Harmonic suppression circuit adopting dual active modulation

Abstract

The invention provides a harmonic suppression circuit adopting dual-active modulation, and a rectifier adds a dual-active modulation circuit on a direct current side on the basis of an average value current prediction control strategy. A conventional 12-pulse-wave rectifier is improved into a 12-pulse-wave controllable rectifier with controllable load voltage and low grid-side current harmonic content. According to the parallel 12-pulse rectifier provided by the invention, the THD value of the grid-side current can be reduced, and meanwhile, the load current can be conveniently adjusted.

Description

Technical Field

[0001] The invention relates to the technical field of high-power rectification, and in particular to a harmonic suppression circuit using dual-active modulation. Background Art

[0002] The parallel 12-pulse rectifier has the advantages of simple structure, high reliability, low cost and low EMI, and is often used in high-power industrial occasions such as urban rail power supply, electrolytic plating, metal smelting and ship shore power. However, due to the lack of auxiliary regulation mechanism, the high-order harmonics in the multi-pulse rectifier system will still affect the performance of the rectifier system. In order to meet the strict requirements of the IEEE-519 standard on harmonics, relevant scholars have proposed the following three methods.

[0003] Specifically, there are three main methods for suppressing the grid-side harmonics of parallel 12-pulse rectifiers. The first is to change the working mode of the circuit through variable topology phase-controlled rectification technology to reduce the harmonic content of the grid-side current. It can suppress the grid-side current harmonics while quickly switching the topology. However, its harmonic suppression capability is limited and often cannot meet the requirements of the IEEE-519 harmonic standard. The second is to multiply the number of pulses of the rectifier by increasing the number of output windings of the phase-shifting transformer to achieve the suppression of the input current harmonic content and output voltage pulsation, but this method requires doubling the number of output windings of the phase-shifting transformer or the phase-shifting transformer, which increases the difficulty of transformer manufacturing and the complexity of the rectifier. The third is the DC side harmonic suppression technology, which can ensure the simple circuit structure of the multi-pulse rectifier system and effectively reduce the grid-side harmonics of the harmonic rectification system. In view of the clear correspondence between the currents on the AC side and the DC side of the multi-pulse rectifier system, by adding a modulation circuit on the DC side, the modulation current generated by the small-capacity modulation circuit is superimposed on the output current of the rectifier bridge, which can effectively reduce the harmonic content of the AC side current. Thus, the grid-side current harmonics can be effectively suppressed without increasing the complexity of the rectifier system. The DC-side harmonic suppression technology of the multi-pulse rectifier system has the advantages of simple structure, small modulation circuit capacity, and excellent ability to suppress grid harmonics.

[0004] Referring to the above methods for suppressing grid-side harmonics of rectifiers, how to propose a 12-pulse controlled rectifier that can effectively suppress grid-side current harmonics and easily adjust the rectifier output voltage or output current without increasing system complexity is a problem that needs to be solved urgently.

[0005] In view of this, this application is filed. Summary of the invention

[0006] The present invention provides a harmonic suppression circuit using dual active modulation, which can at least partially improve the above problems.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A harmonic suppression circuit using dual active modulation, comprising: a three-phase AC power supply, a phase-shifting transformer and a thyristor rectifier bridge, a dual active modulation circuit, an inductor component, a load, and a control circuit;

[0009] The output end of the three-phase AC power supply is electrically connected to the input end of the phase-shifting transformer and the thyristor rectifier bridge, the positive pole of the phase-shifting transformer and the thyristor rectifier bridge is electrically connected to the positive pole of the inductor component, the dual-active modulation circuit, and the load, the negative pole of the load is electrically connected to the negative pole of the phase-shifting transformer and the thyristor rectifier bridge, and the control end of the dual-active modulation circuit is electrically connected to the output end of the control circuit;

[0010] The control circuit is configured to collect the load voltage, the instantaneous value of the inductor current and the inductance value, and calculate the load current increment to control the on or off of the switch tube of the dual active modulation circuit; the dual active modulation circuit is configured to reduce the harmonic content of the grid-side current.

