Method for powering an energy network
Patent Information
- Application Number
- EP2023790241
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-10-05
- Filing Date
- 2023-09-28
- Publication Date
- 2025-08-13
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Title of the invention: Method for supplying an energy network
[0003] The invention relates to the energy supply of an energy network by means of an intermittent energy source and an energy storage system.
[0004] Under certain conditions, particularly in isolated energy systems such as those located on islands, the electricity system operator requires commitments from operators of energy plants located on the system regarding the amount of energy that the plants plan to supply to the system over predetermined time periods during a day, so that the operator can have a forecast of the energy that will be available at any given moment on the system. Each operator must then respect its commitments, supplying the system with the amount of energy it has committed to over each planned time period during the day.However, for a power plant producing energy solely by means of an intermittent energy source, such as solar energy, the energy supplied to the electricity grid depends entirely on the availability of this energy source, so it is difficult to meet commitments without resorting to other means. In particular, a storage system, such as batteries, is associated with the intermittent energy source to store part of the energy from the intermittent energy source and to discharge it into the electricity grid at the appropriate times.
[0005] To decide on the discharge instruction of the storage system into the network, a state-of-the-art solution is to discharge the storage system as often as necessary, if the intermittent energy source is not sufficient, so that at each instant the quantity of energy supplied to the network by the power plant is equal to the quantity of energy to which the power plant is committed over the current period of time.
[0006] A disadvantage of this strategy is that it places a heavy strain on the storage system for its discharge. The storage system wears out, becomes less efficient, and may even need to be replaced. As a consequence, a storage system is only guaranteed by its manufacturer for a certain number of charges and discharges, beyond which any incident exposes the plant operator to uninsured damages.
[0007] The invention aims in particular to make it possible to supply a predetermined quantity of energy to an energy network, by means of an intermittent energy source, while limiting as much as possible the discharges of an energy storage system. To this end, the invention relates to a method for supplying energy to an energy network, comprising, for supplying the network by means of an intermittent energy source and an energy storage system, the following steps:
[0008] - determination of an optimal quantity of energy to be supplied to the network by a predetermined future time;
[0009] - determination of a minimum quantity of energy which should be supplied to the network by the future instant, this minimum quantity being less than the optimal quantity of energy;
[0010] - forecast of a hypothetical quantity of energy which could be supplied to the network by a future instant, assuming that there is no discharge into the network, by this future instant, of energy from the storage system;
[0011] - in the case where the determined hypothetical quantity of energy is greater than or equal to the minimum quantity of energy to be supplied to the network at the future time, supply of energy to the network only from the intermittent energy source, without discharging the storage system.
[0012] Thus, an optimal value and a minimum value of the quantity of energy to be supplied to the network are considered and, even if the forecast of the hypothetical quantity of energy indicates a quantity supplied which risks being lower than the optimal quantity of energy at the future instant, the storage system is not discharged as long as this hypothetical quantity of energy is higher than the predetermined minimum value, while waiting for the evolution of the situation. In this way, a possible discharge of the storage system is delayed to a later instant, a later instant where either the discharge will be triggered in a situation which remains acceptable, or the intermittent source of energy will again supply a quantity of energy sufficiently high to reach the desired, optimal quantity of energy supplied to the network without having to use the storage system.In other words, rather than using the storage system as soon as the current quantity of energy transmitted to the network is less than a forecast quantity, we anticipate what the future evolution of the quantity transmitted will be based on current conditions and, if this future evolution is not unreasonable, we do not use the storage system and thus give the intermittent source a chance to provide enough energy again when the time comes, so as to respect the forecast on average. Thanks to the minimum quantity to be respected and this anticipated management of the quantity supplied to the network, we therefore save the storage system while optimizing the transmission of energy to the network.
[0013] Other optional features follow, taken alone or in combination.
[0014] Advantageously, the method comprises, before the step of supplying energy to the network, a step of determining an energy power to be supplied by the intermittent source, based on the optimal quantity of energy and not on the minimum quantity of energy. Thus, given that the hypothetical quantity of energy is greater than the minimum quantity to be supplied to the network at the future instant, the optimal quantity of energy is targeted for this future instant and without discharging the storage system. In other words, the power setpoint aims to use the intermittent source alone to try to achieve the optimal quantity of energy at the future instant.
[0015] Preferably, in the case where the hypothetical amount of energy is less than the minimum amount of energy to be supplied to the network at the future time, the method comprises a step of supplying, into the network, energy from the intermittent energy source and energy from the storage system by discharging the storage system.
