A simulation verification method for multi-level coordinated protection of subway power supply system

Abstract

A simulation verification method for multi-level coordinated protection of subway power supply systems was developed. Based on the MATLAB / Simulink platform, this method established an integrated simulation model that includes automatic reclosing, backup automatic reclosing, and automatic transfer switches. In particular, the advance compensation function of the ATSE was accurately modeled. The model was verified through power outage testing, and the simulation results were highly consistent with the measured data in terms of voltage recovery time. The error in the ATSE's advance compensation action time was less than 2ms, accurately reproducing the dynamic characteristics of the actual system. Model simulation showed that the ATSE's advance compensation strategy can effectively control the voltage sag to within 15%, significantly improving the system's power supply reliability. This application was rigorously verified through a "simulation-measurement" dual-track process. The model accurately reproduced the dynamic characteristics of the actual system and demonstrated significant advantages in improving power supply reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital simulation of power systems, and in particular relates to a multi-level coordinated protection simulation verification method for a subway power supply system based on a multi-level protection coordination mechanism. Background Art

[0002] Urban subway power supply systems, due to their unique electrical architecture and load characteristics, are ideal candidates for studying the impact of transient power quality. Compared to industrial loads, subway systems are more sensitive to voltage sags. This is primarily due to their extensive use of power electronic equipment (such as VVVF inverters) and sophisticated control systems. Protective action is triggered when the voltage drops to 85% of the rated value and lasts for more than 15ms. While their unique "bilateral power supply" model improves power supply reliability, it also increases the impact range of faults. More importantly, subway loads are significantly concentrated in time and space. During the morning peak hour, hourly loads can reach 2-3 times the daily average, and the load density at transfer stations is 4-5 times that of ordinary stations. This creates the risk of passenger backlogs exceeding 200% during peak hours due to short interruptions. These unique electrical and operational characteristics not only make subway systems a prime example for transient power quality research but also provide a realistic testing scenario for the development of new protective measures.

[0003] In the power system protection architecture, automatic reclosing (AR) and backup power automatic activation (BATS) constitute the basic protection system. AR devices are primarily used on transmission lines, automatically recovering from transient faults through a preset delay (typically 100-300ms), with a success rate of 60%-80%. BATS are deployed on the distribution side. Upon detecting a loss of main power voltage, they activate the backup power supply after a 500-1000ms delay, ensuring continuous power supply to the load. However, the response time of these two types of devices is difficult to meet the protection requirements for millisecond-level power outages. This is especially true for subway power supply systems, where sensitive loads account for over 70%. Traditional protection devices have significant limitations in responding to short-term interruptions.

[0004] Automatic transfer switches (ATSEs), with their millisecond-level switching capabilities (typically 15-30ms), have become a key technology for resolving short-term power outages. Compared to uninterruptible power supplies (UPSs), which require energy storage units and face challenges with battery life and maintenance costs, and dynamic voltage restorers (DVRs), which suffer from loss of compensation capabilities during 100% voltage interruptions, ATSEs not only achieve seamless power switching without energy storage components but are also more adaptable to various voltage interruption conditions. Furthermore, their dual-power switching mode perfectly adapts to the metro's bilateral power supply architecture, and their on-load switching capability of up to 5000A fully meets the demands of high-power traction loads, fully demonstrating their technical superiority and engineering applicability in the field of critical load protection.

[0005] A search revealed that Chinese invention patent publication number CN113691009A discloses a power supply system for a subway main substation, comprising a first incoming circuit, a first busbar section, a second incoming circuit, a second busbar section, a bus tie breaker, and a synchronization check device. The first incoming circuit is connected to the first busbar section for supplying power to the first busbar section; the second incoming circuit is connected to the second busbar section for supplying power to the second busbar section; the input of the synchronization check device is used to receive voltage parameters on the line side of the first incoming circuit and the line side of the second incoming circuit; and the output of the synchronization check device is connected to the protection device of the bus tie breaker. This application provides a power supply system for a subway main substation and a closed-loop control method. A synchronization check device is added to the bus tie cabinet of the main substation. If the power voltage amplitudes of the two incoming circuits are equal and the phase sequence is consistent, a closed-loop mode is used to ensure that both 40.5kV busbar sections on the low-voltage side of the main substation are energized when the incoming power to either main transformer low-voltage side is shut down.

[0006] The technical comparison between the above application and this application is as follows:

[0007] The aforementioned application discloses a power switching method for the operation of a 40.5kV switchgear on the low-voltage side of a subway main substation. This method optimizes the operational procedures of two-line incoming lines and busbar tie switchgear in traditional configurations, focusing on addressing the problem of prolonged busbar outages caused by manual operation when a single high-voltage line power source is lost or restored. Specifically, by improving the backup automatic switching logic or operation sequence, the power outage duration during the power switching process is reduced, avoiding disruptions to normal subway operations. This technology is particularly suitable for power supply systems with multiple main substations connected to a single main substation under large-scale power supply systems. This application develops a multi-level protection and coordinated control scheme for urban subway power supply systems based on the MATLAB / Simulink platform. This invention establishes a refined simulation model encompassing an automatic reclosing (AR), an automatic backup power supply (BATS), and an automatic transfer switch (ATSE), focusing on the precise modeling of the ATSE's advance compensation function. By enabling rapid power switching within milliseconds (15-30ms), it effectively addresses transient power quality issues such as voltage sags, controlling voltage sags to within 15%, and significantly improving power supply reliability.

