DE102016111343A1 - Energy management system and energy management process - Google Patents

Abstract

The invention relates to an energy management system and an energy management method. The energy management system (10) is designed to control a battery device (2) and a heating element (3) of a thermal buffer store in a local power grid (7) with a decentralized power generator (4) for generating a current for the local power grid (7), and has the following components: a control module (1); a battery interface (12) configured to connect the control module (1) to the battery device (2); and a heater interface (13) configured to connect the control module (1) to the heating element (3). The control module (1) is designed to direct a first partial flow to the battery device (2) generated by means of the decentralized power generator (4) and a second partial flow generated by the decentralized power generator (4) to the heating element (3) such that the battery device (2 ) and the heating element (3) are supplied at any time within an overlapping period by means of the current from the decentralized power generator (4).

Description

The invention relates to an energy management system and an energy management method.

Decentralized generators play an important role in the planned energy transition. They can be used to supply local power grids with sustainably generated energy. In this case, photovoltaic systems or wind power plants come into consideration as power generators, whose power production, however, is weather-dependent and thus can be variable. In order to be able to store excess electricity in the case of good weather conditions for generating electricity, ie strong solar radiation in photovoltaic systems (PV systems) or strong wind in wind power plants, and to be able to compensate for gaps in the local power grid in bad weather conditions, the local power grid is equipped with a battery.

However, if the battery is already fully charged and the power generated by the decentralized power generator continues to exceed the demand in the local grid, then this excess power can be fed into an external grid. In many countries, however, the amount of electricity that can be fed into the regional or national grid is limited. For example, in Germany since March 2016, the feed-in limit for subsidized PV storage systems has been reduced to 50% of the nominal PV capacity. Usually, a PV system is de-regulated at excess output peaks, ie throttled in their output power.

In order not to leave the excess energy of the PV system so unused, it can alternatively be used to heat buildings or be routed to a heat storage or heat buffer. DE 10 2012 016 846 A1 discloses such an approach, in which an excess power of the local power generator is used for heating. It is proposed to store the excess energy in hot water and buffer storage between them so that it is retrievable at another time. This is done in the simplest case by means of a heating element or immersion heater, which is immersed in a liquid medium of the heat accumulator and this heated by means of the excess PV power. However, commercially available heating rods are usually not controllable, so that they can only be operated with a predetermined power value. There is also the danger here that excess energy is lost.

Partial remedy here create multi-stage heating elements with several tubular heaters, which can be controlled alternatively or in groups. In this way, such a heating element can be operated with different power levels, for example, with a step control of 500 watts distance. However, it can also happen here that the excess power lies between two power levels of the heating element. With a step control of 500 watts, so up to 500 watts of PV power is lost, because the next heat level can not be switched to it. The alternative approach, namely the stepless control of the heating element, has other disadvantages. Phase-angle controllers are known for this, but they are often not approved by the network operators of the external networks. These and other alternative solutions, such as the provision of an inverter for the heating element, are also expensive.

It is the object of the invention to provide an energy management system and an energy management method which ensure an efficient utilization of the excess current generated by a decentralized power generator.

The object is achieved according to the invention by an energy management system having the features of claim 1 and by an energy management method having the features of claim 10.

Advantageous developments of the invention are listed in the subclaims.

The invention is based on the idea of simultaneously operating a first energy store that is infinitely variable in its power consumption and a second energy store that is not infinitely variable, so that the overall resulting total power can be continuously adjusted. While the heating element is not infinitely variable and must be operated with a nominal power, the power consumption of the battery device can be controlled continuously or substantially continuously.

The energy management system according to the invention has a control module with interfaces for connection to a battery device and a heating element. Such a battery device may in particular be a battery or an accumulator. It can also be provided in the battery device, further control and / or control devices to control the flow of current to and from the battery or the accumulator and / or to control. In particular, the battery device can have a battery inverter, which is controlled by means of the control module. The heating element may be a thermal buffer heater. It serves to convert electrical energy into thermal energy and store it in the buffer memory. The buffer memory may be a Hot water tank to act a heat cycle, for example, a building or the like.

The heating element and the battery device are part of a local power network, for example of a private or commercial building or of several buildings, which are connected together to the local power grid. The local power grid also has a decentralized power generator, which is preferably a generator of renewable energy, in particular a photovoltaic system (PV system) or a wind turbine. However, other generators may be provided which are suitable for the supply of a local power grid, such as combined heat and power plants such as combined heat and power plants.

The control module is designed to control the battery device, the heating element, the decentralized power generator and / or a power distribution device of the local power supply so that during a Überlappzeitabschnittes the battery device gets charging current and at the same time the heating element is driven. At any time within the Überlappzeitabschnittes so a first partial flow is passed from the total current generated by the decentralized power generator to the battery device, and a second partial flow thereof is passed to the heating element. The overlap period preferably has a length of at least one millisecond (ms), at least 10 or 100 ms, or at least one, 10 or 100 seconds (s).

