A three-level ANPC bridge arm IGBT short-circuit fault modeling method based on FPGA

Abstract

The present invention relates to a modeling method for an ANPC converter, specifically a three-level ANPC bridge arm IGBT short-circuit fault modeling method based on FPGA. A three-level ANPC bridge arm IGBT short-circuit fault modeling method based on FPGA is characterized by: first, by analyzing the corresponding current paths under each switching sequence of the power device under normal working conditions and bridge arm IGBT short-circuit fault conditions, the corresponding expressions of output voltage and current are obtained, a bridge arm model including the IGBT short-circuit fault state is designed, and then the fault mode is set to trigger a switch to facilitate switching the fault state during normal working conditions. The present invention builds a three-level ANPC bridge arm IGBT short-circuit fault model based on FPGA, which has fast computing speed, high accuracy, and a real-time simulation step length of up to 100ns. It can not only test the three-level controller under normal working conditions, but also provide working condition testing under the bridge arm short-circuit fault mode.

Description

Technical Field

[0001] The present invention relates to a modeling method for an ANPC converter, in particular to a three-level ANPC bridge arm IGBT short-circuit fault modeling method based on FPGA. Background Art

[0002] As power device switching frequencies increase, the application of multilevel inverters is becoming increasingly widespread. The active neutral point clamped (ANPC) three-level topology effectively overcomes the uneven loss distribution problem of the NPC topology and offers simple control, making it increasingly widely used in the modern new energy industry.

[0003] Currently, model-based development is becoming increasingly mainstream for power electronics controller development. Hardware-in-the-loop (HIL) simulation is a typical testing method within this development model. HIL simulation connects a physical controller with a virtual model of the controlled plant (implemented using real-time simulation hardware). This allows for cost-effective and efficient testing of controller functionality and performance. Furthermore, HIL simulation offers advantages in destructive testing, reducing the cost of replacing damaged components.

[0004] Currently, the main circuit of a three-level ANPC converter is typically built using components and switch modules from the SimPowerSystems module library in MATLAB simulation software. Because the IGBT / Diode models included in the SimPowerSystems module library are electrical models that incorporate parasitic parameters and are relatively complex, they are typically used for offline simulation. In real-time online simulation, using components and modules from the SimPowerSystems module library to build the main circuit results in a limited simulation step size due to the model's complexity and high computational complexity. Improving simulation accuracy requires compiling and downloading the model to the FPGA board, but the SimPowerSystems module library does not support this compilation and downloading capabilities.

[0005] Patent CN102710153A, "Modeling Method for a Single-Phase Bridge-Type Three-Level Rectifier," discloses a simple, computationally intensive modeling method for a single-phase bridge-type three-level rectifier. This modeling method only models a single-phase three-level rectifier under normal operating conditions and does not consider short-circuit fault conditions of IGBTs and diodes, making it incapable of simulating fault conditions. Summary of the Invention

[0006] The present invention provides a three-level ANPC bridge arm IGBT short-circuit fault modeling method. This method does not consider parasitic parameters and derives the current-voltage relationship between the device in the on and off states. The model has high accuracy and can be compiled and downloaded to an FPGA board for real-time simulation. This solves the problem that the main circuit model built in the SimPowerSystems module library is complex and cannot be downloaded.

[0007] The present invention is implemented using the following technical solution: a FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method. First, by analyzing the corresponding current paths under each switching sequence of the power device under normal operating conditions and bridge arm IGBT short-circuit fault conditions, the corresponding expressions of output voltage and current are obtained, and a bridge arm model including the IGBT short-circuit fault state is designed. Then, the fault mode is set to trigger a switch to facilitate switching the fault state during normal operating conditions.

