ANPC type three-level inverter in train traction drive system and its control method

Abstract

The present invention discloses an ANPC-type three-level inverter in a train traction drive system and a control method thereof. By establishing a parametric model of the stray inductance of the power module of the train traction drive system and a mathematical model of the influence of different commutation paths on the ANPC-type three-level inverter, a power loss thermal balance method is adopted to achieve a robust controller design. Based on a thermal balance management approach and in conjunction with robust repetitive control, the actual commutation path is switched to avoid system instability caused by repeated switching of critical points of different operating states during train operation. In addition, energy exchange between internal and external tubes and clamping tubes is utilized to achieve system balance control.

Description

Technical Field

[0001] The present invention relates to power electronic control technology, in particular to an ANPC type three-level inverter in a train traction drive system and a control method thereof. Background Art

[0002] With the continuous development of high-power electric transmission, three-level inverters have become widely used in the rail transportation industry. Compared with two-level inverters, ANPC-type three-level inverters in traction transmission systems offer advantages such as lower output voltage and current harmonics, and reduced voltage and losses on power devices. Although the number of power switching devices increases, optimized control strategies can be used to balance power transistor losses, enabling higher voltage levels and higher-capacity transmission. The overall system design still outperforms two-level converters of the same power level. The three-level topology enables higher-performance power conversion.

[0003] Traditional control strategies can easily lead to severely uneven heating of the inner and outer transistors in the single-phase bridge arm of the traction drive inverter, thus affecting the inverter's operating stability and actual output power. The current ANPC (Active Neutral Point Clamping) three-level topology, with the increasing number of switches to be controlled, the diversification of the neutral point commutation paths, and the complexity of the control process, can lead to voltage and current imbalances, overvoltage or overcurrent on some power transistors, and even serious failures that can cause inverter module failure. Adding monitoring equipment to monitor the status of inverter parameters such as voltage, current, and temperature online increases the size and maintenance costs of the inverter design, while also reducing reliability.

[0004] To ensure energy conservation in train traction systems, increasing inverter power levels will become a mainstream railway development model. Therefore, improving power module density and optimizing control strategies are crucial to enhancing the efficiency and operational reliability of the entire train's three-level inverter system.

[0005] In existing traction drive systems, inverters still suffer from issues like overvoltage and uneven current distribution in power devices. Furthermore, trains experience changes in additional resistance during extended operation under complex road conditions, such as curves, tunnels, and slopes. Considering factors such as changes in external wind speed, aging of mechanical and electrical components, and grid voltage fluctuations, the inverter's power devices experience uneven power losses during the train's transitions from traction to cruising to coasting to braking, limiting the power density of the inverter module. Controlling the voltage and current of power devices to ensure stable operation of the three-level ANPC topology remains a pressing technical challenge. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an ANPC type three-level inverter and a control method thereof in a train traction drive system in view of the shortcomings of the existing technology, so as to avoid system instability caused by repeated switching of critical points and realize balanced control of power modules.

[0007] To solve the above technical problems, the present invention adopts a technical solution: a method for controlling an ANPC-type three-level inverter in a train traction drive system, wherein the input side of the ANPC-type three-level inverter is connected to an ANPC-type three-level rectifier; the output side of the ANPC-type three-level inverter is connected to multiple motors through an LCL filter; the method includes:

[0008] The output voltage of the ANPC three-level inverter is controlled using the following formula:

[0009] and / or,

[0010] The output current of the ANPC three-level inverter is controlled using the following formula:

[0011] Among them, u d u q are the d-axis and q-axis components of the output voltage of the ANPC three-level inverter respectively; i d 、i q They represent the output current components of the ANPC three-level inverter on the d-axis and q-axis respectively, i d 、i q * Respectively represent i d 、i q Given value, R represents the equivalent resistance value of LCL filter, L represents the equivalent inductance value of LCL filter, u gd 、u gq They are the output voltage u at the motor end g The component on the d-axis and the component on the q-axis; e is the tracking error, e = i * -i, i represents the output current of the motor, i * Represents the reference current; T * e represents the electromagnetic torque value of the motor, 2n is the number of pole pairs of the motor, and Ψ is the magnetic flux amplitude of the motor; is the bus voltage given value, v dc is the bus voltage (i.e. the voltage across the capacitor branch); K v is the voltage control link gain, τ s is the time constant of the voltage control link, T vSet to N times the time constant of the voltage control link, N is a constant; s is a complex variable; L s is the total stray inductance of the ANPC three-level inverter;

[0012] The process of determining the first weight coefficient ξ includes: if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is equal to the stray inductance value of the lower half bridge arm, ξ is set to a first preset value; if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is less than the stray inductance value of the lower half bridge arm, ξ is set to a second preset value; if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is greater than the stray inductance value of the lower half bridge arm, ξ is set to a third preset value; wherein the second preset value < the second preset value < the third preset value;

[0013] The process of determining the second weight coefficient μ includes: if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is equal to the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a first preset value; if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is less than the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a second preset value; if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is greater than the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a third preset value.