[0016] So, in this case, the storage system is allowed to be discharged into the energy network. The storage system is therefore used only in the case where it is identified that, in the future, the amount of energy is likely to be lower than the optimal amount of energy but the minimum amount of energy to be supplied to the network. Thus, rather than using the storage system at all times, it is used only in this case in order to avoid an amount of energy straying too far from the desired energy trajectory.
[0017] In this case, advantageously, before the energy supply step, the method comprises a step of determining an energy power to be supplied from the intermittent energy source and from the discharge of the storage system, based on the minimum quantity of energy to be achieved and not on the optimal quantity of energy.
[0018] In this case, we want to reach the minimum quantity at the future time, not the optimal quantity. This way, we avoid discharging the storage system too much.
[0019] Advantageously, considering a predetermined period of time, the steps of determining the optimal quantity of energy and the minimum quantity of energy are implemented at the beginning of the period of time and in advance for each instant of the period of time, while the step of determining the hypothetical quantity of energy is implemented at regular intervals during this period of time considering a past quantity of energy supplied to the network since the beginning of this period.
[0020] Thus, the quantities to be respected are defined once and for all at the start of the time period, then the power instructions to be supplied to the network are gradually defined depending on the situation with regard to these objectives.
[0021] Preferably, the method comprises, to determine the minimum and optimal quantities of energy at the start of the time period and for each instant of this period, a step of constructing an affine line corresponding to the minimum quantity of energy during this period and another affine line corresponding to the optimal quantity of energy during this period. Thus, these lines correspond to what would be quantities of energy supplied in a perfectly linear manner, that is to say in accordance with a constant power. The quantity of energy actually transmitted must be located at each instant between these lines to be close to the optimum and never below the minimum, so as to avoid too much underproduction penalizing an operator, but tolerating a certain underproduction to avoid too regular discharges of the storage system.
[0022] Advantageously, prior to the first steps set out, the method comprises the following steps:
[0023] - determination of the optimal quantity of energy to be supplied to the network based on a prior commitment to supply a quantity of energy to the network over a predetermined period of time,
[0024] - determination of the minimum quantity of energy that should be achieved based on an average energy power allowing the absence of financial penalty for under-supply of energy on the network or based on the optimal quantity of energy reduced by a predetermined value.
[0025] Thus, these quantities are based on regulatory requirements associated with the operation of an energy network and optimized to meet these requirements.
[0026] Preferably, the method comprises, to determine the energy power to be supplied to the network by the intermittent source, the following steps:
[0027] - determination of a maximum quantity of energy to be supplied to the network at the future time, greater than the optimal quantity and beyond which the network would be considered oversupplied;
[0028] - determination of the energy power to be transmitted by the intermittent source based on the maximum quantity of energy.
[0029] Thus, a maximum power not to be exceeded is also determined, in particular on the basis of regulatory or technical data, and the power supplied by the intermittent source is determined on this basis. In particular, the maximum power not to be exceeded by the intermittent energy source is determined.
[0030] Advantageously, the maximum amount of energy also comes from an affine line constructed at the beginning of the time period.
[0031] We therefore use three affine lines to determine the power instructions to be achieved over the time period.
[0032] Preferably, the hypothetical amount of energy depends on the power available at a present time from the intermittent energy source.
[0033] Thus, the hypothetical amount of energy is determined by considering that this available power will remain available for a predetermined time interval. The invention also provides an installation for supplying energy to an energy network, comprising an intermittent energy source and an energy storage system configured to implement the method described above.
[0034] Advantageously, the energy being electricity and the network being an electrical network, the source comprises at least one photovoltaic panel and / or a wind turbine and the storage system comprises at least one of the following elements:
[0035] - a battery, preferably lithium-ion type;
[0036] - a flywheel;
[0037] - a super-capacity;
[0038] - an electrolyser;
[0039] - a fuel cell.
[0040] The invention also provides a computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method described above.
[0041] Also provided according to the invention is a computer-readable recording medium comprising instructions which, when executed by a computer, cause the latter to implement the steps of the method described above.
[0042] Brief description of the figures
[0043] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:
[0044] [Fig. 1] is a diagram of an energy supply installation according to one embodiment of the invention;
[0045] [Fig. 2] is a flowchart of an energy supply method according to an embodiment of the invention;
[0046] [Fig. 3] is a graph illustrating one embodiment of the invention;
[0047] [Fig. 4] is a graph illustrating one embodiment of the invention;
[0048] [Fig. 5] is a graph illustrating one embodiment of the invention; and
[0049] [Fig. 6] is a graph illustrating one embodiment of the invention.