[0008] The above-mentioned FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method includes six switch states: P, OU1, OU2, OL1, OL2, and N in the current path;

[0009] In the P switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110001, and the output voltage is +Udc / 2. If iT1=iT2=iac, iac≥0; if -iD1=-iD2=-iac, iac<0;

[0010] In the OU1 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010010, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if -iD2=iT5=-iac, iac<0;

[0011] In the OU2 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010110, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if -iD2=iT5=-iac, iac<0;

[0012] In the OL1 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001001, and the output voltage is 0. If -iD3=iT6=iac, iac≥0; if -iD6=iT3=-iac, iac<0;

[0013] In the OL2 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101001, and the output voltage is 0. If -iD3=iT6=iac, iac≥0; if -iD6=iT3=-iac, iac<0;

[0014] In the N switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001110, and the output voltage is -Udc / 2. If -iD3=-iD4=iac, iac≥0; if iT3=iT4=-iac, iac<0;

[0015] iT1, iT2, iT3, iT4, iT5, iT6 are the currents of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 respectively; -iD1, -iD2, -iD3, -iD4, -iD5, and -iD6 are the currents of the diodes D1, D2, D3, D4, D5, and D6 respectively; iac is the bridge arm output current; and Udc is the DC side voltage.

[0016] The above-mentioned FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method includes nine short-circuit states: T1 short circuit 1, T1 short circuit 2, T1 short circuit 3, T2 short circuit 1, T2 short circuit 2, T2 short circuit 3, T5 short circuit 1, T5 short circuit 2, and T5 short circuit 3.

[0017] In the T1 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110010, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0;

[0018] In the T1 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110110, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0;

[0019] In the T1 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101110, and the output voltage is -Ul. If iT1=iT5=idl1, -iD3=-iD4=iac, iac≥0, if iT1=iT5=idl1, iT3=iT4=-iac, iac<0;

[0020] In the T2 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011001, and the output voltage is 0. If -iD5=iT2=iac / 2, -iD3=iT6=iac / 2, iac≥0, if -iD6=iT3=-iac, iac<0;

[0021] In the T2 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 111001, and the output voltage is +Uh / 2. If iT1=iT2=iT3=-iD6=idl2, iac≥0; if iT1=iT2=iT3=-iD6=idl2, iac<0;

[0022] In the T2 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011110, and the output voltage is -Ul / 2. If iT2=iT3=iT4=-iD5=idl2, iac≥0; if iT2=iT3=iT4=-iD5=idl2, iac<0;

[0023] In the T5 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110011, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0;

[0024] In the T5 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001011, and the output voltage is 0. If -iD3=iT6=iac, iac≥0, if iD2=-iT5=iac / 2, -iT3=iD6=iac / 2, iac<0;

[0025] In the T5 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101011, and the output voltage is 0. If iT1=iT5=idl1, -iD3=iT6=iac, iac≥0, if iT1=iT5=idl1, -iT3=iD6=iac, iac<0;

[0026] Uh and Ul are the upper and lower bridge arm voltages respectively, idl1 is the loop current value of the loop formed by two power devices short-circuiting, and idl2 is the loop current value of the loop formed by four power devices short-circuiting.

[0027] The above-mentioned FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method includes nine short-circuit states: T4 short circuit 1, T4 short circuit 2, T4 short circuit 3, T3 short circuit 1, T3 short circuit 2, T3 short circuit 3, T6 short circuit 1, T6 short circuit 2, and T6 short circuit 3.

[0028] In the T4 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110010, and the output voltage is +Uh. If iT4=iT6=idl1, iT1=iT2=iac, iac≥0, if iT4=iT6=idl1, iD1=iD2=iac, iac<0;

[0029] In the T4 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001101, and the output voltage is -Ul / 2. If iT4=iT6=idl1, -iD3=iac, iac≥0, if iT4=iT6=idl1, -iT3=iac, iac<0;

[0030] In the T4 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101101, and the output voltage is -Ul / 2. If iT4=iT6=idl1, -iD3=iac, iac≥0, if iT4=iT6=idl1, -iT3=iac, iac<0;

[0031] In the T3 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 111001, and the output voltage is +Uh / 2. If iT1=iT2=iT3=-iD6=idl2, iac≥0; if iT1=iT2=iT3=-iD6=idl2, iac<0;

[0032] In the T3 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011010, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if iD2=-iT5=iac / 2, -iT3=iD6=iac / 2, iac<0;