[0011] In summary, the harmonic suppression circuit using dual active modulation adds a dual active modulation circuit on the DC side on the basis of the average current prediction control strategy. The conventional 12-pulse rectifier is improved into a 12-pulse controllable rectifier with controllable load voltage and low grid-side current harmonic content. The parallel 12-pulse rectifier proposed in the present invention can reduce the THD value of the grid-side current and facilitate the adjustment of the load current. In short, the harmonic suppression circuit using dual active modulation can enhance the harmonic suppression capability of the traditional 12-pulse rectifier, while improving the convenience of load voltage regulation, and combining the problems existing in the field of new energy. It aims to solve the problem that it is difficult to consider the grid-side harmonic problem and the dynamic response problem of the load current at the same time in the 12-pulse rectifier, and on the basis of satisfying the fast dynamic response of the rectifier load current, the purpose of suppressing the harmonics of the rectifier input current is achieved. It helps to eliminate the influence of the circulating harmonic component on the load current and reduce the harmonic content of the input current.

[0012] Compared with the 12-pulse rectifier in the prior art, the harmonic suppression circuit using dual active modulation only needs to control two switch tubes and the switch tube to reduce the harmonic content of the grid-side current, and has the advantages of simple circuit structure and easy control. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a harmonic suppression circuit using dual active modulation provided by the first aspect of the present invention, a is the phase a voltage of the three-phase AC power supply, u b is the b-phase voltage of the three-phase AC power supply, u c is the phase c voltage of the three-phase AC power supply, ia is the phase a current of the three-phase AC power supply, i b is the b-phase current of the three-phase AC power supply, i c is the c-phase current of the three-phase AC power supply, i a1 is the a-phase current of a three-phase alternating current output by the phase-shifting transformer, i b1 is the b-phase current of a three-phase alternating current output by the phase-shifting transformer, i c1 is the c-phase current of a three-phase alternating current output by the phase-shifting transformer, i a2 is the a-phase current of another three-phase AC output by the phase-shifting transformer, i b2 is the b-phase current of another three-phase AC output by the phase-shifting transformer, i c2 is the c-phase current of another three-phase AC output by the phase-shifting transformer, u d1 is the voltage output on the DC side of the first three-phase rectifier bridge, u d2 is the voltage output on the DC side of the second three-phase rectifier bridge, i d1 is the current output from the positive output terminal of the first thyristor rectifier bridge, i d2 is the current output from the positive output terminal of the second thyristor rectifier bridge, i d is the load current flowing through the load, u d is the load voltage of the load, i s is the modulation current of the dual active modulation circuit, U s It is the equivalent power supply of the dual active modulation circuit;

[0014] Figure 2 It is a circuit diagram of a harmonic suppression circuit using dual active modulation provided by the second aspect of the present invention;

[0015] Figure 3 It is a schematic diagram of a harmonic suppression circuit using dual active modulation provided by the third aspect of the present invention;

[0016] Figure 4 Schematic diagram of the winding structure of a Y / Δ / Y isolation phase-shifting transformer provided in an embodiment of the present invention;

[0017] Figure 5 1 is a schematic diagram of a current loop of a dual active modulation circuit in a 12-pulse rectifier provided in an embodiment of the present invention when operating in mode 1;

[0018] Figure 6 1 is a schematic diagram of a current loop of a dual active modulation circuit in a 12-pulse rectifier provided in an embodiment of the present invention when operating in mode 2;

[0019] Figure 7 1 is a schematic diagram of a current loop of a dual active modulation circuit in a 12-pulse rectifier provided in an embodiment of the present invention when operating in mode 3;

[0020] Figure 8 1 is a schematic diagram of a current loop of a dual active modulation circuit in a 12-pulse rectifier provided in an embodiment of the present invention when operating in mode 4;

[0021] Fig. 9 is a conduction timing diagram of a dual active modulation circuit provided by an embodiment of the present invention;

[0022] Fig.10 is the AC side output current i provided by the embodiment of the present invention a Waveform and THD value diagram. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the first embodiment of the present invention discloses a harmonic suppression circuit using dual active modulation, which includes: a three-phase AC power supply, a phase-shifting transformer and a thyristor rectifier bridge 1, a dual active modulation circuit 2, an inductor component, a load 3, and a control circuit 4;

[0025] The output end of the three-phase AC power supply is electrically connected to the input end of the phase-shifting transformer and the thyristor rectifier bridge 1, the positive pole of the phase-shifting transformer and the thyristor rectifier bridge 1 is electrically connected to the positive pole of the inductor component, the dual-active modulation circuit 2, and the load 3, the negative pole of the load 3 is electrically connected to the negative pole of the phase-shifting transformer and the thyristor rectifier bridge 1, and the control end of the dual-active modulation circuit 2 is electrically connected to the output end of the control circuit 4;

[0026] The control circuit 4 is configured to collect the load voltage, the instantaneous value of the inductor current and the inductance value, and calculate the load current increment to control the on or off of the switch tube of the dual active modulation circuit 2; the dual active modulation circuit 2 is configured to reduce the harmonic content of the grid-side current.

