Method for operating electrical network

Abstract

The invention relates to a method for operating an electrical network having a DC voltage circuit and an AC voltage circuit which are electrically connected by means of a current converter, the AC voltage circuit having a power supply interface for connection to a power supply network, and an energy store and a power generation device being connected to the DC voltage circuit. A predicted power of the electric power provided by means of the power generation device is ascertained within a time window, and an energy value corresponding to a share of the predicted power higher than the power value of the converter is ascertained. An expected state of charge of the energy store is ascertained, said expected state of charge corresponding to the maximum energy that can be stored by means of the energy store minus the energy value. And if the actual power of the power generation device is smaller than the power value, the energy storage device is maximally charged to the expected charging state. Furthermore, the invention relates to an electrical network, a control unit and a computer program product.

Description

Technical Field

[0001] The invention relates to a method for operating an electrical network having a DC voltage circuit and an AC voltage circuit electrically connected by means of a converter. The invention also relates to an electrical network, a control unit and a computer program product. Background Art

[0002] More and more private households have power generation devices for their own needs and / or for feeding electricity into the power supply network, which power generation devices are mainly operated with regenerative / renewable energy. For example, such power generation devices are photovoltaic systems (PV systems), in the case of which the maximum power is usually less than 30 kW. When electrical power is then provided by means of the photovoltaic system, it is used for the private household's own needs. Any excess power is usually fed into the power supply network. In this case, a direct current voltage is usually provided by means of the photovoltaic system. However, since the electrical consumers of the private household and the power supply network usually operate with an alternating current voltage, it is necessary to connect a converter, which is usually designed as an inverter, between the two, by means of which the (electrical) direct current voltage is converted into an (electrical) alternating current voltage.

[0003] If there are relatively many such private households in a certain area, it is possible that more electrical power is fed into the power supply network than is required. In this case, the operator of the power supply network restricts / limits the feed-in in order to avoid overloading the power supply network. However, in this way, the entire electrical power that is or can be provided by means of the photovoltaic system cannot be utilized.

[0004] Therefore, in order to increase efficiency and / or self-sufficiency, at least some of the private households have energy storage devices, which are designed as electrochemical storage devices, for example. It is thus possible to use the electrical power provided by means of the power generation device to charge the energy storage device when the power supply to the power supply network is limited or interrupted and when the private household itself does not need such a power supply. When no electrical power is provided by means of the power generation device, for example at night, the required electrical power can be drawn from the energy storage device without having to be drawn from the power supply network.

[0005] What is required here is that the various components, namely the energy storage device, the inverter and the photovoltaic facility, as well as their respective powers and benefits, are coordinated with each other. Usually, the maximum power of the photovoltaic facility is selected to be greater than the power of the inverter. The maximum power is only rarely achieved with the help of photovoltaic facilities, because on the one hand, there must be relatively high solar radiation for this purpose, that is, in particular, there must be no cloud cover or the like. On the other hand, for this purpose, the angle of incidence of the light on the photovoltaic facility is relatively good, which only occurs in a short period of time. However, due to the reduction in the size of the inverter, cheaper components that usually have improved benefits can be used. This usually reduces the internal resistance of semiconductor switches with lower current carrying capacity, thereby improving efficiency, especially the efficiency within the partial load range of the inverter. Summary of the invention

[0006] The object of the present invention is to specify a particularly suitable method for operating an electrical network and a particularly suitable electrical network, as well as a particularly suitable control unit and a particularly suitable computer program product, wherein the efficiency is advantageously increased.

[0007] According to the invention, this object is achieved with respect to the method by the features of claim 1, with respect to the electrical network by the features of claim 8, with respect to the control unit by the features of claim 9, and with respect to the computer program product by the features of claim 10. Advantageous developments and embodiments are the subject matter of the respective dependent claims.

[0008] The method is used to operate an electrical network. The electrical network has a DC voltage circuit and an AC voltage circuit. A DC voltage is conducted in the DC voltage circuit, while an AC voltage is conducted in the AC voltage circuit.

[0009] In other words, the AC voltage loop has at least one electrical phase, by means of which a time-varying potential can be guided. The time-varying potential is especially sinusoidal and has a specific frequency and amplitude. Preferably, the frequency is 50 Hz or 60 Hz and the amplitude is 230 V or 110 V. Suitably, the AC voltage loop comprises a plurality of such phases, preferably three phases, and therefore adopts a three-phase design. Here, a sinusoidal potential is especially applied to each phase. In particular, here, the frequency and / or amplitude of the respective potentials are the same, but they are relatively displaced from each other, so that a phase angle of 120° is appropriately formed between them. In particular, the AC voltage loop also has a reference potential or reference potential, for example, with grounding / earth. Therefore, the AC voltage loop has a time-varying potential, which is especially periodically changing, preferably sinusoidally changing.

[0010] The DC voltage circuit and the AC voltage circuit are electrically connected to each other by means of a converter. Here, it is possible to transfer electrical energy from one circuit to the other circuit by means of the converter. For example, the converter can only be operated as an inverter, so that electrical energy can be transferred from the DC voltage circuit to the AC voltage circuit by means of the converter. Preferably, the converter can also be designed to be regenerative, so that the converter can also be operated as a rectifier. It is therefore possible to also transfer electrical energy from the AC voltage circuit to the DC voltage circuit by means of the converter. At the very least, the converter is designed as a DC / AC converter or can be operated in this way.

[0011] The converter is suitably coordinated, for example, with the topology of the AC voltage circuit, that is, in particular with the number of phases. For example, the converter is of three-phase design. If both the converter and the AC voltage circuit are of three-phase design, then when the electric energy is transmitted from the DC voltage circuit to the AC voltage circuit, the electric energy is evenly distributed to all phases, or only or preferentially to one of the phases, by means of the converter. This approach is particularly suitable. Alternatively, the converter is of only single-phase design. In this case, for example, the AC voltage circuit is also single-phase, or the converter is only assigned to one of the phases of the AC voltage circuit.

