Fault-tolerant control method and system for grid-connected converter

Abstract

The invention discloses a fault-tolerant control method and system of a grid-connected converter, and relates to the technical field of fault-tolerant control of grid-connected converters. According to the invention, the bidirectional thyristor module is connected with the capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm, so that topology reconstruction can be carried out on the three-phase grid-connected converter by controlling the bidirectional thyristors. The position of the fault switch tube and the fault type of the switch tube can be determined through the real-time neutral-point voltage of the three-phase grid-connected converter, the fault detection efficiency of the grid-connected converter is improved, and the fault tolerance reliability is further improved. The three-phase grid-connected converter can completely cope with any double-tube fault by performing switch switching on a bidirectional thyristor module when a primary switch tube has a fault and performing topology reconstruction on a capacitor bridge arm and a redundant bridge arm when a secondary switch tube has a fault and combining the capacitor bridge arm and the redundant bridge arm, so that the three-phase grid-connected converter can completely cope with any double-tube fault, and the reliability of the three-phase grid-connected converter is improved. Therefore, the reliability and the stability of fault-tolerant fault control of the three-phase grid-connected converter are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault-tolerant control of grid-connected converters, and particularly relates to a fault-tolerant control method and system for grid-connected converters. Background Art

[0002] Offshore floating photovoltaic power generation is being rapidly promoted and applied due to its significant advantages such as not occupying land resources, high power generation efficiency, and environmental friendliness. As the core device for power conversion and grid connection control, the power converter directly determines the energy transmission efficiency and grid compatibility. Whether it can operate reliably and stably has become the key to the efficient operation of offshore photovoltaic power stations. Due to the influence of the high-humidity and high-salt environment in the ocean on the service life of devices, the switching tubes in the grid-connected converter will fail. Common ones are primary switching tube failures and secondary switching tube failures. The primary switching tube failure, i.e., single-tube failure, means that one switching tube in the grid-connected converter fails. The secondary switching tube failure, i.e., double-tube failure, means that two switching tubes in the grid-connected converter fail.

[0003] When the grid-connected converter fails, it will not only cause large mutations in current and voltage, but also reduce the operation efficiency and power quality of the grid, and even lead to the occurrence of secondary faults and system paralysis. At present, for the fault-tolerant control method of grid-connected converters, it is mainly to diagnose the faulty switching tube by measuring the voltage conversion value of the grid-connected converter, and then achieve the fault-tolerant control of the grid-connected converter by adding redundant switching tubes. However, this fault-tolerant control method requires the measurement of three-phase voltages and can only handle some double-tube failures, resulting in unreliable and unstable fault-tolerant control for grid-connected converters. Therefore, there is an urgent need for a fault-tolerant control method and system for grid-connected converters to solve the defects of the existing technology. Summary of the Invention

[0004] The present invention aims to provide a fault-tolerant control method and system for grid-connected converters to solve the above technical problems. By judging the faulty switching tube of the three-phase grid-connected converter through the real-time midpoint voltage, the fault-tolerant control of the primary switching tube failure and secondary switching tube failure of the three-phase grid-connected converter is realized, and the reliability and stability of the fault-tolerant control of the grid-connected converter are improved.

[0005] To solve the above technical problems, an embodiment of the present invention provides a fault-tolerant control method for a grid-connected converter, which is applicable to a three-phase grid-connected converter. The three-phase grid-connected converter includes: a DC power supply, a capacitor bridge arm, a three-phase bridge arm, a redundant bridge arm, and an AC power supply connected in sequence; the three-phase grid-connected converter further includes: a bidirectional thyristor module;

[0006] The capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply;

[0007] The fault-tolerant control method includes:

[0008] After determining that a fault occurs in the grid-connected converter, obtain the real-time neutral point voltage of the three-phase grid-connected converter, and determine the position information of the faulty switch tube and the type of switch tube fault of the three-phase grid-connected converter according to the real-time neutral point voltage;

[0009] When the type of switch tube fault is a primary switch tube fault, perform a switch switching on the bidirectional thyristor module based on the position information of the faulty switch tube to complete the fault-tolerant control of the primary switch tube fault;

[0010] When the type of switch tube fault is a secondary switch tube fault, perform a topology reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switch tube to complete the fault-tolerant control of the secondary switch tube fault.

[0011] It can be understood that, compared with the prior art, in the present invention, the bidirectional thyristor module is connected to the capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm, and the topology of the three-phase grid-connected converter can be reconstructed by controlling the bidirectional thyristor. The position of the faulty switch tube and the type of switch tube fault can be determined through the real-time neutral point voltage of the three-phase grid-connected converter, avoiding the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and further improving the reliability of fault-tolerant control. By performing switch switching on the bidirectional thyristor module during a primary switch tube fault and performing topology reconstruction on the capacitor bridge arm and the redundant bridge arm during a secondary switch tube fault, with the combination of the capacitor bridge arm and the redundant bridge arm, the three-phase grid-connected converter can fully cope with any double-switch tube fault, thereby improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0012] As a preferred solution, the bidirectional thyristor module includes: a first bidirectional thyristor, a second bidirectional thyristor, a third bidirectional thyristor, a fourth bidirectional thyristor, a fifth bidirectional thyristor, and a sixth bidirectional thyristor;

[0013] The first end of the first bidirectional thyristor is electrically connected to the connection point of phase A of the three-phase bridge arm;

[0014] The second end of the first bidirectional thyristor is electrically connected to the first end of the fifth bidirectional thyristor;

[0015] The first end of the second bidirectional thyristor is electrically connected to the connection point of phase A of the three-phase bridge arm;

[0016] The second end of the second bidirectional thyristor is electrically connected to the connection point of phase B of the three-phase bridge arm;

[0017] The first end of the third triac is electrically connected to the connection point of phase A of the three-phase bridge arm;

[0018] The second end of the third triac is electrically connected to the connection point of phase C of the three-phase bridge arm;

[0019] The first end of the fourth triac is electrically connected to the redundant connection point of the redundant bridge arm;

[0020] The second end of the fourth triac is electrically connected to the first end of the fifth triac;

[0021] The second end of the fifth triac is electrically connected to phase A of the AC power supply;

[0022] The first end of the sixth triac is electrically connected to the capacitor connection point of the capacitor bridge arm;

[0023] The second end of the sixth triac is electrically connected to the second end of the fifth triac.

[0024] In this preferred solution, by electrically connecting the triacs in the triac module to the three-phase bridge arm, capacitor bridge arm, redundant bridge arm and AC power supply, it is possible to achieve fault-tolerant control of any primary switch tube fault and secondary switch tube fault of the three-phase grid-connected converter by controlling the conduction and turn-off of the triacs, improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0025] As a preferred solution, after determining that the grid-connected converter has a fault, obtain the real-time neutral point voltage of the three-phase grid-connected converter, and determine the position information and switch tube fault type of the fault switch tube of the three-phase grid-connected converter according to the real-time neutral point voltage. Specifically, it includes:

[0026] After determining that the grid-connected converter has a fault, obtain the voltage difference between the midpoint of the capacitor bridge arm and the neutral point of the AC power supply, determine the real-time neutral point voltage of the three-phase grid-connected converter, and record the fault duration of the three-phase grid-connected converter;

[0027] Determine the real-time neutral point voltage deviation according to the real-time neutral point voltage;

[0028] Obtain the midpoint voltage deviation threshold of the three-phase bridge arm, compare the real-time neutral point voltage deviation with the midpoint voltage deviation threshold, and determine the real-time switch state of the three-phase bridge arm;

[0029] After determining that the fault duration is greater than or equal to the preset fault time threshold, determine the position information and quantity of the fault switch tube based on the real-time switch state of the three-phase bridge arm;

[0030] Determine the switching tube fault type of the three-phase grid-connected converter based on the number of the faulty switching tubes.

[0031] This preferred solution determines the real-time neutral point voltage of the three-phase grid-connected converter, and then determines the position information and quantity of the faulty switch, avoiding the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter by judging the fault duration.

[0032] As a preferred solution, when the switching tube fault type is a primary switching tube fault, perform switching of the bidirectional thyristor module based on the position information of the faulty switching tube to complete the fault-tolerant control of the primary switching tube fault, specifically including:

[0033] When the switching tube fault type is a primary switching tube fault and the position information of the faulty switching tube is a fault in the A-phase bridge arm, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor to complete the fault-tolerant control of the primary switching tube fault;

[0034] When the switching tube fault type is a primary switching tube fault and the position information of the faulty switching tube is a fault in the B-phase bridge arm, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the second bidirectional thyristor to complete the fault-tolerant control of the primary switching tube fault;

[0035] When the switching tube fault type is a primary switching tube fault and the position information of the faulty switching tube is a fault in the C-phase bridge arm, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the third bidirectional thyristor to complete the fault-tolerant control of the primary switching tube fault.

