NZ588536A

NZ588536A - Adjusting a load of a power generation device to maximise power transfer or to eliminate stall

Info

Publication number: NZ588536A
Application number: NZ588536A
Authority: NZ
Inventors: Murray Raymond Wyma; Michael Richard Mccormick
Original assignee: Enatel Ltd
Priority date: 2010-10-15
Filing date: 2010-10-15
Publication date: 2012-05-25
Also published as: WO2012050462A2; WO2012050462A3

Abstract

To attain maximum and optimum power transfer from an engine driven generator to an electrical load which includes both a primary load and an energy storage load, the generator being connected to the load via a load balancing circuit, output characteristics (such as generator output frequency and RMS voltage) indicative of the stall point of the generator engine are measured. Whilst the output characteristics are tracked the load balancing circuit is adjusted to increase the load on the generator so as to determine the stall point of the engine of the generator, then the load balancing circuit is adjusted to achieve a maximum or optimum power transfer to the load on the basis of preventing the engine from reaching the determined stall point. The load may be a telecommunications base station powered by a battery which is recharged by an intermittently operated engine powered generator.

Description

<div class="application article clearfix" id="description"> James & Wells Ref: 46026 Received at IPONZ 17 February 2011 POST-DATED UNDER SECT. 12(3) to 15 October 2010 PATENTS FORM NO. 5 Fee No. 4: $250.00 PATENTS ACT 1953 COMPLETE SPECIFICATION IMPROVEMENTS IN AND RELATING TO HYBRID POWER SUPPLY APPLICATIONS WE Enatel Limited; of 321 Tuam Street, Christchurch; a New Zealand Company; and Murray Raymond Wyma, of 35 Bourne Crescent, Papanui, Christchurch; a New Zealand Citizen; and Michael Richard McCormick, of 46 Breezes Rd, Avondale, Christchurch; a New Zealand Citizen; hereby declare the invention for which I/We pray that a patent may be granted to me/us, and the method by which it is to be performed to be particularly described in and by the following statement: 1 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 IMPROVEMENTS IN AND RELATING TO HYBRID POWER SUPPLY APPLICATIONS TECHNICAL FIELD The present invention relates to improvements in and relating to hybrid power applications. In particular the present invention relates to hybrid power supplies used with 5 off grid power systems. BACKGROUND ART Hybrid power supply systems' comprising a generator and battery bank are commonly used in off grid power infrastructure, that is to say infrastructure that is not connected to the electrical power grid, this may be due to the economics of extending power lines to a 10 remote location. One organizational infrastructure that commonly uses hybrid power supply systems' is the telecommunications industry. Remotely located telecommunications equipment, such as radio masts for cellular services, and their associated control equipment, may be located in very remote locations and be sufficiently distant from any power supply infrastructure to 15 make any connection uneconomic. In these cases the power is typically supplied by way of a dedicated power generation device and battery storage. These systems have in the past operated from a power generation device in the form of a diesel generator or the like with battery storage for emergency back-up only. However running costs and maintenance issues associated with 24/7 operation and low load conditions of diesel 20 engines has resulted in modification of their usage to one of charging a battery bank in between periods in which the generator is powered off. When the batteries reach a predetermined level of discharge the generator is re-started and the batteries are re-charged. Due to their relatively low cost and high reliability, diesel generators are typically used, however diesel generators are generally not well suited to large load variations as they 2 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 experience reliability and efficiency issues at both the upper and lower limits of their generating capacity. Typically diesel generators should be operated at between 60 - 85% of their maximum rated load to maximize efficiency and prevent damage to the diesel engine due to low load operation. 5 The benefits associated with running a diesel generator at between 60 - 85% of its maximum load introduces a problem in that the generator needs to be closely rated to the expected load. It will be appreciated that in order to charge a battery, the battery charger must supply a higher voltage to the terminals of battery than the batteries own voltage. However, because a battery has very low internal impedance, the slightest increase in 10 charging voltage over the battery voltage results in a very large increase in charging current. It will be appreciated that for a large capacity battery bank the peak current may very high and if the generator is too closely rated it will be unable to meet the demand and will simply stall. As these systems are often automated and, in the case of off grid power systems, remote from support personnel, the generator may enter a continuous state of 15 starting and stalling, eventually leading to the collapse of service at the site. A stalling generator can only be remedied by the load current returning to within the load tolerance of the generator. Depending on the installation this may be achieved by disconnecting or otherwise disabling one or more battery chargers (typically more than one is used in an installation), or reducing the battery capacity, or by turning off one or 20 more of the loads. Once the generator has overcome the initial charge the disabled chargers/load can be reconnected and/or the battery capacity can be restored. Currently the solution to this problem is