[0012] The converter preferably has a bridge circuit, in particular a B6 circuit. In this case, the converter comprises a plurality of bridge branches. If the converter is designed as a three-phase converter, in particular, there are three such bridge branches. Each bridge branch in particular has two semiconductor switches connected in series, preferably field effect transistors, such as MOSFETs, GTOs or IGBTs. If the converter is single-phase, only one bridge branch or a single switch is present.

[0013] The AC voltage loop has a power supply interface for connecting to a power supply network. The power supply interface is suitable for this purpose and is in particular provided and set up for this purpose. The power supply network is not a component of the power grid here, but it is in particular possible to feed power to the power grid via the power supply interface with the aid of the power supply network, or, for example, to transmit electrical energy from the power grid to the power supply network. Suitably, the power supply network is preferably designed in three phases. In particular, an AC voltage of, for example, 230 V or 110 V is guided here with the aid of the power supply network. In particular, the frequency of the AC voltage is 50 Hz or 60 Hz. Suitably, an electric meter or a similar device is provided at the power supply interface, by means of which the electric energy transmitted between the power supply network and the power grid can be known.

[0014] The power supply interface is in particular a house interface or a similar interface, which is provided, for example, by an electricity supplier or a power supply network operator. In contrast, the power grid is preferably a component of a building or a house. Suitably, the power grid is a component of a household, for example a component of a private household. Alternatively, the power grid is a component of an agricultural unit or an industrial plant. At least, the power grid is preferably assigned to one or more regional building units, that is, to a complex of a limited number of buildings, wherein the number of buildings is less than 10. Preferably, the power grid is arranged and set up to conduct electrical power of at most 500 kW, 300 kW, 200 kW, 100 kW or less. However, it is possible to supply power to a plurality of such regional building units / households with the power supply network, which is suitable for this and is arranged and set up for this.

[0015] The power grid also includes an energy storage device electrically connected to the DC voltage loop. Therefore, during operation, a DC voltage is applied to the energy storage device. Here, it is possible to store electrical energy with the aid of the energy storage device. The energy storage device preferably includes a controller and an energy storage unit, wherein the energy storage unit is operated in particular with the aid of a controller. Preferably, the charging / discharging of the energy storage device is controlled / regulated with the aid of a controller. For example, the energy storage unit has individual structural units, such as modules, and the structural element to be fed with electrical energy or to be discharged is selected with the aid of a controller. Here, the converter is preferably designed as a so-called hybrid inverter. Therefore, the charging / discharging of the energy storage device is also at least partially controlled / regulated with the aid of a converter. In other words, the possible controller is at least partially formed with the aid of a converter. Preferably, the controller includes a boost converter and / or a buck converter, with the aid of which the voltage provided with the aid of the energy storage device can be coordinated with the voltage guided with the aid of the DC voltage loop. For example, the energy storage device is a component of a motor vehicle, or is appropriately stationary and / or fixedly connected to a building.

[0016] It is particularly preferred that the energy storage device is an electrochemical storage device and is therefore designed in particular as a battery, preferably as a high-voltage battery. For example, the energy storage device has a plurality of battery cells, which are combined into individual battery modules, for example. Here, the individual battery modules are preferably structurally identical to one another. The individual battery cells / battery modules are suitably at least partially electrically connected in series and / or in parallel. In particular, the controller is therefore a battery management system. With the aid of the battery management system, the individual battery cells / battery modules are selected so that the energy storage device is optimally charged / discharged, wherein the electrical losses that occur are reduced.

[0017] In addition, the power grid also has a power generation device. Here, electric current, that is, in particular electric power, is provided by means of the power generation device. Here, the current provided is in particular time-varying and in particular related to environmental conditions. Preferably, the power generation device operates with regenerative / renewable energy. For example, the power generation device is a wind power generation facility, or particularly preferably a photovoltaic facility. For example, the power generation device is therefore formed with them respectively. Alternatively to this, the power generation device comprises, for example, a plurality of subunits, one of which is a photovoltaic facility. For example, another subunit is a wind power generation facility, as long as a DC voltage is provided in particular by means of the wind power generation facility. Another alternative is that the power generation device is a fuel cell or at least comprises the fuel cell. The power generation device is also electrically connected to the DC voltage circuit and provides a DC voltage by means of the power generation device. For example, the DC voltage is constant or varies with time.

[0018] In this method, within a time window, the predicted power of the electric power provided by means of a power generation device is known. In other words, an assumption is made about the electric power provided by means of a power generation device during the time window. In particular, a time curve of the electric power is thus created. The time window here occurs in the future, for example, immediately after the moment of making a prediction, or at a certain interval from the moment of making a prediction. In particular, in order to determine the predicted power, the assumed power or a value corresponding to the assumed power is directly known, for example, the current provided by means of a power generation device is known. The predicted power is created in particular in different time sections within the time window. Here, a constant predicted power is particularly assumed for each of the time sections, which reduces the cost. It is suitable that the length of the time section is constant, and therefore the time window is divided into several time sections. For example, the length of any of the time sections is between 1 minute and half an hour, preferably between 5 minutes and 20 minutes, or in particular between 10 minutes or 15 minutes. Therefore, it is possible to take into account different environmental influences relatively accurately during the prediction, wherein the cost is reduced.

[0019] The energy value is learned in the next working step. This energy value corresponds to the share of the predicted power that is higher than the power value of the converter. Therefore, the energy value is also created within the time window, and preferably for each time segment, it is checked whether the predicted power is higher than the power value. If this is the case, the product of the time segment length and the difference between the predicted power and the power value is appropriately added to the energy value. In particular, the sum created in this way is equivalent to the energy value. If the predicted power in one of the time segments is lower than the power value, the energy value does not change, especially in the time segment. In an improved scheme, for example, integration can be performed instead of summation, which will improve accuracy. In an alternative scheme, a mathematical model is used to create the energy value, and / or, for example, an optimization method is considered. Therefore, robustness is improved, wherein, based on the optimization method, it is not necessary to accurately express the problem, and therefore the energy value can be learned with relatively few hardware resources, even when, for example, the duration is (slightly) extended and / or the accuracy is (slightly) reduced. No matter which method is used, the values ​​created respectively can be used directly as energy values, for example. In one development, further processing is also performed, for example multiplication by a specific factor, with the aid of which, for example, the losses of the converter are taken into account.

