A series full-bridge sub-module component state evaluation method and system

Abstract

The application discloses a series full-bridge sub-module component state evaluation method and system, the method comprises the following steps: constructing a series full-bridge sub-module group, sequentially evaluating the state of each full-bridge sub-module, obtaining the on-state voltage drop of IGBT and diode based on the state mode of the full-bridge sub-module to be measured and the capacitor voltage value of the valve control system, and evaluating the on-flow state of IGBT and diode; based on the on-state voltage drop of IGBT and diode and the state equation of different discharge processes in the full-bridge sub-module to be measured, the capacitor voltage value and the voltage resistance value of the valve control system are combined to calculate the capacitor capacity and the voltage resistance resistance, the state of the capacitor and the voltage resistance is evaluated, and the state evaluation of the component is completed. The application can effectively improve the fault detection efficiency and accuracy of the series full-bridge sub-module, and guarantee the stable operation of the power electronic equipment.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a method and system for evaluating the status of components in a series full-bridge submodule. Background Technology

[0002] In power electronic devices, FBS (Full Bridge Submodule) and TCVG (Thyristor Cascaded Valve Group) are two commonly used power electronic components, playing a crucial role in high-voltage direct current transmission, flexible AC transmission systems, and power electronic transformers. With increasing demands for reliability and efficiency in power systems, condition assessment and fault detection technologies for these components are becoming increasingly important. FBS typically consists of IGBTs (Insulated Gate Bipolar Transistors) and capacitors, enabling energy storage and release while controlling circuit switching. TCVG, on the other hand, is composed of multiple thyristors connected in series, used to control the flow of high-voltage direct current.

[0003] In high-voltage direct current (HVDC) transmission systems, the reliability of fault-tolerant network (FBS) and transient voltage regulation (TCVG) devices directly impacts the system's stable operation. Failure of any single component can lead to the failure of the entire system; therefore, regular component inspection and condition assessment are crucial. The integration of FBS and TCVG technologies can improve the system's power handling capacity and control flexibility. However, this integration also increases system complexity, making fault detection and condition assessment more challenging. Traditional fault detection methods typically rely on manual inspection and simple electrical tests, which are not only time-consuming and labor-intensive but also lack accuracy, failing to meet the high standards required by modern power systems.

[0004] With the development of computer technology and algorithms, algorithm-based state assessment methods have gradually become a research hotspot in the field of power electronic equipment fault detection. Algorithms can identify potential fault hazards more quickly and accurately.

[0005] Chinese patent application CN115706417A, entitled "An Online Status Assessment System and Method for a Converter Valve Submodule," proposes a system comprising a bridge arm current sampling device, a valve control device, and a submodule control unit. The valve control device includes a trigger signal statistics and assessment module and a capacitor status assessment module for the submodule. The capacitor status assessment module estimates the capacitance value of the submodule. Based on the trigger signal statistics and assessment module's count of triggers of the fully controlled switching devices, the normal value of each submodule in the bridge arm is calculated. Submodules deviating from the normal value by more than a specified deviation are identified. The overall status of the converter valve submodule is determined, and a fault alarm and protection signal are issued after a delay. Chinese patent application CN115902604A, entitled "A Method for Health Status Assessment of Flexible DC Transmission Converter Valve Submodules," includes: a waveform display module, an analog-to-digital conversion module, a data processing module, a human-machine interaction module, a data storage module, a data acquisition module, a converter valve control system, a valve tower environmental monitoring system, a water cooling system, and a voltage and current measurement system. The data processing module is electrically connected to the analog-to-digital conversion module, the data storage module, the human-machine interaction module, and the data acquisition module. The analog-to-digital conversion module is electrically connected to the waveform display module. Through the overall structure of the equipment, and through data acquisition, processing, and analysis, the system can present the operating status of the flexible DC converter valve and its control system graphically, highlighting fault points, thereby improving the intelligent monitoring level of the converter valve and its control system's operating status and enabling rapid location and prediction of fault points. However, both of these patents assess half-bridge submodules and cannot be applied to the assessment of full-bridge submodules. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for evaluating the status of components in a series full-bridge submodule, which realizes the independent evaluation of the capacitor voltage and voltage equalization resistor of a single full-bridge submodule, improves the efficiency and accuracy of fault detection, ensures the stable operation of power electronic equipment, and reduces downtime and maintenance costs caused by faults.

