31 results about "Three phase diode rectifier" patented technology

The invention provides a T-connected autotransformer for converting three-phase ac input voltages to nine phase shifted ac voltages feeding three sets of three-phase diode rectifier bridges. The nine phase shifted voltages are at an angle of +20 degree or −20 degree with respect to the supply voltages and their magnitudes are essentially identical. The present design requires substantially fewer coils than other autotransformers for 18-pulse AC-DC converters, resulting in saving in space, volume, weight, size and cost of the converter. The magnetics requirement is only about 30% of the drive rating. The output voltage ratio can also be selected to give an average dc output from the proposed converter same as that of a conventional three-phase diode bridge rectifier. However, it is also possible to step up or step down the output voltage as required.

A prime mover (28) in a heat recovery system drives an induction generator (8) which feeds power to a utility grid (9) through a breaker (10) but also powers a load including auxiliary induction motors (11, 12). To provide acceptable waveform and power factor, the auxiliary equipment is driven through IGBT switched bridge converters (13) by DC voltage (15) generated by an IGBT switched bridge converter (13a), instead of three-phase diode rectifiers (16). The switched bridge converter controller (14a) is responsive to a system process controller (23a) which causes the switched bridge controller (13a) to be driven in response to the voltage (26) and current (27) on the generator bus (17). This eliminates the need for harmonic filters (18) and power factor capacitors (20) while improving the quality of the power generated. The controller (23a) trips the breaker if the voltage, frequency or power factor is out of limits.

The invention relates to a power electronics control device and aims at providing an improved continuous variable-voltage and variable-frequency soft starter used for a motor. The soft starter comprises a mechanical switch K1 and a series circuit, wherein the series circuit comprises an inverter and full-control high-frequency electronic switches Gd1 and Gd2, and the series circuit and a capacitor C0 are connected in parallel with both ends of the output of a three-phase diode rectifier; a series switch circuit made by connecting a full-control high-frequency electronic switch Gd3 and a diodeDE in series is connected in parallel with both ends of the input of the inverter; and wires respectively from the middle points of three pairs of bridge arms of the inverter are connected with a three-phase asynchronous motor through a switch K2. The soft starter can change frequency and voltage continuously, so that the starting force of the motor is great while the starting current is not too great; the cost is reduced and the overload capacity is enhanced, so that the soft starter can be applicable to high-voltage occasions; and the three functions of regulating voltage, cutting off during failure and turning off an inverter thyristor can be realized by using a few full-control high-frequency elements, so that the full-control high-frequency elements work at high frequency while the thyristor works at low frequency.

The invention discloses a power-on current-limiting circuit and an application circuit of the power-on current-limiting circuit. The input end of the power-on current-limiting circuit is connected with one end of the primary side of a transformer and the positive electrode of the output end of a relay respectively, and the other end of the primary side of the transformer is connected with the negative electrode of the output end of the relay so as to form the output end of the power-on current-limiting circuit; a resonant capacitor and a resonant resistor are in bridge connection with the secondary side of the transformer; a first power diode is in reverse connection with the input end of the relay; and the positive electrode of the input end of the relay and the cathode of the first power diode are respectively connected with a control power supply, and the negative electrode of the input end of the relay is connected with the anode of the first power diode so as to form the control terminal of the power-on current-limiting circuit. The power-on current-limiting circuit and the application circuit are simple in structures, are convenient to control, can be matched with a three-phase diode rectifier, a single-phase diode rectifier, a three-phase IGBT (insulated gate bipolar transistor) controlled rectifier and a single-phase IGBT controlled rectifier, and can be laid on an alternating current side or a direct current side and widely applied to all power electronic convertors, the power-on current is adjustable, the power-on effect is good, the current displacement factor is always 1, and the service life of an electrolytic capacitor is long.

The invention discloses an instantaneous power detection and load identification based induction motor cooperative control system which realizes energy-saving control on a light-loaded or unloaded three-phase induction motor and mainly comprises an instantaneous power detection and load identification cooperative controller using a digital signal processor TMS320F28346 as a core, a three-phase bridge power amplifier, a three-phase bridge driving circuit, the three-phase induction motor, a three-phase diode rectifier bridge, an instantaneous power detection link, a current detection link, a coder rotating speed detection link, a load identification link, a +24V switch power source, a +15V switch power source, a + / -12V switch power source, a +5V power source and the like. An instantaneous power detection and load identification based induction motor cooperative control method is adopted to control stator exciting current of the light-loaded or unloaded three-phase induction motor, and power factors of the three-phase induction motor are adjusted by load rate obtained on the basis of load identification, so that operating efficiency of the three-phase induction motor is effectively improved, and good electricity-saving effect is achieved.

The invention relates to control equipment of power electronics and aims to provide a soft starter used for continuous frequency conversion and voltage transformation of the motor. The soft starter comprises a mechanical switch K1 which is connected with a three-phase electric network power supply, and further comprises a series circuit which consists of an inverter and a fully-controlled high-frequency electronic switch Kd, wherein the series circuit and a capacitor C0 are connected to two output terminals of a three-phase diode rectifier bridge in parallel; the mechanical switch K1 is connected to an input terminal of the three-phase diode rectifier bridge; in the inverter, three pairs of bridge arms are formed by six sets of thyristors Th1,1' to Th6,6'; each pair of bridge arms consistof two anti-parallel thyristors; and the center point of an upper bridge arm and a lower bridge arm of each of the three pairs of bridge arms leads a lead out respectively and is connected to a three-phase asynchronous motor through a mechanical switch K4. In the soft starter used for continuous frequency conversion and voltage transformation of the motor, three functions of regulating voltage, switching off an inverter thyristor, and switching off the main circuit when protection is needed can be simultaneously realized by using only one fully-controlled electronic switch Kd. Simultaneously,due to the adoption of the thyristor inverter, the soft starter has the advantages of simple and reliable circuit, low cost, and great use flexibility.

