 10 including electricity generation. The system 10 also includes an output control apparatus, generally designated 100, which is an embodiment of an apparatus for controlling power output in accordance with the present disclosure.

The electricity generating system 10 comprises an electricity generator 12. The electricity generator 12 is, in this embodiment a photovoltaic generator, in the form of a PV solar panel or array of PV solar panels, but may alternatively be any type of local generator such as, but not limited to, a wind- or water-powered generator, or a combined heat and power unit. The electricity generator 12 is provided with an associated inverter 14 for converting direct current output of the generator 12 to alternating current. The inverter 14 has an output connection 16 to enable power flow from the inverter 14. The output connection 16 of the inverter 14 is connected to a load 17, which may be electrical apparatus within or associated with a house or commercial premises. The output connection runs via the output control apparatus 100 so that the output control apparatus 100 is able to control connection or disconnection of the inverter in the system 10.

The load 17 is also connected to an electricity grid supply 18, via a supply authority meter and switchboard 20, and one or more power premises mains cables 22. A known prior art system allows power from the inverter 14 to be fed into the electricity grid, and to represent this the arrows representing the electricity grid supply 18 and one or more power premises mains cables 22 are shown as bidirectional in Fig. 1.

The output control apparatus 100 comprises a detector 110 for detecting current flow through the one or more power premises mains cables 22. In this embodiment the detector 110 is connected to the one or more power premises mains cables 22 by a detection line 112 which provides input relating to the direction and magnitude of current flow through the one or more power premises mains cables 22. The detector communicates information regarding the detected current flow to a controller 120, which controls output of the inverter 14. In this embodiment the controller 120 is connected to the inverter 14 by a communication cable 140. The controller 120 may be connected to the communication cable 140 via one or more intermediate components, as will be described in due course.

Fig. 2 illustrates a variation 200 of the grid-connected local electricity generating system 10 of Fig. 1, in which there are many similarities, in which corresponding elements are designated by the same reference numerals, and in relation to which only the differences will be described. In the variation 200, second and third generators 212, 213 are provided, each associated with a respective inverter 214, 215. The second and third generators 212, 213 will normally be of the same type as the generator 12 (for example PV solar panels) or may be of one or more different types. The associated inverters 214, 215 have respective output connections 216, 217 to enable connection to the load 17. The output control apparatus 100 is provided with communications cables 240, 241 for connection to the inverter 214, 215. As shown in Fig. 2 the output control apparatus 100 is also shown as including a power management unit (PMU) 230, as an intermediate component between the controller 120 and the communication cables 140, 240, 241, as foreshadowed above. Fig. 2 illustrates that the present disclosure may relate to the control of multiple inverters.

The output control apparatus 100 utilises a feature provided in many known inverters whereby an external device, such as a programmable logic controller (PLC) or computer can instruct the inverter to operate at an output level anywhere between 0 and 100% of its full capacity. Such instruction typically requires instructions to be provided by commands in a proprietary protocol associated with the inverter. In the output control apparatus 100 the controller 120 allows the apparatus to act as such an external device, and the PMU 230 can provide the ‘translation’ of the controller output into the proprietary protocols for controlling the inverter(s). While it would be possible to provide an integrated controller programmed to provide output in the proprietary protocols for controlling the inverter(s), it is currently considered convenient and economical to use a commercially available microprocessor in the form of a PLC as the controller and a distinct commercially available PMU to provide ‘translation’ of the controller output.

The output control apparatus 100 is adapted to monitor the direction and magnitude of power flow through the one or more power premises mains cables 22 (using the detector 110) and to control the output of the inverter(s) 14 with the aim of maintaining the power flow through the one or more power premises mains cables 22 at a desired level. It will be appreciated that the power flow through the one or more power premises mains cables 22 is substantially the power flow from and or into the electricity supply grid. The desired level may be a range between two different values of power flow.

The basic approach is that when the power flow from the grid into the system (typically a premises) is not at the desired level, the output of the inverter(s) 14 is ramped (to increase or decrease) by an incremental amount in an appropriate direction. If the power flow is not at the desired level a short, preferably predetermined, time thereafter, then the output of the inverter(s) 14 is again ramped (to increase or decrease) by a further incremental amount, and this process is repeated until the power flow is at the desired level.

Fig. 3 illustrates the output control apparatus 100 as illustrated in Fig. 2, on an enlarged scale, and schematically illustrates two outputs from the detector 110 to the controller 120, a first output 310 corresponding to the power flow from the grid into the system being below the desired range and a second output 311 corresponding to the power flow from the grid into the system being below the desired range. It will be appreciated that in this context net power flow from the system into the grid (sometimes called power feed-in) can be considered negative power flow from the grid into the system.