[0027] In this embodiment, on the basis of the average current prediction control strategy, a dual active modulation circuit 2 is added on the DC side to improve the conventional 12-pulse rectifier into a 12-pulse controlled rectifier with controllable load 3 voltage and low grid-side current harmonic content. The specific implementation method of harmonic suppression includes the following steps:

[0028] Step 1: Sample the input line voltage of the three-phase grid and send it to the calculation unit of the control circuit 4; sample the load voltage and send it to the calculation unit; sample the instantaneous value of the inductor current and send it to the calculation unit; sample the inductor value and send it to the calculation unit.

[0029] Step 2: Determine the inductor current reference value at the next moment, and then determine the triggering moment of the first thyristor rectifier bridge and the second thyristor rectifier bridge of the phase-shifting transformer and the thyristor rectifier bridge 1.

[0030] Step 3: Add a dual active modulation circuit 2 to the DC side of the 12-pulse controlled rectifier to reduce the harmonic content of the grid-side current.

[0031] Step 4: Under the action of the control circuit 4, the first switch tube S of the dual active modulation circuit 2 is driven 1 and the second switch tube S 2 .

[0032] Step 5: The proposed harmonic suppression method can reduce the grid-side current THD value while facilitating the adjustment of the load current.

[0033] Specifically, in this embodiment, the harmonic suppression circuit using dual active modulation uses active devices, which is more reliable than the passive harmonic suppression method and has stronger system robustness; the thyristor rectifier bridge is used to replace the diode rectifier bridge, and the grid-side current harmonics can still be effectively suppressed on the basis of adjustable load current and voltage; at the same time, a Y / Δ / Y isolation phase-shifting transformer is used, and two groups of three-phase rectifier bridges can be independently connected in parallel without a balancing reactor. A dual active modulation circuit is also used to reduce the THD value of the input current on the AC side from 13.31% to 2.71%, and the dual active modulation circuit does not include a balancing reactor with a complex winding structure, and has a simple structure, low cost, high reliability and good economy.

[0034] Preferably, the phase-shifting transformer and thyristor rectifier bridge 1 include a Y / Δ / Y isolation phase-shifting transformer, a first thyristor rectifier bridge, and a second thyristor rectifier bridge, wherein the output end of the three-phase AC power supply is electrically connected to the input end of the Y / Δ / Y isolation phase-shifting transformer, the first output end of the Y / Δ / Y isolation phase-shifting transformer is electrically connected to the input end of the first thyristor rectifier bridge, the positive polarity output end of the first thyristor rectifier bridge is electrically connected to the O end of the dual active modulation circuit 2, the second output end of the Y / Δ / Y isolation phase-shifting transformer is electrically connected to the input end of the second thyristor rectifier bridge, the positive polarity output end of the second thyristor rectifier bridge is electrically connected to the P end of the dual active modulation circuit 2, the cathode input end of the first thyristor rectifier bridge is connected to the negative polarity end of the load 3, and the cathode input end of the second thyristor rectifier bridge is connected to the negative polarity end of the load 3.

[0035] Preferably, the inductor component includes a first inductor L 1 , the second inductor L 2 , wherein the positive output terminal of the first thyristor rectifier bridge and the first inductor L 1 One end of the first inductor L is connected 1 The other end of the second thyristor rectifier bridge is connected to the positive polarity end of the load 3, and the positive polarity output end of the second thyristor rectifier bridge is connected to the second inductor L 2 One end of the second inductor L 2 The other end is connected to the positive polarity end of the load 3.

[0036] In this embodiment, the phase-shifting transformer and the thyristor rectifier bridge are specifically a Y / Δ / Y isolation phase-shifting transformer and two groups of thyristor rectifier bridges, and the two groups of three-phase voltages are respectively sent to the two groups of thyristor rectifier bridges. The positive output end of the first thyristor rectifier bridge is connected to the O end of the dual active modulation circuit 2, and the residual current flows through the O node and then flows through the first inductor L 1 , the first inductor L 1 The dual active modulation circuit 2 is used to generate modulation current, so that the input current of the rectifier is close to a sine wave. The positive output end of the second thyristor rectifier bridge is connected to the P end of the dual active modulation circuit 2. After the residual current passes through the P node, it flows through the second inductor L 2 , the second inductor L 2 The cathode input terminal of the first thyristor rectifier bridge is connected to the negative polarity terminal of the load 3; the cathode input terminal of the second thyristor rectifier bridge is connected to the negative polarity terminal of the load 3, and the two branches are connected in parallel to form a parallel type 12-pulse rectifier.

