Specifying the operating range

A valid operating range must be specified in the Configuration in order to use the operating mode. Setpoints to the device for the state of charge are always limited to this operating range, irrespective of the set unit. This can be a range between 450 V and 720 V, for example (see figure). This means that this voltage range corresponds to the state of charge from 0% to 100%.

The following figure shows the operating range to be defined:

The device operates primarily with the voltage of the DC link or the connected energy storage unit. For the capacitors used, this is an indicator of the amount of charge or energy in the DC link and consequently also of the state of charge.

The amount of energy in the energy storage unit or in the DC link is quadratically dependent on the current voltage according to the following formula:

In this way, the state of charge can be calculated according to the following formula using only the measured voltages and the defined operating range:

U_o and U_u define the upper and lower voltage limits of the operating range, and U_i the measured voltage at which the state of charge should be calculated. Similarly, this formula is used to convert state of charge setpoints into voltages and to make these voltages available to the device as voltage setpoints. The state of charge cannot be negative but can take on a value above 100%. This case occurs, for example, if the DC link adopts a higher voltage value than defined by the operating range when absorbing excess recuperation energy.