Device and method for intelligent grid power regulation through capacitive energy storage

Abstract

Device (100) for intelligent grid power regulation by means of capacitive energy storage, wherein the device (100) is designed to supply at least one electric drive (150) with electrical energy from a power supply network (110), wherein the device (100) has the following features: - a buffer capacity (220); - a DC intermediate circuit (140, 210) configured to be coupled to the buffer capacitor (220) via a first interface (200a) or which is coupled to the buffer capacitor via the first interface; and - a second interface (200b) via which the DC link (140, 210) can be coupled or connected to the power supply network (110), wherein the second interface (200b) is designed to limit a current flow between the power supply network (110) and the DC link (140, 210) when the voltage in the DC link (140, 210) has a value that is within a set voltage range (U) DC,min - U DC,max ) lies, characterized in that the second interface (200b) is further configured to dynamically increase the current flow between the power supply network (110) and the DC intermediate circuit (140, 210) to the current limit allowed between the power supply network (110) and the DC intermediate circuit (140, 210), if a voltage level of the voltage in the DC intermediate circuit (140, 210) is outside the nominal voltage range (UDC,min - You DC,max ) lies.

Description

[0001] The present invention relates to a device and a method for intelligent grid power regulation by capacitive energy storage according to the independent claims.

[0002] A problem often arises when supplying power to electrical machines if these machines experience uneven loads. In this case, the power supply network that provides the affected electrical machine(s) also experiences uneven loads, so that without appropriate compensation measures, fluctuations, such as voltage fluctuations, can occur in this network. This, however, has a very detrimental effect on other electrical installations that are also connected to the affected power supply network.

[0003] To avoid such adverse effects on an electrical power supply network, a power supply unit can be used that incorporates a DC intermediate circuit. This circuit can absorb fluctuations caused by uneven loads on the electrical machine(s). For example, the system disclosed in German patent application DE 10 2006 033562 B3 uses such a DC intermediate circuit in conjunction with a corresponding flywheel energy storage system. In other power supply unit variants, for instance, a DC intermediate voltage can occur under a smooth load on the electrical machine, fluctuating between 730 and 770 volts due to rapid, short-term power demands. In such cases, a maximum current of 170 A with a maximum network power of 85 kW can be drawn from the power supply network under fluctuating loads on the electrical machine.To enable a power supply for the electric machine or electric drive that has as little impact on the power grid as possible, more extensive design work is required using state-of-the-art methods. This is because the power profile and energy demand over a complete operating cycle of the electric machine must be considered, rather than just the peak power consumption of the machine or drive as before. If such a power supply unit is not adequately designed, significant grid disturbances for electric drives are to be expected during high power peaks.

[0004] Publication US 2005 / 0151503A1 discloses a converter and an inverter comprising a converter.

[0005] The publication DE 35 15 038 A1 discloses a circuit for quenching a thyristor.

[0006] It is therefore the object of the present invention to create an improved device and an improved method for intelligent grid power regulation.

[0007] This problem is solved by a device for intelligent grid power regulation through capacitive energy storage according to claim 1.

[0008] The present invention provides a device for intelligent grid power regulation by means of capacitive energy storage, wherein the device is designed to supply at least one electric drive with electrical energy from a power supply network, and wherein the device has the following features: - a buffer capacity; - a DC link configured to be coupled to the buffer capacitor via a first interface, or which is coupled to the buffer capacitor via the first interface; and - a second interface via which the DC link can be coupled or connected to the power supply network, wherein the second interface is designed to limit a current flow between the power supply network and the DC link when the voltage in the DC link has a value that is within a specified voltage range.