The control module may be equipped with further interfaces, for example with a power generator interface for connection to the power generator. About such a generator interface, the power generator can be controlled and / or send current or stored data to the control module, in particular on the generated power. In addition, one or more measurement interfaces can be provided, via which the control module receives measurement information, for example, about voltage and current values at different points in the local network, weather conditions, the state of charge of the battery device, the temperature of the buffer memory and the like.

In a preferred embodiment, the control module is designed such that the battery device and the heating element are supplied at all times within the overlap period substantially exclusively by means of the current from the decentralized power generator. This means, in particular, that the power from the decentralized power generator covers the power requirements of the battery device and the heating element and no further power must be added, for example, from an external network in order to supply the battery device and / or the heating element.

In an advantageous development, it is provided that the heating element is a non-adjustable consumer with a defined nominal power or a multi-level consumer with several power levels. Thus, for example, the heating element may operate at a fixed nominal power of 800 W, or be operable, for example, in one of three possible power levels, e.g. optionally at 500 W, 1000 W and 1500 W. There may also be more than three power levels, for example 4, 5, 6, 7 or more.

Conveniently, the heating element is a heating element. This is immersed in the medium to be heated, usually a liquid such as water, and this is heated. The heating element has a tubular heater through which a heating wire leads. A multi-stage heating element can be realized in a heating element, if a corresponding number of tubular heaters are provided for each different power levels. For example, three tubular heaters with 500 W, 1000 W and 1500 W nominal power can be provided. By connecting several tubular heaters more power levels can be realized. In the example with three tubular heaters, the additional power levels would be 2000 W, 2500 W and 3000 W.

According to a preferred refinement, the control module is designed to guide the total current absorbed by the battery device and the heating element along an excess current profile solely by controlling the first partial current conducted to the battery device. For this purpose, the excess current profile can preferably be determined continuously, for example by measuring the power generated by the decentralized power generator and the power consumed by consumers in the local power grid. The excess current is preferably the total current generated by the decentralized power generator minus the currents consumed by current consumers in the local power grid. Additionally or alternatively, the current that can be fed into an external grid can also be subtracted from the total current in order to calculate the excess current. As explained in the introduction, the power that can be fed into the external grid may depend on the nominal capacity of the decentralized generator.

The energy management system preferably has a prediction module, or a prediction module is provided which is designed to estimate the current profile generated by the decentralized power generator and from it to determine an expected excess current profile of a total current, which is to be distributed to the battery device and the heating element. Preferably, the power consumption is estimated based on consumers connected to the local power grid. In particular, the estimation may be based on previous stored user information to include the load due to the powered-on consumers. In addition, weather forecasts can be included in the estimation, if the decentralized power generator is, for example, a PV system or a wind turbine. The surplus current profile can be determined several hours in advance. Alternatively or additionally, an estimate of the surplus current profile can be made a few minutes or seconds in advance. Preferably, the estimated excess current waveform is updated at one or more second intervals.

Preferably, the total current taken up by the battery device and the heating element, that is to say the sum of the first and the second partial flow, is guided along the determined excess current profile. In a preferred embodiment, the control module is designed to guide the total current absorbed by the battery device and the heating element along the expected excess current profile solely by controlling the first partial current conducted to the battery device. This means that the current consumption of the heating element is kept constant while the first partial flow is varied by the control module.

The fact that the battery device and the heating element are simultaneously supplied with power at least during an overlapping period means that the battery device or the battery of the battery device is not completely charged when the heating element is switched on. In an expedient embodiment, the control module is designed to guide the second partial flow to the heating element even when the battery device has not yet exceeded a charge state of 90%, 80%, 70%, 60%, 50% 40% or 30% or less , The lower the battery state of charge, the longer a simultaneous operation of battery device and heating element can be ensured, so that the excess current profile is filled without having to throttle the decentralized power generator.

If an excess current or an excess current profile has been determined, then this can first be traced by means of the battery device by selecting the first partial current equal to the excess current. However, it may also be advantageous to switch on the battery device only at a later time, specifically optimized so that battery charging capacity is ensured even for the period in which the maximum of the excess current profile is expected. At a time when the excess current exceeds the value corresponding to a nominal power or a lowest power level of the heating element, the second partial flow can be selected accordingly, the heating element can therefore be switched to it. If the excess current exceeds a value corresponding to another power stage of the heating element, in turn, this higher power level is turned on, so that the first partial flow can be reduced again. Conversely, if the surplus current decreases, then the heating element can be gradually operated at lower power levels or turned off completely so that the surplus current eventually only recharges the battery.

