Abstract: A system (10) for converting power comprising a plurality of modules (14) connected in series and having each at least one DC power source. Storage devices (18) are provided with each module (14) to store power from the power source and voltage control circuitry (19) in each module (14) connects the storage device between a maximum module voltage, a minimum module voltage to create a stepwise approximation of a mains signal. A compensator unit (20) is provided in series with the modules (14) including a storage device charged by the power sources. While each of the modules (14) is supplying either its maximum or minimum voltage to the system a control unit ramps up or down the voltage between the input and output of the compensator unit (20) to follow the desired AC signal.

Abstract: Described is a method for converting power including controlling operation of a plurality of series connected modules including a DC power sources and storage devices such that the total voltage across the series connected modules includes an AC signal. A storage parameter is defined based on a sum of a function of the voltages in the storage devices in the modules and one or more voltage control levels are defined for each of or a plurality of the storage devices. An average current drawn from the series connected modules over a time period is set such that the storage parameter approaches a target value. The target value is decreased for a subsequent time period in the event that none the voltage control levels are reached and increased in the event that one or more of the voltage control levels are reached.

Abstract: A system (10) for converting power comprising a plurality of modules (14) connected in series and having each at least one DC power source. Storage devices (18) are provided with each module (14) to store power from the power source and voltage control circuitry (19) in each module (14) connects the storage device between a maximum module voltage, a minimum module voltage to create a stepwise approximation of a mains signal. A compensator unit (20) is provided in series with the modules (14) including a storage device charged by the power sources. While each of the modules (14) is supplying either its maximum or minimum voltage to the system a control unit ramps up or down the voltage between the input and output of the compensator unit (20) to follow the desired AC signal.