Method for operating power supply network, control device for carrying out such method, and power supply network having such control device

Abstract

The invention relates to a method for operating a power supply network (1) having at least two power supply devices (3), in which a load requirement for the power supply network (1) is divided into the at least two power supply devices (3) and a virtual power supply device (5) while optimizing a cost function, a load distribution is obtained, and wherein the at least two power provision devices (3) are operated in accordance with the obtained load distribution.

Description

Technical Field

[0001] The invention relates to a method for operating a power supply network, a control device for carrying out such a method, and a power supply network having such a control device. Background Art

[0002] Typically, a power provider physically tracks the load demands placed upon it.

[0003] To achieve a load distribution that is in particular computer-assisted, it may be valuable if, for operating a power supply network having at least two power supplies, the load requirement of the power supply network can be mathematically divided between the at least two power supplies such that a cost function is optimized.

[0004] However, the optimization problem caused by the cost function is mathematically allowed only when the sum of the available powers of the at least two power providing devices is at least as large as the load requirement. However, it is conceivable that the sum of the available powers of the at least two power providing devices is less than the load requirement. For example, such a situation occurs that the load requirement increases by a certain value within a few seconds, for example, by 500 kW, and the power of the at least two power providing devices can only be increased at a smaller rate for physical or technical reasons, for example, by 200 kW per minute. Therefore, the optimization problem with the additional condition of the load requirement is not allowed and the load distribution cannot be calculated. Summary of the invention

[0005] The invention is therefore based on the object of providing a method for operating a power supply network, a control device for carrying out such a method, and a power supply network having such a control device, in which the mentioned disadvantages are at least partially eliminated, preferably avoided.

[0006] This object is achieved by providing the present technical teaching, in particular the teaching of the independent claim and the embodiments disclosed in the dependent claims and the description.

[0007] The object is achieved in particular by providing a method for operating a power supply network having at least two (especially physical) power supplies. In the case of an optimization cost function, a load requirement on the power supply network is divided between the at least two power supplies and a virtual power supply, wherein a load distribution is obtained. Subsequently, the at least two power supplies are operated according to the obtained load distribution.

[0008] The load distribution obtained assigns power to each power providing device and assigns virtual power to the virtual power providing device. Advantageously, the sum of the power assigned to the at least two power providing devices and the virtual power of the virtual power providing device can always be just as large as the load requirement. As a result, the optimization of the cost function is allowed at every point in time. Advantageously, the method thus allows a load distribution that is particularly computer-supported and thus simple, precise, computerized and particularly automatic.

[0009] Here, the virtual power is not the power that is actually generated or physically generated, but a purely calculated parameter for solving the optimization problem. When the sum of the powers assigned to the at least two power providing devices at a time point is less than the load requirement, the virtual power particularly adopts a positive value. Alternatively, when the sum of the powers assigned to the at least two power providing devices at a time point is greater than the load requirement, the virtual power adopts a negative value. Physically, the power supply network responds to the load requirement below the load requirement by at least two power providing devices in the following manner, that is, the electrical frequency of the AC voltage in the power supply network first drops rapidly, increases again as the power assigned to the at least two power providing devices increases, and then reaches the theoretical frequency again when the sum of the powers assigned to the at least two power providing devices is as large as the load requirement. Physically, the power supply network responds to a higher load requirement via at least two power supplies (especially in the case of a sudden load drop, wherein the at least two power supplies cannot adjust downward quickly enough due to their inertia) in such a way that the electrical frequency of the AC voltage in the power supply network is first increased, then decreased again as the power assigned to the at least two power supplies decreases, and then returned to the target frequency when the sum of the powers assigned to the at least two power supplies drops to the reduced load requirement.

[0010] In the context of current technical teachings, a distinction is made between (especially physical) power supplies and virtual power supplies. In this context, in particular physical power supplies are real devices that can provide physically usable power. In contrast, virtual power supplies are computational concepts that cannot provide physically usable power.

