Method and system for rapidly removing fault of UPFC (Unified Power Flow Controller) sub-module

Abstract

The invention discloses a UPFC (Unified Power Factor Correction) sub-module fault rapid removal method and system, and the method comprises the steps: carrying out the intrinsic modeling of a UPFC sub-module circuit, and calculating a DC bus voltage, an AC port current and an IGBT (Insulated Gate Bipolar Translator) junction temperature; calculating the absolute value residual error of the direct current bus voltage, the alternating current port current and the IGBT junction temperature; judging whether abnormity exists or not according to the absolute value residual error, if yes, acquiring a circuit fault intrinsic parameter, matching the circuit fault intrinsic parameter with a preset abnormity feature library, and performing multi-level fault screening identification according to a matching result; setting a static priority, and calculating a dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; and according to the dynamic priorities, corresponding fault removal is carried out on different fault types of different sub-modules. The method has better performance in the aspects of response speed, multi-type fault identification and system adaptability.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical engineering, and in particular relates to a method and system for quickly removing a UPFC submodule fault. Background Art

[0002] As the most comprehensive device in the flexible AC transmission system, the Unified Power Flow Controller (UPFC) can independently adjust the active and reactive power of the line and the node voltage to improve the transmission capacity and stability of the power grid. However, its complex submodule structure and high-frequency action characteristics make the design of control and protection strategies face severe challenges, especially in the technical bottleneck of rapid fault identification and dynamic response.

[0003] Existing UPFC projects mostly adopt complex redundant configuration protection strategies at the system level, by adding a large number of redundant equipment to run in parallel, and improving reliability through the "three out of two" logic; however, such solutions usually locate system-level control and protection strategies, which require a lot of economic investment to build, and the static priority arbitration they adopt is prone to response delays due to logical conflicts when multiple faults occur simultaneously, making it difficult to meet the needs of complex fault scenarios; Patent CN118885879A proposes a UPFC equipment fault prediction method based on wavelet neural network, including: defining the fault variables of the unified power flow controller; classifying the fault variables, and defining The data acquisition structure is measured; the signal data of each node of the unified power flow controller is obtained, and the signal data is classified and encoded after filtering and A / D conversion; a wavelet neural network is used to build an equipment fault prediction model; the real-time signal data is input into the trained equipment fault prediction model to obtain the equipment status prediction result output by the equipment fault prediction model; according to the equipment status prediction result, it is judged whether there is an equipment fault; a fault warning signal is issued for the predicted equipment fault, but a single fault still needs training, and the processing is inefficient; and it can only diagnose and predict, without subsequent fault handling methods, processing priority determination, etc., and the object is the system as a whole and the valve level, and does not involve sub-modules. Summary of the invention

[0004] In view of this, the present invention provides a UPFC submodule fault rapid removal method and system, which improves the diagnosis accuracy of composite faults by circuit intrinsic modeling and filtering transient interference, combines BP neural network, and introduces dynamic weight allocation to optimize fault arbitration logic, so as to achieve rapid removal in multi-fault scenarios. Compared with the existing technology, it has significant advantages in response speed, diagnosis accuracy and system adaptability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: The first aspect of the present invention provides a method for quickly removing a UPFC submodule fault, which is characterized by comprising: Perform intrinsic modeling of the UPFC submodule circuit, and calculate the DC bus voltage, AC port current and IGBT junction temperature based on the modeling and the UPFC submodule control strategy; The absolute value residuals of the DC bus voltage, AC port current and IGBT junction temperature are calculated by using the real-time collected DC bus voltage, AC port current and IGBT junction temperature and their corresponding calculated values; all IGBTs of each UPFC submodule are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; Determine whether there is an abnormality based on the absolute value residual. If there is an abnormality, obtain the circuit fault intrinsic parameters, match the circuit fault intrinsic parameters with the preset abnormal feature library, and perform multi-level fault screening and identification based on the matching results; Set a static priority, and calculate a dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; the static priority is the priority of different fault types of the same submodule, and the dynamic priority is the priority of different fault types of different submodules; According to the dynamic priority, corresponding fault removal is adopted for different fault types of different submodules.

