阅读说明：本技术 使用直流侧混合谐波抑制方法的串联型48脉波整流器 (Series 48-pulse rectifier using DC side mixed harmonic suppression method ) 是由 王清媛 丁永强 于 2020-08-05 设计创作，主要内容包括：本发明实施例公开了一种使用直流侧混合谐波抑制方法的串联型48脉波整流器,包括输入电感、隔离变压器、第一三相全桥整流电路、第二三相全桥整流电路、控制电路、第一直流侧电容、第二直流侧电容、负载、谐波注入电路、钳位二极管,其中,第一和第二三相全桥整流电路串联连接且与负载并联；谐波注入电路由注入变压器、单相全波整流电路和开关管组成,控制电路的采样端与注入变压器的同名端相连,输出端与开关管的栅极相连。本发明将直流侧无源谐波抑制方法和有源谐波抑制方法结合起来,与不使用谐波注入电路的整流器相比,输入电压THD值由12%降低到2%以下,极大改善了整流器的电能质量。(The embodiment of the invention discloses a series 48-pulse rectifier using a direct current side mixed harmonic suppression method, which comprises an input inductor, an isolation transformer, a first three-phase full-bridge rectification circuit, a second three-phase full-bridge rectification circuit, a control circuit, a first direct current side capacitor, a second direct current side capacitor, a load, a harmonic injection circuit and a clamping diode, wherein the first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit are connected in series and are connected with the load in parallel; the harmonic injection circuit consists of an injection transformer, a single-phase full-wave rectification circuit and a switching tube, wherein the sampling end of the control circuit is connected with the homonymous end of the injection transformer, and the output end of the control circuit is connected with the grid electrode of the switching tube. According to the invention, the direct-current side passive harmonic suppression method and the active harmonic suppression method are combined, compared with a rectifier without a harmonic injection circuit, the THD value of the input voltage is reduced to below 2% from 12%, and the electric energy quality of the rectifier is greatly improved.)

1. A series 48-pulse rectifier using a direct current side mixed harmonic suppression method comprises an input inductor, an isolation transformer, a first three-phase full-bridge rectification circuit, a second three-phase full-bridge rectification circuit, a control circuit, a first direct current side capacitor, a second direct current side capacitor and a load, wherein the input inductor consists of three inductors with the same size, one ends of the three inductors are respectively connected with a three-phase voltage source, and the other ends of the three inductors are connected with a primary winding of the isolation transformer; the primary windings of the isolation transformer are connected in a triangular mode, and the secondary windings form star connection; the secondary winding generates two groups of three-phase voltages with equal magnitude and 30-degree phase difference; the two groups of secondary windings are respectively connected with the first three-phase full-bridge rectifying circuit and the second three-phase full-bridge rectifying circuit; the series 48-pulse rectifier is characterized by further comprising a harmonic injection circuit and a clamping diode, wherein the first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit are connected in series and then are connected in parallel with a load after being connected in series; the first direct current side capacitor and the second direct current side capacitor are connected in series and then connected in parallel with the load after being connected in series; the harmonic injection circuit consists of an injection transformer, a single-phase full-wave rectifying circuit and a switching tube, wherein two ends of a primary winding of the injection transformer are respectively connected with the middle points of two groups of three-phase full-bridge rectifying circuits and the middle points of two direct-current side capacitors, and a secondary winding is connected with the single-phase full-wave rectifying circuit; the collector of the switching tube is connected with the primary winding of the injection transformer, and the emitter is connected with the anode of the diode of the single-phase full-wave rectification circuit and the cathode of the clamping diode; the anode of the clamping diode is connected between the first three-phase full-bridge rectifying circuit and the first direct-current side capacitor; the sampling end of the control circuit is connected with the homonymous end of the injection transformer, and the output end of the control circuit is connected with the grid electrode of the switching tube.

2. The series 48-pulse rectifier using the dc-side hybrid harmonic suppression method according to claim 1, wherein the isolation transformer is a phase-shifting transformer, and the primary side and the secondary side of the isolation transformer are electrically isolated; the isolation transformer consists of three core columns, each core column is provided with 3 windings which comprise 1 primary winding and 2 secondary windings, the windings are mutually independent, the primary windings form a triangular connection, the secondary windings form a star-angle connection, and two groups of three-phase voltages with equal size and 30-degree phase difference are generated.

