Method for operating a drive system, wherein the drive system comprises a rectifier , an energy storage device , which is connected to the DC voltage-side terminal of the rectifier by means of a bidirectionally operable DC-to-DC converter , and a motor that can be fed from an inverter , wherein the DC voltage-side terminal of the inverter and a first DC voltage-side terminal of the DC-to-DC converter are wired in parallel with the DC voltage-side terminal of the rectifier , wherein the AC voltage-side terminal of the inverter is connected to the motor, and the second DC voltage-side terminal of the DC-to-DC converter is connected to the energy storage device , wherein the energy storage device has a capacitor or a battery, wherein the curve of the voltage applied to the DC voltage-side terminal of the inverter , i.e. the DC link voltage U_ZK, is detected in particular within the converter , within the casing of the converter and thus outside the casing of the inverter , and the value U_ZK_r of a measure for a fluctuation range of the curve is determined therefrom, wherein the value U_ZK_r is determined as the root of the moving, in particular arithmetic, average of the square of the difference between the time curve of the DC link voltage U_ZK and the moving, in particular arithmetic, average of the time curve of the DC link voltage U_ZK, wherein the converter controls the power flow exchanged with the energy storage device in simple dependence on the value U_ZK_r or the curve thereof by controlling the storage current I_S, in particular the charging current, of the energy storage device towards a desired value I_Soll_2, wherein the rectifier is set up such, and just one film capacitor having a capacitance of less than 5 μF per kW of inverter power is arranged in the DC link such, that the ripple of the DC link voltage increases with the total power drawn from the DC link. wherein the drive system comprises a rectifier , an energy storage device , which is connected to the DC voltage-side terminal of the rectifier by means of a bidirectionally operable DC-to-DC converter , and a motor that can be fed from an inverter , wherein the DC voltage-side terminal of the inverter and a first DC voltage-side terminal of the DC-to-DC converter are wired in parallel with the DC voltage-side terminal of the rectifier , wherein the AC voltage-side terminal of the inverter is connected to the motor, and the second DC voltage-side terminal of the DC-to-DC converter is connected to the energy storage device , wherein the energy storage device has a capacitor or a battery, wherein the curve of the voltage applied to the DC voltage-side terminal of the inverter , i.e. the DC link voltage U_ZK, is detected in particular within the converter , within the casing of the converter and thus outside the casing of the inverter , and the value U_ZK_r of a measure for a fluctuation range of the curve is determined therefrom, wherein the value U_ZK_r is determined as the root of the moving, in particular arithmetic, average of the square of the difference between the time curve of the DC link voltage U_ZK and the moving, in particular arithmetic, average of the time curve of the DC link voltage U_ZK, wherein the converter controls the power flow exchanged with the energy storage device in simple dependence on the value U_ZK_r or the curve thereof by controlling the storage current I_S, in particular the charging current, of the energy storage device towards a desired value I_Soll_2, wherein the rectifier is set up such, and just one film capacitor having a capacitance of less than 5 μF per kW of inverter power is arranged in the DC link such, that the ripple of the DC link voltage increases with the total power drawn from the DC link. <EOS>