[0050] Detailed description
[0051] In the application, "intermittent energy" refers to energy whose availability varies over time without the possibility of control. This is the case, for example, of solar energy, available only during the day and depending on the clarity of the sky, or wind energy, available only in the presence of wind. "Intermittent energy source" therefore refers to a system or device capable of providing energy whose flows correspond to the possible capture of this intermittent energy. In particular, in the following example, this involves photovoltaic panels, which are capable of providing electrical energy corresponding to the solar energy flows received on the panels. It may also be a wind turbine, capable of providing electrical energy corresponding to the air flows received. Any intermittent energy source corresponding to this definition according to the person skilled in the art is conceivable.
[0052] Figure 1 shows an installation 1 for supplying electricity to an electrical network 2, i.e., an electrical power station. It will be referred to interchangeably as "installation" or "station" 1. Naturally, only the elements necessary for understanding the invention have been shown diagrammatically. This station 1 comprises a series of photovoltaic panels 3 and a series of lithium-ion batteries 4 for storing electrical energy. The panels 3 form an intermittent energy source and the batteries 4 an energy storage system. The photovoltaic panels 3 will therefore be referred to interchangeably as "panels", "source", or "intermittent energy source" 3, and the lithium-ion batteries 4 will be referred to interchangeably as "batteries", "system" or "storage system" 4.
[0053] This source 3 and this storage system 4 are connected to each other, the source 3 being able to transmit energy to the system 4. This source 3 and this storage system 4 are also connected to the electrical network 2 to supply electricity there. In other words, the panels 3 are configured to transmit, on instruction, to the electrical network 2 or to the batteries 4, electrical energy corresponding at most to the solar energy flows that can be processed in real time by the panels, and the batteries 4 are configured to store energy coming from these panels 3, up to a predetermined maximum energy quantity, and to discharge all or part of this energy into the electrical network 2, on instruction.
[0054] Finally, this source 3 and this system 4 are connected to computer means 5 comprising in particular a database 6 and two computer modules 7 and 8. By "computer module" is meant one or more computer programs, recorded on a recording medium not illustrated and readable by computer, intended to ensure a predetermined functionality. These means are connected to the network 2, in particular to collect network consumption data in real time.
[0055] The database 6 contains all the data necessary for the operation of the modules 7 and 8, in particular the energy, meteorological, tariff or regulatory data which will appear adequate to those skilled in the art, in particular for the implementation of the method 100 described below.
[0056] Module 7 is a planning module. It is responsible for determining what quantity of energy, or what average energy power, is to be supplied to the electricity network 2 by the source 3 over predetermined periods of time, based on prior commitments by the operator of the installation 1 but also on evolving data such as available energy, electricity payment rates, network consumption, etc. It is implemented in particular every fifteen minutes in order to optimize the electricity supply to the network. This module is not the subject of this request.
[0057] Module 8 is the subject of the request, it is the instruction module. It aims to instruct, every five seconds, source 3, system 4 or both to supply, to network 2, a determined energy power, or source 3 to supply to system 4 a determined energy power for storage. The specific objective of module 8 is to allow compliance with an objective of quantity of energy or average power to be supplied to the electrical network 2, objective determined by module 7 for different predetermined periods of time. The particularity of this module 8 is that it also aims to avoid as many discharges as possible from the storage system 4 within the network 2, in order to reduce the wear of system 4, while meeting the objectives of supplying energy to network 2. This module 8 and the manner in which this optimization is carried out will be described in more detail below.
[0058] The computer means 5 also have, even if they are not illustrated, all the characteristics allowing the proper functioning of the modules 7 and 8 associated with the database 6, in particular at least one processor, a memory, means of interaction with a user to possibly modify parameters of the modules 7 and 8, or even means of telecommunications on a communication network.
[0059] The term "electricity network 2" refers to an electricity transmission and distribution network. In particular, this refers to a network of large geographical scope, i.e., one that applies to one or more cities, or even to a region or country. In general, the invention applies to any energy transmission and distribution network of this scope.
[0060] We will first describe the context of implementation of the method 100 described below by returning to some of the elements mentioned above.
[0061] The manager of electricity network 2 requires the operator of installation 1 to provide it in advance with the quantities of energy that it undertakes to supply to network 2 during a day, in ten-minute periods. These forecasts provided to the manager can be referred to as "commitments", the operator of power plant 1 being required to respect these forecasts. In this way, and by grouping together the commitments from the various supply installations supplying network 2, the network manager has a predictability of the quantity of energy that will be available at the end of each of these periods throughout the day on this network. Naturally, the duration of the commitment time period, here ten minutes, can be different.
