Three-level inversion type high-voltage power supply device, system and application thereof

Abstract

The invention discloses a three-level inversion type high-voltage power supply device and system and application thereof, and relates to the technical field of high-voltage power supply. According to the high-voltage power supply scheme, the advantages of pulse step modulation and inversion technologies are combined, improvement is carried out on the basis of a three-level inversion power supply structure, and the improved level inversion power supply comprises a phase-shifting transformer, a three-phase rectification circuit, a three-level inversion circuit, a boosting transformer and an uncontrolled rectification circuit which are connected in sequence. And the uncontrolled rectifying circuits of the multi-level inverter power supply are connected in series to realize high-voltage output. According to the phase-shifting transformer, the multiple of pulse rectification is increased through phase shifting of the secondary winding, the ripple coefficient is reduced, the switching frequency of a controllable device in an inverter circuit is improved through the multi-level inverter power supply, the size of the boosting transformer and the size of a rear-end filter capacitor are reduced, energy release after load ignition is reduced, and the energy consumption is reduced. And low ripple output and low energy release are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage power supply, and particularly to a three-level inverter type high-voltage power supply device, system and its application. Background Art

[0002] In the field of nuclear fusion, the Tokamak device needs to rely on an efficient auxiliary heating system to achieve high-parameter plasma confinement. As one of the mainstream heating technologies, Ion Cyclotron Resonance Heating (ICRH) focuses on raising the plasma temperature to the fusion critical condition through high-frequency electromagnetic wave energy coupling. The engineering implementation of this technology requires a high-reliability and high-stability high-voltage power supply system, especially during the device commissioning stage, which needs to withstand extreme working conditions such as frequent arcing and shutdown.

[0003] In the prior art, high-voltage power supplies mainly adopt two topologies: Pulse Skip Modulation (PSM) and inverter type. The PSM technology is simple to control, but all the control components of the high-voltage power supply are at the high-voltage end, and it is easy to cause failures due to high electric fields; although the inverter type power supply places the control unit at the low-voltage end to improve reliability, the control is relatively complex. Specifically, the frequency of the current three-level inverter high-voltage power supply is generally in the range of several hundred hertz. Since the inverter frequency is not high, a relatively large output capacitance of the inverter power supply is required to meet the load's requirement for the ripple coefficient. However, after the load arcs and shuts down, the energy released by the filter capacitor needs to pass through the load. Therefore, choosing a larger filter capacitor will increase the energy released by the inverter power supply, facing the contradiction between ripple suppression and energy release.

[0004] In summary, the defects of the current three-level inverter high-voltage power supply seriously restrict the high-frequency and long-cycle operation requirements of the high-voltage power supply during the commissioning stage of the fusion device. For the power supply system of controllable nuclear fusion devices such as Tokamak, it is necessary to fully consider the energy release during load arcing and the requirement of the load for the ripple coefficient of the high-voltage power supply. Summary of the Invention

[0005] The present invention provides a three-level inverter type high-voltage power supply system and its application to solve the problems of effective ripple suppression and energy release existing in the current three-level inverter type high-voltage power supply architecture.

[0006] The present invention is achieved through the following technical solutions:

[0007] In the first aspect of the present invention, a three-level inverter type high-voltage power supply device is provided, including:

[0008] An AC incoming line unit cabinet for connecting to the AC power grid;

[0009] The three-level inverter power supply module includes a phase-shifting transformer, a three-phase rectifier circuit, a three-level inverter circuit, a step-up transformer, and an uncontrolled rectifier circuit that are connected in sequence;

[0010] There are multiple levels of the three-level inverter power supply module. The primary windings of the phase-shifting transformers of each level of the three-level inverter power supply module are connected to the three-phase output of the AC incoming unit cabinet, and the uncontrolled rectifier circuits of each level are connected in series;

[0011] The high-voltage output terminal of the series-connected uncontrolled rectifier circuit is used as the positive output terminal of the three-level inverter type high-voltage power supply device, and the low-voltage output terminal is used as the negative output terminal of the three-level inverter type high-voltage power supply device.

