Abstract: A method in connection with control of a grid connected converter and a converter. The control including forming a current reference for the converter, feeding the current reference to a current controller for producing a voltage reference for the converter. The method includes high-pass filtering the produced voltage reference or measured output voltage of the converter and modifying the current reference with the high-pass filtered voltage reference or measured output voltage of the converter.

Abstract: A method for single-phase islanding detection in a three-phase electricity network, can include supplying power into a three-phase electricity network (EN) by a power supply assembly (PSA), the electricity network (EN) having a network voltage, and providing a stimulus signal into a positive sequence electric quantity of the electricity network, the positive sequence electric quantity being current, power or a derived quantity thereof. A magnitude and/or a rate of change of an indicative element of a negative sequence component of the network voltage is monitored, a frequency domain of the indicative element including a frequency corresponding to the stimulus signal. A single phase islanding condition is detected in the electricity network (EN) if the magnitude and/or rate of change of the indicative element exceeds a predetermined limit value.

Abstract: An exemplary method for controlling transfer of electrical power in island mode in an arrangement having a converter and a load connected to the converter through a filter. The method including determining voltage reference components for one or more frequency components of an output voltage of the converter. An effect of a load current is compensated for by forming one or more voltage feedforward terms based on the load current and using the feedforward terms to adjust the voltage reference components. Control reference components for one or more of the frequency components are formed based on the voltage reference components, and a control reference is formed based on the control reference components. The output voltage of the converter is controlled based on the control reference.

Abstract: An exemplary method for detecting a three-phase islanding state in a three-phase electricity network includes supplying power to a three-phase electricity network via a power supply assembly, controlling an output frequency of the power supply assembly with a frequency reference signal adapted to deviate the output frequency of the power supply assembly from a grid frequency representing a frequency of a common electricity network whose portion of the three-phase electricity network is in normal operating conditions. The method also includes detecting a three-phase islanding state in the electricity network if the output frequency of the power supply assembly is outside an allowable value range. During a normal operating state of the electricity network, the frequency reference signal depends on an active output current of the power supply assembly.

Abstract: An exemplary method for detecting a three-phase islanding state in a three-phase electricity network includes supplying power to a three-phase electricity network via a power supply assembly, controlling an output frequency of the power supply assembly with a frequency reference signal adapted to deviate the output frequency of the power supply assembly from a grid frequency representing a frequency of a common electricity network whose portion of the three-phase electricity network is in normal operating conditions. The method also includes detecting a three-phase islanding state in the electricity network if the output frequency of the power supply assembly is outside an allowable value range. During a normal operating state of the electricity network, the frequency reference signal depends on an active output current of the power supply assembly.

Abstract: A method for single-phase islanding detection in a three-phase electricity network, can include supplying power into a three-phase electricity network (EN) by a power supply assembly (PSA), the electricity network (EN) having a network voltage, and providing a stimulus signal into a positive sequence electric quantity of the electricity network, the positive sequence electric quantity being current, power or a derived quantity thereof. A magnitude and/or a rate of change of an indicative element of a negative sequence component of the network voltage is monitored, a frequency domain of the indicative element including a frequency corresponding to the stimulus signal. A single phase islanding condition is detected in the electricity network (EN) if the magnitude and/or rate of change of the indicative element exceeds a predetermined limit value.

Abstract: An exemplary method for controlling transfer of electrical power in island mode in an arrangement having a converter and a load connected to the converter through a filter. The method including determining voltage reference components for one or more frequency components of an output voltage of the converter. An effect of a load current is compensated for by forming one or more voltage feedforward terms based on the load current and using the feedforward terms to adjust the voltage reference components. Control reference components for one or more of the frequency components are formed based on the voltage reference components, and a control reference is formed based on the control reference components. The output voltage of the converter is controlled based on the control reference.