Surge suppressor and operation method thereof

Abstract

A surge suppressor is connected in parallel to a circuit breaker of an input path of a medium-voltage AC conversion circuit. The surge suppressor comprises a plurality of surge suppression circuits, and each surge suppression circuit comprises a rectification circuit, a switch, a controller and a conversion circuit. The rectifying circuit comprises an alternating-current end and a rectifying end, and the surge suppression circuits are coupled in series through the alternating-current end. The switch is coupled to the rectification end, and the controller receives a control command and provides a control signal according to the control command. The conversion circuit is coupled to the controller and the switch and provides a control voltage modulated by the control signal. Wherein the control voltage adjusts the conduction impedance of the switch so as to adjust the magnitude of the first current flowing through the switch through the control voltage.

Description

Technical Field

[0001] The present invention relates to a surge suppressor and an operation method thereof, and particularly to a surge suppressor and an operation method thereof applied to a medium-voltage AC power supply system. Background Art

[0002] Please refer to Figure 1A FIG. 1 is a system block diagram of an existing medium-voltage AC power supply system, and Figure 1B FIG. 2 is a schematic diagram of input voltage and input current waveforms of an existing medium-voltage AC power supply system. Medium-voltage AC (MVAC; Medium voltage AC) generally refers to an input voltage Vac greater than 1500 volts, even up to several tens of kilovolts. Therefore, the input voltage Vac of the medium-voltage AC that the medium-voltage AC power supply system 100A can generally receive is basically in the kilovolt level. Among them, since the backend of the traditional medium-voltage AC power supply system 100A uses a traditional medium-voltage transformer T for power transmission and provides the function of electrical isolation. Therefore, it has the disadvantages of large volume and difficult configuration. On the other hand, when the traditional medium-voltage transformer T starts, if the voltage value of its input voltage Vac is relatively high, there may be an excessive input current Iac surge, and the peak value of the surge is even nearly ten times the rated current. Therefore, it will cause the circuit breaker at the front end to be forced to select a medium-voltage circuit breaker (VCB; Voltage Circuit Breaker) with a larger capacity, thereby increasing the system cost.

[0003] In order to limit the current surge caused by the traditional medium-voltage transformer T when the medium-voltage AC power supply system 100A starts, the existing method is to add a thermistor NTC (Thermistor). Although the characteristic of resistance variation of the thermistor NTC can be used to limit the current surge caused by the traditional medium-voltage transformer T, however, due to the characteristics of the resistance, it will cause continuous power loss during the operation of the medium-voltage AC power supply system 100A. Therefore, it is bound to increase the additional power loss when the medium-voltage AC power supply system 100A operates.

[0004] Therefore, how to design a surge suppressor and an operation method thereof to limit the current surge caused by the transient influence of the medium-voltage AC power supply system is a major issue that the inventor of this case wants to study. Summary of the Invention

[0005] To solve the above problems, the present invention provides a surge suppressor to overcome the problems of the prior art. Therefore, the surge suppressor of the present invention is connected in parallel to the open circuit device in the input path of the medium-voltage AC conversion circuit. The surge suppressor includes a plurality of surge suppression circuits, and each surge suppression circuit includes a rectifier circuit, a switch, a controller, and a conversion circuit. The rectifier circuit includes an AC terminal and a rectified terminal, and each surge suppression circuit is serially coupled through the AC terminal. The switch is coupled to the rectified terminal. The controller receives a control command and provides a control signal according to the control command. The conversion circuit is coupled to the controller and the switch, and provides a control voltage modulated by the control signal. Wherein, the control voltage adjusts the on-resistance of the switch to adjust the magnitude of the first current flowing through the switch by the control voltage.

[0006] To solve the above problems, the present invention provides an operation method of a surge suppressor to overcome the problems of the prior art. Therefore, for the operation method of the surge suppressor of the present invention, the surge suppressor is connected in parallel to the open circuit device in the input path of the medium-voltage AC conversion circuit and includes a plurality of surge suppression circuits connected in series. Each surge suppression circuit includes a rectified terminal and a switch coupled to the rectified terminal, and the operation method of the surge suppressor includes the following steps: (a) receiving a control command and providing a control signal according to the control command; (b) providing a control voltage modulated by the control signal; (c) adjusting the on-resistance of the switch according to the control voltage; (d) adjusting the magnitude of the first current flowing through the switch by adjusting the on-resistance.

[0007] The main purpose and effect of the present disclosure is that in the medium-voltage AC power supply system, by adjusting the on-resistance of each surge suppression circuit, the magnitude of the first current flowing through the switch can be adjusted, thereby achieving the effect of suppressing the surge generated by the influence of the transient on the input current.

[0008] To further understand the technologies, means, and effects adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, features, and characteristics of the present invention can be deeply and specifically understood therefrom. However, the drawings are only for reference and explanation, and are not used to limit the present invention. Description of the Drawings

[0009] Figure 1A It is a system block diagram of an existing medium-voltage AC power supply system;

[0010] Figure 1B It is a schematic diagram of the input voltage and input current waveforms of an existing medium-voltage AC power supply system;

[0011] Figure 2A It is a system block diagram of the medium-voltage AC power supply system disclosed in the present invention;

[0012] Figure 2B It is a circuit block diagram of the medium-voltage switch disclosed in the present invention;

[0013] Figure 3 Waveform diagram of the working area of the disclosed switch;

[0014] Figure 4A Schematic circuit block diagram of the first embodiment of the disclosed conversion circuit;

[0015] Figure 4B Schematic circuit block diagram of the second embodiment of the disclosed conversion circuit;

[0016] Figure 5A Flowchart of the operation method of the disclosed surge suppressor;

[0017] Figure 5B Flowchart of the operation method of the disclosed surge suppressor applied to the on-off period;

[0018] Figure 6A Schematic diagram of conduction impedance adjustment of the first implementation mode of the disclosed surge suppressor applied to the on-off period;

[0019] Figure 6B Schematic diagram of conduction impedance adjustment of the second implementation mode of the disclosed surge suppressor applied to the on-off period; and

[0020] Figure 6C Schematic diagram of conduction impedance adjustment of the third implementation mode of the disclosed surge suppressor applied to the on-off period.

