Transients occur on power transmission lines for unpredictable reasons including breakers opening and closing, load variations, and inputs to the grid from renewable energy sources turning on and off. A recursive technique allows a linear function to be fitted to a non-linear grid dynamic of the power line transients. The technique is adaptive and helps to stabilize an impedance injection unit while it injects correcting impedance into a transmission line for the purpose of achieving power flow control. When applied to many injection units the technique may also help to stabilize the overall grid. The stabilization system using the recursive technique provides real-time monitoring of the associated power line and stabilization with respect to power line transients.

A method for controlling a battery energy storage system and a battery energy storage system including at least three battery energy storage units, a switching arrangement, and a control arrangement configured to select at least two battery energy storage units such that a sum of short circuit currents of the selected battery energy storage units is below a short circuit current limit, which is less than a sum of short circuit currents of the at least three battery energy storage units, and such that a sum of discharge or charge powers of the selected battery energy storage units equals to or exceeds a power limit, and such that states of charge of the selected battery energy storage units are within a determined range, and to control the switching arrangement to couple only the selected at least two battery energy storage units to a DC power connection.

A battery cluster management device and a battery energy storage system are provided. The battery cluster management device includes a networking circuit and an integrated controller, a connecting circuit of the networking circuit and a power conversion circuit connected in series, the integrated controller is respectively connected to the connecting circuit, the power conversion circuit, and a BMU in a battery cluster, and the integrated controller is configured to: perform a preset battery management process according to preset electrical information fed back by the connecting circuit and the BMU, and control the power conversion circuit to perform a preset current conversion process. In the present disclosure, the connecting circuit and the power conversion circuit are integrated, thus repeated voltage and current detection circuits and corresponding soft start circuits are unnecessary, the integration level of the battery cluster management device is improved effectively, and the overall cost is reduced.

The invention provides a method and system for operating an inverter based distributed power generation source with energy storage system, as a Flexible AC Transmission System (FACTS) device—a STATCOM. The inverter based distributed power generation source can provide reactive power compensation, voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. These STATCOM functions are provided when the said energy storage based distributed power generation source is doing at least one of: i) not exchanging active power with said power grid system, or ii) exchanging active power less than a maximum inverter capacity with said power grid system. The present invention thus provides a technological improvement that opens up a new set of applications and potential revenue earning opportunities for energy storage based distributed power generation sources other than simply from exchanging (injecting or absorbing) active power.

An electric vehicle charging station comprises a direct current (DC) bus configured to receive DC power from multiple power sources including at least one battery energy storage system (BESS); at least one electric vehicle charging stall connected to the DC bus and configured to charge an electric vehicle load; and a controller configured to monitor and control power flow from the DC bus to the at least one electric vehicle charging stall and to monitor and control power flow between the BESS and the DC bus.

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.

Disclosed herein is a hybrid resonant capacitor circuit including a first capacitor configured to discharge resonant current to interrupt a load current to a switch in parallel with the hybrid resonant capacitor circuit, a second capacitor coupled in parallel with the first capacitor, wherein the second capacitor is configured to transfer energy stored in the second capacitor to the first capacitor after discharge of the resonant current from the first capacitor, and a current limiter coupled in series with the second capacitor. A static transfer switch including a thyristor switch and the hybrid resonant capacitor circuit is also disclosed herein, as is a method for facilitating multiple consecutive voltage source transfers between a first voltage source and a second voltage source powering a load, using the hybrid resonant capacitor circuit.

An impedance injection unit (IIU) system is coupled to a high-voltage (HV) transmission line. The IIUs are activated in sequences of activation in successive time periods. This injects an impedance waveform onto the HV transmission line. The ordering of IIUs in the sequences of activation is repeatedly changed in successive time periods. This equalizes electrical stress across the IIUs used, leading to overall improvement in IIU system lifetimes.

An apparatus for performing the following: the apparatus maintains, in a database, one or more trained machine learning algorithms for predicting an optimal charging strategy for a time interval based on one or more values of a set of prediction parameters relating to a point of common coupling and one or more electrical load devices and on a state of charge level of the battery energy storage system. The apparatus obtains one or more recent values of the set of prediction parameters relating to one or more previous time intervals and predicts, using the one or more trained machine learning algorithm, an optimal charging strategy for a next time interval based on the one or more recent values and a current state of charge level of the battery energy storage system. Finally, the apparatus operates the battery energy storage system using the predicted optimal charging strategy.

A method of operating an ESS with optimal efficiency includes: collecting charge/discharge efficiency data of a PCS; collecting charge/discharge efficiency data of a battery depending on current state of charge of the battery; creating charge/discharge efficiency data of a unit BESS including the PCS and the battery by using the collected data; determining optimal charge/discharge levels of at least two unit-BESSs included in the ESS by using charge/discharge efficiency data of the at least two unit-BESSs to satisfy commanded input/output power values of the whole ESS at a current point of time; and charging or discharging the at least two unit-BESSs depending on the determined optimal charge/discharge power values.