Three-phase rectification system, control method thereof and intelligent equipment

Abstract

The invention discloses a three-phase rectification system, a control method thereof and intelligent equipment. The three-phase rectification system comprises a rectification module and a bus capacitor connected with the rectification module. The rectifier module is provided with three bridge arms formed by two switching devices connected in series, and each phase of the alternating current power supply is connected to the midpoint of the corresponding bridge arm; the rectification module also comprises a switch unit which is connected with each switch device in parallel; the switching unit is respectively connected with one switching device and the corresponding switching unit; the switching units are used for switching and conducting the switching devices or the corresponding switching units. The switchable switch unit and the switchable unit are introduced into a traditional three-phase rectifier bridge, a rectification system architecture which is uncontrollable during normal power supply and is half-controllable or fully-controllable during phase loss or imbalance is achieved, topology reconstruction of the rectifier bridge is achieved through the switchable unit, and on the premise that the system cost and complexity are not remarkably increased, the system reliability is improved. And the fault-tolerant capability of phase loss or imbalance is also realized.

Description

Technical Field

[0001] This invention relates to the field of power substation technology, and in particular to a three-phase rectifier system, its control method, and intelligent equipment. Background Technology

[0002] In the current field of power electronics technology, three-phase diode uncontrolled rectifier circuits are widely used in small and medium power industrial equipment, such as industrial frequency converters, welding machines, servo drives, photovoltaic inverters, and electric vehicle charging piles, due to their advantages of simple structure, low cost, and maintenance-free operation. However, this type of rectifier system has serious performance defects when a phase loss fault occurs in the three-phase input (i.e., one phase is de-energized), specifically manifested as follows:

[0003] ① Significant bus voltage drop: After a phase loss, the average output voltage of the three-phase bridge rectifier drops by more than 30%, causing the downstream inverter to shut down due to undervoltage protection; ② Increased output voltage ripple: The rectifier output waveform exhibits periodic zero-voltage intervals, and the voltage ripple increases significantly, affecting the stability of load operation; ③ Poor system fault tolerance: Minor grid anomalies (such as loose lines or blown fuses) can cause system interruptions, affecting continuous industrial production.

[0004] To address the above issues, existing technologies have proposed several solutions, mainly including: ① Increasing the bus capacitance: This can only alleviate short-term fluctuations and cannot fundamentally solve the voltage drop problem; it is also bulky and costly. ② Using full IGBT PWM rectification: Although it can achieve active regulation and energy feedback, the IGBTs are always working, resulting in high switching and conduction losses and a 2%~3% reduction in system efficiency. This is considered "over-design" under light load or normal operating conditions. ③ Configuring a UPS or automatic switching power supply: This is costly and bulky, and not suitable for most industrial sites. ④ Bypass boost circuits (such as Boost and CUK): These have complex structures, are difficult to control, and are only suitable for specific power levels.

[0005] Therefore, how to provide a three-phase rectifier system that has fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity is an urgent technical problem to be solved. Summary of the Invention

[0006] This invention provides a three-phase rectifier system, its control method, and intelligent devices to solve the problems of high cost, complex structure, and lack of fault tolerance for phase loss or imbalance in existing three-phase rectifier systems.

[0007] The technical solution of this invention is a three-phase rectification system, including a rectification module and a bus capacitor connected to the rectification module; the rectification module has three bridge arms composed of two series-connected switching devices, and each phase of the AC power supply is connected to the midpoint of the corresponding bridge arm; the rectification module further includes:

[0008] A switching unit, which is connected in parallel with each of the aforementioned switching devices;

[0009] A switching unit is connected to one of the switching devices and its corresponding switching unit; the switching unit is used to switch and turn on the switching device or the corresponding switching unit.

[0010] Furthermore, each of the switching units includes an insulated-gate bipolar transistor (IGBT), the emitter of the IGBT and the input terminal of the corresponding switching device are both connected to one of the switching units, the collector of the IGBT is connected to the output terminal of the corresponding switching device, and the gate of the IGBT is used to connect to a controller.

[0011] Furthermore, each of the aforementioned switching units includes a single-pole double-throw relay and a transistor;

[0012] The collector of the transistor is connected to the first coil pin of the single-pole double-throw relay to control the on / off state of the coil inside the single-pole double-throw relay; the emitter of the transistor is grounded, and the base of the transistor is used to connect to the controller.

[0013] The second coil pin of the single-pole double-throw relay is used to connect to the power supply pin VCC. The common terminal of the single-pole double-throw relay is connected to the corresponding bridge arm. The normally closed contact of the single-pole double-throw relay is connected to the input terminal of the corresponding switching device. The normally open contact of the single-pole double-throw relay is connected to the emitter of the corresponding insulated-gate bipolar transistor.

