Three-phase multi-parallel converter adaptive fault-tolerant topological structure based on redundant unit

Abstract

The present disclosure provides a three-phase multi-parallel converter adaptive fault-tolerant topological structure based on a redundant unit. A redundant module of each phase is connected to a parallel branch by means of a redundant diode; during normal operation, the redundant module is always in an off state and is not connected to the parallel branch; when an IGBT or a diode in a parallel bridge arm has an open-circuit fault, the redundant module is automatically connected to the parallel branch by means of the redundant diode to replace a fault element of the parallel bridge arm, such that a multi-parallel converter works normally. The solution does not need an additional control circuit, for a variety of fault types, can achieve adaptive reconstruction of hardware resources on the basis of actual reliability requirements by flexibly configuring the diode and the redundant unit, and achieves fault-tolerant operation of the topological structure after a fault by means of a fault-tolerant control algorithm.

Description

Adaptive fault-tolerant topology of three-phase multi-parallel converter based on redundant units

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on November 23, 2023, with application number 202311583485.7 and invention name “Adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units”. The entire contents of the patent application are incorporated into this disclosure by reference. Technical Field

[0003] The present disclosure relates to a multi-parallel converter, and in particular to a three-phase multi-parallel converter adaptive fault-tolerant topology structure based on redundant units. Background Art

[0004] The uninterrupted and continuous operation capability of low-speed, high-torque direct-drive devices is a fundamental requirement and a practical need for their large-scale deployment in industrial production. For example, to ensure uninterrupted coal production, mining scraper conveyors must possess high reliability and strong fault-tolerant operation capabilities. The reliability of low-speed, high-torque direct-drive devices is determined by both electrical and mechanical components. Within this electrical component, the multi-parallel converter is a relatively weak link. Therefore, the highly reliable operation of multi-parallel converters is crucial for the successful deployment of low-speed, high-torque direct-drive devices. Industrial field statistics show that power semiconductor switching devices are the most vulnerable components in converters, and the majority of converter failures are related to semiconductor device failures. Converter fault tolerance research typically encompasses three key areas: fault diagnosis, fault topology reconstruction, and fault-tolerant control algorithms. These three areas are interconnected and indispensable, and the latter two complement each other. However, existing literature focuses solely on fault diagnosis, lacking research on fault topology reconstruction and fault-tolerant control. After a fault, multi-parallel converters are typically derated by disconnecting the single converter at the source of the fault.

[0005] However, in some critical production conditions, derating can cause secondary equipment failures. For example, the rated powers of a coal shearer and a mining scraper conveyor are matched. When the scraper is operated at derating, the load capacity (coal and gangue) will exceed the scraper's output power. This will cause the motor speed to drop, resulting in coal and gangue squeezing, which can easily lead to safety accidents. Furthermore, in extreme cases, this can cause the motor to stall, damaging remaining power semiconductor devices and triggering secondary failures in the transmission. Compared to the extensive research on fault tolerance in other high-power topologies, research on fault topology reconstruction and fault-tolerant control for multi-parallel converters remains relatively limited. Furthermore, due to differences in topology and operating characteristics, fault topology reconstruction and fault-tolerant control techniques used in other high-power converters cannot be directly applied to multi-parallel converters. Therefore, given the real need for high-reliability operation of multi-parallel converters in industrial production, research on fault topology reconstruction and fault-tolerant control strategies for multi-parallel converters is urgently needed to provide core enabling technologies for the large-scale deployment of low-speed, high-torque direct-drive devices.

[0006] Summary of the Invention

[0007] The purpose of the present disclosure is to provide a three-phase multi-parallel converter adaptive fault-tolerant topology structure based on redundant units, which can minimize the impact of open-circuit faults on the multi-parallel converter system, realize fault tolerance function, and improve the reliability of the multi-parallel converter system.

[0008] The technical solutions to achieve the purpose of this disclosure are:

[0009] A three-phase multi-parallel converter adaptive fault-tolerant topology based on redundant units includes a DC power supply, a three-phase AC power supply or a three-phase load resistor, a three-phase filter inductor, and a three-phase parallel branch. Each phase parallel branch includes n parallel bridge arms and n parallel filter inductors. Each phase also includes a redundant module based on redundant units and redundant diodes. The redundant module is based on a combination of IGBTs and diodes. The redundant module is connected to the AC output side of the corresponding phase parallel branch via the redundant diode. During normal operation, the redundant module is always in the off state and is not connected to the parallel branch. When an IGBT (switching tube) or diode in a parallel bridge arm has an open circuit fault, the redundant module automatically connects to the parallel branch via the redundant diode to replace the faulty component of the faulty bridge arm, thereby ensuring normal operation of the multi-parallel converter.

