WO2013068233A2

WO2013068233A2 - Method for providing reserve power for stabilizing an alternating current network

Info

Publication number: WO2013068233A2
Application number: PCT/EP2012/071064
Authority: WO
Inventors: Georg Markowz; Wolfgang SCHWEISSTHAL; Carsten Kolligs; Holger BREZSKI; Wolfgang Deis; Michael Igel; Anna FLEMMING; Dennis GAMRAD; Sébastien COCHET; Stefan Winternheimer
Original assignee: Evonik Industries Ag; Evonik Degussa Gmbh; Steag Power Saar Gmbh
Priority date: 2011-11-10
Filing date: 2012-10-24
Publication date: 2013-05-16
Also published as: DE102011055249A1; WO2013068233A3

Abstract

The invention relates to a method for providing reserve power for stabilizing an alternating current network, wherein the alternating current network operates at a specified frequency and a frequency band around the specified frequency is defined, comprising an energy store, which can receive and output electrical energy, wherein the provision of the reserve power by means of the energy store is changed if there is a lasting frequency deviation outside the frequency band over a defined time period, wherein said change comprises a changeover from the specified frequency to a variable control frequency.

Description

Method of providing control power to stabilize an AC grid

The present invention relates to a method for the provision of control power for stabilizing an AC network and to an apparatus for carrying out such a method.

Electricity grids are used to distribute electricity from many energy generators in large areas to many users and to supply households and industry with energy. Energy producers, usually in the form of power plants, provide the required energy. As a rule, power generation is planned and provided based on the forecasted consumption.

Both the generation and the consumption of energy can lead to unplanned fluctuations. These can arise on the energy producer side, for example, in that a power plant or part of the power grid fails or, for example, in the case of renewable energies such as wind, that the energy production is higher than predicted. Consumers may also experience unexpectedly high or low consumption. For example, the failure of a portion of the grid, which cuts off some consumers from the power supply, can lead to a sudden reduction in power consumption. This generally results in power network fluctuations due to unplanned and / or short-term variations in power generation and / or consumption. The desired AC frequency is, for example, 50 Hz in Europe. A reduction in consumption compared to the plan results in an increase in the frequency at planned power fed in by the energy producers, as well as an increase in electricity production compared to the planned consumption plan. On the other hand, a reduction in the output of the energy producers compared to the plan leads to a reduction of the network frequency at scheduled consumption, as well as to an increase in consumption compared to the plan at scheduled production. l For reasons of network stability, it is necessary to keep these deviations within a defined range. For this purpose, depending on the amount and direction of the deviation, it is necessary to provide specifically positive control power by connecting additional generators or switching off consumers, or negative balancing power by shutting down generators or adding consumers. There is a general need for economical and efficient provision of these control powers, where the requirements for the capacities to be kept and the dynamics of the control power sources or sinks can vary depending on the characteristic of the power grid. In Europe, for example, there is a set of rules (UCTE Handbook) that describes three different categories of control power. This also defines the respective requirements and the control power types. The types of balancing power differ, among other things, in the demands on the dynamics and the duration of the service provision. In addition, they are used differently with respect to the boundary conditions. Primary control power (PRL) is to be provided by all integrated sources throughout Europe, regardless of the location of the disturbance, substantially in proportion to the actual frequency deviation. The absolute maximum power is to be provided at frequency deviations of minus 200 mHz and (absolute) below, the absolute minimum power is to be provided at frequency deviations of plus 200 mHz and above. With regard to dynamics, it is necessary to provide the (maximum) performance within 30 seconds from hibernation. In contrast, secondary control power (SRL) and minute reserve power (MRL) are to be provided in the balancing rooms in which the fault has occurred. Their task is to compensate for the disturbance as quickly as possible and thus to ensure that the frequency is back within the desired range as quickly as possible, preferably at the latest after 15 minutes. In terms of dynamics, the SRLs and the MRLs have lower requirements (5 or 15 minutes to full service delivery after activation), and at the same time these services must be provided for longer periods than primary control capacity. In the power grids operated so far, a large part of the control power is provided by conventional power plants, in particular coal and nuclear power plants. Two fundamental problems result from this. On the one hand, the conventional power plants providing control power are not operated at full load and thus maximum efficiencies, but slightly below them in order to be able to provide positive control power if required, if necessary over a theoretically unlimited period of time. On the other hand, with increasing expansion and increasing preferential use of renewable energies, fewer and fewer conventional power plants are in operation, which is often the prerequisite for the provision of balancing services.

For this reason, approaches have been developed to use more memory to store negative control power and provide it as a positive control power when needed.

The use of hydro pumped storage plants to provide control power is state of the art. In Europe, all of the above three types of control are provided by pumped storage. However, hydropumps are also often referred to as the currently most economical technology for the injection and withdrawal of preferably renewable energies, in order to be able to better match the energy supply and demand in terms of time. The potential for expanding storage capacity - especially in Norway - is a matter of controversy, as significant capacity in power lines needs to be approved and installed for use. Consequently, the use for the energy management of load management is in competition with the provision of control power.

Against this background, in the area of primary control power in the recent past, approaches have repeatedly been explored and described for the use of other storage technologies, such as flywheel mass and battery storage, for the provision of control power.

From US 2006/122738 A1 an energy management system is known, which comprises a power generator and an energy store, wherein the energy store can be charged by the power generator. This is intended to be an energy generator in the normal operation does not ensure consistent generation of energy, such as the increasingly favored renewable energy sources, such as wind power or photovoltaic power plants, being able to deliver their energy more evenly into the grid. The disadvantage of this is that in this way a single power plant can be stabilized, but all other disturbances and fluctuations in the power network can not be intercepted or only to a very limited extent.