[0008] While both focus on subway power supply system protection, patent CN113691009A primarily addresses process optimization in traditional switchgear switching operations, targeting planned power outages lasting from seconds to minutes. This patent, on the other hand, addresses millisecond-level transient power quality issues, using advanced simulation modeling and multi-level protection coordinated control to address transient faults such as voltage sags. The two differ fundamentally in terms of technology, the types of problems addressed, and the solutions they offer. Summary of the Invention

[0009] This paper addresses the need for high-precision modeling of power system automatic control devices in Simulink and proposes a simulation and verification method for multi-level coordinated protection of subway power supply systems. This method focuses on overcoming the modeling challenges of three key devices: automatic reclosing (AR), automatic backup switch (ATSE), and automatic switch-on / off switch (ATSE).

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A multi-level coordinated protection simulation verification method for a subway power supply system includes the following steps:

[0012] S1. Simplify the actual subway wiring diagram, draw a schematic diagram for simulation model reference, and then build a simulation model in Matlab / Simulink;

[0013] S2, automatic reclosing minimizes manual intervention and achieves "fault self-healing". Dynamic system protection is achieved through a closed-loop mechanism of "current detection - judgment - disconnection - delayed reclosing - re-detection";

[0014] S3. Design a backup automatic switching control scheme for the subway low-voltage power supply system;

[0015] S4. Design the automatic transfer switch control scheme;

[0016] S5. Design a variable frequency speed regulation simulation modeling scheme based on constant voltage-frequency ratio control.

[0017] As a preferred technical solution of the present invention: Step S2 is specifically as follows:

[0018] S21, real-time monitoring and fault determination;

[0019] The system continuously collects line current signals and converts the real-time current value into and circuit breaker rated current Threshold value is compared, when it is detected that the line current exceeds the rated current continuously When the threshold is exceeded and the duration reaches the preset fault judgment time window, it is judged as a short circuit fault and the circuit breaker opening operation is triggered immediately;

[0020] S22, reclosing start and delay control;

[0021] After the circuit breaker is opened, the system starts the reclosing sequence control module, loads the adjustable preset reclosing delay parameter T, starts timing, initializes the closing times counter, and records the first closing as ;

[0022] S23, delayed closing operation;

[0023] When the delay timer reaches the preset time When the circuit breaker is controlled, it performs the closing operation and records the current closing times. Record to system memory;

[0024] S24, fault persistence detection;

[0025] After each successful closing, the system re-enters the real-time monitoring state. If the real-time current value of the line is detected again Exceeding rated current If the fault exceeds the threshold, it is determined to be a permanent fault and the circuit breaker opening operation is triggered again immediately;

[0026] S25, closing times judgment and locking control;

[0027] Increment the closing times counter and compare the current count value with the preset maximum allowable closing times For comparison, if , then return to step S22 and start the next reclosing attempt. If , the reclosing lock function is activated, the subsequent closing operation is terminated and a lock alarm signal is issued.

[0028] As a preferred technical solution of the present invention: in step S21, the fault judgment time window is set to an adjustable parameter of 10-100ms, and in step S22, the reclosing delay parameter It is adjustable from 0.1 to 5 seconds. In step S25, the maximum number of closing times allowed is Set to a configurable value of 1-3 times.

[0029] As a preferred technical solution of the present invention: Step S3 is as follows:

[0030] S31, system initialization configuration;

[0031] The busbar system of section I is configured to be dedicated to the escalator load, the busbar system of section II is responsible for the automatic ticket vending and air conditioning and ventilation loads, and the fire emergency load is directly powered by the independent circuit self-contained power supply system. The incoming circuit breakers QF1 and QF2 are set to the closed state, and the bus tie switch QF3 is set to the disconnected state;

[0032] S32, fault detection and determination;

[0033] Real-time monitoring of the electrical parameters of the busbar section I system. When a voltage drop or current abnormality exceeding a preset threshold is detected, it is determined that the busbar section I system is faulty.

[0034] S33, fault isolation processing;

[0035] Immediately trigger the QF1 circuit breaker to open and cut off the fault bus connection;

[0036] S34, ATSE fast switching;

[0037] After QF1 is tripped, the ATSE device starts the millisecond-level fast switching program, switching the loads connected to bus section I to bus section II for power supply, completing the temporary power supply in advance;

[0038] S35, delayed start of standby automatic transfer;

[0039] Set the closing delay time t of the bus tie breaker QF3. When the delay time is reached, execute the QF3 closing operation.

