PROCEDURE FOR OPERATING AN ISLAND GRID

Description

[0001] The present invention relates to a method for operating an electrical grid, in particular an isolated grid, as well as the operation of at least one wind turbine connected thereto and a charging station connected to the grid. The present invention also relates to such a grid, a corresponding charging station and a corresponding wind turbine, as well as a wind farm connected to the grid and having such wind turbines.

[0002] An island grid is defined as an electrical grid that is separated from a larger grid, such as the European interconnected grid, and operates autonomously. Such an island grid is usually located on islands or island groups in the geographical sense. However, it can also be an isolated, autonomous grid, especially in a remote area.

[0003] The operation of isolated grids is known and is described, for example, in the two US patent applications US 10 / 380,786 and US 10 / 506,944. These patent applications specifically describe providing as much energy as possible for an isolated grid from wind turbines. If these do not provide sufficient energy, energy is supplemented from energy storage systems, and if this is still insufficient, a diesel generator can be switched on. Documents US 2011 / 273129 A1, WO 2014 / 071459 A1, and US 2012 / 323396 A1 disclose further examples of operating an electrical grid, taking into account a gradient increase limit and / or a gradient decrease limit when changing the feed-in power over time.

[0004] A disadvantage is that primarily consuming a battery's energy can shorten its lifespan, sometimes significantly. In addition to the costs that would then arise from replacing a battery, it is also undesirable, especially in isolated grids, to have to carry out unnecessary maintenance or repair work. This is particularly disadvantageous if it temporarily jeopardizes the operation of the isolated grid.

[0005] Even operating a diesel generator strictly on demand can place an unfavorable strain on it, which in the long run can also shorten its lifespan or maintenance cycles. Furthermore, diesel generators often operate at a specific speed, not only with particularly low wear but also with particularly low energy consumption. Therefore, it is also beneficial for the diesel generator if its characteristics are taken into account when operating an island grid.

[0006] The present invention is therefore based on the object of addressing at least one of the aforementioned problems. In particular, a solution is to be proposed in which the battery and the diesel generator in the stand-alone grid are operated as sustainably as possible. At the very least, an alternative solution to previous solutions is to be proposed.

[0007] According to the invention, a method according to claim 1 is proposed, namely a method for operating an electric charging station on an electrical network, in particular an island network, which, in addition to electrical consumers, has at least one regenerative generator, in particular a wind turbine or a wind farm, at least one generator operated by fossil fuels, in particular a diesel generator, and at least the electric charging station for storing and releasing electrical power, and comprises the following steps: Generating electrical power by means of the at least one wind turbine and feeding the electrical power into the island grid, storing electrical power not consumed by the consumers in the charging station, feeding electrical power through the charging station when the consumers consume more power than the at least one renewable generator and the at least one conventional generator together feed into the grid, where in a first constellation of the network, a feed-in power fed into the network is a sum of the power of the at least one regenerative energy generator and the power of the charging station and optionally additionally of the power of the at least one further generator assigned to the charging station, wherein the charging station is controlled in such a way that the feed-in power is limited in its temporal change, wherein the power to be delivered or supplied by the charging station.the power to be absorbed is changed by a compensation value depending on a state of charge in order to approximate the current state of charge to a predetermined target state of charge, wherein two limit gradients are specified to limit the temporal change in the feed-in power, namely an increase limit gradient which determines the maximum change per time in which the feed-in power should increase, and a decrease limit gradient which determines the maximum change per time in which the feed-in power should decrease, and wherein the charging station is controlled in such a way that the change in the feed-in power is within a positive and negative limit orwithin the increase limit gradient and the decrease limit gradient and that, in the case of the first constellation, the change in the feed-in power is positive if the charging station has a state of charge that is above a predetermined target state of charge or the change in the feed-in power is negative if the charging station has a state of charge that is below a predetermined target state of charge.

[0008] The charging station is therefore a system with one or more batteries that can be charged and discharged. Charging and discharging thus takes place via the connection to the isolated electrical grid. The battery can therefore be charged when there is excess power in the grid and, conversely, discharged to feed power into the grid. Discharging here also describes a process in which the battery is only partially and possibly only a small portion of it is discharged. For the sake of simplicity, the isolated electrical grid is referred to simply as the grid. Such isolated grids are also operated as alternating current grids, and the charging station is accordingly prepared to feed alternating current into the grid. The invention is particularly intended for an isolated grid, but can in principle also be used in another electrical supply grid.

[0009] With the at least one renewable generator, in particular a wind turbine or a wind farm, electrical power is generated from renewable energy sources and fed into the island grid, which is also mentioned here as representative of other grids. The generation of electrical power here simply means the conversion of mechanical or other power, e.g. solar energy, into electrical power. Accordingly, mechanical or other energy is converted into electrical energy. When storing electrical power, instantaneous power is taken from the grid by the charging station and stored in the charging station, in particular in batteries, so that energy is ultimately stored. For the feeding of renewable energy into the island grid, at least one wind farm comprising a plurality of wind turbines is preferably provided.In exceptional cases, if the island grid is sufficiently small or the wind turbine is sufficiently large, the use of only a single wind turbine might be sufficient.

[0010] Furthermore, a diesel generator is present, which is also representative of other possible generators powered by fossil fuels. This could, for example, be an oil- or gas-powered generator. Unless expressly stated otherwise, any subsequent statements made regarding a diesel generator also generally apply to other possible generators powered or driven by fossil fuels.

