A neutral beam negative ion source extra-high voltage power supply system

Abstract

This invention relates to the field of high-voltage power supplies, specifically to a neutral beam negative ion source ultra-high voltage power supply system. It includes: at least one phase-shifting transformer, whose secondary windings output voltages sequentially have a preset phase difference; a multi-stage phase-controlled rectifier, each stage containing multiple rectifier bridges, each rectifier bridge's AC input terminal connected to a secondary winding, and its DC output terminals connected in series to output a multi-pulse DC voltage; a multi-stage filter circuit connected to the DC output terminals of the phase-controlled rectifier; a multi-stage three-level inverter connected to the output terminals of the filter circuit; a multi-stage step-up transformer connected to the AC output terminals of the inverter; a rectifier and filter unit connected to the output terminals of the step-up transformer, with each stage's DC output terminals connected in series to form a total high-voltage output; and a control system electrically connected to the control terminals of each stage's phase-controlled rectifier and the three-level inverter, independently adjusting the DC bus voltage of each stage and the inverter's duty cycle to improve dynamic response speed and grid harmonic compatibility.

Description

Technical Field

[0001] This invention relates to the field of high voltage power supplies, and more specifically to a neutral beam negative ion source ultra-high voltage power supply system. Background Technology

[0002] The neutral beam injection system is the core equipment in a nuclear fusion device for heating plasma and maintaining plasma equilibrium, and its performance directly affects the stability and efficiency of the nuclear fusion reaction. The neutral beam negative ion source, as a key component of this system, needs to generate and accelerate negative ions in a high-vacuum environment. This process relies on a stable output ultra-high voltage DC power supply, with voltage levels typically reaching hundreds of kilovolts, and in some scenarios even exceeding 1 mV.

[0003] Currently, the ultra-high voltage power supply of neutral beam negative ion sources mainly adopts a topology scheme of "phase-shifting transformer + phase-controlled rectifier + three-level converter + step-up rectifier": the phase-shifting transformer converts the grid voltage into a suitable multi-phase low voltage, which is then rectified into DC bus voltage by the phase-controlled rectifier; then the DC-AC conversion is realized through the three-level inverter, and finally the target ultra-high voltage is output by controlling the amplitude of the DC bus voltage and the duty cycle of the three-level converter.

[0004] However, the ion acceleration process of a neutral beam negative ion source requires five independently adjustable high-voltage stages, each of which needs to have its parameters (voltage amplitude) adjusted independently according to the load conditions. In existing solutions, the overall high-voltage output relies on a single phase-controlled rectifier to adjust the DC bus voltage, resulting in the regulation of the five high-voltage stages being mutually coupled—adjusting the parameters of one stage will affect the output stability of other stages. Furthermore, the response speed and adjustment accuracy of a single rectifier are limited, which restricts the need for independent, rapid, and precise adjustment of the five high-voltage stages, thus limiting the beam quality and operational flexibility of the neutral beam negative ion source. Summary of the Invention

[0005] The purpose of this invention is to provide a neutral beam negative ion source ultra-high voltage power supply system, which solves the problems in the prior art.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a neutral beam negative ion source ultra-high voltage power supply system, comprising:

[0008] At least one phase-shifting transformer, wherein the primary winding of the phase-shifting transformer is used for electrical connection to the power supply terminal of the grid, and the secondary side of the phase-shifting transformer includes multiple windings, wherein the output voltages of the multiple secondary windings have a preset phase difference in sequence;

[0009] A multi-stage phase-controlled rectifier, each stage of which contains multiple rectifier bridges. The AC input terminal of each rectifier bridge is electrically connected to a corresponding secondary winding. The DC output terminals of multiple rectifier bridges in the same stage are connected in series. Each stage of the phase-controlled rectifier outputs a multi-pulse DC voltage.

[0010] A multi-stage filter circuit connected to the DC output terminal of the multi-stage phase-controlled rectifier;

[0011] A multi-stage three-level inverter connected to the output terminal of the multi-stage filter circuit;

[0012] A multi-stage step-up transformer connected to the AC output terminal of the multi-stage three-level inverter;

[0013] The rectifier and filter unit is connected to the output terminal of the multi-stage step-up transformer. The DC output terminals of each rectifier and filter unit are connected in series to form the total high-voltage DC output terminal of the system.

[0014] The control system is electrically connected to the control terminal of each stage phase-controlled rectifier and the control terminal of each stage three-level inverter, and is used to independently adjust the DC bus voltage of each stage phase-controlled rectifier and the duty cycle of each stage three-level inverter.

[0015] Preferably, the at least one phase-shifting transformer includes a first phase-shifting transformer and a second phase-shifting transformer;

[0016] The primary winding of the first phase-shifting transformer has a phase shift angle of +7.5°, and the primary winding of the second phase-shifting transformer has a phase shift angle of -7.5°.

[0017] The secondary side of the first phase-shifting transformer includes a delta-connected winding and a star-connected winding, and the secondary side of the second phase-shifting transformer includes a delta-connected winding and a star-connected winding.

[0018] The output voltages of the four secondary windings of the first phase-shifting transformer and the second phase-shifting transformer are sequentially 15° apart.

[0019] Preferably, each stage of the phase-controlled rectifier includes four rectifier bridges; the AC input terminals of the four rectifier bridges in each stage of the phase-controlled rectifier are electrically connected to the four secondary windings one-to-one.

[0020] In each stage of the phase-controlled rectifier, the DC output terminals of the four rectifier bridges are connected in series, so that each stage of the phase-controlled rectifier outputs a 24-pulse DC voltage.

