CN114884365A - Three-phase converter - Google Patents

Abstract

The invention discloses a three-phase converter, comprising a three-phase bridge switch circuit, a resonant cavity, three isolation transformers and a three-phase bridge rectifier circuit, wherein the resonant cavity comprises three resonant circuits, and the three resonant circuits Correspondingly connected between the midpoints of the three bridge arms of the three-phase bridge switch circuit and the primary windings of the three isolation transformers, wherein each resonant circuit includes a first inductance, a second inductance and a first capacitor, and the first One end of a capacitor is connected to one end of the first inductor and one end of the second inductor, the other end of the first capacitor is connected to the midpoint of a bridge arm in the three-phase bridge switch circuit, and the other end of the first inductor and the second inductor is connected A primary winding of an isolation transformer, the ends of the same name of the secondary windings of the three isolation transformers correspond to the midpoints of the three bridge arms of the three-phase bridge rectifier circuit respectively, and the three synonyms of the primary windings and the secondary windings of the isolation transformers The ends are respectively connected to each other to form a Y-shaped connection.

Description

A three-phase converter

technical field

The present invention relates to the technical field of power conversion, and more particularly to a three-phase converter.

Background technique

The bidirectional DC-DC converter is a DC/DC converter that can adjust the bidirectional transmission of energy according to the needs. It is mainly used in energy storage systems, vehicle power supply systems, feedback charging and discharging systems, hybrid energy electric vehicles and other occasions.

In the traditional LLC resonant bidirectional converter, the ZVS conduction of the primary side switch tube and the ZCS conduction of the rectifier side diode can be realized regardless of the forward and reverse operation, but when the energy flows in the reverse direction, its circuit characteristics are no longer It is an LLC resonance characteristic and degenerates into an LC resonance characteristic. The maximum voltage gain of LC resonance becomes 1, which greatly reduces the voltage gain during reverse operation and greatly narrows the output voltage range, so it is not suitable for working in a wide voltage range. The state of bidirectional flow of energy limits its application scenarios.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a three-phase converter that has less loss during forward and reverse operation and can increase the working voltage range.

In order to solve the above technical problems, the present invention provides a three-phase converter, including a three-phase bridge switch circuit, a resonant cavity, three isolation transformers and a three-phase bridge rectifier circuit, the three-phase bridge switch circuit and the three-phase bridge switch circuit. One side of the bridge rectifier circuit is respectively used as the first connection side and the second connection side of the three-phase converter, the resonant cavity includes three resonant circuits, and the three resonant circuits are respectively connected to the three-phase bridge switch circuit. between the midpoints of the three bridge arms and the primary windings of the three isolation transformers, where,

Each resonant circuit includes a first inductor, a second inductor and a first capacitor, one end of the first capacitor is connected to one end of the first inductor and one end of the second inductor, and the other end of the first capacitor is connected to the three-phase bridge switch circuit. The midpoint of a bridge arm, the other ends of the first inductance and the second inductance are connected to the primary winding of an isolation transformer, and the ends of the same name of the secondary windings of the three isolation transformers are respectively connected to the three bridges of the three-phase bridge rectifier circuit. At the midpoint of the arm, the synonymous ends of the primary windings and the secondary windings of the three isolation transformers are respectively connected to each other to form a Y-shaped connection.

Its further technical scheme is as follows: the three-phase bridge switch circuit includes six switch tubes, every two switch tubes are connected in series to form a bridge arm, and the two ends of the three bridge arms are used as the first connection side of the three-phase converter after the three bridge arms are connected in parallel. .

Its further technical scheme is as follows: the three-phase bridge rectifier circuit includes six switch tubes, every two switch tubes are connected in series to form a bridge arm, and the two ends of the three bridge arms are used as the second connection side of the three-phase converter after the three bridge arms are connected in parallel. .

Its further technical scheme is: the switch tube selects MOSFET or IGBT.

A further technical solution is: the three-phase converter further includes a first filter capacitor and a second filter capacitor, both ends of the first filter capacitor are connected to the first connection side of the three-phase converter, and the second filter capacitor Both ends are connected to the second connection side.

