Pfc cooperative control method and system for rail transit multi-motor driving system

Abstract

The present application relates to the field of electrical control technology of rail transit vehicles, and discloses a PFC cooperative control method and system for a rail transit multi-motor drive system. The method collects parameters of the multi-motor and the on-board power grid in real time, predicts THD based on a harmonic superposition model, judges the risk of exceeding the standard, dynamically allocates PFC control parameters in combination with model predictive control and adaptive harmonic cancellation logic, monitors actual THD and power factor after synchronous issuance, forms a closed-loop optimization, and comprises a signal acquisition module, a global optimization algorithm module, an execution control module, and a monitoring feedback module. Application of the present application can reduce THD by more than 30% during parallel operation of the multi-motor, increase the power factor to greater than or equal to 0.98, adapt to load fluctuations and motor switching conditions, is compatible with existing hardware, has low modification costs, and is suitable for rail transit vehicles such as subways and high-speed rails.

Description

Technical Field

[0001] This invention relates to the field of electrical control technology for rail transit vehicles, and in particular to a PFC cooperative control method and system for a multi-motor drive system for rail transit, applicable to rail transit vehicles such as subways, high-speed railways, and light rails. Background Technology

[0002] PFC stands for Power Factor Correction. It is a key technology widely used in core products such as frequency converters and power supplies for rail transit vehicles. Its core function is to optimize the power factor of electrical equipment and reduce current harmonics through specific circuit design and control logic, thereby improving grid compatibility and equipment operating efficiency.

[0003] The specific functions of PFC technology are threefold. First, it enables controllable rectification. For example, in air conditioner fan inverters and air conditioner compressor inverters, PFC controllable rectification converts three-phase AC 380V power into a stable DC bus, while controlling the input current harmonic content to ≤5%, avoiding harmonic interference to the vehicle's power grid. Second, it improves power factor and equipment performance. For instance, in battery chargers, the 3AC 380V input version equipped with PFC function can reduce reactive power loss in the power grid. Furthermore, optimization through PFC high-frequency conversion and PFC inductor miniaturization technologies achieves lighter equipment weight and lower system temperature rise, further adapting to the stringent requirements of rail transit vehicles for equipment size and heat dissipation. Third, it meets industry standards. The application of PFC technology is a crucial support for Bosman products to comply with the EN50155 standard for rail transit (electromagnetic compatibility and power grid compatibility requirements), ensuring stable operation of products in high-speed rail, subway, and other scenarios.

[0004] In the electrical systems of rail transit vehicles, the parallel operation of multiple motors is a typical operating condition. For example, the door control motor is responsible for controlling the opening and closing of the doors, the air conditioning fan motor ensures the ventilation of the carriage, and the compressor motor maintains the cooling function. All of these motors need to be driven by frequency converters. Power factor correction (PFC) technology is a core component of frequency converters. Its role is to optimize the power factor of electrical equipment, reduce current harmonics, and ensure that the equipment meets industry standards and operates stably.

[0005] However, when multiple motors are running in parallel, the existing single-motor PFC independent control scheme has significant defects: (1) Harmonic superposition leads to excessive THD: The PFC unit of each motor works independently, and the characteristic harmonics such as the 3rd, 5th, and 7th are superimposed on the vehicle power grid side, resulting in the total harmonic distortion (THD) often exceeding 10%, which does not meet the requirement of EN50155 that the harmonic interference of vehicle equipment to the power grid is ≤8%; (2) The stability of the power grid decreases: Harmonic superposition will reduce the power factor of the vehicle power grid, increase the additional losses of the traction converter and auxiliary power system, and long-term operation is prone to equipment overheating (such as abnormal temperature rise of the inverter IGBT module) and shortened life (such as accelerated wear of the contactor contacts of the gate motor); (3) Poor compatibility and scalability: The single-motor PFC control logic is solidified in each device (such as the gate controller and the air conditioning controller), and it is impossible to adjust the control strategy according to the dynamic changes of the multi-motor load (such as the frequent opening and closing of the doors during peak hours and the full load operation of the air conditioning), making it difficult to adapt to the multi-condition operation requirements of rail transit vehicles.