[0011] In one embodiment, the optimization problem for two power providers and a virtual power provider is:

[0012] min K(P1,P2,P v )=P1k1+P2k2+|P v k v |

[0013] The additional conditions are:

[0014] P1+P2+P v =P Last

[0015] P 1,min ≤P1≤P 1,max

[0016] P 2,min ≤P2≤P 2,max

[0017] 0≤P v

[0018] The cost function K, the associated powers P1 and P2 of the two power supply devices, the virtual power P of the virtual power supply device v and the predetermined cost or energy price k assigned to each power supply device i , Load requirement P Last .P 1,max and P 2,max is the power upper limit assigned to the power supply device, or in other words, the current maximum available power. In particular, at least one of the power upper limits is time-dependent, in particular dependent on at least one current physical variable of the assigned power supply device, such as the current boost pressure. In particular, at least one time-dependent power upper limit P i,max (t) has a limited rate of change It follows that the available power of at least one power supply device cannot be increased at any speed, which in turn leads to the problem described at the beginning, namely that the sum of the powers P1, P2 assigned to the power supply devices may be less than the load requirement P for a certain period of time. Last .P 1,min and P 2,min is the power lower limit respectively assigned to the power providing device. It can be time-dependent, but can also be constant over time. In particular, it is feasible that the power lower limit P 1,min , P 2,min At least one of them is equal to zero. In particular, it is feasible that the two lower power limits P 1,min , P 2,min are all equal to zero.

[0019] The method is carried out in particular iteratively. In this case, at least one time-dependent upper power limit is changed in particular over time, so that the load distribution also changes accordingly, in particular until the assigned powers P1, P2 are equal in sum to the load requirement P Last In particular, because the virtual power P vThe value of decreases during the repetitive cycle due to the particularly high costs, the power supply network repeatedly adopts the following state, in which the total of the assigned powers P1, P2 is equal to the load requirement P Last It is feasible that when either the load requires P Last Either the energy cost k i Only when the method is changed, the method is executed again. However, it is also possible to execute the method repeatedly continuously.

[0020] According to a development of the invention, it is provided that the cost function is optimized taking into account at least one additional supplementary condition.

[0021] In one embodiment, by means of the at least one additional additional condition, in particular a maximum possible power change per time unit of the current power of at least one of the at least two power providing devices is taken into account.

[0022] In particular, at least one associated power P i Has a limited rate of change It follows that the power of at least one power supply device cannot be increased at any speed, which in particular leads to the problem described at the beginning, namely that the sum of the powers P1, P2 assigned to the power supply devices may be less than the load requirement P for a certain period of time. Last .

[0023] In a preferred embodiment, a first additional condition is obtained in the following form:

[0024]

[0025] With a change rate The minimum power change rate a 1,min and the rate of change Maximum power change rate a 1,max Alternatively or additionally, a second additional condition of the following form is obtained:

[0026]

[0027] With a change rate The minimum power change rate a 2,min and the rate of change Maximum power change rate a 2,max .

[0028] If the maximum feasible power change per time unit is taken into account by an additional condition, the power upper limit P mentioned above 1,min and P 2,minIt can also be a static limit which corresponds in particular to the respective rated power of the power supply device.

[0029] According to an improved solution of the present invention, it is provided that a cost function is calculated based on the energy prices of at least two power providing devices and the predetermined costs of the virtual power providing device. In addition, the predetermined costs of the virtual power providing device are selected to be greater than each individual energy price of the energy prices of the at least two power providing devices.

[0030] Advantageously, it is thereby ensured that the virtual power supply is only initiated when the sum of the powers assigned to at least two power supplies is less than the load requirement.

[0031] In particular, the predetermined cost of the virtual power supply is selected to be at least 1 euro cent per kWh more expensive than the energy price of the at least two, in particular physical, power supplies.

[0032] In one embodiment, the cost function K is preferably additionally calculated based on the maintenance costs for the at least two power providing devices and the virtual maintenance costs of the virtual power providing device. In addition, the virtual maintenance costs of the virtual power providing device are selected to be more expensive than the maintenance costs of the at least two power providing devices. As a result, the at least two power providing devices can be advantageously controlled to operate in a low-loss operating mode.