[0020] The power value of the converter is preferably constant or, for example, depends on the current specific situation. In particular, the power value corresponds to the maximum power of the converter or preferably to the rated power of the converter, i.e. to the power designed for operating the converter. Alternatively, the power value corresponds to the operating point at which the losses occurring are minimal or the efficiency is maximal. In particular, the power value thus corresponds to the optimal operating point of the power converter. For example, the power value is predetermined by the manufacturer of the converter or is known in conjunction with the operating data of the converter, so that aging / heating conditions or other parameters are taken into account.

[0021] Overall, the energy value corresponds to the predicted portion of energy that cannot be fed into the AC voltage circuit by means of the converter during the time window, in particular due to limitations of the converter.

[0022] In the next working step, the expected state of charge of the energy storage device is known. The state of charge corresponds to the maximum energy that can be stored by means of the energy storage device minus the energy value. In particular, the expected state of charge corresponds to the ratio of the difference to the maximum energy that can be stored by means of the energy storage device. The maximum energy that can be stored by means of the energy storage device is predetermined here, in particular according to the design structure of the energy storage device. For example, during the operation of the power grid, the maximum energy that can be stored by means of the energy storage device is assumed to be constant. Alternatively, the maximum energy that can be stored by means of the energy storage device is adjusted at least at a specific time point, wherein the aging effects, environmental effects and / or operating data of the energy storage device are appropriately taken into account. Appropriately, for example, the corresponding adjustments are made every year or every six months. Therefore, the cost is relatively small.

[0023] In the next working step, if the actual power of the generator is less than the power value, the energy storage device is charged to the expected charge state at the maximum. Therefore, this working step is performed within the time window, and therefore, the (electrical) power actually provided by the generator device is known during the time window. If the prediction is relatively accurate, the predicted power corresponds to the actual power, especially for each time segment or at least for most of the time segments. In short, the actual power provided by the generator device is known and used as the actual power. Therefore, here, as long as the converter is operated below the power value, the electrical energy stored by the energy storage device is limited.

[0024] Thus, based on this method, as long as the converter is operated below the power value, there is capacity left in the energy storage. Therefore, if the current concrete situation changes, it is possible to react to this flexibly. In summary, a buffer capacity is thus provided with the aid of the energy storage, which buffer capacity can be used when necessary, wherein it is possible to operate the converter at the power value for a relatively long period of time during the time window. This increases the efficiency. In this case, overloading of the converter and the energy storage is avoided. In this case, in particular, the energy storage is charged to the maximum desired charge state as long as the time window lasts.

[0025] Advantageously, during the method, the converter is operated so that electrical energy is transferred from the DC voltage circuit to the AC voltage circuit by means of the converter. As long as the energy store is not charged at this time and the actual power is less than the power value, the power provided by means of the converter, i.e. the power fed into the AC voltage circuit, corresponds essentially to the power provided by means of the generator, i.e. the actual power minus any losses caused by the operation of the converter.

[0026] If the actual power of the power generation device is greater than the power value, the energy storage device is charged in particular. This prevents the power generation device from being limited. If the energy storage device has not yet been charged to the expected state of charge, it is charged before that. If the energy storage device already has the expected state of charge when the actual power of the power generation device is greater than the power value, the expected state of charge is appropriately increased / adjusted. This is also appropriate when the expected state of charge is reached, as long as the actual power of the power generation device is greater than the power value. The expected state of charge is preferably adjusted / tracked iteratively.

[0027] For example, the expected state of charge is then theoretically known, for which the portion of the actual power that exceeds the power value is time-integrated or multiplied by the length of the respective time segment. Preferably, the expected state of charge is adjusted within a specific time window. For example, the time window is greater than 5 seconds and preferably less than 1 minute or 30 seconds. The time window is expediently 10 seconds.

[0028] Alternatively, as long as the actual power of the power generation device is greater than the power value, the converter is operated in the expected manner, wherein the electrical energy that is originally available is transferred to the energy storage device. If the actual power falls below the power value, the charging of the energy storage device is terminated. The current charge state will then be used as the new expected charge state. The energy storage device is charged with only the portion of the generated power that would otherwise be lost due to the power limitation of the converter.

[0029] For example, if the actual power of the generator is greater than the power value, the converter is operated at a specific power less than the power value. However, it is particularly preferred that the converter is operated at the power value. Therefore, if the actual power is greater than the power value, the electric power provided by the generator that exceeds the power value will be stored in the energy storage device, and the electric power corresponding to the power value will be fed into the AC voltage circuit by the converter. Due to the restrictions on the expected charging state that are still applicable before that, there is enough capacity in the energy storage device, so that basically all the electric energy provided by the generator can be used, which increases the benefit and efficiency. Here, overloading of the energy storage device and the converter is excluded. It is also possible to use a converter with relatively small specifications without causing the provided electric energy to be unusable. In short, based on this method, sufficient capacity is reserved with the help of the energy storage device so that the electric energy that cannot be transmitted to the AC voltage circuit by the converter at that time can be stored under the condition of the maximum power of the generator, especially during the so-called peak time. Therefore, the benefit is improved, and the requirements for the power grid hardware are reduced.

[0030] For example, all the electrical energy provided by the converter is fed into the power supply network via the power supply interface. Alternatively, there is a power limit for the power supply interface, which is, for example, constant or time-varying. In particular, the power limit corresponds to a feed-in limit predetermined by the operator of the power supply network, for example. If the power fed into the AC voltage loop by the converter (which corresponds in particular to the actual power of the generator, or if the actual power of the generator is greater than the power value, corresponds to the power value) is greater than the power limit applicable to the power supply interface, the converter operates with reduced power. In this case, in particular, if no additional electrical energy is extracted from the AC voltage loop, the converter will operate at the value of the power limit. In that case, in particular, it operates with the power limit plus the electrical power required in other ways in the AC voltage loop. Therefore, the converter operates in a throttling manner, and therefore the electrical energy in the DC circuit is used to charge the energy storage device.