[0036] This preferred solution can cope with any primary switching tube fault of the three-phase grid-connected converter by judging the bridge arm position when a primary switching tube fault occurs, and turning off and turning on the corresponding bidirectional thyristors, and in the form of adding redundant bridge arms, improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0037] As a preferred solution, when the switching tube fault type is a secondary switching tube fault, reconstruct the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switching tube to complete the fault-tolerant control of the secondary switching tube fault, specifically including:

[0038] When the switching tube fault type is a secondary switching tube fault, determine the first faulty switching tube and the second faulty switching tube based on the fault time sequence of the faulty switching tubes;

[0039] Perform fault tolerance control for the first faulty switching tube for a switching tube fault;

[0040] After completing the fault tolerance control for the first faulty switching tube, based on the position of the second faulty switching tube, perform topological reconstruction on the capacitor bridge arm and the redundant bridge arm to complete the fault tolerance control for the secondary switching tube fault.

[0041] This preferred solution can handle any secondary switching tube fault of a three-phase grid-connected converter in the form of adding a capacitor bridge arm based on the fault tolerance control of the primary switching tube by judging the fault time sequence of the secondary switching tube fault, improving the reliability and stability of the fault tolerance control of the three-phase grid-connected converter.

[0042] As a preferred solution, the performing topological reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position of the second faulty switching tube to complete the fault tolerance control for the secondary switching tube fault specifically includes:

[0043] When the second faulty switching tube is located in the redundant bridge arm, turn on the sixth bidirectional thyristor so that the capacitor bridge arm serves as the new phase-A bridge arm to complete the fault tolerance control for the secondary switching tube fault;

[0044] When the second faulty switching tube is located in the phase-A bridge arm, turn on the sixth bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor so that the capacitor bridge arm serves as the new phase-A bridge arm to complete the fault tolerance control for the secondary switching tube fault;

[0045] When the second faulty switching tube is located in the phase-B bridge arm, turn on the sixth bidirectional thyristor, the second bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor so that the capacitor bridge arm serves as the new phase-A bridge arm and the redundant bridge arm replaces the bridge arm corresponding to the first faulty switching tube to complete the fault tolerance control for the secondary switching tube fault;

[0046] When the second faulty switching tube is located in the phase-C bridge arm, turn on the sixth bidirectional thyristor, the third bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor so that the capacitor bridge arm serves as the new phase-A bridge arm and the redundant bridge arm replaces the bridge arm corresponding to the first faulty switching tube to complete the fault tolerance control for the secondary switching tube fault.

[0047] This preferred solution can handle any secondary switching tube fault of a three-phase grid-connected converter in the form of adding a capacitor bridge arm by judging the position of the faulty switching tube in the bridge arm and turning on and off the corresponding bidirectional thyristors, improving the reliability and stability of the fault tolerance control of the three-phase grid-connected converter.

[0048] As a preferred solution, the capacitor neutral point control and space vector modulation of the three-phase grid-connected converter specifically include:

[0049] Obtain the voltage value information of the capacitors in the current capacitor bridge arm and the rated modulation wave of each phase in the three-phase grid-connected converter;

[0050] Determine the DC bias voltage according to the voltage value information and a preset low-pass filter, and determine the faulty phase and non-faulty phases of the three-phase grid-connected converter according to the first faulty switch tube and the second faulty switch tube;

[0051] Determine the corrected modulation wave of the faulty phase according to the DC bias voltage, a preset proportional regulator, and the rated modulation wave, and complete the capacitor neutral point control of the three-phase grid-connected converter;

[0052] Obtain the zero vectors of the three-phase grid-connected converter according to a preset volt-second balance algorithm, and determine the duty cycle of the non-faulty phases based on the zero vectors to complete the space vector modulation of the three-phase grid-connected converter.

[0053] This preferred solution can further regulate the three-phase grid-connected converter after topology reconstruction by performing capacitor neutral point control and space vector modulation on the three-phase grid-connected converter, thereby improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0054] As a preferred solution, the three-phase bridge arm includes: an A-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm;

[0055] The A-phase bridge arm includes: a first switch tube and a second switch tube; the B-phase bridge arm includes: a third switch tube and a fourth switch tube; the C-phase bridge arm includes: a fifth switch tube and a sixth switch tube;

[0056] The first ends of the first switch tube, the third switch tube, and the fifth switch tube are all electrically connected to the positive pole of the DC power supply;

[0057] The second end of the first switch tube is electrically connected to the first end of the second switch tube; the second end of the third switch tube is electrically connected to the first end of the fourth switch tube; the second end of the fifth switch tube is electrically connected to the first end of the sixth switch tube;

[0058] The second ends of the second switch tube, the fourth switch tube, and the sixth switch tube are electrically connected to the negative pole of the DC power supply;

[0059] The connection point of the first switch tube and the second switch tube serves as the A-phase connection point of the A-phase bridge arm for electrical connection to the A-phase of the AC power supply;

[0060] The connection point of the third switching transistor and the fourth switching transistor serves as the B-phase connection point of the B-phase bridge arm and is used for electrically connecting to the B-phase of the AC power supply;

[0061] The connection point of the fifth switching transistor and the sixth switching transistor serves as the C-phase connection point of the C-phase bridge arm and is used for electrically connecting to the C-phase of the AC power supply.

[0062] As a preferred solution, the capacitor bridge arm includes a first capacitor and a second capacitor; the redundant bridge arm includes: a seventh switching transistor and an eighth switching transistor;

[0063] The first end of the first capacitor is electrically connected to the positive pole of the DC power supply; the second end of the first capacitor is electrically connected to the first end of the second capacitor; the second end of the second capacitor is electrically connected to the negative pole of the DC power supply;

[0064] The connection point of the first capacitor and the second capacitor serves as the capacitor connection point of the capacitor bridge arm;

[0065] The first end of the seventh switching transistor is electrically connected to the positive pole of the DC power supply; the second end of the seventh switching transistor is electrically connected to the first end of the eighth switching transistor; the second end of the eighth switching transistor is electrically connected to the negative pole of the DC power supply;

[0066] The connection point of the seventh switching transistor and the eighth switching transistor serves as the redundant connection point of the redundant bridge arm.

[0067] Correspondingly, the embodiment of the present invention provides a fault-tolerant control system for a grid-connected converter, which is applicable to a three-phase grid-connected converter. The three-phase grid-connected converter includes: a DC power supply, a capacitor bridge arm, a three-phase bridge arm, a redundant bridge arm, and an AC power supply that are connected in sequence;

[0068] The three-phase grid-connected converter further includes: a bidirectional thyristor module;

[0069] The capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply;

[0070] The fault-tolerant control system includes: a faulty switching transistor acquisition module, a primary switching transistor fault-tolerant control module, and a secondary switching transistor fault-tolerant control module;

[0071] Among them, the faulty switching transistor acquisition module is used to determine the real-time midpoint voltage of the three-phase grid-connected converter after it is determined that the grid-connected converter has a fault, and determine the position information and switching transistor fault type of the faulty switching transistor of the three-phase grid-connected converter according to the real-time midpoint voltage;

[0072] The primary switch tube fault tolerance control module is used to perform switch switching on the bidirectional thyristor module based on the position information of the faulty switch tube when the switch tube fault type is a primary switch tube fault, so as to complete the fault tolerance control of the primary switch tube fault;

[0073] The secondary switch tube fault tolerance control module is used to perform topology reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switch tube when the switch tube fault type is a secondary switch tube fault, so as to complete the fault tolerance control of the secondary switch tube fault.