[0006] Therefore, there is an urgent need for a control scheme that can achieve global coordination of multi-motor PFC, solve the defects of existing technology, and ensure the stable and efficient operation of the electrical system of rail transit vehicles. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a PFC cooperative control method and system for multi-motor drive systems in rail transit, in order to avoid the total harmonic distortion (THD) exceeding the standard due to harmonic superposition, enhance power grid stability, and ensure the stable and efficient operation of the electrical system of rail transit vehicles.

[0008] To achieve the above objectives, the present invention provides the following technical solution: According to one aspect of the present invention, a PFC cooperative control method for a multi-motor drive system in rail transit is provided, comprising the following steps: S1: When multiple motors start or run in parallel, collect the operating parameters of the multiple motors and the parameters of the vehicle's power grid in real time; S2: Based on the collected parameters, predict the THD value when each motor PFC unit is controlled independently using the multi-motor harmonic superposition model, and determine whether there is a risk of exceeding the standard. S3: If there is a risk of exceeding the standard, based on the prediction results and harmonic component analysis, combined with the model predictive control algorithm and adaptive harmonic cancellation logic, the control parameters of each motor PFC unit are dynamically allocated. S4: The allocated control parameters are sent to the corresponding PFC unit of the motor through a synchronous triggering mechanism to ensure that each PFC unit performs actions according to the preset timing sequence; S5: Real-time acquisition of the actual THD value and the actual power factor of the vehicle's electrical grid during the parallel operation of multiple motors; S6: If the actual THD value or actual power factor exceeds the preset standard threshold, repeat steps S2 to S5 to form a PFC collaborative control closed loop.

[0009] According to one embodiment of the present invention, the multi-motor operating parameters include input current, input voltage, load rate, and PFC operating status; the PFC operating status includes normal rectification status, fault status, and standby status; the vehicle-mounted power grid parameters include vehicle-mounted power grid voltage level and harmonic components.

[0010] According to one embodiment of the present invention, the control parameters include switching frequency and duty cycle. The switching frequency ranges from 5kHz to 30kHz, and the duty cycle ranges from 0.3 to 0.8. When dynamically allocating control parameters, it is necessary to ensure that the current ripple of each motor PFC unit is ≤5% of the motor's rated current.

[0011] According to one embodiment of the present invention, the multiple motors are selected from at least two of the following: rail transit vehicle door control motor, air conditioning fan motor, and air conditioning compressor motor.

[0012] According to one embodiment of the present invention, in step S2, the specific implementation method for predicting the THD value based on the multi-motor harmonic superposition model is as follows: The harmonic characteristic curves of each type of motor PFC operating independently are pre-stored; the harmonic amplitude is corrected according to the real-time collected motor load rate; the total THD is calculated using the root mean square superposition method, and the calculation formula is: , among which, I n I1 is the amplitude of the nth harmonic current and I2 is the amplitude of the fundamental current.

[0013] According to one embodiment of the present invention, the harmonic characteristic curve is a curve showing the relationship between motor load rate and harmonic amplitude ratio obtained in advance through experiments; the fitting formula for the correction coefficient is: K h = 0.08 + 0.05 × (load rate ÷ 100), where K h This is the correction coefficient for the amplitude of the nth harmonic.

[0014] According to one embodiment of the present invention, in step S1, the parameter acquisition frequency is 10Hz-50Hz. When the motor load rate fluctuation exceeds ±15%, the acquisition frequency is automatically increased to 2-3 times the original frequency.

[0015] According to one embodiment of the present invention, the method is also applicable to multi-motor load dynamic switching scenarios: when a motor switches from running state to stopping state or from stopping state to running state, the parameter acquisition frequency is increased to 2-3 times the original frequency 500ms-1000ms before the switch, and the control parameters after the switch are pre-calculated in advance through a global optimization algorithm to ensure that the actual THD value fluctuation amplitude during the switching process is ≤2%.

[0016] According to one embodiment of the present invention, step S6, which forms a PFC collaborative control closed loop, further includes a fault handling step: if the actual THD value after secondary optimization still exceeds the standard threshold by ≥2%, an audible and visual alarm is triggered, an alarm signal is output through the rail transit vehicle TCMS system and the faulty motor PFC unit is marked, and at the same time, fault data including the fault time, actual THD value, and control parameter configuration is stored in the local storage unit.