[0014] The present invention introduces two weight coefficient parameters, ξ and μ, to optimize control performance, while stabilizing the intermediate DC link voltage to suppress fluctuations. It can also stably control the output voltage and current, allowing the inverter to operate safely and stably according to the set parameters. The present invention avoids system instability caused by repeated switching of critical points, and utilizes energy exchange between internal and external tubes and clamping tubes to achieve balanced control of the power module.

[0015] The method of the present invention further comprises: converting the d-axis component u of the output voltage of the ANPC type three-level inverter d and the component u on the q axis q The voltage is converted into a voltage in a three-phase ABC stationary coordinate system, and the on / off control of the power devices of the ANPC three-level inverter is performed through sinusoidal pulse width modulation. To further improve control accuracy, the method of the present invention further includes: comparing the output voltage of the ANPC three-level inverter with a target output voltage value; if the deviation between the output voltage of the ANPC three-level inverter and the target output voltage value is less than a set threshold, then the process ends; otherwise, adjusting the stray inductance of the ANPC three-level inverter, and then adjusting the output voltage of the ANPC three-level inverter, until the deviation between the output voltage of the ANPC three-level inverter and the target output voltage value is less than the set threshold.

[0016] To further improve control accuracy, the method of the present invention further includes: comparing the output current of the ANPC three-level inverter with a target output current value; if the deviation between the output current of the ANPC three-level inverter and the target output current value is less than a set threshold, then ending the process; otherwise, adjusting the stray inductance value of the ANPC three-level inverter, and then adjusting the output current of the ANPC three-level inverter, until the deviation between the output current of the ANPC three-level inverter and the target output current value is less than the set threshold.

[0017] In order to stabilize the intermediate DC link voltage and achieve the effect of suppressing fluctuations, the present invention provides a three-level inverter system in a train traction drive system, including an ANPC type three-level inverter; the input side of the ANPC type three-level inverter is connected to an ANPC type three-level rectifier; the ANPC type three-level rectifier is connected to the power grid through a traction transformer; the output side of the ANPC type three-level inverter is connected to multiple motors through an LCL filter; the ANPC type three-level inverter includes a capacitor branch; the capacitor branch includes two capacitors connected in series; the capacitor branch is connected in parallel with a first bridge arm; the first bridge arm includes four power devices connected in series, of which the middle two power devices are connected in parallel with the second bridge arm; the second bridge arm includes two power devices connected in series; the two ends of the capacitor branch are each connected to the two ends of the first bridge arm through an inductor; the midpoint of the capacitor branch is connected to the midpoint of the first bridge arm through an inductor.

[0018] As an inventive concept, the present invention also provides an ANPC type three-level inverter control system in a train traction drive system, which includes:

[0019] one or more processors;

[0020] A memory having one or more programs stored thereon, which, when executed by the one or more processors, enables the one or more processors to implement the steps of the above method of the present invention.

[0021] Compared with the prior art, the present invention has the following beneficial effects: the present invention establishes a model for the relationship between the stray inductance parameters of the power module and the influence of different commutation paths on the power module, adopts a power loss thermal balance method to achieve a controller design with robust performance, and stably switches the actual commutation path based on a thermal balance management method and in conjunction with robust repeated control, avoiding the instability of the system caused by repeated switching of critical points, and realizes power module balance control by utilizing the energy exchange between the inner and outer tubes and the clamping tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of an application of an ANPC three-level inverter system according to an embodiment of the present invention;

[0023] Figure 2 This is a stray inductance distribution diagram of an ANPC three-level inverter according to an embodiment of the present invention;

[0024] Figure 3(a) to Figure 3(d) 3 (a) is a state diagram of a three-level switch according to an embodiment of the present invention; FIG3 (b) is an O1 state; FIG3 (c) is an O2 state; FIG3 (d) is an N state;

[0025] Figure 4 This is a diagram of a robust repetitive controller according to an embodiment of the present invention;

[0026] Figure 5 This is a control circuit diagram of an ANPC three-level inverter system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative efforts shall fall within the scope of protection of the present invention.