[0074] It can be understood that, compared with the prior art, the system of the present invention is connected to the capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm through the bidirectional thyristor module, and can perform topology reconstruction on the three-phase grid-connected converter by controlling the bidirectional thyristor. The position of the faulty switch tube and the switch tube fault type can be determined through the real-time midpoint voltage of the three-phase grid-connected converter, avoiding the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and further improving the reliability of fault tolerance. By performing switch switching on the bidirectional thyristor module during a primary switch tube fault and performing topology reconstruction on the capacitor bridge arm and the redundant bridge arm during a secondary switch tube fault, the combination of the capacitor bridge arm and the redundant bridge arm enables the three-phase grid-connected converter to fully cope with any double-tube fault, thereby improving the reliability and stability of the fault tolerance control of the three-phase grid-connected converter. Description of the Drawings

[0075] Figure 1 : is a flowchart of the steps of a fault tolerance control method for a grid-connected converter provided by an embodiment of the present invention;

[0076] Figure 2 : is a schematic structural diagram of a three-phase grid-connected converter provided by an embodiment of the present invention;

[0077] Figure 3 : is a schematic structural diagram of a fault tolerance control system for a grid-connected converter provided by an embodiment of the present invention;

[0078] Among them, 201: Faulty switch tube acquisition module; 202: Primary switch tube fault tolerance control module; 203: Secondary switch tube fault tolerance control module. Detailed Embodiment

[0079] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0080] Embodiment 1

[0081] Please refer to Figure 1 , which is a flowchart of the steps of a fault-tolerant control method for a grid-connected converter provided by an embodiment of the present invention, including steps S101 to S103.

[0082] Please refer to Figure 2 , which is a schematic structural diagram of a three-phase grid-connected converter provided by an embodiment of the present invention.

[0083] In this embodiment, as Figure 2 shown, the three-phase grid-connected converter includes: a DC power supply, a capacitor bridge arm, a three-phase bridge arm, a redundant bridge arm, and an AC power supply connected in sequence.

[0084] In an optional embodiment, the three-phase bridge arm is connected in series with the DC power supply; the capacitor bridge arm is connected in parallel with the three-phase bridge arm; the redundant bridge arm is connected in parallel with the three-phase bridge arm; each phase of the AC power supply is electrically connected to the corresponding phase bridge arm in the three-phase bridge arm.

[0085] It should be noted that the connections between the DC power supply, the capacitor bridge arm, the three-phase bridge arm, the redundant bridge arm, and the AC power supply described in the above embodiments belong to the connections of a conventional three-phase grid-connected converter, and no further elaboration will be made on this connection here.

[0086] In this embodiment, the three-phase grid-connected converter further includes: a bidirectional thyristor module;

[0087] The capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply.

[0088] In an optional embodiment, as Figure 2 shown, the DC power supply DC can be a DC bus, and the AC power supply includes: phase A u sa , phase B u sb , and phase C u sc .

[0089] In this embodiment, the three-phase bridge arm includes: a phase A bridge arm, a phase B bridge arm, and a phase C bridge arm;

[0090] The phase A bridge arm includes: a first switching tube V1 and a second switching tube V2; the phase B bridge arm includes: a third switching tube V3 and a fourth switching tube V4; the phase C bridge arm includes: a fifth switching tube V5 and a sixth switching tube V6;

[0091] The first ends of the first switch tube V1, the third switch tube V3, and the fifth switch tube V5 are all electrically connected to the positive pole of the DC power supply DC;

[0092] The second end of the first switch tube V1 is electrically connected to the first end of the second switch tube V2; the second end of the third switch tube V3 is electrically connected to the first end of the fourth switch tube V4; the second end of the fifth switch tube V5 is electrically connected to the first end of the sixth switch tube V6;

[0093] The second ends of the second switch tube V2, the fourth switch tube V4, and the sixth switch tube V6 are electrically connected to the negative pole of the DC power supply DC;

[0094] The connection point of the first switch tube V1 and the second switch tube V2 serves as the A-phase connection point a of the A-phase bridge arm and is used for electrical connection with the A-phase u of the AC power supply; sa for electrical connection;

[0095] The connection point of the third switch tube V3 and the fourth switch tube V4 serves as the B-phase connection point b of the B-phase bridge arm and is used for electrical connection with the B-phase u of the AC power supply; sb for electrical connection;

[0096] The connection point of the fifth switch tube V5 and the sixth switch tube V6 serves as the C-phase connection point c of the C-phase bridge arm and is used for electrical connection with the C-phase u of the AC power supply; sc for electrical connection.

[0097] As a preferred solution, the capacitor bridge arm includes a first capacitor C1 and a second capacitor C2; the redundant bridge arm includes: a seventh switch tube V7 and an eighth switch tube V8;

[0098] The first end of the first capacitor C1 is electrically connected to the positive pole of the DC power supply DC; the second end of the first capacitor C1 is electrically connected to the first end of the second capacitor C2; the second end of the second capacitor C2 is electrically connected to the negative pole of the DC power supply DC;

[0099] The connection point of the first capacitor C1 and the second capacitor C2 serves as the capacitor connection point o of the capacitor bridge arm;

[0100] The first end of the seventh switch tube V7 is electrically connected to the positive pole of the DC power supply DC; the second end of the seventh switch tube V7 is electrically connected to the first end of the eighth switch tube V8; the second end of the eighth switch tube V8 is electrically connected to the negative pole of the DC power supply DC;

[0101] The connection point of the seventh switch tube V7 and the eighth switch tube V8 serves as the redundant connection point d of the redundant bridge arm.

[0102] In this embodiment, as Figure 2 shown, the bidirectional thyristor module includes: a first bidirectional thyristor TR1, a second bidirectional thyristor TR2, a third bidirectional thyristor TR3, a fourth bidirectional thyristor TR4, a fifth bidirectional thyristor TR5, and a sixth bidirectional thyristor TR6;

[0103] The first end of the first bidirectional thyristor TR1 is electrically connected to the connection point a of the A phase of the three-phase bridge arm;

[0104] The second end of the first bidirectional thyristor TR1 is electrically connected to the first end of the fifth bidirectional thyristor TR5;

[0105] The first end of the second bidirectional thyristor TR2 is electrically connected to the connection point a of the A phase of the three-phase bridge arm;

[0106] The second end of the second bidirectional thyristor TR2 is electrically connected to the connection point b of the B phase of the three-phase bridge arm;

[0107] The first end of the third bidirectional thyristor TR3 is electrically connected to the connection point a of the A phase of the three-phase bridge arm;

[0108] The second end of the third bidirectional thyristor TR3 is electrically connected to the connection point c of the C phase of the three-phase bridge arm;

[0109] The first end of the fourth bidirectional thyristor TR4 is electrically connected to the redundant connection point d of the redundant bridge arm;

[0110] The second end of the fourth bidirectional thyristor TR4 is electrically connected to the first end of the fifth bidirectional thyristor TR5;

[0111] The second end of the fifth bidirectional thyristor TR5 is electrically connected to the A phase u sa of the AC power supply;

[0112] The first end of the sixth bidirectional thyristor TR6 is electrically connected to the capacitor connection point o of the capacitor bridge arm;

[0113] The second end of the sixth bidirectional thyristor TR6 is electrically connected to the second end of the fifth bidirectional thyristor TR5.

[0114] In this embodiment, by electrically connecting the bidirectional thyristors in the bidirectional thyristor module to the three-phase bridge arm, the capacitor bridge arm, the redundant bridge arm, and the AC power supply, it is possible to achieve fault-tolerant control of any primary switch tube fault and secondary switch tube fault of the three-phase grid-connected converter by controlling the conduction and turn-off of the bidirectional thyristors, improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0115] In an alternative embodiment, as Figure 2As shown, the three-phase grid-connected converter further includes: a first fuse L f1 , a second fuse L f2 , a third fuse L f3 , a fourth fuse L f4 , a fifth fuse L f5 and a sixth fuse L f6 ;

[0116] The first end of the first fuse L f1 is electrically connected to the second end of the fifth bidirectional thyristor TR5;

[0117] The second end of the first fuse L f1 is electrically connected to the first end of the fourth fuse L f4 ;

[0118] The second end of the fourth fuse L f4 is electrically connected to the A-phase u sa of the AC power supply;

[0119] The first end of the second fuse L f2 is electrically connected to the B-phase connection point b;

[0120] The second end of the second fuse L f2 is electrically connected to the first end of the fifth fuse L f5 ;

[0121] The second end of the fifth fuse L f5 is electrically connected to the B-phase u sb of the AC power supply;

[0122] The first end of the third fuse L f3 is electrically connected to the C-phase connection point c;

[0123] The second end of the third fuse L f3 is electrically connected to the first end of the sixth fuse L f6 ;

[0124] The second end of the sixth fuse L f6 is electrically connected to the C-phase u sc of the AC power supply.

[0125] In this alternative embodiment, by connecting the fuses in series, it is ensured that the fuse blows when a short-circuit fault occurs in the three-phase grid-connected converter, converting the short-circuit fault into an open-circuit fault, which can cut off excessive current and prevent secondary faults in the three-phase grid-connected converter. Furthermore, subsequent fault-tolerant control can be performed on the three-phase grid-connected converter, enabling the three-phase grid-connected converter to continue to operate continuously.