In order to solve the above technical problems, the present invention also provides a three-phase converter, which includes a three-phase bridge switch circuit, a resonant cavity, three isolation transformers and a three-phase bridge rectifier circuit. One side of the phase bridge rectifier circuit is respectively used as the first connection side and the second connection side of the three-phase converter, the resonant cavity includes three resonant circuits, and the three resonant circuits are respectively connected to the three-phase bridge switches. Between the midpoints of the three bridge arms of the circuit and the primary windings of the three isolation transformers, where,

Each resonant circuit includes a first inductor, a second inductor and a first capacitor, two ends of the first inductor are respectively connected to one end of the first capacitor and one end of the second inductor, and one end of the first inductor connected to the second inductor is also connected to The midpoint of a bridge arm in the three-phase bridge switch circuit, the other ends of the first capacitor and the second inductance are connected to the primary winding of an isolation transformer, and the ends of the same name of the secondary windings of the three isolation transformers are respectively connected to the three-phase bridge. The midpoint of the three bridge arms of the type rectifier circuit, and the different names of the primary windings and the secondary windings of the three isolation transformers are respectively connected to each other to form a Y-shaped connection.

Compared with the prior art, the equivalent circuit of the resonant circuit in the three-phase converter of the present invention is a three-element resonant circuit when the energy flows in the forward and reverse directions, soft switching is realized in both forward and reverse operation, the loss is small, and the problem is solved. The problem of insufficient reverse gain of the traditional LLC resonant circuit, that is, the three-phase converter of the present invention can boost the voltage when the energy flows in the reverse direction, that is, when the energy flows from the second connection side to the first connection side, which can effectively improve the work of the converter Voltage range to achieve wide voltage range input and output.

Description of drawings

FIG. 1 is a schematic circuit diagram of a first embodiment of a three-phase converter of the present invention.

FIG. 2 is a schematic circuit diagram of a second embodiment of the three-phase converter of the present invention.

Detailed ways

In order for those skilled in the art to more clearly understand the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments.

Referring to FIG. 1 , FIG. 1 is a schematic circuit diagram of a first embodiment of a three-phase converter 10 of the present invention. In the embodiment shown in the drawings, the three-phase converter 10 includes a three-phase bridge switch circuit 100, a resonant cavity 200, three isolation transformers and a three-phase bridge rectifier circuit 300. The three-phase bridge switch One side of the circuit 100 and the three-phase bridge rectifier circuit 300 are respectively used as the first connection side and the second connection side of the three-phase converter 10 to connect the power supply or the load. The resonant cavity includes three resonant circuits, and the three The resonant circuits are respectively connected between the midpoints of the three bridge arms of the three-phase bridge switch circuit 100 and the primary windings of the three isolation transformers. Wherein, each of the resonant circuits includes a first capacitor, a first inductor and a second inductor, one end of the first capacitor is connected to one end of the first inductor and one end of the second inductor, and the other end of the first capacitor is connected to the three-phase bridge The midpoint of a bridge arm in the switch circuit 100, the other ends of the first inductance and the second inductance are connected to the primary winding of an isolation transformer, and the ends of the same name of the secondary windings of the three isolation transformers are respectively connected to the three-phase bridge rectifier. At the midpoint of the three bridge arms of the circuit 300, the synonymous ends of the primary windings and the secondary windings of the three isolation transformers are respectively connected to each other to form a Y-shaped connection, that is, the synonymous ends of the primary windings of the three isolation transformers are connected to each other. A Y-shaped connection is formed, and the opposite ends of the three isolation transformer secondary windings are also connected to each other to form a Y-shaped connection. Preferably, the inductances of the first inductance and the second inductance are the same.

Specifically, in this embodiment, the resonant cavity 200 includes a first resonant circuit, a second resonant circuit and a third resonant circuit, and the three isolation transformers include a first isolation transformer T1, a second isolation transformer T2 and a third isolation transformer T3, the first resonant circuit includes a first inductor L1, a second inductor L2 and a first capacitor C1, the second resonant circuit includes a first inductor L3, a second inductor L4 and a first capacitor C2, the third The resonant circuit includes a first inductor L5 , a second inductor L6 and a first capacitor C3 , and the first capacitor C1 , the first capacitor C2 and the first capacitor C3 are correspondingly connected to the three bridge arms of the three-phase bridge switch circuit 100 The midpoint of the second inductance L2, the second inductance L4 and the second inductance L6 are respectively connected to the opposite ends of the primary windings of the first isolation transformer T1, the second isolation transformer T2 and the third isolation transformer T3.