[0014] The present invention also proposes a control method for a three-phase rectifier system as described above, the control method comprising:

[0015] Determine whether the three phases of the AC power supply are missing or unbalanced;

[0016] If so, the switching unit first disconnects the switching device and then turns on the corresponding switching unit to maintain the stability of the bus voltage of the bus capacitor and control the load unit corresponding to the three-phase rectifier system to reduce its operating frequency.

[0017] Furthermore, the control method includes:

[0018] The bus voltage of the bus capacitor, the three-phase voltage and three-phase current of the AC power supply are collected;

[0019] Determine whether the fault conditions are met;

[0020] If so, the three-phase rectifier system is in a state of phase loss or imbalance;

[0021] If not, the three-phase rectifier system is operating normally;

[0022] The fault conditions are as follows:

[0023] The bus voltage amplitude drops below a first predetermined threshold, or the voltage amplitude of any phase drops below a second predetermined threshold, or the current of any phase is zero, and this continues for a first predetermined time.

[0024] Furthermore, according to the switching unit first disconnecting the switching device and then turning on the corresponding switching unit, the control method includes:

[0025] Determine whether the voltage amplitude drop of any phase is lower than a third predetermined threshold.

[0026] If so, the switching unit first disconnects the switching unit and then turns on the switching device;

[0027] If not, the switching device remains on.

[0028] Furthermore, the control method includes:

[0029] After the switching unit disconnects the switching unit or the switching device, it must delay for a second predetermined time before performing the corresponding conduction action.

[0030] Further, based on the corresponding switching unit being turned on, the control method includes:

[0031] The switching unit is controlled to perform pulse width modulation chopping within the phase interval where the corresponding switching device should be turned on;

[0032] Specifically, the output voltage of the rectifier module is compensated by pulse width modulation chopping to maintain the bus voltage of the bus capacitor within the target range.

[0033] Furthermore, the duty cycle of the pulse width modulation chopper is determined by voltage closed-loop control, which includes:

[0034] Collect the bus voltage of the bus capacitor;

[0035] Calculate the deviation between the bus voltage and a preset reference voltage; based on the deviation, generate the command value of the duty cycle through the regulator.

[0036] The present invention also proposes an intelligent device, which includes the three-phase rectifier system described above.

[0037] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0038] 1. This invention introduces switchable switching units and switching units into a traditional three-phase rectifier bridge to achieve a rectifier system architecture that is "uncontrollable during normal power supply and semi-controllable or fully controllable during phase loss or imbalance." The switching unit realizes "topology reconstruction" of the rectifier bridge, which provides fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity. Without increasing normal operation losses, it enables active regulation of bus voltage and continuous operation of the three-phase rectifier system under phase loss or imbalance faults, thereby improving the reliability of the three-phase rectifier system.

[0039] 2. This invention can also synergistically improve the efficiency and reliability of the three-phase rectifier system: When the AC power supply is normal, the three-phase rectifier system is a pure diode uncontrolled rectifier with no power switching devices and drive losses, thus improving the efficiency of the three-phase rectifier system; under phase loss or imbalance faults, it can switch to a semi-controllable rectifier mode or a fully controllable rectifier mode, and actively adjust the output voltage of the rectifier module through the pulse width modulation chopping of the switching unit, thereby maintaining the bus voltage within the rated value ±5%, avoiding the shutdown of the three-phase rectifier system, improving the reliability of the three-phase rectifier system, and achieving the optimal balance between "economy" and "fault tolerance", breaking through the design limitations of traditional "fully controlled or fully uncontrollable" systems. Attached Figure Description

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects and not to describe a particular order.

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the modules of the three-phase rectifier system proposed in this invention;

[0043] Figure 2 This is a partial circuit diagram of the three-phase rectifier system proposed in this invention;

[0044] Figure 3This is a circuit diagram showing the switching device proposed in this invention in the on state;

[0045] Figure 4 The circuit diagram shows the switching unit proposed in this invention in the on state;

[0046] Figure 5 This is a first logic diagram of the control method for the three-phase rectifier system proposed in this invention.

[0047] Figure 6 This is a second logic diagram of the control method for the three-phase rectifier system proposed in this invention.

[0048] Figure label:

[0049] 10. Rectifier module;

[0050] 101. Switching unit;

[0051] 102. Switching unit;

[0052] 20. Bus capacitors;

[0053] 30. AC power supply;

[0054] 40. Controller;

[0055] 50. Inverter;

[0056] 60. Load Unit. Detailed Implementation

[0057] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Therefore, a feature pointed out in this specification is used to illustrate one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0058] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0059] In the current field of power electronics technology, three-phase diode uncontrolled rectifier circuits are widely used in small and medium power industrial equipment, such as industrial frequency converters, welding machines, servo drives, photovoltaic inverters, and electric vehicle charging piles, due to their advantages of simple structure, low cost, and maintenance-free operation. However, this type of rectifier system has serious performance defects when a phase loss fault occurs in the three-phase input (i.e., one phase is de-energized), specifically manifested as follows:

[0060] ① Significant bus voltage drop: After a phase loss, the average output voltage of the three-phase bridge rectifier drops by more than 30%, causing the downstream inverter to shut down due to undervoltage protection; ② Increased output voltage ripple: The rectifier output waveform exhibits periodic zero-voltage intervals, and the voltage ripple increases significantly, affecting the stability of load operation; ③ Poor system fault tolerance: Minor grid anomalies (such as loose lines or blown fuses) can cause system interruptions, affecting continuous industrial production.