[0010] Furthermore, each phase redundancy module contains an upper tube redundancy module and a lower tube redundancy module, the upper tube redundancy module includes an upper tube redundancy unit and an upper tube redundancy diode, the lower tube redundancy module includes a lower tube redundancy unit and a lower tube redundancy diode, the upper tube redundancy module is used to achieve backup for upper tube IGBT failure and lower tube diode failure in the parallel bridge arm, and the lower tube redundancy module is used to achieve backup for lower tube IGBT failure and upper tube diode failure in the parallel bridge arm.

[0011] Furthermore, the upper tube redundant unit and the lower tube redundant unit are both connected in parallel with all parallel bridge arms, the IGBT emitter of the upper tube redundant unit is connected to the AC output side of the parallel branch through the upper tube redundant diode, and the IGBT collector of the lower tube redundant unit is connected to the AC output side of the parallel branch through the lower tube redundant diode.

[0012] Furthermore, the upper tube redundancy module of phase x includes p upper tube redundancy units and p z (p z ≥p) upper tube redundant diodes, the redundant access scheme is that the IGBT emitter of the first upper tube redundant unit is connected to the anode of p1 (p1≥1) upper tube redundant diode, and its cathode is connected to p1 different parallel bridge arms of the x phase, and the IGBT emitter of the kth (1<k<p) upper tube redundant unit is connected to p k (1≤p k ≤n) the anode of the redundant diode of the upper tube, and its cathode is connected to the x phase p k Different parallel bridge arms, and so on, the IGBT emitter of the pth upper tube redundant unit is connected to p p (1≤p p ≤n) the anode of the redundant diode of the upper tube, and its cathode is connected to the x phase p p This solution realizes the backup of single-phase 1~max(p,n) parallel bridge arms in case of upper tube IGBT failure or lower tube diode failure, and the parameters meet Since there are n parallel bridge arms, based on the permutation and combination, the number of redundant combination schemes is

[0013] Furthermore, the lower pipe redundancy module of phase x includes q lower pipe redundancy units and q z (q z ≥q) lower tube redundant diodes, the redundant access scheme is that the IGBT collector of the first lower tube redundant unit is connected to the cathode of q1 (n≥q1≥1) lower tube redundant diodes, and its anode is connected to q1 different parallel bridge arms of the x phase, and the IGBT collector of the kth (1<k<q) lower tube redundant unit is connected to the cathode of q1 (n≥q1≥1) lower tube redundant diodes. k (1≤q k ≤n) cathodes of redundant diodes on the lower tube, whose anodes are connected to the x phase q k Different parallel bridge arms, and so on, the IGBT collector of the qth lower redundant unit is connected to q q (1≤q q ≤n) cathodes of redundant diodes on the lower tube, whose anodes are connected to the x phase q q This solution realizes the backup of single-phase 1~max(q,n) parallel bridge arms in case of lower tube IGBT failure or upper tube diode failure, and the parameters meet Since there are n parallel bridge arms, based on the permutation and combination, the number of redundant combination schemes is

[0014] The proposed hardware redundancy solution does not require additional control circuits. At the same time, for a wide variety of fault types, the proposed hardware redundancy solution can adaptively reconstruct hardware resources through redundant modules and redundant diodes.

[0015] Furthermore, the upper pipe redundant unit includes four basic topologies:

[0016] Topology 1 contains only one IGBT, topology 2 includes one IGBT and one diode, the emitter of the IGBT is connected to the anode of the diode, and the collector of the IGBT is connected to the cathode of the diode, topology 3 includes one IGBT and one diode in series, and the emitter of the IGBT is connected to the cathode of the diode, and topology 4 includes one IGBT and two diodes, with one diode connected in series on the basis of topology 2, and the emitter of the IGBT is connected to the cathode of the series diode.

[0017] In topology 1 and topology 2, the collector of the IGBT is directly or indirectly connected to the positive pole of the DC bus through a small impedance element, the emitter of the IGBT is connected to the anode of the upper redundant diode, and the cathode of the upper redundant diode is connected to the AC output side of the normal parallel bridge arm. Topology 1 and topology 2 can realize topology adaptive reconstruction after an open-circuit fault of the upper IGBT; in topology 3 and topology 4, the collector of the IGBT is directly or indirectly connected to the positive pole of the DC bus through a small impedance element, the emitter of the IGBT is connected to the anode of the upper redundant diode, and the cathode of the upper redundant diode is connected to the AC output side of the normal parallel bridge arm, and the anode of the series diode is connected to the negative pole of the DC bus. Topology 3 and topology 4 can realize topology adaptive reconstruction after an open-circuit fault of the upper IGBT and the lower diode.

[0018] Furthermore, the downpipe redundant unit includes four basic topologies:

[0019] Topology 5 contains only one IGBT, topology 6 includes one IGBT and one diode, the emitter of the IGBT is connected to the anode of the diode, and the collector of the IGBT is connected to the cathode of the diode, topology 7 includes one IGBT and one diode, and the collector of the IGBT is connected to the anode of the diode, and topology 8 includes one IGBT and two diodes. Based on topology 6, one diode is connected in series, and the collector of the IGBT is connected to the anode of the series diode.