[0021] Preferably, each stage of the filter circuit includes a choke inductor and a DC filter capacitor;

[0022] The choke inductor is connected in series with the positive and negative branches of the DC output terminal of the corresponding stage phase-controlled rectifier; the DC filter capacitor is connected in parallel between the positive and negative terminals of the DC output terminal of the corresponding stage phase-controlled rectifier.

[0023] Preferably, the three-level inverter is a neutral-point clamped three-level inverter;

[0024] Each stage of the three-level inverter includes four fully controlled devices, two clamping diodes, and a DC bus midpoint;

[0025] One end of the clamping diode is connected to the midpoint of the DC bus, and the other end is connected to the middle node of the corresponding bridge arm, so that the voltage stress borne by each fully controlled device when it is turned off is half of the DC bus voltage.

[0026] Preferably, each stage of the rectifier and filter unit includes a high-voltage uncontrolled rectifier, a filter resistor, and a filter capacitor; the input terminal of the high-voltage uncontrolled rectifier is electrically connected to the output terminal of the step-up transformer; the filter resistor and the filter capacitor are connected in series and then in parallel to the DC output terminal of the high-voltage uncontrolled rectifier.

[0027] Preferably, the control system changes the DC bus voltage of the current stage by adjusting the firing angle of the thyristors in the current stage phase-controlled rectifier, and adjusts the duty cycle of the current stage three-level inverter to keep the current stage duty cycle in a preset optimal range.

[0028] Preferably, each step-up transformer is an oil-immersed step-up transformer; the primary voltage of each step-up transformer is adapted to the output voltage of the connected three-level inverter, and the secondary voltage of each step-up transformer is adapted to the voltage required by the single-stage accelerating electrode of the neutral beam negative ion source.

[0029] Preferably, it also includes primary outdoor equipment, which is connected in series between the power grid supply terminal and the primary winding of the phase-shifting transformer; the primary outdoor equipment includes a vacuum circuit breaker and a soft starter cabinet; the vacuum circuit breaker is used to control the on / off of the power grid supply; the soft starter cabinet is connected in series with the vacuum circuit breaker and is used to suppress inrush current when the system is powered on.

[0030] Preferably, the multi-stage phase-controlled rectifier has five stages; the capacitance of each DC filter capacitor in the multi-stage filter circuit is no greater than 30mF, and the inductance of each choke inductor is no greater than 1mH.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] By using the preset phase difference of the multiple windings on the secondary side of the phase-shifting transformer, each stage of the phase-controlled rectifier obtains a phase-staggered AC input. Multiple rectifier bridges within each stage are connected in series to output a high-pulse DC bus voltage, reducing ripple frequency and amplitude. Combined with a filtering circuit, this smooths the ripple and provides stable DC power to the three-level inverter. The low-distortion AC output from the three-level inverter is then passed through a step-up transformer and rectifier / filter units to obtain a single-stage high-voltage DC output. The rectifier / filter units at each stage are connected in series to form the total high-voltage output. The control system independently adjusts the DC bus voltage of each stage of the phase-controlled rectifier and the duty cycle of each stage of the three-level inverter, achieving decoupled control of each stage's voltage. Thus, while eliminating inter-stage adjustment coupling and achieving independent and precise multi-stage voltage adjustment, the system utilizes high-pulse rectification and three-level inversion to reduce output voltage ripple and dependence on filter component capacity, improving dynamic response speed and grid harmonic compatibility, and meeting the ultra-high-voltage power supply requirements of the neutral beam negative ion source for multi-stage accelerating electrodes. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0034] Figure 1 A schematic diagram of the ultra-high voltage power supply system for the neutral beam negative ion source provided by this invention;

[0035] Figure 2 The schematic diagram of the phase-shifting transformer and phase-controlled rectifier provided by this invention;

[0036] Figure 3 The schematic diagram of the three-level inverter provided by this invention;

[0037] The attached diagram shows the markings and corresponding component names:

[0038] 1-Power grid supply terminal; 2-Primary outdoor equipment; 3-Phase shifting transformer; 4-Phase controlled rectifier; 5-Three-level inverter; 6-Step-up transformer; 7-Rectifier and filter unit; 8-High voltage uncontrolled rectifier; 9-Filter resistor; 10-Filter capacitor; 11-Choke inductor; 12-DC filter capacitor; 13-Clamping diode; 14-Fully controlled device. Detailed Implementation

[0039] 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 embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0041] It should be noted that all actions involving the acquisition of signals, information, or data in this invention are carried out in compliance with the relevant data protection laws and regulations of the locality and with authorization from the owner of the relevant device.

[0042] Example 1

[0043] Please see Figure 1 This invention provides a neutral beam negative ion source ultra-high voltage power supply system, characterized in that it includes:

[0044] At least one phase-shifting transformer 3, the primary winding of the phase-shifting transformer 3 is used to be electrically connected to the power supply terminal 1 of the power grid, and the secondary side of the phase-shifting transformer 3 includes multiple windings, and the output voltages of the multiple secondary windings have a preset phase difference in sequence.

[0045] The multi-stage phase-controlled rectifier 4 includes multiple rectifier bridges. The AC input terminal of each rectifier bridge is electrically connected to a corresponding secondary winding. The DC output terminals of multiple rectifier bridges in the same stage are connected in series. Each stage of the phase-controlled rectifier 4 outputs a multi-pulse DC voltage.

[0046] A multi-stage filter circuit connected to the DC output terminal of the multi-stage phase-controlled rectifier 4;

[0047] A multi-stage three-level inverter 5 is connected to the output terminal of the multi-stage filter circuit;

[0048] A multi-stage step-up transformer 6 is connected to the AC output terminal of the multi-stage three-level inverter 5.

[0049] The rectifier and filter unit 7 is connected to the output terminal of the multi-stage step-up transformer 6. The DC output terminals of each rectifier and filter unit 7 are connected in series to form the total high-voltage DC output terminal of the system.