[0033] In particular, the predetermined cost for the virtual power is selected to be at least 10% higher, in particular at least 20% higher, in particular at least 30% higher, in particular at least 40% higher, in particular at least 50% higher, in particular at least 75% higher, in particular at least 100% higher, in particular 150% higher, in particular at least 200% higher than the energy price of the at least two, in particular physical, power providing devices, in order to ensure a stable and rapid optimization of the cost function K. In particular, the predetermined cost k for the virtual power is selected to be at least 10% higher, in particular at least 20% higher, in particular at least 30% higher, in particular at least 40% higher, in particular at least 50% higher, in particular at least 75% higher, in particular at least 100% higher, in particular 150% higher, in particular at least 200% higher than the energy price of the at least two, in particular physical, power providing devices. v The energy price is determined from at least two, in particular physical, power supply devices using the following equation:

[0034]

[0035] Therein, the factor f is predetermined and is greater than 1, in particular greater than 1.1, in particular greater than 1.2, in particular greater than 1.3, in particular greater than 1.4, in particular greater than 1.5, in particular greater than 1.75, in particular greater than 2, in particular greater than 2.5, in particular greater than 3. Alternatively or additionally, the virtual maintenance costs are selected to be at least 10% higher, in particular at least 20% higher, in particular at least 30% higher, in particular at least 40% higher, in particular at least 50% higher, in particular at least 75% higher, in particular at least 100% higher, in particular 150% higher, in particular at least 200% higher than the maintenance costs for the at least two power providing devices.

[0036] According to a further development of the invention, it is provided that the load distribution is determined in such a way that a cost function is minimized.

[0037] Advantageously, this makes it possible to operate the power supply network as cost-effectively as possible taking into account the specific costs of the power supply devices.

[0038] According to a further development of the invention, it is provided that an electric machine which is operatively connected to the internal combustion engine drivingly is used as at least one of the at least two power supply devices.

[0039] According to a development of the invention, it is provided that an energy storage device is used as at least one of the at least two, in particular physical, power providing devices.

[0040] In a preferred design, a heat storage device is used as the energy storage device.

[0041] In a further preferred embodiment, a mechanical device is used as the energy storage device, which is selected from the group consisting of a flywheel accumulator, a spring, a pump accumulator, a compressed air accumulator and a lift accumulator.

[0042] In a further preferred embodiment, an electrical device is used as the energy storage device, which is selected from the group consisting of batteries, accumulators and capacitors.

[0043] In another preferred embodiment, an electric machine operatively connected to the internal combustion engine drive is used as at least one of the at least two power supply devices, wherein the electric machine operatively connected to the internal combustion engine drive is particularly referred to as a generator set. Alternatively or additionally, an energy storage device is used as at least one of the at least two power supply devices.

[0044] In one embodiment, the power supply network has at least one additional power supply device. In particular, a photovoltaic device is used as the at least one additional power supply device. Alternatively or additionally, a wind power device is used as the at least one additional power supply device. Alternatively or additionally, a hydropower device is used as the at least one additional power supply device.

[0045] According to an improved solution of the present invention, it is configured that for a predetermined prediction range The load forecast is preset. Then, the load distribution is determined for a plurality of time points within the predetermined forecast range.

[0046] The object is also achieved by providing a control device, wherein the control device is set up to carry out the method according to the invention or the method according to one or more of the embodiments described above. The control device is preferably designed as a computing device, particularly preferably as a computer or a control device, in particular as a control device for a power supply network. In conjunction with the control device, in particular the advantages already explained in conjunction with the method result.

[0047] The control device is preferably designed to be operatively connected to at least two power supply devices and to control them accordingly.

[0048] A virtual power supply is, in particular, a calculation concept which is stored or executed in the control device.

[0049] Finally, the object is also achieved by providing a power supply network having at least two power supply devices and a control device according to the invention or a control device according to one or more of the embodiments described above. In conjunction with the power supply network, in particular, the advantages already explained in conjunction with the method and the control device result.

[0050] The control device is operatively connected to the at least two power supply devices and is designed to control them accordingly.

[0051] According to a further development of the present invention, at least one of the at least two power supply devices is configured as an electric machine operatively connected to the internal combustion engine. Alternatively or additionally, at least one of the at least two power supply devices is configured as an energy storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In the following, the invention is explained in more detail with reference to the accompanying drawings.

[0053] Figure 1 A schematic diagram showing an embodiment of a power supply network, and

[0054] Figure 2 A flow chart showing an embodiment of a method for operating a power supply network. DETAILED DESCRIPTION

[0055] Figure 1 A schematic illustration of an embodiment of a power supply network 1 is shown.