[0011] One aim of the invention is to operate the charging station and thus the batteries located there as gently as possible, or at least more gently than before, while feeding into the grid as continuously as possible. To do this, particular consideration must be given to the charge level of the batteries in question. It is generally not ideal if such batteries are completely discharged, so so-called deep discharge must be avoided. Even fully charging a battery to 100 percent can be undesirable. In addition, extreme charge levels, i.e. almost full charge or almost full discharge, limit the charging station's ability to act. For example, an almost completely discharged charging station cannot provide enough power to regulate the feed-in.

[0012] The invention now proposes to specify maximum gradients, namely limit gradients, for the charging or discharging of the charging station, i.e. the battery or several batteries of the charging station, which can also be described as maximum flanks.

[0013] This means that an edge is specified with which the power that the charging station feeds into the grid should increase to a maximum. This is also referred to here as the increase limit gradient. In addition, a value is specified with which the power that the charging station draws from the grid and with which the batteries are then charged should increase. In other words, the dynamics of the change are specified here. Surprisingly, this also made it possible to influence the absolute charge level of the charging station or its batteries, which is also referred to here as the state of charge. By selecting these two maximum values ​​accordingly, it is possible to achieve a charge level that tends to move upwards or downwards, or towards an intermediate value over a longer period of time. The charge level can therefore be controlled to an upper limit, a lower limit, or another range.

[0014] Such upper and lower limits can be specified to prevent the battery from being fully charged or completely discharged. For example, if the charge level tends toward the lower limit, reducing the gradient for feeding electrical power by the charging station can prevent the charge level from tending toward this lower limit. This can be achieved by flattening the maximum slope for feeding electrical power into the grid by the charging station.

[0015] This makes it possible to regulate the charging station so that the state of charge remains between these two predefined limits without the state of charge being directly evaluated for control purposes. Of course, a safety query can also be provided to prevent the charge level from falling below the lower limit or exceeding the upper limit. However, this should be an exceptional emergency measure, and the integrated control system can dispense with it, keeping the charge level within the desired limits during normal operation of the stand-alone grid without directly monitoring these limits every time.

[0016] The proposed method can essentially be used for two configurations. In the first configuration, the feed-in power is comprised of the power of at least one renewable generator and the power of the charging station. These renewable generators and the charging station are combined in this respect. For example, the charging station can be part of a wind farm with multiple wind turbines. If the wind power fluctuates too much, to continue with this example, the charging station can counteract this accordingly. The fed-in power is the sum of the power of these wind turbines and the charging station. Thus, if the wind power drops sharply, a corresponding increase in the power output of the charging station can keep the total feed-in power within the desired, specified limit of the change.

[0017] As a result, this combination of renewable generators and the charging station feeds a limited amount of power into the grid. The grid, in particular, perceives this combined feed-in power as having little fluctuation and therefore does not need to compensate for excessive fluctuations.

[0018] Such a combination of renewable energy generators and the charging station, for example, a wind farm with a charging station, can also be supplemented by a conventional or other additional generator. Such a generator would then be assigned to this charging station. This means, in particular, that the output of the corresponding renewable energy generators, the output of the charging station, and the output of this additional generator are all fed into the grid via a common grid connection point.

[0019] In another constellation, the power fed into the grid by at least one conventional generator is considered feed-in power, and its changes are kept to a minimum. In this constellation, the feed-in power of at least one conventional generator is taken into account. The conventional generator can generally run stably and evenly over the long term. However, fluctuations in its feed-in power occur when it counteracts fluctuations in the grid, e.g. as a diesel generator or gas-fired power plant. In this case, the idea of ​​an island grid is particularly important, but this is not a limiting factor. If, for example, the consumers in the grid together consume more power than just a moment before, the conventional generator counteracts and increases its feed-in power to compensate for this increased consumption.

[0020] In this case, the charging station is used, feeding enough power into the grid to compensate for at least some of these power fluctuations. As a result, at least one conventional generator can then operate with less change.

[0021] This reduces the load on at least one conventional generator. Such a conventional generator is also representative of generator stations that have multiple such generators. A sharp increase in the power to be fed in, i.e., the feed-in power, regularly results in another generator being switched on in such a generator station. If the power to be delivered drops accordingly, at least one generator is switched off accordingly. Such excessive switching on and off of conventional generators is particularly avoided in this second configuration.

[0022] In any case, the relieving action by the charging station is carried out in such a way that the feed-in power is limited in its temporal change, i.e. it does not increase too much or decrease too much.

[0023] To limit this temporal change in the feed-in power, at least one limit gradient is preferably specified. This can be an increase limit gradient, which determines the maximum rate of change per unit of time for the feed-in power to increase. A decrease limit gradient is proposed as a second limit gradient, which determines the maximum rate of change per unit of time for the feed-in power to decrease. Depending on the application, it is also possible to specify only one of these two limit gradients; however, both of these limit gradients are preferably specified.

[0024] This allows the limitation of the power change to be controlled, and at the same time, the choice of these limit gradients also provides the opportunity to influence this contribution supported by the charging station. In particular, the choice of limit gradients can influence the charging station's state of charge.

[0025] Preferably, the gradient limit for increasing and decreasing charge levels are different from each other. This also allows, among other things, the average charge level of the charging station to be influenced, which develops over time. "Over time" refers specifically to the period of a day.

[0026] According to the invention, the charging station is controlled such that the change in feed-in power is guided within the increase limit gradient and the decrease limit gradient, and such that the change in feed-in power is positive if the charging station has a state of charge that is above a predetermined target state of charge, or such that the change in feed-in power is negative if the charging station has a state of charge that is below a predetermined target state of charge. The decrease limit gradient is, of course, a negative value here. Illustratively, the increase limit gradient specifies a rising edge and the decrease limit gradient a falling edge as a limit. The change in feed-in power is thus kept within a positive and negative limit.