3. The series 48-pulse rectifier using DC-side hybrid harmonic suppression method according to claim 1, wherein the first DC-side capacitor and the second DC-side capacitor have the same capacitance value.

4. The series 48-pulse rectifier using DC-side hybrid harmonic suppression as claimed in claim 1, wherein the first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit both use uncontrolled rectification devices.

5. The series 48-pulse rectifier using DC-side hybrid harmonic suppression as in claim 1 wherein the injection transformer is comprised of a core leg with a primary winding and two secondary windings on each leg.

6. The series 48-pulse rectifier using DC-side hybrid harmonic suppression as claimed in claim 1 wherein the injection transformer is a single-phase transformer with a turn ratio of 0.02456.

Technical Field

The invention relates to the field of electronic power, in particular to a series 48-pulse rectifier using a direct current side mixed harmonic suppression method.

Background

The multi-pulse rectifier is a high-power electric energy conversion device, has a simple structure and strong robustness, but adopts diode rectification, and because the strong nonlinearity of the diode generates a large amount of harmonic pollution, the input and output electric energy quality of the rectifier is reduced. Therefore, finding an effective method to suppress the input current and voltage harmonics of the multi-pulse rectifier is the key of the current multi-pulse rectifier technology research.

The first method is to increase the number of rectifier bridges by increasing the output phase number of the phase-shifting transformer, thereby increasing the input voltage or current step number, the load voltage and current pulse number of the rectifier, and improving the input and output electric energy quality of the rectifier, but when the output phase number of the phase-shifting transformer exceeds 3, the structure of the transformer is complex, the design is difficult, and the asymmetry problem is serious; the second method is to use an alternating current measurement filter to inject a harmonic signal with the same effective value and opposite phase to the harmonic wave in the alternating current measurement of the rectifier to offset the harmonic wave generated by the rectifier, but the method is difficult to consider the electric energy quality of the direct current side; and the third is to use a direct current side harmonic suppression method, including a direct current side passive harmonic suppression method, an active harmonic suppression method and a mixed harmonic suppression method, to inject voltage or current harmonic to the direct current side of the rectifier to counteract specific times of harmonic generated by the rectifier, wherein the direct current side passive harmonic suppression method does not need a switching tube and a control circuit, the circuit reliability is high, but the harmonic suppression capability is limited, the direct current side active harmonic suppression method has a significant harmonic suppression effect, but the reliability is low, the harmonic injection circuit loss is large, the direct current side mixed harmonic suppression method combines the two methods, the advantages of the two methods are considered, the reliability is high, the loss is low, and the method is the most commonly used method in the current multi-pulse rectification technology.

The invention patent with the application number of 2018104096783 entitled "series 36-pulse rectifier using dc-side mixed voltage harmonic injection method" uses dc-side mixed voltage harmonic injection method, but its harmonic suppression effect is poor and it is not satisfactory.

Disclosure of Invention

The technical problem to be solved by the embodiments of the present invention is to provide a series 48-pulse rectifier using a dc side hybrid harmonic suppression method to improve the harmonic suppression effect and improve the power quality of the rectifier.

In order to solve the technical problem, an embodiment of the present invention provides a series 48-pulse rectifier using a dc side hybrid harmonic suppression method, including an input inductor, an isolation transformer, a first three-phase full-bridge rectification circuit, a second three-phase full-bridge rectification circuit, a control circuit, a first dc side capacitor, a second dc side capacitor, and a load, where the input inductor is composed of three inductors of the same size, one ends of the three inductors are respectively connected to a three-phase voltage source, and the other ends are connected to a primary winding of the isolation transformer; the primary windings of the isolation transformer are connected in a triangular mode, and the secondary windings form star connection; the secondary winding generates two groups of three-phase voltages with equal magnitude and 30-degree phase difference; the two groups of secondary windings are respectively connected with the first three-phase full-bridge rectifying circuit and the second three-phase full-bridge rectifying circuit; the series 48-pulse rectifier further comprises a harmonic injection circuit and a clamping diode, wherein the first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit are connected in series and then connected in parallel with a load after being connected in series; the first direct current side capacitor and the second direct current side capacitor are connected in series and then connected in parallel with the load after being connected in series; the harmonic injection circuit consists of an injection transformer, a single-phase full-wave rectifying circuit and a switching tube, wherein two ends of a primary winding of the injection transformer are respectively connected with the middle points of two groups of three-phase full-bridge rectifying circuits and the middle points of two direct-current side capacitors, and a secondary winding is connected with the single-phase full-wave rectifying circuit; the collector of the switching tube is connected with the primary winding of the injection transformer, and the emitter is connected with the anode of the diode of the single-phase full-wave rectification circuit and the cathode of the clamping diode; the anode of the clamping diode is connected between the first three-phase full-bridge rectifying circuit and the first direct-current side capacitor; the sampling end of the control circuit is connected with the homonymous end of the injection transformer, and the output end of the control circuit is connected with the grid electrode of the switching tube.

