EP3987623A1

EP3987623A1 - Method for operating a local supply network based on a characteristic curve, network control system, computer program and electronically readable data storage medium

Info

Publication number: EP3987623A1
Application number: EP20764009.5A
Authority: EP
Inventors: Frank Jungnickel
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2019-09-12
Filing date: 2020-08-12
Publication date: 2022-04-27
Also published as: EP3793052A1; WO2021047849A1

Abstract

The invention relates to a method for operating a local supply network (10) by means of a network control system (12), in which the local supply network (10) is at least provided with a local power generating unit (16), an electrical load (18), an electrical power storage unit (20) and an electrical power distribution unit (22). At least one first network converter unit (24) of the electrical energy storage unit (20) is controlled based on a characteristic curve and depending on a voltage within the power distribution unit (22), the first network converter unit (24) being additionally controlled based on a characteristic curve and depending on a current state of charge (SOC) of the electrical power storage unit (20), so that in addition, depending on the state of charge, electrical power from the electrical power storage unit (20) is provided for the power distribution unit (22) or the electrical power storage unit (20) is charged with electrical power from the power distribution unit (22). The invention further relates to a network control system (12), a computer program and an electronically readable data storage medium.

Description

description

Method for operating a decentralized supply network as a function of a characteristic curve, network control system, computer program and electronically readable data carrier

The invention relates to a method for operating a decentralized supply network by means of a network control system, in which the decentralized supply network has at least one decentralized energy generation device, an electrical consumer, an electrical energy storage device and an electrical energy distribution device on which the decentralized energy generation device and the electrical energy storage device and the electrical consumer are electrically coupled, is provided, wherein at least one first network converter device of the electrical energy storage device is characteristic-controlled depending on a voltage within the energy distribution device, so that depending on a characteristic, electrical power from the electrical energy storage - Cher is provided for the energy distribution device or the electrical energy storage device with electrical output of the energy distribution device is loaded. The invention also relates to a network control system, a computer program and an electronically readable data carrier.

From an electrical point of view, industrial systems with a central DC bus usually consist of one or more network converters for supply from the higher-level AC or DC network, e.g. a public network, e.g. Active Front End / AFE or DC-DC converter, regenerative Sources, for example photovoltaics or wind power, electrical energy storage devices (storage devices), for example batteries, flywheel storage devices and consumers, for example motors, robots or welding devices. Sources, storage and consumers from different manufacturers are connected via inverters, for example for asynchronous motors or DC-DC converters, for example for batteries, connected to the DC bus, which can also be referred to as an electrical energy distribution device.

In principle, almost all components can feed electrical power into the local system network or draw power from the local DC network. The aim of an energy-efficient power flow control is to operate the network in such a way that the system parts that are predominantly or completely consumers are not fed directly from the higher-level network, but directly from the available power from the regenerative sources or the storage in the local network . The largely local use of energy generation from decentralized sources avoids unnecessary costs arising from the procurement of energy from higher-level networks and additional transmission losses due to multiple feed-in or feed-back from / to the higher-level network.

Since the power of the regenerative sources fluctuates according to the weather situation and may not be sufficient to supply the consumers, a suitable process is required which on the one hand minimizes the consumption of electrical energy from the higher-level network and on the other hand prevents it that the memory is overloaded or discharged. The algorithm must therefore take into account both the current power flows in the network and the charge status of the storage facilities involved.

Two methods are known with which the power flow in industrial networks can be influenced.

The concept of the Local Grid Controller, in which a second PLC (Local Grid Controller / LGC) is installed in addition to the PLC (Programmable Logic Controller) for the production processes of the industrial plant, which deals exclusively with the real-time recording of the power flows of the component - and are concerned with their external management. The PLC is connected to the upstream inverters, from which it reads the current performance data and to which it returns reference signals for power control.

Internally, the LGC assigns priorities for each component, according to which the power flow is controlled. The reference value for the power output of components with the lowest priority is adjusted even in the event of slight temporary deviations from the balanced power balance of the system, while the specifications for components with higher priority only in the case of larger deviations, such as welding processes, short circuits or failure of the higher-level network , to be changed.

With this method, a second powerful PLC is always required due to the high utilization of real-time recording in the range of a few milliseconds. Changes to the processes in the plant require an adaptation of the priority list and, if necessary, a feedback to the PLC of the production control.

The second known method is decentralized network management using component-specific I (U) or P (U) control characteristics, which can also be referred to as droop curve control.

The voltage regulators of the network converters, in particular of the higher-level network, or the usually constant power reference values of the component converters are _{supplemented or replaced by component-specific I set} (V _dc ) or P _set (V _dc ) control characteristics. This means that the control specification changes automatically depending on the voltage V _dc measured on the common DC bus, which can deviate considerably from the nominal voltage of the network in the event of temporary loads. This decentralized procedure can be supplemented by a central coordination that records individual measured variables on the components and changes the course of the characteristic curve depending on the current load situation. tion, similar to the priority lists mentioned above.

However, no method is known that automatically enables exclusively local use of the locally generated energy or the locally generated electrical power under these conditions.

The object of the present invention is to create a method, a network control system, a computer program and an electronically readable data carrier by means of which an improved operation of a decentralized supply network can be implemented.

This object is achieved by a method, a network control system, a computer program and an electronically readable data carrier according to the independent claims. Advantageous embodiments are specified in the independent claims.