[0017] According to another aspect of the present invention, a PFC cooperative control system for a multi-motor drive system of rail transit is also provided to implement the method, comprising: a signal acquisition module, a global optimization algorithm module, an execution control module, and a monitoring feedback module; The signal acquisition module collects the operating parameters of the multiple motors and the on-board power grid parameters in real time when multiple motors start or run in parallel. The global optimization algorithm module is used to predict the THD value of each motor PFC unit independently based on the collected parameters and the multi-motor harmonic superposition model, and to determine whether there is a risk of exceeding the limit. If there is a risk of exceeding the limit, the control parameters of each motor PFC unit are dynamically allocated based on the prediction results and harmonic component analysis, combined with the model predictive control algorithm and adaptive harmonic cancellation logic. The execution control module sends the allocated control parameters to the corresponding motor's PFC unit through a synchronous triggering mechanism, ensuring that each PFC unit executes actions according to the preset timing sequence. The monitoring and feedback module is used to compare and judge the actual THD value and the actual power factor of the vehicle power grid when multiple motors are running in parallel, which are collected in real time by the signal acquisition module. If the actual THD value or the actual power factor exceeds the preset standard threshold, it will be fed back to the global optimization algorithm module to repeatedly optimize the control parameters and form a PFC collaborative control closed loop.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significant harmonic control effect: When multiple motors are running in parallel, THD is reduced by more than 30% (e.g., from 16.97% to 6.8%), fully complying with the EN50155 standard (THD≤8%), thus solving the problem of power grid harmonic interference; 2. Significantly improved grid stability: The on-board grid power factor is improved to ≥0.98, reducing reactive power losses in traction converters and auxiliary power systems (losses are reduced by 25%~35%). 3. Strong compatibility and scalability: Designed based on existing rail transit vehicle hardware platform, it can be directly adapted to Bosman's gate controllers (BSM-G series) and air conditioning frequency converters (BSM-V series). Integration can be achieved simply by upgrading the algorithm firmware, reducing the transformation cost by more than 40%. 4. Flexible operating conditions: Supports dynamic scenarios such as load rate fluctuation of ±15% and motor start-stop switching, with THD fluctuation of ≤2% during the switching process, adapting to various operating conditions such as subway peak hours and high-speed rail long-distance operation. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of a PFC cooperative control method for a multi-motor drive system in rail transit. Figure 2 This is a schematic diagram of a PFC (Power Factor Cooperative Control) system for a multi-motor drive system in rail transit. Detailed Implementation

[0020] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0021] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0022] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0023] like Figure 1 The diagram shows a flowchart of a PFC (Power Factor Control) cooperative control method for a multi-motor drive system in rail transit. This method forms a closed-loop logic through signal acquisition, algorithm optimization, execution control, and monitoring feedback, enabling global cooperative operation of multi-motor PFC. Specifically, it includes the following steps: S101: When multiple motors are started or running in parallel, the operating parameters of the multiple motors and the on-board power grid parameters are collected in real time. The multiple motors include a gate control motor, an air conditioner fan motor, and an air conditioner compressor motor.

[0024] The multi-motor operating parameters include input current, input voltage, load rate, and PFC operating status; the PFC operating status includes whether it is in normal rectification mode.

[0025] The vehicle-mounted electrical grid parameters include the vehicle-mounted electrical grid voltage level (such as DC110V, DC750V, DC1500V or 3AC380V) and harmonic components (at least covering the amplitude and phase of the 3rd, 5th and 7th harmonics).

[0026] S102: Based on the operating parameters of multiple motors and the parameters of the vehicle's electrical grid, predict the THD value when each motor's PFC unit is controlled independently, and determine whether there is a risk of exceeding the standard; S103: Based on the prediction results and harmonic component analysis, dynamically allocate the control parameters of each motor PFC unit to ensure that the characteristic harmonics of different motors complement and cancel each other out. For example, the 3rd harmonic of the gate motor and the 5th harmonic of the air conditioner fan motor complement and cancel each other out. The control parameters include switching frequency (5kHz-30kHz range) and duty cycle (0.3-0.8 range). The harmonic components can be obtained by analyzing the amplitude and phase of the 3rd, 5th, and 7th harmonics using the FFT algorithm.