[0027] While the feed-in power is maintained or controlled within these two limits, the charging station still has some leeway in its actual control. Here, it is proposed that this leeway be used so that the change in feed-in power is more likely to be positive when, to put it simply, the charging station is well charged. In this situation, the charging station has a lot of stored energy available and can therefore tend to feed in slightly more power, thereby simultaneously reducing its charge level toward the target charge level.

[0028] Otherwise, if the state of charge is comparatively low, the charging station can utilize its flexibility to feed in less power, which naturally also means it tends to absorb and store more power from the grid. This brings the state of charge closer to the target state of charge.

[0029] It should be noted that in the event of a particularly severe power drop, which the charging station must counteract, it is still possible that power is fed from the charging station into the grid even though the state of charge is comparatively low, or at least below the specified target state of charge, because compliance with the maximum changes is the priority.

[0030] However, it is based on the knowledge that over longer periods of operation, especially over a day, the development of the charging station's state of charge can be influenced substantially toward the specified target state of charge. On average, this target state of charge, for example, 50% of full charge, could in principle always be achieved. However, the fluctuations that constantly occur in wind turbines in particular can be such that the state of charge does not tend toward the target state of charge, but rather toward a maximum or minimum state of charge. One possible way to counteract this is to change the limit gradients or at least one of the limit gradients, i.e., the increase limit gradient or the decrease limit gradient.

[0031] Preferably, at least one of the limit gradients is set adaptively. The limit gradient(s) can then be changed during operation, e.g., depending on the state of charge. For example, if the state of charge is generally very high, namely above the target state of charge, the increase limit gradient could be increased or the decrease limit gradient could be decreased so that the charging station tends to feed in more stabilizing power than it draws and stores stabilizing power from the grid, to name just one example.

[0032] Preferably, the threshold gradient(s) are set based on the average state of charge of the charging station. This means that, for example, the development of the state of charge is observed over a longer period, such as a few hours or a day, using a filter or integration, and averaged to obtain an average state of charge. The threshold gradient(s), or at least one of them, can then be set based on this.

[0033] To a similar extent, a maximum charge level that should not be exceeded can preferably also be specified. The same applies to the specification of a predetermined minimum charge level. Preferably, the setting can be made such that the average charge level tends to assume a predetermined setpoint charge value, which can also be referred to as the target charge level.

[0034] The specific setting of the limit gradients can be tested beforehand, for example, in a simulation. Alternatively, it is also possible to gradually adjust the limit values ​​slightly, for example, on a daily basis, and observe the development of the charging station's state of charge, then select an appropriate limit gradient(s).

[0035] According to one embodiment, it is proposed that at least one of the limit gradients be calculated from a predefined base limit gradient multiplied by at least one weighting factor. In particular, a limit gradient, i.e., an increase limit gradient or a decrease limit gradient, can be specified as the base limit gradient as a limit that must be strictly adhered to. A weighting factor, or the product of several weighting factors together, can then be selected such that it assumes a maximum value of 1. Thus, the base limit gradient would not be exceeded, or, in the case of a negative value for the decrease limit gradient, it would not be undercut. In both cases, the amount would therefore no longer be increased, but at most reduced by a factor less than 1.

[0036] Preferably, at least one of the weighting factors depends on the charging station's state of charge. Additionally or alternatively, at least one of the weighting factors can vary in the range from 0 to 1. It cannot then increase the baseline gradient in absolute terms.

[0037] Preferably, a further weighting factor can be selected such that it has at least the value 1, in particular in the range from 1 to 10. Preferably, two weighting factors can be combined, one of which is in the range from 0 to 1 and the other in the range above 1, in particular in the range from 1 to 10. If these are multiplied together with the baseline gradient and this baseline gradient is not to increase, the selection of these two weighting factors can be such that their product is not greater than 1.

[0038] One design proposes that the charging station delivers electrical power which is fed into the grid together with electrical power from the at least one renewable energy generator when the electrical power from the renewable energy generator decreases at a gradient which is greater in magnitude than the predetermined reduction limit gradient, or that the charging station absorbs electrical power in order to reduce the electrical power fed into the grid by the at least one renewable energy generator when the electrical power from the renewable energy generator increases at a gradient which is greater in magnitude than the predetermined increase limit gradient.

[0039] Accordingly, the charging station supplies electrical power when the electrical output of the renewable energy generator, in particular the wind turbine or wind farm, decreases too sharply or too quickly. The charging station can then counteract this. Conversely, it is proposed that the charging station absorbs electrical power when the output of the renewable energy generator increases too sharply or too quickly. In both cases, this keeps the total feed-in power within the desired limits.

[0040] It is preferably also proposed that, in order to control the charging station, a time difference between a current second point in time and an earlier first point in time is taken into account, and that, at the earlier first point in time, a gradient of the power which was fed into the grid at the first point in time by the at least one regenerative energy generator and the charging station and possibly at least one further generator together is taken into account as the earlier feed-in gradient.

[0041] To control the charging station, measurements taken at two points in time, including the time difference between these points in time, are used. A power gradient at a previous point in time is used as a basis. Specifically, the gradient at this earlier point in time is used without taking the aforementioned time difference into account.

[0042] Preferably, based on these two measurement times, the time difference, and the previous feed-in gradient, the power to be delivered or received by the charging station at the second time is calculated. This is preferably done depending on the charging station's state of charge. For this purpose, it is proposed that this power to be delivered or received at the second time be calculated from a product composed of the time difference and a difference between the magnitude of the increase limit gradient and the previous feed-in gradient if the charging station has a state of charge that is above a predetermined target state of charge, or otherwise a product of the negative time difference and the sum of the magnitude of the decrease limit gradient and the previous feed-in gradient.

