367 results about "Dc link voltage" patented technology

A method to convert direct current (DC) power generated by a photovoltaic (PV) arrays to alternating current (AC) power using a PV inverter, the method includes: applying the DC power generated the PV array to the PV inverter; boosting the DC power from the PV array from a predetermined voltage level to a predetermine DC link voltage, wherein the PV array is regulated by the boosting to output a voltage at the predetermined voltage level; converting the boosted DC power to AC power, and disabling the boost of the power generated by the PV array after the array has a predetermined voltage level at least as great as the DC link voltage.

A power inverter system includes a DC to AC inverter configured to convert DC voltage from a DC power source to AC voltage. A DC link couples the DC power source and the inverter. An inverter pre-charger operates to pre-charge the inverter to achieve a desired DC link voltage prior to connecting the power inverter system to an AC power grid. A phased lock loop synchronizes the pre-charged inverter to the AC power grid prior to connecting the power inverter system to the AC power grid. The pre-charged inverter regulates the DC link voltage to about the minimum voltage level that allows control of AC grid currents via the inverter subsequent to connecting the power inverter system to the AC grid. The inverter operates in a maximum power point tracking control mode only subsequent to a first voltage transient caused by connecting the DC power source to energize the power inverter system.

An adaptive gate drive for an inverter includes control circuitry having a Field Programmable Gate Array (FPGA) and includes power circuitry having a plurality of FETs for operating a switching device, such as a Trench Gate Insulated Gate Bipolar Transistor (IGBT device). The control circuitry provides switching signals for operating the switching device. In addition, the control circuitry receives signals of output current of the IGBT device, temperature of the IGBT device, and DC link voltage. The FPGA has a plurality of operating points stored therein. Each operating point has corresponding parameters for a control signal that is used to control the turn-on or turn-off behavior of the IGBT device. During operation, the control circuitry compares the measured current, voltage and temperature operating points stored in the FPGA and sends the corresponding parameters to the gate drive circuit. The gate drive modifies the signal on the gate of the IGBT accordingly and thereby optimizes the turn-on and/or turn-off behavior of the device based on actual operating conditions.

A control system for a multilevel converter includes a differential mode current regulator, a neutral point (NP) controller and a PWM controller for generating switching pulses for the multilevel converter. The differential mode current regulator generates reference voltage command signals based on a difference between reference current command signals and actual current command signals, and the NP controller determines a modified neutral point current signal in response to a DC link voltage unbalance. The NP controller utilizes the modified neutral point current signal to generate a common mode reference voltage signal. The switching pulses are generated by the PWM controller based on the reference voltage command signals and the common mode reference voltage signal.

A grid-connected power storage system for coupling a power generation system to a grid, including: a main battery for discharging stored power to the load system; at least one additional battery coupled to the main battery for discharging stored power to the load system; a bidirectional converter coupled to the main and additional batteries, and including a plurality of switches for performing a conversion between a DC link voltage, between the power generation system and the grid, and a battery voltage, a first switch of the plurality of switches corresponding to the main battery and a second switch of the plurality of switches corresponding to the additional battery, wherein the first and second switches are connected to each other in parallel; and an integrated controller for selectively controlling operations of the first switch and the second switch based on an amount of power used by the load system.

A single-stage electronic ballast device outputs a square wave current to drive an HID lamp, which includes a rectifying and power factor correction unit, a bridge converter and a controller circuit. The rectifying and power factor correction unit has an input connected to an AC power source to rectify an AC power to a DC power. The bridge converter comprises two bridge arms formed by four switches, load terminals defined by midpoints of the two bridge arms and the HID lamp is connected between the load terminals. The bridge converter converts DC current to square wave current to drive the HID lamp with power control. The load terminals are selectively connected to output of the rectifying and power factor correction unit to adjust waveform of input current for higher power factor. The controller circuit has output connected to DC link voltage terminal and load terminal of the bridge converter.

An AC-AC Converter for an AC source which in one embodiment has a first rectifier section rectifying the AC source into a first pulsed DC link voltage signal and a high frequency modulating section coupled to the first pulsed DC link voltage signal and producing a high frequency AC voltage signal. A high frequency transformer is coupled to the high frequency AC voltage signal producing a transformed high frequency AC signal. There is a second rectifier section coupled to the transformed high frequency AC signal and producing a second pulsed DC voltage signal and an unfolder section coupled to the second pulsed DC voltage signal and producing an output AC signal.

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 method of providing ride-through capability in a chiller/refrigeration system employs a variable speed drive with an active converter stage, a DC link stage and an inverter stage for providing variable frequency and voltage to power at least one motor. An induction motor is coupled to the output of the inverter stage for driving a compressor in the chiller/refrigeration system. The ride-through method comprises operating the active converter to regulate the DC link voltage of the DC link stage to a predetermined voltage level until the current through the active converter equals a predetermined current limit, then transferring regulation of the DC link to the inverter upon reaching the current limit of the converter. The compressor is unloaded, and the power flow through the inverter is reversed to maintain the voltage level of the DC link stage. Pre-rotation vanes, slide valve, or check valve are used to unload the compressor.

