Modeling method and application of load commutation switch of high-voltage hybrid direct-current circuit breaker

Abstract

The invention discloses a modeling method and application of a load commutation switch of a high-voltage hybrid direct-current circuit breaker, and belongs to the technical field of direct-current circuit breakers. A complete load commutation switch turn-off equivalent circuit is established by constructing a simplified principle model of a high-voltage hybrid direct-current circuit breaker and combining an accurate soft punch-through power electronic switch turn-off analysis model under the condition of an extremely safe working area; by setting an action sequence diagram, an IGBT current limiting mechanism of a main circuit breaker branch in the high-voltage hybrid direct-current circuit breaker is disclosed, dynamic characteristics of the IGBT current limiting mechanism in a load commutation process are predicted, and the performance analysis and optimization capability of the high-voltage hybrid direct-current circuit breaker is enhanced, so that the reliability challenge faced by a load commutation switch in a turn-off stage can be solved, and the reliability of the high-voltage hybrid direct-current circuit breaker is improved. And a solid theoretical basis and technical support are provided for design optimization and practical application of the high-voltage hybrid DC circuit breaker.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current circuit breakers, and in particular to a high-voltage hybrid direct current circuit breaker. Background Art

[0002] In recent years, high-voltage direct current (HVDC) transmission systems have received extensive attention and development around the world due to their unique advantages, such as point-to-point direct current long-distance transmission capability, the characteristic that the voltage polarity remains unchanged when the power flow reverses, and the ability to efficiently interconnect with renewable energy and existing energy systems. However, despite its broad application prospects, the short-circuit fault protection problem of high-voltage direct current transmission systems remains the main obstacle to its promotion.

[0003] In order to cope with this technical challenge, ABB, a global leader in power and automation technology, has proposed an innovative high-voltage hybrid DC circuit breaker with its strong R&D capabilities and industry experience. The circuit breaker consists of a normal branch and a main circuit breaker branch in parallel. The normal branch contains an ultra-fast circuit breaker (UFD) and a load commutation switch (LCS) connected in series, and the main circuit breaker branch is composed of multiple identical modules in series. Each module consists of a metal oxide arrester (MOA) and an IGBT connected in parallel to provide powerful fault current cutting capability.

[0004] Under the high voltage environment of hundreds of kilovolts, this high-voltage hybrid DC circuit breaker can quickly disconnect the fault current of thousands of amperes in a very short time (milliseconds), effectively ensuring the safety and stability of the power system. This technological breakthrough not only greatly improves the ability of the high-voltage DC transmission system to cope with faults, but also further enhances the reliability and resilience of the power grid, laying a solid foundation for the widespread application and sustainable development of high-voltage DC transmission technology in the future.

[0005] However, with the continuous development of high-voltage hybrid DC circuit breaker technology, the complexity of its internal structure has become increasingly prominent. In particular, the load commutation switch (LCS) in the normal branch, due to its integration of IGBT switching elements, time-varying elements and nonlinear elements, exhibits strong nonlinear time-varying characteristics, making the comprehensive understanding and prediction of the IGBT current limiting mechanism of the main circuit breaker branch. The electrical characteristics of the load commutation switch (LCS) have become extremely complex, becoming a key factor restricting the stability and performance improvement of the entire system.

[0006] Therefore, how to provide a modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker to predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during the commutation period of the load commutation switch has become a technical problem that needs to be urgently overcome by current technicians in this field. Summary of the invention

[0007] The object of the present invention is to provide a modeling method and application of a high-voltage hybrid DC circuit breaker load commutation switch to overcome the deficiencies in the prior art in predicting the dynamic response characteristics of a high-voltage hybrid DC circuit breaker load commutation switch (LCS) during commutation.

[0008] The present invention solves the above technical problems through the following technical solutions: A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker comprises the following steps: Step 1: Based on the simulation model of high-voltage hybrid DC circuit breaker and stray inductance L p , construct a simplified principle model of high-voltage hybrid DC circuit breaker; Step 2: Based on the simplified principle model, draw the fault current timing diagram and the fault voltage timing diagram of the high-voltage hybrid DC circuit breaker; based on the fault current timing diagram and the fault voltage timing diagram, determine the working characteristics that the power electronic switch needs to have in the high-voltage DC power grid branch of the high-voltage hybrid DC circuit breaker; Step 3: Based on the working characteristics that the power electronic switch needs to have, select a power electronic switch SPT-IGBT with the working characteristics, perform a shutdown test on the SPT-IGBT, and establish a shutdown analytical model of the SPT-IGBT under extreme safety working area conditions; Step 4: Load commutation switch IGBT-T of high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the SPT-IGBT turn-off analytical model to establish the optimized load commutation switch IGBT-T LCS The turn-off equivalent circuit of Step 5: Based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are used to build an optimized simulation model of high-voltage hybrid DC circuit breaker.