[0009] The present invention is based on the finding that DC capacitors used in the DC link can now be used as energy storage devices by means of the fluctuating DC link voltage, while simultaneously limiting the mains-side currents and power. By limiting the current flowing from the power supply network into the DC link, it can be ensured that even with an uneven load on the electric drive (or drive motor), there is no strongly fluctuating power consumption from the power supply network. Rather, by allowing a greater fluctuation range of the (DC) voltage in the DC link, the device or power supply unit is enabled to ensure the most continuous possible power consumption from the power supply network into the DC link.The energy required by the electric machine or electric drive can be balanced by the buffer capacity or buffer capacities (which, for the sake of simplicity, will be referred to in the singular as buffer capacity in the following) of the DC link. Furthermore, field weakening can also be utilized in electric drives to avoid limitations on the speed range of the drives, i.e., the drives supplied by the mains (DC voltage), when the DC link voltage fluctuates.

[0010] The present invention offers the advantage that the approach presented here provides a device that can be easily retrofitted to existing systems (regardless of the specific control systems), since the proposed approach is drive-based. In particular, a buffer capacity can be easily connected to the DC link, even retroactively. Furthermore, a reduction of peak network power can be easily implemented, and energy buffering during an emergency machine stop is advantageously achievable in a technically simple manner. Controlled shutdown of a machine is also made possible, especially in the event of a power grid failure. The operation of the machine or a drive can also be largely ensured even in the case of poor grid conditions (i.e., sporadic power outages).Additionally, smaller cable cross-sections can be used for electrical lines connecting the electric machine or drive to the power supply network, thus requiring smaller contactors and fuses on the network side. Overall, the approach proposed here leads to reduced network disturbances under uneven load on the machine(s), resulting in reduced power losses P. V in the mains filter and the mains choke that are usually used (according to formula P) V =I 2 *R) setting. Thus, the measures proposed here lead to a more robust control behavior of the device for intelligent grid power regulation in "dirty" grids and a lower energy loss during operation of the drives.

[0011] According to a favorable embodiment of the present invention, the second interface can be configured to limit current flow from the power supply network into the DC link and / or current flow from the DC link into the power supply network. This advantageously prevents not only network overload caused by high power draw from the power supply network, but also avoids excessive stress from excessive energy feed-in from the DC link into the power supply network.

[0012] It is also advantageous if the second interface is designed to limit the current flow between the power supply network and the DC link to a peak current that is two to five times, and in particular 2.5 times, the maximum permissible continuous current across the second interface. In this way, the current flow or power input can be limited to a value that can typically be absorbed by the power supply network without major problems, i.e., network feedback.

[0013] According to one embodiment of the present invention, the second interface can be configured to regulate the voltage of the DC link to a setpoint, in particular to regulate the voltage of the DC link to the setpoint when the voltage of the DC link was outside the setpoint range before regulation. Such an embodiment of the present invention offers the advantage that the predetermined setpoint range allows the full energy storage capacity of the buffer capacitor to be utilized as effectively as possible. Active regulation of the voltage in the DC link should only be carried out in situations where damage to components of the device is to be feared.

[0014] In order to be able to react as flexibly as possible to fluctuations in the power requirements of the drive or an electric motor and at the same time avoid a hard limitation of the current flow, the second interface is designed according to the invention to dynamically increase the current flow between the power supply network and the DC link to the current limit value allowed between the power supply network and the DC link when a voltage level of the voltage in the DC link is outside the target voltage range.

[0015] According to one embodiment of the present invention, the buffer capacity can be designed to absorb a voltage up to the permissible voltage for downstream power electronics which supplies power to the connectable electric drive and can have an energy storage capacity that is dimensioned depending on a maximum energy input or output of the at least one electric drive, wherein the energy storage capacity of the buffer capacity is in particular designed to ensure a fault-free shutdown of the electric drive motor in the event of a failure of the power supply network.Such an embodiment of the present invention offers the advantage that, on the one hand, a buffer capacity designed in this way ensures that it is designed for operation as an energy storage device for the drive and, on the other hand, can also absorb sufficient energy to enable a controlled shutdown of the drive without the risk of damage to the drive or a system operated by the drive.