It is known from WO 2010 042 190 A2 and JP 2008 178 215 A to use energy storage to provide positive and negative control power. When the grid frequency leaves a tolerance range around the desired grid frequency, either energy is provided from the energy store or added to the energy store to regulate the grid frequency. DE 10 2008 046 747 A1 also proposes operating an energy store in an island power grid in such a way that the energy store is used to compensate for consumption peaks and consumption minima. The disadvantage hereof is that the energy stores do not have the necessary capacity to compensate for a longer disturbance or a plurality of disturbances rectified with respect to the frequency deviation one after the other.

In the article "Optimizing a Battery Energy Storage System for Primary Frequency Control" by Oudalov et al., In IEEE Transactions on Power Systems, Vol. 22, No. 3, August 2007, dependency of the capacity of a rechargeable battery of technical and operational It is shown that due to the injection and withdrawal losses in the long term at different time intervals repeatedly charging or discharging the memory is unavoidable, the authors suggest the time periods Although the frequency may be in the deadband (ie in the frequency range where there is no control power available), it may happen temporarily or temporarily that the memory becomes overloaded, and the authors suggest that (limited Use) of loss-generating resistors, which extremal the complete negative nominal Regelei stung record, so it must be interpreted. In addition to the additional investment required for the resistors and their cooling, however, this leads, as already mentioned by the authors, to a more or less undesirable energy depreciation, with the resulting waste heat usually can not be used. The authors point out that a lower utilization of loss production is only possible through a higher storage capacity, combined with higher investment costs.

In view of the prior art, it is therefore an object of the present invention to provide a technically improved method for providing control power for stabilizing an AC network, which is free from the disadvantages of conventional methods.

In particular, the process should be as simple and inexpensive as possible. In particular, the installations with which the procedure can be carried out should be associated with the least possible investment in terms of the provision of control power.

It should be possible to provide control power at a high efficiency of the components used.

Another object of the invention is to be seen in that the capacity of the energy storage device should be as low as possible in order to provide the required control power.

Furthermore, the energy producers and energy consumers should have the most efficient possible energy yield as control power suppliers.

The inventive method should also be able to provide the necessary control power as needed as quickly as possible. In addition, the process should be able to be carried out with as few process steps as possible, whereby they should be simple and reproducible. Other tasks not explicitly mentioned emerge from the overall context of the following description and the claims.

These are solved as well as other tasks that are not explicitly mentioned, but which are readily derivable or deducible from the contexts discussed in the introduction, by a method having all the features of patent claim 1. Advantageous modifications of the method according to the invention for the provision of control power for a power grid, in which control power is provided are placed in the subclaims 2 to 12 under protection. Furthermore, claim 13 has an apparatus for performing such a method to the subject.

The subject of the present invention is accordingly a method for the provision of control power for stabilizing an AC network, wherein the AC mains operates at a default frequency and a frequency band is defined around the default frequency, comprising an energy store which can receive and deliver electrical energy characterized in the case of a permanent frequency deviation outside the frequency band over a defined period of time, the provision of the control power to the energy store is changed, this change comprising a changeover from the default frequency to a variable control frequency. By the method according to the invention, among others, the following advantages can be achieved:

This makes it possible in an unpredictable manner to provide a method for providing control power for stabilizing an AC network, which does not suffer from the disadvantages of conventional methods. In particular, the present invention allows to provide control power with a high efficiency of the components used. Furthermore, with the use of galvanic elements, such as accumulators, the capacity of the energy storage can be kept very low in order to provide a required control power.

Furthermore, the energy producers and energy consumers have a very efficient energy yield as a control power suppliers.

The inventive method is also suitable to provide the necessary control power very quickly.

In particular, the method can be carried out as simply and inexpensively as the storage capacity required for full availability can be reduced or the number of charging and discharging that must be made to adjust the state of charge of the energy storage with external energy sources can be reduced. It should be noted that the energy storage can draw power through the power network through energy trading. This service must be purchased and recalled at a specific time, otherwise the system will malfunction. Actual grid frequency is insignificant for this process as it does not affect the frequency of the grid in the case of a planned, simultaneous feed-in and take-out of a power. Rather, it is important that the feed-in and the removal of this power take place as synchronously as possible. With a constant capacity of the energy storage, as a result of the reduced charging / discharging cycles, the operational life of the storage can be increased, this being an important consideration, in particular for accumulators, which can be surprisingly improved by the present invention.

Furthermore, the control power suppliers, in particular the energy producers and / or energy consumers, selectively provide a sufficient amount of positive or negative control power regardless of the amount and direction of the deviation of the grid frequency.

Moreover, the process can be carried out with very few process steps, the same being simple and reproducible. The present method serves to provide control power for stabilizing an AC network. As already explained in the introduction, the frequency changes in an AC grid if the balance between energy consumption and energy supply is not maintained. The control energy or control power is delivered to the power grid (positive control energy or positive control power) or taken from the mains (negative control energy or negative control power). Positive control power can be supplied by energy supply, such as energy input of an energy storage or by connecting a power plant, or by throttling a consumer in the network. Negative control power may be supplied to the grid by absorbing energy from an energy store, throttling an energy source, such as a power plant, or by connecting a load to the grid. Further important information on this can be found in the prior art, reference being made in particular to the documents discussed in the introduction. In this context, it should be noted that the terms control power and control power have similar meaning for purposes of this invention.

