Attenuation circuit for an energy storage device and method for attenuating oscillations of the output current of an energy storage device
The invention relates to an attenuation circuit for an energy storage device having one or more energy storage modules which are connected in series in one or more energy supply lines and have at least one energy storage cell and a coupling device which has a multiplicity of coupling elements and is designed to selectively switch or bridge the energy storage cell in the respective energy supply line. The attenuation circuit comprises a current detection device which is designed to detect an output current of the energy supply lines or of the energy storage device and to generate an output current signal dependent on the output current, a control circuit which is coupled to the current detection device and is designed to control the output current signal to a desired current signal and to output a corresponding current control signal, and a pulse width modulation device which is coupled to the control circuit and is designed to control the coupling device of at least one of the energy storage modules in a clocked manner on the basis of the current control signal.
1. A damping circuit for an energy storage device ( 10 ) which comprises an energy supply string having a plurality of energy storage modules ( 3 ; 30 ) connected in series, said energy storage modules ( 3 ) having at least one energy storage cell ( 5 a , . . . , 5 k ) and a coupling device ( 7 ) having a multiplicity of coupling elements, which coupling device is designed to connect the energy storage cell ( 5 a , . . . , 5 k ) selectively into the respective energy supply string or to bridge said energy storage cell, comprising:
a current detection device ( 8 ), configured to detect an output current of the energy storage device ( 10 ) and to generate an output current signal dependent on the output current;
a closed-loop control circuit ( 6 ), coupled to the current detection device ( 8 ) and configured to adjust the output current signal to a setpoint current signal ( 6 c ) and to output a corresponding current control signal; and
a pulse width modulation device ( 4 ), coupled to the closed-loop control circuit ( 6 ) and configured to actuate the coupling device ( 7 ) of at least one of the plurality of energy storage modules ( 30 ) in clocked fashion depending on the current control signal.
2. The damping circuit according to claim 1 , further comprising:
a bandpass filter ( 11 ), coupled between the current detection device ( 8 ) and the closed-loop control circuit ( 6 ) and configured to filter frequency components of the output current signal outside a predeterminable frequency range.
3. The damping circuit according to either of claim 1 , wherein the pulse width modulation device ( 4 ) is designed to actuate the coupling device ( 7 ) of the at least one of the plurality of energy storage modules ( 30 ) in such a way that the at least one of the plurality of energy storage modules ( 30 ) generates a compensation current, which compensates for fluctuations in the output current of the energy storage device ( 10 ).
4. The damping circuit according to claim 1 , wherein the closed-loop control circuit ( 6 ) has a summing element ( 6 b ), which subtracts the output current signal from the setpoint current signal ( 6 c ), and a current controller ( 6 a ), which generates the current control signal depending on the output signal of the summing element ( 6 b ).
5. A system, comprising:
an energy storage device ( 10 ), which has a plurality of energy storage modules ( 3 ; 30 ), which are connected in series in one or more energy supply strings, said plurality of energy storage modules comprising at least one energy storage cell ( 5 a , . . . , 5 k ) and a coupling device ( 7 ) having a multiplicity of coupling elements, which coupling device is designed to connect the energy storage cell ( 5 a , . . . , 5 k ) selectively into the respective energy supply string or to bridge said energy storage cell; and
a damping circuit according to claim 1 .
6. The system according to claim 5 , further comprising:
a DC voltage intermediate circuit ( 9 a ), which is coupled to output connections ( 1 a , 1 b ) of the energy storage device ( 10 ).
7. The system according to claim 6 , further comprising:
an inverter ( 12 ), which is coupled to the DC voltage intermediate circuit ( 9 a ); and
an electric machine ( 13 ), which is coupled to the inverter ( 12 ),
wherein the inverter ( 12 ) is designed to convert the voltage of the DC voltage intermediate circuit ( 9 a ) into an input voltage for the electric machine ( 13 ).
8. A method ( 20 ) for damping oscillations of the output current of an energy storage device ( 10 ), which has a plurality of energy storage modules ( 3 , 30 ) connected in series, in one or more energy supply strings, said energy storage modules comprising at least one energy storage cell ( 5 a , . . . , 5 k ) and a coupling device ( 7 ) having a multiplicity of coupling elements, which coupling device is designed to connect the energy storage cell ( 5 a , . . . , 5 k ) selectively into the respective energy supply string or to bridge said energy storage cell, said method comprising the following steps:
detecting ( 21 ) an output current of the energy supply strings or the energy storage device ( 10 );
generating ( 22 ) an output current signal which is dependent on the detected output current;
applying closed-loop control ( 23 ) to the output current signal to adjust it to a setpoint current signal ( 6 c );
outputting ( 24 ) a current control signal corresponding to the closed-loop control;
actuating ( 25 ) the coupling device ( 7 ) of at least one energy storage module ( 30 ) in clocked fashion in order to generate a compensation current, which compensates for fluctuations in the output current of the energy storage device ( 10 ).