[0021] Explanation of reference numerals in the drawings:

[0022] 100A: Medium-voltage AC power supply system

[0023] T: Traditional medium-voltage transformer

[0024] NTC: Thermistor

[0025] MVAC: Medium-voltage AC

[0026] 100: Medium-voltage AC power supply system

[0027] 2: First circuit breaker

[0028] 4: Medium-voltage AC conversion circuit

[0029] MVS: Medium-voltage switch

[0030] 42: Medium-voltage AC converter

[0031] L: Input path

[0032] 5: Second circuit breaker

[0033] 52: Mechanical switch

[0034] 54: Semiconductor switch

[0035] 6: Surge suppressor

[0036] 62: Surge suppression circuit

[0037] 622: Rectifying circuit

[0038] Eac1, Eac2: AC terminals

[0039] Er1, Er2: Rectifying terminals

[0040] 624, 624-1~624-n: Switches

[0041] R, R1~Rn: Conduction impedance

[0042] C, D: Input terminals

[0043] E, S: Output terminals

[0044] G: Control terminal

[0045] Vce, Vds: Voltage difference

[0046] Vge, Vgs: Control terminal voltage

[0047] Vth: Threshold voltage

[0048] Ice, Ids: Current

[0049] WL: Linear region

[0050] 626: Controller

[0051] 628: Conversion circuit

[0052] SW: Switching circuit

[0053] Q1: Upper bridge switch

[0054] Q2: Lower bridge switch

[0055] CF: Filter circuit

[0056] L: Inductor

[0057] C: Capacitor

[0058] Rg: Current limiting resistor

[0059] 630: Protection circuit

[0060] Rv: Variable resistor

[0061] ZD: Clamping circuit

[0062] 200: Load

[0063] Vac: Input voltage

[0064] Iac: Input current

[0065] I1: First current

[0066] I2: Second current

[0067] CL: Control command

[0068] Sc: Control signal

[0069] Sc1: Upper bridge control signal

[0070] Sc2: Lower bridge control signal

[0071] Vc: Control voltage

[0072] Vcc: Operating voltage

[0073] t1~t4: Time

[0074] (S100)~(S240): Steps Detailed implementation manners

[0075] Regarding the technical content and detailed description of the present invention, it is described in detail below in conjunction with the accompanying drawings:

[0076] Please refer to Figure 2A which is the system block diagram of the medium-voltage AC power supply system disclosed herein. Referring to Figures 1A to 1B . The medium-voltage AC power supply system 100 receives power (i.e., power) of medium-voltage AC (MVAC; Medium voltage AC), and the medium-voltage AC power supply system 100 includes a first circuit breaker 2 and a plurality of medium-voltage AC conversion circuits 4. Specifically, when the medium-voltage AC MVAC is coupled to the medium-voltage AC power supply system 100, the medium-voltage AC power supply system 100 receives the input voltage Vac (AC voltage) provided by the medium-voltage AC MVAC, and the medium-voltage AC MVAC provides the input current Iac to the medium-voltage AC power supply system 100 according to the requirements of the medium-voltage AC power supply system 100 (i.e., load requirements). The medium-voltage AC conversion circuit 4 receives the medium-voltage AC MVAC (i.e., the input voltage Vac and the input current Iac) by coupling to the first circuit breaker 2, and the first circuit breaker 2 can be a medium-voltage circuit breaker (VCB; Voltage Circuit Breaker) or a medium-voltage sectional switch (DS; Disconnect Switch). Each medium-voltage AC conversion circuit 4 includes a medium-voltage switch (MVS; Medium Voltage Switch) and a medium-voltage AC converter 42, and the medium-voltage AC conversion circuit 4 is coupled to the first circuit breaker 2 through the medium-voltage switch MVS to receive the medium-voltage AC MVAC through the first circuit breaker 2. Therefore, in the application of a plurality of medium-voltage AC conversion circuits 4, the first circuit breaker 2 can be shared.

[0077] When a medium-voltage AC conversion circuit 4 fails, the medium-voltage AC power supply system 100 can cut off individual medium-voltage switches MVS, forming a high impedance between the faulty medium-voltage AC converter 42 and the power supplier (such as, but not limited to, the power grid, etc.) that provides medium-voltage AC MVAC, without having to trip the front-stage first circuit breaker 2, making the medium-voltage AC power supply system 100 more robust. On the other hand, the medium-voltage AC converter 42 can be, for example, but not limited to, an AC / DC converter or an AC / AC converter to convert medium-voltage AC MVAC into low-voltage AC LVAC or low-voltage DC LVDC, and supply power to the load 200 coupled to the rear end by providing the low-voltage AC LVAC or low-voltage DC LVDC to the load 200. Preferably, since the medium-voltage switch MVS has an overcurrent protection function, the front-stage medium-voltage circuit breaker VCB can be replaced with a low-cost medium-voltage sectional switch DS.

[0078] Please refer to Figure 2B the circuit block diagram of the medium-voltage switch in this disclosure, and also refer to Figure 2A Figure. The medium-voltage switch MVS includes a second circuit breaker 5 and a surge suppressor 6, and the second circuit breaker 5 is coupled to the input path L of the medium-voltage AC conversion circuit 4. Among them, one end of the input path L is coupled to the first circuit breaker 2, and the other end is coupled to the medium-voltage AC converter 42. When the second circuit breaker 5 controls the input path L to be short-circuited, the medium-voltage AC MVAC can be provided to the medium-voltage AC converter 42 through the input path L, and when the second circuit breaker 5 controls the input path L to be open-circuited, the medium-voltage AC MVAC cannot be provided to the medium-voltage AC converter 42 through the input path L. Among them, as Figure 2B shown, the second circuit breaker 5 can include a set of mechanical switches 52 and a set of semiconductor switches 54. The semiconductor switches 54 can preferably be in a back-to-back connection structure, that is, the two semiconductor switches 54 are in a reverse series connection structure (the junction diode directions are opposite), so as to achieve the function of bidirectional turn-off by turning off the two semiconductor switches 54. Among them, the two semiconductor switches 54 can be, for example, but not limited to, semiconductor elements such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). The two mechanical switches 52 can preferably be respectively arranged outside the two semiconductor switches 54 to form a structure with the mechanical switches 52 on the outside and the semiconductor switches 54 on the inside. In this way, it can be achieved that each medium-voltage AC conversion circuit 4 satisfies the insulation withstand voltage requirements of the medium-voltage AC MVAC through a set of mechanical switches 52 and a set of semiconductor switches 54.

[0079] The surge suppressor 6 is connected in parallel to the second breaking device 5, and the surge suppressor 6 is mainly used to reduce the peak value of the surge when the input current Iac generates an excessive surge due to the influence of transients, so as to avoid the components inside the medium-voltage AC power supply system 100 being broken down and damaged, or the situation of accidentally touching the upper limit of the protection value of the second breaking device 5. Specifically, since the back end of the medium-voltage switch MVS is usually coupled to magnetic components such as transformers or inductors. When the magnetic flux of the magnetic component changes instantaneously (for example, but not limited to, the input source changes, the load changes instantaneously by a large amplitude, etc., especially at the moment of opening and closing of the medium-voltage AC power supply system 100), the input current Iac will generate a higher surge, and its peak value may even be several times higher than the rated current. Therefore, if the excessive surge is not suppressed, it is easy to cause the components inside the medium-voltage AC power supply system 100 to have the potential risk of being broken down and damaged, or accidentally touching the upper limit of the protection value of the second breaking device 5, resulting in the second breaking device 5 tripping. Therefore, when the input current Iac generates a higher surge, the surge suppressor 6 can be used to suppress it to avoid the above situation. It is worth mentioning that in an embodiment, the medium-voltage AC converter 42 of the present disclosure can be a solid-state transformer (SST; Solid state transformer), and the medium-voltage switch MVS can be placed in the front stage of the solid-state transformer. However, the medium-voltage AC converter 42 can also be Figure 1A the traditional medium-voltage transformer shown in the figure, so the circuit structure of the medium-voltage AC converter 42 is not limited.