[0043] Accordingly, the increase limit gradient is used when the charging station has a comparatively high state of charge and the decrease limit gradient is used when the charging station has a comparatively low state of charge, to put it clearly.

[0044] This calculation ensures compliance with the limit gradients, i.e., the increase limit gradient and the decrease limit gradient, and simultaneously calculates the power to be supplied or received by the charging station depending on its state of charge. Thus, as far as the situation allows, the development of the charging station's state of charge is simultaneously influenced in order to steer it as close to a desired range as possible.

[0045] Preferably, different measuring locations are used for the different measuring times. For the first time, it is proposed to select a measured value from a first measuring point and to use a measured value from a second measuring point for the second time. During operation, measurements are therefore taken simultaneously at the first and second measuring points or measuring locations, but the measured value from the first time point is used at the first measuring point, i.e. the earlier measured value, and at the second measuring point, the measured value from the second time point, i.e. the current measured value. The earlier measured value and thus the first measuring point relate to the earlier feed-in gradient. This is measured accordingly at the point where the same power is transmitted.

[0046] At the first measuring point and at the first point in time, the current power output or consumption of the charging station is measured in order to adjust the newly calculated power to be output or consumed by the charging station. In this respect, the measurement at the first point in time at the first measuring point has a particular influence on the specific setting of the power to be provided by the charging station. Accordingly, it is also proposed that the second measuring point be located at the output of the charging station. Such a measurement at different locations at different times can potentially prevent instability that could arise from the immediate use of a measured value in a calculation that directly influences this measured value.

[0047] According to a further embodiment, it is proposed that the power to be delivered or received by the charging station be changed by a compensation value depending on a state of charge in order to approximate the current state of charge to a predetermined target state of charge. It is thus proposed that the charging station be charged or discharged to a small extent, independently of the control of the charging station such that the limit gradients are maintained. For example, the charging station can be charged with a low power while it is not active for control purposes anyway, for example when there is no wind at the wind farm when it forms the renewable generator. This can counteract a situation in which the state of charge deviates further and further from the desired target state of charge. This can also be a phenomenon that only occurs on one day, for example.

[0048] According to one embodiment, it is proposed that the charging station feeds electrical power into the grid when the electrical power fed into the grid by the at least one conventional generator increases at a gradient which is greater in magnitude than the predetermined increase limit gradient, or that the charging station receives electrical power from the grid when the electrical power fed into the grid by the at least one conventional generator decreases at a gradient which is greater in magnitude than the predetermined decrease limit gradient.

[0049] This embodiment is particularly proposed for the case where the at least one conventional generator and the charging station do not feed into the grid via a common feed-in point. The charging station thus feeds into the grid in such a way that it compensates for at least some of the power fluctuations in the grid, eliminating the need for the conventional generator to make excessive power changes.

[0050] One embodiment proposes that the at least one regenerative generator, in particular the wind turbine briefly increases its fed-in power above the maximum power available from the wind at that moment, briefly increases its fed-in power above the currently fed-in power, briefly reduces its fed-in power below the maximum power available from the wind at that moment, or briefly reduces its fed-in power below the currently fed-in power, in order to reduce power peaks that can be compensated for by the charging station or by at least one conventional generator.

[0051] According to the invention, an advantageous limitation of power fluctuations in fed-in power is proposed by appropriate control of a charging station. However, it has been recognized that this can be combined synergistically with control of the renewable generator, in particular with control of one or more wind turbines. Renewable generators, in particular wind turbines, preferably generate as much power as is possible given the current conditions. A wind turbine therefore generates as much power as can be drawn from the wind at the current moment. The resulting fluctuations can be limited by using the charging station. Nevertheless, it can be helpful to also use the wind turbine for control. Especially if the charging station has an unfavorable charge level, a short-term takeover or supplementation of control by the wind turbine can be helpful.The wind turbine can increase or decrease its output. It can increase it above or below the current value, or it can increase it above or below the available power from the wind. Such an increase is possible, especially in the short term, by using the kinetic energy of the wind turbine's rotor.

[0052] This also makes it possible, among other things, to make the charging station smaller and more cost-effective. A charging station can be dimensioned so that it can fulfill its function, for example, 95% of all days of the year. To cover these last 5% of days of the year, it might have to be designed significantly larger. In this case, it would be unnecessary if the wind turbine(s) were to take over or supplement the function of the charging station in exceptional cases.

[0053] According to the invention, an electrical supply network is also proposed, which can also be referred to simply as an electrical network. In particular, an isolated electrical network is proposed. This network is prepared to be operated using a method according to one of the above embodiments.

[0054] According to the invention, a charging station is also proposed which is prepared to be operated in the proposed network.

[0055] According to the invention, a wind turbine is also proposed which is prepared to be operated in the said electrical grid.

[0056] According to the invention, a wind farm is also proposed which is prepared to be used as a regenerative generator in an electrical grid as described above.

[0057] The invention is explained in more detail below using exemplary embodiments with reference to the accompanying figures. Fig. 1 shows a wind turbine schematically in a perspective view. Fig. 2 shows a wind farm with several wind turbines in a schematic view. Fig. 3 shows an electrical grid with a wind turbine, a charging station, a conventional generator, and consumers according to a first configuration. Figs. 4 to 9 illustrate the control of a charging station according to an embodiment and for the configuration according to Fig. 3 for different states or boundary conditions with respect to specified limit gradients. Fig. 10 shows the temporal course of some powers for different parameterizations of the charging station control. Fig. 11 shows the Fig. 10The underlying control system shows the temporal progression of the charge state of the controlled charging station. Fig. 12 shows an electrical grid with a wind turbine, a charging station, a conventional generator, and consumers according to a second configuration.