A method of providing ride-through capability in a chiller/refrigeration system employs a variable speed drive with an active converter stage, a DC link stage and an inverter stage for providing variable frequency and voltage to power at least one motor. An induction motor is coupled to the output of the inverter stage for driving a compressor in the chiller/refrigeration system. The ride-through method comprises operating the active converter to regulate the DC link voltage of the DC link stage to a predetermined voltage level until the current through the active converter equals a predetermined current limit, then transferring regulation of the DC link to the inverter upon reaching the current limit of the converter. The compressor is unloaded, and the power flow through the inverter is reversed to maintain the voltage level of the DC link stage.

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.

A control system and method for an electric machine includes a first calculation module that receives a modified torque command and a calculated stator flux command and that generates first and second current commands and first and second voltage commands. A voltage magnitude calculation module generates a voltage magnitude based the first and second voltage commands. A reference voltage calculator module generates a reference voltage based on a DC link voltage, an angular stator velocity and the first and second current commands. A flux weakening module generates the calculated flux command based on the angular stator velocity, the reference voltage and the voltage magnitude.

A method for powering a pitch motor drive system for at least one DC pitch motor of a wind turbine includes rectifying a voltage using a bridge circuit to thereby supply a DC link voltage to a bridge comprising active switching devices, and utilizing at least one link capacitor to smooth the DC link voltage and act as an energy sink and source for the DC pitch motor or motors.

The present invention relates to a method and a control system for driving a three-strand brushless, electronically commutated electric motor (2), wherein a line AC voltage (U_N) is rectified and fed via a slim DC link (8) with minimum DC link reactance as a DC link voltage (U_Z) to an inverter (10) that can be driven to supply and commutate the electric motor (2). A pulsating DC voltage (U_G) initially generated by rectifying the line AC voltage (U_N) is dynamically increased with respect to its instantaneous values by a step-up chopper (18) in such a manner that the resulting DC link voltage (U_Z) with a reduced ripple always lies above a defined limit voltage (U₁₈/U₁) over time. The control system consists of a network rectifier (6), a downstream slim DC link (8) with minimum DC link reactance and a controllable inverter (10) that can be supplied via the DC link and driven to commutate the electric motor (2). A step-up chopper (18) is integrated therein with a controller (20) designed in such a manner that, the pulsating DC voltage (U_G) rectified by the network rectifier (6) is dynamically increased with respect to its instantaneous values in such a manner that the resulting DC link voltage (U_Z) with a reduced ripple always lies above a defined limit voltage (U₂₀/U₁) over time. Stray inductances (Ls1-Ls3) of the motor winding heads present in the electric motor (2) are used as inductor (L) for the step-up chopper (18).

A system and method for detecting ground faults in an AC motor drive is disclosed. A fault detection and protection system for an AC motor drive includes current sensors to measure first and second phase output currents, a voltage sensor to measure a DC link voltage, and a desaturation control circuit to determine a voltage and associated current across PWM inverter switches for a third phase of the output. A controller compares the first and second phase currents, the measured DC link voltage, and the voltage across the PWM inverter switches on the third phase, to a plurality of thresholds. The controller detects a ground fault on one of the first, second, and third phases of the three phase output to the AC motor based on the comparisons of the first and the second phase currents, the DC link voltage, and the voltage across the switches to the thresholds.

An inverter control apparatus and a control method thereof are provided. The inverter control apparatus and a control method thereof stably operate a three-phase motor using a capacitor having a small capacitance for a DC link. The inverter control apparatus includes a current sensor to sense an output current of the inverter, a voltage sensor to sense a DC-link voltage of the inverter, and a controller to generate an average of a periodically varying rotor based q-axis current boundary value based on the output current and the DC-link voltage to generate a current reference on the basis of the average of the rotor based q-axis current boundary value, and to drive a three-phase motor based on the current reference. Stabilized variable speed control of a motor by using a small-capacitance capacitor for a DC link of an inverter is performed and reliability of an inverter circuit improved.

The present invention provides an electronic ballast for a high intensity discharge lamp such as a metal halide lamp. The ballast includes an inverter and a resonant circuit with an ignition capacitor between the resonant circuit and the lamp. The ignition capacitor serves to provide the necessary start-up energy and also serves to provide a low impedance discharge path. A single ignition capacitor may be sufficient, but if a long cable is used to connect the lamp to the ballast, then two ignition capacitors in parallel at opposite ends of the cable may be used. The ballast further provides means for monitoring and controlling lamp power by monitoring a nominally constant dc link voltage, and means for detecting short-circuit and open circuit conditions. A retrial mechanism is provided in the event of the lamp failing to ignite that includes a temporary disabling of the inverter in order to keep the rms lamp voltage low.

A power storage system and a method of controlling the same include supplying power to a load by connecting a power generation system and a grid. The system includes a power converting unit that operates in one of at least two control modes including a maximum power point tracking control mode in which the power generation system is controlled to generate maximum power and a voltage control mode in which a boosting ratio is adjusted according to a change in the amount of power consumed by a load. The system also includes a direct current (DC)/DC converter for converting an output voltage of the power converting unit into a DC link voltage, an inverter for converting the DC link voltage into an alternating current (AC) voltage appropriate for the grid, and a central controller for controlling operations of the power converting unit, the DC/DC converter, and the inverter.