Normally, control power for a given nominal power is provided by the provider to the network operator. In this case, the nominal power is to be understood as meaning the power with which the control power source, which is operated by a method according to the invention, is at least prequalified. However, the prequalification performance may be higher than the nominal power provided to the network operator at maximum. This nominal power can also be referred to as contracted maximum power, as this power is provided to the grid at maximum.

The method according to the invention serves to stabilize an AC network. AC grids are characterized by a change in the polarity of the electrical current, with positive and negative instantaneous values complementing each other so that the current is zero on average over time. These networks are generally used for the transmission of electrical energy. The alternating current networks are usually operated at a default frequency, which is 50 Hz in Europe, especially in Germany. In contrast, in North America, the default frequency is 60 Hz. This default frequency is often referred to as the desired frequency. Frequency bands are usually defined by the network operator around this default frequency outside of which positive or negative control power must be provided. Exact details can be found in European standards (Handbook), which were developed to operate the European network system UCTE (Union for the Coordination of Transmission of Electricity) and are implemented in national guidelines (eg Transmission Code for Germany).

At present, there are two tolerances for sources of primary control power that are relevant to frequency deviations. First, this is the frequency measurement accuracy. This must not exceed +/- 10 mHz. In addition, there is a so-called insensitivity range of a maximum of +/- 10 mHz, which is granted to the primary control power sources. In order to avoid operating the control power sources in any case contrary to the desired direction, the transmission system operators in Germany have specified in their framework contracts, for example, a band of +/- 10 mHz around the setpoint of 50 Hz, in which no primary control power is to be provided. Even at maximum frequency accuracy of + 10 mHz or - 10 mHz, the provision of control power against the desired direction is excluded. Outside these limits, reserve power must be provided in accordance with the terms of the contract.

The bandwidth of the frequency band, which is used to assess a permanent frequency deviation is not critical to the present invention and can be adapted accordingly to the requirements of the network operator. Here, the frequency band used according to the invention for determining the control power supply according to a changed mode may differ from the frequency range which serves to describe the provision of control power according to the standard specifications. So For example, the term deadband will be used hereinafter to indicate the provision of a control power in accordance with the standard specifications, whereas the term frequency band describes a range of frequencies used to determine whether control can be made to a variable control frequency, as described below.

Here, the frequency band, which is defined by the default frequency, correspond to the dead band. According to another alternative, the frequency band may be larger than the deadband. Furthermore, the deadband may be larger than the frequency band. According to the present invention, the provision of the control power is changed with the energy storage at a permanent frequency deviation outside the frequency band over a specified period. Accordingly, it is checked whether the network frequency is permanently outside the frequency band defined by the default frequency. In the event of a permanent deviation of the mains frequency over a defined period, the provision of the control power is changed.

The specified period of time depends on the requirements of the network operator and can accordingly be variable. According to the regulations currently in force in Europe, a primary balancing power source must be able to provide the primary balancing power in Europe for a minimum of 15 minutes. In America, other rules apply, and the present invention should not be limited to a particular region or a specific set of rules. Advantageously, the specified period may for example be in the range of 0 minutes to 24 hours, preferably 1 minute to 8 hours, preferably 2 minutes to 1 hour and more preferably 5 minutes to 30 minutes. Preferably, such time periods should be chosen within which the other types of control power (for example SRL and if necessary MRL) should be able to compensate for any disturbances.

A permanent frequency deviation outside the frequency band is given if the network frequency at least over the specified period of time set out above to 60%, preferably at least 80%, preferably at least 90%, more preferably at least 95%, and most preferably at least 99% on one side above or below the frequency band, within which no control is required. According to a particularly preferred embodiment, a permanent frequency deviation outside the frequency band means that the frequency is outside the frequency band over the entire period.

If there is a permanent frequency deviation outside the frequency band over a specified period of time, a change in the preset frequency of the energy store to a variable control frequency takes place after this specified period of time. Accordingly, the fixed preset frequency is replaced by a variable frequency control. In this case, it is possible to control to a previously defined frequency which, depending on the deviation, can be above or below the predetermined frequency band. For example, upon entering the previously defined conditions, a control frequency can be set, for example, 10 mHz, 20 mHz, 30 mHz higher or lower than the default frequency, depending on the nature of the previously determined permanent deviation of the network frequency. In the case of a deviation of the mains frequency to lower values, that is to say for example with an average value of 49.95 Hz, a control frequency of 49.98 Hz can likewise be set. Here, in a continued unilateral frequency deviation in stages further changes can be made so that, for example, in a permanent frequency deviation after 5 minutes to a control frequency of 49.99 Hz and after another 5 minutes to 49.98 Hz is regulated. In this case, the change in the default frequency to a changeable control frequency can be very small, so that, if appropriate, the frequency value of the default frequency is maintained, but a comparison with the standard specifications modified control power is provided.

According to a preferred embodiment, the variable control frequency can be determined by a sliding averaging of the measured frequency. Guiding averaging means that not all data points are used to calculate the mean, but only part of it. Preferably, the moving average is calculated by taking into account the data determined over a period not exceeding three times, preferably not more than twice that of the previously defined period. In particular, it may also only be part of the defined period of time defined above. For example, the time period over which the values for determining the conducting average are collected may be in the range of 3 minutes to 2 hours, preferably 5 minutes to 1 hour and more preferably 10 minutes to 30 minutes.

Here, the mean values can be formed in a variety of ways, such as a simple shift, without weighting the data (simple moving average (SMA)). According to a preferred embodiment, a weighted moving average (WMA) in which the younger data is preferably of a higher weight than the older one may be used to determine the variable frequency. Here, a simple weighting can be done or an exponential smoothing can be performed. The number of data points depends on the frequency of the frequency measurement, whereby the average values of the data can be used to reduce the memory space. According to a preferred embodiment, within a period of 1 minute at least 10 data points are formed, which can be used to determine the mean value.