[0016] To enable the DC link to absorb or release particularly large amounts of energy, a flywheel energy storage system can also be provided. This flywheel energy storage system is designed to be supplied with electrical energy via the DC link or to feed electrical energy back into the DC link. A flywheel energy storage system offers the possibility of storing significantly more energy than a buffer capacitor. However, the storage losses in such a flywheel energy storage system are also greater than in a buffer capacitor, and the flywheel energy storage system also exhibits a greater time delay in energy absorption or release compared to a buffer capacitor.

[0017] The application of the approach described above is particularly advantageous in an automation device, especially a press, machine tool, or manufacturing machine, which includes a device for intelligent grid power regulation according to one of the preceding claims. The invention presented here can realize its optimal benefits in such an application area.

[0018] The invention is explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a block diagram of an application scenario of an embodiment of the present invention; Fig. 2 a block diagram of a device for intelligent grid power regulation, such as that which can be used according to an embodiment of the present invention; Fig. 3 diagrams showing the time profiles of different electrical parameter values ​​when using an embodiment of the present invention; Fig. 4 Diagrams showing the time profiles of different electrical parameter values ​​when using a further embodiment of the present invention; Fig. 5 a diagram of different voltage value ranges in the DC voltage part of the DC intermediate circuit, wherein these voltage value ranges can be used to control the device; and Fig. 6 a flowchart of an embodiment of the present invention as a method.

[0019] Identical or similar elements in the figures may be designated by identical or similar reference numerals, without the need for repeated descriptions of these elements. Furthermore, the figures of the drawings, their description, and the claims contain numerous features in combination. It is clear to a person skilled in the art that these features can also be considered individually or combined into further combinations not explicitly described here. The invention is further explained in the following description using different measures and dimensions, but the invention is not to be understood as being limited to these measures and dimensions. Furthermore, process steps according to the invention can be repeated and carried out in a different sequence than described.If an embodiment includes an “and / or” connection between a first feature / step and a second feature / step, this can be interpreted as meaning that the embodiment according to one embodiment has both the first feature / step and the second feature / step, and according to another embodiment either only the first feature / step or only the second feature / step.

[0020] In all applications where one or more electric drives are connected to a common intermediate circuit supplied by a power grid (e.g., via DC coupling) and the total power of the electric drives fluctuates significantly (i.e., exhibits high peaks), problems arise due to the feedback effects of uneven drive loads on the power grid. One goal of potential optimization approaches can therefore be to reduce these grid feedback effects (i.e., grid peaks) during operation and emergency stops of the electric drive motors by storing energy in the capacitive part of the intermediate circuit, ideally limiting the grid load to the average continuous power of a recurring process.

[0021] To achieve such a goal, according to an embodiment of the present invention, an arrangement with a device 100 for intelligent grid power regulation can be selected, as exemplified in the block diagram from Fig. Figure 1 illustrates this. Power or energy is drawn from a power supply network 110, which, for example, provides three-phase alternating current with 400 V each. The energy supplied from the power supply network 110 is fed to the intelligent power regulation device 100 via a network filter 120 and a network choke 130. From the network choke 130, the electrical energy from the power supply network 110 is fed to a DC link 140 via a power supply network interface 135. Electrical energy (for example, using a 5 mF smoothing inductor) can then be supplied to one or more electric drives 150 via drive interfaces 145 of the DC link 140.To implement the invention, a control unit 160 can be provided which, on the one hand, can record and / or read the voltage in the intermediate circuit and, on the other hand, is designed to control or regulate the supply network interface 135 in such a way that a current flow from the supply network 110 into the DC intermediate circuit 140 or from the DC intermediate circuit 140 back into the supply network 110 is limited.

