AU2014201758A1 - Generation Load Compensation - Google Patents

Abstract

Generation Load Compensation 5 This invention relates in general to renewable energy generation within a utility grid. The renewable energy generation load compensation system comprising: a mains power supply; a renewable energy source comprising: a first series comprising at least one renewable energy supply connected to a first inverter; at least one further series comprising at least one further renewable energy 10 supply connected to a further inverter; and a contactor connected to each said inverter to electrically isolate and connect each said series to and from the system; a controllable switch comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising means connected to each said contactor to isolate and energise each said series; and 15 a microprocessor programmable to control the energising and isolation of each series; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; and wherein said first series and inverter are sized and connected to export renewable energy to the mains power supply, and said further series and inverters are switched 20 depending on the load or consumption on the mains power supply. 24 25 10 23>26 -26 -26 45 .. >

Description

1 Generation Load Compensation FIELD OF THE INVENTION 5 This invention relates in general to renewable energy generation within a utility grid. In particular, the present invention relates to a system, method and apparatus for renewable energy generation for the purpose of compensating the load from the utility grid and providing a network protection device which incorporates isolation from the utility grid and the renewable energy system. 10 BACKGROUND OF THE INVENTION It should be noted that reference to the prior art herein is not to be taken as an acknowledgement that such prior art constitutes common general 15 knowledge in the art. Electricity or power is an essential part of modern life. In residences, in businesses, in institutions and in other locations, consumers use electricity in a variety of ways. Utilities deliver power generated by power plants through a 20 network of transmission and distribution lines. This network is hereinafter referred to as the "power transmission and distribution grid," "the electric grid," "the grid" or "power grid." Renewable energy is a practical and environmentally conscious 25 alternative to traditional utility production. One of the more desirable renewable sources is solar power. Solar equipment consumes no fossil fuels and generates no air pollutants. The use of solar power is generally regarded as environmentally safe. Utilities in most countries are required (or voluntarily do so) for public policy reasons to credit or actually buy excess power generated 30 by a solar generating system from a consumer. In addition to these benefits, solar systems can provide customers with significant cost savings in the long run. As an incentive to install solar systems, government entities may provide rebates or tax deductions to customers who purchase and install solar systems.

2 Such programs have met with limited success for various reasons most particularly the inability of some types of energy users to curtail energy use and the lack of real-time information regarding the immediate cost of energy usage. 5 The use of power generated from renewable energy resources is rapidly increasing, attention is being focused on systems and methods in which such power is produced, transmitted, delivered, and consumed. The technology used in developing renewable energy resources, electricity grids and current energy infrastructure suffer from many limitations. Furthermore, as the demand 10 for such power increases, and regulatory requirements for use of "green" resources become more prominent there is a growing need to provide a useful alternative or at least an improvement on what has previously been done. In recent years, concerns have been raised that high demand for 15 electricity is taxing the capacity of existing electricity generating plants. Furthermore, concerns regarding the availability and environmental safety of fossil and nuclear fuel are being raised. As a result of the above factors, the price of electricity has been on a path of steady increase. Likewise, the electrical utility industry has for some time laboured under the problem of 20 supplying cost effective power to comply with system peak-demand period requirements. Renewable energy systems have been used with gained popularity to resolve at least partially the peak-demand issue of the power grid. For 25 example, a solar power system may convert generated DC electricity from solar panels into AC electricity and be used to power electrical appliances. The generated DC power is also converted to AC power by an inverter so that power grid companies may purchase AC power produced. 30 These systems are typically being developed for the home or business which remains connected to the main electricity grid, so any electricity that your system generates above what you use is fed back into the grid. When you require more electricity than you are producing, your system imports it from the grid automatically. Your electricity bill is calculated as the difference between 3 the amount of electricity you export from your renewable energy system and the amount you import from the grid - you only pay for the electricity you use that is over and above what your renewable energy system produces. 5 At present, feed-in regulations or tariffs for renewable energy exist in over 40 countries, states or provinces internationally, all involving the payment of a premium for the electricity fed into the grid from a variety of renewable energy sources. These feed in tariffs (FiT) are typically applied in two forms. A first form is a gross FiT - whereby all electricity generated from a renewable 10 source is purchased from the generator at a generous price, with the generator buying-back any electricity they need to use from the grid. The second form of FiT is a net FiT - whereby only unused or surplus electricity is purchased from the generator. 15 In order to recover some of the expenses out laid in converting to a grid fed renewable energy system users are looking for ways to maximise the FiT benefit. Presently, consumers are maximising their financial benefit by improving the energy efficiency of their home to export more electricity to the grid. This could be achieved by reducing standby power consumption, 20 switching to controlled load tariffs and minimising the use of energy intensive appliances such as air-conditioners. The fact that the FiT payment levels are performance-based puts the incentive on producers to maximise the overall output and efficiency of their system. 25 The problems with current domestic solar grid feed systems is that they are creating problems on the energy network regarding power quality and voltage spikes/abnormalities which requires expensive equipment to rectify it. Furthermore domestic solar grid feed systems are reducing the amount of power that can be sold by the generators and distributors, yet the actual 30 amount of energy produced by the generators has to remain constant due to the fluctuating nature of small scale solar energy production. This means that the power generation companies, and distributors, still have the same or higher network costs, yet their income from selling and distributing the power has 4 reduced. Thus there have been increases seen in electricity bills for items such as service charges. Clearly it would be advantageous if a renewable energy generation load 5 compensation system, method and apparatus could be devised that helped to at least ameliorate some of the shortcomings described above. In particular, it would be beneficial for a renewable energy generation load compensation system to improve on these deficiencies in renewable energy generation for the purpose of compensating the load from the utility grid, or to at least provide a 10 useful alternative. SUMMARY OF THE INVENTION In accordance with a first aspect, the present invention provides a 15 renewable energy generation load compensation system comprising: a mains power supply; a renewable energy source comprising: a first series comprising at least one renewable energy supply connected to a first inverter; at least one further series comprising at least one further renewable energy supply connected to a further inverter; and a contactor connected to each said inverter 20 to electrically isolate and connect each said series to and from the system; a controllable switch comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising means connected to each said contactor to isolate and energise each said series; and a microprocessor programmable to control the energising and isolation of each 25 series; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; and wherein said first series and inverter are sized and connected to export renewable energy to the mains power supply, and said further series and inverters are switched depending on the load or consumption on the mains power supply. 30 Preferably, the size of the first series and inverter may be determined by the requisite feed in tariff. The system may be connected to any single, two or three phase mains power supply.