[0027] S104: The control parameters are synchronously sent to the PFC unit of the corresponding motor to ensure that each PFC unit performs the action according to the preset timing sequence; S105: Real-time acquisition of actual THD values ​​and actual power factor of vehicle-mounted power grid during multi-motor parallel operation; S106: If the actual THD value or actual power factor exceeds the preset standard threshold, repeat steps S102 to S105 to form a PFC collaborative control closed loop. The preset standard threshold is: THD ≤ 8%, power factor ≥ 0.98.

[0028] In step S102, the total THD value is predicted based on the multi-motor harmonic superposition model when a single motor is independently controlled by PFC. The specific implementation method is as follows: First, for each type of motor, its harmonic characteristic curves when PFC operates independently are pre-stored. Among them, when the gate motor operates independently, the amplitude of the 3rd harmonic accounts for 5%~8% of the fundamental frequency, and the 5th harmonic accounts for 3%~5%; when the air conditioner fan motor operates independently, the 3rd harmonic accounts for 4%~6%, and the 5th harmonic accounts for 6%~9%.

[0029] Then, the harmonic amplitude is corrected based on the real-time load rate. For example, when the load rate of the gate motor increases from 30% to 60%, the third harmonic amplitude increases from 5% to 7%. The correction coefficient is obtained by fitting experimental data: K h = 0.08 + 0.05 × (load rate ÷ 100), where K h This is the correction coefficient for the amplitude of the nth harmonic.

[0030] Next, the total THD is calculated using the root mean square superposition method. The calculation formula is as follows: Where In is the amplitude of the nth harmonic current. This refers to the fundamental current amplitude. A preset standard threshold of 8% is used. For example, in independent control, the total THD is approximately 16.97%, far exceeding the 8% standard threshold, thus indicating a "risk of exceeding the standard."

[0031] As a further optimization, the THD value is predicted based on a harmonic superposition model specific to multiple motors in rail transit; the model pre-stores independent harmonic characteristic libraries for different types of on-board motors: Gate-controlled motor (DC110V): At a load rate of 30%, the 3rd harmonic accounts for 5% and the 5th harmonic accounts for 3%; for every 10% increase in load rate, the proportion of the 3rd harmonic increases by 0.5% and the proportion of the 5th harmonic increases by 0.3%. Air conditioner fan motor (3AC380V): At a load rate of 40%, the 3rd harmonic accounts for 4% and the 5th harmonic accounts for 6%; for every 10% increase in load rate, the proportion of the 3rd harmonic increases by 0.4% and the proportion of the 5th harmonic increases by 0.6%. When superimposing calculations, a motor coupling interference coefficient is introduced. The coupling coefficient is 1.2 when the gate motor and the air conditioning motor run in parallel, and 1.0 when they run alone. The total THD calculation results are corrected to ensure that the prediction error is ≤ ±0.5%.

[0032] In step S103, based on the prediction results of S102, the control parameters (switching frequency f) of each motor PFC unit are dynamically allocated using a model predictive control (MPC) algorithm combined with adaptive harmonic cancellation logic. s Duty cycle D) ensures that the characteristic harmonics of different motors complement and cancel each other out.

[0033] The specific modeling of the Model Predictive Control (MPC) algorithm is as follows: State variables: Definition in For example, power factor , These are the switching frequency and duty cycle of the gate motor PFC. , These are the switching frequency and duty cycle of the PFC for the air conditioner fan motor. Objective function: Minimize THD (weight 0.6) + Maximize power factor (weight 0.4), i.e.: Target value Constraints: Switching frequency 5kHz ≤ fs ≤ 30kHz, duty cycle 0.3 ≤ D ≤ 0.8, current ripple , This is the rated current of the motor.

[0034] Adaptive harmonic cancellation logic, specifically including: The dominant harmonics of each motor were analyzed using FFT (e.g., the dominant harmonic of the gate motor is the 3rd order, and the dominant harmonic of the air conditioner fan motor is the 5th order). Adjust control parameters to make the dominant harmonics opposite in phase and cancel each other out in amplitude: for example, if the amplitude of the third harmonic of the gate motor is A3=0.07I1, then adjust the switching frequency of the PFC of the air conditioner fan motor to f. s2 =18kHz (originally 15kHz), which reduces the amplitude of the third harmonic of the air conditioner fan motor to A'3=0.07I1, and the phase is 180° different from the third harmonic of the gate motor, thus achieving third harmonic cancellation.