[0037] The modulation current of the dual active modulation circuit 2 flows in from point O and passes through the third inductor L of the dual active modulation circuit 2. S1 and the fourth inductor L S2 , auxiliary inductor L s The current on the bridge is modulated into a triangular wave with 6 times the grid voltage frequency, the peaks and troughs of which correspond to the peaks and troughs of the rectifier bridge output voltage, and the amplitude is half of the load current; the output current of the rectifier bridge is further modulated into a triangular wave with 6 times the grid voltage frequency and an amplitude equal to the load current, thereby realizing the modulation of the rectifier bridge output current and making the rectifier input current approximately a sine wave.

[0038] Specifically, in this embodiment, a thyristor bridge is used, and current prediction control is adopted to control the triggering of the thyristor; two groups of thyristor rectifier bridges, the control strategy adopts average current prediction control, and the 12-pulse rectifier based on the isolated phase-shifting transformer is taken as the research object, and the thyristor current prediction control strategy is adopted. While the thyristor can be accurately triggered, the grid-side current harmonics can be significantly suppressed. The phase-shifting transformer is a Y / Δ / Y isolated phase-shifting transformer, which greatly reduces the equivalent capacity of the rectifier system. Through the phase-shifting transformer, a group of three-phase power supplies can generate multiple groups of voltages with equal amplitudes and a certain angle difference in phase. The three primary windings of the phase-shifting transformer are respectively connected to the a phase, b phase and c phase of the three-phase AC power supply. The output ends of the three-phase AC power supply are respectively connected to the two groups of thyristor rectifier bridges to generate two groups of three-phase voltages with a phase difference of 30° and equal amplitudes. That is, the phase-shifting transformer 1 can be a zigzag autotransformer shifted to 30°; it is used to shift the phase of the received three-phase voltage of the power grid, generate two sets of three-phase voltages with a phase difference of 30° and equal amplitude, and send the two sets of three-phase voltages generated to the first thyristor rectifier bridge and the second thyristor rectifier bridge respectively.

[0039] Preferably, the dual active modulation circuit 2 includes a first switch tube S 1 , the second switch tube S 2 , the first capacitor C 1 , the second capacitor C 2 , the first diode D 11 , the second diode D 12 , the third diode D 21 , the fourth diode D 22 , the third inductor L s1 and the fourth inductor L s2 , wherein the first switch tube S 1 The first end and the second switch tube S 2 The first end of the first thyristor rectifier bridge is electrically connected to the output end of the control circuit 4, and the positive output end of the first thyristor rectifier bridge is electrically connected to the fourth inductor L s2 One end of the first diode D 11 The negative pole of the fourth inductor L s2 The other end of the third diode L s1 The positive electrode of the second switch tube S 2 The second end of the third diode L s1 The negative electrode of the second capacitor C 2 One end of the second capacitor C 2 The other end of the second switch tube S 2 The third end of the fourth diode D 22 The positive electrode of the second thyristor rectifier bridge is connected to the positive electrode of the fourth diode D 22 The negative pole of the third inductor Ls1 One end of the third inductor L s1 The other end of the second diode D 12 The positive electrode of the first switch tube S 1 The third end of the second diode D 12 The negative electrode of the first capacitor C 1 One end of the first switch tube S 1 The second end of the first capacitor C 1 The other end of the first diode D 11 positive connection.

[0040] Preferably, the first switch tube S 1 and the second switch tube S 2 is an NMOS tube, the first switch tube S 1 The first end of the NMOS tube is the gate of the NMOS tube, and the first switch tube S 1 The second end of the first switch tube S 1 The third end of the NMOS tube is the drain of the second switch tube S 2 The first end of the NMOS tube is the gate of the second switch tube S 2 The second end of the NMOS tube is the drain of the second switch tube S 2 The third end is the source of the NMOS tube.