Fig. 4 is a conceptual representation of three levels, or bands of detected power flow from the grid into the system. The horizontal line or axis 400 represents increasing detected power flow from the grid into the system from left to right. A first, more leftward, vertical line 402 intersecting the axis 400 represents the minimum target power flow from the grid into the system. A second vertical line 404, to the right of the first vertical line 402, represents the maximum target power flow from the grid into the system. A first band 410, to the left of the first vertical line 402, represents the power flow from the grid into the system being below the desired or target level. A second band 420, between the first and second vertical lines 402, 404, represents the power flow from the grid into the system being within the desired or target range. A third band 430, to the right of the second vertical line 404, represents the power flow from the grid into the system being above the desired or target level.

When the power flow from the grid into the system is detected as being below the desired or target level, i.e. in the first band 410, this means that the output from the inverter(s) 14 is higher than is desired. Accordingly when such power flow is detected the controller 120 ramps the inverter output down.

When the power flow from the grid into the system is detected as being within the desired or target range, i.e. in the second band 420, this means that the output from the inverter(s) 14 is substantially as desired. Accordingly when such power flow is detected the controller 120 does not instruct the inverter(s) to vary output.

When the power flow from the grid into the system is detected as being above the desired or target level, i.e. in the third band 430, this means that the output from the inverter(s) 14 is lower than is desired. (It will be appreciated that this may be due to factors other than the setting of the inverter: for example the electrical power provided by the generator(s) may be low, for example at night, or the load may be high). Accordingly when such power flow is detected the controller 120 ramps the inverter output up if it is not already at one hundred percent. A primary envisaged use of the output control apparatus 100 is where there is a restriction on the amount of power that may be fed into the grid. It is becoming increasingly common for electricity providers to require that at least certain local electricity generation systems be arranged so that they do not feed any substantial amount of power into the grid. To comply with this requirement it is important that if power is at some stage being fed into the grid, for example because of a rapid drop in the power consumption of the load to which the generator(s) supply power, the situation is rapidly remedied. The output control apparatus 100 can achieve this by having the low bound of the target range (the second band 420) set at zero power flow from the grid into the system, so that the first band 410 includes all net feed-in from the system into the grid, and by ensuring that the inverter output is ramped downward rapidly when there is any feed in to the grid. The output control apparatus 100 is arranged to ramp down the power output of the inverter(s) at a rate of 20% per second (1% decrement every 50ms), so that inverter output and thus exported power should reach zero within a maximum of five seconds. As a safeguard (for example if the inverter is not designed to have power output reduced to zero per cent) the output control apparatus 100 is arranged to electrically disconnect the inverter(s) from the system power network if net export power to the grid remains greater than zero for a further five seconds. Once the net imported power rises into the third band 430, and remains there for a minimum of 30 seconds, the inverters will be re-connected to the building power network. As a further precaution, if five such disconnections occur within 20 minutes, this may indicate that the communication to the inverter has malfunctioned, and the output control apparatus 100 will enter a fault state, disconnecting the inverter(s) from the system power network, and requiring resetting to reconnect the inverter(s).

While it is important to reduce power output of the inverters rapidly, for the reasons discussed above, it is also important to avoid excessive power flow from the grid into the system, since this would result in unnecessarily high power costs and a failure to utilise the system’s electricity generators effectively. Thus when the power flow from the grid into the system is above the target range (i.e. when it is in the third band 430) the output control apparatus 100 ramps up the power output of the inverters with the aim of bringing the power flow from the grid into the system down to within the target range.

It will be appreciated that the target range for power flow from the grid into the system is intended to represent a state in which the inverter output is substantially equal to the power consumption of the load, and in which little power is imported from the grid. Thus the target range may desirably have a maximum bound of a few tenths of a kilowatt, and in an embodiment of the output control apparatus 100 is set to have an upper bound of 0.3 kW. The output control apparatus 100 is arranged to ramp up the inverter power output fairly rapidly, although where avoiding power feed-in to the grid is a priority the rate at which inverter power output is ramped up may desirably be considerably slower than the rate at which power is ramped down. In an embodiment the rate at which inverter power output is ramped is 3% per second (a 1% increment every 330ms).

It will therefore be appreciated that the inverter power output will be continually, dynamically, adjusted (ramped up or down) so as to with the aim of maximising the inverter output provided the output does not result in the power flow from the grid into the system falling below the target range (for example, in the described example, preventing net export of power to the grid).

It will be appreciated that the target range for power flow from the grid into the system described above, of OkW to (for example) 0.3kW may be varied, if desired, according to the circumstances. For example, if the electricity grid operator has mandated a maximum power feed-in rate other than zero (for example, of 1 kilowatt) then the target range may be set appropriately to maximise allowable power feed in and any associated payment therefor (for example by setting the target range as between -1 kilowatt and -0.7 kilowatts).