[0031] In this case, in particular, the energy store is charged up to the expected state of charge. If the energy store has reached the expected state of charge, the state of charge is appropriately increased or, in particular, the limitation is removed as long as the converter is operated at a reduced power due to a power limitation. If the power limitation is removed or the actual power of the power generation device is less than the power limitation, in particular the charging of the energy store is terminated and the state of charge of the energy store then present is used as the expected state of charge. Thus, the electrical energy provided by means of the power generation device is always used, even when it cannot be fed into the power supply network, for example due to the current specific situation, even when the converter is not yet operated at its power value. This further increases the efficiency.

[0032] For example, the current circuit has an electrical consumer which is electrically connected to the AC voltage circuit. However, it is at least possible that an electrical consumer is connected to the AC voltage circuit. In this case, the electrical consumer is formed, for example, only by means of a single unit. As an alternative to this, the electrical consumer comprises a plurality of independent units, but these units have no other relationship with each other, for example, except that they are powered and / or operated by means of the AC voltage circuit. For example, in this case, at least one of the units is used to increase the comfort of users of the current circuit. Suitably, one of the units is a heat pump, which is used in particular for heating building units having the current circuit. Alternatively or in combination therewith, one of the units is, for example, an air conditioning system or a so-called charging wallbox.

[0033] In this case, electrical energy / power is preferably fed into the supply network only if at least one desired operation of the consumer can be achieved with the electrical energy present in the AC voltage circuit. For example, if the actual power of the generator is not sufficient to operate the consumer, additional electrical power is drawn from the supply network in order to enable the desired operation of the consumer. Alternatively or in combination therewith, the energy store is discharged, for example, and in this way the AC voltage circuit is fed with power by means of a converter, so that the consumer can be operated.

[0034] In the method, the power required by the consumer is preferably determined. For example, if the actual power cannot be achieved with the aid of the generator or is too low for operating the consumer, the energy store is preferably discharged and in this way electrical energy is provided for the operation of the converter, by means of which the AC voltage circuit is fed. The converter is preferably operated at a value corresponding to the required power or at a power value slightly increased above this value, so that possible losses can be compensated. Thus, operation of the consumer can be achieved, in which the energy store is at least partially discharged and in which no electrical energy needs to be drawn from the supply network.

[0035] For example, the charging of the energy storage device is independent of the required power. However, preferably, the energy storage device is charged only when the actual power is greater than the required power. In particular, possible electrical losses due to the operation of the converter should be taken into account and the required power should be corrected accordingly. Therefore, in the method, the operation of the electrical consumer is first ensured, and then the energy storage device is charged with a lower priority. In this way, electrical energy needs to be drawn from the power supply network only in very rare cases, wherein a relatively large buffer capacity is maintained with the help of the energy storage device. If both the required power and the actual power are greater than the power value, the converter operates at the power value and, in addition, the energy storage device is charged. The additional power / energy required for the operation of the electrical consumer is then preferably drawn from the power supply network via the power supply interface. Based on this method, it is ensured that as little energy as possible is drawn from the power supply network, thereby increasing the self-sufficiency of the power grid.

[0036] For example, the predicted power is known only once, preferably before the start of the time window. Alternatively, the predicted power is adjusted during the time window, for example continuously or at specific time intervals, for example every hour, every 15 minutes, every 5 minutes or every 10 seconds. Depending on the respectively adjusted predicted power, the expected state of charge is also appropriately adjusted accordingly. As a result, errors in the creation of the prediction due to changes in environmental conditions are quickly compensated, so that the expected operation of the energy storage device and the converter can be achieved subsequently. Therefore, despite the relatively large initial inaccuracies, the benefits are still relatively high.

[0037] For example, a week or 1 hour is selected as the time window. Particularly preferably, the time window has a length between 6 hours and 72 hours, in particular a length equal to 12 hours or 24 hours. In the case of the length of this time window, the predicted power is sufficiently accurate to be consistent with the actual power, so that a relatively high operating efficiency of the power grid can be achieved. This also reduces the cost. In addition, the difference in actual power of consecutive days is relatively small, which facilitates the creation of predictions. In particular, the length of the possible time segment is between 10 minutes and 20 minutes, and is, for example, equal to 15 minutes. In particular, the expected charging state is known every 15 minutes and / or a value for the predicted power is created.

[0038] Preferably, an "artificial intelligence" algorithm (AI), in particular a machine learning or neural network, is used to create the predicted power. For example, the predicted power is obtained in conjunction with a theoretical model. Suitably, the predicted power is obtained in conjunction with the actual power that has been achieved. For this purpose, for example, the actual power in a certain number of previous time windows is used, and for example the average value derived therefrom is used as the predicted power. For example, the individual actual powers are weighted differently here. In an alternative, the predicted power is preferably obtained from the actual power by means of a spline interpolation method. For example, the number of time windows actually considered for use is less than 10 and preferably greater than 2, thereby reducing the cost.

[0039] Preferably, the predicted power is obtained by means of a spline interpolation method, wherein in particular the average value of the actual power from the immediately preceding time range is used. The length of the time range is suitably between 1 minute and 30 minutes, and preferably between 10 minutes and 20 minutes, and suitably equal to 15 minutes. Preferably, for this purpose, the actual power is sampled every 10 seconds. In conjunction with these learned values, the predicted power of the other time range that follows suitably is created. Suitably, at this, the length of the other time range is between 30 minutes and 2 hours, for example equal to 1 hour.