[0040] S36, power supply mode switching;

[0041] By closing the QF3 circuit breaker, the interconnected power supply between bus section I and bus section II is realized, forming a two-way mutual backup power supply mode, while keeping the one-way power supply relationship between the self-contained power supply system and bus section I unchanged.

[0042] As a preferred technical solution of the present invention: in step S32, the fault judgment threshold is 70%-85% of the rated voltage for more than 100ms; in step S34, the ATSE switching time is controlled within the range of 20-50ms; in step S35, the delay time t is set to an adjustable parameter of 0.5-2s.

[0043] The present invention provides a multi-level coordinated protection simulation verification method for a subway power supply system, wherein step S4 is specifically as follows:

[0044] S41, system initialization configuration;

[0045] Configure the ATSE workstation structure as a two-position or three-position structure. The two-position structure has two positions: "main power" and "backup power", while the three-position structure has three positions: "main power", "backup power" and "zero". All load branch protection circuit breakers QF3 to QF5 are set to the closed state.

[0046] S42, power supply connection and detection;

[0047] The main power supply and backup power supply are connected to the system after being stepped down by transformers T1 and T2 respectively, and supplied through circuit breakers QF1 and QF2. The voltage, frequency and phase parameters of the dual power supplies are monitored in real time.

[0048] S43, operating status control;

[0049] Under normal working conditions, keep the QS1 intelligent contactor connected to the main power supply position, and the QS2 intelligent contactor disconnected from the backup power supply position;

[0050] S44, Fault detection and determination:

[0051] Continuously monitor the main power supply electrical parameters and determine that the main power supply is faulty when voltage drops, frequency deviations, or power outages exceeding preset thresholds are detected;

[0052] S45, switching logic execution;

[0053] Execute the corresponding switching procedure according to the ATSE station structure:

[0054] For two-position architecture: directly control QS1 to disconnect the main power position, and QS2 to connect the backup power position;

[0055] For the three-position architecture: first control QS1 to disconnect the main power position and enter the zero position, then detect the backup power parameters after a delay of T1, and control QS2 to connect the backup power position after confirming that they are qualified;

[0056] S46, resume logic execution;

[0057] When it is detected that the main power parameters return to normal and remain stable for T2, the recovery procedure is executed according to the station structure:

[0058] For two-position architecture: directly control QS2 to disconnect the backup power supply and QS1 to connect the main power supply;

[0059] For the three-position architecture: first control QS2 to disconnect the backup power supply and enter the zero position, then detect the main power supply parameters after a delay of T3, and control QS1 to connect the main power supply after confirming that they are qualified.

[0060] As a preferred technical solution of the present invention: in step S44, the fault judgment threshold is 75%-85% of the rated voltage for more than 100ms; in step S45, the delay time T1 is set to 5-200ms; in step S46, the stabilization time T2 is set to 5-30ms, and the delay time T3 is set to 5-200ms.

[0061] As a preferred technical solution of the present invention: Step S5 is specifically as follows:

[0062] S51, first, the system gives the signal as the motor speed instruction , as the target input value of the speed control system;

[0063] S52, speed control link:

[0064] Real-time detection of actual motor speed , with the given motor speed command Compare and generate speed error signal , ;

[0065] S53, speed error processing:

[0066] Speed ​​error signal Processed by PI regulator with output limiting to generate slip frequency instruction ;

[0067] S54, frequency synthesis link:

[0068] The slip frequency command With actual speed Synthesize and generate stator synchronous frequency instruction , ;

[0069] S55, voltage-frequency conversion:

[0070] Stator synchronous frequency command and stator current Common input V / F function generator, V / F function generator generates corresponding stator voltage instruction according to the preset constant voltage frequency ratio curve and low frequency voltage compensation algorithm ;

[0071] S56, power output link:

[0072] The stator voltage command With stator frequency command As the input parameter of the space vector PWM algorithm, through the power switch control of the inverter, the output amplitude and frequency adjustable three-phase AC voltage is realized to achieve variable voltage and variable frequency speed control of the induction motor.

[0073] As a preferred technical solution of the present invention: In step S53, the PI regulator is provided with an output limiting mechanism, which makes the slip frequency instruction meet the output limiting mechanism. ≤ ,in It is the maximum slip frequency allowed by the system.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] This paper innovatively constructs an integrated simulation model based on the MATLAB / Simulink platform, encompassing the automatic reclosing (AR), backup automatic switching (BATS), and automatic transfer switch (ATSE). This model offers three key advantages: First, by accurately modeling the ATSE's early compensation function, it achieves ultra-high simulation accuracy with an operating time error of less than 2ms, and its voltage recovery characteristics are largely consistent with measured data. Second, the proposed ATSE early compensation strategy effectively controls voltage sags to within 15%, improving voltage quality by 40% compared to traditional methods. Finally, its modular design enables the model to combine system-level collaborative simulation with device-level characteristic analysis, providing a reliable tool for design optimization and operation and maintenance decision-making for subway power supply systems. Through rigorous "simulation-measurement" dual-track verification, the model accurately replicates the dynamic characteristics of the actual system, demonstrating significant advantages in improving power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 Simplify schematics for electrical wiring diagrams;

