A method and device for fault diagnosis of LLC module of ISOP medium voltage DC converter, medium voltage DC power supply system and storage medium

Abstract

The present invention discloses a fault diagnosis method, device, medium voltage DC power supply system and storage medium for LLC modules of ISOP medium voltage DC converter. It includes monitoring the input capacitor voltage, input current, output voltage and output current of each LLC module port; judging whether the fault condition of ISOP medium voltage DC converter is reached according to the output voltage and output current; when it is judged that the fault condition is reached, calculating the difference of input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module; judging the LLC module having switch tube open circuit fault or input capacitor aging fault in each LLC module according to the input capacitor voltage change rate, input voltage amplitude and input current amplitude. The scheme of the present invention utilizes the difference of electrical quantity amplitude and change rate between LLC modules to complete the online detection and positioning of faulty LLC modules, avoiding the misdiagnosis phenomenon caused by large input voltage fluctuation.

Description

Technical Field

[0001] The present invention relates to the technical field of fault diagnosis of direct current converters, and in particular to a fault diagnosis method and device for an LLC module of an ISOP type medium voltage direct current converter, a medium voltage direct current power supply system and a storage medium. Background Art

[0002] The medium-voltage DC power supply system is the energy supply heart of the submarine scientific observation network and an important cornerstone for ensuring the normal operation of marine defense, resource development, and monitoring and early warning. Among them, the submarine medium-voltage DC converter is responsible for converting thousands or tens of kilovolts of DC medium voltage into hundreds of volts of DC low voltage. It is the "power heart" of the entire submarine observation network and directly affects the safety and reliability of the entire system operation. The submarine medium-voltage DC converter adopts an input series output parallel (ISOP) structure and uses LLC modules (i.e. resonant conversion modules) as submodules, which can well meet the needs of high-ratio and high-power density power conversion on the seabed.

[0003] At present, relevant research has been carried out on fault diagnosis of medium voltage DC converters. However, existing fault diagnosis methods have high requirements for data volume and computing power. However, due to the compact size of the subsea converter, it lacks too many sensors and high-performance processors, making it difficult to obtain more data and support complex training. It is also susceptible to measurement noise and model uncertainty, leading to misdiagnosis.

[0004] In summary, although the existing technology has conducted relevant research on the DC converter fault diagnosis method, considering that the submarine DC converter in the extreme deep-sea environment is installed in a small, highly sealed titanium alloy cavity, the number of electrical quantity sensors deployed is relatively small, and the compactness of the fault diagnosis circuit is extremely high. In addition, the long-distance high-impedance optoelectronic composite submarine cable causes large fluctuations in the input voltage of the submarine converter. In view of the above characteristics, the existing methods have problems such as large diagnostic circuit volume and great influence of the converter working point. It is urgent to study a strong and compact online fault diagnosis method suitable for submarine converters that is resistant to input disturbances. Summary of the invention

[0005] In order to solve the technical problem that the existing fault diagnosis method is not applicable due to the characteristics of the submarine ISOP type DC conversion, such as large input voltage fluctuations, limited monitored electrical quantity and small and sealed internal space of the cavity, the embodiments of the present invention provide an ISOP type medium-voltage DC converter LLC module fault diagnosis method, device, medium-voltage DC power supply system and storage medium.

[0006] The technical solution of the embodiment of the present invention is achieved as follows:

[0007] An embodiment of the present invention provides a fault diagnosis method for an LLC module of an ISOP medium voltage DC converter, the method comprising: monitoring the input capacitor voltage, input current, output voltage and output current of each LLC module port in the ISOP medium voltage DC converter; judging whether a fault condition of the ISOP medium voltage DC converter is reached according to the output voltage and the output current; when it is judged that the fault condition of the ISOP medium voltage DC converter is reached, calculating the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module; judging which LLC module has a switch tube open circuit fault or input capacitor aging fault among the LLC modules according to the difference in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module.

[0008] In one embodiment, determining whether a fault condition of the ISOP medium voltage DC converter is reached according to the output voltage and the output current includes: obtaining a voltage diagnosis upper threshold, a current diagnosis upper threshold, a voltage diagnosis lower threshold, and a current diagnosis lower threshold; determining whether a fault condition of the ISOP medium voltage DC converter is reached according to the voltage diagnosis upper threshold, the current diagnosis upper threshold, the voltage diagnosis lower threshold, the current diagnosis lower threshold, the output voltage, and the output current using the following calculation formula:

[0009] Formula (1)

[0010] in, Indicates the output voltage, Represents the output current, Indicates the voltage diagnosis upper threshold, Indicates the voltage diagnosis lower threshold, Indicates the upper threshold of current diagnosis. Indicates the current diagnosis lower threshold.