5 Preferably, the controllable switch may be designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply. When power is in the forward direction the controllable switch may connect said further series to compensate for the usage of load 5 from the mains power supply. When forward power or load decreases the controllable switch may isolate said further series to prevent over generation from the renewable energy source. Preferably, the system may further comprise any one or more of the 10 following protection devices: (i) over voltage protection; (ii) under voltage protection; (iii) over frequency protection; (iv) under frequency protection; (v) differential frequency protection between the phases; (vi) phase failure protection; or (vii) reverse power flow protection. Should any one of the protection devices be energised the system may isolate and protect the mains 15 power supply. Preferably, the system may further comprise an event logger to monitor and analyse each phase of the mains power supply. 20 Preferably, the controllable switch may be programmed to allow the requisite feed in tariff to be exported with all series connected to the mains power supply. Preferably, the system may automatically disconnect from the mains 25 power supply in order to protect the mains power supply from an islanding fault. Preferably, the system may further comprise a grid load measurement module which measures the grid load of the mains power supply by measuring the frequency of the mains power supply. 30 Preferably, the renewable energy source may be any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising at least one wind turbine; or (iii) a hydro 6 energy source comprising a water source using the gravitational force of falling or flowing water. Preferably, the system may further comprise a data network for 5 transferring information between the controllable switch, the mains power supply, the renewable energy source, and the domestic power supply network. According to a further aspect, the present invention provides a method comprising managing renewable energy generation load compensation by 10 linking together a mains power supply, a renewable energy source, and a domestic power supply network through a controllable switch; said method comprising the steps of: (i) monitoring the load on the mains power supply; (ii) connecting a first series and an inverter to export energy to the mains power supply; (iii) sensing the load is in the forward direction connecting further series 15 and inverters to compensate the usage of the load in the mains power supply; (iv) sensing a decrease in the load or forward power and isolating the further series to prevent over generation from the renewable energy source. Preferably, the method may further comprise any one of the features of 20 the first aspect. According to a still further aspect, the present invention provides a renewable energy generation load compensating apparatus comprising a computer readable media which stores computer instructions; and computer 25 instructions stored on said media accessibly to a microprocessor of a controllable switch device which links together a mains power supply, a renewable energy source, and a domestic power supply network through the controllable switch, the instructions when executed on the microprocessor: (i) monitoring the load on the mains power supply; (ii) connecting a first series and 30 an inverter to export energy to the mains power supply; (iii) sensing the load is in the forward direction connecting further series and inverters to compensate the usage of the load in the mains power supply; and (iv) sensing a decrease in the load or forward power and isolating the further series to prevent over generation from the renewable energy source.

7 According to a still further aspect, the present invention provides a system for managing renewable energy generation load compensation comprising: a mains power supply; a master controllable switch and at least one slave controllable switch; at least one dwelling comprising said at least 5 slave controllable switch, said at least one dwelling comprising: a renewable energy source comprising at least one renewable energy source, at least one inverter, a contactor connected to each said inverter to isolate and connect each said dwelling to and from the system, and a domestic supply network connected to either the renewable energy source or the mains power supply; 10 wherein said master controllable switch controls the system by: (i) monitoring the load on the mains power supply; (ii) connecting at least one dwelling to export energy to the mains power supply; (iii) sensing the load is in the forward direction connecting a further dwelling to compensate the usage of the load in the mains power supply; (iv) sensing a decrease in the load or forward power 15 and isolating the further dwelling to prevent over generation from the renewable energy source. Preferably, each master controllable switch and slave controllable switch may further comprise: a voltage and/or a current sensing devices to sense the 20 load on the mains power supply; an energising coil connected to each said contactor in each dwelling to isolate and energise each said dwelling; and a microprocessor programmable to control the energising and isolation of each dwelling. 25 Preferably, the at least one dwelling connected to export energy from the renewable energy source to the mains power supply may be rated and size determined by the requisite feed in tariff. The system may be connected to any single, two or three phase mains power supply. The master controllable switch may be designed to continuously measure and monitor both forward and 30 reverse direction of power flow in the mains power supply. The renewable energy source may be any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising at least one wind turbine; or (iii) a hydro energy source comprising a water source using the gravitational force of falling or flowing water.