[0007] To solve the above technical problems, the present invention adopts the following technical solution:

[0008] A method for evaluating the condition of components in a series full-bridge submodule includes the following steps:

[0009] S1. Construct a series full-bridge submodule group, and evaluate the component status of each full-bridge submodule in turn. Based on the state mode of the full-bridge submodule under test, combined with the capacitor voltage value of VBC (Valve Base Controller), obtain the on-state voltage drop of IGBT and diode, and evaluate the current-carrying state of IGBT and diode.

[0010] S2. Based on the on-state voltage drop of IGBTs and diodes and the state equations of different discharge processes in the full-bridge submodule under test, the capacitance value and the resistance value of the equalizing resistor are calculated in combination with the capacitor voltage value of the valve control system. The state of the capacitor and the equalizing resistor are evaluated to complete the state assessment of the components.

[0011] Furthermore, in step S1, evaluating the current-carrying state of the IGBT and diode includes the following:

[0012] A set number of full-bridge submodules are connected in series to obtain a series full-bridge submodule group.

[0013] The two bypasses of the full-bridge submodule under test include upper bypass and lower bypass. The upper bypass is divided into a first upper bypass including the first IGBT and the second diode, and a second upper bypass including the first diode and the second IGBT, depending on the current direction. The lower bypass is divided into a first lower bypass including the third IGBT and the fourth diode, and a second lower bypass including the third diode and the fourth IGBT, depending on the current direction.

[0014] The six state modes of the full-bridge submodule under test include two discharge modes and four bypass power-on modes; the two discharge modes include the first discharge mode with the first IGBT and the fourth IGBT turned on, and the second discharge mode with the second IGBT and the third IGBT turned on; the four bypass power-on modes include the upper bypass forward current mode, the upper bypass reverse current mode, the lower bypass forward current mode, and the lower bypass reverse current mode.

[0015] Turn on the first and second IGBTs of all full-bridge submodules except the one under test, and obtain the valve control system capacitor voltage, DC power supply voltage, and current values ​​of the full-bridge submodule under test in six state modes. Then calculate the on-state voltage drop of the IGBTs. The specific formula is as follows:

[0016] ;

[0017] in, These represent the on-state voltage drops of the four IGBTs, respectively. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under forward current. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under reverse current. These represent constants under the six state modes. This represents the ratio between the theoretical on-state voltage drop of a diode and the theoretical on-state voltage drop of an IGBT; it is a constant. , This represents the theoretical on-state voltage drop of a diode. This represents the theoretical on-state voltage drop of the IGBT.

[0018] The current and the capacitor voltage of the valve control system are obtained through a current transformer. The specific formula is as follows:

[0019] ;

[0020] Among them, V C1 This represents the capacitor voltage of the valve control system in the first discharge mode, V. C2 This represents the capacitor voltage of the valve control system in the second discharge mode, V. S1 This represents the power supply voltage in the upper bypass forward current mode, V. S2 This represents the power supply voltage in the upper bypass reverse current mode, V. S3 This represents the power supply voltage in the lower bypass forward current mode, V. S4 The voltage represents the power supply voltage in the reverse current mode of the bypass circuit, I represents the circuit current, and R represents the current-limiting resistor.

[0021] Based on the on-state voltage drop of the IGBT, the on-state voltage drop of the diode is obtained.

[0022] When the on-state voltage drop is greater than 105% of the factory value, it indicates that the component corresponding to the on-state voltage drop is in an abnormal current-carrying state, thus completing the evaluation of the current-carrying state of the IGBT and diode.

[0023] Furthermore, in step S2, evaluating the state of the capacitor and the equalizing resistor includes the following:

[0024] The first and fourth IGBTs of the full-bridge submodule under test are turned on, and the capacitor of the full-bridge submodule under test is rapidly discharged through the IGBTs to obtain the relationship between the capacitor voltage and time. Among them, rapid discharge is defined as the full-bridge submodule discharging through an external discharge resistor, and natural discharge is defined as the full-bridge submodule discharging through an equalizing resistor.

[0025] The expression for rapid capacitor discharge is:

[0026] ;

[0027] in, Indicates the capacitance value. Indicates instantaneous current. Indicates instantaneous current The capacitor voltage under the condition, Indicates the first time, This represents the sum of the on-state voltage drops of all diodes and IGBTs through which current flows. This indicates the resistance value of the external discharge resistor for rapid discharge. This indicates the resistance value of the voltage equalizing resistor. This indicates the average power consumption of the board.

