Abstract
A method is provided for an energy transmission between at least two energy stores (914, 924) in a respective zero system of at least two n-phase electric machines (912, 922), in which one respective n-phase electric machine (912, 922) has a field winding that is brought together at a star point. The respective field winding is provided with n-windings corresponding to respective n-phases and has a neutral point (902), a respective energy store (914, 924) is assigned, and an electric connection is established in terms of circuitry between windings of corresponding phases, or between the neutral points (902) of the respective field windings of the at least two n-phase electric machines (912, 922) and a respective identical pole of the energy stores (914, 924). Thus, an energy transmission between the at least two energy stores (914, 924) that have a different charge state is carried out.
Claims
1. A method for energy transmission between at least two energy stores (114, 124, 914, 924) in a respective zero-phase sequence system of at least two operational N-phase electric machines (112, 122, 912, 922) in a motor vehicle, in which the energy stores (114, 124, 914, 924) are assigned respectively to the N-phase electric machines (112, 122, 912, 922), by way of which for N=3 a three-phase motor is realized and which comprises a field winding (113, 123) joined at a star point, wherein the respective field winding has N windings corresponding to respective N phases and a neutral point (217, 227, 902), and an electrical connection is established in terms of circuitry between windings of corresponding phases or between the neutral points (217, 227, 902) of the respective field windings (113, 123) of the at least two N-phase electric machines (112, 122, 912, 922) and also between a respective identical pole of the energy stores (114, 124, 914, 924), as a result of which energy is transmitted between the at least two energy stores (114, 124, 914, 924) that have a different state of charge, by means of the field windings and the neutral points thereof of the at least two N-phase electric machines (112, 122, 912, 922).
2. The method of claim 1, in which a respective switch (330, 930) is arranged between windings of corresponding phases and/or between the neutral points of the respective field windings (113, 123) for establishing the electrical connection in terms of circuitry.
3. The method of claim 1, wherein the windings of corresponding phases and/or the neutral points of the respective field windings are electrically fixedly wired to one another and a respective switch (330) is arranged between a respective identical pole of the at least two energy stores for establishing the electrical connection in terms of circuitry.
4. The method of claim 3, in which the circuitry connection is established only at a time at which there is no voltage loading in the respective zero-phase sequence system of the at least two N-phase electric machines (112, 122, 912, 922).
5. The method of claim 3, in which the switch (330, 930) is a semiconductor switch or a mechanical switch.
6. The method of claim 1, wherein a flow of energy is controlled by monitoring a potential difference between the energy stores of the at least two N-phase electric machines (112, 122, 912, 922), said monitoring being effected by means of at least one inverter.
7. The method as claimed in claim 6, wherein the flow of energy is limited to a prescribed value.
8. The method of claim 3, in which the switch (330, 930) to be closed to establish an electrical connection to at least one second field winding of a second N-phase electric machine is opened because the voltage loading in the zero-phase sequence system of a first N-phase electric machine is caused by way of an infeed of an N-th harmonic of a fundamental of a supply voltage.
9. The method of claim 3, wherein the switch (330, 930) to be closed to establish an electrical connection to at least one second field winding of a second N-phase electric machine is opened because the voltage loading in the zero-phase sequence system of a first N-phase electric machine is caused by way of a generative retroactive effect of the first N-phase electric machine.
10. The method of claim 3, wherein the switch (330, 930) to be closed to establish an electrical connection to at least one second field winding of a second N-phase electric machine is opened because the voltage loading in the zero-phase sequence system of a first N-phase electric machine is caused by way of a surge current produced in the energy store by way of switching processes.
11. The method of claim 1, wherein at least N battery modules (802), which each comprise at least two circuit breakers and at least one energy cell connected to the circuit breakers, are selected as respective energy store.
12. A system of a motor vehicle, the system comprises at least two energy stores (114, 124, 914, 924), at least two N-phase electric machines, by way of which for N=3 a three-phase motor is realized and which are each operated by way of an energy store (114, 124, 914, 924) of the at least two energy stores (114, 124, 914, 924) and assigned to the respective energy stores (114, 124, 914, 924), at least one control unit equipped with a computer processor and a computer program running on the computer processor the control unit being designed to control a respective energy store to operate the N-phase electric machine assigned to said energy store, and at least one switch (330, 930), wherein the system is designed to execute the method of claim 1, wherein the system is configured to transmit energy between the at least two energy stores (114, 124, 914, 924) when they have a different state of charge, by means of the field windings and the neutral points thereof of the at least two N-phase electric machines (112, 122, 912, 922).