[0035] After iterative calculation (≤10 iterations, ≤20ms per iteration), the algorithm outputs optimized parameters, such as the gate motor f. s1 =20kHz, D1=0.5; Air conditioner fan motor f s2 =18kHz, D2=0.6.

[0036] like Figure 2 As shown, a schematic diagram of a PFC cooperative control system for a multi-motor drive system in rail transit is presented. The system includes: a signal acquisition module, a global optimization algorithm module, an execution control module, and a monitoring feedback module. The signal acquisition module collects the operating parameters of the multiple motors and the on-board power grid parameters in real time when multiple motors start or run in parallel. The global optimization algorithm module is used to predict the THD value of each motor PFC unit independently based on the collected parameters and the multi-motor harmonic superposition model, and to determine whether there is a risk of exceeding the limit. If there is a risk of exceeding the limit, the control parameters of each motor PFC unit are dynamically allocated based on the prediction results and harmonic component analysis, combined with the model predictive control algorithm and adaptive harmonic cancellation logic. The execution control module sends the allocated control parameters to the corresponding motor's PFC unit through a synchronous triggering mechanism, ensuring that each PFC unit executes actions according to the preset timing sequence. The monitoring and feedback module is used to compare and judge the actual THD value and the actual power factor of the vehicle power grid when multiple motors are running in parallel, which are collected in real time by the signal acquisition module. If the actual THD value or the actual power factor exceeds the preset standard threshold, it will be fed back to the global optimization algorithm module to repeatedly optimize the control parameters and form a PFC collaborative control closed loop.

[0037] Step S106, which forms the PFC collaborative control closed loop, also includes a fault handling step: if the actual THD value still exceeds the standard threshold by ≥2% after secondary optimization, an audible and visual alarm is triggered, and an alarm signal is output through the rail transit vehicle TCMS system to mark the faulty motor PFC unit. At the same time, the fault data, including the fault time, actual THD value, and control parameter configuration, is stored in the local storage unit.

[0038] Under normal operating conditions, if the actual THD is ≤8% and the power factor is ≥0.98, the current control parameters are maintained and the monitoring feedback module continuously records data. Under deviation conditions, if the actual THD > 8% or the power factor < 0.98, the monitoring feedback module will transmit the deviation signal (e.g., THD = 9.2%, power factor = 0.97) to the global optimization algorithm module, and repeat S102~S105 for secondary optimization. Under fault conditions, if the THD is still >10% (≥2% exceeding the standard) after secondary optimization, an audible and visual alarm will be triggered (a red alarm light and buzzer will be output through the TCMS system), the faulty PFC unit will be marked (e.g., "Air conditioner fan motor No. 1 PFC fault"), and the fault data (fault time, THD value, parameter configuration) will be stored in the 16GB local storage unit. Logs can be exported via USB / RS232 interface for fault analysis.

[0039] Example 1: Coordinated Control Scheme for Door Control Motors and Air Conditioning Fan Motors in Subway Vehicles The multi-motor system includes two gate motors (DC110V, rated power 1.5kW, load rate 30%~60%) and two air conditioning fan motors (3AC380V, rated power 5kW, load rate 40%~80%). The vehicle's electrical grid parameters are DC1500V, fundamental current I1=50A; preset standard requirements: THD≤8%, power factor≥0.98.

[0040] First, parameters were collected at a frequency of 30Hz. The specific parameters are as follows: Gate motor parameters: input current 8A~16A, input voltage 110V±5%, load rate 50%, PFC normal rectification; Air conditioner fan motor parameters: input current 6A~12A, input voltage 380V±5%, load rate 60%, PFC normal rectification; Power grid harmonic parameters: 3rd harmonic amplitude 3A, 5th harmonic amplitude 2A.

[0041] Then, THD prediction is performed based on the collected parameters.

[0042] When controlled independently, the third harmonic of the gate motor is I3 = 0.07 × 50 = 3.5A, and the fifth harmonic is I5 = 0.04 × 50 = 2A. The third harmonic of the air conditioner fan motor is I3 = 0.05 × 50 = 2.5A, and the fifth harmonic is I5 = 0.08 × 50 = 4A. Total THD = The risk of exceeding the standard is determined to be "high"; then, the control parameters are calculated.

[0043] At this point, the objective function of the MPC algorithm, J = 0.6 × 16.97% + 0.4 × (1 - 0.95) = 0.1218, needs to be reduced to ≤ 0.056.