[0062] During the production day, operator 1 ensures that it respects its commitments, i.e., that it supplies the electricity network 2, over each commitment period, via source 3 and storage system 4, with the quantity of energy committed for that period. If the quantity of energy it supplies over a period of time is less than the quantity to which it is committed, it is financially penalized by the manager. If the quantity of energy produced is greater than its commitment, it is not remunerated for this surplus by the manager and therefore suffers a loss of earnings.
[0063] To meet these commitments, module 7 identifies, throughout the day, as mentioned above, energy supply objectives re-evaluated every fifteen minutes, based on available data, in particular the current weather and short-term weather forecasts. For example, module 7 may determine that it is preferable to supply less energy than expected to network 2 for a few minutes and store this energy in system 4, even if it means receiving a slight financial penalty for the current commitment period, in order to anticipate a significant unavailability of energy during a future period and therefore avoid a heavier financial penalty at that time.
[0064] As an output, module 7 provides module 8 with an average power target to be supplied to the electricity network during predetermined time periods. These time periods correspond to the commitment periods, but may alternatively correspond to other predetermined time periods, the final objective being to respect the average powers to be supplied during the commitment periods.
[0065] Alternatively, rather than assigning an average power, it could be a quantity of energy, a quantity of energy corresponding to a power supplied over a certain period. An average power to be supplied over a period therefore corresponds to a determined quantity of energy supplied over this entire period.
[0066] The input data available to the module 8 are in particular this average energy power to be supplied during each period of time or the quantity of energy to be supplied during this period, the available power from the source 3 at each instant, and the state of the load of the system 4 at each instant. The output data of this module 8 is an instruction for supplying energy to the source 3 intended for the network 2 or the system 4 (supply called in this case “load”), and a possible instruction for discharging the system 4 towards the network 2, so as to reach the average power to be supplied during the predetermined period.
[0067] We will now describe the method 100 implemented by the module 8, with reference to figures 2 and following. It is implemented over a time period of ten minutes, in an automated manner. This time period corresponds to a commitment time period. Alternatively, it is a time period different from the commitment time period. In both cases, an average power objective is assigned for this time period by the module 7. It should be noted that this average power can be negative, this corresponds to “under-drawing”, that is to say that the installation withdraws electricity from the electricity network 2. The invention works in both cases. For convenience, however, we will consider the case of a positive average power in the following explanations, unless otherwise stated.
[0068] For convenience, the elements implementing this process will be referred to as "automated means" or "means". They naturally refer to the memory processors presented, the computer program(s) of module 8, the database 6 as well as any element allowing an instruction to be sent to source 3 and to system 4.
[0069] In step 101, the means construct on a diagram, visible in figure 3, having as abscissa a duration and as ordinate a quantity of energy, an affine straight line 11 representing the optimal quantity of energy to be supplied to the electrical network 2 throughout this period of time. By "optimal quantity of energy", we mean the quantity of energy that would have to be supplied at each instant of the period in a perfectly linear manner to maintain the average power objective. In other words, it is the quantity of energy resulting from a constant power supplied at each instant and making it possible to maintain the assigned objective. The end point 12 of the straight line 11 therefore corresponds to the quantity of energy to be supplied at the end of this period.Thus, if module 7 has identified an average power objective to be supplied during this period, the optimal quantity of energy to be supplied during this period corresponds to this average power multiplied by the duration of the period, as follows:.
[0070] [Math 1]
[0071] Where Epian is the optimal amount of energy to have been supplied to network 2 between the start of the period and a specific time, tfj n the last instant of this period, therefore corresponding to the total duration of the period of time, P pian the average power to be supplied during this period, determined by module 7. This is the ordinate of end point 12.
[0072] More generally, the term "optimal quantity of energy" therefore refers to the quantity of energy to be supplied during a current time interval and during subsequent intervals in order to achieve a final quantity supplied objective at the end of a period of time encompassing these intervals and previous time intervals.
[0073] We do not set the initial point 13 of this line 11 to zero. Indeed, the initial point 13 of the line 11 corresponds to the average power to be supplied over this period multiplied by a duration of 30 seconds. The objective is thus to set the initial point 13 to a slightly positive ordinate. The effect of this upward movement of the initial point 13 is to encourage the sending of a higher than necessary energy power instruction at the beginning of the time period, so as to get ahead in the event of unavailability of intermittent energy later, for example in the event of a cloud passing. On the other hand, if the average power is negative - this is the case of underdrawing -, the initial point is set to 0. Thus, the ordinate E pian (0) of this initial point 13 corresponds to the following formula:
[0074] [Math 2] plane (0) max(Pp; an * 30s, 0)
[0075] The line 11 thus constructed, between the initial point and the final point, makes it possible to have the optimal quantity of energy which must theoretically be supplied at each instant to network 2 by installation 1 since the start of the time period, if this supply were perfectly linear.