[0058] Fig. 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. During operation, the rotor 106 is set into rotation by the wind and thereby drives a generator in the nacelle 104.

[0059] Fig. 2shows a wind farm 112 with, for example, three wind turbines 100, which may be identical or different. The three wind turbines 100 are thus representative of essentially any number of wind turbines in a wind farm 112. The wind turbines 100 provide their power, namely in particular the generated electricity, via an electrical farm grid 114. The currents or power generated by the individual wind turbines 100 are added together, and a transformer 116 is usually provided, which steps up the voltage in the farm and then feeds it into the supply grid 120 at the feed-in point 118, which is also generally referred to as a PCC. Fig. 2is only a simplified representation of a wind farm 112, which, for example, does not show a control system, although a control system is of course present. The farm network 114 can also be designed differently, for example, by also providing a transformer at the output of each wind turbine 100, to name just one other embodiment.

[0060] The present invention thus relates to a strategy for charging and discharging an energy storage device coupled to a grid, which makes it possible to limit power gradients which can arise, for example, from renewable energy generators such as wind turbines or photovoltaic systems.

[0061] The energy storage device is also referred to here as a charging station or simply as a battery. However, the energy storage device or charging station can include control devices for controlling charging and discharging.

[0062] Different network configurations can be used, which can be characterized by the interconnection of the wind turbine, the charging station or battery, and the conventional generator. In the following, an exemplary explanation of the invention is given in Fig. 3 The network configuration shown is used as a basis.

[0063] According to Fig. 3An electrical supply network 1 is schematically shown, which is intended to supply consumers 2 with electrical power. A conventional generator 4 is connected to the network 1 as the energy generator. In addition, at least one wind turbine 6 and a charging station 8 are connected to the network via a grid feed-in point 10. All schematically shown parts of the network 1, namely consumers 2, conventional generator 4, wind turbine 6, and charging station 8, can each contain or represent several such elements of their type. In particular, the wind turbine 6 is also representative of a wind farm 6.

[0064] The wind turbine 6 provides a power P wec (t) and the charging station 8, which can also be referred to simply as battery 8, provides a power P bat (t). These powers can therefore vary over time and their sum is fed into the grid 1 at the grid feed-in point 10. Both the power of the wind turbine P wec (t) and the power of the charging station P bat (t) can be fed into the grid or taken from the grid. When taken from the grid, this means for the power P bat (t) of the charging station 8 that the charging station or a battery in the charging station is charged. The wind turbine 6 essentially feeds in power, but could also, for example, take power from the grid via chopper resistors or buffers and thus consume or temporarily store it if this is necessary or helpful for grid support. In addition, Fig. 3Various switches S are symbolically represented, which can disconnect the respective element from the network.

[0065] In this constellation according to Fig. 3 The feed-in power fed into grid 1 is the sum of the power P wec of the wind turbine 6 and the power P bat of the charging station 8. This sum can also be referred to as P grid. This is the power that is fed into the grid at the grid feed-in point 10 or, in the case of a negative sign, is taken out from there. The conventional generator 4 also feeds in power, which, when viewed in the context of the Fig. 3 underlying, but not mentioned.

[0066] Optionally, another conventional generator could be assigned to the wind turbine 6 and the charging station 8, the power of which would then also be part of the feed-in power P grid at the grid connection point 10. Such a conventional generator, in particular a diesel generator, could be switched on, for example, in light wind conditions, to name just one example.

[0067] In this configuration, it is proposed that the feed-in power P grid be limited in its temporal variation. It is therefore proposed that power changes and thus power gradients of the power fed into the grid at the grid feed-in point 10 be kept within limits. According to the invention, this can be achieved via a corresponding control of the charging station 8.

[0068] According to Fig. 3One or more wind turbines 6 and the battery system 8, which can also be referred to as a charging station, feed into an electrical grid 1 via a common grid feed-in point 10, which additionally has a conventional generator 4 and various consumers.

[0069] A performance gradient Δ P Δ t grid t at time t, which is fed into the grid at grid feed-in point 10, can be defined as follows: Δ P Δ t grid t = P wec t 2 − P grid t 1 Δ t where P wec ( t 2) the wind farm power measured at time t 2 and P grid ( t 1) is the feed-in power measured at the grid feed-in point at time t1. t2 is the current time following t1. Δ t is the time step chosen to determine the power gradients and results from the difference between t 2 and t 1 .

[0070] If the active power gradient fed into the grid at the grid feed-in point is to be limited to a maximum or minimum limit value ( Δ P Δ t lim down , Δ P Δ t lim up ) are limited or kept within such limits, depending on the type (positive or negative) and amount of the gradient (above or below the limit), a certain active power ( P bat ) or withdrawn. For such power, it is proposed that it be absorbed or released by an energy storage system, which in this application is referred to synonymously as charging station 8 and which can, for example, be designed as a battery or can contain a battery.

[0071] In Fig. 4 Both the wind turbine power P wec as well as the power at the grid feed-in point P grid at the successive times t 1 and t 2 . P grid consists additively of P wec and P bat together.