[0061] To address the above issues, existing technologies have proposed several solutions, mainly including: ① Increasing the bus capacitance: This can only alleviate short-term fluctuations and cannot fundamentally solve the voltage drop problem; it is also bulky and costly. ② Using full IGBT PWM rectification: Although it can achieve active regulation and energy feedback, the IGBTs are always working, resulting in high switching and conduction losses and a 2%~3% reduction in system efficiency. This is considered "over-design" under light load or normal operating conditions. ③ Configuring a UPS or automatic switching power supply: This is costly and bulky, and not suitable for most industrial sites. ④ Bypass boost circuits (such as Boost and CUK): These have complex structures, are difficult to control, and are only suitable for specific power levels.

[0062] Therefore, in some embodiments, such as Figures 1-2 As shown, this invention proposes a highly reliable three-phase rectifier system with fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity. The system includes a rectifier module 10 and a bus capacitor 20 connected to the rectifier module 10. The rectifier module 10 has three bridge arms composed of two series-connected switching devices, with each phase of the AC power supply 30 connected to the midpoint of its corresponding bridge arm. The rectifier module 10 also includes:

[0063] A switching unit 101 is connected in parallel with each of the aforementioned switching devices;

[0064] The switching unit 102 is connected to one of the switching devices and its corresponding switching unit 101 respectively; the switching unit 102 is used to switch and turn on the switching device or the corresponding switching unit 101.

[0065] The three-phase rectifier system proposed in this embodiment also includes an inverter 50 and a load unit 60;

[0066] The two ends of the three bridge arms of the rectifier module 10 are connected to the two ends of the bus capacitor 20, and the two ends of the bus capacitor 20 are also connected to the two ends of the input side of the inverter 50, and the two ends of the output side of the inverter 50 are connected to the load unit 60.

[0067] The three-phase rectifier system also includes: a bus voltage sensor to convert 0-1000V DC voltage into 0-5V analog signals and send them to the ADC port of the controller 40; a three-phase voltage sensor to collect the three-phase voltage to N respectively, and send the output signals to the controller 40 through a signal conditioning circuit; and a controller 40, which uses a microcontroller to perform phase loss detection, relay control, IGBT driving and alarm output.

[0068] It should be noted that the switching device proposed in this embodiment is illustrated using diodes, that is, the rectifier module 10 includes a three-phase diode rectifier bridge composed of six diodes D1 to D6, which is used to achieve uncontrolled rectification under normal operating conditions; of course, the switching device can also be selected as IGBT or SiC MOSFET depending on the actual situation, and is not limited here. In addition, the three-phase rectifier system proposed in this embodiment also includes a controller 40, which is connected to the switching unit 101 and the switching unit 102 respectively.

[0069] Thus, when AC power supply 30 is normally supplied, such as Figure 3 As shown, the three-phase rectifier system operates normally, i.e., in uncontrolled rectification mode. At this time, the controller 40 controls the switching unit 102 to turn on the switching device and ensures that the corresponding switching unit 101 remains in the open state (at this time, the switching unit 101 has no switching and conduction losses). The six diodes D1 to D6 form a complete three-phase uncontrolled rectifier bridge. Then, after the AC power is rectified by the three-phase uncontrolled rectifier bridge, a stable DC voltage is formed in the bus capacitor 20, which is about 540V under no-load and 510-530V under full load. The controller 40 samples the three-phase input voltage and the bus voltage at a frequency of 10kHz through the ADC to determine the status of the three-phase rectifier system in real time.

[0070] When a phase loss or imbalance occurs in the three phases of the AC power supply 30, the controller 40 will execute the following safe and disturbance-free topology reconfiguration process:

[0071] First, disconnect the corresponding switching device where the fault occurred to prevent a short circuit, then delay for a third predetermined time to ensure the switching device is completely disconnected; then turn on the corresponding switching unit 101 (e.g., Figure 4As shown, the three-phase rectifier system can switch to the switching unit 101 in the event of a phase loss or imbalance fault, operating in either semi-controllable rectification mode (only one diode in the faulty bridge arm is switched) or fully controllable rectification mode (all diodes in the faulty bridge arm are switched). This allows the PWM chopping control of the switching unit 101 to actively adjust the output voltage of the rectifier module 10, thereby maintaining the bus voltage within ±5% of the rated value, preventing the three-phase rectifier system from shutting down. At this time, the load unit 60 will enter the "derating operation" state, and the controller 40 will simultaneously issue audible, visual, and communication alarms to prompt manual maintenance, achieving "operation with fault + planned maintenance".