13. The system of claim 12, wherein the respective energy store (114, 124) comprises an energy module (116, 126) and an inverter, wherein the inverter is configured to generate from a direct current provided by the energy module N phases of an alternating current necessary for operating the N-phase electric machine (112, 124) assigned to the energy store (114, 124).
14. The system of claim 12, wherein the respective energy store (914, 924) comprises at least N battery modules (802), wherein each respective battery module (802) comprises at least two circuit breakers and at least one energy cell electrically connected to the at least two circuit breakers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic illustration according to the prior art of two drive systems that are associated with a respective axle of a motor vehicle and that do not have an electrical connection.
[0028] FIG. 2 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems associated with a respective axle of a motor vehicle.
[0029] FIG. 3 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, with a switch between the respective electric motors and fixedly wired negative poles of the respective energy stores.
[0030] FIG. 4 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, with a fixedly wired connection between the electric motors and a switch between the negative poles of the respective energy stores.
[0031] FIG. 5 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, with fixedly wired positive poles of the respective energy stores and a switch between the respective electric motors.
[0032] FIG. 6 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, with a fixedly wired connection between the electric motors and a switch between the positive poles of the respective energy stores.
[0033] FIG. 7 is a schematic illustration of two embodiments of an interconnection, provided in accordance with the invention, with a switch between different windings of the same phase of the respective field windings of the electric motors and fixedly wired negative poles of the respective energy stores.
[0034] FIG. 8 is a schematic illustration of a multi-level converter, which has been connected into two separate energy stores for a respective drive system.
[0035] FIG. 9 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, of a multi-level converter, divided into two energy stores, for two drive systems associated with a respective axle of the motor vehicle and having a switch between a connection of the neutral points of the respective electric motors.
[0036] FIG. 10 is a schematic illustration of an embodiment of an interconnection, provided in accordance with the invention, of a multi-level converter, divided into two energy stores, for two drive systems associated with a respective axle of the motor vehicle and having a switch between different windings of the same phase of the respective field windings of the electric motors.
DETAILED DESCRIPTION
[0037] FIG. 1 shows a schematic illustration 100 according to the prior art of two drive systems 110, 120, which are associated with a respective axle of a motor vehicle and which do not have an electrical connection. A respective drive system consists of an energy store 114, 124 and an N-phase electric machine 112, 122. The respective energy store 114, 124 consists of an energy module 116, 126 and an inverter 115, 125, which from the DC voltage of the energy modules 116, 126 forms an N-phase AC voltage for a field winding 113, 123 of the N-phase electric machine 112, 122.
[0038] FIG. 2 shows a schematic illustration 200 of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems 110, 120 associated with a respective axle of a motor vehicle. A negative pole 218 of the energy module 116 is connected to the negative pole 228 of the energy module 126 by way of a fixedly wired connection 202. A neutral point 217 of the field winding 113 is likewise connected to a neutral point 227 of the field winding 123 by way of a fixedly wired connection 204. If the energy modules 116 and 126 have different states of charge, an energy transfer takes place between the respective energy stores 114 and 124 by means of the respective zero-phase sequence system of the N-phase electric machines 112 and 122 that are otherwise in running operation.
[0039] FIG. 3 shows a schematic illustration 300 of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems 110, 120 associated with a respective axle of a motor vehicle. While respective negative poles of the batteries 116 and 126 are wired to one another by way of a fixed connection 302, a switch 330 is located between neutral points of the respective field windings 113 and 123. If there is voltage loading in one of the N-phase electric machines 112 and 122, for example owing to a third harmonic of the fundamental of a supply voltage of the corresponding field winding 113 or 123 being fed in, the switch 330 must be opened in order to prevent uncontrollable flows of current. Otherwise, when the switch 330 is closed, an energy transfer can take place between the respective energy stores 114 and 124 by means of the respective zero-phase sequence systems of the N-phase electric machines 112 and 122 that are otherwise in running operation.
[0040] FIG. 4 shows a schematic illustration 400 of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems 110 and 120 associated with a respective axle of a motor vehicle. In comparison with FIG. 3, there is a fixedly wired connection 404 between the neutral points of the respective field windings 113 and 123. The switch 330, which interrupts an energy transmission between the two energy stores 114, 124, is arranged between a connecting line 402 of the two negative poles of the energy stores 114, 124. In general, a switch 330 can be introduced at any location of a circuit including the connection between the respective field windings 113, 123, wherein, however, said switch must be arranged so that upon opening it does not stop the functioning of a system, assigned to said switch, composed of the respective energy store 114, 124 and the respective electric machine 112, 122 assigned to said energy store.
