Provided is a power supply system comprising: distributed energy resources (2) connected to a power line (L1) for feeding power from a commercial power system (10) to an important load (30); a switch (3) provided in the power line (L1) for opening and closing the power line (L1); an impedance element (4) connected in parallel to the switch (3) in the power line (L1); a voltage detection unit (5) for detecting a voltage on the commercial power system (10) side with respect to the switch (3); and a control unit (6) for releasing, when a voltage detected by the voltage detection unit (5) becomes equal to or lower than a set point, the switch (3) such that the distributed energy resources (2) and the commercial power system (10) are connected through the impedance element (4), and the distributed energy resources (2) continue operation including reverse power flow.

Described are systems and methods for black-starting an electrical grid, comprising disconnecting an energy farm from the grid at a first location, said first location being located between the electrical grid and the energy storage with the associated converter, providing a synchronous condenser, energizing the AC export cable using said energy storage and the associated converter, energizing at least one part of the energy farm electrical infrastructure via said AC export cable using said energy storage and the associated converter, re-establishing energy supply to said energy farm electrical infrastructure by said electric generators, energizing said synchronous condenser, and reconnecting the energy farm to said electrical grid at said first location.

A method of controlling assets connected to an electricity distribution grid operating at a predetermined grid frequency is disclosed. The assets comprise assets supplying electrical energy to and/or consuming electrical energy from the grid, with at least some of the assets being configurable to adjust energy flow to or from the grid to counteract grid frequency fluctuations. The method includes configuring an aggregate response by a group of assets to fluctuations in the grid frequency, wherein the aggregate response comprises respective adjustments of energy flow between each of the group of assets and the grid. The adjustments are arranged in combination to counteract a fluctuation in grid frequency. A divergence is detected between a first grid frequency measured in a portion of the grid comprising a first asset of the group of assets and a second grid frequency measured in a portion of the grid comprising a second asset of the group of assets. In response to detecting the divergence, at least one of the first and second assets is reconfigured to alter the energy flow adjustment for that asset. Reconfiguration may involve clustering assets based on grid frequency and reconfiguring aggregated responses for assets within clusters.

A method and a wind turbine are provided. The wind turbine includes a gearless generator that is a synchronous generator and includes a stator and a generator rotor. The wind turbine includes a generator filter with modifiable filter properties that is coupled to the stator and configured to filter a stator current. The wind turbine includes a filter controller configured to control the generator filter.

A control device for a power generation system comprising an energy storage system (ESS) and a power plant is provided. The control device includes: a controller configured to compare a supply frequency of a supply power supplied to a consumer with a reference frequency, compare a charge amount of the ESS with a reference charge amount, and control the ESS and the power plant such that the supply power is controlled according to a result of the frequency comparison and a result of the charge amount comparison, an opening degree control device configured to control an opening degree of a steam valve disposed in the power plant by the control of the controller, and a fuel quantity control device configured to control a quantity of fuel injected into the power plant for power generation by the control of the controller.

A control unit for an active filter for reducing resonance in an electric system is provided. The electric system comprises a power source distributing an alternating current to an AC conductor connected to a power consuming unit for distributing the AC to the power consuming unit. The active filter comprises a DC power source and a DC conductor connecting the DC power source to the AC conductor. The control unit comprises: a voltage measurement unit adapter to create a voltage signal on the basis of a measured voltage; a computing unit adapted to compute, using a biquadratic filter, a first compensating current on the basis of the voltage signal for reducing resonance in the electric system and a switching system placed between the DC power source and the DC conductor for creating the calculated first compensating current.

A voltage stability monitoring device and a method capable of obtaining information of voltage stability that can be served to practical use within a range of assumed conditions during a predetermined monitoring period are provided. The present invention provides a voltage stability monitoring device for estimating a voltage stability by using a voltage stability curve representing the voltage stability in an electric power system, including a voltage stability limit prediction unit for predicting a voltage stability limit, a voltage stability calculation condition determination unit for determining voltage stability calculation conditions by using a prediction result of voltage stability limit, a voltage stability curve calculation unit for calculating the voltage stability curve using a result of the voltage stability calculation condition determination, and a voltage stability margin calculation unit for calculating a voltage stability margin using a calculation result of the voltage stability curve.

A power demand/supply adjustment power procurement plan support device supports a power system through a power transaction in the power market and has an added power transmission capacity analysis means and a target power transmittable capacity determination means. The added power transmission capacity analysis means obtains: actual power supply data including a power supply having supplied power to the power system and the actual value of a power supply amount; an actual power system stabilization data including a power supply performing power supply restriction for power system stabilization, an electric control amount or a customer facility performing a load restriction, and the actual value of a load control amount; and an actual power demand/supply adjustment power procurement data including a procurement amount of the power demand/supply adjustment power of a power supply participating in the power market and the actual value of the total procurement cost.

Technologies for controlling forced oscillations in electrical power grids include a processing unit and a phasor measurement unit and a control device coupled to a power grid. The processing unit receives a measurement indicative of active power in the power grid from the phasor measurement unit and determines a frequency of a forced oscillation active in the power grid based on the measurement. The processing unit injects a corrective signal with the control device into the power grid. The processing unit determines a corrective phase and a corrective amplitude in response to injecting the corrective signal. The processing unit continues to inject the corrective signal with the corrective phase and the corrective amplitude. The control device may be a static VAR compensator, a synchronous generator, a static synchronous compensator, a synchronous condenser, an electric storage device, or a solar power plant. Other embodiments are described and claimed.

The present invention relates to a method for operating a power plant comprising a plurality of power producing units, the power plant being operatively connected to an associated power grid having a nominal grid frequency, the method comprising the steps of determining grid frequency variations of the associated power grid, and providing, in response to the determined grid frequency variations, an active power set-point to each of the plurality of power producing units, said active power set-point causing each of the plurality of power producing units to produce active power in response to said active power set-point, said produced active power comprising, in a frequency domain, one or more active power frequency components being different from one or more undesired frequency modes. The present invention also relates to a power plant controller for performing the method.