One aspect of the invention relates to a method for operating a decentralized supply network by means of a network control system, in which the decentralized supply network has at least one decentralized energy generation device, an electrical consumer, an electrical energy storage device and an electrical energy distribution device on which the decentralized energy generating device and the electrical energy storage device and the electrical consumer are electrically coupled, is provided, at least one first network converter device of the electrical energy storage device is controlled depending on a voltage within the energy distribution device, so that depending a characteristic curve electrical power is provided by the electrical energy store for the energy distribution device or the electrical energy storage device with electrical power ng of the energy distribution device is charged. It is provided that the first network converter device is additionally characteristic-controlled as a function of a current state of charge of the electrical energy storage device, so that electrical power is additionally provided by the electrical energy store for the energy distribution device depending on the state of charge or the electrical energy storage device with electrical power of the Energy distribution device is charged.

This results in improved operation of the decentralized supply network. In particular, this enables the decentralized supply network to be operated, compared with the prior art, without having to draw power from a higher-level network. In particular, the difference between the power generated and the consumption during normal operation of the decentralized supply network is always supplied by the electrical energy storage device or used to recharge it. In particular, all locally generated power remains in the decentralized supply network. As a result, an increase in efficiency and a reduction in consumption costs can be achieved. In particular, it can thereby be realized that the electrical energy storage device is automatically recharged in normal operation so that there is always enough power available for extraordinary loads.

Under normal operation, for example, the operation of the network with at least one consumer, for example a robot, the average power of which fluctuates by only a few kW around an average value of a few kW, can be viewed. The operation of the network with an additional consumer, eg a spot welder, which requires a very high output of eg 550 kW over a comparatively short period of time, eg of 150 milliseconds, can be seen as an extraordinary temporary load. In particular, the characteristic curve according to the method shown describes the dependence of the power reference value at the network converter device of the store on the voltage at the energy distribution device, whereby it depends on a power measurement of the consumers in normal operation, the measurement of the current power input of the regenerative sources and the state of charge of the store changed.

Furthermore, compared to the prior art, it can be realized that the network control system can be implemented with simple circuits, in particular with a simple electronic computing device, without having to use an additional PLC or contact the PLC for production control. In particular, this is due to the fact that the control of an optimal power flow in the method according to the invention only involves the implementation of the characteristic curve, the acquisition of the performance data on the consumer in normal operation and on the regenerative sources as well as the implementation of the algorithm in network management, especially within an electronic computing device of the network control system.

It can preferably be provided that the decentralized supply network has a large number of electrical energy storage devices, a large number of decentralized generating devices and a large number of electrical consumers. In particular, the respective elements can then be provided with respective network converter devices, with the network converter devices of the electrical energy storage devices in particular each being characteristic curve-controlled.

In particular, the method according to the invention serves to use all regeneratively generated energy or power in the decentralized supply network, this being carried out with the corresponding characteristic curve control. An exemplary embodiment is given below in which a direct voltage is provided by the energy distribution device. The corresponding network converter devices are then designed for direct voltage at least on the power distribution device side. Alternatively, an alternating voltage can also be provided by the energy distribution device, the corresponding network converter devices then being designed at least on the energy distribution device side for alternating voltage.

According to an advantageous embodiment, the energy distribution device is provided in such a way that it is additionally coupled to a higher-level network and is designed to receive electrical energy from the higher-level network. A public network or a plant network, for example, can be provided as the higher-level network. The higher-level network can provide both AC voltage and DC voltage. In particular, the energy distribution device can be provided with a network converter for the higher-level network. In particular, electrical power can thus be received from the higher-level network. If, for example, too little electrical energy or power is available within the decentralized supply network, the electrical power can be correspondingly received from the higher-level network without a power drop within the decentralized supply network. The network converter can be designed both as an inverter and as a DC voltage controller. This enables the decentralized supply network to be operated reliably both on a higher-level DC network and from a higher-level AC network.

Alternatively, it can be proposed if the installed capacity of the regenerative sources, for example, is sufficient to generate more energy on average under the corresponding climatic conditions than for the operation of the system and the replenishment of the storage, i.e. the electrical ones Energy storage device, is required, then you can do without the energy supply from the higher-level network even during spot welding. The fourth grid converter would then only be used to feed excess energy back into the grid. If necessary, the output of the memory would have to be increased or the bus capacity increased in order to prevent the AFE from going into the unregulated state during welding.

In a further advantageous embodiment, the energy distribution device is provided in such a way that it is additionally coupled to a higher-level network and is designed to transmit electrical power from the energy distribution device to the higher-level network. In other words, it can be provided that if an excess of electrical power can be found within the energy distribution device, which in particular cannot be absorbed by charging the electrical energy storage device, it can be provided that this excess electrical power is fed into the higher-level network is fed. In particular, it can be provided for this purpose that corresponding feed-in tariffs can be paid out for feeding in the excess electrical power. In particular, this makes it possible that, even if there is an excess of electrical power, it is not lost, but can be fed back into the higher-level network accordingly. This enables improved operation of the decentralized supply network.