[0050] The control system is electrically connected to the control terminal of each stage phase-controlled rectifier 4 and the control terminal of each stage three-level inverter 5, and is used to independently adjust the DC bus voltage of each stage phase-controlled rectifier 4 and the duty cycle of each stage three-level inverter 5.

[0051] The phase-shifting transformer 3 is a device that converts the power frequency AC input from the grid supply terminal 1 into multiple sets of AC voltage outputs with specific phase differences. The primary winding of the phase-shifting transformer 3 is connected to the grid supply terminal 1, while the secondary winding contains multiple windings. By adjusting the number of turns or the connection method, such as delta connection, star connection, or extended delta connection, a preset phase difference, for example, 15°, is formed between the output voltages of each secondary winding. The core function of the phase-shifting transformer 3 is to provide the phase-staggered AC power supply required for multi-pulse rectification of the subsequent phase-controlled rectifier 4, thereby reducing the pollution of the power grid by harmonic currents generated during the rectification process.

[0052] Phase-controlled rectifier 4 is a controllable rectifier device composed of thyristors, used to convert alternating current (AC) to direct current (DC). Each stage of phase-controlled rectifier 4 contains multiple rectifier bridges, such as four rectifier bridges. The AC input terminal of each rectifier bridge is electrically connected to a secondary winding of the phase-shifting transformer 3. The DC output terminals of multiple rectifier bridges within the same stage are connected in series, so that the pulsating DC voltages output by each rectifier bridge are superimposed, ultimately outputting a multi-pulse DC voltage, such as a 24-pulse DC voltage. By adjusting the firing angle of the thyristors, the magnitude of the DC bus voltage output by each stage of phase-controlled rectifier 4 can be independently controlled, thereby achieving independent regulation of the voltage at each stage. The multi-stage phase-controlled rectifier 4 can have up to five stages.

[0053] A filter circuit is connected in series between the DC output terminal of the phase-controlled rectifier 4 and the input terminal of the three-level inverter 5 to suppress ripple in the DC bus voltage. Specifically, the filter circuit includes a choke inductor 11 and a DC filter capacitor 12: the choke inductor 11 is connected in series between the positive and negative branches of the DC output terminal to suppress current ripple; the DC filter capacitor 12 is connected in parallel between the positive and negative terminals to absorb voltage fluctuations. Together, they stabilize the DC bus voltage input to the three-level inverter 5. Furthermore, the capacitance of each DC filter capacitor in the multi-stage filter circuit is no greater than 30mF.

[0054] The three-level inverter 5 is a DC / AC converter capable of outputting positive, zero, and negative voltage levels. This system employs a neutral-point clamped three-level inverter 5, where the DC bus is divided into positive, neutral, and negative terminals by two series capacitors. Each stage of the three-level inverter 5 includes four fully controlled devices 14 (such as IGCT and IEGT) and two clamping diodes 13. By controlling the switching on and off combinations of the fully controlled devices 14, the inverter outputs an AC voltage synthesized from the +Udc / 2, 0, and -Udc / 2 levels. The clamping diodes 13 forcibly clamp the potential of the intermediate node of the bridge arm to the midpoint of the DC bus, ensuring that the voltage stress borne by each fully controlled device 14 when turned off is only half of the DC bus voltage, thereby reducing the device withstand voltage requirements and improving reliability.

[0055] The step-up transformer 6 is a transformer that raises the medium-to-low voltage AC output from the three-level inverter 5 to a high voltage level. The primary side of the step-up transformer 6 is connected to the AC output terminal of the three-level inverter 5, and the secondary side is connected to the uncontrolled rectifier 8. Each step-up transformer 6 is independently configured, and its turns ratio is designed according to the required high voltage for a single stage (e.g., 200kV~250kV). The secondary output terminals of multiple step-up transformers 6 are connected in series to achieve voltage superposition.

[0056] The rectifier and filter unit 7 is a combined device that converts high-voltage AC power into smooth high-voltage DC power.

[0057] The control system is electrically connected to the control terminals (thyristor gates) of each stage of the phase-controlled rectifier 4 and the control terminals (fully controlled device gates) of each stage of the three-level inverter 5. The control system receives the output voltage reference values ​​set by the host computer for each stage, and independently calculates the firing angle of each stage of the phase-controlled rectifier 4 and the duty cycle of each stage of the three-level inverter 5 by detecting the actual bus voltage and the actual output voltage, and then issues corresponding control pulses. The control system can achieve decoupled regulation of the voltage at each stage, meaning that adjusting the parameters of one stage will not affect the output of other stages.

[0058] Specifically, the power supply terminal 1 is connected to the phase-shifting transformer 3, whose secondary windings have output voltage phases that are sequentially staggered by a preset value. These phase-staggered AC currents are sent to multiple rectifier bridges in each stage of the phase-controlled rectifier 4. Each rectifier bridge outputs a six-pulse DC current. Due to the phase shift, the peaks and troughs of the pulsating waveforms of each rectifier bridge are misaligned. The DC output terminals of multiple rectifier bridges in the same stage are connected in series and superimposed to obtain a high-pulse-number DC bus voltage. After further smoothing by the filter circuit, the voltage is input to the three-level inverter 5.

[0059] The three-level inverter 5 converts DC to three-level AC according to the duty cycle given by the control system, resulting in a small voltage step and minimal waveform distortion. This AC voltage is stepped up by the step-up transformer 6 and then rectified and filtered by the rectifier and filter unit 7 to output the high-voltage DC voltage of this stage. The DC output terminals of each rectifier and filter unit 7 are connected in series, and the total voltage is equal to the sum of the voltages of each stage.