In this embodiment, when the energy flows in the forward direction, that is, when the energy flows from the first connection side to the second connection side, the first connection side of the three-phase converter 10 is used as the DC input end, and an external power supply can be connected. The second connection side of the three-phase converter 10 is used as the DC input end, and when the energy flows in the reverse direction, that is, when the energy flows from the second connection side to the first connection side, the second connection side of the three-phase converter 10 is used as the DC input end, and its The first connection side serves as a DC output terminal. The three-phase converter 10 of the present invention has a simple structure, and the equivalent circuits when the energy flows in the forward and reverse directions are all three-element resonant circuits. Soft switching can be realized in the forward and reverse operation, and the loss is small, which solves the problem of the reverse direction of the traditional LLC resonant circuit. The problem of insufficient gain, that is, the voltage can be boosted when the energy flows from the second connection side to the first connection side, which can effectively improve the input and output voltage range of the converter, realize a wide voltage range input and output, and can be applied to high-power circuits; and The primary windings and secondary windings of the three isolation transformers are Y-connected, and the total current flowing into the midpoint of the Y-connection is equal to the total current flowing out of the midpoint of the Y-connection, that is, the sum of the currents of the three resonant circuits is " 0”, so the current of one resonant circuit is always the sum of the currents of the other two resonant circuits at any time, then even if the resonant parameters of each resonant circuit have a certain tolerance during the entire switching cycle, their current RMS The deviation is also small, so as to ensure the current balance among the three resonant circuits, and avoid excessive current in a certain resonant circuit, which may cause damage or overheating of the devices of the circuit.

In some embodiments, the three-phase bridge switch circuit 100 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5 and a sixth switch The tube Q6 has a total of six switching tubes, and every two switching tubes are connected in series to form a bridge arm. After the three bridge arms are connected in parallel, their two ends serve as the first connection side of the three-phase converter 10, wherein the first switching tubes Q1 and The midpoint of the bridge arm formed by the second switch transistor Q2 in series is connected to the first resonant circuit, the midpoint of the bridge arm formed by the third switch transistor Q3 and the fourth switch transistor Q4 in series is connected to the second resonant circuit, and the fifth switch transistor Q3 and the fourth switch transistor Q4 are connected in series. The midpoint of the bridge arm formed by the switch tube Q5 and the sixth switch tube Q6 in series is connected to the third resonant circuit. In this embodiment, the PFM method is used to control the operation of the switching tubes, that is, the duty cycle is constant, and the frequency of the modulating wave is variable, so that each switching tube of the three-phase converter 10 can be a soft switch.

In the embodiment shown in the drawings, the three-phase bridge rectifier circuit 300 includes a seventh switch transistor Q7, an eighth switch transistor Q8, a ninth switch transistor Q9, a tenth switch transistor Q10, and an eleventh switch transistor Q11 And the twelfth switch tube Q12 has six switch tubes, and every two switch tubes are connected in series to form a bridge arm. After the three bridge arms are connected in parallel, their two ends are used as the second connection side of the three-phase converter 10, wherein the seventh The midpoint of the bridge arm formed by the switch tube Q7 and the eighth switch tube Q8 in series is connected to the secondary winding of the first isolation transformer T1, and the midpoint of the bridge arm formed by the ninth switch tube Q9 and the tenth switch tube Q10 in series It is connected to the secondary winding of the second isolation transformer T2, and the midpoint of the bridge arm formed by the eleventh switch Q11 and the twelfth switch Q12 in series is connected to the secondary winding of the third isolation transformer T3. Based on this design, when the energy flows in the forward direction, the three-phase bridge rectifier circuit 300 can rectify the voltage waveform periodically output by the isolation transformer to generate the working voltage required by the load. Preferably, MOS, IGBT or other controllable power switch tubes can be selected as the switch tubes to achieve better circuit performance. In some other embodiments, a diode can also be connected in parallel with each switch tube. If the MOS tube is selected as the tube, a diode is connected in parallel between its drain and source, and if the switch tube is selected as an IGBT tube, a diode is connected in parallel between its emitter and collector.