It can also be provided according to the invention that the absolute difference between the mean network frequency and the default frequency in the provision of the service by the energy store is taken into account. The mean network frequency can be done, for example, from the network frequencies via an averaging, which is based on previously set out procedures that are also used to determine the variable control frequency, the average power frequency obtained may correspond, for example, a theoretically adjustable variable control frequency. So can with a strong deviation of the mean network frequency of the default frequency be provided that a control to a fixed higher or lower variable control frequency, this fixed higher or lower frequency between the average power frequency and the default frequency is. In this way, an impermissible shift of the preset frequency can be avoided with a very high proportion of control power provided by the method according to the invention. Furthermore, a system-compliant control can be ensured.

According to a further embodiment, the state of charge of the energy store can be taken into account in the determination of the variable control frequency. For example, if the state of charge of the energy store is relatively high at the beginning of a phase at which positive control power is to be provided, the fixed period over which the default frequency is controlled may be extended. In the case of a relatively low state of charge of the energy store, if a negative control power is to be provided, this period can likewise be increased. Furthermore, it can be provided that it is checked whether a change in the control power supply to a variable control frequency leads to an optimization of the state of charge. In this context, with a corresponding state of charge and a standard control can be maintained, according to the control power is provided at a deviation from the default frequency, although a change to a variable control frequency would be possible.

Control to a variable control frequency can be maintained for any period of time. A return of the provision of control power according to the standard specifications, in which is controlled to the default frequency, can be achieved, for example, that is terminated at a predetermined state of charge of the energy storage, the control on the variable control frequency.

Furthermore, it can be checked whether the variable control frequency is without special measures over a longer period in the frequency band, which is defined by the default frequency. In this embodiment, the variable control frequency may be determined, for example, by a weighted averaging become. If this check results in the variable control frequency being in the frequency band for an extended period of time, the control can be reversed to a variable control frequency.

This longer period is not subject to any special conditions, so that it can be chosen arbitrarily. For example, this longer period of time may be identical to the specified period of time determined with respect to the permanent frequency deviation. Furthermore, this longer period may also be significantly shorter, so that this period may for example be in the range of 1 second to 1 hour, preferably 1 minute to 30 minutes. Furthermore, it can be provided that, when the frequency enters the previously defined frequency band, a dead band or another frequency value range, the regulation to a variable control frequency is terminated.

Alternatively, it can be provided that after a predetermined period of time, was regulated by a variable control frequency, this exception rule is reversed and regulated according to the rules on the default frequency. For example, the network operator can provide a time limit for the change of the control frequency, so that, for example, after a maximum of 2 days, preferably after a maximum of 1 day, preferably after a maximum of 6 hours and more preferably at most 2 hours, the original default frequency is regulated. Any necessary adjustment of the state of charge of the energy storage device can be done via the power grid by electricity trading, as stated above. It is important to ensure the most synchronous feeding and removal of energy or power.

However, this can be associated with disadvantages in terms of compliance with the default frequency of the AC mains, if there are many units in the power grid, the default frequency is replaced according to the present method after a specified period by a variable control frequency. Accordingly, in a preferred embodiment, the variable control frequency be maintained until the state of charge of the energy storage allows control to the default frequency.

According to a particular embodiment, the possibility of changing the control frequency may be dependent on the time of day. As a result, for example, a high stability of the network can be ensured even with expected special load conditions in the network. Thus, at peak loads an adjustment of the control frequency, which would be useful for the regeneration of the energy storage due to the deviation of the mains frequency from the default frequency over a longer period, are excluded. A further preferred embodiment consists in that the method according to the invention is practiced only by a part of the primary control power providers, in particular stores, or up to a maximum total primary control power to be provided by these sources.

In a further embodiment, the time periods set forth above and the adjustment of the control frequency for longer duration deviations of the frequency are set differently upwards than for longer duration deviations of the frequency.

In this context, it should be noted that the method can contribute to the stabilization of the network even with a relatively small capacity of the energy store, since provision of control power can also take place if the network frequency is outside the deadband for a very long period of time, within which no regulation is necessary.

According to a particular embodiment, a regeneration of the energy storage even then take place when the measured frequency is longer term on one side outside a deadband. In particular, an energy storage in the event of a permanent negative deviation outside a dead band can also absorb energy by transitioning to a variable control frequency, for example, if the frequency is below the preset frequency and actually positive control power would have to be provided. These Embodiment is particularly in connection with the way of exploiting tolerances, which, for example, in terms of the amount of control power delivery, the time within which the control power is to be provided, and the frequency tolerances to optimize the state of charge. For example, more negative control power can be provided if the state of charge of the energy storage is very low due to a network frequency, which is on average over a longer period below the default frequency. In this case, tolerances, for example the tolerances granted to the control power provider by the network operator, with regard to the mains frequency, the amount of control power depending on the frequency deviation, the insensitivity to the frequency change, and the period within which the control power is to be provided, can be exploited adjust the state of charge of the energy storage to the requirements. Thus, for example, at least 105%, preferably at least 1 10% and particularly preferably at least 1 15% of this control power can be provided instead of the planned negative control power. If, in the case of a low state of charge, positive control power now has to be provided, then the power to be provided by contract is provided as precisely as possible in this case. Furthermore, the energy intake can take place immediately in the case of a low charge state, while the energy is fed in at the latest possible time according to the regulations or with a rise which is as slow as possible according to the regulations. Furthermore, the frequency tolerance granted by the network operator can be used by carrying out a measurement with a higher accuracy, whereby the difference thus obtained is specifically used for the given inaccuracy of measurement in order to minimize the power in accordance with the regulations, ie within the given tolerance range to feed in the network or to record as much power as possible from the network. In a high state of charge can be mirrored procedure. For example, a high energy output when providing a positive control power and a low power consumption while providing a negative control power is possible or realized. The tolerance with regard to the amount of the control power provided and the tolerance in determining the frequency deviation, etc., is to be understood by the network operator to be certain deviations between an ideal nominal power due to technical conditions, such as the measurement accuracy in determining the control power supplied or the grid frequency and the actual control power actually delivered. The tolerance may be granted by the network operator, but could also comply with a legal requirement.