[0033] In the T3 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011110, and the output voltage is -Ul / 2. If iT2=iT3=iT4=-iD5=idl2, iac≥0; if iT2=iT3=iT4=-iD5=idl2, iac<0;

[0034] In the T6 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010011, and the output voltage is 0. If -iD5=iT2=iac / 2, -iD3=iT6=iac / 2, iac≥0, if iD2=-iT5=iac, iac<0;

[0035] In the T6 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010111, and the output voltage is 0. If iT4=iT6=idl1, -iD5=iT2=iac, iac≥0, if iT4=iT6=idl1, iD2=-iT5=iac, iac<0;

[0036] In the T6 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001110, and the output voltage is -Ul. If -iD3=-iD4=iac, iac≥0, and if iT3=iT4=-iac, iac<0.

[0037] The FPGA-based modeling method for a three-level ANPC bridge arm IGBT short-circuit fault is constructed using the Xilinx model library in MATLAB. This FPGA-based model can be compiled and downloaded to the FPGA board and used with a controller for real-time hardware-in-the-loop simulation verification.

[0038] The FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method has the following beneficial effects:

[0039] 1) The model includes normal operating conditions and bridge arm short-circuit fault conditions, and the fault conditions can be switched;

[0040] 2) The logic of each working condition model is clear, the structure is simple, and it is easy to verify;

[0041] 3) The three-level ANPC bridge arm does not consider parasitic parameters, but adopts logic modeling, which is simple and takes up less resources;

[0042] 4) This bridge arm model can be encapsulated as a module and can be used alone or combined into single-phase, three-phase and other topological applications, which is universal;

[0043] 5) The model can be compiled and downloaded to the FPGA board, and can be used with the controller for real-time semi-physical simulation verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the block diagram of the three-level ANPC bridge arm IGBT short-circuit fault model.

[0045] Figure 2This is the topology diagram of the three-level ANPC bridge arm circuit.

[0046] Figure 3 Schematic diagram of the ANPC current path.

[0047] Figure 4 This is the typical current flow diagram corresponding to the short circuit fault of the upper bridge arm of the ANPC three-level bridge arm IGBT.

[0048] Figure 5 This is the typical current flow diagram corresponding to the short circuit fault of the lower bridge arm of the ANPC three-level bridge arm IGBT.

[0049] Figure 6 This is the schematic diagram of the three-phase ANPC inverter circuit.

[0050] Figure 7 This is the FPGA model diagram of the three-phase three-level ANPC inverter with motor.

[0051] Figure 8 The figure is a Simpower model diagram of a three-phase three-level ANPC inverter with a motor for comparison.

[0052] Figure 9 This is the waveform of the three-phase stator current of the motor.

[0053] Figure 10 The following is a comparison diagram of the current waveforms of IGBT1~IGBT6 in the U-phase bridge arm of the inverter.

[0054] Figure 11 This is a comparison chart of the motor U-phase current and line voltage waveforms.

[0055] Figure 12 The comparison diagram of the DC side current waveform of the inverter.

[0056] Figure 13 This is the waveform of the three-phase stator current of the motor.

[0057] Figure 14 The following is a comparison diagram of the current waveforms of IGBT1~IGBT6 in the U-phase bridge arm of the inverter.

[0058] Figure 15 This is a comparison chart of the motor U-phase current and line voltage waveforms.

[0059] Figure 16 The comparison diagram of the DC side current waveform of the inverter.

[0060] Figure 17 This is the waveform of the three-phase stator current of the motor.

[0061] Figure 18 The following is a comparison diagram of the current waveforms of IGBT1~IGBT6 in the U-phase bridge arm of the inverter.

[0062] Figure 19 This is a comparison chart of the motor U-phase current and line voltage waveforms.

[0063] Figure 20 The comparison diagram of the DC side current waveform of the inverter.

[0064] Figure 21 This is the schematic diagram of the single-phase ANPC rectifier circuit.

[0065] Figure 22 This is the FPGA model diagram of the single-phase ANPC rectifier circuit.

[0066] Figure 23 This is the Simpower model diagram of the single-phase ANPC rectifier circuit.

