2323results about "Ac-ac conversion" patented technology

A grid-connected power system includes a primary power source, a back-up power source, a DC/AC inverter and a DC/DC converter. Direct current from the primary power source is supplied to the DC/AC inverter to obtain an alternating current output supplied to a utility grid when power from the utility grid is available to power a load. The output of the inverter is supplied to a selected portion of the load when power from the utility grid is unavailable to the load. Direct current from the back-up power source is supplied to the inverter through a DC/DC converter when power from the utility grid is unavailable to the load. The DC/DC converter converts the voltage of direct current from the back-up power source to direct current having a voltage compatible with the voltage of the primary power source and the inverter. The back-up power source may be charged by the primary power source or by the utility grid. Methods of providing back-up power include converting the voltage of direct current from a back-up power source to direct current of converted voltage and supplying the direct current of converted voltage to a DC/AC inverter.

A soft-switched single-phase quasi-single-stage (QSS) bi-directional inverter/charger converts AC-DC or DC-AC. The inverter/charger comprises a push-pull inverter/rectifier on the dc-side, an isolation transformer which provides ohmic isolation and voltage scaling, two full-bridges on the ac side in cascade, a voltage clamp branch comprising a capacitive energy storage element in series with an active switch with its anti-parallel diode, a passive filter at the ac side to smooth out the high frequency switching voltage ripple at the output, and a corresponding PWM scheme to seamlessly control the converter to operate in all four quadrant operation modes in the output voltage and output current plane, and is capable of converting power in both directions.

A galvanic isolated DC-DC and DC-AC power conversion system is coupled to a plurality of DC sources which are derived from a combination of a plurality of single-phase and three-phase AC-DC converters. The DC-DC and DC-AC power conversion system in one embodiment is configured to provide mixed type outputs (mixed frequency, e.g. DC with 50 or 60 Hz, with 400 Hz; mixed voltage levels).

A power converter system for supplying an output voltage is provided. The power converter system is adapted to operate in a normal mode and a fault mode. The system comprises a plurality of bridges and a plurality of transformers. The system further comprises a plurality of dc link capacitors, each coupled across a corresponding bridge. The system also includes a controller adapted for, during the normal mode, switching each bridge with a respective normal phase shift. During the fault mode, the controller is adapted for switching each of the remaining ones of the bridges with a respective adjusted phase shift to generate the output voltage. During the fault mode, at least one of the plurality of bridges is bypassed.

Apparatus and methods for regulating delivery of electrical energy to a lighting load are disclosed. An electrical waveform is received from a source of electrical energy. An integration value is generated based on a square of an amplitude of the received waveform. Electrical energy is delivered to the load until the integration value exceeds a threshold value. Thereafter, the delivery of electrical energy to the load is discontinued.

A variable speed wind turbine is disclosed comprising a turbine rotor that drives a doubly-fed induction generator, a matrix converter which converts variable frequency output into constant frequency output, and a control unit and a protection circuit for the matrix converter. Power is circulated in the system allowing for sensorless detection of rotor position and better output ratios of power from the system.

The invention in the simplest form is an improved variable speed engine/generator set with an integrated power conditioning system and control method, used to generate high quality AC power with optimum fuel efficiency and reduced emissions. The variable speed generator control scheme allows for load adaptive speed control of engine and generator field. The transformerless power inverter topology and control method provides the necessary output frequency, voltage and/or current waveform regulation, harmonic distortion rejection, and provides for single phase, or unbalanced loading.

The invention is directed to controlling an electric motor by means of a frequency converter. The frequency converter can be connected to one of several different mains voltages. According to the present invention, the maximum output power of the frequency converter, is limited when the actual mains voltage is lower than the maximum nominal mains voltage, for which the frequency converter is designed, and during the limitation the frequency converter controls the speed of the motor within a power range up to a limited maximum output power. This gives a genuine multi-voltage unit, which can be connected to a wide range of mains voltages.

The use of low permeability magnetic material (NSME) with the disclosed design strategies form a two-stage isolated output converter system with the distinct advantages of superior density, efficiency, thermal operating bandwidth, service life, transient survival, and form factor flexibility over the prior art. These improvements are realized by, optimized application of NSME, efficient rectifying flyback management techniques, inclusion of switching buffers that substantially reduce switching losses. The instant invention provides power factor correction, output regulation, inrush limiting, over voltage, over current, over temperature, and transient protection, multi-converter load sharing, hot swapability, and fault signals.