[0006] Preferably, according to the UPFC submodule circuit intrinsic modeling and the UPFC submodule control strategy, a mathematical formula of the DC bus voltage, the AC port current and the IGBT junction temperature is established:

[0007] In the above formula, for t The calculated value of the DC bus voltage at the moment, for t The calculated value of the AC port current at the moment, for t The calculated value of IGBT junction temperature at time, S bridge is the switch tube switching function of the bridge arm; I dc It is the sum of the DC currents input to the three-phase bridge arms from the DC side; ω 1 is the angular frequency of the AC side voltage; I S and They are the current amplitude and phase of the AC side of the converter in UPFC respectively; MI s / 4、 are the amplitude and phase of the second harmonic of the circulating current respectively; M is the modulation ratio, is the switch function of the submodule. C is the DC bus capacitance, is the DC bus voltage, is the number of converter arm submodules in UPFC, is the equivalent series resistance of the DC bus capacitor, T a ( t ) is obtained by measurement t The IGBT substrate temperature at the moment, P thIGBT is the IGBT heat loss, Z thIGBT is the IGBT thermal resistance network.

[0008] Preferably, the switch switching function of the bridge arm is S bridge And the switch switching function of the submodule It is obtained through the control strategy adopted by the UPFC submodule. The control strategy adopted by the UPFC submodule includes the submodule voltage equalization control strategy and the double frequency circulating current suppression strategy; among which the double frequency circulating current suppression strategy outputs the modulated wave through carrier shift modulation.

[0009] Preferably, judging whether there is an abnormality according to the absolute value residual is specifically: The absolute value residual of each sampling point of the collected DC bus voltage, AC port current and IGBT junction temperature is recorded using a set sampling window, and the mean and standard deviation of all absolute value residuals of each sampling window of the DC bus voltage, AC port current or IGBT junction temperature are calculated; If the absolute value of the difference between the absolute value residual of the DC bus voltage, AC port current or IGBT junction temperature at the sampling point and the mean of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window is greater than 3 times the standard deviation of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window, the UPFC submodule is judged to be abnormal.

[0010] Preferably, the circuit fault intrinsic parameters include the DC bus voltage measurement value, the DC bus voltage deviation rate, the AC port current measurement value, the AC port current change rate d arm / dt , IGBT junction temperature measurement and IGBT junction temperature gradient dT j / dt ; The DC bus voltage deviation rate DVR Uc、 AC port current change rate darm / dt, IGBT junction temperature gradient dT j / dt The calculation formula is:

[0011] In the above formula, u c,m ( t )for t The measured value of DC bus voltage at the moment, for t The calculated value of the DC bus voltage at time , U c,rated is the rated value of DC bus voltage, I arm,m ( t ), I arm,m ( t -1) respectively t , t -1 AC port current measurement value, T j,m ( t ), T j,m ( t -1) respectively t , t IGBT junction temperature measurement value at -1 time, is the set sampling window.

[0012] Preferably, the circuit fault intrinsic parameters are matched with a preset abnormal feature library, and multi-level fault screening and identification is performed according to the matching results, specifically: First, the first-level fault screening is performed, and the intrinsic parameters of the circuit fault within a sampling window after the abnormality is judged are recorded. The DC bus voltage, DC bus voltage deviation rate, and AC port current are formed into a vector, and the cosine similarity of the first abnormal reference vector corresponding to various faults in the preset abnormal feature library is calculated. If there is a cosine similarity greater than the set first threshold, it is considered that the corresponding fault exists; if all cosine similarities are less than or equal to the first threshold and greater than the second threshold, the second-level fault screening is used; if all cosine similarities are less than or equal to the second threshold, the third-level fault screening is used; The second-level fault screening is to widen the sampling window, and form a vector of all circuit fault intrinsic parameters, and calculate the cosine similarity of the second abnormal reference vector corresponding to various faults in the preset abnormal feature library. If the cosine similarity is greater than the set first threshold, it is considered that the corresponding fault exists; The third-level fault screening is to input the circuit fault intrinsic parameters of adjacent modules into the pre-trained BP neural network and output the probability of each fault; if the probability exceeds the set third threshold, it is considered that the corresponding fault exists; The first abnormal reference vector corresponding to the various faults is a vector composed of historical data of the DC bus voltage, DC bus voltage deviation rate, and AC port current within a set sampling window after the occurrence of the various faults; the second abnormal reference vector corresponding to the various faults is a vector composed of historical data of all circuit fault intrinsic parameters within the widened sampling window after the occurrence of the various faults obtained through historical data.