[0020] The emitter of the IGBT in topology structure 5 and topology structure 6 is directly or indirectly connected to the negative pole of the DC bus through a small impedance element, the collector of the IGBT is connected to the cathode of the lower tube redundant diode, and the anode of the lower tube redundant diode is connected to the AC output side of the normal parallel bridge arm, which can realize topology adaptive reconstruction after the lower tube IGBT open circuit fault; the emitter of the IGBT in topology structure 7 and topology structure 8 is directly or indirectly connected to the negative pole of the DC bus through a small impedance element, the collector of the IGBT is connected to the cathode of the lower tube redundant diode, the anode of the lower tube redundant diode is connected to the AC output side of the normal parallel bridge arm, and the cathode of the series diode is connected to the positive pole of the DC bus, which can realize topology adaptive reconstruction after the lower tube IGBT and the upper tube diode open circuit fault.

[0021] Furthermore, according to the number of parallel branches n, which can be any positive integer, the upper tube redundant unit and the lower tube redundant unit satisfy:

[0022] In order to cope with the simultaneous failure of IGBTs in all branches of n parallel converters and ensure the normal operation of the system, the number of redundant IGBT units is set to p ≥ n, and the number of redundant diodes can be in the range [p, pn];

[0023] In order to cope with the simultaneous failure of the lower-side IGBTs in all branches of n parallel converters and ensure the normal operation of the system, the number of lower-side redundant units is q≥n, and the number of lower-side redundant diodes can be in the range [q,qn].

[0024] Furthermore, the operating conditions of the parallel converter include a normal operating state and a fault-tolerant operating state, specifically:

[0025] During normal operation, the redundant module is always in the off state and is not connected to the parallel topology, which does not affect normal operating conditions;

[0026] When an open-circuit fault occurs in the upper IGBT of the k-th parallel branch of phase x, the upper redundant unit (topology 1 to topology 4) connected in parallel to the k-th branch is driven. The IGBT emitter of the upper redundant unit is automatically connected to the parallel topology through the upper redundant diode, replacing the faulty upper IGBT to achieve hardware topology reconstruction.

[0027] When an open-circuit fault occurs in the upper-arm diode of the kth parallel branch of phase x, the current that originally passed through the faulty diode will flow through the lower-arm redundant diode into the series diode of the lower-arm redundant unit (topology 7 and topology 8) connected in parallel with the faulty bridge arm, thus reconfiguring the hardware topology.

[0028] When an open-circuit fault occurs in the lower IGBT of the k-th parallel branch of phase x, the lower redundant unit connected in parallel to the k-th branch (topology 5 to topology 8) is driven. The IGBT collector of the lower redundant unit is automatically connected to the parallel topology through the redundant diode, replacing the faulty lower IGBT to achieve hardware topology reconstruction.

[0029] When an open-circuit fault occurs in the upper-bridge arm diode of the kth parallel branch of phase x, the current that originally passed through the faulty diode will flow through the upper-bridge redundant diode into the series diode of the upper-bridge redundant unit (topology structure 3 to topology structure 4) connected in parallel with the faulty bridge arm, thereby reconstructing the hardware topology.

[0030] Furthermore, the control mode of the redundancy module is:

[0031] During normal operation, the driving signal of the redundant module is always at a low level, the redundant module is always in the off state and is not connected to the topology. The normal bridge arm can use the normal operation control strategy to achieve system operation;

[0032] When a fault occurs, the drive signal of the redundant module in parallel with the faulty phase bridge arm is started. The redundant module automatically connects to the hardware topology through the redundant diode, and synchronizes the drive signals of all parallel branches of the faulty bridge arm with the signals of the redundant unit to achieve fault-tolerant operation after the fault. The synchronization signal can select the signal of any bridge arm in the parallel branch.

[0033] Compared with the prior art, the beneficial effects of the present disclosure are as follows: the present disclosure proposes a fault redundancy unit access scheme for open-circuit faults of switch tubes and diodes in multi-parallel converters; the scheme does not require additional control circuits and can adaptively reconstruct hardware resources by flexibly configuring diodes and fault redundancy units according to actual reliability requirements for a wide variety of fault types; at the same time, through a fault-tolerant operation algorithm, the fault-tolerant operation of the topology structure after a fault is achieved, providing a core guarantee technology for the large-scale promotion of low-speed, high-torque direct-drive devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a topological diagram of an adaptive fault-tolerant three-phase multi-parallel converter proposed in the present disclosure;

[0035] Figure 2(a) shows the structure of a high-side redundant unit with only one IGBT, Figure 2(b) shows the structure of a high-side redundant unit with one IGBT and one diode, Figure 2(c) shows the structure of a high-side redundant unit with one IGBT and one diode, and Figure 2(d) shows the structure of a high-side redundant unit with one IGBT and two diodes.