[0040] Alternatively or in combination therewith, the predicted power is determined in conjunction with a weather forecast. In this case, the forecast is created, for example, during the method, or it is retrieved from an external source, preferably via the Internet. For example, in this case, the predicted power is determined in conjunction with weather data, or already processed weather data, such as radiation intensity, are retrieved and the predicted power is determined in conjunction with these weather data. This increases the accuracy when determining the predicted power, wherein no knowledge of special meteorological models is required. If the power generation device is formed by means of a photovoltaic facility or comprises this, in this case, in particular, a radiation forecast is retrieved from a meteorological service. In this way, environmental conditions that influence the operation of the power generation device are taken into account.

[0041] The power grid has a DC voltage circuit, to which the energy storage device and the power generation device are electrically connected. In particular, the power generation device is operated with the aid of regenerative or renewable energy. In this case, the actual power provided by the power generation device is not constant, in particular with respect to time, but is dependent on environmental conditions. For example, the power generation device is formed with the aid of a photovoltaic system or at least comprises the photovoltaic system. The energy storage device suitably has a controller and an energy storage unit. Suitably, the energy storage device comprises an electrochemical storage device, such as a battery.

[0042] The power grid also includes an AC voltage circuit, which is electrically connected to the DC voltage circuit by means of a converter. Preferably, the converter is designed as a so-called hybrid inverter, and the energy storage device is operated at least partially by means of the hybrid inverter, for example. The AC voltage circuit is preferably designed as a three-phase circuit, and a three-phase AC current is guided by means of it during operation. Here, the amplitude of each electrical phase is preferably the same, and is, for example, 230 V or 110 V. The potential guided by each phase has a frequency of 50 Hz or 60 Hz. In particular, the potential of each phase is sinusoidal, and the potentials of the individual phases are preferably shifted by 120° from each other.

[0043] The AC voltage loop has a supply connection for connection to the power supply network. For example, a supply connection, also called a "point of common coupling" (PCC) or a house connection, is suitable for this purpose and is provided and configured in particular for this purpose. It is thus possible to transfer electrical energy between the power supply network and the power grid, wherein in particular a current flows between them. The voltage in the power supply network is preferably equal to the voltage in the AC voltage loop.

[0044] The power grid is operated according to a method in which a power forecast of the electric power provided by the generator is created within a time window. An energy value is determined, which corresponds to the proportion of the forecast power that is above the converter power value, and an expected state of charge of the energy store is determined, which corresponds to the maximum energy that can be stored by the energy store minus the energy value. If the actual power of the generator is less than the power value, the energy store is charged to the expected state of charge at most.

[0045] In particular, the power grid has a control unit, which is arranged and configured to perform the method. For example, the control unit includes an application-specific integrated circuit (ASIC), or particularly preferably includes a computer, which is appropriately designed to be programmable. In particular, the control unit includes a storage medium, on which a computer program product, also referred to as a computer program, is stored, wherein when the computer program product (i.e., the program) is implemented, the computer is prompted to perform the method. Suitably, the control unit is connected to the power generation device, the energy storage device and / or the converter in terms of signal technology, preferably by means of corresponding interfaces of the control unit. Preferably, the converter and / or the energy storage device are controlled and / or adjusted according to the method. In particular, a communication network is at least partially formed by means of the control unit, the power generation device, the energy storage device and / or the converter, for example a communication network designed in the form of a bus system.

[0046] For example, the control unit is a separate component, or is integrated into the energy storage device, for example, and the control unit is used to control / regulate the charging / discharging of the energy storage device. Thus, in particular, a possible controller of the energy storage device is formed by means of the control unit. In an improved solution, the control unit is integrated into the converter and / or the power generation device, for example. Thus, for example, other functions are also performed and / or taken over by means of the control unit, such as coordinating the converter with the frequency and / or phase of the AC voltage guided by the AC voltage loop. In particular, here, possible weather forecasts are obtained by means of the control unit and / or forecasts are retrieved from external sources. The control unit is suitably suitable for, in particular, being arranged and set up to be connected to a network, in particular the Internet, in terms of signaling technology.

[0047] For example, the converter is designed only as an inverter, so that it is only possible to transfer energy from the DC voltage circuit to the AC voltage circuit with the help of the inverter. Alternatively to this, the converter is also designed to be able to feedback and can therefore also operate as a rectifier. In particular, the converter is single-phase, thereby reducing manufacturing costs. However, it is appropriate that the converter is multi-phase, preferably three-phase. Suitably, the number of phases of the converter corresponds to the number of phases of the AC voltage circuit. If electrical power / energy is transmitted from the DC circuit to the AC voltage circuit with the help of the converter, the electrical power / energy is fed into all phases or only into specific phases. The phase is preferably selected with the help of an algorithm. Suitably, the phase with the highest power requirement of a possible electrical consumer connected to the AC voltage circuit and / or the phase with the highest power requirement of the power supply network is selected here.

[0048] The control unit has an interface for connecting to the inverter and / or energy storage unit in terms of signal technology. For example, the interface is configured in the manner of a plug and in particular complies with a specific standard. It is possible to connect the interface to the line in terms of signal technology and electrical connection. Alternatively, the interface is formed by means of a radio device (such as a mobile phone, a wireless local area network or a Bluetooth standard) that complies with a specific standard, for example. Based on the interface, it is at least possible to exchange information / signals / data between the control unit and the inverter and / or between the control unit and the energy storage unit. For example, the interface is designed to be only unidirectional or preferably bidirectional.

[0049] The control unit is provided and configured to execute a method for operating a power grid having a DC voltage circuit and an AC voltage circuit electrically connected by means of a converter, wherein the AC voltage circuit has a power supply interface for connecting to a power supply network, and wherein an energy storage device and a generator are connected to the DC voltage circuit. In the method, a predicted power of the electric power provided by means of the generator is determined within a time window. An energy value corresponding to the proportion of the predicted power that is higher than the power value of the converter is determined, and an expected charge state of the energy storage device is determined, which corresponds to the maximum energy that can be stored by means of the energy storage device minus the energy value. If the actual power of the generator device is less than the power value, the energy storage device is charged to the expected charge state at most.