[0009] The present invention is further improved in that: in step 1, the simplified principle model of the high-voltage hybrid DC circuit breaker includes a high-voltage DC grid branch, a normal branch and a main circuit breaker branch, the high-voltage DC grid branch is connected in series with the normal branch, and the normal branch is an ultra-fast circuit breaker UFD and a load commutation switch IGBT-T connected in series. LCS , the main circuit breaker branch is connected in parallel with the normal branch, and the series node of the high-voltage DC grid branch and the normal branch is connected through the stray inductance L p Connect the main circuit breaker branch, the main circuit breaker includes a parallel lightning arrester MOA and an insulated gate bipolar transistor IGBT-T m .

[0010] A further improvement of the present invention is that step 2 specifically includes the following steps: Based on the simplified principle model, the commutation process of the load current is simulated, and the fault current timing diagram and fault voltage timing diagram of the high-voltage hybrid DC circuit breaker are drawn; Based on the fault current timing diagram and fault voltage timing diagram, analyze the insulated gate bipolar transistor IGBT-T m Current limiting mechanism and load commutation switch IGBT-T LCS The dynamic switching process of the load commutation switch IGBT-T in the high-voltage DC grid branch is determined LCS Required job characteristics.

[0011] A further improvement of the present invention is that step three specifically comprises the following steps: Based on the working characteristics that the power electronic switch in the high-voltage DC power grid branch needs to have, a power electronic switch SPT-IGBT with such working characteristics is selected, and a shutdown test is performed on the SPT-IGBT under the conditions of the extreme safe working area. The shutdown timing diagram of the SPT-IGBT is drawn, and the shutdown process of the SPT-IGBT is analyzed. According to the shutdown process, the shutdown equivalent circuit of the SPT-IGBT is established; based on the shutdown equivalent circuit of the SPT-IGBT, parameter calculation is performed and a shutdown analytical model of the SPT-IGBT is established.

[0012] A further improvement of the present invention is that step 4 specifically includes the following steps: Load commutation switch IGBT-T for high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the SPT-IGBT turn-off analytical model to establish the optimized load commutation switch IGBT-T LCS Turn-off analytical model, based on the turn-off analytical model, draw the turn-off timing diagram and analyze the optimized load commutation switch IGBT-T LCS According to the shutdown process, an optimized load commutation switch IGBT-T is established. LCS The turn-off equivalent circuit.

[0013] The present invention is further improved in that: the optimization is specifically: in the load commutation switch IGBT-T LCS The output port is connected in parallel with the buffer circuit.

[0014] A further improvement of the present invention is that the buffer circuit adopts an RCD buffer circuit.

[0015] The present invention is further improved in that: Step 5 specifically includes the following steps: Based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are determined, the electrical parameters are determined, the simulation equivalent circuit is constructed, and based on the simulation equivalent circuit, an optimized simulation model of the high-voltage hybrid DC circuit breaker is built.

[0016] A further improvement of the present invention is that in step five, the electrical parameters include electrical parameters of the high voltage DC power grid branch, the normal branch and the main circuit breaker branch.

[0017] The present invention also provides an application of a high-voltage hybrid DC circuit breaker load flow switch simulation model, using an optimized simulation model built using the above-mentioned modeling method to predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during load flow switch commutation.

[0018] Compared with the prior art, the positive and progressive effects of the present invention are: The modeling method of the load commutation switch of the high-voltage hybrid DC circuit breaker provided by the present invention establishes a complete load commutation switch shutdown equivalent circuit by constructing a simplified principle model of the high-voltage hybrid DC circuit breaker and combining it with an accurate soft-through power electronic switch shutdown analytical model with the working characteristics of the high-voltage DC power grid under extreme safety working conditions; by setting the action timing diagram, the IGBT current limiting mechanism of the main circuit breaker branch in the high-voltage hybrid DC circuit breaker is revealed, and its dynamic characteristics in the load commutation process are predicted, thereby enhancing the performance analysis and optimization capabilities of the high-voltage hybrid DC circuit breaker, thereby being able to solve the reliability challenges faced by the load commutation switch in the shutdown stage, and providing a solid theoretical basis and technical support for the design optimization and practical application of the high-voltage hybrid DC circuit breaker.