[0077] Figure 2 This is the automatic reclosing closed-loop control flow chart;

[0078] Figure 3 It is a low-voltage control system with standby automatic switching;

[0079] Figure 4 It is a two-position diagram of the ATSE station;

[0080] Figure 5 This is a three-dimensional diagram of the ATSE workstation;

[0081] Figure 6 This is the principle diagram of constant voltage-frequency ratio speed regulation;

[0082] Figure 7 for Load voltage simulation waveform;

[0083] Figure 8 for Load voltage simulation waveform;

[0084] Figure 9 for Load voltage simulation waveform;

[0085] Figure 10 for Load voltage simulation waveform;

[0086] Figure 11 To compensate for the load voltage response waveform before;

[0087] Figure 12 is the load voltage response waveform after compensation;

[0088] Figure 13 The DC bus voltage response waveform before compensation;

[0089] Figure 14 is the DC bus voltage response waveform after compensation;

[0090] Figure 15 To compensate for the stator current response waveform of the motor before;

[0091] Figure 16 This is the stator current response waveform of the motor after compensation. DETAILED DESCRIPTION

[0092] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0093] like Figure 1 As shown, the present invention proposes a multi-level coordinated protection simulation verification method for a subway power supply system, comprising the following steps:

[0094] S1. Simplify the actual subway wiring diagram, draw a schematic diagram for simulation model reference, and then build a simulation model in Matlab / Simulink

[0095] The electrical wiring schematic is divided as shown in Table 1. The corresponding list is listed next to it, covering the reference input files.

[0096] Table 1: Electrical wiring schematic

[0097] Schematic Schematic Level source 110-35kv high voltage main circuit First-level schematic diagram Primary scheme and structural foundation diagram of 35kV switchgear for Phase II of Metro Line 10 in a certain city 0.4kv low voltage main circuit Secondary schematic Low voltage power distribution schematic diagram Load wiring diagram Three-level schematic diagram Escalator wiring diagram

[0098] S2, automatic reclosing to minimize manual intervention, achieve "fault self-healing", through the "current detection - judgment - disconnection - delayed reclosing - re-detection" closed-loop mechanism to achieve system dynamic protection, such as Figure 2 As shown,

[0099] Step S2 is specifically as follows:

[0100] S21, real-time monitoring and fault determination;

[0101] The system continuously collects line current signals and converts the real-time current value into and circuit breaker rated current Threshold value is compared, when it is detected that the line current exceeds the rated current continuously When the threshold is exceeded and the duration reaches the preset fault judgment time window, it is judged as a short circuit fault and the circuit breaker opening operation is triggered immediately;

[0102] S22, reclosing start and delay control;

[0103] After the circuit breaker is opened, the system starts the reclosing sequence control module, loads the adjustable preset reclosing delay parameter T, starts timing, initializes the closing times counter, and records the first closing as ;

[0104] S23, delayed closing operation;

[0105] When the delay time reaches the preset time T, the circuit breaker is controlled to perform the closing operation and the current closing times are recorded. Record to system memory;

[0106] S24, fault persistence detection;

[0107] After each successful closing, the system re-enters the real-time monitoring state. If the real-time current value of the line is detected again Exceeding rated current If the fault exceeds the threshold, it is determined to be a permanent fault and the circuit breaker opening operation is triggered again immediately;

[0108] S25, closing times judgment and locking control;

[0109] Increment the closing times counter and compare the current count value with the preset maximum allowable closing times For comparison, if , then return to step S22 and start the next reclosing attempt. If , the reclosing lock function is activated, the subsequent closing operation is terminated and a lock alarm signal is issued.

[0110] In step S21, the fault judgment time window is set to an adjustable parameter of 10-100ms. In step S22, the reclosing delay parameter T is set to an adjustable parameter of 0.1-5s. In step S25, the maximum allowable closing times is set to Set to a configurable value of 1-3 times.

[0111] S3. Design a backup automatic switching control scheme for the subway low-voltage power supply system, such as Figure 3 As shown;

[0112] Step S3 is as follows:

[0113] S31, system initialization configuration;

[0114] The busbar system of section I is configured to be dedicated to the escalator load, the busbar system of section II is responsible for the automatic ticket vending and air conditioning and ventilation loads, and the fire emergency load is directly powered by the independent circuit self-contained power supply system. The incoming circuit breakers QF1 and QF2 are set to the closed state, and the bus tie switch QF3 is set to the disconnected state;

[0115] S32, fault detection and determination;

[0116] Real-time monitoring of the electrical parameters of the busbar section I system. When a voltage drop or current abnormality exceeding a preset threshold is detected, it is determined that the busbar section I system is faulty.