[0028] Keep the IGBTs of the full-bridge submodule under test locked, allow the capacitors of the full-bridge submodule under test to discharge naturally, and obtain the voltage values ​​of the capacitors at various times.

[0029] In rapid discharge, ignoring natural discharge, the expression for rapid capacitor discharge can be simplified as follows:

[0030] .

[0031] The expressions for capacitor voltage and current during rapid discharge are obtained, and thus the capacitance value is derived, specifically:

[0032] ;

[0033] in, Indicates the first intermediate variable. , express initial value, express The initial value.

[0034] The expression for the natural discharge of a capacitor is:

[0035] .

[0036] The expressions for capacitor voltage and current during natural discharge are obtained, and thus the resistance value of the voltage-equalizing resistor is derived, specifically:

[0037] ;

[0038] in, Indicates the second intermediate variable. .

[0039] Calculate the capacitance value The difference between the capacitance value and the standard capacitance value is used to determine the capacitor's condition. When this difference exceeds a threshold, it indicates that the capacitor is in an abnormal state, thus completing the capacitor condition assessment.

[0040] Calculate the resistance value of the equalizing resistor The difference between the voltage equalization resistor and the standard resistance value is used to determine whether the voltage equalization resistor is in an abnormal state. When the difference exceeds the threshold, it indicates that the voltage equalization resistor is in an abnormal state, thus completing the assessment of the voltage equalization resistor's state.

[0041] Furthermore, this invention also proposes a system for evaluating the status of components in a series full-bridge submodule, comprising:

[0042] The evaluation module for IGBTs and diodes is used to construct a series full-bridge sub-module group. The component status of each full-bridge sub-module is evaluated in turn. Based on the state mode of the full-bridge sub-module under test and combined with the capacitor voltage value of the valve control system, the on-state voltage drop of the IGBT and diode is obtained, and the current-carrying state of the IGBT and diode is evaluated.

[0043] The evaluation module for capacitors and equalizing resistors is used to calculate the capacitance and resistance values ​​based on the on-state voltage drop of IGBTs and diodes and the state equations of different discharge processes in the full-bridge submodule under test, combined with the capacitor voltage value of the valve control system, to evaluate the state of the capacitors and equalizing resistors and complete the state evaluation of the components.

[0044] Furthermore, the present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the serial full-bridge submodule component status assessment method.

[0045] Furthermore, the present invention also proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the aforementioned method for evaluating the status of components in a series full-bridge submodule.

[0046] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0047] This invention evaluates the status of diodes, IGBTs, capacitors, voltage equalizing resistors, and thyristor cascaded valve groups in a full-bridge submodule, locates abnormal components, and provides handling methods. It optimizes the targeting of field testing and valve group maintenance, significantly improves maintenance efficiency and accuracy while ensuring safety, and provides strong support for lean maintenance of converter valves. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the overall implementation of the present invention.

[0049] Figure 2 This is a structural diagram of the upper bypass in the full-bridge submodule under test in this invention.

[0050] Figure 3 This is a structural diagram of the lower bypass in the full-bridge submodule to be tested in this invention.

[0051] Figure 4 This is a structural diagram of the discharge mode in the full-bridge submodule under test in this invention.

[0052] Figure 5 This is a simulation structure diagram of the on-state voltage drop test of the full-bridge submodule under test in an embodiment of the present invention.

[0053] Figure 6 This is a voltage and current waveform diagram in the first discharge mode of an embodiment of the present invention.

[0054] Figure 7 This is a voltage and current waveform diagram in the second discharge mode of an embodiment of the present invention.

[0055] Figure 8 This is a simulation structure diagram of the on-state voltage drop test of the full-bridge submodule under test in the upper bypass forward current mode in an embodiment of the present invention.

[0056] Figure 9 This is a voltage and current waveform diagram in the upper bypass forward current mode in an embodiment of the present invention.

[0057] Figure 10 This is a voltage and current waveform diagram in the upper bypass reverse current mode in an embodiment of the present invention.

[0058] Figure 11 This is a voltage and current waveform diagram in the lower bypass forward current mode in an embodiment of the present invention.

[0059] Figure 12 This is a voltage and current waveform diagram in the lower bypass reverse current mode in an embodiment of the present invention.