[0060] The control system independently adjusts each stage: based on the output voltage reference value of its stage, the firing angle of the phase-controlled rectifier 4 is adjusted to ensure the bus voltage tracks the target value; then, based on the reference value and the actual bus voltage, the duty cycle of the three-level inverter 5 is adjusted. There is no electrical coupling between stages, so adjusting one stage does not affect other stages, eliminating the inter-stage constraints found in traditional solutions. The combination of multi-pulse DC and three-level inverter results in low bus ripple and low inverter output harmonics, ultimately ensuring that the DC high-voltage ripple meets the requirements for ion acceleration. The overall system achieves decoupled, low-ripple, and fast-response multi-stage ultra-high voltage power supply.

[0061] In some embodiments, the at least one phase-shifting transformer 3 includes a first phase-shifting transformer and a second phase-shifting transformer; the primary winding of the first phase-shifting transformer has a phase shift angle of +7.5°, and the primary winding of the second phase-shifting transformer has a phase shift angle of -7.5°; the secondary winding of the first phase-shifting transformer includes a delta-connected winding and a star-connected winding, and the secondary winding of the second phase-shifting transformer includes a delta-connected winding and a star-connected winding; the output voltages of the four secondary windings of the first and second phase-shifting transformers are sequentially 15° apart.

[0062] The primary windings of the first and second phase-shifting transformers have phase shift angles of +7.5° and -7.5°, respectively. The phase shift angle refers to the electrical angular offset of the transformer's primary winding relative to the grid reference phase. By adjusting the turns distribution of the primary windings or using an extended delta connection, the phase of the transformer's input voltage can be made to lead (+) or lag (-) by a specified angle.

[0063] The secondary winding is connected in a delta (Δ) configuration, meaning the three windings are connected end-to-end to form a closed triangle, and the line voltage equals the phase voltage. The AC voltage output from the delta connection has a fixed phase lag or lead of 30° compared to the star connection.

[0064] The secondary winding adopts a star (Y) connection, that is, the ends of the three windings are connected together to form a neutral point, and the line voltage is equal to √3 times the phase voltage. The AC voltage output by the star connection leads or lags by 30° compared to the delta connection.

[0065] Specifically, to achieve a 15° phase difference between the output voltages of the four secondary windings, the primary-side phase shifts of the two transformers need to be combined with the secondary-side connection design. First, the primary-side phase shift of the first phase-shifting transformer is +7.5°, and the primary-side phase shift of the second phase-shifting transformer is -7.5°, resulting in a 15° phase difference between the primary-side voltages of the two transformers. Then, each transformer's secondary side is configured with both delta-connected and star-connected windings. Due to the inherent 30° phase difference between delta and star connections, the output voltages of the delta and star windings of the same transformer also differ by 30°. After superimposing the primary-side phase shifts with the inherent secondary-side phase shifts, the actual phases of the four windings are obtained: first Δ winding phase = +7.5°; first Y winding phase = +7.5° - 30° = -22.5°; second Δ winding phase = -7.5°; second Y winding phase = -7.5° - 30° = -37.5°. If a reference offset (e.g., +22.5°) is added to all phases, a sequence of 30°, 0°, 15°, and -15° is obtained, which, after sorting, becomes -15°, 0°, 15°, and 30°, with adjacent phases differing by 15°. Since the phase order can be rearranged, there exists an order in which the four output voltages are sequentially 15° apart. In actual wiring, simply connect the four windings to the four rectifier bridges of each stage of the phase-controlled rectifier according to the calculated phase order to ensure that the input voltages of each rectifier bridge are sequentially staggered by 15°. This design utilizes simple primary-side phase shifting and standard Δ / Y connections, eliminating the need for complex winding structures, to generate the four sets of AC power supplies separated by 15° for 24-pulse rectification. Compared to using four independent phase-shifting transformers or complex multi-winding transformers, this solution can be achieved using only two conventional phase-shifting transformers, reducing manufacturing costs and system complexity. Furthermore, since the four windings are shared by two transformers, each with the same capacity, standardized design and redundant configuration are facilitated.

[0066] In some embodiments, each stage of the phase-controlled rectifier 4 includes four rectifier bridges; the AC input terminals of the four rectifier bridges in each stage of the phase-controlled rectifier 4 are electrically connected to the four secondary windings respectively; the DC output terminals of the four rectifier bridges in each stage of the phase-controlled rectifier 4 are connected in series, so that each stage of the phase-controlled rectifier 4 outputs a 24-pulse DC voltage.

[0067] The four rectifier bridges refer to the four independent six-pulse rectifier bridges integrated within each stage of the phase-controlled rectifier 4. Each rectifier bridge consists of six thyristors, which can convert three-phase alternating current into pulsating direct current. The AC input terminals of the four rectifier bridges are respectively connected to the four secondary windings of the phase-shifting transformer 3, so the AC voltage received by each rectifier bridge is in a different phase.

[0068] A 24-pulse DC voltage refers to a rectifier output DC voltage containing 24 pulses within one power frequency cycle (20ms). The number of pulses equals the number of rectifier bridges multiplied by the pulse count of each bridge, i.e., 4 × 6 = 24 pulses. The ripple frequency of a 24-pulse DC voltage is 24 times the power frequency, and the ripple amplitude is much lower than that of a 6-pulse or 12-pulse rectification.