[0076] In step 102, the means construct an affine line 14 representing the so-called “minimum” quantity of energy to be supplied to the network throughout this period of time. By “minimum” quantity, we mean a quantity less than the optimal quantity of energy, making it possible to tolerate a portion of momentary underproduction of energy in anticipation of greater availability of energy from the source 3 later. To determine the end point 15, the means determine two values. First, they identify the minimum average power that it is possible to supply to the electrical network 2 over this predetermined period of time without suffering an underproduction penalty. To do this, they rely on the regulatory data from the database 6 and deduce therefrom the average commitment power over the period, P ann, to which the operator is required, and subtract a value representing 5% of the installed power at the power station 1. Here again, the installed power is a known value, recorded in the database 6. They determine a second value from the average power objective P pian supplied by module 7, from which a value representing 5% of the electrical power installed at power station 1 is also subtracted. The means compare these two values and select the lowest. The latter is multiplied by the duration of the predetermined time period, forming the ordinate of the end point 15 of this line 14 corresponding to the “minimum” quantity of energy to be supplied to the network. Thus, the ordinate of this point corresponds to the following formula:
[0077] [Math 3]
[0078] Where Emin is the minimum quantity of energy to be supplied to network 2 between the start of the period and a specific moment, Psousprod is the average power that can be supplied at a minimum without underproduction penalty, and kWc is the installed power of power station 1.
[0079] To determine the initial point 16 of this line 14, the means multiply the theoretical average power to be supplied by a duration of 30 seconds, and invert this value to make it negative. Placing this initial point 16 below 0 makes it possible to tolerate a certain underproduction at the start of the time period. If the average power to be supplied from module 7 is negative, this initial point is at 0.
[0080] The initial point of this line therefore corresponds to the following formula:
[0081] [Math 4]
[0082] Emi (0) = min(- P plan* 30s, 0). Line 14 connecting the initial point 16 and the final point 15 therefore represents the minimum quantity of energy which must have been supplied to the network at least at each instant since the start of the time period to remain close to the optimal quantity while tolerating a momentary under-production.
[0083] In step 103, the means construct an affine line 17 representing the so-called “maximum” quantity of energy to be supplied to the network throughout this period of time. Above this curve, the electrical network 2 would be considered to be oversupplied. To determine the end point, the means identify, using the regulatory data from base 6, the maximum power that it is possible to supply without overproduction penalty: this is the average commitment power P annto which we add 4% of the installed power kWc. This value is multiplied by the duration of the time period, i.e. ten minutes, forming the ordinate of the end point 18 of this line 17.
[0084] This final point 18 therefore responds to the following formula:
[0085] [Math 5]
[0086] Where Emax is therefore the maximum quantity of energy to be supplied to network 2 between the start of the period and a specific moment, and P an n + 4% * kWc is the average power that can be supplied to network 2 at most without overproduction penalty.
[0087] The initial point 19 of the line 17 is determined by multiplying the 4% of the power value of installation 1 by the duration tfj n of the time period and by the number 3, according to the following formula:
[0088] [Math 6]
[0089] This formula results in a strongly positive initial value. As we will see below, this line 17 allows the choice of a setpoint for the power sent by source 3 to network 2. By forming a very positive initial point, we therefore tolerate a high production at the beginning of the time period to "unclip" the solar panels, that is to say to temporarily waive any power limit of the solar panels. By "unclipping", we mean the inverse operation of "clipping" or "clipping" consisting of limiting the power of the panels.
[0090] The means have thus constructed the three lines which will be useful in the rest of the process.
[0091] All parameters used to construct the initial and final points of these lines, such as percentages and durations, can be modified by a user. However, it should be noted that it is preferable to choose values that allow for the technical effects presented, i.e., tolerance to overproduction and underproduction at the beginning of the time period, particularly in view of potential adverse weather conditions, or to "unclip", i.e., no longer clip the power of the solar panels.
[0092] Steps 104 and following are then implemented, starting from the abscissa point 0, that is to say at the initial instant of the predetermined time period, then at regular intervals, in this case every five seconds, until the end of the time period.