[0072] Therefore, this invention introduces switchable switching unit 101 and switching unit 102 into a traditional three-phase rectifier bridge to achieve a rectifier system architecture that is "uncontrollable during normal power supply and semi-controllable or fully controllable during phase loss or imbalance." The switching unit 102 realizes "topology reconstruction" of the rectifier bridge, which provides fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity. It also achieves active regulation of bus voltage and continuous operation of the three-phase rectifier system under phase loss or imbalance faults without increasing normal operation losses.

[0073] It can also synergistically improve the efficiency and reliability of the three-phase rectifier system: when the AC power supply 30 is supplying power normally, the three-phase rectifier system is a pure diode uncontrolled rectifier with no power switching devices and drive losses, thus improving the efficiency of the three-phase rectifier system; under the fault of phase loss or imbalance, it can switch to semi-controllable rectification mode or fully controllable rectification mode, and actively adjust the output voltage of rectifier module 10 through pulse width modulation chopping of switching unit 101, thereby maintaining the bus voltage within the rated value ±5%, avoiding the shutdown of the three-phase rectifier system, improving the reliability of the three-phase rectifier system, achieving the best balance between "economy" and "fault tolerance", breaking through the traditional design limitations of "fully controlled or fully uncontrollable".

[0074] Among them, the topology reconfiguration mechanism is as follows: a switching unit 101 is connected in parallel with each switching device, and the physical switching of "switching device ↔ switching unit 101" is realized through the switching unit 102, so that the three-phase rectifier system can be reconfigured from uncontrollable rectification to semi-controllable rectification and fully controllable rectification when there is a phase loss or imbalance fault. This is an essential change in the circuit structure.

[0075] In other embodiments (not shown in the figure), the bus capacitor 20 may be composed of an electrolytic capacitor connected in series with an equalizing resistor, and connected between the positive and negative busbars.

[0076] In other embodiments (not shown in the figures), each switching device is connected in parallel to two or more switching units 101, and the power devices in the plurality of switching units 101 may be the same or different, which is not limited here. Moreover, the switching unit 102 can only turn on the switching device or any one of the corresponding switching units 101 at the same time, and cannot turn on the switching device and any one of the corresponding switching units 101 at the same time, or can not turn on any two of the corresponding switching units 101 at the same time.

[0077] In some embodiments, to ensure the high reliability of the three-phase rectifier system after the switching unit 101 is turned on, such as Figure 2 As shown, each of the switching units 101 includes an insulated gate bipolar transistor (IGBT). The emitter of the IGBT and the input terminal of the corresponding switching device (equivalent to the anode of a diode, the same throughout) are both connected to a switching unit 102. The collector of the IGBT is connected to the output terminal of the corresponding switching device (equivalent to the cathode of a diode, the same throughout). The gate of the IGBT is used to connect to the controller 40.

[0078] It should be noted that the insulated gate bipolar transistor proposed in this embodiment can also automatically select the optimal device, such as silicon-based MOSFET or SiC MOSFET, based on the load and temperature, which is not limited here.

[0079] Thus, when AC power supply 30 is normally supplied, the three-phase rectification system is a pure diode uncontrolled rectification system with no IGBT switching and drive losses. The efficiency of the three-phase rectification system can reach 98.5%, which improves the efficiency of the three-phase rectification system and is superior to the all-IGBT rectification scheme. The IGBT is only activated when a phase loss or imbalance fault occurs. The IGBT and its drive circuit can be designed for "intermittent operation", reducing heat dissipation and device costs.

[0080] Specifically, each of the switching units 102 includes a single-pole double-throw relay and a transistor;

[0081] The collector of the transistor is connected to the first coil pin of the single-pole double-throw relay to control the on / off state of the coil inside the single-pole double-throw relay; the emitter of the transistor is grounded, and the base of the transistor is used to connect to the controller 40.

[0082] The second coil pin of the single-pole double-throw relay is used to connect to the power supply pin VCC. The common terminal of the single-pole double-throw relay is connected to the corresponding bridge arm. The normally closed contact of the single-pole double-throw relay is connected to the input terminal of the corresponding switching device. The normally open contact of the single-pole double-throw relay is connected to the emitter of the corresponding insulated-gate bipolar transistor.

[0083] It should be noted that this embodiment can also use a MOSFOR thyristor to replace the single-pole double-throw relay, achieving contactless, wear-free, microsecond-level switching, suitable for high-frequency switching or long-lifespan requirements. Furthermore, this embodiment uses six single-pole double-throw relays, K1~K6, and six transistors, Q1~Q6.