[0069] Specifically, in each stage of the phase-controlled rectifier 4, the AC input terminals of the four rectifier bridges are electrically connected to the four secondary windings of the phase-shifting transformer 3, one-to-one. Since the output voltage phases of the four secondary windings differ by 15° sequentially, the three-phase AC voltages received by each rectifier bridge are sequentially staggered by 15°. Each rectifier bridge itself is a six-pulse rectifier, meaning it outputs six pulsating wavefronts within one power frequency cycle, with adjacent wavefronts spaced 60° apart. When the input phases of the four rectifier bridges differ by 15° sequentially, the peak positions of their output six-pulse DC voltages are also correspondingly staggered by 15°. Connecting the DC output terminals of these four rectifier bridges in series is equivalent to superimposing four sets of pulsating wavefronts. Due to the phase stagger, the trough positions of the outputs of each rectifier bridge are filled by the peaks of another rectifier bridge, resulting in a total superimposed DC voltage with 4 × 6 = 24 wavefronts within one power frequency cycle, i.e., a 24-pulse DC voltage. With the ripple frequency increased to 1200Hz, the ripple amplitude is significantly reduced relative to the average value, thus eliminating the need for large-capacity DC filter capacitors to achieve a smooth DC bus voltage. This characteristic directly reduces the size and cost of the filter capacitors, while also reducing the current stress during capacitor charging and discharging, improving reliability. Furthermore, because the AC input current phases of each rectifier bridge are staggered, their characteristic harmonics (such as the 5th, 7th, 11th, and 13th harmonics) cancel each other out when superimposed on the grid side. This significantly reduces the total amount of current harmonics absorbed from the grid by each stage of the phase-controlled rectifier 4, meeting the stringent power quality requirements of nuclear fusion devices. More importantly, the 24-pulse rectified output bus voltage fluctuation is extremely small, providing a near-constant DC input for the subsequent three-level inverter 5. This prevents the inverter from generating additional output distortion due to bus voltage fluctuations when adjusting the duty cycle, further reducing the ripple of the final output DC high voltage. The entire system achieves high pulse counts through a simple series connection of rectifier bridges, eliminating the need for complex multi-pulse rectifier transformers (such as designing the secondary side of the transformer as multiple phase-shifting windings), thus reducing transformer manufacturing costs. Furthermore, since the four rectifier bridges are independent of each other, even if one bridge fails, it can be bypassed and the system can still operate in 18-pulse mode, providing fault redundancy and improving system availability.

[0070] Please refer to the following: Figure 2The schematic diagram of the phase-shifting transformer and phase-controlled rectifier shown includes, in some embodiments, each stage of the filter circuit including a choke inductor 11 and a DC filter capacitor 12; the choke inductor 11 is connected in series with the positive and negative branches of the DC output terminal of the phase-controlled rectifier 4; the DC filter capacitor 12 is connected in parallel between the positive and negative terminals of the DC output terminal of the phase-controlled rectifier 4.

[0071] Among them, the choke inductor 11 is an inductor element connected in series in the DC output circuit. In this system, the two choke inductors 11 are connected in series in the positive and negative branches of the DC output terminals of the phase-controlled rectifier 4, respectively. Inductance has the effect of suppressing current changes, smoothing the pulsating current of the rectifier output, and suppressing current ripple. In addition, the inductance value of each choke inductor is not greater than 1mH.

[0072] The DC filter capacitor 12 is a capacitor connected in parallel between the positive and negative terminals of the DC output. In this system, the DC filter capacitor 12 is connected in parallel between the positive and negative terminals of the DC output of the phase-controlled rectifier 4. Capacitors can store charge and absorb voltage fluctuations, thus filtering out high-frequency ripple in the DC voltage.

[0073] Specifically, at the DC output terminal of each stage of the phase-controlled rectifier 4, two choke inductors 11 are first connected in series, and then a DC filter capacitor 12 is connected in parallel after the choke inductors 11. The choke inductors 11 and the DC filter capacitor 12 together form an inductor-capacitor two-stage filter structure. When the phase-controlled rectifier 4 outputs a 24-pulse DC voltage, its pulsation frequency is 1200Hz, and the ripple amplitude is already low. When this pulsating DC current flows through the choke inductor 11, since the inductor current cannot change abruptly, the high-frequency ripple component in the current is suppressed by the inductor, making the current waveform smoother. The suppressed current charges the DC filter capacitor 12, and the voltage across the capacitor cannot change abruptly, further absorbing the voltage ripple. Because the ripple frequency is high and the capacitive reactance of the capacitor is very small, the bypass effect on the ripple voltage is significant. Therefore, even if a small capacitance value (such as ≤30mF) is used, extremely low voltage ripple can be obtained. The choke inductor 11, in conjunction with the DC filter capacitor 12, converts the pulsating DC output from the rectifier into a stable DC bus voltage, providing a high-quality DC input for the subsequent three-level inverter 5. Compared to a solution using only capacitor filtering, adding the choke inductor 11 reduces the peak charging current of the capacitor, avoiding the inrush current at the moment of closing the circuit breaker and extending the capacitor's lifespan.

[0074] Please refer to the following: Figure 3The schematic diagram of the three-level inverter shown is, in some embodiments, described as a neutral-point clamped three-level inverter 5. Each stage of the three-level inverter 5 includes four fully controlled devices 14, two clamping diodes 13, and a DC bus midpoint. One end of each clamping diode 13 is connected to the DC bus midpoint, and the other end is connected to the intermediate node of the corresponding bridge arm, so that the voltage stress borne by each fully controlled device 14 when it is turned off is half of the DC bus voltage.

[0075] Among them, the neutral point clamped three-level inverter is an inverter topology that limits the voltage stress of the switching devices to half of the bus voltage through clamping diodes, and the DC bus is provided with the neutral point potential by two series capacitors.

[0076] The fully controlled device 14 refers to a power switching element that can be controlled to turn on and off, such as an IGCT or IEGT. Each stage of the inverter contains four fully controlled devices 14, forming two bridge arms.

[0077] Clamping diode 13 refers to the diode that clamps the potential of the intermediate node of the bridge arm to the midpoint of the DC bus. Each stage of the inverter contains two.