[0126] In an optional embodiment, as Figure 2 shown, the three-phase grid-connected converter further includes: a first filter capacitor C f1 , a second filter capacitor C f2 and a third filter capacitor C f3 ;

[0127] The first end of the first filter capacitor C f1 is electrically connected to the second end of the first fuse L f1 ;

[0128] The first end of the second filter capacitor C f2 is electrically connected to the second end of the second fuse L f2 ;

[0129] The first end of the third filter capacitor C f3 is electrically connected to the second end of the third fuse L f3 ;

[0130] The second ends of the first filter capacitor C f1 , the second filter capacitor C f2 and the third filter capacitor C f3 are grounded;

[0131] The connection point n of the first filter capacitor C f1 , the second filter capacitor C f2 and the third filter capacitor C f3 serves as the neutral point of the AC power supply of the three-phase grid-connected converter.

[0132] In this optional embodiment, by setting the first filter capacitor C f1 , the second filter capacitor C f2 and the third filter capacitor C f3 , it is possible to buffer the voltage fluctuations in the three-phase grid-connected converter and improve the stability of the three-phase grid-connected converter.

[0133] Step S101: After determining that the grid-connected converter has a fault, obtain the real-time neutral point voltage of the three-phase grid-connected converter, and determine the position information of the faulty switch tube and the type of switch tube fault of the three-phase grid-connected converter according to the real-time neutral point voltage.

[0134] In this embodiment, the step of, after determining that the grid-connected converter has a fault, obtaining the real-time neutral point voltage of the three-phase grid-connected converter, and determining the position information of the faulty switch tube and the type of switch tube fault of the three-phase grid-connected converter according to the real-time neutral point voltage specifically includes:

[0135] After determining that a fault has occurred in the grid-connected converter, obtain the voltage difference between the midpoint of the capacitor leg and the neutral point of the AC power supply, determine the real-time midpoint voltage of the three-phase grid-connected converter, and record the fault duration of the three-phase grid-connected converter;

[0136] Determine the real-time midpoint voltage deviation based on the real-time midpoint voltage;

[0137] Obtain the midpoint voltage deviation threshold of the three-phase leg, compare the real-time midpoint voltage deviation with the midpoint voltage deviation threshold, and determine the real-time switching state of the three-phase leg;

[0138] After determining that the fault duration is greater than or equal to the preset fault time threshold, determine the position information and quantity of the faulty switch tubes based on the real-time switching state of the three-phase leg;

[0139] Determine the switch tube fault type of the three-phase grid-connected converter based on the quantity of the faulty switch tubes.

[0140] In an alternative embodiment, the voltage difference u between the midpoint of the capacitor leg (i.e., the capacitor connection point o of the DC-side capacitor leg) and the neutral point of the AC power supply (i.e., the connection point n) on is used as the real-time midpoint voltage, and the real-time midpoint voltage deviation is determined based on the real-time midpoint voltage; when an open-circuit fault occurs in a switch tube, different switching states thereof will result in different midpoint voltage deviations.

[0141] Taking the first switch tube V1 as an example, when the first switch tube V1 is operating normally without a fault, the midpoint voltage is:

[0142]

[0143] The midpoint voltage in the case of a fault is:

[0144]

[0145] In the formula, S a 、S b and S c respectively represent the switching states of the A-phase leg, B-phase leg, and C-phase leg in the three-phase leg. When the value is 0, it means that the upper-bridge-arm switch tube in the corresponding phase leg is conducting and the lower-bridge-arm switch tube is off; when the value is 1, it means that the upper-bridge-arm switch tube in the corresponding phase leg is off and the lower-bridge-arm switch tube is conducting; the upper-bridge-arm switch tubes are the first switch tube V1, the third switch tube V3, and the fifth switch tube V5, and the lower-bridge-arm switch tubes are the second switch tube V2, the fourth switch tube V4, and the sixth switch tube V6; u dc represents the voltage value of the DC power supply (DC bus); u sa is the grid voltage value of phase A (i.e., phase A of the AC power supply);

[0146] Therefore, the midpoint voltage deviation Δu on is 0 when S a = 0,

[0147] and is a when S

[0148] The midpoint voltage deviation will take the maximum value when the switching states of the three-phase bridge arms are (S a , S b , S c ) = (1, 0, 0), and this maximum value is taken as the midpoint voltage deviation threshold u m corresponding to the switching state when the first switching tube V1 fails;

[0149] After obtaining the midpoint voltage deviation threshold of the first switching tube V1, the corresponding midpoint voltage deviation thresholds of the other switching tubes can be obtained in the same way;

[0150] After determining that the grid-connected converter has a fault, obtain the voltage difference between the midpoint of the capacitor bridge arm (i.e., connection point o) and the neutral point of the AC power supply (i.e., connection point n), determine the real-time midpoint voltage of the three-phase grid-connected converter, and record the fault duration T c of the three-phase grid-connected converter; Determine the real-time midpoint voltage deviation according to the real-time midpoint voltage, obtain the above midpoint voltage deviation threshold, compare the real-time midpoint voltage deviation with the midpoint voltage deviation threshold, filter out the midpoint voltage deviation threshold that is less than the absolute value of the real-time midpoint voltage deviation, and determine the real-time switching state of the three-phase bridge arm based on the filtered midpoint voltage deviation threshold;

[0151] Determine the fault duration T c is greater than or equal to the preset fault time threshold T0, and determine the position information and quantity of the faulty switching tube based on the real-time switching state of the three-phase bridge arm; Among them, the quantity of the faulty switching tube can also be determined based on the quantity of the filtered midpoint voltage deviation threshold;

[0152] Determine the switching tube fault type of the three-phase grid-connected converter based on the quantity of the faulty switching tube. When only one switching tube fails, it is a primary switching tube fault (i.e., single-tube fault), and when only two switching tubes fail, it is a secondary switching tube fault (i.e., double-tube fault).

[0153] In this embodiment, by determining the real-time midpoint voltage of the three-phase grid-connected converter, and then determining the position information and quantity of the faulty switch, it avoids the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improves the efficiency of fault detection of the grid-connected converter, and improves the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter by judging the fault duration.

[0154] Step S102: When the fault type of the switching tube is a primary switching tube fault, perform a switching operation on the bidirectional thyristor module based on the position information of the faulty switching tube, so as to complete the fault tolerance control for the primary switching tube fault.

[0155] In this embodiment, the performing a switching operation on the bidirectional thyristor module based on the position information of the faulty switching tube when the fault type of the switching tube is a primary switching tube fault, so as to complete the fault tolerance control for the primary switching tube fault specifically includes:

[0156] When the fault type of the switching tube is a primary switching tube fault and the position information of the faulty switching tube is an A-phase bridge arm fault, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor, so as to complete the fault tolerance control for the primary switching tube fault;

[0157] When the fault type of the switching tube is a primary switching tube fault and the position information of the faulty switching tube is a B-phase bridge arm fault, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the second bidirectional thyristor, so as to complete the fault tolerance control for the primary switching tube fault;

[0158] When the fault type of the switching tube is a primary switching tube fault and the position information of the faulty switching tube is a C-phase bridge arm fault, turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the third bidirectional thyristor, so as to complete the fault tolerance control for the primary switching tube fault.

[0159] In an alternative embodiment, please refer to Table 1, which is a schematic table of the reconstruction operation for coping with the primary switching tube fault provided by the embodiment of the present invention;

[0160] Table 1

[0161]

[0162] As shown in Table 1, when the three-phase grid-connected converter is in the rated operating state, the first bidirectional thyristor TR1 and the fifth bidirectional thyristor TR5 are turned on, and the rest of the switching tubes are turned off.

[0163] When the fault type of the switching tube is a primary switching tube fault and the position information of the faulty switching tube is the first switching tube V1 or the second switching tube V2 fault (i.e., an A-phase bridge arm fault), turn off the first bidirectional thyristor TR1 and turn on the fourth bidirectional thyristor TR4. At this time, the reconstructed A-phase bridge arm is composed of the seventh switching tube V7 and the eighth switching tube V8.

[0164] When the fault type of the switching tube is a primary switching tube fault, and the position information of the faulty switching tube is that the third switching tube V3 or the fourth switching tube V4 is faulty (i.e., when the B-phase bridge arm is faulty), turn off the first bidirectional thyristor TR1, turn on the fourth bidirectional thyristor TR4 and the second bidirectional thyristor TR2. At this time, the reconstructed A-phase bridge arm is composed of the seventh switching tube V7 and the eighth switching tube V8, and the B-phase bridge arm is composed of the first switching tube V1 and the second switching tube V2.