[0080] The surge suppressor 6 includes a plurality of surge suppression circuits 62, and the surge suppression circuits 62 are connected in series to share the high input voltage Vac of the medium-voltage alternating current MVAC. Therefore, the number of surge suppression circuits 62 connected in series can be increased or decreased according to the magnitude of the input voltage Vac, mainly depending on the withstand voltage specification of the surge suppression circuit 62 and the magnitude of the input voltage Vac. On the other hand, since the second breaking device 5 includes two mechanical switches 52, providing a sufficient insulation withstand voltage distance, it is not necessary to connect a plurality of surge suppression circuits 62 in series like the surge suppressor 6. Each surge suppression circuit 62 includes a rectifier circuit 622, a switch 624, a controller 626, and a conversion circuit 628, and each surge suppression circuit 62 may also selectively include a protection circuit 630. The rectifier circuit 622 includes an AC terminal Eac1, Eac2 and a rectifier terminal Er1, Er2, and each surge suppression circuit 62 is connected in series through the AC terminals Eac1, Eac2. For the convenience of explanation, in Figure 2BAmong them, the controller 626 and the conversion circuit 628 are shown schematically as a single unit, but this does not exclude that each surge suppression circuit 62 may individually include a controller 626 and a conversion circuit 628 to independently control the switch 624 of each surge suppression circuit 62. The switch 624 is coupled to the rectification terminals Er1 and Er2, and the switch 624 can be, for example but not limited to, an insulated gate bipolar transistor (IGBT, hereinafter simply referred to as IGBT) or a metal oxide semiconductor field effect transistor (MOSFET, hereinafter simply referred to as MOSFET).

[0081] Among them, since the IGBT is suitable for medium to high current conduction and control, and the IGBT can operate well at kHz frequencies, it is a preferred embodiment to use the IGBT for the switch 624. In addition, the rectifier circuit 622 can be, for example but not limited to, a half-bridge circuit or a full-bridge circuit, and it is a preferred embodiment to use a full-bridge circuit. Therefore, when the input current Iac is positive, the first current I1 allocated to this path of the surge suppressor 6 will flow from the AC terminal Eac1 to the AC terminal Eac2, and flow from the rectification terminal Er1 to the rectification terminal Er2 through the conduction of the switch 624. Conversely, when the input current Iac is negative, the first current I1 will flow from the AC terminal Eac2 to the AC terminal Eac1, but the direction of flow through the rectification terminals Er1 and Er2 remains unchanged. Therefore, through the rectification (commutation) of the rectifier circuit 622, the current direction of the first current I1 when flowing through the switch 624 can be made a fixed direction.

[0082] The conversion circuit 628 is coupled to the control terminal of the controller 626 and the switch 624, so that the controller 626 can operate the switch 624 by controlling the conversion circuit 628. Specifically, the controller 626 receives a control command CL and provides a control signal Sc according to the control command CL. Among them, the control command CL can be provided by a system controller (not shown in the figure) of the medium voltage AC power supply system 100, or provided by a controller (not shown in the figure) inside the medium voltage AC conversion circuit 4, and no limitation is imposed here. The control signal Sc can preferably be a pulse width modulation signal, and the conversion circuit 628 receives the control signal Sc to provide a control voltage Vc modulated by the control signal Sc according to the control signal Sc. Due to the control method of the IGBT (or MOSFET), mainly by adjusting the control voltage Vc, the channel size of the IGBT (or MOSFET) can be changed, and then the on-resistance R of the switch 624 (i.e., Rce_on of the IGBT or Rds_on of the MOSFET) can be adjusted to limit the magnitude of the first current I1 flowing through the switch 624. For the convenience of explanation, the IGBT will be mainly described hereinafter. Among them, the above operation mainly utilizes the working region of the switch 624 as the control of the conduction degree of the switch 624, so only the rectifier circuit 622 in combination with a single switch 624 (or several, depending on its voltage withstand and current withstand specifications) can form the surge suppression circuit 62.

[0083] Therefore, the main purpose and effect of the present disclosure is that the medium-voltage AC power supply system 100 can adjust the magnitude of the first current I1 flowing through the switch 624 by adjusting the on-resistance R of each surge suppression circuit 62, thereby suppressing the surge generated by the input current Iac due to transient effects. On the other hand, since the surge suppression circuit 62 of the present disclosure does not include an additional (parallel) path formed by a resistor (i.e., there is only a single path formed by the switch 624 on the surge suppressor 6 path), when the switch 624 is turned off, the first current I1 will not flow through the resistor on the additional path, and there will be no additional power consumption of the surge suppression circuit 62 or an increase in the internal ambient temperature of the medium-voltage switch MVS due to resistor consumption. Therefore, the surge suppressor 6 of the present disclosure can completely isolate the voltage across the switch 624 and is easy to detect whether the switch 624 is damaged (for example, but not limited to, by configuring a single current sensor to detect whether there is current flowing through the switch 624 when the control signal Sc is output, it can be known whether the switch 624 is damaged).

[0084] Furthermore, due to the instantaneous change of the magnetic flux of the magnetic component, it usually occurs during the on-off period when the medium-voltage AC conversion circuit 4 starts or shuts down (but it does not exclude any period during the operation of the medium-voltage AC conversion circuit 4). Therefore, during the on-off period, the surge suppression circuit 62 is enabled (which can be enabled by any device inside the medium-voltage AC power supply system 100, preferably by the system controller of the medium-voltage AC power supply system 100 to perform this operation) to limit the input current Iac within a predetermined range by adjusting the on-resistance R (for example, but not limited to, limiting the surge within twice the rated current), to avoid damage to the components inside the medium-voltage AC power supply system 100 due to breakdown or the situation of accidentally touching the upper limit of the protection value of the second breaking device 5. Conversely, at the end of the on-off period, the surge suppression circuit 62 is disabled (for example, but not limited to, the controller 626 stops providing the control signal Sc, or disconnects the connection between the conversion circuit 628 and the switch 624 through an internal switch (not shown in the figure), etc.) to avoid continuous power consumption of the surge suppression circuit 62. In addition, during the operation of the medium-voltage AC power supply system 100, if it is necessary to use the surge suppression circuit 62 to suppress the surge of the input current Iac, the surge suppression circuit 62 can also be selectively enabled.