[0078] The midpoint of a DC bus refers to the intermediate potential point between the positive and negative terminals of the DC bus, and its potential is half of the bus voltage.

[0079] Specifically, the four fully controlled devices 14 are divided into two upper bridge arms and two lower bridge arms. The series connection point of the upper and lower bridge arms is the AC output terminal of the inverter. When the two fully controlled devices in the upper bridge arm are turned on, the output terminal is connected to the positive terminal of the DC bus; when the two lower bridge arms are turned on, the output terminal is connected to the negative terminal of the DC bus; when only the lower tube of the upper bridge arm and the upper tube of the lower bridge arm are turned on, the output terminal is connected to the midpoint of the DC bus through the clamping diode 13, and the output is zero level. The two types of clamping diodes 13 are connected to the midpoint of the DC bus and the middle node of the upper and lower bridge arms, respectively. When the fully controlled device 14 is turned off, the diode limits the voltage across its two ends to half of the DC bus voltage (because the midpoint potential is half the bus voltage, the middle node of the bridge arm is clamped at the midpoint, and the other end of the turned-off device is connected to the positive or negative bus, the voltage difference is only half the voltage). This allows each fully controlled device 14 to only bear half the voltage stress of a traditional two-level inverter, so devices with lower withstand voltage ratings can be selected, reducing device cost and conduction losses. Meanwhile, with three output levels, the voltage change steps are reduced, the output AC waveform is closer to a sine wave, the harmonic content is low, and the DC ripple is small after subsequent boost rectification. Clamping diode 13 also avoids the risk of bridge arm shoot-through short circuits, improving system reliability. Low voltage stress reduces device switching losses, allowing for higher switching frequencies, which further reduces the size of the boost transformer 6 and passive filter components, increasing system power density.

[0080] In some embodiments, each stage of the rectifier and filter unit 7 includes a high-voltage uncontrolled rectifier 8, a filter resistor 9, and a filter capacitor 10; the input terminal of the high-voltage uncontrolled rectifier 8 is electrically connected to the output terminal of the step-up transformer 6; the filter resistor 9 and the filter capacitor 10 are connected in series and then in parallel to the DC output terminal of the high-voltage uncontrolled rectifier 8.

[0081] Among them, the high-voltage uncontrolled rectifier 8 is a full-bridge rectifier circuit composed of high-voltage silicon stacks. It does not require an external trigger signal and relies on the unidirectional conductivity of diodes to rectify high-voltage AC power into pulsating DC power.

[0082] The filter resistor 9 and the filter capacitor 10 are connected in series to limit the capacitor charging current and provide an energy discharge path.

[0083] Specifically, the high-voltage AC output from the step-up transformer 6 is connected to the high-voltage uncontrolled rectifier 8, and after full-bridge rectification, it outputs pulsating DC. A filter resistor 9 and a filter capacitor 10 are connected in series and then in parallel to the DC output terminal of the rectifier. When the rectifier output voltage rises, the filter capacitor 10 charges through the filter resistor 9; the resistor limits the peak charging current, preventing damage to the silicon stack or capacitor. When the output voltage drops or the load changes, the capacitor discharges slowly through the resistor, smoothing voltage fluctuations. The RC circuit constitutes a first-order low-pass filter, and the time constant τ = R × C determines the ripple suppression capability. Since the preceding stage has already obtained low-distortion AC through 24-pulse rectification and a three-level inverter, the rectified pulsating DC ripple frequency is high and the amplitude is low; therefore, only a small capacitor is needed to meet the filtering requirements. When arcing or short-circuiting occurs in the load, the filter resistor 9 limits the peak discharge current of the capacitor, preventing equipment damage and avoiding protection malfunctions. The series RC structure increases damping compared to a directly parallel capacitor, suppressing LC resonance and making the output more stable. After RC filtering, the DC high voltage ripple of each stage meets the requirements of the negative ion source accelerating electrode (e.g., <±3%), and the total high voltage ripple after each stage is connected in series also meets the standard, and the dual functions of filtering and safety protection are achieved at low cost.

[0084] In some implementations, the control system changes the DC bus voltage of each stage by adjusting the firing angle of the thyristors in each stage phase-controlled rectifier 4, and adjusts the duty cycle of each stage three-level inverter 5 to keep the duty cycle of that stage within a preset optimal range; the optimal range refers to the duty cycle range in which the level switching logic of the three-level inverter 5 is stable and the output waveform distortion rate is less than a preset threshold.

[0085] The firing angle is the electrical angle between the zero-crossing point and the point where the thyristor is triggered to conduct during an AC voltage cycle. The smaller the firing angle, the higher the rectifier output voltage; the larger the firing angle, the lower the output voltage.

[0086] The optimal duty cycle range is the range of duty cycles when the distortion rate of the output waveform of the three-level inverter is lower than a preset threshold (e.g., <5%). Within this range, the duration of the positive, zero, and negative levels is evenly distributed, and there will be no zero-crossing distortion or switching harmonic amplification.

[0087] Output waveform distortion rate is the degree of difference between the inverter output AC voltage waveform and the ideal sine wave, expressed as the ratio of the total effective value of harmonic content to the effective value of the fundamental wave.