According to a particular embodiment, the supply of energy in the energy storage may be dependent on the time of day. As a result, a high stability of the network can be ensured even at a high load at certain times of the day. Thus, at peak loads, a regeneration of the energy storage, which would be useful due to the deviation of the mains frequency from the default frequency over a longer period, are excluded.

Furthermore, it can be provided that a plurality of energy stores are used in accordance with the present method. In a particular embodiment, in this case, all or only a part of these energy stores can provide a control power adapted to the state of charge of the energy store, as has been explained above.

The size of the energy storage within the pool can vary. In a particularly preferred embodiment, in the various energy stores of a pool in the use of tolerances, in particular the choice of bandwidth in the deadband, the change from one parameter setting to another not synchronously, but deliberately offset in time to minimize any disturbances in the network or at least tolerable.

In a further preferred embodiment, the tolerances used in the various methods, in particular the choice of bandwidth in the dead band, vary depending on the time of day, the day of the week or the season. For example, in a period of 5 min before to 5 min after the Hours change tolerances are defined more closely. This is due to the fact that often very rapid frequency changes take place here. It may be in the interest of transmission system operators that there are lower tolerances and thus the control energy supply is more secure in the sense of sharper. According to a further embodiment, it can be provided within the scope of the specifications for the provision of control power that on average more energy is absorbed by the energy store than is fed in by the energy store. This can be done by providing very much negative control power in accordance with the regulations including the procedure outlined above, whereas according to the regulations including the procedure set out above, preferably only the at least guaranteed power is provided at positive control power. Preferably, an average of at least 0.1% more energy is withdrawn from the network than is supplied, in particular at least 0.2%, preferably at least 0.5%, more preferably at least 1.0%, especially preferably 5%, these values being based on a Average measured over a period of at least 15 minutes, preferably at least 4 hours, more preferably at least 24 hours and especially preferably at least 7 days, and refer to the energy fed.

In this case, the control power provision set out above can be used to extract a maximum of energy from the network, whereby the maximum possible negative control power is provided, whereas only a minimum of positive control power is provided.

In the embodiments for the preferred and especially for the maximum energy consumption, the energy thus extracted from the network can be sold via the energy trade described above, preferably at times when the highest possible price is to be achieved. For this purpose, forecasts of the price development based on historical data can be used.

Furthermore, the state of charge of the energy store at the time of a planned sale of energy may preferably be at least 70%, especially preferably at least 80% and particularly preferably at least 90% of the storage capacity, wherein the state of charge after sale is preferably at most 80%, in particular at most 70% and particularly preferably at most 60% of the storage capacity. In the case of a permanent frequency deviation outside the frequency band, the control power can be provided in accordance with the usual regulations, which are also provided for a short-term regulation of the network frequency. In Europe, according to current regulations, the amount of the service to be provided is to be increased largely linearly with increasing frequency deviation from the default frequency. Thus, with a deviation of 100 mHz, a control power is usually provided which amounts to 50% of the maximum power. This maximum power is provided at a deviation of 200 mHz and corresponds to the previously defined rated power or contracted maximum power, for which the energy storage is at least prequalified. With a deviation of 50 mHz, accordingly, 25% of the rated power is provided.

This regulation can, however, be maintained with the change in the default frequency to a variable control frequency as explained above. In this case, the frequency values at which the maximum power or nominal power is to be provided can be shifted accordingly. Alternatively, these frequencies can be maintained. For example, with a variable control frequency of 49.90 Hz (change from -100 mHz to the normal default frequency) and a power frequency of 49.80 Hz (deviation from -200 mHz to the normal default frequency) only 50% of the actual maximum power can be provided because the originally lower limit of 49.80 Hz was reached, however, with a deviation of 100 mHz only 50% of the maximum power is to be provided.

Alternatively, for example, with a variable control frequency of 49.90 Hz (change from -100 mHz to the normal default frequency) and a power frequency of 49.80 Hz (deviation from -200 mHz to the normal default frequency) 100% of the actual maximum power can be provided, although the Deviation from variable frequency is only 100 mHz, but the lower threshold for the maximum power has been reached according to the default frequency.

According to another variant, a control power can be provided, which is preferably system-supporting, but by no means counterproductive. In this context, it should be noted that, for example, at a sufficiently large deviation of the variable control frequency of the default frequency down the state may occur that the energy storage due to a comparatively small positive frequency deviation to the new control frequency provides negative control power, ie energy from the network receives, although the frequency deviation to the default frequency is negative and according to the standard control to the default frequency a positive control power would have to be provided. For example, with a variable control frequency of 49.90 Hz (change from -100 mHz to default frequency) and a current power frequency of 49.95 Hz (deviation from -50 mHz to default frequency) according to the dependency set out above, a negative control power can be provided the grid frequency is 50 mHz greater than the frequency that the system controls. This type of control is not system-compliant, as it is regulated against the actual requirements or the actual system requirements, according to which positive control power is to be provided at a mains frequency of 49.95 Hz. A system-compliant control may accordingly provide that no control power is provided at a mains frequency that is between the default frequency and the variable control frequency. Although the energy storage device is not regenerated by this measure, it is spared from operation based on the preset frequency. In this context, it should be noted in particular that with a greater deviation of the mains frequency, a lower control power is provided than provided by the standard, which is regulated to the default frequency.

