A resonant switch, a resonant circuit, and a resonant circuit control method

Abstract

The application belongs to the technical field of power electronics, and particularly relates to a resonant switch, a resonant circuit and a resonant circuit control method, wherein the resonant circuit comprises a resonant capacitor, a resonant inductor and a resonant control unit in series in a resonant loop for controlling the working state of the resonant circuit, the resonant control unit comprises an H-bridge circuit composed of four switch tubes and a pre-charge capacitor, wherein the pre-charge capacitor is located between two midpoints of the H-bridge, and the four switch tubes are respectively located on four bridge arms. The resonant circuit disclosed by the application can accelerate the increase of the resonant current in the oscillation period; the resonant current is prevented from gradually decaying after the first positive oscillation half-wave period, and the resonant current can be quickly increased in each oscillation half-wave period.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a resonant switch, a resonant circuit, and a resonant circuit control method. Background Technology

[0002] In the field of power electronics, electrical switches can be divided into hard switches and soft switches. Hard switches operate under high current or high voltage conditions during both switching on and off, making them highly susceptible to damage. Soft switches, such as resonant switches composed of circuit breakers and resonant circuits, can achieve zero-voltage turn-on and zero-current turn-off across the circuit breaker, reducing switching losses and mitigating voltage and current changes in the electrical circuit containing the circuit breaker. Currently, artificial resonant circuits used in DC circuit breakers typically have the switching transistor directly connected in series within the resonant circuit, and the pre-charge capacitors are discharged only once. This results in the resonant current reaching its maximum value during the first forward oscillation, followed by a gradual decay, failing to achieve the rapid increase in resonant current during each half-wave of forward and reverse oscillations. Summary of the Invention

[0003] The purpose of this invention is to provide a resonant switch, a resonant circuit, and a resonant circuit control method to solve the problem that the resonant current of the resonant circuit gradually decays after the first positive oscillation half-wave cycle.

[0004] To achieve the above objectives, the present invention provides a resonant circuit, including a resonant capacitor and a resonant inductor connected in series in the resonant circuit, and a resonant control unit for controlling the operating state of the resonant circuit. The resonant control unit includes an H-bridge circuit composed of four switching transistors and a pre-charge capacitor, wherein the pre-charge capacitor is located between the two midpoints of the H-bridge, and the four switching transistors are respectively located on the four arms of the H-bridge circuit.

[0005] Its beneficial effects are as follows: by setting a pre-charge capacitor, the increase of resonant current can be accelerated during the oscillation cycle; by setting four switching transistors, the connection or disconnection of the pre-charge capacitor and the resonant circuit can be easily controlled, and the polarity of the pre-charge capacitor can be kept consistent with the polarity of the oscillation capacitor in each oscillation half-wave cycle, thereby avoiding the gradual decay of the resonant current after the first positive oscillation half-wave cycle, and ensuring that the resonant current can increase rapidly in each oscillation half-wave cycle.

[0006] Furthermore, a diode is connected in anti-parallel across each of the aforementioned switching transistors.

[0007] Its beneficial effect is that when all four switching transistors are turned off, the resonant current, whether forward or reverse, can charge the pre-charge capacitor through the diode connected in parallel with the switching transistors, and the resonant current is reduced to zero more quickly.

[0008] Furthermore, a current transformer is connected in series in the resonant circuit.

[0009] Furthermore, a circuit breaker is connected in series with the resonant circuit.

[0010] Its beneficial effect is that by setting up a current transformer, it is easy to detect the magnitude and direction of the resonant current.

[0011] Furthermore, the switching transistor is an integrated gate-commutated thyristor, an insulated-gate bipolar transistor, or a fast thyristor.

[0012] To address the aforementioned technical problems, the present invention also provides a control method for a resonant circuit. The resonant circuit includes a resonant capacitor and a resonant inductor connected in series in the resonant circuit, and a resonant control unit for controlling the operating state of the resonant circuit. The resonant control unit comprises an H-bridge circuit consisting of four switching transistors and a pre-charge capacitor, wherein the pre-charge capacitor is located between the two midpoints of the H-bridge, the four switching transistors are respectively located on the four bridge arms, and a diode is connected in anti-parallel across the two ends of each switching transistor. The control method for the resonant circuit includes the following steps:

[0013] (1.1) Control the four switching transistors in the resonant control unit to turn on / off, so that the pre-charge capacitor forms a discharge circuit through the resonant inductor, the resonant capacitor and the switching transistors in the resonant control unit, and the resonant circuit generates a positive resonant current.