[0041] In this embodiment, a dual active modulation circuit 2 is added to modulate the output current of the rectifier bridge, and the dual active modulation circuit 2 adopts PWM control; the dual active modulation circuit 2 is a dual active modulation circuit. On the basis of realizing fast dynamic response of load current, the harmonic content of grid-side current can still be reduced. Specifically, the dual active modulation circuit 2 is composed of two parts. Compared with the traditional single-phase voltage-type half-bridge / full-bridge circuit, since the two modulation units cooperate to generate a 300Hz triangular wave, it is less affected by load changes and has higher stability. This not only effectively suppresses the harmonics of the rectifier system, but also significantly improves the power factor of the controllable rectifier system.

[0042] Among them, the first switch tube S 1 and the second switch tube S 2 are all controlled by the driving signal of the control circuit, which is used to adjust the inductor current reference value i L-ref and the actual current value i at the current moment L To calculate the difference, the two driving signals respectively control the first switch tube S of the dual active modulation circuit 1 and the second switch tube S 2 . Only the first switch tube S 1 and the second switch tube S 2Control can reduce the harmonic content of the grid-side current, and has the advantages of simple circuit structure, easy control and high power density.

[0043] Preferably, the control circuit 4 includes a calculation unit and a controller, wherein the output end of the calculation unit is electrically connected to the input end of the controller, the output end of the controller is electrically connected to the control end of the dual active modulation circuit, and the calculation unit is configured to collect the load voltage, the instantaneous value of the inductor current and the inductance value, and calculate the load current increment.

[0044] Preferably, the calculation unit is an analog multiplier.

[0045] Preferably, the calculation unit calculates the load current increment Δi using the formula: Where L is the filter inductance, corresponding to Figure 1 L1, L2, U LL is the three-phase input line voltage, u d is the DC side load voltage, and dt is the integral variable.

[0046] In this embodiment, the control circuit 4 adopts the PI control strategy. The average current prediction control strategy is used to determine the trigger angle of the thyristor rectifier bridge, and the thyristor conduction angle is controlled to make the load voltage adjustable. Through the control circuit 4, the input line voltage U LL , load voltage u d , and send it to the sampling unit to calculate the load current increment Δi. When the difference meets the conditions, the thyristor is turned on to achieve predictive control. The control circuit is based on the inductor current reference value i L-ref and the actual current value i at the current moment L To calculate the difference, the two driving modes are as follows: the control circuit 4 samples the input line voltage for zero-crossing detection, and obtains the modulated rectifier bridge output current given signal i through calculation. L-ref , by comparing with the triangular wave, a triangular wave with a certain phase and amplitude is obtained; when the reference current changes, the load current of the rectifier system changes, and the inductor current given signal i output by the analog multiplier L-ref The input current changes accordingly, and the PWM signal is isolated and power-amplified by the driving circuit to generate two driving signals; the two driving signals are used to control the first switch tube S of the dual active modulation circuit 2 respectively. 1 and the second switch tube S of the dual active modulation circuit 2 2 In conjunction with the main circuit control strategy, the load current can respond quickly while input current harmonics are suppressed.

[0047] Specifically, in this embodiment, the first thyristor rectifier bridge control strategy is average current prediction control, sampling the three-phase input line voltage ULL , DC side load current i d and DC side load voltage u d , and send it to the sampling unit to calculate the load current increment. The formula is as follows: The first thyristor rectifier bridge, when the difference between the load current reference value and the current value at the current moment is equal to the calculated difference, the thyristor is turned on to achieve predictive control, the formula is as follows: Δi ref =i d1-ref -i d1 , Δi=k×Δi ref .

[0048] The second thyristor rectifier bridge control strategy is average current prediction control, sampling the three-phase input line voltage U LL , DC side load current i d and DC side load voltage u d , and send it to the sampling unit to calculate the load current increment. The formula is as follows: For the second thyristor rectifier bridge, when the difference between the load current reference value and the current value at the current moment is equal to the calculated difference, the thyristor is turned on to implement predictive control, and the formula is as follows: Δiref=id2-ref-id2, Δi=k×Δiref.

[0049] According to U s and the modulation current i s1 、i s2 It can be seen from the positive and negative of that the 12-pulse rectifier has four working modes, specifically:

[0050] WhenU s <0, the modulation circuit works on the first switch tube S 1 In the active circuit, the second switch tube S 2 The active circuit does not work. s1 ≥0, the modulation circuit operates in working mode 1. At this time, the first switch tube S 1 Disconnect, the modulation circuit output voltage Up = -Uc 1 ,like Figure 5 As shown. 1 <0, the modulation circuit operates in working mode 3, at which time the first switch tube S 1 conduction, due to D 11 The existence of the modulation circuit output voltage Up = 0, such as Figure 7 shown.