[0011] In one embodiment, the voltage diagnosis upper limit threshold is set to 1.2 times the output voltage rating, the voltage diagnosis lower limit threshold is set to 0.8 times the output voltage rating, the current diagnosis upper limit threshold is set to 1.2 times the output current rating, and the current diagnosis lower limit threshold is set to 0.8 times the output current rating.

[0012] In one embodiment, calculating the input capacitor voltage change rate of each LLC module includes: calculating the input capacitor voltage change rate of each LLC module using the following calculation formula:

[0013] Formula (2)

[0014] in, represents the input capacitor voltage change rate, and Indicates the input voltage value of adjacent sampling intervals, Indicates the sampling period.

[0015] In one embodiment, according to the differences in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module, determining the LLC module in each LLC module that has a switch tube open circuit fault or input capacitor aging fault includes: for each LLC module, determining whether the input capacitor voltage change rate of the LLC module is greater than 0, and whether the input capacitor voltage change rate of other LLC modules is less than 0, and whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, determining that the LLC module has a switch tube open circuit fault; and, for each LLC module, determining whether the input capacitor voltage change rate of the LLC module is greater than the input capacitor voltage change rate of other LLC modules, and whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, determining that the LLC module has an input capacitor aging fault.

[0016] In one embodiment, for each LLC module, the following calculation formula is used to determine whether a switch tube open circuit fault occurs in the LLC module:

[0017] Formula (3)

[0018] in, Indicates The input capacitor voltage change rate of each LLC module, Indicates The input capacitor voltage change rate of each LLC module, Indicates The input voltage amplitude of each LLC module, Indicates The input voltage amplitude of each LLC module, Indicates The input current amplitude of each LLC module, Indicates The input current amplitude of each LLC module.

[0019] In one embodiment, for each LLC module, the following calculation formula is used to determine whether the LLC module has an input capacitor aging fault:

[0020] Formula (4)

[0021] in, Indicates The input capacitor voltage change rate of each LLC module, Indicates The input capacitor voltage change rate of each LLC module, Indicates The input voltage amplitude of each LLC module, Indicates The input voltage amplitude of each LLC module, Indicates The input current amplitude of each LLC module, Indicates The input current amplitude of each LLC module.

[0022] The embodiment of the present invention further provides an ISOP medium voltage DC converter LLC module fault diagnosis device, the device comprising: a monitoring module, used to monitor the input capacitor voltage, input current, output voltage and output current of each LLC module port in the ISOP medium voltage DC converter; a determination module, used to determine whether the ISOP medium voltage DC converter fault condition is reached according to the output voltage and the output current; a calculation module, used to calculate the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module when it is determined that the ISOP medium voltage DC converter fault condition is reached; a diagnosis module, used to determine the LLC module in each LLC module that has a switch tube open circuit fault or an input capacitor aging fault according to the differences in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module.

[0023] An embodiment of the present invention also provides a medium voltage DC power supply system, comprising: a processor and a memory for storing a computer program that can be run on the processor; wherein the processor executes the steps of any one of the above methods when running the computer program.

[0024] An embodiment of the present invention further provides a storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of any of the above methods are implemented.

[0025] The ISOP medium-voltage DC converter LLC module fault diagnosis method, device, medium-voltage DC power supply system and storage medium provided in the embodiments of the present invention fully consider the characteristics of large input voltage fluctuations of submarine ISOP DC converters, limited monitored electrical quantities and narrow and sealed internal cavity space, and analyze the time domain characteristics of the ports of each cascade sub-module at the early stage of faults such as open switches and severe aging of input capacitors, and use the differences in the amplitudes and change rates of electrical quantities between sub-modules to complete online detection and positioning of faulty sub-modules, thereby avoiding misdiagnosis caused by large input voltage fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flowchart of a method for diagnosing LLC module faults of an ISOP medium voltage DC converter according to an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the topological structure of an ISOP converter based on two LLC sub-modules according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the current and voltage waveforms at the output port of the ISOP converter after the switch tube of submodule 1 fails in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of current and voltage waveforms at the input port of the ISOP converter after a switch failure in submodule 1 of an embodiment of the present invention;

[0030] Figure 5 A simplified equivalent model schematic diagram of a two-module cascade converter according to an embodiment of the present invention;

