A photovoltaic apparatus according to an embodiment of the present invention may comprise: a photovoltaic cell array for generating electricity by using solar energy; a battery energy storage system for charging electric energy supplied from the photovoltaic cell array and discharging the charged electric energy to a system; and a processor for controlling a generated power amount to be supplied to the system on the basis of the generated power amount of the photovoltaic cell array and power consumption of the photovoltaic apparatus.

A voltage compensation device according to an embodiment includes a controller including first and second coordinate transformation circuits, and first and second arithmetic parts. The first coordinate transformation circuit generates first and second outputs that are mutually-orthogonal by performing a rotating coordinate transformation of the normal-phase components of a three phase AC. The first arithmetic part calculates a system voltage based on a DC component of the first output and generates a first compensation amount corresponding to a compensation voltage set to compensate a shift of the system voltage from a preset target voltage. The second coordinate transformation circuit generates third and fourth outputs that are mutually-orthogonal by performing a rotating coordinate transformation of reverse-phase components of the three-phase AC. The second arithmetic part generates second compensation amount of a reverse-phase component of the system voltage based on DC components of the third and fourth outputs.

The disclosure discloses a system and method for suppressing unbalanced voltage at the Point of Common Coupling (PCC) of dispersed wind farm. According to the disclosure, the wind farm comprising a STATCOM and plurality of wind turbines, dispersed wind farm controller, STATCOM controller, wind turbine controller. The dispersed wind farm controller decides that whether the STATCOM or the wind turbines inject negative-sequence current or not. Adaptive virtual negative-sequence output admittance controller is incorporated into the STATCOM controller and wind turbine controller, which can provide the negative-sequence current reference according to their participation factor. The compensation efforts of STATCOM and wind turbines can be flexibly controlled by changing their participation factor, which is related to the voltage unbalance voltage reference and the remaining capacity. The disclosure has significant advantages in cost and effectiveness to suppress the unbalanced voltage of PCC and improve the wind farm Low voltage fault recovery capability.

Systems and methods for supplying power (both active and reactive) at a medium voltage from a DCSTATCOM to an IT load without using a transformer are disclosed. The DCSTATCOM includes an energy storage device, a two-stage DC-DC converter, and a multi-level inverter, each of which are electrically coupled to a common negative bus. The DC-DC converter may include two stages in a bidirectional configuration. One stage of the DC-DC converter uses a flying capacitor topology. The voltages across the capacitors of the flying capacitor topology are balanced and switching losses are minimized by fixed duty cycle operation. The DC-DC converter generates a high DC voltage from a low or high voltage energy storage device such as batteries and/or ultra-capacitors. The multi-level, neutral point, diode-clamped inverter converts the high DC voltage into a medium AC voltage using a space vector pulse width modulation (SVPWM) technique.

In prior art grid systems, power-line control is done by substation based large systems that use high-voltage (HV) circuits to get injectable impedance waveforms that can create oscillations on the HV power lines. Intelligent impedance injection modules (IIMs) are currently being proposed for interactive power line control and line balancing. These IIMs distributed over the high-voltage lines or installed on mobile platforms and connected to the HV power lines locally generate and inject waveforms in an intelligent fashion to provide interactive response capability to commands from utility for power line control. These IIMs typically comprise a plurality of impedance-injection units (IIUs) that are transformer-less flexible alternating current transmission systems interconnected in a series-parallel connection and output pulses that are additive and time synchronized to generate appropriate waveforms that when injected into HV transmission lines are able to accomplish the desired response and provide interactive power flow control.

A hierarchical control method for an island power grid energy storage system for increasing new energy generation fluctuation is disclosed. The method includes implementing a rolling dispatch method based on an idea of model predictive control; comprehensively considering a response capability of the energy storage system to grid-wide economic dispatch instructions and life loss of energy storage lithium batteries, and constructing an objective function of an intraday control model of the energy storage system with economic optimization; and constructing, on a basis of satisfying the objective function of the intraday control model, a real-time control model of the energy storage system and solving the model, and determining charge and discharge plans of a lithium battery energy storage system and a supercapacitor energy storage system.

An uninterruptible power supply (UPS) system operable in an energy saver mode includes: a static bypass switch connected between an input connector and an output connector of the UPS system and being activatable to operate the UPS system in the energy saver mode; a plurality power modules, each of the plurality of power modules being connected between the input connector and the output connector of the UPS system and at least some of the plurality of power modules being controllable for a reactive power compensation; and a controller for controlling one or more of the controllable power modules depending on a data input related to a reactive power compensation. The controller controls one or more of the controllable power modules depending on the data input such that a reactive power flow via the UPS system is adjusted.

A device for controlling a load flow in an alternating-voltage network includes first and second modular series connections of double-pole switching modules interconnected in a parallel circuit to be inserted in series into a phase line of the alternating-voltage network. At least one switching module of each connection has an energy store and semiconductor switches to be switched on and off. The semiconductor switches can be controlled in such a way that a switching module voltage can be generated at terminals of the switching module. The switching module voltage corresponds to a positive or negative storage voltage or a zero voltage. A control apparatus for controlling the switching modules is configured to generate an equalizing current between the modular series connections. A method for controlling a load flow by using the device is also provided.

A power quality compensator device and a control method thereof are provided. The power quality compensator device is electrically connected to a power grid and a nonlinear load, and includes a current controller, a converter, a ripple predictor, a processing unit and a voltage controller. The current controller is configured to receive an instruction current and output a switch control signal. The converter is configured to output an output current and an actual DC bus voltage according to the switch control signal. The ripple predictor is configured to receive an intermediate voltage and a first current and output a predicted ripple voltage. The processing unit is configured to output a processing result according to the actual DC bus voltage, the predicted ripple voltage and a reference DC bus voltage. The voltage controller is configured to receive the processing result and output a voltage control signal to the current controller.

A battery energy storage system is provided with: a charging/discharging control device capable of controlling charging/discharging of each of a plurality of electricity storage units in accordance with the supply and demand state of a power system; and a management device for adjusting the progression of deterioration of each of the electricity storage units by differentiating the charging/discharging amount of each of the electricity storage units and managing by differentiating the electricity storage units having a low degree of progression of deterioration from the electricity storage units having a high degree of progression deterioration.