Method and system for state-of-charge monitoring of an AC battery

A system for state-of-charge monitoring of an AC battery, in which the AC battery comprises a central controller having a scheduler, measuring sensors and at least two battery modules, wherein the at least two battery modules each have at least one energy storage element and at least two power semiconductor switches, which connect the respective battery module in series or in parallel or in bypass with another battery module, wherein the central controller is configured to control the AC battery, and the scheduler is configured to preset a respective switching state of the at least two battery modules, wherein a state-of-charge monitor within the scheduler is implemented by a control program and is configured, during operation of the AC battery,

• (a) to determine a respective current flow at a respective energy storage element using continued evaluation of measured values of preset battery parameters which are detected by measuring sensors,
• (b) to estimate a measurement state of charge based upon the determination at (a),
• (c) to calculate a respective current flow using continued logging of the respective switching states of the at least two battery modules, of a respective phase current, and of impedances present given respective switching states of the AC battery, wherein the respective switching states of the at least two battery modules indicate whether the respective battery module is connected in series or in parallel or in bypass with another battery module,
• (d) to estimate a monitoring state of charge from the calculation at (c), and
• (e) form the state-of-charge monitoring from a combination of the measurement state of charge and the monitoring state of charge.