[0117] S33, fault isolation processing;

[0118] Immediately trigger the QF1 circuit breaker to open and cut off the fault bus connection;

[0119] S34, ATSE fast switching;

[0120] After QF1 is tripped, the ATSE device starts the millisecond-level fast switching program, switching the loads connected to bus section I to bus section II for power supply, completing the temporary power supply;

[0121] S35, delayed start of standby automatic transfer;

[0122] Set the closing delay time t of the bus tie breaker QF3. When the delay time is reached, execute the QF3 closing operation.

[0123] S36, power supply mode switching;

[0124] By closing the QF3 circuit breaker, the interconnected power supply between bus section I and bus section II is realized, forming a two-way mutual backup power supply mode, while keeping the one-way power supply relationship between the self-contained power supply system and bus section I unchanged.

[0125] In step S32, the fault judgment threshold is 70%-85% of the rated voltage for more than 100ms; in step S34, the ATSE switching time is controlled within the range of 20-50ms; in step S35, the delay time t is set to an adjustable parameter of 0.5-2s.

[0126] S4. Design an automatic transfer switch (ATSE) control scheme, such as Figure 4-5 As shown,

[0127] Step S4 is specifically as follows:

[0128] S41, system initialization configuration;

[0129] Configure the ATSE workstation structure as a two-position or three-position structure. The two-position structure has two positions: "main power" and "backup power", while the three-position structure has three positions: "main power", "backup power" and "zero". All load branch protection circuit breakers QF3 to QF5 are set to the closed state.

[0130] S42, power supply connection and detection;

[0131] The main power supply and backup power supply are connected to the system after being stepped down by transformers T1 and T2 respectively, and supplied through circuit breakers QF1 and QF2. The voltage, frequency and phase parameters of the dual power supplies are monitored in real time.

[0132] S43, operating status control;

[0133] Under normal working conditions, keep the QS1 intelligent contactor connected to the main power supply position, and the QS2 intelligent contactor disconnected from the backup power supply position;

[0134] S44, fault detection and determination: Continuously monitor the electrical parameters of the main power supply. When a voltage drop, frequency deviation, or power outage exceeding a preset threshold is detected, it is determined that there is a main power supply fault;

[0135] S45, switching logic execution;

[0136] Execute the corresponding switching procedure according to the ATSE station structure:

[0137] For two-position architecture: directly control QS1 to disconnect the main power position, and QS2 to connect the backup power position;

[0138] For the three-position architecture: first control QS1 to disconnect the main power position and enter the zero position, then detect the backup power parameters after a delay of T1, and control QS2 to connect the backup power position after confirming that they are qualified;

[0139] S46, resume logic execution;

[0140] When it is detected that the main power parameters return to normal and remain stable for T2, the recovery procedure is executed according to the station structure:

[0141] For two-position architecture: directly control QS2 to disconnect the backup power supply and QS1 to connect the main power supply;

[0142] For the three-position architecture: first control QS2 to disconnect the backup power supply and enter the zero position, then detect the main power supply parameters after a delay of T3, and control QS1 to connect the main power supply after confirming that they are qualified.

[0143] In step S44, the fault judgment threshold is 75%-85% of the rated voltage for more than 100ms; in step S45, the delay time T1 is set to 5-200ms; in step S46, the stabilization time T2 is set to 5-10ms, and the delay time T3 is set to 5-200ms.

[0144] All modules utilize standardized interfaces, supporting seamless integration with Simulink / SimPowerSystem. Parametric design tools and experimental verification methods have been developed alongside these modules, providing a powerful simulation platform for design optimization and operational analysis of power system automatic control devices. This solution not only enables full-dimensional simulation capabilities from the device to the system level, but also achieves industry-leading levels of model accuracy and functional completeness.

[0145] S5. According to the driving control characteristics of the escalator in the subway power supply system, a variable frequency speed regulation simulation modeling scheme based on constant voltage-frequency ratio (V / f) control is designed, such as Figure 6 As shown,

[0146] Step S5 is specifically as follows:

[0147] S51, first, the system gives the signal as the motor speed instruction , as the target input value of the speed control system;

[0148] S52, speed control link: real-time detection of the actual speed of the motor , with the given motor speed command Compare and generate speed error signal , ;

[0149] S53, speed error processing: speed error signal The slip frequency command is generated by processing through the PI regulator (speed regulator ASR) with output limiting ;

[0150] S54, frequency synthesis link: the difference frequency instruction With actual speed Synthesize and generate stator synchronous frequency instruction , ;

[0151] S55, voltage-frequency conversion: stator synchronous frequency instruction and stator current Common input V / F function generator, V / F function generator generates corresponding stator voltage instruction according to the preset constant voltage frequency ratio curve and low frequency voltage compensation algorithm ;

[0152] S56, power output link: the stator voltage instruction With stator frequency command As the input parameter of the space vector PWM algorithm, through the power switch control of the inverter, the output amplitude and frequency of the three-phase AC voltage are adjustable, realizing the variable voltage and variable frequency (VVVF) speed control of the induction motor.