Further, the three-phase converter 10 further includes a first filter capacitor C8 and a second filter capacitor C9, both ends of the first filter capacitor C8 are connected to the first connection side of the three-phase converter 10, and the second filter capacitor C8 is connected to the first connection side of the three-phase converter 10. Both ends of the filter capacitor C9 are connected to the second connection side of the three-phase converter 10 .

Understandably, in this embodiment, when the energy is transmitted in the forward direction, by controlling the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5 and the sixth switch The switching frequency of the switch tube Q6 is used to realize the wide-range voltage output of the three-phase converter 10, and the two switch tubes on each bridge arm are complementarily turned on, which can realize the soft switching of the circuit; The effective circuit is also a three-element resonant circuit. Therefore, by controlling the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, the tenth switch Q10, the eleventh switch Q11 and the twelfth switch Q12 The switching frequency can achieve the same wide-range voltage output as the forward transmission, and the two switching tubes on each bridge arm are complementarily turned on, which can realize circuit soft switching. Moreover, when the switching frequency of the switch tube is equal to the resonant frequency, the capacitor in the resonant circuit connected to the primary winding of the isolation transformer can avoid the situation where the impedance is zero.

The three-phase converter 10 of the present invention adopts three-phase interleaving technology, the conduction phase differences of Q1 and Q2, Q3 and Q4, Q5 and Q6 are all 180 degrees, and the conduction timings of Q1, Q3, and Q5 are 120 degrees different from each other; therefore, The turn-on timings of Q2, Q4, and Q6 also differ by 120 degrees, and the three-phase input and output currents differ by 120 degrees. The input and output current fluctuations of the three-phase circuit complement each other, so that the input and output current ripple is small, thereby achieving better circuit performance. At any time, at least one of Q1, Q3, and Q5 will be turned on, and at least one of Q2, Q4, and Q6 will be turned on, and the number of turned-on switches is always equal to three. Taking one of the three resonant circuits as an example, when Q1, Q4 and Q6 are turned on, the resonant DC voltage is transmitted to the first isolation transformer T1 through the first switch tube Q1, and the current value of the first resonant circuit increases, and the Energy storage, the seventh switch tube Q7 is turned on, and the second filter capacitor C9 is used to rectify and filter the output voltage of the first isolation transformer T1 to output a stable voltage and control the output current; when Q2, Q3 and Q5 are turned on When , the resonant DC reverse voltage is transmitted to the first isolation transformer T1 through the second switch tube Q2, and at the same time, the reverse current value of the first resonant circuit increases to supply power to the first isolation transformer T1, and the eighth switch tube Q8 is turned on, The output voltage of the first isolation transformer T1 is rectified and filtered to output a stable voltage and control the output current. In the same way, the working principle of the other two resonant circuits is the same as this one.

Referring to FIG. 2, FIG. 2 is a schematic circuit diagram of a second embodiment of the three-phase converter 10 of the present invention. The difference between this embodiment and the first embodiment is the specific structure of the resonant circuit, and the other circuit structures are the same or similar. Specifically, in this embodiment, the resonant circuit includes a first inductor, a second inductor, and a first capacitor, two ends of the first inductor are respectively connected to one end of the first capacitor and one end of the second inductor, and the first inductor One end of the inductor connected to the second inductor is also connected to the midpoint of a bridge arm in the three-phase bridge switch circuit, and the other ends of the first capacitor and the second inductor are connected to the primary winding of an isolation transformer. In this embodiment, the first resonant circuit includes a first inductor L1, a second inductor L2 and a first capacitor C1, and the second resonant circuit includes a first inductor L3, a second inductor L4 and a first capacitor C2, The third resonant circuit includes a first inductor L5, a second inductor L6 and a first capacitor C3; the first capacitor C1, the first capacitor C2 and the first capacitor C3 are respectively connected to the first isolation transformer T1 and the second isolation transformer T1, respectively. The same-named ends of the primary windings of the transformer T2 and the third isolation transformer T3, the second inductance L2, the second inductance L4 and the second inductance L6 are respectively connected to the primary windings of the first isolation transformer T1, the second isolation transformer T2 and the third isolation transformer T3 The first inductance L1 , the first inductance L3 and the first inductance L5 are respectively connected to the midpoints of the three bridge arms of the three-phase bridge switch circuit 100 . The resonant circuit in this embodiment has less loss when the energy flows in the forward and reverse directions, which can also effectively increase the operating voltage range of the converter 10 and realize a wide voltage range of input and output.