[0067] Figure 24 This is a comparison diagram of the current waveforms of IGBT1 to IGBT6 in the A bridge arm.

[0068] Figure 25 This is a comparison diagram of bus voltage, four-quadrant voltage and current waveforms.

[0069] Figure 26 The figure is a comparison of the DC current waveforms of the upper and lower busbars.

[0070] Figure 27 This is a comparison diagram of the current waveforms of IGBT1 to IGBT6 in the A bridge arm.

[0071] Figure 28 This is a comparison diagram of bus voltage, four-quadrant voltage and current waveforms.

[0072] Figure 29 The figure is a comparison of the DC current waveforms of the upper and lower busbars.

[0073] Figure 30 This is a comparison diagram of the current waveforms of IGBT1 to IGBT6 in the A bridge arm.

[0074] Figure 31 This is a comparison diagram of bus voltage, four-quadrant voltage and current waveforms.

[0075] Figure 32 The figure is a comparison of the DC current waveforms of the upper and lower busbars. DETAILED DESCRIPTION

[0076] First, by analyzing the corresponding current paths of each switching sequence of the power device under normal working conditions and bridge arm IGBT short-circuit fault conditions, the corresponding expressions of output voltage and current are obtained, and a bridge arm model including the IGBT short-circuit fault state is designed. Then, the fault mode is set to trigger the switch to facilitate switching the fault state during normal working conditions. The overall block diagram is shown as follows: Figure 1 shown.

[0077] The three-level ANPC bridge arm circuit topology is as follows Figure 2 As shown, each phase of the ANPC contains six bidirectional switches. These switches form eight current paths—CP1-CP4, CPP, CPP-, CPN, and CPN-—based on the phase current direction and output level, as shown in Figure 3. Current path CPP connects the output level terminal to the DC side's positive current terminal, P, while CPN connects the output level terminal to the DC side's negative current terminal, N. In this case, the converter operates at unity power factor (PF=1). Conversely, current paths CPP- and CPN- produce a PF=-1 operation. Each of these four current paths uniquely corresponds to an output level and current operating state.

[0078] For the midpoint current terminal, there are two current paths CP1 and CP2 for the positive phase current. Similarly, CP3 and CP4 are the current paths for the negative phase current. Figure 4 As can be seen, each current path includes two power devices. Current paths CPP and CPN each have two active switching IGBTs, CP1-CP4 each have one IGBT and one freewheeling diode, and CPP- and CPN- each have two freewheeling diodes. The current paths containing active switching IGBTs can be controlled by controlling the power switching devices.

[0079] Through the above analysis of the current path, we can obtain the switching sequence table shown in Table 1. The IGBT / Diode current is in the positive direction from collector to emitter, and the commutation method is as follows:

[0080] Table 1 ANPC bridge arm switching sequence table

[0081]

[0082] Since the IGBT and diode are in parallel, the impact of an IGBT short circuit and a diode short circuit is the same and can be analyzed together.

[0083] When an ANPC bridge arm short-circuit fault occurs, the DC bus capacitor discharges through the short-circuit loop, generating overcurrent. This overcurrent significantly increases the probability of component damage. Furthermore, due to the rapid discharge of the DC bus capacitor, the voltage across the capacitor suddenly drops to zero, leaving some components to withstand the overvoltage alone, increasing the probability of breakdown damage. In this case, even if the DC bus capacitor and components can withstand the overcurrent and overvoltage, the inverter's three-phase output current will become asymmetrical and even severely distorted when the inverter circuit output is connected to a motor, impacting overall system performance.

[0084] When the power switch devices of the upper bridge arm are short-circuited, the typical current conduction circuit is as follows: Figure 4 As shown, CP5, CP6, and CP7 are newly added short-circuit loops, Uh and Ul are the upper and lower bridge arm voltages respectively, idl1 is the loop current value of the loop formed by two power devices short-circuiting, and idl2 is the loop current value of the loop formed by four power devices short-circuiting.