[0019] Furthermore, the use of an RCD snubber circuit as a snubber circuit can achieve shock wave suppression, noise reduction and signal smoothing, voltage spike reduction, device protection, and high-frequency oscillation suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 is a schematic diagram of a simulation model of a high voltage hybrid DC circuit breaker; Figure 2 It is a simplified schematic diagram of the principle model; Figure 3 It is a schematic diagram of the fault current and voltage timing; Figure 4 This is a schematic diagram of the turn-off timing of the SPT-IGBT under extreme SOA conditions; Figure 5 is the equivalent circuit and graphic symbol of SPT-IGBT, where: Figure 5 (a) is the schematic diagram of the turn-off equivalent circuit of SPT-IGBT. Figure 5 (b) Yes Figure 5 (a) Graphical symbol; Figure 6 It is the optimized load commutation switch IGBT-T LCS Schematic diagram of the shutdown equivalent circuit; Figure 7 It is the optimized load commutation switch IGBT-T LCS Schematic diagram of shutdown timing; Figure 8 It is the optimized load commutation switch IGBT-T LCS Schematic diagram of the turn-off equivalent circuit in the interval [t0, t1]; Fig. 9 It is the optimized load commutation switch IGBT-T LCS Schematic diagram of the turn-off equivalent circuit in the interval [t1, t2]; Fig.10 It is the optimized load commutation switch IGBT-T LCS Schematic diagram of the turn-off equivalent circuit in the interval [t2, t3]; Fig.11 is the simulation equivalent circuit schematic; Fig.12 It is a schematic diagram of simulation and experimental voltage curves of the unoptimized simulation model, where ① is the experimental voltage curve and ② is the simulation voltage curve; Fig.13 It is a schematic diagram of simulation and experimental current curves of the unoptimized simulation model, where ③ is the experimental current curve and ④ is the simulation current curve; Fig.14 It is a schematic diagram of simulation and experimental voltage curves of the optimized simulation model, where ① is the experimental voltage curve and ② is the simulation voltage curve; Fig.15 It is a schematic diagram of simulation and experimental current curves of the optimized simulation model, where ③ is the experimental current curve and ④ is the simulation current curve. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0024] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0025] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0026] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0027] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0028] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0030] A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker comprises the following steps: Step 1: Based on the simulation model of high-voltage hybrid DC circuit breaker and stray inductance L p, construct a simplified principle model of high-voltage hybrid DC circuit breaker; Step 2: Based on the simplified principle model, draw the fault current timing diagram and the fault voltage timing diagram of the high-voltage hybrid DC circuit breaker; based on the fault current timing diagram and the fault voltage timing diagram, determine the working characteristics that the power electronic switch needs to have in the high-voltage DC power grid branch of the high-voltage hybrid DC circuit breaker; Step 3: Based on the working characteristics that the power electronic switch needs to have, select a power electronic switch SPT-IGBT with the working characteristics, perform a shutdown test on the SPT-IGBT, and establish a shutdown analytical model of the SPT-IGBT under extreme safety working area conditions; Step 4: Load commutation switch IGBT-T of high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the SPT-IGBT turn-off analytical model to establish the optimized load commutation switch IGBT-T LCS The turn-off equivalent circuit of Step 5: Based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are determined, the electrical parameters are determined, and an optimized simulation model of the high-voltage hybrid DC circuit breaker is built based on the electrical parameters.

[0031] The modeling method of the load commutation switch of the high-voltage hybrid DC circuit breaker provided by the present invention establishes a complete load commutation switch shutdown equivalent circuit by constructing a simplified principle model of the high-voltage hybrid DC circuit breaker and combining it with an accurate soft-through power electronic switch shutdown analytical model with the working characteristics of the high-voltage DC power grid under extreme safety working conditions; by setting the action timing diagram, the IGBT current limiting mechanism of the main circuit breaker branch in the high-voltage hybrid DC circuit breaker is revealed, and its dynamic characteristics in the load commutation process are predicted, thereby enhancing the performance analysis and optimization capabilities of the high-voltage hybrid DC circuit breaker, thereby being able to solve the reliability challenges faced by the load commutation switch in the shutdown stage, and providing a solid theoretical basis and technical support for the design optimization and practical application of the high-voltage hybrid DC circuit breaker.

[0032] Specifically, in step 1, the simplified principle model of the high-voltage hybrid DC circuit breaker includes a high-voltage DC grid branch, a normal branch and a main circuit breaker branch, the high-voltage DC grid branch is connected in series with the normal branch, and the normal branch is an ultra-fast circuit breaker UFD and a load commutation switch IGBT-T connected in series. LCS , the main circuit breaker branch is connected in parallel with the normal branch, and the series node of the high-voltage DC grid branch and the normal branch is connected through the stray inductance L p Connect the main circuit breaker branch, the main circuit breaker includes a parallel lightning arrester MOA and an insulated gate bipolar transistor IGBT-T m .

