Abstract: A grid forming vector current control system can be used for controlling a grid intertie. A first terminal is connected to a first power grid and a second terminal is connected to a second power grid. The terminals each include current control unit, a virtual admittance unit, and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of a virtual synchronous machine (VSM) and a virtual current source is connected in parallel to the VSM. A controller is configured to use transient power consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use transient power consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source.

Abstract: A grid forming vector current control system can be used for controlling a grid intertie. A first terminal is connected to a first power grid and a second terminal is connected to a second power grid. The terminals each include current control unit, a virtual admittance unit, and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of a virtual synchronous machine (VSM) and a virtual current source is connected in parallel to the VSM. A controller is configured to use transient power consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use transient power consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source.

Abstract: A switching circuit for a voltage source converter includes a string of series-connected switches and a string of capacitors. A first conductor interconnects a first end of the string of series-connected switches with a first end of the string of capacitors at a first switch and a second conductor interconnects a second end of the string of series-connected switches with a second end of the string of capacitors at a second switch. A first string of components is connected between the first end of the string of series-connected switches and the first end of the string of capacitors and includes a snubber component for the first switch. A second string of components is connected between the second end of the string of series-connected switches and the second end of the string of capacitors and includes a snubber component for the second switch.

Abstract: The present disclosure provides a grid forming vector current control system configured to emulate a virtual synchronous machine (VSM). The disclosed system comprises a droop control unit, a current control unit, a virtual admittance unit and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of the VSM. A virtual current source is connected in parallel to the VSM.

Abstract: A switching circuit for a voltage source converter includes a string of series-connected switches and a string of capacitors. A first conductor interconnects a first end of the string of series-connected switches with a first end of the string of capacitors at a first switch and a second conductor interconnects a second end of the string of series-connected switches with a second end of the string of capacitors at a second switch. A first string of components is connected between the first end of the string of series-connected switches and the first end of the string of capacitors and includes a snubber component for the first switch. A second string of components is connected between the second end of the string of series-connected switches and the second end of the string of capacitors and includes a snubber component for the second switch.

Abstract: The present disclosure relates to a converter cell (4) for an MMC. The cell comprises a primary energy storage (Cm), an inductor (Lf), and a secondary energy storage (Cf); and first and second converter valves (T1, T2). The secondary energy storage (Cf) is connected in series with the first converter valve (T1), and together with said first converter valve in parallel with the inductor (Lf), and the primary energy storage (Cm) is connected in series with the second converter valve (T2), and together with said second converter valve (T2) in parallel with the inductor (Lf).

Abstract: The present disclosure relates to a converter cell (4) for an MMC. The cell comprises a primary energy storage (Cm), an inductor (Lf), and a secondary energy storage (Cf); and first and second converter valves (T1, T2). The secondary energy storage (Cf) is connected in series with the first converter valve (T1), and together with said first converter valve in parallel with the inductor (Lf), and the primary energy storage (Cm) is connected in series with the second converter valve (T2), and together with said second converter valve (T2) in parallel with the inductor (Lf).

Abstract: A voltage-source converter, VSC, control system including an active damper, AD, a direct-voltage controller, DVC, and an alternating-voltage controller, AVC. The VSC control system is configured to control a VSC. The AVC is configured to regulate, using an integrator, an ac-bus voltage of the VSC by calculating a q component of a current reference vector for the VSC. The DVC is configured to regulate, using an integrator, a dc-bus voltage of the VSC by calculating a d component of the current reference vector. The AD is configured to amplify a vectoral difference between the ac-bus voltage and a corresponding reference, and to add the q component of the amplified vectoral difference to the q component of the current reference vector and to an input of the integrator of the AVC.

Abstract: A voltage-source converter, VSC, control system including an active damper, AD, a direct-voltage controller, DVC, and an alternating-voltage controller, AVC. The VSC control system is configured to control a VSC. The AVC is configured to regulate, using an integrator, an ac-bus voltage of the VSC by calculating a q component of a current reference vector for the VSC. The DVC is configured to regulate, using an integrator, a dc-bus voltage of the VSC by calculating a d component of the current reference vector. The AD is configured to amplify a vectoral difference between the ac-bus voltage and a corresponding reference, and to add the q component of the amplified vectoral difference to the q component of the current reference vector and to an input of the integrator of the AVC.

Abstract: A method of controlling a grid-connected voltage source converter, VSC, using power-synchronisation control, wherein the method includes: determining an active power control error, determining a VSC phase angle based on an integration of a sum including a scaled active power control error and a scaled imaginary part of a voltage of common coupling, determining a damping component based on a virtual damping resistance, a VSC current vector and a reference current vector for the VSC current vector, determining a voltage vector based on a VSC voltage magnitude and the damping component, transforming the voltage vector to a current vector, comparing a magnitude of the current vector with a maximum threshold current value, and in case the magnitude of the current vector is greater than the maximum threshold current value: reducing the magnitude of the current vector to a value below the maximum threshold current value to obtain a limited current vector, transforming the limited current vector to a limited voltage