[0028] In this document, the terms "first", "second" and other similar words are not intended to imply any order, quantity and importance, but are merely used to distinguish different elements. In this document, the terms "one", "an" and other similar words are not intended to indicate that there is only one of the things described, but rather that the relevant description is only for one of the things described, and the things described may have one or more. In this document, the terms "comprise", "include" and other similar words are intended to indicate logical relationships, and cannot be regarded as indicating relationships in spatial structure. For example, "A includes B" is intended to indicate that B logically belongs to A, and does not mean that B is spatially located inside A. In addition, the meanings of the terms "comprise", "include" and other similar words should be regarded as open, not closed. For example, "A includes B" is intended to indicate that B belongs to A, but B does not necessarily constitute the whole of A, and A may also include other elements such as C, D, and E.

[0029] The embodiment of the present invention establishes a relationship model between the stray inductance parameters of the power module and the influence of different commutation paths on the power module. A power loss thermal balance method is used to implement a robust controller design. Based on a thermal balance management approach (the controller is related to the parameters ξ and μ, i.e., the related stray inductance and device case temperature) and combined with robust repetitive control to destabilize the actual commutation path, system instability caused by repeated switching of critical points is avoided. In addition, balanced control of the power module is achieved by utilizing energy exchange between the internal and external transistors and the clamping transistor.

[0030] Example 1

[0031] The ANPC three-level inverter system structure used in this embodiment is as follows: Figure 1 shown.

[0032] The input end of the ANPC type three-level inverter is connected to the power grid through the ANPC type three-level rectifier, and the output end is connected to multiple traction motors. The traction transformer takes power, passes through the ANPC type three-level rectifier, and obtains stable direct current, which is then output through the ANPC type three-level inverter to control a single or multiple motors in the system. The ANPC type three-level inverter includes a three-port DC busbar link (P, O, N), a three-level ANPC topology circuit composed of six power devices such as IGBT or IGCT or SiC, and a three-phase AC copper busbar output (A, B, C). This embodiment can take into account the stabilization of the intermediate DC link voltage to achieve the effect of suppressing fluctuations, and can also stably control the output voltage and current, so that the inverter can operate safely and stably according to the set parameters.

[0033] Figure 2 This is the internal stray inductance distribution diagram of the ANPC three-level inverter. Figure 2 The voltage between the positive and negative bus capacitors is Vc1 = Vc2, and stray inductances Ls1-Ls6 exist within the power module. The diagram shows three operating states: P, O, and N. The O state is more flexible, with the output current flowing through D5 and T2, or T6 and D3. Traditionally, when switching from a positive or negative level to a zero level, the inner and outer transistors can be controlled to alternate within a fixed cycle. This method shifts some of the outer transistor's switching losses to the inner transistor and the clamping transistor. However, when the parameters corresponding to Ls1 and Ls6, and Ls2 and Ls5, are designed to be unequal, conventional control methods cannot fully balance the power device losses.

[0034] In this embodiment, the stray inductance parameter model takes into account the parasitic inductance parameters of the DC bus capacitor itself, the stray inductance parameters of the laminated busbar in a symmetrical structure, and the stray inductance parameters of the internal and external copper busbars connecting the power device. The process of constructing the stray inductance parameter model is as follows: the positive bus capacitor is between bus P and bus O, and the parasitic inductance parameter of the positive bus capacitor device itself, and then the stray inductance parameter from the positive port of the capacitor through the positive busbar to the terminal of the power device T1, these two parts constitute Ls1; the part from the connection between the positive bus capacitor and the negative bus capacitor, through busbar O to the connection between power devices T5 and T6 constitutes Ls3; the negative bus capacitor is between bus O and bus N, and the parasitic inductance parameter of the negative bus capacitor device itself, and then the stray inductance parameter from the negative port of the capacitor through the positive busbar to the terminal of the power device T4, these two parts constitute Ls6; the part connecting the midpoint of power devices T1 and T5 and the end of power device T2 constitutes Ls2; the part connecting the midpoint of power devices T6 and T4 and the end of power device T3 constitutes Ls5; the part connecting the midpoint of power devices T6 and T4 and the three-phase AC output port of the inverter constitutes Ls4.