[0085] Figure 4 The current flow path shown in (a) corresponds to the drive sequence and output voltage: T1 has a short-circuit fault when the bridge arm output voltage is zero (specifically the two drive sequences of 0U1 and 0U2) and -Udc / 2. At this time, the short-circuit loop is formed by the upper bus capacitor C1, T1 and T5;

[0086] Figure 4 The short-circuit loops shown in (b) and 4(c) have similar characteristics. Figure 4 The current flow path shown in (b) corresponds to the following drive sequence and output voltage: T2 short-circuit fault occurs when the bridge arm output voltage is -Udc / 2. At this time, the short-circuit loop is composed of the lower bus capacitor C2, D5, T2, T3 and T4; when T2 short-circuit fault occurs when the bridge arm output voltage is zero (specifically the 0L1 drive sequence), the short-circuit loop is composed of the upper bus capacitor C1, D6, T1, T2 and T3.

[0087] Figure 4 The current flow path shown in (d) corresponds to the drive sequence and output voltage: T5 has a short circuit fault when the inverter single-phase output voltage is zero (specifically 0L1 drive sequence) and +Udc / 2. At this time, the short circuit loop is composed of the upper bus capacitor C1, T1 and T5.

[0088] Through the above analysis of the current path, we can obtain the newly added switching sequence table for the ANPC high-arm short-circuit fault shown in Table 4. The IGBT / Diode current is in the positive direction from collector to emitter, and the commutation method is as follows:

[0089] Table 4 New sequence list of ANPC upper arm IGBT short circuit fault

[0090]

[0091] When the power switch devices of the lower bridge arm have short circuit faults, the fault analysis is similar to that of the upper bridge arm. A new typical current conduction circuit is added as follows: Figure 5As shown, the CP6 and CP7 circuits are the same as those of the upper bridge arm, CP8 is a new circuit when T4 and T6 are short-circuited, Uh and Ul are the voltages of the upper and lower bridge arms respectively, idl1 is the loop current value of the circuit formed by two power devices short-circuiting, and idl2 is the loop current value of the circuit formed by four power devices short-circuiting.

[0092] By analyzing the current path, we can obtain the newly added switching sequence table for the ANPC lower arm short-circuit fault as shown in Table 5. The IGBT / Diode current is in the positive direction from collector to emitter, and the commutation method is as follows:

[0093] Table 5 New sequence list of ANPC lower arm IGBT short fault

[0094]

[0095] Implementation example of three-phase inverter model

[0096] Build a three-phase ANPC inverter circuit, the schematic diagram is as follows Figure 6 shown.

[0097] For comparison, a three-phase ANPC inverter circuit based on MATLAB / Simpower model library and a model based on FPGA were built respectively, such as Figure 7 and Figure 8 As shown in the figure, a fault is set to occur at 0.1s.

[0098] Due to the symmetry of the structure, the consistency between the FPGA model and the Simpower model under the short-circuit conditions of T1, T2, and T5 among the six IGBTs is only analyzed.

[0099] T1 short circuit

[0100] Depend on Figure 9 It can be seen that after the T1 short-circuit fault occurs 0.1s, the stator current becomes three-phase unbalanced, iu is positively biased, and iv and iw are negatively biased.

[0101] Depend on Figure 10 It can be seen that after T1 is short-circuited, the current of IGBT1 and IGBT5 is only positive current, and the negative current is 0.

[0102] Depend on Figures 10-12 It can be seen that the output voltage and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T1 short circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

[0103] T2 short circuit

[0104] Depend on Figure 13It can be seen that after the T2 short-circuit fault occurred 0.1s later, the stator current became three-phase unbalanced and exceeded 5 times that of normal operation, with iu being positively biased and iv and iw being negatively biased.

[0105] Depend on Figure 14 It can be seen that after T2 is short-circuited, the currents of IGBT1, IGBT2, IGBT3, and IGBT4 are only positive currents and are very large, and the negative current is 0; the currents of IGBT5 and IGBT6 are only negative currents and are very large, and the positive current is 0.