[0060] Figure 13 This is a diagram of the fast discharge structure of the capacitor of the full-bridge submodule under test in an embodiment of the present invention.

[0061] Figure 14 This is a simulation structure diagram of the capacitor fast discharge test of the full-bridge submodule under test in an embodiment of the present invention.

[0062] Figure 15 This is a waveform diagram showing the change of capacitor voltage over time during rapid discharge in an embodiment of the present invention.

[0063] Figure 16 This is a waveform diagram showing the change of capacitor voltage over time during natural discharge in an embodiment of the present invention. Detailed Implementation

[0064] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0065] To achieve the above objectives, this invention proposes a method for evaluating the status of components in a series full-bridge submodule, such as... Figure 1 As shown, the specific steps are as follows:

[0066] S1. Construct a series full-bridge submodule group, and sequentially evaluate the component status of each full-bridge submodule. Based on the state mode of the full-bridge submodule under test, combined with the capacitor voltage value of VBC (Valve Base Controller), obtain the on-state voltage drop of IGBT and diode, and evaluate the current-carrying state of IGBT and diode. Specifically:

[0067] A set number of full-bridge submodules are connected in series to obtain a series full-bridge submodule group.

[0068] The two bypass methods of the full-bridge submodule under test include upper bypass and lower bypass; such as Figure 2 As shown, the upper bypass is divided into several types according to the direction of the current, including: Figure 2 The first upper bypass of the first IGBT and the second diode shown in (a) and including as follows Figure 2 (b) shows the second upper bypass of the first diode and the second IGBT; as shown Figure 3 As shown, the lower bypass is divided into several types according to the direction of the current, including: Figure 3 The first lower bypass of the third IGBT and fourth diode shown in (a) and including as follows Figure 3 The third diode and the second lower bypass of the fourth IGBT are shown in (b).

[0069] The six state modes of the full-bridge submodule under test include two discharge modes and four bypass power-on modes; among them, such as Figure 4 As shown, the two discharge modes include, for example: Figure 4 The first discharge mode of the first IGBT and the fourth IGBT shown in (a), and as shown in (a) Figure 4 (b) shows the second discharge mode of the second IGBT and the third IGBT.

[0070] Figure 2 , Figure 3 , Figure 4 In the diagram, VT1 represents the first IGBT, VT2 represents the second IGBT, VT3 represents the third IGBT, VT4 represents the fourth IGBT, VD1 represents the first diode, VD2 represents the second diode, VD3 represents the third diode, VD4 represents the fourth diode, C represents the capacitance value, and R1 represents the discharge resistor.

[0071] The four bypass power-on modes include upper bypass forward current mode, upper bypass reverse current mode, lower bypass forward current mode, and lower bypass reverse current mode.

[0072] Turn on the first and second IGBTs of all full-bridge submodules except the one under test, and obtain the valve control system capacitor voltage, DC power supply voltage, and current values ​​of the full-bridge submodule under test in six state modes. Then calculate the on-state voltage drop of the IGBTs. The specific formula is as follows:

[0073] ;

[0074] in, These represent the on-state voltage drops of the four IGBTs, respectively. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under forward current. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under reverse current. These represent constants under the six state modes. This represents the ratio between the theoretical on-state voltage drop of a diode and the theoretical on-state voltage drop of an IGBT; it is a constant. , This represents the theoretical on-state voltage drop of a diode. This represents the theoretical on-state voltage drop of the IGBT.

[0075] The current and the capacitor voltage of the valve control system are obtained through a current transformer. The specific formula is as follows:

[0076] ;

[0077] Among them, V C1 V represents the capacitor voltage of the valve control system in the first discharge mode; C2 V represents the capacitor voltage of the valve control system in the second discharge mode; S1 This indicates the power supply voltage in the upper bypass forward current mode; V S2 This indicates the power supply voltage in the upper bypass reverse current mode; V S3 This indicates the power supply voltage in the lower bypass forward current mode; V S4 The voltage represents the power supply voltage in the reverse current mode of the bypass; I represents the circuit current, which is the same in all modes; R represents the current-limiting resistor, which remains unchanged in all modes.

[0078] The first and second discharge modes acquire the capacitor voltage under a set current. The upper bypass forward current mode, upper bypass reverse current mode, lower bypass forward current mode, and lower bypass reverse current mode adjust the power supply voltage to make the current reach the set value.