to install a larger generator so that stalling will not occur, this may prove cost effective as the increased maintenance costs associated with running a generator at low loads is typically far less than the callout fee for support 25 personnel to attend to the stalling issue. The problem with this is that the generator needs to be chosen based on each particular installation, which may have different load 3 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 requirements and different storage capacities, plus effects such as altitude on the generator performance must be taken into account. Furthermore any further expansion in the equipment installed may result in the generator once again being under rated. The ideal solution would be to provide a single standard sized generator and power supply system regardless of the load requirements. It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. James & Wells Ref: 46026 Received at IPONZ 17 February 2011 DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided a method of automatically achieving maximum and/or optimum power transfer between a power generation device and an associated load, the method including the steps of: a) continuously measuring one or more output characteristics of the power generation device; b) tracking said output characteristics to determine the point of maximum power generation; c) adjusting a load balancing circuit to achieve maximum and/or optimum power transfer based upon the determined point of maximum power generation; d) continuously repeating steps a - c; wherein the load comprises at least one primary load and an energy storage device, wherein the load is electronically connected to the power generation device by way of said load balancing circuit. According to a further aspect of the present invention there is provided a process for providing an anti-stall capability on a power generation device, comprising the steps of: a) connecting the power generation device to a load circuit via a load balancing circuit; b) adjusting the output voltage from the load balancing circuit so as to increase the current consumption of the load from the power generation device; James & Wells Ref: 46026 Received at IPONZ 17 February 2011 c) assessing whether the output characteristics produced by the power generation device are outside a predetermined ideal threshold range; if they are, performing step d), if they are not, repeating steps b - c; d) adjusting the output voltage from the load balancing circuit so as to decrease the current consumption of the load from the power generation device. Optimum power transfer between a power generation device and an associated load should be understood to mean the balance between the maximum power that can be supplied by the power generation device, whilst achieving one or more of: • maximizing the period between service intervals; • minimizing stress in terms of mechanical wear due to high and/or low loading of the generator with respect to its maximum starting capacity; • maximizing fuel efficiency (for combustion engine generators); • achieving operation within the specifications of the generator, for example in very hot or very cold environments. A power generation device includes any device which is capable of converting one form of energy into another for the purpose of generating electrical power. A power generation device may include, but should not be limited to: • solar panels; • fuel cells; • mechanical turbines - wind or water driven; • combustion engines. It will be appreciated that each of the devices detailed above exhibit one or more of: James & Wells Ref: 46026 Received at IPONZ 17 February 2011 • a peak power generating efficiency for a given environmental state; • a effective stall point; • an optimum operating point, which may be in terms of, but should not be limited to, reliability, peak power generation or maximum fuel efficiency. In especially preferred embodiments the power generation device may be an internal combustion engine driving an electrical alternator. In preferred embodiments the primary load is the associated power supply infrastructure associated with one or more telecommunications apparatus, and may include transmission lines, power supplies or the like. It will be apparent to a person skilled in the art that the primary load will vary greatly depending upon: • the type of apparatus being supplied; • the power supply infrastructure in use. In preferred embodiments the energy storage device may be a battery bank, however the energy storage device could be any other device capable of storing electrical energy for later retrieval, such as, but not limited to: capacitor bank(s), flywheel(s), thermal masses. In preferred embodiments the load balancing circuit converts the power output from the power generation device to a controlled DC voltage. In especially preferred embodiments the DC output voltage of the load balancing circuit may be adjustable on a mV scale. In preferred embodiments the load balancing circuit may be an AC - DC switch mode power supply having a controllable output voltage level. James & Wells Ref: 46026 Received at IPONZ 17 February 2011 In preferred embodiments the controllable output voltage level may be used to control the amount of power that is fed into the energy storage device and therefore indirectly control the load applied to the power generation device. It will be appreciated that the output characteristics of the power generation device that are monitored will vary depending on the particular power generation device that is used. In preferred embodiments where the power generation device is an internal combustion engine driving an electrical alternator, the output characteristics used to determine the point of maximum power generation may be any one of, or a combination of: • the AC