[0085] Furthermore, during the opening and closing period when the medium voltage alternating current (MVAC) accesses the medium voltage alternating current power supply system 100 to start the medium voltage alternating current conversion circuit 4, the medium voltage alternating current power supply system 100 first turns on the surge suppression circuit 62, and adjusts the on-resistance R of the surge suppression circuit 62 through the controller 626 to suppress the surge of the input current Iac. At this time, the second breaking device 5 has not turned on the input path L, making the input path L an open circuit. Then, the medium voltage alternating current power supply system 100 first turns on the two mechanical switches 52 and then turns on the two semiconductor switches 54 to avoid the large current flowing through when the two mechanical switches 52 are turned on instantaneously and generating an arc. Finally, after the input path L is turned on, each surge suppression circuit 62 is disabled to avoid the continuous power consumption of the surge suppression circuit 62. On the contrary, during the opening and closing period when the medium voltage alternating current power supply system 100 is turned off to close the medium voltage alternating current conversion circuit 4, the medium voltage alternating current power supply system 100 first turns on the surge suppression circuit 62, and adjusts the on-resistance R of the surge suppression circuit 62 to suppress the surge of the input current Iac. At this time, the second breaking device 5 has not broken the input path L, making the input path L a short circuit. Then, the medium voltage alternating current power supply system 100 first turns off the two semiconductor switches 54 and then turns off the two mechanical switches 52 to avoid the large current flowing through when the two mechanical switches 52 are turned off instantaneously and generating an arc. Finally, after the input path L is broken, each surge suppression circuit 62 is disabled or does not work to turn off the medium voltage alternating current power supply system 100. It is worth mentioning that in one embodiment, the adjustment method of the on-resistance R will be further described later and will not be elaborated here.

[0086] Refer back to Figure 2B, the protection circuit 630 is connected in parallel to the AC terminals Eac1 and Eac2 and is used to provide overvoltage protection for the surge suppression circuit 62. Further, after the medium-voltage AC MVAC is connected to the medium-voltage AC power supply system 100, each surge suppression circuit 62 needs to withstand a high input voltage Vac. When the input voltage Vac becomes too high due to certain factors (such as but not limited to voltage distortion, overvoltage, etc.) (such as but not limited to, when both the disconnecting device 5 and the surge suppressor 6 are open), the protection circuit 630 can limit the voltage at the AC terminals Eac1 and Eac2 to be less than or equal to a predetermined voltage to prevent the voltage from exceeding the withstand voltage specification of the surge suppression circuit 62 and causing damage to it. Among them, the protection circuit 630 preferably includes a variable resistor Rv and at least one clamping circuit ZD. The variable resistor Rv is mainly used to limit the current flowing through this path to avoid overcurrent. The clamping circuit ZD mainly clamps the voltage across the two terminals of the AC terminals Eac1 and Eac2 at a specific voltage to prevent the voltage across the two terminals of the AC terminals Eac1 and Eac2 from being too high. Among them, the clamping circuit ZD can be, for example but not limited to, a Zener diode, and the number of the clamping circuits ZD is mainly designed according to the withstand voltage specification of the surge suppression circuit 62. Specifically, the number of the clamping circuits ZD can be selectively connected in series with 1 to several clamping circuits ZD according to the withstand voltage specification of the surge suppression circuit 62 to limit the voltage across the two terminals of the AC terminals Eac1 and Eac2 to be lower than its withstand voltage specification.

[0087] Refer to Figure 3 is a waveform schematic diagram of the working area of the switch disclosed herein. Please also refer to Figure 2A and Figure 2B . Taking the switch 624 as an IGBT as an example, the horizontal axis is the voltage difference Vce between the input terminal C and the output terminal E of the IGBT. The vertical axis is the current Ice flowing from the input terminal C to the output terminal E of the IGBT. Each curve represents the relationship curve between the voltage difference Vce and the current Ice between the input terminal C and the output terminal E of the IGBT when different voltages are applied to the control terminal G of the IGBT. Among them, the symbols of the input terminal C and the output terminal E are mainly labeled according to the actual polarity of the IGBT (such as the collector C and the emitter E), but their labels can be changed according to the different current directions, the forward / backward connection of the switch, or the type of the switch (such as the collector C as the output terminal and the emitter E as the input terminal).

[0088] When the voltage of the control terminal G of the IGBT is lower than the threshold value (that is, the control terminal voltage Vge is lower than the critical voltage Vth), the switch 624 does not establish a channel, so that the input terminal C and the output terminal E of the switch 624 are open circuit and no current can flow through (Ice is equal to 0). When the voltage of the control terminal G of the switch 624 gradually increases (that is, Vge gradually rises to exceed the critical voltage Vth), a channel starts to be established between the input terminal C and the output terminal E of the switch 624, and the channel gradually becomes larger (that is, Vge gradually rises from 5V to 10V), so that the current Ice that can flow through the input terminal C and the output terminal E gradually increases. When a channel starts to be established between the input terminal C and the output terminal E, the conduction impedance R (Rce_ON) at both ends of the switch 624 gradually decreases contrary to the gradual increase of the channel. Therefore, it can be regarded as a controlled variable resistor.

[0089] When the conduction impedance R of the switch 624 gradually decreases, the current Ice that can flow through the switch 624 gradually increases. Conversely, the current Ice that can flow through the switch 624 gradually decreases. Therefore, when the surge suppression circuit 62 is enabled, the controller 626 can adjust the conduction impedance R of the switch 624 by adjusting the control voltage Vc to limit the magnitude of the first current I1 flowing through the input terminal C and the output terminal E of the switch 624, thereby reducing the surge peak value of the input current Iac. Since the surge characteristic of the input current Iac is generally that the first surge at the time of surge occurrence is the highest value (for example, but not limited to, 10 times the rated current), and most of the subsequent ones recover to the stable value (for example, but not limited to, the rated current) after exponential decay. Therefore, when the opening and closing period is about to end, the switch 624 can be fully turned on (that is, the duty cycle of the control signal is set to 100%, or the frequency of the control signal is adjusted to 0, etc.), so that when the current Ice flows through the switch 624, the lower conduction impedance R can save the power loss of the surge suppressor 6. Therefore, in summary, the present disclosure mainly operates the IGBT switch 624 in the linear region WL, regards it as a controlled variable resistor, and adjusts its channel size and conduction impedance R by adjusting its control terminal voltage Vge.

[0090] For convenience of explanation, the adjustment of the duty cycle will be used as a schematic example hereinafter, and the adjustment of the frequency can be inferred by analogy with the adjustment method of the duty cycle and will not be elaborated further. It is worth mentioning that when the switch 624 uses a MOSFET, the horizontal axis is the voltage difference Vds between the input terminal D and the output terminal S of the MOSFET. The vertical axis is the current Ids flowing from the input terminal D to the output terminal S of the MOSFET. Each curve represents the relationship curve between the voltage difference Vds and the current Ids between the input terminal D and the output terminal S when different voltages are applied to the control terminal G of the MOSFET. Its effect and control method also utilize the voltage (i.e., Vgs) of the control terminal G to control the current Ids that can flow between the input terminal D and the output terminal S. Therefore, the switch 624 of the MOSFET is also operated in the linear region WL to use it as a controlled variable resistor, and the channel size and conduction impedance R are adjusted by adjusting the control terminal voltage Vgs.