[0084] Thus, when AC power supply 30 is supplying power normally, controller 40 will output a low level to all transistors, the coils of single-pole double-throw relays K1~K6 will not be energized, the common terminal of single-pole double-throw relays K1~K6 will be connected to the normally closed contact, and all diodes will be turned on. When a phase loss or imbalance fault occurs in the three phases of AC power supply 30, controller 40 will output a high level to the transistor corresponding to the fault, so that the coil of the single-pole double-throw relay corresponding to the fault will be energized, the common terminal of the single-pole double-throw relay will be connected to the normally open contact, and the corresponding IGBT will be turned on.

[0085] Furthermore, when a phase loss or imbalance fault occurs in the three phases of the AC power supply 30, the controller 40 will execute the following safe and disturbance-free topology reconfiguration process:

[0086] Firstly, relay switching timing control:

[0087] S1: Controls the single-pole double-throw relay to open the normally closed contact (NC contact) to first disconnect the diode corresponding to the location of the fault, preventing a short circuit. Timing requirement: 0ms.

[0088] S2: Delay 10ms to wait for the contacts of the single-pole double-throw relay to completely separate, thus avoiding arcing;

[0089] S3: Controls the single-pole double-throw relay to close its normally open contact (NO contact) to turn on the corresponding IGBT. Timing requirement: 10ms.

[0090] S4: Confirmed via feedback from the auxiliary contact of a single-pole double-throw relay or a fixed delay of 10ms;

[0091] S5: The IGBT drive signal that enables conduction, realizing PWM chopping control, with a timing requirement of 10ms.

[0092] Thus, the "break-before-connect" timing sequence is the key design of this invention to prevent short circuits in the main circuit and ensure a safe and reliable switching process.

[0093] Secondly, the PWM chopping control of IGBT:

[0094] S1: Enable voltage outer loop PI control, and set the bus voltage reference value Vref to 540V;

[0095] S2: Sample the actual bus voltage Vdc and calculate the deviation e=Vref−Vdce=Vref−Vdc;

[0096] S3: Outputs PWM duty cycle command via PI regulator;

[0097] S4: The IGBT that is controlled to conduct is chopping controlled at a PWM frequency of 10kHz within the phase range where its corresponding diode should be conducting.

[0098] S5: The initial duty cycle is set to 30%, and it linearly increases to the closed-loop regulation value within 100ms (soft start) to prevent current surges;

[0099] S6: The remaining phases that have not experienced phase loss or imbalance are still naturally conducted by the diodes, forming a hybrid rectification topology.

[0100] In this way, PWM chopper control is equivalent to "boosting" the output voltage of the faulty phase, maintaining the bus voltage between 520 and 550V, and improving the reliability of the three-phase rectifier system. After the bus voltage stabilizes, the downstream inverter 50 can continue to operate, the load unit 60 is derated to 70% of its rated power, and the controller 40 drives the red LED to flash, triggers the buzzer to sound, and pops up an alarm to the host computer monitoring system, prompting maintenance personnel to check the faulty phase connection; and the three-phase rectifier system can continue to operate in this state for several hours, waiting for planned maintenance.

[0101] Of course, the timing parameters mentioned above can be selected with other values ​​depending on the actual situation, and no restrictions are imposed here.

[0102] The three-phase rectifier system proposed in this invention brings the following beneficial effects:

[0103] 1. High reliability: By introducing the switching mechanism of IGBT and single-pole double-throw relay, the three-phase rectifier system can switch to semi-controllable rectification mode or fully controllable rectification mode under phase loss or imbalance faults. The output voltage of rectifier module 10 is actively adjusted by the pulse width modulation chopping of IGBT, thereby maintaining the bus voltage within the rated value ±5% range and avoiding the shutdown of the three-phase rectifier system.

[0104] 2. High efficiency: When the AC power supply is normally supplied at 30V, the three-phase rectification system is a pure diode uncontrolled rectification system with no IGBT switching and drive losses. The efficiency of the three-phase rectification system can reach 98.5%, which is better than the full IGBT rectification scheme.

[0105] 3. Low cost: IGBTs are only activated when a phase loss or imbalance occurs. IGBTs and their drive circuits can be designed for "intermittent operation", reducing heat dissipation and device costs.

[0106] 4. Strong engineering compatibility: It can be modularly modified without changing the original main circuit structure and is compatible with existing diode rectifier equipment.

[0107] 5. Flexible control: The controller 40 enables closed-loop control of "detection-switching-adjustment-alarm", supporting remote monitoring and maintenance.

[0108] 6. Good maintainability: When the three-phase rectifier system is missing a phase or unbalanced, it enters the "derating operation" state and issues audible, visual and communication alarms to prompt manual maintenance, realizing "operation with defects + planned maintenance".

[0109] In some embodiments, such as Figure 5 As shown, the present invention also proposes a control method for a three-phase rectifier system as described above, the control method comprising:

[0110] Determine whether the three phases of AC power supply 30 are missing or unbalanced;

[0111] If so, the switching unit 102 first disconnects the switching device and then turns on the corresponding switching unit 101 to maintain the stability of the bus voltage of the bus capacitor 20 and control the load unit 60 corresponding to the three-phase rectifier system to reduce its operating frequency.