[0012] The present invention combines the advantages of pulse step modulation (PSM) and inverter technology. By separately controlling the outputs of multiple levels of three-level inverter power supplies and connecting them in series at the output, a high DC voltage output is achieved. Specifically, the phase-shifting transformer performs phase-shifting processing on the input AC voltage to provide multiple AC inputs with a certain phase difference for the subsequent three-phase rectifier circuit, effectively reducing the ripple coefficient. The three-phase rectifier circuit rectifies each phase of the three-phase AC voltage output by the phase-shifting transformer to output a relatively smooth DC voltage. The three-level inverter circuit inverses the DC voltage into a three-phase AC voltage. The output AC voltage has more levels, reducing the harmonic content of the output voltage, making the output AC waveform closer to a sine wave, while also reducing the voltage stress borne by the switching devices, reducing potential fault points, and improving the reliability and stability of the power supply system. The step-up transformer boosts the amplitude of the AC voltage to meet the high-voltage requirements in practical applications. The uncontrolled rectifier circuit rectifies the AC high voltage again to convert it into a DC high voltage, and the outputs of multiple levels of three-level inverter power supplies are connected in series to achieve high-voltage output. The output voltage of each level of inverter power supply is reduced, effectively reducing the control difficulty of the controllable devices in the inverter circuit, and the switching frequency of the controllable devices in the inverter circuit can be increased, thereby reducing the volume of the step-up transformer and the size of the backend filter capacitor, reducing the energy release after the load arcs, and thus achieving low-ripple output and low-energy release.

[0013] In addition, the use of a three-level inverter circuit in each level of inverter power supply reduces the harmonic content of the output voltage, making the output voltage waveform closer to a sine wave, and the level switching is relatively smoother, effectively reducing the harmonic distortion of the output voltage, reducing the generation of high-frequency voltage fluctuations, and thus reducing the electromagnetic interference to surrounding electronic devices. In the three-level inverter circuit, the voltage stress borne by each switching device is relatively low, reducing potential fault points and improving the reliability and stability of the power supply system.

[0014] As a preferred embodiment, a buffer circuit is further connected in series to the high-voltage output terminal, and the output terminal of the buffer circuit serves as the positive output terminal of the three-level inverter type high-voltage power supply device.

[0015] As a preferred embodiment, the buffer circuit is composed of a buffer inductor, a buffer resistor, and a high-voltage silicon stack.

[0016] As a preferred embodiment, the phase-shifting transformer and the boost transformer adopt dry-type transformers.

[0017] As a preferred embodiment, the three-phase rectifier circuit is a single-stage three-phase rectifier circuit, and the single-stage three-phase rectifier circuit includes three rectifier bridge arms connected in parallel and a first filter capacitor;

[0018] The middle points of the three rectifier bridge arms are respectively connected to the three-phase AC outputs of the secondary winding of the phase-shifting transformer;

[0019] The first filter capacitor includes a first capacitor and a second capacitor connected in series, and the middle point of the first capacitor and the second capacitor is connected to the middle point of the three-level inverter circuit through a neutral point connection line.

[0020] As a preferred embodiment, the three-phase rectifier circuit is a two-stage three-phase rectifier circuit, and the two-stage three-phase rectifier circuit includes two groups of rectifier bridges and a second filter capacitor; wherein, the two groups of rectifier bridges are connected in series and then connected in parallel with the filter capacitor, and each group of rectifier bridges includes three rectifier bridge arms;

[0021] The secondary winding of the phase-shifting transformer has two groups of coils, and the two groups of coils are respectively connected to the two groups of rectifier bridges correspondingly;

[0022] The second filter capacitor includes a third capacitor and a fourth capacitor connected in series, and the middle point of the third capacitor and the fourth capacitor is connected to the series connection point of the two groups of rectifier bridges through a midpoint balance ability connection line, and the middle point of the third capacitor and the fourth capacitor is also connected to the middle point of the three-level inverter circuit through a neutral point connection line.

[0023] As a preferred embodiment, the switching device on the rectifier bridge arm adopts an IGBT switching tube.

[0024] As a preferred embodiment, the AC incoming line unit cabinet includes a vacuum switch, a soft start resistor, and a soft start switch; the vacuum switch is connected in series at the incoming line end of the three-phase wire, and the soft start resistor and the soft start switch are connected in series and then connected in parallel at both ends of the vacuum switch.