output frequency of the generator; • the RMS output voltage of the generator; • the RMS output current of the generator. In more advanced embodiments, the generator may communicate output characteristics to a suitably programmed microprocessor associated with the load balance circuit. For example by way of serial communication, or wireless data link, such parameters may include, in addition to the above; • Fuel consumption data; • Internal overload data; • Internal state-of-health data; • Environmental conditions. A suitably programmed microprocessor should be understood to mean any device capable of executing computer instructions in order to: 8 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 • continuously measure one or more output characteristics of a power generation device to determine the point of maximum power generation of that power generation device; and • adjust an associated load balancing circuit to achieve maximum and/or optimum power transfer based upon the determined point of maximum power generation; Continuous measurement of the characteristics of AC output frequency and RMS output voltage of the generator should be understood to mean that the characteristics are measured frequently and autonomously. It will be appreciated by a person skilled in the art that a microprocessor is not capable of 'continuous' measurement, rather measurements are made at finite time intervals and at a rate which is substantially faster than the generator can irrevocably overload and hence stall. In preferred embodiments the characteristics of the power generation device are tracked to determine the point of maximum power transfer, it will be appreciated that on increasing load one or more of the output characteristics that are being tracked will diverge from a pre-determined range of acceptable operating conditions. In preferred embodiments the characteristics of the power generation device are tracked by a suitably programmed microprocessor. In the preferred embodiment of an internal combustion engine driving an electrical alternator (the combination of which will now be referred to as a generator), it will be appreciated that as the load on the alternator is increased beyond the power generating limit of that internal combustion engine/alternator combination, the AC frequency and/or RMS voltage of the output voltage from the generator will drop. James & Wells Ref: 46026 Received at IPONZ 17 February 2011 In preferred embodiments the measurement of the characteristics of AC output frequency and RMS output voltage of the generator are measured by dedicated electronic circuits. Any number of electronic circuits could be designed to perform this task and therefore the exact electronic circuits used should not be seen as being limiting. 5 From the background art it will be understood that the profile of charging current versus supply voltage is not linear for batteries. In particular, virtually no current will be supplied by the generator until the DC output voltage of the load balancing circuit becomes near to and greater than the terminal voltage of the battery. Once the battery terminal voltage has been overcome, the charge current is proportional to the voltage differential between the 10 DC voltage of the load balancing circuit and the terminal voltage of the battery and the impedance of the parallel battery load and any associated wiring (it should be noted that at this time the primary load will also be supplied by the generator). Because the impedance of the parallel battery load and any associated wiring is very low, even the slightest increase in the DC output voltage of the load balancing circuit can result in a 15 large increase in charge current. In preferred embodiments once the peak power output is reached the DC output voltage of the load balancing circuit is reduced to prevent the power generation device from stalling. In preferred embodiments once the peak power output is determined it is used to calculate 20 the point of optimum power level by applying a de-rating factor. The de-rating factor may be based on: • the environmental conditions, such as temperature; • the age of the generator; • the service history of the generator; 10 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 • the point of maximum generator efficiency; • the point of maximum generator life, • the point of minimum generator service intervals • the required rate of recharge of the battery bank, 5 In preferred embodiments the de-rating factor is substantially between 0.6 and 0.9. It will be appreciated however that in some situations it may be necessary to apply a de-rating factor outside this range so as to achieve one or more further outcomes, such as, but not limited to: • maximum fuel efficiency; 10 • minimum load due to the existence of fault conditions; • maximum charging rate. It will be appreciated that the peak power point of a generator will vary over time, for example, as the combustion engine becomes warmed up or the environmental conditions change, therefore the process of determining the peak power point can be repeated at 15 regular intervals. In some preferred embodiments an alarm may be provided if the peak power level falls below a pre-defined limit. Preferred embodiments of the present invention may provide a number of advantages over the prior art, those advantages including: 20 • reduced fuel consumption; • reduced mechanical stress on engine components; 11 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 • the ability to prevent the generator stalling due to electrical overload, • operation of the generator at peak efficiency, • periodical assessment of the maximum power capability of the generator, readjusting the load as necessary, • providing alarms when the generator output power is less than expected, BRIEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a pictorial representation of a typical hybrid power system; and Figure 2 shows a flow diagram of one preferred embodiment of the present invention. BEST MODES FOR CARRYING OUT THE INVENTION With respect to Figure 1, and as generally indicated by arrow 1, there is shown a hybrid power system. The hybrid power system 1 is shown supplying power to a telecommunications installation comprising an equipment rack 2 and an associated transmitter 3. For the sake of example, equipment rack 2 also contains air conditioning capabilities (not shown), thereby adding further load to the batteries. The hybrid power system 1 has a power generation device in the form of a diesel generator 4, a load balancing circuit in the form of an AC - DC switch mode power supply 5 and an energy storage device in the form of battery bank 6. 