[0112] Thus, by introducing switchable switching unit 101 and switching unit 102 into a traditional three-phase rectifier bridge, this invention achieves a rectifier system architecture that is "uncontrollable during normal power supply and semi-controllable or fully controllable during phase loss or imbalance." The switching unit 102 enables "topology reconfiguration" of the rectifier bridge, providing fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity. It also enables active regulation of bus voltage and continuous operation of the three-phase rectifier system under phase loss or imbalance faults without increasing normal operation losses.

[0113] It can also synergistically improve the efficiency and reliability of the three-phase rectifier system: when the AC power supply 30 is supplying power normally, the three-phase rectifier system is a pure diode uncontrolled rectifier with no power switching devices and drive losses, thus improving the efficiency of the three-phase rectifier system; under the fault of phase loss or imbalance, it can switch to semi-controllable rectification mode or fully controllable rectification mode, and actively adjust the output voltage of rectifier module 10 through pulse width modulation chopping of switching unit 101, thereby maintaining the bus voltage within the rated value ±5%, avoiding the shutdown of the three-phase rectifier system, improving the reliability of the three-phase rectifier system, achieving the best balance between "economy" and "fault tolerance", breaking through the traditional design limitations of "fully controlled or fully uncontrollable".

[0114] Therefore, this invention not only solves the technical problem of bus voltage drop and system shutdown in three-phase rectifier systems when a phase is missing or unbalanced, but also achieves synergistic optimization of efficiency and reliability through topology reconfiguration mechanism and intelligent control logic; and supports full lifecycle management of three-phase rectifier systems, improving maintainability. High reliability: After topology reconfiguration, the bus voltage is stable, the three-phase rectifier system operates without interruption and achieves high efficiency, with no IGBT losses under normal conditions, reaching an efficiency of 98.4%; Safety: Single-pole double-throw relay "break-before-connect" timing + IGBT PWM chopping control; Precise control: Voltage closed-loop PI regulation, fast response, and small steady-state error; Maintainability: Alarm output, supporting remote monitoring; Engineering feasibility: All components are industrial-grade, easy to mass-produce.

[0115] Among them, the intelligent control logic proposes a switching control logic with timing protection, including: delaying confirmation of phase loss or imbalance >15ms to prevent false triggering; first disconnecting the diode, delaying for 10ms, and then turning on the IGBT to avoid short circuit; and using PWM soft start when the IGBT is enabled to prevent current surge.

[0116] In some embodiments, to accurately determine whether a three-phase rectifier system has experienced a phase loss or imbalance, such as Figure 5 As shown, the control method includes:

[0117] The bus voltage of the bus capacitor 20, and the three-phase voltage and three-phase current of the AC power supply 30 are collected.

[0118] Determine whether the fault conditions are met;

[0119] If so, the three-phase rectifier system is in a state of phase loss or imbalance;

[0120] If not, the three-phase rectifier system is operating normally;

[0121] The fault conditions are as follows:

[0122] The bus voltage amplitude drops below a first predetermined threshold, or the voltage amplitude of any phase drops below a second predetermined threshold, or the current of any phase is zero, and this continues for a first predetermined time.

[0123] Among them, the fault detection and judgment logic, the controller 40 identifies phase loss or imbalance faults through the following anti-interference detection algorithm:

[0124] Bus voltage, three-phase voltage, and three-phase current are collected every 100μs.

[0125] If the amplitude of the bus voltage drops by ≥15%, or the voltage amplitude of any phase drops by ≥15%, or the current of any phase is zero;

[0126] If this state lasts for 15ms (about 3 / 4 of the power frequency cycle) or more, it is determined to be a phase loss or imbalance fault.

[0127] Record the fault type and proceed to the topology reconfiguration preparation phase.

[0128] Furthermore, the delay design of the first predetermined time can effectively avoid false triggering caused by instantaneous fluctuations in the power grid or voltage dips, thereby improving the reliability of the three-phase rectifier system.

[0129] Furthermore, the first predetermined threshold, the second predetermined threshold, and the first predetermined time proposed in this embodiment can be selected as other values ​​according to the actual situation, which are not limited here.

[0130] In some embodiments, such as Figure 6 As shown, according to the switching unit 102 first disconnecting the switching device and then turning on the corresponding switching unit 101, the control method includes:

[0131] Determine whether the voltage amplitude drop of any phase is lower than a third predetermined threshold.

[0132] If so, the switching unit 102 first disconnects the switching unit 101, and then turns on the switching device;

[0133] If not, the switching device remains on.

[0134] It should be noted that the third predetermined threshold is preferably 15% of the rated value. Of course, the third predetermined threshold can be selected as other values ​​according to the actual situation, which are not limited here.