The disclosed system is designed, specified, and certified to function from −40 deg. C. to +65 deg. C. from a 180 vac to 264 vac 50/60 Hz input line and supports 1000 watts of output or 600 watts from 90 vac to 120 vac 50/60 Hz line input at greater then 0.95 power factor and features a packaged power density of 14 watts per cu. in. at high line.

A wind powered turbine with low voltage ride-through capability. An inverter is connected to the output of a turbine generator. The generator output is conditioned by the inverter resulting in an output voltage and current at a frequency and phase angle appropriate for transmission to a three-phase utility grid. A frequency and phase angle sensor is connected to the utility grid operative during a fault on the grid. A control system is connected to the sensor and to the inverter. The control system output is a current command signal enabling the inverter to put out a current waveform, which is of the same phase and frequency as detected by the sensor. The control system synthesizes current waveform templates for all three-phases based on a sensed voltage on one phase and transmits currents to all three-phases of the electrical system based on the synthesized current waveforms.

An inductive power transfer system (10) for roadways includes at least one drive unit arrangement (50) coupled to at least one drive coil arrangement (40) disposed along a roadway (20) for generating a magnetic field extending upwardly from the roadway (20), and at least one vehicle (30) including a corresponding pickup coil arrangement (60) coupled to a power conditioning circuit arrangement (80, 200) for receiving the extending magnetic field for providing power to operate the at least one vehicle (30). The at least one drive unit arrangement (50) is operable to excite, for example at resonance, the at least one drive coil arrangement (40) at a fundamental frequency (f₀) of at least 30 kHz, preferably at least 50 kHz, more preferably at least 100 kHz, and most preferably at least 140 kHz. The at least one drive coil arrangement (40) is implemented to be substantially devoid of ferromagnetic components for providing a path for the extending magnetic field. Optionally, the at least one drive unit arrangement (50) is operable to employ a balanced class-E amplifier arrangement for exciting the at least one drive coil arrangement (40) at the fundamental frequency (f₀). Optionally, the at least one drive unit arrangement (50) is operable to employ one or more Silicon Carbide semiconductor devices for switching the currents provided to the corresponding at least one drive coil arrangement (40). Optionally, there is further included a passive and/or active suppression arrangement (100, 110, 120, 130, 140) for suppressing harmonic magnetic field components generated by the system (10) at multiples of the fundamental frequency (f₀) when in operation.

An AC/DC/AC power converter is constructed without using any electrolytic capacitor, such that it is more compact, durable and reliable. This converter only required a small capacitance for its DC link and this capacitor can be easily obtainable with other types of capacitors such as film or ceramic type. The system further includes means to disconnect both input and output to this DC bus capacitor. A controller capable of fast monitoring the DC bus voltage is also able of quickly disconnecting the capacitor out of either input or output energy path to prevent the capacitor from being charged to over-voltage. The controller also possesses capability of re-connecting the disrupted energy path once the DC bus voltage returns to normal.

Disclosed herein is a capacitor mounting type inverter unit having a cooling block, an inverter including a plurality of phases of switching circuits provided on the cooling block, and a smoothing capacitor. The inverter unit includes a cover having a first recess for accommodating the inverter and a second recess for accommodating the smoothing capacitor. The second recess has a depth larger than that of the first recess. The second recess is filled with resin in the condition where the smoothing capacitor is accommodated in the second recess.

An ac/ac converter for accepting a pulsating dc input with encoded sinusoidal modulation and providing a multiphase modulated output. The converter comprises a bridge including a plurality of switches having switch legs for modulating the pulsating dc input at a carrier frequency over a plurality of phases. The bridge is coupled at one end to a pulsating dc source and coupled at another end to a modulated signal output. A controller is provided for the plurality of switches for causing, for each of the plurality of phases, under unity power factor, one of the switch legs to modulate the pulsating dc input at the carrier frequency while the other switch legs do not modulate the pulsating dc input at the carrier frequency.

The present invention is directed to Bidirectional Multimode Power Converter which employs a high frequency dynamically varying amplitude modulation and voltage steering method to convert the source AC or DC voltages to output AC or DC voltages, with programmable output voltage levels, output voltage frequency and duration. The inrush current control, turning off the idle converter, line voltage brown out protection, soft start, high pre-charge voltage generation, soft shut down of converter, dimming operation modes are inherent characteristics of the Bidirectional Multimode power converter. The Bidirectional Multimode Power Converters of the present invention facilitates bidirectional conversion and coupling multiple bidirectional sources and or loads.