8 Preferably, the system may further comprise a data network for transferring information between the master controllable switch, the slave controllable switch, the mains power supply, the renewable energy source, and the domestic power supply network. 5 Preferably, the system may further comprise a multi-unit installation comprising two or more dwellings. Each dwelling may comprise a slave controllable switch and the multi-unit installation has the master controllable switch to continuously measure and monitor both forward and reverse direction 10 of power flow in the mains power supply for the multi-unit installation. According to a still further aspect, the present invention provides a renewable energy generation load compensation system comprising: a mains power supply; a renewable energy source with at least one renewable energy 15 supply; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; an inverter connected to each said renewable energy source, said inverter comprising: a contactor connected to each said inverter to electrically isolate and connect each said renewable energy supply to and from the system; a controllable switch 20 comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising coil connected to each said contactor to isolate and energise each said renewable energy supply; and a microprocessor programmable to control the energising and isolation of each said renewable energy supply; and wherein at least one of said renewable energy supplies is 25 sized and connected to export renewable energy to the mains power supply, and said further renewable energy supplies are switched depending on the load or consumption on the mains power supply. Preferably the system may be connected to any single, two or three 30 phase mains power supply. The inverter and said controllable switch may be designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply. The renewable energy source may be any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising 9 at least one wind turbine; or (iii) a hydro energy source comprising a water source using the gravitational force of falling or flowing water. According to a still further aspect, the present invention provides an 5 integrated renewable energy system, comprising: a mains power supply; a renewable energy source with at least one renewable energy supply and an inverter connected to the each renewable energy supply; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; a load compensation device comprising: a 10 contactor connected to each said inverter to electrically isolate and connect each said renewable energy supply to and from the system; a controllable switch comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising coil connected to each said contactor to isolate and energise each said renewable energy supply; and a 15 microprocessor programmable to control the energising and isolation of each said renewable energy supply; and wherein at least one of said renewable energy supplies is sized and connected to export renewable energy to the mains power supply, and said further renewable energy supplies are switched depending on the load or consumption on the mains power supply. 20 Preferably, the load compensation device may be retrofitted to any type or size inverter to facilitate the load compensation on the mains power supply. The load compensation device may be part of the inverter for the load compensation on the mains supply. 25 BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the 30 preferred embodiment of the present invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only.

10 Figure 1 is a single line drawing for a renewable energy load compensation system in accordance with the present invention; Figure 2 is a block diagram of the renewable energy load compensation system of Figure 1; 5 Figure 3 is a schematic view of a three phase renewable energy load compensation system in accordance with the present invention; Figure 4 is a schematic view of the renewable energy load compensation system of Figure 3 with at least one inverter linked to each phase; Figure 5 shows a single line drawing showing the system of Figure 1 10 connected with the agreed feed in tariff; Figure 6 shows a single line drawing showing the system of Figure 1 excluding the connection of the agreed feed in tariff; Figure 7 illustrates the load compensation device of Figure 1 showing the switching of contactor coils of the system of Figure 3; 15 Figure 8 shows the voltage sensing and input from the main supply to the load compensation device of Figure 3; Figure 9 shows the current sensing and input from the main supply to the load compensation device of Figure 3; Figure 10 shows a flow chart of only the first inverter of the system 20 showing timing for connection and disconnection; Figure 11 shows the flow chart for all inverters in the system of Figure 1; Figure 12 illustrates the system of Figure 1 installed in a master slave relationship; Figure 13 shows a further embodiment of the present invention in which 25 the renewable energy load compensation device is installed within an inverter used in the renewable energy source; Figure 14 shows a single line drawing of the renewable energy load compensation device installed within the inverter of Figure 13; Figure 15 shows the current sensing and input of the current sensing into 30 the inverter of Figure 13; Figure 16 shows the voltage sensing and input of the voltage sensing into the inverter of Figure 13; Figure 17 shows a further embodiment in which the load compensation device is installed as an add on or retrofit of an inverter; 11 Figure 18 shows a block diagram of the main components of the load compensation device of Figure 1; Figure 19 shows a block diagram of the main components of the load compensation device of Figure 13; 5 Figure 20 shows a block diagram of the main components of the load compensation device of Figure 17; and Figure 21 shows a schematic of a further embodiment of the present invention in which micro-inverters are used to replace conventional inverters. 10 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description, given by way of example only, is described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments. 15 Described embodiments relate generally to methods, systems and apparatus for a renewable energy generation load compensation and computer readable storage configured to control the performance of such methods, systems and apparatus. The renewable energy load compensation system is 20 typically used for solar photovoltaic fed grid installations for the purpose of compensating the load from the mains supply grid and the described embodiments are particularly suited to such purposes. Embodiments are not, however, limited to such use. 25 Photovoltaics (PV) are a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels 26 composed of a number of solar cells containing a photovoltaic material. A PV system is made up of one or more photovoltaic (PV) panels 26, 30 a DC/AC power converter or inverter 25, electrical interconnections, and associated switches and contactors 23, 24. The electricity generated can be either stored, used directly (island/standalone plant), or fed into the electricity grid 11, or combined with one or many domestic renewable energy generators to feed into a small grid.