[0013] Preferably, the static priorities of capacitor overvoltage fault, IGBT short circuit fault and IGBT overheat fault are set to 80, 70 and 60 respectively.

[0014] Preferably, the calculation of dynamic priority , specifically:

[0015] In the above formula, P static For the static priority setting, α , β and γ are the DC bus voltage, IGBT junction temperature and AC port current weight coefficients respectively, U c,m ( t )for t The measured value of DC bus voltage at the moment, U c,rated is the rated value of DC bus voltage, for t The measured value of IGBT junction temperature at the moment, is the maximum junction temperature of the IGBT, for t The measured current value of the AC port at the moment, It is the maximum current of AC port.

[0016] Preferably, the method of taking corresponding fault removal for different fault types according to the dynamic priority is specifically as follows: When a single fault occurs, if it is an IGBT short-circuit fault, the submodule drive is locked and the bypass switch is triggered, and the redundant module is put into operation; if it is a capacitor overvoltage fault, the faulty module is removed and the redundant unit is put into operation, and the bridge arm level output is maintained stable through the modulation control algorithm; if it is an IGBT overheating fault, the redundant unit is cut off or the submodule output is reduced; If multiple faults occur, an excision sequence is generated according to the dynamic priority from high to low, the faulty sub-modules are isolated in sequence and the redundant modules are put into use. When the redundant modules are insufficient, the converter is triggered to stop operating emergently.

[0017] The second aspect of the present invention provides a fast fault excision system for UPFC sub-modules using the method described in the first aspect of the present invention, including a circuit physical intrinsic modeling module, an abnormal state identification module, and a fault processing module, characterized in that: The circuit physical intrinsic modeling module: is used for performing circuit physical intrinsic modeling of the UPFC sub-module, and calculating the DC bus voltage, AC port current, and IGBT junction temperature; The abnormal state identification module: is used for calculating the absolute value residuals of the DC bus voltage, AC port current, and IGBT junction temperature through the DC bus voltage, AC port current, and IGBT junction temperature collected in real time and their corresponding calculated values; all IGBTs of each UPFC sub-module are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; it is judged whether there is an abnormality according to the absolute value residuals. If there is an abnormality, the circuit fault intrinsic parameters are obtained, the circuit fault intrinsic parameters are matched with a preset abnormal feature library, and multi-level fault screening and identification are performed according to the matching result; The fault processing module: is used for setting a static priority, and calculating a dynamic priority in combination with the collected DC bus voltage, AC port current, or IGBT junction temperature; the static priority is the priority of different fault types of the same sub-module, and the dynamic priority is the priority of different fault types of different sub-modules; corresponding fault excision is performed on different fault types of different sub-modules according to the dynamic priority.

[0018] The beneficial effects of the present invention compared with the prior art are as follows: Based on the control strategy and circuit physical intrinsic modeling, the DC bus voltage, AC port current, and IGBT junction temperature are calculated; it is judged whether there is an abnormality according to the residuals of the calculated value and the collected value. If there is an abnormality, the circuit fault intrinsic parameters are obtained, the circuit fault intrinsic parameters are matched with a preset abnormal feature library, and multi-level fault screening and identification are performed according to the matching result; it can quickly and accurately locate the fault type, reduce misjudgment and missed judgment, and at the same time, through the multi-level screening mechanism, effectively improve the comprehensiveness and reliability of fault diagnosis, and provide a more targeted basis for fault handling. Set a static priority, and calculate a dynamic priority in combination with the collected DC bus voltage, AC port current, or IGBT junction temperature, and perform corresponding fault excision on different fault types of different sub-modules to ensure that key sub-modules are preferentially protected, thereby maximizing system stability; it can effectively avoid over-cutting or under-cutting, and improve the accuracy and efficiency of fault handling. The present invention has better performance than the traditional method in terms of response speed, multi-type fault identification, and system adaptability. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the UPFC submodule system, control strategy and rapid fault removal system of the present invention; Figure 2 Schematic diagram of the UPFC submodule pressure equalization control strategy according to an embodiment of the present invention; Figure 3 Schematic diagram of a double frequency circulating current suppression strategy according to an embodiment of the present invention; Figure 4 It is the BP network topology diagram; Figure 5 The present invention adopts corresponding fault removal flow chart for different fault types; Figure 6 It is a waveform diagram of a fault occurrence and its removal by using the fault fast removal method disclosed in the embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0021] Embodiment 1 of the present invention proposes a method for quickly removing a UPFC submodule fault, comprising: Perform intrinsic modeling of the UPFC submodule circuit to calculate the DC bus voltage, AC port current and IGBT junction temperature; The absolute value residuals of the DC bus voltage, AC port current and IGBT junction temperature are calculated by using the real-time collected DC bus voltage, AC port current and IGBT junction temperature and their corresponding calculated values; all IGBTs of each UPFC submodule are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; Determine whether there is an abnormality based on the absolute value residual. If there is an abnormality, obtain the circuit fault intrinsic parameters, match the circuit fault intrinsic parameters with the preset abnormal feature library, and perform multi-level fault screening and identification based on the matching results; Set a static priority, and calculate a dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; the static priority is the priority of different fault types of the same submodule, and the dynamic priority is the priority of different fault types of different submodules; According to the dynamic priority, corresponding fault removal is adopted for different fault types of different submodules.

