1007 results about "Voltage sag" patented technology

A power electronics interface in a microsource controller allows efficient connection in a power system of small, low cost and reliable distributed generators such as microturbines, fuel cells and photovoltaic. Power electronics provide the control and flexibility to insure stable operation for large numbers of distributed generators. The power electronics controls are designed to insure that new generators can be added to the system without modification of existing equipment. A collection of sources and loads can connect to or isolate from the utility grid in a rapid and seamless fashion, each inverter can respond effectively to load changes without requiring data from other sources, and voltage sag and system imbalances can be corrected.

A wind turbine 36 has a back-to-back AC/DC/AC power electronic converter chain in which the grid side converter 48 is connected in series with DFIG stator windings 64.

The machine side converter 56 is fed from the rotor windings 54 of the DFIG 44.

Series connection of the grid side converter 48 enables voltage sag ride-through capability via control of the stator flux.

In the event of a grid voltage sag, the series converter allows for a controlled response in the stator flux and electromagnetic shaft torque, protects the machine side converter and enables continued power delivery to the grid.

The method of the invention in one aspect involves electronic power control by varying the amplitude of an electrical power supply voltage, independent of frequency, whereby the output frequency will always be the same as the input frequency. An electrical circuit apparatus for accomplishing this function in a specific embodiment is also disclosed herein. The specific circuitry of this aspect of the invention uses eight solid state switches, such as IGBT's, eight diodes, an inductor, input and output filters and novel controlling circuitry. The controller apparatus and methods of the invention may be used to implement all otherwise conventional converter types, buck, boost, and inverting (and duals of these) versions to obtain different regulating characteristics, including galvanic isolation of the output from the input. Indeed, the eight-switch controller can act to either buck or boost the input voltage, and can switch between bucking and boosting during a cycle, thus providing more control of the regulated output voltage. The inventive methods and devices may be used in power factor correction, voltage and/or current harmonic filtering and neutralization, line and load conditioning, control of power transfer between two power grids, and programmable control of surges, sags, dropouts and most other voltage regulation problems.

The method of the invention in one aspect involves electronic power control by varying the amplitude of an electrical power supply voltage, independent of frequency, whereby the output frequency will always be the same as the input frequency. An electrical circuit apparatus for accomplishing this function in a preferred embodiment is also disclosed herein. The preferred circuitry of this aspect of the invention uses four solid state switches, such as IGBT's, four diodes, an inductor, input and output filters and novel controlling circuitry. The controller apparatus and methods of the invention may be used to implement all otherwise conventional converter types, buck, boost, and inverting (and duals of these) versions to obtain different regulating characteristics, including galvanic isolation of the output from the input. The inventive methods and devices may be used in power factor correction, voltage and/or current harmonic filtering and neutralization, line and load conditioning, control of power transfer between two power grids, and programmable control of surges, sags, dropouts and most other voltage regulation problems.

The invention discloses a hybrid energy-storage DC micro grid hierarchical control method. The DC micro grid comprises a photovoltaic power generation unit, a hybrid energy storage unit, a load unit, a networking interface unit and a DC bus, wherein each unit is connected with the DC bus respectively. By adopting the hierarchical control method, a system control layer and a current converter control layer are used for controlling the DC micro grid, the system control layer acquires networking operation mode parameters, DC bus voltage and a battery charge state to judge the current operation mode of the DC micro grid, a control mode of each unit of the DC micro grid is given, and a control instruction is sent to the current converter control layer. Each current converter can adjust the self control mode according to a different DC micro grid operation state, network voltage stability and power balance can be maintained effectively, and relative to master-slave control, excessive dependence on the master current converter is reduced; relative to a multi-agent control mode, communication is simpler; and relative to a voltage sag control mode, the network voltage is more stable and controllable.