[0031] Figure 6 This is a waveform diagram of the input port of the ISOP converter after the severe aging failure of the input capacitor of submodule 1 according to an embodiment of the present invention; wherein, Figure 6 (a) is a schematic diagram of the input voltage waveform. Figure 6 (b) is a schematic diagram of the input current waveform;

[0032] Figure 7 This is a schematic diagram of switch fault diagnosis results of submodule 1 according to an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the fault module diagnosis result when the input voltage fluctuates by 50% in an embodiment of the present invention;

[0034] Fig. 9 It is a structural schematic diagram of an LLC module fault diagnosis device for an ISOP medium voltage DC converter according to an embodiment of the present invention;

[0035] Fig.10 The figure is a diagram showing the internal structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0037] The embodiment of the present invention provides a method for diagnosing faults of an LLC module of an ISOP medium voltage DC converter, such as Figure 1 As shown, the method includes:

[0038] Step 101: monitoring the input capacitor voltage, input current, output voltage and output current of each LLC module port in the ISOP medium voltage DC converter;

[0039] Step 102: determining whether a fault condition of the ISOP medium voltage DC converter is reached according to the output voltage and the output current;

[0040] Step 103: when it is determined that the ISOP medium voltage DC converter has a fault condition, calculating the input capacitor voltage change rate, input voltage amplitude, and input current amplitude of each LLC module;

[0041] Step 104: According to the differences in the input capacitor voltage change rate, input voltage amplitude, and input current amplitude of each LLC module, determine the LLC module in which the switch tube open circuit fault or input capacitor aging fault occurs.

[0042] This embodiment studies the fault diagnosis method that is not affected by the input voltage fluctuation of the submarine DC converter from the LLC module (also called submodule) level, and the fault diagnosis type is more comprehensive. By analyzing the transient characteristics of the voltage and current at the port of the submarine DC converter at the initial stage of the fault of the internal switch tube and input capacitor of the submodule, the voltage and current of each submodule port used for voltage and current equalization control is directly used to design a fast fault diagnosis method suitable for the submarine ISOP type DC converter, without the need to add additional measurement sensors.

[0043] Before introducing the fault diagnosis method of this embodiment, the initial transient characteristics of two faults (switch tube open circuit fault or input capacitor aging fault) of the submarine ISOP medium voltage DC converter are analyzed.

[0044] (1) Analysis of submodule port characteristics at the initial stage of switch open circuit failure

[0045] Due to the characteristics of the switch tube itself and the popularity of existing switch tube drivers with integrated short-circuit protection functions, even if the switch tube has a short-circuit fault, it will eventually evolve into an open-circuit fault. This embodiment will focus on the overall ISOP DC converter system and study the voltage and current transient characteristics of each cascade module port at the initial stage of the switch tube open-circuit fault.

[0046] Take the cascade mode of two LLC resonant submodules with series input and parallel output as an example for analysis. Figure 2 The input voltage of ISOP DC converter is V in , the input current is I in , the output voltage is V out , the output current is I outf The input voltage of submodule 1 is V in1 , the current flowing into the input filter capacitor is I Cin1 , the current flowing into the switching full bridge is I inf1 , the current flowing out of the uncontrolled rectifier bridge is I out1 , the current flowing into the output filter capacitor is I Cf1 , the output current is I outf1 The input voltage of submodule 2 is V in2 , the current flowing into the input filter capacitor is V Cin2 , the current flowing into the switching full bridge is I inf2 , the current flowing out of the uncontrolled rectifier bridge is I out2 , the current flowing into the output filter capacitor is I Cf2 , the output current is I outf2 Obviously, the relationship is as follows:

[0047] Formula (1)

[0048] Formula (2)

[0049] Assume that the switch tube T in the submodule 1 of the ISOP DC converter system 11 An open circuit fault occurs. In the transient process after the fault occurs, due to T 11 The branch is disconnected, and the current flowing into the primary side switch full bridge I inf1 will decrease, the input current I in will also decrease. From equations (1) and (2), we can see that when the input current I in The rate of change is less than the current I inf1 When the current flowing through the input filter capacitor will increase, the input filter capacitor of submodule 1 will beC in1 Charging is performed. At this moment, the input voltage of submodule 1 is V in1 will increase. At the same time, due to the DC bus voltage V in remains unchanged, the input voltage of submodule 2 V in2 will decrease. From equations (1) and (2), we can see that the input filter capacitor of submodule 2 is C in2 Will discharge, flowing into the primary side switch full bridge current of submodule 2 I inf2 will increase. On the output side, due to the current I inf1 The output current of submodule 1 decreases. I outf1 will also decrease. I inf2 The output current of submodule 2 increases I outf2 will also increase. However, due to the voltage V in1 Increase and voltage V in2 The decrease in will cause the control system to lose the ability to regulate the converter output voltage Vout, and the output voltage will show a drop characteristic.

