Abstract: A first direct-current to direct-current (DC-to-DC) converter is configured to convert an input direct-current voltage to an output direct-current voltage with a regulated charging current consistent with a target charging current limit or range established by the current estimator for the charging mode and respective cell identifier(s) determined by a cell balancing module for the charging mode for the time interval. A first controller is capable of controlling the charging, individually or collectively, of each of the battery cells by adjusting/controlling the regulated charging current outputted by the first DC-DC converter and/or the duty cycle of switches of the first DC-to-DC converter based on the target charging current limit or range for the time interval.

Abstract: Exemplary embodiments are directed to methods and systems for producing a three-phase current to a three-phase output. Switching converters are used to generate a positive current, a negative current, and an intermediate current. The system is configured such that the produced positive current follows a path of a highest phase of a sinusoidal three-phase signal at a given time, the produced negative current follows a path of a lowest phase of the three-phase signal at the given time, and the produced intermediate current follows a path of a phase of the three-phase signal between the highest and the lowest phase at the given time. The produced currents are switched to each phase conductor of the three-phase output in sequence so that phase currents of the three-phase current are formed in the output conductors.

Abstract: Exemplary embodiments are directed to an snubber circuit and a power converter having an active circuit. The snubber circuit includes a series connection of a first diode and a first inductor connected between a first interfacing point and a first connection point, a second diode connected between a second connection point and a second interfacing point, a series connection of a third diode and a second inductor between a third interfacing point and the second connection point, a switching device connected between the first connection point and the third interfacing point, and a first capacitor connected between the first connection point and the second connection point. The first, the second, and the third diode are forward-biased along a path between the first interfacing point and the second interfacing point and through the third interfacing point.

Abstract: An exemplary method and apparatus for detecting islanding conditions of a distributed grid are disclosed, wherein transfer of power through a power electrical unit is controlled on the basis of a control reference. The apparatus includes a first stage and a second stage performing a respective portion of the method. The first stage injects a reactive component to the control reference, and, for at least one electrical quantity of the grid, determines a change in the quantity induced by the injected component, and determines, on the basis of the change in the electrical quantity, whether to move to the second stage of the method.

Abstract: An exemplary method and an apparatus implementing the method for an arrangement having a three-phase, multi-level inverter, an output LCL-filter connecting the inverter to a grid, and a virtual-ground connection between the LCL-filter and the neutral point of the DC-link. The method includes determining a zero-sequence component of an LCL-filter inverter-side current, calculating a zero-sequence damping and balancing voltage term based on the LCL-filter inverter-side current zero-sequence component and voltages over the two halves of the DC-link, and adding the zero-sequence damping and voltage balancing term to the output voltage reference.

Abstract: A method and an apparatus for controlling a grid-connected converter which includes a boost converter, a buck converter, and a current source inverter having an output CL filter. An input of the buck converter input is connected to an output of the boost converter, and an input of the current source inverter is connected to an output of the buck converter. The method includes controlling a boost converter input voltage, controlling a boost converter output voltage through control of a buck converter output voltage, and controlling the current source inverter to produce an AC current from the buck converter output voltage. The apparatus implements the method.

Abstract: Exemplary embodiments are directed to an snubber circuit and a power converter having an active circuit. The snubber circuit includes a series connection of a first diode and a first inductor connected between a first interfacing point and a first connection point, a second diode connected between a second connection point and a second interfacing point, a series connection of a third diode and a second inductor between a third interfacing point and the second connection point, a switching device connected between the first connection point and the third interfacing point, and a first capacitor connected between the first connection point and the second connection point. The first, the second, and the third diode are forward-biased along a path between the first interfacing point and the second interfacing point and through the third interfacing point.

Abstract: Exemplary embodiments are directed to methods and systems for producing a three-phase current to a three-phase output. Switching converters are used to generate a positive current, a negative current, and an intermediate current. The system is configured such that the produced positive current follows a path of a highest phase of a sinusoidal three-phase signal at a given time, the produced negative current follows a path of a lowest phase of the three-phase signal at the given time, and the produced intermediate current follows a path of a phase of the three-phase signal between the highest and the lowest phase at the given time. The produced currents are switched to each phase conductor of the three-phase output in sequence so that phase currents of the three-phase current are formed in the output conductors.