Furthermore, it can be provided that, in the case of particularly strong deviations of the grid frequency, a higher power is provided by the energy store at least for a short time than, for example, according to a control power provision a linear dependence is provided. Thus, for very large deviations or high increases in frequency deviation over time, changes in the slope of this frequency-dependent power delivery curve may be provided. These changes in the frequency-dependent power output curve can be provided, for example, with an absolute difference of the mains frequency from the default frequency by at least 100 MHz, preferably by at least 150 MHz. In this case, the change in the slope is dependent on the requirements of the network operator, wherein in general, the nominal power to be provided at 200 mHz (based on the default frequency in a standard control power delivery) can be provided at this frequency.

According to the invention, an energy store is used to carry out the method, which can absorb and deliver electrical energy. The type of energy storage is not essential to the practice of the present invention.

Preferably, it can be provided that as energy storage a flywheel, a heat storage, a hydrogen generator with fuel cell, a natural gas generator with gas power plant, a pumped storage power plant, a compressed air storage power plant, a superconducting magnetic energy storage, a redox flow element and / or a galvanic element is preferably used, an accumulator or combinations ("pools") of memories or memories with conventional control power sources or of memories with consumers and / or power generators.

A heat storage device operated as an energy store must be operated together with a device for producing electricity from the stored heat energy.

Accumulators include in particular lead-acid batteries, sodium-nickel-chloride accumulators, sodium-sulfur accumulators, nickel-iron accumulators, nickel-cadmium accumulators, nickel-metal hydride accumulators, nickel-hydrogen accumulators, nickel-zinc accumulators, Tin-sulfur lithium-ion batteries, sodium ion batteries and potassium ion batteries.

Here, accumulators are preferred, which have a high efficiency and a high operational and calendar life. The preferred accumulators accordingly include, in particular, lithium ion accumulators (for example lithium polymer accumulators, lithium titanate accumulators, lithium manganese accumulators, lithium iron phosphate accumulators, lithium iron manganese phosphate Accumulators, lithium-iron-yttrium-phosphate accumulators) and developments thereof, such as lithium-air accumulators, lithium-sulfur accumulators and tin-sulfur lithium-ion accumulators.

In particular, lithium-ion secondary batteries are particularly suitable for methods according to the invention because of their rapid reaction time, that is, both in terms of the response time and the rate at which the power can be increased or reduced. In addition, the efficiency is good, especially for Li-ion batteries. Furthermore, preferred accumulators exhibit a high power to capacity ratio, this characteristic being known as the C rate.

It can also be provided that an energy of at least 4 kWh can be stored in the energy store, preferably of at least 10 kWh, particularly preferably at least 50 kWh, very particularly preferably at least 250 kW h.

According to a further embodiment, the energy storage device can have a capacity of 1 Ah, preferably 10 Ah and particularly preferably 100 Ah.

When using memories based on electrochemical elements, in particular accumulators, this memory can advantageously be operated with a voltage of at least 1 V, preferably at least 10 V and particularly preferably at least 100 V.

The capacity can be adjusted to the rated capacity and the predefined set period. Larger capacities are needed for higher power ratings and longer periods of time. Depending on the course of the frequency deviation, the supply of control power to the AC grid can be constant, via pulses or via ramps which are characterized by an increase in power supply over a defined period of time. An over Pulse (pulses) provided control power allows an improvement in the efficiency of the device and the method for providing control power, as this, the, in particular when using accumulators, necessary power electronics can be operated at a higher efficiency. A pulse is to be understood as a time-limited, jerky current, voltage or power curve, whereby these pulses can also be used as a repetitive series of pulses. The duty cycle according to DIN IEC 60469-1 can be selected here from the type of power electronics and the control power to be provided, wherein this in the range of greater than zero to 1, preferably in the range of 0.1 to 0.9, particularly preferably in the range of 0.2 to 0.8.

In the case of changes in power required, it may preferably be provided that the power of the energy store is increased over a period of at least 0.5 s, preferably over a period of at least 2 s, particularly preferably over a period of time, depending on the level of the required power change at least 30 s.

These slower ramps ensure that there are no suggestions of unwanted disturbances or oscillations in the power network or in the connected consumers and generators by a too steep power gradient. The desired state of charge of the energy store may preferably be in the range from 20 to 80% of the capacity, more preferably in the range from 40 to 60%. Compliance with and / or the return to these state of charge areas can be achieved, for example, by using the mode of operation on which this invention is based and / or via the energy trade, which was explained in more detail above, via the power grid. The state of charge corresponds in particular in the case of Accumulators as energy storage the state of charge (English: "State-of-Charge", SoC) or the energy content ("State-of-Energie", SoE).

The desired state of charge of the energy store may depend on forecast data. In particular, consumption data can be used to determine the optimum state of charge, which depends on the time of day, the day of the week and / or the season.

It can also be provided that the output of the power storage of the energy storage or recorded from the power grid power of the energy storage after a permanent frequency deviation outside the frequency band at several times, in particular continuously measured and the state of charge of the energy storage at several times, preferably continuously calculated is set, wherein the output or recorded power of the energy storage in response to this state of charge is set such that the variable control frequency is considered in the power consumption or Abgäbe.