[0022] Fig. Figure 2 shows a block diagram of a basic structure of the DC link 140 and the connection of the DC link 140 to the supply network 110 and the drives 150, wherein in Fig. 2 For the sake of simplicity, only a drive 150 is shown. A DC intermediate circuit 140 constructed in this way can be installed in the device 100 according to the one shown in Fig. The block diagram shown in section 1 is used. The DC intermediate circuit 140 has a supply network interface 200 (which corresponds to interface 135). Fig. 1 corresponds to), through which energy is drawn from a supply network 110 (usually after prior use of the network filter 120 and / or the network choke 130) via a second interface 200a. This energy is converted into a direct current at the supply network interface 200 and fed into a DC voltage section 210 via a first interface 200a. The DC voltage section 210 includes a buffer capacitor 220, the connection contacts 225 of which are connected between current-carrying elements 210 of the DC intermediate circuit 140, between which the DC voltage of the DC voltage section 210 is present or can be present. In addition to an existing capacitor, one or more further buffer capacitors 220 can be connected in the DC intermediate circuit 140 to ensure a sufficiently large storage capacity for electrical energy.The buffer capacity is designed in such a way that it can withstand the voltage between the current-carrying elements on the one hand and has a sufficiently large energy absorption capacity on the other hand to be able to stop at least one connected drive 150 without disruption, for example in the event of a failure of the power supply network.

[0023] Furthermore, in the Fig. 2 the control unit 160 is shown, which is connected to the DC voltage part 140 in order to detect or read a voltage of the DC voltage part 210 in the DC intermediate circuit 140.

[0024] Responding to the detected or read voltage in the DC intermediate circuit 140, the current can then be limited via the first and / or second interface in order to limit the network effects of the uneven load of the machine, as will be described in more detail below.

[0025] Furthermore, the current-carrying elements are connected to a switchable braking resistor 230 in order to convert any excess energy that can no longer be stored in the buffer capacity 230 or a possibly connected flywheel storage device into heat, so that the components of the DC voltage section 210 or the DC voltage intermediate circuit 140 are not damaged in the event of an excessively high voltage between the current-carrying elements.

[0026] Furthermore, the current-carrying elements of the DC voltage section 210 are connected to a drive interface 240 (which is the interface 145 from Fig. 1), which is designed to convert energy from the DC voltage section 210 into a three-phase AC current in order to operate the electric drives or motors 150. The buffer capacity 220 can be used as a dynamic energy storage device for rapid start-stop applications and as an energy storage device for the drive's retraction movements after a mains voltage failure. At the same time, the buffer capacity used can minimize heat loss in the control cabinet of the supply unit 140, which, according to the prior art, results solely from the conversion of excess energy into heat by the braking resistor.

[0027] In order to minimize the effects of uneven loading of the electric drives 150 on the supply network 110, the DC intermediate circuit 140 is regulated by the control unit 160 (for example, as shown in the diagram). Fig. 1) using specific parameters. For example, this control unit 160 normally (i.e., according to the prior art) regulates a DC voltage in the DC link 140 "hard," so that the DC voltage in the DC link 140 fluctuates by only about + / -20 V. In order to be able to use the buffer capacity in the DC link 140 as an energy storage device, according to an embodiment of the invention, certain fluctuations of the voltage between the current-carrying elements of up to + / -50 V are permitted in the DC link 140, in particular in the DC section 210 of this DC link 140.This makes it possible to utilize the buffer capacity 220 as an electrical energy storage device when using a nominal voltage value of, for example, 750 volts in the DC voltage section 210 of the DC intermediate circuit 140, if the voltage between the current-carrying elements in the DC voltage section 210 assumes values ​​of, for example, 750 V to 800 V.

[0028] This can be achieved, for example, through two different measures. A first option for achieving these fluctuations in the DC voltage section 210 is to use soft controller parameters for regulating the voltage in the DC voltage section 210, whereby a fixed, soft parameter setting is always active. A second option for achieving these voltages in the DC voltage section 210 is to use a "dead zone" for the control loop for the voltages in the DC voltage section 210.This means that within a voltage range of, for example, 50 volts above the nominal setpoint voltage in the DC section 210 and 150 volts below the nominal setpoint voltage in the DC section 210, the voltage regulator for the current-carrying elements in the DC section 210 does not intervene. Instead, the buffer capacitance (consisting, for example, of one or more electrolytic capacitors) can act as a buffer or energy storage device. Only when the voltage between the current-carrying elements in the DC section 210 is outside the aforementioned setpoint voltage range does the regulator in the control unit 160 become active again to regulate the voltage in the DC section 210 or in the DC intermediate circuit.