[0135] Thus, when the switching device is first disconnected and then the corresponding switching unit 101 is turned on, the controller 40 drives the red LED to flash, triggers the buzzer to sound, and pops up an alarm to the host computer monitoring system, prompting the maintenance personnel to check the faulty connection. After the maintenance is completed, if the voltage amplitude of any phase of the controller 40 drops below the third predetermined threshold, the three-phase rectifier system will operate normally. At this time, the single-pole double-throw relay corresponding to the IGBT that is turned on will open its normally open contact, and then wait for 10ms before closing the normally closed contact of the corresponding single-pole double-throw relay, thus switching the previously disconnected diode to the on state, restoring the normal uncontrolled rectification mode of the three-phase rectifier system, and clearing the alarm state.

[0136] The control method includes:

[0137] After the switching unit 102 disconnects the switching unit 101 or the switching device, it must delay for a second predetermined time before performing the corresponding conduction action.

[0138] This ensures that the mechanical contacts of the single-pole double-throw relay in the switching unit 102 are completely separated before closing the other contact, thus avoiding electric arc.

[0139] Specifically:

[0140] The switching unit 102 first disconnects the IGBT and delays for 10ms before turning on the corresponding diode.

[0141] Alternatively, the switching unit 102 may first disconnect the diode and then, after a 10ms delay, turn on the corresponding IGBT.

[0142] It should be noted that the second scheduled time can be selected as other values ​​depending on the actual situation, and is not limited to 10ms.

[0143] In some embodiments, the control method includes, based on the switching unit 101 corresponding to the conduction, the control method includes:

[0144] The switching unit 101 is controlled to perform pulse width modulation chopping within the phase interval where the corresponding switching device should be turned on;

[0145] The output voltage of the rectifier module 10 is compensated by the pulse width modulation chopping to maintain the bus voltage of the bus capacitor 20 within the target range.

[0146] In this way, PWM chopper control is equivalent to "boosting" the output voltage of the faulty phase, maintaining the bus voltage between 520 and 550V, and improving the reliability of the three-phase rectifier system. After the bus voltage stabilizes, the downstream inverter 50 can continue to operate, the load unit 60 is derated to 70% of its rated power, and the controller 40 drives the red LED to flash, triggers the buzzer to sound, and pops up an alarm to the host computer monitoring system, prompting maintenance personnel to check the faulty phase connection; and the three-phase rectifier system can continue to operate in this state for several hours, waiting for planned maintenance.

[0147] It should be noted that the target range can be selected as other values ​​depending on the actual situation, and is not limited to 520-550V.

[0148] In other embodiments (not shown in the figure), the controller 40 can dynamically adjust the PWM frequency according to the current of the load unit 60: reduce the frequency to reduce losses under light load and increase the frequency to improve the adjustment accuracy under heavy load.

[0149] Specifically, to ensure "boost compensation" of the faulty phase output voltage and maintain the bus voltage between 520 and 550V, the duty cycle of the pulse width modulation chopper is determined through voltage closed-loop control, which includes:

[0150] Collect the bus voltage of bus capacitor 20;

[0151] Calculate the deviation between the bus voltage and a preset reference voltage;

[0152] Based on the deviation, the regulator generates the command value for the duty cycle.

[0153] It is understood that, in some cases, the preset reference voltage proposed in this embodiment can be equivalent to the rated value of the bus voltage.

[0154] In some embodiments, the present invention also proposes an intelligent device, the intelligent device comprising the three-phase rectifier system described above.

[0155] Thus, when AC power supply 30 is supplying power normally, the three-phase rectifier system operates normally, that is, it operates in uncontrolled rectification mode. Then, after the AC power is rectified by the three-phase uncontrolled rectifier bridge, a stable DC voltage is formed in the bus capacitor 20, which is about 540V under no-load and 510~530V under full load. The controller 40 samples the three-phase input voltage and bus voltage at a frequency of 10kHz through ADC to judge the status of the three-phase rectifier system in real time.

[0156] When a phase loss or imbalance occurs in the three phases of the AC power supply 30, the controller 40 will execute the following safe and disturbance-free topology reconfiguration process:

[0157] First, disconnect the corresponding switching device where the fault occurred to prevent short circuit. Then, delay for a third predetermined time to ensure that the switching device is completely disconnected. Then, turn on the corresponding switching unit 101 so that the three-phase rectifier system can switch to the switching unit 101 under the fault of phase loss or imbalance, and run in semi-controllable rectification mode or fully controllable rectification mode. In this way, the output voltage of the rectifier module 10 is actively adjusted by the PWM chopping control of the switching unit 101, thereby maintaining the bus voltage within the rated value ±5% range, avoiding the shutdown of the three-phase rectifier system. At this time, the load unit 60 will enter the "derating operation" state, and the controller 40 will issue audible, visual and communication alarms to prompt manual maintenance, realizing "operation with fault + planned maintenance".