According to a particular embodiment of the present invention, the method may be performed with an additional control power provider. Additional control power supplies in this context are devices that can provide control power, but that do not represent energy storage. The additional reserve balances include in particular energy producers and energy consumers.

It can be inventively provided that a power plant is used as an energy generator, preferably a coal power plant, a gas power plant or a hydroelectric power plant and / or a plant for producing a substance is used as an energy consumer, in particular an electrolysis plant or a metal -Werk, preferably one Aluminum plant or a steel plant.

Such energy producers and consumers are well-suited to providing longer-term balancing services. Their inertia, according to the invention, does not constitute a hindrance if suitably combined with dynamic storage. In this case, particular preference is given to those additional control power generators which can also be used in connection with renewable energies, such as, for example, electrolysis works or metal works, whose production can be reduced in order to provide positive control power. By this configuration, the nominal power of the energy storage can be surprisingly increased without the capacity of the same must be increased. In this case, the energy storage can be provided by the additional control power provider even with a high network load in a very short time if needed, without a lengthy energy trading is necessary. Surprisingly, therefore, a relatively high capacity can be delivered at a relatively low capacity of the memory, which can generally be delivered only for a short period of time. Due to the direct access to the additional control power provider, the latter can provide or substitute the control power actually to be provided by the energy store after a short time. In particular, a regeneration of the energy storage by the energy or power of the additional control power provider can be carried out. Here, the energy storage contributes to the quality of the control power delivery, as a result, a fast response time is achieved. In contrast to this, the additional control power provider contributes above all to the quantity, since it can supply control power at a relatively low cost over a design-related, significantly longer time.

Furthermore, it can be provided that the default frequency of the additional control power supply is not varied even with a permanent frequency deviation outside the frequency band. Furthermore, it may be provided that the energy generator and / or the energy consumer has or have a power of at least 10 kW individually or in the pool, preferably at least 100 kW, more preferably at least 1 MW and most preferably at least 10 MW. The ratio of rated power of the energy storage device to maximum power of the additional control power supply may preferably be in the range of 1: 10,000 to 100: 1, more preferably in the range of 1: 1000 to 40: 1.

The method of the present invention may preferably be carried out with a device comprising a controller and an energy store, wherein the device is connected to a power grid and the controller is connected to the energy store, wherein the controller is provided with a unit for determining the duration and a Unit for determining a variable control frequency is connected. It can be provided that the device comprises a frequency meter for measuring the mains frequency of the power network and a data memory, wherein in the memory at least one limit value (eg default frequency ± 10 mHz, default frequency ± 200 mHz, etc.) of the network frequency is stored, the controller is designed to compare the mains frequency with the at least one limit value and to control the power of the energy store and possibly the energy consumer and / or the energy generator as a function of the comparison.

Under a control according to the invention is understood in the present case a simple control. It should be noted that each control comprises a control, as in a control, a control in dependence on a difference of an actual value to a desired value takes place. Preferably, the controller is thus designed as a control, in particular with respect to the state of charge. Particularly preferably, the controller is a control system.

Furthermore, it can be provided that the unit for determining the time duration has a data memory, wherein at least historical data about the deviation and the duration of the network frequency from the default frequency are recorded in the data memory, this historical data having a period of preferably at least a day, preferably at least one week, more preferably at least one month and especially preferably at least one year. The unit for determining a variable control frequency can according to the Type of variable control frequency be configured, wherein at a fixed setting of the variable control frequency outside the frequency band, which is defined by the default frequency, a simple memory is sufficient, in which the respective values are stored. In a determination of the variable control frequency by a moving average, the unit for determining a variable control frequency comprises a corresponding arithmetic unit and at least one memory for storing the corresponding frequency data.

Alternatively, the data is collected at a remote location and evaluated as set forth above, and the appropriate signal is appropriately transmitted to the memory (s) for control power provision. In a particularly preferred embodiment, this can be done via the known methods of remote data transmission and communication.

Exemplary embodiments of the invention will be explained below with reference to two diagrammatically illustrated figures, without, however, limiting the invention. Showing:

Figure 1: a schematic representation of a device according to the invention for the provision of control power; and

FIG. 2: a flowchart for a method according to the invention.

FIG. 1 shows a schematic structure of a preferred embodiment of a device 10 according to the invention for a method according to the invention comprising a controller 1 1 and an energy store 12, the device being connected to a power grid 13.

In particular, even in such cases, a particularly fast-reacting and easy to charge and discharge energy storage 12 is particularly advantageous. Batteries are best suited for this purpose. In particular, Li-ion batteries are quickly and frequently charged and discharged with little harmful effects on the battery, so that they are particularly suitable and preferred for all embodiments according to the invention. This requires Li-ion batteries considerable capacity. For example, these can be easily accommodated in one or more 40-foot ISO containers.

Here, the controller 1 1 is connected to the energy storage 12. Furthermore, the controller 1 1 is connected to a unit for determining the time duration 14 and a unit for determining a variable control frequency 15. Of course, these units can be accommodated spatially in a housing with the controller. The connection between the unit 14 for determining the period of time 14 and the unit for determining a variable control frequency 15 with the controller 1 1 allows communication of the determined data, which are processed in the control unit. Furthermore, the controller 1 1 may be connected to the power grid 13, this connection, not shown in Figure 1, a transmission of requests for required control power, both positive and negative, may allow.