[0153] In step S53, the PI regulator (speed regulator ASR) is equipped with a strict output limiting mechanism to ensure that the output limiting mechanism makes the slip frequency command meet ≤ ,in It is the maximum slip frequency allowed by the system.

[0154] In response to the multi-level protection and coordinated control requirements of urban subway power supply systems, this paper established a refined simulation model based on the MATLAB / Simulink platform, including AR, BATS, and ATSE. In particular, the advance compensation function of ATSE was accurately modeled. The model was verified through power outage testing, and the simulation results were highly consistent with the measured data in terms of voltage recovery time. The error in the advance compensation action time of ATSE was less than 2ms, accurately reproducing the dynamic characteristics of the actual system. Model simulation shows that the advance compensation strategy of ATSE can effectively control the voltage sag to within 15%, significantly improving the system power supply reliability.

[0155] The specific implementation of this application is as follows:

[0156] 1. This application first passes the power-off test. For the action time of ATSE, four delays of 9.5ms, 10ms, 13ms and 24ms are set manually. The load voltage simulation waveform is as follows Figure 7-10 shown. When the system is powered off, the voltage drops to zero quickly. The zero voltage stage is the switch conversion time. After different conversion delays, the voltage quickly returns to the rated voltage. The simulation results show that under different switch conversion times, 、 、 and It quickly recovers to the rated operating voltage of 220V, and the dynamic response meets the design requirements.

[0157] 2. Then, we worked with industry partners to conduct a dual power switching test on the escalator system. The test strictly followed the IEC61000-4-34 standard and was repeated three times under rated load to ensure data reliability. The test settings were the same as the simulation settings for the four switching times. The load voltage waveform is as follows: Figure 7-10 The test list is shown in Table 2. The oscilloscope's horizontal scale is 5ms / div. The period where the voltage reaches zero on the oscilloscope represents the switch transition time. After varying switching delays, the voltage quickly returns to the rated voltage. Comparison shows that the dynamic response of the simulated and measured load voltage waveforms is essentially consistent. In the actual measurement, voltage distortion occurs for approximately 2ms when the switch is connected to the backup power supply. This is likely due to high-frequency oscillation caused by the bounce time and line distribution parameters in the physical process of switch contact closure.

[0158] Table 2: Test list

[0159] Test items Escalator system testing Test Objectives Escalator system load side voltage Test escalator brand Kone Distribution box number AT-02-FT2 Automatic transfer switch brand Kyoritsu SSK

[0160] 3. Multi-level collaborative protection model simulation;

[0161] The transient response waveform of the fault under composite protection is as follows: Figure 11-16 As shown in Table 3, the key performance parameters are as follows:

[0162] Parameter explanation:

[0163] (1) Load-end voltage: refers to the power frequency voltage directly applied to the input terminal of electrical equipment (such as motors, lighting systems, etc.) in the power supply system, which serves as the energy source for the normal operation of the load. Stable load-end voltage is a prerequisite for ensuring the reliable operation of electrical equipment. Its amplitude, frequency and waveform distortion rate must be maintained within the allowable range. Otherwise, it may cause abnormal shutdown of equipment, performance degradation or even insulation damage.

[0164] (2) Inverter DC bus voltage: In an AC-DC-AC inverter, the intermediate DC voltage stored on the DC bus capacitor after conversion by the rectifier stage provides a stable DC power supply for the subsequent inverter stage. The stability of the DC bus voltage directly affects the output performance of the inverter. When the load-side voltage temporarily sags, the DC bus voltage will drop. If the voltage drop exceeds 15% and lasts for more than 10ms, it may trigger overcurrent protection of the IGBT module or overvoltage damage to the electrolytic capacitor.

[0165] (3) Motor stator current: This refers to the power frequency current flowing through the stator winding of an AC motor. Its effective value determines the motor output torque, and its harmonic content affects the motor temperature rise. During the voltage sag recovery process, the stator current changes through two stages: first, the transient inrush stage. Due to magnetic circuit saturation, a closing inrush current of 6-8 times the rated current may be generated, which lasts for about 5-10 power frequency cycles. Then, it enters the steady-state stage, and the current gradually decays to the rated value. Excessive inrush current will produce significant electromagnetic force impact and Joule heating, accelerating the aging of the winding insulation.

[0166] The system status indications are as follows:

[0167] S0 (after 0.63s): ATSE switching stage;

[0168] S1 (0.703-0.731s): AR operation stage;

[0169] S2 (0.731-0.84s): system locking stage;

[0170] S3 (after 0.84s): standby operation stage.

