Patent ID: 7729142

Claim:
In a power distribution and transmission system, a method for controlling at least three converters that can be controlled as rectifiers or as inverters and that are connected to one another via a DC power supply system, the method which comprises: measuring a respective measured DC voltage and a respective measured direct current at each converter and transmitting to a rectifier control system in order to control the respective rectifier, or to an inverter control system in order to control a respectively associated inverter; defining a respectively associated rectifier nominal DC power and a respective inverter nominal DC power for each rectifier control system and for each inverter control system, with a sum of all the rectifier nominal DC powers and all the inverter nominal DC powers being equal to zero; determining a respectively associated inverter nominal DC voltage from each inverter nominal DC power; defining a lowest inverter nominal DC voltage of all the inverters connected to the DC power supply system as a minimum DC voltage; respectively calculating a rectifier nominal direct current and an inverter nominal direct current by way of the minimum DC voltage from each rectifier nominal DC power and from each inverter nominal DC power; with each rectifier control system, forming a difference between the minimum DC voltage and the respectively received rectifier measured DC voltage, resulting in a rectifier difference DC voltage, and forming a difference between the respective rectifier nominal current and the respectively received rectifier measured direct current, resulting in a rectifier difference direct current, and controlling the associated rectifier to minimize a sum of the difference DC voltage and the difference direct current; and with each inverter control system, forming a difference between the minimum DC voltage and the respectively received inverter measured DC voltage, resulting in an inverter difference DC voltage, and forming a difference between the respective inverter nominal current and the respectively received inverter measured direct current, resulting in an inverter difference direct current, and controlling the respectively associated inverter to minimize a difference between the inverter difference direct current and the inverter difference DC voltage.