12 Renewable energy is energy that comes from resources which are continually replenished such as sunlight, wind, rain, tides, waves and geothermal heat. Therefore the present invention is not limited to any particular renewable energy. For example, in addition to the solar systems, wind turbines 5 have also been employed to provide clean or renewable energy. The wind turbine generates an AC power from the kinetic energy of the wind through a system comprising a rotator, a gearbox and a generator. The AC power is rectified into a DC power and is further converted into AC power with the same frequency as the AC power from the power grid. Likewise, hydroelectricity is 10 the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. The following description will be described with reference to solar energy 15 and the use of photovoltaic panels however, the production of renewable energy is not limited to only such use. Likewise, isolation referred to in the following paragraphs refers to both electrical and mechanical isolation. Therefore isolation for both the mains grid and the renewable energy supply may incorporate both mechanical and electrical isolation in order to protect both 20 the main and the renewable energy supplies and their associated components. Figures 1 and 2 show a schematic diagram and a block diagram of a renewable energy load compensation system 10 in accordance with a first embodiment of the present invention. Figure 1 shows a single line drawing of 25 the mains power supply 11 and Figure 2 shows a block diagram of the main components in the load compensation system 10. Figure 3 shows a schematic diagram of a three phase mains power supply 11 in accordance with a first embodiment of the present invention. In order to provide the compensation for the load or sub circuits 16 on the mains power supply 11 the present invention 30 incorporates a load compensation device 20 and associated circuitry. A mains power supply 11 provides mains electricity in the form of general-purpose alternating-current (AC) electric power supply. Worldwide, many different mains power systems are found for the operation of household and light commercial electrical appliances and lighting. The main differences between 13 the systems are primarily characterised by their voltage, frequency, plugs and sockets (receptacles or outlets), and earthing system (grounding). The mains power or grid supply 11 is fed via transmission lines 12 to 5 dwellings and a consumer meter 13. An electricity meter or energy meter 13 is a device that measures the amount of electric energy consumed by a residence or dwelling. Incorporating grid fed renewable energy generating equipment, means when a customer may be generating more electricity than required for his own use, the surplus may be exported back to the power grid. Customers 10 that generate back into the "grid" usually must have special equipment and safety devices to protect the grid components (as well as the customer's own) in case of faults (electrical short circuits) or maintenance of the grid (say voltage potential on a downed line going into an exporting customers facility). 15 Power export metering 13 provides metering which is capable of separately measuring imported and exported energy as used or required. Typically these meters 13 are a bi-directional import/export meter which can measure both how much electricity is used in the home, and how much electricity gets fed back into the grid from the solar power system. A main 20 switch 14 isolates the main power grid from the residence or dwelling sub circuits 16. Likewise, the renewable energy main switch 15 isolates the renewable energy source from the mains power supply 11 and the residence or dwelling sub circuits 16. 25 The renewable energy load compensation device 20 is designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply 11. When power is in the forward direction (consumption) the load compensation device 20 will first connect solar string 41 with the inverter 25 and solar array 26 to feed the sub-circuits 16. Alternatively, 30 if power is in the forward direction (consumption) and the system is configured for export then load compensation device 20 will first connect solar string 41 with the inverter 25 and solar array 26 designed and sized to the agreed feed in tariff to export renewable energy fed to the grid. As is shown in Figure 5 when configured for export of energy to the mains power supply 11, solar string 41 14 does not include contactor K1. If further forward power or consumption is generated by sub circuits 16 the load compensation device 20 will energise further solar strings 42, 43, 44, 45 to compensate for the usage of load from the mains power supply 11. Likewise, when forward power or load decreases the 5 load compensation device 20 will isolate the further solar strings 42, 43, 44, 45 to prevent over generation from the renewable energy source 26. If no load is sensed by the load compensation device 20, the first solar string 41 will also be isolated. 10 In order to isolate and energise the solar strings 41, 42, 43, 44, 45 the renewable energy load compensation system 10 uses contactors 24 (K1 to K5) to energise or isolate each solar string. A contactor 24 is an electrically controlled switch used for switching a power circuit. The contactor 24 is controlled by an energising means or circuit 22, with separate circuits 22 used 15 to energise each of the K1 to K5 contactors 24. The generator (renewable energy) services board 40 also incorporates string isolation switches 23 which open should an error condition or protection device energise due to an over or under voltage, current or frequency event occur. The switch 23 will isolate and protect each solar string 41, 42, 43, 44, 45 to protect the inverters 25 and solar 20 array 26. Figure 3 shows a detailed schematic drawing of the renewable energy load compensation system 10 for a three phase mains power supply 11. With any multi-phase system the components are typically the same for each phase 25 and similar to that of a single phase system. In Figure 3 the load compensation device 20 shows the sensing of the load using current sensing 30 in the three phases. Current transformers (CT) 31, 32, 33 are used for measurement of electric currents in each of the phases. 30 As discussed above the sensing of the load in the mains supply 11 can be performed by either current transformers or voltage transformers (VT) (also known as potential transformers (PT)), which are known as instrument transformers. When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current 15 accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer also isolates the measuring instruments from what may be very high voltage in the monitored circuit. 5 Figure 3 also shows a number of circuit breakers 19, 21, 23 used to protect the respective circuits. The circuit breakers 19, 21, 23 are typically an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Circuit breaker 19 provides a 10 power input 18 to be fed to the load compensation device 20 to provide AC power when the renewable energy source 26 is connected. Further protection devices 27, 28, and 29 are used to isolate and protect the respective components from the system 10. 15 Figure 4 shows the three phase system of Figure 3 with inverters 25 on each phase. This provides the added advantage of being able to compensate the load on a single phase without affecting the other two phases. Therefore any one or more of the phases of a multiple phase system can be implemented to compensate for the load on that phase. 20 Figures 5 to 9 show the operation of respective parts of the renewable energy load compensation system 10. Figure 5 illustrates the connection of each string 41, 42, 43, 44, 45 of the renewable energy source 26 with string 41 connected for export of energy to the mains power supply 11 in line with the 25 agreed feed in tariff for the system 10. Figure 6 shows a similar schematic to Figure 5 however all inverters 25 are connected through the energising of contactors 24 and therefore there is no export of renewable energy to the mains power supply 11. 30 Figure 7 shows the switching of the coils 22 to control the contactors 24 (K1 to K5). For example, when consumption is generated by sub circuits 16 as sensed by the voltage or current sensing 30, 34 the load compensation device 20 will energise solar strings 41, 42, 43, 44, 45 to compensate for the usage of load from the mains power supply 11. Figure 8 (voltage sensing 34) and Figure 16 9 (current sensing 30) show the two forms of sensing the load on the mains power supply 11. In Figure 8 the voltage 35, 36, 37 on each phase of a three phase system is sensed and returned to the load compensation device 20. The voltage sensing 34 can be connected or isolated from the system 10 by circuit 5 breaker 38. Figure 8 shows current sensing 30 using CT's 31, 32, 33 on each phase of a three phase system. Figures 10 and 11 show flow charts of the control process and timing for the renewable energy load compensation system 10. Figure 10 shows only the 10 energising and de-energising of the K1 contactor. The process starts at step 50 at which OkW of energy is being produced. If OkW of energy is produced for greater than 10 seconds then there is no consumption and contact or K1 remains de-energised. At step 52 if consumption is greater than X kW for a preset time period of 90 seconds then contactor K1 energises at step 53. At 15 step 55 if consumption decreases to 0 kW or greater for more than 10 seconds then K1 de-energises at step 56 and remains de-energised if no consumption is sensed at step 58. At step 54, K1 remains energised as consumption is greater than X kW for a preset period of greater than 90 seconds. Step 56, K1 remains de-energised, however if load becomes greater than X kW for the preset time 20 period then K1 is energised at step 53. Figure 11 shows the flow chart for the energising and de-energising of all strings 41, 42, 43, 44, 45. Steps 50 to 58 are the same as Figure 10 and each string as represented by steps 60, 61, 62 and 63 are replicated with the 25 exception that if energy continues above X kW then each contactor K1 to K5 are energised respectively. Likewise as energy decreases below X kW contactors K5 to K1 are de-energised. Alternatively and an advantage of the present system comprising a programmable microprocessor in the load compensation device 20, allows the order of energising to be changed and any 30 order may be programmed into the load compensation device 20. Figure 12 illustrates another use of the present invention with the renewable energy load compensation system used as a master and slave installation. Master/slave is a model of communication where one device or 17 process, the master 70 has unidirectional control over one or more other devices, slaves 73, 74, 75. The master load compensation device 70 has control over each slave 73, 74 and 75. In each dwelling 46 a slave load compensation device 73, 74, 75 is controlled by respective contactors 72 (S1 to 5 S3) which are energised and de-energised by the master load compensation device 70. Each dwelling has a renewable energy source 26 (PV array), inverter 25, sub-circuits 16, and slave isolation switch 23. The master load compensation device 70 is in control of a mini-grid of grid connected renewable energy installations as well as other loads 16. Like the load compensation 10 device 20 the master load compensation device 70 has been designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply 11. For example if export of renewable energy is connected, when power is 15 in the forward direction (consumption) the master load compensation device 70 will connect first slave 73 with the inverter 25 and solar array 26 designed and sized to the agreed feed in tariff to export renewable energy fed to the grid. If further forward power or consumption is generated by sub circuits 16 the master load compensation device 70 will energise further slaves 74, 75 to 20 compensate for the usage of load from the mains power supply 11. Likewise, when forward power or load decreases the master load compensation device 70 will isolate the further slaves 74, 75 to prevent over generation from the renewable energy source 26. If no load is sensed by the master load compensation device 70 the first slave 73 will also be isolated. It should be 25 identified by a person skilled in the art that any number of slaves may be implemented and the order in which each slave is energised may also be changed, and that the present invention only illustrates three slaves by way of example only. 30 An example use of the master slave configuration is in a caravan park with rental caravans 46 and permanent sites with privately metered installations 16 and other amenities 16 (other loads) such as toilets etc. As illustrated in Figure 12 the master load compensation device 70 may monitor and control the rental sites as slaves.