[0050] After the ISOP DC converter system experiences a short fault transient process, the input voltage of submodule 1 V in1 and submodule 2 input voltage V in2 There will be an uneven voltage phenomenon, the two voltage values ​​are stable, and the voltage V in1 Greater than V in2 At this moment, the ISOP DC converter system enters an unhealthy stable operating state, ignoring the current flowing through the two input filter capacitors. I Cin1 and I Cin2 , since the input terminals are connected in series, the current I inf1 and I inf2 Therefore, the input power of submodule 1 is P in1 Higher than the input power of submodule 2 P in2, assuming that the efficiency of the two submodules does not change much, the output currents of the two submodules connected in parallel will no longer be equal, and the output current of submodule 1 will be greater than the output current of submodule 2.

[0051] Based on the above analysis, in the multi-submodule ISOP cascaded DC converter system, when an open-circuit fault occurs in the internal switch tube of any LLC submodule, its input voltage will increase to a certain stable value, and the input current will first decrease rapidly and then rise to recover to a nearly normal value. At the input port of the non-faulty submodule, the input voltage will decrease to a certain stable value, and the input current will first increase rapidly and then decrease to recover to a nearly normal value. At the same time, the voltage and current at the output port of the ISOP converter system both show a downward trend and eventually approach stability.

[0052] Figure 3 and Figure 4 The voltage and current waveforms at the ports of the submarine ISOP DC converter when the switch tube of the simulated submodule 1 fails. Figure 3 It can be seen that during the switching fault transient, the change in input voltage causes control imbalance, which in turn causes the output voltage V out and output current I out There is a certain drop, and the output current of each submodule changes in the same way as the input current. Similarly, after a period of transient process, the input voltage of each module is redistributed and stabilized, then the output voltage V out and output current I out It will eventually stabilize at a constant value.

[0053] from Figure 4 As can be seen in Figure 1, at 0.2s, the drive signal of a switch in submodule 1 is blocked, simulating an open circuit fault state and entering a fault transient process. The current flowing into submodule 1 during this process is I inf1 will decrease, charging its input capacitor, thereby raising the input voltage of submodule 1 V in1 Since the total input voltage is constant and the parameters of each submodule are consistent, the input voltage of non-faulty modules 2 and 3 is V in2 and V in3 The input voltage of non-faulty modules 2 and 3 decreases, which requires the input capacitor to discharge. Therefore, the input current I inf2 and I inf3At about 0.22s, it begins to enter the fault steady state stage. The input voltage of each submodule is stable and runs at a constant value, and the input voltage of fault module 1 is V in1 Higher than the input voltage of healthy modules 2 and 3 V in2 and V in3 At this moment, the input current of submodule 1 is I inf1 The input voltage will rise to a stable value again due to the high input voltage, and the input current of healthy modules 2 and 3 I inf2 and I inf3 As the input voltage drops, it will slowly drop to a stable value. The above results are almost consistent with the theoretical analysis results of the switch open circuit failure.

[0054] (2) Analysis of submodule port characteristics at the initial stage of input capacitor failure

[0055] Although capacitor aging is a slow process, the general converter system will not spend extra cost to configure a capacitor aging detection device. The heat dissipation problem in the extreme deep-sea environment will seriously aggravate the aging process of the input capacitor. When the capacitor ages to a certain stage, its capacitance will also be reduced to affect the normal operation of the submarine ISOP DC converter system. Therefore, this embodiment will focus on the sub-module port voltage circuit characteristics at the initial stage of the serious aging failure of the input filter capacitor of each sub-module, and carry out analysis.

[0056] Metal film capacitors have higher frequency characteristics and longer service life, and are suitable as input filter capacitors for submarine converters. However, long-term operation in a small, closed cavity with poor heat dissipation efficiency and humidity causes the temperature inside and outside the insulating film to rise over time, accelerating the thermal degradation of the insulating film. At the same time, due to the presence of air and water molecules in the air gap, electrochemical corrosion occurs inside the dielectric and metallized electrodes, accelerating the failure process of the capacitor. The general failure characteristics include the capacitance value C Reduce the equivalent series resistance ESR Increase. Equivalent series resistance ESR The increase in temperature will increase the loss of capacitors, and the temperature will continue to rise, which will accelerate the aging of capacitors. Under standard working conditions, it is generally believed that when the capacitance of metal film capacitors decreases by more than 20% and ESR If it rises to more than twice the initial value, it is considered to be failed and cannot be used in the circuit.