The invention relates to a method for the intelligent analysis of transient power quality disturbance based on networking, which comprises the following steps of: combining disturbance signals of a plurality of monitoring points in an electric network, and performing disturbance detection to determine the starting time and the ending time of the transient power quality disturbance by using form non-sampling wavelet analysis; performing disturbance identification to perform feature extraction and encoding on power quality disturbance signals by combining window Fourier transform and S transform, and comparing the features of the power quality disturbance signals with a binary threshold matrix to identify the type of the disturbance; and during disturbance positioning, switching disturbance to a capacitor, taking the disturbance energy and the power spectrum of the disturbance signals as characteristics, combining a support vector machine to determine the switching position of the capacitor, and for voltage sag disturbance, judging the change polarity of current components at the time of voltage sag to position the relative position of a disturbance source so as to position the disturbance source. The method uses transient signals of a plurality of the monitoring points in the electric network, provides a comprehensive intelligent analysis result of the transient power quality disturbance, and can provide comprehensive and accurate data support for evaluating and controlling the problems of the transient power quality disturbance.

In a chiller system, an electronic control transformer is powered by the DC link of a variable speed drive that drives a compressor motor. The electronic control transformer converts the DC voltage to a constant 120 VAC at 60 Hz, for providing power to auxiliary electrical devices associated with the chiller system. The electronic transformer includes four semiconductor switches to convert the DC voltage to AC. The energy stored in the compressor motor is transferred to the DC link of the VSD during an input voltage sag. The electronic control transformer maintains the control voltage and prevents the system auxiliary loads from dropping out during a voltage sag. The chiller system is able to ride through the input voltage sag or interruption. A boost converter may be provided at the input of the VSD to increase ride through capability.

The invention relates to a movable low-voltage ride-through testing device for a wind generating set. The device is connected between a tested wind generating set and an electric network in series, uses an impedance voltage-dividing type and a vehicle container structure, and tests the low-voltage ride-through performance of the wind generating set through analog voltage sag fault; a main connecting wire of the device consists of a serial reactor group, a parallel reactor group and a circuit breaker; the serial reactor group and the parallel reactor group both consist of at least one adjustable reactor; the impedance voltage-dividing ratio can be changed by regulating the impedance value of each adjustable reactor and/or the connecting manner of each adjustable reactor so as to change the voltage sag depth of testing points; and once recovery or a step recovery of the voltage sag can be implemented according to the system requirements. The device can complete the low-voltage ride-through testing experiments for various wind generating sets having a maximum rated capacity of 6 MW, and meet the requirements to the low-voltage ride-through testing experiment in wind electric network integrations in states in Europe and America and Technical Rule for Connecting Wind Farm to Power Networks.

A sag corrector apparatus for providing voltages temporarily (ride-through) to a load during momentary electrical disturbances in the power supply line. In one embodiment, the disclosed apparatus compensates for voltage sags by using a variable duty cycle boost converter to boost the sagged line voltage to resemble desired voltage levels during occurrence of voltage sags. The boosted voltage available to a connected load during a sag depends on a sequence of operation of various control pulses. Duty cycle of the boost converter is controlled by changing the width (duration) of the control pulses. To prevent voltage shoot-throughs from over-boosting, an energy clamp circuit is provided to dissipate excess energy. Embodiments of the sag corrector circuit can be additionally integrated with power protection functions.

The high temperature secondary battery based energy storage and power compensation system is so formed that electric power supply system, electric load, and electric energy storage system including a high temperature secondary battery and a power conversion system, are electrically connected with one another. When operating normally, electric power is supplied from the electric power supply system to the electric load, while the electric energy storage system operates to effect peak shaving running and load leveling running. A high speed switch is provided between the electric power supply system and the electric energy storage system, so that when a voltage sag or a service interruption occurs while the electric power is being supplied from the electric power supply system, the voltage sag is immediately detected and the circuit is immediately shut off, an electric power is immediately supplied from the electric energy storage system to the electric load so as to compensate for the voltage sag or the service interruption.