[0044] Combine adaptive harmonic cancellation logic to optimize control parameters: The gate motor has fs1=20kHz, D1=0.5, and the third harmonic amplitude drops to 3A with a phase of 0°; the air conditioner fan motor has fs2=18kHz. =0.6, 3rd harmonic amplitude 3A, phase 180°, 5th harmonic amplitude 4A, phase 180°; Optimized prediction THD= The objective function of the MPC algorithm is J = 0.6 × 5.66% + 0.4 × (1 - 0.99) = 0.038, which satisfies the objective optimization requirements. Perform parameter validation, parameter f s Both D and F are within the constraints. Parameter f is synchronously transmitted via the CANopen bus. s With up to 100 motors, the timing error is 0.8ms, and the PFC unit of multiple motors operates synchronously. Real-time monitoring of the indicators yielded an actual THD of 6.8% and a power factor of 0.99, which meet the standard requirements. Maintaining the current parameters and continuously monitoring in real time, the THD fluctuation range was 6.5%~7.2% within 1 hour, and the power factor remained stable at 0.98~0.99.

[0045] Through the empirical demonstration of PFC collaborative control in Example 1, THD decreased from 16.97% under independent control to 6.8%, a reduction of 60%, meeting the EN50155 standard; the power factor improved from 0.95 to 0.99, and the reactive power loss of the power grid decreased by 36%; the contact temperature of the gated motor contactor decreased from 65°C to 52°C, the IGBT temperature of the frequency converter decreased from 78°C to 63°C, and the equipment life was extended by 18%.

[0046] Example 2: Coordinated Control Scheme for Air Conditioning Fan Motor and Air Conditioning Compressor Motor in High-Speed ​​Rail Vehicles The multi-motor configuration includes: 4 air conditioner fan motors (3AC380V, rated power 8kW, load rate 50%~90%) and 2 air conditioner compressor motors (3AC380V, rated power 15kW, load rate 60%~100%); the vehicle's electrical grid is 3AC380V, with a fundamental current I1=100A; the preset standard requirements are: THD≤8%, power factor≥0.98.

[0047] First, parameters were collected at a frequency of 50Hz, as follows: Air conditioner fan motor parameters: input current 10A~18A, load rate 80%; Air conditioner compressor motor parameters: input current 20A~30A, load rate 90%; Power grid harmonic parameters: 3rd harmonic amplitude 6A, 5th harmonic amplitude 4A.

[0048] Then, THD prediction was performed based on the collected parameters. Referring to the calculation method in Example 1, the total THD was 14.2% when controlled independently, which was judged as "high risk of exceeding the standard".

[0049] Next, control parameters were optimized, including: air conditioner fan motor f. s =22kHz, D=0.55; Air conditioner compressor motor f s =16kHz, D=0.65; predicted THD=6.2%.

[0050] After synchronous execution according to the control parameters, the actual THD was 7.1% and the power factor was 0.992, meeting the preset standards, and continuous operation showed no deviation. The implementation results showed that THD was reduced by 49.3%, the power factor improved by 4.4%, and the air conditioning system energy consumption was reduced by 28%.

[0051] This invention, through the core algorithm design of model predictive control combined with adaptive harmonic cancellation, breaks through the technical bottleneck of existing single-motor PFC independent control, effectively solving the harmonic superposition problem of multiple motors operating in parallel in rail transit. It also has advantages such as strong compatibility, low modification cost, and flexible adaptation to operating conditions. It can be widely used in various rail transit vehicles such as subways, high-speed railways, and light rails, which is in line with the national development direction of "green and efficient rail transit equipment" and has significant technological innovation and industrial application value.