Furthermore, the isolation transformer is a phase-shifting transformer, and the primary side and the secondary side of the isolation transformer are electrically isolated; the isolation transformer consists of three core columns, each core column is provided with 3 windings which comprise 1 primary winding and 2 secondary windings, the windings are mutually independent, the primary windings form a triangular connection, the secondary windings form a star-angle connection, and two groups of three-phase voltages with equal size and 30-degree phase difference are generated.

Furthermore, the capacitance values of the first direct current side capacitor and the second direct current side capacitor are the same.

Furthermore, the first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit both adopt uncontrolled rectification devices.

Furthermore, the injection transformer consists of a core column, and each core column is provided with a primary winding and two secondary windings.

Further, the injection transformer is a single-phase transformer with a turn ratio of 0.02456.

The invention has the beneficial effects that: the secondary winding of the isolation transformer is connected in a star-delta manner, so that third harmonic generated by the rectifier is effectively inhibited; the harmonic injection circuit adopted by the invention consists of the passive harmonic injection circuit and the active harmonic injection circuit, the harmonic injection circuit has better adaptability, and even if the switch tube fails, the passive harmonic injection circuit still can work and still has a certain inhibiting effect on harmonic; the rectifier bridge adopted by the invention is a diode rectifier bridge, does not need complex control, has high reliability and is suitable for high-power occasions.

Drawings

Fig. 1 is a circuit diagram of a series 48-pulse rectifier using a dc-side hybrid harmonic suppression method according to an embodiment of the present invention.

Fig. 2 is a winding structure diagram of an isolation transformer according to an embodiment of the present invention.

Fig. 3 is a winding structure diagram of an injection transformer according to an embodiment of the present invention.

Fig. 4 is a circuit diagram of the operation mode I of the harmonic injection circuit according to the embodiment of the present invention.

Fig. 5 is a circuit diagram of the harmonic injection circuit operating mode II according to an embodiment of the present invention.

Fig. 6 is a circuit diagram of a mode III of operation of the harmonic injection circuit according to an embodiment of the present invention.

Fig. 7 is a circuit diagram of the harmonic injection circuit operating mode IV according to an embodiment of the present invention.

Fig. 8 is an operation waveform of a series 48-pulse rectifier using a dc-side hybrid harmonic suppression method according to an embodiment of the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict, and the present invention is further described in detail with reference to the drawings and specific embodiments.

If directional indications (such as up, down, left, right, front, and rear … …) are provided in the embodiment of the present invention, the directional indications are only used to explain the relative position relationship between the components, the movement, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only used for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

Referring to fig. 1, a series 48-pulse rectifier using a dc-side hybrid harmonic suppression method according to an embodiment of the present invention includes an input inductor 1, an isolation transformer 2, a first three-phase full-bridge rectifier circuit 3, a second three-phase full-bridge rectifier circuit 4, a harmonic injection circuit 5, a clamping diode 6, a control circuit 7, a first dc-side capacitor 8, a second dc-side capacitor 9, and a load 10.

The input inductor 1 is composed of three inductors with the same size, the left end of the input inductor is connected with a three-phase voltage source respectively, the right end of the input inductor is connected with a primary winding of an isolation transformer, and an input power supply is equivalent to a three-phase balanced current source.

