Method of pre-charging dc link capacitors in a bidirectional dc power supply having a three-phase input

Abstract

A power factor correction (PFC) input stage for pre-charging a DC link has a three-phase power input, rectifiers in a primary electrical path between the three-phase power and the DC link, controllable semiconductor devices configured as constant current sources between the rectifiers and the DC link, a controller, and a relay.

Description

[0001] Cross-reference with related applications This disclosure is a non-provisional content of, and claims to benefit from, U.S. Provisional Application No. 63 / 794972, filed April 25, 2025, entitled “Method for precharging a DC link capacitor in a bidirectional DC power supply with three-phase inputs,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to power supplies, and more particularly to precharging the DC link capacitor in a bidirectional DC power supply with three-phase input. Background Technology

[0003] A DC laboratory power supply typically consists of a line filter, a bidirectional power factor correction (PFC) input stage, a current-isolated DC transmission path, and an optional application-specific output stage. Figure 1 This is a diagram illustrating a power supply circuit with a three-phase power input 10, a line filter 12, a bidirectional PFC input stage 14, and a current-isolated DC transmission path 18. Some examples have further application-specific regulation stages 20.

[0004] The PFC stage 14 in this type of equipment includes a controlled three-phase full-wave bridge rectifier circuit (B6C) stage or a variant thereof, such as a neutral-point clamped (NPC) inverter or a T-type inverter. The term "B6" refers to a three-phase bridge rectifier, and may also refer to a B6C bridge, where "C" means "controlled." In this discussion, the term "B6C" will be used to cover both types. In some instances, other inverter topologies suitable for PFC applications are used. One component of the PFC stage is capacitor 16, also known as the DC link. Without proper pre-charging, turning on equipment with an uncharged DC link will generate a very high current from the grid, which could potentially trip an upstream circuit breaker or damage the equipment itself.

[0005] Figure 2 An example of a pre-charging method is shown, which involves an arrangement of resistors bypassed by relay 26, such as linear resistors, negative temperature coefficient thermistors (NTCs), or positive temperature coefficient thermistors (PTCs), such as PTC 24. This arrangement can be located on the AC side or on the DC side after auxiliary rectification or B6C bridge 14. Figure 1 and Figure 2The drawbacks of the methods and architectures shown are that the resistors used must be designed for the corresponding high peak power, resulting in a large structure size, or alternatively, a long pre-charge time. A known solution exists in the form of a switching regulator, but this is primarily suitable for high-power converters. For low-power versions, this solution is costly and requires relatively large installation space. Attached Figure Description

[0006] Figure 1 An example of a bidirectional power factor correction (PFC) input stage is shown.

[0007] Figure 2 An example of a bidirectional PFC input stage using relay bypass is shown.

[0008] Figure 3 An embodiment of a bidirectional PFC input stage using controllable elements is shown.

[0009] Figure 4 Another embodiment of a bidirectional PFC input stage using controllable elements is shown.

[0010] Figure 5 A flowchart illustrating an embodiment of a method for pre-charging a DC link capacitor is shown. Detailed Implementation

[0011] The embodiments disclosed herein relate to controllable devices, such as semiconductor switches or actuators in the DC section of a power factor correction (PFC) stage. The controllable semiconductor device may reside directly after the B6C stage or after a separate auxiliary rectification, both of which are described in more detail below. The controllable semiconductor device acts as a constant current source and is used during pre-charging. After the controller determines that pre-charging is complete, the controller uses a relay to bypass the controllable semiconductor device to avoid power loss during normal operation.

[0012] This disclosure relates to monitoring voltage in a PFC stage to determine the completion of the pre-charging process. This may involve measuring the DC link voltage as well as auxiliary voltages, such as the voltage preceding the pre-charging equipment, to detect the completion of the pre-charging process. The threshold for completion detection can be determined as a high percentage of the peak AC grid voltage.