12 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 The hybrid system of Figure 1 operates in two modes, in the first mode power the generator 4 is not running and all power required to operate the equipment rack 2 and associated transmitter 3 is derived from the battery bank 6, as shown by arrow 7. In the second mode, the generator 4 is running and supplies power to AC - DC switch mode 5 power supply 5, as shown by arrow 8. The AC - DC switch mode power supply 5 provides a regulated DC output voltage which recharges battery bank 6, as shown by arrow 9 and also directly provides power to the equipment rack 2 and associated transmitter 3, as indicated by arrow 10. In prior art installations, the power requirements dictated by the load applied to the AC -10 DC switch mode power supply 5, comprise battery bank 6 and equipment rack 2 and associated transmitter 3. More advanced AC - DC switch mode power supplies 5 may include current limiting and battery management features, but they do not measure any output characteristics of the generator 4 and apply those to continuous load adjustment. This requires the generator 4 to be selected so as to have a continuous load current 15 capacity greater than the maximum expected load. Variability in the load can occur due to heavy use of equipment rack 2 and associated transmitter 3 in routing telecommunications signals, or deep discharge of battery bank 6 which causes the batteries to be charged at the maximum rate allowed by the AC - DC switch mode power supply 5. Also, variability in the power output capacity of the generator can occur due to 20 atmospheric conditions, fuel line supply problems, poor maintenance and the like. If the load applied to the AC - DC switch mode power supply 5 exceeds the power output capacity of the generator 4 the generator will stall. Whereas, in the present invention, the load balancing circuit, in the form of an AC - DC switch mode power supply 5, is capable of adjusting its DC output voltage in response to 25 changes in the output characteristics of the generator 4 as well as providing similar current limiting and battery management features to prior art AC - DC switch mode power supplies 5. Typically telecommunications equipment is supplied with a nominal regulated James & Wells Ref: 46026 Received at IPONZ 17 February 2011 48V DC supply operating at a float voltage charge point of the batteries, which is typically 54V. The electronics provided in a standard telecommunications equipment rack 2 is typically capable of operating over a voltage range of between 40 - 60V DC. The present invention takes advantage of this fact by gradually incrementing the DC voltage from 5 below the terminal voltage of the battery bank, thereby gradually increasing the power that is required from the generator by increasing the charge rate of the batteries. The current is increased until the generator 4 is detected as being at maximum load, the load current is then reduced to achieve the desired optimal generator 4 load. Figure 2 provides a flow diagram, as generally indicated by arrow 100, of the process by 10 which the hybrid power system of Figure 1 is controlled by the method of the present invention. During a first mode of operation, the generator 4 is not running and all power required to operate the equipment rack 2 and associated transmitter 3 is derived from the battery bank 6, at this time the process of Figure 2 is at stage 101 whereby the generator start conditions are assessed. It will be apparent to a person skilled in the art that there 15 are a number of conditions which if met results in the generator being started, a non-limiting list of examples being: • the battery bank has reached a predetermined discharge threshold; • a certain time period has elapsed since the last generator run cycle. • the power consumption of the equipment rack 2 and associated transmitter 3 20 exceeding a predetermined level; • an environmental condition is met, for example extreme temperatures; If one or more generator start conditions are met the generator is started, as indicated by stage 102. Stage 102 may also include monitoring of one or more characteristics of the generator to determine whether the generator is operating within specifications and is 25 sufficiently warmed up. It will be understood by a person skilled in the art that a diesel 14 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 engine operates more efficiently once it is at its optimal running temperature, therefore to apply a load prior to the engine being warmed up will result in inefficient running. Once the diesel generator is determined to be running, and sufficiently warmed up, the DC output of AC - DC switch mode power supply 5 is ramped upwards. Typically this will 5 be from a preset voltage level rather than 0V, however the exact voltage will be dictated by the particular installation and state of charge of the battery, and therefore should not be seen as being limiting. In the preferred embodiment of