18 Another optional addition to the present system is the use of a data network (not shown) to monitor and control the transmission of data around the system 10. By way of example and as illustrated in Figure 12 the master controller 70 controlling each slave load compensation device 73, 74, 75 in 5 respective unit installations 46. A data network is an electronic communications process that allows for the orderly transmission and reception of data in this present invention this includes load sensed on the mains power supply 11 and control signals to the respective installations 46. The data network could be either a private data network or a public data network designed to transfer data 10 between various installations 46. The present invention has been illustrated as a new installation in which the load compensation device 20 and 70 are installed in various new installations with associated components. The present invention also extends 15 to an installation in which only the conventional inverter is replaced (Figure 13) or a modulator device off the inverter (Figure 17) is installed. In Figure 13 an inverter 90 comprising the load compensation device 20 which can measure and monitor the load on the mains power supply 11 by 20 voltage and current sensing 30, 34 and adjust the power output at the inverter 90. All of the components being installed in the inverter 90 during manufacture. The present embodiment has been designed so that the conventional inverter 25 can be replaced by inverter 90 in accordance with another embodiment of the present invention. 25 Figures 14 to 16 also show single line diagrams of the present embodiment in which inverter 90 is installed as well as showing the voltage (Figure 16) and current sensing (Figure 15) and inputs into the inverter 90 from the voltage and current sensing circuits. 30 Figure 17 shows a further arrangement in which the load compensation system 100 is installed as a modulator device 101 off the inverter 25. In this arrangement the device 101 is a separate device with the same capabilities as the previous load compensation device 20, but supplied separately from the 19 inverter 25. In this arrangement the device 101 is easily used as a retro-fit of an existing renewable energy installation. Retrofit projects typically replace or add equipment to existing installations to be able to continuously measure and monitor both forward and reverse direction of power flow in the mains power 5 supply 11. The modulator device 101 provides a variable output to the mains supply 11 and to the loads 16 and can measure and monitor the load on the mains power supply 11 by voltage and current sensing 30, 34 and adjust the power output at the modulator 101 in line with the load sensed. 10 Figure 18 to 20 show block diagrams of the respective load compensation devices 20, 90, 100. In Figure 18 shows the load compensation device 20 including a microprocessor 111, a display 110, voltage and current sensing input terminals 112 with inputs from the voltage and current sensing 30, 34. Control relays 22 and output terminals 115 which connect the control 15 signal outputs 113 are also provided in load compensation device 20. Figure 19 illustrates a block diagram of inverter 90 including microprocessor 111, a display 110, voltage and current sensing input terminals 112 with inputs from the voltage and current sensing 30, 34. Inputs from the 20 renewable energy source 26 (PV arrays) are fed to input terminals 116 and then to both the microprocessor 111 and the electronic control board/regulator 114 of the inverter 90. Outputs 113 and control relays including output terminals are also provided at 115. 25 Figure 20 illustrates the modulator 101 which includes input from the inverter 25 and renewable energy source and all the remaining componentry of the load compensation device 20 including a microprocessor 111, a display 110, voltage and current sensing input terminals 112 with inputs from the voltage and current sensing 30, 34. The electronic control board/regulator 114 30 of the load compensation device 20 and outputs 113 and control relays including output terminals are also provided at 115.