[0050] For example, the control unit comprises an application specific integrated circuit (ASIC) and / or a microprocessor, by means of which the method is at least partially executed. In particular, the control unit comprises a computer program product which is stored in a memory and which, when the program is executed by a computer (such as a microprocessor), causes the computer to execute the method. Preferably, in the installed state, the control unit is a component of the inverter / generator or preferably a component of an electrical consumer of the power grid, in particular a component of a heat pump, and is suitable for this, in particular is provided and set up for this. For example, possible electrical consumers, preferably heat pumps, are also expediently regulated / controlled by means of the control unit.

[0051] The present invention also relates to a computer program product. The computer program product includes a certain number of instructions, which, when the program (computer program product) is implemented by a computer, cause the computer to execute a method for operating a power grid, the power grid having a DC voltage circuit and an AC voltage circuit electrically connected by means of a converter, wherein the AC voltage circuit has a power supply interface for connecting to a power supply network, and wherein an energy storage device and a power generation device are connected to the DC voltage circuit. In this method, a predicted power of the electric power provided by means of a power generation device is obtained within a time window. An energy value corresponding to a portion of the predicted power higher than the power value of the converter is obtained, and an expected charging state of the energy storage device is obtained, which corresponds to the maximum energy that can be stored by means of the energy storage device minus the energy value. If the actual power of the power generation device is less than the power value, the energy storage device is charged to the expected charging state at most. Suitably, the computer is a component of a control unit and is formed, for example, by means of the control unit. The computer preferably includes a microprocessor or is formed by means of a microprocessor. The computer program product is, for example, a file or a data carrier, which contains an executable program, which automatically implements the method when installed on a computer.

[0052] The invention also relates to a storage medium on which the computer program product is stored. For example, the storage medium is a CD-ROM, a DVD or a Blu-ray disc. Alternatively, the storage medium is a USB flash drive or other storage medium that is, for example, rewritable or can only be written once. The memory may be, for example, a flash memory, a RAM or a ROM.

[0053] The developments and advantages explained in conjunction with the method also apply to the electrical system / control unit / computer program product to the same extent and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The embodiments of the present invention are explained in detail below in conjunction with the accompanying drawings.

[0055] Figure 1 A power grid having an AC voltage circuit and a DC voltage circuit is schematically shown, with a power generation device and an energy storage device being connected to the DC voltage circuit;

[0056] Figure 2 A method for operating a power grid is shown;

[0057] FIG3 shows a time curve of the predicted power of the electric power provided by the power generation device;

[0058] Figure 4 The time course of the state of charge of the energy store is shown.

[0059] Parts that correspond to one another are provided with the same reference symbols in all the figures. DETAILED DESCRIPTION

[0060] Figure 1 Schematically shown is a power grid 2, which is a component of a private household. The power grid 2 has an AC voltage loop 4, by means of which a three-phase AC voltage is guided. Each phase has a sinusoidal potential that varies over time. Here, the voltage level is 230 V, and the frequency is 50 Hz. Here, a 120° phase shift occurs between the three phases. The AC voltage loop 4 has a power supply interface 6, which is also called a house interface or PCC. A power supply network 8 is connected to the power supply interface 6, and a three-phase AC voltage of 230 V is also guided by the power supply network. Here, each phase of the power supply network 8 is electrically contacted with each phase of the AC voltage loop 4 via the power supply interface 6 and is electrically contacted with the AC voltage loop in phase. Therefore, it is possible to exchange electrical energy between the power supply network 8 and the AC voltage loop 4, and to feed the AC voltage loop 4 via the power supply network 8 with the power supply interface 6.

[0061] Electrically contacting the AC voltage circuit 4 is an electrical consumer 10. The electrical consumer 10 itself has a plurality of units, not shown in detail, one of which is, for example, a heat pump and other units are coffee machines, refrigerators, televisions and / or freezers. The individual units of the electrical consumer 10 are functionally independent of one another and have only one thing in common: they are operated with the aid of the AC voltage circuit 4.

[0062] In addition, the power grid 2 also has a DC voltage loop 12, by means of which a DC voltage is conducted during operation. This DC voltage is, for example, up to 60 V or several hundred V. The DC voltage loop 12 is electrically connected to the AC voltage loop 4 by means of a converter 14. In the example shown, the converter 14 is designed in a three-phase manner and therefore has a bridge circuit, i.e., a B6 circuit. The bridge circuit has three bridge branches, wherein each bridge branch is connected between two potentials of the DC voltage loop 12, and wherein each bridge branch is respectively assigned to one of the phases of the AC voltage loop 4. The converter 14 operates as an inverter, thereby making it possible to transfer electrical energy from the DC voltage loop 12 to the AC voltage loop 4. In addition, here, the inverter 14 can also be designed in a feedback manner, so that reverse electrical energy transfer can also be achieved, i.e., electrical energy transfer from the AC voltage loop 4 to the DC voltage loop 12.

[0063] The power grid 2 also has a power generation device 16 connected to the DC circuit 12. In the variant shown, the power generation device 16 is designed as a photovoltaic system and has a plurality of photovoltaic modules 18, two of which are shown in the figure. Here, the photovoltaic modules 18 are suitably electrically interconnected with one another in series and / or in parallel, so that as long as the photovoltaic modules 18 are exposed to sunlight, the DC voltage conducted in the DC voltage circuit 12 is provided by means of the power generation device 16.

[0064] In addition, the power grid 2 also has an energy storage device 20, which is also connected to the DC voltage circuit 12 and is therefore electrically connected to the DC voltage circuit. The energy storage device 20 includes an energy storage unit 22, which is designed as an electrochemical energy storage device, that is, it is designed as a battery, in particular, it is designed as a secondary battery or storage battery. In addition, the energy storage device 20 also includes a controller 24, which is designed as a battery management system, and with the help of which the charging / discharging of the energy storage unit 22 can be controlled. In addition, the energy storage device 20 also includes a step-up / step-down converter, which is not shown in detail, by which the DC voltage provided by means of the energy storage device 20 is coordinated with the DC voltage provided by means of the DC voltage circuit 12.