[0035] The train's ANPC-type three-level inverter corresponds to three voltages in the switching states P, O, and N. Each current flows through the DC bus capacitors, the laminated busbars, and specific switch positions. The degree of current path overlap must be quantitatively determined, taking into account the worst-case scenario. During actual operation, currents from each capacitor converge to the power module, resulting in a certain degree of current overlap at the DC input.

[0036] In this embodiment, a robust repetitive controller is designed to control the output of an ANPC three-level inverter. The input signal y(s) and the output signal u of the controller K(s) are considered as the evaluation output of the system (ANPC three-level inverter). The performance of the controller is optimized by introducing two weight coefficient parameters ξ and μ.

[0037] The robust repetitive controller is designed in detail based on a hybrid solution method in five processes. The weight coefficients ξ and μ range from 0 to 1, and the initial value is 0.5. During actual operation, if the stray inductance parameter is greater than or less than the preset value, the weight coefficient ξ is increased or decreased accordingly. Similarly, if the shell temperature of the power device increases or decreases during the temperature change, the weight coefficient μ is increased or decreased in time until the controller parameters determined after adjustment can meet the stable operation conditions of the system.

[0038] In this embodiment, the controller design process is as follows: select the initial ξ and μ weight coefficient values, obtain the stray inductance value, adjust the input ξ weight coefficient, obtain the power device case temperature, adjust the output μ weight coefficient, determine the controller parameters and judge the system stability. Figure 2 As shown, the method for adjusting ξ is to obtain the upper half bridge arm stray inductance parameter Ls1 +L s2 and the lower half bridge arm stray inductance parameter L s5 +L s6 , when the two are equal, the default initial value is 0.5, if L s1 +L s2 <L s5 +L s6 At this time, ξ is adjusted to 0, if L s1 +L s2 >L s5 +L s6 , ξ is adjusted to 1. Compare the shell temperature T of all power tubes in the upper half bridge arm c1 +T c2 +T c5 The shell temperature T of the lower half bridge arm power tube c3 +T c4 +T c6 , when the two are equal, μ defaults to the initial value of 0.5 and remains unchanged. c1 +T c2 +T c5 <T c3 +T c4 +T c6 , at this time μ is adjusted to 0, if T c1 +T c2 +T c5 >T c3 +T c4 +T c6 , μ is adjusted to 1. Compare the actual voltage and current output of the inverter with the target values ​​respectively. When the deviation is less than 5%, the controller is considered stable and the controller design is completed.

[0039] Switching laws typically depend on the system state or time, operating the corresponding subsystem within a specific timeframe. In practical applications, all system state variables cannot be accurately and in real time, making it difficult to implement system switching based on the full state. The switching behavior of actuators is closely linked to the system state, and the same switching law will produce different switching processes under different system states.

[0040] In this embodiment, the temperature of the three power devices located in the upper half bridge arm or the lower half bridge arm is controlled within a reasonable range by switching the control mode. When the temperature difference is small, the switching is stopped to make the heat distribution balanced. Figure 3(a) to Figure 3(d)As shown, in this embodiment, the ANPC three-level inverter has four operating states, enabling four-quadrant operation and bidirectional energy flow. In the P state in Figure 3(a), current flows out through T1 and T2, and flows in through D2 and D1. In the O1 state in Figure 3(b), current flows out through D5 and T2, and flows in through D2 and T5. In the O2 state in Figure 3(c), current flows out through T6 and D3, and flows in through T3 and D6. In the O2 state in Figure 3(d), current flows out through T6 and D3, and flows in through T3 and D6. The ANPC type is based on the NPC three-level topology, replacing the uncontrollable devices in the clamping part. The main difference is that two controllable power devices T5 and T6 are connected in anti-parallel to the two clamping diodes D5 and D6. Therefore, when the bridge arm modulates the positive half-wave voltage, the output of zero level can flow through D5 to T2 and T6 to D3. Similarly, when modulating the negative half-wave voltage, the output of zero level can flow through D2 to T5 and T3 to D6. Compared to the NPC three-level circuit, which can only generate zero level by turning off the outer transistors T1 or T4, the ANPC three-level circuit can also achieve zero level output by turning off the inner transistors T2 and T3. Therefore, the switching action previously performed solely by the outer transistor is now shared by both the outer and inner transistors, effectively reducing the switching losses of the outer transistor and further improving the bridge arm's conduction current capability. Because power module design cannot completely equalize these stray parameters, the paths from the P state to the O1 and O2 states will be different, and the paths from the N state to the O1 and O2 states will be different. When the two have a large deviation, the thermal deviation of the power device will also be large, thereby limiting the power module's output current capacity.