[0052] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0053] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A PFC cooperative control method for a multi-motor drive system in rail transit, characterized in that, Includes the following steps: S1: When multiple motors start or run in parallel, collect the operating parameters of the multiple motors and the parameters of the vehicle's power grid in real time; S2: Based on the collected parameters, predict the THD value when each motor PFC unit is controlled independently using the multi-motor harmonic superposition model, and determine whether there is a risk of exceeding the standard. S3: If there is a risk of exceeding the standard, based on the prediction results and harmonic component analysis, combined with the model predictive control algorithm and adaptive harmonic cancellation logic, the control parameters of each motor PFC unit are dynamically allocated. S4: The allocated control parameters are sent to the corresponding motor PFC unit through a synchronous triggering mechanism to ensure that each PFC unit performs actions according to the preset timing sequence; S5: Real-time acquisition of the actual THD value and the actual power factor of the vehicle's electrical grid during the parallel operation of multiple motors; S6: If the actual THD value or actual power factor exceeds the preset standard threshold, repeat steps S2 to S5 to form a PFC collaborative control closed loop. The multi-motor operating parameters include input current, input voltage, load rate, and PFC operating status; the PFC operating status includes normal rectification status, fault status, and standby status; the vehicle-mounted power grid parameters include vehicle-mounted power grid voltage level and harmonic components. In step S2, the specific implementation method for predicting the THD value based on the multi-motor harmonic superposition model is as follows: The harmonic characteristic curves of each type of motor PFC when working independently are pre-stored, and the harmonic amplitude is corrected according to the real-time collected motor load rate. The total THD is calculated using the root mean square superposition method. The formula is as follows: Where In is the amplitude of the nth harmonic current. This represents the amplitude of the fundamental current. The harmonic characteristic curve is a curve showing the relationship between motor load rate and harmonic amplitude ratio obtained in advance through experiments. The fitting formula for the correction coefficient is: = 0.08 + 0.05 × (load rate ÷ 100), where This is the correction coefficient for the amplitude of the nth harmonic.

2. The method according to claim 1, characterized in that, The control parameters include switching frequency and duty cycle. The switching frequency ranges from 5kHz to 30kHz, and the duty cycle ranges from 0.3 to 0.

8. When dynamically allocating control parameters, it is necessary to ensure that the current ripple of each motor PFC unit is ≤5% of the motor's rated current.

3. The method according to claim 1, characterized in that, The multiple motors are selected from at least two of the following: rail transit vehicle door control motors, air conditioning fan motors, and air conditioning compressor motors.

4. The method according to claim 1, characterized in that, In step S1, the parameter acquisition frequency is 10Hz-50Hz. When the motor load rate fluctuates by more than ±15%, the acquisition frequency is automatically increased to 2-3 times the original frequency.

5. The method according to claim 1, characterized in that, The method is also applicable to multi-motor load dynamic switching scenarios: when a motor switches from running state to stopping state or from stopping state to running state, the parameter acquisition frequency is increased to 2-3 times the original frequency 500ms-1000ms before the switch, and the control parameters after the switch are pre-calculated through a global optimization algorithm to ensure that the actual THD value fluctuation amplitude during the switching process is ≤2%.

6. The method according to claim 1, characterized in that, Step S6, which forms the PFC collaborative control closed loop, also includes a fault handling step: if the actual THD value still exceeds the standard threshold by ≥2% after secondary optimization, an audible and visual alarm is triggered, and an alarm signal is output through the rail transit vehicle TCMS system to mark the faulty motor PFC unit. At the same time, the fault data, including the fault time, actual THD value, and control parameter configuration, is stored in the local storage unit.

7. A PFC cooperative control system for a multi-motor drive system in rail transit, used to implement the method according to any one of claims 1 to 6, characterized in that, include: Signal acquisition module, global optimization algorithm module, execution control module, monitoring and feedback module; The signal acquisition module collects the operating parameters of the multiple motors and the on-board power grid parameters in real time when multiple motors start or run in parallel. The global optimization algorithm module is used to predict the THD value of each motor PFC unit independently based on the collected parameters and the multi-motor harmonic superposition model, and to determine whether there is a risk of exceeding the limit. If there is a risk of exceeding the limit, the control parameters of each motor PFC unit are dynamically allocated based on the prediction results and harmonic component analysis, combined with the model predictive control algorithm and adaptive harmonic cancellation logic. The execution control module sends the allocated control parameters to the corresponding PFC unit of the motor through a synchronous triggering mechanism, ensuring that each PFC unit executes actions according to the preset timing sequence. The monitoring and feedback module is used to compare and judge the actual THD value and the actual power factor of the vehicle power grid when multiple motors are running in parallel, which are collected in real time by the signal acquisition module. If the actual THD value or the actual power factor exceeds the preset standard threshold, it will be fed back to the global optimization algorithm module to repeatedly optimize the control parameters and form a PFC collaborative control closed loop.

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