[0036] Figure 3(a) shows the structure of a lower-side redundant unit containing only one IGBT, Figure 3(b) shows the structure of a lower-side redundant unit containing one IGBT and one diode, Figure 3(c) shows the structure of a lower-side redundant unit containing one IGBT and one diode, and Figure 3(d) shows the structure of a lower-side redundant unit containing one IGBT and two diodes.

[0037] Figure 4 shows the switch status when (S 11 ,S 21 ,S 31 )=(1,0,1);

[0038] Figure 5 shows the switch status when (S 11 ,S 21 ,S 31 )=(1,1,0);

[0039] Figure 6(a) shows the current path diagram when the upper tube IGBT operates normally and outputs a positive level, taking phase a as an example. When the phase a switching signal is completely synchronized and the parallel current is positive, Figure 6(b) shows the current path diagram when a single upper tube IGBT fails and outputs a positive level, taking phase a as an example. Figure 6(c) shows the current path diagram when the phase a switching signal is completely synchronized and the parallel current is positive, taking phase a as an example. When the lower tube diode operates normally and outputs a negative level, Figure 6(d) shows the current path diagram when the phase a switching signal is completely synchronized and the parallel current is positive, taking phase a as an example. When a single lower tube diode fails and outputs a negative level, Figure 6(e) shows the current path diagram when the lower tube IGBT operates normally and outputs a positive level, taking phase a as an example, when the phase a switching signal is completely synchronized and the parallel current is negative. Figure 6(f) shows the current path diagram when a single lower tube IGBT fails and outputs a positive level, taking phase a as an example, when the phase a switching signal is completely synchronized and the parallel current is negative. Figure 6(g) shows the current path diagram when the upper tube diode operates normally and outputs a negative level, taking phase a as an example, when the phase a switching signal is completely synchronized and the parallel current is negative. Figure 6(h) shows the current path diagram when a single upper tube diode fails and outputs a negative level, taking phase a as an example, when the phase a switching signal is completely synchronized and the parallel current is negative.

[0040] Figure 7(a) is a three-phase parallel current waveform from the time when the two IGBTs in the first branch of phase b have an open-circuit fault to the time when the converter is operating with adaptive fault tolerance. Figure 7(b) is a three-phase current waveform of the first converter from the time when the two IGBTs in the first branch of phase b have an open-circuit fault to the time when the converter is operating with adaptive fault tolerance. Figure 7(c) is a three-phase current waveform of the second converter from the time when the two IGBTs in the first branch of phase b have an open-circuit fault to the time when the converter is operating with adaptive fault tolerance. Figure 7(d) is a three-phase current waveform of the third converter from the time when the two IGBTs in the first branch of phase b have an open-circuit fault to the time when the converter is operating with adaptive fault tolerance.

[0041] Figure 8(a) shows the steady-state three-phase parallel current waveform after an open-circuit fault occurs in the two IGBTs in the first branch of phase b. Figure 8(b) shows the steady-state three-phase current waveform of the first converter after an open-circuit fault occurs in the two IGBTs in the first branch of phase b. Figure 8(c) shows the steady-state three-phase current waveform of the second converter after an open-circuit fault occurs in the two IGBTs in the first branch of phase b. Figure 8(d) shows the steady-state three-phase current waveform of the third converter after an open-circuit fault occurs in the two IGBTs in the first branch of phase b. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0043] This solution aims at the open circuit faults of IGBT and diode in multi-parallel converters, and proposes a redundant unit access solution. A three-phase multi-parallel converter adaptive fault tolerant topology based on redundant units is shown in Figure 1. Based on the existing converter topology, a redundant module is added. When an open circuit fault occurs in the switch tube or diode, the redundant module adaptively accesses the fault bridge arm through the redundant diode to provide a current branch for the fault phase bridge arm. This topology minimizes the impact of the open circuit fault on the parallel converter system through hardware reconstruction, realizes fault tolerance function, and improves the reliability of the multi-parallel converter system. This topology contains: DC power supply, three Phase AC power supply, three-phase filter inductor and three-phase parallel branch, each phase parallel branch contains n parallel bridge arms and n parallel filter inductors, at the same time, each phase contains an upper tube redundant module and a lower tube redundant module, the upper tube redundant module includes an upper tube redundant unit and an upper tube redundant diode, and the lower tube redundant module includes a lower tube redundant unit and a lower tube redundant diode. Its characteristics are: the upper tube redundant unit and the lower tube redundant unit are both connected in parallel with all parallel bridge arms, the IGBT emitter of the upper tube redundant unit is connected to the AC output side of the parallel branch through the upper tube redundant diode, and the IGBT collector of the lower tube redundant unit is connected to the AC output side of the parallel branch through the lower tube redundant diode.