[0057] This embodiment still takes the cascade mode of two LLC resonant submodules with serial input and parallel output as an example to analyze the port characteristics when the input filter capacitor is severely aged. Figure 2 Assume that the input filter capacitor of submodule 1 is seriously aged and the capacitance isC in1 Reduce by 20%, equivalent resistance in series ESR 1 increases by 2 times, which has a certain impact on the input voltage of each submodule. When the input voltage of the submarine ISOP converter system is stable, the reduction of the submodule capacitance and the increase of the series equivalent resistance will not cause a significant change in the input voltage, but will cause the input voltage ripple of the faulty module to increase, the system's operating efficiency to decrease, and the power quality to deteriorate.

[0058] When the system input voltage undergoes a step fluctuation, Figure 2 Simplified analysis is performed. Assuming that except for the deviation of the input capacitance, the other circuit parameters of the two submodules are consistent with the control method. Without considering the input capacitance, the input impedance of submodule 1 is Z in1 ( s ) and the input impedance of submodule 2 Z in2 ( s ) can be considered equal, then the two-module cascade converter can be equivalent to a model with equivalent input capacitance and input impedance, such as Figure 5 According to KVL and KCL, the input voltage distribution relationship expression of the two submodules can be obtained:

[0059] Formula (3)

[0060] in, , ,and Z in1 ( s )= Z in2 ( s ).

[0061] From formula (3), we can get the value of Δ for the input disturbance voltage v in , the input voltage change difference of the two submodules Δ v in12 for:

[0062] Formula (4)

[0063] For the step disturbance signal, at the initial moment:

[0064] Formula (5)

[0065] Likewise, in the stable phase there are:

[0066] Formula (6)

[0067] It can be seen from equations (5) and (6) that when the DC bus input voltage is disturbed, the input capacitor voltage of each submodule changes and is related to the capacitance value. The smaller the capacitance value, the higher the voltage jump. At the same time, due to the existence of the voltage balancing loop control, it will eventually stabilize and balance at a new voltage value. In addition, the equivalent resistance of the capacitor in series is not considered in the analysis process. ESR , because its value is still very small, and the step disturbance signal is high frequency. Therefore, for the sub-module with severely aged input capacitor, after the DC input voltage is disturbed, the input capacitor voltage rises rapidly and the amplitude reaches the highest point, and then drops to a new stable point. However, the capacitor voltage of the non-faulty sub-module will also rise, but the rise rate and amplitude are lower than those of the faulty module, and they are also stable at the same voltage value. The entire ISOP DC converter will reach a new voltage-equalizing reference value. At the same time, it can be obtained from formula (1) that the rise rate and amplitude of the input current of the faulty module will also be higher than those of the non-faulty module, and they will also eventually drop back to a new stable state.

[0068] Figure 6 The voltage and current waveforms at the input port of the ISOP DC converter are shown in Figure 1 when the input capacitor of the simulated submodule 1 is seriously aged. Figure 6 It can be seen that at 0.2s, the input capacitance of submodule 1 dropped from 220µF to 176µF, and the equivalent series resistance increased from 0.375Ω to 1.05Ω. At this time, there was no input voltage disturbance, and the input voltage and input current of each module did not change significantly. At 0.3s, a 5% disturbance was injected into the total input voltage of 3000V, and the input voltage of each submodule increased rapidly, but the input voltage of submodule 1 V in1 The rising speed and amplitude are higher than the input voltage of healthy modules 2 and 3. V in2 and V in3 After reaching the highest value, due to the existence of the voltage equalizing ring, the input voltage of each submodule gradually stabilizes at 1050V and remains balanced. Similarly, the output current of each submodule increases, and the output current of submodule 1 I inf1 The rising speed and amplitude are higher than the output current of healthy modules 2 and 3. I inf2 and I inf3 Finally, due to the balanced input voltage, the output current of each submodule is also balanced and stable. The simulation results are consistent with the theoretical analysis.

