617 results about "Dc capacitor" patented technology

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.

A power converter apparatus having a configuration of a plurality of unit cells, including a DC capacitor and semiconductor devices, connected in cascade, includes a variable voltage source that is connected with a DC link, and a unit having a function that initially charges up the DC capacitor in the unit cell alone selected at a time of an initial charge.

In addition to the construction of a typical elevator control device in which power generated during regenerative operation is dissipated by a resistance chopper (18), an elevator control device is newly provided with: an electric double layer capacitor (21) connected in parallel with the DC capacitor (3) that smoothes the DC ripple of the rectifier circuit (2) that rectifies the AC power of the AC power source (1) and having an electrostatic capacitance that is considerably larger than this DC capacitor; a voltage detection circuit (22) that detects the terminal voltage of this electric double layer capacitor; and a drive control unit (5) that uses a voltage in the vicinity of the rated voltage of the electric double layer capacitor as the operating voltage of resistance chopper and, when the terminal voltage detected by a voltage detection circuit reaches the voltage in the vicinity of the rated voltage of the electric double layer capacitor, operates and controls the resistance chopper.

The adaptive superconductive magnetic energy storage (SMES) control method and system control a SMES device connected to a power generation system. A radial basis function neural network (RBFNN) connected to the controller adaptively adjusts gain constants of the controller. A processor executes an improved particle swarm optimization (IPSO) procedure to train the RBFNN from input-output training data created by the IPSO, and thereafter generate starting weights for the neural network. Tests carried out show that the proposed adaptive SMES controller maintains the DC capacitor voltage constant, thus improving the efficiency of wind energy transfer. The power output (reactive and real) of the SMES device improves the voltage profile following large voltage dips and provides added damping to the system.

The invention discloses an AC-DC hybrid micro grid bidirectional power converter virtual synchronization motor control method, and relates to the AC-DC hybrid micro grid virtual synchronization motorcontrol field; the bidirectional power converter is a three-phase voltage source type PWM converter formed by IGBT switch tubes; the AC side is connected to a AC bus via a LC filter and a line impedance Z ac; the DC side is connected to a DC bus via a DC capacitor Cdc and an line impedance Zdc; the energy bidirectional transmission can be realized respectively via a frequency control unit, a virtual excitation control unit and a bidirectional power transmission control unit; the AC frequency and DC voltage can be directly controlled so as to keep AC-DC subnet load balancing; throughput characteristics of various types of power supplies and loads of the AC-DC subnet can be fully utilized so as to provide inertia for the AC frequency and DC voltage, thus enabling the bidirectional power converter to present sagging characteristics under a stable state, and building a bidirectional power converter closed loop system small signal model so as to provide a key parameter design method.

The excitation overcurrent detection unit for the doubly-fed electric machine is provided with a function to determine an excitation current magnitude relationship among three phases. The firing pulse is held to on-state or off-state to cause the largest-current phase and the second-largest-current phase to charge the DC capacitor by the operation of diodes. The conduction ratio of the third-largest-current phase or minimum current phase is controlled according to the detected current value to protect against a possible short-circuit across the DC capacitor. When the voltage of the DC capacitor exceeds a preset value, the voltage is suppressed by operating active or passive power devices.

The invention relates to a cascading-type STATCOM (Static Synchronous Compensator) DC (Direct Current) side capacitor voltage balance control method. In the control method, the direct current control and the indirect current control are combined. The method comprises the following steps: generating an active current reference value; selecting a special bridge; generating an STATCOM output current reference value; carrying out indirect current control of the special bridge; and carrying out direct current control of a non-special bridge. The control method provided by the invention is used for controlling the cascading-type STATCOM DC side capacitor voltage balance. The method not only ensures the balance of a DC capacitor voltage between H bridges and improves the response speed of a control link and optimizes the system performance, but also does not require an additional hardware circuit and cannot ensure the hardware cost of a STATCOM device to be increased.

An improved power sensor having an input connector connected to an input port having a center pin and a ground side; an amplifier; first and second detectors; and a thermal stabilization system, including a thermal mass disposed between the ground side of the input connection and the detectors, a ground plane for holding the temperature of thermally sensitive components constant to within 2 degrees C., and a thermal impedance disposed between the center pin of the input port, preferably including a splitter and at least one DC capacitor, and a temperature sensor disposed on the ground plane.

A power converter 100 includes a DC capacitor C, semiconductor switch groups each of which includes semiconductor switches connected in series to each other, bridge-cells 11u-j, 11v-j, and 11w-j each of which includes the DC capacitor C and two semiconductor switch groups connected in parallel to the DC capacitor C, a delta connection unit 10 including delta-connected bridge-cells and a integrated control unit 1 for controlling a circulating current flowing in the delta connection unit such that each of DC-capacitor by-phase average values follows a DC-capacitor three-phase average value, each of the DC-capacitor by-phase average values being obtained by averaging voltage values of the DC capacitors at a corresponding phase of three phases, and the DC-capacitor three-phase average value being obtained by averaging voltage values of the DC capacitors at all of the three phases.