[0088] Specifically, the control system independently performs two-stage adjustments for each stage: In the coarse adjustment stage, the target value of the DC bus voltage is determined based on the comparison between the output voltage reference value and the preset voltage threshold. The actual bus voltage follows the target value by adjusting the firing angle of the thyristors in the phase-controlled rectifier 4. Since the bus voltage of each stage is adjusted independently, a change in the firing angle of one stage will not affect other stages. The coarse adjustment sets the bus voltage to a reasonable range, so that the duty cycle required by the subsequent inverters automatically falls into the optimal range, avoiding waveform distortion caused by an excessively small or large duty cycle. In the fine adjustment stage, the control system further fine-tunes the duty cycle of the three-level inverter 5, keeping it always within the preset optimal range. The optimal range is determined through pre-testing: within this range, the level switching sequence of the four fully controlled devices is stable, and there will be no false triggering or bridge arm shoot-through; the waveform distortion rate of the output AC voltage is less than the threshold, the positive and negative half-waves are symmetrical, and the content of low-order harmonics (such as the 3rd and 5th harmonics) is low. By limiting the duty cycle to the optimal range, zero-crossing distortion caused by excessively long zero-level duration in non-optimal ranges and additional harmonics introduced by abnormal switching frequencies are avoided, making the inverter output waveform closer to a sine wave. After boost rectification, the low-distortion AC voltage significantly reduces DC ripple, not only meeting the voltage stability requirements of the neutral beam negative ion source but also reducing the burden on subsequent filter resistors 9 and 10, allowing for the use of smaller filter components. Simultaneously, because the duty cycle adjustment range is limited to the optimal range, the computational load of the control system is reduced, the response speed is improved, and it can track load changes more quickly.

[0089] In some embodiments, each step-up transformer 6 is an oil-immersed step-up transformer; the primary voltage of each step-up transformer 6 is adapted to the output voltage of the connected three-level inverter 5, and the secondary voltage of each step-up transformer 6 is adapted to the voltage required by the single-stage accelerating electrode of the neutral beam negative ion source.

[0090] Among them, oil-immersed step-up transformers refer to high-voltage transformers whose core and windings are immersed in insulating oil. They utilize the insulating and heat dissipation properties of oil and are suitable for high-voltage and large-capacity applications.

[0091] Primary voltage matching refers to matching the rated primary voltage of the step-up transformer 6 with the output voltage of the connected three-level inverter 5 (for example, the inverter outputs 3kV~7kV, and the primary side of the transformer is designed to be of the same voltage level) to ensure that the transformer is not saturated and the loss is minimized when the inverter is operating in the optimal duty cycle range.

[0092] Secondary voltage matching refers to the matching of the rated secondary voltage of the step-up transformer 6 with the DC high voltage (such as 200kV~250kV) required by the single-stage accelerating electrode of the neutral beam negative ion source. Considering the voltage drop after rectification and filtering, the effective value of the secondary AC voltage is about 0.9 times the DC target value.

[0093] Specifically, the medium- and low-voltage AC output from each three-level inverter 5 is connected to the primary side of the corresponding step-up transformer 6. The step-up transformer 6 employs an oil-immersed structure; the insulating oil provides high withstand voltage and good heat dissipation, enabling it to withstand secondary voltages of hundreds of kilovolts without breakdown or partial discharge. The primary voltage is matched to the inverter output voltage, ensuring that when the inverter operates within its optimal duty cycle range, the transformer core flux density is in the linear region, resulting in low excitation current and low no-load loss. The secondary voltage is matched to the voltage required for a single-stage accelerating electrode (e.g., 200kV), with a fixed turns ratio, eliminating the need for additional voltage taps and simplifying the transformer structure. The secondary windings of the multi-stage step-up transformers 6 are connected in series to achieve voltage superposition. Since each stage is independent, manufacturing errors or temperature rise in one stage will not affect other stages; the total voltage after series connection remains the sum of the voltages of each stage, eliminating the need for voltage equalization measures. Oil-immersed transformers also have the advantages of strong short-circuit withstand capability and large overload capacity, enabling them to withstand short-term overvoltages and overcurrents generated by frequent load arcing in nuclear fusion devices, thus extending system life. Their compact size facilitates the installation of five high-voltage transformers within a limited space, meeting the device layout requirements.

[0094] In some embodiments, a primary outdoor device 2 is also included, which is connected in series between the power grid supply terminal 1 and the primary winding of the phase-shifting transformer 3; the primary outdoor device 2 includes a vacuum circuit breaker and a soft starter cabinet; the vacuum circuit breaker is used to control the on / off of the power grid supply; the soft starter cabinet is connected in series with the vacuum circuit breaker and is used to suppress inrush current when the system is powered on.

[0095] Among them, primary outdoor equipment 2 refers to a collection of protection and control equipment installed outdoors and directly connected to the power grid, including vacuum circuit breakers and soft starter cabinets, used to realize the safe connection between the system and the power grid and start-up protection.

[0096] A vacuum circuit breaker is a switching device that uses vacuum as the arc-extinguishing medium. It can interrupt high voltage and high current in a very short time and is used to disconnect the electrical connection between the system and the power grid under normal or fault conditions.

[0097] A soft starter cabinet is a device that contains a current-limiting resistor or a thyristor voltage regulation circuit, which suppresses the inrush current at the moment of power-on by gradually increasing the output voltage.

[0098] Inrush current refers to the instantaneous peak current generated when inductive equipment such as transformers is powered on, which is several times the rated current due to the magnetic saturation of the iron core. It can reach 5 to 10 times the rated current.