According to a preferred embodiment, the control module is designed to always switch the heating element or to switch the heating element into the next power level whenever the battery device (possibly in combination with the heating element in its lower power level) encounters an upper power limit and can not absorb more power while the excess current continues to rise. Conversely, the heating element can then be moved to a lower power level or switched off completely whenever, when the excess current sinks, the excess current profile reaches a value at which the battery device can be flexibly regulated again. If the heating element is switched on or switched to another power stage, then it may be necessary to lower the battery charging current, ie the first partial current, in order to follow the excess current.

The invention will be explained below with reference to embodiments with reference to the figures. Hereby show:

1 a block diagram of the energy management system;

2 a current flow diagram during operation of a battery;

3 a current waveform diagram when operating a heater;

4 a Stromverlaufsdiagramm in successive operation of a battery and a heating element;

5 a Stromverlaufsdiagramm with partially simultaneous operation of a battery and a heating element; and

6a and 6b further current waveform diagrams with partially simultaneous operation of a battery and a heater.

In the 1 becomes an energy management system 10 schematically shown in a block diagram. It includes a local power grid 7 which is used to supply several consumers 5 , For example, in a building, is provided. The local power grid 7 is powered by a decentralized power generator 4 powered, for example from a PV system. In addition, the local power grid is via a grid connection 6 connected to an external power supply (not shown). When the power generator 4 insufficient electricity to meet the electricity needs of the local power grid 7 can generate additional power from the external network. On the other hand, there is an overproduction of electricity by the power generator 4 before, then this overcurrent, usually for a fee, can be fed into the external network.

As electrical energy storage is a battery device 2 , hereafter briefly as a battery 2 even if this is a battery in combination with a battery inverter. When the power generator 4 generates so much power that the power generated regularly at fully charged battery at least temporarily exceeds the maximum possible or allowed grid feed, then the excess energy by means of a heating element 3 in a buffer memory (not shown) passed.

The battery device 2 , the heating element 3 and the power generator 4 are via appropriate interfaces 12 . 13 . 14 with a control module 1 connected, which performs an energy management method. For simplicity, power switching elements, power conversion elements, current, voltage and power meters and the like, which are connected to the local power network, in the 1 not shown.

The 2 to 5 such as 6a and 6b show current flow diagrams for illustrating the operation of the energy management system 10 out 1 , In all four diagrams, the time is along the abscissa, while current values or power values are plotted along the ordinate. Furthermore, in all four diagrams there is an excess current profile 21 located. This can be determined by means of a prediction module. It is a difference between that from the generator 4 generated total power and a maximum in the external grid feed-in feed and / or consumers 5 used electricity. If the generator is a PV system, then the maximum current profile shown here is located 21 naturally at lunchtime. There would be no battery 2 present, then the energy would have to be that of the area below the surplus current profile 21 corresponds, remain unused, or the power generator 4 would have to be adjusted so far that he generates less energy.

In the 2 corresponds to the hatched area of energy entering the battery 2 is passed to load these. It is therefore a battery charging curve 22 in the event that the available excess electricity 21 completely in the battery 2 is directed. The battery charging curve 22 is first of the excess current flow 21 and then limited by the maximum power of the battery inverter or another component of the battery device, for example, by a battery management system, by a limited connected load, and the like. The rest of the electricity goes as unused energy 24 lost.

In the 3 a situation is shown in which only a multi-stage heating element 3 is used to the excess current 21 take. The step-like black filled area is that of the heating element 3 absorbed energy, which at the top of a step-like heating curve 23 is limited. The heating element 3 can always be operated only in the power level, which by the excess current 21 can be served. Again, the rest of the surplus electricity goes 21 as unused energy 24 lost. If in the determination of the surplus current profile 21 The maximum possible grid feed is not taken into account, then the unused energy 24 also via the mains connection 6 be fed into the external network. In the 4 the situation is illustrated according to the prior art described in the introduction. Here is the battery first 2 as far as possible with the excess current 21 provided. Once the battery 2 is fully charged, the heating element 3 turned on according to its power levels to the excess current 21 continue to use. Due to the step-like nature of the heating curve 23 There is also a lot of unused energy in this scenario 24 ,

The 5 shows the case of the invention. Although here too, as in the cases according to 2 and 4 , the battery 2 right at the beginning of the excess current flow 21 turned on and she starts to charge. However, at an appropriate time, the heating element will also become 3 switched on, leaving the battery 2 and heating element 3 over a period of time, namely during an overlap period, together with the excess current 21 be supplied. With others Words, the total flow of the first and second partial flow follows as exactly as possible the excess current flow 21 , The control, ie addition, of the heating element 3 should be optimized so that the unused energy 24 is kept as low as possible, with the proviso that no additional power from the external network is obtained.