[0158] Therefore, this invention introduces switchable switching unit 101 and switching unit 102 into a traditional three-phase rectifier bridge to achieve a rectifier system architecture that is "uncontrollable during normal power supply and semi-controllable or fully controllable during phase loss or imbalance." The switching unit 102 realizes "topology reconstruction" of the rectifier bridge, which provides fault tolerance for phase loss or imbalance without significantly increasing system cost and complexity. It also achieves active regulation of bus voltage and continuous operation of the three-phase rectifier system under phase loss or imbalance faults without increasing normal operation losses.

[0159] It can also synergistically improve the efficiency and reliability of the three-phase rectifier system: when the AC power supply 30 is supplying power normally, the three-phase rectifier system is a pure diode uncontrolled rectifier with no power switching devices and drive losses, thus improving the efficiency of the three-phase rectifier system; under the fault of phase loss or imbalance, it can switch to semi-controllable rectification mode or fully controllable rectification mode, and actively adjust the output voltage of rectifier module 10 through pulse width modulation chopping of switching unit 101, thereby maintaining the bus voltage within the rated value ±5%, avoiding the shutdown of the three-phase rectifier system, improving the reliability of the three-phase rectifier system, achieving the best balance between "economy" and "fault tolerance", breaking through the traditional design limitations of "fully controlled or fully uncontrollable".

[0160] In some embodiments, the present invention also provides an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the control method for the three-phase rectifier system as described above.

[0161] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A three-phase rectification system, comprising a rectifier module and a bus capacitor connected to the rectifier module; the rectifier module having three bridge arms consisting of two series-connected switching devices, each phase of the AC power supply being connected to the midpoint of the corresponding bridge arm; characterized in that, The rectifier module also includes: A switching unit, which is connected in parallel with each of the aforementioned switching devices; A switching unit is connected to one of the switching devices and its corresponding switching unit; the switching unit is used to switch and turn on the switching device or the corresponding switching unit.

2. The three-phase rectifier system according to claim 1, characterized in that, Each of the switching units includes an insulated-gate bipolar transistor (IGBT), the emitter of which and the input of the corresponding switching device are both connected to one of the switching units, the collector of which is connected to the output of the corresponding switching device, and the gate of which is used to connect to a controller.

3. The three-phase rectifier system according to claim 2, characterized in that, Each of the switching units includes a single-pole double-throw relay and a transistor; The collector of the transistor is connected to the first coil pin of the single-pole double-throw relay to control the on / off state of the coil inside the single-pole double-throw relay; the emitter of the transistor is grounded, and the base of the transistor is used to connect to the controller. The second coil pin of the single-pole double-throw relay is used to connect to the power supply pin VCC. The common terminal of the single-pole double-throw relay is connected to the corresponding bridge arm. The normally closed contact of the single-pole double-throw relay is connected to the input terminal of the corresponding switching device. The normally open contact of the single-pole double-throw relay is connected to the emitter of the corresponding insulated-gate bipolar transistor.

4. A control method for a three-phase rectifier system as described in any one of claims 1 to 3, characterized in that, The control method includes: Determine whether the three phases of the AC power supply are missing or unbalanced; If so, the switching unit first disconnects the switching device and then turns on the corresponding switching unit to maintain the stability of the bus voltage of the bus capacitor and control the load unit corresponding to the three-phase rectifier system to reduce its operating frequency.

5. The control method according to claim 4, characterized in that, The control method includes: The bus voltage of the bus capacitor, the three-phase voltage and three-phase current of the AC power supply are collected; Determine whether the fault conditions are met; If so, the three-phase rectifier system is in a state of phase loss or imbalance; If not, the three-phase rectifier system is operating normally; The fault conditions are as follows: The bus voltage amplitude drops below a first predetermined threshold, or the voltage amplitude of any phase drops below a second predetermined threshold, or the current of any phase is zero, and this continues for a first predetermined time.

6. The control method according to claim 4, characterized in that, The control method, which involves first disconnecting the switching device and then turning on the corresponding switching unit, includes: Determine whether the voltage amplitude drop of any phase is lower than a third predetermined threshold. If so, the switching unit first disconnects the switching unit and then turns on the switching device; If not, the switching device remains on.

7. The control method according to claim 4, characterized in that, The control method includes: After the switching unit disconnects the switching unit or the switching device, it must delay for a second predetermined time before performing the corresponding conduction action.

8. The control method according to claim 4, characterized in that, Based on the corresponding switching unit that is turned on, the control method includes: The switching unit is controlled to perform pulse width modulation chopping within the phase interval where the corresponding switching device should be turned on; Specifically, the output voltage of the rectifier module is compensated by pulse width modulation chopping to maintain the bus voltage of the bus capacitor within the target range.

9. The control method according to claim 8, characterized in that, The duty cycle of the pulse width modulation chopper is determined by voltage closed-loop control, which includes: Collect the bus voltage of the bus capacitor; Calculate the deviation between the bus voltage and a preset reference voltage; based on the deviation, generate the command value of the duty cycle through the regulator.

10. A smart device, characterized in that, The intelligent device includes the three-phase rectifier system as described in any one of claims 1 to 3.

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