Figure 1 the DC output voltage of the AC - DC switch mode power supply 5 is ramped quickly upwards until a voltage is achieved just below the battery terminal voltage. If the current limit is <12.5% of the 10 predetermined current limit, then the voltage is ramped up at 50mV/500msec, and if the current is greater than this, the voltage is ramped up at 10mV/500msec. As the DC output voltage (not shown) exceeds the terminal voltage of the battery bank, the AC - DC switch mode power supply 5 begins to relieve the battery bank 6 of the load from equipment rack 2 and associated transmitter 3. The reason for this is that as the load on the battery bank 15 is reduced, the terminal voltage of the batteries increases. As the DC output voltage of the AC - DC switch mode power supply 5 increases further, the battery is eventually relieved of all load, at this point the generator 4 is providing all of the power required by the equipment rack 2 and associated transmitter 3. At this point the no load terminal voltage of the battery may well be the nominal 48V DC voltage of the equipment rack 2. 20 Increasing the voltage beyond the terminal voltage of the battery bank 6 results in a charging current into the battery bank 6. A typical battery bank 6 may be capable of consuming the entire power generating capacity of the generator used in this application. Unless a current controlled supply is used, the only mechanism by which the current is regulated, is by way of the internal impedance of the battery bank and the charging 25 capacity of the AC - DC switch mode power supply 5. Typically the internal impedance of a battery bank is very low and therefore any uncontrolled increase in the DC output 15 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 voltage of the AC - DC switch mode power supply 5 can result in large increases in current consumption and subsequently large load increases on the generator 4. Without knowing the power generating capacity of the generator 4, the only way to know whether the maximum power generating capacity has been reached is by measuring one 5 or more characteristics of the generator 4. The preferred embodiment of Figure 1 and 2 measures: • the AC frequency of the generator 4; and • the RMS output voltage of the generator. It will be appreciated by a person skilled in the art, that when the diesel engine associated 10 with a generator reaches maximum load, it loses its ability to maintain optimal rotational speed. This results in the AC frequency dropping. In addition to the frequency of the generated voltage, a generator has a limited ability to supply current. Once the upper limit of excitation of the generator winding is reached and the generator is supplying full rated power, the peak voltage of the AC output from the generator begins to drop. This results 15 in the RMS value of the output voltage falling. The process of measuring the output characteristics of the generator 4 are performed in step 103 of Figure 2. Measurement of AC frequency is well known in the art of electronics and can be performed by way of any number of contactless or physically connected devices. In the preferred embodiment measurement of the AC frequency and voltage is 20 made by resistive sensor contact with the AC source. . However, the measurement of the RMS voltage & frequency is not new to the art and can be performed in any number of ways without departing from the scope of the present invention. If the output characteristics of the generator 4 are within a pre-determined range of acceptable values, for example: 16 James & Wells Ref: 46026 Received at IPONZ 17 February 2011 • AC frequency : 50Hz +/- 2%; • RMS Voltage : 230 V +/-10%, the generator is deemed to be operating below its peak power output. The status of the optimum generator power tracking (OGPT) algorithm is assessed at step 106. When the 5 generator is first started the OGPT algorithm is always active. If OGPT is active the DC output voltage of the AC - DC switch mode power supply 5 is incremented after a short delay time, shown as steps 111 and 110. After incrementing the output voltage, step 110, the characteristics of the generator 4 are re-assessed and the process steps 103, 106, 111 and 110 repeat until the characteristics of the generator 4 diverge from the pre-10 determined range of acceptable values, for example: • the frequency falls below 49.0Hz and/or, • the RMS output voltage falls below 207 V. As soon as the generator 6 is detected as being at peak power, the DC output voltage of the AC - DC switch mode power supply 5 is dropped by 100mV (this is a user-adjustable 15 level selectable between 10mV and 500mV, and as will be apparent to a person skilled in the art, will be chosen for best fit for the application), as indicated by step 104, concurrently the peak power is recorded at step 112 and, at step 113, the optimum peak power level is calculated from the recorded peak power from step 112 and a predetermined de-rating factor, of typically between 0.6 and 0.9. 20 At step 114 the OGPT algorithm is disabled and the optimum peak power level from step 113 is set. At step 105 the DC output voltage of the AC - DC switch mode power supply 5 is adjusted to achieve the optimum peak power level determined in step 113. Because OGPT is now disabled, at step 106 the DC output voltage of the AC - DC switch mode power supply 5 is maintained at the optimum peak power level. The generator 6 stop 25 conditions are assessed at step 108, and if true (i.e. the stop conditions are met) the James & Wells Ref: 46026 Received at IPONZ 17 February 2011 generator is powered down, allowing any offline warm down period as required. Offline should be understood to mean the condition whereby the generator load is reduced to an acceptable low power level so as to allow the engine to cool slowly if required. It will also be apparent to a person skilled in the art that there are a number of conditions 5 which if met may result in the generator being stopped, a non-limiting list of examples being: • the battery bank has reached a predetermined charge level; • an environmental condition is met, for example high/abnormal engine temperature; • the power consumption of the equipment rack 2, associated transmitter 3 and 10 battery bank exceed a predetermined level; • the generator fuel or coolant supply is low. A further aspect of the present invention shown in Figure 2 is that the OGPT algorithm may be re-enabled at regular intervals to ensure that as the generator becomes further warmed up the optimum peak power level is re-calculated 110, 111. 