Of course, it will be appreciated that there will be circumstances where despite use of the output control apparatus 100 the power flow from the grid into the system will be outside the desired target range. For example, the output of inverters associated with PV generators will be substantially zero at night during the hours of darkness, even if the inverter output is set to 100%. Thus the aim is to maintain the power flow from the grid into the system within the desired range as much as possible, rather than at all times or in all circumstances. Flowever, it will be appreciate that the power flow from the grid into the system may be kept above the minimum of the target range (that is, for example, preventing feed-in to the grid) at substantially all times.

Fig. 5 is a block diagram, generally designated 500, providing an alternative, and complementary, representation of the methodology illustrated by Fig. 4, albeit with some additional assumptions which will be appreciated from consideration of the above description and of the text set out in Fig. 5.

Fig. 6 is a state model diagram, generally designated 600, illustrating a number of states of the output control apparatus 100. States are represented by ovals, and transitions between states are represented by arrows with the trigger conditions which cause a state change from one state to another included adjacent the corresponding arrow. These states and conditions are implemented on and by, and programmed into, the controller 120.

The state model diagram 600 illustrates initial states after start-up or resetting at states 601 and 602.

As indicated by state 601 and the associated arrow, after switching on, there is a start delay (for example of 30 seconds) during which net system load is measured during which the inverter(s) are not turned on. A minimum load (for example one per cent of inverter capacity or 300W whichever is the greater) must be met for 30 seconds. After 30 seconds of minimum load, the inverter is switched on. If the minimum load is not detected a suitable indication of this may be provided to a user, for example in an embodiment a “waiting for load” message will be displayed on a display of the apparatus, as will be described in due course.

As indicated by state 602 and the associated arrow, after the inverter is switched on there is a start-up period (for example 60 seconds), allowing the inverter to go through its start delay, during which the inverter output is limited to 2% of its capacity. After the delay the output control apparatus 100 will operate as described above with reference to Figs. 4 and 5, meaning that inverter output will be ramped up subject to the detected power flow from the grid into the system being above the desired or target level. This allows the inverter to be controlled to output up to 100% of its capacity, or a percentage which results in the power flow from the grid into the system being within the desired target range.

The state model diagram 600 also illustrates ongoing operative states, corresponding to those described above with reference to Figs. 4 and 5: when the power flow from the grid into the system is detected as being within the desired or target range, i.e. in the second band 420, designated by state 603; when the power flow from the grid into the system is detected as being below the desired or target level, i.e. in the first band 410, designated by state 604; and when the power flow from the grid into the system is detected as being above the desired or target level, i.e. in the third band 430, designated by state 605. These operative states have been described in detail above as will be appreciated by the addressee.

The state model diagram 600 also illustrates disconnection of the inverter, as described above, designated by state 606.

Figs. 7 to 12 illustrate particular embodiments in terms of componentry and structure, which may be regarded as exemplifications of the output control apparatus 100 described more generally above.

Fig. 7 shows the overall cable topology for installation of an embodiment of an output control apparatus into a grid connected power generating system, generally designated 700, which has many similarities to power generating system 10. In this embodiment the output control apparatus is generally designated 710. The system 700 comprises an array of solar panels 712 and an associated inverter 714, with outputs 716 connected to premises mains cables 722 via the output control apparatus 710 and an inverter main switch/circuit breaker 711. The premises mains cables 722 are connected to a supply authority meter and switchboard 720 via a mains switch/circuit breaker 723.

The output control apparatus 710 is connected to the inverter by a communication cable 740, which is in the form of an RS485 or other suitable network communications cable such as for example USB cable (although other forms of connection, such as wireless network connection could be used if desired). The communication cable interface type may be selected according to the interface type of an inverter with which the output control apparatus 710 is intended to be used.

The output control apparatus 710 has inputs provided by detection lines 752 to enable detection and measurement of power flow in each of three premises mains cables 722. The detection/measurement of power flow is enabled by power detectors, which in this embodiment are current transformers CT1, CT2, CT3 which are provided around respective premises mains cables 722. In practice power detectors, such as the current transformers CT1, CT2, CT3, may be installed relative to (and, in the case of current transformers, around) the three premises mains cables 722 in the main switchboard of the building or system 700, although it will be appreciated that other installation locations are possible.

It will be appreciated that the description of grid connected power generating system, generally designated 700 corresponds in many important ways with the power generating system 10 described above and illustrated in Figs. 1 and/or 2.

Fig. 8 illustrates, in detail, internal components and connection topology of an embodiment of an output control apparatus, generally designated 810. The output control apparatus 810 may be considered an example of the output control apparatus 110 and/or of the output control apparatus 710, but this does not preclude that there are other many embodiments and variations of those output control apparatuses.

The output control apparatus 810 is specifically designed to work with Power One inverters, as sold by Power One Pty Ltd of Australia, which is part of the ABB Group (based in Zurich Switzerland). Accordingly, the control apparatus 810 includes facility to output instructions to one or more inverters in an instruction protocol compatible with Power One inverters, as will be described in more detail below. Of course, alternative embodiments may alternatively or additionally include facility to output instructions to one or more other proprietary inverters in an instruction protocol compatible therewith. It is to be noted that inverter manufacturers generally make the communication protocol details available to potential developers upon request, and may supply hardware or software which facilitates communication of a controller with their inverters. Thus adaption of the described embodiments for use with various other brands of inverter and/or inverters using different instructions protocols should be taken to be within the scope of the present disclosure.