[0013] Figure 3An embodiment of a PFC stage including a controllable semiconductor device is shown. The PFC stage receives a three-phase power input 10 and includes a line filter 12. In this embodiment, the controllable semiconductor device follows directly after the B6C rectifier 14. A controller 32 can monitor the charging current at measurement point 36 and / or the DC link voltage at measurement point 38. The controller may include analog circuitry, a microcontroller, a processor, a field-programmable gate array (FPGA), or other circuitry or devices that can receive inputs and perform actions based on the inputs being received by the controller. For example, the controller may receive voltage measurements from these points and calculate the percentage of the peak AC grid voltage, then compare it to a defined threshold and determine whether the process is complete. When the process is complete, the controller then triggers a relay 34 to bypass the controllable semiconductor device in the PFC stage.

[0014] exist Figure 3 In this embodiment, B6C stage 14 acts as a rectifier during pre-charging. When relay 34 is closed, the circuit behaves as follows: Figure 1 The circuitry in this configuration has a low component count. The main B6C stage is always connected to the grid, which can lead to a shortened lifespan. Relays in DC circuits are typically more expensive and may present some reliability issues.

[0015] exist Figure 4 In this embodiment, precharging is accomplished via auxiliary rectification. Diode 40 acts as the B6 rectifier during precharging. Once controller 32 has determined that precharging is complete, it causes relay 44 to close the path to include the AC portion of the PFC, which consists of line filter 12 and rectifier 14. This method and architecture result in the main B6C rectifier 14 being disconnected from the grid during precharging. The relay resides only in the AC portion of the path, mitigating some of the problems associated with DC relays. This architecture involves a higher component count, but is a more cost-effective solution. Furthermore, the system can measure the auxiliary voltage at 42 as an input to the controller.

[0016] In any embodiment, determining whether the pre-charging process has been completed may involve charging measurements at 36, 38, DC link measurements, and / or auxiliary voltage measurements, or a combination thereof. In one embodiment, the completion of the pre-charging process is determined using the DC link voltage measurement at 38 and the auxiliary voltage at 42.

[0017] In any embodiment, the rectifier is located in the electrical path between the three-phase power input and the DC link, such as Figure 3 The main electrical path shown, or as Figure 4The auxiliary rectifier path is shown. Depending on the architecture, activating the relay will bypass the controllable semiconductor and thus remove it from the electrical path that includes the main electrical path, or activating the relay will bypass the entire auxiliary rectifier path that includes the controllable semiconductor and remove it from the electrical path.

[0018] Figure 5 A flowchart illustrating an embodiment of the pre-charging process for the DC link is shown. At 50, rectification of the three-phase input is applied between the input and the DC link. At 52, the DC link is pre-charged using a controllable semiconductor device, and at 54, the voltage is monitored to determine the completion of the pre-charging. Once the pre-charging is complete, a relay is activated to bypass the controllable semiconductor device, thereby returning the system to normal operation.

[0019] Especially for DC links with rated voltages up to approximately 1000V DC, the embodiments disclosed herein offer cost-effectiveness compared to other solutions. The power electronics in this voltage range are designed for switching operation and therefore must be selected and sized very carefully. Possible options include metal-oxide-semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs) with appropriate power capabilities. Transient thermal behavior must be given special consideration when taking into account the necessary cooling.

[0020] The advantages of this disclosure also include smaller installation space, faster pre-charging with reduced inrush current, utilization of existing infrastructure (such as heat sinks, control units, etc.), automated manufacturability of components available in surface mount devices (SMDs), and reduced costs. As described above, Figure 4 The method described in the text has a higher component count, but is more cost-effective.

[0021] If a constant power supply is used instead of a constant current source for pre-charging at the input stage, the pre-charging time can be further reduced. This constant power is particularly convenient if the system has already digitized (making such an implementation easier) the measurement of the required quantity via digital signal processing. In such a system, the constant current source can be controllable, and the measured current and voltage quantities can be digitally recorded and processed. In some embodiments, the controller may include a digital signal processor for processing the digitized measurements. Control using a constant power supply allows for maximum utilization of the equipment used, which can operate close to its maximum power dissipation.