[0171] Table 3: Key performance parameters

[0172] Parameter name Parameter value Asynchronous motor capacity 30kw Rated voltage of asynchronous motor 380v Motor rated speed 1450rpm Inverter capacitor capacity 5.4mF ATSE action time 30ms

[0173] The steps of composite protection are as follows:

[0174] Step 1: ATSE fast switching, corresponding to system state S0

[0175] The voltage anomaly is detected within 5ms of the circuit breaker tripping, and the backup power supply is switched after a 30ms delay (0.63s), maintaining the DC bus voltage drop within 12% of the rated value.

[0176] Step 2: AR protection response, corresponding to system states S1 and S2

[0177] First reclosing operation (0.703-0.731s), entering the locked state after confirmation of reclosing failure (0.731-0.84s);

[0178] Step 3: BATS backup protection, corresponding to system state S3

[0179] After 0.84 seconds, the backup automatic switching program is started, and the bus section II supplies power to the bus section I, ensuring that the system eventually resumes stable operation.

[0180] Step 4: Conclusion Analysis:

[0181] By comparing the waveforms of the load-end voltage, inverter DC bus voltage, and motor stator current in the system before and after ATSE compensation, it can be found that after configuring the automatic transfer switch ATSE, the system's dynamic response characteristics are significantly improved, with the actual power loss time of critical loads ≤50ms; the inverter DC bus voltage ≥88% of the rated value; and the motor closing inrush current ≤2 times the rated current. This truly achieves uninterrupted power supply to critical loads and safe protection of the system's core components, thereby improving the overall reliability of the power supply to the grid.

[0182] The ATSE switching delay in step 1 is adjustable; the AR action delay in step 2 is adjustable; and the BATS action delay in step 3 is adjustable.

[0183] In summary, the multi-level collaborative protection simulation verification method for a subway power supply system disclosed in the present invention is particularly suitable for critical load scenarios such as urban rail transit.

[0184] The method of this application builds a three-level coordinated protection system of "automatic reclosing-backup automatic switching-fast switching" (AR-BATS-ATSE):

[0185] 1. An innovative multi-level protection control strategy based on timing coordination was proposed. This strategy can achieve rapid reconstruction and stable control of energy flow under high-voltage fault conditions by precisely coordinating the operation timing of AR, BATS, and ATSE.

[0186] 2. Model-based verification demonstrates that ATSE's millisecond-level rapid compensation technology can ensure that the inverter's DC bus voltage sag is controlled within 15% and the motor's closing inrush current is limited to less than 2 times the rated value, significantly improving equipment operation safety.

[0187] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A multi-level collaborative protection simulation verification method for a subway power supply system, characterized in that: The steps include: S1. Simplify the actual subway wiring diagram, draw a schematic diagram for simulation model reference, and then build a simulation model in Matlab / Simulink; S2, automatic reclosing minimizes manual intervention and achieves "fault self-healing". Dynamic system protection is achieved through a closed-loop mechanism of "current detection - judgment - disconnection - delayed reclosing - re-detection"; S3. Design a backup automatic switching control scheme for the subway low-voltage power supply system; Step S3 is as follows: S31, system initialization configuration; The busbar system of section I is configured to be dedicated to the escalator load, the busbar system of section II is responsible for the automatic ticket vending and air conditioning and ventilation loads, and the fire emergency load is directly powered by the independent circuit self-contained power supply system. The incoming circuit breakers QF1 and QF2 are set to the closed state, and the bus tie switch QF3 is set to the disconnected state; S32, fault detection and determination; Real-time monitoring of the electrical parameters of the busbar section I system. When a voltage drop or current abnormality exceeding a preset threshold is detected, it is determined that the busbar section I system is faulty. S33, fault isolation processing; Immediately trigger the QF1 circuit breaker to open and cut off the fault bus connection; S34, ATSE fast switching; After QF1 is tripped, the ATSE device starts the millisecond-level fast switching program, switching the loads connected to bus section I to bus section II for power supply, completing the temporary power supply in advance; S35, delayed start of standby automatic transfer; Set the closing delay time t of the bus tie breaker QF3. When the delay time is reached, execute the QF3 closing operation. S36, power supply mode switching; By closing QF3, the interconnected power supply between bus section I and bus section II is realized, forming a two-way mutual backup power supply mode, while maintaining the unidirectional power supply relationship between the self-contained power supply system and bus section I unchanged; S4. Design the automatic transfer switch control scheme; Step S4 is specifically as follows: S41, system initialization configuration; Configure the ATSE workstation structure as a two-position or three-position structure. The two-position structure has two positions: "main power" and "backup power"; the three-position structure has three positions: "main power", "backup power", and "zero". All load branch circuit breakers QF3 to QF5 are set to the closed state. S42, power supply connection and detection; The main power supply and backup power supply are connected to the system after being stepped down by transformers T1 and T2 respectively, and supplied through circuit breakers QF1 and QF2. The voltage, frequency and phase parameters of the dual power supplies are monitored in real time. S43, operating status control; Under normal working conditions, keep the QS1 intelligent contactor connected to the main power supply position, and the QS2 intelligent contactor disconnected from the backup power supply position; S44, Fault detection and determination: Continuously monitor the main power supply electrical parameters and determine that the main power supply is faulty when voltage drops, frequency deviations, or power outages exceeding preset thresholds are detected; S45, switching logic execution; Execute the corresponding switching procedure according to the ATSE station structure: For two-position architecture: directly control QS1 to disconnect the main power position, and QS2 to connect the backup power position; For the three-position architecture: first control QS1 to disconnect the main power supply and enter the zero position, then detect the backup power supply parameters after a delay of T1, and control QS2 to connect the backup power supply after confirming that they are qualified; S46, resume logic execution; When it is detected that the main power parameters return to normal and remain stable for T2, the recovery procedure is executed according to the station structure: For two-position architecture: directly control QS2 to disconnect the backup power supply and QS1 to connect the main power supply; For the three-position architecture: first control QS2 to disconnect the backup power supply and enter the zero position, then detect the main power supply parameters after a delay of T3, and control QS1 to connect the main power supply after confirming that they are qualified; S5. Design a variable frequency speed regulation simulation modeling scheme based on constant voltage-frequency ratio control; Step S5 is specifically as follows: S51, first, the system gives the signal as the motor speed instruction , as the target input value of the speed control system; S52, speed control link: Real-time detection of actual motor speed , with the given motor speed command Compare and generate speed error signal , ; S53, speed error processing: Speed ​​error signal Processed by PI regulator with output limiting to generate slip frequency instruction ; S54, frequency synthesis link: The slip frequency command With actual speed Perform synthesis to generate stator synchronous frequency instruction , ; S55, voltage-frequency conversion: Stator synchronous frequency command and stator current Common input V / F function generator, V / F function generator generates corresponding stator voltage instruction according to the preset constant voltage frequency ratio curve and low frequency voltage compensation algorithm ; S56, power output link: The stator voltage command With stator frequency command As the input parameter of the space vector PWM algorithm, through the power switch control of the inverter, the output amplitude and frequency adjustable three-phase AC voltage is realized to achieve variable voltage and variable frequency speed control of the induction motor.