[0093] In step 104, it is a matter of predicting what would be the quantity of hypothetical future energy Efutur which will have been supplied to the network 2 since the beginning of the period of time, at a determined future instant. This duration tfutur, located between the present instant t and the future instant, is set by default to 60 seconds. To determine this quantity of hypothetical energy, the means are based on the quantity of energy E res already supplied to the network since the beginning of the time period and on the power available to panels 3 at the present time t, so that this hypothetical quantity responds to the following formula:
[0094] [Math 7]
[0095] Where Pp V represents the available power from the intermittent energy source 3 at a specific time, in space at the present time t.
[0096] Alternatively, this hypothetical quantity of energy, which could be supplied to the network 2 by the installation 1 at a future time, could be determined according to other formulas known to those skilled in the art.
[0097] The duration tfutur could be configured to be different from 60 seconds. Increasing it limits fluctuations in the power injected into the electricity network 2, but increases the use of the storage system 4.
[0098] In step 105, the means compare this value to the minimum amount of energy associated with the determined future time. In other words, the means place the point Efutur on the graph and determine whether it is located above or on the affine line 14 at this future time. This comparison thus amounts to comparing Efutur and E m in (t+tfuture).
[0099] In step 106, the means set a target for the amount of energy to be achieved based on the result of this comparison. Thus, if the hypothetical amount of energy Efutur is greater than or equal to Emin (t+tfutur), the means set as the target to be achieved the optimal amount of energy expected at this future time, i.e. E pian (t+tfuture), and this without using the storage system 4. Graphically, this means that the objective to be reached is the line 11, and this without discharging the storage system. We therefore assign to a variable that we call Eobjective the quantity Epian (t+tfuture), which must therefore be reached only by means of source 3.
[0100] On the other hand, if the hypothetical energy quantity Efutur is less than Emin (t+tfutur), that is to say if the point Efutur is located under the line 14, then the means assign to the variable Eobjectif the quantity Emin (t+tfutur), in other words the line 14, and authorize the discharge of the batteries 4 into the network 2. We will see below what power this discharge is. In summary, if the hypothetical energy quantity at the future time is greater than or equal to the line 14, the means assign the line 11 to the objective without authorizing the use of the batteries 4 to discharge energy into the network. This system 4 is therefore economized. On the other hand, if the hypothetical quantity of energy at the future instant is less than the line 14, the means aim at the line 14 and this by authorizing the use of the storage system 4 to discharge energy into the network in order to try to reach, at the future instant, this line 14.
[0101] In step 107, the means determine the powers which should be supplied by the source 3 and / or the storage system 4 to the electrical network 2 to meet the assigned objective, i.e. either to reach the line 14, or to reach the line 11.
[0102] The means first determine the power P res that should theoretically be supplied to network 2 at the present time t based on the average amount of energy assigned as an objective by module 7 and the amount of energy already supplied in the past, according to the following formula:
[0103] [Math 8]
[0104] Then, the means determine the power that one should theoretically obtain from the storage system 4 or on the contrary store in the storage system 4, depending on the theoretical power P res to supply to the network and available power P pvat the present time t from source 3, as follows:
[0105] [Math 9]
[0106] Pbat ( = Near (0 — Ppv (
[0107] If this power is negative, it means that the storage system 4 can be charged using the surplus power from source 3. If it is positive, it means that this is the power that would need to be supplied to network 2 by the storage system 4 to reach the theoretical power by compensating for insufficient power from source 3.
[0108] In step 108, the means determine the power instructions to be applied based on the theoretical powers calculated in step 107 and based on whether or not the discharge of the storage system into the electrical network 2 is authorized.
[0109] Thus, the means determine the maximum power P max that it is possible to supply to network 2 by the future instant, by means of the affine line 17 whose ordinate at the future instant is known, that is to say by means of the maximum quantity of energy that could have been supplied to the network by the future instant, and also by means of the quantity of energy E res supplied to the network from the beginning of the period until the present time t. This maximum power therefore corresponds to the following formula: [Math 10]
[0110] Then, the means determine the power instructions to be transmitted by the intermittent energy source 3 to the network 2 or to the storage batteries 4, the possible discharge instruction of the storage system 4 into the network 2 or the possible charging instruction.
[0111] First of all, in all cases, if Pbat(t) is negative, that is, the power available at the source 3 P pv (t) is greater than the power P res(t) to be theoretically supplied to network 2, then the means ask source 3 to supply the energy power corresponding to (- Pbat(t)) to storage system 4, which therefore stores this surplus energy. This is the charge of batteries 4. There is no discharge from storage system 4 into network 2. In addition, the means ask source 3 to supply the rest of the available power to network 2, within the limit of the value P m ax(t) so as not to overload network 2.