[0041] FIG. 5 shows a schematic illustration 500 of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems 110 and 120 associated with a respective axle of the motor vehicle, wherein a positive pole 519 of the energy module 116 is connected to a positive pole 529 of the energy module 126 by way of a fixedly wired connection 502. A switch 330 is located between the neutral points of the respective field windings 113 and 123.
[0042] FIG. 6 shows a schematic illustration 600 of an embodiment of an interconnection, provided in accordance with the invention, of two drive systems 110 and 120 associated with a respective axle of a motor vehicle and having a fixedly wired connection 204 between the neutral points of the respective field windings 113 and 123. The switch 330, which interrupts an energy transmission between the two energy stores 114, 124, is arranged in a connecting line of the two positive poles 519 and 529 of the energy modules 116 and 126.
[0043] FIG. 7 shows a schematic illustration of two embodiments of an interconnection 701 and 702, provided in accordance with the invention, of two drive systems 110 and 120 associated with a respective axle of a motor vehicle, wherein a respective switch 330 is arranged between different windings 711, 721 and 712, 722 of the same phase of the respective field windings of the electric motors and the negative poles 218 and 228 of the respective energy stores are fixedly wired to one another via a connection 202. In the interconnection 701, the switch 330 is arranged in the connection to a connection point to the winding 711 of the field winding in the drive system 110 and a connection point to the winding 721 of the field winding in the drive system 120. In the interconnection 702, the switch 330 is arranged in the connection to a connection point to the winding 712 of the field winding in the drive system 110 and a connection point to the winding 722 of the field winding in the drive system 120. In general, N such connection point options are conceivable in the case of an N-phase electric motor.
[0044] FIG. 8 shows a schematic illustration 800 of a multi-level converter, which has been connected into two separate energy stores for accordingly two drive systems and represents a special case for a system consisting of separate energy stores. The multi-level converter comprises a plurality of battery modules 802, wherein the battery modules 802 each have at least two circuit breakers and at least one energy cell electrically connected to the at least two circuit breakers. If there are a plurality of energy cells present per battery module 802, they are fixedly wired among one another in a predetermined series-parallel configuration. The battery modules 802 are arranged in N strings 804 per drive system, which form the respective phases. In the example shown here having a three-phase motor 812 and a three-phase motor 822, there are N=3 phases, which are present at the string end points 814, 816 and 818 for the three-phase motor 812 and are present at the string end points 824, 826 and 828 for the three-phase motor 822. The circuit breakers of the battery modules 802 permit a change in configuration of the battery modules 802 among one another during running operation. The shown configuration of the multi-level converter is affected exactly like the illustration 100 shown in FIG. 1 of different discharging by way of differently arising loadings of the respective drive systems.
[0045] FIG. 9 shows a schematic illustration 900 of an embodiment of an interconnection, provided in accordance with the invention, of a multi-level converter, divided into two energy stores 914, 924, for accordingly two respective drive systems 912 and 922 associated with a respective axle of a motor vehicle. A switch 930 is advantageously introduced into a connecting line of the two neutral points 902 of the three-phase motors of the respective drive systems 912, 922. The method according to the invention makes provision for the switch 930 to be opened as soon as for example a third harmonic of the fundamental of the supply voltage produced by the multi-level converter is fed in for at least one of the two three-phase motors 912, 922. In the closed state of the switch 930, an energy transfer takes place between the energy stores 914 and 924. If for example the energy store 914 has a higher state of charge and therefore a higher voltage potential than the energy store 924, when the switch 930 is closed a current flows from the energy store 914 through the field winding of the three-phase motor 912 to the neutral point 916 thereof, and from there via the closed switch 930 to the neutral point 902 of the three-phase motor in the drive system 922, and by means of the field winding thereof to the energy store 924. This occurs as long as a potential difference prevails between the two energy stores 914, 924.
[0046] FIG. 10 shows a schematic illustration 1000 of an embodiment of an interconnection, provided in accordance with the invention, of a multi-level converter, divided into two energy stores 914 and 924, for two drive systems 912 and 922 associated with a respective axle of a motor vehicle, wherein a switch 930 is arranged between a connection point 1011 and a connection point 1021 to windings of the same phase of the respective field windings of the electric motors. In general, N such connection point options are conceivable in the case of an N-phase electric motor. In the embodiment shown in illustration 1000 having a three-phase motor, connections between the connection points 1012 and 1022, and between the connection points 113 and 123, respectively, to the respective windings of the respective field windings of the three-phase motors are alternatively conceivable.