[0051] WhenU s ≥0, the modulation circuit works on the second switch tube S 2 In the active circuit, the first switch tube S 1 The active circuit does not work. s2≥0, the modulation circuit operates in working mode 2, at which time the second switch tube S 2 Disconnect, the modulation circuit output voltage Up = Uc 2 ,like Figure 6 As shown. 2 <0, the modulation circuit operates in working mode 4, at which time the second switch tube S 2 conduction, due to D 22 The existence of the modulation circuit output voltage Up = 0, such as Figure 8 shown.

[0052] According to the analysis of the circuit mode, the timing diagram of the dual active modulation circuit is as follows: Fig. 9 The control circuit is used to control the inductor current reference value i L-ref and the actual value of the inductor current i at the current moment L To calculate the difference, the two drivers are used to respectively control the first switch tube S of the dual active modulation circuit. 1 and the second switch tube S 2 Take control.

[0053] The control circuit samples the input line voltage for zero-crossing detection and determines the inductor current reference value i L-ref The phase of the inductor current is compared with the triangular wave to obtain a triangular wave with a certain phase and amplitude. L-ref and the actual value of the inductor current i at the current moment L The current difference is compared and sent to the PI regulator. The PI regulator calculates the duty cycle D according to the input current error. The duty cycle D passes through the PWM signal generator. After the PWM signal is isolated and power amplified by the drive circuit, two drive signals are generated. The two drive signals are used to control the first switch tube S of the dual active modulation circuit respectively. 1 and the second switch tube S of the dual active modulation circuit 2 .

[0054] The phase-shifting transformer adopts a Y / Δ / Y isolation phase-shifting transformer. In order to realize the convenient and adjustable load current, the first thyristor rectifier bridge and the second thyristor rectifier bridge adopt an average current prediction control strategy. In order to reduce the harmonic content of the grid-side current on this basis, the dual-active modulation circuit adopts a control circuit. At this time, the harmonic suppression circuit using dual-active modulation can still suppress the grid-side current harmonics on the basis of the fast dynamic response of the load current.

[0055] Compared with the prior art, the harmonic suppression circuit using dual active modulation has the following advantages:

[0056] 1. The harmonic suppression circuit adopts dual active modulation, and modulates the output current of two groups of rectifier bridges through the synergistic effect of four independent working modes to achieve the suppression of input current harmonics, such as Figures 5 to 8 As shown;

[0057] 2. Two sets of three-phase rectifier bridges can work independently in parallel without balancing reactors; an active dual-active modulation circuit is used to reduce the THD value of the AC side input current from 13.31% to 2.71%. Fig.10 As shown;

[0058] 3. By making improvements on the harmonic suppression dual active modulation circuit and the rectifier bridge, the dual active modulation circuit adopts PWM control and the thyristor rectifier bridge adopts average current prediction control.

[0059] In summary, the harmonic suppression circuit using dual active modulation sets the modulation current of the dual active modulation circuit, thereby converting the output current i of the positive polarity output end of the first thyristor rectifier bridge into d1 The output current i at the positive output end of the second thyristor rectifier bridge d2 Modulate into a triangle wave with 6 times the grid voltage frequency and an amplitude equal to the load current, realize the modulation of the output current of the rectifier bridge, and make the rectifier input current approximate to a sine wave. By designing the control circuit, according to the voltage and current relationship on the AC and DC sides, the harmonic content of the input current is reduced, and the input current THD value is reduced. The harmonic suppression circuit using dual active modulation solves the problems of high harmonic content of the input current and unadjustable output voltage of the existing parallel type 12-pulse rectifier without basically increasing the complexity of the rectifier and reducing the stability of the output voltage.