[0065] The power grid 2 also includes a control unit 26, which has two interfaces 28. One interface 28 is connected to the converter 14 for signaling, and the other interface is connected to the energy storage 20 for signaling, so that information / data can be exchanged between them. In an embodiment not shown in detail, there is only a single interface 28, by means of which the control unit 26 is connected to the converter 14 and the energy storage 20 via a bus system. The control unit 26 also includes a further interface 30, by means of which a signaling connection to the Internet is realized.

[0066] The control unit 26 has a computer 32 in the form of a programmable microprocessor and a storage medium in the form of a memory 34. The memory 34 stores a computer program product 36, which includes a plurality of instructions that, when executed by the computer 32, cause the computer to implement the program. Figure 2 , for operating the electrical network 2 . In other words, the electrical network 2 is operated according to the method 38 , and the control unit 26 is provided and configured to carry out the method 38 .

[0067] In the method 38, in a first working step 40, a predicted power 42 of the electric power provided by means of the power generation device 16 is determined within a time window 44. The length of the time window 44 is 24 hours in this case, and as shown in FIG. 3, the predicted power 42 has a varying level over the time window 44. Thus, during the night phase, the predicted power 42 is substantially 0 W. At sunrise 46, the predicted power 42 increases slightly and then rises relatively sharply until noon. Subsequently, the predicted power 42 drops relatively sharply until sunset 48 and then continues to drop continuously.

[0068] The predicted power 42 is known in conjunction with the weather forecast. For this purpose, the radiation forecast is retrieved from the meteorological service via a further interface 30 by means of the control unit 26, and the time variation curve of the predicted power 42 is known based on the radiation forecast. In the example shown, the forecast includes the absence of cloud cover, so that the predicted power 42 rises and falls basically continuously. The predicted power 42 known in this way is adjusted in conjunction with the actual power achieved by means of the power generation device 16. Therefore, the predicted power 42 is also known in conjunction with the actual power achieved. In this way, aging effects are particularly taken into account. For example, the actual power of the first five time periods is known after being sorted around the weather that existed at the time, and its average value corresponds in particular to the predicted power 42.

[0069] In a subsequent second working step 50, an energy value 52 is determined. The energy value 52 corresponds to the portion of the predicted power 42 that is above the power value 54 of the converter 14. The power value 54 is predetermined by the manufacturer of the converter 14 and corresponds to the maximum power at which the converter 14 can be operated. The energy value 52 corresponds to the time integral of the portion of the predicted power 42 that is above the power value 54. The energy value 52 is determined here by means of a mathematical optimization method, so that a relatively complex and lengthy integration method does not need to be carried out.

[0070] Furthermore, in the second working step 50, an expected state of charge 56 of the energy store 20 is also determined. The expected state of charge 56 corresponds to a state of charge (“State of Charge”; SoC) which is equal to the maximum energy 58 that can be stored by means of the energy store 20 minus the energy value 52. In the example shown, the expected state of charge 56 corresponds exactly to this difference. In an alternative embodiment, the expected state of charge 56 is specified as a percentage and is related to the maximum storable energy 58. The maximum storable energy 58 is predetermined based on the design of the energy store 20 and may change due to aging effects.

[0071] The first and second working steps 40, 50 are performed at or before the start of the time window 44. After the start of the time window 44, a third working step 60 is performed. In this third working step, the actual power 62 provided by means of the power generation device 16 is determined. For this purpose, in particular, measurement data of the power generation device 16 are retrieved. In the example shown, the actual power 62 is substantially consistent with the predicted power 42. However, it is also possible that they deviate from each other, in particular if the local weather changes and / or other environmental conditions change compared to the assumptions when determining the predicted power 42.

[0072] During the time window 44, the power 64 required by the consumer 10 is also known. During the time window 44, this required power is not constant and depends, for example, on the operation of the consumer 10 by the user. If, as in the example shown, the energy store 20 is initially charged relatively little, the power 64 required to operate the consumer 10 is drawn from the power supply network 8 via the power supply connection 6. As soon as the actual power 62 increases, it is used for the operation of the consumer 10, wherein only the difference between the actual power 62 and the required power 64 is taken from the power supply network 8. During this time, the energy store 20 is not charged and the actual power 62 is fully fed into the AC voltage circuit 4 via the converter 14.

[0073] Only when the actual power 62 exceeds the required power 64 is the excess used to charge the energy store 20. Therefore, the energy store 20 is only charged when the actual power 62 is greater than the required power 64. Here, the energy store 20 is only charged to the expected charge state 56. In summary, the energy store 20 is charged to the expected charge state 56 at most when the actual power 62 of the power generation device 16 is less than the power value 54. After this, as long as the actual power 62 is below the power value 54, the entire actual power 62 is fed into the AC voltage circuit 4 by means of the converter 14. From there, the portion of the power that exceeds the required power 64 is fed into the power supply network 8 via the power supply interface 6.

[0074] If the actual power 62 reaches and rises above the power value 54, the converter 14 will be operated at the power value 54, i.e. at its maximum power. Therefore, the power corresponding to the power value 54 is fed into the AC grid 4. From there, the portion of the power 64 that exceeds the required power is also fed into the power supply network 8. The difference between the actual power 62 present in the DC voltage circuit 12 and the power value 54 is then used to charge the energy storage device 20. Since the energy storage device has only been charged to the expected charge state 56 before, there is still enough capacity there to receive, more precisely, receive this difference over the entire time window 44. In other words, since in the example shown the actual power 62 corresponds to the predicted power 42, additional electrical energy at the level of the energy value 52 is stored in the energy storage device 20. Therefore, even in the case of a relatively small size of the converter 14, it is avoided that the power generation device 16 is turned down.

[0075] As long as the actual power 62 is above the power value 54, the charging limitation to the maximum up to the expected state of charge 56 is canceled and the difference between the actual power 62 and the power value 54 is used to charge the energy store 20. If the actual power 62 falls below the power value 54, which can occur several times during the time window 44, for example when there is cloud cover, the current state of charge of the energy store 20 is taken into account as the new expected state of charge 56.