[0091] Please refer to Figure 4A is a circuit block diagram of the first embodiment of the disclosed conversion circuit, and please refer to it in combination with Figures 2A to 3 . In Figure 4A , the controller 626 receives a control command CL and provides control signals Sc1 and Sc2 to the conversion circuit 628 according to the control command CL. The conversion circuit 628 is coupled to the controller 626 and the switch 624, and provides a control voltage Vc to the switch 624 according to the control signals Sc1 and Sc2. Specifically, the conversion circuit 628 receives the control signals Sc1 and Sc2, and converts the operating voltage Vcc into the control voltage Vc to the switch 624 according to the control signals Sc1 and Sc2. The switch 624 is coupled to the rectification terminals Er1 and Er2 of the rectification circuit 622, and adjusts the channel of the switch 624 and its corresponding conduction impedance R by receiving the control voltage Vc through the control terminal G to adjust the first current I1 that can flow through this channel. Among them, the operating voltage Vcc can be provided by converting the input voltage Vac or provided by an external electronic device, and this is not limited herein.

[0092] On the other hand, the control command CL can be an analog signal provided by an analog controller or a digital signal provided by a digital controller. Since the surge characteristic of the input current Iac is generally that the first surge at the time of surge occurrence is the highest value, and most of the subsequent ones decay exponentially and then return to the stable value. Therefore, the controller 626 can gradually increase the duty cycle of the control signals Sc1 and Sc2 according to the control command CL to perform corresponding control corresponding to the size of the surge. As described above, since the duty cycle of the control signals Sc1 and Sc2 is gradually increased, the voltage value of the control voltage Vc output by the conversion circuit 628 is also gradually increased. Therefore, the channel of the switch 624 can be gradually enlarged, and the conduction impedance R is gradually decreased, so that the first current I1 that can flow through is increased.

[0093] Among them, if the operation is performed in the form of duty cycle adjustment, the preferred operation method is to increase the duty cycle in an equal magnification manner, so that the voltage value of the control voltage Vc also increases in an equal magnification manner. For example but not limited to, the duty cycles of the control signals Sc1 and Sc2 increase at a magnification of 1%, but this is not the limit. Thereby, a better surge current suppression effect can be achieved, and it will not cause the conduction speed of the switch 624 to be too slow and the maintenance time of the on-off period to be forced to be extended, or the conduction speed of the switch 624 to be too fast and the surge of the input current Iac cannot be effectively suppressed. Thereby, the present disclosure utilizes the operating characteristics of the switch 624 as a semiconductor switch, so that the controller 626 only needs to control the duty cycles of the control signals Sc1 and Sc2 to control the current flowing through the switch 624.

[0094] Specifically, the conversion circuit 628 includes a switching circuit SW and a filtering circuit CF, and the controller 626, the switching circuit SW, and the filtering circuit CF constitute a switching converter. The switching circuit SW is coupled to the controller 626, and the filtering circuit CF is coupled to the switching circuit SW and the switch 624. The switching circuit SW is switched on and off according to the control signals Sc1 and Sc2, and the filtering circuit CF generates a control voltage Vc according to the switching on and off of the switching circuit SW. The switching circuit SW may include an upper bridge switch Q1 and a lower bridge switch Q2. The upper bridge switch Q1 receives the operating voltage Vcc and is coupled to the controller 626 and the filtering circuit CF. The lower bridge switch Q2 is coupled to the output terminal E of the upper bridge switch Q1, the controller 626, and the switch 624.

[0095] The filtering circuit CF may include an inductor L and a capacitor C. One end of the inductor L is coupled to the contact point between the upper bridge switch Q1 and the lower bridge switch Q2, and the other end of the inductor L is coupled to one end of the capacitor C and the control terminal G of the switch 624. The other end of the capacitor C is coupled to the output terminal E of the switch 624 to establish a control voltage Vc that can adjust the conduction impedance R (channel size) of the switch 624 between the control terminal G and the output terminal E of the switch 624. It is worth mentioning that in an embodiment, the controller 626, the switching circuit SW, and the filtering circuit CF can just form a buck converter, but its structure can also use, for example but not limited to, switching converters such as boost converters. Therefore, if the conversion circuit 628 is a switching converter, the difference lies only in the circuit cost of the circuit structure and the difficulty of the control method, but all can generate a control voltage Vc by controlling the switching circuit SW. Among them, the circuit structure of the buck converter is simple and the cost is low, and the control method is also the simplest, which is a preferred implementation method.

[0096] Among them, the above-mentioned switching conduction refers to the control signals Sc1 and Sc2 respectively controlling the continuous conduction / turn-off of the upper-bridge switch Q1 and the lower-bridge switch Q2. Specifically, the upper-bridge switch Q1 and the lower-bridge switch Q2 respectively receive the upper-bridge control signal Sc1 and the lower-bridge control signal Sc2, and the upper-bridge control signal Sc1 and the lower-bridge control signal Sc2 are complementary control signals. When the upper-bridge control signal Sc1 controls the upper-bridge switch Q1 to conduct, the lower-bridge control signal Sc2 controls the lower-bridge switch Q2 not to conduct. At this time, the working voltage Vcc charges the filter circuit CF through the upper-bridge switch Q1 (taking Figure 4A as an example, the working voltage Vcc stores energy in the inductor L, so that the second current I2 generated by the inductor L charges the capacitor C). Therefore, the voltage value of the control voltage Vc across the capacitor C begins to increase. Then, when the upper-bridge control signal Sc1 controls the upper-bridge switch Q1 not to conduct, the lower-bridge control signal Sc2 controls the lower-bridge switch Q2 to conduct. At this time, the filter circuit CF releases energy through the lower-bridge switch Q2 (taking Figure 4A as an example, the inductor L, the capacitor C and the lower-bridge switch Q2 form a closed loop, and the second current I2 on the inductor L releases energy to the capacitor C. Among them, since the conversion circuit 628 is not like a general switching conversion circuit that maintains the control voltage Vc across the capacitor C as a constant DC voltage by adjusting the duty cycle, but is to suppress the surge of the input current Iac to adjust the on-resistance R. Therefore, the control voltage Vc is not a constant value during the adjustment of the on-resistance R. Moreover, according to the surge characteristics of the input current Iac, the duty cycles of the control signals Sc1 and Sc2 can preferably be gradually increased to reduce the on-resistance R, and the control voltage Vc is increased accordingly. Finally, when the duty cycle is the largest (ideally 100%, actually based on the limit of the controller 626), the control voltage Vc is a constant value, so that the channel of the switch 624 is opened to the maximum, and the on-resistance R is reduced to the minimum (that is, entering the saturation region, and the switch 624 is in a fully conducting state).