The output control apparatus 810 comprises a detector 815 in the form of an energy meter which in this embodiment is a Lovato Energy Meter as sold by Mectrich Pty Ltd under product code LOVMED310T2. This corresponds to an embodiment of the detector 110 of output control apparatus 100.

The output control apparatus 810 further comprises a controller in the form of a programmable logic controller 820 (sometimes called a smart relay) which in this embodiment is of the type sold by Schneider Electric under product code SR2B122BD. This corresponds to an embodiment of the controller 120 of output control apparatus 100.

The output control apparatus 810 further comprises a PMU 830, which in this embodiment is of the type provided by ABB Group under product name Aurora PVI-PMU. This PMU 830 provides digital output compatible with Power One inverters and provides an RS485 interface 832. This PMU has an analogue input 834 (suitable for receiving control signals from the programmable logic controller 820). The digital RS485 output is suitable for providing instructions to Power One inverters which include one or more RS485 connections. This PMU 830 corresponds to an embodiment of the PMU 230 of output control apparatus 100. The full capabilities of the commercially available Aurora PVI-PMU (and/or other commercially available PMUs) will be known to, or readily ascertainable by, the person skilled in the relevant art. The manufacturer of the Aurora PVI-PMU (and/or its parent company) makes such details publically available, for example at the time of writing full details are available at: https://aurora.power-one.it/Shared%20Documents/ltaliano/Documentazione%20Tecnica/ Manuali/PVI-PMU/Aurora%20PMU-Specification%20Rev1 .pdf

In this embodiment an analogue signal conditioner 825 is provided between the programmable logic controller 820 and the PMU 830.

The output control apparatus 810 further comprises a power supply 840, which is this embodiment is a 24 volt DC power supply, for example of the type sold by Mectrich Pty Ltd under product code PSL1M02424.

The detector 815 and the power supply 840 are connected to wiring 850 which in use is connected between a switchboard and the inverter(s).

In a commercial embodiment the detector 815, programmable logic controller 820, analogue signal conditioner 825, PMU 830, power supply 840 and wiring 850 are housed within a housing (not shown in Fig. 8, but see Figs. 9 and 10) and these components are electrically connected in a suitable manner, for example as shown in Fig. 8. The output control apparatus 810, including these components can therefore be supplied as a single pre-programmed and ready to install unit, which greatly aids installation compared to the provision of individual components which must be installed separately, connected together and, possibly, reconfigured and/or programmed to provide mutual compatibility and compatibility with other components of the generating/load system.

The external connections of the output control apparatus 810 are indicated by the small black circles in Fig. 8. These are: six connections, designated by numerals 1 to 6, for connection to three current transformers (two wires for each current transformer); three connections, designated 7, 8, 9, which provide the RS485 interface; four connections, designated N1, 71, 72, 73, for connection to wiring from a switchboard; and four connections, designated N2, 81, 82, 83, for connection to one or more solar inverters. These (and one or more earth connections) are the only connections that need to be connected to when installing the output control apparatus 810.

Fig. 9 is a schematic illustration of a physical embodiment 900 of apparatus for controlling power output in accordance with the present disclosure, showing internal components. Using as an example, the components described in relation to Fig. 8, the detector 815, programmable logic controller 820, analogue signal conditioner 825 (not shown in Fig. 9), PMU 830, power supply 840 and wiring 850 are housed within a housing 910, which in this embodiment is a robust housing suitable for installation on (or within) a wall of a building. The electrical connections between the components may be substantially as illustrated in Fig. 8.

The housing 910 may be made, for example, from sheet metal or a suitably robust plastic.

The detector 815 and the programmable logic controller 820 are each provided with a respective visual output arrangement, which in this embodiment comprises a respective LCD display 915, 920.

The visual output arrangements allow communication of information regarding operation of the mains-connected electricity generating system to a user.

The visual output, in this embodiment LCD display 915, of the detector 815, displays the instantaneous net power flow from the grid to the system (which may correspond to net power flow from the grid to a building in which the system is provided). Positive power indicates power flowing into the system from the grid. Negative power indicates power feed-in back to the grid. Negative power flow should persist only for very short periods of time (a maximum of a few seconds while the inverter is ramped down). An indicium indicating that the power flow is displayed, such as “BUILDING MAINS NET POWER FLOW”, may be provided adjacent the display, such that this indicium can be seen by a user when the apparatus 900 is in use.

