1442results about "Active power filtering" patented technology

The present invention provides a method, computer program product, and apparatus and control system and method for providing substantially uninterrupted power to a load. The apparatus includes a control system coupled with an electrical power storage subsystem and a electrical power generator. The control system is configured to provide a plurality of modes of operation including at least a static compensator (STATCOM) mode, an uninterruptible power supply (UPS) mode and a generator mode (gen set), and to control transitions between each of the plurality of modes. In one embodiment, the control system is an integrated closed loop control system that includes a current control system and a voltage control system. The apparatus is capable of operating at least two of the plurality of modes simultaneously, including ramping the gen set mode up and simultaneously ramping the UPS mode down as the gen set mode is ramped down.

The invention provides a method and system for operating a solar farm inverter as a Flexible AC Transmission System (FACTS) device—a STATCOM—for voltage control. The solar farm inverter can provide voltage regulation, damping enhancement, stability improvement and other benefits provided by FACTS devices. In one embodiment, the solar farm operating as a STATCOM at night is employed to increase the connectivity of neighbouring wind farms that produce peak power at night due to high winds, but are unable to connect due to voltage regulation issues. The present invention can also operate during the day because there remains inverter capacity after real power export by the solar farm. Additional auxiliary controllers are incorporated in the solar farm inverter to enhance damping and stability, and provide other benefits provided by FACTS devices.

A power conversion device connected with a three-phase power system through a transformer, including unit converters cascade-connected so that reactors are unnecessary, and volume and weight are reduced. The secondary winding of the transformer is an open winding having six terminals. A first converter group, includes a circuit which has three converter arms, which are star-connected, connected to three of the terminals of the secondary winding. A second converter group, having three different converter arms which are star-connected, is connected to three other terminals of the secondary winding. A neutral point (the point where the star connection is made) of the first converter group, and a neutral point of the second converter group are made to be the output terminals of the power conversion device.

The present invention comprises a controller for the cascade H-bridge three-phase multilevel converter used as a shunt active filter. Based on the proposed mathematical model, the controller is designed to compensate harmonic distortion and reactive power due to a nonlinear distorting load. Simultaneously, the controller guarantees regulation and balance of all capacitor voltages. The idea behind the controller is to allow distortion of the current reference during the transients to guarantee regulation and balance of the capacitors voltages. The controller provides the duty ratios for each H-bridge of the cascade multilevel converter.

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.

A method of balancing the voltage of DC links in a cascaded multi-level converter (CMC) semiconductor circuit, including the steps of providing a plurality of H-bridge converters per phase in the CMC circuit and utilizing a three phase duty cycle value from the main controller to determine a normalized duty cycle value, a ceiling duty cycle value and a floor duty cycle value. The normalized duty cycle value and an output current of the CMC is used to determine the direction and polarity of a capacitor current, and utilizing the capacitor current to determine a plurality of output capacitor voltages. A voltage summation result and direction is obtained from a ceiling index pointer and a floor index pointer and the voltage summation result, direction from the ceiling index pointer and a floor index pointer are used to create a combined switching table for the H-bridge converters. A pulse width modulator is utilized to balance the voltage of the DC links and thereby eliminate DC-capacitor voltage imbalance.

The invention discloses an energy-saving type cascade multilevel photovoltaic grid-connected generating control system comprising an energy-saving cascade multilevel photovoltaic generating inverter, a controller and a power grid, wherein the multilevel inverter consists of 3n energy-saving type photovoltaic generating modules, wherein n modules are connected in series into one phase of a three-phase inverter; and the single-stage power of each module is converted to realize the buck-boost, the inverting and energy saving and adapt to the wide-range change of the battery voltage with high reliability. 3n photovoltaic cells and energy-saving cells are distributed on 3n modules; the generation of each module is independently controlled, thereby realizing the distributed maximum power track, collecting solar energy to the maximum extent, realizing high efficiency and avoiding the problems of power loss and hot spot caused by the local shade generated when the photovoltaic cells are connected in series; and the invention can flexibly control the stable power of a feeder grid of the multilevel inverter and achieve the functions of reactive power consumption, the power pitch peak control and the like, has the advantage of multilevel inversion and low output harmonic voltage and is suitable for high-voltage, high-power and transformer-free grid connection.

A method of providing reactive power support is proposed. The method includes detecting at least one of a plurality of network parameters in a distributed solar power generation system. The generation system includes a plurality of photovoltaic modules coupled to a grid via inverters. The method further includes sensing a state of the photovoltaic modules coupled to the distributed solar power generation system and determining a reactive power measure based upon the sensed state and the detected network parameters. The reactive power measure is used to generate a reactive power command. The reactive power command is further used to compensate reactive power in the distributed solar power generation system.

A power conversion apparatus includes a current component control section which outputs q axis and d axis negative-sequence components and q axis and d axis positive-sequence components based on a detected current value or a voltage value, a current component control which compares a current component with the current instruction value from an instruction value generator and outputs to an adder/subtractor the result, a converter converting a control signal output from the adder/subtractor into three-phase components, and an adder adding these three-phase components to respective phases and outputting the result to a power conversion section.

An active filter (300) generates multi-phase compensating current in an AC power supply system (10) that supplies a load (200). The filter (300) includes a compensating current output device (34) outputting multi-phase compensating current to an AC power line (50); and a controller (310) for controlling the compensating current output (340) such that the multi-phase compensating current compensates for current harmonics and power factor on said AC power line (50). The controller (310) estimates current harmonics and power factor compensating values as a function of multi-phase power measurements.