20 Figures 1 and 6 do not include export of energy to the mains power supply 11. The K1 contactor may be programmed so that a feed in tariff and export are provided. 5 The inverters 25 used in the present invention and as illustrated in Figure 3 show a polyphase inverter 25. Alternatively the present invention may also be implemented using single phase inverters 25 on each phase. This provides the added advantage of being able to compensate the load on a single phase without affecting the other two phases. Therefore any one or more of the 10 phases of a multiple phase system can be implemented to compensate for the load on that phase. Alternatively the inverter 25 can include a micro-inverter 120 as shown in Figure 21 for each panel of a solar array 26. A micro-inverter 120 converts 15 direct current (DC) electricity from one or two solar panels 26 of a solar array to alternating current (AC). The output from several micro-inverters 120 is combined and often fed to the electrical grid. Micro-inverters 120 contrast with conventional string or central inverter devices, which are connected to multiple solar panels. 20 Micro-inverters 120 have several advantages over conventional central inverters. The main advantage being small amounts of shading, debris or snow lines on any one solar panel, or even a complete panel failure, does not disproportionately reduce the output of the entire array. Each micro-inverter 25 harvests optimum power by performing maximum power point tracking for its connected panel. By way of example only, a micro-inverter 120 system can be implemented as shown in Figure 21 where each micro-inverter 120 is treated as 30 a slave and is controlled by a master load compensation device 125. Likewise each micro-inverter 120 may have its own load compensation device 20 for each photovoltaic module 26. This would be similar to the embodiment described with reference to Figures 13 to 16 in which a micro-inverter 120 would replace inverter 90.