[0025] In the second aspect of the present invention, a three-level inverter type high-voltage power supply system is provided, which includes the three-level inverter type high-voltage power supply device according to any one of the first aspects of the present invention and a pulse step modulation control system.

[0026] The third aspect of the present invention provides an application of a three-level inverter type high-voltage power supply system, including being applied to a controllable nuclear fusion device.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] Combining the advantages of pulse step modulation (PSM) and inverter technology, by separately controlling the outputs of multiple three-level inverter power supplies, a DC high voltage output is achieved in series at the output. By phase-shifting, the multiple of pulse rectification is increased, the ripple coefficient is reduced, and since the output voltage of each inverter power supply is reduced, the switching frequency of the controllable devices in the inverter circuit is effectively increased, the volume of the step-up transformer and the size of the backend filter capacitor are reduced, so that the energy release after the load arcs is reduced, thereby achieving low-ripple output and low-energy release;

[0029] Utilizing the combination of pulse step modulation technology and inverter technology, on the basis of the existing process, the highest frequency of the step-up transformer and the operating frequency of the three levels are increased, effectively reducing the output filter parameters and reducing the energy release after the load arcs;

[0030] A phase-shifting transformer is added in front of the rectifier circuit. Through different winding connection methods and phase-shifting angles, multi-pulse rectification is conveniently achieved, the efficiency of the overall power supply is improved and harmonics are reduced, and the influence of voltage fluctuations on the three-level inverter type high-voltage power supply can be reduced, improving the stability and reliability of the system;

[0031] The DC voltage is inverted into a three-phase AC voltage through a three-level inverter circuit. The output AC voltage has more levels, reducing the harmonic content of the output voltage, making the output AC waveform closer to a sine wave, and at the same time reducing the voltage stress borne by the switching devices, reducing potential fault points, and improving the reliability and stability of the power supply system;

[0032] In the three-level control circuit, the number of windings of the phase-shifting transformer is doubled. Through topological balance, there is no need for capacitor midpoint balance control. This greatly simplifies the control algorithm and the complexity of the control system, reduces the requirements for the performance of the controller, makes the control of the system more concise, efficient, easy to implement and debug. It reduces the risk of system failure caused by faults in the midpoint balance control circuit or algorithm, improves the reliability and stability of the entire system. It improves the dynamic response speed of the system, can more quickly track load changes and input voltage fluctuations, and ensures the stability and accuracy of the system output;

[0033] The transformer equipment adopts a dry epoxy casting process, which can make the transformer have the characteristics of maintenance-free, moisture-proof, and anti-humid heat, reducing the workload and cost of daily maintenance. And the uncontrolled rectifier circuit at the backend of the step-up transformer does not need to be immersed in insulating oil, and maintenance and rectification are more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on these drawings. In the drawings:

[0035] Figure 1 is a schematic diagram of the main circuit of a three-level inverter type high voltage power supply according to an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of a single-stage three-phase rectifier circuit without midpoint balancing ability according to an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of a two-stage three-phase rectifier circuit with midpoint balancing ability according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments and the 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.

[0039] It should be noted that the terms "including" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily limit to or the other steps or units inherent in the device.

[0040] The terms used in the various embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as those defined in a general dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or being overly formal unless clearly defined in the various embodiments of the present invention.

[0041] Embodiments of the present invention provide a three-level inverter-type high-voltage power supply device, system and its application. The power supply device and system are suitable for supplying power to high-power high-voltage load systems, especially for controlled nuclear fusion devices, and are beneficial to providing high-quality electric energy with low ripple and low released energy.

[0042] See Figure 1 As shown, the three-level inverter-type high-voltage power supply device of the present invention is based on a three-level inverter architecture and mainly consists of an AC input unit cabinet 1 and a multi-stage three-level inverter power module. The three-level inverter power module includes a phase-shifting transformer 2, a three-phase rectifier circuit 3, a three-phase inverter circuit 4, a step-up transformer 5 and an uncontrolled rectifier circuit 6 connected in sequence. Figure 1 Shown is an eight-level inverter-type power supply topology structure, and the DC outputs of the inverter-type power supplies are connected in series to achieve the output of DC high voltage, and a 30 kV high-voltage power supply can be provided.