[0033] Specifically, step 2 includes the following steps: Based on the simplified principle model, the commutation process of the load current is simulated, and the fault current timing diagram and fault voltage timing diagram of the high-voltage hybrid DC circuit breaker are drawn; Based on the fault current timing diagram and fault voltage timing diagram, analyze the insulated gate bipolar transistor IGBT-T m Current limiting mechanism and load commutation switch IGBT-T LCS The dynamic switching process of the load commutation switch IGBT-T in the high-voltage DC grid branch is determined LCS Required job characteristics.

[0034] Specifically, step three includes the following steps: Based on the working characteristics that the power electronic switch in the high-voltage DC power grid branch needs to have, a power electronic switch SPT-IGBT with such working characteristics is selected, and a shutdown test is performed on the SPT-IGBT under the conditions of the extreme safe working area. The shutdown timing diagram of the power electronic switch SPT-IGBT is drawn, and the shutdown process of the power electronic switch SPT-IGBT is analyzed. According to the shutdown process, the shutdown equivalent circuit of the power electronic switch SPT-IGBT is established; based on the shutdown equivalent circuit of the power electronic switch SPT-IGBT, parameter calculation is performed to establish a shutdown analytical model of the power electronic switch SPT-IGBT.

[0035] Specifically, step 4 includes the following steps: Load commutation switch IGBT-T for high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the turn-off analytical model of the power electronic switch SPT-IGBT to establish the optimized load commutation switch IGBT-T LCS Turn-off analytical model, based on the turn-off analytical model, draw the turn-off timing diagram and analyze the optimized load commutation switch IGBT-T LCS According to the shutdown process, an optimized load commutation switch IGBT-T is established. LCS The turn-off equivalent circuit.

[0036] Specifically, the optimization is as follows: in the load commutation switch IGBT-T LCS The output port is connected in parallel with the buffer circuit.

[0037] Specifically, the buffer circuit adopts an RCD buffer circuit; adopting the RCD buffer circuit as the buffer circuit can achieve shock wave suppression, noise reduction and signal smoothing, voltage spike reduction, device protection and high-frequency oscillation suppression.

[0038] Specifically, step five specifically includes the following steps: based on the optimized load commutation switch IGBT-TLCS The shutdown equivalent circuit and shutdown analytical model are determined, the electrical parameters are determined, the simulation equivalent circuit is constructed, and based on the simulation equivalent circuit, an optimized simulation model of the high-voltage hybrid DC circuit breaker is built.

[0039] Specifically, in step five, the electrical parameters include electrical parameters of the high-voltage direct current grid branch, the normal branch and the main circuit breaker branch.

[0040] Based on the same inventive concept, the present invention also provides an application of a high-voltage hybrid DC circuit breaker load flow switch simulation model, which uses an optimized simulation model built using the above-mentioned modeling method to predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during the load flow switch commutation period.

[0041] In a specific embodiment of the present invention, a modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker includes the following steps: Step 1 specifically includes: Step 1.1, ABB established a principle model of a high-voltage hybrid DC circuit breaker using IGBT as an electronic switch, which consists of three parts: an equivalent circuit branch of a high-voltage DC grid, a normal branch, and a main circuit breaker; See also Figure 1 ① is the equivalent circuit branch of the high-voltage DC power grid, ② is the normal branch, and ③ is the main circuit breaker. IGBT-T is used in the main circuit breaker. m As an electronic switch to replace thyristors; the equivalent circuit of the high-voltage DC grid (part ①) is electrically connected to the normal branch (part ②) to provide a power transmission path; under normal working conditions, the normal branch remains closed to allow current to pass; the main circuit breaker (part ③) is connected in series with the normal branch and is connected to the equivalent circuit of the high-voltage DC grid by controlling the switch state; in a fault-free state, the main circuit breaker remains closed to maintain the continuous operation of the circuit; when a fault or abnormal situation occurs, the main circuit breaker is quickly disconnected, thereby cutting off the current flow to the normal branch and ensuring the safety of the power grid system.

[0042] Step 1.2: Based on step 1.1, add the stray inductance L of the main circuit breaker between the normal branch and the main circuit breaker branch. P , construct a simplified principle model of a high-voltage hybrid DC circuit breaker, see Figure 2 .

[0043] Step 2 specifically includes: Step 2.1, based on the simplified principle model of the high-voltage hybrid DC circuit breaker, draw the fault current timing diagram and fault voltage timing diagram of the high-voltage hybrid DC circuit breaker, see Figure 3 .