The isolation transformer 2 is used as a phase-shifting transformer, the primary windings are connected in a triangular mode, the secondary windings form star-delta connection, the secondary windings generate two groups of three-phase voltages with the same size and the phase difference of 30 degrees, the primary windings are connected with the input inductor, and the two groups of secondary windings are respectively connected with the first three-phase full-bridge rectification circuit 3 and the second three-phase full-bridge rectification circuit 4.

First three-phase full-bridge rectifier circuit 3 and second three-phase full-bridge rectifier circuit 4 series connection, first direct current side electric capacity 8 and second direct current side electric capacity 9 are established ties, first three-phase full-bridge rectifier circuit 3 and second three-phase full-bridge rectifier circuit 4, first direct current side electric capacity 8 and second direct current side electric capacity 9 and load 10 are parallelly connected in parallel, and output voltage becomes the twice. The first three-phase full-bridge rectification circuit and the second three-phase full-bridge rectification circuit both adopt uncontrolled rectification devices, and reliability is high.

The first direct current side capacitor 8 and the second direct current side capacitor 9 are equal in size, and the output voltage of the rectifier is direct current after being filtered by the capacitors. The upper end of the first direct current side capacitor 8 is connected with the positive electrode of the output end of the first three-phase full-bridge rectification circuit 3 and the positive electrode of the load 10, and the lower end of the first direct current side capacitor is connected with the upper end of the second direct current side capacitor 9. The lower end of the second direct current side capacitor 9 is connected with the negative electrode of the output end of the second three-phase full-bridge rectification circuit 4 and the negative electrode of the load 10.

The harmonic injection circuit 5 is composed of an injection transformer, a single-phase full-wave rectification circuit and a switching tube, wherein a primary winding of the single-phase transformer is respectively connected with a midpoint of the single-phase full-bridge rectification circuit and midpoints of two direct-current side capacitors, a secondary winding is connected with the single-phase full-wave rectification circuit, a collector of the switching tube is connected with the primary winding of the injection transformer, and an emitter of the switching tube is connected with an anode of a diode of the single-phase full-wave rectification circuit. The harmonic injection circuit 5 of the invention is composed of a passive harmonic suppression circuit and an active harmonic suppression circuit, when the switch tube has a fault, the rectifier still has a good suppression effect on the harmonic, and the reliability is high. The single-phase full-wave rectification circuit only consists of two diodes, and the loss is small.

The anode of the clamping diode 6 is connected between the first three-phase full-bridge rectification circuit 3 and the first direct current side capacitor 8, and the cathode is connected with the diode anode of the single-phase full-wave rectification circuit. According to the embodiment of the invention, the harmonic suppression effect is improved by changing the position of the switching tube, and when the switching tube is conducted, the voltage of the primary winding of the injection transformer is +/-N₄/(2N₅)u_oIncrease notesInput voltage u_FPThe step number of the harmonic suppression effect is more obvious.

The sampling end of the control circuit 7 is connected with the homonymous end of the injection transformer, and the output end of the control circuit is connected with the grid electrode of the switching tube.

As an embodiment, referring to fig. 1 and 8, a specific method for suppressing harmonics of a series 48-pulse rectifier using a dc side hybrid harmonic suppression method according to an embodiment of the present invention is as follows:

control circuit 7 for current i_xSampling is carried out, a sampling signal and a sampling current are in the same phase, and the sampling signal generates a square wave signal u through zero-crossing comparison_t，u_tGenerating a ramp signal u via an integrating circuit_i，u_iComparing with each reference voltage signal to obtain the control signal u shown in FIG. 8_cControl signal u_cThe injection voltage u in FIG. 8 is generated by controlling the on and off of the switch tube_FPThe output voltage of the rectifier bridge is modulated, the harmonic component of the input voltage of the rectifier bridge is eliminated, and then the input voltage harmonic of the rectifier is suppressed, so that the input voltage waveform of the rectifier tends to be sinusoidal. The capacity of the harmonic injection circuit 5 of the rectifier is only 2% of the input power, and the embodiment of the invention realizes a better harmonic suppression effect with lower cost.