[0069] According to the above analysis, the switches and capacitors inside the submodules will cause regular changes in the port voltage and current, and there will be differences in the electrical quantities of the faulty module and the healthy module. However, the large fluctuations in the input voltage of the submarine converter will also cause changes in the port voltage and current of each module, but there is no difference in the electrical quantities of all submodules. Based on this, a fault diagnosis principle that is not affected by the large fluctuations in the input voltage of the submarine ISOP DC converter can be designed. In the early stage of an open circuit fault or a serious aging fault of the input capacitor, the capacitor voltage and input current of the faulty submodule will change, and the input voltage of the faulty submodule will show a transient rising process, but in the transient process of the switch tube open circuit fault, the non-faulty submodule will show a transient falling process, and the output voltage of the ISOP converter system will drop to a stable value. For the serious aging fault of the input capacitor, the capacitor voltage of the non-faulty submodule will also rise, but the rate of change is much lower than that of the faulty module, and the system output voltage will be disturbed and quickly return to normal. For the input current, when the switch tube is open circuit fault, the input current of the faulty submodule will decrease in the capacitor voltage increase stage, and the input current of the non-faulty module will increase in the capacitor voltage decrease stage. When the input capacitor ages severely and the disturbance voltage is increased, the average input current of the faulty submodule is higher than that of the non-faulty module.

[0070] The specific fault diagnosis process is as follows:

[0071] First, the submarine ISOP converter monitors the input capacitor voltage of each submodule port. V ini , Input current I infi , output voltage V out and output current I out In the early stage of a switch open circuit failure or severe aging failure of the input capacitor in the submodule, the output voltage or current of the converter will change. However, when the input voltage fluctuates, the output voltage remains stable because this problem has been considered in the early design. Considering the normal operation waveform of the system, the upper limit of the abnormal operation diagnosis threshold of the system is set to V oth1 and I oth1 , the lower threshold is V oth2 and oth2 , this section is set to 20% higher or lower than the rated value. When it is detected that the output voltage and current meet the following formula, it is considered that the submarine ISOP DC converter system has a fault and the fault diagnosis function is triggered; otherwise, monitoring continues.

[0072] Formula (7)

[0073] Then, after determining that the submarine ISOP DC converter system has failed, the input capacitor voltage change rate of each submodule is calculated. dV ini / dt , can be obtained through formula (8), and the input voltage and current amplitude of each submodule can also be obtained V iniA and I infiA .

[0074] Formula (8)

[0075] in, V ini ( k +1) and V ini ( k ) represents the input voltage value of adjacent sampling intervals, T Indicates the sampling period. For the capacitor voltage change. This section uses the slope of the input voltage to indicate that if it is positive, it means that the input capacitor voltage increases; if it is negative, it means that the input capacitor voltage decreases.

[0076] Next, based on the above analysis of the time domain characteristic quantity changes of the switch tube open circuit fault and the input capacitor severe aging fault in the early stage, the input capacitor voltage change rate of all sub-modules is calculated. dV ini / dt , input voltage and current amplitude V iniA and I infiA Compare with each other to locate the faulty module. Assuming that a switch tube open circuit fault occurs in a submodule, the proposed diagnostic method can also locate the faulty submodule. If equation (9) is satisfied, the submodule is determined j Similarly, assuming that a certain submodule’s input capacitor has a serious aging failure, if all of equation (10) are satisfied, then the submodule is determined to be j A failure occurred.

[0077] Formula (9)

[0078] Formula (10)

[0079] Finally, the location of the faulty submodule is determined based on the module-level fault diagnosis circuit and transmitted to the main controller.

[0080] This embodiment fully considers the characteristics of large input voltage fluctuation of submarine ISOP type DC conversion, limited monitored electrical quantity and small and sealed space inside the cavity. Based on the analysis of the time domain characteristics of the ports of each cascaded sub-module at the initial stage of faults such as open switch and severe aging of input capacitor, a sub-module diagnosis method integrating the time domain characteristic quantities of voltage and current of each sub-module at the initial stage of fault is proposed. The traditional fixed diagnostic threshold method is abandoned, and the differences in the amplitude and change rate of electrical quantities between sub-modules are used to complete the online detection and positioning of the faulty sub-module, so as to avoid misdiagnosis caused by large input voltage fluctuations.

[0081] In addition, experimental verification was carried out for the solution of this embodiment.