[0044] Step 2.2, based on the fault current timing diagram and fault voltage timing diagram of the high-voltage hybrid DC circuit breaker, study the IGBT-T in the high-voltage hybrid DC circuit breaker. m Current limiting mechanism of the power electronic switch of the main circuit breaker and the load commutation switch IGBT-T LCS In the high-voltage direct current transmission system, 1.2 times the maximum rated current is set as the triggering threshold I of the short-circuit fault protection. LST The interval [0, t0] is the normal working condition, and the load current i Ls Flows to the load through the normal branch. In the interval [t0, t1], a short circuit fault occurs in the DC transmission line, and the fault current i Ls From the normal value I norm Rapidly increases. In the interval [t1, t2], the stray inductance L p The current cannot jump through the IGBT-T m The current gradually increases, and the fault current i Ls At the same time, it passes through the normal branch and the switch branch of the main circuit breaker. [t2, t3] interval, IGBT-T LCS (Load commutation switch) is completely turned off, and the current i through the normal branch LCS The fault current is forced to commutate from the normal branch to the main circuit breaker branch. At the same time, the two contacts of the ultra-fast circuit breaker (UFD) begin to separate gradually until they are completely disconnected. In the interval [t3, t4], the fault voltage u Tm Rise to the rated voltage U of the metal oxide arrester (MOA) r MOA enters the pre-breakdown region, the inductor current i p From IGBT-T m Gradually commutates to the MOA energy absorption branch, the fault current i Ls Reach the maximum value I in a short time max In the interval [t4, t5], MOA enters the breakdown region, u Tm Rising to MOA reference voltage U ref , reference voltage U ref Equal to 1.5 times the rated DC voltage U dc Under the action of MOA, the fault current i Ls Decreases linearly until it reaches zero.

[0045] Step 2.3, according to the above analysis process, it is found that the high-voltage DC grid has a fault current i when a short-circuit fault occurs. LsThe characteristics of rapid development are as follows: the transient current rises rapidly and the peak value of the steady-state current is high. Therefore, for the application of flexible DC transmission systems, the IGBTs used should have the important working characteristic of being able to provide a larger short-circuit safe operating area (SOA) to adapt to the harsh working environment faced by high-voltage DC grids under short-circuit conditions, ensuring that the IGBTs can work safely and reliably when short-circuit faults occur and avoiding damage or failure. This requires that the high-voltage hybrid DC circuit breaker can respond quickly to ensure that the switching devices in the equipment can be turned off and on in a timely manner. In addition, considering the advantages of high power and low loss of high-voltage DC systems, the IGBTs applied to such systems should have important working characteristics such as large capacity (including high maximum withstand voltage and rated current), high switching speed, and low loss to meet the strict requirements of high-voltage DC grids for reliability and efficiency.

[0046] Step 3 specifically includes: Step 3.1, according to the working characteristic requirements of the IGBTs for the hybrid high-voltage circuit breakers in the high-voltage DC grid in Step 2, select a power electronic switch of the SPT-IGBT type. The SPT-IGBT is a soft punch-through power electronic switch, which is a new type of IGBT proposed by ABB for high-voltage high-power applications and is named SPT-IGBT; based on the physical structure of the SPT-IGBT, combined with semiconductor physics theory and circuit theory, conduct a turn-off test of the SPT-IGBT under extreme SOA conditions, draw the turn-off waveform and study the turn-off process of the SPT-IGBT to establish the turn-off equivalent circuit of the SPT-IGBT. Specifically: conduct turn-off tests on multiple SPT-IGBTs with rated voltages of 3.3 kV to 6.5 kV under extreme SOA conditions, draw the turn-off timing diagram, see Figure 4 , and through analysis, the following turn-off process can be obtained: when t < t o , the SPT-IGBT is in the deep saturation region, and the output current i c and the output voltage u ce remain unchanged; when t o ≤ t < t1, the Miller capacitance C gc is charged approximately at a constant current, causing the output voltage u ce to increase; when t1 ≤ t < t2, when u ce = U DA , dynamic avalanche starts, and begins to consume the electron-hole pairs stored inside the device; when t2 ≤ t < t3, u ce is greater than the power supply voltage U DC , and the inductor L sThe voltage at both ends reverses, and the current begins to decline. When t3 ≤ t < t4, the electron-hole pairs stored inside the device are all consumed, the collector current of the SPT-IGBT drops to zero, and it enters the self-clamping mode. When t > t4, the SPT-IGBT is completely turned off; the external circuit begins to enter the resonance stage of the RLC series circuit. Therefore, the SPT-IGBT has five operating states, including turn-on, turn-off, constant current, dynamic avalanche, and switch self-clamping mode; Based on the electrical symbol of the standard IGBT, an equivalent turn-off circuit of the SPT-IGBT is established according to the turn-off process. See Figure 5 , this equivalent circuit is a transistor composed of an n-channel MOSFET T3 driving the emitter follower of a PNP bipolar junction transistor T1, and T2 is an NPN transistor. R m is the conductivity modulation resistance of the n-base region of the SPT-IGBT, and the diode D p and the virtual capacitor C in parallel with it p connect the base and the collector to describe the dynamic avalanche phenomenon and its electrical characteristics of the SPT-IGBT. The Zener diode D ZRm charges the virtual capacitor C p constantly to describe the linear and smooth increase of the output voltage u ce of the device during dynamic avalanche. The Zener diode D z connects the collector and the emitter to simulate the switch self-clamping mode.