[0165] When the fault type of the switching tube is a primary switching tube fault, and the position information of the faulty switching tube is that the fifth switching tube V5 or the sixth switching tube V6 is faulty (i.e., when the C-phase bridge arm is faulty), turn off the first bidirectional thyristor TR1, turn on the fourth bidirectional thyristor TR4 and the third bidirectional thyristor TR3. At this time, the reconstructed A-phase bridge arm is composed of the seventh switching tube V7 and the eighth switching tube V8, and the C-phase bridge arm is composed of the first switching tube V1 and the second switching tube V2.

[0166] In this embodiment, by judging the bridge arm position when a primary switching tube fault occurs, and turning off and turning on the corresponding bidirectional thyristors, the form of adding redundant bridge arms can cope with any primary switching tube fault of the three-phase grid-connected converter, improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0167] Step S103: When the fault type of the switching tube is a secondary switching tube fault, perform topological reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switching tube to complete the fault-tolerant control of the secondary switching tube fault.

[0168] In this embodiment, when the fault type of the switching tube is a secondary switching tube fault, performing topological reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switching tube to complete the fault-tolerant control of the secondary switching tube fault specifically includes:

[0169] When the fault type of the switching tube is a secondary switching tube fault, determine the first faulty switching tube and the second faulty switching tube based on the fault time sequence of the faulty switching tube;

[0170] Perform fault-tolerant control of the primary switching tube fault on the first faulty switching tube;

[0171] After completing the fault-tolerant control of the first faulty switching tube, perform topological reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position of the second faulty switching tube to complete the fault-tolerant control of the secondary switching tube fault.

[0172] In this embodiment, by judging the fault time sequence during the secondary switch tube failure, based on the fault-tolerant control of the primary switch tube failure, the form of adding a capacitor bridge arm can cope with any secondary switch tube failure of the three-phase grid-connected converter, improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0173] In this embodiment, based on the position of the second faulty switch tube, topological reconstruction is performed on the capacitor bridge arm and the redundant bridge arm to complete the fault-tolerant control of the secondary switch tube failure, specifically including:

[0174] When the second faulty switch tube is located in the redundant bridge arm, turn on the sixth bidirectional thyristor to make the capacitor bridge arm serve as the new phase-A bridge arm, completing the fault-tolerant control of the secondary switch tube failure;

[0175] When the second faulty switch tube is located in the phase-A bridge arm, turn on the sixth bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor to make the capacitor bridge arm serve as the new phase-A bridge arm, completing the fault-tolerant control of the secondary switch tube failure;

[0176] When the second faulty switch tube is located in the phase-B bridge arm, turn on the sixth bidirectional thyristor, the second bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor to make the capacitor bridge arm serve as the new phase-A bridge arm, and to make the redundant bridge arm replace the bridge arm corresponding to the first faulty switch tube, completing the fault-tolerant control of the secondary switch tube failure;

[0177] When the second faulty switch tube is located in the phase-C bridge arm, turn on the sixth bidirectional thyristor, the third bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor to make the capacitor bridge arm serve as the new phase-A bridge arm, and to make the redundant bridge arm replace the bridge arm corresponding to the first faulty switch tube, completing the fault-tolerant control of the secondary switch tube failure.

[0178] In an alternative embodiment, please refer to Table 2, which is a schematic table of reconstruction operations for coping with secondary switch tube failures using a redundant bridge arm and a capacitor bridge arm provided by an embodiment of the present invention;

[0179] Table 2

[0180]

[0181]

[0182] In an alternative embodiment, as shown in Table 1 and Table 2, when the switch tube failure type is a secondary switch tube failure, based on the fault time sequence of the faulty switch tube, the first faulty switch tube and the second faulty switch tube are determined, where the first faulty switch tube fails earlier than the second faulty switch tube;

[0183] According to the reconstruction operation shown in Table 1, perform fault tolerance control for the first faulty switch tube for a switch tube fault.

[0184] When the second faulty switch tube is located at the seventh switch tube V7 or the eighth switch tube V8 (i.e., the redundant bridge arm), turn on the sixth bidirectional thyristor TR6; at this time, the reconstructed phase A bridge arm is composed of the first capacitor C1 and the second capacitor C2.

[0185] When the second faulty switch tube is located at the first switch tube V1 or the second switch tube V2 (i.e., the phase A bridge arm), and the first faulty switch tube is located at the third switch tube V3 or the fourth switch tube V4 (i.e., the phase B bridge arm), turn on the sixth bidirectional thyristor TR6 and the first bidirectional thyristor TR1, and turn off the fifth bidirectional thyristor TR5. At this time, the reconstructed phase A bridge arm is composed of the first capacitor C1 and the second capacitor C2, and the phase B bridge arm is composed of the seventh switch tube V7 and the eighth switch tube V8.

[0186] When the second faulty switch tube is located at the first switch tube V1 or the second switch tube V2 (i.e., the phase A bridge arm), and the first faulty switch tube is located at the fifth switch tube V5 or the sixth switch tube V6 (i.e., the phase C bridge arm), turn on the sixth bidirectional thyristor TR6 and the first bidirectional thyristor TR1, and turn off the fifth bidirectional thyristor TR5. At this time, the reconstructed phase A bridge arm is composed of the first capacitor C1 and the second capacitor C2, and the phase C bridge arm is composed of the seventh switch tube V7 and the eighth switch tube V8.

[0187] When the second faulty switch tube is located at the third switch tube V3 or the fourth switch tube V4 (i.e., the phase B bridge arm), turn on the sixth bidirectional thyristor TR6, the second bidirectional thyristor TR2, and the first bidirectional thyristor TR1, and turn off the fifth bidirectional thyristor TR5. At this time, the reconstructed phase A bridge arm is composed of the first capacitor C1 and the second capacitor C2, and the phase B bridge arm is composed of the seventh switch tube V7 and the eighth switch tube V8.

[0188] When the second faulty switch tube is located at the fifth switch tube V5 or the sixth switch tube V6 (i.e., the phase C bridge arm), turn on the sixth bidirectional thyristor TR6, the third bidirectional thyristor TR3, and the first bidirectional thyristor TR1, and turn off the fifth bidirectional thyristor TR5. At this time, the reconstructed phase A bridge arm is composed of the first capacitor C1 and the second capacitor C2, and the phase C bridge arm is composed of the seventh switch tube V7 and the eighth switch tube V8.

[0189] In this embodiment, by judging the bridge arm position where the faulty switch tube is located, and conducting and turning off the corresponding bidirectional thyristors, it is possible to cope with any secondary switch tube fault of the three-phase grid-connected converter in the form of adding a capacitor bridge arm, improving the reliability and stability of the fault tolerance control of the three-phase grid-connected converter.

[0190] In this embodiment, the capacitor neutral point control and space vector modulation of the three-phase grid-connected converter specifically include:

[0191] Obtain the voltage value information of the capacitors in the current capacitor bridge arm and the rated modulation wave of each phase in the three-phase grid-connected converter;

[0192] Determine the DC bias voltage according to the voltage value information and a preset low-pass filter, and determine the faulty phase and non-faulty phases of the three-phase grid-connected converter according to the first faulty switch tube and the second faulty switch tube;

[0193] Determine the corrected modulation wave of the faulty phase according to the DC bias voltage, a preset proportional regulator, and the rated modulation wave, and complete the capacitor neutral point control of the three-phase grid-connected converter;

[0194] Obtain the zero vector of the three-phase grid-connected converter according to a preset volt-second balance algorithm, and determine the duty cycle of the non-faulty phases based on the zero vector to complete the space vector modulation of the three-phase grid-connected converter.

[0195] In an alternative embodiment, obtain the voltage value information of the capacitors in the current capacitor bridge arm, that is, the voltage values of the first capacitor C1 and the second capacitor C2. After subtracting the voltage values of the first capacitor C1 and the second capacitor C2, extract the DC bias voltage through a preset low-pass filter Wherein, is the bias voltage across the second capacitor C2, is the bias voltage across the second capacitor C1. After that, add the DC bias voltage to the modulation wave voltage of the faulty phase through a proportional regulator to obtain the corrected modulation wave of the faulty phase;

[0196] Taking the A-phase fault as an example, the corrected modulation wave of the A phase is: Wherein, u ra is the rated modulation wave, u ′ ra is the corrected modulation wave, and K is the gain of the proportional regulator.