21 The present invention also allow the consumer to continuously measure, control, and monitor both forward and reverse direction of power flow in the mains power supply. With the use of a data network connecting a computer system having a computer readable program stored on the computer the 5 renewable energy load compensation system can be automated or manually controlled by the consumer with the use of a computer. Also and as is sometimes the case, when the renewable energy load compensation system is not connected for export of energy to the mains supply 10 the inverters may be configured to whatever value desired by the consumer. For example, a site may be configured for 6.73 kW reverse power on one phase with 5.28 kW on a second phase and 3.45 kW on the third phase. For all of the above options the circuitry has been designed to be 15 energised to connect. Therefore if any fault or failure in the system occurs all items are protected on de-energise. The present invention provides a number of additional programmed protection devices such as over voltage protection, under voltage protection, over frequency protection, under frequency protection, differential frequency protection between the phases, phase failure protection 20 and reverse power flow protection. All of the above are programmable into the load protection device in order to further protect and isolate the system should any one of the faults occur. This also applies to all mechanical isolation devices within the renewable energy load compensation systems which are designed to be energised to connect and therefore on failure or faults will be 25 de-energised to protect both the mains power supply and the renewable energy power supply and associated components. It is also envisaged that a data logger to log and graph each phase over a predetermined time scale. A data logger or data recorder is an electronic 30 device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. The data logger can be based on a digital processor (or computer). The data logger may be a small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. The data logger may interface with a 22 personal computer and utilize software to activate the data logger and view and analyse the collected data. Likewise the data logger may have a local interface device (keypad, LCD) and can be used as a stand-alone device. 5 The ability of the present invention to monitor power flow at a point and adjust the current output of the inverter is particularly important when considering the real and reactive power flow to the load and as shown in Figure 13 (inverter 90) and Figure 17 (modulator 101) the present invention also extends to the monitoring of the reactive power or power factor at the same 10 point or any other relative point and the ability to adjust the supply of reactive power, power factor or phase position of the current output to suit the load. Typically, any practical load will have resistance, inductance, and capacitance therefore both real and reactive power will flow to the load. The 15 ratio between real power and apparent power in a circuit is called the power factor. It is a practical measure of the efficiency of a power distribution system. The power factor is unity (one) when the voltage and current are in phase. It is zero when the current leads or lags the voltage by 90 degrees. Power factors are usually stated as "leading" or "lagging" to show the sign of the phase angle 20 of current with respect to voltage. The renewable energy load compensation system of Figures 13 and 17 which incorporates the monitoring of the power factor, the power factor would typically be between - 0.8 to + 0.8 monitored at the monitoring point and 25 supported by the output of the inverter 90 or modulator 101. ADVANTAGES By using renewable energy systems to power your home or business 30 you are reducing greenhouse gas emissions and your electricity bills. The present invention provides the added advantage of being able to allow additional solar generation in an installation to be used for the purpose of compensating the load from the grid only. Furthermore the present invention monitors and protects the grid by way of isolation from unwanted exporting of 23 over generated renewable energy. The load compensation device in accordance with the present invention allows for the continuous measuring and monitoring of forward and reverse direction of power supply in the mains power supply of an installation. The present invention manages and limits the export 5 of power to the mains supply by way of isolation. Likewise both the renewable energy source and componentry and the mains power componentry are energised to connect therefore any fault or failure in the system all items are protected on de-energise. 10 The present invention also extends to the retrofitting of existing installations therefore allowing for the extended ability to easily fit the present invention to an inverter in a renewable energy system. Likewise upon failure of an inverter the present invention extends to the fitting of a new inverter with the load compensation circuitry installed within the inverter. 15 The ability of the present invention to monitor power flow at a point and adjust the current output of the inverter is particularly important when considering the real and reactive power flow to the load. A number of advantages exist in the ability to monitor the reactive power or power factor at 20 the same point or any other relative point and the ability to adjust the supply of reactive power, power factor or phase position of the current output to suit the load. Apart from power factor correction, current loads and minimising voltage rises the present invention also allows the network or retailer who supplies the power the ability to minimise voltage rise issues on the network created by the 25 renewable energy site, minimise power quality issues transposed to the renewable energy site and also minimise taking needed reactive power from the grid. For the networks, suppling reactive power is an expense and is not something they can properly measure and charge for. The present invention provides a consumer with the ability to manage the output of their renewable 30 energy supply using the AC side and the load on the mains supply.

24 VARIATIONS It will be realized that the foregoing has been given by way of illustrative example only and that all other modifications and variations as would be 5 apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. 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 10 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".

Claims (33)

1. A renewable energy generation load compensation system comprising: a mains power supply; 5 a renewable energy source comprising: a first series comprising at least one renewable energy supply connected to a first inverter; at least one further series comprising at least one further renewable energy supply connected to a further inverter; and 10 a contactor connected to each said inverter to electrically isolate and connect each said series to and from the system; a controllable switch comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; 15 an energising means connected to each said contactor to isolate and energise each said series; and a microprocessor programmable to control the energising and isolation of each series; a domestic power supply network adapted to be connected to either the 20 mains power supply or the renewable energy source; and wherein said first series and inverter are sized and connected to export renewable energy to the mains power supply, and said further series and inverters are switched depending on the load or consumption on the mains power supply. 25

2. The system as claimed in claim 1, wherein the size of the first series and inverter are determined by the requisite feed in tariff.

3. The system as claimed in claim 1 or claim 2, wherein the system is 30 connected to any single, two or three phase mains power supply.

4. The system as claimed in any one of the preceding claims, wherein said controllable switch is designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply. 26

5. The system as claimed in claim 4, wherein when power is in the forward direction the controllable switch will connect said further series to compensate for the usage of load from the mains power supply. 5

6. The system as claimed in claim 4, wherein when forward power or load decreases the controllable switch will isolate said further series to prevent over generation from the renewable energy source.

7. The system as claimed in any one of the preceding claims, wherein the 10 system further comprises any one or more of the following protection devices: (i) over voltage protection; (ii) under voltage protection; (iii) over frequency protection; (iv) under frequency protection; 15 (v) differential frequency protection between the phases; (vi) phase failure protection; or (vii) reverse power flow protection.

8. The system as claimed in claim 7, wherein should any one of the 20 protection devices be energised the system will isolate and protect the mains power supply.

9. The system as claimed in any one of the preceding claims, wherein the system further comprises an event logger to monitor and analyse each phase of 25 the mains power supply.

10. The system as claimed in any one of the preceding claims, wherein the controllable switch may be programmed to allow the requisite feed in tariff to be exported with all series connected to the mains power supply. 30

11. The system as claimed in any one of the preceding claims, wherein the system will automatically disconnect from the mains power supply in order to protect the mains power supply from an islanding fault. 27

12. The system as claimed in any one of the preceding claims, wherein the system further comprises a grid load measurement module which measures the grid load of the mains power supply by measuring the frequency of the mains power supply. 5

13. The system as claimed in any one of the preceding claims, wherein the renewable energy source is any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising at least one wind turbine; or 10 (iii) a hydro energy source comprising a water source using the gravitational force of falling or flowing water.

14. The system as claimed in any one of the preceding claims, further comprising a data network for transferring information between the controllable 15 switch, the mains power supply, the renewable energy source, and the domestic power supply network.