[0082] Figure 7 It is the fault diagnosis result of the DC converter when the switch of the simulated submodule 1 fails. V in1 , V in2 Input voltage for the submodule, F M1 , F M2 The fault status information of the two submodules is shown in Figure 1. A high level indicates a fault. When the submarine ISOP DC converter is operating at a voltage level of 2000V, a switch in submodule 1 suddenly fails. At this time, the module input voltage and input current will change, and the proposed fault diagnosis principle is met. After about 38μs, F M1 From low to high, F M2 If it remains unchanged, it is determined that submodule 1 fails. Figure 8 This is the result of fault diagnosis when the simulated input voltage drops by 50%. Due to the drop in input voltage, the input voltage of each submodule will change according to the same rule, which is completely different from the change after the submodule fails and does not meet the module fault diagnosis principle. F M1 , F M2 The above results show that the proposed module-level fault diagnosis method for submarine ISOP DC converter can accurately locate the faulty module and is not affected by the wide range of input voltage fluctuations, which meets the submarine application scenario.

[0083] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides an ISOP type medium voltage DC converter LLC module fault diagnosis device, such as Fig. 9 As shown, the ISOP medium voltage DC converter LLC module fault diagnosis device 900 includes: a monitoring module 901, a determination module 902, a calculation module 903 and a diagnosis module 904; wherein:

[0084] Monitoring module 901, used to monitor the input capacitor voltage, input current, output voltage and output current of each LLC module port in the ISOP type medium voltage DC converter;

[0085] A determination module 902 is used to determine whether a fault condition of the ISOP medium voltage DC converter is reached according to the output voltage and the output current;

[0086] A calculation module 903, configured to calculate the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module when it is determined that the ISOP medium voltage DC converter has reached a fault condition;

[0087] The diagnosis module 904 is used to determine the LLC module having a switch tube open circuit fault or an input capacitor aging fault among the LLC modules according to the differences in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of the LLC modules.

[0088] In actual application, the monitoring module 901 , the determination module 902 , the calculation module 903 and the diagnosis module 904 may be implemented by a processor in the ISOP medium voltage DC converter LLC module fault diagnosis device 900 .

[0089] It should be noted that: when the above-mentioned device provided in the above-mentioned embodiment is executed, only the division of the above-mentioned program modules is used as an example. In actual application, the above-mentioned processing can be assigned to different program modules as needed, that is, the internal structure of the terminal is divided into different program modules to complete all or part of the above-mentioned processing. In addition, the above-mentioned device provided in the above-mentioned embodiment belongs to the same concept as the above-mentioned method embodiment. The specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0090] In order to implement the method of an embodiment of the present invention, an embodiment of the present invention also provides a medium voltage DC power supply system, including: a processor and a memory for storing a computer program that can be run on the processor; wherein, when the processor is used to run the computer program, the steps of any one of the above methods are executed.

[0091] The above-mentioned system provided in this embodiment belongs to the same concept as the above-mentioned method embodiment. The specific implementation process thereof is detailed in the method embodiment and will not be repeated here.

[0092] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides a computer program product, which includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the steps of the above method.

[0093] Based on the hardware implementation of the above program modules, and in order to implement the method of the embodiment of the present invention, the embodiment of the present invention further provides an electronic device (computer device). Specifically, in one embodiment, the computer device may be a terminal, and its internal structure diagram may be as follows: Fig.10 As shown. The computer device includes a processor A01, a network interface A02, a display screen A04, an input device A05 and a memory (not shown in the figure) connected through a system bus. Among them, the processor A01 of the computer device is used to provide computing and control capabilities. The memory of the computer device includes an internal memory A03 and a non-volatile storage medium A06. The non-volatile storage medium A06 stores an operating system B01 and a computer program B02. The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 in the non-volatile storage medium A06. The network interface A02 of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor A01, the method of any one of the above embodiments is implemented. The display screen A04 of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device A05 of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse, etc.

[0094] Those skilled in the art will understand that Fig.10 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0095] The device provided by the embodiment of the present invention includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, the method of any one of the above embodiments is implemented.

[0096] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0097] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0098] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0099] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0100] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0101] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0102] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0103] It can be understood that the memory of the embodiment of the present invention can be a volatile memory or a non-volatile memory, and can also include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic random access memory (FRAM), a flash memory, a magnetic surface memory, an optical disc, or a compact disc read-only memory (CD-ROM); the magnetic surface memory can be a disk memory or a tape memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), synchronous static random access memory (SSRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM, SyncLink Dynamic Random Access Memory), and direct RAMbus random access memory (DRRAM, Direct Rambus Random Access Memory).The memories described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memories.