[0106] Depend on Figures 14-16 It can be seen that the output voltage and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T1 short circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

[0107] T5 short circuit

[0108] Depend on Figure 17 It can be seen that after the T5 short-circuit fault occurred 0.1s, the stator current became three-phase unbalanced, iu was negatively biased, and iv and iw were positively biased.

[0109] Depend on Figure 18 It can be seen that after T1 is short-circuited, the current of IGBT1 and IGBT5 is only positive current, and the negative current is 0.

[0110] Depend on Figures 18-20 It can be seen that the output voltage and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T1 short circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

[0111] Single-phase Rectification Simulation Model Implementation Example

[0112] Build a single-phase ANPC rectifier circuit, the schematic diagram is as follows Figure 21 shown.

[0113] For comparison, a single-phase ANPC rectifier circuit based on MATLAB / Simpower model library and a FPGA-based model were built, such as Figure 22 and Figure 23 As shown in the figure, the waveform is set to start at 0.05s and the fault occurs at 0.1s.

[0114] Similarly, the single-phase rectifier short-circuit condition only analyzes the consistency between the FPGA model and the Simpower model under the short-circuit conditions of T1, T2, and T5 among the six IGBTs.

[0115] T1 short circuit

[0116] Depend on Figure 24It can be seen that after T1 is short-circuited, the current of IGBT5 is 0.

[0117] Depend on Figures 24-26 It can be seen that the output bus voltage, four-quadrant voltage and current, and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T1 short-circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

[0118] T2 short circuit

[0119] Depend on Figure 27 It can be seen that after T2 is short-circuited, IGBT4 only has positive current and the negative current is 0, and IGBT5 only has negative current and the forward current is 0.

[0120] Depend on Figures 27-29 It can be seen that the output bus voltage, four-quadrant voltage and current, and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T2 short-circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

[0121] T5 short circuit

[0122] Depend on Figure 30 It can be seen that after T5 is short-circuited, the current of IGBT4 is 0.

[0123] Depend on Figures 30-32 It can be seen that the output bus voltage, four-quadrant voltage and current, and DC side current waveforms of the FPGA model and Simpower under normal operating conditions and after T5 short-circuit fault are almost completely consistent, verifying the correctness of the FPGA model.

Claims

1. A three-level ANPC bridge arm IGBT short-circuit fault modeling method based on FPGA, characterized by: First, by analyzing the current paths corresponding to each switching sequence of the power device under normal operating conditions and bridge arm IGBT short-circuit fault conditions, the corresponding expressions of output voltage and current are obtained. A bridge arm model that includes the IGBT short-circuit fault state is designed. The fault mode is then set to trigger the switch to facilitate switching the fault state during normal operation. The current path includes six switching states: P, OU1, OU2, OL1, OL2, and N. The upper arm IGBT short circuit fault includes nine short circuit states: T1 short circuit 1, T1 short circuit 2, T1 short circuit 3, T2 short circuit 1, T2 short circuit 2, T2 short circuit 3, T5 short circuit 1, T5 short circuit 2, and T5 short circuit 3; In the T1 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110010, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0; In the T1 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110110, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0; In the T1 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101110, and the output voltage is -Ul. If iT1=iT5=idl1, -iD3=-iD4=iac, iac≥0, if iT1=iT5=idl1, iT3=iT4=-iac, iac<0; In the T2 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011001, and the output voltage is 0. If -iD5=iT2=iac / 2, -iD3=iT6=iac / 2, iac≥0, if -iD6=iT3=-iac, iac<0; In the T2 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 111001, and the output voltage is +Uh / 2. If iT1=iT2=iT3=-iD6=idl2, iac≥0; if iT1=iT2=iT3=-iD6=idl2, iac<0; In the T2 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011110, and the output voltage is -Ul / 2. If iT2=iT3=iT4=-iD5=idl2, iac≥0; if iT2=iT3=iT4=-iD5=idl2, iac<0; In the T5 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110011, and the output voltage is +Uh / 2. If iT1=iT5=idl1, iT2=iac, iac≥0, if iT1=iT5=idl1, iD2=iac, iac<0; In the T5 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001011, and the output voltage is 0. If -iD3=iT6=iac, iac≥0, if iD2=-iT5=iac / 2, -iT3=iD6=iac / 2, iac<0; In the T5 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101011, and the output voltage is 0. If iT1=iT5=idl1, -iD3=iT6=iac, iac≥0, if iT1=iT5=idl1, -iT3=iD6=iac, iac<0; Uh and Ul are the upper and lower bridge arm voltages respectively, idl1 is the loop current value of the loop formed by two power devices short-circuiting, and idl2 is the loop current value of the loop formed by four power devices short-circuiting; The lower arm IGBT short circuit faults include nine short circuit states: T4 short circuit 1, T4 short circuit 2, T4 short circuit 3, T3 short circuit 1, T3 short circuit 2, T3 short circuit 3, T6 short circuit 1, T6 short circuit 2, and T6 short circuit 3.