[0029] The others, in Fig. 1 shown, however, in Fig. The two drives not shown would be operated according to the arrangement made of Fig. 2 further drive interfaces connected in parallel to the drive interface 200, 145 shown, to the DC intermediate circuit 140.

[0030] In order to store the highest possible amounts of electrical energy, a tumbling wheel energy storage system can be provided in addition to the buffer capacity of 220, which is located in Fig. 1 or Fig. 2 is not shown and should be connected in parallel to the buffer capacity 220. This flywheel energy storage device can include an electric motor that rotates a flywheel mass, thereby converting electrical energy from the DC circuit into kinetic energy of the flywheel. Using a flywheel energy storage device offers the advantage of storing a larger amount of energy compared to a buffer capacity. However, the response time of a flywheel energy storage device is longer than that of a buffer capacity. If energy is needed from the kinetic energy storage device, i.e., the flywheel energy storage device, the flywheel mass can be decelerated by the electric motor in response to a signal from the control unit 160, and the electrical energy generated in this way can be fed into the DC intermediate circuit 140.

[0031] Fig. Figure 3 shows different sub-diagrams for a simulation result of the advantageously modified control described above for the device 100 for intelligent grid power regulation. In all four sub-diagrams, time in seconds is plotted on the abscissa. In the upper representation from Fig. Figure 3 further shows the phase angle of the target current from a supply network via the supply network interface (line marked with a triangle) compared to a simulation result for an actual current via the supply network interface (solid line) in degrees. In the second sub-diagram from the top in Fig. Figure 3 shows power output in kilowatts, drawn from the supply network (solid line) and the intermediate circuit (line marked with a triangle). The third sub-diagram from the top shows... Fig. 3 shows the intermediate circuit voltage in volts and in the fourth sub-diagram from the top. Fig. Figure 3 shows the resulting network current in amperes for each of the three phases of the supply network.

[0032] To ensure the representation corresponds to the sub-diagrams from Fig. To obtain the diagrams from 3, a control of the voltages in the DC link 140 was used, in which the controller parameters (i.e., the parameters for the maximum permissible current and the maximum permissible voltage, respectively) were each halved compared to the prior art. In particular, for the simulation to obtain the diagrams from Fig. 3. The second variant described above for regulating the voltage in the DC section 210 is used, in which the controller or control unit 160 is not active within the "dead zone" and the buffer capacity can be used as an energy storage device. As a result of this optimized measure, a reduction in peak grid power from 85 kW to 60 kW and a reduction in the maximum grid current from 170 A to 120 A are possible. In particular, reducing the current via the first interface to two to five times, especially 2.5 times, the maximum permissible continuous current via the first interface is very promising with regard to minimizing grid feedback, as this prevents the strongest feedback effects on the supply network. This shows that a reduction in grid load is possible through adapted parameterization of the voltage control in the DC section 210.

[0033] To further reduce the effects of uneven loading on the electric drives 150, the current draw via the first interface 200 or 135 can be limited in the control unit 160. This means that the mains-side charging current, i.e., a current flowing from the mains supply 110 via the first interface 200 into the DC section 210 of the DC intermediate circuit 140, is regulated or at least limited in the supply unit. The charge flowing via the first interface 200 remains the same compared to the unregulated or unlimited charging current via the first interface. This would mean that the area under the current curve remains the same for a given observation period in both scenarios presented. In other words, the regulation or...Limiting the grid-side charging current achieves a smoothing of the power consumption of the supply unit 100, which in turn ensures that the effects of the uneven load of the electric drives 150 on the supply network 110 remain as low as possible.