Abstract: An exemplary method and arrangement for estimating the frequency and the positive sequence of a fundamental component of a measured three-phase voltage are disclosed (???).

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 phase-locked loop and method for estimating a phase angle of a three-phase reference signal is disclosed, which includes an adaptive quadrature signal generator configured to calculate an estimated first state and an estimated second state of a model of an unbalanced three-phase system at a fundamental frequency of the reference signal on a basis of the reference signal and an estimated fundamental frequency; a reference frame transformation block configured to calculate a direct component and a quadrature component in a rotating reference frame synchronous with an estimated phase angle on a basis of the fundamental positive sequence component and the estimated phase angle, and configured to determine an estimate of an amplitude of the fundamental positive sequence component on the basis of the direct component; and an estimator configured to determine estimates of the estimated fundamental frequency and the estimated phase angle on the basis of the quadrature component.

Abstract: An exemplary method and an apparatus implementing the method for an arrangement having a three-phase, multi-level inverter, an output LCL-filter connecting the inverter to a grid, and a virtual-ground connection between the LCL-filter and the neutral point of the DC-link. The method includes determining a zero-sequence component of an LCL-filter inverter-side current, calculating a zero-sequence damping and balancing voltage term based on the LCL-filter inverter-side current zero-sequence component and voltages over the two halves of the DC-link, and adding the zero-sequence damping and voltage balancing term to the output voltage reference.

Abstract: A method of controlling the grid-side current of a single-phase grid-connected converter having an LCL filter connected between the output of the converter and the grid includes measuring a grid voltage and at least one signal in a group of signals consisting of a grid-side current, a converter-side current and a capacitor voltage, estimating the fundamental component of the grid voltage, forming a grid-side current reference, a converter-side current reference and a capacitor voltage reference for the grid-side current of the LCL filter, forming estimates for the non-measured signals in the group of signals, forming a grid-side current difference term, a converter-side current difference term and a capacitor voltage difference term, and controlling the output voltage of the converter based on the grid voltage, a formed injection term and a formed estimate of the harmonic distortion term to produce a grid side current corresponding to the current reference.

Abstract: A method and an apparatus for controlling a grid-connected converter which includes a boost converter, a buck converter, and a current source inverter having an output CL filter. An input of the buck converter input is connected to an output of the boost converter, and an input of the current source inverter is connected to an output of the buck converter. The method includes controlling a boost converter input voltage, controlling a boost converter output voltage through control of a buck converter output voltage, and controlling the current source inverter to produce an AC current from the buck converter output voltage. The apparatus implements the method.

Abstract: An exemplary method is disclosed for searching a global maximum power point in an arrangement comprising a series connection of photovoltaic power sources. The method can include determining a value of a reference by adding an increment to a previous value of the reference, wherein the value of the increment is determined on the basis of the power produced by the power sources.

Abstract: A method and apparatus are provided for detecting islanding conditions for distributed generators connected to a grid. The method includes estimating a grid impedance, and inducing, on the basis of the estimated grid impedance, a variation on a value of a first electrical quantity of the grid. The method also includes monitoring a grid response to the variations, and determining islanding conditions on the basis of the monitored response.

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: An exemplary method and arrangement for estimating the frequency and the positive sequence of a fundamental component of a measured three-phase voltage are disclosed (???).

Abstract: A method of controlling the grid-side current of a single-phase grid-connected converter having an LCL filter connected between the output of the converter and the grid. The method includes measuring a grid voltage (vS) and at least one signal in a group of signals consisting of a grid-side current (i0), a converter-side current (i1) and a capacitor voltage (vC0).

Abstract: A non-isolated DC-DC converter assembly includes a boost converter and a ?uk converter connected together in a specific way. The non-isolated DC-DC converter assembly allows for grounding of a source and load at the same time, and provides a complete adjustability of the output voltage of the non-isolated DC-DC converter.