[0097] Refer back to Figure 4A , the conversion circuit 628 further includes a current-limiting resistor Rg, and the current-limiting resistor Rg is coupled between the upper-bridge switch Q1, the lower-bridge switch Q2 and the filter circuit CF. Since the filter circuit CF does not store any energy when the conversion circuit 628 is not working, when the conversion circuit 628 starts to operate and the upper-bridge switch Q1 conducts, a momentary large current will flow to the filter circuit CF. Just like Figure 4AFor example, when the conversion circuit 628 is not in operation, the capacitor C has no voltage and is close to being short-circuited. Therefore, when the conversion circuit 628 starts to operate and the upper bridge switch Q1 is turned on, an instantaneous large current will flow to the capacitor C. Thus, the voltage value of the control voltage Vc will be instantaneously too high, causing the switch 624 to misoperate and turn on, and unable to effectively suppress the surge of the input current Iac. Therefore, the current-limiting resistor Rg can limit the magnitude of the current flowing from the operating voltage Vcc through the upper bridge switch Q1 to the filter circuit CF path when the upper bridge switch Q1 is turned on, so as to avoid the above-mentioned misoperation of the switch 624 and provide an excessive channel, and further protect the upper bridge switch Q1 from being damaged due to excessive current flow. It is worth mentioning that the current-limiting resistor Rg can also be called a driving resistor.

[0098] Please refer to Figure 4B FIG. is a schematic block diagram of a second embodiment of the conversion circuit of the present disclosure. Please also refer to Figures 1A to 4A . The conversion circuit 628 of this embodiment is different from Figure 4A in that the switching circuit SW only has the lower bridge switch Q2, and the controller 626 also only provides the lower bridge control signal Sc2 to the lower bridge switch Q2. The lower bridge switch Q2 receives the operating voltage Vcc and is coupled to the controller 626 and the filter circuit CF to receive the lower bridge control signal Sc2 and switch to turn on. When the lower bridge control signal Sc2 is at the first level (i.e., low level), the lower bridge switch Q2 is not turned on. At this time, the operating voltage Vcc charges the filter circuit CF (taking Figure 4B as an example, the operating voltage Vcc stores energy in the inductor L, so that the second current I2 generated by the inductor L charges the capacitor C). Therefore, the voltage value of the control voltage Vc across the capacitor C begins to increase. Then, when the lower bridge control signal Sc2 is at the second level (i.e., high level), the lower bridge switch Q2 is turned on. At this time, the filter circuit CF discharges energy through the lower bridge switch Q2 (taking Figure 4A as an example, the inductor L, the capacitor C, and the lower bridge switch Q2 form a closed loop, and the second current I2 on the inductor L discharges energy to the capacitor C. It is worth mentioning that in an embodiment, Figure 4B the circuit connection method and control method not mentioned are the same as Figure 4A and will not be elaborated here.

[0099] Similarly, the conversion circuit 628 also includes a current-limiting resistor Rg, and the current-limiting resistor Rg receives the operating voltage Vcc and is coupled to the lower bridge switch Q2 and the filter circuit CF, and its function is equivalent to Figure 4A the current-limiting resistor Rg. Among them, Figure 4A the coupling position of the current-limiting resistor Rg can also be the same as Figure 4B the coupling position. That is to say, regardless of whether the current-limiting resistor Rg is configured at Figure 4A or Figure 4BAt their positions, the same effects can be achieved. Optionally, after the opening and closing period ends, the controller 626 can also consume all the remaining energy stored in the filter circuit CF (especially the energy remaining in the capacitor C) by providing a normally-conducting lower-bridge control signal Sc2 to turn on the lower-bridge switch Q2, to prevent the residual control voltage Vc from still being able to control the switch 624 to wrongly provide a channel and its corresponding conduction impedance R. It is worth mentioning that the current-limiting resistor Rg can also be called a drive resistor. In addition, Figure 4A and Figure 4B the controller 626, the upper-bridge switch Q1, and the lower-bridge switch Q2 in and

[0100] can be practically included in a single driver IC.

[0100] Please refer to Figure 5A which is a flowchart of the operation method of the present disclosed surge suppressor, and also refer to Figures 1A to 4B . The surge suppressor 6 is mainly applied to the medium-voltage AC power supply system 100 of medium-voltage AC MVAC, and the surge suppressor 6 is connected in parallel to the disconnection device 5 on the input path L of the medium-voltage AC conversion circuit 4. The surge suppressor 6 includes a plurality of surge suppression circuits 62 connected in series, and each surge suppression circuit 62 includes a rectification terminal Er1, Er2 and a switch 624 coupled to the rectification terminals Er1, Er2. Among them, the surge suppression circuit 62 is used to rectify the first current I1 flowing through the path of the surge suppressor 6, so as to provide a first current I1 in a fixed direction from the rectification terminal Er1 to the rectification terminal Er2. The operation method of the surge suppressor 6 first includes receiving a control command and providing a control signal according to the control command (S100). In a preferred embodiment, the control command CL is received by the controller 626, and the controller 626 provides a control signal Sc according to the control command CL. The control signal Sc can preferably be a pulse-width modulation signal.

[0101] Then, a control voltage modulated by a control signal is provided (S120). In a preferred embodiment, the control signal Sc is received by a conversion circuit 628 to provide a control voltage Vc modulated by the control signal Sc, and the control voltage Vc is not a constant value during the process of suppressing the input current Iac surge. Then, the on-resistance of the switch is adjusted according to the control voltage (S140). In a preferred embodiment, the switch 624 is coupled to the conversion circuit 628 to provide the control voltage Vc to control the channel size of the switch 624 and its corresponding on-resistance R. Finally, the magnitude of the first current flowing through the switch is adjusted by adjusting the on-resistance (S160). Due to the control method of IGBT (or MOSFET), the channel size of IGBT (or MOSFET) can be changed by adjusting the control voltage Vc, thereby adjusting the on-resistance R of the switch 624 (i.e., Rce_on of IGBT or Rds_on of MOSFET). Therefore, the channel size of IGBT (or MOSFET) and its corresponding on-resistance R can be changed by adjusting the control voltage Vc to limit the magnitude of the first current I1 flowing through the switch 624.

[0102] Please refer to Figure 5B FIG. is a flowchart of an operation method of the present disclosure's surge suppressor applied to the opening and closing period, and is further combined with reference to Figures 1A to 5A . Due to the situation where the magnetic flux of the magnetic component changes instantaneously, it usually occurs during the opening and closing period when the medium-voltage AC conversion circuit 4 starts or shuts down (but it does not exclude any period during the operation of the medium-voltage AC conversion circuit 4). Therefore, the application during the opening and closing period further includes setting the opening and closing period when the medium-voltage AC conversion circuit starts or shuts down (S200). The medium-voltage AC power supply system 100 can set the opening and closing period according to the start or shutdown time of the medium-voltage AC conversion circuit 4, mainly based on Figure 2B the time required for the second breaking device 5 of the medium-voltage switch MVS to fully conduct the input path L or fully cut off the input path L.