[0079] Since the environmental conditions of the IGBTs and diodes connected in parallel at the same location in the full-bridge submodule under test are highly similar, it is assumed that the aging degree of the IGBTs and diodes connected in parallel at the same location is similar. Even if they age, the on-state voltage drop of the IGBTs and diodes will still maintain the same proportion as before. Therefore, the on-state voltage drop of the diodes can be obtained based on the on-state voltage drop of the IGBTs.

[0080] When the on-state voltage drop is greater than 105% of the factory value, it indicates that the component corresponding to the on-state voltage drop is in an abnormal current-carrying state and should be replaced. The current-carrying state of the IGBT and diode should be evaluated.

[0081] The series-connected full-bridge submodule group consists of two full-bridge submodules connected in series, with the upper full-bridge submodule being the full-bridge submodule under test.

[0082] Figure 5 This diagram shows a simulation structure for testing the on-state voltage drop of IGBTs and diodes in PLECS (Power Electronics Circuit Simulator). On-state voltage drops are set for both the IGBTs and diodes in the full-bridge submodule under test. The ratio of the on-state voltage drops of IGBTs and diodes connected in reverse parallel at the same location is a constant value, set to 7 / 6. That is, the on-state voltage drop of the IGBT is 7 / 6 of the on-state voltage drop of the diode at the same location. The initial voltage values ​​of the first capacitor C1 and the second capacitor C2 are both 100V, and their capacitance values ​​are both 0.013F. The resistance of the discharge resistor R1 is 1Ω. The signal source is a step signal that jumps from 0 to 1 within 1 second of the simulation time, thereby triggering the corresponding IGBT to conduct. A current transformer is connected to the discharge resistor and an oscilloscope is connected to it to monitor the current change in the discharge resistor during capacitor discharge. Voltage transformers are connected across the capacitors in the full-bridge submodule under test. These voltage transformers represent the valve control system in the actual testing process and are used to monitor the capacitor voltage.

[0083] One second after the simulation starts, the two step signal sources step to 1, turning on their connected IGBTs, thereby enabling the full-bridge submodule under test to discharge through the first and fourth IGBTs, while the other full-bridge submodules are bypassed, with current flowing through the sixth diode VD6 and the fifth IGBT.

[0084] Figure 6 This is the voltage and current waveform during the on-state voltage drop test in the first discharge mode. One second after the simulation starts, the IGBT turns on, causing the first capacitor C1 to discharge and generating current flowing through the discharge resistor. When the current reaches the set current of 50A, the capacitor voltage is 61.25V. Therefore, the state equation is:

[0085] .

[0086] Figure 7 This is the voltage and current waveform diagram during the on-state voltage drop test in the second discharge mode. One second after the simulation starts, the IGBT turns on, causing the first capacitor C1 to discharge and generating current flowing through the discharge resistor. When the current reaches the set current of 50A, the capacitor voltage is 60.90V. Therefore, the state equation is:

[0087] .

[0088] Figure 8This is a simulation diagram of the on-state voltage drop test in the upper bypass forward current mode. A DC power source is used for power supply. The voltage is continuously changed until the current in the circuit reaches the set current of 50A, and the corresponding power supply voltage is recorded.

[0089] Figure 9 This is the voltage and current waveform diagram under the forward current mode of the upper bypass during the on-state voltage drop test. When the current reaches the set current of 50A, the power supply voltage is 59.80V. Therefore, the state equation is:

[0090] .

[0091] Figure 10 This is the voltage and current waveform diagram under the reverse current mode of the upper bypass during the on-state voltage drop test. One second after the simulation starts, the IGBT turns on, causing current to flow through the full-bridge submodule. When the current reaches the set current of 50A, the power supply voltage is 61.50V. Therefore, the state equation is:

[0092] .

[0093] Figure 11 This is the voltage and current waveform diagram under the lower bypass forward current mode during the on-state voltage drop test. One second after the simulation starts, the IGBT turns on, causing current to flow through the full-bridge submodule. When the current reaches the set current of 50A, the power supply voltage is 59.90V. Therefore, the state equation is:

[0094] .

[0095] Figure 12 This is the voltage and current waveform diagram under the reverse current mode with bypass during the on-state voltage drop test. One second after the simulation starts, the IGBT turns on, causing current to flow through the full-bridge submodule. When the current reaches the set current of 50A, the power supply voltage is 61.45V. Therefore, the state equation is:

[0096] .

