A method for characterizing power quality events in an electrical system includes deriving electrical measurement data for at least one first virtual meter in an electrical system from (a) electrical measurement data from or derived from energy-related signals captured by at least one first IED in the electrical system, and (b) electrical measurement data from or derived from energy-related signals captured by at least one second IED in the electrical system. In embodiments, the at least one first IED is installed at a first metering point in the electrical system, the at least one second IED is installed at a second metering point in the electrical system, and the at least one first virtual meter is derived or located at a third metering point in the electrical system. The derived electrical measurement data may be used to generate or update a dynamic tolerance curve associated with the third metering point.

There is disclosed herein an energy storage system for a direct current (DC) transmission system, the energy storage system being configured to be connected to a DC link. The energy storage system comprises a first system terminal, a second system terminal, a first converter connected to the first system terminal, and a second converter connected to the first converter and the second system terminal. The energy storage system further comprises an AC loop device providing an alternating current (AC) path, and a plurality of energy storage devices connected in parallel with the second converter comprising a cell having power electronic switches, and an energy storage element connected to the cell, wherein the cells are individually switchable. The present disclosure further relates to a method for providing energy storage to a DC transmission system.

Electrical apparatus (20) includes an inverter (24) having input terminals for receiving DC input power and output terminals for coupling to an AC power grid. A pulse-width modulation (PWM) generator and drivers (26) drive the switches so as to control respective amplitudes, frequencies, and phases of the output current waveforms of the inverter. Control circuitry (28) receives measurements of respective time-varying voltages and currents on the input and output terminals, computes a model (40) that includes three virtual currents flowing in a synchronous machine that is emulated by the apparatus, wherein the three virtual currents are associated respectively with the three output current waveforms, and controls the PWM generator and drivers responsively to the three virtual currents so as to synchronize the amplitudes, frequencies, and phases of the three output current waveforms of the inverter with the three phases of the AC power grid.

Disclosed are a method and system for verifying a low-frequency oscillation damping control effect of a governor power system stabilizer (GPSS), relating to the technical field of power systems. The method includes: selecting a wiring working condition for a fault-free disconnection test, and constructing a unit test working condition; performing the fault-free disconnection test on an outgoing line of a power plant, and collecting an electromagnetic power fluctuation recording curve; and comparing low-frequency oscillation damping effects under different GPSS settings, evaluating the effects, and performing a cyclic test. A success rate of the test is increased, safety of the test is improved, and the overall stability and anti-oscillation capacity of the system are improved in the disclosure.

An energy storage valve submodule and a high-voltage direct-connected energy storage system having the energy storage valve submodule. A suppression circuit for underdamped oscillation is provided in the energy storage valve submodule. The suppression circuit is connected in series with a first capacitor, and a resistance-capacitance branch formed by the suppression circuit and the first capacitor connected in series is connected in parallel with a power conversion unit and an energy storage unit.

Power control apparatus for modulating electrical power signals and methods for modulating electrical power signals are disclosed. In one example, a power control apparatus comprises a magnetic core comprising a first limb and a second limb, with a primary winding around the first limb, and a secondary winding around the second limb. The power control apparatus comprises a voltage source converter having an AC connection, a DC connection, and a controller. The controller is configured to receive data associated with parameters of a first signal in the primary winding, compare the parameters of the first signal to parameters of a reference signal for the secondary winding, determine a harmonization signal which, when applied to the first limb, causes a second signal in the secondary winding to approximate the reference signal. The controller is configured to cause application of the harmonization signal to the first limb using the voltage source converter.

The present disclosure relates to computer-implemented method of operating a battery for providing frequency response to a power grid, the battery comprising a plurality of containers each configured to store electrical energy, the method comprising, for a given container: determining a container target response by dividing a system target response by the plurality of containers; determining a container capacity by dividing a battery capacity by the plurality of containers; determining a state-of-charge offset between an average state of charge across the plurality of containers and a state of charge of the given container; determining a response adjustment by multiplying the container capacity by the state-of-charge offset; and determining a response for the given container by adjusting the container target response by the response adjustment.

Provided are a frequency modulation method, device and system based on a new energy support machine and an energy storage device, and a new energy field station. The method includes: acquiring a system frequency offset value; determining a frequency modulation scheme for the new energy support machine and/or the energy storage device according to the system frequency offset value; generating a frequency modulation instruction for the new energy support machine and/or the energy storage device according to the frequency modulation scheme, so that the new energy support machine and/or the energy storage device execute a corresponding frequency modulation instruction and modulate the system frequency. The method has high regularity, flexibility in rule adjustment and good real-time performance. When the system frequency of a power grid fluctuates, a new energy support machine with higher durability is selected to support the power grid. The electrochemical energy storage device with poorer durability is selected to support the power grid only when the frequency fluctuation of the system is excessive, thereby reducing the number of times the energy storage device is used, realizing the safe operation of the energy storage device, and improving the use safety of the energy storage device.

A method identifies asymmetrical vibrations during the operation of an electric device which is connected to a high-voltage grid. Vibrations of the electric device are detected using vibration sensors which provide measured values on the output side. The measured values and/or values derived from the measured values are transmitted to a communication unit via a close-range communication connection. The measured values and/or the values are transmitted by the communication unit to a data processing cloud via a far-range communication connection. The measured values are separated into frequency components by the data processing cloud using a Fourier transformation, thereby obtaining a frequency spectrum. Odd and even frequency components of the frequency spectrum are ascertained based on a base frequency of the high-voltage supply grid and put into a ratio R relative to one another. The presence of asymmetrical vibrations is indicated if the ratio R exceeds a specified threshold.

The field of power systems includes a switching control method for a converter apparatus in a power supply system and the apparatus. This solution may be applied to a power conversion system in scenarios such as a new energy microgrid or an electrochemical energy storage station. In the method, a voltage of the converter apparatus at a control switching moment is stored, the voltage is used as an initial value after switching is performed, and the voltage is transited to a rated voltage in a first time period.