The invention discloses a three-phase bridge-type rectifier load harmonic superposition method based on capacitor filtering. The method is characterized in that an alternating current side bus is connected to two same capacitor-filtering-type three-phase bridge rectifier circuits; and each capacitor-filtering-type three-phase bridge rectifier circuit includes a three-phase diode rectifier connected to the alternating current side bus, a filtering capacitor and a load resistor, wherein the filtering capacitor and the load resistor are connected in parallel to a direct current side of the three-phase diode rectifier; and a capacitance difference of the filtering capacitors in the two capacitor-filtering-type three-phase bridge rectifier circuits exceeds a threshold. By using the method, an influence of a three-phase bridge-type rectifier load harmonic of the capacitor filtering on a power grid can be actively reduced, harmonic treatment measures can be well made and cost of electric power system harmonic treatment is reduced.

The invention discloses a high-power and high-step-up ratio photovoltaic DC converter device and a control method. An intermediate frequency 400Hz transformer-based high-power and high-step-up ratio photovoltaic DC converter device with low cost and high efficiency is firstly provided. The high-power and high-step-up ratio photovoltaic DC converter device comprises a multi-channel boost DC transformer, a modular parallel photovoltaic inverter, an intermediate frequency 400Hz three-winding boost transformer, three-phase diode rectifier bridges and high-voltage filter circuits. A control method is disclosed according to the converter device. According to the control method, voltage of an output end of a photovoltaic array is firstly adjusted by using the boost DC transformer, so that the power of the output end of the photovoltaic array is adjusted, and then the power of the output end of the photovoltaic array is transmitted to a transformer side through double loop control of AC / DC side voltage and bridge arm side inductance current of the modular parallel photovoltaic inverter and is transmitted to the final high-voltage DC bus through transformer boosting conversion, diode rectification and the high-voltage filter circuit.

A direct power control system of a high power factor induction motor realizes energy-saving control of a three-phase induction motor under the condition of light load or no load. The direct power control system of the high power factor induction motor comprises a controller using a digital signal processor TMS320F2808 as the core, a three-phase bridge power amplification device, a three-phase bridge driving circuit, the three-phase induction motor, a three-phase diode rectifier, a power factor detecting link, a current detecting link, an encoder rotating speed detecting link, a power factor measuring link, a + 24V switching power supply, a +15V switching power, a + / - switching power supply, a +5V switching power and the like. By means of the direct power control system applying power factor measurement, the stator flux linkage amplitude of the three-phase induction motor under the condition of light load or no load is controlled, instantaneous reactive power of the motor is adjusted, and therefore the motor power factor is effectively improved and a good energy-saving effect is achieved.

The invention discloses a novel spare topological structure of a sparse two-stage matrix converter. The structure comprises three two-way controllable switches, a three-phase diode rectifier bridge and a three-phase inverter. With the adoption of the novel topological structure of the sparse two-stage matrix converter, the shortage that the rectifier stage of other two-stage matrix converter easily generates negative pressure which leads to short circuit fault can be overcome, and the system reliability can be effectively improved; in addition, the input reactive power angle adjusting range is expanded to be [-90 degrees, 90 degrees], and therefore, the problem that the input side power factor angle of the traditional two-stage matrix converter can be adjusted within the range of [-30 degrees, 30 degrees]; the topological structure is simple and reliable to control, and relatively high in practical value.

The invention relates to a rectifying technology in the field of power electronics, aiming at providing a three-phase rectifier for realizing current distribution by utilizing auxiliary bridge feedback. The three-phase rectifier comprises k numbered main rectifiers connected in parallel, and k numbered current transformers, wherein the current transformers are respectively connected to the input ends of the main rectifiers, the output ends of the current transformer are respectively connected with three-phase diode rectifiers serving as auxiliary rectifiers; and the auxiliary rectifiers are mutually connected in series, and then are connected in parallel to both ends of the output ends of the main rectifiers connected in parallel. In the invention, the three-phase rectifier of the invention does not need active devices in the process of realizing current distribution, the circuit is simple and reliable, the cost is low; and particularly, the invention can automatically keep current equalization along with the change of loads. Meanwhile, the main rectifiers distribute currents according to a certain ratio rather than a current equalization mode according to the difference of turn ratios of the current transformers matched with the main rectifiers, thereby adapting to the demands of different conditions.

The present invention proposes a high-power high-voltage photovoltaic DC step-up converter device and a control method thereof suitable for direct-current transmission of photovoltaic power stations. The high-power high-voltage photovoltaic DC step-up converter device includes N-way photovoltaic power generation units and Corresponding N-way boost conversion unit, high-power three-phase square wave inverter, modular high-frequency three-phase step-up transformer unit and modular three-phase diode rectifier bridge unit. The converter device modulation adopts open-loop square wave PAM (pulse amplitude modulation), and the pulse amplitude is controlled by the photovoltaic power generation unit and the boost conversion unit, and the control is simple and efficient.