[0044] An embodiment of an upper tube redundancy module and a lower tube redundancy module satisfies:

[0045] The upper tube redundancy module of phase a includes p upper tube redundancy units and p z (p z ≥p) upper tube redundant diodes, the redundant access scheme is that the first upper tube redundant unit is connected to the anode of p1 (p1≥1) upper tube redundant diodes, and its cathode is connected to p1 different parallel bridge arms of phase a, and the kth upper tube redundant unit is connected to p k (p k ≥1) The anode of the redundant diode of the upper tube, its cathode is connected to the a phase p k Different parallel bridge arms, and so on, the p-th upper tube redundant unit is connected to p p (p p ≥1) The anode of the redundant diode of the upper tube, its cathode is connected to the a phase p p This solution realizes the backup of single-phase 1~max(p,n) parallel bridge arms in case of upper tube IGBT failure or lower tube diode failure, and the parameters meet The number of redundant combination schemes is

[0046] The lower pipe redundancy module of phase a includes q lower pipe redundancy units and q z (q z≥q) redundant diodes, the redundant access scheme is that the first lower tube redundant unit is connected to the cathode of q1 (q1≥1) lower tube redundant diodes, and its anode is connected to q1 different parallel bridge arms of phase a, and the kth lower tube redundant unit is connected to q k (q k ≥1) cathode of the redundant diode of the lower tube, whose anode is connected to phase a q k Different parallel bridge arms, and so on, the qth lower tube redundant unit is connected to q q (q q ≥1) cathode of the redundant diode of the lower tube, whose anode is connected to phase a q q This solution realizes the backup of single-phase 1~max(q,n) parallel bridge arms in case of lower tube IGBT failure or upper tube diode failure, and the parameters meet The number of redundant combination schemes is

[0047] The proposed hardware redundancy solution does not require additional control circuits. At the same time, for a wide variety of fault types, the proposed hardware redundancy solution can adaptively reconstruct hardware resources through redundant modules and redundant diodes.

[0048] Among them, the upper tube redundant unit includes four basic structures: topology structure 1 contains only one IGBT, as shown in Figure 2(a); topology structure 2 includes one IGBT and one diode, the emitter of the IGBT is connected to the anode of the diode, and the collector of the IGBT is connected to the cathode of the diode, as shown in Figure 2(b); topology structure 3 includes one IGBT and one diode, the emitter of the IGBT is connected to the cathode of the diode, as shown in Figure 2(c); topology structure 4 includes one IGBT and two diodes, and one diode is connected in series on the basis of topology structure 2, and the emitter of the IGBT is connected to the cathode of the series diode, as shown in Figure 2(d);

[0049] In topology 1 and topology 2, the collector of the IGBT is directly or indirectly connected to the DC bus positive pole P through a small impedance element, the emitter Xp of the IGBT is connected to the anode of the upper tube redundant diode, and the cathode of the upper tube redundant diode is connected to the AC output side of the normal parallel bridge arm. Topology 1 and topology 2 can realize topology adaptive reconstruction after the upper tube IGBT open circuit fault; in topology 3 and topology 4, the collector of the IGBT is directly or indirectly connected to the DC bus positive pole P through a small impedance element, the emitter Xp of the IGBT is connected to the anode of the upper tube redundant diode, and the cathode of the upper tube redundant diode is connected to the AC output side of the normal parallel bridge arm, and the anode of the series diode is connected to the DC bus negative pole N. Topology 3 and topology 4 can realize topology adaptive reconstruction after the upper tube IGBT and the lower tube diode open circuit fault.

[0050] Similarly, the lower-side redundant unit includes four basic structures: topology 5 contains only one IGBT, as shown in Figure 3(a); topology 6 includes one IGBT and one diode, with the emitter of the IGBT connected to the anode of the diode, and the collector of the IGBT connected to the cathode of the diode, as shown in Figure 3(b); topology 7 includes one IGBT and one diode, with the collector of the IGBT connected to the anode of the diode, as shown in Figure 3(c); topology 8 includes one IGBT and two diodes, with one diode connected in series on the basis of topology 6, and the collector of the IGBT connected to the anode of the series diode, as shown in Figure 3(d).

[0051] The emitter of the IGBT in topology structure 5 and topology structure 6 is directly or indirectly connected to the negative pole N of the DC bus through a small impedance element, the collector Xn of the IGBT is connected to the cathode of the lower tube redundant diode, and the anode of the lower tube redundant diode is connected to the AC output side of the normal parallel bridge arm, which can realize topology adaptive reconstruction after the lower tube IGBT open circuit fault; the emitter of the IGBT in topology structure 7 and topology structure 8 is directly or indirectly connected to the negative pole N of the DC bus through a small impedance element, the collector Xn of the IGBT is connected to the cathode of the lower tube redundant diode, and the anode of the lower tube redundant diode is connected to the AC output side of the normal parallel bridge arm, and the cathode of the series diode is connected to the positive pole P of the DC bus, which can realize topology adaptive reconstruction after the lower tube IGBT and the upper tube diode open circuit fault.