In a further advantageous embodiment, the first grid converter device is controlled by means of the characteristic curve in such a way that a maximum possible electrical power of the electrical energy storage device is provided for the energy distribution device at a first predetermined voltage threshold value within the energy distribution device. For example, it can be provided that in a network which is operated on average at a voltage of 650V, the specified voltage threshold value at 600 V. If the voltage within the energy distribution device is then below 600 V, it can be provided that the electrical energy storage device feeds the maximum possible electrical power into the energy distribution device. The reason for this, in particular, is that if, for example, high electrical powers are required briefly within the energy distribution device, then these can be provided by the electrical energy storage device. In particular, this makes it possible that no additional electrical power has to be drawn from a higher-level network. In other words, the electrical energy is provided locally, even if high short-term powers are called up within the decentralized supply network, which place an extraordinary load on the decentralized supply network, as is the case, for example, with spot welding. The high currents lead to a clear transient drop in the voltage within the energy distribution device, for example by 100 V. Traditionally in the prior art, the fourth network converter device is designed in such a way that the decentralized supply network briefly draws 600 kW from the higher-level network can. If the average consumer load in normal operation is, for example, 10kW, then a corresponding network converter on the higher-level network side almost always works in the area of low-loss loads. Should such a spot welding process now occur within the decentralized supply network, provision is made in particular for the electrical energy store to provide the maximum possible electrical power regardless of the state of charge of the electrical energy store in order to counteract a voltage drop within the energy distribution device. In particular, should the decentralized supply network have a large number of electrical energy storage devices, it can be provided here that the large number of electrical energy storage devices provide the maximum possible electrical power for the energy distribution device, regardless of their state of charge, in order to cause a voltage drop within the energy distribution device prevent. It is also advantageous if the first network converter device is controlled by means of the characteristic curve in such a way that the electrical energy storage device is charged with a maximum possible electrical power from the energy distribution device at a second predetermined voltage threshold value within the energy distribution device. In particular, it is provided that the locally generated energy or power of the electrical energy generating device is thus used to charge the electrical energy storage device. In particular, excess power from the decentralized supply network is used to charge the electrical energy storage device. This makes it possible for the locally generated energy or power to remain in the local network and, in particular, for a corresponding amount of electrical power to be made available for the energy distribution device when required.

It is also advantageous if the first power converter device is controlled by means of the characteristic curve in such a way that no electrical power is exchanged between the electrical energy storage device and the energy distribution device within a specified voltage range within the energy distribution device, in particular if the average consumer power is the same in normal operation the power input of the regenerative sources. In the example, this can be, for example, at an average value of 650 V, so that the range between 640 V and 660 V, for example, is drawn. This voltage range thus characterizes normal operation at the same time, in contrast to the extraordinary load that the voltage of the energy distribution device leads out of this range. It can then be provided within this area that no electrical power is exchanged between the energy distribution device and the electrical energy storage device. The reason for this in particular is that the electrical energy storage device is otherwise in the Normal operation permanently involved in covering the consumer load and thus unnecessarily discharged.

In a further advantageous embodiment, the first grid converter device is controlled by means of the characteristic curve in such a way that the electrical energy storage device is charged with a maximum possible electrical power P _max from the energy distribution device below a first predetermined charge status of the electrical energy storage device. If, for example, a charge level of the electrical energy storage device is below 20%, there is a risk of a corresponding undercharging and this can lead to impairment of the electrical energy storage device. As a result, it is provided in particular that, should the state of charge be below this predetermined state of charge, the electrical energy storage device is recharged as quickly and efficiently as possible. In this way, undercharging of the electrical energy storage device can be prevented.

It is also advantageous if the first network converter device is controlled by means of the characteristic curve in such a way that a maximum possible electrical power P _max 'is provided by the electrical energy storage device for the energy distribution device above a second predetermined charge state of the electrical energy storage device. In particular, this can prevent overcharging. If, for example, the state of charge is above 95%, the electrical power is provided for the energy distribution device. If this excess power is not required within the energy distribution device, it can be provided, for example, that this excess electrical power is then fed back into the higher-level network. This prevents overcharging and the excess power cannot be used locally but in the higher-level network. According to a further advantageous embodiment, the first grid converter device is controlled by means of the characteristic curve in such a way that the electrical energy storage device is switched between a third predetermined state of charge of the electrical energy storage device and a fourth predetermined state of charge of the electrical energy storage device as a function of an electrical energy storage device. Position of the decentralized energy generating device provides the electrical power or is charged with the electrical power. This state of charge range can be defined, for example, by 25% to 90% of the state of charge, which can also be referred to as SOC (state of charge). It is therefore a middle range, with the network converter device then being designed for the effective feed-in power of DP = - (P _{load RQ} ) (taking into account the sign rule that the positive current direction is always from the corresponding component to the energy energy distribution device shows), that is, the energy storage device charges or feeds in, depending on whether the decentralized energy generation device delivers more or less power than the load demands in normal operation. _{P RQ} corresponds to the power of the regenerative energy source and P _{load to} the consumer load. This enables improved operation of the decentralized supply network.

In particular with, for example, regenerative energy sources as a decentralized energy generating device, the generation conditions for generating the electrical power cannot be reliably foreseen, so that the development of the state of charge of the electrical energy storage device is based on the current possibilities of the regenerative sources. For an energy-efficient driving style, however, electrical power should only be exchanged with the higher-level network, in particular with a public network, if temporarily exceptionally high power is required, for example welding, or if the state of charge is electrical energy storage device assumes one of the critical values. Otherwise everything will be regenerative generated energy or power used in the decentralized supply network. In particular, the method according to the invention thus serves to show how this can be achieved with the corresponding characteristic curve control.

It can also be provided that between the first specified state of charge and the third specified state of charge, this being for example in particular between 20% and 25% of the state of charge, and the second state of charge and the fourth state of charge, this being in particular for example between 90% and 95% of the state of charge is, for reasons of stability a mediation between the middle and the outer areas can take place. This can be done, for example, by SOC-dependent linear interpolation between a maximum output and DP.

In a further advantageous embodiment, the first network converter device is controlled by means of the characteristic curve in such a way that an electrical power provided by the decentralized energy generation device is taken into account when the electrical power is provided by the electrical energy storage device. In particular, the current generation of electrical power by the electrical energy generation device is taken into account. This means that the decentralized supply network can advantageously be operated.