[0022] It should be noted that if Figure 1As shown, the UPFC submodule includes a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a positive AC port AC_P, a negative AC port AC_N, a positive DC port DC_P, a negative DC port DC_N, a DC bus capacitor C, a voltage sensor MV, a current sensor MC, a temperature sensor MT, and a sensor Ethernet interface Eth. The first switch tube and the second switch tube are connected in series to form a first branch, and the third switch tube and the fourth switch tube are connected in series to form a second branch. The first branch and the second branch are connected in parallel. The positive AC port is connected to the midpoint of the first branch, the negative AC port is connected to the midpoint of the second branch, the positive DC port is connected to the positive end of the first branch, the positive end of the second branch, and the positive end of the DC bus capacitor, and the negative DC port is connected to the negative end of the first branch, the negative end of the second branch, and the negative end of the DC bus capacitor. The current sensor MC measures the bridge arm current input at the positive AC port. i arm , the voltage sensor MV measures the DC bus voltage u c , the temperature sensor MT is connected to the thermistor of the switching device to measure the IGBT junction temperature T j , the three-way sensor sampling signals are transmitted to the main control unit via Ethernet; According to the UPFC submodule circuit intrinsic modeling and UPFC submodule control strategy, the mathematical formulas of DC bus voltage, AC port current and IGBT junction temperature are established:

[0023] In the above formula, for t The calculated value of the DC bus voltage at the moment, for t The calculated value of the AC port current at the moment, for t The calculated value of IGBT junction temperature at time, S bridge is the switch tube switching function of the bridge arm; I dc It is the sum of the DC currents input to the three-phase bridge arms from the DC side; ω 1 is the angular frequency of the AC side voltage; I S and They are the current amplitude and phase of the AC side of the converter in UPFC respectively; MI s / 4、 are the amplitude and phase of the second harmonic of the circulating current respectively; M is the modulation ratio, is the switch function of the submodule. C is the DC bus capacitance, is the DC bus voltage, is the number of converter arm submodules in UPFC, is the equivalent series resistance of the DC bus capacitor, T a ( t ) is obtained by measurement t The IGBT substrate temperature at the moment, P thIGBT is the IGBT heat loss, Z thIGBT is the IGBT thermal resistance network; According to the actual topological parameters of UPFC , , C, measured I dc , I S , ω 1 , , , according to the UPFC submodule control strategy S bridge , , M ; Input these values ​​into the above formula to obtain the calculated values ​​of DC bus voltage, AC port current and IGBT junction temperature.

[0024] Switching function of the bridge arm S bridge And the switch switching function of the submodule It is obtained by the control strategy adopted by the UPFC submodule, such as Figure 1 As shown, the UPFC submodule control strategy includes a submodule voltage equalization control strategy and a double frequency circulating current suppression strategy; wherein the double frequency circulating current suppression strategy outputs a modulated wave through carrier shift modulation.

[0025] Specifically, the submodule voltage balancing control strategy and the double frequency circulating current suppression strategy are as follows: Figure 2 and Figure 3 In the submodule voltage equalization control strategy, the driving signals of each submodule output by the carrier phase shift modulation unit are redistributed through the capacitor voltage sorting algorithm. If the capacitor voltages of each module are balanced, the output is normally driven without redistributing the driving signal. The double frequency circulating current suppression strategy decomposes the bridge arm circulating current by abc-αβ coordinates. i zj Suppression is applied through a quasi-PR controller to output a modulation wave compensation voltage.