[0103] Then, enable the surge suppression circuit during the opening and closing period, and operate each surge suppression circuit to execute steps (S100) to (S160) (S220). During the opening and closing period, the surge suppression circuit 62 is enabled (it can be enabled by any device inside the medium-voltage AC power supply system 100, preferably, the system controller of the medium-voltage AC power supply system 100 provides a control command CL to perform this operation), so as to limit the input current Iac within a predetermined range by adjusting the conduction impedance R (for example, but not limited to, limiting the surge within twice the rated current), to avoid damage to the components inside the medium-voltage AC power supply system 100 due to breakdown, or the situation of accidentally touching the upper limit of the protection value of the second breaking device 5. Finally, disable the surge suppression circuit at the end of the opening and closing period (S240). At the end of the opening and closing period, the surge suppression circuit 62 is disabled (for example, but not limited to, the controller 626 stops providing the control signal Sc, or disconnects the connection between the conversion circuit 628 and the switch 624 through an internal switch (not shown in the figure), etc.), to avoid continuous power consumption of the surge suppression circuit 62. It is worth mentioning that in one embodiment, Figures 5A to 5B The detailed operation methods not described can be referred to in conjunction with Figures 2A to 4B , and will not be elaborated here.

[0104] Please refer to Figures 6A to 6C The schematic diagrams of conduction impedance adjustment for the first to third implementation manners of the disclosed surge suppressor applied to the opening and closing period, and also refer to Figures 1A to 5B . Since the conduction impedances R1 to Rn of the switches 624-1 to 624-n are controlled by the control voltage Vc and can be regarded as adjustable resistors, the impedance adjustment methods in the above step (S220) can include, for example, but not limited to, Figures 6A to 6C . In Figure 6A , the most basic adjustment method is shown, where the vertical axis is the impedance magnitude of the conduction impedance Rn, and the horizontal axis is the actual configured positions of the switches 624-1 to 624-n. Each surge suppression circuit 62 provides substantially the same control voltage Vc, so that the channels of the switches 624-1 to 624-n are substantially the same, and thus the corresponding conduction impedances R1 to Rn are also the same.

[0105] In Figure 6BIn the medium-voltage AC power supply system 100, according to the number of surge suppression circuits 62, the opening and closing period is divided into multiple periods. Taking 5 surge suppression circuits 62 as a schematic example, the opening and closing period can be divided into more than 5 periods. Assuming that the opening and closing period is divided into 5 periods, then the 5 surge suppression circuits 62 can exactly correspond to 1 period. Therefore, one of the switches 624 of the 5 surge suppression circuits 62 can be selected to provide a larger on-resistance R during each period. That is to say, each surge suppression circuit 62 provides a larger on-resistance R exactly during its own period, having a corresponding relationship. In addition, assuming that the opening and closing period is divided into 7 periods, in addition to corresponding to 1 period, 2 of the 5 surge suppression circuits 62 are each additionally responsible for 1 more period, and so on, which will not be elaborated here. Furthermore, since heat is generated when current flows through the switches 624-1 to 624-n, therefore Figure 6B the operation method can evenly disperse the heat among the switches 624-1 to 624-n, and through the method of dividing periods, the remaining switches 624-1 to 624-n can have time to dissipate heat, so as to achieve the effect of improving the heat dissipation efficiency.

[0106] In addition, in addition to the switches 624-1 to 624-n that provide larger on-resistances R1 to Rn (assuming it is 624-1), the remaining switches 624-2 to 624-n can preferably be fully turned on by providing a higher control voltage Vc to provide a lower on-resistance R. On the other hand, as Figure 6B shown, the medium-voltage AC power supply system 100 can preferably control the corresponding switches 624-1 to 624-n to provide larger on-resistances R1 to Rn in sequence according to the series connection positions of the surge suppression circuits 62. That is to say, in the first period, the surge suppression circuit 62 at the series head end controls its own switch 624-1 to provide a higher on-resistance R1, and in the second period, the surge suppression circuit 62 connected in the second position controls its own switch 624-2 to provide a higher on-resistance R2. And so on, which will not be elaborated here. Thus, the operation of the surge suppression circuits 62 can have better regularity and is easier to operate.

[0107] In Figure 6CIn the medium-voltage AC power supply system 100, according to the magnitude of the voltage value of the input voltage Vac received by the medium-voltage AC conversion circuit 4, the on-resistances R1 to Rn of the switches 624-1 to 624-n of each surge suppression circuit 62 are controlled. Specifically, in addition to providing substantially the same control voltage Vc for each surge suppression circuit 62 to make the channels of the switches 624-1 to 624-n substantially the same, the on-resistances R1 to Rn of the switches 624-1 to 624-n are adjusted according to the magnitude of the voltage value of the input voltage Vac. When the voltage value of the input voltage Vac approaches the zero crossing point (time t1), the on-resistances R1 to Rn are small, and when the voltage value of the input voltage Vac starts to move from the zero crossing point to the positive peak value (times t2 to t3), the on-resistances R1 to Rn gradually increase. When the voltage value of the input voltage Vac reaches the positive peak value, the on-resistances R1 to Rn are adjusted to the maximum value (time t4).

[0108] Furthermore, since the energy conducted to the medium-voltage AC power supply system 100 is low when the voltage value of the input voltage Vac approaches the zero crossing point, the surge of the input current Iac caused is also small. On the contrary, the surge of the input current Iac caused is large. Therefore, if the on-resistances R1 to Rn of the switches 624-1 to 624-n are adjusted according to the magnitude of the voltage value of the input voltage Vac, a larger on-resistance R1 to Rn can be provided when the energy conduction is large and a higher impedance is required to suppress the surge. On the contrary, a smaller on-resistance R1 to Rn can be provided when the energy conduction is small and a high impedance is not required to suppress the surge. In this way, a better surge suppression effect can be provided, and at the same time, the heat consumption of the surge suppressor 6 can be reduced. Among them, Figure 6C the values of the on-resistances R1 to Rn can be further combined with the above-mentioned Figure 6A way of impedance average sharing (i.e., the channels are substantially the same) to carry out, and can also be further combined with Figure 6B the way of providing a larger impedance in turn to carry out. The detailed content can be inferred from the above operation method and will not be elaborated here.