According to a further advantageous embodiment, the network control system is provided with at least one detection device for detecting at least one required electrical power of the electrical consumer and / or for detecting provided electrical power of the decentralized energy generating device. In particular, for this purpose the network control system can have an electronic computing device which evaluates the recorded values and, as a function thereof, controls the decentralized supply network accordingly. In particular, the characteristic curve is thus during ongoing plant operation shifted continuously so that the corresponding values for P _max / P _max 'and DP are passed on to the electrical energy storage device as manipulated variables. The required electrical power and the provided electrical power are a slowly changing variable in normal operation, so that no particularly high demands are placed on this resolution of the measurement. The same also applies to the reaction time of the electrical energy storage device.

Furthermore, it is provided in particular that a regenerative energy source is provided as the decentralized energy generation device. A photovoltaic system or a wind turbine, for example, can be viewed as a regenerative energy source. In particular, since these generate the electrical energy as a function of the weather, the method according to the invention enables improved operation.

Another aspect of the invention relates to a network control system for a decentralized supply network, with at least one electronic computing device, the network control system being designed to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the network control system.

Yet another aspect of the invention relates to a computer program which can be loaded directly into a memory of an electronic computing device of a magnetic resonance system, with program means to carry out the steps of the method according to one of the preceding aspects when the program is in the electronic Computing device of the magnetic resonance system is executed.

Yet another aspect of the invention relates to an electronically readable data carrier with electronically readable control information stored thereon, which comprises at least one computer program according to the preceding aspects and is designed in such a way that when the data carrier is used in an electronic computing device, a Magnetic resonance system carry out a method according to one of the previous aspects.

Advantageous embodiments of the method are to be regarded as advantageous embodiments of the network control system, the computer program and the electronically readable data carrier. For this purpose, the network control system has objective features which enable the method or an advantageous embodiment thereof to be carried out.

Further features of the invention emerge from the claims, the figures and the description of the figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention.

The invention will now be explained in more detail on the basis of preferred exemplary embodiments and with reference to the accompanying drawings.

Show:

1 shows a schematic view of an embodiment of a decentralized supply network;

FIG. 2 shows an example characteristic curve of a regenerative, decentralized energy generation device;

3 shows an example characteristic curve of an electrical energy storage device;

4 shows a basic circuit diagram of a charging behavior of an electrical energy storage device; 5 shows a characteristic curve of a first network converter device in a first situation;

6 shows a further characteristic curve of the first network converter device in a second situation; and

7 shows a further characteristic curve of the first network converter in a third situation,

Identical or functionally identical elements are provided with the same reference symbols in the figures.

1 shows a schematic view of an embodiment of a decentralized supply network 10. The decentralized supply network 10 is operated with a network control system 12. The network control system 12 has in particular an electronic computing device 14. The decentralized supply network 10 has a decentralized energy generation device 16, this being designed in particular as a regenerative energy source. For example, the regenerative energy source can be a photovoltaic system or a wind power system. The decentralized supply network 10 also has an electrical consumer 18. The electrical consumer 18 can be a motor, for example. Furthermore, the decentralized supply network 10 has an electrical energy storage device 20. Furthermore, the decentralized supply network 10 has an electrical energy distribution device 22, which can in particular be designed as a DC voltage bus. Alternatively, this can also be designed as an alternating voltage bus. The decentralized energy generation device 16, the electrical energy storage device 20 and the electrical consumer 18 are electrically coupled to the electrical energy distribution device 22. A first network converter device 24 is arranged at least between the electrical energy storage device 20 and the electrical energy distribution device 22. In particular, in the present embodiment For example, the first grid converter device 24 is designed as a DC / DC converter.

The first grid converter device 24 is characteristic-controlled in particular as a function of an electrical voltage within the energy distribution device 22, so that, depending on a characteristic 26, electrical power is provided by the electrical energy storage device 20 for the energy distribution device 22 or the electrical energy storage device 20 with electrical power from Energy distribution device 22 is charged.

It is provided that the first grid converter device 24 is additionally characteristic-controlled as a function of a current state of charge 28 (FIG. 4) of the electrical energy storage device 20, so that electrical power is additionally provided by the electrical energy storage device 20 for the energy distribution device 22 as a function of the state of charge or the electrical energy storage device 20 is charged with electrical power from the energy distribution device 22.

In particular, FIG. 1 also shows that a further second network converter device 32 can be formed between the decentralized energy generation device 16. In the present exemplary embodiment, this is also designed, in particular, as a DC / DC controller. Alternatively, this can also be designed as a combination of inverter and DC / DC converter. Furthermore, it can be provided that a third network converter device 34 is also formed in front of the electrical consumer 18. This can be designed both as an inverter and as a DC / DC converter.

Furthermore, it can be provided that the energy distribution device 22 is provided in such a way that it is additionally coupled to a higher-level network 36 and is designed to receive electrical power from the higher-level network 36. In particular, this can be done between A fourth network converter device 38, which can be configured as an inverter or as a DC / DC converter, can be configured in the higher-level network 36 and the energy distribution device 22. For this purpose, it can also be provided that the energy distribution device 22 is provided in such a way that it is additionally coupled to a higher-level network 36 and is designed to transmit electrical power from the energy distribution device 22 to the higher-level network 36. In other words, a bidirectional exchange of energy between the superordinate network 36 and the energy distribution device 22 can be carried out. In particular, for this purpose the electronic computing device 14 can carry out a corresponding control according to the electrical voltage present within the energy distribution device 22.