In the 6a and 6b further situations according to the invention are shown. However, in both cases this is a less optimal solution than, for example, in 5 shown. Unlike in the case of 5 but similar to in 2 and 4 , takes in the situation in 6a first the battery 2 the entire excess current 21 until the maximum possible charging power is reached. To the unused energy 24 From a certain point in time, the unused power will keep the heating power of the heating element low 3 exceeds the heating element 3 switched on (see heating curve 23a ). When the battery 2 then fully charged, then the heating element 3 again turned on, as long as the surplus current 21 sufficient for his operation.

Finally, in the 6b a similar situation as in the 6b illustrated. Again, the battery is 2 regulated to maximum possible power until it is fully charged. When the excess current flow 21 the maximum possible charging current is exceeded here is the heating element 3 switched on. However, this is operated with such a high power that the entire excess current 21 is being used. Is then the excess current curve 21 below the heating curve 23a , as in 6b shown, then additional power must be taken from the external network, or if already fed into the external network, then this feed must be throttled accordingly. This also applies to the operation of the heating element 3 after completely charging the battery 2 according to the heating curve 23b ,

LIST OF REFERENCE NUMBERS

10

Energy Management System

1

control module

12

Battery interface

13

Heizelementschnittstelle

14

Power generator interface

2

Battery device, battery

3

heating element

4

decentralized power generator

5

consumer

6

Power connection to the external power grid

7

local power grid

21

Excess current, excess current flow

22

Battery charging curve

23, 23a, 23b

heating curve

24

unused energy

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012016846 A1 [0004]

Claims (10)

Energy Management System ( 10 ) for controlling a battery device ( 2 ) and a heating element ( 3 ) of a thermal buffer store in a local power grid ( 7 ) with a decentralized power generator ( 4 ) for generating a power for the local power grid ( 7 ), comprising: - a control module ( 1 ); - a battery interface ( 12 ), which is designed, the control module ( 1 ) with the battery device ( 2 ) connect to; and a heating element interface ( 13 ), which is designed, the control module ( 1 ) with the heating element ( 3 ), characterized in that the control module ( 1 ) is formed, one by means of the decentralized power generator ( 4 ) generated first partial flow to the battery device ( 2 ) and one by means of the decentralized power generator ( 4 ) generated second partial flow to the heating element ( 3 ) such that the battery device ( 2 ) and the heating element ( 3 ) at any time within an overlap period by means of the power from the distributed power generator. Energy management system according to claim 1, characterized in that the control module ( 1 ) is designed such that the battery device ( 2 ) and the heating element ( 3 ) at any time within the overlap period substantially exclusively by means of the power from the decentralized power generator ( 4 ) are supplied. Energy management system according to claim 1 or 2, characterized in that the heating element ( 3 ) is a non-regulated consumer with a specified nominal power or a multi-level consumer with multiple power levels. Energy management system according to claim 3, characterized in that the heating element ( 3 ) is a heating element. Energy management system according to one of the preceding claims, characterized in that the control module ( 1 ) is formed, solely by means of controlling the battery device ( 2 ) guided first partial flow from the battery device ( 2 ) and the heating element ( 3 ) total current taken along a surplus current profile to lead. Energy management system according to one of the preceding claims, characterized by a prediction module, which is formed by the decentralized power generator ( 4 ) generated current flow and / or by the local power grid ( 7 ) connected consumers ( 5 ) and to determine therefrom an expected excess current profile of an overcurrent which is applied to the battery device ( 2 ) and the heating element ( 3 ) is to be distributed. Energy management system according to claim 6, characterized in that the control module ( 1 ) is formed, solely by means of controlling the battery device ( 2 ) guided first partial flow from the battery device ( 2 ) and the heating element ( 3 ) total current taken along the expected excess current profile. Energy management system according to one of the preceding claims, characterized in that the battery device ( 2 ) has a battery inverter, which by means of the control module ( 1 ) is controlled. Energy management system according to one of the preceding claims, characterized in that the control module ( 1 ) is formed, then already the second partial flow to the heating element ( 3 ) when the battery device ( 2 ) has not yet exceeded a state of charge of 90%, 80%, 70%, 60%, 50%, 40% or 30% or less. Energy management method for controlling a battery device ( 2 ) and a heating element ( 3 ) of a thermal buffer store in a local power grid ( 7 ) with a decentralized power generator ( 4 ) for generating a power for the local power grid ( 7 ), wherein a control module ( 1 ), a battery interface, which is designed, the control module with the battery device ( 2 ) and a heating element interface ( 13 ), which is designed, the control module ( 1 ) with the heating element ( 3 ), the method being characterized in that the control module ( 1 ) one by means of the decentralized power generator ( 4 ) generated first partial flow to the battery device ( 2 ) and one by means of the decentralized power generator ( 4 ) generated second partial flow to the heating element ( 3 ), the battery device ( 2 ) and the heating element ( 3 ) at any time within an overlapping period by means of the electricity from the decentralized electricity generator ( 4 ) are supplied.

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