[0034] More precisely, in the embodiment described above, the charging current is limited to defined values, thereby allowing the voltage in the DC section 210 to be adjusted so that the buffer capacity 220 can act as an electrical energy storage device. As the following illustration shows in more detail, this creates a practical and efficient solution that, on the one hand, reduces peak current on the grid side and, on the other hand, enables the effective use of the buffer capacity in the DC section 210 as an energy buffer in the power supply unit (especially at high voltages in the DC section 210, for example, 750 V).

[0035] Fig. Figure 4 shows different sub-diagrams for a simulation result of the above-described implementation variant, but now using a current limit for a current via the supply network interface 200 of the DC intermediate circuit 140. At the same time, a fluctuation of the voltage in the DC voltage section 210 was simulated in accordance with the reference to Fig. The 3 described implementation variant is permitted. The individual sub-diagrams of the Fig. 4 are corresponding to the sub-diagrams from the Fig. 3. When regulating the device 100 by the control unit 160, it was specifically specified that a maximum network current of 50 A (instead of 170 A) may be drawn from the supply network 110 by the device 100 for intelligent network power regulation. As a result of this simulation, the individual sub-diagrams in the Fig. It can be seen from Figure 4 that a reduction in peak grid power from 85 kW to 30 kW and a reduction in the maximum grid current (i.e., the current via the supply network interface 200) from 170 A to 50 A can be achieved by means of the current limiting controlled by the control unit 160 via the supply network interface 200 or 135. This results in a maximum power output of the DC link 140 (via its drive interface 240) of 95 kW. This corresponds to an identical value for the power output of the DC link 140, which can also be achieved by the previously described regulation of the voltage of the DC section 210 of the DC link 140, which corresponds to parameter values ​​according to the sub-diagrams from Figure 4. Fig. 3. However, if the maximum network current is limited via the first interface, a maximum power draw from the supply network 110 of 30 kW can be achieved, whereas a power draw from the supply network 110 of 60 kW would result if a control system according to the embodiment described above were used with regard to Fig. 3 would be used.

[0036] Overall, it is evident that by using a limit on the maximum current that can be drawn from the supply network 110 in conjunction with the buffer capacity 220, a reduction in the maximum network load is achieved, which is also independent of the load case of the electric drives.

[0037] Fig. Figure 5 shows a diagram of different voltage ranges between the current-carrying elements of the DC voltage section 210, which are used to regulate the DC intermediate circuit 140 and the current flow, respectively. The levels of these voltages, shown in the diagram, are Fig. The 5 units shown on the ordinate are used for control in the control unit 160, in particular for limiting the charging current via the supply network interface 200 or 135. The diagram initially shows... Fig. 5 in the middle section designates a range of 500, which has a deviation of + / -50 V (i.e. U). Schwanungsreserve = 50 V) to a nominal DC voltage of U DC,nominal= 750 V. This range, which is significantly wider than the state of the art, allows for a higher usable voltage swing for dynamic energy storage of the power supply unit 100 in fast start-stop applications. If the voltage in the DC section 210 drops below 700 V, a voltage range 510 is reached, which is permissible in special cases and can be used as a usable voltage swing for energy storage for recovery movements in the event of a mains voltage failure. If the voltage in the DC section 210 drops to 75 percent of the nominal DC voltage, a voltage range 520 is reached, in which a warning is issued and the control unit 160 shuts down the DC link.If the voltage in the DC section 210 rises above 800 V, a voltage range of 530 V is reached, which can be used as a voltage boost for energy storage in the event of an emergency shutdown of an electric drive 150 or an overload of the intelligent power control device 100. Should a voltage range of 540 V be reached in the DC section 210, where the voltage is greater than 820 V, the control unit 160 will connect the braking resistor 230 between the current-carrying elements of the DC intermediate circuit 140 to prevent damage to components of the intelligent power control device 100 and to convert excess energy into heat.