[0052] Taking a three-parallel converter as an example, the adaptive fault-tolerant topology structure of a three-phase multi-parallel converter based on redundant units implements adaptive topology reconstruction of the multi-parallel converter for IGBT and diode open circuit faults according to the following steps:

[0053] The three-parallel converter includes a DC power supply, a three-phase AC power supply, and a three-phase filter inductor. At the same time, each phase contains three parallel branches and a redundant module. The redundant module includes one upper tube redundant unit and one lower tube redundant unit. Taking phase a as an example, the upper tube redundant unit of phase a adopts the scheme of Figure 2(d), and its AC output side is connected to the anodes of three upper tube redundant diodes, and the cathodes of the upper tube redundant diodes are respectively connected to the three parallel branches; the lower tube redundant unit of phase a adopts the scheme of Figure 3(d), and its AC output side is connected to the cathodes of three lower tube redundant diodes, and the anodes of the lower tube redundant diodes are respectively connected to the three parallel branches.

[0054] Taking phase a as an example, the current flows from the DC side to the AC side as the positive direction of the current. During normal operation, when the switch state is (S 11 ,S 21 ,S 31 )=(1,0,1), as shown in Figure 4, S 11 =1 indicates the upper arm switch tube S of the first branch of phase a 11 The lower bridge arm switch tube S is turned on.14 At this point, the current paths of the three parallel branches satisfy: a) PS 11 -a1-L a1 -a;b)aL a2 -a2-S 24 -N;c)PS 31 -a3-L a3 -a. For redundant units, its switch status S ap1 =S an1 =0, indicating that the IGBT of the redundant module is always in the off state, the redundant bridge arm is not connected to the normal bridge arm, and the system operates normally.

[0055] When the switch state is (S 11 ,S 21 ,S 31 )=(1,1,0), as shown in Figure 5. At this time, the current paths of the three parallel branches satisfy: a) PS 11 -a1-L a1 -a;b)PS 21 -a2-L a2 -a;c)aL a3 -a3-S 34 -N. Similarly, for the redundant bridge arm, its switch state S ap1 =S an1 =0, indicating that the IGBT of the redundant module is always in the off state, the redundant module is not connected to the normal bridge arm, and the system operates normally.

[0056] When a single device open-circuit fault occurs in branch 2 of phase a of the converter, all branches of phase a adopt fully synchronous control, and all possible current paths are shown in Figure 6. A single device open-circuit fault in branch 2 can be categorized into four types: upper IGBT fault, upper diode fault, lower IGBT fault, and lower diode fault.

[0057] a) When the upper IGBT fails and the shunt current is positive, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(b) and 6(c). Figure 6(b) corresponds to a high output level, and Figure 6(c) corresponds to a low output level. When the shunt current is negative, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(e) and 6(g). Figure 6(g) corresponds to a high output level, and Figure 6(e) corresponds to a low output level.

[0058] b) When the high-side diode fails and the shunt current is positive, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(a) and 6(c). Figure 6(a) corresponds to a high output level, and Figure 6(c) corresponds to a low output level. When the shunt current is negative, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(e) and 6(h). Figure 6(h) corresponds to a high output level, and Figure 6(e) corresponds to a low output level.

[0059] c) When the lower IGBT fails and the parallel current is positive, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(a) and 6(c). Figure 6(a) corresponds to a high output level, and Figure 6(c) corresponds to a low output level. When the parallel current is negative, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(f) and 6(g). Figure 6(g) corresponds to a high output level, and Figure 6(f) corresponds to a low output level.

[0060] d) When the lower diode fails and the parallel current is positive, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(a) and 6(d). Figure 6(a) corresponds to a high output level, and Figure 6(d) corresponds to a low output level. When the current is negative, the topology is adaptively reconfigured to the two operating conditions shown in Figures 6(e) and 6(g). Figure 6(g) corresponds to a high output level, and Figure 6(e) corresponds to a low output level.

[0061] The experimental conditions are as follows: DC bus voltage 400V, switching frequency 5kHz, load resistance 10Ω, and converter filter inductance 10mH.

