System for an electrically driven vehicle, and vehicle therewith and method therefor

1. A system for an electrically-driven vehicle, comprising:

at least one first energy store, which is of an accumulator type, and

at least one second energy store, of a type which differs from an accumulator type,

wherein the second energy store has an energy density lower than an energy density of the first energy store, and has a power density higher than a power density of the first energy store,

wherein the first energy store and the second energy store are designed to supply electrical energy for an electric drive of the vehicle, and

wherein the second energy store comprises a flywheel having an electric motor-generator set which is assigned to the flywheel and a converter which is assigned to the flywheel,

wherein the energy density of the second energy store is less than one half the energy density of the first energy store, and the power density of the second energy store corresponds to at least five times the power density of the first energy store.

2. The system as claimed in claim 1 , where the second energy store further comprises a capacitor.

3. The system as claimed in claim 1 , wherein the system comprises a DC voltage connection, which is designed to deliver electrical energy from the first energy store and/or electrical energy from the second energy store for the supply of the electric drive, and the DC voltage connection is designed to store energy from the electric drive, during operation in a generator mode, in the first energy store and/or the second energy store, and the DC voltage connection is designed to transmit energy from the second energy store to the first energy store.

4. The system as claimed in claim 1 , wherein the system comprises a DC voltage converter, by which the second energy store is detachably connected to the DC voltage connection, wherein the DC voltage converter is a flyback converter, a forward converter or a buck/boost converter.

5. The system as claimed in claim 1 , wherein the electric drive comprises at least one electric motor, at least one inverter and at least one motor control device for actuating the inverter, and also comprises an intermediate DC voltage circuit.

6. The system as claimed in claim 1 , wherein the system comprises an energy management circuit, which is designed to control or regulate energy which is exchangeable between the DC voltage connection and the first energy store, between the DC voltage connection and the second energy store, and between the intermediate DC voltage circuit and the DC voltage connection, wherein, to this end, the energy management circuit is designed to communicate with the motor control device, with the DC voltage converter, and with an accumulator management circuit of the first energy store.

7. The system as claimed in claim 1 , wherein the system comprises a first switch, particularly a semiconductor switch, by means of which the first energy store and the second energy store are detachably connected to the electric drive, and the energy management circuit is designed to actuate the first switch.

8. The system as claimed in claim 7 , wherein the energy management circuit is designed to be operated in a first mode, in which the first switch and the second switch are closed, such that electrical energy which is generated by the electric drive is stored in the first energy store and/or in the second energy store, and energy from the first energy store and/or energy from the second energy store is employed for the supply of the electric drive, wherein the energy management circuit is particularly designed to switch over to the first mode if a charge of the first energy store lies below a predefined first threshold value.

9. The system as claimed in claim 8 , wherein, in the event that the second energy store has a charge which exceeds a second threshold value, the energy management circuit is designed to limit energy which is delivered by the electric drive.

10. The system as claimed in claim 7 , wherein the energy management circuit is designed to be operated in a second mode, in which the first switch is closed and the second switch is opened, such that electrical energy which is supplied by the electric drive is stored in the second energy store, or energy from the second energy store is employed for the supply of the electric drive, wherein the energy management circuit is particularly designed to switch over to the second mode, if a charge of the first energy store exceeds the predefined first threshold value.

11. The system as claimed in claim 7 , wherein the energy management circuit is designed to be operated in a third mode, in which the first switch is opened and the second switch is closed, such that energy is charged from the second energy store to the first energy store.

12. The system as claimed in claim 1 , wherein the system comprises a second switch, particularly a semiconductor switch, by means of which the first energy store is detachably connected to the DC voltage connection, wherein the energy management circuit is designed to actuate the second switch.

13. A vehicle, comprising a system as claimed in claim 1 .

14. A method for operating a system as claimed in claim 1 , the method comprising:

generation of energy by an electric drive,

storage of the generated energy in the second energy store, and

charging of energy from the second energy store to the first energy store.