[0041] Each phase has 6 switching tubes and corresponding anti-parallel freewheeling diodes. By controlling the switching tubes to open and close according to their specific requirements, multiple commutation paths will be formed, corresponding to the output of P level, O level or N level respectively.

[0042] (1) In the P state, the bridge arm outputs a positive level, the voltage of T1 is 0, the voltage of T2 is 0, and the voltage of T3 is V dc / 2, T4 voltage is V dc / 2, T5 voltage is V dc / 2, the voltage of T6 is 0, and T6 and D6 clamp the emitter potential of T3.

[0043] (2) In the O state, the bridge arm outputs zero level, and the voltage of T1 is V dc / 2, T2 voltage is 0, T3 voltage is 0, T4 voltage is V dc / 2, T5 voltage is 0, T6 voltage is 0.

[0044] (3) In the N state, the bridge arm outputs a negative level, and the voltage of T1 is V dc / 2, T2 voltage is Vdc / 2, T3 voltage is 0, T4 voltage is 0, T5 voltage is 0, T6 voltage is V dc / 2, T5 and D5 clamp the emitter potential of T1.

[0045] Figure 4 and Figure 5 This is the robust repetitive controller and the overall control diagram of the inverter system. According to the mathematical model, there is a gain matching between the feedback controller and the low-pass filter in the control system, and the two parameters affect the steady-state performance of the system. Figure 4 The total stray inductance of the external input is expressed as L s , L s =L s1 +L s2 +L s3 +L s4 +L s5 +L s6 , its product with the ξ weight coefficient is L s ξ. The external input of the control system can be the voltage u at the motor end g , current i, and reference current i * Signal. The tracking error of the control system is e=i * -i. The front-end input y = L of the controller K(s) s ξ+e, the back-end output of the controller K(s) is u=Ky, and the controller can process the tracking error of the control system.

[0046] This control method targets the bus voltage link and uses the stray inductance parameters obtained previously to input L s ξDe-duplication compensation bus voltage fluctuation, bus voltage set value With v dc After comparison, it is input into the transfer function G1(s).

[0047]

[0048] where K v is the voltage control link gain, τ s is the time constant of the voltage control link, T v Generally, four times the time constant of the voltage control link is taken.

[0049] The inverter control output current d-axis given value can be given by the voltage link

[0050]

[0051] The inverter control output current q axis given value can be given by the motor parameter M

[0052]

[0053] Where T * e represents the electromagnetic torque value of the motor, 2n is the number of pole pairs of the motor, and Ψ is the magnetic flux amplitude of the motor.

[0054] Three-level inverter controls output voltage u d 、u q The expression is

[0055]

[0056] u d 、u q Indicates the components of the inverter control output voltage on the d-axis and q-axis respectively, is the robust repetitive controller parameter, i d Indicates the component of the inverter control output current on the d-axis, i * d It means i d Given value, R represents the equivalent resistance value of LCL filter, L represents the equivalent inductance value of LCL filter L1+L2, u gd is the voltage u at the motor end g The component on the d-axis.

[0057] For the voltage component u output by the ANPC three-level inverter d 、u q The 3s / 2r coordinate transformation described above converts the voltage into a three-phase ABC stationary coordinate system. Then, a sinusoidal pulse width modulation strategy is used to control the on / off switching of the power devices, balancing the losses of each power transistor. By adjusting the controller in real time based on the previously determined stray inductance parameters, motor efficiency can be improved and system safety can be guaranteed.

[0058] Example 2

[0059] Embodiment 2 of the present invention provides a terminal device corresponding to the above-mentioned embodiment 1. The terminal device can be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of the above-mentioned embodiment.

[0060] The terminal device of this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in the above-mentioned embodiment 1.

[0061] In some implementations, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk storage.

[0062] In other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors, which are not limited herein.

[0063] Example 3

[0064] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to the above-mentioned embodiment 1, on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps of the method of the above-mentioned embodiment 1 are implemented.

[0065] Computer readable storage media can be tangible devices that hold and store instructions used by instruction execution devices. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any combination thereof.