[0038] In the event that, despite the activation of the braking resistor 230 in the DC voltage section 210, a voltage level greater than 900 V occurs between the current-carrying elements, the diagram will show Fig. 5. A voltage range of 550 is reached, in which the final stage of the device 100 for intelligent grid power regulation is blocked. In this case, for example, the drive interface 240 or 145 is blocked, so that no more power can be transferred from the drives 150 to the DC link 140 in order to reliably prevent damage to the components of the device 100 for intelligent grid power regulation.

[0039] In summary, it can be stated that with a regulated intermediate circuit, the intermediate circuit voltage (in the DC voltage section 210) is set to 750 V + / -50 V (i.e., the fluctuation reserve is U). SchwanungsreserveThe DC link voltage (50 V) can be regulated "softly" so that the buffer capacitor 220 can act as an energy storage device. The target voltage range of the DC link 140 is thus optimally located between 700 V and 800 V. The braking resistor 230 is only switched on in the drive as an emergency bleeder when the DC voltage level exceeds 820 V, in order to prevent the voltage level in the DC section 210 from rising further to a maximum value of 900 V, for example, if the regenerative power is exceeded or a power outage occurs. A threshold value for limiting the current flow from the DC link 140 to the supply network 110 can also be dynamically increased if the voltage in the DC section 210 is greater than 800 V.In this way, a "soft" regulation is implemented, ensuring increased power discharge into the supply network when high power levels are present in the intermediate circuit 140. This at least slows down any further increase in the voltage of the DC section 210.

[0040] Using the in Fig. The function of the current limiting can now be explained in more detail using the voltage ranges shown in Figure 5. Limiting the current flow between the supply network 110 and the DC link 140 is particularly helpful when the DC link voltage lies within a permissible target voltage range. According to the diagram in Figure 5, the current limiting function of the DC link is limited to 140°C. Fig. In the voltage range shown in Figure 5 for an embodiment of the present invention, the voltage values ​​of 700 V to 800 V lie within this target voltage range. If an actual voltage of U_ZwK_max (maximum DC link voltage) of, for example, U is exceeded,BW,ein Downstream inverter units 240, for example those used in electric drives 150, should be protected against overvoltage at a voltage of 820 V. As previously described, this protection can be achieved by a switchable bleeder 230. Furthermore, if the DC link voltage U_ZwK is exceeded, the limit for the current fed back into the supply network from the DC link can be dynamically increased. This also allows for optimized protection of downstream inverter components, as excess power is diverted into the supply network 110.

[0041] If the DC link actual voltage falls below a lower limit voltage U_ZwK_min (for example, U DC,minThe current flow can no longer be regulated, but is determined solely by the voltage potentials between the supply network 110 and the DC link 140, as well as the buffer capacity 220 in the DC link 140. For this reason, current flow between the supply network 110 and the DC link 140 should be limited and permitted within a target voltage range, and outside this range, it should be dynamically increased to the current limit permitted for the feed-in unit or the supply network interface 200 between the supply network 110 and the DC link 140.

[0042] The effects of an uneven load on the electric drives on the power grid are minimized when both the current fed into the DC link and the current fed back from the DC link to the power grid are limited. Ideally, the buffer capacity and the current limiting logic should be parameterized or implemented so that only a constant current flows from the power grid into the DC link, thus covering the average power loss of the connected electric drives.

[0043] In order to ensure the most optimal adaptation of the device 100 for intelligent grid power regulation to the electric drives 150 to be supplied, the design of the buffer capacity 220 C should also be considered. DC the required electrical power W elektrin the electric drives 150. For this purpose, the following formulaic relationship can be used, for example: Weiektr=12CDC(U12−U22)

[0044] After equivalent transformation, the following relationship can be determined for the required buffer capacity as energy storage: CDC=2Weiektr(U12−U22) where C DC an optimal size of the buffer capacity, in the DC voltage section 210 a predefined target voltage range between the voltages U1 and U2 is used and the buffer capacity is for an electrical power W elektr is designed to be delivered by the device 100 for intelligent grid power regulation to the electric drive or electric drives 150.