[0097] Based on the above 6 sets of state equations, the matrix can be obtained as follows:

[0098] .

[0099] The solutions to the six sets of state equations can be obtained using Gaussian elimination, as follows:

[0100] .

[0101] The on-state voltage drops of the IGBT and diodes in the full-bridge submodule under test at a current of 50A are shown in Table 1.

[0102] Table 1. On-state voltage drop of IGBTs and diodes

[0103]

[0104] As can be seen from Table 1, the calculated on-state voltage drop is the same as that obtained from simulation, indicating that the method proposed in this invention is consistent with reality and can be implemented.

[0105] S2. Based on the on-state voltage drop of IGBTs and diodes, and the state equations of different discharge processes in the full-bridge submodule under test, the capacitance value and the resistance value of the voltage equalizing resistor are calculated in conjunction with the capacitor voltage value of the valve control system. The state of the capacitor and the voltage equalizing resistor are evaluated to complete the state assessment of the components. Specifically:

[0106] like Figure 13 As shown, the first and fourth IGBTs of the full-bridge submodule under test are turned on, and the capacitor of the full-bridge submodule under test is rapidly discharged through the IGBTs to obtain the relationship between the capacitor voltage and time. Here, rapid discharge is defined as the full-bridge submodule discharging through an external discharge resistor, and natural discharge is defined as the full-bridge submodule discharging through an equalizing resistor.

[0107] The expression for rapid capacitor discharge is:

[0108] ;

[0109] in, Indicates the capacitance value. Indicates instantaneous current. Indicates instantaneous current The capacitor voltage under the condition, Indicates the first time, This represents the sum of the on-state voltage drops of all diodes and IGBTs through which current flows. This indicates the resistance value of the external discharge resistor for rapid discharge. This indicates the resistance value of the voltage equalizing resistor. This indicates the average power consumption of the board.

[0110] Keep the IGBTs of the full-bridge submodule under test locked, allow the capacitors of the full-bridge submodule under test to discharge naturally, and obtain the voltage values ​​of the capacitors at various times.

[0111] Figure 14 The simulation structure diagram for the capacitor fast discharge test is shown in Table 2. The preset parameters of the relevant components are shown in Table 2.

[0112] Table 2 Preset parameters of components

[0113]

[0114] One second after the simulation starts, the first and fourth IGBTs are turned on. At this time, the first capacitor C1 discharges rapidly through the discharge resistor R1 and simultaneously through the voltage equalization resistor. Natural discharge. However, since the resistance of the voltage equalization resistor is much larger than that of the discharge resistor, natural discharge is negligible. Therefore, the expression for rapid capacitor discharge can be simplified as:

[0115] .

[0116] The expressions for capacitor voltage and current during rapid discharge are obtained, and thus the capacitance value is derived, specifically:

[0117] ;

[0118] in, Indicates the first intermediate variable. , express initial value, express The initial value.

[0119] Figure 5 , Figure 8 , Figure 13 , Figure 14 In the diagram, VT1 represents the first IGBT, VT2 represents the second IGBT, VT3 represents the third IGBT, VT4 represents the fourth IGBT, VD1 represents the first diode, VD2 represents the second diode, VD3 represents the third diode, VD4 represents the fourth diode, VT5 represents the fifth IGBT, VT6 represents the sixth IGBT, VT7 represents the seventh IGBT, VT8 represents the eighth IGBT, and R1 represents the discharge resistor.

[0120] Figure 15 The waveform of capacitor voltage changing over time during rapid discharge is shown. Since the simulation starts turning on the IGBT at the 1st second, the discharge time should be the simulation time minus 1 second. It is 500V. The value is 0s. When t is 0.1s, The voltage is 237.23V. The switching of the IGBTs in the full-bridge submodule does not consume capacitor power, therefore... If it is 0, then This result has an error of 3.17% compared to the simulated capacitance value of 0.013F.

[0121] Since natural discharge does not enable the IGBT to discharge externally, natural discharge only requires deleting the step signal in the fast discharge simulation structure diagram to prevent the IGBT from being turned on.

[0122] The expression for the natural discharge of a capacitor is:

[0123] .