The visual output, in this embodiment LCD display 920, of the controller 820, displays information regarding the status of the apparatus (and/or the system in which the apparatus is connected). An indicium indicating display of the state of the system, such as “SYSTEM STATUS”, may be provided adjacent the display, such that this indicium can be seen by a user when the apparatus 900 is in use.

In normal operation, the percentage of full capacity that the inverter(s) are operating at will be shown.

Other conditions or states of the system may be displayed as appropriate. This can allow a user to easily identify the state of the system.

For example, start-up conditions and any detected fault conditions can be shown. Some example will be presented with reference to Fig. 6 which illustrates various states of an embodiment of an apparatus in accordance with the present disclosure.

As a first example, if the inverter(s) are ramped down to a minimum output but export power continues to be detected, for example as shown by the legend “5 seconds elapsed after inverter ramped down to minimum output” in Fig. 6, so that the inverter(s) are temporarily disconnected, a message indicating this state, for example a string of non-alphanumeric symbols, such as hash symbols (e.g. “##################”) or any other appropriate message may be displayed.

As a second example, if a predetermined number of disconnection events occur within a predetermined period (for example more than five disconnection events in twenty minutes, illustrated by state 606 in Fig. 6) so that a power cycle is required, a message indicating this state, for example wording such as “trip count exceeded” or any other appropriate message may be displayed.

As a third example, if during start-up a power flow from the grid into the system above a predetermined minimum is not detected over a predetermined period load greater than a predetermined minimum (at the state illustrated by state 601 and that state’s change condition in Fig. 6), a message indicating this state, for example wording such as “waiting for load” or any other appropriate message may be displayed.

The apparatus 900 provides a connection arrangement 930, which provides most or all of the connections 1 to 9, N1, 71, 72, 73, N2, 81, 82, 83, required for connection of the apparatus 900 in a mains-connected electricity generating system.

The connections may be provided in an array, for example as one or more rows of connections, and in the illustrated embodiment the array of connections is in the form of a substantially straight row of connections or connectors. It will be appreciated that prior to installation the ‘connections’ will not be connected to other parts of the mains-connected electricity generating system and are provided as terminals suitable for providing connection to those parts. In this embodiment the connection arrangement 930 also provides ‘earth’ connections E. In this embodiment the connection arrangement 930 provides all of the connections (in the form of connectors or terminals) required for connection of the apparatus 900 in a mains-connected electricity generating system.

Upon or adjacent the connection arrangement 930 are provided indicia to assist in identifying the connections. This can facilitate connecting the apparatus 900 to the rest of the mains-connected electricity generating system. In this embodiment the indicia are provided in an identification region 932. The indicia may be provided as one or more stickers, plates or in any other suitable form.

In this embodiment the connection array 930 is provided in a dedicated connection region 935 of the housing 910. The connection region 935 may be distinct from a component region 937 of the apparatus 900 (or housing 910) in which most or all of the detector 815, programmable logic controller 820, analogue signal conditioner 825, PMU 830, and power supply 840 are provided. The connection region 935 may be provided in different box-like section to the component region 937.

Fig. 10 is a schematic illustration of the physical embodiment 900 of Fig. 9 with covers attached. A first cover 1002 covers a part of the housing that contains most or all of the detector 815, programmable logic controller 820, analogue signal conditioner 825, PMU 830, and power supply 840. The first cover 1002 is provided with a lock 1004 which may be of a type known in the field of switchboard cabinets and is operable by a key, such as a triangle, square, slotted type key. In the illustrated embodiment a lock sold by Dore Electrics (of Mansfield, Queensland, Australia) under product code SL8K/604 is used. The first cover 1002 may be attached to the housing 910 by one or more hinges (not shown).

The first cover 1002 provides information 1006, for example on its exterior, relating to the apparatus. The first cover 1002 provides one or more transparent or window regions 1007, 1008 so that the visual outputs (in this embodiment LCD displays 915, 920) of the detector 815 and controller 820 are visible when the cover 1002 is closed. Adjacent the window the legends identifying the displays are provided (in this embodiment “BUILDING MAINS NET POWER FLOW” and “SYSTEM STATUS”) as part of the information 1006. The information 1006 may be provided on a plate or sticker 1009, attached to, or forming part of, the first cover 1002. A second cover 1010 covers a part of the housing that contains the connections or terminals (in this embodiment connections 1 to 9, N1, 71, 72, 73, N2, 81,82, 83), and may be marked to indicate this (for example with the legend “CONNECTION TERMINALS”). In this embodiment the second cover 1010 is attached to the housing 910 by screws 1012, which can be removed to access the connections.

Of course, if desired, fewer or more than two covers could be used.

Fig. 11 is an enlarged representation of the connection arrangement 930 and the associated indicia which assist in identifying the connections.

The indicia include mains connection indicia 1102 which relate to the connections E, N1,71,72, 73 for connecting the apparatus to the building mains cables via the inverter main switch/circuit breaker. The mains connection indicia 1102 include identifiers (in this embodiment E, N, L1, L2, L3) relating to the connections, and a graphic representation of mains supply 1103.