[0045] For example, when using the voltage level U1 = U BW, ein and U2 = U DC, nominalIt can be achieved that during a return stroke, virtually no energy can be stored in the buffer capacity 220, provided that this energy is converted into heat in the braking resistor 230. On the other hand, when using U1 = U DC,nominal and U2 = U DC, min The required buffer capacity should be designed so that it can be used as an energy storage device for retraction movements in the event of a mains voltage failure. Overall, this is also possible when using voltage levels of U1 = U DC,nominal + U Schwanungsreserve and U2 = U DC,nominal - U Schwanungsreserve The buffer capacity 220 should be designed in such a way as to ensure the least possible feedback effect on the supply network 110 in the event of an uneven load on the electric drives 150.

[0046] Fig.Figure 6 shows a flowchart of an embodiment of the present invention as method 600 for intelligent grid power regulation by capacitive energy storage, wherein the method 600 uses a device 100 for supplying at least one electric drive motor 150 with electrical energy from a power supply network 110. This device 100 has a buffer capacity 220 and a DC link 140, which is configured to be coupled to the buffer capacity via a first interface 200a or is coupled to the buffer capacity via the first interface 200a. The device 100 also has a second interface 200b, via which the DC link 140 can be coupled to or is coupled to the power supply network.The procedure 600 comprises a step of determining 610 the voltage in the DC link and a further step of limiting 620 a current flow between the DC link and the power supply network via the second interface when the voltage of the DC link has a value that is within a target voltage range.

Claims

[1] Device (100) for intelligent grid power regulation by capacitive energy storage, wherein the device (100) is designed to supply at least one electric drive (150) with electrical energy from a power supply network (110), wherein the device (100) has the following features: - a buffer capacity (220); - a DC intermediate circuit (140, 210) configured to be coupled to the buffer capacitor (220) via a first interface (200a) or which is coupled to the buffer capacitor via the first interface; and - a second interface (200b) via which the DC link (140, 210) can be coupled or connected to the power supply network (110), wherein the second interface (200b) is designed to limit a current flow between the power supply network (110) and the DC link (140, 210) when the voltage in the DC link (140, 210) has a value that is within a set voltage range (U) DC,min - U DC,max ) lies, characterized by , that the second interface (200b) is further configured to dynamically increase the current flow between the power supply network (110) and the DC intermediate circuit (140, 210) to the current limit allowed between the power supply network (110) and the DC intermediate circuit (140, 210), if a voltage level of the voltage in the DC intermediate circuit (140, 210) is outside the nominal voltage range (U DC,min- U DC,max ) lies. [2] Device (110) according to claim 1 characterized by , that the second interface (200b) is designed to limit the current flow between the power supply network (110) and the DC intermediate circuit (140, 210) to a peak current that is two to five times, in particular 2.5 times, a continuous current via the second interface. [3] Device (100) according to any one of the preceding claims, characterized by , that the second interface (200b) is designed to regulate the voltage of the DC intermediate circuit (140, 210) to a setpoint, in particular to regulate the voltage of the DC intermediate circuit (140, 210) to the setpoint when the voltage of the DC intermediate circuit (140, 210) was outside the setpoint voltage range before regulation. [4] Device (100) according to any one of the preceding claims, characterized by, that the buffer capacity (220) is designed to absorb a voltage up to the permissible voltage for a downstream power electronics (240, 145) which supplies power to the connectable electric drive (150) and has an energy storage capacity which is dimensioned depending on a maximum energy input or output of the at least one electric drive (150), wherein the energy storage capacity of the buffer capacity is designed in particular to ensure that the electric drive motor is shut down in the event of a failure of the power supply network (110). [5] Device (100) according to any one of the preceding claims, characterized by, furthermore, a flywheel energy storage device is provided, wherein the flywheel energy storage device is designed to be supplied with electrical energy via the DC intermediate circuit (140, 210) or to supply electrical energy back to the DC intermediate circuit (140, 210).

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