As an implementation manner, referring to fig. 1 and fig. 2, an isolation transformer 2 according to an embodiment of the present invention is composed of 3 identical core legs, each core leg has 3 windings, including 1 primary winding and 2 secondary windings, and the turn ratio of the 3 windings is N₁:N₂:N₃1.73:1.73: 1; winding a₁、a₂、a₃On the same core column, winding b₁、b₂、b₃On the same core column, winding c₁、c₂、c₃Are positioned on the same core column; primary winding a₁、b₁、c₁Form a triangular connection, and the positive ends of the triangular connection are respectively connected with point A, B, C; secondary winding a₂、b₂、c₂Form a triangular connection and are connected with a first single-phase full-bridge rectification circuit 3; secondary winding a₃、b₃、c₃Forming a star connection and connected to a second single-phase full-bridge rectifier circuit 4.

The embodiment of the invention adopts the isolated transformer, and the primary side and the secondary side of the transformer are electrically isolated, so that the transformer has higher safety.

As an implementation manner, referring to fig. 1 and fig. 3, an injection transformer according to an embodiment of the present invention is a single-phase transformer, the transformer is composed of 1 core column, the core column has 3 windings, a primary winding and two secondary windings, the left side of the input end of the injection transformer is connected to a connection point F of a rectifier bridge, the right side of the input end of the injection transformer is connected to a connection point P of two dc-side capacitors, the secondary winding of the injection transformer has a center tap and is connected to the input end of a single-phase full-wave rectifier circuit, and the injection transformer and the single-phase full-wave rectifier circuit together form a harmonic injection circuit.

The injection transformer adopted by the embodiment has the advantages of simple structure, strong symmetry, small capacity and low harmonic suppression cost.

As an embodiment, referring to fig. 1, 4, 5, 6, and 7, the operation mode of the harmonic injection circuit 5 according to the embodiment of the present invention is as follows:

the harmonic injection circuit 5 comprises an injection transformer and a single-phase full-wave rectification circuit, and i can be known according to the structure of the transformer and the conduction mode of the rectification bridge_xA triangular wave 6 times the power supply frequency; when i is_x>0, when Q is on, u_FP＝N₄/(2N₅)u_oThe working mode I of the harmonic injection circuit 5 is shown in fig. 4; when i is_x>0, Q is off, u_FP＝N₄/N₅u_oThe working mode II of the harmonic injection circuit 5 is shown in fig. 5; when i is_x<0, Q is off, u_FP＝-N₄/N₅u_oThe working mode III of the wave injection circuit 5 is shown in fig. 6; when i is_x<0, when Q is on, u_FP＝-N₄/(2N₅)u_oThe mode IV of operation of the harmonic injection circuit 5 is shown in fig. 7.

As an implementation manner, referring to fig. 1, fig. 4, fig. 5, fig. 6, and fig. 7, an injection transformer according to an embodiment of the present invention is a single-phase transformer, and an input voltage effective value and a fundamental amplitude expression thereof can be obtained according to kirchhoff's voltage law:

according to the above formula and the definition of THD value, when the turn ratio (the ratio of the number of primary turns to the number of secondary turns) is N₄/N₅At 0.02456, the THD value of the rectifier input current is minimal. The turn ratio of the injection transformer is N₄/N₅0.02456, the input voltage THD of the rectifier reaches the minimum value of 3.83%, and the harmonic suppression effect of the rectifier is obviously improved by the embodiment of the invention.

According to the invention, by changing the turn ratio of the injection transformer, the position of the switching tube and the control method, the voltage waveform of the primary winding of the injection transformer is changed from 6 step waves to 8 step waves, the step value of the input voltage of the rectifier is increased from 36 to 48, the THD theoretical value is reduced from 5.093% to 3.83%, and the harmonic suppression effect is obviously improved; and the effective value of the current flowing through the switching tube is halved, and the loss of the harmonic suppression circuit is reduced.

The method combines a direct current side passive harmonic suppression method and an active harmonic suppression method, utilizes the direct current side passive harmonic suppression method to suppress low-order harmonics generated by a rectifier, and utilizes the active harmonic suppression method to suppress higher-order harmonics generated by the rectifier; compared with a rectifier without a harmonic injection circuit, the input voltage THD value is reduced to below 2% from 12%, and the electric energy quality of the rectifier is greatly improved.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.