2. The FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method according to claim 1, characterized in that: In the P switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110001, and the output voltage is +Udc / 2. If iT1=iT2=iac, iac≥0; if -iD1=-iD2=-iac, iac<0; In the OU1 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010010, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if -iD2=iT5=-iac, iac<0; In the OU2 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010110, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if -iD2=iT5=-iac, iac<0; In the OL1 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001001, and the output voltage is 0. If -iD3=iT6=iac, iac≥0; if -iD6=iT3=-iac, iac<0; In the OL2 switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101001, and the output voltage is 0. If -iD3=iT6=iac, iac≥0; if -iD6=iT3=-iac, iac<0; In the N switching state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001110, and the output voltage is -Udc / 2. If -iD3=-iD4=iac, iac≥0; if iT3=iT4=-iac, iac<0; iT1, iT2, iT3, iT4, iT5, iT6 are the currents of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 respectively; -iD1, -iD2, -iD3, -iD4, -iD5, and -iD6 are the currents of the diodes D1, D2, D3, D4, D5, and D6 respectively; iac is the bridge arm output current; and Udc is the DC side voltage.

3. The FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method according to claim 2, characterized in that: In the T4 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 110010, and the output voltage is +Uh. If iT4=iT6=idl1, iT1=iT2=iac, iac≥0, if iT4=iT6=idl1, iD1=iD2=iac, iac<0; In the T4 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001101, and the output voltage is -Ul / 2. If iT4=iT6=idl1, -iD3=iac, iac≥0, if iT4=iT6=idl1, -iT3=iac, iac<0; In the T4 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 101101, and the output voltage is -Ul / 2. If iT4=iT6=idl1, -iD3=iac, iac≥0, if iT4=iT6=idl1, -iT3=iac, iac<0; In the T3 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 111001, and the output voltage is +Uh / 2. If iT1=iT2=iT3=-iD6=idl2, iac≥0; if iT1=iT2=iT3=-iD6=idl2, iac<0; In the T3 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011010, and the output voltage is 0. If -iD5=iT2=iac, iac≥0; if iD2=-iT5=iac / 2, -iT3=iD6=iac / 2, iac<0; In the T3 short circuit state 3, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 011110, and the output voltage is -Ul / 2. If iT2=iT3=iT4=-iD5=idl2, iac≥0; if iT2=iT3=iT4=-iD5=idl2, iac<0; In the T6 short circuit 1 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010011, and the output voltage is 0. If -iD5=iT2=iac / 2, -iD3=iT6=iac / 2, iac≥0, if iD2=-iT5=iac, iac<0; In the T6 short circuit 2 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 010111, and the output voltage is 0. If iT4=iT6=idl1, -iD5=iT2=iac, iac≥0, if iT4=iT6=idl1, iD2=-iT5=iac, iac<0; In the T6 short circuit 3 state, the switching sequence of the bidirectional switch devices T1, T2, T3, T4, T5, and T6 is 001110, and the output voltage is -Ul. If -iD3=-iD4=iac, iac≥0, and if iT3=iT4=-iac, iac<0.

4. The FPGA-based three-level ANPC bridge arm IGBT short-circuit fault modeling method according to claim 3, characterized in that: The model is built using the Xilinx model library in MATLAB. The model built is an FPGA-based model.

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