[0014] (1.2) When the positive resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay.

[0015] (1.3) During the reverse resonant current period, control the on / off of the four switching transistors in the resonant control unit, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor.

[0016] (1.4) When the reverse resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay.

[0017] (1.5) During the forward resonant current period, control the on / off of the four switching transistors in the resonant control unit, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor.

[0018] (1.6) Repeat steps (1.2) to (1.5) until the resonant circuit stops working.

[0019] Its beneficial effect is that by controlling the switching transistor to be turned on or off, the pre-charge capacitor is connected in series in the resonant circuit and keeps the polarity the same as that of the resonant capacitor, so that the increase of harmonic current can be accelerated during both the positive oscillation half-wave and the reverse oscillation half-wave.

[0020] Furthermore, when the control resonant circuit stops working, the four switching transistors of the resonant control unit must be turned off simultaneously when the current crosses zero.

[0021] Its beneficial effects are as follows: When the resonant circuit needs to be stopped, the resonant current, whether forward or reverse, can disconnect the resonant circuit. After the resonant circuit stops, the pre-charge capacitor can be charged through the diode connected in parallel with the switching transistor, thereby accelerating the resonant current to zero.

[0022] Furthermore, a current transformer for detecting whether the resonant current crosses zero is also connected in series in the resonant circuit.

[0023] Furthermore, a circuit breaker is connected in series in the resonant circuit.

[0024] To solve the above-mentioned technical problems, the present invention also provides a resonant switch, including a resonant circuit and a switching device electrically connected thereto, characterized in that the resonant circuit is the resonant circuit disclosed in the present invention.

[0025] Its beneficial effects are as follows: The resonant circuit of the present invention can accelerate the increase of the resonant circuit in each half-wave cycle, and accelerate the decrease of the resonant current when the resonance stops, thereby improving the conduction efficiency and turn-off efficiency of the switching devices in the resonant switch, and making the resonant switch perform better. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the resonant circuit of the present invention;

[0027] Figure 2 This is a schematic diagram of the method steps of the present invention;

[0028] Figure 3 This is a flowchart of the method of the present invention;

[0029] Figure 4 This is a schematic diagram of the resonant current of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Resonant circuit example:

[0032] like Figure 1As shown, the resonant circuit of the present invention includes a resonant capacitor and a resonant inductor connected in series in the resonant circuit, and a resonant control unit for controlling the operating state of the resonant circuit. The resonant control unit includes an H-bridge circuit composed of a first switch T1, a second switch T2, a third switch T3, a fourth switch T4, and a pre-charge capacitor C1, wherein the pre-charge capacitor is located between the two midpoints of the H-bridge, and the four switches are respectively located on the four arms of the H-bridge circuit. By setting the pre-charge capacitor, the increase of the resonant current can be accelerated during the oscillation cycle; by setting four switches, the connection or disconnection of the pre-charge capacitor and the resonant circuit can be easily controlled, and the polarity of the pre-charge capacitor can be kept consistent with the polarity of the oscillation capacitor in each oscillation half-wave cycle, thereby avoiding the gradual decay of the resonant current after the first positive oscillation half-wave cycle and ensuring that the resonant current can increase rapidly in each oscillation half-wave cycle. A first diode D1, a second diode D2, a third diode D3, and a fourth diode D4 are connected in anti-parallel across the first switch T1, the second switch T2, the third switch T3, and the fourth switch T4, respectively. By setting four diodes connected in antiparallel to the switching transistors, when all four transistors are turned off, the resonant current, whether forward or reverse, can charge the pre-charging capacitor through the diodes connected in parallel with the switching transistors, thus accelerating the reduction of the resonant current to zero. A circuit breaker K and a current transformer CT are also connected in series in the resonant circuit. The inclusion of the current transformer facilitates the detection of the magnitude and direction of the resonant current.

[0033] The switching transistor can be an integrated gate-commutated thyristor, an insulated-gate bipolar transistor, or a fast thyristor.

[0034] The working process of the resonant circuit of this invention is as follows:

[0035] (1.1) Control the four switching transistors in the resonant control unit to turn on / off, so that the pre-charge capacitor forms a discharge circuit through the resonant inductor, the resonant capacitor and the switching transistors in the resonant control unit, and the resonant circuit generates a positive resonant current.