The invention discloses a method for controlling the balance of capacitive voltages of a five-level diode neutral point clamped converter. The method has the advantages that an integral modulation degree area is divided into a low modulation degree area (with an m<SV> smaller than or equal to 0.5) and a high modulation degree area (with an m<SV> larger than 0.5), and direct-current-side voltages of different modulation degree areas are controlled by different processes; a process for optimizing objective functions and a process for decomposing a reference voltage are combined with each other in a process for controlling the direct-current capacitive voltages in the low modulation degree area, the process for controlling the direct-current capacitive voltages in the low modulation degree area can be implemented easily, redundant switch states of various vectors are sufficiently utilized, and waveforms outputted by a system are improved; and complicated overlap area judging algorithms are omitted in an optimized process for selecting balancing vectors in the high modulation degree area, and the system is high in the response speed.

An auxiliary quasi-resonant DC tank (AQRDCT) power converter with fast current charging, voltage balancing (or charging), and voltage clamping circuits is provided for achieving soft-switched power conversion. The present invention is an improvement of the invention taught in U.S. Pat. No. 6,111,770, herein incorporated by reference. The present invention provides faster current charging to the resonant inductor, thus minimizing delay time of the pulse width modulation (PWM) due to the soft-switching process. The new AQRDCT converter includes three tank capacitors or power supplies to achieve the faster current charging and minimize the soft-switching time delay. The new AQRDCT converter further includes a voltage balancing circuit to charge and discharge the three tank capacitors so that additional isolated power supplies from the utility line are not needed. A voltage clamping circuit is also included for clamping voltage surge due to the reverse recovery of diodes.

The invention relates to a direct current (DC) side capacitor voltage balancing control circuit for an H-bridge cascaded active power filter, which comprises a single-phase transformer bank (2), wherein the single-phase transformer bank comprises m single-phase transformers, and primary windings are connected in parallel through a public alternating current (AC) bus (1); n secondary windings of the M single phase transformers are connected with n single-phase half-bridge converters through an inductor and a DC isolation capacitor; the n single phase half-bridge converters are respectively connected with DC voltage supporting capacitor of cascaded power units of an H-bridge cascaded multi-level converter, wherein m and n are natural numbers no less than 2, and m is no more than n. The balancing control circuit can balance DC capacitor voltages in same cascaded power units of the cascaded multi-level converter and DC capacitor voltages of different cascaded power units.

The invention relates to a measurement device for stray inductance in an IGBT module. The measurement device is characterized in that the measurement device comprises a power supply device, a to-be-measured IGBT module, a current probe, a voltage probe, an oscilloscope, a pulse triggering device, controllable switches S1, S2, S3, a DC capacitor C1, a DC discharging resistor R1, a load inductor L1 and a freewheeling diode D1; the controllable switch S2 is serially connected with the DC discharging resistor R1 and is parallelly connected with the DC capacitor C1; the freewheeling diode D1, the controllable switch S3 and the to-be-measured IGBT module are serially connected; the pulse triggering device is connected with the controllable switch S3; and the load inductor L1 is parallelly connected with two sides of the freewheeling diode D1. The measurement device can effectively evaluate induction voltage of an inner packaging parasitic parameter when the IGBT module is in a switching-off transient state. The packaged stray inductance which is calculated according to the voltage and current over two ends of a parasitic inductor is more practical and can be used for evaluating an IGBT safety margin, and furthermore can be used for verifying IGBT module designing. The measurement device and the measurement method have a certain meaning to semiconductor manufacturers and IGBT application parties.

Method of controlling a voltage controlled PWM (Pulse Width Modulated) frequency converter comprising a single phase rectifier bridge (10) connectable to a sinusoidal single phase supply, a DC intermediate circuit (11) and a controlled inverter bridge (12) for generating an AC output voltage with varying amplitude and frequency to a load, said inverter bridge (12) having PWM controlled semiconductor switches (V11–V16) and flywheel diodes (D11–D16) connected in inverse-parallel with the semiconductor switches, wherein the DC intermediate circuit (11) is provided with a DC capacitor unit, and wherein the frequency converter is controlled so that the supply line current (I_in) is essentially sinusoidal and in phase with the supply line voltage (U_in). The inverter bridge is controlled so that the curve of filtered average current (I_dc) in the DC intermediate circuit follows essentially the curve of the rectified AC supply voltage (U_dc), the rectifier bridge is (10) connected to the inverter bridge (12) directly without a DC capacitor unit acting as an intermediate energy storage, and the curve of the power fed to the load has essentially the form sin²(2πft) (f=line frequency t=time).