15. A method comprising managing renewable energy generation load compensation by linking together a mains power supply, a renewable energy 20 source, and a domestic power supply network through a controllable switch; said method comprising the steps of: (i) monitoring the load on the mains power supply; (ii) connecting a first series and an inverter to export energy to the mains power supply; 25 (iii) sensing the load is in the forward direction connecting further series and inverters to compensate the usage of the load in the mains power supply; (iv) sensing a decrease in the load or forward power and isolating the further series to prevent over generation from the renewable energy source. 30

16. The method as claimed in claim 15, and further comprising any one of the features of claims 2 to 14 of the first aspect. 28

17. A renewable energy generation load compensating apparatus comprising a computer readable media which stores computer instructions; and computer instructions stored on said media accessibly to a microprocessor of a controllable switch device which links together a mains power supply, a 5 renewable energy source, and a domestic power supply network through the controllable switch, the instructions when executed on the microprocessor: (i) monitoring the load on the mains power supply; (ii) connecting a first series and an inverter to export energy to the mains power supply; 10 (iii) sensing the load is in the forward direction connecting further series and inverters to compensate the usage of the load in the mains power supply; and (iv) sensing a decrease in the load or forward power and isolating the further series to prevent over generation from the renewable energy source. 15

18. A system for managing renewable energy generation load compensation comprising: a mains power supply; a master controllable switch and at least one slave controllable switch; 20 at least one dwelling comprising said at least slave controllable switch, said at least one dwelling comprising: a renewable energy source comprising at least one renewable energy source, at least one inverter, a contactor connected to each said inverter to isolate and connect each said dwelling to and from the system, and a 25 domestic supply network connected to either the renewable energy source or the mains power supply; wherein said master controllable switch controls the system by: (i) monitoring the load on the mains power supply; (ii) connecting at least one dwelling to export energy to the 30 mains power supply; (iii) sensing the load is in the forward direction connecting a further dwelling to compensate the usage of the load in the mains power supply; 29 (iv) sensing a decrease in the load or forward power and isolating the further dwelling to prevent over generation from the renewable energy source. 5

19. The system as claimed in claim 18, wherein each master controllable switch and slave controllable switch further comprises: a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising coil connected to each said contactor in each dwelling to 10 isolate and energise each said dwelling; and a microprocessor programmable to control the energising and isolation of each dwelling.

20. The system as claimed in claim 18 or claim 19, wherein the at least one 15 dwelling connected to export energy from the renewable energy source to the mains power supply is rated and size determined by the requisite feed in tariff.

21. The system as claimed in any one of claims 18 to 20, wherein the system is connected to any single, two or three phase mains power supply. 20

22. The system as claimed in any one of claims 18 to 21, wherein said master controllable switch is designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply. 25

23. The system as claimed in any one of claims 18 to 22, wherein the renewable energy source is any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising at least one wind turbine; or (iii) a hydro energy source comprising a water source using the 30 gravitational force of falling or flowing water.

24. The system as claimed in any one of claims 18 to 23, further comprising a data network for transferring information between the master controllable 30 switch, the slave controllable switch, the mains power supply, the renewable energy source, and the domestic power supply network.

25. The system as claimed in any one of claims 18 to 24, wherein the 5 system further comprises a multi-unit installation comprising two or more dwellings.

26. The system as claimed in claim 25, wherein each dwelling comprises a slave controllable switch and the multi-unit installation has the master 10 controllable switch to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply for the multi-unit installation.

27. A renewable energy generation load compensation system comprising: 15 a mains power supply; a renewable energy source with at least one renewable energy supply; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; an inverter connected to each said renewable energy source, said 20 inverter comprising: a contactor connected to each said inverter to electrically isolate and connect each said renewable energy supply to and from the system; a controllable switch comprising: 25 a voltage and/or a current sensing devices to sense the load on the mains power supply; an energising coil connected to each said contactor to isolate and energise each said renewable energy supply; and 30 a microprocessor programmable to control the energising and isolation of each said renewable energy supply; and wherein at least one of said renewable energy supplies is sized and connected to export renewable energy to the mains power supply, and said 31 further renewable energy supplies are switched depending on the load or consumption on the mains power supply.

28. The system as claimed in claim 27, wherein the system is connected to 5 any single, two or three phase mains power supply.

29. The system as claimed in claim 27 or claim 28, wherein said inverter and said controllable switch are designed to continuously measure and monitor both forward and reverse direction of power flow in the mains power supply. 10

30. The system as claimed in any one of claims 27 to 29, wherein the renewable energy source is any one or more of the following: (i) a solar energy source comprising at least one photovoltaic panel; (ii) a wind energy source comprising at least one wind turbine; or 15 (iii) a hydro energy source comprising a water source using the gravitational force of falling or flowing water.

31. An integrated renewable energy system, comprising: a mains power supply; 20 a renewable energy source with at least one renewable energy supply and an inverter connected to the each renewable energy supply; a domestic power supply network adapted to be connected to either the mains power supply or the renewable energy source; a load compensation device comprising: 25 a contactor connected to each said inverter to electrically isolate and connect each said renewable energy supply to and from the system; a controllable switch comprising: a voltage and/or a current sensing devices to sense the load on the mains power supply; 30 an energising coil connected to each said contactor to isolate and energise each said renewable energy supply; and a microprocessor programmable to control the energising and isolation of each said renewable energy supply; and 32 wherein at least one of said renewable energy supplies is sized and connected to export renewable energy to the mains power supply, and said further renewable energy supplies are switched depending on the load or consumption on the mains power supply. 5

32. The system as claimed in claim 31, wherein the load compensation device is retrofitted to any type or size inverter to facilitate the load compensation on the mains power supply. 10

33. The system as claimed in claim 31, wherein the load compensation device is part of the inverter for the load compensation on the mains supply.