[0112] If Pbat(t) is positive, there are two cases depending on whether the discharge is authorized or not. Let us first deal with the case where the discharge was not authorized at step 106. In this case, the storage system 4 is instructed not to transmit any power to the electrical network 2. For its part, the power instruction to be supplied by source 3 to network 2 is limited to a maximum of P m ax(t) so as not to overload network 2.
[0113] In the case where the discharge has been authorized in step 106, then the storage system 4 receives the instruction to transmit the energy power Pbat(t), to the electrical network 2. The source 3 receives the instruction to transmit the rest of the power to the network 2, respecting a maximum equal to P m ax(t) - Pbat(t) so as not to oversupply network 2. Thus, at most, the power P m ax(t) is transmitted to the electrical network 2, part of this power coming from the batteries 4 with the power Pbat(t), part coming from the source 3 with the available power from this source, limited by the maximum value P max(t)-Pbat(t).
[0114] Once the instructions have been transmitted, steps 104 to 108 are repeated every five seconds, until the end of the predetermined time period. Thus, every five seconds, power and limit instructions are sent to the source 3 and possibly to the storage system 4, to supply the electrical network 2.
[0115] Naturally, this five-second interval can be configured to be different.
[0116] At the end of the time period, when there are less than 60 seconds remaining, the duration tfutur set at 60 seconds is reduced second by second down to a predetermined minimum duration so that steps 104 to 108 can continue to be implemented as close as possible to the end of this time period. The smaller this minimum end-of-period duration, the more it is ensured that the objective of the quantity of energy set for the entire time period is achieved, but the more the fluctuation of power injected into the network is increased. As already mentioned, the period tfutur can generally be set at a duration other than 60 seconds.
[0117] Steps 101 to 108 are then implemented for the next predetermined period.
[0118] We will now return to the three cases resulting from the results of the comparison between Efutur and Emin (t+tfutur) with reference to figures 4 and following, on the graphic level.
[0119] We place ourselves at any instant t during a period of time, the lines 11, 14 and 17 having been drawn for this entire period from the beginning of this period in accordance with steps 101 to 103. Curve 22 represents the quantity of energy supplied to the electrical network 2 up to this present instant t, from the beginning of this period of time. Point 20 is the point corresponding to the quantity supplied up to this instant t. Point 21 represents the hypothetical quantity of energy at the future instant determined in step 104, that is to say for the instant t+tfuture where tfuture is equal to 60 seconds.
[0120] In Figure 4, this point 21 is above curve 14 corresponding to the minimum quantity of energy to be supplied to network 2. The means therefore carry out the assignment Eobjectit = E pian(t+ tfutur), and the discharge of the storage system 4 is not allowed. But this point 21 is also above the line 11, which mathematically means that Pbat(t) is negative, the available power from source 3 being greater than the power P res (t) which should theoretically be supplied to the network at the present time. In this case, the storage system 4 is charged with energy of power Pbat(t) from source 3, and this same source supplies the rest to the electrical network 2, limiting this power so as not to exceed the line 17. The drawn arrows indicate the setpoint 24 allowing the batteries 4 to be charged while reaching the curve 11, and the setpoint 25 sets the maximum power not to be exceeded in the supply of the network 2 so as not to exceed the curve 17.
[0121] In Figure 5, point 21 is above curve 14, so that, again, the means carry out the association Eobjective = E pian(t+tfuture) , and the discharge of storage system 4 into network 2 is not allowed. This point is located below line 11 , so there is also no charge of system 4. Storage system 4 is therefore neither charged nor discharged.
[0122] In Figure 6, point 21 is located below curve 14. This time, the means perform the association Eobjective = Emin (t+tfuture), that is to say that the means aim at line 11 corresponding to the optimal quantity of energy to be supplied to the network, and the discharge of the storage system 4 into the network is therefore authorized to achieve this objective. The arrow allows us to see the discharge instruction 24 to reach line 14.
[0123] In all three cases the power and limit instructions are implemented in accordance with the steps and formulas set out above.
[0124] As a result, over a predetermined period of time, the quantity of energy actually supplied to the electrical network 2 by the source 3 and possibly the storage system 4 forms a curve 22 evolving between the straight lines 14 and 11 corresponding respectively to the minimum quantity of energy to be supplied and to the optimal quantity of energy, desired, to be supplied to the network 2. In this way, rather than asking the system 4 to discharge into the electrical network 2 each time that the available power from the source 3 is not sufficient, a certain momentary underproduction is tolerated, controlled by predicting the hypothetical quantity of energy that could be supplied in the future. The discharges from the storage system are therefore limited while approaching as closely as possible the optimal quantity of energy to be supplied to the electrical network over a predetermined period.
