The present invention proposes a hybrid converter branch operating mode for a Modular Multilevel power Converter MMC with MMC cells in distinct subsets operating according to a “pulse blocked” cell operation mode with DC cell voltage increase or according to a “bypass” cell operation mode without DC cell voltage increase. Repeated cell subset assignment and corresponding alternation of cell operating mode allows to reduce or at least manage a mean deviation of the cell capacitor DC voltages of the converter cells. The invention also reduces no-load losses of the MMC in standby mode and a charging voltage in an MMC charging mode.

The present invention provides a power control circuit connectable to a load adapted to receive a power supply, the power control circuit adapted to absorb power from the power supply and adapted to deliver power to the power supply to stabilize at least one electrical parameter of the power supply. The present invention also provides an associated method of stabilizing at least one electrical parameter of a power supply connectable to a load, the method including absorbing power from the power supply or delivering power to the power supply. The at least one electrical parameter of the power supply includes parameters such as voltage and frequency.

A device is for reactive power compensation in a high-voltage network having a phase conductor. The device has a first high-voltage terminal, which is configured to be connected to the phase conductor. For each first high-voltage terminal, a first and a second core section, which are part of a magnetic circuit, a first high-voltage winding, which encloses the first core section, and a second high-voltage winding are provided. Moreover, the device has a saturation switching branch, which saturates the core sections and has controllable power semiconductor switches. A control unit is used to control the power semiconductor switches. The first and the second high-voltage windings are connected by the high-voltage end to the associated first high-voltage terminal and on the low-voltage side can be connected to one or the saturation switching branch. To be able to be connected in series into the high-voltage network, a second high-voltage terminal is provided.

The invention provides a method and system for operating a solar farm inverter as a Flexible AC Transmission System (FACTS) device—a STATCOM—for voltage control. The solar farm inverter can provide voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. In one embodiment, the solar farm operating as a STATCOM at night is employed to increase the connectivity of neighbouring wind farms that produce peak power at night due to high winds, but are unable to connect due to voltage regulation issues. The present invention can also operate during the day because there remains inverter capacity after real power export by the solar farm. Additional auxiliary controllers are incorporated in the solar farm inverter to enhance damping and stability, and provide other benefits provided by FACTS devices.

A method and system for locally controlling delivery of electrical power along a distribution feeder. For a feeder segment in the distribution feeder the method includes: obtaining an actual voltage magnitude at an upstream node and at a downstream node of the feeder segment, and a real power value at the upstream node; setting a target voltage phasor at the downstream node as a value when a power flow across the feeder segment is maintained, and when equal reactive power is injected at the upstream and downstream nodes that consumes all the reactive power in the feeder segment; and adjusting operation of the at least one controllable reactive power resource so that the actual voltage magnitude at the downstream node moves towards a target voltage magnitude of the target voltage phasor.

A hybrid cascaded APF topology and control method therefor for improving the ability of a system to compensate for higher harmonics, raise the quality of electric energy of output currents, and reduce costs. The topology includes: a three-phase cascaded H-bridge including bridge arms of three phases, each bridge arm including a plurality of H-bridge cells connected in series, and the bridge arms of the three phases connected to a power system needing active filtering via inductors; and a three-phase H-bridge circuit connected at star connection points of the three-phase cascaded H-bridge, the three-phase H-bridge circuit including branches of the three phases and two capacitors connected in parallel across the branches of the three phases, and the branch of each phase including two switching transistors connected in series, where switching transistors of the H-bridge cells use Si devices, and the switching transistors of the three-phase H-bridge circuit use SiC devices.

Systems and methods for supplying power (both active and reactive) at a medium voltage from a DCSTATCOM to an IT load without using a transformer are disclosed. The DCSTATCOM includes an energy storage device, a two-stage DC-DC converter, and a multi-level inverter, each of which are electrically coupled to a common negative bus. The DC-DC converter may include two stages in a bidirectional configuration. One stage of the DC-DC converter uses a flying capacitor topology. The voltages across the capacitors of the flying capacitor topology are balanced and switching losses are minimized by fixed duty cycle operation. The DC-DC converter generates a high DC voltage from a low or high voltage energy storage device such as batteries and/or ultra-capacitors. The multi-level, neutral point, diode-clamped inverter converts the high DC voltage into a medium AC voltage using a space vector pulse width modulation (SVPWM) technique.

A hybrid cascaded APF topology and control method therefor for improving the ability of a system to compensate for higher harmonics, raise the quality of electric energy of output currents, and reduce costs. The topology includes: a three-phase cascaded H-bridge including bridge arms of three phases, each bridge arm including a plurality of H-bridge cells connected in series, and the bridge arms of the three phases connected to a power system needing active filtering via inductors; and a three-phase H-bridge circuit connected at star connection points of the three-phase cascaded H-bridge, the three-phase H-bridge circuit including branches of the three phases and two capacitors connected in parallel across the branches of the three phases, and the branch of each phase including two switching transistors connected in series, where switching transistors of the H-bridge cells use Si devices, and the switching transistors of the three-phase H-bridge circuit use SiC devices.

A distribution feeder of an electricity grid comprises a substation and a plurality of nodes with at least one controllable reactive power resource. A method is provided for locally controlling delivery of electrical power along the distribution feeder, wherein for a feeder segment in the distribution feeder the method comprises: obtaining an actual voltage magnitude at an upstream node and at a downstream node of the feeder segment, and a real power value at the upstream node; setting a target voltage phasor at the downstream node as a value when a power flow across the feeder segment is maintained, and when equal reactive power is injected at the upstream and downstream nodes that consumes all the reactive power in the feeder segment; and adjusting operation of the at least one controllable reactive power resource so that the actual voltage magnitude at the downstream node moves towards a target voltage magnitude of the target voltage phasor.

A power quality compensator device and a control method thereof are provided. The power quality compensator device is electrically connected to a power grid and a nonlinear load, and includes a current controller, a converter, a ripple predictor, a processing unit and a voltage controller. The current controller is configured to receive an instruction current and output a switch control signal. The converter is configured to output an output current and an actual DC bus voltage according to the switch control signal. The ripple predictor is configured to receive an intermediate voltage and a first current and output a predicted ripple voltage. The processing unit is configured to output a processing result according to the actual DC bus voltage, the predicted ripple voltage and a reference DC bus voltage. The voltage controller is configured to receive the processing result and output a voltage control signal to the current controller.