[0197] It should be noted that before the three-phase grid-connected converter fails, it adopts vector control based on voltage orientation. The modulation waves of the A phase, B phase, and C phase are respectively compared with the triangular carrier wave to obtain the switching pulses of their respective phases.

[0198] In an alternative embodiment, there are 6 basic vectors in the space vector adjustment of the three-phase grid-connected converter before the fault. After fault-tolerant control, there are only two basic vectors in operation. Equivalently synthesize two of the opposite basic vectors, and then obtain the zero vector of the three-phase grid-connected converter according to the volt-second balance principle, and further deduce the duty cycles of the two non-faulty phases in the vector plane;

[0199] Taking the A-phase fault and the normal operation of the B-phase and C-phase as an example, at this time, there are:

[0200]

[0201] In the formula, d b and d c are the duty cycles of the B-phase and C-phase respectively, V DC2 is the voltage of the second capacitor, u ra , u rb and u rc are the rated modulation waves of the A-phase, B-phase and C-phase respectively; V DC is the voltage of the DC bus.

[0202] In this embodiment, by performing capacitor neutral point control and space vector modulation on the three-phase grid-connected converter, the three-phase grid-connected converter after topology reconstruction can be further regulated, thereby improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0203] In this embodiment, the bidirectional thyristor module is connected to the capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm, and the topology of the three-phase grid-connected converter can be reconstructed by controlling the bidirectional thyristor. The position of the faulty switch tube and the type of switch tube fault can be determined through the real-time neutral point voltage of the three-phase grid-connected converter, avoiding the low measurement efficiency caused by the need to measure the three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and further improving the reliability of fault tolerance. By switching the bidirectional thyristor module during the first switch tube fault and reconstructing the topology of the capacitor bridge arm and the redundant bridge arm during the second switch tube fault, and combining the capacitor bridge arm and the redundant bridge arm, the three-phase grid-connected converter can fully cope with any double-tube fault, thereby improving the reliability and stability of the fault-tolerant control of the three-phase grid-connected converter.

[0204] Embodiment 2

[0205] Please refer to Figure 3 , which is a schematic structural diagram of a fault-tolerant control system of a grid-connected converter provided by an embodiment of the present invention. The fault-tolerant control system is applicable to a three-phase grid-connected converter, and the three-phase grid-connected converter includes: a DC power supply, a capacitor bridge arm, a three-phase bridge arm, a redundant bridge arm and an AC power supply connected in sequence;

[0206] The three-phase grid-connected converter further includes: a bidirectional thyristor module;

[0207] The capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply.

[0208] In this embodiment, the bidirectional thyristor module includes: a first bidirectional thyristor, a second bidirectional thyristor, a third bidirectional thyristor, a fourth bidirectional thyristor, a fifth bidirectional thyristor, and a sixth bidirectional thyristor;

[0209] The first end of the first bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm;

[0210] The second end of the first bidirectional thyristor is electrically connected to the first end of the fifth bidirectional thyristor;

[0211] The first end of the second bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm;

[0212] The second end of the second bidirectional thyristor is electrically connected to the B-phase connection point of the three-phase bridge arm;

[0213] The first end of the third bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm;

[0214] The second end of the third bidirectional thyristor is electrically connected to the C-phase connection point of the three-phase bridge arm;

[0215] The first end of the fourth bidirectional thyristor is electrically connected to the redundant connection point of the redundant bridge arm;

[0216] The second end of the fourth bidirectional thyristor is electrically connected to the first end of the fifth bidirectional thyristor;

[0217] The second end of the fifth bidirectional thyristor is electrically connected to the A-phase of the AC power supply;

[0218] The first end of the sixth bidirectional thyristor is electrically connected to the capacitor connection point of the capacitor bridge arm;

[0219] The second end of the sixth bidirectional thyristor is electrically connected to the second end of the fifth bidirectional thyristor.

[0220] In this embodiment, the three-phase bridge arm includes: an A-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm;

[0221] The A-phase bridge arm includes: a first switching tube and a second switching tube; the B-phase bridge arm includes: a third switching tube and a fourth switching tube; the C-phase bridge arm includes: a fifth switching tube and a sixth switching tube;

[0222] The first ends of the first switching tube, the third switching tube, and the fifth switching tube are all electrically connected to the positive pole of the DC power supply;

[0223] The second terminal of the first switching tube is electrically connected to the first terminal of the second switching tube; the second terminal of the third switching tube is electrically connected to the first terminal of the fourth switching tube; the second terminal of the fifth switching tube is electrically connected to the first terminal of the sixth switching tube;

[0224] The second terminals of the second switching tube, the fourth switching tube, and the sixth switching tube are electrically connected to the negative pole of the DC power supply;

[0225] The connection point of the first switching tube and the second switching tube serves as the A-phase connection point of the A-phase bridge arm and is used to be electrically connected to the A-phase of the AC power supply;

[0226] The connection point of the third switching tube and the fourth switching tube serves as the B-phase connection point of the B-phase bridge arm and is used to be electrically connected to the B-phase of the AC power supply;

[0227] The connection point of the fifth switching tube and the sixth switching tube serves as the C-phase connection point of the C-phase bridge arm and is used to be electrically connected to the C-phase of the AC power supply.

[0228] In this embodiment, the capacitor bridge arm includes a first capacitor and a second capacitor; the redundant bridge arm includes: a seventh switching tube and an eighth switching tube;

[0229] The first terminal of the first capacitor is electrically connected to the positive pole of the DC power supply; the second terminal of the first capacitor is electrically connected to the first terminal of the second capacitor; the second terminal of the second capacitor is electrically connected to the negative pole of the DC power supply;

[0230] The connection point of the first capacitor and the second capacitor serves as the capacitor connection point of the capacitor bridge arm;

[0231] The first terminal of the seventh switching tube is electrically connected to the positive pole of the DC power supply; the second terminal of the seventh switching tube is electrically connected to the first terminal of the eighth switching tube; the second terminal of the eighth switching tube is electrically connected to the negative pole of the DC power supply;

[0232] The connection point of the seventh switching tube and the eighth switching tube serves as the redundant connection point of the redundant bridge arm.

[0233] The fault-tolerant control system includes: a faulty switching tube acquisition module 201, a primary switching tube fault-tolerant control module 202, and a secondary switching tube fault-tolerant control module 203.

[0234] Among them, the faulty switching tube acquisition module 201 is used to determine the real-time neutral point voltage of the three-phase grid-connected converter after the grid-connected converter fails, and determine the position information and switching tube fault type of the faulty switching tube of the three-phase grid-connected converter according to the real-time neutral point voltage.

[0235] In this embodiment, the faulty switch tube acquisition module 201 includes: a faulty switch tube acquisition unit;

[0236] The faulty switch tube acquisition unit is configured to, after determining that the grid-connected converter fails, acquire the voltage difference between the midpoint of the capacitor bridge arm and the neutral point of the AC power supply, determine the real-time midpoint voltage of the three-phase grid-connected converter, and record the fault duration of the three-phase grid-connected converter;

[0237] Determine the real-time midpoint voltage deviation according to the real-time midpoint voltage; [[ID=SE7]]

[0238] Acquire the midpoint voltage deviation threshold of the three-phase bridge arm, compare the real-time midpoint voltage deviation with the midpoint voltage deviation threshold, and determine the real-time switching state of the three-phase bridge arm;

[0239] After determining that the fault duration is greater than or equal to the preset fault time threshold, determine the position information and quantity of the faulty switch tube based on the real-time switching state of the three-phase bridge arm;

[0240] Determine the switch tube fault type of the three-phase grid-connected converter based on the quantity of the faulty switch tube.

[0241] When the switch tube fault type is a primary switch tube fault, the primary switch tube fault tolerance control module 202 is configured to perform switch switching on the bidirectional thyristor module based on the position information of the faulty switch tube, so as to complete the fault tolerance control of the primary switch tube fault.

[0242] In this embodiment, the primary switch tube fault tolerance control module 202 includes: a primary switch tube fault tolerance control unit;

[0243] When the switch tube fault type is a primary switch tube fault and the position information of the faulty switch tube is a fault in the A-phase bridge arm, the primary switch tube fault tolerance control unit is configured to turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor, so as to complete the fault tolerance control of the primary switch tube fault;

[0244] When the switch tube fault type is a primary switch tube fault and the position information of the faulty switch tube is a fault in the B-phase bridge arm, the primary switch tube fault tolerance control unit is configured to turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the second bidirectional thyristor, so as to complete the fault tolerance control of the primary switch tube fault;

[0245] When the switch tube fault type is a primary switch tube fault and the position information of the faulty switch tube is a fault in the C-phase bridge arm, the primary switch tube fault tolerance control unit is configured to turn off the first bidirectional thyristor and turn on the fourth bidirectional thyristor and the third bidirectional thyristor, so as to complete the fault tolerance control of the primary switch tube fault.