It can preferably be provided that the decentralized supply network 10 has a multitude of electrical energy storage devices 20, a multitude of decentralized generating devices 16, a multitude of electrical consumers 18 and a multitude of network converters between the local and the higher-level or several higher-level Has networks 36. In particular, a plurality of network converter devices 24, 32, 34, 38 or rectifiers can also be used between the decentralized supply network 10 and the higher-level network 36 in order to create redundancy, for example. In particular, the respective elements can then be provided with respective network converter devices 24, 32, 34, 38, in particular the network converter device 24 of the electrical energy storage device 20 being characteristic-controlled in each case.

1 further shows that the network control system 12 with at least one detection device 40 for detecting at least one required electrical power as consumer power P _{1 of} the electrical consumer 18 and / or for detecting a provided electrical power as energy generation power P _{2 of} the decentralized generation direction 16 is provided. In particular, storage _{energy can also be recorded as storage power P 3} and network energy as higher-level network power P ₄ .

In particular, FIG. 1 thus shows a simplified structure of the decentralized supply network 10. Electrical consumers 18 are all system components which, on average, draw more power from the system than they feed back. The consumption resulting therefrom must be made available by the decentralized supply network 10 under all circumstances in order to secure production. Characteristic curves which would restrict the power requirement of the third network converter device 34 would therefore be rather counterproductive, so that no P (U) profiles are specified for the electrical consumer 18. The fourth network converter device 38 provides, in particular, electrical power from the higher-level network 36 if the electrical power present within the energy distribution device 22 is temporarily insufficient to supply the electrical consumer 18. The regenerative energy source, which in the present exemplary embodiment corresponds to the decentralized energy generation device 16, is generally not capable of being fed back, that is, it feeds power into the decentralized supply network 10 according to the weather conditions, from 0 to the nominal output. A corresponding characteristic curve is shown in particular in FIG. FIG. 2 thus shows a generator characteristic curve 42. In FIG. 2, in particular, the voltage U is plotted in volts on an abscissa and a power P in watts is plotted on the ordinate. FIG. 2 shows, purely by way of example, that the regenerative energy source can generate 10 kW of power at 400 V and no longer generates power at 700 V. It should be noted in particular that the positive current direction in the following always points from the corresponding component to the energy distribution device 22. At a given point in time, the decentralized energy generation device 16 supplies a constant power up to a voltage slightly above the nominal voltage of the energy distribution device 22, which corresponds in particular to 650 V in this exemplary embodiment. If the voltage continues to rise, the feed-in power is reduced to 0. The upper limit of the power, in particular 10 kW here, can change, for example, according to the solar radiation.

In order to be able to safely manage a corresponding excess of energy or power within the energy distribution device 22, corresponding network-side network converters, in the present exemplary embodiment the fourth network converter device 38, can have a characteristic curve on the higher-level network 36. A corresponding Active Front End (AFE) does not regulate the power output, but the fed-in current at a given bus voltage. The zero crossing lies in particular at the nominal voltage of the energy distribution device 22, so that the network converter feeds back into the network or draws electrical power from the higher-level network 36 in the event of overvoltage or undervoltage. Without an electrical energy storage device 20 and a decentralized energy generation device 16, the consumer load shifts the bus voltage downward, unless electrical consumers 18 that are running out would, for example, temporarily feed power back.

In particular, FIG. 2 thus shows that it can be provided that the first network converter 24 is controlled by means of the characteristic curve 26 in such a way that an electrical power provided by the decentralized energy generation device 16 when the electrical power is provided by the electrical energy storage device 20 is taken into account.

In order to avoid the permanent charging / discharging of the electrical energy storage device 20 during normal load changes of the electrical loads 18 in the vicinity of the nominal voltage, a storage characteristic is suitable, for example 44, as shown in FIG. 3 thus shows in particular that the first grid converter device 24 is controlled by means of the characteristic curve 26 in such a way that no electrical power is exchanged between the electrical energy storage device 20 and the energy distribution device 22 within a predetermined voltage range 46 within the energy distribution device 22, when the regenerative energy generation unit just covers the needs of the consumer in normal operation. The range without feed, in the present exemplary embodiment between 640 V and 660 V, can be selected, for example, so that the bus voltage does not move out of this voltage range 46 in the event of any moderate load fluctuations within the decentralized supply network 10, i.e. in normal operation.

In the following, no distinction is made according to what type of electrical energy storage device 20 is involved, provided that it provides or retrieves electrical power at its system interface. The state of charge of the memory (State of Charge / SOC) can then be in accordance with the sign convention with the charging current I (t), the nominal electrical storage capacity C _nom and the definition SOC (t ₀ ) = SOC are _initially calculated. It is assumed that the charging current disappears below SOC = 0 and above SOC = 1. This understanding is easy to understand for batteries. For a motor operated as a flywheel mass storage device, for example, the current flow that is necessary to accelerate the motor from the lower limit speed to its nominal speed in the field weakening range would be added up.

Because of the sign rule, the following general current balance applies in the system P _NU (V _dc ) + P _RQ ( _dc ) + P _V (V _dc ) + P _Sp (V _dc ) = 0 with the power of the grid converter P _NU (P ₄ ), the regenerative source P _RQ (P ₂ ), the consumer P _V (P ₁ ) and the memory P _Sp (P ₃ ). It is assumed that the voltage V _dc depends only insignificantly on the location, which is a good approximation for normal line lengths in decentralized supply networks. In normal operation without a network control system 12, the stores are inactive (P _Sp (V _dc ) = 0), that is, the fourth network converter device 38 provides or feeds exactly the negative total power from additional feed from the regenerative sources and the current consumption at any point in time back, depending on whether | P _RQ | the consumption | P _V | falls below or exceeds.