[0036] The contacts of circuit breaker K are also connected in series in the main electrical circuit powered by AC power. When circuit breaker K is closed, it provides AC power to the resonant circuit. It can control the first and fourth switching transistors to conduct. The pre-charge capacitor C1 forms a discharge circuit through the first switching transistor T1, the fourth switching transistor T4, circuit breaker K, resonant inductor L, and resonant capacitor C2. The pre-charge capacitor discharges, and the polarity of the pre-charge capacitor is positive at the bottom and negative at the top, which accelerates the increase of the resonant current.

[0037] (1.2) When the forward resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay. After the forward current crosses zero, a reverse resonant current is generated in the resonant circuit, and the pre-charge capacitor begins to charge. At this time, the fourth switching transistor can be turned off first, and after a dead time delay, the second switching transistor can be turned on to disconnect the pre-charge capacitor from the resonant circuit.

[0038] (1.3) During the reverse resonant current period, control the on / off of the four switching transistors in the resonant control unit, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor.

[0039] The first switch can be turned off after a dead time delay, and the third switch can be turned on after another dead time delay. This allows the pre-charge capacitor to form a discharge circuit through the resonant inductor, resonant capacitor, second switch, and third switch. At this time, the polarity of the pre-charge capacitor is negative at the top and positive at the bottom, and the polarity of the resonant capacitor is positive on the right and negative on the left. The two have the same polarity, and the resonant circuit in the resonant circuit accelerates.

[0040] (1.4) When the reverse resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay. After the reverse current crosses zero, a positive resonant current is generated in the resonant circuit, and the pre-charge capacitor begins to charge. At this time, the second switching transistor can be turned off first, and after a dead time delay, the fourth switching transistor can be turned on to disconnect it from the resonant circuit.

[0041] (1.5) During the positive resonant current period, control the on / off state of the four switches in the resonant control unit to reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor; after a dead time delay, control the third switch to turn off, and after another dead time delay, control the first switch to turn on, so that the pre-charge capacitor forms a discharge circuit through the resonant inductor, the resonant capacitor, the first switch and the fourth switch. At this time, the polarity of the pre-charge capacitor is negative at the top and positive at the bottom, and the polarity of the resonant capacitor is positive on the right and negative on the left. The polarities of the two are consistent, and the resonant current in the resonant circuit increases rapidly.

[0042] (1.6) Repeat steps (1.2) to (1.5) until the resonant circuit stops working.

[0043] When the resonant circuit needs to be stopped, the first, second, third, and fourth switching transistors are simultaneously turned off when the current crosses zero. By simultaneously turning off the first, second, third, and fourth switching transistors, the resonant current, whether forward or reverse, can quickly disconnect the resonant circuit. Furthermore, after the resonant circuit stops, the pre-charging capacitor can be charged through the diode connected in parallel with the switching transistors, thereby accelerating the reduction of the resonant current to zero.

[0044] After two complete oscillation cycles, i.e., when the second reverse current crosses zero, T1-T4 are simultaneously turned off. The waveform diagram of the oscillation current during the two oscillation cycles is shown below. Figure 4 As shown.

[0045] Example of resonant circuit control method:

[0046] like Figure 2 and Figure 3 As shown, the control method of the resonant circuit of the present invention includes the following steps:

[0047] (1.1) Control the four switching transistors in the resonant control unit to turn on / off, so that the pre-charge capacitor forms a discharge circuit through the resonant inductor, the resonant capacitor and the switching transistors in the resonant control unit, and the resonant circuit generates a positive resonant current.

[0048] (1.2) When the positive resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay.

[0049] (1.3) During the reverse resonant current period, control the on / off of the four switching transistors in the resonant control unit, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor.

[0050] (1.4) When the reverse resonant current crosses zero, control the four switching transistors in the resonant control unit to turn on / off, and disconnect the pre-charge capacitor from the resonant circuit after a delay.

[0051] (1.5) During the forward resonant current period, control the on / off of the four switching transistors in the resonant control unit, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor.

[0052] (1.6) Repeat steps (1.2) to (1.5) until the resonant circuit stops working.

[0053] When the resonant circuit stops working, the method for stopping the resonant circuit is as follows: the four switching transistors of the resonant control unit must be turned off simultaneously when the current crosses zero.

[0054] The beneficial effects and specific details of the control method for the resonant circuit of the present invention have been described in the above circuit embodiments and will not be repeated here.