[0072] The performance P grid ( t 1) at the grid connection point and the wind turbine power P wec ( t 1) are in this Fig. 4 and also in the Fig. 5 to 9 at time t 1 is assumed to be equal. At time t 2 the wind turbine power is P wec ( t 2). Equation [1] then gives the power gradient Δ P Δ t t 2 , which in the example according to Fig. 4 greater than the upper limit Δ P Δ t lim up which is given as the upper limit, namely as the gradient limit.

[0073] In order to achieve a power gradient of Δ P Δ t lim up To ensure this, the battery must at time t 2 deliver the power P bat ( t 2). In the described case, this is negative and is calculated as P bat t = Δ P Δ t lim up − Δ P Δ t grid t ⋅ Δ t ;

[0074] The capacity of an energy storage device, which allows the battery power P batThe availability of battery power P bat depends on the battery charge level, which is SoC If the storage is uncharged (SoC=0%), no additional power can be fed in. If the storage is fully charged (SoC=100%), no additional power can be absorbed.

[0075] It is therefore suggested that the storage system should be operated with a charge level that is as constant as possible SoC between the two extreme charge levels. Such a target charge level can be used as a setpoint SoC target To ensure that the charging status is SoC as low as possible from the target charge level SoC target deviates, it is proposed that charging and discharging powers correspond over a time average.

[0076] It was recognized that the magnitude of the boundary gradients Δ P Δ t lim down and Δ P Δ t lim up , which is known as the reduction limit gradient Δ P Δ t lim down or gradient limit Δ P Δ t lim up can be specified, has the following influence on battery operation: It affects the probability of battery charging or discharging It affects the power to be provided or absorbed by the battery

[0077] It is now proposed to influence the state of charge of the battery by appropriate selection of the limit gradients.

[0078] This means that it will depend on the difference in the state of charge SoC to the target charge level SoC target a lower or upper limit ( Δ P Δ t lim down bzw . Δ P Δ t lim up ) of a power gradient. This allows you to control whether the battery is charged at a maximum / minimum power or discharged at a maximum / minimum power.

[0079] The Fig. 4 to 9 illustrate for three exemplary positions of a power gradient Δ P Δ t t , namely for the feed-in power P grid , resulting battery performance P bat ( t ) that are achieved by the proposed method. The basic type of representation has already been partially described above. Fig. 4 explained and applies mutatis mutandis to the other Fig. 5 to 9 .

[0080] These three exemplary positions also represent three possible positions of the performance gradient and these are: 1. The performance gradient Δ P Δ t t is greater than the upper limit gradient Δ P Δ t lim up 2. The performance gradient Δ P Δ t t is smaller than the lower limit gradient Δ P Δ t lim down 3. The performance gradient Δ P Δ t t is smaller than the upper limit gradient Δ P Δ t lim up and greater than the lower limit gradient Δ P Δ t lim down

[0081] The upper limit gradient Δ P Δ t lim up is also synonymously referred to as the rising limit gradient and the lower limit gradient Δ P Δ t lim down is also synonymously referred to as reduction limit gradient.

[0082] In addition to the possible power gradient positions mentioned above, the state of charge of the charging station or its battery(ies) also has an influence. For simplicity, we will simply refer to the battery. The state of charge is referred to as the SoC in the figures and is viewed in relation to a target state of charge, which is referred to as the SoC target.

[0083] The battery can be in the following two charge states: SoC > SoC target SoC < = SoC target

[0084] The theoretical condition that the state of charge corresponds exactly to the target charge (SoC = SoC target ) has been assigned to the second variant here, which is not essential.

[0085] Thus, six possible cases regarding the power gradient and state of charge can be combined, which are shown in Table 1 and the Fig. 4 to 9 are shown.

[0086] Table 1 gives the equations for these six cases according to an embodiment through which the battery power P bat ( t ) is determined to allow the state of charge (SoC) to converge as closely as possible to the target state of charge (SoC target). The table also includes figures showing the corresponding power gradients for these six different cases.

[0087] The cases shown in Table 1 can be summarized as follows: the power to be provided by the battery P bat ( t ) can be calculated as follows: P bat t = − Δ P Δ t lim down + Δ P Δ t grid t ⋅ Δ t ; for SoC bat t < SoC target P bat t = Δ P Δ t lim up − Δ P Δ t grid t ⋅ Δ t ; for SoC bat t ≥ SoC target

[0088] The temporal deviation of the battery charge level SoC ( t ) to the target value SoC targetdepends on how the wind power changes, which leads to unpredictable power changes and thus power gradients. In other words, this temporal deviation depends on a stochastic sequence of negative or positive power gradients. These should be limited by battery operation. The more often negative gradients are compensated, the more quickly the storage system is depleted, and vice versa.

[0089] The Figures 4 to 9 It can be seen that the charging station is controlled to maintain a gradient that brings the feed-in power within a range defined by the increase limit gradient and the decrease limit gradient. The gradient is attempted to be changed either to the increase limit gradient or to the decrease limit gradient. The choice between these depends on the state of charge. If the state of charge is above its target value, the increase limit gradient is selected; otherwise, the decrease limit gradient is selected.

[0090] It is further proposed to increase the feed-in power P grid to the time-averaged performance of the wind farm P wec ˜ This can be achieved if the battery is charged with an average power P bat ˜ t This power can be compared to the dynamic power that the battery can deliver according to the Fig. 4 to 9 emits or absorbs. It is proportional to the difference between P wec ˜ and P grid and it can be adjusted using a weighting F as follows: P bat ˜ t = P wec ˜ t 2 − P grid t 1 ⋅ F

[0091] The weighting F is therefore a suitable proportionality factor to be chosen.