An essential idea of the method described below is to enable the exchange of energy via the fourth network converter device 38 only during exceptional loads such as spot welding or for recharging or discharging the accumulator when critical charge states are reached. When spot welding with the power P _PS , for example, loads of approximately 550 kW occur over 150 ms. The high currents lead to a clearly transient drop in the bus voltage, approximately 100 V. According to the prior art, the higher-level network 36 then provides electrical power for a short time. If the average consumer load in normal operation P _load = P _V -P _PS in the system is a few kW, then a corresponding AFE almost always works in the area of low-loss loads. If a smaller fourth network converter device 38 is to be used, the nominal power must be able to cover the base load of the remaining consumers 18 if the decentralized energy generating device 16 runs dry. Furthermore, the energy generating device 16 and the electrical energy storage _{device 20 must be able to provide the remaining 500 kW during spot welding P PS} without the fourth network converter device 38 being switched to the unregulated rectifier. drive decays. _{Furthermore, when P RQ} + P _load > 0 in normal operation, in particular without spot welding P _PS , the electrical storage device 20 should be charged from the excess P _RQ + P _load , so that the current within the fourth network converter device 38 disappears. Furthermore, the electrical energy storage device 20 should _{deliver the deficit P RQ} + P _load _{when P RQ} + P _load <0 in normal operation, so that the current of the fourth network converter device 38 again disappears and the electrical power from the decentralized energy generation device 16 and the previous memory entry within the energy distribution device 22 remains. Furthermore, the electrical energy storage device 20 may only be charged from the higher-level network 36 when the state of charge SOC is critical, for example when the state of charge is less than 25%, and into the higher-level network 36, in particular the public one, when the state of charge SOC is greater than 90% Network, discharged.

4 shows in a schematic view an example of a characteristic control with the current state of charge 28. FIG. 4 thus shows in particular that the first network converter device 24 is controlled by means of the characteristic curve 26 in such a way that the electrical energy storage device 20 _{below a first predetermined state of charge SOC 1} Energy storage device 20 is charged with a maximum possible electrical power P ^max from the energy distribution device 22. Furthermore, FIG. 4 shows that the first network converter device 24 is controlled by means of the characteristic curve 26 in such a way that, above a second predetermined charge state SOC _{2 of} the electrical energy storage device 20, a maximum possible electrical power P ^{max '} from the electrical energy storage device 20 for the energy Distribution device 22 is provided.

Furthermore, FIG. 4 shows that the first network converter device 24 is controlled by means of the characteristic curve 26 in such a way that between a third predetermined state of charge SOC _{3 of} the electrical energy storage device 20 and a fourth predetermined state of charge SOC _{4 of} the electrical energy Energy storage device 20 the electrical energy storage device 20 provides the electrical power or is charged with the electrical power as a function of an electrical energy supply of the decentralized energy generating device 16. This is shown in particular by area 48. Furthermore, FIG. 4 shows a respective transition area 50, 52. The first transition area 50 is formed between the second state of charge SOC ₂ and the fourth state of charge SOC ₄ . A second transition region 52 is formed between the first state of charge SOC ₁ and the third state of charge SOC ₃ .

In particular, since the weather conditions cannot be reliably predicted, the development of the state of charge SOC of the electrical energy storage device 20 is based on the current possibilities of the decentralized energy generation device 16. For an energy-efficient driving style, however, electrical power should in any case only be The ordered network 36 can be exchanged, for example, when welding or when the state of charge SOC of the electrical energy storage device 20 assumes one of the critical values. Otherwise, all regeneratively generated energy or power in the decentralized supply network 10 is used.

FIG. 4 shows, by way of example, the charging behavior of the electrical energy storage device 20 in normal operation. In the area 48, in which the state of charge SOC is between 25% and 90%, the first grid converter 24 regulates the effective feed-in power DP = - (P _load P _RQ ), that is to say it charges or feeds in, depending according to whether the decentralized energy generating device 16 delivers more or less power than the load demands in normal operation. 4 shows, purely by way of example, how corresponding charge state ranges can be defined. It goes without saying that further charge status ranges can also be defined. In the range above 95%, which _{corresponds to the second state of charge SOC 2} , and below 20%, which in the present exemplary embodiment corresponds to the first state of charge SOC ₁ , there is a risk of overcharging or undercharging the electrical energy storage device 20, so that it is charged with a maximum load P ^max or discharged with P ^{max '.}

In the transition areas 50, 52, which in the present exemplary embodiment correspond to a state of charge SOC of 90% to 95% and a state of charge SOC between 20% and 25%, mediation between the middle and outer areas can take place for reasons of stability . This can be done, for example, by linear interpolation between P ^max and DP depending on the state of charge.

FIGS. 5 to 7 show different characteristic curves within the first network converter device 24. In FIG. 5, in particular, a characteristic curve with a DP of 0 W can be seen, that is, when the feed power of the regenerative energy generating device just covers the average consumer power in normal operation . FIG. 6 shows a characteristic curve with a DP = -5 kW, that is, when more energy is fed in than is consumed, and FIG. 7 shows a characteristic curve with a DP = 7.2 kW, that is, if more energy is consumed than is available, for example, from the PV system.

5 to 7 thus show that it can be provided that the first grid converter device 24 is controlled by means of the characteristic curve 26 in such a way that up to a first predetermined voltage threshold value 54 within the energy distribution device 22, the maximum electrical power of the electrical Energy storage device 20 is provided for the energy distribution device 22. Furthermore, FIGS. 5 to 7 show that the first grid converter device 24 is controlled by means of the characteristic curve 26 in such a way that above a second predetermined voltage threshold value 56 within the energy distribution device 22, the electrical energy storage cheinrichtung 20 with the maximum electrical power - from the energy distribution device 22 is charged.