15 In some embodiments if the calculated optimum peak power level is below a predetermined threshold an automated message may be sent informing the required service agency that the generator is operating poorly and may require servicing. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without 20 departing from the scope thereof as defined in the appended claims. 18 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> Received at IPONZ on 13 July 2011 WHAT WE CLAIM IS: 1) A method of automatically achieving maximum and/or optimum power transfer between a power generation device having a stall point and an associated load, wherein the load comprises at least one primary load and an energy storage device, wherein the load is electronically connected to the power generation device by way of said load balancing circuit, the method including the steps of: a) measuring one or more output characteristics indicative of the stall point of the power generation device; b) tracking said one or more output characteristics whilst adjusting the load balancing circuit to increase the load on the power generation device to determine the stall point of the power generation device; c) adjusting the load balancing circuit to achieve maximum and/or optimum power transfer based upon the determined stall point of the power generation device. 2) The method as claimed in claim 1, wherein the power generation device is an internal combustion engine driving an electrical alternator. 3) The method as claimed in either claim 1 or claim 2, wherein the energy storage device is a battery bank. 4) The method as claimed in any one of claims 1 - 3, wherein the load balancing circuit is an AC - DC switch mode power supply having a controllable DC output voltage level. 5) The method of claim 4, wherein the controllable DC output voltage is adjustable on a mV scale. 19 Received at IPONZ on 13 July 2011 The method as claimed in either one of claim 4 or claim 5, wherein the controllable output voltage level of the AC - DC switch mode power supply is used to control the amount of power that is fed into the energy storage device and therefore control the load applied to the power generation device. The method as claimed in any one of claims 4 - 6, wherein once the stall point is determined the DC output voltage of the load balancing circuit is reduced to prevent the power generation device from stalling. The method as claimed in any one of claims 2, and claims 3-7 when dependent on claim 2, wherein the output characteristics used to determine the point of maximum or optimum power generation is one or more of: • the AC output frequency of the generator; • the RMS output voltage of the generator; • the RMS output current of the generator. The method as claimed in claim 8, wherein the output characteristics used to determine the point of maximum or optimum power generation are communicated to a microprocessor from the internal combustion engine driving an electrical alternator. The method as claimed in any one of claims 1 - 8, wherein the output characteristics of the power generation device are tracked by a microprocessor. The method as claimed in either one of claim 9 or claim 10, wherein once the stall point is determined it is used to calculate a point of optimum power by applying a de-rating factor. 20 Received at IPONZ on 13 July 2011 12) The method as claimed in claim 11, wherein the de-rating factor is substantially between 0.6 and 0.9. 13) The method of any one of the preceding claims, wherein the method includes the further step of: d. periodically repeating steps a-c to re-determine the stall point of the power generating device. 14) A process for providing an anti-stall capability on a power generation device exhibiting a stall point and capable of producing one or more output characteristics representative of said stall point, the process including the steps of: a) connecting the power generation device to a load circuit via a load balancing circuit; b) monitoring the characteristic(s) representative of the power generation devices stall point whilst automatically adjusting the output voltage from the load balancing circuit so as to increase the power supplied to the load from the power generation device until one or more output characteristics produced by the power generation device is/are outside a predetermined ideal threshold range; and ; d) adjusting the output voltage from the load balancing circuit so as to decrease the power consumption of the load from the power generation device and thereby preventing the power generation device from stalling. 15) A method of automatically achieving maximum and/or optimum power transfer substantially as described herein with reference to any drawings and/or examples thereof. 21 Received at IPONZ on 13 July 2011 A process for providing an anti-stall capability on a power generation device substantially as described herein with reference to any drawings and/or examples thereof. Enatel Limited; and Murray Raymond Wyma; and Michael Richard McCormick by their authorised agents JAMES & WELLS INTELLECTUAL PROPERTY 22 </div>