[0062] Figures 7(a) to 7(d) and 8(a) to 8(d) show the experimental results of fault-tolerant operation with a modulation index of 1.0. The experimental conditions were that the upper and lower IGBTs of the first branch of phase b failed sequentially. Figure 7 shows the dynamic process of fault-tolerant operation, recording the current changes in the parallel current and the three-phase current of the three parallel branches from normal operation, to an open-circuit fault of the upper IGBT of phase b, to the switching-in of the upper redundant unit, to an open-circuit fault of the lower IGBT of phase b, and finally to the switching-in of the lower redundant unit. Figure 7(a) shows the parallel current waveform, Figure 7(b) shows the three-phase current waveform of the first parallel branch, Figure 7(c) shows the three-phase current waveform of the second parallel branch, and Figure 7(d) shows the three-phase current waveform of the third parallel branch. Figure 8 shows the steady-state waveforms after fault-tolerant operation. Figure 8(a) shows the parallel current waveforms, Figure 8(b) shows the three-phase current waveforms of the first parallel branch, Figure 8(c) shows the three-phase current waveforms of the second parallel branch, and Figure 8(d) shows the three-phase current waveforms of the third parallel branch. Experimental results demonstrate that the proposed hardware redundancy scheme can achieve fault-tolerant operation after a fault without the need for additional control circuits. Furthermore, the proposed hardware redundancy scheme can adaptively reconfigure hardware resources through diodes for a wide variety of fault types. Furthermore, this topology minimizes the impact of open-circuit faults on the multi-parallel converter system through hardware reconfiguration, achieving fault tolerance and improving the reliability of the multi-parallel converter system.

[0063] The above description of the preferred embodiments enables one skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without requiring inventiveness. Therefore, the present disclosure is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-phase multi-parallel converter adaptive fault-tolerant topology structure based on redundant units, comprising a DC power supply, a three-phase AC power supply or a three-phase load resistor, a three-phase filter inductor and a three-phase parallel branch, wherein each phase parallel branch comprises n parallel bridge arms and n parallel filter inductors, and is characterized in that: Each phase also includes a redundant module based on a redundant unit and a redundant diode. The redundant unit is based on a combination of an IGBT and a diode. The redundant unit is connected to the AC output side of the same-phase parallel bridge arm through a redundant diode. During normal operation, the redundant module is always in an off state and is not connected to the parallel branch. When an open-circuit fault occurs in the IGBT or diode in the parallel bridge arm, the redundant unit automatically connects to the faulty branch through the redundant diode to replace the faulty component of the faulty branch, so that the multi-parallel converter can work normally.

2. The three-phase multi-parallel converter adaptive fault-tolerant topology structure based on redundant units according to claim 1, characterized in that: The control of the redundant module is specifically as follows: In normal operation, the driving signal of the redundant module is always at a low level, the redundant module is always in a shutdown state and is not connected to the topology, and the multi-parallel converter adopts the normal operation control strategy to realize system operation; After a fault occurs, the driving signal of the redundant module in parallel with the faulty phase bridge arm is started, and the redundant module is automatically connected to the hardware topology through the redundant diode. At the same time, the driving signals of all parallel branches of the faulty bridge arm are synchronized with the signals of the redundant module to achieve fault-tolerant operation after the fault. The synchronization signal can select the signal of any bridge arm in the parallel branch.

3. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to any one of claims 1 or 2, characterized in that: The redundancy module includes an upper tube redundancy module and a lower tube redundancy module. The upper tube redundancy module is used to realize backup for upper tube IGBT failure and lower tube diode failure of the parallel bridge arm, and the lower tube redundancy module is used to realize backup for lower tube IGBT failure and upper tube diode failure of the parallel bridge arm.

4. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 3 is characterized in that: The upper tube redundancy module includes p upper tube redundancy units and p z The upper tube redundant diodes, the lower tube redundant module includes q lower tube redundant units and q z The upper tube redundant unit and the lower tube redundant unit are both connected in parallel with the parallel bridge arm, the IGBT emitter of the upper tube redundant unit is connected to the AC output side of the parallel bridge arm through the upper tube redundant diode, and the IGBT collector of the lower tube redundant unit is connected to the AC output side of the parallel bridge arm through the lower tube redundant diode.

5. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 4, characterized in that: For p upper tube redundant units, the IGBT emitter of the kth upper tube redundant unit is connected to p k The anode of the redundant diode of the upper tube is connected to the cathode of p k The AC output side of different parallel bridge arms can realize the backup of single-phase 1 to max(p,n) parallel bridge arms upper tube IGBT failure or lower tube diode failure, where 1≤k≤p, 1≤p k ≤n, Since there are n parallel bridge arms, based on the permutation and combination, the number of redundant combination schemes is 6. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 4, characterized in that: For q lower redundant units, the IGBT collector of the kth lower redundant unit is connected to q k The cathode of the redundant diode of the lower tube is connected to the anode of q k The AC output side of different parallel bridge arms can realize the backup of lower tube IGBT failure or upper tube diode failure in 1 to max(q,n) parallel bridge arms of a single phase, where 1≤k≤q, 1≤q k ≤n, Since there are n parallel bridge arms, based on the permutation and combination, the number of redundant combination schemes is 7. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 4, characterized in that: When all upper tube IGBTs of n parallel bridge arms fail at the same time, the number of upper tube redundant units is p ≥ n, and the number of upper tube redundant diodes is p z The range is [p, pn]; when all lower IGBTs of n parallel bridge arms fail at the same time, the number of lower redundant units is q≥n, and the number of lower redundant diodes is q z The possible range is [q,qn].

8. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 4, characterized in that: The upper tube redundant unit includes four structures, the first structure includes only one IGBT, the second structure includes one IGBT and one diode, the emitter of the IGBT is connected to the anode of the diode, the collector of the IGBT is connected to the cathode of the diode, the third structure includes one IGBT and one diode connected in series, the emitter of the IGBT is connected to the cathode of the diode, and the fourth structure includes one IGBT and two diodes, one diode is connected in series on the basis of the second structure, and the emitter of the IGBT is connected to the cathode of the series diode; In the first and second structures of the upper tube redundant unit, the collector of the IGBT is directly or indirectly connected to the positive electrode of the DC power supply through an impedance element, the emitter of the IGBT is connected to the anode of the upper tube redundant diode, and the cathode of the upper tube redundant diode is connected to the AC output side of the parallel bridge arm, so as to realize the topological adaptive reconstruction after the upper tube IGBT in the parallel bridge arm has an open circuit fault; the third structure of the upper tube redundant unit In the structure and the fourth structure, the collector of the IGBT is directly or indirectly connected to the positive electrode of the DC power supply through an impedance element, the emitter of the IGBT is connected to the anode of the upper redundant diode, the cathode of the upper redundant diode is connected to the AC output side of the parallel bridge arm, and the anode of the series-connected diode is connected to the negative electrode of the DC power supply, so as to realize topology adaptive reconstruction after an open-circuit failure of the upper IGBT and the lower diode in the parallel bridge arm; The impedance element includes a resistor or an inductor.

9. The adaptive fault-tolerant topology structure of three-phase multi-parallel converter based on redundant units according to claim 4, characterized in that: The lower tube redundant unit includes four structures. The first structure is 1 IGBT. The second structure includes 1 IGBT and 1 diode, the emitter of the IGBT is connected to the anode of the diode, and the collector of the IGBT is connected to the cathode of the diode. The third structure includes 1 IGBT and 1 diode connected in series, the collector of the IGBT is connected to the anode of the diode, and the fourth structure includes 1 IGBT and two diodes, that is, 1 diode is connected in series on the basis of the second structure, and the collector of the IGBT is connected to the anode of the series diode. The emitter of the IGBT of the first structure and the second structure is directly or indirectly connected to the negative pole of the DC power supply through an impedance element, the collector of the IGBT is connected to the cathode of the redundant diode of the lower tube, and the anode of the redundant diode of the lower tube is connected to the AC output side of the parallel bridge arm, so as to realize the topological adaptive reconstruction after the open circuit failure of the lower tube IGBT; the emitter of the IGBT of the third structure and the fourth structure is directly or indirectly connected to the negative pole of the DC power supply through a small impedance element, the collector of the IGBT is connected to the cathode of the redundant diode of the lower tube, the anode of the redundant diode of the lower tube is connected to the AC output side of the parallel bridge arm, and the cathode of the series-connected diode is connected to the positive pole of the DC power supply, so as to realize the topological adaptive reconstruction after the open circuit failure of the lower tube IGBT and the upper tube diode; The impedance element includes a resistor or an inductor.

10. The three-phase multi-parallel converter adaptive fault-tolerant topology structure based on redundant units according to claim 9, characterized in that: The control of the redundant module is specifically as follows: After an open-circuit fault of the upper tube IGBT occurs in the kth parallel branch of the x-phase, the upper tube redundant unit connected in parallel to the kth branch is driven, and the emitter of the IGBT of the upper tube redundant unit is automatically connected to the parallel topology through the upper tube redundant diode to replace the upper tube IGBT of the faulty branch, thereby realizing the reconstruction of the hardware topology; When an upper tube diode of the kth parallel branch of phase x fails, the current that originally passed through the faulty diode will flow through the lower tube redundant diode into the series diode of the lower tube redundant unit connected in parallel to the faulty bridge arm, thereby realizing the reconstruction of the hardware topology. After an open-circuit fault of the lower tube IGBT occurs in the k-th parallel branch of the x-phase, the lower tube redundant unit connected in parallel to the k-th branch is driven, and the collector of the IGBT of the lower tube redundant unit is automatically connected to the parallel topology through the lower tube redundant diode, replacing the lower tube IGBT of the faulty branch to work, thereby realizing the reconstruction of the hardware topology; After an open-circuit fault occurs in the lower tube diode of the kth parallel branch of phase x, the current originally passing through the faulty diode will flow through the upper tube redundant diode into the series diode of the upper tube redundant unit connected in parallel to the faulty bridge arm, thereby realizing the reconstruction of the hardware topology.

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