[0076] During the third working step 60, which is performed during the duration of the time window 44, it is monitored whether the power provided in the AC voltage circuit 4 by means of the converter 14, which corresponds to the minimum of the actual power 62 and the power value 54, is greater than the power limit 66 applicable to the power supply interface 6. In addition, in a modified solution, the required power 64 is taken into account here. In the example shown, the power limit 66 is always greater than the power value 54, but it is possible that the operator of the power supply network 8 reduces the power limit 66 during the time window 44. In this case, the converter 14 will be operated with a reduced power, in particular with a power corresponding to the power limit 66. In addition, the energy store 20 is charged. If the energy store has already been charged to the charge state 56, the limit is removed and additional energy is therefore stored in the energy store 20.

[0077] If the actual power 62 falls below the required power 64, the energy store 20 is discharged and the converter 14 is operated at a power corresponding to the required power 64. It is thus possible to operate the electrical consumer 10 without drawing electrical energy from the supply network 8 for this purpose. After the time window 44 has expired, or shortly before the time window 44 expires, the method 38 is executed again for the next time window 44, i.e., the next 24 hours.

[0078] Furthermore, in a further development, the predicted power 42 is adjusted continuously or multiple times during the time window 44. Here, the average value of the actual power 62 within a certain time range is obtained. The time range corresponds to 15 minutes before the time point at which the predicted power 42 is adjusted. Based on the average value and the predicted power 42 that has not yet been adjusted, the predicted power 42 within a further time range (i.e. 1 hour) is adjusted by means of a spline interpolation method. This improves the accuracy of the predicted power 42 and enables it to be dynamically adapted to changing environmental conditions. In conjunction with the adjusted predicted power 42, the energy value 52 and the expected state of charge 56 can also be adjusted. As a result, the power generation device 16 can basically always operate at the maximum possible power at the respective time point and avoids adjustment down.

[0079] The present invention is not limited to the above-described embodiments. On the contrary, a person skilled in the art / professional can also derive other variants of the present invention without departing from the subject matter of the present invention. In particular, all individual features described in conjunction with the embodiments can be combined with each other in other ways without departing from the subject matter of the present invention.

[0080] Reference numerals list

[0081] 2. Power Grid

[0082] 4 AC voltage circuit

[0083] 6 Power supply interface

[0084] 8 Power supply network

[0085] 10 Electrical consumption

[0086] 12 DC voltage loop

[0087] 14 Inverter

[0088] 16 Power generation device

[0089] 18 Photovoltaic modules

[0090] 20 Energy storage device

[0091] 22 Energy storage unit

[0092] 24 Controller

[0093] 26 Control Unit

[0094] 28 Interface

[0095] 30 Additional interfaces

[0096] 32 Computer

[0097] 34 Memory

[0098] 36 Computer program products

[0099] 38 Methods

[0100] 40 First working step

[0101] 42 Predicted Power

[0102] 44 Time Window

[0103] 46 Sunrise

[0104] 48 Sunset

[0105] 50 Second working step

[0106] 52 Energy

[0107] 54 Power value

[0108] 56 Expected charging status

[0109] 58 Maximum energy storage

[0110] 60 Third working step

[0111] 62 Actual Power

[0112] 64 Power required

[0113] 66 Power Limit

Claims

1. A method (38) for operating an electrical network (2) having a DC voltage circuit (12) and an AC voltage circuit (4) which are electrically connected by means of a converter (14), wherein: The AC voltage circuit (4) has a power supply connection (6) for connecting to a power supply network (8), and an energy store (20) and a generator (16) are connected to the DC voltage circuit (12), wherein: - determining a predicted power (42) of the electrical power to be provided by means of the power generation device (16) within a time window (44), - determining an energy value (52) corresponding to the proportion of the predicted power (42) which is higher than the power value (54) of the converter (14), - determining an expected state of charge (56) of the energy store (20), which corresponds to the maximum energy (58) that can be stored by means of the energy store (20) minus the energy value (52), and - If the actual power (62) of the power generation device (16) is less than the power value (54), the energy storage device (20) is charged to the maximum value of the desired charge state (56).

2. The method (38) according to claim 1, It is characterized in that If the actual power (62) of the power generation device (16) is greater than the power value (54), the inverter (14) is operated at the power value (54) and the energy storage device (20) is charged.

3. The method (38) according to claim 1 or 2, It is characterized in that If the power provided in the AC voltage circuit (4) by means of the converter (14) is greater than a power limit (66) applicable to the supply connection (6), the converter (14) is operated at a reduced power and the energy store (20) is charged.

4. The method (38) according to any one of claims 1 to 3, It is characterized in that The power (64) required by an electrical consumer (10) connected to the AC voltage circuit (4) is determined, and the energy store (20) is charged only when the actual power (62) is greater than the required power (64).

5. The method (38) according to any one of claims 1 to 4, It is characterized in that Select 24 hours as the time window (44).

6. The method (38) according to any one of claims 1 to 5, It is characterized in that The predicted power is obtained by combining the actual power achieved (42).

7. The method (38) according to any one of claims 1 to 6, It is characterized in that The predicted power (42) is obtained in conjunction with the weather forecast.

8. A power grid (2) comprising a DC voltage circuit (12) to which an energy store (20) and a generator (16) are connected, and an AC voltage circuit (4) having a power supply interface (6) for connection to a power supply network (8), wherein: The DC voltage circuit (12) and the AC voltage circuit (4) are electrically connected by means of a converter (14), and the power supply network is operated according to the method (38) according to any one of claims 1 to 7.

9. A control unit (26) having an interface (28) for signal connection to a converter (14) and / or an energy store (20) and being provided and configured to carry out a method (38) according to any one of claims 1 to 7.

10. A computer program product (36), comprising instructions which, when the program is executed by a computer (32), cause the computer to carry out the method (38) according to any one of claims 1 to 7.

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