[0099] Specifically, an outdoor device 2 is connected in series between the power grid supply terminal 1 and the primary winding of the phase-shifting transformer 3, wherein a vacuum circuit breaker is connected in series with a soft starter cabinet. When the system is powered on, the vacuum circuit breaker is closed first, but the current-limiting resistor in the soft starter cabinet is connected in series in the circuit to limit the inrush current to a safe range (e.g., within 1.2 times the rated current), preventing instantaneous large current from damaging the winding insulation of the phase-shifting transformer 3 and the thyristors in the subsequent rectifier. After the system voltage stabilizes, the current-limiting resistor is bypassed to complete the startup process. The current-limiting function of the soft starter cabinet extends the transformer's lifespan and prevents the inrush current from causing a voltage drop in the power grid, avoiding interference with other nuclear fusion devices on the same power grid. When the system detects overcurrent, overvoltage, or requires maintenance, the vacuum circuit breaker quickly trips, cutting off the power grid supply and protecting the phase-shifting transformer 3 and subsequent power devices from damage caused by the escalation of the fault. Because the vacuum circuit breaker has strong arc-extinguishing capability and fast breaking speed, it can isolate faults within milliseconds, making it suitable for the harsh operating conditions of frequent load arcing in nuclear fusion devices. The outdoor equipment 2 centralizes protection functions outdoors, facilitating maintenance and reducing insulation requirements for indoor equipment. Through the combination of a vacuum circuit breaker and a soft starter cabinet, it achieves triple functions of safe start / stop, fault isolation, and surge suppression, effectively improving system availability and safety.

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A neutral beam negative ion source ultra-high voltage power supply system, characterized in that, include: At least one phase-shifting transformer, wherein the primary winding of the phase-shifting transformer is used for electrical connection to the power supply terminal of the grid, and the secondary side of the phase-shifting transformer includes multiple windings, wherein the output voltages of the multiple secondary windings have a preset phase difference in sequence; A multi-stage phase-controlled rectifier, each stage of which contains multiple rectifier bridges. The AC input terminal of each rectifier bridge is electrically connected to a corresponding secondary winding. The DC output terminals of multiple rectifier bridges in the same stage are connected in series. Each stage of the phase-controlled rectifier outputs a multi-pulse DC voltage. A multi-stage filter circuit connected to the DC output terminal of the multi-stage phase-controlled rectifier; A multi-stage three-level inverter connected to the output terminal of the multi-stage filter circuit; A multi-stage step-up transformer connected to the AC output terminal of the multi-stage three-level inverter; The rectifier and filter unit is connected to the output terminal of the multi-stage step-up transformer. The DC output terminals of each rectifier and filter unit are connected in series to form the total high-voltage DC output terminal of the system. The control system is electrically connected to the control terminal of each stage phase-controlled rectifier and the control terminal of each stage three-level inverter, and is used to independently adjust the DC bus voltage of each stage phase-controlled rectifier and the duty cycle of each stage three-level inverter.

2. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, The at least one phase-shifting transformer includes a first phase-shifting transformer and a second phase-shifting transformer; The primary winding of the first phase-shifting transformer has a phase shift angle of +7.5°, and the primary winding of the second phase-shifting transformer has a phase shift angle of -7.5°. The secondary side of the first phase-shifting transformer includes a delta-connected winding and a star-connected winding, and the secondary side of the second phase-shifting transformer includes a delta-connected winding and a star-connected winding. The output voltages of the four secondary windings of the first phase-shifting transformer and the second phase-shifting transformer are sequentially 15° apart.

3. The neutral beam negative ion source ultra-high voltage power supply system according to claim 2, characterized in that, Each stage of the phase-controlled rectifier contains four rectifier bridges; the AC input terminals of the four rectifier bridges in each stage of the phase-controlled rectifier are electrically connected to the four secondary windings one by one. In each stage of the phase-controlled rectifier, the DC output terminals of the four rectifier bridges are connected in series, so that each stage of the phase-controlled rectifier outputs a 24-pulse DC voltage.

4. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, Each stage of the filter circuit includes a choke inductor and a DC filter capacitor; The choke inductor is connected in series with the positive and negative branches of the DC output terminal of the corresponding stage phase-controlled rectifier; the DC filter capacitor is connected in parallel between the positive and negative terminals of the DC output terminal of the corresponding stage phase-controlled rectifier.

5. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, The three-level inverter is a neutral-point clamped three-level inverter; Each stage of the three-level inverter includes four fully controlled devices, two clamping diodes, and a DC bus midpoint; One end of the clamping diode is connected to the midpoint of the DC bus, and the other end is connected to the middle node of the corresponding bridge arm, so that the voltage stress borne by each fully controlled device when it is turned off is half of the DC bus voltage.

6. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, Each stage of the rectifier and filter unit includes a high-voltage uncontrolled rectifier, a filter resistor, and a filter capacitor; the input terminal of the high-voltage uncontrolled rectifier is electrically connected to the output terminal of the step-up transformer; the filter resistor and the filter capacitor are connected in series and then in parallel to the DC output terminal of the high-voltage uncontrolled rectifier.

7. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, The control system changes the DC bus voltage of the current stage by adjusting the firing angle of the thyristors in the current stage phase-controlled rectifier, and adjusts the duty cycle of the current stage three-level inverter to keep the current stage duty cycle in the preset optimal range.

8. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, Each step-up transformer is an oil-immersed step-up transformer; the primary voltage of each step-up transformer is adapted to the output voltage of the connected three-level inverter, and the secondary voltage of each step-up transformer is adapted to the voltage required by the single-stage accelerating electrode of the neutral beam negative ion source.

9. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, It also includes primary outdoor equipment, which is connected in series between the power grid supply end and the primary winding of the phase-shifting transformer; the primary outdoor equipment includes a vacuum circuit breaker and a soft starter cabinet; the vacuum circuit breaker is used to control the on / off of the power grid supply; the soft starter cabinet is connected in series with the vacuum circuit breaker and is used to suppress inrush current when the system is powered on.

10. The neutral beam negative ion source ultra-high voltage power supply system according to claim 1, characterized in that, The multi-stage phase-controlled rectifier has five stages; the capacitance of each DC filter capacitor in the multi-stage filter circuit is no greater than 30mF, and the inductance of each choke inductor is no greater than 1mH.

Images