[0047] Step 3.2, perform parameter calculations for the turn-off equivalent circuit of the SPT-IGBT, including the conductivity modulation resistance R m , the p+-base region bulk resistance R s , the virtual capacitor C p , and determine the accurate turn-off analysis model of the SPT-IGBT, specifically including: calculating the conductivity modulation resistance R m , indirectly calculating the saturation voltage of the SPT-IGBT by calculating the total voltage of the series branch composed of the three components T1, R m and T3; according to KVL, the expression of the IGBT saturation voltage obtained by superimposing the three parts of the voltage is:

[0048] In the formula, U T is the thermoelectric potential (25 mV at room temperature); I C is the collector current of the SPT-IGBT; I s is the reverse saturation current of the base-emitter junction; α NPN is the current gain of the NPN transistor T1; R m is the modulation resistance of the n-base region; R T3（on） is the on-resistance of the MOSFET T3; Depend on Figure 4 It can be obtained when t <t o , the IGBT has entered a deep saturation state, and the output voltage u ce Equal to the collector-emitter saturation voltage U ce (sat) , therefore, the conductivity modulation resistor R m(sat) The calculation formula is,

[0049] Where U ce (sat) is the collector-emitter saturation voltage, U T3（on） is the on-state voltage of MOSFET T3, I C is the collector current of SPT-IGBT, α NPN is the current gain of NPN transistor T1; Step 3.3.2, calculate p + Base resistance R s , during the conduction period of T3, the capacitor C p and R s For parallel connection, they have the same voltage, expressed as,

[0050] In the formula, u Cp is the capacitance C p The voltage across the two ends, u Rs For p + Base resistance R s The voltage across the terminals, i T1 is the current of transistor T1, α NPN is the current gain of NPN transistor T1, I C is the collector current of SPT-IGBT; In order to suppress the current holding phenomenon of SPT-IGBT, even if the current I c Reaching its maximum value I cmax , and also requires voltage u Rs Less than 0.5V to avoid T2 conduction and current holding phenomenon, expressed as,

[0051] In the formula, I cmax is the current I c The maximum value, I cnom is the rated value of the collector DC current; p+ base resistance R s The expression evaluates to,

[0052] Calculate the virtual capacitance C p,Depend on Figure 4 Available ce The rising slope is

[0053] In the formula, u ce is the collector-emitter voltage, Uz is the Zener breakdown threshold voltage, U DA for u ce Rising to the threshold voltage of dynamic avalanche, I o is the output current, C p is the virtual capacitor; From the above formula, we can calculate C p The formula is,

[0055] Step 4 specifically includes: Step 4.1, Load commutation switch IGBT-T in high voltage hybrid DC circuit breaker LCS A conventional RCD snubber circuit is added and optimized to reduce dv / dt and reduce turn-off loss; then, based on the simplified principle model of the high-voltage hybrid DC circuit breaker in step 2 and the precise SPT-IGBT turn-off analytical model in step 3, an optimized load commutation switch IGBT-T is established. LCS Shutdown analytical model, see Figure 6 ; The shutdown analytical model is studied, which consists of four parts. Part ① uses a DC voltage source U dc Represents a high voltage DC power supply device; Part ② is the stray inductance L p With ideal switch S Tm The series circuit is composed of 3 parts; the 3rd part is the normal branch, in which the UFD model is an ideal flow control switch with a delay of 2ms, and the IGBT-T is used as the load commutation switch. LCS It is not a standard IGBT, but an SPT-IGBT; Part ④ is a conventional RCD snubber circuit connected in parallel with the IGBT-T LCS The output port of

[0056] Step 4.2, according to the shutdown analytical model, set the shutdown timing diagram of the conventional RCD snubber circuit, see Figure 7 ; After analysis, it can be concluded that the shutdown process is as follows, t≤t0, IGBT-T LCS The current is equal to I LST , output voltage U ce Approximately zero. t0<t≤t1, is the LCS turn-off process, IGBT-T LCS The voltage waveform depends on the buffer capacitor C s Charging waveform; According to the analysis of the shutdown timing diagram, IGBT-T LCS The current expression of the shutdown process is:

[0057] Among them, t f For IGBT-T LCS The off time, I LST is the current limiting reactor L s The current, i c1 is the load current. To simplify the analysis, assume that I LST Keep it constant.