[0022] To achieve constant power supply pre-charging, it is necessary to measure the device's power consumption. This power consumption measurement can be accomplished, for example, by multiplying the pre-charging current by the difference between the DC link voltage and the auxiliary voltage. When pre-charging is complete, meaning the capacitor has been charged to the required level, the relay on the input side closes, and power flows through the B6C bridge, such as... Figure 4As shown, bridge B6C will leave the path until the relay closes.

[0023] Based on the PFC structure, it is recommended to perform synchronization on the input side before switching relays to prevent high current from flowing into the PFC filter capacitor during relay switching.

[0024] Various aspects of this disclosure can operate on specially created hardware, on firmware, on a digital signal processor, or on a specially programmed general-purpose computer including a processor that operates according to programmed instructions. The terms controller or processor used herein are intended to include microprocessors, microcomputers, application-specific integrated circuits (ASICs), and special-purpose hardware controllers. One or more aspects of this disclosure can be embodied in computer-usable data and computer-executable instructions, such as in one or more program modules executed by one or more computers (including monitoring modules) or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc., which perform specific tasks or implement specific abstract data types when executed by a processor in a computer or other device. Computer-executable instructions can be stored on a non-transitory computer-readable medium, such as a hard disk, optical disk, removable storage medium, solid-state memory, random access memory (RAM), etc. As those skilled in the art will understand, the functionality of a program module can be combined or distributed in various aspects as needed. Furthermore, functionality can be embodied, in whole or in part, in firmware or hardware equivalents, such as integrated circuits, FPGAs, etc. Specific data structures can be used to more efficiently implement one or more aspects of this disclosure, and such data structures are considered to be within the scope of the computer-executable instructions and computer-usable data described herein.

[0025] In some cases, the disclosed aspects may be implemented in hardware, firmware, software, or any combination thereof. The disclosed aspects may also be implemented as instructions carried on or stored on one or more non-transitory computer-readable media, which may be read and executed by one or more processors. Such instructions may be referred to as a computer program product. As discussed herein, a computer-readable medium means any medium accessible by a computing device. By way of example and not limitation, a computer-readable medium may include computer storage media and communication media.

[0026] Computer storage media refers to any medium that can be used to store computer-readable information. By way of example and not limitation, computer storage media may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital video disc (DVD) or other optical disc storage, cassette tape, magnetic tape, disk storage or other magnetic storage devices, and any other volatile or non-volatile, removable or non-removable media implemented in any technology. Computer storage media does not include the signal itself or the temporary form of signal transmission.

[0027] A communication medium is any medium that can be used for the communication of computer-readable information. By way of example and not limitation, a communication medium may include coaxial cable, fiber optic cable, air, or any other medium suitable for communication of electrical, optical, radio frequency (RF), infrared, acoustic, or other types of signals.

[0028] Example Illustrative examples of the disclosed technology are provided below. Embodiments of the technology may include one or more of the examples described below, as well as any combination thereof.

[0029] Example 1 is a power factor conversion (PFC) input stage for precharging a DC link, comprising: a three-phase power input; a rectifier located in the main electrical path between the three-phase power input and the DC link; a controllable semiconductor device configured as a constant current source between the rectifier and the DC link; a controller; and a repeater.

[0030] Example 2 is the PFC input stage of Example 1, wherein the semiconductor device is directly connected to the rectifier after the rectifier in the main electrical path, and the rectifier includes the main B6C rectifier.

[0031] Example 3 is the PFC input stage of Example 2, including one or more measurement points, which include measurement points adjacent to the semiconductor device, and the controller is configured to use measurements from the measurement points to determine the completion of the pre-charge process.