2. A subway power supply system multi-level coordinated protection simulation verification method according to claim 1, characterized in that: Step S2 is specifically as follows: S21, real-time monitoring and fault determination; The system continuously collects line current signals and converts the real-time current value into and circuit breaker rated current Threshold value is compared, when it is detected that the line current exceeds the rated current continuously When the threshold is exceeded and the duration reaches the preset fault judgment time window, it is judged as a short circuit fault and the circuit breaker opening operation is triggered immediately; S22, reclosing start and delay control; After the circuit breaker is opened, the system starts the reclosing sequence control module, loads the adjustable preset reclosing delay parameter T, starts timing, initializes the closing times counter, and records the first closing as ; S23, delayed closing operation; When the delay timer reaches the preset time When the circuit breaker is controlled, it performs the closing operation and records the current closing times. Record to system memory; S24, fault persistence detection; After each successful closing, the system re-enters the real-time monitoring state. If the real-time current value of the line is detected again Exceeding rated current If the fault exceeds the threshold, it is determined to be a permanent fault and the circuit breaker opening operation is triggered again immediately; S25, closing times judgment and locking control; Increment the closing times counter and compare the current count value with the preset maximum allowable closing times For comparison, if , then return to step S22 and start the next reclosing attempt. If , the reclosing lock function is activated, the subsequent closing operation is terminated and a lock alarm signal is issued.

3. A subway power supply system multi-level coordinated protection simulation verification method according to claim 2, characterized in that: In step S21, the fault judgment time window is set to an adjustable parameter of 10-100ms, and in step S22, the reclosing delay parameter It is adjustable from 0.1 to 5 seconds. In step S25, the maximum number of closing times allowed is Set to a configurable value of 1-3 times.

4. The multi-level coordinated protection simulation verification method for a subway power supply system according to claim 1 is characterized in that: In step S32, the fault judgment threshold is 70%-85% of the rated voltage for more than 100ms; in step S34, the ATSE switching time is controlled within the range of 20-50ms; in step S35, the delay time t is set to an adjustable parameter of 0.5-2s.

5. The multi-level coordinated protection simulation verification method for a subway power supply system according to claim 1 is characterized in that: In step S44, the fault judgment threshold is 75%-85% of the rated voltage for more than 100ms; in step S45, the delay time T1 is set to 5-200ms; in step S46, the stabilization time T2 is set to 5-30ms, and the delay time T3 is set to 5-200ms.

6. The multi-level coordinated protection simulation verification method for a subway power supply system according to claim 1 is characterized in that: In step S53, the PI regulator is provided with an output limiting mechanism, which makes the slip frequency instruction meet the ≤ ,in It is the maximum slip frequency allowed by the system.

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