Abstract: For converting a first DC voltage to a second DC voltage, a first bridge circuit comprised in a power converter is controlled to convert the first DC voltage to a first AC voltage. The first AC voltage is transformed to a second and possibly further AC voltage. The second and each possibly further AC voltage is converted to a DC voltage by respective bridge circuits. To increase efficiency of the power converter switches of the power converter are controlled to operate in soft switching. Thereto a duty cycle of each AC voltage is controlled. In an embodiment, a half-cycle voltage-time integral of each AC voltage is controlled to be substantially equal.

Abstract: In a system for the conversion between DC power and AC power, including a buffercapacitor and a controllable converting arrangement, said conversion is controlled by a power control quantity that in turn depends on a first component assuring a balance between DC power and AC power and a second component indicating a change in energy stored in the buffer capacitor on a predetermined sampling time instant in the cycle of the voltage ripple on the buffer capacitor.

Abstract: In a system for the conversion between DC power and AC power, including a buffercapacitor and a controllable converting arrangement, said conversion is controlled by a power control quantity that in turn depends on a first component assuring a balance between DC power and AC power and a second component indicating a change in energy stored in the buffer capacitor on a predetermined sampling time instant in the cycle of the voltage ripple on the buffer capacitor.