The invention discloses a transient power quality detection device and a method for the same, belonging to the technical field of power transmission and distribution. The method comprises the following steps of: acquiring an undisturbed standard signal, processing the undisturbed standard signal with an improved S transformation method to get a base matrix of the undisturbed standard signal; acquiring voltage sag, voltage swell, voltage interruption, high-frequency transient disturbing signals and low-frequency disturbing signals, scaling a curve chart of the signals after being processed by the improved S transformation, building a standard template, and storing the template in a database; acquiring three-phase voltage and three-phase current data in a power grid; and matching the digital image curve with the standard template in the database according to a digital image matching principle so as to get the disturbance patterns. The invention provides the transient power quality detection device and the method for the same based on the improved S method, optimal design is provided in the aspects of detection accuracy, function implementation, data storage and the like of the device, so that real-time analytical ability and remote communication capability of transient power quality detection are improved.

A battery charging apparatus comprises an inductive charging platform including a charging surface on which an electrical device to be charged is to be placed, and a first winding for generating lines of magnetic flux generally perpendicular to the charging surface. To compensate for voltage sag caused by a reduction in the flux generated by the first winding, a second winding is located within an area defined by the first winding for generating an auxiliary magnetic flux generally perpendicular to the charging surface.

Systems and methods are provided for pre-charging the DC bus on a motor drive. Pre-charging techniques involve pre-charge circuitry including a manual switch, an automatic switch, and pre-charge control circuitry to switch the automatic switch between pre-charge and pre-charge bypass modes in response to an initialized pre-charge operation, input voltage sags, and so forth. In some embodiments, the pre-charge operation may be initialized by switching the manual switch closed. In some embodiments, the pre-charge operation may also be initialized by a detected voltage sag on the DC bus. The pre-charge circuitry may also be configured to disconnect to isolate a motor drive from the common DC bus under certain fault conditions.

Dual feed power supply system provides high reliability of a dual utility feed, with minimal interruptions in power supplied to critical loads during switching, and compensation for voltage sags occurring on the primary power feed. AC input buses are connected through a transfer switching apparatus to phase lines of a distribution bus. The transfer switching apparatus has a first input terminal connected to one of the phase lines of the first input bus and a second input terminal connected to one of the phase lines of the second input bus, and an output terminal connected to one of the phase lines of the distribution bus. Input switches allow switching from one or the other of the AC input buses to the distribution bus, with a fast transfer switch used to interrupt the supply of power from the input buses to the distribution bus during switching of the input switches.

The invention relates to a voltage sag detection method. The method comprises the following steps: (1) when a voltage sag fault is caused, the system three-phase voltage containing positive-sequence component, negative-sequence component and fifth harmonic component is sent in a dq coordinate transformation module; (2) after coordinate transformation, the positive-sequence component is DC component, the negative-sequence component is 100Hz component, the fifth harmonic component is 300Hz component, the 100Hz component and 300Hz component are filtered by an equivalence filter network to obtain the DC components of the d axis and the q axis, the sum of squares of the two DC components is calculated, then the root-mean-square value is calculated, finally system positive-sequence voltage amplitude is obtained; and (3) 90% of rated voltage amplitude is selected to be the threshold value of voltage sag, the system positive-sequence voltage amplitude is compared with the threshold value, when the positive-sequence voltage amplitude is less than the threshold value, voltage sag occurs; and when the positive-sequence voltage amplitude is more than or equal to the threshold value, the voltage sag does not occur. The invention adopts the equivalence filter network to solve the harmonic enlargement problem. The invention can be widely used for the voltage fault detection of various power systems.

The invention discloses a super-capacitor-based DC voltage sag suppression device and a super-capacitor-based DC voltage sag suppression method thereof, which belong to the technical field of power equipment. The device consists of a super capacitor array (CS), a Buck/Boost type bidirectional power conversion circuit and a contactor (KD). When a voltage sag suppressor is powered on and run, the super capacitor array (CS) is charged by the Buck/Boost type bidirectional power conversion circuit; and when a DC bus has voltage sag due to a failure of an AC system, the super capacitor array (CS) provides energy to realize boosting by the Buck-Boost type bidirectional power conversion circuit to support the voltage of the DC bus. The invention has the characteristics of simple structure, high reliability, low loss, long service life, no maintenance, no environmental pollutions and the like.