[0125] As already mentioned, each predetermined time period may correspond to a commitment period for which the operator has committed to supplying a specific quantity of energy to the network. Alternatively, a time period may also be a sub-period of a commitment period or a combination of commitment periods.
[0126] The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art.
[0127] In particular, it is possible to apply the method to an installation comprising other types of intermittent energy, such as wind energy, and other types of storage system, such as other types of battery, a flywheel, a supercapacitor, an electrolyser or even a fuel cell.
Claims
Claims
1. Method (100) for supplying energy to an energy network (2), comprising, for supplying the network (2) by means of an intermittent energy source (3) and an energy storage system (4), the following steps: - determination (101) of an optimal quantity of energy to be supplied to the network by a predetermined future time; - determining (102) a minimum quantity of energy which should be supplied to the network by the future instant, this minimum quantity being less than the optimal quantity of energy; - forecast (104) of a hypothetical quantity of energy which could be supplied to the network by a future instant assuming an absence of discharge into the network, by this future instant, of energy from the storage system; - in the case where the determined hypothetical quantity of energy is greater than or equal to the minimum quantity of energy to be supplied to the network at the future instant, supply (108) of energy in the network only from the intermittent energy source, without discharging the storage system.
2. Method (100) according to the preceding claim, comprising, before the step of supplying (108) energy in the network, a step of determining an energy power to be supplied by the intermittent source, based on the optimal quantity of energy and not on the minimum quantity of energy.
3. The method (100) of claim 1, comprising, in the case where the hypothetical amount of energy is less than the minimum amount of energy to be supplied to the network at the future time, a step of supplying (108), into the network, energy from the intermittent energy source and energy from the storage system by discharging the storage system.
4. Method (100) according to the preceding claim, comprising, before the energy supply step, a step of determining (108) an energy power to be supplied from the energy source intermittent and from the discharge of the storage system, based on the minimum amount of energy to be achieved and not on the optimal amount of energy.
5. A method (100) according to any preceding claim, wherein, considering a predetermined period of time, the steps of determining (101) the optimal amount of energy and the minimum amount (102) of energy are implemented at the beginning of the period of time and in advance for each instant of the period of time, while the step of determining the hypothetical amount of energy (104) is implemented at regular intervals during this period of time considering a past amount of energy supplied to the network since the beginning of this period.
6. Method (100) according to the preceding claim, comprising, to determine (101, 102) the minimum and optimal quantities of energy at the start of the time period and for each instant of this period, a step of constructing an affine line corresponding to the minimum quantity of energy during this period and another affine line corresponding to the optimal quantity of energy during this period.
7. Method (100) according to any one of the preceding claims, comprising, prior to the steps of claim 1, the following steps: - determination (101) of the optimal quantity of energy to be supplied to the network based on a prior commitment to supply a quantity of energy to the network over a predetermined period of time, - determination (102) of the minimum quantity of energy which should be reached as a function of an average energy power allowing the absence of financial penalty of under-supply of energy on the network or as a function of the optimal quantity of energy reduced by a predetermined value.
8. Method (100) according to at least claim 2 or 4, comprising, for determining the energy power to be supplied to the network by the intermittent source, the following steps: - determination (103) of a maximum quantity of energy to be supplied to the network at the future instant, greater than the optimal quantity and beyond which the network would be considered oversupplied; - determination (108) of the energy power to be transmitted by the intermittent source based on the maximum quantity of energy.
9. Method (100) according to at least claims 6 and 8, wherein the maximum amount of energy also comes from an affine line constructed at the start of the time period.
10. A method (100) according to any preceding claim wherein the hypothetical amount of energy depends on the power available at a present time from the intermittent energy source.
11. Installation (1) for supplying energy to an energy network, comprising an intermittent energy source (3) and an energy storage system (4) configured to implement the method according to any one of the preceding claims.
12. Installation (1) according to the preceding claim, in which the energy is electricity and the network (2) is an electrical network, the source (3) comprises at least one photovoltaic panel and / or a wind turbine and the storage system (4) comprises at least one of the following elements: - a battery, preferably lithium-ion type; - a flywheel - a super-capacity; - an electrolyser; - a fuel cell.
13. A computer program (8) comprising instructions which, when the program is executed by a computer, cause the computer to implement the steps of the method (100) according to any one of claims 1 to 10.
14. A computer-readable recording medium comprising instructions which, when executed by a computer, lead the latter to implement the steps of the method (100) according to any one of the preceding claims.