The indicia include inverter connection indicia 1104 which relate to the connections E, N2, 81, 82, 83 for connecting the apparatus to the inverter. The inverter connection indicia 1104 include identifiers (in this embodiment E, N, L1, L2, L3) relating to the connections, and a graphic representation of an inverter and/or generator 1105.

The indicia include detector connection indicia 1106 which relate to the connections 1 to 6 for connecting the apparatus to the detectors CT1, CT2, CT3 which allow current flow to be detected by the detector 815. The detector indicia 1106 include identifiers (in this embodiment CT1, CT2, CT2) relating to the connections, and a graphic representation of the detectors 1107.

The indicia include communications indicia 1108 which relate to the connections 7 to 9 for the connection (in this embodiment the network, RS485 interface) which allows the apparatus 900 to control the inverter(s). The communications indicia 1108 may include a graphic representation of the communications output, in this embodiment a graphic 1109 showing connection to the graphic representation of the inverter 1105.

The provision of indicia 1102, 1104, 1106, 1108, assists in connection of the apparatus into the system.

It will be appreciated that various cables must enter the housing 910. Apertures (not shown) are provided in a housing wall to allow this. The apertures may be provided in a bottom gland plate (not shown) of the connection region 935 of the housing, and appropriate cable glands (not shown) may be used to allow sealed passage of the cables into the housing 910. The connection region 935 may be provided in a bottom part of the housing 910. The cables may enter through the bottom of the housing 910.

It will be appreciated that the described embodiment provides a ‘one-box’ product, in which only the external detectors are provided outside the box (housing 910), and the main components and connections are provided preassembled within the box. The components are electrically connected during manufacture and prior to installation, and the apparatus is preconfigured to communicate with the inverter(s) the output of which it is to control. This can significantly reduce the time and expertise required of an installer compared to an apparatus which is provided for installation as a number of separate components which are not electrically connected. The described embodiment allows installation by a person (for example an electrician) who does not have specialist knowledge of the inverters or their communication protocols. It is envisaged that any competent electrician would be capable of installing the apparatus.

The apparatus may include, or be provided with, a mounting bracket (not shown) to allow attachment to a wall in a desired position. It can be installed adjacent to the main switch board of the system, adjacent the inverter(s) themselves, or at any other appropriate and convenient location.

In the described embodiments the housing (including ingress points of the cables thereinto) is fully weather proof, for example having an IP (ingress protection rating or international protection marking) code of IP54 standard, so outdoor installation is permitted, and the apparatus can be mounted on an exterior wall if desired.

Fig.s 12(a) and 12(b) are schematic illustrations of embodiments of power flow detectors (which could be used as detectors CT1, CT2, CT3) showing the correct connection configuration for a split core current transformer 1202 in Figure 12(a) and for a solid core current transformer 1204, for use with a building mains cable 1206. It is envisaged that these types of detector would be options, of which a selected type will be supplied as part of the apparatus upon request.

As will be appreciated from the above the present disclosure provides a single-box solution for controlling inverter output that can limit or substantially eliminate feed-in, while substantially maintaining inverter output at a maximum level that avoids undesirable levels of feed-in, by continuously monitoring power flow into the system from the grid and smoothly ramping the output of the inverter(s) towards (and rapidly to) a level which is desirable at any given time.

Other than in unusual circumstances the described apparatus does not switch off or disconnect the inverter(s). Avoidance of sudden disconnection or switching off of the inverters is beneficial, since it can shorten inverter life. Further, incremental control of inverter output, rather than switching off or disconnection of inverters as a primary form of feed-in control, allows inverter output to be maintained at a maximum desired level, and avoids the consequence of making generators effectively inoperative while substantial power is being imported from the grid. Thus effective use of the generators is provided.

It will be appreciated that although some commercially available inverters are configured so that they can be instructed (for example by a PMU) to output only a selected proportion of their maximum power output, additional logic, calculation and/or input regarding the operation of the mains-connected generation system is required to determine what level of inverter output is desired at a given time. The apparatus described above provides these additional requirements.