[0043] The AC input unit cabinet 1 is mainly used to connect an external AC power supply and the three-level inverter power module. The input end of the AC input unit cabinet 1 is connected to the upper-level power station, and the output end is connected to the primary side of the phase-shifting transformer 2, playing a role of transmitting electric energy from top to bottom, and providing the energy required for conversion and output for the inverter-type high-voltage power supply. The AC input unit cabinet 1 can also preliminarily monitor parameters such as the input AC current and voltage, and can provide certain overcurrent, overvoltage and other protection functions to prevent damage to subsequent equipment caused by abnormal external AC input.

[0044] The main function of the phase-shifting transformer 2 is to perform phase-shifting processing on the input AC voltage and provide multiple AC inputs with a certain phase difference for the subsequent three-phase rectifier circuit 3. The primary winding of the phase-shifting transformer 2 is connected to the three-phase power output of the AC input unit cabinet 1, and the secondary winding is connected to the input end of the three-phase rectifier circuit 3. The phase-shifting transformer 2 can change the phase of the input AC voltage through phase-shifting, so as to achieve a specific phase difference between multiple output voltages, effectively reduce the harmonic content of the input AC current, improve the power factor of the power supply, and optimize the power quality of the entire system.

[0045] The function of the three-phase rectifier circuit 3 is to convert the AC voltage output by the phase-shifting transformer 2 into a DC voltage. It utilizes the unidirectional conductivity of rectifier devices such as thyristors to rectify each phase of the input three-phase AC voltage. By controlling the switching devices in the rectifier circuit, the input DC voltage of the three-level inverter circuit is reduced, and preliminary output voltage control is performed.

[0046] The three-phase rectifier circuit 3 preferably adopts a bridge rectifier circuit. For a three-phase bridge rectifier circuit, it can rectify the positive and negative half-cycles of the three-phase AC voltage respectively, and output a relatively smooth DC voltage, which provides a DC power input for the subsequent three-level inverter circuit 4. Compared with a single-phase rectifier circuit, the three-phase bridge rectifier circuit has a higher utilization efficiency of the power grid and can improve the power factor.

[0047] The main function of the three-level inverter circuit 4 is to convert the DC voltage output by the three-phase rectifier circuit 3 into an AC voltage. It controls the on and off of the power switch devices in the circuit and inverts the DC voltage into a three-phase AC voltage according to a certain rule. The three-level inverter circuit has three levels, namely the positive level, the zero level and the negative level. Compared with the traditional two-level inverter circuit, the AC voltage it outputs has more levels. This multi-level structure makes the waveform of the output voltage closer to a sine wave. The level switching of the three-level inverter circuit is relatively smoother, which can effectively reduce the harmonic distortion of the output voltage. In high-voltage and high-power application scenarios, through a special circuit topology, each switching device in the three-level inverter circuit only needs to bear about half of the DC bus voltage, reducing the voltage stress on the switching devices, reducing potential failure points, and improving the reliability and stability of the power supply system.

[0048] The step-up transformer 5 is used to increase the amplitude of the AC voltage output by the three-phase inverter circuit. According to the principle of electromagnetic induction, it realizes the voltage increase through the turns ratio of the primary winding and the secondary winding, and raises the inverted AC voltage to the required high-voltage level to meet the high-voltage requirements in practical applications. At the same time, the step-up transformer 5 can isolate the electrical circuits on the input side and the output side, separating the commercial power from the high-voltage part of the equipment to prevent patients and operators from contacting dangerous voltages.

[0049] Preferably, the step-up transformer 5 adopts high-isolation epoxy casting to achieve the potential isolation between the DC high-voltage power supply and the inverter circuit, ensuring that the controllable devices are in a relatively low voltage range to avoid damage. Compared with an oil-immersed transformer, the epoxy-cast step-up transformer does not require regular inspection of the oil level, detection of the oil quality and oil change and other maintenance work, greatly reducing the maintenance cost and workload. The epoxy-cast insulation system has a long service life and stable performance. Under normal operating conditions, only regular visual inspections and simple electrical tests are required, improving the operating reliability and economy of the transformer.

[0050] The uncontrolled rectifier circuit 6 is used to rectify the AC high voltage output by the step-up transformer 5 again. It uses uncontrollable rectifier devices such as diodes to convert the AC high voltage into a DC high voltage.