[0056] The power supply network 1 has at least two, in particular physical, power supply devices 3 , in particular a first power supply device 3 . 1 and a second power supply device 3 . 2 , a control device 7 and a schematically illustrated virtual power supply device 5 implemented as a mathematical calculation concept in the control device 7 .

[0057] Preferably, at least one of the at least two power supply devices 3 is an energy storage device 9. Alternatively or additionally, at least one of the at least two power supply devices 3 is preferably an electric machine 13 which is drive-operably connected to the internal combustion engine 11.

[0058] In one embodiment, the power supply network 1 has at least one additional power supply device 3. In one embodiment, the at least one additional power supply device 3 is a photovoltaic device. Alternatively or additionally, the at least one additional power supply device 3 is a wind power device. Alternatively or additionally, the at least one additional power supply device 3 is a hydropower device.

[0059] The control device 7 is operatively connected to at least two power supply devices 3 and is configured to control them accordingly. The control device 7 is further configured to execute a method for operating a power supply network 1 and to calculate a load distribution for at least two, in particular physical, power supply devices 3. The method is described below according to Figure 2 Explain in more detail.

[0060] Figure 2 A flow chart of an exemplary embodiment of a method for operating a power supply network 1 is shown.

[0061] In a first step S1 , a load requirement on the power supply network 1 is predefined.

[0062] In a second step S2, the preset load requirement is divided among the at least two power supply devices 3 and the virtual power supply device 5 while optimizing the cost function. Preferably, the cost function is calculated based on the energy prices of the at least two power supply devices 3 and the energy prices of the virtual power supply device 5. Here, preferably, the energy price of the virtual power supply device 5 is set to be greater than the energy price of the at least two power supply devices 3. Alternatively or additionally, the cost function is preferably minimized.

[0063] In a third step S3, the load distribution is obtained.

[0064] Next, in a fourth step S4 , the at least two power providing devices 3 are operated according to the obtained load distribution.

[0065] In an optional fifth step S5 , at least one additional additional condition is provided, wherein in the second step S2 the cost function is optimized taking into account the at least one additional additional condition.

[0066] In an optional sixth step S6, a load forecast is preset for a predetermined forecast horizon, in particular based on the load demand. Then, in a second step S2 and a third step S3, a load distribution is determined for each time point within the predetermined forecast horizon.

[0067] Preferably, steps S1 to S4 , in particular including the fifth step S5 and / or the sixth step S6 , are performed repeatedly or cyclically, in particular at predetermined time intervals, in order to determine the load distribution and to operate the power supply network in accordance with the load distribution.

Claims

1. A method for operating a power supply network (1) having at least two power supply devices (3), wherein: - dividing the load requirement of the power supply network (1) between the at least two power supply devices (3) and the virtual power supply device (5) while optimizing a cost function, wherein a load distribution is obtained, and wherein: - operating the at least two power providing devices (3) according to the load distribution obtained.

2. The method according to claim 1, wherein: The cost function is optimized taking into account at least one additional condition.

3. A method according to any one of the preceding claims, wherein: The cost function is calculated based on the energy prices of the at least two power supply devices (3) and based on the predetermined cost of the virtual power supply device (5), wherein the predetermined cost of the virtual power supply device (5) is set to be greater than each of the energy prices of the at least two power supply devices (3).

4. A method according to any one of the preceding claims, wherein: The load distribution is determined by minimizing the cost function.

5. A method according to any one of the preceding claims, wherein: An electric machine (13) operatively connected to the internal combustion engine (11) is used as at least one of the at least two power supply devices (3).

6. A method according to any one of the preceding claims, wherein: An energy storage device (9) is used as at least one of the at least two power supply devices (3) as a power supply device (3).

7. A method according to any one of the preceding claims, wherein: A load forecast is preset for a predetermined forecast horizon, wherein the load distribution is determined for each point in time within the predetermined forecast horizon.

8. A control device (7) which is designed to carry out the method according to any of the preceding claims.

9. A power supply network (1) having a control device (7) according to claim 8 and at least two power supply devices (3) operatively connected to the control device (7).

10. The power supply network (1) according to claim 9, wherein: - at least one of the at least two power supply devices (3) is designed as an electric machine (13) operatively connected to the internal combustion engine (11) in terms of drive, and / or, At least one of the at least two power supply devices (3) is designed as an energy storage device (9).

Images