[0032] Example 4 is the PFC input stage of Example 2, wherein the controller is configured to activate a relay to bypass the controllable semiconductor device from the main electrical path when the pre-charging of the DC link is complete.

[0033] Example 5 is a PFC input stage of any of Examples 1 to 4, wherein a semiconductor device is connected to the rectifier in an auxiliary rectifier path that includes an electrical path parallel to the main electrical path.

[0034] Example 6 is the PFC input stage of Example 5, and also includes one or more measurement points, including one or more measurement points at the DC link voltage point and auxiliary measurement points between the three-phase power input and the semiconductor device. The controller is configured to use measurements from the DC link voltage point and the auxiliary measurement points to determine the completion of the pre-charge process.

[0035] Example 7 is the PFC input stage of Example 6, wherein the controller is configured to activate a relay to bypass the auxiliary rectification path when the precharge voltage is complete, so that the PFC input stage uses the primary electrical path.

[0036] Example 8 is a method for precharging a DC link in a power supply with a three-phase input, comprising: applying rectification in an electrical path between the three-phase input and the DC link to rectify the three-phase input; using a controllable semiconductor device as a constant current source to precharge the DC link after rectification in the electrical path; monitoring one or more voltages in the electrical path with a controller to determine when precharging has been completed; and activating a relay to bypass the controllable semiconductor device from the electrical path.

[0037] Example 9 is the method of Example 8, wherein applying rectification in the electrical path includes applying rectification in the main electrical path using the main B6C rectifier.

[0038] Example 10 is a method of Example 9, wherein activating a relay causes a controllable semiconductor device to be bypassed in the main electrical path.

[0039] Example 11 is a method of any one of Examples 8 to 10, wherein monitoring one or more voltages includes measuring voltages at one or more measurement points, including measurement points adjacent to a semiconductor device, and the controller is configured to use measurements from the measurement points to determine the completion of precharging.

[0040] Example 12 is a method of any one of Examples 8 to 11, wherein applying rectification includes applying rectification in an auxiliary rectification path, and the controllable semiconductor device resides in the auxiliary rectification path.

[0041] Example 13 is the method of Example 12, wherein activating the relay causes the bypass auxiliary rectifier path to be used in the main electrical path.

[0042] Example 14 is a power factor conversion (PFC) input stage for precharging a DC link, comprising: a three-phase power input; a rectifier located in the main electrical path between the three-phase power input and the DC link; a controllable semiconductor device configured as a constant power supply between the rectifier and the DC link; a controller; and a repeater.

[0043] Example 15 is the PFC input stage of Example 14, including one or more measurement points, including measurement points adjacent to the semiconductor device, and the controller is configured to use measurements from the measurement points to determine the completion of the pre-charge process.

[0044] Example 16 is the PFC input stage of Example 15, where the measurement is a digital measurement and the controller includes a digital signal processor.

[0045] Example 17 is the PFC input stage of Example 15, where the controller is configured to measure the power dissipated by the device.

[0046] Example 18 is the PFC input stage of Example 17, where the controller is configured to measure the power dissipated by the device by multiplying the precharge current by the difference between the DC link voltage and the auxiliary voltage.

[0047] Example 19 is the PFC input stage of Example 17, where the controller includes analog circuitry.

[0048] All features disclosed in the specification (including the claims, abstract, and drawings), and all steps in any disclosed method or process, may be combined in any combination, except that at least some of such features and / or steps are mutually exclusive combinations. Each feature disclosed in the specification (including the claims, abstract, and drawings) may be replaced by an alternative feature for the same, equivalent, or similar purpose, unless otherwise expressly stated.

[0049] Furthermore, this written description also refers to specific features. It should be understood that the disclosure in this specification includes all possible combinations of those specific features. For example, where a specific feature is disclosed in the context of a particular aspect, that feature may also be used, to the extent possible, in the context of other aspects.

[0050] Furthermore, when a method having two or more defined steps or operations is mentioned in this application, the defined steps or operations may be performed in any order or simultaneously, unless the context precludes such possibilities.