The Bidirectional Multimode Power Converter of the present invention supports local and remote control for changing operational characteristics of the converter on demand or on a programmed time of the day for a specified duration of time.

Methods and apparatus are provided for protecting a motor control circuit in a permanent magnet electric motor system. The permanent magnet electric motor system includes a permanent magnet electric motor having a predetermined number of windings corresponding to the phases of the permanent magnet electric motor and a direct current (DC) bus coupled to a power source for providing operational power for the electric motor system. A motor control circuit is connected to the DC bus for receiving the operational power therefrom and is connected to the windings of the permanent magnet electric motor for controlling the permanent magnet electric motor. A protection circuit is connected to the DC bus for receiving the voltage therefrom for operation of the protection circuit and for detecting predetermined motor control circuit fault conditions from voltage sensed on the DC bus and in response thereto providing protection for the motor control circuit.

The functionality of electronic convertors for low voltage filament lamp applications, such as halogen lamps, can be increased by including auxiliary circuits. Such auxiliary circuits may include gate drive resistors; a charge pump for sustaining the DC supply; open circuit protection; short circuit protection; thermal protection; extended resetting time; latched shutdown; self-dimming; a digital (DALI) interface; and line voltage compensation.

In the inverter device of the invention, when a power source connected to an electrolytic capacitor 5 is interrupted, a switching control circuit 6a controls switching elements of an inverter main circuit 7a to operate to supply a current to a load, thereby discharging charges of the electrolytic capacitor 5, and an electrolytic capacitor electrostatic capacitance calculator 10a calculates the electrostatic capacitance of the electrolytic capacitor, on the basis of: a discharged charge amount which is obtained from an outflow current Ic from the electrolytic capacitor 5, and a discharge time; and a discharge voltage ΔV which is a voltage drop from beginning of discharging of the electrolytic capacitor 5.

An improved power converter that produces reduced-levels of common-mode voltages, or even entirely eliminates such voltages, is disclosed herein, along with a method of reducing common-mode voltages. In at least some embodiments, the improved power converter is equipped with common-mode filter inductors and a link coupling input and output ports of the power converter with one another to communicate a ground point associated with the input ports of the converter (and the source) to the load. Further, in at least some embodiments, the method includes providing common mode filter inductors as part of the converter, where the inductors are connected at least indirectly to at least one of a rectifier and an inverter of the converter, and communicating a grounded neutral from input ports of the converter to output ports of the converter by way of at least one additional linkage.

The invention relates to a method of controlling a wind turbine connected to an electric utility grid during malfunction in said electric utility grid (9). The method comprises the steps of detecting a malfunction in said electric utility grid and operating at least two control units of said power converter (12) in relation to at least one power converter limit value. The invention also relates to a control system for a wind turbine connected to a utility grid and a wind turbine.

The drive for an a.c. induction motor features a rectifier for converting alternating current into direct current and a current source inverter for converting direct current into alternating current supplied to a motor. A d.c. link choke interconnects the rectifier and the inverter. The inverter includes a first control loop which provides a desired or command d.c. link choke current to a second control loop responsible for the rectifier. For the purposes of the second control loop the actual d.c. link choke current and an input voltage of the inverter are detected. The difference or error between the desired and actual d.c. choke currents are minimized by a compensator. The output of the compensator is added to the detected inverter input voltage, and the sum is fed to a switching pattern generator which controls the switches in the rectifier. In this manner the feedback of the inverter input voltage is decoupled from the compensator responsible for the d.c. link choke current. This makes the parameters of the second control loop substantially independent of the load, thereby enhancing the ease with which the control loop may be tuned and hence the stability of the drive.

A system and method for single phase AC power conversion for delivery to a load of AC voltage less than or equal to the supply voltage. The system includes a high frequency chopper converter having a series diode-switch assembly and a shunt diode-switch assembly. During intervals when the inductor carries current in phase with the power line, the diode-switch assemblies are configured such that the system operates as a buck converter, and during intervals when the inductor carries current out of phase with the power line, and power flow is reversed, the diode-switch assemblies are configured such that the system operates as a boost converter, boosting the load voltage to the power line voltage. Optionally, feedback is used to adjust the duty cycles of the diode-switch assemblies to shape the input and/or output current and to optimize performance of the load.