[0092] In order to ensure compliance with limit power gradients using the battery, especially as it is related to the Fig. 4 to 9described, and at the same time to ensure the operation of the storage medium at a stable charge level, it is proposed to assign the storage medium a nominal power P bat_total ( t ) resulting from the superposition of P bat ( t ) and P bat ˜ as follows: P bat _ gesamt t = P bat t + P bat ˜ t

[0093] To improve the feed-in performance of the wind turbine together with the battery, it is also proposed to reduce the boundary gradients Δ P Δ t lim down and Δ P Δ t lim up of equations [3] and [4] depending on the state of charge SoC. It was recognized that this can influence the state of charge, especially the average state of charge, at least if the charging station is controlled in the way Fig. 4 to 9 was described.

[0094] Fig. 10 shows an example of the constellation according to Fig. 3Two temporal power curves, namely the power P wec of at least one wind turbine and the total feed-in power P Grid of the wind turbine and charging station or battery combined. Basically, two parameterizations are considered. The first parameterization sets the aforementioned weighting factor F to zero and is also based on two equal and constant values ​​for the increase limit gradient and the decrease limit gradient. This configuration is mathematically defined below as "Parameterization 1."

[0095] However, a parameterization called "Parameterization 2" is preferred, which is used in the Fig. 10 and 11 is simply referred to as "Wind+Battery (optimized)". In this preferred embodiment, the weighting factor F is not set to zero and different and variable values ​​are used for the increase limit gradient and the decrease limit gradient. Fig. 10 and 11 show results only for this second parameterization.

[0096] Fig. 11 shows the battery state of charge curve for the second power feed-in control configuration. A target state of charge of 50% is shown in the diagram and is labeled "SoC target." • Parameterization 1: Wind+Battery: F=0 (equation [5]) and Δ P Δ t lim down , Δ P Δ t lim up = konstant • Parameterization 2: Wind+Battery (optimized): F≠0 (equation [5]) and Δ P Δ t lim down , Δ P Δ t lim up = variabel F is therefore temporally variable in the second parameterization and depends on: ∘ the current state of charge SoC, ∘ the target state of charge "SoC target and / or ∘ the time-averaged power curve of the wind farm P wec ˜ .

[0097] The dimensionless, positive factor F varies over time depending on the application between the values ​​0 and 1 (or greater). The greater the difference between the current state of charge (SoC) and the target state of charge (SoC_target), the larger the factor F is selected, at least according to a preferred embodiment. The factor F is changed or adjusted depending on the state of charge. Δ P Δ t lim down , Δ P Δ t lim up is also time-variable in the case of parameterization 2 and depends on the difference between the current charge state SoC and the target charge state SoC_target.

[0098] The result of the Fig. 10 shows that the proposed control of charging station 8, namely a control based on parameterization 2, can achieve a highly stable feed-in power compared to the feed-in of the wind turbine without battery.

[0099] The Fig. 11shows the course of the total feed-in power P Grid of the wind turbine and charging station together according to Fig. 10 the corresponding SoC charge level. Fig. 11 It can be seen that with parameterization 2, the preferred control system, the battery can be operated with a comparatively stable state of charge. If the battery's state of charge drops as a result of a brief drop in wind turbine power, which occurs approximately after 550 seconds, the state of charge converges back to its target value (SoC target) after a short time.

[0100] Fig. 12 shows in contrast to Fig. 3 a second constellation of an underlying or considered network 201. Basically, this network 202 also has the elements or

[0101] Participants who are in Fig. 3explained, namely consumer 202, a wind turbine 206, which can also be representative of a wind farm, a battery 208, which here also represents the charging station, and at least one conventional generator 204.

[0102] For this constellation, it is now proposed to control the charging station 208 or battery 208 such that the power P Gen fed into the grid by the generator 204 is limited in its temporal change. This power P Gen fed into the grid by the generator thus forms the feed-in power, the change of which is limited in its temporal change. The underlying consideration here is that fluctuations in the consumer 202 as well as fluctuations in the fed-in power P wec of the wind turbine 206 without the charging station 208 or battery 208 would result in these fluctuations having to be compensated by the power P Gen fed in by the generator. If these temporal changes are too great, the conventional generator would have to change its load too quickly, or in the case of generator banks, this would mean that generators would have to be switched on or off too quickly.This is particularly detrimental to the service life of fossil fuel-based engines, especially diesel engines. The charging station or battery 208 is designed to compensate for this. To do so, the change in the feed-in power P Gen is detected and the charging station or battery 208 is controlled accordingly.

[0103] If the consumers 202 essentially consume their power constantly, this constellation and corresponding control of the battery 208 or charging station 208 can lead to very similar results as in the constellation according to Fig. 3 In this case, the aforementioned power fluctuations arise only from power fluctuations of the wind turbine 206. The battery 208 or charging station 208 would therefore also prevent an excessive power change of the wind turbine 206 in this case.

[0104] However, in the event that the consumers also fluctuate, the battery 208 will record and take into account the entire power fluctuation resulting from the consumers 202 and the wind turbine 206.

[0105] For further details, reference is made above to the parts of the general description that describe features and embodiments of this second constellation.

