The invention relates to an energy storage system for storing heat and coldness and for providing electrical energy, characterized by an energy converter, wherein the energy converter is designed to produce electrical energy from heat and coldness and to produce heat and coldness from electrical energy, the energy converter being in heat-transferring contact with a hot heat exchanger and with a cold heat exchanger, the hot heat exchanger being connected to a heat reservoir and the cold heat exchanger being connected to a coldness reservoir, and a control unit being provided, which operates the energy storage system in a first operating mode, in which heat and coldness are formed from electrical energy by means of the energy converter, and in a second operating mode, in which electrical energy is produced from heat and coldness.

An electrical energy storage system is provided in this dislosure, which includes: M battery packs; M first DC/DC converters, where first terminals of the M first DC/DC converters are respectively connected to the M battery packs, the M first DC/DC converters are classified into N first DC/DC converter sets; and N second DC/DC converters, where the N second DC/DC converters one-to-one correspond to the N first DC/DC converter sets, a first terminal of each second DC/DC converter is connected to second terminals of all first DC/DC converters in a first DC/DC converter set corresponding to the second DC/DC converter, a second terminal of each second DC/DC converter is connected to a first interface of the electrical energy storage system, the first interface is to receive a direct current from a power generation system or output a direct current to the power generation system.

Provided is a method for analyzing the stability of a PMSG-WT connected to a weak power grid considering the influence of power control. New energy power generation mostly uses a perturbation and observation (P&O) method for maximum power point tracking, and nonlinear discontinuous links therein make stability analysis difficult. The present application analyzes the stability of the PMSG-WT connected to the weak grid system based on a describing function method, and fully considers the nonlinear discontinuous links in the power loop, thus making the analysis result more accurate. At the same time, the describing function method is a method that can quantitatively calculate the frequency and amplitude of oscillation. The analysis method of the present application can provide a powerful and good reference for oscillation suppression and controller design.

An exemplary renewable-energy system including a back end system coupled to an isolated DC power source and a generator powered by a renewable energy source and including first circuitry configured to convert first AC power from the generator to DC power and to provide the DC power to a DC power bus, the first circuitry further configured to initiate operation using power from the isolated DC power source. The example system further includes a front end system comprising an inverter coupled to an isolated DC power source generator. The inverter includes a ground isolation monitor interrupter (IMI) circuit coupled to the DC power bus and configured to receive the DC power and convert the DC power to second AC power for provision to a power grid. The isolated power source generator ground-isolates third AC power of the power grid for conversion to DC power for the isolated DC power source.

A computer-implemented method and system is provided. The system adaptively switches prediction strategies to optimize time-variant energy demand and consumption of built environments associated with renewable energy sources. The system analyzes a first, second, third, fourth and a fifth set of statistical data. The system derives of a set of prediction strategies for controlled and directional execution of analysis and evaluation of a set of predictions for optimum usage and operation of the plurality of energy consuming devices. The system monitors a set of factors corresponding to the set of prediction strategies and switches a prediction strategy from the set of derived prediction strategies. The system predicts a set of predictions for identification of a potential future time-variant energy demand and consumption and predicts a set of predictions. The system manipulates an operational state of the plurality of energy consuming devices and the plurality of energy storage and supply means.

Provided is a method of controlling wind turbine converters of wind turbines parallel connected at a point of common coupling, the method including: generating for each converter within a same length of a pulse width modulation period a pulse, wherein the pulses start for different converters at different pulse start phases, wherein pulse start phase differences of the pulse start phases between at least two of adjacent converters are unequal.

A method for exchanging or feeding electric power into an electricity supply grid that has a grid frequency using a converter-controlled generator at a grid connection point is provided. The method includes feeding in electric power depending on a control function, where the electric power may comprise active and reactive power, and the control function controls the power depending on at least one state variable of the grid. It is possible to select between a normal control function and a support control function, different from the normal control function, as the control function. The normal control function is selected when it has been detected that the grid is operating stably and the support control function is selected when a grid problem, grid fault or an end of the grid fault has been detected. The support control function controls the fed-in power to counteract an oscillation in the grid.

This invention relates to a method of controlling at least one wind turbine of a plurality of wind turbines connected to an electrical grid at a predefined point in the electrical grid. The wind turbine comprises a DC link connecting a generator side converter to a line side converter, where the line side converter is controlled according to a modulation index requested by a power converter controller. The method comprises determining a harmonic frequency signal indicative of a harmonic frequency value at the predefined point in the electrical grid; determining a deviation between the harmonic frequency signal and a permissible harmonic frequency value; determining a permissible modulation index based on the deviation; comparing the permissible modulation index to the modulation index requested by the power converter controller; and, altering a DC link voltage set-point based on the comparison between the permissible modulation index and the requested modulation index.

Example embodiments of systems, devices, and methods are provided herein for energy systems having multiple modules arranged in cascaded fashion for storing power from one or more photovoltaic sources. Each module includes an energy source and converter circuitry that selectively couples the energy source to other modules in the system over an AC interface for generating AC power or for receiving and storing power from a charge source. Each module also includes a DC interface for receiving power from one or more photovoltaic sources. Each module can be controlled by control system to route power from the photovoltaic source to that modules energy source or to the AC interface. The energy systems can be arranged in single phase or multiphase topologies with multiple serial or interconnected arrays. The energy systems can be arranged such that each module receives power from the same single photovoltaic source, or multiple photovoltaic sources.

The present disclosure provides an energy storage system comprising a plurality of input ports connectable to receive electrical power from one or more energy sources, a plurality of output ports connectable to deliver electrical power to one or more loads, a plurality of battery modules, a switching matrix connected between the plurality of battery modules and the plurality of inputs, and between the plurality of battery modules and the plurality of outputs, the switching matrix configured to selectively connect each battery module to any number of the plurality of input ports or any number of the plurality of output ports, each input port to any number of battery modules, and each output port to any number of battery modules, and a main battery management controller operably coupled to the switching matrix for controlling connections between each battery module and any number of the plurality of input ports or any number of the plurality of output ports.