The embodiment set forth in Figure 1 comprises an additional control power generator 16, which in the present invention is an optional component. The additional control power generator 16 may be a power generator and / or a power consumer, wherein the additional control power generator 16 is connected to both the power grid 13 and the energy storage 12, so that the control power provided by the additional control power provider can be fed directly into the power grid 13 or can be used to regenerate the energy storage 12. The control of the additional control power supply 16 can be carried out by conventional components, which may be in communication with the controller 1 1 of the device 10 according to the invention. Please refer to the Forum Netztechnik / Netzbetrieb in the VDE (FNN) "TransmissionCode 2007" of November 2009 for details on the regulation of control power and the exchange of information with the network operators.

FIG. 2 shows a flowchart for a preferred method according to the invention. In the method, an energy storage is used. In step 1, the Grid frequency of the power network measured. In decision step 2, it is then checked whether the network frequency lies within or outside the frequency band which was previously determined. This frequency band can be identical to a deadband, which is predetermined by the network regulations or by the network operator. Furthermore, this frequency band may be larger or smaller than the deadband determined by the network operators or by the network regulations.

If the measured network frequency is within the frequency band, according to the present embodiment of the method, a control power supply is performed according to the standard specifications, as shown in step 8.

If the grid frequency is outside the frequency band, it is checked in decision step 3 whether there is a permanent frequency deviation over a specified period of time. Here it can also be checked whether there is another restriction which excludes a deviation from the standard specifications. For example, it may be provided that a regulation to the default frequency is mandatory at certain times of the day. If there is no permanent frequency deviation or a regulation to a variable control frequency is excluded, control power is provided according to the usual specifications, being regulated to the default frequency. If there is a permanent frequency deviation and no exception applies, decision step 4 continues.

In decision step 4 it is checked whether an abort criterion is present, so that a transition from a control with a variable control frequency must be made to a control with the default frequency. These termination criteria may, for example, be given by a period of time to which a provision of control power with a variable control frequency is limited. Furthermore, a state of charge can be achieved by a regeneration of the energy storage, which allows a control to the default frequency. In this case, in the present embodiment, according to step 5, the time measurement with respect to Restarted period, for which a permanent frequency deviation must be present before a control to a variable default frequency is allowed. Subsequently, control power is provided according to the usual specifications using the default frequency, as shown schematically in step 8.

If this abort criterion is not met, it is tested in the present embodiment in decision step 6, whether the application of a control power application using a variable control frequency is appropriate to convert the state of charge of the energy storage in the shortest possible time in a desired state of charge. If this is not the case, the default frequency is used to provide the control power. This case may occur, for example, if the state of charge was very low at the beginning of a phase in which negative control power is to be provided. If, after a longer period of time over which negative control power was provided, the state of charge is higher, but below the desired state of charge, it may be expedient to continue to provide more negative control power and not to regulate to a variable control frequency, which is above the preset frequency lies.

In general, however, it will be convenient to make a change in the default frequency to a variable control frequency, as set forth in step 7, with control power provided according to the specifications that apply here.

Subsequently, the grid frequency is measured again, so that a cycle is given. This also applies in the event that the provision of control services is performed in accordance with the standard requirements, as described in step 8.

The order of the steps set forth in Figure 2 may be partially changed. In particular, decision step 6 can take place before decision step 4, so that the check is made on the desirability of a regulation to a variable control frequency before the presence of a termination criterion. The features of the invention disclosed in the foregoing description as well as the claims, figures and embodiments may be essential both individually and in any combination for the realization of the invention in its various embodiments.

Claims

claims

Method of providing control power to stabilize a

AC mains, wherein the AC mains at a

Default frequency operates and a frequency band is defined by the default frequency, comprising an energy storage device, which can absorb and deliver electrical energy, characterized in that at a permanent frequency deviation outside the frequency band over a fixed period of time providing the control power with the

Energy storage is changed, this change includes a change from the default frequency to a variable control frequency.

A method according to claim 1, characterized in that the variable control frequency is determined by a sliding averaging of the measured frequency.

Method according to claim 1 or 2, characterized in that the absolute difference between the average network frequency and the

Default frequency is considered in the performance of the energy storage.

Method according to at least one of the preceding claims, characterized in that the state of charge of the energy store in the

Conversion of the default frequency to the variable control frequency

is taken into account.

Method according to at least one of the preceding claims, characterized in that the energy storage device is protected if the measured frequency lies outside the frequency band.

Method according to at least one of the preceding claims, characterized in that a regeneration of the energy storage takes place if the measured frequency is outside the frequency band.

7. The method according to any one of the preceding claims, characterized in that at a corresponding state of charge of

Energy storage a conversion of the variable control frequency on the

Default frequency is made. 8. The method according to at least one of the preceding claims, characterized in that the energy store is an accumulator.

9. The method according to claim 7, characterized in that the accumulator is a lithium-ion accumulator.

10. The method according to any one of the preceding claims, characterized in that the method in combination with an additional

Control power provider is performed.

1 1. Method according to at least one of the preceding claims, characterized in that the default frequency of the additional

Regeleristungserbringers is not varied in a permanent frequency deviation outside the frequency band.

12. The method according to any one of the preceding claims, characterized in that in the context of the provisions for the provision of

On average, more energy is absorbed from the grid than is fed into the grid. 13. A device for carrying out a method according to claims 1 to 12, characterized in that the device (10) comprises a controller (1 1) and an energy store (12), wherein the device to a

Power supply (13) is connected and the controller (1 1) with the

Energy storage (12) is connected, wherein the controller (1 1) with a unit for determining the time duration (14) and a unit for determining a variable control frequency (15) is connected.