Modifications and improvements may be incorporated without departing from the scope of the invention as set out in the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An apparatus for controlling power output comprising: a controller configured to adjust a power output of an inverter of a power generation system which comprises a load to which the power output of the inverter is connected, said power generation system being connected to an electricity supply grid; and a detector for providing input to the controller, the detector being adapted to detect the input of the electricity supply grid to the power generation system; wherein the controller is adapted to adjust the power output of the inverter downwards when the detected input power of the electricity supply grid to the power generation system is below a first, lower, predetermined threshold and to adjust the power output of the inverter upwards when the detected power input of the electricity supply grid to the power generation system is above a second, higher, predetermined threshold.
2. An apparatus as claimed in claim 1, wherein the first, lower, predetermined threshold is substantially zero or negative detected power input of the electricity supply grid to the power generation system.
3. An apparatus as claimed in either preceding claim, wherein the first, lower, predetermined threshold is substantially zero detected power input of the electricity supply grid to the power generation system.
4. An apparatus as claimed in any preceding claim, wherein the second, higher, predetermined threshold is less than one kilowatt greater than the first, lower, predetermined threshold.
5. An apparatus as claimed in any preceding claim, wherein the second, higher, predetermined threshold is less than half a kilowatt greater than the first, lower, predetermined threshold.
6. An apparatus as claimed in any preceding claim, wherein the adjustment of the power output of the inverter downwards is an incremental adjustment.
7. An apparatus as claimed in any preceding claim, wherein the adjustment of the power output of the inverter upwards is an incremental adjustment.
8. An apparatus as claimed in any preceding claim, wherein the controller is adapted to adjust the power output of the inverter upwards at a predetermined ramping rate.
9. An apparatus as claimed in claim 8, wherein the predetermined ramping rate comprises a percentage of the maximum power output of the inverter per unit time.
10. An apparatus as claimed in any preceding claim, wherein the controller is adapted to adjust the power output of the inverter downwards at a predetermined ramping rate.
11. An apparatus as claimed in claim 10, wherein the predetermined downwards ramping rate comprises a percentage of the maximum power output of the inverter per unit time.
12. An apparatus as claimed in either of claims 10 or 11 when dependent upon either of claims 8 or 9, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is different to the predetermined ramping rate for adjustment of the power output of the inverter upwards.
13. An apparatus as claimed in claim 12, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than the predetermined ramping rate for adjustment of the power output of the inverter upwards.
14. An apparatus as claimed in claim 11 or either of claims 12 or 13 when dependent thereon, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than five percent of the maximum power output of the inverter per second.
15. An apparatus as claimed in claim 14, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is greater than ten percent of the maximum power output of the inverter per second.
16. An apparatus as claimed in claim 11 or any of claims 12 to 15 when dependent thereon, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is less than eighty percent of the maximum power output of the inverter per second.
17. An apparatus as claimed in claim 16, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is less than fifty percent of the maximum power output of the inverter per second.
18. An apparatus as claimed in claim 17, wherein the predetermined ramping rate for adjustment of the power output of the inverter downwards is approximately twenty percent of the maximum power output of the inverter per second.
19. An apparatus as claimed in claim 9 or any of claims 10 to 18 when dependent thereon, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is greater than one percent of the maximum power output of the inverter per second.
20. An apparatus as claimed in claim 19, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is greater than two percent of the maximum power output of the inverter per second.
21. An apparatus as claimed in claim 9 or any of claims 10 to 20 when dependent thereon, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than eighty percent of the maximum power output of the inverter per second.
22. An apparatus as claimed in claim 21, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than fifty percent of the maximum power output of the inverter per second.
23. An apparatus as claimed in claim 22, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than twenty percent of the maximum power output of the inverter per second.
24. An apparatus as claimed in claim 23, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than ten percent of the maximum power output of the inverter per second.
25. An apparatus as claimed in claim 24, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is less than five percent of the maximum power output of the inverter per second.
26. An apparatus as claimed in any of claims 19 to 25, wherein the predetermined ramping rate for adjustment of the power output of the inverter upwards is approximately three percent of the maximum power output of the inverter per second.
27. An apparatus as claimed in any preceding claim, wherein the detector comprises a power meter.
28. An apparatus as claimed in any preceding claim, wherein the controller comprises a microprocessor.
29. An apparatus as claimed in any preceding claim, wherein the controller comprises a programmable logic controller.
30. An apparatus as claimed in any preceding claim, wherein the controller is adapted to adjust the output of the inverter by providing control signals.
31. An apparatus as claimed in claim 30, wherein the controller is adapted to adjust the output of the inverter by providing control signals via a network interface.
32. An apparatus as claimed in claim 31, wherein the network interface comprises a network cable.
33. An apparatus as claimed in claim 32, wherein the network interface comprises a USB or RS485 network cable.
34. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a translation module for providing control instructions to the inverter in a control protocol suitable for controlling the inverter.
35. An apparatus as claimed in claim 34, wherein the apparatus comprises a translation module for providing control instructions to the inverter in a digitally communicated control protocol suitable for controlling the inverter.
36. An apparatus as claimed in either of claims 34 or 35, wherein the translation module is provided by a component distinct from the controller.
37. An apparatus as claimed in any of claims 34 to 36, wherein the translation module is provided by a component adapted to convert control signals from the controller into a control protocol suitable for controlling the inverter.