To sum up, the equivalent circuit of the resonant circuit in the three-phase converter of the present invention is a three-element resonant circuit when the energy flows in the forward and reverse directions. Soft switching is realized in the forward and reverse operation, and the loss is small, which solves the problem of the traditional LLC resonance. The problem of insufficient reverse gain of the circuit, that is, the three-phase converter of the present invention can boost the voltage when the energy flows in the reverse direction, that is, when the energy flows from the second connection side to the first connection side, which can effectively increase the working voltage range of the converter. Realize wide voltage range input and output.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Those skilled in the art can apply various equivalent changes and improvements on the basis of the above embodiments, and all equivalent changes or modifications made within the scope of the claims shall fall within the protection scope of the present invention.

Claims (6)

1. A three-phase converter, characterized in that: the three-phase converter comprises a three-phase bridge switch circuit, a resonant cavity, three isolation transformers and a three-phase bridge rectifier circuit, and the three-phase bridge switch circuit and one side of the three-phase bridge rectifier circuit are respectively used as the first connection side and the second connection side of the three-phase converter, the resonant cavity includes three resonant circuits, and the three resonant circuits are respectively connected to the three-phase bridge. between the midpoints of the three bridge arms of the switch circuit and the primary windings of the three isolation transformers, where, Each resonant circuit includes a first inductor, a second inductor and a first capacitor, one end of the first capacitor is connected to one end of the first inductor and one end of the second inductor, and the other end of the first capacitor is connected to the three-phase bridge switch circuit. The midpoint of a bridge arm, the other ends of the first inductance and the second inductance are connected to the primary winding of an isolation transformer, and the ends of the same name of the secondary windings of the three isolation transformers are respectively connected to the three bridges of the three-phase bridge rectifier circuit. At the midpoint of the arm, the synonymous ends of the primary windings and the secondary windings of the three isolation transformers are respectively connected to each other to form a Y-shaped connection. 2 . The three-phase converter according to claim 1 , wherein the three-phase bridge switch circuit comprises six switch tubes, every two switch tubes are connected in series to form a bridge arm, and three bridge arms are connected in parallel to form a bridge arm. 3 . Both ends serve as the first connection side of the three-phase converter. 3 . The three-phase converter according to claim 1 , wherein the three-phase bridge rectifier circuit comprises six switch tubes, every two switch tubes are connected in series to form a bridge arm, and three bridge arms are connected in parallel to form a bridge arm. 4 . Both ends serve as the second connection side of the three-phase converter. 4. The three-phase converter according to claim 2 or 3, wherein the switch tube is selected from MOSFET or IGBT. 5. The three-phase converter of claim 1, wherein the three-phase converter further comprises a first filter capacitor and a second filter capacitor, and both ends of the first filter capacitor are connected to the three-phase converter The first connection side of the second filter capacitor is connected to the second connection side. 6. A three-phase converter, characterized in that: the three-phase converter comprises a three-phase bridge switch circuit, a resonant cavity, three isolation transformers and a three-phase bridge rectifier circuit, and the three-phase bridge switch circuit and one side of the three-phase bridge rectifier circuit are respectively used as the first connection side and the second connection side of the three-phase converter, the resonant cavity includes three resonant circuits, and the three resonant circuits are respectively connected to the three-phase bridge. between the midpoints of the three bridge arms of the switch circuit and the primary windings of the three isolation transformers, where, Each resonant circuit includes a first inductor, a second inductor and a first capacitor, two ends of the first inductor are respectively connected to one end of the first capacitor and one end of the second inductor, and one end of the first inductor connected to the second inductor is also connected to The midpoint of a bridge arm in the three-phase bridge switch circuit, the other ends of the first capacitor and the second inductance are connected to the primary winding of an isolation transformer, and the ends of the same name of the secondary windings of the three isolation transformers are respectively connected to the three-phase bridge. The midpoint of the three bridge arms of the type rectifier circuit, and the different names of the primary windings and the secondary windings of the three isolation transformers are respectively connected to each other to form a Y-shaped connection.

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