[0058] Based on the above analysis, the load commutation switch IGBT-T of each timing is established. LCS The shutdown equivalent circuit is as follows: buffer capacitor C s Charging interval [t0, t1], IGBT-T LCS Turn off, IGBT-T m Open at the same time, the ideal switch S Tm In the closed state. The equivalent circuit is a ramp current source i d (t) driven undamped parallel resonant circuit, the equivalent circuit of the shutdown phase is shown in Figure 8 ; Switch self-clamping mode interval [t1, t2], IGBT-T LCS Entering the switch self-clamping mode interval, u Cs Approximately equal to U SSCM The equivalent circuit of the shutdown phase is shown in Fig. 9 , Zener diode D z The circuit model is a circuit with an amplitude of U SSCM DC voltage source; the discharge interval of buffer capacitor Cs [t2, t3], IGBT-T LCS Completely off, the Zener diode D z Stop clamping, buffer capacitor C s Start with R s , UFD and L p Discharge, the equivalent circuit of this stage is turned off. Fig.10 .

[0059] Step 5 specifically includes: Step 5.1, based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are determined to determine the electrical parameters of the high-voltage DC power grid branch, normal branch and main circuit breaker branch, and to construct the PSCAD / EMTDC simulation equivalent circuit of the high-voltage hybrid DC circuit breaker, specifically: Normal branch ②, UFD In the simulation circuit, an ideal switch with a delay time of 0.25~2ms is used to model the UFD; IGBT-T LCSThe device used is an SPT-IGBT module with a withstand voltage of 3.3kV or 4.5kV; the main circuit breaker ③ is composed of four 80kV modules in series; the RCD snubber circuit is a conventional RCD snubber circuit; R L It is the load of the DC system under normal operating conditions.

[0060] Step 5.2: Based on the PSCAD / EMTDC simulation equivalent circuit of the high-voltage hybrid DC circuit breaker, build an optimized simulation model of the high-voltage hybrid DC circuit breaker. Fig.11 , determine L s , C s and U dc The relevant experimental parameters are used to predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during the load commutation switch commutation period, specifically: the power supply voltage U dc =40kV, output current I o =3.07kA, inductance L s =25mH, stray inductance L p =24μH, buffer capacitor C s =13μF, IGBT-T LCS The output capacitor C ou1 =250nF, junction capacitance C of the reverse blocking diode D2 =49nF, using an 80kV IGBT-T m The module acts as a switch branch of the main circuit breaker; Analysis of simulation results and experimental waveforms of the simulation model of the unoptimized high-voltage hybrid DC circuit breaker, see Fig.12 and Fig.13 , where solid lines ① and ③ represent the voltage and current curves of the experimental waveform, respectively, and dashed lines ② and ④ represent the voltage and current curves of the simulation results. As can be seen from the figure, the change trend of the simulation curve is consistent with the experimental curve, and the current curve is better than the voltage simulation curve. This shows that the system model can qualitatively characterize the load commutation switch IGBT-T LCS The overall characteristics of the commutation process. However, at special points such as A, B, C, D, E, and F, there are significant errors between the simulation results and the experimental results, which cannot meet the engineering requirements. One of the reasons for the error is that the new SPT-IGB is used in the hybrid circuit breaker; there are only standard IGB models in the PSCAD / EMTD component library, and there is no SPT-IGBT model of any type. Therefore, the system model has a certain reference value for the qualitative analysis of the hybrid circuit breaker, but it cannot complete the quantitative analysis.

[0061] Analyze the simulation results and experimental waveforms of the optimized simulation model of high-voltage hybrid DC circuit breaker, see Fig.14 and Fig.15, where solid lines ① and ③ represent the voltage and current curves of the experimental waveform, respectively, and dashed lines ② and ④ represent the voltage and current curves of the simulation results. As can be seen from the figure, the simulation curve is highly consistent with the experimental curve, and the analysis error is within 5%.

[0062] In summary, it can be seen that the optimization simulation model constructed by the modeling method of the present invention has more superior performance than the traditional system model, and can accurately predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during the commutation process of the load commutation switch, and solves the reliability problem of the load commutation switch of the high-voltage hybrid DC circuit breaker in the prior art during the shutdown process; it provides an effective analysis tool for the research on the load commutation switch branch buffer circuit and the design of the main circuit breaker MOA module. This modeling method provides a theoretical basis and technical support for the optimal design and practical application of high-voltage hybrid DC circuit breakers.