[0124] The expressions for capacitor voltage and current during natural discharge are obtained, and thus the resistance value of the voltage-equalizing resistor is derived, specifically:

[0125] ;

[0126] in, Indicates the second intermediate variable. .

[0127] Figure 16 This is a waveform diagram showing the change of capacitor voltage over time during natural discharge. Figure 16 It can be seen that, 100V The value is 0s. When t is 50s, The voltage is 90.832426V. Since the switching of the IGBTs in the full-bridge submodule does not consume capacitor power, therefore... If it is 0, then The error between this result and the simulated voltage equalization resistor value of 4kΩ is less than 1%.

[0128] Calculate capacitance value using NumPy's comparison operations. The difference between the capacitance value and the rated capacitance value should be checked in accordance with the standard Q / GDW 493-2010 "Technical Specification for High Voltage Direct Current Transmission Converter Valves". When the difference exceeds 5% of the rated capacitance value, it indicates that the capacitor is in an abnormal state and should be replaced. The capacitor condition assessment is then completed.

[0129] Calculate the resistance value of the voltage equalizing resistor using NumPy's comparison operations. The difference between the voltage equalization resistor and its rated resistance value should be checked in accordance with the standard Q / GDW 493-2010 "Technical Specification for High Voltage Direct Current Transmission Converter Valves". When the difference exceeds 3% of the rated resistance value of the voltage equalization resistor, it indicates that the voltage equalization resistor is in an abnormal state and should be replaced. The condition of the voltage equalization resistor should then be assessed.

[0130] This invention also proposes a system for evaluating the status of components in a series full-bridge submodule, including evaluation modules for IGBTs and diodes, evaluation modules for capacitors and voltage-equalizing resistors, and a computer program that can run on a processor. It should be noted that each module in the above system corresponds to a specific step of the method provided in this invention, possessing the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in this invention.

[0131] This invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. It should be noted that when the processor executes the computer program, it corresponds to the specific steps of the method provided in this invention, possessing the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in this invention.

[0132] This invention also proposes a computer-readable storage medium storing a computer program. It should be noted that when the computer program is executed by a processor, it corresponds to the specific steps of the method provided in this invention, possessing the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in this invention.

[0133] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of evaluating the state of a series full-bridge sub-module component, characterized by, include: S1. Construct a series full-bridge sub-module group, and evaluate the component status of each full-bridge sub-module in turn. Based on the state mode of the full-bridge sub-module under test, combined with the capacitor voltage value of the valve control system, obtain the on-state voltage drop of IGBT and diode, and evaluate the current-carrying state of IGBT and diode. S2. Based on the on-state voltage drop of IGBTs and diodes and the state equations of different discharge processes in the full-bridge submodule under test, the capacitance value and the resistance value of the equalizing resistor are calculated in combination with the capacitor voltage value of the valve control system. The state of the capacitor and the equalizing resistor are evaluated to complete the state assessment of the components.

2. The method of claim 1, wherein, In step S1, the evaluation of the current-carrying state of the IGBT and diode includes the following: A set number of full-bridge submodules are connected in series to obtain a series full-bridge submodule group; The two bypasses of the full-bridge submodule under test include the upper bypass and the lower bypass; The upper bypass is divided into a first upper bypass including a first IGBT and a second diode, and a second upper bypass including a first diode and a second IGBT, depending on the direction of the current. The lower bypass is divided into the first lower bypass, which includes the third IGBT and the fourth diode, and the second lower bypass, which includes the third diode and the fourth IGBT, depending on the direction of the current. The six state modes of the full-bridge submodule under test include two discharge modes and four bypass power-on modes; among them, the two discharge modes include the first discharge mode with the first IGBT and the fourth IGBT turned on, and the second discharge mode with the second IGBT and the third IGBT turned on. The four bypass power-on modes include upper bypass forward current mode, upper bypass reverse current mode, lower bypass forward current mode, and lower bypass reverse current mode. Turn on the first and second IGBTs of all full-bridge submodules except the one under test, and obtain the valve control system capacitor voltage, DC power supply voltage, and current values ​​of the full-bridge submodule under test in six state modes. Then calculate the on-state voltage drop of the IGBTs. The specific formula is as follows: ； in, These represent the on-state voltage drops of the four IGBTs, respectively. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under forward current. This represents the sum of the on-state voltage drops of all full-bridge submodules except the one under test under reverse current. These represent constants under the six state modes. This represents the ratio between the theoretical on-state voltage drop of a diode and the theoretical on-state voltage drop of an IGBT; it is a constant. , This represents the theoretical on-state voltage drop of a diode. This represents the theoretical on-state voltage drop of the IGBT; The current and the capacitor voltage value of the valve control system are obtained by the current transformer, and the formula is as follows: , and the specific formula is as follows: ； where V C1 represents the capacitor voltage of the valve control system in the first discharge mode, V C2 represents the capacitor voltage of the valve control system in the second discharge mode, V S1 represents the supply voltage in the upper bypass forward current mode, V S2 represents the supply voltage in the upper bypass reverse current mode, V S3 represents the supply voltage in the lower bypass forward current mode, V S4 represents the supply voltage in the lower bypass reverse current mode, I represents the circuit current, and R represents the current limiting resistance. Based on the on-state voltage drop of the IGBT, the on-state voltage drop of the diode is obtained; When the on-state voltage drop is greater than 105% of the factory value, it indicates that the component corresponding to the on-state voltage drop is in an abnormal current-carrying state, thus completing the evaluation of the current-carrying state of the IGBT and diode.