The invention discloses an improved switched capacitor-accessed two-way DC transformer and a control method thereof, and belongs to the technical field of electric power. The transformer is formed by connecting n identical DC conversion units at one port in series and at the other port in parallel; and each DC conversion unit comprises eight semiconductor switches, two auxiliary semiconductor switches, two DC capacitors, a high-frequency inductor and a high-frequency transformer. The method comprises the steps as follows: under the normal condition, high-voltage sides of the n DC conversion units are connected in series and then are connected to a high-voltage DC side through a DC electric reactor; low-voltage sides of the n DC conversion units are connected in parallel and then are directly connected to a low-voltage DC side; when smaller than k DC conversion units have internal faults, the DC conversion units with the faults are directly bypassed; and when an external fault appears at the high-voltage or low-voltage DC side, the semiconductor switches and the auxiliary semiconductor switches of all DC conversion units are turned off and the capacitor voltage can be kept constant. According to the improved switched capacitor-accessed two-way DC transformer, the operation economy and reliability of a device are improved.

The invention discloses a zero-voltage switching energy storage bridge-type inverter without additional voltage and a modulation method for the inverter. The zero-voltage switching energy storage bridge-type inverter comprises a direct-current-side energy storage battery, direct-current capacitors, an alternating-current filter inductor and a single-phase bridge arm. The single-phase bridge arm comprises four fully-controlled main switches with antiparallel diodes, an auxiliary switch with an antiparallel diode is connected between the energy storage battery and a direct-current bus of the single-phase bridge arm, the capacitors are respectively connected to two ends of each main switch and two ends of the auxiliary switch in parallel, the two ends of the auxiliary switch are connected with a resonance branch circuit, and a resonance inductor and a clamping resistor are serially connected to form the resonance branch circuit. The zero-voltage switching energy storage bridge-type inverter and the modulation method have the advantages that the zero-voltage switching energy storage bridge-type inverter can run independently in an on-load manner or run in a grid-connected manner, and is simple in structure, power flows in two directions, and a storage battery can be charged and discharged; the sinusoidal pulse width modulation method is implemented for the main switches, and modulation signals of the auxiliary switch are synchronous with the main switches; zero-voltage switching of all the main switches can be realized only by one-step action of the auxiliary switch in each switching period, reverse recovery current of the antiparallel diode of each main switch is suppressed, the zero-voltage switching energy storage bridge-type inverter is low in switching loss, high in circuit efficiency and beneficial to increasing working frequency, and the power density is increased.

The invention discloses a system and method for high-voltage direct-current starting and power generation of a stator duplex winding asynchronous motor. A main loop comprises the stator duplex winding asynchronous motor, a rectifier bridge, a power converter, a direct-current power source, a diode, a control side direct-current capacitor and a power side direct-current capacitor. A detecting loop comprises a first voltage transducer, a second voltage transducer, a first current transducer and a second current transducer. A control loop comprises a digital signal processor and a driving circuit. Five-phase centralized full-pitch star-shaped structures are adopted by both sets of stator windings which are a power winding and a control winding of the stator duplex winding asynchronous motor. In the starting and power generating process, the power converter implants three times of proper harmonic currents to the motor through the control winding under the control of the digital signal controller, an air-gap magnetic field is controlled to be a standard square wave, and therefore the torque density and the power density of the motor are improved. The system and method for the high-voltage direct-current starting and power generation of the stator duplex winding asynchronous motor is simple in structure and free of electric brush sliding rings, can achieve the integration of start and power generation, and has the advantages of being high in power density and torque density, easy to operate with fault-tolerance and the like.

An electric power conversion device includes a power conversion unit and a converter control unit. The power conversion unit includes three arms connected to an AC circuit. The converter control unit includes a phase DC voltage control unit, a negative sequence current command value calculation unit, an output current control unit, a circulating current control unit, a voltage command value calculation unit, and a gate signal generation unit, and imbalance of cell DC capacitor voltages among phases due to grid imbalance is controlled by circulating current and negative sequence current.

The invention discloses an open type grid-connection experiment system of a variable-speed constant-frequency double-fed wind power generator unit and an open type grid-connection experiment method. The open type grid-connection experiment system is applied to a power grid. The open type grid-connection experiment system comprises a plurality of fuses, a plurality of contactors, a first voltage and current transducer, a second voltage and current transducer, a grid-side converter, a DC capacitor, a rotor-side converter and a double-fed motor. The open type grid-connection experiment system is characterized by further comprising a voltage adjustable isolation transformer, a DSP/FPGA control system, an encoder and an optical coupling isolation unit. The voltage adjustable transformer is arranged between the power grid and the fuses in series and can be adjusted manually so as to simulate and achieve grid connection of various voltage amplitudes. The DSP/FPGA control system is used for controlling a first set of control signals and a second set of control signals according to sampling signals of the first voltage and current transducer, wherein the first set of control signals and the second set of control signals are required by the grid-side converter and the rotor-side converter and outputted to the grid-side converter and the rotor-side converter. The encoder is connected with the double-fed motor and used for detecting the rotating speed of the rotor side of the double-fed motor. The optical coupling isolation unit is connected between the encoder and an FPGA unit and used for inputting the signals into the FPGA unit after the signals are subjected to filtering processing.