Abstract: A method for operating an inverter for driving a generator is described. The inverter comprises a DC-link having a DC-link capacitor and the inverter configured to convert a three-phase AC voltage generated by the generator into a DC-link voltage to be applied to the DC-link capacitor. The method comprises receiving a power reference value which is representative of a power to be provided by the generator, and determining an estimated mechanical frequency of the generator. The method further comprises determining a harmonic component of the estimated mechanical frequency, and determining a torque reference value based on the power reference value and the determined harmonic component. The torque reference is representative of a torque to be generated by the generator. The method additionally comprises generating a switching signal for the inverter based on the determined torque reference value, and operating the inverter by supplying the switching signal to the inverter.

Abstract: A method for operating an inverter configured to drive a generator is provided. The inverter comprises a direct current link (DC-link) having a DC-link capacitor, and the inverter is configured to convert a three-phase alternating current (AC) voltage generated by the generator into a DC-link voltage to be applied to the DC-link capacitor. The method includes receiving a DC-link voltage reference to be applied to the DC-link, receiving an actual DC-link voltage currently present over the DC-link, determining a stator parameter reference based on the received DC-link voltage reference and the received actual DC-link voltage, modifying the determined stator parameter reference by adding a dynamic stabilizing term to the stator parameter reference, generating a switching signal for the inverter based on the modified stator parameter reference, and operating the inverter by supplying the switching signal to the inverter.

Abstract: A method and an arrangement of tracking a selected (e.g., maximum) power point of a photovoltaic system is disclosed, in which method an operation point of the photovoltaic system is changed based on the change of operation point and a change of power generated by the photovoltaic system. The method can include repeatedly determining a current or voltage of the photovoltaic system, determining a power of the photovoltaic system, determining a change of power of the photovoltaic system with respect to a previous determined power, and changing the operation point of the photovoltaic system by changing a current or voltage reference of the system stepwise depending on the change of power and a direction of a previous change of the current or voltage reference.

Abstract: A method and apparatus of tracking the maximum power point of a photovoltaic module. The method includes measuring an output voltage of the photovoltaic module, determining an output voltage of the inverter connected to the photovoltaic module, and measuring output current of the inverter connected to the photovoltaic module. A variable relating to energy of the capacitor is defined using the measured PV module output voltage, and a second harmonic component is extracted from the defined variable. A second harmonic component of the module output power is estimated using the defined variable, measured output current of the inverter, and the determined output voltage of the inverter. The estimated and extracted second harmonic components are multiplied, and a DC component is extracted from the product. A control signal for controlling the inverter connected to the photovoltaic module is formed by using the extracted DC component in a PI algorithm.

Abstract: A method and an arrangement of tracking a selected (e.g., maximum) power point of a photovoltaic system is disclosed, in which method an operation point of the photovoltaic system is changed based on the change of operation point and a change of power generated by the photovoltaic system. The method can include repeatedly determining a current or voltage of the photovoltaic system, determining a power of the photovoltaic system, determining a change of power of the photovoltaic system with respect to a previous determined power, and changing the operation point of the photovoltaic system by changing a current or voltage reference of the system stepwise depending on the change of power and a direction of a previous change of the current or voltage reference.

Abstract: A method and apparatus of tracking the maximum power point of a photovoltaic module. The method includes measuring an output voltage of the photovoltaic module, determining an output voltage of the inverter connected to the photovoltaic module, and measuring output current of the inverter connected to the photovoltaic module. A variable relating to energy of the capacitor is defined using the measured PV module output voltage, and a second harmonic component is extracted from the defined variable. A second harmonic component of the module output power is estimated using the defined variable, measured output current of the inverter, and the determined output voltage of the inverter. The estimated and extracted second harmonic components are multiplied, and a DC component is extracted from the product. A control signal for controlling the inverter connected to the photovoltaic module is formed by using the extracted DC component in a PI algorithm.