3. The method of claim 2, wherein, In step S2, evaluating the state of the capacitor and the equalizing resistor includes the following: The first and fourth IGBTs of the full-bridge submodule under test are turned on, and the capacitor of the full-bridge submodule under test is rapidly discharged through the IGBTs to obtain the relationship between the capacitor voltage and time. Here, rapid discharge is defined as the full-bridge submodule discharging through an external discharge resistor, and natural discharge is defined as the full-bridge submodule discharging through an equalizing resistor. The expression for rapid capacitor discharge is: ； wherein, represents a capacitance value, represents an instantaneous current, represents a capacitance voltage under the instantaneous current represents a capacitance voltage under the instantaneous current represents a first represents a first represents a sum of on-state voltage drops of diodes and IGBTs through which all currents flow, represents a resistance value of a fast discharge external discharge resistor, represents a resistance value of a voltage equalization resistor, represents an average power consumed by a board card; Keep the IGBT of the full-bridge submodule under test locked, allow the capacitor of the full-bridge submodule under test to discharge naturally, and obtain the voltage value of the capacitor at each time point. In rapid discharge, ignoring natural discharge, the expression for rapid capacitor discharge can be simplified as follows: ； The expressions for capacitor voltage and current during rapid discharge are obtained, and thus the capacitance value is derived, specifically: ； in, Indicates the first intermediate variable. , express initial value, express The initial value; The expression for the natural discharge of a capacitor is: ； The expressions for capacitor voltage and current during natural discharge are obtained, and thus the resistance value of the voltage-equalizing resistor is derived, specifically: ； in, Indicates the second intermediate variable. ; Calculate the capacitance value The difference between the capacitance value and the standard capacitance value is used to determine the capacitor's condition. When the difference exceeds a threshold, it indicates that the capacitor is in an abnormal state, thus completing the capacitor condition assessment. Calculate the resistance value of the equalizing resistor The difference between the voltage equalization resistor and the standard resistance value is used to determine whether the voltage equalization resistor is in an abnormal state. When the difference exceeds the threshold, it indicates that the voltage equalization resistor is in an abnormal state, thus completing the assessment of the voltage equalization resistor's state.

4. A system applied to the component condition assessment method for a series full-bridge submodule as described in claim 1, characterized in that, include: The evaluation module for IGBTs and diodes is used to construct a series full-bridge sub-module group. The component status of each full-bridge sub-module is evaluated in turn. Based on the state mode of the full-bridge sub-module under test and combined with the capacitor voltage value of the valve control system, the on-state voltage drop of the IGBT and diode is obtained, and the current-carrying state of the IGBT and diode is evaluated. The evaluation module for capacitors and voltage equalizing resistors calculates the capacitance and resistance values ​​based on the on-state voltage drop of IGBTs and diodes and the state equations of different discharge processes in the full-bridge submodule under test, combined with the capacitor voltage value of the valve control system, and evaluates the state of the capacitors and voltage equalizing resistors to complete the state evaluation of the components.

5. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the serial full-bridge submodule component status assessment method according to any one of claims 1 to 3.

6. A computer-readable storage medium storing a computer program, characterized in that, The computer program is executed by the processor to perform the serial full-bridge submodule component status assessment method according to any one of claims 1 to 3.

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