According to one aspect, embodiments of the invention provide power converter circuitry including an input including a plurality of input lines each configured to be coupled to a phase of a multiphase AC power source having a sinusoidal waveform, a plurality of DC buses including a first positive DC bus having a first nominal DC voltage, a second positive DC bus having a second nominal DC voltage, a first negative DC bus having a third nominal DC voltage and a second negative DC bus having a fourth nominal DC voltage; a first power converter coupled to the input and configured to supply power from the multiphase AC power source to the plurality of DC buses during a first positive region of the sinusoidal waveform and a first negative region of the sinusoidal waveform; and a second power converter coupled to the input and configured to supply power from the multiphase AC power source to at least some of the plurality of DC buses during a second positive region of the sinusoidal waveform and a second negative region of the sinusoidal waveform.

A cross current control system for multiple, parallel-coupled power converters includes common mode chokes, local cross current feedback controllers, and local converter controllers. Each common mode choke is coupled to a respective power converter. Each local cross current feedback controller is configured for receiving common mode cross currents from a respective local cross current detector, calculating a resultant cross current, and generating a local feedback control signal. Each local converter controller is configured for using a respective local feedback control signal to drive the respective power converter in accordance with a coordinated switching pattern. An integral choke assembly includes a common mode choke and a differential mode choke with common and differential mode choke cores configured with at least one magnetic flux path being shared by magnetic flux generated by common mode coils and differential mode coils.

A system and method are provided to isolate outputs of parallel converter threads of a power system converter of a wind turbine generator by utilizing isolated power windings on the output transformer from the converter. Such isolation eliminates the circulating common mode current between the parallel converters of the wind turbine system and eliminates the need for a common mode inductor. System reliability is enhanced and total system cost is reduced.

A method and system of power factor optimization and total harmonic distortion are provided under the premise of efficient power management and distribution on an electrical grid. The method and system include a novel optimization technique based on a novel current profiling methodology enabling real-time power management with power factor correction as a function of the optimization. The optimization can be performed under dynamic current constraints. When deployed on an electrical grid, the method and system can provide a new technique for power management targeting an efficiency of the electrical grid. The method and system can thus provide for reduced costs of energy production and reduced carbon emissions into the atmosphere.

The invention discloses a control circuit for a voltage dropping type power factor corrector, which is used for controlling a voltage dropping converter to realize the power factor correction function. Inductance current critical intermittent control of changed on-time is performed on a Buck circuit through the control circuit to ensure that the on-time of a switching tube rises in the power frequency period along with increase of input voltage; and the critical intermittent working mode of inductance current in the Buck circuit is controlled, and when the inductance current is greater than zero, the junction capacitance of the switching tube and inductance are resonated, and the switching tube is connected when the voltage resonance of the junction capacitance reaches the volley bottom. The control circuit for the voltage dropping type power factor corrector has the characteristics of ensuring high power factors in the whole input voltage range, and meeting the harmonic requirements of IEC 61000-3-2 Class C, Class D, along with high efficiency.

A system and method are provided for variable speed operation of a screw compressor to obtain increased capacity and efficiency. The screw compressor is connected to an induction motor driven by a variable speed drive, wherein the screw compressor has a variable output capacity that is dependent on the output speed of the motor. To obtain increased capacity and efficiency, the screw compressor is operated at a speed greater than the screw compressor's rated speed and does not include a slide valve. The maximum operating speed of the screw compressor, which speed is greater than the rated speed, is related to the maximum operating speed of the motor when operated at a voltage and frequency provided by the variable speed drive that is greater than the motor's rated voltage and frequency in a constant flux or constant volts/Hz mode.

A power supply connectable to a source of AC line voltage for AC electric arc welding by an AC arc current across a welding gap between an electrode and a workpiece, the power supply comprises a high capacity transformer that converts said line voltage to an AC output voltage, and a rectifier that converts the AC output voltage to a DC voltage between a positive terminal and a common terminal at generally zero volts and a negative terminal and the common terminal. The power supply has a first switch that connects the positive terminal to the common terminal across the gap when a gate signal is applied to the first switch, a second switch for connecting the negative terminal to the common terminal across the gap when a gate signal is applied to the second switch and a pulse width modulator operated for generating pulses at a frequency of at least about 18 kHz. A logic network has a first circuit for directing the pulses to the first switch for a first time, a second circuit for directing the pulses to the second switch for a second time and a controller to alternately operate first and second circuits to create AC arc welding current.

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.