[0063] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker, characterized in that: The following steps are involved: Step 1: Based on the simulation model of high-voltage hybrid DC circuit breaker and stray inductance L p , construct a simplified principle model of high-voltage hybrid DC circuit breaker; Step 2: Based on the simplified principle model, draw the fault current timing diagram and the fault voltage timing diagram of the high-voltage hybrid DC circuit breaker; based on the fault current timing diagram and the fault voltage timing diagram, determine the working characteristics that the power electronic switch needs to have in the high-voltage DC power grid branch of the high-voltage hybrid DC circuit breaker; Step 3: Based on the working characteristics that the power electronic switch needs to have, select a power electronic switch SPT-IGBT with the working characteristics, perform a shutdown test on the SPT-IGBT, and establish a shutdown analytical model of the SPT-IGBT under extreme safety working area conditions; Step 4: Load commutation switch IGBT-T of high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the SPT-IGBT turn-off analytical model to establish the optimized load commutation switch IGBT-T LCS The turn-off equivalent circuit of Step 5: Based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are used to build an optimized simulation model of high-voltage hybrid DC circuit breaker.

2. A modeling method for a high-voltage hybrid DC circuit breaker load commutation switch according to claim 1, characterized in that: In step 1, the simplified principle model of the high-voltage hybrid DC circuit breaker includes a high-voltage DC grid branch, a normal branch and a main circuit breaker branch. The high-voltage DC grid branch is connected in series with the normal branch. The normal branch is an ultra-fast circuit breaker UFD and a load commutation switch IGBT-T connected in series. LCS , the main circuit breaker branch is connected in parallel with the normal branch, and the series node of the high-voltage DC grid branch and the normal branch is connected through the stray inductance L p Connect the main circuit breaker branch, the main circuit breaker includes a parallel lightning arrester MOA and an insulated gate bipolar transistor IGBT-T m .

3. A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker according to claim 2, characterized in that: Step 2 specifically includes the following steps: Based on the simplified principle model, the commutation process of the load current is simulated, and the fault current timing diagram and fault voltage timing diagram of the high-voltage hybrid DC circuit breaker are drawn; Based on the fault current timing diagram and fault voltage timing diagram, analyze the insulated gate bipolar transistor IGBT-T m Current limiting mechanism and load commutation switch IGBT-T LCS The dynamic switching process of the load commutation switch IGBT-T in the high-voltage DC grid branch is determined LCS Required job characteristics.

4. A modeling method for a high-voltage hybrid DC circuit breaker load commutation switch according to claim 3, characterized in that: Step three specifically includes the following steps: Based on the working characteristics that the power electronic switch in the high-voltage DC power grid branch needs to have, a power electronic switch SPT-IGBT with such working characteristics is selected, and a shutdown test is performed on the SPT-IGBT under the conditions of the extreme safe working area. The shutdown timing diagram of the SPT-IGBT is drawn, and the shutdown process of the SPT-IGBT is analyzed. According to the shutdown process, the shutdown equivalent circuit of the SPT-IGBT is established; based on the shutdown equivalent circuit of the SPT-IGBT, parameter calculation is performed and a shutdown analytical model of the SPT-IGBT is established.

5. A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker according to claim 4, characterized in that: Step 4 specifically includes the following steps: Load commutation switch IGBT-T for high voltage hybrid DC circuit breaker LCS Optimize and combine the simplified principle model and the SPT-IGBT turn-off analytical model to establish the optimized load commutation switch IGBT-T LCS Turn-off analytical model, based on the turn-off analytical model, draw the turn-off timing diagram and analyze the optimized load commutation switch IGBT-T LCS According to the shutdown process, an optimized load commutation switch IGBT-T is established. LCS The turn-off equivalent circuit.

6. A modeling method for a high-voltage hybrid DC circuit breaker load commutation switch according to claim 5, characterized in that: The optimization is specifically as follows: in the load commutation switch IGBT-T LCS The output port is connected in parallel with the buffer circuit.

7. A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker according to claim 6, characterized in that: The buffer circuit adopts an RCD buffer circuit.

8. The modeling method of a high-voltage hybrid DC circuit breaker load commutation switch according to claim 5, characterized in that: Step 5 specifically includes the following steps: Based on the optimized load commutation switch IGBT-T LCS The shutdown equivalent circuit and shutdown analytical model are determined, the electrical parameters are determined, the simulation equivalent circuit is constructed, and based on the simulation equivalent circuit, an optimized simulation model of the high-voltage hybrid DC circuit breaker is built.

9. A modeling method for a load commutation switch of a high-voltage hybrid DC circuit breaker according to claim 8, characterized in that: In step 5, the electrical parameters include electrical parameters of the high voltage DC grid branch, the normal branch and the main circuit breaker branch.

10. An application of a high voltage hybrid DC circuit breaker load current switch simulation model, characterized in that: The optimization simulation model constructed by the modeling method as described in any one of claims 1 to 9 above is used to predict the dynamic response characteristics of the high-voltage hybrid DC circuit breaker during the commutation period of the load commutation switch.

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