[0246] The secondary switch tube fault tolerance control module 203 is configured to perform topology reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switch tube when the switch tube fault type is a secondary switch tube fault, so as to complete the fault tolerance control of the secondary switch tube fault.

[0247] In this embodiment, the secondary switch tube fault tolerance control module 203 includes: a secondary switch tube fault tolerance control unit;

[0248] The secondary switch tube fault tolerance control unit is configured to determine a first faulty switch tube and a second faulty switch tube based on the chronological order of the fault time of the faulty switch tube when the switch tube fault type is a secondary switch tube fault;

[0249] Perform fault tolerance control for the first faulty switch tube for a primary switch tube fault;

[0250] After completing the fault tolerance control for the first faulty switch tube, perform topology reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position of the second faulty switch tube, and perform capacitor neutral point control and space vector modulation on the three-phase grid-connected converter, so as to complete the fault tolerance control of the secondary switch tube fault.

[0251] In this embodiment, the secondary switch tube fault tolerance control unit includes: a topology reconstruction sub-unit;

[0252] The topology reconstruction sub-unit is configured to turn on the sixth bidirectional thyristor when the second faulty switch tube is located in the redundant bridge arm, so that the capacitor bridge arm serves as a new phase-A bridge arm to complete the fault tolerance control of the secondary switch tube fault;

[0253] When the second faulty switch tube is located in the phase-A bridge arm, turn on the sixth bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor, so that the capacitor bridge arm serves as a new phase-A bridge arm to complete the fault tolerance control of the secondary switch tube fault;

[0254] When the second faulty switch tube is located in the phase-B bridge arm, turn on the sixth bidirectional thyristor, the second bidirectional thyristor and the first bidirectional thyristor, and turn off the fifth bidirectional thyristor, so that the capacitor bridge arm serves as a new phase-A bridge arm, and so that the redundant bridge arm replaces the bridge arm corresponding to the first faulty switch tube to complete the fault tolerance control of the secondary switch tube fault;

[0255] When the second fault switch tube is located in the C phase bridge arm, the sixth bidirectional thyristor, the third bidirectional thyristor and the first bidirectional thyristor are turned on, and the fifth bidirectional thyristor is turned off, so that the capacitor bridge arm serves as the new A phase bridge arm, and the redundant bridge arm replaces the bridge arm corresponding to the first fault switch tube, thereby completing the fault-tolerant control of the secondary switch tube failure.

[0256] In this embodiment, the secondary switch tube fault tolerance control unit includes: a grid-connected converter control subunit;

[0257] The grid-connected converter control subunit is used to obtain the current voltage value information of the capacitor in the capacitor bridge arm and the rated modulation wave of each phase in the three-phase grid-connected converter;

[0258] Determining a DC bias voltage according to the voltage value information and a preset low-pass filter, and determining a fault phase and a non-fault phase of the three-phase grid-connected converter according to the first fault switch tube and the second fault switch tube;

[0259] determining a modified modulation wave of the fault phase according to the DC bias voltage, a preset proportional regulator, and a rated modulation wave, thereby completing capacitor neutral point control of the three-phase grid-connected converter;

[0260] The zero vector of the three-phase grid-connected converter is obtained according to a preset volt-second balance algorithm, and the duty cycle of the non-fault phase is determined based on the zero vector to complete space vector modulation of the three-phase grid-connected converter.

[0261] This embodiment connects the bidirectional thyristor module with the capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm, and can reconfigure the topology of the three-phase grid-connected converter by controlling the bidirectional thyristor. The real-time midpoint voltage of the three-phase grid-connected converter can determine the position of the faulty switch tube and the type of switch tube fault, avoiding the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and thus improving the reliability of fault tolerance. By switching the bidirectional thyristor module when the primary switch tube fails, and reconfiguring the topology of the capacitor bridge arm and the redundant bridge arm when the secondary switch tube fails, the combination of the capacitor bridge arm and the redundant bridge arm enables the three-phase grid-connected converter to fully cope with any dual-tube fault, thereby improving the reliability and stability of the fault-tolerant fault control of the three-phase grid-connected converter.

[0262] In summary, this embodiment connects the bidirectional thyristor module with the capacitor bridge arm, the three-phase bridge arm, and the redundant bridge arm, and can reconfigure the topology of the three-phase grid-connected converter by controlling the bidirectional thyristor. The real-time midpoint voltage of the three-phase grid-connected converter can determine the position of the faulty switch tube and the type of switch tube fault, avoiding the low measurement efficiency caused by the need to measure all three-phase voltages in the prior art, improving the efficiency of fault detection of the grid-connected converter, and thus improving the reliability of fault tolerance. By switching the bidirectional thyristor module when the primary switch tube fails, and topologically reconfiguring the capacitor bridge arm and the redundant bridge arm when the secondary switch tube fails, the combination of the capacitor bridge arm and the redundant bridge arm enables the three-phase grid-connected converter to fully cope with any dual-tube fault, thereby improving the reliability and stability of the fault-tolerant fault control of the three-phase grid-connected converter.

[0263] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A fault-tolerant control method for a grid-connected converter, applicable to a three-phase grid-connected converter, the three-phase grid-connected converter comprising: A DC power supply, a capacitor bridge arm, a three-phase bridge arm, a redundant bridge arm, and an AC power supply connected in sequence; Characterized in that, the three-phase grid-connected converter further comprises: a bidirectional thyristor module; The capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply; The fault-tolerant control method comprises: After determining that the grid-connected converter has a fault, obtaining the real-time midpoint voltage of the three-phase grid-connected converter, and determining the position information and the fault type of the faulty switch tube of the three-phase grid-connected converter according to the real-time midpoint voltage; When the switch tube fault type is a primary switch tube fault, switching the bidirectional thyristor module based on the position information of the faulty switch tube to complete fault tolerance control of the primary switch tube fault; When the switch tube failure type is a secondary switch tube failure, the capacitor bridge arm and the redundant bridge arm are topologically reconstructed based on the position information of the faulty switch tube to complete fault-tolerant control of the secondary switch tube failure.

2. The fault-tolerant control method for a grid-connected converter according to claim 1, wherein: The bidirectional thyristor module includes: a first bidirectional thyristor, a second bidirectional thyristor, a third bidirectional thyristor, a fourth bidirectional thyristor, a fifth bidirectional thyristor and a sixth bidirectional thyristor; The first end of the first bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm; The second end of the first bidirectional thyristor is electrically connected to the first end of the fifth bidirectional thyristor; The first end of the second bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm; The second end of the second bidirectional thyristor is electrically connected to the B-phase connection point of the three-phase bridge arm; The first end of the third bidirectional thyristor is electrically connected to the A-phase connection point of the three-phase bridge arm; The second end of the third bidirectional thyristor is electrically connected to the C-phase connection point of the three-phase bridge arm; The first end of the fourth bidirectional thyristor is electrically connected to the redundant connection point of the redundant bridge arm; The second end of the fourth bidirectional thyristor is electrically connected to the first end of the fifth bidirectional thyristor; The second end of the fifth bidirectional thyristor is electrically connected to phase A of the AC power supply; The first end of the sixth bidirectional thyristor is electrically connected to the capacitor connection point of the capacitor bridge arm; The second end of the sixth bidirectional thyristor is electrically connected to the second end of the fifth bidirectional thyristor.

3. The fault-tolerant control method for a grid-connected converter according to claim 1, wherein: After determining that the grid-connected converter has failed, obtaining the real-time midpoint voltage of the three-phase grid-connected converter, and determining the position information and the fault type of the faulty switch tube of the three-phase grid-connected converter according to the real-time midpoint voltage, specifically includes: After determining that the grid-connected converter has a fault, obtaining a voltage difference between a midpoint of a capacitor bridge arm and a neutral point of an AC power supply, determining a real-time midpoint voltage of the three-phase grid-connected converter, and recording a fault duration of the three-phase grid-connected converter; determining a real-time midpoint voltage deviation according to the real-time midpoint voltage; Obtaining a midpoint voltage deviation threshold of the three-phase bridge arm, comparing the real-time midpoint voltage deviation with the midpoint voltage deviation threshold, and determining the real-time switching state of the three-phase bridge arm; After determining that the fault duration is greater than or equal to a preset fault time threshold, determining the location information and number of the faulty switching tubes based on the real-time switching state of the three-phase bridge arm; The fault type of the switch tube of the three-phase grid-connected converter is determined based on the number of the faulty switch tubes.