[0104] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0105] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for fault diagnosis of LLC module of ISOP medium voltage DC converter, characterized in that: The method comprises: Monitor the input capacitor voltage, input current, output voltage and output current of each LLC module port in ISOP medium voltage DC converter; Determining whether a fault condition of the ISOP medium voltage DC converter occurs according to the output voltage and the output current; When it is determined that the ISOP medium voltage DC converter has reached a fault condition, calculating the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module; According to the differences in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module, determine the LLC module in which the switch tube open circuit fault or input capacitor aging fault occurs in each LLC module; According to the difference of the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module, determining the LLC module in which the switch tube open circuit fault or input capacitor aging fault occurs in each LLC module includes: For each LLC module, determine whether the input capacitor voltage change rate of the LLC module is greater than 0, and whether the input capacitor voltage change rate of other LLC modules is less than 0, and whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, determine that the LLC module has a switch tube open circuit fault; And, for each LLC module, determine whether the input capacitor voltage change rate of the LLC module is greater than the input capacitor voltage change rate of other LLC modules, whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, it is determined that the LLC module has an input capacitor aging fault.

2. The fault diagnosis method of LLC module of ISOP medium voltage DC converter according to claim 1 is characterized in that: Determining whether a fault condition of the ISOP medium voltage DC converter occurs according to the output voltage and the output current includes: Obtaining a voltage diagnosis upper threshold, a current diagnosis upper threshold, a voltage diagnosis lower threshold, and a current diagnosis lower threshold; According to the voltage diagnosis upper threshold, the current diagnosis upper threshold, the voltage diagnosis lower threshold, the current diagnosis lower threshold, the output voltage and the output current, the following calculation formula is used to determine whether the ISOP medium voltage DC converter fault condition is met: Formula (1) in, Indicates the output voltage, Represents the output current, Indicates the voltage diagnosis upper threshold, Indicates the voltage diagnosis lower threshold, Indicates the upper threshold of current diagnosis. Indicates the current diagnosis lower threshold.

3. The fault diagnosis method of LLC module of ISOP medium voltage DC converter according to claim 2 is characterized in that: The voltage diagnosis upper limit threshold is set to 1.2 times the output voltage rated value, the voltage diagnosis lower limit threshold is set to 0.8 times the output voltage rated value, the current diagnosis upper limit threshold is set to 1.2 times the output current rated value, and the current diagnosis lower limit threshold is set to 0.8 times the output current rated value.

4. The fault diagnosis method of LLC module of ISOP medium voltage DC converter according to claim 1, characterized in that: Calculate the input capacitor voltage change rate of each LLC module, including: The input capacitor voltage change rate of each LLC module is calculated using the following formula: Formula (2) in, represents the input capacitor voltage change rate, and Indicates the input voltage value of adjacent sampling intervals, Indicates the sampling period.

5. An ISOP medium voltage DC converter LLC module fault diagnosis device, characterized in that: The device comprises: A monitoring module is used to monitor the input capacitor voltage, input current, output voltage and output current of each LLC module port in the ISOP medium voltage DC converter; A determination module, used for determining whether a fault condition of the ISOP medium voltage DC converter is reached according to the output voltage and the output current; A calculation module, used for calculating the input capacitor voltage change rate, input voltage amplitude and input current amplitude of each LLC module when it is determined that the ISOP medium voltage DC converter has reached a fault condition; A diagnosis module, used to determine which LLC module has a switch tube open circuit fault or an input capacitor aging fault among the LLC modules according to the difference in the input capacitor voltage change rate, input voltage amplitude and input current amplitude of the LLC modules; Among them, the diagnostic module is specifically used to determine, for each LLC module, whether the input capacitor voltage change rate of the LLC module is greater than 0, and whether the input capacitor voltage change rate of other LLC modules is less than 0, and whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, it is determined that the LLC module has a switch tube open circuit fault; and for each LLC module, it is determined whether the input capacitor voltage change rate of the LLC module is greater than the input capacitor voltage change rate of other LLC modules, and whether the input voltage amplitude of the LLC module is greater than the input voltage amplitude of other LLC modules, and whether the input current amplitude of the LLC module is greater than the input current amplitude of other LLC modules; if so, it is determined that the LLC module has an input capacitor aging fault.

6. A medium voltage DC power supply system, characterized in that: include: A processor and a memory for storing a computer program that can be run on the processor; wherein, when the processor is used to run the computer program, the steps of the method according to any one of claims 1 to 4 are performed.

7. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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