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

A method is provided for determining a control scheme for a neutral point clamped (NPC) voltage source converter (VSC) with at least 3 levels and a topology of three bridge legs between each of three phases of a grid and a neutral point. Each leg includes at least four active switches, and a clamping carrier modulator synchronized with the grid is provided for the control of no-switching intervals. The method includes: analyzing the waveform of the grid and/or a load voltage and determining windows defining an allowed period for no-switching of the corresponding bridge leg; operating or simulating the operation of the voltage source converter with different clamping carrier modulator frequencies, and then analyzing the balance in the operating junction temperatures and/or power losses across the active switches and also analyzing the total losses of the voltage source converter; comparing the balance and the total losses of different clamping carrier modulator frequencies and selecting either the clamping carrier modulator frequency according to showing, as primary criterion, the better balance and, as secondary criterion, the lower total losses; operating or simulating the operation of the voltage source converter with the selected clamping carrier modulator frequency, while iteratively changing at least one of the following operating parameters of the voltage source converter: switching frequency, DC-link voltage reference, duty cycle of clamping carrier modulator, phase shift of the clamping carrier modulator relative to the grid, and optimizing the balance in the operating junction temperatures and/or power losses across the active switches and the total losses of the voltage source converter as a function of the adjustment of these operating parameters until reaching optimum operation parameters for the control scheme.

A voltage source converter having a plurality of cell modules connected in series, each cell module including a converter unit having an ac-side and a dc-side, and the voltage source converter includes a control unit adapted to control the converter units, where at least one of the cell modules includes a second redundant converter unit having an ac-side which is connected in parallel with the ac-side of the first converter unit and the control unit is configured to substantially synchronously control the first and the second converter units.

A wind mill apparatus for generating electric power to a grid point of an electric network. The apparatus includes a wind rotor, an electric generator operatively connected to the wind rotor, and an electric multiphase ac link operatively connecting the generator to the grid point. The ac link includes a first current path including a switchgear, a second current path including a dc link including a first converter operatively connected to the generator, a second converter operatively connected to the grid point, and a capacitor operatively connected between the conductors of the dc link. The ac link further includes a connectable multiphase dump load for blocking during a fault condition on the network the reactive power flow in the ac link, yet providing a reduced transfer of active power.

The present invention provides a power control circuit connectable to a load adapted to receive a power supply, the power control circuit adapted to absorb power from the power supply and adapted to deliver power to the power supply to stabilize at least one electrical parameter of the power supply. The present invention also provides an associated method of stabilizing at least one electrical parameter of a power supply connectable to a load, the method including absorbing power from the power supply or delivering power to the power supply. The at least one electrical parameter of the power supply includes parameters such as voltage and frequency.

Voltage source converter based on a chain-link cell topology including one or more phases, each of the phases having one or more series-connected chain-link cell modules connected to each other. The output voltage of the voltage source converter is controlled by control signals applied to the series-connected chain-link cell modules. In case of failure of a chain-link cell module, that module is controlled, by the control signals, such that zero output voltage is provided at its output voltage AC terminal.

A VAR dispatch system. A central control system connected to a network is configured to receive data reflecting local variations in conditions on a power grid and to transmit system control commands over the network. A plurality of VAR dispatch devices are connected to the network and to the power grid. Each VAR dispatch device is configured to detect local variations in conditions on the power grid and to transmit the data reflecting such local variations to the central control system and to receive control commands from the central control system. Each VAR dispatch device is configured to store power and to output stored power to the power grid based on local variations in conditions on the power grid. Each VAR dispatch device is further configured to output stored power to the power grid when the VAR dispatch device receives system control commands from the central control system.

The invention discloses a direct current de-icing device based on a full-bridge modular multilevel converter. The full-bridge modular multilevel converter has a three-phase bridge structure, each phase of the converter comprises an upper bridge arm and a lower bridge arm, the upper and lower bridge arms which are respectively formed by serially connecting N full-bridge power modules end to end, and the full-bridge power modules form a chain type multilevel structure, the front ends of the first power modules of the upper bridge arms of all phases are connected to form the positive pole of a public direct current bus; the tail ends of the Nth power modules of all lower bridge arms of all phases are connected to form the negative pole of the public direct current bus; the tail ends of the Nth power modules of all upper bridge arms are connected with the front ends of the first power modules of the respective lower bridge arms of the phases by smoothing reactors; and the center of the electric reactor serves as the alternating current bus of the phase. The device has high high-voltage direct current output capacity and the direct current voltage of the device can be regulated continuously from zero; on the other hand, the fully compatible chain type scalable vector graphics (SVG) topology can realize quick dynamic reactive regulation; and the device has the combined functions of direct current de-icing and alternating current dynamic reactive compensation.

A harmonic predictor for a wind farm comprising at least two wind turbines, each having a generator with a converter for generating electrical energy. The harmonic predictor determines the harmonic component expected from the wind farm in order to limit the harmonic component to a harmonic limit. The harmonic predictor comprises a calculation module, an iteration module and a summing module. The calculation module calculates a complex mean value over at least one period of the harmonic component of one of the wind turbines and determines a first equivalent vector therefrom. The iteration module successively connects the calculation module to at least one other of the wind turbines to form at least one second equivalent vector. The summing module sums the equivalent vectors to form a total vector and compares the total vector with the harmonic limit.