[0051] The present invention combines the advantages of pulse step modulation (PSM) and inverter technology, controls the output of multi-stage three-level inverter power supply modules respectively, and connects the outputs of each stage in series, that is, the uncontrollable rectifiers at the ends of each stage of power supply modules are connected in series in turn to form a high-voltage DC output. Therefore, the output voltage of each inverter-type power supply is reduced, which can effectively reduce the manufacturing difficulty of the dry-type step-up transformer, reduce the control difficulty of the controllable devices in the inverter circuit, and can increase the switching frequency of the controllable devices in the inverter circuit, thereby reducing the volume of the step-up transformer and the size of the backend filter capacitor, and reducing the energy release after the load sparks. In addition, a three-level inverter circuit is adopted in each stage of power supply module, reducing high-order harmonics and the generation of high-frequency voltage fluctuations, thereby reducing the electromagnetic interference to surrounding electronic devices, and at the same time reducing the sensitivity of itself to external electromagnetic interference.

[0052] The high-voltage DC output after series connection can be used as the final high-voltage power supply output, that is, the high-voltage output terminal of the uncontrollable rectifier circuit after series connection ( Figure 1 the high-voltage output terminal of the uppermost uncontrollable rectifier circuit 6 in Figure 1 is used as the positive output terminal of the three-level inverter-type high-voltage power supply device, and the low-voltage output terminal of the uncontrollable rectifier circuit after series connection (that is,

[0053] the low-voltage output terminal of the lowermost uncontrollable rectifier circuit 6 in Figure 1 is used as the negative output terminal of the three-level inverter-type high-voltage power supply device, and the negative output terminal is grounded. Figure 1 the low-voltage output terminal of the lowermost uncontrollable rectifier circuit 6 in

[0054] The buffer circuit plays a role in further converting the voltage form and can protect the power switch devices in the system. In parts such as the three-phase inverter circuit, high current spikes will be generated during the on and off processes of the power switch devices. The buffer circuit can absorb these spike energies, suppress overcurrent, and during the load sparking process, can also suppress the rising rate of the current during the sparking process, thereby providing a longer buffer time for power supply protection.

[0055] In this embodiment, the buffer circuit is composed of a buffer inductor, a buffer resistor and a high-voltage silicon stack to ensure reducing the rising rate of the current when the load sparks.

[0056] In a preferred embodiment, the AC input unit cabinet 1 is further provided with a vacuum switch 12, a soft start switch 13 and a soft start resistor 14. There are three vacuum switches 12, which are respectively connected in series at the incoming line ends of the three-phase wires. The soft start switch 13 and the soft start resistor 14 are connected in series and are connected in parallel at both ends of the vacuum switch 12.

[0057] When it is necessary to input the AC power supply into the high-voltage power supply, first close the soft start switch 13, input through soft start current limiting, and then close the vacuum switch 12 after a certain time, so as to delay the power supply of the AC power supply to the high-voltage power supply. Since the latter stage of the AC input unit cabinet 1 is a transformer, therefore, in the initial startup process, the startup current is limited by the soft start switch and the soft start resistor, reducing the impact on the power grid. At the same time, the AC input unit cabinet is equipped with overvoltage and overcurrent protection devices, providing a certain guarantee for the safe operation of the high-voltage power supply system.

[0058] In a preferred embodiment, both the phase-shifting transformer 2 and the step-up transformer 5 adopt dry-type transformers, making the high-voltage power supply suitable for use in laboratories and avoiding the potential safety hazards brought by transformer oil during use.

[0059] The all-dry phase-shifting transformer can, through a clever phase-shifting design, cancel or weaken the harmonics generated by each phase winding of the transformer, reduce the harmonic current injected into the power grid, and protect other sensitive devices from harmonic interference. The phase-shifting transformer also reduces the grid voltage to the voltage level required by the three-level inverter circuit.

[0060] At the same time, the setting of the three-level inverter power module also effectively reduces the manufacturing difficulty of the dry-type step-up transformer and the control difficulty of the controllable devices. Adopting the dry-type epoxy casting process, the transformer has the characteristics of maintenance-free, moisture-proof, and anti-humid heat, reducing the workload and cost of daily maintenance, and the uncontrolled rectifier circuit at the back end of the step-up transformer does not need to be immersed in insulating oil, making maintenance and rectification more convenient.