In order to limit the corresponding behavior according to FIG. 4 to normal operation, however, the state of charge SOC may only influence the storage characteristic curve in the voltage range in which there is no feed without an active network control system 12, as shown in FIG. 3, in the present case between 640 V and 660 V. In the case of heavy loads, such as in the case of spot welding P _PS , all electrical energy storage devices 20, in particular a large number of electrical energy storage devices 20 within the decentralized supply network 10 can be arranged, regardless of their state of charge SOC, immediately participate in maintaining the plant operation and thus in providing the welding power.

This is shown in particular by the first predetermined voltage threshold value 54.

FIGS. 5 to 7 each show, in their embodiment, five different characteristic curves 26 for five different charge states SOC. A first characteristic curve 58 shows, for example, the course at a state of charge of 95%. A second characteristic curve 60 is for a state of charge SOC of 92%, a third characteristic curve shape 62 is for a state of charge SOC of 80%, a fourth characteristic curve shape 64 is for a state of charge SOC of 23% and a fifth characteristic curve shape 66 is for a state of charge SOC of 20 % to see.

If the regenerative source just covers the consumption in normal operation (FIG. 5), then the electrical energy storage device does not intervene in the middle SOC range (SOC = 80%) - the output is regulated to zero. The linear interpolated transition area begins at the upper limit of the middle SOC range at 90%. The discharge power of the electrical energy storage device 20 thus reaches just 2/5 of the maximum possible discharge power P ^{max '} at 92%. The same thing happens with the opposite sign at 23%. The maximum possible borrowed charging / discharging power in normal operation P ^max / P ^{max '}

(here -42.8kW or 37.2kW) are achieved at 20% and 95% respectively. The same applies to the other two DP values. Here, in the middle SOC range, the excess / deficit DP is always compensated for by the electrical energy storage device 20, the above-described 2/5 value now in each case referring to the difference between DP and P ^max / P ^{max '} .

The maximum possible charging / discharging capacities in normal operation P ^max / P ^{max '} are directly dependent on the control behavior of the line converter. If the grid converter (as with the AFE) works in the usual control mode with constant reference voltage, i.e. without a characteristic, then it can deliver the full rated power P _NUN _{for every V dc in normal operation.} In accordance with the equation given above, the electrical energy storage device 20 can then maximally use the power

P ^max / P ^{max '} = - (± P _NUN + P _load + P _RQ ) can be charged or discharged. When using the characteristic control on the AFE, note that the bus voltage now depends on the load on the line converter. The maximum available power of the network converter at a given V _dc can be determined from the characteristic curve, thus avoiding, among other things, that the load generated by the charging / discharging power of the electrical energy storage device 20 does not drop the bus voltage V _dc below / above the limits of the Normal operating range, in the example 640V and 660V, presses. In a more refined variant, the P ^max / P ^{max 'can} also be updated in each case in accordance with the current value of P _RQ .

In order to be able to continuously shift the characteristic 26 during ongoing system operation, P _load and P _RQ must be recorded by a central network management system, in this case the network control system 12, and the corresponding values for P ^max / P ^{max '} and DP must be sent to the electrical energy storage device 20 can be passed on as manipulated variables. P _RQ is similar to the mean consumer power P _{load is} a slowly changing variable in normal operation, so that no particularly high demands are placed on the resolution of the measurement. The same applies to the reaction time of the electrical energy storage device 20.

The method described above regulates the autonomous behavior of the electrical energy storage device 20 as a function of its own state of charge SOC. In addition, if one or more electrical energy storage devices 20 are to act as a function of the state of charge SOC of other electrical energy storage devices 20, then the current SOC value of all electrical energy storage devices 20 must also be transmitted to the network management become.

The method can be applied to several regenerative sources i = 1 ... n and to several electrical energy storage devices 20 k = 1... m, for example after expand with the individual manipulated variable DP _k.

A method described herein can also be in the form of a computer program (product) that implements the method on a control unit, in particular the electronic computing device 14, when it is executed on the control unit. There can also be an electronically readable data carrier (not shown) with electronically readable control information stored on it, which comprises at least one described computer program product and is designed in such a way that it can be used when the data carrier is used. Carry out a described method in a control unit of an MR system.

Alternatively, it can be proposed if the installed power of the regenerative sources is sufficient to generate more energy than is required for the operation of the system and the filling of the storage, ie the electrical energy storage device 20, under the corresponding climatic conditions , then the energy supply from the higher-level network 36 can also be dispensed with during spot welding. The fourth network converter 38 would then only serve to feed excess energy back to the network. If necessary, the output of the memory would have to be increased or the bus capacity increased in order to prevent the AFE from going into the unregulated state during welding.

As an alternative, it can be suggested that the following applies at all times:

P _SP = -P _NU _{-P Last} _{-P RQ} = -P _NU + DP

If the electrical energy storage device 20 regulates to DP in normal operation, as described above, then P _NU disappears accordingly. If P _{NU is} to be kept constant at a value P _{NUfix other than} 0, the memory must be set to:

DP '= -P _NUfix + DP = - (P _RQ + P _Load + P _NUfix ).

This procedure can be used, for example, if the regenerative energy sources are not supplying any energy (P _RQ = 0) or if they are not available for a certain period of time. In this case, the control to DP = would - P _load the memory, so the electrical energy store 20 chereinrichtung discharged in normal operation until the SOC lower critical zone is achieved. The network converter would then become the superordinate network 36, the storage system gradually recharge from the network. However, this would mean that all the energy required to operate the system is ultimately first brought from the higher-level network 36 into the storage system and from there to the consumers. This would generate increased dynamic conversion losses at all the converters involved in the entire operation.