[0026] The method of judging whether there is an abnormality based on the absolute value residual is as follows: The absolute value residual of each sampling point of the collected DC bus voltage, AC port current and IGBT junction temperature is recorded using a set sampling window, and the mean and standard deviation of all absolute value residuals of each sampling window of the DC bus voltage, AC port current or IGBT junction temperature are calculated; If the absolute value of the difference between the absolute value residual of the DC bus voltage, AC port current or IGBT junction temperature at the sampling point and the mean of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window is greater than 3 times the standard deviation of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window, the UPFC submodule is judged to be abnormal.

[0027] The absolute value residual is calculated as:

[0028] In the above formula, r Uc,t and U c,m ( t )respectively t The time is the DC bus voltage residual and the measured value, r Iarm,t and I arm,m ( t ) are respectively t The residual and measured value of the bridge arm current at the moment, r Tj,t and T j,m ( t ) are respectively t IGBT junction temperature residual and measured value at the moment; Through the residual r i Calculate the mean μ With standard deviation σ The formula is:

[0029] In the above formula, n 1 is the total number of residuals recorded within the sampling window, The sampling window i residuals; The number of converter bridge arm submodules in this embodiment is 4, and the DC bus voltage U c,rated =200V, bridge arm current rating I arm,rated =12A. t = πActual measurement of DC bus voltage at time / 2 U c,m ( π / 2)=208V, bridge arm current I arm,m ( π / 2)=14.8A, at this time, the intrinsic model calculation values ​​under normal conditions are 198V and 11.8A respectively; the sliding window selection n 1 =50, the standard deviations of the residuals of the bridge arm current data are calculated as follows: σ Iarm =0.5, μ Iarm =0.2A, the calculation for judging abnormality is:

[0030] So there is an anomaly; The circuit fault intrinsic parameters include the DC bus voltage measurement value, the DC bus voltage deviation rate, the AC port current measurement value, the AC port current change rate d arm / dt , IGBT junction temperature measurement and IGBT junction temperature gradient dT j / dt ; The DC bus voltage deviation rate DVR Uc、 AC port current change rate d arm / dt, IGBT junction temperature gradient dT j / dt The calculation formula is:

[0031] In the above formula, u c,m ( t )for t The measured value of DC bus voltage at the moment, for t The calculated value of the DC bus voltage at time , U c,rated is the rated value of DC bus voltage, I arm,m ( t ), I arm,m ( t -1) respectively t , t -1 AC port current measurement value, T j,m( t ), T j,m ( t -1) respectively t , t IGBT junction temperature measurement value at -1 time, is the set sampling window.

[0032] The circuit fault intrinsic parameters are matched with a preset abnormal feature library, and multi-level fault screening and identification is performed according to the matching results, specifically: First, the first-level fault screening is performed, and the intrinsic parameters of the circuit fault within a sampling window after the abnormality is judged are recorded. The DC bus voltage, DC bus voltage deviation rate, and AC port current are formed into a vector, and the cosine similarity of the first abnormal reference vector corresponding to various faults in the preset abnormal feature library is calculated. If there is a cosine similarity greater than the set first threshold, it is considered that the corresponding fault exists; if all cosine similarities are less than or equal to the first threshold and greater than the second threshold, the second-level fault screening is used; if all cosine similarities are less than or equal to the second threshold, the third-level fault screening is used; The second-level fault screening is to widen the sampling window, and form a vector of all circuit fault intrinsic parameters, and calculate the cosine similarity of the second abnormal reference vector corresponding to various faults in the preset abnormal feature library. If the cosine similarity is greater than the set first threshold, it is considered that the corresponding fault exists; The third level of fault screening is to input the circuit fault intrinsic parameters of adjacent modules into Figure 4 The pre-trained BP neural network shown outputs the probability of each fault; if the probability exceeds the set third threshold, it is considered that the corresponding fault exists; The first abnormal reference vector corresponding to the various faults is a vector composed of historical data of the DC bus voltage, DC bus voltage deviation rate, and AC port current within a set sampling window after the occurrence of the various faults; the second abnormal reference vector corresponding to the various faults is a vector composed of historical data of all circuit fault intrinsic parameters within the widened sampling window after the occurrence of the various faults obtained through historical data.