[0051] Although specific aspects of this disclosure have been described and illustrated for illustrative purposes, it will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Therefore, the invention should not be limited to any aspect other than the appended claims.

Claims

1. A power factor conversion (PFC) input stage for pre-charging a DC link, comprising: Three-phase power input; The rectifier is located in the main electrical path between the three-phase power input and the DC link; A controllable semiconductor device is configured as a constant current source between the rectifier and the DC link; Controller; and Repeater.

2. The PFC input stage of claim 1, wherein the semiconductor device is directly connected to the rectifier after the rectifier in the main electrical path, and the rectifier includes a main B6C rectifier.

3. The PFC input stage of claim 2, comprising one or more measurement points, the one or more measurement points including measurement points adjacent to the semiconductor device, and the controller being configured to use measurements from the measurement points to determine the completion of the pre-charge process.

4. The PFC input stage of claim 2, wherein the controller is configured to activate the relay when precharging of the DC link is complete to bypass the controllable semiconductor device from the main electrical path.

5. The PFC input stage of claim 1, wherein the semiconductor device is connected to the rectifier in an auxiliary rectification path, the auxiliary rectification path including an electrical path parallel to the main electrical path.

6. The PFC input stage of claim 5 further includes one or more measurement points, said one or more measurement points including a measurement point at the DC link voltage point and one or more auxiliary measurement points between the three-phase power input and the semiconductor device, the controller being configured to use measurements from said DC link voltage point and said auxiliary measurement points to determine the completion of the pre-charge process.

7. The PFC input stage of claim 6, wherein the controller is configured to activate the relay to bypass the auxiliary rectification path when the precharge voltage is completed, such that the PFC input stage uses the primary electrical path.

8. A method for pre-charging a DC link in a power supply with three-phase input, comprising: Rectification is applied in the electrical path between the three-phase input and the DC link to rectify the three-phase input; A controllable semiconductor device is used as a constant current source to precharge the DC link after rectification in the electrical path; The controller monitors one or more voltages in the electrical path to determine when pre-charging has been completed. and Activate the relay to bypass the controllable semiconductor device from the electrical path.

9. The method of claim 8, wherein applying rectification in the electrical path comprises applying rectification in the main electrical path using a main B6C rectifier.

10. The method of claim 9, wherein activating the relay causes the controllable semiconductor device to be bypassed in the main electrical path.

11. The method of claim 8, wherein monitoring one or more voltages includes measuring voltages at one or more measurement points, said measurement points including those adjacent to the semiconductor device, and the controller is configured to use measurements from said measurement points to determine the completion of the precharge.

12. The method of claim 8, wherein applying rectification includes applying rectification in an auxiliary rectification path, and the controllable semiconductor device resides in the auxiliary rectification path.

13. The method of claim 12, wherein activating the relay causes the auxiliary rectifier path to be bypassed to use the main electrical path.

14. A power factor conversion (PFC) input stage for pre-charging a DC link, comprising: Three-phase power input; The rectifier is located in the main electrical path between the three-phase power input and the DC link; A controllable semiconductor device is configured as a constant power source between the rectifier and the DC link; Controller; and Repeater.

15. The PFC input stage of claim 14, comprising one or more measurement points, the one or more measurement points including measurement points adjacent to the semiconductor device, and the controller being configured to use measurements from the measurement points to determine the completion of the pre-charge process.

16. The PFC input stage of claim 15, wherein the measurement is a digital measurement, and the controller includes a digital signal processor.

17. The PFC input stage of claim 15, wherein the controller is configured to measure the power dissipated by the semiconductor device.

18. The PFC input stage of claim 17, wherein the controller is configured to measure the power dissipated by the device by multiplying the pre-charge current by the difference between the DC link voltage and the auxiliary voltage.

19. The PFC input stage of claim 17, wherein the controller comprises analog circuitry.

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