Abstract: A method of controlling a grid-connected voltage source converter, VSC, using power-synchronisation control, wherein the method includes: determining an active power control error, determining a VSC phase angle based on an integration of a sum including a scaled active power control error and a scaled imaginary part of a voltage of common coupling, determining a damping component based on a virtual damping resistance, a VSC current vector and a reference current vector for the VSC current vector, determining a voltage vector based on a VSC voltage magnitude and the damping component, transforming the voltage vector to a current vector, comparing a magnitude of the current vector with a maximum threshold current value, and in case the magnitude of the current vector is greater than the maximum threshold current value: reducing the magnitude of the current vector to a value below the maximum threshold current value to obtain a limited current vector, transforming the limited current vector to a limited voltage

Abstract: A method of controlling a grid-connected voltage source converter, VSC, using power-synchronization control, wherein the method includes: determining a VSC current vector (i) based on a VSC phase angle (?) which is determined based on an integration of a power control error, determining an active power producing current component (idref) of a reference current vector (iref) based on an active power reference (Pref) for the VSC, determining the reference current vector (iref) based on the active power producing current component (idref), determining a damping component based on a virtual damping resistance (Ra), the reference current vector (iref) and the VSC current vector (i), determining a voltage vector (v) based on a VSC voltage magnitude (V) and the damping component, and controlling the VSC based on the voltage vector (v).

Abstract: A method of controlling a grid-connected voltage source converter, VSC, using power-synchronisation control, wherein the method includes: determining a VSC current vector (i) based on a VSC phase angle (?) which is determined based on an integration of a power control error, determining an active power producing current component (idref) of a reference current vector (iref) based on an active power reference (Pref) for the VSC, determining the reference current vector (iref) based on the active power producing current component (idref), determining a damping component based on a virtual damping resistance (Ra), the reference current vector (iref) and the VSC current vector (i), determining a voltage vector (v) based on a VSC voltage magnitude (V) and the damping component, and controlling the VSC based on the voltage vector (v).

Abstract: A multilevel power converter includes at least one phase leg. The phase leg includes a plurality of cascaded chain link connected cells, each cell including a capacitor and two semiconductor switches in series, each with an anti-parallel connected diode. The plurality of cascaded chain link connected cells includes first and second cells which form a mirrored cell-pair such that the two semiconductor switches of each of the first and second cells are all connected in series with each other. The converter further includes an energy storage connected between the first and second cells.

Abstract: A multi-level power converter for one or more phases includes one or more converter arms including a plurality of serial connected switching cells. Each switching cell includes a plurality of switching devices, a primary energy storage, a secondary energy storage and a first inductor. The switching devices are arranged to selectively provide a connection to the primary energy storage, wherein each switching cell includes a bridge circuit including the switching devices and the primary energy storage, a battery circuit connected to the bridge circuit and including the secondary energy storage, and an arm circuit providing a connection between two adjacent switching cells. The first inductor of each switching cell is arranged in the arm circuit.

Abstract: A Voltage Source Converter control system for active damping of a resonance oscillation in the VSC includes a regular Phase-Locked Loop 2, and a slow PLL 3. The control system is arranged such that an imaginary part of the AD is obtainable from the slow PLL. The slow PLL is configured for having a closed-loop bandwidth which is less than a frequency, in a synchronous dq frame, of the resonance oscillation to be dampened.

Abstract: A Voltage Source Converter control system for active damping of a resonance oscillation in the VSC includes a regular Phase-Locked Loop 2, and a slow PLL 3. The control system is arranged such that an imaginary part of the AD is obtainable from the slow PLL. The slow PLL is configured for having a closed-loop bandwidth which is less than a frequency, in a synchronous dq frame, of the resonance oscillation to be dampened.

Abstract: A multi-level power converter for one or more phases includes one or more converter arms including a plurality of serial connected switching cells. Each switching cell includes a plurality of switching devices, a primary energy storage, a secondary energy storage and a first inductor. The switching devices are arranged to selectively provide a connection to the primary energy storage, wherein each switching cell includes a bridge circuit including the switching devices and the primary energy storage, a battery circuit connected to the bridge circuit and including the secondary energy storage, and an arm circuit providing a connection between two adjacent switching cells. The first inductor of each switching cell is arranged in the arm circuit.

Abstract: A multilevel power converter includes at least one phase leg. The phase leg includes a plurality of cascaded chain link connected cells, each cell including a capacitor and two semiconductor switches in series, each with an anti-parallel connected diode. The plurality of cascaded chain link connected cells includes first and second cells which form a mirrored cell-pair such that the two semiconductor switches of each of the first and second cells are all connected in series with each other. The converter further includes an energy storage connected between the first and second cells.

Abstract: An arrangement for tapping power from a DC power line to an AC power line includes power transfer modules between two DC potentials, each including a first branch with a string of converter cells in parallel with a second branch including a capacitor and being connected to an AC phase. There is at least one control unit that controls the arrangement considering one or more of a) distributing appropriate AC and DC voltages in converter output voltages of all series connected modules, b) maintaining/setting cell capacitor voltages in specific range and allowing boost mode operation, c) performing possible balancing of the introduced capacitor and d) employing an alternate approach of using passive filters to mitigate low order harmonics.