[0033] In this embodiment, the first threshold is 0.9, and the second threshold is 0.7; In this embodiment, the DC bus voltage, DC bus voltage deviation rate, and AC port current in a sampling window after the abnormality form a vector, and the cosine similarity between the vector and the first abnormal reference vector corresponding to various faults in the preset abnormal feature library is calculated, wherein the cosine similarity with the first abnormal reference vector of the IGBT short circuit fault exceeds the first threshold value of 0.9, and the calculation process is:

[0034] In the formula, S is the cosine similarity, , are respectively the DC bus voltage, the DC bus voltage deviation rate, the vector composed of the AC port current, and the value of the first abnormal reference vector of the IGBT short - circuit fault at the i th sampling point in the sampling window; S = 0.92 > 0.9, directly matching as an IGBT short - circuit fault, without triggering the second and third - layer fault screening; The static priorities of the capacitor over - voltage fault, the IGBT short - circuit fault, and the IGBT over - heat fault are respectively set to 80, 70, and 60.

[0035] The calculated dynamic priority , specifically:

[0036] In the above formula, P static is the set static priority, α , β and γ are respectively the weight coefficients of the DC bus voltage, the IGBT junction temperature, and the AC port current, U c,m ( t ) is the measured value of the DC bus voltage at time t , U c,rated is the rated value of the DC bus voltage, is t the measured value of the IGBT junction temperature at time, is the maximum value of the IGBT junction temperature, is t the measured value of the AC port current at time, is the maximum value of the AC port current.

[0037] In this embodiment α , β and γ are respectively set to 0.5, 0.2, and 0.3.

[0038] As Figure 5 shown, according to the dynamic priority, corresponding fault removal is taken for different fault types, specifically: When a single fault occurs, if it is an IGBT short - circuit fault, the sub - module drive is blocked and the bypass switch is triggered to put the redundant module into operation; if it is a capacitor over - voltage fault, the faulty module is removed and the redundant unit is put into operation, and the bridge - arm level output is maintained stable through the modulation control algorithm; if it is an IGBT over - heat fault, the redundant unit is put into operation or the output of the sub - module is reduced; If multiple faults occur, a removal sequence is generated from high to low according to the dynamic priority, the faulty sub-modules are isolated in sequence and the redundant modules are put into use. When the redundant modules are insufficient, the converter is triggered to shut down urgently.

[0039] It should be noted that when clearing a fault, a clearing instruction is sent to a module controlling UPFC for clearing. The clearing instruction adopts 16-bit instruction coding and is transmitted through high-speed optical fiber.

[0040] The instruction code for clearing the IGBT short-circuit fault in this embodiment is in the following format: 0x1A3F, where the first 4 bits 0x1 represent an IGBT short circuit, the module address is 0xA3, and the operation code 0xF represents lockout+bypass.

[0041] Figure 6 Table 1 and Table 2 respectively give the waveform corresponding to the UPFC submodule fault condition and the comparison between the fault response time of the embodiment of the present invention and different methods under different fault types. Figure 6 It can be seen that after the switch tube open circuit fault at 3s, the DC bus voltage surges, and then the capacitor voltage overvoltage fault occurs. At this time, the submodule drive needs to be locked and the bypass switch is triggered. It can be seen from Table 1 that the method provided by the present invention is superior to the hardware method in terms of response time, and has better dynamic and complex fault handling capabilities than the static fault arbitration method.

[0042] Table 1 Comparison of fault response time

[0043] like Figure 1 As shown, embodiment 2 of the present invention provides a UPFC submodule fault rapid removal system using the method described in embodiment 1 of the present invention, including a circuit physical intrinsic modeling module, an abnormal state identification module, and a fault processing module, characterized in that: Circuit physics intrinsic modeling module: used to perform UPFC submodule circuit intrinsic modeling and calculate DC bus voltage, AC port current and IGBT junction temperature; Abnormal state identification module: used to calculate the absolute value residual of DC bus voltage, AC port current and IGBT junction temperature through the real-time collected DC bus voltage, AC port current and IGBT junction temperature and their corresponding calculated values; all IGBTs of each UPFC submodule are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; judge whether there is an abnormality based on the absolute value residual, if there is an abnormality, obtain the circuit fault intrinsic parameters, match the circuit fault intrinsic parameters with the preset abnormal feature library, and perform multi-level fault screening and identification based on the matching results; Fault processing module: used to set static priority and calculate dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; the static priority is the priority of different fault types of the same submodule, and the dynamic priority is the priority of different fault types of different submodules; according to the dynamic priority, corresponding fault removal is adopted for different fault types of different submodules.