4. The fault-tolerant control method for a grid-connected converter according to claim 2, characterized in that, When the switch tube fault type is a primary switch tube fault, switching the bidirectional thyristor module based on the position information of the faulty switch tube to complete fault tolerance control of the primary switch tube fault specifically includes: When the switch tube fault type is a primary switch tube fault and the location information of the faulty switch tube is a phase A bridge arm fault, turning off the first bidirectional thyristor and turning on the fourth bidirectional thyristor to complete fault tolerance control of the primary switch tube fault; When the switch tube fault type is a primary switch tube fault and the location information of the faulty switch tube is a B-phase bridge arm fault, turning off the first bidirectional thyristor and turning on the fourth bidirectional thyristor and the second bidirectional thyristor to complete fault-tolerant control of the primary switch tube fault; When the switch tube fault type is a primary switch tube fault and the location information of the faulty switch tube is a C-phase bridge arm fault, the first bidirectional thyristor is turned off, and the fourth bidirectional thyristor and the third bidirectional thyristor are turned on to complete fault-tolerant control of the primary switch tube fault.

5. The fault-tolerant control method for a grid-connected converter according to claim 2, wherein: When the switch tube fault type is a secondary switch tube fault, reconstructing the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switch tube to complete fault-tolerant control of the secondary switch tube fault specifically includes: When the fault type of the switch tube is a secondary switch tube fault, determining a first faulty switch tube and a second faulty switch tube based on a fault time sequence of the faulty switch tube; Performing a fault-tolerant control of the first faulty switch tube; After completing the fault-tolerant control of the first fault switch tube, the capacitor bridge arm and the redundant bridge arm are topologically reconstructed based on the position of the second fault switch tube, and the capacitor neutral point control and space vector modulation are performed on the three-phase grid-connected converter to complete the fault-tolerant control of the secondary switch tube fault.

6. The fault-tolerant control method of a grid-connected converter according to claim 5, characterized in that, The topological reconstruction of the capacitor bridge arm and the redundant bridge arm based on the position of the second faulty switch tube to complete the fault-tolerant control of the secondary switch tube failure specifically includes: When the second fault switch is located in the redundant bridge arm, the sixth bidirectional thyristor is turned on to make the capacitor bridge arm serve as the new A-phase bridge arm, thereby completing the fault-tolerant control of the secondary switch failure; When the second fault switch is located in the A-phase bridge arm, the sixth bidirectional thyristor and the first bidirectional thyristor are turned on, and the fifth bidirectional thyristor is turned off, so that the capacitor bridge arm serves as the new A-phase bridge arm, completing the fault-tolerant control of the secondary switch failure; When the second faulty switch is located in the B-phase bridge arm, the sixth bidirectional thyristor, the second bidirectional thyristor, and the first bidirectional thyristor are turned on, and the fifth bidirectional thyristor is turned off, so that the capacitor bridge arm serves as the new A-phase bridge arm, and the redundant bridge arm replaces the bridge arm corresponding to the first faulty switch, thereby completing fault-tolerant control of the secondary switch failure; When the second fault switch tube is located in the C phase bridge arm, the sixth bidirectional thyristor, the third bidirectional thyristor and the first bidirectional thyristor are turned on, and the fifth bidirectional thyristor is turned off, so that the capacitor bridge arm serves as the new A phase bridge arm, and the redundant bridge arm replaces the bridge arm corresponding to the first fault switch tube, thereby completing the fault-tolerant control of the secondary switch tube failure.

7. A fault-tolerant control method for a grid-connected converter according to any one of claims 5 or 6, characterized in that: The performing capacitor neutral point control and space vector modulation on the three-phase grid-connected converter specifically includes: Acquiring current voltage value information of the capacitor in the capacitor bridge arm and rated modulation wave of each phase in the three-phase grid-connected converter; Determining a DC bias voltage according to the voltage value information and a preset low-pass filter, and determining a fault phase and a non-fault phase of the three-phase grid-connected converter according to the first fault switch tube and the second fault switch tube; determining a modified modulation wave of the fault phase according to the DC bias voltage, a preset proportional regulator, and a rated modulation wave, thereby completing capacitor neutral point control of the three-phase grid-connected converter; The zero vector of the three-phase grid-connected converter is obtained according to a preset volt-second balance algorithm, and the duty cycle of the non-fault phase is determined based on the zero vector to complete space vector modulation of the three-phase grid-connected converter.

8. The fault-tolerant control method of a grid-connected converter according to claim 2, characterized in that, The three-phase bridge arm includes: an A-phase bridge arm, a B-phase bridge arm and a C-phase bridge arm; The A-phase bridge arm includes: a first switch tube and a second switch tube; the B-phase bridge arm includes: a third switch tube and a fourth switch tube; the C-phase bridge arm includes: a fifth switch tube and a sixth switch tube; The first end of the first switching tube, the first end of the third switching tube, and the first end of the fifth switching tube are all electrically connected to the positive electrode of the DC power supply; The second end of the first switch tube is electrically connected to the first end of the second switch tube; the second end of the third switch tube is electrically connected to the first end of the fourth switch tube; the second end of the fifth switch tube is electrically connected to the first end of the sixth switch tube; The second end of the second switching tube, the second end of the fourth switching tube, and the second end of the sixth switching tube are electrically connected to the negative electrode of the DC power supply; The connection point between the first switching tube and the second switching tube serves as the A-phase connection point of the A-phase bridge arm, and is configured to be electrically connected to the A-phase of the AC power supply; The connection point between the third switching tube and the fourth switching tube serves as the B-phase connection point of the B-phase bridge arm, and is configured to be electrically connected to the B-phase of the AC power supply; The connection point between the fifth switching tube and the sixth switching tube serves as the C-phase connection point of the C-phase bridge arm, and is used to be electrically connected to the C-phase of the AC power supply.

9. The fault tolerance control method of a grid-connected converter according to claim 2, wherein, The capacitor bridge arm includes a first capacitor and a second capacitor; the redundant bridge arm includes a seventh switch tube and an eighth switch tube; The first end of the first capacitor is electrically connected to the positive electrode of the DC power supply; the second end of the first capacitor is electrically connected to the first end of the second capacitor; the second end of the second capacitor is electrically connected to the negative electrode of the DC power supply; The connection point of the first capacitor and the second capacitor serves as the capacitor connection point of the capacitor bridge arm; The first end of the seventh switching tube is electrically connected to the positive electrode of the DC power supply; the second end of the seventh switching tube is electrically connected to the first end of the eighth switching tube; the second end of the eighth switching tube is electrically connected to the negative electrode of the DC power supply; The connection point of the seventh switching tube and the eighth switching tube serves as the redundant connection point of the redundant bridge arm.

10. A fault-tolerant control system for a grid-connected converter, applicable to a three-phase grid-connected converter, the three-phase grid-connected converter comprising: The DC power supply, the capacitor bridge arm, the three-phase bridge arm, the redundant bridge arm and the AC power supply are connected in sequence; Characterized in that, the three-phase grid-connected converter further includes: a bidirectional thyristor module; The capacitor bridge arm, the three-phase bridge arm and the redundant bridge arm are all electrically connected to the first end of the bidirectional thyristor module; the second end of the bidirectional thyristor module is electrically connected to the AC power supply; The fault-tolerant control system includes: a faulty switching tube acquisition module, a primary switching tube fault-tolerant control module and a secondary switching tube fault-tolerant control module; Wherein, the faulty switching tube acquisition module is used to determine the real-time midpoint voltage of the three-phase grid-connected converter after determining that the grid-connected converter fails, and determine the position information and switching tube fault type of the faulty switching tube of the three-phase grid-connected converter according to the real-time midpoint voltage; The primary switching tube fault-tolerant control module is used to perform switching of the bidirectional thyristor module based on the position information of the faulty switching tube when the switching tube fault type is a primary switching tube fault, so as to complete the fault-tolerant control of the primary switching tube fault; The secondary switching tube fault-tolerant control module is used to perform topological reconstruction on the capacitor bridge arm and the redundant bridge arm based on the position information of the faulty switching tube when the switching tube fault type is a secondary switching tube fault, so as to complete the fault-tolerant control of the secondary switching tube fault.

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