[0066] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

[0067] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0068] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0069] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0070] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for controlling an ANPC-type three-level inverter in a train traction drive system, wherein the input side of the ANPC-type three-level inverter is connected to an ANPC-type three-level rectifier; the output side of the ANPC-type three-level inverter is connected to multiple motors through an LCL filter; characterized in that: The method includes: The output voltage of the ANPC three-level inverter is controlled using the following formula: and / or, The output current of the ANPC three-level inverter is controlled using the following formula: Among them, u d u q are the d-axis and q-axis components of the output voltage of the ANPC three-level inverter respectively; i d 、i q They represent the output current components of the ANPC three-level inverter on the d-axis and q-axis respectively, i d * 、i q * Respectively represent i d 、i q Given value, R represents the equivalent resistance value of LCL filter, L represents the equivalent inductance value of LCL filter, u gd 、u gq They are the output voltage u at the motor end g The component on the d-axis and the component on the q-axis; e is the tracking error, e = i * -i, i represents the output current of the motor, i * Represents the reference current; T * e represents the electromagnetic torque value of the motor, 2n is the number of pole pairs of the motor, and Ψ is the magnetic flux amplitude of the motor; is the bus voltage given value, v dc is the bus voltage; K v is the voltage control link gain, τ s is the time constant of the voltage control link, T v Set to N times the time constant of the voltage control link, N is a constant; s is a complex variable; L s is the total stray inductance of the ANPC three-level inverter; The process of determining the first weight coefficient ξ includes: if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is equal to the stray inductance value of the lower half bridge arm, ξ is set to a first preset value; if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is less than the stray inductance value of the lower half bridge arm, ξ is set to a second preset value; if the stray inductance value of the upper half bridge arm of the ANPC type three-level inverter is greater than the stray inductance value of the lower half bridge arm, ξ is set to a third preset value; wherein the second preset value < the second preset value < the third preset value; The process of determining the second weight coefficient μ includes: if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is equal to the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a first preset value; if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is less than the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a second preset value; if the sum of the case temperatures of all the switching tubes in the upper half bridge arm of the ANPC type three-level inverter is greater than the sum of the case temperatures of all the switching tubes in the lower half bridge arm, μ is set to a third preset value.

2. The ANPC type three-level inverter control method in a train traction drive system according to claim 1, characterized in that: Also includes: The d-axis component u of the output voltage of the ANPC three-level inverter is d and the component u on the q axis q It is converted into a voltage in the three-phase ABC stationary coordinate system, and the on and off of the power devices of the ANPC type three-level inverter are controlled by sinusoidal pulse width modulation.

3. The ANPC type three-level inverter control method in a train traction drive system according to claim 1, characterized in that: Also includes: The output voltage of the ANPC three-level inverter is compared with a target output voltage. If a deviation between the output voltage of the ANPC three-level inverter and the target output voltage is less than a set threshold, the operation is terminated. Otherwise, the stray inductance value of the ANPC three-level inverter is adjusted, and then the output voltage of the ANPC three-level inverter is adjusted until the deviation between the output voltage of the ANPC three-level inverter and the target output voltage is less than the set threshold.

4. The ANPC type three-level inverter control method in a train traction drive system according to claim 1, characterized in that: Also includes: Comparing the output current of the ANPC type three-level inverter with the output current target value, and ending the operation if the deviation between the output current of the ANPC type three-level inverter and the output current target value is less than a set threshold; Otherwise, the stray inductance value of the ANPC type three-level inverter is adjusted, and then the output current of the ANPC type three-level inverter is adjusted until the deviation between the output current of the ANPC type three-level inverter and the output current target value is less than a set threshold.

5. A three-level inverter system in a train traction drive system, for implementing the control method according to any one of claims 1 to 4, comprising an ANPC three-level inverter; the input side of the ANPC three-level inverter is connected to an ANPC three-level rectifier; the ANPC three-level rectifier is connected to the power grid via a traction transformer; the output side of the ANPC three-level inverter is connected to multiple motors via LCL filters; characterized in that: The ANPC three-level inverter includes a capacitor branch; the capacitor branch includes two capacitors connected in series; the capacitor branch is connected in parallel with the first bridge arm; the first bridge arm includes four power devices connected in series, of which the middle two power devices are connected in parallel with the second bridge arm; the second bridge arm includes two power devices connected in series; the two ends of the capacitor branch are each connected to the two ends of the first bridge arm via an inductor; and the midpoint of the capacitor branch is connected to the midpoint of the first bridge arm via an inductor.

6. An ANPC type three-level inverter control system in a train traction drive system, characterized in that: include: one or more processors; A memory having one or more programs stored thereon, which, when executed by the one or more processors, enables the one or more processors to implement the steps of the method according to any one of claims 1 to 4.

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