[0044] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal 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, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0045] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for quickly removing a UPFC submodule fault, characterized in that: include: Perform intrinsic modeling of the UPFC submodule circuit to calculate the DC bus voltage, AC port current and IGBT junction temperature; The absolute value residuals of the DC bus voltage, AC port current and IGBT junction temperature are calculated by using the real-time collected DC bus voltage, AC port current and IGBT junction temperature and their corresponding calculated values; all IGBTs of each UPFC submodule are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; Determine whether the UPFC submodule has an abnormality based on the absolute value residual. If an abnormality exists, obtain the circuit fault intrinsic parameters, match the circuit fault intrinsic parameters with the preset abnormal feature library, and perform multi-level fault screening and identification based on the matching results; Set a static priority, and calculate a dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; the static priority is the priority of different fault types of the same submodule, and the dynamic priority is the priority of different fault types of different submodules; According to the dynamic priority, corresponding fault removal is adopted for different fault types of different submodules.

2. A UPFC submodule fault rapid removal method according to claim 1, characterized in that: By intrinsically modeling the UPFC submodule circuit, mathematical formulas for DC bus voltage, AC port current and IGBT junction temperature are established: In the above formula, for t The calculated value of the DC bus voltage at the moment, for t The calculated value of the AC port current at time, for t The calculated value of the IGBT junction temperature at the time, S bridge is the switch tube switching function of the bridge arm; I dc It is the sum of the DC currents input to the three-phase bridge arms from the DC side; ω 1 is the angular frequency of the AC side voltage; I S and They are the current amplitude and phase of the AC side of the converter in UPFC respectively; MI s / 4, are the amplitude and phase of the second harmonic of the circulating current respectively; M is the modulation ratio, is the switch function of the submodule. C is the DC bus capacitance, is the DC bus voltage, is the number of converter arm submodules in UPFC, is the equivalent series resistance of the DC bus capacitor, T a ( t ) is obtained by measurement t The IGBT substrate temperature at the moment, P thIGBT is the IGBT heat loss, Z thIGBT is the IGBT thermal resistance network.

3. A UPFC submodule fault rapid removal method according to claim 2, characterized in that: Switching function of the bridge arm S bridge And the switch switching function of the submodule It is obtained through the control strategy adopted by the UPFC submodule. The control strategy adopted by the UPFC submodule includes the submodule voltage equalization control strategy and the double frequency circulating current suppression strategy; among which the double frequency circulating current suppression strategy outputs the modulated wave through carrier shift modulation.

4. A UPFC submodule fault rapid removal method according to claim 1, characterized in that: The method of judging whether there is an abnormality based on the absolute value residual is as follows: The absolute value residual of each sampling point of the collected DC bus voltage, AC port current and IGBT junction temperature is recorded using a set sampling window, and the mean and standard deviation of all absolute value residuals of each sampling window of the DC bus voltage, AC port current or IGBT junction temperature are calculated; If the absolute value of the difference between the absolute value residual of the DC bus voltage, AC port current or IGBT junction temperature at the sampling point and the mean of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window is greater than 3 times the standard deviation of the DC bus voltage measurement value, AC port current measurement value or IGBT junction temperature measurement value in the corresponding sampling window, the UPFC submodule is judged to be abnormal.

5. A UPFC submodule fault rapid removal method according to claim 1, characterized in that: The circuit fault intrinsic parameters include a DC bus voltage measurement value, a DC bus voltage deviation rate, an AC port current measurement value, an AC port current change rate, an IGBT junction temperature measurement value, and an IGBT junction temperature gradient; The DC bus voltage deviation rate DVR Uc、 AC port current change rate d arm / dt, IGBT junction temperature gradient dT j / dt The calculation formula is: In the above formula, u c,m ( t )for t The measured value of DC bus voltage at the moment, for t The calculated value of the DC bus voltage at time , U c,rated is the rated value of DC bus voltage, I arm,m ( t ), I arm,m ( t -1) respectively t , t -1 AC port current measurement value, T j,m ( t ), T j,m ( t -1) respectively t , t IGBT junction temperature measurement value at -1 time, is the set sampling window.

