The disclosure relates to an active damping control method and system for sub-synchronous oscillation of DFIG, and storage medium. The method comprises the following steps: collecting oscillation components of stator current and/or stator voltage; determining each energy branch in DFIG converter according to the flow path of the oscillation component(s) of the stator current and/or the stator voltage in DFIG converter; determining the corresponding function of each energy branch according to oscillation component(s) the stator current and/or the stator voltage; determining the energy compensation branch and its corresponding energy compensation function in DFIG converter according to the corresponding function of each energy branch and converter parameters; controlling the sub-synchronous oscillation of DFIG by controlling the energy compensation branch according to the energy compensation function.

A frequency stabilization arrangement for a power transmission grid has a modular multi-level converter with a first terminal for electrical connection to a power transmission grid, and an electrical resistor unit with a second terminal for electrical connection to the power transmission grid.

A method and a system for evaluating inertia of a power system and a storage medium. The method includes: injecting a cosine active power disturbance into the power system by small-disturbance injection, and obtaining frequency response at a node where the disturbance is injected, where the active power disturbance can be an energy storage, wind power, or photovoltaic power; acquiring an evaluation framework of inertia and frequency regulation capability of the power system according to relative characteristics of a frequency response function; and constructing a mathematical relationship between the impedance and frequency response characteristics according to a relationship among active power disturbance, frequency fluctuation and impedance.

A method of controlling output levels of an MMC converter to reduce fluctuation in a power grid frequency, which adjusts an output level of the MMC converter in response to a change in a power grid frequency of a power grid system in the MMC converter connected to a grid system, is proposed. The method includes a detection step of detecting a power grid frequency of a grid connected to the MMC converter in real time, a comparison step of comparing the detected power grid frequency with a preset reference power grid frequency, and an adjustment step of adjusting a number of output levels of the MMC converter to reduce a difference between the detected power grid frequency and the reference power grid frequency when the detected power grid frequency and the reference power grid frequency are different from each other.

An electrical power source includes a power converter and either an electrical generator or an electrical energy storage device. Power flow is controlled through controlling power converter based on a voltage source and resistance model of the electrical power source. A power converter for an electrical generator is controlled to synthesize or produce a constant voltage of the voltage source and a variable value of the resistance. The resistance value is controlled to deliver a maximum available output power to the electrical microgrid over a range of microgrid voltages up to a voltage below a maximum allowable voltage of the electrical microgrid. For an electrical energy storage device, the power converter is controlled to synthesize or produce a resistance value of the resistance that is dependent upon a phase angle between the voltage at the microgrid side of the electrical power source and current of the electrical energy storage device.

A system includes a converter configured to be coupled between an energy storage unit and a grid and a control circuit configured to detect frequency and voltage variations of the grid and to responsively cause the converter to transfer power and reactive components to and/or from the grid. The control circuit may implement a power control loop having an inner frequency control loop and a reactive component control loop having an inner voltage control loop. The control circuit may provide feedforward from the inner frequency control loop to the inner voltage control loop to inhibit reactive component transfer in response to a voltage variation deviation of the grid due to a power transfer between the energy storage unit and the grid.

A power conditioning system (PCS) includes: a grid blackout determiner, a voltage controller, and a processor electrically connected to the grid blackout determiner and the voltage controller. The processor is configured to identify a state of a grid as a blackout state or an unstable state based on at least one of an amplitude or a frequency of a voltage of the grid that is detected by the grid blackout determiner, control the voltage controller to adjust, based on the identified state of the grid being the blackout state or the unstable state, load voltage input to the voltage controller to be equal to a command voltage, and adjust, based on the identified state of the grid being the blackout state or the unstable state, a first frequency of the detected voltage of the grid to a second frequency that is different from the first frequency.

A frequency support system arranged for providing frequency support to an AC grid. The system includes an ES arrangement, and a bi-directional DC/AC power electronic converter interface configured for connecting the ES arrangement with the grid. The ES arrangement includes a plurality of series connected ES groups, each ES group including a plurality of parallel connected ES modules, each ES module including an energy storage interfaced by a bi-directional power electronic ES converter configured for connecting the ES with a DC side of the converter interface.

Aspects of the present invention relate to a method for controlling a renewable power plant connected to a power network to reduce deviation of a measured frequency of the power network from a target frequency. The method comprises determining a forecasted power gradient over a forecast interval defined between a first time point and a second time point, and, at a third time point during the forecast interval, controlling the power plant to output active power according to a minimum active power level if the measured frequency at the third time point is below the target frequency, controlling the power plant to output active power according to a maximum active power level if the measured frequency at the third time point is above the target frequency. The maximum and minimum active power levels are based on the forecasted power gradient.

Demand response methodologies for primary frequency response (PFR) for under or over frequency events. Aspects of the present disclosure include methods for controlling a fleet of distributed energy resources equipped for PFR and quantifying in real time an amount of primary frequency control capacity available in the fleet. In some examples, the DERs may be configured to consume and discharge electrical energy in discrete energy packets and be equipped with a frequency response local control law that causes each DER to independently and instantaneously interrupt an energy packet in response to local frequency measurements indicating a grid disturbance event has occurred.