[0060] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A harmonic suppression circuit using dual active modulation, characterized in that: include: Three-phase AC power supply, phase-shifting transformer and thyristor rectifier bridge, dual-active modulation circuit, inductor component, load, and control circuit; The output end of the three-phase AC power supply is electrically connected to the input end of the phase-shifting transformer and the thyristor rectifier bridge, the positive pole of the phase-shifting transformer and the thyristor rectifier bridge is electrically connected to the positive pole of the inductor component, the dual-active modulation circuit, and the load, the negative pole of the load is electrically connected to the negative pole of the phase-shifting transformer and the thyristor rectifier bridge, and the control end of the dual-active modulation circuit is electrically connected to the output end of the control circuit; The control circuit is configured to collect the load voltage, the instantaneous value of the inductor current and the inductance value, and calculate the load current increment to control the on or off of the switch tube of the dual active modulation circuit; the dual active modulation circuit is configured to reduce the harmonic content of the grid-side current.

2. The harmonic suppression circuit using dual active modulation according to claim 1, characterized in that: The phase-shifting transformer and the thyristor rectifier bridge include a Y / Δ / Y isolation phase-shifting transformer, a first thyristor rectifier bridge, and a second thyristor rectifier bridge, wherein the output end of the three-phase AC power supply is electrically connected to the input end of the Y / Δ / Y isolation phase-shifting transformer, the first output end of the Y / Δ / Y isolation phase-shifting transformer is electrically connected to the input end of the first thyristor rectifier bridge, the positive polarity output end of the first thyristor rectifier bridge is electrically connected to the O end of the dual active modulation circuit, the second output end of the Y / Δ / Y isolation phase-shifting transformer is electrically connected to the input end of the second thyristor rectifier bridge, the positive polarity output end of the second thyristor rectifier bridge is electrically connected to the P end of the dual active modulation circuit, the cathode input end of the first thyristor rectifier bridge is connected to the negative polarity end of the load, and the cathode input end of the second thyristor rectifier bridge is connected to the negative polarity end of the load.

3. A harmonic suppression circuit using dual active modulation according to claim 2, characterized in that: The inductor component includes a first inductor and a second inductor, wherein the positive polarity output end of the first thyristor rectifier bridge is connected to one end of the first inductor, and the other end of the first inductor is connected to the positive polarity end of the load, the positive polarity output end of the second thyristor rectifier bridge is connected to one end of the second inductor, and the other end of the second inductor is connected to the positive polarity end of the load.

4. The harmonic suppression circuit using dual active modulation according to claim 3, characterized in that: The dual active modulation circuit includes a first switch tube, a second switch tube, a first capacitor, a second capacitor, a first diode, a second diode, a third diode, a fourth diode, a third inductor and a fourth inductor, wherein the first end of the first switch tube and the first end of the second switch tube are electrically connected to the output end of the control circuit, the positive polarity output end of the first thyristor rectifier bridge is connected to one end of the fourth inductor and the negative electrode of the first diode, the other end of the fourth inductor is connected to the positive electrode of the third diode and the second end of the second switch tube, the negative electrode of the third diode is connected to one end of the second capacitor, the other end of the second capacitor is connected to the third end of the second switch tube and the positive electrode of the fourth diode, the positive polarity output end of the second thyristor rectifier bridge is connected to the negative electrode of the fourth diode and one end of the third inductor, the other end of the third inductor is connected to the positive electrode of the second diode and the third end of the first switch tube, the negative electrode of the second diode is connected to one end of the first capacitor, and the second end of the first switch tube is connected to the other end of the first capacitor and the positive electrode of the first diode.

5. According to the harmonic suppression circuit using dual active modulation as claimed in claim 4, the first switch tube and the second switch tube are NMOS tubes, the first end of the first switch tube is the gate of the NMOS tube, the second end of the first switch tube is the source of the NMOS tube, the third end of the first switch tube is the drain of the NMOS tube, the first end of the second switch tube is the gate of the NMOS tube, the second end of the second switch tube is the drain of the NMOS tube, and the third end of the second switch tube is the source of the NMOS tube.

6. The harmonic suppression circuit using dual active modulation according to claim 1, characterized in that: The control circuit includes a calculation unit and a controller, wherein the output end of the calculation unit is electrically connected to the input end of the controller, the output end of the controller is electrically connected to the control end of the dual active modulation circuit, and the calculation unit is configured to collect the load voltage, the instantaneous value of the inductor current and the inductance value, and calculate the load current increment.

7. A harmonic suppression circuit using dual active modulation according to claim 6, characterized in that: The calculation unit is an analog multiplier.

8. The harmonic suppression circuit using dual active modulation according to claim 6, characterized in that: The formula for calculating the load current increment Δi by the calculation unit is: Among them, L is the filter inductance, U LL is the three-phase input line voltage, u d is the DC side load voltage, and dt is the integral variable.

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