In this case, it would be more efficient not to operate the network converter in normal operation in idle mode (P _NU = 0), but in such a way that it just compensates the load on average. Since P _load generally depends on the time, the storage systems would only compensate for the slight fluctuations in the load around its time average value <P _{load> in normal operation.} Otherwise, they would only be used during spot welding and reloading. In normal operation, the memory now regulates to:

DP '= - (P _Load + P _NUfix ) = - (P _Load -P _Load The grid converter would accordingly feed in with a comparatively dynamic and thus low loss with constant power P _NUfix = - <P _Load >.

List of reference symbols

10 decentralized supply network

12 Network Control System

14 electronic computing device

16 decentralized energy generation facility

18 electrical consumers

20 electrical energy storage device

22 Energy distribution equipment

24 first line converter device

26 characteristic

28 current charge status

32 second line converter device

34 third line converter device

36 superordinate network

38 fourth line converter device

40 detection device

42 Generating equipment characteristic

44 Storage curve

46 Voltage range

48 area

50 first transition area

52 second transition area

54 first predetermined voltage threshold value

56 second predetermined voltage threshold value

58 first form of characteristic curve

60 second form of characteristic curve

62 third form of characteristic

64 fourth form of characteristic

66 fifth form of characteristic curve

P ₁ consumer power

P ₂ power generation capacity

P ₃ storage capacity

P ₄ public network power

P ^max maximum power

SOC state of charge

SOC ₁ first state of charge

SOC ₂ second state of charge SOC ₃ third state of charge

SOC ₄ fourth state of charge

Claims

1. A method for operating a decentralized supply network (10) by means of a network control system (12), in which the decentralized supply network (10) has at least one decentralized energy generating device (16), an electrical consumer (18), an electrical one Energy storage device (20) and an electrical energy distribution device (22) to which the decentralized energy generation device (16) and the electrical energy storage device (20) and the electrical consumer (18) are electrically coupled is provided , wherein at least one first network converter device (24) of the electrical energy storage device (20) is characteristic-controlled as a function of a voltage within the energy distribution device (22), so that, depending on a voltage-dependent characteristic (26), electrical power of the electrical energy storage device (20) for the energy distribution device (22) t or the electrical energy storage device (20) is charged with electrical power from the energy distribution device (22), characterized in that the first network converter device (24) is additionally dependent on a current state of charge (SOC) of the electrical energy storage device ( 20) is characteristic-controlled, so that in addition, depending on the state of charge, electrical power is provided by the electrical energy storage device (20) for the energy distribution device (22) or the electrical energy storage device (20) is charged with electrical power from the energy distribution device (22).

2. The method according to claim 1, characterized in that the energy distribution device (22) is provided in such a way that it is additionally coupled to a higher-level network (36) and is designed to receive electrical power from the higher-level network (36).

3. The method according to claim 1 or 2, characterized in that the energy distribution device (22) is provided in such a way that it is additionally coupled to a higher-level network (36) and for transmitting electrical power from the energy distribution device (22) into the higher-level network (36) is formed.

4. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) such that a maximum possible electrical power of the at a first predetermined voltage threshold value (54) within the energy distribution device (22) electrical energy storage device (20) is provided for the energy distribution device (22).

5. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) in such a way that at a second predetermined voltage threshold value (56) within the energy distribution device (22) the electrical energy storage device ( 20) is charged with a maximum possible electrical power from the energy distribution device (22).

6. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) such that within a predetermined voltage range (46) within the power distribution device (22) no electrical power between the electrical energy storage device (20) and the energy distribution device (22) are exchanged, in particular if the feed-in power of the regenerative energy generation source just covers the consumption in normal operation.

7. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) in such a way that below a first predetermined state of charge (SOC ₁ ) of the electrical energy storage device (20) the electrical energy storage device (20) is charged with a maximum possible electrical power from the energy distribution device (22).

8. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) such that above a second predetermined state of charge (SOC ₂ ) of the electrical energy storage device (20) a maximum possible electrical power is provided by the electrical energy storage device (20) for the energy distribution device (22).

9. The method according to any one of the preceding claims, characterized in that the first network converter device (24) is controlled by means of the characteristic curve (26) such that between a third predetermined state of charge (SOC ₃ ) of the electrical energy storage device (20) and a four - th predetermined state of charge (SOC ₄ ) of the electrical energy storage device (20) the electrical energy storage device (20) depending on an electrical energy supply of the decentralized energy generating device (16) provides the electrical power or is charged with the electrical power.

10. The method according to any one of the preceding claims, characterized in that the first power converter device (24) is controlled by means of the characteristic curve (26) in such a way that an electrical power provided is provided by the decentralized energy generating device (16) the electrical power is taken into account by the electrical energy storage device (20).

11. The method according to any one of the preceding claims, characterized in that the network control system (12) is provided with at least one detection device (40) for detecting at least one required electrical power of the electrical consumer (18) and / or for detecting a provided electrical power of the decentralized energy generating device (16).

12. The method according to any one of the preceding claims, characterized in that a regenerative energy source is provided as the energy generating device (16).

13. Network control system (12) for a decentralized supply network (10), with at least one electronic computing device (14), the network control system (12) being designed to carry out a method according to one of Claims 1 to 12.

14. Computer program which can be loaded directly into a memory of an electronic computing device (14) of a magnetic resonance system, with program means to carry out the steps of the method according to one of claims 1 to 12 when the program in the electronic computing device (14 ) the magnetic resonance system is executed.

15. Electronically readable data carrier with electronically readable control information stored on it, which comprises at least a computer program according to claim 14 and is designed in such a way that it executes a method when the data carrier is used in an electronic computing device (14) of a magnetic resonance system carry out according to one of claims 1 to 12.