38. An apparatus as claimed in claim 37, wherein the translation module is provided by a component adapted to convert control signals from the controller into a digital control protocol suitable for controlling the inverter.
39. An apparatus as claimed in claim 38, wherein the translation module is provided by a component adapted to convert analogue control signals from the controller into a digital control protocol suitable for controlling the inverter.
40. An apparatus as claimed in any preceding claim, wherein the apparatus is preconfigured, prior to installation in a power generation system, to: detect, using the detector, the power input of a electricity supply grid into a system, based on input from one or more power detectors associated with one or more respective mains cables of the system; transmit signals indicative of the detected power input from the detector to the controller; provide control instructions, based on the power input detected by the detector, to adjust the power output of the inverter, in a control protocol suitable for controlling the inverter.
41. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a housing.
42. An apparatus as claimed in claim 41, wherein the apparatus is provided, prior to installation in a power generation system, with at least the detector and the controller provided within the housing.
43. An apparatus as claimed in claim 41 when dependent upon any of claims 34 to 39, wherein the apparatus is provided, prior to installation in a power generation system, with at least the detector, the controller and the translation module provided within the housing.
44. An apparatus as claimed in claim 43, wherein the apparatus is provided, prior to installation in a power generation system, with at least the detector, the controller and the translation module provided within the housing, the detector being electrically connected to the controller, the controller being electrically connected to the translation module, the apparatus providing at least one input connection to the detector adapted for connection of the detector to one or more power detectors associated with one or more respective mains cables of the system, the apparatus providing at least one output connection from the translation module adapted for connection to one or more inverters, and wherein the translation module is preconfigured to convert control signals from the controller into a digital control protocol suitable for controlling the inverter of the system.
45. An apparatus as claimed in any of claims 41 to 44, wherein substantially all electrical and/or electronic components of the apparatus are arranged within the housing, prior to installation.
46. An apparatus as claimed in any of claims 41 to 45, wherein the housing has at least one access part for allowing access to an interior of the housing.
47. An apparatus as claimed in any of claims 41 to 46, wherein the housing is suitable for mounting on a wall.
48. An apparatus as claimed in claim 47, wherein the housing is such that the apparatus is suitable for mounting on an external wall.
49. An apparatus as claimed in any of claims 41 to 48, wherein the housing is compliant with an IP code IP54.
50. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a system status display which displays information relating to the operating state of the apparatus.
51. An apparatus as claimed in any preceding claim, wherein the apparatus comprises an inverter status display which displays information relating to the operating state of the inverter.
52. A method of controlling power output of an inverter of a power generation system which comprises a load to which the power output of the inverter is connected, said power generation system being connected to an electricity supply grid, comprising: detecting the input of the electricity supply grid to the power generation system; adjusting the power output of the inverter downwards when the detected input power of the electricity supply grid to the power generation system is below a first, lower, predetermined threshold, and adjusting the power output of the inverter upwards when the detected power input of the electricity supply grid to the power generation system is above a second, higher, predetermined threshold.
53. A method as claimed in claim 52, wherein the method comprises providing a controller to adjust the power output of an inverter.
54. A method as claimed in either of claims 52 or 53, wherein the method comprises providing a detector to detect the input of the electricity supply grid to the power generation system.
55. A method as claimed in any of claims 52 to 54, wherein the method comprises adjusting the output of the inverter by providing control signals to the inverter.
56. A method as claimed in claim 55, wherein the method comprises adjusting the output of the inverter by providing control signals via a network interface.
57. A method as claimed in either of claims 55 or 56, wherein the method comprises providing control instructions to the inverter in a control protocol suitable for controlling the inverter.
58. A method as claimed in claim 57, wherein the method comprises providing control instructions to the inverter in a digitally communicated control protocol suitable for controlling the inverter.
59. A method as claimed in either of claims 57 or 58, wherein the method comprises providing a translation module for providing control instructions to the inverter.
60. A method as claimed in claim 59, wherein the translation module is provided by a component distinct from a controller provided to adjust the power output of an inverter.
61. A method as claimed in either of claims 59 or 60, wherein the method comprises converting control signals from the controller into a control protocol suitable for controlling the inverter.
62. A method as claimed in claim 61, wherein the control protocol suitable for controlling the inverter is a digital control protocol suitable for controlling the inverter.
63. A method as claimed in claim 62, wherein converting control signals from the controller into a control protocol suitable for controlling the inverter comprises converting analogue control signals from the controller into a digital control protocol suitable for controlling the inverter.
64. A method as claimed in any of claims 52 to 63, wherein the method comprises providing an apparatus in accordance with any of claims 1 to 51.
65. A method of providing an apparatus for controlling power output in accordance with any of claims 1 to 51, comprising: providing the apparatus, prior to installation in a power generation system, with at least the detector and the controller provided within a housing, the detector being electrically connected to the controller, the apparatus providing at least one input connection to the detector adapted for connection of the detector to one or more power detectors associated with one or more respective mains cables of the system, the apparatus providing at least one output connection adapted for connection to one or more inverters of the system, and wherein the apparatus is preconfigured to provide instructions in a digital control protocol suitable for controlling the one or more inverters of the system of the system.