[0061] In one embodiment, a single-stage three-phase rectifier circuit is used as the three-phase rectifier circuit 3, and the output filter capacitor is adjusted through midpoint balance control. The structure is simple and the device cost is low. The structure is shown in Figure 2 as shown. The single-stage three-phase rectifier circuit includes three rectifier bridge arms connected in parallel and a filter capacitor. The three rectifier bridge arms are composed of controllable switch devices connected in series by an upper arm and a lower arm, and preferably IGBT switch tubes are used. In this embodiment, only one set of coils is required for a secondary winding of the phase-shifting transformer 2, and the output AC voltage is connected to the single-stage three-phase rectifier circuit, that is, the midpoints of the three rectifier bridge arms are respectively connected to the three-phase AC output of the secondary winding of the phase-shifting transformer 2. The filter capacitor includes a first capacitor 8 and a second capacitor 9 connected in series, and the midpoint of the first capacitor 8 and the second capacitor 9 is connected to the midpoint of the three-level inverter circuit 4 through a neutral point connection line 10.

[0062] For a level inverter without self-balancing ability, a large amount of calculations and complex control algorithms are executed for the capacitor midpoint balancing control strategy, which undoubtedly increases the design difficulty and cost of the control system. In view of this, the present invention preferably adopts a two-stage three-phase rectifier circuit with midpoint balancing ability as the three-phase rectifier circuit 3, see Figure 3 as shown. This structure does not require additional midpoint balancing control, greatly simplifies the complexity of the control algorithm and the control system, reduces the requirements for the performance of the controller, makes the control of the system more concise, efficient, easy to implement and debug.

[0063] The two-stage three-phase rectifier circuit includes two groups of rectifier bridges and filter capacitors. Each group of rectifier bridges has the same structure and includes three rectifier bridge arms. The rectifier bridge arms are composed of controllable switch devices connected in series by an upper arm and a lower arm, and IGBT switch tubes are preferably used. Among them, the two groups of rectifier bridges are connected in series and then connected in parallel with the filter capacitors to form a two-stage three-phase rectifier circuit.

[0064] In this scheme, an additional set of coils is added to the secondary winding of the phase-shifting transformer. The two groups of coils are respectively connected to the two groups of rectifier bridges. The connection method is that the three-phase AC outputs of one group of coils are respectively connected to the midpoints of the three rectifier bridge arms of the rectifier bridge located at the upper end, and the three-phase AC outputs of the other group of coils are respectively connected to the midpoints of the three rectifier bridge arms of the rectifier bridge located at the lower end.

[0065] The filter capacitor of the two-stage three-phase rectifier circuit includes a third capacitor 8' and a fourth capacitor 9' connected in series. The midpoint of the third capacitor 8' and the fourth capacitor 9' is connected to the series connection point of the two groups of rectifier bridges through the midpoint balancing ability connection line 11. The midpoint of the third capacitor 8' and the fourth capacitor 9' is also connected to the midpoint of the three-level inverter circuit 4 through the neutral point connection line 10, realizing a circuit with midpoint balancing ability.

[0066] Since the midpoint balancing control link is omitted, the risk of system failure caused by midpoint balancing control circuit or algorithm failure is reduced. At the same time, the relevant control components and circuits are reduced, the hardware complexity of the system is reduced, thereby reducing potential failure points, improving the reliability and stability of the entire system, and reducing the maintenance cost and downtime of the system. And, the control system can use more resources and time for the rapid adjustment and control of key parameters such as output voltage and current, thereby improving the dynamic response speed of the system, being able to track load changes and input voltage fluctuations more quickly, and ensuring the stability and accuracy of the system output.

[0067] At the same time, if it is necessary to test the midpoint balancing scheme, as long as the midpoint balancing ability connection line 11 of the two-stage three-phase rectifier circuit is disconnected, it can be equivalent to a level inverter without midpoint self-balancing ability.

[0068] In a second aspect of the present invention, there is provided a three-level inverter type high-voltage power supply system, which includes a three-level inverter type high-voltage power supply device according to any implementation manner of the first aspect, and a control system for controlling the three-level inverter type high-voltage power supply device. In this embodiment, a pulse step modulation control system is preferably used to control each controllable device of the three-level inverter power supply.