Claims

1. Method for operating an electrical charging station (8) at an electrical grid (1) comprising, alongside electrical loads (2), at least one regenerative energy generator (6), at least one conventional generator (4) operated by fossil fuels, and at least the electrical charging station (8) for storing and re-emitting electrical power, comprising the following steps: - generating electrical power by means of the at least one regenerative energy generator (6) and feeding the electrical power into the grid (1), - storing electrical power not consumed by the loads (2) in the charging station (8), - feeding electrical power into the grid (1) by means of the charging station (8) if the loads (2) consume more power than is fed into the grid (1) jointly by the at least one regenerative generator (6) and the at least one conventional generator, wherein - in a first configuration of the grid (1), a feed-in power fed into the grid (1) is a sum of - the power of the at least one regenerative energy generator (6) and - the power of the charging station (8) and optionally in addition - the power of the at least one further generator assigned to the charging station (8), wherein the charging station (8) is controlled in such a way that the feed-in power is limited in terms of its change over time, and wherein the power to be emitted or taken up by the charging station (8) is altered by a compensation value depending on a state of charge in order to approximate the present state of charge to a predefined target state of charge, and wherein for limiting the change over time of the feed-in power, two limiting gradients are predefined, namely - a rise limiting gradient, which determines with what change per time the feed-in power is intended maximally to increase, and - a decrease limiting gradient, which determines with what change per time the feed-in power is intended maximally to decrease, characterized in that the charging station (8) is controlled in such a way - that the change of the feed-in power is guided within a positive and negative limit or within the rise limiting gradient and the decrease limiting gradient and that for the case of the first configuration - the change of the feed-in power is positive if the charging station (8) has a state of charge that is above a predefined target state of charge, or - the change of the feed-in power is negative if the charging station (8) has a state of charge that is below a predefined target state of charge.

2. Method according to Claim 1, characterized in that the rise limiting gradient and the decrease limiting gradient differ from one another in terms of absolute value.

3. Method according to any of the preceding claims, characterized in that at least one of the limiting gradients - is set adaptively, - is set depending on a mean state of charge of the charging station (8), - is set in such a way that the charging station (8) does not fall below a predetermined minimum state of charge, - is set in such a way that the charging station (8) does not exceed a predetermined maximum state of charge, and / or - is set in such a way that a mean state of charge of the charging station (8) assumes a predetermined charging setpoint value, SoC_target.

4. Method according to any of the preceding claims, characterized in that at least one of the limiting gradients is calculated from a predefined basis limiting gradient multiplied by at least one weighting factor, wherein in particular - at least one of the weighting factors is dependent on a state of charge, SoC, of the charging station (8), - at least one of the weighting factors can vary in the range of 0 to 1, - at least one of the weighting factors has a value of at least 1, in particular is in the range of 1 to 10, and / or - at least two weighting factors are used for the calculation of a respective limiting gradient.

5. Method according to any of the preceding claims, characterized in that for the case of the first configuration - the charging station (8) emits electrical power which is fed into the grid (1) together with electrical power of the at least one regenerative energy generator if the electrical power of the regenerative energy generator (6) decreases with a gradient which, in terms of absolute value, is greater than the predefined decrease limiting gradient, or that - the charging station (8) takes up electrical power (P) in order to decrease the electrical power (P) of the at least one regenerative energy generator (6) that is fed into the grid (1) if the electrical power (P) of the regenerative energy generator (6) increases with a gradient which, in terms of absolute value, is greater than the predefined rise limiting gradient.

6. Method according to any of the preceding claims, characterized in that a time difference between a present second point in time and an earlier first point in time is taken into account for controlling the charging station (8), and in that at the earlier first point in time, as earlier feed-in gradient, account is taken of a gradient of the power which was fed into the grid at the first point in time jointly by the at least one regenerative energy generator and the charging station and, if appropriate, at least one further generator.

7. Method according to Claim 6, characterized in that for the case of the first configuration the power to be emitted or taken up by the charging station (8) at the second point in time is calculated from a product of - the time difference and - a difference between - the absolute value of the rise limiting gradient and - the earlier feed-in gradient if the charging station (8) has a state of charge, SoC, that is above a predefined target state of charge, SoC_target, or otherwise from a product of - the negative time difference and - the sum - of the absolute value of the decrease limiting gradient and - the earlier feed-in gradient, wherein furthermore or alternatively a measurement value of a first measurement point is used at the first point in time and a measurement value of a second measurement point is used at the second point in time.

8. Method according to any of the preceding claims, characterized in that the at least one regenerative generator (6), in particular the wind energy installation (6), - momentarily increases its fed-in power above the power maximally available from the wind at the moment, - momentarily increases its fed-in power above the instantaneously fed-in power, - momentarily decreases its fed-in power below the power maximally available from the wind at the moment, or - momentarily decreases its fed-in power below the instantaneously fed-in power, in order thereby to decrease power spikes to be compensated for by the charging station or by the at least one conventional generator, and / or that also the at least one regenerative energy generator, in particular a wind energy installation, is controlled in such a way that the feed-in power is limited in its change.

9. Electrical grid (1), in particular island grid (1), prepared to be operated by a method according to any of the preceding claims, wherein instead of the first configuration a second configuration of the network (1) is proposed in which the feed-in power fed into the grid (1) is the power generated by the at least one conventional generator (4).

10. Electrical grid (1) according to claim 9, characterized in that the electrical grid prepared for a method according to any of claims 1 to 4 for the case of the second configuration - the charging station (8) emits electrical power to the grid (1) if the electrical power fed into the grid (1) by the at least one conventional generator increases with a gradient which, in terms of absolute value, is greater than the predefined rise limiting gradient, or that - the charging station (8) takes up electrical power from the grid if the electrical power fed into the grid (1) by the at least one conventional generator decreases with a gradient which, in terms of absolute value, is greater than the predefined decrease limiting gradient.

11. Charging station (8), prepared for use in a grid (1) according to Claim 9 or 10.

12. Wind energy installation (6), prepared for use in an electrical grid (1) according to Claim 9 or 10.

13. Wind farm (112) prepared for use as a regenerative energy generator (6) in an electrical grid (1) according to Claim 9 or 10.