6. A method for rapid removal of UPFC submodule faults according to claim 5, characterized in that: The circuit fault intrinsic parameters are matched with a preset abnormal feature library, and multi-level fault screening and identification is performed according to the matching results, specifically: First, the first-level fault screening is performed, and the intrinsic parameters of the circuit fault within a sampling window after the abnormality is judged are recorded. The DC bus voltage, DC bus voltage deviation rate, and AC port current are formed into a vector, and the cosine similarity of the first abnormal reference vector corresponding to various faults in the preset abnormal feature library is calculated. If there is a cosine similarity greater than the set first threshold, it is considered that the corresponding fault exists; if all cosine similarities are less than or equal to the first threshold and greater than the second threshold, the second-level fault screening is used; if all cosine similarities are less than or equal to the second threshold, the third-level fault screening is used; The second-level fault screening is to widen the sampling window, and form a vector of all circuit fault intrinsic parameters, and calculate the cosine similarity of the second abnormal reference vector corresponding to various faults in the preset abnormal feature library. If the cosine similarity is greater than the set first threshold, it is considered that the corresponding fault exists; The third-level fault screening is to input the circuit fault intrinsic parameters of adjacent modules into the pre-trained BP neural network and output the probability of each fault; if the probability exceeds the set third threshold, it is considered that the corresponding fault exists; The first abnormal reference vector corresponding to the various faults is a vector composed of historical data of the DC bus voltage, DC bus voltage deviation rate, and AC port current within a set sampling window after the occurrence of the various faults; the second abnormal reference vector corresponding to the various faults is a vector composed of historical data of all circuit fault intrinsic parameters within the widened sampling window after the occurrence of the various faults obtained through historical data.

7. A method for rapid removal of UPFC submodule faults according to claim 1, characterized in that: The static priorities of capacitor overvoltage fault, IGBT short circuit fault, and IGBT overheat fault are set to 80, 70, and 60 respectively.

8. A method for rapid removal of UPFC submodule faults according to claim 7, characterized in that: The calculation dynamic priority , specifically: In the above formula, P static For the static priority setting, α , β and γ are the DC bus voltage, IGBT junction temperature and AC port current weight coefficients respectively, U c,m ( t )for t The measured value of DC bus voltage at the moment, U c,rated is the rated value of DC bus voltage, for t The measured value of IGBT junction temperature at the moment, is the maximum junction temperature of the IGBT, for t The measured current value of the AC port at the moment, It is the maximum current of AC port.

9. A method for rapid removal of UPFC submodule faults according to claim 1, characterized in that: According to the dynamic priority, corresponding fault removal is adopted for different fault types, specifically: When a single fault occurs, if it is an IGBT short-circuit fault, the submodule drive is locked and the bypass switch is triggered, and the redundant module is put into operation; if it is a capacitor overvoltage fault, the faulty module is removed and the redundant unit is put into operation, and the bridge arm level output is maintained stable through the modulation control algorithm; if it is an IGBT overheating fault, the redundant unit is cut off or the submodule output is reduced; If multiple faults occur, a removal sequence is generated from high to low according to the dynamic priority, the faulty sub-modules are isolated in sequence and the redundant modules are put into use. When the redundant modules are insufficient, the converter is triggered to shut down urgently.

10. A UPFC submodule fault rapid removal system using the method according to any one of claims 1 to 9, comprising a circuit physical intrinsic modeling module, an abnormal state identification module, and a fault processing module, characterized in that: Circuit physics intrinsic modeling module: used to perform UPFC submodule circuit intrinsic modeling and calculate DC bus voltage, AC port current and IGBT junction temperature; Abnormal state identification module: used to calculate the absolute value residual of DC bus voltage, AC port current and IGBT junction temperature through the real-time collected DC bus voltage, AC port current and IGBT junction temperature and their corresponding calculated values; all IGBTs of each UPFC submodule are located on the same substrate, and the measured IGBT junction temperature is the substrate temperature; judge whether there is an abnormality based on the absolute value residual, if there is an abnormality, obtain the circuit fault intrinsic parameters, match the circuit fault intrinsic parameters with the preset abnormal feature library, and perform multi-level fault screening and identification based on the matching results; Fault processing module: used to set static priority and calculate dynamic priority in combination with the collected DC bus voltage, AC port current or IGBT junction temperature; the static priority is the priority of different fault types of the same submodule, and the dynamic priority is the priority of different fault types of different submodules; according to the dynamic priority, corresponding fault removal is adopted for different fault types of different submodules.

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