[0069] In a third aspect of the present invention, there is provided an application of the three-level inverter type high-voltage power supply device of the first aspect and the three-level inverter type high-voltage system of the second aspect, preferably applied to a controllable nuclear fusion device, and more preferably applied to a tokamak device.

[0070] The specific implementation manners described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-level inverter high voltage power supply device, characterized in that: include: AC incoming line unit cabinet (1), used for connecting to the AC power grid; A three-level inverter power supply module comprises a phase-shifting transformer (2), a three-phase rectifier circuit (3), a three-level inverter circuit (4), a boost transformer (5) and an uncontrolled rectifier circuit (6) which are connected in sequence; The three-level inverter power module has multiple stages, the primary winding of the phase-shifting transformer (2) of each stage of the three-level inverter power module is connected to the three-phase output of the AC incoming line unit cabinet (1), and the uncontrolled rectifier circuit (6) of each stage of the three-level inverter power module is connected in series; The high voltage output end of the series-connected uncontrolled rectifier circuit (6) serves as the positive output end of the three-level inverter high voltage power supply device, and the low voltage output end serves as the negative output end of the three-level inverter high voltage power supply device.

2. The three-level inverter high-voltage power supply device according to claim 1, characterized in that: The high-voltage output end is also connected in series with a buffer circuit (7), and the output end of the buffer circuit (7) serves as the positive output end of the three-level inverter-type high-voltage power supply device.

3. The three-level inverter high-voltage power supply device according to claim 2, characterized in that: The buffer circuit is composed of a buffer inductor, a buffer resistor and a high-voltage silicon stack.

4. The three-level inverter high-voltage power supply device according to claim 1, characterized in that: The phase-shifting transformer (2) and the step-up transformer (5) are dry-type transformers.

5. The three-level inverter high-voltage power supply device according to claim 1, characterized in that: The three-phase rectifier circuit (3) is a single-stage three-phase rectifier circuit, and the single-stage three-phase rectifier circuit comprises three rectifier bridge arms connected in parallel and a first filter capacitor; The middle points of the three rectifier bridge arms are respectively connected to the three-phase AC output of the secondary winding of the phase-shifting transformer (2); The first filter capacitor comprises a first capacitor (8) and a second capacitor (9) connected in series, and a midpoint between the first capacitor (8) and the second capacitor (9) is connected to a midpoint of the three-level inverter circuit (4) via a neutral point connection line (10).

6. The three-level inverter high-voltage power supply device according to claim 1, characterized in that: The three-phase rectifier circuit (3) is a two-stage three-phase rectifier circuit, and the two-stage three-phase rectifier circuit comprises two groups of rectifier bridges and a second filter capacitor; wherein the two groups of rectifier bridges are connected in series and then in parallel with the filter capacitor, and each group of rectifier bridges comprises three rectifier bridge arms; The secondary winding of the phase-shifting transformer (2) has two groups of coils, and the two groups of coils are respectively connected to the two groups of rectifier bridges; The second filter capacitor comprises a third capacitor (8') and a fourth capacitor (9') connected in series, wherein the middle point of the third capacitor (8') and the fourth capacitor (9') is connected to the series connection of the two groups of rectifier bridges via a midpoint balancing capability connection line (11), and the middle point of the third capacitor (8') and the fourth capacitor (9') is also connected to the middle point of the three-level inverter circuit (4) via a neutral point connection line (10).

7. The three-level inverter high-voltage power supply device according to claim 5 or 6, characterized in that: The switch device on the rectifier bridge arm adopts an IGBT switch tube.

8. The three-level inverter high-voltage power supply device according to claim 1, characterized in that: The AC incoming line unit cabinet (1) comprises a vacuum switch (12), a soft-start resistor (14) and a soft-start switch (13); the vacuum switch (12) is connected in series to the incoming line end of the three-phase electric wire, and the soft-start resistor (14) and the soft-start switch (13) are connected in series and then connected in parallel to the two ends of the vacuum switch (12).

9. A three-level inverter high voltage power supply system, characterized in that: It comprises the three-level inverter high-voltage power supply device and pulse step modulation control system as described in any one of claims 1 to 8.

10. An application of the three-level inverter high voltage power supply system as claimed in claim 9, characterized in that: Including applications in controlled nuclear fusion devices.

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