[0109] In addition, in Figures 6A to 6C the medium-voltage AC power supply system 100 can also selectively control the on-resistances R1 to Rn of the switches 624-1 to 624-n of each surge suppression circuit 62 to gradually decrease according to the duration of the on-off period. Specifically, in Figures 1A to 1BIt can be clearly seen that the surge characteristic of the input current Iac is generally that the first surge at the time of surge occurrence is the highest value, and most of the subsequent ones decay exponentially and then return to the stable value. Therefore, a relatively large conduction impedance R1~Rn needs to be provided for the first surge at the time of surge occurrence. Since the peak value of the subsequent surges will gradually decrease, the conduction impedance R1~Rn can be gradually reduced accordingly. In this way, a better surge suppression effect can be provided, and at the same time, the heat consumption of the surge suppressor 6 can be reduced. It is worth mentioning that in one embodiment, the above Figures 6A to 6C way of adjusting the conduction impedance can also be used in the occasion where the surge suppressor 6 needs to be enabled to suppress surges during the operation of the medium-voltage AC power supply system 100. Its operation method is the same as that described above and will not be elaborated here.

[0110] However, as described above, it is only a detailed description and drawings of a preferred specific embodiment of the present invention. The features of the present invention are not limited thereto and are not intended to limit the present invention. The entire scope of the present invention shall be subject to the following scope of the claims. All embodiments that conform to the spirit of the claims of the present invention and its similar variations shall be included in the scope of the present invention. Any changes or modifications that can be easily conceived by any person skilled in the art within the field of the present invention can be covered by the following claims of this case.

Claims

1. A surge suppressor is connected in parallel to a circuit breaker device in the input path of a medium-voltage AC conversion circuit, and the surge suppressor includes: A plurality of surge suppression circuits, and each surge suppression circuit includes: A rectifier circuit including an AC terminal and a rectified terminal, and each surge suppression circuit is serially coupled through the AC terminal; A switch coupled to the rectified terminal; A controller that receives a control command and provides a control signal according to the control command; and A conversion circuit coupled to the controller and the switch and providing a control voltage modulated by the control signal; Wherein, the control voltage adjusts the on-resistance of the switch to adjust the magnitude of a first current flowing through the switch through the control voltage.

2. The surge suppressor according to claim 1, wherein during the on-off period when the medium-voltage AC conversion circuit starts or shuts down, the plurality of surge suppression circuits are enabled to limit the input current received by the medium-voltage AC conversion circuit to a predetermined range by adjusting the on-resistance.

3. The surge suppressor according to claim 1, wherein the conversion circuit includes: A switching circuit coupled to the controller; And A filter circuit coupled to the switching circuit and the switch; Wherein, the switching circuit is switched on according to the control signal, and the filter circuit generates the control voltage according to the switching on of the switching circuit.

4. The surge suppressor according to claim 3, wherein the filter circuit includes: An inductor coupled to the switching circuit; And A capacitor coupled to the inductor and the switch; Wherein, the controller controls the switching on of the switching circuit to charge the inductor with a working voltage, or controls the inductor to discharge energy to the capacitor, and the control voltage is generated across the capacitor through the energy storage and release of the inductor.

5. The surge suppressor according to claim 3, wherein the switching circuit includes: An upper-bridge switch that receives a working voltage and is coupled to the controller and the filter circuit; And A lower-bridge switch coupled to the upper-bridge switch and the controller; Wherein, the control signal includes complementary upper-bridge control signal and lower-bridge control signal; when the upper-bridge control signal turns on the upper-bridge switch, the working voltage charges the filter circuit through the upper-bridge switch; when the lower-bridge control signal turns on the lower-bridge switch, the filter circuit discharges energy through the lower-bridge switch.

6. The surge suppressor according to claim 5, wherein the conversion circuit further includes: A current-limiting resistor coupled to the upper-bridge switch, the lower-bridge switch, and the filter circuit; Wherein, when the upper-bridge switch is turned on, the current-limiting resistor limits the magnitude of a second current flowing from the upper-bridge switch to the filter circuit by the working voltage.

7. The surge suppressor according to claim 3, wherein the switching circuit includes: A lower-bridge switch that receives a working voltage and is coupled to the controller and the filter circuit; Wherein, the control signal is a lower-bridge control signal; when the lower-bridge control signal does not turn on the lower-bridge switch, the operating voltage charges the filter circuit, and when the lower-bridge control signal turns on the lower-bridge switch, the filter circuit discharges energy through the lower-bridge switch.

8. The surge suppressor according to claim 7, wherein the conversion circuit further comprises: A current-limiting resistor that receives the operating voltage and is coupled between the lower-bridge switch and the filter circuit; Wherein, when the lower-bridge switch is not turned on, the current-limiting resistor limits the magnitude of the second current of the operating voltage flowing to the filter circuit.

9. The surge suppressor according to claim 1, wherein the rectifying circuit is a full-bridge circuit, and the direction of the current when providing the first current flowing through the switch is a fixed direction.

10. The surge suppressor according to claim 1, wherein each surge suppression circuit further comprises: A protection circuit connected in parallel to the AC terminal and including a variable resistor and at least a clamping circuit; Wherein, the protection circuit is used to limit the voltage at the AC terminal to be less than or equal to a predetermined voltage when both the breaking device and the surge suppressor are open.

11. An operation method of a surge suppressor, the surge suppressor is connected in parallel to a breaking device on the input path of a medium-voltage AC conversion circuit, and comprises a plurality of surge suppression circuits connected in series, each of the plurality of surge suppression circuits includes a rectifying terminal and a switch coupled to the rectifying terminal, and the operation method of the surge suppressor comprises the following steps: (a) Receive a control command and provide a control signal according to the control command; (b) Provide a control voltage modulated by the control signal; (c) Adjust the on-impedance of the switch according to the control voltage; and (d) Adjust the magnitude of the first current flowing through the switch by adjusting the on-impedance.

12. The operation method of the surge suppressor according to claim 11, further comprising the following steps: (e) Set the opening and closing period for starting or closing the medium-voltage AC conversion circuit; (f) Enable the plurality of surge suppression circuits during the opening and closing period, and operate each surge suppression circuit to execute steps (a) to (d); and (g) Disable the plurality of surge suppression circuits at the end of the opening and closing period.

13. The operation method of the surge suppressor according to claim 12, wherein step (f) further comprises the following steps: (f1) Control the switches of each surge suppression circuit to provide the same magnitude of on-impedance.

14. The operation method of the surge suppressor according to claim 12, wherein step (f) further comprises the following steps: (f2) Control the on-impedance of the switches of each surge suppression circuit according to the magnitude of the input voltage received by the medium-voltage AC conversion circuit.

15. The operation method of the surge suppressor according to claim 12, wherein step (f) further comprises the following steps: (f31) Divide the opening and closing period into a plurality of periods according to the number of the plurality of surge suppression circuits; and (f32) Select one of the switches of the plurality of surge suppression circuits to provide a larger on-impedance during each period.

16. The operating method of the surge suppressor according to claim 15, wherein step (f32) further comprises the following steps: (f322) According to the positions where the plurality of surge suppression circuits are connected in series, sequentially control the corresponding switches to provide a larger conduction impedance.

17. The operating method of the surge suppressor according to claim 12, wherein step (f) further comprises the following steps: (f4) Control the conduction impedance of the switch of each surge suppression circuit to gradually decrease according to the duration of the on-off period.

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