[0055] Resonant switch example:

[0056] The resonant switch of the present invention includes a resonant circuit and a switching device electrically connected thereto, wherein the resonant circuit is the resonant circuit disclosed in the present invention.

[0057] A resonant switch is a type of soft switch that enables zero-voltage turn-on and zero-current turn-off of the switching device. The resonant circuit of this invention can accelerate the increase of the resonant circuit within each half-wave cycle and accelerate the decrease of the resonant current when the resonance stops, thereby improving the turn-on and turn-off efficiency of the switching device in the resonant switch and resulting in better performance of the resonant switch.

Claims

1. A resonant circuit, comprising a circuit breaker, a resonant capacitor, a resonant inductor connected in series in a resonant circuit, and a resonant control unit for controlling the operating state of the resonant circuit, characterized in that, The resonant control unit includes an H-bridge circuit consisting of four switching transistors and a pre-charge capacitor; the pre-charge capacitor is located between the two midpoints of the H-bridge, and the four switching transistors are located on the four arms of the H-bridge circuit respectively; the four switching transistors are used to control the connection or disconnection of the pre-charge capacitor and the resonant circuit so that the polarity of the pre-charge capacitor is consistent with the polarity of the resonant capacitor in each half-wave cycle of oscillation. The pre-charge capacitor is used to disconnect from the resonant circuit when the forward resonant current crosses zero and the reverse resonant current crosses zero, and to connect to the resonant circuit during the reverse resonant current and the forward resonant current, while maintaining the same polarity as the resonant capacitor, so as to accelerate the increase of the resonant current during the oscillation period.

2. The resonant circuit as described in claim 1, characterized in that, Each of the aforementioned switching transistors has a diode connected in anti-parallel across its two ends.

3. The resonant circuit as described in claim 1, characterized in that, A current transformer for detecting whether the resonant current crosses zero is also connected in series in the resonant circuit.

4. The resonant circuit as described in claim 1, characterized in that, When the control resonant circuit stops working, the four switching transistors are used to turn off simultaneously when the current crosses zero.

5. The resonant circuit as described in any one of claims 1 to 4, characterized in that, The switching transistor is an integrated gate-commutated thyristor, an insulated-gate bipolar transistor, or a fast thyristor.

6. A resonant circuit control method, wherein the resonant circuit comprises a circuit breaker, a resonant capacitor, a resonant inductor connected in series in the resonant circuit, and a resonant control unit for controlling the operating state of the resonant circuit, characterized in that, The resonant control unit includes an H-bridge circuit consisting of four switching transistors and a pre-charge capacitor; the pre-charge capacitor is located between the two midpoints of the H-bridge, the four switching transistors are located on the four arms of the H-bridge circuit respectively, and a diode is connected in anti-parallel across the two ends of each switching transistor. The method includes: (1.1) Control the on / off state of the four switching transistors so that the pre-charge capacitor forms a discharge circuit through the resonant inductor, the resonant capacitor and the switching transistors in the resonant control unit, and the resonant circuit generates a positive resonant current. (1.2) When the positive resonant current crosses zero, control the on / off state of the four switching transistors to disconnect the pre-charge capacitor from the resonant circuit after a delay; (1.3) During the reverse resonant current, control the on / off state of the four switching transistors, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor; (1.4) When the reverse resonant current crosses zero, control the on / off state of the four switching transistors to disconnect the pre-charge capacitor from the resonant circuit after a delay. (1.5) During the forward resonant current period, control the on / off state of the four switching transistors, reconnect the pre-charge capacitor to the resonant circuit and make its polarity consistent with that of the resonant capacitor; (1.6) Repeat steps (1.2) to (1.5) until the resonant circuit stops working.

7. The resonant circuit control method as described in claim 6, characterized in that, When the control resonant circuit stops working, the four switching transistors of the resonant control unit must be turned off simultaneously when the current crosses zero.

8. The resonant circuit control method as described in claim 7, characterized in that, A current transformer for detecting whether the resonant current crosses zero is also connected in series in the resonant circuit.

9. The resonant circuit control method as described in claim 8, characterized in that, When the resonant circuit stops working, the four switching transistors are simultaneously turned off when the current crosses zero.

10. A resonant switch, comprising a resonant circuit and a switching device electrically connected thereto, characterized in that, The resonant circuit described herein is the resonant circuit described in any one of claims 1-4.

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